Title of Invention	A FUEL INJECTION CONTROLLING METHOD FOR AN INTERNAL COMBUSTION ENGINE
Abstract	The present invention relates to a fuel injection controlling method for an internal combustion engine, in which at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used and a plurality of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount of fuel to each of the cylinders, characterized in that: a rate of an amount of the fuel injected for every fuel injection is changed for one cycle in response to a temperature of cooling water and other operational condition of the internal combustion engine.

Title of Invention

A FUEL INJECTION CONTROLLING METHOD FOR AN INTERNAL COMBUSTION ENGINE

Abstract

The present invention relates to a fuel injection controlling method for an internal combustion engine, in which at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used and a plurality of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount of fuel to each of the cylinders, characterized in that: a rate of an amount of the fuel injected for every fuel injection is changed for one cycle in response to a temperature of cooling water and other operational condition of the internal combustion engine.

Full Text	The present invention relates to a fuel injection controlling apparatus for, for example, an automotive internal combustion engine, and more particularly to a fuel injection controlling apparatus for an internal combustion engine, which may control a fuel amount with high precision. In general, in a fuel injection controlling apparatus for an internal combustion engine, a fuel amount needed for the engine is calculated in accordance with operational information such as an intake air amount and an engine RPM, thereby driving an injector to feed necessary fuel to the engine, and igniting the fuel at a suitable ignition timing to drive the engine. According to a type of a fuel injection system, the fuel injection controllers are roughly categorized into an MPI (multi¬point injection) system having injectors corresponding to the number of cylinders of the engine, a system which has a smaller number of the injectors than the number of the cylinders, and an SPI (single point injection) system for feeding the fuel by a single injector irrespective of the number of the cylinders. In general, in the MPI system, each injectoi is mounted in the vicinity of an intake port of the associated intake port in the intake manifold passage within the intake pipe and supply the fuel between half the latter exhaust stroke and the intake stroke of the associated cylinder for feeding necessary fuel to the associated cylinder. On the other hand, in the system having the smaller number of injectors than that of the cylinders or in the SPI system for supplying the fuel by a single injector, it is necessary to feed the fuel to a plurality of cylinders by a single injector. Fig. 19 is a block diagram schematically showing an overall system of the conventional fuel injection controlling apparatus for an internal combustion engine, and shows, for example, the SPI system for supplying the fuel by ci single injector. In Fig. 19, numeral 101 denotes a body of an internal combustion engine, i.e., an engine having four cylinders. ~ Numeral 102 denotes an air cleaner provided in an intake port of an intake pipe for purifying intake air, numeral 103 denotes a throttle valve which is driven to open and close within the intake pipe for adjusting an intake air amount to the engine 101, and numeral 104 denotes a throttle opening degree sensor for detecting a throttle openin■• degree a of the throttle valve 103. Numeral 105 is an intake manifold provided in a joint portion between the intake pipe and the engine 101, numeral 106 denotes an intake air pressure sensor for detecting an intake manifold pressure Pb within the intake manifold 105, and numeral 107 denotes an injector provided upstream of the throttle valve 103 for injecting the fuel. Numeral 108 denotes a crank angle detecting sensor for outputting a crank angle signal 6 in correspondence with a rotation of a crankshaft of the engine 101, numeral 109 denotes an exhaust manifold provided in a joint portion between the engine 101 and an exhaust pipe, numeral 110 denotes an oxygen concentration detecting sensor provided in the exhaust pipe for detecting an oxygen concentration Gd of the exhaust gas, and numeral 111 denotes a catalyst provided at an exhaust outlet of the exhaust pipe for purifying the exhaust gas. Incidentally, needless to say, there are provided many kinds of sensors such as a sensor for detecting a temperature of cooling water of the engine although not shown. Numeral 112 denotes an ignition coil built-in type distributor for applying a high voltage for ignition to spark plugs for the respective cylinders of the engine 101. Numeral 113 denotes an electronic control unit (ECU) for outputting drive signals, i.e., a fuel injection signal J and an ignition signal Q to the injector 107 and the distributor 112 on the basis of operational information a, Pb, 6 and Gd from the various sensors 104, 106, 108 and 110. Numeral 114 denotes a control relay for supplying a power source to the electronic control unit 113. Fig. 20 is a waveform diagram showing the fuel injection timing and the ignition timing of the engine 101 in accordance with the fuel injection controlling apparatus for an internal ■ combustion engine shown in Fig. 19, and shows the various produced timings of the crank angle signal 6 from the crank angle detecting sensor 108, and the fuel injection signal J and the ignition signal Q from the ECU 113. In fig. 20, the rising edge of the crank angle signa: ■ corresponds to a first reference position B 75 ^ (a crank angle position 7 5° prior to the compression top dead center) of the first to fourth cylinders. The dropping edge of the crank angle signal 8 shows a second reference position B5° Also, the ECU 113 starts the calculation of the f u--l amount using as a trigger the first reference position B 75° of the crank angle signal 0 and produces the fuel injection signal Jyhaving a pulse width Tj corresponding to a necessary fuel amount for driving the injector 107. In this case, since the single injection 107 is provided, the single injector 107 feed the necessary fuel needed for the four cylinders in one cycle of the engine 101. Also, with respect to the ignition signal Q, normally, the ignition power is fed by a timer control from the first reference position B75° and is interrupted close to the dropping edge (second reference position B5°) of the crank angle signal 8 for ignition of each cylinder. Fig, 2 L is a graph illustrating & relationship bt=Lwuun the drive time Tj [msec] and the fuel injection amount. Jo (mcc/pls] of the injector 107. Lj is the curve showing the linearity of the fuel injection amount Jo, Tx is the drive tipm .which is a border between an insufficient region and a sufficient region of the linearity curve Lj. The drive time Tj of the injector 107 may be aiven from the following formula (1) by the calculation within the ECU 113 in correspondence with the necessary fuel amount Jp [mcc] per one injection: Tj=KjxJp+Td (1) where Kj is the gain [msec/mcc] of the injector 107, and Td is the loss time [msec] of the injector 107. Incidentally, the loss time Td is the time period from the time when the fuel injection signal J is applied until the injector 107 actually injects the fuel. > As is apparent from formula (1), in the characteristics of the injector 107, the drive time Tj is substantially in proportion to the fuel injection amount Jo but the proportional relationship is not always applied in the entire region to thj necessary fuel amount Jp. For example, the linearity Lj showing the relationship between the drive time Tj and the fuel injection amount Jp of the injector 107 is expressed by the following formula (2): Lj where Jr is the actual fuel injection amount. Also, formula (2) is expressed by formula (1 ) as the following formula (3): Lj=Jr/{{Tj-Td)/Kj> (3} As shown in Fig, 21, the linearity Lj is in a go,j condition in a region (Tj>Tx) where the drive time Tj is long, but the linearity Lj is insufficient in a low flow rate region (Tj Also,.the shorter the dynamic range of the injector 107, the smaller the minimum fuel injection amount in the good linearity region will become. The longer the dynamic range of the injection 107, the larger the minimum fuel injection amount will become. By the way, in the MPI system (not shown) having injectors corresponding to the number of the cylinders, since the fuel amount needed for the single cylinder may be fed during one cycle, even if the injector that may keep the linearity in the region where the fuel feeding amount is small is used, it. is possible to feed a maximum fuel amount needed for the single cylinder during one cycle. However, in the SPI system for feeding the fuel by the single injection 107 as shown in Fig, 19, it is necessary to feed the fuel amount needed for the four cylinders by dividing the fuel amount in one cycle of the engine 101. Accordingly, in order to make it possible to feed the fuel in the operational condition where the fuel amount is at maximum, it is necessary to set the larger dynamic range of the injector 107. Thus, in the case where the injector 107 having the larger dynamic range is used, as shown in Fig. 21, the } Lj is worse in the region (Tj is a fear that the combustion would not be stable or the exhaust gas would be worse. Also, in the MPI system, a single injector is provided in the vicinity of the intake port of each cylinder, and eac."i injector injects the fuel aiming the intake port. Accordingly, all the fuel is filled into the respective cylinders so that it is possible to control the air/fuel ratio of each cylinder with high precision. In contrast thereto, in the SPI system, if the injector 107 is disposed in the vicinity of the intake port of the engine 101, the injected fuel is concentrated on a specific cylinder. It is impossible to uniformly distribute the fuel to each cylinder. Accordingly, in order to uniformly distribute the injected fuel to the respective cylinders, as shown in Fig. 1^, the injector 107 is disposed at a position away from the intake port of the engine 101 so as to fill the fuel together with the intake air into the respective cylinders. However, in general, the intake air amount and the intake air flow rate to the respective cylinders of the engine 101 are not kept constant. A deflected flow would be generated in !"■■ intake manifold 105. It is therefore difficult to uniformly distribute the fuel to the respective cylinders. Also, the flow of the air is not kept constant but" may be changed in accordance with the operational conditions. As a result, the fuel distribution condition among the respective cylinder is changed in accordance with the operational condition. For those reasons, since the displacement or non-uniformity occurs in the fuel distribution condition among the cylinders in the SPI system, it is impossible to control the air/fuel ratio for each cylinder with high precinion. ^ In particular, in the cylinder in which the actually fed fuel amount is considerably different from the target air/fuel ratio, the combustion is unstable, the,output of the engine 101 is reduced and the exhaust gas would be worse. Also, if the difference in air/fuel ratio among u.e respective cylinders is remarkable, the deviation of the combustion torque among the cylinders would be remarkable. The balance of the torque when the engine 101 rotates is unstable, resulting in adverse affect to the durability and the service life of the engine. Therefore, in the conventional SPI system, in order to make uniform the fuel distribution for the respective cylinders, as shown in Fig. 19, the injector 107 is disposed upstream of the throttle valve 103 remote from the intake port of the engine 101 so that the injected fuel is collided directly with the throttle valve 103 to thereby realize the atomization of the fuel and the diffusion of the fuel to the air. Also, in the SPI system as shown in Fig. 19, since the above-described deviation of the fuel distribution condition among the respective cylinders occurs, a method (to b However, since the injector 107 is disposed upstream of the throttle valve 103, the injected fuel is collided with the throttle valve 103 to be diffused. It is therefore; difficult, r.t; suck the fuel into the engine 101 exactly in accordance with the target timing. Accordingly, now, due to the structure of the system, it is difficult to actually reduce the deviation of the air/fuel ratios among the cylinders. Also, as described above, in the MPI system, since the injectors each of which may keep the maximum fuel amount needed for the single cylinder during the one cycle of the engine 101 are used, an injector drive time for one tin.j is shorter than the periodical time of one cycle. In contrast, in the SPI system, the injector 107 having tfte large dynamic range is used, and the injector 107 is driven at every reference position B75° of the crank angle signal 6 as shown in Fig. 20, the maximum value of the drive time Tj of the injector 107 for one time corresponds to one cycle of the crank angle signal 6. In the case where the one drive time Tj is less than one cycle of the crank angle signal 6, the value obtained by adding the loss time Td to the effective time period of the injector 107 becomes the drive time Tj in one cycle of the crank angle signal 0 and the fuel amount Jo is changed in correspondence with the drive time T j. However, if the drive time Tj is ecjuai to the one cycle of the crank angle signal 8, this causes the condition that the injector 107 is always driven. The drive time Tj within one eye" -"■ of the crank angle signal 9 does not include the loss time Td but just include the effective time period of the injector 107. Thus, in the case where the drive time Tj is hanged in the range less than one cycle to one cycle of the crank angle signal 6, the time obtained by subtracting the loss time Td from the drive time Tj is the effective time period of the injector 107 in the range less than the cycle of the crank angle signal 6. In the case where the drive time Tj is equal to the cycle ot the crank angle signal 0, the drive time Tj becomes equal to the injector effective time period without any loss time Td. Namely, at the moment when the drive time Tj of the injector 107 is equal to the cycle of the crank angle signal 0 from the period less than the cycle, all the period corresponding to the loss time Td immediately before that (in the range less than the cycle) becomes the injector effective time period. Accordingly, at this moment, the fuel injection amount of the injector 107 is rapidly increased to rapidly decrease the air/fuel ratio. Also, it is impossible to .ontrol the supply of the fuel amount between the fuel supply amount when the drive time Tj is equal to the cycle of the crank angle signal 6 and the fuel supply amount when the drive time Tj is less than the cycle of the crank angle signal 0. In the case where the fuel injection controlling apparatus for an internal combustion engine is the Spi system as described above, the fuel injection signal J composed of pulses corresponding to each cylinder is produced, it is therefore impossible to exactly feed the fuel amount in the low flow rate region where the drive time Tj of the injector 107 is short. The system suffers from a problem that the combustion is unstable and the exhaust gas is worse. Also, in order to uniformly distribute the fuel to each cylinder, the injector 107 is arranged upstream of the throttle valve 103. However, the intake air amount and the intake air velocity to each cylinder are not kept constant but may be Changed also in accordance with the operational condition so that the deflected flow is caused within the intake manifold 105. Accordingly, the system suffers from the problems that it is impossible to uniformly distribute the fuel to each cylinder, aud it is impossible to control the air/fuel ratio of each cylinder with high precision. In particular, when the deviation of the combustion torque among the cylinders is remarkable, the torque balance upon the engine rotation becomes unstable, resulting in adverse affect against the durability and the service life of the inner rial combustion engine. Also, since the injector 107 is arranged upstream of the throttle valve 103, the injected fuel is collided with the throttle valve 103 to be diffused. As a result, it is impossible to suck the fuel to the engine 101 exactly in accordance with the target timing. Also, since the dynamic range of the injector 107 is s« at a high level, and the injector 107 is driven at every rising timing {first reference position B75°) of the crank angle signal 6, the maximum, value of the drive time Tj for one time is equal to the time period of one cycle of the crank angle signal 0 to exclude the loss time Td (becomes the injector effective time period without any loss). When the drive time Tj is increased from the range less than one cycle, the fuel injection amount is rapidly increased. It is therefore impossible to control the fuel supply amount with high precision. SUMMARY OF THE INVENTION In view of the above-noted problems, an object of zhe present invention is to provide a fuel injoction controlling apparatus for an internal combustion engine, in which in a system using an injector or injectors whose number is smaller than the number of cylinders, a high precision fuel injection control i: response to the necessary fuel amount is possible, and deviation of air/fuel ratios among the cylinders is suppressed to realize stable operationability. According to the present invention, in a fuel injection controlling apparatus for an internal combustion engine, at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used, a plm^.ity of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount of fuel to each of the cylinders, and the number of the fuel injections is chanqed : one cycle in response to an operational condition of the internal combustion engine whereby the fuel amount needed in response to the operational condition for each of the cylinders is kept. Also, according to the present invention, in a fuel injection controlling apparatus for an internal combustion engine, in which at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used, a plurality of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount of fuel to each of the cylinders, and a fuel injection timing is changed for one cycle in response to an operational condition ot tliu internal combustion (jnyiiiL.- wheLuby the fuel amount needed in response to the operational condition for each of the cylinders is kept. Also, according to the present invention, in a fuel injection controlling apparatus for an internal combustion engine, at least one injecto. whose number is smaller than the number of cylinders of the internal combustion engine is used, a plurality of fuel injections are effected for one cycle of the internal combustion engine far feeding a predetermined amount of fuel to each of the cylinders, and the number of the fuel injections and an injection timing of the fuel are changed for one cycle in response to an operational condition of the internal combustion engine whereby the fuel amount needed in response to the operational condition for each of the cylinders is kept. Also, according to the present invention, in a fu^ injection controlling apparatus for an internal combustion engine, at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used, a plurality of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount of fuel to each of the cylinders, the number of the fuel injections is changed for one cycle in response to an operational condition of the internal combustion engine, and whether or not an injection timing of the fuel should be changed is switched in response to the number of the fuel injections for one cycle, whereby the fuel amount needed in response to the operational condition for each of the cylinders is kept. Also, according to the present invention, in the fuel injection controlling apparatus for an internal combustion engine, the injection timing of the fuel is changed for each injection. Also, according to the present invention, in the fuel injection controlling apparatus for an internal combustion engine, the injection timing of the fuel is set in correspondence with a time from the fuel injection until the fuel has reaches each cylinder. Also, according to the present invention, in the fuel injection controlling apparatus for an internal combustion engine, the injection timing of the fuel is changed in response to a temperature of cooling water of the internal combustion engine. Also, according to the present invention, in a fuel injection controlling apparatus for an internal combustion engine, at least one injector whose number is smaller than the number of cylinders of the internal combustion engii:-- is used, a plurality of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount ot fuel to each of the cylinders, a rate of an amount of the fuel injected for every fuel injection is changed for one cycle m response to an operational condition of the internal combustion engine whereby the fuel amount needed in response to the operational condition for each of the cylinders is kept. Also, according to the present invention, in a fuel injection controlling apparatus for an internal combustion engine, at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used, a plurality of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount of fuel to each of the cylinder-, and whether or not an injection timing of the fuel should be changed is switched in response to an operational condition of the internal combustion engine for one cycle, whereby the fuel amount needed in response to the operational condition for each of the cylinders is kept. Also, according to the present invention, in a fuel injection controlling apparatus for an interna i. combustion engine, at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used, a plurality of fuel injections are effected for one cycle of LJ.---internal combustion engine for feeding a predetermined amount of fuel to each of the cylinders, and a rate between a drive time and a stop time of the injector is changed for one cycle in response to an operational condition of the internal combustion engine whereby the fuel amount needed in response to the operational condition for each of the cylinders is kept. Also, according to the present invention, in the fuel injection controlling apparatus for on inLurnal CUIHIJUS.-.L ion engine, the engine operation condition is selected as at least one out of a drive time of the injector, a fuel injection amount during one cycle of the internal combustion engine, an amount of fuel of one injection of the injector, an idle operational condition of the internal combustion engine, a non-idle operational condition of the internal combustion engine, an engine RPM of the internal combustion engine, an intake pressure of the internal combustion engine, a step-in amount of the accelerator of the internal combustion engine, a throttle valve opening degree of the internal combustion engine, a temperature of cooling water of the internal combustion engine, a temperature of intake air of the internal combustion engine and an atmospheric pressure. Also, according to the present invention, in the fuel injection controlling apparatus for an internal combustion engine, the injector is disposed downstream of the throttle valve provided in the intake pipe of the internal combustion engine. fiiUEF PESCRIPTIQN OF THE PRfiWI^QS In the accompanying drawings: Fig. 1 is a block diagram schematically showing an overall system in accordance with a first embodiment of the invention; Fig. 2 ia a flowchart showing a judgement process operation of the number of the fuel injections for one cycle in accordance with the first embodiment of the invention; Fig. 3 is a waveform diagram showing an example oi a switching operation between a four-injection mode and a two-injection mode in accordance with the first embodiment of the invention; Fig. 4 is a waveform diagram showing an example of a switching operation between a four-injection mode and a two-injection mode in accordance with the first embodiment of the invention; Fig. 5 is a waveform diagram showing an example of a switching operation between a four-injection mode and a two-injection mode in accordance with the first embodiment of the invention; Fig. 6 is a waveform diagram showing an example of a switching operation between a four-injection mode and a two-injection mode in accordance with the first embodiment of the invention; Fig. 7 is a graph showing an example ot a relationship between the operation condition (load) and an air/fuel ratio oi each cylinder used in the first enbodiment of the invention; Fig. 8 is an illustration showing a change operation of a rate of the fuel amount at each injection timing in accordance with the first embodiment of the invention; Fig. 9 is a waveform diagram showing a fuel injection operation in the case where the fuel injection amount needed for one cycle is large in accordance with the first embodiment o£ the invention; Fig. 10 is a waveform diagram showing a fuel injection operation in the case where the fuel injection amount needed for one cycle is large in accordance with the first embodiment of the invention; Fig. 11 is a waveform diagram showing a fuel injection operation in the case where the fuel injection amount needed for one cycle is large in accordance with the first embodiment of thn invention; Fig. 12 is an illustration of a relationship between the fuel injection timing and the air/fuel ratio in the two-injection mode and in an idle operation in accordance with a second embodiment of the invention; Fig. 13 is an illustration of a relationship between the-fuel injection timing and the air/fuel ratio in the LWO- S n iect m:: mode and in a 2,000 rpm operation in accordance with the second embodiment of the invention; Fig. 14 is an illustration of a relationship between ". fuel injection timing and the air/fuel ratio in the two-idjection mode and in a 4,000 rpm operation in accordance with the second embodiment of the invention; Fig. 15 is a waveform diagram showing the opereition in the two-injection mode in the case where the fuel injection timing is changed in a constant manner in accordance with the second embodiment of the invention; Fig. 16 is a waveform diagram showing the operation in the two-injection mode in the case where the fuel injection timing is changed for each injection in accordance with the second embodiment of the invention; * Fig. 17 is an illustration of a relationship between the fuel injection timing and the air/fuel ratio in the two-injection mode in the case where the fuel injection timing is set for each injection in accordance with a second embodiment of the invention; Fig. 18 is an illustration of a relationship between the fuel injection timing and the air/fuel ratio in the four-injection mode in the case where the fuel injection timing is changed for each injection in accordance with the second embodiment of the invention; Fig. 19 is a block diagram schematically showing an overall system of a general internal combustion engine; Fig. 2 0 is a waveform diagram showing the injecti ^n timing in the case where four fuel injections are effected for one cycle in a general internal combustion engine; and Fig. 21 is a graph showing a linearity am. the fuel injection amount relative to the injector drive time of a general internal combustion engine. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 An embodiment of the invention will now be described with reference to the accompanying drawings. Fig. 1 is a block diagram schematically showing the overall SPI system in accordance with a first embodiment. The arrangement of each element shown in Fig. 1 is the same as that shown in Fig. 19 except that the injector 10 7 as arranged downstream of the throttle valve 103. The d.plication of the explanation therefor will be omitted. In this case, ECU 113A renews the fuel injection signal J in correspondence with the operational coridition as described later. Fig. 2 is a flowchart illustrating the fuel injection operation by the ECU 113A in accordance with the first embodiment of the invention. In Fig. 2, there is shown the fuel injection operation in the case where the fuel injection amount is in a low fUbw rate mode. In Fig. 2, the ECU 113A first calculates the fuel injection amount jp needed for one cycle from the current operational condition {step SI). Subsequently, the ECU 113A determines whether or not the fuel amount in the case where the amount of the fuel needed for i_ i „ ^^pf0H seDarately for four ^hots is in the rarge (±5%) where the linearity may be kept (step S2). If the fuel amount is in the range where the linearity may be kept (i.e., YES), the four-injection mode is taken (step S3). The ECU calculates the drive time Tj4 for one time in case of the four injections during one cycle in accordance with formula (4) similar to the above-described formula (1) (step 24). Tj4=KjxJp/4+Td (4) On the other hand, if the fuel amount is in the range where the linearity could not be kept (i.e., NC), the two-injection mode is taken (step S5). The ECU calculates the drive time Tj2 for one time in case of the two injections during one cycle,- in accordance with formula (5) in the same way (step S6). Tj2=KjxJp/2+Td (5) The fuel injection operation when the mode conditions are switched between the four-injection mode (steps S3 and S4) and the two-injection mode (steps S5 and S6) in the first embodiment of the invention will now be described specifically with reference to Figs. 3 to 6. In this case, it is assumed that, in the four-injection mode, the necessary fuel amount injected to one cylinder WILJI reference to the rising timing B75~ of the crank angle signal 0 of all the cylinders, and in the two-inject ion mode, the necessary fuel amount injected to two cylinders with reference to the rising timing B75° of the crank angle signal 6 of, for example, first and fourth cylinders. Figs. 3 and 4 show the respective waveforms of the crank angle signal 9 and the fuel injection signal J when the modes are switched from the four-injection mode to the two-injection mode at different timings from each other. Figs. 5 and 6 show the respective waveforms of the crank angle signal 9 and the fuel injection signal J when the modes arc switched from the two-injection mode to the four-injection mode at different timings from each other. > In each figure, rl to x8 represent periods of the rising edge (first reference position B75°) of the respective pulses of the crank angle signal 6. In Fig. 3, the injection mode conditions are switched from the four-injection mode to the two-injection mode in the midway of the period T4 and ;.re the four-injection mode in the periods T1 to T4. Accordingly, the ECU 113A drives the injector 107 at every rise (first reference position B75°) of the crank angle signal 6 to inject the fuel. Also, since the two-injection mode condition is established in the midway of the period i4, the fuel is injected at a rate of one per every two of the crank angle signals 6 from the period T5. In this case, since the fuel is injected with reference to the rises (first reference position B75°) of the crank angle signals 6 of the first and fourth cylinders in the peri ds i5 and 17. In Fig. 4, the injection mode conditions are switched from the four-injection mode to the two-injection mode in the midway of the period T3 and are the four-injection mode in the periods il to T3. Accordingly, the ECU 113A drives the injector 107 at every rise (first reference position B75") of the crank angle ■ignol 0 to inject the fuel in the periods il to i3. -^ Also, the period T4 is the period when the fuel injection is not performed, after the switch to the two-injection mode. However, if the fuel is not injected, ±he fuel amount in the period T4 is insufficient. Accordingly, the fuel that is the same as the four-injection mode is injected in the period T4. Subsequently, since the period T5 is the period when the fuel is injected in the two-injection mode, the fuel is injected at an amount in-the two-injection mode from the period(=T5. In Fig. 5, the injection mode conditions are switched from the two-injection mode to the four-injection mode in the midway of the period r4 and are the two-injection mode in the periods \X to T4 . In this case, since the periods up to T4 is the two- injection mode, the fuel is injected on the basis of the rises cylinders. After the period t5, since the mode is the four- injection mode, the fuel is injected at every rise (B75°) of each crank angle signal 6. a In Fig. 6, the injection mode conditions are switched from the two-injection mode to the four-injection mode in the midway of the period x3 and are the two-injection mode in the periods T1 to t3. In this case, since the fuel injection in the two-injection mode has been attained in the period T3, the fuel is not injected in the period i4 and the fuel injection is u£iectud in the four-injection mode from the period T5. The rate of the fuel injection amount at each injection timing during one cycle in accordance with the first embodiment of the invention will now be" described with reference to the characteristic diagram of Fig. 7 and the illustration of Fig. 8. Fig. 7 is a characteristic graph showing a change of air/fuel ratio A/F relative to the load change and shows a deviation of the air/fuel ratio A/F at each cylinder (#1 to $4) in the case where the RPM of the engine 101 is kept constant and the load {corresponding to the intake manifold pressure 9b) is changed. In Fig. 7, the deviation of the air/fuel ratio airong the first to fourth cylinders is increased as the load of the engine 101 is increased (that is, throttle valve opening degree a is increased to increase the intake manifold pressure Pb). This means that, since the fuel is injected U"ora a position relatively remote from each cylinder in the SPI system UBing the single injector 107, the distribution condition of the fuel ,-to each cylinder is changed in accordance with the operational condition (load). The deviation of the air/fuel ratio of each cylinder is not limited to that shown in Fig. 7 but may change entirely in accordance with the specification of the individual internal combustion engine. In the case of the air/fuel ratio characteristics shown in Fig. 7, in order to make uniform the air/fuel ratio A/F among the first to fourth cylinders, the air/fuel ratio fc/F of the first and second cylinders that are in a lean condition must be caused to be rich, and the third and fourth cylinders that are in a rich condition must be caused to be lean. In this case, in order to suppress the deviation of the air/fuel ratio A/F of the first to fourth cylinders, the fuel control is performed as follows. performed under the operational conditions of the intake manifold . . pressure Pb-0 [nmHg]. Fig. 8 is an illustration of the fuel distribution condition in each fuel injection, in which the waveforms of the crank angle signal 9 and the fuel injection signal J are caused to correspond to the strokes of the first to fourth cylinders. In Fig. 8, in the case where the drive time Tjl of the fuel injection signal J is determined on the basis of the rise (B75°) of the crank angle signal 0 of the first cylindcr, thn timing of the drive time Tjl corresponds to half the latter intake stroke of the third cylinder, the distribution o£ the air/fuel ratio A/F of the control cylinder (i.e., fourth cylinder) next to the third cylinder is effected. In this case, in the case where the fuel amount distribution is not compensated for, since the air/fuel ratio A/F of the fourth cylinder is in the rich condition, in order to reduce the rate- of the amount of fuel inject -id at the timing of the drive time Tjl, it is necessary to compensate for the drive time Tjl in accordance with the following formula (6): Tjl"=kl-Tjl+Td (6) where Tj 1" is the drive time after compensation, and k 1 is a compensation coefficient to the drive time Tjl. In this case, in order to reduce and compensate for the fuel amount, the compensation coefficient kl is set in the range of 0 The injector 107 is driven by the drive time Tjl* compensated in accordance with the formula (6) so that the air/fuel ratio A/F of the fourth cylinder is compensated for to be lean. The deviation of the air/fuel ratio A/F among the cylinders is moderated. In the same way, in the case where the drive time Tj4 of the fuel injection signal J is determined on the basis of the rise (B75°) of the crank angle signal d of the fourth cylinder, the timing of the drive time Tj4 corresponds to half thy lattei intake stroke of the second cylinder, the distribution of the air/fuel ratio A/F of the control cylinder (i.e., first cylinder) next to the second cylinder is affected. In this case, in the case where the fuel amount distribution is not compensated for, since the air/fuel ratio A/F of the first- cylinder is in the lean condition, in order to increase the rate of the amount of fuel injected at the timinq of the drive time Tj4, it is necessary to compensate for the drive time Tj4 in accordance with the following formula (7): Tj4"=k4xTj4+Td (7) where Tj4" is the drive time after compensation, and k.4 is a compensation coefficient to the drive time Tj4. In this case, in order to increase and compensate for the fuel amount, the compensation coefficient k4 is set to be greater than 1. The injector 107 is driven by the drive time Tj4" compensated in accordance with the formula (7) so that the air/fuel ratio A/F of the first cylinder is compensated for to be rich. The deviation of the air/fuel ratio A/F among the cylinders is moderated. In this case, the case where the rate of the luul injection amount is changed in the region of the intake manifold pressure Pb is zero [mmHg] in Fig. 7 has been explained but needless to say, the like control may be effected in all the operational region. Also, Fig. 8 shows the case where the rate of the fuel injection amount is changed in the four-injection mode, but it is possible to perform the like control in the two-injection mode. Also, the control is possible for either the four- injection mode or the two-injection mode and may be performed only in one of these modes. The fuel injection operation in the case where the fuel supply amount is large in one cycle in accordance with the first embodiment of the present invention will now be described with reference to the waveform diagrams of Figs. ? to 11. Figs. 9 to 11 show the fuel injection signals J in the case where the fuel amounts needed for one cycle are different from each other. As the necessary fuel amounts are increased, the control operation of each fuel injection signal J are changed in order as shown in Fig. 9 to Fig. 11. In Fig. 9, the fuel injection (the rise control of the fuel "injection signal J) is carried out at every one cycle (rising timing B75°) of he crank angle signal 6. A rate at which the injector is driven during one cycle of the crank angle signal 8 in accordance with the luel injection signal J is high, and the injector 107 is driven over almost all the cycle of the crank angle signal 6. At this time, the rate Da (drive duty ratio of Da=Tja/Ta =Tja/(Tja+t) (8) where t is the necessary minimum drive stop time needed for stopping the drive of the injector 107. In the operational condition that requires tlie fuel amount as shown in Fig. 9, the rate of the drive time Tja of the injector 107 during one cycle of the crank anqle signal 8 is high and is set at a maximum possible value relative to the one cycle or he crank angle signal 9. If the rate of the drive time of the injector in one cycle of the crank angle signal 0 is increased more than this, the drive time would be overlapped with the next drive time, the fuel injection signal J is left at an H level and continuous. It is therefore impossible to increase the drive duty of the injector 107 as desired. Accordingly, in the case where the fuel amount-needed for one cycle is further increased, the drive cycle (one cycle of the fuel injection signal J) Tb and the drive time rjb of the injector 107 are extended as shown in Fig. 10, and it is possible to increase the drive duty of the injector 107 as desired. At this time, the rate Db (drive duty of the injector 107) of the drive time Tjb relative to the drive cycle Tb of ;!-■•■ injector is g-iven by the following formula (9) similar to the formula (8): Db~Tjb/Tb Tjb/(Tjb+t) (9) where the drive time Tjb meets the relationship, Tjb>"rja, in comparison with the drive time Tja of formula (8). Thus, the drive duty Db of the injector 107 is set at a high level so that the amount of the fuel fed during one cycle may be increased. Accordingly, in the case where the amount of fuel needed for one cycle of the engine is small and the drive linearity of the injector 107 is insufficient, the injector 107 is driven twice in one cycle to thereby keep the sufficient linearity. Also, in the case where the fuel amount needed for one cycle "is further increased, the drive cycle Tc and the drive time Tjc of the injector 107 are extended as shown in Fig. 11, and i-is possible to increase the drive duty Dc of the injector 107. At this time, the drive duty Dc of the injector 107 is given by the following formula (10): DC=TJc/Tc -Tjc/(Tjc+t) (10) where the drive time Tjc meets the relationship, Tjc>Tjb, ±n comparison with the drive time Tjb of formula (9). Thus, -the drive cycle and the drive time of the injector is extended in order so that it is possible to increase continuously the drive duty as desired while keeping the drive stop time t. In the case where the fuel injection amount needed for one cycle is further increased exceeding that of the case of Fig. 11, finally, the fuel injection signal J is fixed at an H level and the drive duty of the injector 107 is set at 100% so that the injector 107 is always driven to keep the maximum fuel. Embodiment 2 Incidentally, in the first embodiment, the cycle and the number of the shots of the fuel injection are switched in order to optimize the fuel injection amount. For the purpose ol optimizing the control of the fuel injection amount, it is possible to reduce the deviation AA/F of the air/fuel ratio A/F of each cylinder, for example, by shifting the start timing of the fuel injection. A second embodiment of the present invention in which the fuel injection timing is shifted to optimize the fuel injection control will now be described with reference to the accompanying drawings. Figs. 12 to 14 are illustrations of a relationship between the injector, injection timing [3 and the A/F of each cylinder in the case where the fuel is injected twice for every cycle. Fig. 12 shows the case of the idle operation (engine RPM Ne=600 [rpm]), Fig. 13 shows the case of the operation (engine RPM Ne=2,000 [rpm]), and Fig. 14 shows the case of the operation (engine RPM Ne=4,000 [rpm]). In Figs. 12 to 14, the abscissa represents the injection. timing of the injector 107, whereas the ordinate represents the air/fuel ratio A/F and the deviation &A/F of the air/fuel ratio. Namely, the air/fuel ratio A/F of each cylinder (#1 to #4) is shown by a bent line graph corresponding to the ordinate axis on the left side, the deviation AA/F obtained by subtracting the minimum value from the maximum value of the air/fuel ratio A/F at each injection timing 3 is represented by a bar graph relative to the ordinate axis on the right side. Also, Fig. 15 is a waveform diagram showing a shitt amount of the injection timing (3 and shows the case where the injection is performed by a delay of (3° with reference to the rise (B75°) of the crank angle signal 6,. In general, in the case where the fuel is injected four times in one cycle {four-injection mode), any one of the cylinders takes an intake stroke at any injection timing. Accordingly, there is.almost no affect to the air/fuel ratio A/F of each cylinder due to the difference in the fuel, injection timing. However, in the case where the fuel is injected twice in one cycle of the engine (two-injection mode}, the rates of the fuel to be sucked into the respective cylinders art caused to be different from each other according to the respective injection timings (5. Accordingly, as is apparent from Figs. 12 to 14, the air/fuel ratio A/F is changed in accordance with the differ e:. of the injection timing [3. Accordingly, in case of the two-injection mode, if the fuel is injected at random as desired, the deviation u\/)? of the air/fuel ratio between the respective cylinders is remarkable to make worse the operationability. Accordingly, it is preferable to set the injection timing B suitably so that the deviation AA/F of the air/fuel ratio is at minimum. For example, in Fig. 12, in order to keep beat Lliu unynu.-operatifnability in the idle uundiLiun, IL .i.a BUII IUIL-ML U.J select the injection timing (i so that the air/fuel ratio A/F ot each cylinder is made uniform. in this case, comparing the deviations AA/F of the air/fuel ratios according to the injection timings with each other, it is understood that the deviation AA/F of the air/fuel ratio is at minimum at the injection timing 3=270°, and the operationability is best. Accordingly, under the operational conditions in the idle operation, the fue± is injected at the injection timing 13=270°. On the other hand, in case of Ne=2,Q00 Irpm] which is different in operational condition from the case of Fig. 12, as shown in Fig. 13, the behavior of the change in air/fuel ratio A/F relative to the injection timing 3 is changed. However, in this case, since the deviation AA/F of the air/fuel ratio is at minimum at the injection timing (3=270°, the fuel is injected ■:■: the injection timing 3=270°. In case of Ne=4,0Q0 [ rpm] as shown in Fig. 1 A , r.inco ulio deviation AA/F of the, air/fuel ratio is at minin ,,u at the injection timing (3=240°, the fuel is injected at the injection timing 3=240°. In this case, the optimum fuel injection timing & is shown under the three different operational conditions as in Figs. 12 to 14. However, in other operational conditions, in the same manner, the fuel is injected at the injection timing {"> so that the deviation AA/F is at minimum whereby it is possible to make optimum the engine combustion condition and the exhaust gas. Incidentally,, it is difficult to set the optimum fuel injection timing J3 relative to all the operational conditions on the program within the actual ECU 113A. Accordingly, it is possible to set the optimum fuel injection timing, for example, by linearly compensating for the optimum fuel injection timing (5 between 2,000 and 3,000 [rpm] for the operational region between Ne 2,000 and Ne 3,000 [rpm] of the engine. Also, in this case, the injection timing (3 is simply selected so that the deviation AA/F of the air/fuel ratio is at minimum. The time from the fuel injection until the fuel reaches the cylinders is substantially determined by the engine specification, and it is possible to expect in advance how the change of the in jaction timing fi affects the ,i i vIJ ui.-1 i,:t. i o h. i of the cylinders. Accordingly, the fuel injection timing may be changed a predetermined time period prior to the reach oi" the fuel in view of the fuel reach time relative to the cylinder to be compensated for in the air/fuel ratio A/F. Also, for example, it is possible to switch the fuel injection timing [J in accordance with a cooling water temperature representative of the warming-up condition of the engine. The operation in the case where the injection timings fi are switched in response to the temperature of the cooling water will now be described in detail. In general, the fuel composition sucked iuLu Luiub > cylinder may "be classified into two kinds of a liquid flow component to be fed to the cylinder while flowing along a bottom surface of the intake manifold 105 and a gas flow component to be sucked into the cylinder together with the air while draftinq in the air. Among these fuel components, the distribution rate of the fuel of the liquid flow component to be fed into each cylinaer is determined by the direction of flow of the fuel. Accordingly, even if the injection timing 3 is changed, the rate of the fuel flowing through each cylinder is not so changed. The change of the injection timing \|3 would not so much affect the air/fuel ratio. However, with respect to the gas flow component when the injection timing P is changed, the cylinders into which the fi> is fed are changed. Accordingly, this would affect the air/fuel ratio of each cylinder. Namely, as the causes for changing the air/fuel ratio A/F by the change of the fuel injection timing p, the affect of the gas flow component fuel is large. Accordingly, in accordance with the rate of the gas flow component in the injected fuel, it is determined how the air/fuel ratio A/F may be compensated for. Accordingly, in the warming-up condition in which the temperature of the cooling water of the engine is high, since the rate of the component atomized within the intake manifold 105 and caused to flow in the form of a gas flow is high, the change of the fuel injection timing (3 largely affects the change of the air/fuel ratio A/F. On the other hand, in the casewhere the temperature of the cooling water of the engine is low, the rate of the component atomized within the intake manifold 105 is low- The air/fuel ratio A/F that may be changed by the fuel injection timing p is lower than that in the above-described warming-up condition. Thus, the change of the air/fuel ratio A/F by the change of the fuel injection timing p is varied in accordance with the temperature of the cooling water of the engine. Accordingly, in order to change the air/fuel ratio A/F of a predetermined cylinder by a predetermined value, it is desirable to chanye the injection timing 3 in response to the temperature of the cooling water. Thus, it is possible to set the highly reliable injection timing [J. Also, the case where the injection timing \i of the injector 107 in the two-injection mode is changed in a constant manner as shown in Fig. 15 in the second embodiment has been described. It is possible to change the injection timing & at every injection control. Fig. 16 is a waveform diagram in the case where the injection timings {shift amounts) are different from each other, and shows the case, the injection timings are set at P [ °) (=270°) and 0+5 [ °] for each injection control on the basis of the rise (B75°) of the crank angle signal e corresponding to the first and fourth cylinders, and the injection is effected with a time lag by 5 [°] (for example, about 10°) for the fourth cylinder. Namely, the fuel is injected with a time lag of 3 [" j (=270°) in terms of the crank angle on the basis of the first reference position B75° for the fourth and second cylinders, and the fuel is injected with a time lag of p+a [°J (=280°) in terms of the crank angle on the basis of the firsc reference position B75° for the first and third cylinders. The specific fuel injection operation will now be described with reference to Fig. 16 as well as the above-described Fig. 13. As described above, in the case where the fuel injection timing 3 is changed in a constant manner in Fig, 13 (Ne=2,QOQ [rpm]), the deviation AA/F of the air fuel ratio at the inject.i In this case, noticing the air/fuel ratio A/F of each cylinder at the injection timing p=270°, it is unde; . tood that the air fuel ratios A/F of the second and fourth cylinders are substantially, equal to each other and are close to the stoichiometric air/fuel ratio (=14.7}. I However, as is apparent from Fig. 13, it is understood that the deviation £A/F of the air/fuel ratios of the first and third cylinders is smaller at the injection timing 0o=28O" Accordingly, the injection timing (3 [ °] and injection tftning fi+6 [°] are set for the fourth and second cylinders and for the first and third cylinders at the injection timing "3=270" and compensation amount 5=10° as shown in Fig. 16. Fig. 17 is an illustration of the relationship between the fuel injection timing 0 and the air/fuel ratio A/F in the case where the fuel injection timing S is compensated for as shown in Fig. 16. - As shown in Fig. 16, the compensation amount 6 {=10°) is set so that the deviation AA/F of the air /fuel ratio at the injection timing & (=270°) is considerably suppressed as shown in Fig. 17. Accordingly, the two-injection mode operation may be more improved than the case, shown in Fig. 13. Also, the case where the injection timing [3 in the two-injection mode is varied and set in the second embodiment has been described. It is possible to change and set the injection timing in the four-injectj.on mode. Fig. 18 is a waveform diagram showing tli: change operation of the injection timing in the four-injection mode, in Fig. 18, [31 to £4 are injection timings for the first to fourth cylinders with reference to the first reference position B75". In this case, in the injection control on the basis of the crank angle signal 9 of the first cylinder, the fuel is injected with a time lag of [31 [°] with reference to the first reference position B75°. In the same manner, the fuel is injected with a time lag of [J3 [°] with reference to the first reference position B75° of the third cylinder/ the fuel is injected with a time lag of 34 [°] with reference to the first reference position B75° of the fourth cylinder, and the fuel is injected with a time lag ot: 1^2 [°] with reference to the first reference position B75" of ti.u second cylinder. Thus, in the same manner as the change of the fuel injection timing \|3 in the two-injection mode as described above (see Fig. 16), it is possible to make uniform the air/fuel ratio A/F of each cylinder (#1 to #4) to thereby enhance the operationability. Also, in the second embodiment, the control is effected only one of the two-injection mode and the four-injection mode but the control may be effected both in the two-injection mode and the four-injection mode. Embodiment 3 In the first embodiment, the drive time Tj of the injector 107 is the switching condition between uie four-injection mode and the two-injection mode. It is possible to take various conditions, for example, the following (1) to (3) therefor. (1) The injection modes are switched in accordance with whether or not the idle operation is effected. Namely, in the idle operation, the two-injection mode is effected, and in the non-idle operation, the four-injection mode is effected. (2) The injection modes are switched in accordance with the operational condition of the engine. " Namely, if engine RPM N.e (3) The injection modes are switched in accordance with various kinds of sensor information representative of the engine operational conditions. The engine operation conditions may be selected as at least one out of, for example, a fuel injection amount during one cycle of an internal combustion engine, an amount of fuel of one injection of the injector, an idle operational condition, a non- idle operational condition, an engine RPM Re, an intake pressure, an intake air amount, a step-in amount of the accelerator, a throttle valve opening degree a, a temperature of cooling water, a temperature of intake air and atmospheric pressure. However, in the case where the above-described items (1) to (3) are the switching condition between two-injection mode and the four-injection mode, for example, the priority is given to the operationability not to the drive linearity of the injector 107, and the region where the four-injection mode is effected may be obtained although the two-injection mode is effected. For oxnmplo, in the case wlmru Uiu lull t him L it-acceleration {abrupt acceleration) is effected in the two-injection mode, the four-injection mode may be selected although the condition is directed to the two-injection mode. The region in which the four-injection mode is effected for better operationability may be selected rather than the two-injection mode for better linearity. Also, in the respective forgoing embodiments, the SPI system in which the single injector 107 s used for the four cylinders has been described. The same controller may^be applied to the case where the two or three injectors are used for the four cylinders to ensure the same effect. Also, the same controller may be applied to the case where the injectors whose number is smaller than the number of the cylinder are used for the multi-cylinder engine other than the four-cylinder engine. For example, in a three-cylinder engine, three injections for one cycle may be changed two Injections for one cycle. Also, in the second embodiment, the rate of the fuel amount is changed in response to the operational condition. It is possible to select whether or not the rate of the fuel amount. should be changed. In the same way, in the second embodiment, the injection timing & is changed in response to the operational condition. It is possible to select whether or not the injection timing At) tiotta t: ihati a hove, fcho Jlijoi."iui 107 in "I" ivon in t IKJ region where the linearity is good, and the number of the fuel injection in one cycle, the drive cycle, the drive time or the switching of the injection- timings are., well judged in response to the operational condition to thereby control the fuel supply to each cylinder uniformly and exactly irrespective to thy operational condition. Also, since each cylinder is driven at a uniform air/fuel ratio, the combustion torque among the cylinders is made uniform, and the operationability is stable to thereby enhance the durability of the engine. > Also, since the air/fuel ratio of all the cylinders may be controlled to a target air/fuel ratio, it is possible to keep the condition of the exhaust gas in a good condition. Also, even in the engine apparatus using an intake system in which the fuel distribution is deflected to the cylinders with a bad balance, it is possible to make uniform the distribution of the fuel to each cylinder irrespective of the operational condition of the engine. For instance, in the operational region where the fuel injection amount is small, the number of the fuel injection in a cycle is decreased and the fuel injection amount per one fuel injection is increased so that the injector is driven in the region where the linearity of the injector 107 is good, to thereby make it possible to control the fuel injection with hi:--. precision. Also, the rate of the amount of the fuel injected is changed in accordance with the operational condition of the engine, and it is possible to compensate for and control the fuel injection amount to be filled to be small for the cylinders which would be rich in fuel, and to compensate for and control the fuel injection amount to be filled to be large for the cylinders which would be lean in fuel. In the operation region where the fuel injection amount needed for one cycle is large, without increasing the drive time Tj of the injector 107 during a unit time period, the drive cycle of the injector 107 is changed, the rate of the drive time Tj oi the injector 107 is changed to thereby gradually change the supply fuel amount for one cycle to make it possible to control the amount of fuel to be fed for one cycle with high precision. Also, since the injector 107 is located downstream of the throttle valve 103, the time required for feeding the injected fuel to each cylinder may be shortened, the adhesion to the throttle valve 103 is avoided, the change of the fuel amount and the fu,el injection timing is rapidly reflected to the supply fuel to the engine, and it is possible to control the s; ^ply of the fuel to each cylinder further uniformly with high precision. Various details of the invention may be changed without departing from its spirit nor its scope. Furthermore, the foregoing description of the embodiments according to the presto.■,. invention is provided for the purpose of illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. FIG. 2 51 CALCULATE FUEL INJECTION AMOUNT JP NEEDED FOR ONE CYCLE 52 IS LINEARITY WITHIN ±5% IN THE CASE WHERE FOUR INJECTIONS ARE EFFECTED FOR ONE CYCLE? 53 FOUR-INJECTION MODE 54 CALCULATE INJECTOR DRIVE TIME Tj4 55 TWO-INJECTION MODE 56 CALCULATE INJECTOR DRIVE TIME Tj2 F*G. 3 1 FOUR-INJECTION MODE 2 TWO-INJECTION MODE 3 . CRANK ANGLE SIGNAL 9 4 FUEL INJECTION SIGNAL J FIG. 4 5 FOUR-INJECTION MODE 6 TWO-INJECTION MODE 7 CRANK ANGLE SIGNAL 6 8 FUEL INJECTION SIGNAL J FIG. 5 9 TWO-INJECTION MODE 10 FOUR-INJECTION MODE 11 CRANK ANGLE SIGNAL B 12 FUEL INJECTION SIGNAL J FIG. 6 13 TWO-INJECTION MODE 14 FOUR-INJECTION MODE 15 CRANK ANGLE SIGNAL 6 16 FUEL INJECTION SIGNAL J PIG. 7 1 AIR/FUEL RATIO 2 RICH 3 INTAKE MANIFOLD PRESSURE Pb (nimHg) FIG. 8 1 CRANK ANGLE SIGNAL 0 2 FUEL INJECTION SIGNAL J 3 FIRST CYLINDER 4 THIRD CYLINDER 5 FOURTH CYLINDER 6 SECOND- CYLINDER 7 COMPRESSION 8 INTAKE 9 EXHAUST 10 COMBUSTION 11 COMBUSTION 12 COMPRESSION 13 INTAKE 14 EXHAUST 15 EXHAUST 16 COMBUSTION 17 COMPRESSION 18 INTAKE 19 INTAKE 20 EXHAUST 21 COMBUSTION 22 COMPRESSION 23 COMPRESSION 24 INTAKE 25 EXHAUST 2# COMBUSTION FIG. 9 1 CRANK^ANGLE SIGNAL 9 2 FUEL INJECTION SIGNAL J FIG. 10 1 CRANK ANGLE SIGNAL 9 2 FUEL INJECTION SIGNAL J FIG. 11 1 CRANK ANGLE SIGNAL 6 2 FUEL INJECTION SIGNAL J FIG. 12 1 IDLE 2 INJECTION TIMING B° > FIG. 13 2 INJECTION TIMING (3° FIG. 14 2 INJECTION TIMING (5°. FIG. 15 1 CRANK ANGLE SIGNAL 6 2 FUEL INJECTION SIGNAL J FIG. 16 1 CRANK ANGLE SIGNAL 8 2 FUEL INJECTION SIGNAL J FIG. 17 2 INJECTION TIMING 0° FIG. 18 1 CRANK ANGLE SIGNAL 9 2 FUEL INJECTION SIGNAL J FIG. 20 1 CRANK ANGLE SIGNAL 6 2 FUEL INJECTION SIGNAL J 3 IGNITION SIGNAL Q FIG. 21 1 FUEL INJECTION AMOUNT 2 LINEARITY INSUFFICIENT REGION 3 LINEARITY SUFFICIENT REGION 4 DRIVE TIME T ms WE CLAIM: 1. A fuel injection controlling method for an internal combustion engine, in which at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used and a plurality of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount of fuel to each of the cylinders, characterized in that: a rate of an amount of the fuel injected for every fuel injection is changed for one cycle in response to a temperature of cooling water and other operational condition of the internal combustion engine. 2. The fuel injection controlling method according to claim 1, wherein a rate between a drive time and a stop time of the injector is changed for one cycle in response to an operational condition of the internal combustion engine whereby the fuel amount needed in response to the operational condition for each of the cylinders is kept. 3. The fuel injection controlling method according to claim 1 or 2, wherein the engine operation condition is selected as at least one out of a drive time of the injector, a fuel injection amount during one cycle of the internal combustion engine, an amount of fuel of one injection of the injector, an idle operational condition of the internal combustion engine, a non-idle operational condition of the internal combustion engine, an engine RPM of the internal combustion engine, an intake pressure of the internal combustion engine, a step-in amount of the accelerator of the internal combustion engine, a throttle valve opening degree of the internal combustion engine, a temperature of intake air of the internal combustion engine and an atmospheric pressure. 4. A fuel injection controlling method for an internal combustion engine substantially as herein described with reference to the accompanying drawings.

Full Text

The present invention relates to a fuel injection controlling apparatus for, for example, an automotive internal combustion engine, and more particularly to a fuel injection controlling apparatus for an internal combustion engine, which may control a fuel amount with high precision.
In general, in a fuel injection controlling apparatus for an internal combustion engine, a fuel amount needed for the engine is calculated in accordance with operational information such as an intake air amount and an engine RPM, thereby driving an injector to feed necessary fuel to the engine, and igniting the fuel at a suitable ignition timing to drive the engine.
According to a type of a fuel injection system, the fuel injection controllers are roughly categorized into an MPI (multi¬point injection) system having injectors corresponding to the number of cylinders of the engine, a system which has a smaller number of the injectors than the number of the cylinders, and an SPI (single point injection) system for feeding the fuel by a single injector irrespective of the number of the cylinders.
In general, in the MPI system, each injectoi is mounted

in the vicinity of an intake port of the associated intake port in the intake manifold passage within the intake pipe and supply the fuel between half the latter exhaust stroke and the intake stroke of the associated cylinder for feeding necessary fuel to the associated cylinder.
On the other hand, in the system having the smaller number of injectors than that of the cylinders or in the SPI system for supplying the fuel by a single injector, it is necessary to feed the fuel to a plurality of cylinders by a single injector.
Fig. 19 is a block diagram schematically showing an overall system of the conventional fuel injection controlling apparatus for an internal combustion engine, and shows, for example, the SPI system for supplying the fuel by ci single injector.
In Fig. 19, numeral 101 denotes a body of an internal combustion engine, i.e., an engine having four cylinders.
~ Numeral 102 denotes an air cleaner provided in an intake port of an intake pipe for purifying intake air, numeral 103 denotes a throttle valve which is driven to open and close within the intake pipe for adjusting an intake air amount to the engine 101, and numeral 104 denotes a throttle opening degree sensor for detecting a throttle openin■• degree a of the throttle valve

103.
Numeral 105 is an intake manifold provided in a joint portion between the intake pipe and the engine 101, numeral 106 denotes an intake air pressure sensor for detecting an intake manifold pressure Pb within the intake manifold 105, and numeral 107 denotes an injector provided upstream of the throttle valve 103 for injecting the fuel.
Numeral 108 denotes a crank angle detecting sensor for outputting a crank angle signal 6 in correspondence with a rotation of a crankshaft of the engine 101, numeral 109 denotes an exhaust manifold provided in a joint portion between the engine 101 and an exhaust pipe, numeral 110 denotes an oxygen concentration detecting sensor provided in the exhaust pipe for detecting an oxygen concentration Gd of the exhaust gas, and numeral 111 denotes a catalyst provided at an exhaust outlet of the exhaust pipe for purifying the exhaust gas.
Incidentally, needless to say, there are provided many kinds of sensors such as a sensor for detecting a temperature of cooling water of the engine although not shown.
Numeral 112 denotes an ignition coil built-in type distributor for applying a high voltage for ignition to spark plugs for the respective cylinders of the engine 101. Numeral 113 denotes an electronic control unit (ECU) for outputting drive

signals, i.e., a fuel injection signal J and an ignition signal Q to the injector 107 and the distributor 112 on the basis of operational information a, Pb, 6 and Gd from the various sensors 104, 106, 108 and 110.
Numeral 114 denotes a control relay for supplying a power source to the electronic control unit 113.
Fig. 20 is a waveform diagram showing the fuel injection timing and the ignition timing of the engine 101 in accordance with the fuel injection controlling apparatus for an internal ■ combustion engine shown in Fig. 19, and shows the various produced timings of the crank angle signal 6 from the crank angle detecting sensor 108, and the fuel injection signal J and the ignition signal Q from the ECU 113.
In fig. 20, the rising edge of the crank angle signa: ■ corresponds to a first reference position B 75 ^ (a crank angle position 7 5° prior to the compression top dead center) of the first to fourth cylinders. The dropping edge of the crank angle signal 8 shows a second reference position B5° Also, the ECU 113 starts the calculation of the f u--l amount using as a trigger the first reference position B 75° of the crank angle signal 0 and produces the fuel injection signal

Jyhaving a pulse width Tj corresponding to a necessary fuel amount for driving the injector 107.
In this case, since the single injection 107 is provided, the single injector 107 feed the necessary fuel needed for the four cylinders in one cycle of the engine 101.
Also, with respect to the ignition signal Q, normally, the ignition power is fed by a timer control from the first reference position B75° and is interrupted close to the dropping edge (second reference position B5°) of the crank angle signal 8 for ignition of each cylinder.
Fig, 2 L is a graph illustrating & relationship bt=Lwuun the drive time Tj [msec] and the fuel injection amount. Jo (mcc/pls] of the injector 107. Lj is the curve showing the linearity of the fuel injection amount Jo, Tx is the drive tipm .which is a border between an insufficient region and a sufficient region of the linearity curve Lj.
The drive time Tj of the injector 107 may be aiven from the following formula (1) by the calculation within the ECU 113 in correspondence with the necessary fuel amount Jp [mcc] per one injection:
Tj=KjxJp+Td (1)
where Kj is the gain [msec/mcc] of the injector 107, and Td is the loss time [msec] of the injector 107. Incidentally, the loss

time Td is the time period from the time when the fuel injection signal J is applied until the injector 107 actually injects the
fuel.
>
As is apparent from formula (1), in the characteristics of the injector 107, the drive time Tj is substantially in proportion to the fuel injection amount Jo but the proportional relationship is not always applied in the entire region to thj necessary fuel amount Jp.
For example, the linearity Lj showing the relationship between the drive time Tj and the fuel injection amount Jp of the injector 107 is expressed by the following formula (2):
Lj where Jr is the actual fuel injection amount.
Also, formula (2) is expressed by formula (1 ) as the following formula (3):
Lj=Jr/{{Tj-Td)/Kj> (3}
As shown in Fig, 21, the linearity Lj is in a go,j condition in a region (Tj>Tx) where the drive time Tj is long, but the linearity Lj is insufficient in a low flow rate region (Tj Also,.the shorter the dynamic range of the injector 107, the smaller the minimum fuel injection amount in the good

linearity region will become. The longer the dynamic range of the injection 107, the larger the minimum fuel injection amount will become.
By the way, in the MPI system (not shown) having injectors corresponding to the number of the cylinders, since the fuel amount needed for the single cylinder may be fed during one cycle, even if the injector that may keep the linearity in the region where the fuel feeding amount is small is used, it. is possible to feed a maximum fuel amount needed for the single cylinder during one cycle.
However, in the SPI system for feeding the fuel by the single injection 107 as shown in Fig, 19, it is necessary to feed the fuel amount needed for the four cylinders by dividing the fuel amount in one cycle of the engine 101. Accordingly, in order to make it possible to feed the fuel in the operational condition where the fuel amount is at maximum, it is necessary to set the larger dynamic range of the injector 107.
Thus, in the case where the injector 107 having the larger dynamic range is used, as shown in Fig. 21, the } Lj is worse in the region (Tj
is a fear that the combustion would not be stable or the exhaust gas would be worse.
Also, in the MPI system, a single injector is provided in the vicinity of the intake port of each cylinder, and eac."i injector injects the fuel aiming the intake port. Accordingly, all the fuel is filled into the respective cylinders so that it is possible to control the air/fuel ratio of each cylinder with high precision.
In contrast thereto, in the SPI system, if the injector 107 is disposed in the vicinity of the intake port of the engine 101, the injected fuel is concentrated on a specific cylinder. It is impossible to uniformly distribute the fuel to each cylinder.
Accordingly, in order to uniformly distribute the injected fuel to the respective cylinders, as shown in Fig. 1^, the injector 107 is disposed at a position away from the intake port of the engine 101 so as to fill the fuel together with the intake air into the respective cylinders.
However, in general, the intake air amount and the intake air flow rate to the respective cylinders of the engine 101 are not kept constant. A deflected flow would be generated in !"■■ intake manifold 105. It is therefore difficult to uniformly distribute the fuel to the respective cylinders.

Also, the flow of the air is not kept constant but" may be changed in accordance with the operational conditions. As a result, the fuel distribution condition among the respective cylinder is changed in accordance with the operational condition.
For those reasons, since the displacement or non-uniformity occurs in the fuel distribution condition among the cylinders in the SPI system, it is impossible to control the air/fuel ratio for each cylinder with high precinion. ^ In particular, in the cylinder in which the actually fed fuel amount is considerably different from the target air/fuel ratio, the combustion is unstable, the,output of the engine 101 is reduced and the exhaust gas would be worse.
Also, if the difference in air/fuel ratio among u.e respective cylinders is remarkable, the deviation of the combustion torque among the cylinders would be remarkable. The balance of the torque when the engine 101 rotates is unstable, resulting in adverse affect to the durability and the service life of the engine.
Therefore, in the conventional SPI system, in order to make uniform the fuel distribution for the respective cylinders, as shown in Fig. 19, the injector 107 is disposed upstream of the throttle valve 103 remote from the intake port of the engine 101

so that the injected fuel is collided directly with the throttle valve 103 to thereby realize the atomization of the fuel and the diffusion of the fuel to the air.
Also, in the SPI system as shown in Fig. 19, since the above-described deviation of the fuel distribution condition among the respective cylinders occurs, a method (to b However, since the injector 107 is disposed upstream of the throttle valve 103, the injected fuel is collided with the throttle valve 103 to be diffused. It is therefore; difficult, r.t; suck the fuel into the engine 101 exactly in accordance with the target timing.
Accordingly, now, due to the structure of the system, it is difficult to actually reduce the deviation of the air/fuel ratios among the cylinders.
Also, as described above, in the MPI system, since the injectors each of which may keep the maximum fuel amount needed for the single cylinder during the one cycle of the engine 101 are used, an injector drive time for one tin.j is shorter than the periodical time of one cycle.
In contrast, in the SPI system, the injector 107 having

tfte large dynamic range is used, and the injector 107 is driven at every reference position B75° of the crank angle signal 6 as shown in Fig. 20, the maximum value of the drive time Tj of the injector 107 for one time corresponds to one cycle of the crank angle signal 6.
In the case where the one drive time Tj is less than one cycle of the crank angle signal 6, the value obtained by adding the loss time Td to the effective time period of the injector 107 becomes the drive time Tj in one cycle of the crank angle signal 0 and the fuel amount Jo is changed in correspondence with the drive time T j.
However, if the drive time Tj is ecjuai to the one cycle of the crank angle signal 8, this causes the condition that the injector 107 is always driven. The drive time Tj within one eye" -"■ of the crank angle signal 9 does not include the loss time Td but just include the effective time period of the injector 107.
Thus, in the case where the drive time Tj is hanged in the range less than one cycle to one cycle of the crank angle signal 6, the time obtained by subtracting the loss time Td from the drive time Tj is the effective time period of the injector 107 in the range less than the cycle of the crank angle signal 6. In the case where the drive time Tj is equal to the cycle ot the crank angle signal 0, the drive time Tj becomes equal to the

injector effective time period without any loss time Td.
Namely, at the moment when the drive time Tj of the injector 107 is equal to the cycle of the crank angle signal 0 from the period less than the cycle, all the period corresponding to the loss time Td immediately before that (in the range less than the cycle) becomes the injector effective time period.
Accordingly, at this moment, the fuel injection amount of the injector 107 is rapidly increased to rapidly decrease the air/fuel ratio. Also, it is impossible to .ontrol the supply of the fuel amount between the fuel supply amount when the drive time Tj is equal to the cycle of the crank angle signal 6 and the fuel supply amount when the drive time Tj is less than the cycle of the crank angle signal 0.
In the case where the fuel injection controlling apparatus for an internal combustion engine is the Spi system as described above, the fuel injection signal J composed of pulses corresponding to each cylinder is produced, it is therefore impossible to exactly feed the fuel amount in the low flow rate region where the drive time Tj of the injector 107 is short. The system suffers from a problem that the combustion is unstable and the exhaust gas is worse.
Also, in order to uniformly distribute the fuel to each cylinder, the injector 107 is arranged upstream of the throttle

valve 103. However, the intake air amount and the intake air velocity to each cylinder are not kept constant but may be Changed also in accordance with the operational condition so that the deflected flow is caused within the intake manifold 105. Accordingly, the system suffers from the problems that it is impossible to uniformly distribute the fuel to each cylinder, aud it is impossible to control the air/fuel ratio of each cylinder with high precision.
In particular, when the deviation of the combustion torque among the cylinders is remarkable, the torque balance upon the engine rotation becomes unstable, resulting in adverse affect against the durability and the service life of the inner rial combustion engine.
Also, since the injector 107 is arranged upstream of the throttle valve 103, the injected fuel is collided with the throttle valve 103 to be diffused. As a result, it is impossible to suck the fuel to the engine 101 exactly in accordance with the target timing.
Also, since the dynamic range of the injector 107 is s« at a high level, and the injector 107 is driven at every rising timing {first reference position B75°) of the crank angle signal 6, the maximum, value of the drive time Tj for one time is equal to the time period of one cycle of the crank angle signal 0 to

exclude the loss time Td (becomes the injector effective time period without any loss). When the drive time Tj is increased from the range less than one cycle, the fuel injection amount is rapidly increased. It is therefore impossible to control the fuel supply amount with high precision.
SUMMARY OF THE INVENTION
In view of the above-noted problems, an object of zhe present invention is to provide a fuel injoction controlling apparatus for an internal combustion engine, in which in a system using an injector or injectors whose number is smaller than the number of cylinders, a high precision fuel injection control i: response to the necessary fuel amount is possible, and deviation of air/fuel ratios among the cylinders is suppressed to realize stable operationability.
According to the present invention, in a fuel injection controlling apparatus for an internal combustion engine, at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used, a plm^.ity of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount of fuel to each of the cylinders, and the number of the fuel injections is chanqed : one cycle in response to an operational condition of the internal combustion engine whereby the fuel amount needed in response to

the operational condition for each of the cylinders is kept.
Also, according to the present invention, in a fuel injection controlling apparatus for an internal combustion engine, in which at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used, a plurality of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount of fuel to each of the cylinders, and a fuel injection timing is changed for one cycle in response to an operational condition ot tliu internal combustion (jnyiiiL.- wheLuby the fuel amount needed in response to the operational condition for each of the cylinders is kept.
Also, according to the present invention, in a fuel injection controlling apparatus for an internal combustion engine, at least one injecto. whose number is smaller than the number of cylinders of the internal combustion engine is used, a plurality of fuel injections are effected for one cycle of the internal combustion engine far feeding a predetermined amount of fuel to each of the cylinders, and the number of the fuel injections and an injection timing of the fuel are changed for one cycle in response to an operational condition of the internal combustion engine whereby the fuel amount needed in response to the operational condition for each of the cylinders is kept.

Also, according to the present invention, in a fu^ injection controlling apparatus for an internal combustion engine, at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used, a plurality of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount of fuel to each of the cylinders, the number of the fuel injections is changed for one cycle in response to an operational condition of the internal combustion engine, and whether or not an injection timing of the fuel should be changed is switched in response to the number of the fuel injections for one cycle, whereby the fuel amount needed in response to the operational condition for each of the cylinders is kept.
Also, according to the present invention, in the fuel injection controlling apparatus for an internal combustion engine, the injection timing of the fuel is changed for each injection.
Also, according to the present invention, in the fuel injection controlling apparatus for an internal combustion engine, the injection timing of the fuel is set in correspondence with a time from the fuel injection until the fuel has reaches each cylinder.
Also, according to the present invention, in the fuel

injection controlling apparatus for an internal combustion engine, the injection timing of the fuel is changed in response to a temperature of cooling water of the internal combustion engine.
Also, according to the present invention, in a fuel injection controlling apparatus for an internal combustion engine, at least one injector whose number is smaller than the number of cylinders of the internal combustion engii:-- is used, a plurality of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount ot fuel to each of the cylinders, a rate of an amount of the fuel injected for every fuel injection is changed for one cycle m response to an operational condition of the internal combustion engine whereby the fuel amount needed in response to the operational condition for each of the cylinders is kept.
Also, according to the present invention, in a fuel injection controlling apparatus for an internal combustion engine, at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used, a plurality of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount of fuel to each of the cylinder-, and whether or not an injection timing of the fuel should be changed is switched in response to

an operational condition of the internal combustion engine for one cycle, whereby the fuel amount needed in response to the operational condition for each of the cylinders is kept.
Also, according to the present invention, in a fuel injection controlling apparatus for an interna i. combustion engine, at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used, a plurality of fuel injections are effected for one cycle of LJ.---internal combustion engine for feeding a predetermined amount of fuel to each of the cylinders, and a rate between a drive time and a stop time of the injector is changed for one cycle in response to an operational condition of the internal combustion engine whereby the fuel amount needed in response to the operational condition for each of the cylinders is kept.
Also, according to the present invention, in the fuel injection controlling apparatus for on inLurnal CUIHIJUS.-.L ion engine, the engine operation condition is selected as at least one out of a drive time of the injector, a fuel injection amount during one cycle of the internal combustion engine, an amount of fuel of one injection of the injector, an idle operational condition of the internal combustion engine, a non-idle operational condition of the internal combustion engine, an engine RPM of the internal combustion engine, an intake pressure

of the internal combustion engine, a step-in amount of the accelerator of the internal combustion engine, a throttle valve opening degree of the internal combustion engine, a temperature of cooling water of the internal combustion engine, a temperature of intake air of the internal combustion engine and an atmospheric pressure.
Also, according to the present invention, in the fuel injection controlling apparatus for an internal combustion engine, the injector is disposed downstream of the throttle valve provided in the intake pipe of the internal combustion engine. fiiUEF PESCRIPTIQN OF THE PRfiWI^QS
In the accompanying drawings:
Fig. 1 is a block diagram schematically showing an overall system in accordance with a first embodiment of the invention;
Fig. 2 ia a flowchart showing a judgement process operation of the number of the fuel injections for one cycle in accordance with the first embodiment of the invention;
Fig. 3 is a waveform diagram showing an example oi a switching operation between a four-injection mode and a two-injection mode in accordance with the first embodiment of the invention;
Fig. 4 is a waveform diagram showing an example of a

switching operation between a four-injection mode and a two-injection mode in accordance with the first embodiment of the invention;
Fig. 5 is a waveform diagram showing an example of a switching operation between a four-injection mode and a two-injection mode in accordance with the first embodiment of the invention;
Fig. 6 is a waveform diagram showing an example of a switching operation between a four-injection mode and a two-injection mode in accordance with the first embodiment of the invention;
Fig. 7 is a graph showing an example ot a relationship between the operation condition (load) and an air/fuel ratio oi each cylinder used in the first enbodiment of the invention;
Fig. 8 is an illustration showing a change operation of a rate of the fuel amount at each injection timing in accordance with the first embodiment of the invention;
Fig. 9 is a waveform diagram showing a fuel injection operation in the case where the fuel injection amount needed for one cycle is large in accordance with the first embodiment o£ the invention;
Fig. 10 is a waveform diagram showing a fuel injection operation in the case where the fuel injection amount needed for

one cycle is large in accordance with the first embodiment of the invention;
Fig. 11 is a waveform diagram showing a fuel injection operation in the case where the fuel injection amount needed for one cycle is large in accordance with the first embodiment of thn invention;
Fig. 12 is an illustration of a relationship between the fuel injection timing and the air/fuel ratio in the two-injection mode and in an idle operation in accordance with a second embodiment of the invention;
Fig. 13 is an illustration of a relationship between the-fuel injection timing and the air/fuel ratio in the LWO- S n iect m:: mode and in a 2,000 rpm operation in accordance with the second embodiment of the invention;
Fig. 14 is an illustration of a relationship between ". fuel injection timing and the air/fuel ratio in the two-idjection mode and in a 4,000 rpm operation in accordance with the second embodiment of the invention;
Fig. 15 is a waveform diagram showing the opereition in the two-injection mode in the case where the fuel injection timing is changed in a constant manner in accordance with the second embodiment of the invention;
Fig. 16 is a waveform diagram showing the operation in

the two-injection mode in the case where the fuel injection timing is changed for each injection in accordance with the second embodiment of the invention; * Fig. 17 is an illustration of a relationship between the fuel injection timing and the air/fuel ratio in the two-injection mode in the case where the fuel injection timing is set for each injection in accordance with a second embodiment of the invention;
Fig. 18 is an illustration of a relationship between the fuel injection timing and the air/fuel ratio in the four-injection mode
in the case where the fuel injection timing is changed for each injection in accordance with the second embodiment of the invention;
Fig. 19 is a block diagram schematically showing an overall system of a general internal combustion engine;
Fig. 2 0 is a waveform diagram showing the injecti ^n timing in the case where four fuel injections are effected for one cycle in a general internal combustion engine; and
Fig. 21 is a graph showing a linearity am. the fuel injection amount relative to the injector drive time of a general internal combustion engine.
DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment 1
An embodiment of the invention will now be described with reference to the accompanying drawings. Fig. 1 is a block diagram schematically showing the overall SPI system in accordance with a first embodiment.
The arrangement of each element shown in Fig. 1 is the same as that shown in Fig. 19 except that the injector 10 7 as arranged downstream of the throttle valve 103. The d.plication of the explanation therefor will be omitted.
In this case, ECU 113A renews the fuel injection signal J in correspondence with the operational coridition as described later.
Fig. 2 is a flowchart illustrating the fuel injection operation by the ECU 113A in accordance with the first embodiment of the invention. In Fig. 2, there is shown the fuel injection operation in the case where the fuel injection amount is in a low fUbw rate mode.
In Fig. 2, the ECU 113A first calculates the fuel injection amount jp needed for one cycle from the current operational condition {step SI).
Subsequently, the ECU 113A determines whether or not the
fuel amount in the case where the amount of the fuel needed for
i_ i „ ^^pf0H seDarately for four ^hots is in the rarge

(±5%) where the linearity may be kept (step S2).
If the fuel amount is in the range where the linearity may be kept (i.e., YES), the four-injection mode is taken (step S3). The ECU calculates the drive time Tj4 for one time in case of the four injections during one cycle in accordance with formula (4) similar to the above-described formula (1) (step 24).
Tj4=KjxJp/4+Td (4)
On the other hand, if the fuel amount is in the range where the linearity could not be kept (i.e., NC), the two-injection mode is taken (step S5). The ECU calculates the drive time Tj2 for one time in case of the two injections during one cycle,- in accordance with formula (5) in the same way (step S6).
Tj2=KjxJp/2+Td (5)
The fuel injection operation when the mode conditions are switched between the four-injection mode (steps S3 and S4) and the two-injection mode (steps S5 and S6) in the first embodiment of the invention will now be described specifically with reference to Figs. 3 to 6.
In this case, it is assumed that, in the four-injection mode, the necessary fuel amount injected to one cylinder WILJI reference to the rising timing B75~ of the crank angle signal 0

of all the cylinders, and in the two-inject ion mode, the necessary fuel amount injected to two cylinders with reference to the rising timing B75° of the crank angle signal 6 of, for example, first and fourth cylinders.
Figs. 3 and 4 show the respective waveforms of the crank angle signal 9 and the fuel injection signal J when the modes are switched from the four-injection mode to the two-injection mode at different timings from each other.
Figs. 5 and 6 show the respective waveforms of the crank angle signal 9 and the fuel injection signal J when the modes arc switched from the two-injection mode to the four-injection mode at different timings from each other.
> In each figure, rl to x8 represent periods of the rising edge (first reference position B75°) of the respective pulses of the crank angle signal 6.
In Fig. 3, the injection mode conditions are switched from the four-injection mode to the two-injection mode in the midway of the period T4 and ;.re the four-injection mode in the periods T1 to T4.
Accordingly, the ECU 113A drives the injector 107 at every rise (first reference position B75°) of the crank angle signal 6 to inject the fuel.
Also, since the two-injection mode condition is

established in the midway of the period i4, the fuel is injected at a rate of one per every two of the crank angle signals 6 from the period T5.
In this case, since the fuel is injected with reference to the rises (first reference position B75°) of the crank angle signals 6 of the first and fourth cylinders in the peri ds i5 and 17.
In Fig. 4, the injection mode conditions are switched from the four-injection mode to the two-injection mode in the midway of the period T3 and are the four-injection mode in the periods il to T3.
Accordingly, the ECU 113A drives the injector 107 at every rise (first reference position B75") of the crank angle ■ignol 0 to inject the fuel in the periods il to i3.
-^ Also, the period T4 is the period when the fuel injection is not performed, after the switch to the two-injection mode. However, if the fuel is not injected, ±he fuel amount in the period T4 is insufficient. Accordingly, the fuel that is the same as the four-injection mode is injected in the period T4.
Subsequently, since the period T5 is the period when the fuel is injected in the two-injection mode, the fuel is injected at an amount in-the two-injection mode from the period(=T5.
In Fig. 5, the injection mode conditions are switched

from the two-injection mode to the four-injection mode in the midway of the period r4 and are the two-injection mode in the periods \X to T4 .
In this case, since the periods up to T4 is the two-
injection mode, the fuel is injected on the basis of the rises
cylinders. After the period t5, since the mode is the four-
injection mode, the fuel is injected at every rise (B75°) of each
crank angle signal 6. a
In Fig. 6, the injection mode conditions are switched from the two-injection mode to the four-injection mode in the midway of the period x3 and are the two-injection mode in the periods T1 to t3.
In this case, since the fuel injection in the two-injection mode has been attained in the period T3, the fuel is not injected in the period i4 and the fuel injection is u£iectud in the four-injection mode from the period T5.
The rate of the fuel injection amount at each injection timing during one cycle in accordance with the first embodiment of the invention will now be" described with reference to the characteristic diagram of Fig. 7 and the illustration of Fig. 8.
Fig. 7 is a characteristic graph showing a change of

air/fuel ratio A/F relative to the load change and shows a deviation of the air/fuel ratio A/F at each cylinder (#1 to $4) in the case where the RPM of the engine 101 is kept constant and the load {corresponding to the intake manifold pressure 9b) is changed.
In Fig. 7, the deviation of the air/fuel ratio airong the first to fourth cylinders is increased as the load of the engine 101 is increased (that is, throttle valve opening degree a is increased to increase the intake manifold pressure Pb).
This means that, since the fuel is injected U"ora a position relatively remote from each cylinder in the SPI system UBing the single injector 107, the distribution condition of the fuel ,-to each cylinder is changed in accordance with the operational condition (load).
The deviation of the air/fuel ratio of each cylinder is not limited to that shown in Fig. 7 but may change entirely in accordance with the specification of the individual internal combustion engine.
In the case of the air/fuel ratio characteristics shown in Fig. 7, in order to make uniform the air/fuel ratio A/F among the first to fourth cylinders, the air/fuel ratio fc/F of the first and second cylinders that are in a lean condition must be caused to be rich, and the third and fourth cylinders that are

in a rich condition must be caused to be lean.
In this case, in order to suppress the deviation of the air/fuel ratio A/F of the first to fourth cylinders, the fuel control is performed as follows.
performed under the operational conditions of the intake manifold . . pressure Pb-0 [nmHg].
Fig. 8 is an illustration of the fuel distribution condition in each fuel injection, in which the waveforms of the crank angle signal 9 and the fuel injection signal J are caused to correspond to the strokes of the first to fourth cylinders.
In Fig. 8, in the case where the drive time Tjl of the fuel injection signal J is determined on the basis of the rise (B75°) of the crank angle signal 0 of the first cylindcr, thn timing of the drive time Tjl corresponds to half the latter intake stroke of the third cylinder, the distribution o£ the air/fuel ratio A/F of the control cylinder (i.e., fourth cylinder) next to the third cylinder is effected.
In this case, in the case where the fuel amount distribution is not compensated for, since the air/fuel ratio A/F of the fourth cylinder is in the rich condition, in order to reduce the rate- of the amount of fuel inject -id at the timing of the drive time Tjl, it is necessary to compensate for the drive

time Tjl in accordance with the following formula (6):
Tjl"=kl-Tjl+Td (6)
where Tj 1" is the drive time after compensation, and k 1 is a compensation coefficient to the drive time Tjl.
In this case, in order to reduce and compensate for the fuel amount, the compensation coefficient kl is set in the range of 0 The injector 107 is driven by the drive time Tjl* compensated in accordance with the formula (6) so that the air/fuel ratio A/F of the fourth cylinder is compensated for to be lean. The deviation of the air/fuel ratio A/F among the cylinders is moderated.
In the same way, in the case where the drive time Tj4 of the fuel injection signal J is determined on the basis of the rise (B75°) of the crank angle signal d of the fourth cylinder, the timing of the drive time Tj4 corresponds to half thy lattei intake stroke of the second cylinder, the distribution of the air/fuel ratio A/F of the control cylinder (i.e., first cylinder) next to the second cylinder is affected.
In this case, in the case where the fuel amount distribution is not compensated for, since the air/fuel ratio A/F of the first- cylinder is in the lean condition, in order to increase the rate of the amount of fuel injected at the timinq

of the drive time Tj4, it is necessary to compensate for the drive time Tj4 in accordance with the following formula (7):
Tj4"=k4xTj4+Td (7)
where Tj4" is the drive time after compensation, and k.4 is a compensation coefficient to the drive time Tj4.
In this case, in order to increase and compensate for the fuel amount, the compensation coefficient k4 is set to be greater than 1.
The injector 107 is driven by the drive time Tj4" compensated in accordance with the formula (7) so that the air/fuel ratio A/F of the first cylinder is compensated for to be rich. The deviation of the air/fuel ratio A/F among the cylinders is moderated.
In this case, the case where the rate of the luul injection amount is changed in the region of the intake manifold pressure Pb is zero [mmHg] in Fig. 7 has been explained but needless to say, the like control may be effected in all the operational region.
Also, Fig. 8 shows the case where the rate of the fuel injection amount is changed in the four-injection mode, but it is possible to perform the like control in the two-injection mode.
Also, the control is possible for either the four-

injection mode or the two-injection mode and may be performed only in one of these modes.
The fuel injection operation in the case where the fuel supply amount is large in one cycle in accordance with the first embodiment of the present invention will now be described with reference to the waveform diagrams of Figs. ? to 11.
Figs. 9 to 11 show the fuel injection signals J in the case where the fuel amounts needed for one cycle are different from each other. As the necessary fuel amounts are increased, the control operation of each fuel injection signal J are changed in order as shown in Fig. 9 to Fig. 11.
In Fig. 9, the fuel injection (the rise control of the fuel "injection signal J) is carried out at every one cycle (rising timing B75°) of he crank angle signal 6.
A rate at which the injector is driven during one cycle of the crank angle signal 8 in accordance with the luel injection signal J is high, and the injector 107 is driven over almost all the cycle of the crank angle signal 6.
At this time, the rate Da (drive duty ratio of Da=Tja/Ta

=Tja/(Tja+t) (8)
where t is the necessary minimum drive stop time needed for stopping the drive of the injector 107.
In the operational condition that requires tlie fuel amount as shown in Fig. 9, the rate of the drive time Tja of the injector 107 during one cycle of the crank anqle signal 8 is high and is set at a maximum possible value relative to the one cycle or he crank angle signal 9.
If the rate of the drive time of the injector in one cycle of the crank angle signal 0 is increased more than this, the drive time would be overlapped with the next drive time, the fuel injection signal J is left at an H level and continuous. It is therefore impossible to increase the drive duty of the injector 107 as desired.
Accordingly, in the case where the fuel amount-needed for one cycle is further increased, the drive cycle (one cycle of the fuel injection signal J) Tb and the drive time rjb of the injector 107 are extended as shown in Fig. 10, and it is possible to increase the drive duty of the injector 107 as desired.
At this time, the rate Db (drive duty of the injector 107) of the drive time Tjb relative to the drive cycle Tb of ;!-■•■ injector is g-iven by the following formula (9) similar to the formula (8):

Db~Tjb/Tb
*Tjb/(Tjb+t) (9)
where the drive time Tjb meets the relationship, Tjb>"rja, in comparison with the drive time Tja of formula (8).
Thus, the drive duty Db of the injector 107 is set at a high level so that the amount of the fuel fed during one cycle may be increased.
Accordingly, in the case where the amount of fuel needed for one cycle of the engine is small and the drive linearity of the injector 107 is insufficient, the injector 107 is driven twice in one cycle to thereby keep the sufficient linearity.
Also, in the case where the fuel amount needed for one cycle "is further increased, the drive cycle Tc and the drive time Tjc of the injector 107 are extended as shown in Fig. 11, and i*-is possible to increase the drive duty Dc of the injector 107.
At this time, the drive duty Dc of the injector 107 is given by the following formula (10):
DC=TJc/Tc
-Tjc/(Tjc+t) (10)
where the drive time Tjc meets the relationship, Tjc>Tjb, ±n comparison with the drive time Tjb of formula (9).
Thus, -the drive cycle and the drive time of the injector is extended in order so that it is possible to increase

continuously the drive duty as desired while keeping the drive stop time t.
In the case where the fuel injection amount needed for one cycle is further increased exceeding that of the case of Fig. 11, finally, the fuel injection signal J is fixed at an H level and the drive duty of the injector 107 is set at 100% so that the injector 107 is always driven to keep the maximum fuel.
Embodiment 2
Incidentally, in the first embodiment, the cycle and the number of the shots of the fuel injection are switched in order to optimize the fuel injection amount. For the purpose ol optimizing the control of the fuel injection amount, it is possible to reduce the deviation AA/F of the air/fuel ratio A/F of each cylinder, for example, by shifting the start timing of the fuel injection.
A second embodiment of the present invention in which the fuel injection timing is shifted to optimize the fuel injection control will now be described with reference to the accompanying drawings.
Figs. 12 to 14 are illustrations of a relationship between the injector, injection timing [3 and the A/F of each cylinder in the case where the fuel is injected twice for every cycle. Fig. 12 shows the case of the idle operation (engine RPM

Ne=600 [rpm]), Fig. 13 shows the case of the operation (engine RPM Ne=2,000 [rpm]), and Fig. 14 shows the case of the operation (engine RPM Ne=4,000 [rpm]).
In Figs. 12 to 14, the abscissa represents the injection. timing of the injector 107, whereas the ordinate represents the air/fuel ratio A/F and the deviation &A/F of the air/fuel ratio.
Namely, the air/fuel ratio A/F of each cylinder (#1 to #4) is shown by a bent line graph corresponding to the ordinate axis on the left side, the deviation AA/F obtained by subtracting the minimum value from the maximum value of the air/fuel ratio A/F at each injection timing 3 is represented by a bar graph relative to the ordinate axis on the right side.
Also, Fig. 15 is a waveform diagram showing a shitt amount of the injection timing (3 and shows the case where the injection is performed by a delay of (3° with reference to the rise (B75°) of the crank angle signal 6,.
In general, in the case where the fuel is injected four times in one cycle {four-injection mode), any one of the cylinders takes an intake stroke at any injection timing. Accordingly, there is.almost no affect to the air/fuel ratio A/F of each cylinder due to the difference in the fuel, injection timing.

However, in the case where the fuel is injected twice in one cycle of the engine (two-injection mode}, the rates of the fuel to be sucked into the respective cylinders art caused to be different from each other according to the respective injection timings (5. Accordingly, as is apparent from Figs. 12 to 14, the air/fuel ratio A/F is changed in accordance with the differ e:. of the injection timing [3.
Accordingly, in case of the two-injection mode, if the fuel is injected at random as desired, the deviation u\/)? of the air/fuel ratio between the respective cylinders is remarkable to make worse the operationability.
Accordingly, it is preferable to set the injection timing B suitably so that the deviation AA/F of the air/fuel ratio is at minimum.
For example, in Fig. 12, in order to keep beat Lliu unynu.-operatifnability in the idle uundiLiun, IL .i.a BUII IUIL-ML U.J select the injection timing (i so that the air/fuel ratio A/F ot each cylinder is made uniform.
in this case, comparing the deviations AA/F of the air/fuel ratios according to the injection timings with each other, it is understood that the deviation AA/F of the air/fuel ratio is at minimum at the injection timing 3=270°, and the operationability is best. Accordingly, under the operational

conditions in the idle operation, the fue± is injected at the injection timing 13=270°.
On the other hand, in case of Ne=2,Q00 Irpm] which is different in operational condition from the case of Fig. 12, as shown in Fig. 13, the behavior of the change in air/fuel ratio A/F relative to the injection timing 3 is changed. However, in this case, since the deviation AA/F of the air/fuel ratio is at minimum at the injection timing (3=270°, the fuel is injected ■:■: the injection timing 3=270°.
In case of Ne=4,0Q0 [ rpm] as shown in Fig. 1 A , r.inco ulio deviation AA/F of the, air/fuel ratio is at minin ,,u at the injection timing (3=240°, the fuel is injected at the injection timing 3=240°.
In this case, the optimum fuel injection timing & is shown under the three different operational conditions as in Figs. 12 to 14. However, in other operational conditions, in the same manner, the fuel is injected at the injection timing {"> so that the deviation AA/F is at minimum whereby it is possible to make optimum the engine combustion condition and the exhaust gas.
Incidentally,, it is difficult to set the optimum fuel injection timing J3 relative to all the operational conditions on the program within the actual ECU 113A. Accordingly, it is

possible to set the optimum fuel injection timing, for example, by linearly compensating for the optimum fuel injection timing (5 between 2,000 and 3,000 [rpm] for the operational region between Ne 2,000 and Ne 3,000 [rpm] of the engine.
Also, in this case, the injection timing (3 is simply selected so that the deviation AA/F of the air/fuel ratio is at minimum. The time from the fuel injection until the fuel reaches the cylinders is substantially determined by the engine specification, and it is possible to expect in advance how the change of the in jaction timing fi affects the ,i i vIJ ui.-1 i,:t. i o h. i of the cylinders. Accordingly, the fuel injection timing may be changed a predetermined time period prior to the reach oi" the fuel in view of the fuel reach time relative to the cylinder to be compensated for in the air/fuel ratio A/F.
Also, for example, it is possible to switch the fuel injection timing [J in accordance with a cooling water temperature representative of the warming-up condition of the engine.
The operation in the case where the injection timings fi
are switched in response to the temperature of the cooling water
will now be described in detail.
In general, the fuel composition sucked iuLu Luiub > cylinder may "be classified into two kinds of a liquid flow
component to be fed to the cylinder while flowing along a bottom

surface of the intake manifold 105 and a gas flow component to be sucked into the cylinder together with the air while draftinq in the air.
Among these fuel components, the distribution rate of the fuel of the liquid flow component to be fed into each cylinaer is determined by the direction of flow of the fuel. Accordingly, even if the injection timing 3 is changed, the rate of the fuel flowing through each cylinder is not so changed. The change of the injection timing |3 would not so much affect the air/fuel ratio.
However, with respect to the gas flow component when the injection timing P is changed, the cylinders into which the fi> is fed are changed. Accordingly, this would affect the air/fuel ratio of each cylinder.
Namely, as the causes for changing the air/fuel ratio A/F by the change of the fuel injection timing p, the affect of the gas flow component fuel is large. Accordingly, in accordance with the rate of the gas flow component in the injected fuel, it is determined how the air/fuel ratio A/F may be compensated for.
Accordingly, in the warming-up condition in which the temperature of the cooling water of the engine is high, since the rate of the component atomized within the intake manifold 105 and caused to flow in the form of a gas flow is high, the change of

the fuel injection timing (3 largely affects the change of the air/fuel ratio A/F.
On the other hand, in the casewhere the temperature of the cooling water of the engine is low, the rate of the component atomized within the intake manifold 105 is low- The air/fuel ratio A/F that may be changed by the fuel injection timing p is lower than that in the above-described warming-up condition.
Thus, the change of the air/fuel ratio A/F by the change of the fuel injection timing p is varied in accordance with the temperature of the cooling water of the engine. Accordingly, in order to change the air/fuel ratio A/F of a predetermined cylinder by a predetermined value, it is desirable to chanye the injection timing 3 in response to the temperature of the cooling water. Thus, it is possible to set the highly reliable injection timing [J.
Also, the case where the injection timing \i of the injector 107 in the two-injection mode is changed in a constant manner as shown in Fig. 15 in the second embodiment has been described. It is possible to change the injection timing & at every injection control.
Fig. 16 is a waveform diagram in the case where the injection timings {shift amounts) are different from each other, and shows the case, the injection timings are set at P [ °)

(=270°) and 0+5 [ °] for each injection control on the basis of the rise (B75°) of the crank angle signal e corresponding to the first and fourth cylinders, and the injection is effected with a time lag by 5 [°] (for example, about 10°) for the fourth cylinder.
Namely, the fuel is injected with a time lag of 3 [" j (=270°) in terms of the crank angle on the basis of the first reference position B75° for the fourth and second cylinders, and the fuel is injected with a time lag of p+a [°J (=280°) in terms of the crank angle on the basis of the firsc reference position B75° for the first and third cylinders.
The specific fuel injection operation will now be described with reference to Fig. 16 as well as the above-described Fig. 13.
As described above, in the case where the fuel injection timing 3 is changed in a constant manner in Fig, 13 (Ne=2,QOQ [rpm]), the deviation AA/F of the air fuel ratio at the inject.i In this case, noticing the air/fuel ratio A/F of each cylinder at the injection timing p=270°, it is unde; . tood that the air fuel ratios A/F of the second and fourth cylinders are substantially, equal to each other and are close to the stoichiometric air/fuel ratio (=14.7}.

I
However, as is apparent from Fig. 13, it is understood that the deviation £A/F of the air/fuel ratios of the first and third cylinders is smaller at the injection timing 0o=28O" Accordingly, the injection timing (3 [ °] and injection tftning fi+6 [°] are set for the fourth and second cylinders and for the first and third cylinders at the injection timing "3=270" and compensation amount 5=10° as shown in Fig. 16.
Fig. 17 is an illustration of the relationship between the fuel injection timing 0 and the air/fuel ratio A/F in the case where the fuel injection timing S is compensated for as shown in Fig. 16.
- As shown in Fig. 16, the compensation amount 6 {=10°) is set so that the deviation AA/F of the air /fuel ratio at the injection timing & (=270°) is considerably suppressed as shown in Fig. 17. Accordingly, the two-injection mode operation may be more improved than the case, shown in Fig. 13.
Also, the case where the injection timing [3 in the two-injection mode is varied and set in the second embodiment has been described. It is possible to change and set the injection timing in the four-injectj.on mode.
Fig. 18 is a waveform diagram showing tli: change operation of the injection timing in the four-injection mode, in

Fig. 18, [31 to £4 are injection timings for the first to fourth cylinders with reference to the first reference position B75".
In this case, in the injection control on the basis of the crank angle signal 9 of the first cylinder, the fuel is injected with a time lag of [31 [°] with reference to the first reference position B75°.
In the same manner, the fuel is injected with a time lag of [J3 [°] with reference to the first reference position B75° of the third cylinder/ the fuel is injected with a time lag of 34 [°] with reference to the first reference position B75° of the fourth cylinder, and the fuel is injected with a time lag ot: 1^2 [°] with reference to the first reference position B75" of ti.u second cylinder.
Thus, in the same manner as the change of the fuel injection timing |3 in the two-injection mode as described above (see Fig. 16), it is possible to make uniform the air/fuel ratio A/F of each cylinder (#1 to #4) to thereby enhance the operationability.
Also, in the second embodiment, the control is effected only one of the two-injection mode and the four-injection mode but the control may be effected both in the two-injection mode and the four-injection mode.
Embodiment 3

In the first embodiment, the drive time Tj of the injector 107 is the switching condition between uie four-injection mode and the two-injection mode. It is possible to take various conditions, for example, the following (1) to (3) therefor.
(1) The injection modes are switched in accordance with
whether or not the idle operation is effected.
Namely, in the idle operation, the two-injection mode is effected, and in the non-idle operation, the four-injection mode is effected.
(2) The injection modes are switched in accordance with
the operational condition of the engine.
" Namely, if engine RPM N.e (3) The injection modes are switched in accordance with
various kinds of sensor information representative of the engine
operational conditions.
The engine operation conditions may be selected as at least one out of, for example, a fuel injection amount during one cycle of an internal combustion engine, an amount of fuel of one injection of the injector, an idle operational condition, a non-

idle operational condition, an engine RPM Re, an intake pressure, an intake air amount, a step-in amount of the accelerator, a throttle valve opening degree a, a temperature of cooling water, a temperature of intake air and atmospheric pressure.
However, in the case where the above-described items (1) to (3) are the switching condition between two-injection mode and the four-injection mode, for example, the priority is given to the operationability not to the drive linearity of the injector 107, and the region where the four-injection mode is effected may be obtained although the two-injection mode is effected.
For oxnmplo, in the case wlmru Uiu lull t him L it-acceleration {abrupt acceleration) is effected in the two-injection mode, the four-injection mode may be selected although the condition is directed to the two-injection mode. The region in which the four-injection mode is effected for better operationability may be selected rather than the two-injection mode for better linearity.
Also, in the respective forgoing embodiments, the SPI system in which the single injector 107 s used for the four cylinders has been described. The same controller may^be applied to the case where the two or three injectors are used for the four cylinders to ensure the same effect.
Also, the same controller may be applied to the case

where the injectors whose number is smaller than the number of the cylinder are used for the multi-cylinder engine other than the four-cylinder engine.
For example, in a three-cylinder engine, three injections for one cycle may be changed two Injections for one cycle.
Also, in the second embodiment, the rate of the fuel amount is changed in response to the operational condition. It is possible to select whether or not the rate of the fuel amount. should be changed.
In the same way, in the second embodiment, the injection timing & is changed in response to the operational condition. It is possible to select whether or not the injection timing At) tiotta t: ihati a hove, fcho Jlijoi."iui 107 in "I" ivon in t IKJ
region where the linearity is good, and the number of the fuel injection in one cycle, the drive cycle, the drive time or the switching of the injection- timings are., well judged in response to the operational condition to thereby control the fuel supply to each cylinder uniformly and exactly irrespective to thy operational condition.
Also, since each cylinder is driven at a uniform air/fuel ratio, the combustion torque among the cylinders is made uniform, and the operationability is stable to thereby enhance the

durability of the engine.
>
Also, since the air/fuel ratio of all the cylinders may
be controlled to a target air/fuel ratio, it is possible to keep
the condition of the exhaust gas in a good condition.
Also, even in the engine apparatus using an intake system in which the fuel distribution is deflected to the cylinders with a bad balance, it is possible to make uniform the distribution of the fuel to each cylinder irrespective of the operational condition of the engine.
For instance, in the operational region where the fuel injection amount is small, the number of the fuel injection in a cycle is decreased and the fuel injection amount per one fuel injection is increased so that the injector is driven in the region where the linearity of the injector 107 is good, to thereby make it possible to control the fuel injection with hi:--. precision.
Also, the rate of the amount of the fuel injected is changed in accordance with the operational condition of the engine, and it is possible to compensate for and control the fuel injection amount to be filled to be small for the cylinders which would be rich in fuel, and to compensate for and control the fuel injection amount to be filled to be large for the cylinders which would be lean in fuel.

In the operation region where the fuel injection amount needed for one cycle is large, without increasing the drive time Tj of the injector 107 during a unit time period, the drive cycle of the injector 107 is changed, the rate of the drive time Tj oi the injector 107 is changed to thereby gradually change the supply fuel amount for one cycle to make it possible to control the amount of fuel to be fed for one cycle with high precision.
Also, since the injector 107 is located downstream of the throttle valve 103, the time required for feeding the injected fuel to each cylinder may be shortened, the adhesion to the throttle valve 103 is avoided, the change of the fuel amount and the fu,el injection timing is rapidly reflected to the supply fuel to the engine, and it is possible to control the s; ^ply of the fuel to each cylinder further uniformly with high precision.
Various details of the invention may be changed without departing from its spirit nor its scope. Furthermore, the foregoing description of the embodiments according to the presto.■,. invention is provided for the purpose of illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

FIG. 2
51 CALCULATE FUEL INJECTION AMOUNT JP NEEDED FOR ONE CYCLE
52 IS LINEARITY WITHIN ±5% IN THE CASE WHERE FOUR INJECTIONS ARE EFFECTED FOR ONE CYCLE?
53 FOUR-INJECTION MODE
54 CALCULATE INJECTOR DRIVE TIME Tj4
55 TWO-INJECTION MODE
56 CALCULATE INJECTOR DRIVE TIME Tj2
F*G. 3
1 FOUR-INJECTION MODE
2 TWO-INJECTION MODE
3 . CRANK ANGLE SIGNAL 9
4 FUEL INJECTION SIGNAL J
FIG. 4
5 FOUR-INJECTION MODE
6 TWO-INJECTION MODE
7 CRANK ANGLE SIGNAL 6
8 FUEL INJECTION SIGNAL J
FIG. 5
9 TWO-INJECTION MODE

10 FOUR-INJECTION MODE
11 CRANK ANGLE SIGNAL B
12 FUEL INJECTION SIGNAL J
FIG. 6
13 TWO-INJECTION MODE
14 FOUR-INJECTION MODE
15 CRANK ANGLE SIGNAL 6
16 FUEL INJECTION SIGNAL J
PIG. 7
1 AIR/FUEL RATIO
2 RICH
3 INTAKE MANIFOLD PRESSURE Pb (nimHg)
FIG. 8
1 CRANK ANGLE SIGNAL 0
2 FUEL INJECTION SIGNAL J
3 FIRST CYLINDER
4 THIRD CYLINDER
5 FOURTH CYLINDER
6 SECOND- CYLINDER
7 COMPRESSION

8 INTAKE
9 EXHAUST
10 COMBUSTION

11 COMBUSTION
12 COMPRESSION

13 INTAKE
14 EXHAUST
15 EXHAUST

16 COMBUSTION
17 COMPRESSION

18 INTAKE
19 INTAKE
20 EXHAUST

21 COMBUSTION
22 COMPRESSION
23 COMPRESSION

24 INTAKE
25 EXHAUST
2# COMBUSTION
FIG. 9
1 CRANK^ANGLE SIGNAL 9
2 FUEL INJECTION SIGNAL J

FIG. 10
1 CRANK ANGLE SIGNAL 9
2 FUEL INJECTION SIGNAL J
FIG. 11
1 CRANK ANGLE SIGNAL 6
2 FUEL INJECTION SIGNAL J
FIG. 12
1 IDLE
2 INJECTION TIMING B°
>
FIG. 13
2 INJECTION TIMING (3°
FIG. 14
2 INJECTION TIMING (5°.
FIG. 15
1 CRANK ANGLE SIGNAL 6
2 FUEL INJECTION SIGNAL J
FIG. 16

1 CRANK ANGLE SIGNAL 8
2 FUEL INJECTION SIGNAL J
FIG. 17
2 INJECTION TIMING 0°
FIG. 18
1 CRANK ANGLE SIGNAL 9
2 FUEL INJECTION SIGNAL J
FIG. 20
1 CRANK ANGLE SIGNAL 6
2 FUEL INJECTION SIGNAL J
3 IGNITION SIGNAL Q
FIG. 21
1 FUEL INJECTION AMOUNT
2 LINEARITY INSUFFICIENT REGION
3 LINEARITY SUFFICIENT REGION
4 DRIVE TIME T ms

WE CLAIM:
1. A fuel injection controlling method for an internal combustion engine, in which at least one injector whose number is smaller than the number of cylinders of the internal combustion engine is used and a plurality of fuel injections are effected for one cycle of the internal combustion engine for feeding a predetermined amount of fuel to each of the cylinders, characterized in that: a rate of an amount of the fuel injected for every fuel injection is changed for one cycle in response to a temperature of cooling water and other operational condition of the internal combustion engine.
2. The fuel injection controlling method according to claim 1, wherein a rate between a drive time and a stop time of the injector is changed for one cycle in response to an operational condition of the internal combustion engine whereby the fuel amount needed in response to the operational condition for each of the cylinders is kept.
3. The fuel injection controlling method according to claim 1 or 2, wherein the engine operation condition is selected as at least one out of a drive time of the injector, a fuel injection amount during one cycle of the internal combustion engine, an amount of fuel of one injection of the injector, an idle operational condition of the internal combustion engine, a non-idle operational condition of the internal combustion engine, an engine RPM of the internal combustion engine, an intake pressure of the internal combustion engine, a step-in amount of the accelerator of the internal

combustion engine, a throttle valve opening degree of the internal combustion engine, a temperature of intake air of the internal combustion engine and an atmospheric
pressure.
4. A fuel injection controlling method for an internal combustion engine substantially as herein described with reference to the accompanying drawings.

Documents:

150-mas-1998 abstract-duplicate.pdf

150-mas-1998 abstract.pdf

150-mas-1998 claims-duplicate.pdf

150-mas-1998 claims.pdf

150-mas-1998 correspondence-others.pdf

150-mas-1998 correspondence-po.pdf

150-mas-1998 description (completed)-duplicate.pdf

150-mas-1998 description (completed).pdf

150-mas-1998 drawings.pdf

150-mas-1998 form-19.pdf

150-mas-1998 form-2.pdf

150-mas-1998 form-26.pdf

150-mas-1998 form-4.pdf

150-mas-1998 form-6.pdf

150-mas-1998 others.pdf

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Patent Number

200715

Indian Patent Application Number

150/MAS/1998

PG Journal Number

08/2007

Publication Date

23-Feb-2007

Grant Date

31-May-2006

Date of Filing

22-Jan-1998

Name of Patentee

M/S. MITSUBISHI DENKI KABUSHIKI KAISHA

Applicant Address

2-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100

Inventors:

#	Inventor's Name	Inventor's Address
1	SHIRO YONEZAWA	C/O MITSUBISHI DENKI KABUSHIKI KAISHA, 2-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100.
2	HIROFUMI OHUCHI	C/O MITSUBISHI DENKI KABUSHIKI KAISHA, 2-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100.
3	HIRONORI MATSUMORI	C/O MITSUBISHI DENKI KABUSHIKI KAISHA, 2-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100.
4	TOSHIKI KURODA	C/O MITSUBISHI ELECTRIC CONTROL SOFTWARE CO., LTD., 1-2, HAMAYAMA-DORI 6-CHOME, HYOGO-KU, KOBE-SHI, HYOGO 652
5	TAKESHI KITAO	C/O MITSUBISHI ELECTRIC CONTROL SOFTWARE CO., LTD., 1-2, HAMAYAMA-DORI 6-CHOME, HYOGO-KU, KOBE-SHI, HYOGO 652

PCT International Classification Number

F02D 41/34

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	9-182675	1997-07-08	Japan