Title of Invention

FUEL INJECTION QUANTITY CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINE

Abstract A fuel injection quantity control apparatus of an internal combustion engine includes valve opening time computation device which computes a valve opening time of a fuel injection valve according to an operating condition of the internal combustion engine. The computation device controls the valve opening time of the fuel injection valve to regulate a fuel injection quantity. The control apparatus includes an acquisition device for acquiring a rotation speed of a fuel pump, and an estimation device for estimating pressure of fuel discharged from the fuel pump to the fuel injection valve by the use of a predetermined pump characteristic on the basis of the rotation speed of the fuel pump. A valve opening time correction device corrects the valve opening time of the fuel injection valve on the basis of estimated fuel pressure.
Full Text

FUEL INJECTION QUANTITY CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINE
FIELD OF THE INVENTION The present invention relates to a fuel injection quantity control apparatus of an internal combustion engine.
BACKGROUND OF THE INVENTION
In an electronically controlled fuel injection system, a reference fuel injection time of an injector is determined on the basis of the load of an internal combustion engine, and this reference fuel injection time is corrected according to the operating conditions of the internal combustion engine to thereby determine a final fuel injection time. For the correction of the reference fuel injection time according to the operating conditions of the internal combustion engine, the reference fuel injection time is corrected, for example, by the cooling water temperature of the internal combustion engine, the atmospheric pressure, an air-fuel ratio, and the like. Generally, fuel is injected according to this corrected fuel injection time to control a fuel injection quantity.
However, when the voltage of a battery is low, for example, at the time of startup of the internal combustion engine, there are cases in which the driving voltage of a fuel pump supplying fuel to the injector is lowered to reduce the pressure of fuel applied to the injector. For this reason, there are cases where even if fuel is injected from the injector on the basis of the fuel injection time determined in the above-mentioned manner, a fuel injection quantity cannot be appropriately controlled.
Thus, technologies have been known in which the driving voltage of the fuel pump is detected and in which the fuel injection time of the injector is corrected according to the driving voltage (for example, JP-63-235632A, JP-61-255234A

(EP-0206485B1), JP-U-63-67639A)
However, the coil of a motor for driving a fuel pump has its resistance varied by temperature. For this reason, even if the same voltage is applied to the motor for driving a fuel pump, the rotation speed of the motor differs depending on temperature. As a result, even if the same voltage is applied to the motor for driving the fuel pump, the pressure of fuel applied to the injector differs. Accordingly, even if the fuel injection time is corrected according to the driving voltage of the motor when the voltage of the battery is low, there are cases where the fuel injection quantity cannot be appropriately controlled.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-mentioned problems. It is the main object of the present invention to provide a fuel injection quantity control apparatus of an internal combustion engine that can control a fuel injection quantity properly by controlling the valve opening time of a fuel injection valve properly.
According to the present invention, a fuel injection quantity control apparatus is applied to an fuel injection system of an internal combustion engine including an electrically operated fuel pump and a fuel injection valve for injecting fuel into the internal combustion engine. The fuel injection quantity control apparatus includes valve opening time computation means for computing a valve opening time of the fuel injection valve according to an operating condition of the internal combustion engine, and controls the valve opening time of the fuel injection valve to regulate a fuel injection quantity. The fuel injection quantity control apparatus of an internal combustion engine is characterized by including: pump rotation speed acquisition means for acquiring a rotation speed of the fuel pump; fuel pressure estimation means for estimating pressure of fuel discharged from the fuel pump to the fuel injection

valve Dy tne use or a predetermined pump cnaractenstic on me oasis OT a roianon speed of the fuel pump acquired by the pump rotation speed acquisition means; and valve opening time correction means for correcting a valve opening time of the fuel injection valve on the basis of pressure of fuel estimated by the fuel pressure estimation means.
According to this apparatus, the pressure of fuel discharged from the fuel pump to the fuel injection valve is estimated by the use of the predetermined pump characteristic on the basis of the rotation speed of the fuel pump. The rotation speed of the fuel pump is a more direct factor to determine a fuel quantity (pump flow rate) supplied from the fuel pump as compared with a driving voltage of the fuel pump. For this reason, the accuracy of the estimated value of the pressure of fuel can be increased by computing the estimated vale of the pressure of fuel on the basis of the rotation speed of the fuel pump. The valve opening time of the fuel injection valve is corrected on the basis of the estimated value of the pressure of fuel, the estimated value being of high accuracy. With this, a fuel injection quantity can be appropriately controlled.
Moreover, according to the present invention, a fuel injection quantity control apparatus includes valve opening time computation means for computing a valve opening time of the fuel injection valve according to an operating condition of the internal combustion engine, and controls the valve opening time of the fuel injection valve to regulate a fuel injection quantity. The fuel injection quantity control apparatus is characterized by including: pump rotation speed acquisition means for acquiring a rotation speed of the fuel pump; fuel supply system abnormality detection means for detecting an abnormality in a fuel supply system for supplying fuel to the fuel injection valve; abnormal-time fuel pressure estimation means for estimating pressure of fuel at the time of abnormality in the fuel supply system by the use of a predetermined pump characteristic at the time of abnormality in the fuel supply system

on the basis of a rotation speed of the fuel pump acquired by the pump rotation speed acquisition means; and abnormal-time valve opening time correction means that corrects the valve opening time of the fuel injection valve on the basis of pressure of fuel estimated by the abnormal-time fuel pressure estimation means when an abnormality in the fuel supply system is detected.
When an abnormality occurs in the fuel supply system, the pressure of fuel is brought to a state in which the pressure of fuel differs from a desired pressure. Thus, the pressure of fuel is estimated on the basis of the rotation speed of the fuel pump by the use of the predetermined pump characteristic at the time of abnormality in the fuel supply system and the valve opening time of the fuel supply valve is corrected on the basis of the estimated value of the pressure of fuel. With this, a fuel injection quantity can be brought close to a proper value, and the internal combustion engine can be operated within a short period in a state in which an abnormality occurs in the fuel supply system, whereby the vehicle can be run for repair to a repair factory.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings, in which like parts are designated by like reference numbers and in which:
FIG. 1 is a construction diagram showing the general engine control system in an embodiment of the present invention;
FIG. 2 is a flow chart showing a computation routine of a final fuel injection time;
FIG. 3 is a graph showing a relationship between the rotation speed of a motor for rotating and driving a pump body and pressure of fuel supplied from a pump module;

FIG. 4 is a graph showing a relationship between voltage applied to a motor and a pump flow rate;
FIG. 5 is a graph showing a relationship between the rotation speed of a motor and a pump flow rate;
FIG. 6 is a flow chart showing a computation routine of a final fuel injection time in a second embodiment; and
FIG. 7 is a flow chart showing a failure detection routine of a pressure regulator in a third embodiment.
DETAILED DESCRIPTION OF EMBODIMENTS [First Embodiment]
A first embodiment embodying the present invention will be described below with reference to the drawings. This embodiment constructs an engine control system for a gasoline engine for a two-wheel vehicle that is an internal combustion engine. In this control system, an electronic control unit (hereinafter referred to as ECU) as a central unit controls a fuel injection quantity and ignition timing. First, the general schematic construction diagram of the engine control system will be described with reference to FIG. 1.
In an engine 10 shown in FIG. 1, an air cleaner 12 is disposed at the most upstream portion of an intake pipe 11 and a throttle valve 14 is disposed downstream of the air cleaner 12. The air cleaner 12 is provided with an intake air temperature sensor 13 for detecting an intake air temperature. The throttle valve 14 is provided with a throttle position sensor 15 for detecting a throttle opening. An intake pipe pressure sensor 16 for detecting an intake pipe pressure is disposed downstream of the throttle valve 14. Further, an electromagnetically driven injector 17 is disposed near the intake port of the intake pipe 11.
The intake port and the exhaust port of the engine 10 are provided with an

intake valve 21 and an exhaust valve 22, respectively. An air-fuel mixture of air and fuel is introduced into a combustion chamber 23 by an opening operation of the intake valve 21. Exhaust gas after combustion is discharged into an exhaust pipe 24 by an opening operation of the exhaust valve 22. An ignition plug 25 is mounted in each of the respective cylinders of the cylinder head of the engine 10. A high voltage is applied to each of the ignition plugs 25 at a desired timing through an ignition unit 26 composed of an ignition coil and the like. Spark discharge is generated between opposed electrodes of each ignition plug 25 by the application of this high voltage, whereby the air-fuel mixture introduced into the combustion chamber 23 is ignited and combusted.
The exhaust pipe 24 is provided with a catalyst 31, such as a three-way catalyst, for cleaning CO, HC, NOx and the like in the exhaust gas. An A/F sensor 32 for detecting the air-fuel ratio of air-fuel mixture for the exhaust gas is disposed upstream of this catalyst 31. Moreover, the engine 10 is provided with a cooling water temperature sensor 33 for detecting a cooling water temperature and a crank angle sensor 34 for outputting an crank angle signal of a rectangular shape at intervals of a specified crank angle (for example, at intervals of 30° CA) along with the rotation of the engine 10.
Moreover, in a fuel system, an in-tank-type pump module 42 is disposed in the fuel tank 41. A delivery pipe 45 is connected to the fuel pump module 42 via fuel piping 43. The fuel pump module 42 is composed of a pump body 46 and a pressure regulator 44. Moreover, the fuel pump module 42 is composed of a fuel filter, return piping, a motor, and the like, which are not shown in FIG. 1. The motor rotates and drives the pump body 46. In this embodiment, a well-known sensor-less brushless motor of which rotation speed can be controlled without using a rotational position sensor is used as the motor.
The pressure regulator 44 regulates the pressure of fuel supplied from the fuel

pump module 42. wnen tne pressure or ruei aiscnargea rrom tne pump ooay 4b or the fuel pump module 42 becomes higher than a set pressure of the pressure regulator 44, excess fuel is returned to the fuel tank 41 via return piping. That is, fuel having pressure regulated to a specified pressure by the pressure regulator 44 is discharged to the delivery pipe 45 via the fuel piping 43 from the fuel pump module 42 and excess fuel is returned to the fuel tank 41 through the return piping.
The pressure of fuel supplied from the fuel pump module 42 will be further described. FIG. 3 is a graph showing the relationship between the rotation speed (NEP) of the motor for rotating and driving the pump body 46 (hereinafter referred to as "pump rotation speed") and the pressure (Pf) of fuel supplied from the fuel pump module 42. As shown in FIG. 3, when the pump rotation speed NEP becomes a specified rotation speed or more, the supply of fuel from the fuel pump module 42 is started. As the pump rotation speed NEP increases, the pressure of fuel Pf increases linearly. When the pressure of fuel Pf reaches a reference fuel pressure PfO of a set pressure of the pressure regulator 44, a part of fuel discharged from the pump body 46 of the fuel pump module 42 is returned as excess fuel to the fuel tank 41 via the return piping. Thus, even if the pump rotation speed NEP becomes larger than a pump rotation speed NEPO corresponding to the reference fuel pressure PfO, the pressure of fuel Pf increases only a little and the pressure of fuel Pf is held substantially at the reference fuel pressure PfO.
An ECU 50 is mainly constructed of a microcomputer composed of a CPU, a ROM, a RAM, and the like. Detection signals of the various sensors described above and the like are inputted to the ECU 50. The ECU 50 executes various control programs stored in the ROM to control the fuel injection time of the injector 17 and the ignition timing by the ignition plug 25 on the basis of the engine operating conditions. In particular, in fuel injection time control, the ECU 50 computes a fuel pressure correction factor FPf from the estimated value of pressure of fuel Pf based on a pump

rotation speed NEP and computes a final fuel injection time TAU affected by the correction factor FPf.
Here, the ECU 50 controls the rotation speed of the pump body 46 and outputs a pulse width modulation signal to the motor so as to bring the pump rotation speed NEP to a desired rotation speed. That is, a rotational position sensor or the like does not need to be used for finding a pump rotation speed NEP but the pump rotation speed NEP can be detected by observing the driving signal waveform (pulse width modulation signal waveform) of the motor outputted by the ECU 50 itself.
FIG. 2 is a flow chart showing a computation routine of a final fuel injection time TAU and this computation routine is executed by the ECU 50, for example, for each specified angle. In FIG. 2, in step S101, it is determined whether it is the timing of computing a final fuel injection time TAU. The final fuel injection time TAU needs to be computed at each fuel injection timing. Hence, in step S101, it is determined on the basis of a crank angle signal outputted from a crank angle sensor 34 whether it is specified timing. When determination result in step S101 is NO, the final fuel injection time TAU is not computed but this processing is finished. When determination result in step S101 is YES, the routine proceeds to step S102.
In step S102, various operating condition parameters are read. Specifically, a cooling water temperature THW computed from a detection value of a cooling water temperature sensor 33, an intake air temperature THA computed from a detection value of an intake air temperature sensor 13, an intake air pressure PM computed from a detection value of an intake air pressure sensor 16, an atmospheric pressure PA computed from a detection value of an atmospheric pressure sensor, an engine rotation speed NE computed on the basis of a crank angle signal outputted from the crank angle sensor 34, and an air-fuel ratio A/F computed from a detection value of an A/F sensor 32 are read.
In step S103, correction factors according to the respective operation

condition parameters are computed. Specifically, a cooling water temperature correction factor FTHW, an atmospheric pressure correction factor FPA, an A/F sensor correction factor FAF are computed. The relationship between the respective operating condition parameters and the correction factors are previously stored as a map in the ECU 50. In step S103, the respective correction factors are computed by the use of the map stored in the ECU 50.
In step S104, the pump rotation speed NEP is computed from the driving signal waveform of the motor outputted from the ECU 50. In step S105, the estimated value of pressure of fuel Pf is computed from the pump rotation speed NEP. The pump rotation speed NEP and the pressure of fuel Pf is in the relationship shown in FIG. 3, and this relationship is previously stored as a map in the ECU 50. In step S105, the estimated value of pressure of fuel Pf is computed from the pump rotation speed NEP by the use of the map stored in the ECU 50.

In step S108, a reference fuel injection time TP is computed form the engine rotation speed NE and engine load (intake air pressure PM). The relationship between the reference fuel injection time TP and the engine rotation speed NE and the intake air pressure PM is previously stored as a map in the ECU 50. In step S108, the reference fuel injection time TP is computed by the use of the map.

Finally, in step S109, a final fuel injection time TAU is computed by the use of the following equation from the total correction factor FTOTAL and the reference fuel injection time TP, which have been found in step S107 and step S108.
TAU = TP x FTOTAL
The ECU 50 outputs an injector driving signal to the injector 17 on the basis of the final fuel injection time TAU. With this, the injector 17 is opened on the basis of the injector driving signal to inject fuel.
In this embodiment, the estimated value of the pressure of fuel Pf supplied from the fuel pump module 42 is computed, and the final fuel injection time TAU is computed by the use of the fuel pressure correction factor FPf computed from the estimated value of the pressure of fuel Pf. The estimated value Pf of the pressure of fuel Pf is computed on the basis of not the driving voltage of the motor but the pump rotation speed NEP With this, the estimated value of the pressure of fuel Pf can be computed with high accuracy. The final fuel injection time TAU is computed by the use of the estimated value of the pressure of fuel Pf of high accuracy and hence a fuel injection quantity can be appropriately controlled.
This point will be further described with reference to FIG. 4 and FIG. 5. FIG. 4 is a graph showing a relationship between voltage applied to a motor (V) and pump flow rate (Q). In the drawing, a single dot and dash line designates the upper limit of variations, a solid line designates the central value of variations, and a broken line designates the lower limit of variations. FIG. 5 is a graph showing a relationship between pump rotation sped (NEP) and pump flow rate (Q). In the drawing, a single dot and dash line designates the upper limit of variations, a solid line designates the central value of variations, and a broken line designates the lower limit of variations. The resistance of the coil of a motor is changed by temperature. Thus, even if the same voltage is applied to the motor, the pump rotation speed NEP will differ. When the pump rotation speed NEP differs, the quantity of fuel (pump flow rate Q) supplied

from the fuel pump module 42 also differs. Therefore, as shown in FIG. 4, a pump flow rate Q corresponding to a given applied voltage varies within a certain range above and below the central value of variations.
In contrast to this, as shown in FIG. 5, in the relationship between the pump rotation speed NEP and the pump flow rate Q, variations in the pump flow rate Q to a certain pump rotation speed NEP become small. This is because the pump rotation speed NEP is a more direct factor to determine the pump flow rate Q. In this embodiment, the pressure of fuel Pf that is determined by the pump flow rate Q and is supplied from the fuel pump module 42 is computed by estimation from the pump rotation speed NEP. For this reason, the pressure of fuel Pf can be computed with higher accuracy than when the pressure of fuel Pf is computed from voltage applied to the motor. As a result, a final fuel injection time TAU can be computed on the basis of the estimated value of the pressure of fuel Pf of higher accuracy and hence a fuel injection quantity can be appropriately controlled.
In this embodiment, a sensor-less brushless motor of which rotation speed can be controlled without a rotational position sensor is used as the motor for rotating and driving the pump body 46. In other words, the rotation speed of the brushless motor can be computed by the observation of the driving signal waveform of the motor, the driving signal being outputted from the ECU 50 itself. For this reason, the pump rotation speed NEP can be computed without an additional rotational position sensor and the like. Moreover, the elimination of need for the rotational position sensor can simplify the construction of the motor. [Second Embodiment]
In the first embodiment, when a final injection time TAU is computed, the estimated value of the pressure of fuel Pf is always computed on the basis of a pump rotation speed NEP. Then, a fuel pressure correction factor FPf is computed by the use of the estimated value of the pressure of fuel Pf.

In contrast to this, in a second embodiment, only when a pump rotation speed NEP is smaller than a specified rotation, the estimated value of pressure of fuel Pf is computed. When the pump rotation speed NEP is not smaller than the predetermined rotation speed, a fuel pressure correction factor FPf based the estimated value of the pressure of fuel Pf is not computed but the fuel pressure correction factor FPf is set to 1.0. That is, since the fuel pressure correction factor FPf is set to 1.0, the fuel pressure correction factor FPf does not actually contribute to the computation of a total correction factor FTOTAL.
FIG. 6 is a flow chart showing a computation routine of a final fuel injection time TAU in this embodiment. In FIG. 6, in step S201, it is determined whether it is TAU computation timing. When determination result in step S201 is NO, this processing is finished without executing any processing. When determination result in step S201 is YES, the routine proceeds to step S202 where respective operating condition parameters are read.
In step S203, correction factors according to respective operation condition parameters are computed. In step S204, a pump rotation speed NEP in the fuel pump module 42 is computed from the driving signal waveform of the motor, the driving signal waveform being outputted from the ECU 50. The processing of step S201 to step S204 is the same as the processing of step S101 to step S104 in FIG. 2 in the first embodiment.
In step S205, it is determined whether the pump rotation speed NEP is smaller than a predetermined rotation speed. When determination result in step S205 is YES, the routine proceeds to step S206. In step S206, the estimated value of the pressure of fuel Pf is computed from the pump rotation speed NEP In step S207, a fuel pressure correction factor FPf is computed. The processing of step S206 and step S207 is the same as the processing of step S105 and step S106 in FIG. 2 in the first embodiment. After executing the processing of step S207, the routine proceeds

to step S209. Conversely, when determination result in step S205 is NO, the routine proceeds to step S208 where a fuel pressure correction factor FPf is set to 1.0. Thereafter, the routine proceeds to step S209.
In step S209, a total correction factor FTOTAL is computed. In step S210, a reference fuel injection time TP is computed from the engine rotation speed NE and engine load (intake air pressure PM). In step S211, a final fuel injection time TAU is computed from the total correction factor FTOTAL and the reference fuel injection time TP, which have been found in step S209 and step S210. The processing of step S209 to step S211 is also the same as the processing of step S107 to step S109 in FIG. 2 in the first embodiment.
The ECU 50 outputs an injector driving signal to the injector 17 on the basis of the final fuel injection time TAU. With this, the injector 17 is opened on the basis of the injector driving signal to inject fuel.
In this embodiment, only when the pump rotation speed NEP is smaller than the specified speed, the estimated value of the pressure of fuel Pf based on the pump rotation speed NEP is computed, and the final fuel injection time TAU is computed by the use of the fuel pressure correction factor FPf computed from the estimated value of the pressure of fuel Pf. When the pump rotation speed NEP is not smaller than the specified speed, the estimated value of the pressure of fuel Pf is not computed and a fuel pressure correction factor FPf based on the estimated value of the pressure of fuel Pf is not computed, but a fuel pressure correction factor FPf is set to 1.0. Thus, the fuel pressure correction factor FPf does not actually contribute to the computation of a final fuel injection time TAU.
When a pump rotation speed NEP is smaller than the predetermined rotation speed, there is a case in which the pressure of fuel Pf supplied from the fuel pump module 42 is smaller than the reference fuel pressure PfO that is a set pressure of the pressure regulator 44. In this case, when a final fuel injection time TAU is

determined without consideration given to the pressure of fuel Pf, a sufficient quantity of fuel cannot be injected. In this point, in this embodiment, when a pump rotation speed NEP is smaller than the predetermined rotation speed, a fuel pressure correction factor FPf based on the pressure of fuel Pf supplied from the fuel pump module 42 is computed and a final fuel injection time TAU is computed on the basis of this fuel pressure correction factor FPf. With this, even when the pressure of fuel Pf supplied from the fuel pump module 42 is small because a pump rotation speed NEP is small, a fuel injection quantity can be appropriately controlled.
Conversely, when a pump rotation speed NEP is not smaller than the predetermined rotation speed, the pressure of fuel Pf supplied from the fuel pump module 42 is pressure of fuel close to the reference fuel pressure PFO that is a set pressure of the pressure regulator 44. Thus, eve if a fuel pressure correction factor FPf based on the pressure of fuel Pf is computed, the fuel pressure correction factor FPf becomes a value close to 1.0 and hence slightly affects a total correction factor FTOTAL and a final fuel injection time TAU. Accordingly, when a pump rotation speed NEP is not smaller than the predetermined rotation speed, the pressure of fuel Pf and the fuel pressure correction factor FPf are not computed and hence the computation load of the ECU 50 can be reduced.
As for the specified rotation speed, it is recommended to set, for example, NEPO that is a pump rotation speed NEP corresponding to the reference set pressure PfO of the pressure regulator 44. [Third Embodiment]
In the second embodiment, only when the pump rotation speed NEP is smaller than the specified speed, the estimated value of the pressure of fuel Pf is computed and the fuel pressure correction factor FPf is computed by the use of the estimated value of the pressure of fuel Pf. In contrast to this, in a third embodiment, only when the failure of the pressure regulator 44 in the fuel pump module 42 is

detected, the estimated value of the pressure of fuel Pf is computed and a fuel pressure correction factor FPf is computed from the estimated value of the pressure of fuel Pf. When the failure of the pressure regulator 44 in the fuel pump module 42 is not detected, a fuel pressure correction factor FPf based on the estimated value of the pressure of fuel Pf is not computed but the fuel pressure correction factor FPf is set to 1.0.
That is, in this embodiment, a failure detection routine of pressure regulator 44 is executed between step S204 and step S205 of the flow chart in FIG. 6 in the second embodiment. In place of step S205 in the flow chart in Fig 6, it is determined whether the failure of the pressure regulator 44 is detected.
FIG. 7 is a flow chart showing the failure detection routine of the pressure regulator 44 in this embodiment. First, in step S301, it is determined whether an engine rotation speed NE is within a specified range. When determination result in step S301 is YES, the routine proceeds to step S302 and when determination result in step S301 is NO, the routine proceeds to step S303. In step S302, it is determined whether an intake air pressure is within a specified range. When determination result in step S302 is YES, the routine proceeds to step S306 and when determination result in step S301 is NO, the routine proceeds to step S303. In the step S301 and step S302, it is determined whether the failure detection condition of the pressure regulator 44 is satisfied. Specifically, it is determined whether the engine 10 is in a normal state. When the engine 10 is in the normal state, it is determined that the failure detection condition of the pressure regulator 44 is satisfied.
When it is determined that the failure detection condition of the pressure regulator 44 is not satisfied, that is, when determination result in step S301 or step S302 is NO, a pressure regulator failure flag FPRCHK is set to 0 in step 303. Then, the routine proceeds to step S304 where a failure detection condition continuation counter flag CPRCHK is set to 0. Thereafter, the routine proceeds to step S305

where a pressure regulator abnormality detection flag FPRJDG is set to 0 and this processing is finished.
Conversely, when it is determined that the failure detection condition of the pressure regulator 44 is satisfied, that is, when both determination results in step S301 and step S302 are YES, the routine proceeds to step S306. In step S306, it is determined whether the pressure regulator failure detection flag FPRCHK is 1. When determination result in step S306 is YES, the routine proceeds to step S307 where the failure detection condition continuation counter CPRCHK is incremented by 1 and then the routine proceeds to step S309. Conversely, when determination result in step S306 is NO, the routine proceeds to step S308 where the pressure regulator failure detection flag FPRCHK is set to 1 and then the routine proceeds to step S309.
In step S309, it is determined whether the failure detection continuation flag CPRCHK is a specified value or more. In step S309, specifically, it is determined whether the failure detection condition of the pressure regulator 44 continues for a specified period. In other words, in this step, it is determined whether the failure detection state of the pressure regulator 44 stands at a level in which the failure detection state can be stably determined. When determination result in step S309 is NO, it is determined that the failure detection state of the pressure regulator 44 does not stand at a level in which the failure detection state can be stably determined and the routine proceeds to step S305 where the pressure regulator abnormality detection flag FPRJDG is set to 0 and this processing is finished. Conversely, when determination result in step S309 is YES, it is determined that the failure detection state stands at a level in which the failure detection state can be stably determined and the routine proceeds to step S310.
In step S310, it is determined whether an A/F sensor correction factor FAF is 1.20 or more. A case where an A/F sensor correction factor FAF is 1.20 or more is a

case where a fuel injection quantity is too small for a target air-fuel ratio. That is, in step S310, it can be detected that the pressure regulator 44 has a malfunction in a pressure regulation function and hence is faulty so as to make the pressure of fuel Pf smaller than the reference fuel pressure PfO. When determination result in step S310 is YES, the routine proceeds to step S311. In step S311, the pressure regulator failure detection flag FPRCHK is set to 1 and this processing is finished.
When determination result in step S310 is NO, the routine proceeds to step 312. In step S312, it is determined whether the A/F sensor correction factor FAF is 0.8 or less. A case where the A/F sensor correction factor FAF is 0.8 or less is a case where a fuel injection quantity is too large for a target air-fuel ratio. That is, in step S312, it can be detected that the pressure regulator 44 has a malfunction in a fuel return function and hence is faulty so as to make the pressure of fuel Pf larger than the reference fuel pressure PfO. When determination result in step S312 is YES, the routine proceeds to step S311. In step S311, the pressure regulator failure detection flag FPRCHK is set to 1 and this processing is finished. Conversely, when determination result in step S312 is NO, the routine proceeds to step S305 where the pressure regulator abnormality detection flag FPRJDG is set to 0 and this processing is finished.
When the pressure regulator abnormality detection flag FPRJDG set by the failure detection routine of the pressure regulator 44 is 0, a fuel pressure correction factor FPf based on the estimated value of the pressure of fuel Pf is not computed but is set to 1.0. Conversely, when the pressure regulator abnormality detection flag FPRJDG is 1, the estimated value of a pressure of fuel Pf based on a pump rotation speed NEP is computed, and a fuel pressure correction factor FPf is computed by the use of the estimated value of the pressure of fuel Pf. The ECU 50 outputs an injection driving signal to the injector 17 on the basis of a final injection time TAU multiplied by this fuel pressure correction factor FPf. With this, the injector 17 is

opened on the basis of the injector driving signal to inject fuel.
When the pressure regulator 44 is faulty, the relationship between the pump rotation speed NEP and the pressure of fuel Pf does not become the relationship shown in FIG. 3. Thus, when the pressure regulator 44 is faulty, the estimated value of the pressure of fuel Pf is computed from the pump rotation speed NEP by the use of a map storing a relationship different from the relationship shown in FIG. 3.
In this embodiment, only when the failure of the pressure regulator 44 in the fuel pump module 42 is detected, the estimated value of the pressure of fuel Pf based on the pump rotation speed NEP is computed, and a final fuel injection time TAU is computed by the use of the fuel pressure correction factor FPf computed from the estimated value of the pressure of fuel Pf. When the failure of the pressure regulator 44 is not detected, the estimated value of the pressure of fuel Pf and a fuel pressure correction factor FPf based on the estimated value of the pressure of fuel Pf are not computed, but the fuel pressure correction factor FPf is set to 1.0, so the fuel pressure correction factor FPf does not actually contribute to the computation of the final fuel injection time TAU.
When the pressure regulator 44 is faulty, even if the pump rotation speed NEP reaches the predetermined rotation, the pressure of fuel Pf cannot be regulated to the reference fuel pressure PFO and hence the actual pressure of fuel is brought to a state different from a desired pressure of fuel. Hence, in this case, the fuel injection quantity can be brought close to an appropriate value by determining the final fuel injection time TAU by the use of the fuel pressure correction factor FPf based on the estimated value of the pressure of fuel Pf. Hence, a vehicle having the pressure regulator 44 failed can be run for repair to be moved to a repair factory. [Other Embodiments]
In the respective embodiments, the brushless motor is used as the motor for rotating and driving the pump body 46. In the respective embodiments, a

sensor-less brushless motor is used as the brushless motor. With this, the pump rotation speed NEP can be detected without specially providing the rotational position sensor or the like. However, the mode of the motor is not limited to this. That is, a sensor for detecting the rotational position of the motor may be provided, the rotation speed of the motor may be detected on the basis of the rotational position of the motor detected by the sensor, and the estimated value of the pressure of fuel Pf may be computed from the rotation speed of the motor. Moreover, the motor may be not a brushless motor but a motor with a brush.
In the respective embodiments, the final fuel injection time TAU is computed by the use of the cooling water temperature correction factor FTHW, the atmospheric pressure correction factor FPA, and the A/F sensor correction factor FAF as well as the fuel pressure correction factor FPf. However, the final fuel injection time TAU may be also computed by the further use of correction factors based on the detected values of the other operating condition parameters.
In the second embodiment, only when the pump rotation speed NEP is smaller than the predetermined rotation, the estimated value of the pressure of fuel Pf based on the pump rotation speed NEP is computed, and the fuel pressure correction factor FPf is computed by the use of the estimated value of the pressure of fuel Pf. Moreover, in the third embodiment, only when the failure of the pressure regulator 44 is detected, the estimated value of the pressure of fuel Pf based on the pump rotation speed NEP is computed, and the fuel pressure correction factor FPf is computed by the use of the estimated value of the pressure of fuel Pf. However, a case in which the estimated value of the pressure of fuel Pf based on the pump rotation speed NEP is computed and in which the fuel pressure correction factor FPf is computed by the use of the estimated value of the pressure of fuel Pf is not limited to the above-mentioned case.
For example, only when the engine rotation speed NE is a predetermined

rotation or less, tne estimated value or tne pressure or ruei KT cased on tne pump rotation speed NEP may be computed and the fuel pressure correction factor FPf may be computed by the use of the estimated value of the pressure of fuel Pf. When the engine rotation speed NE is the predetermined rotation speed or more, the estimated value of the pressure of fuel Pf based on the pump rotation speed NEP may be not computed. The computation load of the ECU 50 becomes large in a state in which the engine rotation speed NE is large. However, if the estimated value of the pressure of fuel Pf and the fuel pressure correction factor FPf are not computed, the computation load of the ECU 50 can be reduced.
When the pump rotation speed NEP increases with the startup of the engine 10, the estimated value of the pressure of fuel Pf based on the pump rotation speed NEP may be computed and the fuel pressure correction factor FPf may be computed by the use of the estimated value of the pressure of fuel Pf. When a starter motor is operated at the startup of the engine, the voltage of a battery is lowered and hence sufficient electric power is not supplied to the motor. Moreover, an engine rotation speed does not increase sufficiently at the startup and hence sufficient electric power is not supplied to the motor from a generator. In this manner, when the pump rotation speed NEP is in the process of increase with the startup of the engine 10, the pressure of fuel Pf supplied from the fuel pump module 42 does not become sufficiently large and hence the fuel injection time based on the pressure of fuel Pf needs to be corrected. Thus, if the fuel pressure correction factor FPf is computed by the use of the pressure of fuel Pf when the pump rotation speed NEP increases with the startup of the engine and the final fuel injection time TAU is computed by the use of the fuel pressure correction factor FPf, a fuel injection quantity can be appropriately controlled.
In an engine without a battery, the estimated value of the pressure of fuel Pf based on the pump rotation speed NEP may be computed at the time of startup or

idling and the fuel pressure correction factor FPf may be computed by the use of the estimated value of the pressure of fuel Pf. In the engine without a battery, electric power is supplied to the motor by a generator mounted in a vehicle. When the rotation of the engine 10 is transmitted to the generator mounted in the vehicle, the rotor is rotated to generate electric power. For this reason, when the engine rotation speed NE is small, for example, at the time of startup or idling, the quantity of electric power generated by the generator also becomes small. Thus, also in this case, the pressure of fuel Pf supplied from the fuel pump module 42 becomes small. Hence, if the fuel pressure correction factor FPf is computed by the use of the pressure of fuel Pf and the final fuel injection time TAU is computed by the fuel pressure correction factor FPf in the engine without a battery at the time of startup or idling, a fuel injection quantity can be appropriately controlled.
When the failure of the pressure regulator 44 is detected in the third embodiment, the estimated value of the pressure of fuel Pf may be computed from the pump rotation speed NEP by the use of a plurality of maps in which the relationships different from the relationship shown in FIG. 3 are stored. Specifically, when the pressure regulator abnormality detection flag FPRJDG is set to 1 in step S311, it is stored which condition of step S310 or step S312 has been satisfied. Moreover, a relationship in which the pressure of fuel Pf increases as compared with the relationship shown in FIG. 3 and a relationship in which the pressure of fuel Pf decreases as compared with the relationship shown in FIG. 3 are stored as the maps, respectively.
When the pressure regulator 44 fails so as to make the pressure of fuel Pf larger than the reference fuel pressure PfO (when the condition of step S312 is satisfied), the estimated value of the pressure of fuel Pf is computed from the pump rotation speed NEP by the use of the map of the relationship in which the pressure of fuel Pf increases as compared with the relationship shown in FIG. 3. Moreover, when

the pressure regulator 44 fails so as to make the pressure ot Tuel Pf smaller than the reference fuel pressure PfO (when the condition of step S310 is satisfied), the estimated value of the pressure of fuel Pf is computed from the pump rotation speed NEP by the use of the map of the relationship in which the pressure of fuel Pf decreases as compared with the relationship shown in FIG. 3. In this manner, the estimated value of the pressure of fuel Pf can be brought to an actual pressure of fuel by computing the estimated value of the pressure of fuel Pf by the different map depending on the fact that the pressure regulator 44 fails so as to increase the pressure of fuel or the fact that the pressure regulator 44 fails so as to decrease the pressure of fuel. As a result, a fuel injection quantity can be controlled more properly.
Moreover, the degree of abnormality of the pressure regulator 44 may be detected by more finely classifying the determination of the A/F sensor correction factor FAF of step S310 and step S312. The estimated value of the pressure of fuel Pf may be computed by the use of different map depending on the degree of abnormality of the pressure regulator 44.
In the embodiments described above, the present control system is applied to the two-wheel vehicle engine. However, the application of this control system is not limited to the two-wheel vehicle, but may be applicable to other vehicles. In particular, this control system is applicable to small-size vehicles such as vehicle for agriculture as well as the two-wheel vehicle. With this, also in a vehicle of simple system, a fuel injection quantity can be appropriately controlled by using as small a number of additional units as possible.


What is claimed is:
1. A fuel injection quantity control apparatus of an internal combustion engine
that is applied to a fuel injection system of an internal combustion engine including an
electrically operated fuel pump and a fuel injection valve for injecting fuel discharged
from the fuel pump into the internal combustion engine, the fuel injection quantity
control apparatus comprising:
a computation means for computing a valve opening time of the fuel injection valve according to an operating condition of the internal combustion engine;
a control means for controlling the valve opening time of the fuel injection valve to regulate a fuel injection quantity;
an acquisition means for acquiring a rotation speed of the fuel pump;
an estimation means for estimating a pressure of fuel discharged from the fuel pump to the fuel injection valve by the use of a predetermined pump characteristic on the basis of the rotation speed of the fuel pump; and
a correction means for correcting the valve opening time of the fuel injection valve on the basis of the pressure of fuel estimated by the fuel pressure estimation means.
2. The fuel injection quantity control apparatus of an internal combustion engine
as claimed in claim 1, wherein
the fuel pump is driven by a blushless motor of which rotation speed is controlled by a rotation speed control means for outputting a pulse width modulation signal, and
the acquisition means computes a rotation speed of the fuel pump on the basis of the pulse width modulation signal outputted from the rotation speed control means.

3. The fuel injection quantity control apparatus of an internal combustion engine
as claimed in claim 1 or claim 2, wherein
the correction means corrects the valve opening time of the fuel injection valve when a rotation speed of the fuel pump is smaller than a predetermined rotation speed.
4. The fuel injection quantity control apparatus of an internal combustion engine
as claimed in any one of claims 1 to 3, wherein
the correction means corrects a valve opening time of the fuel injection valve when a rotation speed of the fuel pump increases with startup of the internal combustion engine.
5. The fuel injection quantity control apparatus of an internal combustion engine
as claimed in any one of claims 1 to 4, wherein
the fuel pump is driven by electric power from a generator driven by the internal combustion engine, and
the correction means corrects a valve opening time of the fuel injection valve at the time of startup or idling of the internal combustion engine.
6. The fuel injection quantity control apparatus of an internal combustion engine
as claimed in any one of claims 1 to 5, further comprising:
an abnormality detection means for detecting an abnormality in a fuel supply system for supplying fuel to the fuel injection valve;
an abnormal-time fuel pressure estimation means for estimating the pressure of fuel by the use of a predetermined pump characteristic at the time of abnormality in the fuel supply system on the basis of a rotation speed of the fuel pump acquired by the acquisition means; and

an abnormal-time valve opening time correction means that corrects a valve opening time of the fuel injection valve on the basis of pressure of fuel estimated by the abnormal-time fuel pressure estimation means when an abnormality in the fuel supply system is detected.
7. A fuel injection quantity control apparatus of an internal combustion engine
that is applied to a fuel injection system of an internal combustion engine including an
electrically operated fuel pump and a fuel injection valve for injecting fuel discharged
from the fuel pump into the internal combustion engine, the fuel injection quantity
control apparatus comprising:
a computation means for computing a valve opening time of the fuel injection valve according to an operating condition of the internal combustion engine;
a control means for controlling a valve opening time of the fuel injection valve to regulate a fuel injection quantity;
an acquisition means for acquiring a rotation speed of the fuel pump;
an abnormality detection means for detecting an abnormality in a fuel supply system for supplying fuel to the fuel injection valve;
an abnormal-time fuel pressure estimation means for estimating pressure of fuel at the time of abnormality in the fuel supply system by the use of a predetermined pump characteristic at the time of abnormality in the fuel supply system on the basis of a rotation speed of the fuel pump acquired by the acquisition means; and
an abnormal-time valve opening correction means that corrects a valve opening time of the fuel injection valve on the basis of pressure of fuel estimated by the abnormal-time fuel pressure estimation means when an abnormality in the fuel supply system is detected.
8. The fuel injection quantity control apparatus of an internal combustion engine

as claimed in claim 6 or claim 7, wherein
the abnormality detection means determines an abnormal state of the fuel supply system, and
the abnormal-time fuel pressure estimation means estimates pressure of fuel on the basis of one of a plurality of predetermined pump characteristics at the time of abnormality in the fuel supply system according to an abnormal state of the fuel supply system.
9. The fuel injection quantity control apparatus of an internal combustion engine
as claimed in any one of claims 6 to 8, wherein
the abnormality detection means determines whether the fuel supply system is brought to an abnormal state on a fuel pressure increasing side or is brought to an abnormal state on a fuel pressure decreasing side,
when the fuel supply system is brought to the abnormal state on the fuel pressure increasing side, the abnormal-time valve opening time correction means corrects a valve opening time of the fuel injection valve so as to shorten the valve opening time, and
wherein when the fuel supply system is brought to the abnormal state on the fuel pressure decreasing side, the abnormal-time valve opening time correction means corrects a valve opening time of the fuel injection valve so as to elongate the valve opening time.
10. The fuel injection quantity control apparatus of an internal combustion engine
as claimed in any one of claims 6 to 9, wherein
the fuel injection quantity control apparatus is applied to a fuel injection system of an internal combustion engine provided with a pressure regulator for regulating pressure of fuel discharged from the fuel pump, and

the abnormality detection means detects an abnormality in the pressure regulator.
11. The fuel injection quantity control apparatus of an internal combustion engine
as claimed in any one of claims 1 to 5, further comprising:
a speed detection means for detecting a rotation speed of the internal combustion engine,
wherein when it is detected by the speed detection means that a rotation speed of the internal combustion engine is larger than a predetermined rotation speed, the estimation means stop estimating pressure of fuel and the correction means stops correcting a valve opening time of the fuel injection valve.
12. The fuel injection quantity control apparatus of an internal combustion engine
as claimed in any one of claims 1 to 11, wherein
the fuel injection quantity control apparatus is applied to a fuel injection system of an internal combustion engine mounted in an agricultural vehicle or a two-wheel vehicle.


Documents:

637-CHE-2007 CORRESPONDENCE OTHERS 11-02-2010.pdf

637-CHE-2007 AMANDED CLAIMS 04-02-2010.pdf

637-CHE-2007 AMANDED PAGE OF SPECIFICATION 04-02-2010.pdf

637-CHE-2007 EXAMINATION REPORT REPLY RECIEVED 04-02-2010.pdf

637-che-2007-abstract.pdf

637-che-2007-claims.pdf

637-che-2007-correspondnece-others.pdf

637-che-2007-description(complete).pdf

637-che-2007-drawings.pdf

637-che-2007-form 1.pdf

637-che-2007-form 26.pdf

637-che-2007-form 3.pdf

637-che-2007-form 5.pdf

637-che-2007-form18.pdf


Patent Number 241981
Indian Patent Application Number 637/CHE/2007
PG Journal Number 32/2010
Publication Date 06-Aug-2010
Grant Date 04-Aug-2010
Date of Filing 28-Mar-2007
Name of Patentee DENSO CORPORATION
Applicant Address 1-1,SHOWA-CHO,KARIYA-CITY,AICHI-PREF. 448-8661,JAPAN
Inventors:
# Inventor's Name Inventor's Address
1 KURODA, TAKAHIKO C/O DESO CORPORATION 1-1,SHOWA-CHO,KARIYA-CITY,AICHI-PREF. 448-8661,JAPAN
2 NAGATA,KIYOSHI C/O DENSO CORPORATION 1-1,SHOWA-CHO,KARIYA-CITY,AICHI-PREF. 448-8661,JAPAN
3 OOTAKE ,MASAYA C/O DENSO CORPORATION 1-1,SHOWA-CHO,KARIYA-CITY,AICHI-PREF. 448-8661,JAPAN
PCT International Classification Number F02D47/04
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2006-93079 2006-03-30 Japan