Title of Invention

A FLOW RATE CONTROLLING DEVICE FOR AN INTERNAL COMBUSTION ENGINE

Abstract ABSTRACT A FLOW RATE CONTROLLING DEVICE FOR AN INTERNAL COMBUSTION ENGINE The present invention provides a flow rate controlling device for an internal combustion engine, comprising; a flow rate computing means for computing a flow rate of fluid to be supplied to an internal combustion engine a driving signal generating means for generating a driving signal having a duty ratio corresponding to the flow rale thus computed; a frequency changing means for changing the frequency of said driving signal in accordance with the duty ratio of said driving signal; and a flow rate control valve which is driven in accordance with the driving signal outputted from said frequency changing means.
Full Text

FLOW RATE CONTROLLING DEVICE FOR INTERNAL COMBUSTION ENGINE
BACKGROUND OF THE INVENTION
The present invention relates to a flow rate controlling device for controlling the flow rate of fluid to be supplied to an internal combustion engine.
Such a kind of previously known device is disclosed in e.g. Postexamined Japanese Patent Publn. No. 61-6263. This device determines the duty ratio in accordance with the flow rate of fluid to be supplied to the internal combustion engine and drives a plunger of the flow rate control valve by the driving signal having this duty ratio.
Meanwhile, in the conventional device, the frequency of the driving signal is selected so that the plunger always pulsates. This intends to prevent deposits (dust particles) contained in the fluid from being applied to the interior of the flow rate control valve to increase friction resistance so that the shift of the plunger is hindered.
The frequency of the driving signal is set to provide a shorter period than the time required for the plunger to make its entire travel, and so set at the value giving slight ripple to the driving signal supplied to the flow rate control valve.
However, the frequency of the driving signal has been controlled always at the same value irrespectively of the duty ratio of the driving signal.

For example, where the plunger is being driven by the driving signal having the high duty ratio or the low duty ratio, the plunger has be forced to either ON or OFF condition during the most range in one period of the driving signal. In this state, the plunger does not almost move. Therefore, the friction resistance due to the deposits applied to the sliding surface of the plunger may hinder the movement of the plunger. When the application of the deposits is severe, the plunger may be fixed.
For this reason, the frequency of the driving signal must be lowered to increase the current ripple of the driving signal applied to the flow rate control valve, thereby causing the plunger to pulsate.
On the other hand, when the plunger is driven by a driving signal with an intermediate duty ratio in the vicinity of 50%, the plunger repeats an on/off operation half-and-half during the one period of the driving signal so that it pulsates sufficiently.
Therefore, if the driving frequency is set at a low value in order to assure the pulsation of the plunger, this time, the plunger will pulsate excessively at the intermediate duty ratio. As a result, the vibration and pressure pulsation of the fluid to be controlled increases so that the good control performance cannot be obtained.
Therefore, in the conventional device, the driving frequency has been decided by trade-off between such contradicting characteristics.

Summary of the Invention
The present invention has been accomplished to solve the above problem, and intends to make the contradicting characteristics compatible and improve the freedom of design,
The present invention provides an apparatus for controlling the flow rate of an internal combustion engine which does not hinder the operation of the plunger of a flow rate control valve and has an improved performance.
The flow rate controlling device for an internal combustion engine according to the present invention comprises: a flow rate computing means for computing a flow rate of fluid to be supplied to an internal combustion engine; a driving signal generating means for generating a driving signal having a duty ratio corresponding to the flow rate thus computed; a frequency changing means for changing the frequency of said driving signal in accordance with the duty ratio of said driving signal; and a flow rate control valve which is driven in accordance with the driving signal outputted from said frequency changing means.
In the flow rate control device for an internal combustion engine according to the present invention, said frequency changing means increases the frequency of said driving means as the duty ratio approaches an intermediate value.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is an arrangement view showing the schematic arrangement of the first embodiment;

Fig. 2 is a sectional view showing the schematic configuration of a flow rate control valve;
Fig. 3 is a block diagram showing the control operation in the first embodiment;
Fig. 4 is a flow rate characteristic graph for the duty ratio of the flow rate control valve;
Fig. 5 is a conversion table for determining the frequency of a driving signal;
Fig. 6 is a timing chart showing the operation of a conventional device; and
Fig. 7 is a timing chart showing the operation of the first embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1
Fig. 1 is an arrangement view showing the schematic arrangement of the first embodiment. In Fig. 1, reference numeral 1 denotes an internal combustion engine for generating power by combustion a mixture gas of fuel and air; 2, an air cleaner for cleaning the air to be absorbed by the internal combustion engine; 3, an air flow sensor serving as an intake quantity detecting means for detecting the air intake quantity to be taken into the internal combustion; 4, a throttle valve engaged with an accelerator pedal (not shown) operated by a driver; 5, an idle speed control valve (hereinafter referred to as "ISCV") which is provided in the air intake passage bypassing the throttle valve 4 and serves as a flow rate control valve for adjusting the idle rotary

speed by adjustment of the air intake quantity when the internal combustion engine is in an idle state; 6, an air intake tube for introducing the intake air into the internal combustion engine; 7, an exhaust tube for exhausting the exhaust gas exhausted from the internal combustion engine; 8, an ternary catalyst which is provided in the exhaust tube 7 and serves to clean HC, CO and Nox contained in the exhaust gas when the internal combustion engine 1 is controlled in proximity to a theoretical air/fuel rate; 9, an injector for injecting fuel into the internal combustion engine 1; 10, a water temperature sensor serving as a temperature detecting means for detecting the temperature of the cooled water in the internal combustion engine; 11, an oxygen sensor which is provided in the exhaust tube 7 and serves as an air/fuel rate detecting means for detecting the oxygen concentration of the exhaust gas (the fuel quantity supplied from the injector 9 is adjusted on the basis of the detection output from the oxygen sensor 11 so that the air/fuel rate of the mixed air supplied is controlled to the internal combustion engine 1 to a desired value, e.g. theoretical air/fuel ratio); 12, a fuel tank for storing fuel to be supplied to the internal combustion engine; 13, a fuel pump for supplying the fuel to the injector 9; 14, canister for storing vapor gas evaporated from the fuel tank 9; 15, a purge control valve (hereinafter referred to as "PCV") which is served as a flow rate control valve for introducing the vapor gas stored in the canister 14 into the air intake tube and adjusting the introduced

quantity; and 16, a control unit for executing several kinds of controls such as air/fuel ratio controlling, firing timing control, idle rotary speed control and purged quantity control, etc. The control unit 16 receives an intake air signal SI from the air flow sensor 3, water temperature signal S2 from the sensor 10, an air/fuel rate signal S3 from the oxygen sensor 11 and produces an driving signal S4 for the ISCV 5, a driving signal 55 for the injector 9 and an driving signal S6 for PCV.
Fig. 2 is a sectional view showing the schematic diagram a flow rate control valve such as ISCV 5 or PCV 15. In Fig. 2, reference numeral 21 denotes a valve serving as a valve body; 22 a valve sheet which abuts on the valve 21 when the flow rate control valve is in a completely closed state and closes the flowing passage of fluid in cooperation with the valve 21; 23 a plunger which is secured to the valve 21 and slides in a horizontal direction shown; 24 a spring for urging the plunger 23 leftward as shown; and 25 a coil for generating electromagnetic force in response to a driving signal.
In the flow rate control valve, when a current is supplied to the coil 25, electromagnetic force is generated so that the plunger 2 3 slides rightwards against the urging force of the spring 24. Thus, the area of the flowing passage between the valve 21 and valve sheet 22 increases. Accordingly, the fluid flows as an arrow as shown. On the other hand, when the current to the coil 2 5 is interrupted.

the electromagnetic force disappears, the plunger 23 slides leftwards as shown by the urging force of the spring 24. Then, the valve 21 abuts on the valve sheet 22 to make the flowing passage zero.
Namely, this flow rate control valve is so designed that the current supply by the driving signal shifts the plunger 23 so as to open the valve, and current interruption by the driving signal shifts the plunger 23 to close the valve. The frequency of the driving signal is set so that its one period is shorter than the time required for the plunger 23 make its entire travel. Therefore, on the basis of the rate of the time of current supply to the one period of the driving signal, i.e. duty ratio of the driving signal, the opening rate of the valve is controlled and the flow rate of the fluid is controlled.
The control operation of the first embodiment will be explained in connection with the control of the idle rotary speed.
Fig. 3 is a block diagram showing the control operation of the first embodiment. Although the control unit 16 makes the other controls than shown in this figure as described above, they are not shown here.
When an idle switch (not shown) or a no-load switch operates to detect the idle state while the internal combustion engine 1 is running, the idle rotary speed control is executed so that the idle rotary speed is fixed. The control of the idle rotary speed is carried out in a manner

of controlling the intake air quantity flowing into the internal combustion engine 1 through ISCV 5 when the throttle valve 4 is completely closed.
The control unit 16 computes the air quantity Q necessary to control a target rotary speed from the following equation (1) when the internal combustion engine 1 is in the idle state. This computation will be carried out by a flow rate computing means 31.
Q = Ql + Q2 + Q3 .••(!)
Here, Ql represents a basic intake air quantity necessary to maintain the speed of the internal combustion engine 1 in the idle state at the target speed. This quantity is previously stored in a read-only-memory (hereinafter referred to as "ROM"). Q2 represents a load correction quantity when the load such as a "head light", "rear defogger switch" or air conditioner switch is turned on, which corresponds to the load detected when these switches turn on. Q3 represents a feedback correction quantity which corresponds to a difference between the target rotary speed and the actual rotary speed detected by a crank angle sensor.
The necessary air quantity Q computed by the flow rate control means 31 is given to a driving signal generating means 32 at a next stage where it is converted into a driving signal having a duty signal corresponding to the necessary intake air quantity Q.
This conversion is carried out by the following Equation (2).

T = fT(Q) X TX ... (2)
Here, fT(Q) represents a basic duty ratio which is set by interpolation reference using a conversion table storing the flow rate characteristic for the duty ratio in the ISCV only previously measured. This flow rate characteristic is shown in Fig. 4. TX represents correction quantities inclusive of the voltage correction for a battery voltage, water temperature correction based on cooled water temperature, and coil temperature correction based on the coil temperature in ISCV 5.
Therefore, by referring to the conversion table and interpolation computing, the necessary intake air Q computed by the flow rate computing means 31 is converted into the basic duty ratio fT(Q). This ratio is multiplied by the correction quantity TX to provide a driving signal having the output duty ratio T.
The driving signal generated by the driving signal generating means 32 is sent to a frequency changing means 33 which changes the signal frequency according to the output duty ratio T.
The frequency changing means 33 determines the driving frequency fF{T) on the basis of the output duty ratio T by the interpolation computation referring to the conversion table stored in a storage means 34. The conversion table stored in the storage means 34 is as shown in Fig. 5. Fig. 5 is a conversion table for determining the driving frequency

f(T) in which it is set to be higher as the output duty ratio approaches an intermediate value, e.g. 50%.
The driving signal with the output duty ratio and frequency thus determined are supplied to drive the flow rate control valve such as ISCV 5 or PCV 15.
Comparison will be made between the first embodiment and the conventional device.
Figs. 6A and 6B are timing charts showing the operation of the conventional device. In the ISCV 5 used, the response time for complete open or close used is 5 ms, and the driving frequency is fixed at 250 Hz (corresponding to the period 4 ms shorter than the response time of 5 ms). Of the figure. Fig. 6A shows the case when the output duty ratio is 2 0%, and Fig. 6B shows the case where the output duty ratio is 50%. Likewise, Figs. 7A and 7B are timing charts showing the operation of the first embodiment in which the driving frequency has been changed according to the output duty ratio. Of the figure. Fig. 7A shows the case where the output duty ratio is 20% and Fig. 7B shows the case where it is 50%.
Incidentally, the output duty ratio of 20% represents, for example, the case where the engine is idle and no load is energized, and that of 50% represents, for example, the case where the engine is idle and the load such as an air conditioner is energized.
In the first embodiment, when the output duty ratio of ISCV 5 is 20%, the frequency of the driving signal is 240 Hz

from the conversion table of Fig. 5. This value is lower than that in the conventional device. For this reason, the time of the one period and the current ripple are larger in Fig. 7A than in Fig. 6A. Thus, the pulsation of the plunger 23 increases so that application of deposits does not hinder the movement of the plunger 23.
Where the output duty ratio is low, ISCV 5 is off during almost all the period of the driving signal. Therefore, this also means less pulsation of the fluid. For this reason, no problem occurs even when the pulsation of the plunger 23 is increased slightly in order to improve the operation of the plunger 23.
Now it is assumed that owing to poor adjustment of an idle adjust screw (not shown) for adjusting the bypass intake air quantity in the idle state, the plunger has been driven at the output duty ratio of 15% in the ISVC 5 in the idle state. In this case, as seen from Fig. 4, ISCV 5 is in an insensitive range and is at a completely closed position in the flow rate. In this state, the plunger 23 is most likely to fix. However, in accordance with the first embodiment, since the driving signal is given at the frequency of 230 Hz with the duty ratio of 15%, the plunger 23 pulsates sufficiently by the current ripple generated by the above driving signal so that it will not fix.
Meanwhile, when the output duty ratio is high (e.g. 80%), the output duty ratio of 80% leads to 240 Hz from the

conversion table of Fig. 5. The operation in this case is similar to the case of the duty ratio of 20%.
Where the output duty ratio is high, ISCV 5 is ON in the most part in the period of the driving signal. In this case also, the pulsation of the fluid is little.
Like where the output duty ratio is low, increasing the pulsation of the plunger 23 slightly in order to improve the operation of the plunger 23 does not provide any actual problem.
Further, also where the output duty ratio exceeds 80% so as to place ISCV 5 at the completely open position in the flow rate in Fig. 4, the ISCV operates in the same manner as the case where the output duty ratio is 15% or less, thereby preventing the plunger 23 from being fixed.
Comparison will be made between the above cases and the case where the output duty ratio is an intermediate value.
In the first embodiment, when the output duty ratio of ISCV 5 is determined 50%, the frequency is set at 300 Hz from the conversion table of Fig. 5. This frequency is higher than that in the conventional device. Therefore, the time of the one period and the current ripple are smaller in Fig. 7B than in Fig. 6B. This makes the pulsation of the plunger 23 small so that the vibration and pressure pulsation of fluid and pressure pulsation does not become excessively large.
Incidentally, where the duty ratio is in proximity to the intermediate value, ISVC 5 is ON and OFF during substantially the half periods of the driving period, respectively. For

this reason, even the pulsation of the plunger 23 is reduced slightly, the plunger 23 pulsates sufficiently so that the movement of the plunger 23 will not be hindered by the application of deposits.
In accordance with the first embodiment, by changing the frequency of the driving signal, contradicting characteristics can be made compatible. In addition, the frequency of the driving signal can be set freely to improve the freedom of design.
When the duty ratio is a high or low value, the driving signal is set at a low frequency, and as the duty ratio approaches an intermediate value, the driving signal is set at a high frequency. For this reason, the operation of the plunger is not hindered, thereby providing an improved control performance.
In the first embodiment, the ISCV 5 was driven at the output duty ratio and frequency which was computed by the microcomputer in the control unit 16. But, without computing the correction amount TX by the control unit 16, the correction for changes in the battery voltage and coil resistance due to the change in the coil temperature can be realized in a circuit of hardware.
In this case also, the correction amount by the circuit of hardware is estimated to provide the driving frequency corresponding to the duty ratio. This can provide the same effects as the first embodiment.

In the first embodiment, the concept of the present invention has been applied to ISCV 5, but it can be equally applied to the PCV 15.
In this case, fixing of the PCV 15 can be prevented and the purging flow rate can be controlled accurately, thereby suppressing a change in the air/fuel ratio.
In the first embodiment, the present invention can be explained in connection with the electromagnetic valve which is operated by electromagnetic force, but can be also applied to a hydraulic flow rate control valve which controls duty ratio using pressurized oil.
The first embodiment of the present invention described above is only an embodiment of the present invention, and can be realized in its various modifications within a scope of the spirit of the present invention.
The flow rate controlling device for an internal combustion engine according to the present invention comprises: a driving signal generating means for generating a driving signal having a duty ratio corresponding to a computed flow rate; and a frequency changing means for changing the frequency of said driving signal in accordance with the duty ratio of said driving signal, thereby improving the freedom of design.
In accordance with the flow rate control device for an internal combustion engine according to the present invention, the frequency of the driving signal is increased as the duty ratio approaches an intermediate ratio. For this

reason, the operation of the plunger is not hindered, thereby providing an improved control performance.


WE CLAIM :
1. A flow rate controlling device for an internal combustion ,
comprising a flow rate computing means for computing a flow rate of
fluid to be supplied to an internal combustion engine; a driving signal
generating means for generating a driving signal having a duty ratio
corresponding to the flow rate thus computed; a frequency changing
means for changing the frequency of said driving signal in accordance
with the duty ratio of said driving signal; and a flow rate control valve
which is driven in accordance with the driving signal outputted from said
frequency changing means.
2. The flow rate control device as claimed in claim 1, wherein said
frequency changing means increases the frequency of said driving means
as the duty ratio approaches an intermediate value.
3. The flow rate control device as claimed in claim 1, wherein said fluid to
be supplied to the internal combustion engine is a gaseous body.
4. The flow rate control device as claimed in claim 1, further comprising a
storage means for storing a conversion table which represents a
correspondence of the frequency of the driving signal and the duty ratio.
5. A flow rate controlling device for an internal combustion engine,
substantially as herein described with reference to the accompanying
drawings.


Documents:

2679-mas-1997 abstract duplicate.pdf

2679-mas-1997 abstract.pdf

2679-mas-1997 claims duplicate.pdf

2679-mas-1997 claims.pdf

2679-mas-1997 correspondence others.pdf

2679-mas-1997 correspondence po.pdf

2679-mas-1997 description (complete) duplicate.pdf

2679-mas-1997 description (complete).pdf

2679-mas-1997 drawings duplicate.pdf

2679-mas-1997 drawings.pdf

2679-mas-1997 form-1.pdf

2679-mas-1997 form-19.pdf

2679-mas-1997 form-26.pdf

2679-mas-1997 form-4.pdf


Patent Number 196406
Indian Patent Application Number 2679/MAS/1997
PG Journal Number 30/2009
Publication Date 24-Jul-2009
Grant Date
Date of Filing 24-Nov-1997
Name of Patentee MITSUBISHI DENKI KABUSHIKI KAISHA
Applicant Address 2-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO
Inventors:
# Inventor's Name Inventor's Address
1 TATSUHIKO TAKAHASHI C/O MITSUBISHI ELECTRIC CONTROL SOFTWARE CO., LTD., 1-2, HAMAYAMADORI 6-CHOME, HYOGO-KU, KOBE-SHI, HYOGO
2 TAKAHIKO OONO C/O MITSUBISHI ELECTRIC CONTROL SOFTWARE CO., LTD., 1-2, HAMAYAMADORI 6-CHOME, HYOGO-KU, KOBE-SHI, HYOGO
3 TERUHIKO MORIGUCHI C/O MITSUBISHI ELECTRIC ENGINEERING CO., LTD., 6-2, OTEMACHI 2-CHOME, CHIYODA-KU, TOKYO
PCT International Classification Number F02D41/08
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA