JPH07224708A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a fuel injection control device using a Zener diode in an arc-extinguishing circuit for emitting back electromotive force generated when the exciting of an injector is interrupted, by which a fuel oil consumption error in a low flow region of a fuel in the injector can be prevented by a simple constitution. CONSTITUTION:According to the operating condition of an engine 1, an effective injection pulse width TAUE is calculated, on the basis of the effective injection pulse width TAUE, a correction injection pulse width TH for correcting a fuel coil consumption error is calculated, and according to the voltage BAT of a battery 15, a noneffective injection pulse width TV of an injector 6 is calculated. The final injection pulse width TAU showing the current-carrying time of the injector 6 is calculated by adding the calcualted effective injection pulse width TAUE, correction injection pulse width TH and noneffective injection pulse width TV. Accordingly, even in the device having a Zener diode as an arc-extinguishing circuit, an injection quantity error caused in a very low flow region of a fuel can be corrected always accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an internal combustion engine, which controls the energization time of a solenoid valve (fuel injection valve) for injecting fuel into the internal combustion engine in accordance with the operating state of the internal combustion engine. The present invention relates to a fuel injection control device for an internal combustion engine equipped with a Zener diode as an arc extinguishing circuit that releases a counter electromotive voltage generated when the electromagnetic valve is de-energized by the magnetic energy stored in the electromagnetic valve when energized.

[0002]

2. Description of the Related Art Conventionally, in a fuel injection control device for an internal combustion engine, as a fuel injection valve (injector) for injecting and supplying fuel to the internal combustion engine, the valve body is changed from a closed position to an open position by energizing a solenoid. A switchable solenoid valve is used. In such an injector, there is a response delay between the start of energization of the solenoid and the actual opening of the valve body, so the valve opening time of the valve body is shorter than the energization time of the solenoid. Further, such a valve opening delay of the valve body changes depending on the power supply voltage used for energizing the solenoid, and becomes larger as the power supply voltage is lower.

Therefore, in the conventional fuel injection control device, in order to optimally control the amount of fuel injected and supplied from the injector to the internal combustion engine in accordance with the operating state of the internal combustion engine, the valve element is adjusted in accordance with the operating state of the internal combustion engine. Time to open the valve and actually execute fuel injection from the injector (effective injection time)
Along with the calculation of the power supply voltage, the time during which fuel is not injected from the injector when the solenoid is energized due to the response delay (invalid injection time) is calculated, and the time obtained by adding these effective injection time and invalid injection time is calculated. The driving time is set.

Further, when the injector driving time is set in consideration of the invalid injection time, the amount of fuel injected into the internal combustion engine is relatively large and the effective injection time is longer than the invalid injection time. When it is large, the fuel injection amount can be controlled satisfactorily according to the operating state of the internal combustion engine, but, for example, when the internal combustion engine is operating at low load, the amount of fuel to be injected and supplied to the internal combustion engine is very low In the region, there is a problem that the amount of fuel actually injected and supplied to the internal combustion engine causes an error in the amount of fuel injection due to the magnetic characteristics of the injector.

Therefore, in order to solve such a problem, conventionally, as disclosed in, for example, Japanese Patent Laid-Open No. 61-190146, a correction coefficient for the invalid injection time is obtained based on the effective injection time, and this correction coefficient is calculated. The invalid injection time is multiplied to correct the invalid injection time.

Using a three-dimensional map composed of the effective injection time, the battery voltage, and the invalid injection time, the invalid injection time corresponding to the magnetic characteristics of the injector is directly obtained from the effective injection time and the battery voltage. Therefore, even when the effective injection time is short, it is possible to inject and supply the amount of fuel corresponding to the operating state of the internal combustion engine to the internal combustion engine without being affected by the magnetic characteristics of the injector. There is.

[0007]

However, as described above, the correction coefficient for the invalid injection time is obtained based on the effective injection time, and the invalid injection time is multiplied by this correction coefficient to correct the invalid injection time. In this case, even if the effective injection time is the same, if the invalid injection time set according to the power supply voltage is different, the correction amount of the invalid injection time becomes a different value. That is, for example, when the power supply voltage is low and the invalid injection time is long, the correction amount also becomes large.

Therefore, in the above measures, when the power supply voltage is low and the invalid injection time is set to a large value, the invalid injection time is overcorrected. This problem becomes a serious problem in a device using a Zener diode ZD as shown in FIG. 2 as an arc extinguishing circuit that absorbs a counter electromotive voltage generated when the injector is de-energized. Hereinafter, this problem will be described in detail.

First, conventionally, for driving the injector INJ, as shown in FIGS. 2 and 3, a switching transistor T provided in a current path of the injector INJ.
R is used, and as shown in FIG. 4, by applying a drive pulse having a pulse width corresponding to the fuel injection time calculated from the effective injection time or the invalid injection time to the transistor TR, the injector TR of the injector INJ is applied. The energization time is controlled.

Further, in such a drive circuit, the injector INJ is energized when the transistor TR is turned off and energized.
The back electromotive force is generated by the magnetic energy stored in
The transistor TR may be destroyed by this back electromotive force. Therefore, conventionally, in order to prevent the transistor TR from the back electromotive force, as shown in FIG. 3, the connection point between the transistor TR and the injector INJ has an arc extinguishing circuit (hereinafter, referred to as a resistor R and a capacitor C). It is grounded by a CR circuit), and the counter electromotive voltage generated when the transistor TR is turned off is discharged by this CR circuit so that the connection point voltage is quickly converged to the power supply voltage.

Further, recently, for the purpose of reducing the number of elements of the arc extinguishing circuit, simplifying the circuit structure, and reducing the cost, as shown in FIG. 2, the arc extinguishing circuit is replaced with the CR circuit of FIG. , A Zener diode ZD has been proposed and is being put to practical use. However, as shown in FIG. 4, when the Zener diode ZD is used as the arc extinguishing circuit (hereinafter referred to as the Zener circuit), the maximum voltage when the back electromotive force is generated is higher than that when the Zener diode ZD is used. Since the breakdown voltage of the diode ZD can be limited, the applied voltage to the transistor TR can be made smaller than that in the CR circuit, but the discharge time of the counter electromotive voltage becomes longer and the injector INJ closes after the transistor TR is turned off. (When the valve lift amount shown in the figure becomes 0), the time until the fuel injection actually ends becomes longer.

This is because when the arc extinguishing circuit is composed of a Zener circuit, the anode of the Zener diode ZD is grounded as in the CR circuit.
If a discharge current is made to flow to the Zener diode Z
Since a large current flows through D to destroy the same, the Zener diode ZD is connected between the collector and the base of the transistor TR as shown in FIG.
When the breakdown voltage of the Zener diode ZD is set near the power supply voltage in order to discharge the counter electromotive voltage promptly, the discharge current flows through the transistor for a long time when the counter electromotive voltage occurs, and the transistor becomes longer. This is because the TR may generate heat and be destroyed.

That is, when the arc extinguishing circuit is composed of a Zener circuit, the Zener diode ZD is connected between the collector and the base of the transistor TR so that the breakdown voltage thereof is higher than the power supply voltage and the transistor TR is not destroyed. Since the counter electromotive voltage generated in the injector INJ is discharged via the transistor TR by setting the voltage value of
The discharge time becomes longer, and the time until the fuel injection actually ends after the driving of the transistor TR is stopped by the drive pulse corresponding to the fuel injection time becomes longer.

Further, when the arc extinguishing circuit is constituted by the Zener circuit as described above, the time until the fuel injection is actually ended after the driving of the transistor TR is stopped becomes longer than in the case where the CR circuit is used. Not only that, in the extremely low flow rate range of the fuel, the time greatly changes depending on the fuel flow rate.

That is, the pulse width of the drive pulse for turning on the transistor TR is sufficiently long, and when the transistor TR is turned off while the current flowing through the injector INJ is saturated, the pulse width of the drive pulse is short and the injector INJ is short. When the transistor TR is turned off while the current flowing in the transistor TR is not saturated,
Although the time until the current flowing through the injector INJ becomes “0” after the turn-off is different, the time difference becomes smaller as shown in FIG. 5 when the CR circuit is used for the arc extinguishing circuit. When a Zener circuit is used for the arc circuit, it becomes large as shown in FIG.

Further, the suction force of the valve element in the injector INJ is determined by the number of turns N of the solenoid and the current i (N × i), and changes depending on the current i. Therefore, after the transistor TR is turned off, the current is " In the CR circuit in which the time difference until it becomes "0" is small, the behavior of the valve body (valve lift amount) hardly changes as shown in FIG. 5, but the time difference after the transistor TR is turned off until the current becomes "0" is small. In a large Zener circuit, the behavior of the valve body (valve lift amount) changes greatly as shown in FIG.

Therefore, as shown in FIG. 7, the error of the fuel injection amount with respect to the valve opening time of the injector INJ which occurs in the extremely low flow rate range of the fuel is larger than that when the CR circuit is used as the arc extinguishing circuit. It becomes larger when a Zener circuit is used. Therefore, in the fuel injection control device having the Zener circuit as described above as the arc extinguishing circuit, as described above, the correction coefficient for the invalid injection time is obtained based on the effective injection time, and this correction coefficient is multiplied by the invalid injection time. Therefore, if the error of the fuel injection amount is corrected, the value of the correction coefficient must be set larger than that when the CR circuit is used as the arc extinguishing circuit.

As a result, when the Zener circuit is used for the arc extinguishing circuit, the correction amount changes greatly with respect to the change of the invalid injection time, as compared with the case where the CR circuit is used. Even in a non-problem area, the Zener circuit excessively corrects the invalid injection time, which causes a problem that a control error of the fuel injection amount occurs.

On the other hand, as described above, the effective injection time, the battery voltage, and the invalid injection time are used to directly determine the invalid injection time corresponding to the magnetic characteristics of the injector from the effective injection time and the battery voltage. If the fuel injection amount error in the extremely low flow rate range of the fuel is to be prevented by obtaining it, if the three-dimensional map is set accurately in accordance with the magnetic characteristics of the injector to be used, It is possible to favorably prevent the injection amount control error.

However, in order to realize such measures, 3
A large amount of labor is required to create the three-dimensional map, a large-capacity storage element for storing the three-dimensional map is required, and in addition, during control, interpolation calculation of the invalid injection time obtained from the three-dimensional map is required. Since it takes time, it is necessary to use a high-speed arithmetic device, which increases the cost of the entire device and cannot be easily adopted.

The present invention has been made in view of the above problems, and in a fuel injection control device using the above-mentioned Zener circuit for an arc extinguishing circuit, without using a three-dimensional map, in a low flow rate range of fuel in an injector. The purpose of the present invention is to prevent the fuel injection amount error.

[0022]

SUMMARY OF THE INVENTION The invention according to claim 1 made in order to achieve the above object is, as illustrated in FIG. 1, a solenoid valve which is opened by energization to inject and supply fuel to an internal combustion engine. And a switching element provided in a current path for supplying power from the DC power source to the solenoid valve, and the switching element is turned on according to the operating state of the internal combustion engine.
Based on the power supply voltage of the DC power supply, the effective injection time calculating means for calculating the effective injection time for executing the fuel injection from the electromagnetic valve and the invalid injection in which the fuel is not injected from the electromagnetic valve when the switching element is ON. An invalid injection time calculating means for calculating a time; and a drive time calculating means for calculating a drive time for turning on the switching element and energizing the solenoid valve based on the fuel injection time and the invalid injection time. In a fuel injection control device for an internal combustion engine, a Zener diode is provided as an arc extinguishing circuit for releasing a counter electromotive voltage generated in the current path when the switching element is turned off by the magnetic energy stored in the solenoid valve when energized, The effective injection time calculated by the effective injection time calculating means or a predetermined parameter corresponding to the effective injection time. A correction value calculating means for calculating an injection time correction value for correcting a fuel injection error caused by the magnetic characteristic of the solenoid valve based on a meter, wherein the drive time calculating means has the effective injection time and the invalid injection time. And the injection time correction value are added to calculate the drive time.

According to a second aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the first aspect, the correction value calculation means uses the correction parameter calculation means as a predetermined parameter corresponding to the effective injection time. It is characterized by using a parameter representing the load of the internal combustion engine.

Furthermore, the invention according to claim 3 is the fuel injection control device for an internal combustion engine according to claim 1, wherein the correction value calculating means uses the correction parameter calculation means as a predetermined parameter corresponding to the effective injection time. It is characterized in that a parameter representing the current state when the switching element is OFF is used.

[0025]

As described above, in the fuel injection control device for the internal combustion engine according to the first aspect of the present invention, the current path for supplying power to the solenoid valve for injecting fuel from the direct current power supply to the internal combustion engine. In addition, a switching element for controlling the opening and closing of the solenoid valve is provided, and at the time of turning off the switching element, as an arc extinguishing circuit for releasing the counter electromotive voltage generated by the magnetic energy stored in the solenoid valve,
Zener diode is provided.

Then, the effective injection time calculating means calculates the effective injection time for turning on the switching element to execute the fuel injection from the solenoid valve according to the operating state of the internal combustion engine, and the invalid injection time calculating means Based on the power supply voltage of the DC power supply that supplies power to the solenoid valve, the invalid injection time during which fuel is not injected from the solenoid valve when the switching element is ON is calculated, and the correction value calculation means is calculated by the effective injection time calculation means. An injection time correction value for correcting a fuel injection error caused by the magnetic characteristics of the solenoid valve is calculated based on the effective injection time thus obtained or a predetermined parameter corresponding to the effective injection time. Then, the drive time calculation means adds the effective injection time, the invalid injection time, and the injection time correction value calculated by each of the above calculation means to determine the drive time for turning on the switching element and energizing the solenoid valve. calculate.

That is, in the fuel injection control device having the Zener diode as an arc extinguishing circuit for releasing the counter electromotive voltage generated when the energization of the solenoid valve is interrupted, as in the present invention, the extremely low fuel amount is caused by the magnetic characteristics of the solenoid valve. In order to correct the fuel injection amount error that occurs in the flow rate range, like the conventional device,
If the correction coefficient is calculated and the invalid injection time is multiplied by this correction coefficient, the correction amount changes greatly due to the change of the invalid injection time due to the fluctuation of the power supply voltage. The drive time for energizing may be overcorrected. Therefore, in the present invention, the correction value for correcting the fuel injection amount error is calculated according to the effective injection time as an addition term added to the drive time.

Therefore, according to the present invention, the drive time is always corrected by a constant correction amount corresponding to the effective injection time without being affected by the change of the invalid injection time due to the fluctuation of the power supply voltage. Therefore, the fuel injection amount error that occurs in the extremely low flow rate range of the fuel due to the magnetic characteristics of the solenoid valve can always be accurately corrected.

Further, in the present invention, the injection time correction value is calculated based on the effective injection time or a parameter corresponding to the effective injection time, and this is added to the drive time to correct the fuel injection amount. Therefore, it can be realized without using a three-dimensional map. Therefore, as compared with the conventional device that calculates the invalid injection time using the three-dimensional map, the correction value calculation data can be created more easily and the capacity of the storage element that stores the data can be reduced. Further, since the correction value can be easily calculated, it is not necessary to use a high-speed arithmetic device. Therefore, according to the present invention, the device configuration can be simplified and realized at low cost, as compared with the conventional device using the three-dimensional map.

Here, since the injection time correction value is for preventing the fuel injection amount error that occurs in the low fuel flow rate region, it may be directly calculated from the effective injection time corresponding to the fuel flow rate. However, the effective injection time is usually a parameter indicating the load of the internal combustion engine (the intake air amount Q of the internal combustion engine.
Is divided by the number of revolutions Ne, Q / Ne, the intake pipe pressure P of the internal combustion engine, etc.) is used to obtain a reference time, and this reference time is corrected according to various operating states such as the water temperature and the acceleration state of the internal combustion engine. Therefore, the injection time correction value corresponding to the effective injection time can also be calculated from the load of the internal combustion engine used to calculate the reference time of the effective injection time. Therefore, in the fuel injection control device for the internal combustion engine according to the second aspect, the parameter representing the load of the internal combustion engine is used as the predetermined parameter corresponding to the effective injection time.

Further, the effective injection time is also determined by the value of current supplied to the solenoid valve for injecting fuel into the internal combustion engine. Therefore, in the fuel injection control device for the internal combustion engine according to claim 3, when the switching element provided in the current path for supplying power to the solenoid valve is turned off as a predetermined parameter corresponding to the effective injection time. The parameter indicating the current state of is used.

As described above, also in the fuel injection control device for the internal combustion engine according to the second or third aspect, the same effect as that of the device according to the first aspect can be obtained.

[0033]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 8 is a schematic configuration diagram showing the overall configuration of a fuel injection control device for an internal combustion engine for a vehicle (4-cylinder spark ignition gasoline engine) according to an embodiment of the present invention.

As shown in FIG. 8, an intake pipe 2 and an exhaust pipe 3 are connected to the 4-cylinder spark ignition gasoline engine 1. An air cleaner 4 is provided in the most upstream part of the intake pipe 2, and air is sucked into the intake pipe 2 from the air cleaner 4. A surge tank 5 is installed in the middle of the intake pipe 2.
Is provided. An injector (electromagnetic valve) 6 is arranged in an intake pipe (intake port) of each cylinder of the engine 1. Further, the fuel in the fuel tank 7 is sucked up by the fuel pump 8, supplied to the pressure regulator 10 through the fuel filter 9, regulated by the pressure regulator 10 and returned to the fuel tank 7 again. The fuel whose pressure has been adjusted to this constant pressure is supplied to the injector 6.

The injector 6 is provided in the electronic control unit (ECU) 27 through the drive circuit shown in FIG. 2 provided with the Zener diode ZD as an arc extinguishing circuit.
The valve is opened by receiving power from the battery 15 as a DC power source. Then, by opening the valve, fuel is injected from the injector 6 and mixed with intake air to form an air-fuel mixture, which is supplied to the combustion chamber 12 of each cylinder in the engine 1 via the intake valve 11.

Next, a spark plug 13 is arranged in each combustion chamber 12 of each cylinder of the engine 1. Then, the igniter 14 generates a high voltage from the voltage of the battery 15, and the distributor 16 distributes the high voltage to the spark plug 13 of each cylinder.

Further, a bypass passage 18 is formed so as to bypass the throttle valve 17 provided in the middle of the intake pipe 2, and an idle speed control valve 19 is arranged in the bypass passage 18. When the engine is idle, the engine speed (idle speed) is controlled by adjusting the opening of the idle speed control valve 19.

Next, the intake air temperature sensor 2 is attached to the air cleaner 4.
0 is provided, and the intake air temperature can be detected by the sensor 20. A throttle opening sensor 21 is provided near the position of the throttle valve 17 on the intake pipe 2, and the opening of the throttle valve 17 can be detected by the throttle opening sensor 21. Further, the intake pipe internal pressure sensor 22 can detect the intake pipe internal pressure in the surge tank 5.

On the other hand, the engine 1 is provided with a water temperature sensor 23 for detecting the temperature of the engine cooling water. A cylinder discrimination sensor 24 and a crank angle sensor 25 are arranged in the distributor 16.
The crank angle sensor 25 is provided for each predetermined crank angle (for example, 3
A crank angle signal of 0 ° A is generated. In addition, the cylinder discrimination sensor 24 generates a cylinder discrimination signal for each specific position of a specific cylinder associated with rotation of the crankshaft or camshaft of the engine 1.

Next, an oxygen concentration sensor 26 is provided in the exhaust pipe 3 of the engine 1, and the oxygen concentration sensor 26 is provided.
Thus, the oxygen concentration in the exhaust gas of the engine 1 can be detected. Next, the ECU 27
It is mainly composed of a microcomputer such as an AM. A signal associated with the starter motor drive from the starter switch 28 is input to the ECU 27. Also, E
An intake air temperature sensor 20, a throttle opening sensor 21, an intake pipe pressure sensor 22, a water temperature sensor 23, a cylinder discrimination sensor 24, and a crank angle sensor 25 are connected to the CU 27. Then, the ECU 27 inputs signals from these sensors to detect the intake air temperature, the opening of the throttle valve 17, the intake pipe internal pressure, the engine cooling water temperature, the oxygen concentration in the exhaust gas, and the like.

A battery 15 is connected to the ECU 27, and the ECU 27 detects the voltage of the battery 15 and controls the energization from the battery 15 to the injector 6 via the injector drive circuit described above. The injection control and the ignition timing control for controlling the high voltage generation timing of the igniter 14 through an igniter drive circuit (not shown) are executed. Further, the engine 1 is provided with a starter motor (not shown), and when the starter switch 28 is turned on, the starter motor receives power supply from the battery 15 to start (crank) the engine 1. There is.

Next, referring to FIG. 9 and FIG. 10, the injector 6 is executed in the ECU 27 at every predetermined rotation angle (for example, every 180 ° C.A) of the internal combustion engine for fuel injection control.
6 is a flowchart showing a driving time (ejection pulse width) calculation process of FIG. As shown in FIG. 9, in this drive time calculation process, first in step 110, the crank angle sensor 25
The rotation speed Ne of the engine 1 calculated this time based on the output signal from is determined whether the engine 1 is started or not depending on whether it is lower than a preset start determination speed (400 [rpm] in this embodiment). If the number Ne is equal to or higher than the start determination speed (Ne ≧ 400 [rpm]), it is assumed that the engine 1 has already been started, the process proceeds to step 300, and the effective injection pulse width calculation process after start is executed. Conversely, the rotation speed Ne is less than the start determination speed (Ne <400 [rp
m.]), the process proceeds to step 120.

Then, in step 120, it is determined whether or not the rotation speed Ne of the engine 1 calculated when the relevant processing was executed last time is equal to or higher than the start determination speed (400 [rpm]), and the rotation speed Ne calculated last time. Is less than the start judgment speed (N
If e <400 [rpm]), it is determined that the engine 1 has not been started yet, and the process proceeds to step 140.

On the contrary, if it is determined that the previously calculated rotation speed Ne is equal to or higher than the start determination speed (Ne ≧ 400 [rpm]), the routine proceeds to step 130, where the rotation speed Ne calculated this time is the start determination speed. After the engine 1 is started, it is determined whether the rotation speed Ne has decreased to this determination speed or not, depending on whether the speed is less than the determination speed (200 [rpm] in this embodiment) smaller than the speed. If the rotation speed Ne calculated this time is less than this determination speed (Ne <200 [rpm]), the process proceeds to step 140, and if the rotation speed Ne is at least this determination speed (Ne ≧ 200 [rpm]). Then, the process shifts to step 300 to execute the effective injection pulse width calculation process after the start.

Next, at step 140, the water temperature sensor 2
The temperature of the engine cooling water (water temperature THW) is detected based on the detection signal from No. 3, and in the following step 150, the starting injection pulse width TSTA is determined according to the detected water temperature THW.
To calculate. Then, in the following step 160, the calculated starting injection pulse width TSTA is set as the effective injection pulse width TAUE as the effective injection time.

Incidentally, this step 140 to step 16
The process of 0 is the effective injection pulse width T when the engine 1 is started.
It is a process for calculating the AUE, and together with the effective injection pulse width calculation process after the start performed in step 300,
It corresponds to the effective injection time calculating means of the present invention.

Next, the processing for calculating the effective injection pulse width after the start, which is executed in step 300, is executed as shown in FIG. That is, first, at step 310, the rotational speed Ne of the engine 1 is detected based on the detection signal from the crank angle sensor 25, and at subsequent step 320, the intake pipe internal pressure (suction pressure) is detected based on the detection signal from the intake pipe internal pressure sensor 22. The atmospheric pressure Pm) is detected. And the following step 33
At 0, the variation ΔPm of the intake pressure is calculated from the detected intake pressure Pm and the previously detected intake pressure Pm.

In the following step 340, the intake air temperature THA is obtained based on the detection signal from the intake air temperature sensor 20, in step 350 the engine cooling water temperature THW is obtained based on the detection signal from the water temperature sensor 23, and in step 360,
The opening of the throttle valve 17 (throttle opening TA) is detected based on the detection signal from the throttle opening sensor 21, and the oxygen concentration in the exhaust gas is detected at step 370 based on the detection signal from the oxygen concentration sensor 26.

That is, in steps 310 to 370, various parameters representing the operating state of the engine 1 are detected based on the detection signals from various sensors provided in the engine 1. Then, in the following step 380, a process as a reference time calculating means for calculating the basic injection pulse width Tp as the reference time is executed based on the detected rotational speed Ne and the intake pressure Pm representing the engine load.

Then, in the following step 390, a water temperature correction coefficient FWL for increasing and correcting the amount of fuel for warm-up operation of the engine 1 is calculated according to the detected water temperature THW, and in the next step 400, A post-starting correction coefficient FASE for correcting the increase in the amount of fuel after the engine is started is calculated according to the water temperature THW and the elapsed time after the start.

Further, in the following step 410, the intake air temperature T
An intake air temperature correction coefficient FTHA is calculated according to HA, and in the following step 420, a high value for increasing the amount of fuel to be corrected during high load operation of the internal combustion engine is calculated according to the throttle opening TA, the rotational speed Ne, and the intake pressure Pm. Calculate the load correction factor FOTP.

Next, at step 430, the feedback correction coefficient FA / F for feedback controlling the air-fuel ratio to the target air-fuel ratio is calculated according to the oxygen concentration in the exhaust gas, and at step 440, the intake pressure change amount is calculated. An acceleration correction pulse width TACC for increasing and correcting the fuel amount during acceleration operation of the engine 1 is calculated according to ΔPm.

Finally, at step 450, based on the calculation results at steps 380 to 440, the following equation TAUE = TpFWLFTHA (FASE + TOTP) FA
The processing as the effective injection time determining means for calculating the effective injection pulse width TAUE using / F + TACC is executed.

Thus, step 160 or step 3
At 00, when the effective injection pulse width TAUE at the time of engine start or after engine start is calculated, this time, step 1
Moving to 70, the calculated effective injection pulse width TAU
As an injection time correction value calculating means for calculating a correction injection pulse width TH as an injection time correction value for correcting a fuel injection amount error that occurs in the extremely low flow rate region of fuel due to the magnetic characteristics of the injector 6 based on E Processing is executed, and the process proceeds to the subsequent step 180. The process of step 170 is executed using a map as shown in FIG. 11 for calculating the corrected injection pulse width, which is stored in advance in the ROM constituting the ECU 27.

As shown in FIG. 11, generally, until the first value of the effective injection pulse width (point a in FIG. 11), the corrected injection pulse width becomes shorter as the effective injection pulse width becomes longer. Is set. Then, from the first value to the second value (point b in FIG. 11), the correction injection pulse width is set to be longer as the effective injection pulse width is longer.

This is because the injection is made based on the relationship between the valve opening time of the injector and the injection amount error shown in FIG. 7. Therefore, by setting the correction injection pulse width as described above, the invalid injection is performed. It is possible to suppress an injection amount error caused by a change in time. In order to correct the error more simply, the correction injection pulse width may be set to be shorter as the effective injection pulse width is longer, but in this case, the correction injection pulse width is set as shown in FIG. Since it is not possible to make a negative correction, the accuracy of the error correction is slightly degraded.

Next, at step 180, the battery voltage BAT is detected, and at step 190, the process as the invalid injection time calculating means for calculating the invalid injection pulse width TV according to the detected battery voltage BAT. Run. Finally, in step 200, the corrected injection pulse width TH and the invalid injection pulse width TV are added to the calculated effective injection pulse width TAUE to turn on the transistor TR provided in the drive circuit of the injector 6. , The drive time for energizing the injector 6 is determined by the final injection pulse width TA
U (= TAUE + TH + TV) is calculated, and the process as the drive time calculating means is executed, and the process is once ended.

The final injection pulse width TAU calculated in this way is set in a timer for driving the injector, and the final injection pulse width of the transistor TR in the drive circuit shown in FIG. 2 is set at a preset predetermined timing. Width TAU
Used to turn on for a corresponding time.

As described above, in this embodiment, the effective injection pulse width TAUE as the effective injection time is calculated according to the operating state of the engine 1, and the injector 6 is calculated based on the calculated effective injection pulse width TAUE. The correction injection pulse width TH for correcting the fuel injection amount error that occurs in the extremely low flow rate region of the fuel due to the magnetic characteristics of is calculated, and further, the invalid injection pulse width TV of the injector 6 is calculated according to the battery voltage BAT, By adding the calculated effective injection pulse width TAUE, the corrected injection pulse width TH, and the invalid injection pulse width TV, the final injection pulse width TAU representing the energization time of the injector 6 is calculated.

For this reason, even though the Zener diode is provided in the drive circuit of the injector 6 as an arc extinguishing circuit for discharging the counter electromotive voltage generated when the power supply to the injector 6 is cut off, it is ineffective due to the fluctuation of the power supply voltage. The final injection pulse width TAU can always be corrected with a constant correction amount corresponding to the effective injection time without being affected by changes in the injection time, and the magnetic characteristics of the injector 6 allow the fuel to be injected in an extremely low flow rate range. The fuel injection amount error that occurs can always be corrected accurately.

Further, the correction injection pulse width TH is calculated by using the map as shown in FIG. 11 in which the effective injection pulse width TAUE is used as a parameter, and therefore, the correction injection pulse width TH is calculated as compared with the conventional apparatus which calculates the invalid injection time by using the three-dimensional map. Thus, the calculation data can be easily created, and the storage capacity of the ROM for storing the created map can be reduced. Further, the correction injection pulse width TH can be calculated more easily than in the case where a three-dimensional map is used, so that it is not necessary to use a high-speed CPU for arithmetic processing. Therefore, according to the present embodiment, the device structure can be simplified and the cost can be reduced as compared with the conventional device using the three-dimensional map.

In this embodiment, in calculating the effective injection pulse width TAUE after starting, the intake pressure Pm is detected as the engine load, and the basic injection is performed from the detected intake pressure Pm and the engine speed Ne of the engine 1. Although the so-called D-j type fuel injection control device for calculating the pulse width Tp has been described, the present invention has replaced the intake pressure Pm with the flow rate of intake air sucked into the intake pipe 2 (intake air amount Q). Is detected, the engine load Q / Ne is obtained from the detected intake air amount Q and the rotational speed Ne of the engine 1, and the basic injection pulse width Tp is calculated based on this engine load. It goes without saying that it can be applied to a control device.

Further, in this embodiment, the corrected injection pulse width T
Although H is configured to be calculated based on the effective injection pulse width TAUE calculated according to the operating state of the engine 1, the corrected injection pulse width TH is used to prevent the fuel injection amount error that occurs in the low fuel flow rate region. Since it suffices to calculate using a parameter corresponding to the effective injection pulse width TAUE representing the fuel flow rate, for example, the corrected injection pulse width TH is based on the basic injection pulse width Tp which is the reference value of the effective injection pulse width TAUE. May be calculated, and further, the engine load which is a reference value used for calculating the basic injection pulse width Tp (in the case of the Dj type device as in this embodiment, the intake pressures Pm, Lj In the case of the apparatus of the system, the corrected injection pulse width TH may be calculated using Q / Ne) obtained by dividing the intake air amount Q by the rotation speed Ne.

Similarly, the effective injection pulse width TAUE is shown in FIG.
Since it can be estimated by the current state at the time when the power supply to the injector 6 is turned off as shown in, the corrected injection pulse width TH may be obtained from this current state.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is an electric circuit diagram showing a drive circuit of an injector provided with a Zener diode as an arc extinguishing circuit.

FIG. 3 is an electric circuit diagram showing a drive circuit of an injector including a CR circuit including a capacitor and a resistor as an arc extinguishing circuit.

FIG. 4 is an explanatory diagram showing a behavior of an injector when a drive pulse is applied to a transistor for driving the injector.

FIG. 5 is an explanatory diagram illustrating the behavior of the injector after energization interruption when a CR circuit is used as an arc extinguishing circuit.

FIG. 6 is an explanatory diagram for explaining the behavior of the injector after the interruption of energization when a Zener diode is used as an arc extinguishing circuit.

FIG. 7 is an explanatory diagram showing an error in a fuel injection amount that occurs in an extremely low fuel flow rate region.

FIG. 8 is a schematic configuration diagram showing an overall configuration of a fuel injection control device for an internal combustion engine for a vehicle according to an embodiment.

FIG. 9 is a flowchart showing an injection pulse width calculation process executed for fuel injection control in an ECU.

FIG. 10 is a flowchart showing an effective injection pulse width calculation process after the engine is started.

FIG. 11 is an explanatory diagram showing a map used to calculate a corrected injection pulse width in the example.

[Explanation of symbols]

1 ... Engine 6, INJ ... Injector (solenoid valve)
TR ... Transistor R ... Resistor C ... Capacitor ZD ... Zener diode 15 ... Battery (DC power supply) 22 ... Intake pipe pressure sensor 25 ... Crank angle sensor 27 ... Electronic control unit (EC
U)

Front page continued (72) Inventor Hideto Takeda 1-1, Showa-cho, Kariya, Aichi Prefecture, Nihon Denso Co., Ltd. (72) Innovator Nobuo Ota 1-1-1-1, Showa-cho, Kariya, Aichi Nihon Denso Co., Ltd. (72) Inventor Keisuke Takeda 1 Toyota-cho, Toyota-cho, Aichi Prefecture Toyota Automobile Co., Ltd. (72) Inventor Kenji Okubo 1 Toyota-cho, Toyota-shi, Aichi Toyota Automobile Co., Ltd.

Claims (3)

[Claims] 1. An electromagnetic valve which is opened by energization to inject fuel to an internal combustion engine, a switching element provided in a current path for supplying power to the electromagnetic valve from a DC power source, and an operation of the internal combustion engine Depending on the state, effective injection time calculating means for calculating the effective injection time for turning on the switching element to execute fuel injection from the solenoid valve; and, based on the power supply voltage of the DC power supply, turning on the switching element. Based on the invalid injection time calculating means for calculating the invalid injection time in which fuel is not injected from the solenoid valve, and the drive time for turning on the switching element to energize the solenoid valve based on the fuel injection time and the invalid injection time. In a fuel injection control device for an internal combustion engine, the drive time calculating means for The Zener diode is provided as an arc extinguishing circuit that discharges the counter electromotive voltage generated in the current path when the switching element is turned off, and the effective injection time calculated by the effective injection time calculating means or corresponding to the effective injection time is provided. Comprising a correction value calculation means for calculating an injection time correction value for correcting a fuel injection error caused by the magnetic characteristic of the solenoid valve based on a predetermined parameter, wherein the drive time calculation means comprises the effective injection time and the invalid time. A fuel injection control device for an internal combustion engine, wherein the drive time is calculated by adding an injection time and the injection time correction value. 2. The internal combustion engine according to claim 1, wherein the correction value calculation means uses a parameter representing a load of the internal combustion engine as a predetermined parameter corresponding to the effective injection time. Fuel injection control device. 3. The correction value calculation means uses a parameter representing a current state when the switching element is OFF as a predetermined parameter corresponding to the effective injection time. Fuel injection control device for internal combustion engine.