JPH0794813B2 - Fuel injection amount and ignition timing control method for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection amount control method and an ignition timing control method for an internal combustion engine, and more particularly, when ignition timing is retarded when knocking occurs and no knocking occurs. The present invention relates to a fuel injection amount and an ignition timing control method for an internal combustion engine, in which the ignition timing is corrected based on a correction retard amount for advancing the ignition timing, and the fuel injection amount is controlled according to an engine load and an engine rotation speed. .

[Conventional technology]

Conventionally, the basic fuel injection time (Q / λ · N, where λ is the target air-fuel ratio) is calculated based on the intake air amount Q detected by the air flow meter and the engine rotation speed N, and this basic fuel injection time is calculated. 2. Description of the Related Art There is known an internal combustion engine in which a fuel injection time is obtained by making a correction according to an intake air temperature, an engine cooling water temperature, etc., and a fuel injection valve is opened for a time corresponding to this fuel injection time to control a fuel injection amount. In this internal combustion engine, the basic ignition advance angle is calculated based on the intake air amount per engine revolution and the engine rotation speed, and the ignition timing is retarded when knocking occurs and the ignition timing when no knocking occurs. Is calculated, and the ignition timing is controlled on the basis of the basic ignition advance amount and the corrected retard amount.

[Problems to be solved by the invention]

However, since the basic fuel injection time and the basic ignition advance angle are calculated based on the detected value of the intake air amount obtained from the air flow meter output, the output characteristics of the air flow meter may change due to manufacturing errors, changes over time, weather conditions, etc. Fluctuates,
If the air flow meter output does not correspond to the actual intake air amount, the air-fuel ratio will become over-lit or over-lean and the ignition timing will be controlled to the advanced side or the retarded side, which will cause a decrease in output or knocking. was there. That is, as shown in FIG. 2 (1), when the air flow meter output changes largely (upper limit value characteristic) or smaller (lower limit value characteristic) with respect to the median value characteristic indicating the actual intake air amount, the case of the upper limit value characteristic Since the detected value of the intake air amount becomes larger than the actual intake air amount, the fuel injection amount with respect to the actual intake air amount increases, resulting in an air-fuel ratio latch as shown in FIG. 2 (2). On the other hand, when the air flow meter output shows the lower limit characteristic, the value detected by the air flow meter becomes smaller than the actual intake air amount, so the fuel injection amount with respect to the actual intake air amount decreases, and as shown in FIG. 2 (2). The air-fuel ratio becomes lean. Further, when the air flow meter output shows the upper limit value characteristic, the ignition timing is controlled to the delay side as shown in FIG. 2 (3), and when the air flow meter output shows the lower limit value characteristic, FIG. As shown in (), the ignition timing is controlled to the advanced side. Therefore, the engine torque is shown in Fig. 2 (4).
When the air flow meter output shows the upper limit value characteristic, the air-fuel ratio becomes over-lit and the ignition timing becomes excessively retarded, resulting in a drastic output reduction. On the other hand, when the output of the air flow meter exhibits the lower limit value characteristic, the air-fuel ratio becomes over lean and the ignition timing becomes excessively advanced, resulting in excessive knocking.

The present invention has been made to solve the above-mentioned problems, and it is possible to obtain a detected value of an engine load (intake air amount, intake pipe pressure, intake air amount per engine revolution, etc.) that determines a fuel injection amount and an ignition timing. A method for controlling the fuel injection amount and ignition timing of an internal combustion engine that prevents the air-fuel ratio from becoming over-rich or over-lean even when the actual value is no longer displayed, and prevents the ignition timing from becoming over-advanced or over-retarded The purpose is to do.

As a technique related to the present invention, there is one disclosed in Japanese Patent Laid-Open No. 32968/1983 which corrects the output of the air flow meter by the value of the air / fuel ratio feedback back coefficient.

[Means for Solving the Problems] In order to achieve the above object, the present invention controls the fuel injection amount and the ignition timing based on the detected value of the engine load and the detected value of the engine rotation speed, and at the same time, causes knocking. A fuel injection amount and an ignition timing control method for an internal combustion engine, wherein the ignition timing is retarded when the ignition timing is generated and the ignition timing is corrected by a correction retard amount that advances the ignition timing when no knocking occurs. The detected value of the engine load is corrected according to the magnitude of

[Action]

According to the present invention, the detected value of the engine load is corrected based on the value of the correction retard amount that retards the ignition timing when the knocking occurs and advances the ignition timing when the knocking does not occur. That is, when the detected value of the engine load that determines the fuel injection amount is different from the actual value, the ignition timing is controlled to the advance side or the retard side as described with reference to FIG. , The over-advanced value of the ignition timing caused by the difference between the detected value and the actual value is determined by the correction retardation amount,
The detection of the engine load is corrected based on this determination result. By correcting the detected value of the engine load in this way, the corrected detected value becomes equal to the actual engine load, and the fluctuations of the basic fuel injection time and the basic ignition advance due to the fluctuations of the detected value are prevented. This prevents fuel ratio over-litch, over lean, and ignition timing over-advance and over-retard.

Here, when the detected value of the engine load is larger than the actual value, the ignition timing is controlled to the retard side, and the frequency of occurrence of knocking is reduced. Conversely, when the detected value is smaller than the actual value, Since the ignition timing is controlled to the advance side and the frequency of knocking increases and the correction retard amount changes according to the deviation of the detection value, the engine load is detected when the correction retard amount is equal to or greater than the first set value. The correction value is corrected so as to increase, and when the correction delay amount is less than or equal to the second setting value that is smaller than the first setting value, the detection value of the engine load is corrected to decrease, and the correction delay amount is set to the first setting value. It is preferable not to change the engine load detection value when it is between the set value and the second set value.

〔The invention's effect〕

As described above, according to the present invention, the air-fuel ratio over-litch and over lean due to the change in the detected value of the engine load due to the characteristic change of the sensor and the over-advancement and over-retardation of the ignition timing are prevented. It is possible to prevent the engine output from decreasing and the knocking from occurring due to the fluctuation of the detection value of 1.

Example of Invention

Embodiments of the present invention will be described in detail below with reference to the drawings.
FIG. 3 shows an example of an internal combustion engine (engine) including an ignition timing control device and a fuel injection amount control device to which the present invention can be applied. The four-cycle six-cylinder gasoline engine 10 has a distributor 14 which includes a cylinder discriminating sensor 16 and a rotation angle sensor 18 each of which is composed of a signal rotor fixed to the distributor shaft and a pick-up fixed to the distributor housing. Is installed. The cylinder discrimination sensor 16 generates one pulse each time the distributor controller is rotated, that is, every two rotations of the crankshaft (every 720 ° CA). The position where this pulse is generated is, for example, the top dead center (TDC) of the first cylinder.
Is. The rotation angle sensor 18 generates, for example, 24 pulses for each revolution of the distributor system, and thus one pulse for every 30 ° CA. The cylinder discrimination sensor 16 and the rotation angle sensor 18 are connected to a control circuit 20 composed of a microcomputer or the like, and an electric signal generated by each sensor is input to the control circuit 20. Further, the control circuit 20 is supplied with an intake air amount signal from an air flow meter 24 mounted on the upstream side of the throttle valve 25 in the intake passage 22 and having an intake air temperature sensor. Although not shown, the intake air temperature signal is also input. A cylinder block of the engine 10 is provided with a knocking sensor 12 including a magnetostrictive element for detecting engine vibration, and an electric signal output from the knocking sensor 12 is input to the control circuit 20. . Further, an engine cooling water temperature sensor 30 is attached so as to penetrate through the cylinder block and project into the water jacket. On the other hand, the control circuit 20 outputs an ignition signal to the igniter 26, the high voltage generated by the igniter 26 is distributed by the distributor 14, and is sequentially supplied to the ignition plug 28 attached to each cylinder. Further, the control circuit 20 is connected so as to control the fuel injection amount by opening the fuel injection valve 29 for a time corresponding to the calculated fuel injection time.

A control circuit 20 including a microcomputer
As shown in FIG. 4, a random access memory (RA
M) 58, read only memory (ROM) 60, micro processing unit (MPU) 62, first input / output port 64,
It has a second input / output port 66, a first output port 68, a second output port 70, and a bus 72 such as a data bus or a control bus connecting these. The first input / output port 64 is connected to the air flow meter 2 via an analog-digital (A / D) converter 74, a multiplexer 76 and a buffer 78A.
4 is connected to the engine cooling water temperature sensor 30 via a buffer 78B, and is also connected to an intake air temperature sensor or the like (not shown). In addition, the first input / output port 64 is A /
It is connected to supply control signals to the D converter 74 and the multiplexer 76. To the second input / output port 66, the cylinder discrimination sensor 16 and the rotation angle sensor 18 are connected via a waveform shaping circuit 80, and the knocking sensor 12 is connected via an input circuit 82.

As shown in FIG. 5, the input circuit 82 is connected in parallel to a series circuit composed of a knock gate circuit 82A and a peak hold circuit 82B, one ends of which are connected to the knocking sensor 12, and the series circuit. An integrating circuit 82E, a multiplexer 82C connected to the series circuit and the integrating circuit 82E,
It is composed of an A / D converter 82D connected to a multiplexer 82C. The knock gate circuit 82A, the multiplexer 82C and the A / D converter 82D are connected to the second input / output port 6
It is connected to be controlled by the control signal from 6.

The first output port 68 is connected to the igniter 26 via a drive circuit 86, and the second output port 70 is connected to the fuel injection valve 29 via a drive circuit 88 having a down counter. Note that 90 is a clock and 92 is a timer. RO above
A program of a control routine described below is stored in the M60 in advance.

Next, the operation of the embodiment of the present invention will be described in detail while explaining the above control routine. FIG. 6 shows the main routine of this embodiment. In step 100, the engine speed N and the detected value Q of the intake air amount (corrected in the routine of FIG. 1) are taken in. And the detected value Q of the intake air amount, the basic fuel injection time TP (= Q / λ · N, where λ is the target air-fuel ratio) is calculated, and in the next step 104, it is determined according to the intake air temperature, the engine cooling water temperature, etc. The basic fuel injection time TP is corrected and the basic fuel injection time TP is corrected using the air-fuel ratio feedback back correction coefficient FAF obtained from an O ₂ sensor (not shown) to calculate the fuel injection time TAU. In the next step 106,
Based on the cylinder discrimination signal and the rotation angle signal, it is determined whether the current piston position is at top dead center (TDC). In the case of TDC, in step 114, the multiplexer 82C is controlled to input the output of the knocking sensor 12 to the A / D converter 82D via the integrating circuit 82E and the multiplexer 82C, and the integrating circuit 82E output, that is, the A / D of the background level b Start D conversion. As a result, a digital value of the engine vibration level that does not depend on knocking, that is, the back ground level b is obtained, and this digital value is stored in a predetermined area of the RAM at the end of A / D conversion. On the other hand, when it is determined that the TDC is not TDC in step 106, it is determined in step 108 whether the current piston position is, for example, 15 ° CA ATDC, and the step is performed.
If the determination in step 108 is affirmative, in step 110, the control signal is output from the second input / output port 66 to the knock gate circuit 82A to open the knock gate circuit 82A, and the knocking sensor 12 outputs the knock gate circuit 82A and the peak hold circuit 82B. Notting sensor 12 via multiplexer 82C
The output is input to the A / D converter 82D. At the next step 112, the time t (corresponding to 90 ° CA ATDC) at which the knock gate circuit 82A is closed is calculated from the present time and the time corresponding to the predetermined crank angle range, and is set in the compare register.

FIG. 7 shows a time coincidence interrupt routine which is interrupted when the time set in step 112 is reached.
When the current time matches the time set in the compare register, the second input / output port 66 A
Outputs a control signal to the / D converter 82D for peak hold circuit 8
Start A / D conversion of 2B output and return to the main routine.

Fig. 8 shows A / D when A / D conversion of integrating circuit 82E output is completed.
This shows the interrupt routine interrupted by the A / D conversion end signal from the D converter 82D.
The / D conversion value is stored as a peak value a in a predetermined area of the RAM, and in step 120, a control signal is output from the second input / output port 66 to the knock gate circuit 82A to close the knock gate circuit 82A.

FIG. 1 shows a routine for correcting the digitally converted air flow meter output QAD. In step 140, the load Q / N represented by the detected value Q of the intake air amount and the engine speed is a predetermined value (for example, 0.7 / rev) It is judged whether or not it is in the knocking control region by judging whether or not it is above, and if it is not in the knocking control region, it returns to the main routine. On the other hand, when it is determined in step 140 that the control range is the knocking control region, the peak value a and the back ground level b are taken in, and the peak value a and the determination level K · b are compared in step 142. When the peak value a is larger than the determination level K · b, it is determined that knocking has occurred, and the correction retard angle θ _K is increased in step 144 by a predetermined value (for example, 0.1 ° CA). On the other hand, when it is determined that the peak value a is equal to or lower than the determination level K · b, it is determined that knocking does not occur, and it is determined in step 146 whether a predetermined number of ignitions (for example, 100 ignitions) has elapsed, and the predetermined number of ignitions is determined. If the time has elapsed, the correction retard angle amount θ _K is reduced in step 148 by a predetermined value (for example, 0.1 ° CA). The next step 150 in the delay correction amount theta _K is first set value (for example, 3 ° CA) is less than whether the determined correction retard amount theta _K is step 154 when more than a first set value Count value CQN
After decrementing, proceed to step 160. On the other hand, when it is determined that the corrected retard amount θ _K is less than the first set value, in step 152, the corrected retard amount θ _K is set to the second set value smaller than the first set value (for example, 1 ° CA). Judge whether or not it exceeds. When it is determined that the corrected retard angle amount θ _K is less than or equal to the second set value, the count value CQN is incremented in step 156, and then the process proceeds to step 160. On the other hand, when it is determined that the corrected retard amount θ _K exceeds the second set value, that is, when the corrected retard amount θ _K is between the first set value and the second set value, the step is performed. At 158, the airflow meter output QAD that has been digitally converted is set as the detected value Q of the intake air amount, and the process returns to the main routine.
In step 160, the detected value Q of the intake air amount is calculated according to the following equation.

FIG. 9 shows the ignition timing calculation routine.
In 162, the detected value Q of the intake air amount and the engine speed N are taken in, and in step 164 the intake air amount (engine load) Q / N per engine revolution is calculated, and at the same time the intake air amount Q / The basic ignition advance angle θ _BASE is calculated from N and the engine speed N, and the execution ignition advance angle θ _i is calculated in step 166 by subtracting the corrected retard amount θ _K from the basic ignition advance angle θ _BASE . Then, the ignition timing is controlled to the execution ignition advance angle by turning on the igniter a predetermined time before the execution ignition advance angle and turning off the igniter when the execution ignition advance angle θ _i is reached.

Here, since the count value CQN of the equation (1) is incremented or decremented by 1 in step 154 and step 156, the intake air amount QAD digitally converted every time the calculation of step 160 is performed is ± 2%. (1/5
0) will be corrected one by one. In addition, the correction delay angle θ _K
Is greater than or equal to the first set value, the count value CQN is decremented, so the detected value Q is corrected to be large, which increases the fuel injection amount and corrects the ignition timing to the retard side, which is optimal. It is corrected to the value. On the other hand, when the correction delay amount θ _K is less than or equal to the second set value, the count value CQN is incremented, so the detected value Q is corrected to be small, and thus the fuel injection amount is corrected to be small. At the same time, the ignition timing is corrected to the advance side and set to the optimum value.

Although the internal combustion engine that calculates the basic fuel injection time and the basic ignition advance angle based on the intake air amount detected by the air flow meter and the engine rotation speed has been described above, the present invention is not limited to this. Instead, it can be applied to an internal combustion engine that calculates the basic fuel injection time and the basic ignition advance angle based on the intake pipe absolute pressure detected by the pressure sensor and the engine rotation speed.

[Brief description of drawings]

FIG. 1 is a flow chart showing a detection value correction routine of an embodiment of the present invention, and FIGS. 2 (1) to (4) are graphs showing changes in air flow meter output, air-fuel ratio, ignition advance angle and engine torque. FIG. 3 is a schematic diagram of an internal combustion engine equipped with a fuel injection amount control device and an ignition timing control device to which the present invention is applicable;
FIG. 5 is a block diagram showing the details of the control circuit of FIG. 3, FIG. 5 is a block diagram showing the details of the input circuit of FIG. 4, FIG. 6 is a flow chart showing the main routine of the above embodiment, and FIG. Flowchart showing the time coincidence interrupt routine of the above embodiment,
FIG. 9 is a flow chart showing the A / D conversion end interrupt routine of the above embodiment, and FIG. 9 is a flow chart showing the ignition timing calculation routine of the above embodiment. 12 …… notching sensor, 16 …… cylinder discrimination sensor, 18 …… rotation angle sensor, 20 …… control circuit, 24 …… air flow meter.

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Claims (2)

[Claims] 1. A fuel injection amount and an ignition timing are controlled based on a detected value of an engine load and a detected value of an engine rotational speed, and an ignition timing is retarded when knocking occurs and ignition is performed when no knocking occurs. In a fuel injection amount and ignition timing control method for an internal combustion engine that corrects the ignition timing by a correction retard amount that advances the timing, the detected value of the engine load is corrected according to the magnitude of the correction retard amount. A method for controlling fuel injection amount and ignition timing of an internal combustion engine, the method comprising: 2. When the correction delay amount is greater than or equal to a first set value, correction is performed so as to increase the detected value of the engine load, and the correction delay amount is set to a second set value that is smaller than the first set value. The fuel injection amount and ignition timing control method for an internal combustion engine according to claim (1), wherein the detected value of the engine load is corrected so as to be smaller than a set value.