JPS635168A - Ignition timing control method for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the generation of a trouble like a torque change or the like, by calculating the substitute ignition timing of a cylinder, equipped with an abnormal sensor, on the basis of the pressure information of a cylinder equipped with a normal pressure detecting means. CONSTITUTION:A pressure sensor 24 detects the pressure in a cylinder to be input to a maximum position-knocking signal generating circuit 32, and its output is input to a control unit 48. Then the control unit can detect a pressure maximum value generated position by measuring the time till the point of pulse generation time and the presence of knocking generation by counting a number of pulses further the sensor fail by taking into consideration of both the generation position and the generation presence. And in order to determine the ignition timing of a cylinder, equipped with an abnormal sensor, calculation, which is based on the ignition timing of the other cylinder equipped with a normal pressure sensor, determines the substitute ignition timing of the cylinder with the abnormal sensor by utilizing the detection value of the said other normal pressure sensor. consequently, the ignition timing can be determined accurately corresponding to even a change of every moment varying operative conditions, and a trouble of torque change or the like is prevented from being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for controlling ignition timing of an internal combustion engine, and more specifically to a method for controlling ignition timing while detecting internal cylinder pressure and knocking. , relates to an ignition timing i1J control method for an internal combustion engine that detects an abnormality in a cylinder pressure detection means and performs fail-safe control when an abnormality is detected.

(Prior Art) A control method that detects the cylinder pressure of a multi-cylinder internal combustion engine for each cylinder via a plurality of pressure detection means to control the ignition timing, and also detects non-king and corrects the ignition timing. As an example, the technique described in Japanese Patent Application Laid-Open No. 59-39974 can be mentioned (problem to be solved by the invention) Although it is not necessarily clear in the above conventional example, in this technique, at the same time, the cylinder pressure detection means is If an abnormality is to be detected, it is customary to add a separate type of circuit and compare its output with a sensor fail reference level to detect the abnormality. was controlled by retarding the normal ignition timing by a predetermined amount,
This causes problems such as torque fluctuation, deterioration of fuel efficiency, and temperature rise in the part of the abnormal cylinder that constitutes the combustion chamber.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to solve the problem of torque fluctuation, etc. by calculating alternative ignition timing for an abnormal cylinder based on pressure information of a cylinder equipped with a normal pressure detection means. An object of the present invention is to provide an ignition timing control method for an internal combustion engine that does not cause any inconvenience.

(Means and Effects for Solving the Problem) In order to achieve the above object, the present invention detects the pressure inside the cylinders of a multi-cylinder internal combustion engine for each cylinder via a plurality of pressure detection means, as shown in FIG. and control the ignition timing (step 10).
), knocking is also detected and the ignition timing is corrected (step 12.14) In the ignition timing control method for an internal combustion engine, an abnormality in the pressure detection means is detected from the detected pressure (step 16), and at least When one abnormality is detected, an alternative ignition timing is calculated based on the ignition timing of another cylinder equipped with a normal pressure detection means to control the engine (step 18).

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First, for convenience of explanation, the apparatus used to implement the method according to the present invention will be explained in detail. FIG. 2 is a block diagram of the device, and FIG. 3 is a diagram of its output waveform. In FIG. 2, reference numeral 24 indicates a piezoelectric pressure sensor which is the cylinder pressure detection means described above, and this sensor is disposed at a position facing a combustion chamber (not shown) of an internal combustion engine 26. In the embodiment, the internal combustion engine has four cylinders, and the pressure sensor 24 is provided for each cylinder. The output of the sensor 24 is connected to a charge-voltage conversion amplifier (
(not shown) to a low-pass filter 28. The cutoff frequency of the filter is set higher than the preset knocking frequency, and a multiplexer 30 is provided at the next stage of the low-pass filter 28, which is configured so that knocking can also be detected. 24
The output is selectively sent to the next stage in a cylinder explosion type according to commands from a control unit, which will be described later. A maximum position/non-king signal generation circuit 32 is connected to the next stage, and the circuit 3
2 specifically includes a differentiating circuit 34, a comparing circuit 36, and a pulse down edge detecting circuit 38. Differential circuit 3
4 is composed of a resistor 34a, a capacitor 34b, a resistor 34c, a capacitor 34d, and an operational amplifier 34e.

As shown in FIGS. 3(a) and 3(b), this differentiating circuit 34 is for shifting the phase of the sensor output waveform by 90 degrees so that it crosses zero at the position where the maximum pressure value occurs. Even when superimposed, the differential circuit output crosses zero at that position as long as the cough high frequency rises and falls. Note that the voltage Vr is applied to the non-inverting input terminal of the operational amplifier 34e.
ef 1 is input. The comparison circuit 36 is composed of a resistor 36a and an operational amplifier 36b, and outputs a pulse when the output of the differentiation circuit is input and exceeds the reference voltage Vref2. In the case of M tatami, a zero-crossing waveform is output every time the high frequency goes up and down, and one or more pulses are output accordingly. Incidentally, the comparison reference voltage ref2 of the non-inverting input terminal of the operational amplifier 36b is set slightly lower than the voltage Vref1 of the operational amplifier 34e of the differentiating circuit. The output of the comparison circuit 36 is input to a pulse down edge detection circuit 38. The circuit 38 includes a resistor 38a
, a capacitor 38b, a resistor 38C, an inverter 38d, and a NOR gate (NOR gate) 38e, which grasps the falling edge timing of the comparator output pulse and outputs a pulse with a predetermined time width to facilitate processing by a subsequent control unit.

An engine piston (
A crank angle sensor 42 is arranged to detect the crank angle position of the engine (not shown), and outputs a cylinder discrimination signal once per 720 degrees of crank angle, a TDC signal once per 180 degrees, and once per degree of crank angle. Outputs a unit angle signal that is subdivided. Furthermore, the throttle valve 4 in the intake passage of the internal combustion engine 26
A negative pressure sensor 46 is provided at an appropriate position downstream of engine 4 and outputs a signal indicating the load condition of the engine.

A control unit 48 is connected to the next stage of the pulse down edge detection circuit 38 and inputs its output. The output of the crank angle sensor 42 is also waveform-shaped by a waveform shaping circuit 50 and then input to the control unit 48 .
The output of 6 is also input to the control unit 48 after being digitally converted by the A/D conversion circuit 52. In this embodiment, the control unit 48 is composed of a microcomputer, and is composed of an input/output interface 48a, a CPU 48b, a clock 48c, and a memory 48d.

Furthermore, the control unit 48 includes a timer counter 48e that counts the output pulses of the clock 48C to measure the elapsed time from a predetermined position to the point at which the output pulse of the pulse down edge detection circuit 38 is generated, and a timer counter 48e that counts the output pulses of the clock 48C. A pulse counter 48f for counting is provided. The counts of both counters 43e and 48f are sent to the CPU 48b.

An ignition device 54 is connected to the next stage of the control unit 48, and ignites the air-fuel mixture in the engine combustion chamber in accordance with the ignition command. The output of control unit 48 is also sent to multiplexer 30 to command its gate switching as described above.

Next, an embodiment of the method according to the present invention will be described based on the flow chart of FIG. 4 while referring to the timing chart of FIG.

First, in step 60, the arrival of the TDC signal from the crank angle sensor 42 is confirmed, and in step 62, the cylinder is determined based on the cylinder discrimination signal of the sensor 42, and the cylinder address (C/A=n) is determined. The cylinder addresses are assumed to be 1st cylinder n=1, 3rd cylinder n=2, 4th cylinder n=3, and 2nd cylinder n=4.

Subsequently, in step 64, the current cylinder (C/A=n)
It is determined whether or not the sensor fail flag indicating an abnormality in the pressure sensor 24 is on, and if it is not on, the timer counter 48e and pulse counter 48f are started in step 66 to start time measurement and pulse counting. .

Next, while confirming in step 68 that ATDC 30 degrees has not been reached, the process waits for the first pulse to occur in step 70. As shown in Figure 3(a),
The output waveform of the pressure sensor 24 crosses zero at the position where the maximum pressure value occurs in the differentiating circuit 34.
6 outputs a pulse, the pulse is input to the pulse down edge detection circuit 38, and a pulse of a predetermined width is output. In step 70, the generation of this pulse is awaited. When it occurs, the timer counter 48e is activated in step 72. to stop time measurement. Let this count value be T pmax. Furthermore, even if no pulse is generated, time measurement is stopped when ATDC reaches 30 degrees (steps 68, 70, and 72). As shown in FIG. 3(b), when non-king occurs, a plurality of pulses are output each time the pressure sensor output waveform rises and falls, and as shown in FIG. 3(c), when the pressure sensor 24 fails, as described above, Voltage Vref 1 is set slightly higher than Vref 2, so no pulse is generated, so measuring the elapsed time until the pulse occurs will determine the position of the maximum pressure value, and counting the number of pulses will determine the occurrence of knocking. The presence or absence of
Furthermore, sensor failure can be detected by taking both factors into consideration.

Next, in step 74, it is confirmed that ATDC has reached 30 degrees, and in step 76, the pulse counter 48f is
to stop pulse counting. The reason for setting the ATDC to 30 degrees is to limit the counting interval to the minimum range necessary for detecting knocking.

Next, in step 78, it is determined whether the timer counter value overflows and the pulse counter value is O'. As described above, if an abnormality occurs in the pressure sensor 24, no pulse is output, and therefore the timer counter value overflows and the pulse counter value becomes "O". Therefore, sensor failure can be detected by referring to both counter values.

If no sensor fail is detected, continue with step 8
0, it is determined whether the pulse counter value is greater than or equal to a predetermined value. As shown in FIG. 3(b), since multiple pulses are output when knocking occurs, by setting the predetermined value to, for example, 2, it is possible to detect whether or not knocking has occurred. Incidentally, in order to provide a dead zone, it may be set to a value higher than that.Furthermore, even when knocking occurs, the first pulse is determined to be the first pulse in steps 68 to 70, and the timer counter 48e is stopped. In that case, the system will shift to knocking control, so there will be no problem.

If knocking is not detected in step 80, the timer counter value T is determined in step 82.
Multiply pmax by time-angle conversion value k to obtain maximum pressure angle θPm
Find ax. Note that this conversion value includes the rotation speed rp+++
X 360 degrees = □ Calculate in 60 seconds.

Subsequently, in step 84, the maximum pressure angle θPrmax
The ignition timing θig is calculated based on the ignition timing θig, and an ignition command is issued to the ignition device 54 in step 86.

If the sensor fail flag for the current cylinder is on in step 64, the process moves to the sensor fail subroutine (step 88).

FIG. 5 shows this subroutine. First, in step 88a, it is determined whether the sensor fail flag of the cylinder before one ignition (C/A=nt) is on, that is, abnormal. In this case, the ignition timing θigC/A = n-1 calculated for that cylinder in step 88b
Load.

Subsequently, in step 88c, the second cylinder before ignition (C/
A = n-2) is determined to be abnormal, and if it is not abnormal,
In step 88d, the ignition timing θigc of that cylinder is determined.
/A = Read n-2.

Subsequently, in step 88e, the third cylinder before ignition (C/
A = n-3) is determined to be abnormal, and if it is not abnormal,
In step 88, the ignition timing θigC/
^ = read n-3 0 Next, in step 88g, it is determined whether all sensor fail flags are on, and if not, in step 88h, the ignition timing θigC/A-n of the cylinder read so far is determined. -1~n
-3, the most retarded value θ1gm1n is selected and calculated as the ignition timing θig of the relevant cylinder equipped with the abnormality sensor in step 88i. In addition, when sensor failure is detected in all cylinders, the value retarded by the first predetermined amount is calculated as the ignition timing θig of the cylinder (
Step 88j). This first predetermined angle is determined as appropriate.

If a sensor fail is detected in step 78, the sensor fail flag for the current cylinder (cylinder address C/A=n) is turned on (step 90). Also, if knocking is detected in step 80, the angle is retarded by an appropriate amount, and after non-king is avoided, the advance angle is corrected as appropriate (steps 92, 84, and 86).

As shown above, the ignition timing θig of the cylinder equipped with the abnormal sensor
By using the ignition timing of the cylinder equipped with another normal sensor as the basis for calculation, the detection value of the other normal pressure sensor is used to determine the alternative ignition timing of the abnormal sensor cylinder. Therefore, the ignition timing can be determined in response to changes in the operating conditions that fluctuate from moment to moment, and problems such as torque fluctuations do not occur.

FIG. 6 shows a second embodiment of the present invention, and shows another example of the subroutine.

To explain only the differences from the first embodiment, step 8
The most retarded ignition timing θig from 8a to 88h
After selecting n+in, in step 88k, a value obtained by retarding the ignition timing θig by a second predetermined amount is obtained as the ignition timing of the abnormal cylinder, and in step 881, the ignition timing θig of the cylinder is calculated. This second predetermined amount is determined as appropriate by detecting the engine operating state. This second embodiment has similar advantages to the first embodiment.

FIG. 7 shows a third embodiment of the present invention, and shows yet another example of the subroutine.

To explain only the points that are different from the first and second embodiments, after steps 88a to 88g, the average value θigave of the ignition timings of the other normal sensor cylinders is calculated, and a third predetermined amount of delay is further calculated from the average value. The squared value is set as the ignition timing θig (step 88m, step 88n, 8
8o). This third predetermined amount is also determined in the same manner as the second predetermined amount.

In this case, step 88n is omitted and the average value θ is immediately calculated.
igave may be used as the ignition timing θig of the abnormal cylinder. In this example, the calculation is based on the average value, so
Torque fluctuations and the like can be more effectively avoided.

(Effects of the Invention) As described above, the present invention detects an abnormality in the pressure detection means from the detected pressure value, and also detects an abnormality in the pressure detection means from the detected pressure value. Since the engine is controlled by calculating the alternative ignition timing based on the ignition timing of the abnormal sensor cylinder, the alternative ignition timing of the abnormal sensor cylinder can be determined immediately in response to changes in the operating condition that fluctuate from moment to moment. It is possible to prevent problems such as deterioration of fuel efficiency or rise in temperature in the combustion chamber of the abnormal cylinder, and even if some of the plurality of detection means become abnormal, the output of the remaining detection means can be reduced. It has the advantage of being able to achieve the desired control goal by using it.

[Brief explanation of drawings]

Fig. 1 is a claim correspondence diagram of the present invention, Fig. 2 is a block diagram showing a device used to realize the method according to the present invention, Fig. 3 is a timing chart showing its operation, and Fig. 4 is a diagram of the present invention. Flows and charts showing examples of 5th FI! J is a flow chart showing a subroutine of the flow chart in FIG. 4, FIG. 6 is a flow chart showing a second embodiment of the present invention, and FIG. 7 is a flow chart showing a third embodiment of the present invention.
It is a chart. [0) No. 97 Figure 3 (b) No. 7 tomorrow

Claims (5)

[Claims] (1) Ignition of an internal combustion engine in which the cylinder pressure of a multi-cylinder internal combustion engine is detected for each cylinder via a plurality of pressure detection means to control the ignition timing, and also knocking is detected and the ignition timing is corrected. In the timing control method, an abnormality in the pressure detection means is detected from the detected pressure value, and if at least one of the abnormalities is detected, alternative ignition is performed based on the ignition timing of another cylinder equipped with a normal pressure detection means. A method for controlling ignition timing for an internal combustion engine, which comprises controlling the engine by calculating timing. (2) Ignition timing control for an internal combustion engine according to claim 1, wherein the alternative ignition timing is determined by selecting the most retarded ignition timing among the ignition timings of the other cylinders. Method. (3) The ignition timing control method for an internal combustion engine according to claim 2, wherein the alternative ignition timing is determined by further retarding the most retarded ignition timing by a predetermined amount. (4) The ignition timing control method for an internal combustion engine according to claim 1, wherein the alternative ignition timing is determined by calculating an average value of the ignition timings of the other cylinders. (5) The alternative ignition timing is determined by further retarding the average value by a predetermined amount.
Ignition timing control method for internal combustion engine described in section