JPH0539769A - Ignition timing control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To provide an ignition timing control device of an internal combustion engine which can decide a knock accurately, and can carry out an accurate ignition timing control even in case that a noise is given to a knock detecting signal and the wave form is disturbed. CONSTITUTION:A knock detecting signal is A/D converted in the step 101, and it is decided whether the A/D converted value exceeds a standard level Vref or not in the step 103. When the A/D converted value is less than the standard level Vref, the difference between the A/D converted value and the standard level is found in the step 105, and the resultant value is converted to an absolute value in the step 105. And when it is decided that the value converted to the absolute value is larger than a specific threshold level Vth, an operation is carried out depending on the A/D converted value, and an ignition timing control is carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knock control system for an internal combustion engine, and more particularly to an ignition timing control device for an internal combustion engine having improved knock detection signal processing means.

[0002]

2. Description of the Related Art In an ignition timing control system for performing knock control of an internal combustion engine, a knock detector for detecting the occurrence of knock is provided in the internal combustion engine, and the occurrence of knock is detected based on a detection signal from the knock detector. The engine ignition timing is controlled so as to suppress the knock.

In such a knock control system, a microcomputer having a built-in A / D converter is usually used. In this knock control system, attention is paid to the fact that the knock detection signal usually appears as a sine wave. Consists of That is, the vicinity of the peak of the signal waveform generated a predetermined time after the knock detection signal exceeds a reference level such as "0" level is A / D converted, and arithmetic processing based on this A / D converted digital value is performed. Is performed (for example, JP-A-59-90019).

Here, when the internal combustion engine is operated in a low speed, light load state, the resonance of the engine is small and the knock detection signal level is correspondingly small. When a high-power transmitter or the like mounted on the vehicle is used in such a state, the signal generated by this transmission acts on the knock detection signal as electrical noise, and the waveform of the knock detection signal is disturbed.

When the waveform of the knock detection signal is disturbed in this way, the waveform at the time of A / D conversion may have a negative value with respect to the reference level. As it is converted into a digital value, a value smaller than the reference level will be read.

In such a situation, even if the knock detector and the signal line are normal, the digital value taken in by the microcomputer for knock control becomes extremely small, and therefore there is a possibility that the knock control fails.

When the knock control failure is actually confirmed, the ignition timing of the internal combustion engine is set to the most retarded side, the power performance is greatly reduced, and the check lamp is turned on. It will be a complaint without any abnormality.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above point, and a noise signal is mixed in, for example, a knock detection signal while the knock detector, the signal line, and the like are operating normally. Even in such a case, a detection input larger than the reference level is always obtained, and the ignition timing control of the internal combustion engine is made so that the ignition timing is not controlled to the retard side even if the knock does not occur. It is intended to provide a device.

[0009]

In the ignition timing control apparatus for an internal combustion engine according to the present invention, the knock detection signal is digitalized when the detection signal from the knock detection means is delayed for a predetermined time after crossing the reference level. Value, and when the disturbance of the knock detection signal is detected, the digital value is converted into an absolute value, and it is confirmed that the absolute value converted digital value exceeds a specific level. Ignition timing control is executed based on the digital value.

[0010]

In the ignition timing control device configured as described above, the digital value is higher than the reference level when the knock detection means and the signal line are normal and no noise signal is mixed. Calculation is executed based on the digital value, and normal knocking control is performed. Further, when noise is mixed in the knock signal and, for example, the digital value becomes smaller than the reference level and the disturbance of the waveform is detected, the digital value is converted into an absolute value and the converted value is specified at a level. In the above cases, it is used for knocking control. Therefore,
The ignition timing control calculation is executed so that the fail determination is made only when the knock detection means or the signal line has a failure without making an erroneous determination of the fail.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows the configuration of the knock control device.
The knock detector 11 is mounted on a block portion of an internal combustion engine (not shown), and the knock detector 11 is composed of a piezoelectric element or the like that detects mechanical vibration generated by knocking of the internal combustion engine.

The knock detector 11 outputs a knock detection signal which changes in response to mechanical vibration of the internal combustion engine generated in response to knocking. The knock detector 11 detects knock. The signal is input to the control circuit 13 via the filter circuit 12 that removes noise.

The control circuit 13 is composed of, for example, a microcomputer and has an A / D converter 131 for converting an analog knock detection signal into a digital signal.
Built-in, converts the analog knock detection signal into a digital value and captures it. Although not shown in detail, the control circuit 13 is configured to include a CPU, a ROM, a RAM and the like, and calculates and outputs the ignition timing of the internal combustion engine based on the knock detection signal taken in. 14 is an amplifier whose amplification factor can be changed.

In FIG. 2, the output signal from the knock detector 11 is A
This shows the timing of the D / D conversion, and the knock detection signal of FIG. 7B is read in the gate section corresponding to the determination section of FIG.

In the judgment (gate) section of FIG. 7A, the high level section for knock detection is ATDC 10 ° CA of the crank angle of the internal combustion engine, and the low level section is ATDC 90 ° CA-100 ° CA. Becomes A / D conversion is
The knock detection signal from the knock detector 11 is performed only in the section where the determination section in FIG.

The knock detection signal from the knock detector 11 is
As shown in FIG. 3, it appears as a sine wave, and in the control circuit 13 to which this knock detection signal is input, a reference level Vref that is a virtual ground level is set therein, and this reference level (zero) is set as the center. Then, the knock detection signal is fetched.

When the knock detection signal exceeds the reference level (point a in FIG. 3), a zero-cross trigger is generated, the conversion timing is set at point b after a predetermined time t from point a, and this point b is set. A / D conversion is performed in the vicinity of the peak of the knock detection signal corresponding to. Here, the waiting time t from when the signal exceeds the reference level until A / D conversion is performed is set based on the resonance frequency characteristic of the knock detector 11 that is set for each internal combustion engine.

FIG. 3 shows a case where the knock detection signal input from the knock detector 11 to the control circuit 13 is normal. For example, a high-power transmitter or the like is used near the control circuit 13. Then, as shown in FIG. 4, the waveform of the knock detection signal is disturbed. In such a state, at the A / D conversion timing at the point b after the lapse of the predetermined time t after the reference level at the point a is exceeded, the signal waveform has a value (negative value) smaller than the reference level as shown in the figure. ) May occur. Therefore, the digital value after A / D conversion in such a case becomes a minimum value.

FIG. 5 shows the flow of processing in the control circuit 13 that ensures normal ignition timing control even in such a state. First, in step 100, the previous average value (VMEAN) is calculated. , Initial value of this smoothing process (VMAD)
It is said that.

In step 101, the knock detection signal from the knock detector 11 is A / D converted, and then in step 102, it is checked whether the A / D conversion is normally performed. If it is confirmed in this step 102 that the A / D conversion is normally performed, this A / D conversion is performed in the next step 103.
The magnitude of the converted value VAD and the reference level Vref is judged.

If it is determined in step 103 that the A / D converted value VAD is smaller than the reference level Vref, the waveform of the knock detection signal is disturbed by electrical noise, and the A / D converted value becomes negative. Then, in step 104, the difference between the reference level Vref and the A / D conversion value VAD is calculated. Then, the value calculated in this step 104 is converted into an absolute value in the next step 105.

Digital value ADC converted to this absolute value
Compares with a predetermined threshold level Vth in step 106, and when it is determined that the digital value ADC is higher than this threshold level Vth, the process proceeds to steps 107 and 108 to perform the smoothing process. The value VMAD obtained by this smoothing process is used to calculate the determination level and the fail detection signal of the knock detector according to a known calculation procedure.

If it is determined in step 106 that the digital value converted into the absolute value is lower than the threshold level Vth, the process proceeds to step 109 to cancel the data so that it will not be used in the subsequent calculation. To do. If it is determined in step 102 that the A / D conversion has not been performed, the process proceeds to steps 110 and 111 to perform the smoothing process and return.

In the device constructed in this way, A /
When the A / D converted digital value is negative in the control circuit 13 constituted by the microcomputer having the D converter 131 built-in, absolute value conversion is performed to make it a positive value, and the threshold value is higher than a specified threshold level. In this case only, this digital value is used for the next arithmetic processing. Therefore, when the knock detector 11 is normal, the A / D conversion value is surely larger than the zero level, so that the failure of the knock detector is not erroneously determined and the knocking is not erroneously detected.

If the resonance frequency of the knock detector 11 is 7.1 KHz, for example, the cycle T of the knock detection signal from the knock detector 11 shown in FIG. 6 is 140 μsec. The following table shows the gate time (judgment interval time) when the judgment interval angle is constant at 60 ° CA at each rotation speed of the internal combustion engine, and the knock detector 11 that is A / D converted within this gate time. The number of detection signal peaks is shown.

[0026]

[Table 1]

FIG. 7 shows a flow of processing for explaining the second embodiment. In this embodiment, attention is paid to the number of peaks of the knock detection signal A / D converted in the gate. If the number of data A / D converted with a negative value exceeds a predetermined number during one ignition, the calculation data is cleared.

First, in step 201, gate (judgment)
The section ends, and the A / D conversion during one ignition ends. After that, in step 202, the negative value is A /
Whether or not the D-converted number (-VADt) is greater than the set number N (N in the above table, for example, 2/3 of the number of pulses in the judgment section at each rotation speed of the internal combustion engine) If the total number of negative A / D converted values is N or more, it is determined that the noise is affected by electrical noise, and step 203
Go to and clear VMAD obtained by calculation. After that, the routine proceeds to step 204, and the check lamp is turned on to notify that electrical noise is present.

When the negative A / D conversion value is judged to be N or less in step 202, the routine proceeds to step 205, where the judgment level calculation is carried out, and further knock judgment is carried out at step 206 and fail at step 207. Normal processing for detection is performed.

That is, in this embodiment, the number of negative A / D converted values during one ignition (within the gate) is counted, and when the counted value is equal to or more than a predetermined value, the data is cleared and The check engine lamp is turned on to prompt the user for treatment.

[0031]

As described above, according to the ignition timing control apparatus for an internal combustion engine according to the present invention, the knock detector and the signal line are normal, the knock detection signal is accompanied by the noise signal, and the signal waveform is disturbed. Even in such a case, an A / D-converted knock detection signal larger than the reference level can always be obtained, and reliable ignition timing control can be executed.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a knock detection unit for explaining an ignition timing control device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a knock determination section and a knock detection signal.

FIG. 3 is a diagram showing a normal knock detection signal.

FIG. 4 is a diagram showing a knock detection signal disturbed by noise.

FIG. 5 is a flowchart illustrating a processing flow in the control circuit of the above embodiment.

FIG. 6 is a diagram illustrating a knock detection signal for explaining another embodiment of the present invention.

FIG. 7 is a flowchart showing the flow of processing of the other embodiment.

[Explanation of symbols]

11 ... Knock detector, 12 ... Filter, 13 ... Control circuit, 131
... A / D converter.

Claims (1)

[Claims] 1. A knock detection means for detecting knocking of an internal combustion engine, and a knock detection signal having a digital value at a time point after a specific time delay from a time point when a detection signal from the knock detection means crosses a set reference level. A / D conversion means for converting, means for detecting that the waveform of the knock detection signal is disturbed, and absolute value for converting the digital value into an absolute value in the state where the disturbance of the signal waveform is detected by this means. Conversion means and knocking control means for comparing the absolute-value-converted digital value with a specified level and controlling the ignition timing of the internal combustion engine by using the digital value exceeding this level. A characteristic ignition timing control device for an internal combustion engine.