JP3084930B2 - Knocking control device for internal combustion engine - Google Patents

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 controlling knock control factors such as ignition timing, air-fuel ratio, and supercharging pressure of an internal combustion engine in response to occurrence of knock in the internal combustion engine. The present invention relates to a knocking control device for an internal combustion engine having improved knock determination means when a large-level knock has occurred.

[0002]

2. Description of the Related Art In a knock control system for an internal combustion engine, knocking is suppressed in the internal combustion engine based on a detection signal from a knock detection sensor that detects mechanical vibration when an illegal explosion occurs in the internal combustion engine. Knocking is controlled in the direction of

In the knock detection sensor for detecting the occurrence of such a knock, the level of the knock detection signal greatly changes in accordance with the operation state of the internal combustion engine, particularly, the rotation speed of the internal combustion engine. The knock state of the internal combustion engine is determined by comparing the level of the knock detection signal with a set threshold level, and determining that knock has occurred when the knock detection signal exceeds the threshold level. Then, the ignition timing of the internal combustion engine is controlled based on the knock determination result. For example,
The ignition timing is retarded to suppress knocking.

However, in a situation where the level of the knock detection signal changes according to the operating state of the internal combustion engine, it may be difficult to effectively use the detection signal from the knock detection sensor. In order to cope with such problems, for example, in the invention disclosed in Japanese Patent Application Laid-Open No. 60-138427, switching control of the gain of an amplifier circuit to which a detection signal from a knock detection sensor is supplied has been considered. I have.

However, in such an apparatus in which the signal gain is switched, the reference signal for generating the gain switching command is based on the average value of the detection signal from the knock detection sensor or the rotational speed of the internal combustion engine. Is set. Therefore, the normal knock determination level is not a problem, but since the knock determination level is set according to the knock detection signal level, the large knock determination level is set to be larger than the normal state. Is saturated, and the knock determination cannot be accurately performed.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and reliably copes with a case where a knock detection signal level from a knock detection sensor becomes larger than a normal state. It is an object of the present invention to provide a knocking control device for an internal combustion engine that can stably execute knock control accompanying the knock determination together with good knock determination.

[0007]

SUMMARY OF THE INVENTION The present invention achieves the above object.
To achieve this, a knock that detects the knock state of the internal combustion engine
Knock detection means and a knock detection signal from the knock detection means.
Switching to variably control the gain to amplify the signal
Means and knock detection amplified by the gain switching means.
Compares the signal with the set first knock determination level
First knock determination means, and the amplified knock detection signal
The second knock determination higher than the first knock determination level.
A second knock determination means for comparing with a constant level;
And the determination output from the second knock determination means,
Knock control means for controlling knock of the internal combustion engine;
The gain switching based on the second knock determination level
Switching control means for switching the gain of the switching means
Is provided.

[0008]

According to the knocking control device for an internal combustion engine constructed as described above, when the knock detection signal from the knock detection means is determined to be higher than the set first determination level and the second determination level. In addition, the ignition timing of the internal combustion engine is controlled so as to suppress knock generation according to the level. In such a knock determination operation, gain switching control is performed to increase or decrease the gain so that the large knock determination level, which is the second determination level, falls within a predetermined range. Therefore, the level of the knock determination signal provided for knock determination is appropriately switched, and good and stable knock determination and knock control accompanying this knock determination are executed.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration, and a knock sensor 11 is attached to an internal combustion engine (not shown). The knock sensor 11 detects a mechanical vibration accompanying the knock phenomenon when a knock occurs in the internal combustion engine, and an electric vibration signal corresponding to the vibration is transmitted to the knock sensor.
It will be output from 11.

A detection signal corresponding to the mechanical vibration of the internal combustion engine from the knock sensor 11 is supplied to a band-pass filter (BPF) 12. Only the signal is passed. The knock detection signal that has passed through the band-pass filter 12 is supplied to a gain switching circuit 13,
This knock detection signal level is switched.

The knock detection signal for which the gain is set in the gain switching circuit 13 is supplied to first and second comparators 14 and 15 for performing knock determination. The first and second comparators 14 and 15 have a normal determination level from a normal knock determination level setting circuit 16, respectively.
The large knock determination level from the large knock determination level setting circuit 17 is supplied as a comparison value. An output signal from the first or second comparator 14 or 15 is supplied to a knock control circuit 18 as a control command signal to control the ignition timing of the internal combustion engine. Specifically, the ignition timing retard amount is determined according to the knock detection intensity.

Here, knock detection level setting circuits 16 and 17 are supplied with a knock detection signal from gain switching circuit 13. Based on the knock detection signal level, normal and large knock determination levels are created. I am trying to be.

The output signal from the large knock determination level setting circuit 17 is further supplied to a gain switching control circuit 19, for example, in a state where the large knock determination level is set.
A switching command is given to the gain switching circuit 13 to increase or decrease the gain of the knock detection signal.

FIG. 2 shows an example of a circuit specifically embodying the gain switching circuit 13 and includes a gain switching amplifier.
131, resistors R1, R2, R3 connected in series.
Are selectively short-circuited by switches S1, S2 and S3, respectively.

An output signal from the gain switching amplifier 131 is supplied to a control circuit 133 via a peak hold circuit 132. The control circuit 133 has the function of the gain switching control circuit 19 of FIG. 1. In response to a command from the control circuit 133, the switches S1 to S3 are selectively turned on to control the series connection of the resistors R1 to R3. , That is, the amplification gain is switched and set. Here, since there is a possibility that switching noise may occur at the time of this gain switching, it is effective to perform this gain switching operation immediately after the end of the knock determination section.

FIG. 3 shows a routine of gain switching for performing such ignition timing control and knock determination processing. First, in step 101, the gain magnification G obtained at the time of the previous ignition is set. Then, in step 102, the maximum value (V peak value) Vp of the detection signal of the knock detection sensor 11 detected in the predetermined knock determination section is detected. In step 103, the constant K is multiplied by the background value Vbg,
A knock determination level Vref for performing knock determination is set.

In this manner, the maximum value Vp of the knock detection signal is obtained.
Is detected, and when the knock determination level Vref is set, the routine proceeds to step 104, where the maximum value Vp is compared with a predetermined knock determination level Vref, and the maximum value Vp of the knock detection value is set to be smaller than the knock determination level Vref. If it is determined that it is smaller, the routine proceeds to step 105, where it is determined that "no knock".

Specifically, as shown in FIG. 4, a knock determination section is set corresponding to the rotation angle of the internal combustion engine, that is, corresponding to the explosion process, and a signal corresponding to the knock determination section is set. Is used as a gate signal for detecting a knock detection signal. The output signal from knock sensor 11 output based on this gate signal is used as a knock sensor signal, and the peak value of this signal is compared with a predetermined determination level Vref.

If it is determined in step 104 that the maximum value Vp is larger than the determination level Vref, the flow advances to step 106 to compare the maximum value Vp with twice the determination level 2Vref. Then, according to the result of this determination, step 10
Proceed to 7 and 108 to make a small knock determination or a large knock determination. Thereafter, in step 109, the background value Vbg is updated according to the maximum value Vp of the knock detection signal.

Here, an upper limit judgment level Vup and a lower limit judgment level Vund for gain switching are set. For example, the upper limit judgment level Vup is set to a value twice as large as the lower limit judgment level Vund.

In step 110, the upper limit judgment level Vup set in this way is compared with a value twice as large as the knock judgment level Vref, and the value twice as large as the knock judgment value Vref is higher than the upper limit judgment level Vup. If it is determined that the gain is large, the routine proceeds to step 111, where the gain G set so far is set to "1/2". Also, in step 112, the background value Vbg is set to "1/2", and this processing is terminated.

If it is determined in step 110 that the value twice the knock determination value Vref is smaller than the upper limit determination level Vup, the process proceeds to step 113 where the value twice the knock determination value Vref is compared with the lower limit determination level Vund. I do. And Vref
When it is determined that the value of twice is smaller than the lower limit determination level Vund, the routine proceeds to step 114, where the gain G is doubled, and in step 115, the background value Vbg is doubled, and this processing is terminated. .

If it is determined in step 113 that the value twice as large as the knock determination level Vref is equal to or larger than the lower limit determination level Vund, the flow advances to step 116 to proceed to step 116 where the gain G and the back G are determined. This processing is terminated while maintaining the ground value Vbg as it is.

By executing such a knock determination routine, the large knock determination level is reduced to the lower limit determination level Vund.
The gain G is set so as to be set between the upper limit determination level Vup.

In the timing chart shown in FIG. 4, the left half shows the operation of increasing the gain.
In this range, since the large knock determination level “2 × Vref” is smaller than the lower limit determination level Vund, the gain is increased at the next ignition timing. On the other hand, the right half is an operation of decreasing the gain, and since the knock determination level is higher than the upper limit determination level Vup, the gain is reduced at the next ignition timing.

Conventionally, the gain is switched according to the knock determination level and the output signal. Therefore, the knock determination level Vref does not saturate the dynamic range, but large knock determination becomes difficult.

In this regard, in the apparatus shown in the embodiment,
The gain is set in a predetermined range such that the large knock determination level does not saturate the dynamic range,
Therefore, the large knock determination is reliably performed.

In the embodiment, the large knock determination level has been described as being twice the normal determination level, but the present invention is not limited to this. In addition, although the judgment level is set to two levels, the number of steps may be further increased. In this case, the gain is switched according to the highest level.

Further, the gain is set to a power of two, which is not limited to this because, when handled by a digital computer, the processing of steps 111 to 115 can be easily performed by software operation. Further, in this embodiment, the number of cylinders of the internal combustion engine is not taken into consideration. However, in the case of a multi-cylinder engine, it goes without saying that a gain is set for each cylinder. Although the ignition timing is controlled by the determination of the knock state, other factors such as the air-fuel ratio and the supercharging pressure may be controlled.

[0030]

As described above, according to the knocking control apparatus for an internal combustion engine according to the present invention, when the detection signal from the knock sensor is switched in gain by the gain switching means, it is used for large knock determination. By using the determination level, the gain can be switched accurately according to the situation, and the knock can be appropriately controlled by the determination of the good knock state.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a knocking control device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a diagram showing a circuit example of a gain switching control part of the embodiment.

FIG. 3 is a flowchart illustrating a knock determination routine.

FIG. 4 is a timing chart for explaining a relationship with a gain change associated with a knock determination.

[Explanation of symbols]

11: knock sensor, 12: band-pass filter, 13: gain switching circuit, 14, 15: comparator, 16, 17: knock determination level setting circuit, 18: knock control circuit, 19: gain switching control circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-294748 (JP, A) JP-A-2-45716 (JP, A) JP-A-3-70844 (JP, A) JP-A-2- 308971 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 45/00

Claims (1)

(57) [Claims] 1. A knock detection means for detecting a knock state of an internal combustion engine, and a knock detection signal from the knock detection means is amplified.
Gain switching means for variably controlling the gain of the knock detection signal amplified by the gain switching means,
Comparing the first knock determining means for comparing the set first knock determination level, and the amplified knock detection signal is higher than the first knock determination <br/> level second knock determination level A second knock determination unit, based on a determination output from the first and second knock determination units, a knock control unit that controls knock of the internal combustion engine, based on the second knock determination level , A knocking control device for an internal combustion engine, comprising: a gain switching control means for switching and controlling the gain of the gain switching means.