JP2002047993A - Knock detector for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately judge a knock based on a signal level extracted from a vibration waveform signal generated in an internal combustion engine and improve knock detectability. SOLUTION: Signal levels of central frequencies f1, f2,..., f4 in frequency bands peculiar to a plurality of knocks at 1 combustion timing of the internal combustion engine and a signal level of a central frequency f5 in a frequency band differing from the frequency bands peculiar to knocks and being free from the influence of knock are extracted (step S102). If the signal levels of each central frequency f1, f2,..., f4 exceed corresponding knock judgement levels (f5×K1), (f5×K2),..., (f5×K4), it is judged that a knock occurs (step S108). Consequently, whether a knock occurs or not is accurately judged by only signal levels depending on a plurality of frequency bands extracted at 1 combustion timing of each cylinder of the internal combustion engine to improve knock detectability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knock detection device for an internal combustion engine that determines knock based on a signal level extracted from a vibration waveform signal generated in the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, a knock determination level for knock detection in a knock detection device for an internal combustion engine is obtained by extracting a signal level output from a knock sensor, obtaining a peak value thereof,
It is set according to a so-called background level generated from an integral value or the like. At this time, the peak value, integral value, etc.
Smoothing (averaging / averaging) processing is performed for each combustion cycle. There is known a technique of comparing the knock determination level set in this way with the original signal level to determine whether knock has occurred.

[0003]

When the signal level output from the knock sensor changes suddenly, for example,
Even if there is a sudden change in the engine speed or load of the internal combustion engine, smoothing is performed for each combustion cycle, and therefore, there is a case where the occurrence of knocking is erroneously determined due to a response delay.

[0004] Further, even if knock actually occurs, knock detection may not be possible if the background level is too high.

Accordingly, the present invention has been made to solve such a problem, and a knock determination can be accurately made based on a signal level extracted from a vibration waveform signal generated in an internal combustion engine, and knock detectability can be improved. It is an object to provide a knock detection device for an internal combustion engine.

[0006]

According to the knock detecting apparatus for an internal combustion engine of the present invention, a plurality of signal extracting means extract from a vibration waveform signal generated in the internal combustion engine detected by the signal detecting means. The signal levels for each of a plurality of frequency bands at one combustion timing are compared by knock determination means, and knock determination is made based on the magnitude relation therebetween. Therefore, even if the background level changes transiently due to the occurrence of knock, it is not necessary to consider the influence of the knock history up to that point, that is, the response delay due to the smoothing of the knock determination level. As described above, only the signal levels for each of the plurality of frequency bands extracted at one combustion timing of each cylinder of the internal combustion engine are used, and the magnitude relation therebetween is compared to accurately determine whether knock has occurred. .

The knock determination means in the knock detection device for an internal combustion engine according to claim 2 compares the signal level of another predetermined signal extraction means with the signal level of another predetermined signal extraction means as a reference. You. As described above, only the signal levels for a plurality of frequency bands extracted at one combustion timing of each cylinder of the internal combustion engine are used,
By comparing the magnitude relations based on one of the predetermined signal levels, the presence / absence of knock occurrence is accurately determined, and the knock detectability is also improved.

In the knock detection device for an internal combustion engine according to the third aspect, the signal level in a frequency band which is not affected by the knock, which is different from the frequency band unique to the knock, is extracted by the other signal extracting means. A signal level of a specific frequency band is extracted. in this way,
Only the signal level for each of a plurality of frequency bands extracted at one combustion timing of each cylinder of the internal combustion engine is used, and one of the signal levels is different from a knock-specific frequency band and is not affected by knock. It is determined whether knocking has occurred accurately by comparing the magnitude relationship with other signal levels on the basis thereof,
Knock detection is also improved.

According to a fourth aspect of the present invention, there is provided a knock detecting device for a knock detecting device for an internal combustion engine, wherein a knock signal is determined by another signal extracting means based on an average value of signal levels of a plurality of predetermined signal extracting means. Compared to the level. As described above, only the signal levels for each of the plurality of frequency bands extracted at one combustion timing of each cylinder of the internal combustion engine are used, and the magnitude relation is compared based on the average value of predetermined signal levels among them. As a result, the presence / absence of knock occurrence is accurately determined, and the knock detectability is also improved.

In the knock detection device for an internal combustion engine according to claim 5, signal levels in a frequency band which is not affected by knock, unlike a knock-specific frequency band, are extracted. A signal level in a frequency band specific to knock is extracted. As described above, only the signal levels for each of the plurality of frequency bands extracted at one combustion timing of each cylinder of the internal combustion engine are used, and some of the predetermined signal levels are different from the knock-specific frequency bands and knocked. The signal level is set to a signal level of a frequency band that is not affected, and the magnitude relationship with other signal levels is compared with reference to the average value of the signal levels, so that the presence / absence of knock occurrence is accurately determined, and knock detectability is also improved. .

In the knock determination device in the knock detection device for an internal combustion engine according to claim 6, the number of signal extraction devices used for knock determination is changed for each operating condition of the internal combustion engine or for each cylinder. That is, for example, if it is known in advance that noise is generated at a predetermined frequency and is likely to be superimposed for each operating condition or cylinder of the internal combustion engine, the knock determination is not performed at that frequency. As a result, the presence / absence of knock occurrence is accurately determined, and knock detectability is also improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples.

FIG. 1 is a block diagram showing an overall configuration of a knock detection device for an internal combustion engine according to one embodiment of the present invention, and FIG. 2 is a time chart showing transition states of various signals in FIG. is there. Here, FIG. 2A shows the TDC (Top Degree) of each cylinder (# 1 cylinder to # 6 cylinder) of the internal combustion engine.
ad center: compression top dead center). FIG. 2B shows signal processing at one combustion timing from # 1 cylinder TDC to # 2 cylinder TDC in FIG. 2A. It is shown enlarged.

In FIG. 1, knock sensors 11 and 12 are provided for two cylinder blocks in a V-type six-cylinder four-stroke internal combustion engine (not shown).
The knock sensors 11 and 12 convert vibrations of a cylinder block of the internal combustion engine into electric signals. In the present embodiment, non-resonant sensors are used for frequency analysis.

Output signals from the knock sensors 11 and 12, for example, are passed through LPFs (Low Pass Filters) 13 and 14 for filtering low frequency components of 20 kHz or less, respectively. Is removed (refer to the knock sensors 11 and 12 shown in FIG. 2A). Then, an output signal from the knock sensors 11 and 12 corresponding to one combustion timing of each cylinder is selected by an MPX (Multiplexer) 15, and a DSP (Digital Signal Processor: DSP) capable of high-speed multiplication processing is selected.
Digital signal processor) 20 (see DSP input signal shown in FIG. 2A).

The DSP 20 mainly includes an A / D converter (A
nalog to Digital Converter) 21, frequency analysis unit 2
2. The knock determination unit 23 is provided. In the DSP 20, a knock determination section setting signal is input from the knock determination section 23 to the A / D converter 21, and output signals from the knock sensors 11, 12 in the knock determination section set in accordance with the knock occurrence section are output as 200. High-speed A / D conversion is performed at about [kHz]. Subsequently, after the knock determination section based on the knock determination section setting signal ends, the frequency analysis unit 22 performs, for example, a well-known FFT (Fast Fou
rier Transform: fast Fourier transform), wavelet
(Wavelet) conversion, digital filter processing, and the like are performed. Then, a signal level (spectral intensity) for each frequency band extracted as a result of the frequency analysis by the frequency analysis unit 22 is output to the knock determination unit 23, and the presence or absence of knock is determined by a knock determination process described later (see FIG. 2
(See DSP processing shown in (b)).

The result of this determination is transmitted from the DSP 20 to the microcomputer 30 by communication. Then, the microcomputer 30 executes advance / delay control of ignition timing, fuel injection correction control, and the like as knock suppression processing according to the determination result of the presence / absence of knock from the DSP 20.

Next, an outline of the DSP processing by the DSP 20 will be described with reference to the block diagram of FIG.

In FIG. 3, as described above, the LPF 1
Knock sensor 11, 1 via MPX15
2 is input to the A / D converter 21 at a high speed A / D
D conversion is performed. Then, the frequency analysis unit 22 performs FFT,
The center frequencies f 1, f 2,
The signal levels at f3,..., fn-1, fn are determined. Here, f1, f2, f3,..., Fn-1 are preset center frequencies of a knock-specific frequency band.
n is a center frequency of a frequency band which is not affected by knock unlike a preset knock-specific frequency band.

The center frequency f 1, f 2, f 3,.
.., Fn-1 and the signal level of the center frequency fn of the reference frequency band because they are not affected by knock unlike the knock-specific frequency band.
The knock determination levels obtained by multiplying K2, K3,..., Kn-1 are respectively compared by a comparator, and the presence / absence of knock occurrence is determined for each knock-specific frequency band. Sent to

Next, a DSP used in a knock detection apparatus for an internal combustion engine according to an embodiment of the present invention.
FIG. 4 showing a specific knock determination processing procedure at 20.
This will be described with reference to FIG.
Here, FIG. 5 shows the signal level of the center frequency of each frequency band corresponding to the frequency analysis processing of FIG. 4, FIG. 5 (a) shows the case where knock occurs, and FIG. 5 (b) shows the case where knock does not occur. . The knock determination routine is repeatedly executed by the DSP 20 at each combustion timing of each cylinder of the internal combustion engine.

In FIG. 4, first, at step S101, the vibration waveform signal from the knock sensor 11 or the knock sensor 12 read into the A / D converter 21 at one combustion timing via the LPFs 13, 14 and the MPX 15 is A / D. D conversion is performed. Next, the process proceeds to step S102, in which frequency analysis is performed on the preset center frequencies f1, f2, f3, and f4 of the knock-specific frequency band and the center frequency f5 of the frequency band that is not affected by knock unlike the knock-specific frequency band. Is performed, and the signal level at each center frequency is obtained. Next, step S
The routine proceeds to step 103, where it is determined whether the signal level of the center frequency f1 obtained in step S102 exceeds a value obtained by multiplying the signal level of the center frequency f5 by a predetermined gain K1, that is, the knock determination level (= f5 × K1). Is determined. The determination condition of step S103 is not satisfied, that is, the signal level of the center frequency f1 is equal to the knock determination level (= f5 × K
1) If smaller than the following, the process proceeds to step S104.

In step S104, the signal level of the center frequency f2 is a value obtained by multiplying the signal level of the center frequency f5 by a predetermined gain K2, that is, the knock determination level (= f5 ×
K2) is determined. Step S104
When the determination condition is not satisfied, that is, when the signal level of the center frequency f2 is lower than the knock determination level (= f5.times.K2), the process proceeds to step S105. Step S
At 105, it is determined whether or not the signal level of the center frequency f3 exceeds a value obtained by multiplying the signal level of the center frequency f5 by a predetermined gain K3, that is, a knock determination level (= f5 × K3). If the determination condition of step S105 is not satisfied, that is, if the signal level of the center frequency f3 is lower than the knock determination level (= f5 × K3), the process proceeds to step S106.

In step S106, the signal level of the center frequency f4 is a value obtained by multiplying the signal level of the center frequency f5 by a predetermined gain K4, that is, the knock determination level (= f5 ×
K4) is determined. Step S106
If the determination condition is not satisfied, that is, if the signal level of the center frequency f4 is lower than the knock determination level (= f5.times.K4), the process proceeds to step S107. Step S
At 107, it is determined that no knock has occurred at this one combustion timing, and the routine ends (see FIG. 5B). The result of this determination is sent to the microcomputer 30, and the ignition timing advance control and the like, which are well-known as control when there is no knock, are executed.

On the other hand, when the determination condition of step S103 is satisfied, that is, when the signal level of the center frequency f1 is higher than its knock determination level (= f5 × K1), or when the determination condition of step S104 is satisfied, that is, the center frequency f
2 is the knock determination level (= f5 × K2
), Or when the determination condition of step S105 is satisfied, that is, when the signal level of the center frequency f3 exceeds the knock determination level (= f5 × K3),
Alternatively, the determination condition of step S106 is satisfied, that is, the signal level of the center frequency f4 is equal to the knock determination level (= f
If it exceeds 5 * K4), the process proceeds to step S108. In step S108, it is determined that knocking has occurred at this combustion timing, and this routine ends (see FIG. 5A). The result of this determination is sent to the microcomputer 30, and a well-known ignition timing retard control or the like is performed as control when there is knock.

As described above, the knock detection apparatus for an internal combustion engine according to the present embodiment is detected by the knock sensors 11 and 12 as signal detection means for detecting a vibration waveform signal generated in the internal combustion engine. , F2,..., F
5, the frequency analysis unit 2 of the DSP 20 for extracting the signal level
The DSP 20 compares the signal levels of the plurality of signal extraction means achieved in step 2 with each signal level at one combustion timing of the internal combustion engine extracted by the plurality of signal extraction means, and determines a knock based on their magnitude relation. And a knock determination means achieved by knock determination section 23. The knock determination means achieved by the knock determination unit 23 of the DSP 20 of the knock detection device for an internal combustion engine of the present embodiment is a predetermined one of a plurality of signal extraction means achieved by the frequency analysis unit 22 of the DSP 20. With reference to the signal level of the center frequency f5 by the two signal extracting means,
The center frequencies f1, f2,
.., F4. And
The predetermined one signal extraction means achieved by the frequency analysis unit 22 of the DSP 20 of the knock detection device for an internal combustion engine according to the present embodiment extracts a signal level of a center frequency f5 which is a frequency band different from a knock-specific frequency band. Is what you do.

That is, as signal levels for a plurality of frequency bands at one combustion timing of the internal combustion engine, signal levels of center frequencies f1, f2,... And the signal level of the center frequency f5 of the frequency band not affected by Then, each center frequency f1, f2,
,.., K4 are multiplied by the signal level of the center frequency f5 and the signal level of the center frequency f5, the knock determination levels (f5 × K1), (f5 × K2),.
K4) is compared and determined, and each center frequency f1 is determined.
, F2,..., F4 correspond to the knock determination levels (f5 × K1), (f5 × K2),.
If it exceeds (f5 × K4), it is determined that knock has occurred. Even if there is a transient change in the background level due to the occurrence of knock, it is not necessary to consider the influence of the knock history up to that point, that is, a response delay due to smoothing of the knock determination level. As a result, the presence or absence of knock can be accurately determined based only on the signal levels for a plurality of frequency bands extracted at one combustion timing of each cylinder of the internal combustion engine, and knock detectability can be improved.

Next, a DSP used in a knock detection device for an internal combustion engine according to an embodiment of the present invention will be described.
6 showing a modification of the processing procedure for knock determination in FIG.
A description will be given based on the flowchart of FIG. The knock determination routine is repeatedly executed by the DSP 20 at each combustion timing in each cylinder of the internal combustion engine.

In FIG. 6, first, at step S201, the vibration waveform signal from the knock sensor 11 or the knock sensor 12 read into the A / D converter 21 at one combustion timing via the LPFs 13, 14 and the MPX 15 is A / D. D conversion is performed. Next, the process proceeds to step S202, where the predetermined center frequencies f1, f2, f3, and f4 of the knock-specific frequency bands and the center frequencies f5 and f6 of the frequency bands that are not affected by knock unlike the knock-specific frequency bands are respectively set. A frequency analysis is performed to determine a signal level at each center frequency.

Next, the process proceeds to step S203, where the average value fbg ｛= (f5 + f6) / 2｝ of the signal levels at the center frequencies f5 and f6 determined in step S202 is calculated. Next, the process proceeds to step S204, where the signal level at the center frequency f1 is a value obtained by multiplying the average value fbg of the signal levels at the center frequencies f5 and f6 by a predetermined gain K1.
That is, it is determined whether or not the knock exceeds the knock determination level (= fbg × K1). When the determination condition of step S204 is not satisfied, that is, when the signal level of the center frequency f1 is lower than the knock determination level (= fbg × K1), the process proceeds to step S205.

In step S205, whether the signal level at the center frequency f2 exceeds a value obtained by multiplying the average value fbg of the signal levels at the center frequencies f5 and f6 by a predetermined gain K2, that is, whether the knock determination level (= fbg × K2) is exceeded. Is determined. If the determination condition of step S205 is not satisfied, that is, if the signal level of the center frequency f2 is lower than the knock determination level (= fbg × K2), step S2
Shift to 06. In step S206, the center frequency f
It is determined whether the signal level of No. 3 exceeds a value obtained by multiplying the average value fbg of the signal levels at the center frequencies f5 and f6 by a predetermined gain K3, that is, a knock determination level (= fbg × K3). When the determination condition of step S206 is not satisfied, that is, when the signal level of the center frequency f3 is lower than the knock determination level (= fbg × K3), the process proceeds to step S207.

In step S207, it is determined whether the signal level of the center frequency f4 exceeds a value obtained by multiplying the average value fbg of the signal levels at the center frequencies f5 and f6 by a predetermined gain K4, that is, the knock determination level (= fbg × K4). Is determined. If the determination condition of step S207 is not satisfied, that is, if the signal level of the center frequency f4 is lower than the knock determination level (= fbg × K4), step S2 is performed.
08. In step S208, it is determined that no knock occurs at this combustion timing, and this routine ends. The result of this determination is sent to the microcomputer 30, and the ignition timing advance control and the like, which are well-known as control when there is no knock, are executed.

On the other hand, when the determination condition of step S204 is satisfied, that is, when the signal level of the center frequency f1 is higher than the knock determination level (= fbg × K1), or when the determination condition of step S205 is satisfied, that is, the center frequency f
2 is the knock determination level (= fbg × K2
), Or when the determination condition of step S206 is satisfied, that is, when the signal level of the center frequency f3 exceeds the knock determination level (= fbg × K3),
Alternatively, the determination condition of step S207 is satisfied, that is, the signal level of the center frequency f4 is equal to the knock determination level (= f
If it is larger than (bg × K4), the flow shifts to step S209. In step S209, it is determined that knock has occurred at this combustion timing, and this routine ends.
This determination result is sent to the microcomputer 30, and
A well-known ignition timing retard control or the like is performed as the knock control.

As described above, the knock determination means achieved by the knock determination section 23 of the DSP 20 of the knock detection apparatus for an internal combustion engine of the present modified example includes a plurality of signal extraction means achieved by the frequency analysis section 22 of the DSP 20. Of the center levels fbg 周波 数 = (f5 + f6) / 2｝ of the center frequencies f5 and f6 of some of the predetermined signal extraction means, and the center frequencies f1, f2,.
This is to compare with the signal level of f4. Some predetermined signal extraction means achieved by the frequency analysis unit 22 of the DSP 20 of the knock detection device for an internal combustion engine according to the present modification include center frequencies f5 and f6 which are different from the knock-specific frequency band. Is to extract the signal level.

That is, as the signal level for each of a plurality of frequency bands at one combustion timing of the internal combustion engine, the signal level of the center frequency f1, f2,... The center frequency f of the frequency band that is not affected by knock unlike the frequency band
5, and the signal level of f6 are extracted. Then, the average value fbg of the signal levels of the center frequencies f1, f2,..., F4 and the signal levels of the center frequencies f5, f6 == (f5 + f6).
) / 2} to predetermined signal levels K1, K2,.
4, the knock determination level (fbg × K1), (fbg
× K2),..., (Fbg × K4) are compared, and the signal levels of the center frequencies f1, f2,..., F4 correspond to the knock determination levels (fbg × K1),
If it exceeds (fbg × K2),..., (Fbg × K4), it is determined that knock has occurred. As a result, the presence or absence of knock can be accurately determined based only on the signal levels for a plurality of frequency bands extracted at one combustion timing of each cylinder of the internal combustion engine, and knock detectability can be improved.

Next, a DSP used in a knock detection device for an internal combustion engine according to one embodiment of the present invention.
20 will be described with reference to FIGS. 8 and 9 based on a flowchart of FIG. 7 showing another modification of the knock determination processing procedure in 20. Here, FIG. 8 shows the center frequencies f1 and f2 of the respective frequency bands when knock occurs at different engine speeds 2000 and 4000 [rpm] with respect to the frequency [kHz].
,..., F5 are illustrations showing the difference in signal level. FIG. 9 shows the relationship between the engine speed [rpm] and the 1
FIG. 4 is an explanatory diagram showing a relationship between signal levels of two center frequencies f2 and their knock determination levels (= f5.times.K2). The knock determination routine is repeatedly executed by the DSP 20 at each combustion timing in each cylinder of the internal combustion engine.

In FIG. 7, first, at step S301, the vibration waveform signal from the knock sensor 11 or the knock sensor 12 read into the A / D converter 21 at one combustion timing via the LPFs 13, 14 and the MPX 15 is A / D. D conversion is performed. Next, the process proceeds to step S302, in which frequency analysis is performed on the preset center frequencies f1, f2, f3, and f4 of the knock-specific frequency band and the center frequency f5 of the frequency band that is not affected by knock unlike the knock-specific frequency band. Is performed, and the signal level at each center frequency is obtained. Next, step S
The routine proceeds to 303, where the engine speed of the internal combustion engine is 4000
It is determined whether it is less than [rpm]. Step S30
3 is not satisfied, that is, the engine speed is 400
If it is higher than 0 [rpm], the flow shifts to step S304, where the signal level of the center frequency f1 exceeds the value obtained by multiplying the signal level of the center frequency f5 by the predetermined gain K1, that is, the knock determination level (= f5 × K1). Is determined. The determination condition of step S304 is not satisfied, that is,
If the signal level of the center frequency f1 is lower than the knock determination level (= f5.times.K1), step S30 is executed.
Move to 5.

In step S305, the signal level of the center frequency f2 is a value obtained by multiplying the signal level of the center frequency f5 by a predetermined gain K2, that is, the knock determination level (= f5 ×
K2) is determined. Step S305
If the determination condition is not satisfied, that is, if the signal level of the center frequency f2 is smaller than the knock determination level (= f5.times.K2), the process proceeds to step S306. On the other hand, when the determination condition of step S303 is satisfied, that is, when the engine speed is lower than 4000 [rpm], step S30 is performed.
4 and step S305 are skipped and step S30
By shifting to 6, the knock determination in the low frequency band is prohibited.

The reason for this is that, as shown in FIG. 8, the engine rotational speed at the time of knock occurrence is smaller than 4000 [rpm] when the knock occurrence is less than 4000 [rpm]. For example, the center frequency at 2000 [rpm] is used. f1,
At f2, the signal level tends to decrease. That is, as shown in FIG. 9, the relationship between the signal level of the center frequency f2 and the knock determination level (= f5.times.K2) with respect to the engine speed [rpm] indicates that the lower the engine speed, the higher the signal level of the center frequency f2. The knock determination level (= f
5 × K2). This is because if low frequency noise occurs in such a region where the engine speed is low, the probability of erroneously determining whether knock has occurred is increased.

In step S306, the signal level of the center frequency f3 is a value obtained by multiplying the signal level of the center frequency f5 by a predetermined gain K3, that is, the knock determination level (= f5 ×
K3) is determined. Step S306
If the determination condition is not satisfied, that is, if the signal level of the center frequency f3 is lower than the knock determination level (= f5.times.K3), the flow shifts to step S307.

In step S307, the signal level of the center frequency f4 is a value obtained by multiplying the signal level of the center frequency f5 by a predetermined gain K4, that is, the knock determination level (= f5 ×
K4) is determined. Step S307
If the determination condition is not satisfied, that is, if the signal level of the center frequency f4 is lower than the knock determination level (= f5.times.K4), the process proceeds to step S308. Step S
At 308, it is determined that no knock occurs at this combustion timing, and this routine ends. The result of this determination is sent to the microcomputer 30, and the ignition timing advance control and the like, which are well-known as control when there is no knock, are executed.

On the other hand, when the determination condition of step S304 is satisfied, that is, when the signal level of the center frequency f1 is higher than the knock determination level (= f5 × K1), or when the determination condition of step S305 is satisfied, that is, the center frequency f
2 is the knock determination level (= f5 × K2
), Or when the determination condition of step S306 is satisfied, that is, when the signal level of the center frequency f3 exceeds the knock determination level (= f5 × K3),
Alternatively, the determination condition of step S307 is satisfied, that is, the signal level of the center frequency f4 is equal to the knock determination level (= f
If it exceeds 5 * K4), the flow shifts to step S309. In step S309, it is determined that knock has occurred at this combustion timing, and this routine ends.
This determination result is sent to the microcomputer 30, and
A well-known ignition timing retard control or the like is performed as the knock control.

As described above, the knock determination means achieved by the knock determination unit 23 of the DSP 20 of the knock detection device for an internal combustion engine according to the present modification uses the signal achieved by the frequency analysis unit 22 of the DSP 20 used for knock determination. The number of extraction means
The operating conditions of the internal combustion engine are changed according to the engine speed. That is, the engine rotation speed is 4000 [rpm
m], the center frequency f1 of the frequency band which is not affected by knock unlike the frequency band unique to knock,
The signal level of f2 tends to be low even when knock occurs. Therefore, the engine rotation speed is 4000
[Rpm] or more, the center frequency f of a frequency band that is not affected by knock unlike a frequency band unique to knock.
Knock determination is made using four signal levels of 1, f2,..., F4. When the engine speed is less than 4000 [rpm], knock determination is made by changing to two signal levels of center frequencies f3 and f4. As a result, the presence or absence of knock can be accurately determined based only on the signal levels for a plurality of frequency bands extracted at one combustion timing of each cylinder of the internal combustion engine, and knock detectability can be improved.

By the way, in the above modification, the number of signal levels at the center frequency of the frequency band which is not affected by knock unlike the frequency band unique to knock used for knock determination, that is, the number of signal extracting means is set as the operating condition of the internal combustion engine. Although it is changed according to the engine rotation speed, the present invention is not limited to this when practicing the present invention, and the number of signal extraction means is changed according to the knock occurrence situation for each cylinder of the internal combustion engine. You may do so.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a knock detection device for an internal combustion engine according to one example of an embodiment of the present invention.

FIG. 2 is a time chart showing transition states of various signals in FIG.

FIG. 3 is a block diagram showing an outline of DSP processing by the DSP of FIG. 1;

FIG. 4 is a flowchart showing a procedure for knock determination in a DSP used in a knock detection device for an internal combustion engine according to one embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a signal level of a center frequency of each frequency band corresponding to the frequency analysis processing of FIG. 4;

FIG. 6 is a flowchart illustrating a modified example of a knock determination processing procedure in a DSP used in a knock detection device for an internal combustion engine according to one example of an embodiment of the present invention.

FIG. 7 is a flowchart showing another modified example of the procedure of the knock determination in the DSP used in the knock detection device for the internal combustion engine according to one embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a difference in signal level at the center frequency of each frequency band when knock occurs at different engine rotational speeds with respect to the frequency in the processing of FIG. 7;

9 is an explanatory diagram showing the relationship between the signal level of one center frequency and the knock determination level with respect to the engine rotational speed in the processing of FIG. 7;

[Explanation of symbols]

 11, 12 knock sensor (signal detection means) 20 DSP (signal extraction means, knock determination means)

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Naoki Kokubo 1-1-1 Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (reference) 3G084 DA04 DA27 DA38 EA11 EB08 EB25 EC01 FA25 FA33

Claims (6)

[Claims] 1. A signal detecting means for detecting a vibration waveform signal generated in an internal combustion engine, and a plurality of signal extraction means for receiving the vibration waveform signal detected by the signal detecting means and extracting a signal level for each of a plurality of frequency bands. And a knock determination unit that compares respective signal levels at one combustion timing of the internal combustion engine extracted by the plurality of signal extraction units and determines a knock based on their magnitude relationship. Knock detection device for an internal combustion engine. 2. The knock determination unit according to claim 1, wherein a signal level of a predetermined one of the plurality of signal extraction units is used as a reference and compared with a signal level of another signal extraction unit. Item 2. A knock detection device for an internal combustion engine according to Item 1. 3. The knock detection device for an internal combustion engine according to claim 2, wherein the predetermined one signal extraction unit extracts a signal level in a frequency band different from a knock-specific frequency band. 4. The knock determination means according to claim 1, wherein said knock determination means compares the signal levels of a plurality of predetermined signal extraction means with the signal levels of other signal extraction means. The knock detection device for an internal combustion engine according to claim 1, wherein: 5. The knock detection apparatus for an internal combustion engine according to claim 4, wherein said predetermined some signal extraction means extracts a signal level in a frequency band different from a knock-specific frequency band. 6. The knock of an internal combustion engine according to claim 1, wherein said knock determination means changes the number of said signal extraction means used for knock determination for each operating condition or cylinder of said internal combustion engine. Detection device.