JP2003278592A - Knock control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a knock control device of an internal combustion engine, wherein in generation torque of the internal combustion engine and drivability are improved by preventing wrong knock restraint control due to a pseudo knock signal. <P>SOLUTION: The reason why a current value of a peak value LVPK becomes larger than the preceding value after the start of lag side control in S120 is considered to be a wrong lag due to pseudo knock. Therefore, in the step S140, in the case where the current value of peak value LVPK becomes larger than the preceding value after the start of lag side control, Q value of a band-pass filter is changed to be larger. Thus, the band width of a vibration waveform signal extracted by the band-pass filter becomes narrow so that a pseudo knock signal is not extracted by the filter. Accordingly, a wrong lag due to pseudo knock is ended. As a result, lowering of generation torque of an engine due to continuation of a wrong lag and deterioration of drivability are prevented. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knock control device for an internal combustion engine, which controls an operating state of the internal combustion engine based on a knock determination result.

[0002]

2. Description of the Related Art Generally, a knock control device for an internal combustion engine extracts a knock signal in a knock frequency band (for example, 12 to 14 KHz) from an output of a knock sensor for detecting vibration of the internal combustion engine by a filter such as a bandpass filter. The peak value of the extracted knock signal is compared with the knock determination value. If the peak value of the knock signal exceeds the knock determination value by the comparison and it is determined that there is knock, the ignition timing is controlled to the retard side. As the knock sensor, for example, a piezoelectric block vibration sensor that is attached to a cylinder block of an internal combustion engine and detects vibration transmitted to the block is used.

[0003]

In the above prior art, when the Q value of the bandpass filter is set to a wide band of about 10 dB, signals of various frequencies that do not have a specific frequency characteristic such as a pseudo knock signal. The component is extracted by the same filter. "Pseudo knock" here
The main causes of the electric noise are electrical noise, mechanical noise of valve system and piston system. Also, the "Q value" here is
In FIG. 6A showing the output distribution of the bandpass filter, when the central wavelength (resonance wavelength) is f0 and the bandwidth at a position 3 dB lower than the maximum value of the gain is Δf, Q value = 20log (f0 / Δf) It is represented by. From this definition, it can be seen that the smaller the Q value of the bandpass filter, the wider the bandwidth, and the larger the Q value, the narrower the bandwidth (see FIG. 6B). This can be seen from FIGS. 7 and 8. Fig. 7 (a) shows a Q value of 25 dB.
7 shows the characteristics of the bandpass filter when
(B) shows the characteristics of the filter when the Q value is set to 10 dB. Then, in FIG. 8A, the Q value is 25 dB.
The vibration waveform signal extracted by the band-pass filter when set to is shown by the curve of reference numeral 10. Also, FIG.
In (b), the vibration waveform signal extracted by the bandpass filter when the Q value is set to 10 dB is shown by a curve of reference numeral 11.

As described above, when the Q value of the bandpass filter is set to a wide band of about 10 dB, the pseudo knock signal is easily extracted. However, when the peak value of the signal exceeds the knock determination value, the pseudo knock signal is knocked. And the ignition timing is controlled to the retard side. In this way, if the erroneous retard control (erroneous retard) by the pseudo knock signal is performed, even if the ignition timing is retarded as shown by the straight line 21 in FIG. The peak value (knock peak level) of the knock signal does not decrease,
Rather, it goes up. Originally, the knock disappears if the ignition timing is retarded, but the pseudo knock, for example, the pseudo knock due to mechanical noise of the piston system, changes the posture of the piston as the ignition timing is retarded. It tends to increase as the value increases.
In this manner, the false retard angle due to the pseudo knock signal increases the peak value of the pseudo knock signal, and thus the false retard angle due to the pseudo knock may be further continued. If the erroneous retardation due to the pseudo knock signal is continued in this way, the torque generated by the internal combustion engine is reduced and the driver's viability is deteriorated.

The present invention has been made by paying attention to such a conventional problem, and an object thereof is to prevent erroneous knock suppression control by a pseudo knock signal from being performed, and to generate torque of an internal combustion engine. Another object of the present invention is to provide a knock control device for an internal combustion engine, which improves the driver's fuel efficiency.

[0006]

[Means for Solving the Problems] Means for achieving the above-mentioned objects and their effects will be described below. The invention according to claim 1 is a knock sensor for detecting vibration of an internal combustion engine, a vibration waveform extracting means for extracting a vibration waveform signal in a predetermined frequency band from an output signal of the knock sensor, and a vibration extracted by the extracting means. In a knock control device for an internal combustion engine, which comprises knock determination means for determining the presence or absence of knock based on a waveform signal, and which controls a knock control factor such as ignition timing to the knock suppression side when the knock determination means determines that knock is present. During the control of the knock control factor to the knock suppression side, the vibration waveform signal at the time of knock determination is,
The signal discrimination means for discriminating whether it is a true knock signal or a pseudo knock signal, and the vibration when the vibration waveform signal at the time of knock determination is a pseudo knock signal by the signal discrimination means. The gist is to provide a Q value changing means for changing the Q value of the waveform extracting means to a larger side.

According to this structure, when the signal determining means determines that the vibration waveform signal at the time of knock determination is a pseudo knock signal, the Q value changing means changes the Q value of the vibration waveform extracting means to the larger side. To do. As a result, the bandwidth of the vibration waveform signal extracted by the vibration waveform extracting means is narrowed, and the pseudo knock signal is not extracted by the extracting means, so that the control to the wrong knock suppression side by the pseudo knock signal is ended. . As a result, it is possible to prevent a decrease in the torque generated by the internal combustion engine and a deterioration in the driver's ability due to the erroneous control to the knock suppression side being continued. Therefore, it is possible to prevent erroneous knock suppression control due to the pseudo knock signal, and it is possible to improve the torque generated by the internal combustion engine and the driver's vitality. The term "control to the knock suppression side" as used herein means to control the ignition timing, which is one of the knock control factors, to the retard side.

According to a second aspect of the present invention, in the knock control device for the internal combustion engine according to the first aspect, peak value detecting means for detecting the peak value of the vibration waveform signal for each ignition cycle of each cylinder is provided, and The signal determination means, while controlling the knock control factor to the knock suppression side, the peak value of the vibration waveform signal detected in the current ignition cycle by the peak value detection means is equal to or less than the peak value detected in the previous ignition cycle. In the above case, the gist is to determine that the vibration waveform signal at the time of knock determination is a pseudo knock signal, and otherwise determine that the vibration waveform signal is a true knock signal.

Pseudo knock, for example, pseudo knock due to mechanical noise of the piston system, changes the posture of the piston as the knock control factor is controlled toward the knock suppression side, for example, the ignition timing is retarded. It tends to be louder as the sound increases. According to this configuration,
By utilizing this tendency, it is possible to determine whether the vibration waveform signal at the time of knock determination is a true knock signal or a pseudo knock signal while controlling the knock control factor to the knock suppression side. You can That is, when the peak value of the vibration waveform signal detected in the current ignition cycle by the peak value detection means is equal to or less than the peak value detected in the previous ignition cycle during the control to the knock suppression side, the true knock signal is used. It can be determined that normal knock suppression control is being performed. If this determination is made,
The Q value of the vibration waveform extracting means is maintained as it is. on the other hand,
If the current peak value is larger than the previous peak value during the control to the knock suppression side, it can be determined that the false knock suppression control is being performed by the pseudo knock signal. When this determination is made, the Q value is changed to the larger side.

According to a third aspect of the present invention, in the knock control device for the internal combustion engine according to the first or second aspect, the Q value changing means is configured to perform the knock control on the knock control side of the knock control factor. The gist is to change the Q value of the vibration waveform extracting means.

According to this structure, the Q of the vibration waveform extracting means is
Since the value is changed according to the control amount of the knock control factor to the knock suppression side, for example, the retard amount of the ignition timing, the bandwidth of the vibration waveform signal extracted by the extracting means is the required amount according to the control amount. Can only be properly narrowed.

According to a fourth aspect of the present invention, in the knock control device for an internal combustion engine according to any one of the first to third aspects, the vibration waveform extracting means is a bandpass filter having a variable Q value. That is the summary.

According to this structure, when the bandpass filter is used to extract the vibration waveform signal of the predetermined frequency band from the output signal of the knock sensor, erroneous knock suppression control by the pseudo knock signal is performed. It is possible to prevent the above, and it is possible to improve the torque generated by the internal combustion engine and the driver viability.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a knock control device for an internal combustion engine embodying the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of an entire knock control device for an internal combustion engine according to an embodiment. This knock control device includes a knock sensor 11 that detects engine vibration as an internal combustion engine, an electronic control device 12, and a bandpass filter 13 that serves as vibration waveform extraction means.

The knock sensor 11 is a piezoelectric block vibration sensor which is attached to a cylinder block (not shown) of each cylinder of the engine, detects the vibration of the engine transmitted to the cylinder block, and outputs a vibration waveform signal. .

The electronic control unit 12 is equipped with a bandpass filter 13, an amplifier 14, a peak hold circuit 15, a microcomputer and the like. This microcomputer includes an A / D converter 16, a CPU 17 that executes various arithmetic processes, a ROM 18 that stores various control programs (host programs), and an R that stores various data.
It is configured as a logical operation circuit composed of AM or the like.

The band pass filter 13 is a vibration waveform signal of a predetermined frequency band from the output signal of the knock sensor 11,
That is, the vibration waveform signal including the knock signal in the knock frequency band (for example, about 12 to 14 KHz) is extracted. This bandpass filter 13 has the above-mentioned Q value of 10 dB.
(See FIG. 8 (a)) to 25 dB (see FIG. 8 (b)).

The peak hold circuit 15 detects the peak value of the vibration waveform signal extracted by the bandpass filter 13 and amplified by the amplifier 14. "Peak value" here
Is the maximum value (knock peak level) of the vibration waveform signal extracted in one ignition cycle of each cylinder.

The peak value detected by the peak hold circuit 15 is converted into a digital signal by the A / D converter 16 and taken into the microcomputer. Signals from various sensors of the engine, such as a crank angle sensor, an intake air amount sensor, a water temperature sensor, etc., are taken into the microcomputer. The microcomputer calculates ignition timing, fuel injection amount and the like on the basis of the signals from the various sensors thus fetched, and controls the igniter, injector and the like of each cylinder of the engine (not shown). Then, the microcomputer executes the "knock control process" shown in FIG. 2 based on the peak value of the vibration waveform signal captured via the A / D converter 16 for each ignition cycle of each cylinder. The microcomputer performs the knock control process in a predetermined control cycle during engine operation,
For example, in the case of a 4-cylinder engine, it is executed every 180 ° CA.

The "knock control process" executed by the microcomputer will be described below with reference to the flow chart shown in FIG. During the engine operation shown in step S100, a vibration waveform signal in a predetermined frequency band is extracted from the output signal of the knock sensor 11 by the bandpass filter 13 and amplified by the amplifier 14 for each ignition cycle of each cylinder. The peak value (knock peak level) of the amplified vibration waveform signal is detected by the peak hold circuit 15.

During such engine operation, the microcomputer executes knock determination processing at a predetermined control cycle (step S110). This knock determination process will be described based on the flowchart shown in FIG.

First, in step S200, the peak value (knock peak level) of the vibration waveform signal detected by the peak hold circuit 15 for each ignition cycle of each cylinder is set to A
It is converted into a digital signal by the / D converter 16 and taken in.

Thereafter, a logarithmic value obtained by logarithmically converting the peak value of the vibration waveform signal fetched for each ignition cycle of each cylinder in step S200 (hereinafter, this value is referred to as "peak value LVP").
K ”. ) Is obtained (step S210).

Thereafter, the average value VMED of N ignition cycles of the peak value LVPK obtained in step S210 is calculated (step S220), and the peak value LVPK is calculated.
The standard deviation SGM for N cycles is calculated (step S230).

Thereafter, the compatible value U is calculated by map search or the like based on the standard deviation SGM calculated in step S230 (step S240). After this, step S25
In step 0, the knock determination level (knock determination value) VKD is calculated. Here, the knock determination level VKD is set to VK
It is calculated by the formula of D = U × SGM + VMED.

After that, the process proceeds to step S260, and the peak value LVPK obtained in step S210 and step S25.
0 is compared with the knock determination level VKD, and LVP is compared.
It is determined whether K is larger than VKD. That is, in step S260, the presence or absence of knock is determined.

If LVPK is larger than VKD, that is, if the result of the determination in step S260 is YES, the process proceeds to step S270, and it is determined that knock is present (knock determination).
do. If it is determined here that there is a knock,
Both a case where the vibration waveform signal is a true knock signal and a case where the vibration waveform signal is a pseudo knock signal are included. That is, even if the true knock signal is not generated, if the pseudo knock signal mainly caused by the mechanical noise is generated and the peak value LVPK of the pseudo knock signal exceeds the knock determination level VKD, It is determined that there is a knock. In this way, when knock determination (determination of knock presence) is made in step S270, the process proceeds to step S120 in FIG. 2 and retard angle side control is started. In this step S120, the retard side control for changing the ignition timing to the retard side is started.

On the other hand, if LVPK is equal to or lower than VKD, that is, if the result of the determination in step S260 is NO, it is determined that there is no knock and the process proceeds to step S170 in FIG.
In this step S170, the retard side control is ended,
Alternatively, when the retard side control is not performed, the current ignition timing is maintained (the retard side control is not executed).

When the retard side control is started in step S120, the process proceeds to step S130. In step S130, the peak value LVPK for each ignition cycle of each cylinder obtained in step S210 is read.

After that, the process proceeds to step S140, and after the retard side control is started in step S120 (during the retard side control), the peak value L obtained in the current ignition cycle of each cylinder is obtained.
It is determined whether VPK (current value) is less than or equal to the peak value LVPK (previous value) obtained in the previous ignition cycle of the same cylinder. If this determination result is YES, that is, if the current value of the peak value LVPK is less than or equal to the previous value, the process proceeds to step S150, and the Q value of the bandpass filter 13 is maintained constant. Here, the true knock signal is
By retarding the ignition timing as shown by the straight line 21 in (a), the peak value LVPK (knock peak level) of the same signal is obtained.
Is utilized as shown by the straight line 22 in FIG. That is, the current value of the peak value LVPK becomes equal to or smaller than the previous value after the start of the retard side control, that is, when the true knock signal is generated, it is determined that the knock is present, and the retard side control is normally started. It is thought that this is due to "normal retardation due to". Therefore, in such a case, the Q value of the bandpass filter 13 is maintained as it is, as indicated by the straight line 23 in FIG.

On the other hand, the determination result of step S140 is NO.
In the case of, that is, after the start of the retard side control, the peak value LVP
If the current value of K is larger than the previous value, the process proceeds to step S160, and the Q value of the bandpass filter 13 is changed to the larger value. Here, since the pseudo knock signal mainly caused by mechanical noise of the piston system and the like becomes larger as the ignition timing is retarded, its peak value LVPK (knock peak) is indicated by a straight line 22 in FIG. 4B. level)
It takes advantage of the fact that That is, the current value of the peak value LVPK becomes larger than the previous value after the start of the retard side control, that is, it is determined that there is knock due to the occurrence of the pseudo knock and the retard side control is started. It is thought that it is due to being "horn". Therefore, in such a case, the Q value of the bandpass filter 13 is not maintained as it is, as indicated by the straight line 23 in FIG.
As shown by the straight line 23 in FIG. 4C, the Q value is changed to the larger side. Further, the change amount of the Q value here is set according to the retard amount of the ignition timing by referring to a map as shown in FIG. 5, for example.

By changing the Q value in this way, the bandwidth of the bandpass filter 13 is narrowed,
The frequency region of the vibration waveform signal extracted by the filter is narrowed so that the frequency band does not include the pseudo knock signal. Then, the above step S150 or S1
After executing 60, the process returns to step S110.

Incidentally, the knock determination processing in step S110, particularly step S2 in the knock determination processing.
Reference numeral 60 corresponds to knock determination means for determining the presence or absence of knock based on the vibration waveform signal. In addition, the above step S14
0 corresponds to a signal discriminating means for discriminating whether the vibration waveform signal at the time of knocking determination is a true knock signal or a pseudo knock signal while controlling a knock control factor such as ignition timing to the knock suppressing side. To do. Further, the above step S160
However, when it is determined by the signal determination means that the vibration waveform signal at the time of determination of knock is a pseudo knock signal,
It corresponds to Q value changing means for changing the Q value of the vibration waveform extracting means to the larger side. Then, the above step S210
Corresponds to peak value detecting means for detecting the peak value of the vibration waveform signal for each ignition cycle of each cylinder.

According to the embodiment configured as described above, the following operational effects are exhibited. (A) The reason why the current value of the peak value LVPK becomes larger than the previous value after the retard side control is started in step S120 is that it is determined that there is knock due to the occurrence of the pseudo knock, and the retard side control is started. It is considered that it is due to "erroneous retardation due to pseudo knock". Therefore, step S140
Then, when the current value of the peak value LVPK becomes larger than the previous value after the start of the retard side control, the Q value of the bandpass filter 13 is changed to the larger side. That is, if it is determined in step S140 that the vibration waveform signal at the time of knock determination is a pseudo knock signal (N in step S140).
O), the Q value of the bandpass filter 13 is changed to the larger side.

As a result, the bandwidth of the vibration waveform signal extracted by the bandpass filter 13 becomes narrower, and the pseudoknock signal is not extracted by the bandpass filter 13, so that the "erroneous delay angle due to pseudoknock" is ended. .
As a result, it is possible to prevent a decrease in the torque generated by the engine and a deterioration in the driver's ability due to the continued erroneous retardation. Therefore, it is possible to prevent erroneous knock suppression control due to the pseudo knock signal, and it is possible to improve the torque generated by the engine and the driver viability.

(B) The Q value of the bandpass filter 13 is
Since the map is changed according to the retard amount of the ignition timing with reference to the map as shown in FIG. 5, the bandwidth of the vibration waveform signal extracted by the bandpass filter 13 is appropriate for the necessary amount according to the retard amount. Can be narrowed to

(C) When the bandpass filter 13 is used to extract a vibration waveform signal of a predetermined frequency band from the output signal of the knock sensor 11, it is possible to prevent erroneous retard control by the pseudo knock signal. Can be prevented,
It is possible to improve the torque generated by the engine and the driver power.

[Modification] The present invention can be modified and embodied as follows. -In the above-mentioned one embodiment, when it is determined that there is a knock,
Although the ignition timing is controlled to the retard side (knock suppression side), knock control factors other than the ignition timing, such as the fuel injection amount, may be controlled to the knock suppression side.

In the above embodiment, the bandpass filter 13 is used as the vibration waveform extracting means, but instead of this filter, the bandwidth of the vibration waveform signal extracted from the output signal of the knock sensor 11 is made variable. SCF (Switched Capacitor Filter) may be used.

In the above embodiment, the peak hold circuit 15 detects the maximum value (knock peak level) of the vibration waveform signal extracted by the bandpass filter 13 for each ignition cycle of each cylinder as its peak value. But
You may make it detect the peak waveform of the same signal. In this case, in step S210, the peak waveform is integrated in a predetermined section in one ignition cycle of each cylinder, and the integrated value is compared with the knock determination level. This knock determination level is an average value of the integrated values obtained in step S210 for N ignition cycles, and a standard deviation for the N ignition cycles.
It is calculated from a matching value obtained by map search or the like based on this standard deviation.

In short, the present invention comprises a knock sensor, means for extracting a vibration waveform signal in a predetermined frequency band from the output signal thereof, and means for judging the presence or absence of knock based on the vibration waveform signal, and there is knocking. It can be widely applied to those in which the knock control factor is controlled to the knock suppression side at the time of determination.

In the above embodiment, the knock sensor 11
Although a piezoelectric type is used as the above, the present invention is also applicable to a knock control device using a knock sensor other than the piezoelectric type, for example, an electromagnetic knock sensor.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an entire knock control device for an internal combustion engine according to an embodiment.

FIG. 2 is a flowchart showing knock control processing by the knock control device.

FIG. 3 is a flowchart showing knock determination processing of FIG.

FIG. 4A is an explanatory diagram showing a normal retard angle due to knocking, FIG. 4B is an erroneous retard angle due to pseudo knock, and FIG. 4C is an explanatory diagram showing erroneous retard angle prevention due to pseudo knock.

FIG. 5 is a map showing the relationship between the retard amount and the Q value change amount.

FIG. 6A is a graph showing the output distribution of the bandpass filter, and FIG. 6B is an explanatory diagram showing the relationship between the Q value and the bandwidth.

FIG. 7A is a graph showing a filter characteristic when the Q value is 25 dB, and FIG. 7B is a graph showing a filter characteristic when the Q value is 10 dB.

8A is a graph showing a frequency band extracted when a Q value is 25 dB, and FIG. 8B is a Q value of 10 dB.
Is a graph showing the frequency band extracted when.

[Explanation of symbols]

11 ... Knock sensor, 13 ... Band pass filter as vibration waveform extracting means.

Claims (4)

[Claims] 1. A knock sensor for detecting vibration of an internal combustion engine, a vibration waveform extracting means for extracting a vibration waveform signal in a predetermined frequency band from an output signal of the knock sensor, and a vibration waveform signal extracted by the extracting means. In the knock control device of an internal combustion engine, which comprises a knock determination means for determining the presence or absence of a knock based on the knock determination means, and controls a knock control factor such as an ignition timing to a knock suppression side when the knock determination means determines that there is knock, While controlling the control factor to the knock suppression side, the vibration waveform signal at the time of knock determination is a signal determining means for determining whether it is a true knock signal or a pseudo knock signal, and the signal determining means When it is determined that the vibration waveform signal at the time of knock determination is a pseudo knock signal,
A knock control device for an internal combustion engine, comprising: a Q value changing means for changing the Q value of the vibration waveform extracting means to a larger side. 2. A peak value detecting means for detecting a peak value of the vibration waveform signal for each ignition cycle of each cylinder, wherein the signal determining means is configured to detect the peak value while the knock control factor is being controlled to a knock suppressing side. When the peak value of the vibration waveform signal detected in the current ignition cycle by the value detection means is less than or equal to the peak value detected in the previous ignition cycle, it is determined that the vibration waveform signal at the time of knock determination is a pseudo knock signal. However, if not, it is determined that the vibration waveform signal is a true knock signal, and the knock control device for the internal combustion engine according to claim 1. 3. The Q value changing means changes the Q value of the vibration waveform extracting means according to a control amount of the knock control factor to the knock suppressing side.
A knock control device for an internal combustion engine according to item 1. 4. The knock control device for an internal combustion engine according to claim 1, wherein the vibration waveform extracting means is a bandpass filter having a variable Q value.