JPH0476249A - Knocking detecting device and ignition timing correcting device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the knocking detecting accuracy to favorably avoid kocking by discriminating the generation of knocking based on the intensity of a specific frequency component of a detection signal from a vibration sensor. CONSTITUTION:The intensity of a specific frequency component of a detection signal from a vibration sensor A is detected by an intensity detecting means B, the intensity change pattern of the specific frequency component is detected by an intensity change detecting means C, and the generation of knocking is discriminated based on the intensity of the specific frequency component and the intensity change pattern. In a knocking discriminating means D, a first discriminant value setting means d1 is provided to compare the intensity detected by the intensity detecting means B to a specified value and to set a first discriminant value indicating the degree of generation of knocking. Further, a second discriminant value setting means d2 is provided to compare the intensity change pattern to a specified standard change characteristic and to set a second discriminant value similarly. A final discriminant value setting means d3 sets a final discriminant value based on the first and second discriminant values.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a knocking detection device and an ignition timing correction device for an internal combustion engine, and more specifically, to a knocking detection device that can accurately detect the occurrence of knocking from an engine vibration detection signal. and an ignition timing correction device using the device.

<Prior art> When knocking occurs above a predetermined level in an internal combustion engine, it not only reduces the output but also causes suction and
Some models are equipped with an ignition timing control device that detects knocking and corrects the ignition timing to quickly avoid knocking, since it has an adverse effect on exhaust valves and pistons. (See Publication No. 105036, etc.).

Knocking detection for correcting the ignition timing due to the occurrence of knocking has been performed as follows.

That is, as shown in FIG. 8, a knock sensor 11 that outputs a detection signal according to the vibration level using a piezoelectric element is attached to the cylinder block of the engine 12, etc., and the detection signal from this knock sensor 11 is sent to a bandpass filter 13. After inputting the signal and passing only the signal near the center frequency peculiar to knocking and performing half-wave rectification, the integrator 14 integrates over a predetermined integration interval (for example, ATDCIO° to 60°). The peak value (accumulation of specific frequency component intensity in the integration interval) is A/D converted by the A/D converter 15 and inputted to the microcomputer 16.

The microcomputer 16 determines whether or not knocking is occurring based on the difference between the peak of the integral value when knocking occurs and the peak of the integral value when knocking does not occur.

<Problem to be Solved by the Invention> Incidentally, in the configuration as described above in which the occurrence of knocking is determined based on the peak level of the integral value, it is desirable that there be a sufficient difference in the peak level of the integral value depending on whether or not knocking has occurred. In reality, depending on the shape of the engine and the mounting position of the knock sensor, it may not be possible to sufficiently secure the above-mentioned difference, especially in areas where the signal level is small. Because there was no significant difference, knocking could be falsely detected.

Furthermore, conventionally, the presence or absence of knocking was determined based on the integral value, and therefore the ignition timing was advanced or retarded by a fixed angle, regardless of the strength of the knocking. Therefore, it has been difficult to avoid excessive correction while avoiding knocking with good responsiveness.

The present invention was made in view of the above problems, and it is possible to detect knocking with high accuracy even when the signal level from the knocking sensor is small, and it is also possible to judge the knocking intensity and determine whether the ignition timing is corrected or not. The purpose is to ensure that the

<Means for Solving the Problems> Therefore, a knocking detection device for an internal combustion engine according to the present invention is configured as shown in FIG.

In FIG. 1, a vibration sensor is attached to an engine body to detect engine vibration. The intensity detection means detects the intensity of a specific frequency component of the detection signal of the vibration sensor, and the intensity change detection means detects a pattern of intensity changes of the specific frequency component.

Then, the knocking determining means determines whether knocking has occurred based on the intensity of the specific frequency component of the vibration sensor detected as described above and the pattern of intensity change.

Here, the intensity detecting means and the intensity change detecting means may be configured to detect the intensity and intensity change pattern for each of a plurality of types of specific frequency components.

In the ignition timing correction device according to the present invention using the knocking detection device according to the present invention configured as described above, the ignition timing correction means adjusts the ignition timing of the internal combustion engine based on the determination result of the occurrence of knocking by the knocking determination means. Corrects the lead/retard angle.

By the way, the knocking determination means can be configured to include each of the means shown in the first diagram.

Here, the first discrimination value setting means sets a first discrimination value indicating the degree to which knocking has occurred by comparing the intensity detected by the intensity detection means with a predetermined value, and
The second discriminant value setting means determines the degree to which knocking has occurred by comparing the intensity change pattern detected by the intensity change detection means with a predetermined standard change characteristic.
Set the judgment value.

The final discriminant value setting means determines a final discriminant value indicating the degree of occurrence of knocking based on the first discriminant value and the second discriminant respectively set by the first discriminant value setting means and the second discriminant value setting means. Set.

As a device for correcting the ignition timing in response to the knocking detection result in the knocking detection device according to the present invention configured as described above, the ignition timing correction amount setting means shown in FIG. The ignition timing advance/retard correction amount is variably set according to the set final discrimination value, and the ignition timing correction means based on the discrimination value level adjusts the ignition timing advance/retardation set by the ignition timing correction amount setting means. The ignition timing is advanced or retarded based on the angle correction amount.

<Operation> According to this configuration, in addition to the intensity of the specific frequency component of the vibration sensor, the pattern of intensity change of the specific frequency component is used as information for knocking determination, and the pattern of intensity change is determined based on the intensity of the detection signal. Since it is not related to the absolute level, it is possible to improve the accuracy of knocking detection even when the overall detection signal level is low compared to the case where knocking detection is performed based only on intensity, and the ignition timing can be determined based on such detection results. Advance/retard angle correction will be performed appropriately.

Furthermore, the first frequency component, which indicates the degree to which knocking occurs, is determined based on the intensity of the specific frequency component and the pattern of intensity changes.
If the discriminant value and the second discriminant value are calculated and the final discriminant value is set using these, the ignition timing can be corrected by increasing or decreasing the ignition timing correction amount depending on the degree to which knocking occurs. This makes it possible to further improve the responsiveness and accuracy of knock avoidance control through ignition timing correction.

<Example> The present invention will be explained in detail below.

In FIG. 2 showing one embodiment, a knock sensor (vibration sensor) 1 attached to a cylinder block of an internal combustion engine (not shown) has a built-in piezoelectric element and outputs a waveform detection (voltage) signal according to engine vibration. do.

The detection signal (analog signal) of the knock sensor 1 is A
The signal is A/D converted by the /D converter 2 and input to the comb filter 3.

The comb filter 3 is composed of a delay circuit 4 consisting of a plurality of stages of unit delay elements, and an adder 5 that subtracts the output data of the delay circuit 4 from the data that has bypassed the delay circuit 4. A circuit in which a number of resonators 6a to 6e corresponding to the number of frequencies to be extracted from the detection signal of the knock sensor 1 are connected in parallel is connected to the shaped filter 3 in tandem.

The resonators 6a to 6e are configured to resonate at different frequency components, and in this embodiment, the resonant frequencies are set to 7kHz and 8kHz in accordance with the frequency range of 7kHz to 9kHz in which knocking vibrations are considered to be noticeable. ,
9kHz2, 10kHz.

The frequency is 11kHz.

In the comb filter 3, by subtracting the data delayed by the delay circuit 4 from the data bypassed by the delay circuit 4, the detected signal level is attenuated as a whole, and in particular, the frequency corresponding to the delay time is added. 5, and a so-called comb-shaped result is obtained as a frequency characteristic.

Thereby, it is possible to prevent each of the resonators 6a to 6e from continuing to resonate based on the signals canceled by the adder 5, and the intensity of each frequency component can be obtained sequentially.

In this embodiment, a specific frequency component is extracted from the signal from the knock sensor I by the configuration of the comb filter 3 and the resonators 6a to 6e as described above, but an analog bandpass filter is not required. The output of each bandpass filter is A/
The data may be converted into D and read into the microcomputer 7.

The outputs of the resonators 6a to 6e, that is, the intensity signals for each frequency component, are input to a microcomputer 7. The occurrence of knocking in the internal combustion engine (not shown) is detected based on the specific frequency components of the knock sensor 1 that are input via the respective resonators 6a to 6e in the predetermined detected frequency analysis section, and based on the detection results. The ignition timing in the ignition device 9 is corrected and controlled.

The details of the detection of the occurrence of knocking and the ignition timing correction means associated therewith will be explained below with reference to the flowchart shown in FIG. In this embodiment, the strength detection means 2, the strength change detection means, the knocking discrimination means, the first discrimination value setting means, the second discrimination value setting means, the final discrimination value setting means 1, the ignition timing correction means 1, the ignition timing correction amount setting. The function of the means 2 as an ignition timing correction means based on the discrimination value level is provided by the microcomputer 7 in the form of software, as shown in the flowchart of FIG.

The knocking occurrence detection shown in the flowchart of Fig. 3 is as follows:
This is carried out in a predetermined frequency analysis section, and the predetermined frequency analysis section is, for example, a section in which combustion vibrations of each cylinder can be sampled while avoiding ignition noise. For example, in a 6-cylinder engine, A T D C10' ~A
TDC600, and the predetermined frequency analysis section is detected based on the detection signal from the crank angle sensor 8.

First, when it is detected that the frequency analysis section has entered, the intensity dB (amplitude) of each frequency component as shown in FIG. 5 input through each resonator 6a to 6e is stored as an initial value. (Sl).

Then, assuming that the initial values stored for each frequency component do not change and that the intensity continues at a constant level in the frequency analysis section, the time axis change of the integrated value of the intensity at this time is calculated from the resonators 6a to 6a. This is set based on the output interval (sampling period) from 6e and the initial value, and this is set as the standard change characteristic when knocking does not occur (S2).

Next, the intensity of each frequency component that will be input at predetermined time intervals in the frequency analysis section is stored, and the temporal transition of intensity (pattern of intensity change) is detected for each frequency component (sixth (see figure).

Then, based on the detection, the intensity is integrated for each sample period on the time axis, so that the pattern of intensity change within the frequency analysis interval or the slope of the integrated value is observed (S3).

Then, as mentioned above, the standard change characteristics for each frequency component obtained assuming that the intensity remains unchanged are compared with the characteristics of the change in the intensity integral value for each frequency component that are actually detected. The amount of deviation is determined at each intensity sampling interval as plus on the increasing side and negative on the decreasing side with respect to the standard change characteristic, and is accumulated, so that the cumulative value E represents the deviation amount of the actual change with respect to the standard change characteristic ( S4).

Here, the standard change characteristic assumes that there is no change in intensity, so it will increase linearly, but on the other hand, if the change pattern of the intensity integral value obtained based on the actual detection signal does not match, is estimated to be unstable at a constant intensity because its frequency component includes knocking vibration, but the intensity integral value based on the actual detection signal is also approximately linear like the reference change characteristic. If the frequency component increases and changes, it can be estimated that the frequency component is only mechanical vibration (see Fig. 4).

That is, as shown in FIG. 4, in the same frequency component,
When knocking vibration is included, the knocking vibration due to abnormal combustion is gradually attenuated, so the intensity of the frequency component is initially greatly attenuated and gradually returns to the level of only mechanical vibration; conversely, when knocking vibration is included, When it is not possible, the intensity changes at a nearly constant mechanical vibration level.

Therefore, when knocking vibration is not included, the initial intensity of the analysis section is substantially maintained, and the integrated value of the intensity increases substantially linearly.

Therefore, as mentioned above, if we assume that the initial intensity of the analysis interval does not change thereafter and estimate the time-axis change in the integrated value of the intensity, this change characteristic (predetermined standard change characteristic) will be determined to prevent knocking from occurring. When the actual strength is integrated on the time axis when knocking occurs,
As shown in FIG. 4, a change pattern is shown that does not match the change characteristics estimated as corresponding to the case where knocking does not occur, and the larger the knocking intensity, the larger the difference in the change characteristics.

Therefore, the knocking intensity can be detected by calculating the integral value of the actual intensity on the time axis, comparing it with the value when no knocking occurs, and accumulating the differences.

In this way, knocking is detected based on the intensity change pattern of specific frequency components, so it can be identified even when the signal level is low, and even in the high rotation range where mechanical vibration is strong. Therefore, knocking can be detected by easily distinguishing between knocking vibration and mechanical vibration.

Depending on the frequency, there are frequency ranges that exhibit characteristics such that the intensity becomes weaker than the engine vibration level due to the occurrence of knocking, and returns to the engine vibration level as the knocking vibration is attenuated. Knocking can be detected because it does not show a linear change, which is the change characteristic when no knocking occurs. In addition, although the intensity at the beginning of the frequency analysis section was set as constant and the change characteristics when knocking did not occur were set, the intensity change (decreasing change or increasing change) when knocking vibration was included for each frequency component was set in advance. The characteristics of the knocking are calculated, and the intensity change characteristics predicted to appear when this knocking occurs are compared with the intensity change pattern for each frequency component obtained from the actual detection signal, and the degree of non-knocking and knocking is shown. It is also possible to calculate the cumulative amount of deviation between the two.

For each frequency component corresponding to each resonator 6a to 6e, if the cumulative value E of the deviation amount from the reference change characteristic corresponding to the non-knock time of the actual intensity change in the frequency analysis interval is determined as described above, for each frequency component Find the sum of the absolute values of the cumulative value E found, or the average value, or the maximum value, etc.
Based on the absolute value of the cumulative deviation value E finally set from the cumulative deviation value E for each frequency, a first discrimination value f1 indicating the degree to which knocking has occurred is set (S
5).

The cumulative value E of the deviation amount indicates the size of the deviation from the non-knocking characteristics, so it is generally estimated that the larger the cumulative value E is, the greater the knocking intensity is. Conversely, when the cumulative value E is small, the knocking intensity is estimated to be larger. , since the frequency components showed change characteristics that are similar to the non-knocking state, it is estimated that the state is close to the state where no knocking occurs.

For this reason, the first discrimination value f1 is set smaller as the cumulative value E is smaller, and conversely, the first discrimination value f1 is set larger when the cumulative value E is larger. This allows the intensity of the knocking occurring to be determined based on the level of the value f1.

When converting the cumulative value E into the first discriminant value f1, the first discriminant value f1 may be simply increased in proportion to the cumulative value E, but in reality, the cumulative value E and the knocking intensity are is not proportional, so the actual knocking strength with respect to the cumulative value E is experimentally and empirically determined in advance, and a membership function is set that converts the cumulative value E into the knocking strength, which is a human subjective interpretation. It is preferable that the first discriminant value f, (membership value) representing the knocking intensity is set using the Fiji set.

In addition, when setting the first discriminant value f indicating the knocking intensity based on the intensity change of a specific frequency component in a predetermined frequency analysis interval as described above, one of the knocking vibrations that is expected to appear particularly Alternatively, only the frequency component may be extracted from the detection signal, and the first discrimination value f1 may be set based only on the intensity change of this frequency component.

A first discrimination value f1 indicating the knocking intensity is set based on the intensity change pattern of each frequency component within the frequency analysis interval, and a second discrimination value f2 indicating the knocking intensity is similarly set for each frequency component. The process of setting based on the intensity level of is performed in parallel.

Since the resonators 6a to 6e output frequency spectra as shown in FIG. 5 at predetermined intervals, such frequency spectra obtained in the frequency analysis section are sequentially stored (S6).

Then, the integral value for each frequency component of the intensity determined within the frequency analysis interval is determined as shown in FIG. 7 (S7), and the intensity integral value for each frequency component and the integral value for each frequency component are calculated. Compare the background level BGL (
S8).

The background level BGL is a weighted average value of the integrated intensity values of each frequency component obtained for each frequency analysis interval, and is weighted averaged with heavier weighting on past data, and is also used for knocking determination. This prevents the intensity integral values from being weighted averaged. Therefore, the background level BGL can be considered to be the level of the intensity integral value indicating only mechanical vibration in a state where knocking does not occur, and this background level BGL is the intensity value obtained in this frequency analysis interval. If the integral value is exceeded, it is presumed that knocking has occurred.

Therefore, the intensity integral value obtained in the current frequency analysis interval for each frequency component is equal to the background level BGL.
Based on the sum, average value, or maximum value, determine the degree to which knocking occurs, in other words,
A second discrimination value f2 indicating the knocking intensity is set (S9
).

When large knocking occurs, the intensity of the frequency component in which knocking vibration appears becomes higher than when knocking does not occur, and greatly exceeds the background level BGL. Therefore, the detected intensity integral value or BGL The larger the second discriminant value f2 is set, the larger the second discriminant value f2 is.
Similarly to the first discrimination value f, the knocking intensity is a value that can be compared to the same level as the first discrimination value f.

Here, too, only the intensity integral value of one frequency component is determined, and this intensity integral value is compared with the background level BGL, which is determined by weighted averaging of the intensity integral values, to determine the second discriminant value f2. You can also set it. Furthermore,
When the first discriminant value f1 is set using a fuzzy set as described above, the second discriminant value f2 is also set using a fuzzy set.

It is possible to determine whether or not knocking has occurred based on each of the discriminant values f+ and f2 set in this way.More specifically, it is possible to detect the knocking intensity, but in particular, it is possible to detect the knocking intensity based on the knocking intensity level. The second discrimination value f2, which is set as follows, cannot accurately indicate the knocking intensity when the distance from the knocking cylinder to the knock sensor 1 is far and the signal level is low. By using both to estimate the final knocking intensity, detection accuracy is improved compared to when knocking is determined based on only one detection result.

Each of the above discriminant values f4. Estimation of the final knocking intensity based on fx (setting of the final discriminant value f) can be performed, for example, by calculating the sum of the discriminant values f, , f2, calculating the average value,
One may be selected by comparing the magnitudes, and based on the discriminant value f finally derived from each discriminant value fl+f2, it is possible to determine not only the presence or absence of knocking but also the knocking intensity with high accuracy.

In addition, when each discriminant value f, , f2 which becomes a membership value is set using a fuzzy set, each discriminant value fl,
Fuzzy sets may be used again when ultimately setting a discriminant value indicating the degree to which knocking occurs based on fz.

If the discriminant value f indicating the knocking intensity is finally determined as described above, it becomes possible to correct the ignition timing according to the knocking intensity at that time. As such, when the discrimination value f is equal to or greater than a predetermined value, it is determined that knocking has occurred, and the ignition timing retard correction amount is increased in accordance with the increase in the discrimination value.
When the discriminant value f does not clearly indicate the occurrence of knocking, but is at a level that cannot be said to be non-knocking, the ignition timing correction amount is set to zero so that no ignition timing correction is performed, and the discriminant value f When the level of is sufficiently small and it is recognized that it is a non-knocking time, the smaller the value of the discrimination value f is, the larger the advance angle correction amount is set in order to obtain the engine output (S10).

Here, based on the discriminant value f, for example, "knocking has occurred".
, "Knocking may occur", and "Knocking does not occur", and the ignition timing advance/retard correction amount may be selected in accordance with each state.

In addition, when each discriminant value f,, f2 is set using a fuzzy set, defuzzification is performed to convert each discriminant value f,, f2 into an ignition timing correction amount, and from each discriminant value fl + f2 The center of gravity of the required ignition timing correction amount may be set as the final ignition timing correction amount.

When the ignition timing is set based on the correction amount or the knocking intensity level as described above, the microcomputer 7
advances or retards the basic ignition timing stored in advance in accordance with the operating conditions based on the correction amount, outputs an ignition signal to the ignition device 9 based on the corrected ignition timing, and makes corrections. The ignition process is executed based on the ignition timing determined. Here, the knocking intensity is detected with high precision from the intensity level and intensity change pattern of the specific frequency component of the detection signal of the knock sensor 1, and the ignition timing correction amount is set according to the knocking intensity. Knocking control is now possible, allowing quick knocking avoidance and MBT
(Minimum 5park Advance for
It is possible to secure ignition near Be5tTorque).

In addition, in this embodiment, 7k is detected from the detection signal of the knock sensor 1.
Hz, 8 kHz, 9 kHz, 10 kHz.

Although five types of frequency components of 11 kHz are extracted, this does not limit the frequencies to be extracted, nor does it limit the number of frequencies.

<Effects of the Invention> As explained above, according to the present invention, occurrence of knocking is determined based on the intensity and intensity change pattern of a specific frequency component of a detection signal from a vibration sensor.
Since the accuracy of knocking detection is improved, knocking can be effectively avoided by performing ignition timing correction control to avoid knocking based on the detection result. If this setting is made, the amount of correction of the ignition timing can be set in accordance with the knocking intensity at that time, which has the effect of allowing even more accurate knocking control.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a system block diagram showing an embodiment of the present invention, and FIG. 3 is a flowchart showing control details of knocking detection and ignition timing correction in the above embodiment. FIG. 4 is a time chart for explaining knocking discrimination based on the intensity change pattern of a specific frequency, FIGS.
The figure is a block diagram showing an example of a conventional knocking detection device. 1...Knock sensor (vibration sensor) 2...A
/D converter 3... Comb filter 4... Delay circuit 5... Adder 6a to 6e... Resonator 7... Microcomputer 8... Crank angle sensor 9... Ignition device Patent applicant: Japan Electronics Co., Ltd. Agent: Fujio Sasashima

Claims (5)

[Claims] (1) A vibration sensor attached to the engine body to detect engine vibration; an intensity detection means for detecting the intensity of a specific frequency component of the detection signal of the vibration sensor; and an intensity of the specific frequency component of the detection signal of the vibration sensor. Knocking detection for an internal combustion engine, comprising: an intensity change detection means for detecting a change pattern; and a knocking determination means for determining occurrence of knocking based on the detected intensity of the specific frequency component and the intensity change pattern. Device. (2) Knocking in an internal combustion engine according to claim 1, wherein the intensity detecting means and the intensity change detecting means are configured to detect respective intensities and intensity change patterns for a plurality of types of specific frequency components. Detection device. (3) first discrimination value setting means, wherein the knocking discrimination means sets a first discrimination value indicating the degree to which knocking has occurred by comparing the intensity detected by the intensity detection means with a predetermined value; a second discriminant value that indicates the degree to which knocking has occurred by comparing the intensity change pattern detected by the intensity change detection means with a predetermined standard change characteristic;
a discriminant value setting means; and a final discriminant value indicating the degree of occurrence of knocking based on the first discriminant value and the second discriminant respectively set by the first discriminant value setting means and the second discriminant value setting means. 3. The knocking detection device for an internal combustion engine according to claim 1, further comprising: final discrimination value setting means. (4) An ignition timing correction means for advancing or retarding the ignition timing of the internal combustion engine based on the determination result of the occurrence of knocking by the knocking determination means in the knocking detection device for an internal combustion engine according to claim 1 or 2. An ignition timing correction device for an internal combustion engine, comprising: (5) Ignition timing correction amount setting means for variably setting the ignition timing advance/retard correction amount according to the final discrimination value set by the final discrimination value setting means in the knocking detection device for an internal combustion engine according to claim 3; , the ignition timing advance/adjustment set by the ignition timing correction amount setting means;
An ignition timing correction device for an internal combustion engine, comprising: ignition timing correction means based on a discrimination value level that advances or retards the ignition timing of the internal combustion engine based on the retardation correction amount.