JPH0477629A - Knocking detecting apparatus of inernal combustion engine - Google Patents

Abstract

PURPOSE:To detect knocking with excellent accuracy by providing a vibration sensor, a specified-frequency-component extracting means, a strength sampling means, a maximum-level operating means, an average-level operating means, a knocking discriminating means and a background-level operating means. CONSTITUTION:The vibration of an engine is detected with a vibration sensor 1. A specified-frequency component extracting means extracts the specified frequency component through a comb-shaped filter 3. A strength sampling means extracts the strength for every specified period within a specified section. A maximum-level operating means operates the total sum of the maximum values of the strengths as the maximum level. A knocking-level discriminating means compares the difference between the maximum level and the average level with a background level and discriminates the presence or absence of the knocking. When no knocking is determined, a background-level operating means operates the weighted means value obtained by the weighted mean method as the background level. Thus, the knocking is detected based on the difference between the maximum level of the strength and the average level in the specified strength sampling section for every specified period. Therefore, the highly accurate knocking detection matching the vibration characteristics of the knocking vibration can be performed.

Description

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

<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 a negative effect on exhaust valves and pistons (Japanese Patent Application Laid-Open No. 1983-1999). (See Publication No. 105036, etc.).

Detection of knocking, which prevents the ignition timing from being corrected due to the occurrence of knocking, was 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°). A/D converter 15 A/D converts the peak value (total sum of specific frequency component intensities in an integral interval) and inputs it to 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 (mechanical vibration level).

<Problems to be Solved by the Invention> Incidentally, the vibration waveform of knocking has a tendency for the vibration level to locally increase in a predetermined section.

Therefore, in the configuration described above in which the occurrence of knocking is determined by the peak level of the integral value, that is, the sum of the strengths of specific frequency components in the integral interval, the engine vibration level increases on average in the detection interval due to factors other than knocking. Even in such cases, there was a risk that knocking would be mistakenly detected.

In particular, depending on conditions such as the shape of the engine and the mounting position of the knock sensor, it may not be possible to ensure a sufficient difference in the total sum in areas where the signal level is small. Since this does not occur, the probability of falsely detecting knocking increases.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a knocking detection device that can accurately detect knocking even if the signal level from a knocking sensor is small, using a knocking detection method that matches the knocking characteristics. With the goal.

<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 the engine body to detect engine vibration, and a specific frequency component extraction means extracts a specific frequency component from the detection signal of the vibration sensor.

The intensity sampling means samples the intensity of the extracted specific frequency component at predetermined intervals within a predetermined interval.

The maximum level calculation means calculates the sum of maximum values of a plurality of sampled intensities in a predetermined section of each specific frequency component as a maximum level.

The average level calculation means calculates the sum of average values of a plurality of sampled intensities in a predetermined section of each specific frequency component as an average level.

The knocking determination means compares the difference between the maximum level calculated by the maximum level calculation means and the average level calculated by the average level calculation means with a background level to determine the presence or absence of knocking.

The background level calculating means calculates the difference between the maximum level calculated by the maximum level calculating means and the average level calculated by the average level calculating means, when the knocking determining means determines that there is no knocking.
The weighted average value is calculated as the background level.

Further, the frequency contribution storage means stores the frequency contribution ratio contributing to knocking of the particular frequency component for each particular frequency component, and the maximum level calculation means and the average level calculation means are configured to store the maximum value and the average value of the particular frequency component. may be multiplied by the frequency contribution rate of the corresponding frequency component, and the sum of the products may be calculated as the maximum level and the average level.

Further, as shown by the chain line in FIG. 1, a frequency contribution storage means is provided for storing the frequency contribution ratio contributing to knocking of the particular frequency component for each specific frequency component, and a maximum level calculation means and an average level calculation means are provided. , the maximum level and the average level may be calculated as the sum of values obtained by correcting the maximum value and the average value of the specific frequency component by the frequency contribution rate of the corresponding frequency component.

In addition, as shown by the dotted line in FIG. 1, there is also an intensity change detection means for detecting an intensity change for each specific frequency component, and a relationship between the intensity change of the specific frequency component detected by the intensity change detection means and a predetermined standard change characteristic. an intensity change correction coefficient calculation means for calculating an intensity change correction coefficient by comparing the intensity change correction coefficient, and the average level calculated by the average level calculation means or the maximum level calculated by the maximum level calculation means is determined by the intensity change correction coefficient. It may be configured such that it is corrected and determined by.

Further, the weighting coefficient used for calculating the background level in the background level calculating means may be set as a function of the intensity correction coefficient calculated by the intensity change correction coefficient calculating means.

<Operation> According to this configuration, knocking is detected based on the difference between the maximum level and the average level of the intensity within a predetermined section sampled at predetermined intervals.
Highly accurate knocking detection commensurate with the knocking vibration characteristics can be performed.

In addition, if the maximum level and average level of the intensity are corrected using the frequency contribution rate, the intensity of frequencies that contribute to knocking can be reflected at a larger rate in knocking detection. Accuracy will be improved.

Furthermore, if the average level or the maximum level is corrected by the intensity change correction coefficient,
When the vibration characteristics estimated by the intensity change are close to the knocking vibration characteristics, the average level or maximum level is corrected in a direction that makes it easier to judge it as knocking.
The knocking detection accuracy can be further improved, and if the weighting coefficient used to calculate the background level is similarly corrected by the intensity change correction coefficient, the knocking detection accuracy can be further improved.

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

In FIG. 2 showing an example, a knock sensor (vibration sensor) (not shown) attached to the cylinder block of an internal combustion engine 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. ,
9kHz, 10kHz and 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. They are canceled in the unit 5 to obtain a so-called comb-shaped frequency characteristic.

Thereby, it is possible to prevent each resonator 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 one after another. The comb filter 3 and the resonators 6a to 6e constitute a specific frequency component extraction means in this embodiment.

In this embodiment, the 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, or an analog device is used as the specific frequency component extracting means. Bandpass filters may be provided corresponding to the number of required frequencies, and the output of each bandpass filter may be A/D converted 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. Occurrence of knocking in an internal combustion engine (not shown) is detected based on specific frequency components of the knock sensor 1 input via the respective resonators 6a to 6e in a predetermined detected frequency analysis section.

The details of such knocking occurrence detection will be explained below with reference to the flowchart of FIG. 3. In addition, in this example,
The functions of the intensity sampling means, maximum level calculation means, average level calculation means, knocking discrimination means, and background level calculation means are provided by the microcomputer 7 as software, as shown in the flowchart of FIG. 3, The frequency contribution rate storage means is constituted by a nonvolatile memory built into the microcomputer 7.

The knocking occurrence detection shown in the flowchart of Fig. 3 is as follows:
This is carried out in a predetermined frequency analysis interval, and the predetermined frequency analysis interval is, for example, an interval in which combustion vibrations of each cylinder can be sampled while avoiding ignition noise. For example, in a 6-cylinder engine, ATDCIO° to ATDC6
0°, and such a predetermined frequency analysis section is detected based on the detection signal from the crank angle sensor 8.

When entering the frequency analysis period, the frequency spectra as shown in FIG. 7 output from the resonators 6a to 6e at predetermined time intervals (predetermined period) are stored in order, and the frequency spectra shown in FIGS. 4 and 5 are stored in sequence. , the intensity (fo
o, fzo, f2゜f,...f,,), (fo3.f
ll , f21 , f3+' ”・f, ), (
fe2. f1□, f22. fs□"' f, z)
---(f,,,f,,,f2゜,f2.,f3.--
f, , ) (Sl). This function corresponds to intensity sampling means.

Next, based on these sampled intensity data, the maximum level KSi of the overall intensity of all frequencies is calculated using the following equation (S2). This function corresponds to the maximum level calculation means.

KSi = f, o(max) XKFo + f
, (max) xKF+ +-・-+f ,,, (ma
X) XKF.

Here, f , +(max) is the sampling intensity (fat , fz , f2r , f3+'
KF is the maximum value of ``f,), and KF is the frequency contribution factor that indicates the degree of contribution to knocking.The frequency contribution factor KF varies depending on the cylinder and engine rotation speed, so Accuracy can be improved by searching for the cylinder and engine speeds stored in a three-dimensional map.

This maximum level KSLi is a value that is an index representing the magnitude of knocking.

Next, based on the intensity data, the average level SLi of the overall intensity of all frequencies is calculated using the following formula (S3
). This function corresponds to average level calculation means.

5Li= (KFo/mΣfso+KF+/mΣf,,
, I+...KF, /mΣf, 4) The difference between the maximum level KSLi and the average level SLi obtained in this manner is compared with the background BGL i to determine whether or not there is knocking (S4).

That is, when BGLi+α<KSi-3Li,
It is determined that knocking is occurring.S5), BG
When Li≧KSLi −SLi +α (α is a threshold value), it is determined that knocking has not occurred (
S6). This function corresponds to a means for determining knocking.

The background level BGLi is the background level BGLi.
Maximum level KSi and average level SL compared with Li
When it is determined that there is no knocking in the above-mentioned knocking determination, the difference from i is calculated by weighted average calculation using the following formula (S7). This function corresponds to a background calculation means.

According to this knocking determination, the difference between the maximum level KSi and the average level SLi is basically the sum of the differences between the maximum value and the average value of the vibration levels, and when knocking occurs,
This difference increases due to the above-mentioned characteristic of the knocking vibration that the vibration level locally increases.

On the other hand, the background level BGLi is a weighted average value of the sum of the differences between the maximum level KSi and the average level SLi during non-knocking.

Therefore, when knocking occurs, (KSiSLi)
The value of is sufficiently large compared to BGLi, and knocking can be accurately determined even for signals with low levels.

In addition, since multiple specific frequencies with a high contribution rate to knocking are selected and knocking is determined based on the sum of the intensities, the knocking detection accuracy is improved. In particular, in this embodiment, weighting is performed using the frequency contribution rate for each frequency component. The knocking detection accuracy is further improved because the summation is calculated.

Next, an embodiment will be described in which knocking is determined by more accurately capturing knocking vibration characteristics and clearly distinguishing them from mechanical vibrations.

In this method, when calculating the average level SLi, the sum of the intensity average values for each frequency obtained in the same manner as in the above embodiment is
Correction is performed using a value called intensity change correction coefficient KLP. Also, B
When calculating GLi, the weighting X is changed to the intensity change correction coefficient K.
Set as a function of LP. The routine of this embodiment for detecting knocking using the intensity correction coefficient KLP is described in the sixth section.
The explanation will be given according to the flowchart shown in the figure.

First, the intensity of the frequency contribution rate is sampled at predetermined time intervals (Sll) in the same manner as 81 in FIG. . . f, o) are stored as initial values, respectively (S12).

Then, assuming that the initial values stored for each frequency component do not change and the intensity continues at a constant level in the frequency analysis interval, the time-axis change in the integrated value of the intensity at this time is calculated as the sampling period and the initial value. This is set based on the value and is set as the standard change characteristic (S13).

Next, based on the time course of the intensity determined for each frequency component that is actually input (see Figure 7), the intensity is integrated for each sample period on the time axis, and the intensity within the frequency analysis interval is Detect characteristics of intensity change (S14)
. This function corresponds to intensity change detection means.

Then, as mentioned above, the standard change characteristic for each frequency component obtained assuming that the intensity remains unchanged is compared with the characteristic of the change in the intensity integral value for each frequency component actually detected (
S15).

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 characteristic of the intensity integral value obtained based on the actual detection signal does not match. It is presumed that the frequency component of the oscilloscope contains knocking vibration, so it is not stable at a constant intensity. Therefore, it is determined whether the intensity integral value matches the standard change characteristic on the frequency component side at predetermined time intervals, and the total number C of cases where the intensity does not match within the detection interval is measured by a counter.

Then, the intensity change correction coefficient KLP is set according to the total number C. Specifically, the larger the total number C, the greater the proportion of knocking vibrations included, so it is set to a smaller value in order to make it easier to determine knocking, that is, to decrease the average level SLi and increase the difference from the maximum level KSi. (S16).

The functions of S15 and S16 constitute an intensity change correction coefficient calculation means.

After calculating the maximum intensity level KSi in the same manner as 82 in FIG. 3 (S17), the average level SLi is calculated using the intensity change correction coefficient KLP set as described above.
is calculated using the following equation (S18).

5Li = (KFo/mΣf, o+KP, /mΣf,
+---KF,,/mΣf,,) -NLP Next, the difference between the maximum level KSi and the average level SL,i is compared with Pack Brown 1 and Lebel BGLi to determine the presence or absence of knocking.S19) BG → −α＜
When using KSi-SLi, it is determined that there is knocking.5
20) When BGLi+α≧KSi−SLi, it is determined that there is no knocking (S21).

When it is determined that there is no knocking, the background level BGL i is calculated and updated, or the weighting coefficient X used for the calculation is changed to the intensity correction coefficient NLP before that.
Set as a function of Specifically, since the larger the NLP, the smaller the proportion of knocking vibrations included, the weighting coefficient
).

Using X set in this way, 87 in FIG.
BGLi is calculated using the formula used in (S23).

In this way, by using the intensity correction coefficient KLP,
By capturing the knocking intensity change characteristics, knocking can be detected with higher accuracy.

In this embodiment, the intensity change correction coefficient KLP is set as a value for correcting the average level, but it may be set as a value for correcting the maximum level.

<Effects of the Invention> As explained above, according to the present invention, the intensities of a plurality of specific frequency components are sampled from the detection signal from the vibration sensor every predetermined period within a predetermined interval, and the maximum level and the average Since knocking is detected based on the difference from the average level, it is possible to perform highly accurate detection commensurate with the knocking characteristics. Further, by performing correction calculations using the frequency contribution factor and the intensity change correction coefficient, it is possible to obtain the effect that the knocking accuracy can be further improved.

[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, FIG. 3 is a flowchart showing the details of knocking detection control in the above embodiment, and FIGS. Fig. 5 is a time chart showing how the intensity is sampled for each specific frequency component in the above embodiment, Fig. 6 is a flowchart showing the contents of knocking detection control in another embodiment, and Fig. 7 is the same embodiment as above. FIG. 8 is a block diagram showing an example of a conventional knocking detection device. l...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 patent applicant Nippon Electronics Agent Co., Ltd. Patent Attorney Fujio SasashimaFigure 3Figure 4Figure 5

Claims (4)

[Claims] (1) A vibration sensor attached to the engine body to detect engine vibration, a specific frequency component extraction means for extracting a plurality of specific frequency components from the detection signal of the vibration sensor, and Intensity sampling means for sampling the intensities of a plurality of specific frequency components at predetermined intervals within predetermined intervals, and calculating the sum of the maximum values of the intensities sampled in the plurality of intensities in the predetermined intervals of each of the specific frequency components as a maximum level. maximum level calculation means; average level calculation means for calculating the sum of average values of a plurality of sampled intensities in a predetermined section of each specific frequency component as an average level; and a maximum level calculated by the maximum level calculation means. knocking determination means for determining the presence or absence of knocking by comparing the difference between the average level calculated by the average level calculation means and a background level; and the maximum level calculated by the maximum level calculation means and the average level calculation. background level calculating means for calculating a weighted average value, which is a weighted average of the difference between the average level calculated by the means and the average level calculated by the means when no knocking is determined by the knocking determining means, as a background level; A knocking detection device for an internal combustion engine, characterized in that: (2) Frequency contribution storage means that stores the frequency contribution ratio contributing to knocking of the particular frequency component for each particular frequency component, and the maximum level calculation means and the average level calculation means are configured to calculate the maximum value and the average of the particular frequency component. Claim 1 wherein the maximum level and the average level are calculated by calculating the sum of values corrected by the frequency contribution rate of the corresponding frequency component.
The knocking detection device for an internal combustion engine described in . (3) An intensity change detection means for detecting an intensity change for each specific frequency component, and an intensity change correction coefficient that is determined by comparing the intensity change of the specific frequency component detected by the intensity change detection means with a predetermined standard change characteristic. 2. An intensity change correction coefficient calculation means for calculating, wherein the average level calculated by the average level calculation means or the maximum level calculated by the maximum level calculation means is determined by correction using the intensity change correction coefficient. Or the knocking detection device for an internal combustion engine according to 2. (4) Knocking in an internal combustion engine according to claim 3, wherein the weighting coefficient used for calculating the background level in the background level calculating means is set as a function of the intensity correction coefficient calculated by the intensity change correction coefficient calculating means. Detection device.