JPH0474933A - Detector of knocking of internal combustion engine - Google Patents

Abstract

PURPOSE:To detect knocking precisely by correcting a sampled strength with a different weighting correction rate according to a region which is formed by subdividing a prescribed section and wherein the strength is sampled. CONSTITUTION:Sampled strengths (a, b, c, ...) are corrected respectively on the basis of weighting correction rates (Kphi, K1, K2, ...) set for discrete regions in a frequency analysis section respectively, and the total amount of the strengths (= a.Kphi + b.K1 + c.K2 + ...) is determined for each frequency component. Then, this total amount detecting most afresh is compared with a background level BGL corresponding to the total amount of the strengths of a mechanical vibration level determined for each frequency component, and occurrence of knocking is thereby discriminated. By this method, precision in detection of the knocking can be improved.

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, not only does the output decrease, but the impact also causes suction and
Some engines are equipped with an ignition timing control device that detects knocking and corrects the ignition timing to promptly avoid knocking since it has a negative effect on exhaust valves and pistons (Japanese Patent Laid-Open No. 58-105036). (See official bulletins, etc.)

Knocking detection for correcting the ignition timing due to the occurrence of knocking is 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, ATDC 10' to 60°); The peak value (total sum of specific frequency component intensities 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 (mechanical vibration level).

<Problems to be Solved by the Invention> By the way, in the above-mentioned configuration 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 said sum is determined by the presence or absence of the occurrence of knocking. Is it desirable to have a sufficient level difference? In reality, depending on conditions such as the shape of the engine and the installation position of the knock sensor, it may not be possible to ensure a sufficient level difference, especially in areas where the signal level is small. In this case, since there is no clear difference in the total sum depending on whether or not knocking occurs, knocking may be erroneously detected.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a knocking detection device that can accurately detect knocking even when the signal level from a knocking sensor is small.

<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.

On the other hand, the weighting correction factor storage means stores a weighting correction factor for the intensity sampling value for each region obtained by subdividing the predetermined interval in which the intensity sampling means samples the intensity of the specific frequency component.

The intensity weighting correction means corrects the sampled intensity based on the weighting correction factor stored for each subdivided region within the predetermined section.

Then, the knocking determination means calculates the sum of the intensities sampled within a predetermined interval and corrected as described above, and determines the occurrence of knocking based on the sum of the intensities of the specific frequency components.

<Operation> According to this configuration, within a predetermined section in which the intensity is sampled every predetermined period, the intensity is corrected with a different weighting correction factor depending on which region of the subdivided regions of the predetermined section the intensity is sampled. Therefore, in areas where knocking vibration tends to affect the strength,
A correction is made in the direction of increasing the strength difference between when knocking occurs and when no knocking occurs, and conversely, in a region where the presence or absence of knocking does not easily affect the strength, correction is made in the direction of reducing the strength difference. I can do it.

As a result, a clearer level difference is generated depending on the total strength within a predetermined section or whether or not knocking occurs, and even if the intensity change due to the presence or absence of knocking is small, the accuracy of knocking detection can be ensured. .

<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 a /D converter 2 and input to a 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 vibration is conspicuous. ,
9kHz, 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. They are canceled in the unit 5 to obtain a so-called comb-shaped 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. 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 of the knock sensor 1 by the configuration of the comb filter 3 and the resonators 6a to 6e as described above, or an analog specific frequency component extraction means is used. 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 2 as the intensity weighting correction means and the knocking determination means are provided in the microcomputer 7 as software, as shown in the flowchart of FIG. It corresponds to non-volatile memory installed in

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 intensities (a, b, c, . . . ) of each frequency component obtained at predetermined time intervals within the analysis interval are sampled (Sl).

Here, for each frequency component, the sum of the intensities sampled in the analysis interval is determined, and the occurrence of knocking is determined based on whether or not this sum is higher than the level during non-knocking. Instead of directly integrating the sampled intensities for each frequency component, the intensities are corrected using preset weighting correction factors (Kφ, K1, K2, ...) according to the sampling timing, and then integrated. (S2).

In other words, the analysis section is set in a region where knocking vibration occurs, or because knocking vibration gradually attenuates from the time it occurs, within the analysis section there is a region where knocking vibration easily affects intensity changes and a region where knocking vibration does not have much influence. There are areas where it is not possible.

Therefore, for example, for the intensity sampled in a region where the knocking vibration is likely to affect the intensity at the early stage of knocking, an increase correction is applied to magnify the intensity change that occurs depending on the presence or absence of knocking, and vice versa. For areas where knocking vibration does not have much influence on intensity changes, if the intensity change is unrelated to knocking vibration or is corrected to reduce it so as not to affect knocking discrimination, the total intensity will have a large effect depending on the presence or absence of knocking. When no difference occurs (see FIGS. 4 and 5), it is possible to calculate the sum by magnifying only the difference caused by the occurrence of knocking, as shown in FIG. 6.

In this way, a weighted correction factor (K
φ, Kl, 2. ) is determined based on the degree of influence on the occurrence or intensity of knocking for each region obtained by subdividing the analysis section through experiments, and is set based on the degree of influence.

Note that the timing at which the peak of knocking vibration is detected may differ depending on the operating conditions such as engine rotation and the positional relationship between the knock sensor 1 and the cylinder, so the weighting correction for each region may be performed depending on the engine operating condition or the cylinder. The rate may be set variably.

As described above, the weighting correction factors (Kφ, Kl, K2. . . ) for each region within the frequency analysis interval are calculated.
Intensities sampled based on (a, b.

C2...) is corrected and the sum of the intensities for each frequency component (=a- to φ+b-Kl+C- to 2+...
) is determined, this latest detected sum is compared with a background level BGL corresponding to the strength sum of the mechanical vibration level found for each frequency component to determine whether knocking has occurred (S3).

The background level BGL is obtained by weighted averaging for each frequency component the sum of the intensities for each frequency component obtained by accumulating after correcting with a weighted correction factor for each region as described above, While the calculation is performed by setting a relatively heavy weight, the sum of the intensities determined to be knocking occurrence is not weighted and averaged, so that the level when knocking is not occurring can be accurately indicated.

When the detected total strength is greater than the sum of the background level BGL and the predetermined value α, it is assumed that the total strength has increased due to the occurrence of knocking vibration, and it is determined that knocking has occurred (S4).
When the sum of the detected strengths is smaller than L0α, it is determined that knocking has not occurred (S5).

When calculating the sum of the above-mentioned intensities, the intensities are corrected for each region of the analysis interval so that a level change clearly appears due to the occurrence of knocking, so whether there is a large change in the intensity depending on the presence or absence of knocking. Even under conditions where knocking does not occur, the occurrence of knocking can be detected with high accuracy.

The knocking determination described above is performed for each frequency component, and for example, when it is determined that knocking has occurred in a majority of the frequency components as a result of knocking determination for each frequency component, it is finally determined that knocking has occurred. do.

When it is determined that knocking has occurred in this way,
The occurrence of knocking can be quickly avoided by retarding the ignition timing of the internal combustion engine.

In addition, in this embodiment, 7k is detected from the detection signal of the knock sensor 1.
Hz, 8 kHz, 9 kHz, 10 kHz and 11 kHz. However, the frequency and number of frequencies to be extracted are not limited, and only one specific frequency component can be extracted as described above. Knocking may be determined.

Furthermore, even when extracting a specific frequency component from the detection signal of the knock sensor 1 using an analog filter,
Similarly, by correcting the sampled intensity using a weighted correction factor for each region within the frequency analysis interval, the same effect as in this embodiment can be obtained. In the case of such analog frequency analysis, the integration by the integrator is reset at predetermined time intervals within the frequency analysis interval, and the peak of the integral value is determined at every predetermined time period within the frequency analysis interval. The integrated peak value (intensity) may be corrected depending on which region within the analysis interval the data was obtained as described above.

<Effects of the Invention> As explained above, according to the present invention, the intensity of a specific frequency component of a detection signal from a vibration sensor is sampled at every predetermined period within a predetermined section, and knocking is determined based on the sum of the sampled values. Even under conditions where there is no large difference in the intensity depending on the presence or absence of knocking, it is possible to magnify the intensity change that occurs due to the knocking vibration to determine knocking. This has the effect of improving detection accuracy.

[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, and Fig. 6 is a diagram illustrating the effect when the intensity is corrected by the weighting correction factor in the above embodiment. , FIG. 7 is a diagram showing an example of a frequency spectrum in the same embodiment, and FIG. 8 is a block diagram showing an example of a conventional knocking detection device. ■...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 Japan Electronics Co., Ltd. Representative Patent attorney Fujio Sasashima M3 Fig. 4 Fig. 5

Claims (1)

[Scope of Claims] A vibration sensor attached to an engine body to detect engine vibration, a specific frequency component extracting means for extracting a specific frequency component from a detection signal of the vibration sensor, and a frequency component extracted by the specific frequency component extracting means. intensity sampling means for sampling the intensity of the specific frequency component within a predetermined interval at predetermined intervals; weighting correction factor storage means for storing a weighting correction factor for the intensity sampling value for each region obtained by subdividing the predetermined interval; intensity weighting correction means for correcting the intensity sampled by the intensity sampling means based on the weighting correction factor stored in the weighting correction factor storage means; and intensity weighting correction means for correcting the intensity sampled by the intensity sampling means within the predetermined interval. 1. A knocking detection device for an internal combustion engine, comprising: knocking determining means for calculating the sum of the intensities of the specific frequency components and determining whether knocking has occurred based on the sum of the intensities of the specific frequency components.