JPH0489535A - Detecting device of knocking of internal combustion engine - Google Patents

Abstract

PURPOSE:To ensure the precision of frequency analysis from the initial stage of a section of analysis and thereby to improve the precision of detection by making a filter take in simulated data when a plurality of specific frequency components are extracted from a detection signal of a vibration sensor. CONSTITUTION:A vibration sensor detects the vibration of an engine, a detection signal is subjected to A/D conversion and digital data are obtained therefrom. The data are inputted to a comb filter and the data subjected to the A/D conversion and data delayed by delay elements in a plurality of stages are added up. The data processed in the filter are inputted to a plurality of resonators, and a knocking discriminating means conducts an arithmetic processing of the digital data on a plurality of specific frequency components obtained through the resonators in a prescribed section of frequency analysis and discriminates the occurrence of knocking. Meanwhile, a means of taking in simulated data makes the filter take in simulated data forcedly in a prescribed section just before the prescribed section of frequency analysis. According to this constitution, an initial performance of the frequency analysis in the initial stage of the section of frequency analysis 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 technique for improving a device that detects 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 the exhaust pulp and pistons (Japanese Patent Application Laid-Open No. 1983-1999). (See Publication No. 105036, etc.).

Knocking detection for correcting the ignition timing due to the occurrence of knocking has conventionally been performed as follows. That is, as shown in FIG. 5, a knock sensor 11 that outputs a detection signal according to the vibration level using a piezoelectric element is attached to a cylinder block of an engine, etc., and band-pass filters 13 and 14 set to mutually different center frequencies are used. .15, frequency components specific to knocking are extracted from the detection signal of the knock sensor 11, passed through a noise filter consisting of a resistor R and a capacitor C, and then analog/digital (hereinafter simply referred to as A/D). ) A/D conversion is performed by the converter 16 and input to the microcomputer 17.

The microcomputer 17 then checks the level difference between non-knocking and knocking of each frequency component obtained in a predetermined interval by the bandpass filter 13, 14, 15, the temporal change characteristics of the waveform of a specific frequency, etc. The occurrence of knocking is detected based on the

Further, as shown in FIG. 6, the detection signal of the knocking sensor 11 is A/D converted by the A/D converter 16 and inputted to the microcomputer 17. In some cases, the occurrence of knocking is detected as described above by performing signal analysis through calculations and extracting frequency components specific to knocking.

<Problems to be Solved by the Invention> By the way, in the case of a configuration in which a band-pass filter is used to extract frequency components that are noticeable as knocking vibrations, as shown in FIG. 5 above, when trying to detect knocking using multiple types of frequency components, However, the number of parts increases accordingly, and matching time is required as the number of filters increases, resulting in an increase in cost.

Furthermore, when using the configuration shown in Figure 6 to perform signal analysis such as fast Fourier transform calculations in a microcomputer to obtain a frequency spectrum, it is difficult to use the analog bandpass filter, which increases the number of parts and the matching time. However, since the calculation requires a large amount of memory capacity and takes a relatively long time, it is possible to obtain the temporal change in the intensity of the extracted specific frequency component in real time. Therefore, there is a problem in that knocking cannot be detected based on the temporal change in intensity.

Therefore, by A/D converting the detection signal of the knock sensor and inputting the digital data to a digital filter consisting of a combination of a comb filter including a delay element and an adder, and a resonator. , we considered adopting a method that extracts multiple frequency components from the detection signal of the knock sensor.

However, using a digital filter as described above,
A predetermined frequency analysis interval (e.g. ATDC 10° to 60°
), when attempting to detect knocking by analyzing the specific frequency component extracted from the detection signal of the knock sensor, after entering the frequency analysis interval, each delay element of the comb filter is There is a problem in that the frequency analysis within the frequency analysis section cannot be performed accurately until the detection signal data is satisfied.

In other words, for example, if the comb filter starts to take in data after entering the frequency analysis section, the delay element is in an empty state and the first stage is The desired frequency analysis cannot be performed until the first input data taken into the delay element is sequentially fed and output. Furthermore, even if data is always input to the comb filter, at the beginning of the frequency analysis interval, the data that was taken into the comb filter before the analysis interval is being output from the delay element. It was not possible to perform accurate frequency analysis.

The present invention has been made in view of the above-mentioned problems, and uses a digital filter consisting of a comb filter and a resonator to extract a specific frequency component from the detection signal of a knock sensor to detect knocking. It is an object of the present invention to enable accurate frequency analysis in a frequency analysis section and to perform accurate knocking detection from the beginning of a predetermined analysis section.

<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, the vibration sensor is attached to the engine body to detect engine vibration, and the detection signal of the second vibration sensor is
A/D conversion is performed by a converter to obtain digital data of engine vibration.

This digital data of engine vibration is then input to a comb filter and processed. This comb filter is
A plurality of stages of delay elements into which A/D converted detection signals are input; data A/D converted by the A/D converter; and data delayed by the plurality of stages of delay elements. It is configured to include an adder that performs addition.

The data processed by the comb filter is input to a plurality of resonators resonating with mutually different frequency components, and the knocking determination means uses the plurality of resonators obtained through the plurality of resonators in a predetermined frequency analysis interval. The occurrence of knocking is determined by processing digital data of specific frequency components.

On the other hand, the simulated data acquisition means forces the comb filter to acquire simulated data in a predetermined section immediately before the predetermined frequency analysis section.

Here, it is preferable that the simulated data imported into the comb filter by the simulated data importing means be data for each cylinder that substantially corresponds to the detection signal of the vibration sensor when no knocking occurs.

<Operation> According to this configuration, a plurality of specific frequency components are extracted from the detection signal of the vibration sensor by the configuration of the comb filter and the plurality of resonators, and the knocking discriminating means extracts the frequency components as described above in the predetermined frequency analysis interval. Knocking is determined by arithmetic processing of digital data of a plurality of specific frequency components, and simulated data is taken into the comb filter in a predetermined section immediately before the predetermined frequency analysis section. As a result, when the predetermined frequency analysis section is reached, it is avoided that the delay element is empty or contains unnecessary data before the analysis section. It becomes possible to output the simulated pig from the delay element of the comb-shaped filter, thereby improving the start-up performance of frequency analysis at the beginning of the frequency analysis section.

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

In FIG. 2 showing one embodiment, a knock sensor (vibration sensor) l 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 is A
The signal is A/D converted by a /D converter 2 and input to a comb filter 3.

The comb filter 3 includes a delay circuit 4 consisting of a plurality of stages of unit delay elements corresponding to the number of extraction frequencies, and an adder 5 that subtracts the output data of the delay circuit 4 from the data bypassing the delay circuit 4. The comb filter 3 is connected in tandem with a number of resonators 6a to 6e or parallel-connected circuits corresponding to the number of frequencies to be extracted from the detection signal of the knock sensor 1.

The resonators 6a to 6e are configured to resonate at specific frequency components that are different from each other, and in this embodiment, the resonance frequency is set to 7kHz in accordance with the frequency range of 7kHz to 9kHz that is said to appear in knocking vibrations. ,8kHz
, 9kHz, 10kHz.

The frequency is 11kHz. However, the number of frequency components to be extracted and each frequency are not limited to the above.

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 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 outputs of the resonators 6a to 6e, that is, the intensity signals for each frequency component, are input to a microcomputer 7. A predetermined frequency analysis interval to be detected (in this example, ATDCIO° to 60°
), the occurrence of knocking in the internal combustion engine (not shown) is detected by analyzing the specific frequency components of the knock sensor 1 inputted through the resonators 6a to 6e, and the ignition device 9 controls the ignition based on the detection result. By controlling the timing, knocking can be quickly avoided and the ignition timing can be advanced.

As described above, the microcomputer 7 performs knocking detection based on the frequency components inputted into the frequency analysis section via the resonators 6a to 6e, or, as a configuration according to the present invention, the In the simulated data acquisition period, in order to perform control to force the comb filter 3 to acquire simulated data instead of the A/D conversion value of the detection signal of the knock sensor 1 (see FIG. 4), the comb filter 3 is The input can be switched between the input from the A/D converter 2 and the input from the microcomputer 7.

That is, it is originally desirable to output the data taken in the frequency analysis section from the delay circuit 4 and perform addition processing in the adder 5, or from the viewpoint of frequency analysis in the analysis section, this embodiment is ATDCIO° ~ 6C10. At the beginning of the predetermined frequency analysis section, the delay circuit 4 outputs the data that was captured immediately before the analysis section. The data is taken into the comb filter 3, and the simulated data is output from the delay circuit 4 until the data taken in between ATDCIO° and 60° is output from the delay circuit 4. It is something to do.

Therefore, if the simulated data is set to the basic data (frequency intensity data when not knocking) that is predicted to be obtained in the frequency analysis section, it is possible to perform almost the desired frequency analysis from the beginning of entering the frequency analysis section. It is possible to prevent the accuracy of frequency analysis from deteriorating until the data actually input in the analysis section is output from the delay circuit 4, thereby improving the accuracy of knocking detection based on the detected data in the frequency analysis section. I can do it.

The simulated data acquisition period in which the simulated data is taken in is determined according to the delay characteristics of the delay circuit 4, and at least the first time the analysis period is entered, the simulated data is taken into each delay element. The simulated data acquisition period may be determined by crank angle or time.

The details of the knocking detection performed by the microcomputer 7 will now be described in accordance with the flowchart of FIG.

In this embodiment, the knocking determination means.

The function as a simulated data importing means is performed by the microcomputer 7 as shown in the flowchart of FIG.
Or is it prepared in terms of software?

The program shown in the flowchart of FIG. 3 is executed by interruption at a preset time to start importing simulated data.

In this embodiment, as shown in FIG. 4, the frequency analysis interval (
A predetermined interval immediately before ATDCIO°~60°) is set as a simulated data acquisition interval, and the comb filter 3 is configured to acquire simulated data, and the start time of this simulated data acquisition interval is determined by the output of the crank angle sensor 8. If detected, the program shown in the flowchart of FIG. 3 is executed.

First, it is determined whether or not it is a simulated data acquisition period (Sl), and when it is a simulated data acquisition period, the background level B for each cylinder, which is calculated from the microcomputer 7 side for knocking determination to be described later, is performed.
The simulated data based on GL is output, and the simulated data applied to the comb filter 3 is forcibly taken in (S2).

As will be described later, the background level BGL is a weighted average of the integral values of the intensities of each frequency component inputted through the resonators 6a to 6e within the frequency analysis interval for each frequency when no knocking occurs. Since the intensity level obtained for each cylinder differs depending on variations in the distance of each cylinder from the knock sensor l, it is set for each cylinder.

In the above simulated data acquisition section, for example, from the background level BGL, the average value of the intensity of each frequency component in the frequency analysis section is calculated for each cylinder, and from this average intensity value for each cylinder, this time The data corresponding to the combustion cylinders are selected as simulated frequency intensity data corresponding to a state in which knocking does not occur, and are input to the comb filter instead of the data from the A/D converter 2.

In this way, the simulated data is input to the comb filter during the simulated data acquisition interval, and then the frequency analysis interval (A
TDCIO° to 60°) (S3), the detection signal of the knock sensor 1 is A/D converted by the A/D converter 2, and the data is input to the comb filter 3 (S4). .

Then, during this frequency analysis period, the microcomputer 7 inputs and sequentially stores the intensity of each frequency component output from each resonator 6a to 6e at a predetermined period (S5
). At the beginning of the frequency analysis section, the delay circuit 4 outputs the simulated data, and the accuracy of the frequency analysis is almost ensured from the beginning of the frequency analysis section.

During the frequency analysis period, data output from each resonator 6a to 6e at a predetermined period is inputted and stored respectively,
When the frequency analysis interval has elapsed, a metering determination is performed based on the data input and stored during the analysis interval (S6).

That is, the integral value for each frequency component of the intensity determined within the frequency analysis interval is determined, and the intensity integral value for each frequency component is calculated.
The background level BGL calculated for each frequency component corresponding to the current combustion cylinder is compared. The background level BGL is a weighted average value of the intensity integral values of each frequency component obtained for each frequency analysis section, so that the intensity integral value determined for knocking is not weighted averaged.

Therefore, the background level BGL can be considered to be the level of the intensity integral value indicating only the mechanical vibration in the state where knocking does not occur, and this background level BGL can be considered as the level of the intensity integral value that indicates only the mechanical vibration in the state where knocking does not occur. If the integral value is exceeded, it is determined that knocking has occurred.

As described above, the background level BGL is set for each cylinder and for each frequency in order to accommodate differences in detection intensity levels due to variations in the distance between the knock sensor 1 and each cylinder.

After knocking has been determined as described above, the background level BGL is then updated (S7). When it is determined that knocking has not occurred this time, the background level BGL and the current integral value are weighted averaged for each frequency component, and the weighted average result is updated as a new background level BGL, or it is determined whether knocking has occurred. When this happens, the background level BGL for each frequency component used for knocking determination this time is carried over to the next time without being updated.

In this embodiment, the frequency component intensities input at predetermined time intervals in the frequency analysis interval are integrated for each frequency, and
Is knocking determined by comparing this intensity integral value with the background level BGL?
The determination of knocking is not limited to the above embodiment, and for example, knocking may be detected based on the change characteristics of frequency intensity in a frequency analysis section.

In addition, the average level of the frequency intensity within the frequency analysis interval when knocking does not occur is determined, and the average level is calculated in the simulated data acquisition interval immediately before the frequency analysis interval corresponding to the next combustion stroke of the same cylinder. The data may be taken into the comb filter 3 as simulated data.

Furthermore, simulated data is stored in advance for each operating condition and cylinder, and the simulated data corresponding to the relevant operating conditions and combustion stroke cylinder is searched, and the comb filter 3 is used in the simulated data acquisition section immediately before the frequency analysis section. It may also be possible to have it incorporated into.

<Effects of the Invention> As explained above, according to the present invention, when a plurality of specific frequency components are extracted from a detection signal of a vibration sensor by a combination of a comb filter and a resonator, Since the simulated data is taken into the comb filter in a predetermined interval, the accuracy of frequency analysis can be ensured from the beginning of the analysis interval, thereby improving the knocking detection accuracy.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a system schematic diagram showing an embodiment of the invention, and Fig. 3 shows contents of input switching and knocking detection for the comb filter in the above embodiment. FIG. 4 is a flowchart, FIG. 4 is a time chart showing the state of input switching to the comb filter in the above embodiment, and FIGS. 5 and 6 are block diagrams each 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-6e-...Resonator 7...Microcomputer 8...Crank angle sensor patent applicant Nippon Electronic Equipment Fujio Sasashima, Patent Attorney, Agent Co., Ltd.

Claims (2)

[Claims] (1) A vibration sensor attached to the engine body that detects engine vibration, an analog/digital converter that converts the detection signal from the vibration sensor from analog to digital, and a signal that is converted from analog to digital by the analog/digital converter. a comb-shaped filter configured to include a plurality of stages of delay elements into which the detected signal is input, and an adder which adds the data delayed by the plurality of stages of delay elements and the output data of the analog/digital converter; , a plurality of resonators that input the output of the comb filter and resonate with mutually different specific frequency components, and calculate digital data of a plurality of specific frequency components obtained through the plurality of resonators in a predetermined frequency analysis interval. knocking determination means for processing to determine the occurrence of knocking; and simulated data importing means for forcibly importing simulated data into the comb filter in a predetermined section immediately before the predetermined frequency analysis section. Engine knocking detection device. (2) The simulated data taken into the comb filter by the simulated data import means is data for each cylinder that substantially corresponds to the detection signal of the vibration sensor when no knocking occurs. knocking detection device for internal combustion engines.