JPH08151949A - Knocking detecting device for internal combustion engine - Google Patents

Abstract

PURPOSE: To attain forming into small size an engine vibration signal processing device and reducing its cost, by constituting an initial data and integrated value data of a specific frequency component deliverable between these data and a control device by serial communication, to markedly reduce a number of terminals for delivering the data. CONSTITUTION: A detection signal from a knocking sensor 11 is inputted to a signal processor IC21 through an interface circuit 12, here to apply a high speed Fourier arithmetic operation or the like, and a knocking particular specific frequency component is extracted, to calculate an extracted frequency component level integrated. Next, a calculated integrated value data is inputted to a microcomputer 22, here to detect the occurrence of knocking based on the integrated value data of the frequency component and based on a level difference or the like between non-knocking time and knocking time of the frequency component. Here, a data between the signal processor IC21 and the microcomputer 22 is transmitted from the microcomputer 22 by serial communication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knocking detection device for an internal combustion engine, and more particularly to an improved technique for detecting the presence or absence of knocking from a detection signal of engine vibration.

[0002]

2. Description of the Related Art In an internal combustion engine, when knocking of a predetermined level or more occurs, not only the output is reduced but also
Since the impact adversely affects the intake / exhaust valve and the piston, there is an ignition timing control device that detects knocking and corrects the ignition timing to avoid knocking promptly.

The knocking is detected as follows. A knock sensor that outputs a detection signal corresponding to the engine vibration level is attached to a cylinder block of the engine by a piezoelectric element, and one or more bandpass filters (hereinafter referred to as BPFs) are used to detect the knocking-specific frequency After extracting each component, passing through a noise filter and smoothing (integrating), A /
D-convert and input to microcomputer. The microcomputer detects the occurrence of knocking based on the level difference between the non-knocking time and the knocking time of the frequency component obtained by the BPF, the temporal change characteristic of the specific frequency, and the like.

By the way, if a plurality of BPFs for processing analog signals are provided as described above, the number of parts increases and the cost increases. Therefore, it is conceivable that the digital signal obtained by A / D converting the detection signal from the knock sensor is subjected to Fourier transform operation or the like by a microcomputer to extract the frequency component peculiar to knocking to detect the knocking. Since a large memory capacity is required for the calculation and the temporal transition of the waveform of the specific frequency cannot be obtained in real time, it is practically difficult to adopt.

Therefore, in recent years, as shown in FIG. 3, the engine vibration detection signal from the knock sensor 11 is converted into a digital signal through an interface circuit 12 and input to a signal processing IC 13 constituted by a digital processor. The signal processing IC 13 performs a fast Fourier operation or the like on the detection signal to extract a specific frequency component specific to knocking and an integration operation of each extracted frequency component level, and the integrated value is a microcomputer (CPU). There is proposed a system in which the microcomputer 14 detects the presence or absence of knocking on the basis of the integrated value by inputting the data to the microcomputer 14 (see Japanese Patent Publication No. 6-35937, etc.).

[0006]

However, in the above-mentioned one, since the integrated value calculated by the signal processing IC is transmitted to the microcomputer by using the address bus / data bus, the microcomputer for knocking determination is used. As a result, it was impossible to use a single-chip microcomputer that does not have an address bus / data bus to / from an external RAM.

Further, since the knocking occurrence state differs depending on the engine type, it is necessary to initialize the optimum value while changing variously each specific frequency (center frequency in each BPF) extracted in the signal processing IC. As the specific frequency was set while changing the level of each of the external setting terminals (pins) provided one by one as shown in the figure, it takes time to match the settings, and the number of pins is large and the package size is large. Because of the large size, the disadvantages in terms of cost and mounting area were large.

The present invention has been made in view of the above conventional problems, and provides a knocking detection device for an internal combustion engine, which solves the above problems by changing the transmission method of data for signal processing. The purpose is to

[0009]

Therefore, the invention according to claim 1 is a specific frequency component extracting means for extracting a specific frequency component from a signal detected by a vibration sensor attached to an engine body for detecting engine vibration. An engine vibration signal processing device including an integrating unit that integrates the level of the extracted specific frequency component, and a control device that detects the presence or absence of knocking based on the integrated value from the engine vibration signal processing device. In a knocking detection device for an internal combustion engine that is configured, the initial frequency of the specific frequency component and the integrated value data in the specific frequency component extraction means are exchanged by serial communication with the control device. To do.

Further, in the invention according to claim 2, in the serial communication, a data section signal is output each time transmission of a unit amount of data is completed, and a deviation of data received by the data section signal is corrected. It is characterized by having a function to do.

[0011]

According to the first aspect of the present invention, since the initial data of the specific frequency component and the integrated value data are exchanged by the serial communication with the control device, the number of terminals for exchanging the data is significantly increased. According to the invention according to claim 2, in which the engine vibration signal processing device can be downsized and the cost can be reduced together with the simplification of the internal circuit, the noise generated in the synchronous clock in serial communication can be reduced. Even if there is a timing difference between the transmission data and the reception data due to the influence, it can be kept within the unit amount of data, and it does not affect the subsequent data. Can be suppressed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1 showing the configuration of one embodiment, a knock sensor 11 attached to a cylinder block or the like of an engine outputs a detection signal according to an engine vibration level by a piezoelectric element.

The detection signal from the knock sensor 11 is input to the signal processing IC 21 as a signal processing device composed of a digital processor as a digital signal through the interface circuit 12. The signal processing IC 21 performs a fast Fourier operation or the like on the detection signal to extract a specific frequency component peculiar to knocking and an integration operation of the extracted frequency component level.

Then, the data of the integrated value calculated by the signal processing IC 21 is input to a microcomputer 22 as a control device, and the microcomputer 22
Based on the data of the integrated value of the frequency component, the occurrence of knocking is detected based on the level difference between the non-knocking state and the knocking state of the frequency component, the temporal change characteristic of the specific frequency, and the like.

Here, as a configuration according to the present invention, a microcomputer for data of integrated values from the signal processing IC 21
The transmission to the signal processing IC 22 and the transmission of the data to the signal processing IC when the specific frequency (center frequency in each BPF) extracted by the signal processing IC 21 is initialized to the optimum value by serial communication from the microcomputer 22. It is configured to do.

In order to perform the above serial communication, a transmission line Tx for transmitting data from the microcomputer 22 to the signal processing IC 21 (a reception line when viewed from the signal processing IC 21 side) and the signal processing IC 21 to the microcomputer
22 is provided with a reception line Rx for receiving data (also a transmission line when viewed from the signal processing IC 21 side), and a clock signal line CLK issued from the transmission side for synchronizing transmission and reception.

At the time of initializing the specific frequency of the signal processing IC 21, the microcomputer 22 transmits the data for initial setting through the transmission line Tx in synchronism with the clock signal by serial communication while performing signal processing. The IC 21 reads the data in synchronization with the clock signal. When knocking is detected, the signal processing IC21
While transmitting the data of the integrated value for each specific frequency calculated in step 1 through serial communication through the line Rx,
The microcomputer 22 reads the data via the line Tx.

Further, in the present embodiment, the data section signal is output each time the communication of the data of a unit amount, for example, 1 byte is completed, and the data section signal is transmitted when the microcomputer 22 transmits to the signal processing IC 21. The data section signal line DEL for outputting For example, when data is transmitted from the microcomputer 22 to the signal processing IC 21 by serial communication, if the clock signal generated from the microcomputer 22 causes noise during transmission via the clock signal line as shown in FIG. As a result, the same data value (D2 shown in the figure) is read twice, and the subsequent data values are shifted by one. In this case, the effect of 1 byte of data is small, but as it is, all the data values of the subsequent bytes are displaced as in the illustrated conventional method.
It will have a great impact. Therefore, by outputting the data interval signal and inputting it to the signal processing IC 21, the signal processing IC 21 is reset by the data interval signal, and then the data read after the clock signal is input as the data value. If it is handled, the data value of the byte after the noise is generated becomes normal as in the present system shown in the figure, so that it can be made as small as possible so that the influence of the noise can be ignored.

The same applies when data is transmitted from the signal processing IC 21 to the microcomputer 22 by serial communication. Thus, according to this embodiment, the signal processing IC
Since the data is sent and received between the microcomputer 21 and the microcomputer 22 by serial communication, a single-chip microcomputer having neither a data bus nor an address bus for transmission to and from an external RAM can be used as the microcomputer. Also, the signal processing IC 21 side does not have the data bus, the address bus and the external setting terminal. Instead, a total of 3 terminals for serial communication and a total of 4 terminals can be added even if the data section signal line is added. Can be reduced, and the internal circuit therefor can be simplified, so that the package of the signal processing IC 21 can be significantly downsized, and the cost can be significantly reduced.

Further, since the specific frequency initialization is performed by a simple operation of changing the input data of the microcomputer 22, the matching time can be shortened and the cost can be reduced in this respect as well. Further, by outputting the data section signal, the influence of noise, which is a problem in serial communication, can be suppressed as much as possible.

[0021]

As described above, according to the first aspect of the present invention, the initial data of the specific frequency component and the integral value data are exchanged between the engine vibration signal processing device and the control device by serial communication. Therefore, the number of terminals for data transmission / reception can be significantly reduced, and in combination with the simplification of the internal circuit, the engine vibration signal processing device can be downsized and the cost can be reduced. According to this, even if there is a timing difference between the transmission data and the reception data due to the influence of noise generated in the synchronous clock,
Since the data can be retained within the unit amount of data and the subsequent data is not affected, the knocking detection error can be suppressed as much as possible.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention.

FIG. 2 is a time chart showing a state at the time of serial communication in the above-mentioned embodiment in comparison with a conventional method.

FIG. 3 is a block circuit diagram showing a conventional example.

[Explanation of symbols]

 11 knock sensor 21 signal processing IC 22 microcomputer CLK clock signal line Tx transmission line Rx reception line DEL data section signal line

Claims (2)

[Claims] 1. A specific frequency component extracting means for extracting a specific frequency component from a signal detected by a vibration sensor attached to an engine body for detecting engine vibration, and an integral for integrating a level of the extracted specific frequency component. An engine vibration signal processing device including: a control device that detects the presence or absence of knocking based on an integrated value from the engine vibration signal processing device; and a knocking detection device for an internal combustion engine that comprises: A knocking detection device for an internal combustion engine, wherein the initial data of a specific frequency component and the integrated value data in the component extraction means are exchanged by serial communication with the control device. 2. In the serial communication, a function of outputting a data section signal each time transmission of a unit amount of data is completed and correcting a deviation of data received by the data section signal is provided. An internal combustion engine knocking detection device.