JP3188998B2 - Knock detection device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting knocking of an internal combustion engine, and more particularly to an improved technique for processing a detection signal of engine vibration to form a signal for determining knocking.

[0002]

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

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

By the way, if a BPF for processing an analog signal is provided as described above, the number of parts increases and the cost increases. Therefore, the detection signal from the knock sensor is set to A
It is conceivable to detect the knocking by performing a Fourier transform operation or the like on the / D-converted digital signal with a microcomputer to extract a knock-specific frequency component, but a large memory capacity is required for the operation,
In addition, since it is not possible to obtain a temporal transition of a waveform of a specific frequency in real time, it is practically difficult to employ the waveform.

In recent years, as shown in FIG. 2, a detection signal of engine vibration from the knock sensor 11 is input to a signal processing IC 13 via an interface circuit 12, and the signal processing IC 13 performs high-speed processing on the detection signal. A specific frequency component specific to knocking is extracted by performing a Fourier operation or the like, and an integration operation of each of the extracted frequency component levels is performed.The integrated value is input to a microcomputer (CPU) 14, and the microcomputer 14 A device that detects the presence or absence of knocking based on a value has been proposed (see Japanese Patent Publication No. 6-35937).

In the above-described conventional knocking detection device, the interface is used in order to improve the knocking detection accuracy by always using the output of the knock sensor 10 that changes according to the operating state of the internal combustion engine in the dynamic range of the A / D converter. A gain switching circuit section 12B is provided at the subsequent stage of the filter circuit section 12A of the circuit 12, and the gain is switched by an external switching signal to control the A in the signal processing IC 13.
/ D converter.

[0007]

However, when the analog gain switching circuit for adjusting the gain by the operational amplifier or the like is provided as described above, the interface circuit 12 becomes complicated, the mounting area increases, and the cost increases. was there. The present invention has been made in view of such conventional problems, and has as its object to provide a knocking detection device for an internal combustion engine that can simplify an interface circuit while performing a gain adjustment function.

[0008]

According to the present invention, a specific frequency component is extracted from a signal detected by a vibration sensor attached to an engine main body and detecting an engine vibration and converted into a digital signal. And an integration means for integrating the level of the extracted specific frequency component. The engine vibration signal processing device is configured to detect the presence or absence of knocking based on the integrated value. In the knocking detection device for an internal combustion engine, the engine signal processing device includes the specific frequency component.
The data length of the data obtained by multiplying the integration level by the
An integral gain adjusting means for adjusting the integral gain so as to have a constant value is provided.

Further, the invention according to claim 2 is characterized in that the integral gain adjusting means is configured to be capable of adjusting the integral gain by external communication.

[0010]

In accordance with the invention according to claim 1, in integrating the signal level of the digital specific frequency component in the engine vibration processing apparatus, adjustment is performed a specific frequency component of the integral gain
The data obtained by multiplying the minute level by the integral gain is the specified data
Since the signal length is long , knocking can be detected with as high accuracy as possible without truncating the data value of the lower digit even for a signal of a low level.

According to the second aspect of the present invention, the integral gain can be adjusted by communication from outside such as a control device for determining knocking based on the integral value.

[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 a configuration of an embodiment, a knock sensor 11 attached to a cylinder block or the like of an engine outputs a detection signal corresponding to an engine vibration level by a piezoelectric element.

A detection signal from the knock sensor 11 is input via an interface circuit 20 to a signal processing IC 21 as a signal processing device composed of a digital processor. The signal processing IC 21 converts the detection signal into a digital signal by the A / D converter 21A, and a specific frequency component peculiar to knocking is extracted from the engine vibration signal converted into the digital signal by the specific frequency extraction circuit 21B. You. The extraction is performed by the fast Fourier transform operation or the like.

The extracted level of each specific frequency component is multiplied by the integral gain adjusted by the integral gain adjusting circuit 21C and input to the integrator 21D, where integration is performed. The data of the integrated value is input to a microcomputer 22 as a control device, and the microcomputer 22
Detects the occurrence of knocking based on the level difference between non-knocking and knocking of each frequency component, a temporal change characteristic of a specific frequency, and the like, based on the data of the integral value of the frequency component.

Here, an integral gain signal from the microcomputer 22 is input to the integral gain adjusting circuit 21C via a communication circuit 23 such as an address bus / data bus or a serial communication line. The integral gain signal is preset according to a knocking level generated according to the engine speed and the engine load (for example, the basic fuel injection amount _TP ) based on the detection signal of the engine operation state input to the microcomputer 22. What was done is obtained by searching from a map table or the like. Then, for example, by setting the integral gain to be small in an operation region where the knocking level is high and by increasing the integral gain in an operation region where the knocking level is low, the data length obtained by multiplying the level of the specific frequency component by the integral gain becomes a predetermined value, for example, 1 It is set to be bytes. In this way, if the register in which the data of the integration value by the integrator 21D is set to 1 byte, data having an 8-bit effective data value is always set, and even if the knocking level is low. Knock detection can be performed with as high a precision as possible. Note that the microcomputer 22 adjusts the slice level for knocking determination in accordance with the adjustment of the integral gain.

In addition, since the integral gain of the signal converted into the digital signal in the signal processing IC 21 is adjusted by software as in the present invention, the interface circuit 20 is provided with an analog gain switching circuit. Is unnecessary, and the interface circuit 20 can be downsized.
Cost can be reduced. In addition, if a floating-point shift register is used, the effective data length can always be made constant, but using such a shift register increases the cost. By performing gain adjustment in advance so as to have a predetermined data length as in the present invention, an inexpensive fixed-point register can be used.

Further, since the setting of the integral gain is performed by software processing by an external microcomputer 22 and transmitted to the signal processing IC 21 by communication, the signal processing IC 21 itself stores the data of the integral gain in the RAM. It is only necessary to make it possible to change the circuit configuration, and there is almost no change in the hardware circuit configuration.

[0018]

As described above, according to the first aspect of the present invention, the level of the specific frequency component is multiplied by the integral gain.
Since the integral gain is adjusted so that the obtained data always has a constant data length, knocking can be detected with as high accuracy as possible even with a low-level signal.

[Brief description of the drawings]

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

FIG. 2 is a block circuit diagram of a conventional example.

[Explanation of symbols]

 11 Knock sensor 20 Interface circuit 21 Signal processing IC 21A A / D converter 21B Specific frequency extraction circuit 21C Integral gain adjustment circuit 21D Integrator 22 Microcomputer 23 Communication circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 45/00 368 F02D 45/00 358

Claims (2)

(57) [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 main body and detecting an engine vibration and converted into a digital signal, said specific frequency component being extracted. A knocking detection device for an internal combustion engine, which is configured to include an engine vibration signal processing device including an integrating means for integrating the level of the engine signal, and configured to detect the presence or absence of knocking based on the integrated value. Processing device, the level of the specific frequency component
The data length of the data multiplied by the integral gain becomes the specified value
A knocking detection device for an internal combustion engine provided with integral gain adjusting means for adjusting the integral gain. 2. The knocking detection device for an internal combustion engine according to claim 1, wherein said integral gain adjusting means is configured to be capable of adjusting the integral gain through external communication.