JPH05223001A - Knocking control device - Google Patents

Abstract

PURPOSE:To provide a knocking control device which can surely detect an abnormality of a knocking sensor and which incorporates a simple abnormal detecting circuit. CONSTITUTION:A knock sensor (vibration sensor) 1 attached to the cylinder wall or the like of an engine delivers a signal having a fixed level when it fails. The signal having a fixed level is applied to an abnormality detecting circuit 5 through a buffer 2, a band pass filter 3 and a wave shaping circuit 4. An output signal delivered from the wave shaping circuit 4 is differentiated by a differentiating circuit 6, and is then compared with a first reference value V1 by a first comparator 7. An output delivered from the first comparator 7 is integrated by a rectifying and integrating circuit 8, and is then compared with a second reference value V2 by a second comparator 8. An output (e) from the second comparator 8 has a high level the knock sensor 1 is normal and detects vibration, but has a low level if the knock sensor 1 is abnormal and does not detects vibration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knocking control device, and more particularly to a knocking control device capable of coping with an abnormality of a knock sensor for detecting engine vibration or a circuit for processing its output.

[0002]

2. Description of the Related Art When knocking occurs, the engine ignition timing is delayed from the normal timing to suppress a decrease in fuel consumption and output, and to prevent damage and deterioration of the engine. A control device has been proposed.

In this knocking control device, when an abnormality occurs in the knock sensor and the vibration of the engine cannot be detected, the knocking cannot be detected even if the knocking occurs. Therefore, the abnormality of the knock sensor can be detected reliably and early. ,
It is important to take some measures.

From this point of view, for example, JP-A-56-
There is proposed a knocking control device capable of detecting abnormality of a knock sensor as described in Japanese Patent No. 83568.

In this prior art, the output of a vibration sensor for detecting engine vibration is input to a bandpass filter having a pass center frequency of about 7 KHz via a buffer. The knocking signal extracted by the bandpass filter is input to the waveform shaping circuit, and is envelope-detected and then amplified. The output signal of the waveform shaping circuit is then sent to the knocking detection means, and is also sent to an abnormality detection circuit that detects an abnormality of the vibration sensor.

The abnormality detection circuit is a peak value hold circuit,
It is composed of four comparators, two integrators, and a logical sum circuit, and whether the peak value of the output signal of the waveform shaping circuit continues for a predetermined period and is larger than a predetermined first value. Alternatively, when it becomes smaller than the second value (where the first value> the second value), it is determined to be abnormal.

[0007]

As described above, the abnormality detection circuit of the knocking control device has the peak level of the signal obtained by sampling and holding the output of the waveform shaping circuit between the first and second values. Since it is determined that the knock sensor is normal at one time and abnormal when it is not between the first and second values, the circuit from the knock sensor to the abnormality detection circuit, that is, the buffer, the bandpass filter or When an abnormality occurs in the waveform shaping circuit and the peak level of the signal obtained by sampling and holding the input signal of the abnormality detection circuit falls between the first and second values, it is determined to be normal, and the knock sensor is detected as abnormal. There was a problem that it could not be detected.

Further, since the abnormality detection circuit is composed of a peak value hold circuit, four comparators, two integrators and an OR circuit, there is a problem that the circuit is complicated and expensive. It was

An object of the present invention is to eliminate the above-mentioned problems of the conventional device and to correctly detect an abnormality of the knock sensor,
Another object of the present invention is to provide a knocking control device provided with an abnormality detection circuit having a simple circuit configuration.

[0010]

To achieve the above object, the present invention provides a knock sensor for detecting engine vibration, and a bandpass filter for extracting a knocking signal of a specific frequency band from an output signal of the knock sensor. In a knocking control device provided with a waveform shaping circuit for shaping the waveform of the extracted signal, an abnormality detection circuit for detecting that the output signal of the waveform shaping circuit is at a fixed level for a certain period of time and detecting an abnormality of the knock sensor. It is characterized by the provision of.

[0011]

According to the present invention, the output signal of the waveform shaping circuit is detected to be at the fixed level for a certain period of time to determine the abnormality of the knock sensor. Signal is output, and even if the level of the fixed level signal becomes a level that is judged to be normal in the conventional device due to an abnormality in the bandpass filter, the waveform shaping circuit, etc., the knock sensor fails. Can be reliably detected.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 shows a block diagram of one embodiment of the present invention.

In the figure, 1 is a knock sensor (vibration sensor) installed on a cylinder wall of an engine, 2 is a buffer, 3 is a bandpass filter, and 4 is a waveform shaping circuit. Since these are the same as the configuration disclosed in the above-mentioned publication, detailed description will be omitted.

Reference numeral 5 is an abnormality detection circuit according to the present invention.
The abnormality detection circuit 5 includes a differentiating circuit 6, a first comparator 7,
It is composed of a rectifying and integrating circuit 8 and a second comparator 9.

Next, the operation of this embodiment will be described with reference to FIG. FIG. 2 shows the waveform of the signal at each point in FIG.
The reference numerals (a to e) in FIGS. 1 and 2 correspond to each other.

It is assumed that the waveform shaping circuit 4 outputs a signal a having the waveform shown in FIG. 2 (a). This signal a is
Before time t1, a normal knocking signal is shown, and time t1
After that, an abnormal knocking signal after the knock sensor failure, that is, a fixed level waveform is shown.

In this embodiment, the time t1
The subsequent level of the signal a may be any of the first value or more, the second value or less, or an intermediate value between these two values, as referred to in the above publication.

When the signal a is input to the differentiating circuit 6, the signal a is differentiated and the signal b having the waveform shown in FIG. 2B is output. The signal b is input to the first comparator 7 and compared with the predetermined first reference value V1. As a result, the first
The waveform of the output signal c of the comparator 7 is as shown in FIG.

Next, the signal c is input to the rectification / integration circuit 8 and is subjected to integration processing. The waveform of the signal d subjected to the integration processing is as shown by the solid line in FIG. 2 (d). The signal d is input to the second comparator 9 and compared with a second predetermined reference value V2. As a result, the waveform of the output signal e of the second comparator 9 becomes as shown in FIG. 2 (e).

The signal e is a signal indicating that the knock sensor 1 is normal at the H (high) level and abnormal at the L (low) level.

Therefore, according to this embodiment, when the knock sensor 1 becomes abnormal and the output thereof becomes a fixed level, the signal e becomes the L level regardless of the value of the fixed level. As a result, the fixed level of the output signal a of the waveform shaping circuit 4 becomes one of the first and second values disclosed in the above publication due to an abnormality in the buffer 2, the bandpass filter 3 or the waveform shaping circuit 4. Even if it becomes an intermediate value, it is possible to detect the abnormality of the knock sensor 1.

[0022]

As is apparent from the above description, according to the present invention, when the knock sensor fails due to an abnormality in the circuit processing the output signal of the knock sensor, for example, the buffer, the bandpass filter or the waveform shaping circuit. Even if the level of the generated fixed signal changes from the level when the processing circuit is normal, there is an effect that the abnormality of the knock sensor can be correctly detected.

Further, since the fault detection circuit of the present invention can be formed by a differential circuit composed of a diode, a resistor, a capacitor and a rectification / integration circuit and two comparators, it has a simple structure and can be manufactured at low cost. effective.

[Brief description of drawings]

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

FIG. 2 is a waveform diagram of signals of a main part of the circuit of FIG.

[Explanation of symbols]

1 ... Knock sensor, 2 ... Buffer, 3 ... Bandpass filter, 4 ... Waveform shaping circuit, 5 ... Abnormality detection circuit, 6 ... Differentiation circuit, 7 ... First comparator, 8 ... Rectification integration circuit, 9 ... Second
Comparator

Claims (2)

[Claims] 1. A knocking control including a knock sensor for detecting engine vibration, a bandpass filter for extracting a knocking signal in a specific frequency band from an output signal of the engine, and a waveform shaping circuit for shaping the waveform of the extracted signal. The knocking control device according to claim 1, further comprising an abnormality detection circuit that detects that the output signal of the waveform shaping circuit is at a fixed level for a certain period of time and detects an abnormality of the knock sensor. 2. An abnormality detecting circuit, wherein a differentiation circuit for differentiating an output signal of the waveform shaping circuit is compared with an output of the differentiation circuit and a first reference value to extract the vibration. A comparator, an integrating circuit for integrating the output of the first comparator, an output of the integrating circuit, and a second reference value to detect the absence of the vibration for a certain period of time. The knocking control device according to claim 1, wherein the knocking control device comprises a comparator.