JPS58139046A - Detector for knocking - Google Patents

Abstract

PURPOSE:To perform a reliable detection of knocking, by a method wherein a circuit time constant of an output of an average value of an oscillating sensor at a given crank angle range of an engine is made larger than a time constant outside the given crank angle range, and is compared with a peak value of an output. CONSTITUTION:An oscillating signal is applied to an input terminal 21, and an ignition timing signal connected to a contact point is inputted to an input terminal 37. A signal, at a given crank range in the proximity of an upper dead point, of the oscillating sensor signals passes an analogue switch (S) 23, and a peak value is outputted by a peak hold circuit 24. Further, it is integrated by a rectifying circuit 26. At a given crank angle range, an S27 is closed, an S28 is opened, and at a crank angle range other than the given crank angle range, the S28 is closed, and the S27 is opened. Thus, at the given crank angle range, a time constant is made large, and through comparision of outputs of circuits 24 and 25 by means of a comparator 34, a result is provided to an FF35. This permits to obtain a reliable knocking signal from a knocking detecting output terminal 36.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a knocking detection device for detecting knocking in an engine of an automobile or the like.

Engine knocking in automobiles and the like is one of the factors that increases fuel consumption and impairs vehicle safety and drivability.

Such knocking can be detected by observing engine vibration.

In a conventional knocking detection device, in a predetermined crank angle range near top dead center, the peak value of the output of a vibration sensor installed in the engine block in the predetermined crank angle range and the average/difference output of the vibration sensor output are calculated. When the ratio was greater than a certain value, it was determined that knocking was occurring.

Such a conventional example will be explained using FIGS. 1 and 2.

In FIG. 1, 1 is the input terminal for the vibration sensor signal.

2 is a selective amplifier, 3 is an analog switch, 4 is a peak hold circuit, and 5 is an average value output circuit.This average value output circuit 6 is composed of a rectifier circuit 6, an integration circuit 7, and an amplifier 8. It is configured. 9 is a comparator, 1o is a 7-lip flop, 11 is a knocking detection output terminal, 12 is a timing signal input terminal connected to a contact point, 13 is a waveform shaping circuit, and 14 is a timing generation circuit.

In FIG. 2, A is the ignition timing signal applied to the input terminal 12 in FIG. 1, and the rising edge of this ignition timing signal is the ignition timing. B is the output of the timing generation circuit 14 in FIG. 1, and indicates a predetermined crank angle range near the top dead center. In the second NC, a is a signal from the vibration sensor, and b is a signal from the vibration sensor when knocking occurs. Further, a broken line C in FIG. 2C is the output of the average value output circuit 6.

That is, in the conventional knocking detection device, the peak value of the vibration sensor signal in the predetermined crank angle range (shown in the second [9B) is compared with the average value of the vibration sensor output, and the peak value of the vibration sensor signal is determined as When the output was larger than the average output, it was determined that knocking was occurring, and a knocking pulse output was generated.

However, as is clear from Figure 2C, with the conventional device,
As knocking occurs and the vibration sensor signal increases, the output level of the average value output circuit, which is the reference voltage of the comparator for the knocking signal, also increases, making it difficult to determine knocking. had.

The present invention eliminates these drawbacks and provides a knocking detection device with excellent knocking detection accuracy.

An embodiment of the present invention will be described using FIGS. 3 and 4.

In FIG. 3, A7 is an ignition timing signal, and B' is a predetermined crank angle range near the upper hole, which is set at the timing at which knocking occurs. For example, in a 4-cylinder engine, this predetermined crank angle range changes the ignition timing to
If o is a crank angle, it is a crank angle (300 to 90 degrees). In C', al is the vibration sensor signal, b' is the vibration sensor signal when knocking occurs o
1 is the output of the average value output circuit.

In the present invention, the time constant of the integrating circuit of the average value output circuit is made larger in the predetermined crank angle range than the time constant of the integrating circuit outside the predetermined crank angle range. Therefore, even if knocking occurs and the vibration sensor signal increases as shown by the broken line 0 in Figure 3 C', the average value output of the average value output circuit does not increase proportionally, so conventional knocking detection devices By comparison, knocking can be determined accurately.

FIG. 4 shows a diagram of a second embodiment of the present invention.

In the fourth factor, 21 is the input terminal of the vibration sensor signal, 22
23 is a selection amplifier, 23 is an analog switch, 24 is a peak hold circuit, and 26 is an average value output circuit. (7) Resistance R2
, 31 (7): M' Consisting of a capacitor C132 amplifier and 33 inverters. Also, 34 is a comparator, 36
is a flip-flop, 36 is a knocking detection output terminal, 3
7 is an ignition timing signal input terminal connected to a contact point, 38 is a waveform shaping circuit, and 39 is a timing generation circuit.

Among the vibration sensor signals, a signal in a predetermined crank angle range near the top dead center (H period 'IJff in FIG. 3B') passes through an analog switch 23, and a peak value is outputted by a peak hold circuit 24. On the other hand, the vibration sensor signal passes through the rectifier circuit 26 and enters an integrating circuit consisting of a resistor and a capacitor. The predetermined crank angle range (H in Fig. 3 B')
period), the analog switch 27 is "closed",
The analog switch 28 is "open", and in the other crank angle range (period L in FIG. 3B'), the analog switch 28 is "closed" and the analog switch 27 is "open". Therefore, when B' in FIG. 3 is H, the integral time constant is "R
1C", and when B' in FIG. 3 is L, "R2OJ".

If R1 is chosen more closely than R2, IhC>R2O, and the time constant of integration is different between the H and L periods of the signal in Figure 3B', and the integration time constant of the H period is greater than that of L. It is larger than the time constant of the period.

By doing this, even if knocking occurs and the vibration sensor signal increases, the output level of the average value output circuit will not increase, and a more accurate reference voltage for the knocking signal of the comparator can be obtained. Therefore, the knocking detection accuracy becomes higher.

The present invention has the above configuration, and according to the present invention, more accurate knocking determination can be made by comparing the average right circular force and the peak value of the vibration sensor signal in the predetermined crank angle range.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional knocking detection device, Figure 2 is a block diagram of a conventional knocking detection device.
3A-C are explanatory diagrams of the operation of the same device, FIGS. 3A'-C' are explanatory diagrams of the operation of the knocking detection device according to an embodiment of the present invention, and FIGS. 45 and 45 are block diagrams of the same device. 21... Vibration sensor signal input terminal, 22...
...Selection amplifier, 23...Analog switch,
24...Peak hold circuit, 26...
- Average value output circuit, 26... Rectifier circuit, 27.
28-...Analog switch, 29,30...
...Resistor, 31...Capacitor, 32...
...Amplifier, 33...Inverter, 34...
... Comparator, 36 ... Flip-flop, 3
6... Knocking detection output end %37...
- Contact point, 38... Waveform shaping circuit, 39... Timing generation circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person 1 case Indication Patent application No. 22341 of 1988 Name of the invention Knocking detection device 3 Amendment person Relationship with the case Patent application Address Kadoma, Osaka City Oaza Kadoma 1006 address name
(582) Matsushita Electric Industrial Co., Ltd. Representative Yama
Toshihiko Shimo 4 Agent 571 Address 1006-6 Oaza Kadoma, Kadoma City, Osaka Prefecture The date of the amendment order [Figure 3 A'-C'] is corrected to ``Figure 3 A-C''. 2 Correct Figure 3 as shown in the attached sheet. 1′

Claims (2)

[Claims] (1) A vibration sensor that detects engine vibration, an average value output circuit that obtains the average value of the output of this vibration sensor, and a peak value of the output of the vibration sensor in a predetermined crank angle range near the top dead center of the engine. a comparator for comparing the output of the average value output circuit; a means for making a time constant of the average value output circuit in the predetermined crank angle range larger than a time constant outside the predetermined crank angle range; A knocking detection device includes a knocking determination means for determining knocking. (2) The average value output circuit includes a rectifying circuit that rectifies the output of the vibration sensor and an integrating circuit that integrates the output of the rectifying circuit, and within a predetermined crank angle range. 2. The knocking detection device according to claim 1, wherein the time constant of said integrating circuit is changed outside the knocking detection device.