JPH0429017B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a knocking detection device that determines knocking based on engine speed, and an object of the present invention is to accurately detect knocking up to high engine speeds.

Knocking in an automobile engine can be detected by observing engine vibrations and from the vibrations characteristic of knocking. Furthermore, since knocking occurs within a certain crank angle range, the occurrence of knocking can be detected more accurately by observing the vibration pickup signal within this crank angle range. That is, as shown in FIG. 1, knocking can be detected accurately by aligning a certain crank angle range (hereinafter referred to as knock gate) with the timing of knocking occurrence and examining the vibration pickup signal only during this knock gate period. In FIG. 1, the dotted line A indicates the ignition timing, and the knock gate b is set to a period in which knocking occurs when it is at "H".

FIG. 2 shows a conventional knocking detection device. In Figure 2, 1 is a vibration pickup that converts engine vibrations into electrical signals, 2 is an amplifier,
3 is a rectifier, 4 is an averaging circuit, 5 is an amplifier, 6 is a comparator, 7 is an AND circuit, 8 is a flip-flop,
9 is an ignition timing input, 10 is a waveform shaping circuit,
11 is a timing generation circuit, and 12 is a knocking detection output terminal. The signal from the vibration pickup 1 (FIG. 1c) is amplified by an amplifier 2, averaged by a rectifier 3 and an averaging circuit 4, and amplified by an amplifier 5. This average value output and the output of amplifier 2 are connected to comparator 6
When the output of the amplifier 2 is larger than the average value output, the comparator 6 changes the output from "L" to "H". Further, the waveform of the ignition timing input signal (FIG. 1a) is shaped by the waveform shaping circuit 10. A timing generation circuit 11 generates timing such as a knock gate (FIG. 1b). AND circuit 7
is the logical product (AND) of comparator 6 and the knock gate.
The flip-flop 8 outputs a knock detection signal (FIG. 1d). In this way, knocking is detected only during a certain crank angle range in which knocking occurs.

However, in the conventional example, when the engine speed becomes high, the time in the crank angle range becomes shorter, so that the timing of knocking cannot be matched. For example, when the crank angle range is 60° in a 4-cylinder engine, the time is 8.3 msec at 1200 revolutions, and 6000 revolutions.
In rotation, it is as short as 1.7m seconds. Furthermore, the timing at which knocking occurs varies depending on the engine speed and ignition timing. Therefore, it is difficult to set the range of the knock gate to be the same crank angle range for low speed rotation and high speed rotation. If the knock gate is to cover the entire range of high-speed rotation and low-speed rotation, it is necessary to increase the knock gate range, but increasing this range reduces the advantage of providing the knock gate to accurately detect knocking. Particularly in low-speed rotation, the knock gate time becomes long, and noise vibrations other than knocking become widespread, creating the possibility that knocking may be erroneously detected. On the other hand, if the knock gate range is made small, there will be a risk of missing knocking at high speed rotation.

The present invention provides a knocking detection device that eliminates the above-mentioned conventional drawbacks and has excellent knocking detection accuracy up to high speed rotation.

In the present invention, a knock gate for detecting knocking is not generated at high speed rotations above a certain number of rotations, and knocking is detected over the entire crank angle range. In this way, the knock gate range can be set accurately at low speed rotation, and knocking can be detected even at high speed rotation.

An embodiment of the present invention is shown in FIG. In Figure 3, 1 is a vibration pickup, 2 is an amplifier, 3 is a rectifier, 4 is an averaging circuit, 5 is an amplifier, 6 is a comparator, 7 is an AND circuit, 8 is a flip-flop, 9
is the ignition timing input, 10 is the waveform shaping circuit, 1
1 is a timing generation circuit, 12 is a knock detection output terminal, 13 is a rotation speed detection circuit, and 14 is an OR circuit. In this embodiment, the output of the timing generation circuit 11 and the output of the rotational speed detection circuit 13 are logically summed (OR), thereby inhibiting the generation of knock gates above a certain rotational speed. That is, as shown in Fig. 4, when the rotation speed is low, a knock gate is output by setting the output of the rotation speed detection circuit 13 to "L", but above a certain rotation speed, the rotation speed detection output is set to "H". As a result, the output of the OR circuit 14 is always "H" and the knock gate is prohibited. In this manner, at low speed rotation, knocking detection is performed while the knock gate is at "H", and above a certain rotation speed, knocking detection is performed regardless of the knock gate. FIG. 5 shows the rotation speed detection circuit 13. In FIG. 5, 15 is a triangular wave generation circuit;
16 is an averaging circuit, 17 is a comparator, and VR is a potentiometer. The triangular wave generating circuit 15 generates a triangular wave from one ignition timing to the next ignition timing, and the output thereof is averaged by the averaging circuit 16. Therefore, the average value output of the averaging circuit 16 changes depending on the rotation speed. This average value output and potentiometer
A predetermined rotation speed can be detected by comparing a voltage predetermined by VR with a comparator 17.

As described above, the present invention provides a vibration pickup for converting engine vibration into an electrical signal, an average value means for determining the average value of the output level of the vibration pickup, and a knock gate for detecting a predetermined crank angle range of the engine. crank angle range detection means for outputting a signal; detection means for detecting knocking by comparing the output of the vibration pickup and the output of the average value means during the period in which the knock gate signal is output; and a prohibition means for prohibiting output of the knock gate signal from the crank angle range detection means when the rotation speed detection means detects a rotation speed equal to or higher than a predetermined value. When the engine speed is low, knocking is detected during the knock gate signal generation period, and when the engine speed is higher than a predetermined value, knocking is detected over the entire crank angle range. This has the advantage that knocking will not be erroneously detected during low-speed rotation, and knocking will not be overlooked during high-speed rotation.

[Brief explanation of drawings]

1A to 1D are timing diagrams of a conventional knocking detection device, FIG. 2 is a block diagram of a conventional knocking detection device, FIG. 3 is a block diagram of a knocking device according to an embodiment of the present invention, and FIG. 4A is a block diagram of a conventional knocking detection device. -c are timing diagrams of the same device, and FIG. 5 is a block diagram of the rotation speed detection circuit of the same device. 1... Vibration pickup, 2... Amplifier, 3...
... Rectifier, 4 ... Averaging circuit, 5 ... Amplifier, 6
... Comparator, 7 ... AND circuit, 8 ... Flip-flop, 9 ... Ignition timing input, 10 ...
Waveform shaping circuit, 11...timing generation circuit, 1
2... Knock detection output terminal, 13... Rotation speed detection circuit, 14... OR circuit.

Claims (1)

[Claims] 1 A vibration pickup for converting engine vibration into an electrical signal, an average value means for determining the average value of the output level of the vibration pickup, and a crank angle range detection unit for detecting a predetermined crank angle range of the engine and outputting a knock gate signal. means for detecting knocking by comparing the output of the vibration pickup and the output of the average value means during the period in which the knock gate signal is output; and rotation speed detection means for detecting the rotation speed of the engine. and a knocking detection device comprising inhibiting means for prohibiting output of the knock gate signal from the crank angle range detecting means when the rotational speed detecting means detects a rotation speed of a predetermined value or more.