JPH0192624A - knock detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a knock detection device.

[Conventional technology]

Conventionally, in an internal combustion engine that has a function of controlling ignition timing based on a knock signal from a knock sensor and preventing the occurrence of knocking, the above-mentioned knock sensor is installed in the cylinder block or cylinder head of the internal combustion engine. When one predetermined frequency component is detected, knock control is performed, assuming that a knock has occurred.

[Problem that the invention seeks to solve]

By the way, frequency analysis of the knock sensor output when knock occurs shows that the vibration caused by knock is transmitted to the knock sensor through various paths (for example, those that pass through the cylinder block and the cylinder head). There are two frequency components, but when piston slap occurs due to deformation of the piston over time, the vibration due to this piston slap has almost the same frequency component as the knock frequency component passing through the cylinder block, so the knock transmitted through the cylinder block When frequency components are used as knock signals.

Even if knocking is not occurring, the knock sensor may output the same signal as when knocking occurs.

In addition, the vibration caused by the impact when the valve seat is seated due to the expansion of pulp clearance has a frequency component that is almost the same as the knock frequency component that passes through the cylinder head, so the knock frequency component that is transmitted through the cylinder head is used as the knock signal. Even when used as a knock sensor, the knock sensor sometimes outputs the same signal as when a knock occurs even when no knock occurs.

In other words, whether the frequency component conventionally used for knock control is a knock frequency component transmitted through the cylinder block section or a knock frequency component transmitted through the cylinder head section, the frequency component has approximately the same characteristics as the respective frequency components. There has been a problem in that knock control is performed even though no knock is occurring due to the generation of vibrations.

[Failure to solve the problem]

The present invention was devised in view of the above, and includes a knock sensor that detects vibrations of an internal combustion engine, a first frequency component peculiar to knock from the output signal of the knock sensor, and a first frequency component that is unique to knock. a first knock detection circuit that outputs a signal based on the knock sensor; a second knock detection circuit that detects a second frequency component peculiar to knock from the output signal of the knock sensor;
A second knock detection circuit outputs a signal based on the frequency component of , and the output signal from the first knock detection circuit and the output signal from the second knock detection circuit are inputted to generate a nine-way signal. A knock detection device comprising: a logic circuit that outputs a logical product; and a knock signal output circuit based on an output signal of the logic circuit. ” is the gist.

[For production]

According to the above configuration, the knock signal is output only when the logical product of two frequency components specific to knock is obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 10. In the block circuit diagram shown in FIG. 1, a knock sensor 10 is attached to an engine block (not shown) and detects engine vibration. A first knock detection circuit 20 detects a first frequency component peculiar to knock from the output signal of the knock sensor 10, and outputs a pulse signal based on the first frequency component. A second sensor detects a second frequency component peculiar to knock from the output signal of the knock sensor 10 and outputs a pulse signal based on the second frequency component.

detection circuit 30. AND gate 40 that operates when a pulse signal from the first knock detection circuit 20 and a pulse signal from the second knock detection circuit 30 are obtained. Same A
It is constituted by an integrating circuit 50, which is a knock signal output circuit that integrates the output signal from the ND gate 40 and generates an integrated voltage matching the integrated value.

Here, the first knock detection circuit 20 includes a band pass filter (hereinafter referred to as BPF) 22. which passes only a first frequency component from the output signal of the knock sensor 10. Same BP
A half-wave rectifier circuit 24 for half-wave rectifying the output signal waveform that has passed through F22. A background level generation circuit (hereinafter referred to as BGL) 26 that outputs an average value based on the output signal waveform of the half-wave rectifier circuit 24 to be compared with the same output signal waveform.
゜Output signal waveform from the half-wave rectifier circuit 24 and the BG
It is constituted by a comparator 28 that compares the average value from L26. Further, the BGL 26 includes a low-pass filter 26a that converts the output signal waveform of the half-wave rectifier circuit 24 into a DC voltage level, and a gain adjuster 26b that adjusts the DC voltage level outputted by the low-pass filter 26cL to a desired level. ing.

Next, the second knock detection circuit 30 detects the knock sensor 1.
B to pass only the second frequency component from the output signal of 0
PF32. A half-wave rectifier circuit 34 that half-wave rectifies the output signal waveform that has passed through the BPF 32.BGL 36 that outputs an average value to be compared with the output signal waveform based on the output signal waveform of the half-wave rectifier circuit 34. and a comparator 38 that compares the output signal waveform from the half-wave rectifier circuit 34 and the average value from the BGL 36. Furthermore, the BGL 36 includes a low-pass filter 36α that converts the output signal waveform of the half-wave rectifier circuit 34 into a DC voltage level, and a gain adjuster 36b that adjusts the DC voltage level output to the low-pass filter 36a to a desired level. It is configured.

The operation will be explained below with reference to FIG. 2 a''-n, where the horizontal axis of FIG. 2 a''-n represents time.

The knock sensor 10 normally detects mechanical vibrations during engine operation, but if knock occurs in the engine at this time, it will detect knock vibrations in addition to the mechanical vibrations.

At this time, the output signal from the knock sensor 10 is the B
Although it is input to the PF 22, the four BPF 22 passes only the first frequency component peculiar to knocking, near 8KH2,
In order to suppress noise components other than knock, a signal with a good SN ratio as shown in FIG. 2 α is output.

Furthermore, in the half-wave rectifier circuit 24, the BPF 22
The output signal of is converted into a half-wave rectified signal as shown in FIG. Also, the same signal (Fig. 2b).

It is also input to the BGL 26, and passes through the low-pass filter 26α and the gain adjuster 26b, so that the output signal of the half-wave rectifier circuit 24 as shown in FIG. It is converted into a DC voltage that is amplified to a lower level than the other components. And the half wave rectifier circuit 24
(Figure 2b) and the output signal of the BGL26 (Fig. 2b)
The output signal of the half-wave rectifier circuit 24 (Fig. 2 h) is compared with the output signal of the BGL 26 (Fig. 2 C) by the comparator 28, and if no knock has occurred (Fig. The comparator 28 outputs a continuous low level signal so as not to exceed the output signal (C in Figure 2), and when a knock occurs (section g in Figure 2), the output signal from the half-wave rectifier circuit 24 (section b in Figure 2) is output.
) exceeds the output signal of the BGL 26 (FIG. 2C), the comparator 8 outputs a pulse train as shown in FIG. 2D.

Further, the output signal of the knock sensor 10 is transmitted to the BPF 32.
Although it is input to
In order to suppress noise components other than knocking, a signal with a good SN ratio as shown in FIG. 2g is output. Further, in the half-wave rectifier circuit 34, the output signal of the BPF 32 is converted into a second
Convert to a half-wave rectified signal as shown in the figure. The same signal (Fig. 2h) is also input to the BGL 36, and is processed by the low-pass filter 36a and gain adjuster 36b from the noise component of the output signal of the half-wave rectifier circuit 34 (Fig. 2h) as shown in Fig. 2m. is converted into a DC voltage that is amplified to a high level and lower than the knock component. And the above half wave rectifier circuit 3
The comparator 38 compares the output signal of 4 (h in Fig. 2) with the output signal (m in Fig. 2) of the BGL 36, and if knocking does not occur (part in Fig. 2), half-wave rectification is performed. The output signal of the circuit 34 (Fig. 2 h) is the output signal of the BGL 36 (Fig. 2 m
), the comparator 38 outputs a continuous low level signal, and when knocking occurs (Fig. 2)
The output signal of the half-wave rectifier circuit 34 (h in Figure 2) is the BGL
36 (FIG. 2m), the comparator 38 outputs a pulse train as shown in FIG.

Then, the pulse train from the comparator 28 (Fig. 2d)
) and the pulse train from the comparator 34 (Fig. 2 m)
is input to the AND gate 40.

If the logical product is obtained, it is determined that a knock has occurred in the engine, and the AND gate 40 outputs a corresponding signal (FIG. 2m).

The output signal from the AND gate 40 (FIG. 2m) is input to an integrating circuit 50, which outputs an integrated voltage based on the output signal of the AND gate 40 as a knock signal. (Second
(Fig. m) Therefore, according to this embodiment, a knock signal is output only when two frequency components (8KH2, 13K) (Z') unique to knock are detected, so that the knock signal is outputted only when two frequency components (8KH2, 13K) (Z') unique to knock are detected. A knock signal is erroneously output due to vibration from the piston step that outputs the frequency, and a knock signal is erroneously output due to vibration when the pulp is seated, which outputs a frequency component that is almost the same as the frequency component of 13KH2. This has the effect of completely eliminating this problem.

In this example, 8KH2,
I used two frequency components of 13KH2.

When there are three or more frequency components that significantly indicate the occurrence of knock, the same number of knock detection circuits may be provided, and the occurrence of knock may be determined when two or more or all of the frequency components are detected.

〔effect〕

According to the configuration of the present invention, it is determined that a knock has occurred only when the logical product of the output of the first knock detection circuit and the output of the second knock detection circuit is obtained, and a knock signal is output. It is possible to completely eliminate a signal due to vibration from the piston slap or a signal due to vibration from when the valve is seated from the knock (output) signal.

[Brief explanation of the drawing]

Figures 1 and 2 show a knock detection device as an embodiment of the wooden device. Figure 1 is a block circuit diagram, and Figure 2 is a waveform diagram corresponding to each symbol shown in Figure 1. shows. 10... Knock sensor 20...
...... First knock detection circuit 30 ......
... Second knock detection circuit 40 ......
AND gate 50 ・・・・・・・・・ Integration circuit

Claims (1)

[Claims] a knock sensor that detects vibrations of an internal combustion engine; and a first knock detection circuit that detects a first frequency component unique to knock from an output signal of the knock sensor and outputs a signal based on the first frequency component. , a second knock detection circuit that detects a second frequency component peculiar to knock from the output signal of the knock sensor and outputs a signal based on the second frequency component; a logic circuit that receives the output signal and the output signal from the second knock detection circuit and outputs a logical product of both signals; and a knock signal output circuit that outputs a knock signal based on the output signal of the logic circuit. A knock detection device characterized by comprising: