JPH0645645Y2 - Knock detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a knock detection device that can be used in an ignition timing control device for an internal combustion engine.

<Prior Art> A conventional knock detection device obtains a signal corresponding to engine vibration from a knock sensor, inputs the signal to a bandpass filter, and passes only a signal of a frequency component corresponding to knock vibration, and This is input to an integration circuit, integrated at a predetermined crank angle (for example, ATDC 10 ° to 60 °), and the integrated value is compared with a predetermined value to determine the presence or absence of knock.

Then, in the ignition timing control device for the internal combustion engine, the ignition timing (ignition advance) is set based on the engine speed and the load, which are parameters of the engine operating state, and the ignition control is performed based on the ignition timing. When it is present, for example, the ignition timing is corrected at a rate of 1 ° / ignition to avoid knock, and when it is not knocked, the angle is advanced at a rate of 1 ° / sec, for example, to advance to the knock limit and output. The characteristics and the like are improved (see Japanese Patent Laid-Open No. 62-126273).

<Problems to be solved by the invention> By the way, such a conventional knock detection device determines a section where a knock is likely to occur by a crank angle in advance, and detects a knock sensor output only in a certain crank angle section, It is to determine whether knock has occurred.

Incidentally, the detection section of the knock sensor output is delimited in this way because the knock sensor detects not only the knock signal but also the vibration such as the seating of the valve and the ignition, and can pass through the band pass filter. This is to eliminate it.

However, as the engine speed increases, the angular velocity of engine rotation increases, but the combustion speed does not change much.

Therefore, the waveform of the knock signal is relatively extended toward the larger angle of the crank angle of ATDC, the waveform does not fit in a certain integration section depending on the crank angle, and the knock signal generation section and the integration section are deviated from each other. There was a problem.

As a result, the controllability of knock control deteriorates.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a knock detection device capable of changing the knock detection section (integration section) according to the engine operating state.

<Means for Solving the Problems> Therefore, according to the present invention, as shown in FIG. 1, a knock sensor (a) for outputting a signal corresponding to the vibration of the engine and a knock sensor out of the signals from the knock sensor are provided. Bandpass filter (b) that passes the frequency component corresponding to vibration
An integrating circuit (c) for integrating a signal passed through the bandpass filter in a predetermined crank angle section, and a knock level judging means (d) for judging a knock level based on an integrated value of the integrating circuit, A knock detecting device having: an engine speed detecting means (e) for detecting an engine speed; and an integration interval varying means for changing a crank angle interval to be integrated by the integrating circuit according to the detected engine speed. (F) and are provided.

<Operation> In the above configuration, as the engine speed changes,
In response to the deviation of the knock signal generation section, the integration section of the crank angle is changed, and the knock level is determined by the integration value of the knock signal in that section.

Specifically, as the engine speed increases, the knock signal extends toward the larger crank angle.
The larger the crank angle, the longer the integration interval.

<Example> An example of the present invention will be described below.

Referring to FIG. 2, knock sensor 2 is attached to a cylinder block of engine 1. The knock sensor 2 has a piezoelectric element and outputs an electric signal corresponding to the vibration of the engine 1.

The signal from the knock sensor 2 is transmitted by the bandpass filter 3 to a frequency component (for example, 7 to 11) corresponding to knock vibration.
KHz) only, and is input to the integrating circuit 4.

The integration circuit 4 has a predetermined integration start angle (ATDC10 °)
To the integration end angle determined by the microcomputer 6 described below, the knock signal that has passed through the bandpass filter 3 is integrated.

Then, the integrated value is converted into a digital signal by the A / D converter 5 and read into the microcomputer 6.

The microcomputer 6 includes a CPU, a ROM and a RAM, determines a knock level based on the integrated value, corrects the ignition timing accordingly, and finally controls the ignition operation of the spark plug 7.

The engine 1 is provided with a crank angle sensor 8 as an engine speed detecting means for outputting a signal for each predetermined rotation angle of the engine, and the signal is input to the microcomputer 6.

The control of the integration section (integration end angle) determination and knock level determination in the microcomputer 6 is shown in FIGS.
It will be described with reference to the drawings.

The integration end angle determination routine will be described with reference to FIG.

This routine corresponds to the integration interval changing means.

In step 1 (denoted as S1 in the figure. The same applies hereinafter), the engine speed N detected by the signal from the crank angle sensor 8 is input.

In step 2, the integration end angle D is set in accordance with the rotation speed N input in step 1 from the preset integration end angle map so that the integration end angle D increases as the engine speed N increases. Search for.

As a result, the integration section is determined.

The knock level determination routine will be described with reference to FIG.

In step 11, the crank angle is read from the crank angle sensor 8.

In step 12, it is determined whether or not the crank angle input in step 11 is the integration start angle (for example, ATDC 10 °), and YE
Only in the case of S, the routine proceeds to step 13, where the integrating circuit 4 is reset and the integrating operation is started.

In step 14, it is judged whether or not the crank angle is the integration end angle D, and only when YES, the routine proceeds to step 15, where the integrated value integrated by the integrating circuit 4 is A / D converted and read. Then, in step 16, the integrated value is compared with a predetermined value (slice level) set in advance.

If integrated value ≧ predetermined value, the routine proceeds to step 17, and it is determined that knock is present.

The ignition timing correction control is performed based on the knock determination.

As described above, it is possible to further improve the knock detection accuracy by predicting the knock occurrence section by the rotation speed and integrating the section.

In this embodiment, when the integration interval is changed, only the integration end angle is changed, but it goes without saying that the integration start angle may also be changed.

<Effect of the Invention> As described above, according to the present invention, even if the knocking section changes due to the change in the rotation speed,
Since the integration section can also be changed, the knock generation section and the integration section are almost always matched, and the reliability of knock determination is improved.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention, FIG. 2 is a system diagram showing an embodiment of the present invention, and FIGS. 3 and 4 are flow charts showing control contents. 1 ... Engine, 2 ... Knock sensor, 3 ... Band pass filter, 4 ... Integrator circuit, 6 ... Microcomputer, 7 ... Spark plug, 8 ... Crank angle sensor

Claims (1)

[Scope of utility model registration request] 1. A knock sensor for outputting a signal corresponding to vibration of an engine, a bandpass filter for passing a frequency component corresponding to knock vibration among signals from the knock sensor, and a signal passed through the bandpass filter. In a knock detection device having an integrator circuit for integrating the engine in a predetermined crank angle section, and a knock level determining means for determining a knock level based on the integrated value of the integrator circuit, an engine for detecting the engine speed. A knock detection device comprising: a rotation speed detection means; and an integration section variable means for changing the crank angle section to be integrated by the integration circuit according to the detected rotation speed of the engine.