JPH0566151A - Knocking detecting device - Google Patents

Abstract

(57) [Summary] [Purpose] Minimize the deterioration of knocking detection accuracy due to mechanical noise. [Composition] A means for detecting engine knocking vibration,
Knocking means for setting a discontinuous detection period so as to exclude the generation period of mechanical noise and predetermined signal processing for the signal of the vibration detection means included in the detection period to obtain a knocking determination index and comparing with a predetermined value. A means for determining the presence or absence of is provided. [Effect] Even if mechanical noise occurs during the knocking occurrence period, the detection period excluding only the mechanical noise occurrence period can be set to ensure the knocking detection accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knocking detection device for an internal combustion engine.

[0002]

2. Description of the Related Art A conventional knocking detection device detects a knocking by providing a predetermined continuous detection period. However, when mechanical noise of an engine occurs, the position and width of the knocking detection period are changed. In this way, the detection period is set so as to avoid the generation period of mechanical noise, and the deterioration of detection accuracy due to mechanical noise is prevented. As an example, there is JP-A 61-221623.

[0003]

In the above prior art, since the continuous detection period is set, when mechanical noise is generated near the center of the knocking generation period, the detection period becomes a very narrow range. However, there is a problem that the knocking detection accuracy cannot be sufficiently obtained.

[0004]

In order to solve the above problems, a vibration detecting means for detecting the vibration of the internal combustion engine, a detection period setting means, and a judging means for judging the presence or absence of knocking are provided.

[0005]

The detecting period setting means is included in the predetermined period 1.
A period other than the predetermined period 2 is set as a knocking detection period. The determination unit performs predetermined signal processing on an output signal of the vibration detection unit in the set detection period, calculates a knocking determination index, and knocks based on the determination index. The presence or absence of is determined.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of setting a detection section, which is a feature of the present invention, will be described with reference to FIG. As shown in the waveform of the vibration sensor signal in the figure, when mechanical noise occurs during the knocking occurrence period, if the detection period is matched with the knocking occurrence period, there is a high possibility of false detection. Also,
If a conventional continuous detection period is provided so as to avoid mechanical noise, the detection period is narrowed like w ₁ , so that the increase in vibration due to knocking cannot be detected sufficiently, or the knocking generation period fluctuates. In this case, there is a problem in that the missed detection is caused and the accuracy of knocking detection is lowered. Therefore, in the present invention, a discontinuous detection period is provided so as to exclude the mechanical noise occurrence portion of the knocking occurrence period like w ₂ , so that the influence of the mechanical noise is eliminated and a sufficient detection period for knocking detection is secured. It is something to do.

A system configuration diagram of an engine control device to which the present invention is applied is shown in FIG. The intake air of the engine is taken into the combustion chamber through an air cleaner 1, an intake air amount sensor 2, a throttle valve 5 and an intake valve. A knock sensor 17 for detecting vibration of the engine block is attached. The crankshaft of the engine has a position sensor 12-1 and a reference sensor 12 for measuring the rotation speed.
-2 is attached.

Signals from the intake air amount sensor, the position sensor, the reference sensor, and the knock sensor are input to the control unit 9. In the control unit, the fuel injection charge and the ignition timing are operated from these signals, and the results are converted into a drive signal for the injector 16 and a control signal for the ignition coil 13 and output. Next, the operation of the knock sensor signal capturing section in the control unit 9 will be described with reference to FIG.

The position counter 21 measures the crank angle by counting the number of position signals with reference to the reference signal. The start angle of A / D conversion is set in the compare register by the CPU 20.
The A / D converter 23 A / D converts the signal from the knock sensor a predetermined number of times at a predetermined sampling period. RAM2
In step 4, the time-series data of the A / D-converted knock sensor signal is stored for subsequent data processing.

The operation timing of signal acquisition will be described with reference to FIG. When the position counter is incremented and coincides with the value of the compare register corresponding to the start angle of A / D conversion, a coincidence interrupt is generated in the CPU. A / D conversion is started when the coincidence interrupt is generated, and the converted data is stored in the RAM. Here, the signals included in the knocking occurrence period are continuously A / D converted. The signal processing in the CPU removes the signal in the portion where the mechanical noise occurs. The A / D conversion ends after being performed a predetermined number of times.

The operation of the CPU 20 will be described with reference to FIG. In the flowchart of FIG. 4A, step 10
At 0, the signal of the knock sensor is continuously fetched into the RAM for the knocking occurrence period by the processing described above. In step 110, signal mask processing is performed to remove data during the mechanical noise generation period. Here, as shown in FIG. 4B, the masking process of the signal is performed by a process of fixing the data corresponding to the mechanical noise generation period to a DC voltage. The period of occurrence of mechanical noise is confirmed in advance by an experiment, and is set in the table according to the number of rotations. In step 120 of FIG. 4A again, frequency analysis such as FFT is performed on the signal masked data to calculate the spectrum level corresponding to the characteristic frequency of knocking. Then in step 130,
The presence or absence of knocking is determined by comparing the above spectrum level with a predetermined threshold value. After that, the knocking detection result can be reflected in the ignition timing control and the like.

By the above processing, even when mechanical noise is generated during the knocking occurrence period, the detection period is discontinuously set so as to avoid the mechanical noise occurrence period, whereby the knocking detection accuracy is deteriorated by the mechanical noise. Can be kept to a minimum.

[0013]

As described above, even when mechanical noise occurs during the knocking occurrence period, the detection period excluding only the mechanical noise occurrence period can be set to ensure the knocking detection accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing setting of a knocking detection period in the present invention.

FIG. 2 is a configuration diagram of an engine control device.

FIG. 3 is an explanatory diagram of a signal capturing unit.

FIG. 4 is a diagram showing a knocking detection processing procedure.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Air cleaner, 2 ... Intake air amount sensor, 5 ... Throttle valve, 6 ... Intake manifold, 9 ... Control unit, 13 ... Ignition coil, 15 ... Spark plug, 16 ... Injector, 17 ... Knock sensor, 20 ...
CPU, 23 ... A / D converter, 24 ... RAM.

Claims (1)

[Claims] 1. A knocking detection device, comprising a vibration detection means for detecting vibration of an internal combustion engine, wherein knocking detection is performed by an output signal of the vibration detection means within a predetermined period 1, the predetermined period included in the predetermined period 1. Detection period setting means for setting a period other than 2 as a knocking detection period,
Knocking characterized by providing a determination means for performing a predetermined signal processing on the output signal of the vibration detection means within the detection period, calculating a knocking determination index, and determining the presence or absence of knocking based on the determination index. Detection device.