JPS587538A - Knocking detecting device - Google Patents

Abstract

PURPOSE:To detect the knocking accurately by extracting a specified frequency component from an electric signal corresponding to the vibration of an internal combustion engine, judging the knocking by the ratio of two consecutive sampled values at every specified time interval, thereby facilitating the determination of a threshold value. CONSTITUTION:The vibration of the internal combustion engine is converted into the electric signal by an electric signal converter part 1. The specified frequency component, whose variation becomes large at the knocking part within said electric signal, is extracted in a specified frequency extracting part 2. Sampling is performed in a sampling part 3 at every specified time interval. The ratio computation of the two consecutive sampled values from the sampling part 3 is performed in a ratio value computing part 4. The knocking is judged by a knocking detecting part 5 based on whether this ratio exceeds the thrshold value or not. In this constitution, the threshold value in the detecting part 5 is determined readily and positively regardless of the effect such as the signal level variation due to the causes other than the knocking. Therefore the accurate knocking detection can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a knocking detection device for detecting knocking in an internal combustion engine such as a gasoline engine.

Figures 1, 2, and 3 show that the number of ignitions of a spark plug, which is a component of an internal combustion engine such as a gasoline engine, is 1oO
This figure shows the results of frequency analysis of the electric signal obtained by converting the vibration of the internal combustion engine in the case of o times/minute. FIG. 1 shows a state in which no knocking occurs in the internal combustion engine. Figures 2 and 3
The figures show a case where the internal combustion engine is in a trace knock state, and FIG. 2 shows a non-knocking part, and FIG. 3 shows a knocking part. However, the trace knock state refers to a state in which the internal combustion engine changes over time between a non-knocking state and a knocking state. In addition, Figures 4, 6, and 6 are
The frequency analysis results are shown for the case where the number of ignitions is 26 oO times/min, in which, in the internal combustion engine, Fig. 4 shows a state where no knocking occurs at all, and Fig. 6 shows a state where no knock occurs. FIG. 6 shows the non-knocking part, and FIG. 6 shows the knocking part in the trace knock state.

When comparing these figures, the non-knocking parts (Fig. 1, Fig. 2, Fig. 4, Fig. 6) and the knocking parts (Fig. 3, Fig. 6) show that in this case the frequency is around 8kHz. The change in level is particularly remarkable in the frequency component (specific frequency component).

Conventionally proposed knocking detection methods are:
For example, if the level of a specific frequency component of an electrical signal obtained by converting vibrations of the internal combustion engine exceeds a predetermined threshold, it is determined that knocking has occurred in the internal combustion engine. However, as is clear from FIGS. 1 and 4, even in a state where no knocking occurs, as the number of ignitions increases from 1000 times/second to 260 times/minute, the While the level at frequencies other than the specific frequency hardly changes, the level at the specific frequency changes from about 64 dB to about e s dB. Therefore, as the number of ignitions increases, the level of the specific frequency increases,
The electric signal level increases, and according to the conventional method, there is a high possibility that knocking will be erroneously detected due to the increase in the number of ignitions. On the other hand, in the non-knocking parts (Fig. 2, Fig. 6) and the knocking parts (Fig. 3, Fig. 6) in Figs. 2, 3, 5, and 6, While the level of the signal hardly changes, the level changes at the specific frequency is significant. For example, when the number of ignitions is 1000 times/min, the specific frequency is 75 dB in the non-knocking part as shown in Figure 2, whereas in the non-knocking part it is 75 dB as shown in Figure 3. This is approximately 90 dB, an increase of approximately 15 dB. Similarly, when the number of ignitions is 2,500 times/minute, the specific frequency is about 77 dB in the non-knocking part as shown in FIG. 5, while it is about 92 dB in the knocking part. and about 16d
B is increasing. In this way, with respect to the specific frequency component, the degree of change in level is approximately constant regardless of the change in the number of ignitions.

By the way, the magnitude of the level is expressed as decibel (d B, )
Expressed as 20 Zog, o a (dB), the difference in levels expressed in dB is originally a value of the ratio of levels. Therefore, the fact that the degree of level change is constant at 16 dB as described above means that the value of the level ratio is constant.

As described above, in the conventional method, in order to accurately detect knocking, it is necessary to determine the threshold value in consideration of level fluctuations due to fluctuations in the number of ignitions, etc., and it is not easy to determine the threshold value.

On the other hand, since the ratio a value of the level of the specific frequency is almost constant, there is no need to consider the increase in the number of ignitions, etc. when determining the threshold value for this value, and the threshold value can be easily determined and accurately determined. knocking detection can be performed.

The present invention was made against the above-mentioned background, and is a method for detecting knocking using an electrical signal obtained by converting vibrations of an internal combustion engine such as a gasoline engine.
By sampling a signal consisting of a specific frequency component of the electric signal at regular intervals and performing knocking detection using the ratio of two consecutive sample values in the sample value series, the signal is detected due to causes other than non-king. The purpose of this method is to easily determine a threshold value without considering the influence of level fluctuations, etc., and to perform more accurate non-king detection.

An embodiment of the present invention will be described below with reference to FIG.

Reference numeral 1 denotes an electrical signal converter that converts vibrations of an internal combustion engine such as an engine into an electrical signal and outputs the electrical signal. Reference numeral 2 denotes a specific frequency extraction section, which is used to extract a specific frequency component from the output of the electrical signal conversion section 1. 3 is a sampling section that samples the output of the specific frequency extraction section 2 at regular time intervals and obtains a sample value 51 (i, = 1.)
・) is output sequentially.

4 is a ratio value calculation unit which calculates the ratio value rt-s, 1 between the previous output 81-1 of the sampling unit 3 and the new output si.
/st (i=1.2.3.-) -.-(1) is output. 6 is a knocking detection unit that detects knocking when the output r, (i=1.2.3...) of the ratio value calculation unit 4 exceeds a predetermined threshold; Outputs a detection signal.

FIGS. 8 and 9 show temporal changes in the frequency analysis results of the electrical signal obtained by converting the vibrations of the internal combustion engine for non-knocking parts and knocking parts, respectively. As is clear from these figures, the change in the specific frequency component (here fft, near 8.25KH2) is extremely large in the knocking part compared to the non-knocking part, and using the value of the ratio of the levels of the specific frequency component, It is obvious that knocking can be detected easily.

FIG. 10 is an example of the output of the ratio value calculation unit 4, and represents a temporal change in the ratio value of the level of a specific frequency component. In the figure, the horizontal axis represents time, and the vertical axis represents the magnitude of the level ratio.

The value of the ratio in the state where there is no knocking at all is represented by #. The value of the ratio in the trace knock state is expressed in units of 1, and the ratio value is generally 10 or more, especially for the knocking part. Therefore, it is clear that knocking can be easily detected by setting the threshold value to 10, for example, and determining that knocking has occurred when the value of the ratio exceeds the threshold value. In this way, according to the configuration of the present invention, knocking can be easily and accurately detected.

The present invention calculates the ratio of sample values of a signal consisting of a specific frequency component whose level change is particularly remarkable in the knocking part compared to the non-knocking part of the electrical signal obtained by converting the vibration of an internal combustion engine such as an engine. Accurate non-king detection can be performed even when the electric signal level increases due to an increase in the number of firings of a spark plug, which is a component of the internal combustion engine.

Further, even if the level increases due to a cause other than knocking itself, the ratio value is not affected, so it is easy to determine the threshold value.

[Brief explanation of drawings]

Figures 1 to 6 show the frequency analysis results of electrical signals obtained by converting the vibrations of an internal combustion engine such as a gasoline engine, and Figures 1 to 3 show one component of the internal combustion engine. When the number of ignitions of a certain spark plug is 1ooo@/min, FIGS. 4 to 6 show the results when the number of ignitions is 2500/min. FIG. 7 is a block diagram of a knocking detection device according to an embodiment of the present invention, FIGS. 8 and 9 are diagrams showing temporal changes in the frequency analysis results of the electric signal, and FIG.
FIG. 0 is a diagram showing an example of the output of the ratio value calculation unit 4 in FIG. 1...Electrical signal conversion unit, 2...Specific frequency extraction unit, 3...Sampling unit, 4...1 ratio value calculation unit, 6...Knocking detection Department. Name of agent: Patent attorney Toshi Nakao Haga 1 person system 1
Fig. 14 Liquid fall Fig. 2 Fig. 3 Fig. 4 Shuhorei Fig. 5 River J bed

Claims (1)

[Claims] a converting means for converting vibrations of an internal combustion engine such as a gasoline engine into an electrical signal; a specific frequency extracting means for extracting a specific frequency component of the output signal of the converting means; comprising a sampling means for sampling, a means for determining the ratio of two consecutive sample values of the sampled sample value series, and a determining means for determining whether the value of the ratio exceeds a predetermined threshold; A knocking detection device characterized in that abnormal vibrations of the internal combustion engine are detected using the output of the means.