JPH0227614B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a knocking detection device for detecting the presence or absence of knocking in an internal combustion engine for an automobile. BACKGROUND OF THE INVENTION Knotting in automobile internal combustion engines is one of the factors that impairs fuel efficiency and vehicle safety. Such knocking can be detected by observing the vibration of an automobile internal combustion engine and from the amplitude and frequency peculiar to knocking. A knocking detection device that detects vibrations of an automobile internal combustion engine using a vibration pickup and detects knocking from this detection signal is disclosed in, for example, Japanese Patent Application Laid-Open No. 1983-1999.
It is described in Publication No. 103911. This device detects knocking from the average value of the vibration pickup output in a predetermined crank angle range before the vicinity of top dead center of the internal combustion engine and the peak vibration value of the vibration pickup. Problems to be Solved by the Invention In order to improve the detection accuracy of knotting, in addition to the characteristic that knotting occurs at a specific rotation angle (crank angle) of the automobile internal combustion engine, it is necessary to It is necessary to take into account the knocking signal level and noise signal level, which increase as the value increases. This point will be explained next. Fig. 1 shows a characteristic diagram of an automobile internal combustion engine in a low-speed rotation state (for example, 800 rpm), in which Fig. 1a shows a timing pickup signal in the distributor, Fig. 1b shows a knocking sensor signal, and Fig. 1b shows a timing pickup signal in the distributor. c is a knocking signal detection window circuit (hereinafter referred to as a knocking gate circuit)
and opening/closing control signals of the noise signal detection window circuit (hereinafter referred to as noise gate circuit). On the other hand, FIG. 2 shows a characteristic diagram of an automobile internal combustion engine in a high-speed rotation state (for example, 4000 rpm).
Figure a shows the timing pickup signal in the distributor, Figure 2 b shows the knocking sensor signal,
FIG. 2c shows the opening/closing control signals of the knocking gate circuit and the noise gate circuit, respectively. Also the first
In the figures and FIG. 2, the broken line indicates the ignition timing. When the opening/closing control signal is "H" in Figures 1c and 2c, the knocking gate circuit is closed,
This is when the noise gate circuit is open, and on the other hand, when the switching control signal is "L", the noise gate circuit is closed and the knocking gate circuit is open. In Fig. 1b and Fig. 2b, the knocking signals A and A' are the vibration signals with large amplitude during the period when the knocking gate circuit is closed, and the others are the noise signal B, which is the vibration noise of the automobile internal combustion engine. , B′. As is clear from FIGS. 1 and 2, the noise signal B' especially during high speed rotation (FIG. 2) is larger than the noise signal B during low speed rotation (FIG. 1). By the way, knocking is detected by using, for example, the maximum level of the knocking signals A, A' and the noise signals B,
The ratio of the maximum levels of B′ is taken, and when the value is above a certain level, it is determined that knocking is occurring, and when the value is below a certain level, it is judged that knocking is not occurring. In addition, the detection of knotting is
The maximum level of the knocking signals A, A' is compared with the maximum level of the knocking signals A, A', and the maximum level of the knocking signals A, A' is the maximum level of the noise signals B, B'. Knocking is determined when the level is greater than the level multiplied by a predetermined number, and knocking occurs when the level obtained by multiplying the maximum level of the noise signals B and B' by a predetermined number is greater than the maximum level of the knocking signals A and A'. It is determined that there is no. Therefore, unless consideration is given to the noise signal level and the knocking signal level, which increase as the rotational speed increases even if the degree of knocking is the same, it is impossible to accurately detect knocking within the entire rotational speed range of an automobile internal combustion engine. It turns out that it is difficult. However, conventional knocking detection devices do not take into account the noise signal level and the knocking signal level, which increase as the rotational speed increases. The maximum level of the output of the knocking gate circuit (hereinafter this level will be referred to as a) and the maximum level of the output of the noise gate circuit (hereinafter this level will be referred to as b)
Even if the degree of knocking is the same, the ratio (a/b) changes depending on the rotational speed of the automobile internal combustion engine as shown in the table below.

[Table] In this case, between low speed and high speed, the value of (a/b) changes in proportion to the rotational speed within the range shown in the table. In this way, when the rotational speed of an automobile internal combustion engine increases from low to high speed, the knocking signal level and the noise signal level increase, but the rate of increase is not the same, and the rate of increase in the noise signal level is higher than the knocking signal level. greater than the rate of increase. For this reason, when detecting the occurrence of knocking by comparing the knocking signal level and the noise signal level, there is a problem in that the knocking detection accuracy is poor. An object of the present invention is to provide a knocking detection device with excellent knocking detection accuracy. Means for Solving the Problems The knocking detection device of the present invention includes a vibration pickup for detecting vibrations of an automobile internal combustion engine, a knocking gate circuit for passing a knocking signal among the output signals of the vibration pickup, and a knocking gate circuit for passing a knocking signal among the output signals of the vibration pickup. a noise gate circuit that passes a noise signal among the output signals of the pickup; a comparator that detects knocking by comparing the outputs of the knocking gate circuit and the noise gate circuit; an amplifier circuit that amplifies either one of the input signals to the gate circuit to change the knocking signal level or the noise signal level; and a gain control circuit that controls the gain of the amplifier circuit according to the rotational speed of an automobile internal combustion engine. It is characterized by consisting of. Effects According to the configuration of the present invention, there is provided an amplifier circuit that amplifies either the input signal to the knocking gate circuit or the input signal to the noise gate circuit to change the knocking signal level or the noise signal level; A gain control circuit is provided to control the gain of the amplifier circuit according to the rotational speed of the internal combustion engine.
The difference in the rate of change of the knocking signal level and the noise signal level with respect to changes in the rotational speed is compensated, and when the degree of knocking is the same, the rate of change of the knocking signal level and the rate of change of the noise signal level are made the same regardless of the rotational speed. This makes it possible to improve the knocking detection accuracy. Embodiment An embodiment of the present invention will be described based on FIGS. 3 and 4. In FIG. 3, reference numeral 1 denotes a signal pickup for extracting the vibrations of an automobile internal combustion engine as an electrical signal, and examples of the output waveforms of this vibration pickup 1 are shown in FIGS. 1b and 2b. 2 is a selective amplification circuit for amplifying the output of the vibration pickup 1;
Reference numeral 3 denotes a selective amplifying circuit for amplifying the output of the selective amplifying circuit 2, and a gain control circuit 4 is connected in parallel to this selective amplifying circuit 3. FIG. 4 shows details of the gain control circuit, which includes a feedback resistor that determines the gain of the selective amplifier circuit 3.
R ₁ , R ₂ ,...R _o and analog switches S ₁ , S ₂ ,...S _o
This is a series circuit in which multiple series circuits are connected in parallel. The analog switches S ₁ , S ₂ , . . . S _o are on/off controlled by the output of the multiplexer 14 . For example, when only the analog switch _S1 is turned on, only the feedback resistor _R1 is connected in parallel to the selective amplifier circuit 3, and the selective amplifier circuit 3 has a gain determined by the resistance value of the feedback resistor _R1 . In FIG. 3, 5 is a knocking gate circuit, and this knocking gate circuit 5 is closed while the high level signal "H" shown in FIGS. 1c and 2c is applied to its gate terminal. It is closed to allow the output of the selective amplifier circuit 2 to pass through, and is closed while the low level signal "L" shown in Figures 1c and 2c is applied to the gate terminal to allow the output of the selective amplifier circuit 2 to pass. to prevent 6 is a noise gate circuit, and this noise gate circuit 6
is closed while a high level signal "H" is applied to its gate terminal to allow the output of the selective amplification circuit 3 to pass through, and is open while a low level signal "L" is applied to selectively amplify. Prevents passage of the output of circuit 3. Note that although the same output of the timing generation circuit 15 is applied to the gate terminal of the knocking gate circuit 5 and the gate terminal of the noise gate circuit 6, the inverter 16 is connected only to the gate terminal of the knocking gate circuit 5. Therefore, when the output of the timing generation circuit 15 is "L" and a high level signal "H" is applied to the gate terminal of the knocking gate circuit 5, the output of the timing generation circuit 15 is applied to the gate terminal of the noise gate circuit 6. Since "L" is applied as is, the knocking gate circuit 5 is "closed".
The noise gate circuit 6 becomes "open". On the other hand, the output of the timing generation circuit 15 is "H", and the gate terminal of the knocking gate circuit 5 receives a low level signal "L".
is applied, the output "H" of the timing generation circuit 15 is directly applied to the gate terminal of the noise gate circuit 6, so the knocking gate circuit 5 is "open" and the noise gate circuit 6 is "closed". Become.
That is, "H" in Figure 1c or Figure 2c
In the section, the knocking gate circuit 5 is "closed" and the noise gate circuit 6 is "open", and also as shown in FIG.
Alternatively, in the "L" section in FIG. 2c, the knocking gate circuit 5 is "open" and the noise gate circuit 6 is "closed". 7 is a peak hold circuit, and this peak hold circuit 7 holds the maximum value of the output of the selective amplifier circuit 2 which has passed through the knocking gate circuit 5. 8 is a peak hold circuit, and the peak hold circuit 8 holds the maximum value of the output of the selective amplifier circuit 3 that has passed through the noise gate circuit 6. 9 is a comparator, and this comparator 9 compares the levels held in the peak hold circuits 7 and 8, and outputs "H" when the output level of the peak hold circuit 7 is higher than the output level of the peak hold circuit 8. In the opposite case, "L" is output. 10 is a flip-flop circuit (D-type flip-flop), and this flip-flop circuit 10 is connected to the comparator 9 when a timing signal is output from the timing generation circuit 15.
The output is outputted to the output terminal 11. 12 is an ignition signal input terminal, 13 is a rotation speed detection circuit that detects the rotation speed from the period of the ignition signal, and 14 is an analog switch S ₁ , S ₂ ,...S _o (fourth
This is a multiplexer that outputs a switching signal for on/off control (see figure). Reference numeral 15 denotes a timing generation circuit that outputs a timing signal when a predetermined rotation angle (crank angle) has elapsed based on the ignition timing of the ignition signal (broken line in FIGS. 1 and 2). In the above configuration, the output of the vibration pickup 1 is amplified by the selective amplification circuits 2 and 3, gated by the knocking gate circuit 5 and the noise gate circuit 6, and divided into a knocking signal and a noise signal, and each output is sent to the peak hold circuit. 7,8
The peak is held, and knocking is detected by the comparator 9. That is, the presence or absence of knocking is determined based on the level difference between the knocking gate output and the noise gate output. On the other hand, the difference in the rate of change between the knocking signal level and the noise signal level, which changes depending on the rotation speed of the automobile internal combustion engine, can be made by automatically changing the gain of the selection amplification circuit 3 that amplifies the noise signal level according to the rotation speed. If the degree of knocking is the same, it is controlled to have the same value. The gain of this selective amplification circuit 3 is adjusted by a gain control circuit 4.
The details are shown in the figure. That is, the gain control circuit 4 uses the output of the multiplexer 14 that decodes the output of the rotation speed detection circuit 13 and outputs the decoded output.
Any one of n analog switches S ₁ to _{S o}
is closed, and the selection amplifier circuit 3 is connected by resistors R ₁ to R _o connected in series to the closed analog switches S ₁ to S _o .
The payoff of is determined. Therefore, depending on the rotation speed,
Analog switch S ₁ to S _o and resistance to close drive
If the resistance values of R ₁ to _{R o} are appropriately determined, the gain of the selective amplifier circuit 3 will change according to the rotation speed, and the rate of change in the noise signal level with respect to the change in the rotation speed can be determined as the rate of change in the knocking signal level. Almost the same result can be achieved, and the knocking detection accuracy can be improved. Note that in the above embodiment, the noise gate circuit 6
A selection amplification circuit 3 and a gain control circuit 4 are connected to the front stage of the 1. As mentioned above, the selection amplification circuit 3 and the gain control circuit 4 control the knocking signal level with respect to changes in the rotational speed of the automobile internal combustion engine. This is provided to make the rate of change almost the same as the rate of change of the noise signal, and as a matter of course, by connecting the selective amplification circuit 3 and the gain control circuit 4 before the knocking gate circuit 5, Alternatively, the rate of change in the knocking signal level with respect to the change in rotational speed may be set to be approximately the same as the rate of change in the noise signal level. Effects of the Invention According to the knocking detection device of the present invention, an amplifier circuit that amplifies either the input signal to the knocking gate circuit or the input signal to the noise gate circuit to change the knocking signal level or the noise signal level; Since a gain control circuit is provided that controls the gain of the amplifier circuit according to the rotational speed of the automobile internal combustion engine, the difference between the rate of change in the knocking signal level and the rate of change in the noise signal level with respect to changes in the rotational speed is compensated for. When the level of knotking is the same,
Regardless of the rotational speed, the rate of change in the knocking signal level and the rate of change in the noise signal level can be made substantially the same, and knocking detection accuracy can be improved.

[Brief explanation of drawings]

FIG. 1 is a signal waveform diagram in a low speed rotation state of an automobile internal combustion engine to explain the drawbacks of the conventional example.
FIG. 2 is a signal waveform diagram also in a high-speed rotation state, FIG. 3 is a block diagram of a knocking detection device according to an embodiment of the present invention, and FIG. 4 is a detailed diagram of a gain control circuit of the same device. DESCRIPTION OF SYMBOLS 1... Vibration pickup, 3... Selection amplification circuit (amplifier circuit), 4... Gain control circuit, 5... Knocking gate circuit, 6... Noise gate circuit, 9...
…comparator.

Claims (1)

[Claims] 1. A vibration pickup for detecting vibrations of an automobile internal combustion engine, a knocking gate circuit for passing a knocking signal among the output signals of the vibration pickup, and a noise gate circuit for passing a noise signal among the output signals of the vibration pickup. ,
a comparator that detects knocking by comparing the outputs of the knocking gate circuit and the noise gate circuit; an amplifier circuit that amplifies the knocking signal or the noise signal to change the knocking signal level or the noise signal level; a gain control circuit that controls the gain of the amplifier circuit according to the rotational speed of the automobile internal combustion engine, the rate of change of the knocking signal level and the rate of change of the noise signal level with respect to a change in the rotational speed of the automobile internal combustion engine; A knocking detection device is characterized in that it compensates for the difference between.