JPS58187831A - Knocking signal processing circuit - Google Patents

Abstract

PURPOSE:To make possible the detection of knocking with high accuracy by a method wherein reference voltage and knocking voltage being detected are obtained from a sampling signal and both the voltages are compared, so that a knocking detection signal can be outputted. CONSTITUTION:The output of an oscillation detector 32 becomes a signal 54 via a band filter 34 and is divided into two pahts; one of them is applied to an input terminal of a voltage comparator 37 through a switching circuit 35 and the like. This signal is treated as knocking voltage Vn being detected. The other is applied to a switching circuit 40 and then the other input terminal of the voltage comparator 37 as reference voltage Vs. Of the two signals Vn, Vs applied to the voltage comparator 37, while the voltage Vn' being detected exceeds the reference voltage Vs', the voltage comparator 37 outputs a pulse train as a knocking detection signal through a second integrating circuit 38. Since variation in sensitivity can thus be corrected, knocking is detectable with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a knocking signal processing circuit for detecting the presence or absence of knocking in an internal combustion engine and its degree.

Knocking occurs when an internal combustion engine is in a certain operating state, and the flame generated at the ignition part in the cylinder spontaneously ignites before it propagates to the unburned part at the end, causing the mixed gas in the cylinder to suddenly suddenly ignite. This is a phenomenon in which the fuel burns. It goes without saying that the occurrence of knocking is undesirable as it leads to a decrease in the output of the internal combustion engine and overheating.

Generally, it is efficient to advance the ignition timing of an internal combustion engine as much as possible under the operating conditions without causing knocking. but.

If the ignition timing is advanced too much, knocking may occur depending on the load condition, in which case it is necessary to adjust the ignition timing to TY'. For this purpose, it is necessary to accurately detect the occurrence of non-king.

It is known that when knocking occurs, the cylinder internal pressure and the internal combustion engine body undergo abnormal vibrations, and vibrations with specific frequency components in the range of 5 to 10 KHz occur near the second dead center of the cylinder. During normal operation of an internal combustion engine, the vibration frequency of the internal combustion engine body mainly has frequency components of several tens to hundreds of Hz, but in addition to this, the internal combustion engine body also vibrates due to the opening and closing of the intake and exhaust valves, and this vibration is caused by knocking. Since it also has the same frequency component as the vibration of time, it is considered noise from the point of view of knocking detection. Induction noise caused by ignition also becomes an obstacle to knocking detection.

Conventionally, several knocking detection methods have been proposed, but the above-mentioned noise components may also be detected as knocking, and weak knocking cannot be detected with high accuracy.

FIG. 1 is a conventional knocking signal processing circuit. FIG. 2 is a signal waveform diagram of each part of FIG. 1.

In Fig. 1, 2 is a vibration detector attached to the internal combustion engine main body 1, and during its output signal u, a signal 2 is shown in Fig. 2.
As shown by 1, many frequency components are included.

This blade signal is passed through an amplifier 3 and a bandpass filter 4 having a center frequency approximately equal to the frequency of the knocking vibration, and further passed through a rectifier circuit 5 to extract components such as signal 22 in FIG.

In FIG. 2, 22a and 22c respectively indicate an induced noise component due to ignition and a vibration noise component due to the valve system, and 22b indicates a vibration component due to non-king. The signal 22 is divided into two paths, one of which is input as is to one input terminal of the voltage comparator B,
This becomes the knocking detection signal voltage vN. The other voltage is converted through the low-pass filter 7 and the amplifier circuit 8 into a voltage Vs as shown by the broken line 22d in FIG. Ru. Furthermore, (the quasi-voltage VS is 1, normally when there is no knocking (
, T S ;, the gain of the amplifier circuit 8 is adjusted so that it is slightly larger than the peak voltage of the voltage VN.

While the two borrowed voltages VN and VS entering the voltage comparator 6 are larger than the knocking detection voltage vN, an output is generated in the voltage comparator B.

The output is accumulated in the integrator 9 and outputted as a knocking detection signal as signal 23 in FIG. 2. This output voltage is maintained for a suitable period of time until the ninth ignition is performed, and is reset by a reset doubler "sR". 11 is an amplifier circuit.

In the case of the circuit described in -1-, this occurs singly].

Although knocking can be detected relatively well, if knocking occurs continuously, the reference voltage Vs becomes large, so knocking may not be detected correctly. Further, during acceleration and deceleration, a time delay in the reference voltage VS due to the time constant of the low-pass filter 7 causes an error in knocking detection. Furthermore, when the same frequency components other than the knocking signal become large, the signal 22C in FIG.

It detects that there is a king.

1] An object of the present invention is to provide a knocking signal processing circuit that eliminates the above-mentioned drawbacks and can detect knocking with high accuracy.

The present invention extracts a specific frequency component in the output signal of the vibration detector using a bandpass filter, and for the extraction No. 411, from the time T1 has elapsed from the ignition timing to the predetermined time.
A reference voltage is obtained by sampling r3, rectifying and integrating this signal, and sampling the extracted signal by TN from the sampling end point to a predetermined time corresponding to a predetermined crank angle.

is compared with the reference voltage as a knocking detection voltage, and a knocking detection signal is output corresponding to the time when a value multiplied by a constant of the knocking detection voltage exceeds the reference voltage.

Hereinafter, a detailed explanation will be given based on examples.

FIG. 5 shows the results of an experiment investigating the occurrence of knocking in a four-cylinder internal combustion engine.

The figure shows the time TA from the start of primary current supply to the ignition coil to the end of the ignition induced noise r and the time 'ra to the peak of the knocking signal, using the rotational speed of the internal combustion engine as a variable. The ignition induction noise end time TA is approximately constant and approximately 1 m5ec, regardless of the number of revolutions. On the contrary,
The peak knocking reliability time 'ra varies depending on the rotation speed.

The smaller the rotation speed, the slower the speed 9 For example, 10001I, 1
The special rule for rotation is 4 m5ec, while at 4000 revolutions it is about 1.5 m5ec.

On the other hand, when the number of revolutions increases, the knocking signal level increases even if the knocking level is the same, and similarly, the noise signal level other than the knocking signal (so-called back ground noise level) also increases almost in proportion to the knocking signal level. From this, it can be understood that if the noise level in a region that does not include ignition induction noise or knocking signals is used as the reference voltage, knocking can be detected correctly even when the number of revolutions changes.

Also, according to Fig. 6 ζ'-9, the time TA until the ignition induction noise occurs and the time TB at which the knocking signal reaches its peak become closer as the rotational speed of the internal combustion engine increases, but when knocking occurs, the 111, the problem arises in the range of rotational speeds below 400 rpm, so in the example of FIG. 3, it is better to create the reference voltage from signals in the shaded range.

The present invention has been made based on the results of detailed analysis of the circumstances in which knocking occurs as shown above, and will be explained in more detail.

FIG. 4 is a block diagram of a knocking signal processing circuit according to the present invention, and FIG. 5 is a waveform diagram of signal A1X of each part thereof.

In FIG. 4, reference numeral 62 denotes a vibration detector attached to the internal combustion engine body 31 (2), and 1 uses, for example, an acceleration-responsive vibration detector using a piezoelectric vibrator.

The output of the vibration detector 62 includes many frequency components, as shown in the signal 54 in FIG. This signal 54 passes through an amplifier 64, and passes through a bandpass filter 64 having a center frequency approximately equal to the knocking vibration frequency (. On the other hand, the gate pulse generation circuit 44 generates a 9° waveform.
In synchronization with the rise of the gate pulse 51, a first gate with a pulse width of a certain time ΔTS is applied to the gate pulse 51 from the time when a certain time Δ′1゛1 has elapsed from the time of ignition to the time corresponding to the predetermined crank angle θ0. Pulse 52 and game
A second gate pulse 56 having a pulse width ΔTN from the falling edge of the gate pulse 52 to the falling edge of the rising gate pulse 51 is created.

Note that the date pulse 51 is obtained from a crank angle detector.

The signal 54 of the bandpass filter 34 is divided into two paths, one of which is sampled by the second gate pulse 55 in the switching circuit 35 to obtain a signal as shown in FIG. 56. This signal 56 is further passed through a rectifier circuit 56 to be converted into a half-wave rectified waveform as shown in FIG. This signal 57 is referred to as a knocking detection voltage (hereinafter referred to as a detected voltage) VN.

The other signal 54 is manually input to the switching circuit 40;
The signal is sampled by the first gate pulse 52, resulting in a signal as shown in FIG. 558. The signal 58 is further converted into a DC signal as shown in FIG. The DC signal voltage 59 is maintained at its signal source voltage 5
As shown in the figure, the voltage comparator 67 as an A-D converter is 5. Output a pulse train as shown in FIG. 60. This pulse train is subjected to a second integral cycle and output, and the output level is maintained until the gate pulse 51 falls and is reset. This angle J° is shown in FIG. 561. The level of the DC voltage 10 outputted from the integrating circuit 38 changes depending on the number of pulses and the pulse width of the pulse train 60. Further, the number and pulse width of the pulse train 60 correspond to the magnitude of the detected voltage VN'.
An amplifier circuit 39 whose final stage is a DC voltage Vo corresponding to the voltages v and l.
is output from. 7-11-, the operation of the present invention has been explained in two parts, but based on the experimental results shown in Figure 6 (1), the time △'1゛1 from 11JI at 9 ignition until the gate pulse 51 rises is 1m5ec. , !<1, the pulse width ATS of the gate pulse 52 is 0.5 m5ec,
The time it takes for the gate pulse 51 to go down to \γ is the time it takes for the crank angle θ0 to reach approximately 50° from the top dead center (by making the two correspond.

ignition induced noise during the high level of the first gate pulse 52 over a wide range of operating conditions.

It is best to avoid including vibrational vibration signals. At the same time, during the time period when the second gate pulse 53 is at a high level, only the non-king vibration signal can be generated without including ignition induction noise or valve vibration noise.

Further, the average signal level while the first gate pulse 52 is at a high level is normal compared to the average signal level while the second gate pulse 53 is at a low level in the absence of knocking.

The setting condition for the reference voltage V3 is to set the reference voltage Vs to a value slightly larger than the maximum level while the second gate pulse 53 is at a high level when there is no knocking. good.

In the present invention, as described above, the signal for obtaining the reference voltage VS is generated from the output of the vibration detector.

This has the advantage of being able to correct variations in the type of internal combustion engine and in the sensitivity of the vibration detector. Furthermore, since the signal for the reference voltage is sampled after a certain period of time has elapsed from the ignition timing, the influence of ignition induction noise is not reduced. Furthermore, since the sampling of the signal for the wide standard voltage is performed just before the sampling period 1i1J of the detected voltage signal starts, the level of both the reference voltage signal and the detected voltage signal -J when there is no knocking is The correlation is large and knocking can be detected with good viscosity. Furthermore, since the sampling time is constant, even if the rotational speed changes, there is no need to make corrections based on the rotational speed.

Furthermore, since a time domain in which knocking is likely to occur is selected as the voltage signal to be detected, the ratio of 12/l and 1 is greatly improved. Further, since the knocking signal processing circuit according to the present invention completes the detection of knocking within one ignition cycle, it can sufficiently cope with fluctuations in the engine speed of 0]114 during acceleration and deceleration.

1. As explained above, there are five knocking signals of the present invention.
According to the processing circuit, it is possible to detect knocking with high viscosity with few false detections, and using this, it is possible to appropriately perform 1-1 control at the time of ignition of a C-C internal combustion engine, which is extremely useful. It is.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an example of a conventional knocking signal processing circuit, Fig. 2 is a diagram showing changes in signal waveforms in each part over time, and Fig. 3 is an ignition timing that varies by χ・1 to the rotational speed of the internal combustion engine. Fig. 4 is a block diagram of the knocking signal processing circuit of the present invention, and Fig. 5 shows the time changes of the signal waveform of each part of the knocking signal processing circuit. This is a diagram. In the figure, 1.31 is the internal combustion engine body, 2.32 is a vibration detector, 3.33 is an amplifier, and 4.44 is a bandpass filter. 5, 36.41 is a rectifier circuit, 6.37 is a voltage comparator. 7 is a low-pass filter, 8.11.39.43 is an amplifier circuit. 9 is an integrator, 35.40 is a switching circuit, 68°4
2 is an integration circuit, 39.43 is an amplifier circuit, and 44 is a gate pulse generation circuit 2.

Claims (1)

[Claims] 1. In the No. 1 processing circuit that detects knocking from the output signal of a detector that detects vibrations of the internal combustion engine body, means for extracting a specific frequency component from the output signal and 9. Predetermined time △T] Time △ after elapsed time
means for generating a first gate signal spanning Ts and a second gate signal spanning a time corresponding to a predetermined crank angle from a predetermined time (ΔT1+ΔlI's) after ignition. 1) The first gate signal is applied to the extracted signal from II.
means for sampling at J and obtaining a reference voltage from the sampled signal;
The present invention is characterized by comprising means for performing sampling with a gate signal and obtaining a voltage for detecting knocking from the sampling signal, and means for comparing the reference voltage and the voltage for detecting knocking and outputting a knocking detection signal. knocking signal processing circuit.