JPS58225340A - Circuit for treating knocking signal - Google Patents

Abstract

PURPOSE:To accurately judge knocking, by carrying out comparison by using a noise level in a partial region directly prior to ignition from an upper dead point through a crank angle of 90 deg. after a valve noise is generated. CONSTITUTION:By the output from a crank angle detector 50, a gate pulse generating circuit 51 fabricates a first gate pulse for sampling the space signal 64 of a definite time DELTAT1 directly after a lower dead point and a second pulse 62 for sampling the space signal 64 of a time DELTAT2 corresponding to a predetermined angle theta2 from an upper dead point. The output of a vibration detector 42 is divided into two parts through an amplifier 43 and a zone filter 44 and one of them is sampled by the gate pulse 62 to be inputted to the one side of a voltage comparator 47 through a rectification circuit 46 while the other is sampled by the gate pulse 61 to be inputted to the other side of the comparator 47 as reference voltage Vs through a rectification circuit 53, an integration circuit 54 and an amplifier circuit 55 to carry out the determination of knocking.

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 when such a knocking phenomenon occurs, it causes a decrease in the output of the internal combustion engine and overheating, which is undesirable.

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. If the ignition timing is advanced too far, knocking may occur depending on the load condition.

In that case, it is necessary to retard the ignition timing. For this purpose, it is necessary to accurately detect the occurrence of knocking.

It is known that when knocking occurs, the cylinder internal pressure and the internal combustion engine body undergo abnormal vibrations, and vibrations with a specific frequency component in the range of 5 to 10 kHz occur near the top dead center of the cylinder. During normal operation of the internal combustion engine, the vibration frequency of the internal combustion engine body mainly includes frequency components of several tens to several hundred Hz. In addition to this, the internal combustion engine main body vibrates due to the opening and closing of the intake air valve, and this vibration includes the same frequency component as the vibration during knocking, which becomes an obstacle to knocking detection.

Induction noise caused by ignition also becomes an obstacle to knocking detection.

Conventionally, several knocking signal processing circuits have been proposed, but since the above-mentioned noise components are also detected as knocking, the detection accuracy is poor and weak knocking cannot be detected accurately.

This will be explained with reference to the drawings.

Figure 1 shows block 07 of an example of a conventional knocking signal processing circuit.
A diagram is shown below.

FIG. 2 is a signal waveform diagram of each part of FIG. 1.

The reference number in FIG. 1 is a vibration detector installed in the internal combustion engine main body J, and its output signal includes the signal 2 in FIG.
As shown in 1, many frequency components are included.・
This output signal is passed through an amplifier 3 and a band F wave generator 4 having a center frequency approximately equal to the frequency of the knocking vibration, and further passed through a rectifier circuit 5 to extract a component such as signal 22 in FIG. .

In FIG. 2, 22a and 22c represent the induced noise component due to one ignition and the vibration noise component due to the valve system, respectively, and 22b represents the vibration noise component due to knocking.

The signal 22 is divided into two paths, one of which is input to one input terminal of the voltage comparator 6.

This becomes the knocking determination signal voltage VN. On the other hand.

Low-frequency P wave device7. It is converted into a voltage V8 as shown by the broken line 22d in FIG. 2 through the amplifier circuit 8, and this voltage V8 is input to the other input terminal of the comparator 6 as a reference voltage.

Note that the reference voltage v8 is normally equal to the peak voltage of the signal voltage VN when there is no knocking.

The gain of the amplifier circuit 8 is adjusted so that it becomes slightly louder,
ing. Two signal voltages Hi■N, V entering the voltage comparator 6
Of S, the knocking determination signal voltage VN is the base Q voltage v
8, an output is produced in the voltage comparator 6. The output is accumulated in the integrator 9 and outputted as a knocking detection voltage as signal 23 in FIG. This output voltage is maintained for an appropriate amount of time until the primary ignition occurs.

It is reset by a reset signal SR. 11 is a J-wide circuit.

In the case of the circuit aC above, knocking that occurs singly can be detected relatively well, but if knocking occurs continuously, the reference voltage Vs becomes large, so knocking may not be detected correctly. Also, during acceleration and deceleration,
Because of the time delay of the reference voltage V8 due to the time constant of the low-pass P wave generator 7, an error occurs in the determination of knocking. Furthermore, if the same frequency components other than the knocking signal become larger, for example,
The input signal shown in FIG. 22c is erroneously judged as if there is knocking.

The present invention aims to eliminate the above-mentioned drawbacks and provide a knocking signal processing circuit with high discrimination accuracy.

9 from top dead center for the extracted signal.
Zeroing is performed for a predetermined period of time just before or after the crank angle of 0°, and the sampling signal is rectified and integrated, and then used as a reference voltage that is a predetermined times the rectified voltage. A knocking detection voltage obtained by sampling over a predetermined time period corresponding to a predetermined crank angle of is compared with the reference voltage, and a knocking detection signal voltage corresponding to the time when the knocking detection voltage exceeds the reference voltage is generated. It is characterized by

The present invention will be explained in detail below based on examples.

FIG. 3 shows the results of an experiment investigating the occurrence of knocking in a four-cylinder internal combustion engine. Here, the output waveform obtained from a vibration detector attached to the internal combustion engine body is passed through a band E waveform generator with light knocking occurring, and the output waveform is shown on the rotating bedding of the internal combustion engine. The waveform has a time axis with equal graduations on the horizontal axis, and has two ignition cycles (crank angle 180').
) The time for one cycle becomes shorter in inverse proportion to the number of rotations.

A detailed analysis of these output waveforms revealed the following.

(1) What is the timing at which knocking signal a is generated?

/' just after top dead center! ? ! The crank angle θ1 is within a constant range, and the value of the crank angle θ1 is within a range of 10° to 3()0.

Q) The loudest noise is valve noise b.

- occurs after a period of time corresponding to a substantially constant crank angle θ2 (approximately 600 degrees) has elapsed from the dead center.

(2) Ignition induction noise C occurs in the crank angle range of 0 to 60 degrees before dead center.

(!!9 When the level of the knocking signal a increases when the number of revolutions increases, the noise levels other than the noises b and c also increase almost proportionally.

■ The times at which valve noise b and ignition induction noise C occur vary depending on the rotational speed of the internal combustion engine and the control of ignition timing, but at any rotational speed, the time corresponding to crank angle θ2 at which valve noise b occurs. No particular noise occurs from the top dead center to the point corresponding to around the crank angle of 901°.

From this, the reference voltage is the noise level in the area where the ignition induction noise (ignition induction noise) and king signal are not included, that is, the part of the area from the time when the above-mentioned valve noise occurs, through the crank angle of 90° from top dead center to just before ignition. If compared with the voltage for knocking detection.

It will be understood that knocking can be accurately determined even when the rotation speed changes.

The present invention has been made based on this point of view.
By multiplying the noise level in a part of the region from the crank angle of ° to ignition by several times and using it as a reference voltage, and comparing it with the level of the non-king signal a generated near top dead center, it is possible to detect knocking. It is an attempt to make a judgment.

FIG. 4 shows a professional knocking signal processing circuit according to the present invention.
FIG. 5 is a signal waveform diagram of each part thereof.

In FIG. 4, reference numeral 42 indicates a vibration detector attached to the internal combustion engine 41. For example, an acceleration responsive vibration detector using a piezoelectric vibrator is used. The output of the vibration detector 42 includes frequency components in a wide range, as shown in FIG. 5 63,
Ru. This signal 63 is passed through the amplifier 43 and then through the band r wave generator 44, which has a center frequency approximately equal to the knocking vibration frequency and has a Q of several tens or less, and becomes a waveform as shown in FIG. 564. .

On the other hand, a crank angle detector 50 provided in the internal combustion engine 41
Based on the output signal from the gate pulse generation circuit 51
A first slide signal 61 for sampling the open signal 64 for a certain period of time ΔT1 immediately after bottom dead center. and-
An open signal 6 for a time ΔT2 corresponding to a predetermined crank angle θ2 from top dead center to the point at which the above-mentioned valve noise b occurs.
A second gate pulse 62 for sampling 4
Create.

A. The signal 64 from the 7-band r wave generator 44 is divided into two paths, one of which is sampled by the switching circuit 45 which is opened by the second dart pulse 62, to obtain a signal as shown in FIG. 567. This signal 67 is.

Further, by passing through the rectifier circuit 46, the waveform is converted into a half-wave rectified waveform as shown in FIG.
is input to one input terminal of received this signal 68),
King detection voltage vN (below).

(referred to as the detected voltage).

Signal 64 also. The signal is sampled by the switching circuit 52 which is opened at the first node 61.

The waveform becomes as shown in FIG. 565. Signal 65 is.

Furthermore, a rectifier circuit 53. First integrating circuit 54 and amplifier circuit 5
5, it is converted into a DC voltage as shown in FIG. 566,
The output level is held until reset at the falling edge of the second dart pulse 62.

The DC voltage 66 has its gain adjusted appropriately by the amplifier circuit 55, and is inputted to the other input terminal of the voltage comparator 47 as a reference voltage V8. The gain of the amplifier circuit 55 is adjusted to compensate for the type of internal combustion engine or large variations in the vibration detector 42, and the value of the reference voltage VS is determined experimentally to maximize knocking detection accuracy. It will be done.

The voltage comparator 47 as an A-D converter receives the input 2
Two of the two signals VN and Vs are detected voltages V as shown in the figure.
The 51st agent 69 corresponds to the time when N exceeds the reference voltage Vs.
Outputs a pulse train as shown in .

This pulse train is converted into a second pulse train by a second integrating circuit 48.
The DC voltage V accumulates while the tonacle 62 is at - level.
. is output as a knocking signal, and the second gate ξ
The output level is held until reset when the signal 62 falls. This signal is shown in FIG. 570. This DC voltage V. The level changes depending on the pulse number and pulse width of the pulse train 69.

The number and pulse width of the pulse train 69 correspond to the level of the detected voltage VN. Therefore, depending on the voltage vN, the DC' voltage V. is output from the final stage amplifier circuit 49. And this voltage V. You can also know the degree of non-king by checking the height of.

Although the two inventions have been described above, based on the results shown in FIG.
High level time ΔT1 fill '& 0.5m
s r M'r 2's f" -) / (' It is decided to correspond to the time corresponding to approximately 50 degrees in terms of the value of crank angle θ2 from the top dead center of the high level time ΔT2 of cis62,
Over a wide range of operating conditions, the first cell noculus 61
But... within the time period), King vibration signal.

It is possible to eliminate ignition induction noise and valve vibration noise, and at the same time, the second
System 62 is now available for Hireperno R: It is possible to make it so that only the knocking vibrations are generated and do not include ignition induction noise or valve vibration noise.

In the present invention, as described above, since the signal for obtaining the reference voltage Vs is generated from the output of the vibration detector, variations in the type of internal combustion engine and the sensitivity of the vibration detector can be corrected. In addition, since special noise components such as ignition induction noise and valve vibration noise are not included within the sampling time for creating the reference signal, there is no influence from these noises, and the sampling time ΔT1 is kept constant. Therefore, even if the rotational speed changes, correction based on the rotational speed is not necessary.

In addition, since the signal in the crank angle range where knocking is likely to occur is selected as the voltage signal to be detected by the time ΔT2 corresponding to the crank angle, even if the rotation speed changes, the running will not be affected by special noise signals. None (The S/N ratio is greatly improved. Furthermore, the knocking signal processing circuit according to the present invention finishes detecting knocking within one ignition cycle, resulting in acceleration.

It can also adequately handle fluctuations in rotational speed during deceleration.

By the way, in the above-mentioned embodiment, the sampling timing for creating the reference voltage is set at a certain time ΔT! from a crank angle of 90 degrees from top dead center. Although we have explained the case where it is carried out over the entire range, as mentioned above, there is a region where no special noise is included even just before the crank angle of 90° from top dead center, so
It is also possible to sample at a fixed time just before the crank angle of 90'' from top dead center. It is sufficient to set the timing a certain time ΔTl before the dead center, that is, the timing of the rise of the first gate pulse 61.

As explained above, according to the king signal processing circuit (9) of the present invention, it is possible to detect the sinking with high accuracy with few malfunctions, and this can be used to appropriately control the ignition timing of the internal combustion engine. This is extremely useful in practice.

[Brief explanation of drawings]

Figure 1 is a block diagram of an example of a conventional knocking signal processing circuit, Figure 2 is a diagram showing changes in signal waveforms in each part over time, and Figure 3 is a diagram showing various types of noise when the engine speed is changed. FIG. 4 is a block diagram of a knocking signal processing circuit according to the present invention, and FIG. 5 is a diagram showing changes over time in signal waveforms of various parts thereof. In the figure, 1.41 is an internal combustion engine, 2.32 is a vibration detector,
3 and 43 are amplifiers, and 4.4/1 is a band R wave amplifier. 5, 4.6, 53 are rectifier circuits, (i, 47 is a voltage comparator, 7 is a low-frequency p-wave generator, 8, 11./19.55
is an amplifier circuit, 9 is an integrator, 45.52 is a switching circuit, 48.54 is an integration circuit, 50 is a crank angle detector,
51Fi gate pulse generation circuit.

Claims (1)

[Claims] 1. In a knocking signal processing circuit that detects knocking using the output signal of a vibration detector provided in the internal combustion engine body, there is a means for extracting a specific frequency component from the output signal, and a top dead end detection circuit that detects knocking using the output signal of a crank angle detector. 9 from the point
means for creating a first slope-1 signal for a predetermined time period ΔTl immediately before or immediately after a crank angle of 00, and a second slope-1 signal for a predetermined time period ΔT2 corresponding to a predetermined crank angle near top dead center; Means for sampling the extracted specific frequency signal using the first gate signal to obtain a reference voltage from the sampling signal; and means for sampling the extracted specific frequency signal using the second gate signal and obtaining a reference voltage from the sampling signal. A knocking signal processing circuit comprising: means for obtaining a knocking detection voltage; and means for comparing the reference voltage with the knocking detection voltage and outputting a knocking detection signal.