JPH05248305A - Knocking controller - Google Patents

Abstract

PURPOSE:To simplify the structure by comparing knocking signal with a back ground level both of which are detected so as to make knocking judgement. CONSTITUTION:A knocking signal S1 and a valve knock-sound signal S2 are included in a signal (a) from a knock sensor 7. An output signal of a buffer filter 15 is converted into the waveform of a signal (b) in a retification integrating circuit 16. A CPU 12 computes a timing t1 expected to occur the knocking and a timing t2 expected to end the occurrence of the knocking on the basis of the output signal of a waveform shaping circuit 11. Next, a timing B when neither knocking nor valve knock-sound is produced is computed on the basis of the output signal of the waveform shaping circuit 11. Moreover, a signal for clearing the value of a maximum value detecting circuit 17 is output at a timing t1, the value of the maximum value detecting circuit 17 is read in A/D for storing them as a knocking signal. And then an A/D conversion value of a signal (b) is read in at the timing B for storing them as a background level. By comparing the taken-in knocking signal with taken-in background level if the former is larger than the latter, it is judged that knocking occurs, on the contrary, if the former is smaller than the latter, it is judged that no knocking does not occur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knocking control device, and more particularly to a knocking control device capable of detecting knocking of an internal combustion engine with a simple and inexpensive structure.

[0002]

2. Description of the Related Art The presence or absence of knocking of an internal combustion engine is determined by a knock sensor detection signal input during a period in which knocking is predicted to occur and a signal during a period considered to be unrelated to the knocking detected by the knock sensor (hereinafter referred to as back (Called a ground signal).

As a prior art which discloses a method for detecting the presence or absence of knocking, there is one disclosed in Japanese Patent Laid-Open No. 58-28641. According to this prior art, the output of the knock sensor is rectified and smoothed to obtain the envelope signal of the sensor signal, and then the maximum value during the knocking detection period and the minimum value during the background detection period are detected, If the maximum value is larger than the minimum value k times (k is a constant), it is determined that knocking has occurred, and if it is smaller, it is determined that knocking has not occurred.

[0004]

According to the above-mentioned prior art, in order to obtain the background signal, the minimum value detection circuit for holding and detecting the minimum value of the envelope signal of the knock sensor signal is used, The minimum value of the sensor signal was detected for each operation cycle of the engine. As described above, in the prior art, since the minimum value detection circuit is required, there is a problem that the device becomes complicated and expensive.

An object of the present invention is to eliminate the above-mentioned problems of the prior art and provide a knocking control device capable of detecting the minimum value of a sensor signal without providing a minimum value detection circuit.

[0006]

In order to achieve the above object, the invention of claim 1 uses the envelope detection signal at a background level at a point in time during which it is expected that neither knocking nor valve striking will occur. It is characterized in that it is provided with a means for capturing as, and a determination means for performing knocking determination by comparing the detected knocking signal with the background level.

The invention of claim 2 further comprises means for taking in the envelope detection signal at a plurality of time points during a period in which no knocking or valve striking is expected, and the taken values are averaged. It is characterized in that it is provided with a means for setting the background level and a determination means for comparing the detected knocking signal and the background level to perform knocking determination.

[0008]

According to the first aspect of the present invention, the envelope detection signal at a point of time during which no knocking or valve striking is expected is taken in as the background level. It is possible to detect the minimum value of the knock sensor signal without providing the knock sensor signal.

According to the second aspect of the present invention, the envelope detection signals at a plurality of time points during a period in which neither knocking nor valve striking is expected are taken in and averaged to obtain a background level. Therefore, the false detection of the background level due to noise can be reduced as much as possible.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention.

In the figure, reference numeral 1 is a first crank angle sensor, which is used, for example, to detect a cylinder number. 2 is a second crank angle sensor, which is used to detect the crank angle. 3 is a PB sensor, 4 is a water temperature sensor, 5 is a throttle sensor, 6 is an oxygen sensor, and 7 is a knock sensor. Further, 8 is an igniter.

The detection signals of the respective sensors are sent to the control device 9. The igniter 8 receives an ignition signal from the control circuit 9 at an appropriate timing.

The control device 9 includes the following components. That is, the control device 9 includes first and second waveform shaping circuits 10 and 11 for shaping the output signals of the first and second crank angle sensors 1 and 2, and a knocking detection which is the main point of the present invention. CPU 12 for controlling the operation of the internal combustion engine including the A / D converter 13, the driver 14 for converting the ignition signal output from the CPU 12 into a drive signal and supplying the drive signal to the igniter 8, and the detection by the knock sensor 7. It includes a buffer filter 15 that receives a signal, a rectification integration circuit 16, and a maximum value detection circuit 17.

Next, the operation of one embodiment of the knocking control device of the present invention will be described with reference to FIGS. Figure 2
Shows the waveform diagram of the signal of the main part of FIG. 1, and the waveform of FIG.
2 shows the waveforms of the corresponding signals of FIG. Further, FIG. 3 is a flowchart showing the operation of this embodiment.

The knock sensor 7 outputs a signal having a waveform as shown in FIG. This signal includes a knocking signal S1 and a valve tapping signal S2. This signal a is input to the buffer filter 15,
A signal in the frequency domain of about 6-8 KHz is extracted. Knocking signals are known to be in this frequency band.
The output signal of the buffer filter 15 is the rectifying and integrating circuit 1
6, the envelope is detected, and the waveform is converted into the waveform of the signal b in FIG. This signal b is supplied to the maximum value detection circuit 17 and A
Input to the / D converter 13.

Now, the CPU 12, as shown in step S1 of FIG. 3, has the second waveform shaping circuit 1.
Based on the output signal of 1, the timing t1 at which knocking is expected to occur and the timing t2 at which knocking is expected to end are calculated.

Here, t1 is, for example, 10 from the compression top dead center.
The timing t2 is, for example, 30 ° from the compression top dead center.

Next, in step S2, the CPU 12
Based on the output signal of the second waveform shaping circuit 11, the timing B at which neither knocking nor valve tapping sound occurs is calculated. This timing B is, for example, 120 from the compression top dead center.
This is one point of the period in which neither knocking of 150 ° to 150 ° nor the tapping sound of the valve occurs. For example, the timing is 130 °.

In step S3, the CPU 12 causes the t1
At the timing of, the signal for clearing the value of the maximum value detection circuit 17 is output, and then at step S4, the t2
At the timing of, the value of the maximum value detection circuit 17 is A / D read and accumulated as a knocking signal. As a result, during the timings t1 to t2, the maximum value held in the maximum value detection circuit 17 is used as a knocking signal by the CPU 1
2 will be read.

Next, in step S5, the CPU 12
Reads the A / D converted value of the signal b at the timing B and stores it as a background level. In step S6, the CPU 12 compares the knocking signal acquired in step S4 with the background level read in step S5 multiplied by k (where k is a constant), and if the former is larger than the latter, knocks. Is determined to have occurred. On the contrary, if the former is smaller than the latter, it is determined that knocking has not occurred.

As described above, according to this embodiment, the timing B at which neither knocking nor valve striking occurs is calculated, and the A / D conversion value of the signal b is read at this timing B,
Since the background level is used, the minimum value detection circuit required in the conventional device can be eliminated.

Next, a second embodiment of the present invention will be described. In the first embodiment, if noise occurs in the output of the knock sensor 7 at timing B, the CPU
Since 12 reads this noise as the background level, the background level cannot be detected normally. The second embodiment solves this problem.

FIG. 4 shows a block diagram of the second embodiment, in which the same or equivalent parts as in FIG. 1 are designated by the same reference numerals.
4 is different from FIG. 1 in that after the rectifying and integrating circuit 16,
The point is that the time constant circuit 18 is provided.

Next, the operation of this embodiment will be described with reference to FIG. The reference numerals in FIG. 5 indicate the waveforms of the corresponding signals in FIG. Now, as shown in FIG. 5 (a), at the timing B, if a surge noise due to ON / OFF of a relay arranged in the vehicle compartment or the engine room is generated, this noise 5 through the buffer filter 15 and the rectifying / integrating circuit 16 shown in FIG.
The waveform shown in (b) is obtained and input to the time constant circuit 18.

The time constant circuit 18 delays the input signal by the time constant determined by the circuit constant and absorbs a steep pulse such as surge noise. Therefore, the waveform of the output signal of the time constant circuit 18 is The waveform is as shown in Figure (e). That is, the noise is almost flat as shown by the solid line. Therefore, even if the signal e is read at the timing B and used as a background signal, there is no problem. The broken line in (e) of the figure indicates the signal (b)
3 shows the same waveform as the above, that is, the waveform of the input signal of the time constant circuit 18.

As described above, according to the second embodiment, even if noise such as surge noise happens to occur at the timing B, it is possible to detect the background signal that is not affected by the noise.

Next, a third embodiment of the present invention will be described. In this embodiment, like the second embodiment, the noise generated at the timing B is not taken in as a background signal.

The operation of this embodiment will be described with reference to FIGS. 6 and 7. The hardware configuration of the present embodiment is the same as or equivalent to that of FIG. 1, so illustration and description thereof will be omitted.

In this embodiment, as shown in FIG. 6 (b), two timings of reading the background signal are taken, B1 and B2, and as shown in FIG. 6 (d), The average of the read values is used as the background signal.

Regarding the operation of the CPU 12, the present embodiment is different from the first embodiment in that, as shown in FIG. 7, step S2 of FIG. 3 is changed to step S2a, step S5 is changed to steps S5a and S5b, This is the point changed to S5c. Therefore, only the changed processing will be described. In step S2a, from the crank angle sensor signal,
Two timings B where neither knocking nor valve tapping sound occurs
1 and B2 are calculated.

Here, the timings B1 and B2 are appropriate timings within a range of 120 ° to 150 ° from the compression top dead center, which is a period in which neither knocking nor valve striking occurs, for example, 130 ° from the compression top dead center, The timing is 140 °.

In step S5a, the CPU 1
2 reads the A / D conversion value "B1" of the signal b at the timing B1 and reads and stores the A / D conversion value "B2" of the signal b at the timing B2. Succeedingly, in a step S5c, the A / D converted values "B1", "B2"
The average value of “” is calculated and accumulated as a background level.

According to the present embodiment, even if the timing B1 happens to coincide with the noise that has entered the signal b and the read value "B1" is not at the correct background level, the read value of the signal b at the timing B2. Since "B2" stochastically becomes the correct background level, it is possible to avoid the risk of erroneous knocking determination by adopting noise as the background level by averaging both read values.

In the present embodiment, two timings at which neither knocking nor valve tapping sound is generated are calculated in step S2a, but the present embodiment is not limited to this, and three or more timings are calculated, and step S5C is performed. The average value of the read values of 3 or more may be set as the background level.

The technique of the second embodiment is applied to the technique of the third embodiment.
Of course, it may be applied to the embodiment.

[0036]

As is apparent from the above description, according to the present invention, the minimum value of the sensor signal can be detected without providing the minimum value detection circuit, and the number of circuits of the knocking control device can be reduced. There is an effect that the configuration can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a waveform diagram showing a waveform of a signal of a main part of FIG. 1 and a background level.

FIG. 3 is a flowchart for explaining the operation of the above embodiment.

FIG. 4 is a block diagram of a second embodiment of the present invention.

5 is a waveform diagram showing a waveform of a signal of a main part of FIG. 4 and a background level.

FIG. 6 is a waveform of a signal of an essential part of a third embodiment of the present invention,
It is a waveform diagram which shows a background level.

FIG. 7 is a flow chart for explaining the operation of the third embodiment.

[Explanation of symbols]

7 ... Knock sensor, 9 ... Control device, 12 ... CPU, 13
... A / D converter, 15 ... Buffer filter, 16 ... Rectification integration circuit, 17 ... Maximum value detection circuit, 18 ... Time constant circuit

Claims (3)

[Claims] 1. A knocking control device for performing envelope detection of a signal detected by a knock sensor and performing knocking determination using the envelope-detected signal, in a period during which no knocking or valve striking is expected. Knocking, characterized in that it comprises means for taking in the envelope detection signal as a background level at one point in time, and judgment means for comparing the detected knocking signal with the background level to make knocking judgment. Control device. 2. A knocking control device for performing envelope detection of a signal detected by a knock sensor, and performing knocking determination using the envelope-detected signal, in a period in which no knocking or valve striking is expected. A means for fetching the envelope detection signal at a plurality of time points, a means for averaging the fetched values to obtain a background level, and a knocking determination by comparing the detected knocking signal with the background level. A knocking control device, comprising: 3. The knocking control device according to claim 1 or 2, further comprising means for smoothing the envelope detection signal, wherein noise generated at least during a period in which it is expected that neither knocking nor valve tapping sound will occur. A knocking control device characterized by being reduced.