JPH11270451A - Knocking sensing device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid misjudgement of knocking due to combustion noises in a system to judge occurrence of knocking through sensing of the ion current generated in a combustion chamber. SOLUTION: An ion current sensing signal given from an ion current sensing circuit 24 is fed to a band-pass filter 25, which extracts the signal components belonging to the knocking generating frequency band, followed by a peak hold process made by a peak hold circuit 26, and the peak value is read into a microcomputer 28. When the ignition timing is delayed, the microcomputer 28 judges that it is the noise generation region if the signal peak value read from the peak hold circuit 26 is incremental. In this case, knocking judgement is prohibited, and misjudgement of knocking due to combustion noise is avoided. If the ignition timing is advanced and the signal peak value is incremental, judgement is passed that it is knocking generation region, and the moderating value of the signal peak value is compared with the knocking judgement value, and the result is used to judge whether knocking exists.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knocking detection apparatus for an internal combustion engine which detects an ion current generated in a combustion chamber of the internal combustion engine to determine whether knocking has occurred.

[0002]

2. Description of the Related Art In recent years, attention has been paid to the fact that ions are generated when an air-fuel mixture burns in a combustion chamber of an internal combustion engine and an ionic current flows to an electrode of a spark plug. It has been proposed to determine the presence or absence of knocking (see, for example, JP-A-58-24832 and JP-A-6-159129).

[0003]

However, in the knocking determination method based on the ion current, there is a possibility that the knocking is erroneously determined due to noise superimposed on the ion current detection signal. If the ignition timing is excessively retarded due to erroneous determination of knocking, combustion becomes unstable and combustion noise is likely to occur, thereby making it more likely that knocking will be erroneously determined and further retarding the ignition timing. A vicious cycle of inevitable. As a result, the ignition timing becomes the most retarded, which causes a decrease in engine output and a deterioration in fuel efficiency.

As a countermeasure against this, the present applicant has filed Japanese Patent Application No.
As shown in the specification of JP-A-233006, in order to avoid erroneous determination of knocking due to noise, an output signal of the ion current detection circuit is set to a signal in a knocking occurrence frequency band,
It has been proposed to separate the signal into signals in a frequency band other than the knocking occurrence frequency band and to prohibit knocking determination when a signal in a frequency band other than the knocking occurrence frequency band is equal to or higher than a predetermined level.

In this configuration, it is determined whether or not the signal is in the noise generation region based on a signal in a frequency band other than the knocking frequency band. The noise component includes a noise component in the knocking frequency band. For example, when combustion noise occurs, a fluctuation occurs in the ion current waveform, and the fluctuation component may become a noise component in a knocking occurrence frequency band. In this case, combustion noise may be superimposed on the ion current detection signal in the knocking occurrence frequency band, and erroneous determination of knocking may occur. ) → Incorrect determination of knocking →...

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances. Accordingly, it is an object of the present invention to avoid the erroneous determination of knocking due to combustion noise when determining the presence or absence of knocking from an ion current. Another object of the present invention is to provide a knocking detection device for an internal combustion engine that can improve the knocking determination accuracy.

[0007]

To achieve the above object, a knocking detection apparatus for an internal combustion engine according to the present invention extracts a knocking frequency band signal from an output signal of an ion current detection means. When the knocking determination unit determines the presence or absence of knocking from the signal extracted by the knocking signal extraction unit,
At least a knocking occurrence area or a noise occurrence area is determined by the area determination means from at least the tendency of the output of the knocking signal extraction means. When it is determined that the region is a noise generation region, the knocking determination by the knocking determination unit is prohibited by the knocking determination prohibition unit. In this case, in order to determine whether the knocking occurrence area or the noise occurrence area at least from the tendency of the output of the knocking signal extraction means, when the noise component of the knocking occurrence frequency band such as combustion noise is superimposed on the output signal of the knocking signal extraction means. Can determine this as a noise generation region, avoid erroneous knocking determination, and improve knocking determination accuracy.

As described above, the more the ignition timing is retarded, the more the combustion noise tends to occur. Also,
As the ignition timing is advanced, knocking tends to occur, and the output signal of the knocking signal extracting means tends to increase.

Focusing on such characteristics, the peak value of the output of the knocking signal extracting means is detected, and the ignition timing is retarded to increase the output peak value. If it is determined that the ignition peak is advanced and the output peak value increases, it may be determined that the knocking occurs. With this configuration, it is possible to accurately determine whether the region is a noise occurrence region or a knock occurrence region from only the output of the knocking signal extraction unit.

Further, the distribution of the signal in the knocking occurrence frequency band extracted by the knocking signal extraction means and the distribution of the signal in the frequency band other than the knocking occurrence frequency band extracted by the out-of-band signal extraction means are determined. A comparison may be made to determine whether the region is a knocking region or a noise region. The relationship between the signal in the knocking occurrence frequency band and the signal in the other frequency band shows a clearly different distribution between the time of knocking occurrence and the time of combustion noise occurrence (see FIG. 7). , The knocking occurrence area or the noise occurrence area can be accurately determined.

According to a fourth aspect of the present invention, a signal in a knocking occurrence frequency band is smoothed and a signal in a frequency band other than the knocking occurrence frequency band is smoothed to obtain a ratio of the smoothed value of the two signals. It may be determined from the difference whether the region is a knocking occurrence region or a noise occurrence region. In this way, the characteristics of the distribution of both signals can be evaluated with high accuracy by a simple calculation method called smoothing.

When the signal value is small, the difference between the two signals is small, and the area determination accuracy is reduced accordingly. Therefore, at least one of the smoothed values of the two signals is set to a predetermined value or more. May be obtained by smoothing the output signal. In this way, only signals that are easy to determine the region can be extracted and subjected to the averaging process, so that accurate region determination can be performed.

[0013]

[Embodiment (1)] Next, an embodiment (1) of the present invention will be described with reference to FIGS.
First, a circuit configuration of an ignition control system and an ion current detection system will be described with reference to FIG. Primary coil 1 of ignition coil 11
2 is connected to a power supply terminal (+ B), and the other end of the primary coil 12 is connected to a power transistor 1 for ignition control.
5 collectors. One end of a secondary coil 16 of the ignition coil 11 is connected to a spark plug 17, and the other end of the secondary coil 16 is connected to two Zener diodes 18,
19 is connected to the ground.

The two Zener diodes 18 and 19 are connected in series in opposite directions, a capacitor 20 is connected in parallel to one Zener diode 18, and an ion current detecting resistor 21 is connected in parallel to the other Zener diode 19. I have. Capacitor 20 and ion current detection resistor 2
1 is applied to the inverting amplifier circuit 2 via the resistor 22.
3 is input to the inverting input terminal (-) and is inverted and amplified.
The ion current detection circuit 24 (ion current detection means) includes zener diodes 18 and 19, a capacitor 20, an ion current detection resistor 21, an inverting amplifier circuit 23, and the like.

The output voltage of the ion current detection circuit 24 (the output voltage of the inverting amplifier circuit 23) is input to a band-pass filter (BPF) 25 as an ion current detection signal. The band-pass filter 25 detects a knocking frequency band (for example, 6 to 7 KH) from the ion current detection signal.
It functions as knocking signal extracting means for extracting the signal of z). The signal in the knocking occurrence frequency band that has passed through the band-pass filter 25 is
Is read into the microcomputer 28 for engine control via the A / D converter 27.

During operation of the engine, the power transistor 15 is turned on / off at the rise / fall of the ignition signal IGt output from the microcomputer 28. When the power transistor 15 is turned on, a primary current flows from the battery (not shown) to the primary coil 12. Thereafter, when the power transistor 15 is turned off, the primary current of the primary coil 12 is cut off, and a high voltage is applied to the secondary coil 16. Is electromagnetically induced, and the high voltage causes the electrode 2
Spark discharge occurs between 9 and 30. At this time, the spark discharge current flows from the ground electrode 29 of the spark plug 17 to the center electrode 30, charges the capacitor 20 via the secondary coil 16, and flows to the ground via the Zener diodes 18 and 19.

On the other hand, the ion current flows in the opposite direction to the spark discharge current. That is, the ionic current flows from the center electrode 30 to the ground electrode 29, and further flows from the ground through the ionic current detection resistor 21 to the capacitor 20. At this time, the input potential Vin of the inverting amplifier circuit 23 changes according to the change of the ion current flowing through the ion current detection resistor 21, and an ion current detection signal of a voltage corresponding to the ion current is output from the output terminal of the inverting amplifier circuit 23. Pass filter 2
5 is output. The bandpass filter 25 extracts a signal component in the knocking occurrence frequency band from the ion current detection signal, and inputs the extracted signal component to the peak hold circuit 26. As shown in FIG. 4, the peak hold circuit 26 starts the peak hold of the output signal of the bandpass filter 25 after a lapse of a predetermined time from the ignition (after the end of the LC resonance). The peak value held by the peak hold circuit 26 is read into an engine control microcomputer 28 via an A / D converter 27.

The microcomputer 28 smoothes the peak value of the signal in the knocking occurrence frequency band,
The presence or absence of knocking is determined by whether or not the smoothed value exceeds the knocking determination value. At this time, in order to avoid erroneous determination of knocking due to combustion noise, a knocking occurrence area or a noise occurrence area is determined from a change tendency of a signal peak value in a knocking occurrence frequency band. , Prohibits knocking determination.

In this embodiment (1), the knocking occurrence area and the noise occurrence area are determined based on the following principle. As shown in FIG. 5, as the ignition timing is retarded, the combustion noise tends to increase, and the signal peak value in the knocking occurrence frequency band tends to increase. Further, as the ignition timing is advanced, knocking tends to occur, and the signal peak value in the knocking occurrence frequency band tends to increase. Focusing on such characteristics, if the signal peak value is increased by retarding the ignition timing, it is determined that the noise is generated,
If the ignition timing is advanced and the signal peak value increases, it is determined that the knocking has occurred.

Such area determination is performed in accordance with the knocking control programs shown in FIGS. 2 and 3 stored in the ROM (storage medium) of the microcomputer 28. Hereinafter, the processing contents of these programs will be described.

The knocking control program shown in FIG. 2 is executed by the microcomputer 28 by an interruption process at each fall of the ignition signal IGt (that is, every ignition).
When this program is started, first, in step 101,
By determining whether or not the signal peak value of the knocking occurrence frequency band has increased due to the retardation of the ignition timing, it is determined whether or not the signal is in the noise generating region.If the signal peak value has not increased, It is determined that it is not a noise generation area,
Proceed to step 103.

On the other hand, if it is determined in step 101 that the signal peak value has increased due to the ignition timing retard,
When it is determined that the region is in the noise generation region, the process proceeds to step 102, in which the knocking determination is prohibited, the erroneous determination of knocking due to combustion noise is avoided, and the ignition timing is advanced, and the process proceeds to step 103. The processing in step 101 functions as an area determining means in the claims, and the processing in step 102 functions as a knocking determination prohibiting means in the claims.

In step 103, it is determined whether or not the result of the knocking determination prohibition / permission switching program shown in FIG. 3 to be described later is a knocking determination permission (knocking occurrence area). If "No", that is, knocking determination prohibition ( In the case of the noise generation region), the process proceeds to step 107, in which the advance of the ignition timing is permitted, and the program ends.

On the other hand, if it is determined in step 103 that the knocking determination is permitted (knocking occurrence area), the process proceeds to step 104 to determine whether knocking has occurred. As this determination method, for example, the peak value of the signal in the knocking occurrence frequency band is smoothed, and the presence or absence of knocking is determined based on whether or not the smoothed value exceeds the knocking determination value. As a result, if it is determined that there is no knocking, the process proceeds from step 105 to step 107,
The ignition timing is advanced and the program ends. The processing of steps 104 and 105 functions as a knocking determination unit referred to in the claims.

If it is determined in step 105 that knocking has occurred, the process proceeds to step 106, in which knocking is suppressed by retarding the ignition timing, and the program ends.

The knocking determination prohibition / permission switching program shown in FIG. 3 is executed by the microcomputer 28 by interruption processing at each fall of the ignition signal IGt (that is, each ignition). When the program is started, first, in step 201, it is determined whether or not the knocking determination is prohibited in step 102 in FIG. 2, and if the knocking determination is not prohibited (in the case of the knocking determination permission state).
In this case, the program is terminated without performing the subsequent processing.

On the other hand, when the knocking determination is prohibited, the process proceeds from step 201 to step 202, in which the ignition timing is advanced, and the process proceeds to step 203, where the signal peak in the knocking occurrence frequency band is determined by the advance of the ignition timing. By determining whether or not the value has increased, it is determined whether or not it is a knocking occurrence area, and if the signal peak value has not increased, it is determined that it is not a knocking occurrence area,
This program ends as it is. On the other hand, if it is determined in step 203 that the signal peak value has increased due to the advance of the ignition timing, it is determined that the knocking has occurred, and the process proceeds to step 204 where knocking determination is permitted and the program is terminated. I do. The processing of the above step 105 functions as an area determining means referred to in the claims.

By interrupting the above-described program shown in FIGS. 2 and 3 for each ignition, the tendency of the signal peak value in the knocking occurrence frequency band due to the retardation / advance of the ignition timing to change the knocking occurrence region or noise occurrence It is possible to accurately determine whether the region is a region, and by prohibiting knocking determination in the case of a noise occurrence region, it is possible to avoid erroneous determination of knocking due to combustion noise, and to improve knocking determination accuracy. This makes it easy to control the ignition timing to the knocking limit at which combustion efficiency is highest (the ignition timing that is most advanced in a range where knocking does not occur), thereby improving engine output and fuel efficiency.

[Embodiment (2)] Next, an embodiment (2) of the present invention will be described with reference to FIGS. Also in the present embodiment (2), the configuration of the ion current detection circuit 24 is the same as that in the above-described embodiment (1). The output voltage of the ion current detection circuit 24 (the output voltage of the inverting amplification circuit 23)
High-pass filter (HPF) 31 is input to, for example, 3
Ion signal components below KHz are cut off, and signal components above 3 KHz pass through the high-pass filter 31 and are input to the mask circuit 32. In the mask circuit 32, an LC resonance component generated immediately after ignition is cut.

The ion current detection signal output from the mask circuit 32 is supplied to a band-pass filter (hereinafter "BPF").
) 33 and a band elimination filter (hereinafter abbreviated as “BEF”) 34. BP
F33 functions as a knocking signal extracting unit that extracts a signal in a knocking occurrence frequency band (for example, 6 to 7 KHz) from the ion current detection signal. The BEF 34 functions as an out-of-band signal extracting unit that extracts a signal in a frequency band other than the knocking occurrence frequency band from the ion current detection signal. The signals that have passed through both filters 33 and 34 are input to peak hold circuits 35 and 36, respectively, where the peak values are held. Each peak hold circuit 35, 36
Are stored in the A / D converter 37,
Microcomputer 3 for controlling the engine via
9 is read.

In this embodiment (2), the knocking occurrence area and the noise occurrence area are determined based on the following principle. When knocking occurs, the output of the BPF 33 (a signal in the knocking frequency band) is large, and the output of the BEF 34 (a signal outside the knocking frequency band) is small. On the other hand, when combustion noise occurs, fluctuations occur in the waveform of the ion current detection signal, and the fluctuation components may become noise components in the knocking occurrence frequency band. In this case, the combustion noise is superimposed on the output of the BPF 33,
Although the output of the PF 33 increases, as shown in FIG.
The output of the EF 34 greatly varies, and the presence or absence of combustion noise cannot be accurately determined only by the output of the BEF 34.

Then, as shown in FIG. 7, when the distribution of the output of the BPF 33 and the distribution of the output of the BEF 34 were evaluated, it was found that the distributions when knocking and combustion noise were distinctly different. Focusing on this characteristic, BPF3
The output of BEF34 and the output of BEF34 are each subjected to a smoothing process at a predetermined value or more, and it is determined from the ratio of the smoothed values of the two signals whether the knocking region or the noise region is present. Here, the reason for smoothing the output that is equal to or more than the predetermined value is that when the output level is low, the difference between the smoothed values of both outputs is small,
This is because the area determination accuracy is reduced accordingly.

Such area determination is performed in accordance with the knocking control programs shown in FIGS. 8 to 10 stored in the ROM (storage medium) of the microcomputer 39. Hereinafter, the processing contents of these programs will be described.

The smoothing processing program shown in FIG. 8 is executed by the microcomputer 39 by interruption processing every ignition. When this program is started, first, step 3
At 01, it is determined whether or not the output of the BPF 33 is equal to or more than the predetermined value A. If the output is less than the predetermined value A, the program is terminated without performing the smoothing process. Here, the predetermined value A is B
It is set according to the standard deviation of the distribution of the output of the PF 33.

On the other hand, if the output of the BPF 33 is equal to or more than the predetermined value A, the process proceeds to step 302, where it is determined whether or not the output of the BEF 34 is equal to or more than the predetermined value B. This program ends without performing any further processing. Here, the predetermined value B is set according to the standard deviation of the distribution of the output of the BEF 34.

If the outputs of the BPF 33 and the BEF 34 are both equal to or larger than the predetermined values A and B, the routine proceeds to step 303, where the smoothed output of the BPF 33 and the smoothed output of the BEF 34 are calculated by the following equations. BPF output smoothed value (i) = (n−1) / n × BPF output smoothed value (i−1) + 1 / n × BPF output (i) BEF output smoothed value (i) = (n−1) / N × BEF output smoothed value (i−1) + 1 / n × BEF output (i) where n is the smoothing coefficient, (i) is the current value, and (i−1) is the previous value.

The knocking control program shown in FIG. 9 is executed by interrupt processing for each ignition. Steps other than the step 101a are the same as the steps in FIG. 2 described in the embodiment (1). When the program is started, first, in step 101a, the BPF output smoothed value and B
By determining whether or not the ratio of the smoothed EF output value is smaller than the determination value C, it is determined whether or not the noise is in the noise generation area, and the ratio between the smoothed BPF output value and the smoothed BEF output value is determined. If the value is equal to or larger than the value C, it is determined that the area is not the noise generation area, and the process proceeds to step 103. This step 103
Subsequent processing is the same as in the embodiment (1).

On the other hand, in step 101a, the BPF
If it is determined that the ratio between the smoothed output value and the smoothed BEF output value is smaller than the determination value C, it is determined that the region is a noise generation region, and the process proceeds to step 102, where knocking determination is prohibited and knocking due to combustion noise is performed. Is avoided, and the advance of the ignition timing is permitted, and the routine proceeds to step 103. The processing of the above step 101a functions as an area determining means referred to in the claims.

The knocking determination prohibition / permission switching program shown in FIG. 10 is executed by an interrupt process for each ignition. When the program is started, first, in step 401, it is determined whether or not the knocking determination is prohibited in step 102 in FIG. 9, and if the knocking determination is not prohibited (if the knocking determination is permitted). This program ends without performing the subsequent processing.

On the other hand, when the knocking determination is prohibited, the process proceeds from step 401 to step 402, where B
By determining whether or not the ratio between the smoothed PF output value and the smoothed BEF output value is larger than the determination value D, it is determined whether or not the knocking occurs, and the smoothed BPF output value and the BE value are determined.
If the ratio with the F output smoothed value is equal to or less than the determination value D, it is determined that the knocking does not occur, and the program is terminated.

On the other hand, if the ratio between the smoothed BPF output value and the smoothed BEF output value is larger than the determination value D in step 402, it is determined that the knocking has occurred, and the flow advances to step 403 to determine knocking. And terminate this program.

In this case, the determination value D used in step 402 is set to a value larger than the determination value C used in step 101a in FIG. 9, and hysteresis is added to the switching between the knocking determination prohibition and the knocking determination permission. ing. The processing of the above step 402 functions as an area determining means referred to in the claims.

In the embodiment (2) described above, the BPF
From the ratio of the smoothed output value to the smoothed BEF output value, it is possible to accurately determine whether the knocking region or the noise region is present. By prohibiting the knocking determination in the noise region,
An erroneous determination of knocking due to combustion noise can be avoided, and knocking determination accuracy can be improved.

In the smoothing processing program shown in FIG.
With respect to the output of the PF 33 and the output of the BEF 34, the output of the predetermined values A and B or more is smoothed to improve the area discrimination accuracy.
02 is omitted and BPF33 and BEF3
The output of a predetermined value or more may be processed for only one of the four types. Or step 30
1,302 may be omitted, and all outputs of the BPF 33 and the BEF 34 may be subjected to the smoothing process. In this case, the intended object of the present invention can be achieved.

In the embodiment (2), the knocking occurrence area and the noise occurrence area are determined by the ratio between the smoothed BPF output value and the smoothed BEF output value. This may be performed based on the difference between the value and the smoothed BEF output value.

The ratio between the smoothed BPF output value and the smoothed BEF output value is determined by using either the smoothed BPF output value / the smoothed BEF output value or the smoothed BEF output value / the smoothed BPF output value. Is also good.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an ignition control system and an ion current detection system according to an embodiment (1) of the present invention.

FIG. 2 is a flowchart showing a processing flow of a knocking control program according to the embodiment (1).

FIG. 3 is a flowchart showing a processing flow of a knocking determination prohibition / permission switching program according to the embodiment (1).

FIG. 4 is a time chart showing waveforms of an ion current detection signal and an output of a peak hold circuit.

FIG. 5 is a diagram schematically showing a relationship between an ignition timing and a signal peak value in a knocking occurrence frequency band.

FIG. 6 is a circuit diagram showing a configuration of an ignition control system and an ion current detection system according to the embodiment (2) of the present invention.

FIG. 7 is a diagram showing distribution characteristics of a BPF output and a BEF output.

FIG. 8 is a flowchart showing the flow of processing of an annealing program according to the embodiment (2).

FIG. 9 is a flowchart showing a processing flow of a knocking control program according to the embodiment (2).

FIG. 10 is a flowchart showing a processing flow of a knocking determination prohibition / permission switching program according to the embodiment (2).

[Explanation of symbols]

11: ignition coil, 17: ignition plug, 21: ion current detection resistor, 24: ion current detection circuit (ion current detection means), 25: band pass filter (BPF: knocking signal extraction means), 26: peak hold circuit, 28
.. Microcomputer (knocking judging means, area judging means, knocking judging prohibiting means) 33 band-pass filter (BPF: knocking signal extracting means) 34
Band elimination filters (BEF: out-of-band signal extraction means), 35, 36... Peak hold circuits, 39... Microcomputer (knock determination means, area determination means, knock determination inhibition means).

 ──────────────────────────────────────────────────の Continued on front page (72) Inventor Kazuhisa Mogi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (5)

[Claims] 1. An ion current detecting means for detecting an ion current generated in a combustion chamber of an internal combustion engine; a knocking signal extracting means for extracting a signal in a knocking frequency band from an output signal of the ion current detecting means; A knocking detection device for an internal combustion engine, comprising: a knocking determination unit that determines the presence or absence of knocking from a signal extracted by a signal extraction unit. A knocking detection device for an internal combustion engine, comprising: a region determination unit that performs knocking determination; and a knocking determination prohibition unit that prohibits knocking determination by the knocking determination unit when the region determination unit determines that the region is a noise generating region. 2. The region discriminating means detects a peak value of an output of the knocking signal extracting means. If the ignition peak is retarded and the output peak value increases, it is determined that the region is a noise generating region, and the ignition timing is determined. 2. A knocking occurrence area is determined if the output peak value increases due to advancement.
A knocking detection device for an internal combustion engine according to claim 1. 3. An out-of-band signal extracting unit for extracting a signal in a frequency band other than a knocking frequency band from an output signal of the ion current detecting unit, wherein the region discriminating unit includes the knocking extracted by the knocking signal extracting unit. It is characterized by comparing the distribution of the signal in the generation frequency band with the distribution of the signal in the frequency band other than the knocking generation frequency band extracted by the out-of-band signal extraction means to determine whether the region is a knocking generation region or a noise generation region. The knocking detection device for an internal combustion engine according to claim 1. 4. The region discriminating means performs a smoothing process on the signal in the knocking occurrence frequency band and a smoothing process on a signal in a frequency band other than the knocking occurrence frequency band to obtain a ratio of the smoothed value of the two signals. 4. The knocking detection device for an internal combustion engine according to claim 3, wherein a knocking occurrence region or a noise occurrence region is determined from the difference. 5. The internal combustion engine according to claim 4, wherein the area determining means obtains at least one of the smoothed values of the two signals by smoothing an output signal having a predetermined value or more. Knock detection device.