JPH0996559A - Vibration detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a pressure vibration generated by pre-ignition distinguishing from another vibration by comparing the magnitudes of the detected vibration components of a plurality of frequency regions with a preset threshold value. SOLUTION: A vibration detecting sensor 5 detects the vibration along the frequency regions of, e.g. 1-10kHz, and transduces the vibration into electric signals. From these electric signal, the vibration components in the narrow bandwidths of, e.g. 8.0kHz and 4.5kHz are separated by BPFs 61 and 62. The electric signals passing through the BPFs 61 and 62 undergo amplifications 63 and 64 and A/D conversions 71 and 72, respectively, and the high-region side detected signal and the low-region side detected signal are inputted to an operating part 3. In the operating part 3, the magnitudes of these signal components are compared with a threshold value set by a vibration-component comparing means beforehand. When there are a plurality of the vibration components, which are generated at the magnitudes larger than the threshold level, including the vibration components other than the frequency region of the vibration components that are intrinsic to knocking, it is judged that a pre-ignition is generated in a combustion chamber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration detecting device for detecting precession or the like by detecting pressure vibration in a combustion chamber of an internal combustion engine.

[0002]

2. Description of the Related Art In recent years, gasoline engines for automobiles and the like are generally equipped with a knock control system. The knock control system detects knocking by providing a knocking sensor in the cylinder block that detects pressure oscillations in the combustion chamber in a frequency range peculiar to knocking, and when knocking occurs, the ignition timing is retarded to retard the combustion chamber temperature. To prevent knocking from expanding.
As a result, the knocking point at which knocking occurs is MBT (M
minimum advance for Best T
The ignition timing is set to a knock point to obtain a high output when the ignition timing is on the retard side.

By the way, recently, in order to improve fuel efficiency and reduce emissions, a high compression ratio and a stoichiometric air-fuel ratio have been advanced. For this reason, the temperature of the combustion chamber tends to increase, and if the temperature of the combustion chamber further increases due to knocking, there is a risk of inducing a preignition that spontaneously ignites before the set ignition timing. So, actually Kaihei 1-
In Japanese Patent No. 88042, attention is paid to pressure vibration in the combustion chamber detected by the knocking sensor when a preignition occurs, and when the knocking sensor detects the pressure vibration in a predetermined period before a set ignition timing, it is determined as preignition. A vibration detection method for determining knocking when the knocking sensor detects pressure vibration after ignition is shown.

[0004]

However, in the above vibration detecting method, the vibration is generated by preignition, for example, vibration generated by the collision between the deposit accumulated on the end surface of the piston on the combustion chamber side and the inner wall of the combustion chamber. Vibrations other than pressure vibrations may be erroneously detected, resulting in reliability problems.

Therefore, it is an object of the present invention to provide a vibration detecting device capable of accurately detecting preignition by distinguishing pressure vibration generated by preignition from other vibrations.

[0006]

In order to solve the above-mentioned problems, the inventors have conducted experiments and researches, and as a result, when the preignition occurs, the pressure vibration in the combustion chamber has a wide frequency range including the frequency range of the vibration component peculiar to knocking. I confirmed what was happening in the area. The present invention has been made on the basis of this finding. In the configuration according to claim 1 of the present invention, the vibration component comparing means determines the magnitudes of the vibration components in the plurality of frequency ranges detected by the vibration detecting means. Compare with a preset threshold. If there are a plurality of vibration components having a magnitude equal to or greater than the threshold value, including a vibration component other than the frequency range of the vibration component peculiar to knocking, it can be seen that the pressure vibration occurs in a wide frequency range. At this time, the vibration determination means determines that preignition has occurred in the combustion chamber. If other vibrations due to knocking or the like occur, the pressure vibrations occur only in a specific frequency range, so that the pressure vibrations at the time of preignition can be accurately detected without erroneously detecting these vibrations.

By using the vibration detecting means as the means according to claim 2, it is possible to detect the vibration components in a plurality of frequency ranges from one vibration detector provided in the internal combustion engine. This can simplify the configuration.

Further, by adopting the vibration detecting means as the means according to claim 3, each vibration detector can be arranged in the vicinity of the cylinder where the vibration component detected by each vibration detector appears strongly, and the gain can be increased. It can be taken large.

Further, by using the vibration detecting means as the means described in claim 4, knocking can be detected in addition to preignition.

Still further, the vibration detecting means may be the means according to claim 5. According to the invention described in claim 5, the knocking determination means for determining that knocking occurs when the magnitude of the vibration component peculiar to knocking before and after the ignition timing is retarded is provided, so that before ignition In the preignition that spontaneously ignites, since the magnitude of the vibration component does not depend on the timing of the ignition timing, the magnitude of the vibration component specific to knocking before and after the ignition timing is retarded is limited to knocking. This allows knocking to be detected in addition to preignition.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) The knowledge obtained by the inventors prior to the description of the vibration detecting device of the present invention will be described. When the inventors analyzed the behavior of pressure oscillation (hereinafter referred to as combustion pressure oscillation) in the combustion chamber, the following was found. 6 (A), 6 (B) and 6 (C) are examples of the power spectrum of the output of the vibration detection sensor when the combustion pressure is measured by the vibration detection sensor provided in the engine block. The frequency distribution of the magnitude is shown. FIG. 6 (A) shows the case of normal combustion, and there are no vibration components other than a very low frequency region of 1 kHz or less. FIG. 6B shows the case where knocking occurs, and a strong peak appears in the frequency range near 8.0 kHz. This peak is a vibration component peculiar to knocking, and has been conventionally used for detecting knocking. Figure 6 (C) is when a pre-ignition occurs,
1-10 including the frequency range of the vibration component peculiar to knocking
Vibration appears over a wide frequency range of kHz. The place where auto-ignition due to knocking occurs is almost a fixed position, and since the resonance mode is constant, the combustion pressure oscillation due to knocking always appears in the same frequency range. However, when preignition occurs, the temperature inside the combustion chamber is considerably high, and it is recognized that spontaneous combustion occurs in many places and the frequency distribution of combustion pressure oscillation spreads. Of the vibrations detected by the vibration detection sensor, vibrations not related to preignition, such as vibrations generated by the impact of the deposit accumulated on the end surface of the piston on the combustion chamber side and the inner wall of the combustion chamber, are in the frequency range. Does not spread. Therefore, when the vibration appears over the wide frequency range, preignition is occurring. The present invention is based on this finding.

FIG. 1 shows a vibration detecting device according to the present invention, in which a cylinder block of a gasoline engine 1 which is an internal combustion engine is provided with a vibration detecting sensor 5 which is a vibration detector, and combustion pressure vibration is converted into an oscillating electric signal. It is designed to be converted. As shown by the solid line in FIG. 2, the frequency characteristic of the vibration detection sensor 5 has a gain in a wide frequency range of 1 to 15 kHz in which the combustion pressure vibration is distributed in a slightly upward tendency. In the frequency range where the vibration detection sensor 5 has a gain,
As shown in Fig. 6, around 8kHz, which is the frequency range peculiar to knocking, and 1kHz where the output appears at pre-ignition
The range from to 8kHz is included. An ECU (electronic control unit) 2 is connected to the vibration detection sensor 5.

The ECU 2 receives the output of the vibration detecting sensor 5 as an input, and a band pass filter 61, which is a signal separating means,
62 are provided. As shown by the broken line in FIG. 2, one of the bandpass filters 61 and 62 has a narrow band (A in FIG. 2) having a center frequency of 8.0 kHz, and the other 62 has a center frequency. 4.
It is set as a narrow band (B in FIG. 2) of 5 kHz. 8.0kH
The band centered on z is within the frequency range of the vibration component peculiar to knocking. The narrow band centered at 4.5 kHz is outside the frequency range of the vibration component peculiar to knocking.
Amplifiers 63 and 64 are provided with the outputs of the bandpass filters 61 and 62 as inputs.
It is designed to increase the gain of the electric signal that has passed through 1, 62. A / D converters 71 and 72 are provided with the outputs of the amplifiers 63 and 64 as inputs, and the electric signals whose gains are increased by the amplifiers 63 and 64 are converted into digital signals. Vibration detection sensor 5, bandpass filter 6
1, 62 and amplifiers 63, 64 constitute the vibration detecting means 4A.

An electrical signal obtained by digitizing a narrow band component having a center frequency of 8.0 kHz (hereinafter referred to as a high frequency side detection signal) and an electrical signal obtained by digitizing a narrow band component having a center frequency of 4.5 kHz (hereafter , The low-frequency side detection signal) as input, and is adapted to perform the signal processing of the high-frequency side detection signal and the low-frequency side detection signal. Means, knock strength determination means, knocking determination means. An ignition timing control signal is input from the ECU 2 to an ignition circuit (not shown) of the gasoline engine 1, and the arithmetic unit 3 serves as ignition timing control means to control the ignition timing. In addition to the ignition timing control, the ECU 2 also controls fuel supply, throttle opening, air-fuel ratio, and the like.

The operation of the vibration detecting device will be described. The vibration detection sensor 5 detects vibration over a frequency range of 1 to 10 kHz and converts it into an electric signal. From this electric signal, a signal of a vibration component in a narrow band centering on 8.0 kHz is separated by one band pass filter 61. The other band-pass filter 62 separates a signal of a vibration component in a narrow band centering on 4.5 kHz. And the bandpass filter 61,
The electric signal that has passed through 62 is digitized through amplifiers 63 and 64 and A / D converters 71 and 72, and is input to the arithmetic unit 3 as a high frequency side detection signal and a low frequency side detection signal.

FIG. 3 shows an operation flow in the calculation unit 3. First, for each cylinder, from TDC to 9 during normal combustion.
The peak values of the high-frequency side detection signal and the low-frequency side detection signal in the period up to 0 ° CA are respectively held, and the average of the held peak values is calculated. The respective averages are held as high-frequency side background noise BGH and low-frequency side background noise BGL. On the other hand, the peak value KI0 of the high frequency side detection signal (hereinafter referred to as knock intensity) and the peak value PI of the low frequency side detection signal are held. Next, the knock intensity KI0 is compared with the high frequency side background noise BGH, and the magnitude of the knock intensity KI0 is divided into stages. The knock intensity belonging to the lowest stage in the stages is such that the knock intensity KI0 is smaller than a value obtained by multiplying the high frequency side background noise BGH by 2, and at this time it is determined that there is no knock. If the knock intensity KI0 is larger than the value obtained by multiplying the high frequency side background noise BGH by 2, it is determined that knocking may occur (step 101). Here, the value obtained by multiplying the high frequency side background noise BGH by 2 is a threshold value for determining whether or not there is a risk of knocking, and at the same time, the knock intensity KI, which is the magnitude of the vibration component peculiar to knocking.
This is a threshold value set to a value larger than the background noise BGH on the high frequency side when the magnitude of 0 is known.

If it is determined in step 101 that there is a risk of knocking, the retard amount of the ignition timing is determined according to the above-mentioned step, and the ignition timing control signal is sent to the ignition circuit based on the determined retard amount. To send. Therefore, the ignition timing in the combustion chamber is retarded (step 102), and the temperature of the combustion chamber is lowered.

The knock intensity KI1 after retarding the ignition timing in the combustion chamber is compared with the knock intensity KI0 before retarding the ignition timing to determine the magnitude (step 103).
When KI1 ≧ KI0, KI in step 101
KI1> 2BGL together with 0> 2BGL, which means that the knock intensity KI1 which is the magnitude of the vibration component peculiar to knocking is larger than the threshold value set in advance to a value higher than the high frequency side background noise BGH. ing.

Next, the peak value PI of the low frequency side detection signal after retarding the ignition timing is compared with a value obtained by multiplying the low frequency side background noise BGL by 4 (step 104). Here, the value obtained by multiplying the low frequency side background noise BGL by 4 is a threshold value set to a value larger than the background noise BGL of the vibration component other than the vibration component peculiar to knocking. PI> 4BG in step 104
When L, the peak value PI of the low-side detection signal, which is the magnitude of the vibration component in the frequency range other than the frequency range of the vibration component peculiar to knocking, is set to a value larger than the low-side background noise BGL in advance. It means that it is larger than the threshold value. As described above, since the knock intensity KI1 which is the magnitude of the vibration component peculiar to knocking is larger than the threshold value set in advance to a value larger than the background noise BGH on the high frequency side, the frequency distribution of the combustion pressure vibration is expanded together with this. It is determined that a preignition has occurred (step 1
05). Then, control such as fuel cut, throttle opening reduction, air-fuel ratio enrichment, etc. is performed to avoid pre-ignition.

When it is determined in step 101 that there is no knocking, step 101 is repeated,
The peak value of the high frequency side detection signal, the peak value of the low frequency side detection signal, the high frequency side background noise BGH, and the low frequency side background noise BGL are updated for each cylinder.

When KI1 <KI0 in step 103, the vibration component peculiar to knocking decreases with time due to the retard of the ignition timing performed in step 102. Therefore, there is no possibility of preignition in which the magnitude of the vibration component does not depend on the ignition timing, and it is determined that knocking has occurred. Returning to step 101 again, it is determined from the high frequency side detection signal whether or not there is a risk of knocking.

(Second Embodiment) FIG. 4 shows another vibration detecting device of the present invention. Vibration detection means 4 of the vibration detection device of FIG.
A different vibration detecting means 4B is used instead of A, and the difference will be mainly described. The vibration detecting means 4B is composed of two resonance type vibration detecting sensors 81 and 82 which are vibration detectors, and outputs of the resonance type vibration detecting sensors 81 and 82 are inputted to the amplifiers 91 and 92. FIG. 5 shows the frequency characteristics of the resonance type vibration detection sensors 81 and 82.
On the other hand, as shown by A, the resonance type vibration detection sensor 81 has a frequency range of 8.0 which is a frequency range of a vibration component peculiar to knocking.
It has gain selectively in a narrow band centering on kHz.
The other resonance-type vibration detection sensor 82 is provided in the vicinity of a cylinder block (not shown) where preignition is likely to occur, and as shown by B, has a gain selectively in a narrow band centering on 4.5 kHz. are doing.

In the vibration detecting device, the vibration detecting means 4B is used.
Is composed of two resonance type vibration detection sensors 81 and 82, and the other resonance type vibration detection sensor 82 is provided in the vicinity of the cylinder where preignition easily occurs, so that the spread of the frequency distribution of combustion pressure oscillation due to preignition is sensitive. It can be detected well.

Although the frequency range of the vibration component is a narrow band centering on 4.5 kHz and a narrow band centering on 8.0 kHz, it may be another frequency range as long as it is not against the gist of the present invention, for example, 4 Instead of a narrow band centering on 0.5 kHz, a narrow band centering on 9.5 kHz may be used. Further, if knocking detection is not necessary, it is not necessary to set the frequency range of the vibration component peculiar to knocking such as a narrow band centering on 8.0 kHz. Further, since the frequency distribution of the combustion pressure vibration changes depending on the shape of the cylinder of the internal combustion engine, etc., the pass band of the bandpass filter and the resonance frequency of the resonance type vibration detection sensor should be set appropriately for each type of internal combustion engine according to the frequency distribution. Good.

The threshold value for comparing the magnitudes of vibration components is set to 2
BGH and 4BGL have been described, but the present invention is not limited to this, and it may be smaller than this to increase the detection sensitivity of pre-ignition, and larger than this to decrease the detection sensitivity.

In the flowchart of FIG. 3, step 103 is omitted, and step 102 is replaced with N of step 104.
The arithmetic unit 2 may be set to follow the output. In this case, when No at step 104, that is, KI0> 2
When BGH and PI ≦ 4BGL, it is determined to be knocking,
If Yes in step 104, that is, KI0> 2BG
When H and PI> 4BGL, preignition is determined.

It should be noted that although the number of vibration components to be detected is two, the number may be more than this, and it is sufficient that the vibration components in the frequency range other than the frequency range of the vibration component peculiar to knocking are included therein. The threshold value for comparing the magnitude of each vibration component may be set in the same manner as the threshold value described in each embodiment. In this case, the preignition is determined by the above-described threshold with respect to the magnitudes of the vibration components in a plurality of frequency regions including at least one frequency region other than the frequency region of the vibration component unique to knocking among the vibration components to be detected. When it is larger than the value, it is determined that preignition has occurred in the combustion chamber.

[Brief description of drawings]

FIG. 1 is an overall block diagram of a vibration detection device of the present invention.

FIG. 2 is a graph illustrating a main part of the vibration detection device of the present invention.

FIG. 3 is a flowchart explaining the operation of the vibration detection device of the present invention.

FIG. 4 is an overall block diagram of another vibration detection device of the present invention.

FIG. 5 is a graph illustrating a main part of another vibration detection device of the present invention.

6 (A), (B) and (C) are first, second and third graphs for explaining the knowledge on which the present invention is based.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Gasoline engine (internal combustion engine) 2 ECU (ignition timing control means) 3 Computing unit (vibration component comparison means, vibration determination means, knocking strength determination means, knocking determination means) 4A, 4B Vibration detection means 5 Vibration detection sensor (vibration detection 61) 62 bandpass filter (signal separation means) 81 82 resonance type vibration detection sensor (vibration detector)

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location G01M 15/00 (72) Inventor Yoshihiko Watanabe 14 Iwatani, Shimohakakucho, Nishio-shi, Aichi Japan Auto Parts Research Institute (72) Inventor Hideo Kobayashi 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (72) Inventor Katsuhiko Arisawa 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (5)

[Claims] 1. A vibration for detecting respective magnitudes of vibration components in a plurality of frequency ranges including at least one frequency range other than a frequency range of a vibration component peculiar to knocking among pressure vibrations in a combustion chamber of an internal combustion engine. Detecting means, a plurality of vibration component comparing means for comparing the magnitude of each of the vibration components with a threshold value set in advance to a value larger than the background noise of each of the vibration components, and a vibration component of the plurality of frequency ranges Among them, if it is determined that the vibration component comparison means is larger than the threshold value with respect to the magnitudes of the vibration components in a plurality of frequency regions including the at least one frequency region, it is determined that preignition has occurred in the combustion chamber. And a vibration determining means for controlling the vibration. 2. The vibration detecting device according to claim 1, wherein
The vibration detection means, for the pressure vibration in the combustion chamber,
A vibration detector having a gain in a plurality of frequency ranges including at least one frequency range, and an output of the vibration detector as an input, and a plurality of frequency ranges including at least one frequency range as pass bands. A vibration detection device including a plurality of signal separating means for 3. The vibration detection device according to claim 1, wherein
A vibration detecting device comprising: the vibration detecting means; and a plurality of vibration detectors for selectively detecting respective frequency ranges of vibration components of a plurality of frequency ranges including the at least one frequency range. 4. The vibration detecting device according to claim 1, wherein one of the frequency ranges detected by the vibration detecting means is a frequency range of a vibration component specific to knocking, and the vibration determining means is specific to knocking. The vibration detection device is set so as to determine that knocking occurs when the signal comparison unit determines that only the magnitude of the vibration component is larger than the threshold value. 5. The vibration detecting device according to any one of claims 1 to 3, wherein when it is found that the vibration component comparing means is larger than the threshold value with respect to the magnitude of the vibration component specific to knocking detected by the vibration detecting means. An ignition timing control means for delaying the ignition timing in the combustion chamber, and a knock strength determination means for determining the increase or decrease in the magnitude of the vibration component peculiar to knocking before and after the ignition timing is retarded by the ignition timing control means. If the knock intensity determination means does not know that the magnitude of the vibration component peculiar to knocking before and after the ignition timing is retarded by the ignition timing control means is reduced, it is determined that knocking has occurred in the combustion chamber. A vibration detection device equipped with knocking determination means for determination.