JP3131892B2 - Self-diagnosis device in knocking detection device of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-diagnosis device for a knocking detection device of an internal combustion engine, and more particularly to a failure diagnosis device for a knocking detection device mounted on an engine body and detecting knocking using a vibration sensor for detecting engine vibration. About.

[0002]

2. Description of the Related Art In an internal combustion engine, when knocking of a predetermined level or more occurs, not only the engine output is reduced but also a shock may adversely affect intake / exhaust valves and pistons. Therefore, an ignition timing correction device that attaches a knock sensor that detects engine vibration to the cylinder block, detects knocking vibration with the sensor, and retards the ignition timing when knocking occurs so that knocking is quickly avoided is provided. Some are provided (Japanese
8-105036 and the like).

[0003]

In the control for avoiding knocking based on the above-mentioned ignition timing correction, a knock sensor for detecting engine vibration is a seat pressure type piezoelectric sensor which is mounted integrally with a washer of an ignition plug. However, since the output impedance of this type of piezoelectric sensor is extremely high (in units of MΩ), the sensor value of the piezoelectric sensor 1 is set high so as not to affect the characteristics of the piezoelectric sensor 1 as shown in FIG. After being amplified by the input impedance amplifier 2, the signal is input to the control unit 3 for frequency analysis.

In such knocking control, if the piezoelectric sensor breaks, it becomes impossible to detect the engine vibration level, and the accuracy of knocking detection deteriorates, and the knocking control for advancing the ignition timing as much as possible while avoiding knocking is performed. The initial purpose cannot be achieved. Therefore, in such a case, it is necessary to clamp (fail-safe) the ignition timing to the middle point in order to avoid an abnormality in knocking control. However, in order to detect such a disconnection state, a resistor R is connected between point A and GND to connect A If the disconnection is detected by the voltage fluctuation at the point, the output impedance of the piezoelectric sensor is extremely high, and the sensor characteristics change due to the resistance R. Therefore, connect the resistance R between the point A and GND. Can not.

[0005] Therefore, when the piezoelectric sensor is disconnected, the disconnection state cannot be detected, and there has been a problem that knocking control is abnormal. The present invention has been made in view of such a conventional problem, and an internal combustion engine capable of performing disconnection diagnosis of a vibration sensor without affecting characteristics of the vibration sensor to avoid occurrence of an abnormality in knocking control. It is an object of the present invention to provide a self-diagnosis device in the knocking detection device.

[0006]

For this purpose, the invention according to claim 1 includes, as shown in FIG. 1, a vibration sensor attached to an engine main body to detect engine vibration, and the vibration sensor detects the vibration. A knocking detection device for an internal combustion engine configured to detect the occurrence of knocking based on engine vibrations; operating state detection means for detecting an operating state of the engine; and a predetermined signal from a detection signal detected by the vibration sensor. and the predetermined frequency component extraction means for extracting the knocking frequency component, the operation detected by the operating condition detecting means
The state is within a predetermined partial area belonging to the knocking control area
After a predetermined time has passed while staying at the predetermined frequency
Of the knocking frequency component extracted by the
The bell is compared with a predetermined level for disconnection diagnosis, and
Self-diagnosis means for diagnosing a disconnection of the vibration sensor when the level is lower than the level .

Further, the operating state detecting means includes an engine rotation
Detect speed and load and belong to the knocking control area
In the predetermined partial area, the engine speed and the load
It is set narrower than the range that determines the knocking control area
It is preferable that the area is within the range. Further, the frequency component in the predetermined level range may be a frequency component in a range of 2 to 20 kHz of the detection signal detected by the vibration sensor.

The vibration sensor may be a seat pressure type piezoelectric sensor which is mounted integrally with a washer of an ignition plug. Further, as shown in FIG. 2, the invention according to claim 5 further comprises a knocking control means for delaying the ignition timing when knocking is detected, and advancing the ignition timing when knocking is not detected. When the diagnosis unit diagnoses that the vibration sensor has failed, the knocking control unit stops the knocking control and includes a fail-safe unit that clamps the ignition timing to a predetermined value.

[0009]

According to this configuration, the operation state detected by the operation state detection means belongs to the knocking control area.
After staying in the specified partial area for a predetermined time,
Knocking extracted by the predetermined frequency component extracting means
Frequency components, for example, detection signals detected by vibration sensors
Knocking frequency components in the range of 2 to 20 kHz
When the level is lower than the predetermined level, the self-diagnosis unit diagnoses that the vibration sensor, for example, the seat pressure type piezoelectric sensor has failed, that is, is disconnected.

According to this, disconnection diagnosis of the vibration sensor can be performed without connecting a special resistor or the like and without affecting the characteristics of the vibration sensor. Further, when the self-diagnosis unit diagnoses the failure of the vibration sensor, the knocking control unit controls the ignition timing to be retarded when knocking is detected by the knocking control unit and the ignition timing to be advanced when knocking is not detected. The control is stopped, and the ignition timing is clamped to a predetermined value, for example, a middle point.

According to this, it is possible to avoid occurrence of an abnormality in knocking control based on disconnection of the piezoelectric sensor.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 3 showing one embodiment, a knock sensor (vibration sensor) 11 attached to a cylinder block (engine body) of an internal combustion engine (not shown) is mounted integrally with a washer of an ignition plug, and incorporates a weight and a piezoelectric element. And a seat pressure type piezoelectric sensor that outputs a detection (voltage) signal of a waveform corresponding to engine vibration.

A detection signal (analog signal) of the knock sensor 11 is A / D-converted by an A / D converter 12 and then a DSP (digital signal) as a predetermined frequency component extracting means.
Signal processor 13 and the DSP 13
After the input signal is subjected to a Fourier transform operation, for example, only a frequency component of 2 to 20 kHz is passed through a filter, and a frequency analysis of a detection signal of the knock sensor 11 is performed.

The result of the frequency analysis by the DSP 13 is input to a microcomputer 14, which performs knocking detection based on the frequency analysis result, and advances the ignition timing of the ignition device 15 in accordance with the presence or absence of knocking detection. Perform retard correction control,
The ignition timing is advanced as much as possible while avoiding knocking.

The ignition device 15 includes an ignition plug, an ignition coil, a power transistor, and the like. The ignition timing is advanced and retarded by on / off control of the power transistor. The detection of knocking based on the frequency analysis result is performed, for example, as follows.

That is, as shown in FIG.
When knocking vibration is included in the predetermined frequency component extracted from the output of (1), a frequency analysis section detected based on the detection signal from the crank angle sensor 16 (a predetermined section in which ignition noise is avoided; (ATDC10 ° to ATDC60 ° in a cylinder engine), the knocking vibration is gradually attenuated from the occurrence of abnormal combustion.
At the beginning, the intensity of the frequency component also largely gradually attenuates and returns to a level that does not include knocking vibration.On the contrary, when knocking vibration is not included, the intensity changes at a substantially constant level of engine vibration. Become. For this reason, when knocking vibration is not included, the initial intensity of the analysis section is maintained, and the integrated value of the frequency component intensity (db) increases substantially linearly.

Therefore, assuming that the initial intensity of the frequency analysis section does not change thereafter, if the time axis change of the integrated value of the intensity is estimated, the change characteristic is that when knocking does not occur. When the actual intensity is integrated on the time axis when knocking has occurred, FIG.
As shown in (1), a change characteristic that does not match the change characteristic estimated to correspond to the case where knocking does not occur is shown. For this reason, the presence / absence of knocking can be detected by calculating the integrated value of the actual intensity on the time axis and comparing the integrated value with the value when the knocking does not occur.

The microcomputer 14 detects the occurrence of knocking as described above, and diagnoses the knock sensor 11 based on the result of the frequency analysis by the DSP 13 based on the flowchart of FIG. . In this embodiment, the function as the self-diagnosis means is provided by the microcomputer 14 as software as shown in the flowchart of FIG.

Next, a self-diagnosis routine of the knock sensor 11 will be described with reference to the flowchart of FIG. First, in step 1 (hereinafter referred to as S1), a knock control region, that is, a knock control for retarding the ignition timing when knocking is detected by the knock sensor 11, and for advancing the ignition timing when knocking is not detected. It is determined whether or not it is in the area to be performed. If it is in the knock control area, the process proceeds to S2, and if not, the timer TM is reset to 0 in S12, and then the present routine ends.

In S2 and S3, the crank angle sensor 16
Engine speed Ne and intake air flow rate Q detected by
The basic fuel injection amount Tp (= K × Q / Ne; K is a constant) representative of the engine load determined from the engine speed Ne and the engine speed Ne is set to be smaller than the range for determining the knocking control region.
Region in the constant range examined whether (see FIG. 6)
Put out. And the region where Ne and Tp are within a predetermined range.
If it is within the range, the process proceeds to S4, and if it is outside the range, the timer is reset to 0 in S12, and this routine ends.

In S4, since both the engine speed Ne and the engine load Tp are within the above-mentioned range, which is within the predetermined range, the measurement of the timer TM is started, and in S5, it is determined whether or not the timer value TM exceeds the predetermined time T1. Is determined. And if it exceeds, the operating state stays in the above-mentioned area and stably
Is determined, that is, it is determined to be in a steady state, and the routine proceeds to S6, and if not, the routine is terminated. In S6, the sensor value Vs detected by knock sensor 11 is
, And A / D converted by the A / D converter 12.
Then, the read signal Vs is subjected to a Fourier transform operation in S7, and then a filter is extracted in S8 to extract a frequency component Vsf (knocking power spectrum) of 2 to 20 kHz as shown in FIG.

In S9, it is determined whether or not the frequency component Vsf exceeds a predetermined level value. And beyond
If not , proceed to S10. If it exceeds, knock sensor 1
Since 1 is normal, the timer is reset to 0 in S12, and this routine ends. In S10, as shown in FIG. 8, it is determined whether the timer value TM of starting the measurement in the S4 is further beyond the predetermined time T ₂ from the predetermined time T _1. If it exceeds, it is determined in S11 that knock sensor 11 is NG, that is, knock sensor 11 is disconnected.

Here, S2 and S3 correspond to operating state detecting means, S8 corresponds to predetermined frequency component extracting means, and S9 to S11 correspond to self-diagnosing means. At the same time, when knocking is detected, the ignition timing is retarded, and when knocking is not detected, the knocking control for advancing the ignition timing is stopped, and the ignition timing is clamped at the middle point.

As described above, the disconnection diagnosis of the vibration sensor can be performed without affecting the characteristics of the vibration sensor without connecting a special resistor or the like, and the knocking control based on the disconnection of the piezoelectric sensor becomes abnormal. Can be avoided.

[0025]

As described above, according to the first aspect of the present invention, predetermined frequency component extracting means for extracting a frequency component in a predetermined level range representing engine vibration from a detection signal detected by the vibration sensor. During a predetermined period in the knocking control area detected by the operating state detecting means,
Self-diagnosis means for diagnosing the vibration sensor as a failure when the predetermined frequency component extraction means does not detect a knocking frequency component equal to or higher than a predetermined level. Without this, disconnection diagnosis of the vibration sensor becomes possible.

According to the fifth aspect of the present invention, there is provided knocking control means for retarding the ignition timing when knocking is detected, and for advancing the ignition timing when knocking is not detected. When the sensor is diagnosed as having failed, the knock control by the knock control means is stopped, and the fail-safe means for clamping the ignition timing to a predetermined value is provided. Can be avoided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 is a block diagram showing a basic configuration of the present invention.

FIG. 3 is a system diagram showing a system configuration of an embodiment according to the present invention.

FIG. 4 is a time chart for explaining characteristics of knocking detection using a knocking frequency analysis result.

FIG. 5 is a flowchart showing self-diagnosis control of the knock sensor according to the embodiment of the present invention.

FIG. 6 is a diagram showing a steady operation region in which a basic fuel injection amount Tp representing an engine rotation speed Ne and an engine load is within a predetermined range.

FIG. 7 is a diagram showing a frequency component Vsf of 2 to 20 kHz extracted through a filter.

FIG. 8 is a diagram showing measurement sections of a timer TM.

FIG. 9 is a system diagram showing a self-diagnosis device of a conventional knocking detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Knock sensor 12 A / D converter 13 DSP 14 Microcomputer 15 Ignition device 16 Crank angle sensor

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01M 17/007 F02D 45/00 368 G01M 15/00

Claims (5)

(57) [Claims] 1. A knocking detection device for an internal combustion engine, comprising: a vibration sensor attached to an engine main body for detecting engine vibration, and configured to detect occurrence of knocking based on engine vibration detected by the vibration sensor. in the operating condition detecting means for detecting an operating condition of the engine, a predetermined frequency component extraction means for extracting a predetermined knocking frequency component from a detection signal detected by the vibration sensor, is detected by the operating condition detecting means operating The state is no
Stays in a predetermined sub-area belonging to the locking control area
After a lapse of a predetermined time, the predetermined frequency component extracting means
The level of the knocking frequency component extracted by
Compared with a predetermined level for line diagnosis and less than the predetermined level
And a self-diagnosis means for diagnosing the vibration sensor as a disconnection when . 2. The engine according to claim 1, wherein said operating state detecting means detects an engine speed and a load, and determines a predetermined value belonging to said knocking control area.
Subregions load engine speed, each Nokki
The self-diagnosis device in the knocking detection device for an internal combustion engine according to claim 1, wherein the self-diagnosis device is a region within a range set to be narrower than a range for determining the knocking control region . 3. The method according to claim 2, wherein the predetermined knocking frequency component is a vibration.
2 to 20 kHz out of the detection signals detected by the sensor
The frequency component in a range, wherein the frequency component is within a range.
A self-diagnosis device in the knocking detection device for an internal combustion engine according to claim 2 . 4. The vibration sensor is integrated with a washer of an ignition plug.
A seat pressure type piezoelectric sensor to be mounted;
A self-diagnosis device in the knocking detection device for an internal combustion engine according to any one of claims 1 to 3 . 5. The ignition timing is retarded when knocking is detected.
The ignition timing is advanced when knocking is not detected.
A self-diagnosis means,
When the sensor is diagnosed as having failed, the knocking control is performed.
Stop knocking control by means and set ignition timing
It includes fail-safe means to clamp to the value
Any one of claims 1 to 4 characterized in that:
Self-diagnosis device in device for detecting knocking in an internal combustion engine according to.