JPH07310585A - Cylinder pressure sensor diagnostic device - Google Patents

Abstract

(57) [Abstract] [Purpose] Accurately diagnose failures in the cylinder pressure sensor, including output deterioration due to deterioration and leakage. [Constitution] The in-cylinder pressure detected by the in-cylinder pressure sensor is integrated in a predetermined integration section to obtain an in-cylinder pressure integrated value IMEP (S1).
On the other hand, a reference value IMEP _INT corresponding to the normal combustion state of the integrated value IMEP is set from the basic fuel injection amount Tp (S2). Then, the deviation ΔIMEP between the reference value IMEP _INT and the actually detected integral value IMEP is calculated (S3). Here, when the deviation ΔIMEP is equal to or greater than the predetermined value K (S4) and the normal combustion state is detected from the crank angular velocity detected by the crank angle sensor (S7), it is determined that the in-cylinder pressure sensor has failed. Do (S
8).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic device for an in-cylinder pressure sensor, and more particularly to a diagnostic device for determining whether or not a sensor for detecting an in-cylinder pressure of an internal combustion engine has a failure.

[0002]

2. Description of the Related Art Conventionally, an in-cylinder pressure sensor for detecting the pressure in a cylinder of an internal combustion engine (in-cylinder pressure) is provided, and the combustion state (presence or absence of misfire) of the engine is detected based on the detection result of the in-cylinder pressure sensor. Is performed (Japanese Patent Laid-Open No. 62-2).
See, for example, No. 6345 and No. 64-15937.

Specifically, the presence or absence of misfire is determined by whether or not the peak occurrence time of the in-cylinder pressure (combustion pressure), the integrated value of the in-cylinder pressure, etc. indicate a value corresponding to a normal combustion state. Has been done.

[0004]

By the way, in the in-cylinder pressure sensor, in addition to disconnection, short circuit, and the like, there is a possibility that a malfunction such as deterioration or output reduction due to water leakage (see FIG. 5) may occur. Then, when a failure of the in-cylinder pressure sensor as described above occurs, there is a risk that the occurrence of misfire may be erroneously detected despite the fact that combustion is actually normal. Various engine controls (fuel supply amount control, ignition timing control, etc.) performed become inadequate due to the misfire detection, resulting in a problem that the exhaust property is deteriorated.

The present invention has been made in view of the above circumstances, and provides a diagnostic device capable of surely diagnosing a failure of an in-cylinder pressure sensor, in addition to disconnection, short circuit and the like, including deterioration and reduction in output due to flooding or the like. The purpose is to

[0006]

Therefore, the in-cylinder pressure sensor diagnostic device according to the invention of claim 1 is an in-cylinder pressure sensor diagnostic device for detecting an in-cylinder pressure of an internal combustion engine, and is configured as shown in FIG. To be done. In FIG. 1, the predicted value setting means sets the predicted value of the in-cylinder pressure detected by the in-cylinder pressure sensor during normal combustion based on the engine operating conditions.

The detection error detecting means calculates the deviation between the predicted value set by the predicted value setting means and the detected value by the in-cylinder pressure sensor. On the other hand, the combustion state detecting means is provided separately from the in-cylinder pressure sensor, detects the state quantity correlated with the combustion state of the engine, and the combustion state determining means is based on the state quantity detected by the combustion state detecting means. Determine normal / abnormal combustion conditions.

Here, the in-cylinder pressure sensor failure determination means is such that the absolute value of the deviation calculated by the detection error detection means is a predetermined value or more, and the combustion state is normal by the combustion state determination means. Is determined, it is determined that the in-cylinder pressure sensor is out of order. In the diagnostic device according to the invention of claim 2, the predicted value setting means sets an integrated value of the in-cylinder pressure in a predetermined integration section as a predicted value, and the detection error detection means detects the in-cylinder pressure detected by the in-cylinder pressure sensor. Is configured to calculate a deviation between a value obtained by integrating in the predetermined integration section and a predicted value set as the integrated value.

In the diagnostic device according to the third aspect of the present invention, the combustion state detecting means detects the crank angular velocity of the engine as a state quantity correlated with the combustion state. In the diagnostic device according to the invention of claim 4, the predictive value setting means sets the predictive value based on the intake air amount of the engine or the intake air amount equivalent value as the engine operating condition.

[0010]

According to the diagnostic device of the first aspect of the present invention, the deviation between the actual detected value of the in-cylinder pressure sensor and the in-cylinder pressure predicted from the operating condition is detected. Further, normality / abnormality of combustion is determined from the detection result of the combustion state detecting means provided separately from the in-cylinder pressure sensor. Then, although the absolute value of the deviation is equal to or greater than a predetermined value and an abnormal combustion state is recognized from the detection value of the in-cylinder pressure sensor, the combustion state is determined to be normal from the detection result of the combustion state detection means. In this case, it is considered that the detected value that does not correspond to the actual in-cylinder pressure is output due to the failure of the in-cylinder pressure sensor, and the failure of the in-cylinder pressure sensor is determined.

In the diagnostic apparatus according to the second aspect of the present invention, the in-cylinder pressure detected by the in-cylinder pressure sensor is integrated in a predetermined integration section, and the predicted value is also given as the integrated value.
The detection error of the in-cylinder pressure sensor is detected by the deviation of the integrated value so that the detection error is not erroneously detected due to the influence of noise or the like. In the diagnostic device according to the third aspect of the present invention, the crank angular velocity of the engine is detected as a state quantity that correlates with the combustion state, and the angular velocity fluctuation is detected due to an abnormality (misfire) in the combustion state to determine whether the combustion state is normal or abnormal. It was decided to determine whether or not.

According to the fourth aspect of the present invention, the in-cylinder pressure that will be detected by the in-cylinder pressure sensor is predicted based on the intake air amount of the engine or the intake air amount equivalent value. Here, since the intake air amount of the engine is a parameter required for controlling the fuel amount in the electronically controlled fuel injection device, it is relatively simple and accurately predicted in an internal combustion engine equipped with the electronically controlled fuel injection device. You will be able to find the value.

[0013]

EXAMPLES Examples of the present invention will be described below. In FIG. 2 showing an embodiment, air is taken into the internal combustion engine 1 through an air cleaner 2, a throttle chamber 3 and an intake manifold 4. The combustion exhaust from the engine 1 is exhausted from the exhaust manifold 5, the exhaust duct 6, the three-way catalyst 7,
It is discharged into the atmosphere through the muffler 8.

The throttle chamber 3 is provided with a throttle valve 9 which opens and closes in conjunction with an accelerator pedal (not shown), and the throttle valve 9 adjusts the intake air amount of the engine 1. Each cylinder (#
Ignition plugs (not shown) are mounted so as to face the combustion chambers 1 to # 4), and in-cylinder pressure sensors 10a to 10d are provided for each cylinder in pairs with the ignition plugs.

The in-cylinder pressure sensors 10a to 10d are actually opened 6
The type used as the washer of the spark plug as disclosed in Japanese Patent Publication No. 3-17432 is used. That is, the in-cylinder pressure sensors 10a to 10d are composed of ring-shaped piezoelectric elements, electrodes, etc., and are sandwiched between the spark plug and the cylinder head. It is what is output.

However, the in-cylinder pressure sensors 10a to 10d are not limited to the above-mentioned washer type, but are disclosed in JP-A-4-815.
It may be of a type in which the sensor portion disclosed in Japanese Patent Publication No. 57 is directly exposed to the combustion chamber to detect the in-cylinder pressure as an absolute pressure. Further, a cam shaft (not shown) of the engine 1 is provided with a crank angle sensor 11 that detects a crank angle through rotation of the cam shaft.

This crank angle sensor 11 is the same as the crank angle sensor 11 of the present embodiment.
The cylinder engine 1 outputs a reference angle signal REF for each crank angle of 180 ° corresponding to a stroke phase difference between cylinders, and a unit angle signal POS for each unit crank angle (1 ° or 2 °). Then, the engine rotation speed Ne can be calculated based on the reference angle signal REF or the unit angle signal POS.

An air flow meter 12 for detecting the intake air flow rate Q of the engine is provided on the upstream side of the throttle valve 9, and the throttle valve 9 is provided with a potentiometer type throttle sensor 13 for detecting its opening TVO. It is provided. On the other hand, in each branch part of the intake manifold 4,
An electromagnetic fuel injection valve 14 is provided for each cylinder. The fuel injection valve 14 intermittently injects and supplies the fuel adjusted to a predetermined pressure by a pressure regulator (not shown) to the engine in response to an injection pulse signal.

Here, the detection signals from the in-cylinder pressure sensors 10a to 10d, the crank angle sensor 11, the air flow meter 12, and the throttle sensor 13 are output to a control unit 15 provided for engine control. The control unit 15 including a microcomputer controls the injection amount (injection pulse width Ti) of the fuel injection valve 16 based on the output of each sensor to form a mixture having a predetermined air-fuel ratio.

The control unit 15 controls the basic injection pulse width Tp (basic injection pulse width Tp based on the intake air flow rate Q detected by the air flow meter 12 and the engine speed Ne calculated based on the detection signal from the crank angle sensor 11). Fuel injection amount) ← K × Q / Ne (K is a constant) is calculated. Further, various correction factors C based on engine operating conditions such as the cooling water temperature Tw
A correction amount Ts or the like depending on O or the battery voltage is set, the basic injection pulse width Tp is corrected based on these values, and the correction result is used as a final injection pulse width (fuel injection amount) Ti (←
Tp × CO + Ts). Then, an injection pulse signal having the injection pulse width Ti is output to the fuel injection valve 14 at a predetermined injection timing to control the fuel injection by the fuel injection valve 14.

Further, the control unit 15 detects whether or not a misfire has occurred, based on the in-cylinder pressure for each cylinder detected by the in-cylinder pressure sensors 10a to 10d. Such misfire detection involves changing the timing at which the cylinder pressure reaches a peak due to the occurrence of misfire, decreasing the maximum combustion pressure or the combustion pressure at a predetermined crank angle position due to the occurrence of misfire, and further detecting the cylinder pressure in the predetermined integration section. It is performed based on the fact that the integrated value decreases due to the occurrence of misfire.

Specifically, the crank angle at which the in-cylinder pressure reaches a peak is detected, or the in-cylinder pressure and the peak in-cylinder pressure at a predetermined crank angle position are sampled, or the in-cylinder pressure detection value is detected within a predetermined integration interval. And the presence or absence of misfire is determined by whether or not these values correspond to the normal combustion state.
Here, the control unit 15 is the in-cylinder pressure sensor.
In order to ensure the accuracy of misfire detection using 10a-10d,
The configuration is such that failure diagnosis of the in-cylinder pressure sensors 10a to 10d is performed as shown in the flowchart of FIG.

In this embodiment, the predicted value setting means,
As shown in the flow chart of FIG. 3, the control unit 15 has software functions as a detection error detection means, an in-cylinder pressure sensor failure determination means, and a combustion state determination means. In the flowchart of FIG. 3, in step 1 (denoted as S1 in the figure. The same applies hereinafter), the in-cylinder pressure detected by the in-cylinder pressure sensors 10a to 10d is integrated for each cylinder in a predetermined integration interval, and the integrated value is calculated. Set it to the label name IMEP.

The predetermined integration interval is, for example, BT
DC10 ° ~ ATDC70 ° or BTDC10 ° ~ ATDC
Although 100 ° and the like are preferable, it is obvious that the interval is not limited to these intervals. In addition, the misfire detection is based on the integrated value IME.
In the case of using P, it is possible to use the value calculated for misfire detection as the integrated value IMEP.

In step 2, the map in which the reference value IMEP _INT of the integrated value IMEP is stored in advance so as to correspond to the basic injection pulse width Tp which is a value representing the engine load, is referred to as the current basic injection pulse width Tp. Corresponding reference value IM
_Calculate EP _INT . The reference value IMEP _INT is a value predicted to be obtained during normal combustion under the engine operating condition specified by the basic injection pulse width Tp, and the basic injection pulse width Tp is a value corresponding to the engine intake air amount. Therefore, the reference value IMEP _INT is accurately set according to the intake air amount of the engine that correlates with the in-cylinder pressure.

Instead of the basic injection pulse width Tp, the reference value IMEP _INT may be set in correspondence with Q / Ne which is the intake air amount per engine rotation. Further, the in-cylinder pressure at the time of normal combustion is greatly affected by the intake air amount and changes, and does not show a large change due to the change of the engine rotation speed Ne, but in order to set the reference value IMEP _INT more accurately, The reference value IMEP _INT is stored for each of the operating regions divided into a plurality using the engine speed Ne and the basic injection pulse width Tp as parameters (see FIG. 4), and the engine speed Ne at that time is stored. The reference value IMEP _INT may be set based on the basic injection pulse width Tp.

In step 3, the reference value IMEP _{INT is set.}
And an integrated value IMEP calculated from the detected values of the in-cylinder pressure sensors 10a to 10d, a deviation ΔIMEP (← IMEP _INT -IME
P) is calculated. In the next step 4, the deviation ΔIM
The EP is compared with the predetermined value K. Like the reference value IMEP _INT , the predetermined value K is set in advance to the basic injection pulse width Tp.
(And engine rotation speed Ne) is a value stored in the map and is set based on the basic injection pulse width Tp (and engine rotation speed Ne) at that time.

If the engine is burning normally and the in-cylinder pressure sensors 10a to 10d have the desired detection performance, the deviation ΔIMEP should be a sufficiently small value. When it is determined that ΔIMEP is less than the predetermined value K, the routine proceeds to step 5, where the cylinder pressure sensor 10
The normality judgment of a to 10d is performed. Here, the cylinder pressure sensor 10a
If the deviation ΔIMEP is not 0, it means that there is an error in the detection value although there is no great problem in misfire detection. Therefore, in step 6, the deviation ΔIM
It is preferable that the correction value of the detection value of the in-cylinder pressure sensors 10a to 10d is learned in the direction of approaching EP, and at the time of misfire detection, the presence or absence of misfire is determined based on the detection value corrected by the correction value. .

On the other hand, in step 4, the deviation ΔIMEP
When it is determined that is equal to or greater than the predetermined value K, the detected output may be reduced due to a failure of the cylinder pressure sensors 10a to 10d, but on the other hand, the cylinder pressure is decreased because a misfire has occurred. May have actually decreased, and it is not possible to immediately determine the failure of the in-cylinder pressure sensors 10a to 10d.

Therefore, in step 4, the deviation ΔIME
When it is determined that P is equal to or greater than the predetermined value K, the process proceeds to step 7 and it is determined whether or not the normal combustion state is detected based on the detection signal (crank angular velocity) from the crank angle sensor 11. The detection of the combustion state using the crank angle sensor 11 will be described later. That is, the deviation ΔIM
Even if EP is equal to or greater than the predetermined value K, if abnormal combustion (misfire) actually occurs at that time, the deviation ΔIMEP that is equal to or greater than the predetermined value K indicates a failure of the in-cylinder pressure sensors 10a to 10d. Not a thing. On the other hand, the crank angle sensor
Although the normal combustion state is detected based on the detection signal from 11, when the deviation ΔIMEP is equal to or larger than the predetermined value K, the detection results are different, and in this case, There is a high possibility that the in-cylinder pressure sensors 10a to 10d are out of order.

Therefore, when it is determined in step 7 that the normal combustion state is detected based on the detection signal from the crank angle sensor 11, the process proceeds to step 8 to determine the failure of the in-cylinder pressure sensors 10a-10d. Cylinder pressure sensor 10
The detection of the combustion state using a to 10d is prohibited, and preferably, the driver is warned of the failure determination result by a lamp or the like.

On the other hand, in step 7, the crank angle sensor is
When it is determined that the abnormal combustion state is detected based on the detection signal from 11, the deviation ΔIMEP calculated as a value equal to or greater than the predetermined value K corresponds to the fact that the abnormal combustion actually occurs. Since it can be considered that the in-cylinder pressure sensors 10a to 10d are normal, in this case, the routine proceeds to step 9.

As described above, according to the above embodiment, the integral value IMEP obtained from the detection values of the in-cylinder pressure sensors 10a to 10d.
Based on the detection signal (crank angular velocity) of the crank angle sensor 11, the deviation from the reference value IMEP _INT corresponding to the normal combustion state, which is a predicted value of the integrated value under operating conditions, is When the normal combustion state is detected, it is determined that the in-cylinder pressure sensors 10a to 10d are not outputting a detection signal commensurate with the actual in-cylinder pressure in the normal combustion state, so that the in-cylinder pressure sensors 10a to 10d fail. To judge.

Therefore, it is possible to judge the failure of the output signal level fluctuation due to deterioration or water leakage (leakage) as well as the failure such as disconnection or short circuit in the detection signal lines of the in-cylinder pressure sensors 10a to 10d. It is possible to provide highly accurate failure diagnosis results. In the above embodiment, the in-cylinder pressure integrated value IMEP is calculated from the detection signals of the in-cylinder pressure sensors 10a to 10d, and the calculation result and the reference value IMEP are calculated.
_Although it was made to compare with _INT , the in-cylinder pressure detection value at a predetermined crank angle position is sampled, or the in-cylinder pressure peak value is sampled, and the reference value predicted from such sump link value and operating condition (engine load). You may make it compare with. However, if the configuration is such that the in-cylinder pressure detection value is integrated, there is an effect that deterioration of diagnostic performance can be suppressed even if noise occurs in the detection signal.

By the way, the detection of the combustion state using the detection signal from the crank angle sensor 11 is performed as follows, for example. First, the TDC cycle TINT is measured based on the detection signal from the crank angle sensor 11, and the cycle TINT is stored in time series. here,
The latest measurement cycle is TINT1, and the previous measurement cycle is T
INT2, the measurement cycle of the last two times is TINT3, and similarly, n of TINTn is increased by 1 as the measurement order becomes older.

Then, the misfire determination value MISA is calculated using the cycle TINT as follows: MISA = {3 × (TINT4−TINT5) + (TINT4−TINT
1} / TINT5 ³ , and when the misfire determination value MISA is greater than or equal to the reference value S / L, it is determined that the crank angular velocity (state amount that correlates with the combustion state of the engine) fluctuates due to abnormal combustion. To do.

Therefore, in the present embodiment, the combustion state detecting means corresponds to the crank angle sensor 11, and in an electronically controlled fuel injection device, the crank angle sensor 11 is generally provided. It is not necessary to provide a dedicated sensor for diagnosis, and the cylinder pressure sensors 10a to 10d can be easily diagnosed. However, the determination of the combustion state based on the crank angular velocity is not limited to the configuration using the misfire determination value MISA.

[0038]

As described above, according to the diagnostic device of the first aspect of the present invention, the output of the in-cylinder pressure sensor is inconsistent with the predicted value, and the normal combustion state is detected by the separate combustion state detection. If it is detected, it is considered that the detected output does not correspond to the actual in-cylinder pressure due to the in-cylinder pressure sensor failure, and the in-cylinder pressure sensor failure is determined. There is an effect that it is possible to perform failure diagnosis for output fluctuations caused by deterioration and water leakage (leak), and to provide a highly reliable diagnosis result.

According to the diagnosing device of the second aspect of the present invention, since the failure diagnosis is performed by using the integrated value of the in-cylinder pressure, deterioration of the diagnostic performance is suppressed even if noise is generated in the detection signal. The effect is that you can do it. According to the diagnostic device of the third aspect of the present invention, whether or not the in-cylinder pressure sensor outputs a correct detection value can be easily diagnosed based on the combustion state detected based on the crank angular velocity.

According to the diagnostic device of the fourth aspect of the present invention, there is an effect that the predicted value of the in-cylinder pressure that will be detected by the in-cylinder pressure sensor during normal combustion can be accurately set.

[Brief description of drawings]

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

FIG. 2 is a system schematic diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing failure diagnosis control in the embodiment.

FIG. 4 is a diagram showing a correlation between engine load and rotation and an in-cylinder pressure integrated value.

FIG. 5 is a diagram showing a change in output characteristic due to a failure of a cylinder pressure sensor.

[Explanation of symbols]

 1 Internal combustion engine 10a-10d Cylinder pressure sensor 11 Crank angle sensor 12 Air flow meter 15 Control unit

Claims (4)

[Claims] 1. A diagnostic device for an in-cylinder pressure sensor for detecting an in-cylinder pressure of an internal combustion engine, wherein a predicted value for setting a predicted value of the in-cylinder pressure detected by the in-cylinder pressure sensor during normal combustion based on engine operating conditions. Setting means, detection error detecting means for calculating a deviation between the predicted value set by the predicted value setting means and the detected value by the in-cylinder pressure sensor; and the in-cylinder pressure sensor, which is provided separately from the in-cylinder pressure sensor. Combustion state detection means for detecting a correlated state quantity, combustion state determination means for determining normality / abnormality of the combustion state based on the state quantity detected by the combustion state detection means, and calculation by the detection error detection means In-cylinder pressure sensor failure determination for determining a failure of the in-cylinder pressure sensor when the absolute value of the deviation is equal to or greater than a predetermined value, and when the combustion state determining means determines that the combustion state is normal. Diagnostic device of the in-cylinder pressure sensor, characterized in that it is configured to include a stage, a. 2. The predicted value setting means sets an integrated value of the in-cylinder pressure in a predetermined integration section as a predicted value, and the detection error detection means sets the in-cylinder pressure detected by the in-cylinder pressure sensor in the predetermined integration section. The in-cylinder pressure sensor diagnostic device according to claim 1, wherein the in-cylinder pressure sensor is configured to calculate a deviation between an integrated value and a predicted value set as the integrated value. 3. The in-cylinder pressure sensor diagnostic device according to claim 1, wherein the combustion state detecting means detects the crank angular velocity of the engine as a state quantity that correlates with a combustion state. 4. The predictive value setting means is configured to set the predictive value based on an intake air amount of the engine or an intake air amount equivalent value as an engine operating condition.
2. The in-cylinder pressure sensor diagnostic device according to either 2 or 3.