JPH07167745A - Diagnosing device of sensor for pressure in cylinder - Google Patents

Abstract

PURPOSE:To diagnose the clamping torque failure of an ignition plug in a sensor for pressure in a washer type cylinder which is clamped with the ignition plug. CONSTITUTION:A resonance frequency of the output of a sensor for pressure in a cylinder is determined (S3) based on an engine rotary speed Ne (S2). Then, the frequency analysis of the sensor output is performed (S1) and the power spectrum of resonance frequency is obtained (S4). When the power spectrum exceeds a specific value SL, it is estimated that the power spectrum of the resonance frequency is large due to the shortage in the clamping torque, thus judging the failure in the clamping torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder pressure sensor diagnostic device, and more particularly to a function diagnosis of a ring-shaped in-cylinder pressure sensor sandwiched between an ignition plug and a mounting seat surface.

[0002]

2. Description of the Related Art There is a method for detecting the pressure of combustion gas in a cylinder as a method for ascertaining the combustion state of an internal combustion engine.
There is known a cylinder pressure sensor as disclosed in Japanese Patent Publication No. The cylinder pressure sensor disclosed in Japanese Utility Model Laid-Open No. 63-70049 is a spark plug in which a ring-shaped pressure sensor is sandwiched between an ignition plug screwed into a cylinder head and a mounting seat surface of the ignition plug. The pressure sensor and the pressure sensor are fastened together, and is generally called a washer-type cylinder pressure sensor.

The washer-type in-cylinder pressure sensor is a stack of a ring-shaped piezoelectric element and an electrode, which is fastened as a washer for a spark plug, so that when the combustion pressure in the cylinder acts on the spark plug, The tightening force is increased or decreased, whereby the output of the piezoelectric element changes according to the combustion pressure (cylinder pressure).

[0004]

By the way, if the in-cylinder pressure sensor cannot realize the intended pressure detecting function, an error will occur in the detection of the combustion state.
It is desired to provide an apparatus capable of diagnosing whether the in-cylinder pressure is normally detected by the in-cylinder pressure sensor. Particularly, in the washer-type cylinder pressure sensor, since the tightening torque of the spark plug greatly affects the correlation between the cylinder pressure and the sensor output, it is necessary to tighten the spark plug and the cylinder pressure sensor together with a predetermined tightening torque. However, when replacing the spark plug, there is a risk that tightening will be performed with a torque other than the normal tightening torque. in this case,
The combustion state is detected based on the output of the in-cylinder pressure sensor while the desired output characteristics are not exhibited, and the reliability of combustion state detection using the in-cylinder pressure sensor is greatly reduced. There was a problem of being lost.

The present invention has been made in view of the above circumstances, and provides a diagnostic device for a washer-type cylinder pressure sensor which is fastened together with an ignition plug, and which is capable of diagnosing a defective detection function of the sensor due to a poor tightening torque. The purpose is to

[0006]

Therefore, a diagnostic device for an in-cylinder pressure sensor according to the present invention includes a ring-shaped in-cylinder pressure sensor which is sandwiched between an ignition plug screwed into a cylinder head of an internal combustion engine and a mounting seat surface. The diagnostic device is configured as shown in FIG. In FIG. 1, the power spectrum detecting means detects the power spectrum of a predetermined resonance frequency from the output signal of the in-cylinder pressure sensor.

The sensor diagnosing means determines an abnormality in the detection function of the in-cylinder pressure sensor when the power spectrum detected by the power spectrum detecting means exceeds a predetermined value.

[0008]

With this structure, the power spectrum of the predetermined resonance frequency is detected from the output of the cylinder pressure sensor.
The power spectrum of the resonance frequency tends to increase as the actual tightening torque becomes smaller than the regular tightening torque. Therefore, by comparing the detected power spectrum with a predetermined value corresponding to the regular tightening torque (the lower limit of the allowable tightening torque), the spark plug can be attached to the cylinder head at the desired tightening torque together with the spark plug. It is possible to estimate whether or not it is tightened, and if the tightening torque is smaller than the desired value and the power spectrum exceeds the specified value, there is an abnormality in the detection function of the in-cylinder pressure sensor due to such tightening torque failure. It can be diagnosed as occurring.

[0009]

EXAMPLES Examples of the present invention will be described below. In FIG. 2 showing an embodiment, a spark plug 3 is screwed into a screw hole 2 provided in a cylinder head 1 of an internal combustion engine.
A ring-shaped in-cylinder pressure sensor 5 is sandwiched between the spark plug 3 of each cylinder and the spark plug mounting seat surface 4 of the cylinder head 1 and tightened together.

Reference numeral 6 is a washer interposed between the in-cylinder pressure sensor 5 and the spark plug 3. In-cylinder pressure sensor 5
Is, for example, a ring-shaped center electrode with two piezoelectric elements above and below the center electrode as a center, and an upper surface electrode and a lower surface electrode sequentially laminated on the outside thereof. It is fixed integrally with the material. The lead wire 7 is taken out from the center electrode through a resin material.

Since the in-cylinder pressure sensor 5 is tightened as a washer of the spark plug 3, the combustion pressure in the cylinder 8 acts on the spark plug 3 to increase or decrease its tightening force, which causes the output of the piezoelectric element. Is a sensor that can detect the combustion pressure (cylinder pressure) as a relative pressure. A high tension cord (not shown) is connected to the terminal of the spark plug 3, and a spark discharge is generated by a high voltage supplied through the high tension cord to ignite and burn the air-fuel mixture in the cylinder 8.

The sensor output taken out through the lead wire 7 is input to an engine control unit 9 containing a microcomputer. In addition to the output of the in-cylinder pressure sensor 5, the crank angle signal from the crank angle sensor 10 is also input to the engine control unit 9. The engine control unit 9 includes a washer mold in-cylinder pressure sensor 5 The combustion state (for example, the presence or absence of misfire) of the engine is detected based on the combustion pressure detected based on the output of the engine and the information on the crank angle position detected by the crank angle sensor 10.

Further, as shown in the flow chart of FIG. 3, the engine control unit 9 diagnoses whether or not the pressure detection function of the in-cylinder pressure sensor 5 is abnormal due to a defective tightening torque of the spark plug 3. It has a function to do. still,
In this embodiment, the functions as the power spectrum detecting means and the sensor diagnosing means are provided in the engine control unit 9 as shown in the flow chart of FIG.

In the flow chart of FIG. 3, in step 1 (denoted as S1 in the figure; the same applies hereinafter), frequency analysis of the output of the in-cylinder pressure sensor 5 is performed within a predetermined analysis section detected by the crank angle signal, and each is analyzed. Obtain the power spectrum for each frequency. In the next step 2, the engine speed Ne is calculated based on the crank angle signal output from the crank angle sensor 10.

Then, in step 3, the map in which the resonance frequency f of the in-cylinder pressure sensor 5 corresponding to the engine rotation speed Ne is stored in advance is referred to based on the engine rotation speed Ne calculated in step 2, and the current The resonance frequency f corresponding to the engine rotation speed Ne is set. In step 4, the frequency analysis result corresponding to the resonance frequency f obtained in step 3 is searched to obtain the power spectrum of the current resonance frequency f.

Then, in step 5, step 4
The power spectrum obtained in step S1 is compared with the predetermined value SL, and if the detected power spectrum exceeds the predetermined value SL, the process proceeds to step 6 and the pressure detection function of the in-cylinder pressure sensor 5 becomes abnormal due to a tightening torque failure. It is determined that When it is determined that the tightening torque is defective, it is advisable to warn the driver of the determination result by a warning lamp or the like provided in the driver's seat of the vehicle.

On the other hand, when it is determined in step 5 that the power spectrum is equal to or less than the predetermined value SL, the process proceeds to step 7 and it is determined that at least the abnormality in the detection function due to the insufficient tightening torque has not occurred. . Since the in-cylinder pressure sensor 5 of the present embodiment is a washer-type cylinder pressure sensor that is tightened together with the spark plug 3, the tightening torque of the spark plug 3 has a large effect on its output characteristics and is constant with respect to the in-cylinder pressure. In order to obtain an output having a correlation of, it is necessary to be tightened together with the spark plug 3 with a constant tightening torque.

There is a possibility that the spark plug 3 will be tightened with a torque weaker than the normal tightening torque when the spark plug 3 is replaced, but if the tightening torque is weaker than the normal level, Since the power spectrum of the resonance frequency of the sensor increases, the power spectrum at the resonance frequency that changes at the engine speed Ne at that time is obtained as described above, and when the tightening work is performed with the normal torque. If the level significantly exceeds the level that occurs in 1), it is possible to estimate the tightening torque failure.

Therefore, when a tightening torque failure occurs, the occurrence of such a failure can be diagnosed, and thus the combustion state is erroneously detected by using the in-cylinder pressure sensor 5 having the tightening torque failure. Can be avoided, and early warning can be promoted by issuing a warning. By the way, in the washer-type cylinder pressure sensor 5 as described above, the tightening torque when tightening together with the spark plug 3 has a great effect on the sensor output. It is desirable to adjust the tightening torque to the required level, and it is convenient if a defect of the cylinder pressure sensor 5 itself can be found during the tightening work.

Therefore, an automatic tightening device capable of tightening the spark plug 3 with a desired tightening torque and at the same time detecting a defect in the sensor itself will be described below. In FIG.
Reference numeral 51 is a main unit of the working device, which is a motor control circuit 52, a sensor input interface 53, and a signal processing unit.
54, a CPU 55, a cylinder selection switch 56, a tightening torque adjusting volume 57, and a tightening torque OK indicator 58. Further, the main body unit 51 is provided with a monitor 59 for displaying various messages.

When tightening the spark plug 3 for replacement of the spark plug 3 or the like, the output of the in-cylinder pressure sensor 5 is input to the main body unit 51 through the sensor input interface 53, and the crank The signal of the angle sensor 10 is read. Further, the inner periphery of the cylindrical motor 60 controlled via the motor control circuit 52 is engaged with the hexagonal nut portion of the spark plug 3 of each cylinder so that the outer periphery is locked to the cylinder head 1 side. By rotating the inner periphery of the cylindrical motor 60 with the outer periphery being the fixed side, the ignition plug 3 can be tightened with the drive torque generated by the cylindrical motor 60.

By operating the engine in this state and starting the main unit 51, the tightening work and the sensor failure diagnosis are performed as shown in the flowchart of FIG. In the flowchart of FIG. 5, first, step 21
Then, the in-cylinder pressure detected by the in-cylinder pressure sensor 5 is integrated for each cylinder in a predetermined integration period, and the integrated value is set in IMEP for each cylinder.

In the next step 22, the crank angle sensor 10
The engine rotation speed Ne is calculated based on the signal from. In step 23, the selection of the work target cylinder by the cylinder selection switch 56 is determined. In step 24, the average of the in-cylinder pressure integrated value IMEP calculated for each cylinder in all cylinders is compared with the integrated value IMEP in the cylinder determined in step 23, and the integral of the cylinder is compared with the average level in all cylinders. When the value has a deviation of a predetermined value or more, diagnostic control is executed to diagnose that the in-cylinder pressure sensor 5 of the cylinder has some abnormality.

When diagnosing the abnormality of the sensor itself based on the in-cylinder pressure integrated value IMEP as described above, the integrated value IMEP of each cylinder is weighted averaged and compared with the average value of all cylinders. Good to do. In step 25, the tightening torque failure is diagnosed by the frequency analysis shown in the flow chart of FIG.

Then, in step 26, steps 24 and 25
It is determined whether or not the normal determination is made in any of the diagnoses. If it is determined by the two diagnostic controls that both are normal, the process proceeds to step 27, where the tightening torque O
By turning on the K indicator 58, the in-cylinder pressure sensor 5 in the selected cylinder is informed that there is no abnormality in the sensor itself and that it is tightened together with the spark plug 3 at the desired tightening torque. Furthermore, since the tightening torque is the desired value, in the next step 28, the cylindrical motor 60
Stop driving.

On the other hand, when it is determined in step 26 that at least one of steps 24 and 25 is determined to be abnormal,
Proceed to step 29, and in-cylinder pressure integrated value I in step 24
It is determined whether the normal determination is made only by the diagnosis based on the MEP. If the diagnosis in step 24 is normal and the diagnosis in step 25 is abnormal, it is determined that the tightening torque of the spark plug 3 is inappropriate although the sensor itself has no abnormality. Therefore, proceed to step 30, and set the cylindrical motor through the motor control circuit 52.
The spark plug 3 is tightened by controlling the drive of 60.

If it is judged normal only in step 25, or if any of the diagnosis in steps 24 and 25 is judged as abnormal, step 29 to step
Proceeding to 31, it is determined whether or not a normal determination is made only by the diagnosis in step 25. Here, if the abnormality of the sensor itself is diagnosed in step 24 and it is determined in step 25 that the tightening torque is the desired value, even if the tightening is properly performed, the desired pressure is detected due to the defective sensor itself. Since it cannot be performed, the routine proceeds to step 32, where an abnormality of the cylinder pressure sensor 5 itself provided in the selected cylinder is displayed on the monitor 59.

If both steps 24 and 25 are determined to be abnormal, steps 31 to 33 are performed.
Then, the process goes to the step 59 and the monitor 59 displays the abnormality of the working apparatus of the present embodiment, which is composed of the main body unit 51, the cylindrical motor 60, and the like. That is, if the intended tightening work cannot be performed, an abnormality in the sensor itself may be erroneously determined, so that the warning of the sensor diagnosis and the automation of the tightening work cannot be performed.

As described above, according to this embodiment, the spark plug 3 can be tightened while confirming the proper level of the tightening torque based on the frequency analysis of the sensor output, and the abnormality of the sensor itself can be diagnosed. Therefore, it is possible to prevent the abnormal sensor from being fastened together with the spark plug 3, and it is possible to prevent the occurrence of the tightening torque failure.

[0030]

As described above, according to the present invention, in the washer-type cylinder pressure sensor that is tightened together with the spark plug, by detecting the power spectrum of the resonance frequency of the sensor output, the sensor due to the defective tightening torque is detected. There is an effect that it is possible to diagnose the malfunction of the above, and to prevent the combustion state from being detected by using the sensor output when the tightening torque is in a defective state.

[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 a state of tightening torque diagnosis of the embodiment.

FIG. 4 is a block diagram showing a configuration of an automatic tightening device using tightening torque diagnosis control according to an embodiment.

FIG. 5 is a flowchart showing the control contents of the automatic tightening device.

[Explanation of symbols]

 1 Cylinder Head 2 Screw Hole 3 Spark Plug 4 Mounting Seat Surface 5 Cylinder Pressure Sensor 8 Cylinder 9 Engine Control Unit 10 Crank Angle Sensor

Claims (1)

[Claims] 1. A diagnostic device for a ring-shaped in-cylinder pressure sensor sandwiched between an ignition plug screwed into a cylinder head of an internal combustion engine and a mounting seat surface, wherein a predetermined resonance is generated from an output signal of the in-cylinder pressure sensor. A power spectrum detecting means for detecting a power spectrum of a frequency; and a sensor diagnosing means for judging an abnormality in the detecting function of the in-cylinder pressure sensor when the power spectrum detected by the power spectrum detecting means exceeds a predetermined value. An in-cylinder pressure sensor diagnostic device comprising: