JPH07332150A - Intra-cylinder pressure sensing device of engine - Google Patents

Abstract

PURPOSE:To sense the intra-cylinder pressure even in the noise-affected division by storing the sensing signal of an intra-cylinder pressure sensor immediately before and after the mask processing using a masking means, and presuming and setting the sensing signal in the specified masked period by means of interpolational calculation based upon the stored sensing signal. CONSTITUTION:A mask circuit 24 is furnished on the way of the output path of an intra-cylinder pressure sensor 5, and a noise mask signal is read. Judgement is made whether the situation is immediately before the start of the mask processing, and if at starting, the intra-cylinder pressure sensing signal at that time is A/D converted and read, and the A/D converted value is stored as the intra-cylinder pressure sensing value Ps. When the passed judgement is that the situation is at the end of the mask processing, the data Pe immediately after the end of mask processing i,s alike stored. Then the intra-cylinder pressure sensing signal during the period of mask processing is presumed through the linear interpolational calculation, and diagnosis etc., of the combusting condition is executed on the basis of the integral value of the intre-cylinder pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine in-cylinder pressure detecting device, and more specifically, it is possible to secure a desired detection result even during an ignition noise generation period while avoiding deterioration of in-cylinder pressure detection accuracy due to ignition noise. Regarding the device.

[0002]

2. Description of the Related Art As a method for grasping the combustion state of an engine, there is a method for detecting the pressure of combustion gas in a cylinder.
A cylinder pressure sensor as disclosed in Japanese Patent No. 049 is known. The cylinder pressure sensor disclosed in Japanese Utility Model Laid-Open No. 63-70049 is a stack of a ring-shaped piezoelectric element and an electrode, and has an ignition plug screwed into a cylinder head and a mounting seat surface of the ignition plug. It is sandwiched between and tightened together.
Then, the tightening load (seat pressure) of the sensor, which is tightened as a washer of the spark plug, increases or decreases as the pressure in the cylinder (cylinder pressure) acts on the spark plug, which causes the output of the piezoelectric element to burn. It changes according to the pressure (cylinder pressure).

[0003]

By the way, since the washer-type cylinder pressure sensor as described above is provided in the vicinity of the spark plug, it is affected by the ignition noise emitted from the spark plug to the surroundings, and the sensor output is affected. There is a problem in that it is difficult to maintain high detection accuracy of the in-cylinder pressure based on the above. As a method of eliminating the influence of the ignition noise, the detection signal of the sensor is masked during the period when the ignition noise is expected to affect, and the detection of the in-cylinder pressure based on the detection signal affected by the ignition noise is canceled. It is possible.

However, when the detection signal of the sensor is masked in the predetermined period as described above, when the detection result of the in-cylinder pressure is required in the section including the mask period (for example, the measurement of the cylinder filling efficiency). However, there is a problem in that the detection of the detection signal during the mask period causes an error in grasping the in-cylinder pressure state.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an in-cylinder pressure detecting device which can secure the detection result of the in-cylinder pressure even in a noise influence section while avoiding the influence of ignition noise. To do.

[0006]

Therefore, an in-cylinder pressure detecting device for an engine according to the invention of claim 1 is constructed as shown in FIG. In FIG. 1, the in-cylinder pressure sensor is a sensor that detects the in-cylinder pressure of the engine, and the masking unit masks the detection signal of the in-cylinder pressure sensor for a predetermined period.

On the other hand, the detection value storage means stores the detection signals of the in-cylinder pressure sensor immediately before and immediately after the mask processing by the mask means. Then, the interpolation calculation means estimates and sets the detection signal masked by the mask means in the predetermined period by interpolation calculation based on the detection signal stored in the detection value storage means.

In the detection device according to the second aspect of the present invention, the detection value storage means detects the timing immediately before and immediately after the mask processing based on the rate of change of the detection signal of the in-cylinder pressure sensor through the mask means. It was configured to do. In the detection device according to the third aspect of the present invention, the masking means is configured such that at least a predetermined time from ignition is a predetermined period for performing the masking process.

In the detection device according to the fourth aspect of the present invention, a predetermined section including at least the mask processing period by the masking means is set as an integration section, and the detection signal interpolated by the interpolation calculating means is integrated during the masking period. In the integration section other than the mask processing period, the detection signal of the in-cylinder pressure sensor via the mask means is directly integrated, and the integrated value is output as a parameter indicating the in-cylinder pressure of the engine (FIG. 1). It is configured to have a medium dotted line).

[0010]

According to the in-cylinder pressure detecting device for an engine of the first aspect of the present invention, the detection signal of the in-cylinder pressure sensor is masked for a predetermined period, but the detection signals immediately before and immediately after the masking process are stored. Then, the detection signal in the mask period is estimated by the interpolation calculation based on the stored detection signal. Therefore, even if the detection signal is lost by the mask processing, the detected value of the in-cylinder pressure can be finally obtained including the mask processing section.

In the detection device according to the second aspect of the present invention, when the detection signal of the in-cylinder pressure sensor is masked, the detection signal via the mask means changes abruptly at the start and end of the masking process. Therefore, the mask processing period is detected based on the rate of change of the detection signal after the mask processing. In the detection device according to the third aspect of the present invention, the influence of the ignition noise on the in-cylinder pressure detection can be eliminated by masking the detection signal at a predetermined time after ignition.

In the detecting device according to the fourth aspect of the present invention, the detection value of the in-cylinder pressure is integrated in a predetermined integration section, and the integrated value is output as a parameter indicating the in-cylinder pressure of the engine. When the period is included, the detection signal that has been interpolated is integrated during the mask processing period, and an integrated value commensurate with the actual in-cylinder pressure can be obtained even if the integration period includes the mask processing period. I did it.

[0013]

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 formed through a cylinder head 1 of an engine. A ring-shaped in-cylinder pressure sensor 5 is sandwiched between the spark plug 3 and the spark plug mounting seat surface 4 of the cylinder head 1 and fastened together.

Reference numeral 6 denotes a washer interposed between the in-cylinder pressure sensor 5 and the spark plug 3. In-cylinder pressure sensor 5
For example, a ring-shaped center electrode is used as the center, two piezoelectric piezoelectric elements are arranged above and below the center electrode, and an upper surface electrode and a lower surface electrode are sequentially laminated on the outer side of the center electrode. Covered with material and fixed together. The lead wire 7 is taken out from the center electrode through the resin material.

As described above, the in-cylinder pressure sensor 5 is tightened as a washer of the spark plug 3 and a predetermined tightening load is applied thereto, while the combustion pressure in the cylinder 8 acts on the spark plug 3 to cause the spark plug 3 to move. When the sensor load is pushed up, the sensor load decreases and the combustion pressure (in-cylinder pressure P) can be detected as a relative pressure by the decrease change of the sensor load based on the tightening load.

The metal pipe 9 has the outer peripheral portion of the in-cylinder pressure sensor 5 fitted and inserted into the opening at the lower end thereof, and extends to the base end side of the spark plug 3 and has a rubber at the open end of the spark plug insertion hole 10. It is inserted through the bush 11. And the lead wire 7
Is extended along the outer peripheral wall of the metal pipe 9 and is taken out to the outside through a through hole provided in the rubber bush 11.

On the other hand, an ignition unit 23 comprising an ignition coil and an ignition coil drive circuit (including a power transistor) for driving the ignition coil based on an ignition signal is provided. The ignition coil drive circuit controls the energization to the primary side of the ignition coil based on the ignition signal from the control unit 15 so that the high voltage generated on the secondary side when the energization is cut off is applied to the spark plug 3. Has become.

The ignition unit 23 may be directly attached to the head of the ignition plug 3 for each cylinder without a high tension cord. Further, a mask circuit 24 (mask means) is provided in the output path of the in-cylinder pressure sensor 5, and a detection signal via the mask circuit 24 is output to the control unit 15.

The mask circuit 24 includes the ignition unit.
The ignition signal supplied to 23 is distributed and supplied, and the ignition signal is influenced by masking the detection signal of the in-cylinder pressure sensor 5 at least for a predetermined time from ignition based on the ignition signal. It is possible to prevent the detection signal from being output to the control unit 15.

The mask circuit 24 may be incorporated in the control unit 15 or the ignition unit 23. The noise mask circuit 24 is specifically shown in FIG.
It is composed of a circuit as shown in. In FIG. 3, 31
Is a charge amplifier (feedback amplifier) for amplifying the sensor output, and a switching element 32 is provided in parallel with the feedback resistor R2 that determines the amplification factor of the charge amplifier 31 by the resistor R1. The switching element 32
Is controlled to be turned on / off based on the ignition signal (noise mask signal) delayed by the delay circuit 33.

When the ignition signal is at a high level, the power transistor 22 forming the ignition coil drive circuit 22.
This is a signal for turning on a. The energization to the primary side of the ignition coil 21 is started in synchronization with the rising of the ignition signal, and the energization to the primary side of the ignition coil 21 is cut off in synchronization with the falling of the ignition signal. At this time, the high voltage generated on the secondary side is supplied to the spark plug 3 to generate an ignition spark.

Since the delay circuit 33 delays the ignition signal, the switching element 32 is switched from OFF to ON after the rising of the ignition signal, and
ON → O after a delay (ignition) of the ignition signal
The FF is switched, whereby the switching element 32 is turned on and the amplification operation of the charge amplifier 31 is stopped for at least a predetermined time after ignition (interruption of energization to the primary side).

Here, so-called ignition noise is generated along with the interruption of the power supply to the primary side of the ignition coil 21, that is, the ignition operation.
This affects the output of the in-cylinder pressure sensor 5, but the amplification operation of the charge amplifier 31 is stopped by the switching element 32 for a predetermined time (predetermined period) from ignition, and as a result, Since the detection signal is masked (see FIG. 4), it is possible to prevent the sensor output affected by the ignition noise from being input to the control unit 15 and deteriorating the S / N ratio of the detection signal.

In the noise mask circuit 24 shown in FIG.
The in-cylinder pressure detection signal affected by ignition noise is masked by stopping the amplification operation, but the circuit configuration shown in FIG. 5 stops the output of the in-cylinder pressure detection signal affected by ignition noise. You may make it the structure made to let. Figure 5
The mask circuit 24 shown in, based on the noise mask signal generated in the delay circuit 33 based on the ignition signal as described above,
The output of the in-cylinder pressure sensor 5 is masked for at least a predetermined time from ignition, but here, the transistor 35 is ON / OFF controlled by the noise mask signal.
The sensor output line is selectively grounded by.

That is, when the transistor 35 grounds the output line of the in-cylinder pressure sensor 5 at least for a predetermined time from ignition based on the delay signal (mask signal) of the ignition signal output from the delay circuit 33, During this period, the output of the in-cylinder pressure detection signal is stopped, so that the detection signal affected by noise is masked.

An in-cylinder pressure detection signal masked at a predetermined time from ignition by the mask circuit 24 having the above-described configuration is input to the control unit 15, which controls the control unit 15 as shown in the flow charts of FIGS. 6 and 7. Process the detection signal. In this embodiment, the control unit 15 has the functions of the detected value storage means, the interpolation calculation means, and the in-cylinder pressure integration means, as shown in the flow charts of FIGS. 6 and 7.

In the flow chart of FIG. 6, first, in step 1 (denoted as S1 in the figure, the same applies hereinafter),
The noise mask signal in the mask circuit 24 is read. The noise mask signal read in step 1 may be a signal generated in the mask circuit 24, or a circuit having the same function as the delay circuit 33 provided in the mask circuit 24 may be provided in the control unit 15 to provide an ignition signal. It may be a signal originally generated based on the above.

In the next step 2, it is judged whether or not it is just before the start of the mask processing, and if it is the start time, the routine proceeds to step 3, where the in-cylinder pressure detection signal at that time is A / D converted and read, In the next step 4, the A / D conversion value is stored as the in-cylinder pressure detection value Ps immediately before the mask processing. On the other hand, if it is determined in step 2 that it is not the start time of the mask processing, the process proceeds to step 5, and it is determined whether it is the end time of the mask processing. When it is the end time, the in-cylinder pressure detection signal is A / D converted and read in step 6, and in the next step 7, the read in-cylinder pressure detection value is stored as the data Pe immediately after the mask processing is completed.

The detection value Ps immediately before the mask processing and the detection value Pe immediately after the mask processing thus stored are
Used in the flowchart of FIG. The flowchart of FIG. 7 shows a routine executed at every sampling period of the in-cylinder pressure P. First, at step 11, it is judged whether or not the noise mask signal is being generated (within the mask processing period).

If it is not within the mask processing period, the detection signal of the in-cylinder pressure sensor 5 is normally input to the control unit 15. Therefore, the process proceeds to step 12, where the in-cylinder pressure detection signal is A / D converted. Read. Meanwhile, step
When it is determined in 11 that the mask processing period is within, the process proceeds to step 13 and it is determined whether or not the mask processing period has ended.

When the mask processing is in progress, the process proceeds to step 14 and the number N of sampling timings within the mask processing period is counted. Also, step 13
When it is determined that the mask processing period has ended, the process proceeds to step 15, and the mask processing period is determined using the detection value Ps immediately before the mask processing and the detection value Pe immediately after the mask processing stored in the flowchart of FIG. The in-cylinder pressure detection signal inside is estimated by linear interpolation calculation.

Then, in the next step 16, the in-cylinder pressure detection signal at a time corresponding to each of N sampling timings in the mask processing period is obtained from the interpolation calculation result. That is, since the in-cylinder pressure detection signal is input to the control unit 15 via the mask circuit 24, the in-cylinder pressure detection signal is lost during the mask processing period, and the in-cylinder pressure P during the mask processing period can be known. Can not. Therefore, the detection signal Ps immediately before being masked and missing
And the detection signal Pe immediately after the end of the mask processing are stored, so that the detection signal Ps missing due to the mask processing is stored.
The in-cylinder pressure between Pe and Pe is predicted by interpolation calculation, and the detected value that would have been sampled when the mask processing is not performed is obtained.

In step 17, the sampling number N is reset to zero for the processing in the next mask processing period. In step 18, the in-cylinder pressure is integrated in a predetermined integration section including at least the mask processing period. Specifically, if it is not within the mask processing period, the step
While the in-cylinder pressure P A / D converted in 12 is integrated as it is, the detection signal of the in-cylinder pressure sensor 5 is masked by the mask circuit 24 during the mask processing period and is lost. The in-cylinder pressure P at the sampling timing within the mask processing period estimated in step 16 is integrated from the result of the linear interpolation calculation in step 15.

Then, the integrated value Pi is output as a parameter indicating the in-cylinder pressure state of the engine, and the integrated value P
Based on i, the combustion state of the engine is diagnosed and the charging efficiency is measured. According to the above configuration, in order to eliminate the influence of ignition noise, the detection signal of the in-cylinder pressure sensor 5 is masked in a predetermined period from ignition, and even if the in-cylinder pressure detection signal is missing in the predetermined period (mask processing period). Since the missing cylinder pressure detection signal is estimated and set by linear interpolation from the detection results immediately before and immediately after the mask processing period, it is possible to obtain the cylinder pressure detection signal in all strokes while avoiding the influence of ignition noise. Is possible.

Therefore, when the cylinder pressure detection value is integrated in the integration section including the mask processing period as described above and the cylinder filling efficiency is measured using the integration value, the measurement accuracy is improved by the mask processing. You can avoid getting worse. In the above embodiment, the mask processing period is detected based on the noise mask signal, and the in-cylinder pressure Ps immediately before the mask processing and the in-cylinder pressure Pe immediately after the mask processing are sampled and stored respectively. It is also possible to detect the mask processing period based on the in-cylinder pressure detection signal via the circuit 24, and such an embodiment is shown in the flowchart of FIG.

The flow chart of FIG. 8 shows a routine executed at every sampling cycle of the in-cylinder pressure. First, in step 21, the in-cylinder pressure detection signal inputted through the mask circuit 24 is A / D converted. Read. Then, in the next step 22, the deviation between the in-cylinder pressure P read this time and the in-cylinder pressure P _-1 read last time (change rate of the detection signal after the mask processing) is set as a reference for a preset increasing change side. Value + Δ
P and the reference value on the decreasing change side −ΔP.

That is, when the mask circuit 24 masks the in-cylinder pressure detection signal in a predetermined period from ignition (FIG. 4).
However, a sudden signal change that is not normally shown is shown at the start of the mask processing and at the end of the mask processing.
Therefore, by presetting the reference values + ΔP and −ΔP as change rates that do not normally exceed and only exceed at the start or end of the mask processing, the start time and end time of the mask processing can be set. It can be detected from the deviation (P-P- ₁ ).

In step 22, when it is shown that the in-cylinder pressure detection signal is decreasingly changed at the rate that the deviation (P-P- ₁ ) exceeds the reference value -.DELTA.P on the decreasing side, the actual masking process is started. It is estimated that the detection signal has dropped from the level of the detection signal corresponding to the in-cylinder pressure to the mask level. Then, the process proceeds to step 23, and the cylinder pressure P read last time is read.
_-1 is set and stored in Ps as the detection value immediately before the mask processing.

On the other hand, if it is shown in step 22 that the in-cylinder pressure detection signal is increasing and changed at the rate that the deviation (P-P _-1 ) exceeds the reference value + ΔP on the increasing side, it means that the mask processing is completed. It is estimated that the detection signal has increased from the mask level to the level of the detection signal corresponding to the actual in-cylinder pressure. Then, the routine proceeds to step 24, where the previously read in-cylinder pressure P ₋₁ is set and stored in Pe as the detection value immediately after the mask processing is completed.

When the detection value immediately after the mask processing is obtained, the routine proceeds to step 25, where the in-cylinder pressure detection signal during the mask processing period is stored as the detected values Ps, P.
Estimate by linear interpolation calculation based on e, step 26
Then, the in-cylinder pressure at N sampling times in the mask processing period is read from the estimation result by the interpolation calculation.

In the next step 27, the result of measuring the number of sampling times N within the mask processing period is reset to zero. If it is determined in step 22 that the in-cylinder pressure detection signal does not indicate a rapid change corresponding to the start or end time of the mask processing, the process proceeds to step 28 and the read in-cylinder pressure P is substantially zero. By determining whether or not there is, it is determined whether or not it is within the mask processing period.

When it is judged that the in-cylinder pressure P is substantially zero and is within the mask processing period, the routine proceeds to step 29,
The number N of sampling timings during the mask processing period is counted. Based on the counting result, in step 26, the in-cylinder pressure at N sampling times in the mask processing period is obtained from the interpolation calculation result.

On the other hand, if it is determined in step 28 that the in-cylinder pressure P is not zero, it is determined that it is not the mask processing period, and the routine proceeds to step 30, where the in-cylinder pressure P read this time is directly integrated. Further, for the in-cylinder pressure within the mask processing period, the value obtained in step 26 is adapted to be integrated in step 30, and as a result, within a predetermined integration section including the mask processing period, The detected values are integrated without omission.

As described above, if the start point and the end point of the mask processing are detected from the detection signal through the mask processing, the noise mask signal is read or the noise mask signal is generated independently. No need to
The missing part can be easily estimated by mask processing. still,
In the above embodiment, the interpolation calculation in the mask processing period is a linear interpolation. However, since the mask processing period is a relatively short time, even if the linear interpolation that is easy to calculate is performed,
This is because there is no problem in accuracy. Therefore, although the calculation becomes complicated, a configuration using circular interpolation or the like may be used.

[0045]

As described above, according to the in-cylinder pressure detecting device for an engine of the first aspect of the present invention, even if a part of the in-cylinder pressure detection signal is missing due to the mask processing, the detection signal of the missing part is estimated and set. Therefore, there is an effect that the in-cylinder pressure detection signal can be secured in the entire stroke.

According to the detecting device of the second aspect of the present invention, the mask processing period is detected based on the rate of change of the masked in-cylinder pressure detection signal. Therefore, the interpolation of the detection value within the mask processing period is performed. There is an effect that the estimation by can be performed easily. According to the detection device of the third aspect of the present invention, since the masking process is performed in a predetermined time from ignition, the effect of ignition noise can be avoided and the in-cylinder pressure detection value can be obtained without omission. is there.

According to the detecting device of the fourth aspect of the present invention, in the configuration in which the integrated value of the in-cylinder pressure detection value is output as the parameter indicating the in-cylinder pressure state of the engine, the estimation result by the interpolation calculation is integrated during the mask processing period. Since the configuration is made, there is an effect that a value corresponding to the actual in-cylinder pressure state can be obtained as the integrated value even when the integration section including the mask processing period is 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 circuit diagram showing a configuration example of a mask circuit.

FIG. 4 is a time chart showing a state of mask processing and interpolation calculation.

FIG. 5 is a circuit diagram showing another configuration example of a mask circuit.

FIG. 6 is a flowchart showing an in-cylinder pressure detection process of the first embodiment.

FIG. 7 is a flowchart showing an in-cylinder pressure detection process of the first embodiment.

FIG. 8 is a flowchart showing in-cylinder pressure detection processing of the second embodiment.

[Explanation of symbols]

 1 Cylinder Head 3 Spark Plug 5 Cylinder Pressure Sensor 15 Control Unit 21 Ignition Coil 22 Ignition Coil Drive Circuit 23 Ignition Unit 24 Mask Circuit 31 Charge Amplifier 32 Switching Element 33 Delay Circuit 35 Transistor

Claims (4)

[Claims] 1. An in-cylinder pressure sensor for detecting an in-cylinder pressure of an engine, a mask means for masking a detection signal of the in-cylinder pressure sensor for a predetermined period, and an in-cylinder pressure sensor immediately before and after mask processing by the mask means. A detection value storage unit that stores a detection signal; and an interpolation calculation unit that estimates and sets the detection signal in the predetermined period masked by the masking unit by an interpolation calculation based on the detection signal stored in the detection value storage unit. An in-cylinder pressure detection device of an engine configured to include. 2. The detection value storage means detects the timing immediately before and immediately after the mask processing based on the rate of change of the detection signal of the in-cylinder pressure sensor via the mask means. An in-cylinder pressure detection device for the engine described. 3. The in-cylinder pressure detecting device for the engine according to claim 1, wherein the masking means sets at least a predetermined time from ignition to a predetermined period for performing the masking process. 4. A predetermined section including at least the mask processing period by the masking unit is defined as an integration section, and the detection signal interpolated by the interpolation computing unit is integrated during the masking processing period, while the period other than the masking processing period is integrated. The in-cylinder pressure integrating means for integrating the detection signal of the in-cylinder pressure sensor via the mask means as it is in the integration section and outputting the integrated value as a parameter indicating the in-cylinder pressure of the engine is provided. The in-cylinder pressure detection device for the engine according to any one of 1, 2, and 3.