JP2002364450A - Pressure detecting method using piezoelectric type sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine control method which calculates an effective pressure index with accuracy based on a cylinder pressure detected by a seat-type pressure sensor and optimally controls a combustion state of the internal combustion engine based on the calculated effective pressure index. SOLUTION: A pressure integrating value A before top dead center calculated by integrating a cylinder pressure detection value is subtracted from a pressure integrating value B after top dead center calculated by integrating the cylinder pressure detection value detected in an ignition plug 11 into which a pressure sensor as the piezoelectric-type sensor is built. The subtracted value is divided by a first correction reference value C which is a difference in the cylinder pressure detection value between a two points of BTC2O deg. CA and BTDC9O deg. CA thereby calculating the effective pressure index An. Accordingly, an error of detected pressure is corrected, and the accurate effective pressure index An can be found. At a steady state of the internal combustion engine, an ignition timing, an air-fuel ratio, an EGR amount, and a fuel injection timing are controlled based on the effective pressure index An, whereby the combustion state is optimally controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure detecting method for detecting a pressure in a combustion chamber from an output of a piezoelectric sensor provided in an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine, as a method for determining the combustion state of the internal combustion engine, detecting knocking, improving fuel efficiency, normalizing exhaust gas, and the like, the pressure (in-cylinder pressure) in a combustion chamber is detected. There is a method of making a determination based on the in-cylinder pressure. Further, since the in-cylinder pressure changes according to the operation of the internal combustion engine, the indicated average effective pressure used as the power source of the internal combustion engine can be calculated based on the change in the in-cylinder pressure. In particular, by calculating the indicated mean effective pressure based on the change in the in-cylinder pressure in one entire combustion cycle, the indicated mean effective pressure accurately reflecting the combustion state of the internal combustion engine can be obtained.

[0003] As a method of detecting the in-cylinder pressure,
For example, it has been proposed to use a piezoelectric sensor having a piezoelectric element. Specifically, a pressure sensor is arranged on a mounting seat portion of a spark plug, and a variation in a tightening load when the spark plug is tightened to a cylinder head. Has proposed a seat-type pressure sensor for detecting an in-cylinder pressure (see Japanese Patent Application Laid-Open No. 6-290853).

[0004]

However, the seat-type pressure sensor has a structure in which the in-cylinder pressure is detected by a change in the tightening load of the spark plug. There is a problem that the output signal of the in-cylinder pressure (in-cylinder pressure detection value) greatly deviates from the actual pressure change. Therefore, when a seat-type pressure sensor is used, it is difficult to accurately detect the in-cylinder pressure for the entire combustion cycle including the operation of the intake and exhaust valves, and it is difficult to detect the in-cylinder pressure (in-cylinder pressure detection value) in the entire combustion cycle. )), It is difficult to accurately calculate the indicated mean effective pressure of the internal combustion engine calculated based on the above.

Here, in order to confirm the influence of noise due to the intake valve and the exhaust valve, FIG. 2 shows an output signal waveform (output waveform of the detected value of the in-cylinder pressure) from the seat type pressure sensor during operation of the internal combustion engine. Show. According to the output signal waveform shown in FIG.
In the seat type pressure sensor, when the intake valve is closed (INTAKE V
ALVE CLOSE) and when the exhaust valve is open (EXHAU
It can be seen that the output signal waveform (in-cylinder pressure) fluctuates in (ST VALVE OPEN).

[0006] The piezoelectric element constituting the pressure sensor includes:
It is also known that output characteristics change with temperature.
Here, a change in characteristics of the piezoelectric element with respect to a temperature change is shown in FIG.
0 (a). FIG. 10A shows the rate of change of the output charge of the pressure sensor due to temperature change, with the output charge of the pressure sensor at 20 ° C. being 0%. The horizontal axis represents temperature, and the vertical axis represents the rate of change. The rate of change is represented on a coordinate plane. From the characteristics of the pressure sensor shown in FIG. 10A, it is understood that the output charge (hereinafter, also referred to as an output signal) of the pressure sensor changes due to a temperature change.

It is known that the sensitivity of the piezoelectric elements constituting the pressure sensor slightly differs from individual to individual, and that the output signal has a slight error due to the individual difference. Further, since the electric charge output from the piezoelectric element is very small, the output signal of the piezoelectric element is generally used after being amplified by an amplifier circuit. For this reason, if an error that is within an allowable range for the piezoelectric element alone is amplified by the amplifier circuit, the error becomes a value that cannot be ignored.

FIG. 3 shows a measurement result of the measurement performed to confirm the presence or absence of an error in the output signal of the piezoelectric element.
(A). The measurement uses an amplifier circuit to detect the in-cylinder pressure using two seat-type pressure sensors (sensor 1 and sensor 2) of the same type and an in-cylinder insertion pressure sensor provided in a pressure conducting hole communicating with the combustion chamber. , By calculating the difference between the integral values of the in-cylinder pressure before and after top dead center. FIG. 3 (a)
In the following, the difference between the integral values will be referred to as an effective pressure index, and shows the relationship between the effective pressure index calculated using the in-cylinder insertion type pressure sensor and each effective pressure index calculated using the seat type pressure sensor. From the measurement results shown in FIG. 3A, it can be seen that the calculated effective pressure indices are different even for the same type of seat-type pressure sensor. This indicates that there is an error in the output signal (in-cylinder pressure detection value) due to the individual difference in the sensitivity of the piezoelectric element.

Further, the seat-type pressure sensor detects in-cylinder pressure by detecting a tightening load of the ignition plug.
If the tightening load at the time of mounting the spark plug is different, a change occurs in the change in the tightening load due to the change in the in-cylinder pressure. Even if a device for measuring the tightening load such as a torque wrench is used, it is practically difficult to strictly unify the tightening loads to such an extent that the torque does not affect the pressure detection of the seat-type pressure sensor. Therefore, the output characteristics from the seat-type pressure sensor are affected by individual differences in the tightening load of the ignition plug.

FIG. 10B shows the rate of change of the pressure detected by the seat type pressure sensor due to the change in the tightening torque.
FIG. 10B shows the relationship between the tightening torque and the output signal when the tightening torque is changed, assuming that the output signal of the seat-type pressure sensor when the tightening torque is 25 N · m is 100%. As shown in FIG. 10B, when the tightening torque decreases, the change rate decreases (output charge decreases), and when the tightening torque increases, the change rate increases (output charge increases). From this,
It can be seen that the output signal of the seat-type pressure sensor changes due to the change in the tightening torque.

As described above, the seat-type pressure sensor detects an in-cylinder pressure with high accuracy because the output signal (in-cylinder pressure detection value) includes an error due to individual differences such as temperature, sensitivity, and tightening torque. May not be possible. Therefore, it is difficult to accurately calculate the effective pressure index of the internal combustion engine based on the change in the in-cylinder pressure detected by the seat type pressure sensor.

The change in the tightening load due to the in-cylinder pressure is caused by the combustion gas pressing the spark plug. At the same time, the combustion gas enters the gap existing between the screw portion of the metal shell of the ignition plug and the thread portion of the cylinder head. Therefore, even if the actual in-cylinder pressure is reduced, the combustion gas existing in the gap of the screw portion is reduced. Residual pressure is generated due to the outflow delay.

FIG. 4 shows the results of measurements performed to confirm that the in-cylinder pressure detected by the seat-type pressure sensor is affected by residual pressure. The measurement was performed by detecting the in-cylinder pressure in the same combustion chamber by using a seat-type pressure sensor and an in-cylinder insertion type pressure sensor provided in a pressure guide hole communicating with the combustion chamber. In FIG. 4A, the in-cylinder pressure detected by the seat-type pressure sensor is indicated by a solid line, and the in-cylinder pressure detected by the in-cylinder insertion type pressure sensor is indicated by a solid line on a coordinate plane in which the horizontal axis is the crank angle and the vertical axis is the in-cylinder pressure. Is indicated by a dotted line, and the measurement results are shown. From the measurement results shown in FIG. 4 (a), each pressure sensor detects the same value of the in-cylinder pressure until the peak value of the in-cylinder pressure is reached. The value of the in-cylinder pressure detected by the seat-type pressure sensor is larger than the value of the in-cylinder pressure detected by the insertion-type pressure sensor. In FIG. 4B, the vertical axis represents the in-cylinder pressure detected by the seat-type pressure sensor, and the horizontal axis represents the in-cylinder pressure detected by the in-cylinder insertion pressure sensor. 3 shows a Lissajous waveform. From the result of FIG.
It can be seen that the value of the in-cylinder pressure detected by the seat-type pressure sensor is larger than the value of the in-cylinder pressure detected by the in-cylinder insertion type pressure sensor.

From the measurement results, the top dead center (hereinafter, TDC)
After that, in the seat type pressure sensor, a pressure (residual pressure) higher than the in-cylinder pressure detected by the in-cylinder insertion type pressure sensor
It can be seen that is detected. Due to the influence of the residual pressure, the in-cylinder pressure detected by the seat-type pressure sensor after the combustion of the air-fuel mixture decreases more gently than the in-cylinder pressure detected by the in-cylinder insertion pressure sensor. It becomes difficult to accurately detect the internal pressure.

Therefore, the effective pressure index calculated on the basis of the in-cylinder pressure detected by the seat type pressure sensor is determined by the following equation.
Errors may occur due to noise caused by the exhaust valve, individual differences due to the tightening torque and temperature of the spark plug, and the effects of residual pressure in the screw portion. The error due to the influence of individual differences and residual pressure is determined when the seat-type pressure sensor is actually attached to the internal combustion engine body. It is impossible to measure and set a correction reference value to perform correction. It is also possible to measure the error when the seat-type pressure sensor is attached, and to correct the error using a correction reference value set according to the error.However, the state of the operating internal combustion engine always changes. Since the output characteristics of the seat-type pressure sensor may change over time,
There is a problem that errors due to aging cannot be corrected.

The present invention has been made in view of such a problem, and uses a high-precision piezoelectric pressure sensor even when the piezoelectric element is affected by individual differences due to temperature and the like and deterioration due to aging. An object of the present invention is to provide a pressure detection method capable of performing pressure detection.

[0017]

According to a first aspect of the present invention, there is provided a piezoelectric sensor having a piezoelectric element, which outputs an in-cylinder pressure detection value corresponding to an in-cylinder pressure of an internal combustion engine. A pressure detection method using a piezoelectric sensor as described above, wherein the difference between the detected values of the in-cylinder pressure at two different points in time between the detected values of the in-cylinder pressure obtained by the piezoelectric sensor from before the intake valve closes to before the ignition timing. Is calculated as a correction reference value for each combustion cycle, while the combustion state of the internal combustion engine is determined based on the in-cylinder pressure detection value obtained from the piezoelectric sensor at least during the period from when the crank angle reaches the top dead center to when the exhaust valve opens. Is calculated for each combustion cycle, and the control pressure value is corrected by the correction reference value in the combustion cycle.

Further, in the pressure detecting method using the piezoelectric sensor according to the first aspect of the present invention, as described in the second aspect, after the intake valve is closed until the crank angle reaches the top dead center. A pressure integral value before the top dead center is calculated by integrating the above-described in-cylinder pressure detection value within a certain period, and the cylinder within a certain period determined from when the crank angle reaches the top dead center to when the exhaust valve is opened. The pressure integral value after top dead center is calculated by integrating the internal pressure detection value, and the effective pressure index calculated for each combustion cycle as the difference between the pressure integral value after top dead center and the pressure integral value before top dead center is: A control pressure value may be used.

Further, in the pressure detecting method using the piezoelectric sensor according to the second aspect, the integrated value before the top dead center is calculated by setting the integral value before the top dead center to 90% before the top dead center. °
It is calculated by integrating the in-cylinder pressure signal during the period from CA to the top dead center, and the integrated value after the top dead center reaches 90 ° CA after the crank angle reaches the top dead center after the crank angle reaches the top dead center. The effective pressure index calculated by integrating the in-cylinder pressure signal within the period up to and calculating the difference between the pressure integrated value after top dead center and the pressure integrated value after top dead center for each combustion cycle is the control pressure. It should be a value.

Further, in the pressure detecting method using the piezoelectric sensor according to any one of claims 1 to 3, as described in claim 4, the piezoelectric sensor has a built-in piezoelectric element. It is preferable that the pressure sensor is provided on a mounting seat of a spark plug mounted on the internal combustion engine, and outputs a detected value of the in-cylinder pressure based on a change in a tightening load of the spark plug.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing a configuration of an internal combustion engine to which the internal combustion engine control method of the present invention is applied.

The components other than the control device (ECU) 19, the EGR valve 17, and the crankshaft 47 are provided for each cylinder of the internal combustion engine, but FIG. 1 shows one cylinder for easy understanding of the drawing. Only represents. As shown in FIG. 1, the ignition device for an internal combustion engine according to the present embodiment generates a spark discharge for burning an air-fuel mixture and detects a pressure (in-cylinder pressure) of a combustion chamber 31 from a change in a tightening load. And a igniter 13 for generating a high voltage for ignition for generating a spark discharge in the spark plug 11.
A fuel injection valve (injector) 15 for injecting fuel to generate an air-fuel mixture; and an EGR valve 17 for circulating exhaust gas from an exhaust port 35 to an intake port 33.
And outputs a command signal to the igniter 13, the fuel injection valve 15, and the EGR valve 17 in accordance with a command from the outside,
A control device (ECU) 19 comprising a microcomputer for controlling the operation of the internal combustion engine 1 is provided. Since the internal combustion engine of this embodiment is a direct injection type internal combustion engine, the fuel injection valve 15 is provided so as to directly inject fuel into the combustion chamber.

The ignition plug 11 has a structure as shown in FIG. 13, and includes a pressure sensor 1 inside a metal shell 11a.
1b (not shown), detects the in-cylinder pressure by detecting a change in tightening load, and outputs the output cable 11c.
Output an electric charge corresponding to the in-cylinder pressure. Since the output charge of the pressure sensor 11b is very small, for example, the pressure signal amplified by the amplifier circuit 61 as shown in FIG. FIG.
Here, illustration of the amplifier circuit is omitted. Further, the ignition plug 11 receives the ignition high voltage supplied from the igniter 13 at the terminal portion 11f, and the central electrode 11e and the outer electrode 1
1d, spark discharge is generated.

The internal combustion engine 1 is a cylinder (cylinder).
A piston 41 reciprocating inside 43 is provided with a connecting rod 45.
The power is transmitted to the outside of the internal combustion engine 1 by rotating the crankshaft 47 via the. Further, since the internal combustion engine 1 is a direct injection type, when the piston 41 descends in the intake stroke, the intake valve 37 opens to feed air into the combustion chamber 31, and when the piston 41 rises in the compression stroke, fuel is injected. The injection valve 15 injects fuel into the combustion chamber 31 to generate an air-fuel mixture. The fuel injection timing and fuel injection amount at this time are determined by EC
It is set by a control process described later executed in U19.

In the combustion process, a spark discharge is generated by the spark plug 11 before the piston 41 reaches the top dead center, and the air-fuel mixture is burned, so that the pressure (in-cylinder pressure) in the combustion chamber is increased to increase the piston pressure. By lowering 41, the power of the internal combustion engine is generated. Subsequently, when the piston 41 rises in the exhaust stroke, the exhaust valve 39 is opened to exhaust the exhaust gas inside the combustion chamber 31 to the exhaust port 35.
Then, the compression stroke is performed, and the process of shifting to the next combustion cycle is repeated, whereby the operation of the internal combustion engine is performed.

The operation of the internal combustion engine is controlled by the ECU 19
The ignition timing control, the air-fuel ratio control (fuel injection amount control), the EGR
The control and the fuel injection timing control will be described. In addition,
The control device 19 separately performs an intake air amount (intake pipe pressure), a rotation speed,
An operating state detection process is performed to detect the operating state of each part of the engine, such as the throttle opening, cooling water temperature, intake air temperature, and the like.

First, the ignition timing control processing of this embodiment will be described with reference to the flowchart shown in FIG. This ignition timing control process is started when the operation of the internal combustion engine is started, and is executed until the operation of the internal combustion engine is stopped. As shown in FIG. 6, when the ignition timing control process is started, first, in S110 (S indicates a step), the engine speed and the throttle opening detected in the separately executed operation state detection process are measured. I do. Subsequently, in S120, it is determined whether or not the operation state of the internal combustion engine is in a stable state (whether the internal combustion engine is within specified conditions).
It is determined whether the fluctuations of the engine speed and the throttle opening measured at 110 converge within a certain range. If an affirmative determination is made in S120, the process proceeds to S140, and if a negative determination is made in S120, the process proceeds to S130.

At S120, if the operating state of the internal combustion engine has changed, a negative determination is made in S120 and S1
Move to 30. In S130, the ignition timing Tig is set by reading the ignition timing Tig from a preset map based on the engine speed and the throttle opening measured in S110, and the initial FLG is reset (RESET). . The initial FLG is an index indicating that an initial value for comparing the effective pressure index An has been calculated. When the process of S130 is performed, the process proceeds to S240.

Then, in S240, ignition is performed at the latest ignition timing Tig calculated last, and when ignition is performed, the process proceeds to S110. If the operation state of the internal combustion engine is stable when the process proceeds to S120, an affirmative determination is made in S120, and the process proceeds to S140. In S140, it is determined whether or not the initial FLG is set (SET). If the determination is affirmative, the process proceeds to S160, and if the negative determination is made, the process proceeds to S150. At this time, if the initial FLG has been reset, a negative determination is made in S140, and S1
Move to 50.

In S150, first, the ignition timing Tig is set by reading the ignition timing Tig from a preset map based on the engine speed and the throttle opening measured in S110. A crank angle of 90 ° CA (B) is stored in a storage unit (not shown) in which the combustion pressure signal detected by the pressure sensor 11b of the ignition plug 11 is stored.
TDC 90 ° CA) to 270 ° CA (ATDC 90 °)
The combustion pressure signal (in-cylinder pressure) up to CA) is fetched, and the effective pressure index An is calculated using the fetched in-cylinder pressure.

Here, to calculate the effective pressure index An, first, of the captured combustion pressure signal (in-cylinder pressure), the crank angle from 90 ° CA (BTDC 90 ° CA) to the top dead center (T
DC), the in-cylinder pressure during the period of
The pressure integration value A before the top dead center is obtained by integrating the values for each A. Similarly, using the taken in-cylinder pressure, the in-cylinder pressure during the period in which the crank angle moves from the top dead center (TDC) to 270 ° CA (ATDC 90 ° CA) is integrated for each crank angle 1 ° CA. The post-point pressure integral value B is obtained. Further, a difference between the in-cylinder pressure when the crank angle is 160 ° CA (BTDC 20 ° CA) and the in-cylinder pressure when the crank angle is 90 ° CA (BTDC 90 ° CA) is obtained and set as the first correction reference value C.

The cumulative interval of the in-cylinder pressure is 1 ° crank angle.
The number of data of the in-cylinder pressure can be increased by shortening the integration interval without limiting to each CA, and a more accurate effective pressure index An can be calculated. Conversely, by increasing the integration interval, the processing load on the ECU 19 can be reduced, but at the same time, the number of data of the in-cylinder pressure to be integrated decreases, and the accuracy of the effective pressure index An decreases. . Therefore, the integration interval may be set to be long enough to collect at least the number of data required for calculating the effective pressure index An, and set short enough to prevent the processing load of the ECU 19 from becoming abnormally high.

Further, in this step, it is determined whether or not the combustion cycle at this time is a fuel cut (fuel cut-off). If not, the value of the effective pressure index at the time of the fuel cut is stored. The obtained second correction reference value D is taken in. Then, after dividing the value obtained by subtracting the pressure integrated value A before top dead center A from the pressure integrated value after top dead center B from the pressure integrated value after top dead center B according to the calculation formula described in Expression 1, the effective pressure index An is divided by a first correction reference value C. It is calculated by subtracting the second correction reference value D.

[0034]

## EQU1 ## An = {(BA) / C} -D

If the combustion cycle at this time is fuel cutoff, the second correction reference value D is not subtracted in Equation 1 but the pressure integral before top dead center is calculated from the pressure integrated value B after top dead center. A value obtained by dividing the value obtained by subtracting the value A by the first correction reference value C is calculated as the effective pressure index An,
This effective pressure index An is substituted for the second correction reference value D and stored.

Further, in S150, the value of the calculated effective pressure index An is substituted for the previous effective pressure index An-1, and the ignition timing Tig is updated to a value advanced by a predetermined advance amount Ta. And set the initial FLG (SE
T). When the processing of S150 is performed in this manner, S2
Move to 40.

In S240, ignition is performed at the last calculated ignition timing Tig.
Move to 10. In addition, when the process proceeds to S140, if the initial FLG is set, an affirmative determination is made in S140, and the process proceeds to S160. In S160, first, the crank angle is set to 90 from a storage unit (not shown) in which the combustion pressure signal detected by the pressure sensor 11b of the ignition plug 11 is stored.
° CA (BTDC90 ° CA) to 270 ° CA (AT
A combustion pressure signal (in-cylinder pressure) up to DC 90 ° CA) is fetched, and an effective pressure index An is calculated using the fetched in-cylinder pressure. The calculation method of the effective pressure index An is the same as the calculation method in the process of S150.

At S170, the latest (n-th) effective pressure index An is set to the previous (n-1) th effective pressure index An-
It is determined whether or not the value is greater than 1. If an affirmative determination is made, the process proceeds to S180, and if a negative determination is made, the process proceeds to S210. When shifting to S170, the latest effective pressure index An
Is larger than the previous effective pressure index An-1, S17
If the determination is 0, the process proceeds to S180. In S180, the value of the latest effective pressure index An is changed to the previous effective pressure index An.
The ignition timing Tig is updated to a value advanced by a predetermined advance amount Ta.

At S190, it is determined whether or not the value of the ignition timing Tig updated at S180 is greater than an advance limit ignition timing TLa predetermined as an advance limit value of the ignition timing. If so, the process proceeds to S200, and if a negative determination is made, the process proceeds to S240. At this time,
If the ignition timing Tig is greater than the advance limit ignition timing TLa, an affirmative determination is made in S190 and the process proceeds to S200. In S200, the value of the advance limit ignition timing TLa is substituted for the ignition timing Tig. This prevents the ignition timing from being excessively advanced and the operating state of the internal combustion engine from becoming unstable. When the processing of S200 is performed, S
Move to 240.

When the process proceeds to S190, the ignition timing Tig
Is less than or equal to the advance limit ignition timing TLa, S19
If the determination is 0, the process proceeds to S240.
Finally, ignition is performed at the calculated ignition timing Tig, and when ignition is performed, the process proceeds to S110.

If the latest effective pressure index An is less than or equal to the previous effective pressure index An-1 when the process proceeds to S170, a negative determination is made in S170 and the process proceeds to S210. S
At 210, the latest effective pressure index An is substituted into the previous effective pressure index An-1, and the ignition timing Tig is updated to a value delayed by a predetermined retard amount Tr.

At S220, it is determined whether or not the value of the ignition timing Tig updated at S210 is smaller than a retard limit ignition timing TLr predetermined as a retard limit value of the ignition timing. If so, the process proceeds to S230, and if a negative determination is made, the process proceeds to S240. At this time,
If the ignition timing Tig is smaller than the retard limit ignition timing TLr, an affirmative determination is made in S220, and the routine proceeds to S230, where the value of the retard limit ignition timing TLr is substituted for the ignition timing Tig. This prevents the ignition timing from being excessively retarded and the operating state of the internal combustion engine from becoming unstable. When the process of S230 is performed, S
Move to 240.

When shifting to S220, the ignition timing Tig
Is greater than or equal to the retard limit ignition timing TLr, S22
If the determination is 0, the process proceeds to S240.
Finally, ignition is performed at the calculated ignition timing Tig, and when ignition is performed, the process proceeds to S110.

As described above, in this ignition timing control processing, S
When ignition is performed at 240, the process proceeds to S110, and the above processing is repeatedly executed to update the ignition timing Tig based on the effective pressure index An and control the ignition timing Tig. As described above, in the present ignition timing control processing,
When the operating state is changing, the ignition timing Tig is controlled based on the engine speed and the throttle opening. When the operating state is stable, the ignition timing Tig set based on the engine speed and the throttle opening is set as an initial value, and based on a change in the effective pressure index An caused by changing the ignition timing Tig. The ignition timing Tig is controlled by determining the combustion state of the internal combustion engine.

That is, after the ignition timing Tig is advanced in S150, the effective pressure index An calculated in S160 is calculated.
Is larger than the effective pressure index An-1 calculated before the advance is made (when a positive determination is made in S170), it can be determined that the combustion state has become good. For this reason,
In the following S180, the next ignition timing Tig is further advanced, so that the combustion state in the next ignition is further improved.

Conversely, after the ignition timing Tig is advanced in S150, the effective pressure index An calculated in S160 is calculated.
Is less than or equal to the effective pressure index An-1 calculated before the advance (when a negative determination is made in S170), it can be determined that the combustion state has become defective. Therefore, the following S
By retarding the next ignition timing Tig at 210,
In the next ignition, the combustion state is improved.

Then, while the operation state of the internal combustion engine is stable, S110, S120, S140, S1
Steps S60 to S240 are repeatedly executed,
The ignition timing Tig is controlled to an optimal value based on the effective pressure index An. Thereby, MBT (Minimum SparkAd) which is the ignition timing at which the efficiency of the internal combustion engine is the best.
It becomes possible to operate the internal combustion engine by setting the ignition timing to "vance for best torque".

In the present embodiment, the advance amount Ta and the retard amount Tr are set to fixed values set in advance, but may be set to, for example, variable values set in accordance with the driving state.
Further, by setting the retard amount Tr to a value larger than the advance amount Ta, it is possible to quickly avoid an unstable combustion state. Further, the advance limit ignition timing TLa and the retard limit ignition timing TLr are also, for example,
It may be a variable value set according to the operation state.

In addition, the process of calculating the effective pressure index An without subtracting the second correction reference value D in Equation 1 and substituting the effective pressure index An for the second correction reference value D and storing the same is as follows. It is not limited to the time of cut (fuel cutoff), and may be performed when a specific engine condition under which the residual pressure of the in-cylinder pressure can be detected during misfire operation.

Next, the air-fuel ratio control processing of this embodiment will be described with reference to the flowchart shown in FIG. This air-fuel ratio control process is started when the operation of the internal combustion engine is started, and is executed until the operation of the internal combustion engine is stopped.
Further, since the air-fuel ratio represents the ratio of fuel and air forming the air-fuel mixture, in the internal combustion engine of the present embodiment, the air-fuel ratio control is performed by controlling the fuel injection amount.

As shown in FIG. 7, when the air-fuel ratio control process is started, first in S310 (S represents a step),
The engine speed and the throttle opening detected in the operation state detection processing executed separately are measured. Following, S3
At 20, it is determined whether or not the operating state of the internal combustion engine is in a stable state (whether or not it is within specified conditions). Specifically, the fluctuations in the engine speed and the throttle opening measured in S310 are determined. Are converged within a certain range. If an affirmative determination is made in S320, S3
The process proceeds to S40, and if a negative determination is made in S320, the process proceeds to S330.

If the operation state of the internal combustion engine has changed at the time of shifting to S320, a negative determination is made in S320 and S3
Move to 30. In S330, the fuel injection amount Fin is set by reading the fuel injection amount Fin from a preset map based on the engine speed and the throttle opening measured in S310, and further, the initial FLG is reset (RESET). ) And an initial S calculation counter SPCNT
Clear The initial FLG is an index indicating that an initial value for comparing the effective pressure index An has been calculated, and the initial S calculation counter SPCNT has an effective pressure index A
This is a counter for counting the number of data for calculating the standard deviation and the average of n. When the process of S330 is performed, the process proceeds to S460.

Then, in S460, fuel injection is performed with the latest fuel injection amount Fin calculated last, and when fuel injection is performed, the process proceeds to S310. Further, when the operation state of the internal combustion engine is stable when the process proceeds to S320, S
An affirmative determination is made in 320, and the flow proceeds to S340. S340
Then, it is determined whether or not the initial FLG is set (SET). If the determination is affirmative, the process shifts to S380,
If a negative determination is made, the process proceeds to S350. At this time, if the initial FLG has been reset, a negative determination is made in S340, and the process proceeds to S350.

In step S350, the fuel injection amount Fin is set by reading the fuel injection amount Fin from a preset map based on the engine speed and the throttle opening measured in step S310. And the spark plug 1
The storage unit (not shown) in which the combustion pressure signal detected by the first pressure sensor 11b is stored has a crank angle of 90 ° CA.
(BTDC 90 ° CA) to 270 ° CA (ATDC9
The combustion pressure signal (in-cylinder pressure) up to 0 ° CA) is taken in, and an effective pressure index An is calculated using the taken-in cylinder pressure. In addition,
The calculation method of the effective pressure index An is the same as the calculation method in the processing in S150 of the above-described ignition timing control processing.

Then, the standard deviation and the average of the latest N number of effective S indices An calculated during the execution of the air-fuel ratio control process are calculated, and the standard deviation is divided by the average. Is set as the deviation / average S. At this time, the formula of Equation 2 is used to calculate the standard deviation, and the formula of Equation 3 is used to calculate the average.

[0056]

(Equation 2)

[0057]

(Equation 3)

If the number of the effective pressure indices An is less than the number N of times of the initial S calculation, the standard deviation and the average are not calculated. Further, in S350, the initial S calculation counter SPCNT is updated by adding 1 to the initial S calculation counter SPCNT.

At S360, an initial S calculation counter S
It is determined whether or not PCNT is equal to or greater than the initial S calculation count N. If the determination is affirmative, the process proceeds to S370, and if the determination is negative, the process proceeds to S460. At this time, if the initial S calculation counter SPCNT is smaller than the initial S calculation count N, a negative determination is made in S360 and the process proceeds to S460.
Then, in S460, the last calculated fuel injection amount F
in, fuel injection is performed, and when fuel injection is performed, S31
Move to 0.

If the initial S calculation counter SPCNT is equal to or more than the initial S calculation number N when the process proceeds to S360, the affirmative determination is made in S360, and the process proceeds to S370.
Then, in S370, the initial FLG is set. S3
If the process of 70 is performed or if the determination in S340 is affirmative, the process proceeds to S380, in which the combustion pressure signal detected by the pressure sensor 11b of the ignition plug 11 is stored (not shown). From the storage unit, the crank angle is changed from 90 ° CA (BTDC 90 ° CA) to 270 °
The combustion pressure signal (in-cylinder pressure) up to CA (ATDC 90 ° CA) is fetched, and the effective pressure index An is calculated using the fetched in-cylinder pressure by the same calculation method as the process in S350. Then, similarly to the case where the calculation is performed in S350, the standard deviation and the average of the latest N effective number of effective S indices An calculated during the execution of the present air-fuel ratio control process are calculated, and the standard deviation is calculated. Is set as deviation / mean S.

At S390, it is determined whether or not the deviation / average S calculated at S380 is equal to or less than a lean limit determination value LL preset as a lean limit of the air-fuel ratio. The process proceeds to S430 if a negative determination is made. At this time, if the deviation / average S is equal to or less than the lean limit determination value LL, an affirmative determination is made in S390, and the process proceeds to S400. In S400, the fuel injection amount Fin is updated to a value reduced by a predetermined fuel reduction amount Fa.

At S410, it is determined whether or not the value of the fuel injection amount Fin updated at S400 is smaller than an injection fuel reduction limit FLa predetermined as a lean limit value of the fuel injection amount. If so, the process proceeds to S420, and if a negative determination is made, the process proceeds to S460. At this time, if the fuel injection amount Fin is smaller than the injection fuel reduction limit FLa, an affirmative determination is made in S410 and the process proceeds to S420. In S420, the value of the injection fuel reduction limit FLa is substituted for the fuel injection amount Fin. This prevents the fuel injection amount from being excessively reduced, thereby preventing the operation state of the internal combustion engine from becoming unstable. After the process of S420 is performed, the process proceeds to S460.

If the fuel injection amount Fin is equal to or greater than the injection fuel reduction limit FLa when the process proceeds to S410, a negative determination is made in S410 and the process proceeds to S460.
At 60, the fuel injection is performed with the fuel injection amount Fin calculated last, and when the fuel injection is performed, the process proceeds to S310.

If the deviation / average S is larger than the lean limit determination value LL when the process proceeds to S390,
A negative determination is made in 390, and the flow shifts to S430. S430
Then, the fuel injection amount Fin is changed to a predetermined fuel increase amount F.
Update to a value increased by b.

At S440, it is determined whether or not the value of the fuel injection amount Fin updated at S430 is larger than a fuel injection amount increase limit FLb predetermined as a fuel injection amount increase limit value. If so, the flow shifts to S450, and if negative, the flow shifts to S460. At this time, if the fuel injection amount Fin is larger than the injection fuel increase limit FLb, an affirmative determination is made in S440 and the process proceeds to S450. In S450, the value of the injection fuel increase limit FLb is substituted for the fuel injection amount Fin. This prevents the amount of fuel injection from being excessively increased and the operating state of the internal combustion engine from becoming unstable. When the process in S450 is performed, the process proceeds to S460.

When the fuel injection amount Fin is equal to or less than the injection fuel increase limit FLb at the time of shifting to S440, a negative determination is made in S440, and the process shifts to S460.
At 60, the fuel injection is performed with the fuel injection amount Fin calculated last, and when the fuel injection is performed, the process proceeds to S310.

As described above, in the present air-fuel ratio control process, S4
When the fuel injection is performed at 60, the process shifts to S310, and the above processing is repeatedly executed, whereby the fuel injection amount Fin is determined based on the value of the deviation / average S calculated from the standard deviation and the average of the effective pressure index An. The fuel injection amount Fin is updated and updated.

The standard deviation of the effective pressure index An is a scale indicating the spread of the calculated effective pressure index An.
The smaller this value is, the smaller the dispersion of the calculated effective pressure index An is, indicating that the combustion state is stable. Conversely, the larger this value is, the larger the dispersion of the calculated effective pressure index An is, the larger the combustion state is. Is unstable.

Further, the standardized deviation / average S of the effective pressure index An is divided by the average of the effective pressure index An.
By determining the combustion state of the internal combustion engine by comparing the determination value with the determination value, it is not necessary to update the determination value according to the operating state, and a constant value can be used as the determination value.

As described above, in the present air-fuel ratio control process, when the operating state is changing, the fuel injection amount Fin is controlled based on the engine speed and the throttle opening. When the operating state is stable, the standard deviation of the effective pressure index An by changing the fuel injection amount Fin is set as an initial value with the fuel injection amount Fin set based on the engine speed and the throttle opening. , The combustion state of the internal combustion engine is determined, and the fuel injection amount Fin is controlled.

That is, when the deviation / average S calculated in S380 is equal to or less than the lean limit determination value LL (S3
When the determination is affirmative at 90), it can be determined that the combustion state is stable. Therefore, in the following S400, the fuel consumption of the internal combustion engine is improved by reducing the next fuel injection amount Fin (increase the air-fuel ratio).

When the deviation / average S calculated in S380 is larger than the lean limit judgment value LL (S3
When a negative determination is made at 90), it can be determined that the combustion state is unstable. Therefore, in the next S430, the fuel state of the internal combustion engine is stabilized by increasing the next fuel injection amount Fin (lowering the air-fuel ratio).

Then, while the operation state of the internal combustion engine is stable, S310, S320, S340, S3
Steps from 80 to S460 are repeatedly executed, and the fuel injection amount Fin is controlled to an optimum value based on the standard deviation of the effective pressure index An. As a result, the internal combustion engine can be operated at the air-fuel ratio (lean limit) at which the air-fuel mixture becomes the thinnest.

In calculating the average of the effective pressure index An,
Equation 4 may be used.

[0075]

(Equation 4)

When calculating the average value, it is necessary to store n pieces of data (effective pressure index An) for the calculation using the equation (3). Since the average can be calculated from the two data of the average value and the effective pressure index An up to the previous time, the memory capacity can be saved.

In the present embodiment, the fuel reduction amount Fa and the fuel increase amount Fb are fixed values set in advance, but may be variable values set in accordance with the operation state, for example. Further, by setting the fuel increase amount Fb to a value larger than the fuel decrease amount Fa, it is possible to quickly avoid an unstable combustion state. Further, the injection fuel reduction limit FLa and the injection fuel increase limit FLb may be, for example, variable values set in accordance with the operation state.

Next, the EGR amount control processing of this embodiment will be described with reference to the flowchart shown in FIG. This EGR amount control process is started and started when the operation of the internal combustion engine is started, and is executed until the operation of the internal combustion engine is stopped. In addition, since the flow of the EGR amount control process is basically the same as that of the air-fuel ratio control process, steps having the same processing contents are denoted by the same step numbers, and a flowchart is shown. The EGR amount control process will be described below, focusing on portions different from those described above.

First, in S530 and S550 of the EGR amount control processing corresponding to S330 and S350 in which the fuel injection amount Fin was read in the air-fuel ratio control processing, S3
Based on the engine speed and the throttle opening measured at 10, the EGR amount Egr is obtained from a preset map.
Is read to set the EGR amount Egr. Also,
When the processing in S530 is performed, the flow shifts to S660.

At S590 corresponding to S390, the deviation / average S calculated at S380 is equal to the EGR amount limit determination value EL set in advance as the EGR amount increase limit.
It is determined whether or not the following is true.
The process proceeds to S600, and if a negative determination is made, the process proceeds to S630. In addition, from S400 to S46 in the air-fuel ratio control process.
0 is from S600 to S660 in the EGR amount control process.
Corresponding to

When the process proceeds to S590, if the deviation / average S is equal to or less than the EGR amount limit determination value EL, the process proceeds to S590.
Is affirmatively determined, and the routine goes to S600. In S600,
The EGR amount Egr is updated to a value increased by a predetermined EGR increase amount Ea. In subsequent S610, the value of the EGR amount Egr updated in S600 is equal to the EGR amount increase limit EL which is predetermined as the increase limit value of the EGR amount Egr.
It is determined whether it is larger than a. If the determination is affirmative, the process proceeds to S620, and if the determination is negative, the process proceeds to S660. At this time, if the EGR amount Egr is larger than the EGR amount increase limit ELa, an affirmative determination is made in S610, and
The process shifts to 620, and in S620, the value of the EGR amount increase limit ELa is substituted into the EGR amount Egr. When the process in S620 is performed, the process proceeds to S660.

If the EGR amount Egr is equal to or less than the EGR amount increase limit ELa when the process proceeds to S610,
A negative determination is made in S610, the process proceeds to S660, and S660
Then, the EGR control operation is performed with the last calculated EGR amount Egr, and when the EGR control operation is performed, the process proceeds to S310.

When the flow shifts to S590, if the deviation / average S is larger than the EGR amount limit determination value EL,
A negative determination is made in S590, and the flow shifts to S630. S63
At 0, the EGR amount Egr is updated to a value reduced by a predetermined EGR reduction amount Eb.

At S640, the E updated at S630
It is determined whether or not the value of the GR amount Egr is smaller than an EGR amount reduction limit ELb predetermined as a reduction limit value of the EGR amount Egr.
The process proceeds to S660 if a negative determination is made. At this time, if the EGR amount Egr is smaller than the EGR amount reduction limit ELb, an affirmative determination is made in S640, the process proceeds to S650, and in S650, the value of the EGR amount reduction limit ELb is substituted for the EGR amount Egr. After the process of S650 is performed, the process proceeds to S660.

If the EGR amount Egr is equal to or larger than the EGR amount reduction limit ELb when the process proceeds to S640,
A negative determination is made in S640, the process proceeds to S660, and S660
Then, the EGR control operation is performed with the last calculated EGR amount Egr, and when the EGR control operation is performed, the process proceeds to S310.

As described above, in the present EGR amount control process, S
When the EGR control operation is performed at 660, the process proceeds to S310,
By repeatedly executing the above processing, the effective pressure index An
The EGR amount Egr is updated based on the value of the deviation / average S calculated from the standard deviation and the average of the EGR amount Egr.
Is controlling.

As described above, in the present EGR amount control process, when the operating state is changing, the EGR amount Egr is controlled based on the engine speed and the throttle opening. When the operating state is stable, the EGR amount Eg set based on the engine speed and the throttle opening is set as an initial value, and the EGR amount Eg is set.
The combustion state of the internal combustion engine is determined based on the value of the standard deviation of the effective pressure index An resulting from changing r, and the EGR amount Egr is controlled.

That is, when the deviation / average S calculated in S380 is equal to or smaller than the EGR amount limit determination value EL (S
When the determination is affirmative at 590), it can be determined that the combustion state is stable. For this reason, in the next S600, the next E
By increasing the GR amount Egr, harmful substances in the exhaust gas are further reduced.

When the deviation / average S calculated in S380 is larger than the EGR amount limit determination value EL (S
When the determination is negative in 590), it indicates that the combustion state is unstable, and in S630, the next EGR amount Eg
By reducing r, the fuel state of the internal combustion engine is stabilized.

Then, while the operation state of the internal combustion engine is stable, S310, S320, S340, S3
80, each step from S590 to S660 is repeatedly executed, and the EGR amount Egr is controlled to an optimum value based on the standard deviation of the effective pressure index An. Thus, it is possible to operate the internal combustion engine in a state in which the generation of harmful substances is suppressed without lowering the combustion state.

In the present embodiment, the EGR increase amount Ea and the EGR decrease amount Eb are fixed values set in advance, but may be variable values set in accordance with the operation state, for example. Also, the EGR amount increase limit ELa and the EGR amount decrease limit ELb may be, for example, variable values set in accordance with the operation state.

Next, the fuel injection timing control processing of this embodiment will be described with reference to the flowchart shown in FIG.
The fuel injection timing control process is started and started when the operation of the internal combustion engine is started, and is executed until the operation of the internal combustion engine is stopped. In the fuel injection timing control process, since the flow method of the ignition timing control process and the basic control process is the same, steps having the same processing content are denoted by the same step numbers, and a flowchart is shown. The fuel injection timing control will be described below, focusing on the differences from the control processing.

First, in S730 and S750 of the fuel injection timing control processing corresponding to S130 and S150 in which the ignition timing Tig was read in the ignition timing control processing,
The fuel injection timing Tin is set by reading the fuel injection timing Tin from a preset map based on the engine speed and the throttle opening measured in S110. Then, in S750, the fuel injection timing Tin is updated to a value advanced by a predetermined advance amount Tia.

S180 to S240 in the ignition timing control correspond to S780 to S240 in the fuel injection timing control.
If the latest effective pressure index An is larger than the previous effective pressure index An-1 when the process proceeds to S170, the affirmative determination is made in S170 and the process proceeds to S780. In S780, the latest value of the effective pressure index An is substituted for the previous effective pressure index An-1, and the fuel injection timing Tin is updated to a value advanced by a predetermined advance amount Tia.

At S790, it is determined whether or not the value of the fuel injection timing Tin updated at S780 is larger than an injection timing advance limit TLia predetermined as an advance limit value of the fuel injection timing. If a positive determination is made, S8
The process proceeds to S840, and if a negative determination is made, the process proceeds to S840.
At this time, if the fuel injection timing Tin is larger than the injection timing advance limit TLia, an affirmative determination is made in S790,
The process proceeds to S800, in which the value of the injection timing advance limit TLia is substituted for the fuel injection timing Tin. S8
After the processing of 00 is performed, the flow shifts to S840.

If the fuel injection timing Tin is equal to or less than the injection timing advance limit TLia when the process proceeds to S790, a negative determination is made in S790 and the process proceeds to S840.
In S840, fuel injection is performed at the last calculated fuel injection timing Tin, and when fuel injection ignition is performed, S110 is performed.
Move to

If the latest effective pressure index An is less than or equal to the previous effective pressure index An-1 when the process proceeds to S170, a negative determination is made in S170 and the process proceeds to S810. S
In step 810, the latest value of the effective pressure index An is substituted for the previous effective pressure index An-1, and the fuel injection timing Tin is updated to a value delayed by a predetermined retard amount Tir.

At S820, it is determined whether or not the value of the fuel injection timing Tin updated at S810 is smaller than an injection timing retard limit TLir predetermined as a fuel injection timing retard limit value. If a positive determination is made, S8
The process proceeds to S840, and if a negative determination is made, the process proceeds to S840.
At this time, if the fuel injection timing Tin is smaller than the injection timing retard limit TLir, an affirmative determination is made in S820 and the process proceeds to S830. In S830, the value of the injection timing retard limit TLir is substituted for the fuel injection timing Tin. S8
After the process of S30 is performed, the process proceeds to S840.

If the fuel injection timing Tin is equal to or greater than the injection timing retard limit TLir when the process proceeds to S820, a negative determination is made in S820 and the process proceeds to S840.
In S840, fuel injection is performed at the last calculated fuel injection timing Tin, and when fuel injection is performed, the process proceeds to S110.

As described above, in the present fuel injection timing control process, when ignition is performed in S840, the process proceeds to S110, and the above process is repeatedly executed to update the fuel injection timing Tin based on the effective pressure index An. And the fuel injection timing T
controlling in. As described above, in this fuel injection timing control process, when the operating state is changing,
The fuel injection timing Tin is controlled based on the engine speed and the throttle opening. When the operation state is stable, the fuel injection timing Tin set based on the engine speed and the throttle opening is set as an initial value, and the fluctuation of the effective pressure index An caused by changing the fuel injection timing Tin is determined. Based on this, the combustion state of the internal combustion engine is determined, and the fuel injection timing Tin is controlled.

That is, at S750, the fuel injection timing Tin
, The effective pressure index An calculated in S160
Is larger than the effective pressure index An-1 calculated before proceeding (when a positive determination is made in S170),
It can be determined that the combustion state has become good. For this reason, in the subsequent S780, the next fuel injection timing Tin is advanced, so that the combustion state in the next combustion is further improved.

On the other hand, at S750, the fuel injection timing Tin
, The effective pressure index An calculated in S160
However, if it becomes equal to or less than the effective pressure index An-1 calculated before proceeding (if negative determination is made in S170), it can be determined that the combustion state has become poor. Therefore, the following S81
By delaying the next fuel injection timing Tin at 0, the combustion state is improved in the next combustion.

Then, while the operation state of the internal combustion engine is stable, S110, S120, S140, S1
Steps S60, S170, S780 to S840 are repeatedly executed, and the fuel injection timing Tin is controlled to an optimum value based on the effective pressure index An. Thus, the internal combustion engine can be operated with the fuel injection timing set to the fuel injection timing at which the internal combustion engine has the highest efficiency.

In this embodiment, the advance amount Tia and the retard amount Tir are fixed values set in advance.
For example, it may be a variable value set according to the operating state. Further, the injection timing advance limit TLia and the injection timing retard limit TLir may be, for example, variable values set in accordance with the operation state.

As described above, in the internal combustion engine of this embodiment, the in-cylinder pressure used for calculating the effective pressure index is detected by the spark plug with a built-in pressure sensor.
Since the in-cylinder pressure in the period from 0 ° CA to 90 ° CA after the top dead center is used, the effective pressure index can be accurately calculated without being affected by the seating noise of the intake valve and the exhaust valve. Then, an effective pressure index is calculated by correcting an in-cylinder pressure error caused by individual differences in sensitivity, tightening torque, temperature, and the like in the spark plug with a built-in pressure sensor. Further, an error due to the effect of the residual pressure in the in-cylinder pressure detected by the spark plug with a built-in pressure sensor is corrected to calculate the effective pressure index. From these facts, in the internal combustion engine of the present embodiment, the effective pressure index can be accurately calculated.

Therefore, the internal combustion engine of this embodiment controls the ignition timing, the air-fuel ratio (fuel injection amount), the EGR amount, and the fuel injection timing based on the effective pressure index calculated in this manner. Thus, the combustion state of the internal combustion engine can be optimally controlled. As a result, the combustion efficiency can be improved, and the fuel efficiency can be improved and harmful substances can be reduced.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments.
Various embodiments can be adopted. In the present embodiment, the in-cylinder pressure integral value for calculating the effective pressure index is set to a crank angle of 1 °.
Although the calculation is performed by integrating for each CA, for example, a method of storing the charge output from the piezoelectric element in a capacitor and calculating the in-cylinder pressure integrated value based on the capacity of the stored charge may be used. Further, as a pressure sensor for detecting the in-cylinder pressure, provided separately from the ignition plug, and sandwiched together with a gasket between the ignition plug and the internal combustion engine body,
A type that detects a change in tightening load may be used. Further, the pressure sensor may be of a type in which a pressure conducting hole communicating with the combustion chamber is provided in the cylinder head and a piezoelectric element mounted in the pressure conducting hole is built in.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of an internal combustion engine according to an embodiment.

FIG. 2 is an explanatory diagram showing a waveform of an in-cylinder pressure detected by a seat-type pressure sensor.

FIG. 3 is a graph showing an effective pressure index before and after sensitivity correction calculated using a seat-type pressure sensor.

FIG. 4 is an explanatory diagram showing waveforms of an in-cylinder pressure detected by a seat-type pressure sensor and an in-cylinder insertion type pressure sensor.

FIG. 5 is an explanatory diagram showing a result of measuring an effective pressure index.

FIG. 6 is a flowchart illustrating an ignition timing control process performed by a control device.

FIG. 7 is a flowchart illustrating an air-fuel ratio control process performed by a control device.

FIG. 8 is a flowchart illustrating an EGR amount control process performed by a control device.

FIG. 9 is a flowchart illustrating a fuel injection timing control process performed by a control device.

FIG. 10 is a graph showing output characteristics of a piezoelectric element with respect to a change in temperature and a change in tightening torque of an ignition plug.

FIG. 11 is an explanatory diagram illustrating a configuration of an amplifier circuit.

FIG. 12 is a graph showing a relationship between an effective pressure index calculated using a seat type pressure sensor and an indicated average effective pressure calculated using an in-cylinder insertion type pressure sensor.

FIG. 13 is an explanatory diagram showing a configuration of a plug with a built-in pressure sensor.

[Description of Signs] 1 ... internal combustion engine, 11 ... spark plug, 11a ... metal shell,
11b ... pressure sensor, 11c ... output cable, 11d ...
Outer electrode, 11e ... Center electrode, 11f ... Terminal part, 13 ...
Igniter, 15: fuel injection valve, 17: EGR valve,
19: control unit (ECU), 31: combustion chamber, 61: amplifier circuit, 63: operational amplifier.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 41/08 H01L 41/08 Z F-term (Reference) 2F055 AA23 BB20 CC11 CC60 DD20 EE23 FF11 3G019 GA01 GA15 KA28 KD17 3G084 DA04 DA21 DA22 DA23 DA24 EA01 EA05 EA08 EB02 EC02 FA21 FA38

Claims (4)

[Claims] 1. A piezoelectric sensor having a piezoelectric element,
A pressure detection method using a piezoelectric sensor that outputs an in-cylinder pressure detection value corresponding to an in-cylinder pressure of an internal combustion engine, wherein the pressure sensor is obtained from the piezoelectric sensor until an ignition timing after an intake valve is closed. The difference between the detected values of the in-cylinder pressure at two different points in time among the detected values of the in-cylinder pressure is calculated as a correction reference value for each combustion cycle, and at least during the period from when the crank angle reaches the top dead center to when the exhaust valve opens. A control pressure value for detecting a combustion state of the internal combustion engine is calculated for each combustion cycle based on the in-cylinder pressure detection value obtained from the piezoelectric sensor, and in the combustion cycle, the control pressure value is calculated based on the correction reference value. A pressure detection method using a piezoelectric sensor, wherein the pressure value is corrected. 2. A pressure integral value before the top dead center is calculated by integrating the in-cylinder pressure detection value within a certain period from when the intake valve closes to when the crank angle reaches the top dead center. Calculates the post-top dead center pressure integrated value by integrating the in-cylinder pressure detection value within a certain period determined from when the top dead center is reached until the exhaust valve opens, after the top dead center. The piezoelectric sensor according to claim 1, wherein an effective pressure index calculated for each combustion cycle as a difference between a pressure integral value and the pressure integral value before the top dead center is the control pressure value. The pressure detection method used. 3. An integrated value before the top dead center is calculated by integrating the in-cylinder pressure signal in a period from a crank angle of 90 ° CA before the top dead center to the top dead center. An integrated value after the dead center is calculated by integrating the in-cylinder pressure signal during a period from when the crank angle reaches the top dead center to when the crank angle reaches 90 ° CA after the top dead center. 3. The control pressure value, wherein the effective pressure index calculated for each combustion cycle as a difference between the control pressure value and a pressure integral value after the top dead center is calculated.
A pressure detection method using the piezoelectric sensor according to 1. 4. The piezoelectric sensor according to claim 1, wherein the piezoelectric sensor includes a built-in piezoelectric element, and is provided on a mounting seat of an ignition plug mounted on the internal combustion engine. The pressure detection method for a piezoelectric sensor according to any one of claims 1 to 3, wherein a detected value of the in-cylinder pressure is output.