JPH0972809A - Combustion pressure detector for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the combustion pressure accurately by setting a correction value for each cylinder based on the combustion pressure detected for each cylinder in order to substantially equalize the detection values combustion pressure, setting the combustion pressures correctively based on the correction values and outputting final detection results thereby correcting the fluctuation of combustion pressure detection means provided for each cylinder. SOLUTION: A control unit 11 determines a fuel injection based on an intake air detected through a hot-wire air flow meter 12 and a detection signal from a crank angle sensor 14 and then then delivers a signal to a fuel injection valve 6. Specified operational conditions, where the ignition timing and air-fuel ratio are identical among the cylinders, are then determined during a specified operation. Subsequently, the combustion pressure detected through an inner pressure sensor 16 for each cylinder is integrated over a specified section thus obtaining an integrated value. The integrated values are averaged for each cylinder and then the mean integrated values are averaged for all cylinders. A correction value is set for each cylinder based on the difference between the averaged value for each cylinder and the means value for all cylinders before correcting the integrated value for each cylinder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion pressure detecting device for an internal combustion engine, and more particularly to a technique for correcting detection variations of a combustion pressure detecting means provided for each cylinder.

[0002]

2. Description of the Related Art Conventionally, engine output fluctuations have been detected, and the air-fuel ratio and ignition timing have been adjusted to combustion stability limits based on the detection results. Specifically, an engine output fluctuation (combustion pressure fluctuation rate in all cylinders) is calculated based on a combustion pressure sensor (combustion pressure detection means) provided for each cylinder, and the fluctuation rate is a predetermined value (combustion stability). The air-fuel ratio is made lean within a range that does not exceed the limit), and
It was configured to retard the ignition timing.

[0003]

However, if the output characteristics of the combustion pressure sensor vary, the combustion pressure detected for each cylinder also varies, so that combustion is stable in each cylinder. Also, the variation in the detected combustion pressure between cylinders was erroneously detected as the deterioration of combustion stability, and although the combustion stability limit was not actually reached, the lean air-fuel ratio and the ignition timing retardation were advanced. In some cases, it disappeared (see Fig. 4).

In particular, when a ring-shaped piezoelectric element is mounted as a washer for a spark plug and a sensor for detecting combustion pressure as a relative pressure with respect to the tightening load of the spark plug is used, in addition to variations in the sensor itself, Due to the variation in load, there is a possibility that the output characteristics may vary greatly among the sensors, and it may not be possible to accurately control the air-fuel ratio and the ignition timing to the combustion stability limit.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a combustion pressure detecting device capable of correcting the detection variation of the combustion pressure detecting means provided for each cylinder.

[0006]

Therefore, the invention according to claim 1 is constructed as shown in FIG. In FIG.
The combustion pressure detecting means detects the combustion pressure for each cylinder of the engine. Further, the correction value setting means burns each cylinder based on the combustion pressure of each cylinder detected by the combustion pressure detecting means under a predetermined operating condition so that the combustion pressure detection value of each cylinder becomes substantially the same. Set the correction value for the pressure detection value.

The combustion pressure correcting means corrects and sets the combustion pressure of each cylinder detected by the combustion pressure detecting means based on the corresponding correction value set by the correction value setting means, and finally. It outputs as a detection result. According to such a configuration, the variation in the combustion pressure of each cylinder detected under the predetermined operating condition is regarded as the variation in the detection of the combustion pressure detecting means, and the combustion pressure of each cylinder is the same as the final detection result. A correction value is set for each cylinder so that it is output.

According to a second aspect of the present invention, the predetermined operating condition in the correction value setting means is either one of an idle operation of the engine and an operating operation with a constant running resistance. With such a configuration, the combustion pressure is stable during idle operation of the engine or during operation where running resistance is constant, so that the detection variation of the combustion pressure detection means can be specified with high accuracy, and thus the correction value can be set with high accuracy. Is possible.

According to the third aspect of the present invention, the predetermined operating condition in the correction value setting means is an operating condition in which the ignition timing and the air-fuel ratio in each cylinder are the same. With such a configuration, it is possible to prevent the combustion pressure variation due to the difference in the ignition timing or / and the air-fuel ratio between the cylinders from being detected as the detection variation of the combustion pressure detecting means.

According to a fourth aspect of the present invention, the correction value setting means integrates the combustion pressure of each cylinder detected by the combustion pressure detecting means into a predetermined integration interval, and the correction value setting means of each cylinder The configuration is such that the correction value for each cylinder is set based on the combustion pressure integrated value. According to such a configuration, by integrating the combustion pressure in a predetermined integration section, even if noise is superimposed on the detection signal of the combustion pressure detection means, it is possible to prevent the correction value from being erroneously set due to the noise.

According to a fifth aspect of the present invention, the correction value setting means obtains an average value of the combustion pressure integrated value for each cylinder, and based on the average value of each cylinder, the combustion pressure integrated value in all cylinders. Is calculated, and the correction value for each cylinder is set based on the deviation between the average value for each cylinder and the average value for all cylinders. With such a configuration, by averaging the combustion pressure integrated values for each cylinder, it is possible to suppress the influence of variations in combustion pressure for each combustion cycle in each cylinder, and based on the average value obtained for each cylinder. By obtaining the integrated value average value of the cylinders, it is possible to accurately set the target combustion pressure integrated value, by setting a correction value based on the deviation between the average value for each cylinder and the average value in all cylinders,
The correction value for each cylinder can be set accurately.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. In FIG. 2 showing the system configuration, air is taken into the internal combustion engine 1 through an air cleaner 2, an intake duct 3, and an intake manifold 4. In the intake duct 3,
A butterfly-type throttle valve 5 that interlocks with an accelerator pedal (not shown) is interposed, and the throttle valve 5 adjusts the intake air amount of the engine.

An electromagnetic fuel injection valve 6 is provided for each cylinder in each branch portion of the intake manifold 4, and a predetermined amount is controlled by electronically controlling the amount of fuel injected and supplied from the fuel injection valve 6. A fuel-air mixture is formed. Here, by individually controlling the fuel injection valve 6 provided for each cylinder, it is possible to form an air-fuel mixture having a different air-fuel ratio for each cylinder.

The air-fuel mixture sucked into the cylinder through the intake valve 7 is ignited and burned by spark ignition by the spark plug 8 provided for each cylinder, and the combustion exhaust gas is discharged through the exhaust valve 9 and the exhaust manifold. Catalyst not shown by 10,
Guided by the muffler. The control unit 11 for controlling the fuel injection amount by the fuel injection valve 6 and the ignition timing of the spark plug 8 is constituted by including a microcomputer, and the intake air amount signal Q from the hot wire type air flow meter 12 and the throttle sensor 13 The throttle valve opening signal TVO, the crank angle signal from the crank angle sensor 14, the cooling water temperature signal Tw from the water temperature sensor 15, the cylinder pressure signal P from the cylinder pressure sensor 16, and the like are input.

The hot-wire air flow meter 12 directly detects the intake air amount of the engine 1 as a mass flow rate based on the resistance change of the temperature-sensitive resistance due to the intake air amount.
The throttle sensor 13 is an opening TV of the throttle valve 5.
O is detected by a potentiometer. The crank angle sensor 14 outputs a unit angle signal for each unit crank angle and a reference angle signal for each predetermined piston position. Here, the engine rotation speed Ne can be calculated by measuring the number of generations of the unit angle signal within a predetermined time or the generation cycle of the reference angle signal.

The water temperature sensor 15 detects the cooling water temperature Tw in the water jacket of the engine 1 as a temperature representing the engine temperature. In-cylinder pressure sensor 16
The (combustion pressure detecting means) is composed of a ring-shaped piezoelectric element mounted as a washer of the spark plug 8 as disclosed in Japanese Utility Model Laid-Open No. Sho 63-17432, and is relative to the tightening load of the spark plug. This is a sensor that detects combustion pressure as pressure, and by mounting it on each spark plug 8 of each cylinder, the in-cylinder pressure P (combustion pressure) can be detected for each cylinder.
The in-cylinder pressure sensor 16 is of a type that is mounted as a washer of the spark plug 8 as described above, and is of a type that directly detects the in-cylinder pressure in the combustion chamber and detects the in-cylinder pressure as an absolute pressure. Is also good.

The control unit 11 determines the basic ignition timing (basic ignition advance value) based on engine operating conditions such as engine load and engine speed, and controls the ignition timing by the spark plug 8. The control of the injection amount of the fuel injection valve 6 by the control unit 11 is performed as follows.

Based on the intake air amount Q detected by the hot wire air flow meter 12 and the engine speed Ne calculated from the detection signal from the crank angle sensor 14, the basic fuel injection amount Tp (corresponding to the target air-fuel ratio is calculated. = K × Q / Ne: K is a constant), and the cooling water temperature T is added to the basic fuel injection amount Tp.
A final fuel injection amount Ti is obtained by performing a correction according to an operating condition such as w. Then, a drive pulse signal having a pulse width corresponding to the fuel injection amount Ti is output to the fuel injection valve 6 at a predetermined timing. The fuel, which is adjusted to a predetermined pressure by a pressure regulator (not shown), is supplied to the fuel injection valve 6, and an amount of fuel proportional to the pulse width of the drive pulse signal is injected and supplied to a predetermined space. A fuel-air mixture is formed.

Further, the control unit 11 detects the combustion state based on the detection signal from the in-cylinder pressure sensor 16. However, the variation in the in-cylinder pressure sensor 16 (the output due to the variation of the sensor itself and the variation of the tightening load). (Including variations) is corrected as shown in the flowchart of FIG. The control unit 11 is, as shown in the flow chart of FIG.
It has a function as a correction value setting means and a combustion pressure correction means.

In the flow chart of FIG. 3, in step 1 (denoted as S1 in the figure; the same applies hereinafter), it is determined whether or not a predetermined operating condition for learning the sensor variation is satisfied. The predetermined operating conditions include an idle operation in which combustion pressure is stable or an operation in which running resistance is constant, and the ignition timing and air-fuel ratio (fuel injection amount) of each cylinder.
Are preferably the same during operation. When the ignition timing and the fuel injection amount are individually controlled for each cylinder based on the combustion pressure detection for each cylinder, the ignition timing and the air-fuel ratio (fuel injection amount) are compulsorily set for learning the variation. All cylinders should be the same.

If the predetermined operating conditions are met, the routine proceeds to step 2, where the detection signals of the cylinder pressure sensor 16 provided in each cylinder are A / D converted and read, and the read cylinder pressure is read in each cylinder. In addition, a predetermined integration interval (for example, compression TD
C to ATDC 100 °) and integrate value P for each cylinder
i (# 1) to Pi (#n) are obtained. In step 3, average values Piav (# 1) to Piav (#n) are obtained for the respective integrated values Pi (# 1) to Pi (#n) for each cylinder.

[0022]

[Equation 1]

In step 4, the average value P for each cylinder is
An average value Piav of iav (# 1) to Piav (#n) is obtained as an average value in all cylinders. Piav = {Piav (# 1) + Piav (# 2) ... + Piav (#n)} / n In step 5, the average value Piav (# 1) for each cylinder.
.About.Piav (#n) and the average value Piav of all cylinders are calculated respectively, and a correction value L (# 1) for each cylinder
~ L (#n) is set.

L (# 1) =-{Piav (# 1) -Piav} L (# 2) =-{Piav (# 2) -Piav} :: L (#n) =-{Piav (#n) -Piav} The correction values L (# 1) to L (#n) are given by
The integrated values Pi (# 1) to Pi (#n) for each cylinder are set to match the average value Piav for all cylinders.

In step 6, based on the set correction values L (# 1) to L (#n) for each cylinder, the integrated values Pi (# 1) to Pi (#n) for each cylinder are set. Is corrected and set, and the correction result is output as a final detection result. Pi (# 1) = Pi (# 1) + L (# 1) Pi (# 2) = Pi (# 2) + L (# 2) :: Pi (#n) = Pi (#n) + L (#n) Based on the integrated values Pi (# 1) to Pi (#n) for each cylinder corrected and set by the correction values L (# 1) to L (#n), the combustion pressure fluctuations (engine Output fluctuation), the in-cylinder pressure sensor 16
It is possible to prevent the combustion pressure fluctuation from being erroneously determined due to the variation of.

In step 7, the combustion pressure fluctuation ΔΣPi in all the cylinders is calculated as follows, for example. ΣPi = {Pi (# 1) + Pi (# 2) + ... + Pi (#n)} / n ΔΣPi = ΣPi / ΣPi ₋₁ Note that ΣPi ₋₁ represents the previous value of the average integrated value ΣPi. .

Here, the ignition timing is retarded within a range in which the combustion pressure fluctuation ΔΣPi does not exceed an allowable level, and
By making the air-fuel ratio lean, it is possible to improve exhaust properties and fuel efficiency without impairing engine stability. Then, the integrated value Pi for each cylinder used for the calculation of ΣPi
Since (#n) is a value in which the detection variation is corrected, the detection variation is not misjudged as the combustion pressure variation and the retardation and the leaning cannot be advanced, and the maximum retardation and the leaning are obtained. To be

[0028]

As described above, according to the first aspect of the present invention, the combustion pressure detection values are made uniform for each cylinder based on the variation in the combustion pressure of each cylinder detected under a predetermined operating condition. Since the combustion pressure correction value is set for each cylinder, the variation of the detection value due to the detection variation of the combustion pressure detection means is corrected, and thus the combustion pressure fluctuation in all the cylinders can be detected with high accuracy. effective.

According to the second aspect of the present invention, the detection variation of the combustion pressure detecting means can be specified with high accuracy under the operating condition where the combustion pressure is stable, so that the correction value can be set with high accuracy. is there. According to the invention described in claim 3, the variation in the combustion pressure due to the difference in the ignition timing or / and the air-fuel ratio between the cylinders is not detected as the variation in the detection by the combustion pressure detecting means, and the correction value for each cylinder is obtained. Has an effect that can be set with high accuracy.

According to the invention described in claim 4, by integrating the combustion pressure in a predetermined integration section, even if noise is superposed on the detection signal of the combustion pressure detecting means, the noise greatly influences the correction value. This has the effect of avoiding erroneous settings. According to the invention of claim 5, it is possible to suppress the influence of variations in the combustion pressure in each combustion cycle in each cylinder, and to set the target combustion pressure integrated value with high accuracy, so that the correction value for each cylinder is accurate. The effect is that it can be set well.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an apparatus according to the invention of claim 1.

FIG. 2 is a system configuration diagram of the engine in the embodiment.

FIG. 3 is a flowchart showing how combustion pressure is detected in the embodiment.

FIG. 4 is a diagram showing how combustion pressure detection varies.

[Explanation of symbols]

 1 Internal Combustion Engine 4 Intake Manifold 5 Throttle Valve 6 Fuel Injection Valve 8 Spark Plug 10 Exhaust Manifold 11 Control Unit 12 Hot Wire Air Flow Meter 13 Throttle Sensor 14 Crank Angle Sensor 15 Water Temperature Sensor 16 Cylinder Pressure Sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G01M 15/00 G01M 15/00 Z

Claims (5)

[Claims] 1. Combustion pressure detection means for detecting combustion pressure for each cylinder of the engine, and combustion in each cylinder based on combustion pressure for each cylinder detected by the combustion pressure detection means under predetermined operating conditions. A correction value setting means for setting a correction value for the combustion pressure detection value for each cylinder so that the pressure detection values are substantially the same, and the combustion pressure for each cylinder detected by the combustion pressure detection means by the correction value setting means. A combustion pressure detection device for an internal combustion engine, comprising: a combustion pressure correction unit that performs correction settings based on corresponding set correction values and outputs the final detection results. 2. The internal combustion engine according to claim 1, wherein the predetermined operating condition in the correction value setting means is either one of an idle operation of the engine and an operation with a constant running resistance. Engine combustion pressure detector. 3. The internal combustion engine according to claim 1, wherein the predetermined operating condition in the correction value setting means is an operating condition in which the ignition timing and the air-fuel ratio in each cylinder are the same. Combustion pressure detector. 4. The correction value setting means integrates the combustion pressure of each cylinder detected by the combustion pressure detecting means in a predetermined integration section, and based on the combustion pressure integration value of each cylinder. The combustion pressure detecting device for an internal combustion engine according to claim 1, wherein a correction value is set for each cylinder. 5. The correction value setting means obtains an average value of the combustion pressure integral values for each cylinder, and obtains an average value of the combustion pressure integral values for all cylinders based on the average value for each cylinder. The combustion pressure detecting device for an internal combustion engine according to claim 4, wherein a correction value for each cylinder is set based on a deviation between the average value for each cylinder and the average value for all cylinders.