JP3502206B2 - Indicated mean effective pressure detection device for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, indicated average effective pressure (or indicated average effective pressure equivalent value) Pi for each cylinder based on the detection result of an in-cylinder pressure sensor (in-cylinder pressure detection means) provided in each cylinder of an engine.
Is calculated and the misfire diagnosis is performed based on the indicated mean effective pressure Pi, or the surge torque is detected based on the fluctuation of the indicated mean effective pressure Pi to control the air-fuel ratio and the ignition timing. It was

[0003]

By the way, in the in-cylinder pressure sensor, there is an output variation in the sensor itself, and
Especially, a ring-shaped piezoelectric element is attached as a washer for the spark plug,
When a sensor configured to detect the in-cylinder pressure as a relative pressure to the tightening load of the spark plug is used, the sensor output varies due to the variation of the tightening load in addition to the variation of the sensor itself.

Therefore, for example, even if there is actually no difference in the indicated mean effective pressure between the cylinders, a deviation in the indicated mean effective pressure between the cylinders is apparently caused by the variation in the sensor output, and a surge occurs. There was a fear that the torque was erroneously detected. Further, in misfire diagnosis and the like, when the absolute value of the indicated mean effective pressure varies due to variations in the output of the in-cylinder pressure sensor, the diagnostic accuracy deteriorates especially under operating conditions where the difference in the indicated mean effective pressure due to the presence or absence of misfire is small. There is also the problem of doing it.

The present invention has been made in view of the above problems, and it is an object of the present invention to accurately detect the indicated mean effective pressure of each cylinder even if there is a variation in the output of the in-cylinder pressure sensor.

[0006]

Therefore, the invention according to claim 1 is configured as follows . Cylinder pressure detection means
Is provided in each cylinder of the engine and detects the cylinder pressure of each cylinder individually. The indicated mean effective pressure calculating means calculates a value corresponding to the indicated mean effective pressure for each cylinder based on the in-cylinder pressure for each cylinder detected by the in-cylinder pressure detecting means.

Here, the correction value learning means compares the value for each cylinder calculated by the indicated mean effective pressure calculation means with a reference value common to each cylinder stored in advance corresponding to the engine operating condition. Then, the correction value for each cylinder is learned. Also, the standard value
The correction means uses the reference value in the correction value learning means as a function.
Correct according to the exhaust gas recirculation rate of Seki. Then, the correction means corrects the value for each cylinder calculated by the indicated mean effective pressure calculation means based on the correction value for each cylinder learned by the correction value learning means, and the corrected value Is output as the final indicated equivalent effective pressure value for each cylinder.

According to this structure, when the indicated mean effective pressure estimated from the engine operating condition and the indicated mean effective pressure actually calculated based on the detection result of the in-cylinder pressure do not match, the in-cylinder pressure detecting means operates. It is considered that this is due to output variation, and a correction value for correcting the indicated mean effective pressure equivalent value is learned. Therefore, it is possible to avoid the apparent deviation of the indicated mean effective pressure between cylinders from occurring, and it is also possible to correct the deviation of the absolute value of the indicated mean effective pressure. Well
Further, the reference value in the correction value learning means is set to the exhaust gas of the engine.
Since the correction is made according to the reflux rate, the indicated average effective pressure is
The charging efficiency changes depending on the exhaust gas recirculation rate.
Of the indicated average effective pressure due to the difference in exhaust gas recirculation rate.
The change is mistaken as a detection variation in the cylinder pressure detection means.
You can avoid learning.

According to the second aspect of the present invention, the in-cylinder pressure for each cylinder detected by the in-cylinder pressure detecting means and the indicated mean effective pressure equivalent value for each cylinder calculated by the indicated mean effective pressure calculating means are set. Based on at least one, misfire discrimination means for discriminating the presence or absence of misfire for each cylinder, and when the misfire discrimination means discriminates the occurrence of misfire, the correction value learning means learns the correction value for at least the misfiring cylinder. The learning prohibition means for prohibiting is provided.

With this configuration, it is possible to prevent the correction value from being erroneously learned as the decrease in the indicated mean effective pressure due to misfire due to the variation in the detection by the in-cylinder pressure detection means, and it is possible to improve the learning accuracy. In the invention according to claim 3, the correction value learning means is configured to learn the correction value only under preset engine operating conditions.

According to this structure, the correction value can be learned under the operating condition in which the in-cylinder pressure and the indicated mean effective pressure equivalent value are stable. By learning the correction value under the operating condition that can be discriminated well, it is possible to surely avoid erroneously learning the decrease in the indicated mean effective pressure equivalent value due to misfire.

According to another aspect of the invention, the predetermined engine operating condition is specified based on the engine load and the engine speed, and the reference value is set according to the engine load and the engine speed. It has a configuration. According to this configuration,
Since the indicated mean effective pressure can be specified from the combination of the engine load and the engine rotation speed, by specifying the engine load and the engine speed, it is possible to accurately set the indicated mean effective pressure.

[0013]

According to a fifth aspect of the invention, the correction value learning means learns the ratio between the reference value and the value for each cylinder as the correction value. According to this configuration, the correction value is learned by setting the correction value as the multiplication correction term of the indicated average effective pressure equivalent value so that the indicated average effective pressure equivalent value calculated for each cylinder is aligned with the reference value. Become.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. In FIG. 1 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.

Further, an electromagnetic fuel injection valve 6 is provided for each cylinder in each branch portion of the intake manifold 4, and a target space is controlled by electronically controlling the amount of fuel injected and supplied from the fuel injection valve 6. A fuel-air mixture is formed. 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 is discharged through the exhaust valve 9 and illustrated by the exhaust manifold 10. Not guided by the catalyst and 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
A microcomputer is included, and the intake air amount signal Q from the heat ray type air flow meter 12, the throttle valve opening signal TVO from the throttle sensor 13, the crank angle signal from the crank angle sensor 14, the cooling water from the water temperature sensor 15 The temperature signal Tw, the in-cylinder pressure signal P from the in-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 (in-cylinder 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. 63-17432, and is relative to the tightening load of the spark plug. This is a sensor for detecting the in-cylinder pressure as a pressure, and the in-cylinder pressure P (combustion pressure) can be detected for each cylinder by mounting it on each spark plug 8 of 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.

The basic fuel injection amount Tp (corresponding to the target air-fuel ratio 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 = 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 the target space. A fuel-air mixture is formed.

Further, the control unit 11 calculates the indicated mean effective pressure equivalent value Pi for each cylinder based on the detection signal from the in-cylinder pressure sensor 16, and the combustion state based on the indicated mean effective pressure equivalent value Pi. Detects (misfire, surge torque, etc.) and corrects ignition timing and fuel injection control. Specifically, the in-cylinder pressure P is integrated for each cylinder in a predetermined integration interval, and the integrated value is set as the indicated mean effective pressure equivalent value Pi. Then, the indicated average effective pressure equivalent value Pi is compared with the misfire determination level set on the basis of the engine load and the engine rotation speed to determine the presence or absence of misfire. On the other hand, stop fuel injection,
It warns the driver of a misfire. Further, the surge torque is detected based on the fluctuation of the indicated mean effective pressure equivalent value Pi, and the air-fuel ratio is made lean or the ignition timing is retarded within a range in which the surge torque does not exceed the allowable level. The control based on the indicated mean effective pressure equivalent value Pi is not limited to the above.

By the way, the in-cylinder pressure sensor 16 has variations in output due to variations in the sensor itself and variations in tightening load. For this reason, the accuracy of the indicated mean effective pressure equivalent value Pi of each cylinder deteriorates. For example, although the indicated mean effective pressure of each cylinder is actually the same, the apparent indicated mean effective pressure between the cylinders is caused by the variation. There is a risk that the surge torque may be erroneously detected due to the step difference.

Therefore, the control unit 11 is shown in FIG.
As shown in the flowchart of FIG. 3 , a correction value for correcting the indicated mean effective pressure equivalent value Pi is learned for each cylinder, and the Pi is corrected and set for each cylinder according to the learned correction value. ing. In the present embodiment, the functions of the indicated mean effective pressure calculation means, the correction value learning means, the correction means, the misfire determination means, the learning prohibition means, and the reference value correction means are as shown in the flow charts of FIGS. In addition, the control unit 11 is equipped with software.

In the flowchart of FIG . 2 , first, in step 1 (denoted as S1 in the figure, the same applies hereinafter),
Based on the output of the in-cylinder pressure sensor 16, the indicated mean effective pressure equivalent value Pi is calculated for each cylinder. In step 2, the Pi
It is determined whether or not the correction values KBL # 1 to KBL # 4 are within a learning area set in advance as an area to be learned.

The learning region is a region where the presence or absence of a misfire can be reliably determined even if there is a large change in the in-cylinder pressure (indicated average effective pressure) due to the presence or absence of a misfire, and the in-cylinder pressure sensor 16 has some output variation. It is preferable that the learning region is specified based on the basic fuel injection amount Tp representing the engine load and the engine rotation speed Ne, and the learning region is set to a relatively high load and low rotation side. I am doing it.

If it is determined in step 2 that the position is within the learning region, the process proceeds to step 3 to determine whether or not there is a misfire in each cylinder based on Pi. The misfire determination based on the Pi can be performed by comparing the reference value preset according to the engine load and the rotation speed with the Pi of each cylinder. Also,
The in-cylinder pressure sensor 16 may detect misfire based on the in-cylinder pressure detected at a predetermined crank angle timing, the maximum in-cylinder pressure, or the like.

If it is determined in step 3 that a misfire has occurred, the effect of misfire is included in Pi and the output variation of the in-cylinder pressure sensor 16 cannot be extracted from the value of Pi. Therefore, learning is performed. End this routine.
On the other hand, if it is determined in step 3 that no misfire has occurred in any of the cylinders, the process proceeds to step 4, and the operation is divided into a plurality of operating regions in advance based on the basic fuel injection amount Tp and the engine rotation speed Ne. Referring to a map that stores the reference value Pis of Pi, the current basic fuel injection amount T
A reference value Pis common to each cylinder corresponding to p and the engine rotation speed Ne is obtained.

The reference value Pis is a value obtained when the cylinder pressure sensor 16 has no output variation and Pi obtained under the operating condition is stored in a map. In the next step 5, when the engine is equipped with an exhaust gas recirculation device, the reference value P is set according to the exhaust gas recirculation ratio (EGR ratio) at that time.
A correction value K _EGR for correcting is is set.

This is because the indicated mean effective pressure fluctuates due to the change in the charging efficiency due to the exhaust gas recirculation, and the reference value Pis is corrected to be smaller as the exhaust gas recirculation rate is higher. The exhaust gas recirculation rate can be estimated from the engine load and the engine rotation speed. In step 6, the correction value KBL # for each cylinder of Pi is calculated according to the following equation.
1 to KBL # 4 (in case of 4 cylinders) is learned.

KBL # 1 = Pis / Pi # 1 KBL # 2 = Pis / Pi # 2 KBL # 3 = Pis / Pi # 3 KBL # 4 = Pis / Pi # 4 That is, the correction values KBL # 1 to KBL # 4 functions as a multiplication correction term that matches the Pi calculated based on the output of each in-cylinder pressure sensor 16 with the reference value Pis.

The correction by the correction value KBL # 1~KBL # 4 is performed in accordance with the flowchart of FIG. Figure 3
In the flowchart, first, in step 11, the indicated mean effective pressure equivalent values Pi # 1 to Pi # 4 for each cylinder are calculated based on the output of each in-cylinder pressure sensor 16.

Then, in the next step 12, the correction values KBL # 1 to KBL # 4 are set to the indicated average effective pressure equivalent value Pi.
Each of # 1 to Pi # 4 is multiplied, and the result is output as final indicated equivalent effective pressure values Pi # 1 to Pi # 4 of each cylinder. The corrected Pi is used for detection of surge torque, detection of misfire, etc., so that the surge torque can be detected with high accuracy, and the operating pressure has a small deviation in combustion pressure due to the presence or absence of misfire. Also, the presence or absence of misfire can be accurately determined based on the Pi.

In the above description, when it is determined that misfire has occurred in any of the cylinders, learning is prohibited for all cylinders, but learning may be prohibited only for misfiring cylinders.

[0035]

As described above, according to the first aspect of the invention, the error corresponding to the indicated mean effective pressure due to the output variation of the in-cylinder pressure detection means is based on the indicated mean effective pressure estimated from the engine operating conditions. since detects and learns the correction value each, can be avoided in practice can result apparent deviation indicated mean effective pressure is not among the cylinders, also, it is possible to correct also the deviation of the absolute value of the indicated mean effective pressure, exhaust Difference in reflux rate
The change in the indicated mean effective pressure due to
There is an effect that erroneous learning as force variation can be avoided .

According to the second aspect of the present invention, it is possible to prevent a decrease in the indicated mean effective pressure due to a misfire from being erroneously learned as a detection variation of the in-cylinder pressure detection means, thereby improving the learning accuracy of the correction value. The effect is that you can.
According to the invention as set forth in claim 3, by limiting the operating conditions to learn, the error of the indicated mean effective pressure can be detected accurately, and the influence of misfire can be reliably eliminated, so that the correction value can be increased. There is an effect that it can be learned accurately.

[0037] According to a fourth aspect of the present invention, cylinder pressure detection means can accurately set the indicated mean effective pressure in the absence of the output variation, than Te, the effect that it is possible to improve the learning accuracy of the correction value is there.

According to the fifth aspect of the present invention, the correction value is a multiplication correction term of the indicated mean effective pressure equivalent value so that the indicated mean effective pressure equivalent value calculated for each cylinder matches the reference value. There is an effect that it is corrected and an error due to an output variation of the in-cylinder pressure detecting means is eliminated.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an engine according to an embodiment.

FIG. 2 is a flowchart showing how correction value learning is performed in the embodiment.

FIG. 3 is a flowchart showing how the indicated mean effective pressure is corrected in the embodiment.

[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 In-cylinder pressure sensor

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F02D 45/00 368 G01M 15/00

Claims (5)

(57) [Claims] 1. An in-cylinder pressure detecting means provided in each of the cylinders of the engine for individually detecting the in-cylinder pressure of each cylinder, and each cylinder based on the in-cylinder pressure of each cylinder detected by the in-cylinder pressure detecting means. Separately, the indicated mean effective pressure calculating means for calculating a value corresponding to the indicated mean effective pressure, the value for each cylinder calculated by the indicated mean effective pressure calculating means, and each prestored corresponding to the engine operating condition A reference value common to each cylinder is compared to learn a correction value for each cylinder, and a reference value in the correction value learning means is used as an exhaust gas recirculation engine.
A reference value correcting means for correcting in accordance with the rate, based on the correction value for each respective cylinders learned by the correction value learning means corrects the indicated mean effective pressure calculating each cylinder of the value calculated by means An indicated average effective pressure detecting device for an internal combustion engine, comprising: a correction unit that outputs the corrected value as a final indicated average effective pressure equivalent value for each cylinder. 2. Based on at least one of an in-cylinder pressure for each cylinder detected by the in-cylinder pressure detecting means and an indicated average effective pressure equivalent value for each cylinder calculated by the indicated average effective pressure calculating means, A misfire discrimination means for discriminating the presence or absence of misfire for each cylinder; and when the misfire discrimination means discriminates the occurrence of misfire,
2. The indicated mean effective pressure detecting device for an internal combustion engine according to claim 1, further comprising: learning prohibiting means for prohibiting learning of the correction value by the correction value learning means for at least the misfiring cylinder. 3. The indicated mean effective pressure detecting device for an internal combustion engine according to claim 1, wherein the correction value learning means learns the correction value only under preset engine operating conditions. 4. The predetermined engine operating condition is specified based on the engine load and the engine speed, and the reference value is set according to the engine load and the engine speed. The indicated mean effective pressure detecting device for an internal combustion engine according to claim 3. Wherein said correction value learning means, the reference value and the internal combustion engine according to any one of claims 1-4, characterized in that to learn the ratio of each cylinder value as a correction value Mean effective pressure detection device shown.