JP2008069714A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a variation in an output characteristic of cylinder internal pressure sensors with a simple constitution. <P>SOLUTION: The cylinder internal pressure sensors 11 to 14 are arranged in respective cylinders of an engine 10. When controlling so that a combustion state of the respective cylinders becomes uniform, based on detected cylinder internal pressure, a correction is made for eliminating a variation in the output characteristic of the respective cylinder internal pressure sensors. This correction expresses the output characteristic of the respective cylinder internal pressure sensors by a linear function, and gain and offset of the output characteristic of the respective cylinder internal pressure sensors are corrected so that the output characteristic of the respective cylinder internal pressure sensors coincides with a predetermined common reference output characteristic. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that controls the engine based on a cylinder combustion pressure detected by a cylinder pressure sensor.

  An in-cylinder pressure sensor capable of detecting the in-cylinder pressure is provided in each cylinder of the internal combustion engine, and the variation of the combustion state between the cylinders is corrected based on the in-cylinder pressure (combustion pressure) detected during engine operation. Control devices are known.

  However, when an in-cylinder pressure sensor is arranged in each cylinder and the in-cylinder pressure is individually detected in this way, variations in output characteristics between the sensors become a problem.

  That is, there is an initial variation for each individual in the relationship (output characteristics) between the actual detected pressure of the in-cylinder pressure sensor and the sensor output. In addition, since the output characteristics may change as time passes, the output characteristics may vary among individuals as they are used.

  Thus, when variations in output characteristics occur between the sensors, for example, even if there is an ideal state where there is no variation in the combustion state of each cylinder and there is a perfect match, it is obtained based on the output from the in-cylinder pressure sensor. In addition, there appears to be a variation in the combustion state of each cylinder. In this case, since the variation correction is performed in a direction that eliminates the apparent variation in the combustion state of each cylinder, the variation in the correction results even though there is no actual variation.

  For this reason, various methods for correcting variations in sensor output characteristics when cylinder pressure sensors are provided for a plurality of cylinders have been proposed (see Patent Documents 1 and 2).

  For example, in Patent Document 1, variations in sensor output are corrected by simultaneously measuring the combustion pressure in the same cylinder using two in-cylinder pressure sensors.

  That is, in the apparatus of Patent Document 1, for example, an in-cylinder pressure sensor is disposed in an inter-cylinder portion of a cylinder head, and each in-cylinder pressure sensor is connected to cylinders on both sides via a pressure introduction passage that can be opened and closed. Thereby, the in-cylinder pressure sensor disposed between the cylinders can be selectively connected to the cylinders on both sides, and any one of the in-cylinder pressures of the cylinders on both sides can be measured with one sensor.

  In Patent Document 1, during engine operation, two sensors arranged on both sides of a certain cylinder are simultaneously connected to this cylinder, and the peak value of the in-cylinder pressure of the same cylinder is simultaneously measured by the two in-cylinder pressure sensors. ing.

  In Patent Document 1, the output characteristics of one sensor are corrected so that the peak values (average values of several cycles) measured by the respective sensors match as described above, and the correction of the peak values is sequentially repeated to adjacent sensors. Thus, the output characteristics of all the in-cylinder pressure sensors are finally matched.

Patent Document 2 discloses that an intake pressure sensor for detecting the intake pressure of the engine is provided separately from the in-cylinder pressure sensor, and the output characteristics of each in-cylinder pressure sensor are corrected based on the output of the intake pressure sensor. Yes.
That is, in Patent Document 2, using a cylinder pressure sensor provided in each cylinder, a predetermined timing in the intake stroke when combustion is not performed in the cylinder such as during cranking or during fuel cut such as during deceleration. To detect the cylinder pressure.

  In Patent Document 2, the intake pressure of the engine is further detected using an intake pressure sensor, and the cylinder pressure during the intake stroke of each cylinder detected by each in-cylinder pressure sensor is changed to the engine intake pressure detected by the intake pressure sensor. The offset (in-cylinder pressure at the time of sensor zero output) of each in-cylinder pressure sensor output characteristic is corrected so as to match.

  In Patent Document 2, the theoretical value of the cylinder pressure at the compression top dead center of each cylinder is calculated by multiplying the intake pressure detected by the intake pressure sensor by the compression ratio of the engine, and combustion is performed in the cylinder. Under actual conditions, the pressure (peak value) at the compression top dead center of each cylinder is detected by each in-cylinder pressure sensor, and the gain (sensor) of the output characteristics of each sensor so that these peak values match the above theoretical values. The slope of the straight line representing the relationship between the output and the in-cylinder pressure sensor is corrected.

  Thereby, in the apparatus of Patent Document 2, the offset and the gain are corrected so that the output characteristics of each sensor are the same.

JP 63-268955 A JP-A-1-262348

  In the device of Patent Document 1, it is necessary to connect one in-cylinder pressure sensor to two cylinders. For this reason, the arrangement of the in-cylinder pressure sensor is limited, and it is necessary to provide a pressure introduction passage for connecting the in-cylinder pressure sensor and the two cylinders.

  In addition, since the apparatus of Patent Document 1 only performs correction based on the in-cylinder pressure peak value of each cylinder, variations in the offset of the sensor output characteristics remain and completely eliminate variations in the output characteristics of each sensor. There is a problem that cannot be done.

  On the other hand, in the apparatus of Patent Document 2, the output characteristics of the in-cylinder pressure sensors are matched by correcting the gain and offset of the in-cylinder pressure sensor output characteristics using an intake pressure sensor.

  However, since the apparatus of Patent Document 2 requires an intake pressure sensor in order to correct variation in output characteristics of each sensor, an engine having no intake pressure sensor can correct the output characteristics of the in-cylinder pressure sensor. A problem that cannot be done arises.

  In view of the above problems, the present invention eliminates the need for a pressure introduction passage for connecting two cylinders and in-cylinder pressure sensors, an intake pressure sensor, and the like, and accurately varies the output characteristics of a plurality of in-cylinder pressure sensors with a simple configuration. It is an object of the present invention to provide a control device for an internal combustion engine that can correct the above.

  According to the first aspect of the present invention, in the internal combustion engine provided with an in-cylinder pressure sensor for detecting the in-cylinder pressure in each of the plurality of cylinders, two predetermined points during the stroke cycle of the cylinder under predetermined operating conditions are provided. The control apparatus for an internal combustion engine that corrects an output characteristic representing a relationship between an output of each in-cylinder pressure sensor and an in-cylinder pressure based on an in-cylinder pressure detected by using each in-cylinder pressure sensor, wherein the output characteristic is Given as a linear function of the sensor output and the in-cylinder pressure, the correction is performed by using the offset and gain of the output characteristic of each sensor so that the output characteristic of each in-cylinder pressure sensor matches a pre-stored common reference output characteristic. A control device for an internal combustion engine, which is performed by correcting the above, is provided.

  According to a second aspect of the present invention, there is provided the control apparatus for an internal combustion engine according to the first aspect, wherein the reference output characteristic is an output characteristic of one of the in-cylinder pressure sensors.

  According to a third aspect of the present invention, there is provided the control apparatus for an internal combustion engine according to the first aspect, wherein the reference output characteristic is an output characteristic predetermined according to an operating condition of the engine.

  According to a fourth aspect of the invention, the reference output characteristic is given as an average value of an offset and a gain of the output characteristic before correction of each in-cylinder pressure sensor. An engine control device is provided.

  That is, according to the first to fourth aspects of the present invention, the gain (inclination of the output characteristic straight line) and the offset (at the time of zero output) of each sensor output characteristic are obtained by using two in-cylinder pressure sensor outputs detected under the same conditions in each cylinder. Pressure), and correction is performed so that the gain and the offset coincide with the reference value.

  This reference value is not necessarily related to the actual pressure (intake pressure) as in Patent Document 2 described above, and is set only to match the output characteristics of the sensors.

  That is, if the actual in-cylinder pressure is detected using another means as in Patent Document 2 and the output characteristics of each sensor are corrected using the pressure as a reference value, the output characteristics of the sensors only match each other. Instead, the output of each sensor shows the actual in-cylinder pressure.

  However, in actuality, when correction is made to eliminate variation in the combustion state of each cylinder using the in-cylinder pressure sensor, it is important that the output characteristics of the in-cylinder pressure sensors match and there is no variation. The pressure value calculated from the output of each in-cylinder pressure sensor due to the output characteristics does not necessarily exactly match the true pressure.

  In the present invention, the reference characteristics common to the in-cylinder pressure sensors stored in advance (not necessarily based on the true pressure) are used to match the output characteristics of the sensors. The in-cylinder pressure may have a value slightly different from the true in-cylinder pressure, but since the output characteristics of the sensors match, the variation in the combustion state of each cylinder can be accurately detected.

  Therefore, according to the present invention, it is possible to accurately match the output characteristics of each sensor with a simple configuration without adding an extra configuration such as an intake pressure sensor for correcting the output characteristics of each in-cylinder pressure sensor. It becomes possible.

  Further, as a reference value commonly used for each sensor in the above correction, for example, the output characteristic of the in-cylinder pressure sensor of one cylinder is obtained, and the output characteristic of the in-cylinder pressure sensor of this one cylinder is used as a reference value. The output characteristics of the in-cylinder pressure sensor of the other cylinder may be corrected so as to match the output characteristics of the in-cylinder pressure sensor of this one cylinder, or according to the engine operating state (load, speed) in advance. Thus, the reference output characteristic may be set, and the output characteristic of the in-cylinder pressure sensor of each cylinder may be corrected so as to match the reference output characteristic.

  As the reference value, an average value of output characteristics (offset, gain) of the in-cylinder pressure sensor of each cylinder obtained under a predetermined condition may be used.

  According to a fifth aspect of the present invention, the predetermined operating condition is a state in which the engine is performing a fuel cut operation. The internal combustion engine according to any one of the first to fourth aspects, A control device is provided.

  That is, in the invention of claim 5, the correction of the output characteristics of each in-cylinder pressure sensor is performed during the fuel cut operation such as when the engine is decelerated. When the fuel is cut, combustion does not occur in each cylinder, so that in-cylinder pressure does not vary due to variations in combustion. For this reason, when correcting the in-cylinder pressure sensor output characteristics, the in-cylinder pressures are substantially the same, so that the output characteristics can be accurately corrected.

  According to the sixth aspect of the present invention, one of the two predetermined points in the stroke cycle of the cylinder that performs pressure detection using each in-cylinder pressure sensor has a peak in-cylinder pressure of each cylinder. The control apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the control timing of the internal combustion engine is provided.

  That is, in the invention of claim 6, one of the two points for detecting the in-cylinder pressure sensor output is a timing at which the in-cylinder pressure peaks. For example, under operating conditions where there is little variation in in-cylinder pressure such as during fuel cut operation, the peak value of in-cylinder pressure (for example, compression top dead center pressure during fuel cut operation) is substantially the same for each cylinder. Therefore, it is possible to correct the output characteristic with high accuracy by using the peak value of the in-cylinder pressure for correcting the output characteristic.

  According to the seventh aspect of the present invention, one of the two predetermined points in the stroke cycle of the cylinder that detects each in-cylinder pressure sensor output is within a predetermined interval of the intake stroke of the cylinder. An internal combustion engine control apparatus according to any one of claims 1 to 6 is provided.

  That is, in the seventh aspect of the present invention, one of the two points for detecting the in-cylinder pressure sensor output is set as a predetermined section during the intake stroke of the cylinder. In the intake stroke, the in-cylinder pressures substantially coincide with each other. Therefore, by correcting the output characteristics of each sensor using the in-cylinder pressure in the intake stroke, the accuracy of correcting the output characteristics is improved.

  According to an eighth aspect of the present invention, one of the two predetermined points in the stroke cycle of the cylinder that detects the in-cylinder pressure sensor output is within a predetermined section of the exhaust stroke of the cylinder. An internal combustion engine control apparatus according to any one of claims 1 to 6 is provided.

  That is, in the invention of claim 8, one of the two points for detecting the in-cylinder pressure sensor output is a predetermined section in the exhaust stroke of the cylinder. In the exhaust stroke, the in-cylinder pressures substantially coincide with each other. Therefore, by correcting the output characteristics of each sensor using the in-cylinder pressure in the exhaust stroke, the accuracy of correcting the output characteristics is improved.

  According to the invention described in claim 9, any one of claims 1 to 7, wherein an average value of detected values in a predetermined number of cycles is adopted as a detected value of each sensor output at the two predetermined points. An internal combustion engine control device according to claim 1 is provided.

  That is, in the invention of claim 9, the detected value of the output of each sensor does not use a single measured value, but adopts an average value of values measured in a predetermined number of cycles. Thereby, the influence of the measurement error due to noise or the like is reduced.

  According to the invention described in each claim, there is a common effect that correction that eliminates variations in output characteristics of the in-cylinder pressure sensors can be performed with a simple configuration.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration of an embodiment in which the present invention is applied to an internal combustion engine for automobiles.
In FIG. 1, reference numeral 10 denotes an automobile internal combustion engine. In this embodiment, the engine 10 is a spark ignition engine having four cylinders denoted by # 1 to # 4.

  Each cylinder # 1 to # 4 is provided with in-cylinder pressure sensors 11 to 14 capable of detecting the in-cylinder pressure.

  In the present embodiment, the in-cylinder pressure sensors 11 to 14 are known types of pressure sensors using piezoelectric elements or the like. The in-cylinder pressure sensor of this embodiment is of a type that is disposed in a cylinder block or a cylinder head and communicates with the inside of the cylinder via a connection hole, or a washer type that is attached to a spark plug (not shown) of each cylinder. Any of the formats can be used.

1 is an electronic control unit (ECU) of the engine 10.
In this embodiment, the ECU 30 is a known type of microcomputer, and performs basic control of the engine such as fuel injection control and ignition timing control of the engine 10, and in this embodiment, as described later, the combustion state of each cylinder. Control for equalization and correction for eliminating variations in output characteristics of the in-cylinder pressure sensors 11-14.

  In order to execute these controls, the output voltage of the in-cylinder pressure sensors 11 to 14 is input to the ECU 30 via an AD converter (not shown), and the crank angle sensor 31 disposed in the vicinity of the crankshaft of the engine 10 A pulse signal representing the crankshaft rotation angle CA and a signal representing the intake flow rate of the engine are input from an air flow meter 33 provided in the intake passage of the engine 10.

  The output port of the ECU 30 is connected to the ignition circuit 41 and the fuel injection circuit 43, and controls the ignition timing and fuel injection of the engine 10.

  The ECU 30 inputs the engine rotational speed N (rpm) from the frequency of the pulse signal input from the crank angle sensor 31 and a reference position signal that is separately generated every time the compression stroke reaches the top dead center of a specific cylinder (for example, # 1 cylinder). The crankshaft rotation angle is calculated from the number of crank angle pulses.

  Further, the ECU 30 sets the engine fuel injection amount and the engine ignition timing based on the engine intake flow rate detected by the air flow meter 33 and the engine speed. Since any known method can be used for the fuel injection amount calculation and the ignition timing calculation, detailed description thereof is omitted here.

  In the present embodiment, the ECU 30 further calculates the combustion parameters such as the total calorific value of combustion of each cylinder and the indicated mean effective pressure based on the outputs at the respective crank angles of the in-cylinder pressure sensors 11 to 14, and The fuel injection amount and ignition timing calculated above are corrected so as to eliminate variations in these combustion parameters, and uniformization control is performed so that the combustion state of each cylinder becomes uniform.

  Any of the known methods can be used for the equalization control itself, but in any method, if the output characteristics of the in-cylinder pressure sensor of each cylinder vary, the combustion state of each cylinder is made uniform. I can't.

  FIG. 2 is a diagram showing output characteristics of a general in-cylinder pressure sensor, which is a relationship between sensor output and in-cylinder pressure, where pressure is plotted on the vertical axis (y-axis) and sensor output on the horizontal axis (x-axis). Is shown.

As shown in FIG. 2, the output of the in-cylinder pressure sensor increases substantially in proportion to the pressure, so that the output characteristic is a straight line.
In this specification, the intersection of the output characteristic line and the y-axis (that is, the in-cylinder pressure at which the sensor output becomes zero) is called an offset, and the slope of the output characteristic line is called a gain.

Therefore, the output characteristic uses gain a and offset b,
y = ax + b
Represented as:

  However, in actuality, the values of the gain a and the offset b are not only initially varied within the tolerance of each sensor, but also may vary with use time, and a plurality of in-cylinder pressure sensors are used. In this case, the pressure detection value varies.

  For example, FIG. 3 schematically shows a state of variation in output characteristics of the in-cylinder pressure sensors 11 to 14 of FIG. In FIG. 3, I to IV represent the output characteristics of the sensors 11 to 14, respectively.

  As shown in FIG. 3, when the output characteristics of the in-cylinder pressure sensors vary, the output of the in-cylinder pressure sensor of each cylinder differs even in an ideal state where there is no variation in the combustion state of each cylinder. Thus, the total calorific value calculated based on the output of each in-cylinder pressure sensor, the illustrated effective pressure, and the like do not match. In this case, if the above-described equalization control is performed, the combustion state of each cylinder may vary.

Therefore, in this embodiment, variations in output characteristics of the in-cylinder pressure sensors are corrected by the following method.
FIG. 4 is a view similar to FIG. 2 for explaining the output characteristic variation correction method.

  In the present embodiment, a reference output characteristic (shown by a one-dot chain line in FIG. 4) is set by a method described later, and an actual sensor output characteristic (shown by a solid line in FIG. 4) so as to coincide with the reference output characteristic. Correct.

  Specifically, first, two sets of data regarding the output of the actual in-cylinder pressure sensor and the pressure displayed by the sensor are taken, and the gain a and the offset b of the output characteristics of the actual in-cylinder pressure sensor are calculated based on this data. .

For example, if the sensor outputs are xe and xp when the in-cylinder pressure measured by an actual sensor is ye and yp, respectively, the gain a and the offset b of the output characteristics of the in-cylinder pressure sensor are respectively
a = (yp-ye) / (xp-xe)
b = (ye * xp-yp * xe) / (xp-xe)
As required.

  In order to make this output characteristic coincide with the reference output characteristic indicated by the one-dot chain line in FIG. 4, when the gain of the reference output characteristic is A and the offset is B, the correction coefficient α = A / a is the actual output. The characteristic gain a may be multiplied and the correction coefficient β = (B−b) may be added to the actual output characteristic offset.

Therefore, the corrected output characteristics are
y = α · (a · x) + b + β
As required.

  In the description of FIGS. 2 to 4, the output characteristic is expressed in the form of pressure on the y-axis, sensor output on the x-axis, and y (pressure) as a function of x (sensor output). Conversely, when the output characteristic is expressed in the form of sensor output on the y-axis and pressure on the x-axis and the sensor output (y) as a function of the pressure (x), the same correction can be performed. .

Next, the reference output characteristic of FIG. 4 will be described.
As described above, in the present invention, in order to easily give priority to eliminating variations in output characteristics of the in-cylinder pressure sensors, the output characteristics are not calibrated using separately measured in-cylinder pressure.
For this reason, the in-cylinder pressure calculated using the corrected output characteristics may not exactly match the actual pressure.

  Therefore, the reference output characteristics used for the correction are those corresponding to the true pressure as much as possible. Not only the corrected output characteristics of the in-cylinder pressure sensors match, but also the corrected output characteristics are used. It is preferable that the obtained pressure value be as close to the true pressure as possible.

  Therefore, in the following embodiments, (1) when using the output characteristics of the in-cylinder pressure sensor of any cylinder as the reference output characteristics, (2) when using the output characteristics that are predetermined according to the operating conditions, (3) When the average of the output characteristics of the in-cylinder pressure sensors of all the cylinders is used, the correction of the output characteristics will be described in detail by taking three examples as examples.

  (1) When the cylinder pressure sensor output characteristic of any cylinder is used as the reference output characteristic.

  In this embodiment, the output characteristics (gain, offset) of each cylinder are obtained by the above-described method, the output characteristics of one of the cylinders are used as the reference output characteristics, and the output characteristics of the other cylinders are used as the reference output characteristics. To match.

  Originally, the variation in the output characteristics is not so large, and the output characteristics of each in-cylinder pressure sensor are not so large, so by matching the output characteristics of one in-cylinder pressure sensor with the output characteristics of the other in-cylinder pressure sensors, Variations in the output characteristics of the in-cylinder pressure sensors can be eliminated without the pressure values detected by the in-cylinder pressure sensors greatly deviating from the true values.

  FIG. 5 is a flowchart for explaining the correction operation of the in-cylinder pressure sensor output characteristic in the present embodiment. This operation is executed by the ECU 30.

  In FIG. 5, step 501 determines whether or not a correction execution condition for the in-cylinder pressure sensor output characteristic is satisfied. In this embodiment, the output characteristic is corrected only when the engine is performing the fuel cut operation. This is because during the fuel cut operation, combustion is not performed in the cylinders, so that variations in pressure within each cylinder due to variations in combustion do not occur, and, for example, the pressure peak values in the cylinders etc. match best among the cylinders.

  If the fuel cut operation is currently being performed in step 501, next, in step 502, the in-cylinder pressure is actually measured using each in-cylinder pressure sensor at two predetermined points in the stroke cycle of each cylinder.

  In this embodiment, the two points at which the above measurement is performed are a point at which the in-cylinder pressure reaches a peak (compression top dead center) and a predetermined section in the exhaust stroke (or intake stroke), and the in-cylinder peak pressure (Pp) and An average value (Pe) of the in-cylinder pressure in a predetermined section during the exhaust stroke (or intake stroke) is obtained. That is, by using the maximum value and the minimum value of the in-cylinder pressure, the calculation accuracy of the output characteristics calculated below is improved.

  In addition, the measurement at the two points is not a single measurement value, but a plurality of cycles (for example, 10 cycles) are measured, and the average value is adopted as Pp, Pe, Vp, Ve, and the influence of noise becomes the measurement value. Prevent entry.

After the measurement by all the cylinder internal pressure sensors is completed, in step 505, the gain a of each sensor is calculated from the above-described equation using the measured values Pp and Pe in each cylinder and the sensor outputs Vp and Ve at that time. And the offset b are calculated. That is,
a = (Pp−Pe) / (Vp−Ve)
b = (Pe · Vp−Pp · Ve) / (Vp−Ve)
After obtaining the gain a and offset b of each cylinder as described above, in step 507, the gain and offset calculated above of the in-cylinder pressure sensor of any one of the cylinders (for example, # 1 cylinder) are respectively determined. The correction coefficient α = A / a and the correction coefficient β = (B−b) are obtained for each cylinder using the reference values A and B, and the correction operation is terminated.

When the correction coefficients α and β are obtained by this operation, the ECU 30 corrects the output characteristics of each in-cylinder pressure sensor using these correction coefficients,
P = α · (a · V) + b + β
In-cylinder pressure is obtained as follows (P is the in-cylinder pressure, and V is the output of the sensor).

  As a result, variations in the output characteristics of the in-cylinder pressure sensors are corrected, and the in-cylinder pressure obtained by the in-cylinder pressure sensors can be used to accurately equalize the combustion state of each cylinder.

  (2) When using a predetermined reference output characteristic according to operating conditions.

  In this embodiment, a reference output characteristic is determined in advance according to the engine operating state (rotation speed, intake air amount), and the reference output characteristic to be used according to the rotation speed and intake air amount during fuel cut operation of the engine is determined. select.

  As described above, since combustion does not occur during engine fuel cut operation, variations in the in-cylinder pressure peak value in each cylinder and in-cylinder pressure in the intake stroke (or exhaust stroke) are reduced. Further, the in-cylinder pressure peak value (compression top dead center pressure) and the in-cylinder pressure during the intake stroke (or exhaust stroke) are almost always the same value if the engine speed and the intake air amount are determined.

  Therefore, using a calibrated in-cylinder pressure sensor, a reference output characteristic is created in advance from the peak value of the in-cylinder pressure and the in-cylinder pressure in the intake stroke or the exhaust stroke in accordance with each rotation speed and air volume. By selecting the reference output characteristic according to the operating condition during the operation of the cylinder and correcting the output characteristic of each in-cylinder pressure sensor, the variation in the output characteristic of each in-cylinder pressure sensor is eliminated and the pressure detected by each in-cylinder pressure sensor The value can be close to the true value.

  FIG. 6 is a flowchart similar to FIG. 5 for explaining the correction operation of the in-cylinder pressure sensor output characteristics in the present embodiment.

  In FIG. 6, steps 601, 603, and 605 are the same operations as steps 501, 503, and 505 in FIG. 5, respectively.

  That is, also in the present embodiment, the correction of the output characteristics is performed when the engine is performing the fuel cut operation (step 601), and the average in-cylinder in the predetermined section of the pressure peak value and the exhaust stroke of each cylinder during the fuel cut operation. The pressure is measured for a plurality of cycles using each in-cylinder pressure sensor, and the peak value Pp and the in-cylinder pressure Pe in the exhaust stroke are calculated as the cycle average value of each cylinder (step 603). Then, using these, the output characteristics (gain a and offset b) of each in-cylinder pressure sensor are calculated (step 605).

In the present embodiment, the gain A and the offset B of the reference output characteristic determined in advance are read out in accordance with the current engine speed and the intake air amount. As described above, in this embodiment, the reference output characteristic in each operating state is obtained based on the actual measured value of the in-cylinder pressure when the engine is operated with each combination of the rotational speed and the intake air amount. The gain A and the offset B are stored in the ROM of the ECU 30 with the engine speed and the air amount as parameters.
In step 607, the corresponding data is read from the gain A and offset B stored in the ROM in accordance with the rotational speed and the intake air amount.

  In step 609, the output characteristic of each in-cylinder pressure sensor is corrected using the gain A and the offset B of the reference output characteristic read out as described above. Since this operation is the same as step 507 in FIG. 5, description thereof is omitted here.

  (3) When the average of the output characteristics of the in-cylinder pressure sensors of all cylinders is used as the reference output characteristic.

  In this embodiment, after calculating the output characteristics of each in-cylinder pressure sensor at the time of correcting the output characteristics, a total average value of the calculated output characteristics (gain a and offset b) of the in-cylinder pressure sensor is obtained, and this average value is used as a reference output characteristic. The gain A and the offset B are used.

  That is, in the first embodiment, the output characteristics of all the in-cylinder pressure sensors are matched with the output characteristics based on the output characteristics of any of the in-cylinder pressure sensors calculated in the first embodiment. The difference is that instead of the output characteristic of one in-cylinder pressure sensor, the average of the output characteristics of all the in-cylinder pressure sensors is used as the reference output characteristic.

  FIG. 7 is a flowchart similar to FIGS. 5 and 6 for explaining the output characteristic correction operation of the in-cylinder pressure sensor in the present embodiment.

  In the operation of FIG. 7, Steps 701, 703, and 705 are the same as Steps 501, 503, and 505 of FIG. 5, and the gain a and the offset b of each in-cylinder pressure sensor output characteristic are calculated by these operations. The

  Next, in this embodiment, average values A and B of the gains a and offsets b of all the in-cylinder pressure sensors obtained as described above are calculated in step 707.

  In step 709, the average values A and B of the gain and offset calculated as described above are used as the gain and offset of the reference output characteristic, and the output characteristic of each in-cylinder pressure sensor is corrected. The operation in step 709 is the same as that in step 507 in FIG. 5 and step 609 in FIG.

  Thereby, also in this embodiment, the output characteristics of each in-cylinder pressure sensor can be matched while preventing the pressure value detected by each in-cylinder pressure sensor from greatly deviating from the true pressure value.

  As described above, in each of the embodiments described above, the output characteristic of the in-cylinder pressure sensor has been described by taking an example in which the pressure value is given as a function of the sensor output. Needless to say, even when the output characteristic is given as a function, the same correction as in each of the above embodiments can be performed.

It is a figure explaining schematic structure of an embodiment at the time of applying the present invention to an internal-combustion engine for vehicles. It is a figure explaining the output characteristic of a cylinder pressure sensor. It is a figure explaining the dispersion | variation in the output characteristic of a cylinder pressure sensor. It is a figure explaining the correction method of the output characteristic variation of a cylinder pressure sensor. 5 is a flowchart for explaining a first embodiment of a variation correction operation for in-cylinder pressure sensor output characteristics. It is a flowchart explaining 2nd Embodiment of the dispersion | variation correction operation of a cylinder pressure sensor output characteristic. It is a flowchart explaining 3rd Embodiment of the dispersion | variation correction operation of a cylinder pressure sensor output characteristic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine main body 11-14 In-cylinder pressure sensor 30 Electronic control unit (ECU)
31 Crank angle sensor 33 Air flow meter

Claims (9)

In an internal combustion engine provided with an in-cylinder pressure sensor for detecting an in-cylinder pressure for each of a plurality of cylinders, detection is performed using the in-cylinder pressure sensors at two predetermined points in a stroke cycle of the cylinder under predetermined operating conditions. A control device for an internal combustion engine that corrects an output characteristic representing a relationship between an output of each in-cylinder pressure sensor and an in-cylinder pressure based on an in-cylinder pressure,
The output characteristic is given as a linear function of the sensor output and the in-cylinder pressure, and the correction is performed on the output characteristic of each sensor so that the output characteristic of each in-cylinder pressure sensor matches a pre-stored common reference output characteristic. A control apparatus for an internal combustion engine, which is performed by correcting an offset and a gain.   The control apparatus for an internal combustion engine according to claim 1, wherein the reference output characteristic is an output characteristic of one of the in-cylinder pressure sensors.   The control apparatus for an internal combustion engine according to claim 1, wherein the reference output characteristic is an output characteristic predetermined according to an operating condition of the engine.   The control apparatus for an internal combustion engine according to claim 1, wherein the reference output characteristic is given as an average value of an offset and a gain of the output characteristic before correction of each in-cylinder pressure sensor.   The control apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein the predetermined operating condition is a state in which the engine is performing a fuel cut operation.   The one of two predetermined points in a stroke cycle of a cylinder that performs pressure detection using each of the in-cylinder pressure sensors is a timing at which the in-cylinder pressure of each cylinder reaches a peak. The control device for an internal combustion engine according to any one of claims 5 to 6.   One of the two predetermined points in the stroke cycle of the cylinder for detecting the output of each in-cylinder pressure sensor is within a predetermined section of the intake stroke of the cylinder. The control apparatus for an internal combustion engine according to the item.   7. The system according to claim 1, wherein one of the two predetermined points in the stroke cycle of the cylinder that detects the in-cylinder pressure sensor output is within a predetermined section of the exhaust stroke of the cylinder. The control apparatus of the internal combustion engine described in 1.   The control device for an internal combustion engine according to any one of claims 1 to 7, wherein an average value of detection values in a predetermined number of cycles is adopted as a detection value of each sensor output at the two predetermined points. .

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