JPH11257149A - Internal combustion engine controller using cylinder internal pressure signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine controller capable of accurately detecting a value of a cylinder internal pressure signal even if drift is generated on the cylinder internal pressure signal. SOLUTION: A controller controls an internal combustion engine on the basis of the level of a cylinder internal pressure signal to be obtained from a cylinder internal pressure sensor in a cylinder of an internal combustion engine 10. It is provided with a reference value setting means 31 for setting a reference value according to a specified sample value of a cylinder pressure signal corresponding to the specified crank angle in the intake and/or exhaust stroke or the crank angle period, and a reading means 31 for taking the value corresponding to the difference between the reference value and the sample value of the cylinder internal pressure signal as the level of the cylinder internal pressure signal. Therefore, since the proper reading reference value of the cylinder internal pressure signal is set while following up drift of the cylinder internal pressure signal, the level of the cylinder pressure signal can be accurately read.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly, to an internal combustion engine that controls the engine based on an in-cylinder pressure signal corresponding to a pressure in a cylinder of the internal combustion engine (hereinafter referred to as an in-cylinder pressure). Related to a control device.

[0002]

2. Description of the Related Art It is known to use an in-cylinder pressure sensor for detecting the gas pressure in a cylinder of an internal combustion engine, that is, the in-cylinder pressure, in order to grasp the operating state of the internal combustion engine. For example, an in-cylinder pressure sensor disclosed in JP-A-8-50072 has a ring-shaped piezoelectric element, and the piezoelectric element is provided between a spark plug mounting surface of a cylinder head and a spark plug washer. It is clamped and fixed by being screwed into the cylinder head and fixed by being screwed into the cylinder head. Such an in-cylinder pressure sensor generates a detection voltage indicating an in-cylinder pressure, and the voltage is supplied to an engine control circuit as an in-cylinder pressure signal, and a parameter indicating an engine operation state for controlling a fuel injection amount, an ignition timing, and the like. Used as one.

A conventional engine control device detects a value of an in-cylinder pressure signal supplied from an in-cylinder pressure sensor based on a fixed value such as a ground level, and performs various engine controls based on the detected value. I'm trying to do it. The in-cylinder pressure indicated by the in-cylinder pressure signal changes, for example, as shown in FIG. 1, in a manner corresponding to the crank angle and each stroke that changes with the operation of the engine, and exhibits a peak in the combustion stroke of the engine. The peak value of the in-cylinder pressure signal having a level change as shown by the curve a in FIG. 1 is measured with reference to the ground level set in the engine control circuit as corresponding to the in-cylinder pressure having a value of zero. If the reference ground level is always zero potential, the engine control circuit can recognize that the value of the in-cylinder pressure signal correctly indicates the in-cylinder pressure, and the in-cylinder pressure when the in-cylinder pressure signal exhibits a peak. The signal value (Pmaxa) can be correctly detected as a peak value as it is.

However, due to variations in the in-cylinder pressure sensor, instantaneous changes in the operating environment due to changes over time or changes in the sensor temperature, etc., the pressure is supplied to the engine control circuit as shown by a curve b in FIG. The in-cylinder pressure signal may level shift or drift. In this case, if the value of the in-cylinder pressure signal at the time when the in-cylinder pressure signal exhibits a peak with respect to the ground level (zero potential) set in the engine control circuit is detected as the peak value as it is, the in-cylinder pressure signal of curve a and Despite having the same peak value (Pcr), the peak value (P
maxb) will be detected.

[0005] Such drift of the in-cylinder pressure signal cannot be ignored in performing accurate engine control in accordance with the in-cylinder pressure.
Further, there is a system disclosed in Japanese Patent Application Laid-Open No. 8-50072 as a system for performing exhaust gas recirculation control based on a detection output of an in-cylinder pressure sensor. This system uses exhaust gas recirculation (E
In a multi-cylinder internal combustion engine in which exhaust gas is recirculated to each cylinder by a GR) device, the indicated mean effective pressure is detected in each cycle of each cylinder, and the detected mean effective pressure for each cylinder is calculated based on the detected mean effective pressure. A variation between cylinders of the variation and the indicated average effective pressure is obtained, and the exhaust gas recirculation rate of each cylinder is controlled based on the variation between cycles and the variation between cylinders.

In such a system for obtaining the value of the indicated mean effective pressure from the output of the in-cylinder pressure sensor and performing engine control based on the value, if the drift of the in-cylinder pressure signal as described above is neglected, Cannot be accurately obtained, so that accurate engine control cannot be performed.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of such a problem, and an object of the present invention is to accurately determine the value of an in-cylinder pressure signal even if a drift occurs in the in-cylinder pressure signal. An object of the present invention is to provide an engine control device that can detect the engine.

[0008]

An apparatus according to the present invention is an internal combustion engine control apparatus for controlling an internal combustion engine based on a level of an in-cylinder pressure signal obtained from an in-cylinder pressure sensor in a cylinder of the internal combustion engine. Reference value setting means for setting a reference value corresponding to a specific sample value of the in-cylinder pressure signal corresponding to a predetermined crank angle or a crank angle period in an intake and / or exhaust stroke of the cylinder, and a sample of the reference value and the in-cylinder pressure signal Reading means for setting a value corresponding to the difference from the value to the level of the in-cylinder pressure signal. According to this internal combustion engine control device,
An appropriate reading reference value of the in-cylinder pressure signal is set following the drift of the in-cylinder pressure signal, and the level of the in-cylinder pressure signal is read correctly.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 shows an engine control device to which the in-cylinder pressure sensor according to the present invention is applied. In-cylinder pressure sensors 1A to 1 used in this engine control device
D is provided for each cylinder of the internal combustion engine 10 (four cylinders in this embodiment) composed of a plurality of cylinders. Each of the in-cylinder pressure sensors 1A to 1D has a sensor element section composed of a piezoelectric element and an amplification section for amplifying a voltage generated from the sensor element section, and the amplified output is used as a cylinder pressure detection signal as a control circuit 20. Supplied to

The control circuit 20 includes a CPU 31, a ROM 3
2. RAM 33, A / D (analog / digital) converter 34, actuator drive circuit 35, and counter 37
And they are interconnected by a common bus (not shown). A plurality of sensors are connected to the A / D converter 34, and the injector 43 is connected to the drive circuit 35.
A-43D, ignition devices 44A-44D, EGR valve 4
Actuators such as 5A to 45D are connected. Although schematically shown in the figure, the injectors 43A to 43D and the ignition devices 44A to 44D and the EGR valves 45A to 45D
45D is provided corresponding to each cylinder.

[0011] As a sensor to be connected to the A / D converter 34, in addition to the cylinder pressure sensor 1A~1D described above, the throttle valve of the internal combustion engine 10 (not shown) from the pressure P _b in the downstream of the intake pipe There are engine parameter sensors such as an intake pipe internal pressure sensor 41 that generates a corresponding voltage and a cooling water temperature sensor 42 that detects a cooling water temperature T _W of the internal combustion engine 10. The A / D converter 34 sequentially converts the analog output voltage of each sensor into a digital value every time a crankshaft (not shown) makes one rotation, outputs the digital value for each sensor, and repeatedly updates the digital value.

A counter 37 has a crank angle sensor 38.
Supplies a pulse synchronized with the rotation of the crankshaft.
The counter 37 generates a signal indicating the engine speed Ne by measuring the interval between the pulses output from the crank angle sensor 38 by counting the number of clock pulses generated.
The crank angle sensor 38 also includes a reference position signal indicating a time when the crank angle is at a predetermined angle (for example, a start time of an intake stroke) and a TDC indicating the top dead center of the piston of each cylinder.
Signal, a BDC signal indicating the time of the bottom dead center of the piston of each cylinder, and 1 [deg] of the crankshaft of the engine 10.
Crank pulses synchronized with the rotation of
It is supplied to PU31. The CPU 31 performs a counting operation of counting crank pulses while being reset in response to the reference position signal. Therefore, the CPU 31 determines the crank angle θ in units of 1 [deg] by the counting operation.
Can be grasped, and a crank angle signal corresponding to the count value is generated and used for various processes as needed.

The CPU 31 of the control circuit 20 includes a ROM 32
Operates in accordance with a program stored in advance in the A / D converter, reads the output values of the plurality of sensors through the A / D converter 34, stores the read values in the RAM 33, and based on the output values of the sensors, the injectors 43A to 43D and Ignition devices 44A-44D and EGR valves 45A-45D
, Etc., to the drive circuit 35. The drive circuit 35 generates a drive signal having a level and a waveform necessary for actually driving the actuator according to the control signal, and supplies the drive signal to the corresponding actuator.

The CPU 31 is also responsible for calculating the indicated mean effective pressure, and calculates the indicated mean effective pressure Pmi at the time of ignition and the stroke (net) mean effective pressure Pme. The indicated average effective pressures Pmi and Pme are obtained based on digitized in-cylinder pressure signal data transferred from the A / D converter 34. The CPU 31 further performs a reference value setting process and a peak value calculation process. The reference value setting process is a process for setting a reference value for properly reading the value of the in-cylinder pressure signal data generally transferred from the A / D converter 34, and is a process for setting a predetermined value in the intake stroke and / or the exhaust stroke of the engine 10. A reference value is set based on the sample value data of the in-cylinder pressure signal during the crank angle period or a predetermined crank angle, and the value of the in-cylinder pressure signal data is read using the set reference value.

The peak value calculation process is a process for calculating the peak value of the in-cylinder pressure signal based on the reference value set by the reference value setting process. FIG. 3 shows the procedure of the reference setting process, and the CPU 31 executes this process in the form of a subroutine for each cylinder. When shifting to this subroutine, the CPU 31 first reads the current crank angle θ from the crank angle signal based on the output of the crank angle sensor 38 (step S11), and determines whether or not the crank angle θ is in the range of θ0 to θ1. Is determined (step S12). Here, the range of θ0 to θ1 corresponds to the intake stroke of the engine 10, as shown in FIG.

In step S12, if the crank angle .theta. Is not in the range of .theta.0 to .theta.1, the routine exits from the reference value setting subroutine and returns to the main routine (not shown). on the other hand,
In step S12, if the crank angle θ is in the range of θ0 to θ1, the CPU 31 determines the timing at which the piston of the cylinder reaches the bottom dead center (BDC) based on the BDC signal supplied from the crank angle sensor 38. Wait for arrival (step S13). When the bottom dead center timing arrives, the CPU 31 determines that the sample value P of the in-cylinder pressure signal at the bottom dead center timing or a timing near the bottom dead center timing is obtained.
0 'is set as the reference value P0 (step S14). After step S14, the CPU 31 returns to the main routine.

According to this reference value setting process, as shown in FIG. 4, the value P0 'of the in-cylinder pressure at the end of the intake stroke of the cylinder is set to the reference value P0 each time the time comes. Can be. Therefore, the reference value P0 is the value of the engine 1
0, the value is updated to the value P0 'every cycle.
Even if the in-cylinder pressure sensor varies from cycle to cycle due to some cause, in addition to variations and changes over time, a reference value suitable for the current state of the in-cylinder pressure signal can be immediately set.

The above steps S12 to S14
Corresponds to reference value setting means. FIG. 5 shows the procedure of the peak value calculation process, and the CPU 31 also executes this process in the form of a subroutine for each cylinder. When the CPU 31 shifts to this subroutine, first, the crank angle sensor 3
The current crank angle θ is read from the crank angle signal based on the output of step 8 (step S21), and it is determined whether or not the crank angle θ is in the range of θ2 to θ3 (step S22). Here, the range of θ2 to θ3 corresponds to the combustion stroke of the engine 10, as shown in FIG.

In step S22, if the crank angle θ is not in the range of θ2 to θ3, the process exits this peak value calculation subroutine and returns to the main routine (not shown). On the other hand, in step S22, when the crank angle θ is θ2 to θ3
Is within the range, the CPU 31 determines the peak based on the data of the in-cylinder pressure signal (step S23).
More specifically, in such peak determination, for example,
The CPU 31 sequentially compares the values before and after each sample value data of the in-cylinder pressure signal obtained in time series, and the in-cylinder pressure signal peaks based on the comparison result that the subsequent value is smaller than the preceding value for the first time. It can be determined that it has been presented. This is supported by the fact that the level of the in-cylinder pressure signal during the combustion stroke should rise and peak as shown in FIG. However, the present invention is not limited to such a peak determination, and the peak determination can be performed by another method.

If it is not determined in step S23 that the in-cylinder pressure signal has peaked, the CPU 31
Return to the main routine. Conversely, when determining that the in-cylinder pressure signal has a peak, the CPU 31 calculates the difference between the sample value Pp 'of the in-cylinder pressure signal having the peak and the reference value P0, and obtains the value of the difference obtained thereby. Is stored in the RAM 33 as the peak value Pp (step S24). After step S24, CPU 31 returns to the main routine.

According to the peak value calculating process, as shown in FIG. 4, the peak value Pp of the in-cylinder pressure signal is measured with the reference value P0 set by the reference value setting process. Even if the signal drifts, the peak value can be obtained correctly with an appropriate reference value. Note that P
Both the value of 0 'and the value of Pp' are obtained with reference to a zero value corresponding to, for example, a ground level set in the A / D converter 34. Here, if it is guaranteed that the in-cylinder pressure signal supplied to the A / D converter 34 always exhibits a negative value at the end of the suction stroke, the above-described step S24 is performed.
The processing of

[0022]

Equation 1 Pp = Pp '+ | P0' | (1) It suffices to perform the following operation. Step S24 corresponds to reading means. FIG. 6 shows a procedure of a reference value setting process according to a second embodiment which is a modification of the first embodiment. Steps equivalent to those shown in FIG. 3 are denoted by the same reference numerals.

The CPU 31 determines in steps S11 and S12
, The current crank angle θ is read from the crank angle signal, and it is determined whether or not the crank angle θ is in the range of θ0 to θ1 corresponding to the intake stroke of the engine 10. If the crank angle θ is not in the range of θ0 to θ1 in step S12, the process exits this subroutine for setting the reference value and returns to the main routine (not shown). On the other hand, if the crank angle θ is in the range of θ0 to θ1 in step S12, C
The PU 31 takes in the sample value Pi of the in-cylinder pressure signal corresponding to the crank angle θ and stores it in the RAM 33 (Step S31). Next, the CPU 31 determines whether or not the crank angle θ has reached θ1 corresponding to the end of the intake stroke (step S32). If not, the CPU 31 exits this subroutine and returns to the main routine. Therefore, the CPU 31 sequentially stores the sample value Pi of the in-cylinder pressure signal in the RAM 33 in step S31 every time the CPU 31 shifts to this subroutine while the crank angle θ is in the range of θ0 to θ1.

If it is determined in step S32 that the crank angle θ has reached θ1, the CPU 31 determines the sample value group Pi (i = 1, 2, 2) of the in-cylinder pressure signal in the range of θ0 to θ1 stored in step S31. …, N)
Is read from the RAM 33, and the average value PAV is calculated (step S33). If the calculation for this average is expressed by an equation,

[0025]

(Equation 2)

## EQU1 ## Thus, when the average value PAV is obtained,
The CPU 31 sets the average value PAV to the reference value P0 (step S34). After step S34, the CPU 31
Returns to the main routine. According to this reference value setting process, as shown in FIG. 7, a sample value group Pi (i = 1, 2,...) Of the in-cylinder pressure signal in the intake stroke of the cylinder concerned.
The average value PAV of N) can be set to the reference value P0 every time the suction stroke ends. Therefore, the reference value P0
Is updated to the average value PAV for each cycle of the engine 10, and a reference value suitable for the current state of the in-cylinder pressure signal can be immediately set, as in the embodiment of FIG.

Moreover, in the second embodiment, since the average value of the plurality of sample values of the in-cylinder pressure signal in the suction stroke is used as the reference value, some of the plurality of sample values are of low reliability. In this case, a reference value relatively close to the best value can be set. On the other hand, in the first embodiment shown in FIG. 3, since the reference value is set based on only one sample value of the in-cylinder pressure signal, the only sample value is low in reliability. In such a case, an appropriate reference value may not be guaranteed. However, the first embodiment has an advantage over the second embodiment in that the process for obtaining the reference value is simple.

The reference value P0 obtained by the processing shown in FIG. 6 is also effectively used in the peak value calculation processing shown in FIG. FIG. 8 shows a procedure of a reference value setting process according to a further modified third embodiment,
Steps equivalent to those shown in FIG. 3 are denoted by the same reference numerals. When reading the current crank angle θ from the crank angle signal in step S11, the CPU 31 determines whether or not the crank angle θ is θ ′ corresponding to the center point in the intake stroke of the engine 10 (step S41). .

In step S41, if the crank angle θ is not θ ′, the process exits this subroutine for setting the reference value and returns to the main routine (not shown). On the other hand, if the crank angle θ is θ ′ in step S41, C
The PU 31 takes in the sample value P0 '(n) (n is a sample number) of the in-cylinder pressure signal corresponding to the crank angle θ and stores it in the RAM 33 (Step S42).

Next, the CPU 31 calculates the sample value P
0 '(n) and a predetermined number of sample values P0' (n-1), P0 '(n-n) stored in the RAM 33 by step S42 in the subroutine executed up to the last time.
2),..., And their moving average value P0ma (n)
Is calculated (step S43). Thus, the average value P0ma
After calculating (n), the CPU 31 calculates the average value P0ma
(N) is set to the reference value P0 (step S44). After step S44, the CPU 31 returns to the main routine.

The method of obtaining the moving average value is as follows. FIG. 9 shows, in chronological order, sample values P0 'of the in-cylinder pressure signal corresponding to θ' obtained at one cycle intervals including the exhaust, suction, compression, and combustion strokes. In FIG. 9, if it is assumed that, for example, P0 '(n) is newly obtained, the CPU 31 determines, for example, two sample values P0' (n-1) and P0 'obtained before the sample value.
The value of (n-2) is read from the RAM 33, and the latest P
0 '(n) and its preceding P0' (n-1), P0 '(n-
The values of 2) are weighted and averaged. That is,

[0032]

The value of {K ₁ P0 ′ (n) + K ₂ P0 ′ (n−1) + K ₃ P0 ′ (n−2)} / 3 (3) is obtained. Here, K ₁ , K ₂ , and K ₃ are weighting coefficients, K _{1 to} K ₃ <1.0, and K ₁ + K ₂ + K
₃ = 1.0. In FIG. 9, the sample value P0 'used for the calculation at this time is indicated by a dotted frame.

Similarly, when the sample value P0 '(n + 1) of the in-cylinder pressure signal corresponding to θ' is newly obtained again, the CPU 31 similarly sets the two sample values P0 obtained before the sample value. '(N), P0' (n-1)

[0034]

## EQU4 ## The value of {K ₁ P0 ′ (n + 1) + K ₂ P0 ′ (n) + K ₃ P0 ′ (n−1)} / 3 (4) is obtained. In this way, the latest sample value corresponding to θ ′ and the sample value corresponding to θ ′ obtained two times before the weight are weighted and their average is calculated, and each time a new sample value corresponding to θ ′ is obtained. The average value is calculated. As can be seen from FIG. 9, the sample values required to calculate the average value, in other words, the object to be averaged, changes in the time series (the dotted frame shifts to the right), and the 1 The moving average value is obtained sequentially for each cycle interval.

Here, the case where a moving average is obtained from three sample values has been described. In the present embodiment, the number N of objects to be averaged is made variable, and the N number of objects corresponding to the sample number n are changed. Moving average value P0ma of sample value P0 '
(N) is generally as follows.

[0036]

(Equation 5)

If expanded,

[0038]

[6] P0ma (n) = (1 / N) {K 1 P0 '(n) + K 2 P0' (n-1) + ... + K N P0 '(n-N + 1)} ...... ( 6)

In this embodiment, the above equation (5) and
And in (6)₁= K_Two= ... = K _N Or K₁≧ K_Two≧
… ≧ K_N And K₁> K_Two>…> K_N To be
That are more suitable for the actual engine characteristics.
We have obtained good results. Of such a cylinder pressure signal sample value
According to the reference value setting processing based on the moving average value, FIG.
As shown, at the center point in the intake stroke of the cylinder,
Moving average value P0 of sample value P0 'of corresponding in-cylinder pressure signal
It is possible to set ma to the reference value P0 every time the center point passes.
it can. Therefore, the reference value P0 is 1
Updated to the moving average value P0ma at each cycle interval
3 and FIG. 6, the current in-cylinder pressure signal
The reference value suitable for the state can be set immediately.

Furthermore, in the third embodiment, the moving average value of the in-cylinder pressure signal sample values for several cycles corresponding to the center point in the suction stroke is used as the reference value. Even if the sample value in the cycle is unreliable, a reference value relatively close to the best can be set. On the other hand, in the first and second embodiments shown in FIGS. 3 and 6, the reference value is set based on only one sample value of the in-cylinder pressure signal or the sample value in one intake stroke. If such a single sample value or each sample value in a single intake stroke is unreliable, an appropriate reference value may not be guaranteed. However, the first and second embodiments have an advantage over the third embodiment in that the process for obtaining the reference value is simple.

Although the first to third embodiments have been described above, each embodiment can be appropriately modified according to the engine to which the embodiment is applied. In the first to third embodiments, the reference value is set using the sampled value of the in-cylinder pressure signal in the suction stroke, regardless of whether the difference is singular or plural, or the average value or the moving average value. Then it is common. However, it can be modified to use the sample values in the exhaust stroke in addition to the sample values in the intake stroke to set the reference values, or modified to use the sample values in the intake and exhaust strokes to set the reference values. You can also. In short, the reference value may be set substantially using the sample value of the predetermined crank angle or the predetermined crank angle period in the intake and / or exhaust stroke.

In the third embodiment, the moving average value of the in-cylinder pressure signal sample values for several cycles corresponding to the center point in the suction stroke is used as the reference value. It is also possible to calculate an average value of a plurality of sample values in the suction stroke period as described above, use the average value for, for example, five cycles, obtain a moving average value thereof, and use this as a reference value. By doing so, it is possible to set a more stable reference value that is resistant to sudden deterioration in reliability within and between sample value cycles (in this case, the intake stroke).

On the other hand, when calculating the indicated mean effective pressure Pmi and the stroke mean effective pressure Pme as reading means different from FIG. 5, it may be convenient to set a reference value as in the following fourth embodiment. is there. First, the illustrated mean effective pressure Pmi and the stroke mean effective pressure Pme will be described in detail. FIG. 11 shows the engine 10
FIG. 3 shows a change in the in-cylinder pressure with respect to the stroke of the piston operating in each of the cylinders. First, at a point P, the suction valve is opened to start a suction stroke for sucking the air-fuel mixture, and at a point N which is a top dead center (TDC), the exhaust valve is closed. The cylinder pressure is BDC (bottom dead ce)
nter) to the vicinity of the point K. At point Q, the suction valve is closed to enter the compression stroke, and the in-cylinder pressure gradually increases. At a point R, the spark plug is ignited and enters a combustion stroke. The in-cylinder pressure rapidly increases and passes through a point L which is TDC, and then reaches a maximum at a point S. Point M where piston is BDC
, The in-cylinder pressure decreases, the exhaust valve is opened at point T, and the exhaust stroke starts.

The indicated mean effective pressure Pmi at the time of ignition means the work per unit volume that the piston makes with respect to the crankshaft from the point K to the point M via the point L.

[0045]

(Equation 7)

Is defined as On the other hand, the non-ignition indicated mean effective pressure Pmf means the work per unit volume of the combustion chamber that the piston makes with respect to the crankshaft from the point M to the point K via the point N,

[0047]

(Equation 8)

Is defined as In the equations (7) and (8), V represents the volume (volume) of the combustion chamber that changes with the progress of the stroke, V _MAX and V _MIN represent the maximum volume and the minimum volume, respectively. , TDC at the position of the combustion chamber. Further Pme
Means the work per unit volume that the piston performs on the crankshaft during one cycle,

[0049]

Pme≡Pmi−Pmf (9) On the other hand, FIG. 12 plots the level of the in-cylinder pressure signal with respect to the crank angle indicated by the crank angle signal stored in the RAM 33, and shows the change in the in-cylinder pressure with respect to the crank angle. Stroke points corresponding to the stroke points described in FIG. 11 are denoted by the same reference numerals.

In FIG. 12, calculating the amount of work that the piston uses as the crankshaft is nothing less than calculating the area of the region surrounded by the curve indicating the change in the in-cylinder pressure. That is, S _AA'B'B , S _BB'C'C , S _{CC'DD '} and S _DD'A'A
Are respectively AA'B'B, BB'C'C, CC 'shown in FIG.
Assuming the area of a region surrounded by DD 'and DD'A'A,
For each workload in equations (7) and (8),

[0051]

(Equation 10)

Can be expressed as follows. Further, when the in-cylinder pressure is sampled at every predetermined crank angle (for example, every one degree), the above-mentioned area can be expressed as the sum of only the in-cylinder pressure. V _MAX and V _MIN can be omitted because they are common to Pmi and Pmf. Therefore, Pmi and Pmf
Is

[0053]

[Equation 11]

And

[0055]

(Equation 12)

Can be obtained. Here, Pi represents the in-cylinder pressure at the i-th crank angle position θi as shown in FIG. Therefore, in order to calculate Pmi and Pmf in the CPU 31, it is sufficient to calculate the sum of the in-cylinder pressures Pi. That is, the area S between the stroke point L and the point M
_AA'B'B is calculated from the sum of the in-cylinder pressures as described above, and similarly,
Area S _BB'C'C between the stroke point M to the point N, the area between the area S _{CC'DD 'and} stroke point K between the stroke point N to point K to the point L S _{DD'A '} Calculate _A. The _'calculated by subtracting the area S _DD'A'A from _B, the area S _CC'DD the Pmf from the area S _BB'C'C' the Pmi area S _AA'B determined by subtracting, Pmi a Pme
Is subtracted from Pmf.

The CPU 31 calculates the indicated mean effective pressure Pmi or the stroke mean effective pressure Pme thus obtained at the time of ignition.
Is sequentially stored in the RAM 33 by a predetermined number, and necessary value data is read from the RAM 33 to perform engine control based on the indicated mean effective pressure Pmi or the stroke mean effective pressure Pme at the time of ignition. FIG. 12 shows that the level of the in-cylinder pressure signal is equal to the reference value P0 of the CPU 31 (corresponding to the output value of the A / D converter 34 of zero in this example) in any stroke.
Examples that are much higher than are shown. In this example, A
Since the sample value Pi of the in-cylinder pressure signal, which is the output value of the / D converter 34, is converted to a value of Pi-P0 in the CPU 31, the CPU 31 can treat all the values of Pi-P0 as positive values. .

However, in the above-described first to third embodiments, as can be seen from FIGS. 4, 7 and 10, an in-cylinder pressure signal having a level lower than the set reference value is generated (for example, FIG. 4, the value of Pi-P0 may be negative. If the value of Pi-P0 is negative,
In the calculation of the area and the like as in the equations (11) and (12), the sample value of the negative in-cylinder pressure signal is used, and the calculation process tends to be complicated. In other words, as shown in FIG. 12, if the level of the in-cylinder pressure signal is sufficiently higher than the reference value P0 of the CPU 31 in any stroke, it is guaranteed that all the sample values of the in-cylinder pressure signal are treated as positive values. In addition, the processing of various calculations can be simplified.

Therefore, in the fourth embodiment, the level of the in-cylinder pressure signal is set to the reference value P0 of the CPU 31 in any stroke.
The reference value P0 is set based on the sample value of the in-cylinder pressure signal in the exhaust stroke so as to be sufficiently higher than the reference value P0. FIG. 13 shows the procedure of the reference value setting process according to the fourth embodiment. The CPU 31 determines in step S1
After reading the current crank angle θ from the crank angle signal by 1, it is determined whether or not the crank angle θ is in the range of θ3 to 760 ° corresponding to the exhaust stroke of the engine 10 (step S51).

In step S51, if the crank angle θ is not in the range of θ3 to 760 °, the process exits this subroutine for setting the reference value and returns to the main routine (not shown).
On the other hand, in step S52, the crank angle θ is
If it is within the range of 760 °, the CPU 31 takes in the sample value Pi of the in-cylinder pressure signal corresponding to the crank angle θ and stores it in the RAM 33 (step S52). Next, the CPU 31 determines whether or not the crank angle θ has reached 760 ° corresponding to the end point of the exhaust stroke (step S53). If not, the CPU 31 exits this subroutine and returns to the main routine. Therefore, the CPU 31 successively stores the sample value Pi of the in-cylinder pressure signal in the RAM 33 in step S52 each time the routine shifts to this subroutine while the crank angle θ is in the range of θ3 to 760 °.

If it is determined in step S53 that the crank angle θ has reached 760 °, the CPU 31
Represents the sample value group Pi (i = 1, i = 1, 2) of the in-cylinder pressure signal in the range of θ3 to 760 ° stored in step S52.
2,..., N) are read from the RAM 31 and the average value PAV is calculated (step S54). The calculation formula for calculating the average is the same as the above formula (2).

When the average value PAV in the exhaust stroke is obtained in this manner, the CPU 31 calculates a predetermined value ΔP from the average value PAV.
Is set to the reference value P0 (step S55). After step S55, the CPU 31 returns to the main routine. According to this reference value setting process, FIG.
As shown in the figure, the exhaust stroke is terminated by a value smaller than the average value PAV of the sample value group Pi (i = 1, 2,..., N) of the in-cylinder pressure signal in the exhaust stroke by the predetermined value ΔP. Each time it is performed, it can be set to the reference value P0.
Therefore, the reference value P0 is sequentially updated to the value of PAV-ΔP for each cycle of the engine 10, and is suitable for the current state of the in-cylinder pressure signal as in the first to third embodiments. A reference value can be set.

Further, the predetermined value ΔP is calculated from the average value of the sample value group of the in-cylinder pressure signal in the exhaust stroke.
Since a value is set that ensures that the value obtained when P is reduced is sufficiently lower than the level in the suction stroke of the in-cylinder pressure signal, the level of the in-cylinder pressure signal in any stroke including the exhaust and suction strokes Is sufficiently higher than the reference value P0 of the CPU 31. Therefore, there is no possibility that the value of Pi-P0 becomes negative as described above, and it is necessary to exclusively use the sample value of the positive in-cylinder pressure signal in the calculation of the area and the like as in the above equations (11) and (12). This contributes to the simplification of the calculation process.

It is possible to modify the fourth embodiment. For example, the reference value P0 may be obtained by subtracting the predetermined value ΔP from the average value of the sample value group of the in-cylinder pressure signal in the intake stroke, instead of the exhaust stroke, or the in-cylinder pressure signal in both the exhaust and intake strokes The reference value P is obtained by subtracting the predetermined value ΔP from the average value of the sample value group.
0 may be obtained. However, it is preferable that the calculation of Pmi and Pme be performed in one cycle unit starting from the intake and ending with the exhaust, and that the level of the in-cylinder pressure signal is more than the level in the intake stroke immediately before the intake stroke which is the first stroke of the cycle. It is realistic to set a lower reference value.

In the fourth embodiment, the reference value is set based on the average value of a plurality of sample values of the in-cylinder pressure signal.
A value obtained by subtracting P may be set as a reference value. In short, it is sufficient to set a reference value sufficiently lower than a possible level of the in-cylinder pressure signal using a predetermined crank angle period or a sample value of the predetermined crank angle in the intake and / or exhaust strokes.

Further, a single sample value of a predetermined crank angle in the intake and / or exhaust stroke may be used for a plurality of cycles (for example, five cycles), and a reference value may be set based on the moving average value. In addition, an average value of a plurality of sample values during a predetermined crank angle period in the exhaust stroke may be obtained, and a reference value may be set based on the moving average value using the average value for a plurality of cycles.

The reference value P0 obtained by the processing shown in FIG. 13 is also effectively used in the peak value calculation processing shown in FIG. In the above description, only the example in which the peak value is finally calculated is described. However, the level of the in-cylinder pressure signal at any stroke point can be determined using the set reference value, not limited to the peak point. Needless to say, it can be read correctly.

[0068]

As described in detail above, according to the present invention,
Since the appropriate reading reference value of the in-cylinder pressure signal is set following the drift of the in-cylinder pressure signal, the level of the in-cylinder pressure signal can be read correctly. Moreover, by using the average value of a plurality of specific sample values of the in-cylinder pressure signal in one cycle as a reference value, even when some of the plurality of specific sample values are low in reliability, A reference value close to optimal can be set.

Also, a single specific sample value of the in-cylinder pressure signal in one cycle is obtained for a predetermined number of cycles, and the moving average value of the obtained predetermined number of the specific sample values is used as a reference value, thereby obtaining such a number. Even when the sample value in any one of the cycles is low in reliability, it is possible to set a reference value close to the optimum.

Further, an average value of a plurality of specific sample values of the in-cylinder pressure signal in one cycle is obtained for a predetermined number of cycles, and a moving average value of the obtained predetermined number of average values is used as a reference value to obtain a cycle value. Even when the reliability of the in-cylinder pressure signal sample value is reduced both inside and between cycles, it is possible to set a reference value that is close to optimal. Further, by setting a value obtained by subtracting a predetermined value from a value obtained based on a specific sample value of the in-cylinder pressure signal as a reference value, the predetermined value can be determined from a value obtained based on the specific sample value. Since a value that guarantees that the value obtained by subtracting the value is sufficiently lower than the level in the suction stroke of the in-cylinder pressure signal can be set, the level of the in-cylinder pressure signal is set to the reference value in any stroke including the suction stroke. Higher than that of the internal combustion engine control device, so that there is no possibility that the value of the in-cylinder pressure signal handled by the internal combustion engine control device becomes negative. This contributes to the simplification of the calculation process.

In the setting of the reference value by the predetermined value subtraction, the specific sample value is set as the sample value of the in-cylinder pressure signal in the exhaust stroke of the cylinder.
An appropriate reference value can be accurately set immediately before calculation processing such as the indicated mean effective pressure performed in one cycle unit starting from the suction stroke and ending with the exhaust stroke. Thus, according to the present invention, it is possible to provide an engine control device that can accurately detect the value of the in-cylinder pressure signal even if a drift occurs in the in-cylinder pressure signal.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a relationship between a crank angle of an engine and an in-cylinder pressure for explaining a problem in a conventional example.

FIG. 2 is a block diagram showing a schematic configuration of an engine control device according to an embodiment of the present invention.

FIG. 3 shows a CP in the engine control device shown in FIG. 2;
9 is a flowchart showing a procedure of a reference value setting process of the in-cylinder pressure signal executed by U.

FIG. 4 is a diagram illustrating a relationship between a crank angle of an engine and an in-cylinder pressure for explaining a reference value setting mode performed by the process shown in FIG. 3;

FIG. 5 shows a CP in the engine control device shown in FIG. 2;
9 is a flowchart showing a procedure of a peak value calculation process of an in-cylinder pressure signal executed by U.

FIG. 6 is a flowchart illustrating a procedure of a reference value setting process of an in-cylinder pressure signal according to a second embodiment.

FIG. 7 is a diagram illustrating a relationship between a crank angle of an engine and an in-cylinder pressure for explaining a reference value setting mode performed by the process shown in FIG. 6;

FIG. 8 is a flowchart illustrating a procedure of a reference value setting process of an in-cylinder pressure signal according to a third embodiment.

9 is a diagram showing, in chronological order, each sample value corresponding to a predetermined stroke point obtained at each cycle interval of the engine 10 shown in FIG. 2;

FIG. 10 is a diagram illustrating a relationship between a crank angle of an engine and an in-cylinder pressure for explaining a reference value setting mode performed by the process shown in FIG. 8;

FIG. 11 is a finger pressure diagram showing a change in in-cylinder pressure with respect to a stroke of a piston operating in each cylinder constituting engine 10 shown in FIG. 2;

FIG. 12 is a diagram showing a relationship between a crank angle and an in-cylinder pressure of the engine 10 shown in FIG.

FIG. 13 is a flowchart illustrating a procedure of a reference value setting process of an in-cylinder pressure signal according to a fourth embodiment.

FIG. 14 is a diagram illustrating a relationship between a crank angle of an engine and an in-cylinder pressure for explaining a reference value setting mode performed by the process shown in FIG. 13;

[Explanation of symbols]

 Reference Signs List 10 internal combustion engine 1A to 1D cylinder pressure sensor 38 crank angle sensor 41 intake pipe pressure sensor 42 cooling water temperature sensor 43A to 43D injector 44A to 44D ignition device 45A to 45D EGR valve 20 engine control circuit 31 CPU 32 ROM 33 RAM 34 A / D Converter 35 Actuator drive circuit 37 Counter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazunori Sawamura 1-4-1 Chuo, Wako-shi, Saitama Prefecture Inside Honda R & D Co., Ltd. (72) Hironao Fukuchi 1-4-1 Chuo, Wako-shi, Saitama (72) Inventor Hideyuki Oki 1-4-1 Chuo, Wako-shi, Saitama Prefecture Honda Research Institute Co., Ltd. (72) Inventor Hiroaki Kato 1-4-1 Chuo, Wako-shi, Saitama Company Honda R & D Center

Claims (1)

[Claims] 1. An internal combustion engine control device for controlling an internal combustion engine based on a level of an in-cylinder pressure signal obtained from an in-cylinder pressure sensor in a cylinder of the internal combustion engine, wherein a predetermined crank in an intake and / or exhaust stroke of the cylinder is provided. Reference value setting means for setting a reference value corresponding to a specific sample value of the in-cylinder pressure signal corresponding to an angle or a crank angle period; and a value corresponding to a difference between the reference value and a sample value of the in-cylinder pressure signal. An internal combustion engine control device, comprising: reading means for setting a level of an in-cylinder pressure signal.