JPH09329049A - Engine control method and engine controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control an engine with higher accuracy with its dependence suppressed on the detection accuracy of a cylinder pressure sensor and with easier precise, continuous grasp of combustion conditions. SOLUTION: The pressure P in a cylinder is detected for a symmetric phase ranging from ahead of and to behind the compression top dead center(TDC) between its compression and combustion strokes at every specified rotational angle of the crankshaft like P-n ...P-3 ...P0 ...P3 ...Pn to calculate the integral value ∫PdVcomb. of the cylinder pressures P ahead of the compression TDC and the integral value ∫PdVcomb. thereof behind the compression TDC. From their difference ∫PdVcomb. -∫PdVcomb. , the value D equivalent to the indicated mean effective pressure is thereafter calculated. The value D is then calculated for every cylinder with the value D/Qf obtained by dividing the value D by the quantity of fuel supplied Qf as its divisional value to obtain the combustion index for use in engine control. The division of the value D equivalent to the indicated mean effective pressure by the quantity of fuel supplied Qf frees the engine control from the effect of the opening angle of the throttle valve and thus deterioration in its accuracy even in a transient phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting an in-cylinder pressure of an engine and controlling an operating state of the engine, and more particularly to an engine control device suitable for a fuel injection type gasoline engine for an automobile.

[0002]

2. Description of the Related Art Among internal combustion engines such as gasoline engines, especially automobile engines, there are strict exhaust gas regulations and strong demands for improvement of fuel consumption, and therefore appropriate control of the fuel supply amount is a very important issue. For this purpose, how to accurately grasp the operating state of the engine is a prerequisite.

Therefore, in recent years, a technology for controlling the engine by paying attention to the cylinder pressure (pressure in the cylinder) and grasping the operating state of the engine from this aspect has been suddenly attracting attention. , For example, JP-A-1-27163
In Japanese Patent No. 4 publication, the indicated mean effective pressure is calculated from the detected in-cylinder pressure, the dispersion is obtained from the 16 cycles, and the supply fuel amount is reduced when the dispersion value is small, and increased when the dispersion value is large. It discloses a technique that enables stable operation up to the lean air-fuel ratio limit.

[0004] And, further, JP-A-7-119534
Japanese Patent Laid-Open No. 7-34958 and Japanese Patent Laid-Open No. 7-34958 disclose a method of further normalizing the calculated average effective pressure by the average value thereof in order to avoid the influence of the signal drift of the in-cylinder pressure sensor.

[0005]

In the above-mentioned prior art, it cannot be said that sufficient consideration has been given to the fact that the accuracy of the in-cylinder pressure sensor must be relied upon, and there is a problem in terms of further improvement in accuracy. there were. Because the sensor that detects the cylinder pressure is
In an environment where the combustion gas and intake air are alternately exposed in the cylinder and the temperature changes drastically, it is necessary to detect the pressure that changes over a wide range from the intake pressure to the explosion pressure. Because it is difficult.

Here, it can be said that the conventional technique of normalizing with the average value described above is a very effective means in terms of maintaining the accuracy. However, even with this conventional method, the cylinder pressure suddenly changes when the engine is in a transient operating state such as during acceleration or deceleration, so even if it is normalized, the change does not correspond to the combustion state. Therefore, there is a problem that the precision is unavoidable.

That is, the average value at this time is only a past value, and the value to be normalized by this is a value after the fuel amount is further increased or decreased, so that, for example, the combustion state is normal. Even at times, the normalized value will not be 1.

Further, since an engine usually has a plurality of cylinders, a plurality of in-cylinder pressure sensors are required in accordance with the number of cylinders. At this time, however, the characteristics of each sensor are generally inevitable. At this time, in the conventional technology, it is impossible to distinguish whether the fluctuation of the average effective pressure calculated from the detection result is due to the fluctuation of the actual combustion state or the fluctuation of the sensor characteristics, and therefore the accuracy is lowered. I was supposed to escape.

An object of the present invention is to suppress dependence on the detection accuracy of the in-cylinder pressure sensor, to always easily obtain an accurate combustion state, and to control the engine with high accuracy. It is to provide a control method and an engine control device.

[0010]

According to the present invention, the above object can be achieved by adopting any one of the following means.

First, according to the first aspect of the invention, based on the in-cylinder pressure detected from the cylinder of the engine and the cylinder volume change rate detected from the crank angle, the cylinder has a symmetrical section before and after top dead center from the compression stroke to the explosion stroke. Is calculated by dividing the indicated average effective pressure equivalent value by the supplied fuel amount, and an average value of the divided values up to a predetermined number of times is calculated. A method is adopted in which the combustion index value is calculated by dividing the divided value, and the supplied fuel amount is controlled so that the fluctuation amount appearing in the product of the combustion index value and the supplied fuel amount falls within a predetermined range.

Next, a second aspect of the present invention is provided with an in-cylinder pressure sensor for detecting the in-cylinder pressure of the engine, and the result of detecting the in-cylinder pressure in a symmetrical section before and after top dead center in the section from the compression stroke to the explosion stroke of the cylinder. In the engine control device for calculating the indicated mean effective pressure equivalent value on the basis of the above, and controlling the engine, means for calculating a divided value of the indicated mean effective pressure equivalent value by the supply fuel amount, and an average of the divided values. A means for calculating a value and normalizing the divided value by the average value,
A means for calculating the result as a combustion index value is provided, and the combustion index value is used to control the engine.

A third aspect of the present invention is provided with an in-cylinder pressure sensor for detecting the in-cylinder pressure of the engine, wherein the in-cylinder pressure is detected in a symmetrical section before and after the top dead center of the section from the compression stroke to the explosion stroke. An engine control device for controlling the engine by calculating the indicated mean effective pressure equivalent value based on the means for calculating a divided value of the indicated mean effective pressure equivalent value by the supplied fuel amount, and an average value of the divided values. A means for calculating, and normalizing the divided value by the average value,
A means for calculating the result as a combustion index value and a means for calculating a variation amount of the product of the combustion index value and the supplied fuel amount are provided, and the supplied fuel amount is controlled so that the variation amount falls within a predetermined range. It is something that is done.

Further, a fourth aspect of the present invention is provided with an in-cylinder pressure sensor for detecting the in-cylinder pressure of the engine, and the in-cylinder pressure detection result is obtained in a symmetrical section before and after the top dead center in the section from the compression stroke to the explosion stroke of the cylinder. An engine control device for controlling the engine by calculating the indicated mean effective pressure equivalent value based on the means for calculating a divided value of the indicated mean effective pressure equivalent value by the supplied fuel amount, and an average value of the divided values. A means for calculating, and normalizing the divided value by the average value,
A means for calculating the result as a combustion index value, a means for calculating a variation amount of the product of the combustion index value and the supplied fuel amount, and a calculation of the supply fuel amount necessary for keeping the variation amount within a predetermined range. Is provided, and means for storing the correction coefficient and sequentially calculating the supplied fuel amount are provided so that the supplied fuel amount is learned and controlled.

Still another invention is provided with an in-cylinder pressure sensor for detecting the in-cylinder pressure of the engine, and based on the detection result of the in-cylinder pressure in the symmetrical section before and after the top dead center from the compression stroke to the explosion stroke of the cylinder. In the engine control device for calculating the indicated average effective pressure equivalent value and controlling the engine, means for calculating a divided value of the indicated average effective pressure equivalent value by the supplied fuel amount, and up to a predetermined rotation speed of the divided value Means for calculating the average value of the above, a means for normalizing the division value by the average value, and calculating the result as a misfire determination value, a means for storing the misfire determination value for each operating condition of the engine, and the engine A means for detecting whether or not the fuel is being cut is provided, and when the fuel is not being cut, the misfire determination value corresponding to the current engine operating condition is selected from the stored misfire determination values. Out is it that so as to determine the misfire when compared with the calculated misfire determination value.

The divided value obtained by dividing the indicated average effective pressure equivalent value by the supplied fuel amount represents the combustion efficiency of the engine, and is therefore a value peculiar to the engine, regardless of the throttle valve opening. It is almost constant. As a result, there is no influence of the throttle valve opening, and it is possible to eliminate the possibility that the accuracy will deteriorate even during a transition.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an engine control device according to the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 shows an example of an embodiment in which the engine control device according to the present invention is applied to a four-cylinder engine, and therefore each cylinder is provided with four in-cylinder pressure sensors 1a, 1b, 1c, 1d.

These four in-cylinder pressure sensors 1a, 1b, 1
c and 1d each serve to detect the pressure in the cylinder, and its output is in the engine control circuit 20 together with the outputs from other sensors such as an air flow rate sensor, an air-fuel ratio sensor, and a cooling water temperature sensor. Is input to the multiplexer 3 provided in the.

Next, the cylinder discrimination sensor 2 is a sensor which outputs a pulse signal (REF signal) having a different pulse width for each cylinder so that the cylinder can be discriminated. The output is a digital signal in the engine control circuit 20. It is input to the IO port 30 and used in the cylinder discrimination processing unit 4 for the cylinder discrimination.

The crank angle sensor 18 is a sensor for generating a signal (POS signal) indicating the rotation angle of the crank shaft, and its output is connected to an interrupt port in the digital IO port 30 to activate interrupt processing. It is used to control the multiplexer 3 and take in the in-cylinder pressure in the symmetrical section before and after the top dead center in the section from the compression stroke to the explosion stroke of each cylinder to the A / D converter 5 and the bandpass filter amplifier 6.

In-cylinder pressure sensors 1a, 1b, 1 converted into digital data by the A / D converter 5 in this manner.
The signals of c and 1d are input to the θpmax equivalent value calculation unit 7,
The crank angle θpmax that maximizes the in-cylinder pressure or its equivalent value is calculated, and is also input to the combustion index value calculation unit 8 to calculate the combustion index value described later.

Then, the combustion index value calculated here is input to the combustion diagnosis unit 9 and the misfire diagnosis unit 11. First, the combustion diagnosis unit 9 obtains the variation amount of the combustion index value, and this is calculated by the fuel injection amount correction unit. Correction coefficient C required to supply a lean air-fuel mixture of which the fluctuation amount does not exceed a predetermined value.
Ask for.

The correction coefficient C thus obtained is stored in the storage device 15 as a two-dimensional table of the engine speed N and the engine load L, as will be described later. Here, the engine load L is L = Qa / N, where Qa is the intake air flow rate.
Is represented by On the other hand, when the combustion index value is smaller than the predetermined value, the misfire diagnosis unit 11 determines that there is a misfire.

The correction coefficient thus stored in the storage device 15 is read by the fuel injection amount calculation unit 13 as necessary and used for calculating the valve opening time of the fuel injection valve. The calculation of the valve opening time of the fuel injection valve is as follows.

First, the basic fuel amount calculation unit 12 sets the fuel amount proportional to the engine load L = Qa / N and the engine operating condition at this time, that is, the intake air flow rate Qa and the engine rotation speed N. The basic fuel amount Tp is corrected by performing the correction using the air-fuel ratio correction coefficient k necessary for obtaining the air-fuel ratio.
Is calculated.

Next, the fuel injection amount calculation unit 13 retrieves the correction coefficient C by searching the two-dimensional table stored in the storage device 15, calculates the product of the basic fuel amount and the correction coefficient C, and calculates the fuel injection valve. The fuel injection valve is driven by obtaining the valve opening time of.

Further, in the ignition timing adjusting section 16, the value equivalent to θpmax is within a predetermined crank angle range (10 to 20 degrees ATDC).
The ignition timing correction amount is calculated so that the knock intensity signal obtained from the knock detection unit 14 becomes equal to or less than a predetermined value.

In the knock detection at this time, the signal of the in-cylinder pressure sensor taken in through the multiplexer 3 is processed by the bandpass filter and the amplifier 6 to take out only the knock signal, and the strength of the knock is determined from the magnitude of the knock signal. It is designed to judge.

The ignition timing correction amount calculated in this manner is also stored in the storage device 15. At this time, as will be described later, the ignition timing is determined by the engine rotation speed N and the load L = Qa / It is designed to be stored in a two-dimensional table of N.

Then, the actual ignition timing is calculated by the ignition timing calculating section 16, and first, the engine operating condition Qa,
After determining the basic ignition timing from N, the basic ignition timing is corrected and determined by the ignition timing correction amount read from the two-dimensional table of the storage device 15.

Therefore, according to this embodiment, as will be described later, it is possible to obtain the θpmax equivalent value and the combustion index value, and to control the optimum supply fuel amount and ignition timing for each cylinder based on these values. The diagnosis of misfire detection can also be enabled.

Next, FIG. 2 shows a second embodiment of the present invention, in which a part of the signal processing is carried out in the cylinder pressure sensor to output two kinds of signals, a cylinder pressure signal and a knock signal. This corresponds to a modification of the embodiment shown in FIG.

Therefore, the embodiment of FIG. 2 also has four in-cylinder pressure sensors like the number of cylinders.
Only the individual parts are shown, and the parts having the same functions as those in FIG. 1 are denoted by the same reference numerals.

The in-cylinder pressure sensors 1a and 1b include a bandpass filter 21a and an amplifier 22 for zero span adjustment.
a and 23a are individually provided, and a knock signal and an in-cylinder pressure signal are output via these.

These signals are supplied to the crank angle sensor 18, the cylinder discrimination sensor 2, the cylinder discrimination processing 4, and the multiplexers 26 and 27 controlled by the pulse generators 24 and 25.
It is taken into the engine control circuit 20 via.

At this time, the knock signal is supplied from the multiplexer 26 to the knock detection section 14 via the bandpass filter and the amplifier 6, and the degree of knock is detected here, while the cylinder pressure signal is It is supplied to the θpmax equivalent value calculation unit 7 and the combustion index value calculation unit 8 via the A / D converter 5, and is used to calculate the θpmax equivalent value and the combustion index value as described above.

The processes downstream of the knock detector 14, the θpmax equivalent value calculator 7, and the combustion index value calculator 8 are as follows:
However, in this embodiment, as described above, the in-cylinder pressure signal and the knock signal are output in a state where they are already separated in the signal processing circuit portion of each in-cylinder pressure sensor. Since it is configured as described above, even a signal of a minute level such as a knock signal can be sufficiently amplified and then output, so that the signal can be reliably sent to the engine control circuit 20 even in an environment where electrical noise is strong. effective.

Next, the function and operation of the combustion index value calculator 8 which is a feature of the present invention will be described with reference to FIG. First, as shown in FIG. 3, the combustion index value calculation unit 8 sets the cylinder internal pressure P of each cylinder to the top dead center between the compression stroke and the explosion stroke.
(TDC), that is, in the symmetrical section before and after the compression top dead center, the process of sequentially reading in synchronization with the crank angle is executed. For example, the crank angle before compression top dead center (BTDC) is 60 degrees to 60 degrees after compression top dead center (ATDC).
Cylinder pressure P _-n for each rotation angle of 2 to 10 degrees
_{......, P -3, ......, P} 0, ......, P 3, is read the ...... P _n.

Since the combustion fluctuation when the air-fuel mixture is lean (lean) mainly appears only near the point where the cylinder pressure reaches its peak, it is sufficient to read the range of ± 60 degrees around the top dead center. Therefore, in this embodiment, the above range is set.

Next, the combustion index value calculation unit 8, based on the thus read-cylinder pressure P, and the integrated value ∫PdV _compression of the in-cylinder pressure P of the compression top dead center First, the cylinder pressure after the compression top dead center P
The integrated value of ∫PdV _combustion is calculated, and then the difference (∫
The indicated mean effective pressure equivalent value D given by PdV _combustion -PdV _compression) is calculated and further, the divided value by the value D of the fuel supply amount Q _f (D / Q _f) as a division value for each cylinder The calculation process is executed.

Here, dV is the rate of change of the cylinder volume V, and is obtained from the crank angle θ. The details of how to obtain it will be described with reference to FIG. 4 of the drawing of Japanese Patent Laid-Open No. 7-119534 cited as a prior art. The method described therein may be used, and at this time, as shown in the figure, the cylinder volume V is determined by the radius of the crank and the connecting rod (connecting rod).
From the length ratio λ = (crank radius) / (connecting rod length) and crank angle θ, it is calculated as shown in the figure, that is, V = (1-cosθ) + λ / 4 (1-cos2θ) .

Further, as shown in the figure, the valve opening time of the fuel injection valve (pulse width of the signal output from the fuel injection amount calculation unit 13) described later is used as the supplied fuel amount Q _f. Has become.

As in this embodiment, if the in-cylinder pressure signal read in synchronization with the crank angle in the symmetrical section before and after the compression top dead center is used to calculate the indicated mean effective pressure equivalent value, the cylinder volume Since the value of the rate of change dV is symmetrical before and after the compression top dead center, it is possible to remove the influence of the bias (the signal value when the pressure is zero) of the in-cylinder pressure sensor signal.

Further, in this embodiment, the value D / Q _f thus obtained is normalized by its moving average value, so that the influence of the gain of the in-cylinder pressure sensor signal is eliminated, and as a result, Even if the gains and biases of the in-cylinder pressure sensors of the respective cylinders are different, the values can be made uniform as the variation ratios with respect to the average value, and the combustion index value and the magnitude of the variation value can be compared side by side in all cylinders.

Here, the present invention and the prior art (Japanese Patent Laid-Open No. 7-1
The major difference with the present invention is that the indicated mean effective pressure equivalent value is divided by the supplied fuel amount in the present invention. In this way, the value obtained by dividing the indicated average effective pressure equivalent value by the supplied fuel amount represents the combustion efficiency of the engine, and therefore is a value unique to the engine and is a substantially constant value regardless of the throttle valve opening. Become.

As shown in FIG. 4, if the opening degree of the throttle valve is increased at a certain time t ₀ , the amount of air and fuel taken into the cylinder of the engine is increased, so that the cylinder pressure is high. Therefore, the indicated mean effective pressure equivalent value obtained from this suddenly increases. On the contrary, when the throttle valve opening is reduced, the indicated mean effective pressure equivalent value sharply decreases. Therefore, in the conventional technique, the accuracy is reduced when the engine is accelerated or decelerated.

In the present invention, however, as described above,
Since the indicated mean effective pressure equivalent value is divided by the amount of supplied fuel, the influence of the throttle valve opening is not affected, and the possibility of deterioration of accuracy even during a transition can be eliminated.

Further, in the above embodiment, not only the indicated average effective pressure equivalent value is divided by the supplied fuel amount but also the combustion index value is normalized by the moving average value, so that during transient operation of opening and closing the throttle valve. Also, the index indicating the combustion state can be sufficiently obtained regardless of the engine operating conditions such as the throttle valve opening.

Next, referring to FIG. 5, the process of reading the in-cylinder pressure signal in the crank angle synchronization will be described. First, the REF signal output from the cylinder discrimination sensor 2 and the crank angle output from the crank angle sensor 18
From the (POS) signal, a start signal for starting the reading of the in-cylinder pressure signal is generated as shown in the figure. Then, a predetermined number of in-cylinder pressures are read in synchronization with the rising or falling of the crank angle signal from when the start signal becomes H (High) level.

For example, before the top dead center of the cylinder in the compression stroke 1
If the REF signal is output at 10 degrees, then 5
A start signal is generated at a timing of 0 degree (that is, 60 degrees before top dead center), and after the start of the start signal, as shown in the figure, the cylinder pressure signals P _{-5 to} P ₅ are synchronized with the crank angle and 60 It is read up to a degree.

Normally, the REF signal and the crank angle signal are input to the interrupt port of the microcomputer in the engine control circuit, and a predetermined number of in-cylinder pressures are read in the symmetrical section before and after the compression top dead center by software. I am trying.

Next, the misfire detection by the misfire diagnosis unit 11 will be described with reference to FIG. First, FIG. 6 (a) shows that the engine operating condition is intentionally deteriorated, for example, by changing the air-fuel ratio to a lean state, and the engine is allowed to rotate for a predetermined period of time, and the crank angle of a certain cylinder during that period. FIG. 7 is a diagram in which the in-cylinder pressure with respect to is overwritten over a plurality of revolutions.

As is clear from FIG. 6 (a), the in-cylinder pressure changes greatly depending on the combustion state of the engine. At this time, most of the change appears after the compression top dead center and the compression top dead center. The previous change is slight. And when the engine has completely misfired, as shown by the curve at the bottom of the figure,
The change state of the in-cylinder pressure before and after the compression top dead center approaches a symmetrical state.

Next, FIG. 6 (b) is a diagram showing the combustion index value described in FIG. 3 from the in-cylinder pressure data for each cycle, and showing it in cycle order. When the engine completely misfires, the change in the cylinder pressure before and after the compression top dead center becomes symmetrical, so the combustion index value becomes zero.

Therefore, if a threshold value for misfire determination is set according to the degree of misfire detection and compared with the obtained combustion index value, the misfiring cylinder can be identified and the number of misfires can be obtained. The misfire diagnosis can be obtained by the unit 11.

Next, the operation of the entire embodiment of FIG. 1 will be described with reference to the flow chart of FIG. The process of FIG. 7 is started when the ignition key switch of the automobile is turned on, and first, in step S1, data is initialized.

Then, in step S2, the cylinder number i for which the cylinder pressure data is to be taken is determined. This is done by using the signal of the cylinder discrimination sensor 2. Specifically, as shown in FIG. 5, the REF signal (the cylinder discrimination sensor 2
The cylinder number i is determined based on the length of time that the signal (1) is at the H level.

In the next step S3, it is determined whether or not the start signal shown in FIG. 5 has risen, that is, the level thereof has changed from the L (LoW) level to the H level. Then, when it changes to the H level, that is, when the result is Y (Yes), the processing proceeds to step S4 and subsequent steps, but when there is no change,
That is, when the result is N (No), the process returns to the step before step S3.

Therefore, only when the start signal changes from the L level to the H level, the process proceeds to the next step. With this, when the process proceeds to step S4, the i-th step will be described in detail with reference to FIG. The combustion index of the cylinder is calculated. When the process of step S4 is completed, the process proceeds to step S15, where it is determined whether or not it is in the operation range in which the closed loop control of the ignition timing using the in-cylinder pressure sensor is executed.

When it is determined that the engine is not in the operating range in which the closed loop control of the ignition timing is executed, such as during idling, throttle valve full opening, and catalyst warm-up operation, that is, when the result in step S15 is N, the routine proceeds to step S16. Here, the ignition timing is obtained from the operating conditions such as the engine speed, the air flow rate, and the cooling water temperature, and the process proceeds to step S17.

On the other hand, when the result in step S15 is Y, that is, when the engine is not in the idling state, the throttle valve is fully opened, or the catalyst is warming up, the steps from S5 to S5.
The routine proceeds to step S6, where the processing for obtaining the optimum ignition timing from θpmax (the crank angle at which the in-cylinder pressure is maximum) and the knock signal is executed, and then the routine proceeds to step S17. Note that θpm at this time
Regarding the process for obtaining the optimum ignition timing from the ax and the knock signal, a process known from Japanese Patent Publication No. 6-97028 may be used.

In step 17, using the table shown in FIG. 8, engine operating conditions (rotational speed N, air flow rate Qa)
From this, it is determined whether the current engine operating conditions are in the lean limit operating range. Then, if the result is N, that is, if it is determined that the current engine operating condition is in the theoretical air-fuel ratio region or the air-fuel ratio setting region other than the lean limit operating region of FIG. 8, the process proceeds to step S10, and the result is Y, That is, the process proceeds to step S7 only when it is determined that the lean limit operation range is set.

In step S7, it is determined whether or not the number of data required to calculate the variance of the combustion index value is prepared. This variance is usually calculated from 10 to 20
Therefore, when it is determined that the number of data is insufficient, the result at step S7 is N, and step S8 is skipped and step S9 is skipped.
Proceed to.

When it is determined in step S7 that the result is Y, that is, the number of data is sufficient, step S8
Then, as will be described in detail with reference to FIG. 11, here, the correction coefficient C required to supply the fuel amount of the lean limit at which the dispersion of the combustion index value becomes the predetermined value or less is calculated.

In step S9, the ignition timing Adv for each cylinder and the correction coefficient C of the supplied fuel amount obtained in steps S6 and S8 are stored in the table shown in FIG. 9A and the table shown in FIG. 9B, respectively. To do. 9 (a) and 9 (b).
Is the rotation speed N of the engine on the horizontal axis,
It is a two-dimensional table having the (air flow rate Qa) / (rotational speed N) as the vertical axis and is provided for each cylinder and is used for optimal control of ignition timing and fuel amount for each cylinder.

In step S10, the supplied fuel amount is obtained by the method described in detail in FIG. 12, and subsequently, in step S11, the ignition timing and the fuel amount signal are output to the ignition device and the fuel injection valve to perform the ignition operation for each cylinder. And fuel injection operation is performed. Then, after this, it is determined in step S12 whether or not the misfire diagnosis is performed. If the result is Y, the process proceeds to step S13,
Diagnosis of misfire etc. by the method detailed in FIG. 13,
The diagnosis result is output in step S14, and the process proceeds to the next cylinder.

Next, step S4 and step S in FIG.
The details of the processing in step S10, step S13, and step S13 will be described. First, the details of the processing in step S4 of FIG. 7 are as shown in FIG. 10. When this processing is entered, first, in step S20, the integral values S and S ′ are initialized, and then step S4.
At 21, the valve opening time Tinj of the fuel injection valve, which represents the amount of fuel injected per cylinder of the i-th cylinder, and various data (engine flow rate Qa, engine speed N, cooling water temperature Tw), which represent engine operating conditions, are read. .

Next, steps S22 to S25
In step, the cylinder pressure of the i-th cylinder is set to N in synchronization with the crank angle.
₀ times, i.e., the compression top dead center before and after reads N _0/2 times increments equal number of cylinder pressure, executes a process of storing in the storage device.

Next, in step S26, the crank angle θj
The cylinder volume change ΔVj corresponding to is read from the table. As this table, for example, the table described in FIG. 4 of JP-A-7-119534 mentioned above may be used.

Subsequently, in step S27, the work ∫PdV _explosion (integral value of PdV) in the explosion stroke is calculated, and then in step S27.
In step 28, the work ∫PdV _compression of the compression stroke is obtained, and in step S29, the difference (corresponding to the indicated mean effective pressure) between the two is divided by the valve opening time Tinj. In step S30, the moving average value of the values obtained in step S29 five to ten times in the past is obtained, and then in step S31, the moving average value is normalized to obtain a combustion index value.

In the above-mentioned Japanese Patent Laid-Open No. 7-119534, the table of ΔVj has a minus sign in the compression process. In this case, therefore, the subtraction in steps S29 and S30 and S31 is addition. Becomes

In the process of FIG. 10, the process of step S24 corresponds to the in-cylinder pressure detecting means, the process of step S26 corresponds to the volume change rate calculating means, and step S27.
The process from step S29 corresponds to the indicated mean effective pressure equivalent amount calculating means and the means for obtaining the value obtained by dividing the indicated mean effective pressure equivalent amount by the supplied fuel amount, and the portion of step S30 corresponds to the divided value. It corresponds to a means for obtaining an average value up to a predetermined number of times before, and the portion of step S31 corresponds to a means for obtaining a combustion index value for each cylinder.

Next, the processing in step S8 of FIG.
As shown in FIG. 11, when this processing is started, first in step S40, the combustion index value obtained in step S31 of FIG.
The zero burned portion is read from the storage device.

Next, in step S41, the variance CVAL of the product of the just read combustion index value and the fuel supply amount is obtained. This distributed CVAL is 1 from each combustion index value as shown in the figure.
The sum of values obtained by multiplying the absolute value of the value obtained by subtracting the valve opening time of the fuel injection valve is obtained, and the sum is divided by the number n of data of the combustion index value.

In this way, by obtaining the product of the fuel supply amount, the distributed CVAL can represent only the fluctuation of the torque generated by the engine. That is, the influence of the variation in gain / offset of the in-cylinder pressure sensor is reduced by the calculation of the combustion index value described in FIG. 3, and the product with the fuel supply amount is obtained. Has the effect of being accurately requested.

In the next step S42, the calculated variance CV
When AL is larger than the set value, that is, when the fluctuation of the engine output is large, step S43.
When the distributed CVAL is smaller than the set value, that is, when the variation in the engine output is small, the process of adding the constant α to the correction coefficient C of the supplied fuel amount by The process of subtracting the constant β from the amount correction coefficient C is selected and the process returns.
Then, the correction coefficient C thus obtained is stored in the storage device in step S9 of FIG.

Next, the process of step S10 in FIG. 7 is as shown in FIG. 12, and in this process, first, in step S50, the air flow rate Qa, the engine rotation speed N, and the air-fuel ratio correction coefficient k. The basic fuel amount Tp is calculated from
Similarly, in step S51, the correction coefficient C is obtained from the air flow rate Qa and the rotation speed N using the table of FIG. 9 (b).
Then, in step S52, the basic fuel amount Tp is multiplied by the correction coefficient C to obtain the valve opening time Tinj of the fuel injection valve.

In this embodiment, the processes of step S8 and step S9 are provided, whereby the correction coefficient of the supplied fuel amount is obtained so that the fluctuation of the combustion index value converges within the predetermined range, and this correction coefficient is calculated. FIG. 9 shows the storage device of the computer.
It is stored as the table of (b), and the learning control for obtaining the fuel amount using the stored correction coefficient can be obtained at the time of the next fuel calculation, and as a result, the operating conditions of the engine have changed. Even at this time, the effect that the fluctuation of the combustion index value can be quickly brought within the predetermined range is obtained.

Next, the misfire diagnosis processing in step S13 of FIG. 7 is as shown in FIG. 13. When this processing is entered, first in step S61, the valve opening time of the fuel injection valve obtained in step S10 is determined. It is judged from Tinj whether or not the fuel cut control is being performed (no fuel supply).

If it is determined that the engine is in the normal operating state without fuel cut, the routine proceeds to step S62, and the routine shown in FIG.
The threshold value ε for detecting misfire is calculated from the engine operating condition (Qa, N) using the table of No. 4.

In the next step S63, the threshold value ε is compared with the combustion index value obtained in step S4, and the result is N,
That is, when it is determined that the combustion index value is larger than the threshold value ε, it is determined that there is no misfire, and the process proceeds to return.

On the other hand, when the result is Y, that is, when it is determined that the combustion index value is smaller than the threshold value ε, it is determined that misfire has occurred, the number of misfires is counted in step S64, and the predetermined value Nm0 is not exceeded in step S65. When it is determined that the number of misfires exceeds the predetermined value Nm0, the misfire warning process is performed in step S66 to display the misfire cylinder and the number of misfires.

Returning to step S61, if it is determined that the fuel cut control is being performed, the process proceeds to step S67, where the combustion index value obtained in step S4 is written in the table of FIG. 14 as the threshold for misfire detection. , Update the threshold. As a result, when the engine is fuel cut, that is, the combustion index value when fuel is not supplied is set as the threshold value for misfire detection, so even if the signal characteristic of the in-cylinder pressure sensor changes over time, There is an effect that misfire can always be detected accurately.

The in-cylinder pressure sensor 1 can be used in any form, and may be, for example, an in-cylinder pressure sensor composed of a piezoelectric element individually attached to each cylinder, or disclosed in JP-A-6-307953. As described above, the pressure-sensitive portion is composed of a resistance wire, a pressure-sensitive conductive rubber, a carbon pile, an optical fiber, etc., and the signal line may be an in-cylinder pressure sensor that superimposes the pressure signals of each cylinder and retrieves them collectively. good.

[0085]

According to the present invention, even if the in-cylinder pressure sensor to be used has variations in gain or offset, or characteristics change over time or deterioration, misfire and combustion stability are not affected. Can be detected with high accuracy,
The fuel amount and ignition timing for each cylinder can always be controlled to optimal values.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an engine control device according to the present invention.

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

FIG. 3 is an explanatory diagram of a combustion index calculation process according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a change in cylinder pressure of the engine in a transient state.

FIG. 5 is an explanatory diagram of a process of capturing in-cylinder pressure data according to the embodiment of the present invention.

FIG. 6 is a characteristic diagram illustrating the relationship between the crank angle of the engine and the in-cylinder pressure and the change in the combustion index value.

FIG. 7 is a flowchart illustrating an overall operation according to the exemplary embodiment of the present invention.

FIG. 8 is an explanatory diagram of a table used for operating area determination in the embodiment of the present invention.

FIG. 9 is an explanatory diagram of a table used to calculate an ignition timing and a correction coefficient in the embodiment of the present invention.

FIG. 10 is a flowchart of a combustion index value calculation process according to the embodiment of the present invention.

FIG. 11 is a flowchart of a correction coefficient calculation process according to the embodiment of the present invention.

FIG. 12 is a flowchart of a supply fuel amount calculation process according to the embodiment of the present invention.

FIG. 13 is a flowchart of a misfire diagnosis process according to the embodiment of the present invention.

FIG. 14 is an explanatory diagram of a table used for calculating a threshold value for misfire diagnosis in the embodiment of the present invention.

[Explanation of symbols]

 1a-1b In-cylinder pressure sensor 2 Cylinder discrimination sensor 3 Multiplexer 4 Cylinder discrimination processing unit 5 A / D converter 6 Bandpass filter amplifier 7 θpmax equivalent value calculation unit 8 Combustion index value calculation unit 9 Combustion diagnosis unit 10 Fuel injection amount Correction unit 11 Misfire diagnosis unit 12 Basic fuel amount calculation unit 13 Fuel injection amount calculation unit 14 Knock detection unit 15 Storage device 16 Ignition timing adjustment unit 17 EGR diagnosis unit 18 Crank angle sensor 19 Ignition timing calculation unit 20 Engine control circuits 21a, 21b Band pass filter 22a, 22b, 23a, 23b Amplifier 24, 25 Pulse generator 26, 27 Multiplexer 30 I / O port

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location F02D 45/00 340 F02D 45/00 340F 340C 358 358Z 368 368S 368Z 370 370B

Claims (10)

[Claims] 1. Based on an in-cylinder pressure detected from an engine cylinder and a cylinder volume change rate detected from a crank angle,
Calculate the indicated mean effective pressure equivalent value in the symmetrical section before and after the top dead center of the section from the compression stroke to the explosion stroke of the cylinder, and divide the indicated mean effective pressure equivalent value by the supply fuel amount to calculate The average value of the calculated values up to a predetermined number of times is calculated, the division value is normalized by the average value to calculate a combustion index value, and the fluctuation amount appearing in the product of the combustion index value and the supplied fuel amount falls within a predetermined range. An engine control method characterized in that the fuel supply amount is controlled so as to be within the range. 2. An in-cylinder pressure sensor for detecting an in-cylinder pressure of an engine, wherein the indicated mean effective pressure is based on a detection result of the in-cylinder pressure in a symmetrical section before and after top dead center in a section where the cylinder extends from the compression stroke to the explosion stroke. In an engine control device for calculating an equivalent value and controlling an engine, means for calculating a divided value of the indicated average effective pressure equivalent value by the supplied fuel amount, means for calculating an average value of the divided values, An engine control device comprising means for normalizing the divided value by the average value and calculating the result as a combustion index value, and controlling the engine using the combustion index value. 3. An in-cylinder pressure sensor for detecting the in-cylinder pressure of the engine, wherein the indicated mean effective pressure is based on the detection result of the in-cylinder pressure in a symmetrical section before and after top dead center in the section where the cylinder extends from the compression stroke to the explosion stroke. An engine control device for calculating an equivalent value and controlling an engine, means for calculating a divided value of the indicated average effective pressure equivalent value by the supplied fuel amount, and means for calculating an average value of the divided values, Means for normalizing the divided value by the average value and calculating the result as a combustion index value, and means for calculating a variation amount of the product of the combustion index value and the supplied fuel amount are provided, and the variation amount is predetermined. An engine control device configured to control the supplied fuel amount so as to be within a range. 4. An in-cylinder pressure sensor for detecting the in-cylinder pressure of the engine, wherein the indicated mean effective pressure is based on the detection result of the in-cylinder pressure in a symmetrical section before and after top dead center in the section where the cylinder extends from the compression stroke to the explosion stroke. An engine control device for calculating an equivalent value and controlling an engine, means for calculating a divided value of the indicated average effective pressure equivalent value by the supplied fuel amount, and means for calculating an average value of the divided values, Means for normalizing the divided value by the average value and calculating the result as a combustion index value; means for calculating a variation amount of the product of the combustion index value and the supplied fuel amount; and a variation amount within a predetermined range. Means for calculating a correction coefficient for calculating the supply fuel amount necessary to store the supply fuel amount and means for storing the correction coefficient and sequentially calculating the supply fuel amount. Done The engine control apparatus characterized by being configured so. 5. The invention of claims 2 to 4, means for calculating the combustion index value, the cylinder pressure P, the supply fuel amount Q _f, it the (V _n -V _n-1) An engine control device configured to obtain a combustion index value as a cylinder volume change rate by a calculation according to the following equation. [Equation 1] 6. The invention according to any one of claims 2 to 4, wherein an in-cylinder pressure including a knock signal output means including a bandpass filter for extracting a knock signal from the output of the in-cylinder pressure sensor and an amplifier, and an amplifier for extracting an in-cylinder pressure signal. An engine control device, wherein signal output means is provided in the vicinity of the sensor element of the in-cylinder pressure sensor. 7. The invention according to any one of claims 2 to 4, wherein a decrease in the combustion index value to a predetermined value or less is detected as misfire, and when the number of misfires reaches a predetermined number, an alarm is displayed. An engine control device characterized by being configured as follows. 8. The invention according to claim 3 or 4, wherein the control of the supplied fuel amount is made effective only when the engine operating condition is set to a lean air-fuel ratio region. An engine control device characterized by the above. 9. An in-cylinder pressure sensor for detecting an in-cylinder pressure of an engine is provided, and the indicated mean effective pressure equivalent value is obtained based on the detection result of the in-cylinder pressure in a symmetrical section before and after the top dead center of the cylinder from the compression stroke to the explosion stroke. In the engine control device for controlling the engine, means for calculating a divided value of the indicated average effective pressure equivalent value by the supplied fuel amount, and an average value of the divided values up to a predetermined rotation speed. Means, a means for normalizing the divided value by the average value, calculating the result as a misfire determination value, a means for storing the misfire determination value for each engine operating condition, and a means for determining whether or not the engine is in the fuel cut state. When a fuel cut is not in progress, a misfire determination value corresponding to the current engine operating condition is read out from the stored misfire determination values, and this is calculated as described above. An engine control device configured to judge a misfire by comparing with a misfire judgment value issued. 10. The invention according to claim 9, wherein during a fuel cut, a misfire determination value corresponding to a current engine operating condition among the stored misfire determination values is set to the calculated misfire determination value. An engine control device characterized by being configured to be updated by.