JPH0710057Y2 - Combustion control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a combustion control device for an internal combustion engine such as an automobile. More specifically, the present invention relates to a combustion control device for an internal combustion engine such as an automobile. The present invention relates to a device for accurately detecting a combustion state in a cylinder such as partial combustion and controlling ignition timing based on the detected information to improve engine performance.

(Prior Art) In recent years, the control of the internal combustion engine and its peripheral devices has also been electronically controlled, enabling more precise control. In such control, the combustion state of the internal combustion engine is detected, and the ignition timing, the air-fuel ratio, etc. that can control the combustion state are operated based on the detection result. In general, considering the efficiency and fuel efficiency of the engine, the minimum advance angle at maximum torque, so-called MBT (Minimum advance for
It is known that it is best to ignite in the vicinity of Best T-orque), and so-called MBT control is performed in which the MBT ignition timing is changed depending on the engine condition.

Further, from the viewpoint of improving fuel economy, so-called knocking control is performed in which a knocking signal of the engine is detected from a cylinder pressure signal and the ignition timing is retarded when the knocking level exceeds a predetermined value.

In MBT control, it is necessary to detect a crank angle (hereinafter, referred to as combustion peak position) θpmax at which the pressure in the combustion chamber (hereinafter, referred to as in-cylinder pressure) becomes maximum. There is an ignition timing control device described in JP-A-59-39974. In this device, the cylinder pressure is detected by the cylinder pressure sensor and the combustion peak position θpm is detected.
In order to find ax, the in-cylinder pressure is A / D converted from TDC to ATDC 50 ° every 1 °. As other devices, Japanese Patent Laid-Open No. 61-1
There is one described in Japanese Patent No. 4479. In this device, a pressure signal from an in-cylinder pressure sensor provided in advance in a cylinder in which knock resistance is relatively high is selected, and by selecting this pressure signal, only cylinders in which knocking has not occurred are selected. By controlling the ignition timing to MBT, the fuel ratio is improved and the control is simplified.

In addition, there is also one that determines the high octane number gasoline and the normal gasoline and switches the ignition timing characteristics (Japanese Patent Laid-Open No. 61-85).
(See Japanese Patent No. 578).

Further, the applicant previously proposed a device for judging misfire based on the difference between the maximum cylinder pressure and the TDC pressure (see Japanese Utility Model Application No. 60-181263).

(Problems to be Solved by the Invention) However, such a conventional combustion control device for an internal combustion engine has a configuration in which an engine using gasoline (specific fuel) is symmetrical, and has a predetermined structure. A / D conversion is performed on the in-cylinder pressure in the crank angle section (TDC to ATDC50 °), and the crank angle when the converted value becomes maximum is detected as θpmax, that is, θpmax exists under the condition of normal combustion. Since the range is predicted and limited, there are the following problems.

(I) Problems in alcohol-blended gasoline When gasoline (hereinafter simply referred to as “alcohol-blended gasoline”) in which alcohol (different fuel) is blended is used, it is optimal for alcohol-blended gasoline due to the difference in fuel properties. The ignition timing may deviate significantly from the ignition timing, which will be described with reference to FIG.

Fig. 15 shows an example of the load characteristics of the optimum ignition timing for gasoline and for alcohol-only single fuel. In alcohol (dashed line), the ignition timing is delayed compared to gasoline (solid line) because early combustion is early at low load. Is optimal.
On the other hand, when the load is high, in the case of gasoline, knocking is likely to occur, and the optimum ignition timing comes to a position where the ignition timing is greatly retarded, but in alcohol, since knocking resistance is high, there is almost no need to delay it. Therefore, the load characteristics are reversed between the low load range and the high load range.

On the other hand, FIG. 16 shows an example of the rotation speed characteristic of the optimum ignition timing for both fuels, and alcohol (dashed line) can be advanced much more than gasoline (solid line) at low rotation speed. On the other hand, as the rotation increases, knocking is less likely to occur even in the case of gasoline, so that it is possible to gradually advance. As a result, in this case as well, the characteristics are reversed at high speed.

Fig. 15 shows the engine speed constant (1000 rpm),
The figure is an example of constant load (throttle fully open, but no turbocharger). A in the figure is 1000rp.
It corresponds to m and full throttle opening. Even in the conventional device, it is possible to control the ignition timing optimal for alcohol or alcohol-blended gasoline by using the ignition timing characteristic for gasoline in a steady state. This is because when these fuels are used, a deviation corresponding to the difference with gasoline is initially generated, but this deviation is eventually eliminated by configuring a feedback control system.

However, the situation is different during the transition. Considering the state where alcohol is used when the optimal ignition timing for gasoline is stored in the memory as the basic ignition timing, the characteristics shown in FIG. It is shifted to the retard side. Therefore, since the ignition timing is controlled while being greatly retarded from the optimum point due to the response delay immediately after the throttle is suddenly fully depressed from a low load, fuel is wasted and output is not sufficiently drawn out. Similarly, when the throttle is suddenly returned from full opening, the control is performed with the angle advanced from the optimum ignition timing, so that the engine may be over-advanced and knocking may occur.

Further, if a method of detecting the fuel property of alcohol-blended gasoline and switching the basic ignition timing is applied, a huge amount of memory is required. This is because in the case of alcohol-blended gasoline, the variation range of the ignition timing characteristic is large, and therefore it is necessary to switch and use many characteristics.

Furthermore, not only will the cost be increased if a sensor that directly detects the fuel property is provided, but if the fuel property changes due to refueling, etc., the alcohol content rate detected by the sensor and the alcohol content rate of the fuel actually injected will increase. However, the optimum ignition timing cannot be set.

(II) Problems in detecting the fuel peak position θpmax If the ignition timing is advanced (or retarded) too much, or if misfire or partial fuel occurs in an operating range where combustion is not normally performed due to low load, etc. There is a possibility that the mere compression pressure maximum value may be detected as θpmax. In particular, θpmax is TDC in both cases of misfire due to excessive retardation and maximum fuel pressure near TDC due to excessive advancement.
Although it is detected as a vicinity by the sensor, there is a possibility that the position where the ignition timing should originally be retarded like the former is erroneously controlled as the latter. Therefore, in the control system that controls the combustion of the engine by using θpmax as the detection information, the accuracy of the detection information is deteriorated and the drivability of the engine and the fuel consumption are deteriorated. In addition, when the misfire is determined, it may be erroneously determined that an error occurs in the maximum cylinder pressure due to noise, and the detection accuracy is not always sufficient.

(Purpose of the Invention) Therefore, the present invention focuses on the fact that there is a certain correlation between the combustion speed and the air-fuel ratio, and accurately determines the mixing ratio of different kinds of fuel contained in the fuel injected into the cylinder and abnormal combustion. The purpose is to improve the drivability and fuel efficiency by correcting the ignition timing on the basis of these pieces of information by making a good detection.

(Means for Solving the Problems) In order to achieve the above object, a combustion control device for an internal combustion engine according to the present invention has a basic conceptual diagram as shown in FIG. The detecting means a, the operating state detecting means b for detecting the operating state of the engine using the load and the rotational speed of the engine as parameters, and the crank angle at which the cylinder pressure becomes maximum based on the output of the pressure detecting means a. A maximum timing detecting means c for detecting the maximum internal pressure and an air-fuel ratio detecting means d for detecting the air-fuel ratio of the intake air-fuel mixture.
And a combustion time calculation means e for calculating the combustion time in the cylinder based on the difference between the output of the maximum timing detection means c and the final ignition timing, and the output of the air-fuel ratio detection means d and the output of the combustion time calculation means e. Based on the output of the correction means f for calculating the correction amount for correcting the basic ignition timing according to the mixing ratio of the different types of fuel contained in the injected fuel, and the basic ignition timing based on the output of the operating state detecting means b. And an ignition timing setting means g that determines the final ignition timing by correcting the basic ignition timing according to the correction amount, and an ignition means h that ignites the air-fuel mixture based on the output of the ignition timing setting means g.
And are equipped with.

In order to achieve the above-mentioned object, the combustion control device for an internal combustion engine according to the second aspect of the present invention has a basic conceptual diagram thereof as shown in FIG.
And the operating state detecting means b for detecting the operating state of the engine using the engine load and engine speed as parameters, and the crank angle at which the in-cylinder pressure becomes maximum based on the output of the pressure detecting means a. The maximum combustion timing detection means c, the air-fuel ratio detection means d for detecting the air-fuel ratio of the intake air-fuel mixture, and the actual combustion time in the cylinder based on the difference between the output of the maximum combustion timing detection means c and the final ignition timing. An actual combustion time calculation means e for calculating, a target combustion time calculation means f for calculating a target combustion time in the cylinder based on the output of the air-fuel ratio detection means d, an output of the actual combustion time calculation means e and a target combustion A correction unit g that determines a predetermined combustion state in the cylinder based on the difference from the output of the time calculation unit f, and calculates a correction amount that corrects the basic ignition timing according to the determination result, and an operating state. Output of the ignition timing setting means h for setting the basic ignition timing based on the output of the output means b, and correcting the basic ignition timing according to the correction amount to determine the final ignition timing, and the ignition timing setting means h. Ignition means i for igniting the air-fuel mixture based on

(Operation) In the first invention, the in-cylinder pressure sensor detects the crank angle at which the in-cylinder pressure becomes maximum as the in-cylinder pressure maximum timing, and the combustion in the cylinder is performed based on the difference between the in-cylinder pressure maximum timing and the final ignition timing. Time is calculated. Then, the mixing ratio of different types of fuel contained in the injected fuel is obtained from the correlation between the fuel time and the air-fuel ratio, the correction amount is calculated according to this mixing ratio, and the basic ignition timing is corrected according to this correction amount. To be done.

Therefore, even when using a fuel such as alcohol-blended gasoline in which the variation range of the ignition timing characteristics is large, the ignition timing is optimally controlled, and the drivability and fuel efficiency are improved.

In the second invention, the target combustion time is calculated based on the air-fuel ratio, and the ignition timing advance angle at the time of abnormal combustion in the cylinder is calculated based on the difference between the target combustion time and the actual combustion time. Alternatively, it is determined that the vehicle is retarding too much. Then, the basic ignition timing is corrected according to the determination result.

Therefore, even if the maximum cylinder pressure timing is near TDC, the engine is operated at the optimum ignition timing, and the drivability and fuel economy are further improved.

(Embodiment) Hereinafter, a first device and a second device will be described with reference to the drawings.

2 to 7 are views showing an embodiment of a combustion control device for an internal combustion engine according to the first invention.

First, the configuration will be described. In FIG. 2, reference numeral 1 is a crank angle sensor, and the crank angle sensor is an explosion interval (120 degrees for a 6-cylinder engine, 1 degree for a 4-cylinder engine).
80 °) every predetermined position before compression top dead center (TDC) of each cylinder,
For example, a reference signal that becomes a [H] level pulse at BTDC 70 °
A unit signal PO that outputs REF and becomes a pulse of [H] level for each unit angle of crank angle (for example, 2 °)
Output S. The engine speed N can be known by counting the pulses of the unit signal POS. The engine load such as the intake air amount Qa is detected by the load sensor 2, and the idle switch or the like is used as the load switch 3.
ON-OFF signal is detected. Reference numeral 4 denotes an in-cylinder pressure sensor (pressure detecting means), and the in-cylinder pressure sensor 4 is formed as a washer of an ignition plug (not shown) screwed to the cylinder head of the engine and is fastened together. The in-cylinder pressure sensor 4 converts the combustion pressure in the cylinder into an electric signal by a piezoelectric element, and outputs this electric signal to the knocking processing circuit 5 and the in-cylinder pressure detection circuit 6. Knocking detection circuit 5 and in-cylinder pressure detection circuit 6 convert this electrical signal into knocking signal S ₁ and in-cylinder pressure signal S ₂ , respectively.

The crank angle sensor 1, the load sensor 2, and the load switch 3 constitute an operating state detecting means 7, and signals from the operating state detecting means 7, the knocking processing circuit 5 and the in-cylinder pressure detecting circuit 6 are sent to the control unit 11. Is entered.
The control unit 11 has a function as a maximum timing detection means, an air-fuel ratio detection means, a combustion time calculation means, a correction means and an ignition timing setting means, and is composed of an I / O 12, a CPU 13, a ROM 14, and a RAM 15, which are connected to a bus. 16 connected to each other. The CPU13 takes in the external data required from the I / O12 according to the program written in the ROM14, and also exchanges the data with the RAM15, while calculating the processing values etc. necessary for combustion control. Then, the processed data is output to the I / O 12 as needed. The I / O 12 receives signals from the knocking processing circuit 5, the bus 16 and the operating state detecting means 7, and outputs an ignition signal Sp from the I / O 12 to the output amplification circuit 17. Output amplifier circuit 17,
The power transistor 18, the ignition coil 19 and the spark plug (not shown) constitute an ignition device (ignition means) 20, and the ignition device 20 generates a high voltage based on the ignition signal Sp to ignite the air-fuel mixture.

Although FIG. 2 shows the configuration of a single cylinder engine for simplification, in a multi-cylinder engine, the crank angle sensor 1, the in-cylinder pressure sensor 4, the in-cylinder pressure detection circuit 6, the output amplification circuit 17 and the ignition coil 19 are used in the cylinder. Suppose there is a few minutes.

Next, the operation will be described.

FIG. 3 is a flow chart showing a combustion control plug, and this program is executed once every predetermined period.

First, the engine speed N is read at P ₁ , and the basic pulse width Tp is calculated at P ₂ according to the following equation.

However, the constant basic pulse width Tp that determines the value of the K: air-fuel ratio is not only a calculation load equivalent amount but also a basic value in fuel injection control. Then, the fuel peak position P ₃ (cylinder pressure maximum time), but detects the signal, the detection method as described in JP-A-59-39974, the predetermined crank angle interval (TDC~ATDC50 ° ) Until 1
The in-cylinder pressure is A / D converted for each °, and the crank angle when the converted value becomes maximum is detected as θpmax. Then
At P ₄ , the basic ignition timing BASE is looked up from the table with the engine speed N and the basic pulse width Tp as parameters. The basic ignition timing BASE determines the optimum ignition timing for gasoline that is not mixed with alcohol, and it is not necessary to perform a new matching to obtain the basic ignition timing BASE for alcohol-blended gasoline. The basic ignition timing BASE used can be used as it is.

Next, at P ₅ , the difference DADV (DADV = θpmax-STADV) between the fuel peak position θpmax and the ignition timing STADV is converted into time T
Calculate ADV according to the following formula.

TADV = DADV ÷ N × C ...... However, C = constant Here, focusing on TADV, TADV can be regarded as a quantity representative of the combustion time from ignition to the end of fuel. Further, the ignition timing STADV is set in Step P ₁₂ described later.
Therefore, the final ignition timing ADV stored as STADV in a predetermined memory is used.

Next, in P ₆ , the fuel injection amount Ti is calculated according to the following equation based on the basic pulse width Tp, and in P ₇ , the air-fuel ratio AF is calculated according to the following equation based on this Ti and the intake air amount Qa.

Ti = α × Tp + Ts …… where α: Air-fuel ratio feedback correction amount Ts: Battery voltage correction amount However, K ': constant Next, look up the alcohol content R contained in the injected fuel in the case of using an alcohol blended gasoline from a map as a parameter of the combustion time TADV fuel ratio AF at P _8. There is a correlation as shown in FIG. 4 between the combustion time TADV and the air-fuel ratio AF, and a map as shown in FIG. 5 is stored in advance in the memory (ROM 14). As is clear from FIG. 5, the combustion rate tends to increase as the content R increases.

Next, at P ₉ , the ignition timing correction amount (correction amount) Δ ₁ is calculated based on the engine speed N, the basic pulse width Tp, and the alcohol content rate R.

Here, a method for obtaining Δ ₁ will be described with reference to FIGS. 6 and 7 and FIGS. 15 and 16.

When the content ratio R is determined, it means that the position of the broken line (characteristic of alcohol) shown in FIGS. 15 and 16 is determined, but when the load and the rotational speed are different, the solid line (characteristic of gasoline) is shown.
Since the amount of deviation (correction amount) from the difference is also different, it is necessary to determine the content rate R according to the load and the rotational speed at that time in order to specify even this amount of deviation.

Therefore, in this embodiment, Δ ₁ is calculated by the sum of the correction amounts Δ ₁₂ and Δ ₁₁ obtained from the characteristics shown in FIGS. 6 and 7 (Δ ₁
= Δ ₁₂ + Δ ₁₁ ).

First, the correction amount delta ₁₂ obtained from Figure 7, a value for characteristic to gasoline in Figure 15 (solid line) varies the characteristic (broken line) to alcohol-containing gasoline, delta ₁₂
For the load, a value corresponding to the difference between the solid line and the broken line is selected with the load as the variable. In the figure, since it is necessary to retard the ignition timing on the left side of the point where the two curves intersect, the value of Δ ₁₂ is made negative and becomes larger as the load becomes lower. On the contrary, the value on the right side of the intersection is a positive value because it evolves and becomes larger as the load increases.

Further, the position of the broken line in FIG. 15 moves while the value of the alcohol content R is different, and therefore when R changes, Δ
The value of ₁₂ also changes. In this case, it means that there is an axis having R as a variable in the direction orthogonal to the paper surface in the figure, and as a result, it can be seen from FIG. 7 that Δ ₁₂ is determined with load and R as parameters. That is.

FIG. 7 shows the characteristic of Δ ₁₂ obtained in this way, and the slope of the curve increases as R increases.

Similarly, the correction amount Δ ₁₁ obtained from FIG. 6 is determined using the engine speeds N and R as parameters. However,
Unlike FIG. 6, the relative positions of the two curves are opposite to each other in FIG. 7, so that the slope of the curve shown in FIG. 6 is also opposite to that of FIG.

The alcohol content rate R = 0 in FIGS. 6 and 7.
In the case of%, the correction amount for the fuel of gasoline only (that is, zero) is given, whereas in the case of the alcohol content R = 100%, the correction amount for the fuel of alcohol only is given.
Therefore, even if a fuel with an unknown alcohol content R is used, the alcohol content R is detected and the values of Δ ₁₁ and Δ ₁₂ are determined from the alcohol content R and the operating conditions at that time. The value corrected by this Δ ₁₁ and Δ ₁₂ (BA
According to SE + Δ ₁₁ + Δ ₁₂ ), the optimum ignition timing can be given to the fuel having any alcohol content R.

To obtain Δ ₁₁ and Δ ₁₂ , a table having the characteristics shown in FIGS. 6 and 7 is stored in the memory (ROM 14),
Similar to reading the basic ignition timing BASE, Δ ₁₁ is read from the engine speed N and the alcohol content rate R, and Δ ₁₂ is read from the basic pulse width Tp and the alcohol content rate R, and these are added to obtain Δ _1. Good.

Next, the feedback correction amount Δ ₂ of the ignition timing is calculated at P ₁₀ , and Δ ₂ is given by the sum of the correction amount Δ ₂₁ by the knocking control and the correction amount Δ ₂₂ by the MBT control, for example. Then, the feedback correction amount Δ ₂ is the basic ignition timing.
Adding to BASE means that a feedback control system is configured. The feedback control is convenient for absorbing the control error associated with the open loop control.
That is, since the control by BASE + Δ ₁ is an open loop control, an error may occur in the ignition timing correction amount Δ ₁ , but this error is absorbed by Δ ₂ .

Conversely, since the high-precision correction is compensated by the correction by the feedback correction amount Δ _2, so much accuracy is not required for the ignition timing correction amount Δ _1, that is, the ignition timing correction amount Δ ₁ . _The correction by ₁ means that it is rough and good. Therefore, the number of grid points storing Δ ₁₁ or Δ ₁₂ can be reduced, and the ignition timing correction amount Δ
_The amount of memory for ₁ may be small.

For knocking control and MBT control, various methods conventionally used for gasoline can be applied. For example, if there is knocking, it will be greatly retarded, and if there is no knocking, the value that is advanced little by little will be Δ ₂₁ , and Θr (at the crank angle that maximizes engine efficiency,
Deviation ΔΘ from the compression top dead center value near 15 °) (ΔΘ = Sr
The value obtained by performing a proportional operation based on −Θ pmax) may be adopted as Δ ₂₂ . Further, the method described in the above-mentioned Japanese Patent Laid-Open No. 61-14479 may be used.

Next, at P ₁₁ , the final ignition timing ADV is calculated according to the following formula, and at P ₁₂ ADV is calculated as the ignition timing corresponding to the operating state at this time.
It is stored in a predetermined memory (ROM 14) as STADV.

ADV = BASE + Δ ₁ + Δ ₂ ...... Then, at P ₁₃ , the ignition signal Sp is set based on the final ignition timing ADV.
Output to I / O12 and finish this routine.

Here, the operation associated with the above correction will be described. In this embodiment, _two correction amounts, that is, the ignition timing correction amount Δ ₁ and the feedback correction amount Δ ₂ are introduced, and one correction amount Δ ₁ is applied to various mixed fuels having different alcohol content ratios R. The optimum ignition timing is roughly given. In this case, BASE
The value of + Δ ₁ does not feed back the result of combustion to the ignition timing but is an open loop correction,
According to this, the optimum ignition timing can be given without a response delay even in the initial stage of the transition.

The reason why it is allowed to be rough is that the ignition timing correction amount Δ
_{This is because} the purpose of item ₁ is to improve the responsiveness to a transient time rather than the accuracy, and it is needless to say that sufficient responsiveness can be obtained even if the accuracy is rough.

Moreover, by making the accuracy of the ignition timing correction amount Δ ₁ rough, the memory amount of Δ ₁ can be reduced, and thus the responsiveness and the cost can be balanced.

Further, according to the other correction amount Δ ₂ , since Δ ₂ is the feedback amount, high accuracy is compensated even in the steady state. For example, even if there are variations in characteristics of other sensors or changes over time, or if there are changes in engine characteristics such as the cooling state of the engine, these are absorbed and maximum torque is extracted within the range where knocking does not occur. Become.

In other words, what is required for control is quick response and good accuracy. However, instead of trying to cover both with a single correction amount, they are separated and one correction amount Δ ₁ gives priority to accuracy. And give good responsiveness to deal with transients,
The other feedback correction amount Δ ₂ gives high accuracy that cannot be obtained by Δ ₁ . As a result, even when the variation range of the ignition timing characteristic is large like alcohol blended gasoline, the cost is not increased,
It is possible to control the optimum ignition timing quickly and accurately according to the operation change, and maintain the optimum combustion state.

8 to 14 are views showing an embodiment of a combustion control device for an internal combustion engine according to the second invention, and in explaining the present embodiment, the same components as those of the first invention shown in FIG. The same reference numerals are given and the description thereof is omitted.

First, the configuration will be described. In FIG. 8, 21 is an O ₂ sensor, and the O ₂ sensor 21 detects the oxygen concentration in the exhaust gas. The crank angle sensor 1, the load sensor 2, the load switch 3, and the O ₂ sensor 21 constitute an operating state detecting means 22, and the signal from the operating state detecting means 22 is the control unit 11.
Has a function as a maximum timing detection means, an air-fuel ratio detection means, an actual combustion time calculation means, a target combustion time calculation means, a correction means, and an ignition timing setting means. Reference numeral 23 denotes a fuel injection device, which supplies fuel to the cylinder based on the injection signal Si from the control unit 11.

Next, the operation will be described.

FIG. 9 is a flowchart showing a main program for combustion control, and this program is executed once every predetermined period.

First, the engine speed N is read at P ₂₁ , and the intake air amount Qa is read at P ₂₂ . Then, the basic pulse width Tp is calculated according to the following equation by P _23, it calculates the fuel injection pulse width Ti according to the following equation on the basis of Tp in P _24.

However, K1: a constant that determines the value of the air-fuel ratio Ti = K2 x Tp + Ts ... where K2: correction amount of the air-fuel ratio Ts: battery voltage correction amount Tp is the engine load equivalent amount, and even the basic value in fuel injection control is there.

Next, at P ₂₅ , the basic ignition timing BASE is looked up from a map using the engine speed N and the basic pulse width Tp as parameters, and at P _{26 the} final ignition timing ADV is calculated according to the following equation.

ADV = BASE + MBTCS …… However, MBTCS: Ignition timing correction amount (correction amount). Details will be described later.

Then stores the final ignition timing ADV at P ₂₇ in a predetermined memory (ROM 14) as a corresponding ignition timing ATADV the operating state at this time. Then, in P ₂₈ , the injection pulse width Ti obtained in step P ₂₄ is output to the fuel injection device 23 via the I / O 12, and P
₂₉ an ignition signal Sp based on the final ignition timing ADV calculated in step P ₂₆ of the ignition device 20 from the I / O12 by the power transistor 17
Is output to and the routine of this time is ended.

FIG. 10 is a flow chart showing a program for judging abnormality of the combustion peak position θpmax, and this program is executed once every predetermined period.

First, the combustion peak position θpmax is calculated in P ₃₁ , and as the calculation method, for example, the method described in JP-A-59-39974 is used. Next, at P ₃₂ , it is determined whether or not θpmax is near the compression top dead center TDC, and when θpmax is near TDC, it is determined that the inside of the cylinder is in the abnormal combustion state and P ₃₃
Then, the determination flag Sh0 is set (Sh0 = 1). Then P
_{At 34} , the air-fuel ratio AF is calculated according to the following equation, and at P ₃₅ , the ideal combustion time (target combustion time) Texp is calculated.

However, the C2: constant ideal combustion time Texp is calculated based on a table having the combustion time and the air-fuel ratio AF as parameters as shown in FIG.
This table is stored in the memory (ROM 14) in advance.

Then, it calculates the actual combustion time Treal according to the following equation by P _36, and compares the difference with a predetermined value C3 of the ideal burning time Texp and the actual burn time Treal with _{P 37 (Treal-Treal: C3} ).

Treal = (θpmax-STADV) / N × C1 ...... However, C1: the ignition timing of the occurrence of abnormal combustion such as misfire in constant step P ₃₇ in the cylinder, it is intended to determine the correlation between the burning time However, the principle will be described with reference to FIGS.

Focusing on the change in the in-cylinder pressure (the output waveform of the in-cylinder pressure sensor 4), when the misfire occurs due to the ignition timing being retarded too much, the combustion peak position θpmax appears at the compression top dead center TDC as shown in FIG. Timing STADV and θpmax are close.
On the other hand, as shown in FIG. 13, when the combustion peak position θpmax appears at the compression top dead center TDC due to excessive advance of the ignition timing, the map of the ignition timing STADV and θpmax is separated by a predetermined time, that is, the combustion time. ing. This gives STADV and θp
Focusing on the amount Treal obtained by time-converting the difference from max, it is possible to distinguish between too much advance and too much advance. Also, the combustion time in the cylinder is determined by the air-fuel ratio AF as shown in Fig. 11.
It is necessary to consider (ideal combustion time Texp).

In this embodiment, the value C3 corresponding to the combustion time between the ignition timing being advanced too much and the ignition timing being too late is previously obtained based on the above-mentioned principle by experiments and stored in the ROM 14.

Thus, step P ₃₇ in (Texp-Treal) ≦ C3 sets the determination flag Sh1 at P ₃₈ judges that are too advanced when the (Sh1 = 1) and ends the current routine. (Tex
When p−Treal)> C3, it is judged that the angle is too late and P
_{At 39} , the determination flag Sh1 is reset (Sh1 = 0), and this routine ends.

On the other hand, when the combustion peak position θpmax is not near the compression top dead center TDC in step P ₃₂ , it is determined that the combustion in the cylinder is normal, and the determination flag Sh0 is reset (Sh = 0) in P ₄₀ to execute this routine. finish. FIG. 14 shows the judgment flag Sh.
6 is a flowchart showing a program for calculating an ignition timing correction amount MBTCS based on 0 and Sh1, and this program is executed once every predetermined period.

First, a determination flag Sh0 at P ₄₁ [1] (Sh0 = 1)
Whether determined, when the Sh0 = 1 determines whether or not the Sh1 at P ₄₂ is [1] (Sh1 = 1). Sh0 = 1, and Sh1 = 1 when misfire occurs and advanced to the ignition timing at P ₄₃ judges that are too correction amount MBTCS as predetermined retard correction amount KRTD the (MBTCS = KRTD), this routine ends. Sh0 = As 1 Sh1 = 0 predetermined advance angle correction amount KADV the ignition timing correction amount MBTCS at P ₄₄ and determined to be too retarded when the (MBTCS = KRTD), the present routine is ended . Meanwhile, since it is the normal combustion when the determination flag Sh0 = 0 in step P _41, a crank crank angle θr (the period efficiency of combustion peak position θpmax and near MBT at that time as performing the normal MBT control is maximum Angle Δθ (Δθ = θr-
The ignition timing correction amount MBTCS is calculated in P ₄₅ according to the following equation so that the proportional operation is performed based on θpmax), and the current routine is ended.

MBTCS = Δθ × C4 ...... However, C4: constant As described above, in the present embodiment, the actual combustion time Treal and the target combustion time Te are calculated from the difference between the combustion peak position θpmax and the ignition timing STADV.
Based on the difference from xp, it is possible to reliably determine whether the ignition timing at the time of misfire occurs is too advanced or retarded too much. Then, the ignition timing correction amount MBTCS is calculated according to the determination result.
Therefore, even if the combustion peak position θpmax is close to the compression top dead center TDC, θpmax at the time of misfire can be accurately detected and the ignition timing can be optimally controlled. It is possible to further improve the drivability and fuel efficiency of the vehicle.

In the present embodiment, the air-fuel ratio AF was calculated based on the intake air amount Qa and the injection pulse width Ti, but if the engine is equipped with an air-fuel ratio sensor, the air-fuel ratio AF will be calculated based on the output of this air-fuel ratio sensor. May be calculated.

(Effect) According to the first invention, the combustion time in the cylinder is calculated based on the difference between the cylinder internal pressure maximum timing and the final ignition timing, and the different types of fuel contained in the injected fuel are calculated from the correlation between the combustion time and the air-fuel ratio. Since the basic ignition timing is corrected according to the correction amount corresponding to the mixing ratio of the fuel, injection is performed without increasing the cost even when using the fuel in which different types of fuel are mixed. The fuel property of the fuel can be accurately detected, and the ignition timing can be optimally controlled.
As a result, the drivability and fuel efficiency of the engine can be improved.

Further, according to the second aspect, the target combustion time is calculated based on the air-fuel ratio, and the ignition timing advance when abnormal combustion occurs in the cylinder is calculated based on the difference between the target combustion time and the actual combustion time. Since the basic ignition timing is corrected according to the result of the determination, the ignition timing can be optimally controlled even when the maximum cylinder pressure timing is near TDC. The engine drivability and fuel consumption can be further improved.

[Brief description of drawings]

FIG. 1 (A) is a basic conceptual diagram of the first invention, and FIG. 1 (B).
FIG. 2 is a basic conceptual diagram of the second invention, and FIGS. 2 to 7 are diagrams showing an embodiment of a combustion control device for an internal combustion engine according to the first invention;
FIG. 2 is an overall configuration diagram thereof, FIG. 3 is a flowchart showing a program of its combustion control, FIG. 4 is a characteristic diagram showing the relationship between its combustion speed and air-fuel ratio, and FIG. 5 is its alcohol content and combustion. FIG. 6 is a characteristic diagram showing the relationship with time, FIG. 6 and FIG. 7 are characteristic diagrams showing the relationship between the correction amount, the alcohol content rate and the operating state, and FIGS. FIG. 8 is a diagram showing an embodiment of the apparatus, FIG. 8 is an overall configuration diagram thereof, FIG. 9 is a flow chart showing a program for its combustion control, and FIG. 10 is a flow chart showing a program for making an abnormality determination of its combustion peak position. , FIG. 11 is a characteristic diagram showing the relationship between the combustion time and the air-fuel ratio,
FIG. 14 is a diagram for explaining the relationship between the combustion peak position and ignition timing, FIG. 14 is a flowchart showing a program for obtaining the ignition timing correction amount, and FIGS. 15 and 16 are conventional combustion control devices for internal combustion engines. FIG. 4 is a characteristic diagram showing a relationship between gasoline and alcohol and ignition timing for explaining a problem. 4 ... In-cylinder pressure sensor (pressure detection means), 7 ... Operating state detection means, 11 ... Control unit (maximum timing detection means, air-fuel ratio detection means, combustion time calculation means, correction means,
Actual combustion time calculation means, target combustion time correction means, correction means, ignition timing setting means), 20 ... Ignition device (ignition means).

Claims (2)

[Scope of utility model registration request] 1. A pressure detecting means for detecting an in-cylinder pressure of the engine; b) an operating state detecting means for detecting an operating state of the engine using a load and a rotational speed of the engine as parameters; and c) a pressure detecting means. Maximum timing detecting means for detecting the crank angle at which the cylinder pressure becomes maximum based on the output as the cylinder pressure maximum timing; d) air-fuel ratio detecting means for detecting the air-fuel ratio of the intake air-fuel mixture; and e) maximum timing. Combustion time calculating means for calculating the combustion time in the cylinder based on the difference between the output of the detecting means and the final ignition timing; and f) included in the injected fuel based on the output of the air-fuel ratio detecting means and the output of the combustion time calculating means. And a correction unit for calculating a correction amount for correcting the basic ignition timing according to the mixing ratio, and g) setting the basic ignition timing based on the output of the operating state detection unit. In addition, an ignition timing setting means for correcting the basic ignition timing according to the correction amount to determine a final ignition timing, and h) an ignition means for igniting an air-fuel mixture based on an output of the ignition timing setting means. A combustion control device for an internal combustion engine. 2. A) pressure detection means for detecting the in-cylinder pressure of the engine; b) operating state detection means for detecting the operating state of the engine using the engine load and engine speed as parameters; and c) pressure detection means. Maximum timing detecting means for detecting the crank angle at which the cylinder pressure becomes maximum based on the output as the cylinder pressure maximum timing; d) air-fuel ratio detecting means for detecting the air-fuel ratio of the intake air-fuel mixture; and e) maximum timing. An actual combustion time calculation means for calculating the actual combustion time in the cylinder based on the difference between the output of the detection means and the final ignition timing; and f) a target combustion time in the cylinder based on the output of the air-fuel ratio detection means. Target combustion time calculating means for calculating, and g) a predetermined combustion state in the cylinder is determined based on the difference between the output of the actual combustion time calculating means and the output of the target combustion time calculating means, Correcting means for calculating a correction amount for correcting the basic ignition timing, and h) setting the basic ignition timing based on the output of the operating state detecting means, and correcting the basic ignition timing according to the correction amount, and finally A combustion control device for an internal combustion engine, comprising: an ignition timing setting means for determining an ignition timing; and i) an ignition means for igniting an air-fuel mixture based on an output of the ignition timing setting means.