JPH0648134Y2 - Combustion state control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a device for detecting combustion pressure of an internal combustion engine and optimally controlling a combustion state of an engine such as an automobile.

(Prior Art) Conventionally, in order to perform more precise combustion control of an internal combustion engine, a maximum timing of combustion pressure (hereinafter referred to as "cylinder pressure maximum timing") is detected, and this timing becomes an optimum crank angle θop. A technique for advancing / retarding the ignition timing is known (Japanese Patent Publication No.
-13973). Further, a technique is known in which knocking is discriminated from the magnitude of a high-frequency component of a combustion pressure waveform, and ignition timing is advanced or retarded so as to suppress knocking (Japanese Patent Publication No. 58-13749).

(Problems to be solved by the invention) However, in such a conventional technique, for example, even when combustion is not stable due to partial misfire, detection information (combustion pressure) at that time is generated. Since the ignition timing is controlled based on the above, there is a problem that the ignition timing is corrected unnecessarily, and as a result, the stability of the combustion state is rather deteriorated.

FIG. 6 is a distribution state diagram of the maximum cylinder pressure Pmax and the maximum cylinder pressure timing θpmax when the engine speed, the fuel injection amount, and the air-fuel ratio are fixed, and only the ignition timing is changed. Three ranges surrounded by broken lines are typical distribution ranges of the average values of Pmax and θpmax when combustion is stable without partial misfire or the like. If the ignition timing is appropriate, it falls within the range, but if the ignition timing is too late, it falls within the range of region (c), and if it is too early, it falls within the range of region (d).

However, in rare cases, combustion may not be stable due to partial misfire, etc. depending on operating conditions. In such a case, the average values of Pmax and θpmax are in the range (a) and the range (b).
May be distributed in. Particularly, in an engine that performs lean combustion or an engine that applies a large amount of EGR, such a distribution phenomenon in the area (a) and the area (b) is likely to occur.

Therefore, the regions (a) and (b) are not the regions where the average values of Pmax and θpmax are originally distributed due to the deviation of the ignition timing, but other factors other than the ignition timing (for example, ignition delay, fuel atomization state). Or, since it is a region that is distributed depending on (combustion state variation due to turbulence of intake air, etc.), for example, if the ignition timing is controlled only by the comparison result of the in-cylinder pressure maximum timing θpmax and θop, the ignition timing will be appropriate. Nevertheless, the ignition timing is unnecessarily modified.

Therefore, the present invention compares the average value of the maximum in-cylinder pressure value with a predetermined maximum in-cylinder pressure reference value Po, and determines the average value of the maximum in-cylinder pressure timing and the predetermined in-cylinder pressure maximum reference time θop. A region where the ignition timing advance / retard correction is to be performed based on the comparison result (see regions C and D in FIG. 6) and a region to be prohibited (see regions A and B in FIG. 6) are compared. By discriminating, it is intended to avoid unnecessary correction operation of the ignition timing.

(Means for Solving Problems) In order to achieve the above object, a combustion state control device for an internal combustion engine according to the present invention has a basic conceptual diagram as shown in FIG. Based on the output of the detection means a, the crank angle detection means b for detecting the crank angle of the engine, and the pressure detection means a, the in-cylinder pressure is sampled at every predetermined crank angle or continuously, and the cylinder pressure in the current combustion stroke is calculated. Combustion waveform detection means c for detecting the combustion pressure waveform, and extraction means d for extracting the cylinder pressure maximum value Pnew and the cylinder pressure maximum timing θnew based on the output of the combustion waveform detection means c.
An average value of the maximum cylinder pressure Pnew and the maximum cylinder pressure before it, and an averaging means e for calculating the average value of the maximum cylinder pressure time θnew and the maximum cylinder pressure before it. The average value is compared with a predetermined maximum in-cylinder pressure reference value Po, and the average value is compared with a predetermined maximum in-cylinder pressure reference time θop, and the comparison result is> θop and ≦ Po. When the comparison result is the ignition timing, the ignition timing is advanced, when the second comparison result is ≤ θop and> Po, the ignition timing is retarded, and when the result is other than the first and second comparison results, the ignition timing is It is characterized by comprising a correction means f that does not perform any retardation correction and an operation means g that operates the ignition timing based on the output of the correction means f.

(Operation) In the present invention, the region where the ignition timing advance / retard correction should be performed (see regions C and D in FIG. 6) and the region that should be prohibited (see regions A and B in FIG. 6) are determined. Therefore, the problem that the ignition timing is unnecessarily corrected despite the proper ignition timing is eliminated, and the ignition timing is maintained at an appropriate value to improve fuel efficiency and reduce surging.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

2 to 7 are views showing an embodiment of the present invention.

First, the configuration will be described. In FIG. 2, reference numeral 1 denotes an in-cylinder pressure sensor (pressure detecting means), and the in-cylinder pressure sensor 1 is formed as a washer of an ignition plug screwed to a cylinder head of an engine and is fastened together. The in-cylinder pressure sensor 1 converts the combustion pressure in the cylinder into electric charges by a piezoelectric element, and outputs a charge output S ₁ to the charge amplifier 2. The charge amplifier 2 comprises a so-called charge-voltage conversion amplifier, which converts the sensor output S ₁ into a voltage signal S ₂ and outputs the voltage signal S ₂ to the A / D converter 3. The A / D converter 3 converts the signal S ₂ input as an analog signal into a digital signal and outputs it to the characteristic parameter detection circuit 4. The characteristic parameter detection circuit 4 detects a characteristic parameter representing the characteristic of the combustion pressure waveform from the input digital signal S ₃ and outputs it to the averaging circuit 5. In addition,
The characteristic parameter is a concept representing the characteristics of the combustion pressure waveform, and includes, for example, the maximum value of the combustion pressure (hereinafter referred to as the "maximum value of the cylinder pressure") Pmax and the detected crank angle of this Pmax (hereinafter referred to as the "maximum time of the cylinder pressure"). )) Θpmax is used.

The averaging circuit 5 averages the input feature parameters to suppress variations and outputs the feature parameters to the basic control circuit 7. An output signal S _{4 from} a sensor group (crank angle detecting means) 6 other than the cylinder pressure sensor 1 of the engine, for example, a crank angle sensor, an air flow meter, etc., is further input to the basic control circuit 7. , A processing value required for appropriately controlling the combustion state is calculated based on the output signal S ₄ and the output signal of the averaging circuit 5, and the control signal S _{5 is set} to the actuator group ( Output to (operation means) 8.
The actuator group 8 changes a combustion operation parameter capable of operating the combustion state of the engine, and includes, for example, an ignition device that ignites the air-fuel mixture in response to a control signal S ₅ from the basic control circuit 7.

The characteristic parameter detection circuit 4, the averaging circuit 5, and the basic control circuit 7 are composed of a microcomputer 9, and the microcomputer 9 is a combustion waveform detecting means,
It has a function as an extracting unit, an averaging unit, and a correcting unit. The microcomputer 9 implements the functions of the above circuits according to a program stored in an internal memory.

Next, the operation will be described. First, the basic principle of the present invention will be described.

As an example, consider the case where the maximum cylinder pressure is detected and the ignition timing is controlled as described in Japanese Patent Publication No. 49-17973. As shown in FIG. Even if the ignition timing is fixed, the maximum cylinder pressure timing θpmax is distributed before and after the peak of ATDC 15 ° as shown by the curve a, and is not always constant. On the other hand, if the ignition timing is advanced too far from the optimum value, the distribution will be as shown by the curve b, and if it is delayed too much, the distribution will be as shown by the curve c.
Now, assuming that the in-cylinder pressure maximum timing θpmax of ATDC 15 ° is obtained in this combustion cycle, this state can occur under any of the conditions of the curves a to c. Also, ATDC 10 °
When .theta.pmax is obtained, this state is included in the distribution of the curve b with a high probability, and therefore it can be determined that the ignition timing is too advanced. However, even in this case, since it is included in the distribution of the curve a, that is, a part of the distribution of the appropriate ignition timing, it is not preferable to immediately retard the ignition timing. Conventionally, even in the above case, the ignition timing may be immediately corrected on the basis of the extracted data, so that the combustion state control may not be stable.

Therefore, in this embodiment, when the distribution data of the curves a to c shown in FIG. 3 are averaged, the averaged data does not overlap like the curves a to c shown in FIG. By paying attention to the above, and using the averaged data as a characteristic parameter, the control stability of the combustion state is improved.

By the way, when only θpmax is used as the characteristic parameter, it may not be possible to immediately determine whether the ignition timing should be advanced or retarded or prohibited.

That is, FIG. 5 is a graph in which the vertical axis represents Pmax and the horizontal axis represents θpmax. When the ignition timing is appropriate, the parameters have a distribution in the range shown by the curve A, and the average value thereof is the point. Similarly, curve B is too late, curve C is too far, and points are average values. Now, in the figure a
If the parameter of the point (x mark) is obtained, it cannot be immediately determined whether it belongs to the range of the curve A or the range of the curve B.

Therefore, in the present embodiment, by using the respective averaged data of the two parameters of θpmax and Pmax, as shown in FIG. 6, analytical characteristics of curves ~ which do not overlap each other are obtained and used for control. There is.

FIG. 7 is a flow chart of the combustion control program in this embodiment.

In this flowchart, first, at P ₁₁ , the cylinder pressure maximum timing θpmax new (hereinafter simply referred to as θnew) in the present combustion cycle and the cylinder pressure maximum value Pmax new at that time
(Hereinafter, simply referred to as Pnew) is detected. Next, at P ₁₂ , the average value of θnew is calculated according to the following expression, and the average value of Pnew is calculated according to the following expression.

However, ′: previous average value However, ′: previous average value In the above equation, n is an integer, for example, n
= 16 is selected. This kind of weighted average calculation is performed based on only new data this time, avoiding or updating, and weighting the data by adding the values up to the previous time to ensure the reliability of the data. In the meanwhile, the data is updated to the latest data one by one. By performing such weighted average calculation, the distribution shown in FIG. 3 becomes a non-overlapping distribution as shown in FIG.

Next, in P ₁₃ , the average value is compared with the predetermined value θop, and after this comparison and determination, the average value is further calculated in P ₁₄ and P ₁₅ as the predetermined value Po.
Finally, the processing shown in Table 1 below is performed according to the determination results of P _{13 to} P ₁₅ . It should be noted that θop is a value corresponding to the optimum position where the combustion state is appropriate, and for example, the value is obtained in advance from experiments or the like according to the engine model, etc., and is stored in the memory.

Therefore, in this embodiment, the detection data are averaged,
The combustion state is controlled based on the averaged value. Therefore, regardless of variations in the combustion state, the ignition timing can be corrected appropriately, and the combustion state control can be stabilized unlike the conventional case. Particularly, in the present embodiment, the combustion state is controlled based on the theoretical product of the average value data of the two detected values, so that, for example, a in FIG.
Even if it is impossible to immediately determine whether it belongs to the range of the curve A or the range of the curve B like the parameter of the point (x mark), it is divided into the four areas (a) to (d) of FIG. The determination can be made without any trouble, and the stability and reliability of control can be improved.

Further, only in the case of the upper left region (d) in FIG. 6 corresponding to Case III (corresponding to the first comparison result), the ignition timing is retarded, and the opposite lower right region (c) is changed. In the case (corresponding to the second comparison result) only, the advance angle correction is performed, while in the other regions, that is, in the region (a) where it should rarely occur,
In (b), neither advance nor retard is performed (prohibited), so that the stability of control is extremely high.

(Effect) According to the present invention, since the combustion detection data is averaged and reflected in the combustion state control, it is possible to appropriately correct the combustion operation parameter (ignition timing) regardless of variations in the combustion state. Therefore, the combustion state control can be stabilized.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 7 are diagrams showing an embodiment of the present invention, and FIG. 2 is an overall configuration diagram thereof.
FIG. 3 is a diagram showing the distribution of the cylinder internal pressure maximum timing when the ignition timing is changed, FIG. 4 is an averaged distribution of the cylinder internal pressure maximum timing of FIG. 3, and FIG. Maximum internal pressure θpm
Fig. 6 shows the distribution of ax and maximum cylinder pressure Pmax.
FIG. 7 is a diagram in which the distribution of the in-cylinder pressure maximum timing θpmax and the in-cylinder pressure maximum value Pmax is averaged, and FIG. 1 ... In-cylinder pressure sensor (pressure detecting means), 6 ... Sensor group (crank angle detecting means), 8 ... Actuator group (operating means), 9 ... Microcomputer (combustion pressure waveform detecting means,
Extraction means, averaging means, correction means).

Claims (1)

[Scope of utility model registration request] 1. A) pressure detecting means for detecting an in-cylinder pressure of the engine; b) crank angle detecting means for detecting a crank angle of the engine; and c) for each predetermined crank angle based on the output of the pressure detecting means. , Or a combustion waveform detecting means for continuously sampling the cylinder pressure to detect the combustion pressure waveform in the present combustion stroke, and d) the maximum cylinder pressure Pn based on the output of the combustion waveform detecting means.
ew and an in-cylinder pressure maximum timing θnew, and e) an average value of the in-cylinder pressure maximum value Pnew and previous in-cylinder pressure maximum values, and the in-cylinder pressure maximum timing θnew and previous in-cylinder pressures. Averaging means for calculating an average value with the maximum time, and f) comparing the average value with a predetermined maximum cylinder pressure reference value Po, and comparing the average value with a predetermined maximum cylinder pressure reference time θop. , The comparison result is> θop and ≦
When the first comparison result is Po, the ignition timing is advanced, and when the second comparison result is ≦ θop and> Po, the ignition timing is retarded, and other than the first and second comparison results. In this case, the combustion state of the internal combustion engine is provided with: a correction means for performing neither advance angle correction nor retard angle correction; and g) operating means for operating the ignition timing based on the output of the correction means. Control device.