JP2522769B2 - Combustion state control device for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a combustion pressure of an internal heat engine and controlling a combustion state of an engine such as an automobile. (Prior Art) It is necessary to determine the ignition timing of the internal heat engine according to the state of the engine so that the engine operates optimally. And, generally considering the fuel efficiency of the engine, the minimum advance angle at maximum torque,
It is known that it is best to ignite near the so-called MBT (Minimum advance for Best Torque), depending on the engine condition.
It is necessary to change the ignition timing of MBT. In addition, during MBT control, the crank angle (hereinafter referred to as the combustion peak position) θpm at which the pressure inside the combustion chamber (hereinafter referred to as cylinder pressure) is maximum
Need to detect ax. By the way, it is known that knocking occurs when the ignition timing is advanced too much in a certain engine state, and the ignition timing of the knocking limit that causes this knocking exists on the delay side from the MBT depending on the Engin state, and the ignition timing is There is also an area where knocking occurs when proceeding to MBT. Therefore, as a control device that determines knocking for each cylinder and corrects the retardation correction value to avoid knocking, for example, a control device disclosed in Japanese Patent Publication No. 58-13749 is known. This device determines knocking from the magnitude of the high-frequency component of the combustion pressure waveform, calculates the retard correction amount for each cylinder according to the determination result, and controls the ignition timing to reduce fuel consumption and engine output. This is to control the occurrence of knocking without lowering. That is, knocking is determined and ignition timing is controlled by using only one piece of information, which is the magnitude of the high-frequency component, from the combustion pressure waveform that takes various shapes due to the influence of ignition timing, air-fuel ratio, etc. . (Problems to be Solved by the Invention) However, in such a conventional combustion state control device for an internal heat engine, the information on the combustion pressure waveform is used as only one piece of information (for example, information on the magnitude of the high frequency component). ),
Since only the ignition timing was controlled based on that one piece of information, the ignition timing, air-fuel ratio and EG
It is hard to say that the information of the combustion pressure waveform determined by a plurality of operating parameters such as R is used sufficiently effectively.
It was not always the case that proper combustion state control was performed. The above-mentioned operating parameter is a factor capable of controlling the combustion state of the engine as represented by ignition timing, air-fuel ratio, EGR and the like. This will be described in detail later. For example, the combustion peak value θpmax is at the same crank angle position as the combustion pressure waveform when the ignition timing only advances too much and the combustion pressure waveform when the air-fuel ratio only is rich (or lean). However, in the current technology (that is, the conventional device), since the ignition timing control is performed using only one parameter (that is, the position information of θpmax) as the information parameter of the combustion pressure waveform, the ignition timing is actually Even if the air-fuel ratio is normal and the air-fuel ratio is rich, the combustion peak value θ
The parameter of pmax alone cannot be distinguished from the case where only the ignition timing is advanced too much. Therefore, the ignition timing may be unnecessarily and erroneously corrected, resulting in deterioration of control accuracy and deterioration of engine drivability and fuel consumption. (Object of the Invention) Therefore, in the present invention, when each operation parameter such as the ignition timing and the air-fuel ratio is changed, it is noted that each has a unique combustion pressure waveform, and these combustion pressure waveforms are used as reference parameters in many cases. By dimensionally storing and comparing the characteristic parameter based on the combustion pressure waveform at that time with the reference parameter, the operating parameter to be corrected according to the combustion state of the engine can be accurately selected, and the combustion required by the engine The purpose is to accurately and surely correct the state control. (Means for Solving Problems) In order to achieve the above object, the combustion state control device for an internal heat engine according to the present invention has a basic conceptual diagram as shown in FIG. Detection means a, crank angle detection means b for detecting the crank angle of the engine, and cylinder pressure for each predetermined crank angle based on the output of the pressure detection means a to detect the combustion pressure waveform in the current combustion stroke. Combustion waveform detection means c that performs two-dimensionally, and a combustion parameter that two-dimensionally represents the characteristics of the combustion pressure waveform based on the output of the combustion waveform detection means c with the maximum cylinder pressure time (θpmax) and the center of gravity (MEAN) of the combustion pressure waveform. Means d for extracting
And the combustion state of the engine as a plurality of operating parameters that can be manipulated, the characteristics of the combustion pressure waveform when each operating parameter is deviated from the optimum value are two-dimensionally determined by the cylinder pressure maximum timing and the center of gravity of the combustion pressure waveform. A reference value setting means e for setting a plurality of reference parameters, and a two-dimensional deviation between the combustion parameter extracted by the extraction means d and the reference parameter are obtained, and the operation corresponding to the reference parameter is minimized. Selection means f for selecting parameters
And a correction value calculating means g for calculating a correction value of the operating parameter selected by the selecting means f so that the combustion state is optimum, and an operating means for operating the corresponding operating parameter based on the output of the correction value calculating means g. and h. (Operation) In the present invention, for example, the characteristics of the combustion pressure waveform when the ignition timing of the engine, the air-fuel ratio, and the EGR amount are used as the operating parameters and the operating parameters are deviated from the optimum values are the maximum cylinder pressure timing and the combustion pressure waveform. A plurality of reference parameters which are two-dimensionally represented by the center of gravity of the engine are set by the selecting means, and the operating parameter corresponding to the reference parameter that minimizes the two-dimensional deviation from the combustion parameter extracted by the extracting means is selected by the selecting means. After being selected, the correction value of the operating parameter is calculated so that the combustion state becomes optimum. Therefore, the operating parameter to be corrected is accurately selected, and the combustion state required by the engine is reliably controlled. (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. An output from a crank angle sensor (crank angle detecting means) 4 is further input to the A / D converter 3, and the crank angle sensor 4 detects the crank angle of the engine. For example, in the case of a 6-cylinder engine, the crank angle is detected. Reference signal C every 120 ° C
The position signal C ₁ is output every 1 ° of crank angle (3rd
See figure). The A / D converter 3 converts the signal S ₂ input as an analog signal into a digital signal in synchronization with the crank angle and outputs it to the control unit 5. The control unit 5 detects a combustion pressure waveform and selects an operating parameter based on sensor information of the in-cylinder pressure sensor 1 and an air flow meter (not shown) according to a program stored in an internal memory. Based on this, a processing value for controlling the combustion state appropriately is calculated, and the injection signal Si or the ignition signal Sp corresponding to the calculation result is output to the injector (operating means) 6 or the ignition device (operating means) 7. That is, as will be described in detail later, the control unit 5 detects the combustion pressure waveform in the present combustion stroke by sampling the in-cylinder pressure at every predetermined crank angle based on the output of the in-cylinder pressure sensor 1 to detect the combustion pressure waveform. And the combustion pressure waveform characteristics based on the output of the combustion waveform detection means as a two-dimensional combustion parameter represented by the cylinder pressure maximum timing θpmax and the center of gravity MEAN of the combustion pressure waveform (hereinafter, also referred to as a characteristic parameter ), The ignition timing, the air-fuel ratio and the EGR that can control the combustion state of the engine.
A criterion for setting a plurality of reference parameters that two-dimensionally expresses the characteristics of the combustion pressure waveform when each operation parameter is deviated from the optimum value using the amount as the operation parameter and with the cylinder pressure maximum timing and the center of gravity of the combustion pressure waveform. A function as a value setting means and a selection means for obtaining a two-dimensional deviation between the combustion parameter extracted by the extracting means and the reference parameter and selecting an operating parameter corresponding to the reference parameter such that this deviation is minimized. It has a function and a function as a correction value calculation means for calculating the correction value of the operation parameter selected by the selection means so that the combustion state becomes optimum. The ignition device 7 is composed of an ignition coil, an ignition plug, and the like, and generates a high voltage based on the ignition signal Sp to ignite the air-fuel mixture. Next, the operation will be described. 4 and 5 are flowcharts showing a combustion state control program, and this program is executed once every predetermined time. In FIG. 4, when the reference signal Ci from the crank angle sensor 4 is input at P ₁ , the counter CNT is

Set to [0]. For multi-cylinder engines, this reference signal
Switches multiple in-cylinder pressure signal multiplexers based on Ci. Further, in FIG. 5, first, at P ₁₁ , A / D conversion is performed in synchronization with the crank angle of the in-cylinder pressure sensor 1, and the converted value Xi is stored in the memory. For example, in the present embodiment, as shown in FIG. 6, the cylinder pressure A / D converters having the crank angles θ _{1 to} θ ₁₁ corresponding to within the predetermined pressure before and after the top dead center (TDC) are designated as X _{1 to} X _11. Store in RAM (not shown). Here, the interval for A / D conversion is
90 degrees before and after TDC is sufficient, but a six-cylinder engine that can handle only 60 degrees before and after TDC to process six cylinders with one A / D converter 3 may be used. Next, when the A / D converter is started based on the crank angle position signal C ₁ at P ₁₂ , [1] is added to the counter CNT for each sampling, and the count number is checked at P ₁₃ . When the counter CNT reaches [11], the specified A / D conversion value (X ₁
It is determined that all of X to X ₁₁ ) are complete, and at P ₁₄ , the cylinder pressure maximum timing (combustion peak position) θpmax and the center of gravity MEAN of the combustion pressure waveform are calculated to detect the combustion parameter. On the other hand, counter CN
If T is not [11], the process is terminated. The details of the calculation of the combustion peak position θpmax are well known in the art, for example, Pmax that is the maximum value of the cylinder pressure is obtained from the A / D converters X _{1 to} X ₁₁ , and the crank angle corresponding to this Pmax is calculated. There is a method of detecting the combustion peak position θpmax (in this embodiment, θpmax is equal to θ ₈ as shown in FIG. 6). The center of gravity MEAN is calculated according to the following equation. In this way, the parameter indicated by the combustion peak position θpmax and the center of gravity MEAN is detected as the combustion parameter corresponding to the operating parameters such as the ignition timing, the air-fuel ratio and the EGR amount of the engine at that time. Combustion parameter and Figure 7 detected by the P ₁₄ in P ₁₅ (b) to indicate the reference parameters A, B, C, and calculates the distance between D (deviation), the closest reference parameter to the combustion parameters at that time By detecting, the operating parameter to be corrected is appropriately selected. That is, FIG. 7 shows the reference parameters of the combustion pressure waveform when the operating parameters (air-fuel ratio, ignition timing, EGR, etc.) are changed. In FIG. Indicates that the ignition timing is too advanced, C indicates that the ignition timing is too late, and D indicates that the air-fuel ratio is too rich or too thin. For example, if the combustion pressure characteristic parameter of U ₁ (•) is obtained as shown in FIG. 7 (b), the ignition timing is advanced because it is the closest to B among the reference parameters A to D. Therefore, the ignition timing is corrected so that it is delayed. On the other hand, when U ₂ is obtained, it is the closest to the reference parameter of D, so it is judged that the air-fuel ratio is deviated even if the ignition timing is appropriate, and it is judged by the O ₂ sensor (not shown) whether it is rich or lean. Correct the air-fuel ratio. Further, in P ₁₆ , the correction value of the parameter to be corrected selected in P ₁₅ is calculated, and the current process is ended. For example, in the case of B, the ignition timing is advanced, so the ignition timing retard control is performed by another routine (not shown). As described above, in the present embodiment, the ignition timing of the engine, the air-fuel ratio, the combustion pressure waveform corresponding to the operating parameters such as EGR is set as a reference parameter consisting of a two-dimensional parameter of the combustion peak value θpmax and the center of gravity MEAN of the combustion pressure waveform. However, since the operating parameter to be corrected is accurately determined by calculating the distance (deviation) between the characteristic parameter and the reference parameter based on the combustion pressure waveform at that time, it is possible to accurately control the combustion state required by the engine. It can be executed well and surely, and maneuverability and fuel consumption can be further improved. For example, if only θpmax is used as a parameter for combustion state control (ignition timing control, air-fuel ratio control, etc.) as in the conventional case, in the case of a combustion state such as U ₂ (•) in FIG. 7 (b), Actually, even when the ignition timing is normal and the air-fuel ratio is richer (thinner) (eg, D), it is determined that the ignition timing is too advanced (eg, B). As a result, there is a possibility that an unnecessary and wrong operating parameter may be selected and its correction may be performed, which may deteriorate maneuverability and fuel efficiency. In the present embodiment, such a problem can be effectively prevented and highly accurate combustion state control can be performed. In this embodiment, the reference parameter and the characteristic parameter are two-dimensionally described using only the combustion peak value θpmax based on the combustion pressure and the center of gravity MEAN of the combustion pressure waveform. It is of course possible to use the value Pmax or the like to make it multidimensional, and in this case, more detailed information can be handled and extremely accurate combustion state control can be performed. (Effect) According to the present invention, for example, the ignition timing of the engine, the air-fuel ratio, and the EGR amount are used as operating parameters, and the characteristics of the combustion pressure waveform when each operating parameter is deviated from the optimum value are A plurality of reference parameters that are two-dimensionally represented by the center of gravity of the pressure waveform are set, and an operating parameter corresponding to the reference parameter that minimizes the two-dimensional deviation from the combustion parameter extracted by the extracting means is selected. The operating parameter correction value is calculated so that the combustion state is optimized, so that the operating parameter to be corrected can be selected accurately and the combustion state control can be corrected accurately and reliably. It can be carried out.

[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, FIG. 2 is a circuit configuration diagram thereof, and FIG.
FIG. 4 is a waveform diagram showing a signal waveform of the in-cylinder pressure sensor, FIGS. 4 and 5 are flowcharts showing a program for the combustion state control, and FIG. 6 shows changes in in-cylinder pressure for explaining the operation. FIG. 7 and FIG. 7 are views for explaining the effect. 1 ... In-cylinder pressure sensor (pressure detection means), 4 ... Crank angle sensor (crank angle detection means), 5 ... Control unit (combustion waveform detection means, extraction means, reference value setting means, selection means, correction value calculation Means), 6 ... Injector (operating means) 7 ... Ignition device (operating means).

Claims (1)

(57) [Claims] 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. Combustion waveform detection means for sampling the in-cylinder pressure and detecting the combustion pressure waveform in the current combustion stroke, and d) the characteristics of the combustion pressure waveform based on the output of the combustion waveform detection means as the in-cylinder pressure maximum timing (θpmax) Extraction means for extracting combustion parameters two-dimensionally represented by the center of gravity (MEAN) of the combustion pressure waveform, and e) As a plurality of operation parameters that can operate the combustion state of the engine, each operation parameter is deviated from the optimum value. A reference value setting means for setting a plurality of reference parameters that two-dimensionally represents the characteristics of the combustion pressure waveform with the cylinder pressure maximum timing and the center of gravity of the combustion pressure waveform; and f) extracting means. Selective means for obtaining a two-dimensional deviation between the extracted combustion parameter and the reference parameter, and selecting an operating parameter corresponding to the reference parameter that minimizes this deviation, and g) so that the combustion state is optimal. A correction value calculating means for calculating a correction value of the operating parameter selected by the selecting means, and h) an operating means for operating a corresponding operating parameter based on the output of the correction value calculating means. Combustion state control device for internal heat engine.