JPH0571792B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control device for a multi-cylinder engine that controls the combustion state (knocking and other abnormal combustion) of each cylinder based on the output of a single vibration sensor. .

(Conventional technology) Conventionally, one knock sensor (vibration sensor)
A control device for a multi-cylinder engine is known in which the occurrence of knocking is detected from the output of the knock sensor, and when knocking occurs, the combustion state of the engine is controlled to suppress the occurrence of knocking. (Refer to Utility Model Application Publication No. 1983-61933).

However, with the above control method, even if knocking is detected by the knock sensor,
It is not possible to detect in which cylinder knocking actually occurs, and combustion control is performed uniformly for all cylinders.

Incidentally, in a multi-cylinder engine, the combustion conditions of each cylinder may not necessarily be the same, and even if knocking occurs in a certain cylinder, knocking does not necessarily occur in the remaining cylinders.
In such a case, if uniform combustion control is performed as described above, for example, the ignition advance angle will be retarded even for cylinders in which no knocking actually occurs, and the output of the cylinder will be higher than necessary. There is a problem when it gets lowered.

In order to solve this problem, it is possible to detect knocking in each cylinder and control only the cylinder in which knocking occurs, but if one sensor is used to detect the knocking status of each cylinder, Depending on the mounting position, the detected value differs from cylinder to cylinder even with the same knocking strength, making accurate control impossible.

(Object of the Invention) The present invention is capable of accurately detecting the combustion state such as the presence or absence of knocking for each cylinder constituting a multi-cylinder engine using a single vibration sensor. It is an object of the present invention to provide a control device for a multi-cylinder engine that can accurately perform combustion control for each cylinder.

(Structure of the Invention) Therefore, as shown in the block diagram of the invention in FIG. and a determination level determining means that reads the output of the vibration sensor in accordance with the combustion timing of each cylinder when the combustion state of each cylinder is equalized, and determines a determination level regarding the combustion of each cylinder from the read output value. C, and combustion control means D that controls the combustion state of each cylinder based on the determination level for each cylinder determined by the determination level determination means.

(Effects of the Invention) According to the present invention, although a single vibration sensor is used, the combustion state of each cylinder can be accurately detected, and accurate combustion control can be performed for each cylinder.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in the system configuration diagram in FIG. 2, the engine control unit 1 includes temperature sensors 3-1 to 3-4 installed in exhaust passages (branched exhaust passages) 2-1 to 2-4 of each cylinder of the engine. Exhaust temperature ExT(i) (i=1~
4), engine vibration detected by one vibration sensor 4 attached to the side wall of the central part of the engine;
Crank angle of output shaft from distributor 5
The cylinder discrimination signal etc. output every 720 degrees is input, and each branch intake passage 6-1 to 6-4 of the intake passage 6
It controls the injectors 7-1 to 7-4 and the ignition system 8 installed therein. The control unit 1 controls the injection timing and injection time of the injectors 7-1 to 7-4, but since this control is not directly related to the subject matter of the present invention, the explanation will be omitted below. do.

As shown in FIG. 3, the output of the vibration sensor 4 is
As the cylinders are ignited in the order of the first, third, fourth, and second cylinders, the output level differs for each cylinder, and as shown in Figure 2, vibrations occur in the center of the side wall of the engine. Due to the provision of the sensor 4, a high output level is shown during combustion in the second and third cylinders that are close to the vibration sensor 4, and a low level is shown during combustion in the first and fourth cylinders that are far from the vibration sensor 4.

In response to such fluctuations in the output level of the vibration sensor 4, the control unit 1 sets a determination level for abnormal combustion for each cylinder in accordance with the flowchart shown in FIG.

As shown in FIG. 4, when this control is started, first, in step 101, it is determined whether the current engine operating state is in steady operation (or not in acceleration/deceleration mode), and then At step 102, the temperature sensors 3 installed in the branch exhaust passages 2-1 to 2-4 of each cylinder are
The exhaust gas temperature ExT(i) of each cylinder is read from -1 to 3-4 and stored as TE(i). In the next step 103, the average exhaust temperature of all cylinders for a certain period of time is calculated from the exhaust gas temperatures of each cylinder sampled as described above. Then, in step 104, the exhaust temperature ExT(i) of the i-th cylinder is
Find the deviation ΔTe(i) between and the average exhaust temperature.
The absolute value of this deviation ΔTE(i) is compared with a predetermined value ΔTED in the next step 105, and if it is larger than this value ΔTED, advance angle correction is performed in step 106 as follows. As shown in block A in connection with step 106 in FIG.
The lead angle is preset for the above deviation ΔTE(i), and if the deviation ΔTE(i) is within the range of the above value ΔTED, the lead angle is not corrected, but if it exceeds that range. Sometimes, a corrected advance angle ΔSA is provided depending on the deviation ΔTE(i).
Therefore, in this step 106, the deviation ΔTE(i)
The corrected advance angle ΔSA corresponding to the engine is added to the basic advance angle determined according to the operating state of the engine. With this advance angle control, the exhaust temperature ExT(i) of the square cylinder becomes
The average exhaust gas temperature, which is the target temperature, is equalized within a range of at least ±ΔTED.

After this calculation, in step 107, the cylinder number i that is the target of the calculation is incremented by 1, and the resulting cylinder number i is used in the next step 108.
It is determined whether the value is "3" or not. If i is not "3", loop to step 104 and repeat step
Controls from 104 to 107 are executed to perform the necessary ignition advance correction for the next cylinder. If i=3, the process moves to step 109, where i is set to "0", and in step 110, the time set in advance in the timer built in the control unit 1 is set.
_T1 is set, and thereafter this timer is decremented toward "0".

In the next step 111, it is determined whether or not it is the sample period set by the timer, and if it is the sample period, the output Vs of the vibration sensor 4 is read in step 112 in accordance with the combustion timing of each cylinder. The integral value M(i) of the output is stored in memory. After this one sampling, the number of cylinders i is incremented by 1 (step
113), until it is determined that the incremented value has reached "3" in step 114.
Steps 112 and 113 are repeated to obtain the integral value M(i) of the sensor output for each cylinder. When i=3 is reached, at this stage vibration sensor 4 is activated for all four cylinders.
This means that the output has been read, so in step 115 i is set to 0, and the process moves to the next subroutine 116. In this subroutine 116, the average value (i) of the integral values M(i) obtained in step 112 for each cylinder is calculated.
Then, a determination level for determining the presence or absence of knocking for each cylinder is set as shown in block B in accordance with this average value (i) for each cylinder.
That is, regarding the third cylinder and the second cylinder, the determination level is determined from the position near the vibration sensor 4.
The determination level will be set higher than the determination level of the first and fourth cylinders, which are far from the target. Therefore, whether or not knocking has occurred in each cylinder can be determined by reading the output from the vibration sensor 4 in accordance with the combustion timing of each cylinder based on the determination level set in the subroutine 116. Judgment can now be made for each cylinder. Based on this determination, a so-called knock control is executed in subroutine 117. That is, when occurrence of knocking is detected in a certain cylinder, a predetermined retard amount is set for the cylinder, and subsequent knocking is prevented by retarding the ignition timing by the retard amount.

In this manner, the presence or absence of knocking in each cylinder is detected based on the output of one vibration sensor, and combustion control for each cylinder is accurately performed.

In the above embodiment, the exhaust gas temperature of each cylinder is controlled to be constant to equalize the combustion state of each cylinder, but the present invention is not limited to such an equalization method.

In addition, as shown in Figure 5, a maximum load condition is set that provides a range in which knocking does not occur at a certain engine speed, that is, a knocking limit, and the output of the vibration sensor is calculated for each cylinder under that maximum load condition. The determination level for each cylinder may be set based on the read output level.

[Brief explanation of the drawing]

Fig. 1 is an invention configuration diagram of the present invention, Fig. 2 is a system configuration diagram of a control device for a multi-cylinder engine according to the invention, and Fig. 3 is a waveform diagram showing the relationship between the vibration sensor output and the combustion pressure of each cylinder. , FIG. 4 is a flowchart showing the judgment level setting flow executed by the control unit of FIG. 2, and FIG. 5 is a graph showing the knock occurrence limit used in another embodiment of the present invention. A... Vibration sensor, B... Equalization means, C...
Judgment level determining means, D... combustion control means.

Claims (1)

[Scope of Claims] 1. One vibration sensor that detects vibrations of the engine, equalization means that equalizes the combustion state of each cylinder, and when the combustion state of each cylinder is equalized, the vibration sensor Judgment level determining means for reading the output in accordance with the combustion timing of each cylinder and determining a judgment level regarding the combustion of each cylinder from the read output value; and a judgment level for each cylinder determined by the judgment level determining means. 1. A control device for a multi-cylinder engine, comprising: combustion control means for controlling the combustion state of each cylinder based on the combustion condition of each cylinder.