JPH0759931B2 - Ignition timing control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in an ignition timing control device for an internal combustion engine.

(Problems to be Solved by Related Art and Invention) In an internal combustion engine for an automobile, etc., it is necessary to determine an appropriate ignition timing over a wide operating range.

Conventionally, when controlling the ignition timing by using a microcomputer or the like, the ignition timing is determined according to the operating conditions such as the intake air amount of the engine, the engine speed and the engine temperature.

In addition, when the ignition timing is advanced so that good combustion is obtained, knocking occurs in a certain engine operating state, and in order to prevent this knocking, a pressure sensor that detects the internal cylinder pressure of the engine and the detected pressure are used. In some cases, the ignition timing is corrected to the retard side by a predetermined amount when knocking occurs by detecting whether or not the waveform contains a high frequency component due to knocking (for example, Japanese Patent Publication No. 59-48).
(See Japanese Patent No. 308).

By the way, in the low load operation region where the throttle valve opening is small, such as during idling operation, the distribution characteristics of the air-fuel mixture between cylinders are likely to become non-uniform due to differences in the residual gas ratio, etc. Although the conditions vary widely, the ignition timings of the cylinders are controlled to be the same, so that the ignition rates become non-uniform among the cylinders and the combustion stability deteriorates.

The present invention aims to solve the above problems.

(Means for Solving Problems) The present invention, as shown in FIG. 1, represents the means 1 for detecting the operating state of the engine and the predicted value of the in-cylinder residual gas ratio of the next cycle for each cylinder. Means 2 for detecting an amount (for example, cylinder pressure) to be used, means 4 for determining a low load operation region based on the detection signal of the operation state detecting means 1, and a predicted value of the residual gas ratio in the low load operation region. Ignition timing control means 3 for controlling the ignition timing for each cylinder is provided so that the ignition timing is advanced as it increases.

(Operation) Even if the residual gas ratio varies between cylinders due to an increase in intake negative pressure in a low load operation region such as during idling, the optimum ignition timing is determined according to each residual gas ratio for each cylinder. The combustion rate of each cylinder is kept good, that is, the combustion stability is significantly improved.

(Example) Hereinafter, an example of the present invention is described based on an accompanying drawing.

In FIG. 2, 7 is an engine body which is a V-type 6 cylinder internal combustion engine, 8 is an intake passage, 9 is an exhaust passage, and a combustion chamber 10 is provided with a spark plug 11. A control unit 13 for operating the spark plug 11 via an ignition device 12 is provided.

Signals from various sensors as means for detecting the operating state of the engine 7 are input to the control unit 13. That is, the intake air amount signal, the rotation signal, the water temperature signal for detecting the engine cooling water temperature is input, and the throttle valve switch signal for detecting the full closing of the throttle valve and the pressure sensor 14 for detecting the pressure in each cylinder. Input the detection signal.

The control unit 13 is an A / D converter that converts the output from each sensor into a digital signal, an input / output interface that receives a signal from this A / D converter, and outputs a calculation result, and based on each of the above signals. Central calculation circuit (CP that calculates the optimum fuel injection amount and ignition timing according to the operating condition
U) and a memory circuit (RAM, ROM) that stores the ignition advance value etc. according to the operating state. The calculated fuel injection signal is sent to a fuel injection valve (not shown) The signal is output to the ignition device 12.

The calculation of the ignition timing, which is the gist of the present invention, will be described with reference to the flowchart of FIG.

The calculation of the ignition timing is performed for each cycle of each cylinder to be ignited.

First, in S1, the output signal from each sensor is read, and in S2, the ignition timing is calculated from the engine speed and the basic fuel injection amount.

At S3, it is determined whether the engine is idling or not by the throttle valve switch signal. Then, when it is determined that the throttle valve switch signal is in the idling state in which the signal is ON, the process proceeds to S4 and S5 to correct the ignition timing.

First, in S4, the residual gas ratio of the next cycle is calculated from the output signal of the pressure sensor 3 based on the maximum pressure P _max of the cycle by table lookup from the map shown in FIG.

Next, in S5, based on the calculated residual gas ratio, the fifth
The ignition timing is calculated from the map shown in the figure by table lookup, and the ignition timing is corrected to the advanced side in accordance with the predicted residual gas ratio. That is, the ignition timing is controlled for each cylinder such that the ignition timing is advanced according to the detection signal of each pressure sensor 3 as the cylinder pressure is higher.

4 and 5 show the results obtained from the experiments, respectively, in which the maximum pressure P _max in the cylinder and the residual gas ratio in the next cycle are approximately proportional, and the residual gas ratio and the advance angle of the optimum ignition timing are shown. Has been found to be approximately proportional. That is, the combustion is stabilized by advancing the ignition timing as the residual gas ratio increases.

In this way, at the time of idling, the ignition timing of each cycle is optimally corrected and controlled based on the combustion pressure of each cylinder, so that the residual gas ratio between the cylinders increases as the suction negative pressure increases. , The ignition rate is increased according to the residual gas ratio, the combustion state of each cylinder is maintained in good condition, and the stability at idling can be greatly improved.

It is also conceivable that the correction control of the ignition timing is performed in an operating region where the combustion pressure in each cylinder may fluctuate other than during idling.

The calculation of the ignition timing may be performed as shown in FIG.

First, in S11, read the output signal from each sensor,
At 12, it is judged whether the engine is idling or not by the throttle valve switch signal. Then, when it is determined that the throttle valve switch signal is in the idling state in which the signal is ON, the routine proceeds to S13 and S14 to calculate the ignition timing.

First, in S13, the residual gas ratio of the next cycle is calculated from the output signal of the pressure sensor 3 based on the maximum pressure P _max of the cycle by table lookup from the map shown in FIG.

Next, in S14, the ignition timing is calculated by table lookup from the map shown in FIG. 5 based on the calculated residual gas ratio, and the ignition timing is corrected to the advanced side according to the predicted residual gas ratio.

On the other hand, when it is determined in S12 that the operating state is such that the throttle valve switch signal is OFF, the ignition timing is calculated from the engine rotation and the basic fuel injection amount in S15.

The ignition timing for the maximum pressure P _max in the cylinder may be stored in the form of a map, and the ignition timing may be directly calculated from the detected P _max by a table lookup.

(Effect of the invention) As described above, the present invention is configured to advance the ignition timing as the proportion of the residual gas in the cylinder of the next cycle predicted based on the cylinder pressure and the like in the low load operation region such as idling increases. The optimum ignition timing is controlled for each cylinder according to the residual gas ratio that tends to vary between the cylinders, the combustion state of each cylinder is improved, and the combustion stability during idling or the like can be significantly improved.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention. FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention, FIG. 3 is a flow chart showing a control operation, FIG. 4 is a map for predicting a residual gas ratio from the cylinder pressure P _max, and FIG. 5 is an ignition timing. A map showing the relationship between the characteristics and the residual gas ratio, and FIG. 6 is a flow chart showing another control operation. 1 ... Operating state detecting means, 2 ... Pressure detecting means, 3 ...
Ignition timing control means 4 ... Operating area determination means.

Claims (1)

[Claims] 1. A means for detecting an operating state of an engine, a means for detecting an amount representative of a predicted value of a residual gas ratio in a cylinder for the next cycle for each cylinder, and a detection signal of the operating state detecting means. A means for determining a load operation area and an ignition timing control means for controlling the ignition timing for each cylinder so that the ignition timing is advanced as the predicted value of the residual gas ratio in the low load operation area is increased are provided. An ignition timing control device for an internal combustion engine, comprising: