JPS6198970A - Ignition timing control method of internal-combustion engine - Google Patents

Abstract

PURPOSE:To enable an accurate idle speed control to be continually performed, by continuously obtained the mean value of an air-fuel ratio feedback correction coefficient determined in accordance with an output from an O2 sensor and controlling the ignition timing in accordance with a deviation of the mean value from the air-fuel ratio feedback correction coefficient. CONSTITUTION:When an internal-combustion engine 14 is in operation, an electronic control circuit 34 first calculates a basic fuel injection quantity tau0 in accordance with an intake air quantity Q and an engine speed N obtained by an air flow meter 2 and a rotary angle sensor 32. Next the circuit 34, when the engine is in idling operation with an idle switch 7 turned on, fetches from a RAM an air-fuel ratio feedback correction coefficient and its mean value after the basic ignition timing at idling time for the engine speed N is referred to a map, calculating a correction angle corresponding to a deviation of the both correction coefficient and the mean value. Subsequently, the circuit 34, adding the correction angle to said basic ignition timing and calculating a required ignition advance angle theta, controls an ignitor 28 in accordance with this ignition advance angle theta.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ignition timing control method for an internal combustion engine, and more particularly to an ignition timing control method for an internal combustion engine for stabilizing the idle speed.

[Conventional technology]

In a general internal combustion engine, it is detected whether the exhaust gas air-fuel ratio is υ richer or leaner than the exhaust gas air-fuel ratio when a mixture with the stoichiometric air-fuel ratio is combusted. t Attach the sensor to the exhaust passage and set it to 0. The air-fuel ratio feedback correction coefficient is determined based on the sensor output, and the basic fuel injection amount determined by the engine load and engine speed is corrected using the air-fuel ratio feed variation correction coefficient to control the air-fuel ratio of the mixture to near the stoichiometric air-fuel ratio. things are being done. In such internal combustion engines, there is a recent tendency to set the target idle speed low from the perspective of improving fuel efficiency, and as a result, the speed of air-fuel ratio feedback control becomes slow, causing engine speed fluctuations and increasing engine speed. There was a problem in that if the number of idle revolutions υ fell below the target idle speed, it would cause discomfort to the driver.

For this reason, the conventional method was to retard the ignition timing according to the deviation between the engine speed and the target idle speed (%
176470) and a method of controlling ignition timing based on an air-fuel ratio feedback correction coefficient described below is known.

A method of controlling ignition timing based on this air-fuel ratio feedback correction coefficient will be explained. First, the causes of fluctuations in engine speed will be explained. 0! The sensor detects whether the exhaust gas air-fuel ratio is richer than the exhaust gas air-fuel ratio corresponding to the stoichiometric air-fuel ratio and outputs an air-fuel ratio signal shown in FIG. 2(A). Air-fuel ratio feedback correction coefficient f (A/F)
is 0. When the sensor output indicates a rich air-fuel ratio, it is decreased, and when the 0° sensor output indicates a lean air-fuel ratio, it is increased, and changes periodically around 1.0 as shown in FIG. 2 (B). do. Then, the valve opening time of the fuel injection valve is controlled based on the value obtained by multiplying the basic fuel injection amount and the air-fuel ratio feedback correction coefficient f (A/F), so that the υ fuel injection amount is controlled. The fuel ratio is controlled near the stoichiometric air-fuel ratio. Accordingly, if the basic fuel injection amount is constant, the fuel injection amount will be maximum when the correction coefficient f (A/F) is maximum, and the fuel injection amount will be maximum when the correction coefficient f (A/F) is minimum. becomes the minimum and the fuel injection amount fluctuates, as shown in Figure 2 (
As shown by the broken line in C), the engine speed during idling will fluctuate.

Then, the correction coefficient f is calculated based on the value 1.0 of the air-fuel ratio feedback correction coefficient f (A/F) corresponding to the stoichiometric air-fuel ratio.
(A/F) deviation is calculated, and when the deviation is positive, the angle is retarded according to the magnitude of the deviation, and when the deviation is negative, the angle is advanced according to the magnitude of the deviation, as shown in Figure 5. Determine the angle θiac,
If the basic ignition advance angle θBig is corrected using this correction angle θisc as shown in Figure 2 (D), the torque will increase when the basic ignition advance angle is advanced, and the torque will decrease when it is retarded. Therefore, as shown in FIG. 2(C), fluctuations in engine rotation during idling can be suppressed.

[Problem that the invention seeks to solve]

However, the conventional air-fuel ratio feedback correction coefficient f
In the (A/F) ignition timing control method, the ignition timing is corrected according to the deviation from the value corresponding to the stoichiometric air-fuel ratio. However, if the fuel injection amount changes for the same valve opening time due to changes in the fuel injection system over time, the value of the air-fuel ratio feedback correction coefficient f(A/F) will deviate by 1.0. For example, if the fuel injection amount increases for the same valve opening time due to wear of the valve body of the fuel injection valve, the As shown in Figure (A), the correction coefficient f(A/F
) is small, one of the injection holes of the fuel injector! When the fuel injection amount decreases due to reasons such as air leakage, the correction coefficient f (A/F) is set as shown in Fig. 5 (A) in order to increase the valve opening time and control the air-fuel ratio to the stoichiometric air-fuel ratio. becomes larger. In this way, the correction coefficient f(A/F) +7) value di
If it deviates from 1.0, the ignition timing becomes over-advanced and misfire occurs as shown in Figure 4 (B).
), there was a problem in that the ignition timing was too retarded, resulting in poor fuel efficiency.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an ignition timing control method for an internal combustion engine that can stabilize idle rotation without causing misfires or worsening fuel efficiency. shall be.

[Failure to solve the problem]

In order to achieve the above object, the present invention provides an O! The air-fuel ratio feedback correction coefficient for controlling the air-fuel ratio near the stoichiometric air-fuel ratio based on the sensor output is calculated based on the air-fuel ratio feedback correction coefficient and the basic fuel injection amount determined by the centripetal engine load and engine speed. In controlling the ignition timing during idling of an internal combustion engine, the average value of the air-fuel ratio feedback correction coefficient is continuously determined, and the average value of the air-fuel ratio feedback correction coefficient and the air-fuel ratio feedback correction coefficient are calculated. It is characterized by retarding the insect and fire timing in accordance with the deviation of the temperature.

[For production]

According to the present invention, as shown in FIG. 6(A), even if the air-fuel ratio feedback correction coefficient f(A/F) deviates significantly from the value 1.0 corresponding to the stoichiometric air-fuel ratio, Average value G(A/F') of feedback correction coefficient f(A/F)
By continuously obtaining , it is possible to obtain a value near the center value of the feedback correction coefficient f(A/F).

Then, the ignition timing is retarded according to the deviation between the feedback correction coefficient f (A/F) and the average value G (A/?), so the ignition timing is basically adjusted as shown in Figure 6 (B). The ignition advance angle θB8m does not deviate significantly from υ, and over-advancement and over-retardation can be prevented.

〔Effect of the invention〕

Therefore, according to the present invention, even if the air-fuel ratio feedback correction coefficient deviates significantly due to changes in the fuel injection system over time, it is possible to stabilize the idle speed without causing a misfire or deterioration of fuel efficiency. It will be done.

〔Example〕

Next, an example of an internal combustion engine equipped with an ignition timing control device to which the present invention is applied will be described in detail with reference to FIG. This carrot is controlled by an electronic control circuit such as a microcomputer, and as shown in the figure, is equipped with an air flow meter 2 as an intake air amount sensor downstream of an air cleaner (not shown). The air flow meter 2 includes a measuring grate 2A rotatably provided in the damping chamber and a measuring grate 2A rotatably provided in the damping chamber.
It is composed of a potentiometer 2B that detects the opening degree of A. Therefore, the amount of intake air is determined by potentiometer 2B.
The voltage output from the sensor is detected.

A throttle valve 6 is arranged downstream of the air flow meter 2, and the throttle valve 6 is turned on when the throttle valve 6 is at the idle position (fully closed) and turned off when the throttle valve 6 is opened from the idle position. An idle switch is attached, and a surge tank 8 is provided downstream of the throttle valve 6. This surge tank 8 has
An intake manifold 10 is connected to the intake manifold 10, and a fuel injection valve 1 protrudes into the intake manifold 10.
2 is placed. The intake manifold 10 is
It is connected to a combustion chamber 14A of the engine body 14, and the combustion chamber 14A of the engine is connected via an exhaust manifold 16 to a catalytic converter (not shown) filled with a three-way catalyst. In addition, 20 is a spark plug, 24 is a cooling water temperature sensor that detects the engine cooling water temperature, 1. is 0. The spark plug 2°, which is a sensor, is attached to the engine body 14, and is connected to a distributor 26, which in turn is connected to an igniter 2. The distributor 26 is provided with a cylinder discrimination sensor 30 and an engine rotation angle sensor 32, each of which includes a pickup fixed to the distributor housing and a signal rotor fixed to the distributor shaft. This cylinder discrimination sensor 30 outputs a cylinder discrimination signal to an electronic control circuit 54 composed of a microcomputer or the like every 720 degrees of the crank angle, and sends a cylinder discrimination signal to the engine rotation angle sensor A signal is output to the electronic control circuit 34.

As shown in FIG. 8, the electronic control circuit 54 includes a random access memory (RAM) 56 and a read only memory (RO).
M) 5B, microgrossing unit (MPU)
40, an input/output port 46, an input port 48, an output port 50, 52, and a bus 54 connecting these.The MPU 40 has a clock (cLocx) 4.
2 and a timer 44 are connected. Input/output port 4
6, buffers ss, ss; multiplexer 5, air flow meter 2 and engine coolant temperature sensor 2
4 is connected. The input port 48 has a buffer 6
01 and sensor 1 are connected through the comparator 64 and the cylinder discrimination sensor 30 and the rotation angle sensor 52 through the waveform shaping circuit 66, and the idle switch 7 is connected through the input circuit 65. ing. The output port 50 is connected to the igniter 2B via the drive circuit 6, and the output port 52 is connected to the drive circuit 70.
It is connected to the fuel injection valve 12 via.

The above ROM contains the control program described below and the feedback correction coefficient f (A/F) shown in FIG.
and the average value G(A/F) f(A/y) - G(A/
A map of the correction angle θisc determined according to the engine rotation speed N, a map of the basic ignition advance angle θBs5 during idling determined according to the engine speed N, etc. are stored in advance, as shown in FIG.

Next, referring to Fig. 1, determine the ignition advance angle θ and the basic fuel injection amount τ.
. A part of the main routine in one embodiment of the present invention for calculating . In step 100, the Otori aphrometer output is digitally converted and written as the intake air amount Q in the RAM, and the engine rotational speed N is derived from the rotation angle sensor output and written in the RAMK. Step 1
In 02, the intake air amount Q and the engine speed N are read out from the RAM and the basic fuel injection amount τ is calculated according to the following equation.

In the next step 104, it is determined whether the idle switch is on or not, thereby determining whether or not the idle state is in the idling state.
At step 06, the base nine ignition advance angle θBBE2 is calculated based on the engine speed N and the intake air fcQ/N per engine revolution. On the other hand, when idling, step 1
In 08.

A stone that calculates the basic ignition advance angle θBSEt at idling for the current carrot rotation of 13N from the map shown in wJ10. In the next step 110, the air-fuel ratio feedback correction coefficient f(A/IF)i calculated by the routine shown in FIG. 11 and stored in the RAM, and the average value G(A/F)i of the air-fuel ratio feedback correction coefficient Step 1
12, the deviation f(A/')i-G(A
/F) Calculate the correction angle θisc corresponding to 1. Then, in the next step 114, the correction angle θisa is added to the basic ignition advance angle θB8Σ1 during idling to calculate the ignition advance angle θ.

Then, in a routine not shown, the igniter is adjusted so that the ignition is ignited at the ignition advance angle calculated as above.
Wholesale.

FIG. 11 shows the air-fuel ratio feedback correction coefficient f(A/F
), average value G(A/F), etc. are executed every predetermined time (for example, 4m5ec). - In step 120, it is determined whether or not the air-fuel ratio control is in the open control region, and if it is in the air-fuel ratio feedback control region, it is determined in step 122 whether or not the sensor output indicates a lean air-fuel ratio. 0. When the sensor output indicates that the air-fuel ratio is rich, the air-fuel ratio feedback correction coefficient t (A/F
) it is reduced by a predetermined value (for example, 0.001) to obtain a new correction coefficient f(A/F)1, while 0. If the sensor output indicates a lean air-fuel ratio, step 12
The air-fuel ratio feedback correction coefficient f(A/
F) Increase 1-5 by a predetermined value (for example, 0.001) to obtain a new correction coefficient f(A/F)1.

In step 128, the previously calculated average value G (A/IF)
In addition to increasing the weight of 1-1, the correction coefficient f(
A new average value G(A/F)1 is calculated according to the linear equation by reducing the weight of A/F)1.

On the other hand, if the air-fuel ratio is in the open control region, step 15
0 and the average value G(A/F)t calculated in step 128
-t is set as the feedback correction coefficient f(A/')1 and the process proceeds to step 152. In step 152, the feedback correction coefficient f(A/F' calculated as described above) is
1 and the basic fuel injection amount τ. The fuel injection amount τ is calculated by multiplying by

Then, in a routine not shown, the opening time of the fuel injection valve is controlled so that an amount of fuel corresponding to the fuel injection amount τ calculated as described above is injected.

Next, as shown in FIG. 12 (A), this example shows the changes in ignition timing and rotational fluctuation when the feed/lock correction coefficient f (A/F) is smaller than 1.0. This will be explained by comparing it with a conventional example. The ignition timing of the conventional example is the 12th
As shown by the line in FIG. 12(B), the engine angle is overadvanced, and as a result, as shown by the line a in FIG. 12(C), the engine rotation is greatly reduced due to occasional misfires. On the other hand, in this embodiment, the basic ignition advance angle changes around the basic ignition advance angle θIMIIcl as shown in the line in FIG. 12(B), and therefore, as shown in the line in FIG. 12(C), The engine speed is controlled close to the target speed.

In addition, although the engine which determines the basic fuel injection amount and the basic ignition advance angle at off-idle based on the intake air amount and the engine speed has been described above, the present invention is not limited to this, and the invention is not limited to this. It is also possible to apply this invention to an engine in which the basic fuel injection amount and the basic ignition advance angle during off-idling are determined based on the engine speed.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing a routine for calculating ignition advance angle, etc. according to an embodiment of the present invention, FIGS. 2(A) to (D) are diagrams for explaining a conventional ignition timing control method, and FIG. The figures are diagrams showing conventional correction angles, Fig. 4 (A), (B) and Fig. 5 (
A) and (B) are diagrams for explaining conventional problems, FIG. 6 is a diagram for explaining the present invention in detail, and FIG. 7 is a diagram showing an ignition timing control device to which the present invention is applied. 8 is a block diagram showing details of the control circuit shown in FIG. 7, FIG. 9 is a diagram showing the correction angle of the above embodiment, and FIG.
The figure is a line diagram showing the basic ignition advance angle at idle in the above embodiment, Figure 11 is a flowchart showing an interrupt routine for calculating feedback correction coefficients, etc., and Figures 12 (A) to (C) are diagrams showing the basic ignition advance angle at idle in the above embodiment. FIG. 3 is a diagram showing a comparison of ignition timing and rotational fluctuations between the conventional example and the conventional example. 1...0. sensor. 7...Idle switch, 12...Fuel injection valve, 28...Igniter. Agent Tatsu Unuma 2 Figure 1, Figure 2, Figure 3, Figure 5 (A) --------1. (3) , 7N ME WQsSE to dp axis Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 -------1,0

Claims (1)

[Claims] (1) Based on the O_2 sensor output that detects whether the exhaust gas air-fuel ratio is richer or leaner than the value corresponding to the stoichiometric air-fuel ratio, determine the air-fuel ratio feedback correction coefficient to control the air-fuel ratio near the stoichiometric air-fuel ratio, and calculate the engine load. In controlling the ignition timing during idling of the internal combustion engine, the air-fuel ratio is controlled to be near the stoichiometric air-fuel ratio based on the basic fuel injection amount and the air-fuel ratio feedback correction coefficient determined by the engine speed and the engine speed. Ignition timing for an internal combustion engine, characterized in that the average value of feedback correction coefficients is continuously determined, and the ignition timing is retarded in accordance with the deviation between the air-fuel ratio feedback correction coefficient and the average value of the air-fuel ratio feedback correction coefficient. Control method.