JPH03237244A - Air-fuel ratio controller for each cylinder in idling in internal combustion engine - Google Patents

Abstract

PURPOSE:To supply the fuel for realizing the optimum air-fuel ratio in all the cylinders in idling by jetting the proper value of the fuel injection quantity for realizing the optimum air-fuel ratio free from misfire in each cylinder after the lapse of a certain time from the time when idling operation state is detected. CONSTITUTION:During the engine operation, if an electronic control part 15 detects that a neutral switch 20 is ON, throttle valve 4 is in perfect opened state, idle switch 16 is ON, and the output of a turning angle sensor 17 reaches an aimed idle revolution speed, a built-in timer is driven, and after the lapse of a certain time, control is performed so that the proper value of the fuel injection quantity for generating the optimum air-fuel ratio free from misfire which is previously set in each cylinder is jetted from a fuel injection valve 12. Further, the change of the engine through the lapse of time is detected according to the output signal of an O2 sensor 40, and the difference from the theoretical air-fuel ratio is corrected by the feedback constant calculated from the allowable width of each cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to air-fuel ratio control of an internal combustion engine, and particularly to cylinder-specific air-fuel ratio control during idling.

[Conventional technology]

Conventional control methods, as disclosed in Japanese Unexamined Patent Publication No. 62-276240, set the fuel injection amount to a target engine speed based on fluctuations in engine speed.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, when controlling the air-fuel ratio for each cylinder during idling, no consideration is given to non-uniformity of the air-fuel ratio between cylinders or misfire caused by a specific cylinder.

There was a problem with unstable idle.

An object of the present invention is to set the air-fuel ratio of each cylinder at idle to the optimum air-fuel ratio.

[Means to solve the problem]

In order to achieve the above objective, we set in advance the fuel injection amount that is the optimal air-fuel ratio that minimizes the number of misfires during idling for each cylinder, and after determining that it is idling and connecting for a certain period of time, By setting the above-mentioned set injection amount, the idling is stabilized.

Furthermore, in order to maintain the above-mentioned optimum air-fuel ratio for each cylinder in consideration of engine deterioration over time, cylinder-by-cylinder air-fuel ratio feedback control is performed.

[Effect]

The engine is in the idle state when the throttle opening becomes O and the idle switch is accordingly turned on. And the neutral switch is turned ON by gear discrimination detection. The determination is made based on the fact that the engine rotational speed reaches the target rotational speed. After the idle state is maintained for a certain period of time, a preset fuel injection amount is injected for each cylinder, so that the idle state is always stable.

Further, aging deterioration of the engine is detected by the 02 sensor and determined from the difference with respect to the stoichiometric air-fuel ratio. As a result, idling stability can be maintained at all times by performing air-fuel ratio feedback control for each cylinder.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The air-fuel ratio control device according to the present invention will be described in detail below with reference to illustrated embodiments.

First, Figure 1 shows an example of an automobile engine system to which an embodiment of the present invention is applied. In the figure, air sucked from an air cleaner passes from a throttle body 2 containing a throttle valve 4 through a surge tank 5. It passes through the branch pipe 6 and is introduced into the combustion chamber 9 of the engine via the intake valve 7. And this time.

The opening degree of the throttle valve 4 is operated by the driver using the access pedal 3, thereby controlling the intake air amount of the engine 8.

On the other hand, exhaust gas from the engine 8 is guided from an exhaust valve 10 to an exhaust branch pipe 11, from which it is discharged into the atmosphere.

A fuel injection valve 12 is provided upstream of the intake valve 7 and supplies air-fuel mixture to the engine 8.

Ignition of the engine 8 is performed by supplying high voltage from the ignition coil 13 to the ignition plug 60 via the distributor 14.

The electronic control unit 15 controls the fuel supply and ignition of the engine 8.
Therefore, the throttle valve opening sensor 162 and the rotation angle sensor 17. Cooling water temperature sensor 18, ignition switch 19
．． Neutral switch 20, starter switch 21.
It takes in signals from the 02 sensor 40, etc., generates a predetermined control signal as a result of calculating these signals, and supplies it to the fuel injection valve 12 and ignition coil 13, thereby performing engine control. It looks like this.

Here, the fuel injected from the fuel injection valve 12 is injected according to the injection time calculated by the electronic control section 15.

2nd rj! i is an embodiment of the electronic control section 15, which is mainly composed of a microcomputer, and includes a CPU 3 which serves as an arithmetic section.
0. ROM31. ROM32. Clock generator 33. A
/D converter 34. Counting section 35. Latch self-path 36. Output register 37. It is composed of a drive circuit 38 and a bus 39 that connects these, and the signals from the various sensors mentioned above, the 02 sensor 40, the intake air temperature sensor 41, etc. are sent to the A/D converter 34 for analog signals. Furthermore, among the signals from the rotation angle sensor 17, the angle signal 17a is input to the counting section 35 to calculate the rotation speed N, and is then fetched.These calculations determine the predetermined fuel injection. The time signal is applied to the output register 37, which supplies the fuel injector 12 via the drive circuit 38. Note that the signal supplied to the ignition coil 13 is also supplied in the same manner.

Here, one embodiment according to the present invention will be described. FIG. 3 shows the air-fuel ratio of each cylinder of the engine at idle. here,
This is a case where the injection amount is the same for all cylinders so that the ideal air-fuel ratio is achieved on average for all cylinders. This result shows 1 cylinder rich, 2 cylinder rich
The air-fuel ratio is different for each cylinder, with cylinders close, 3 cylinders rich, and 4 cylinders lean.

Further, FIG. 4 shows a graph of the relationship between the air-fuel ratio of each cylinder during idling and the number of misfires. According to this, since the minimum number of misfires is different for each cylinder, the optimum air-fuel ratio is 42.43, 44.45 from the first cylinder in Figure 4.
The air-fuel ratio is as shown in .

In the present invention, when the engine is running as shown in FIG. 5, the neutral switch is ON, the throttle is fully open and the idle switch is ON as shown in FIG. 14, and the rotation angle sensor shown in FIG. When the output from No. 17 reaches the idle target rotation speed, the timer 50 is activated and after a certain period of time, the fuel amount Tl5TI for one cylinder is set to the air-fuel ratio shown in FIG. 42.

2 cylinders are 43 Tl5T2.3 cylinders are 44 Tl5T3
．． For 4 cylinders, each injection amount TII is 45 TI Sr1.
, TI2. TI3. Inject as TI4.

Furthermore, engine deterioration over time is detected by the 02 sensor shown in Figure 1, 40, and the deviation from the stoichiometric air-fuel ratio is determined by Figure 4, 46.47.
, 48, 49, and is used to perform correction for each cylinder using a feedback constant calculated from the permissible width for each cylinder.

〔Effect of the invention〕

According to the present invention, it is possible to always supply fuel in an amount that provides the optimum air-fuel ratio to all cylinders in an idling state, and it is possible to eliminate idle instability caused by misfire.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of an engine control system to which an embodiment of the present invention is applied, FIG. 2 is a block diagram showing details of an electronic control section in the same embodiment of the present invention, and FIG. A diagram showing the air-fuel ratio of each cylinder when the fuel injection amount is the same for all cylinders, FIG. 4 is a diagram showing the relationship between the number of misfires depending on the air-fuel ratio of each cylinder, and FIG. 5 is a diagram showing the control in one embodiment of the present invention. It is a flowchart explaining processing. 12・Fuel injection valve, 15...Electronic control unit, 17...
Rotation angle sensor, 42, 43, 44.45...optimum air-fuel ratio for each cylinder, 72...feedback constant for each cylinder. rate 3 figure + L qmh high figure 5

Claims (1)

[Claims] 1. A fuel injection device provided for each cylinder of the engine,
In a fuel injection system that is equipped with a means for setting fuel injection amount for each cylinder, a means for detecting engine speed, throttle opening, and gear discrimination, idling is detected by engine speed, throttle opening, and neutral switch. 1. A cylinder-specific air-fuel ratio control device during idling for an internal combustion engine, characterized in that, after being connected for a certain period of time, an appropriate fuel injection amount is injected in each cylinder in advance so that each cylinder has an optimum air-fuel ratio with few misfires.