JPH0219627A - Air-fuel ratio control device - Google Patents

Abstract

PURPOSE:To make it possible to quickly activate a catalyst by stopping fuel injection to specific cylinders or reducing injection quantity. CONSTITUTION:When a fixed time has elapsed after starting an engine 1 and the starting of the engine is completed, the temperature of coolant is in a range of setting values, load is below a preset value, and engine speed is below the speed setting, injectors 6-1, 6-2, 6-4, 6-5 are operated at a specified timing to inject fuel, and fuel injecting operation of injectors 6-3, 6-6 are stopped on a command of a control device 7. Thus, a mixture of high gasoline concentration is, as usual, sucked into first, second, fourth, fifth cylinders, in which burning, explosion take place, but no burning, explosion take place in third and sixth cylinders. The concentration of oxygen in exhaust gas periodically becomes excessively thick or thin. As a result, highly concentrated oxygen is periodically supplied to a three component catalytic converter 11 to accelerate its oxidation, and thereby the temperature of catalyst is rapidly raised.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an air-fuel ratio control method, and is a method for rapidly promoting the activation of a three-way catalyst during @machine operation.

<Prior Art> The three components of automobile exhaust gas, Co, HC, and NOx, cause air pollution and are therefore subject to exhaust gas regulations. Therefore, a three-way catalyst converter is installed in the exhaust system of automobiles to simultaneously reduce Co, HC, and NOx in Bimaru exhaust gas. In order to obtain a high purification rate for all three components at the same time with a three-way catalytic converter, it is necessary to accurately control the air-fuel ratio (A/F ratio) within a narrow range (window) around the stoichiometric air-fuel ratio under all conditions. be. Therefore, when warm-up is finished and the coolant is at a predetermined temperature or higher, the 0□ sensor attached to the exhaust manifold detects the oxygen concentration in the exhaust gas, and the exhaust side detects whether there is excess or insufficient oxygen. In other words, on the intake side, the fuel injection time is feedback corrected and controlled so that the stoichiometric air-fuel ratio is maintained.

A three-way catalytic converter is formed by including a large number of pellets (granular catalyst) in a case, which are made by loading precious metals such as platinum and rhodium on the surface of an alumina matrix (applying them as an rtI film). This catalyst is activated and can fully exert its catalytic action at a certain temperature (
For example, when the temperature exceeds 300°C. Therefore, when the catalyst temperature is low during warm-up operation, the catalytic action cannot be sufficiently exerted and Co, HC, and NOx cannot be effectively reduced, and A/F ratio feedback correction control is not performed.

<Problems to be solved by the invention> Conventionally, in order to promote activation of the catalyst, the loading amount of catalyst precious metals was increased or a heat-retaining structure was adopted for the catalytic converter, but both of these methods resulted in increased costs. It was a disadvantage.

In view of the above prior art, the present invention provides an air-fuel ratio control method that quickly activates a catalyst during warm-up operation and is inexpensive.

Means for Solving the Problems> The present invention achieves the above problems by stopping fuel injection to a specific cylinder, or by stopping fuel injection to a specific cylinder in order to periodically make the air-fuel ratio over or under 1 with respect to the stoichiometric air-fuel ratio. , or reduce the injection amount.

Effect〉 When fuel injection is stopped for a specific cylinder and the φ injection amount is reduced, the oxygen concentration at the catalyst periodically increases or decreases, and in particular, the oxidation reaction increases due to the periodic increase in oxygen concentration. The catalyst is activated rapidly.

Example of implementation Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 shows an engine system of an automobile to which the method of the present invention is applied. As shown in the figure, the air sucked under negative pressure from the air cleaner 2 by the downward movement of the piston in the 6-cylinder engine 1 is guided to the Karman vortex type air flow meter 3, where the amount of intake air is detected. reactor. Air that has flowed into the intake pipe 4 (the amount of air passing through is controlled by the throttle valve 5).
Each intake manifold 4a has an injector 6-
~6. Each injector 6-1 to 6-6 operates individually according to a command from a control device (ECU) 7 to inject fuel, and the air-fuel mixture is sent to each cylinder of the engine 1. The engine 1 is supplied with an air-fuel mixture and is driven to rotate, and the engine rotation speed is detected by a rotation speed sensor 8. Exhaust gas from engine 1 is transferred to exhaust manifold 9. exhaust pipe 10
It is guided through the three-way catalytic converter 11 and discharged. The exhaust manifold 9 is equipped with an 0 sensor 12, which detects the oxygen concentration in the exhaust gas. Also, the temperature of the coolant is detected by a temperature sensor 13 connected to the engine 1.

Air 70-Make 3. Rotation speed sensor 8,0□sensor 12
The detection signal detected by the temperature sensor 13 is sent to the control device 7.

The operation during warm-up operation in such a Niresin system will be explained with reference to FIGS. 1 and 2.

When the engine 1 starts, the air flow meter 3 detects the intake air iA, the rotation speed sensor 8 detects the engine speed N, and the sensor 12 detects the oxygen in the exhaust gas. concentration, temperature sensor 13
Obtain the coolant temperature T from the detection signal, and divide the intake air amount A by the rotational speed N to find the load A/N.

Even if engine 1 is starting, or after a certain period of time has passed after engine starting has been completed, the coolant may
When is lower than the set lower limit temperature T0 (e.g. 15°C) or higher than the set upper limit temperature T, (e.g. 30°C), the load A/N is greater than the set load A0/N0. or when the rotational speed N is larger than the set rotational speed N., the control device 7 commands six injectors 6- as before.

- Operate 6-6 at the predetermined timing to inject fuel. In this case, as has been the case in the past, since warm-up operation is in progress, the injection amount per injection is adjusted so that the air-fuel ratio of the mixture is smaller than the stoichiometric air-fuel ratio but the soli' concentration is rich. It is set. Further, the idle up confirmation flag in the control device 7 is set to O, and I5C (idle speed control) by the control device 7 is performed as usual. Therefore, combustion occurs in all cylinders as usual.

After a certain period of time has elapsed after engine 1 has started, the engine start has been completed, and the coolant temperature T has reached the set lower limit temperature T0.
(e.g. -15°C) or above is the set upper limit temperature T, and is below (e.g. 30°C) and the load A/N is the set load A. /
If it is below N0, the rotation speed N will be the set rotation! If the number is 2 No. or less, the control unit 7 commands the 1st No. 2nd゜4th. Fifth each injector 6- HI 6-216-4
16-5 is operated at a predetermined timing to inject fuel, while the 3rd. Stop the fuel injection operation of the sixth injector 6□)"-6. In other words, in Fig. 3 ta+ (
As shown in b+, the engine drive timing; l
p f'2p w4* Injector 6- at #5
．． ．． 6. ．． 2,6-4.I issue a drive command to 6-5,
Even if the injector drive timing fP 3 + #'' arrives, the drive pulse is not output.Therefore, in the first step.
Second. 4th. The fuel-air mixture with a rich gasoline concentration is sucked into the fifth cylinder as usual, and combustion and explosion take place. Explosion of the 6th cylinder (not done).

As mentioned above, the injector 6-. ．． When the operation stop control in 6-6 is performed, the oxygen concentration in the exhaust gas becomes as shown in Figure 3 (c).
As shown in the figure, it periodically becomes too dense or too thin. As a result, high-concentration oxygen is periodically supplied to the three-way catalytic converter 11 to promote the oxidation reaction, the catalyst temperature rapidly increases, and the catalyst is quickly activated.

In addition, 3rd. Fuel injection from the sixth injectors 6-, , 6-6 is performed by the first injectors 6-, 6-6. Second. 4th. fifth injector 6-,
, 6 to 216-416-5, even if the fuel injection amount is controlled to be smaller than the fuel injection amount, the amount of oxygen supplied to the catalyst can be increased in the same way, and rapid activation of the catalyst can be used. reactor.

As shown in FIG. 4, the difference between lean and rich air-fuel ratios (A/F), that is, the first. 2nd゜4th. 5th injector 6-11' 6-216-A) A/F of the air-fuel mixture sucked into 6-5 and 3rd. 6th injector 6
-3.6-, the larger the difference between the A/F inhaled,
Catalyst temperature rises quickly.

When the injection operation of the injectors 6-, , 6-, etc. is stopped or the injection amount is reduced, the control device 7
Set the idle up confirmation flag in 1 to 1,
The ISC by the control device is corrected to compensate for the lack of output of the 3rd p.

Note that a specific injector (in the above example, injector 6-
3, 6-, ...) will not be stopped in the following cases. In other words, combustion is unstable immediately after startup, the rotational speed drops significantly at extremely low temperatures, and the exhaust gas temperature becomes too high under high loads or high rotational speeds, risking exceeding the permissible temperature. The operation will not be stopped or the injection amount will not be reduced.

When the coolant temperature exceeds the set upper limit temperature T1, the control device 7 causes all the injectors 6 to 6-6 to perform the injection operations as usual, and the 0□ sensor 12 detects the oxygen concentration in the exhaust gas. At the same time, the fuel injection time is feedback-corrected so that the air-fuel ratio of the mixture sucked into each cylinder is close to the stoichiometric air-fuel ratio.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, by stopping fuel injection of a specific injector or reducing the fuel injection amount during warm-up operation,
The oxidation reaction at the catalyst is promoted by periodically increasing the oxygen concentration in the exhaust gas, so the catalyst can be activated quickly. In this way, harmful components in the exhaust gas can be reliably removed even during warm-up operation. Also,
Since the injector only needs to control the injection, it is only necessary to modify the control program, and no mechanical additions or modifications are required.As a result, no special cost is required to realize the present invention.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an engine system of an automobile to which the method of the present invention is applied, FIG. 2 is a flow diagram showing a specific control method of the present invention, and FIG. 3 is a time chart showing a specific control method of the present invention. , FIG. 4 is a characteristic diagram showing the catalyst activity characteristics according to the present invention in comparison with the conventional characteristics. In the drawing, 1 is the engine, 2 is the air cleaner, 3 is the air flow meter, 4 is the intake pipe, 4 and 11 are the intake manifolds, 5 is the throttle valve, 6 to 6 are the injectors, 7 is the control device, and 8 is the rotation speed. 9 is an exhaust manifold) 10 is an exhaust sound, 11 is a three-way catalytic converter, 12 is a 0 sensor, and 13 is a temperature sensor. Figure 22 Figure 4 Elapsed time after startup

Claims (2)

[Claims] (1) In a method for controlling the air-fuel ratio of an automobile engine that is equipped with injectors in the intake manifold corresponding to each of a plurality of cylinders, a specific An air-fuel ratio control method characterized by stopping fuel injection by an injector. (2) In a method for controlling the air-fuel ratio of an automobile engine that is equipped with injectors in the intake manifolds corresponding to each of a plurality of cylinders, a specific An air-fuel ratio control method characterized by reducing the amount of fuel injected by an injector.