JPH0694846B2 - Air-fuel ratio control method for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air-fuel ratio control method for an internal combustion engine of the present invention, and more particularly to an air-fuel ratio control method for an internal combustion engine that purifies exhaust gas during re-acceleration after deceleration. .

[Prior Art] An internal combustion engine for a vehicle has extremely large fluctuations in the vehicle running speed, that is, the engine rotation speed and the load. Requested. Therefore, it is necessary to make the air-fuel ratio appropriate under various operating conditions.

In order to properly control the air-fuel ratio, the air-fuel ratio is adjusted and controlled by the O ₂ sensor signal that detects the concentration in the exhaust gas, for example, the oxygen concentration, so that the best combustion state is always obtained for the various operating states described above. The air-fuel ratio control method in which the air-fuel ratio is feedback-controlled is used in.

[INVENTION Problems to be Solved point Incidentally, in the air-fuel ratio control method of the conventional internal combustion engine, as shown in FIG. 9, the control unit a signal from the O ₂ sensor 32
20 (ECU), and the control unit 20 feedback-controls the electromagnetic valve 22 provided in the carburetor 6 to control the air-fuel ratio. Then, particularly during deceleration, deceleration feedback control is performed in order to prevent catalyst overheating due to HC or improve fuel efficiency.

The feedback control is stopped when the fuel is cut, and the engine efficiency is fixed by the open control.
The fixed duty (DUTY) cannot be made too large (to the lean side) from the driving performance such as engine stall during braking after deceleration. Further, after the fuel cut is released, the following of the fuel is delayed, so that the duty is fixed for a certain period even under the fuel cut release condition, and the drivability is improved.

As a result, the duty during deceleration is set low, and running →
The transition of the duty ratio under the operating conditions of deceleration → idle is as shown by A in FIG.

In FIG. 10, control is performed by a partial feedback constant during traveling, and idle operation is controlled by an idle feedback constant after a fixed duty during deceleration. At this time, regarding the feedback constant,
It is set considering the delay of the system between the carburetor, engine, and O ₂ sensor, and the partial is set from both aspects of operating performance and exhaust gas, but the delay time becomes longer when the air volume is low, so control It is necessary to delay the speed to eliminate the rotation fluctuation due to overshoot and to secure the stability of the idle.

However, since the duty is set low during deceleration, as shown in FIG. 10, there is an inconvenience that the L period becomes uncontrolled and the CO emission amount increases due to the enrichment.

When the vehicle is accelerated again during the L period, the partial feedback constant is switched as shown by B in FIG. 10, but the duty at the initial stage of acceleration starts from a low level value. The shaded area is rich with respect to the required air-fuel ratio, and there is a disadvantage that harmful CO emissions increase and exhaust gas cannot be purified.

Therefore, in order to eliminate the above-mentioned inconvenience, an object of the present invention is to perform fixed duty control with a fixed duty during deceleration of an internal combustion engine and to idle feedback control with an idle feedback constant during re-acceleration during deceleration. The air-fuel ratio, which has been enriched by the control unit for a certain time until transfer, is feedback-controlled by the feedback constant at the partial time to make the air-fuel ratio lean, thereby reducing harmful exhaust gas such as CO without deteriorating operating performance. An object is to realize a possible air-fuel ratio control method for an internal combustion engine.

[Means for Solving the Problems] In order to achieve this object, the present invention provides an air-fuel ratio control method for an internal combustion engine in which a control unit for inputting a signal from an O ₂ sensor feedback-controls an electronically controlled carburetor. ,
Fixed duty control is performed with a fixed duty during deceleration of the internal combustion engine, and during re-acceleration after deceleration, the air-fuel ratio enriched by the control unit is lean for a certain period of time until transition to idle feedback control with an idle feedback constant. It is characterized in that feedback control is performed by a feedback constant at the partial time in order to realize.

[Advantages] According to the present invention, fixed duty control is performed during deceleration of the internal combustion engine, and during reacceleration after deceleration of the internal combustion engine, the air-fuel ratio that has been enriched by the control unit for a certain period of time before transitioning to idle feedback control is lean. In order to reduce the air-fuel ratio, feedback control is performed with a feedback constant at the partial time, and the air-fuel ratio fixed by the control is quickly returned to an appropriate value to prevent unnecessary enrichment of the air-fuel ratio.
Exhaust gas such as CO is reduced without deteriorating operating performance.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

1 to 6 show a first embodiment of the present invention.
In FIG. 1, 2 is an air cleaner and 4 is an intake passage. An electronically controlled venturi type carburetor 6 is provided in the middle of the intake passage 4 on the downstream side of the air cleaner 2.
In a part, the intake passage 4 is branched into a low load primary intake passage 4a and a high load secondary intake passage 4b. In addition, the intake passage 4
Is terminated in the combustion chamber 12 of the engine 10 via the intake valve 8. An exhaust passage 16 is opened in the combustion chamber 12 via an exhaust valve 14, and a catalytic converter 18 composed of a three-way catalyst for performing post-exhaust treatment is provided in the exhaust passage 16.

The carburetor 1 is provided with an electromagnetic valve 22 whose opening and closing is controlled by a control unit 20 which will be described later.

Further, in order to detect the engine operating state, a throttle opening switch 28 for detecting the throttle valve opening by the idle switch 24 and the full-open switch 26 is provided, and a water temperature switch 30 for detecting the engine temperature is provided. Further, an O ₂ sensor 32, which is an exhaust sensor for detecting the exhaust gas concentration such as the O ₂ concentration, is mounted in the exhaust passage 16.

A control unit 20 is provided which receives detection signals from the throttle opening switch 28, the water temperature switch 30, and the O ₂ sensor 32. This control unit 20 performs feedback control with a feedback constant at the partial time so as to lean the air-fuel ratio that has been enriched for a certain period of time before shifting to the idle feedback control during reacceleration after deceleration of the internal combustion engine. More specifically, at the time of re-acceleration after deceleration of the internal combustion engine,
The fixed duty is released by the control unit 20 and then controlled by a partial feedback constant for a fixed time (Tsec), for example, 5 seconds to control the air-fuel ratio to quickly return to an appropriate value.

Reference numeral 34 is a choke valve, 36 is a primary venturi of the carburetor 6, 38 is a secondary venturi of the carburetor 6, and 40 is a carburetor 6.
Float chamber, 42 is the air vent chamber of the float chamber, 44 is 1
Secondary throttle valve, 46 is the secondary throttle valve,
48 is an ignition coil.

Next, description will be given along the flowchart of FIG.

First, when the internal combustion engine is started, it is judged from the start whether the engine speed Ne is 300 rpm or more. If NO, the output is stopped, and if YES, the water temperature is 43 ° C or more. Make a decision. In the case of NO performs open-loop control, in the case of YES performs determination of whether O ₂ is activated by the O ₂ sensor 32. If this determination is NO, open loop control is performed, if YES, it is determined whether or not it has waited for 3 seconds, if NO, open loop control is performed, and if YES, closed loop control is performed. And after opening and closing both loop control,
Check if the throttle valve is fully open, and fix the throttle valve. After that, feedback control and air control are performed.

Next, as shown in FIG. 4, general closed loop control will be described.

In closed loop control, first determine whether or not it is idle, and then NO
In the case of, the control by the partial feedback constant is performed, in the case of YES, it is determined whether the engine speed supplement Ne is 1800 rpm or more, and in the case of NO, the control by the idle feedback constant is performed, If YES, it is determined whether the engine speed Ne is 1950 rpm or more. If this judgment is YES, the deceleration fixed duty (D
UTY) to determine if the solenoid valve is locked or not in the case of NO, control with the feedback constant of the idle in the case of NO, and to perform the deceleration fixed duty as described above in the case of YES. It is a thing.

Then, the general closed loop control as described above operates as described later (see FIG. 5) in the embodiment of the present invention.

That is, it is determined whether the engine speed Ne is 1800 rpm or more, and if NO, it is determined whether or not it has waited for 5 seconds. If YES, control is performed using the idle feedback constant as described above. In the case of NO, control by partial feedback constant is added.

Next, the idle-up control during deceleration of the internal combustion engine will be described with reference to FIG.

First, it is judged whether or not it is idle. If NO, the idle up control is not performed, and if YES, the engine speed Ne
Is 1400 rpm or more. If YES, the idle-up control is not performed, and if NO, the idle-up control is performed. Next, it is determined whether or not the idle-up control operation is continued for 3 seconds. If NO, the idle-up control is continued, and if YES, the idle-up control is ended.

At the time of re-acceleration after deceleration of the internal combustion engine according to the above-described flowchart, as shown in FIG. 2, the air-fuel ratio can be controlled for a fixed time (Tsec) from the fixed duty by the partial feedback constant.

As a result, the control unit can perform correction control to quickly return the duty to an appropriate value without deteriorating the operating performance, can reduce the air-fuel ratio uncontrolled period, and reduce harmful exhaust gas such as CO. You can

FIG. 7 shows a second embodiment of the present invention.
In the second embodiment, the portions having the same functions as those of the first embodiment will be described with the same reference numerals.

The feature of the second embodiment is that in the first embodiment, it is judged whether or not it has been waiting for 5 seconds. However, after releasing the fixed duty after deceleration of the internal combustion engine, the air-fuel ratio is judged O ₂ The point is to control by the partial feedback constant until the sensor signal crosses the slice level, that is, during the period indicated by H in FIG.

By the way, similarly to the above-described first embodiment, at the time of re-acceleration after deceleration of the internal combustion engine, the control section corrects the duty to eliminate the non-control period and contributes to the reduction of exhaust gas.

Further, by controlling with the O ₂ sensor signal, the air-fuel ratio and the exhaust gas can be closely related, and the exhaust gas can be reduced more effectively.

FIG. 8 shows a third embodiment of the present invention.

The feature of the third embodiment is that when the control is performed by the feedback constant performed after the fixed duty is released after the internal combustion engine is decelerated, the value P (proportional amount) is always shifted from the fixed duty to the lean side. There is a point.

Then, the duty can be corrected and controlled to a proper value more quickly, the non-control period of the hatched portion shown in FIG. 8 can be shortened, and the emission amount of harmful exhaust gas such as CO can be reduced. .

[Effects of the Invention] As described in detail above, according to the present invention, fixed duty control is performed with a fixed duty during deceleration of the internal combustion engine, and during re-acceleration after deceleration, the idle feedback control by the idle feedback constant is performed. Since the air-fuel ratio, which has been enriched by the control unit for a certain period of time, is feedback-controlled by the feedback constant at the partial time, it reduces harmful exhaust gas such as CO without deteriorating the uncontrolled period of the air-fuel ratio. It can be achieved.

[Brief description of drawings]

1 to 6 show a first embodiment of the present invention, FIG. 1 is a diagram showing a control state of an internal combustion engine, FIG. 2 is a diagram showing duty after deceleration, and FIG. 3 is a flowchart of air-fuel ratio control. 4 and 5 are flowcharts of closed loop control, and FIG. 6 is a flowchart of idle up control. FIG. 7 is a relationship diagram between the duty and the O ₂ sensor signal showing the second embodiment of the present invention. FIG. 8 is a diagram showing the duty after deceleration showing the third embodiment of the present invention. 9 and 10 show the prior art of the present invention, FIG. 9 is a schematic diagram showing air-fuel ratio control of an internal combustion engine, and FIG. 10 is a diagram showing duty. In the figure, 2 is an air cleaner, 4 is an intake passage, 6 is an electronically controlled venturi type carburetor, 10 is an engine, 16 is an exhaust passage, 20 is a control unit, 22 is a solenoid valve, 24 is an idle switch, 26 is a fully open switch. , 28 is a throttle opening switch,
30 is a water temperature switch and 32 is an O ₂ switch.

Claims (1)

[Claims] 1. An air-fuel ratio control method for an internal combustion engine, wherein an electronically controlled carburetor is feedback-controlled by a control unit for inputting a signal from an O ₂ sensor. At the same time, at the time of re-acceleration after deceleration, the feedback control is performed by the feedback constant at the partial time in order to make the air-fuel ratio rich by the control unit for a certain time until the idle feedback control by the idle feedback constant is performed. Air-fuel ratio control method for internal combustion engine.