JPS5848740A - Method of controlling air-fuel ratio of internal- combustion engine - Google Patents

Abstract

PURPOSE:To prevent overcompensation and to improve control on the air-fuel ratio and performance of engine, by effecting switching of an integration constant used for feedback control of the air-fuel ratio by use of an O2-sensor a predetermined time later after the engine operation is shifted from idling operation to off-idling operation. CONSTITUTION:Output of a rich-lean judging means 14, to which output signal of an O2-sensor 10 is applied, is afforded to integrators 16, 18 having integration constants K0, K1, respectively, and an air-fuel ratio controlling actuator 12 is controlled via a switching circuit 30 on the basis of the output signals of the two integrators 16, 18. On the other hand, output signal of a vacuum operated switch 26 for detecting the negative pressure at a throttle valve port 24 is applied, via a delay valve 34, to a condition judging means 28 which controls the switching circuit 30. At the time of idling operation, negative pressure in an intake pipe is increased and resultantly the switch 26 is turned ON, so that integration is executed by use of the integration constant K0. However, when the engine operation is shifted to off-idling operation and a predetermined time is passed via the delay valve 34, the switch 26 is turned OFF, so that integration is executed by use of another integration constant K1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control method for an internal combustion engine, and in particular, to a method for controlling an air-fuel ratio of an internal combustion engine, and in particular to a method for controlling an air-fuel ratio of an internal combustion engine. An oxygen concentration sensor that senses the residual oxygen concentration in the inflow gas and an air-ratio control actuator that controls the air-fuel ratio of the air-fuel mixture or the catalyst inflow gas are used, and an integral is included for the oxygen concentration sensing O output. The present invention relates to an improvement of an air-fuel ratio control method for an internal combustion engine, in which the air-fuel ratio control actuator is feedback-controlled by a feedback control signal obtained by applying a control signal to bring the air-fuel ratio of the air-fuel mixture or catalyst inflow gas to a desired air-fuel ratio.

In recent years, in automobile internal combustion engines, which require strict exhaust gas purification measures, it has become necessary to perform extensive air-fuel ratio control. It is equipped with an oxygen concentration sensor that senses the concentration, and an air-fuel ratio control actuator that controls the air-fuel ratio of the air-fuel mixture or expansion catalyst inflow gas O, and performs lI&processing including integration on the output of the oxygen concentration sensor. Accordingly, the air-fuel ratio control actuator is feedback-controlled (by the *m control signal obtained) to make the residual oxygen concentration in the catalyst inflow gas equal to the residual oxygen concentration when a stoichiometric air-fuel ratio O mixture is ignited. The air-fuel ratio control system has been put into practical use.It is possible to obtain good exhaust gas purification performance regardless of changes in engine operating conditions.
In general, in this kind of air-fuel ratio control, the integral constant in idle state U < suitable 9 and the integral constant suitable for off-idle state are different, and the integral constant in idle state and OR idle state is different. Conventionally, however, the integration constant is switched immediately after the transition from the idle state to the off-idle state 11, or depending on the presence or absence of the intake pipe negative pressure O on the downstream side of the intake throttle valve, for example. This is done immediately after the transition from the off-idle state to the idle state, so in particular, the transition from the idle state where the intake air amount is small and the integral constant is small to the off-idle state where the intake air amount is large and the integral constant is large. Immediately after nine months, that is, at the time of starting, due to the influence of discharge disturbances in the fuel system, controlling with a particularly large integral constant results in 1 over compensation, which corrects the air-fuel ratio, giving a stiffness when driving. There are six problems in terms of control and driving performance.The present invention has been made to solve the above-mentioned drawbacks of the conventional technology, and can prevent excessive overcompensation when shifting from an idle state to an off-idle state. Therefore, it is an object of the present invention to provide an air-fuel ratio control method for an internal combustion engine that can improve controllability and drivability.

The present invention uses an oxygen concentration sensor that senses the residual oxygen concentration in the catalyst inflow gas and an air-fuel ratio control actuator that controls the air-fuel ratio of the air-fuel mixture or the catalyst inflow gas. In the air-fuel ratio control method for an internal combustion engine, the air-fuel ratio control actuator is feedback-controlled (by a feedback control signal obtained by applying a section including The above objective was achieved by changing from the idle state to the offide state 11 and switching the integral constant at the edge of the circle after a predetermined period of time had passed since the state became 1 or idle state 11. Hereinafter, with reference to the drawings, an embodiment of an air-fuel ratio control device in which the air-fuel ratio control method for an internal combustion engine according to the present invention is adopted will be described in detail. In this embodiment, as shown in FIG. An oxygen concentration sensor 10 is installed in an exhaust manifold from which exhaust gas is discharged from the exhaust manifold, and is arranged downstream of the exhaust manifold to detect the residual oxygen concentration in the catalyst inflow gas flowing into the catalyst, for example, a three-way catalyst. By controlling the effective area of the fuel passage or air bleed passage for forming the mixture, or by controlling the flow rate of secondary air mixed into the exhaust gas], the mixture or the catalyst inflow gas The air-fuel ratio control actuator 12, which controls the air-fuel ratio of the catalyst, and the output of the oxygen temperature sensor 100, which controls the air-fuel ratio of the catalyst, is compared with a reference voltage. The output pipe of the pre-allocated lean determiner 14 is integrated using a first integration constant 4 suitable for the idle state, and a feedback control signal corresponding to the air-fuel ratio is created. a second integrator 18 that integrates the output of the rich-lean determiner 14 with a second integral constant Kl suitable for an off-idle state and creates a feedback control signal according to the air-fuel ratio. , vaporizer!
A negative pressure switch 26 is formed directly below the fully closed position of the intake throttle valve 22 and a negative pressure switch 26 is switched according to the intake pipe negative pressure generated at the valve port 24, and a negative pressure switch 26 is switched depending on the output state of the , a condition discriminator 28 that discriminates whether the engine operating state is an idle state or an off-idle state.
According to the output of the condition discriminator 28, if the condition is in the idle state, the feedback control signal of the output of the integrator 16 is input to the air-fuel ratio control actuator 12; The feedback control signal of the second integrator 18 output is transmitted to the air-fuel ratio control actuator 1211.
In the internal combustion engine zero air-fuel ratio control device, which has a switching circuit 3o that inputs C, a check valve 3 is installed in the middle of a negative pressure line 32 that communicates the throttle valve port 24 with the negative pressure switch 26.
By disposing the negative pressure delay valve 34 consisting of 4m and throttle) 34b, the idle state shifts to the or-idle state 11, the first intake throttle valve 22 is closed, the intake pipe negative pressure is increased, and then the negative pressure is increased. After a predetermined period of time determined by the pressure delay valve 34 has elapsed, the negative pressure switch 26 is switched so that the integral constant is changed when the idle state shifts from the idle state to the off-idle state. This is to be carried out after a predetermined period of time has elapsed since then.

The operation will be explained below with reference to FIG. First, in an idling state where the intake throttle valve 22 is closed and the intake pipe negative pressure generated in the throttle valve boat 24 is large, the negative pressure switch 26
is turned on, and the switching circuit 30 outputs the output of the first integrator 16 to the air-fuel ratio control actuator 1'2 according to the output of the condition discriminator 28K). Therefore, in this idle state 11, the air-fuel ratio control actuator 12 is controlled by the first integral constant 4 suitable for the idle state.

Meanwhile, in order to shift to driving mode, the driver opens the intake throttle valve j! 2
When the valve is opened, the negative pressure in the intake pipe decreases, and after this decrease in the negative pressure in the intake pipe is delayed for a predetermined time via the negative pressure delay valve 34, the negative pressure switch is closed. Therefore, after the predetermined time T has elapsed, the switching circuit 3
0 is switched, and the output of the second integrator 1s, which has been processed to a nine integral constant KsK suitable for the off-idle state 111, is input to the air-fuel ratio control actuator 12. In this II, when transitioning from the idle state to the off-idle state 11, the integral constant is switched to 1, the second integral constant over the off-idle state 11, at the same time as the sill throttle valve 22 is operated. Since there is no control, the control state can be smoothly transitioned.In contrast, in the past, the output of the throttle valve boat 24 was directly transmitted to the negative pressure switch 26, so the change state of each signal was As shown by the broken line B in FIG. 2, the state shifts from the idle state to the off-idle state 11, and after the vehicle is running, the control current value of the air-fuel ratio control actuator 12 momentarily becomes large, causing a warning when the vehicle is running. The time T required for transition to the off-idle state is
d, 0, which is a value within a range that does not worsen the start-up of the control after transitioning to the off-idle state.In the above embodiment, the present invention is designed to reduce the It is applied to an air-fuel ratio control device that switches between an idle state and an off-idle state according to the pressure, and a negative pressure delay is provided in the middle of a negative pressure pipe 320 that communicates the throttle valve boat 24 and the negative pressure switch 26 connected to the air-fuel ratio control device. By providing the valve 34, the integral constant is switched after a predetermined period of time has elapsed since the off-idle state. The method of delaying the switching for a predetermined period of time is not limited to this.

According to the present invention, overcompensation after moving from an idle state to an off-idle state is prevented,
This has the excellent effect of improving air-fuel ratio controllability and drivability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of an air-fuel ratio control device in which the air-fuel ratio control method for an internal combustion engine according to the present invention is adopted, and FIG. 12--Air-fuel ratio control actuator, 14--Rich-Lean determiner, 16.18--Integrator, 2z--Intake throttle valve, 24-- Throttle valve Valve port, 26--Negative pressure switch, 28--Condition discriminator, 30--Switching circuit, 34--Negative pressure delay valve. Agent Takaya Ron (and 1 other person)

Claims (1)

[Claims] (1) Using an oxygen concentration sensor that senses the residual oxygen concentration in the catalyst inflow gas and an air-fuel ratio control actuator that controls the air-fuel ratio of the air-fuel mixture or the catalyst inflow gas, an integral is calculated for the output of the oxygen concentration sensor. In an air-fuel ratio control method for an internal combustion engine, the air-fuel ratio control actuator is feedback-controlled by a feedback control signal obtained by applying the appropriate temperature control to bring the air-fuel ratio of the air-fuel mixture or the catalyst inflow gas to a desired air-fuel ratio. , an air-fuel ratio control method for an internal combustion engine O, characterized in that the integral constant is switched when transitioning from an idle state to an off-idle state IIK every 9 minutes after a predetermined period of time has elapsed after the state has changed to an off-idle state.