JPS5828566A - Method and device for controlling air fuel ratio of internal combustion engine - Google Patents

Abstract

PURPOSE:In an engine in which the air fuel ratio of the mixture is feedback-controlled depending on the concentration of oxygen, to adequately reaccelerate the engine after its deceleration in which the temperature of cooling water is lower than a prescribed level, by ceasing the feedback control at the time of said deceleration. CONSTITUTION:In an air fuel ratio control method, an electronic control circuit 38 first judges on the basis of the output of a throttle valve opening degree sensor 22 whether or not a throttle valve 20 is completely closed. When the throttle valve 20 is not completely closed, the operation of the engine is regarded as ordinary and the feedback compensation of a basic injection time Tp calculated from the outputs of an air flow meter 12 and a distributor 14 is carried out by the output of an oxygen sensor 28. When the throttle valve 20 is completely closed, a fuel injection signal is determined on the basis of the outputs of a water temperature sensor 16, the oxygen sensor 28 and a vehicle speed sensor 32. For example, the fuel injection signal is determined without the air fuel ratio feedback compensation of the basic injection time Tp, at the time of such deceleration of the engine that the temperature of cooling water is lower than 70 deg.C and the vehicle speed is not lower than 10km/h.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control method and device for an internal combustion engine,
Particularly suitable for use in automobile internal combustion engines that have undergone exhaust gas purification measures, t-feedback of the air-fuel ratio of the air-fuel mixture is performed so that the air-fuel ratio of the air-fuel mixture becomes close to the stoichiometric air-fuel ratio according to the oxygen concentration in the exhaust gas. The present invention relates to improvements in an air-fuel ratio control method and device for an internal combustion engine.

In an automobile internal combustion engine, particularly an automobile internal combustion engine equipped with a three-way catalytic converter, in order for the three-way catalytic converter to exhibit sufficient exhaust gas purification performance,
It is necessary that the oxygen concentration in the exhaust gas flowing into the three-way catalytic converter corresponds to the oxygen concentration when a mixture near the stoichiometric air-fuel ratio is combusted. Therefore, conventionally, an oxygen concentration sensor is provided in the exhaust system to detect the oxygen concentration in the exhaust gas, and the air-fuel ratio of the air-fuel mixture becomes close to the stoichiometric air-fuel ratio according to the oxygen concentration in the exhaust gas output from the oxygen concentration sensor. An air-fuel ratio control method is known in which the air-fuel ratio of an air-fuel mixture is feedback-controlled by changing the amount of fuel or air supplied.

Such air-fuel ratio feedback control is extremely effective under normal conditions. However, if feedback control is activated before the engine warms up and the oxygen concentration sensor is fully activated, the air-fuel ratio control means malfunctions due to an abnormal output from the oxygen concentration sensor, causing the air-fuel ratio of the mixture to The air-fuel ratio will not be close to the stoichiometric air-fuel ratio. Also, when starting the engine,
Engine starting performance is better when the air-fuel ratio of the air-fuel mixture is richer than near the stoichiometric air-fuel ratio. Furthermore, during no-load operation,
If the oxygen concentration sensor becomes inactive due to a drop in exhaust gas temperature, there is a risk of output abnormality. Therefore, when starting the engine, increasing the amount after starting, or driving under high load, the engine cooling water temperature should not be set to a predetermined temperature, e.g. When the temperature is 50° C. or lower, the feedback control is stopped in operating states such as no-load operation, and the engine is operated at a predetermined air-fuel ratio suitable for each operating state. However, conventionally, during deceleration, feedback control was performed in the same way as in normal times. However, during this deceleration, the fuel valve is closed and the fuel adhering to the inner wall of the intake manifold is rapidly vaporized and sucked into the combustion chamber, so the oxygen concentration detected by the oxygen concentration sensor decreases. As shown in Figure 1 (FIJK), the air-fuel ratio of the mixture is unilaterally controlled to the lean side.As a result, when reaccelerating after deceleration, the air-fuel ratio of the mixture deviates excessively to the lean side. It had the disadvantage of poor acceleration performance during re-acceleration.

This phenomenon is particularly noticeable when the engine cooling water temperature is low.

The present invention was made to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide an air-fuel ratio control method and apparatus for an internal combustion engine that has excellent acceleration performance during re-acceleration after low-temperature deceleration.

The present invention mixes the air-fuel mixture so that the air-fuel ratio of the air-fuel mixture becomes close to the stoichiometric air-fuel ratio according to the oxygen concentration in the exhaust gas.

In the air-fuel ratio control method for an internal combustion engine, the air-fuel ratio of the engine is feedback-controlled, and when the engine cooling water temperature is less than a predetermined value and the engine decelerates, the above-mentioned feet ° This is what I did.

Further, the throttle valve dl is in a fully closed state, the engine cooling water temperature is less than a predetermined value, and
The vehicle is configured to stop when the traveling speed of the vehicle is equal to or higher than a predetermined value.

Furthermore, an air-fuel ratio control device for an internal combustion engine in which the method is implemented includes an intake air amount sensor that detects the intake air amount of the engine, a rotation speed sensor that detects the engine rotation speed, and a cooling water temperature that detects the engine cooling water temperature. A sensor, a throttle valve opening sensor that detects whether the throttle valve is in a fully closed state, an oxygen concentration sensor that detects the oxygen concentration in exhaust gas, a vehicle speed sensor that detects the vehicle running speed, and an engine internal sensor. The basic fuel injection time is calculated based on the injector that fully injects the fuel, the intake air cover of the engine, and the engine speed. The fuel injection time is corrected by feedback. On the other hand, when the throttle valve is fully closed, the engine cooling water temperature is less than a predetermined value, and the vehicle running speed is above a predetermined value, the fuel injection time is feedback-corrected. and an electronic control circuit that outputs a fuel injection signal to the injector without correction.

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

An embodiment of an electronically controlled fuel injection device employing the air-fuel ratio control method for an internal combustion engine according to the present invention is as shown in FIGS. an air flow meter 12 that detects the amount of intake air;
A distributor 14 that generates a pulse signal according to engine rotation, a cooling water temperature sensor 16 that detects the engine cooling water temperature, and an intake air temperature sensor 1 that detects the engine intake air temperature, which is disposed within the air flow meter 12.
8, a throttle position sensor 22 disposed in the intake passage 10 that detects the opening of the throttle valve 20 and all changes in the throttle valve opening, a starter switch 24 that generates a starter signal during engine starting, and a starter switch 24 that generates a starter signal during engine starting; An oxygen concentration sensor 28 for detecting the oxygen concentration in exhaust gas, a vehicle speed sensor 32 for detecting the running speed fTh of the vehicle from the rotation speed of the shaft of the transmission 30, and an intake manifold 3 of the engine are provided.
The ninth injector 36 injects fuel into the fourth injector, calculates the basic fuel injection time according to the intake air amount of the engine and the engine speed, and normally injects fuel into the exhaust gas of the oxygen concentration sensor 28 output. The fuel injection time is feedback-corrected according to the oxygen concentration of , and a digital electronic control circuit 38 that outputs a fuel injection signal to the injector 36 without feedback correcting the fuel injection time. In Figure 2, 4
0 is an air cleaner, 42 is a surge tank, 44 is a spark plug, and 46 is a catalytic converter.
48 is a battery.

As shown in detail in FIG. 3, the digital electronic control circuit 38 is an analog circuit for converting analog signals output from the air flow meter 12 (including the intake air temperature sensor 18), the cooling water temperature sensor 16, and the battery 48 into digital signals. −
a digital converter 50; the distributor 14;
Throttle position sensor 22, starter switch 2
4. Ninth input interface circuit 5 that inputs digital signals of the II elementary concentration sensor 28 and vehicle speed sensor 32 outputs
2, a central processing circuit 54, a read-only memory 56, a random access memory 58, and an output interface circuit that converts the calculation results in the central processing circuit 54 into a solvent injection signal suitable for outputting to the injector 36. It consists of 60.

The operation will be explained below. First, the digital electronic control circuit 38 calculates the basic injection time 'rp using the following equation based on the intake air amount Q of the air flow meter 2 output and the engine rotation speed N calculated from the distributor 14 output.

T、＝に一且・・・・・・・・・・・・・・・・・・
(1) Here, K is a coefficient.

Furthermore, by correcting the basic injection time TP using a quadratic formula according to the signals from each sensor, 1 is calculated as the effective synchronous injection time.

TI = Tp-f(A/F) ・f(wt,) ・f
(TnA) ・(1+f(*sE)+f(u+v) +
f(oTp) ) (1-f(Rs) )-=(2)
Here, f(ψ) is an air-fuel ratio correction coefficient, fCvn, ) is a warm-up increase correction coefficient, f(TEA) is an intake air temperature correction coefficient,
f(muaX) is an increase correction coefficient after startup, f(AEW) is an acceleration increase correction coefficient during warm-up, f(oTp) is an over and one (output) increase coefficient, and Z(as) is a reduction coefficient.

With the effective synchronous injection time obtained in this way, as shown in the IK linear equation, the invalid injection time γ7t- corresponds to the response delay time of the injector 36 when the battery voltage decreases.
By adding, the synchronous injection time 1B is calculated.

78=7□+τ7・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・(8) This synchronous injection time 7sVc
A corresponding fuel injection signal is output to the injector 36, and in synchronization with engine rotation, the injector 36 is opened for a synchronous injection time to inject fuel into the intake manifold 34 of the engine.

The air-fuel ratio foot check control in this embodiment is performed as follows. That is, as shown in FIG.
According to the output of the throttle position sensor 22,
It is determined whether the throttle valve is in a fully closed state. When the throttle valve is not in the fully closed state, it is determined that it is normal, and the basic injection time 'rpf: is adjusted according to the output of the oxygen concentration sensor 28 by feedback correction according to equation (2) above. Injection signal f: Find. On the other hand, when the throttle valve is in the fully closed state, it is determined whether the engine cooling water temperature is less than 70° C. according to the output of the cooling water temperature sensor 16. When the temperature of the engine coolant @ is 70° C. or higher, it is determined that it is normal, and feedback correction is performed according to the basic injection t'rptl - the output of the oxygen concentration sensor 28. On the other hand, if the engine cooling water temperature is less than 70°C, one more vehicle speed sensor 32
Depending on the output of the vehicle, the traveling speed of the vehicle, that is, the vehicle speed or
It is determined whether or not it is greater than or equal to h. Vehicle speed: 10km/h
If it is less than 100%, it is determined that it is normal, and the basic injection time Tpi is feedback corrected according to the output of the oxygen sensor 28. On the other hand, the vehicle speed is 10
/h or more, that is, the throttle valve is fully closed,
During low-temperature deceleration when the engine cooling water temperature is less than 70C and the vehicle running speed is 101 m/h or more, a fuel injection signal is obtained without performing air-fuel ratio feedback correction for the basic injection time TP. Therefore, the 9 fuel ratios of the air-fuel mixture during low-temperature deceleration and during re-acceleration after deceleration in this embodiment are as shown in FIG. Therefore, the air-fuel ratio at the time of re-acceleration does not become excessively lean due to the influence of air-fuel ratio feedback correction as in the conventional case, and good acceleration performance can be obtained at the time of re-acceleration.

In the above embodiment, the present invention is applied to an internal combustion engine equipped with an electronically controlled fuel injection device, but the scope of application of the present invention is not limited to this, and the present invention is applied to an internal combustion engine equipped with an electronically controlled fuel injection device. It is clear that the same applies to internal combustion engines.

As explained above, according to the present invention, the air-fuel ratio of the air-fuel mixture does not become excessively lean during low-temperature deceleration, and therefore excellent re-acceleration performance can be obtained. have

[Brief explanation of drawings]

FIG. 1 is a diagram showing how the air-fuel ratio changes during low-temperature deceleration and re-acceleration in the conventional example and the embodiment of the present invention, and FIG. 2 is a diagram showing how the air-fuel ratio control method for an internal combustion engine according to the present invention is adopted. A partial block diagram showing an internal combustion engine equipped with an electronically controlled fuel injection device, which is an embodiment of the air-fuel ratio control device.
FIG. 3 is a block diagram showing the circuit configuration of the electronically controlled fuel injection device, and FIG. 4 is a flowchart showing part of the air-fuel ratio feedback routine in the embodiment. 12°°・Air 70-meter, 14・Pad distributor, 16・Cooling water temperature sensor, 20・Throttle valve, 22・
... Throttle position sensor, 26... Exhaust passage, 28... Oxygen concentration sensor, 32... Vehicle speed sensor, 36... Injector, 38... Digital electronic control circuit. Agent Patent attorney Takaya Ron C11 or 1 person) Figure f Lean

Claims (1)

[Scope of Claims] (1) An air-fuel ratio of an internal combustion engine that performs feedback control of the air-fuel ratio of the air-fuel mixture so that the air-fuel ratio of the air-fuel mixture becomes close to the stoichiometric air-fuel ratio according to the oxygen concentration in exhaust gas. An air-fuel ratio control method for an internal combustion engine, characterized in that the feedback control is stopped during deceleration when the engine cooling water temperature is less than a predetermined value. (2) A patent claim in which the feedback control is stopped when the throttle valve is in a fully closed state, the engine cooling water temperature is less than a predetermined value, and the vehicle running speed is above a predetermined value. The air-fuel ratio control method for an internal combustion engine according to item 1. (8) An intake air amount sensor that detects the intake air amount of the engine, a rotation speed sensor that detects the engine speed, a coolant temperature sensor that detects the engine coolant temperature, and detects that the throttle valve is in the fully closed state. an oxygen concentration sensor that detects the oxygen concentration in exhaust gas; a vehicle speed sensor that detects the entire running speed of the vehicle; an injector that injects fuel into the engine; The basic fuel injection time 'tl is calculated according to the rotation speed, and under normal conditions, the fuel injection time is feedback-corrected according to the oxygen concentration in the exhaust gas output from the oxygen concentration sensor. When the valve is in the closed state, the engine cooling water temperature is less than a predetermined value, and the vehicle speed is greater than or equal to a predetermined value, a fuel injection signal is output to the injector without feedback correction of the fuel injection time. An air-fuel ratio control device for an internal combustion engine that is equipped with an electronic control circuit and all e* characteristics.