JPS60119334A - Air-fuel ratio control device - Google Patents

Abstract

PURPOSE:To improve the economy of fuel consumption, by inhibiting the enrichment of mixture if the vehicle speed is higher than a predetermined value althrough the engine runs under a low load condition. CONSTITUTION:An enrichment control circuit 36 enriches the mixture of an engine in a predetermined running condition. The enrichment control circuit 36 receives a signal corresponding to the rotational speed of the engine detected by a rotational speed sensor 30, a vehicle speed signal from a vehicle speed sensor 32 and a signal issued from a throttle valve full-close switch and indicating that the throttle valve is fully closed, and detects such as condition that the vehicle speed is lower than a predetermined value under low load operation. If this condition is detected, the circuit 36 enriches the mixture, thereby the economy of fuel consumption may be improved.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention includes a control means that controls the air-fuel mixture to around the stoichiometric air-fuel ratio during normal operation and enriches the air-fuel mixture during low-load engine operation. This invention relates to improvements in air-fuel ratio control devices for engines.

(Prior Art) In engine air-fuel ratio control, the air-fuel mixture is generally controlled to around the stoichiometric air-fuel ratio in order to improve fuel efficiency and to float exhaust gas. but,
If the above-mentioned control is performed at low load on an engine with a small amount of intake air, combustion will become unstable and engine vibration will increase, causing discomfort to the passengers. It is known to perform fuel ratio control to stabilize combustion and suppress engine vibration.

In the operating state other than idling, the 02 concentration in the exhaust gas is detected using the 02 sensor, and the fuel mixture is controlled by feedback control of the fuel supply. An air-fuel ratio control device has been disclosed that performs air-fuel ratio control to maintain the air-fuel ratio near the stoichiometric air-fuel ratio, and also releases the feedback control to enrich the air-fuel mixture during idling operation. However, engine vibration caused by unstable combustion as described above becomes a problem when the vibration of the entire vehicle is small. Akira! ; g-11
The air-fuel ratio control described in Japanese Patent No. 9949 cannot necessarily be said to be effective; rather, it is desirable to limit the control to enrich the air-fuel mixture from the viewpoint of fuel efficiency and exhaust gas purification unless engine vibration becomes a problem.

(Objective of the present invention) The present invention was made in consideration of the above-mentioned circumstances, and reduces fuel consumption by limiting air-fuel ratio control that enriches the air-fuel mixture within a range where engine vibration is not a problem. It is an object of the present invention to provide an air-fuel ratio control device for an engine that can perform several adjustments.

(Configuration of the present invention) In order to achieve the above-mentioned object, the present invention is configured as follows. That is, the present invention provides an air-fuel ratio control device for an engine that is equipped with a control means that reduces the air-fuel ratio and enriches the air-fuel mixture when the engine is operating at low load. The present invention is characterized in that it includes a limiting means for limiting the enrichment control of the air-fuel mixture when the value is greater than or equal to the value. The present invention focuses on the fact that even if engine vibration occurs, if the vehicle speed is relatively high, engine vibration is not a problem because it is canceled out by vibrations caused by other conditions. Even if the vehicle speed is higher than the set value, control to enrich the air-fuel mixture is not performed.

(Effects of the present invention) According to the present invention, as described above, the control to enrich the air-fuel mixture is limited to the extent possible, and the air-fuel mixture is controlled to be maintained near the stoichiometric air-fuel ratio, thereby reducing fuel consumption. It can be improved. At low loads and low vehicle speeds, the mixture is enriched to stabilize combustion, eliminating problems caused by engine vibration.

(Description of Embodiment) Referring to FIG.
An intake passage 12 for feeding intake air into the combustion chamber 0 and an exhaust passage 14 for exhausting combustion gas are connected to each other. A throttle valve 18 and a fuel injection solenoid valve 20 are provided. Throttle valve 18
is equipped with a throttle valve fully closed switch 22 that detects when the valve 18 is fully closed. In the exhaust passage 14, there is an exhaust sensor 24 that detects the concentration of a specific component in the exhaust gas, for example, the concentration of 02, and downstream thereof a catalyst device 26 that has a catalyst that oxidizes incompletely burned components in the exhaust gas. provided. A controller 28 for controlling the amount of fuel injected from the solenoid valve 20 is provided. The controller 28 includes a rotation sensor 30 that detects the engine rotation speed from the rotation speed of the engine crankshaft, a vehicle speed sensor 32 that detects the vehicle speed from the rotation of the axle, a signal from the throttle valve fully closed switch 22, and a signal representing the intake air amount. Signals and the like are input, and a valve opening signal is output to the solenoid valve 20. FIG. 2 shows an example of the control circuit of the controller 28. The controller 2B includes a circuit 34 for performing normal feedback control to maintain the air-fuel mixture near the stoichiometric air-fuel ratio, and a circuit 34 for maintaining the air-fuel mixture near the stoichiometric air-fuel ratio. It includes a circuit 36 for enriching the mixture, a switching circuit 38 for switching between the feedback control and the mixture enrichment control, and a solenoid drive circuit 40 that outputs a predetermined valve opening signal to the solenoid valve 20 at a predetermined timing. ing. The feedback control circuit 34 detects the concentration of a specific component of the exhaust gas, for example, 02, by the exhaust sensor 24, inputs a corresponding voltage signal, and determines the concentration of the specific component after combustion of the air-fuel mixture near the set value, that is, the stoichiometric air-fuel ratio. A comparison circuit 42 for comparing with a voltage signal corresponding to the voltage signal, an ON state from the comparison circuit 42,
Integration circuit 4 for integrating the OFF signal and performing delay control
4. When the switching circuit 38 is switched as the signal from the concentration control circuit 36 turns ON, the signal from the integrating circuit 44 is appropriately amplified and inverted and inputted to the comparing circuit 42, which outputs the signal from the integrating circuit 44. An integral output holding circuit 46 is provided to converge the output signal to a constant value. Concentration control circuit 36
is 4 corresponding to the engine rotation speed from the rotation sensor 30.
Comparison circuit 4 which inputs No. M and compares it with a set value signal corresponding to a predetermined engine speed, and outputs a high level signal if the engine speed input signal is smaller than the set value.
8, a comparator 50 which inputs the vehicle speed signal from the vehicle speed sensor 32, compares it with a set vehicle speed signal value, and outputs a high level signal when the input vehicle speed signal value is smaller than the set value, and a comparator 50 which outputs a high level signal when the input vehicle speed signal value is smaller than the set value. An AND circuit 52 receives a signal from the throttle valve fully closed switch 22, which outputs a high-level signal when the throttle valve is closed, and a signal from the comparison circuit 48, and a signal from the AND circuit 52 and the comparison circuit 50. and an AND circuit 54.

To explain the control of the controller 28 having the above circuit configuration, in the region up to time T1 shown in FIG. 3I, the accelerator pedal is depressed and the throttle valve 18
has a predetermined opening degree, and in this case, the concentration control circuit 36
Since the output from the exhaust sensor 24 is at a low level, the switching circuit 38 inputs the signal from the exhaust sensor 24 to the comparison circuit 42. The comparison circuit 42 compares this input signal with a set value for maintaining the air-fuel mixture near the stoichiometric air-fuel ratio, and when the input signal is large, it outputs a high level signal, and when it is small, it outputs a low level signal. do. This signal is input to the integration circuit 44 and integrated. The integral signal from the integral circuit 44 is input to the solenoid drive circuit 40, which determines the injection pulse width of the solenoid valve 20 according to the level of the integral signal, and injects the solenoid valve 20 with the injection pulse width at a predetermined timing. A command signal is output to open the valve only for a predetermined period according to the 4-rus width. In this control, the fuel injection amount is feedback-controlled based on the concentration of a specific component in the exhaust gas, and the integral value output from the integrating circuit 44 is maintained near a certain constant value, as shown in Fig. 3 (■). Figure 3 V
As shown in , the air-fuel mixture is maintained near the stoichiometric air-fuel ratio.

Then, at time T1, when the accelerator pedal is released and the throttle valve 18 is closed, the vehicle speed and engine speed decrease as shown in FIG. 3 (2) and FIG. 3 (1). In this case, if the clutch is engaged, the engine speed will decrease in a similar manner to the vehicle speed, as shown by the imaginary line in Figure 3 In, or if the clutch is not engaged, the engine speed will decrease. , as shown by the solid line in Fig. 3 (■), shows a decreasing tendency different from the tendency of the vehicle speed. And time T
2, when the vehicle speed becomes less than the set value, the comparator circuit 50 outputs a high level signal. Then, at an earlier time, that is, at time T1, the throttle valve fully closed switch 22 is activated at time Ts, h, or time T1.
Since the comparators 48 each output a high level signal at time T2, the concentration control circuit 36 outputs a high level signal at time T2. As a result, the switching circuit 38 cuts the signal from the exhaust sensor 24 and inputs the signal from the integral output holding circuit 46 to the comparison circuit 42 . The integral output holding circuit 46 performs inversion and amplification processing using the fixed value of the output value of the integrating circuit 44 as a reference, so that the output of the integrating circuit 44 is held at a constant value. This constant value is maintained, for example, at a value shown by level a in Figure 3 (■), and therefore the air-fuel ratio is reduced accordingly as shown in Figure 3 (V), and the air-fuel mixture is is concentrated. Then, at time T4, when the accelerator pedal is depressed, the throttle valve fully closed switch 22 is turned off, so the output of the enrichment control circuit 36 becomes low level, the enrichment control is canceled, and the output from the exhaust sensor 24 is turned off. Feedback control based on the signal is performed again.

In the above control, the enrichment control is not performed even after one hour T, (T3') when the engine speed decreases and becomes below the set value, and the enrichment control is not performed until the time T2 when the vehicle speed becomes below the set value. Concentration control is performed only after the lapse of time. This makes it possible to improve υ fuel efficiency compared to the conventional model. When such control is performed, even if engine vibration occurs, since the vehicle speed is relatively high, no actual harm such as discomfort to the occupants will occur.

In addition, in this example, the control when concentration control is not performed is as follows.
Although feedback control is performed based on the signal from the exhaust sensor 24, it is not necessary to do so, and control such as open control based on the intake air amount may be used.

[Brief explanation of drawings]

FIG. 7 is a schematic diagram of an engine according to an embodiment of the present invention, FIG. 2 is a control circuit diagram of the controller of the engine in FIG. 1, FIG. 3 I is a throttle valve opening degree and time, and FIG. is a graph showing the relationship between vehicle speed and time, FIG. 3 111 is a graph showing the relationship between engine rotation speed and time, FIG. 3 1■ is a graph showing the relationship between the output of the integrating circuit and time, and FIG. Explanation of symbols 10... Engine, 12...
... Intake passage, 14... Exhaust passage,
]8... Throttle valve, 22...
...Throttle valve fully closed switch, 28...
... Controller, 30 ...... Rotation sensor, 32 ...... Vehicle speed sensor,

Claims (1)

[Claims] In an engine air-fuel ratio control device equipped with a control means for enriching the air-fuel mixture by reducing the air-fuel ratio during low-load operation of the engine, when the vehicle speed is equal to or higher than a set value even during low-load operation of the engine, An air-fuel ratio control device for an engine, comprising a limiting means for limiting air-fuel mixture enrichment control.