JPS6035140A - Air-fuel ratio control method for electronically controlled fuel supply device with priority on the fuel - Google Patents

Abstract

PURPOSE:To improve acceleration feeling by controlling change in the air-fuel ratio with respect to the acceleration stroke so that the maximum acceleration stroke will provide an air-fuel ratio corresponding to the condition of the throttle valve being full opened, in case the number of engine revolutions is comparatively low. CONSTITUTION:While the engine 10 is in operation, a comuter 28 calculates the number of engine revolutions N, the rate of air flow QA from the output of a rotation sensor 30 and from the output of pressure sensors 24, 26 at the upper and lower streams of a throttle valve 12, and further calculates the fuel supply amount QF made by a fuel supply mechanism 16. These calculations determine the air-fuel ratio A/F. If the sensing reveals that the number of engine revolutions N is lower than a specific lower value N1, the current air-fuel ratio A/F1 and acceleration stroke S1 provides selection of a corrective curve of air-fuel ratio A/F with reference to the acceleration stroke S so that the air-fuel ratio A/F1 is obtained at the max. acceleration stroke So, and thereafter the air-fuel ratio is controlled on the basis of this corrective curve.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a fuel system configured such that air-fuel ratio control can be performed by controlling the air flow rate to be supplied to the engine based on various engine information using an actuator operated by a computer. The present invention relates to an air-fuel ratio control method in a priority electronically controlled fuel supply system.

Conventionally, as a fuel priority type electronically controlled fuel supply system, for example, one disclosed in Japanese Patent Application Laid-Open No. 57-91343 is known, but this will be explained with reference to FIG.
12 is a throttle valve, 14 is an actuator of the throttle valve, 16 is a fuel supply mechanism, 18 is a fuel injection device, 20 is an accelerator pedal, 22 is an accelerator pedal 20
24 is a pressure sensor that detects the pressure upstream of the throttle valve 12, 26 is a pressure sensor that detects the pressure downstream of the throttle valve 12, 28 is a computer, and 30 is a rotation sensor.

9, when the engine speed is low, the actual effective accelerator stroke will be very small compared to the entire stroke. That is, the characteristics of the air flow rate QA when the throttle valve is fully open with respect to the engine speed N change as shown in FIG. 2, and at a relatively low engine speed N, the air flow rate becomes QAl.

At this time, the fuel supply amount QF is QR, which is given when the accelerator stroke S is 81. Thus, the air-fuel ratio A/
F is A/F 1 (= Q Al / Q F+)
Therefore, the A/F becomes substantially fully open with the accelerator stroke S, but even if the accelerator pedal 20 is further depressed, that is, from the accelerator stroke S to the maximum (So) i, A/F 1 is maintained ( Figure 4 dotted line). Therefore, the effective accelerator stroke S is from 0 to 81
This caused the accelerator feel to become sensitive and the fuel consumption to decrease due to over-depression of the accelerator pedal.

In view of the above points, it is an object of the present invention to provide an air-fuel ratio control method that effectively utilizes the entire accelerator stroke even at relatively low engine speeds to improve the accelerator feeling and improve fuel efficiency. The purpose is to use a fuel-priority electronic control system configured to perform air-fuel ratio control by controlling the air flow rate to be supplied to the engine based on various engine information using an actuator operated by a computer. In the fuel supply system, when the engine speed is relatively low, the air-fuel ratio is controlled so that the air-fuel ratio corresponding to the fully open state is obtained at the maximum accelerator stroke. This is achieved by a fuel ratio control method.

The air-fuel ratio control method according to the present invention will be explained below.The configuration of the fuel priority type electronically controlled fuel supply system itself is the conventional configuration shown in FIG. be done. Next, the air-fuel ratio control method will be explained with reference to the flowchart shown in FIG. When it is detected that the engine speed N is relatively low, that is, lower than a predetermined speed, the air-fuel ratio control method according to the present invention is started. First, the engine rotation speed N1 is detected by the rotation sensor 30, and the air flow rate QAl and fuel supply amount QF+ at this time are detected by the rotation sensor 30.
is calculated, the air-fuel ratio A/F1 is determined, and at the same time, the accelerator stroke S1 at this time is determined.

Next, the accelerator stroke S is determined based on the air-fuel ratio A, /Fl and the accelerator stroke S. At air-fuel ratio A/Fl
The air-fuel ratio A at the maximum accelerator stroke is
/F correction curve (solid line in Figure 4) is selected. Subsequently, the air-fuel ratio is controlled according to the engine state according to the correction curve.

As described above, according to the present invention, the structure of the fuel-priority type electronically controlled fuel supply system remains unchanged, but by changing the computer software, it is possible to adjust the engine speed to a fully open state when the engine speed is relatively low. Since the change in air-fuel ratio with respect to the accelerator stroke is controlled so that the fuel ratio is given at the maximum accelerator stroke, the entire accelerator stroke can be used effectively even at relatively low engine speeds, improving the accelerator feeling and improving fuel efficiency. This method is extremely effective, since it does not require any special equipment for this purpose, and there is almost no increase in cost.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a fuel priority type electronically controlled fuel supply system, Fig. 2 is a graph showing the relationship between engine speed N and full-open air flow rate QA, and Fig. 3 is a flowchart of the air-fuel ratio control method according to the present invention. , FIG. 4 is a graph showing air-fuel ratio control according to the method of the present invention. DESCRIPTION OF SYMBOLS 10... Engine, 12... Throttle valve, 14... Actuator, 16... Fuel supply mechanism, 18... Fuel injection device, 20... Accelerator pedal, 22... ...Position sensor, 24.26...
・・Pressure sensor, 28・・Computer, 30・
...Rotation sensor. Agent Yasushi Shinohara

Claims (1)

[Claims] In a fuel priority type electronically controlled fuel supply system configured to perform air-fuel ratio control by controlling the air flow rate to be supplied to the engine based on various engine information using an actuator operated by a computer,
An air-fuel ratio control method characterized by controlling changes in the air-fuel ratio with respect to the accelerator stroke so that an air-fuel ratio corresponding to a fully open state is given at the maximum accelerator stroke when the engine speed is relatively low.