JPS6299646A - Air-fuel ratio controlling method for engine - Google Patents

Abstract

PURPOSE:To perform air-fuel ratio control in an extensive control range in a stable manner, by reducing a rate in a fundamental supply of fuel at a specified driving range, while increasing a rate of compensation fuel, and increasing the control allotment of a control valve. CONSTITUTION:Fuel delivered to a suction passage 7 from a nozzle 6 is mixed with air and fed to an engine 12. Each electric signal out of sensors 15-19 detecting a driving state of the engine 12 is inputted into a control unit 9, and the proper driving signal calculated on the basis of these information data is fed to a control valve 10. The control unit 9 reduces a rate of a fundamental supply in a fuel flow rate to be demanded at a driving zone where a suction air quantity of the engine is little, while it increases a rate of compensation fuel, and control allotment of the control valve 10 is increased. Thus, air-fuel ratio control is performable in an extensive control range so stable enough.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the air-fuel ratio of an engine, particularly in an operating range where the amount of intake air is small, and is used as a power source for automobiles, work vehicles, industrial machinery, etc. Used for engine air-fuel ratio control.

Technology that detects engine operating conditions and controls the air-fuel ratio using a feedback method is widely known. In addition to air, a predetermined air-fuel ratio is used.

Here, a jet for setting the basic supply amount is provided in the fuel passage opening into the intake passage.

A correction fuel passage having a control valve is provided, and the control valve is opened and closed by a drive signal sent from an electronic control unit, thereby controlling the flow rate of the correction fuel so that a desired air-fuel ratio can be obtained. It is used in the fuel system of engines that use

That is, as shown in a part of FIG. 1 showing an embodiment of the present invention, LPG in a pressure container 1 is depressurized to about atmospheric pressure by a vaporizer 2, and a fuel passage 4 having a jet 3 is passed through a venturi. A correction fuel passage 8 is provided in the fuel passage 4 and is supplied to the intake passage 7 from a slit-shaped nozzle 6 formed in the fuel passage 5 and bypasses the jet 3, and is opened and closed by a drive signal sent from an electronic control unit 9. The flow rate of the correction fuel is controlled by the control valve lO.

Jet 3 sets the basic supply amount of LPG, which is fuel, and supplies a lean air-fuel mixture to the engine.
The %lIJ control valve 10 corrects the fuel and supplies the engine with an air-fuel mixture at the stoichiometric air-fuel ratio or higher concentration.

However, during engine idling operation and low-speed operation when the opening degree of the throttle valve 110 in the intake passage 7 is small, the amount of intake air is small (the fuel flow rate required by the engine is also small, so the correction fuel is controlled in an extremely small flow rate range). As a result, the opening/closing operation of the control valve IO is controlled with a small opening degree or a small valve opening time, which not only tends to become unstable, but also causes the problem that the air-fuel ratio control width cannot be widened. When the fuel flow rate fluctuates due to changes in each component over time, there is also the problem that control to an appropriate air-fuel ratio is not performed effectively in an operating range where the amount of intake air is small for the same reason as described above.

As described above, the present invention provides a fuel system that includes, in addition to a fuel passage for setting the basic supply amount of fuel, a correction fuel passage having a control valve that opens and closes in response to a drive signal sent from a preset control unit. It is an object of the present invention to provide a method that can perform air-fuel ratio control stably and appropriately over a wide control range in an operating range where the amount of intake air is small.

Components of the Invention The present invention provides a fuel system for controlling an engine using a fuel system that includes, in addition to a fuel passage that sets the basic supply amount of fuel, a correction fuel passage that has a control valve that opens and closes in response to a drive signal sent from an electronic control unit. Perform air fuel ratio control and reach 5.

The ratio of the basic supply amount to the fuel flow rate required in the operating range where the intake air amount of the engine is small is reduced, and the ratio of the correction fuel is increased, thereby increasing the control portion of the control valve.

Embodiment 1 The first embodiment of the present invention will be explained based on FIG. 1.2. The parts indicated by reference numerals 1 to 11 in FIG. The fuel sent to the intake passage 7 is mixed with air and supplied to the engine 12, and the exhaust gas is purified by the catalytic converter 14 in the exhaust passage 13 and discharged to the atmosphere.

The control unit 9 includes a position sensor 15 for the throttle valve 11 and a pressure sensor 16 provided in the intake passage 7. Engine 12 rotational speed sensor 17 and temperature sensor 18. An oxygen sensor 19 provided in the exhaust passage 13 further receives electrical signals from sensors (not shown) for detecting the operating state of the engine 12, such as intake air temperature, an ignition switch, a brake valve, and other sensors provided as necessary. , an appropriate drive signal calculated based on this information is sent to the control valve 10. The control valve 10 is composed of an electromagnetic valve that opens and closes at a duty ratio determined by a drive signal consisting of a pulse wave.

The jet 3 of the fuel passage 4 has a small hole 20 as shown in FIG.
The shutoff valve 21 is connected to the diaphragm 23 of the negative pressure drive mechanism 22 by a connecting rod 24, and when a certain level of negative pressure is introduced into the negative pressure chamber 25, the diaphragm closes. 23 is sucked to block the jet 3, but otherwise the spring 2
It is separated from jet 3 by an elastic force of 6.

The negative pressure chamber 25 is communicated with either the slightly downstream side of the throttle valve 11 in the closed position of the intake path 7 and the manifold portion by means of a directional control valve 27 and an idle correction negative pressure path 28 and a normal negative pressure path 29.

When the engine 12 is idling and the throttle valve 11 is slightly open, the direction control valve 27 communicates the idle correction negative pressure path 28 with the negative pressure chamber 25 in response to a drive signal from the control unit 9. Negative pressure is diaphragm 2
3, the shutoff valve 21 closes the jet 3 and closes the small hole 2.
A small amount of fuel will now flow through 0. At this time, the control valve 10 opens and closes with a large duty value to control the fuel flow rate.

When the opening degree of the throttle valve 11 increases and the negative pressure on the upstream side of the throttle valve 11 reaches (6) (5) in the negative pressure path 28, the negative pressure introduced into the negative pressure chamber 25 rapidly decreases. However, the cutoff valve 21 moves away from the jet 3 and the basic supply amount of fuel metered by the jet 3 comes to flow, and at this time, the control valve 10 becomes 5 so as to perform the original correction fuel flow rate control. The control valve 27 operates the cutoff valve 21 by communicating the normal negative pressure path 29 with the negative pressure chamber 25 as necessary, and supplying fuel only from the small hole 2o during deceleration, for example.

FIG. 3 shows a second embodiment of the present invention, in which an auxiliary fuel passage 28 is provided in the fuel passage 4 leading from the vaporizer 2 to the nozzle 6 of the venturi 5, bypassing the jet 3, and further upstream thereof. A correction fuel passage 29 branched from the nozzle 6 is connected to the nozzle 6. The auxiliary fuel passage 28 is provided with a flow control valve 31 having a jet 30, and the control valve 10 of the correction fuel passage 29 and the flow control valve 31 are controlled by drive signals sent from the control unit 9, respectively. be made to work. Since the configuration other than the above is the same as that in FIG. 1, the explanation will be omitted.

During idle operation of the engine and in an operating range where the opening degree of the throttle valve 11 is small, the flow rate control valve 31 blocks the auxiliary fuel passage 28, and a small amount of fuel flows through the jet 3 whose effective cross-sectional area is set small. At this time, the control valve 10 opens and closes with a large duty value to control the fuel flow rate.

When the opening degree of the throttle valve 110 increases, the flow rate control valve 31 opens the auxiliary fuel passage 28 and the jet 30 also measures fuel, so that the basic supply amount of fuel measured in 3.30 When supplied, the control valve IO performs the original correction/fuel flow rate control.

In the above two embodiments, when the engine intake negative pressure is above a certain value or when the engine speed is below a certain value, the control valve 10 opens and closes at the commanded duty value to reach the stoichiometric air-fuel ratio. , when the suction negative pressure is below a certain value or when the rotational speed is above a certain value, the control valve 10 is kept closed and a lean air-fuel mixture is supplied to the engine 12 using the fuel measured in step 3.30. do. Also, acceleration and deceleration, low temperature.

Correction for high output, etc. is performed by opening/closing the control valve 10, jet 3
Of course, this is done by opening and closing the auxiliary fuel passage 28.

However, it is needless to say that the present invention is applicable not only to gaseous fuels such as LPG but also to fuel systems that handle liquid fuels.

Effects of the Invention According to the present invention, during engine idling operation and low-speed operation with a small throttle valve opening, the ratio of the basic supply amount by the fuel passage to the required fuel flow rate is reduced, and the ratio of corrected fuel supplied by the correction fuel passage is reduced. Since this increases the control amount of the control valve, the control valve must be controlled with a relatively large opening or a large duty value for a valve opening time, which enables stable control over a wide air-fuel ratio range. In addition, even if the fuel flow rate fluctuates due to changes in each part of the fuel system over time, it is easy to correct it with the control valve, and the air-fuel ratio can be controlled in regions where the amount of intake air is small. It can be done properly.

[Brief explanation of drawings]

Fig. 1 is a layout diagram showing a first embodiment of the present invention, Fig. 2 is a detailed view showing the jet and a shutoff valve, and Fig. 3 is a layout diagram showing a second embodiment of the invention. It is. 3.30...Jet, 4...Fuel passage, 7...Intake passage, 8.29...Correction fuel passage, 9...・Sharpening unit, 10...
...Control valve, 11... Throttle valve. 12...Engine, 21...Shutoff valve,
28... 1 auxiliary fuel route.・λ

Claims (1)

[Claims] In addition to the fuel passage that sets the basic supply amount of fuel, the fuel system includes a correction fuel passage that has a control valve that opens and closes in response to a drive signal sent from an electronic control unit. When controlling the air-fuel ratio of the engine, the ratio of the basic supply amount is decreased and the ratio of the correction fuel is increased within the fuel flow rate required in the operating region where the intake air amount of the engine is small, and the control portion of the control valve is An air-fuel ratio control method characterized by increasing.