JPH1182082A - Fuel supply system for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel supply system that offers stable higher power even when using liquid or gaseous fuel. SOLUTION: A fuel supply system for an engine uses a gas mixer 16 arranged in an intake duct connected to a combustion chamber, and a liquid-fuel injection nozzle situated in the intake system on the downstream side of the mixer 16 in relation to the intake flow direction. The mixer 16 includes a choke valve 24 and a throttle valve 25 arranged from the upstream side in this order in relation to the intake flow direction to thus define an intake passage 23 with no constrictions between these valves 24 and 25. This intake passage 23 is formed with a gaseous-fuel supply port 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device for an engine, and more particularly to a fuel supply device for a spark ignition type engine that selectively supplies liquid fuel and gas fuel.

[0002]

2. Description of the Related Art As a prior art of a fuel supply apparatus for supplying a liquid fuel and a gas fuel to a spark ignition type engine, a gas mixer and a carburetor are arranged in series in an intake passage of the engine, and the gas mixer and the gas mixer are arranged in series. There is one that selectively uses a vaporizer.

[0003]

However, in the prior art described above, a venturi passage is formed in an intake passage in a carburetor and a gas mixer, and a liquid fuel nozzle is provided in a venturi portion of the carburetor and a gas mixer of the gas mixer. The gas supply nozzles are arranged in the venturi section with each of them facing the venturi passage. For this reason, the above-mentioned prior art has the following problems. a. Since the venturi passage of the carburetor and the venturi passage of the gas mixer are arranged in series, the intake resistance increases due to the two-stage throttle resistance, and the charging efficiency of the intake decreases, and the output decreases. b. Because the gas mixer is located upstream of the intake of the carburetor,
Turbulence occurs in the intake air flow introduced into the venturi passage of the carburetor, and the metering accuracy of the liquid fuel decreases. c. Since a vaporizer and a gas mixer are used, the size of the apparatus is increased.

Therefore, in order to solve the above-mentioned problem, it is conceivable to omit the carburetor and to inject the liquid fuel into the intake air flow. However, even in this case, it is necessary to adopt a configuration in which the gas fuel is sucked out by the negative pressure generated by the intake air flow and the intake air and the fuel gas are mixed, so that a venturi portion is formed in the intake passage of the gas mixer. become.

As a result, during operation of the engine using liquid fuel, there is a problem that the output of the engine is reduced due to the presence of the venturi portion in the intake passage, and when the engine is operated using gas fuel. The gas engine has a problem that an unnecessary choke valve remains.

It is an object of the present invention to provide a fuel supply device capable of obtaining a stable high output even when using liquid fuel or gas fuel. I do.

[0007]

In order to solve the above-mentioned problems, the present invention selectively supplies a mixture of injected liquid fuel and intake air and a mixture of gas fuel and intake air to a combustion chamber. In the fuel supply device for a low-pressure injection spark ignition engine configured as described above, the gas mixer is disposed in the intake passage formed so as to be in communication with the combustion chamber, and the intake air is disposed at a position higher than the gas mixer. The liquid fuel injection nozzle is arranged in the intake system on the downstream side in the flow direction of the gas, the choke valve and the throttle valve are arranged in the gas mixer in order from the upstream in the flow direction of the intake air, and the space between the choke valve and the throttle valve is restricted. The gas fuel supply port is formed in a passage portion between the choke valve and the throttle valve.

[0008]

According to the present invention, a choke valve is arranged together with a throttle valve in a gas mixer disposed in an intake passage of an engine, and a space between the choke valve and the throttle valve is formed by a passage having no throttle. Since the gas fuel supply port is opened in the passage between the choke valve and the throttle valve, when operating as a gas engine,
By operating the choke valve so as to close it, a negative pressure region is formed downstream of the choke valve, so this choke valve acts as a substitute for the venturi section and generates an appropriate negative pressure in the gas mixer. Then, the gaseous fuel can be sucked to generate an air-fuel mixture. Also, at the time of low-temperature start or the like in the case of operating as a liquid fuel injection engine, the choke valve can function as a suppressor of the intake air amount similarly to the choke valve in the engine with a carburetor. Thus, it is possible to provide a fuel supply device that can be used for both a gas fuel engine and a liquid fuel injection engine.

[0009]

Embodiments of the present invention will be described with reference to the drawings. 1 and 2 are views for explaining a spark ignition engine according to an embodiment of the present invention. The structure of this engine is as follows. That is, the cylinder block
A cylinder head (2) is assembled on the upper side of (1), and the cylinder head (2) has an intake port (3) and an exhaust port.
(4) is drawn out in the opposite direction, and a spark plug (6) is mounted facing the combustion chamber (5) of the engine.

The intake port (3) has an intake manifold (7).
A fuel injection nozzle (8) is arranged in the intake manifold (7) with its injection direction facing the intake port (3). (9) is connected for communication. This liquid fuel supply path (9)
Is a fuel tank storing liquid fuel such as gasoline (10)
And the above-mentioned fuel injection nozzle (8). The fuel filter (11), the flow path cutoff valve (12), the fuel pressurizing pump (13)
Are arranged in order from the fuel tank (10) side.

On the other hand, an air cleaner (15) and an air-fuel mixer (gas mixer) (16) are arranged in an air intake passage (14) connected to the air intake manifold (7). The mixer (16) is connected to a gas fuel container (20) storing gaseous fuel such as LP gas through a gas fuel supply line (19) interposed with a flow path shutoff valve (17) and a zero governor (18). It is.

Then, the flow path shut-off valve (12) provided in the liquid fuel supply path (9) and the flow path cut-off valve (17) provided in the gas fuel supply path (19) are selectively opened. By operating, a state of operating by injecting liquid fuel and a state of operating by sucking and mixing gaseous fuel are selected. In the figure, the symbol (2
1) is a control device for controlling the opening and closing of both flow path shutoff valves (12) and (17).

As shown in FIG. 2, the air-fuel mixer (16) has an intake passage (23) formed through a main body (22).
A choke valve (24) is attached to a portion near one end and a throttle valve (25) is attached to a portion near the other end so that the opening amount can be adjusted, and a choke valve (24) and a throttle valve (25) are provided between the choke valve (24) and the throttle valve (25). A gas fuel supply port (26) is formed so as to open toward the intake passage (23).

The intake passage (23) in the air-fuel mixer (16)
Is formed so as to maintain a uniform flow path cross-sectional area as a whole except that the choke valve (24) and the throttle valve (25) are provided, and there is no so-called venturi portion (throttle portion) provided. .

In the air-fuel mixer (16) configured as described above,
When the engine is operated using gas fuel, the flow path shutoff valve (12) interposed in the liquid fuel supply path (9) is closed, and the flow interposed in the gas fuel supply path (19) is closed. Road isolation valve (17)
The gas fuel regulated by the zero governor (18) is sucked into the intake passage (23) from the gas fuel supply port (26) facing the intake passage (23) of the air-fuel mixer (16), and The air is mixed with the suction air flowing in the passage (23) and supplied to the combustion chamber of the engine from the intake manifold (7).

At this time, the throttle valve (25) is controlled to open and close so as to adjust the flow rate of the air-fuel mixture. On the other hand, the choke valve (24) is closed in a state in which the choke valve (24) is in a half-open position, thereby forming a negative pressure region in a downstream portion of the choke valve (24). That is, when the engine is operated using gas fuel, the choke valve (24) acts as a substitute for the venturi section.

When the engine is operated using liquid fuel, a flow path shut-off valve (17) interposed in a gas fuel supply path (19)
Is closed, and the flow path shutoff valve (12) interposed in the liquid fuel supply path (9) is opened to use the air-fuel mixer (16) as a passage for intake air. In this case, the opening and closing of the throttle valve (25) is controlled to adjust the intake air amount, and the choke valve (2) is controlled.
4) is fully open. As described above, since there is no so-called throttle portion in the intake system, the output performance of the fuel injection engine can be exhibited.
If a richer mixture than the air-fuel ratio controlled in the normal operation state is required, such as during cold start, the choke valve
By performing the valve closing operation of (24), it is possible to function as a normal choke valve.

In the above embodiment, the liquid fuel system and the gas fuel system are always connected and the liquid fuel and the gas fuel are selectively used. However, as shown in FIG. A sealing plug (27) is selectively screwed into a main body part forming a gas fuel supply port (26) and a connecting fitting (28) fixed to the tip of a gas fuel supply path (19). It may be.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an intake system of an engine.

FIG. 2 is a longitudinal sectional view of the air-fuel mixer.

[Explanation of symbols]

5: combustion chamber, 8: liquid fuel injection nozzle, 14: intake passage, 16: gas mixer, 23: intake passage, 24: choke valve, 25: throttle valve, 26: gas fuel supply port.

Claims (1)

[Claims] 1. A fuel supply for a low-pressure injection spark ignition engine configured to selectively supply a mixture of injected liquid fuel and intake air and a mixture of gas fuel and intake air to a combustion chamber of the engine. In the apparatus, an intake air introduction passage formed in a state communicating with the combustion chamber (5)
A gas mixer (16) is arranged in (14), and a liquid fuel injection nozzle (8) is arranged in the intake system on the downstream side in the flow direction of the intake air from the place where the gas mixer (16) is arranged. The choke valve (24) and the throttle valve (25) are arranged in the mixer (16) in order from the upstream side in the flow direction of the intake air.
Between the (24) and the throttle valve (25)
(23), this choke valve (24) and throttle valve (25)
A fuel supply device for an engine, characterized in that a gas fuel supply port (26) is opened in a portion of an intake passage (23) between the fuel supply device and the engine.