JPS61178221A - Evaporating fuel emission preventer for vehicles including motorcycle and the like - Google Patents

Abstract

PURPOSE:To smooth the feed of fuel of fuel to an engine as well as keep the adsorption function of a canister ever so better, by installing a valve, which opens with suction pressure inside a fuel tank and leads fresh air inside, in a midway part of an interconnecting pipe interconnecting the canister and an upper part of the fuel tank inside. CONSTITUTION:The upper end side of a canister preventing evaporating fuel from being emitted in the air and a fuel tank are interconnected through an interconnecting pipe 18, and a roll-over valve 20 is installed in the midway part. In this case, a fresh-air intake valve 21 is installed in the interconnecting pipe 18 lying between the valve 20 and the canister 15. When ventilating resistance in the canister 15 grows large and suction pressure inside the fuel tank 9 comes high, the valve 21 is opened by differential pressure between atmospheric pressure and the suction pressure inside the furl tank 9. Therefore, fresh air is led into an upper part of the inside of the fuel tank 9 so that pressure inside the furl tank 9 is nearly maintained in the atmospheric pressure. In addition, evaporating fuel inside the interconnecting pipe 18 is put back to the inside of the fuel tank 9 by the fresh air being led out of the valve 21, thus liquefaction is obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a device for preventing evaporated fuel from dissipating from a fuel tank of a vehicle such as a motorcycle.

(Prior art) Fuel for vehicles such as motorcycles is generally stored in a fuel tank, but since this fuel is volatile, when the outside air is hot, such as in the summer, it evaporates inside the fuel tank and releases it into the atmosphere. There is a risk of radiation.

Therefore, devices for preventing this radiation have been proposed, and these devices are configured as follows, for example.

That is, a canister is provided that has an adsorption layer that can adsorb and release evaporated fuel. When the engine takes in outside air through this adsorption layer as part of its intake air, the adsorbed fuel is separated and taken into the engine (for example, Japanese Utility Model Publication No. 58-55103).

(Problem to be Solved by the Invention) By the way, when the amount of evaporated fuel adsorbed in the canister increases and the ventilation resistance in the canister increases, fuel is supplied by flowing down from the fuel tank to the engine to cope with this. When introducing the atmosphere into the fuel tank through the adsorption layer, the introduction of the atmosphere through the adsorption layer is inhibited, and the negative pressure within the fuel tank becomes high. As a result, a problem arises in that the smooth supply of fuel from the fuel tank to the engine is obstructed by the negative pressure.

Further, as described above, when the ventilation resistance in the adsorption layer becomes large, the air circulation in the communication pipe that communicates the canister and the upper part of the fuel tank becomes poor, and there is a risk that the evaporated fuel will remain and liquefy. In this case, if the liquefied fuel flows directly into the canister, the adsorption function will be impaired.

(Purpose of the Invention) This invention has been made in view of the above-mentioned circumstances, and is intended for vehicles such as motorcycles that are equipped with a canister that adsorbs and detaches evaporated fuel from the fuel tank. Avoid negative pressure as much as possible so that the fuel in this fuel tank can be smoothly supplied to the engine.
Moreover, the purpose is to maintain the suction function of the canister well.

(Structure of the Invention) A feature of the present invention for achieving the above object is that the communication pipe has a valve opening in the middle part of the communication pipe that communicates the canister and the upper part of the fuel tank with the negative pressure inside the fuel tank. The main feature is that an outside air intake valve is provided to introduce atmospheric air into the fuel tank through the fuel tank.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

A motorcycle 1 has a front wheel 4 supported at the front of a body frame 2 via a front fork 3, and a rear wheel 5 supported at the rear of the body frame 2.

Further, an engine 7 is installed within the frame of the vehicle body frame 2, and the rear wheels 5 are driven by the engine 7.

A carburetor 8 is connected to the intake side of the engine 7, and an air cleaner 8a is further connected to the carburetor 8. Further, a fuel tank 9 is supported on the upper part of the vehicle body frame 2. 11 is a fuel injection cap, and 9a is the liquid level of the injected fuel. The lower part of the fuel tank 9 and the float chamber of the carburetor 8 are connected by a fuel supply pipe 13,
Fuel in the fuel tank 9 is supplied to the carburetor 8 by gravity flow.

On the other hand, a canister 15 is provided below the fuel tank 9 to prevent the vaporized fuel in the fuel tank 9 from dissipating into the atmosphere. The canister 15 is made of activated carbon or the like, and has an adsorption layer that adsorbs and detaches evaporated fuel. The canister 15 partitioned by this adsorption layer
The lower end side is communicated with the atmosphere via a conduit 16.

Further, the upper end side of the canister 15 and the venturi portion of the carburetor 8 are connected through a suction pipe 17. Further, the upper end side of the canister 15 and the fuel tank 9 are connected by a communication pipe 18.

The upper end of the communication pipe 18 is opened at the upper part of the fuel tank 9, and automatically prevents the fuel in the fuel tank 9 from flowing out toward the carburetor 8 or the canister 15, for example, when the motorcycle l rolls over. A rollover valve 20 for preventing rollover is installed in the middle of the communication pipe 18.

An outside air introduction valve 21 is provided in the communication pipe 18 between the rollover valve 20 and the canister 15. This outside air introduction valve 21 is opened by negative pressure in the fuel tank 9, and allows outside air to be introduced into the fuel tank 9 through the communication pipe 18, and is constructed as follows.

That is, a circular pipe 22 is interposed in the middle of the communication pipe 18. A through hole 22a is formed in the lower surface of this circular pipe 22, and a valve box 23 is attached so as to cover this through hole 22a. Further, a valve hole 24 is formed on the lower surface of the valve box 23, and a valve body 25 that elastically closes the valve hole 24 via a spring 26 is provided.

(for production) Next, the effect of the above configuration will be explained.

When the ventilation resistance of the canister 15 becomes large and the negative pressure inside the fuel tank 9 becomes high, for example, to about 50 mm of water column, the elastic force of the spring 269 is resisted due to the differential pressure between the atmospheric pressure and the pressure inside the fuel tank 9. The valve body 25 is pushed upward (arrow A in FIG. 2). As a result, the valve hole 24 is opened, and outside air is introduced into the second part of the fuel tank 9 through the valve hole 24 and the through hole 22a, and the pressure inside the fuel tank 9, which had been at negative pressure, is reduced to approximately atmospheric pressure. It is said that

In addition, the outside air introduced from this outside air introduction valve 21 causes
The evaporated fuel remaining in the communication pipe 18 is pushed back into the fuel tank 9, and liquefaction of the evaporated fuel within the communication pipe 18 is prevented.

(Effects of the Invention) According to the present invention, an outside air introduction valve is provided in the middle part of the communication pipe that communicates the canister and the two parts inside the fuel tank, so that the outside air is introduced when the valve is opened by the negative pressure inside the fuel tank. When the pressure inside the fuel tank becomes negative, outside air is introduced into the fuel tank through the outside air intake valve, thereby keeping the pressure inside the fuel tank at approximately atmospheric pressure at all times. Therefore, negative pressure in the fuel tank is prevented, and fuel is smoothly supplied to the engine.

Moreover, in this case, by introducing outside air into the communication pipe that communicates the canister and the upper part of the fuel tank, it is possible to improve the air circulation within the communication pipe, so that the evaporated fuel liquefies in the communication pipe and flows into the canister. is prevented from doing so. Therefore, the adsorption function of the canister can be maintained well.

[Brief explanation of the drawing]

The drawings show an embodiment of the invention, with FIG. 1 being a partially omitted side view of a motorcycle, and FIG. 2 being an enlarged sectional view of the main part in FIG. 1. 1--Motorcycle, 7--Engine, 9--Fuel tank, 15--Canister, 18--Communication pipe, 21--Outside air introduction valve.

Claims (1)

[Claims] 1. Equipped with an engine and a fuel tank that supplies fuel to the engine, a canister is provided that has an adsorption layer that adsorbs and freely removes evaporated fuel, and one end of the canister that is partitioned by this adsorption layer is exposed to the atmosphere. In a vehicle such as a motorcycle in which the other end of the canister is connected to the intake side of the engine and the upper part of the fuel tank, the canister is connected to the upper part of the fuel tank in the middle part of the communication pipe. A vaporized fuel diffusion prevention device for a vehicle such as a motorcycle, characterized by being provided with an outside air introduction valve that opens due to negative pressure in the fuel tank and introduces outside air into the fuel tank through the communication pipe.