GB2343427A

GB2343427A - Fuel tank assembly

Info

Publication number: GB2343427A
Application number: GB9824318A
Authority: GB
Inventors: Christopher John Bibby
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1998-11-06
Filing date: 1998-11-06
Publication date: 2000-05-10
Also published as: GB9824318D0

Abstract

A motor vehicle fuel tank assembly includes a fuel tank 11, a fuel filler neck 12 and a fuel filler pipe 14 connecting the filler neck to the tank. A breather pipe 17 connects an air space above the level of liquid fuel in the fuel tank to the filler neck. A breather valve 18 which provides the connection of the breather pipe 17 to the tank at the flange 16 of a tank module 15 includes a caged ball 28 which floats to close an aperture 31 when the tank is full.

Description

A Motor Vehicle Fuel Tank Assemblv The invention relates to fuel tank assemblies for motor vehicles. A typical fuel tank assembly on a motor vehicle comprises a fuel tank for the storage of liquid fuel, a fuel filler neck, a fuel filler pipe connecting the filler neck to the tank and a breather pipe connecting an air space above the level of liquid fuel in the fuel tank to the filler neck. During refilling a nozzle of the fuel pump of a fuel filling station is inserted into the filler neck so that fuel flows down the filler pipe and air from the air space is displaced through the breather pipe.

A problem in use of a fuel tank assembly of the kind described above is that under certain conditions liquid can flow up the breather pipe and escape from the filler neck before the cut-off mechanism in the petrol station fuel pump can take effect. The present invention aims to overcome this problem.

According to the invention there is provided a fuel tank assembly of the kind described in which breather valve is provided for impeding the flow of air from the air space through the breather pipe when the level of fuel in the fuel tank reaches a full level during refilling.

Conveniently the breather valve comprises a float which can in use float on the fuel and operate to close an aperture connecting the air space to the breather pipe, in which case the float may comprise a ball which also acts as a valve member to directly close the aperture.

However, the breather valve-may comprise a valve member in a restricted passage connecting the air space to the breather pipe, the valve member being moved during refilling of the tank onto a valve seat by the flow of liquid fuel in the passage but not movable by the flow of air from the air space.

The invention will now be described by way of example and with reference to the accompanying drawings, in which :- Fig. 1 is a perspective view of a fuel tank assembly for a motor vehicle according to the invention; and Fig. 2 is a partial cross-section of a part of the assembly as shown in Fig. 1.

The fuel tank assembly includes a fuel tank 11 which is supported on the body or chassis of a motor vehicle (not shown). A fuel filler neck 12 is positioned so that a filler orifice which is normally closed by a filler cap 13 is positioned on the outside of a vehicle where it is accessible for the replenishment of fuel at a fuel filling station. A fuel filler pipe 14 connects the filler neck 12 to the fuel tank 11.

A tank module 15 is supported by a circular flange 16 in an aperture in the roof of the fuel tank 11. The module 15 includes an electric fuel pump and a level sensor for a fuel level gauge. A breather pipe 17 is connected to the filler neck 12 and to a breather valve 18 on the tank module flange 16. A fuel feed pipe 19 is also connected to the flange 16 and delivers fuel from the pump/tank module 15 to an injector rail 21. A vent pipe 22 vents the tank to the filler neck 12 from where a further vent pipe 23 can vent through a charcoal filter 24 to an engine inlet manifold 25.

The breather valve 18 includes a pipe elbow 20 which is flared outwardly below the flange 16 to form a frusto-conical valve seat 26. Four legs 27 extend downwardly from the valve seat 26 to guide and support a ball 28, the lower end 29 of each leg 27 being an inwardly directed to capture the ball.

In normal use of the vehicle the ball 28 rests on the lower ends 29 of the legs 27. During re-fuelling of the vehicle at a filling station, the filler cap 13 is removed and fuel from the filler nozzle enters the tank through the filler neck 12 and the filler pipe 14. As the level of fuel in the tank 11 rises, air above the liquid level is displaced past the ball 28, through the breather valve 18 and the breather pipe 17 and out to atmosphere at the filler neck 12. When the fuel level is near to the top of the tank 11 the ball 28 floats on the liquid surface and rises onto the valve seat 26 to seal the aperture 31. This prevents fuel rising suddenly through the breather pipe 17 and out through the filler neck 12. This is particularly useful where the tank 11 is made of a plastics material. In these circumstances the change in temperature and loading on the tank walls during filling can produce sudden surges of flow in the breather pipe 17 which the normal cut-off in the fuel filler pump cannot react to.

A small orifice 32 is provided in the pipe elbow 20 between the aperture 31 and the flange 16 to allow equalisation of pressures after the ball 28 has seated.

In a modification (not shown) the legs 27 are replaced by a cylindrical section to form a restricted passage so that air escaping into the breather pipe 17 has to flow through the restricted passage between the cylindrical section and the ball 28.

In this modified arrangement it may not be necessary for the ball 28 to be lighter than the fuel and actually float on the liquid surface. The flow of air in the restricted passage is normally insufficient to lift the ball onto the valve seat 26 but when liquid fuel flows through the passage the drag on the ball 28 increases, thereby lifting it to seal the aperture 31. This is assisted by the apparent weight loss due to the volume of fuel displaced by the ball 28 (Archimedes principle).

In a further modification (not shown) the ball 28 is replaced by a float on a hinged arm, the arm also carrying a valve member which can seat against the aperture 31. Both types of breather valve (ball or hinged float) may be mounted directly onto the tank-top surface instead of on the module flange 16.

Claims

CLAIMS 1. A fuel tank assembly for a motor vehicle, and including a fuel tank for the storage of liquid fuel, a fuel filler neck, a fuel filler pipe connecting the filler neck to the tank, a breather pipe connecting an air space above the level of liquid fuel in the fuel tank to the filler neck and a breather valve for impeding the flow of air from the air space through the breather pipe when the level of fuel in the fuel tank reaches a full level during refilling.
2. An assembly according to Claim 1 wherein the breather valve comprises a float which can in use float on the fuel and operate to close an aperture connecting the air space to the breather pipe.
3. An assembly according to Claim 2 wherein the float comprises a ball which also acts as a valve member to directly close the aperture.
4. An assembly according to any preceding claim wherein the breather valve comprises a valve member in a restricted passage connecting the air space to the breather pipe, the valve member being moved during refilling of the tank onto a valve seat by the flow of liquid fuel in the passage but not movable by the flow of air from the air space.
5. A fuel tank assembly substantially as described herein with reference to the accompanying drawings.