GB2252300A

GB2252300A - A fuel tank

Info

Publication number: GB2252300A
Application number: GB9101996A
Authority: GB
Inventors: David Thomas Bowles
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1991-01-30
Filing date: 1991-01-30
Publication date: 1992-08-05
Also published as: GB9101996D0

Abstract

A fuel tank 10 has a sensing tube 14 which allows the venting of air from the upper part of the tank whilst the tank is being filled. The sensing tube runs internally of the tank to a position close to the top of the tank to allow air to be vented and substantially the whole of the tank interior to be filled. <IMAGE>

Description

A FUEL TANK This invention relates to a fuel tank, particularly a fuel tank for use in a motor vehicle.

In order for a fuel tank to provide the greatest possible fuel volume, it is often necessary for the tank itself to be of a complex shape so that it can be packaged, along with other chassis components, underneath the vehicle whilst having the maximum possible internal volume.

It may be impossible for the fuel inlet pipe, through which fuel is charged to the tank during refuelling, to be located at the highest point of the tank. In order to avoid a large volume of air being trapped in the top of the tank and thereby preventing complete filling of the tank, it is known to provide a sensing tube which provides an air vent from a position close to the top of the tank and determines the maximium level to which the tank can be filled.

According to the present invention, there is provided a fuel tank having a cavity for containing fuel, a fuel inlet pipe leading into the cavity at a point below the top of the cavity, and an auxiliary pipe which enters the cavity at a point below the top of the cavity and which extends within the cavity to a position close to the top of the cavity, which position is above the point at which the auxiliary pipe enters the cavity.

This construction with the sensing tube passing within the cavity ensures that there are a minimum of external pipes connected to the tank, and this facilitates the fitting of the tank in a vehicle.

In a preferred embodiment, the sensing tube has a vent in its lowermost part, and a float valve which can be lifted to close the vent. As a result of this feature, any liquid fuel which accumulates in the sensing tube will drain whenever the fuel level in the tank drops below the level of the float valve.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a motor vehicle fuel tank; Figure 2 is a cross section through the tank of Figure 1, with a type of sensing tube in accordance with the prior art; and Figures 3, 4 and 5 are all cross sections through a fuel tank in accordance with the invention, showing three different stages of operation.

In Figure 1, the fuel tank 10 has an inlet pipe 12 and a sensing tube 14. The pipe 12 will be closed by a conventional fuel filler cap of any known design, and the sensing tube 14 leads into the pipe 12 close to the upper end of the pipe.

It will be seen from Figure 1 that the tank shown is bigger on one side than the other.

Looking now at Figure 2, it will be seen that as fuel is poured into the tank through the inlet pipe 12, a position will be reached (indicated by the dotted line 16) at which fuel can only continue to flow into the tank if the air in the otherwise closed top of the tank is vented. This air is in fact vented through the sensing tube 14, so that the fuel level can continue to rise until the sensing tube 14 is also blocked by the fuel level and air can no longer escape. This leaves the unsatisfactory situation shown in Figure 2 where the large internal volume 18 cannot be filled with fuel because it contains a volume of trapped air.

In order to overcome this problem, the sensing tube is extended within the tank at 14a and 14b as shown in Figure 3. Figure 3 shows the tank before any fuel has been poured into it. It will be seen that at the junction between the parts 14a and 14b of the sensing tube, a float valve 20 is fitted. In the situation shown in Figure 3, where the tank is empty, the float of the valve 20 will fall thereby opening a vent passage 22 which is located at the lowermost point of the sensing tube 14.

As fuel is poured into the tank, and reaches the level of the float valve 20, the float will rise up to close the vent passage 22 before any fuel enters the tube section 14a. As the tank is filled above the level 16, the air will be vented from the upper space of the tank via the tube sections 14b and 14a. This venting will continue as the fuel level rises to the level 24 indicated in Figure 4.

At this point the opening of the sensing tube section 14b is closed by the surface of the fuel, and the position of this tube section 14b will be determined so that a predetermined ullage space 26 is maintained in the tank for the purposes of allowing fuel expansion.

If fuel were to flow into the sensing tube 14 as a result for example of the motion of the vehicle in which the tank is mounted, then it could happen that the sensing tube itself could be blocked so that it would not operate in the manner described to allow the tank to be completely filled.

However when the fuel level in the tank falls, as it will during operation, to the position shown in Figure 5, then the float 20 drops and any fuel which may have accumulated in the sensing pipe 14 will drain back into the tank.

The arrangement of sensing tube described here allows maximum utilisation of the internal tank space without the need for any external hoses surrounding the tank. Such external hoses can require a number of connections to be made around other chassis members, all the connections being possible leak sites.

Claims

1. A fuel tank having a cavity for containing fuel, a fuel inlet pipe leading into the cavity at a point below the cavity, and an auxiliary pipe which enters the cavity at a point below the top of the cavity and which extends within the cavity to a position close to the top of the cavity, which position is above the point at which the auxiliary pipe enters the cavity.

2. A fuel tank as claimed in Claim 1, wherein the auxiliary pipe has a closeable vent passage close to its lowest point.

3. A fuel tank as claimed in Claim 2, wherein the vent passage is closed by a float valve which operates to close the passage when the fuel level in the tank is sufficiently high, and operates to open the vent passage when the fuel level drops below that height.

4. A fuel tank for a motor vehicle substantially as herein described with reference to and as shown in Figures 3, 4 and 5 of the accompanying drawings.