GB2107659A

GB2107659A - Fuel tank for motor vehicles

Info

Publication number: GB2107659A
Application number: GB08130949A
Authority: GB
Inventors: Stephen Lewis Bruford
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1981-10-14
Filing date: 1981-10-14
Publication date: 1983-05-05
Also published as: GB2107659B

Abstract

A fuel tank for a motor vehicle comprises a fuel chamber (1), a filler duct (2) projecting into the chamber and arranged to deliver fuel into the chamber up to a desired maximum level (A) below the top of the chamber, a closure cap removably mounted on the neck (6) of the filler duct, a vent duct (5) connected to the fuel chamber (1) above the maximum level (A) and a valve for closing the vent duct. The valve is positioned on the neck (6) and is opened only when the cap is in place so that overfilling of the tank is prevented. The valve may be electrically or mechanically operated. A breather 13 is provided. <IMAGE>

Description

SPECIFICATION Fuel tank for motor vehicles This invention relates to fuel tanks for motor vehicles.

Conventional fuel tanks for motor vehicles comprise a fuel chamber, a filler duct having a closure cap removably mounted in its neck and projecting into the fuel chamber so that fuel is delivered into the fuel chamber up to a desired maximum level below the top of the chamber, thereby leaving an expansion volume in the chamber. In order to allow the fuel to expand, a vent duct is provided in the fuel chamber at a level above the maximum level.

Normally the rate of delivery of fuel into the tank is much faster than the rate at which vapour is displaced therefrom along the vent duct. Hence, when the fuel level reaches the desired maximum level, fuel begins to overflow from the filler duct, at which stage the operator should cease filling the tank.

It is however possible to fill the fuel chamber to a level above the desired maximum by introducing fuel sufficiently slowly into the tank so that the additional fuel displaces vapour from the expansion volume through the vent duct. Such overfilling of the tank produces a build-up of pressure within the tank as the fuel expands on heating, leading to possible loss of fuel through the vent duct, or a blow-back of fuel when the filler cap is next released.

According to the present invention there is provided a fuel tank for a motor vehicle comprising a fuel chamber, a filler duct projecting into the chamber and arranged to deliver fuel into the chamber up to a desired maximum level below the top of the chamber, a closure cap removably mounted on the neck of the filler duct, and a vent duct connected at its lower end with the fuel chamber above the desired maximum level, characterised by a valve for closing the vent duct and means for opening the valve only when the filler cap is mounted on the neck.

Since the valve in the vent duct is closed when the filler cap is not mounted on the neck, it is not possible to over-fill the tank. Nevertheless, since the valve is opened when the filler cap is mounted on the neck of the filler duct, the fuel is free to expand within the tank on heating without causing undesirable increases in pressure within the tank.

Any suitable means may be used to operate the valve. For example the valve may be electrically operable and controlled by a switch which is closed when the filler cap is mounted on the filler neck.

Preferably however the valve is mechanically operable. Thus, the upper end of the vent duct is preferably connected to the neck of the fuel duct, and the valve is mounted in the upper end of the vent duct for operation by the filler cap. For example, an operating member for the valve may be mounted in the neck of the filler duct, the operating member being engageable by the filler cap when the cap is mounted on the neck to open the valve.

In the preferred embodiment of the invention, the operating member is movable radially in the neck of the filler duct to open the valve as a result of rotation of the filler cap relative to the neck. This construction is especially suitable for filler caps having a conventional bayonet-type connection with the filler neck.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which Figure 1 is a schematic cross-section through a fuel tank in accordance with the invention.

Figure 2 is a radial cross-section of the neck of the fuel tank of Figure 1, taken along line ll-ll of Figure 1.

Figure 3 is a cross-section taken along line Ill-Ill of Figure 2, and Figure 4 is a cross-section taken along line IV-IV of Figure 2.

Referring to the drawings, a motor vehicle fuel tank comprises a fuel chamber 1 and a filler duct indicated generally at 2 projecting into the chamber.

The filler duct 2 is made up of a fuel delivery pipe 3 and a sensing pipe 4 of smaller diameter. The sensing pipe 4 communicates with the upper end of the delivery pipe 3 and terminates at a level A within the fuel chamber corresponding to the desired maximum level of fuel in the tank. The delivery pipe 3 terminates within the fuel chamber 1 below the maximum level A.

A vent duct 5 or narrower cross-sectional area communicates at one end with the top of the fuel chamber 1 and is connected at its other end with the neck 6 of the filler duct 2, best seen in Figures 2 to 4.

The neck 6 includes a conventional locking flange 7 of U-shaped radial cross-section construction for engagement with a bayonet-type connection on a filler cap 10 Fig. 3. The end of the vent duct 5 is secured to a plunger valve assembly 8 mounted in the neck 6. The plunger valve assembly 8 is of the type commonly used in tyre inner tubes, and includes an actuating pin 12 which projects radially from the end of the valve assembly with the nect 6 beneath the flange 7, which protects the pin 12 from damage. The valve assembly 8 is normally closed, and outward radial movement of the pin 12 opens the valve to place the vent duct 6 in communication with the filler duct 2. A breather pipe 13 mounted in the neck 6 communicates the filler duct 2 with the outside atmosphere.

A leaf spring 15 is secured at one end to the wall of the neck 6 by the breather pipe 13 and extends circumferentially around the neck 6 beneath the locking flange 7. The leaf spring includes a shaped section 14 so that the free end 16 of the leaf spring lies against the inner wall of the locking flange 7. The leaf spring 16 can therefore move radially within the neck 6, and acts as an operating member for the actuating pin 12 of the valve assembly 8. Radial outward movement of the end of the leaf spring 15 is effected by engagement of the locking lugs on the filler cap with the radially shaped section 14 when the filler cap is inserted into the neck 6.

The drawing(s) originally filed was/were informal and the print here reproduced is taken from a later filed formal copy. To fill the tank, the filler cap 10 is removed from the neck 6 so that the free end of the leaf spring 15 is disengaged from the actuating pin 12 of the valve assembly 8, thereby closing the vent duct 5. Fuel is then poured into the fuel chamber 1 through the delivery pipe 3. Vapour displaced by the fuel passes up the sensing pipe 4 thereby permitting the tank to be filled rapidly. When the level of the fuel reaches the maximum level A corresponding to the level of the end of the sensing pipe 4, no further vapour can escape from the fuel chamber 1. When the fuel duct 2 has been filled to the level of the neck 6, no further fuel can be introduced in to the tank.

The filler cap 10 is then mounted in the neck 6 with its locking lugs in registry with complementary recesses in the locking flange 7. Initial rotation of the filler cap 10 (anticlockwise as seen in Figure 2) causes the free end of the leaf spring to move radially outwardly into engagement with the actuating pin, thereby opening the valve assembly 8. The small volume of fuel in the filler duct 2 can then drain into the fuel chamber 1, displacing the corresponding amount through the vent duct to the atmosphere via the breather pipe 13. Sufficient space then still remains in the tank above the fuel to accommodate expansion of the fuel on heating, displaced vapour escaping to atmosphere through the open valve in the vent duct 5.

Claims

1. Afuel tankfor a motor vehicle comprising a fuel chamber, a filler duct projecting into the chamber and arranged to deliver fuel into the chamber up to a desired maximum level below the top of the chamber, a closure cap removably mounted in the neck of the filler duct, and a vent duct connected at its lower end with the fuel chamber above the desired maximum level, characterised by a valve for closing the vent duct and means for opening the valve only when the filler cap is mounted in the neck.

2. A fuel tank according to claim 1 wherein the filler duct comprises a fuel delivery pipe projecting into the chamber to a level below the desired maximum level, and a sensing pipe having an upper end communicating with the fuel delivery pipe adjacent the neck of the filler duct, and a lower end communicating with the fuel chamber at the desired maximum level.

3. A fuel tank according to claim 1 or claim 2 wherein the upper end of the vent duct is connected to the neck of the fuel duct, and the valve is mounted in the upper end of the vent duct and is operable by the filler cap.

4. A fuel tank according to claim 3 further comprising an operating memberforthe valve mounted in the neck of the filler duct, the operating member being engageable by the filler cap when the cap is mounted on the neck to open the valve.

5. A fuel tank according to claim 4 wherein the operating member is movable radially in the neck to open the valve as a result of rotation of the filler cap relative to the neck.

6. Afuel tank according to claim 4 or claim 5 wherein the operating member comprises a leaf spring.

7. A fuel tank for a motor vehicle substantially as hereinbefore described, and as illustrated in the drawings.