GB2238041A

GB2238041A - Fuel tank venting

Info

Publication number: GB2238041A
Application number: GB8926085A
Authority: GB
Inventors: Ronald Pardy; David Bowles
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1989-11-17
Filing date: 1989-11-17
Publication date: 1991-05-22
Also published as: GB8926085D0

Abstract

A separator trap 22 for separating vapour from liquid is fitted directly in the roof of a fuel tank and has a lower opening 28 through which fuel returns to the tank, a vapour opening 30 above the lower opening and a third opening 32 through which vapour leaves the separator; a settlement chamber 26 may be provided above the baffle chamber; a vent pipe 20 leads to atmosphere. <IMAGE>

Description

FUEL TANK VENTING This invention relates to the venting of motor vehicle fuel tanks.

It is conventional for a fuel tank to have a vapour vent in the form of a pipe which leads from the roof of the fuel tank to a point at a higher level on the vehicle and which is vented to atmosphere. Because it is possible for liquid fuel to enter the vent passage, it is conventional to include a relatively large volume reservoir in the vent passage where liquid can collect and where the vapour can leave the liquid behind as it passes to atmosphere. An arrangement of this type is shown for example in DE-OS-3027970. Liquid fuel which collects in the reservoir will eventually trickle back into the tank. However the use of a separate reservoir in the vent passage introduces packaging difficulties and additional assembly complexity.

According to the present invention, there is provided a vent arrangement for a fuel tank, the arrangement comprising a baffle chamber fitted on the roof of a fuel tank and having a first opening at its lowermost point through which fuel can return from the chamber to the tank, a second opening above the first opening through which fuel vapour can leave the tank, and a third opening from the top of the chamber through which fuel vapour can leave the chamber to pass to atmosphere.

The third opening preferably leads into a settlement chamber above the baffle chamber, and the settlement chamber has an outlet opening for connection to a vent pipe.

The baffle chamber and the settlement chamber are preferably assembled from plastics moulding, and where the fuel tank itself is made of plastics, the moulding assembly making up the baffle and settlement chambers can be welded or moulded in to the roof of the tank.

The baffle chamber is preferably of an inverted conical shape with the first opening being at the downwardly pointing apex of the cone.

The invention will now be further described, by way of example, with reference to the accompanying drawings in which: Figure 1 shows a cross section through a fuel tank with a vent arrangement in accordance with the invention; and Figure 2 shows a cross section through an alternative form of vent arrangement in accordance with the invention.

The tank shown in the Figure is moulded from plastics material, although the invention could be equally applied to a pressed steel tank. The tank 10 has a filler neck 12 with a filler cap 14 and contains fuel 16. A fuel feed pipe 18 picks up fuel to pass to the engine of the vehicle in which the tank is mounted.

Since fuel is a volatile substance, it is necessary to have a gas pressure relief arrangement to prevent the internal pressure in the tank from rising too high.

This is accomplished by connecting a vent pipe 20 into the roof of the tank. However if the vent pipe enters the tank through a simple passage through the wall, fuel splashes which touch the vent passage can be blown into the vent system. It is highly undesirable for liquid fuel to be discharged from the vent system, and in order to prevent this happening the invention includes a separator 22 mounted in the roof of the tank. The separator 22 has a baffle chamber 24 and a settlement chamber 26. The baffle chamber 24 has a first opening 28 through which fuel trickles back into the main part of the tank, and a second opening 30 through which vapour leaves the tank. Any fuel splashes which touch the vent 30 will pass into the baffle chamber 24 but will then accumulate in the chamber and will trickle back into the tank.The vapour then passes through a third opening 32 from the baffle chamber to the settlement chamber, and from the settlement chamber the vapour passes out to atmosphere through the vent pipe 20.

The settlement chamber 26 prevents any fuel splashes which might reach the opening 32 from being carried up the pipe 20 with the vapour, but if the chamber unit is carefully designed it may be possible to eliminate a separate settlement chamber.

The separator 22 could be a moulded assembly which is fixed into the tank roof by welding (when both components are plastics) or could be held in place in a metal tank by means of a rubber grommet.

An arrangement as described above is simpler to package in the available space in a motor vehicle because there is no requirement for a separate reservoir high up on the vent pipe 20.

The alternative arrangement shown in Figure 2 differs from the arrangement of Figure 1 in omitting a separate settlement chamber. In this arrangement, a lower moulding 41 fits in an opening 43 in the roof of a fuel tank 45 and itself has a first opening 48 through which liquid fuel returns to the tank, and a second opening 50 through which vapour leaves the tank. An upper moulding 47 fits over and is welded to the lower moulding and defines a baffle chamber 44 with internal baffle walls 52 and an outlet 40.

Claims

1. A vent arrangement for a fuel tank, the arrangement comprising a baffle chamber fitted on the roof of a fuel tank and having a first opening at its lower most point through which fuel can return from the chamber to the tank, a second opening above the first opening through which fuel vapour can leave the tank, and a third opening from the top of the chamber through which fuel vapour can leave the chamber to pass to atmosphere.

2. A vent arrangement as claimed in Claim l, wherein the third opening leads into a settlement chamber above the baffle chamber, and the settlement chamber has an outlet opening for connection to a vent pipe.

3. A vent arrangement as claimed in Claim 1 or Claim 2, wherein the baffle chamber and the settlement chamber are a single plastics moulding.

4. A vent arrangement as claimed in Claim 3, wherein the fuel tank itself is made of plastics, and the moulding making up the baffle and settlement chamber can be welded or moulded in to the roof of the tank.

5. A vent arrangement as claimed in any preceding claim, wherein the baffle chamber is of an inverted conical shape with the first opening being at the downwardly pointing apex of the cone.

6. A vent arrangement for a fuel tank, substantially as herein described with reference to any one embodiment shown in the accompanying drawings.