GB2257694A

GB2257694A - A fuel tank arrangement for a motor vehicle

Info

Publication number: GB2257694A
Application number: GB9115532A
Authority: GB
Inventors: Ronald Pardy
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1991-07-18
Filing date: 1991-07-18
Publication date: 1993-01-20
Also published as: GB9115532D0

Abstract

In a motor vehicle fuel tank 10, fuel vapour pressure can build up whilst the tank is closed, in order to prevent a sudden expulsion of vapour and/or liquid fuel from the filler pipe 14 when the tank is opened, a by-pass passage 26 by-passes a flow restriction 24 in a vent passage 20 and allows the escape of excess vapour pressure without opening the filler cap 16 by means of valve 28 fitted in the by-pass passage 26 which is open when the engine is not running but is closed at all other times. <IMAGE>

Description

A FUEL TANK ARRANGEMENT FOR A MOTOR VEHICLE This invention relates to a fuel tank arrangement for use in a motor vehicle to avoid a sudden expansion and resulting expulsion of vapour and/or liquid fuel from the tank when the tank is opened for re-fuelling.

Particularly at high ambient temperatures, it can happen that the vapour space in the tank is at a pressure substantially above atmospheric pressure. When this happens, removal of the filler cap can cause a sudden expulsion of vapour and, in extreme cases, expulsion of liquid fuel. This is unpleasant for the person removing the cap and also releases undesirable vapours into the atmosphere.

It is known to provide the filler cap with a partially open and a fully open position. The user is instructed to open the cap to the partially open position, in which vapour is vented through a restricted orifice, to wait for any hissing to stop and then to fully open the cap. The disadvantage of this is that the restricted orifice must be very small and as a result it can take a considerable time for the hissing to stop. It is necessary that the area of the orifice in the partially open position be sufficiently restricted to prevent the fuel from boiling up the filler tube. Furthermore the escaping vapours are vented directly to atmosphere.

It is also known to provide a remote release for the fuel filler cap so that the filler cap can be fully or partially released when the driver operates a remote control lever from the driver's seat. Using this type of arrangement, a certain period of time elapses between the moment when the filler cap is released and the moment when the driver actually approaches that part of the car where the filler cap is located. At least the first stage of the vapour expulsion can then take place before the driver arrives beside the location of the filler cap. This proposal has the disadvantage that it requires a physical linkage between the driver's seat and the filler cap location. This can be difficult to package.

According to the present invention, there is provided a fuel tank arrangement for a motor vehicle, the arrangement comprising a fuel tank, a filler pipe through which the tank can be re-filled, a vent passage having a flow restriction therein, a tank pressure relief passage which by-passes the flow restriction, an open/closed valve in the pressure relief passage and means for closing the valve when the engine is running and opening the valve when the engine is not running.

The vent passage preferably extends from the tank to a vapour recovery arrangement.

The means for closing the valve when the engine is running and opening the valve when the engine is not running may be either electrically or mechanically operated. In the case of electrical operation, the open/closed valve may be connected to a solenoid so that the opening or closing action is effected immediately the ignition of the vehicle is switched off or on.

In the case of mechanical operation, the open/closed valve may be operated for example by a pressure signal produced when the vehicle fuel pump starts to pump fuel out of the tank. The pressure surge then produced may be used to open or close the valve.

The pressure relief passage preferably has a cross-sectional area which is large relative to that of the restriction or restrictions in the vent passage, so that when the open/closed valve is open a large flow cross-section is available for expulsion of pressure from the tank.

In this way equalisation of pressures within and outside the tank can begin immediately the vehicle's engine is switched off, and the escaping vapours can be processed, for example through a vapour recovery system rather than being vented directly to the atmosphere.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a first fuel tank arrangement in accordance with the invention; and Figure 2 is a corresponding diagram of a second fuel tank arrangement in accordance with the invention.

Figure 1 shows a tank 10 containing fuel 12 and with a filler neck 14. A filler cap 16 is fitted at the top of the neck 14.

A vapour space 18 is maintained above the surface of the fuel 12.

It is conventional for the vapour space 18 to be vented through a vent tube 20. A roll-over valve 22 is fitted in the vent tube to prevent liquid fuel escaping from the tank through the tube in the event that the vehicle turns over. A flow restriction 24 is also located in the vent tube to help prevent trickle filling of the tank. Once the fuel level rises above the level shown in Figure 1, the only way in which air or vapour can escape from the space 18 is through the restriction 24, and this escape can only take place very slowly. It therefore becomes very difficult to fill the tank above the designed maximum fuel level. Vapour passing through the restriction 24 is directed to a vapour recovery canister 30.

During normal running, the restriction also restricts the flow of vapour to to the canister to prevent canister saturation.

Because the flow restriction 24 in the vent passage 20 is only small, excess pressure only escapes slowly. However when the filler cap 16 is removed, any excess pressure in the tank can escape quickly to atmosphere. In order to avoid a blast of fuel vapour leaving the tank and discharging over the person opening the filler cap, a tank pressure relief passage 26 is provided. This passage has an unrestricted cross-sectional area, but is provided with a valve 28 which is either fully open or is fully closed. When the valve 28 is open, a full flow cross-section is available via the passage 26 to the full cross-sectional area of the vent passage 20, by-passing the roll-over valve 22 and the restriction 24. However when the valve 28 is closed, there is no flow through the by-pass passage 26.When the valve 28 is open, it is desirable that a small level of back pressure be maintained to prevent trickle filling of the tank.

The valve 28 shown in Figure 1 is solenoid operated. The valve 28 will be normally closed, but when the ignition switch is switched off, current will flow in a circuit which includes the valve, so that the valve will be opened when the engine is switched off. Thus when the driver switches off his engine at a petrol station, so that he can refill the tank, as soon as the ignition is switched off the valve 28 will open and any excess pressure in the tank will be dumped. The vapour which leaves the tank as a result can be passed through a vapour extraction canister 30.

An alternative arrangement is shown in Figure 2. In this Figure parts which have the same function as those in Figure 1 will carry the same reference numerals. Figure 2 shows an intank fuel pump 32 which has a fuel feed line 34 leading to the engine. The pump 32 is electrically operated and will be pumping fuel all the time the engine of the car is switched on.

A check valve 36 is located downstream of the pump so as to ensure that fuel can only flow in one direction through the feedline 34.

Between the pump 32 and the check valve 36 there is a pressure signal line 38 which is connected to a valve 28a. The valve 28a is either fully open or is fully closed. The normal position will be fully open but as soon as there is a pressure developed in the signal line 38, as a result of operation of the pump 32, then the valve will be closed. The effect of this will be as described above in respect of the embodiment shown in Figure 1.

With this by-pass passage, it is therefore possible to ensure that the ullage space in the tank is fully vented as soon as the engine is switched off, but that the normal functioning of the flow restriction 24 is maintained at all times whilst the engine is running.

Claims

1 A fuel tank arrangement for a motor vehicle, the arrangement comprising a fuel tank, a filler pipe through which the tank can be re-filled, a vent passage having a flow restriction therein, a tank pressure relief passage which bypasses the flow restriction, an open/closed valve in the pressure relief passage and means for closing the valve when the engine is running and for opening the valve when the engine is not running.

2 An arrangement as claimed in Claim 1, wherein the vent passage extends from the tank to a vapour recovery arrangement.

3 An arrangement as claimed in Claim 1 or Claim 2, wherein the means for closing the valve when the engine is running and for opening the valve when the engine is not running is electrically operated.

4 An arrangement as claimed in Claim 3, wherein a valve is connected to a solenoid and the solenoid is connected in a circuit which includes the vehicle ignition switch so that the opening and closing action is effected immediately the ignition of the vehicle is switched off or on.

5 An arrangement as claimed in Claim 1 or Claim 2, wherein the means for closing the valve when the engine is running and for opening the valve when the engine is not running is mechanically operated.

6 An arrangement as claimed in Claim 5, wherein the valve can be moved between its open position and its closed position by an applied pressure, and wherein a signal pressure line is connected between the vehicle fuel tank and the valve so that when the fuel pump starts to operate, a pressure is produced in the signal line which operates the valve.

7 An arrangement as claimed in Claim 6, wherein the fuel pump is mounted inside the fuel tank.

8 A fuel tank arrangement for a motor vehicle substantially as herein described with reference to either Figure 1 or Figure 2 of the accompanying drawings.