GB2253464A

GB2253464A - A valve arrangement

Info

Publication number: GB2253464A
Application number: GB9104684A
Authority: GB
Inventors: Ronald Pardy
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1991-03-06
Filing date: 1991-03-06
Publication date: 1992-09-09
Also published as: GB9104684D0

Abstract

In a fluid system where fluid is drawn from and returned to a common reservoir 12, a valve 32 allowing fluid to leave the reservoir is held in an open condition by the differential pressure in the feed and return lines 16, 20. When this differential pressure falls away. the valve closes and fluid can no longer be drawn from the reservoir. In an alternative embodiment. spring-biassed outlet valve 40 is replaced by a duck-bill type one-way valve (140, Fig. 4) and in a further alternative embodiment valve 32 is replaced by a check valve (232, Fig. 5). <IMAGE>

Description

A VALVE ARRANGEMENT This invention relates to a valve arrangement in which a valve is opened or closed as a result of pressure differences in different parts of the arrangement. The invention is particularly, but not exclusively, applicable to an anti-syphon valve for use in the fuel system of a motor vehicle.

It is important in a vehicle fuel system that the fuel outlet from the fuel tank should be closed in the event of an accident. For example if a fuel line is severed between the engine and the fuel tank, it is necessary to prevent further fuel being drawn from the tank. If the vehicle rolls over in an accident, again it is important that the fuel tank be closed when the engine stops running.

US patent specification 3 994 358 describes a safety shutoff fuel system which uses a valve where a valve member is normally biased by a spring into the closed position. The valve member is also connected to a diaphragm and when a suction acts on the diaphragm (the suction being produced by the feed side of a fuel pump) the diaphragm lifts the valve off its seat and allows fuel flow. As soon as the fuel pump stops running, the suction disappears and the spring closes the valve again.

It is a disadvantage of this type of arrangement that a relatively high suction is required in order to keep the valve open. The suction has to be sufficient to overcome the biasing force of the spring, and also to overcome the closing pressure exerted on the valve by the pressure of the fuel flowing through the valve seat.

According to the present invention, there is provided a valve arrangement comprising a valve body incorporating a pressure deflectable member, a first inlet and a first outlet on one side of the pressure deflectable member, a second inlet and a second outlet on the other side of the pressure deflectable member, and a valve member for opening and closing communication between the first inlet and the first outlet, the pressure deflectable member and the valve member being arranged so that when the pressure at the first outlet is less than the pressure at the second outlet, the deflectable member is biased in a direction in which it assists opening of the valve member.

The use of a differential pressure in this way to open the valve member results in a lower pressure being required on the suction side of the deflectable member than is the case with the prior art. This increases the fuel system's ability to operate at elevated temperatures because it reduces the risk of fuel boiling.

The pressure deflectable member is preferably a diaphragm, but alternatively a piston may be used.

The valve member is preferably spring-loaded into a closed position, and the diaphragm or piston provides a force on the valve member opposed to the spring force.

The second outlet is preferably restricted relative to the second inlet and may be closed by a spring-loaded valve which can be opened as the fluid pressure on that side of the diaphragm or piston increases.

The invention also provides a fuel flow valve arrangement comprising a valve body incorporating a pressure deflectable member, a first inlet and a first outlet arranged on one side of the pressure deflectable member and a second inlet and a second outlet arranged on the other side of the pressure deflectable member, the first inlet being arranged so as to pick up the fuel from a fuel tank, and the first outlet and the second inlet forming fuel feed and return lines to and from an engine, and a valve for opening and closing communication between the first inlet and the first outlet, wherein the pressure deflectable member and the valve member are arranged so that when the fuel pump is operating, the suction in the feed line acts on one side of the deflectable member and the pressure in the return line acts on the other side of the deflectable member so that the deflectable member is biased in a direction which assists opening of the valve member.

The fuel flow valve arrangement may be mounted inside a fuel tank with the valve body sitting on the bottom of the tank so that the first inlet is in direct communication with the fuel in the tank.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows schematically a motor vehicle engine fuel system; Figure 2 is a cross section through a first embodiment of valve arrangement in accordance with the invention; Figure 3 is a cross section through part of the valve arrangement of Figure 1, showing the valve member in an open position; Figure 4 is a cross section through a second embodiment of valve arrangement in accordance with the invention; and Figure 5 shows an alternative type of valve member.

Figure 1 shows an internal combustion engine 10 which runs on fuel drawn from a fuel tank 12. Fuel is pumped from the tank 12 by a pump 14 which draws the fuel along a feed line 16, through the pump itself, to a fuel rail 18. The rate at which the pump 14 pumps fuel is greater than the rate at which the engine consumes the fuel, and the excess fuel is returned to the tank 12 along a return line. Within the tank 12, both the feed line 16 and the return line 20 are connected to a valve arrangement 22. The present invention is concerned with this valve arrangement which is shown in more detail in the following figures of the drawings.

Figure 2 shows a valve arrangement 22 sitting on the floor of a fuel tank 12. A feed line 16 and a return line 20 provide respectively a first outlet and a second inlet to a valve body 24. The valve body also has a first inlet constituted by the bottom part of the body 24, where the walls of the body are formed by filter mesh 26.

Additionally a second outlet is shown at 28.

The valve body has a diaphragm 30. The second inlet 20 and the second outlet 28 are on one side of this diaphragm whereas the first inlet 26 and the first outlet 16 are on the opposite side of this diaphragm.

A valve member 32 closes a passage 34 which allows communication between the first inlet 26 and the first outlet 16. A spring 36 acts on this valve member and, in the absence of any externally applied pressure, keeps the valve member 32 in the closed position shown in Figure 2 in which fuel in the tank cannot pass out through the first inlet 16.

However once the pump 14 starts to operate, it generates a suction or negative pressure in the first outlet 16. The valve 32 is closed at this point and therefore the suction will act in a chamber bounded at the top by the diaphragm 30. This will cause the diaphragm to deflect downwards to the position shown in Figure 3, and in this position the diaphragm makes contact with the top of the valve member 32 and provides a force on the valve member opposing the spring 36. ' As a result, the valve member 32 moves downwards and the passage 34 is opened. Fuel can now flow (as indicated by arrows in Figure 3) from the first inlet 26 to the first outlet 16 which forms the feed line, to the fuel rail 18 and back along the return line 20. The returning fuel enters the valve body 24 above the diaphragm 30 and can only escape if the second outlet 28 is opened.

The pressure of the fuel returning to the tank along the return line 20 will therefore act on the top of the diaphragm 30 and will reinforce the effect of the suction acting below the diaphragm. The position shown in Figure 3 will therefore be maintained.

The returning fuel 20 flows into a chamber 38 above the diaphragm and can only escape through the passage 28. As shown in Figure 2, this passage is closed by a valve member 40 which is biased by a spring 42 in the same way as the valve member 32 is biased by the spring 36. The valve member 40 however has an enlarged head 44 within the chamber 38 and when the pressure in the chamber builds up, the hydrostatic pressure acting on the head 44 will overcome the force of the spring 42 and the valve member 40 will open as shown in Figure 3 to allow the returning fuel to flow back into the fuel tank 12.

If the fuel pump 14 stops running or for some reason becomes no longer connected to the fuel tank, then the pressures in the feed and return lines 16, 20 will revert to atmospheric pressure, the diaphragm 30 will return to its unstressed condition and the valve member 32 will close. Fuel cannot therefore escape from the fuel tank 12 through either the feed or the return lines 16, 20.

Figure 4 shows an alternative embodiment where the valve arrangement has a valve body 124 which can be mounted outside the fuel tank. The fuel is drawn into the body through a first inlet 126 and is returned to the tank through a second outlet 128. A fuel feed line 116 and a fuel return line 120 correspond to the feed and return lines 16, 20 of Figures 2 and 3.

A diaphragm 130 divides the body 124 into two spaces, and a valve member 132 opens or closes a passage 134. At the end of the outlet pipe 128 which will be located inside the fuel tank 12, the pipe ends in a duck-bill type one-way valve 140 which restricts the flow of fuel and therefore allows a pressure to build up in the chamber 138. The principle of operation of this second embodiment is the same as that of the first embodiment.

It will be clear to a skilled man that the principles described here can be embodied in different ways. For example the diaphragm 30, 130 could be replaced by a piston which slides up and down in the body 24, 124 in response to the differential pressure across it. Furthermore the valve members 32, 40, 132, 140 could be replaced by a variety of different types of valves, one such type being a mushroom valve as shown in Figure 5 which has a rubber, mushroomshaped valve member 232 which normally closes passages 234 but can be lifted when the pressure below the wall 235 is greater than the pressure above the wall, so that flow is allowed through the passages 234.

By using the pressure in the return line 20 to assist (or even replace) the suction in the feed line, the absolute level of suction achieved does not need to be particularly high, and the use of the differential pressure of these two pressures results in there being little or no effect on the hot fuel handling performance of the arrangement.

Claims

1. A valve arrangement comprising a valve body incorporating a pressure deflectable member, a first inlet and a first outlet on one side of the pressure deflectable member, a second inlet and a second outlet on the other side of the pressure deflectable member, and a valve member for opening and closing communication between the first inlet and the first outlet, the pressure deflectable member and the valve member being arranged so that when the pressure at the first outlet is less than the pressure at the second outlet, the deflectable member is biased in a direction in which it assists opening of the valve member.

2. A valve arrangement as claimed in Claim 1, wherein the pressure deflectable member is a diaphragm.

3. A valve arrangement as claimed in Claim 1, wherein the pressure deflectable member is a piston.

4. A valve arrangement as claimed in any preceding claim, wherein the valve member is spring-loaded into a closed position, and, in use, the deflectable member provides a force on the valve member opposed to the spring force.

5. A valve arrangement as claimed in any preceding claim, wherein the second outlet is restricted relative to the second inlet.

6. A valve arrangement as claimed in Claim 5, wherein the second outlet is closed by a spring-loaded valve which can be opened as the fluid pressure on that side of the deflectable member increases.

7. A fuel flow valve arrangement comprising a valve body incorporating a pressure deflectable member, a first inlet and a first outlet arranged on one side of the pressure deflectable member, a second inlet and a second outlet arranged on the other side of the pressure deflectable member, the first inlet being arranged so as to pick up the fuel from a fuel tank, and the first outlet and the second inlet forming fuel feed and return lines to and from an engine, and a valve for opening and closing communication between the first inlet and the first outlet, wherein the pressure deflectable member and the valve member are arranged so that when the fuel pump is operating, the suction in the feed line acts on one side of the deflectable member and the pressure in the return line acts on the other side of the deflectable member so that the deflectable member is biased in a direction which assists opening of the valve member.

8. A fuel flow valve arrangement as claimed in Claim 7, mounted inside a fuel tank with the valve body sitting on the bottom of the tank so that the first inlet is in direct communication with fuel in the tank.

9. A valve arrangement substantially as herein described with reference to the accompanying drawings.

10. A fuel flow arrangement substantially as herein described with reference to the accompanying drawings.