GB2286182A - A fuel tank venting arrangement for a motor vehicle - Google Patents

Abstract

A fuel tank (1) having filler pipe 2 extending into the tank below the maximum desired fuel level (6), and at least one high flow vapour valve 8 attached to the tank for venting vapour from the space above the fuel, at least with the tank horizontal, includes a pressure transducer 22 for monitoring the fuel system integrity and a sensor means to sense tank filling and prevent trickle overfilling. A vent pipe 9 connects the valve 8 to an absorption canister 10, and a breather tube extends from the filler pipe 2 above the tank 1 down into the tank 1 to the level 6 (23, Figure 2), the canister (10) being connectable via ducting 13 and a solenoid operated valve 14 to the induction manifold of the engine and via ducting 15 and a solenoid operated valve 16 to the free atmosphere. The pressure transducer 22 may be in the tank, filler pipe or filler cap and it is calibrated to sense a predetermined negative tank pressure. The valves 14, 16 are operable whereby the tank 1 and the canister 10 may be connected to the manifold and the negative pressure thereafter isolated and its decay monitored in a test of the integrity of the tank 1 and connections thereto. The sensor means, such as an electrical circuit which is broken by the removal of the filler cap, produces a signal employed to cause both of the valves 14, 16 to be closed during tank filling to prevent trickle over-filling. <IMAGE>

Description

A Fuel Tank Arrangement For A Motor Vehicle This invention relates to a fuel tank arrangement for a motor vehicle fitted with an internal combustion engine.

With an increasing awareness of the effects of environmental pollution on health, much attention has been directed to developing means whereby pollution may be reduced. One area of particular concern has been the pollution arising from the release of hydrocarbon and other fuel vapours into the atmosphere.

In this connection, the motor industry has developed what are commonly called on-board diagnostics whereby the integrity of the fuel system, including an associated fuel vapour control system, of a motor vehicle can be tested during each journey undertaken. To this end, provisions have been made on vehicles for the fuel tank and associated venting ducts and vapour filter devices to be subjected to an elevated or reduced pressure, the level of which is then monitored over a set period of time to check whether it is held or changes significantly.

Depending on the degree of any change, it is assessed as indicating either a significant leak in the system or an acceptable pressure variation.

In addition to making the above-mentioned provisions for testing the integrity of the fuel system, it is also desirable to make provisions for preventing the overfilling of the fuel tank, particularly by so-called trickle filling.

To this end, means for preventing the venting of the space above the maximum desired fuel level in the fuel tank, when such level has been reached during tank filling, have been provided. One such means includes a pressure sensitive valve which is sensitive to a pressure change caused by the removal of the fuel tank filler cap and shuts off the communication between the said space, otherwise vented via a fuel vapour absorption canister to the free atmosphere, and the free atmosphere.

According to the present invention there is provided a fuel tank arrangement for a motor vehicle fitted with an internal combustion engine, said arrangement comprising a fuel tank with filler pipe, the free end of which is closable by a filler cap and the other end of which extends below the maximum desired fuel level in the tank, at least one high flow vapour valve (as hereinafter defined) attached to the tank for venting vapour from the space above the fuel level in the tank at least with the tank horizontal, a vent pipe connecting said at least one high flow valve on its outlet side to an absorption canister for said vapour, a breather tube having one end extending down into the space above the fuel level in the tank to the maximum desired fuel level in the tank and having the other end connected to the filler pipe above the tank, wherein the canister is connectable via first ducting and a first solenoid operated valve to the induction manifold of the engine and via second ducting and a second solenoid operated valve to the free atmosphere, and wherein a pressure transducer is positioned and calibrated to sense a negative pressure of predetermined magnitude in the space above the fuel level in the tank to produce a signal registering such negative pressure level being reached with the filler cap in position, and wherein the first and second valves are operable whereby during running of the engine the fuel tank and the canister may be connected to the manifold and the negative pressure thereafter isolated, so that the integrity of the fuel tank and connections thereto can be checked by correlating the negative pressure decay with time, and wherein a sensor means is provided to produce a signal employed to cause the first and second solenoid valves to be both closed during filling of the tank to thereby prevent venting of the space above the fuel level in the tank when the maximum desired fuel level in the tank is reached and prevent trickle over-filling of the tank.

As a consequence of making this invention, a fuel tank arrangement may be provided with means to carry out a fuel system integrity check and additionally with means to prevent trickle over-filling while minimizing the number of required components.

The filler cap is preferably such that it is capable of substantially sealing the free end of the filler pipe against loss of fuel vapour to the free atmosphere.

However, it is preferably also provided with means, such as a pressure relief valve, whereby in the event of any undesirable positive or negative pressure condition it may be released automatically, for example.

The at least one high flow vapour valve is defined as a valve which under normal circumstances is open, allowing the free passage of fuel vapour but which closes if liquid fuel might otherwise pass through the valve, such as if the attitude of the tank becomes such that this would occur, for example , if the motor vehicle was on a steep gradient or, indeed, if the motor vehicle over-turned.

Thus, the at least one high flow valve may be floatand/or weight- operated to close it to the passage of liquid fuel.

Preferably, only one high flow valve is connected directly to the tank. In such a case, it is preferred also that a branch pipe is provided on the vent pipe to connect the vent pipe to the upstream side of a pressure-operated vapour valve having its downstream side connected to the filler pipe. A secondary valve is preferably incorporated with the pressure operated valve to allow the free reverse flow of vapour from the filler pipe to the branch pipe whereby a pressure build-up within the filler tube can be prevented by any excess vapour being released through the secondary valve to the free atmosphere, for example via the vent pipe, canister, second ducting and the second solenoid valve. It is preferred that the pressureoperated valve is incorporated in a modified high flow valve wherein the modification is such that the pressureoperated valve is biassed into a position to close it to the passage of vapour in the direction from the vent pipe to the filler pipe up to a predetermined pressure. Such predetermined pressure may be set to be in excess of a pressure head created by the filling of the filler pipe to the fuel nozzle shut-off level.

It will be appreciated that if only one high flow valve is directly connected to the tank and it is flooded with liquid fuel for example, such as may occur in the case of the motor vehicle being on a steep incline, a pressure build-up might occur in the tank and the filler pipe as a consequence of a heat-soak situation. Such a heat-soak situation can arise if the motor vehicle is parked with the tank exposed to the heat of the sun, for example.

It will be appreciated that the above pressure-operated valve modification to a high flow valve connected to the filler pipe as described above is desirable to avoid a trickle over-filling possibility arising from the venting of the space above the maximum desired fuel level in the tank via the two high flow valves and the open free end of the filler pipe during the filling of the tank.

The fuel vapour absorption canister may be of known type and may contain activated carbon as the absorption medium.

The connection of the breather tube to the filler pipe is preferably at a point near to the free end of the filler pipe.

The pressure transducer may be positioned in the top of the fuel tank but other locations are possible, such as in the fuel filler pipe, for example. In this latter connection, the pressure transducer may be incorporated in the filler cap such as is described in our co-pending British Patent application number 9322455.8 entitled "Fuel Tank Pressure-Sensing Arrangement" which is hereby incorporated by reference.

The signal produced by the pressure transducer in registering the predetermined negative pressure level being reached is preferably an electrical signal.

The sensor means may be a sensor to sense the removal of the filler cap from the filler pipe. Alternatively, the sensor means may be a sensor connected to the ignition switch or equivalent mobilizing switch to sense that the switch is in the off position, for example.

The sensor means may be connected to the fuel tank pressure transducer which may be additionally adapted to provide an electrical signal to register a predetermined positive pressure, which electrical signal may be employed to cause one, for example the second, solenoid operated valve, or both solenoid valves, to open to prevent such predetermined positive pressure being exceeded.

Alternatively, the electrical signal may be employed to cause a third solenoid operated valve, which may be positioned, for example in a branch in the second ducting and in front of the second solenoid valve, to be opened to vent excess pressure directly to the free atmosphere.

The predetermined positive pressure to which the fuel tank pressure transducer may be adapted to sense is preferably lower than any predetermined pressure to which any pressure relief valve incorporated in the filler cap may be set to operate at.

It will be appreciated that any build-up of any undesirable pressure in the vent pipe may be prevented by a pressure operated pressure relief valve preferably positioned in a branch in the second ducting and in front of the second solenoid valve and preferably also in front of any third solenoid valve that may be incorporated in the fuel tank arrangement as described above.

It is preferred that the sensor means is such that the signal it produces is an electrical signal which sensor electrical signal may be produced directly or by way of a sensor transducer, such as a sensor pressure transducer, for example.

The invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a diagrammatic sketch of a fuel tank arrangement according to the present invention but, for the sake of clarity, not showing the breather tube.

Figure 2 is a diagrammatic sketch of a portion of the fuel tank and filler pipe of Figure 1, showing the breather tube omitted from Figure 1 for the sake of clarity.

With reference to Figures 1 and 2 in which like numbers correspond; the fuel tank 1 has filler pipe 2, the free end 3 of which is closable by the filler cap 4 and the other end 5 of which extends into the tank 1 to a point below the maximum desired fuel level in the tank. This maximum is indicated by the broken line 6 for the tank in a substantially horizontal position and the corresponding level with the tank inclined, due to a motor vehicle in which the fuel tank arrangement is fitted, being positioned on a gradient, is indicated by the broken line 7. Attached to the tank 1 is the high flow rollover valve 8, being a commercially available valve such as that supplied by Stant Inc. under the designation F5DC 9B593-AB, to the outlet side of which is the vent pipe 9 connecting the valve 8 to the vapour absorption canister 10 having the baffle plate 11 and the packing 12 of activated carbon. To the canister 10 is attached the first ducting 13 provided with the first solenoid operated valve 14 by means of which the canister 10 is connectable to the induction manifold of the engine of the motor vehicle (not shown). To the canister 10 is also attached the second ducting 15 provided with the second solenoid operated valve 16 by means of which the canister 10 is connectable to the free atmosphere. As shown in broken lines, a pressure relief valve 17 is optionally positioned in a branch of the second ducting 15 in front of the solenoid valve 16. The valve 17 may be of the pressure operated type or it may be solenoid operated in which case it would be the third solenoid operated valve in the arrangement.

A second high flow valve 18, similar to valve 8, shown in broken lines may be directly attached to the tank 1 and with its outlet side connected to the vent pipe 9, an alternative arrangement in which a modified second high flow rollover/back pressure-operated valve 19 similar to that produced by Kayser GmbH under the designation 90BB9A153AA, is attached to the filler pipe 2 is shown.

The modified valve 19 incorporates a one-way valve 20 biassed towards closing against the passage of fuel vapour to the filler pipe 2 from valve 8 during re-fuelling, that is to say when the filled cap 4 has been removed. The position at which this modified valve 19 connects into the filler pipe 15 advantageously above the normal fuel nozzle shut-off level. The modified valve 19 incorporates with valve 20 a secondary valve which will allow the free reverse flow of vapour from the filler pipe 2 to the branch pipe 21. The free-flow outlet side of the modified valve 19 is connected to the vent pipe 9 by the branch pipe 21.

Attached to the tank 1 is the pressure transducer 22 which is sensitive to negative pressure in the space above the fuel level in the tank. The transducer 22 produces a signal proportional to the negative pressure to which it is subjected, thereby indicating when the desired pressure has been achieved and whereby the rate at which is subsequently decays can be determined.

The free end 3 of the filler pipe 2 is provided with two mutually isolated electrical contacts (not shown) on its outside wall. Electrical connection between the contacts is made by the filler cap 4 when it is in its closing position on the filler pipe 2. The electrical contacts are included in a circuit which, when broken by the removal of the filler cap 4 from the free end 3 of the filler pipe, activates the first and second solenoid valves 14 and 16 to their closed positions respectively.

As shown in Figure 2, the tank 1 of Figure 1 is provided with a breather tube 23 having one end 24 extending down into the tank 1 to the maximum fuel level 6, and having the other end 25 connected to the filler pipe 2 above the tank 1 and near to the free end 3 of the filler pipe 2.

Operation of the fuel tank arrangement shown in Figures 1 and 2 is as follows. With the motor vehicle (not shown) in which the arrangement is fitted, positioned substantially level, the filler cap 4 is removed from the filler pipe 2 whereby connection between the electrical contacts on the outside wall of the filler pipe is broken and the solenoid operated valves 14 and 16 are both energised to the closed state. A fuel feed nozzle inserted into the free end 3 of the filler pipe 2, can feed fuel into the tank 1 via the filler pipe 2. As the fuel level in the tank 1 rises, the air and fuel vapour mixture above the fuel is displaced up the filler pipe 2 and also up the breather tube 23 until their lower ends are respectively covered by liquid fuel. Displacement through the vent pipe 9 is prevented by the closed valves 14 and 16 and by the pressure-operated valve 20 acting against the passage of such mixture from the branch pipe 21 to the filler tube 2. Further displacement of the mixture from the space above the fuel which is now at its maximum desired level 6 is therefore prevented. Further fuel fed into the filler pipe 2 is prevented from entering the tank 1 by back pressure created in the space above the fuel in the tank 1 and the tank is thereby prevented from being over-filled, even by trickle filling. The filler pipe 2 quickly fills and the rising level of liquid fuel in the filler pipe 2 shuts off the fuel feed from the fuel feed nozzle in known manner.

The fuel feed nozzle is removed from the filler pipe 2 and the filler cap 4 replaced to close the free end 3 of the filler pipe 2 whereby connection of the electrical contacts on the outside wall of the filler pipe is restored and the solenoid operated valves 14 and 16 both de-energised to the open state.

By means of separate electrical circuitry associated with the ignition switch of the engine, the solenoid valve 14 is activated to its closed position on switching on the ignition switch. On starting the engine, a reduced pressure is created in the inlet manifold. Venting of the space above the fuel level 6 in the tank 1 occurs via the high flow valve 8, the vent pipe 9, the canister 10 and the second solenoid valve 16.

The fuel system integrity check is then applied. By means of a switch in the energising circuit associated with the solenoid valve 14, the valve 14 is de-energised whereby the valve 14 is opened to thus establish communication between the reduced pressure in the inlet manifold and the canister, the vent pipe 9, the branch pipe 21, the high flow valve 8, the tank 1 and the pressure transducer 22.

Similarly, by means of a switch in separate electrical circuitry associated with the solenoid valve 16, the valve 16 is energised to the closed position. As the pressure in the tank 1 falls, the pressure transducer 22 produces a signal proportional to the pressure it senses. When the pressure reaches a pre-determined negative pressure, electrical circuitry monitoring the output of the transducer causes the activation of a relay switch whereby the solenoid valve 14 is again energised to the closed state. The level of the output of the transducer 22 is then monitored against time. If the loss of the reduced pressure exceeds a pre-determined rate the fuel system is deemed defective and requiring attention.

If the integrity check is favourable, the solenoid valve 16 is de-energised, by means of the switch in the separate electrical circuitry associated therewith, whereby the venting of the fuel system to the atmosphere via the canister 10 is restored. The electrical circuitry controlling the operation of each of the solenoid valves 14 and 16 is such as to be reset to its starting point on turning off the ignition switch for the engine.

It will be seen that if the motor vehicle in which the fuel tank arrangement specifically described above is fitted, is positioned on a steep gradient, the high flow valve 8 becomes flooded and a float member therein shuts it off to prevent any flow through it from the tank 1 to the vent pipe 9. Venting of the space above the fuel level in the tank 1, now in the position indicated by the broken line 7, might only occur via the filler pipe 2 and the pressure-operated valve 20 to the canister 10 and beyond.

In order to prevent an undesirable pressure build-up in the fuel tank arrangement, should the arrangement be left with the solenoid valve 16 in its closed state, the optional pressure relief valve 17 may be installed and set to operate at an appropriate pressure. The relief valve 17 may be a pressure operated valve or a third solenoid operated valve which may be energised via electrical circuitry responding to a positive pressure signal produced by a pressure transducer 22 modified so to do.

Claims (12)

Claims

1. A fuel tank arrangement for a motor vehicle fitted with an internal combustion engine, said arrangement comprising a fuel tank with a filler pipe, the free end of which is closable by a filler cap and the other end of which extends below the maximum desired fuel level in the tank, at least one high flow vapour valve (as hereinbefore defined) attached to the tank for venting vapour from the space above the fuel level in the tank at least with the tank horizontal, a vent pipe connecting said at least one high flow valve on its outlet side to an absorption canister for said vapour, a breather tube having one end extending down into the space above the fuel level in the tank to the maximum desired fuel level in the tank and having the other end connected to the filler pipe above the tank, wherein the canister is connectable via first ducting and a first solenoid operated valve to the induction manifold of the engine and via second ducting and a second solenoid operated valve to the free atmosphere, and wherein a pressure transducer is positioned and calibrated to sense a negative pressure of predetermined magnitude in the space above the fuel level in the tank to produce a signal registering such negative pressure level being reached with the filler cap in position, and wherein the first and second valves are operable whereby during running of the engine the fuel tank and the canister may be connected to the manifold and the negative pressure thereafter isolated, so that the integrity of the fuel tank and connections thereto can be checked by correlating the negative pressure decay with time, and wherein a sensor means is provided to produce a signal employed to cause the first and second solenoid valves to be both closed during filling of the tank to thereby prevent venting of the space above the fuel level in the tank when the maximum desired fuel level in the tank is reached and prevent trickle over-filling of the tank.

2. A fuel tank arrangement as claimed in Claim 1 wherein the sensor means is such that the signal it produces is an electrical signal.

3. A fuel tank arrangement as claimed in either Claim 1 or Claim 2 wherein the filler cap is provide with a pressure relief valve.

4. A fuel tank arrangement as claimed in any one of the preceding claims wherein only one high flow valve is connected directly to the tank and a branch pipe is provided on the vent pipe to connect the vent pipe to the upstream side of a pressure-operated vapour valve having its downstream side connected to the filler pipe.

5. A fuel tank arrangement as claimed in Claim 4 wherein the pressure-operated valve is incorporated in a modified high flow valve, the pressure-operated valve being biassed into a position to close it to the passage of vapour in the direction from the vent pipe to the filler pipe.

6. A fuel tank arrangement as claimed in any one of the preceding claims wherein the connection of the breather tube to the filler pipe is at a point near to the free end of the filler pipe.

7. A fuel tank arrangement as claimed in any one of the preceding claims wherein the pressure transducer is positioned in the filler cap.

8. A fuel tank arrangement as claimed in any one of the preceding claims wherein the sensor means is a sensor to sense the removal of the filler cap from the filler pipe or a sensor connected to the ignition switch to sense that the switch is off.

9. A fuel tank arrangement as claimed in any one of the preceding claims wherein the sensor means is connected to the fuel tank pressure transducer which is adapted to additionally provide an electrical signal to register a predetermined positive pressure which signal may be employed to cause one or both solenoid valves to open or alternatively a third solenoid operated valve to open to prevent such predetermined positive pressure being exceeded.

10. A fuel tank arrangement as claimed in Claim 9 wherein the predetermined positive pressure is lower than any predetermined pressure to which any pressure relief valve incorporated in the filler cap is set to operate at.

11. A fuel tank arrangement as claimed in any one of the preceding claims wherein a pressure operated relief valve is positioned in a branch in the second ducting and in front of the second solenoid valve and also in front of any third solenoid valve.

12. A fuel tank arrangement substantially as described herein with reference to the accompanying drawings.