GB2334026A

GB2334026A - Fuel vapour system with a control valve

Info

Publication number: GB2334026A
Application number: GB9802341A
Authority: GB
Inventors: Guy Hoffmann; Goede Nick J De
Original assignee: General Motors Corp
Current assignee: Motors Liquidation Co
Priority date: 1998-02-05
Filing date: 1998-02-05
Publication date: 1999-08-11
Anticipated expiration: 2018-02-05
Also published as: GB9802341D0; GB2334026B

Abstract

A fuel vapour system for use with a motor vehicle fuel tank 12 having a filler pipe 14, comprises a control valve 26, a valve inlet pipe 36 for receiving fuel vapour from the tank, and a valve outlet pipe 38 for transferring fuel vapour to the filler pipe. The valve includes a housing 28, a valve member 30, such as a diaphragm or piston, which is movable and defines a first and second chamber within the housing, and a spring 42 located in the second chamber 34. The valve inlet pipe opens into the first chamber 32, and the valve outlet pipe has an end 40 inside the first chamber, said end being normally closed by the valve member due to the bias of the spring, and opening when fuel vapour pressure in the first chamber exceeds a predetermined level. The second chamber may be connected to atmospheric pressure, or may be connected to the filler pipe via a vacuum pipe 44. The system recirculates fuel vapour during refuelling, and restricts air entrainment into the fuel tank.

Description

FUEL FILL VAPOUR RECOVERY SYSTEM Technical Field The present invention relates to a vapour recovery system for a fuel tank of a motor vehicle which substantially prevents the escape of fuel vapour into the atmosphere during filling of the fuel tank.

Background of the Invention When a fuel tank in a motor vehicle is filled with fuel, the refuelling process draws atmospheric air into the fuel tank, which generates additional fuel vapour inside the fuel tank. These vapours increase the size of the vapour recovery canister required to substantially prevent the escape of hydrocarbons into the atmosphere during the refuelling process. US-A4762156 describes a vapour recovery system in which a regulator valve is situated in a line between the fuel tank vapour outlet and the fuel tank filler pipe. The valve is operated by pressure differential and opens due to the negative pressure (compared to atmospheric pressure) created in the filler pipe during refuelling of the fuel tank. According to US-A-4762156, such an arrangement requires an annular shield in the inlet pipe adjacent the inlet (pipe neck) which substantially blocks the inflow of atmospheric air. The combination of a small clearance and the flow of incoming fuel generates the negative pressure in the filler pipe required to operate the regulator valve.

Summary of the Invention It is an object of the present invention to provide an improved fuel vapour recovery system.

A fuel vapour recovery system in accordance with the present invention for use with a fuel tank of a motor vehicle comprises a control valve; a valve inlet pipe connected to the control valve and connectable to the fuel tank to receive fuel vapour from the fuel tank; and a valve outlet pipe connected to the control valve and connectable to a filler pipe for the fuel tank adjacent a fuel filling opening in the filler pipe; wherein the control valve includes a housing, a valve member movable inside the housing and defining a first chamber and a second chamber inside the housing, and a spring positioned in the second chamber and acting on the valve member, the valve inlet pipe opening into the first chamber, and the valve outlet pipe having an end positioned inside the first chamber, said end being normally closed by the valve member due to the bias of the spring and opening when fuel vapour pressure in the first chamber exceeds a predetermined pressure level.

The fuel vapour recovery system of the present invention operates under the influence of the pressure increase in the fuel tank during refuelling to actively recirculate fuel vapour and restrict entrainment of atmospheric air into the fuel tank.

Brief Description of the Drawings The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a partial cross-sectional view of a fuel vapour recovery system in accordance with the present invention.

Description of the Preferred Embodiment Referring to the drawing, the fuel vapour recovery system 10 of the present invention is for use with a fuel tank 12 of a motor vehicle. The fuel tank 12 has a filler pipe 14 with an opening 16 at one end. The opening 16 of the filler pipe 14 is normally closed by a cap (not shown). During refuelling, a filler nozzle 18 is inserted into the filler pipe 14 through the opening 16. Fuel vapours trapped within the fuel tank 12 pass into a vapour recovery canister 20 (typically containing vapour absorbing carbon) by way of a float limiting valve 22 and a fuel vapour outlet pipe 24. A vapour flow control valve 26 is connected between the fuel vapour outlet pipe 24 and the filler pipe 14.

The control valve 26 comprises a housing 28 with a movable valve member (preferably in the form of a diaphragm or piston 30) which defines first and second chambers 32,34 within the housing. The first chamber 32 is connected to the fuel vapour outlet pipe 24 by a valve inlet pipe 36 which opens into the first chamber. A valve outlet pipe 38 is connected between the control valve 26 and the filler pipe 14 and opens into the filler pipe adjacent the opening 16, upstream of the end of the filler nozzle 18. The other end 40 of the valve outlet pipe 38 is positioned inside the first chamber 32 and is normally closed by the diaphragm or piston 30. The diaphragm or piston 30 is biased against the other end 40 of the valve outlet pipe 38, to normally close the other end 40, by a spring 42 positioned in the second chamber 34. The diameter of the opening at the other end 40 has to be large enough for the expected maximum flow rates. Alternatively, the diameter of the opening at the other end 40 or the valve outlet pipe 38 may be restricted by an orifice to limit the maximum flow rates. The second chamber 34 is open to atmospheric air or, optionally, may be connected to the filler pipe 14 by a vacuum pipe 44 which opens into the filler pipe downstream of the end of the filler nozzle 18. Also optionally, the valve outlet pipe 38 may have a restricted orifice 46 formed therein which opens directly into the first chamber 32.

During refuelling, the incoming fuel 48 from the filler nozzle 18 causes the pressure on the fuel vapour inside the fuel tank 12 to increase.

This increase in pressure also increases the pressure on the fuel vapour inside the first chamber 32 of the control valve 26. At a predetermined pressure level, determined by the size of the spring 42 and the surface area of the diaphragm or piston 30, the diaphragm or piston moves away from the other end 40 of the valve outlet pipe 38, against the bias of the spring, to connect the first chamber 32 to the filler pipe 14. Such an arrangement recirculates fuel vapour (as shown by the arrows in Figure 1) into the filler pipe 14 and reduces or eliminates entrainment of atmospheric air into the filler pipe, thereby limiting further generation of fuel vapour. The opening and closing of the other end 40 of the valve outlet pipe 38 is directly dependent on the rate of flow of fuel into the fuel tank 12 from the fuel nozzle 18, because the increase in pressure in the fuel vapour in the fuel tank is directly dependent on such a rate of flow. The present invention therefore actively compensates for fluctuations in fuel flow into the fuel tank 12. The present invention can be attached to filler pipes 14 (including filler pipes which are currently available) without the need of a shield with a controlled small clearance relative to an inserted filler nozzle 18 as required in US-A4762156.

When present, the vacuum pipe 44 generates a negative pressure (relative to atmospheric pressure) in the second chamber 34 to have an effect on the predetermined pressure level at which the control valve 26 opens the other end 40 of the valve outlet pipe 38.

The restricted orifice 46 provides a minimum vapour bias (recirculation) during refuelling at low refuelling rates when the control valve 26 remains closed. The predetermined pressure level at which the control valve 26 opens will also be dependent on the size of the restricted orifice 46.

As an alternative to the above described embodiment, the control valve 26 and the float level valve 22 may be integrated in a single housing. As further alternatives, the control valve 26 may be integral with the filler pipe 14 or the canister 20. Also, the valve outlet pipe 38 could be conceived as being concentric with the filler pipe.

Claims

1. A fuel vapour recovery system for use with a fuel tank of a motor vehicle comprising a control valve; a valve inlet pipe connected to the control valve and connectable to the fuel tank to receive fuel vapour from the fuel tank; and a valve outlet pipe connected to the control valve and connectable to a filler pipe for the fuel tank adjacent a fuel filling opening in the filler pipe; wherein the control valve includes a housing, a valve member movable inside the housing and defining a first chamber and a second chamber inside the housing, and a spring positioned in the second chamber and acting on the valve member, the valve inlet pipe opening into the first chamber, and the valve outlet pipe having an end positioned inside the first chamber, said end being normally closed by the valve member due to the bias of the spring and opening when fuel vapour pressure in the first chamber exceeds a predetermined pressure level.

2. A fuel vapour recovery system as claimed in Claim 1, wherein the second chamber is connected to air at atmospheric pressure.

3. A fuel vapour recovery system as claimed in Claim 1, further comprising a vacuum pipe connected to the second chamber and connectable to the filler pipe at a position downstream of the opening to the filler pipe.

4. A fuel vapour recovery system as claimed in any one of Claims 1 to 3, wherein the valve outlet pipe has a restricted orifice opening into the first chamber.

5. A fuel vapour recovery system as claimed in any one of Claims 1 to 4, wherein the valve member comprises a diaphragm or piston.

6. A fuel vapour recovery system as claimed in any one of Claims 1 to 5, wherein the end of the valve outlet pipe positioned inside the first chamber has an opening of predetermined diameter.

7. A fuel vapour recovery system substantially as herein described with reference to, and as shown in, the accompanying drawing.