Fuel tank system

Abstract: A fuel tank sealing system for a fuel tank filler tube (14) is disclosed in which the fuel system is sealed when a fuel cap (30) is not installed, or improperly installed and allows pressure equalisation during the insertion of a refuelling nozzle. A vent valve (40) is first actuated by partial insertion of the nozzle and allows pressure equalising flow to bypass the refuelling nozzle. A flap valve (42) is then actuated by complete insertion of the refuelling nozzle to allow fuel to enter the fuel tank.

Description: The present invention relates to a fuel tank sealing system for an automobile having a fuel filler pipe in which a positive seal retainer is employed. Conventional vehicle fuel tank systems have a removable fuel tank cap for sealing the unburned hydrocarbon fuel in the fuel tank system. In general, the fuel tank cap contains pressure relief and vacuum relief valves for relieving excessive pressure or vacuum. However, if the cap is improperly installed or is not installed at all, fuel vapours may escape into the atmosphere due to even slight pressure build-up in the fuel tank. Recent regulation related to the emission of unburned hydrocarbon fuel has required a solution to this problem. One approach to preventing fuel vapour discharge out of the fuel tank is to use an onboard diagnostic leak detection system. In such a system, a vacuum is applied to the fuel tank and the corresponding fuel tank pressure is measured. If a leak is present, a corresponding pressure response is observed. When no leak is preset, a different pressure response is observed. Thus, it is possible to diagnose a possible fuel tank leak, or an improperly installed fuel tank cap. Another approach, which may combined with the previous approach, is to use a flap valve, spring biased in the closed position, in the fuel tank filler tube. This allows the fuel tank filler tube to be sealed if the gas tank cap is not properly installed. This system uses hardware to guarantee a physical seal regardless of the installation of the cap. In addition, a valve element is provided that provides pressure equalisation across the flap valve when the cap is properly installed. This is necessary because when refuelling, a small amount of residual fuel retained in the refuelling nozzle will enter the fuel tank filler tube before the flap valve opened. Thus, without the valve element, fuel may spray back on the nozzle operator due to pressure build-up in the fuel tank system. Such a system is disclosed in U.S. 5,595,222. The inventor herein has recognised a disadvantage with the above approach. For example, the system still relies on the fuel tank cap to allow pressure equalisation. Thus, if the fuel tank cap is improperly installed, while no vapours in the fuel system will be emitted, residual fuel in the refuelling nozzle may be sprayed on the nozzle operator due to unreleased pressure in the fuel tank system. Another example is that the system still relies on the fuel tank cap to provide a seal when properly installed. In other words, a cap may be properly installed; however, if defective, it may create a poor seal, which can lead to a leak. It is known from WO 00/02778 (prior art under Art. 54(3) EPC and showing the features of the preamble of claim 1) to provide a fuel tank filler tube having a vent valve adapted to be operated by a fuel nozzle to release vapour and thereby to achieve pressure equalisation before the nozzle operates a flap valve to enable refuelling. US-A-4 966 299 discloses a fuel tank sealing system for a fuel tank filler tube comprising: an upper portion of the fuel tank filler tube communicating with atmosphere; a lower portion of the fuel tank filler tube communicating with a fuel tank; a biased closed vent valve located in the fuel tank filler tube between said upper portion and said lower portion, and a biased closed flap valve located in the fuel tank filler tube between said upper portion and said lower portion, said flap valve adapted to be actuated by the refuelling nozzle so as to allow fuel flow between said upper portion and said lower portion of the fuel tank filler tube. In one particular aspect of the invention, the system includes an upper portion of the fuel tank filler tube communicating with atmosphere, a lower portion of the fuel tank filler tube communicating with a fuel tank, and a biased closed vent valve located in the fuel tank filler tube between the upper portion and the lower portion. The vent valve is adapted to be actuated by a refuelling nozzle so as to also allow vapour flow between said upper portion and said lower portion of the fuel tank filler tube. The system also includes a biased closed flap valve located in the fuel tank filler tube between the upper portion and the lower portion. The flap valve is adapted to be actuated by the refuelling nozzle so as to allow fuel flow between the upper portion and the lower portion of the fuel tank filler tube only after the vent valve is actuated by the refuelling nozzle, thereby achieving pressure equalisation before the refuelling nozzle actuates the flap valve. The system is characterised by the vent valve comprising a vent valve lever pivotally attached within the filler tube between the upper portion and the lower portion and a vent passage communicating between the upper portion and the lower portion, with the vent valve lever biased to close the vent passage. By actuating the vent valve before the flap valve, it is possible to equalise the fuel tank pressure with the atmosphere whereby the pressure equalising flow passes through the vent valve and bypasses the refuelling nozzle. Then, when the flap valve is actuated, any residual fuel left in the refuelling nozzle from previous operation that falls onto the flap valve may not experience pressure equalisation flow. Thus, the residual fuel may not be forced out of the fuel filler tube into the atmosphere. An advantage of the above aspect of the invention is reduced emissions. Another advantage of the above aspect of the invention is a reduction in malfunction indicator warnings. The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view showing a fuel tank sealing system with a fuel cap installed; Figure 2 is a cross-sectional view showing the fuel tank sealing system with a fuel filler nozzle partially inserted; Figure 3 is a cross-sectional view showing the fuel tank sealing system with a fuel filler nozzle fully inserted; and . Figure 4 is a cross-sectional view showing an alternative embodiment of a fuel tank sealing system with a fuel cap installed. Referring to Figure 1, according to the present invention, system 10 includes cylindrically shaped retainer 12 coaxially located within filler tube 14, which, in turn, is attached to vehicle 16. Filler tube 14 is generally cylindrically shaped and has longitudinal axis 18 and communicates with fuel tank 20 as indicated in Figure 1. Filler tube 14 includes upper portion 22 communicating with atmosphere and lower portion 24 communicating with tank 20. In addition, any arrangement of carbon canisters known to those skilled in the art may be used with the present invention as needed. Retainer 12 includes proximal end 26, located generally adjacent tank 20, and distal end 28 adapted to receive fuel fill cap 30. System 10 further includes vent valve 40 and flap valve 42. Vent valve 40 includes vent lever 44 pivotally attached at pivot 46 to proximal end 26 of retainer 12. Vent passage 48, having axis 49 (which is offset from axis 18), is disposed in distal end 26 of retainer 12 and communicates between upper portion 22 and lower portion 24 to allow fuel vapour to flow therethrough. Vent valve 40 further includes vent seal 50 located between vent lever 44 and 16 and retainer 12. Vent lever 44 is biased to close vent passage 48 through, for example, the use of a torsion spring. Alternatively, vent lever 44 may be integrally moulded into a plastic retainer and hinged in a manner to allow selective opening of passage 48. Thus, as used herein, "pivotally attached" includes any means which will allow selective opening of passage 48. Flap valve 42 includes flap lever 60 pivotally attached at pivot 62 to bracket 63, which is attached to proximal end 26 of retainer 12. Fuel fill passage 64, having axis 66 (which is also offset from axis 18), is disposed in distal end 26 of retainer 12 and communicates between upper portion 22 and lower portion 24 to allow fuel to flow therethrough. Flap valve 42 further includes flap seal 68 located between flap lever 60 and 16 and retainer 12. Flap lever 60 is biased to close fuel fill passage 64 through, for example, the use of a torsion spring. Alternatively, flap lever 60 may be integrally moulded into a plastic retainer and hinged in a manner to allow selective opening of fuel fill passage 64. Thus, as used herein, "pivotally attached" includes any means which will allow selective opening of fuel fill passage 64. In a preferred embodiment, vent lever pivot 46 is located between distal end 28 of retainer 12 and flap valve 42. Further, vent lever pivot 46 is located within upper volume 22 and flap lever pivot 62 is located within lower volume 20. Continuing with Figure 1, in a preferred embodiment, fuel cap 30 does not contain any pressure relief or vacuum relief valves. Rather, pressure relief and vacuum relief valves 70 and 72, respectively, which relieve exceptionally large fuel tank pressures and vacuums, may be incorporated in flap valve lever 60. Both the pressure relief and vacuum relief valves 70, 72 have a calibratable level at which they will open. Alternatively, the pressure relief and vacuum relief valves 70, 72 could be incorporated in vent valve lever 44. Similarly, the pressure relief valve 70 could be incorporated into vent valve lever 44 and the vacuum relief valve 72 could be incorporated into flap valve lever 44 or vice versa. In another embodiment, the function of the pressure relief valve 70 could be accomplished by vent valve 40 and the function of the vacuum relief valve 72 could be accomplished by flap valve 42. This is possible if the biasing method of flap valve 42 can be acceptably set to relieve a desired vacuum level and if the biasing method vent valve 40 can be acceptably set to relieve a desired pressure level, while still maintaining their functionality. In other words, vent valve 40 and flap valve 42 would each have a dual function. Turning now to Figures 2 and 3, operation of the present invention will now be described. Referring first to Figure 2, fuel fill cap 30 is first removed and refuelling nozzle 30 is inserted through retainer 12 to refuel the vehicle. As a refuelling nozzle 80 is inserted, the refuelling nozzle 80 first contacts vent valve lever 44 to open vent passage 48 such that pressurised fuel vapour in lower portion 20 can pass through passage 48 to upper portion 22. Further, because axis 49 is offset from axis 18, the pressurised fuel vapour flows around the refuelling nozzle 80 avoiding the opening 82 of the refuelling nozzle. When lower portion 24 is pressurised, fuel vapours flow along path 84, allowing pressure equalisation. In particular, any residual gas in refuelling nozzle 80 that falls from refuelling nozzle opening 82 onto flap valve 42 before refuelling nozzle 80 is actuated does not contact fuel vapours flowing along path 84. Also, fuel vapours flowing along path 84 bypass refuelling nozzle opening 82. Thus, there is a reduction in the possibility of residual fuel encountering pressure equalising flow and exiting into the atmosphere. Further, this system is independent of the state of fuel cap 30. For example, even if fuel cap 30 is left off, or improperly installed, pressure equalisation will still be achieved during refuelling without the possibility of spilling residual fuel. In addition, if fuel cap 30 is left off or improperly installed, this system will prevent constant vapour loss through the biased closed vent valve 40 and flap valve 42. Referring now to Figure 3, refuelling nozzle 80 is shown fully inserted into fuel filler pipe 14, whereby flap valve lever 60 pivots about pivot 62 to allow nozzle 80 to enter lower portion 24 thus allowing fuel delivery from refuelling nozzle 80 to enter fuel tank 20. When refuelling nozzle 80 is removed, both vent valve 40 and flap valve 42 return to the closed position as shown in Figure 1, thus sealing the fuel system. Then, fuel cap 30 can be installed. However, the system does not rely on any seal created by fuel cap 30. Referring now to Figure 4, an alternative embodiment of system 10 is shown having vent valve 88. In particular, retainer 12 comprises vent path 90 with spool valve 92 located therein. Vent seal 94 is located between spool valve 92 and retainer 12. Vent path 90 communicates with lower volume 20 of filler pipe 14. Vent path 90 also may communicate with upper volume 22 of filler pipe 14 depending on the position of spool valve 92. Spool valve 92 is biased closed by spring 96 or any other biasing methods known to those skilled in the art and suggested by this disclosure. Spool valve 92 is hinged to lever 98, which, in turn is pivotally attached to retainer 12 at pivot 100. As discussed with reference to Figures 1-3, upon insertion of nozzle 80 (not shown in Figure 4), lever 98 rotates to pull on spool valve 90, overcoming the force of spring 96, to allow vapour flow from lower portion 24 to upper portion 22 through vent path 90.

Claims: A fuel tank sealing system for a fuel tank filler tube comprising: an upper portion (22) of the fuel tank filler tube (14) communicating with atmosphere; a lower portion (24) of the fuel tank filler tube (14) communicating with a fuel tank; a biased closed vent valve (40) located in the fuel tank filler tube (14) between said upper portion and said lower portion, said vent valve (40) adapted to be actuated by a refuelling nozzle so as to also allow vapour flow between said upper portion (22) and said lower portion (24) of the fuel tank filler tube (14); and a biased closed flap valve (42) located in the fuel tank filler tube (14) between said upper portion and said lower portion, said flap valve adapted to be actuated by the refuelling nozzle so as to allow fuel flow between said upper portion and said lower portion of the fuel tank filler tube (14) only after said vent valve (40) is actuated by the refuelling nozzle, thereby achieving pressure equalisation before said refuelling nozzle actuates said flap valve (42) characterised by said vent valve comprising: a vent valve lever (44) pivotally attached within said filler tube (14) between said upper portion (22) and said lower portion (24); and a vent passage (48) communicating between said upper portion and said lower portion, with said vent valve lever (44) biased to close said vent passage (48). A system as claimed in Claim 1, wherein said flap valve (42) comprises a pressure relief valve (70) disposed therein for relieving a fuel tank pressure when said fuel tank pressure reaches a predetermined level. A system as claimed in Claim 1, wherein said flap valve comprises a vacuum relief valve (72) disposed therein for relieving a fuel tank vacuum when said fuel tank vacuum reaches a predetermined level. A system as claimed in Claim 1, wherein said upper portion (22) of the fuel tank filler tube is adapted to be connected to a fuel cap (30). A system as claimed in any of the preceding claims, wherein said vapour flow between said upper portion (22) and said lower portion (24) of the fuel tank filler tube bypasses an exit hole (82) of the refuelling nozzle (80), thereby allowing pressure equalisation flow to avoid said exit hole. A system as claimed in claim 5, wherein: said fuel tank filler tube is generally cylindrically shaped having a longitudinal axis (18); a generally cylindrically shaped retainer (12) coaxially located within said filler tube, said retainer having a proximal end (26) adjacent to the tank (20) and a distal end (28) adjacent to the fuel fill cap (30), with said distal end being adapted to be connected to the fuel fill cap; said vent passage (48) being offset (49) from said filler tube axis (18); said vent valve lever (44) being pivotally attached to said retainer (12) at said proximal end (26) between said upper portion and said lower portion and being adapted to be actuated by a refuelling nozzle (80) so as to allow said vapour flow between said upper portion and said lower portion of said filler tube through said vent passage (48) to bypass said exit hole (82); and said flap valve (42) having: a flap valve lever (60) pivotally attached to said retainer (12) at said proximal end (26) between said upper portion and said lower portion; and a fuel fill passage (64) communicating between said upper portion (22) and said lower portion (24), with said flap valve lever (60) biased to close said fuel fill passage (64), and with said fuel fill passage (64) being offset (66) from said filler tube axis.

Inventors: ARMESTO CARLOS, FAIRBAIRN JAMES ALLAN, ARMESTO, CARLOS, FAIRBAIRN, JAMES ALLAN
Applicants: FORD GLOBAL TECH INC, FORD GLOBAL TECHNOLOGIES, INC.
Application year: 1999
Main classification: B60K15
IPC codes: B60K15