The present invention relates to filler tube assemblies for fuel tank installations having a fuel vapor recirculation tube ported to the upper end of the filler tube in an enlarged nozzle receiving end.
Fuel vapor recirculation tubes are used in motor vehicle fuel tank filler tubes to recirculate fuel vapor during refueling from a nozzle inserted in the filler tube with a mechanical seal provided about the nozzle. The recirculated vapor provides a make-up flow below the nozzle seal to prevent the flow discharging from the nozzle from creating a vacuum in the filler tube and prematurely activating the automatic nozzle shutoff.
Known fuel tank filler tube installations having a vapor recirculation tube attached to a port in the filler tube below the nozzle seal. This configuration sometimes allows liquid fuel to enter the vapor recirculation tube and flow into the vapor vent system when liquid fuel rises in the filler tube as the tank is filled. Liquid fuel in the vapor vent system can block the vapor vent lines, trap fuel in low regions of the system or even cause degradation of the vapor storage medium in the vapor storage canister if fuel enters the canister.
Known filler tubes also have a tapered nozzle chamber in the vicinity of the recirculation tube. The nozzle chamber surrounds the end of the nozzle when it is inserted into the filler tube and helps generate a vacuum condition in when mechanical seals are used. The diameter of the nozzle chamber around the nozzle should allow enough liquid to flow between the inner diameter of the nozzle chamber and the outer diameter of the nozzle to avoid excess fuel tank pressure when the nozzle fails to shut off. However, the length of the nozzle can vary, causing the ends of different nozzles to reach different areas in the nozzle chamber. Because the vacuum created in the filler tube depends on how much space is between the tip of the nozzle and the surrounding filler tube, filler tubes with a tapered nozzle chamber will generate inconsistent vacuum conditions because different nozzle lengths will end at different diameter portions of the nozzle chamber.
There is a desire for a way to protect a fuel vapor recirculation system from liquid fuel flowing into the vapor lines and to do so in a manner that is simple and low in cost and does not require substantial reworking or retooling of the fuel tank filler tube. There is also a desire for a reliable way to generate a consistent vacuum in the nozzle chamber regardless of the nozzle length.
The present invention prevents liquid fuel from entering into the vapor recirculation line, which is tapped into the filler tube below the nozzle seal, when fuel rises in the filler tube when the tank is full. The invention includes a check valve having a flapper attached to the insert that is placed in the filler tube. The flapper is sensitive to fluid viscosity and distinguishes between liquid fuel and fuel vapor due to the inherently different viscosities of liquid and vapor. During use, the check valve response to the changes in viscosity of fuel surrounding the flapper as well as the differential pressure on either side of the flapper to open and close the vapor port.
The flapper of the present invention therefore closes when liquid fuel enters the upper end of the filler tube and opens in response to vapor pressure to allow proper vapor recirculation. By responding to both viscosity and differential pressure around the check valve, the check valve can distinguish between fuel vapor and liquid fuel in a simple yet reliable manner.
The invention is also directed to a filler tube assembly having a nozzle chamber with a constant diameter. The constant diameter nozzle chamber ensures that the space between the nozzle and the chamber remains consistent regardless of the nozzle length, making the vacuum condition within the chamber consistent as well. A failed nozzle relief valve may also be included to provide an alternative flow path for fuel and vapor in the case of nozzle shutoff failure.
Referring to
A vapor check valve assembly 24 is disposed in the filler tube 10 and includes an annular flange 26 formed about an upper circumference of a cylinder 27. Upon installation of the assembly 24 in tube 16, the annular flange 26 engages the lip 18 of the tube portion 16 to maintain the insert against the shoulder 14. The check valve assembly 24 includes a flexible flapper 36 that can flex and move to open and close the recirculation port 20. In one embodiment, the flapper 36 is made of a material that is stiff enough to hold its shape yet flexible enough to bend and flex in response to forces applied to it. One possible material for the flapper 36 is a polymer film, such as TEFLON® or MYLAR® film, or other material having similar properties.
The check valve assembly 24 is shown in the open position in
Referring to
As shown in the figures, the assembly 12 also includes an annular lip seal 60 that is sized and configured to seal about the periphery of a refueling nozzle 62 when the nozzle is inserted therein, thereby forming a mechanical seal. The seal 60 is retained between a stepped portion 65 of the cylinder 27 and a sealing insert 66, which is in turn frictionally held in place within the enlarged diameter portion 16 of the tube 12.
The tube 12 itself has a nozzle chamber 80 that surrounds the end portion of the refueling nozzle 62 when is it inserted into the tube 12. The nozzle chamber surrounds the end of the nozzle helps generate a vacuum condition in when mechanical seals are used. During refueling, liquid flows along the path shown by the arrows in the figure and also flows between the outside diameter of the nozzle 62 and the inner wall of the nozzle chamber 80. There should be enough space between the two to avoid excess fuel tank pressure when the nozzle 62 fails to shut off automatically. A jet-pump action created by fuel flow helps generate a vacuum condition in the tube 12 when a mechanical seal, such as the lip seal 60, is used to prevent overfilling of the fuel tank.
The nozzle chamber 80 in the invention has a constant diameter rather than a tapered, semi-conical shape. Because the vacuum created in the filler tube 62 depends on how much space is between the tip of the nozzle and the surrounding nozzle chamber 80, the constant diameter of the nozzle chamber 80 ensures that the distance between the nozzle 62 and the nozzle chamber 80 is consistent regardless of the length of the nozzle 62. As a result, the vacuum generated within the nozzle chamber is more consistent, creating a more reliable and predictable response to nozzle shut-off failures.
As noted above, the flapper 24 prevents liquid fuel from entering the port 20 in the case of a failed nozzle shutoff and resulting overfill. As shown in the figures, the system 10 also includes a failed nozzle relief (FNR) valve 90 that provides an alternative flow path in the case of a failed nozzle shutoff. The arrows in
As shown in
When the FNR valve 90 is in the open position, the reset lever 94 extends far enough upward to contact a fuel cap (not shown) when it is replaced. When the operator replaces the fuel cap, the fuel cap presses downward on the reset lever 94, thereby pushing the entire FNR valve 90 downward back to the closed position to reset the valve 90. As a result, the FNR valve 90 eliminates the need for a separate resetting mechanism.
By responding to both viscosity and differential pressure around the check valve, the check valve can distinguish between fuel vapor and liquid fuel in a simple yet reliable manner. The present invention thus provides a one-way check valve for closing the vapor vent recirculation port in a fuel tank filler tube and which is formed as an insert subassembly which may be inserted in an existing filler tube. Further, the tube includes a nozzle chamber having a constant diameter, ensuring that the vacuum condition generated in the chamber is independent of the fuel nozzle length and keeping the nozzle shut-off response consistent when there is a mechanical seal in the system. The FNR valve may also be included and is designed to reset easily when a filler cap is replaced over the filler tube.
Although the invention has hereinabove been described with respect to the illustrated embodiments, it will be understood that the invention is capable of modification and variation and is limited only by the following claims.