A vent apparatus is opened to allow free flow of fuel vapor from a vehicle fuel tank through the vent apparatus to a fuel vapor recovery canister during tank refueling until a predetermined level of liquid fuel is reached in the vent apparatus. Once refueling has been completed, the vent apparatus i
A vent apparatus is opened to allow free flow of fuel vapor from a vehicle fuel tank through the vent apparatus to a fuel vapor recovery canister during tank refueling until a predetermined level of liquid fuel is reached in the vent apparatus. Once refueling has been completed, the vent apparatus is closed to block or limit further flow of liquid fuel to the vent apparatus. At the same time, fuel vapor discharge passageways in the vent apparatus that had been closed once the fuel tank had been filled to a predetermined capacity with liquid fuel are reopened so that fuel vapor can flow freely from the fuel tank to the canister even though the volume or height of liquid fuel in the fuel tank has not decreased since the tank was filled during refueling.
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The invention claimed is: 1. A vent apparatus to be located in a fuel tank to regulate discharge of fuel vapor from the tank to a destination outside of the tank, the vent apparatus comprising a fill-limit vent valve adapted to be mounted in the tank and having a venting outlet adapted to be connec
The invention claimed is: 1. A vent apparatus to be located in a fuel tank to regulate discharge of fuel vapor from the tank to a destination outside of the tank, the vent apparatus comprising a fill-limit vent valve adapted to be mounted in the tank and having a venting outlet adapted to be connected to a vent outlet of the tank and a flow port, the fill-limit vent valve being responsive to fuel level in the tank to open and allow venting of vapor in the fuel tank through the venting outlet until a predetermined liquid fuel level in the fill-limit vent valve is reached, a control valve connected to the flow port of the fill-limit vent valve and having a fuel port receiving fuel from the tank and a drain port draining fuel, and an actuator coupled to the control valve to provide a first control signal causing the control valve to move to a fuel-delivery position during refueling of the fuel tank to block the drain port and to open the fuel port to deliver liquid fuel from the tank to the fill-limit vent valve allowing discharge of tank fuel vapor from a vapor space in the tank to the fill-limit vent valve module until the fuel level closes the fill-limit vent valve, and to provide a second control signal after refueling causing the control valve to move to a fuel-shutoff position to block further flow of liquid fuel from the fuel tank to the fill-limit vent valve module and to open the drain port to drain liquid fuel from the fill-limit vent valve module into the fuel tank to allow the fill-limit vent valve to open. 2. The apparatus of claim 1, further comprising a fuel drainage pump connected to the drain port, and wherein the actuator provides a third control signal after refueling turning on the fuel drainage pump to drain liquid fuel from the fill-limit vent valve module. 3. The apparatus of claim 1, further comprising a vent unit connected to the venting outlet and having an inlet connected to one of a rollover valve and a run/loss valve, the vent value unit opening in response to pressure from one of the rollover valve and the run/loss valve. 4. The apparatus of claim 1, wherein the actuator is also responsive to the state of one of a fuel door and filler neck closure cap. 5. The apparatus of claim 1, wherein the fill-limit vent valve module includes a float chamber having an outlet connected to the venting outlet and having the flow port, a float valve in the float chamber to open and close the outlet of the float chamber, and a fuel retention chamber having an inlet port connected to the fuel tank and an outlet connected to the fuel port of the control valve. 6. The apparatus of claim 5, further comprising a vent orifice connecting the two chambers at a height above the maximum liquid fuel level to allow vapor flow between the chambers. 7. The apparatus of claim 6, wherein the fuel retention chamber includes a second inlet port at a height above the maximum liquid fuel level to allow vapor flow into fuel retention chamber. 8. The apparatus of claim 1, wherein the control valve is a solenoid-controlled valve and the actuator is responsive to a signal from an engine ignition. 9. The apparatus of claim 8, wherein the actuator is also responsive to the state of one of a fuel door and filler neck closure cap. 10. The apparatus of claim 8, wherein the actuator is also responsive to the state of at least one of an engine ignition, a fuel door and filler neck closure cap. 11. A vent apparatus to be located in a fuel tank to regulate discharge of fuel vapor from the tank to a destination outside of the tank, the vent apparatus comprising a fill-limit vent valve adapted to be mounted in the tank and having a venting outlet adapted to be connected to a vent outlet of the tank and a flow port, the fill-limit vent valve bring responsive to fuel level in the tank to open and allow venting of vapor in the fuel tank through the venting outlet until a predetermined liquid fuel level in the fill-limit vent valve is reached, a solenoid-controlled valve connected to the flow port of the fill-limit vent valve and having a fuel port receiving fuel from the tank and a drain port draining fuel, a pump connected to the drain port of the solenoid-controlled valve draining fuel when turned on, and an actuator coupled to the solenoid-controlled valve to provide a first control signal causing the solenoid-controlled valve to move to a fuel-delivery position during refueling of the fuel tank to block the drain port and to open the fuel port to deliver liquid fuel from the tank to the fill-limit vent valve allowing discharge of tank fuel vapor from a vapor space in the tank to the fill-limit vent valve module until the fuel level closes the fill-limit vent valve, to provide a second control signal after refueling causing the solenoid-controlled valve to move to a fuel-shutoff position to block further flow of liquid fuel from the fuel tank to the fill-limit vent valve module and to open the drain port to drain liquid fuel from the fill-limit vent valve module into the fuel tank to allow the fill-limit vent valve to open, and to provide a third control signal after refueling turning on the fuel drainage pump to drain liquid fuel from the fill-limit vent valve module. 12. The apparatus of claim 11, further comprising the fill-limit vent valve module includes a float chamber having an outlet connected to the venting outlet and having the flow port, a float valve in the float chamber to open and close the outlet of the float chamber, and a fuel retention chamber having an inlet port connected to the fuel tank and an outlet connected to the fuel port of the solenoid-controlled valve. 13. The apparatus of claim 12, including a vent orifice connecting the two chambers at a height above the maximum liquid fuel level to allow vapor flow between the chambers. 14. The apparatus of claim 13, wherein the fuel retention chamber includes a second inlet port at a height above the maximum liquid fuel level to allow vapor flow into fuel retention chamber. 15. A method of controlling a vent apparatus located in a fuel tank to regulate discharge of fuel vapor from the tank to a destination outside of the tank, the method comprising providing the vent apparatus having a control valve and a fill-limit vent valve, the control valve being connected to a flow port of the fill-limit vent valve and having a fuel port for receiving fuel from the tank and a drain port for draining fuel, and an actuator coupled to the control valve to provide signals to fill or drain the fill-limit vent valve, providing flow of liquid fuel to the vent apparatus during tank refueling to operate the vent apparatus allowing flow of fuel vapor from the fuel tank through the vent apparatus to the destination until a predetermined fluid level is reached in the vent apparatus which stops the flow of fuel vapors through the vent apparatus, determining that refueling has been completed, stopping the flow of liquid fuel to the vent apparatus during tank refueling after determining that refueling has been completed to block further flow of liquid fuel to the vent apparatus, and draining liquid fuel from the vent apparatus after determining that refueling has been completed to operate the vent apparatus allowing flow of fuel vapor from the fuel tank through the vent apparatus to the destination. vapor from the fuel tank through the vent apparatus to the destination. 16. The method of claim 15, further comprising providing a pump connected to the venting apparatus and operating the pump to drain the liquid fuel from the vent apparatus. 17. The method of claim 15, wherein determining that refueling has been completed includes determining the state of at least one of an engine ignition, a fuel door, and filler neck closure cap. 18. The method of claim 15, further comprising the step of operating the control valve to provide and stop the flow of liquid fuel to the vent apparatus and to drain liquid fuel from the vent apparatus. 19. The method of claim 18, further comprising providing a pump connected to the control valve and operating the pump to drain the liquid fuel from the vent apparatus. 20. A fuel tank including the venting apparatus of claim 1.
Dudar, Aed M.; Yang, Dennis Seung-Man; Ognjanovski, Jr., Robert; Pearce, Russell Randall, Systems and methods for detection and mitigation of liquid fuel carryover in an evaporative emissions system.
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