FIELD

The present disclosure relates generally to fuel tanks on passenger vehicles and more particularly to a fuel tank having an electronically controlled module that manages the complete evaporative system for the vehicle, the fuel system implementing a method that isolates the fuel tank from a purge canister.

BACKGROUND

Fuel vapor emission control systems are becoming increasingly more complex, in large part in order to comply with environmental and safety regulations imposed on manufacturers of gasoline powered vehicles. Along with the ensuing overall system complexity, complexity of individual components within the system has also increased. Certain regulations affecting the gasoline-powered vehicle industry require that fuel vapor emission from a fuel tank's ventilation system be stored during periods of an engine's operation. In order for the overall vapor emission control system to continue to function for its intended purpose, periodic purging of stored hydrocarbon vapors is necessary during operation of the vehicle.

The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

SUMMARY

A method for operating an evaporative emissions control system for use with a fuel tank that stores and delivers fuel to an internal combustion engine is provided. A vent shut-off assembly is provided that selectively opens and closes at least one valve to provide overpressure and vacuum relief for the fuel tank. The vent shut-off assembly selectively vents to a purge canister. The at least one valve is closed whereby vapor is precluded from passing from the fuel tank to the purge canister. A purge event is performed wherein dedicated fresh air is drawn into the purge canister and delivered from the purge canister to the engine.

According to additional features, vapor is precluded from passing from the fuel tank to the purge canister during the purge event. Closing the at least one valve includes rotating at least one cam that in turn closes a respective at least one valve. Rotating the at least one cam includes rotating a rotary actuator that rotates a camshaft having the at least one cam arranged thereon. The at least one valve comprises a first and a second valve. The at least one cam comprises a first and a second cam. Closing the at least one valve comprises rotating the first and second cams that in turn close the respective first and second valves. Performing the purge event includes delivering the fresh air drawn into the purge canister to the engine through an engine vent line.

An evaporative emissions control system configured to recapture and recycle emitted fuel vapor on a vehicle fuel tank includes a first vent tube, a first vent valve, a vent shut-off assembly, a purge canister and a control module. The first vent tube is disposed in the fuel tank. The first vent valve is disposed on the first vent tube that is configured to selectively open and close a first port fluidly coupled to the first vent tube. The vent shut-off assembly is configured on a housing that selectively opens and closes the first valve to provide overpressure and vacuum relief for the fuel tank. The purge canister is fluidly coupled to the vent shut-off assembly through a canister vent line. The purge canister has a canister inlet configured to accept fresh air therethrough. The control module regulates operation of the vent shut-off assembly based on operating conditions. The control module is configured to close the first valve during a purge event wherein dedicated fresh air is drawn into the canister inlet and delivered from the purge canister to an engine.

According to other features, the evaporative emissions control system includes a second vent tube and second vent valve. The second vent tube is disposed in the fuel tank. The second vent valve is disposed on the second vent tube and is configured to selectively open and close a second port fluidly coupled to the second vent tube. The vent shut-off assembly is configured to selectively open and close the second valve to provide overpressure and vacuum relief for the fuel tank. The control module is configured to close the second valve during a purge event. The vent shut-off assembly precludes vapor from passing through the canister vent line during a purge event.

A method for operating an evaporative emissions control system for use with a fuel tank that stores and delivers fuel to an internal combustion engine according to another example is provided. A vent shut-off assembly is provided that selectively opens and closes first and second valves to provide overpressure and vacuum relief for the fuel tank. A fill rate of fuel is determined during a refueling event. The vent shut-off assembly is operated based on the determined fill rate.

According to other features, determining the fill rate comprises monitoring a signal from a fuel tank level sensor. Determining the fill rate according to another example comprises monitoring a signal from a fuel tank pressure sensor. Operating the vent shut-off assembly includes opening at least one of the valves based on the determined fill rate. Operating the at least one valve includes opening the at least one valve a predetermined minimal amount as a function of tank pressure during a refueling event. A trickle fill portion of the refueling event is determined. The vent shut-off assembly is operated during the trickle fill portion to mitigate at least one of spit, spray and well back.

A method for operating an evaporative emissions control system for use with a fuel tank that stores and delivers fuel to an internal combustion engine according to another example is provided. A vent shut-off assembly is provided that selectively opens and closes first and second valves to provide overpressure and vacuum relief for the fuel tank. A fill rate of fuel is monitored during a refueling event. A spike in pressure during the monitoring is determined. A determination whether the spike will influence a premature shut-off of a fill nozzle dispensing the fuel is determined. The vent shut-off assembly is operated to prevent premature shut-off. The vent shut-off assembly is operated by opening at least one of the valves to relieve pressure.

A fuel tank system constructed in accordance to one example of the present disclosure includes a fuel tank, a first vent tube, an evaporative emissions control system, a cam driven tank venting control assembly and a controller. The first vent tube is disposed in the fuel tank. The evaporative emissions control system is configured to recapture and recycle emitted fuel vapor. The cam driven tank venting control assembly has a rotary actuator that rotates a cam assembly based on operating conditions. The cam assembly has at least a first cam having a first cam profile configured to selectively open and close the first vent tube based on operating conditions. The controller commands a signal to the tank venting control assembly to open the vent tube a predetermined minimal amount as a function of tank pressure during a refueling event.

According to additional features, the predetermined minimal amount does not trigger a premature shut off (PSO). The predetermined minimal amount is further a function of at least one of fill rate, fill level and temperature. The controller operates the tank venting control assembly to minimize an amount of vapor delivered to the canister during refueling.

A method for operating an evaporative emissions control system for use with a fuel tank that stores and delivers fuel to an internal combustion engine according to another example is provided. A vent shut-off assembly is provided that selectively opens and closes first and second valves to provide overpressure and vacuum relief for the fuel tank. The vent shut-off assembly has a liquid trap pump. The at least one valve is closed. The liquid trap pump is activated to raise a pressure in the fuel tank to a predetermined test pressure. A leak test is conducted while the fuel tank is at the predetermined test pressure. The tank pressure is monitored with a fuel tank pressure sensor.

A method for operating an evaporative emissions control system for use with a fuel tank that stores and delivers fuel to an internal combustion engine according to another example is provided. A vent shut-off assembly is provided that selectively opens and closes first and second valves to provide overpressure and vacuum relief for the fuel tank. The vent shut-off assembly has a liquid trap pump. Liquid fuel is accumulated within a housing of the vent shut-off assembly. The liquid trap pump is activated to pump the liquid fuel back out into the fuel tank from the housing. Control continues to accumulate and activate to recirculate liquid fuel between the fuel tank and the housing of the vent shut-off assembly. Accumulating liquid fuel comprises receiving liquid fuel through a fuel inlet defined through the housing.

An evaporative emissions control system configured to recapture and recycle fuel vapor on a vehicle fuel tank is provided. The evaporative emissions control system includes a first vent tube, a first vent valve, a vent shut-off assembly, a fuel inlet port, a liquid trap pump and a control module. The first vent tube is disposed in the fuel tank. The first vent valve is disposed on the first vent tube and is configured to selectively open and close a first port fluidly coupled to the first vent tube. The vent shut-off assembly is configured on a housing that selectively opens and closes the first valve to provide overpressure and vacuum relief for the fuel tank. The fuel inlet port is defined on the housing that selectively permits liquid fuel to enter the housing. The liquid trap pump pumps the liquid fuel back out into the fuel tank from the housing. The control module regulates operation of the vent shut-off assembly based on operating conditions. The evaporative emissions control system further includes a second vent tube disposed in the fuel tank and a second vent valve disposed on the second vent tube that is configured to selectively open and close a second port fluidly coupled to the second vent tube. The vent shut-off assembly selectively opens and closes the second valve to provide overpressure and vacuum relief for the fuel tank. The liquid trap pump can recirculate the liquid fuel between the fuel tank and the housing of the vent shut-off assembly. The liquid trap pump can be one of a venturi pump and a piston pump.

