METHOD AND SYSTEM FOR FUEL VAPOR CONTROL
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Abstract
A method and system for fuel vapor control in a hybrid vehicle (HEV). The HEV fuel vapor recovery system includes a fuel tank isolation valve, which is normally closed to isolate storage of refueling from storage of diurnal vapors. The method for fuel vapor control includes selectively actuating the fuel tank isolation valve during interrelated routines for refueling, fuel vapor purging, and emission system leak detection diagnostics to improve regulation of pressure and vacuum the HEV fuel vapor recovery system.
12 Citations
39 Claims
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1-21. -21. (canceled)
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22. A method for a fuel vapor recovery system including a fuel tank coupled to a canister, comprising, under a first condition, applying positive pressure in the fuel tank before applying the pressure on the canister;
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under a second condition, applying negative vacuum on the canister before applying the vacuum on the fuel tank; and under each condition, indicating degradation based on a fuel vapor recovery system pressure change upon the respective pressure or vacuum application. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A method of monitoring flow of fuel vapors and/or air through a vehicle fuel vapor recovery system including a fuel tank with a refueling valve on an outer body of a vehicle, the fuel tank coupled to a canister and an engine, the canister coupled to an engine intake, and further coupled to a vacuum accumulator, the engine coupled to a battery, the method comprising,
selectively providing engine-on vehicle operation and engine-off vehicle operations, the engine selectively operated in response to a battery state of charge falling below a threshold; -
during a first engine-off condition, when a fuel tank absolute pressure is greater than a threshold, applying a pressure on the fuel tank before applying a pressure on the canister; during a second engine-off condition, when a fuel tank absolute pressure is lower than the threshold, monitoring a change in fuel tank and canister pressure upon applying a pressure on the canister before applying a pressure on the fuel tank; and during the first engine-off condition or the second engine-off condition, indicating degradation based on a monitored change in fuel tank and canister pressure. - View Dependent Claims (33, 34, 35, 36, 37, 38)
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39. A method of monitoring flow of fuel vapors and/or air through a hybrid vehicle fuel vapor recovery system including a fuel tank with a refueling valve on an outer body of a vehicle, the fuel tank coupled to a canister and an engine, the canister coupled to an engine intake, and further coupled to a vacuum accumulator, the engine coupled to a battery, the method comprising,
selectively providing engine-on vehicle operation and engine-off vehicle operations, the engine selectively operated in response to a battery state of charge falling below a threshold; -
storing vacuum in the vacuum accumulator during engine-on vehicle operation and engine-off vehicle operations from the engine and/or from a brake booster pump; during a first engine-off condition, when a fuel tank absolute pressure is greater than a threshold, applying a pressure on the fuel tank before applying a pressure on the canister; during a second engine-off condition, when a fuel tank absolute pressure is lower than the threshold, monitoring a change in fuel tank and canister pressure upon applying a pressure on the canister before applying a pressure on the fuel tank; and during the first engine-off condition or the second engine-off condition, indicating degradation based on a monitored change in fuel tank and canister pressure.
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Specification