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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

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.

대표청구항 ▼

1. A method, comprising: monitoring a fuel system including a fuel tank, a vacuum accumulator, a venturi, and a canister between the tank and an engine, including:during an engine-on condition, storing vacuum in the accumulator via flow through the venturi; andduring a subsequent engine-off conditio

1. A method, comprising: monitoring a fuel system including a fuel tank, a vacuum accumulator, a venturi, and a canister between the tank and an engine, including:during an engine-on condition, storing vacuum in the accumulator via flow through the venturi; andduring a subsequent engine-off condition and while the canister is isolated from the tank: applying the stored vacuum on the canister, and indicating degradation based on a fuel system pressure change following vacuum application. 2. The method of claim 1, further comprising applying vacuum on the fuel tank during the engine-off condition after applying the stored vacuum on the canister. 3. The method of claim 1, wherein a brake pump exhaust flows through the venturi to generate the vacuum. 4. The method of claim 3, wherein applying the stored vacuum includes opening a vacuum accumulator valve coupling the vacuum accumulator to the canister, and closing a canister purge valve coupling the canister to an engine intake. 5. The method of claim 4, wherein indicating degradation includes indicating fuel tank isolation valve degradation in response to, following vacuum application, a change in canister pressure over time being greater than a threshold, and indicating purge valve degradation in response to a change in canister pressure over time being greater than a threshold. 6. The method of claim 1, wherein vacuum application is delayed based on an amount of vacuum in the vacuum accumulator. 7. The method of claim 6, wherein the delay includes continuing engine operation until the amount of vacuum in the vacuum accumulator exceeds a threshold, and discontinuing engine operation when the amount of vacuum exceeds the threshold. 8. The method of claim 2, further comprising, during a purging condition, purging a first amount of fuel vapors from the canister to an engine intake, and after purging the first amount, purging a second amount of fuel vapors from the fuel tank to the canister, the second amount of fuel vapors adjusted based on the first amount. 9. The method of claim 2, further comprising, during a first engine-off condition, when a fuel tank absolute pressure is greater than a threshold, applying the stored vacuum on the fuel tank before applying the stored vacuum on the canister; andduring a second engine-off condition, when a fuel tank absolute pressure is lower than the threshold, applying the stored vacuum on the canister before applying the stored vacuum on the fuel tank. 10. The method of claim 9, wherein indicating degradation includes, during the first or second engine-off condition, indicating degradation based on a change in fuel tank pressure over time or a change in canister pressure, upon vacuum application. 11. A method, comprising: monitoring a fuel system including a canister, a fuel tank, a vacuum accumulator, and a venturi, the canister coupled between the tank and an engine intake manifold, including:during an engine-on condition, storing vacuum in the accumulator via flow through the venturi;during a subsequent engine-off condition, applying the stored vacuum on the fuel tank before the canister during higher fuel tank pressures, and applying the stored vacuum on the canister before the tank during lower fuel tank pressures; andindicating degradation based on a fuel system pressure response to the vacuum applications. 12. The method of claim 11, wherein the canister is coupled to the intake manifold via a purge line, the vacuum accumulator being coupled to the purge line between the canister and the intake manifold. 13. The method of claim 12, wherein the vacuum accumulator is coupled to the purge line via a control valve, the method further comprising adjusting the control valve to apply the stored vacuum to the canister. 14. A method, comprising: monitoring a fuel system including a fuel tank, a vacuum accumulator, a venturi, and a canister between the tank and an engine intake, the vacuum accumulator coupled to a purge line connecting the canister to the engine intake, including:during an engine-on condition, storing vacuum in the accumulator via flow through the venturi; andduring a subsequent engine-off condition and while the canister is isolated from the tank: applying the stored vacuum on the canister, and indicating degradation based on a fuel system pressure change following vacuum application.