Method and system for fuel vapor control
First Claim
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1. A method of monitoring a fuel system including a canister, a fuel tank, a vacuum accumulator, and a venturi, comprising,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 fuel tank;
applying the stored vacuum on the canister, and indicating degradation based on a fuel system pressure change following vacuum application.
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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.
74 Citations
16 Claims
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1. A method of monitoring a fuel system including a canister, a fuel tank, a vacuum accumulator, and a venturi, comprising,
during an engine-on condition, storing vacuum in the accumulator via flow through the venturi; - and
during a subsequent engine-off condition and while the canister is isolated from the fuel tank; applying the stored vacuum on the canister, and indicating degradation based on a fuel system pressure change following vacuum application. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of monitoring a vehicle fuel vapor recovery system including a fuel tank, a canister, and a vacuum accumulator, the vacuum accumulator including a venturi, the method comprising,
during a first engine-on condition, flowing exhaust through the venturi to generate a vacuum, and storing the vacuum in the vacuum accumulator; - and
during a subsequent engine-off condition, applying a vacuum from the vacuum accumulator on the fuel tank or the canister, and indicating fuel vapor recovery system degradation based on a change in fuel vapor recovery system pressure following the vacuum application wherein the venturi is coupled to a brake pump, and wherein flowing exhaust through the venturi includes flowing brake pump exhaust through the venturi during brake pump operation. - View Dependent Claims (12, 13, 14, 15)
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16. A method of monitoring a fuel system including a canister, a fuel tank, a vacuum accumulator, and a venturi, comprising,
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; and indicating degradation based on a fuel system pressure response to the vacuum applications.
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Specification