Method and system for fuel vapor control
First Claim
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1. A method of operating a fuel system including a fuel tank coupled to a fuel vapor canister via an isolation valve, comprising,purging fuel vapors from the canister to an engine intake at a higher purge rate for a duration with the isolation valve open until a threshold level of fuel tank vacuum is generated;
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Abstract
Methods and systems are provided for generating sufficient vacuum to enable a leak detection routine. While a fuel tank pressure is within mechanical limits, fuel vapors are purged from a canister to an engine with an isolation valve open to generate a desired level of vacuum in the fuel tank. Thereafter, the fuel tank is isolated and leak detection is performed concurrent to the purging.
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Citations
18 Claims
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1. A method of operating a fuel system including a fuel tank coupled to a fuel vapor canister via an isolation valve, comprising,
purging fuel vapors from the canister to an engine intake at a higher purge rate for a duration with the isolation valve open until a threshold level of fuel tank vacuum is generated; - and
after the duration, purging fuel vapors from the canister to the engine intake at a lower purge rate with the isolation valve closed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of operating a fuel system including a fuel tank coupled to a canister via an isolation valve, comprising:
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during a first purging condition, purging fuel vapors from the canister to an engine intake at a first, higher purge flow rate, with the isolation valve open; and during a second purging condition, purging fuel vapors from the canister to the engine intake at a second, lower purge flow rate, with the isolation valve closed, wherein during each of the first and second purging conditions, a fuel tank pressure is within a mechanical pressure limit of the fuel tank. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A fuel system for a vehicle comprising:
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a fuel tank; a canister coupled to the fuel tank via a valve; an engine including an intake; a pressure sensor coupled to the fuel tank and configured to estimate a fuel tank vacuum level; and a control system with computer readable instructions for; purging fuel vapors from the canister to the engine intake with the isolation valve open for a duration until the fuel tank vacuum level is higher than a threshold vacuum level; after the duration, purging fuel vapors from the canister to the engine intake with the isolation valve closed while simultaneously detecting a leak in the fuel system; determining an initial purge flow rate of the purging with the isolation valve open based on engine speed, engine load, and canister load; and increasing the purge flow rate of the purging with the isolation valve open in response to the estimated fuel tank vacuum level being lower than the threshold level. - View Dependent Claims (18)
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Specification