Method and system for fuel system control
First Claim
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1. A method for a fuel system in a vehicle, comprising:
- purging hydrocarbons from a canister to an engine intake with a vent valve and a purge valve open; and
selectively closing the vent valve while the purge valve remains open and before purge is triggered to stop responsive to fuel tank pressure being lower than a threshold pressure during engine operation.
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Abstract
Methods and systems are provided for controlling a fuel system in a hybrid vehicle. Before canister purging is stopped by closing a purge valve, a canister vent valve is closed to hold fuel tank vacuum. Then, during a subsequent canister purge, the purge valve is opened before opening the vent valve, allowing canister purge to initiate under fuel tank vacuum conditions.
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Citations
20 Claims
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1. A method for a fuel system in a vehicle, comprising:
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purging hydrocarbons from a canister to an engine intake with a vent valve and a purge valve open; and selectively closing the vent valve while the purge valve remains open and before purge is triggered to stop responsive to fuel tank pressure being lower than a threshold pressure during engine operation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for a hybrid vehicle fuel system, comprising:
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responsive to canister load being above a first threshold, opening a purge valve followed by a vent valve to purge hydrocarbons stored in a canister to an engine intake; and responsive to canister load falling below the first threshold before purge is triggered to stop, closing the vent valve while maintaining the purge valve open to hold vacuum in a fuel tank. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A vehicle fuel system, comprising:
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an engine including an intake; a fuel tank coupled to the engine intake via a canister, a vent valve, and a purge valve; a pressure sensor coupled to the fuel tank for estimating a fuel tank vacuum; and a control system with computer readable instructions for, in response to purge conditions being met, opening the purge valve followed by the vent valve to purge canister hydrocarbons to the engine intake while drawing vacuum into the fuel tank; and during purging, selectively closing the vent valve responsive to fuel tank vacuum being higher than a threshold to hold vacuum in the fuel tank. - View Dependent Claims (17, 18, 19, 20)
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Specification