Method and System for Fuel Vapor Control
First Claim
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1. A method of operating a fuel vapor recovery system, comprising,purging fuel vapors from a canister to an engine intake to reduce a stored fuel vapor amount in the canister;
- andintermittently purging fuel vapors from a fuel tank to the canister to increase a stored fuel vapor amount in a canister buffer, a duration and interval of the intermittent purging based on the stored fuel vapor amount in the buffer.
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Abstract
Methods and systems are provided for operating a fuel vapor recovery system having a fuel tank isolation valve coupled between a fuel tank and a canister. Fuel vapors are purged from the fuel tank to a canister buffer over a plurality of purge pulses. The pulses are adjusted based on the buffer capacity, a purge flow rate, and a fuel tank pressure to improve control of canister loading and reduce air-to-fuel ratio disturbances.
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Citations
20 Claims
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1. A method of operating a fuel vapor recovery system, comprising,
purging fuel vapors from a canister to an engine intake to reduce a stored fuel vapor amount in the canister; - and
intermittently purging fuel vapors from a fuel tank to the canister to increase a stored fuel vapor amount in a canister buffer, a duration and interval of the intermittent purging based on the stored fuel vapor amount in the buffer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of operating a fuel vapor recovery system including a fuel tank coupled to a canister through an isolation valve, comprising,
purging fuel vapors from the canister to an engine intake until a stored fuel vapor amount in a canister buffer is below a threshold; - and
pulsing the isolation valve to purge fuel vapors from the fuel tank to the canister to increase the stored fuel vapor amount, a duration of each pulse, and an interval between consecutive pulses adjusted based on each of a buffer capacity, purge flow rate and a fuel tank pressure at an onset of the pulsing. - View Dependent Claims (14, 15, 16, 17, 18)
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19. An engine system, comprising,
an engine including an intake; -
a fuel tank; a canister coupled to the intake through a first valve and coupled to the fuel tank through a second valve, the canister including a buffer; a pressure sensor coupled to the fuel tank for estimating a fuel tank pressure; an exhaust gas sensor coupled downstream of the canister for providing air-to-fuel ratio feedback, a capacity of the buffer estimated from the air-to-fuel ratio feedback; and a controller with computer readable instructions for, opening the first valve to purge fuel vapors from the canister and increase the buffer capacity; and when the buffer capacity is higher than a threshold capacity, intermittently opening the second valve to purge fuel vapors from the fuel tank to the canister buffer, a duration of each opening and an interval between consecutive openings based on the buffer capacity, purge flow rate and the fuel tank pressure at an onset of the intermittent opening. - View Dependent Claims (20)
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Specification