Device for controlling operation of fuel evaporative purge system of an internal combustion engine

Claim 1

A device for controlling operations of a fuel evaporative purge system of an internal combustion engine provided with a canister for absorbing fuel vapor, a purge passage communicating said canister with an intake passage of the engine at a part thereof downstream of a throttle valve, and a solenoid valve arranged in said purge passage, wherein said device activates said solenoid valve in successive duty cycles to purge the fuel vapor by an appropriate value corresponding to an actual intake air flow when said engine is operating within a predetermined purging range, said device comprising: means for determining and updating a maximum amount of fuel vapor to be purged into said intake passage corresponding to an actual current driving condition, which maximum amount is attained when said solenoid valve is fully opened; means for detecting a current amount of intake air aspirated into said engine; means for calculating an updated maximum purging ratio of an updated value of said maximum amount of fuel vapor to said current amount of intake air; means for setting a target purging ratio, when the engine operating condition is in said predetermined purging range, at a value that changes gradually; and means for activating said solenoid valve during each duty cycle at a duty ratio identical to a ratio of said target purging ratio to said updated maximum purging ratio.

Claim 2

A device for controlling operations of a fuel evaporative purge system of an internal combustion engine provided with a canister for absorbing fuel vapor, a purge passage communicating said canister with an intake passage of the engine at a part thereof downstream of a throttle valve, and a solenoid valve arranged in said purge passage, wherein said device activates said solenoid valve in successive duty cycles to purge the fuel vapor by an appropriate value corresponding to an actual intake air flow when said engine is operating within a predetermined purging range, said device comprising: means for determining and updating a maximum amount of fuel vapor to be purged into said intake passage corresponding to an actual current driving condition, which maximum amount is attained when said solenoid valve is fully opened; means for detecting a current amount of intake air aspirated into said engine; means for calculating an updated maximum purging ratio of an updated value of said maximum amount of fuel vapor to said current amount of intake air; means for setting a target purging ratio, when the engine operating condition is in said predetermined purging range, at a value that changes gradually; and means for activating said solenoid valve during each duty cycle at a duty ratio identical to a ratio of said target purging ratio to said updated maximum purging ratio.