SYSTEM AND METHOD FOR CATALYST PURGE CONTROL

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PURPOSE : A catalyst purge control device and a controlling method thereof are provided to improve The purifying efficiency of catalyst by controlling the purge of a catalyst by sensing a signal of front and rear oxygen sensors. CONSTITUTION : An output of a second oxygen sensor is integrated if a fuel cutoff control is released(S106). It is determined whether the integrated value is above a preset minimum critical value(S107). If the integrated value is above the minimum critical value, it is determined whether the output of a first oxygen sensor is detected as a rare combustion(S108). If the output of a first oxygen sensor is detected as the rare combustion, the fuel amount of a correction factor is determined according to the integrated value of the second oxygen sensor. A catalyst purge control is executed by injecting the over-rich fuel(S109). If the output integrated value of the second oxygen sensor is above the maximum critical value in the purge control state of the catalyst(S112). If the output of the first oxygen sensor is detected(S113), the air fuel ratio is controlled after the catalyst purge control is released.