| 摘要 |
PURPOSE: A method for controlling downshift from a second speed to a first speed of an automatic transmission is provided to realize the stable and soft shift feeling by minimizing the torque change of an output shaft without the increase of turbine RPM. CONSTITUTION: A method for controlling downshift from a second speed to a first speed comprises the steps of deciding the output of a power-off downshift control signal(S100), deciding the output of a brake switch on signal(S110), deciding if turbine RPM(Nt) and output shaft RPM(No) are zero(S120,S130), deciding the stoppage of a vehicle(S140), outputting a solenoid valve driving signal to a drive unit to engage a shift range to a first speed if a vehicle is stopped over a reference time(S150), and outputting a solenoid valve on/off driving control signal to the drive unit to disengage a second speed after the predetermined time is elapsed(S160). According to the value on/off driving control signal, a second brake solenoid valve is turned on to unengaged the second speed gear ratio. Therefore, the torque change of the output shaft is minimized.
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