Abstract:
The automatic transmission for electric automobiles comprises an input shaft extending from a vehicle driving motor and an output shaft connected to the input shaft via planetary gearing provided with a clutch assembly for effecting gear changes. The speed change controlling device adapted in the transmission comprises a hydraulic circuit having a change-over valve designed to switch the oil passage by connection or disconnection of power to a solenoid valve to supply pressurized, operating oil to the clutch, an electric control circuit including a transistor for changing the field current of the vehicle driving motor, a comparison circuit for comparing the field current with a reference voltage, and the rotational frequency of the motor with that of the output shaft which may or may not be multiplied by the gear ratio, an oil pressure detector device for detecting oil pressure in the clutch, a circuit for generating a pulse for changing the normal condition of the transistor, and a logic element connected between the pulse generating circuit and the solenoid valve, whereby smooth speed changing operation is effected.