FOUR-WHEEL DRIVE VEHICLE

PROBLEM TO BE SOLVED: To suppress and prevent damage of an inverter switching element by excess voltage when front wheels or rear wheels are driven by an engine and the other wheels by a motor, AC voltage of a power generator driven by the engine is rectified, voltage is converted by an inverter and AC voltage is given to the motor. SOLUTION: When a rollback state of the motor 4 is detected, target armature current is set so as to make q-axis current generating torque and d-axis current that does not contribute to torque flow. Thus, generation power by regeneration of the motor 4 is consumed and an increase of DC link voltage is suppressed and prevented, thereby suppressing and preventing damage of the switching element of the inverter 10. When the motor 4 moves from the rollback state to power running, field current of the power generator 7 is controlled so that a power generation amount for generating torque required for power running is increased at the time of the rollback state. Consequently, torque lack when the motor 4 moves from rollback to power running can be avoided. COPYRIGHT: (C)2009,JPO&INPIT