Patent ID: 7455133

Claim:
A control unit for use in an electric four-wheel drive vehicle wherein said electric four-wheel drive vehicle comprises an internal combustion engine for driving front wheels, a field coil AC synchronous motor for driving rear wheels, said motor being a field-coil synchronous motor having a field coil; a generator driven by a rotating force of said internal combustion engine and outputting DC power; and an inverter for converting the DC power outputted from said generator to AC power, and supplying the AC power to said AC synchronous motor, said generator and said inverter; said control unit comprising: control means for outputting control signals for controlling said AC synchronous motor, said generator and said inverter, wherein said control means outputs a control signal to said inverter for controlling said inverter such that driving torque of said AC synchronous motor is reduced as a rotation speed of said AC synchronous motor increases, thereby controlling the AC power supplied to an armature coil of said synchronous motor, outputs a control signal to a control circuit of said field coil for controlling a field current flowing through the field coil of said synchronous motor based on at least one input signal of a signal relating to the rotation speed of said AC synchronous motor; or a torque control signal for said AC synchronous motor, and outputs a control signal to a control circuit of said generator for controlling said generator such that said generator generates power output required by said AC synchronous motor to generate the driving torque.