ELECTRIC POWER STEERING DEVICE

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of reducing failures in a relay circuit caused by a huge oxide film generated at a relay contact. SOLUTION: This device is provided with an electric motor 12 for imparting steering assist force for reducing steering burden of a driver to a steering system, a motor driving circuit 22 for driving the electric motor 12, and a relay circuit 30 capable of energizing and shutting off a power supply line for driving and controlling the electric motor 12. When non-energizing time (off state continuation time) TOFFof the relay circuit 30 is prescribed time TTHor more, a potential difference is imparted between both ends of the relay contact 31 by making the relay contact 31 a closed state after driving the electric motor 12 in an initial diagnosis of the motor driving circuit 22 when starting energizing of the relay circuit 30. COPYRIGHT: (C)2008,JPO&INPIT