ELECTRIC POWER STEERING DEVICE

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of using cells of an auxiliary power supply to a temperature close to an allowable temperature limit. SOLUTION: This electric power steering device is provided with: a main power supply 7 which feeds an electric power to a motor 4; the auxiliary power supply 8 which has a plurality of cells connected in series and/or in parallel and can feed an electric power to the motor 4; a charge and discharge circuit 9 which charges the auxiliary power supply 8 based on the main power supply 7 and is configured to selectively change over between a first output state for feeing the power to the motor 4 by only the main power supply 7 and a second output state for feeding the power from the main power supply 7 and the auxiliary power supply 8 to the motor 4; temperature sensors 12 attached to the plurality of cells respectively and detect temperatures of the respective cells; and a control circuit 6 which selects an output state of the charge and discharge circuit 9 according to a necessary auxiliary steering force and, when at least one of the temperatures detected by the respective temperature sensors 12 reaches a predetermined upper limit threshold, restricts the charge and discharge of the auxiliary power supply 8. COPYRIGHT: (C)2009,JPO&INPIT