| 摘要 |
PROBLEM TO BE SOLVED: To estimate the overheated state of an electric motor with high accuracy. SOLUTION: The electric power steering device of this invention is provided with an electric motor 30 which generates assist force for turning-operating a steering wheel 31 by allowing current to flow in response to the operating condition of a vehicle, and an overheated state estimating means for estimating the overheated state of the electric motor based on the current of the electric motor. The overheated state estimating means determines a current value (heat balance current IMBARA) after balancing by subtracting a current value by which the electric motor is not overheated even when it is energized all the time, from a current value of the electric motor, determines a square current value obtained by squaring the current after balancing, and estimates the overheated state of the electric motor based on the square-current value. The current value after balancing is a value to which the heat radiation property of the electric motor is added, and since its squared value is strongly correlated with an amount of temperature change from a balanced temperature, the overheated state of the electric motor can be estimated with high accuracy. |
