Patent ID: 8783118

Claim:
A control unit for an electric power steering device provided with a first magnetostrictive film and a second magnetostrictive film with magnetic anisotropic properties opposite in direction to each other, each formed circumferentially on a surface of a steering shaft, and a first detection coil and a second detection coil provided around the first magnetostrictive film and the second magnetostrictive film, respectively, for detecting a twisting torque applied to the steering shaft based on an actual detection value of each of the first detection coil and the second detection coil to adjust an assist amount for the steering shaft, the control unit further comprising: a storage unit for storing an initial characteristic curve C 1 formed from an initial detection value Z 1 of the first detection coil when only the twisting torque T 1 is applied to the steering shaft, and an initial characteristic curve C 2 formed from an initial detection value Z 2 of the second detection coil when only the twisting torque T 1 is applied to the steering shaft; and a characteristic curve C 3 being formed from the actual detection value P 1 of first detection coil, and a characteristic curve C 4 being formed from the actual detection value P 2 of the second detection coil; and a bending load detector for detecting the bending load amount acting on the steering shaft based on a difference ΔS between the actual detection value P 1 on the characteristic curve C 3 and the initial detection value Z 1 on the initial characteristic curve C 1 , and on a difference ΔS between the actual detection value P 2 on the characteristic curve C 3 and the initial detection value Z 2 on the initial characteristic curve C 2 .