Torque sensor

Abstract

A sensor for sensing torque applied to a shaft such as the steering wheel shaft of a vehicle has a magnetostrictive sleeve and a sensing element responsive to torsional strain in the magnetostrictive sleeve. Each end of the magnetostrictive sleeve is torsionally engaged to a shear leveling member. Each shear leveling member has a region of varying torsional stiffness and a flared end. Each shear leveling member is bonded to the shaft by adhesive at its region of varying torsional stiffness and at its flared end. The regions of varying torsional stiffness and flared ends operate to level the shear stress in the adhesive resulting in uniform shear stress without peaks throughout the adhesive bond. With uniform adhesive shear stress, the maximum torque the adhesive can transmit is limited only by the yield torque of the shaft and the area of adhesive bond. The area of adhesive bond can be increased without limit by increasing the length of the shear leveling member thereby making the yield torque of the shaft the only limit to the torque transmitted. In one embodiment a stack of washers provides radial forces to stabilize the surface of the magnetostrictive sleeve without applying torque to the sleeve. The response of the sensor is made independent of angular position by providing a circularly symmetric sensing element located on the axis of rotation of the sleeve.

Dependencies are inferred from the claim text.