Magnetostrictive torque sensor shaft

Abstract

Method for producing a magnetostrictive torque sensor shaft and a torque sensor shaft made according to the method. Knurl grooves are formed on the surface of shaft base material in oblique relation to the axis thereof, which are then subjected to heat treatment. Subsequently, material having less crystallomagnetic anisotropy and a large magnetostriction constant is deposited by plating, thermal spraying or otherwise at least on the surface of the knurl grooves included in the outer periphery of the shaft base material thereby to form a magnetostrictive layer. Preferably, the magnetostrictive layer is comprised of an FeNi alloy plated layer whose Fe component content is more than 0% but less than 25%. Thus, a sensor shaft is obtained which can be suitably used in constructing a magnetostrictive torque sensor having high performance characteristics. In order to improve the bond between the shaft base material and the magnetostrictive layer, it is preferable to subject the surface of the shaft base material to surface treatment such as shot peening and/or nickel strike plating, prior to the step of magnetostrictive layer forming. This surface treatment makes it possible to obtain a torque sensor having good service durability.

Dependencies are inferred from the claim text.