Method of producing torque sensor shafts
AssigneeKubota Corporation
InventorsRenshiro Ishino, Yoshio Shibata
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Abstract
The invention relates to a method of producing magnetostriction type torque sensor shafts adapted to detect a change in permeability when a torque is applied. A plurality of shot peening operations are applied to the surface of a torque sensor shaft in such a manner that the diameter of shot particles to be used is decreased each time. This arrangement ensures that the region in which the residual stress is at a maximum and approximately constant lies over a wide range as seen in the direction of the depth from the outermost surface of the shaft and extends from a deep area to an area close to the surface of the shaft. As a result, the hysteresis and nonlinearity of the shaft are improved and it becomes possible to use a wide range of excitation frequencies.
Claims6
A method of improving the magnetic performance characteristics of a magnetostriction type torque sensor in respect of hysteresis, sensitivity and non-linearity, said torque sensor having a torque sensor shaft, comprising:
- forming on the surface of said torque sensor shaft a magnetostrictive portion comprised of a plurality of knurled grooves each having a radius at its bottom;
- applying to the surface of said torque sensor shaft including at least said magnetostrictive portion a plurality of shot peening operations successively using shot particles of different, decreasing diameters;
- and,
- using for the second and any subsequent one of said shot peening operations shot particles having a diameter smaller than two times said radius of said knurled grooves.
Dependencies are inferred from the claim text.