Noriyoshi Hirao

Magnetic screw rod using dual state 0.6C–13Cr–Fe bulk magnetic material

A magnetic screw rod that can replace a mechanical ball screw has been successfully fabricated. This type of device provides linear motion from a rotating motor. The magnetic screw rod is made from dual state 0.6C–13Cr–Fe bulk magnetic rod stock. The material, originally soft magnetically, can be heat treated to obtain a nonmagnetic region which substitutes for the groove of a conventional magnetic screw rod. This method produces a magnetic screw rod with a smooth, round outer shape and a longer, cleaner operational life. This experiment successfully yielded a 300 mm long, 25 mm diameter magnetic rod with 10 mm pitch, 4 mm width, 4 mm depth spiral nonmagnetic region.

Study of internal permanent magnet rotor made of 0.6C–13Cr–Fe dual state magnetic material

We have successfully developed an internal permanent magnet (IPM) rotor using dual state bulk magnetic material to increase usable magnetic flux dramatically. The most significant benefit of the IPM rotor is its mechanical reliability, because permanent magnets are inserted in slots of soft magnetic material. On the other hand, there is significant leakage flux between adjoining permanent magnets in the soft magnetic rotor core, reducing the usable magnetic flux flowing into the stator core. To solve this problem, we used a dual state magnetic material, 0.6C–13Cr–Fe alloy. This soft magnetic material could locally be changed into nonmagnetic material by localized heat treatment. By changing the material at leakage flux path into nonmagnetic, we can reduce the leakage flux, while keeping the rotor mechanically sound. By applying the dual state magnetic material to an experimental eight pole IPM rotor, the useful flux flowing in the stator core differs by 8% when compared to an all soft magnetic rotor core.