Japan Servo Co.,ltd.

Youji Unoki

Masafumi Sakamoto

Shoji Ohiwa

Kazuo Ohnishi

Atushi Yamamoto

Shinji Shimizu

Yukinori Kurita

The magnetic pole position detector for an electric motor comprises a detection rotor, a detection stator, and magnetic flux concentration tips and magneto electro transducers. The detection rotor is fixed to an axis of rotation of the motor and comprised of disc-like rotors having first toothlike protrusions and a permanent magnet. The disc-like rotors are assembled so as to make the first toothlike protrusions coincide in the axial direction and the permanent magnet is fixed between the disc-like rotors. The detection stator is comprised of stator cores comprised of an annular yoke and stator teeth formed at regular intervals on the former. Second toothlike protrusions are formed on the inner end of the stator teeth. The stator cores are assembled with a gap in the axial direction so as to make respective second toothlike protrusions coincide in the axial direction. The magnetic flux concentration tips and the magneto electro transducers are placed in the gaps in the axial direction. The detection rotor and the detection stator are assembled with a gap in the radial direction. The magnetic pole position is obtained by detecting the magnetic flux flowing through the stator teeth that varies in accordance the rotation of the detection rotor.

Magnetic pole position detector for an electric motor

A permanent magnet type stepping motor wherein and that at least one pitch formed by two adjacent small pole teeth of each of stator magnetic poles is different from other pitch formed by other two adjacent small pole teeth of each of the stator magnetic poles, wherein the tooth width of at least one of the two adjacent small pole teeth forming the different pitch is made different from that of the remaining small pole teeth, each stator magnetic poles having at least four small pole teeth and wherein a rotor has a rotor magnetic pole having a plurality of small pole teeth arranged at equal pitches, facing said stator magnetic poles through a gap. A permanent magnet type stepping motor has a stator having n pieces of stator magnetic pole each having m pieces of pole tooth, and a rotor having a plurality of pole teeth arranged at equal pitches n is an integer not less than three, m is an even number not less than four, a pitch of the rotor pole teeth is 2.pi., a pitch formed between (m/2)th stator pole tooth and �(m/2)+1!th stator pole tooth is set to (.tau..+-..theta..sub.0), and the other pitch is set to .tau., where .vertline.2.pi.-.tau..vertline.&lt;.pi./12, .pi./5.ltoreq..theta..sub.0 &lt;.pi./2, and .tau. and .theta..sub.0 are each electrical angle.

Permanent magnet type stepping motor

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Kiryu, Japan

Youji Unoki