US 6,552,453 B2Granted

Magnetic pole position detector for an electric motor

AssigneeJapan Servo Co., Ltd.

InventorsShoji Ohiwa, Kazuo Ohnishi, Atushi Yamamoto, Shinji Shimizu, Youji Unoki, Yukinori Kurita

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Abstract

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.

Claims26

Dependent claims

A magnetic pole position detector for an electric motor comprising a detection rotor, a detection stator, magnetic flux concentration tips and magneto electro transducers,

said detection rotor is fixed to a rotatable shaft of said electric motor and comprised of a pair of disc-shape rotor elements having a plurality of first tooth protrusions on their circumferences and a permanent magnet of an N-S pole thereof is in the axial direction of said electric motor and the diameter thereof is smaller than those of said disc-shape rotor elements,
said disc-shape rotor elements are assembled concentrically with each other so as to make respective first tooth protrusions coincide with each other in said axial direction,
said permanent magnet is fixed concentrically between said disc-shape rotor elements,
said detection stator is comprised of a pair of stator cores,
said stator core is comprised of an annular portion and a plurality of stator teeth for collecting magnetic flux flowing through said first tooth protrusions of said detection rotor,
said stator teeth are formed at regular intervals on the inner circumference of said annular yoke, each of said stator teeth has inner end portion on which a plurality of second tooth protrusions are formed,
said stator cores are assembled concentrically with each other with a gap in said axial direction between them so as to make respective second tooth protrusions of said stator teeth coincide with each other in said axial direction,
said magnetic flux concentration tips are placed in said gaps in said axial direction for concentrating magnetic flux in said gaps in said axial direction,
said magneto electro transducers are placed in said gaps in said axial direction for transforming said magnetic flux into electrical signals,
said detection rotor and said detection stator are assembled so as to make said first tooth protrusions of said detection rotor and said second tooth protrusions of said stator teeth of said detection stator oppose with each other with a gap in the radial direction of said electric motor between them,
wherein the magnetic pole position of said electric motor is detected by measuring the magnetic flux flowing through said stator teeth that varies in accordance the rotation of said detection rotor.

8 more elements

A magnetic pole position detector for an electric motor comprising a detection rotor, a detection stator, magnetic flux concentration tips and magneto electro transducers,

said detection rotor is fixed to a rotatable shaft of said electric motor and comprised of a cylindrical permanent magnet with multiple magnetization on its circumference,
said detection stator is comprised of a pair of stator cores,
said stator core is comprised of an annular portion and a plurality of stator teeth for collecting magnetic flux flowing through said first tooth protrusions of said detection rotor,
said stator teeth are formed at regular intervals on the inner circumference of said annular yoke, each of said stator teeth has inner end portion on which a plurality of second tooth protrusions are formed,
said stator cores are assembled concentrically with each other with a gap in said axial direction between them so as to make respective second tooth protrusions of said stator teeth coincide with each other in said axial direction,
said magnetic flux concentration tips are placed in said gaps in said axial direction for concentrating magnetic flux in said gaps in said axial direction,
said magneto electro transducers are placed in said gaps in said axial direction for transforming said magnetic flux into electrical signals,
said detection rotor and said detection stator are assembled so as to make said first tooth protrusions of said detection rotor and said second tooth protrusions of said stator teeth of said detection stator oppose with each other with a gap in the radial direction of said electric motor between them,
wherein the magnetic pole position of said electric motor is obtained by detecting the magnetic flux flowing through said stator teeth that varies in accordance the rotation of said detection rotor,
said stator cores are made of a magnetic material,
a printed circuit board is attached to an outer surface of said stator core,
each of said magnetic flux concentration tips is composed of a pair of magnetic flux concentration protrusions, and
each of said magneto electro transducers is placed between said pair of magnetic flux concentration protrusions with the magnetism sensitive plane of said magneto electro transducer approximately parallel to the surface of said printed circuit board.

10 more elements

Dependencies are inferred from the claim text.