The disclosed assembly comprises a housing and a stator inserted inside a cylindrical cavity in said housing. Said assembly comprises a means for point-to-point attachment of the stator to the housing.

A rotor includes a shaft extending in an axial direction, a cylindrical magnet portion provided at an outer peripheral portion of the shaft, a cylindrical scattering-prevention member provided so as to cover an outer peripheral surface of the magnet portion, a first balancing member provided at one end of the magnet portion in the axial direction, and a second balancing member provided at the other end of the magnet portion in the axial direction from which one end side of the shaft extends in the axial direction and having a diameter smaller than the inner diameter of the scattering-prevention member and the second balancing member has an end surface in contact with the magnet portion, the end surface being not surrounded by the scattering-prevention member.

A stator includes a yoke extending in a circumferential direction about an axis line, a tooth extending from the yoke in a first direction toward the axis line, and a coil wound around and fixed to the tooth. The yoke has an inner wall surface facing the axis line. The tooth has a root part connected to the yoke. The inner wall surface of the yoke is a flat surface extending from an end of the root part of the tooth in the circumferential direction to an inner circumferential side relative to a plane passing through the end and perpendicular to the first direction.

A stator includes a yoke extending in a circumferential direction about an axis line, a tooth extending from the yoke in a first direction toward the axis line, and a coil wound around and fixed to the tooth. The yoke has an inner wall surface facing the axis line. The tooth has a root part connected to the yoke. The inner wall surface of the yoke is a flat surface extending from an end of the root part of the tooth in the circumferential direction to an inner circumferential side relative to a plane passing through the end and perpendicular to the first direction.

A rotor includes a cylindrical magnet structure extending in an axial direction to cover a shaft, and a protective tube including a fiber body covering an outer circumferential surface of the magnet structure. The outer circumferential surface of the magnet structure has a first tapered surface gradually decreasing in diameter toward a first end surface of the magnet structure, and a second tapered surface gradually decreasing in diameter toward a second end surface opposite the first end surface in the axial direction. The protective tube includes a first end portion that is bonded to the first tapered surface of the magnet structure, and a second end portion that is bonded to the second tapered surface of the magnet structure.

A motor rotor includes an inner sleeve, a cylindrical permanent magnet disposed around the inner sleeve, and a resin portion formed by charging a gap between the inner sleeve and the permanent magnet with a resin. The inner sleeve includes a small diameter portion. The small diameter portion is located to face an inner peripheral surface of an end portion of the permanent magnet in an axial direction. The small diameter portion is formed to have a diameter smaller than a diameter of a portion facing an inner peripheral surface of a center portion of the permanent magnet in the axial direction.

A motor rotor includes an inner sleeve, a cylindrical permanent magnet disposed around the inner sleeve, and a resin portion formed by charging a gap between the inner sleeve and the permanent magnet with a resin. The inner sleeve includes a small diameter portion. The small diameter portion is located to face an inner peripheral surface of an end portion of the permanent magnet in an axial direction. The small diameter portion is formed to have a diameter smaller than a diameter of a portion facing an inner peripheral surface of a center portion of the permanent magnet in the axial direction.

Electrical machines as provided herein can include a shaftless rotor with an annular array of permanent magnets; and a stator with an annular ferromagnetic core and a plurality of electromagnetic inductors about the ferromagnetic core. The stator is located adjacent to and substantially co-axial with the shaftless rotor; and a fluid thrust bearing located in an axially planar gap between the stator and the shaftless rotor.

A motor drive assembly having an electric motor with a rotor that includes a rotor shaft and a heat exchanger received in the rotor shaft. The heat exchanger has an insert body with an outer insert surface that is engaged to an inside surface of the rotor shaft. The insert body includes a plurality of segments. Each of the segments defines a first through-hole, and a plurality of second through-holes. Each of the segments is fixedly coupled to one another. A first flow passage extends through the first through-holes in the plurality of segments. Each of the second through-holes defines a portion of a corresponding second flow passage. The second flow passages are disposed concentrically about the first flow passage.

A rotor for an electric motor includes: a rotating element extending along an axis; and a retaining body formed of metal and configured to hold the rotating element from an outer peripheral side, where the retaining body includes: a plurality of annular members annularly surrounding an outer peripheral surface of the rotating element and arranged at intervals in the axis direction; and a plurality of connecting members arranged in a circumferential direction between the annular members adjacent to each other so as to connect the annular members. As a result, a path of eddy current is limited and the eddy current can be reduced.