A field magnet manufacturing method where a bonded magnet's inner surface press-fitted in a yoke has a certain accuracy irrespective of the accuracy of the yoke's outer circumferential surface. A cylindrical bonded magnet from binding magnet particles with a thermosetting resin is fixed in a tubular yoke of magnetic material. The method includes reheating and softening the bonded magnet after thermal curing; and press-fitting in the bonded magnet after the softening step from a tapered portion on one end side of the yoke to press the bonded magnet's outer circumferential surface against the yoke's inner surface. The press-fitting includes feeding the bonded magnet relatively into the yoke while allowing a relative posture variation between the bonded magnet and the yoke so the bonded magnet's inner surface to be remolded into a shape along the inner surface of the yoke exhibits almost the same accuracy as the yoke's inner surface.

A field magnet manufacturing method where a bonded magnet's inner surface press-fitted in a yoke has a certain accuracy irrespective of the accuracy of the yoke's outer circumferential surface. A cylindrical bonded magnet from binding magnet particles with a thermosetting resin is fixed in a tubular yoke of magnetic material. The method includes reheating and softening the bonded magnet after thermal curing; and press-fitting in the bonded magnet after the softening step from a tapered portion on one end side of the yoke to press the bonded magnet's outer circumferential surface against the yoke's inner surface. The press-fitting includes feeding the bonded magnet relatively into the yoke while allowing a relative posture variation between the bonded magnet and the yoke so the bonded magnet's inner surface to be remolded into a shape along the inner surface of the yoke exhibits almost the same accuracy as the yoke's inner surface.

A motor includes a rotor molded by resin casting, and a stator disposed inside the rotor. The rotor includes a cylindrical portion in which a plurality of magnets are arranged side by side in a circumferential direction. The magnets are exposed on a side of an open end as one end of the cylindrical portion in an axial direction of the cylindrical portion. The cylindrical portion includes an inner resin located inside each of the magnets in a radial direction of the cylindrical portion. The inner resin includes a first resin portion, and a second resin portion closer to the open end than the first resin portion in the axial direction. A sectional area of the second resin portion perpendicular to the axial direction is smaller than a sectional area of the first resin portion perpendicular to the axial direction.

A motor includes a rotor molded by resin casting, and a stator disposed inside the rotor. The rotor includes a cylindrical portion in which a plurality of magnets are arranged side by side in a circumferential direction. The magnets are exposed on a side of an open end as one end of the cylindrical portion in an axial direction of the cylindrical portion. The cylindrical portion includes an inner resin located inside each of the magnets in a radial direction of the cylindrical portion. The inner resin includes a first resin portion, and a second resin portion closer to the open end than the first resin portion in the axial direction. A sectional area of the second resin portion perpendicular to the axial direction is smaller than a sectional area of the first resin portion perpendicular to the axial direction.

A motor rotor includes a rotatable shaft, and a magnet structure mounted around the shaft. The magnet structure includes magnet pieces including a first magnet piece and a second magnet piece. The first magnet piece has a fracture surface facing the second magnet piece, and an outer surface forming a circumferential surface of the magnet structure. A surface roughness of the fracture surface is greater than a surface roughness of the outer surface of the first magnet piece.

A motor rotor includes a rotatable shaft, and a magnet structure mounted around the shaft. The magnet structure includes magnet pieces including a first magnet piece and a second magnet piece. The first magnet piece has a fracture surface facing the second magnet piece, and an outer surface forming a circumferential surface of the magnet structure. A surface roughness of the fracture surface is greater than a surface roughness of the outer surface of the first magnet piece.

A rotor core includes a magnet pocket defined by the rotor core and extending longitudinally in an axial direction of the rotor core. The rotor core also includes a magnet structure disposed within the magnet pocket and extending transversely in a radial direction and/or circumferential direction of the rotor core to define a magnet width, the magnet structure extending longitudinally in the axial direction of the rotor core, wherein the magnet structure has a varied axial length.

A rotor core includes a magnet pocket defined by the rotor core and extending longitudinally in an axial direction of the rotor core. The rotor core also includes a magnet structure disposed within the magnet pocket and extending transversely in a radial direction and/or circumferential direction of the rotor core to define a magnet width, the magnet structure extending longitudinally in the axial direction of the rotor core, wherein the magnet structure has a varied axial length.

An interior permanent magnet (IPM) electric machine has an improved rotor configuration to manage mechanical stresses induced by electro-magnetic force acting upon permanent magnets housed therein. This includes providing magnet cavities in the rotor with sufficient clearances in the corners wherein a portion of a slot corner is formed with certain curvature shapes using a novel geometry. By doing this, more surface area is obtained to evenly distribute stress that is induced by centrifugal force acting upon the rotor during rotation, thus reducing the stress concentration. Furthermore, an expanded space is achieved between the magnet corner and the rotor lamination, thus providing robust packaging and dynamic support of the permanent magnets in the magnet cavities. Furthermore, the expanded space provides improved clearance for ease of manufacturing and assembly.

An interior permanent magnet (IPM) electric machine has an improved rotor configuration to manage mechanical stresses induced by electro-magnetic force acting upon permanent magnets housed therein. This includes providing magnet cavities in the rotor with sufficient clearances in the corners wherein a portion of a slot corner is formed with certain curvature shapes using a novel geometry. By doing this, more surface area is obtained to evenly distribute stress that is induced by centrifugal force acting upon the rotor during rotation, thus reducing the stress concentration. Furthermore, an expanded space is achieved between the magnet corner and the rotor lamination, thus providing robust packaging and dynamic support of the permanent magnets in the magnet cavities. Furthermore, the expanded space provides improved clearance for ease of manufacturing and assembly.