Patent ID: 7551051

Claim:
A ring magnet comprising a plurality of ring-shaped preliminarily molded pieces, stacked in an axial direction of the molded pieces to form a tubular body for sintering, wherein each ring-shaped preliminarily molded piece includes first and second generally annular end faces that are transverse to the axial direction of each of the ring-shaped preliminarily molded pieces, each of the first end faces includes a plurality of recesses that are spaced apart along a circumferential direction of the first end faces, each of the second end faces includes a plurality of protrusions that are spaced apart along a circumferential direction of the second end faces and that are complementary in shape and location to the recesses on the first end faces, and the recesses and the protrusions of the ring-shaped preliminarily molded pieces adjacent to each other in the tubular body are engaged with each other to establish and maintain, with respect to rotation about the axial direction and translation transverse to the axial direction, relative rotational orientation and axial alignment between the ring-shaped preliminarily molded pieces in the tubular body.