Patent ID: 7598645

Claim:
A permanent magnet rotor, comprising: a rotor core having a generally cylindrical shape with an outer circumferential surface and a rotational axis; a plurality of magnet insertion holes formed in the rotor core and arranged circumferentially at a preset angular interval about the rotational axis, each hole extending in a direction parallel to the rotational axis and having a cross section of a generally elongated slit; the elongated slit curved concave relative to the circumferential surface and having a radially inward side, a radially outward side, and two ends that are respectively spaced apart from the circumferential surface by two bridges thereby to form a rotor center core section located circumferentially between the bridges and located radially between the radially outward side of the slit and the outer circumferential surface of the rotor core, each of the bridges having a thicker portion and a thinner portion that are respectively positioned near the radially inward and outward sides; and one or more permanent magnets inserted in each of the holes; wherein, if there are more than one permanent magnet in each hole, the magnets in each hole are arranged such that each of the magnets is in direct contact with an adjacent magnet so that centrifugal forces imparted on a center portion of the magnets is transferred through outer portions of the magnets to the bridges.