Stress distributing permanent magnet rotor geometry for electric machines

An electrical motor, comprising:

• a stator having a generally hollow cylindrical shape with an inner circumferential surface and including one or more coils coupled to a power source;
• a rotor core positioned within the inner circumferential surface of the stator and having a generally cylindrical shape with an outer circumferential surface and a rotational axis, the outer circumferential surface being positioned coaxially with respect to the inner surface of the stator in a spaced apart relationship;
• 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 outer circumferential surface and having a radially inward side, a radially outward side, and two ends that are respectively spaced apart from the outer circumferential surface by two bridges, 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 and arranged to transfer a centrifugal force from a center portion of the permanent magnets to portions of the bridges,
• wherein the rotor core rotates along the rotational axis when the power source provides an electrical current to the coils.

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, each of the bridges having a thicker portion and a thinner portion that are respectively positioned near the radially inward and outward sides;
• and
• a center magnet and two outer magnets inserted in each of the holes, each of the center and outer magnets having a generally trapezoidal cross section, each of the two outer magnets having a first non-parallel side in contact with a non-parallel side of the center magnet and a second non-parallel side in contact with one of the bridges.