Patent ID: 8159094

Claim:
An electric motor comprising: a housing; a stator mounted in the housing; a rotor mounted in the housing for rotation relative to the stator about a central axis, the rotor having first and second opposite ends and a plurality of fluid flow passages extending through the rotor between the first and second ends; an electro-magnetic drive system operatively connected to the rotor for driving rotation of the rotor relative to the stator; and a fluid circulation system in fluid communication with the fluid flow passages for providing fluid flow from the first end of the rotor to the second end of the rotor through at least one of the fluid flow passages and fluid flow from the second end of the rotor to the first end of the rotor through at least one other of the fluid flow passages, wherein the fluid circulation system comprises at least one impeller mounted in the housing for rotation relative to the stator, the impeller having a peripheral edge margin, an inlet positioned radially inward from the peripheral edge margin, and an outlet positioned radially outward from the inlet, the impeller being adapted to produce at least some of said fluid flow by propelling said fluid radially outward from the inlet to the outlet when the impeller is rotated relative to the stator, the rotor includes a plurality of openings at each of the first and second ends of the rotor, each of said fluid flow passages extending between at least one of said openings at the first end and at least one of said openings at the second end, the circulation system further comprises a hub adjacent one of said ends of the rotor, the hub including an outward-facing surface having at least one outward-facing channel aligned with one of said plurality of openings and an inward-facing surface defining at least in part at least one conduit through the hub aligned with another of said plurality of openings, and the impeller is positioned relative to the hub so the impeller inlet is adjacent the outward-facing channel and said inward-facing surface of the hub substantially prevents fluid flow directly to the inlet from the opening aligned with the conduit.