US Patent 7615897 Cooling device of motor

A motor cooling device including an impeller 2, supported by a rotary shaft 1a of a motor 1, and a fan cover 4, which encases a front portion and a peripheral portion of the impeller 2 and has an air inlet 5 in a front surface and an air outlet 6 in the rear. A constricting flow space S1 is arranged at an exit side of the impeller 2 and defined by a motor end surface 1b, which includes an entrance in the proximity of a rear surface of a vane 3 of the impeller 2 and a circumferential surface expanding radially and diagonally in the rearward direction, and a space formation member 10, which is formed on an inner surface of the fan cover 4.