Patent ID: 8841814

Claim:
An electric motor comprising: a rotary shaft having an outer circumferential surface with a diameter that decreases from a larger diameter section having a first diameter toward a smaller diameter section having a second diameter smaller than said first diameter; a sleeve mounted to said rotary shaft by interference fit with an inner circumferential surface having a diameter that decreases from a front end adjoining said larger diameter section toward a rear end adjoining said smaller diameter section, to the outer circumferential surface of said rotary shaft; and a cylindrical rotor part mounted by interference fit to an outer circumferential surface of said sleeve, wherein said sleeve comprises a fluid passageway extending through from an outer face of said sleeve including the outer circumferential surface of said sleeve to the inner circumferential surface of said sleeve, wherein said electric motor further comprises: an annular passageway formed between the inner circumferential surface of said sleeve and the outer circumferential surface of said rotary shaft, the annular passageway extending annularly around a rotation axis of said rotary shaft and being connected to said fluid passageway; and an axial passageway formed between the inner circumferential surface of said sleeve and the outer circumferential surface of said rotary shaft, the axial passageway extending from said annular passageway toward said larger diameter section in the direction of said rotation axis.