Patent ID: 8863873

Claim:
An in-wheel motor system installed at a wheel of a vehicle to transmit a rotational force, the in-wheel motor system comprising: an axle installed at the wheel of the vehicle and rotating together with the wheel; an in-wheel motor mounted inside the wheel and provided with a rotor and a stator that are used to generate a rotational force to drive the wheel, the rotor, and the stator disposed to face each other while having an accommodation space thereinbetween; a cycloid decelerator installed at a center of the in-wheel motor, and provided with an output shaft to transmit a rotational force at a reduced speed from the in-wheel motor to the axle and an input shaft that passes through the in-wheel motor and rotates together with the rotor; a disc installed at one end portion of the input shaft that protrudes by passing through the in-wheel motor; and a disc brake configured to provide a braking force by pressing the disc, wherein the in-wheel motor and the cycloid decelerator are disposed in a space formed inside the wheel, and wherein the cycloid decelerator comprises: a pair of eccentric bearings connected to the input shaft rotating together with the rotor to eccentrically transmit a rotation; a pair of cycloid discs each installed at the eccentric bearings, respectively, to have the eccentric bearing positioned at a center thereof, each of the pair of cycloid discs provided with a plurality of through holes in a radial direction from a center thereof and configured to eccentrically rotate; a ring gear housing installed to surround the pair of cycloid discs and having a roller installed along an inner circumferential surface thereof, the roller making contact with an outer circumferential surface of the cycloid disc such that the cycloid disc performs a revolution and a rotation; and the output shaft rotatably coupled to the axle, and having a plurality of output pins installed thereto, the plurality of output pins inserted into the plurality of through-holes, respectively, to compensate for an eccentricity of a center of the cycloid disc.