In-wheel motor system

1. 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.

2. The in-wheel motor system of claim 1 , wherein an output housing having a hollowness allowing the output shaft to pass therethrough and an input housing having a hollowness allowing the input shaft to pass therethrough are further provided at a front side of the output shaft and a rear side of the ring gear housing, respectively.

3. The in-wheel motor system of claim 2 , wherein the output housing, the input housing and the ring gear housing are coupled to one another through a fastening bolt, and the fastening bolt is fastened to the in-wheel motor to prevent the ring gear housing from being rotated.

4. The in-wheel motor system of claim 2 , wherein a hub bearing is installed between the output housing and the axle.

5. The in-wheel motor system of claim 1 , wherein the input shaft is provided in a predetermined length, and has a middle portion thereof inserted into the rotor so as to rotate together with the rotor by an input shaft fixing nut that is installed at each of a front side and a rear side of the rotor while being in close contact.

6. The in-wheel motor system of claim 5 , wherein the other end portion of the input shaft is provided with a key protruding from an outer circumferential surface thereof, and the eccentric bearing is provided with a key groove matching to the key in shape.

7. The in-wheel motor system of claim 5 , wherein a tip of the other end portion of the input shaft is provided with a connecting ring to prevent the eccentric bearing from being separated from the input shaft.

8. The in-wheel motor system of claim 5 , wherein the disc is fixed to a tip of the one end portion of the input shaft by a disc fixing nut such that the disc rotates together with the input shaft.

9. The in-wheel motor system of claim 1 , wherein a ball bearing is provided between the input shaft and the output shaft.

10. The in-wheel motor system of claim 1 , wherein the output shaft is provided in a predetermined length and having a shaft portion coupled to the axle and a flange portion radially extending from an end portion of the shaft portion, and the plurality of output pins are installed at a rear side of the flange portion.

11. The in-wheel motor system of claim 1 , wherein a rubber ring is interposed between the pair of cycloid discs.

12. The in-wheel motor system of claim 1 , wherein the roller is installed at a ring pin rotatably installed at the ring gear housing, so as to make contact with the outer circumferential surface of the cycloid disc.

13. The in-wheel motor system of claim 1 , wherein the in-wheel motor comprises:

a front housing provided at a center thereof with an opening portion;

a rear housing assembled to the front housing through a bolt to form an accommodation space therein;

a rotor disposed in the accommodation space, and having a plurality of magnets installed along an outer circumferential surface thereof while being spaced apart from each other by a predetermined interval;

a stator spaced apart from the outer circumferential surface of the rotor to surround the rotor, the stator wound by a coil; and

a three-phase power port provided at a rear side wall of the rear housing to supply the coil with a power.

14. The in-wheel motor system of claim 13 , wherein the rear side wall of the rear housing is provided with an installation portion at which the disc brake is installed.

15. The in-wheel motor system of claim 14 , wherein the input shaft passes through the installation portion, and a bearing is installed between the installation portion and the input shaft.