Reducer of electric power steering apparatus

1. A reducer of an electric power steering apparatus in which a first shaft and a second shaft are connected to each other to transfer driving force of a driving motor, the reducer comprising:

an inner rotor including an insertion hole formed axially with respect to the second shaft and a first protrusion formed radially with respect to the second shaft;

an elastic body formed to surround an outer circumferential surface of the inner rotor, the elastic body including a second protrusion formed radially with respect to the second shaft and an elastic protrusion formed on the second protrusion axially with respect to the second shaft, wherein one surface of the elastic body formed opposite to another surface of the elastic body, from which the elastic protrusion formed on the second protrusion protrudes, is supported by at least a part of the first protrusion of the inner rotor; and

an outer rotor coupled to the inner rotor, the outer rotor including a third protrusion coupled to the first shaft and formed radially with respect to the second shaft.

2. The reducer of claim 1 , wherein the elastic body is formed to surround an outer circumferential surface of the first protrusion, and the inner rotor protrudes outward from the elastic body.

3. The reducer of claim 1 , wherein the elastic protrusion is formed on the second protrusion toward the first shaft.

4. The reducer of claim 1 , wherein the elastic protrusion includes a first surface formed vertically to the second protrusion and a second surface connected to one end of the first surface and a portion of the second protrusion and formed in a curved shape.

5. The reducer of claim 4 , wherein the first surface of the elastic protrusion has a smaller gradient than the second surface of the elastic protrusion.

6. The reducer of claim 1 , wherein in the inner rotor, an adhesive is applied to an upper surface of the first protrusion that is in contact with the elastic body.

7. A reducer of an electric power steering apparatus, the reducer comprising:

a first shaft having at least one protrusion provided at an outer circumferential surface;

a second shaft having at least one axial extension at one end; and

a power transfer member having a first coupling part including an insertion hole, into which the at least one protrusion is to be inserted so that the first shaft is coupled to the first coupling part which is in a center area of the power transfer member, and a second coupling part, wherein the at least one axial extension of the second shaft is mounted on an outer circumferential surface of the second coupling part of the power transfer member so that the second shaft is coupled to the outer circumferential surface of the second coupling part.

8. The reducer of claim 7 , wherein when the at least one protrusion includes two or more protrusions which are spaced apart from one another circumferentially with respect to the first shaft.

9. The reducer of claim 8 , wherein when the at least one axial extension includes two or more extensions which are circumferentially arranged corresponding to the two or more protrusions.

10. The reducer of claim 8 , wherein the two or more protrusions are equally spaced apart from one another circumferentially with respect to the first shaft, and the two or more extensions are equally spaced apart from one another circumferentially according to the space between the two or more protrusions.

11. The reducer of claim 8 , wherein the power transfer member comprises:

a damping member formed of an elastic material, the damping member having the first coupling part and the second coupling part in a center area and on an outer circumferential surface, respectively; and

supporting members provided at both axial ends of the damping member and formed of a material having greater strength than the damping member.

12. The reducer of claim 11 , wherein the supporting members are formed integrally with the damping member or are pressed-fitted to coupling holes formed on both side surfaces of the damping member.

13. The reducer of claim 12 , wherein the supporting members have supporting protrusions protruding radially and inwardly on an inner circumferential surface.

14. The reducer of claim 13 , wherein the supporting protrusions are circumferentially arranged corresponding to the insertion hole.

15. The reducer of claim 1 , wherein the elastic protrusion formed on the second protrusion axially protrudes toward the first shaft from the another surface of the elastic body formed opposite to the one surface of the elastic body supported by the at least a part of the first protrusion of the inner rotor.

16. The reducer of claim 7 , wherein the at least one axial extension of the second shaft surrounds at least a part of the outer circumferential surface of the second coupling part of the power transfer member.