Reducer of electronic power steering apparatus and electronic power steering apparatus using the same

The present invention relates to a motor-driven power steering apparatus using the auxiliary reduction gear, and this, of the electric power assistance steering system. One embodiment, the worm bearing coupled to the worm shaft motor shaft connecting portion opposite end of the present invention; And the worm doedoe coupled to the outer peripheral side of the bearing to absorb play of the worm wheel is meshing with said worm and elastically deformed so that, provided in the at least one hollow portion that is formed in the circumferential direction to the position of the direction in which the meshing the worm and the worm wheel to provide a speed reducer and a motor-driven auxiliary power steering apparatus including the same of the electric power assistance steering system being configured to include; a resilient support. According to the invention, or produced by the increase of the backlash due to the wear of the worm and worm wheel, it decreases also rattle noise generated by the impact that is transmitted through the axis wheels and steering from the road, reduces rolling resistance sense of engagement of the worm and worm bearing driver the thereby an effect of increasing a sense of steering.