| 摘要 |
An electric power steering system includes an electric motor and a worm speed reducer 15. The worm speed reducer 15 includes a worm shaft 20, a worm wheel 30, and a ring member 40. The worm wheel 30 includes an annular tooth portion 32 and an annular support 33 formed of a material that is softer than a material of a shaft 72. The ring member 40 includes an outer periphery 40a press-fitted with the annular support 33 so as to form plastically deformed portions 34 in part of the annular support 33, and an inner periphery 40b with which the shaft 72 is press-fitted. The ring member 40 is formed of a material with a hardness equivalent to a hardness of the material of the shaft 72. |
