| 摘要 |
A curvature radius R1 of a raceway groove 31d of an inner ring 31a of a first bearing 31 supporting a first end portion 22 of a worm shaft 20 and a curvature radius R2 of a raceway groove 31e of an outer ring 31b of the first bearing 31 are larger than 50% of a diameter D1 of each rolling element 31 of the first bearing 31, whereby the worm shaft 20 is pivotable about the first end portion 22. Internal clearances in the first bearing 31 are eliminated because the first bearing 31 is pressed in a radial direction Q1 by a pressing member 35. When the worm shaft 20 vibrates relative to a housing 70 in an axial direction S1, paired second elastic members 63 and 67 damp and absorb the vibration. |
