| 摘要 |
<p>A worm gear mechanism (44) is configured to comprise a worm (70) which is connected to an electric motor, and a worm wheel (80) engaged with the worm. In the worm wheel (80), at least a tooth flank (81a) is formed of a resin material. In the tooth flank (81a), an engagement recess (81dr), which is based on a the trajectory of a contact point being in contact with a tooth (71) of the worm (70) according to a rotation of the worm (70), is formed by injection molding only, together with the tooth flank, using a mold (100). The engagement recess (81dr) comprises a plurality of points (P1a-P9a) which are recessed the most in a the direction of a tooth of the tooth flank of the worm wheel correspondingly to the trajectory of the contact point with which the most convex portion of the tooth (71) of the worm (70) is in contact. A line (Loa) which connects the plurality of points intersects with respect to a tooth width center line (Ct) of the tooth flank (81a) of the worm wheel (80).</p> |
