| 摘要 |
PROBLEM TO BE SOLVED: To provide an electric power steering device equipped with a worm gear capable of reducing surface pressure between a tooth top on a worm side and a tooth face at the side of a worm wheel. SOLUTION: Regarding a tooth profile of the screw thread 13 of a worm shaft 11 which is one of elements constituting the worm gear, the curvature radius R1 of the tooth face 14 is set larger than the curvature radius R2 of the tooth face 22 of a gear cutting tool 20 for gear cutting at the side of the worm wheel 12, and the pressure angleα1 on the pitch line M of the tooth face 14 is set larger than the pressure angleα2 on the pitch line N of the tooth face 22 of the gear cutting tool 20. In engagement between the worm shaft 11 and the worm wheel 12, the tooth top 14c at the side of the worm shaft 11 is detached from the tooth face 17 at the side of the worm wheel 12, thereby reducing the surface pressure of the tooth top 14c at the side of the worm shaft 11 with respect to the tooth face 17 at the side of the worm wheel 12. COPYRIGHT: (C)2011,JPO&INPIT
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