| 摘要 |
PROBLEM TO BE SOLVED: To provide a gear in which the radius of an addendum circle is uniform in the circumferential direction. SOLUTION: Ribs 26 are disposed at a tooth bottom 30 of a tooth part 16. Thereby, the local increase of the thickness can be prevented, and a radius R of the addendum circle can be made uniform in the circumferential direction. Accordingly, the angular velocity of a body to be driven, to which a driving force is transmitted by this gear 10 will not vary, and since a rotation dispersion is not generated at the body to be driven, a performance of the driving device is enhanced using the gear 10. Ribs 28 are arranged at positions deviating from extended lines of the ribs 26. Thereby, tensile strengths caused by a shrinkage at the time of molding of the ribs 28 and the ribs 26 are cancelled with each other, by an annular rib 24 and the surface sink of a tooth crest surface 32A becomes smaller. |
