| 摘要 |
PROBLEM TO BE SOLVED: To improve a gear dropout proof stress of an idle gear used for a reverse mechanism and improve the fatigue strength of each gear used for the reverse mechanism. SOLUTION: A driving side tooth flank 44a of the idle gear 44 and a driven side tooth flank 44b of the idle gear 44 is formed to set angles of inclinationθ3 ,θ4 with respect to the axial direction, so as to gradually increase the tooth thickness toward the engaging direction of a driving gear 41 for reverse and a driven gear for reverse 42. Chamfered faces 44c, 44d are formed asymmetrically to the right and to the left, toward the axle direction so as to offset an engaging point 50 at driving side and an engaging point 51 at driven side formed at the boundary of the chamfer faces 44c, 44d, the driving side tooth flank 44a and the driven side tooth flank 44b in the axial direction.
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