| 摘要 |
PROBLEM TO BE SOLVED: To improve durability by restraining heat generation of a resin-made insert bearing of an automatic tensioner. SOLUTION: An outer cylinder 7 of an arm member 6 is supported on an inner shaft 4 of a base member 1 through a synthetic resin-made insert bearing 12 so as to be freely oscillated, and a tension pulley 20 supported on the tip of the arm member 6 is brought in pressure-contact with an endless belt by energizing the arm member 6 by a spring 5. Shot peening is applied to the inner peripheral surface of the outer cylinder 7 to be brought in slide-contact with the outer peripheral surface of the insert bearing 12, and the arithmetical mean roughness Ra and the maximum height Ry of the inner peripheral surface is so adjusted as to satisfy the expressions 1×10<-6> m<=Ra<=10×10<-6> m and Ry<=60×10<-6> m.
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