| 摘要 |
To provide an inexpensive auto tensioner capable of stably ensuring sufficient durability, and capable of achieving light weight. The auto tensioner includes: a plunger (4) slidably arranged along an axial direction of a cylinder (1), the plunger (4) partitioning interior of the cylinder (1) into a pressure chamber (12) and a reservoir chamber (13); a path (16) communicating the pressure chamber (12) and the reservoir chamber (13) with each other; and a closure means (20) provided to the path (16), for closing the path (16) when pressure in the pressure chamber (12) is higher than pressure in the reservoir chamber (13). The closure means (20) is constituted by a check valve (22) provided with a check ball (21). The check ball (21) is constituted by a sintered body including: as a main component, ²-sialon expressed by a composition formula of Si 6-Z Al Z O Z N 8-Z where 0.1‰¤z‰¤2. 0 is satisfied; and impurities as remainder.
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