| 摘要 |
PROBLEM TO BE SOLVED: To provide an auto tensioner in which a seating face of a check valve is hard to wear. SOLUTION: The auto tensioner 5 includes a sleeve 8 having a bottom and fitted in the cylinder 7. Hydraulic oil is stored in the cylinder 7. A plunger 10 is slidably inserted in the sleeve 8, thereby partitioning the interior of the cylinder 7 into a pressure chamber 11 and a reservoir chamber 12. The pressure chamber 11 communicates with the reservoir chamber 12 through an oil passage 14. A check valve 13 is provided at the oil passage that permits only the flow of the hydraulic oil from the reservoir chamber 12 into the pressure chamber 11 through the oil passage. The check valve 13 includes a ceramic ball 15 configured to come into contact with and separate from a seating surface 16 formed on the end of the oil passage 14 facing the pressure chamber 11, and a retainer 17 restricting the moving range of the ceramic ball 15. The ceramic ball 15 has a surface roughness Ra of not more than 0.01. COPYRIGHT: (C)2010,JPO&INPIT
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