| 摘要 |
A chain or belt tensioner comprises a plunger displaceable in a bore of a housing between retracted and extended positions. The plunger and the bore between them define a variable volume chamber for receipt of pressurised hydraulic fluid. The tensioner is designed for insertion into a supporting bore of the cylinder head of an internal combustion engine such that the plunger has only a limited number of possible orientations so that it can engage with the tensioner arm. The plunger has an air purge passage that extends from adjacent to the chamber to atmosphere. The passage formation is designed so that there is a portion of it adjacent to the chamber is uppermost in any orientation of the plunger so as to ensure rapid and effective air purging. There may be a single air purge passage extending in an axial direction along the length of the plunger or a combination of several axial and circumferential portions that permit the plunger to be disposed in more than one orientation.
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