To provide a hydraulic auto tensioner for suppressing damage to a bellows in which pressure is increased with a reduction in the capacity of a reservoir chamber during retraction to greatly deform the bellows outward in the radial direction with a pressure change.
A sleeve 4 is provided in a cylinder 1 in which operating oil is filled, and a rod 5 is slidably inserted at its lower end into the sleeve 4 to form a pressure chamber 6 in the sleeve 4. A spring seat 7 provided at the upper part of the rod 5 is energized in a direction to be elongated by a return spring 8. Cylinder portions 14, 15 provided at both ends of the bellows 12 are fitted to the outer periphery of the spring seat 7 and to the outer periphery of the upper part of the cylinder 1, respectively, to form the sealed reservoir chamber 17 between the cylinder 1 and the sleeve 4. The cylinder portion 14 at one end of the bellows 12 is fastened with a bellows band 16 elastically deformable in the radial direction. The cylinder portion 14 at the one end is expanded during pressure rise in the reservoir chamber 17 due to the retraction of the bellows 12 so that air in the reservoir chamber 17 flows from a clearance 21 formed between the fitting faces of the cylinder portion 14 and the spring seat 7 to the outside for preventing the great deformation of the bellows 12 to suppress damage to the bellows 12.
Takayoshi Tagawa
Higashio Masahiro
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