Hydraulic tensioner with porous vent

摘要

The hydraulic chain tensioner comprises a housing having a bore, the bore defining a fluid chamber and a hollow plunger slidably received within the bore and having an upper end, the upper end having an aperture. There is a spring biasing the plunger in a protruding direction from the bore and a check valve provided between the chamber and a source of pressurized fluid to permit fluid flow into the chamber while blocking flow in the reverse direction. It has a passage in the housing to connect the chamber with the source of pressurized fluid and a vent formed of sintered powder metal located at the upper end of the plunger. The vent is in the shape of a disc and biased by the spring against the inside of the upper end of the plunger. It also has a movable rack associated with the plunger and a ratchet biased by a spring in meshing engagement with the rack.