Rotary hydraulic automatic tensioner

Abstract

Disclosed is a tensioner for use in an engine. The tensioner comprises a fixed structure that fixes to the engine. A movable structure is mounted for movement relative to the fixed structure in a belt tensioning and opposite directions. A pulley member has a belt engaging surface that engages with the belt. One of the fixed and movable structures has an interior surface defining a fluid chamber containing fluid and the other includes a chamber dividing structure. The chamber dividing structure defines first and second chamber portions on opposing sides thereof. A biasing element biases the movable structure in the tensioning direction to tension the belt. Relative movement of the movable structure in the tensioning direction displaces fluid from the first to the second chamber portion and increases fluid pressure in the first chamber portion and decreases fluid pressure in the second chamber portion, and the reverse occurs during movement of the movable structure in the opposite direction. The chamber dividing structure allows the fluid to flow between the chamber portions in a restricted manner so as to yieldingly resist the relative movement of the movable structure and thereby dampen such movement. The chamber dividing structure is constructed such that the fluid flow restriction is greater when the movable structure moves in the opposite direction than in the tensioning direction, thereby providing the movable structure with greater resistance to movement in the opposite direction than in the tensioning direction.