Rotary hydraulic automatic tensioner

A tensioner for use in an engine, said tensioner comprising:

• a fixed structure constructed and arranged to be fixed to the engine;
• a movable structure mounted for movement relative to said fixed structure in a tension applying direction and an opposite direction opposite said tension applying direction;
• a rotatable member rotatably mounted on said movable structure, said rotatable member having a driving element engaging surface positioned and configured to be engaged with an endless driving element such that engine driven movement of the driving element rotates said rotatable member;
• one of said fixed structure and said movable structure having an interior surface defining a fluid chamber containing substantially incompressible fluid;
• the other of said fixed structure and said movable structure including a chamber dividing structure disposed within said fluid chamber, said chamber dividing structure cooperating with the interior surface defining said fluid chamber so as to define first and second chamber portions within said fluid chamber on opposing sides of said chamber dividing structure, said chamber dividing structure having a fluid passageway formed therethrough to enable fluid communication between said first and second chamber portions;
• a resiliently flexible member mounted to said chamber dividing structure in covering relation with respect to said fluid passageway, said flexible member being movable away from said fluid passageway to enable said fluid to flow between said first and second chamber portions;
• a biasing element engaged with said movable structure, said biasing element applying a biasing force to bias said movable structure in said tension applying direction to tension the endless driving element;
• said fixed structure, said movable structure, and said biasing element being constructed and arranged such that, when the driving element engaging surface of said rotatable member is engaged with the endless driving element as aforesaid and said endless driving element is subject to an increase in tension and then a subsequent decrease in tension, the increase in the tension of said driving element moves said movable structure relative to said fixed structure in said opposite direction thereof against the biasing force of said biasing element to compensate for the increase in tension and then said biasing element responsively moves said movable structure relative to said fixed structure in the tension applying direction thereof to compensate for the subsequent decrease in the tension of said driving element and maintain the driving element engaging surface of said rotatable member in engagement with said endless driving element;
• said chamber dividing structure being constructed and arranged such that (a) the relative movement of said movable structure in said tension applying direction increases fluid pressure in said first chamber portion and decreases fluid pressure in said second chamber portion so as to displace fluid from said first chamber portion to said second chamber portion, and (b) relative movement of said movable structure in said opposite direction increases fluid pressure in said second chamber portion and decreases fluid pressure in said first chamber portion so as to displace fluid from said second chamber portion to said first chamber portion, said chamber dividing structure being configured to allow the fluid to flow between said chamber portions in a restricted manner so as to yieldingly resist the relative movement of said movable structure and thereby dampen the relative movement of said movable structure;
• said resiliently flexible member covering said fluid passageway so as to prevent said fluid from flowing from said second chamber portion to said first chamber portion through said fluid passageway as said movable structure moves in said opposite direction and so as to flex away from and uncover said fluid passageway and allow said fluid to flow from said first chamber portion to said second chamber portion as said movable structure moves in said tension applying direction such that the fluid flow restriction is greater when said movable structure moves in said opposite direction than when said movable structure moves in the tension applying direction so that, when the driving element engaging surface of said rotatable member is engaged with the endless driving element and the driving element is subject to the increase in tension and then the subsequent decrease in tension as aforesaid, the yielding resistance to the relative movement of said movable structure provided by the fluid flow restriction is greater in the opposite direction than in the tension applying direction.