Hydraulic timing chain tensioner assembly

Abstract

A hydraulic timing chain tensioner assembly includes a shoe configured to contact a timing chain, and a plunger having a distal end abutting the shoe. The plunger is movable within a cylindrical opening formed in a tensioner body. The cylindrical opening includes oil and a spring member therein to cushion chain loads transmitted through the shoe and plunger. A spring-controlled oil pressure relief structure is operatively associated with the cylindrical opening to vent the oil when the oil is pressurized above a predetermined level by the plunger, thereby enabling further movement of the plunger into the cylindrical opening to reduce maximum loads experienced by the timing chain.

1 . A hydraulic timing chain tensioner assembly comprising: 
 a shoe configured to contact a timing chain;    a hydraulic tensioner including a plunger having a distal end abutting said shoe, said plunger being movable within an opening formed in a tensioner body, said opening including oil and a spring member therein to cushion chain loads transmitted through the shoe and plunger; and    said hydraulic tensioner further including a spring-controlled oil pressure relief structure operatively associated with said opening to vent the oil when the oil is pressurized above a predetermined level by movement of the plunger into the opening, thereby enabling further movement of the plunger into the opening to regulate loads experienced by the timing chain.    
     
     
         2 . The hydraulic timing chain tensioner of  claim 1 , wherein said oil pressure relief structure comprises a pressure relief valve in fluid communication with the opening for selectively venting the oil, said pressure relief valve including a ball spring-loaded toward a valve seat, such that said predetermined level of oil pressure causes movement of the ball away from the seat against said spring-load to open the valve and vent the pressurized oil.  
     
     
         3 . The hydraulic timing chain tensioner of  claim 2 , further comprising a control orifice between the pressure relief valve and the opening.  
     
     
         4 . The hydraulic timing chain tensioner of  claim 2 , further comprising an oil reservoir in selective fluid communication with said opening through an inlet check valve to store oil needed for engine start-up.  
     
     
         5 . The hydraulic timing chain tensioner of  claim 4 , wherein said oil reservoir includes a purge hole formed thereabove to purge air entrained within the oil.  
     
     
         6 . The hydraulic timing chain tensioner of  claim 2 , wherein said pressure relief valve is positioned vertically above the opening.  
     
     
         7 . The hydraulic timing chain tensioner of  claim 1 , wherein said oil pressure relief structure comprises a poppet valve structure formed by the plunger, the plunger including a plunger sleeve, a shoe contact end, a valve head end and an internal spring compressed between the shoe contact end and a rim of said plunger sleeve, said rim also being in contact with the oil and with the valve head end for closing the poppet valve, said poppet valve opening when force from pressure of the oil and force from the spring member against the rim overcomes force of the internal spring against the rim.  
     
     
         8 . The hydraulic timing chain tensioner of  claim 7 , wherein the spring member abuts the plunger sleeve.  
     
     
         9 . The hydraulic timing chain tensioner of  claim 7 , wherein said valve head end is positioned on a shaft which is threaded into the shoe contact end, said plunger sleeve and shaft cooperating to form a spill chamber having a relief opening to vent oil spilling past the poppet valve when opened.  
     
     
         10 . The hydraulic timing chain tensioner of  claim 9 , wherein the shaft includes a vent channel therethrough for communicating the spill chamber with the relief opening.  
     
     
         11 . The hydraulic timing chain tensioner of  claim 10 , wherein said relief opening is formed by a cap plug positioned within the shoe contact end of the plunger, said cap plug having a control orifice therethrough.  
     
     
         12 . The hydraulic timing chain tensioner of  claim 9 , wherein said valve head end forms an angled valve seat which cooperates with the rim of the sleeve to open and close the poppet valve.  
     
     
         13 . The hydraulic timing chain tensioner of  claim 7 , wherein the shoe contact end is adjustable with respect to the valve head end for adjusting compression of the spring, thereby setting said predetermined level.  
     
     
         14 . A hydraulic timing chain tensioner assembly comprising: 
 a shoe configured to contact a timing chain;    a hydraulic tensioner including a plunger having a distal end abutting said shoe, said plunger being movable within an opening formed in a tensioner body, said opening including oil and a spring member therein to cushion chain loads transmitted through the shoe and plunger; and    said hydraulic tensioner further including a pressure relief valve in fluid communication with the opening for selectively venting the oil, said pressure relief valve including a ball spring-loaded toward a valve seat, such that a predetermined level of oil pressure causes movement of the ball away from the seat against said spring load to open the valve and vent the pressurized oil.    
     
     
         15 . A hydraulic timing chain tensioner assembly comprising: 
 a shoe configured to contact a timing chain;    a hydraulic tensioner including a plunger having a distal end abutting said shoe, said plunger being movable within an opening formed in a tensioner body, said opening including oil and a spring member therein to cushion chain loads transmitted through the shoe and plunger; and    said hydraulic tensioner further including a poppet valve structure formed by the plunger, the plunger including a plunger sleeve, a shoe contact end, a valve head end, and an internal spring compressed between the shoe contact end and a rim of said plunger sleeve, said rim also being in contact with the oil and with the valve head end to define a poppet valve, said poppet valve opening when force from pressure of the oil and force from the spring member against the rim overcomes force of the internal spring against the rim to vent the pressurized oil to regulate loads experienced by the timing chain.