Mechanical function control of continuously variable transmission hydraulic system

Abstract

A simplified continuously variable transmission system control provides a variable clamping force and a differential cylinder pressure manipulation to change sheave ratios. The system control uses two pumps. The first pump provides the variable clamping force. The second pump provides pressure changes to effect ratio changes. The clamping force can be varied based upon operator demand on an associated engine.

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         16 . A bypass relief valve adapted to automatically control clamping pressures of a continuously variable transmission, the valve comprising an inlet passage, the inlet passage being fluidly connected to a bypass passage, a valve seat and a valve member being positioned between the inlet passage and the bypass passage, the valve member being biased with a biasing force toward the valve seat by a biasing member, and an adjustment portion altering the biasing force based upon operator engine demand. 
     
     
         17 . The bypass relief valve of  claim 16 , wherein the adjustment portion comprises an input member, the input member adapted to receive an input indicative of increased operator engine demand, the input member being connected to the valve member such that increased operator engine demand results in increased clamping force. 
     
     
         18 . The bypass relief valve of  claim 16 , wherein the adjustment portion comprises an input member, the input member being adapted to move toward the valve seat with increased operator engine demand. 
     
     
         19 . The bypass relief valve of  claim 18 , wherein a bushing is interposed between the input member and the valve member, the bushing transferring forces from the input member to the valve member. 
     
     
         20 . The bypass relief valve of  claim 19 , wherein a spring is interposed between the input member and the bushing such that force from the input member is transferred to the bushing through the spring. 
     
     
         21 . The bypass relief valve of  claim 18 , wherein the adjustment portion comprises a stop, the stop being adapted to limit a range of movement of the input member.