HYDRAULIC OPERATION CONTROL DEVICE FOR CONTINUOUSLY VARIABLE TRANSMISSION

摘要

PURPOSE: To provide a continuously variable transmission positioned by a hydraulic control piston, comprising a driving sheave and a driven sheave respectively having adjustable pistons. CONSTITUTION: For suitably positioning each adjustable portion, the piston is pressurized by a control system, and a flexible driving member hung on a sheave operates with a desired diameter so that a desired gear ratio is established between a driving sheave and a driven sheave. A control device has two variable displacement pump assemblies for supplying working fluid at a desired pressure for keeping a desired ratio and generating ratio change required by an operation condition. One pump supplies a primary pressure proportional to a torque request of a CVT, and the other pump supplies a pressure required to generate the ratio change. A ratio control pump is movable to both sides of a neutral position so that a primary pump can keep a torque capacity pressure required in a system and simultaneously supply ratio control fluid to one of adjustable portions.