Patent ID: 7114332

Claim:
In a hydrostatic continuously variable transmission of the type comprising a support shaft, a hydraulic pump and a hydraulic motor respectively mounted on the support shaft, connected to each other through a hydraulic closed circuit, and wherein the capacity of said hydraulic motor is variably controlled to modify a speed of input rotation of said hydraulic pump and to transmit the speed-modified rotation as an output rotation of said hydraulic motor, the improvement comprising a clutch apparatus integrated into said transmission, said clutch apparatus comprising: a hollow internal bore extending axially inside said support shaft; a valve spool which is slidably disposed in said internal bore of said support shaft, and which operates to allow or to interrupt fluid communication between a high pressure side oil passage and a low pressure side oil passage of said hydraulic closed circuit, according to the position thereof; a rotatable clutch cap operatively attached to said hydraulic pump; and a governor mechanism which is operatively associated with said clutch cap, and which operates to generate a governor force corresponding to a rotating speed of said clutch cap by use of a centrifugal force generated by rotation of said clutch cap; wherein said valve spool is moves in said internal bore in response to said governor force generated by said governor mechanism during the operation of said clutch device.