Hydraulic continuously variable speed transmission with relief valve to prevent engine stall

摘要

A hydraulic continuously variable speed transmission includes a hydraulic pump and a hydraulic motor, at least one of said hydraulic pump and motor being of variable displacement type. A hydraulic path is formed in a member of the pump which rotates in synchronism with an output shaft of engine, for communicating hydraulic a pressure chamber of the hydraulic pump with a drain. A check valve is provided in the hydraulic path for closing the hydraulic path under centrifugal force created by the rotation of the member when this member is in rotation faster than a predetermined speed, and for opening the hydraulic path against a centrifugal force when the member is in rotation slower than the predetermined speed.