To provide a hydrostatic continuously variable transmission in which a high-pressure oil passage for feeding operation fluid from the hydraulic pump to the hydraulic motor side, a low-pressure oil passage for feeding operation fluid from a hydraulic motor side to a hydraulic pump and a hydraulic circuit including a switching valve for switching between a high-pressure oil passage and a low-pressure oil passage in the plunger are formed in an inner/outer double structure in a valve body disposed between a hydraulic pump plungers and a hydraulic motor and which executes switching of power transmission by sliding a clutch valve provided in the transmission shaft and short-circuiting the high-pressure oil passage and low-pressure oil passage between the hydraulic pump comprising a plurality of plungers and hydraulic motor comprising a plurality of plungers, wherein an arrangement structure of an oil passage for a short circuit having a sufficiently large diameter so as to sufficiently reduce pressure in the high-pressure oil passage when a clutch is in an OFF state.
An oil passage for communicating between an oil passage positioned outward and a clutch valve is provided between adjacent opening passages. A distance between the back end face of a plunger hole and an end surface of a valve body on a side to which an oil passage is provided is made longer than a distance between the back end face of the plunger hole and the end surface of the valve body on the other side.
NAKAMURA KAZUHIKO
OKUZAKI HIDEO
Nakamura Kun
Mitsuharu Oda