To solve the problem that, when a hydraulic pressure is made excessive by high-load operation or the like, in a conventional hydrostatic stepless transmission, a gap between plunger blocks and a center case is forcibly opened and a hydraulic fluid is leaked outside.
A first plunger block 19 includes a plunger chamber 19a into which a plurality of plungers 20 are inserted in a freely slidable manner, and is rotated together with a pump shaft 11 of a hydraulic pump 14. A second plunger block 24 includes a plunger chamber 24a into which a plurality of plungers 25 are inserted in a freely slidable manner, and is rotated together with a motor shaft 12 of a hydraulic motor 15. The first plunger block 19 and the second plunger block 24 are provided consecutively, a tubular center case 16 is provided into which plunger blocks 19, 24 is inserted. A closed circuit is comprised of: in-case oil passages 36 to 41 which are provided along an axial direction inside the center case 16; plunger ports 19c1, 24c1 which are provided in a circumferential direction of the plunger blocks 19, 24; and first and second supply/discharge grooves 16e1 to 16e4 on an inner peripheral surface 16e of the center case 16.
MATSUURA JUN
MURASHIMA DAIYU
