CONTINUOUSLY VARIABLE TRANSMISSION

PROBLEM TO BE SOLVED: To increase output shaft torque in a low speed region by supplying a discharge liquid pressure to the vicinity of a meshing part of connected gears of both mechanical transmission and static liquid pressure type transmission when the discharge liquid pressure of a liquid pressure pump exceeds predetermined pressure to drive the gears. SOLUTION: When a liquid pressure pump 5 is driven in a condition in which a movable swash plate of a static liquid pressure type transmission (HST) 4 is inclined on the plus side, liquid pressure in a communicating pipe 57a increases, and pressure liquid is supplied to a liquid pressure operation chamber 26a of a gear motor constituent part 21 from a relief valve 23a when the liquid pressure exceeds an operation set value of the relief valve 23a. Consequently, gears 66, 76 are rotated and driven in arrow Al, A2 directions in which a volume of a clearance in a meshing part between the gears 66 and 76 increases so that output torque of a hydromechanical transmission in the same direction as output torque of HST 4 increases. This is the same even when the movable swash plate of HST 4 is inclined on the opposite side. As a result, it is possible to increase the maximum transmission torque in a low speed running mode and output shaft torque at the time of start of a vehicle can also be increased.