TRANSMISSION CONTROL DEVICE DURING TRAVELING FOR WORKING VEHICLE SUCH AS TRACTOR WITH CONTINUOUSLY VARIABLE HYDROSTATIC TRANSMISSION, COMPOSED OF HYDRAULIC VARIABLE DISPLACEMENT PUMP, SHIFTING MECHANISM, MAIN HYDRAULIC MOTOR, AND SUB HYDRAULIC MOTOR

摘要

PURPOSE: A transmission control device for a working vehicle with a continuously variable hydrostatic transmission is provided to simplify the structure, and to cut down cost by automatically coping with fluctuation of load of the engine. CONSTITUTION: A transmission control device is composed of a hydraulic variable displacement pump(35), a shifting mechanism converting displacement of an operating unit into the operation displacement for adjusting the angle of the swash plate of the hydraulic pump, and a main hydraulic motor(36) and a sub hydraulic motor(37) connected to the hydraulic pump in parallel. The angle of the swash plate of the main hydraulic motor is fixed, and the angle of the swash plate of the sub hydraulic motor is varied. A common output shaft(32) receives rotation of the main and sub hydraulic motors. A control piston(38) for modifying the angle of the swash plate of the sub hydraulic motor is connected to a hydraulic pressure supply passage. The angle of the swash plate of the sub hydraulic motor is modified by the control piston to increase the capacity of the sub hydraulic motor.