VARIABLE-SPEED CONTROL UNIT FOR WORKING VEHICLE

PROBLEM TO BE SOLVED: To provide a variable-speed control unit solving the problem that, in a conventional tractor, since a torque control for keeping travel driving force constant is designed to turn on/off with a switching instrument, the switch needs to be operated each time a work is started and ended, with such operations being troublesome, leading to be subject to misoperations including being left to be turned on. SOLUTION: The variable-speed control unit has the following construction and mechanism: The variable-speed position of the stepless variable-speed gear of a tractor is made changeable by an actuator. There is equipped a sensor 3s for detecting the turning angle of a lift arm 3. There is also equipped a controller C working in such a way that if the detection value given by the sensor 3s is less than a predetermined value, a torque control that keeps the output revolutions of an engine E constant by driving the actuator is selected, otherwise a ratio control that keeps vehicle speed constant by driving the actuator is selected. COPYRIGHT: (C)2007,JPO&INPIT