Patent ID: 8447479

Claim:
A speed change system for a work vehicle having a continuously variable transmission device comprising: a pump swash plate operation mechanism configured to operate a swash plate of a variable capacity pump for the continuously variable transmission device; a motor swash plate operation mechanism configured to operate a swash plate of a variable capacity motor for the continuously variable transmission device; a swash plate angle control unit configured to non-stepwise adjust a swash plate angle of the variable capacity pump through the pump swash plate operation mechanism and stepwise adjust a swash plate angle of the variable capacity motor through the motor swash plate operation mechanism; and an operation position detector configured to detect an operation position of a speed change operation tool; wherein the swash plate angle control unit sets the swash plate angle of the variable capacity pump and the swash plate angle of the variable capacity motor based on an output from the operation position detector, and controls the pump swash plate operation mechanism and the motor swash plate operation mechanism so that the swash plate angle of the variable capacity pump and the swash plate angle of the variable capacity motor become respective set swash plate angles, and when the swash plate angle of the variable capacity motor is changed based on the output from the operation position detector, the swash plate angle control unit controls the pump swash plate operation mechanism in such a manner that the swash plate angle of the variable capacity pump is changed with a control amount which is set so as to compensate an amount of change in a change gear ratio of the continuously variable transmission device caused along with the change of the swash plate angle of the variable capacity motor.