Speed control structure and method for work vehicle

Abstract

A speed control structure for a work vehicle comprises: a speed change operating element for manipulation by an operator; a device for detecting operated position of the speed change operating element; a continuously variable speed change device that receives power from an engine of the work vehicle; speed change position detecting device for detecting a speed change operation position of the continuously variable speed change device; operating device for speed-shifting the continuously variable speed change device; control device for controlling the operating means, wherein the control means: sets a target speed change operating position based on detected information by the operated position detection device and a predetermined correlation data that correlates the operated position of the speed change operating element and the speed change operation position of the continuously variable speed change device, and calculates a deviation between the target speed change operating position and of the continuously variable speed change device and the actual speed change operation position based on the set target speed change operating position and detected information from the speed change position detecting device, and sets a target operating speed for the continuously variable speed change device based on the calculated deviation and a further correlation data that correlates the deviation with an operating speed at which the continuously variable speed change device is operated, and controls the operating means such that the continuously variable speed change device is operated toward the target speed change operating position and at the target operating speed.