Abstract: A load control structure for a work vehicle comprises: a device for detecting operating position of a manually operated speed change operating element; an engine load detection device for detecting load on an engine of the work vehicle; a swash plate position detecting device for detecting an operating position of a swash plate of a variable displacement pump of a hydrostatic continuously variable speed change device; a pump operating device for steplessly operating the swash plate of the variable displacement pump; a motor operating device for operating a swash plate of a variable displacement motor of the hydrostatic continuously variable speed change device between at least two speed change positions including a higher speed position and a lower speed position; a control device for controlling the operations of the pump operating device and the motor operating device.

Abstract: A load control structure for a work vehicle comprises: a device for detecting operating position of a manually operated speed change operating element; an engine load detection device for detecting load on an engine of the work vehicle; a swash plate position detecting device for detecting an operating position of a swash plate of a variable displacement pump of a hydrostatic continuously variable speed change device; a pump operating device for steplessly operating the swash plate of the variable displacement pump; a motor operating device for operating a swash plate of a variable displacement motor of the hydrostatic continuously variable speed change device between at least two speed change positions including a higher speed position and a lower speed position; a control device for controlling the operations of the pump operating device and the motor operating device.

Abstract: A hydraulically operable transmission comprises a hydraulic clutch, a change speed control valve, change speed actuators controllable by the control valve, a pilot oil line for varying pressure states in response to operation of the actuators, an oil supply line extending to the hydraulic clutch, a clutch control valve operable with a pilot pressure applied from the pilot oil line to close the oil supply line, and a pressure buildup device mounted on the oil supply line. The pressure buildup device includes an oil chamber for producing predetermined pressure increase characteristics with a pilot pressure applied from the oil supply line and a spring load, a drain line extending from the oil chamber, and a drain control valve mounted on the drain line for opening and closing the drain line in response to the pilot pressure applied from the pilot oil line.

Abstract: A change speed control structure for a hydraulic transmission comprising a rotary valve for controlling a plurality of hydraulic actuators, a shift lever extending through a crooked guide groove, and a relay assembly for transmitting movements of the shift lever to the rotary valve on a reduced scale. The guide groove includes three straight portions extending parallel to one another in series and offset in a transverse direction thereof, each straight portion including a plurality of change speed positions. An adjacent pair of the straight portions are interconnected end to end by a bight portion.