Working vehicle, vehicle speed control method of working vehicle, and vehicle speed controller of working vehicle

A method for controlling the vehicle speed of a working vehicle comprising an engine, a clutch connected to the engine, a torque converter connected to the clutch, a transmission connected to the torque converter and transmitting drive force to drive wheels, and a vehicle speed detection means which detects actual vehicle speed, wherein the following steps are executed:

• a step of calculating a target drive force required for implementing a target vehicle speed set in advance, using a standard traveling resistance set in advance and vehicle body weight;
• a step of calculating a target input rotational speed, being a target value for rotational speed to be inputted to said torque converter to provide the calculated target drive force;
• a step of detecting an actual rotational speed inputted to said torque converter;
• and
• a step of setting a clutch pressure for said clutch so that the detected actual input rotational speed becomes equal to said target input rotational speed.

A vehicle speed controller for controlling the vehicle speed of a working vehicle comprising an engine, a splitter for dividing an output of the engine between a working apparatus system and a traveling system, a clutch connected to said engine via the splitter, a torque converter connected to the clutch, a transmission connected to the torque converter and transmitting drive force to drive wheels, and a vehicle speed detection means which detects actual vehicle speed, comprising:

• a target drive force calculation means which calculates a target drive force required for implementing said target vehicle speed using a standard traveling resistance set in advance and vehicle body weight;
• a target input rotational speed calculation means which calculates a target input rotational speed, being a target value for rotational speed to be inputted to said torque converter to provide this calculated target drive force;
• an actual input rotational speed detection means which detects an actual rotational speed inputted to said torque converter;
• and
• a clutch pressure setting means which sets a clutch pressure for said clutch so that the detected actual input rotational speed becomes equal to said target input rotational speed.