UNDER SPEED CONTROL SYSTEM FOR HYDROMECHANICAL DRIVE SYSTEM AND OPERATION METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To prevent lowering of productivity of a machine due to the excessive reduction of engine speed. SOLUTION: An engine 12 is connected to drive a hydromechanal drive system containing a variable displacement pump 48. An engine speed sensor 76 detects the rotation speed of an engine and generates an actual engine speed signal to indicate the rotation speed of an engine. A movement speed sensor detects the movement speed of a machine and generates an actual movement speed signal indicating the movement speed of a machine. A controller 18 compares an actual engine speed signal with an under speed value and generates a speed error signal indicating a difference between the intensity of the actual engine speed signal and an underspeed value. The speed error signal is corrected by a proportional and an integration feedback controller, and a command signal is generated according to the correction value. Since a pump discharge amount controller 50 receives a command signal and regulates an engine load according to the command signal, a discharge amount of a variable displacement pump is controlled.