CONTROL CIRCUIT FOR EXCAVATOR-HAS PROGRAMMED CONTROL FOR HYDRAULIC SWING-MOTOR AND BOOM CYLINDER

摘要

The method selectively controls the turning speed of a swing motor related to the lifting speed of a boom according to the condition of work load when lifting of the boom and turning of the swing motor are simultaneously performed. The apparatus comprises a speed ratio control switch (26) for setting a relative operating speed ratio of the boom cylinder related to turning speed of the swing motor when the swing motor and the boom cylinder are simultaneously operated; electronic proportional control blocks (23a,23b) and skew plate angle adjusting valves (20a,20b) for operating the swing motor and cylinder by receiving a controlling current value. When one in respective maneuvering amounts of an operating lever/pedal (22) is not the maximum value, the apparatus outputs controlling current to the valves (20a,20b), the blocks (23a,23b) in order to operate the motor (10), cylinder (16) at a speed according to the maneuvering amount.