| 摘要 |
PURPOSE: A construction mechanism and a hydraulic circuit thereof are provided to prevent a rotation shock from being generated due to the conversion of confluence value when the operations for lifting and rotating a boom are performed at the same time, thereby maintaining the satisfactory operability. CONSTITUTION: A hydraulic circuit of construction mechanism is a hydraulic actuator circuit that includes a first circuit (A) having a boom cylinder (6), a second circuit (B) having an arm cylinder (7), and a third circuit (C) having a rotation motor (18). The first, second, and third circuits include control valves, respectively, and are connected with respective first, second, and third pumps (19,20,21). The hydraulic circuit further includes a confluence passage, a tank passage, a confluence valve, and a confluence valve conversion means. The confluence valve simultaneously causes the confluence passage to connect with the third pump in the position of neutral and causes the tank passages to connect with the unload passage, and blocks the tank passage from the unload passage in the position of tank blocking. [Reference numerals] (19) First pump; (20) Second pump; (21) Third pump; (AA) Circuit; (BB) Boom descending pilot pressure; (CC) Joining valve; (DD) Boom ascending pilot pressure; (EE,HH) Boom; (FF) Driving on the right; (GG) Driving on the left; (II) Bucket |
