HYDRAULIC CIRCUIT OF WORK MACHINE

摘要

PROBLEM TO BE SOLVED: To prevent reduction of the load which a lift arm 22 can lift even when the horizontal distance from the fulcrum of the lift arm 22 to the gravity center of an attachment with a load increases due to changes of the load position inside the tip attachment of the lift arm 22 or changes of types of the attachment.SOLUTION: An auxiliary cylinder 60 is installed in parallel with a lift cylinder 21 which raises or lowers a lift arm 22. The scoop operation chamber 24a of a dump cylinder 24 which rotates upward or downward a bucket attachment 23, and a lift-up operation chamber 60a of the auxiliary cylinder 60, are connected with a third hydraulic piping 63. The pressure oil created in the scoop operation chamber 24a by a weight W of a load acting on the bucket 23 is fed through the third piping 63 to be utilized as a lifting power of the auxiliary cylinder 60. The angle of the bucket 23 against the ground is maintained constant by a shunt control valve 56 regardless of the rising or lowering actions of the lift arm 22.