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|1. (WO2018079194) HYDRAULIC SHOVEL DRIVE SYSTEM|
|Applicants:||KAWASAKI JUKOGYO KABUSHIKI KAISHA
|Title:||HYDRAULIC SHOVEL DRIVE SYSTEM|
A hydraulic shovel drive system is provided with: first and second pumps; an arm cylinder; an arm first control valve connected with the arm cylinder by an arm pulling supply line and an arm pushing supply line; an arm second control valve connected with the arm pulling supply line and the arm pushing supply line by a first replenishing line and a second replenishing line; and an arm operation device that outputs an operation signal corresponding to the incline angle of an operation lever. The arm second control valve is configured so that during arm pulling operation, the area of an opening on a meter-in side changes in accordance with the operation signal, the area of an opening on a meter-out side is maintained at zero when said area does not fulfill a predetermined condition, and when said area fulfills the predetermined condition, the area of the opening on the meter-out side is maintained at zero until the operation signal becomes equal to or greater than a set value, then increases to the maximum value thereof when the operation signal becomes equal to or greater than the set value.