HYDRAULIC DRIVE SYSTEM OF CIVIL ENGINEERING MACHINERY

摘要

PURPOSE: A hydraulic drive system is provided to prevent a shock caused by the sudden down drive of a boom and to finely operate an equipment. CONSTITUTION: A hydraulic drive system is used by: switching left and right center bypass valves(24) with the pilot pressure through pilot pressure lines when operating an arm lever and a boom lever at the same time; switching an arm confluent signal spool(40) as well as a boom spool(16) with the down pilot; transferring flow from a right main pump to a relief valve(30) via a bucket spool(14), a traveling motor spool(6) and the arm confluent signal spool connected to the upper flow of a center bypass valve(26) through a notch(17) of the boom spool even if the boom spool is completely switched; transferring the signal pressure generated from the relief valve to a flow control regulator of the main pump. Therefore, the main pump is not driven in the maximum discharge state and driven in the discharge state corresponding to the notch limit of the arm confluent signal spool.