公开(公告)号：EP4293236A1

公开(公告)日：2023-12-20

申请号：EP21931579.3

申请日：2021-03-18

申请人： Hitachi Construction Machinery Co., Ltd.

发明人： AMANO, Hiroaki ,  KUMAGAI, Kento ,  OOHIRA, Hiroto ,  NISHIKAWA, Shinji ,  NARAZAKI, Akihiro ,  KODAKA, Katsuaki

IPC分类号： F15B11/042

摘要： A work machine includes: a main circuit that supplies a working fluid from a pump to an actuator; a pilot circuit that introduces part of the working fluid from the pump, to a pilot pressure receiving section of a control valve; a bleed-off passage that connects the pump and a tank. The pilot circuit is provided with: a first pressure reducing valve that generates a pilot primary pressure; and second and third pressure reducing valves that generate a pilot secondary pressure to be applied to the control valve and a bleed-off valve. A moving area of a spool of the bleed-off valve has a first moving area where an opening area of a restrictor changes stepwise, and a second moving area where the opening area of the restrictor changes continuously. A controller controls the third pressure reducing valve such that the spool is positioned in the first moving area at the time of non-operation of the actuator, and the spool is positioned in the second moving area at the time of operation of the actuator. The restrictor of the bleed-off valve has a restricting hole that gives a resistance to the working fluid passing therethrough in a case the spool is positioned in the first moving area.