Title:
CONSTRUCTION MACHINERY
Document Type and Number:
WIPO Patent Application WO/2017/061220
Kind Code:
A1
Abstract:
A boom lever device (35) is operated by an operator and switches a boom direction control valve (31). A variable throttle (43) is provided in the middle of a center bypass pipeline (27) and variably narrows the flow channel area of the center bypass pipeline (27). A boom operation-determining unit (48) of a controller (47) determines whether a lowering action of a boom (12) is a free fall or is a car body-lifting action for lifting a car body on the basis of the bottom pressure of a bottom pressure sensor (44) and the boom-lowering operation pilot pressure of an operation pressure sensor (45). When the boom operation-determining unit (48) determines that the boom (12) is performing a car body-lifting action, a variable throttle flow channel area-modifying unit (49) of the controller (47) controls a variable throttle control valve (46) so as to narrow the flow channel area of the variable throttle (43).
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Inventors:
SHIMIZU RAITO (JP)
Application Number:
PCT/JP2016/076165
Publication Date:
April 13, 2017
Filing Date:
September 06, 2016
Export Citation:
Assignee:
HITACHI CONSTRUCTION MACH CO (JP)
International Classes:
F15B11/02; E02F9/20; F15B11/024; F15B11/028; F15B11/08
Domestic Patent References:
| WO2014073338A1 | 2014-05-15 |
Foreign References:
| JP2011127727A | 2011-06-30 | |||
| JP2006292068A | 2006-10-26 |
Attorney, Agent or Firm:
HIROSE Kazuhiko (JP)
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