To delay the responsiveness of a control spool at the simultaneous operation of a boom and an optional device of an excavator, to prevent the abrupt operation of the boom, and to improve compound operability.
A hydraulic system includes: main hydraulic pumps 1, 1a and a pilot pump 2; a boom cylinder 18 and the optional device; a main control valve 4 including a boom spool 6 and an optional device spool 19; an operation lever 9 which controls the boom spool 6; an optional operation pedal 10 which controls the optional device spool 19; a merging spool 7 which feeds an operation oil to the boom cylinder 18 when operating the boom to lift, blocks a merging operation oil fed to the boom cylinder 18 at a compound operation, and feeds the operation oil to the optional device; and controller 3 which outputs an electric control signal to a proportion control valve 5 for the optional device so that the pressure of a pilot signal fed to the merging spool 7 at the compound operation can be delayed at the start and end of feeding.
| JP2005016720A | 2005-01-20 | |||
| JP2009024393A | 2009-02-05 | |||
| JP2006342663A | 2006-12-21 | |||
| JPS63198644U | 1988-12-21 | |||
| JP2000213005A | 2000-08-02 |
Hideo Shimizu
Yuichi Takagi
Yoshinao Nakano
Ryoichi Mizobuchi
Hideki Akiba