To provide a hydraulic control circuit of a construction machine equipped with working attachments which can avoid the deceleration of working speed when a hydraulic actuator for attachment and the other hydraulic actuator work together while preventing an excessive flow amount from flowing into the hydraulic actuator for attachment.
First and second pumps 11, 12 are controlled in discharge flow independently by the use of an electromagnetically proportional pressure reducing valve 35 for first pump control which outputs signal pressure to a capacity variable means 11a of the first pump 11 based on operations of control valves 20-24 supplied with hydraulic oil from the first pump 11 when a hydraulic actuator 18 for attachment is driven, and an electromagnetically proportional pressure reducing valve 36 for second pump control which outputs the signal pressure to a capacity variable means 12a of the second pump 12 based on operations of control valves 25-29 supplied with hydraulic oil from the second pump 12 when the actuator is driven.
SHIMABARA SEI
NAKANISHI MANABU
SHIBATA MASAFUMI
| JP2008032175A | 2008-02-14 | |||
| JPH0586635A | 1993-04-06 | |||
| JPH09105154A | 1997-04-22 |
Suzuki Yuko
Naozumi Ono
Sachiko Okunuki