| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To increase an operating speed of a bucket while securing a stable boom hoisting operation, and to enhance a heat balance and fuel consumption. <P>SOLUTION: In this hydraulic circuit of a hydraulic excavator, a bucket switching valve 14 and a boom switching valve 15 are connected in tandem to a center bypass oil passage 11 communicating with a hydraulic pump 2, and are also parallelly connected to a parallel oil passage 13 branching off from the center bypass oil passage 11. A flow rate control means 30 is provided in a feeder oil passage 32 for connecting the bucket switching valve 14 and the parallel oil passage 13 together. The flow rate control means 30 limits a flow rate of the feeder oil passage 32 when the load pressure of a bucket cylinder 28 is low, and opens the feeder oil passage 32 when the load pressure of the bucket cylinder 28 is high. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
