| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a hydraulic control unit of a hydraulic excavator, which can inexpensively suppress the generation of extra heat from a tandem circuit and a decrease in arm speed during the combined operations of making an arm-pulling operation and, for example, a boom-raising or bucket-excavation operation concurrently performed. <P>SOLUTION: A control valve 12 for an arm is arranged on the most downstream side in a first group G1 in which a first hydraulic pump 7 serves as a hydraulic source, and a diaphragm 20 is provided on the side of its entrance, so that the circuit can be constituted in such a manner that boom raising or bucket excavation is prioritized. On the precondition for this, during the combined operations, a controller 35 makes the upper limit value of the ejection amount of the pump 7, which is determined by the amount of the arm-pulling operation, limited depending on the amount of the boom-raising or bucket-excavation operation, and makes the regeneration rate of oil with respect to the side of elongation of an arm cylinder 5, increased depending on the amount of the boom-raising or bucket-excavation operation. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
