Patent ID: 7499783

Claim:
A hydraulic control apparatus for a hydraulic excavator comprising: a plurality of control valves that control operations of hydraulic actuators, the plurality of control valves including first and second arm control valves operated by a common operating means, the plurality of control valves being separated into a first group including one of the first and second arm control valves and a second group including the other arm control valve; first and second hydraulic pumps to which the first and second groups are connected respectively, each arm control valve being disposed at the most downstream position in the group, control valves of each group being connected in series by a tandem circuit and in parallel by a parallel circuit, the tandem circuit connecting center bypass passages of the control valves, the parallel circuit connecting pump ports of the control valves; a throttle provided at the entrance of the arm control valve in the parallel circuit of the first group for preferentially supplying oil discharged from the first hydraulic pump to the other control valves in the first group; and a control means that controls the pump discharge amounts according to the operation amounts of the arm control valves, wherein during a combined operation in which arm pulling operation of the arm control valve in the first group and operation of another control valve in the first group are performed simultaneously, the control means decreases the upper limit of the discharge amount of the first hydraulic pump determined by the operation amount of arm pulling operation, according to the increase in the operation amount of the other control valve.