| 摘要 |
<p>During swing start-up, a control operation for changing the maximum absorption torque of a second hydraulic pump to Tb or Tc according to the discharge pressure of the second hydraulic pump (3) is performed in a pump torque calculating unit (43) using discharge pressure, a pump torque calculating unit (44) using swing operating pressure, and a maximum value selecting section (45), of a controller (38). During a swing-combined operation where swing is combined with other actions, a calculation for subtracting the maximum absorption torque Tp2 of the second hydraulic pump (3) from the total pump torque Tr0 is performed in a subtraction section (47). Thereby a control operation is performed wherein the amount of the torque of the second hydraulic pump (3) by which a reduction is made is allocated to a first hydraulic pump (2) which pertains to actuators other than a swing motor (7). On account of the above, a reduction is made in energy loss due to pressure relief during swing start-up, resulting in increased energy efficiency. Furthermore, in a transition process to constant speed subsequent to swing start-up, a required flow rate is supplied to the swing motor, with the result that a constant speed swing state is smoothly reached, leading to operational efficiency and combined operability being improved.</p> |
