| 摘要 |
A hydraulic drive system (1A) having first and second multi-control valves (4A, 4B) connected to first and second hydraulic pumps (21, 22). First and second regulators (3A, 3B) adjust the tilt angle of the first and second hydraulic pumps (21, 22) such that the discharge flow rate thereof decreases the higher the discharge pressure thereof and the higher the power shift pressure. A proportional valve (72) that sets the power shift pressure is controlled such that the power shift pressure increases and the discharge flow rate of the first and second hydraulic pumps (21, 22) decreases, when only a rotation spool (41) operates or when the rotation spool (41) operates and at least one spool included in the second multi-control valve (4B) operates in the direction of lower required flow rate. |
