| 摘要 |
The pump discharge flow rate of a bidirectional piston pump (31) is set to a reference pump discharge flow rate Qa if the operation state of a lifting/lowering cylinders (15) is in a no-load state, and is set to a small-flow-rate pump discharge flow rate Qb that is smaller than the reference pump discharge flow rate Qa if the operation state of the lifting/lowering cylinders (15) is in a high-load state. The value Qb·Pb found by multiplying the pump discharge flow rate Qb and the pump discharge pressure Pb of the bidirectional piston pump (31) for when the operation state of the lifting/lowering cylinders (15) is in a high-load state is set substantially equal to or less than the value Qa·Pa found by multiplying the pump discharge flow rate Qa and the discharge pressure Pa of the bidirectional piston pump (31) for when the operation state of the lifting/lowering cylinders (15) is in a no-load state. |
