| 摘要 |
PROBLEM TO BE SOLVED: To provide a closed circuit hydraulic drive device capable of securing excellent fine operability by achieving an extending and contracting action of a hydraulic cylinder not corresponding to a load state but corresponding to an operation.SOLUTION: A closed circuit hydraulic drive device includes: ducts 13 and 15 connected to a head chamber 1a of a hydraulic cylinder 1; ducts 14 and 16 connected to a rod chamber 1b; a hydraulic pump 12 connected to the hydraulic cylinder 1 in a closed circuit state through the ducts 13, 15 and 14, 16; a drain duct 30 connecting the duct 15 or 16 to a working oil tank 23; a flow rate control valve 20 controlling the flow rate of a working oil flowing in the drain duct 30; an operation lever device 10 which instructs an action of the hydraulic cylinder 1; and a control device 50 which controls the flow rate control valve 20 according to an operation amount of the operation lever device 10 so that, when the hydraulic cylinder 1 is contracted, the working oil flows into the rod chamber 1b at the flow rateαQp obtained by multiplying a discharge flow rate Qp of the hydraulic pump 12 by a rateαof the pressure reception area of the oil chamber 1b to that of the oil chamber 1a, 1b, and flows out of the head chamber 1a at the flow rate Qp. |
