| 摘要 |
PROBLEM TO BE SOLVED: To smoothly perform the turning with a good riding quality in an automatic transmission mechanism of a construction machine. SOLUTION: A variable capacity type hydraulic motor 1 is shiftable to a second speed and a first speed. A capacity control cylinder 18 shifts the hydraulic motor 1 to the second speed when the pressure oil is supplied to a cylinder chamber 20, and to the first speed when the pressure oil is discharged. A capacity switching valve 21 is switchable between a supply position f for connecting the capacity control cylinder 18 with a hydraulic source and a discharge position d for connecting the capacity control cylinder 18 with a tank 45. A driving pressure passage 23 is formed to introduce a driving pressure of the hydraulic motor 1 to achieve the oil pressure for moving a valve element 22 of the capacity switch valve 21 to one side. When the construction machine is turned, a flow rate in supplying the pressure oil to the cylinder chamber 20 of the capacity control cylinder 18 is restricted by a first throttle 31, and a flow rate in discharging the pressure oil from the cylinder chamber 20 is restricted by the first throttle 31 and a second throttle 32. COPYRIGHT: (C)2005,JPO&NCIPI
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