| 摘要 |
PROBLEM TO BE SOLVED: To obtain an inexpensive valve device capable of automatically operating a speed change cylinder by pilot hydraulic pressure supplied from a motor drive circuit so as to switch a variable capacity type hydraulic motor from a small capacity state to a large capacity state in proportion to increase in driving load and preventing generation of hunting caused by switching of its capacity. SOLUTION: A small-diameter section 52 and large-diameter section 59 are arranged on one end of a spool 50, and an oil chamber hole 54 is arranged on the other end of the spool 50. When the spool 50 is positioned on a large capacity position VL and is positioned on a small capacity position, the command hydraulic pressure from an command port 46 operates on the small-diameter section 52 and large-diameter section 59 so as to interconnect the oil chamber hole 54 into a pilot port 43. When the spool 50 is positioned on the large capacity position VL, the command pressure from the command port 46 operates on the small-diameter section 52 and does not operate on the large-diameter section 59 while the small-diameter section 52 brings into contact with an annular stopper section 65, and a drain port 44 is also opened on a peripheral surface of the large-diameter section 59. COPYRIGHT: (C)2006,JPO&NCIPI
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