| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic control device requiring little labor for machining the air-vent structure. SOLUTION: This hydraulic control device is provided with a valve housing 1, a spool hole 2 formed in the valve housing 1, a spool 3 slidably built in in the spool hole 2, pilot chambers 5 and 10 facing to an end of the spool 3, and a circulation passage 17 communicated with the spool hole 2 at a position adjacent to the pilot chambers 5 and 10. This hydraulic control device is also provided with an annular groove 20 formed in the inner peripheral surface of the spool hole 2 at a position between the pilot chambers 5, 10 and the circulation passage 17, an air-vent flow passage 21 for always communicating the pilot chambers 5 and 10 with the annular groove 20, and an annular air-vent groove 24 formed in the spool 3. When the pilot pressure is led into the pilot chambers 5 and 10 and the spool 3 is moved by the predetermined quantity, the annular groove 20 and the circulation passage 17 are communicated with each other through the air-vent groove 24. COPYRIGHT: (C)2005,JPO&NCIPI
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