| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic control device with reduced energy loss that compensates for a drawback of a link mechanism in which a main spool cannot completely return to the neutral position. SOLUTION: In the hydraulic control device, a sub spool SS applied with elastic force of a spring 27 is assembled in the main spool MS, and the sub spool SS faces first and second pressure chambers 25, 26. When the main spool MS is at the neutral position or near the neutral position, the first pressure chamber 25 is communicated with a tank passage 7, and the second pressure chamber 26 is communicated with a pump passage 2 via a port p and a communication passage 28. The sub spool SS moves by the balance of pressure in the second pressure chamber 26 and the elastic force of the spring 27 to communicate the pump passage 2 with the tank passage 7 via the communication passage 28, while when the main spool is switched to a lifting position, load pressure of a single acting cylinder S acts on the first and second pressure chambers 25, 26, and the sub spool SS is moved by elastic force of the spring 27 to close the communication passage 28. COPYRIGHT: (C)2008,JPO&INPIT
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