| 摘要 |
PROBLEM TO BE SOLVED: To restrain the speed at the time when a poppet reaches a stroke end in valve opening, in a logic valve. SOLUTION: A logic valve 41 is provided with a poppet 51, a return spring 52 and a plug 53. A damper chamber 55 housing a return spring 52 is formed behind (on the right side in Fig.) a plug 54 fixed to the poppet 51. A check ball 59 is arranged on an oil chamber 56 for communicating the damper chamber 55 and the outer peripheral surface of the poppet 51 with each other and a passage 54b out of respective passages 54b, 57. When the damper chamber 55 is switched to oil tank pressure and the poppet 51 receives high pressure of operating oil flowing out to an oil passage 45 by the whole front surface after being opened by negative pressure P to be received by the tip side annular part (the pressure receiving area Sx-Sy), the poppet 51 is accelerated. However, since the damper chamber 55 is closed when the poppet 51 is moved by the specified distance L, the poppet 51 is decelerated by the damper effect.
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