| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an automatic shift switching valve for switching a two-speed hydraulic motor between a high-speed state and a low-speed state.SOLUTION: An automatic shift switching valve 7 includes a hollow two-speed spool 10, a first small-diameter spool C and a second small-diameter spool B fitted to both ends of the two-speed spool 10 movably in the axial direction, and a spring 8 provided between a hollow hole shoulder part 19 of the two-speed spool 10 and the second small-diameter spool B. An external pilot pressure Pis guided to the first small-diameter spool C and a two-speed spool outer end, and a high port pressure Pab of a hydraulic motor 1 to counteract the external pilot pressure Pis guided from a center port A.B into a hollow hole 20 so as to consistently operate on the inside faces of the first small-diameter spool C and the second small-diameter spool B in the second-speed spool 10. Drain ports DR are provided between an A' port and a Pport and between the A.B port and the Pport, respectively.</p> |
