| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact and economical automatic transmission for a two speed type hydraulic motor reduced in the number of part items and facilitated in boring finish work of a housing thereof in comparison with a current one, without causing a lowering of volume efficiency due to a leak from a shuttle valve when traveling at a low speed. SOLUTION: A sequence valve 50 has a main spool 2, a middle diameter spool 6 slidably inserted into a middle diameter blind hole 14 provided in one end of the main spool 2, and a small diameter spool 16 slidably inserted into a small diameter blind hole 15 provided in the other end of the main spool 2. When the pressure of a load pressure port P exceeds a first pressure P1, the sequence valve 50 is switched, and a communication passage 24 communicated with the inner end surface of the small diameter spool is communicated with a third drain port DR3 to automatically switch rotation of the two speed type hydraulic motor to the low-speed rotation. When the pressure of the load pressure port P becomes a second set pressure, which is lower than the first set pressure, or less, the main spool 2 moves to the original position. COPYRIGHT: (C)2003,JPO
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