| 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, without causing a lowering of volume efficiency due to a leak from a shuttle valve when traveling at a low speed. SOLUTION: A two-speed control valve 50 has a two speed spool 2, a middle diameter spool 6 slidably inserted into a middle diameter blind hole 14 provided in one end of the two speed spool 2, and a small diameter spool 15 slidably inserted into a small diameter blind hole 15 provided in the other end of the two speed spool 2. When the pressure of a pilot load pressure port P is at a first set pressure P1 or less (at a position expressed in a figure 1), the pressure is supplied to a cylinder 17 to tilt a cam plate 11 and to rotate the hydraulic motor 10 at a high speed. When the pressure of the load pressure port P exceeds the first pressure P1, a communication passage 24 communicated with the inner end surface of a small diameter spool is communicated with a third drain port DR3 to automatically switch rotation of the two speed type hydraulic motor 10 to the low-speed rotation. COPYRIGHT: (C)2003,JPO
|
