Pilot-operated three-position switching valve

摘要

Embodiments of the invention provide a first piston with a smaller diameter and a second piston with a larger diameter that switch a spool between a first switching position at one end and a second switching position at the other end, and a return spring that moves the spool to a neutral switching position are provided, at the neutral switching position, some of a plurality of ports communicate with one another and remaining ports are closed; at the first switching position, the communication-and-closure relationship of the plurality of ports is the reverse of that in the neutral switching position; and at the second switching position, all the plurality of ports are closed, and when the spool is switched to the neutral switching position and the first switching position, only the first piston is operated, and when the spool is switched to the second switching position, the second piston is operated.

主权项

1. A pilot-operated three-position switching valve comprising:
a valve body having a plurality of ports; a valve hole provided inside the valve body so as to communicate with the ports; a spool accommodated in the valve hole so as to be slidable in an axial direction and having three switching positions, namely, a first switching position at one end of the valve hole, a second switching position at the other end, and a neutral switching position between the first switching position and the second switching position; a first piston and a second piston that are disposed at one end and the other end of the spool and switch the spool between the first switching position and the second switching position when subjected to a pilot fluid pressure; and a return spring that returns the spool to the neutral switching position, wherein the first piston has a smaller diameter than the second piston, wherein the neutral switching position is such a switching position where a first communication state is established, in which some of the plurality of ports communicate with one another and other remaining ports of the plurality of ports are closed, wherein the first switching position is such a switching position where a second communication state is established, in which the spool has been moved toward the second piston with a larger diameter by the first piston with the smaller diameter, and the communication-and-closure relationship of the plurality of ports is different from that in the first communication state, and wherein the second switching position is such a switching position where the spool has been moved toward the first piston with the smaller diameter by the second piston with the larger diameter, and all the plurality of ports are closed and in a mutually non-communication state.