| 摘要 |
A control valve has a control valve body with a bore and a plurality of fluid connections. A spool valve assembly is moveable within the bore between a first position and a second position. The spool valve assembly has a first hydraulic surface and a second opposing hydraulic surface in fluid communication with a first fluid connection and a second fluid connection, respectively, of the plurality of fluid connections. An actuator has a fluid connection between ambient and the second hydraulic surface of the spool valve assembly. When a current is applied to the actuator, the fluid connection is opened to ambient and the hydraulic force acting on the first hydraulic surface is greater than the hydraulic force acting on the second hydraulic surface such that the spool assembly is moveable to the first or open position. When the actuator is closed, the fluid connection to ambient is blocked and the fluid pressure increases against the second hydraulic surface via fluid supplied by the second fluid connection. In this scenario, the hydraulic force acting on the second hydraulic surface is greater than the hydraulic force acting on the first hydraulic surface such that the spool valve assembly is moveable to the second or closed position
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