| 摘要 |
<p>A valve assembly couples a plurality of hydraulic actuators (21,22,23) to a variable displacement pump (20) and to a tank (18). A separate valve (14,15,16) is associated with each hydraulic actuator and comprises a variable flow source orifice (34a,34b,34c) between the supply conduit (28) and a summation node (44) coupled to a pump control port (19), a variable metering orifice (45) between the summation node and the associated hydraulic actuator, and a variable bypass orifice (50a,50b,50c) between the summation node and the tank. As a valve operates to enlarge the metering orifice, the flow source orifice also enlarges, and the bypass orifice shrinks. When the valve operates to shrink the metering orifice, the flow source orifice also shrinks and the bypass orifice enlarges. Those operations vary fluid flow in and out of the summation node (44), which alters pressure applied to the pump control, thereby causing the pump output to vary as required to drive the associated hydraulic actuator.</p> |
