第8章液压系统控制元件资料

第八章液压系统控制元件（Control Components in Hydraulic Systems）

8.1概述（INTRODUCTION）

在任何液压传动系统中最重要的条件之一是控制。如果控制元件选择不正确，整个系统起不到所需要的作用。液压传动主要是通过称为液压阀的控制元件来实现控制的。控制元件的选择不仅涉及到它的类型而且还要考虑其尺寸大小，操纵技术和远控能力。控制元件有三种基本类型（One of the most important considerations in any fluid power system is control. If control components are not properly selected, the entire system will not function as required. Fluid power is controlled primarily through the use of control devices called

valves. The selection of these control devices not only involves the type but also the size, the actuating technique, and remote-control capability. There are three basic types of control devices）：

✵方向控制阀（directional control valves）；

✵压力控制阀（pressure control valves）；

✵流量控制阀（flow control valves）。

方向控制阀在回路内部确定流动路线。例如，它们确定液压缸或液压马达的工作方向。控制流动路线的元件主要有单向阀、梭形阀和二位、三位、四位方向控制阀（Directional control valves determine the path through which a fluid traverses within a given circuit. For example, they establish the direction of motion of a hydraulic cylinder or motor. This control of the fluid path is accomplished primarily by cheek valves, shuttle

valves, and two-way, three-way, and four-way directional control valves）。

压力控制阀防止系统超载，它可能是由于流体需要压缩而逐渐形成的可能是由于阀开启或关闭所产生的突然冲击。逐渐形成的压力是由溢流阀、减压阀、顺序阀、卸荷阀和平衡阀来控制的。当然，压力反馈的油泵也能用于防止超载。压力冲击能瞬时产生比正常系统压力高四倍的压力。吸震器是用来消除压力冲击和衰减液压震动的液压装置（Pressure control valves protect the system against overpressure, which may occur due to a gradual buildup as fluid demand decreases or due to a sudden surge as valves open or close. The gradual buildup of pressure is controlled by pressure relief, pressure reducing, sequence, unloading, and counterbalance valves. Of course, pressure-compensated

pumps can also be used. Pressure surges can produce an instantaneous in pressure as much as four times the normal system pressure. Shock absorbers are hydraulic devices designed to smooth out pressure surges and to dampen out hydraulic shock）。

此外，对液压回路的各管道中的流量也必须进行控制。例如，控制决定于流量的执行元件的速度。这类控制是通过使用流量控制阀来实现的。变量泵也能用来控制执行元件的速度除非系统包含每一个都必须以不同的速度工作的几个执行元件。在这种情况下就需要独立式的流量控制阀。无补偿的流量控制阀用于不需精确的速度控制，此时由于经过流量控制阀的压降而使流量发生变化。压力补偿流量控制阀自动调节压降的大小以保持恒定的流量（In addition, fluid flow rate must be controlled in various lines of a hydraulic circuit. For

example, the control of actuator speeds depends on flow rates. This type of control is accomplished through the use of flow control valves. A variable displacement pump can also be used to control actuator speed unless the system contains several actuators each of which must operate at different speeds. In such a case separate flow control valves are required. Noncompensated flow control valves are used where precise speed control is not required since flow rate varies with pressure drop across a flow control valve. Pressure-compensated flow control valves automatically adjust to changes in pressure drop to produce a constant flow rate）。