An element used in a hydraulic drive to control liquid pressure, flow, and direction. Which control the pressure called the pressure control valve, the control flow called the flow control valve, control through, off and flow direction called the direction control valve.

Directional control valve

According to the use of one-way valve and valve.

① check valve: only allows the fluid in the pipeline in one direction, reverse that cut off.

② change valve: to change the relationship between the different piping, broken, according to the spool in the valve body in the number of working positions in two, three, etc .; according to the number of channels controlled by two links, three links, , Five pass, etc .; according to the spool drive way manual, mobile, electric, hydraulic and so on.

Flow control valve

use
Regulating valve
The flow of the actuator between the core and the valve body and the local resistance generated by it adjust the flow rate to control the speed of the actuator. Flow control valves are divided into five types.

① throttle valve: in the adjustment of the orifice area, can make the load pressure is not changed and the movement uniformity of the requirements of the implementation of the components of the speed is basically stable.

② speed control valve: in the load pressure changes can keep the throttle valve inlet and outlet pressure for the fixed value. In this way, after the throttle area is set, regardless of how the load pressure changes, the governor can keep the flow through the throttle constant, thus stabilizing the speed of the actuator.

③ diverter valve: regardless of the size of the load, so that the same oil source of the two actuators are equal flow equal to the amount of diversion valve or synchronous valve; get proportional distribution of the proportion of the flow distribution valve.

④ collector valve: the role of the opposite with the diversion valve, so that the flow into the flow of the proportional distribution of the valve.

⑤ shunt flow valve: both flow distribution valve and the two functions of the collector.

Pressure control valve

According to the use of overflow valve,
Pressure reducing valve
And sequential valves.

① relief valve: can control the hydraulic system to achieve the set pressure to maintain a constant state. The relief valve used for overload protection is called
Safety valve
The When the system fails, the pressure rises to the limit may cause damage, the valve port will open and overflow, to ensure the safety of the system.

②
Pressure reducing valve
: Can control the branch loop to get a lower pressure than the main circuit oil pressure. Pressure relief valve according to its control of the pressure function is different, but also divided into the value of the pressure relief valve (output pressure is constant), differential pressure relief valve (input and output pressure difference is set) and the ratio of pressure reducing valve (The input and output pressure to maintain a certain ratio).

③ sequence valve: can make an implementation of components (such as hydraulic cylinders, hydraulic motors, etc.) after the action, and then in order to make other executive elements.

In the late 1960s, electro-hydraulic proportional control valves were developed on the basis of several types of hydraulic control valves. Its output (pressure, flow) can be continuously changed with the input electrical signal. Electro-hydraulic proportional control valve according to the role of different, correspondingly divided into electro-hydraulic proportional pressure control valve, electro-hydraulic proportional flow control valve and electro-hydraulic proportional directional control valve.