Directional Control
According to their application, valves are divided into check valves and directional valves. Check valve: only allows fluid to flow in one direction in the pipeline, and cuts off when the flow reverses. Directional valve: changes the on/off relationship between different pipelines. According to the number of working positions of the valve core in the valve body, valves are divided into two-position, three-position, etc.; according to the number of channels controlled, valves are divided into two-way, three-way, four-way, five-way, etc.; according to the valve core drive method, valves are divided into manual, motorized, electric, hydraulic, etc. In the late 1960s, based on the above-mentioned hydraulic control valves, electro-hydraulic proportional control valves were developed. Its output (pressure, flow) can change continuously with the input electrical signal. Electro-hydraulic proportional control valves are divided into electro-hydraulic proportional pressure control valves, electro-hydraulic proportional flow control valves, and electro-hydraulic proportional directional control valves according to their functions.
Pressure Control
According to their application, valves are divided into relief valves, pressure reducing valves, and sequence valves.
(1) Relief valve: can control the hydraulic system to maintain a constant state when the set pressure is reached. Relief valves used for overload protection are called safety valves. When a system malfunctions and the pressure rises to a potentially damaging level, the valve will open and overflow to ensure system safety.
(2) Pressure reducing valve: This valve controls branch circuits to obtain a stable pressure lower than the main circuit oil pressure. Pressure reducing valves can be further classified according to their pressure control function: constant pressure reducing valve (output pressure is constant), differential pressure reducing valve (the difference between input and output pressure is constant), and proportional pressure reducing valve (maintains a certain ratio between input and output pressure).
(3) Sequence valve: This valve enables one actuator (such as a hydraulic cylinder or hydraulic motor) to operate first, and then sequentially activates other actuators.
