What is the main function of the solenoid valve?

First of all, both pneumatic and hydraulic sub-sectors use the valves mentioned above.

Secondly, pneumatic and hydraulic systems are generally divided into gas and liquid sources and processing systems, control components, and executive components. The various valves mentioned above belong to control components. As the name implies, it is to control various media or parameters of the gas-liquid system. Nothing more than direction, flow, pressure, etc., the above valves play this role.

Let me talk about the directional control valve first. As the name implies, it controls the direction of the fluid. The reversing valve and one-way valve you mentioned are all directional control valves. The reversing valve is almost the most varied and the largest amount of all gas-hydraulic components, and relatively speaking, it is also the most concerned type of component. What you often hear, two-way two-way, two-way three-way, three-way five-way, etc., all belong to the directional control valve.

The relief valve is a pressure control valve, which means that after the pressure reaches or exceeds a certain set value, the gas flows out from the overflow port to protect the system pressure.

Proportional valves and servo valves classify valves from another dimension. For example, the flow proportional valve is to automatically and steplessly adjust the flow of the valve, and the input current signal and the output gas flow are in a certain proportional relationship. This is very different from traditional valves. The servo valve is used in the servo control system to improve the response speed of the system. These two valves also include pressure control valves and flow control valves. Proportional valves and servo valves are much more expensive than traditional electromagnetic direction and pressure control valves, and are rarely used in the general automation industry.