Solenoid valve is an automatic basic component used to control fluids. It belongs to the actuator and is not limited to hydraulic and pneumatic. Different solenoid valves play a role in different positions of the control system, the most commonly used are check valves, safety valves, directional control valves, speed control valves, etc.
In principle, solenoid valves are divided into three categories: direct-acting, step-by-step direct-acting, and pilot-operated.
1. Direct acting
solenoid valve
Principle: When the normally closed type is energized, the electromagnetic coil generates electromagnetic force to lift the opening piece from the valve seat, and the valve opens; when the power is off, the electromagnetic force disappears, the spring presses the opening piece on the valve seat, and the valve opens. (Normally open is the opposite of this)
Features: It can work normally in vacuum, negative pressure and zero pressure, but the diameter generally does not exceed 25mm.
2. Step-by-step direct-acting solenoid valve
Principle: It is a combination of direct action and pilot type. When there is no pressure difference between the inlet and the outlet, after the power is turned on, the electromagnetic force directly lifts the pilot small valve and the main valve closing piece up in turn, and the valve opens. When the inlet and outlet reach the starting pressure difference, after the power is turned on, the electromagnetic force pilots the small valve, the pressure in the lower chamber of the main valve rises, and the pressure in the upper chamber drops, so as to use the pressure difference to push the main valve upwards; when the power is off, the pilot valve uses a spring The force or medium pressure pushes the closing member, moving downward, causing the valve to close.
Features: It can also operate under zero pressure difference or vacuum and high pressure, but the power is large, and it must be installed horizontally.
3. Indirect pilot solenoid valve
Principle: When the power is turned on, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, and a pressure difference between upper and lower parts is formed around the opening, and the fluid pressure pushes the opening to move upward, and the valve opens; The hole is opened, and the inlet pressure passes through the bypass hole to rapidly form a pressure difference around the valve closing member, which is low and high and high, and the fluid pressure pushes the opening member to move downward to open the valve.
Features: Small size, low power, high upper limit of fluid pressure range, can be installed arbitrarily (need to be customized) but must meet the fluid pressure differential conditions
