Solenoid valve is an automatic basic element used to control the direction of fluid, belonging to actuator. It is usually used for mechanical control and industrial valve to control the direction of medium, so as to achieve the control of valve switch.

Solenoid valves are divided into three categories in principle: direct action, step by step direct action and pilot type.

Direct acting solenoid valve has two types: constant closed type and normally open type. When the coil is turned on, the electromagnetic force is produced, so that the moving iron core can overcome the spring force and absorb the static iron core directly to open the valve, and the medium is in a path. When the coil is off, the electromagnetic force disappears, the moving iron core is reset under the action of spring force, the valve port is closed directly, and the medium is impassable. The structure is simple, the action is reliable, and works normally under zero pressure difference and micro vacuum. The normally open type is the opposite. For example, a solenoid valve with a flow diameter of less than φ 6.

Principle: when the normally closed type is electrified, the electromagnetic coil produces the electromagnetic force to lift the open part from the valve seat and the valve opens. When the power is cut off, the electromagnetic force disappears, the spring presses the open part on the valve seat, and the valve opens(the normally open type is the opposite).

Features: it can work normally in vacuum, negative pressure and zero pressure, but the diameter is not more than 25mm.