The structure and principle of solenoid valve

Update:05 Nov 2020
Direct acting solenoid valve
There are two types,normally closed type and normally open type,Normally closed type is in a closed state when power off,the coil generates electromagnetic force when it is energized,then the moving iron core overcome the spring force and is directly pulled to the static iron core to open the valve,and the mediumwill ve a pathway;when the power is off,the electromagnetic force of coil disappears,then the moving core will reset under the action of spring force and  valve port is directly closed,so the medium is blockde.Its structure is simple and the action is reliable,it can work under the zero pressure and micro vacuum,Normal open type is just the opposite,Such as solenoid valve with flow diameter under Φ6 (Figure 1 is atypical structure figure)
Step by step direct acting solenoid valve
The valve connects the primary opening valve and the second opening valve,the main valve and pilot valve step by step use the electromagnetic force and pressure to directly open the main valve port.When the coil is energized,it generates electromagnetic force to pull the dynamic iron core to static iron core,then the pilot valve which is on top of the main valve opens while the dynamic iron core is connected with the static iron core,At this time,the upper plenum pressure of the main vlve unloads through the pilot valve port,then the main valve core move upward under the pressure difference and the effect of  electromatnetic force and finally oppen the main valve while the medium flows.When the coil is power off while the electromagnetic force disappears,then the dynamic iron core will close the pilot valve under the effect of self weight and spring force,At the same time the medium flows into the upper plenum of the main valve from the balance hole and the pressure inside of upper plenum rises up which makes the main valve closed also under the force of spring-restoration.Then the medium flow is cut off.This type of solenoid valve can work reliably under zero pressure differential situation with reasonable structure and reliable action.
Indirect pilot type solenoid valve
This series solenoid valve is combined by pilot valve and main valve which connect together and form a passageway.Normally closed type is closed when power off.When the coil is energized,the generated electromagnetic force makes the dynamic iron core move to the static iron core,then the pilot valve port opens and medium flows to the outlet,then the upper chamber pressure of the main valve decreased to lower than the inlet side pressure and the formed pressure differential overcome the spring resistance and subsequently moves upward and makes the main valve port open and medium flows.When the coil is power off,the electromagnetic force disappears and dynamic iron core close the pilot port under the force of spring-restoration,then the medium flows in from the balance hole which makes the upper chamber pressure increase and the main valve core move downwards under the force of spring-restoration to close up the main valve port.The principle of normally open type is just the opposite.Such as XSP.DF(Diameter above Φ15),ZCZ and so on.(Fogure 3 is a typical structure figure)