Microvalves - Valve types and functional principles

3. Microvalves - Valve types and functional principles

There are innumerable valve designs and variants and they in part fulfil completely different functions. In order to get an overview of the confusing product landscape, different segments for the categorization and differentiation of valves were defined.

3.1 Differentiation by task

Since microvalves in hydraulic or pneumatic systems are given a wide variety of tasks, a distinction can be made according to the specific tasks of the valves.

3.1.1 Switching/stop valves (on/off)

Switch valves or stop valves control the flow of a fluid by either blocking or opening the fluid channel. In case of microvalves, which withstand a high switching frequency, quasi-proportional regulation of the fluid can nevertheless be achieved by lightning-fast switching.

3.1.2 Flow control valves (proportional valves)

With flow control valves or proportional valves, the flow in the fluid channel can only be partially opened or closed, depending on the applied voltage (current). Gases or fluids thus can be precisely metered externally.

3.1.3 Directional valves

Microvalves can be differentiated by the number of connections per switching position and the number of switching positions. For example, a 2/2-way valve has two ports (A, P) and two switching positions (closed, open).

  
2/2-way microvalveDirectly controlled, NO (normally open)At rest, the leaf spring presses the seal into the lower end position. The medium can flow from P to A. After switching on the solenoid, the plunger is pulled into position. The seal is pressed against the valve seat, the valve is closed.
2/2-way microvalveDirectly controlled, NC (normally closed)At rest, the leaf spring presses the seal against the lower valve seat. The valve is closed, A can vent to R. After switching on the solenoid, the plunger is pulled into position. The seal is pressed against the upper valve seat. The valve is open and the medium can flow from P to A.

3/2-way microvalveDirectly controlled, NO (normally open)
At rest, the leaf spring presses the seal against the lower valve seat. The medium can flow from P to A. After switching on the solenoid, the plunger is pulled into position. The seal is pressed against the upper valve seat. The valve is closed, A can vent to R.
3/2-way SPIDER® microvalveDirectly controlled, NC (normally closed)At rest, the leaf spring presses the disc armature with integrated sealing element against the valve seat P. The outlet A is connected to R. After switching on the solenoid, the disc armature is pulled into position and closes venting R. The connection from P to A is open. The medium flows around the armature. After switching off the solenoid, the leaf spring pushes the disc armature back to the rest position, the valve is closed.

4. Microvalves - General symbols

Symbol	meaning
	Directional valve with two switch positions
	Directional valve with three switch positions
	Directional valve with three switch positions and four connections
	Directional valve with intermediate positions and two end positions, also proportional valve
	A flow path
	Two blocked connections
	Two flow paths
Examples
	2/2 way valve
	2/3 way valve