The Cushioning Groove for Solenoid Switching Valves - Concept and Theoretical Analysis

A proper cushioning of the spool and armature of a switching valve at the end stops is important for a high lifetime and a low impact sound. Squeeze gap concepts are often employed. Oil between two basically parallel surfaces, which come into contact and which form the mechanical end stop, provides an excellent damping mechanism. But this oil film may exhibit high stiction forces, which cause a high response delay of even a total failure of the valve, unless cavitation in the oil film limits the stiction force. A new cushioning concept based on a notched groove is presented in this paper. Its basic functional principle is studied by compact mathematical models. The basic differences to squeeze gap cushioning are worked out and basic dimensioning rules are derived. This concept overcomes the stiction force problem fully.