Electromagnetic Valve Recess Geometry for Anti-Stick Spool Motion

The invention introduces tapered portions at specific locations where the spool contacts the sleeve, creating localized differences in surface geometry. The tapered portions have different taper angles at different contact locations, allowing the spool to move smoothly at critical abutment points while maintaining appropriate contact pressure elsewhere. This local modification resolves the contradiction by improving movement smoothness only where needed without uniformly increasing surface pressure.

Instead of applying a uniform taper to the entire valve hole, the invention applies tapered portions only at specific locations where the spool contacts the sleeve. The tapered portions have carefully controlled taper angles that are sufficient to reduce sliding resistance at contact points but not so large as to create significant clearance for oil leakage. This localized approach resolves the contradiction by reducing friction only where contact occurs while maintaining sealing elsewhere.

The tapered portions create a geometric configuration where the spool naturally centers itself through the geometry of the contact surfaces. When the spool moves off-center, the tapered surfaces generate restoring forces that push the spool back toward the centered position. This geometric centering mechanism prevents sticking by maintaining appropriate contact pressure without requiring permanent decentering, thereby preventing both sticking and excessive leakage.