Internal Name: Flat Lam

What’s New: In a dual-acting linear valve actuation solenoid, it is difficult to use laminations, orient them optimally, and simultaneously achieve good mechanical strength. A favorable compromise orients the armature laminations in a plane perpendicular to the motion. Eddy current losses are only slightly higher, while the design is mechanically robust.

Status: Issued in U.S. on April 22, 2003

Why: Early engine valve solenoid designs used solid iron armatures. Eddy currents in these armatures were a major source of dissipation. Perhaps even more significant, eddy currents delayed the magnetic force response to applied current, making the solenoids very difficult to control and soft-land. Composite magnetic materials resisted eddy currents but saturated at lower flux densities, necessitating larger, heavier armatures. The increase in moving mass compromised actuation speed. Iron alloy laminations (for example, silicon-iron) combined high flux density with low eddy currents, but the armature tended to cleave at the laminations. Lamination reinforcement with welds or pins tended to reintroduce undesirable eddy current pathways. Our invention, orienting the laminations in a flat plane perpendicular to the solenoid stroke, yields a mechanically robust armature whose eddy currents are only slightly worse than with the magnetically optimum vertical lamination arrangement.

How: Laminations are stamped in the plan-view shape of the armature, then stacked, impregnated with adhesive, and finally welded or soldered at the edges, in places that have negligible effect on eddy currents. The resulting structure is strong, carries a high flux density, and has moderately low eddy current losses.

Download: Flat Lamination Solenoid U.S. 6,550,745 Gary Bergstrom

Magnesense LLC Gorham,ME (207) 839-8637

©2009 Joseph Seale