Novel mechanism of self-injecting magnetic fluid seal applying switch of magnetic force direction on yoke surface

The magnetic force distribution on the yoke surface of a magnetic fluid seal is clarified using finite element analysis. Calculations are performed for two kinds of typical magnetic fluid shape, that is, film shape and spike shape. It is interesting to note that the magnetic force direction switches halfway the yoke length. The region wherein the magnetic fluid flows to the yoke top direction is found to be wider for a thicker magnet, thicker yoke and the case with a spindle. This leads to a new concept of magnetic fluid seal having self-injection action.