Investigation of magnetic separation for the cleaning of automatic transmission fluids

The growing demands on filter elements for automatic transmission fluids in terms of filter lifetime (longer service intervals), cleanliness level of the oil and lower pressure drop represent a great challenge for product designers. In order to ensure good performance of the filters at the widest possible range of operating conditions (e.g. cold start vs. high oil temperature) and facing more restrictive installation space specifications, intense research and development is required for product innovation and optimization. The fact that the wear in automatic transmissions contains magnetizable shares suggests magnetic separation as a way to support the cleaning of the oil by the filter media. The present work is devoted to the investigation of magnetic separation for cleaning automatic transmission fluids. For the experimental study, a test bench along the lines of the TFEM (Transmission Filter Effectiveness Method) efficiency test was set up and different magnet materials were compared. The separation efficiency for different magnetic materials was determined using particle counting and gravimetric methods. Amongst others, the relations between magnetic field (magnet material) and capture efficiency was investigated. In addition, the evolution of the separation efficiency over time was studied.