A study on the shape of polar anisotropic magnetizing yoke to reduce dead zone of ring magnet

Abstract

A ring magnet attached under the safety window motor is used for detecting the position of the window with a hall sensor. A dead zone that the magnetic flux is weak appears between the poles of the ring bonded magnet and the larger the angle of the dead zone, the more difficult it is to detect the precise position of window. In this study, the shape of polar anisotropic magnetizing yoke with a magnetic flux concentration structure is proposed to reduce the range of the dead zone. A magnetic equivalent circuit (MEC) was presented to prove the theoretical validity. With the design variables as the inner width, outer width, and magnetic flux angle of the teeth of the yoke, the response value for the dead zone minimization was obtained using the response surface method, which is an optimization technique. And to examine this result as the tendency of flux line change in the model, finite element analysis was performed, and the final model was obtained. The prototype of the final model was manufactured, and the validity of the analysis result was verified.