Abstract
Isotropic Nd-Fe-B-based ring-shaped resin-bonded magnets have been generally used in small motors and actuators for PCs and their peripherals. However, development of a new type of magnet with superior magnetic properties is essential for a further reduction of the size of such motors. Although usage of anisotropic Nd-Fe-B powder made by the HDDR process is a promising method of preparing anisotropic magnets to replace the conventional isotropic magnets, its high coercivity of over 1.2 MA/m, which is required for thermal stability of the magnetic flux comparable with that of conventional isotropic Nd-Fe-B magnets, makes it difficult to magnetize the prepared magnets. Therefore, magnets prepared from anisotropic HDDR powder have not been used to create ring-shaped magnets for small motors up to now. To overcome the above difficulty, we developed a new technology that makes it possible to prepare axially oriented ring-shaped magnets for small motors. This paper reports a method of preparing axially oriented ring-shaped magnets for small motors from anisotropic HDDR powder. To use this process, it is possible to product an anisotropic Nd-Fe-B-based flexible bonded magnet. These flexible bonded magnets are able to keep a high efficiency, like a radially oriented magnet. And, their magnet powders are covered with elastomer.
