| 摘要 |
PURPOSE:To reduce easily the current distortion due to the non-linearity of the permeability of a magnetic circuit, by forming a coating layer made of metallic materials on the side of a permanent magnet by means of plasma metallizing. CONSTITUTION:A coating layer 6 formed by using metallic materials such as copper and aluminum by means of plasma metallizing is formed in one process on the internal surface of a cylindrical permanent magnet 2 by means of the plasma coating. Since the coating layer 6 is formed on the internal surface of the cylindrical permanent magnet 2, a voice coil 4 generates almost no current distortion so that driving force proportional to voice voltage is obtained. In this case, it is sufficient, if the coating layer 6 is the one which works as the secondary winding of a voice coil. The below figure shows the case where the coating is applied to a magnetic circuit for a dynamic speaker of inside magnetic type. A coating layer 10 is formed on the external surface of a cylindrical permanent magnet by using metallic materials such as copper and aluminum by means of plasma metallizing. |
