| 摘要 |
PURPOSE:To increase the efficiency of electroacoustic conversion and to obtain the construction with good sound producing characteristic and low cost, by forming a magnet core and a lower yoke incorporatedly in an electromagnetic type sound body used for a wrist watch. CONSTITUTION:A magnet core 1 incorporated with a lower yoke 2 is formed by forming a material with good permeability such as iron and permalloy with contraction. Next, heat treatment is made as required, and a coil 5 is assembled with a magnet 4 processed in ring shape in advance and the assembly is fixed by mounting an upper yoke 3 and external frame 8. Further, the magnet 4 is magnetized and a diaphragm plate 6 welded with an electromagnetic plate 7 is located on the outer frame 8 and fixed along the external circumference. Next, a connecting terminal 9 is connected to the coil 5. Thus, by forming the magnet core 1 and the lower yoke 2 incorporatedly, the magnetic loss is reduced and a magnetic circuit with good efficiency is formed, allowing to increase the efficiency of electroacoustic conversion. |
