| 摘要 |
PURPOSE:To prevent reduction in magnetic energy and increase in the total weight of a voice coil without reducing joining force between the coil and bobbin by providing a reinforcing leg formed incorporatedly with the bobbin to the outer periphery of the voice coil and increasing the air gap of the magnetic circuit corresponding to the reinforcement leg larger than the other air gap parts. CONSTITUTION:Two or over of the reinforcement legs 6 formed incorporatedly with the bobbin 5 made of a synthetic resin are provided to the outer peripheral part of the voice coil 4 and then the coil 4 and the bobbin 5 are joined. The outer peripheral part of the coil 4 other than the reinforcement leg 6 has a cross section in a way that the bobbin 5 and the coil 4 are butted together. As the air gap to which the voice coil 4 is inserted, the air gap of the magnetic circuit having a width of slit 7 slightly larger than the width of the reinforcement leg 6 of the coil outer peripheral part by a prescribed size is used to improve the magnetic energy. Moreover, since the quantity of resin other than the reinforcement legs 6 is saved, the total weight of the coil is reduced.
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