| 摘要 |
PROBLEM TO BE SOLVED: To provide a "magnetic circuit for a speaker" whereby an amplitude region of a voice coil linearly changed with respect to a level of a signal current can be extended and the component cost can also be suppressed. SOLUTION: The magnetic circuit for a speaker, wherein an inner circumferential face of an annular magnet 13 magnetized in the radial direction is joined with an outer circumferential face of a pole piece 1 and the outer circumferential face of the magnet 13 is opposed to the inner circumferential face of a yoke 2 via an air gap, includes: an annular V groove 14 whose cross sectional shape is almost V-shaped and extended in the circumferential direction that is located in the middle part of the magnet 13 in the axial direction of the outer circumferential face; and an annular split groove 8 narrower than the annular V groove 14 and opposed to the deepest part of the annular V groove 14 that is located on the inner circumferential face of the yoke 2. Thus, the part existing upward from the annular split groove 8 and the part existing downward from the groove 8 in the air gaps respectively act like magnetic gaps G1, G2 and the magnetic flux density toward the annular split groove 8 in each of the magnetic gaps G1, G2 can be set to have the distribution nearly equal to that of the magnetic flux density toward the side opposed to the annular split groove 8. COPYRIGHT: (C)2005,JPO&NCIPI
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