JP4154347B2 - Magnetic circuit of speaker - Google Patents

Description

  The present invention relates to a magnetic circuit of an electrodynamic speaker, and in particular, a pair of upper and lower magnetic gaps are provided on the outer peripheral side or inner peripheral side of an annular magnet, and a voice coil is disposed so as to straddle both magnetic gaps. The present invention relates to a magnetic circuit of a speaker.

  A speaker in which an annular magnet magnetized in the radial direction is interposed between a pole piece and a yoke surrounding the pole piece, and a magnetic gap is formed on the outer peripheral side or inner peripheral side of the annular magnet, When the voice coil disposed in the gap is energized to vibrate the voice coil, the diaphragm is driven. In such a speaker, a magnetic circuit designed so as not to cause driving force distortion even when the amplitude of the voice coil is large is desired. Therefore, conventionally, in order to expand the amplitude region of the voice coil that changes linearly with respect to the level of the signal current (sound current), a magnetic structure having a pair of upper and lower magnetic gaps formed using two annular magnets. A circuit is known (see, for example, Patent Document 1).

  FIG. 4 is a sectional view showing the main part of such a conventional magnetic circuit. As shown in FIG. 4, a yoke 2 integrated with the pole piece 1 is erected so as to surround the pole piece 1. Two annular magnets 3 and 4 that are magnetized in the radial direction are joined to the inner peripheral surface of the yoke 2. These annular magnets 3 and 4 are arranged side by side in a predetermined amount in the axial direction (the vertical direction in the figure), and between the inner peripheral surface of each annular magnet 3 and 4 and the outer peripheral surface of the pole piece 1, respectively. Magnetic gaps G1 and G2 are formed. Since the annular magnets 3 and 4 have the same shape, the gap lengths of the magnetic gaps G1 and G2 are equal. Therefore, the magnetic flux density distribution in the magnetic gap G1 generated by the annular magnet 3 and the magnetic gap G2 generated by the annular magnet 4 Magnetic flux density distribution is equivalent.

  In the conventional magnetic circuit shown in FIG. 4, the upper end of a cylindrical bobbin 5 is joined to the inner edge (small diameter part) of a diaphragm (not shown), and the voice coil 6 wound around the bobbin 5 is magnetic. It arrange | positions so that it may straddle in the gaps G1 and G2. That is, the voice coil 6 is set to face the lower half of the annular magnet 3 and the upper half of the annular magnet 4 when not energized. Therefore, even when the voice coil 6 is vibrated in a wide amplitude region from the upper end of the magnetic gap G1 to the lower end of the magnetic gap G2 during energization, the amount of magnetic flux acting on the voice coil 6 is substantially constant. As a result, a speaker equipped with this type of magnetic circuit can improve performance by expanding the amplitude region of the voice coil 6 that changes linearly with respect to the level of the signal current.

  However, in such a conventional magnetic circuit, two annular magnets 3 and 4 that are magnetized in the radial direction are used. In general, such an annular magnet has low productivity and is a high-priced part. When two annular magnets are used, there is a problem that the cost of parts increases and the cost increases.

  Thus, an inexpensive magnetic circuit has been proposed in which a pair of upper and lower magnetic gaps can be formed by a single annular magnet. FIG. 5 is a cross-sectional view of a speaker employing such a conventional technique, and the same reference numerals are given to the portions corresponding to FIG.

  In the magnetic circuit of the speaker shown in FIG. 5, the pole piece 1 disposed at the center is integrated with a yoke 2 disposed around the pole piece 1. The inner peripheral surfaces of the annular magnets 7 magnetized in the are joined. The outer peripheral surface of the annular magnet 7 is opposed to the inner peripheral surface of the yoke 2 through a gap, and the inner peripheral surface of the yoke 2 is opposed to the central portion in the axial direction (vertical direction in the figure) of the annular magnet 7. An annular dividing groove 8 extending along the circumferential direction is formed in the inner periphery. As a result, in the gap between the annular magnet 7 and the yoke 2, the portion above the annular dividing groove 8 becomes the magnetic gap G <b> 1, and the portion below the annular dividing groove 8 becomes the magnetic gap G <b> 2. The gap lengths of G1 and G2 are equal. That is, such a conventional magnetic circuit has a configuration in which only one annular magnet 7 is used, but the magnetic flux density distribution in the magnetic gap G1 and the magnetic flux density distribution in the magnetic gap G2 can be set to be equal.

  In this speaker, the voice coil 6 is disposed so as to straddle the magnetic gaps G1 and G2, and the upper end of the cylindrical bobbin 5 around which the voice coil 6 is wound is cone-shaped cone paper. It joins to the inner edge part (small diameter part) of the diaphragm 9 which consists of. A frame 10 is fixed on the yoke 2, and the frame 10 supports an outer edge portion (large diameter portion) of the vibration plate 9 through a deformed joint portion 11 and a bobbin 5 through a damper 12. Is supported freely.

In the speaker schematically configured as described above, when a signal current is supplied to the voice coil 6 to vibrate, the voice coil 6 drives the diaphragm 9 to generate a sound corresponding to the signal current. At this time, even if the voice coil 6 is vibrated in a wide amplitude region from the upper end of the magnetic gap G1 to the lower end of the magnetic gap G2, the magnetic flux density distribution in the magnetic gaps G1 and G2 is set to be equal. As long as the magnetic flux density distribution in each of the magnetic gaps G1 and G2 is substantially symmetric with respect to the vibration direction (vertical direction) of the voice coil 6, the driving force distortion hardly occurs.
Japanese Patent No. 2917578 (page 3, FIG. 1)

  However, when the present inventors examine the magnetic flux density distribution in the magnetic gaps G1 and G2 of the magnetic circuit shown in FIG. 5 in detail, as shown in FIG. Since the peak of the magnetic flux density is greatly biased toward the annular dividing groove 8 side, it has been found that the magnetic flux density distribution is asymmetric between the region on the annular dividing groove 8 side and the region on the anti-annular dividing groove 8 side. That is, in the loudspeaker shown in FIG. 5, when the height position of the voice coil 6 with respect to the magnetic gaps G1 and G2 changes, the amount of magnetic flux acting on the voice coil 6 changes not a little. The change in driving force is not necessarily linear, and there is room for improvement in performance.

  The present invention has been made in view of the actual situation of the prior art, and an object thereof is to provide a magnetic circuit for a speaker that is inexpensive and has little driving force distortion.

  The present invention provides a magnet having a substantially V-shaped cross-section at the center in the axial direction of the circumferential surface on the air gap side of the magnet that is interposed between the pole piece and the yoke and is opposed to any one of the magnets via the air gap. An annular V-groove extending along the gap is provided, and an annular surface that is narrower than the annular V-groove and is opposed to the deepest portion of the annular V-groove on the circumferential surface of the yoke or pole piece facing the magnet through the gap A dividing groove is provided. As a result, a portion existing above and below the annular dividing groove in the gap can be used as a magnetic gap, and the magnetic flux density on the annular dividing groove side in each magnetic gap can be changed to the anti-annular dividing groove. The distribution can be set substantially equal to the magnetic flux density on the side.

  The magnetic circuit of the speaker according to the present invention is provided with an annular dividing groove on the circumferential surface of a yoke or pole piece facing the magnet through a gap to form a pair of upper and lower magnetic gaps, and the circumference of the magnet on the gap side. An annular V groove wider than the annular dividing groove is provided on the surface so that the magnetic flux density on the annular dividing groove side in each magnetic gap does not increase undesirably compared to the magnetic flux density on the anti-annular dividing groove side. The magnetic flux density distribution can be set almost symmetrically in the region on the annular dividing groove side and the region on the anti-annular dividing groove side in each magnetic gap, and the driving force can be changed linearly with respect to the signal current level. It becomes. In other words, since only one annular magnet needs to be used, the cost of components can be suppressed, and the amplitude region of the voice coil can be expanded without impairing the linearity with respect to the signal current level. An inexpensive magnetic circuit with high performance can be realized.

  In the present invention, a pole piece arranged at the center, a yoke arranged around the pole piece, an annular magnet magnetized in the radial direction and arranged between the pole piece and the yoke, In the magnetic circuit of the speaker, the magnet is joined to one of the circumferential surfaces of the pole piece and the yoke, and is opposed to the other circumferential surface via a gap, and the circumference of the magnet on the gap side An annular V-groove having a substantially V-shaped cross section and extending in the circumferential direction is provided at the center in the axial direction of the surface, and the deepest portion of the annular V-groove is narrower than the annular V-groove on the other circumferential surface. Opposing annular dividing grooves were provided, and a portion existing above and below the annular dividing groove in the gap was used as a magnetic gap.

  Specifically, in the case of the inner magnet type, the inner peripheral surface of the magnet is joined to the outer peripheral surface of the pole piece to provide an annular V-groove on the outer peripheral surface of the magnet, and the annular dividing groove is formed on the inner peripheral surface of the yoke. It only has to be provided. In the case of the outer magnet type, the outer peripheral surface of the magnet is joined to the inner peripheral surface of the yoke to provide an annular V-groove on the inner peripheral surface of the magnet, and the annular split groove is provided on the outer peripheral surface of the pole piece. It ’s fine.

  Since the magnetic circuit configured in this manner has an annular V-groove wider than the annular dividing groove on the circumferential surface on the air gap side of the magnet, the magnetic flux density on the annular dividing groove side in each magnetic gap is undesirable. As a result, the distribution of the magnetic flux density can be set almost symmetrically in the region on the annular dividing groove side and the region on the anti-annular dividing groove side in any of the upper and lower magnetic gaps. Can do. As a result, the driving force can be changed linearly with respect to the level of the signal current. Further, since a pair of upper and lower magnetic gaps are formed by using one annular magnet, the cost of parts can be reduced. Therefore, this magnetic circuit has a wide amplitude region of the voice coil that changes linearly with respect to the level of the signal current, and is difficult to cause driving force distortion, and can be manufactured at low cost.

  In the magnetic circuit having such a configuration, if the groove shape of the annular V-groove is formed so that the inclination gradually decreases from the deepest portion toward the opening, in the region on the annular dividing groove side in each magnetic gap. The distribution curve of the magnetic flux density becomes smooth and the magnetic flux density is easily lowered between the two magnetic gaps. Therefore, in any of the upper and lower magnetic gaps, it becomes easy to set the magnetic flux density distribution substantially symmetrically in the region on the annular dividing groove side and the region on the anti-annular dividing groove side, and the driving force with respect to the signal current level It becomes easy to increase the linearity of change.

  Embodiments will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a speaker according to a first embodiment of the present invention, and FIG. 2 is a characteristic diagram showing a magnetic flux density distribution in the magnetic gap of the speaker. The parts corresponding to are assigned the same reference numerals.

  The magnetic circuit of the speaker shown in FIG. 1 is an internal magnet type, and includes a pole piece 1 disposed in the center, a yoke 2 disposed around the pole piece 1, and the pole piece 1 and the yoke 2 An annular magnet 13 disposed between them is schematically configured, and the inner peripheral surface of the magnet 13 magnetized in the radial direction is joined to the outer peripheral surface of the pole piece 1. The pole piece 1 and the yoke 3 are integrated, and the outer peripheral surface of the magnet 13 is opposed to the inner peripheral surface of the yoke 2 through a gap. An annular V-shaped groove 14 having a substantially V-shaped cross section and extending in the circumferential direction is formed in the central portion of the outer peripheral surface of the magnet 13 in the axial direction (vertical direction in the drawing). An annular dividing groove 8 extending along the circumferential direction is formed on the inner peripheral surface of the yoke 2 at a position facing the deepest portion of the annular V groove 14. A portion existing above the dividing groove 8 is a magnetic gap G1, and a portion existing below the annular dividing groove 8 is a magnetic gap G2. However, since the annular V-groove 14 is formed wider than the annular dividing groove 8, the opening of the annular V-groove 14 has an annular dividing groove 8 and the vicinity thereof (the annular dividing grooves 8 of the magnetic gaps G1 and G2). On the side area).

  In this speaker, the voice coil 6 is disposed so as to straddle the magnetic gaps G1 and G2, and the upper end of the cylindrical bobbin 5 around which the voice coil 6 is wound is cone-shaped cone paper. It joins to the inner edge part (small diameter part) of the diaphragm 9 which consists of. A frame 10 is fixed on the yoke 2, and the frame 10 supports an outer edge portion (large diameter portion) of the vibration plate 9 through a deformed joint portion 11 and a bobbin 5 through a damper 12. Is supported freely.

  The loudspeaker schematically configured as described above is configured such that the voice coil 6 drives the diaphragm 9 to generate a sound corresponding to the signal current by energizing the voice coil 6 with a signal current. . The magnetic circuit of the speaker is provided with an annular V-groove 14 wider than the annular dividing groove 8 on the outer peripheral surface of the magnet 13, and the annular V-groove 14 causes the annular division within each magnetic gap G1, G2. Since the magnetic flux density on the groove 8 side and the magnetic flux density between the two magnetic gaps G1 and G2 are intentionally reduced, as shown in FIG. 2, the annular dividing groove is formed in any of the upper and lower magnetic gaps G1 and G2. The distribution of magnetic flux density is set to be approximately symmetrical between the region on the 8 side and the region on the anti-annular dividing groove 8 side. Therefore, the driving force can be changed linearly with respect to the level of the signal current. That is, even if the voice coil 6 is vibrated in a wide amplitude region from above the magnetic gap G1 to below the magnetic gap G2, the magnetic flux density distributions in the magnetic gaps G1 and G2 are substantially equal, and the respective magnetic fluxes Since all density distributions are set substantially symmetrically in the vibration direction (vertical direction) of the voice coil 6, the amplitude region of the voice coil 6 can be expanded without impairing the linearity (linearity) with respect to the signal current level. This makes it difficult to cause drive force distortion. In addition, since the magnetic circuit of this speaker uses a single annular magnet 13 to form a pair of upper and lower magnetic gaps G1, G2, the cost of components can be reduced.

  In the present embodiment, the groove shape of the annular V-groove 14 is formed so that the inclination gradually becomes gentler from the deepest portion toward the opening, so that the annular divided grooves in the magnetic gaps G1 and G2 are formed. In the region on the 8 side, the magnetic flux density distribution curve is smooth, and the magnetic flux density between the magnetic gaps G1 and G2 is sufficiently reduced. Therefore, in both the upper and lower magnetic gaps G1 and G2, it is easy to set the magnetic flux density distribution substantially symmetrically in the region on the annular dividing groove 8 side and the region on the anti-annular dividing groove 8 side. However, even when the annular V-groove 14 is formed in another groove shape, for example, an inclination that is substantially constant from the deepest portion toward the opening, it is opposite to the region on the annular dividing groove 8 side in each of the magnetic gaps G1 and G2. It is possible to set the magnetic flux density distribution substantially symmetrically in the region on the annular dividing groove 8 side.

  FIG. 3 is a cross-sectional view of the main part of the magnetic circuit of the speaker according to the second embodiment of the present invention, and parts corresponding to those in FIG.

  The second embodiment is an example in which the present invention is applied to an outer magnet type magnetic circuit. The outer peripheral surface of the annular magnet 13 is joined to the inner peripheral surface of the yoke 2, and the inner peripheral surface of the magnet 13 is It faces the outer peripheral surface of the pole piece 1 through a gap. An annular V-groove 14 is provided on the inner peripheral surface of the magnet 13, and an annular dividing groove that is narrower than the annular V-groove 14 at a location facing the deepest portion of the annular V-groove 14 on the outer peripheral surface of the pole piece 1. 8 is provided, a portion of the gap between the pole piece 1 and the magnet 13 that exists above the annular dividing groove 8 is a magnetic gap G1, and a portion that is below the annular dividing groove 8 is a magnetic gap G2. It has become.

  Also in the second embodiment, similarly to the first embodiment described above, by providing the annular V-groove 14, the magnetic flux density on the annular dividing groove 8 side in each of the magnetic gaps G1 and G2 is changed to the anti-annular dividing groove 8 side. The magnetic flux density can be set to a distribution substantially equal to the magnetic flux density, so that the drive for the level of the signal current can be achieved while using a single annular magnet 13 to form the pair of upper and lower magnetic gaps G1 and G2. The linearity of the force change is increased and the performance of the speaker can be improved.

It is sectional drawing of the speaker which concerns on 1st Example of this invention. It is a characteristic view which shows magnetic flux density distribution in the magnetic gap of the magnetic circuit shown in FIG. It is principal part sectional drawing of the magnetic circuit which concerns on 2nd Example of this invention. It is principal part sectional drawing which shows an example of the conventional magnetic circuit. It is sectional drawing of the speaker which concerns on another prior art example. FIG. 6 is a characteristic diagram showing a magnetic flux density distribution in a magnetic gap of the magnetic circuit shown in FIG. 5.

Explanation of symbols

1 pole piece 2 yoke 5 bobbin 6 voice coil 8 annular dividing groove 9 diaphragm 10 frame 12 damper 13 magnet 14 annular V groove G1, G2 magnetic gap

Claims (4)

A speaker provided with a pole piece arranged at the center, a yoke arranged around the pole piece, and an annular magnet magnetized in the radial direction and arranged between the pole piece and the yoke In the magnetic circuit of
The magnet is joined to one of the peripheral surfaces of the pole piece and the yoke and is opposed to the other peripheral surface through a gap, and the cross-sectional shape is in the axial center of the peripheral surface of the magnet on the gap side. Is provided with an annular V-groove that is substantially V-shaped and extends in the circumferential direction, and an annular dividing groove that is narrower than the annular V-groove and faces the deepest portion of the annular V-groove on the other circumferential surface, A magnetic circuit for a speaker, wherein a portion of the air gap that is above and below the annular dividing groove is a magnetic gap.   2. The annular circumferential groove according to claim 1, wherein the inner circumferential surface of the magnet is joined to the outer circumferential surface of the pole piece, the annular V groove is provided on the outer circumferential surface of the magnet, and the annular dividing groove is formed on the inner circumferential surface of the yoke. A magnetic circuit for a speaker, comprising:   The outer circumferential surface of the magnet according to claim 1 is joined to the inner circumferential surface of the yoke, the annular V groove is provided on the inner circumferential surface of the magnet, and the annular dividing groove is formed on the outer circumferential surface of the pole piece. A magnetic circuit for a speaker, comprising: 4. The magnetic circuit of a speaker according to claim 1, wherein the annular V-shaped groove is formed so that the inclination gradually becomes gentler from the deepest portion toward the opening. .

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