JP2013219427A - Speaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a speaker in which magnetic efficiency is improved easily even when a low-priced magnet is used for a magnetic circuit, and which is appropriate for reduction in size and in cost.SOLUTION: A magnetic circuit 1 is an inner magnet type, a magnet 10 magnetized in a thickness direction is held between an outer yoke 11 and an inner yoke 12, and a magnetic gap G is provided between an inner peripheral surface of the outer yoke 11 at an open end side and an outer peripheral surface of a flange part 12a of the inner yoke 12. An outer magnetic pole surface 10a of the magnet 10 in tight contact with the outer yoke 11 is a convex hemisphere surface, and an inner magnetic pole surface 10b of the magnet 10 in tight contact with the inner yoke 12 is a concave hemisphere surface but since a radius of the magnetic pole surface 10a is longer than a radius of the magnetic pole surface 10b just by a thickness dimension of the magnet 10, an area of the magnetic pole surface 10a is larger than that of the magnetic pole surface 10b. Furthermore, an end face 10c of the magnet 10 at the open end side is disposed in a position facing the magnetic gap G in a depth direction.

Description

  The present invention relates to an electrodynamic loudspeaker that energizes a voice coil to vibrate a diaphragm, and more particularly to an internal magnet type magnetic circuit provided in the loudspeaker.

  The inner magnet type magnetic circuit in which the magnet is arranged inside the voice coil is suitable for downsizing the speaker, and has an advantage that the leakage magnetic flux is smaller and the magnetic efficiency is better than the outer magnet type magnetic circuit.

  FIG. 4 is a cross-sectional view of a speaker provided with a conventional general internal magnetic circuit. The speaker shown in FIG. 1 includes a magnetic circuit 30, a voice coil 34 disposed in the magnetic gap G of the magnetic circuit 30, a diaphragm 35 whose outer peripheral portion is integrated with the voice coil 34, and a damper 36. The frame 37 is elastically supported by the voice coil 34 and the diaphragm 35, and the frame 37 is fixed to the magnetic circuit 30. The magnetic circuit 30 includes a flat plate-like (for example, disk-like) magnet 31 magnetized in the thickness direction, a flat plate-like inner yoke 32, and a bottomed cylindrical outer yoke 33. The portion excluding the outer peripheral portion is a laminated structure portion in which the magnet 31 is sandwiched between the inner yoke 32 and the outer yoke 33. Further, the magnetic circuit 30 is provided with a magnetic gap G between the inner peripheral surface on the opening end side of the outer yoke 33 and the outer peripheral surface of the inner yoke 32, and the magnetic gap G is formed by the magnetic energy of the magnet 31. The necessary magnetic flux density is secured. The voice coil 34 is often wound around a cylindrical (for example, cylindrical) coil bobbin, but a configuration in which the voice coil 34 is formed into a cylindrical shape and the coil bobbin is omitted is also known.

  When a signal current is supplied to the voice coil 34, the speaker schematically configured as described above generates a known electromagnetic driving force, and the voice coil 34 vibrates in the vertical direction in FIG. As a result, the diaphragm 35 vibrates integrally with the voice coil 34, and a sound corresponding to the signal current is generated.

  By the way, since a large-diameter magnet cannot be used for the inner magnet type magnetic circuit of a small speaker, a high-performance neodymium (Nd) magnet is often used even with a small diameter. In addition, in a vehicle-mounted speaker or the like that may be used in a high-temperature environment, heat resistance is required for a magnetic circuit. Therefore, a neodymium magnet added with dysprosium (Dy) has become the mainstream. Yes. However, neodymium magnets added with dysprosium are expensive, which has been a factor in increasing the cost of speakers. In addition, the future supply prospect of dysprosium is considered unstable, and it is expected that the supply will be drastically reduced or soared. In recent years, development of a small diameter and high performance magnet that does not require dysprosium is required. ing.

  In the speaker disclosed in Patent Document 1, an inner magnet type magnetic circuit is configured by using a magnet having a curved magnetic pole surface, so that the magnet magnetized in the thickness direction is magnetic without increasing its diameter. I try to improve performance. The magnetic pole surface of the magnet used in the magnetic circuit is the surface of the magnet that is in close contact with the yoke. For example, in the case of the magnet 31 in FIG. 4, the upper surface of the magnet 31 that is in contact with the inner yoke 32, The lower surface of the magnet 31 in contact with the outer yoke 33 is a magnetic pole surface magnetized to the S pole or the N pole. The magnet 31 in FIG. 4 has a flat magnetic pole surface. However, if a magnet with a curved magnetic pole surface is used, the contact area with the yoke increases without increasing the diameter of the magnet. As described above, the magnetic flux density in the magnetic gap can be increased.

JP-A-5-103393

  In the magnetic circuit disclosed in Patent Document 1 described above, one magnetic pole surface and the other magnetic pole surface of the magnet are set to have the same size (same area), and the inner pole has a smaller center pole than the magnet. The center pole portion is surrounded by the magnetic gap. Therefore, magnetic energy is wasted at the outer peripheral portion of the magnet whose magnetic pole surface is curved, and magnetic flux is likely to leak from a portion of the inner yoke having a larger diameter than the center pole portion. Therefore, in the magnetic circuit disclosed in Patent Document 1, the magnetic flux density in the magnetic gap cannot be increased so much, and an internal magnet type magnetic circuit with good magnetic efficiency can be realized using an inexpensive magnet. Have difficulty.

  The present invention has been made in view of the actual situation of the prior art, and its purpose is to easily increase the magnetic efficiency even if an inexpensive magnet is used for the magnetic circuit, and to reduce the size and cost. The object is to provide a suitable speaker.

  In order to achieve the above object, the present invention has a laminated structure in which a magnet magnetized in the thickness direction is sandwiched between an inner yoke and an outer yoke having a larger diameter than the inner yoke, In a speaker comprising a magnetic circuit having a magnetic gap between an inner peripheral surface on the opening end side of a yoke and an outer peripheral surface of the inner yoke, and energizing a voice coil disposed in the magnetic gap to vibrate a diaphragm, The inner yoke excluding the vicinity of the magnetic gap is provided with a protruding portion that protrudes toward the magnet, and the inner magnetic pole surface of the magnet becomes a concave surface that is in close contact with the outer wall surface of the protruding portion, and the outer magnetic pole surface of the magnet And a convex surface having a surface area approximately similar to the inner magnetic pole surface and having an area larger than the inner magnetic pole surface, the outer magnetic pole surface is brought into close contact with the inner wall surface of the outer yoke, and the magnet The end surface of the mouth end has a configuration that is disposed in a position facing the magnetic gap from the depth direction.

  In the magnetic circuit of the speaker configured as described above, of the magnets sandwiched between the inner yoke and the outer yoke, the inner magnetic pole surface that is in close contact with the inner yoke is a concave surface, and the outer magnetic pole surface that is in close contact with the outer yoke is Since it is a convex surface that is substantially similar to the inner magnetic pole surface and has an area larger than that of the inner magnetic pole surface, the outer peripheral portion of the magnet can be magnetized in the thickness direction, and there is little waste of magnetic energy. In addition, since this magnet has an end face on the open end side, that is, an end face extending between the peripheral edges of both magnetic pole faces, arranged so that the magnetic gap faces from the depth direction, the inner yoke is located near the end face. And the possibility of magnetic flux leakage from the outer yoke is low. Therefore, the magnetic flux density in the magnetic gap can be sufficiently increased even with a magnet that does not use an expensive material.

  In the above speaker, the magnet may be, for example, a hollow hemisphere having hemispherical inner and outer magnetic pole surfaces. In this case, both the magnetic pole surfaces of the magnet are formed as hemispherical surfaces. Is larger than the area of the inner magnetic pole surface, so that a magnet magnetized radially including the outer peripheral portion can be obtained.

  Further, in the above magnetic circuit for a speaker, the magnet includes a flat bottom plate portion, a tapered portion that surrounds the bottom plate portion and inclines so as to widen the opening area, and a cylindrical portion that stands up from the tapered portion to the opening end. If the cylindrical body with a bottom is made continuous, the area of the inner magnetic pole surface and the outer magnetic pole surface increases compared to a hollow hemispherical magnet with the same outer diameter, so the inner yoke and outer yoke The contact area between the magnet and the magnet can be increased, and the magnetic flux density in the magnetic gap can be greatly increased.

  In the speaker of the present invention, the magnet used in the magnetic circuit has a concave surface on the inner magnetic pole surface that is in close contact with the inner yoke, and a convex shape that is substantially similar to the inner magnetic pole surface and the outer magnetic pole surface in close contact with the outer yoke exceeds the area. Since the surface can be magnetized in the thickness direction even at the outer peripheral portion of the magnet, the waste of magnetic energy is reduced. Further, since the end face on the opening end side of the magnet is arranged at a position where the magnetic gap faces from the depth direction, the possibility of magnetic flux leaking from the inner yoke and the outer yoke in the vicinity of the end face is low. Therefore, even with a magnet that does not use an expensive material, the magnetic flux density in the magnetic gap can be sufficiently increased. In other words, since this magnetic circuit has a structure in which the magnetic efficiency is easily increased, the required magnetic performance can be ensured while using an inexpensive magnet. Therefore, the speaker of the present invention can be reduced in size and cost. Is easy.

1 is a cross-sectional view of a speaker according to a first exemplary embodiment of the present invention. It is a characteristic view which shows the magnetic flux density of the magnetic gap vicinity in the magnetic circuit of this speaker. It is sectional drawing of the speaker which concerns on the 2nd Example of this invention. It is sectional drawing of the speaker which concerns on a prior art example.

  Embodiments of the present invention will be described below with reference to the drawings. First, a speaker according to a first embodiment of the present invention will be described with reference to FIG. 1 and FIG.

  The speaker shown in FIG. 1 is a small vehicle-mounted speaker provided with an internal magnet type magnetic circuit 1, and the structure of the magnetic circuit 1 is greatly different from the conventional internal magnet type magnetic circuit shown in FIG. The magnet 10 incorporated in the magnetic circuit 1 is a hollow hemisphere, and the magnetization direction of the magnet 10 is set in the thickness direction. The outer magnetic pole surface 10a of the magnet 10 is in close contact with the inner wall surface of the outer yoke 11 formed in a hemispherical shape. Further, the inner yoke 12 is formed as a hemispherical protruding portion 12b whose portion excluding the annular flange 12a protrudes toward the magnet 10, and the inner magnetic pole surface 10b of the magnet 10 is formed on the outer wall surface of the protruding portion 12b. It is in close contact. Furthermore, the inner wall surface of the protruding portion 12b defines a recess 12c, and this recess 12c faces the diaphragm 3 of the speaker.

  More specifically, in the magnetic circuit 1, the laminated structure portion 13 in which the magnet 10 is sandwiched between the inner yoke 12 and the outer yoke 11 has a hollow hemispherical shape, and a concave portion is formed in the central portion on the front side of the laminated structure portion 13. A location 12c is provided. The magnet 10 has an inner magnetic pole surface 10b as a concave hemispherical surface that is in close contact with the outer wall surface of the protruding portion 12b of the inner yoke 12, and an outer surface as a convex hemispherical surface that is in close contact with the inner wall surface of the outer yoke 11. A magnetic pole surface 10a is formed. Since the radius of the outer magnetic pole surface 10a is longer than the radius of the inner magnetic pole surface 10b by the thickness dimension of the magnet 10, the area of the outer magnetic pole surface 10a is larger than the area of the inner magnetic pole surface 10b. Further, in the magnetic circuit 1, a magnetic gap G is provided between the inner peripheral surface of the outer yoke 12 on the opening end side and the outer peripheral surface of the flange 12a of the inner yoke 12, and the magnetic gap G is deepened. An end face 10c on the opening end side of the magnet 10 is arranged at a position facing from the direction.

  The overall configuration of the loudspeaker shown in FIG. 1 will be described. The loudspeaker includes a magnetic circuit 1 described above, a voice coil 2 disposed in the magnetic gap G, and a diaphragm in which the outer peripheral portion is integrated with the voice coil 2. 3 and a frame 5 that elastically supports the voice coil 2 and the diaphragm 3 via a damper 4, and the frame 5 is fixed to the outer yoke 11 of the magnetic circuit 1. In addition, when a signal current is supplied to the voice coil 2, the speaker having such a configuration generates a known electromagnetic driving force and the voice coil 2 vibrates in the vertical direction in FIG. 3 vibrates, and a sound corresponding to the signal current is generated.

  In this embodiment, the inner diameter of the open end of the outer yoke 11 is 27 mm, and the outer diameter of the flange portion 12a of the inner yoke 12 is 25 mm. Therefore, a magnetic field is formed between concentric circles having a radius of 13.5 mm and a radius of 12.5 mm. A gap G is defined. The graph shown by the solid line in FIG. 2 is the result of measuring the magnetic flux density in the vicinity of the magnetic gap G of the magnetic circuit 1, where the horizontal axis indicates the distance from the center line of the magnetic circuit 1 and the vertical axis indicates the magnetic flux density. Yes. Also, the graph shown by the broken line in FIG. 2 is the result of measuring the magnetic flux density near the magnetic gap with the magnetic circuit of the comparative example. This comparative example is the magnetic circuit having the conventional structure shown in FIG. 4, and the size and material of the components (magnet and yoke) in front view are the components of the magnetic circuit 1 (magnet 10 and yokes 11 and 12). ) Is the same as the size and material of the front view. As apparent from FIG. 2, in the magnetic circuit 1 of the loudspeaker according to this embodiment, the magnetic flux density in the magnetic gap G increases to nearly twice the magnetic flux density in the magnetic gap in the comparative example.

  The reason why the magnetic flux density in the magnetic gap G is remarkably increased as compared with the conventional structure will be described. First, in the magnetic circuit 1 of this embodiment, the magnetic pole surfaces 10a and 10b of the magnet 10 are hemispherical. Since it is formed as a surface, the contact area with the outer yoke 11 and the inner yoke 12 is increased. Further, the hollow hemispherical magnet 10 has an outer magnetic pole face 10a having a larger area than the inner magnetic pole face 10b, and can be magnetized radially including the outer peripheral portion. Therefore, the outer peripheral portion of the magnet 10 can be magnetized in the thickness direction, and the waste of magnetic energy is reduced. In addition, the magnet 10 has an annular end surface 10c extending between the peripheral edges of the magnetic pole surfaces 10a and 10b disposed at a position facing the magnetic gap G from the depth direction. The possibility of leakage of magnetic flux from the inner yoke 12 and the outer yoke 11 is low. Therefore, the magnetic circuit 1 can sufficiently increase the magnetic flux density in the magnetic gap G without using an expensive magnet such as a neodymium magnet to which dysprosium is added.

  As described above, the speaker magnetic circuit 1 according to the present embodiment has a large contact area between the magnetic pole faces 10a and 10b of the magnet 10 and the yokes 11 and 12, and in addition, the magnetic circuit 1 is magnetic at the outer periphery of the magnet 10. There is little waste of energy, and furthermore, since the magnetic flux is hardly leaked from the yokes 11 and 12 near the end face 10c of the magnet 10, the magnetic flux density in the magnetic gap G is sufficient even with the magnet 10 that does not use expensive materials. Can be increased. That is, since the magnetic circuit 1 has a structure that can easily increase the magnetic efficiency, the required magnetic performance can be ensured while using the inexpensive magnet 10. Therefore, this speaker can be easily reduced in size and cost.

  In the speaker according to the present embodiment, the space capacity on the back side of the diaphragm 3 is increased by the recess 12c of the inner yoke 12 of the magnetic circuit 1, so that the back pressure during operation is reduced and the period is low. Playback is possible up to several bands.

  Next, a speaker according to a second embodiment of the present invention will be described with reference to FIG. In FIG. 3, the same reference numerals are given to the portions corresponding to FIG.

  The speaker shown in FIG. 3 is different from the first embodiment in the shape of the magnetic circuit 1. That is, in the magnetic circuit 1 of the speaker according to the second embodiment, the magnet 10 includes a disc-shaped bottom plate portion 10d, and a tapered portion 10e that surrounds the bottom plate portion 10d and is inclined to widen the opening area. A cylindrical body having a bottom is formed by continuously connecting the cylindrical portion 10f rising from the tapered portion 10e to the opening end. In addition, the shape of the protruding portion 12 b of the inner yoke 12 and the outer yoke 11 is also a substantially cylindrical shape with a bottom in accordance with the shape of the magnet 10. Therefore, the magnet 10 has the inner magnetic pole surface 10 b that is a concave surface in close contact with the outer wall surface of the protruding portion 12 b, and the outer magnetic pole surface 10 a that is a convex surface is in close contact with the inner wall surface of the outer yoke 11.

  Also in the second embodiment, both the magnetic pole faces 10a and 10b of the magnet 10 are substantially similar, and the area of the outer magnetic pole face 10a is larger than the area of the inner magnetic pole face 10b. Further, the end surface 10c on the opening end side of the magnet 10 has an annular shape, and the end surface 10c is disposed at a position facing the magnetic gap G from the depth direction.

  As described above, in the second embodiment, the magnet 10 has a bottomed cylindrical body. Therefore, when compared with a hollow hemispherical magnet having the same outer diameter (the first embodiment), the outer magnetic pole surface Both the area of 10a and the area of the inner magnetic pole surface 10b increase. As a result, the contact area between the outer yoke 11 and the inner yoke 12 and the magnet 10 increases, so that the magnetic flux density in the magnetic gap G can be significantly increased.

  In the first and second embodiments described above, the magnetic circuit for a speaker having a circular front view is exemplified, but for a speaker whose front view has a square shape, a rectangular shape, an elliptical shape, or the like. Of course, even a magnetic circuit can be reduced in size and cost by applying the present invention.

DESCRIPTION OF SYMBOLS 1 Magnetic circuit 2 Voice coil 3 Diaphragm 4 Damper 5 Frame 10 Magnet 10a Outer magnetic pole surface 10b Inner magnetic pole surface 10c End surface 10d Bottom plate part 10e Tapered part 10f Cylindrical part (cylinder part)
DESCRIPTION OF SYMBOLS 11 Outer yoke 12 Inner yoke 12a Gutter part 12b Protrusion part 12c Recess 13 Laminated structure part G Magnetic gap

Claims (3)

A laminated structure in which a magnet magnetized in the thickness direction is sandwiched between an inner yoke and an outer yoke having a larger diameter than the inner yoke; and an inner peripheral surface on the opening end side of the outer yoke and the inner yoke In a speaker comprising a magnetic circuit having a magnetic gap between the outer peripheral surface of the speaker and energizing a voice coil arranged in the magnetic gap to vibrate the diaphragm,
The inner yoke excluding the vicinity of the magnetic gap is provided with a protruding portion that protrudes toward the magnet, and the inner magnetic pole surface of the magnet becomes a concave surface that is in close contact with the outer wall surface of the protruding portion, and the outer magnetic pole surface of the magnet The outer magnetic pole surface is closely contacted with the inner wall surface of the outer yoke, and the end surface on the opening end side of the magnet has a deeper gap for the magnetic gap. A speaker characterized by being arranged at a position facing from the vertical direction.   2. The speaker according to claim 1, wherein the magnet is a hemisphere having a hollow structure in which an inner magnetic pole surface and an outer magnetic pole surface are hemispherical surfaces.   2. The magnet according to claim 1, wherein the magnet includes a flat bottom plate portion, a tapered portion that surrounds the bottom plate portion and inclines in a direction to widen the opening area, and a cylindrical portion that rises from the tapered portion to the opening end. A speaker having a bottomed cylindrical body made continuous.