JP3902066B2 - Magnetic circuit for speakers - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a speaker magnetic circuit for converting an electric signal into sound.
[0002]
[Prior art]
Many proposals have been made for improvement of speakers. For example, Japanese Patent Laid-Open No. 9-284888 describes a speaker (FIG. 8) in which the resonance sharpness at the lowest resonance frequency is reduced and sound reproduction in a low frequency band can be performed satisfactorily.
The speaker shown in FIG. 8 includes a magnetic circuit and a frame 208 supported on the magnetic circuit. This magnetic circuit includes a disk-shaped yoke 202a having a center pole portion 201, an annular first magnet 216 disposed on the front surface of the yoke 202a, and a disk-shaped plate disposed on the first magnet 216. 202b, an annular second magnet 203 disposed on the plate 202b, and a disk-shaped plate 204 disposed on the second magnet 203. The first and second magnets 216 and 203 are each magnetized in the axial direction, and the magnetic poles formed on the front and rear surface portions of both are opposite in the axial direction. The plates 202b and 204 and the center pole portion 201 are opposed to each other through the magnetic gaps 214b and 214a.
[0003]
[Problems to be solved by the invention]
In recent years, the demand for higher performance of speakers has become increasingly severe, and there is a demand for high performance speakers capable of obtaining high output while minimizing the increase in size. That is, there is a demand for a speaker magnetic circuit having a novel structure suitable for a large output type speaker.
From the study of the present inventors, in the conventional speaker magnetic circuit represented by FIG. 8, the effective magnetic flux density (gap magnetic flux density) of the magnetic gap in the interlinked region of the voice coil has almost reached the upper limit value. It was found that the gap magnetic flux density of the magnetic gap could not be increased beyond the current level unless new improvements were made to the speaker magnetic circuit structure.
[0004]
Therefore, the problem to be solved by the present invention is to provide a speaker magnetic circuit in which the gap magnetic flux density is remarkably increased without increasing the size, weight and cost of the speaker.
[0005]
[Means for Solving the Problems]
A magnetic circuit for a speaker according to the present invention that has solved the above-described problems is provided with a first yoke formed in a disk shape from a ferromagnetic material, a magnetization direction in the thickness direction, and disposed on the front surface of the first yoke. A ring-shaped first permanent magnet, a second yoke formed in a ring shape from a ferromagnetic material and disposed on the front surface of the first permanent magnet, a thickness direction is a magnetization direction, and the first permanent magnet A magnetic pole having a polarity opposite to that of the magnet is formed on the front surface portion and the rear surface portion, and is formed in a cylindrical shape by a ring-shaped second permanent magnet disposed on the front surface of the second yoke, and a ferromagnetic material, A center pole disposed on the front surface of the first yoke and facing the inner surfaces of the first permanent magnet and the second yoke via a gap; a thickness direction is a magnetization direction; and a second permanent magnet Is formed with magnetic poles of opposite polarity on the front and rear surfaces, Disposed in front of, it is characterized in that a third permanent magnet that faces through the inner peripheral surface and the gap of the second permanent magnet.
[0007]
The magnetic circuit for a speaker according to the present invention includes a first yoke formed in a disk shape from a ferromagnetic material, and a ring-shaped second yoke disposed in front of the first yoke, the thickness direction being a magnetization direction. 1 permanent magnet, a second yoke formed in a ring shape with a ferromagnetic material and disposed on the front surface of the first permanent magnet, and the thickness direction is the magnetization direction, opposite to the first permanent magnet A magnetic pole having a polarity is formed on the front surface portion and the rear surface portion, and is formed in a ring shape by a ring-shaped second permanent magnet disposed on the front surface of the second yoke and a ferromagnetic material. A third yoke disposed on the front surface of the magnet, a cylindrical shape made of a ferromagnetic material, disposed on the front surface of the first yoke, and an inner peripheral surface of the first permanent magnet and the second yoke; The center pole facing the gap and the thickness direction is the magnetization direction, and the second permanent A magnetic pole having a polarity opposite to that of the stone is formed on the front surface portion and the rear surface portion. The third permanent magnet is disposed on the front surface of the center pole and faces the inner peripheral surface of the second permanent magnet through a gap. And a fourth yoke formed of a ferromagnetic material and disposed on the front surface of the third permanent magnet and facing the inner peripheral surface of the third yoke with a gap interposed therebetween. And
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a longitudinal sectional view showing an example of a speaker magnetic circuit according to the present invention.
In FIG. 1, reference numeral 1 denotes a disk-shaped first yoke made of a ferromagnetic material, and a columnar center pole 4 made of a ferromagnetic material is coaxially disposed at the center of the front surface of the first yoke 1. ing. The first yoke 1 and the center pole 4 are screwed together by a fastener (bolt) (not shown). In addition, a ring-shaped first permanent magnet 2 magnetized in the thickness direction coaxially with the yoke 1 is disposed on the front surface of the first yoke 1, and an inner peripheral surface thereof faces the center pole 4 through a gap 8. is doing. A ring-shaped second yoke 3 made of a ferromagnetic material is disposed coaxially with the first permanent magnet 2 on the front surface of the first permanent magnet 2, and the inner peripheral surface of the second yoke 3 is a magnetic gap 7. Through the center pole 4. A disc-shaped third permanent magnet 12 magnetized in the thickness direction is disposed coaxially with the center pole 4 on the front surface of the center pole 4. A ring-shaped second permanent magnet 5 magnetized in the thickness direction is disposed on the front surface of the second yoke 3, and the inner peripheral surface thereof opposes the outer peripheral surface of the third permanent magnet 12 through the gap 9. is doing. The first, second, and third permanent magnets 2, 5, and 12 are formed with magnetic poles having the polarities shown in FIG.
[0009]
With such a magnetic circuit configuration, a closed magnetic path exemplified by arrows 13 and 14 is formed, and the gap magnetic flux density of the magnetic gap 7 is significantly increased. An arrow 13 is a main magnetic flux 13 that exits from the first permanent magnet 2 and passes through the second yoke 3, the magnetic gap 7, the center pole 4, and the yoke 1. In addition to this, a supplementary magnetic flux 14 exiting from the second permanent magnet 5 and passing through the second yoke 3, the magnetic gap 7, the center pole 4, and the third permanent magnet 12 is generated. The conventional speaker magnetic circuit of FIG. 8 also generates a supplementary magnetic flux that exits from the second magnet 203 and passes through the plate 204, the magnetic gap 214a, the center pole 201, the magnetic gap 214b, and the plate 202b. It is less than the amount of one auxiliary magnetic flux 14 generated. This difference is the contribution of the third permanent magnet 12 of FIG. 1, and is specifically shown in Example 1 of FIG. 5 described later. 1, the magnetic flux density in the magnetic gap 7 is remarkably increased, a large driving force is generated in the voice coil 11, and the speaker diaphragm connected to the voice coil 11 is constructed. (Not shown) vibrates and can generate a high output sound.
In FIG. 1, the magnetic gap 7 is a gap in a region where the outer peripheral surface of the center pole 4 and the inner peripheral surface of the second yoke 3 face each other, and is a stroke region where the voice coil 11 is driven.
[0010]
  Figure 2Magnetic circuit for speaker of reference exampleFIG.
  In FIG. 2, reference numeral 21 denotes a disk-shaped first yoke made of a ferromagnetic material, and a cylindrical center pole 24 made of a ferromagnetic material is coaxially disposed at the center of the front surface of the first yoke 21. ing. The first yoke 21 and the center pole 24 are screwed together by a fastener (bolt) (not shown). A ring-shaped first permanent magnet 22 magnetized in the thickness direction coaxially with the yoke 21 is disposed on the front surface of the first yoke 21 and faces the center pole 24 through a gap 26. A ring-shaped second yoke 23 made of a ferromagnetic material is disposed coaxially with the first permanent magnet 22 on the front surface of the first permanent magnet 22, and the inner peripheral surface of the second yoke 23 is a magnetic gap 27. Is opposed to the outer peripheral surface of the center pole 24. A disc-shaped second permanent magnet 28 magnetized in the thickness direction is provided on the front surface of the center pole 24 so as to protrude coaxially with the center pole 24. The first and second permanent magnets 22 and 28 are respectively formed with magnetic poles having the polarities shown in FIG.
[0011]
With such a magnetic circuit configuration, the second yoke 23, the magnetic gap 27, the center pole 24, and the first yoke come out of the first permanent magnet 22 as illustrated by the arrow in FIG. A main magnetic flux 18 passing through 21 is generated. In addition, a supplementary magnetic flux 25 is generated that passes through the second yoke 23, the magnetic gap 27, the center pole 24, and the second permanent magnet 28. In the speaker magnetic circuit of FIG. 2, there is no permanent magnet corresponding to the second magnet 203 in the conventional speaker magnetic circuit of FIG. 8, but the magnetic flux generated from the second permanent magnet 28 compensates for the absence. As a result, the gap magnetic flux density in the magnetic gap 27 of the speaker magnetic circuit of FIG. 2 is larger than the magnetic flux density of the magnetic gap 214b of the conventional speaker magnetic circuit of FIG. The speaker magnetic circuit of FIG. 2 is suitable for a small, lightweight, high-performance speaker.
In FIG. 2, the magnetic gap 27 is a gap in a region where the outer peripheral surface of the center pole 24 and the inner peripheral surface of the second yoke 23 face each other, and is a stroke region where a voice coil (not shown) is driven.
[0012]
  FIG. 3 shows a magnetic circuit for a speaker according to the present invention.Other examplesFIG.
  In FIG. 3, reference numeral 51 denotes a disk-shaped first yoke made of a ferromagnetic material, and a cylindrical center pole 54 made of a ferromagnetic material is coaxially disposed at the center of the front surface of the first yoke 51. ing. The first yoke 51 and the center pole 54 are screwed together by a fastener (bolt) (not shown). A ring-shaped first permanent magnet 52 magnetized in the thickness direction coaxially with the yoke 51 is disposed on the front surface of the first yoke 51, and an inner peripheral surface thereof is an outer peripheral surface of the center pole 54 via a gap 58. Is facing. A ring-shaped second yoke 53 made of a ferromagnetic material is disposed coaxially with the first permanent magnet 52 on the front surface of the first permanent magnet 52, and the inner peripheral surface of the second yoke 53 is a magnetic gap 57. Is opposed to the outer peripheral surface of the center pole 54. A disc-shaped third permanent magnet 62 magnetized in the thickness direction is disposed coaxially with the center pole 54 on the front surface of the center pole 54. A ring-shaped second permanent magnet 55 magnetized in the thickness direction is disposed on the front surface of the second yoke 53, and its inner peripheral surface faces the outer peripheral surface of the third permanent magnet 62 through a gap 59. is doing. On the front surface of the third permanent magnet 62, a fourth yoke 67 formed in a disk shape from a ferromagnetic material is disposed coaxially with the third permanent magnet 62. A third yoke 56 formed in a ring shape from a ferromagnetic material is disposed on the front surface of the second permanent magnet 55, and the inner peripheral surface thereof faces the outer peripheral surface of the fourth yoke 67 through the gap 60. is doing. The first, second, and third permanent magnets 52, 55, and 62 are formed with magnetic poles having the polarities shown in FIG. The magnetic circuit configuration in FIG. 3 corresponds to a structure in which third and fourth yokes are added to the speaker magnetic circuit in FIG.
[0013]
As shown by the arrows in FIG. 3, a main magnetic flux 63 is generated that exits from the first permanent magnet 52 and passes through the second yoke 53, the magnetic gap 57, the center pole 54, and the first yoke 51. In addition to this, the second yoke 53, the magnetic gap 57, the center pole 54, the third permanent magnet 62, the fourth yoke 67, the gap 60, and the third yoke 56 are removed from the second permanent magnet 55. A complementary magnetic flux 64 is generated. The effectiveness of the speaker magnetic circuit of FIG. 3 is specifically shown in Example 2 of FIG. 5 described later.
In FIG. 3, the magnetic gap 57 is a gap in a region where the outer peripheral surface of the center pole 54 and the inner peripheral surface of the second yoke 53 face each other, and is a stroke region where a voice coil (not shown) is driven. Note that the magnetic flux density of the gap 60 is smaller than the magnetic gap 57 but larger than the gaps 58 and 59. Therefore, if a voice coil is arranged in the gap 60 and the magnetic flux is linked, the driving power of the voice coil can be further increased. it can.
[0014]
FIG. 4 is a sectional view showing still another example of the speaker magnetic circuit of the present invention.
In FIG. 4, reference numeral 111 denotes a disk-shaped first yoke made of a ferromagnetic material, and a columnar center pole 114 made of a ferromagnetic material is coaxially disposed at the center of the front surface of the first yoke 111. ing. A taper portion 114 a is provided on the joint surface of the center pole 114 with the first yoke 111. The first yoke 111 and the center pole 114 are screwed together by a fastener (bolt) (not shown). A ring-shaped first permanent magnet 112 magnetized in the thickness direction coaxially with the yoke 111 is disposed on the front surface of the first yoke 111, and an inner peripheral surface thereof is an outer peripheral surface of the center pole 114 via a gap 118. Is facing. A ring-shaped second yoke 113 made of a ferromagnetic material is disposed coaxially with the first permanent magnet 112 on the front surface of the first permanent magnet 112, and the inner peripheral surface of the second yoke 113 is a magnetic gap 117. It faces the outer peripheral surface of the center pole 114 via A disc-shaped third permanent magnet 122 magnetized in the thickness direction is disposed coaxially with the center pole 114 on the front surface of the center pole 114. A ring-shaped second permanent magnet 115 magnetized in the thickness direction is disposed on the front surface of the second yoke 113, and its inner peripheral surface faces the outer peripheral surface of the third permanent magnet 122 through the gap 119. is doing. On the front surface of the third permanent magnet 122, a fourth yoke 127 formed in a disk shape from a ferromagnetic material is disposed coaxially with the third permanent magnet 122. A third yoke 116 formed in a ring shape with a ferromagnetic material is disposed on the front surface of the second permanent magnet 115, and the inner peripheral surface thereof faces the outer peripheral surface of the fourth yoke 127 through the gap 120. is doing. The first, second, and third permanent magnets 112, 115, and 122 are formed with magnetic poles having the polarities shown in FIG. In the magnetic circuit configuration of FIG. 4, a taper portion is provided on the joint surface of the center pole 54 of the speaker magnetic circuit of FIG. 3 with the first yoke 51.
[0015]
As shown by the arrows in FIG. 4, a main magnetic flux 123 is generated that exits from the first permanent magnet 112 and passes through the second yoke 113, the magnetic gap 117, the center pole 114, and the first yoke 111. In addition, the second yoke 113, the magnetic gap 117, the center pole 114, the third permanent magnet 122, the fourth yoke 127, the gap 120, and the third yoke 116 are removed from the second permanent magnet 115. A complementary magnetic flux 124 is generated. The effectiveness of the speaker magnetic circuit of FIG. 4 is specifically shown in Example 3-1 of FIG. 5 described later.
In FIG. 4, the magnetic gap 117 is a gap in a region where the outer peripheral surface of the center pole 114 and the inner peripheral surface of the second yoke 113 face each other, and is a stroke region where a voice coil (not shown) is driven. Note that the magnetic flux density of the gap 120 is smaller than the magnetic gap 117 but larger than the gaps 118 and 119. Therefore, if the voice coil is also arranged in the gap 120 and the magnetic flux is linked, the driving power of the voice coil can be further increased. it can.
[0016]
The permanent magnets disposed in the magnetic circuit for speaker according to the present invention may not be integrated, and for example, a plurality of divided permanent magnets can be bonded together. When the ring-shaped magnet, cylindrical magnet, or disk-shaped magnet is composed of an assembly of permanent magnets, the outer periphery or inner periphery of the assembly's permanent magnet is not limited to an arc, and is partially a linear portion You may have.
[0017]
【Example】
  Hereinafter, the present invention will be described in detail by way of examples.ofThe present invention is not limited to the examples.
[0018]
  Example 1
  The speaker magnetic circuit of the present invention shown in FIG. 1 has an outer diameter D of a first yoke 1, a first permanent magnet 2, a second yoke 3, and a second permanent magnet 5.₁= 173 mm, the inner diameter of the first permanent magnet 2, the second yoke 3, and the second permanent magnet 5: D₂= 93 mm, outer diameter of center pole 4 and third permanent magnet 12: D₁₂= 75 mm, thickness of first yoke 1: L₁= 30 mm, center pole 4 thickness: L_Four= 52.5 mm, thickness of first permanent magnet 2: L₂= 25 mm, thickness of second yoke 3: L_Three= 27.5 mm, thickness of the second and third permanent magnets 5 and 12: L_Five= 25 mm and configured. The first, second and third permanent magnets 2, 5, and 12 are all R-Fe-B anisotropic sintered magnets (R is at least one rare earth element mainly composed of Nd, Hitachi Metals HS-46CH) was used. The first yoke 1, the center pole 4, and the second yoke 3 were all made of JISG3101 general structural rolled steel SS400.
  In the speaker magnetic circuit of FIG. 1 configured as described above, the air gap magnetic flux density along the axial direction x of the magnetic gap 7 was measured from the radial center position O of the magnetic gap 7 (the lower end position of the magnetic gap 7). . The results are shown in Example 1 in FIG. From Figure 51.25 T or moreIt can be seen that a high gap magnetic flux density was obtained.
[0019]
(Example 2)
The speaker magnetic circuit of the present invention shown in FIG. 3 has the first yoke 51, the first permanent magnet 52, the second yoke 53, the second permanent magnet 55, and the outer diameter of the third yoke 56: D₅₁= 173 mm, the inner diameter of the first permanent magnet 52, the second yoke 53, the second permanent magnet 55, and the third yoke 56: D₅₂= 93 mm, outer diameter of center pole 54, third permanent magnet 62, and fourth yoke 67: D₆₂= 75 mm, thickness of first yoke 51: L₅₁= 30 mm, center pole 54 thickness: L₅₄= 52.5mm, thickness of first permanent magnet 52: L₅₂= 25 mm, thickness of second yoke 53: L₅₃= 27.5mm, thickness of second and third permanent magnets 55 and 62: L₅₅= 25 mm, thickness of third and fourth yokes 56 and 67: L₅₆= 25 mm and configured. The first, second and third permanent magnets 52, 55 and 62 are all R-Fe-B anisotropic sintered magnets (R is at least one rare earth element mainly composed of Nd, Hitachi Metals HS-46CH) was used. The first, second, and third yokes 51, 53, and 56 and the center pole 54 are all made of JISG3101 general structural rolled steel SS400.
In the speaker magnetic circuit of FIG. 3 configured as described above, the air gap magnetic flux density along the axial direction x of the magnetic gap 57 was measured from the radial center position O of the magnetic gap 57 (the lower end position of the magnetic gap 57). . The results are shown in Example 2 in FIG. From FIG. 5, it can be seen that a high gap magnetic flux density exceeding 1.30 T was obtained.
[0020]
(Example 3-1)
The magnetic circuit for a speaker of the present invention shown in FIG. 4 has the outer diameter of the first yoke 111, the first permanent magnet 112, the second permanent magnet 115, and the third yoke 116: D₁₁₁= 173 mm, outer diameter of the second yoke 113: D₁₁₃= Inner diameter of the first permanent magnet 112, the second yoke 113, the second permanent magnet 115, and the third yoke 116: D₁₁₂= 93 mm, outer diameter of center pole 114, third permanent magnet 122, and fourth yoke 127: D₁₂₂= 75 mm, thickness of first yoke 111: L₁₁₁= 60 mm, center pole 114 thickness: L₁₁₄= 105 mm and the thickness of the first permanent magnet 112: L₁₁₂= 50 mm, thickness of second yoke 113: L₁₁₃= 55 mm, the thickness of the second and third permanent magnets 115 and 122: L₁₁₅= 25 mm, thickness of third and fourth yokes 116 and 127: L₁₁₆= 20mm, outer diameter of tapered part 114a: D_114a= 93mm, taper 114a thickness: L_114a= 20 mm and configured. The first, second, and third permanent magnets 112, 115, and 122 are all R-Fe-B anisotropic sintered magnets (R is at least one rare earth element mainly composed of Nd, Hitachi Metals HS-46CH) was used. The first, second, and third yokes 111, 113, and 116, and the center pole 114 are all made of JISG3101 general structural rolled steel SS400.
In the speaker magnetic circuit of FIG. 4 configured as described above, the air gap magnetic flux density along the axial direction x of the magnetic gap 117 was measured from the radial center position O of the magnetic gap 117 (the lower end position of the magnetic gap 117). . The results are shown in Example 3-1 in FIG. FIG. 5 shows that a gap magnetic flux density higher than 1.35 T higher than that in Example 2 was obtained.
[0021]
The reason why such a high air gap magnetic flux density is obtained is that, in the second embodiment shown in FIG. 3, when the main magnetic flux 63 flows from the center pole 54 to the first yoke 51, the magnetic flux is generated at the junction, particularly at the air gap 58 side. concentrate. For this reason, the member in this portion is magnetically saturated and the magnetic resistance is increased. In contrast, in the present embodiment, when the main magnetic flux 123 flows from the center pole 114 to the first yoke 111, it can flow through the tapered portion 114a, and the main magnetic flux 123 can go to the first permanent magnet 112 through a shortcut. It is considered that the magnetic saturation phenomenon is alleviated, the magnetic resistance is reduced, the magnetic loss is reduced, and as a result, the gap magnetic flux density of the magnetic gap 117 is increased. In addition, the connection by the round part connected with the circular arc instead of the taper part may be sufficient.
[0022]
(Conventional example)
The speaker magnetic circuit shown in FIG. 7 has substantially the same structure as the conventional speaker magnetic circuit of FIG. The speaker magnetic circuit of FIG. 7 has the same outer diameter as the first yoke 91, the first permanent magnet 92, the second yoke 93, the second permanent magnet 95, and the third yoke 96: D₉₁= 173 mm, the inner diameter of the first permanent magnet 92, the second yoke 93, the second permanent magnet 95, and the third yoke 96: D₉₆= 93 mm, outer diameter of center pole 94: D₉₄= 75 mm, thickness of first yoke 91: L₉₁= 30 mm, center pole 94 thickness: L₉₄= 102.5mm, thickness of first permanent magnet 92: L₉₂= 25 mm, thickness of second yoke 93: L₉₃= 27.5mm, thickness of second permanent magnet 95: L₉₅= 25 mm, thickness of third yoke 96: L₉₆= 25 mm and configured. Each of the first and second permanent magnets 92 and 95 is an R-Fe-B anisotropic sintered magnet (R is at least one rare earth element mainly composed of Nd, manufactured by Hitachi Metals, Ltd. HS-46CH) was used. The first, second, and third yokes 91, 93, 96, and the center pole 94 are all made of JISG3101 general structural rolled steel SS400.
In the speaker magnetic circuit of FIG. 7 configured as described above, the air gap magnetic flux density along the axial direction x of the magnetic gap 97 was measured from the radial center position O of the magnetic gap 97 (the lower end position of the magnetic gap 97). . The results are shown in the conventional example in FIG. FIG. 5 shows that the gap magnetic flux density is lower than in Examples 1 and 2.
[0023]
(Comparative example)
The speaker magnetic circuit of the comparative example shown in FIG. 6 includes the outer diameters of the first yoke 71, the first permanent magnet 72, the second yoke 73, and the third permanent magnet 75: D₇₁= 173 mm, the inner diameter of the first permanent magnet 72, the second yoke 73, and the third permanent magnet 75: D₇₅= 93 mm, outer diameters of the second permanent magnet 89, the third yoke 74, and the fourth permanent magnet 82: D₈₂= 75 mm, thickness of first yoke 71: L₇₁= 30 mm, thickness of first and second permanent magnets 72 and 89: L₇₂= 25 mm, thickness of second and third yokes 73 and 74: L₇₃= 27.5mm, thickness of third and fourth permanent magnets 75 and 82: L₇₅= 25 mm and configured. The first, second, third and fourth permanent magnets 72, 89, 75 and 82 are all R-Fe-B anisotropic sintered magnets (R is at least one rare earth element mainly composed of Nd). And HS-46CH manufactured by Hitachi Metals, Ltd. was used. The first, second and third yokes 71, 73 and 74 were all made of JISG3101 general structural rolled steel SS400.
In the speaker magnetic circuit of FIG. 6 configured as described above, the air gap magnetic flux density along the axial direction x of the magnetic gap 77 was measured from the radial center position O of the magnetic gap 77 (the lower end position of the magnetic gap 77). . The results are shown in the comparative example in FIG. FIG. 5 shows that the gap magnetic flux density of the comparative example is lower than that of Examples 1 and 2.
[0024]
The reason for this will be described below. The difference between the two examples and the comparative example is that the center poles 4 and 54 are entirely composed of SS400 in both examples, but in the comparative example, the portion corresponding to the center poles 4 and 54 (hereinafter referred to as the center poles 4 and 54). A part of which is described as “center pole portion” is composed of the second permanent magnet 89. Therefore, when comparing the magnetic characteristics with respect to this point, the saturation magnetization of SS400 is about 2.0T, while the magnetic flux generation amount of the second permanent magnet, that is, the residual magnetic flux density is about 1.3T at most. . Here, the amount of magnetic flux generated by the first permanent magnet is Φ1, the axial sectional area of the first permanent magnet is S1, the amount of magnetic flux flowing through the center pole 4, 54 or the center pole portion is Φ2, the center pole 4, 54 or If the axial cross-sectional area of the center pole is S2, Φ1 passes through the first yoke and concentrates on the center pole 4, 54 or the center pole, so that Φ2 = Φ1 x S1 ÷ S2 (however, leakage and magnetic saturation are Since the first yoke is arranged outside the center pole 4, 54 or the center pole, S1 is much larger than S2, so the value of Φ2 is also large. When it becomes a large speaker, it becomes more than the residual magnetic flux density of the second permanent magnet, and the magnetic resistance is increased. For this reason, when a part of center pole part is comprised with the 2nd permanent magnet like a comparative example, a magnetic resistance will increase and a space | gap part magnetic flux density will fall. On the contrary, when a center pole composed of SS400 having a saturation magnetization higher than the residual magnetic flux density of the second permanent magnet is provided as in both embodiments, the magnetic resistance in the center pole is reduced, so that a high gap portion Magnetic flux density can be obtained.
[0025]
From the examination results of Examples 1 and 2 (the magnetic circuit for the speaker in FIGS. 1 and 3) and the examination result of the comparative example (the magnetic circuit for the speaker in FIG. 6), at least part of the center pole is made of a ferromagnetic material and the ferromagnetic It has been found that replacing with a permanent magnet having a residual magnetic flux density lower than that of the material increases the magnetic resistance and decreases the gap magnetic flux density.
From the examination result of Example 2 (speaker magnetic circuit of FIG. 3) and the examination result of Example 3-1 (speaker magnetic circuit of FIG. 4), the first of the center pole 54 of the speaker magnetic circuit of FIG. In the speaker magnetic circuit of FIG. 4 in which the taper portion is provided on the joint surface with the yoke 51, the magnetic resistance is reduced and the gap magnetic flux density is increased.
[0026]
In each of the above embodiments, the case where JISG3101 rolled steel for general structure SS400 is used as the ferromagnetic material constituting the center pole and each yoke is not particularly limited. For example, electromagnetic waves having higher saturation magnetization than SS400 are described. It is preferable to use a material because a large amount of magnetic flux can flow. As an example of the electromagnetic material, an iron-cobalt soft magnetic material YEP27CO manufactured by Hitachi Metals Co., Ltd. and the magnetic pole circuit center pole and each yoke shown in FIG. An iron-cobalt-vanadium soft magnetic material YEP-2V manufactured by the company was used to construct the center pole and each yoke of the speaker magnetic circuit of FIG. FIG. 5 shows the result of measuring the gap magnetic flux density along the axial direction x of the magnetic gap 117 from the radial center position O of the magnetic gap 117 (the lower end position of the magnetic gap 117). As can be seen from the figure, the magnetic flux density in the gap portion was increased by about 2% in Example 3-2 and about 3% in Example 3-3.
[0027]
In the said Example, although the case where the R-Fe-B type anisotropic sintered magnet was used as a permanent magnet was described, it does not specifically limit, A well-known permanent magnet can be used.
In the first and second embodiments, the outer diameter, the inner diameter, and the thickness of each ring-shaped permanent magnet and each ring-shaped yoke are the same, and the outer diameters of the center pole and the disk-shaped permanent magnet are the same. Although described, it is not limited to these. For example, in FIG. 1, the outer diameter of the first yoke 1 can be arbitrarily made larger or smaller than the outer diameter of the first permanent magnet 2. It is also optional to make the outer diameter of the second yoke 3 in FIG. 1 larger or smaller than the outer diameter of the first permanent magnet 2.
[0028]
Although the case where the first yoke and the center pole are separate from each other has been described in the above embodiment, the present invention includes a case where the first yoke and the center pole are integrally formed.
[0029]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a speaker magnetic circuit that significantly increases the magnetic flux density of the magnetic gap without increasing the size, weight, and cost of the speaker. .
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an aspect of a magnetic circuit for a speaker according to the present invention.
[Figure 2]Magnetic circuit for speaker of reference exampleIt is a longitudinal cross-sectional view which shows the aspect of.
FIG. 3 shows a speaker magnetic circuit according to the present invention.otherIt is a longitudinal cross-sectional view which shows an aspect.
FIG. 4 is a longitudinal sectional view showing still another embodiment of the speaker magnetic circuit of the present invention.
FIG. 5 is a diagram illustrating an example of a correlation between a measurement position x in a magnetic gap and a gap magnetic flux density.
FIG. 6 is a cross-sectional view showing a mode of a magnetic circuit for a speaker of a comparative example.
FIG. 7 is a cross-sectional view showing an aspect of a conventional speaker magnetic circuit.
FIG. 8 is a longitudinal sectional view showing a conventional speaker.

Claims (3)

A first yoke formed into a disk shape from a ferromagnetic material;
A ring-shaped first permanent magnet disposed in front of the first yoke, the thickness direction being the magnetization direction;
A second yoke formed in a ring shape from a ferromagnetic material and disposed in front of the first permanent magnet;
A ring-shaped second permanent magnet in which the thickness direction is a magnetization direction and magnetic poles having opposite polarities to the first permanent magnet are formed on the front surface portion and the rear surface portion, and disposed on the front surface of the second yoke. When,
A center pole formed in a cylindrical shape from a ferromagnetic material, disposed on the front surface of the first yoke, and opposed to the inner peripheral surfaces of the first permanent magnet and the second yoke via a gap;
The thickness direction is the magnetization direction, and magnetic poles having opposite polarities to those of the second permanent magnet are formed on the front surface portion and the rear surface portion. The magnetic poles are disposed on the front surface of the center pole, and the inner peripheral surface of the second permanent magnet A speaker magnetic circuit, comprising: a third permanent magnet facing through a gap. A first yoke formed into a disk shape from a ferromagnetic material;
A ring-shaped first permanent magnet disposed in front of the first yoke, the thickness direction being the magnetization direction;
A second yoke formed in a ring shape from a ferromagnetic material and disposed in front of the first permanent magnet;
A ring-shaped second permanent magnet in which the thickness direction is a magnetization direction and magnetic poles having opposite polarities to the first permanent magnet are formed on the front surface portion and the rear surface portion, and disposed on the front surface of the second yoke. When,
A third yoke formed in a ring shape from a ferromagnetic material and disposed in front of the second permanent magnet;
A center pole formed in a cylindrical shape from a ferromagnetic material, disposed on the front surface of the first yoke, and opposed to the inner peripheral surfaces of the first permanent magnet and the second yoke via a gap;
The thickness direction is the magnetization direction, and magnetic poles having opposite polarities to those of the second permanent magnet are formed on the front surface portion and the rear surface portion. The magnetic poles are disposed on the front surface of the center pole, and the inner peripheral surface of the second permanent magnet A third permanent magnet facing through the gap;
It is formed in a disk shape with a ferromagnetic material, and is provided on the front surface of the third permanent magnet, and includes a fourth yoke facing the inner peripheral surface of the third yoke with a gap interposed therebetween. Magnetic circuit for speaker. 3. The speaker magnetic circuit according to claim 1, wherein a connecting portion between the first yoke and the center pole is connected by a taper surface or a round surface.

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