Speaker and method of manufacturing the same

Abstract

 A magnet 200 having different polar surfaces respectively at the inner surface and the outer surface thereof is placed on a table 610 of an assembly jig 600 in such a way that a gap aligning section 620 of the assembly jig 600 engages the inside of the magnet 200. A diaphragm 400 provided with a voice coil 500 that is wound around the outer surface of its substantially cylindrical rising wall in advance is mounted on the assembly jig 600 such that the outer surface of the voice coil 500 engages the inner surface of the gap aligning section 620 and a pinched section 440 of the peripheral edge of the diaphragm 400 is bonded to the magnet 200. An outer shell 310 of a magnetic body 300 is made to engage an outer yoke 230 of the magnet 200 at an end thereof while the pinched section 440 is being pinched and bonded. The operation of assembling a speaker 100 is completed when the assembly jig 600 is removed. Since a magnetic body 300 covers an edge section 430 and partly found within the voice coil 500 to that the speaker 100 can be made to show a low profile with ease and the manufacturing productivity can be improved.

Description

[0001] The present invention relates to a speaker adapted to emit sound by vibrating a diaphragm by a voice coil arranged in a magnetic circuit.

[0002] Conventional speakers can be classified into two types, the inner magnet type and the outer magnet type. As described, for instance, in Japanese Patent Laid-Open Publication No. Sho 58-53299 (see, p.3, upper left column - p.4, lower right column, FIGS. 3 and 6), a speaker of the inner magnet type has a magnet arranged between a substantially dish-shaped yoke that is made of a magnetic material and a disk-shaped top plate and a cylindrical voice coil arranged integrally with one of the surfaces of the diaphragm in the magnetic gap between the peripheral edge of the yoke and that of the top plate so as to be axially movable. A speaker of the outer magnet type, on the other hand, has a ring-shaped magnet arranged between a flange section projecting outward from an axial end of the substantially cylindrical center pole of a yoke and a ring-shaped top plate arranged vis-à-vis the flange section and a cylindrical voice coil arranged integrally with one of the surfaces of the diaphragm in the magnetic gap between the outer peripheral surface of the center pole of the yoke and the inner peripheral surface of the top plate so as to be axially movable.

[0003] Meanwhile, cellular phones, PHSs (Personal Handyphone Systems), PDAs (Personal Digital Assistants), notebook personal computers and other electric equipment have become very popular and hence there is an increasingly large demand for compact and lightweight speakers to be used in them.

[0004] In view of the above identified circumstances, it is therefore an object of the present invention to provide a speaker that can easily be made to show a low profile and a method of manufacturing such a speaker.

[0005] A speaker according to an aspect of the present invention comprises: a magnet; a diaphragm having a vibratory section and an edge section arranged along the peripheral edge of the vibratory section; a voice coil arranged integrally with the diaphragm; and a magnetic body having a part aligning and holding the peripheral edge of the diaphragm, a part continuing from one of the magnetic polar surfaces of the magnet, a part covering the edge section of the diaphragm and a part extending to the inner peripheral side of the voice coil to form a magnetic gap having a predetermined distance in the radial direction of the magnet and axially movably containing the voice coil, a magnetic circuit being formed so as to start from the magnet and return to the magnet via the magnetic gap. Note that the axial direction as used herein refers to a direction perpendicular to the surface plane of the diaphragm in which the height of the speaker is observed.

[0006] A method of manufacturing a speaker according to another aspect of the present invention, comprising: bringing in an assembly jig having a substantially plate-shaped table with a profile substantially matching that of a diaphragm and a substantially closed gap aligning section arranged on one of the surfaces of the table; placing a magnet on the table so as to make the gap aligning section of the assembly jig engage the inside of the magnet; placing the peripheral edge of the diaphragm on the magnet so as to make the voice coil engage the gap aligning section of the assembly jig carrying the magnet; coupling a magnetic body to the magnet so as to pinch the peripheral edge of the diaphragm between the magnet and the magnetic body; and removing the assembly jig from the side opposite to the side of coupling the magnetic body and the magnet.

[0007] A method of manufacturing a speaker according to still another aspect of the present invention, comprising: bringing in an assembly jig having a substantially plate-shaped table and a substantially closed gap aligning section arranged on one of the surfaces of the table and having a predetermined diameter and a predetermined thickness as viewed along the plane of the table; placing a magnet on the table so as to make the gap aligning section of the assembly jig engage the inside of the magnet; mounting on the assembly jig carrying the magnet a diaphragm having a vibratory section provided with a voice coil and an edge section arranged along the peripheral edge of the vibratory section on the gap aligning section so as to make the voice coil engage the gap aligning section while placing the peripheral edge on the magnet; coupling a magnetic body to the magnet placed on the assembly jig so as to pinch the peripheral edge of the diaphragm between the magnet and the magnetic body, while covering the edge section of the diaphragm and partly being located within the inner surface of the voice coil; and removing the assembly jig from the side opposite to the side of coupling the magnetic body and the magnet.

In the Drawings;

[0008] 

FIG. 1 is a schematic plan view showing a speaker of a first embodiment according to the present invention;

FIG. 2 is a schematic lateral view showing the speaker of the first embodiment;

FIG. 3 is a schematic cross sectional view showing the speaker of the first embodiment;

FIGS. 4A through 4D are schematic illustrations showing the operation of assembling the speaker of the first embodiment;

FIG. 5 is a schematic cross sectional view showing a speaker of a second embodiment according to the present invention;

FIG. 6 is a schematic plan view showing a speaker of a third embodiment according to the present invention;

FIG. 7 is a schematic cross sectional view showing the speaker of the third embodiment;

FIG. 8 is a schematic plan view showing a speaker of a fourth embodiment according to the present invention;

FIG. 9 is a schematic cross sectional view showing the speaker of the fourth embodiment according to the present invention;

FIG. 10 is another cross sectional view showing the speaker of the fourth embodiment according to the present invention;

FIG. 11 is a schematic cross sectional view showing a speaker of another embodiment according to the present invention;

FIG. 12 is a schematic cross sectional view showing a speaker of still another embodiment according to the present invention; and

FIG. 13 is a schematic cross sectional view showing a speaker of a further embodiment according to the present invention.

[0009] Now, the first embodiment of a speaker according to the present invention will be described by referring to the accompanying drawings. While this embodiment is described in terms of a small-size speaker, the embodiment is not limited thereto.

[1st Embodiment]

(Configuration of speaker)

[0010] FIG. 1 is a schematic plan view of a speaker. FIG. 2 is a schematic lateral view of the speaker. FIG. 3 is a schematic cross sectional view of the speaker. In FIGS. 1 through 3, reference symbol 100 denotes a speaker, which is a small-size speaker adapted to be used in a cellular phone, a PHS (Personal Handyphone System), a PDA (Personal Digital Assistant) or a notebook personal computer, although it may most suitably be used in a cellular phone. It outputs voices according to voice signals. The speaker 100 has a magnet unit 200, a magnetic body 300, a diaphragm 400 and a voice coil 500.

[0011] The magnet unit 200 has a magnet main body 210, an inner yoke 220 and an outer yoke 230. The magnet main body 210 is made of a magnetic material and shows a substantially ring-shaped profile so as to have opposite magnetic poles respectively at the inner surface and at the outer surface thereof. More specifically, the magnet main body 210 is so magnetized that it has the N-pole on the inner surface and the S-pole on the outer surface thereof. The magnet unit 200 and the magnetic body 300 form a magnetic circuit.

[0012] The inner yoke 220 is made of a magnetic material such as a steel plate containing iron as principal ingredient and shows a substantially ring-shaped profile. The inner yoke 220 has an axial dimension substantially the same as or slightly greater than that of the magnet main body 210 and rigidly engages the inner surface of the magnet main body 210 in an axially slightly offset state such that one of its axial end facets is flush with the corresponding end facet of the magnet main body 210. The inner yoke 220 may alternatively be bonded to the magnet main body 210 by an adhesive agent so as to become integral with the magnet main body 210.

[0013] Like the inner yoke 220, the outer yoke 230 is also made of a magnetic material and shows a substantially ring-shaped profile. The outer yoke 230 has an outer-periphery-engaging section 231 having an inner diameter substantially the same as the outer diameter of the magnet main body 210. An outwardly projecting sword-guard-like flange section 232 is formed at an axial end of and integrally with the outer-periphery-engaging section 231. In other words, the outer-periphery-engaging section 231 is extended bent outward to form the flange section 232. Then, a cylindrical aligning-engaging section 233 is formed on the outer peripheral edge of and integrally with the flange section 232. In other words, the flange section 232 is extended and bent upward to form the aligning-engaging section 233. Thus, the outer-periphery-engaging section 231, the flange section 232 and the aligning-engaging section 233 are coaxial relative to each other. The inner surface of the outer yoke 230 is fitted to and rigidly engaged with the magnet main body 210 in such a way that the axial end of the outer yoke 230 located opposite to the end where the flange section 232 is formed is flush with or slightly displaced from the corresponding axial end of the magnet main body 210 to produce the assembled magnet unit 200. The unit 200 has one of its polar surfaces, or its N-pole, along the inner surface of the inner yoke 220. The outer yoke 230 may alternatively be bonded to the magnet main body 210 by an adhesive agent so as to become integral with the main body 210.

[0014] Like the inner yoke 220 and the outer yoke 230, the magnetic body 300 is made of a magnetic material and shows a substantially ring-shaped profile. The magnetic body 300 has a substantially cylindrical outer shell 310 that has an outer diameter substantially the same as the inner diameter of the aligning-engaging section 233 of the outer yoke 230 and operates as outer frame section. An inwardly-curved bridge section 320 is formed at an axial end of and integrally with the outer shell 310. In other words, the bridge section 320 is extended and inwardly curved from the outer shell 310. An inner shell 330 is formed at the inner peripheral edge of and integrally with the bridge section 320 and operates as inner frame section. In other words, the inner shell 330 is extended and downwardly curved from the inner peripheral edge of the bridge section 320 in such a way that its outer diameter is smaller than the inner diameter of the inner yoke 220 of the magnet unit 200 by a predetermined value. The bridge section 320 may be provided with a plurality of substantially circular through holes 321.

[0015] The magnetic body 300 abuts the flange section 232 of the outer yoke 230 at the end facet of the outer shell 310 located opposite to the bridge section 320 and the outer shell 310 is bonded to the aligning-engaging section 233 of the outer yoke 230 of the magnet unit 200 typically by an adhesive agent so as to be linked to the section 233. However, the outer shell 310 may alternatively be bonded to the aligning-engaging section 233 by claws formed by cutting partly into the outer shell 310 and bending the cut parts upwardly so that they may become engaged with their counterpart of the aligning-engaging section 233 or by welding. The outer surface of the inner shell 330 of the magnetic body 300 is located vis-à-vis the inner surface of the inner yoke 220 with a magnetic gap G of a predetermined length disposed between them and the magnet unit 200 has one of its polar surfaces, or its S-pole, along the outer surface of the inner shell 330 to form a magnetic circuit when the magnetic body 300 is linked to the outer yoke 230 of the magnet unit 200.

[0016] The diaphragm 400 is formed substantially as thin film of magnesium foil or resin thin film with its surface treated for anti-corrosion and has a curved vibratory section 410 located substantially at the center of the diaphragm 400. A substantially cylindrical rising section 420 is formed at the outer peripheral edge of and integrally with the vibratory section 410. In other words, the rising section 420 is located opposite relative to the curved central part of the vibratory section 410. The rising section 420 has an inner diameter greater than the outer diameter of the inner shell 330 of the magnetic body and an outer diameter smaller than the inner diameter of the inner yoke 220 of the magnet unit 200. An arch-shaped edge section 430 is formed at an axial end of and integrally with the rising section 420. More specifically, the edge section 430 is curved in the sense of curvature of the vibratory section 410 and outwardly extended from the rising section 420. An outwardly projecting sword-guard-like pinched section 440 is formed at the outer peripheral edge of and integrally with the edge section 430. The diaphragm 400 has a diameter substantially the same as the inner diameter of the aligning-engaging section 233 of the outer yoke 230 of the magnet unit 200. The width of the pinched section 440 in radial directions is substantially the same as the thickness of the outer shell 310 of the magnetic body 300. Note that the vibratory section 410, the edge section 430 and the rising section 420 may be formed as separate parts. Alternatively, the vibratory section 410 and the rising section 420 may be made integral with each other or the edge section 430 and the rising section 420 may be made integral with each other.

[0017] When the magnetic body 300 is linked to the magnet unit 200, the diaphragm 400 is assembled with them as the pinched section 440 is aligned with the magnetic body 300 and pinched between the flange section 232 of the outer yoke 230 of the magnet unit 200 and the corresponding end of the outer shell 310 of the magnetic body 300. Once the diaphragm 400 is mounted in position, the rising section 420 becomes axially movable between the inner yoke 220 of the magnet unit 200 and the inner shell 330 of the magnetic body 300 without contacting them and the vibratory section 410 is located within the inner surface of the inner shell 330 of the magnetic body 300.

[0018] The voice coil 500 is formed by, for example, directly winding a wire around the outer surface of the rising section 420 of the diaphragm 400. It may be securely held in position typically by an adhesive agent. The opposite ends of the wire are lead out to the lower side of FIG. 2 that is opposite to the side where magnetic body 300 is linked to form a voice signal input terminal. The voice coil may be secured to the inner surface of the rising section 420.

(Operation of assembling the speaker)

[0019] Now, the operation of assembling the speaker 100 will be described below by referring to FIGS. 4A through 4D. FIG. 4A illustrates how the inner yoke 220 and the outer yoke 230 of the magnet main body 210 are aligned with each other. FIG. 4B illustrates how the diaphragm 400 is placed in position. FIG. 4C illustrates how the magnetic body 300 is assembled with other components. FIG. 4D illustrates the completely assembled speaker 100.

[0020] Firstly, an assembly jig 600 that is prepared in advance is brought to a predetermined assembling position. Referring to FIGS. 4A through 4D, the assembly jig 600 is typically made of synthetic resin and has a substantially circular table 610. A substantially cylindrical gap aligning section 620 that is coaxial with the table 610 is projecting from one of the surfaces of the table 610. The gap aligning section 620 may be provided with a plurality of axially extending notches 621 that divide the gap aligning section 620 in a plurality of sections.

[0021] As shown in FIG. 4A, the magnet unit 200 that is assembled on the assembly jig 600 in advance is placed on the table 610 such that the gap aligning section 620 engages the inner surface of the magnet unit 200. Thereafter, an adhesive agent (not shown) is applied to the top surface of the flange section 232 of the outer yoke 230 of the magnet unit 200 that is placed on the table 610.

[0022] Additionally, as shown in FIG. 4B, the rising section 420 of the diaphragm 400 around which the voice coil 500 is arranged in advance is put into the gap aligning section 620 such that the rising section 420 engages the inner surface of the gap aligning section 620. At this time, since the gap aligning section 620 is provided with a plurality of notches 621, the friction that arises there is relatively reduced and the rising section 420 and the gap aligning section 620 come relatively easily into engagement with each other. Then, the pinched section 440 that forms the periphery of the diaphragm 400 is engaged with the aligning-engaging section 233 of the outer yoke 230 of the magnet unit 200 and laid on the flange section 232. The pinched section 440 is bonded to the flange section 232 by the adhesive agent that is applied to them in advance.

[0023] Subsequently, as shown in FIG. 4C, the lower end of the outer shell 310 of the magnetic body 300 is brought into engagement with the aligning-engaging section 233 of the outer yoke 230 of the magnet unit 200, while it is pushed downward until it comes to abut the pinched section 440 of the diaphragm 400 on the flange unit 232 so that the pinched section 440 of the diaphragm 400 comes to be pinched between the flange section 232 and the outer shell 310. Then, in this state, the flange section 232 and the outer shell 310 are bonded to each other by the adhesive agent that is applied to them in advance.

[0024] Then, as shown in FIG. 4D, the gap aligning section 620 is pulled out from the gap between the magnet unit 200 and the voice coil 500 of the diaphragm 400 to remove the assembly jig 600 from the side of the assembly opposite to the side where the magnetic body 300 is bonded to complete the assembly operation of the speaker 100.

(Effects and advantages of the speaker)

[0025] As described above in detail, the speaker 100 of the first embodiment is assembled by aligning and holding the pinched section 440 at the periphery of the diaphragm 400 that is integral with the voice coil 500, rigidly linking the outer shell 310 of the magnetic body 300 to one of the polar surfaces of the magnet unit 200 via the outer yoke 230 of the magnet unit 200 and covering the edge section 430 of the diaphragm 400 with the bridge section 320 inwardly extended from the outer shell 310 of the magnetic body 300 so as to arrange the inner shell 330 of the magnetic body 300 extended from the bridge section 320 vis-à-vis the inner surface of the voice coil 500 and form a magnetic gap G in the radial direction of the magnet unit 200 in order to make the voice coil 500 axially movable and form a magnetic circuit. With this arrangement, the dome-like magnetic body 300 comes into the inner surface side of the voice coil 500 so as to be located between the voice coil 500 and the outer surface of the diaphragm 400 and cover the outer surface of the edge section 430. Thus, the magnet unit 200 is located at the outer surface side of the voice coil 500. Because the amplitude of the diaphragm 400 is relatively small when the diaphragm 400 is applied to a portable electric device, the vibratory section 410 can vibrate and voice satisfactorily if the distance between the edge section 430 and the magnetic body 300 is reduced so that it is possible to thin the thickness and realize a low profile speaker easily. Additionally, since the dome-like magnetic body 300 is located on the voicing outer surface side of the speaker, the speaker can be provided with specific acoustic characteristic features such as horn effect and pipe resonance without using any additional members when the inner shell 330 is made to show a particularly designed profile. Then, the versatility will be dramatically broadened.

[0026] The diaphragm 400 is provided with a substantially cylindrical rising section 420 that is integrally extended from the vibratory section 410 and the edge section 430 is integrally extended from the periphery of the rising section 420. With this arrangement, the voice coil 500 can be directly wound around the outer surface of the rising section 420 of the diaphragm 400 to improve the productivity of manufacturing the speaker. Additionally, the voice coil 500 can be made integral with the diaphragm 400 to eliminate the need of using a bobbin for winding the voice coil 500. Thus, the entire structure can be simplified and the speaker can be made compact and lightweight to reduce the manufacturing cost. Still additionally, due to the provision of the rising section 420, the magnetic body 300 can be arranged at the inside of the voice coil 500 without difficulty so that the speaker can be made to show a low profile without requiring the diaphragm 400 and the magnetic body 300 to show a complex profile so as to further improve the productivity. The voice coil 500 may be wound in advance and bonded to the inner surface of the rising section 420 by an appropriate securing member such as an adhesive agent.

[0027] Furthermore, the pinched section 440 is integrally arranged along the outer periphery of the edge section of the diaphragm 400 so as to project outward like a sword-guard and become pinched between the outer shell 310 and the outer yoke 230 of the magnet unit 200 for the purpose of alignment and positional security. With this arrangement, the magnetic body 300 can align and hold the diaphragm 400 in position with ease. In other words, the diaphragm 400 can be aligned and held in position with ease as the pinched section 440 is pinched between the outer shell 310 and the outer yoke 230 of the magnet unit 200 with a simple arrangement to further improve the productivity.

[0028] Additionally, since the diaphragm 400 is pinched at the peripheral part thereof between an end facet of the outer shell 310 of the magnetic body 300 and the outer yoke of the magnet unit 200. The diaphragm 400 can be aligned and held in position without increasing the radial dimension of the speaker to make the speaker apt to be downsized.

[0029] Since the radial dimension of the diaphragm 400 is made substantially equal to the inner diameter of the aligning-engaging section 233 of the outer yoke 230 of the magnet unit 200, the diaphragm 400 can be aligned with ease and the voice coil 500 can be placed easily in position in the magnetic gap G for alignment without providing any additional members such as alignment bosses to further simplify the entire structure and improve the manufacturing productivity.

[0030] Additionally, the inner yoke 220 is integrally held in engagement with the inner surface of the ring-shaped magnet main body 210 that has different poles in radial directions respectively on the outer surface and the inner surface thereof and the outer yoke 230 is integrally held in engagement with the outer surface of the magnet main body 210 to establish a magnetic circuit before the magnetic body 300 is fitted to the magnet unit 200. With this arrangement, diaphragm 400 is aligned simply by pinching the periphery of the diaphragm 400 between the magnetic body 300 and the outer yoke 230 to improve the productivity and a magnetic gap G is formed simply and easily as the magnetic body 300 is arranged at the inner surface side of the voice coil 500 so as to form a magnetic circuit there.

[0031] Furthermore, the magnetic body 300 is so configured that it covers one of the magnetic polar surfaces of the magnet unit 200 and continuously the edge section 430 of the diaphragm 400 and comes to the inside of the voice coil 500 and the inner end of the outer shell 310 that is bonded to the outer yoke 230 of the magnet unit 200 and the corresponding outer end of the inner shell 330 whose diameter is smaller than that of the outer shell 310 and outer surface is arranged vis-à-vis the voice coil 500 are linked to each other by way of the bridge section 320 that covers the edge section 430 of the diaphragm 400. With this arrangement, the magnetic section 300 is made to show a simple profile and can be prepared with easy by press-molding a steel plate or the like to improve the productivity and make the speaker show a low profile.

[0032] Additionally, the outer yoke 230 of the magnet unit 200 is provided with an aligning-engaging section 233 so that the magnetic body 300 is coaxially arranged relative to the magnet unit 200 when it is linked to the magnetic body 300. With this arrangement, the speaker can be assembled with ease to produce a predetermined magnetic gap G. and improve the manufacturing productivity. Furthermore, the diaphragm 400 can also be aligned by this aligning-engaging section 233 to further simplify the overall configuration and improve the productivity.

[0033] Finally, the bridge section 320 that is arranged vis-à-vis the edge section 430 of the diaphragm 400 is provided with through holes 321. With this arrangement, air in the space defined by the bridge section 320 and the edge section 430 communicates with the external space through the through holes 321. Thus, when the edge section 430 of the diaphragm 400 vibrates as the voice coil 500 is moved in an interlocked manner for the purpose of voicing, the air pressure between the bridge section 320 and the edge section 430 is appropriately raised or reduced to limit the vibrations of the edge section 430 and optimize the vibrations of the diaphragm 400 to improve the effect of reproducing and outputting the input sound signal.

[2nd Embodiment]

[0034] Now, the second embodiment of a speaker according to the present invention will be described by referring to FIG. 5. The second embodiment of FIG. 5 is obtained by modifying the direction of magnetization of the magnet unit 200 of the first embodiment. FIG. 5 is a schematic cross sectional view of a speaker of the second embodiment. Note that, the components of the second embodiment and those of the third embodiment, which will be described hereinafter, that are the same as or similar to those of the first embodiment are denoted respectively by the same reference symbols and will not be described further.

(Configuration of speaker)

[0035] Referring to FIG. 5, reference symbol 700 denotes the speaker of this embodiment. The speaker 700 has a magnet unit 800, a magnetic body 900, a diaphragm 400 and a voice coil 500, the diaphragm 400 and the voice coil 500 being identical with their counterparts of the first embodiment.

[0036] The magnet unit 800 has a magnet main body 810, a coupling yoke 820 and a pole forming yoke 830. The magnet main body 810 is made of a magnetic material and shows a substantially ring-shaped profile so as to have opposite magnetic poles respectively at the axially opposite surfaces thereof. More specifically, the magnet main body 810 may be so magnetized that it has the N-pole on the upper surface in FIG. 5 and the S-pole on the lower surface thereof in FIG. 5.

[0037] The coupling yoke 820 is made of a magnetic material such as a steel plate containing iron as principal ingredient and shows a substantially ring-shaped profile. The coupling yoke 820 has an inner diameter and an outer diameter substantially the same as those of the magnet main body 810 and is bonded to the axially upper surface of the magnet main body 810 by an adhesive agent so as to become integral with the main body 810. The inner peripheral surface of the coupling yoke 820 is sloped so as to have a greater inner diameter at one of the axially opposite surfaces. Then, the coupling yoke 820 is bonded to the magnet main body 810 by an adhesive agent so as to become integral with the magnet main body 810 with its inner peripheral surface facing axially upward. In this bonded state, the inner edge of the magnet main body 810 is in contact with the inner edge of the coupling yoke 820 and the inner peripheral surface of the magnet main body 810 and the inner peripheral surface of the coupling yoke 820 define an obtuse angle. When the pinched section 440 is to be held in contact with the magnet main body 810 over a sufficiently large area, the coupling yoke 820 may be omitted and the pinched section 440 may be directly made to abut the magnet main body 810.

[0038] Like the coupling yoke 820, the pole forming yoke 830 is made of a magnetic material and shows a substantially ring-shaped profile. The pole forming yoke 830 has a ring-shaped pinching plate section 831 whose inner diameter and outer diameter are respectively smaller than and substantially the same as the inner diameter and the outer diameter of the magnet main body 810. A substantially cylindrical pole forming section 832 is formed integrally with the pinching plate section 831 by extending and bending the inner peripheral edge of the section 831. Thus, the pole forming section 832 is coaxial with the pinching plate section 831. The axial end facet, or the upper end facet, of the pole forming section 832 is outwardly sloped. The pole forming yoke 830 is placed in position in such a way that its outer peripheral edge is in contact with the corresponding outer peripheral edge of the magnet main body 810. The magnet main body 810 is sandwiched between the pinching plate section 831 and the coupling yoke 820, which are then bonded to the magnet main body 810 by an adhesive agent so as to become integral with the main body 810. In the bonded state, the pole forming section 832 is separated from the inner surface of the magnet main body 810. The distance from the magnet main body 810 and the coupling yoke 820 increases at an upper position of the pole forming section 832 due to the sloped upper end fact thereof. The comer of the pole forming section 832 that faces the magnet main body 810 shows an obtuse angle.

[0039] As shown in FIG. 5, the magnetic body 900 has an outwardly projecting pinching flange section 910 as integral part thereof like the flange section of the outer yoke 230 of the magnetic body 300 of the first embodiment. The pinching flange section 910 is formed in such a way that the outer diameter of the magnetic body 900 is substantially the same as the outer diameter of the magnet unit 800.

[0040] The pinching flange section 910 of the magnetic body 900 is typically bonded to the upper surface of the coupling yoke 820 of the magnet unit 800 by an adhesive agent so as to make the magnetic body 900 integral with the magnet unit 800. However, the pinching flange section 910 may alternatively be bonded to the coupling yoke 820 by claws formed by cutting partly into the pinching flange section 910 and bending the cut parts so that they may become engaged with their counterpart of the coupling yoke 820 or by welding. The outer surface of the inner shell 330 of the magnetic body 900 is located vis-à-vis the inner surface of the pole forming section 832 of the pole forming yoke 830 with a magnetic gap G of a predetermined length disposed between them. With this arrangement, a magnetic pole, or N-pole, is formed on the outer surface of the inner shell 330, while another pole, or S-pole, is formed on the inner surface of the pole forming section 832 to establish a magnetic circuit. Since the inner peripheral surface of the coupling yoke 820 of the magnet unit 800 and the front end facet of the pole forming section 832 of the pole forming yoke 830 are sloped, the risk of the magnetic flux leaking out from the front end of the pole forming section 832 toward the coupling yoke 820 and the magnet main body 810 is minimized.

[0041] The pinched section 440 of the diaphragm 400 of this embodiment is broader than its counterpart of the first embodiment and the diaphragm 400 has a diameter substantially the same as the outer diameter of the magnet unit 800. In other words, the radial length of the pinched section 440 is equal to the outer diameter of the magnetic body 900 less the inner diameter of the outer shell 310 of the magnet body 900. With this arrangement, the position of the outer peripheral surface of the edge section 430 is defined by the inner surface of the outer shell 310 when the magnetic body 900 is bonded to the magnet unit 800.

(Operation of assembling the speaker)

[0042] Now, the operation of assembling the speaker 700 will be described below.

[0043] As in the case of the first embodiment, firstly, an assembly jig 600 that is prepared in advance is brought to a predetermined assembling position. Then, the magnet unit 800 that is assembled on the assembly jig 600 in advance is placed on the table 610 such that the gap aligning section 620 of the assembly jig 600 engages the inner surface of the magnet unit 800. Thereafter, an adhesive agent (not shown) is applied to the top surface of the coupling yoke 820 of the magnet unit 800.

[0044] Thereafter, the rising section 420 of the diaphragm 400 around which the voice coil 500 is arranged in advance is put into the gap aligning section 620 such that the outer surface of the voice coil 500 engages the inner surface of the gap aligning section 620. Then, the pinched section 440 that is the peripheral edge of the diaphragm 400 is laid on the coupling yoke 820 of the magnet unit 800 and bonded to the latter by an adhesive agent that is applied thereto in advance. Subsequently, the adhesive agent is also applied to the upper surface of the pinched section 440.

[0045] Then, the pinching flange section 910 of the magnetic body 900 is laid on the pinched section 440 of the diaphragm 400 that is bonded to the magnet unit 800 such that its outer peripheral edge is flush with the outer peripheral edge of the pinched section 440 and that of the magnet unit 800 and bonded to the pinched section 440 by the adhesive agent that is applied thereto in advance. When bonding the magnetic body 900, the position of the outer peripheral surface of the edge section 430 of the diaphragm 400 is defined by the lower edge of the outer shell 310 of the magnetic body 900. With this arrangement, the voice coil 500 is placed in position between the inner shell 330 and the pole forming section 832 of the magnet unit 800. Thereafter, the assembly jig 600 is removed as in the case of the first embodiment to complete the operation of assembling the speaker 700.

(Effects and advantages of the speaker)

[0046] As described above, like the first embodiment, the speaker 700 of the second embodiment is assembled by bonding the magnetic body 900 to one of the polar surfaces of the magnet unit 800 via the coupling yoke 820 of the magnet unit 800 and covering the edge section 430 of the diaphragm 400 with the magnetic body 900 in such a way that the magnetic body 900 is partly found within the inner surface of the rising section 420. Thus, the speaker of the second embodiment can easily be made to show a low profile as in the case of the first embodiment. Additionally, the speaker can be provided with specific acoustic characteristic features such as horn effect and pipe resonance without using any additional members when the inner shell 330 of the magnetic body 900 is made to show a particularly designed profile. Then, the versatility will be dramatically broadened.

[0047] The magnetic body 900 is provided with a pinching flange section 910 adapted to pinch and securely hold the pinched section 440 of the diaphragm 400 with the magnet unit 800. With this arrangement, the magnetic body 900 can be reliably bonded to establish a desirable magnetic circuit and securely hold the diaphragm 400 in position.

[0048] Additionally, the diaphragm 400 has a diameter substantially the same as the outer diameter of the magnet unit 800. In other words, the radial length of the pinched section 440 is equal to the outer diameter of the magnetic body 900 less the inner diameter of the outer shell 310 of the magnet body 900. With this arrangement, the position of the outer peripheral surface of the edge section 430 is defined by the inner surface of the outer shell 310 when the magnetic body 900 is bonded to the magnet unit 800. Thus, the voice coil 500 can be easily placed in position without requiring any additional arrangement.

[0049] Furthermore, since the outer diameter of the magnetic body 900 is made equal to that of the magnet unit 800, the magnetic body 900 and the magnet unit 800 can be easily arranged so as to be coaxial with each other to improve the manufacturing productivity. Additionally, an appropriate magnetic gap G can be automatically produced simply by seeing the outer peripheral edge of the magnetic body 900 when bonding it to the magnet unit 800 in the assembling operation.

[0050] Additionally, since the inner peripheral surface of the coupling yoke 820 of the magnet unit 800 is sloped, the risk of the magnetic flux leaking out from the pole forming section 832 toward the coupling yoke 820 to establish an excellent magnetic circuit with a simple configuration. Furthermore, since the front end facet of the pole forming section 832 is also sloped, the risk of leakage of the magnetic flux can be prevented further to make the magnetic circuit even more advantageous. Finally, since the inner peripheral edge of the coupling yoke 820 is held in contact with the corresponding inner peripheral edge of the magnet main body 810 when the coupling yoke 820 and the magnet main body 810 are bonded to each other, the comers of the magnet main body 810 are not exposed and the magnetic flux is prevented from leaking from the front end of the pole forming section 832 to the comer of the magnet main body 810 to make the magnetic circuit further advantageous.

[3rd Embodiment]

[0051] Now, the third embodiment of a speaker according to the present invention will be described by referring to FIGS. 6 and 7. The third embodiment of FIG. 6 is obtained by replacing the ring-shaped magnet unit 200 of the above-described first embodiment with rod-shaped magnets. FIG. 6 is a schematic plan view of a speaker of the third embodiment. FIG. 7 is a cross sectional view taken along the dotted chain line A-A in FIG. 6.

(Configuration of speaker)

[0052] Referring to FIG. 6, reference symbol 100A denotes a speaker. The speaker 100A has magnets 200A, a magnetic body 300A, a diaphragm 400A and a voice coil 500A.

[0053] The magnets 200A have respective magnet main bodies 210A, respective inner yokes 220A and a common outer yoke 230A. Each of the magnet main bodies 210A is made of a magnetic material and shows a longitudinally extending rod-shaped profile so as to have opposite magnetic poles respectively at the inner surface (surface facing the center of the speaker 100A) and at the outer surface (surface facing the outside of the speaker 100A) thereof. More specifically, each of the magnet main bodies 210A is so magnetized that it has the N-pole on the inner surface and the S-pole on the outer surface thereof. The magnets 200A and the magnetic body 300A form magnetic circuits.

[0054] Each of the inner yokes 220A is made of a magnetic material such as a steel plate containing iron as principal ingredient and shows a rod-shaped flat profile. The inner yokes 220A have an axial length slightly greater than the axial length of the magnet main bodies 210A and are bonded to the inner surfaces of the respective magnet main bodies 210A by an adhesive agent with their lower axial end facets flush with the corresponding lower surfaces of the magnet main bodies 210A.

[0055] Like the inner yokes 220A, the outer yoke 230A is also made of a magnetic material. The outer yoke 230A has a pair of straight sections 233A disposed opposite to each other and a pair of curved sections 234A that link the straight sections 233A. The outer yoke 230A has an outer securing section 231A that is to be rigidly secured to the magnet main bodies 210A. An outwardly projecting flange section 232A is extended from an axial end of the outer securing section 231 A so as to be integral with the section 231A. The straight sections 233A of the outer yoke 230A is rigidly secured to and assembled with the magnet main bodies 210A in such a way that the axial end facets thereof located opposite to the flange section 232A are flush with the corresponding end facets of the magnet main bodies 210A. Thus, the magnets 200A are integrally assembled. The magnets 200A have polar surfaces, or N-poles, facing the respective inner yokes 220A and polar surfaces, or S-poles, facing the outer yoke 230A. The speaker 100A has a pair of rod-shaped magnets 200A disposed opposite to each other.

[0056] The magnetic body 300A is made of a magnetic material and realized in the form of a pair of rod-shaped members. The magnetic body 300A has a pair of outer frame sections 310A arranged axially above the outer yoke 230A. The lower end of each of the outer frame sections 310A is extended and bent so as to project outward and produce a keep section 311A. In other words, each of the outer frame sections 310A has a keep section 311 A that is integral with it. The upper end of each of the outer frame sections 310A is extended and inwardly curved so as to produce a bridge section 320A. In other words, each of the outer frame sections 310A has a bridge section 320A that is integral with it. A substantially rod-shaped flat inner frame section 330A is formed at the inner peripheral edge of and integrally with each of the bridge sections 320A. In other words, the inner frame section 330A is extended and downwardly curved from the inner peripheral edge of the bridge section 320A so as to be located opposite to the outer frame section 310A. The bridge sections 320A are provided with a plurality of substantially circular through holes 321.

[0057] The magnetic body 300A abuts the flange section 232A of the outer yoke 230A at the keep sections 311 A of the outer frame section 310A and the keep sections 311 A are bonded to the flange section 232A of the outer yoke 230A. However, the outer frame sections 310A may alternatively be bonded to the flange section 232A by claws formed by cutting partly into the outer frame sections 310A and bending the cut parts upwardly so that they may become engaged with their counterpart of the flange sections 232A or by welding. Each of the outer surface of the inner frame sections 330A of the magnetic body 300A is located vis-à-vis the inner surface of the corresponding inner yoke 220A with a magnetic gap G of a predetermined length disposed between them and each of the magnets 200A has one of its polar surfaces, or its S-pole, along the outer surface of the inner frame section 330A to form a magnetic circuit.

[0058] The diaphragm 400A is formed substantially as thin film of magnesium foil or resin thin film with its surface treated for anti-corrosion. The diaphragm 400A is made to show an elliptic profile having longitudinal sides that matches the rod-shaped magnets 200A and the rod-shaped members of the magnetic body 300A. More specifically, the rod-shaped magnets 200A and the rod-shaped members of the magnetic body 300A are arranged along the respective linear edges of the diaphragm 400A. The diaphragm 400A has a curved vibratory section 410A located substantially at the center thereof. A rising section 420A is formed at the peripheral edge of and integrally with the vibratory section 410A. In other words, the rising section 420A is located opposite relative to the curved central part of the vibratory section 410A. The rising section 420A is arranged between the outer surface of each of the inner frame sections 330A and the inner surface of the inner yoke 220A of the corresponding one of the magnets 200A without touching them. An arch-shaped edge section 430A is formed at an axial end of and integrally with the rising section 420A. More specifically, the edge section 430A is curved in the sense of curvature of the vibratory section 410A and outwardly extended from the rising section 420A. An outwardly projecting sword-guard-like pinched section 440A is formed at the outer peripheral edge of and integrally with the edge section 430A. Note that the vibratory section 410A, the edge section 430A and the rising section 420A may be formed as separate parts. Alternatively, the vibratory section 410A and the rising section 420A may be made integral with each other or each of the edge section 430A and the rising section 420A may be made integral with each other.

[0059] The voice coil 500A is formed by directly winding a wire around the outer surface of the rising section 420A of the diaphragm 400A. It may be securely held in position typically by an adhesive agent. The opposite ends of the wire are lead out to the side opposite to the side where the magnetic body 300A is linked to form a voice signal input terminal.

[0060] The diaphragm 400A has a curved part in each of the curved sections 234A of the outer yoke 230A where the magnets 210A are not found. The voice coil 500A has straight parts in the area where the magnet main body 210A and the magnetic body 300A are arranged. The voice coil 500A additionally has curved parts in areas corresponding to the curved sections 234A of the outer yoke 230A. The curved parts of the voice coil 500A have a profile matching that of the rising section 420A of the diaphragm 400A in those areas.

[0061] The pinched section 440A of the diaphragm 400A is pinched and secured in position between the flange section 232A of the outer yoke 230A and the keep section 311A of one of the outer frame sections 310A in the each of the straight sections 233A where the magnet main body 210A and the magnet body 300A are found, while it is secured to the outer yoke 230A by an adhesive agent or the like in the curved areas. Holders or some other fittings may be used to cover the outer yoke 230A and pinch the diaphragm 400A in the curved areas.

(Effects and advantages of the speaker)

[0062] As described above in detail, like the first embodiment, the speaker 100A of the third embodiment of the present invention is assembled by bonding the magnetic body 300A to one of the polar surfaces of the magnets 200A via the common outer yoke 230A of the magnets 200A and covering the edge section 430A of the diaphragm 400A with the magnetic body 300A in such a way that the magnetic body 300A is partly found within the voice coil 500A. Thus, the speaker of the third embodiment can easily be made to show a low profile as in the case of the first embodiment. Additionally, the speaker can be provided with specific acoustic characteristic features such as horn effect and pipe resonance without using any additional members when the inner frame sections 330A is made to show a particularly designed profile.

[0063] Since a pair of rod-shaped magnets 200A are provided in the third embodiment, it can be prepared with ease if compared with a ring-shaped magnet and the cost of preparing the magnets 200A can be held low. Thus, the third embodiment requires less workload and less cost for manufacturing.

[0064] Additionally, the voice coil 500A is formed by winding a wire around the rising section 420A of the diaphragm 400A that has straight parts so that the straight parts of the voice coil 500A can be arranged vis-à-vis the corresponding respective rod-shaped magnets 200A. With this arrangement, the vice coil 500A can always be separated from the polar surfaces of the magnets 200A by a constant distance without being strained to maintain the magnetic circuits in an excellent state.

[0065] Furthermore, since a pair of rod-shaped magnets 200A are arranged opposite to each other, the magnetic circuits produced by the magnets 200A are symmetrical and hence the diaphragm 400A is vibrated symmetrically in a desired manner by the electric signal flowing to the voice coil 500A to reproduce and output an excellent voice signal.

[0066] Finally, the diaphragm 400A has an elliptic profile having longitudinal sides that match the profile of the voice coil 500A and the profile of the magnets 200A and sides that rectangularly intersect the longitudinal sides. With this arrangement, the pinched sections 440A can be dimensioned properly with ease to facilitate the assembling operation.

[4th Embodiment]

[0067] Now, the fourth embodiment of speaker according to the invention will be described by referring to FIGS. 8 through 10. FIG. 8 is a plan view showing the speaker according to the fourth embodiment. FIG. 9 is a cross sectional view taken along the dotted chain line B-B in FIG. 8. FIG. 10 is a cross sectional view taken along the dotted chain line C-C in FIG. 8.

(Configuration of speaker)

[0068] The fourth embodiment is realized by replacing the voice coil in the speaker of the third embodiment with one having a substantially rectangular plan view. Referring to FIG. 8, in the speaker 100B, the voice coil 500B has a rectangular profile and rod-shaped magnets 200A, 200B are arranged at respective positions located vis-à-vis the four sides of the rectangle. In other words, a pair of rod-shaped magnets 200A are arranged vis-à-vis the respective longitudinal sides of the rectangle, while another pair of rod-shaped magnets 200B are arranged vis-à-vis the respective transversal sides of the rectangle. The magnets 200B are arranged at the opposite ends of each of the magnets 200A and have a length smaller than the length of the magnets 200A. Since the magnets 200A are similar to those of the third embodiment, only the magnets 200B that rectangularly intersect the longitudinal magnets 200A will be described below.

[0069] Each of the magnets 200B has a magnet main body 210B, an inner yoke 220B and an outer yoke 230B. Each of the magnet main bodies 210B is made of a magnetic material and shows a longitudinally extending rod-shaped profile so as to have opposite magnetic poles respectively at the inner surface and at the outer surface thereof just as the magnet main bodies 210A. More specifically, if the magnet main bodies 210A has the N-pole on the inner surface and the S-pole on the outer surface thereof, each of the magnet main bodies 210B is so magnetized that it has the N-pole on the inner surface and the S-pole on the outer surface thereof.

[0070] The inner yokes 220B are made of a material same as the material of the inner yokes 220A of the third embodiment. Since the magnet main bodies 210B that are to be rigidly secured have a length smaller than the length of the magnet main bodies 210A, the longitudinal dimension of the inner yokes 220B is also smaller than the longitudinal dimension of the inner yokes 220A.

[0071] The outer yokes 230B respectively have straight sections 233A disposed opposite to each other and curved sections 234A that link the straight sections 233A. The outer yokes 230B have an outer securing section 231A that is to be rigidly secured to the corresponding magnet main body 210A and another outer securing section 231B that is to be rigidly secured to the corresponding magnet main body 210B. Outwardly projecting flange sections 232A, 232B are extended respectively from corresponding axial ends of the outer securing sections 231A, 232B so as to be integral with the latter. The flange sections 232B in the curved sections 234A are outwardly more extending than the flange sections in the straight sections 233A. The pinched sections 440A of the diaphragm 400B can be rigidly secured to the flange sections 232A, 232B.

[0072] The magnetic body 300B has an outer frame section 310B located axially above the outer securing sections 231B of the outer yokes 230B. The lower end of the outer frame section 310B is extended and bent so as to project outward and produce a keep section 311B. In other words, the outer frame section 310B has a keep section 311B that is integral with it. The keep section 311B projects outward to a large extent so that it may be bonded to the flange sections 232B of the outer yokes 230B. The other end of the outer frame section 310B is extended and inwardly curved so as to produce a bridge section 320B. In other words, the outer frame section 310B has a bridge section 320B that is integral with it. An inner frame section 330B is formed at the inner peripheral edge of and integrally with the bridge section 320B. The outer surface of the inner frame section 330B of the magnetic body 300B is located vis-à-vis the inner surface of the inner yoke 220B with a magnetic gap G of a predetermined length disposed between them and each of the magnets 200B has one of its polar surfaces, or its S-pole, along the corresponding outer surface of the inner frame section 330B to form a magnetic circuit.

[0073] The diaphragm 400B is formed substantially as thin film of magnesium foil or cone paper with its surface treated for anti-corrosion. The diaphragm 400B has an elliptic profile with its longitudinal sides respectively matching the rod-shaped profile of the magnets 200A and that of the magnetic body 300A. The diaphragm 400B has a curved vibratory section 410B substantially at the center thereof. The vibratory section 410B shows a substantially rectangular plan view and a substantially cylindrical rising section 420B is integrally extended from the peripheral edge of the vibratory section 410B at the side opposite to the curved part of the vibratory section 410B. The rising section 420B is arranged between the outer surface of each of the inner frame sections 330A, 330B of the magnetic body and the inner surface of the corresponding one of the inner yokes 220A, 220B of the magnets 200A, 200B without touching them. An arch-shaped edge section 430B is formed at an axial end of and integrally with the rising section 420B. More specifically, the edge section 430B is curved in the sense of curvature of the vibratory section 410B and outwardly extended from the rising section 420B. An outwardly projecting sword-guard-like pinched section 440A is formed at the outer peripheral edge of and integrally with the edge section 430B. Note that the vibratory section 410B, the edge section 430B and the rising section 420B may be formed as separate parts. Alternatively, the vibratory section 410B and the rising section 420B may be made integral with each other or the edge section 430B and the rising section 420B may be made integral with each other.

(Effects and advantages of the speaker)

[0074] As described above in detail, like the first embodiment, the speaker of the fourth embodiment of the present invention is assembled by bonding the magnet bodies 300A, 300B to one of the polar surfaces of the magnets 200A, 200B via the common outer yoke 230B and covering the edge section 430B of the diaphragm 400B with the magnetic bodies 300A, 300B in such a way that the magnetic bodies 300A, 300B are partly found within the voice coil 500B. Thus, the speaker of the fourth embodiment can easily be made to show a low profile as in the case of the first embodiment. Additionally, the speaker can be provided with specific acoustic characteristic features such as horn effect and pipe resonance without using any additional members when the inner frame sections 330A, 330B are made to show a particularly designed profile.

[0075] Additionally, since the voice coil 500B is made to show a rectangular plan view and a pair of rod-shaped magnets 200A are arranged vis-à-vis the respective long sides of the rectangle, while another pair of rod-shaped magnets 200B are arranged vis-à-vis the respective sides of the rectangle that extend from the opposite ends of long sides and rectangularly intersect the long sides. With this arrangement, a magnetic circuit is formed around the entire periphery of the voice coil 500B to excellently reproduce and output voices.

[Modifications to the embodiments]

[0076] The present invention is by no means limited to the above-described embodiments, which may be altered or modified in various different ways as described below without departing from the scope of the invention.

[0077] The magnet unit 200, 800 is not limited to those described-above in terms of configuration and the above-described ones may be modified appropriately. For example, the magnet unit 800 may be arranged without using a coupling yoke 820. The magnetic body 300, 900 may be modified and linked to one of the polar surfaces of the magnet unit 200, 800 in such a way that the magnetic body 300, 900 is partly found within the voice coil 500. For instance, when the magnet unit 800 can be bonded to the corresponding end section of the outer shell 310 of the magnetic body 900 sufficiently rigidly, the pinching flange section 910 may be omitted. Similarly, the flange section 232 may be omitted. Likewise, the aligning-engaging section 233 may be omitted from the first embodiment if the components of the embodiment can be aligned with ease by an assembly jig.

[0078] For example, as shown in FIG. 11, the aligning-engaging section may be omitted from the outer yoke 230 of the magnet unit 200 of the first embodiment and the diaphragm 400 may be pinched and secured in position by using the magnetic body 900 of the second embodiment.

[0079] Furthermore, as shown in FIG. 11, the speaker may be so designed as to be provided with specific acoustic characteristic features such as bass reflex effect, horn effect and pipe resonance. In the instance of FIG. 11, reference symbol 950 denotes a cover having a substantially disk-shaped plate section 951 that is made of a steel plate. The plate section 951 is bent to one of the opposite sides along the peripheral edge thereof to produce a joint section 952 to be bonded to the magnetic body 900. The plate section 951 is provided with a plurality of circular holes 953A. The inner peripheral edge of each of the circular holes 953A is extended to integrally form a substantially cylindrical duct 953 that projects in the sense of projection of the joint section 952. The cover 950 is bonded to the bridge section 320 of the magnetic body 900 in such a way that the ducts 953 project toward the diaphragm 400 typically by welding so that the cover 950 is made integral with the magnetic body 900. The through holes 321 of the magnetic body 900 preferably face the space defined by the cover 950 and the diaphragm 400. With this arrangement, the space between the edge section 430 and the magnetic body 900 can be used as air mass that is resonated with the ducts 953 to produce a bass reflex effect and obtain a desirable acoustic characteristic feature.

[0080] The cover 950A of FIG. 6 has a substantially rectangular plate section 951A. The plate section 951A is bonded to the magnetic body 300A along the peripheral edge thereof to link the oppositely disposed members of the magnetic body 300A. When a pair of rod-shaped magnets 200A are arranged vis-à-vis in a speaker 100A as in the case of the third embodiment, the speaker 100A can be less resistant to pressure applied in a direction perpendicular to the longitudinal direction of the speaker. However, the cover 950A that links the members of the magnetic body 300A reinforces the speaker 100A and, at the same time, protects the diaphragm 400A. The holes 954 arranged at the cover 950A transmits oscillations of the sounds generated from the speaker 100A.

[0081] Since the magnetic body 300, 900 covers the edge section 430 of the diaphragm 400 so as to be partly found within the voice coil 500, the substantially disk-shaped cover 950 can be easily mounted to improve the productivity of manufacturing the speaker and protect the diaphragm 400 with a simple configuration. Additionally, the acoustic effect of the speaker can be improved when the cover 950 is simply provided with a substantially cylindrical horn section 953. When the cover 950 is simply used as cover of diaphragm 400, the plate section 951 is preferably realized in the form of a punched metal plate or a mesh to secure propagation of sounds form the speaker.

[0082] The magnetic body 300, 900 may be bonded to the magnet unit 200, 800 by using an appropriate technique. For example, if a sufficient level of aligning coercive force is secured, the pinching flange section 910 of the magnetic body 300 and the coupling yoke 820 of the magnet unit 800 may be bonded partly and directly as shown in FIG. 12. If such is the case, the aligning operation can be conducted with ease when the pinching flange section 910 is provided with a step having a height equal to the thickness of the pinched section 440. This arrangement is preferable from the viewpoint of improving the tight contact of the pinching flange section 910 and the coupling yoke 820. With the arrangement of FIG. 12, the magnetic body 300 and the magnet unit 800 are bonded to each other directly so that any possible leakage of magnetic flux is effectively prevented to obtain an excellent magnetic circuit. The coupling yoke 820 may alternatively be provided with a step having a height equal to the thickness of the pinched section 440 or both the pinching flange section 910 and the coupling yoke 820 may be provided with a step.

[0083] While the diaphragm 400 is pinched along the peripheral edge thereof when the magnetic body 300, 900 and the magnet unit 200, 800 are bonded together in the above description, the aligning, pinching, securing arrangement is not limited to those described above. For example, the magnetic body 300, 900 may alternatively be provided with an arrangement for aligning and holding the diaphragm 400 so that the diaphragm 400 is aligned and directly held by the magnetic body 300, 900.

[0084] Possible applications of a speaker 100, 700 according to the invention are not limited to the above-described portable electric devices.

[0085] When assembling a speaker 100, 700 according to the invention, an assembly jig 600 may not necessarily be used. Additionally, an assembly jig 600 different from any of the above-described ones may alternatively be used for the purpose of the present invention. For example, a jig having an additional member adapted to align the magnet unit 200, 800 and the magnetic body 900 in such a way that the outer periphery of the magnetic body 900 is continuously extending from the outer peripheral surface of the magnet unit 200, 800 may be used. Furthermore, an assembly jig having no notches 621 or one having a plurality of substantially cylindrical positioning section 620 projecting upward along a circle may alternatively be used.

[0086] A dust-proof member such as one made of net, woven fabric or an unwoven fabric may be provided at the side of the speaker 100, 700 opposite to the rear side where the magnetic body 300, 900 is arranged and hence that is the side from which the assembly jig 600 is removed.

[0087] While the voice coil 500 is wound around the outer surface of the rising section 420 of the diaphragm 400 in the above description, it may alternatively be wound around the inner surface of the rising section 420.

[0088] Additionally, while the diaphragm 400A, 400B of the third and fourth embodiments show an elliptic plan view in the above description, they may alternatively show a rectangular, triangular, hexagonal or some other polygonal plan view so long as they are closed at an end. Then, the voice coil 500A, 500B may show a rectangular, elliptic, triangular, hexagonal or some other polygonal plan view accordingly so long as the diaphragms are closed at an end. When the voice coil shows an elliptic plan view, an elliptic magnet may be used or a combination of arc-shaped magnets and rod-shaped magnets may alternatively be used. When the voice coil shows a polygonal plan view, a rod-shaped magnet may be arranged at a position corresponding to each of the sides of the polygon.

[0089] While a ring-shaped magnet is used in the first and second embodiments and rod-shaped magnets are used in the third and fourth embodiments, a speaker may be formed by combining a ring-shaped magnet and one or more than one rod-shaped magnets. In short, the present invention is by no means limited in terms of the profile of the magnets it comprises. For instance, in the case of an elliptic speaker having linear longitudinal sides, rod-shaped magnets may be used along the linear sides and semi-circular magnets may be used in the arc-shaped areas so as to form a magnetic circuit extending along the entire periphery of the speaker.

[0090] In each of FIGS. 3, 7 and 9 illustrating the first, third and fourth embodiments, the magnet unit 200, 200A or 200B, whichever appropriate, is arranged in such a way that the inner yoke 220, 220A or 220B, the magnet main body 210, 210A or 210B and the outer yoke 230, 230A or 230B, whichever appropriate, are flush with each other at an axial end. However, the present invention is by no means limited thereto. For example, the magnet main body 210 of the magnet unit 200 may be slightly projecting downward as shown in FIG. 13.

[0091] The configurations and the assembling sequences of the above-described embodiments of the invention may be appropriately further modified without departing from the scope of the invention.

(Effects and advantages of the embodiments)

[0092] As described above, the magnetic body 300 is made to continuously extend from one of the polar surfaces of the magnet unit 200 while the diaphragm 400 that is integral with the voice coil 500 is held in position along the peripheral edge thereof in such a way that the magnetic body 300 covers the edge section 430 of the diaphragm 400 and is partly found within the voice coil 500 so that the voice coil 500 may be axially movable and a magnetic gap G is formed in radial directions of the magnet unit 200 to produce a magnetic circuit. Thus, the magnetic body 300 partly comes to the inside of the voice coil 500 from the outer peripheral side of the diaphragm 400 via the surface of the edge section 430, while the magnet unit 200 is located at the outer peripheral side of the voice coil 500. In view of the fact that the amplitude of the diaphragm 400 is relatively small when the diaphragm 400 is applied to a portable electric device, the vibratory section 410 of the diaphragm 400 can vibrate and voice satisfactorily if the distance between the edge section 430 and the magnetic body 300 is reduced so that the it is possible to realize a low profile speaker without any problem. Additionally, since the dome-like magnetic body 300 is located on the voicing outer surface side of the speaker, the speaker can be provided with specific acoustic characteristic features such as horn effect and pipe resonance without using any additional members when the inner shell 330 is made to show a particularly designed profile. Then, the scope of application of this embodiment will be dramatically broadened.

Claims

1. A speaker comprising:

a magnet;

a diaphragm having a vibratory section and an edge section arranged along the peripheral edge of the vibratory section;

a voice coil arranged integrally with the diaphragm; and

a magnetic body having a part aligning and holding the peripheral edge of the diaphragm, a part continuing from one of the magnetic polar surfaces of the magnet, a part covering the edge section of the diaphragm and a part extending to the inner peripheral side of the voice coil to form a magnetic gap having a predetermined distance in the radial direction of the magnet and axially movably containing the voice coil, a magnetic circuit being formed so as to start from the magnet and return to the magnet via the magnetic gap.

2. The speaker according to claim 1, wherein the magnet is formed to show a ring-shaped profile.

3. The speaker according to claim 1, wherein the magnet is formed to show a rod-shaped profile.

4. The speaker according to claim 3, wherein the voice coil has a straight part and the magnet is arranged at a position corresponding to the straight part.

5. The speaker according to claim 3 or 4, wherein at least a pair of magnets are arranged at respective positions to face each other.

6. The speaker according to any of claims 3 through 5, wherein the voice coil is made to show a substantially polygonal profile and the magnets are arranged at positions corresponding to the respective sides of the polygon.

7. The speaker according to any of claims 3 through 6, wherein the diaphragm is made to show a profile having a closed end.

8. The speaker according to any of claims 1 through 7, wherein
   the diaphragm has a substantially cylindrical rising section arranged between the vibratory section and the edge section, and
   the voice coil is wound around the outer or inner surface of the rising section as integral part of the diaphragm.

9. The speaker according to claim 8, wherein the diaphragm has a substantially cylindrical rising section integrally extended from the peripheral edge of the vibratory section located opposite to the curved profile thereof and an edge section having a curved profile and integrally and outwardly extended in a direction of the vibratory section from the axial front end of the rising section.

10. The speaker according to any of claims 1 through 9, wherein the diaphragm is provided with a pinched section as integral part thereof projecting outward from the outer peripheral edge of the edge section so as to be aligned with and pinched by the magnetic body.

11. The speaker according to any of claims 1 through 10, wherein
   the magnet includes a magnet main body having different polar surfaces at the inner surface and the outer surface thereof, an outer yoke adapted to engage the outer surface of the magnet main body and align and hold the peripheral edge of the diaphragm with the magnetic body and an inner yoke having an inner surface engaged with the inner surface of the magnet main body and adapted to form a magnetic gap between itself and the magnetic body when disposed substantially opposite to the magnetic body with the voice coil interposed between them.

12. The speaker according to any of claims 1 through 10, wherein
   the magnet includes a magnet main body having different polar surfaces at the axially opposite end facets thereof, a coupling yoke arranged at one of the axial end facets of the magnet main body and adapted to align and hold the peripheral edge of the diaphragm with the magnetic body and a pole forming yoke arranged at the opposite axial end facet of the magnet main body and adapted to from a magnetic gap between itself and the magnetic body when disposed substantially opposite to the magnetic body with the voice coil interposed between them.

13. The speaker according to claim 12, wherein the inner peripheral edge of the coupling yoke is continued from the inner peripheral edge of the magnet main body.

14. The speaker according to claim 12 or 13, wherein the inner surface of the coupling yoke is sloped toward the pole forming yoke.

15. The speaker according to any of claims 12 through 14, wherein the edge of the pole forming yoke located close to the coupling yoke is made to show an obtuse angle.

16. The speaker according to any of claims 11 through 15, wherein
   the magnetic body includes an outer frame section adapted to pinch and securely hold the peripheral edge of the diaphragm at an axial end thereof with the magnet, an inner frame section formed in the inside of the outer frame section and having an outer surface disposed to face the inner surface of the voice coil and a bridge section linking the outer frame section and the inner frame section and adapted to cover the edge section of the diaphragm.

17. The speaker according to any of claims 1 through 16, wherein at least either the magnetic body or the magnet has an aligning section for coaxially aligning the magnetic body and the magnet at the center positions thereof.

18. The speaker according to any of claims 1 through 17, wherein the magnetic body is provided with through holes at positions facing the edge section of the diaphragm.

19. The speaker according to any of claims 1 through 18, further comprising a cover section fitted to the magnetic body to cover the vibratory section of the diaphragm.

20. The speaker according to claim 19, wherein the cover section has a cylindrical horn section having an axis running in a predetermined direction.

21. A method of manufacturing the speaker according to any of claims 1 through 20, the method comprising:

bringing in an assembly jig having a substantially plate-shaped table with a profile substantially matching that of a diaphragm and a substantially closed gap aligning section arranged on one of the surfaces of the table;

placing a magnet on the table so as to make the gap aligning section of the assembly jig engage the inside of the magnet;

placing the peripheral edge of the diaphragm on the magnet so as to make the voice coil engage the gap aligning section of the assembly jig carrying the magnet;

coupling a magnetic body to the magnet so as to pinch the peripheral edge of the diaphragm between the magnet and the magnetic body; and

removing the assembly jig from the side opposite to the side of coupling the magnetic body and the magnet.

22. A method of manufacturing a speaker comprising:

bringing in an assembly jig having a substantially plate-shaped table and a substantially closed gap aligning section arranged on one of the surfaces of the table and having a predetermined diameter and a predetermined thickness as viewed along the plane of the table;

placing a magnet on the table so as to make the gap aligning section of the assembly jig engage the inside of the magnet;

mounting on the assembly jig carrying the magnet a diaphragm having a vibratory section provided with a voice coil and an edge section arranged along the peripheral edge of the vibratory section on the gap aligning section so as to make the voice coil engage the gap aligning section while placing the peripheral edge on the magnet;

coupling a magnetic body to the magnet placed on the assembly jig so as to pinch the peripheral edge of the diaphragm between the magnet and the magnetic body, while covering the edge section of the diaphragm and partly being located within the inner surface of the voice coil; and

removing the assembly jig from the side opposite to the side of coupling the magnetic body and the magnet.

23. The method according to claim 22, wherein at least either the magnetic body or the magnet has an aligning section for coaxially aligning the magnetic body and magnet at the center positions thereof; and
   the magnetic body is coupled to the magnet while it is being aligned by means of the aligning section.

24. The method according to any of claims 21 through 23, wherein the gap aligning section of the assembly jig includes a plurality of notches formed in the axial direction thereof.

Drawing