WO2011122528A1

WO2011122528A1 - Electroacoustic transducer

Info

Publication number: WO2011122528A1
Application number: PCT/JP2011/057552
Authority: WO
Inventors: 宙軌加藤; 亮渡辺; 有紀畠中; 政人船木
Original assignee: 三洋電機株式会社
Priority date: 2010-03-29
Filing date: 2011-03-28
Publication date: 2011-10-06
Also published as: JP2013128157A; CN202841496U

Abstract

Disclosed is an electroacoustic transducer that can improve heat-resistance strength and save space at a low cost. The electroacoustic transducer (1) comprises a diaphragm (10), a magnetic circuit section (7) that generates a magnetic field and is disposed so as to face the diaphragm (10), and a voice coil (20) disposed within the magnetic field generated by the magnetic circuit section (7). The magnetic circuit section (7) includes a magnet (4) and a yoke (6) that supports the magnet (4). A yoke through-hole (60) that penetrates the yoke (6) in the thickness direction is formed in the yoke (6). The magnet (4) is disposed so as to cover at least a part of the yoke through-hole (60).

Description

Electroacoustic transducer

The present invention relates to an electroacoustic transducer, and more particularly, to an electroacoustic transducer including a magnetic circuit unit including a magnet and a yoke that supports the magnet.

In a conventional electroacoustic transducer having a magnetic circuit part, a magnet and a yoke included in the magnetic circuit part are fixed together by being bonded using an adhesive. When fixing the magnetic circuit part with an adhesive, the adhesive strength decreases at high temperatures due to the limited heat resistance performance of the adhesive, the strength is insufficient due to variations in the application state of the adhesive, and the electroacoustic transducer is downsized. When the magnet is also downsized, there are problems such as insufficient strength due to a decrease in the bonding area and increased man-hours due to the time required for curing the adhesive.

When an electroacoustic transducer is built in a portable information device, the reflow method is used to mount the electroacoustic transducer on the same substrate as other devices constituting the portable information device. There is a demand for downsizing equipment and simplifying the manufacturing process. In the reflow method, solder paste is first applied to the substrate by screen printing, the electroacoustic transducer is placed on the substrate, and then the substrate is heated in a reflow furnace to fix the electroacoustic transducer to the substrate. . When exposed to a high temperature of about 260 ° C. to 300 ° C. inside the reflow furnace, the adhesive for fixing the magnetic circuit portion deteriorates and the reliability decreases. Therefore, the magnetic circuit part fixed by adhesion cannot be used for the electroacoustic transducer fixed by using the reflow method.

Conventionally, as a means for solving the problem in fixing such a magnetic circuit part with an adhesive, a technique for fixing the magnetic circuit part with a coupling component provided through the magnetic circuit part has been proposed (for example, , See Patent Document 1). In Patent Document 1, a connecting part formed in a rod shape is passed through a hole of a permanent magnet sandwiched between a plate and a yoke, and a protruding portion protruding from the plate or the yoke is developed (caulked) or heated and developed. A loudspeaker has been proposed in which three parts are crimped together.

JP 2001-245387 A

When using a coupling part that penetrates the magnetic circuit, it is necessary to make a through-hole in the magnet, resulting in problems such as reduced magnetic performance, increased cost due to the addition of drilling, and difficulty in drilling with a small magnet. . In addition, since coupling parts are added, the cost increases due to an increase in the number of parts. In addition, since the coupling parts are arranged so as to protrude from the lower surface of the yoke and protrude from the yoke, the space required for the arrangement of the electroacoustic transducer increases, and it is difficult to cope with the miniaturization of the electroacoustic transducer. A certain problem occurs.

The present invention has been made in view of the above-mentioned problems, and its main purpose is to provide an electroacoustic transducer that can improve the heat resistance strength, is inexpensive, and can save space.

An electroacoustic transducer according to the present invention includes a diaphragm, a magnetic circuit unit that is disposed to face the diaphragm and generates a magnetic field, and a voice coil that is disposed in the magnetic field generated by the magnetic circuit unit. The magnetic circuit unit includes a magnet and a yoke that supports the magnet. A yoke through hole is formed in the yoke so as to penetrate the yoke in the thickness direction. The magnet is disposed so as to cover at least a part of the yoke through hole.

Preferably, the yoke through hole is formed point-symmetrically with the center point of the yoke as a symmetric point when the yoke is viewed in plan.

Preferably, the yoke through hole is formed so as to penetrate the yoke in the thickness direction at the center point of the yoke.

Preferably, the yoke and the magnet are fixed by welding.

Preferably, the yoke and the magnet are fixed by welding the inner periphery of the yoke through hole and the surface of the magnet facing the yoke.

Preferably, the magnetic circuit unit further includes a plate that sandwiches the magnet together with the yoke. The plate has a plate through hole penetrating the plate in the thickness direction. The magnet is disposed so as to cover at least a part of the plate through hole.

Preferably, the plate through-hole is formed in point symmetry with the center point of the plate as a symmetry point when the plate is viewed in plan.

Preferably, the plate through hole is formed so as to penetrate the plate in the thickness direction at the center point of the plate.

Preferably, the yoke through hole and the plate through hole are formed so as to overlap each other with a magnet interposed therebetween in a plan view.

Preferably, the plate and the magnet are fixed by welding.

Preferably, the plate and the magnet are fixed by welding the inner periphery of the plate through-hole and the surface of the magnet facing the plate.

According to the present invention, the heat resistance strength of the electroacoustic transducer can be improved. The electroacoustic transducer of the present invention is inexpensive and can save space.

2 is a cross-sectional view showing a configuration of an electroacoustic transducer according to Embodiment 1. FIG. It is the figure which looked at the magnetic circuit part from the arrow II direction in FIG. It is the figure which looked at the magnetic circuit part from the arrow III direction in FIG. 6 is a cross-sectional view illustrating a configuration of an electroacoustic transducer according to Embodiment 2. FIG. It is the figure which looked at the magnetic circuit part from the arrow V direction in FIG. It is the figure which looked at the magnetic circuit part from the arrow VI direction in FIG. 6 is a cross-sectional view illustrating a configuration of an electroacoustic transducer according to Embodiment 3. FIG. FIG. 10 is a schematic diagram illustrating a state before the magnetic circuit unit according to the third embodiment is fixed. It is a schematic diagram which shows the state before fixation of the modification of the magnetic circuit part of Embodiment 3.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing the configuration of the electroacoustic transducer 1 according to the first embodiment. As shown in FIG. 1, the electroacoustic transducer 1 mainly includes a frame 2, a cover 3, a diaphragm 10, a voice coil 20, and a magnetic circuit unit 7. The magnetic circuit unit 7 includes a magnet 4, a plate 5, and a yoke 6.

The frame 2 is formed in a planar shape annular shape, and supports the yoke 6 on its inner peripheral surface. A cover 3 is disposed on the upper portion of the frame 2. The cover 3 is formed to have a trapezoidal cross-sectional shape toward the upper surface. The frame 2 and the cover 3 sandwich the diaphragm 10.

The diaphragm 10 is formed of a thin plate so as to vibrate in the vertical direction (the direction of the double arrow A shown in FIG. 1), which is the thickness direction of the electroacoustic transducer 1. The diaphragm 10 is a flexible film having a thickness of 8 to 50 μm, for example. The diaphragm 10 is made of a synthetic resin represented by, for example, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), or PEI (polyetherimide). The diaphragm 10 may be formed of a metal material such as titanium or a paper material.

The diaphragm 10 includes a central portion 11 on a central side in a plan view, an annular fixed portion 12 formed on the outer peripheral portion of the central portion 11 and to which the voice coil 20 is fixed, and a periphery formed on the outer peripheral side of the fixed portion 12. Part 13 and outer peripheral part 14 formed on the outer peripheral side of peripheral part 13. The central portion 11 and the peripheral portion 13 are formed in an arc shape in the cross-sectional view shown in FIG. The voice coil 20 is fixed to the diaphragm 10 by bonding the upper surface of the cylindrical voice coil 20 to the lower surface of the fixing portion 12. The diaphragm 10 is attached to the upper portion of the frame 2 so that the lower surface of the outer peripheral portion 14 and the upper surface of the frame 2 face each other.

The cover 3 is attached to the upper part of the diaphragm 10 so that the upper surface of the outer peripheral part 14 and the lower surface of the outer peripheral part of the cover 3 face each other. The cover 3 is formed so as to cover the diaphragm 10. The cover 3 is supported by the frame 2 via the diaphragm 10. The outer peripheral portion 14 of the diaphragm 10 is placed on the upper surface of the frame 2, and the diaphragm 10 is vibrated inside the electroacoustic transducer 1 by supporting the diaphragm 10 by the upper surface of the frame 2 and the lower surface of the cover 3. Supported as possible.

The yoke 6 has a cylindrical outer peripheral portion disposed on the outer peripheral side of the voice coil 20 at a distance from the outer peripheral surface of the voice coil 20, and a disk-shaped disc disposed on the lower side of the voice coil 20 and the magnet 4. And a lower portion. The yoke 6 is fixed in contact with the inner peripheral surface of the frame 2 on the outer peripheral side of the outer peripheral side portion. The lower part of the yoke 6 is disposed at a distance from the lower surface of the voice coil 20, and the magnet 4 is disposed in the center of the lower part of the yoke 6. The lower part of the yoke 6 supports the magnet 4.

The magnet 4 has a short cylindrical shape. The magnet 4 is disposed on the inner peripheral side of the voice coil 20 with a gap from the inner peripheral surface of the voice coil 20. The magnet 4 is disposed at the center portion of the frame 2. The voice coil 20 is disposed in a magnetic field formed by the magnet 4. The magnet 4 is fixed to the lower part of the yoke 6 and is disposed inside the bowl-shaped yoke 6. The columnar magnet 4 is surrounded by a cylindrical voice coil 20. An outer peripheral side portion of the yoke 6 is disposed around the magnet 4.

The plate 5 is disposed on the upper surface 41 of the magnet 4. The frame 2 supports the magnet 4 and the plate 5 via the yoke 6. The electroacoustic transducer 1 is an internal magnet type in which a cylindrical voice coil 20 surrounds a columnar magnet 4. A gap of the magnetic circuit is formed between the outer peripheral surface of the plate 5 and the outer peripheral side portion of the yoke 6. The cylindrical voice coil 20 is disposed in this gap.

A magnetic circuit portion 7 is formed by the magnet 4, the plate 5 and the yoke 6. The magnetic circuit unit 7 is disposed to face the diaphragm 10 and generates a magnetic field for driving the voice coil 20. The voice coil 20 is disposed in a magnetic field generated by the magnet 4 of the magnetic circuit unit 7.

A plurality of through holes 31 are formed in the frame 2 so as to penetrate the frame 2 in the thickness direction of the frame 2 (vertical direction in FIG. 1). The through hole 31 has a function as a vent hole through which air can flow between the inside and the outside of the electroacoustic transducer 1 through the inside of the through hole 31. When the diaphragm 10 vibrates in the vertical direction when the electroacoustic transducer 1 is driven, an air flow is generated around the diaphragm 10. At this time, air is allowed to flow from the inside to the outside of the electroacoustic transducer 1 and from the outside to the inside of the electroacoustic transducer 1 by forming the plurality of through holes 31 that are ventilation holes. Thereby, it can suppress that the flow of air inhibits the vibration of the diaphragm 10, and the performance of the electroacoustic transducer 1 falls.

A terminal 33 for connecting an electric circuit included in the electroacoustic transducer 1 to another circuit or element is fixed to the lower surface of the frame 2. The frame 2 and the yoke 6 are assembled so that the lower surface of the frame 2 is disposed above the lower portion of the bowl-shaped yoke 6. Therefore, even if the terminal 33 projecting downward from the lower surface of the frame 2 is attached, an increase in the size of the outer shape of the electroacoustic transducer 1 as a whole is suppressed, and the electroacoustic transducer 1 can be downsized. .

The frame 2 is also formed with a communication hole 32 for communicating the internal space and the external space of the electroacoustic transducer 1. The lead wire 21 is disposed through the communication hole 32. The lead wire 21 has one end connected to the voice coil 20 and the other end connected to the terminal 33. The terminal 33 and the voice coil 20 are electrically connected by a lead wire 21. The lead wire 21 is connected to the voice coil 20 and energizes the voice coil 20. A current flows through the voice coil 20 via the terminal 33 and the lead wire 21.

Hereinafter, the magnetic circuit unit 7 will be described in detail. As described above, the magnetic circuit unit 7 includes the magnet 4, the plate 5 fixed to the upper surface 41 of the magnet 4, and the yoke 6 fixed to the lower surface 42 of the magnet 4. The plate 5 and the yoke 6 are made of a ferromagnetic material such as soft iron. The magnet 4 is a permanent magnet such as a ferrite magnet or a neodymium magnet. Both the plate 5 and the yoke 6 sandwich the magnet 4 to form an integral magnetic circuit portion 7.

The plate 5 is formed with a plate through hole 50 that penetrates the plate 5 in the thickness direction. Since the plate through hole 50 is formed, a part of the upper surface 41 of the magnet 4 is exposed when the magnetic circuit unit 7 is viewed from above. The magnet 4 is disposed so as to cover the plate through hole 50 from below. The plate 5 around the plate through hole 50 is in close contact with the upper surface 41 of the magnet 4.

FIG. 2 is a diagram of the magnetic circuit unit 7 viewed from the direction of arrow II in FIG. As shown in FIG. 2, the planar shape of the plate 5 is a disk shape. The center of the circle formed by the planar outer shape of the plate 5 forms the center point of the plate 5. The plate through hole 50 is formed so as to penetrate the plate 5 in the thickness direction at the center point of the plate 5. The plate through hole 50 has a circular planar shape centered on the center point of the plate 5. Therefore, when the plate 5 is viewed in plan, the plate through hole 50 is formed point-symmetrically with the center point of the plate 5 as a symmetric point.

The plate 5 is formed in an annular shape with a plate through hole 50 formed in the center. The plate through-hole 50 is surrounded by the annular contact portion that contacts the magnet 4 in the plate 5. The plate 5 has a cylindrical inner peripheral surface. The cylindrical inner peripheral surface forms the wall surface of the plate through hole 50. The surface of the plate 5 facing the upper surface 41 of the magnet 4 has an annular shape, and a plate through hole 50 is formed on the inner side surrounded by the surface.

The plate 5 and the magnet 4 are fixed by welding. The plate 5 and the magnet 4 are fixed by welding the inner periphery of the plate through-hole 50 and the surface 41 of the magnet 4 facing the plate 5. A welded portion 51 is formed so as to contact both the wall surface of the plate through-hole 50 that forms the inner peripheral surface of the annular plate-shaped plate 5 and the upper surface 41 of the magnet 4. The plate 5 and the magnet 4 are fixed integrally with each other via a welding point 51.

The yoke 6 is formed with a yoke through hole 60 that penetrates the yoke 6 in the thickness direction. Since the yoke through hole 60 is formed, a part of the lower surface 42 of the magnet 4 is exposed when the magnetic circuit unit 7 is viewed from below. The magnet 4 is disposed so as to cover the yoke through hole 60 from above. The lower part of the yoke 6 around the yoke through hole 60 is in close contact with the lower surface 42 of the magnet 4.

FIG. 3 is a diagram of the magnetic circuit unit 7 viewed from the direction of arrow III in FIG. As shown in FIG. 3, the planar shape of the lower portion of the yoke 6 is a disk shape. The center of the circle formed by the planar outer shape of the lower portion of the yoke 6 forms the center point of the yoke 6. The yoke through hole 60 is formed so as to penetrate the lower part of the yoke 6 in the thickness direction at the center point of the yoke 6. The yoke through hole 60 has a circular planar shape centered on the center point of the yoke 6. Therefore, when the yoke 6 is viewed in plan, the yoke through hole 60 is formed point-symmetrically with the center point of the yoke 6 as the symmetry point.

The yoke 6 is formed in an annular shape in which a yoke through hole 60 is formed at the center. The yoke outer hole 60 is entirely surrounded by an annular contact portion that contacts the magnet 4 in the yoke 6. The yoke 6 has a cylindrical inner peripheral surface. The cylindrical inner peripheral surface forms the wall surface of the yoke through hole 60. The surface of the yoke 6 facing the lower surface 42 of the magnet 4 has an annular shape, and a yoke through hole 60 is formed on the inner side surrounded by the surface.

The yoke 6 and the magnet 4 are fixed by welding. The yoke 6 and the magnet 4 are fixed by welding the inner periphery of the yoke through-hole 60 and the surface 42 of the magnet 4 facing the yoke 6. A welded portion 61 is formed so as to contact both the wall surface of the yoke through hole 60 that forms the inner peripheral surface of the annular plate-shaped yoke 6 and the lower surface 42 of the magnet 4. The yoke 6 and the magnet 4 are fixed integrally with each other via a welding point 61.

2 and 3, the plate through hole 50 is formed at the center of the disk-shaped plate 5, and the yoke through hole 60 is formed at the center of the lower part of the disk-shaped yoke 6. Since the plate 5 and the yoke 6 are arranged concentrically, the yoke through-hole 60 and the plate through-hole 50 are formed at overlapping positions. When the magnetic circuit unit 7 is viewed in plan in the thickness direction, the yoke through hole 60 and the plate through hole 50 are formed so as to overlap with the magnet 4 interposed therebetween.

By matching the positions and shapes of the yoke through hole 60 and the plate through hole 50, the flow of the magnetic flux can be made uniform between the yoke 6 side and the plate 5 side, and the magnetic flux can be formed more efficiently. The driving force can be improved, and the sound pressure can be improved. In addition, in the welding process between the yoke 6 and the magnet 4 and the plate 5 and the magnet 4, the positions of the welding points 51 and 61 when viewed in plan can be made the same, and the welding conditions and jigs necessary for the work are unified. The work process can be designed flexibly and the load on the process can be reduced.

In the electroacoustic transducer 1 having the above-described configuration, a yoke through hole 60 that penetrates the yoke 6 in the thickness direction is formed in a part of the lower portion of the yoke 6 that contacts the magnet 4. And the yoke 6 can be fixed by welding. Since the welding location 61 between the magnet 4 and the yoke 6 is provided inside the yoke through hole 60 and is fixed by welding so that the welding location 61 does not protrude below the lower portion of the yoke 6, It can avoid that the location fixed with the yoke 6 obstructs the thinning of the electroacoustic transducer 1 as a whole. Therefore, size reduction of the electroacoustic transducer 1 can be achieved.

Similarly, in part of the plate 5 that comes into contact with the magnet 4, a plate through-hole 50 that penetrates the plate 5 in the thickness direction is formed so that the magnet 4 and the plate 5 can be welded and fixed. It is said that. A welding location 51 between the magnet 4 and the plate 5 is provided inside the plate through hole 50 and is fixed by welding so that the welding location 51 does not protrude above the plate 5. Therefore, it can avoid that the location where the magnet 4 and the yoke 6 are fixed obstructs the vibration of the diaphragm 10, and the acoustic performance of the electroacoustic transducer 1 can be prevented from deteriorating.

When the electroacoustic transducer 1 is fixed to the substrate using the reflow method, even if the magnetic circuit unit 7 is heated in the reflow furnace after welding, The strength of the fixing portion between the magnet 4 and the plate 5 which are fixed by welding can be maintained, and the magnetic circuit portion 7 can be reliably kept integrally fixed after heating in the reflow furnace. Therefore, the heat resistance and reliability of the electroacoustic transducer 1 are improved, and the heat resistance strength of the electroacoustic transducer 1 can be improved.

Since the electroacoustic transducer 1 to which the magnetic circuit unit 7 is fixed by welding can be fixed to the substrate by a reflow method, the flexibility of the method of attaching the electroacoustic transducer 1 to the substrate can be increased and the productivity can be improved. . Since the electroacoustic transducer 1 can be fixed by the reflow method at the same time as other chips mounted on the substrate, a separate process is not required for fixing the electroacoustic transducer 1 and man-hours can be reduced. Can be further improved.

Compared to the conventional technique of fixing the magnetic circuit part using the connecting part penetrating the magnetic circuit part, no connecting part is required for fixing the magnetic circuit part 7, so the number of parts is reduced and the manufacturing is performed. An inexpensive electroacoustic transducer 1 with reduced cost can be provided. If the end of the coupling part protrudes from the magnetic circuit part, and in particular, if the lower end of the coupling part protrudes downward from the magnetic circuit part and protrudes from the magnetic circuit part, it will hinder the thinning of the electroacoustic transducer, In the electroacoustic transducer 1 to which the magnetic circuit unit 7 of this embodiment is fixed by welding, there is no member protruding below the magnetic circuit unit 7. Therefore, thinning of the electroacoustic transducer 1 can be easily achieved, and the space necessary for installing the electroacoustic transducer 1 can be reduced, and space saving can be achieved.

Compared with the case where the coupling component is used, since no hole is formed in the magnet 4, it is possible to avoid the magnetic force generated by the magnetic circuit unit 7 of the present embodiment from being lowered. Therefore, the amplitude with which the diaphragm 10 vibrates via the voice coil 20 by the magnetic field generated by the magnetic circuit unit 7 can be increased, and the sound pressure generated by the electroacoustic transducer 1 can be increased. Although it is difficult to form a through hole in a small magnet, the electroacoustic transducer 1 according to the present embodiment can easily fix the magnetic circuit unit 7 including the small magnet integrally. It is possible to select the optimally shaped magnet 4 for generating an appropriate magnetic field.

Further, by forming the yoke through hole 60 in a symmetrical shape with respect to the center point of the yoke 6, the balance of the yoke 6 is improved. Similarly, by forming the plate through hole 50 in a symmetrical shape with respect to the center point of the plate 5, the balance of the plate 5 is improved. By improving the balance between the yoke 6 and the plate 5 included in the magnetic circuit unit 7, the strength of the magnetic circuit unit 7 can be improved.

By forming the yoke through hole 60 at the center of the yoke 6, the magnetic flux flow that penetrates the yoke 6 becomes uniform, and the disturbance of the magnetic flux can be prevented. Similarly, by forming the plate through hole 50 at the center of the plate 5, the magnetic flux flow that penetrates the plate 5 becomes uniform, and the disturbance of the magnetic flux can be prevented. Therefore, since the diaphragm 10 can be vibrated stably, the acoustic performance of the electroacoustic transducer 1 can be further improved.

Next, the operation of the electroacoustic transducer 1 having the above-described configuration will be described. With the above configuration, the magnetic flux generated from the magnet 4 is guided by the plate 5 and the yoke 6 and converges in the gap where the voice coil 20 is disposed, thereby generating a magnetic field. Then, a current such as an alternating current is input to the voice coil 20. When a current is supplied to the voice coil 20, a driving force is generated between the voice coil 20 and the magnetic circuit unit 7 based on Fleming's left-hand rule by a current flowing through the voice coil 20 and a magnetic field generated from the magnet 4. Will occur.

The magnitude of this driving force varies depending on the current input to the voice coil 20. The voice coil 20 vibrates up and down by the driving force that changes according to the alternating current. The voice coil 20 fluctuates within a gap in the magnetic circuit portion 7 formed by the magnet 4, the plate 5, and the yoke 6, and the diaphragm 10 attached to the voice coil 20 vibrates. As a result, the electric signal (current) is converted into sound (vibration), and the electroacoustic transducer 1 generates sound. Thus, the electroacoustic transducer 1 can be used as a speaker unit.

The electroacoustic transducer 1 of the present embodiment is not limited to use as a speaker unit, and may be used as a microphone, for example. When used as a microphone, the vibration plate 10 vibrates in response to a sound wave, and the voice coil 20 vibrates together with the vibration plate 10, so that the voice coil 20 vibrates in the magnetic field generated by the magnet 4 of the magnetic circuit unit 7. Then, the magnetic flux in the voice coil 20 changes. At this time, an electromotive force is generated in the voice coil 20 by electromagnetic induction. By outputting this electromotive force as an electrical signal, an audio signal can be obtained.

Next, a method for manufacturing the electroacoustic transducer 1 will be described. The electroacoustic transducer 1 of the present embodiment is manufactured by basically the same process as the conventional electroacoustic transducer 1, but in the process of manufacturing the magnetic circuit unit 7, the electroacoustic transducer 1 Is different. Hereafter, each process which manufactures the magnetic circuit part 7 among the manufacturing methods of the electroacoustic transducer 1 of this Embodiment is demonstrated.

First, a cylindrical magnet 4 is prepared. Specifications such as the material and dimensions of the magnet 4 are determined based on the strength of the magnetic field required by the electroacoustic transducer 1. Subsequently, the yoke 6 in which the yoke through hole 60 is formed is prepared. The yoke 6 is formed in a bowl shape having a cylindrical outer peripheral portion and a disc-shaped lower portion. The yoke 6 is formed so that the magnet 4 can be accommodated therein. Then, the plate 5 in which the plate through-hole 50 is formed is prepared. The plate 5 is formed in a disk shape having a diameter capable of covering the upper surface 41 of the columnar magnet 4.

The plate 5 and the yoke 6 are made of a ferromagnetic material. When the plate 5 is formed, the plate 5 in which the plate through hole 50 is formed can be easily formed by using a mold having a shape corresponding to the plate through hole 50. Alternatively, the plate 5 may be formed by preparing a disk-shaped member that forms the outer shape of the plate 5 and drilling a part of the member. Similarly, the yoke 6 may be provided with an appropriate mold to form the yoke 6 with the yoke through hole 60 formed, or the yoke through hole 60 may be formed by machining.

Subsequently, the plate 5 and the magnet 4 are fixed by welding. Inside the plate through hole 50 formed in the plate 5, a welding point 51 for welding the inner periphery of the plate through hole 50 and the surface of the magnet 4 can be provided to fix the plate 5 and the magnet 4. Subsequently, the yoke 6 and the magnet 4 are fixed by welding. Inside the yoke through hole 60 formed in the yoke 6, a welding location 61 for welding the inner periphery of the yoke through hole 60 and the surface of the magnet 4 can be provided to fix the yoke 6 and the magnet 4.

The magnetic circuit unit 7 of the present embodiment can be easily manufactured by the manufacturing method described above. The electroacoustic transducer 1 including the magnetic circuit unit 7 manufactured by this manufacturing method has improved heat resistance, is inexpensive, and can save space. Needless to say, the order of the steps for manufacturing the magnetic circuit unit 7 described above may be appropriately changed.

(Embodiment 2)
FIG. 4 is a cross-sectional view illustrating a configuration of the electroacoustic transducer 1 according to the second embodiment. In the first embodiment, the example in which the connection structure between the diaphragm 10 and the voice coil 20 of the present invention is applied to an inner-magnet type electroacoustic transducer has been described. However, the present invention surrounds the voice coil 20. The present invention can also be applied to an outer magnet type electroacoustic transducer 1 in which a ring-shaped magnet 4 is disposed.

As shown in FIG. 4, the magnet 4 is disposed on the outer peripheral side of the voice coil 20 with a gap from the outer peripheral side of the voice coil 20. The yoke 6 has an inner peripheral portion disposed on the inner peripheral side of the voice coil 20 with a gap from the inner peripheral surface of the voice coil 20, and a lower portion disposed on the lower side of the voice coil 20 and the magnet 4. Have A ring-shaped magnet 4 is placed on the lower portion of the yoke 6. A plate 5 is disposed on the upper surface of the magnet 4.

FIG. 5 is a diagram of the magnetic circuit unit 7 viewed from the direction of the arrow V in FIG. As shown in FIG. 5, the planar shape of the plate 5 is an annular shape. The center of the circle formed by the planar outer shape of the plate 5 forms the center point of the plate 5. The plate through-holes 50 are formed at equal intervals in four places on a circular locus centering on the center point of the plate 5. Each plate through-hole 50 has a circular planar shape. Therefore, when the plate 5 is viewed in plan, the plate through hole 50 is formed point-symmetrically with the center point of the plate 5 as a symmetric point.

The plate 5 and the magnet 4 are fixed by welding. The plate 5 and the magnet 4 are fixed by welding the inner periphery of the plate through-hole 50 and the surface 41 of the magnet 4 facing the plate 5. A welded portion 51 is formed so as to contact both the wall surface of the plate through hole 50 and the upper surface 41 of the magnet 4. The plate 5 and the magnet 4 are fixed integrally with each other via a welding point 51.

FIG. 6 is a diagram of the magnetic circuit unit 7 viewed from the direction of the arrow VI in FIG. As shown in FIG. 6, the planar shape of the yoke 6 is a disk shape. The center of the circle formed by the planar outer shape of the yoke 6 forms the center point of the yoke 6. The yoke through-holes 60 are formed at equal intervals at four locations on a circular locus centering on the center point of the yoke 6. Each yoke through hole 60 has a circular planar shape. Therefore, when the yoke 6 is viewed in plan, the yoke through hole 60 is formed point-symmetrically with the center point of the yoke 6 as the symmetry point.

The yoke 6 and the magnet 4 are fixed by welding. The yoke 6 and the magnet 4 are fixed by welding the inner periphery of the yoke through-hole 60 and the surface 42 of the magnet 4 facing the yoke 6. A welded portion 61 is formed so as to contact both the wall surface of the yoke through hole 60 and the lower surface 42 of the magnet 4. The yoke 6 and the magnet 4 are fixed integrally with each other via a welding point 61.

5 and 6, the plate through hole 50 is formed on a circle centered on the center point of the plate 5, and the yoke through hole 60 is a circle centered on the center point of the lower portion of the yoke 6. The diameters of the two circles formed above are equal. The plate 5 and the yoke 6 are arranged concentrically. Therefore, the yoke through hole 60 and the plate through hole 50 are formed at overlapping positions. When the magnetic circuit unit 7 is viewed in plan in the thickness direction, the yoke through hole 60 and the plate through hole 50 are formed so as to overlap with the magnet 4 interposed therebetween.

Also in the electroacoustic transducer 1 of the second embodiment having such a configuration, a yoke through hole 60 that penetrates the yoke 6 in the thickness direction is formed in a part of the yoke 6 as in the first embodiment. Thus, the magnet 4 and the yoke 6 can be fixed by welding. Similarly, a plate through-hole 50 that penetrates the plate 5 in the thickness direction is formed in a part of the plate 5 so that the magnet 4 and the plate 5 can be welded and fixed. Therefore, the heat resistance strength of the electroacoustic transducer 1 is increased, and the electroacoustic transducer 1 can be fixed to the substrate by a reflow method. Further, the electroacoustic transducer 1 can be reduced in thickness, the space required for installing the electroacoustic transducer 1 can be reduced, and space saving can be achieved.

(Embodiment 3)
FIG. 7 is a cross-sectional view illustrating a configuration of the electroacoustic transducer 1 according to the third embodiment. In the first and second embodiments, the voice coil mounted on the electroacoustic transducer intersects the central axis direction of the voice coil (referred to as the width direction) in the central axis direction (referred to as the thickness direction) of the voice coil. An example having a larger number of layers has been described. The connection structure of the diaphragm 10 and the voice coil 20 according to the present invention can be applied to the electroacoustic transducer 1 equipped with the voice coil 20 having a shape in which the number of laminations in the width direction is larger than the number of laminations in the thickness direction. It is.

As shown in FIG. 7, the voice coil 20 is formed in a shape having a larger number of stacked layers in the width direction than in the thickness direction. The voice coil 20 is disposed on the upper surface of the magnet 4 at an interval. The voice coil 20 is arranged so that the magnetic flux generated by the magnet 4 crosses the voice coil 20.

The magnet 4 is magnetized in the thickness direction. The magnet 4 includes a pair of rectangular parallelepiped

outer magnets

4a and 4c and a rectangular parallelepiped inner magnet 4b. The magnet 4 is fixed with the outer peripheral surfaces of the

outer magnets

4 a and 4 c in contact with the inner peripheral surface of the frame 2. The yoke 6 is fixed to the lower side of the magnet 4. The yoke 6 is fixed by contacting the side surface of the yoke 6 with the inner peripheral surface of the frame 2. The frame 2 supports the magnet 4 and the yoke 6 on the inner peripheral surface.

FIG. 8 is a schematic diagram illustrating a state before the magnetic circuit unit 7 according to the third embodiment is fixed. As shown in FIG. 8, the pair of

outer magnets

4a and 4c and the inner magnet 4b are magnetized in opposite directions. That is, the bottom surfaces of the pair of

outer magnets

4a and 4c are magnetized so as to be N poles, and the top surfaces of the inner magnets 4b are magnetized so as to be N poles. The pair of

outer magnets

4a and 4c and the inner magnet 4b may be magnetized in the opposite directions. Therefore, the upper surfaces of the pair of

outer magnets

4a and 4c may be magnetized so as to be N poles, and the lower surfaces of the inner magnets 4b may be magnetized so as to be N poles.

As shown in FIG. 8, the yoke 6 can be virtually divided into

outer portions

6a, 6c corresponding to the

outer magnets

4a, 4c and an inner portion 6b corresponding to the inner magnet 4b. In a state where the yoke 6 and the magnet 4 are fixed integrally as shown in FIG. 7, a part of the yoke 6 disposed below the outer magnet 4a is an outer portion 6a. Similarly, a part of the yoke 6 disposed below the inner magnet 4b is the inner part 6b, and a part of the yoke 6 disposed below the outer magnet 4c is the outer part 6c. The

outer portions

6a and 6c and the inner portion 6b each have a rectangular parallelepiped shape. The

outer portions

6a and 6c have the same outer shape.

Three yoke through holes 60a are formed in the outer portion 6a. Each yoke through hole 60a has a circular planar shape. The three yoke through holes 60a are formed at equal intervals along the longitudinal direction of the rectangular parallelepiped outer portion 6a. The yoke through hole 60a is formed so as to be arranged in the center of the outer portion 6a in the short direction. The central yoke through hole 60a is formed at the center of the rectangle forming the upper surface of the outer portion 6a (the point where the diagonal lines of the rectangle intersect). Therefore, when the outer portion 6a is viewed in plan, the yoke through hole 60a is formed point-symmetrically with the center point of the outer portion 6a as a symmetric point.

Three yoke through holes 60b are formed in the inner portion 6b. Each yoke through hole 60b has a circular planar shape. The three yoke through holes 60b are formed at equal intervals along the longitudinal direction of the rectangular parallelepiped inner portion 6b. The yoke through hole 60b is formed so as to be arranged in the center of the inner portion 6b in the short direction. The central yoke through hole 60b is formed at the center of the rectangle forming the upper surface of the inner portion 6b (the point where the diagonal lines of the rectangle intersect). Therefore, when the inner portion 6b is viewed in plan, the yoke through hole 60b is formed point-symmetrically with the center point of the inner portion 6b as a symmetric point.

Three yoke through holes 60c are formed in the outer portion 6c. Each yoke through hole 60c has a circular planar shape. The three yoke through holes 60c are formed at equal intervals along the longitudinal direction of the rectangular parallelepiped outer portion 6c. The yoke through hole 60c is formed so as to be arranged in the center in the short direction of the outer portion 6c. The central yoke through hole 60c is formed at the center of the rectangle forming the upper surface of the outer portion 6c (the point where the diagonal lines of the rectangle intersect). Therefore, when the outer portion 6c is viewed in plan, the yoke through hole 60c is formed point-symmetrically with the center point of the outer portion 6c as a symmetric point.

Also in the electroacoustic transducer 1 of the third embodiment having such a configuration, yoke through

holes

60a, 60b, and 60c that penetrate the yoke 6 in the thickness direction are partially formed in the yoke 6 as in the first embodiment. By being formed, the magnet 4 and the yoke 6 can be fixed by welding. Therefore, the heat resistance strength of the electroacoustic transducer 1 is increased, and the electroacoustic transducer 1 can be fixed to the substrate by a reflow method. Further, the electroacoustic transducer 1 can be reduced in thickness, the space required for installing the electroacoustic transducer 1 can be reduced, and space saving can be achieved.

When the

outer magnets

4a, 4c and the inner magnet 4b having a rectangular parallelepiped shape and a small size in the short-side direction are bonded and fixed to the yoke 6, the adhesive protrudes from the magnet 4, and the protruded adhesive adheres to the voice coil 20 or the diaphragm 10. Problems such as abnormal noise may occur due to contact with other parts. In the present embodiment, since the elongated magnet can be fixed by welding, it is possible to prevent the adhesive from protruding, and to avoid the problems that accompany the adhesive protruding.

FIG. 9 is a schematic diagram illustrating a state before fixing of a modification of the magnetic circuit unit 7 according to the third embodiment. The modification shown in FIG. 9 is different from the example shown in FIG. 8 in that long hole-shaped yoke through

holes

60a, 60b, and 60c are formed in the outer portion 6a, the inner portion 6b, and the outer portion 6c, respectively. ing.

The yoke through-hole 60a is formed along the longitudinal direction of the outer portion 6a at the center of the rectangular parallelepiped outer portion 6a in the short direction. The center of the yoke through hole 60a in the longitudinal direction coincides with the center of the rectangle forming the upper surface of the outer portion 6a (the point where the diagonal lines of the rectangle intersect). Therefore, when the outer portion 6a is viewed in plan, the yoke through hole 60a is formed point-symmetrically with the center point of the outer portion 6a as a symmetric point. Although not described, the yoke through

holes

60b and 60c are formed in the same manner.

Also in the electroacoustic transducer 1 having such a configuration, the yoke 4 is formed with yoke through

holes

60 a, 60 b, 60 c that penetrate the yoke 6 in the thickness direction, so that the magnet 4, the yoke 6, It is possible to fix by welding. Therefore, the heat resistance strength of the electroacoustic transducer 1 is increased, and the electroacoustic transducer 1 can be fixed to the substrate by a reflow method. Further, the electroacoustic transducer 1 can be reduced in thickness, the space required for installing the electroacoustic transducer 1 can be reduced, and space saving can be achieved.

In the above description, the yoke through hole 60 is formed so as to penetrate the yoke 6 inside the yoke 6, and the entire periphery of the yoke through hole 60 is surrounded by the yoke 6. The electroacoustic transducer 1 of the present invention is not limited to this configuration. The yoke through hole 60 only needs to be formed so that the yoke 6 and the magnet 4 can be welded and fixed inside thereof, so that the magnet 4 covers the yoke through hole 60 completely. A configuration in which only a part of the yoke through hole 60 is covered may be employed. In other words, the yoke through hole 60 may be formed so that the magnet 4 covers at least a part of the yoke through hole 60. For example, the yoke through hole 60 may be formed on the outer edge of the yoke 6.

As described above, the embodiment of the present invention has been described. However, it should be considered that the embodiment disclosed this time is illustrative and not restrictive in all respects. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

The electroacoustic transducer 1 of the present invention can be applied particularly advantageously to a small electroacoustic transducer mounted on a portable information device such as a mobile phone, a portable game machine, or a digital camera.

1 Electroacoustic transducer, 2 frame, 3 cover, 4 magnet, 5 plate, 6 yoke, 7 magnetic circuit section, 10 diaphragm, 20 voice coil, 41 upper surface, 42 lower surface, 50 plate through-hole, 51 weld location, 60 Yoke through hole, 61 welds.

Claims

A diaphragm,
A magnetic circuit unit disposed opposite to the diaphragm and generating a magnetic field;
A voice coil disposed in a magnetic field generated by the magnetic circuit unit,
The magnetic circuit unit includes a magnet and a yoke that supports the magnet,
The yoke is formed with a yoke through hole penetrating the yoke in the thickness direction,
The electroacoustic transducer, wherein the magnet is disposed so as to cover at least a part of the yoke through hole.
The electroacoustic transducer according to claim 1, wherein the yoke through hole is formed point-symmetrically with a center point of the yoke as a symmetry point when the yoke is viewed in plan.
The electroacoustic transducer according to claim 2, wherein the yoke through hole is formed so as to penetrate the yoke in a thickness direction at a center point of the yoke.
The electroacoustic transducer according to any one of claims 1 to 3, wherein the yoke and the magnet are fixed by welding.
The electroacoustic transducer according to claim 4, wherein the yoke and the magnet are fixed by welding an inner periphery of the yoke through hole and a surface of the magnet facing the yoke.
The magnetic circuit unit further includes a plate that sandwiches the magnet together with the yoke,
The plate is formed with a plate through-hole penetrating the plate in the thickness direction,
The electroacoustic transducer according to claim 1, wherein the magnet is disposed so as to cover at least a part of the plate through hole.
The electroacoustic transducer according to claim 6, wherein the plate through hole is formed point-symmetrically with a center point of the plate as a symmetric point when the plate is viewed in plan.
The electroacoustic transducer according to claim 7, wherein the plate through hole is formed so as to penetrate the plate in a thickness direction at a center point of the plate.
The electroacoustic transducer according to any one of claims 6 to 8, wherein the yoke through hole and the plate through hole are formed so as to overlap each other with the magnet interposed in a plan view.
The electroacoustic transducer according to claim 6, wherein the plate and the magnet are fixed by welding.
The electroacoustic transducer according to claim 10, wherein the plate and the magnet are fixed by welding an inner periphery of the plate through hole and a surface of the magnet facing the plate.