# Patent

## Title
Acoustic conversion device and acoustic conversion device assembly method

## Abstract

An acoustic conversion device includes: a driving unit including a pair of magnets disposed so as to face each other, a yoke to which the pair of magnets are attached, a coil to which driving current is supplied, a vibrating portion which vibrates when driving current is supplied to the coil, and an armature disposed between the pair of magnets with the vibrating portion being passed through the coil; and a diaphragm unit including a diaphragm, and a beam portion for propagating the vibration of the vibrating portion to the diaphragm; with a coil attachment portion to which the coil is attached, located in a state in parallel with the vibrating portion, being provided to the armature.

## Background
BACKGROUND
The present disclosure relates to a technical field regarding acoustic conversion devices and acoustic conversion device assembly methods, and specifically relates to a technical field for providing a coil attachment portion to which a coil through which a vibrating portion is passed is attached, to an armature of a driving unit, thereby realizing facilitation of positional adjustment, and improvement in positional precision of the vibrating portion as to a pair of magnets and the coil.
There is an acoustic conversion device which serves as a small speaker having an oscillator referred to as an armature which is integrated into various types of audio output devices such as headphones, earphones, hearing aids, and so forth.
With such an acoustic conversion device, a driving unit including an armature, and a diaphragm unit including a diaphragm are housed in a storage case having an audio output hole, vibration is propagated to the diaphragm by a beam portion when a vibration portion of the armature vibrates, and the propagated vibration is output as audio (e.g., see Japanese Unexamined Patent Application Publication No. 2007-74499).
The driving unit includes a pair of magnets disposed so as to face one another, a yoke to which the pair of magnets are attached, a coil to which a driving current is supplied, and an armature including the driving portion serving as an oscillator.
The armature is fixed to the yoke in a state in which the vibrating portion is passed through the coil, and a portion protruding from the vibrating portion of the coil is disposed between the pair of magnets. The coil is attached to the yoke.
SUMMARY
However, with the acoustic conversion described in Japanese Unexamined Patent Application Publication No. 2007-74499, the coil and the armature are configured so as to be individually attached to the yoke.
Accordingly, in a state in which the coil is attached to the yoke, when attempting to perform positional adjustment between the vibrating portion of the armature, and the pair of magnets attached to the yoke, the position of the vibrating portion is changed as to both of the pair of magnets, and the coil, which has a problem in that it is difficult to perform positional adjustment for obtaining excellent magnetic properties.
Conversely, in a state in which the coil is attached to the yoke, when attempting to perform positional adjustment between the coil, and the pair of magnets attached to the yoke, the position of the coil is also changed as to both of the pair of magnets, and the vibrating portion, which has also a problem in that it is difficult to perform positional adjustment for obtaining excellent magnetic properties.
It has been found to be desirable to provide an acoustic conversion device and an acoustic conversion device assembly method which can overcome problems of the related art, whereby positional adjustment can be facilitated, and improvement in positional precision of the vibrating portion as to the pair of magnets and the coil can be realized.
An acoustic conversion device according to an embodiment of the present disclosure includes: a driving unit including a pair of magnets disposed so as to face each other, a yoke to which the pair of magnets are attached, a coil to which driving current is supplied, a vibrating portion which vibrates when driving current is supplied to the coil, and an armature disposed between the pair of magnets with the vibrating portion being passed through the coil; and a diaphragm unit including a diaphragm, and a beam portion for propagating the vibration of the vibrating portion to the diaphragm; with a coil attachment portion to which the coil is attached, located in a state in parallel with the vibrating portion, being provided to the armature.
Accordingly, the vibrating portion of the armature is located between the pair of magnets in a state in which the coil is attached to the coil attachment portion of the armature.
There may be provided a holding frame including an opening; with the diaphragm being attached to the inside of the opening of the holding frame via a resin film; and with the holding frame being fixed to the driving unit.
The diaphragm is attached to the inside of the opening of the holding frame via the resin film, and the holding frame is fixed to the driving unit, and accordingly, the diaphragm and the armature are combined via the beam portion in a sure manner.
There may be provided a storage unit which includes a case body and a cover body which store the driving unit and the diaphragm unit, where an audio output hole for outputting audio generated at the time of vibration being propagated to the diaphragm is formed.
A storage unit which includes a case body and a cover body which store the driving unit and the diaphragm unit, where an audio output hole is formed is provided, and accordingly, the driving unit and the diaphragm unit are protected by the storage unit.
A fixed portion to be fixed to the yoke may be formed on the armature integrally with the coil attachment portion.
A fixed portion to be fixed to the yoke is formed integrally with the coil attachment portion, and accordingly, positional precision between the yoke and the fixed portion increases.
An attached face to be attached to the coil attachment portion of the coil may be formed in a planar shape.
The attached face of the coil is formed in a planar shape, and accordingly, a contact area of the coil as to the coil attachment portion increases.
An arrangement may be made wherein the yoke is formed in a frame shape, and also configured of multiple members including a first member to which one of the magnets is attached, and a second member to which the other magnet is attached.
The yoke is configured of multiple members including the first member and the second member, whereby distance between the first member and the second member can be adjusted.
There may be provided a circuit board formed in a plate shape; with both edge portions of the coil being connected to the circuit board, and also the circuit board being adhered to the coil.
Both edge portions of the coil are connected to the circuit board formed in a plate shape, and the circuit board is adhered to the coil, and accordingly, laying wiring does not have to be performed.
An acoustic conversion device assembly method according to an embodiment of the present disclosure includes: preparing for an armature to which a vibrating portion, and a coil attachment portion located in a state in parallel with the vibrating portion are provided; attaching a coil to the coil attachment portion of the armature; inserting a portion protruding from the coil of the vibrating portion being passed through the coil between a pair of magnets disposed on a yoke so as to face one another; and adjusting the positions of the yoke and the armature so that the vibrating portion is located in a predetermined position between the pair of magnets.
Accordingly, in a state in which the coil is attached to the coil attachment portion of the armature, the vibrating portion of the armature is located between the pair of magnets.
Another acoustic conversion device according to an embodiment of the present disclosure includes an armature including a vibrating portion extending in a predetermined direction, and a coil attachment portion disposed along the extending direction of the vibrating portion; a coil attached to the coil attachment portion so that the vibrating portion is passed therethrough; and a pair of magnets disposed on both sides of a portion protruding from the coil of the vibrating portion, separated from the vibrating portion.
Accordingly, in a state in which the coil is attached to the coil attachment portion of the armature, the vibrating portion of the armature is located between the pair of magnets.
An acoustic conversion device according to an embodiment of the present disclosure includes: a driving unit including a pair of magnets disposed so as to face each other, a yoke to which the pair of magnets are attached, a coil to which driving current is supplied, a vibrating portion which vibrates when driving current is supplied to the coil, and an armature disposed between the pair of magnets with the vibrating portion being passed through the coil; and a diaphragm unit including a diaphragm, and a beam portion for propagating the vibration of the vibrating portion to the diaphragm; with a coil attachment portion to which the coil is attached, located in a state in parallel with the vibrating portion, being provided to the armature.
Accordingly, the positional adjustment of the vibrating portion and the coil as to the magnets can be performed by one-time adjustment work, and accordingly, improvement in workability can be realized.
There may be provided a holding frame including an opening; with the diaphragm being attached to the inside of the opening of the holding frame via a resin film; and with the holding frame being fixed to the driving unit.
Accordingly, the diaphragm and the armature are combined in a sure manner via the beam portion, and the holding frame does not cause position error as to the driving unit at the time of occurrence of vibration, or the like, and accordingly, a suitable audio output state can be secured.
There may be provided a storage unit which includes a case body and a cover body which store the driving unit and the diaphragm unit, where an audio output hole for outputting audio generated at the time of vibration being propagated to the diaphragm is formed.
Accordingly, the driving unit and the diaphragm unit are protected by the storage unit, so damage and breakage regarding the driving unit and the diaphragm unit can be prevented.
A fixed portion to be fixed to the yoke may be formed on the armature integrally with the coil attachment portion.
Accordingly, the position of the coil as to the magnets attached to the yoke can be secured with high precision, and also, improvement in the positional precision of the coil as to the magnets can be realized.
An attached face to be attached to the coil attachment portion of the coil may be formed in a planar shape.
Accordingly, a suitable joint state of the coil as to the coil attachment portion can be secured.
An arrangement may be made wherein the yoke is formed in a frame shape, and also configured of multiple members including a first member to which one of the magnets is attached, and a second member to which the other magnet is attached.
Accordingly, distance between the first member and the second member can be adjusted, and also, optimization of the distance between the magnets used for securing suitable magnetic properties can be realized.
There may be provided a circuit board formed in a plate shape; with both edge portions of the coil being connected to the circuit board, and also the circuit board being adhered to the coil.
Accordingly, laying wiring does not have to be performed, whereby improvement in working efficiency can be realized.
An acoustic conversion device assembly method according to an embodiment of the present disclosure includes: preparing for an armature to which a vibrating portion, and a coil attachment portion located in a state in parallel with the vibrating portion are provided; attaching a coil to the coil attachment portion of the armature; inserting a portion protruding from the coil of the vibrating portion being passed through the coil between a pair of magnets disposed on a yoke so as to face one another; and adjusting the positions of the yoke and the armature so that the vibrating portion is located in a predetermined position between the pair of magnets.
Accordingly, the positional adjustment of the coil as to the magnets dose not have to be performed, and accordingly, improvement in working efficiency can be realized.
Another acoustic conversion device according to an embodiment of the present disclosure includes an armature including a vibrating portion extending in a predetermined direction, and a coil attachment portion disposed along the extending direction of the vibrating portion; a coil attached to the coil attachment portion so that the vibrating portion is passed therethrough; and a pair of magnets disposed on both sides of a portion protruding from the coil of the vibrating portion, separated from the vibrating portion.
Accordingly, the positional adjustment of the vibrating portion and the coil as to the magnets can be performed by one-time adjustment work, and accordingly, improvement in workability can be realized.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of an acoustic conversion device, which illustrates an embodiment of the present disclosure along with FIGS. 2 through 32;
FIG. 2 is an enlarged perspective view of the acoustic conversion device;
FIG. 3 is an enlarged cross-sectional view of the acoustic conversion device;
FIG. 4 is an enlarged front view of a driving unit;
FIG. 5 is an enlarged front view of the driving unit indicating an example wherein a first member and a second member differ in shapes;
FIG. 6 is an enlarged front view illustrating an example wherein a yoke is made up of four members;
FIG. 7 is an enlarged exploded perspective view of the driving unit;
FIG. 8 is an enlarged perspective view of the driving unit;
FIG. 9 is an enlarged perspective view illustrating an example wherein an armature is made up of two members;
FIG. 10 is an enlarged perspective view illustrating an example wherein the armature is configured to be combined with the yoke;
FIG. 11 is an enlarged bottom face view of a diaphragm unit;
FIG. 12 in an enlarged cross-sectional view illustrating a state in which an adhesive agent is applied to a gap between the diaphragm and the holding frame;
FIG. 13 is an enlarged cross-sectional view illustrating a state in which the diaphragm unit is fixed to the driving unit;
FIG. 14 is an enlarged cross-sectional view illustrating an example wherein a wall portion is provided to a fixed portion of the armature;
FIG. 15 is an enlarged cross-sectional view illustrating an example wherein a wall portion is provided to the yoke;
FIG. 16 is an enlarged front view illustrating a beam portion is formed with a shape of which the width widens as a base approaches the diaphragm, which illustrates a shape example of the beam portion along with FIGS. 17 through 19;
FIG. 17 is an enlarged front view illustrating an example wherein the base is formed with a shape of which the width is wider than that of a combined portion;
FIG. 18 is an enlarged front view illustrating an example wherein two combined portions are provided, and the base is formed with a shape of which the width is wide;
FIG. 19 is an enlarged perspective view illustrating an example wherein two combined portions are provided, and the base is formed with a shape of which the width is wide and is partially bent;
FIG. 20 is an exploded perspective view illustrating a state before the driving unit, diaphragm unit, and storage unit are combined, which illustrates an acoustic conversion device assembly method along with FIGS. 21 through 25;
FIG. 21 is an exploded perspective view illustrating state in which the driving unit is fixed to the diaphragm unit;
FIG. 22 is an exploded perspective view illustrating a state in which the driving unit and diaphragm unit are stored in the case body;
FIG. 23 is an enlarged cross-sectional view illustrating a state before a sealing agent is loaded in the holding frame of the diaphragm unit;
FIG. 24 is an enlarged cross-sectional view illustrating a state in which the sealing agent is loaded in the holding frame of the diaphragm unit;
FIG. 25 is an enlarged cross-sectional view illustrating a state in which the sealing agent loaded in the holding frame of the diaphragm unit is pressedly deformed by the cover body, and the sealing agent is loaded in a gap;
FIG. 26 is an enlarged back view of the acoustic conversion device;
FIG. 27 is an enlarged plan view illustrating an example wherein a terminal portion is provided to both sides of a circuit board;
FIG. 28 is an enlarged plan view illustrating an example wherein a terminal portion is provided to both sides of the circuit board in a manner isolated forward and backward;
FIG. 29 is an enlarged plan view illustrating an example wherein a terminal portion is provided to the surface of the circuit board in a manner isolated forward and backward;
FIG. 30 is a diagram illustrating relationship between the fulcrum of vibration and tertiary resonance;
FIG. 31 is a graph chart illustrating a measurement result regarding acoustic properties; and
FIG. 32 is a graph chart illustrating anther measurement result regarding the acoustic properties.



DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereafter, an embodiment of the present disclosure will be described in accordance with the appended drawings.
With the following description, directions of forward, backward, upper, lower, left, and right will be used in relation to a direction in which audio is output, which is forward.
Note that the directions of forward, backward, upper, lower, left, and right shown below are for convenience of description, and implementation of the present disclosure is not restricted to these directions.
Entire Configuration
An acoustic conversion device 1 is configured of a driving unit 2, a diaphragm unit 3, and a storage unit 4 (see FIGS. 1 through 3).
The driving unit 2 is configured of a yoke 5, a pair of magnets 6, a coil 7, a circuit board 8, and an armature 9 (see FIGS. 2 and 3).
The yoke 5 is configured by a plate-shaped first member 10 directed in the vertical direction, and a U-shaped second member 11 opened upward being combined. The second member 11 is configured of a bottom face portion 11a directed in the vertical direction, and side face portions 11b protruding upward from both of left and right edge portions of this bottom face portion 11a. 
With the first member 10, both of left and right side faces are attached to the inner faces of the side faces 11b of the second member 11, for example, by adhesion or the like, respectively. The yoke 5 is formed in a square tubular shape where the first member 10 and the second member 11 are combined and pierced backward and forward, and the opening on the front side is formed as a working opening 5a. 
The magnets 6 are disposed in a state isolated in the vertical direction and mutually facing, and the poles on the facing sides are made up of a different pole. The magnet 6 located upward is attached to the lower face of the first member 10, and the magnet 6 located downward is attached to the upper face of the bottom face portion 11a in the second member 11.
As described above, the yoke 5 is configured of the first member 10 and the second member 11.
Accordingly, distance between the first member 10 and the bottom face portion 11a of the second member 11 can be adjusted, and optimization of distance (L shown in FIG. 4) between the magnets 6 used for securing suitable magnetic properties can be realized. In particular, the distance L between the magnets 6 depends on the thickness of an adhesive agent for attaching the magnets 6 to the yoke 5, and the thickness of a later-described vibrating portion of an armature 9 to be inserted into the magnets 6, and accordingly, it is extremely effective for securing suitable magnetic properties and suitable ease of assembly that the distance L between the magnets 6 can be adjusted.
Also, in a state before the first member 10 and the second member 11 are combined, the magnets 6 can be attached to the first member 10 and the second member 11, respectively. Accordingly, insertion of the magnets 6 into the internal space of the yoke 5 integrally formed in a frame shape so as to perform attachment work does not have to be performed, and accordingly, attachment work of the magnets 6 as to the yoke 5 can readily be performed with high precision.
Note that joining between the first member 10 and the second member 11 is performed by inserting an unshown spacer between the magnets 6, or confirming the distance L by image processing.
Though an example has been shown above wherein the yoke 5 is configured of the plate-shaped first member 10 and the U-shaped second member 11, the configuration of the yoke 5 is not restricted to this, and the following yokes 5A and 5B may be configured, for example (see FIGS. 5 and 6).
The yoke 5A is configured of a U-shaped first member 10A opened downward and a U-shaped second member 11A opened upward (see FIG. 5). The first member 10A and the second member 11A are attached to later-described fixed portions 16 of the armature 9 disposed on the outer face side, and are disposed in a manner vertically isolated, for example. With the yoke 5A as well, in the same way as with the yoke 5, optimization of distance in the vertical direction between the magnets 6 can be realized by performing positional adjustment of the first member 10A and the second member 10A.
The yoke 5B is configured by four of two plate-shaped first members 10B and two plate-shaped second members 11B being combined, which are vertically horizontally located (see FIG. 6). The first members 10B are located in a manner vertically isolated, and the second members 11B are located in a manner horizontally isolated. With the yoke 5B as well, optimization of distance in the vertical direction between the magnets 6 can be realized by performing positional adjustment between the first members 10B.
In this way, the number of members making up the yoke 5 is arbitrary as long as the number is greater than one, and distance adjustment of the multiple members is allowed in the vertically direction, whereby optimization of the distance in the vertical direction between the magnets 6 can be realized.
A coil 7 is formed in a tube shape with the axial direction being set as the forward/backward direction, which is formed in a slotted-hole shape as viewed from the forward/backward direction, for example (see FIGS. 1 and 3). The coil 7 is made up of regular winding, wherein the upper face and lower face are formed as attached faces 7a and 7b formed in a planar shape, respectively.
The circuit board 8 is attached to the attached face 7a of the coil 7. The circuit board 8 is configured so that the length in the forward/backward direction is longer than the length in the forward/backward direction of the coil 7, and generally the first half portion is attached to the attached face 7a of the coil 7. Accordingly, generally the second half portion of the circuit board 8 protrudes backward from the coil 7.
An unshown pair of connection terminal portions of the circuit board 8 are connected with both edge portions of the coil 7 respectively, and in a state in which both edge portions of the coil 7 are connected to the pair of connection terminal portions respectively, the circuit board 8 is attached to the attached face 7a of the coil 7 by adhesion or the like. The coil 7 is made up of regular winding, and the attached face 7a is formed in a planar shape, whereby a suitable joint state between the coil 7 and the circuit board 8 can be secured.
The armature 9 is configured by each portion being integrally formed of a magnetic metal material. Specifically, the armature 9 is configured by a coil attachment portion 12 facing the vertical direction, a joint portion 13 protruding upward from the rear edge portion of this coil attachment portion 12, a vibrating portion 14 protruding forward from the upper edge portion of this joint portion 13, side wall portions 15 protruding upward from both of left and right edge portions of the coil attachment portion 12 respectively, and fixed portions 16 protruding forward from the front faces of generally the first half portions of the side wall portions 15 respectively, being integrally formed.
With the vibrating portion 14, the length in the forward/backward direction is set to be longer than the length in the forward/backward direction of the coil attachment portion 12, and the front edge is located more forward than the front edge of the coil attachment portion 12. With the central portion in the horizontal direction of the front face of the vibrating portion 14, a joint recessed portion 14a opened forward is formed.
The upper faces of the side wall portions 15, and the upper faces of the fixed portions 16 are formed as the same planes, and the same planes located in a manner horizontally isolated are formed as fixed faces 17, respectively.
The upper face of the coil attachment portion 12 is attached with the coil 7 by adhesion, for example (see FIGS. 3 and 7). The coil 7 is made up of regular winding, and the lower face serving as the attached face 7b is formed in a planar shape, whereby a suitable joint state of the coil 7 as to the coil attachment portion 12 can be secured.
In a state in which the coil 7 is attached to the coil attachment portion 12, the coil 7 is in a state in which the vibrating portion 14 is passed through the coil 7, and a part thereof protrudes forward from the coil 7.
With the acoustic conversion device 1, both of the coil attachment portion 12 to which the coil 7 is attached, and the vibrating portion 14 passed through the coil 7 are provided to the armature 9. Accordingly, the position of the vibrating portion 14 as to the coil 7 can be secured with high precision, and improvement in the positional precision of the vibrating portion 14 as to the coil 7 can be realized.
With the armature 9, in a state in which the coil 7 is attached to the coil attachment portion 12, the fixed portions 16 are fixed to the outer faces of the side face portions 11b of the yoke 5 by adhesion, welding, or the like, respectively (see FIG. 8).
At the time of fixing work of the armature 9 as to the yoke 5, in order to secure a suitable magnetic balance, positional adjustment between the vibrating portion 14 and the magnets 6 is performed. In particular, with the acoustic conversion device 1, the yoke 5 is configured of the first member 10 and second member 11 which have different volume, and accordingly, though the magnetic balance may be out of balance in the vertical direction, a suitable magnetic balance can be secured by performing positional adjustment between the vibrating portion 14 and the magnets 6.
Positional adjustment between the vibrating portion 14 and the magnets 6 is performed by adjusting the positions of the armature 9 and the yoke 5. Specifically, as illustrated in FIG. 4, gap adjustment of a gap H1 between one of the magnets 6 and the upper face of the vibrating portion 14, and a gap H2 between the other magnet 6 and the lower face of the vibrating portion 14, inclination adjustment of the vibrating portion 14 as to the magnets 6, or the like is performed.
At this time, with the acoustic conversion device 1, since the coil 7 is attached to the coil attachment portion 12 of the armature 9, the position of the vibrating portion 14 as to the coil 7 is not changed, and accordingly, when the positions of the vibrating portion 14 and the magnets 6 are adjusted, the positions as to the magnets 6 of the coil 7 are adjusted at the same time.
Accordingly, preliminary positional adjustment of the coil 7 as to the magnets 6 can be omitted, whereby improvement in workability can be realized.
Note that, with the acoustic conversion device 1, the yoke 5 is configured of the first member 10 and second member 11 which have different volume. Accordingly, for example, a magnetic balance may be adjusted by a technique, such that the first member 10 and the second member 11 are each formed with different thickness, the magnets 6 are each formed with different thickness, the magnets 6 are each made of a different material, the magnets 6 are configured so as to have different magnetic force, or the like.
In a state in which the armature 9 is fixed to the yoke 5, the upper faces of the side face portions 11b of the yoke 5 are located somewhat upward as compared to the fixing portions 17 of the armature 9 (see FIG. 4). Also, the joint recessed portion 14a formed in the front edge portion of the vibrating portion 14 is located somewhat forward as compared to beneath the front edge portions of the magnets 6.
Note that, though the armature 9 where each portion is integrally formed has been shown as an example, the armature may be configured as the following armature 9A or 9B (see FIGS. 9 and 10) as long as the armature is configured so that the vibrating portion serving as a portion to be magnetized is made of a magnetic metal material.
The armature 9A is configured, as illustrated in FIG. 9, by a first member 18 including the vibrating portion 14, and a second member 19 including the fixed portions 16 being combined by adhesion or welding.
The armature 9B is configured, as illustrated in FIG. 10, by the first member 18 including the vibrating portion 14, and a second member 11A of the yoke 5 being combined by adhesion or welding.
In this way, the first member 18 including the vibrating portion 14 is configured as a member different from the other portions, whereby the expensive first member 18 which has to be magnetized, and other portions which can be formed at low cost, can individually be formed, and reduction in manufacturing cost can be realized.
The diaphragm unit 3 is made up of a holding frame 20, a resin film 21, a diaphragm 22, and a beam portion 23 (see FIGS. 1 and 3).
The holding frame 20 is formed, for example, in a vertically long frame shape by a metal material, wherein the width in the horizontal direction is set to generally the same width as the width in the horizontal direction of the armature 9. With the holding frame 20, the lower face is taken as a first joint face 20a, and the upper face is taken as a second joint face 20b. 
The size of the resin film 21 is set to the same as with the outer shape of the holding frame 20, and the resin film 21 is adhered onto the upper face 20b of the holding frame 20 by adhesion or the like so as to close the opening of the holding frame 20, for example.
With the diaphragm 22, the outer shape is formed in a rectangular shape having a size smaller than the inner shape of the holding frame 20, by a thin metal material, for example, aluminum or stainless steel. Three reinforcing ribs 22a located in a manner extending forward/backward and horizontally isolated are provided to the diaphragm 22, and the reinforcing ribs 22a are formed in a shape ticked out upward.
The diaphragm 22 is set in a state adhered to the resin film 21 from below.
The rear edge 22b of the diaphragm 22 is located somewhat forward as compared to the inner face 20c in the rear edge portion of the holding frame 20, and a gap M is formed between the rear edge 22b of the diaphragm 22, and the inner face 20c in the rear edge portion of the holding frame 20 (see FIGS. 11 and 12). The gap M is caused due to dimensional tolerance, assembly error, or the like between the diaphragm 22 and the holding frame 20, and is 0.1 mm or so, for example.
An adhesive agent 24 is applied to the diaphragm unit 3 so as to fill in the gap M. Accordingly, the diaphragm 22 and the holding frame 20 are combined via the adhesive agent 24, and the resin film 21. An acrylic non-curing adhesive agent or acrylic UV cure adhesive agent is used as the adhesive agent 24, for example.
Note that the adhesive agent 24 fills in the gap M and also extends on the opposite side of a side where the resin film 21 of the diaphragm 22 is adhered, i.e., the diaphragm 22 is supported on the holding frame 20 by the resin film 21, but the adhesive agent 24 serves as a reinforcing member for reinforcing this.
The beam portion 23 is formed integrally with the diaphragm 22, and is formed by a part of the diaphragm 22 being bent. The beam portion 23 is formed in a narrow plate shape vertically extending.
The diaphragm unit 3 is fixed to the driving unit 2 from above, for example, by adhesion or laser welding. The diaphragm unit 3 is fixed to the driving unit 2 by the first joint face 20a of the holding frame 20 being jointed to the fixing faces 17 of the armature 9.
The first joint face 20a of the holding frame 20 is jointed to the fixing faces 17 of the armature 9, for example, by laser welding, and laser R is irradiated on the joint portion from the lateral side (see FIG. 13). At this time, as described above, the upper faces of the side face portions 11b of the yoke 5 are located somewhat upward as compared to the fixing faces 17 of the armature 9, and in the event that a plurality of metal m molten by irradiation of the laser R have scattered on the yoke 5 side, the plurality of scattered metal m collide with the outer faces of the upper edge portions on the side face portions 11b. 
Accordingly, adhesion of the plurality of metals m scattered by the irradiation of the laser R to the resin film 21 can be prevented, and damage of the resin film 21 can be prevented. In this way, the upper edge portion of the side face portion 11b in the yoke 5 serves as a wall portion 11c for preventing scattering of the plurality of metal m, and it is desirable to locate the outer face of this wall portion 11c, and the inner face of the holding frame 20 in the closest position possible.
Also, with the acoustic conversion device 1, the upper face of the side face portion 11b in the yoke 5 is located upward as compared to the fixing faces 17 of the armature 9, whereby damage of the resin film 21 can be prevented, and damage of the resin film 21 can be prevented by a simple technique without increasing manufacturing costs.
Note that an example has been shown above wherein the wall portion 11c for preventing scattering of the plurality of metal m is provided to the yoke 5, but for example, as illustrated in FIG. 14, wall portions 17a protruding upward may be provided to the fixing faces 17 of the armature 9, respectively.
In this way, the armature 9 can be fixed to the yoke 5 by providing the wall portions 17a to the armature 9 without considering the heights between the upper face of the yoke 5, and the fixing faces 17 of the armature 9, and damage of the resin film 21 can be prevented in addition to realizing improvement in the flexibility of designing.
Also, the wall portions 17a are provided to the armature 9, and accordingly, the fixing portions 17 are extended long in the forward/backward direction by the yoke 5, whereby the diaphragm unit 2 can tightly be fixed to the driving unit 2 by widening the irradiation range of the laser R.
Further, like the armature 9B illustrated in FIG. 10, in the event that the fixed portions 16 are not provided, the holding frame 20 of the diaphragm unit 3 is fixed to the upper face of the yoke 5, but in this case, as illustrated in FIG. 15, wall portions 11d may be provided to the upper edge portions of the side face portions 11b of the yoke 5, respectively.
In this way, the holding frame 20 is fixed to the yoke 5, and the wall portions 11d are provided to the yoke 5, whereby damage of the resin film 21 can be prevented in addition to realizing reduction in the size of the acoustic conversion device 1 by an amount equivalent to that conserved by the fixed portions 16 of the armature 9 being omitted.
As described above, at the time of fixing the diaphragm unit 3 to the driving unit 2, the lower edge portion of the beam portion 23 is attached to the front edge portion of the vibrating portion 14 in the armature 9 by adhesion (see FIG. 3). The beam portion 23 is combined to the armature 9 by an adhesive agent 25 in a state inserted into the joint recessed portion 14a formed in the vibrating portion 14.
As described above, the beam portion 23 is formed integrally with the diaphragm 22, and accordingly, the diaphragm 22 and the armature 9 are combined via the beam portion 23 only by the lower edge portion of the beam portion 23 being attached to the vibrating portion 14, whereby improvement in working efficiency in joining between the diaphragm 22, beam portion 23, and armature 9 can be realized.
Also, the beam portion 23 is formed integrally with the diaphragm 22, and accordingly, attachment of the upper edge portion of the beam portion 23 as to the diaphragm 22 can be omitted in a state in which the lower edge of the beam portion 23 is attached to the vibrating portion 14 of the armature 9. Accordingly, attachment of the upper edge portion of the beam portion 23 as to the lower face of the diaphragm 22 by feel does not have to be performed, and improvement in yield can be realized without causing shifting of the combined position of the beam portion 23 as to the diaphragm 22, modification of the beam portion 23, bending of the beam portion 23 as to the diaphragm 22, and so forth.
Further, with the acoustic conversion device 1, the yoke 5 is formed in a square tubular shape penetrated forward and backward, and the opening on the front side is formed as the working opening 5a, whereby attachment work of the beam portion 23 as to the vibrating portion 14 can be performed from the working opening 5a, and improvement in workability can be realized. Also, the working opening 5a is formed in the yoke 5, whereby a UV cure adhesive agent can be employed as the adhesive agent 24 for bonding the beam portion 23 to the vibrating portion 14, and improvement in workability with joining of the beam portion 23 as to the vibrating portion 14 can be realized.
Note that a narrow plate shape vertically extending has been shown above as an example of the beam portion 23, but the shape of the beam portion 23 is not restricted to the narrow plate shape, and various types of shape can be employed such as beam portions 23A, 23B, 23C, and 23D illustrated in FIGS. 16 through 19, for example.
The beam portion 23A is provided, as illustrated in FIG. 16, as a narrow joint portion 23a of which the lower edge portion is combined to the vibrating portion 14, and is provided as a base 23b where as the upper side portion of the joint portion 23a advances upward, the width in the horizontal direction increases.
In this way, the beam portion 23A includes the base 23b where as the upper side portion of the joint portion 23a advances upward, the width in the horizontal direction increases, and accordingly, strength is high, whereby the vibration generated at the vibrating portion 14 can be propagated to the diaphragm 22 in a sure manner.
The beam portion 23B is provided, as illustrated in FIG. 17, as a narrow joint portion 23c of which the lower edge portion is combined to the vibrating portion 14, and is provided as a base 23d where the width in the horizontal direction of the upper side portion of the joint portion 23c is wider than the width of the joint portion 23c. 
In this way, the beam portion 23B includes the base 23d of which the width is wider than the width of the joint portion 23c, and accordingly, strength is high, whereby the vibration generated at the vibrating portion 14 can be propagated to the diaphragm 22 in a sure manner.
The beam portion 23C is provided, as illustrated in FIG. 18, as narrow joint portions 23e of which the lower edge portions are connected to the vibrating portion 14, located in a manner horizontally isolated, and is provided as a base 23f where the width in the horizontal direction is wider than the widths of the upper side portions of the joint portions 23e. The beam portion 23C includes the narrow joint portions 23e located in a manner horizontally isolated, and accordingly, two joint recessed portions 14b located in a manner horizontally isolated are provided to the vibrating portion 14.
In this way, the beam portion 23C includes the base 23f of which the width is wider than the widths of the joint portions 23e, and accordingly, strength is high, whereby the vibration generated at the vibrating portion 14 can be propagated to the diaphragm 22 in a sure manner. Also, the beam portion 23C includes the joint portions 23e located in a manner horizontally isolated, whereby stabilization of a joint state with the vibrating portion 14 can be realized.
The beam portion 23D is provided, as illustrated in FIG. 19, as a bent portion 23g where the central portion of the base 23f is formed in a circular arc face shape protruding forward or backward.
In this way, the beam portion 23D includes the bent portion 23g formed in a circular arc face shape, whereby strength can further be increased.
Note that the beam portions 23 (23A, 23B, 23C, and 23D) are formed integrally with the vibrating portion 22, and are made of aluminum or stainless steel.
Reduction in weight can be realized by forming the diaphragm 22 using aluminum. On the other hand, strength is increased by forming the diaphragm 22 using stainless steel, whereby improvement in propagation efficiency of vibration from the vibrating portion 14 to the diaphragm 22 can be realized.
The storage unit 4 is configured of a box-shaped case body 26 opened upward, and a shallow box-shaped cover body 27 opened downward (see FIGS. 1 through 3).
An insertion notch 28a opened upward is formed on the upper edge portion of a rear face portion 28. With the inner face sides of the both edge portions of the case body 26, three installation stepped faces 26a which each face upward are formed.
With the cover body 27, an audio output hole 29a penetrated forward and backward is formed in a front face portion 29.
Acoustic Conversion Deice Assembly Method
Hereafter, an assembly method of the acoustic conversion device 1 will be described (see FIGS. 20 through 25).
First, as described above, the driving unit 2 is assembled using the yoke 5, magnets 6, coil 7, circuit board 8, and armature 9, and the diaphragm unit 3 is assembled using the holding frame 20, resin film 21, diaphragm 22, and beam portion 23 (see FIG. 20).
Next, as described above, the diaphragm unit 3 is fixed to the driving unit 2 (see FIG. 21). Fixing of the diaphragm unit 3 as to the driving unit 2 is performed by jointing the first joint face 20a of the holding frame 20 to the fixing portions 17 of the armature 9. At this time, the lower edge portion of the beam portion 23 is attached to the front edge portion of the vibrating portion 14 in the armature 9 by the adhesive agent 25.
Next, the driving unit 2 and the diaphragm unit 3 are stored in the case body 26 from above (see FIG. 22). With the diaphragm unit 3 stored in the case body 26, both edge portions of the holding frame 20 are installed on the installation stepped faces 26a of the case body 26 respectively, and thus, positioning is determined. At this time, a predetermined gap is formed between the lower face of the driving unit 2, and the upper face of the bottom face portion of the case body 26.
In a state in which the driving unit 2 and the diaphragm unit 3 are stored in the case body 26, the second joint face 20b of the holding frame 20 is located somewhat downward on the immediately inner side of the upper edge face 26b of the case body 26 (see FIG. 23). At this time, a gap S is formed between the outer face 20d of the holding frame 20, and the inner face 26c of the case body 26.
Also, in a state in which the driving unit 2 and the diaphragm unit 3 are stored in the case body 26, generally the second half portion of the circuit board 8 attached to the coil 7 protrudes backward from the insertion notch 28a of the case body 26.
Next, a sealing agent 30 is loaded in the second joint face 20b of the holding frame 20 (see FIG. 24). The sealing agent 30 also has an adhesive property.
Next, the cover body 27 is pressed against the sealing agent 30 loaded in the second joint face 20b from above to pressedly deform this (see FIG. 25). Upon pressedly deforming the sealing agent 30, this sealing agent 30 enters a gap between the outer face 20d of the holding frame 20, and the inner face 26c of the case body 26, and a gap between the outer face 27a of the cover body 27, and the inner face 26c of the case body 26, and thus, the gap S is sealed. Also, the sealing agent 30 remains between the second joint face 20b of the holding frame 20, and the lower edge face 27b of the cover body 27, and also enters the inner side of the holding frame 20, and a gap between the holding frame 20 and the cover body 27 is sealed.
Accordingly, the cover body 27 is pressed against the sealing agent 30 from above to pressedly deform this, and accordingly, each gap between the holding frame 20, cover body 27, and case body 26 is sealed, and these three are adhered and combined.
At this time, the lower face of the cover body 27 is disposed lower and inner than the upper face of the case body 26.
In this way, with the acoustic conversion device 1, one-time work only for covering the holding frame 20 by the cover body 27 to pressedly deform the sealing agent 30 is performed, and accordingly, each gap between the holding frame 20, cover body 27, and case body 26 is sealed, whereby improvement in workability with the assembly work of the acoustic conversion device 1 can be realized.
Next, a sealing agent (adhesive agent) 31 is applied to a gap between the opening edge of the insertion notch 28a and the circuit board 28 in the case body 26 to perform sealing and adhesion (see FIG. 26).
Lastly, the portion of the circuit board 8 protruding backward from the case body 26 is connected with a connection code and a connection terminal for supplying power to the coil 7.
With the acoustic conversion device 1, as described above, the circuit board 8 is adhered to the coil 7 for connection, so laying wiring can be omitted, and improvement in working efficiency can be realized.
Note that there are provided a pair of terminal portions 8a and 8b of a plus pole and a minus pole where the connection code or connection terminal is connected, and the terminal portions 8a and 8b are located on both sides of the circuit board 8 respectively (see FIG. 27).
In this way, the terminal portions 8a and 8b are provided to both sides of the circuit board 8 respectively, whereby electric short-circuiting can be prevented at the time of connecting the connection code or connection terminal, and specifically at the time of connecting by soldering.
Also, the terminal portions 8a and 8b may be located in the circuit board 8 in a manner isolated forward or backward in a state provided on both sides of the circuit board 8 (see FIG. 28), or may be located in a manner isolated forward or backward in a state provided on one of both sides of the circuit board 8 (see FIG. 29).
In this way, even in the event that the terminal portions 8a and 8b are located in a manner isolated forward or backward, electric short-circuiting at the time of connecting the connection code or connection terminal can be prevented.
Note that an example has been shown above wherein the folding frame 20 to which the resin film 21 is adhered is attached between the case body 26 and the cover body 27, but an arrangement may be made wherein the resin film 21 is adhered between the case body 26 and the cover body 27 without providing the holding frame 20.
Acoustic Properties
With the acoustic conversion device 1, upon current being supplied to the coil 7, the vibrating portion 14 of the armature 9 located between the pair of magnets 6 is magnetized, and the polarity of this vibrating portion 14 is repeatedly changed at a position facing the magnets 6. Minute vibration is generated at the vibrating portion 14 by the polarity being repeatedly changed, the generated vibration is propagated from the beam portion 23 to the diaphragm 22, and the propagated vibration is amplified at the diaphragm 22, converted into audio, and output from the audio output hole 29a of the cover body 27.
At this time, in order to realize improvement in acoustic properties by suppressing variation in sound pressure in the frequency region of the output audio, it is desirable to clearly generate a tertiary resonance peak existing in this frequency region, and specifically, in a high-frequency region.
With the acoustic conversion device 1, as described above, the adhesive agent 24 is applied so that the rear edge 22b of the diaphragm 22 is located somewhat forward as compared the inner face 20c of the rear edge portion of the holding frame 20, and the gap M between the rear edge 22b of the diaphragm 22, and the inner face 20c of the rear edge portion of the holding frame 20 is filled (see FIGS. 11 and 12). Accordingly, the diaphragm 22 and the holding frame 20 are in a state combined via the adhesive agent 24 and the resin film 21.
In this way, the adhesive agent 24 is applied so as to fill the gap M between the rear edge 22b of the diaphragm 22, and the inner face 20c of the holding frame 20, and accordingly, the portion where the adhesive agent 24 is applied becomes a clear fulcrum (vibration fulcrum) P for generating tertiary resonance (see FIG. 30). Accordingly, variation in the sound pressure in the frequency region in the acoustic conversion device 1, and specifically, in a high-frequency region is suppressed, whereby stable sound pressure can be obtained, and improvement in acoustic properties can be realized.
Hereafter, results obtained by measuring acoustic properties will be described (see FIGS. 31 and 32).
FIGS. 31 and 32 are graph charts in which the horizontal axis represents frequency (Hz), and the vertical axis represents sensitivity (dB).
In FIG. 31, A indicates a state in which the gap M is set to 0.14 mm, and no adhesive agent is applied to the gap M, B indicates a state in which the gap M is set to 0.07 mm, and no adhesive agent is applied to the gap M, and C indicates a state in which the gap M is set to 0.07 mm, and an adhesive agent is applied to the gap M. The adhesive agent used in C is an acrylic non-curing adhesive agent (pressure sensitive adhesive agent), and the viscosity is set to 100 through 3000 mPa·s.
According to comparison between A and B in FIG. 31, though almost no difference in sensitivity is seen in the frequency region of 3000 through 4000 Hz or less, it can be found that sensitivity deteriorates when the gap M increases in a high-frequency region.
Also, according to comparison between B and C in FIG. 31, in the event that the gap M is constant, though almost no difference in sensitivity is seen depending on whether or not application of the adhesive agent has been performed in the frequency region of 3000 through 4000 Hz or less, it can be found that sensitivity is increased due to application of the adhesive agent in a high-frequency region.
FIG. 32 shows measurement results when changing the adhesive agent to be applied to the gap M with the value of the gap M held constant.
In FIG. 32, D indicates a state in which the same acrylic non-curing adhesive agent as that in C in FIG. 31 has been applied to the gap M, E indicates a state in which an acrylic UV cure adhesive agent of which the degree of hardness is D (shore) 75 has been applied to the gap M, and F indicates a state in which an acrylic UV cure adhesive agent of which the degree of hardness is D (shore) 85 has been applied to the gap M. The hardness of the non-curing adhesive agent in D is lower than the hardness of the UV cure adhesive agent in E.
According to comparison between A, B, and C in FIG. 32, it can be found that with the frequency region of 3000 through 4000 Hz or less, an adhesive agent of which the hardness is lower is higher in sensitivity, and with the frequency region of 10000 Hz or less, an adhesive agent of which the hardness is higher is higher in sensitivity.
According to the above measurement results, a non-curing adhesive agent is employed as the adhesive agent 24, whereby improvement in sensitivity can be realized in high frequency, and improvement in acoustic properties can be realized, without decreasing low-frequency sensitivity.
Also, a UV cure adhesive agent is employed as the adhesive agent 24, whereby improvement in sensitivity can be realized in high frequency, and improvement in acoustic properties can be realized.
In particular, an acrylic UV cure adhesive agent is employed as the adhesive agent 24, whereby improvement in acoustic properties can be realized in addition to securing suitable adhesive strength and reduction in adhesion process.
The specific shape and configuration of each portion shown in the above preferred embodiment are all a mere example of instantiation at the time of implementing the present disclosure, and the technical scope of the present disclosure is not to be interpreted in a limited manner by these.
The present disclosure contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2010-137898 filed in the Japan Patent Office on Jun. 17, 2010, the entire contents of which are hereby incorporated by reference.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.

## Claims

1. An acoustic conversion device comprising:
(a) a driving unit including
(1) a pair of magnets disposed to face each other,
(2) a yoke to which said pair of magnets are attached, said yoke being configured of a plurality of members including a first member to which a first magnet of the pair of magnets is attached, and a second member to which a second magnet of the pair of magnets is attached, the first member and the second member being configured such that a distance between the pair of magnets is adjustable,
(3) a coil operable to receive a driving current, and
(4) an armature spaced from said yoke and having (i) a coil attachment portion attached directly to said coil, (ii) a joint portion protruding from said coil attachment portion, and (iii) a vibrating portion protruding from an uppermost edge of the joint portion so as to at least partially extend through said coil and between said pair of magnets, said vibrating portion operable to vibrate when the driving current is supplied to said coil; and

(b) a diaphragm unit including
(1) a diaphragm, and
(2) a beam portion operable to transmit vibration of said vibrating portion to said diaphragm.

2. The acoustic conversion device according to claim 1, further comprising:
a holding frame including an opening,
wherein,
said diaphragm is attached within said opening of said holding frame via a resin film, and
said holding frame is fixed to said driving unit.

3. The acoustic conversion device according to claim 1, further comprising:
a storage unit having a case body and a cover body for storing said driving unit and said diaphragm unit, said storage unit having an audio output hole that outputs audio generated when vibrations propagate to said diaphragm.

4. The acoustic conversion device according to claim 1, wherein said armature comprises a fixed portion fixed to said yoke, said fixed portion being integral with said coil attachment portion.

5. The acoustic conversion device according to claim 1, wherein an attached face to be attached to said coil attachment portion of said coil comprises a planar shape.

6. The acoustic conversion device according to claim 1, wherein said yoke has a frame shape comprising said first and second members.

7. The acoustic conversion device according to claim 1, further comprising:
a circuit board comprising a plate shape,
wherein,
both edge portions of said coil are connected to said circuit board, and
said circuit board is adhered to said coil.

8. The acoustic conversion device according to claim 1, wherein said coil is adhered to said coil attachment portion.

9. An acoustic conversion device comprising:
(a) an armature including
(1) a vibrating portion extending in a predetermined direction, and
(2) a coil attachment portion extending parallel to the predetermined direction of said vibrating portion;

(b) a coil attached directly to said coil attachment portion so that said vibrating portion is passed therethrough;
(c) a pair of magnets (i) disposed on both sides of a portion of said vibrating portion protruding from said coil, and (ii) spaced from said vibrating portion, and
(d) a yoke to which said pair of magnets are attached, said yoke being configured of a plurality of members including a first member to which a first magnet of the pair of magnets is attached, and a second member to which a second magnet of the pair of magnets is attached, the first member and the second member being configured such that a distance between the pair of magnets is adjustable,
wherein,
the armature further includes a joint portion protruding from said coil attachment portion,
the vibrating portion protrudes from an uppermost edge of the joint portion, and
the armature includes an end that does not protrude beyond the coil.

10. The acoustic conversion device according to claim 9, wherein said coil attachment portion of said armature is attached (i) directly to said coil via adhesion and (ii) along an entire surface of said coil.

11. The acoustic conversion device according to claim 9, wherein said coil attachment portion of said armature and said coil have coplanar end surfaces.

12. An acoustic conversion device assembly method comprising:
providing an armature having a vibrating portion extending in a direction, and a coil attachment portion extending parallel to said vibrating portion in said direction;
attaching a coil directly to said coil attachment portion of said armature;
inserting a portion protruding from said vibrating portion being passed through said coil between a pair of magnets, said pair of magnets facing each other and disposed on a yoke; and
adjusting the positions of said yoke and said armature so that said vibrating portion is located in a predetermined position between said pair of magnets,
wherein,
the yoke is configured of a plurality of members including a first member to which a first magnet of the pair of magnets is attached and a second member to which a second magnet of the pair of magnets is attached, the first member and the second member being configured such that a distance between the pair of magnets is adjustable,
the armature further includes a joint portion protruding from said coil attachment portion,
the vibrating portion protrudes from an uppermost edge of the joint portion, and
said coil attachment portion of said armature and said coil have coplanar end surfaces.

13. The acoustic conversion device according to claim 12, wherein said coil attachment portion of said armature is attached (i) directly to said coil via adhesion and (ii) along an entire surface of said coil.