VOICE COIL DIAPHRAGM

Abstract

A coil body 30 has a conductive part 32, which is made of a conductive body 31 or of a plurality of conductive bodies 31 arranged side by side in a planar shape, and an insulating part 33 for insulating the conductive part 32. The conductive body 31, or the conductive bodies 31, and the insulating part 33 are arranged in a winding state, thereby a plurality of wound parts 34 that are separated from each other and arranged side by side are formed in the coil body 30. The wound parts 34 are arranged in a manner where each wound part 34 comes into a partial contact with an adjacent one or more of the other wound parts 34 at least when vibrating and is linked by movable linking parts 41 with other ones of the wound parts 34 arranged side by side.

Claims

1. A voice coil diaphragm having a planar coil body formed with a conductive part in a winding state, being disposed facing a magnet plate, and being used in (a) an electroacoustic transducer generating sound by vibrating the conductive part by using an electro-magnetic force, the electro-magnetic force generated by a magnetic field and an acoustic signal current, the magnetic field created by the magnet plate, the acoustic signal current flowing in the conductive part, or (b) an electroacoustic transducer generating an acoustic signal current in the conductive part by using a magnetic field and vibrations of the conductive part, the magnetic field created by the magnet plate, the vibrations of the conductive part deriving from sound, the coil body of the voice coil diaphragm comprising: the conductive part composed of a conductive body or of a plurality of conductive bodies arranged side by side so as to be in a planar shape; and an insulating part for insulating the conductive part, wherein a plurality of wound parts that are separated from each other and arranged side by side are formed in the coil body by arranging the conductive body, or the conductive bodies, and the insulating part in a winding state, further wherein the wound parts (1) are disposed in a manner where each of the wound parts comes into a partial contact with an adjacent one or more of the other wound parts at least when vibrating, and are each linked by movable linking parts with other ones of the wound parts arranged side by side, or (2) are each joined intermittently in the winding direction with an adjacent one or more of the other wound parts by using joining parts.

2. The voice coil diaphragm set forth in claim 1, wherein a supporting body with which the movable linking parts are provided is included, the supporting body is disposed on one side of the coil body, and the movable linking parts each include a movable part, which faces the wound parts but is not joined with the wound parts, and two joined supporting parts, which are located one by one at both ends of the movable part and each joined with at least one of the wound parts.

3. The voice coil diaphragm set forth in claim 1, wherein the joining parts are staggered with respect to the winding direction and the width directions of the wound parts.

4. The voice coil diaphragm set forth in claim 1, wherein the conductive part has a coating film on a part of or the whole of the conductive part.

5. The voice coil diaphragm set forth in claim 1, wherein the conductive part is composed of a plurality of the conductive bodies arranged side by side, and adjacent ones of the conductive bodies that have the insulating part therebetween are joined by the insulating part.

6. The voice coil diaphragm set forth in claim 1, wherein the insulating part is composed of a conductive body not for driving and an insulating coating film for covering the outer peripheral surface of the conductive body not for driving.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0042] FIG. 1(A) is an end view of the main part of an electroacoustic transducer using the voice coil diaphragm according to a first embodiment of the present invention.

[0043] FIG. 1(B) is a rear view of the magnet plate in the electroacoustic transducer using the same voice coil diaphragm.

[0044] FIG. 2 is a plan view of the same voice coil diaphragm.

[0045] FIG. 3 is an end view of the main part showing a part of the same voice coil diaphragm cut in a radial direction.

[0046] FIG. 4 is an end view of the main part of an electroacoustic transducer using the voice coil diaphragm according to a second embodiment of the present invention.

[0047] FIG. 5 is a rear view of the same voice coil diaphragm.

[0048] FIG. 6 is an end view of the main part showing a part of the same voice coil diaphragm cut in a radial direction at a position passing through one of supporting bodies.

[0049] FIG. 7 is a rear view showing a first modification of the same voice coil diaphragm.

[0050] FIG. 8 is an end view of the main part showing a part of an inner peripheral side buffer part of the same modification cut in a radial direction.

[0051] FIG. 9 is an end view of the main part showing a part of an outer peripheral side buffer part of the same modification cut in a radial direction at a position passing through one of supporting bodies.

[0052] FIG. 10 is a rear view showing a second modification of the same voice coil diaphragm.

[0053] FIG. 11 is an enlarged rear view of the main part showing a third modification of the same voice coil diaphragm.

[0054] FIG. 12 is an end view of the main part showing a part of the voice coil diaphragm of the same modification cut in a radial direction at a position passing through one of supporting bodies.

[0055] FIG. 13 is an enlarged rear view of the main part showing a fourth modification of the same voice coil diaphragm.

[0056] FIG. 14 is an enlarged rear view of the main part showing a fifth modification of the same voice coil diaphragm.

[0057] FIG. 15 is an enlarged rear view of the main part showing a sixth modification of the same voice coil diaphragm.

[0058] FIG. 16 is an end view of the main part showing a part of the voice coil diaphragm of the same modification cut in a radial direction at a position not passing through any of conductive body combined parts.

[0059] FIG. 17 is an end view of the main part showing a part of the voice coil diaphragm of the same modification cut in a radial direction at a position passing through one of mutual joining parts.

[0060] FIG. 18 is an end view of the main part showing a part of a loudspeaker using a voice coil diaphragm of a conventional example and also showing its operating principle.

DESCRIPTION OF EMBODIMENTS

[0061] The embodiments of the present invention will be described next with reference to the accompanying drawings to provide an understanding of the present invention.

[0062] An electroacoustic transducer 10 shown in FIG. 1(A) is configured by disposing on the front side of a magnet plate 60, which will be mentioned later, a voice coil diaphragm 20 according to the first embodiment of the present invention so as to oppose the magnet plate 60. In here, the axial directions of the voice coil diaphragm 20 are the front-back directions of the electroacoustic transducer 10. The upward direction and the downward direction of FIG. 1(A) are the front side direction and the back side direction, respectively of the electroacoustic transducer 10 (the voice coil diaphragm 20), whereas the leftward direction and the rightward direction of FIG. 1(A) are the width directions (the radial directions) of the electroacoustic transducer 10 (the voice coil diaphragm 20) (The same is also applicable in FIGS. 3, 4, 6, 8, 9, 12, 16, and 17 below). The electroacoustic transducer 10 using the voice coil diaphragm 20 according to this embodiment is suitable as a loudspeaker capable of reproducing to the low-frequency range.

[0063] The voice coil diaphragm 20 includes a coil body 30 formed in a planar annular (ring-like) shape as shown in FIG. 2. The coil body 30 is configured, as shown in FIG. 3, by forming a spiral winding state with a conductive part 32, which is composed of a plurality of (nine, in this embodiment) conductive bodies 31 arranged side by side so as to be in a planar shape and electrically connected in parallel, and an insulating part 33. By forming this spiral winding state, the coil body 30 becomes to have a plurality of wound parts 34, which are arranged side by side and separated from each other between the inner circumference and the outer circumference of the coil body 30. Accordingly, each wound part 34 is composed of one of the conductive bodies 31 or the insulating part 33. In here, the insulating part 33 is arranged side by side with the conductive part 32. Since all the conductive bodies 31 adjacent in the width directions in the conductive part 32 are electrically connected in parallel, there is no need to insulate the adjacent conductive bodies 31 from each other. By this, the adjacent conductive bodies 31 can be disposed in contact with each other or disposed with minute gaps between them. As described above, each wound part 34 (each conductive body 31 or the insulating part 33) is arranged so as to come into a partial contact with an adjacent one or more of the other wound parts 34 at least when vibration.

[0064] As shown in FIGS. 1(A) and 2, an inner peripheral side terminal 38 is electrically connected to the inner peripheral side end of the nine conductive bodies 31 arranged side by side, while an outer peripheral side terminal 39 is connected to the outer peripheral side end. In this embodiment, the inner diameter of the coil body 30 is 40 mm and the outer diameter of the coil body 30 is 140 mm. As each conductive body 31, a copper-clad aluminum wire with a cross-section having a diameter of 100 μm that is formed in a circular shape is used. Also in this embodiment, as the insulating part 33, a copper-clad aluminum wire with a cross-section having a diameter of 80 m that is formed in a circular shape is used, and the outer peripheral surface of which is covered with a polyurethane insulating coating film with a thickness of 6 μm. Then, the nine conductive bodies 31 and the insulating part 33 are spirally wound side by side together, and by connecting the nine conductive bodies 31 electrically in parallel, the impedance of the voice coil diaphragm 20 is made to be approximately 5Ω. The sound quality as a loudspeaker becomes better when the cross-sectional area of each conductive body 31 gets smaller, and by increasing the number of the conductive bodies 31 electrically connected in parallel as described in this embodiment, it is possible to reduce the cross-sectional area of each conductive body 31 while maintaining a predetermined impedance as the voice coil diaphragm 20. Reducing the propagation of the vibrations in each conductive body 31 in this way makes it possible to improve the sound quality in the cases of using the voice coil diaphragm 20 in a loudspeaker.

[0065] As shown in FIG. 3, the voice coil diaphragm 20 has a thin-film supporting body 40 that is disposed on one side of the coil body 30 (the lower side in FIG. 3, the back side of the voice coil diaphragm 20) and covers the entire surface of the back side of the coil body 30. In the supporting body 40, movable linking parts 41, which link each wound part 34 and other ones of the wound parts 34, are provided. Each movable linking part 41 includes a movable part 42, which faces the wound parts 34 but is not joined with the wound parts 34, and two joined supporting parts 43, which are located one by one at both ends of the movable part 42 and each joined with one of the wound parts 34. As the material for the supporting body 40, e.g., a silicone resin is used, and each wound part 34 is joined with one of the joined supporting parts 43 by using a mutual joining part 44 made of a silicone resin.

[0066] Subsequently, the magnet plate 60 that is used in combination with the voice coil diaphragm 20 is explained. As shown in FIGS. 1(A) and 1(B), a central region magnet 61 made of a cylindrical neodymium magnet is arranged in the central region of the magnet plate 60. The dimensions of the central region magnet 61 are, e.g., the outer diameter: 60 mm, the inner diameter: 32 mm, and the thickness (the axial direction length): 16 mm. Along the outer periphery of this central region magnet 61, basic region magnets 62 are arranged. The basic region magnets 62 are composed of small magnets 62′, the number of which is 24 in total, each made of a neodymium magnet. The small magnets 62′ are each formed into a trapezoidal shape when viewed from above in which the inner peripheral side (the side of the central region magnet 61) is the upper bottom and the outer peripheral side is the lower bottom, and are arranged radially around (i.e. along the outer circumference of) the central region magnet 61. When vibrating, the voice coil diaphragm 20 formed in an annular (ring-like) shape deforms into a wavy shape in which the maximum displacement (amplitude) occurs at an intermediate position between the inner peripheral side end and the outer peripheral side end. In light of this, a recess is provided on the upper surface of each small magnet 62′ according to the shape of the voice coil diaphragm 20 during vibration so that the voice coil diaphragm 20 and the basic region magnets 62 do not contact (interfere with) each other when vibrating. When viewed from above, each small magnet 62′ is in a trapezoidal shape with the dimensions of, e.g., the upper bottom: 4.4 mm, the lower bottom: 14 mm, and the height (the radial direction length): 33 mm, and the maximum thickness (the axial direction length) of each small magnet 62′ is 16 mm.

[0067] Around (i.e. along the outer periphery of) the basic region magnets 62 of the magnet plate 60, outer peripheral region magnets 63 are arranged. The outer peripheral region magnets 63 are composed of small magnets 63′, the number of which is 24 in total, radially arranged around (i.e. along the outer periphery of) the basic region magnets 62. Each small magnet 63′ is made of a neodymium magnet formed in a rectangular parallelepiped shape. When viewed from above, each small magnet 63′ is in a rectangular shape with the dimensions of, e.g., the height (the radial direction length): 10 mm, and the width (the circumferential direction length): 14 mm, and the thickness (the axial direction length) of each small magnet 63′ is 16 mm. Between the small magnets 62′ of the basic region magnets 62 adjacent to each other in the circumferential direction and between the small magnets 63′ of the outer peripheral region magnets 63 adjacent to each other in the circumferential direction, openings (gaps) each serving as a sound passage hole 71 are formed. In here, the distance between the voice coil diaphragm 20 and the magnet plate 60 is set to 6 mm at a narrowest part.

[0068] In FIG. 1(A), for convenience of explanation, the right side of the center line shows the cross-sectional surface cut at a position passing through one of the small magnets 62′, whereas the left side of the center line shows the cross-sectional surface cut at a position passing through one of the sound passage holes 71. Note that the shape and the dimensions of each part of the magnet plate are not limited to this embodiment, but may be appropriately selected.

[0069] On the front side of the electroacoustic transducer 10, as shown in FIG. 1(A), a main frame 81 made of a nonmagnetic material and supporting the outer peripheral portion of the voice coil diaphragm 20 from the back side is disposed. Additionally, on the front side of the central region magnet 61, a front frame 82 made of a nonmagnetic material into a circular-plate shape for supporting the inner peripheral portion of the voice coil diaphragm 20 from the back side, is disposed, and into the central hole of the central region magnet 61, a central frame 83 made of a nonmagnetic material into a columnar shape is inserted. Further, along the outer periphery of the outer peripheral region magnets 63, an outer peripheral frame 84 made of a nonmagnetic material into a cylindrical shape is disposed, and behind the magnet plate 60, a back frame 85 made of a nonmagnetic material is disposed. In the back frame 85, sound passage holes 86 are formed, and these sound passage holes 86 serve to emit the sound of the back side of the voice coil diaphragm 20 to the outside of the electroacoustic transducer 10 by communicating with the sound passage holes 71. As shown in FIG. 1(A), the central region magnet 61 is magnetized in the front side direction of the axial directions of the magnet plate 60. The basic region magnets 62 (the small magnets 62′) are magnetized in the center-toward direction of the radial directions of the magnet plate 60. The outer peripheral region magnets 63 (the small magnets 63′) are magnetized in the back side direction of the axial directions of the magnet plate 60.

[0070] Since a magnetic force that pushes the central region magnet 61 forward acts, the central magnet 61 is fixed by being sandwiched between the front frame 82 and the back frame 85. Also, since a magnetic force that pushes the outer peripheral region magnets 63 forward acts, the outer peripheral region magnets 63 are fixed by being sandwiched between the main frame 81 and the back frame 85. Between the front frame 82 and the central frame 83, between the central frame 83 and the back frame 85, between the main frame 81 and the outer peripheral frame 84, and between the outer peripheral frame 84 and the back frame 85, are each bonded. However, if the above-mentioned magnetic forces are too strong and the bonding force is insufficient, the use of bolts or the like is recommended. Regarding the small magnets 62′ composing the basic region magnets 62, a magnetic force that strongly pushes them to the back frame 85 acts and the small magnets 62′ are fixed, and so, any special means for fixing them is not used. Incidentally, in light of the fact that the small magnets 62′ are pushed against the back frame 85, the sound passage holes 86, which are a plurality of openings provided in the back frame 85, are each designed in a shape and a size not allowing the small magnets 62′ to fall out to the back side.

[0071] Hereinafter, the operation of the electroacoustic transducer 10 using the voice coil diaphragm 20 will be described.

[0072] With respect to the annular coil body 30, a magnetic field in the radial directions is created by the magnet plate 60. Then, an electromagnetic force is generated in each conductive body 31 of the spirally wound conductive part 32 by supplying an acoustic signal current from the inner peripheral side terminal 38 and the outer peripheral side terminal 39 to each conductive body 31. Of the magnetic field created by the magnet plate 60, a magnetic field component parallel to the surface of the voice coil diaphragm 20 vibrates the voice coil diaphragm 20 in the front-back directions and generates sound. At this time, if the mechanical properties of the conductive bodies 31 and the insulating part 33 are significantly different, the movable linking parts 41 may be torn and/or the mutual joining parts 44 joining the insulating part 33 with the joined supporting parts 43 may be peeled off when the conductive bodies 31 vibrate, which may result in damaging the voice coil diaphragm 20. In light of this, in order to bring the mechanical properties of the insulating part 33 close to those of the conductive bodies 31, a conductive body not for driving made of the same material as the conductive bodies 31 and covered with a thin insulating coating film, is used as the insulating part 33, as was mentioned above. By matching the mechanical properties of the wound parts 34 in the coil body 30 in this way, damage to the voice coil diaphragm 20 can be prevented. In particular, since the amplitude of the voice coil diaphragm 20 becomes large in a loudspeaker that reproduces to the low-frequency range, making the mechanical properties (of the wound parts 34) in the coil body 30 be uniform is effective. Incidentally, no acoustic signal current is applied to the insulating part 33 in consideration of the influence of the insulating coating film on the sound quality.

[0073] In the voice coil diaphragm 20, each wound part easily vibrates in an independent way because the stiffness of the movable linking parts 41 (the movable parts 42) is low. Accordingly, differences in the front-back direction displacements occur between adjacent ones of the wound parts 34 due to the vibration. If the differences in the front-back direction displacements occur between adjacent ones of the wound parts 34 and they come into contact with each other, it becomes difficult for the wound parts 34 to return to the original positions because of the friction, which can cause the misalignments. Particularly, in the cases of the voice coil diaphragm 20 for a loudspeaker capable of reproducing to the low-frequency range, the amplitude is large and the deformation in a wavy shape becomes large. In such a case, the differences in the front-back direction displacements between the adjacent wound parts 34 also become large and it can lead to a situation where each wound part 34 cannot return to the predetermined position. To cope with this, in this embodiment, a gap of approximately 6 pm that is to be a play is provided between each wound part 34 so that it becomes easier for each wound part 34 to go back to the predetermined (original) position. Although the size of the gap is determined within a range in which each wound part 34 can vibrate while coming into a partial contact with an adjacent one or more of the other wound parts 34 at least when vibrating, the size can be appropriately selected according to the diameter, the amplitude, and the like of each wound part 34, and it does not necessarily have to be uniform.

[0074] In the voice coil diaphragm 20 configured in this way, even if forces in the width directions are applied to the wound parts 34, each wound part 34 comes into contact with an adjacent one or more of the other wound parts 34, thereby being kept from moving into the width directions. Therefore, although the stiffness of the entire voice coil diaphragm 20 is low, the width direction displacements, which have been a problem with the conventional voice coil diaphragms, are hard to occur. This function of preventing the width direction displacements makes it possible to significantly reduce the abnormal vibrations generated mainly due to the width direction displacements of the wound parts 34.

[0075] In order for the voice coil diaphragm 20 to effectively function as a diaphragm, it is necessary to block air flow between the front side and the back side of the voice coil diaphragm 20. Since the voice coil diaphragm 20 capable of reproducing to the low-frequency range has the large amplitude and the differences in the front-back direction displacements between the adjacent wound parts 34 become large, gaps become generated between the adjacent wound parts 34. However, by the film-like supporting body 40 disposed on the back side of the voice coil diaphragm 20, the air flow is reliably blocked.

[0076] Further, not joining the movable part 42 of each movable linking part 41 with the wound parts 34 makes it possible for each wound part 34 to easily vibrate (move) in an independent way. In this way, the stiffness of the entire voice coil diaphragm 20 can be significantly reduced in spite of the winding state having a space with which the adjacent wound parts 34 can come into contact with each other, thereby achieving unprecedented high quality sound. In order to improve the sound quality, it is preferred to reduce the stiffness of the movable linking parts 41 (the movable parts 42). However, when properly setting the stiffness of the movable linking parts 41, the length of each movable part 42 (i.e. the distance between the adjacent joined supporting parts 43), the thickness, and the hardness of each movable part 42 can be appropriately selected. Also in order to improve the sound quality, it is preferred that the mass and the volume of substances other than the conductive bodies 31 that is the driving part, be as small as possible, and the thickness of each movable linking part 41 (the supporting body 40) be as thin as possible.

[0077] Further, when the amplitude of the voice coil diaphragm 20 is large, the differences in the front-back direction displacements occurring between the adjacent wound parts 34 become large. In order to maintain the low stiffness of the supporting body 40 even in such cases, each movable part 42 needs to have a sufficient length. In order to satisfy these conditions, in this embodiment, a half of the radial direction length of the supporting body 40 is secured and allocated to the length of the movable parts 42 as shown in FIG. 3. That is, the ratio occupied by the movable parts 42 and the joined supporting parts 43 to the supporting body 40 are set to 50% each. The supporting body 40 is made of a silicone film that has a shore hardness HS (measured in accordance with JIS B7727) of approximately 15, and a thickness of 8 μm. The mutual joining parts 44 having an only function of joining the joined supporting parts 43 with the wound parts 34 fall into substances other than the driving part, and so, in order to improve the sound quality, it is preferred to reduce the use of the mutual joining parts 44 as much as possible within a scope where the joining does not come off. Thus, in the cases where a same silicone resin is used as the material for both the supporting body 40 and the mutual joining parts 44, it is not necessary to separately provide the mutual joining parts 44 as long as the supporting body 40 can be formed to be directly joined with the wound parts 34.

[0078] As described above, the voice coil diaphragm 20 reduces the propagation of the vibrations from each conductive body 31 to the other conductive bodies 31 or to the insulating part 33, and achieves a great improvement in sound quality. Further, even if the amplitude of the voice coil diaphragm 20 becomes increased for reproducing the low-frequency range, the deterioration of the sound quality is prevented by maintaining the low stiffness, and also, tearing of the supporting body 40 is less likely to occur. Adopting this voice coil diaphragm 20 makes it possible that the electroacoustic transducer 10 makes the best use of the original feature of the voice coil diaphragm of emitting sound directly from the conductive bodies. In this embodiment, the magnet plate 60 is configured by combining the three kinds of magnets of the central region magnet 61, the basic region magnets 62, and the outer peripheral region magnets 63. It should be noted, however, that the configuration of the magnet plate is not limited to this and can be selected as appropriate. Also, in the cases of changing the size of each part of the electroacoustic transducer and using it as a microphone, the voice coil diaphragm needs to be adapted to vibrate by receiving sound. This makes the conductive bodies generate an electromotive force, and the electromotive force can be extracted from the inner peripheral side terminal and the outer peripheral side terminal as an acoustic signal current.

[0079] A voice coil diaphragm 20A according to the second embodiment of the present invention will be explained next. Any components in common with the first embodiment are given the same reference signs and omitted from the explanation.

[0080] FIG. 4 shows an electroacoustic transducer 10A, in which the voice coil diaphragm 20A according to the second embodiment of the present invention is disposed on the front side of a magnet plate 60A so as to oppose the magnet plate 60A.

[0081] The voice coil diaphragm 20A differs from the first embodiment, as shown in FIGS. 5 and 6, in that a conductive part 32a composing a coil body 30a is formed by three conductive bodies 31 arranged side by side and electrically connected in parallel, and in that a plurality of (in this embodiment, 20 of) string-state (line-state) supporting bodies 40a are radially arranged at an equal angle interval instead of the film-like supporting body 40. The magnet plate 60A used in combination with the voice coil diaphragm 20A differs from the magnet plate 60 in that the upper surface of each of small magnets 62a′ composing basic region magnets 62a is formed to be flat, and in that an outer peripheral region magnet 63a is formed by using one neodymium magnet into a cylindrical shape.

[0082] In FIG. 4, for convenience of explanation, the right side of the center line shows the cross-sectional surface cut at a position passing through one of the small magnets 62a′, whereas the left side of the center line shows the cross-sectional surface cut at a position passing through one of the sound passage holes 71.

[0083] Each supporting body 40a includes movable linking parts 41a that links each wound part 34 with other ones of the wound parts 34, as shown in FIGS. 5 and 6. The movable linking parts 41a each includes a movable part 42a, which faces the wound parts 34 but is not joined with the wound parts 34, and two joined supporting parts 43a, which are located one by one at both ends of the movable part 42a and each joined with two of the wound parts 34. In here, the joined supporting parts 43a are each joined with the wound parts 34 by a mutual joining part 44a made of a silicone resin. The mutual joining part 44a also serves as a joining part that partially join the two adjacent ones of the wound parts 34 as shown in FIG. 6. In other words, to the grooves (gaps) formed between two adjacent ones of the wound parts 34, the mutual joining parts 44a are provided intermittently in the winding direction of the wound parts 34, thereby the two adjacent wound parts 34 are joined with the supporting body 40a (the joined supporting parts 43a). By partially joining two adjacent ones of the wound parts 34 using the mutual joining parts 44a in this way, the propagation of the vibrations between the two adjacent wound parts 34 is reduced. Further, by the configuration where the joined supporting parts 43a are securely joined with the wound parts 34 by using the mutual joining parts 44a and also two adjacent ones of the wound parts 34 are securely joined with each other by using the mutual joining parts 44a, each wound part 34 is allowed to independently (freely) vibrate in the front-back directions thanks to the movable part 42a, and at least when vibrating, each wound part 34 comes into contact with an adjacent one or more of the other wound parts 34, and thus, the wound parts 34 are blocked from moving in the width directions. Therefore, the same actions and effects as in the first embodiment can be obtained.

[0084] The voice coil diaphragm 20A is suitably used for a mid-frequency range loudspeaker, a high-frequency range loudspeaker, or a microphone. Since the amplitude does not become large in these cases unlike the voice coil diaphragm 20, the differences in the front-back direction displacements between the adjacent wound parts 34 also do not become large. Accordingly, in the voice coil diaphragm 20A, when the wound parts 34 vibrate, the gaps generated between the adjacent wound parts 34 are also small. Therefore, in this embodiment, the string-like supporting bodies 40a can be used instead of the film-like supporting body. Moreover, since the differences in the front-back direction displacements between the adjacent wound parts 34 do not become large, the gap (play) provided when forming the coil body 30a between each wound part 34 and an adjacent one or more of the other wound parts 34, can be made small. This makes it possible to improve the blocking effect of the air flow between the adjacent ones of the wound parts 34.

[0085] Regarding parts other than the conductive bodies 31, such as the supporting bodies 40a and the mutual joining parts 44a, in order to improve the sound quality, it is preferred to reduce the mass and the volume as much as possible and to minimize the area coming into contact with the conductive bodies 31. The string-like supporting bodies 40a as in this embodiment have an area and a volume that are smaller, as a whole, than the film-like supporting body 40, and thus, the total area where the conductive bodies 31 come into contact with the supporting bodies 40a via the mutual joining parts 44a becomes small, thereby it is advantageous in terms of sound quality. Instead of a plurality of the string-like (line-like) supporting bodies 40a, a supporting body formed into a net shape in advance may be used. Also, instead of the string-like (line-like) supporting bodies 40a as in this embodiment, band-like supporting bodies may be used. However, when a plurality of the supporting bodies are arranged radially as in this embodiment, the arranging intervals of the supporting bodies are narrower on the inner peripheral side than on the outer peripheral side, and thus, when the voice coil diaphragm 20A is viewed as a whole, the stiffness on the inner peripheral side is higher than that on the outer peripheral side. In this case, by using trapezoidal supporting bodies each having a narrower inner peripheral width and a wider outer peripheral width, the entire stiffness of the voice coil diaphragm 20A can be made uniform. Incidentally, since the amplitude of the voice coil diaphragm 20A does not become large when vibrating as was mentioned above, even if a recess is provided on the upper surface of each basic region magnet 62a (each small magnet 62a′) in accordance with the amplitude, the recess becomes extremely shallow. Accordingly, the upper surface of each basic region magnet 62a (each small magnet 62a′) is formed to be flat in consideration of ease of manufacturing.

[0086] A modification of the voice coil diaphragm according to the second embodiment of the present invention will be explained next. Any components in common with the first or second embodiment are given the same reference signs and omitted from the explanation.

[0087] In FIG. 4 explained above, it is known that the strength of the magnetic field, which is created by the magnet plate 60A and drives the conductive bodies 31, rapidly reduces on the inner peripheral side and the outer peripheral side of the voice coil diaphragm 20A. In light of this, by setting the current density in the inner peripheral side and the outer peripheral side regions, where the magnetic field strength is low, lower than the current density in the other (intermediate portion) region, where the magnetic field strength is high, the conversion efficiency to sound can be improved. FIGS. 7 to 9 show a voice coil diaphragm 20B of the first modification corresponding to this. The voice coil diaphragm 20B differs from the voice coil diaphragm 20A in that a coil body 30b, which is composed of three part: an inner peripheral side buffer part 21B, a main vibrating part 22B, and an outer peripheral side buffer part 23B, is used, and in that a film-like supporting body 40b is provided with respect to the inner peripheral side buffer part 21B instead of the string-like supporting bodies 40a. The inner peripheral side buffer part 21B and the outer peripheral side buffer part 23B also have the function as the buffer parts to the vibrations of the main vibrating part 22B on the inner peripheral side and the outer peripheral side of the voice coil diaphragm 20B.

[0088] In the inner peripheral side buffer part 21B, as shown in FIG. 8, the arranging intervals of the three conductive bodies 31, which compose the conductive part 32b, and the insulating part 33 are made wider than the coil body 30a (see FIG. 6) in order to reduce the density of the conductive bodies 31 and also the current density in the conductive part 32b. The configuration as in the inner peripheral side buffer part 21B, in which the arranging intervals of the wound parts 34 (the conductive bodies 31 and the insulating part 33) are widened, can become a factor causing the width direction displacements as same as the conventional example shown in FIG. 18, however, the area of the inner peripheral side buffer part 21B is small, and thus, there is almost no influence from it. Nevertheless, if adopting the configuration same as the inner peripheral side buffer part 21B also for the outer peripheral side buffer part 23B, the displacements in the width directions occur in the entire main vibrating part 22B and the abnormal vibrations become likely to occur. So, as shown in FIG. 9, in the outer peripheral side buffer part 23B, additional conductive bodies 31b made of the same material as the conductive bodies 31 and having the same diameter as the conductive bodies 31 are additionally provided one for each in between the three conductive bodies 31, and the additional conductive bodies 31b are electrically connected in parallel with the conductive bodies 31 to compose the conductive part 32c. This increases the cross-sectional area of the conductive part 32c, and accordingly, reduces the current density. That is, in the outer peripheral side buffer part 23B, by arranging the conductive bodies 31, the additional conductive bodies 31b, and the insulating part 33 in a manner where they are in close contact with each other, not only the current density is reduced, but also the occurrence of the width direction displacements in the wound parts 34 (the conductive bodies 31, the additional conductive bodies 31b, and the insulating part 33) is prevented. Since the configuration of the main vibrating part 22B is the same as the coil body 30a (see FIG. 6), the explanation is omitted.

[0089] In the case of the voice coil diaphragm 20A, by radially arranging a plurality of the supporting bodies 40a, the arranging intervals of the supporting bodies 40a are narrower on the inner peripheral side than the outer peripheral side, and thus, when the voice coil diaphragm 20A is viewed as a whole, the stiffness on the inner peripheral side is higher than that on the outer peripheral side. To cope with this, in the voice coil diaphragm 20B, a thin-film supporting body 40b having a low stiffness is provided with respect to the inner peripheral side buffer part 21B instead of the supporting bodies 40a, thereby making the entire stiffness of the voice coil diaphragm 20B be uniform and blocking the air flow between the wound parts 34 having the widened arranging intervals.

[0090] FIG. 10 shows a voice coil diaphragm 20C of the second modification. The voice coil diaphragm 20C differs from the voice coil diaphragm 20A in that the supporting bodies 40a are arranged to the coil body 30a in a manner where parts of the supporting bodies 40a branch so that the intervals between adjacent ones of the supporting bodies 40a become as even as possible at any positions. Comparing to the case where all the supporting bodies 40a are radially arranged as in the voice coil diaphragm 20A, a rise of the stiffness on the inner peripheral side can be prevented in the voice coil diaphragm 20C, thereby the sound quality can be improved. Note that the number and the arrangement of the supporting bodies are not limited by the above, but it can be selected as appropriate.

[0091] FIGS. 11 and 12 show a voice coil diaphragm 20D of the third modification. The voice coil diaphragm 20D differs from the voice coil diaphragm 20A in that a conductive part 32d composing a coil body 30d includes two quadrilateral-cross-sectional conductive bodies 31d having a same width and two quadrilateral-cross-sectional conductive bodies 31d′ each having a width that is a half of the width of each conductive body 31d, and in that an insulating part 33d is formed to be a thin layer. The two conductive bodies 31d disposed side by side so as to be adjacent to each other, and the two conductive bodies 31d′ each disposed side by side with one of the conductive bodies 31d such that the two conductive bodies 31d′ have the two conductive bodies 31d in between, are electrically connected in parallel. When the conductive part 32d is spirally wound, the conductive body 31d′ on the outer peripheral side and the conductive body 31d′ on the inner peripheral side are adjacent. So, by putting the insulating part 33d between these two conductive bodies 31d′ and joining the two conductive bodies 31d′ while insulating them, the two conductive bodies 31d′ are made into one wound part 34. In the case of the voice coil diaphragm 20A, the coil body 30a is formed by winding the conductive bodies 31 and the insulating part 33, however, in the case of the voice coil diaphragm 20D, e.g., a conductor foil serving as the conductive part 32d is separated into the conductive bodies 31d and the conductive bodies 31d′ by using three parallel separating parts 35d to form the coil body 30d. As a method for forming the separating parts 35d, a method of pressing, laser processing, or etching the conductor foil can be used. The adjacent conductive bodies 31d′ are joined by the insulating part 33d after being separated through the same process as the separating parts 35d.

[0092] As was mentioned above, the width of each of the adjacent conductive bodies 31d′ having the insulating part 33d therebetween is a half of the width of each of the other conductive bodies 31d. Since the total cross-sectional area of the two conductive bodies 31d′ joined by the insulating part 33d is equal to the cross-sectional area of each of the other conductive bodies 31d, the cross-sectional area of the conductive part 32d is equivalent to three times of the cross-sectional area of each conductive body 31d. Therefore, the coil body 30d is in a winding state as in the case where three of the conductive bodies 31d are arranged side by side. Electrically, on the other hand, two each of the conductive bodies 31d and 31d′ insulated by the wound insulating part 33d compose the conductive part 32d, and an acoustic signal current flows in an equipotential state.

[0093] Although the voice coil diaphragm 20A uses the insulating part 33 having a cross-sectional area approximate to the conductive body 31, in the voice coil diaphragm 20D, the insulating part 33d is formed into a layer to reduce the area and the mass, and thus, the sound quality is improved. Since the insulating part 33d is sandwiched and protected by the conductive bodies 31d′, the insulating part 33d can be formed extremely thin, and thus, the influence on the sound quality can be minimized. Also, since the cross-sectional shape and the dimensions of the two conductive bodies 31d′ joined by the insulating part 33d and those of each of the other conductive bodies 31d are almost the same, the mechanical properties in the voice coil diaphragm 20D become entirely uniform. In this way, a uniform vibration state can be obtained over the entire surface of the voice coil diaphragm 20D, and a high sound quality can be achieved. Further, in the voice coil diaphragm 20D, most of the surface (the front surface) of the voice coil diaphragm 20D (the coil body 30d) that is the sound radiating surface is occupied by the conductive bodies 31d and 31d′ that are the driving part, and sound is directly emitted. In this respect as well, it is very advantageous for improving the sound quality.

[0094] FIG. 13 shows a voice coil diaphragm 20E of the fourth modification. The voice coil diaphragm 20E differs from the voice coil diaphragm 20A in that the mutual joining parts 44a intermittently provided in the winding direction of the wound parts 34, are staggered with respect to the winding direction and the width directions of the wound parts 34. By staggering the mutual joining parts 44a, the mutual joining parts 44a can be provided between all the adjacent wound parts 34 in the radial directions (the width directions of the wound parts 34) while maintaining the overall stiffness of the voice coil diaphragm 20E low. Since the mutual joining parts 44a securely fix the adjacent wound parts 34, not only the misalignments become less likely to occur in each wound part 34, but also, even if a misalignment occurs in one of the wound parts 34, the misalignment is prevented from spreading to other parts. This makes it possible to support each wound part 34 (each conductive body 31 or the insulating part 33) at necessary points by using the joined supporting parts 43a, and also to effectively prevent the misalignments of each wound part in the winding direction and the width directions. Further, even if a misalignment occurs in each wound part 34, since the mutual joining parts 44a are provided between all the adjacent wound parts 34 in the radial directions, the misalignment is less likely to spread to other parts of the coil body 30a, thereby deformation or the like of the entire voice coil diaphragm 20E due to the misalignments can be effectively prevented.

[0095] FIG. 14 shows a voice coil diaphragm 20F of the fifth modification. The voice coil diaphragm 20F differs from the voice coil diaphragm 20A in that the mutual joining parts 44a intermittently provided in the winding direction of the wound parts 34, are staggered with respect to the winding direction and the width directions of the wound parts 34, and in that the supporting bodies 40a are eliminated (omitted). That is, the voice coil diaphragm 20F is equivalent to the voice coil diaphragm 20E from which the supporting bodies 40a have been removed. In here, each mutual joining part 44a is a joining part for partially joining one of the wound parts 34 and an adjacent one of the other wound parts 34. By arranging the mutual joining parts 44a in a staggered manner with respect to the winding direction and the width directions of the wound parts 34, necessary points of each wound part 34 are fixed by the mutual joining parts 44a. In this way, the adjacent ones of the wound parts 34 support each other using the mutual joining parts 44a as the supporting points, and meanwhile, each wound part 34 becomes deformable in the front-back directions. Therefore, the supporting bodies 40a can be omitted. In this case, since each wound part 34 takes on the function as a supporting body, the stiffness of the voice coil diaphragm 20F depends on the material (the elasticity modulus) and the cross-sectional area of the wound parts 34, and the distance between the mutual joining parts 44a adjacent to each other in the winding direction. In a configuration like this, since the wound parts 34 are only partially joined with each other by the mutual joining parts 44a, each wound part 34 is less likely to be restrained, and the vibrations are less likely to propagate to the other wound parts 34, thereby the sound quality is improved. Further, in the voice coil diaphragm 20F, the adjacent wound parts 34 are securely fixed to each other by the mutual joining parts 44a, and so, the misalignments of the wound parts 34 in the winding direction or the front-back directions (the vibrating directions) are prevented. Also, the width direction displacement of each wound part 34 that causes the abnormal vibrations can be effectively suppressed.

[0096] For the mutual joining parts 44a, synthetic resin based adhesives such as epoxy-based and cyanoacrylate-based adhesives can be used instead of the silicone resin. However, at the locations where the conductive bodies 31 are joined with each other, a strong joining force can be obtained by using metal bonding such as soldering or wire bonding. In this case, besides, since the metal bonding is hard, it is advantageous also in terms of improving the sound quality. Also, when a highly-elastic (highly-resilient) nonmagnetic material such as beryllium copper, phosphor bronze, or a stainless steel wire for a nonmagnetic spring is selected as the material for the conductive bodies 31, the function of each conductive body 31 itself as a supporting body can be improved and it is effective also in terms of operational stability and durability.

[0097] FIGS. 15 to 17 show a voice coil diaphragm 20G of the sixth modification. The voice coil diaphragm 20G differs from the voice coil diaphragm 20E in that a conductive part 32g composing a coil body 30g includes two quadrilateral-cross-sectional conductive bodies 31g having a same width and two quadrilateral-cross-sectional conductive bodies 31g′ each having a width that is a half of the width of each conductive body 31g, in that an insulating part 33g is formed to be a thin layer, and in that a supporting body 40g in a film-like state is provided. The two conductive bodies 31g disposed side by side so as to be adjacent to each other and the two conductive bodies 31g′ each disposed side by side with one of the conductive bodies 31g such that the two conductive bodies 31g′ have the two conductive bodies 31g in between, are electrically connected in parallel. When the conductive part 32g is spirally wound, the conductive body 31g′ on the outer peripheral side and the conductive body 31g′ on the inner peripheral side are adjacent. So, by putting the insulating part 33g between these two conductive bodies 31g′ and joining the two conductive bodies 31g′, the two conductive bodies 31g′ are made into one wound part 34. Regarding FIG. 15, although the entire surface (the nearer side in the figure) of the coil body 30g is covered by the supporting body 40g, the drawing shows a state where the entire surface of the coil body 30g can be seen through the supporting body 40g since the supporting body 40g is a thin film.

[0098] In the case of the voice coil diaphragm 20E, the coil body 30a is formed by winding the conductive bodies 31 and the insulating part 33, however, in the case of the voice coil diaphragm 20G, e.g., a conductor foil serving as the conductive part 32g is separated into the conductive bodies 31g and the conductive bodies 31g′ by using three parallel separating parts 35g to form the wound parts 34 of the coil body 30g. Further, when forming the wound parts 34 by using the separating parts 35g, unseparated parts are provided, as conductive body combined parts 36g, intermittently in the winding direction of the wound parts 34 and the conductive body combined parts 36g are staggered with respect to the winding direction and the width directions of the wound parts 34. The method for manufacturing the coil body 30g is basically the same as the above-mentioned coil body 30d, and the only difference between the coil bodies 30d and 30g is whether or not having the conductive body combined parts 36g.

[0099] As shown in FIG. 17, to the supporting body 40g, movable linking parts 41g are formed at the positions overlapping the conductive body combined parts 36g. Each movable linking part 41g includes a movable part 42g, which faces the conductive body combined parts 36g each being a part of the wound parts 34 but is not joined with the conductive body combined parts 36g, and two joined supporting parts 43g, which are located one by one at both ends of the movable part 42g and each joined with one of the conductive body combined parts 36g. The conductive body combined parts 36g and the joined supporting parts 43g are joined by using mutual joining parts 44g made of a silicone resin. In here, the major part of the film-like supporting body 40g (i.e. other than the part occupied by the joined supporting parts 43g) is, as shown in FIG. 16, occupied by the movable parts 42g that face the wound parts 34 but are not joined with the wound parts 34. In this way, in the film-like supporting body 40g, the joined supporting parts 43g are provided at the positions that overlap the conductive body combined parts 36g which are less likely to move, i.e. less likely to deform, in the coil body 30g. This prevents the supporting body 40g (the joined supporting parts 43g) from blocking the originally intended operation (vibrations) of the wound parts 34. Furthermore, by joining the wound parts 34 and the joined supporting parts 43g by using the mutual joining parts 44g that are each in a point shape, the volume of the mutual joining parts 44g that fall into substances other than the driving part can be reduced as much as possible in order to improve the sound quality.

[0100] In the voice coil diaphragm 20E, the necessary points of the adjacent wound parts 34 are joined by the mutual joining parts 44a, and the wound parts 34 and the supporting bodies 40a (the joined supporting parts 43a) are joined via the mutual joining parts 44a. However, in the voice coil diaphragm 20G, by providing to the conductive part 32g the unseparated parts that are to be the conductive body combined parts 36g, adjacent ones of the wound parts 34 are partially combined (integrated). As a result, the adjacent wound parts 34 are strongly fixed to each other in the region of the conductive body combined parts 36g, and thus, the width direction displacement of the wound parts 34 (the conductive bodies 31g and 31g′) that causes the abnormal vibrations becomes much less likely to occur.

[0101] Generally speaking, in a loudspeaker that reproduces the low-frequency range, the area of the diaphragm is large and the amplitude of the diaphragm is also large, and so, the misalignments in various directions are likely to occur in each part (each wound part) of the planar coil body. Besides, the range to which these misalignments spread expands, and this significantly influences on the deformation of the coil body. In contrast, in the voice coil diaphragm 20G, since the conductive body combined parts 36g are provided between all the adjacent wound parts in the radial directions, even when a misalignment occurs in one of the wound parts 34 that locates at a position apart from the conductive body combined parts 36g, each conductive body combined part 36g prevents the misalignment from spreading to other parts of the wound parts 34. In this way, unevenness between the wound parts is prevented from occurring and deformation of the entire coil body 30g due to the misalignments is also prevented. If the amplitude of the voice coil diaphragm 20G is large, the deformation in a wavy shape becomes large, and the differences of the front-back direction displacements between the adjacent wound parts 34 become large. In such a case, the gap of each separating part 35g expands in the front-back directions and this facilitates the air flow between the front side and the back side of the voice coil diaphragm 20G. To cope with this, in the voice coil diaphragm 20G, by forming the supporting body 40g in a film state, the air flow is blocked by the supporting body 40g. The voice coil diaphragm 20G having the features explained above can be suitably used especially as a loudspeaker for the low-frequency range.

[0102] The present invention has been described above with reference to the embodiments. However, the present invention is not limited to the structures described in the above embodiments, and the present invention includes other embodiments and modifications conceivable within the scope of the matters described in the scope of the claims.

[0103] Although the voice coil diaphragms each in a planar shape are described in the above embodiments, these voice coil diaphragm can be made, e.g., each in a three dimensional shape having inclined or perpendicular surfaces, as in patent literature 5. That is, e.g., a coil body made in a three dimensional shape by winding the conductive part and the insulating part while folding and/or curving them, or a coil body made in a three dimensional shape by folding and/or curving the conductive part and the insulating part after winding them in a planar shape, can be used. Also, a coating film may be provided to a part or the whole of the conductive part if needed. Although the cases where the conductive part is composed of a plurality of the conductive bodies arranged side by side so as to be in a planar shape are explained in the above embodiments, the number of the conductive bodies can be selected as appropriate, and it can be one.

[0104] As the method for manufacturing the coil bodies 30d and 30g, the method of pressing, laser processing, or etching the conductive part formed in a planar shape in advance and forming the separating parts 35d and 35g or the like, is explained in the above embodiments. However, the portions of the conductive bodies 31d, 31d′, 31g, and 31g′, which are other than the separating parts 35d and 35g and the insulating parts 33d and 33g, can be formed also by using a method of vapor deposition, sputtering, plating or the like.

[0105] Further, the structure of the magnet plate used in combination with each voice coil diaphragm in the above embodiments is not limited to the ones described in the above embodiments, and can be selected as appropriate. Thus, if a diaphragm of an electroacoustic transducer using a conventional magnet plate can be replaced with any one of the voice coil diaphragms of the above embodiments, by adopting these diaphragms, the sound quality can be improved.

INDUSTRIAL APPLICABILITY

[0106] The voice coil diaphragm according to the present invention can be utilized for an electroacoustic transducer which can perform the conversion from electrical signals to sound with an unprecedented high quality such as a loudspeaker, headphones, and earphones, and for an electroacoustic transducer, which can perform the conversion from sound to electrical signals with a high quality such as a microphone and an acoustic wave sensor.

REFERENCE SIGNS LIST

[0107] 10, 10A, 10Z: electroacoustic transducer (loudspeaker), 20, 20A, 20B, 20C, 20D, 20E, 20F, 20G, 20Z: voice coil diaphragm, 21B: inner peripheral side buffer part, 22B: main vibrating part, 23B: outer peripheral side buffer part, 30, 30a, 30b, 30d, 30g: coil body, 31: conductive body, 31b: additional conductive body, 31d, 31d′, 31g, 31g′, 31z: conductive body, 32, 32a, 32b, 32c, 32d, 32g: conductive part, 33, 33d, 33g: insulating part, 33z: gap, 34: wound part, 35d, 35g: separating part, 36g: conductive body combined part, 38: inner peripheral side terminal, 39: outer peripheral side terminal, 40, 40a, 40b, 40g, 40z: supporting body, 41, 41a, 41g: movable linking part, 42, 42a, 42g, 42z: movable part, 43, 43a, 43g, 43z: joined supporting part, 44, 44a, 44g: mutual joining part, 60, 60A, 60Z: magnet plate, 61: central region magnet, 62, 62a: basic region magnet, 62′, 62a′: small magnet, 63, 63a: outer peripheral region magnet, 63′: small magnet, 65z: band-shaped magnet, 71: sound passage hole, 81: main frame, 82: front frame, 83: central frame, 84: outer peripheral frame, 85, 85z: back frame, 86: sound passage hole