Acoustic diaphragm, method of manufacturing acoustic diaphragm, and electroacoustic transducer

Abstract

An acoustic diaphragm 1 according to the present invention includes a center dome member, and a sub dome member. The center dome member includes a center dome 2 and an annular first plane part 2a that is disposed along the outer periphery of the center dome and formed integrally with the center dome. The sub dome member includes a sub dome 3 and an annular second plane part 3a that is disposed along the inner periphery of the sub dome and formed integrally with the sub dome. The first plane part includes a rising part 2b of the center dome, a first front surface, and a first back surface. The second plane part includes an inner peripheral edge 3b, a second front surface, and a second back surface. The center dome is formed of a material different from that of the sub dome. The sub dome surrounds the periphery of the center dome. The inner peripheral edge coincides with the rising part. The first front surface is joined to the second back surface.

Claims

1. A method of manufacturing an acoustic diaphragm, wherein the acoustic diaphragm comprises: a center dome member; and a sub dome member, the center dome member comprises: a center dome; and an annular first plane part that is disposed along an outer periphery of the center dome and formed integrally with the center dome, the sub dome member comprises: a sub dome; and an annular second plane part that is disposed along an inner periphery of the sub dome and formed integrally with the sub dome, the first plane part comprises: a rising part of the center dome; a first front surface; and a first back surface, the second plane part comprises: an inner peripheral edge; a second front surface; and a second back surface, the center dome is formed of a material different from a material of the sub dome, the sub dome surrounds a periphery of the center dome, and the inner peripheral edge coincides with the rising part, the method of manufacturing the acoustic diaphragm comprising the steps of: preparing the center dome member and the sub dome member; and joining the second back surface to the first front surface in a state where the inner peripheral edge is aligned with the rising part.

2. The method of manufacturing an acoustic diaphragm according to claim 1, wherein, in the step of joining the second back surface to the first front surface, an adhesive is interposed between the first front surface and the second back surface to join the first plane part and the second plane part.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a cross-sectional view for explaining a basic configuration and a method of manufacturing an acoustic diaphragm of a first embodiment according to the present invention.

(2) FIG. 2 is a cross-sectional view of an electroacoustic transducer including the acoustic diaphragm of the first embodiment.

(3) FIG. 3 is a cross-sectional view illustrating a second embodiment of the acoustic diaphragm according to the present invention.

(4) FIG. 4 is a cross-sectional view illustrating a third embodiment of the acoustic diaphragm according to the present invention.

(5) FIG. 5 is a cross-sectional view illustrating a fourth embodiment of the acoustic diaphragm according to the present invention.

(6) FIG. 6 is a cross-sectional view illustrating a fifth embodiment of the acoustic diaphragm according to the present invention.

(7) FIG. 7 is a cross-sectional view illustrating a sixth embodiment of the acoustic diaphragm according to the present invention.

(8) FIG. 8 is a cross-sectional view illustrating a seventh embodiment of the acoustic diaphragm according to the present invention.

(9) FIG. 9 is a cross-sectional view illustrating an eighth embodiment of the acoustic diaphragm according to the present invention.

DESCRIPTION OF EMBODIMENTS

(10) An acoustic diaphragm according to the present invention, a method of manufacturing the acoustic diaphragm, and an electroacoustic transducer will now be described based on embodiments illustrated in the drawings. The acoustic diaphragm illustrated in each drawing is illustrated in the form of a cut end surface in a state of being cut at the center thereof, and illustration of some of members appearing on the back side of each drawing will be omitted as appropriate.

(11) FIG. 1 illustrates a first embodiment of an acoustic diaphragm. An acoustic diaphragm 1 of the first embodiment includes a center dome 2 and a sub dome 3 that surrounds the periphery of the center dome 2.

(12) In the center dome 2, a front surface of the diaphragm projects so as to form a part of a spherical surface. In the sub dome 3, the front surface of the diaphragm projects in an annular shape (doughnut shape). The sub dome 3 surrounds the periphery of the center dome 2.

(13) In the center dome 2, an annular first plane part 2a is formed (disposed) along the outer periphery of the center dome 2. The first plane part 2a is formed integrally with the center dome 2. The first plane part 2a is formed in a direction orthogonal to a vibration direction of the diaphragm 1.

(14) A rising part 2b of the center dome 2 between the first plane part 2a and the center dome 2 is formed in a state substantially close to a perfect circle in a plan view. In other words, the rising part 2b of the center dome 2 is an inner peripheral edge of the first plane part 2a. Furthermore, an outer peripheral edge of the first plane part 2a is formed in a state substantially close to a perfect circle. Consequently, as illustrated in the partially enlarged view of FIG. 1, a width W1 of the first plane part 2a along the outer periphery of the center dome 2 is formed to be substantially uniform along the periphery thereof. The width W1 is a length from the rising part 2b of the center dome 2 (the inner peripheral edge of the first plane part 2a) to the outer peripheral edge of the first plane part 2a in the first plane part 2a.

(15) In the first embodiment, the width W1 of the first plane part 2a is set to about 0.5 mm.

(16) Meanwhile, in the sub dome 3, an annular second plane part 3a is formed (disposed) along the inner periphery of the sub dome 3. The second plane part 3a is formed integrally with the sub dome 3. The second plane part 3a is formed in a direction orthogonal to the vibration direction of the diaphragm 1. As indicated by chain lines L1 and L2, an inner peripheral edge 3b of the second plane part 3a coincides with the rising part 2b of the center dome 2 in the first plane part 2a in a concentric circle in an overlapping direction.

(17) Consequently, the center dome 2 is centered and the sub dome 3 is fitted from above the center dome 2 so as to overlap the center dome 2, so that the inner peripheral edge 3b of the second plane part 3a coincides with the rising part 2b of the center dome 2 in the overlapping direction. That is, when the sub dome 3 is overlapped on the center dome 2, the inner peripheral edge 3b of the second plane part 3a coincides with the rising part 2b (the inner peripheral edge of the first plane part 2a) of the center dome 2 in the overlapping direction. In this way, the sub dome 3 can be positioned concentrically with respect to the center dome 2.

(18) In addition, in the sub dome 3, a flange part 3c is formed (disposed) along the outer periphery of the sub dome 3. The flange part 3c is an annular plane part. The flange part 3c is formed integrally with the sub dome 3. The flange part 3c is used to attach the acoustic diaphragm 1 to a unit frame to be described below.

(19) Reference numeral 4 indicates an adhesive for joining a center dome member and a sub dome member. The adhesive 4 is an adhesive including a solvent, for example, and is applied to an upper surface (front surface) of the first plane part 2a or applied to a bottom surface (back surface) of the second plane part 3a. Next, the second plane part 3a is overlapped on the upper surface of the first plane part 2a, so that both (the first plane part 2a and the second plane part 3a) are joined. In this way, the acoustic diaphragm 1 is formed. The center dome member and the sub dome member will be described below.

(20) In such a case, as described above, positioning between the center dome 2 and the sub dome 3 is performed.

(21) In the acoustic diaphragm 1 of the first embodiment illustrated in FIG. 1, after the center dome member (the center dome 2 and the first plane part 2a) and the sub dome member (the sub dome 3, the second plane part 3a, and the flange part 3c) are joined, a voice coil 5 is attached to the side of a back surface of the first plane part 2a.

(22) The voice coil 5 is a wire in which a copper or aluminum wire is covered with an insulating layer made of a high heat-resistant resin and an outer periphery of the insulating layer is covered with a fusion layer of a thermoplastic resin. The voice coil 5 has a bobbin-less structure by heating and solidifying the fusion layer in a state where the wire is wound in a coil shape. The voice coil 5 is attached to the side of the back surface of the first plane part 2a by the adhesive 4.

(23) The voice coil 5 is not limited to the bobbin-less structure. That is, for example, the voice coil 5 may have a structure using a bobbin.

(24) The center dome 2 and the annular first plane part 2a constitute the center dome member. As a material of the center dome member, a metal material such as titanium or aluminum alloy, or a non-metal material made of carbon called dry carbon is preferably used.

(25) On the other hand, the sub dome 3, the annular second plane part 3a, and the flange part 3c constitute the sub dome member. As a material of the sub dome member, for example, a thermoplastic resin material such as polyethylene terephthalate (PET) is preferably used.

(26) That is, the center dome 2 is made of a harder material than the sub dome 3. In this way, for example, the acoustic diaphragm 1 used for dynamic headphones has characteristics of material softness required for the sub dome 3 and material hardness (rigidity) required for the center dome 2.

(27) Consequently, in order to manufacture the aforementioned acoustic diaphragm 1, the center dome member and the sub dome member are prepared. As described above, the center dome member is formed of a material such as titanium or carbon and includes the annular first plane part 2a formed along the outer periphery of the center dome 2. As described above, the sub dome member is formed of a material such as polyethylene terephthalate (PET) and includes the annular second plane part 3a formed along the inner periphery of the sub dome 3. The inner peripheral edge 3b of the second plane part 3a coincides with the rising part 2b of the center dome 2 in the first plane part 2a (the inner peripheral edge of the first plane part 2a).

(28) Next, in the state where the inner peripheral edge 3b of the second plane part 3a is aligned with the rising part 2b of the center dome 2 in the first plane part 2a, the back surface of the second plane part 3a is joined to the front surface of the first plane part 2a by using the adhesive 4. In this way, the acoustic diaphragm 1 is manufactured.

(29) When an adhesive including a solvent is used as the adhesive 4, the adhesive is applied to the front surface of the first plane part 2a or applied to the back surface of the second plane part 3a. In this way, both (the first plane part 2a and the second plane part 3a) are joined and solidified.

(30) On the other hand, for example, when a hot melt adhesive and the like are used as the adhesive 4, the hot melt adhesive is interposed between the first plane part 2a and the second plane part 3a and thermally compressed, so that both are joined and fixed. In this way, the acoustic diaphragm 1 is obtained.

(31) FIG. 2 is a central cross-sectional view illustrating an example of an electroacoustic transducer 11 including the acoustic diaphragm 1 of the present invention.

(32) In the electroacoustic transducer 11, the flange part 3c of the acoustic diaphragm 1 is attached to a front opening edge 12a of a unit frame 12. A magnetic circuit unit 13 is attached to a center part of the unit frame 12. The voice coil 5 is disposed inside an annular magnetic gap 14 in the magnetic circuit unit 13. The magnetic circuit unit 13 includes a yoke 15 formed in a bottomed cylindrical shape. A magnet 16 and a pole piece 17 are accommodated in the yoke 15. The magnetic gap 14 is formed between the pole piece 17 and the yoke 15.

(33) Furthermore, a peripheral side surface of the yoke 15 constituting the outline of the magnetic circuit unit 13 is attached to a central hole formed in the unit frame 12. In this way, the electroacoustic transducer 11 is configured.

(34) The unit frame 12 includes a plurality of circular openings 12b. The plurality of openings 12b are formed at equal intervals along the circumferential direction of the unit frame 12. The plurality of openings 12b are formed along the side of the back surface of the sub dome 3 in the acoustic diaphragm 1 and are formed so as to communicate with a back surface of the unit frame 12.

(35) An acoustic resistance material 18 made of a nonwoven fabric and the like is attached to the side of the back surface of the unit frame 12 so as to block the opening 12b. The acoustic resistance material 18 adjusts an air flow rate between a space, which is formed between the acoustic diaphragm 1 and the unit frame 12, and a back space of the unit frame 12.

(36) The electroacoustic transducer 11, for example, is used for dynamic headphones in which a diameter of the acoustic diaphragm 1 is about 50 mm.

(37) FIG. 3 to FIG. 9 illustrate second to eighth embodiments of the acoustic diaphragm 1 according to the present invention. Each drawing is illustrated in the form of a cut end surface of the acoustic diaphragm 1 in a state of being cut at the center thereof, as in the first embodiment illustrated in FIG. 1.

(38) In each embodiment illustrated in each drawing, since members denoted by the same reference numerals as those of the first embodiment illustrated in FIG. 1 have the same functions as those in the first embodiment, a description thereof will be omitted.

(39) Furthermore, in each embodiment illustrated in each drawing, as in the first embodiment illustrated in FIG. 1, the rising part 2b of the center dome 2 in the first plane part 2a and the inner peripheral edge 3b of the second plane part 3a coincide with each other in a concentric circle in an overlapping direction. Moreover, in each embodiment illustrated in each drawing, the voice coil 5 is attached to the side of the back surface of the first plane part 2a.

(40) In the second embodiment illustrated in FIG. 3, the sub dome member includes an annular extension part 3e that overlaps the center dome 2 subsequent to the second plane part 3a. The annular extension part 3e is formed integrally with the sub dome 3. According to this example, the annular extension part 3e is disposed to overlap the periphery of the center dome 2. Therefore, adhesive force between the center dome member and the sub dome member is further increased.

(41) In the third embodiment illustrated in FIG. 4, the center dome member includes an annular slot part 2d on the outer periphery of the first plane part 2a subsequent to the center dome 2. The annular slot part 2d is formed integrally with the center dome 2. The voice coil 5 is mounted in the slot part 2d.

(42) In the fourth embodiment illustrated in FIG. 5, the center dome member includes a cylindrical part 2e outside the first plane part 2a subsequent to the center dome 2. The cylindrical part 2e extends to the side of the back surface of the first plane part 2a. The cylindrical part 2e is formed integrally with the center dome 2. The voice coil 5 is mounted along an outer peripheral surface of the cylindrical part 2e.

(43) In the fifth embodiment illustrated in FIG. 6, the center dome member includes a cylindrical part outside the first plane part 2a subsequent to the center dome 2 and includes a flange part 2f at a rear end of the cylindrical part. The cylindrical part extends to the side of the back surface of the first plane part 2a. The voice coil 5 is mounted on the cylindrical part in a positioned state by using the flange part 2f.

(44) In the sixth embodiment illustrated in FIG. 7, the center dome member includes an annular convex part 2g along the outer periphery of the center dome 2 on the first plane part 2a subsequent to the center dome 2. The convex part 2g projects to the front surface. Furthermore, the second plane part 3a subsequent to the sub dome 3 is formed with an annular concave part that receives the annular convex part 2g. The second plane part 3a is overlapped on the first plane part 2a by using unevenness between these convex parts 2g and concave parts.

(45) The voice coil 5 is attached by the adhesive 4 (not illustrated in FIG. 7) by using a groove on the side of the back surface of the first plane part 2a in which the annular convex part 2g is formed.

(46) In the seventh embodiment illustrated in FIG. 8, the center dome member includes an annular storage groove 2h for an adhesive along the outer periphery of the center dome 2, in the first plane part 2a subsequent to the center dome 2. The storage groove 2h stores an excess adhesive. Therefore, the problem that an adhesive overflows and solidifies between the center dome member and the sub dome member is solved. The voice coil 5 is attached to the side of a back surface of the storage groove 2h by the adhesive 4 (not illustrated in FIG. 8).

(47) The eighth embodiment illustrated in FIG. 9 is configured in the same manner as the seventh embodiment. That is, for example, the center dome member includes the annular storage groove 2h for an adhesive along the outer periphery of the center dome 2, in the first plane part 2a subsequent to the center dome 2. However, the voice coil 5 is attached by the adhesive 4 (not illustrated in FIG. 9) along the outside of the storage groove 2h.

(48) As apparent from the above description, the acoustic diaphragm 1 according to the present invention obtains the operation effects described in the field of the effects of the invention such as it is possible to improve productivity by facilitating positioning between the center dome member and the sub dome member.

(49) Furthermore, the aforementioned embodiments assume an acoustic diaphragm and an electroacoustic transducer used for dynamic headphones. However, the acoustic diaphragm and the electroacoustic transducer according to the present invention are not limited to the acoustic diaphragm and the electroacoustic transducer used for the dynamic headphones. That is, for example, the acoustic diaphragm according to the present invention can also be employed for canal type headphones (earphones) in which a diameter of an acoustic diaphragm is about 5 mm, and even though the acoustic diaphragm according to the present invention is used for an electroacoustic transducer other than headphones, it is possible to obtain the same operation effects.