Speaker and earphone

Abstract

A speaker (1) comprises: a cylindrical housing (30); a magnetic circuit (50) accommodated in the housing (30); a voice coil (40) partially disposed within a magnetic gap (G); a diaphragm (10) connected to an end portion of the voice coil (40) located outside the magnetic circuit (50) and covering an opening portion (33) of the housing (30); and a magnetic fluid (60) provided between the magnetic circuit (50) and the voice coil (40) within the magnetic gap (G). The magnetic fluid (60) has one surface and another surface in contact with air in a spatial region surrounded by the housing (30) and the diaphragm (10). The spatial region includes: a diaphragm back surface region (s1) that is in contact with one surface of the magnetic fluid (60); a sound hole region (s3) that is joined to the center of the diaphragm back surface region (s1); a magnetic circuit internal region (s2) that is in contact with another surface of the magnetic fluid (60); and a ventilation region (s4) that provides ventilation between the sound hole region (s3) and the magnetic circuit internal region (s2).

Description

Speakers and earphones

[0001] The present disclosure relates to a speaker and an earphone including the speaker.

[0002] Speakers using magnetic fluids have been known in the past. In the speaker shown in Patent Document 1, magnetic fluid is disposed between the voice coil and the magnetic circuit, thereby stabilizing the vibration of the voice coil with low frictional resistance.

[0003] International Publication No. 2019 / 031352

[0004] In conventional speakers, for example, the magnetic fluid provided between the voice coil and the magnetic circuit can scatter, which can destabilize the vibration of the voice coil and make the speaker more susceptible to malfunction.

[0005] The present disclosure provides a speaker and the like that can prevent magnetic fluid provided between a voice coil and a magnetic circuit from scattering.

[0006] A speaker according to one aspect of the present disclosure comprises a cylindrical housing having side walls, a bottom plate, and an opening, a magnetic circuit housed in the housing, a voice coil with a portion disposed within a magnetic gap formed in the magnetic circuit, a diaphragm connected to an end of the voice coil located outside the magnetic circuit and covering the opening, and a magnetic fluid disposed within the magnetic gap between the magnetic circuit and the voice coil, wherein the magnetic fluid has one side and the other side in contact with the air in a spatial region surrounded by the housing and the diaphragm, and the spatial region is disposed between the diaphragm and the magnetic fluid and includes: a diaphragm back region in contact with one side of the magnetic fluid, a sound hole region connected to the center of the diaphragm back region, a magnetic circuit internal region disposed on the opposite side of the diaphragm back region with respect to the magnetic fluid and in contact with the other side of the magnetic fluid, and an air vent region for ventilating between the sound hole region and the magnetic circuit internal region.

[0007] An earphone according to one aspect of the present disclosure includes the above-described speaker.

[0008] The speaker according to the present disclosure can prevent the magnetic fluid provided between the voice coil and the magnetic circuit from scattering.

[0009] FIG. 1 is a perspective view showing the appearance of a speaker according to embodiment 1. FIG. 2 is a perspective cross-sectional view of the speaker according to embodiment 1. FIG. 3 is a diagram schematically showing a cross-section of the speaker according to embodiment 1. FIG. 4 is a perspective cross-sectional view of a speaker according to variation 1 of embodiment 1. FIG. 5 is an exploded perspective view of a speaker according to variation 1 of embodiment 1. FIG. 6 is a diagram schematically showing a cross-section of a speaker according to variation 1 of embodiment 1. FIG. 7 is a perspective cross-sectional view of a speaker according to variation 2 of embodiment 1. FIG. 8 is a diagram schematically showing a cross-section of a speaker according to variation 2 of embodiment 1. FIG. 9 is a perspective view showing the appearance of an earphone according to embodiment 2. FIG. 10 is an exploded perspective view of the earphone according to embodiment 2.

[0010] A speaker and the like according to one embodiment of the present disclosure will be illustrated.

[0011] The speaker of Example 1 comprises a cylindrical housing having side walls, a bottom plate, and an opening, a magnetic circuit housed in the housing, a voice coil with a portion thereof disposed within a magnetic gap formed in the magnetic circuit, a diaphragm connected to an end of the voice coil located outside the magnetic circuit and covering the opening, and a magnetic fluid provided within the magnetic gap between the magnetic circuit and the voice coil, the magnetic fluid having one side in contact with the air in a spatial region surrounded by the housing and the diaphragm, and the spatial region including: a diaphragm back region in contact with one side of the magnetic fluid, a sound hole region connected to the center of the diaphragm back region, a magnetic circuit internal region provided on the opposite side of the diaphragm back region with respect to the magnetic fluid and in contact with the other side of the magnetic fluid, and an air vent region for providing ventilation between the sound hole region and the magnetic circuit internal region.

[0012] According to the above configuration, the diaphragm back area in contact with one side of the magnetic fluid and the magnetic circuit internal area in contact with the other side of the magnetic fluid can be spatially connected, which makes the air pressure in contact with each side of the magnetic fluid equal, and prevents the magnetic fluid provided between the voice coil and the magnetic circuit from scattering.

[0013] A speaker of Example 2 is the speaker of Example 1, wherein the diaphragm back area and the magnetic circuit internal area may be connected via the sound hole area and the ventilation area.

[0014] With the above configuration, the diaphragm back area, which contacts one side of the magnetic fluid, and the magnetic circuit internal area, which contacts the other side of the magnetic fluid, can be connected via the sound hole area and the ventilation area, which makes the air pressures in contact with the one side and the other side of the magnetic fluid equal, and prevents the magnetic fluid provided between the voice coil and the magnetic circuit from scattering.

[0015] A speaker of Example 3 is the speaker described in Example 1 or 2, and the ventilation area may have a bottom surface area provided between the magnetic circuit and the bottom plate portion and connected to the sound hole area, and an air vent that provides ventilation between the bottom surface area and the magnetic circuit internal area.

[0016] This allows the back surface of the diaphragm to be easily connected to the internal area of ​​the magnetic circuit, which makes the air pressure on one side of the magnetic fluid equal to the air pressure on the other side, preventing the magnetic fluid between the voice coil and the magnetic circuit from scattering.

[0017] A speaker of Example 4 is the speaker of Example 3, wherein the magnetic circuit includes a cylindrical magnet, a ring-shaped first yoke connected to one pole of the magnet, and a second yoke connected to the other pole of the magnet that is opposite to the one pole of the magnet, the magnetic gap being formed between the first yoke and the second yoke, and the air vent being formed in the second yoke.

[0018] By forming an air vent in the second yoke, the rear surface area of ​​the diaphragm and the interior area of ​​the magnetic circuit can be easily connected, which makes the air pressure on one side of the magnetic fluid equal to the air pressure on the other side, and prevents the magnetic fluid between the voice coil and the magnetic circuit from scattering.

[0019] A speaker of Example 5 is the speaker of Example 4, wherein the magnet is arranged within the housing so that one pole is located on the opening side of the housing and the other pole is located on the bottom plate side of the housing, the second yoke has a ring-plate-shaped bottom yoke portion connected to the other pole, and a cylindrical outer yoke portion connected to the outer periphery of the bottom yoke portion and located between the outer surface of the magnet and the side wall portion, the magnetic gap is formed between the first yoke and the outer yoke portion, and the air vent may be formed to penetrate the bottom yoke portion in the thickness direction.

[0020] By forming an air vent that penetrates the bottom yoke in the thickness direction, the back surface area of ​​the diaphragm and the internal area of ​​the magnetic circuit can be easily connected, which makes the air pressure on one side of the magnetic fluid equal to the air pressure on the other side, and prevents the magnetic fluid provided between the voice coil and the magnetic circuit from scattering.

[0021] The speaker of Example 6 is the speaker described in Example 5, and the sound hole area may be formed at a position that passes through the center line of the through hole of the first yoke, the center line of the through hole of the magnet, and the center line of the through hole of the bottom yoke portion.

[0022] With the above configuration, the sound hole area can be easily formed, and the diaphragm back area and the magnetic circuit internal area can be easily connected via the sound hole area and the ventilation area. This makes the air pressure on one side of the magnetic fluid equal to the air pressure on the other side, and prevents the magnetic fluid provided between the voice coil and the magnetic circuit from scattering.

[0023] A speaker of Example 7 is the speaker of Example 5 or 6, wherein the diaphragm has a diaphragm whose outer periphery is connected to an end of the voice coil and an outer peripheral edge connected to the outer periphery of the diaphragm and supporting the diaphragm, the diaphragm back region has a diaphragm back region in contact with the diaphragm and an outer peripheral edge back region in contact with the outer peripheral edge, the spatial region further includes a side region located between the side wall portion and the outer yoke portion, and the outer peripheral edge back region and the bottom region may be ventilated via the side region.

[0024] As described above, by ventilating the outer peripheral edge back surface region and the bottom surface region through the side surface region, the outer peripheral edge back surface region and the magnetic circuit internal region can be connected via the side surface region, the bottom surface region and the ventilation holes. This makes the air pressure in the outer peripheral edge back surface region, the magnetic circuit internal region and the magnetic fluid in the region equal, and prevents the magnetic fluid provided between the voice coil and the magnetic circuit from scattering.

[0025] A speaker of Example 8 is the speaker of Example 7, wherein the magnetic fluid includes a first magnetic fluid positioned between the first yoke and the voice coil and a second magnetic fluid positioned between the second yoke and the voice coil, the first magnetic fluid having one side and the other side in contact with the air in the spatial region, the second magnetic fluid having one side and the other side in contact with the air in the spatial region, the diaphragm back region being in contact with the one side of the first magnetic fluid, the outer peripheral edge back region being in contact with the one side of the second magnetic fluid, the magnetic circuit internal region being in contact with the other side of the first magnetic fluid and the other side of the second magnetic fluid, the diaphragm back region and the magnetic circuit internal region being ventilated via the sound hole region and the ventilation region, and the outer peripheral edge back region and the magnetic circuit internal region being ventilated via the side region and the ventilation region.

[0026] According to the above configuration, the diaphragm rear region in contact with one side of the first magnetic fluid can be spatially connected to the magnetic circuit internal region in contact with the other side of the first magnetic fluid. Furthermore, the peripheral edge rear region in contact with one side of the second magnetic fluid can be spatially connected to the magnetic circuit internal region in contact with the other side of the second magnetic fluid. This makes the air pressures in contact with the one and the other sides of the first magnetic fluid and the one and the other sides of the second magnetic fluid equal, thereby preventing the magnetic fluid provided between the voice coil and the magnetic circuit from scattering.

[0027] A speaker of Example 9 is the speaker of Example 4, wherein the magnet has a cylindrical shape having the one pole and the other pole, the second yoke has a ring-plate-shaped bottom yoke portion connected to the other pole, and a cylindrical inner yoke portion connected to the center of the bottom yoke portion and positioned inside the inner surface of the magnet, the sound hole area is formed along the center line of the cylindrical inner yoke portion, and the air hole is formed to penetrate the bottom yoke portion in the thickness direction.

[0028] By forming an air vent that penetrates the bottom yoke in the thickness direction, the back surface area of ​​the diaphragm and the internal area of ​​the magnetic circuit can be easily connected, which makes the air pressure on one side of the magnetic fluid equal to the air pressure on the other side, and prevents the magnetic fluid provided between the voice coil and the magnetic circuit from scattering.

[0029] The speaker of Example 10 is the speaker described in Example 4, wherein the magnet has a cylindrical shape having the one pole and the other pole, the second yoke has a ring-plate-shaped bottom yoke portion connected to the other pole, and a cylindrical inner yoke portion connected to the center of the bottom yoke portion and located inside the inner surface of the magnet, the sound hole area being formed along the center line of the cylindrical inner yoke portion, and the ventilation area being formed to radially penetrate the inner yoke portion.

[0030] By forming an air vent that penetrates the inner yoke radially, the back surface area of ​​the diaphragm and the inner area of ​​the magnetic circuit can be easily connected, which makes the air pressure on one side of the magnetic fluid equal to the air pressure on the other side, and prevents the magnetic fluid provided between the voice coil and the magnetic circuit from scattering.

[0031] A speaker of Example 11 is the speaker according to any one of Examples 1 to 10, and may further include a net that covers the through-hole provided in the bottom plate portion.

[0032] For example, by replacing the mesh of the through-hole with a different mesh, it is possible to adjust the air pressure in the entire space connected by air between the back of the diaphragm, the housing, and the through-hole, making it possible to keep the air pressure almost constant within a small volume. This allows for more stable adjustment of the air pressure on the top and bottom of the magnetic fluid. It also makes it easy to change the sound pressure frequency characteristics of the speaker.

[0033] An earphone of Example 12 includes the speaker of any one of Examples 1 to 12.

[0034] This makes it possible to provide an earphone equipped with a speaker that can prevent the magnetic fluid between the voice coil and the magnetic circuit from scattering.

[0035] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0036] Note that the embodiments described below each illustrate a specific example of the present disclosure. The numerical values, shapes, materials, components, component placement positions, connection configurations, steps, and step sequences shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components not recited in independent claims are described as optional components.

[0037] Furthermore, in this specification, terms indicating the relationship between elements, such as perpendicular and parallel, terms indicating the shape of elements, such as cylindrical, ring-shaped and plate-shaped, and numerical ranges are not expressions that only express a strict meaning, but are expressions that also include a substantially equivalent range, for example, a difference of about a few percent.

[0038] In addition, each drawing is a schematic diagram in which emphasis, omission, or adjustment of proportions has been appropriately made to illustrate the present disclosure, and is not necessarily an exact illustration, and may differ from the actual shape, positional relationship, and proportion. In each drawing, the same reference numerals are used to denote substantially the same components, and duplicated explanations may be omitted or simplified.

[0039] Each figure also shows an X-axis, a Y-axis, and a Z-axis, which represent three mutually orthogonal directions, and these axes and the axial directions along these axes are used as necessary for explanation. Note that these axes are added for explanation purposes only and do not limit the direction or posture in which the speaker can be used.

[0040] First Embodiment [Configuration of Speaker] The configuration of a speaker 1 according to a first embodiment will be described with reference to FIGS. 1 to 3. FIG.

[0041] Fig. 1 is a perspective view showing the appearance of a speaker 1 according to embodiment 1. Fig. 2 is a perspective cross-sectional view of the speaker 1.

[0042] As shown in Fig. 1, the speaker 1 includes a housing 30 and a diaphragm 10. As shown in Fig. 2, the speaker 1 further includes a magnetic circuit 50, a voice coil 40, a stopper 20, and a magnetic fluid 60. In this embodiment, the direction in which sound is output from the speaker 1 will be described as the sound output direction. In Figs. 1 and 2, the sound output direction is the positive direction of the Z axis.

[0043] The housing 30 has a cylindrical shape with a bottom, and includes a cylindrical side wall portion 31, a disk-shaped bottom plate portion 32 provided at one end of the side wall portion 31, and an opening 33 located at the other end of the side wall portion 31. In other words, the housing 30 includes the disk-shaped bottom plate portion 32 and the cylindrical side wall portion 31 connected to the outer periphery of the bottom plate portion 32. In this embodiment, a line passing through the center of the cylindrical side wall portion 31 is referred to as a center line cL. The side wall portion 31 is parallel to the center line cL, and the bottom plate portion 32 is perpendicular to the center line cL.

[0044] The housing 30 is formed of, for example, a metal material and / or a resin material, etc. The housing 30 is formed by combining a side wall portion 31 and a bottom plate portion 32. The housing 30 may be formed by combining a plurality of members, or may be formed by pressure molding a single member.

[0045] Two grooves 31c parallel to the center line cL are formed on the inner surface of the side wall 31. The two grooves 31c are formed at positions facing each other with the center line cL in between. A groove 32c extending perpendicular to the center line cL is formed on the inner bottom of the bottom plate 32 of the housing 30. One end of the groove 31c formed on the side wall 31 is connected to a groove 32c formed on the bottom plate 32, and the other end of the groove 31c is connected to the outer peripheral edge back region s1b, which will be described later. Both ends of the groove 32c on the bottom plate 32 are connected to one end of the groove 31c on the side wall 31.

[0046] The bottom plate 32 has a through-hole 32a formed therethrough in the thickness direction. The through-hole 32a is formed so that the center line of the through-hole 32a coincides with the center line cL of the housing 30 and is connected to a sound hole area s3 (described later). A net 90 is attached to the outer surface of the bottom plate 32 of the housing 30 to cover the through-hole 32a. The net 90 is, for example, a damping cloth with a mesh. By attaching different nets 90 with different mesh sizes to the through-hole 32a, the air pressure in the small space formed by the entire air-connected space between the back surface of the diaphragm 10 (the diaphragm 11 and the outer peripheral edge 12), the housing 30, and the through-hole 32a can be more stably adjusted, and the sound pressure frequency characteristics of the speaker 1 can be changed.

[0047] The housing 30 accommodates a magnetic circuit 50, a voice coil 40, a magnetic fluid 60, and a stopper 20 therein.

[0048] The magnetic circuit 50 is a circuit that generates magnetic flux. The magnetic circuit 50 has a magnet M, a first yoke 51, and a second yoke 52, and the magnetic flux of the magnetic circuit 50 is formed by the magnet M, the first yoke 51, and the second yoke 52.

[0049] The magnet M has a cylindrical shape extending along the center line cL. In other words, the magnet M is cylindrical, and a through hole Ma is formed in the magnet M. The magnet M is arranged so that the center line of the through hole Ma coincides with the center line cL of the housing 30. The magnet M is arranged so that one pole p1 is located on the opening 33 side of the housing 30, and the other pole p2, which is the opposite pole to the one pole p1, is located on the bottom plate portion 32 side of the housing 30. For example, when the one pole p1 is a north pole, the other pole p2 is a south pole, and when the one pole p1 is a south pole, the other pole p2 is a north pole.

[0050] The first yoke 51 has a ring-shaped plate shape. In other words, the first yoke 51 has a disk shape, and a through-hole 51a is formed in the first yoke 51. The first yoke 51 is disposed so that the center line of the through-hole 51a coincides with the center line cL of the housing 30. One of the two surfaces of the disk of the first yoke 51 is connected to one pole p1 of the magnet M. The first yoke 51 may be connected to the magnet M using an adhesive.

[0051] The second yoke 52 has a cylindrical shape with a bottom and is composed of a bottom yoke portion 54 connected to the other pole p2 of the magnet M, and an outer yoke portion 53 connected to the outer periphery of the bottom yoke portion 54.

[0052] The bottom yoke portion 54 has a surface, of both surfaces thereof, that forms the inner bottom of the second yoke 52, connected to the other pole p2 of the magnet M. The bottom yoke portion 54 may be connected to the magnet M using an adhesive. The bottom yoke portion 54 has a ring-shaped plate shape. In other words, the bottom yoke portion 54 is disk-shaped, and a through hole 54a is formed in the bottom yoke portion 54. The bottom yoke portion 54 is positioned so that the center line of the through hole 54a coincides with the center line cL of the housing 30. The bottom yoke portion 54 also has a plurality of ventilation holes s4b formed therein that penetrate the bottom yoke portion 54 in the thickness direction. The ventilation holes s4b are holes that allow ventilation between the magnetic circuit internal region s2, which will be described later, and the bottom region s4a.

[0053] The outer yoke portion 53 has a cylindrical shape and is located between the outer surface Mb of the magnet M and the side wall portion 31 of the housing 30. The outer yoke portion 53 is formed so as to extend toward the opening 33 of the housing 30 along the center line cL, with at least a portion of the outer yoke portion 53 extending to a position facing the outer peripheral edge of the first yoke 51.

[0054] The magnetic circuit 50 is disposed on the bottom plate 32 of the housing 30, with the bottom yoke 54 in contact with a portion of the bottom plate 32 and the outer yoke 53 in contact with a portion of the side wall 31 of the housing 30. A magnetic gap G is formed in the gap between the outer peripheral edge of the first yoke 51 and the outer yoke 53 of the second yoke 52 (see the double-headed arrow in FIG. 2 ). A portion of the voice coil 40 is disposed within the magnetic gap G.

[0055] The voice coil 40 is a coil member formed by winding a metal wire. The voice coil 40 is formed into a cylindrical shape, for example, by winding the wire and then heat-sealing the resin material covering the wire. The voice coil 40 may also be formed by being wound around a cylindrical bobbin. The lead wire of the voice coil 40, for example, passes through the housing 30 and is drawn out to the outside of the bottom plate portion 32 (not shown). By changing the current flowing through the voice coil 40, the voice coil 40 can move in the sound output direction that intersects with the magnetic flux in the magnetic gap G and in the opposite direction. The voice coil 40 is connected to the diaphragm 10.

[0056] The diaphragm 10 is connected to one of the two ends of the cylindrical voice coil 40, specifically, to the end 41 of the voice coil 40 located near the opening 33. In other words, the diaphragm 10 is connected to the end 41 of the voice coil 40 located outside the magnetic circuit 50. The diaphragm 10 is also attached to the housing 30 so as to cover the opening 33 of the housing 30. The diaphragm 10 has a circular shape when viewed in the direction along the center line cL.

[0057] The diaphragm 10 is composed of a diaphragm 11 and a peripheral edge 12 that supports the diaphragm 11. The diaphragm 11 and the peripheral edge 12 are each made of an impermeable material. The peripheral edge 12 is also made of a more flexible material than the diaphragm 11.

[0058] The diaphragm 11 is a component that converts a signal input to the voice coil 40 into sound. The diaphragm 11 is connected to an end 41 of the voice coil 40 and vibrates when the voice coil 40 moves. When viewed from a direction along the center line cL, the diaphragm 11 has a circular shape. When viewed from a direction perpendicular to the center line cL, the diaphragm 11 has a shape in which the central portion bulges out more in the sound output direction than the outer periphery. The outer periphery of the diaphragm 11 is connected to the end 41 of the voice coil 40 and is also connected to the outer periphery edge 12.

[0059] The outer peripheral edge 12 has a ring shape, and the inner peripheral portion of the outer peripheral edge 12 is connected to the outer peripheral portion of the diaphragm 11. The outer peripheral edge 12 may be connected slightly inward from the outer peripheral portion of the diaphragm 11. Meanwhile, the outer peripheral portion of the outer peripheral edge 12 is connected to the outer edge of the opening 33 of the housing 30. Due to these connection relationships, the diaphragm 11 is supported by the housing 30 via the outer peripheral edge 12.

[0060] A ring 15 is provided on the outer periphery of the outer peripheral edge 12. In this example, the outer periphery of the outer peripheral edge 12 is fixed to the upper surface of the ring 15, and the lower surface of the ring 15 is joined to the other end of the side wall portion 31, thereby supporting the outer peripheral edge 12 on the housing 30. Therefore, when the voice coil 40 moves, the diaphragm 11 vibrates, and the outer peripheral edge 12 also vibrates.

[0061] The stopper 20 is provided between the diaphragm 11 and the first yoke 51. The stopper 20 is a member that regulates the position of the diaphragm 11 and is formed of, for example, a metal material or a resin material. The stopper 20 has a shape that follows the bulging shape of the diaphragm 11, and a gap is formed between the stopper 20 and the diaphragm 11. The stopper 20 has a stepped cylindrical shape and includes a regulating portion whose outer diameter is smaller than that of the first yoke 51 and a connecting portion whose outer diameter is smaller than that of the regulating portion. The connecting portion of the stopper 20 is inserted into a through-hole 51a of the first yoke 51 and connected to the first yoke 51. A through-hole 20a is formed in the stopper 20. The stopper 20 is positioned so that the through-hole 20a coincides with the center line cL of the housing 30.

[0062] The magnetic fluid 60 is disposed between the magnetic circuit 50 and the voice coil 40 in the magnetic gap G. The magnetic fluid 60 is made of iron oxide (Fe ３ O ４ The magnetic colloid solution is a mixture of ferromagnetic particles such as ferromagnetic cellulose, a dispersant such as an organic acid that coats the surfaces of the ferromagnetic particles, and a solvent made of a synthetic hydrocarbon oil such as poly-alpha olefin. The magnetic fluid 60 has a viscosity of 300 mPa·s or more at a predetermined reference temperature (e.g., room temperature: 15°C to 35°C), and more preferably 300 mPa·s or more and 3000 mPa·s or less.

[0063] The magnetic fluid 60 is provided in a ring shape on both the inner and outer circumferential sides of the voice coil 40 within the magnetic gap G. The magnetic fluid 60 has a plurality of surfaces that come into contact with the air in the spatial region surrounded by the housing 30 and the diaphragm 10. One of the surfaces (one air boundary surface) is the surface of the outer surface of the ring-shaped magnetic fluid 60 that is located on the opening 33 side, and the other surface (the other air boundary surface) is the surface of the outer surface that is located on the bottom plate portion 32 side. In other words, one surface of the magnetic fluid 60 is the surface of the plurality of surfaces that come into contact with the air in the spatial region that is located on the diaphragm 10 side as viewed from the magnetic fluid 60. The other surface of the magnetic fluid 60 is the surface of the plurality of surfaces that is located on the opposite side of the diaphragm 10 as viewed from the magnetic fluid 60.

[0064] In this example, the magnetic fluid 60 is composed of a first magnetic fluid 61 and a second magnetic fluid 62 .

[0065] The first magnetic fluid 61 is ring-shaped and is located between the first yoke 51 and the voice coil 40. The first magnetic fluid 61 has one surface f1a and another surface f1b that are in contact with the air in the spatial region. The one surface f1a of the first magnetic fluid 61 is the surface of the ring-shaped outer surface that is located on the opening 33 side, and the other surface f1b is the surface of the outer surface that is located on the bottom plate portion 32 side. Each of the one surface f1a and the other surface f1b may have a meniscus-like curved shape.

[0066] The second magnetic fluid 62 is ring-shaped and is located between the outer yoke portion 53 of the second yoke 52 and the voice coil 40. The second magnetic fluid 62 has one surface f2a and another surface f2b that are in contact with the air in the spatial region. The one surface f2a of the second magnetic fluid 62 is the surface of the ring-shaped outer surface that is located on the opening 33 side, and the other surface f1b is the surface of the outer surface that is located on the bottom plate portion 32 side. Each of the one surface f2a and the other surface f2b may have a meniscus-like curved shape.

[0067] The magnetic fluid 60 is a non-permeable viscous fluid that can flow and deform with the movement of the voice coil 40. By arranging the magnetic fluid 60 as described above, it is possible to reduce the movement resistance of the voice coil 40 and stabilize the vibration of the voice coil 40.

[0068] FIG. 3 is a diagram schematically showing a cross section of the speaker 1. As shown in FIG.

[0069] 3, the speaker 1 has a spatial region surrounded by the housing 30 and the diaphragm 10. Air exists in the spatial region.

[0070] The spatial region includes a diaphragm back region s1, a magnetic circuit internal region s2, a sound hole region s3, an air vent region s4, and a side region s5.

[0071] The diaphragm back surface region s1 is a region provided between the diaphragm 10 and the magnetic fluid 60, and is in contact with one surface of the magnetic fluid 60. The one surface of the magnetic fluid 60 is not the surface that contacts the voice coil 40 or the magnetic circuit 50, but is the surface that is located on the diaphragm 10 side as viewed from the magnetic fluid 60, among the multiple surfaces that contact the air.

[0072] More specifically, the diaphragm rear surface region s 1 is composed of a diaphragm rear surface region s 1 a in contact with the diaphragm 11 and a peripheral edge rear surface region s 1 b in contact with the peripheral edge 12 .

[0073] The diaphragm rear area s1a is an area surrounded by the diaphragm 11, the voice coil 40, the first magnetic fluid 61, the first yoke 51, and the stopper 20. The diaphragm rear area s1a is in contact with one surface f1a of the first magnetic fluid 61. The one surface f1a of the first magnetic fluid 61 is not the surface where the first magnetic fluid 61 is in contact with the voice coil 40 or the first yoke 51, but is the surface located on the diaphragm 11 side as viewed from the first magnetic fluid 61, among the multiple surfaces of the first magnetic fluid 61 that are in contact with air.

[0074] The outer peripheral edge back surface region s1b is a region surrounded by the outer peripheral edge 12, the side wall portion 31, the outer yoke portion 53, the second magnetic fluid 62, and the voice coil 40. The outer peripheral edge back surface region s1b is in contact with one surface f2a of the second magnetic fluid 62. The one surface f2a of the second magnetic fluid 62 is not a surface where the second magnetic fluid 62 is in contact with the voice coil 40 or the second yoke 52, but is a surface located on the outer peripheral edge 12 side as viewed from the second magnetic fluid 62, among the multiple surfaces of the second magnetic fluid 62 that are in contact with air.

[0075] The sound hole region s3 is a region connected to the center of the diaphragm back region s1. The center of the diaphragm back region s1 is the region of the diaphragm back region s1 that overlaps with the center line cL of the housing 30. The sound hole region s3 is formed by the through hole Ma of the magnet M, the through hole 20a of the stopper 20 inserted into the first yoke 51, and the through hole 54a of the bottom yoke portion 54. The sound hole region s3 is formed along the center line cL of the housing 30, at a position that passes through the center line of the through hole 51a of the first yoke 51, the center line of the through hole Ma of the magnet M, and the center line of the through hole 54a of the bottom yoke portion 54.

[0076] The magnetic circuit internal region s2 is a region formed inside the magnetic circuit 50. The magnetic circuit internal region s2 is a region surrounded by the outer surface Mb of the magnet M, the first yoke 51, the first magnetic fluid 61, the voice coil 40, the second magnetic fluid 62, and the second yoke 52. The magnetic circuit internal region s2 is provided on the opposite side of the magnetic fluid 60 from the diaphragm back surface region s1, and is in contact with the other side of the magnetic fluid 60. The other side of the magnetic fluid 60 is not the side of the magnetic fluid 60 that is in contact with the voice coil 40 or the magnetic circuit 50, but is one of the multiple surfaces of the magnetic fluid 60 that are in contact with air and that is located on the opposite side of the diaphragm 10 as viewed from the magnetic fluid 60.

[0077] Specifically, the magnetic circuit internal region s2 is in contact with the other surface f1b of the first magnetic fluid 61 and the other surface f2b of the second magnetic fluid 62. The other surface f1b of the first magnetic fluid 61 is not a surface of the first magnetic fluid 61 in contact with the voice coil 40 or the first yoke 51, but is a surface of the first magnetic fluid 61 that is in contact with the air and is located on the opposite side of the diaphragm 11 from the first magnetic fluid 61. The other surface f2b of the second magnetic fluid 62 is not a surface of the second magnetic fluid 62 in contact with the voice coil 40 or the second yoke 52, but is a surface of the second magnetic fluid 62 that is in contact with the air and is located on the opposite side of the outer circumferential edge 12 from the second magnetic fluid 62.

[0078] The ventilation area s4 is an area that provides ventilation between the sound hole area s3 and the magnetic circuit internal area s2. The ventilation area s4 has a bottom area s4a that connects to the sound hole area s3, and ventilation holes s4b that provide ventilation between the bottom area s4a and the magnetic circuit internal area s2.

[0079] The bottom surface region s4a is located between the magnetic circuit 50 and the bottom plate portion 32. The bottom surface region s4a is an area surrounded by the bottom surface yoke portion 54 and the groove portion 32c of the bottom plate portion 32. The ventilation holes s4b are formed in the bottom surface yoke portion 54 of the second yoke 52. The ventilation holes s4b are formed by penetrating the bottom surface yoke portion 54 in the thickness direction.

[0080] The side surface region s5 is located between the side wall portion 31 of the housing 30 and the outer yoke portion 53. The side surface region s5 is an area surrounded by the outer yoke portion 53 and the groove portion 31c of the side wall portion 31. The side surface region s5 provides ventilation between the outer peripheral edge back surface region s1b and the bottom surface region s4a.

[0081] In Figure 3, the thick arrows indicate an example of the direction of pressure generated in the spatial region by vibration of the diaphragm 10. As shown in Figure 3, the diaphragm back surface region s1 and the magnetic circuit internal region s2 are connected via the sound hole region s3 and the ventilation region s4. Therefore, the pressure exerted on one side of the magnetic fluid 60 via the diaphragm back surface region s1 by vibration of the diaphragm 10 is equal to the pressure exerted on the other side of the magnetic fluid 60 via the diaphragm back surface region s1, the sound hole region s3, the ventilation region s4, and the magnetic circuit internal region s2 by vibration of the diaphragm 10, making it possible to prevent the magnetic fluid 60 from scattering.

[0082] More specifically, the diaphragm rear area s1a and the magnetic circuit internal area s2 are spatially connected via the sound hole area s3 and the ventilation area s4. Therefore, the pressure exerted on one surface f1a of the first magnetic fluid 61 via the diaphragm rear area s1a due to the vibration of the diaphragm 11 is equal to the pressure exerted on the other surface f1b of the first magnetic fluid 61 via the diaphragm rear area s1a, the sound hole area s3, the ventilation area s4, and the magnetic circuit internal area s2 due to the vibration of the diaphragm 11, thereby preventing the first magnetic fluid 61 from scattering.

[0083] Furthermore, the outer peripheral edge back surface region s1b and the magnetic circuit internal region s2 are spatially connected via the side surface region s5 and the ventilation region s4. Therefore, the pressure exerted on one surface f2a of the second magnetic fluid 62 via the outer peripheral edge back surface region s1b due to vibration of the outer peripheral edge 12 is equal to the pressure exerted on the other surface f2b of the second magnetic fluid 62 via the outer peripheral edge back surface region s1b, the side surface region s5, the ventilation region s4, and the magnetic circuit internal region s2 due to vibration of the outer peripheral edge 12, thereby preventing the second magnetic fluid 62 from scattering.

[0084] According to the speaker 1 of this embodiment, it is possible to spatially connect the diaphragm back area s1 that contacts one side of the magnetic fluid 60 and the magnetic circuit internal area s2 that contacts the other side of the magnetic fluid 60. This makes the pressure of the air that contacts one side and the other side of the magnetic fluid 60 equal, and it is possible to prevent the magnetic fluid 60 provided between the voice coil 40 and the magnetic circuit 50 from scattering.

[0085] In addition, by selecting the mesh size of the net 90 provided in the through hole 32a provided in the bottom plate portion 32, the air pressure in the small space formed by the entire space connected by air between the back of the diaphragm 10 (vibration plate 11 and outer peripheral edge 12), the housing 30, and the through hole 32a can be more stably adjusted, thereby more stably suppressing the scattering of the magnetic fluid 60.

[0086] 4 to 6, the configuration of a speaker 1A according to a first modification of the first embodiment will be described. In the first modification, an example will be described in which the magnetic fluid 60 is formed only on the inner circumferential side of the voice coil 40. In the first modification, an external magnet type magnetic circuit 50A will be described in which the magnet MA is disposed on the outer side of the second yoke 52A provided in the center.

[0087] Fig. 4 is a perspective cross-sectional view of a speaker 1A according to a first modification of embodiment 1. Fig. 5 is an exploded perspective view of the speaker 1A according to the first modification.

[0088] The appearance of the speaker 1A of the first modification is the same as that of the first embodiment. In the first modification, a cover 91 is provided on the diaphragm 10.

[0089] As shown in FIGS. 4 and 5, the speaker 1A includes a housing 30, a diaphragm 10, a magnetic circuit 50A, a voice coil 40, a stopper 20, and a magnetic fluid 60.

[0090] The housing 30 has a cylindrical shape with a bottom, and includes a cylindrical side wall portion 31, a disk-shaped bottom plate portion 32 provided at one end of the side wall portion 31, and an opening 33 located at the other end of the side wall portion 31. In other words, the housing 30 includes the disk-shaped bottom plate portion 32 and the cylindrical side wall portion 31 connected to the outer periphery of the bottom plate portion 32. In the first modification, the line passing through the center of the cylindrical side wall portion 31 is also referred to as the center line cL. The side wall portion 31 is parallel to the center line cL, and the bottom plate portion 32 is perpendicular to the center line cL.

[0091] A groove 32c extending perpendicular to the center line cL is formed on the inner bottom of the bottom plate 32 of the housing 30. A through hole 32a penetrating the bottom plate 32 in the thickness direction is formed in the bottom plate 32. A net 90 is attached to the outer surface of the bottom plate 32 of the housing 30 to cover the through hole 32a. Note that the side wall 31 of the first modification does not have the groove 31c formed therein as in the first embodiment.

[0092] The housing 30 accommodates a magnetic circuit 50A, a voice coil 40, a magnetic fluid 60, and a stopper 20 therein.

[0093] The magnetic circuit 50A is a circuit that generates magnetic flux. The magnetic circuit 50A has a magnet MA, a first yoke 51A, and a second yoke 52A, and the magnetic flux of the magnetic circuit 50A is formed by the magnet MA, the first yoke 51A, and the second yoke 52A.

[0094] The magnet MA has a cylindrical shape extending along the center line cL. In other words, the magnet MA is cylindrical, and a through hole Ma is formed in the magnet MA. The magnet MA is arranged so that the center line of the through hole Ma coincides with the center line cL of the housing 30. The magnet MA is arranged so that one pole p1 is located on the opening 33 side of the housing 30, and the other pole p2, which is the opposite pole to the one pole p1, is located on the bottom plate portion 32 side of the housing 30.

[0095] The first yoke 51A has a ring-like plate shape. In other words, the first yoke 51A is disk-shaped, and a through-hole 51a is formed in the first yoke 51A. The first yoke 51A is disposed so that the center line of the through-hole 51a coincides with the center line cL of the housing 30. One of the two surfaces of the disk of the first yoke 51A is connected to one pole p1 of the magnet MA.

[0096] The second yoke 52A has a stepped cylindrical shape and is composed of a bottom yoke portion 54 connected to the other pole p2 of the magnet MA, and an inner yoke portion 55 connected to the center of the bottom yoke portion 54 and located inside the magnet MA.

[0097] The bottom yoke portion 54 has a ring-shaped plate-like surface, the inner bottom surface of the second yoke 52A of which is connected to the other pole p2 of the magnet MA. The bottom yoke portion 54 has a circular plate-like shape. In other words, the bottom yoke portion 54 is circular, and a through hole 54a is formed in the bottom yoke portion 54. The bottom yoke portion 54 is positioned so that the center line of the through hole 54a coincides with the center line cL of the housing 30. The bottom yoke portion 54 also has a plurality of ventilation holes s4b that penetrate the bottom yoke portion 54 in the thickness direction. The ventilation holes s4b are holes for ventilating the magnetic circuit internal region s2 (described later) and the bottom region s4a.

[0098] The inner yoke portion 55 has a cylindrical shape and is located inside the inner surface Mc of the magnet MA. The inner yoke portion 55 is formed to extend along the center line cL toward the opening 33 of the housing 30, with at least a portion of the inner yoke portion 55 extending to a position facing the inner peripheral edge of the first yoke 51A. A through hole 55a is formed in the inner yoke portion 55. The inner yoke portion 55 is positioned so that the center line of the through hole 55a coincides with the center line cL of the housing 30.

[0099] The magnetic circuit 50A is disposed on the bottom plate 32 with the bottom yoke 54 in contact with a portion of the bottom plate 32 of the housing 30, and with the outer peripheries of the bottom yoke 54, magnet MA, and first yoke 51A in contact with a portion of the side wall 31 of the housing 30. A magnetic gap G is formed in the gap between the inner peripheral edge of the first yoke 51A and the inner yoke 55 of the second yoke 52A (see the double-headed arrow in FIG. 4). A portion of the voice coil 40 is disposed within the magnetic gap G.

[0100] The voice coil 40 is a coil member formed by winding a metal wire. The configuration of the voice coil 40 is the same as that of the first embodiment.

[0101] The diaphragm 10 is connected to an end 41 of the voice coil 40 located outside the magnetic circuit 50A. The diaphragm 10 is composed of a diaphragm 11 and an outer peripheral edge 12 that supports the diaphragm 11. The configuration of the diaphragm 10 is the same as that of the first embodiment.

[0102] The stopper 20 is provided between the diaphragm 11 and the second yoke 52A. The stopper 20 is a stepped cylinder and has a restricting portion whose outer diameter is smaller than the inner yoke portion 55 of the second yoke 52A, and a connecting portion whose outer diameter is smaller than the restricting portion. The connecting portion of the stopper 20 is inserted into a hole 55b in the inner yoke portion 55 and is connected to the inner yoke portion 55. A through hole 20a is formed in the stopper 20. The stopper 20 is positioned so that the through hole 20a coincides with the center line cL of the housing 30.

[0103] The magnetic fluid 60 is disposed between the magnetic circuit 50A and the voice coil 40 within the magnetic gap G. The magnetic fluid 60 of the first modification is provided in a ring shape on the inner periphery of the voice coil 40 within the magnetic gap G. The magnetic fluid 60 is located between the inner yoke portion 55 of the second yoke 52A and the voice coil 40. By disposing the magnetic fluid 60 in this manner, it is possible to reduce the movement resistance of the voice coil 40 and stabilize the vibration of the voice coil 40.

[0104] FIG. 6 is a diagram schematically showing a cross section of a speaker 1A of the first modified example.

[0105] As shown in Fig. 6, a spatial region is formed in the speaker 1A, and air exists in the spatial region.

[0106] The spatial region includes a diaphragm back region s1, a magnetic circuit internal region s2, a sound hole region s3, and a ventilation region s4. The diaphragm back region s1 is composed of a diaphragm back region s1a that contacts the diaphragm 11 and a peripheral edge back region s1b that contacts the peripheral edge 12.

[0107] The diaphragm rear area s1a is an area surrounded by the diaphragm 11, the voice coil 40, the magnetic fluid 60, the second yoke 52A, and the stopper 20. The diaphragm rear area s1a is in contact with one surface f3a of the magnetic fluid 60. The one surface f3a of the magnetic fluid 60 is not the surface where the magnetic fluid 60 is in contact with the voice coil 40 or the second yoke 52A, but is the surface located on the diaphragm 11 side as viewed from the magnetic fluid 60, among the multiple surfaces of the magnetic fluid 60 that are in contact with air. In other words, the one surface f3a of the magnetic fluid 60 is the surface located on the opening 33 side among the outer surfaces of the ring-shaped magnetic fluid 60.

[0108] The outer peripheral edge back surface region s1b is a region surrounded by the outer peripheral edge 12, the side wall portion 31, the first yoke 51A, and the voice coil 40.

[0109] Sound hole region s3 is a region connected to the center of diaphragm back surface region s1. Sound hole region s3 is made up of through hole 20a of stopper 20 inserted into inner yoke portion 55, through hole 55a of inner yoke portion 55, and through hole 54a of bottom yoke portion 54. Sound hole region s3 is formed along center line cL of housing 30, at a position that passes through the center line of through hole 55a of inner yoke portion 55 and the center line of through hole 54a of bottom yoke portion 54.

[0110] The magnetic circuit internal region s2 is a region formed inside the magnetic circuit 50A. Specifically, the magnetic circuit internal region s2 is a region surrounded by the inner surface Mc of the magnet MA, the second yoke 52A, the magnetic fluid 60, and the voice coil 40. The magnetic circuit internal region s2 is provided on the opposite side of the magnetic fluid 60 from the diaphragm back region s1 and is in contact with the other surface f3b of the magnetic fluid 60. The other surface f3b of the magnetic fluid 60 is one of the multiple surfaces of the magnetic fluid 60 that are in contact with the air and that is located on the opposite side of the diaphragm 11 from the magnetic fluid 60. In other words, the other surface f3b of the magnetic fluid 60 is the surface of the ring-shaped outer surface of the magnetic fluid 60 that is located on the bottom plate portion 32 side.

[0111] The ventilation area s4 is an area that provides ventilation between the sound hole area s3 and the magnetic circuit internal area s2. The ventilation area s4 has a bottom area s4a that connects to the sound hole area s3, and ventilation holes s4b that provide ventilation between the bottom area s4a and the magnetic circuit internal area s2.

[0112] The bottom surface region s4a is located between the magnetic circuit 50A and the bottom plate portion 32. The bottom surface region s4a is an area surrounded by the bottom surface yoke portion 54 and the groove portion 32c of the bottom plate portion 32. The ventilation holes s4b are formed in the bottom surface yoke portion 54 of the second yoke 52A. The ventilation holes s4b are formed by penetrating the bottom surface yoke portion 54 in the thickness direction.

[0113] In Figure 6, the thick arrows indicate an example of the direction of pressure generated in the spatial region due to vibration of the diaphragm 10. As shown in Figure 6, the diaphragm back surface region s1 and the magnetic circuit internal region s2 are connected via the sound hole region s3 and the ventilation region s4. Therefore, the pressure exerted on one surface f3a of the magnetic fluid 60 via the diaphragm back surface region s1 due to vibration of the diaphragm 10 is equal to the pressure exerted on the other surface f3b of the magnetic fluid 60 via the diaphragm back surface region s1, the sound hole region s3, the ventilation region s4, and the magnetic circuit internal region s2 due to vibration of the diaphragm 10, thereby preventing the magnetic fluid 60 from scattering.

[0114] According to the speaker 1A of variant 1, the pressure of the air in contact with one surface f3a and the other surface f3b of the magnetic fluid 60 is equal, which prevents the magnetic fluid 60 provided between the voice coil 40 and the magnetic circuit 50A from scattering.

[0115] In addition, by selecting the mesh size of the net 90 provided in the through hole 32a provided in the bottom plate portion 32, the air pressure in the small space formed by the entire space connected by air between the back of the diaphragm 10 (vibration plate 11 and outer peripheral edge 12), the housing 30, and the through hole 32a can be more stably adjusted, thereby more stably suppressing the scattering of the magnetic fluid 60.

[0116] 7 and 8, the configuration of a speaker 1B according to a second modification of the first embodiment will be described. In the second modification, an example in which the ventilation area s4 is formed in the inner yoke portion 55 of the second yoke 52A will be described.

[0117] Fig. 7 is a perspective cross-sectional view of a speaker 1B according to Modification 2 of Embodiment 1. Fig. 7 is a view of speaker 1B viewed from a direction different from the direction in which speaker 1A in Fig. 4 is viewed.

[0118] As shown in FIG. 7, the speaker 1B includes a housing 30, a diaphragm 10, a magnetic circuit 50A, a voice coil 40, a stopper 20, and a magnetic fluid 60.

[0119] The configurations of the housing 30, the diaphragm 10, the voice coil 40, the stopper 20 and the magnetic fluid 60 are the same as those of the first modified example, and therefore a description thereof will be omitted.

[0120] The magnetic circuit 50A has a magnet MA, a first yoke 51A, and a second yoke 52A, and the magnetic flux of the magnetic circuit 50A is formed by the magnet MA, the first yoke 51A, and the second yoke 52A. The configurations of the magnet MA and the first yoke 51A are the same as those in the first modification.

[0121] The second yoke 52A has a stepped cylindrical shape and is composed of a bottom yoke portion 54 and an inner yoke portion 55 that is connected to the center of the bottom yoke portion 54 and is located inside the magnet MA.

[0122] The bottom yoke part 54 has a ring-shaped plate shape. In other words, the bottom yoke part 54 is disk-shaped, and a through-hole 54a is formed in the bottom yoke part 54. The bottom yoke part 54 is positioned so that the center line of the through-hole 54a coincides with the center line cL of the housing 30. Note that the bottom yoke part 54 of the second modification does not have a vent hole formed therethrough, as in the first modification.

[0123] The inner yoke portion 55 has a cylindrical shape and is located inside the inner surface Mc of the magnet MA. The inner yoke portion 55 is formed to extend along the center line cL toward the opening 33 of the housing 30, with at least a portion of the inner yoke portion 55 extending to a position facing the inner peripheral edge of the first yoke 51A. A through hole 55a is formed in the inner yoke portion 55. The inner yoke portion 55 is positioned so that the center line of the through hole 55a coincides with the center line cL of the housing 30. In the second modification, a ventilation region s4 is formed to radially penetrate the inner yoke portion 55.

[0124] FIG. 8 is a diagram schematically showing a cross section of a speaker 1B of the second modification.

[0125] As shown in Fig. 8, a spatial region is formed in the speaker 1B, and air exists in the spatial region.

[0126] The spatial region includes a diaphragm back region s1, a magnetic circuit internal region s2, a sound hole region s3, and a ventilation region s4. The diaphragm back region s1 is composed of a diaphragm back region s1a that contacts the diaphragm 11 and a peripheral edge back region s1b that contacts the peripheral edge 12.

[0127] The diaphragm back surface area s1a, the outer peripheral edge back surface area s1b, the sound hole area s3, and the magnetic circuit internal area s2 have the same configuration as in the first modified example.

[0128] The ventilation area s4 is an area that provides ventilation between the sound hole area s3 and the magnetic circuit internal area s2. The ventilation area s4 is formed so as to penetrate the inner yoke portion 55 in the radial direction.

[0129] In Figure 8, the thick arrows indicate an example of the direction of pressure generated in the spatial region due to vibration of the diaphragm 10. As shown in Figure 8, the diaphragm back surface region s1 and the magnetic circuit internal region s2 are connected via the sound hole region s3 and the ventilation region s4. Therefore, the pressure exerted on one surface f3a of the magnetic fluid 60 via the diaphragm back surface region s1 due to vibration of the diaphragm 10 is equal to the pressure exerted on the other surface f3b of the magnetic fluid 60 via the diaphragm back surface region s1, the sound hole region s3, the ventilation region s4, and the magnetic circuit internal region s2 due to vibration of the diaphragm 10, thereby preventing the magnetic fluid 60 from scattering.

[0130] According to the speaker 1B of variant example 2, the pressure of the air in contact with one surface f3a and the other surface f3b of the magnetic fluid 60 is equal, thereby preventing the magnetic fluid 60 provided between the voice coil 40 and the magnetic circuit 50A from scattering.

[0131] In addition, by selecting the mesh size of the net 90 provided in the through hole 32a provided in the bottom plate portion 32, the air pressure in the small space formed by the entire space connected by air between the back of the diaphragm 10 (vibration plate 11 and outer peripheral edge 12), the housing 30, and the through hole 32a can be more stably adjusted, thereby more stably suppressing the scattering of the magnetic fluid 60.

[0132] Second Embodiment [Configuration of Earphone] The configuration of an earphone according to a second embodiment will be described with reference to FIGS. 9 and 10. FIG.

[0133] Fig. 9 is a perspective view showing the appearance of the earphone 100 according to embodiment 2. Fig. 10 is an exploded perspective view of the earphone 100.

[0134] 9 and 10 , the earphone 100 includes a speaker 1, a port 2, ear tips 3, a box 4, a cable 5, and a back cover 6. The earphone 100 is an inner-ear headphone. Note that a speaker 1A may be used instead of the speaker 1.

[0135] The speaker 1 has the configuration described in the first embodiment. The port 2 is a substantially cylindrical member that houses the speaker 1 inside. The ear tip 3 is a member that is connected to the tip of the port 2 and is used to place the earphone 100 inside the human ear canal. The box 4 is a member that closes the opening of the port 2 on the side opposite to the side where the ear tip 3 is placed. The cable 5 passes through the box 4 and is connected to the bottom plate 32 of the speaker 1, and is used to input electrical signals to the speaker 1. The back cover 6 is a member that covers the portion where the cable 5 passes through the box 4.

[0136] In the earphone 100 configured in this manner, sound output from the speaker 1 in response to an electrical signal input via the cable 5 is output from the port 2 and the ear tip 3. Therefore, when the ear tip 3 is fitted into a person's ear canal, the person can hear the sound from the earphone 100.

[0137] Although the above description has been given of an example in which the speaker 1 is used in inner-ear headphones, the speaker 1 may also be used in overhead headphones, as a speaker for a mobile terminal, or in a hearing aid.

[0138] Although the speaker 1 has been described above as an example, the present invention is not limited to this and may be the speaker 1A or 1B. In other words, the earphone 100 may include the speaker 1A or 1B instead of the speaker 1.

[0139] (Other Embodiments) The present disclosure is not limited to the above-described embodiments. For example, other embodiments realized by any combination of the components described in this specification or by excluding some of the components may be considered as embodiments of the present disclosure. Furthermore, the present disclosure also includes modifications obtained by applying various modifications to the above-described embodiments that would occur to a person skilled in the art within the scope of the gist of the present disclosure, i.e., the meaning indicated by the wording of the claims.

[0140] In the first embodiment, the magnetic circuit 50 is described as an internal magnet type in which the magnet M is disposed inside the second yoke 52, but this is not limiting. For example, the magnetic circuit 50 may be an external magnet type in which the magnet M is disposed outside the second yoke.

[0141] In the first modification of the first embodiment, the magnetic circuit 50A is an external magnet type in which the magnet MA is disposed on the outside of the second yoke 52. However, the present invention is not limited to this. For example, the magnetic circuit 50A may be an internal magnet type in which the magnet is disposed on the inside of the second yoke.

[0142] In the above embodiment, a dome-shaped diaphragm is exemplified, but the diaphragm may be flat or cone-shaped. Furthermore, the shape of the diaphragm in plan view is not limited to a circle, but may also be an ellipse, a rectangle, or the like.

[0143] The speaker of the present disclosure is useful as a speaker that can suppress the occurrence of operational abnormalities.

[0144] REFERENCE SIGNS LIST 1, 1A, 1B Speaker 2 Port 3 Ear tip 4 Box 5 Cable 6 Back cover 10 Diaphragm 11 Diaphragm 12 Outer peripheral edge 15 Ring 20 Stopper 20a Through hole 30 Housing 31 Side wall portion 31c Groove portion 32 Bottom plate portion 32a Through hole 32c Groove portion 33 Opening 40 Voice coil 41 End portion 50, 50A Magnetic circuit 51, 51A First yoke 51a Through hole 52, 52A Second yoke 53 Outer yoke portion 54 Bottom yoke portion 54a Through hole 55 Inner yoke portion 55a Through hole 55b Hole 60 Magnetic fluid 61 First magnetic fluid 62 Second magnetic fluid 90 Net 91 Cover 100 Earphone f1a, f2a, f3a One side of the magnetic fluid f1b, f2b, f3b The other side of the magnetic fluid G Magnetic gap M, MA Magnet Ma Through hole Mb Outer surface Mc Inner surface s1 Diaphragm back area s1a Vibration plate back area s1b Outer edge back area s2 Magnetic circuit internal area s3 Sound hole area s4 Ventilation area s4a Bottom area s4b Ventilation hole s5 Side area p1 One pole p2 The other pole cL Center line

Claims

1. A speaker comprising: a cylindrical housing having side walls, a bottom plate, and an opening; a magnetic circuit housed in the housing; a voice coil with a portion located within a magnetic gap formed in the magnetic circuit; a diaphragm connected to an end of the voice coil located outside the magnetic circuit and covering the opening; and a magnetic fluid provided within the magnetic gap between the magnetic circuit and the voice coil, wherein the magnetic fluid has one side and the other side in contact with the air in a spatial region surrounded by the housing and the diaphragm, and the spatial region includes: a diaphragm back region provided between the diaphragm and the magnetic fluid and in contact with one side of the magnetic fluid; a sound hole region connected to the center of the diaphragm back region; a magnetic circuit internal region provided on the opposite side of the magnetic fluid from the diaphragm back region and in contact with the other side of the magnetic fluid; and an air vent region for providing ventilation between the sound hole region and the magnetic circuit internal region.

2. The speaker according to claim 1, wherein the diaphragm rear area and the magnetic circuit internal area are connected via the sound hole area and the ventilation area.

3. A speaker as described in claim 1 or 2, wherein the ventilation area has a bottom surface area provided between the magnetic circuit and the bottom plate portion and connected to the sound hole area, and an air vent that provides ventilation between the bottom surface area and the internal area of ​​the magnetic circuit.

4. A speaker as described in claim 3, wherein the magnetic circuit has a cylindrical magnet, a ring-shaped first yoke connected to one pole of the magnet, and a second yoke connected to the other pole of the magnet that is opposite to the one pole, the magnetic gap is formed between the first yoke and the second yoke, and the air hole is formed in the second yoke.

5. The speaker described in claim 4, wherein the magnet is arranged within the housing so that one pole is located on the opening side of the housing and the other pole is located on the bottom plate side of the housing, the second yoke has a ring-plate-shaped bottom yoke part connected to the other pole, and a cylindrical outer yoke part connected to the outer periphery of the bottom yoke part and located between the outer surface of the magnet and the side wall part, the magnetic gap is formed between the first yoke and the outer yoke part, and the air vent is formed so as to penetrate the bottom yoke part in the thickness direction.

6. A speaker according to claim 5, wherein the sound hole area is formed at a position that passes through the center line of the through hole of the first yoke, the center line of the through hole of the magnet, and the center line of the through hole of the bottom yoke portion.

7. The speaker according to claim 5, wherein the diaphragm has a diaphragm whose outer periphery is connected to the end of the voice coil, and an outer peripheral edge connected to the outer periphery of the diaphragm and supporting the diaphragm, the diaphragm back area has a diaphragm back area in contact with the diaphragm, and an outer peripheral edge back area in contact with the outer peripheral edge, the spatial area further includes side areas located between the side wall portion and the outer yoke portion, and the outer peripheral edge back area and the bottom area are ventilated via the side areas.

8. The speaker according to claim 7, wherein the magnetic fluid comprises a first magnetic fluid located between the first yoke and the voice coil, and a second magnetic fluid located between the second yoke and the voice coil, the first magnetic fluid having one surface and the other surface in contact with the air in the spatial region, the second magnetic fluid having one surface and the other surface in contact with the air in the spatial region, the diaphragm back region being in contact with the one surface of the first magnetic fluid, the outer peripheral edge back region being in contact with the one surface of the second magnetic fluid, the magnetic circuit internal region being in contact with the other surface of the first magnetic fluid and the other surface of the second magnetic fluid, the diaphragm back region and the magnetic circuit internal region being ventilated via the sound hole region and the ventilation region, and the outer peripheral edge back region and the magnetic circuit internal region being ventilated via the side region and the ventilation region.

9. A speaker as described in claim 4, wherein the magnet has a cylindrical shape having the one pole and the other pole, the second yoke has a ring-plate-shaped bottom yoke portion connected to the other pole, and a cylindrical inner yoke portion connected to the center of the bottom yoke portion and located inside the inner surface of the magnet, the sound hole area is formed along the center line of the cylindrical inner yoke portion, and the air hole is formed so as to penetrate the bottom yoke portion in the thickness direction.

10. A speaker as described in claim 4, wherein the magnet has a cylindrical shape having the one pole and the other pole, the second yoke has a ring-plate-shaped bottom yoke portion connected to the other pole, and a cylindrical inner yoke portion connected to the center of the bottom yoke portion and located inside the inner surface of the magnet, the sound hole area is formed along the center line of the cylindrical inner yoke portion, and the ventilation area is formed so as to radially penetrate the inner yoke portion.

11. A speaker according to claim 1 or 2, further comprising a net covering the through-hole provided in the bottom plate portion.

12. An earphone comprising the speaker according to claim 1 or 2.

Images