Micro speaker and earphone

Abstract

This micro speaker comprises: a cylindrical first frame which is incorporated into a housing of an earphone and has a first empty chamber; a diaphragm which is provided in one opening of the first frame and has an edge on a peripheral edge of a dome; a cylindrical voice coil which is coaxially fixed to the diaphragm; an annular magnet which is arranged in the first frame and has, as the center thereof, a dome lower ventilation path coaxial with the voice coil; a rear cover which covers at least a part of the other opening of the first frame; and a second frame which is attached to the rear cover and has a second empty chamber communicating with the first empty chamber. In the first frame, the other opening, which is not covered by the rear cover, is blocked by a substrate that partitions the first empty chamber.

Description

Micro speakers and earphones

[0001] The present disclosure relates to a micro-speaker and an earphone.

[0002] Patent Document 1 discloses a speaker unit incorporated into the housing of an earphone. This speaker unit includes a cylindrical frame, a diaphragm that emits sound, and a circuit board to which the wiring of a coil provided on the diaphragm is connected. A space is formed inside the frame, and the diaphragm and the circuit board are arranged inside the frame with the space between them.

[0003] Japanese Patent Application Publication No. 2022-91463

[0004] The frame of Patent Document 1 is composed of a cylindrical first frame having a diaphragm and a second frame provided on the opposite side of the first frame from the diaphragm. In this configuration, a first cavity formed inside the first frame communicates with a second cavity formed inside the second frame via a damping member provided at the boundary between the first and second frames, thereby damping (suppressing) sound vibrations. A plurality of lands are arranged along the circumferential direction on the rear end surface of the second frame, and wiring is connected to each of the lands by solder.

[0005] However, the frame of Patent Document 1 has a cylindrical first frame and a cylindrical second frame that are connected coaxially and with the same outer diameter, which means that the distance (thickness) along the axis of the entire frame tends to be large, making it difficult to reduce the thickness of the earphone.

[0006] The present disclosure has been devised in view of the above-described conventional circumstances, and aims to provide a micro speaker and earphones that can make the frame more compact and contribute to further reducing the thickness size of the earphones.

[0007] The present disclosure provides a microspeaker to be incorporated into the housing of an earphone, the microspeaker comprising: a cylindrical first frame having a first cavity; a diaphragm provided in one opening of the first frame and having an edge on the periphery of a dome; a cylindrical voice coil fixed coaxially to the diaphragm; an annular magnet disposed within the first frame and having an under-dome air passage at its center coaxial with the voice coil; a rear cover covering at least a portion of the other opening of the first frame; and a second frame attached to the rear cover and having a second cavity communicating with the first cavity, wherein the other opening of the first frame not covered by the rear cover is blocked by a substrate that separates the first cavity.

[0008] The microspeaker of the present disclosure allows for a more compact frame, which contributes to reducing the thickness of the earphone.

[0009] 5A, 5B, 5C, 5D, 5E, 5F, 5G, 5H, 5G-5H, 5H ... 16A perspective view of a microspeaker with a second frame attached to the rear cover. A cross-sectional view of the microspeaker taken at the position of the second frame. An explanatory diagram of operation showing air flow. A side view of an earphone equipped with a microspeaker according to embodiment 3, with a portion cut away. A perspective view of the microspeaker shown in FIG. 22, viewed obliquely from above. A plan view of the microspeaker. A side view of the microspeaker. A bottom perspective view of the microspeaker shown in FIG. 13, with the top and bottom turned upside down. A plan view of FIG. 26. An E-E cross-sectional view of FIG. 27. An F-F cross-sectional view of FIG. 27. A perspective view of a microspeaker with a second frame attached to the connection path. A cross-sectional view along the connection path of the microspeaker. An explanatory diagram of operation showing air flow.

[0010] Hereinafter, with reference to the drawings as appropriate, detailed descriptions of embodiments specifically disclosing a microspeaker and earphone according to the present disclosure will be provided. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters or redundant descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

[0011] 1 is a partially cutaway side view of an earphone 13 equipped with a microspeaker 11 according to embodiment 1. The earphone 13 includes a housing 15, the microspeaker 11, a circuit board 17 (see FIG. 4), and a battery 19.

[0012] The interior of the housing 15 of the earphone 13 forms an accommodation space 21 that accommodates the microspeaker 11, the circuit board 17, and the battery 19. The housing 15 has a sound conduit 25 with a sound emission hole 23. In the earphone 13, an earpiece (not shown) is attached to the outer periphery of the sound conduit 25. The earpiece is prevented from coming off by a locking claw 27 of the sound conduit 25. The sound conduit 25 with the attached earpiece is inserted into the ear. That is, in the earphone 13, sound that passes through the sound conduit 25 is emitted from the sound emission hole 23 in the upward direction in FIG. 1 .

[0013] In this specification, unless otherwise specified, "up" refers to the direction in which sound that has passed through the sound guide tube 25 is emitted from the sound emission hole 23 (the upward direction in Figure 1), and "down" refers to the side where the battery 19 is housed.

[0014] The microspeaker 11 is electrically connected to a main body board (not shown) on the opposite side of the battery 19 via a lead wire or a flat cable (neither of which are shown) through the board 17. The main body board is electrically connected to the battery 19 via a lead wire or a flat cable (neither of which are shown). The microspeaker 11 receives audio signals via the board 17 from the main body board, which handles audio signals, power, control signals, etc.

[0015] Figure 2 is a perspective view of the microspeaker 11 shown in Figure 1, seen obliquely from above. The microspeaker 11 has a flat, approximately cylindrical shape. The microspeaker 11 has a cylindrical first frame 29. The first frame 29 is manufactured by injection molding using a resin material, for example. A diaphragm 31 is provided in one (upper) opening of the first frame 29. The diaphragm 31 is formed in a generally circular plate shape with an edge 35 around the periphery of a dome 33.

[0016] At least a portion of the other (lower) opening of the first frame 29 is covered by a rear cover 37. The rear cover 37 may be integral with the first frame 29, or a separate member may be fixed integrally with the first frame 29. An annular front cover 39 that covers the edge 35 of the diaphragm 31 is attached to the first frame 29.

[0017] 3 is a plan view of the microspeaker 11. When the front cover 39 is attached to the first frame 29 of the microspeaker 11, the dome 33 of the diaphragm 31, which is arranged concentrically, is exposed in the circular hole of the front cover 39. In other words, the edge 35 of the diaphragm 31 is positioned below and spaced from the front cover 39, and is covered by the periphery of the front cover 39.

[0018] FIG. 4 is a side view of the microspeaker 11. The first frame 29 has a substrate 17 attached to a portion of its lower end surface 41 (see FIG. 1 ) that is not covered by the rear cover 37. Multiple (e.g., four) solders 43 are provided on the substrate. The solders 43 are provided on lands (not shown) formed on the substrate. The lands are connected to the coil wires at both ends of a voice coil 49 (see FIG. 7 ), which will be described later. Solder is formed on each of two lands. In a device with four lands, lead wires or solder is formed on the remaining two lands for electrically connecting the flat cable to the main substrate. Although not shown in any of the drawings, if the flat cable itself is also used as the substrate, two solders are formed on the two lands to connect the coil wires at both ends of the voice coil.

[0019] Fig. 5 is a bottom perspective view of the microspeaker 11 shown in Fig. 2, turned upside down. A first air passage 45, which will be described later, is opened in the approximate center of the rear cover 37. The first air passage 45 is covered with a first mesh 47, which will be described later.

[0020] Figure 6 is a plan view of Figure 5. In the microspeaker 11, the substrate 17 partially covers the other opening. The substrate 17 is surrounded by a chord connecting two points on the circumference of the other opening and an arc on the shorter side connected to both ends of this chord. This chord also forms a straight edge connecting both ends of the outer periphery of the rear cover 37. The substrate 17 is located lower (closer to the diaphragm) than the bottom end surface 41 of the rear cover 37. In other words, a step is formed between the straight edge of the rear cover 37 and the substrate 17.

[0021] Fig. 7 is a cross-sectional view taken along line A-A in Fig. 6. The outer periphery of edge 35 of diaphragm 31 is fixed to the opening of first frame 29 by a ring-shaped fixing member. By supporting diaphragm 31 on first frame 29 via edge 35, the lower surface of dome 33 becomes a concave curved surface.

[0022] The diaphragm 31 has an edge 35 made of a softer material than the dome 33, which is bonded to the dome 33 as one unit. The edge 35 has a plurality of oblique embossments to allow the diaphragm 31 to move up and down accurately. The edge 35 facilitates vibration of the diaphragm 31, and when no audio signal is input to the voice coil 49, the edge 35 maintains the diaphragm 31 in a neutral position. A cylindrical voice coil 49 is coaxially fixed to the underside (concave surface) of the dome 33 of the diaphragm 31.

[0023] The voice coil 49 is formed by winding a metal wire multiple times into a circular (cylindrical) shape. An audio signal is input to the voice coil 49 from the main body circuit board (not shown) via the circuit board 17. The upper end of the voice coil 49 is fixed to the diaphragm 31, and the voice coil 49 is inserted into the magnetic gap in the magnetic circuit of the magnet 51. The diaphragm 31 vibrates due to a force generated in the fixed voice coil 49 by the magnetic force in the magnetic gap and the current (audio signal) flowing through the voice coil 49, and converts the audio signal input to the voice coil 49 into sound.

[0024] In the first frame 29, an annular magnet 51 is disposed inside the voice coil 49 and coaxial with the voice coil 49. The magnet 51 has an under-dome air passage 53 at its center that is coaxial with the voice coil 49. The magnet 51 is coaxially fixed to the bottom of a cylindrical yoke 55 with a bottom that is fixed to the first frame 29.

[0025] The yoke 55 is made of a magnetic material. A circular plate 57 is fixed coaxially to the upper surface of the magnet 51. The plate 57 is also made of a magnetic material. The plate 57 is fixed by being sandwiched between the magnet 51 and a flange-shaped stopper 59. The upper surface of the stopper 59 has a convex curved surface that follows the concave curved surface of the dome 33. The stopper 59 regulates the displacement of the diaphragm 31 toward the magnet 51.

[0026] The yoke 55, magnet 51, and plate 57 form a magnetic circuit. The magnetic circuit generates a steady magnetic flux in a magnetic gap. The yoke 55 forms a magnetic gap between its inner peripheral surface and the outer peripheral surface of the plate 57. The cylindrical voice coil 49 is inserted into this magnetic gap.

[0027] A magnetic fluid 61 is disposed in the magnetic gap. The magnetic fluid 61 is disposed in a ring shape between the outer periphery of the plate 57 and the inner periphery of the voice coil 49. The gap between the voice coil 49 and the plate 57 is sealed by this magnetic fluid 61. The magnetic fluid 61 is a magnetic colloidal solution that is a mixture of magnetic fine particles, a dispersant that covers the surfaces of the magnetic fine particles, and a solvent. By disposing the magnetic fluid 61 between the voice coil 49 and the plate 57, the microspeaker 11 can stabilize the vibration of the voice coil 49 with low frictional resistance.

[0028] The center of the microspeaker, in which the yoke 55, magnet 51, plate 57 and stopper 59 are fixed in a coaxial hole, is formed with an under-dome air passage 53 passing through the center.

[0029] The first frame 29 is configured to have a first chamber 63 between the yoke 55 and the rear cover 37 in the A-A cross section. The first chamber 63 is connected to the under-dome air passage 53 at the lower end of the stopper 59. The first chamber 63 is formed on the opposite side of the diaphragm 31 with the magnet 51 in between.

[0030] An under-edge air passage 65 is formed between the inner periphery of the first frame 29 and the outer periphery of the yoke 55. The under-edge air passage 65 does not have to be formed around the entire inner periphery of the first frame 29. The under-edge air passage 65 provided under the edge has one end opening facing the edge 35. The other end of the under-edge air passage 65 communicates with the first chamber 63. In other words, the under-dome air passage 53 and the under-edge air passage 65 are both connected to the first chamber 63. A first mesh 47 covering the first air passage 45 is attached to the rear cover 37 from the inside of the first chamber 63 with a fixing member such as double-sided adhesive tape 67.

[0031] Figure 8 is a cross section taken along line B-B in Figure 6. The first air passage 45 connects the first chamber 63 to a second chamber 69 (see Figure 10), which will be described later. Air in the first chamber 63 and air in the second chamber 69 can move through this first air passage 45.

[0032] In the microspeaker 11, the first air passage 45 has a first mesh 47 that determines the air resistance. The first mesh 47 controls the resistance of the air passing through the first air passage 45, and is formed of, for example, a nonwoven fabric made of chemical fiber or a porous plate-like member.

[0033] FIG. 9 is a perspective view of the microspeaker 11 with a second frame 71 attached to the rear cover 37. The microspeaker 11 has a second frame 71, which has a second cavity 69, attached to the rear cover 37 of the first frame 29. The second frame 71 is fixed to the rear cover 37 with, for example, double-sided adhesive tape 67. The second frame 71 is formed in a wedge shape. The wedge shape has two surfaces that intersect in one direction and gradually separate in the other direction. The side of the wedge where these two surfaces meet can be referred to as the tip. One surface of the second frame 71 is attached to the rear cover 37 with double-sided adhesive tape 67.

[0034] FIG. 10 is a cross-sectional view of the microspeaker 11 taken at the position of the second frame 71. The second frame 71 has a second chamber 69 formed in a triangular prism shape. One side of the second chamber 69, which is fixed to the rear cover 37, is wide open. This open portion is closed by the surface of the rear cover 37, including the first air passage 45. In other words, the first air passage 45 of the first frame 29 opens into the sealed second chamber 69 of the second frame 71. A second air passage 73 opens at the rear end of the second frame 71. The outlet of the second air passage 73 is covered by a second mesh 75. The second mesh 75 is made of the same material as the first mesh 47. Like the first mesh 47, the second mesh 75 also controls the resistance of air passing through the second air passage 73.

[0035] FIG. 11 is an explanatory diagram illustrating the operation, showing the flow of air. The top diagram in FIG. 11 is a cross-sectional view taken along line A-A in FIG. 6, the middle diagram is a cross-sectional view taken along line B-B in FIG. 6, and the bottom diagram is an enlarged view of the main portion of FIG. 1. As shown in the top diagram in FIG. 11, in the microspeaker 11, when the voice coil 49 is driven and the diaphragm 31 is displaced downward, the displacement causes air under the dome to move into the under-dome air passage 53. The air in the under-dome air passage 53 is pushed by the movement of the air under the dome, and some of the air moves into the first chamber 63. Similarly, the air under the edge also moves into the under-edge air passage 65. The air in the under-edge air passage 65 is pushed by the movement of the air under the edge, and some of the air moves into the first chamber 63.

[0036] As shown in the middle diagram of Figure 11, some of the air in the first chamber 63 moves through the first air passage 45 to the second chamber 69 as air moves from the under-dome air passage 53 and the under-edge air passage 65.

[0037] 11, the air in the second chamber 69 is pushed by the air moving from the first chamber 63, and some of the air moves to the outside of the second frame through the second air passage 73. If the diaphragm 31 is displaced in the opposite direction, air from the outside moves through the second air passage 73 into the second chamber 69, and then the air flows in the opposite direction and moves into the gap below the diaphragm.

[0038] Earphone 13 pertaining to embodiment 1 houses microspeaker 11 and disk-shaped battery 19 in housing 15. Housing 15 has a sound conduit 25 and houses first frame 29 so that the axis of sound conduit 25 and the axis of first frame 29 are substantially in the same direction. On the opposite side of first frame 29 from sound conduit 25, battery 19 is housed with its axis tilted so that it intersects with the axis of sound conduit 25. In earphone 13, second frame 71 is disposed between first frame 29 and battery 19.

[0039] Next, the operation of the above-described first embodiment will be described.

[0040] The microspeaker 11 according to the first embodiment is a microspeaker 11 that is incorporated into the housing of an earphone 13, and comprises a cylindrical first frame 29 having a first cavity 63, a diaphragm 31 that is provided in one opening of the first frame 29 and has an edge 35 around the periphery of a dome 33, a cylindrical voice coil 49 that is fixed coaxially to the diaphragm 31, a ring-shaped magnet 51 that is disposed within the first frame and has an under-dome air passage 53 at its center that is coaxial with the voice coil 49, a rear cover 37 that covers at least a portion of the other opening of the first frame 29, and a second frame 71 that is attached to the rear cover 37 and has a second cavity 69 that communicates with the first cavity 63, and the other opening of the first frame 29 that is not covered by the rear cover 37 is blocked by a substrate 17 that separates the first cavity 63.

[0041] In the microspeaker 11 according to the first embodiment, a diaphragm 31 is provided at one opening of a first frame 29. A rear cover 37 is provided at the other opening of the first frame 29. The rear cover 37 covers at least a portion of the other opening. In other words, the rear cover 37 may cover the other opening, leaving an opening through which the first chamber 63 is exposed. In this case, the opening is blocked by the substrate 17.

[0042] In the conventional microspeaker disclosed in Patent Document 1, the cylindrical first frame and second frame are coaxially connected, resulting in a large distance (thickness) along the axis of the entire frame. In addition, multiple lands are arranged circumferentially on the bottom end surface of the second frame, and wiring is connected to each of these lands with solder 43, requiring a dedicated space behind the second frame for routing the wiring. For these reasons, earphones incorporating conventional microspeakers have limited freedom in placement, making it impossible to increase the density of component placement, resulting in a bulky housing.

[0043] In contrast, in the microspeaker 11 according to embodiment 1, an open section is provided at the other opening of the first frame 29, where the rear cover 37 and second frame 71 are absent. This open section of the first frame 29 is directly covered by the substrate 17. That is, in the microspeaker 11, the substrate that was provided on the lower end surface of the second frame 71 in the conventional structure is now provided directly on the lower end surface 41 of the first frame 29, at a size that is about one-third of the original size.

[0044] The bottom end surface 41 of the first frame 29, excluding the portion where the substrate 17 is provided, is covered by the rear cover 37. A second frame 71 is attached to the rear cover 37. Here, the second frame 71 can be formed in any shape to fit the excess portion of the housing space 21 for the earphone 13. In other words, there is a high degree of freedom in placement. Therefore, the second frame 71 does not need to be connected coaxially to the first frame, as in conventional structures.

[0045] Furthermore, by attaching the second frame 71 to a portion of the rear cover 37 of the first frame 29, a stepped space is formed between the second frame 71 and the substrate 17. This stepped space can be effectively used as a wiring connection space. In other words, because the microspeaker 11 uses the substrate 17 to cover a portion of the lower end surface 41 of the first frame 29, the space that would previously have been used to arrange the second frame can be used as a wiring routing space.

[0046] As shown in Figure 1, when the microspeaker 11 is housed in the housing space 21 of the housing 15, if the battery 19 is tilted to follow the shape of the ear, it can be placed close to the bottom surface 41 of the first frame 29. In the case of a conventional microspeaker with such a tilted battery structure, the battery 19 must be spaced apart by the thickness of the second frame. Furthermore, because space for connecting wires had to be secured on the bottom surface 41 of the second frame, it was difficult to reduce the thickness of the earphone 13. In other words, this resulted in an increase in the size of the housing 15.

[0047] On the other hand, in the microspeaker 11, the battery 19 can be placed closer to a portion of the lower end surface 41 of the first frame 29 by the amount of the second frame 71 that is eliminated. In addition, because wiring can be connected in the step space between the second frame 71 and the board 17, the component placement density can be increased, the housing 15 of the earphone 13 can be made more compact, and it is easy to make the housing 15 thinner.

[0048] In addition, in the microspeaker 11, the substrate 17 is surrounded by a string connecting two points on the circumference of the other opening and an arc on the short side connected to both ends of the string.

[0049] In this microspeaker 11, the other opening of the first frame 29 is, for example, circular. The substrate 17 is surrounded by a chord connecting two points on the circumference of the other opening and an arc on the shorter side connected to both ends of this chord. In other words, the substrate 17 has a roughly crescent shape with an area that is about one-third of the bottom end surface 41. The other opening is covered by a rear cover 37 except for the part covered by the substrate 17. The rear cover 37 has an area larger than that of the substrate 17. A second frame 71 is attached to the bottom end surface 41 of this rear cover 37.

[0050] A plurality of lands are arranged on the substrate 17, and wiring is connected to each land by solder 43. As described above, a stepped space that is lower than the second frame 71 is formed above the substrate 17. This stepped space can be effectively used as a wiring connection space.

[0051] Therefore, in this microspeaker 11, the circular bottom end surface 41 of the first frame 29 is divided into two by a string, and the approximately crescent-shaped substrate 17 is placed in the smaller one, making it possible to obtain an effectively usable stepped space above it. As a result, the microspeaker 11 allows for a high-density arrangement of components within the housing, contributing to a more compact housing 15.

[0052] In the microspeaker 11, the second frame 71 is formed in a wedge shape.

[0053] In this microspeaker 11, the second frame 71 is formed in a wedge shape. The wedge shape has two surfaces that intersect in one direction and gradually separate in the other direction. The side of the wedge where the two surfaces intersect can be referred to as the tip. One surface of the wedge-shaped second frame 71 is attached to the rear cover 37 with double-sided adhesive tape 67 or the like.

[0054] Therefore, the other surface of the second frame 71 attached to the lower end surface 41 of the first frame 29 is an inclined surface. In some cases, the battery 19 of the earphone 13 is arranged so that its axis intersects with the axis of the sound conduit 25 inserted into the ear canal.

[0055] In the case of this inclined battery structure, a wedge-shaped space is created between the bottom end surface 41 of the first frame 29 and the battery 19, making it possible to accommodate the second frame 71 without creating excess space. In other words, it is possible to increase the component layout density within the housing, prevent the housing 15 from becoming bulky, and make the earphone 13 more compact.

[0056] Furthermore, the earphone 13 according to embodiment 1 is an earphone 13 that houses a microspeaker 11 and a disk-shaped battery 19 in a housing 15, and the housing 15 has a sound conduit 25 and houses a first frame 29 so that the axis of the sound conduit 25 and the axis of the first frame 29 are in the same direction, and houses a battery 19 on the opposite side of the sound conduit 25 across the first frame 29, the battery 19 being inclined so that its axis intersects the axis of the sound conduit 25, and a second frame 71 is arranged between the first frame 29 and the battery 19.

[0057] In the earphone 13 according to embodiment 1, when the housing 15 is formed with a battery inclined structure to fit the shape of the ear, the battery 19 can be positioned close to the bottom end surface 41 of the first frame 29.

[0058] As a result, the earphone 13 can reduce the thickness of the housing 15 in the direction along the axis of the sound conduit 25 by the amount of the thickness of the second frame and the thickness of the wiring space, compared to a conventional structure in which a cylindrical first frame 29 is coaxially connected to a cylindrical second frame.

[0059] Second Embodiment Next, a second embodiment will be described.

[0060] 12 is a partially cutaway side view of an earphone 79 equipped with a microspeaker 77 according to embodiment 2. In embodiment 2, the same components as those shown in embodiment 1 are denoted by the same reference numerals, and redundant explanations will be omitted.

[0061] The earphone 79 houses a microspeaker 77 and a battery 19 in the housing 15. The other opening of the microspeaker 77 is entirely covered by a rear cover 81. The substrate 17 is provided on the opposite side of the rear cover 81 from the first chamber 63. Other configurations of the microspeaker 77 are substantially the same as those in the first embodiment.

[0062] Figure 13 is a perspective view of the microspeaker 77 shown in Figure 12, seen obliquely from above. The microspeaker 77 has a flat, approximately cylindrical shape. The microspeaker 77 has a cylindrical first frame 29. A diaphragm 31 is provided in one (upper) opening of the first frame 29.

[0063] The other (lower) opening of the first frame 29 is entirely covered by a rear cover 81. The rear cover 81 may be integral with the first frame 29, or a separate member may be fixed integrally with the first frame 29. An annular front cover 39 that covers the edge 35 of the diaphragm 31 is attached to the first frame 29.

[0064] 14 is a side view of the microspeaker 77. The first frame 29 has a substrate 17 attached to a portion of a rear cover 81 that covers the entire other opening. A plurality of (for example, four) solders 43 are provided on the substrate. Details of the case where there are four or two solders 43 are omitted as they are the same as those described in FIG. 4.

[0065] Fig. 15 is a bottom perspective view of the microspeaker 77 shown in Fig. 13 , turned upside down. A first air passage 45 is opened in the approximate center of the rear cover 81. The first air passage 45 is covered by a first mesh 47. In the second embodiment, the first mesh 47 is attached from the outside of the rear cover 81, thereby covering the first air passage 45.

[0066] The rear cover 81 may be formed so that only the portion where the substrate 17 is provided is thinner than the other portions by the thickness of the substrate 17. In this case, the substrate 17 is provided by sinking it into this thin portion formed in the rear cover 81. This allows the surface of the rear cover 81 and the surface of the substrate 17 to be connected in approximately the same plane without any steps.

[0067] Figure 16 is a plan view of Figure 15. Microspeaker 77 has substrate 17 fitted into a portion of rear cover 81. Substrate 17 is surrounded by a chord connecting two points on the circumference of the other opening and by arcs on the shorter side connected to both ends of this chord.

[0068] 17 is a cross-sectional view taken along the CC line in FIG. 16. The outer periphery of the edge 35 of the diaphragm 31 is fixed to the opening of the first frame 29 by a ring-shaped fixing member. A cylindrical voice coil 49 is coaxially fixed to the lower surface (concave curved surface) of the dome 33 of the diaphragm 31. The upper end of the voice coil 49 is fixed to the diaphragm 31, and is inserted into the magnetic gap formed between the inner circumferential surface of the yoke 55 and the outer circumferential surface of the plate 57.

[0069] In the first frame 29, an annular magnet 51 is disposed inside the voice coil 49 and coaxial with the voice coil 49. The magnet 51 has an under-dome air passage 53 at its center that is coaxial with the voice coil 49. The magnet 51 is coaxially fixed to the bottom of a cylindrical yoke 55 with a bottom that is fixed to the first frame 29.

[0070] An annular plate 57 is coaxially fixed to the upper surface of the magnet 51. The plate 57 is sandwiched and fixed between the magnet 51 and a flange-shaped stopper 59.

[0071] The yoke 55, the magnet 51, and the plate 57 form a magnetic circuit. A magnetic gap is formed between the inner peripheral surface of the yoke 55 and the outer peripheral surface of the plate 57. The cylindrical voice coil 49 is inserted into the magnetic gap formed between the inner peripheral surface of the yoke 55 and the outer peripheral surface of the plate 57.

[0072] A magnetic fluid 61 is disposed in the magnetic gap. The gap between the voice coil 49 and the plate 57 is sealed by this magnetic fluid 61. By disposing the magnetic fluid 61 between the voice coil 49 and the plate 57, the microspeaker 77 can stabilize the vibration of the voice coil 49 with low frictional resistance.

[0073] The driver section, in which the yoke 55, the magnet 51, the plate 57 and the stopper 59 are coaxially fixed, has an under-dome air passage 53 formed through the center.

[0074] The first frame 29 is configured to have a first chamber 63 between the yoke 55 and the rear cover 37 in the CC cross section. The first chamber 63 is connected to the under-dome air passage 53 at the lower end of the stopper 59. The first chamber 63 is formed on the opposite side of the diaphragm 31 with the magnet 51 in between.

[0075] An under-edge air passage 65 is formed between the inner periphery of the first frame 29 and the outer periphery of the yoke 55. The under-edge air passage 65 does not have to be formed around the entire inner periphery of the first frame 29. One end of the under-edge air passage 65 opens facing the edge 35. The other end of the under-edge air passage 65 communicates with the first chamber 63. In other words, both the under-dome air passage 53 and the under-edge air passage 65 are connected to the first chamber 63. A first mesh 47 covering the first air passage 45 is attached to the rear cover 37 from the outside of the first chamber 63 with a fixing member such as double-sided adhesive tape 67.

[0076] Figure 18 is a cross section taken along line D-D in Figure 16. The first ventilation path 45 connects the first chamber 63 to a second chamber 69 (see Figure 20), which will be described later. The air in the first chamber 63 and the air in the second chamber 69 can move through this first ventilation path 45. In the first embodiment, as shown in Figure 8, the substrate 17 is fixed to the yoke 55, but in the second embodiment, it is provided on the underside of the rear cover 81 that closes the other opening.

[0077] 19 is a perspective view of a microspeaker 77 with a second frame 71 attached to a rear cover 81. The microspeaker 77 has a second frame 71, which has a second cavity 69, attached to the rear cover 81 of the first frame 29. The second frame 71 is wedge-shaped. The wedge shape has two surfaces that intersect in one direction and gradually separate in the other direction. One surface of the second frame 71 is attached to the rear cover 37 with double-sided adhesive tape 67 or the like.

[0078] 20 is a cross-sectional view of the microspeaker 77 taken at the position of the second frame 71. In the second frame 71, a second chamber 69 is formed in the shape of a triangular prism. One surface of the second chamber 69, which is fixed to the rear cover 37, is widely open. This open portion is closed by the surface of the rear cover 37, which includes the first air passage 45. In other words, in the second frame 71, the first air passage 45 of the first frame 29 opens into the sealed second chamber 69. A second air passage 73 opens at the rear end of the second frame 71. The outlet of the second air passage 73 is covered by a second mesh 75.

[0079] FIG. 21 is an explanatory diagram illustrating the operation, showing the flow of air. The top diagram in FIG. 21 is a cross-sectional view taken along the line CC in FIG. 16 , the middle diagram is a cross-sectional view taken along the line DD in FIG. 16 , and the bottom diagram is an enlarged view of the main portion of FIG. 12 . As shown in the top diagram in FIG. 21 , in the microspeaker 77, when the voice coil 49 is driven and the diaphragm 31 is displaced downward, the displacement causes air under the dome to move into the under-dome air passage 53. The air in the under-dome air passage 53 is pushed by the movement of the air under the dome, and some of the air moves into the first chamber 63. Similarly, the air under the edge also moves into the under-edge air passage 65. The air in the under-edge air passage 65 is pushed by the movement of the air under the edge, and some of the air moves into the first chamber 63.

[0080] As shown in the middle diagram of Figure 21, some of the air in the first chamber 63 moves through the first air passage 45 to the second chamber 69 as air moves from the under-dome air passage 53 and the under-edge air passage 65.

[0081] 21, the air in the second chamber 69 is pushed by the air moving from the first chamber 63, and some of the air moves to the outside of the second frame through the second air passage 73. If the diaphragm 31 is displaced in the opposite direction, air from the outside moves through the second air passage 73 into the second chamber 69, and then the air flows in the opposite direction and moves into the gap below the diaphragm.

[0082] An earphone 79 pertaining to embodiment 2 houses a microspeaker 77 and a disk-shaped battery 19 in a housing 15. The housing 15 has a sound conduit 25 and houses a first frame 29 so that the axis of the sound conduit 25 and the axis of the first frame 29 are in the same direction. On the opposite side of the first frame 29 from the sound conduit 25, a battery 19 is housed that is tilted so that its axis intersects the axis of the sound conduit 25. In the earphone 13, a second frame 71 is disposed between the first frame 29 and the battery 19.

[0083] Next, the operation of the second embodiment will be described.

[0084] The other opening of the microspeaker 77 is entirely covered by the rear cover 81 , and the substrate 17 is provided on the opposite side of the first chamber 63 with the rear cover 81 in between.

[0085] In this microspeaker 77, the other opening is entirely covered by the rear cover 81. When the lower end surface 41 (see FIG. 12 ) of the first frame 29 is circular, for example, the rear cover 81 is disk-shaped. By making the rear cover 81 disk-shaped, the other opening (i.e., the first chamber 63) can be easily closed in one go. This increases the thickness of the first frame 29 in the axial direction by the thickness of the rear cover 81, but improves the productivity of the first frame 29.

[0086] The disk-shaped rear cover 81 may have a step formed in only the portion where the substrate 17 is provided, so that the first chamber 63 does not need to be provided. In this case, by sinking the substrate 17 into the step formed in the rear cover 81, the substrate 17 can be made lower than the bottom surface 41 of the rear cover 81. By positioning the substrate 17 so that it does not protrude from the rear cover 81, it is possible to reduce interference with the second frame 71 attached to the bottom surface 41 of the rear cover 81.

[0087] The conversion operation of the audio signal, the air flow in each chamber, and the space-saving effect of the microspeaker 77 relative to the accommodation space 21 for the earphone 79 in the second embodiment are the same as those in the first embodiment.

[0088] Third Embodiment Next, a third embodiment will be described.

[0089] 22 is a side view with a portion cut away of an earphone 85 equipped with a microspeaker 83 according to embodiment 3. Note that in embodiment 3, the same components as those shown in embodiment 1 are denoted by the same reference numerals, and redundant explanations will be omitted.

[0090] The earphone 85 accommodates a microspeaker 83 and a battery 19 in a housing 87 .

[0091] The housing 87 has a sound conduit 25. The housing 87 houses the first frame 29 so that the axis of the sound conduit 25 and the axis of the first frame 29 are in the same direction. On the opposite side of the sound conduit 25 with the first frame 29 in between, the battery 19 is housed, laid flat so that its axis is in the same direction as the axis of the sound conduit 25. Between the sound conduit 25 and the battery 19 are arranged the first frame 29 and a second frame 89 which is offset to the outside of the first frame 29 and is arranged alongside the first frame 29.

[0092] Housing 87 of earphone 85 pertaining to embodiment 3 is preferably used in cases where the housing shape is constrained in distance in the direction along the axis of sound conduit 25 (the up-down direction in FIG. 22 ) but is relatively unconstrained in distance in the direction perpendicular to the axis of sound conduit 25 (the left-right direction in FIG. 22 ). For this reason, housing 87 has a smaller up-down dimension and a larger left-right distance than those of embodiments 1 and 2. Furthermore, housing 87 allows for the provision of routing space 91 below solder 43 for routing a flat cable.

[0093] Figure 23 is a perspective view of the microspeaker 83 shown in Figure 22, seen obliquely from above. The microspeaker 83 has a cylindrical first frame 29. A diaphragm 31 is provided in one (upper) opening of the first frame 29. The diaphragm 31 is formed in a substantially circular plate shape with an edge 35 around the periphery of a dome 33.

[0094] At least a portion of the other (lower) opening of the first frame 29 is covered by a rear cover 93. The rear cover 93 may be integral with the first frame 29, or a separate member may be fixed integrally with the first frame 29. An annular front cover 39 that covers the edge 35 of the diaphragm 31 is attached to the first frame 29.

[0095] A connection path 95 is formed in the rear cover 93. The connection path 95 protrudes outward from the outer periphery of the first frame 29. A first mesh 47 is attached to the protruding tip surface of the connection path 95.

[0096] 24 is a plan view of the microspeaker 83. When the front cover 39 is attached to the first frame 29, the microspeaker 83 exposes the domes 33 of the diaphragm 31, which are concentrically arranged, in the circular holes of the front cover 39. In other words, the edge 35 of the diaphragm 31 is positioned below and spaced from the front cover 39, and is covered by the periphery of the front cover 39.

[0097] Figure 25 is a side view of the microspeaker 83. The first frame 29 has a substrate 17 attached to a portion of the lower end surface 41 (see Figure 22) that is not covered by the rear cover 93. A plurality of (for example, four) solders 43 are provided on the substrate. The solders 43 are provided on lands (not shown) formed on the substrate. Details of the case where there are four or two solders 43 are omitted as they are the same as those described in Figure 4.

[0098] Figure 26 is a bottom perspective view of the microspeaker 83 shown in Figure 13 , turned upside down. A connection path 95 that protrudes radially outward from the outer periphery of the first frame 29 is integrally formed with the rear cover 93. The connection path 95 extends in approximately the same plane as the lower end surface 41 of the rear cover 93. The tip of this protruding connection path 95 is covered by the first mesh 47.

[0099] Figure 27 is a plan view of Figure 26. In the microspeaker 83, the substrate 17 covers a portion of the other opening. The substrate 17 is surrounded by a chord connecting two points on the circumference of the other opening and an arc on the shorter side connected to both ends of this chord. The substrate 17 is located lower (closer to the diaphragm) than the lower end surface 41 of the rear cover 37. There is a step between the straight edge of the rear cover 37 and the substrate 17.

[0100] Figure 28 is a cross-sectional view taken along the line E-E of Figure 27. The outer periphery of the edge 35 of the diaphragm 31 is fixed to the opening of the first frame 29 by a ring-shaped fixing member. A cylindrical voice coil 49 is coaxially fixed to the lower surface (concave curved surface) of the dome 33 of the diaphragm 31. The upper end of the voice coil 49 is fixed to the diaphragm 31, and is inserted into the magnetic gap formed between the inner circumferential surface of the yoke 55 and the outer circumferential surface of the plate 57.

[0101] In the first frame 29, an annular magnet 51 is disposed inside the voice coil 49 and coaxial with the voice coil 49. The magnet 51 has an under-dome air passage 53 at its center that is coaxial with the voice coil 49. The magnet 51 is coaxially fixed to the bottom of a cylindrical yoke 55 with a bottom that is fixed to the first frame 29.

[0102] An annular plate 57 is coaxially fixed to the upper surface of the magnet 51. The plate 57 is sandwiched and fixed between the magnet 51 and a flange-shaped stopper 59.

[0103] The yoke 55, the magnet 51, and the plate 57 form a magnetic circuit. A magnetic gap is formed between the inner peripheral surface of the yoke 55 and the outer peripheral surface of the plate 57. The cylindrical voice coil 49 is inserted into this magnetic gap.

[0104] A magnetic fluid 61 is disposed in the magnetic gap. The gap between the voice coil 49 and the plate 57 is sealed by this magnetic fluid 61. By disposing the magnetic fluid 61 between the voice coil 49 and the plate 57, the microspeaker 83 can stabilize the vibration of the voice coil 49 with low frictional resistance.

[0105] The driver section, in which the yoke 55, the magnet 51, the plate 57 and the stopper 59 are coaxially fixed, has an under-dome air passage 53 formed through the center.

[0106] In the E-E cross section, the first frame 29 is configured to have a first chamber 63 between the yoke 55 and the rear cover 37. The first chamber 63 is connected to the under-dome air passage 53 at the lower end of the stopper 59. The first chamber 63 is formed on the opposite side of the diaphragm 31 with the magnet 51 in between.

[0107] An under-edge air passage 65 is formed between the inner periphery of the first frame 29 and the outer periphery of the yoke 55. The under-edge air passage 65 does not have to be formed along the entire inner periphery of the first frame 29. One end of the under-edge air passage 65 opens facing the edge 35. The other end of the under-edge air passage 65 communicates with the first chamber 63. In other words, both the under-dome air passage 53 and the under-edge air passage 65 are connected to the first chamber 63.

[0108] FIG. 29 is a cross section taken along the line F-F in FIG. 27 . The connection path 95 connects the first chamber 63 to the second chamber 97 (see FIG. 31 ), which will be described later. The connection path 95 protrudes from the outer periphery of the first frame 29 due to the rectangular cylindrical shape of the rear cover 93. The inside of the rectangular cylindrical shape of the connection path 95 serves as a flow path leading to the first chamber 63. Air in the first chamber 63 and the second chamber 69 can move through the connection path 95. The connection path 95 of the microspeaker 83 includes a first mesh 47 that determines air resistance. The first mesh 47 controls the resistance of air passing through the connection path 95. The first mesh 47 is attached to the leading edge slope 101, where the connection opening 99 is formed at the leading edge of the connection path 95, using double-sided adhesive tape 67 or the like.

[0109] Figure 30 is a perspective view of the microspeaker 83 with the second frame 89 attached to the connection path 95. The second frame 89 has a flattened rectangular parallelepiped outer shape. The second frame 89 has a second cavity 97 inside (see Figure 31). The second frame 89 is connected to the connection path 95 by a connection portion 103 formed on one side surface of the long side. The second frame 89 is formed in a box shape with an open bottom, and a sealing plate 105 is attached to the open bottom surface. This seals the second cavity 97 in the second frame 89.

[0110] 31 is a cross-sectional view taken along the connection path 95 of the microspeaker 83. The second frame 89 has a connection portion 103 connected to the connection path 95. The connection portion 103 has a chamber connection port 107 that connects to the second chamber 97. In other words, air can pass between the first chamber 63 and the second chamber 97 by passing through the first mesh 47.

[0111] A second ventilation path 73 is formed on the surface of the second chamber 97 opposite to the sealing plate 105. The second ventilation path 73 is covered with a second mesh 75 attached to the outside of the second frame 89.

[0112] FIG. 32 is an explanatory diagram illustrating the operation, showing the flow of air. The top diagram in FIG. 32 is a cross-sectional view taken along line E-E in FIG. 27 , the middle diagram is a cross-sectional view taken along line F-F in FIG. 27 , and the bottom diagram is an enlarged view of the main portion of FIG. 22 . As shown in the top diagram in FIG. 32 , in the microspeaker 83, when the voice coil 49 is driven and the diaphragm 31 is displaced downward, the displacement causes air under the dome to move into the under-dome air passage 53. The air in the under-dome air passage 53 is pushed by the movement of the air under the dome, and some of the air moves into the first chamber 63. Similarly, the air under the edge also moves into the under-edge air passage 65. The air in the under-edge air passage 65 is pushed by the movement of the air under the edge, and some of the air moves into the first chamber 63.

[0113] As shown in the middle diagram of Figure 32, as air moves from the under-dome air passage 53 and the under-edge air passage 65, some of the air in the first chamber 63 passes through the connecting passage 95 and the first mesh 47 to the second chamber 97.

[0114] 32, the air in the second chamber 97 is pushed by the air moving from the first chamber 63, and some of the air moves to the outside of the second frame through the second air passage 73. If the diaphragm 31 is displaced in the opposite direction, air from the outside moves through the second air passage 73 into the second chamber 97, and then the air flows in the opposite direction and moves into the gap below the diaphragm.

[0115] Next, the operation of the third embodiment will be described.

[0116] The microspeaker 83 has a rear cover 93 that protrudes outward from the outer periphery of the first frame 29, with a connecting path 95 that leads to the first chamber 63, and the tip of the protruding connecting path 95 is connected to a second frame 89 that has a second chamber 97 that leads to the first chamber 63.

[0117] In this microspeaker 83, the rear cover 93 has a connection path 95 that leads to the first chamber 63. The connection path 95 protrudes outward from the outer periphery of the first frame 29. The tip of the connection path 95 that protrudes outward from the outer periphery is connected to the second frame 89. The second frame 89 has a second chamber 97 that is connected to the first chamber 63 via the connection path 95.

[0118] In this microspeaker 83, the second frame 89 is arranged outside the outer periphery of the first frame 29 in parallel.

[0119] The bottom surfaces 41 (see FIG. 22) of the first frame 29 and the second frame 89 are parallel. The solder 43 protruding from the substrate 17 of the first frame 29 and the bottom surface 41 of the second frame 89 are arranged on approximately the same plane. This surface of the microspeaker 83 can be considered the bottom surface 41. In the earphone 85, as shown in FIG. 22, the battery 19 is arranged on this bottom surface 41 with its axis oriented perpendicular to it.

[0120] With this microspeaker 83, if space can be secured around the periphery of the first frame 29, it is possible to position the battery 19 closer to the first frame 29 by approximately the thickness of the offset second frame 89. With this microspeaker 83, the battery 19 can be positioned closer to the first frame 29 by the thickness of the second frame compared to the microspeaker of Patent Document 1.

[0121] The earphone 85 also houses a microspeaker 83 and a disk-shaped battery 19 in a housing 87. The housing 87 has a sound conduit 25 and houses a first frame 29 so that the axis of the sound conduit 25 and the axis of the first frame 29 are in the same direction. The earphone 85 houses a battery 19 that is laid flat on the opposite side of the sound conduit 25 with the first frame 29 in between so that its axis is in the same direction as the axis of the sound conduit 25. Between the sound conduit 25 and the battery 19 are arranged the first frame 29 and a second frame 89 that is offset to the outside of the first frame 29 and is arranged side by side with the first frame 29.

[0122] With this earphone 85, when the housing 87 is formed to fit the shape of the ear and has a battery laid flat structure, the second frame 89 can be offset outward from the first frame 29 and placed next to it. As a result, compared to a conventional structure in which a cylindrical second frame is coaxially connected to a cylindrical first frame 29, the thickness of the housing 87 in the direction along the axis of the sound conduit 25 can be made smaller by the thickness of the second frame.

[0123] Therefore, according to the microspeakers 11, 77, and 83 of the first, second, and third embodiments, the first frame 29 can be made compact, which contributes to reducing the thickness of the earphones 13, 79, and 85.

[0124] Furthermore, with the earphone 13, earphone 79, and earphone 85 according to embodiments 1, 2, and 3, the sound conduit 25 and battery 19 can be positioned close to each other, and the thickness of the housing along the axis of the sound conduit 25 can be reduced.

[0125] (Summary of the present disclosure) The above description of the embodiments discloses technical ideas corresponding to the following items.

[0126] (Item 1) A microspeaker incorporated into an earphone housing, comprising: a cylindrical first frame having a first cavity; a diaphragm provided in one opening of the first frame and having an edge on the periphery of a dome; a cylindrical voice coil fixed coaxially to the diaphragm; an annular magnet disposed within the first frame and having an under-dome air passage coaxial with the voice coil at its center; a rear cover covering at least a portion of the other opening of the first frame; and a second frame attached to the rear cover and having a second cavity communicating with the first cavity, wherein the other opening of the first frame not covered by the rear cover is closed by a substrate that separates the first cavity. This allows the battery to be located closer to a portion of the lower end surface of the first frame by eliminating the second frame. In addition, wiring can be connected in the step space between the second frame and the substrate, thereby increasing the component placement density and facilitating a more compact and thinner earphone housing.

[0127] (Item 2) The microspeaker according to Item 1, wherein the substrate is surrounded by a chord connecting two points on the circumference of the other opening and an arc on the shorter side connected to both ends of the chord. This allows the circular bottom surface of the first frame of the microspeaker to be divided into two by the chord, and the approximately crescent-shaped substrate to be placed in the smaller section, providing an effectively usable stepped space above it. As a result, the microspeaker allows for a high-density arrangement of components within the housing, contributing to a more compact housing.

[0128] (Item 3) The microspeaker according to Item 1, wherein the other opening is entirely covered by the rear cover, and the substrate is provided on the opposite side of the rear cover from the first chamber. This increases the thickness of the microspeaker in the direction along the axis of the first frame by the thickness of the rear cover, but allows for improved productivity of the first frame.

[0129] (Item 4) The microspeaker according to Item 1, wherein the rear cover has a connection path leading to the first chamber and protrudes outward from the outer periphery of the first frame, and the second frame has the second chamber leading to the first chamber, and the tip of the protruding connection path is connected to the second frame. This allows the battery to be positioned closer to the first frame by approximately the thickness of the offset second frame if space is available around the outer periphery of the first frame. With this microspeaker, the battery can be positioned closer to the first frame by the thickness of the second frame.

[0130] (Item 5) The microspeaker according to Item 1 or 3, wherein the second frame is formed in a wedge shape. This increases the component placement density within the housing, prevents the housing from becoming bulky, and makes it possible to make the earphone more compact.

[0131] (Item 6) An earphone housing that houses the microspeaker described in Item 5 and a disk-shaped battery, wherein the housing has a sound conduit and houses the first frame so that the axis of the sound conduit and the axis of the first frame are in the same direction, the battery is housed on the opposite side of the sound conduit across the first frame and is tilted so that its axis intersects the axis of the sound conduit, and the second frame is disposed between the first frame and the battery. This allows the battery to be positioned close to the lower end surface of the first frame when the earphone housing is formed with a tilted battery structure that fits the shape of the ear. In other words, compared to a conventional structure in which a cylindrical first frame and a cylindrical second frame are coaxially connected, the thickness of the earphone housing in the direction along the axis of the sound conduit can be reduced by the thickness of the second frame and the thickness of the wiring space.

[0132] (Item 7) An earphone housing that houses the microspeaker described in Item 4 and a disk-shaped battery, wherein the housing has a sound conduit and houses the first frame so that the axis of the sound conduit and the axis of the first frame are in the same direction, the battery is housed on the opposite side of the sound conduit across the first frame and is laid flat so that its axis is in the same direction as the axis of the sound conduit, and the first frame and the second frame are arranged side by side and offset outward from the first frame between the sound conduit and the battery. This allows the second frame to be arranged side by side and offset outward from the first frame when the earphone housing is formed with a battery laid flat to fit the shape of the ear. This allows the thickness of the earphone housing in the direction along the axis of the sound conduit to be reduced by the thickness of the second frame compared to a conventional structure in which a cylindrical first frame is coaxially connected to a cylindrical second frame.

[0133] Although various embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that those skilled in the art can conceive of various modifications, alterations, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also fall within the technical scope of the present disclosure. Furthermore, the components of the various embodiments described above may be combined in any manner without departing from the spirit of the invention.

[0134] This application is based on a Japanese patent application (Patent Application No. 2024-068409) filed on April 19, 2024, the contents of which are incorporated herein by reference.

[0135] The present disclosure is useful as a microspeaker and earphone that can make the frame more compact and contribute to reducing the thickness of the earphone.

[0136] DESCRIPTION OF SYMBOLS 11...Microspeaker 13...Earphone 15...Housing 17...Substrate 19...Battery 25...Sound guide tube 29...First frame 31...Diaphragm 33...Dome 35...Edge 37...Rear cover 49...Voice coil 51...Magnet 53...Ventilation path under the dome 63...First cavity 69...Second cavity 71...Second frame 77...Microspeaker 79...Earphone 81...Rear cover 83...Microspeaker 85...Earphone 87...Housing 89...Second frame 93...Rear cover 95...Connecting path 97...Second cavity

Claims

1. A microspeaker to be incorporated into the housing of an earphone, comprising: a cylindrical first frame having a first cavity; a diaphragm provided at one opening of the first frame and having an edge on the periphery of a dome; a cylindrical voice coil fixed coaxially to the diaphragm; an annular magnet disposed within the first frame and having an under-dome air passage at its center coaxial with the voice coil; a rear cover covering at least a portion of the other opening of the first frame; and a second frame attached to the rear cover and having a second cavity communicating with the first cavity, wherein the other opening of the first frame not covered by the rear cover is closed by a substrate that partitions the first cavity.

2. The microspeaker according to claim 1, wherein the substrate is surrounded by a string connecting two points on the circumference of the other opening and an arc on the short side connected to both ends of the string.

3. The microspeaker according to claim 1, wherein the other opening is entirely covered by the rear cover, and the substrate is provided on the opposite side of the rear cover from the first cavity.

4. The microspeaker according to claim 1, wherein the rear cover has a connecting path that leads to the first chamber and protrudes outward from the outer periphery of the first frame, and the tip of the protruding connecting path is connected to the second frame, which has the second chamber that leads to the first chamber.

5. The microspeaker according to claim 1 or 3, wherein the second frame is formed in a wedge shape.

6. An earphone housing that houses the microspeaker of claim 5 and a disk-shaped battery, wherein the housing has a sound conduit and houses the first frame so that the axis of the sound conduit and the axis of the first frame are in the same direction, the battery is housed on the opposite side of the sound conduit across the first frame, with the battery tilted so that its axis intersects the axis of the sound conduit, and the second frame is positioned between the first frame and the battery.

7. An earphone housing that houses the microspeaker of claim 4 and a disc-shaped battery, wherein the housing has a sound conduit and houses the first frame so that the axis of the sound conduit and the axis of the first frame are in the same direction, the battery is housed on the opposite side of the sound conduit across the first frame, and is laid flat so that its axis is in the same direction as the axis of the sound conduit, and the first frame and the second frame are arranged side by side and offset to the outside of the first frame between the sound conduit and the battery.

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