MICRO SPEAKER AND EARPHONE

Abstract

 This micro speaker comprises: a frame; a diaphragm provided in an opening of the frame and having an edge; a voice coil fixed to the diaphragm; and a magnet having an air passage under a dome. The frame includes: a first acoustic chamber formed on the opposite side of the diaphragm with the magnet interposed therebetween; a second acoustic chamber formed in an annular shape on the outside of the magnet; an under-edge air passage having one end opening facing the edge, and another end provided opposite the one end and connecting to the first acoustic chamber; a first air passage for connecting the first acoustic chamber with the second acoustic chamber; and a second air passage for opening the second acoustic chamber to the outside of the frame.

Description

TECHNICAL FIELD

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

BACKGROUND ART

[0002] A speaker unit and an earphone that adjusts sound quality and prevents variations in sound quality have been proposed (see, for example, Patent Literature 1). The speaker unit is a speaker unit incorporated in a housing of the earphone, and includes a frame having a cylindrical shape, a diaphragm emitting sound, and a substrate to which a wiring line of a coil provided to the diaphragm is connected. The frame has a space inside, and the diaphragm and the substrate are arranged inside the frame with the space interposed between the diaphragm and the substrate.

CITATION LIST

PATENT LITERATURE

[0003] Patent Literature 1: JP2022-91463A

SUMMARY OF INVENTION

TECHNICAL PROBLEM

[0004] The speaker unit and the earphone disclosed in Patent Literature 1 have a structure in which the diaphragm and the substrate are arranged with the space interposed between the diaphragm and the substrate. This space is provided to adjust sound quality and prevent variation in sound quality. However, this arrangement structure has a problem that a distance between the diaphragm and the substrate (in other words, a thickness of the speaker unit) increases depending on the size of the space. That is, it is difficult to reduce the size of the speaker unit by arranging the diaphragm and the substrate with the space interposed between the diaphragm and the substrate.

[0005] The present disclosure has been made in view of the above circumstances of the related art, and an object of the present disclosure is to provide a micro speaker capable of reducing a thickness of a housing compared with a related configuration while adjusting sound quality and preventing variation in sound quality, and an earphone including the micro speaker.

SOLUTION TO PROBLEM

[0006] The present disclosure provides a micro speaker incorporated into a housing of an earphone, the micro speaker including: a bottomed cylindrical frame; a diaphragm provided at an opening portion of the frame and having an edge on a peripheral edge of a dome; a cylindrical voice coil coaxially fixed to the diaphragm; and an annular magnet arranged in the frame and having an under-dome ventilation passage coaxial with the voice coil at a center, in which the frame includes a first chamber formed on a side opposite to the diaphragm with the magnet interposed therebetween, a second chamber formed in an annular shape outside the magnet, an under-edge ventilation passage having one end portion opened to face the edge and the other end portion provided opposite to the one end portion and connected to the first chamber, a first ventilation passage connecting the first chamber to the second chamber, and a second ventilation passage that opens the second chamber to an outside of the frame.

[0007] The present disclosure provides a micro speaker incorporated into a housing of an earphone, the micro speaker including: a bottomed cylindrical frame; a diaphragm provided at an opening portion of the frame and having an edge on a peripheral edge of a dome; a cylindrical voice coil coaxially fixed to the diaphragm; and an annular magnet arranged in the frame and having an under-dome ventilation passage coaxial with the voice coil at a center, in which the frame includes a third chamber formed on a side opposite to the diaphragm with the magnet interposed therebetween, a fourth chamber formed in an annular shape outside the magnet, an under-edge ventilation passage having one end portion opened to face the edge, the other end portion provided opposite to the one end portion and connected to the third chamber, and an intermediate portion provided between the one end portion and the other end portion and connected to the second chamber, a protruding portion extending radially outward from a part of an outer periphery and having a fifth chamber, a third ventilation passage connecting the third chamber to the fifth chamber, and a fourth ventilation passage that opens the fifth chamber to an outside of the frame.

[0008] The present disclosure provides an earphone including a micro speaker.

ADVANTAGEOUS EFFECTS OF INVENTION

[0009] According to the micro speaker of the present disclosure, the thickness can be reduced as compared with the related configuration while adjusting the sound quality and preventing the variation in the sound quality.

[0010] According to the earphone of the present disclosure, a protrusion amount from the ear canal to which the earphone is inserted to the outside can be reduced to be smaller than that in the related configuration.

BRIEF DESCRIPTION OF DRAWINGS

[0011] 

[Fig. 1] Fig. 1 is a partially cutaway side view of an earphone including a micro speaker according to Embodiment 1.

[Fig. 2] Fig. 2 is a perspective view of the micro speaker illustrated in Fig. 1 as viewed diagonally from above.

[Fig. 3] Fig. 3 is a bottom perspective view of the micro speaker illustrated in Fig. 2, turned upside down.

[Fig. 4] Fig. 4 is a bottom view of the micro speaker illustrated in Fig. 3.

[Fig. 5] Fig. 5 is a cross-sectional view taken along line A-A in Fig. 4.

[Fig. 6] Fig. 6 is a cross-sectional view taken along line B-B in Fig. 4.

[Fig. 7] Fig. 7 is an operation diagram illustrating air flow.

[Fig. 8] Fig. 8 is a cross-sectional view of a micro speaker according to a comparative example.

[Fig. 9] Fig. 9 is a partially cutaway side view of an earphone including a micro speaker according to Embodiment 2.

[Fig. 10] Fig. 10 is a perspective view of the micro speaker illustrated in Fig. 9 as viewed diagonally from above.

[Fig. 11] Fig. 11 is a bottom perspective view of the micro speaker illustrated in Fig. 10, turned upside down.

[Fig. 12] Fig. 12 is a bottom view of the micro speaker illustrated in Fig. 11.

[Fig. 13] Fig. 13 is a cross-sectional view taken along line D-D in Fig. 12.

[Fig. 14] Fig. 14 is a cross-sectional view taken along line E-E in Fig. 12.

[Fig. 15] Fig. 15 is an operation diagram illustrating air flow in the D-D cross section in Fig. 12.

DESCRIPTION OF EMBODIMENTS

[0012] Hereinafter, embodiments specifically disclosing a micro speaker and an earphone according to the present disclosure will be described in detail with reference to the drawings as appropriate. However, unnecessarily detailed description may be omitted. For example, detailed description of well-known matters and the redundant description of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy of the following description and to facilitate understanding of those skilled in the art. The accompanying drawings and the following description are provided for a person skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matters described in the claims.

[0013] In the following description, reference numerals appearing in the accompanying drawings are given as references for describing a configuration of the micro speaker or the earphone, and the same reference numerals in the accompanying drawings indicate the same configuration.

[Embodiment 1]

[0014] Fig. 1 is a partially cutaway side view of an earphone 13 including a micro speaker 11 according to Embodiment 1. The earphone 13 includes a housing 15, the micro speaker 11, a substrate 17, and a battery 19.

[0015] The inside of the housing 15 of the earphone 13 is an accommodation space 21 that accommodates the micro speaker 11, the substrate 17, and the battery 19. The housing 15 includes a sound guide tube 25 having a sound emission hole 23. In the earphone 13, an earpiece (not illustrated) is attached to the outer periphery of the sound guide tube 25. The earpiece is retained by a locking claw 27 of the sound guide tube 25. The sound guide tube 25 to which the earpiece is attached is inserted into an ear of a wearer. That is, in the earphone 13, sound passing through the sound guide tube 25 from the micro speaker 11 is emitted upward (for example, toward the inside of the ear of the wearer) from the sound emission hole 23.

[0016] In the present specification, unless otherwise specified, an upper side refers to a direction in which the sound passing through the sound guide tube 25 is emitted from the sound emission hole 23, and a lower side refers to a side where the battery 19 is accommodated with respect to the micro speaker 11.

[0017] The substrate 17 is electrically connected to the battery 19 by a flexible flat cable 29. The micro speaker 11 is electrically connected to the substrate 17 by a flat cable 31. Various power (power supply), audio signals, and control signals from the substrate 17 are transmitted to the micro speaker 11 via the flat cable 31.

[0018] Fig. 2 is a perspective view of the micro speaker 11 illustrated in Fig. 1 as viewed diagonally from above. The micro speaker 11 is formed in a flat and substantially cylindrical shape. The micro speaker 11 has a bottomed cylindrical frame 33. The frame 33 is formed by injection molding using a resin material, for example. A diaphragm 35 is provided at an opening portion formed on an upper side of the frame 33. The diaphragm 35 includes a dome 37 arranged so as to occupy a central portion of a housing of the micro speaker 11, and an edge 39 formed in a substantially disk shape on a peripheral edge of the dome 37.

[0019] The bottom of the bottomed cylindrical frame 33 may be integrated with the frame 33, or may be a separate member that is integrally fixed to the frame 33. In Embodiment 1, at the bottom of the frame 33, a separate rear box 41 is integrally fixed to the frame 33. The diaphragm 35, the frame 33, and the rear box 41 each having a circular shape are coaxially joined.

[0020] Fig. 3 is a bottom perspective view of the micro speaker 11 illustrated in Fig. 2, turned upside down. On a lower surface of the rear box 41, a pair of second ventilation passages 43 described later are opened on both end sides in a diameter direction. Each of the second ventilation passages 43 is covered with a second mesh material 45 described later.

[0021] Fig. 4 is a bottom view of the micro speaker 11 illustrated in Fig. 3. The rear box 41 has a circular lower surface central portion 47 surrounded by an annular recessed portion 49 that is thinner than the lower surface central portion 47. That is, there is a step between the lower surface central portion 47 and the recessed portion 49 (see Fig. 3). The second ventilation passage 43 and the second mesh material 45 are arranged in the recessed portion 49. Four protrusions 51 are formed on an outer periphery of the lower surface central portion 47 at equal intervals in a circumferential direction so as to protrude into the recessed portion 49. These protrusions 51 are portions inside the frame 33 in which ventilation passages described later are formed.

[0022] Fig. 5 is a cross-sectional view taken along line A-A in Fig. 4. A ring 53 is provided on an outer peripheral edge of the edge 39 of the diaphragm 35. The diaphragm 35 is supported by the frame 33 via the edge 39 by fixing the ring 53 to the opening portion of the frame 33. The lower surface of the dome 37 of the diaphragm 35 is a concave curved surface.

[0023] The diaphragm 35 has the edge 39 that is processed to be more flexibly than the dome 37. The edge 39 has a plurality of diagonal embosses that reduce the strength of the peripheral edge, thereby facilitating the vibration of the diaphragm 35. Regarding the diaphragm 35, the edge 39 facilitates the vibration of the diaphragm 35, and when no audio signal is input to a voice coil 55, the edge 39 maintains the diaphragm 35 in a neutral position. In the diaphragm 35, the cylindrical voice coil 55 is coaxially fixed to the lower surface (concave curved surface) of the dome 37.

[0024] The voice coil 55 is formed by winding a metal wire in an annular shape (cylindrical shape) a plurality of times. The voice coil 55 is connected to an input terminal (not illustrated) to which an audio signal from the substrate 17 is input. An upper end of the voice coil 55 is fixed to the diaphragm 35, and a lower end of the voice coil 55 is inserted into a magnetic gap in a magnetic circuit of a magnet 57. The diaphragm 35 vibrates due to the vibration of the fixed voice coil 55, and converts the audio signal input to the voice coil 55 into sound.

[0025] In the frame 33, the annular magnet 57 is arranged coaxially with the voice coil 55 inside the voice coil 55. The magnet 57 has an under-dome ventilation passage 59 coaxial with the voice coil 55 at the center. The magnet 57 is coaxially fixed to an inside of a bottomed cylindrical yoke 61 fixed in the frame 33.

[0026] The yoke 61 is made of a magnetic material. An annular plate 63 is coaxially fixed to an upper surface of the magnet 57. The plate 63 is made of a magnetic material. A flangeshaped stopper 65 is fixed to an upper surface of the plate 63. An upper surface of the stopper 65 has a convex curved surface following the concave curved surface of the dome 37. The stopper 65 restricts the displacement of the diaphragm 35 toward the magnet 57 and restricts the diaphragm 35 from coming too close to the plate 63.

[0027] The yoke 61, the magnet 57, and the plate 63 constitute a magnetic circuit of the micro speaker 11. The magnetic circuit is a circuit that generates a steady magnetic flux in the magnetic gap. A magnetic gap is formed between an inner peripheral surface of the yoke 61 and an outer peripheral surface of the plate 63. The lower end of the cylindrical voice coil 55 is inserted into the magnetic gap.

[0028] A magnetic fluid 67 is arranged in the magnetic gap. The magnetic fluid 67 is annularly arranged between the outer periphery of the plate 63 and the inner periphery of the voice coil 55. The space between the voice coil 55 and the plate 63 is sealed by the magnetic fluid 67. The magnetic fluid 67 is a magnetic colloidal solution in which ferromagnetic fine particles, a dispersant covering the surface of the ferromagnetic fine particles, and a solvent are mixed. The micro speaker 11 can stabilize the vibration of the voice coil 55 under low frictional resistance by arranging the magnetic fluid 67 between the voice coil 55 and the plate 63.

[0029] In a driver portion of the micro speaker 11 in which the yoke 61, the magnet 57, the plate 63, and the stopper 65 are coaxially fixed, the under-dome ventilation passage 59 is formed through the center.

[0030] Meanwhile, the frame 33 includes a first chamber 69, a second chamber 71, an under-edge ventilation passage 73, first ventilation passages 75, and the second ventilation passages 43.

[0031] In the frame 33 formed in a bottomed cylindrical shape, an opening portion on a side opposite to the diaphragm 35 is closed by the rear box 41. The first chamber 69 is formed between the rear box 41 and the bottomed cylindrical yoke 61 fixed in the frame 33. That is, the first chamber 69 is formed on a side opposite to the diaphragm 35 with the magnet 57 interposed therebetween. The first chamber 69 is a cylindrical space interposed between the bottom of the yoke 61 and a bottom wall of the rear box 41. The first chamber 69 is arranged coaxially with the under-dome ventilation passage 59. A lower end of the under-dome ventilation passage 59 is physically connected to the first chamber 69.

[0032] The second chamber 71 is formed in a side wall portion of the frame 33 in an annular shape outside the magnet 57. The second chamber 71 is a cylindrical space having a predetermined thickness and coaxial with the magnet 57. An upper portion of the second chamber 71 is closed by an upper wall of the frame 33, and a lower portion of the second chamber 71 is closed by an annular partition wall 77 of the rear box 41.

[0033] One end of the under-edge ventilation passage 73 is opened to face the edge 39. The other end of the under-edge ventilation passage 73 is connected to the first chamber 69. The under-edge ventilation passage 73 is surrounded by a vertical wall portion 79 in the second chamber 71, and thus is partitioned from the second chamber 71 without being directly connected thereto. That is, the under-edge ventilation passage 73 has a pipe shaft shape and is arranged in the second chamber 71.

[0034] Fig. 6 is a cross-sectional view taken along line B-B in Fig. 4. The first ventilation passage 75 is formed by eroding a part of the annular partition wall 77 in the protrusion 51 of the rear box 41. The first ventilation passage 75 connects the first chamber 69 to the second chamber 71. The first ventilation passages 75 are provided at two positions on both sides in the diameter direction of the rear box 41. The air inside the first chamber 69 and the air inside the second chamber 71 can move through the first ventilation passage 75.

[0035] Further, in the annular partition wall 77, the second ventilation passage 43 that opens the second chamber 71 to the outside of the frame 33 is formed at a cross-sectional position taken along line C-C illustrated in Fig. 4. The second ventilation passage 43 penetrates the annular partition wall 77 and opens at the recessed portion 49. As illustrated in Fig. 4, the second ventilation passages 43 are provided at two positions on both sides in the diameter direction of the rear box 41. The air in the second chamber 71 and the air outside the frame can move through the second ventilation passage 43.

[0036] As described above, in the micro speaker 11, the first ventilation passage 75 and the second ventilation passage 43 are arranged at different positions in the circumferential direction of the frame 33.

[0037] In the micro speaker 11, the first ventilation passage 75 and the second ventilation passage 43 have a mesh material that determines air resistance. A first mesh material 81 illustrated in Fig. 6 is attached to the first ventilation passage 75. The second mesh material 45 illustrated in Figs. 3 and 4 is attached to the second ventilation passage 43. The first mesh material 81 and the second mesh material 45 control the resistance of air passing through the first ventilation passage 75 and the second ventilation passage 43. The first mesh material 81 and the second mesh material 45 may be, for example, a nonwoven fabric formed of chemical fibers or a porous plate-shaped member.

[0038] Fig. 7 is an operation diagram illustrating air flow. In Fig. 7, an upper diagram is a cross-sectional view taken along line A-A in Fig. 4, a middle diagram is a cross-sectional view taken along line B-B in Fig. 4, and a lower diagram is a cross-sectional view taken along line C-C in Fig. 4. As illustrated in the upper diagram of Fig. 7, in the micro speaker 11, when the voice coil 55 is driven and the diaphragm 35 vibrates, the air under the dome 37 moves to the under-dome ventilation passage 59 due to the displacement of the diaphragm 35. The air in the under-dome ventilation passage 59 is pushed by the movement of the air under the dome 37, and a part or all of the air in the under-dome ventilation passage 59 moves to the first chamber 69. Similarly, the air under the edge 39 also moves to the under-edge ventilation passage 73. The air in the under-edge ventilation passage 73 is pushed by the movement of the air under the edge 39, and a part or all of the air in the under-edge ventilation passage 73 moves to the first chamber 69.

[0039] As illustrated in the middle diagram of Fig. 7, a part or all of the air in the first chamber 69 moves to the second chamber 71 through the first ventilation passage 75 by the movement of the air from the under-dome ventilation passage 59 and the under-edge ventilation passage 73.

[0040] As illustrated in the lower diagram of Fig. 7, the air in the second chamber 71 is pushed by the movement of the air from the first chamber 69, and a part or all of the air in the second chamber 71 moves to the outside of the frame 33 through the second ventilation passage 43. When the diaphragm 35 is displaced in a reverse direction, the air moves from the outside of the frame 33 to the second chamber 71 through the second ventilation passage 43, and then the air moves to the gap below the diaphragm by the reverse flow.

[0041] Next, operations of Embodiment 1 will be described.

[0042] The micro speaker 11 according to Embodiment 1 is the micro speaker 11 incorporated into the housing 15 of the earphone 13, and includes: the bottomed cylindrical frame 33; the diaphragm 35 provided at an opening portion of the frame 33 and having the edge 39 on a peripheral edge of the dome 37; the cylindrical voice coil 55 coaxially fixed to the diaphragm 35; and the annular magnet 57 arranged in the frame 33 and having the under-dome ventilation passage 59 coaxial with the voice coil 55 at a center. The frame 33 includes the first chamber 69 formed on a side opposite to the diaphragm 35 with the magnet 57 interposed therebetween, the second chamber 71 formed in an annular shape outside the magnet 57, the under-edge ventilation passage 73 having one end portion opened to face the edge 39 and the other end portion provided opposite to the one end portion and connected to the first chamber 69, the first ventilation passage 75 connecting the first chamber 69 to the second chamber 71, and the second ventilation passage 43 that opens the second chamber 71 to an outside of the frame.

[0043] In the micro speaker 11 according to Embodiment 1, the frame 33 is formed in a bottomed cylindrical shape. In the bottomed cylindrical shape, one of both ends in an axial direction of the cylinder is closed as a bottom, and the other end serves as an opening portion to open the cylinder interior. The bottom of the frame 33 may be integrated with the frame 33, or may be a separate member that is integrally fixed to the frame 33.

[0044] The circular diaphragm 35 is provided on the opening portion side of the frame 33. The diaphragm 35 has the edge 39 at the peripheral edge of the dome 37. The edge 39 is a soft edge having a plurality of diagonal embosses, and as the edge bends, the dome 37 and the edge 39 vibrate smoothly as one unit.

[0045] The dome 37 has a concave curved surface on the opening portion side of the frame 33. The cylindrical voice coil 55 is coaxially fixed to the surface of the diaphragm 35 on the opening portion side. The voice coil 55 is partially inserted into the cylinder of the frame 33 from the opening portion.

[0046] Inside the frame 33, the magnet 57 separated from the diaphragm 35 is provided inside the voice coil 55. The magnet 57 is arranged coaxially with the voice coil 55. The magnet 57 is formed in an annular shape and has the under-dome ventilation passage 59 coaxially penetrating the center. Accordingly, the air under the dome between the diaphragm 35 and the magnet 57 can move in a direction along the axis of the frame 33 through the under-dome ventilation passage 59.

[0047] Fig. 8 is a cross-sectional view of a micro speaker 83 according to a comparative example. Here, a frame structure of the micro speaker 83 according to the comparative example will be described. A frame 85 of the micro speaker 83 is provided with a driver bottom surface cover 87 that is spaced apart below the yoke 61. The first chamber 69 is formed between the yoke 61 and the driver bottom surface cover 87. The under-edge ventilation passage 73 is formed in the frame 85, and the under-edge ventilation passage 73 is connected to the first chamber 69. A first ventilation passage 89 coaxial with the under-dome ventilation passage 59 is formed in the driver bottom surface cover 87. The first ventilation passage 89 is covered with the first mesh material 81.

[0048] A second chamber 93 is formed between the driver bottom surface cover 87 and a rear box 91. In the rear box 91, a second ventilation passage 95 that opens the second chamber 93 to the outside of the frame is formed coaxially with the under-dome ventilation passage 59. The second ventilation passage 95 is covered with the second mesh material 45. In the micro speaker 83 according to the comparative example, the under-dome ventilation passage 59, the first chamber 69, and the second chamber 93 are vertically arranged in series. For this reason, there is a limit to reducing the total height of the frame 85 when a chamber having a predetermined volume is secured.

[0049] Meanwhile, in the micro speaker 11 according to Embodiment 1, the first chamber 69 is formed in the frame 33 on the side opposite to diaphragm 35 with magnet 57 interposed therebetween. That is, the under-dome ventilation passage 59 connects the gap under the dome and the first chamber 69. Therefore, the air in the gap under the dome, the under-dome ventilation passage 59, and the first chamber 69 moves along with the displacement of the diaphragm 35 that vibrates by the driving of the voice coil 55.

[0050] In the frame 33, the annular second chamber 71 is formed coaxially with the voice coil 55 and positioned between the diaphragm 35 and the first chamber 69. The second chamber 71 is positioned and formed outside the voice coil 55. A lower end side of the second chamber 71 in the axial direction overlaps the first chamber 69 and protrudes to the outside from the first chamber 69.

[0051] That is, in the micro speaker 11, the magnet 57, the voice coil 55, and the second chamber 71 are coaxially arranged radially outward with the under-dome ventilation passage 59 as the center. Then, the diaphragm 35 is arranged on one side in the axial direction of the frame 33 which is the center, and the first chamber 69 is arranged on the other side in the axial direction.

[0052] Further, in the frame 33, the under-edge ventilation passage 73 having one end opened to face the edge 39 and the other end connected to the first chamber 69 is formed. The under-edge ventilation passage 73 is formed by partitioning a part of the second chamber 71. That is, the second chamber 71 contains the under-edge ventilation passage 73. The air in the under-edge ventilation passage 73 does not directly move to the second chamber 71, but temporarily moves to the first chamber 69 to move the air in the first chamber 69 to the second chamber 71.

[0053] In the micro speaker 11, the frame 33 includes the first ventilation passage 75 that connects the first chamber 69 to the second chamber 71. The frame 33 includes the second ventilation passage 43 that opens the second chamber 71 to the outside of the frame.

[0054] Therefore, in the micro speaker 11, when the voice coil 55 is driven, the diaphragm 35 vibrates, and the air in the gap below the diaphragm moves the air in the under-dome ventilation passage 59 and the under-edge ventilation passage 73 due to the displacement of the diaphragm 35. Accordingly, the air in the under-dome ventilation passage 59 moves the air in the first chamber 69. Similarly, the air in the under-edge ventilation passage 73 also moves the air in the first chamber 69. That is, both the air in the under-dome ventilation passage 59 and the air in the under-edge ventilation passage 73 act on the air in the first chamber 69.

[0055] The air moved to the first chamber 69 moves the air in the first chamber 69 to the second chamber 71 having an annular shape outside the magnet 57 through the first ventilation passage 75. When the air moves from the first ventilation passage 75, the air inside the second chamber 71 is pushed, and a part of the air inside the second chamber 71 moves to the outside of the frame through the second ventilation passage 43. When the diaphragm 35 is displaced in the reverse direction, the air moves from the outside of the frame to the second chamber 71 through the second ventilation passage 43, and then the air moves to the gap below the diaphragm by the reverse flow.

[0056] As described above, in the micro speaker 11, the volume in the frame in which the air moves due to the displacement of the diaphragm 35 includes the under-dome ventilation passage 59, the first chamber 69, the second chamber 71, and the under-edge ventilation passage 73. The volume is set to a size that ensures a desired sound quality. The first chamber 69 is formed as a flat space perpendicular to the axis of the frame 33 on the side opposite to the diaphragm 35 with the magnet 57 interposed therebetween. Meanwhile, the second chamber 71 connected to the first chamber 69 is formed in an annular shape outside the magnet 57 between the diaphragm 35 and the first chamber 69. That is, the thickness of the frame 33 in the direction along the axis is reduced.

[0057] That is, in the micro speaker 11, a chamber having a predetermined volume is secured mainly by the first chamber 69 and the second chamber 71 to adjust the sound quality and prevent variations in sound quality, while the second chamber 71 is annularly arranged outside the magnet 57, so that the volume is removed from the serial arrangement of the under-dome ventilation passage 59 and the first chamber 69. As a result, the thickness of the micro speaker 11 can be reduced as compared with the related configuration without depending on the thickness of the second chamber 71.

[0058] In the micro speaker 11, the first ventilation passage 75 and the second ventilation passage 43 are arranged at different positions in the circumferential direction of the frame 33.

[0059] In the micro speaker 11, the first ventilation passage 75 connecting the first chamber 69 to the second chamber 71 and the second ventilation passage 43 that opens the second chamber 71 to the outside of the frame are arranged at different positions in the circumferential direction of the frame 33. The second chamber 71 is formed in an annular shape in the frame between the diaphragm 35 and the first chamber 69. The first chamber 69 is formed as a disk-shaped space at the bottom of the frame 33.

[0060] The annular second chamber 71 is partitioned by the disk-shaped first chamber 69 and the annular partition wall 77. An inner peripheral edge of the annular partition wall 77 of the annular second chamber 71 overlaps the first chamber 69. An outer peripheral side of the annular partition wall 77 is formed to be larger than an outer diameter of the first chamber 69 and extends radially outward of the first chamber 69. That is, the annular partition wall 77 partitioning the second chamber 71 and the first chamber 69 has an inner peripheral side overlapping the first chamber 69 and an outer peripheral side protruding to the outside of the frame.

[0061] Accordingly, in the second chamber 71, the first ventilation passage 75 connected to the first chamber 69 can be formed on the inner peripheral side of the annular partition wall 77, and the second ventilation passage 43 connected to the outside of the frame can be formed on the outer peripheral side of the annular partition wall 77. As a result, in the frame 33, when the first ventilation passage 75 and the second ventilation passage 43 are arranged in the annular partition wall 77 at different positions in the circumferential direction in the second chamber 71, the enlargement in the radial direction can be prevented, and the second chamber 71 is allowed to be connected to both the first chamber 69 and the outside of the frame with a compact structure.

[0062] Further, in the micro speaker 11, the first ventilation passage 75 and the second ventilation passage 43 have a mesh material that determines air resistance.

[0063] In the micro speaker 11, the first ventilation passage 75 and the second ventilation passage 43 have a mesh material that determines air resistance. A desired air resistance can be obtained by changing the mesh size of the mesh material. The micro speaker 11 can change sound pressure frequency characteristics to desired sound pressure frequency characteristics (in other words, obtain desired sound pressure frequency characteristics) by changing the air resistance of at least one of the first ventilation passage 75 and the second ventilation passage 43. That is, the sound pressure frequency characteristics, which determine the sound quality of the sound emitted from the diaphragm 35, can be controlled by the volumes of the first chamber 69 and the second chamber 71 and the air resistance which is the characteristic of the mesh material.

[0064] The earphone 13 according to Embodiment 1 includes the micro speaker 11.

[0065] In the earphone 13 according to Embodiment 1, the micro speaker 11 is accommodated in the housing 15. Since the thickness of the micro speaker 11 can be made thinner than the related configuration while adjusting the sound quality and preventing variations in the sound quality, the dimension of the housing 15 in the thickness direction can be reduced accordingly. Accordingly, the protrusion amount of the earphone 13 from the ear canal to which the earphone 13 is inserted to the outside can be reduced to be smaller than that in the related configuration.

[0066] Therefore, according to the micro speaker 11 of Embodiment 1, the thickness can be reduced as compared with the related configuration while adjusting the sound quality and preventing the variation in the sound quality. Further, according to the earphone 13 of Embodiment 1, the protrusion amount from the ear canal to which the earphone 13 is inserted to the outside can be reduced to be smaller than that in the related configuration.

[Embodiment 2]

[0067] Next, Embodiment 2 will be described.

[0068] Fig. 9 is a partially cutaway side view of an earphone 99 including a micro speaker 97 according to Embodiment 2. In Embodiment 2, the same reference numerals are given to the same members as those described in Embodiment 1, and redundant description will be omitted.

[0069] The housing 15 of the earphone 99 may be formed asymmetrically with respect to an axis of the sound guide tube 25. In this case, in the accommodation space 21, a surplus space 101 is generated immediately below the sound guide tube 25. In the earphone 99, a protruding portion 103 extending from a frame is arranged using the surplus space 101.

[0070] Fig. 10 is a perspective view of the micro speaker 97 illustrated in Fig. 9 as viewed diagonally from above. A main body portion of a frame 105 is formed in a cylindrical shape. The frame 105 has the protruding portion 103 protruding radially outward from a part of an outer periphery of the main body portion. An annular cover 107 that covers an outer peripheral edge of the diaphragm 35 is attached to an upper surface of the main body portion of the frame 105. The cover 107 exposes the dome 37 excluding the outer peripheral edge and about half of the edge 39 in the diameter direction in the entire diaphragm. On a lower surface side of the frame 105, a rear box 109 having substantially the same outer shape as the frame 105 in a plan view and a substrate 111 are integrally stacked. A fourth ventilation passage 113 is opened in a protruding distal end surface of the protruding portion 103. The opening of the fourth ventilation passage 113 is covered with a second mesh material 115.

[0071] Fig. 11 is a bottom perspective view of the micro speaker 97 illustrated in Fig. 10, turned upside down. The frame 105 has a bottom open portion 117 (see Fig. 13) on its lower surface. The bottom open portion 117 is closed by the rear box 109 stacked on a lower surface thereof. The rear box 109 has a recessed open portion 119 (see Fig. 13) on a lower surface thereof. The recessed open portion 119 of the rear box 109 is closed by the substrate 111 stacked on the lower surface thereof.

[0072] Fig. 12 is a bottom view of the micro speaker 97 illustrated in Fig. 11. The rear box 109 is provided with a plurality of positioning ribs 121 for regulating the fixing position of the substrate 111 outside the region where the substrate 111 is fixed.

[0073] Fig. 13 is a cross-sectional view taken along line D-D in Fig. 12. The micro speaker 97 is different from the micro speaker 11 according to Embodiment 1 in that a fourth chamber 123 (see Fig. 14) is connected to a third chamber 127 via an under-edge ventilation passage 125, and that the frame 105 includes the protruding portion 103 extending radially outward and the protruding portion 103 thereof includes a fifth chamber 129. Since other configurations are the same as those of the micro speaker 11 according to Embodiment 1, different points will be mainly described below.

[0074] The frame 105 has the third chamber 127 formed on a side opposite to the diaphragm 35 with the magnet 57 interposed therebetween. The third chamber 127 is formed between the recessed open portion 119 of the rear box 109 and the substrate 111. In the frame 105, a pair of the under-edge ventilation passages 125 are formed on both sides in a diameter direction inside the cylinder. The under-edge ventilation passage 125 has one end portion opened to face the edge 39 and the other end portion provided opposite to the one end portion and connected to the third chamber 127. The under-edge ventilation passage 125 further includes an intermediate portion in an up-down direction connected to the fourth chamber 123 (see Fig. 14).

[0075] Fig. 14 is a cross-sectional view taken along line E-E in Fig. 12. The frame 105 has the fourth chamber 123 formed in an annular shape outside the magnet 57. In the annular fourth chamber 123, both sides in the diameter direction of the main body portion in the direction in which the protruding portion 103 protrudes are connected to the pair of under-edge ventilation passages 125. That is, the fourth chamber 123 is connected to the third chamber 127 via the under-edge ventilation passage 125.

[0076] Fig. 13 will be referred to again. The frame 105 has the fifth chamber 129 in the protruding portion 103 extending radially outward from a part of the outer periphery of the cylinder. The frame 105 has a third ventilation passage 131 connecting the third chamber 127 to the fifth chamber 129. The frame 105 has the fourth ventilation passage 113 that opens the fifth chamber 129 to the outside of the frame 105.

[0077] In the micro speaker 97, an opening portion of the third ventilation passage 131 is covered with a first mesh material 133, and an opening portion of the fourth ventilation passage 113 is covered with the second mesh material 115. The first mesh material 133 and the second mesh material 115 determine the air resistance as described above.

[0078] Fig. 15 is an operation diagram illustrating air flow in the D-D cross section in Fig. 12. In the micro speaker 97, when the voice coil 55 is driven and the diaphragm 35 vibrates, the air under the dome 37 moves to the under-dome ventilation passage 59 due to the displacement of the diaphragm 35. The air in the under-dome ventilation passage 59 is pushed by the movement of the air under the dome 37, and a part or all of the air in the under-dome ventilation passage 59 moves to the third chamber 127. Similarly, the air under the edge 39 also moves to the under-edge ventilation passage 125. The air in the under-edge ventilation passage 125 is pushed by the movement of the air under the edge 39, and a part or all of the air in the under-edge ventilation passage 125 moves to the third chamber 127. At this time, a part or all of the air in the fourth chamber 123 connected to the under-edge ventilation passage 125 also moves to the third chamber 127.

[0079] When the air from the under-dome ventilation passage 59, the under-edge ventilation passage 125, and the fourth chamber 123 moves, a part or all of the air in the third chamber 127 moves to the fifth chamber 129 through the third ventilation passage 131.

[0080] The air in the fifth chamber 129 is pushed by the movement of the air from the third ventilation passage 131, and a part or all of the air in the fifth chamber 129 moves to the outside of the frame 105 through the fourth ventilation passage 113. When the diaphragm 35 is displaced in the reverse direction, the air moves from the outside of the frame 105 to the fifth chamber 129 through the fourth ventilation passage 113, and then the air moves to the gap below the diaphragm 35 by the reverse flow.

[0081] Next, operations of Embodiment 2 will be described.

[0082] The micro speaker 97 is the micro speaker 97 incorporated into the housing 15 of the earphone 99, and includes: the bottomed cylindrical frame 105; the diaphragm 35 provided at an opening portion of the frame 105 and having the edge 39 on a peripheral edge of the dome 37; the cylindrical voice coil 55 coaxially fixed to the diaphragm 35; and the annular magnet 57 arranged in the frame 105 and having the under-dome ventilation passage 59 coaxial with the voice coil 55 at a center. The frame 105 includes the third chamber 127 formed on a side opposite to the diaphragm 35 with the magnet 57 interposed therebetween, the fourth chamber 123 formed in an annular shape outside the magnet 57, the under-edge ventilation passage 125 having one end portion opened to face the edge 39, the other end portion provided opposite to the one end portion and connected to the third chamber 127, and an intermediate portion provided between the one end portion and the other end portion and connected to the fourth chamber 123, the protruding portion 103 extending radially outward from a part of an outer periphery and having the fifth chamber 129, the third ventilation passage 131 connecting the third chamber 127 to the fifth chamber 129, and the fourth ventilation passage 113 that opens the fifth chamber 129 to an outside of the frame 105. The under-edge ventilation passage 125 and the fourth chamber 123 are not directly connected, but connected via the third chamber 127 and the third ventilation passage 131. The fourth chamber 123 and the fifth chamber 129 directly connected to each other to form the same space.

[0083] The micro speaker 97 is different from the micro speaker 11 according to Embodiment 1 in that the fourth chamber 123 is connected to the under-edge ventilation passage 125 via the third chamber 127 and a third ventilation passage 131, and that the frame 105 has the fifth chamber 129 in the protruding portion 103 extending radially outward.

[0084] The micro speaker 97 according to Embodiment 2 is formed such that a width of fourth chamber 123 in the radial direction in the main body portion of cylindrical frame 105 is smaller than that in Embodiment 1. In the micro speaker 97 according to Embodiment 2, since the outer diameter of the main body portion of the frame 105 is the same, it is possible to secure a large accommodation space for the driver portion such as the magnet 57 and the voice coil 55 by an amount corresponding to the decrease in the width in the radial direction of the fourth chamber 123.

[0085] The annular fourth chamber 123 is connected to the intermediate portion of the under-edge ventilation passage 125 at two positions on both sides in the diameter direction. Accordingly, the fourth chamber 123 is connected to the third chamber 127 through the under-edge ventilation passage 125.

[0086] The frame 105 is formed with the protruding portion 103 extending radially outward from a part of the outer periphery. The fifth chamber 129 is formed inside the protruding portion 103. In the micro speaker 97, by securing a large accommodation space for the driver portion, the decrease in volume due to the reduction in size of the fourth chamber 123 is compensated by providing the fifth chamber 129. The third chamber 127 is connected to the fifth chamber 129 through the third ventilation passage 131. The fifth chamber 129 is opened to the outside of the frame 105 by the fourth ventilation passage 113.

[0087] Therefore, in the micro speaker 97, when the voice coil 55 is driven, the diaphragm 35 vibrates, and the air in the gap below the diaphragm moves the air in the under-dome ventilation passage 59 and the under-edge ventilation passage 125 due to the displacement. Accordingly, the air in the under-dome ventilation passage 59 moves the air in the third chamber 127. Similarly, the air in the under-edge ventilation passage 125 also moves the air in the third chamber 127. That is, both the air in the under-dome ventilation passage 59 and the air in the under-edge ventilation passage 125 act on the air in the third chamber 127. Since the under-edge ventilation passage 125 is also connected to the fourth chamber 123, a part or all of the air in the fourth chamber 123 also moves to the third chamber 127.

[0088] The air moved to the third chamber 127 moves the air in the fifth chamber 129 that is connected to the third chamber 127 through the third ventilation passage 131. When the air moves from the third ventilation passage 131, the air inside the fifth chamber 129 is pushed, and a part or all of the air inside the fifth chamber 129 moves to the outside of the frame 105 through the fourth ventilation passage 113.

[0089] In the micro speaker 97, the volume in the frame in which the air moves due to the displacement of the diaphragm 35 includes the under-dome ventilation passage 59, the third chamber 127, the fourth chamber 123, the under-edge ventilation passage 125, and the fifth chamber 129. The volume is set to a size that ensures a desired sound quality. The third chamber 127 is formed as a flat space perpendicular to the axis of the frame 105 on the side opposite to the diaphragm 35 with the magnet 57 interposed therebetween. That is, the thickness of the frame 105 in the direction along the axis is reduced. Meanwhile, the fourth chamber 123 connected to the third chamber 127 via the under-edge ventilation passage 125 is formed in an annular shape outside the magnet 57 between the diaphragm 35 and the third chamber 127.

[0090] In the micro speaker 97, by accommodating a large driver portion having a desired outer diameter, the fourth chamber 123 is secured in a frame thick portion 135 (see Fig. 14) which is a difference between the surplus outer diameter of the frame 105 and the outer diameter of the driver portion. In Embodiment 2, the fourth chamber 123 is formed by effectively using the surplus frame thick portion 135.

[0091] That is, in the micro speaker 97, a chamber having a predetermined volume is secured by the third chamber 127, the fourth chamber 123, and the fifth chamber 129 to adjust sound quality and prevent variations in sound quality. In the micro speaker 97, the fourth chamber 123 is annularly arranged outside the magnet 57, and the fifth chamber 129 is provided in the protruding portion 103 protruding from a part of the frame 105. Accordingly, the volumes of the fourth chamber 123 and the fifth chamber 129 are removed from the serial arrangement of the under-dome ventilation passage 59 and the third chamber 127. As a result, the thickness of the micro speaker 97 can be reduced as compared with the related configuration without depending on the thickness of the fourth chamber 123.

[0092] Further, in the micro speaker 97, the third ventilation passage 131 and the fourth ventilation passage 113 have a mesh material that determines air resistance.

[0093] In the micro speaker 97, the third ventilation passage 131 and the fourth ventilation passage 113 have a mesh material that determines air resistance. The mesh material can obtain a desired air resistance by changing the mesh size. The micro speaker 97 can change sound pressure frequency characteristics to desired sound pressure frequency characteristics by changing the air resistance of at least one of the third ventilation passage 131 and the fourth ventilation passage 113. According to the micro speaker 97, that is, the sound quality of the sound emitted from the diaphragm 35 can be controlled by the volumes of the third chamber 127, the fourth chamber 123, and the fifth chamber 129 and the air resistance which is a characteristic of the mesh material.

[0094] The earphone 99 may not be symmetrical with respect to the axis of the sound guide tube 25. In this case, in the accommodation space 21 of the earphone 99, the surplus space 101 may be present around the micro speaker 97. The surplus space 101 can be effectively used as the accommodation space 21 of the protruding portion 103 when accommodating the micro speaker 97 provided with the protruding portion 103. That is, by effectively using the surplus space 101, the earphone 99 can reduce the protrusion amount from the ear canal to the outside to be smaller than that in the related configuration while adjusting the sound quality and preventing variations in the sound quality.

[0095] Therefore, according to the micro speaker 97 of Embodiment 2, the thickness can be reduced as compared with the related configuration while adjusting the sound quality and preventing the variation in the sound quality. Further, according to the earphone 99 of Embodiment 2, the protrusion amount from the ear canal to which the earphone 99 is inserted to the outside can be reduced to be smaller than that in the related configuration.

<Regarding Techniques of Present Disclosure>

[0096] As described above, the present disclosure discloses the following technical ideas.

<Technique 1>

[0097] A micro speaker (11) incorporated into a housing (15) of an earphone (13), the micro speaker (11) including:

a bottomed cylindrical frame (33);

a diaphragm (35) provided at an opening portion of the frame and having an edge (39) on a peripheral edge of a dome (37);

a cylindrical voice coil (55) coaxially fixed to the diaphragm; and

an annular magnet (57) arranged in the frame and having an under-dome ventilation passage (59) coaxial with the voice coil at a center, in which

the frame includes

a first chamber (69) formed on a side opposite to the diaphragm with the magnet interposed therebetween,

a second chamber (71) formed in an annular shape outside the magnet,

an under-edge ventilation passage (73) having one end portion opened to face the edge and the other end portion provided opposite to the one end portion and connected to the first chamber,

a first ventilation passage (75) connecting the first chamber to the second chamber, and

a second ventilation passage (43) that opens the second chamber to an outside of the frame.

[0098] Accordingly, in the micro speaker, a chamber having a predetermined volume is secured mainly by the first chamber and the second chamber to adjust the sound quality and prevent variations in sound quality, while the second chamber is annularly arranged outside the magnet, so that the volume is removed from the serial arrangement of the under-dome ventilation passage and the first chamber, and the thickness of the micro speaker can be reduced to be small. As a result, the thickness of the micro speaker can be reduced as compared with the related configuration without depending on the thickness of the second chamber.

<Technique 2>

[0099] The micro speaker according to Technique 1, in which
the first ventilation passage and the second ventilation passage are arranged at different positions in a circumferential direction of the frame.

[0100] Accordingly, in the second chamber, the first ventilation passage connected to the first chamber can be formed on the inner peripheral side of the annular partition wall, and the second ventilation passage connected to the outside of the frame can be formed on the outer peripheral side of the annular partition wall. As a result, in the frame, when the first ventilation passage and the second ventilation passage are arranged in the annular partition wall at different positions in the circumferential direction in the second chamber, the enlargement in the radial direction can be prevented, and the second chamber is allowed to be connected to both the first chamber and the outside of the frame with a compact structure.

<Technique 3>

[0101] The micro speaker according to Technique 1 or Technique 2, in which
the first ventilation passage and the second ventilation passage have a mesh material configured to determine air resistance.

[0102] Accordingly, the micro speaker can change sound pressure frequency characteristics to desired sound pressure frequency characteristics (in other words, obtain desired sound pressure frequency characteristics) by changing the air resistance of at least one of the first ventilation passage and the second ventilation passage. That is, the sound pressure frequency characteristics, which determine the sound quality of the sound emitted from the diaphragm, can be controlled by the volumes of the first chamber and the second chamber and the air resistance which is the characteristic of the mesh material.

<Technique 4>

[0103] A micro speaker (97) incorporated into a housing (15) of an earphone (99), the micro speaker (97) including:

a bottomed cylindrical frame (105);

a diaphragm (35) provided at an opening portion of the frame and having an edge (39) on a peripheral edge of a dome (37);

a cylindrical voice coil (55) coaxially fixed to the diaphragm; and

an annular magnet (57) arranged in the frame and having an under-dome ventilation passage (59) coaxial with the voice coil at a center, in which

the frame includes

a third chamber (127) formed on a side opposite to the diaphragm with the magnet interposed therebetween,

a fourth chamber (123) formed in an annular shape outside the magnet,

an under-edge ventilation passage (125) having one end portion opened to face the edge, the other end portion provided opposite to the one end portion and connected to the third chamber, and an intermediate portion provided between the one end portion and the other end portion and connected to the fourth chamber,

a protruding portion (103) extending radially outward from a part of an outer periphery and having a fifth chamber (129),

a third ventilation passage (131) connecting the third chamber to the fifth chamber, and

a fourth ventilation passage (113) that opens the fifth chamber to an outside of the frame.

[0104] Accordingly, the micro speaker secures a chamber having a predetermined volume by the third chamber, the fourth chamber 123, and the fifth chamber 129 to adjust the sound quality and prevent variations in the sound quality. In the micro speaker, the fourth chamber 123 is annularly arranged outside the magnet 57, and the fifth chamber 129 is provided in the protruding portion 103 protruding from a part of the frame 105. Accordingly, the volumes of the fourth chamber 123 and the fifth chamber 129 are removed from the serial arrangement of the under-dome ventilation passage 59 and the third chamber 127, and the micro speaker 97 is thinned. As a result, the thickness of the micro speaker 97 can be reduced as compared with the related configuration without depending on the thickness of the fourth chamber 123.

<Technique 5>

[0105] The micro speaker according to Technique 4, in which
the third ventilation passage and the fourth ventilation passage have a mesh material configured to determine air resistance.

[0106] Accordingly, the earphone may not be symmetrical with respect to the axis of the sound guide tube. In this case, in the accommodation space of the earphone, the surplus space may be present around the micro speaker. The surplus space can be effectively used as the accommodation space of the protruding portion when accommodating the micro speaker provided with the protruding portion. That is, by effectively using the surplus space, the earphone can reduce the protrusion amount from the ear canal to the outside to be smaller than that in the related configuration while adjusting the sound quality and preventing variations in the sound quality.

<Technique 6>

[0107] An earphone including the micro speaker according to any one of Technique 1 to Technique 5.

[0108] Accordingly, the earphone can accommodate the micro speaker in the housing thereof. Since the thickness of the micro speaker can be made thinner than the related configuration while adjusting the sound quality and preventing variations in the sound quality, the dimension of the housing of the earphone in the thickness direction can be reduced accordingly. Accordingly, the protrusion amount of the earphone from the ear canal to which the earphone is inserted to the outside can be reduced to be smaller than that in the related configuration.

[0109] Although various embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited thereto. It is apparent to those skilled in the art that various modifications, corrections, substitutions, additions, deletions, and equivalents can be conceived within the scope described in the claims, and it is understood that such modifications, corrections, substitutions, additions, deletions, and equivalents also fall within the technical scope of the present disclosure. In addition, components in the embodiments described above may be combined freely in a range without departing from the spirit of the invention.

[0110] The present application is based on a Japanese patent application filed on October 27, 2023 (Japanese Patent Application No. 2023-184668), and the contents thereof are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

[0111] The present disclosure is useful as a micro speaker and an earphone capable of reducing the thickness as compared with a related configuration while adjusting sound quality and preventing variations in sound quality.

REFERENCE SIGNS LIST

[0112] 

11: micro speaker

13: earphone

15: housing

33: frame

35: diaphragm

37: dome

39: edge

43: second ventilation passage

45: second mesh material (mesh material)

55: voice coil

57: magnet

59: under-dome ventilation passage

69: first chamber

71: second chamber

73: under-edge ventilation passage

75: first ventilation passage

81: first mesh material (mesh material)

97: micro speaker

99: earphone

103: protruding portion

105: frame

113: fourth ventilation passage

115: second mesh material (mesh material)

123: fourth chamber

125: under-edge ventilation passage

127: third chamber

129: fifth chamber

131: third ventilation passage

133: first mesh material (mesh material)

Claims

1. A micro speaker incorporated into a housing of an earphone, the micro speaker comprising:

a bottomed cylindrical frame;

a diaphragm provided at an opening portion of the frame and having an edge on a peripheral edge of a dome;

a cylindrical voice coil coaxially fixed to the diaphragm; and

an annular magnet arranged in the frame and having an under-dome ventilation passage coaxial with the voice coil at a center, wherein

the frame includes

a first chamber formed on a side opposite to the diaphragm with the magnet interposed therebetween,

a second chamber formed in an annular shape outside the magnet,

an under-edge ventilation passage having one end portion opened to face the edge and the other end portion provided opposite to the one end portion and connected to the first chamber,

a first ventilation passage connecting the first chamber to the second chamber, and

a second ventilation passage that opens the second chamber to an outside of the frame.

2. The micro speaker according to claim 1, wherein
the first ventilation passage and the second ventilation passage are arranged at different positions in a circumferential direction of the frame.

3. The micro speaker according to claim 1, wherein
the first ventilation passage and the second ventilation passage have a mesh material configured to determine air resistance.

4. A micro speaker incorporated into a housing of an earphone, the micro speaker comprising:

a bottomed cylindrical frame;

a diaphragm provided at an opening portion of the frame and having an edge on a peripheral edge of a dome;

a cylindrical voice coil coaxially fixed to the diaphragm; and

an annular magnet arranged in the frame and having an under-dome ventilation passage coaxial with the voice coil at a center, wherein

the frame includes

a third chamber formed on a side opposite to the diaphragm with the magnet interposed therebetween,

a fourth chamber formed in an annular shape outside the magnet,

an under-edge ventilation passage having one end portion opened to face the edge, the other end portion provided opposite to the one end portion and connected to the third chamber, and an intermediate portion provided between the one end portion and the other end portion and connected to the fourth chamber,

a protruding portion extending radially outward from a part of an outer periphery and having a fifth chamber,

a third ventilation passage connecting the third chamber to the fifth chamber, and

a fourth ventilation passage that opens the fifth chamber to an outside of the frame.

5. The micro speaker according to claim 4, wherein
the third ventilation passage and the fourth ventilation passage have a mesh material configured to determine air resistance.

6. An earphone comprising:
the micro speaker according to any one of claims 1 to 5.

Drawing