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JP2018121249

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DESCRIPTION JP2018121249
Abstract: To provide a sound generator capable of performing airtightness inspection without
using a jig for pressing a diaphragm. A sound generator vibrates a diaphragm to generate sound,
and a first space opened to the atmosphere by a sound emission hole and a second space
separated from the first space by a diaphragm. The first space 5 and the first space 5 are
provided with a housing 1 in which the space 6 is formed inside, and a shielding plate 28
disposed in the first space 5 in a state of being separated from the diaphragm 72 so as to face
the diaphragm 72. When the diaphragm 72 is displaced toward the first space 5 due to the
pressure difference with the two spaces 6, the diaphragm 72 contacts the shielding plate 28,
thereby limiting the deformation of the diaphragm 72. [Selected figure] Figure 2
Sound generator
[0001]
The present invention relates to a sound generator.
[0002]
Conventionally, as a sound generator for vehicles used for an alarm for vehicles, an approach
notification device for vehicles, etc., there are some which were indicated, for example in patent
documents 1.
In the sound generator for a vehicle described in Patent Document 1, a shielding plate is installed
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in front of the diaphragm in the inside of the base casing for the purpose of achieving both the
acoustic performance and the intrusion prevention function of water and snow.
[0003]
JP, 2016-25558, A
[0004]
The sound generator is a sealed product, and an airtight test is performed to guarantee the
waterproof performance and the sealing performance of the sound generator.
In this airtight inspection, it is necessary to hold down the diaphragm with a jig or the like in
order to suppress inversion of the diaphragm due to air pressure and stabilize the inspection
result.
[0005]
However, in the configuration in which the shielding plate is installed in front of the diaphragm
in the inside of the base housing, the shielding plate needs to be removed in order to hold down
the diaphragm using a jig, which increases the number of parts and the mold cost. It leads to the
rise.
[0006]
An object of the present invention is to provide a sound generator capable of performing
airtightness inspection without using a jig for pressing a diaphragm.
[0007]
In order to achieve the above object, the invention according to claim 1 is a sound generator for
vibrating a diaphragm (72) to generate a sound, the first space being opened to the atmosphere
by a sound emission hole (84). 5) and a housing (1) in which a second space (6) separated from
the first space by the diaphragm is formed inside, and in the first space separated from the
diaphragm so as to face the diaphragm And a shield plate (28) disposed, and when the
diaphragm is displaced toward the first space due to a pressure difference between the first
space and the second space, the diaphragm contacts the shield plate to deform the diaphragm. Is
limited.
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[0008]
According to this, the deformation of the diaphragm is limited by the contact between the
diaphragm and the shielding plate, and the shielding plate substitutes for a jig for pressing the
diaphragm.
Therefore, the airtight inspection can be performed without using a jig for pressing the
diaphragm.
[0009]
In the invention according to claim 11, the drive portion (73) for vibrating the diaphragm is
provided, and the diaphragm vibrates by the drive portion in the distance between the diaphragm
and the contact surface of the shielding plate in contact with the diaphragm. It is larger than the
displacement of the diaphragm.
[0010]
According to such a configuration, it is possible to suppress the contact between the diaphragm
and the shielding plate due to the sound generation operation.
[0011]
Further, in the invention according to claim 12, the drive portion includes a cylindrical core
portion (75) erected toward the second space in the diaphragm, and a voice coil (76) wound
around the core portion. A magnetic circuit portion (in which the core portion is fitted in the
space by displacing the core portion by forming a cylindrical space (776) in which the core
portion and the axial direction coincide with each other and applying a magnetic field to the
voice coil 77), and the amount of displacement of the diaphragm is defined by the range in which
the core is fitted in the space.
[0012]
The amount of displacement of the diaphragm is defined, for example, by the range in which the
core is kept fitted in the space in this way, and the distance between the diaphragm and the
shield plate is larger than this amount of displacement. Contact with the shielding plate can be
suppressed.
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[0013]
In the invention according to claim 10, the distance between the diaphragm and the contact
surface of the shielding plate in contact with the diaphragm is 1 mm or more and 6 mm or less.
[0014]
By thus setting the distance between the shielding plate and the diaphragm to 1 mm or more and
6 mm or less, the contact between the diaphragm and the shielding plate due to the sound
generation operation can be suppressed.
[0015]
In the invention according to claim 6, the deformation of the diaphragm is limited by the contact
of the outer edge of the inner periphery of the diaphragm with the outer edge of the inner
periphery of the shield, and the deformation of the diaphragm is limited by the shield. At this
time, a gap is formed between the inner periphery of the diaphragm and the inner periphery of
the shielding plate.
[0016]
Although the strength of the inner peripheral part of the diaphragm is low, the diaphragm is
deformed or damaged by making the inner peripheral part of the diaphragm and the inner
peripheral part of the shielding plate contact at the outer edge and forming a gap between them.
It can be suppressed.
[0017]
In the invention according to claim 7, when the diaphragm is provided with a standing portion
(75) erected from the outer edge of the inner peripheral portion toward the second space, the
deformation of the diaphragm is limited by the shielding plate. The diaphragm contacts the
shielding plate at a portion where the erected portion is formed.
[0018]
Thus, when the diaphragm is in contact with the shielding plate at the portion where the
standing portion is formed and the strength is improved, it is possible to suppress the
deformation and breakage of the diaphragm.
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[0019]
In addition, the code ¦ symbol in the parenthesis of each said means shows an example of the
correspondence with the specific means as described in embodiment mentioned later.
[0020]
It is a figure which shows the whole structure of the sound generator concerning 1st
Embodiment, (a) is a front view, (b) is a left view, (c) is a bottom view.
It is sectional drawing which follows the II-II line of Fig.1 (a).
It is an enlarged view of the sounding body of FIG.
It is a front view of the state which removed the cover in the sound generator of FIG.
It is sectional drawing in alignment with the VV line ¦ wire of FIG.
It is sectional drawing in alignment with the VV line ¦ wire of FIG.
It is the enlarged view to which the VII part of FIG. 6 was expanded.
It is an enlarged view of the sounding body of FIG.
It is an enlarged view of the sounding body in the modification of a 1st embodiment.
[0021]
Hereinafter, an embodiment of the present invention will be described based on the drawings.
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In the following embodiments, parts that are the same as or equivalent to each other will be
described with the same reference numerals.
[0022]
First Embodiment A first embodiment will be described with reference to FIGS.
The sound generator of the present embodiment is installed, for example, outside the vehicle, and
is used to generate an alarm sound.
As shown in FIG. 2, the sound generator includes a housing 1 in which two spaces are formed.
[0023]
Specifically, as shown in FIG. 1 and FIG. 2, the housing 1 is composed of a base 2 made of resin, a
cover 3 and a case 4.
The base 2 includes a substantially cylindrical base cylindrical portion 21, and a disk-shaped
cover 3 covering the opening is fitted to an opening at one end side of the base cylindrical
portion 21. A disc-shaped case 4 is airtightly bonded to the other end side opening by adhesion.
[0024]
Then, as shown in FIG. 2, the space in the base cylindrical portion 21 is divided into two in the
axial direction by the partition 22 provided in the base cylindrical portion 21, and the base
cylindrical portion 21, the partition 22 and the cover 3 Thus, a first space 5 is formed, and a
second space 6 is formed by the base cylindrical portion 21, the partition wall 22 and the case 4.
[0025]
As shown to FIG. 2, FIG. 4, the circular through-hole 23 which connects the 1st space 5 and the
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2nd space 6 to the partition 22 is formed.
Then, as shown in FIG. 2, a sounding body 7 that generates a sound based on an electrical signal
is disposed in the second space 6 so as to close the through hole 23.
As described later, the through hole 23 is closed by the diaphragm 72 of the sound generator 7,
and the second space 6 is separated from the first space 5 by the diaphragm 72.
[0026]
Further, as shown in FIG. 4 and FIG. 5, the partition wall 22 is formed with a vent 24 at a position
away from the through hole 23. The vent hole 24 is for suppressing the generation of a pressure
difference between the first space 5 and the second space 6 due to a temperature change. A
ventilation film 25 is stretched in the ventilation holes 24. The air-permeable membrane 25
allows air and blocks water, and is made of, for example, Gore-Tex (registered trademark).
[0027]
As shown in FIG. 2 and FIG. 4, a cylindrical shielding cylindrical portion 26 surrounding the
through hole 23 and projecting from the partition 22 toward the cover 3 is connected to the
opening end of the partition 22. A beam-like connecting portion 27 is connected to a portion of
the shielding cylindrical portion 26 closer to the partition wall 22 than the opening end face on
the cover 3 side. The connecting portion 27 extends from the shielding cylindrical portion 26
radially inward of the through hole 23, and the shielding cylindrical portion 26 is connected to
the shielding plate 28 via the connecting portion 27.
[0028]
The shielding plate 28 is for suppressing the water flow at the time of high pressure car washing
and the snow attached to the surface of the cover 3 from reaching the sounding body 7, and for
preventing breakage of the sounding body 7 due to water adhesion. In the inside of 1, it is
arrange ¦ positioned between the sound emission hole 84 mentioned later and the diaphragm 72.
As shown in FIG.
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[0029]
In addition, the shielding plate 28 contacts the diaphragm 72 when the diaphragm 72 is
displaced during the airtightness inspection, and limits the deformation of the diaphragm 72.
As shown in FIGS. 2 and 5, the shielding plate 28 is disposed in the first space 5 in a state of
being separated from the diaphragm 72 so as to face the diaphragm 72, and has a shape
corresponding to the diaphragm 72. There is.
[0030]
Specifically, the inner circumferential portion 281 of the shielding plate 28 is formed in a dome
shape that is convex toward the side opposite to the diaphragm 72. The outer peripheral portion
282 is inclined to the opposite side to the diaphragm 72. Specifically, the outer peripheral
portion 282 has a hollow frusto-conical shape that extends from the outer edge of the inner
peripheral portion 281 toward the first space 5 side, and the cross section along the radial
direction is directed inward in the radial direction. It is curved to be convex. The inner
circumferential portion 281 and the outer circumferential portion 282 respectively face the
inner circumferential portion 721 and the outer circumferential portion 722 of the diaphragm
72 described later.
[0031]
In the present embodiment, the shielding plate 28 contacts the diaphragm 72 at the outer edge
of the inner circumferential portion 281 and the outer circumferential portion 282. The outer
peripheral portion 282 has a shape corresponding to the outer peripheral portion 722 when the
diaphragm 72 is deformed, whereby damage to the diaphragm 72 is suppressed.
[0032]
The inner circumferential portion 281 is closer to the case 4 than the partition 22 in the axial
direction of the base cylindrical portion 21, and the outer circumferential portion 282 is
disposed so as to pass through the through hole 23. Of the outer peripheral portion 282, the end
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opposite to the inner peripheral portion 281 is in a cylindrical shape projecting toward the cover
3 side, and as shown in FIG. 2, the outer peripheral portion 282 is in a cylindrical shape. The end
portion is connected to the coupling portion 27.
[0033]
As shown in FIG. 4, in the present embodiment, a plurality of connecting portions 27 are formed,
and the sound generated by the sounding body 7 is generated by the shielding cylindrical portion
26, the plurality of connecting portions 27, and the shielding plate 28. A plurality of sound
passages 81 to be passed through are formed.
[0034]
Further, the shielding plate 28 is formed with a cylindrical portion 283 which protrudes toward
the cover 3 from the outer edge of the inner circumferential portion 281.
As shown in FIG. 2, a resonance chamber 82 is formed by the outer peripheral portion 282, the
cylindrical portion 283, and the cover 3, and a resonance chamber 83 is formed by the inner
peripheral portion 281, the cylindrical portion 283, and the cover 3. The sound pressure of the
sound generated by the sound generator 7 is amplified by the resonance chamber 82 and the
resonance chamber 83.
[0035]
As shown in FIGS. 1, 2 and 4, a substantially square cylindrical connector 29 for electrically
connecting the sounding body 7 to an external harness (not shown) is formed on the outer side
of the base cylindrical portion 21. . As shown in FIG. 2, in the portion of the base cylinder 21
where the connector 29 is formed, a through hole is formed through the base cylinder 21 to
connect the inside of the connector 29 and the second space 6. The terminal 9 is disposed to
pass through the through hole.
[0036]
The terminal 9 is fixed to the base cylindrical portion 21 by an adhesive in the inside of the base
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cylindrical portion 21, and the through hole formed for disposing the terminal 9 is closed by the
adhesive and the terminal 9. ing. The terminal 9 is connected to a lead pin 78 described later in
the second space 6.
[0037]
As shown to FIG. 1, FIG. 2, the cover 3 is made into disk shape corresponding to the base cylinder
part 21. As shown in FIG. At a portion of the cover 3 facing the connecting portion 27 and the
sound release hole 81, a protruding portion 31 protruding toward the inside of the housing 1 is
formed. A circular through hole 32 for emitting the sound generated by the sound generator 7 to
the outside is formed in a portion of the cover 3 inside the protrusion 31. A beam-like connecting
portion 33 is connected to the open end of the through hole 32.
[0038]
The connecting portion 33 extends radially inward of the through hole 32 and is connected to
the shielding plate 34. The shielding plate 34 has a disk shape and is disposed so as to cover the
cylindrical portion 283 of the shielding plate 28.
[0039]
As shown in FIG. 1, in the present embodiment, a plurality of connecting portions 33 are formed,
and the plurality of sound emitting holes 84 are formed by dividing the through holes 32 by the
plurality of connecting portions 33. The sound release hole 84 opens the first space 5 to the
atmosphere, and emits the sound generated by the sound generator 7 to the outside.
[0040]
As shown in FIG. 2, a cylindrical tubular portion 35 protruding toward the partition wall 22 is
formed in a portion of the cover 3 which is located radially outward of the projecting portion 31.
The cylindrical portion 35 is disposed in a portion corresponding to the partition 22 in the first
space 5, and the tip of the cylindrical portion 35 is surrounded by the base cylindrical portion
21, the partition 22, and the shielding cylindrical portion 26. It is arranged in the part.
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[0041]
Thereby, a resonance chamber for amplifying the sound pressure of the sound generated by the
sounding body 7 is formed. Specifically, a resonance chamber 85 is formed by the base cylinder
portion 21, the partition wall 22, the outer peripheral portion of the cover 3, and the cylinder
portion 35, and the partition wall 22, the shielding cylinder portion 26 and the outer periphery
of the cover 3 A resonance chamber 86 is formed by the portion, the projecting portion 31 and
the cylindrical portion 35. A part of the protrusion 31 protrudes radially outward, and is
connected to the cylindrical portion 35.
[0042]
As described above, in the first space 5, the resonance chambers 82, 83, 85, 86 for amplifying
the sound pressure of the sound generated by the sounding body 7 are formed. By forming a
plurality of resonance chambers in this manner, a large sound pressure can be obtained in a wide
frequency band.
[0043]
As shown in FIGS. 2 and 3, the sounding body 7 includes a substantially stepped cylindrical
frame 71, a diaphragm 72, and a drive unit 73 that vibrates the diaphragm 72. The frame 71 is
open at both ends in the axial direction, and one of the two openings of the frame 71 having the
wider opening is closed by the diaphragm 72.
[0044]
The frame 71 is bonded airtightly to the partition wall 22 at the end on the side where the
opening is closed by the diaphragm 72. A through hole 74 is formed in the frame 71 to allow the
inside and the outside of the frame 71 to communicate with each other, and a space inside the
frame 71 constitutes a part of the second space 6. That is, the second space 6 is separated from
the first space 5 by the partition wall 22 and the diaphragm 72.
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[0045]
As shown in FIGS. 3 and 5, the inner circumferential portion 721 of the diaphragm 72 is formed
in a dome shape that is convex toward the first space 5 side. Further, the outer peripheral portion
722 of the diaphragm 72 is inclined toward the first space 5 side. Specifically, the outer
peripheral portion 722 is formed in a hollow truncated cone shape extending from the outer
edge of the inner peripheral portion 721 toward the first space 5 side, and the cross section
along the radial direction is directed inward in the radial direction. It is curved to be convex.
[0046]
The inner circumferential portion 721 and the outer circumferential portion 722 respectively
face the inner circumferential portion 281 and the outer circumferential portion 282 of the
shielding plate 28. Further, the outer edges of the inner circumferential portion 721 and the
inner circumferential portion 281 have the same shape. Specifically, the outer edge of the inner
circumferential portion 721 is circular, and the outer edge of the inner circumferential portion
281 is circular with the same diameter as the outer edge of the inner circumferential portion
721.
[0047]
As described later, at the time of the airtightness inspection of the sound generator, the inner
circumferential portion 721 is displaced toward the first space 5, and the diaphragm 72 is
deformed so as to expand to the first space 5 side and contacts the shielding plate 28. Do.
Specifically, as shown in FIGS. 6 and 7, the outer peripheral portion 722 contacts the outer
peripheral portion 282.
[0048]
Further, as described above, in the present embodiment, the outer edges of the inner
circumferential portion 721 and the inner circumferential portion 281 have the same shape. The
diaphragm 72 and the shielding plate 28 are arranged such that the outer edge of the inner
circumferential portion 721 contacts the outer edge of the inner circumferential portion 281
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when the diaphragm 72 is deformed as described above.
[0049]
Further, in the present embodiment, when the diaphragm 72 is deformed as described above, a
gap is formed between the inner circumferential portion 721 and the inner circumferential
portion 281, the inner circumferential portion 281 is closer to the inner circumferential portion
721. Even the curvature is high.
[0050]
As described later, in the sounding body 7, a sound is generated by the vibration of the
diaphragm 72.
In order to generate a sound with a sufficiently high sound pressure, it is necessary to increase
the distance between the diaphragm 72 and the shielding plate 28 to some extent. Further, the
distance between the surface of the diaphragm 72 in contact with the shielding plate 28 and the
surface of the shielding plate 28 in contact with the diaphragm 72 is a diaphragm by sounding
operation so that the diaphragm 72 does not contact the shielding plate 28 by sounding
operation. It is larger than the displacement amount of 72.
[0051]
For example, the distance between the surface of the diaphragm 72 in contact with the shielding
plate 28 and the surface of the shielding plate 28 in contact with the diaphragm 72 is preferably
1 mm or more and 6 mm or less. In the present embodiment, the distance between the outer
peripheral portion 282 and the outer peripheral portion 722 is 2 mm.
[0052]
The distance between the surface of the diaphragm 72 in contact with the shielding plate 28 and
the surface of the shielding plate 28 in contact with the diaphragm 72 is a bobbin 75 described
later when the diaphragm 72 is displaced at the time of the airtight inspection. It is preferable
that the space 776 be set so as to be in a state of being fitted. This is because the displacement of
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the diaphragm 72 needs to return the bobbin 75 to its original position in the space 776 after
the airtight inspection. For example, by adjusting the axial dimension of the bobbin 75 and the
thickness of the top plate 772 described later, the state in which the bobbin 75 is fitted in the
space 776 is maintained. However, when the bobbin 75 returns to the original position due to
the restoring force of the diaphragm 72, as shown in FIG. 8, the bobbin 75 may be out of the
space 776 due to the displacement of the diaphragm 72 in the airtight inspection. .
[0053]
Further, in the present embodiment, the inner circumferential portion 281 is located closer to the
case 4 than the partition 22 in the axial direction of the base cylindrical portion 21, and the outer
circumferential portion 282 is disposed to pass through the through hole 23. Thereby, when the
deformation of the diaphragm 72 is limited by the contact between the shielding plate 28 and
the diaphragm 72, the diaphragm 72 is displaced without being reversed as shown by the broken
line in FIG.
[0054]
That is, when the diaphragm 72 contacts the shielding plate 28, the inner circumferential portion
721 is at the original position of the inner circumferential portion 721 in the axial direction of
the frame 71 than the end of the diaphragm 72 fixed to the frame 71. Get close. More
specifically, assuming that an end portion of the bobbin 75 to be described later connected to the
diaphragm 72 is an end portion 751, the end portion of the diaphragm 72 in the axial direction
is an end portion rather than a portion fixed to the frame 71. 751 comes close to the original
position of the end 751. The dashed-dotted line in FIG. 3 indicates a portion of the diaphragm 72
fixed to the frame 71. The state in which the diaphragm 72 is inverted is a state shown by a twodot chain line in FIG. 3, that is, a state in which the end 751 of the bobbin 75 has moved beyond
the portion shown by a one-dot chain line. When the diaphragm 72 is thus reversed, the
diaphragm 72 does not return to its original position due to its own restoring force.
[0055]
A spring portion 723 having a ring shape at the end of the outer peripheral portion 722 opposite
to the inner peripheral portion 721 when viewed from the axial direction of the outer peripheral
portion 722 and an S-shaped cross section along the radial direction Is connected. The
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diaphragm 72 is bonded to the frame 71 at the end of the spring portion 723. In the present
embodiment, the inner circumferential portion 721, the outer circumferential portion 722, and
the spring portion 723 are formed of one thin film.
[0056]
The drive unit 73 is disposed so as to close the narrower one of the two openings of the frame
71. As shown in FIG. 3, the drive unit 73 includes a bobbin 75, a voice coil 76, and a magnetic
circuit unit 77.
[0057]
The bobbin 75 has a cylindrical shape, is connected to the outer edge of the inner circumferential
portion 721 of the diaphragm 72, and is erected toward the second space 6 from the diaphragm
72. A voice coil 76 is wound on the outside of the bobbin 75. The bobbin 75 corresponds to the
standing portion and the core portion.
[0058]
The magnetic circuit unit 77 is for applying a magnetic field to the voice coil 76, and includes a
disk-shaped magnet 771 having one surface and the other surface, a top plate 772 connected to
one surface of the magnet 771, and a magnet 771. And a yoke 773 connected to the other side.
[0059]
The yoke 773 includes a disc-shaped bottom portion 774 connected to the magnet 771 and a
cylindrical portion 775 projecting in the axial direction of the magnet 771, the top plate 772,
and the bottom portion 774 from the outer peripheral portion of the bottom portion 774 toward
the diaphragm 72. There is.
The top plate 772 and the yoke 773 are each made of a magnetic material such as iron and
correspond to a first magnetic portion and a second magnetic portion.
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[0060]
The magnet 771 and the top plate 772 are disposed inside the cylindrical portion 775, and a
cylindrical space 776 is formed between the magnet 771 and the top plate 772 and the
cylindrical portion 775. The bobbin 75 is disposed in axial alignment with the space 776, and is
fitted into the space 776.
[0061]
In the magnetic circuit portion 77, the magnet 771, the top plate 772 and the cylindrical portion
775 are positioned inside the frame 71, and the bottom portion 774 is disposed so as to close
the opening of the frame 71. Then, the bobbin 75 is fitted in the space 776, and a magnetic field
generated between the side surface of the top plate 772 and the side surface of the cylindrical
portion 775 is applied to the voice coil 76 wound around the bobbin 75. When a current is
supplied to the voice coil 76 in the state where the magnetic field is applied, the bobbin 75 is
axially displaced while being fitted in the space 776. Thereby, the diaphragm 72 vibrates to
generate a sound.
[0062]
The amount of displacement of the diaphragm 72 when the diaphragm vibrates by the driving
portion is defined by a range in which the bobbin 75 is fitted in the space 776. Specifically, in the
axial direction of the bobbin 75, the end of the bobbin 75 on the opposite side to the diaphragm
72 is located at a position farther from the diaphragm 72 than the surface of the top plate 772
on the diaphragm 72 side. The diaphragm 72 vibrates as it does.
[0063]
The sounding body 7 includes a lead pin 78 electrically connected to the voice coil 76, and the
voice coil 76 is electrically connected to the external harness by press-fitting the lead pin 78 to
the terminal 9.
[0064]
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Such a sound generator is disposed outside the vehicle, and more specifically, disposed in the
front bumper of the vehicle such that the cover 3 is positioned on the front side of the vehicle 2
relative to the case 2.
Then, by energization of the voice coil 76, the diaphragm 72 vibrates without contacting the
shielding plate 28, and a sound is generated. The sound emitted by the sounding body 7 passes
through the gap formed between the shielding plate 28 and the diaphragm 72 and the sound
passage 81, and the sound pressure is amplified by the resonance chambers 82, 83, 85, 86, and
released. The sound is emitted from the sound hole 84 and the like to the outside.
[0065]
A pressure difference is generated between the first space 5 and the second space 6 during an
airtightness check of the sound generator. Specifically, the pressure in the first space 5 is
reduced while the vent 24 is closed, or air is sent from the vent 24 to the second space 6 to
pressurize the second space 6, The pressure in the second space 6 becomes higher than the
pressure in the first space 5. As a result, the inner circumferential portion 721 of the diaphragm
72 is displaced toward the first space 5, and the diaphragm 72 is deformed so as to expand
toward the first space 5 side.
[0066]
At this time, the deformed diaphragm 72 comes in contact with the shielding plate 28, whereby
the deformation of the diaphragm 72 is limited. That is, instead of the jig for pressing the
diaphragm 72, the shielding plate 28 disposed inside the housing 1 suppresses the inversion and
the deformation of the diaphragm 72. Therefore, the airtight inspection can be performed
without using a jig for pressing the diaphragm 72.
[0067]
Further, in the present embodiment, when the diaphragm 72 is deformed as described above, the
outer edge of the inner circumferential portion 721 contacts the outer edge of the inner
circumferential portion 281. The outer edge of the inner circumferential portion 721 is
connected with the bobbin 75 and the strength is improved, so that the diaphragm 72 contacts
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the shielding plate 28 at the outer edge of the inner circumferential portion 721, thereby
suppressing the breakage of the diaphragm 72 it can.
[0068]
Further, in the present embodiment, when the diaphragm 72 is deformed as described above, the
diaphragm 72 contacts the shielding plate 28 at the outer peripheral portion 722 and the outer
edge of the inner peripheral portion 721, and the inner peripheral portion 721 and the inner
peripheral portion 281 A gap is formed between the Therefore, damage to the diaphragm 72 in
the inner circumferential portion 721 with low strength can be suppressed.
[0069]
When the diaphragm 72 is inverted due to the displacement of the inner circumferential portion
721 during the airtightness inspection as shown by the two-dot chain line in FIG. 3, when the
pressure difference between the first space 5 and the second space 6 decreases, It is difficult for
the diaphragm 72 to return to its original shape or position due to its own restoring force.
[0070]
On the other hand, in the present embodiment, as described above, the inner circumferential
portion 281 is closer to the case 4 than the partition wall 22 in the axial direction of the base
cylindrical portion 21, and the outer circumferential portion 282 has the through hole 23 It is
arranged to pass through.
Therefore, the inversion of the diaphragm 72 is suppressed, and when the pressure difference
between the first space 5 and the second space 6 decreases, the diaphragm 72 can return to its
original shape or position by its own restoring force.
[0071]
As described above, in the present embodiment, by adjusting the dimensions and the like of the
bobbin 75, it is possible to maintain the state in which the bobbin 75 is fitted into the space 776
at the time of the airtightness inspection. May be maintained in other ways. For example, as
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shown in FIG. 9, the bobbin 75 may be kept fitted in the space 776 by laminating a plate 777
made of a nonmagnetic material such as aluminum on the top plate 772.
[0072]
(Other embodiment) In addition, this invention is not limited to above-described embodiment, In
the range described in the claim, it can change suitably.
[0073]
For example, the inner circumferential portion 721 and the outer circumferential portion 722
may be configured by different members.
Further, for example, by providing a recess on the contact surface of the outer peripheral portion
282 with the outer peripheral portion 722, when the diaphragm 72 contacts the shielding plate
28, a gap is formed between the outer peripheral portion 722 and the outer peripheral portion
282. You may
[0074]
In addition, the inner circumferential portion 281, the outer circumferential portion 282, the
inner circumferential portion 721, and the outer circumferential portion 722 may be shaped
differently from the first embodiment. For example, the inner circumferential portions 281 and
721 may be cylindrical. In addition, the inner circumferential portion 281 may be shaped to be
convex toward the second space 6. Moreover, the cross section along the radial direction of the
outer peripheral part 282 and the outer peripheral part 722 may be made linear.
[0075]
1 case 5 first space 6 second space 28 shielding plate 72 diaphragm 84 sound emission hole
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