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JP2018037918

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DESCRIPTION JP2018037918
Abstract: [Problem] To provide a speaker diaphragm capable of realizing a speaker with high
sound pressure, which is excellent in waterproof performance and lighter than a conventional
speaker diaphragm impregnated with waterproof liquid. The speaker diaphragm has a multilayer
structure having a back surface layer (41) and a front surface layer (42), and the back surface
layer (41) has a waterproofing agent adsorbed to a beaten cellulose paste of about 13 μm. It is
characterized in that it is made of a material and the surface layer (42) is made of a cellulose
fiber material. [Selected figure] Figure 4
Loudspeaker diaphragm and method of manufacturing the same, acoustic apparatus using the
loudspeaker diaphragm, and mobile device
[0001]
The present invention relates to a speaker diaphragm of a speaker used in a harsh environment.
[0002]
For example, in an electric vehicle, a vehicle approach alarm device is mounted to notify a
pedestrian or the like of the approach of the vehicle.
The vehicle approach warning device comprises a speaker, a speaker box accommodating the
speaker, and an electronic circuit for driving the speaker.
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[0003]
The vehicle approach alarm system is mounted in a high temperature environment such as an
engine room in which a motor of a power source of an electric vehicle is mounted, and in a harsh
environment in contact with oil or rain water splashed up while traveling.
[0004]
Therefore, conventionally, diaphragms of resin fibers and resin diaphragms have been adopted.
[0005]
Further, Patent Document 1 discloses that the cross-sectional structure of the speaker diaphragm
has a two-layer structure or a three-layer structure to improve the sound quality of the speaker.
The stock solution of the primary paper making process is pulp, the stock solution of the
secondary paper making process is pulp, and the stock solution of the secondary paper making
process is manila hemp.
[0006]
Patent No. 3517736
[0007]
In the case of a resin diaphragm, since the sound pressure is low, it is necessary to enlarge the
magnetic circuit of the speaker in order to increase the sound pressure, which causes a new
problem that the product weight of the speaker becomes heavy.
[0008]
Therefore, it is an object of the present invention to provide a speaker diaphragm that is
excellent in waterproof performance, is lighter than conventional speaker diaphragms, and can
realize a speaker with high sound pressure.
[0009]
The speaker diaphragm of the present invention is a multilayer structure having a back surface
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layer and a front surface layer, wherein the back surface layer is made of a material in which a
waterproofing agent is adsorbed to a crushed cellulose stock, and the surface layer is a cellulose
fiber material It is characterized by being composed of
[0010]
According to this configuration, the back layer, which is the base layer, has the waterproof agent
adsorbed to the internal cellulose fibers, and the surface layer is made of a resin-like cellulose
fiber material. While being a speaker diaphragm, the waterproof performance can be remarkably
improved, and a lightweight, high sound pressure speaker can be realized.
[0011]
The external appearance perspective view of the speaker box using the speaker diaphragm of
this invention The sectional view of the speaker box The enlarged sectional view of a part of the
speaker box The sectional view of the speaker diaphragm of the embodiment of this invention
Implementation of this invention Fig. 5 is a front view of the speaker box according to the
embodiment of the present invention. Fig. 5 is a schematic view of a mobile unit equipped with
the speaker box according to the embodiment of the present invention. Process drawing of
diaphragm for diaphragm The enlarged view of the water drainage hole 7A of the round hole of
diameter 8.0 mm and the water drainage hole 7B whose hole area is slightly larger than the
water drainage hole 7A The water drainage hole of the round hole of diameter 8.0 mm 7A and an
enlarged view of a drain hole 7C whose hole area is slightly smaller than the drain hole 7A
[0012]
Hereinafter, the speaker diaphragm of the present invention will be described based on a specific
embodiment.
[0013]
FIG. 1 is an external perspective view of a speaker box 1 as an acoustic device using a speaker
diaphragm according to an embodiment of the present invention.
[0014]
The speaker box 1 has a box 2 made of resin and a lid 3 for closing the opening of the box 2.
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As shown in FIG. 2, the speaker 4 is accommodated in the box 2 to which the lid 3 is attached.
As shown in FIG. 3, an annular recess 5 is formed in the box portion 2 corresponding to the outer
peripheral portion on the back surface of the speaker 4.
An O-ring 6 is set in the recess 5, and the O-ring 6 is elastically deformed and sealed by attaching
the lid 3 to the box 2 with a screw 16.
[0015]
A grill 8 having a large number of water drainage holes 7 formed in a hexagonal shape is formed
integrally with the front opening 9 of the lid 3 in the resin-molded lid 3.
[0016]
The outer peripheral portion of the speaker diaphragm 30 of the speaker 4 is supported from the
speaker frame 32 via the edge portion 31.
The speaker diaphragm 30 has a two-layer structure having a back surface layer 41 and a front
surface layer 42 as shown in FIG. 4, and the back surface layer 41 is a stock having a fiber
diameter of about 13 μm with 500 to 700 cc of Canadian freeness. It is made of a material in
which a waterproofing agent and a resin material are adsorbed to a certain wood or bamboo
cellulose.
The surface layer 42 is made of a cellulose fiber material having an average fiber diameter of 10
nm to 100 nm.
[0017]
The conventional paper diaphragm is formed by allowing the surface of a resin diluted with
methyl ethyl ketone (MEK) to be adsorbed on the surface after the pulp is beaten and molded,
and the organic solvent is dried and evaporated. In this embodiment, At the same time as in the
pulp beating process, a water repellent emulsion (wax) or a resin emulsion (wax) having good
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water dispersion is paper-made, and water is evaporated and formed by heat of press molding.
As a result, the wax melts and spreads to the entangled portion of the pulp, so that the adhesive
effect by the resin and reinforcement of the cellulose hydrogen bond portion by the water
repellency of the material are made.
There is also a water repellent material inside the speaker diaphragm 30 and a water repellent
material outside the speaker diaphragm 30, and a strong bond is formed by H-H hydrogen bond
by water evaporation.
[0018]
FIG. 5 shows a front view of the speaker box mounting attitude.
The arrow A direction is the upper direction of the mounting attitude.
[0019]
The grille 8 has a plurality of drainage holes 7 arranged at regular intervals and at regular
intervals.
One shape of the drainage hole 7 is a hexagon having a hole area equivalent to that of a round
hole having a diameter of 6.0 mm to 9.0 mm, and an annular frame 10 for partitioning between
the drainage holes 7 as shown by imaginary lines. It is composed of a series.
The annular frame 10 has a side 11 and a corner 12 to which the side 11 and the side 11 are
connected, and when the front opening 9 is circular, at the lowermost end of the front opening 9
at the side 11 An annular frame 10 is connected to the inner peripheral surface of the front
opening 9.
[0020]
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FIG. 6 shows a mobile device in which the speaker box 1 is mounted as a vehicle approach
warning device.
[0021]
Note that the electronic device (not shown) that generates the signal supplied to the speaker 4
can be implemented regardless of whether it is housed in the box 2 or not housed in the box 2.
[0022]
Although the mobile device 13 is described as an electric vehicle, the mobile device 13 may be a
vehicle driven by an engine or a hybrid type vehicle equipped with an engine and a motor.
Furthermore, the mobile device 13 is not limited to a car.
For example, a motorcycle, an electric bicycle, a forklift, etc. may be used.
[0023]
The speaker box 1 is attached to a motor room 15 in which a motor 14 which is a power source
of the mobile device 13 is installed.
[0024]
FIG. 7 shows Comparative Example 1.
The comparative example 1 is the same as FIG. 5 except that one shape of the drain hole 7A is a
round hole.
[0025]
The embodiment of FIG. 5 and the speaker box 1 of Comparative Example 1 of FIG. 7 were
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mounted on a mobile device 13 and a verification experiment was conducted. The water draining
hole 7 of the embodiment was a hexagon having a hole area equivalent to that of a round hole
having a diameter of 8.0 mm, and the water draining hole 7A of Comparative Example 1 was a
circular hole having a diameter of 8.0 mm.
[0026]
In addition, with the hexagonal water removal hole 7 of the hole area equivalent to the round
hole of diameter 8.0 mm of the product and the water removal hole 7B shown in FIG. There is a
hexagon whose shape is slightly larger than the hole area of the hole 7A or slightly smaller like
the drain hole 7C shown in FIG. Thus, the apexes T of the hexagonal water drainage holes 7B and
7C of the embodiment are located outside the water drainage hole 7A (round hole of diameter
8.0 mm) of Comparative Example 1, and the hexagonal water drainage holes A part of the side
OS of 7B and 7C is a hexagon positioned inside the water draining hole 7A. Here, as a specific
example, it experimented by making one side of the hexagon of draining hole 7 into 4.40 mm.
[0027]
As a result, good sound emission characteristics were obtained for both the embodiment product
and the comparative example 1. With regard to the drainage performance, even in the case
where rainwater did not sufficiently flow out in Comparative Example 1, good drainage
performance was confirmed in the embodiment product. This is considered to be the fact that the
drainage performance is deteriorated due to the surface tension due to the rain water generated
around the drainage hole 7A in the case of the drainage hole 7A whose shape is a round hole. On
the other hand, in the embodiment, since the shape of the water draining hole 7 is hexagonal, the
magnitude of the surface tension due to the rain water generated around the water draining hole
7 is smaller than that of the round hole of Comparative Example 1. It is thought that it is for.
[0028]
With regard to the practical product, when the water removal performance of the water removal
hole 7 of a hexagonal shape (3.30 mm on a side) in the case of a hole area equivalent to a round
hole having a diameter of 6.0 mm is confirmed, Good drainage performance was confirmed.
When the size of the water removal hole 7 was made into the hole area equivalent to the round
hole less than diameter 6.0 mm, the deterioration of the water removal performance was
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confirmed. When the size of the drainage hole 7 is equal to that of a circular hole with a diameter
of 9.0 mm, the hexagonal (one side 4.95 mm) drainage hole 7 is a hole with a diameter of 8.0
mm. The same performance as in the case of the area was confirmed, but when the size of the
water drainage hole 7 was made equal to the area of the round hole larger than the diameter of
9.0 mm, the strength decrease of the grill 8 was confirmed.
[0029]
FIG. 8 shows Comparative Example 2. In Comparative Example 2, only the connection state of the
grille 8 to the inner peripheral surface of the front opening 9 of the annular frame 10 at the
lowermost end of the front opening 9 of the lid 3 differs from that of FIG. It is the same. In
Comparative Example 2, the inner peripheral surface of the lower end of the front opening 9 is
connected to the corner 12 of the annular frame 10. In this case, since the area B of the water
draining hole 7 at the lowermost end of the front opening 9 is smaller than in the case of the
embodiment, the water drainage performance is deteriorated compared to the embodiment.
[0030]
The speaker diaphragm 30 having a two-layer structure can be manufactured by the steps shown
in FIGS. 9 (a) to 9 (f).
[0031]
In the process of (a), the primary papermaking mesh 52 is fixed to the sieving tank 51, and the
primary stock solution 53 is charged into the sieving tank 51.
The fiber diameter of the wood or bamboo pulp is about 13 μm, and the fibers are solidified to
be loosened by beating to make a primary stock solution 53. In the beating, a waterproofing
agent of at least one of a fluorine emulsion and a paraffinic emulsion is added simultaneously
with the pulp to be beaten while adsorbing the waterproofing agent to the pulp. A resin emulsion
may be added to the beating machine to further improve the waterproofness. The mixing ratio of
the waterproofing agent to the stock was 5 to 10% by weight. As a waterproofing agent which
can be used besides the above, a silicone / silane type thing can be used.
[0032]
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The resin emulsion is epoxy, acrylic, ester, or synthetic resin, for example, vinyl acetate polymer,
acrylic acid ester copolymerization, ethylene / vinyl acetate / acrylic acid copolymerization.
[0033]
In the step (b), the back layer 41 of the primary paper is deposited on the primary paper mesh
52 by draining from the bottom of the processing tank 51.
Further, the paper making table 56 to which the secondary paper mesh 55 is fixed is disposed in
the paper processing tank 51. In the conventional method, 100% by weight of the first base layer
is deposited, whereas in this embodiment, the back layer 41 which is the first base layer is 85 to
99% by weight.
[0034]
In the step of (c), the back layer 41 deposited on the primary paper mesh 52 is lowered after
making the paper table 56 up and adsorbed through the secondary paper mesh 55, and then
raised to make the back layer 41 primary. Peel off from the paper mesh 52 and lift it. This
adsorbed state is maintained until the step (e) is completed.
[0035]
In the step of (d), the back layer 41 of the paper making table 56 and the secondary paper mesh
55 are lowered into the liquid of the secondary stock solution 58 in the separation tank 57 and
drained above the paper making table 56. Deposit over time. In addition, this secondary forming
is carried out in a wet state after semi-drying of the back surface layer 41 obtained by the
primary forming. The wet state after semi-drying had a water content of 5 to 30% by weight.
[0036]
The secondary stock solution 58 is composed only of water and a cellulose fiber material having
an average fiber diameter of 10 nm to 100 nm. The Young's modulus of the cellulose fiber
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material used was about 5000 MPa or more.
[0037]
The Young's modulus of ordinary paper pulp is in the range of 700 to 2000 MPa, and here, it is
assumed that a Young's modulus of 2.5 times or more is appropriate. Strictly speaking, the
Young's modulus increases at L / D (fiber length / fiber diameter). Usually, the pulp is L = 2 mm,
D = 13 × e-6 m (μ = 10 e-6), nanofiber L = 0.3 mm, D = 100 × e-9 m (nano = 10 e-9 m),
(usually pulp L / D) / (nanofiber L / D) = 6.7 times, 700 MPa × 6.7 = 4666 MPa, which is about
5000 MPa or more. Specific examples of the use of cellulose nanofibers were fibers obtained by
dispersing nata de coco in water, beaten, bamboo-made fibers, and wood-made fibers.
[0038]
In the step (e), the fibers of the cellulose fiber material of the secondary paper stock solution 58
are entangled with the back layer 41 to complete the deposition of the surface layer 42. The
deposition time in the step (d) was adjusted so that the thickness of the surface layer 42 was 1/4
to 1/10 of the thickness of the back surface layer 41.
[0039]
In addition, about the point which made thickness of the surface layer 42 1/4 to 1/10 of the
thickness of the back surface layer 41, it is based on the following reason. Since the theoretical
specific gravity of cellulose is about 1.2 and the paper pressure is lightened to 0.5 to increase the
sound pressure, increasing the thickness more than necessary lowers the sound pressure. So, in
this embodiment, since the main purpose of the surface layer 42 is reliability that can withstand
severe conditions, it is sufficient that only 1⁄4 to 1/10 of the thickness of the back surface layer
41.
[0040]
In the step of (f), the surface layer 42 and the back surface layer 41 which are integrated in
multiple layers are transferred onto the wire mesh 61 fixed to the mold 60, and are superposed
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on the mold 62 to be heated and pressed. Do. Alternatively, non-press molding is performed
using warm air.
[0041]
In the speaker diaphragm 30 created in such a process, the raw material of the back layer 41 of
the base layer is pulp, but fluorine and a resin are coated, and the surface layer 42 of the speaker
surface has an average fiber diameter of 10 nm to 100 nm Because it is made of cellulose fiber
material, it weighs less than conventional resin diaphragms in which a paper diaphragm is
impregnated with a waterproof liquid, and has low reliability in environments where chemicals
are applied under high temperature environments such as engine compartments The reliability
can be enhanced as compared to the conventional pulp diaphragm. Moreover, high sound
pressure can be realized without enlarging the magnetic circuit of the speaker, and the vehicle
approach alarm device equipped with the speaker 4 using this speaker diaphragm 30 is NHTSA
(National Highway Traffic Safety) established by the US Department of Transportation.
Administration: Sound pressure, water resistance, and chemical resistance that meet regulatory
standards were obtained.
[0042]
In the embodiment, since the weight can be reduced, the sound pressure can be increased by 1 to
1.5 dB as compared with the conventional case.
[0043]
Note that the acoustic device using the speaker diaphragm 30 is not limited to the vehicle
approach warning device.
For example, it may be used for a pseudo engine sound generator or an active noise reduction
device.
[0044]
Also, the installation location of the speakers is not limited to the motor room 15 and the engine
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room. For example, it may be installed in the housing of the door mirror, in the bumper, or in the
trunk room.
[0045]
In the multi-layered structure having the back surface layer and the front surface layer described
above, the back surface layer is made of a material in which the waterproofing agent and the
resin material are adsorbed to the beaten cellulose stock, and the front surface layer is made of
cellulose fiber material. By combining a speaker using a board with a speaker box having a grill
with a large number of hexagonal water drainage holes formed in the lid described above, each
effect can be exhibited for waterproofness, so that The synergetic effect can realize extremely
high waterproofness.
[0046]
Furthermore, with regard to the sound pressure level, the synergistic effect is achieved by the
combination of a lightweight speaker diaphragm using a cellulose stock as a base material and a
grille having a large opening ratio and a large number of water drainage holes. Sound pressure
levels can be significantly improved.
[0047]
Therefore, the speaker diaphragm of the present invention can secure the required sound
pressure level even in a bad environment such as a motor room or an engine room of a car, and
is also remarkable in water resistance and oil resistance such as oil. Since the effect can be
exhibited, high performance can be realized also in the interior of a motor room or an engine
room of a car, which can not be realized by the conventional speaker diaphragm.
[0048]
In the above embodiment, the second surface layer 42 is made of a single cellulose fiber material,
but it is also possible to mix lighter and hard fibers such as carbon fibers and carbon nanotubes
in the surface layer 42.
In the surface layer 42, at least one of carbon fibers, carbon nanotubes, and chitin fibers
contained in shells of crabs and shrimps can be mixed.
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[0049]
The speaker diaphragm of the present invention contributes to the improvement of the reliability
over time of various devices used in a severe environment and the realization of high sound
pressure.
[0050]
DESCRIPTION OF SYMBOLS 1 speaker box 2 box part 3 cover part 4 speaker 5 recessed part 6 O
ring 7 drain hole 8 grille 9 front opening A mounting posture upper direction 10 annular frame
11 side 12 corner part 13 moving body device 14 motor 15 motor room 16 Screws 30
Loudspeaker diaphragms 31 Edges 32 Speaker frames 41 Backing layers 42 Surface layers 51
Whiskers 52 Primary paper net 53 Primary stock solution 55 Secondary paper net 56 Paper
table 57 Blanks 58 Secondary stock solution 60 Mold 61 Wire mesh 62 Mold
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