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JP2009017524

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DESCRIPTION JP2009017524
An object of the present invention is to secure a flat characteristic in which a sound pressure dip
is suppressed from a mid range to a high range, while obtaining natural sound and high
appearance quality by natural wood. SOLUTION: A magnetic circuit 9, a frame 13 for housing the
magnetic circuit 9, a central vibrating portion 19 having a substantially dome-shaped cross
section, and an outer periphery having a substantially dome-shaped cross section which is
formed over the entire outer circumference of the central vibrating portion 19. A first plate
including a vibrating plate 21 having a vibrating portion 21 and an end of an edge portion 21 b
on the outer peripheral side of the outer circumferential vibrating portion 21 fixed to the frame
13, the vibrating plate 11 including the entire central vibrating portion 19 A first thickness
region is formed by forming a second thickness region D-1 including a thickness region D and an
edge portion 21b of the outer peripheral vibration portion 21 and having a thickness smaller
than that of the first thickness region D. D has a laminated structure of a wood sheet 23 made of
natural wood, a sheet 24 of paper, and a synthetic resin film 25, and a second thickness region
D- 1 has a single layer structure of the synthetic resin film 25. [Selected figure] Figure 1
Electro-acoustic transducer and diaphragm
[0001]
The present invention relates to a full band type electroacoustic transducer and a diaphragm
suitable for a headphone or the like.
[0002]
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1
In recent years, one using natural wood as a material of a diaphragm is known.
The reason why wood is used as the material of the diaphragm is, for example,
comprehensiveness such as speed of sound faster than paper or resin, rigidity, large Young's
modulus, large internal loss compared to metal, etc., small density (light) In addition to having
excellent characteristics, the natural sound that a tree originally has is obtained. In addition, it
can be improved in appearance and has an effect of giving high quality, so it is attracting
attention as one of diaphragm materials.
[0003]
In the case of reproducing the sound over a wide band from the low sound range to the high
sound range, for example, as shown in FIG. 6, the diaphragm 111 housed in the frame 113 is
used. The diaphragm 111 is formed of a dome-shaped central vibrating portion 101 and an outer
peripheral vibrating portion 103 disposed continuously on the outer periphery of the central
vibrating portion 101. The combination of the central vibration portion 101 and the outer
peripheral vibration portion 103 covers the entire range from the low tone range to the high
tone range. A general frequency response at this time is shown in FIG.
[0004]
The frequency response shown in FIG. 7 is obtained by automatically measuring the sound
pressure level at a point of 1 m on the reference axis so as to form a continuous curve
corresponding to the frequency. In the frequency response, the frequency range to be
reproduced is called an effective frequency band FB. The frequency of the low band reproduction
limit L and the high band reproduction limit H in which the output sound pressure level is
lowered by -10 dB in the range of the low band resonance frequency fo indicating the low band
limit and the high band resonance frequency fh indicating the high band limit A range is
indicated. The characteristic is divided into a flat characteristic of the piston vibration area PB
and a divided vibration area DB comprised of a complex vibration area of the diaphragm. In the
whole band type, the whole of the effective frequency band FB from the low band reproduction
limit L to the high band reproduction limit H is used.
[0005]
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2
In this case, the frequency characteristic of the output sound pressure is substantially flat in the
low frequency region because the piston vibration region PB vibrates with the edge portion 105
as a fulcrum. In the mid-tone range, influences appear at the edge portion 105 around the
diaphragm and at the connecting portion that is the boundary between the central vibrating
portion 101 and the outer circumferential vibrating portion 103, and due to resonance, the
opposite phases as shown by arrows a and b in FIG. Vibration occurs, the sounds cancel each
other out, and a dip called medium sound valley d occurs. In the high frequency range, the
diaphragm can not vibrate in the piston, and a divided vibration area DB in which each portion of
the diaphragm vibrates in a complicated manner causes many peak dips to occur. At the high
frequency limit, high frequency resonance occurs mainly at the frequency determined by the
stiffness and mass of the central part of the diaphragm and the mass of the voice coil 107, and
the peak at this high frequency limit frequency (high frequency reproduction limit H) is finally
Sound pressure drops sharply.
[0006]
As a means for solving these problems, for example, as shown in Patent Document 1, a
diaphragm material having an acoustic loss characteristic of 0.02 or more is used to expand a
high frequency range, and a division vibration of the diaphragm is used to be 20 kHz or more.
There are known means for enabling regeneration of frequency bands. Alternatively, as shown in
Patent Document 2, there is known a means for suppressing the anti-phase vibration of the edge
portion in the middle tone range to reduce the dip d by using an elastic member to fix and
support the edge portion. JP, 2002-152885, A JP, 2005-204215, A
[0007]
As described above, in the case of the full band type diaphragm, in particular, problems occur in
the mid range to the high range. However, in the means of Patent Document 1 for improving the
mid-range, it is necessary to use a special material having an acoustic loss characteristic of 0.02
or more, and the problem that can not be greatly improved in improving the range other than the
high-range At the same time, no consideration is given to improving the appearance quality.
[0008]
In the means of Patent Document 2 in which the edge portion is supported by the elastic
member, while the vibration characteristics of the edge portion can be improved, the
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3
improvement of the reverse phase occurring at the boundary between the central vibration
portion and the outer peripheral vibration portion is not achieved. No consideration is given to
improving the appearance quality as well as the problems from the tone range to the high tone
range.
[0009]
Therefore, in the present invention, it is possible to obtain the natural sounding that trees
originally have and to improve the sound quality of the range from the middle range to the high
range, and to provide an electro-acoustic transducer with excellent appearance quality and The
purpose is to provide a diaphragm.
[0010]
In order to achieve the object, according to an aspect of the present invention, a magnetic circuit,
a frame for containing the magnetic circuit, a central vibration portion having a substantially
dome-shaped cross section, and a cross section that is formed over the entire outer
circumference of the central vibration portion A diaphragm having a substantially dome-shaped
outer peripheral vibration portion, an end portion of an edge portion on the outer peripheral side
of the outer peripheral vibration portion being fixed to the frame, the vibration plate including
the entire central vibration portion A wooden sheet consisting of a thick area and a second
thickness area including an edge portion of the outer peripheral vibration part and having a
thickness smaller than that of the first thickness area, the first thickness area being made of
natural wood An electro-acoustic transducer is provided, which has a laminated structure of a
sheet of paper, a sheet of resin and a resin film, and the second thickness region has a singlelayer structure of a synthetic resin film.
[0011]
According to another aspect of the present invention, a magnetic circuit, a frame for containing
the magnetic circuit, a central vibration portion having a substantially dome-shaped cross
section, and a substantially dome-shaped cross section are formed over the entire periphery of
the central vibration portion. A diaphragm having an outer peripheral vibration portion, and an
end of an edge portion on the outer peripheral side of the outer peripheral vibration portion
fixed to the frame A first thickness region including a predetermined region contiguous to the
portion and a second thickness region which is a portion other than the predetermined region in
the outer peripheral vibration portion and whose thickness is thinner than the first thickness
region is formed. An electro-acoustic transducer in which the first plate thickness region has a
laminated structure of a wood sheet made of natural wood, a sheet of paper and a resin film, and
the second plate thickness region has a single layer structure of a synthetic resin film; Provided.
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[0012]
According to another aspect of the present invention, a magnetic circuit, a frame for containing
the magnetic circuit, a central vibration portion having a substantially dome-shaped cross
section, and a substantially dome-shaped cross section are formed over the entire periphery of
the central vibration portion. A diaphragm having an outer peripheral vibrating portion, an end
of an edge portion on the outer peripheral side of the outer peripheral vibrating portion being
fixed to the frame, the diaphragm having a first thickness region including a central portion of
the central vibrating portion A central vibration located between a second thickness region
including the edge portion of the outer peripheral vibration portion and having a thickness
smaller than the first thickness region, and between the first thickness region and the second
thickness region An electro-acoustic transducer is provided, which includes a predetermined area
continuous with a connecting portion with an outer peripheral vibration portion in a portion and
forming a third thickness region which is thicker than a first thickness region.
[0013]
According to another aspect of the present invention, a magnetic circuit, a frame for containing
the magnetic circuit, a central vibration portion having a substantially dome-shaped cross
section, and a substantially dome-shaped cross section are formed over the entire periphery of
the central vibration portion. A diaphragm having an outer peripheral vibrating portion, an end
of an edge portion on the outer peripheral side of the outer peripheral vibrating portion being
fixed to the frame, the diaphragm having a first thickness region including a central portion of
the central vibrating portion An outer peripheral vibration positioned between a second
thickness region including the edge portion of the outer peripheral vibration portion and having
a thickness smaller than the first thickness region, and between the first thickness region and the
second thickness region An electro-acoustic transducer is provided, which includes a
predetermined area connected to a connection portion with a central vibration portion in a
portion to form a third thickness region which is thicker than a first thickness region.
[0014]
According to another aspect of the present invention, a magnetic circuit, a frame for containing
the magnetic circuit, a central vibration portion having a substantially dome-shaped cross
section, and a substantially dome-shaped cross section are formed over the entire periphery of
the central vibration portion. A diaphragm having an outer peripheral vibrating portion, an end
of an edge portion on the outer peripheral side of the outer peripheral vibrating portion being
fixed to the frame, the diaphragm having a first thickness region including a central portion of
the central vibrating portion A center located between a first thickness area and a second
thickness area and a second thickness area including an edge portion of the outer peripheral
vibration part and having a thickness smaller than the first thickness area A third plate thickness
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region including a predetermined region continuous with the connection portion with the outer
peripheral vibration portion in the vibration portion and a predetermined region continuous with
the connection portion with the central vibration portion in the outer peripheral vibration portion
And providing an electro-acoustic transducer.
[0015]
According to another aspect of the present invention, there is provided a diaphragm including: a
central vibrating portion having a substantially dome-shaped cross section; and an outer
peripheral vibrating portion having a substantially dome-shaped cross section which is formed
over the entire outer periphery of the central vibrating portion. The plate is formed with a first
thickness region including the entire central vibration portion and a second thickness region
including an edge portion of the outer peripheral vibration portion and having a thickness
smaller than the first thickness region; A diaphragm is provided in which the first thickness
region has a laminated structure of a wood sheet made of natural wood, a sheet of paper, and a
resin film, and the second thickness region has a single layer structure of a synthetic resin film. .
[0016]
According to another aspect of the present invention, there is provided a diaphragm including: a
central vibrating portion having a substantially dome-shaped cross section; and an outer
peripheral vibrating portion having a substantially dome-shaped cross section which is formed
over the entire outer periphery of the central vibrating portion. A first plate thickness area
including a predetermined area in which the plate is continuous with the entire central vibration
area and a connection portion with the central vibration area in the outer peripheral vibration
area, and a portion other than the predetermined area in the outer peripheral vibration area A
second thickness region thinner than the thickness region, and the first thickness region has a
laminated structure of a wood sheet made of natural wood, a sheet of paper, and a resin film; A
diaphragm is provided in which the thickness region is a single-layer structure of a synthetic
resin film.
[0017]
According to another aspect of the present invention, there is provided a diaphragm including: a
central vibrating portion having a substantially dome-shaped cross section; and an outer
peripheral vibrating portion having a substantially dome-shaped cross section which is formed
over the entire outer periphery of the central vibrating portion. The plate includes a first
thickness region including a central portion of the central vibration portion, a second thickness
region including a edge portion of the outer peripheral vibration portion and a thickness smaller
than the first thickness region, and A third plate thickness including a predetermined region
located between the plate thickness region and the second plate thickness region and connected
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6
to the connection portion with the outer peripheral vibration portion in the central vibration
portion, and having a plate thickness thicker than the first plate thickness region A diaphragm is
provided which forms an area.
[0018]
According to another aspect of the present invention, there is provided a diaphragm including: a
central vibrating portion having a substantially dome-shaped cross section; and an outer
peripheral vibrating portion having a substantially dome-shaped cross section which is formed
over the entire outer periphery of the central vibrating portion. The plate includes a first
thickness region including a central portion of the central vibration portion and an edge portion
of the outer peripheral vibration portion, and a second thickness region having a thickness
smaller than the first thickness region, and A third plate including a predetermined region
located between the second thickness region and the second thickness region and connected to
the connection portion with the central vibration portion in the outer peripheral vibration
portion, the third plate being thicker than the first thickness region A diaphragm is provided
which forms a thick region.
[0019]
According to another aspect of the present invention, there is provided a diaphragm including: a
central vibrating portion having a substantially dome-shaped cross section; and an outer
peripheral vibrating portion having a substantially dome-shaped cross section which is formed
over the entire outer periphery of the central vibrating portion. The plate includes a first
thickness region including a central portion of the central vibration portion, a second thickness
region including a edge portion of the outer peripheral vibration portion and a thickness smaller
than the first thickness region, and A predetermined area located between the thickness area and
the second thickness area and including a predetermined area continuous with the connection
portion with the outer peripheral vibration portion in the central vibration portion and a
predetermined area continuous with the connection portion with the central vibration portion in
the outer peripheral vibration portion A diaphragm is provided which has a third thickness
region which is thicker than the first thickness region.
[0020]
According to the present invention, a laminated structure in which a wood sheet made of natural
wood, a sheet of paper having a property close to wood, and a resin film are combined, the
natural sound that wood originally has is obtained and the wood grain of wood Appearance
improves by tone and becomes very desirable in terms of appearance quality.
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7
[0021]
On the other hand, the diaphragm becomes a piston vibration area that vibrates integrally with
the thin second thickness area made as a fulcrum as a fulcrum, and can make the frequency
characteristic of the output sound pressure flat.
Moreover, the thick plate thickness shape of the connection portion including the central
vibration portion and the outer peripheral vibration portion can increase the rigidity of the
connection portion and expand the flat band, and further suppress the vibration of the opposite
phase due to resonance to a small level. It is possible to improve the dip.
At the same time, even in the high-pitched range, the complex division vibration of the
diaphragm is suppressed to a small level by the diaphragm consisting of a laminated structure of
a wood sheet with high surface propagation speed (sound velocity) and a sheet resin film of
paper, thereby improving peak dip. Can.
[0022]
Next, embodiments of the present invention will be described with reference to the drawings.
In the following description of the drawings, the same or similar parts are denoted by the same
or similar reference numerals.
The embodiments described below illustrate apparatuses and methods for embodying the
technical idea of the present invention, and the technical idea of the present invention is for the
structure, arrangement, and the like of components to be described below. It does not identify.
[0023]
As shown in FIG. 1, the electroacoustic transducer 1 according to the embodiment of the present
invention is located above the magnetic circuit 9 and the magnetic circuit 9 formed of the
magnetic pole (yoke) 3, the central pole 5 and the magnet 7. And a diaphragm 11 disposed.
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8
[0024]
The magnetic pole 3, the central pole 5 and the magnet 7 constituting the magnetic circuit 9 are
engaged with the columnar projections 17 rising from the recess 15 of the frame 13 and have a
predetermined gap G between the magnetic pole 3 and the central pole 5 It is housed in the
recess 15.
[0025]
The diaphragm 11 has a central vibrating portion 19 having a dome-shaped cross section and an
outer peripheral vibrating portion 21 having a dome-shaped cross section formed on the outer
periphery of the central vibrating portion 19. It has a shape which continues to the outer
peripheral vibration part 21 continuously and integrally.
On the back surface of the connecting portion 20, the voice coil 22 is bonded and supported via
an adhesive while being centered by dropping into the gap G.
On the other hand, the outer peripheral vibration portion 21 is composed of a plate portion 21a
having the same thickness as that of the central vibration portion 19 and an edge portion 21b
having a smaller thickness than that, and the peripheral edge P of the edge portion 21b is on the
outer peripheral edge of the frame 13. It is a support structure adhered by an adhesive means or
the like.
[0026]
The diaphragm 11 shown in FIG. 1 is defined to include a first thickness area D defined to
include the entire central vibrating portion 19 and the connecting portion 20, and an edge
portion 21b of the outer peripheral vibrating portion 21. A plate thickness is constituted by a
second plate thickness region D-1 thinner than the first plate thickness region D.
[0027]
The first thickness region D has a laminated structure in which a wood sheet 23 made of natural
wood, a sheet 24 of paper, and a synthetic resin film 25 are superimposed.
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9
The outer diameter of the first plate thickness area D is as small as possible in terms of weight
control, has a size that gives sufficient rigidity to the connecting part, and does not overlap the
corrugation area usually formed in the outer peripheral vibration part From the upper and lower
limits are defined.
In the middle tone range, the vibration due to the opposite phase is suppressed to a small value,
and in the high tone range, the thickness α is set to suppress a complicated divided vibration.
[0028]
Since it is important that the diaphragm used for the headphone and earphone be lightweight,
the thickness α is, for example, about 5 μm to 250 μm, more preferably about 20 μm to 100
μm, from the viewpoint of weight control and stiffness assurance. It can be done.
[0029]
For example, as shown in FIG. 2, the wooden sheet 23 is made by applying a so-called wig (rotary
slice) to the cutting blade 29 while rotating a log-shaped wood 27 as shown by an arrow. .
It can also be produced by slicing from board material and grain wood.
The lower limit of thinning depends on the size of the wood conduits and wood cells.
[0030]
Materials of natural wood to be used include materials which are easy to process in addition to
conditions such as uniform and small conduit density, short conduit, long wood fiber, slow
growth of summer season, and the like.
In addition, in consideration of each condition of acoustic characteristics, for example, high
sound velocity propagation speed and moderately high internal loss, it is optimal to satisfy
anisotropy and non-uniformity together with low density and high elastic modulus. For example,
as illustrated in FIG. 5, a wide range of wood is used, from hardwoods to conifers.
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10
As the wood satisfying the above conditions, it is desirable to use a broadleaf tree, and it is
particularly preferable to use a hippopotamus such as a dovetail tree which is closed in a cold
place with a porous material and at a high altitude.
Alternatively, it is preferable to use a maple wood such as a cypress wood or a maple tree such as
a maple wood and a maple wood such as a hard maple.
[0031]
It is difficult to implement each condition of acoustic characteristics with natural wood alone, and
in consideration of formability and shape stability, in this embodiment, a laminated structure in
which sheets of paper 24 similar to the material of wood are superposed and It is preferable to
do.
[0032]
High heat resistance and high mechanical strength such as tension are required for the sheet 24
of paper, and a non-woven fabric of vinylon and pulp mixed system is used, and as a natural
material, it is a means using paper making such as Gumpi and Kozo.
[0033]
On the other hand, the second thickness region D-1 has a single-layer structure made of the
synthetic resin film 25.
The material used is polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether
imide (PEI), polyimide (PI), etc., and is set to a thickness β that provides a piston vibration area
where the entire diaphragm 11 vibrates integrally. It is done.
[0034]
Although the thickness β is not particularly limited, for example, when it is used for a
headphone or earphone, the thickness range can be defined from the viewpoint of weight control
and stiffness ensuring, for example, about 4 μm to 40 μm, and further about 6 μm to 25 μm.
It is preferable to
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11
[0035]
In addition, in consideration of suppression of anti-phase vibration due to resonance and
complicated division vibration of the diaphragm in the high range, the ratio of thickness α to
thickness β is, for example, about 1: 1 of α: β to 25: It is preferable to set it to about 1 and
further about 4: 1 to about 15: 1.
By setting the thickness ratio in the above-mentioned range, it is possible to further suppress the
occurrence of dip and to obtain an acoustic diaphragm in which the range from the middle range
to the high range is improved.
[0036]
In order to make the diaphragm 11 provided with the first thickness region D and the second
thickness region D-1 configured as described above, for example, as shown in FIG. A paper sheet
24 and a synthetic resin film 25 are laminated by bonding means such as resin impregnation or
an adhesive to form a three-layer laminated sheet.
The laminated sheet is heat-pressed by a male and female press (not shown) equipped with a
heating means such as a heater to obtain the diaphragm 11 as shown in FIG. 3 (b). Be
The diaphragm 11 shown in FIG. 3B has a laminated structure of three layers superimposed over
the entire region.
For the thin second plate thickness area D-1 defined to include the edge portion 21b, for
example, the grinding paper is pressed and the wood sheet 23 and the paper sheet 24 are
simultaneously ground and removed as shown in FIG. As shown in), it is possible to make a single
layer structure by only the synthetic resin film 25.
[0037]
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12
The laminated sheet obtained by pressing the wooden sheet 23 and the sheet 24 of paper is
punched into the size of the first plate thickness area D, and the laminated sheet is adhered onto
the synthetic resin film 25 formed in advance. It is also possible to provide the 2nd board
thickness field D-1 by pasting together using.
In this case, the first plate thickness area D has a laminated structure including the wood sheet
23, the sheet 24 of paper, and the synthetic resin film 25.
[0038]
As shown in FIGS. 4 (a) and 4 (b), by removing the synthetic resin film 25 of the central vibrating
portion 19 over the constant region L, a sheet of wood 23 and a sheet of paper are provided at
the central portion of the central vibrating portion 19. A first plate thickness region D1 having a
two-layer laminated structure of 24 may be formed.
If the diaphragm diameter is large as the constant area L, for example, 30 mm or more, the
contribution of the resin film of the central vibration portion to the entire weight also increases,
so it is desirable to remove from the viewpoint of weight control. . The maximum diameter of the
constant region L may be a size that allows a glue margin at the time of bonding with the
laminated sheet to be taken at the rising portion from the connection portion to the central
vibration portion side.
[0039]
In the example shown in FIG. 4, the second thickness region D <b> 1-1 to be the edge portion 21
b has a single-layer structure made of the synthetic resin film 25. The diaphragm 11 of FIG. 4
preferably further includes a third thickness region D1-2 including the connecting portion 20.
[0040]
The third thickness region D1-2 is located between the first thickness region D1 and the second
thickness region D1-1, and the first thickness region D1 (having a thickness of α1 And the
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13
second plate thickness area D1-1 (the thickness is assumed to be .beta.1). The third thickness
region D1-2 is set to, for example, a thickness γ1 which is a piston vibration region in which the
entire vibration plate 11 vibrates constantly.
[0041]
Although the thickness γ1 is not particularly limited, for example, when it is used for a
headphone or earphone, it can be preferably, for example, about 20 μm to about 100 μm in
consideration of required weight, stiffness and the like. In addition, in consideration of
suppression of anti-phase vibration due to resonance and complicated division vibration of the
diaphragm in the high range, the ratio of thickness α1, thickness β1 and thickness γ1 is, for
example, 1: 1 of α1: β1: γ1: It may be about 2 to 25: 1: 35, and further about 4: 1: 6 to 15: 1:
20. By changing the thickness ratio, for example, to the above-mentioned range, it is possible to
further suppress the occurrence of dip, and to obtain an acoustic diaphragm in which the range
from the middle range to the high range is improved.
[0042]
As a result, in the example shown in FIG. 4, the first plate thickness area D1 is a two-layer
laminated structure of the wooden sheet 23 and the sheet 24 of paper, and the second sheet
thickness area D1-1 is a single unit of the synthetic resin film 25. The diaphragm 11 is formed to
have a layered structure, and the third plate thickness region D1-2 has a three-layer laminated
structure of the wooden sheet 23, the sheet 24 of paper, and the synthetic resin film 25.
[0043]
In FIG. 4, a predetermined region (the outer peripheral portion of central vibrating portion 19)
and the outer peripheral vibrating portion 21 connected to the connecting portion of central
vibrating portion 19 with outer peripheral vibrating portion 21 as second plate thickness region
D1-2. It is defined to include a predetermined region (inner peripheral portion of the outer
peripheral vibrating portion 21) connected to the connecting portion with the central vibrating
portion 19.
[0044]
However, the diaphragm in which the second plate thickness region D1-2 is defined to include
one of the connecting portion 20 and the outer peripheral portion of the central vibrating
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portion 19, that is, the thicknesses of the outer peripheral portion of the central vibrating portion
19 and the connecting portion 20 In particular, a diaphragm made thicker than other regions can
also be suitably used.
Alternatively, a diaphragm in which the second plate thickness area D1-2 is defined to include
the connecting portion 20 and the inner peripheral portion of the outer peripheral vibrating
portion 21, that is, the width of L is increased and the central vibrating portion 19 is
substantially a wooden sheet A diaphragm or the like configured only with the sheet 23 and the
paper sheet 24 can also be suitably used with the same effects as in FIGS. 1 and 4.
[0045]
According to the electro-acoustic transducer 1 configured in this manner, the natural sound that
the wood originally has is obtained by the laminated structure in which the wood sheet 23 made
of natural wood and the paper sheet 24 having a property close to wood are combined. At the
same time, the appearance of the wood is improved by the woodgraining of the wood and it is
very preferable in terms of appearance quality.
[0046]
On the other hand, the diaphragm 11 is a piston vibration area that vibrates integrally with the
second plate thickness area D1-1 made thin as a fulcrum, and the frequency characteristic of the
output sound pressure can be made flat.
In addition, the thick plate thickness shape of the connection portion 20 including the central
vibration portion and the outer peripheral vibration portion can increase the rigidity of the
connection portion and widen the flat band, and further suppress the vibration of the opposite
phase due to resonance to a small level. The pressure dip can be improved.
At the same time, even in the high sound range, the complex divided vibration of the diaphragm
can be suppressed to a low level and the peak dip can be improved by the diaphragm formed of a
laminated structure of a wooden sheet and a sheet of paper having high surface propagation
speed (sound velocity).
[0047]
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15
The central vibrating portion 19 is desirably made of a material having a high sound velocity
propagation speed on the surface. The wooden sheet 23 is made of a lightweight material having
a density similar to that of a metal and having a sound velocity propagation speed equivalent to
that of a paper, and thus is very suitable as a material used for the diaphragm. Furthermore,
since the wood sheet has wood fibers, the structure is anisotropic, and the generation of
resonance vibration and division vibration can be suppressed with an appropriate internal loss.
However, if the wood sheet 23 is extremely thin in terms of weight control, the strength in the
direction orthogonal to the fibers is weak, so it is necessary to reinforce the wood sheet 23 with a
paper sheet 24 having good adhesive bonding. Therefore, the acoustic effect using the wooden
sheet 23 can be obtained by forming the central vibration portion 19 with a plurality of layers of
at least a two-layer structure. Further, by expanding the plate thickness region to the connection
portion 20, it is possible to obtain stable piston vibration.
[0048]
On the other hand, since the outer peripheral vibration portion 21 can be defined as a spring
portion when performing piston vibration as described above, it is desirable to select physical
property values of the resin film. A single layer structure of a synthetic resin film 25 having a
thin layer, light weight, airtightness, appropriate rigidity, shape recovery, and good moldability is
preferable.
[0049]
In the case where a plurality of layers, such as a three-layer structure, is formed in a two-layer
structure in the first plate thickness region D1, and further in a third plate thickness region D1-2,
not only the above effects can be obtained but also shape retention It is also excellent in the
property, that is, the configuration is also excellent in the productivity of the diaphragm.
[0050]
Although the present invention has been described by the above embodiment, it should not be
understood that the description and the drawings, which form a part of this disclosure, limit the
present invention.
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Various alternative embodiments, examples and operation techniques are possible from this
disclosure to those skilled in the art, and can be modified and embodied without departing from
the scope of the invention in the implementation stage.
[0051]
The electro-acoustic transducer of the present invention can be applied to a full-band-type
compact electrodynamic-type speaker such as a headphone or an earphone.
[0052]
BRIEF DESCRIPTION OF THE DRAWINGS General ¦ schematic cutting ¦ disconnection explanatory
drawing of the electroacoustic transducer concerning this invention.
Outline explanatory drawing which showed an example which makes a wooden sheet from logshaped wood. The schematic explanatory drawing for making the diaphragm provided with the
1st, 2nd board thickness area. The outline explanatory view showing the diaphragm provided
with the 3rd board thickness field besides the 1st and 2nd board thickness field. Explanatory
drawing which compared the wood and wood other than that which are used as a diaphragm.
The schematic explanatory drawing which showed the diaphragm of the electroacoustic
transducer of a prior art example. Explanatory drawing of a frequency response (output sound
pressure frequency characteristic).
Explanation of sign
[0053]
DESCRIPTION OF SYMBOLS 9 Magnetic circuit 11 Diaphragm 13 Frame 19 Central vibration
part 21 Peripheral vibration part 21b Edge part 23 Wood sheet 24 Sheet of paper 25 Synthetic
resin film D, D1 1st board thickness area D-1, D1-1 2nd board Thickness area D1-2 Third
thickness area
12-05-2019
17
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