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JP2012129838

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DESCRIPTION JP2012129838
The present invention provides an electro-acoustic transducer that can obtain reproduced sound
with a wide reproduction frequency band and high sound quality. SOLUTION: A casing 1 having a
sound emission hole 12a for radiating a sound wave to the outside, a diaphragm 3 of a laminated
structure including a layer made of a wood sheet 31, and a drive unit 4 for vibrating the
diaphragm 3 And The diaphragm 3 is provided in the housing 1 with the fiber direction of the
wood sheet 31 directed in the axial direction L of the sound output hole 12a. The inside of the
housing 1 is divided into two spaces S1 and S2 by the diaphragm 3, the space S1 communicates
with the outside through the sound output hole 12a, and the drive unit 4 is built in the space S2.
And the diaphragm 3 makes the wood sheet 31 the surface layer, and the wood sheet 31 is
turned to the space S1 side. [Selected figure] Figure 3
Electro-acoustic transducer
[0001]
The present invention relates to an electroacoustic transducer, and more particularly to an
electroacoustic transducer capable of obtaining excellent frequency reproduction characteristics.
[0002]
Conventionally, as an electroacoustic transducer, a balance armature (BA) in which the vibration
of an armature (movable iron piece) is indirectly transmitted to a diaphragm via a transmission
member called a drive rod, thereby vibrating the diaphragm. Types of molds are known (e.g.,
Patent Document 1).
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[0003]
Here, the BA type electroacoustic transducer is generally used widely as a hearing aid because of
its high resolution in the middle to high frequency range and easy miniaturization.
[0004]
Japanese Patent Application Publication No. 2002-541749
[0005]
However, although the BA type electroacoustic transducer is useful as a hearing aid because of
its small size, the reproduced sound pressure in the low range is small, and there is room for
improvement as a headphone for music appreciation.
[0006]
In addition, in patent document 1, although the aluminum sheet is used as a diaphragm, it not
only can not expand a bass reproduction ¦ regeneration limit with metal materials like aluminum,
but internal loss is as small as 0.002 to 0.005. Because of this, the occurrence of resonance tends
to generate a standing wave on the surface of the diaphragm.
[0007]
On the other hand, when a general paper sheet or resin film is used as the material of the
diaphragm, the transient characteristics at the rise and fall of the reproduced sound and the
resolution are bad due to the low sound wave propagation speed of them. Become.
[0008]
The present invention has been made in view of the above circumstances, and its main object is
to use an electroacoustic transducer to enhance the resolution of the middle to high frequency
range while improving the reproduction sound quality of the low frequency range, and the
reproduction frequency band Is to make it possible to obtain a high quality reproduced sound.
[0009]
The present invention provides an electro-acoustic transducer as described below in order to
achieve the above object.
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(1) A housing 1 having a sound emission hole 12a for radiating the sound wave to the outside,
and a structure including a layer made of a wood sheet 31, and the fiber direction of the wood
sheet 31 is the axial direction of the sound emission hole 12a An electroacoustic transducer
comprising: a diaphragm 3 provided in the housing 1 toward L; and a drive unit 4 for vibrating
the diaphragm 3.
(2) The inside of the housing 1 is partitioned by the diaphragm 3 into a first space S1
communicated with the outside through the sound output hole 12a and a second space S2 in
which the drive unit 4 is incorporated. The electroacoustic transducer according to (1), wherein
the vibrating plate 3 has the wood sheet 31 as a surface layer, and the wood sheet 31 is directed
to the first space S1 side.
(3) A sheet member 7 is attached to the inner surface of the housing 1 forming the first space S1
so as to face the diaphragm 3, and the sheet direction of the sheet member 7 is also the sound
output An electroacoustic transducer according to the above (2), characterized by comprising a
wood sheet 71 directed in the axial direction of the hole 12a.
(4) The diaphragm 3 is a laminate of the wood sheet 31 and the paper sheet 32 or a laminate of
the wood sheet 31, the paper sheet 32 and the resin film 33 according to the above (1) to (3) The
electroacoustic transducer as described in any one.
(5) The electroacoustic conversion according to the above (3), wherein the sheet member 7 is a
laminate of the wood sheet 71 and the paper sheet 72 or a laminate of the wood sheet 71, the
paper sheet 72 and the resin film 73. vessel.
[0010]
According to the electro-acoustic transducer of the present invention, it is possible to improve
the resolution of the middle to high range and to improve the reproduction sound quality of the
low-pitched sound region, and to obtain reproduction sound having a wide reproduction
frequency band and high sound quality.
[0011]
The perspective view which shows the 1st embodiment of the electroacoustic transducer
concerning the present invention The perspective perspective view which shows the inside of the
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electroacoustic transducer shown in FIG. 1 The longitudinal cross-sectional view of the
electroacoustic transducer shown in FIG. Explanatory drawing which shows an aspect Partially
enlarged sectional view of a diaphragm An enlarged sectional view showing an edge portion of a
diaphragm A longitudinal sectional view showing a second embodiment of an electroacoustic
transducer according to the present invention A partially enlarged sectional view of a sheet
member A longitudinal sectional view showing a third embodiment of the electroacoustic
transducer according to the present invention
[0012]
Hereinafter, an embodiment in which the electro-acoustic transducer of the present invention is
used for headphones will be described in detail based on the drawings.
First, a first embodiment of the present invention will be described based on FIGS. 1 to 6.
In FIGS. 1 to 3, reference numeral 1 denotes a casing which forms an exterior of the
electroacoustic transducer according to the present invention, and the casing 1 is fitted to a boxshaped case main body 11 and an upper end opening of the case main body 11 It is constituted
by the attached lid 12.
Further, the nozzle 2 is fixed to one end face of the housing 1 across the joint portion of the case
main body 11 and the lid 12.
The nozzle 2 is a portion inserted directly into the user's ear canal or through an ear plug (not
shown), and a sound wave (audible sound) is emitted through the nozzle 2 into the ear canal.
[0013]
As is apparent from FIGS. 2 and 3, a flat diaphragm 3 is provided in the housing 1 between the
case main body 11 and the lid 12, and the inside of the housing 1 is formed by the diaphragm 3.
It is divided into a first space S1 located on the lid 12 side and a second space S2 located on the
case body 11 side.
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A sound output hole 12a is formed in the portion covered by the nozzle 2 in the lid 12, and the
first space S1 is in communication with the outside through the sound output hole 12a. The
sound wave is emitted to the outside of the housing 1 by the sound emission hole 12a. The first
space S1 and the second space S2 may not be completely partitioned.
[0014]
On the other hand, in the second space S2 in the housing 1, a drive unit 4 for vibrating the
diaphragm 3 is incorporated. The drive unit 4 includes a pair of magnets 41 constituting a
magnetic circuit, a magnet housing 42 (yoke) for holding the magnets, a coil 43, and an armature
44.
[0015]
Among them, the magnet housing 42 is in the shape of a rectangular tube made of a magnetic
material, and a pair of magnets 41 is fixed to the opposing inner wall surfaces. The pair of
magnets 41 are flat-plate shaped permanent magnets, in which different magnetic poles face
each other and are fixed, and a magnetic gap G that generates a DC magnetic field is formed
between the two.
[0016]
The coil 43 has a configuration in which a winding 43b through which an audio signal current
flows is provided on the outer periphery of a bobbin 43a formed of synthetic resin or the like,
and both ends of the winding 43a are drawn out of the housing 1 and signal input It is connected
to the terminal 5. In addition, the coil 43 is fixed to the case main body 11 in a state where the
inside of the bobbin 43a is continuous with the magnetic gap G, and generates an AC magnetic
field that changes the magnetism of one end of the armature 44 placed in the magnetic gap G. .
[0017]
The armature 44 is formed by bending a metal plate of a soft magnetic material into a U shape as
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shown in FIG. 3, and one end thereof is fixed to the outer wall surface of the magnet housing 42
as a fixed end 44a. One end side of the magnetic coil G penetrates the inside of the coil bobbin
43a and the magnetic gap G as an excitation unit 44b. In particular, the tip of the exciter 44 b
protrudes from the magnetic gap G and is connected to the diaphragm 3 via the drive rod 45.
[0018]
The drive rod 45 is a hard transmission member for transmitting the vibration of the armature
44 (excitation unit 44b) to the diaphragm 3. One end of the drive rod 45 is perpendicular to the
excitation unit 44b of the armature and is fixed to the tip thereof The other end of the rod 45 is
fixed to the diaphragm 3 by an adhesive or the like.
[0019]
The diaphragm 3 has a peripheral edge fixed to the frame 6 via, for example, a roll-shaped edge
portion 3a formed into a semicircular cross section, and the frame 6 is sandwiched between the
case main body 11 and the lid 12 It is held vibratable.
Further, as shown in FIGS. 3 and 4, through holes 3b are formed in the diaphragm 3 for adjusting
the differential pressure of the internal air pressure between the first space S1 and the second
space S2. The hatching shown in FIG. 4 is for clearly showing the edge portion 3a of the
diaphragm 3 and the region (radiation portion) inside the edge portion 3a, and does not
represent a cross section.
[0020]
In the present invention, the diaphragm 3 has a laminated structure using the wood sheet 31 as a
base material. For example, as illustrated in FIG. 5A, the diaphragm 3 has a two-layer structure in
which a wood sheet 31 and a paper sheet 32 are laminated.
[0021]
Wood has the anisotropy that the physical properties are different between the fiber direction
and the orthogonal direction, and the propagation velocity (sound velocity) of the sound wave in
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the fiber direction shows a high value of 4 to 6 km / s comparable to metal. Furthermore, the
internal loss exhibits a high value of 0.02 to 0.04 comparable to that of paper and resin. For this
reason, according to the diaphragm 3 using the wood sheet 31 as a base material, it becomes
possible to obtain a high-resolution reproduced sound free from modulation distortion caused by
the occurrence of standing waves. In addition, the diaphragm 3 based on the wood sheet 31 is
softer and lighter (lower specific gravity) than the metal diaphragm and can lower the minimum
resonance frequency, so that the bass reproducing ability is enhanced compared to the metal
diaphragm. , It becomes possible to expand the reproduction frequency band.
[0022]
As a raw material of wood sheet 31, the propagation speed of a sound wave is high also in wood,
and as a tree species with a large internal loss, hippopotamus, cherry, pear, beech, oak, walnut,
maple, maple, spruce, mahogany, rosewood etc. It is preferably used. On the other hand, tropical
tree species such as Lauan are not suitable as raw materials for the wood sheet 31 because they
have low strength and little anisotropy.
[0023]
Here, the diaphragm 3 is an element whose overall weight is very important in terms of vibration
performance, and an electro-acoustic transducer having only a magnetic circuit with a small
driving force such as a headphone, especially a balanced armature (BA In the case of using a
wood sheet 31 as the diaphragm 3 of the mold), it is required to make it thin to reduce its weight.
For this reason, the wood sheet 31 has a thickness of 0.1 mm or less, preferably 10 to 80 μm,
using a sapwood portion of fine wood which can be extremely thin-processed. For this, a
superfinishing kiln apparatus capable of extremely thin and smooth processing of wood is
suitably used.
[0024]
In the case of a wood sheet 31 having a thickness of 10 to 80 μm, only a slight force acting in
the direction orthogonal to the fiber direction tends to cause a tear in the fiber direction, which
requires careful handling. For this reason, it is preferable that the diaphragm 3 according to the
present invention not have a single layer structure of the wood sheet 31 but have a laminated
structure in which the paper sheets 32 as described above are laminated to reinforce the wood
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sheet 31. As the paper sheet 32, Japanese paper having high strength and thinness, and Gampi
paper having high strength while being thin fibers are preferably used. Furthermore, the
thickness of the paper sheet 32 is preferably 5 to 20 μm.
[0025]
In addition, the paper sheet 32 may be laminated with the wood sheet 31 at the same time as the
wood sheet 31 is machined, or after the wood sheet 31 is machined, it is carefully handled and
laminated with the paper sheet 32. You may The wood sheet 31 and the paper sheet 32 are
joined and integrated by, for example, a hot press after lamination, in which case the paper sheet
32 is impregnated with a thermosetting resin in advance to secure the shape retention of the
diaphragm 3. It is good to keep it. As the thermosetting resin, acrylic resin etc. can be used
besides resol type phenol resin. Since the curing temperature of the phenol resin is about 150 °
C. to 180 ° C., the temperature of the hot press is made higher and the press pressure is 5 to 40
kg / mm at which the cell voids and cell walls of the wood sheet 31 are compressed. It is set to
<2>. At this time, the thermosetting resin also penetrates to the wood sheet 31 side, and the
laminate is integrated. Incidentally, when a 20 μm thick wood sheet 31 is stacked on a 10 μm
thick paper sheet 32 and hot pressed at a pressure of 20 kg / mm <2>, the thickness of
diaphragm 3 obtained thereby is 10 μm. there were.
[0026]
Here, the peripheral portion of the diaphragm 3 is an edge portion 3a which can increase the
amplitude of the radiation portion, but the edge portion 3a is limited to a roll shape having a
semicircular cross section as described above. Alternatively, it may be a corrugated type or a thin
flat type. However, it is desirable to form the edge part 3a of that kind in a laminated member
excluding the wood sheet 31.
[0027]
For example, when the diaphragm 3 has a two-layer structure of a wood sheet 31 and a paper
sheet 32 as shown in FIG. 5A, the paper sheet 32 is more flexible than the wood sheet 31 and
easy to form. As shown in FIG. 6, an edge portion 3a is formed on the periphery of the paper
sheet 32 which is slightly larger than the periphery of the wood sheet 31.
[0028]
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The diaphragm 3 is not limited to the two-layer structure of the wood sheet 31 and the paper
sheet 32, but may have a three-layer structure including the resin film 33 as shown in FIG. 5 (b).
The edge portion 3a can be formed on the peripheral edge thereof.
As the resin film 33, polyester resin films, such as a polyethylene terephthalate and a
polyethylene naphthalate, can be used, The thickness is 2-10 micrometers good. When the
diaphragm 3 has three or more layers, the wood sheet 31 should not be interposed between the
two layers, but it should be a surface layer, that is, the wood sheet 31 should appear on either
surface of the diaphragm 3 preferable.
[0029]
Thus, although the diaphragm 3 is vibratably provided in the housing 1 by sandwiching the
frame 6 between the case body 11 and the lid 12 as described above, regarding the arrangement,
the wood sheet 31 faces forward That is, it is desirable to arrange toward the first space S1 side.
In particular, as shown in FIG. 4, the fiber direction of the wood sheet 31 is the axial direction L
of the sound output hole 12a (the direction along the straight line passing through the center of
the sound output hole 12a and orthogonal to the sound output surface of the sound output hole
12a) Toward (to be along). According to this, it is possible to improve the sound quality of the
reproduction sound radiated to the outside through the inside of the nozzle 2 from the sound
emission hole 12a due to the high propagation speed of the sound wave in the fiber direction of
the wood sheet 31. Although it is desirable to make the fiber direction of the wood sheet 31
completely coincide with the axial direction L of the sound emission hole 12a, it is practically
difficult to make the perfect coincidence, and it is about 10 degrees from the viewpoint of
acoustic characteristics. Deviation is an acceptable range. If the deviation is about 10 degrees, the
sound quality improvement effect can be exhibited.
[0030]
As described above, according to the present invention, since the wood sheet 31 is used for the
diaphragm 3, the bass reproduction capability is improved and the reproduction frequency band
is improved as compared with the electroacoustic transducer using a metal diaphragm made of
aluminum or the like. It is possible to expand the Further, since the wood sheet 31 has a large
internal loss, generation of standing waves on the surface of the diaphragm 3 can be suppressed,
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and furthermore, the fiber direction of the wood sheet 31 is directed to the axial direction of the
sound emission hole 12a. The transient characteristics at the rise and fall of the playback sound,
the resolution is good, and the high-quality playback sound with excellent acoustic
characteristics can be extracted. Furthermore, in the configuration in which the wood sheet 31 is
directed to the first space S1 side in which the wood sheet 31 communicates with the outside
through the sound emission hole 12a with the surface layer, the wood sheet 31 enhances the
positive effect on the reproduced sound. The sound quality can be further improved.
[0031]
In addition to the above configuration, as shown in FIG. 7, the sheet member 7 may be attached
to the inner surface of the housing 1 (lid 12) facing the diaphragm 3 to form the first space S1. .
Here, the sheet member 7 basically has the same configuration as the diaphragm 3. That is, as
shown in FIG. 8, the sheet member 7 is also a laminate of the wood sheet 71 and the paper sheet
72 or a laminate of the wood sheet 71, the paper sheet 72, and the resin film 73. Wood is a
material with ideal characteristics as an acoustic diaphragm with high sound velocity and high
internal loss, so it has high sound reproduction capability, excellent transient characteristics and
resolution in addition to expansion of the reproduction frequency band. By including the wood
sheet 71 in the sheet member 7 in order to reproduce the voice, the sound quality can be
improved.
[0032]
In particular, it is preferable that the sheet member 7 also be disposed so that the wood sheet 71
is directed to the first space S1 side, and the fiber direction thereof is directed to the axial
direction L of the sound output hole 12a. As described above, the wood sheet 71 having an ideal
characteristic as an acoustic diaphragm having a high sound velocity on the outermost surface
and a large internal loss is directed to the first space S1 to lead to the first space S1. Since
excellent reproduction sound is transmitted to the sound emission hole 12a and the nozzle 2,
sound quality can be further improved.
[0033]
Furthermore, if the fiber direction of the wood sheet 71 is oriented in the axial direction L of the
sound emission hole 12a, among the wood sheets, the orientation of the acoustic characteristic
that the sound velocity is high is utilized, and the frequency band reproducing ability is excellent.
The sound quality can be further improved because the reproduced sound excellent in the
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transient characteristics is propagated to the sound emission hole 12a which is the extraction
hole.
[0034]
And even with the electro-acoustic transducer as shown in FIG. 7, it is possible to extract
reproduced sound having a wide reproduction frequency band and excellent acoustic
characteristics.
[0035]
That is, in the configuration in which the sheet member 7 including the wood sheet 71 is adhered
to the inner surface of the housing 1 forming the first space S1 so as to face the diaphragm 3,
generation of noise due to resonance of the housing 1 It is possible to suppress and improve the
reproduction sound quality.
In addition, in a configuration in which the diaphragm 3 and the sheet member 7 are a laminate
of the wood sheet 71 and the paper sheet 72, or a laminate of the wood sheet 71, the paper
sheet 72, and the resin film 73, It is possible to prevent the wood sheet 71 from being broken at
the time of manufacture or use.
[0036]
Although it is desirable to make the fiber direction of the wood sheet 71 completely coincide
with the axial direction L of the sound emission hole 12a, it is practically difficult to make the
perfect coincidence, and it is about 10 degrees from the viewpoint of acoustic characteristics.
Deviation is an acceptable range.
If the deviation is about 10 degrees, the sound quality improvement effect can be exhibited.
[0037]
Further, as shown in FIG. 9, the sheet member 7 may be attached not only to the inner surface of
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the lid 12 but also to the inner surface of the nozzle 2, the outer surface of the lid 12, and the
outer surface of the case body 11. According to this, it is possible to suppress the vibration of the
housing 1 and to prevent the generation of noise due to this.
[0038]
Although the embodiment of the present invention has been described above, the electroacoustic
transducer is not only used as an inner ear type headphone which is used by inserting the nozzle
2 into the ear canal, but also with a pair of left and right ear rests connected by a headband The
housing 1 can be fixed in the housing to form a closed type headphone, or a microphone (not
shown) can be connected to the signal input terminal 5 to be used as a hearing aid. Moreover, it
can be used for other various devices.
[0039]
Reference Signs List 1 housing 12a sound output hole 3 diaphragm 31 wood sheet 32 paper
sheet 33 resin film 4 drive unit 41 magnet 42 magnet housing 43 coil 44 armature 45 drive rod
S1 first space S2 second space 7 sheet member 71 wood sheet 72 paper Sheet 73 resin film
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