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JP2009278168

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DESCRIPTION JP2009278168
An electromagnetic transducer is obtained using a vibrating membrane with increased rigidity.
Kind Code: A1 A permanent magnet plate in which different magnetic poles are alternately
magnetized at regular intervals, and a position which is disposed opposite to the permanent
magnet plate and which faces a gap between the different magnetic poles of the permanent
magnet plate. A diaphragm formed of a meandering conductor pattern on the surface of a low
density and highly rigid support plate and electromagnetically coupled to a permanent magnet
plate by energizing the conductor pattern and vibrating in a thickness direction; Equipped.
[Selected figure] Figure 2
Electromagnetic converter
[0001]
The present invention relates to an electromagnetic converter that performs sound reproduction
from an audio signal by combining a permanent magnet and a diaphragm.
[0002]
In a rectangular electromagnetic transducer using a permanent magnet plate and a vibrating
membrane, the permanent magnet plate and the vibrating membrane are disposed to face each
other, and a buffer material is disposed between the permanent magnet plate and the vibrating
membrane. There is something.
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The permanent magnet plate, the vibrating membrane, and the buffer member are covered so as
to be sandwiched by members such as a frame and attached to, for example, a speaker housing.
The above-mentioned permanent magnet plate has strip-like magnetized portions (also referred
to as multipolar magnetized patterns) alternately made into different polarities at regular
intervals. In addition, the vibrating film is a meandering conductor pattern (serpentine coil) that
acts as an electromagnetic coil, facing a position facing a gap at a boundary of different polarity
of the permanent magnet plate, a portion called a so-called magnetized neutral zone ) Is provided
on the surface of the vibrating film. When the current of the audio signal flows through the
meandering coil pattern formed on the vibrating membrane, the meandering coil pattern and the
multipolar magnetization pattern of the permanent magnet plate are electromagnetically
coupled, and the above meandering coil pattern is formed according to Fleming's law. The
vibrating membrane vibrates by acting. Sound waves generated by this vibration are emitted
through a sound hole formed in a permanent magnet plate and a frame to perform audio
reproduction (see, for example, Patent Document 1). In addition, there has conventionally been
an ultra-thin speaker called "gamouson type", which has a configuration similar to that of the
above-described electromagnetic converter and is replaced with the above-mentioned permanent
magnet plate and has a rod-like magnet configuration. The same poles of the rod-like magnet are
made to face each other (N and N poles, or S and S poles), and different polarities are alternately
arranged in the direction of arrangement perpendicular to the rod-like magnets. It is comprised
by the same thing as the above (for example, refer nonpatent literature 1). According to this
configuration, the sound generation operation of audio reproduction is also the same as the
above-described electromagnetic converter.
[0003]
Patent No. 3192372 supervision 監 伯, speaker & enclosure encyclopedia, Seibundo Shinkosha,
May, 1999 issue (section 2-25 super thin speaker)
[0004]
In any of the above-described electromagnetic transducers, the vibrating film is a so-called fullfield drive type electromagnetic transducer in which the driving force by the meandering coil
pattern is uniformly generated on the vibrating surface.
In other words, the vibration film serves as a piston sound source to realize an electromagnetic
converter exhibiting flat sound pressure frequency characteristics. However, in practice, it is
difficult for the vibrating membrane to generate a uniform driving force over the entire band to
cause piston oscillation, and resonance from a low frequency band causes bending oscillation. In
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addition, as the frequency becomes higher, the displacement of the vibrating film becomes
distributed due to slight imbalance of the driving force, and the phenomenon of complex bending
vibration occurs.
[0005]
The results of vibration analysis of the electromagnetic transducer that causes such bending
vibration are shown in FIGS. FIGS. 8A to 8C are numerical analysis model diagrams using the
finite element method, and are front views of a vibration system of a rectangular diaphragm 100
to be analyzed and an edge 200 supporting the diaphragm 100. FIG. 3 is a perspective view of
the vibrating membrane 100. FIG. The vibrating film 100 has a structure having a conductor 120
printed on a substrate 110 as shown in FIG. 8C. In general, the substrate 110 is a thin sheet of a
polymer material or the like, and the conductor 120 prints a thin film of copper or aluminum on
the surface of the substrate 110 to form a serpentine coil pattern. FIGS. 9 to 13 show the results
of eigenvalue analysis and response analysis numerically analyzed under the condition that the
outer peripheral edge of the vibrating membrane 100 is completely restrained as shown in FIGS.
8 (a) and 8 (b). Point A and point B in FIG. 8A indicate the positions of observation points for
which response analysis was performed. FIG. 9 to FIG. 11 are diagrams showing analysis results
of three frequencies in which eigenvalues exist among the eigenvalue analysis results. FIG. 9
shows an analysis result at a frequency of 9.9 Hz. 9.9 Hz is in the low band out of the audio band,
but is taken as the lowest order eigenvalue for reference. The vibration mode in which the central
portion of the vibrating membrane 100 is the maximum displacement, that is, the eigenmode.
FIG. 10 shows an analysis result at a frequency of 26.3 Hz, which is an eigenmode limited to a
position near the center of the vibrating membrane 100 and showing a large displacement.
Further, the frequency of 56.5 Hz in FIG. 11 is an eigenmode showing a large displacement at
two places in the middle part of the rectangular long side of the vibrating membrane 100. FIG.
12 and FIG. 13 show the results of response analysis, showing the frequency response
characteristics at observation point A and observation point B, respectively. In both figures, the
positions of three frequencies at which the above-described eigenvalues exist are indicated by b,
c and d. The oblique line L is an approximate displacement amplitude characteristic on the
assumption that no eigen value exists, and this slope decreases at -6 dB / octave as going from
low to high. According to the frequency response characteristics of FIG. 12 and FIG. 13, it can be
seen that characteristic fluctuation of the frequency response characteristic occurs around the
frequency where the characteristic value exists. Comparing Fig. 12 and Fig. 13, the maximum
displacement occurs at both observation points A and B at 9.9 Hz in Fig. 9, but the fluctuation
width at observation point A is 20 dB or more at 26.3 Hz in Fig. 10 This difference is larger than
the fluctuation range of the observation point B. At 56.5 Hz in FIG. 11, the width of fluctuation of
the observation point A is larger than the width of fluctuation of the observation point B, and the
difference is about 40 dB.
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In addition, at observation point B in FIG. 13, the width of characteristic fluctuation at
frequencies of 26.3 Hz and 56.5 Hz is smaller than observation point A in FIG. The width is
getting bigger. As described above, a fluctuation exceeding 20 dB is exhibited near the frequency
where the characteristic value exists, and there is a problem that a countermeasure such as
reducing the fluctuation of the diaphragm 100 is required.
[0006]
Also, since the vibrating membrane 100 is generally a thin membrane, sound transmission is
likely to occur. This is because even if the driving force is generated by the coil 120 formed of a
relatively rigid meander-shaped conductor pattern, bending vibration is easily generated because
the thin polymer resin sheet of the base material 110 is thin, and sound transmission is possible.
It is easy to happen. Particularly in the low frequency range, when the electromagnetic
transducer 10 is mounted in the enclosure, the sound radiated to the back surface is reflected
inside the enclosure and transmitted through the diaphragm 100 for radiation. The back surface
transmitted sound interferes with the front surface emission sound to cause fluctuation in the
sound pressure frequency characteristics, and thus the sound quality is deteriorated.
[0007]
The present invention has been made to solve the problems as described above, and it is an
object of the present invention to obtain an electromagnetic transducer by using a vibrating
membrane with increased rigidity.
[0008]
In the electromagnetic converter according to the present invention, a permanent magnet plate
in which different magnetic poles are alternately magnetized at a constant interval, and a
permanent magnet plate disposed opposite to the permanent magnet plate, and a space portion
between the different magnetic poles of the permanent magnet plate In the opposite position, a
coil consisting of a meander-shaped conductor pattern is formed on the surface of a low density
and highly rigid support plate, and by electrically connecting the conductor pattern, it is
electromagnetically coupled to the permanent magnet plate to And a vibrating diaphragm.
[0009]
According to the electromagnetic converter of the present invention, the conductor pattern is
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formed on the surface of the support plate made of a material with low density and high rigidity,
so that uniform vibration amplitude can be realized over a wide band, and the transmission of
sound is reduced. can do.
[0010]
Hereinafter, embodiments of the present invention will be described in detail with reference to
the drawings.
Embodiment 1
FIG. 1 is an exploded perspective view for explaining the configuration of the electromagnetic
converter according to the embodiment of the present invention.
The electromagnetic converter 10 includes permanent magnet plates 11 and 12, a frame 20, and
a diaphragm 30, and the upper frame 21 and the lower frame 22 of the frame are an upper
permanent magnet 11a, a lower permanent magnet 11b, and a diaphragm. It supports so as to
sandwich 30 and.
[0011]
The permanent magnet plate 11 is magnetized alternately in different strip-like magnetic poles,
and at the boundaries of the alternate magnetic poles, the radiation sound holes 11a for radiating
the audio vibration emitted by the diaphragm 30 are formed at a constant interval. It is done.
Similar to the permanent magnet plate 11, the permanent magnet plate 12 is alternately
magnetized in different strip-like magnetic poles, and a sound emission hole 12a for emitting
audio vibration emitted from the diaphragm 30 is formed at the boundary of the alternately
different magnetic poles. It is formed.
[0012]
FIG. 2 is a cross-sectional view showing the diaphragm 30 of the electromagnetic converter 10
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according to the embodiment of the present invention. The diaphragm 30 includes a diaphragm
31 and a support plate 33 for supporting the diaphragm 31. The vibrating film 31 is composed
of a base 31a made of a thin polymer resin sheet, and a conductor (a coil made of a conductor
pattern) 31b formed in a meandering shape on the surface of the base 31a. The conductor 31 b
is formed by punching a metal foil by pressing or etching.
[0013]
The support plate 33 is attached to the base 31 a of the vibrating membrane 31 with an adhesive
or the like to support the vibrating membrane 31. In general, a structure having a certain
thickness is difficult to bend, and the frequency of the natural resonance in which bending
vibration occurs increases in proportion to the thickness, so that the diaphragm 30 is thick for
high rigidity. It should just be a structure. Therefore, the support plate 33 having a certain
thickness is bonded to the flexible vibrating membrane 31 to form a multilayer structure, and
even the support plate 33 which is weak to bending alone is bonded to the vibrating membrane
31 to resist bending. The diaphragm 30 of the structure is formed.
[0014]
The thickness of the conventional vibration film 100 is generally 0.1 mm or less using the sheetlike substrate 110, but the thickness of the vibration plate 30 is preferably 0 by bonding the base
31a and the support plate 33. If it is not less than 5 mm, even if the same material as the base
material 31a is used for the support plate 33, the diaphragm 30 having five times or more
strength can be obtained. However, if the same material as the conventional base material 110 is
used, the mass increases and it becomes difficult to keep the sound pressure level high, so select
a low density material so that the support plate 33 does not increase the mass. It is formed. The
support plate 33 is desirably formed of, for example, a foamed polymer material such as a highly
foamed porous plastic material having a density of about 0.5 to 1.0 gr / cm <3> and a high
strength.
[0015]
As described above, in the first embodiment, the diaphragm 30 in which the rigidity is enhanced
by bonding the vibrating film 31 having the conductor 31b formed on one surface to one surface
of the support plate 33 has been described. The configuration of the diaphragm 30 obtained by
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bonding the diaphragm 31 and the support plate 33 other than the configuration is shown in
FIG. 3 to FIG. FIG. 3 is a cross-sectional view showing the configuration of the diaphragm 30 in
which the diaphragm 31 having the conductors 31b formed on both sides is supported by the
support plate 33. FIG. 4 shows the diaphragm 31 attached to both sides of the support plate 33
for support FIG. 6 is a cross-sectional view showing the configuration of the diaphragm 30. FIG. 5
is a cross-sectional view showing a configuration in which two diaphragms 30 having the
structure shown in FIG. 4 are stacked, and when stacked, the conductors 31 b of the upper and
lower diaphragms 30 are in contact and the conductor shorts It adheres through the insulating
layer 34 so that it may not occur.
[0016]
Although there is a space surrounded by the conductors 31b and between the base 31a and the
support plate 33, since the thickness of the conductor 31b is several tens of microns, the
conductors 31b, the base 31a and the support plate are substantially It is in close contact with
33 and adhered. Further, the diaphragms 30 having such several structures may be combined,
and for example, the diaphragms 30 having the structure of FIG. 3 and FIG. 1 or FIG. .
[0017]
As described above, according to the electromagnetic converter of the first embodiment, the thin
and flexible vibrating film 31 is attached to and supported by the support plate 33 made of a low
density and lightweight material such as a highly foamed porous plastic material. Thus, the
thickness is increased without increasing the mass, and the diaphragm 30 is strong against
bending, so that vibration amplitude occurs with uniform displacement in a wide band, sound
pressure level does not decrease, and sound transmission can be reduced. .
[0018]
Second Embodiment
In the first embodiment, the configuration in which the vibrating membrane 31 is supported by
the support plate 33 formed of a foamed polymer material has been described, but the support
plate 33 may be formed of a honeycomb structure. 6 is a cross-sectional view showing the
structure of a support plate 43 formed of a honeycomb structure, and FIG. 6 (a) is a vertical
cross-sectional view in the thickness direction of the diaphragm 30, and FIG. It is a horizontal
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sectional view of plane direction BB line. The configuration other than the support plate 43 is the
same as the configuration shown in the first embodiment, so the same reference numerals are
given and the description will be omitted. As shown in FIG. 6 (b), the support plate 43 has a core
44 having a structure in which cells of innumerable hexagonal cylinders are gathered in a
honeycomb shape using a foil-like material, and an opening of the honeycomb cells of the core
44. A thin plate-like skin material 45 is adhered to the face where the sheet is placed. The core
material 44 and the skin material 45 are generally made of a combination of various materials in
order to make a light weight and rigid structure, for example, aluminum, plastic, paper, CFRP
(Carbon Fiber Reinforced Plastics) Alternatively, GFRP (Glass Fiber Reinforced Plastics) or the like
may be used, and a polymer material used in the base material 31a of the present invention may
be used. The core material 44 is formed by alternately shifting a line-like foil-like material by half
a pitch, applying the adhesive and stacking the layers, pressing them, and cutting in a necessary
thickness and pulling in the overlapping direction. The skin material 45 coated with an adhesive
is attached to the open surface of the honeycomb-like cell of the core material 44, or the support
plate 43 attached by heat press or the like and the vibrating film 31 are adhered with an
adhesive or the like to vibrate The board 30 is configured.
[0019]
As described above, according to the electromagnetic converter of the second embodiment, the
vibrating plate 30 is bonded to and supported by the thin and flexible vibrating film 31 on the
support plate 43 of the honeycomb structure, thereby achieving the embodiment. It produces the
same effect as 1).
[0020]
Third Embodiment
In the first embodiment, the configuration in which the vibrating film 31 is supported by the
support plate 33 formed of a foamed polymer material has been described, but the support plate
33 may be formed of a microbubble structure. FIG. 7 is a cross-sectional view showing the
structure of a support plate 53 formed of a microbubble structure. The configuration other than
the support plate 53 is the same as the configuration shown in the first embodiment, so the same
reference numerals are given and the description is omitted. The support plate 53 is formed into
a plate shape by sandwiching a large number of minute spheres 56 with a thin plate-like skin
material 55 as shown in FIG. The spheres 56 are made of, for example, a polymer material, and
are connected by a filler 57 filling the gap so that no deviation occurs between the spheres 56.
Also, instead of the filler 57, the spheres 56 may be made of a highly adhesive material, and the
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strong frictional force of the sticky surfaces of the spheres 56 may prevent the displacement
between the spheres 56.
[0021]
As described above, according to the electromagnetic converter of the third embodiment, the
vibrating plate 30 is structured such that the thin and flexible vibrating film 31 is bonded to the
support plate 53 of the micro bubble structure to support the embodiment. The same effect as in
the first aspect is exerted.
[0022]
As described above, in the electromagnetic converter according to the present invention, the
conventional film vibration state is eliminated, and vibration with uniform displacement can be
realized, and there is no reduction in sound pressure level, and the electromagnetic wave vibrates
to high frequency. A converter can be realized.
Further, since the diaphragm has a thickness, transmission of sound is also reduced, and good
sound pressure characteristics can be obtained.
[0023]
In the first embodiment, the diaphragm 30 has a configuration in which the support plate 33 is
bonded to the diaphragm 31. However, even if the conductor 31b is directly bonded to the
support plate 33 and the base material 31a is omitted. The same effects as in the first
embodiment can be achieved, the number of parts can be reduced, and a simpler configuration
can be realized.
[0024]
Further, in the second and third embodiments, the support plates 43 and 53 of the honeycomb
structure or the microbubble structure show an example in which the front and back surfaces are
made of the skin materials 45 and 55. The structure in which the vibrating film 31 is bonded
instead of the members 45 and 55 exhibits the same effect as in the second and third
embodiments, can reduce the number of parts, and can realize a simpler configuration.
[0025]
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Further, in the diaphragm 30 configured as described above, in order to cause appropriate
translational vibration, a support that flexibly supports the outer peripheral portion may be
provided.
For example, as in the case of a conventional cone-type speaker, the support holds the entire
circumference or a part of the diaphragm with a roll-shaped edge.
[0026]
Moreover, each figure shown by embodiment of this invention is exaggerated and expanded and
shown for description, and relations, such as thickness of each structure, may differ from reality.
[0027]
It is an exploded perspective view of an electromagnetic converter of the present invention.
It is sectional drawing which shows the structure which affixes a vibrating membrane on one side
of the support plate of the diaphragm of Embodiment 1 of this invention.
It is sectional drawing which shows the other structure which affixes a diaphragm to one-sided
support plate of the diaphragm of Embodiment 1 of this invention. It is sectional drawing which
shows the structure which affixed the diaphragm to both the support plates of the diaphragm of
Embodiment 1 of this invention. It is sectional drawing which shows the structure which
provided two support plates of the diaphragm of Embodiment 1 of this invention. It is structure
sectional drawing which shows a structure of the diaphragm of Embodiment 2 of this invention.
It is structure sectional drawing which shows a structure of the diaphragm of Embodiment 3 of
this invention. It is a figure which shows the vibration analysis model of the conventional
diaphragm. It is a figure which shows the vibration analysis result in 9.9 Hz of a vibration
analysis model. It is a figure which shows the vibration analysis result in 26.3 Hz of a vibration
analysis model. It is a figure which shows the vibration analysis result in 56.5 Hz of a vibration
analysis model. It is a figure which shows the vibration analysis-response analysis result in the
point A of a vibration analysis model. It is a figure which shows the vibration analysis-response
analysis result in the point B of a vibration analysis model.
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Explanation of sign
[0028]
DESCRIPTION OF SYMBOLS 10 electromagnetic converter, 11, 12 permanent magnet board, 11a,
12a radiation sound hole, 20 frame, 21 upper frame (frame), 22 lower frame (frame), 21a, 22a
radiation sound hole, 30 diaphragms, 31, Reference Signs List 100 vibration film, 31a, 110 base
material,, 120 conductor (coil formed of conductor pattern), 33, 43, 53 support plate, 34
insulating layer, 44 core material, 45, 55 skin material, 56 sphere, 57 filler, 200 edges.
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