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JP2009278171

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JP2009278171
An electromagnetic transducer is obtained using a vibrating membrane with increased rigidity. A
strip-shaped different magnetic pole is disposed at a fixed interval and alternately arranged on a
permanent magnet plate and a position where the permanent magnet plate is disposed opposite
to the permanent magnet plate and opposed to an interval portion of different pole of the
permanent magnet plate A coil formed of a meander-shaped conductor pattern is formed
embedded in a low density and high rigidity base material, and is electrically 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 vibration analysis result of the electromagnetic converter which produces such a bending
vibration is shown in FIGS. 6 (a) to 6 (c) are numerical analysis model diagrams using the finite
element method, and are front views for analyzing the vibration system of the rectangular
diaphragm 110 and the edge 200 supporting the diaphragm 100. , Side view, perspective view.
The vibrating membrane 100 has a structure having a conductor 120 printed on a substrate 110
as shown in FIG. 6 (c). 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. 7 to 11 show the results of the eigen value
analysis and the response analysis numerically analyzed under the condition where the edge
outer peripheral end of the vibrating membrane 100 is completely restrained. Point A and point
B in FIG. 6A indicate the positions of the observation points for which the response analysis was
performed. FIGS. 7-9 is a figure which shows the analysis result of three frequencies in which an
eigen value exists among eigen value analysis results. FIG. 7 shows an analysis result at a
frequency of 9.9 Hz. 9.9 Hz is in the low band outside 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. 8 shows an analysis
result at a frequency of 26.3 Hz, which is an eigenmode limited to a position close to the center
of the vibrating membrane 100 and showing a large displacement. Further, the frequency of 56.5
Hz in FIG. 9 is an eigenmode showing a large displacement at two places in the middle of the
rectangular long side of the vibrating membrane 100. FIG. 10 and FIG. 11 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. 10 and FIG. 11, it can be seen that characteristic fluctuation of
the frequency response characteristic occurs around the frequency where the characteristic
value exists. Comparing Fig. 10 and Fig. 11, at 9.9 Hz in Fig. 7, the maximum displacement
occurs at both observation points A and B, but at 26.3 Hz in Fig. 8 the fluctuation width of
observation point A is 20 dB or more This difference is larger than the fluctuation range of the
observation point B. At 56.5 Hz in FIG. 9, 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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Also, at observation point B in FIG. 11, the width of characteristic fluctuation at frequencies of
26.3 Hz and 56.5 Hz is smaller than that at observation point A in FIG. 10, but at frequencies
higher than that, from FIG. The width is getting bigger. As described above, in the vicinity of the
frequency where the eigen value exists, a fluctuation exceeding 20 dB is exhibited, and there is a
problem that a countermeasure such as reducing the fluctuation 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 is attached to 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]
According to the present invention, the electromagnetic transducer according to the present
invention is a permanent magnet plate in which strip-like different magnetic poles are alternately
magnetized with a constant interval, and an interval portion of the different magnetic poles of the
permanent magnet plate disposed opposite to the permanent magnet plate. A coil consisting of a
meander-shaped conductor pattern is embedded in a low-density, high-rigidity base material at a
position opposite to the surface, and it is electromagnetically coupled to the permanent magnet
plate by energizing the conductor pattern, And a vibrating diaphragm that vibrates.
[0009]
According to the electromagnetic converter of the present invention, since the vibrating
membrane is formed by embedding the conductor pattern in the low density and high rigidity
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base material, uniform vibration amplitude can be realized over a wide band, and sound
transmission is possible. Can be reduced.
[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 is composed of permanent magnet plates 11 and 12, a frame
20, and a diaphragm 31, 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 31 and.
[0011]
The permanent magnet plate 11 is magnetized alternately in different strip-like magnetic poles,
and at the boundaries of these alternate magnetic poles, the radiation sound holes 11a for
radiating the audio vibration emitted by the vibrating film 31 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 at the boundaries of the alternate magnetic
poles, the radiation sound holes 12a for emitting audio vibration emitted by the vibrating film 31
are provided. It is formed.
[0012]
The vibrating film 31 is composed of a base 31a and a conductor (coil formed of a conductive
pattern) 31b. The base 31a is formed into a rectangular shape using a material having a rigidity
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higher than that of the base 110 of the conventional vibrating membrane 100. It is formed. The
conductor 31b is formed by punching a metal foil by pressing, etching or the like, and a position
perpendicular to the strip longitudinal direction and a position opposed to a linear portion along
the strip longitudinal direction of the permanent magnet plates 11 and 12 of the base 31a. It is
disposed at a position opposite to the portion, and is formed in a meandering shape consisting of
the straight portion and the folded portion.
[0013]
FIG. 2 is a sectional view taken along the line A-A showing the vibrating film 31 of the
electromagnetic transducer 10 according to the embodiment of the present invention, and the
thickness direction of the vibrating film 31 is shown larger than it actually is for explanation. .
The vibrating film 31 is formed so as to embed the meander-shaped conductor 31b so as to be
exposed on the surface of the rectangular base 31a. The conductor 31b is fixed to the plane of
the mold, and when the foam material is added to the polymer material in the mold for foaming,
the conductor 31b is crimped to the base 31a and molded. The foam material preferably has an
adhesive affinity with the conductor 31b, but the conductor 31b may be bonded to the base 31a
with an adhesive when the bonding strength is weak.
[0014]
In general, a structure having a certain thickness is difficult to bend, and the frequency of the
natural resonance at which bending vibration occurs is a high frequency in proportion to the
thickness, so a vibrating membrane is necessary to make the rigidity high. It is sufficient to make
31 a thick structure. Therefore, the conductor 31b made of metal is bonded so as to be
embedded in the surface of the base 31a having a thickness equal to or greater than that of the
base 110 of the conventional diaphragm 100 to form a multilayer structure. Even if it is the base
material 31a, the vibration film 31 of a structure resistant to bending is formed by combining the
conductors 31b.
[0015]
The thickness of the conventional vibrating membrane 100 is generally 0.1 mm or less using the
sheet-like base material 110, but the thickness of the vibrating membrane 31 is 0% by bonding
the base material 31a and the conductor 31b. If it is not less than 5 mm, even if the same
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material as the conventional sheet-like base material 110 is used, the vibrating film 31 having a
strength of 5 times or more 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 as not to increase the mass of the base material
31a. It is formed. The base material 31a is, for example, desirably about 0.5 to 1.0 gr / cm <3> in
density, and desirably formed of a foamed polymer material such as a highly foamed porous
plastic material having strength.
[0016]
With respect to the vibrating film 31 composed of the base material 31a made of the abovedescribed foamed polymer material and the like and the conductor 31b made of the metal foil
and the like, structures other than the above are shown in FIGS. FIG. 3 is a cross-sectional view of
the vibrating film 31 formed so as to be embedded inside so that the conductor 31b is covered
by the base material 31a. For example, the material of the base material 31a, the conductor 31b,
and the material of the base material 31a are laminated in order Molded. FIG. 4 is a crosssectional view of the vibrating film 31 in which the conductor 31b is formed on both the front
and back sides of the base material 31a, and the conductor 31b is fixed to the mold as in FIG. At
the time of foaming, the conductor 31b is crimped to the base 31a and molded. In FIG. 5, two
vibrating films 31 of FIG. 3 are stacked and adhered by an adhesive or the like.
[0017]
It should be noted that such a structure may be combined to form the vibrating film 31
configured in FIG. 3 and FIG. 1 or FIG. 2, or three or more may be combined to form the vibrating
film 31 in multiple layers.
[0018]
Further, in order to cause the vibrating membrane 31 having such a structure to perform
appropriate translational vibration, a support that flexibly supports the outer peripheral portion
of the vibrating membrane 31 may be provided.
The support supports the entire circumference or a part of the vibrating membrane 31 by a
rolled edge like a conventional cone-shaped speaker. Furthermore, it is desirable that the base
material 31a be a heat resistant material, and it is desirable that the base material 31a not be
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dissolved in heat generated during energization of the conductor 31b.
[0019]
As described above, according to the electromagnetic converter of the present embodiment, the
conventional vibrating film 10 can be obtained by adopting the base 31 a using the low density
and high rigidity material instead of the thin and flexible base 110. The bending vibration of the
vibrating film is eliminated, and a vibrating film having uniform displacement can be realized,
and high-frequency audio vibration can be emitted without lowering the sound pressure level. In
addition, since the vibrating film 31 is thicker than that of the conventional vibrating film, the
transmission of sound is reduced and good sound pressure characteristics can be obtained.
[0020]
It is an exploded perspective view of an electromagnetic converter of the present invention. It is
sectional drawing which shows the structure of the diaphragm which embedded the conductor
on the surface of one side of the base material of Embodiment 1 of this invention. It is sectional
drawing which shows the structure of the diaphragm which embedded the conductor in the
inside of the base material of Embodiment 1 of this invention. It is sectional drawing which
shows the structure of the diaphragm which embedded the conductor on each surface of the
base-material both surfaces of Embodiment 1 of this invention. It is sectional drawing which
shows the structure of the vibrating film which piled up 2 sheets of vibrating films which
embedded the conductor in the inside of the base material of Embodiment 1 of this invention,
and was made into one sheet. 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.
Explanation of sign
[0021]
DESCRIPTION OF SYMBOLS 10 electromagnetic converter, 11, 12 permanent magnet board, 11a,
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12a radiation sound hole, 20 frame, 21 upper frame (frame) 22 lower frame (frame) 21a, 22a
radiation sound hole 31, 100 diaphragm 31a, 110 base material, 31b, 120 conductor (coil
consisting of conductor pattern), 200 edge.
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