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JP2007281886

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DESCRIPTION JP2007281886
An electromagnetic transducer capable of reducing the generation of a sound pressure drop of
an audio signal by eliminating the back pressure generated between a vibrating membrane and a
permanent magnet plate and suppressing the amplitude resistance of the vibrating membrane.
Do. A lower permanent magnet plate 11, a buffer member 12, an insertion vibration film 13, an
insertion permanent magnet plate 15, a vibration film 17 on which a meandering coil pattern
17a is formed, a buffer member 12, and a sound radiation hole 19a are formed. An
electromagnetic transducer 10 configured by covering a structure 20 in which upper permanent
magnet plates 19 are stacked in parallel with a frame 30 including a back frame 31 and a front
frame 33. The second meandering coil pattern 13a is provided as the same pattern at a position
facing the meandering coil pattern 17a, and the buffer member 12, the insertion vibrating
membrane 13, the vibrating membrane 15, the lower and upper permanent magnet plates 11
and 19 are the same. The vibrating membrane 17 and the insertion vibrating membrane 13 are
driven in the same phase in size and shape. [Selected figure] Figure 1
Electromagnetic converter
[0001]
The present invention relates to, for example, an electromagnetic converter that reproduces an
audio signal.
[0002]
Various techniques have been proposed for an electromagnetic transducer combining a
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permanent magnet and a vibrating membrane.
An electromagnetic transducer of this type usually comprises a permanent magnet plate, a
vibrating membrane disposed to face the permanent magnet plate, and a buffer member
disposed between the permanent magnet plate and the vibrating membrane. There is. The
permanent magnet plate is formed by alternately forming strip-like different magnetic poles at
regular intervals (hereinafter, this parallel stripe-shaped magnetization pattern is also referred to
as a multi-pole magnetization pattern). In addition, the vibrating film is disposed opposite to the
formation surface of the multipolar magnetization pattern, and is formed of a meander-shaped
conductor pattern at a position facing the so-called neutral zone of magnetization in the gap
between different magnetic poles. Coil (hereinafter, also referred to as a meandering coil pattern.
) Is formed on the entire surface. A plurality of sound radiation holes for emitting the generated
sound vibration wave to the outside are formed at a constant pitch in the gap between the
different magnetic poles of the strip shape of the above-mentioned permanent magnet plate (for
example, Patent Document 1) reference).
[0003]
The structure in which the above-mentioned permanent magnet plate, vibrating membrane and
buffer member are stacked has, for example, a plate-like back frame laid under the abovementioned structure and a front frame covering the above and the above-mentioned structure
Covered in a frame that is made up of glued together. The electromagnetic converter configured
as described above is attached to a housing for an audio device such as a speaker, for example,
and used as an audio device that reproduces an audio signal.
[0004]
JP-A-9-331596
[0005]
In the electromagnetic converter configured as described above, when a current (audio signal)
flows through the meandering coil pattern provided on the vibrating membrane, the meandering
coil pattern and the multipolar magnetization pattern of the permanent magnet plate are
electromagnetically generated. The vibrating membrane vibrates in the thickness direction
according to Fleming's left-hand rule, and operates by generating a sound vibration wave.
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Since this type of electromagnetic transducer does not fix the vibrating membrane in place by the
parts, the gap between the permanent magnet plate and the vibrating membrane (space)
compared to the electromagnetic transducer with the part for fixing the vibrating membrane Is
small. The operating range in which the vibrating membrane can vibrate depends on the gap
between the permanent magnet plate and the vibrating membrane. When the frequency band of
the current flowing in the meandering coil pattern is the middle to low frequency band (here, a
band of around 200 Hz or less is indicated), the vibrating membrane requires a large vibration
operation, so when the vibrating membrane vibrates, the vibrating membrane There is a back
pressure between the and the permanent magnet plate. As a result, there is a problem that
amplitude resistance is applied to the diaphragm, which causes a decrease in sound pressure of
the audio signal.
[0006]
The present invention has been made to solve the problems as described above, and in addition
to the electromagnetic transducer of the conventional configuration, by including an insertion
vibrating membrane disposed parallel to the vibrating membrane, a vibrating membrane is
provided. It is an object of the present invention to provide an electromagnetic transducer
capable of reducing the occurrence of the sound pressure drop in the middle to low range by
providing a form in which the insertion vibration film assists the vibration operation of the
above.
[0007]
The electromagnetic converter according to the present invention comprises a permanent
magnet plate in which strip-like different magnetic poles are alternately formed at a constant
interval, and a gap portion of the permanent magnet plates arranged opposite to the permanent
magnet plate. In an electromagnetic transducer provided with a vibrating film on the entire
surface of which a coil having a meander-shaped conductor pattern is formed on the entire
surface, a second coil having a meander-shaped conductor pattern is formed on the entire
surface in parallel with the vibrating film. One or more insertion vibration films are provided.
[0008]
According to the present invention, the electromagnetic transducer is configured by including
one or more insertion vibration films arranged in parallel to the vibration film, so that the
insertion vibration film assists the vibration operation of the vibration film (or The vibration film
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and the insertion vibration film assist each other in the vibration operation).
For this reason, since the back pressure generated between the vibrating membrane and the
permanent magnet plate in the conventional electromagnetic converter can be eliminated and the
amplitude resistance of the vibrating membrane can be suppressed, the sound and vibration
wave generated by only one vibrating membrane A louder oscillatory wave can be obtained.
Therefore, there is an effect that an electromagnetic converter capable of reducing the
occurrence of the sound pressure drop in the middle to low range can be obtained.
[0009]
Hereinafter, various embodiments of the present invention will be described. Embodiment 1 FIG.
1 is an exploded perspective view for explaining a configuration of an electromagnetic converter
10 according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view
showing a configuration of the electromagnetic converter 10 10 shows a part of a cross section
cut in the direction orthogonal to the coil 17a (or the second coil 13a consisting of a meandershaped conductor pattern) consisting of a meander-shaped conductor pattern. The vertical
arrows in FIG. 2 indicate the direction in which the vibrating membrane vibrates. Note that
hatching indicating a cross section is partially omitted. Here, an insertion diaphragm and a
permanent magnet paired with an insertion diaphragm are commonly used in an electromagnetic
transducer having a generally seen configuration in which one diaphragm is sandwiched by two
permanent magnet plates from above and below via a buffer member. It was set as the
electromagnetic converter of the structure which inserted the board one by one. Here, the
permanent magnet plate on the side where the sound radiation hole for radiating the sound
vibration wave is formed is referred to as the upper permanent magnet plate, and the upper
permanent magnet plate, the diaphragm and the insertion diaphragm are interposed. The
opposing permanent magnet plates are referred to as lower permanent magnet plates.
[0010]
In the figure, the electromagnetic converter 10 is configured as follows. In the lower permanent
magnet plate 11, strip-like different magnetic poles (N pole, S pole) made of sintered ferrite
magnets are alternately formed at a predetermined interval on substantially the entire surface
opposite to the insertion vibration film 13 described later. (Hereinafter, this parallel stripe-
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shaped magnetization pattern is also referred to as a multipolar magnetization pattern.) A socalled neutral zone of magnetization exists in the gap between the different magnetic poles (N, S).
[0011]
An insertion vibration film 13 made of a thin and flexible resin film is disposed on the upper side
of the lower permanent magnet plate 11 at a position opposite to the surface on which the
multipolar magnetization pattern is formed. . A second coil (hereinafter, also referred to as a
second meandering coil pattern) formed of a meandering conductor pattern on the entire surface
of the insertion vibration film 13. ) 13a is configured. Each of the linear portions in the
longitudinal direction of the second serpentine coil pattern 13a is located at the gap between the
different magnetic poles (N and S poles) of the lower permanent magnet plate 11, which
corresponds to a so-called neutral zone. It is provided as. The straight portions refer to long
straight portions of the second serpentine coil pattern 13a, which are disposed in parallel to each
other with a predetermined distance. An insertion permanent magnet plate 15 is disposed on the
upper side of the insertion vibration film 13 via a buffer member 12. Furthermore, a vibrating
film 17 is disposed on the upper side of the inserted permanent magnet plate 15 via the buffer
member 12. The vibrating film 17 is also referred to as a coil (hereinafter, also referred to as a
meandering coil pattern) formed of a meandering conductor pattern on the entire surface
thereof. ) 17a is formed. The second meandering coil pattern 13a, which has already been
described, is formed at the position opposite to the meandering coil pattern 17a so as to have the
same pattern.
[0012]
The insertion vibration film 13 can be formed, for example, by the same material and formation
method as the vibration film 17. Further, the insertion permanent magnet plate 15 can also be
formed of the same material as the lower permanent magnet plate 11 and the upper permanent
magnet plate 19 described later. Furthermore, the insertion permanent magnet plate 15 and the
upper permanent magnet plate 19 can be formed by the same formation method. Here, the size
and the shape of the insertion vibration film 13 and the insertion permanent magnet plate 15 are
the same as those of the vibration film 17, the upper permanent magnet plate 19, and the lower
permanent magnet plate 11. When all permanent magnet plates and vibrating membranes have
the same size and shape as in the electromagnetic converter 10, the following effects can be
obtained.
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[0013]
When an electric signal is input to the insertion vibration film 13 and the vibration film 17, if the
insertion vibration film 13 and the vibration film 17 have the same size and shape, theoretically,
the insertion vibration film 13 and the vibration film 17 perform the same vibration operation
(Hereinafter, the same vibration operation is also referred to as driving in the same phase). For
example, it is possible to drive in the same phase by matching the impedances of the insertion
vibration film 13 and the vibration film 17 and simultaneously driving them. In this way, when
the insertion vibration film 13 and the vibration film 17 are driven in the same phase, there is no
extra amplitude or turning back inherent to each vibration film, and the phase shift of the sound
vibration wave accompanying the synchronization failure of the vibration is ignored. It is possible
to minimize the factors that inhibit the amplitude motion of the respective vibrating membranes
13 and 17.
[0014]
An upper permanent magnet plate 19 is disposed on the upper side of the vibrating membrane
17 with a band-shaped multipolar magnetization pattern of sintered ferrite magnets formed on
almost the entire surface facing the vibrating membrane 17 with the buffer member 12
interposed therebetween. It is done. The upper permanent magnet plate 19 is provided with
sound emission holes 19a at a constant pitch along the neutral zone of the gap between the
magnetic poles (N pole, S pole) having different multipolar magnetization patterns.
[0015]
As described above, in the structure 20 in which the lower permanent magnet plate 11, the four
buffer members 12, the insertion vibration film 13, the insertion permanent magnet plate 15, the
vibration film 17, and the upper permanent magnet plate 19 are stacked. On the lower side, a
frame 30 is configured by pasting together a plate-like rear frame 31 on which the structure 20
is mounted and a front frame 33 covering the upper side and the periphery of the structure 20.
Sound emission holes 33a are provided corresponding to the positions of the front frame 33 of
the frame 30 covering the upper side of the structural body 20 where the sound emission holes
19a are formed. In order to operate the electromagnetic transducer of the present invention well,
at least the edge portion E1 of the insertion vibrating membrane 13 and the edge portion E2 of
the vibrating membrane 17 should be covered tightly. Then, the sound vibration wave can be
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radiated only from the sound radiation holes 15a, 19a, 33a, and leakage of air from other
components can be prevented. Therefore, the reduction of the radiation sound pressure can be
reduced more effectively. As described above, the frame 30 is used here to cover the periphery
E1 of the insertion vibrating membrane 13 and the edge E2 of the vibrating membrane 17 by
covering the entire periphery of the structure 20. .
[0016]
Next, the operation will be described. When a signal is input from an input terminal (not shown)
and a current as an audio signal flows through second meandering coil patterns 13a and 17a
formed on the surfaces of insertion vibration film 13 and vibrating film 17, the second
meandering coil The patterns 13a and 17a are electromagnetically coupled to the multipolar
magnetization patterns in the lower permanent magnet plate 11, the insertion permanent magnet
plate 15, and the upper permanent magnet plate 19 disposed opposite to the patterns 13a and
17a, respectively. According to the law, the insertion vibration film 13 and the vibration film 17
vibrate in the thickness direction as indicated by the arrows in FIG.
[0017]
At this time, the second meandering coil patterns 13a and 17a are arranged in the same pattern
in the opposite positions, and the vibration of the insertion vibration film 13 and the vibration
film 17 is vibrated in a state where their respective impedances are matched. Therefore, the
insertion vibration film 13 and the vibration film 17 vibrate in the same phase. Therefore, the
insertion vibration film 13 assists the vibration operation of the vibration film 17 (or the
insertion vibration film 13 and the vibration film 17 assist each other's vibration operation). The
back pressure generated with the permanent magnet plate can be eliminated, and the amplitude
resistance of the vibrating membrane can be suppressed. The sound vibration wave W1
generated by such vibration passes through the sound radiation hole 15a, and when it passes
through the sound radiation holes 19a and 33a, it is emitted into the air as a larger sound
vibration wave W2 (see FIG. 2).
[0018]
As described above, according to the electromagnetic converter 10 of the first embodiment of the
present invention, by including the insertion vibration film 13 disposed in parallel to the
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vibration film 17, the vibration operation of the vibration film 17 is inserted. Since the vibration
film 13 assists (or the insertion vibration film 13 and the vibration film 17 support each other's
vibration operation), it occurs between the vibration film and the permanent magnet plate in the
conventional electromagnetic converter. The back pressure can be eliminated, and the amplitude
resistance of the vibrating membrane can be suppressed. A sound vibration wave generated by
such a vibration is radiated to the air as a larger sound vibration wave W2. For this reason, it is
possible to obtain an electromagnetic converter capable of reducing the occurrence of the sound
pressure drop in the middle to low range. Further, according to the electromagnetic converter 10,
the buffer member 12, the insertion vibration film 13, the insertion permanent magnet plate 15,
the vibration film 17, and the upper permanent magnet plate 19 are all formed in the same size
and shape. If the insertion vibration film 13 and the vibration film 17 are driven in the same
phase, there is no extra amplitude or reflection inherent to each vibration film, and it becomes
possible to ignore the phase shift of the sound vibration wave accompanying the synchronization
failure of the vibration. Thus, it is possible to minimize the factor of inhibiting the amplitude
movement between the vibrating films 13 and 17. For this reason, it is possible to obtain an
electromagnetic converter capable of further reducing the occurrence of the sound pressure drop
in the middle to low range. Furthermore, according to the electromagnetic transducer 10, the
vibrating membrane 17 and the insertion vibrating membrane 13 are characterized in that the
edge portions E1 and E2 are sealed and covered. Therefore, the sound vibration wave can be
radiated only from the sound radiation holes 15a, 19a, 33a, and it is possible to prevent the leak
with the air from the gaps of other components. Therefore, the reduction of the radiation sound
pressure can be reduced more effectively.
[0019]
In the first embodiment, the electromagnetic transducer 10 in which one insertion vibration film
13 is disposed has been described. However, the same effect can be obtained when a plurality
(two or more) insertion vibration films 13 are used. In that case, one insertion permanent magnet
plate as a pair is also added to one insertion vibration film. The number of insertion vibration
films 13 is determined in consideration of the size and function of the electromagnetic
transducer. Further, in the electromagnetic converter 10 according to the first embodiment, the
insertion vibration film 13, the insertion permanent magnet plate 15, the vibration film 17, the
upper permanent magnet plate 19, the lower permanent magnet plate 11, and the buffer
member 12 all have the same size. The same effect can be obtained even with the optimum size
and shape of the vibrating film and permanent magnet plate, depending on the electromagnetic
transducer used. For example, when the electromagnetic converter is configured as a speaker,
even if the design of the speaker has a pyramid shape that gradually expands in the depth
direction from the plane where the sound vibration wave is radiated, In consideration of the
shape of the serpentine coil pattern, the impedances are matched, and the insertion vibration film
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and the vibration film are driven in phase, that is, the insertion vibration film assists the vibration
operation of the vibration film The same effect as 1 is obtained. In addition, if the insertion
vibration film satisfies the function and exhibits the same effect, the size and shape of the
components of the electromagnetic converter are limited to the same as the electromagnetic
converter 10 of 1 of the embodiment. It will not be done.
[0020]
FIG. 1 is an exploded perspective view showing a configuration of an electromagnetic converter
of a first embodiment. FIG. 1 is a cross-sectional view showing a configuration of an
electromagnetic converter according to Embodiment 1.
Explanation of sign
[0021]
DESCRIPTION OF SYMBOLS 10 electromagnetic converter, 11 lower permanent magnet board,
12 buffer member, 13 insertion vibration film, 13a second coil comprising a conductor pattern of
serpentine shape, 15 insertion permanent magnet board, 15a, 19a, 33a sound radiation hole, 17
19a permanent magnet plate, 20 structure, 30 frame, 31 back frame, 33 front frame, E1 edge of
inserted diaphragm, E2 edge of diaphragm, W1 Sound vibration wave, sound vibration wave
larger than W2.
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