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JPH08242498

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPH08242498
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker, a loudspeaker and other electroacoustic transducers, and more particularly to an
electroacoustic transducer which can obtain excellent frequency characteristics over the entire
frequency band without increasing the size. .
[0002]
2. Description of the Related Art Conventionally, a capacitor type is known as an electroacoustic
transducer such as a speaker. A capacitor-type speaker has a thin film-like vibrating film
disposed close to a plate-like fixed electrode, and a vibrating film is formed by applying an audio
voltage to the fixed electrode in a state where a bias voltage is applied to the vibrating film. It
vibrates and radiates as a sound wave.
[0003]
By the way, a condenser type speaker generally has a narrow frequency band of sound
generation, and a speaker having a size smaller than a normal size is generally used for highpitched sound. Moreover, although there is also a speaker whose frequency band is extended to
the bass range, such a speaker not only becomes quite large but also holds a diaphragm having a
large area at a certain distance away from the fixed electrode Things were accompanied by
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considerable difficulties. Furthermore, in order to radiate the vibration of the vibrating film to the
outside as a sound wave signal, it is necessary to use a part having a large number of holes called
pantling metal as a fixed electrode, which increases the manufacturing cost.
[0004]
Therefore, a so-called Haile type has been proposed as an electroacoustic transducer that can
improve the frequency characteristics of the entire frequency band without increasing the size.
For example, as disclosed in Japanese Patent Publication No. 55-42555, this electro-acoustic
transducer bends one diaphragm so as to meander and supports its both ends on a casing, and
on both sides of the diaphragm. It arranges a magnet and is constituted. In such an
electroacoustic transducer, since the diaphragm is bent in a meandering manner, the total area of
the diaphragm can be increased without increasing the size, and there is an advantage that the
bass range can be covered. .
[0005]
SUMMARY OF THE INVENTION However, in the above-mentioned Haile type electroacoustic
transducer, only the both ends of the diaphragm are supported and the space between them is
made free, so the shape of the diaphragm is a predetermined shape. There was a limit to its size
in order to hold it. For this reason, in any case, the bass range could not be sufficiently covered.
In addition, since magnets are arranged on both sides of the diaphragm, the distance between the
magnets is long, so if a large magnet is to be used to form a strong magnetic field that causes the
entire diaphragm to vibrate. There was also the problem of failure.
[0006]
The present invention has been made to solve the above-mentioned problems, and it is an object
of the present invention to provide an electroacoustic transducer which can obtain excellent
frequency characteristics over the entire frequency band without increasing the size.
[0007]
An electroacoustic transducer according to claim 1 comprises an electrode assembly in which a
plurality of plate-like fixed electrodes are arranged in parallel with each other, spaced apart in
parallel with each other, and between the respective fixed electrodes. The diaphragm is
interposed between the spacers disposed at the edge thereof, and a bias voltage is applied to the
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diaphragm and one end and the other end of the audio voltage generating means for generating
an audio voltage at both ends Are alternately connected to the fixed electrode, and air is
discharged from one side of the electrode assembly to the spacer when the vibrating membrane
swings to the fixed electrode side from the other side of the electrode assembly at the same time
It is characterized in that an opening through which air is sucked is provided.
[0008]
In the electro-acoustic transducer according to claim 2, in addition to the feature according to
claim 1, the thickness of the spacer is not more than 1/4 of the maximum length of the vibrating
portion of the vibrating membrane. It is characterized by
[0009]
In the electro-acoustic transducer according to the first aspect, when the potential of the fixed
electrode on one side of the vibrating membrane becomes positive, the potential of the fixed
electrode on the other side becomes negative.
As a result, the vibrating membrane to which the bias voltage is applied is attracted to the side of
the fixed electrode having the potential opposite to that of the vibrating membrane, and receives
a repulsive force from the other fixed electrode.
As a result, the vibrating membrane swings to the side of the fixed electrode opposite in polarity
to the air, and the air is discharged from the space between the two, and the air is drawn to the
space between the fixed electrode and the vibrating membrane separated therefrom.
In this case, since the opening of the spacer is disposed to discharge air from one side of the
electrode assembly and suck air from the other side, compression waves of air are generated on
the side of the electrode assembly. It becomes a sound wave.
[0010]
The maximum output sound pressure in a speaker or the like is proportional to the amount of air
discharged and drawn by the vibration of the vibrating membrane. In this electroacoustic
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transducer, since the vibrating membrane is held between the spacers, the vibrating membranes
can be stacked several times. Therefore, in this electroacoustic transducer, the discharge amount
and the suction amount of air can be increased by forming the vibrating film in multiple layers,
and a large maximum output sound pressure can be obtained without increasing the size of the
vibrating film.
[0011]
In order to improve the output sound pressure frequency characteristic in the low sound range in
a speaker or the like, it is necessary to efficiently convert the vibration energy of the vibrating
membrane into acoustic energy. If the pitch of the air compression wave is long, a larger amount
of air must be pressurized and depressurized. In the electro-acoustic transducer of the above
configuration, the space between the vibrating membrane and the fixed electrodes and the
outside are communicated with each other by the opening provided in the spacer, so the air
entering and leaving the space passes through the opening When you get resistance. For this
reason, pressurization and decompression of air can be efficiently performed in the space
between the vibrating membrane and the fixed electrodes, and therefore, the characteristics in
the bass range can be improved.
[0012]
Furthermore, since the electroacoustic transducer having the above configuration does not
directly form a compressional wave of air by the vibrating membrane, the shape of the vibrating
membrane has little influence on the frequency characteristics. Therefore, the degree of freedom
of the shape of the vibrating membrane is increased, and consequently, the design restrictions of
the cabinet and the like are reduced.
[0013]
A. Configuration of the Embodiment An embodiment of the present invention will be described
below with reference to FIGS. 1 to 4. FIG. 1 is a perspective view showing a part of the
loudspeaker of the embodiment in the vertical direction. Hereinafter, the configuration of the
speaker will be described in order from the upper component. In the figure, reference numeral 1
is a fixed electrode. The fixed electrode 1 is made of an aluminum plate of 50 mm × 100 mm ×
0.5 mm in length, width and thickness. A spacer 2 is bonded to the lower surface of the fixed
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electrode 1. The spacer 2 is a U-shaped frame body made of PET resin, and one side of the open
side is an opening of a space for generating a sound wave described later. The spacer 2 has the
same vertical and horizontal dimensions (50 mm × 100 mm) as the fixed electrode 1 in this
embodiment, and has a thickness of 1 mm and a width of 5 mm. A vibrating film 3 is bonded to
the lower surface of the spacer 1.
[0014]
The vibrating film 3 is configured by vapor-depositing aluminum with a thickness of 5000
angstroms on the surface of a polyimide film (Kapton) 50 mm × 100 mm × 15 μm in length,
width and thickness. The second stage spacer 2 is bonded to the lower surface of the vibrating
membrane 3 in the opposite direction to the spacer 2. The fixed electrode 1 is bonded to the
lower surface of the second-stage spacer 2, and the third spacer 2 is bonded to the lower surface
of the fixed electrode 1 in the same direction as the second-stage spacer 2.
[0015]
As shown in FIG. 1, the spacers 2, 2 adhered to the front and back of the fixed electrode 1 face in
the same direction, and the spacers 2, 2 adhered to the front and back of the fixed electrode 1
adjacent thereto are the spacers 2, 2 described above. And in the opposite direction. Thus, the
pair of spacers 2 2 sandwiching the fixed electrode 1 are alternately reversed in direction for
each fixed electrode 1.
[0016]
A portion surrounded by the vibrating membrane 3, the spacer 2 and the fixed electrode 1 is a
space for sound wave generation. Further, one side where the spacer 2 is opened is openings P1,
P2,... Pn for air to enter and exit from the space. Then, the unadhered portion inside the portion
bonded to the spacers 2 and 2 in the vibrating membrane 3 vibrates in the vertical direction, so
that the air is pressurized or decompressed in the space, and the opening P1, Air flows in and out
of the space through P2, ... Pn.
[0017]
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The transverse length of the vibrating portion of the vibrating membrane 3 is desirably four
times or more of the thickness of the spacer 2, and more desirably ten times or more (90 times in
this embodiment). With such a configuration, pressurization and depressurization in space can be
performed more efficiently, and in particular, the frequency characteristics in the bass range can
be improved.
[0018]
Next, FIG. 3 shows a circuit for supplying an audio signal to the fixed electrode 1 and the
diaphragm 3. In the figure, reference numeral 20 denotes an audio signal input circuit for
inputting an audio signal to a speaker. The audio voltage signal supplied from the audio signal
input circuit 20 is amplified by a step-up transformer (audio voltage generation means) 21. One
end of the output side coil 21a of the step-up transformer 21 is connected to the fixed electrodes
1,... Every other one, and the other end of the output side coil 21a is connected to the fixed
electrodes 1,.
[0019]
Further, the central portion of the output side coil 21a is grounded, whereby voltages at both
ends of the output side coil 21a are equally distributed to plus and minus and applied to the fixed
electrodes 1,. That is, assuming that the voltage at both ends of the output side coil 21a is V0, the
voltage V0 / 2 is applied to one fixed electrode 1 across the vibrating film 3, and the voltage -V0
/ 2 is applied to the other fixed electrode 1 Is applied. On the other hand, assuming that the
voltage at both ends of the output side coil 21a is -V0, the voltage -V0 / 2 is applied to the one
fixed electrode 1, the voltage V0 / 2 is applied to the other fixed electrodes 1, ... Ru.
[0020]
Further, a direct current power supply V is connected to each of the vibrating membranes 3 via a
protective resistance R. The negative side terminal of the DC power supply V is grounded, and
the positive side terminal is connected to each of the diaphragms 3. As a result, a positive bias
voltage is applied to each of the vibrating films 3. Therefore, when an audio voltage signal is
input from the audio signal input circuit 20, the diaphragm 3 is attracted to the fixed electrode 1
to which a negative voltage is applied, and the repulsive force from the fixed electrode 1 to which
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a positive voltage is applied. As a result, the vibrating membrane 3 swings to the fixed electrode
1 side of negative polarity. Then, the polarity and the potential of the fixed electrodes 1 change
according to the audio voltage, and the audio voltage is converted into the vibration of the
diaphragm 3.
[0021]
FIG. 2 is a perspective view showing the assembled speaker of the embodiment. Now, assuming
that a negative voltage is applied to the fixed electrode 1 located at the uppermost stage, the
positive voltage is fixed to the second fixed electrode 1, and the negative voltage is fixed to the
third fixed electrode 1. The polarities of the voltages applied to the electrodes 1,... Alternate. Due
to the voltage polarity of such fixed electrodes 1,..., The vibrating film 3 located at the top swings
upward, and as a result, air is discharged from the opening P1 facing the front side in the figure,
and the other side opens. Air is sucked from the opening P2.
[0022]
Further, since the second-stage vibrating film 3 swings downward from the top, air is sucked
from the opening P3 opened to the other side in the drawing, and air is discharged from the
lower opening P4 facing to the front. Ru. As described above, when the above voltages are
applied to the fixed electrodes 1, ..., air is discharged from the openings P1, P4, P5, ... Pn facing
the front side, and the opening P2 opened to the other side. , P3,... Pn-1 suck in air. Also, when a
voltage of the reverse polarity to the above is applied to the fixed electrodes 1, ..., air is drawn
from the openings P1, P4, P5, ... Pn facing the front side, and the openings P2, P3 opened to the
other side. , ... Pn-1 discharges air. In this way, compression waves of air are formed on both
sides of the speaker to become sound waves.
[0023]
B. Operation and effect of the embodiment In the loudspeaker of the above configuration,
since the diaphragms 3, ... are held between the spacers 2, 2, as in the above embodiment, the
diaphragms 3, ... may be overlapped in layers. it can. Therefore, in this speaker, the discharge
amount and the suction amount of air can be increased, and thus the output sound pressure level
can be increased while having a compact configuration as described above. Specifically, 30
diaphragms 3, ... are arranged in the loudspeaker of the embodiment, and the total area of the
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vibrating portion of the diaphragm 3, ... is (50-10) mm × (100-10) mm × 30 = 108000 mm 2 =
1080 cm 2 This is about the same size as the area of 33 cm square. In the above-mentioned
speaker, a diaphragm having an area equal to that of the above-mentioned speaker is contained
in a volume of 5 cm × 10 cm × 8 cm. Furthermore, the total area of the openings P1,... Is 0.1 cm
× 9 cm × 30 = 27 cm 2, which is about 40 times smaller than the total area of the vibrating
membranes 3. As described above, in the loudspeaker of the embodiment, the area of the portion
emitting the sound wave is very small compared to the total area of the vibrating membrane 3,
and it can be understood how compactly configured.
[0024]
Further, in the above-mentioned speaker, the air entering and exiting the space between the
vibrating membrane 3, ... and the fixed electrodes 1, ... passes through the openings P1, ...
provided in the spacers 4, ... . For this reason, pressurization and depressurization of air can be
efficiently performed in the above-mentioned space, and therefore, the output sound pressure
frequency characteristic in the bass range can be improved. Furthermore, since the speaker does
not directly form compression waves of air by the vibrating membranes 3, ..., the shape of the
vibrating membrane 3 has little influence on the frequency characteristics. Therefore, the degree
of freedom of the shape of the vibrating membrane 3 is increased, and as a result, restrictions on
the design of the cabinet and the like are reduced.
[0025]
Further, in the speaker of the above configuration, since the vibrating membrane 3 is vibrated by
the fixed electrodes 1 and 1 disposed on the front and back sides of the vibrating membrane 3, a
large magnet is disposed on the side of the vibrating membrane like a hail speaker. There is no
need. As described above, in the loudspeaker of the embodiment, since the space for the magnet
is unnecessary, the configuration becomes more compact.
[0026]
In particular, in the above embodiment, since the thickness of the spacer 2 is 1/10 or less of the
maximum length of the vibrating portion of the vibrating membrane 3, pressurization and
decompression of air in the space can be performed more efficiently. The frequency
characteristics in the low frequency range can be further improved.
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[0027]
Next, the result of having measured the output sound pressure frequency characteristic of the
speaker of the said structure is shown in FIG.
In the speaker used for the measurement, the bias voltage applied to the vibrating films 3 was set
to 1000V. Also, for comparison, a direct radiation type speaker is manufactured in which two
punching metals as fixed electrodes are arranged in parallel with each other, and the same
diaphragm as above is arranged between the punching metals via a rectangular spacer did. Since
the output sound pressure frequency characteristic of this speaker was also measured, it is also
shown in FIG. As shown in FIG. 4, in the loudspeaker of the embodiment, a sufficient output
sound pressure level is secured from about 50 Hz, and moreover, it is stable to about 1 KHz. On
the other hand, in the loudspeaker of the comparative example, it was found that the output
sound pressure level was considerably low in the low frequency range, and considerable relief
was generated also in the middle frequency range and the high frequency range.
[0028]
C. The present invention is not limited to the above-described embodiment, and various
modifications can be made as follows. In the above embodiment, the sound waves are emitted
from the two sides on both sides of the speaker, but the sound waves may be emitted from four
sides. However, in this case, in order to prevent the compression waves of the air from being
extinguished, it is necessary to simultaneously discharge air from all the openings opened on the
side and simultaneously suction it. The spacer is formed in a U-shape, but the shape is arbitrary.
For example, spacers bent at a right angle may be arranged at each corner of the vibrating
membrane 3. It is also possible to form a substantially C shape by forming plate portions
extending in the direction approaching each other from both ends of the spacer so that the
opening of the above embodiment becomes narrower. By forming the spacer in this manner, the
resistance of air entering and exiting the space between the vibrating membrane and the fixed
electrodes can be further increased, and the output sound pressure frequency characteristic in
the bass region can be further improved. In the above embodiment, the size of the opening of the
spacer is constant, but openings having various sizes may be mixed. The present invention is not
limited to the above-mentioned loudspeakers, and the objects such as headphones and
loudspeakers are arbitrary.
[0029]
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As described above, according to the present invention, since the vibrating membrane is held
between the spacers, the vibrating membrane can be stacked several times, and therefore, by
forming the vibrating membrane in multiple layers, A large maximum output sound pressure can
be obtained without increasing the size. In addition, since the space between the diaphragms is in
communication with the outside through the opening provided in the spacer, the air receives
resistance when passing through the opening, and the pressure and pressure reduction of the air
are efficiently performed in the space. To be done. Therefore, the output sound pressure
frequency characteristic in the low tone range can be improved.
[0030]
Brief description of the drawings
[0031]
FIG. 1 is an exploded perspective view of a part of a speaker according to an embodiment of the
present invention in the vertical direction.
[0032]
FIG. 2 is a perspective view showing the assembled speaker of the embodiment.
[0033]
FIG. 3 is a diagram showing the wiring of the speaker of the embodiment.
[0034]
FIG. 4 is a graph showing the output sound pressure frequency characteristics of the speaker of
the embodiment and the conventional example.
[0035]
Explanation of sign
[0036]
DESCRIPTION OF SYMBOLS 1 Fixed electrode 2 Spacer 3 Vibrating film 21 Step-up transformer
(audio voltage generating means) P1, ... Opening part
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