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JP2011030420

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2011030420
A novel electromechanical transducer is obtained. The invention provides an electromechanical
transducer comprising a multi-layer structure comprising at least two layers and having at least
one transducer element (2) of variable thickness. The conversion element 2 allows air to flow in
the thickness direction inside the conversion element 2 and to flow into and out of the
conversion element 2 in the thickness direction of the conversion element 2 through at least one
surface of the conversion element 2 . The conversion element can be used, for example, to
convert energy from mechanical energy to electrical energy and / or vice versa. [Selected figure]
Figure 1
Electromechanical converter and method of converting energy
[0001]
The invention relates to an electromechanical transducer comprising a multilayer structure
comprising at least two layers and comprising at least one transducer element whose thickness
can be varied.
[0002]
The invention further provides a method for converting energy from mechanical energy to
electrical energy and / or vice versa, comprising at least a conversion element having a
multilayer structure comprising at least two layers and capable of varying its thickness. It relates
to a method comprising producing two.
[0003]
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1
For example, electrostatic transducers are known in which electrostatically moving membranes
are arranged between porous fixed plates.
In such a solution, the amplitude and force of movement of the membrane is low or the required
control voltage is very high.
An example of such an electrostatic converter is disclosed in International Publication WO
97/31506.
[0004]
WO 99/56498 discloses an electromechanical transducer comprising a plurality of superposed
layers, each layer comprising at least one porous layer and a plastic film placed at a distance
from the porous layer. The porous layer and the plastic membrane are practically in contact with
one another only at the support points. The support points allow the entire structure to change
its thickness. The change in thickness is caused by the electric field. When the thickness is
reduced, these layers are pushed towards one another and at the same time push the air between
the plastic films. However, pushing the air requires a great deal of power. As such, the amplitude
of such transducers is relatively small.
[0005]
The object of the present invention is to provide a novel electromechanical converter and a
method for converting energy.
[0006]
In the electromechanical transducer of the present invention, the conversion element allows air
to flow in the thickness direction inside the conversion element and to flow into and out of the
conversion element in the thickness direction of the conversion element through at least one
surface of the conversion element. To allow.
[0007]
Furthermore, in the method of the present invention, the conversion element allows air to flow in
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the thickness direction inside the conversion element and to flow into and out of the conversion
element in the thickness direction of the conversion element through at least one surface of the
conversion element. It is characterized in that it allows and that the conversion elements are
controlled individually.
[0008]
The idea underlying the invention is that the electromechanical transducer comprises at least one
transducer element having a multilayer structure comprising at least two layers for enabling the
transducer element to change its thickness. It features.
Yet another idea is that the conversion element allows air to flow in the thickness direction inside
the conversion element and to flow into and out of the conversion element in the thickness
direction of the conversion element through at least one surface of the conversion element It is.
The idea underlying one embodiment is that the electromechanical transducer comprises at least
one impermeable layer.
The idea underlying the second embodiment is that the electromechanical transducer comprises
at least two conversion elements which can be controlled separately. The idea underlying the
third embodiment is that the electromechanical transducer comprises at least two transducer
elements, between which an impermeable layer is placed. The idea underlying the fourth
embodiment is that the electromechanical transducer comprises at least two transducer
elements, and the outer surface of the transducer elements has an air-permeable layer, and the
air has a first transducer element to a second transducer element. It is to be allowed to flow
through the surface facing the element or vice versa, the second conversion element.
[0009]
One advantage of the present invention is that air can flow through the surface of the element in
the thickness direction of the element so that no force is generated to resist movement when the
thickness of the conversion element changes. It is to allow the amplitude to be quite large. When
the thickness of the conversion element changes, it does not have to work against pressure, so
this conversion element has very good efficiency. That is, it becomes possible to cause relatively
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large deformation and / or movement at a low control voltage. Also, similarly, deformation and /
or movement of the conversion element produces a very strong signal. When the
electromechanical transducer has at least one impermeable layer, this transducer can generate
sound pressure. If the electromechanical transducer has at least two transducer elements which
can be separately controlled, for example, a structure is realized in which the acceleration of the
center of mass of the transducer produces energy when the transducer is moved. On the other
hand, it is also possible to move the center of mass of the transducer. Furthermore, when the
different transducer elements of the transducer can be separately controlled, a plurality of
different directivity / sound characteristics are obtained. By making the outer surface of the
electromechanical transducer an impermeable layer so that air can actually flow only between
the transducer elements of the electromechanical transducer, and by applying signals of opposite
phase to different transducer elements, 1 When one transducer element becomes thinner, the
other transducer element becomes thicker, and an electromechanical transducer is realized
which operates in the opposite manner. However, the thickness of the entire electromechanical
transducer is constant and the center of mass of the entire structure moves. The non-perforated
surface of the transducer moves in a direction opposite to the center of mass, i.e. the thickness of
the transducer does not change but the surface of the element nevertheless moves. Furthermore,
the surfaces of the transducers move in synchronization, producing sound or vibration.
[0010]
The invention will be described in more detail with reference to the attached drawings. FIG. 1 is a
cross-sectional side view schematically illustrating an electromechanical transducer. FIG. 2 is a
cross-sectional side view schematically illustrating a second electromechanical transducer. FIG. 3
is a cross-sectional side view schematically illustrating a third electromechanical transducer. FIG.
4 is a cross-sectional side view schematically illustrating a fourth electromechanical transducer.
FIG. 5 is a cross-sectional view schematically showing the fifth electromechanical transducer as
viewed obliquely from above. FIG. 6 is a cross-sectional view schematically showing the sixth
electromechanical transducer as viewed obliquely from above. Figures 7a and 7b are illustrations
of an electromechanical transducer according to the invention. Figures 8a, 8b, 8c, 8d and 8e are
illustrations of yet another electromechanical transducer according to the present invention.
Figures 9a, 9b and 9c are schematic side views of an example of an electromechanical
transducer. FIG. 10 is a detail view of the electromechanical transducer according to FIG. 9c. 11a,
11b and 11c are detailed views showing the use of the electromechanical transducer according
to FIG. 9c. FIG. 12 is a cross-sectional side view schematically illustrating an electromechanical
transducer. FIG. 13 is a cross-sectional side view schematically illustrating an electromechanical
transducer. FIG. 14 is a cross-sectional side view schematically illustrating an electromechanical
transducer.
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[0011]
FIG. 1 shows an electromechanical transducer 1. The electromechanical transducer 1 comprises a
transducer element 2 consisting of a multilayer structure. The conversion element 2 comprises a
porous layer 3 made of an elastic material. Elasticity here means that the material bends. The
metal layer 4 is provided on the upper and lower surfaces of the porous layer 3. On the lower
surface of the porous layer 3, a plastic film 5 acting as a nonconductive layer is attached. The
plastic film 5 can be made, for example, of polypropylene, polymethylpentane or a cyclic olefin
copolymer. Furthermore, the plastic film 5 may be charged as an electret film.
[0012]
The porous layer 3 is provided with a projection serving as a support point 6 so that an air gap
10 is formed between the plastic film 5 and the porous layer 3 therebelow. The porous layer 3
can be, for example, approximately 200 microns in thickness, and the air gap 10 can be, for
example, approximately 50 microns in size. The plastic film 5 can likewise be, for example,
approximately 30 microns in thickness.
[0013]
The electrodes 7 are connected to the metal layers 4 and 4 'with an air gap 10 between them. A
control voltage is applied between the electrodes 7. The control voltage moves the adjacent metal
layers 4 and 4 'in relation to each other, ie towards each other or away from each other. The
support points 6 allow the porous layer 3 made of an elastic material to bend when the metal
layers 4 and 4 'are subjected to a force of attraction to one another and to allow the conversion
element 2 to change its thickness substantially throughout it. Therefore, the adjacent air gaps 10
are provided at different positions. The different layers of the conversion element 2 are provided
with passages or holes 8 which allow air to flow in and out of the conversion element 2 in the
thickness direction without being practically compressed.
[0014]
The top surface of the electromechanical transducer is an air impermeable layer 9. This layer can
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be made of a material similar to that of the plastic film 5. Naturally, the air impermeable layer 9
is not provided with a passage or a hole. When the transducer element 2 is compressed, air is
allowed to flow downward through the passages or holes 8 as indicated by the arrow A. When
the effect of the control voltage is removed, the porous layer 3 made of elastic material will
return to the form shown in FIG. In this case, the air flows upward as is apparent from FIG.
Similarly, when the thickness of the conversion element 2 is increased by the effect of the control
voltage between the electrodes 7, air flows upward through the passage or hole 8 as shown in
FIG. When the conversion element 2 is deformed, the impermeable layer 9 is also deformed to
generate sound pressure or vibration.
[0015]
FIG. 2 shows an electromechanical transducer 1 in which the transducer element 2 includes a
plastic film 5 stacked in sequence as shown in FIG. 2 and charged so as to have a positive or
negative charge as an electret film. A metal layer 4 is provided on the lower surface of the plastic
film 5, to which an electrode 7 is connected. In order to form an air gap 10 between the plastic
films 5, support points 6 are arranged between the plastic films 5. Passages or holes 8 are made
in the plastic membrane 5 and the metal layer 4. The support points 6 are different in position in
adjacent layers. Also in this case, the top surface of the electromechanical transducer is an
impervious layer 9. The plastic film 5 can be, for example, 30 microns thick and the air gap 10
can be, for example, approximately 20 microns in size. The operation of the electromechanical
transducer of FIG. 2 is the same as the operation of the electromechanical transducer of FIG.
[0016]
FIG. 3 shows an electromechanical transducer constructed by combining two charged plastic
films 5 with each other, sandwiching a metal layer 4 between them, and connecting an electrode
7 to this metal layer. 1 is shown. The support points 6 may, for example, be an adhesive stub or
an adhesive elongated shape.
[0017]
FIG. 4 shows an electromechanical transducer 1 in which the multi-layer structure of the
conversion element comprises a porous layer 3 with a plastic film 5 applied on both sides. The
porous layer 3 can be made, for example, of carbon fibers or similar conductive porous materials.
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The porous layer can thus also be made of metal fiber material, such as, for example, non-woven
metal fibers. Since the porous layer 3 is made of a conductive material, the electrode 7 can be
connected to the porous layer 3. The electromechanical transducer according to FIG. 4 does not
include the air impermeable layer 9. Therefore, air can pass through the upper and lower
surfaces of the conversion element 2.
[0018]
FIG. 5 shows an electromechanical transducer comprising two transducer elements 2a and 2b.
Both conversion elements 2a and 2b include a porous layer 3 made of a compressible material in
the thickness direction. An air-permeable metal layer 4 is formed on at least one surface of the
porous layer 3 by vacuum evaporation, for example. The porous layer 3 may contain permanent
charge. The electrodes 7 are connected to every other metal layer 4, and every other metal layer
4 is connected to the ground electrode 11. The upper and lower surfaces of the
electromechanical transducer 1 are provided with air impermeable layers 9. The porous layer 3
is made of, for example, a fabric or other breathable material, and the metal layer 4 is also
breathable so that air can flow through the layers in the transducer element one after another,
and Air can also flow from the upper conversion element 2a to the lower conversion element 2b
and vice versa.
[0019]
A signal is applied to the upper transducer element 2a, and a signal of the same but opposite
phase is applied to the lower transducer element 2b. When the upper conversion element 2a
becomes thinner, the lower conversion element 2b becomes thicker, enabling air to flow from the
upper conversion element 2a to the lower conversion element 2b. The total thickness of the
electromechanical transducer is thus approximately the same. However, the center of the mass
m0 of the electromechanical transducer 1 moves at the same time. The air impermeable layer 9
constituting the upper and lower surfaces of the electromechanical transducer 1 moves in the
opposite direction to the movement of the center of the mass m0. That is, although the thickness
of the electromechanical transducer 1 does not change, the element actually moves. The upper
and lower surfaces move in synchronization, thereby producing sound and vibration. The effect
of this control signal on the different conversion elements 2a and 2b is opposite phase by
changing the charge of the porous layer 3 of one conversion element 2a or 2b to be of the
opposite sign to the charge shown in FIG. But you can get it. In this case, converter 1 operates as
disclosed above when the same and in-phase signals are applied to both conversion elements 2a
and 2b. Due to simplicity, such a solution is also advantageous when the transducer 1 is used to
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generate electrical energy from the movement or deformation of the transducer 1.
[0020]
FIG. 6 shows an electromechanical transducer 1 comprising a magnetized layer 12 in which
transducer elements 2 are stacked one after the other with an air gap 10 formed between them.
The magnetized layer 12 is made of, for example, a mixture of plastic and powder magnetic
material such that approximately half of the material is plastic and half of the material is powder
magnetic material. This enables a permanently magnetizable layer to be realized. The magnetized
layer 12 has a thickness of eg 200 microns and the air gap 10 has a size of eg 50 microns. As
shown in FIG. 6, current conductors 13 are disposed between the magnetized layers 12 in every
other air gap. The current I transmitted by the current conductor 13 generates the magnetic field
Φ of the electromagnetic converter 1. The current conductors 13 are provided in the adjacent
current conductors 13 so that the current flows in the opposite direction. This means that the
magnetic fields 強 め strengthen each other. The permanent magnetization of the magnetized
layer 12 provides basic compression to the conversion element 2 and the current I causes
oscillation. The current conductor 13 can be realized by, for example, a printed wiring technique.
This electromechanical transducer, composed of a magnetized layer 12, has a large mass because
the magnetic material is heavy. As a result, the movement of the center of mass of the conversion
element has a considerable effect.
[0021]
FIG. 7 shows a simplified electromechanical transducer 1 that is breathable on both sides thereof.
This is illustrated by the dashed lines in FIGS. 7a, 7b and 8a to 8e. Air can thus flow past the top
and bottom of the electromechanical transducer. That is, for example, when the transducer
element 2 becomes thinner, air is released through both the upper and lower surfaces. In this
case, the electromechanical transducer has no pressure generating capability, ie no sound
pressure. However, this electromechanical transducer generates movement or force. That is, the
conversion can be used to generate electricity. Such an electromechanical transducer 1 can be
used under a membrane key to generate a signal caused by the pressing of the key. At the same
time, this converter 1 can also be used, for example, to charge the battery. Such
electromechanical transducers are very efficient because no work is required to compress the air.
The basic idea of the electromechanical transducer of FIG. 7a is similar to that of the
electromechanical transducer of FIG.
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[0022]
The top surface of the electromechanical transducer of FIG. 7 b is provided with an impermeable
layer 9. The solution of FIG. 7 b thus corresponds to the electromechanical transducers of FIGS.
Since the mass of the conversion element 2 moves the impermeable layer 9 when the thickness
of the conversion element 2 changes, the electromechanical transducer 1 also generates sound
by the impermeable layer 9.
[0023]
FIG. 8a shows an electromechanical transducer 1 comprising two transducer elements 2a and 2b
superimposed on one another. Both conversion elements 2a and 2b can be controlled separately.
When the electromechanical transducer 1 is moved, the acceleration of the center m0 of its mass
generates energy. Since this electromechanical converter generates energy when moved, it can
be used, for example, as a battery charging container for portable devices.
[0024]
FIG. 8 b shows an electromechanical transducer 1 provided with an impermeable layer 9 on the
lower and upper surfaces. The configuration of FIG. 8b corresponds to the electromechanical
transducer of FIG.
[0025]
FIG. 8c shows an electromechanical transducer 1 comprising two transducer elements 2a and 2b
superimposed on one another and an impermeable layer 9 provided therebetween. When the
impermeable layer 9 in such an electromechanical transducer 1 moves, it generates a sound. This
means that the electromechanical transducer 1 generates sound by itself.
[0026]
The basic idea of the solution shown in FIG. 8 d is the same as the idea of FIG. 7 except that the
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9
two conversion elements 2 a and 2 b touch each other. The conversion elements 2a and 2b can
be controlled individually or together in phase or in phase opposition. In FIG. 8e, the upper
transducing element is sealed by providing the air impermeable layer 9 on its upper and lower
surfaces, and air flows freely through the lower surface of the lower transducing element. In
Figures 9a to 9c, the electromechanical transducer is added with one or more additional masses
of air permeability 15. The additional mass 15 makes it possible to increase the weight of the
electromechanical transducer 1 and thus the mass effect. The additional mass 15 may be, for
example, a perforated metal plate or a porous sintered metal plate.
[0027]
FIG. 10 shows a more detailed description of the electromechanical transducer 1 according to
FIG. The conversion elements 2a and 2b have the plastic film 5 stacked in sequence and a
supporting point 6 therebetween. In the upper conversion element 2 a, the metal layer 4 is
provided on the upper surface of the plastic film 5. Then, correspondingly, in the lower
conversion element 2b, the metal layer 4 is provided on the lower surface of the plastic film.
Holes 8 are provided in the plastic film 5 on the side closer to the additional mass 15 of air
permeability.
[0028]
The signal S1 is applied to the upper conversion element 2a through the amplifier 16a, and
similarly, the signal S2 is applied to the lower conversion element 2b through the amplifier 16b.
The plastic film 5 closest to the air impermeable layer 9 is not provided with the holes 8. The
plastic film 5 closest to the impermeable layer 9 and negatively charged is configured to play the
role of the sensor in FIG. The pressure P measured by this layer is applied to the amplifier as
feedback. Here, the pressure P represents the pressure applied to the surface of the transducer 1.
This sensor thus measures the pressure of the sealed air gap closest to the surface of the
transducer 1. This feedback linearizes the operation of the transducer 1 acting, for example, as
an actuator. Real-time linearization is thus performed by the analog system, ie no complex
processor etc. are required for linearization. This feedback can also be performed by so-called
current feedback. This can be done by measuring the current drawn by the conversion element
from the pole of one resistor or capacitor connected in series with the conversion element and
using the measured current signal as a feedback signal.
[0029]
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In noise reduction applications, the goal is to keep the desired surface of the transducer 1
stationary and / or keep the desired void pressure unchanged. In FIG. 10, for example, the goal
would be to keep the lower surface of the transducer 1 stationary and / or keep the pressure in
the air gap unchanged. The signal S2 is then set to zero and feedback is used to keep the lower
surface of the transducer 1 stationary and / or to keep the pressure on the lower surface of the
transducer unchanged. The upper surface of the transducer 1 may simultaneously generate
sound in accordance with the desired signal S1.
[0030]
11a to 11c show how the electromechanical transducer 1 disclosed in FIGS. 9c and 10 can act as
different elements. The electromechanical transducer 1 can, for example according to FIG. 11a,
act as a cardioid sound source. In this case, the change in sound pressure occurs only on one side
of the transducer 1. The arrow B in FIG. 9c shows, for example, that the upper impermeable layer
9 moves downwards and the different layers of the conversion element 2a also move downward
simultaneously. The layer of conversion element 2b also moves downwards, but the lower or
lower impermeable layer 9 of the transducer 1 hardly moves. The lower part of the transducer 1,
ie the lower transducer element 2b, is thus used to generate a signal that compensates for the
downward active movement generated by the upper part of the transducer 1, ie the upper
transducer element 2a. It will be. This can be done in the manner described above by using
feedback. The signal S1 can be added to the upper conversion element 2a, and a signal whose
amplitude is half of S1 and whose phase is opposite to that of the signal S1 can be added to the
lower conversion element 2b. This enables the part of the upper transducer element 2a which
sends vibrations towards the lower transducer element 2b to be attenuated. The magnitude of
the signal to be applied to the lower conversion element 2b can be further reduced according to
the amount of attenuation of the signal of the upper conversion element 2a as it travels through
the converter 1. A feedback configuration can also be used in this embodiment.
[0031]
FIG. 11 b shows how the transducer 1 operates as a dipole source. As shown by arrow C in FIG.
9c, the layers of the upper impermeable layer 9 and the upper conversion element 2a move in
the same direction as the layers of the lower impermeable layer 9 and the lower conversion
element 2b. The pressure effect is therefore opposite in sign on both sides of the transducer 1.
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[0032]
FIG. 11 c shows how the converter 1 operates as a monopole sound source. The sound pressure
on both sides of the transducer 1 is therefore of the same sign. As shown by arrow D in FIG. 9d,
when the upper non-permeable layer 9 and the upper conversion element 2a layer move
downward, the lower non-permeable layer 9 and the lower conversion element 2b layer face
upward Move.
[0033]
FIG. 12 shows a converter 1 in which the converter element 2 comprises a porous layer 3. The
porous layer 3 can be made of, for example, non-woven polyester fiber material. The metal layer
4 is formed on both sides of the porous layer 3 by vacuum evaporation, for example. The metal
layers 4 on both sides of the porous layer are connected to one another, and the porous layer 3
and its both sides constitute a unit to which one electrode is to be connected. Since the
conversion element 2 does not include an electret layer, this solution requires the use of a bias
voltage called U0 in FIG.
[0034]
Signal S1 is filtered using resistors R1, R2 or R3 and applied to different layers. Of course, there
may be a porous layer provided with more metal layers 4, which means that there are also more
resistors. The resistors R1 to R3 have different magnitudes, which means that each resistor filters
out different frequencies from the signal S1. When the resistor R1 is selected to be the smallest
resistor and the resistor R3 is selected to be the largest resistor, nearly all frequencies can be
applied to the top layer, mainly A signal containing low frequencies is applied to the bottom
layer. When a layer vibrates at high frequencies, no significant movement is required. On the
other hand, at low frequencies, the layer movement is very large. In the lower layer, their total
movement is equal to the magnitude of the change in thickness of the conversion element 2. The
lower layer oscillating at low frequencies can thus move very large. The first resistor R1 is for
example of the order of 100 ohms, the second resistor R2 is for example five times larger than
the first resistor R1 and likewise the third resistor R3 is a second resistor 5 times larger than R2,
etc. The number of layers influences the maximum power that the conversion element can
generate. Filtering the signals to be applied to the different layers differently improves the
efficiency of the conversion element 2 as a whole.
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[0035]
Adjacent porous layers 3 constitute one capacitor. In addition to or in place of the resistors R1 to
R3 in filtering, it is also possible to use coils whose inductance is determined to match the
capacitance between the different layers. When oscillating, different layers also generate current.
This also causes losses in the resistor and damping to the structure.
[0036]
In FIG. 13, the porous layer 3 is made of a conductive fibrous material, such as non-woven
carbon fibers or non-woven metal fibers. The electrode 7 can be connected directly to the porous
layer 3. On the fibers of the surface of the porous layer 3, for example, a thin spray varnish may
be applied as a coating material for the fibers. The thickness of the spray varnish may be of the
order of 1 micron, in which case the varnish does not prevent air from passing through the
porous layer. However, the varnish acts as an insulator and the air gap 10 and the varnish
together prevent a short circuit between the porous layers 3.
[0037]
When using a more complex filtering solution than that shown in FIG. 12, the desired frequency
can be applied exactly to each electrode 7. However, most preferably, the signal containing all
frequencies is applied to the top layer, the highest frequency filtered out signal waveform is
applied to the middle layer, and the signal containing practically the lowest frequency is the most
It is added to the lower layer. Energy is emitted from the top layer in both the upward and
downward directions, but the layers below it are made of porous material, so that they absorb the
signals directed to them from the top layer. The solution of FIG. 13 can, for example, be attached
to the wall at its lower surface, yet reflections hardly occur from the rear surface. If the signal has
to be applied from both the top and the bottom from outside, then the signal containing the
higher frequencies can be added to the layers closer to both outer surfaces and the signal
containing the lowest frequency to the middle layer.
[0038]
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13
FIG. 14 shows a conversion element 2 including a porous layer 3 that is entirely conductive or
provided with a conductive surface. The surface of the porous layer 3 is provided with an electret
layer 14 in which an electret material such as cyclic olefin copolymer COC is dropped onto the
surface of the porous layer 3 or is applied as a powder. After dripping, calendering is carried out
and the droplets or particles are pressed against the surface of the porous layer 3 by a roller and
flattened. The size of the electret droplets should be in the range of 0.5 to 1 mm, and the distance
between them must allow air to pass through in the thickness direction of the conversion
element 2. The support points 6 are formed of a non-conductive material. More preferably, the
calender roller that flattens the droplets is provided with a recess that leaves some droplets or
powder higher than the surroundings to form the support points 6 so that the support point 6 is
the same as that of the electret layer 14 It is to be formed of a material. The electret layer 14 can
thus be formed such that the electret material is randomly dispersed on the surface of the porous
layer 3 by either droplets or powder. The electret material can, for example, be in the form of a
desired raster pattern. Furthermore, by using a slit nozzle in the coating process, it is possible to
form, for example, stripes arranged neatly on the surface of the porous layer 3. When the electret
layer 14 consists of spaced spots or areas or stripes of electret material, it is not necessary to
provide separate holes in the layer of electret material.
[0039]
The drawings and the related description are only intended to illustrate the inventive idea. As to
its details, the invention takes various aspects within the scope of the claims. The conversion
element can include any number of layers. As the movements of each layer in the thickness
direction are coupled in series, the amplitude of the movement of the transducer element
increases as the number of layers increases. Furthermore, the electromechanical transducer can
use any number of transducer elements joined together. Furthermore, the electromechanical
transducer may be straight as shown, or may be curved as desired. The electromechanical
transducer can be configured, for example, by forming two films so that a pair of films
constitutes a nonconductive layer and a conductive layer. The layer structure can be constructed,
for example, by winding the pair of membranes in a cylindrical shape. The transducing element
can thus have capacitance between the layers and the winding creates a coil. The converter
therefore has some inductance. This membrane can also be wound around an iron plate to make
an iron core coil. The iron plate also provides a support structure for the transducer and also acts
as an additional mass. The difference in the air permeability of the layers of the conversion
element enables the sound emission characteristics of the converter, ie the directivity
characteristics of the converter, to be influenced locally. Under similar control, the magnitude of
the movement of one layer changes with breathability. Ventilation can vary with the size of the
holes 8 and / or the distance between them.
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