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JPH057397

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DESCRIPTION JPH057397
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electrostatic transducer comprising a diaphragm, a counter electrode, and an electrically
insulating member disposed therebetween.
[0002]
BACKGROUND OF THE INVENTION Electrostatic transducers of the above type belong to the
prior art and are known from the specialist literature. A description of such a transducer is
described, for example, in the special edition of "Funkschau" magazine, published in August
1971, entitled "Technology and acoustical progress in the construction of condensermicrophone-capsule".
[0003]
All electrostatic transducers known to date have the disadvantage that the high surface
resistance of the insulating element breaks inside the transducer if condensation of condensation
forms on the surface when the relative humidity of the air is 100%. Have. In this case, the locally
formed electrically conductive section generates a noise of "Zer", noise increases, and in some
cases, the electrostatic transducer completely fails. Only after a long recovery time can a
complete reuse be possible. These phenomena, which result in very large disturbances due to the
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formation of condensation during operation, are particularly unpleasant in practical use of the
electrostatic transducer provided in the microphone, Complex and time-consuming means are
required to suppress these phenomena, such as climatologically matching the microphones used
to their surrounding climate.
[0004]
SUMMARY OF THE INVENTION It is an object of the present invention to prevent condensation
in the problematic insulating section between the diaphragm and the counter electrode or to at
least prevent the formation of an insulating section which is at least electrically conductive. It is
an object to completely eliminate the above-mentioned drawbacks by means.
[0005]
SUMMARY OF THE INVENTION Starting from the prior art, the object of the invention is that
according to the invention the construction according to the characterizing portion of claim 1
makes the electrical insulation member as a whole or at least partially with a counter electrode.
The solution is achieved by having a volumetric heat capacity which is at least 1/3 smaller and a
thermal conductivity which is at least 10-2 times smaller compared to the casing surrounding the
converter.
[0006]
The ideal of the present invention is that the formation of condensation water on the surface of
the object upon reaching the dew point, as quickly as possible near the surface of the object in
the condensation climate, the relative humidity of the air Is based on reaching a temperature that
has not reached 100% yet.
For this purpose, the heat capacity and the thermal conductivity of the object have to be much
smaller than the heat capacity and the thermal conductivity of the object surrounding the object,
and in the case of this use example the heat capacity and the heat of the insulating member of
the converter The conductivity should be much smaller than the thermal capacity and thermal
conductivity of the other components.
In the ideal case, the insulation zone will form condensation over the entire area except the
insulation surface, which preserves the high resistance properties of the insulation.
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[0007]
Due to the very low thermal capacity of the insulation, the heat exchange between this insulation
and the moist air provides as fast a temperature compensation as possible, whereas, even with
large temperature differences, the insulation The very low thermal conductivity ensures that the
heat dissipation is as minimal as possible. The condition that the heat capacity must be as
minimal as possible can usually be satisfied by making the insulator as minimal mass as possible,
which in practice is achieved by the sheet-like, diaphragm-like embodiment Be done. Very low
thermal conductivity is achieved by a special choice of insulation, for example polyvinyl chloride
with a specific thermal conductivity of about 3.10-5 kcal / msec · deg. In addition to this, the idea
of the invention is reflected in the embodiment of the construction corresponding to this idea of
the insulating section and the part forming it.
[0008]
In one advantageous embodiment of the invention, the electrically insulating ring-shaped
member as a whole forms an electrically insulating member between the diaphragm and the
counter electrode, the volumetric heat capacity of the counter electrode being the volumetric
heat capacity of the counter electrode. The thermal conductivity is 10-2 times smaller than that
of the thermal conductivity.
[0009]
Even if the moist air that has entered the inside of the electrostatic converter reaches the dew
point that causes condensation water to condense on the surface of the object due to pressure
and temperature, the surface of the insulating member formed as a ring-shaped member Is noncondensing because condensation of moisture is not promoted due to the above conditions for
the properties of these parts.
Since the insulating member has a smaller heat capacity than other parts of the electrostatic
converter, heat exchange with air adjacent to the insulating member prevents the insulating
member from continuing formation of condensation on the insulating member. The temperature
of the adjacent air is reached in time.
[0010]
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In one advantageous embodiment of the invention, the electrically insulating member is a disc
made of an insulating material, the disc having a ring-shaped groove, the disc being metal except
for the ring-shaped edge area including the groove. A counter electrode as a vapor deposition
film is formed, and the groove is bridged by a ring made of an insulating sheet, and the volume
heat capacity of the ring is at least 1/1 of the volume heat capacity of the disc supporting the
insulation ring. As small as 3 and the thermal conductivity is at least 10-2 times smaller. The
advantage of this embodiment of the present invention is that the known embodiment of the
electrostatic transducer can be used, and by inserting the ring made of the inventive insulating
sheet of the conventional electrostatic transducer, the prior art can be used. The defects can be
eliminated immediately.
[0011]
In a further advantageous embodiment of the invention, the electrically insulating element is
formed as a collar ring between the counter electrode, which is formed in the form of a dome,
and the retaining ring which bears the edge of the diaphragm. A collar-like raised insulation in
the retaining ring, the volume heat capacity of the insulation being at least one third smaller than
the volume heat capacity of the surrounding transducer part, the thermal conductivity Is at least
10-2 times smaller. The embodiments according to the invention of the collar-like insulation
interrupt the insulating surface which has become conductive due to condensation which is
located between the counter electrode and the diaphragm over a relatively long section, whereby
the disadvantages mentioned at the outset are It will not appear anymore.
[0012]
Finally, in another advantageous embodiment of the invention, the insulation between the
counter electrode and the conductive casing is formed as a frusto-conical insulation former with
a cylindrical part, The volumetric heat capacity is at least 1/3 smaller and the thermal
conductivity is at least 10-2 times smaller than that of the casing and the counter electrode. Such
an electrostatic transducer, which has a casing that can be used as a conductor, and in most
cases the diaphragm is in conductive connection with the casing, has a special insulating member
between the casing and the transducer It is necessary because the casing always forms
condensation on its surface when it reaches the dew point. The inventive embodiment of the
insulation member prevents the formation of a conductive moisture bridge between the casing
and the conductive part of the electrostatic transducer, so that the insulation member retains its
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effect completely Do. This does not cause operational failures of the type described above.
[0013]
Next, the present invention will be described in detail by way of examples with reference to the
drawings.
[0014]
An electrostatic transducer is shown in FIG. 1 that is substantially comprised of a diaphragm 1,
an opposing electrode 2 and an electrical insulation member 3 disposed therebetween.
The diaphragm 1 has a conductive metal film 4 on the surface facing outwards, the metal film 4
being in conductive connection with the conductive casing 6 at its edge 5. The important point is
that when the dew point is reached, the surfaces 7a and 7i of the electrical insulation member 3,
which are shown highlighted by a broken line, are not condensed by the moist air surrounding
these surfaces, thereby insulating The member 3 is to maintain high insulation on the surface
with respect to the other part of the electrostatic transducer, which is wetted by dew
condensation water. The inventive embodiment of the insulation member 3 has adhesion of
condensation water on the surface of the insulation member 3 even at 100% relative humidity,
due to the very small heat capacity and thermal conductivity with respect to the other parts of
the converter Guarantee that there is no. This ensures that the electrostatic converter operates
without problems even at the highest air humidity. The reference numerals 8 and 9 indicate the
electrical terminals of the electrostatic converter, which are drawn out. However, FIG. 1 shows an
embodiment of the insulating member 3 which is generally ring-shaped, and the end of the
insulating member 3 is formed in the shape of the step 10 so that the counter electrode 2 and
the diaphragm 1 The required interval between is maintained. Usually this spacing is between 20
μm and 60 μm, depending on the particular configuration of the electrostatic transducer. The
important point in this case is that if condensation is deposited in the area of this very low step
10, the entire insulation section is formed in such a way that this does not impair the high
resistance of the entire insulation section. For example, other areas of the insulation section may
be realized particularly long.
[0015]
FIG. 2 shows one advantageous embodiment of the invention. The counter electrode 11, which is
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embodied as a disc of ceramic material, has a ring-shaped groove 13 in its edge area 12. In the
present invention, this groove 13 is bridged by a ring-shaped insulating sheet 14 and this
insulating ring is bonded to the counter electrode 11 at its inner and outer edges. For acoustic
reasons, a support member to the bottom of the groove 13 not shown in the drawings, having the
shape of a nodular ridge, a groove-like recess or a wedge-like recess inscribed in the insulating
sheet 14 Sometimes it is necessary.
[0016]
In the embodiment shown in FIG. 3, those indicated by broken lines between the dome-shaped
counter electrode 15 and the retaining ring 17 on which the diaphragm end 16 is stretched. An
insulating surface 18 of a ring 19 in the form of a ring with a ring located between is provided.
At the bottom of this ring-shaped ring 19 a collar-shaped raised insulation 20 is provided, which,
due to the arrangement and the characteristics of this insulation 20 according to the invention,
causes condensation of moisture, The portion of the surface 18 forming the insulating member
that is to be conductive is interrupted, thereby maintaining the required high resistance
insulation.
[0017]
Finally, an example of use is shown in FIG. 4, in which the insulating element between the
counter electrode 21 and the conductive casing 22 is formed as a frusto-conical shaped body 23
with a cylindrical portion. A simple insulation film placed only in the edge area 24 is not
sufficient to guarantee sufficient insulation in the case of condensation, because the insulation
film is so thin that condensation on both sides at its edge This is because it is inevitable that
water will bridge. The desired result can only be achieved by forming the insulating sheet
according to the invention and adding the conditions of the invention thereto.
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