JPS63102500

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DESCRIPTION JPS63102500
[0001]
The invention is a transducer plate for a piezoelectric-electroacoustic transducer, comprising a
piezoelectric layer provided on a carrier and provided with electrodes on both sides, the carrier
comprising It relates to the type supported in the casing at its edge area. Prior Art Transducer
plates for piezoelectric transducers are known from various literatures. This piezoelectric
transducer is increasingly used in modern phones because of its frequency response
compensation and its high operating reliability. For example, according to European Patent
Application No. 0069824, a converter plate with a metallic carrier is known. An adhesive layer is
provided on the entire surface of this carrier. The piezoelectric layer comprises electrodes on
both sides and is fixedly connected to the carrier by means of the adhesive layer. A piece of
connecting band leading to the electrode serves for electrical contact with the electrode. Modern
insulating materials are increasingly used to prevent electrostatic discharge (ESD-ekectrostatic
discharging). Electrostatic charge is often caused by the contemporary interior of a room, for
example a plastic carpet floor. The human body lying on a plastic carpet floor sometimes receives
a strong current impact when in contact with a grounded or conductive object or with a
symmetrical object with a small breakdown strength relative to the load voltage. There is.
Furthermore, when the human body discharges with a high current, a strong electromagnetic
field is generated, which may induce a voltage in the electrical device, thereby interfering with
the function of the device. In order to eliminate these disadvantages, relatively high breakdown
strength is generally required. As known converter boards have a metallic carrier, it is possible,
for example, to increase the breakdown strength by increasing the distance to the outer edge of a
telephone, in particular a desk phone. But of course there is a limit to this means. Problems to be
solved by the present invention The object of the present invention is to provide a converter
plate capable of significantly increasing the dielectric breakdown strength without having to
change the structure in the housing to be accommodated. SUMMARY OF THE INVENTION The
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subject matter of the present invention, which solved the above-mentioned problems, is that the
carrier consists of non-metallic materials, in particular plastics. Operation and Effect of the
Invention According to this means, high dielectric breakdown strength can be obtained. However,
the thickness of the carrier is configured such that the fundamental resonance is maintained
depending on the plastic material. Experiments were performed with commercially available
epoxide materials having lower specific gravities and elastic moduli compared to commonly used
aluminum alloys.
As a result, the support must be somewhat thicker than conventionally used aluminum plates.
Because the internal friction of the plastic material is large compared to aluminum, the
vibrational behavior of the transducer is well damped and a well-compensated frequency
characteristic is obtained. In particular, the excess in the upper range is also low compared to the
known carrier plate made of metal (which is positive because of the frequency linearization). For
this reason, it is possible to dispense with the buffer plate in the front chamber of the converter
plate which is known from DE 28 31 411 A1. It is advantageous if the temperature coefficient of
the plastic is approximately equal to the temperature coefficient of the piezoelectric layer. The
temperature dependence of known converter boards with metal carriers is extremely large
because of the relatively strong bimetal effect, so that the requirements relating thereto are not
fulfilled in connection with the sensitivity changes of many communication controls. With proper
choice of a plastic carrier material with a temperature coefficient similar to that of the
piezoelectric layer, the temperature behavior is significantly altered. At present, the adhesion
between the piezoelectric layer and the carrier can only be controlled indirectly, for example by
means of bending tests. I can not find the adhesion failure point. However, poor adhesion results
in additional variability in transmission data or in poor resistance to the environment. Therefore,
it is effective if the plastic is formed of a transparent material. By this means, it can be optically
detected without any damage to the transducer plate whether the adhesion is uniform over the
entire surface. As already mentioned at the outset, the electrical contact of the transducer plate is
effected by means of the connecting strip. However, this connecting band piece is apt to break
and thus significantly reduces the operation reliability. A new carrier made of plastic is suitable
for the different technology of contact. It is thus advantageous to provide the conductor tracks
on the carrier and to guide them to the electrodes of the piezoelectric layer. A guide rubber,
which can also be a component of the bearing, at the free end of the conductor track is
advantageously arranged for the contact. On plastic carriers, conductor tracks made of graphite
can be provided by simple manufacturing techniques, such as, for example, sieve printing, so that
through contact at the clamping points of the oscillating transducer plate is also possible.
EXAMPLE FIG. 1 shows a transducer plate, which consists of a plastic carrier l. The adhesive
layer 2 is provided on the entire surface of this carrier. A piezo-electric layer 3 is bonded to this
adhesive layer 2, which piezo-electric layer comprises electrodes 4.5 on both sides. Conductor
tracks 6, 7 are provided on the carrier for electrical contact to the electrodes.
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Conductor track 6 leads to electrode 5. The end of the conductor track 7 is electrically connected
to the electrode 4 via the through contact 8. The edge area of the transducer plate is a bearing 9.
It is clamped between the two casings 11.32. A guide rubber 13 is provided for the contact of the
free end of the conductor track 6.7, whose connection 14 is connected to another electrical
device.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a cross-sectional view of a transducer mounted with a transducer plate according to an
embodiment of the present invention, and FIG. 2 is a plan view of the transducer plate according
to an embodiment of the present invention.
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