DE1065880B

DE1065880B -

Info

Publication number: DE1065880B
Application number: DENDAT1065880D
Authority: DE
Publication date: 1959-09-24

Description

Die Erfindung betrifft eine am Rande eingespannte Mikrophon- und/oder Telephonmembran, bestehend aus mehreren Schichten, von denen wenigstens eine aus elektrostriktivem Material besteht.The invention relates to a microphone and / or telephone membrane clamped at the edge, consisting of several layers, at least one of which is made of electrostrictive material.

Es sind bereits Mikrophonmembranen bekannt, die selbst als elektroakustische Wandler wirken. In einem Fall wird eine Membran aus zwei Seignettesalzplatten mit gekreuzten Hauptachsen zusammengesetzt, und die in Sektoren aufgeteilten Elektroden werden abwechselnd entgegengesetzt gepolt zusammengeschaltet (deutsches Patent 590 996). Da Seignettesalz nicht zu beliebig dünnen Platten geschnitten werden kann, ist weder eine günstige Anpassung an das umgebende Schallmedium, beispielsweise Luft, da die Membran sehr steif ist, noch eine unmittelbare Anpassung an das elektrische Übertragungsnetzwerk möglich, da die Wandlermembran zu hochohmig ist. Die gleichen Nachteile hat eine bekannte, als Wandler wirkende Membran, die nur aus einer piezoelektrischen Scheibe besteht, die durch eine Stauchung bzw. Unterdruck vorgespannt ist (deutsches Patent 704 649). Außerdem ist eine Membran bekannt, die aus einer dünnen Schicht elektrostriktiven Materials besteht und auf jeder Seite zwei konzentrische Ringelektroden hat, wobei die jeweils sich gegenüberliegenden Elektroden miteinander verbunden sind, so daß die Spannung zwischen den Ringelektroden mit verschiedenen Radien abgenommen werden kann (französisches Patent 1 072 621). Auch diese Mikrophonmembran ist so hochohmig, daß sie nicht unmittelbar an ein Übertragungsnetzwerk angeschlossen werden kann.Microphone diaphragms are already known which themselves act as electroacoustic transducers. In one Case, a membrane is composed of two Seignette salt plates with crossed main axes, and the electrodes, which are divided into sectors, are connected together alternately with opposite polarity (German patent 590 996). Since Seignette Salt is not cut into slabs of any thickness can be, there is neither a favorable adaptation to the surrounding sound medium, for example air the membrane is very stiff, yet an immediate adaptation to the electrical transmission network possible because the transducer membrane is too high-resistance. The same drawbacks have a well-known one, called a converter acting membrane, which consists only of a piezoelectric disc, which is compressed by a compression or negative pressure is biased (German patent 704 649). In addition, a membrane is known that consists of a thin layer of electrostrictive material and two concentric ring electrodes on each side has, wherein the respective opposing electrodes are connected to one another, so that the voltage between the ring electrodes can be picked up with different radii (French patent 1,072,621). This microphone membrane is also so high-resistance that it is not immediately can be connected to a transmission network.

Um die Nachteile der bekannten, als Wandler wirkenden Membranen zu beseitigen, wird erfindungsgemäß eine am Rande eingespannte Mikrophon- und/ oder Telephonmembran, bestehend aus mehreren Schichten, von denen wenigstens eine aus elektrostriktivem Material besteht, so ausgebildet, daß die auf beiden Seiten jeder elektrostriktiven Schicht angeordneten Elektroden an den Stellen der Änderung des Krümmungssinnes der Membran unterbrochen sind, wodurch verschiedene Zonen gebildet werden, und daß benachbarte Zonen derart gepolt bzw. polarisiert werden, daß sie bei elektrischer Erregung mechanisch entgegengesetzt wirken.-In order to eliminate the disadvantages of the known membranes which act as transducers, the invention a microphone and / or telephone membrane clamped at the edge, consisting of several Layers, at least one of which consists of electrostrictive material, formed so that the electrodes placed on either side of each electrostrictive layer at the points of change the sense of curvature of the membrane are interrupted, creating different zones, and that adjacent zones are poled or polarized in such a way that they are when electrically excited mechanically counteract.

Durch diese Ausbildung der Membran ist es möglich, die gesamte Membranfläche bis auf die schmalen Unterbrechungen an den Wendekurven als Wandler auszunutzen, ohne die Membran vorzuspannen. In einer Weiterbildung der Erfindung werden die elektrostriktiven Schichten und deren Elektroden in bekannter Weise aufgedampft, vorzugsweise in einem elektrischen Felde. Als Träger dient dabei eine äußerst dünne nichtleitende Folie. Auf diese Weise Elektrostriktive Mikrophon- und/oder Telephonmembran This design of the membrane makes it possible to use the entire membrane surface, except for the narrow interruptions at the turning curves, as a converter without pretensioning the membrane. In a further development of the invention, the electrostrictive layers and their electrodes are vapor-deposited in a known manner, preferably in an electrical field. An extremely thin, non-conductive film serves as the carrier. In this way, electrostrictive microphone and / or telephone membrane

Anmelder:Applicant:

ELECTROACUSTIC Gesellschaft mit beschränkter Haftung, Kiel, Westring 425/429ELECTROACUSTIC Company with limited liability, Kiel, Westring 425/429

Dr. Dr. h. c. Heinrich Hecht, Kiel,
ist als Erfinder genannt wordenDr. Dr. hc Heinrich Hecht, Kiel,
has been named as the inventor

können außerordentlich dünne Schichten hergestellt werden, und es ist möglich, eine Membran herzustellen, die die gleiche Empfindlichkeit, den gleichen Anpassungswiderstand und die gleichen Abmessungen wie ein in Telephonapparaten gebräuchliches Kohlemikrophon haben. Beispielsweise ist die Dicke der Membran bei einem Durchmesser von 50 mm kleiner als 0,01 mm. Um eine Zerstörung der Membran bei allzu" großeF'elektrischer oder mechanischer Erregung zu vermeiden, sind auf beiden Seiten der Membran in geringem Abstand Schutzgitter vorgesehen. Die günstigste Anpassung an das Übertragungsnetzwerk kann durch entsprechende Zusammenschaltung der Zonenkapazitäten gewählt werden.extremely thin layers can be made, and it is possible to make a membrane, which have the same sensitivity, the same matching resistance and the same dimensions like a carbon microphone commonly used in telephones. For example, the thickness is the Membrane with a diameter of 50 mm less than 0.01 mm. In order to destroy the membrane To avoid too much electrical or mechanical excitation are on both sides of the membrane Protective grille provided at a short distance. The cheapest adaptation to the transmission network can be selected by interconnecting the zone capacities accordingly.

Die Eigenresonanz der Membran kann durch eine Luftkammer auf der Rückseite der Membran eingestellt werden.The self-resonance of the membrane can be adjusted by an air chamber on the back of the membrane will.

Die Erfindung wird nun an Hand der Figuren näher erläutert. Um die Anschaulichkeit zu erhöhen, ist in den Figuren das Verhältnis von Membrandicke zu Membrandurchmesser sehr stark vergrößert dargestellt. The invention will now be explained in more detail with reference to the figures. To increase the clarity, the ratio of membrane thickness to membrane diameter is shown very greatly enlarged in the figures.

Fig. 1 zeigt eine Membran I_j die am Rande eingespannt ist und bei Erregung durch negative und positive Schalldrucke relativ zu ihrer Ruhelage gleiche Deformationszustände erreicht, so daß sie ein quadratisches Kraft- bzw. Ausschlaggesetz befolgt. Würde man eine solche Membran aus einer oder mehreren Schichten elektrostriktiven Materials aufbauen und die Elektroden jeder aktiven Schicht über die gesamte Membranfläche ausdehnen, so würde diese Membran bei akustischer Erregung keine Spannung abgeben und bei elektrischer Erregung nicht schwingen, da in jeder Schicht gleichzeitig Dehnungen und1 shows a membrane I _j which is clamped at the edge and, when excited by negative and positive sound pressures, achieves the same deformation states relative to its rest position, so that it obeys a quadratic law of force or deflection. If such a membrane were to be constructed from one or more layers of electrostrictive material and the electrodes of each active layer were to be extended over the entire membrane surface, this membrane would not emit any voltage in the event of acoustic excitation and would not oscillate in the event of electrical excitation,

909 629/190909 629/190

Claims

65 compressions occur in the radial direction, so that the sum of the electrostriction effects is equal to zero. 2 shows a two-layer membrane in the deflected state, the compression and expansion zones being shown. The two layers 2 and 3 of the membrane, at least one of which is electrostrictive, are mechanically oppositely stressed when the membrane vibrates. If only one layer is electrostrictive, the neutral surface 9 must lie within the inactive layer or between the layers. If both layers are electrostrictive, the neutral surface 9 must lie between the two layers. In FIG. 2, the layer 2 is stretched in the zone 4 outside the turning circle 8 and compressed in the central zone 5 within the turning circle 8. Layer 3 is compressed in zone 6 outside 8 and stretched in zone 7 inside 8. The ring zones 4, 6 and the central zones 5, 7 thus form two oppositely acting flexural oscillators, the voltages of which compensate each other when electrodes are used that extend over the entire membrane surface. FIGS. 3 a and 3 b show an example of a layered membrane designed according to the invention, in which the zonal bending effect explained with reference to FIG. Fig. 3a shows a section A-B through the membrane., According to Fig. 3b. The membrane is clamped in a ring 10 and constructed as follows. On both sides of an extremely thin insulating film 11, metal electrodes 12, 13, 14, 15, for example made of silver or gold, 0.3 μ thick are vapor-deposited, in the manner as shown in FIG. 3 b. Layers 16, 17 of an electrostrictive material, for example barium titanate, each approximately 1 μm thick are vapor-deposited onto these electrodes, and metal electrodes 18, 19 and 18 are again deposited thereon. 20, 21 of the same form_and,. Thickness like 12, 13, 14, 15. The part of the membrane surface that is not vaporized with metal is the turning circle 8. The neutral surface 9 lies within the inactive insulating carrier film 11. To the connection of the central electrodes 13, 15, 19, 21 after To be guided outside, the ring electrodes 12, 14, 18, 20 are each slotted at one point 22. So that the membrane vibrates in the desired shape when electrically excited, for example as indicated in FIG. 2, or emits voltage when the two electrostrictive layers are the same polarization, adjacent layer zones must be polarized in opposite directions. However, it is also possible to polarize adjacent layer zones in opposite directions and then to polarize all zones of both layers in the same way. The invention is not restricted to the exemplary embodiments. The membrane can also consist of more than two electrostrictive layers or of a single electrostrictive and an inactive layer. In addition, the membrane can have any other suitable shape deviating from the circular shape. Patent claims:

1. Microphone and / or telephone membrane, which is clamped at the edge, consisting of several Layers, at least one of which consists of electrostrictive material, characterized in that, that the electrodes placed on either side of each electrostrictive layer are in place the change in the sense of curvature of the membrane are interrupted, creating different Zones are formed, and that adjacent zones are poled or polarized in such a way that they are at electrical excitation mechanically counteract.

2. microphone and / or telephone membrane according to claim 1, characterized in that the thickness of the entire membrane is smaller than 0.01 mm.

3. microphone and / or telephone membrane according to claims 1 and 2, characterized in that that it consists of an insulating middle layer on which both sides are alternately conductive and electrostrictive Layers, for example made of barium titanate, are vapor-deposited.

4. microphone and / or telephone membrane according to claims 1 and 2, characterized in, that it consists of an inactive and an electrostrictive layer with electrodes.

5. microphone and / or telephone membrane according to claims 1 to 4, characterized in that that the electrostrictive material is vapor deposited in an electric field.

6. microphone and / or telephone membrane according to claims 1 to 5, characterized in that that an air chamber is provided on its rear side to influence the resonance frequency.

7. microphone and / or telephone membrane according to claims 1 to 6, characterized in that that they prevent destruction in the event of excessive electrical or mechanical excitation swings between protective grilles.

8. microphone and / or telephone membrane according to claims 1 to 6, characterized in that, that it is circular.

9. microphone and / or telephone membrane according to claim 8, characterized in that the electrodes are designed as circular zones and that the outer slotted and the inner electrodes are passed through these slots to the outside.

1 sheet of drawings