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WO2006053528A1 - Transducteur electroacoustique - Google Patents

Transducteur electroacoustique Download PDF

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Publication number
WO2006053528A1
WO2006053528A1 PCT/DE2005/002030 DE2005002030W WO2006053528A1 WO 2006053528 A1 WO2006053528 A1 WO 2006053528A1 DE 2005002030 W DE2005002030 W DE 2005002030W WO 2006053528 A1 WO2006053528 A1 WO 2006053528A1
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WO
WIPO (PCT)
Prior art keywords
piezoelectric element
piezoelectric
electroacoustic transducer
transducer according
region
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/DE2005/002030
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German (de)
English (en)
Inventor
Joachim Hillenbrand
Xiaoqing Zhang
Gerhard Sessler
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Technische Universitaet Darmstadt
Original Assignee
Technische Universitaet Darmstadt
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication of WO2006053528A1 publication Critical patent/WO2006053528A1/fr
Anticipated expiration legal-status Critical
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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H04R17/02—Microphones
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2217/00—Details of magnetostrictive, piezoelectric, or electrostrictive transducers covered by H04R15/00 or H04R17/00 but not provided for in any of their subgroups
    • H04R2217/01—Non-planar magnetostrictive, piezoelectric or electrostrictive benders

Definitions

  • the present invention relates to an electroacoustic transducer comprising at least a first piezoelectric element and at least one second piezoelectric element electrically connected in series with the first piezoelectric element, the geometry of the first and second piezoelectric elements being used to generate electrical signals an at least regional exposure to sound waves is changeable, as well as the use of an electro-acoustic converter according to the invention.
  • US Pat. No. 4,670,074 discloses a generic electroacoustic transducer, namely a piezoelectric polymer transducer, and a method for producing the same.
  • this transducer at least one layer of a polymeric substance suitable for forming piezoelectric properties when laminated in the presence of an electric field to a conductive material acting as an electrode is used.
  • the conductive material is a polymeric substance.
  • a converter consists of two sheets each having metallized surfaces and an intermediate electrode, the sheets being welded together. By a bending of the sheets with an impact of sound waves are through the changes in the length of the sheets associated with the bending are generated in the so-called d 3 f direction due to the pizoe- lectric effect.
  • US 4,376,302 discloses a generic electroacoustic transducer in the form of a piezoelectric underwater sound receiver.
  • This underwater sound receiver contains a single flexible sheet of a piezoelectric polymer, which has a plurality of electrode strips on the top and bottom. The electrode strips on the upper side are offset relative to the strips on the underside. This leads to a complicated manufacturing process. Furthermore, the intermediate areas between the electrodes are piezoelectrically inactive, as a result of which a lower sensitivity of the receiver is present.
  • Another disadvantage of this electroacoustic transducer is that the sensitivity of the receiver is additionally lower due to the use of ordinary piezoelectric films, and thus the inherent noise level of the electroacoustic transducer is great.
  • electroacoustic transducers convert mechanical energy that is contained in sound waves into electrical energy (eg microphones) or convert electrical energy into mechanical energy that is emitted in the form of sound waves (eg loudspeakers).
  • the present invention relates to electroacoustic transducers of the first group.
  • the use of cellular piezoelectric polymer foils leads to a simple and inexpensive construction of the electroacoustic transducer, in particular in comparison to dynamic microphones, ceramic microphones, condenser microphones and electret microphones.
  • the quality of an electroacoustic transducer also depends, in particular, on the parameters sensitivity, intrinsic noise level, harmonic distortion factor and linearity.
  • these parameters are essentially determined by the film properties. It has been shown that the harmonic distortion and the linearity of the electroacoustic transducer can be optimized substantially by optimizing the film properties and the film material used. In contrast, when optimizing the sensitivity and the inherent noise level of the electroacoustic transducer, especially when using piezoelectric films, also mutually influencing factors must be considered.
  • the sound pressure acting on the piezoelectric element is converted by means of the piezoelectric effect into an alternating voltage proportional to the pressure.
  • the alternating voltage generated by the piezoelectric element due to the sound pressure change is as high as possible in order to make the sensitivity of the electroacoustic transducer as large as possible and to minimize the inherent noise level of the electroacoustic transducer.
  • an electroacoustic transducer in addition to a high sensitivity and a low inherent noise level in all frequency ranges for which the transducer is to be sensitive, an electroacoustic transducer should have a smooth frequency response, ie the output voltage should be substantially linearly proportional to the applied sound pressure in all frequency ranges. For this purpose, in particular all occurring natural frequencies of the electroacoustic transducer should be above the frequency range for which the transducer should be sensitive.
  • a plurality of piezoelectric elements are mechanically connected to one another and electrically connected in series in order to increase the output voltage and thus the sensitivity of the electroacoustic transducer, it is due to the mechanical coupling of the piezoelectric elements, in particular in the form of foils, that the Piezoelectric elements are no longer individually, but move or oscillate as a coupled system.
  • a system comprising a plurality of piezoelectric elements mechanically coupled to one another has a higher mass and thus a reduced resonance frequency.
  • the resonant frequency of the electroacoustic transducer is reduced substantially inversely proportional to the number of mechanically interconnected films.
  • the usable frequency range of the electroacoustic transducer is already clearly limited in the mechanical coupling of a few piezoelectric elements.
  • cellular piezoelectric polymer films are known which have a resonance frequency of approximately 100 kHz with the greatest sensitivity. If the electroacoustic transducer has a flat frequency response in the area of auditory sound, then the resonant frequency of the entire electroacoustic transducer must be kept well above 20 kHz so that a maximum of four piezoelectric polymer films can be combined by mechanical coupling.
  • the frequency range usable by the electroacoustic transducer is to be extended into the ultrasonic range, in particular in a frequency range above 50 kHz, such a mechanically coupled combination of piezoelectric films is no longer possible without the frequency response and the Sensitivity of the transducer is impaired, since above a resonant frequency, a steep drop in the sensitivity of the electroacoustic transducer occurs and susceptible individual foils have low resonance frequencies.
  • the production of cellular piezoelectric films takes place in the following way:
  • the starting film of the polymer material is first stretched bidirectionally, so that within the polymer material a large number of cavities is formed. For example by corona charging, these polymer films are then charged so electrically that electret charges are formed on opposite sides of these cavities. If sound waves enter such cellular polymer films, the cavities formed in the polymer film are compressed, so that a change in the thickness of the film material occurs. Since the modulus of elasticity of conventional polymer materials is about 1 GPa, whereas the pressure inside the cavities is 0.1 MPa, when an acoustic wave strikes the film, the cavities are compressed about 10,000 times more than the actual polymer material the cellular slides.
  • the films are made softer by, for example, the thickness of the films due to the expansion process
  • Softer foils, ie foils with a smaller modulus of elasticity and a greater thickness have a smaller thickness resonance frequency, ie a smaller natural resonant frequency for vibrations in vibrations, since the mass is the same compared to thinner and stiffer foils the d 33 " direction.
  • One way of increasing the sensitivity of the films could be Although they consist of charging the films better and higher, one is already approaching physical limits in the case of cellular piezoelectric films.
  • an electroacoustic transducer which has a smooth frequency response up to the ultrasonic range is of interest, even for the recording of audio signals.
  • digital recording media SACD and DVD-Audio
  • the invention is therefore based on the object, the generic electro-acoustic transducer such that the disadvantages of the prior art are overcome, in particular an electro-acoustic transducer is provided, which is simple als ⁇ built and thus inexpensive to produce and at the same time good parameters, in particular special has a high sensitivity.
  • first and the second piezo ⁇ electrical element each have at least a first decoupling region and the first piezoelectric element at least in the first decoupling at least partially so mechanically decoupled from at least the first decoupling region of the second piezoelectric element in that the piezoelectric elements can oscillate independently of one another or the geometry of the first piezoelectric element and the geometry of the second piezoelectric element are substantially independently variable and both the first and the second piezoelectric element in each case at least in the first decoupling region At least in certain areas, it is possible to act directly on sound waves.
  • first and / or the second piezoelectric element provision can be made in particular for the first and / or the second piezoelectric element to be or are at least partially foil-shaped, and / or the Changing the geometry of the first and / or second piezoelectric element when subjected to sound waves substantially in a change in thickness of er ⁇ first and / or second piezoelectric element consists.
  • the thickness of the film in the range of 0.5 .mu.m to 500 .mu.m, preferably in the range of 20 .mu.m to 150 .mu.m, more preferably in the range of 30 to 80 microns.
  • the width and / or the length of the first and / or the second piezoelectric element prefferably in the range from 0.5 mm to 500 mm, preferably in the range from 1 to 20 mm, even more preferably in the Range of 3 to 10 mm.
  • first piezoelectric element may be at least partially spaced from the second piezoelectric element, in particular the first decoupling region of the second piezoelectric element, at least in the first decoupling region, where preferably each because the first and / or the second piezoelectric element, in particular in the respective first decoupling region, can be or are acted on substantially on all sides by sound waves.
  • the first and the second piezoelectric element each have at least one first holding region, wherein the first piezoelectric element is at least partially fixable in the first holding region thereof by means of at least one first holding device and the second piezoelectric element by means of at least one second holding device at least partially in the first holding area of the same is fixable.
  • the invention proposes that the first and / or the second piezoelectric element each have or have at least one second holding region, wherein the first piezoelectric element in the second holding portion thereof by means of at least one third holding device is fixable and / or the second piezoelectric element in the second holding portion thereof by means of at least one fourth Garvor ⁇ direction is fixable.
  • This embodiment can be improved in that the first and / or the second piezoelectric element has or have a multiplicity of second holding regions and / or a multiplicity of third and / or fourth holding devices is present.
  • the first and / or the second piezoelectric element each comprise or have at least one second decoupling region, the geometry of the first and / or the second piezoelectric element being at least partially at least in the second decoupling region it is variable for generating electrical signals by means of an application of sound waves, in particular a change in thickness of the first and / or second piezoelectric element can be generated, and preferably the preferably foil-shaped first and / or the second piezoelectric element at least in the second decoupling region des ⁇ same is at least partially mechanically decoupled from the second or the first piezoe tric element.
  • An advantageous embodiment of the invention provides that the first and the second piezoelectric element are arranged so that at least the first and / or the second piezoelectric element at least in the second decoupling region dessel ⁇ ben at least partially from the second or first piezoelectric element is spaced or are, preferably on all sides directly acted upon by sound waves or are.
  • the first and / or the second decoupling region of the first and / or the second piezoelectric element is larger than the first the first and / or the second holding region of the first and the second piezoelectric ele ⁇ Mentes is or are.
  • the first and / or the second piezoelectric element at least partially, preferably at least in the first and / or second decoupling of the same, such surface roughness has or have a spacing between the first and / or second Piezoelectric element can be reached.
  • At least one spacer can be arranged in the region of the first and / or the second piezoelectric element.
  • At least one, preferably elek ⁇ trically insulating, spacers in the region of the first and / or the second Entkopp ⁇ lungs can be arranged.
  • At least one, preferably electrically conductive, Ab ⁇ spacers adjacent to the first and / or the second holding region of the first and / or the second piezoelectric element, preferably between the first and the second piezoelectric element, can be arranged.
  • the spacer comprises at least one on at least one surface of the first and / or the second piezoelectric element at least partially auf ⁇ brought lacquer layer, plastic coating and / or at least one layer of a dried ge th ⁇ adhesives.
  • the first and / or the second piezoelectric element comprises at least one spacer element, in particular in the region of the first and / or second decoupling region. Furthermore, it can be provided that the spacer at least one design of the shape of the first and / or the second, in particular film-shaped, piezoelectric element, preferably in the form of at least one elevation, at least one vertice, at least one fold and / or at least one curvature. comprises
  • the invention also proposes an electroacoustic transducer having a multiplicity of second decoupling regions of the first and / or the second piezoelectric element.
  • At least one surface, preferably at least two opposing surfaces, of the first and / or the second piezoelectric element is or are metallized at least in regions, preferably completely.
  • first and the second holding device, the first and the third, the second and the fourth and the third and the fourth holding device are executed in one, in particular the first and second piezoelectric element by means of the fixation by the first, second , Third and fourth holding device at least partially, preferably in the first and / or second holding area to contact the electrical series circuit directly or indirectly contact.
  • the invention proposes an electroacoustic transducer which is sensitive to sound waves in the audible, in the infrasound and / or in the ultrasonic frequency range.
  • the first and / or the second piezoelectric element at least partially by at least one air- and / or sound-transmitting, grounded shield, which preferably at least partially comprises a metal grid, umge ⁇ ben is. It is further proposed with the invention that a plurality of second piezoelectric elements electrically connected in series, wherein at least two second piezoelectric elements are mechanically decoupled from one another at least in one of the first and / or one of the second decoupling regions.
  • the invention proposes that the second piezoelectric elements are arranged such that at least one of the second piezoelectric elements at least in one of the first and / or one of the second decoupling regions is at least partially spaced from at least one further second piezoelectric element, preferably Sound waves can be applied directly on all sides, in which case at least one spacer, in particular in the region of the first and / or second decoupling region and / or in the region of the first and / or second holding region, can be arranged in the region of each second piezoelectric element.
  • the first or the second decoupling region of the first piezoelectric element and the first or second decoupling region of the second piezoelectric element (s) generate a first projection of the first and second piezoelectric elements and / or at least two second piezoelectric elements, in particular in the region of the first or second decoupling region of the first and / or second piezoelectric elements, have different geometric dimensions, in particular different lengths.
  • the first and / or the second holding region of the first piezoelectric element is at least partially connected to the first and the second piezoelectric element to produce an at least proportional spacing of the first and second piezoelectric elements and / or at least two second piezoelectric elements / or the second holding region of the second piezoelectric element (s) and / or the first and / or the second holding region of two second piezoelectric elements, in particular being offset from one another by means of the geometric configuration of the first, second, third and / or fourth holding device or are.
  • the first, second, third and / or fourth holding device is at least partially V-, U- and / or L-shaped or are.
  • the invention proposes that the first and / or the second piezoelectric element (s) are arranged in the form of at least one stack, in particular a foil stack, and / or the first and the second piezoelectric element zu ⁇ at least partially arranged one above the other.
  • the stack in particular in order to achieve a spacing between the first piezoelectric element and the second piezoelectric element and / or between two second piezoelectric elements, form a spiral, meander-shaped, accordion-shaped, conical, v-shaped, u-shaped is formed shaped and / or semicircular.
  • the first and / or the second or the second piezoelectric element (s) comprises a cellular and / or porous material with electret properties, in particular comprising a polymer foam, preferably based on polypropylene, a fluoropolymer, such as polyvinylidene fluoride, and / or a fluoro ethylene, such as polytetrafluoroethylene, preferably polytetrafluoroethylene FEP, comprise or comprise and / or in the form of layered, in particular foil-shaped elements, which zu ⁇ at least partially connected to form piezoelectrically acting cavities, is formed or are.
  • electroacoustic transducer can be used as an audio, ultrasound and / or infra-sound microphone.
  • the invention is therefore based on the surprising finding that a simply built-up and therefore inexpensive to produce electroacoustic transducer, which has very good sensitivity properties, can be provided by the fact that a plurality of piezoelectric elements, in particular comprising cellular piezoelectric Polymerfo- Lien, are combined so that the piezoelectric elements are electrically switched ge in series, but are mechanically decoupled. Thus, there is a mechanical decoupling of the piezoelectric elements in the decoupling regions.
  • the piezoelectric elements are preferably arranged such that the majority of each piezoelectric element can be excited individually by sound waves and the piezoelectric elements individually, ie mechanically decoupled, can oscillate, in particular variations in thickness, ie changes in the geometry in the d 33 .
  • Direction, inde pendent of each other are excitable.
  • the piezoelectric elements can be deformed independently of each other by the incident sound waves, ie the geometry of the respective piezoelectric element can be changed essentially independently of the geometry of the other piezoelectric elements.
  • the piezoelectric elements are also piezoelectrically active in the entire decoupling region and thus extremely sensitive.
  • the films are arranged so that they are mecha ⁇ nically interconnected only in a small area to achieve an electrical series connection, but freely schwin ⁇ gene over the remaining large area and have such a large distance from each other that sound waves between Each of the films can be excited independently of the others and the sensitivity of the microphone is increased on account of the electrical series connection of the films.
  • an n-fold sensitivity can be achieved with n films.
  • the combination of piezoelectric elements according to the invention leads to the fact that the sensitivity of the electro-acoustic transducer is increased by the fact that the Output voltages of the piezoelectric elements are added without optimizing the sensitivity of the individual piezoelectric elements, especially in cellular piezoelectric polymer films by reducing the modulus of elasticity, which negatively influences the frequency response of the piezoelectric element, as described above is.
  • piezoelectric elements comprising ferroelectrets, such as cellular piezoelectric films, are preferably used.
  • ferroelectrets are elements, such as films, which have piezoelectric properties, comprise a material which has electret properties, ie, is electrically insulating, but carries opposite electrical charges on at least two opposing surfaces, and is cellular or porous.
  • this also means layered elements, in particular layered films.
  • a plurality of film elements in particular thermally, at least partially connected to each other. In this connection, defined cavities form, which act piezoelectrically.
  • FIG. 1a is a schematic side sectional view of a first embodiment of an electroacoustic transducer according to the invention
  • Figure Ib is a plan view of the electro-acoustic transducer of Figure 1 from the direction
  • FIG. 2 a shows a schematic side sectional view of a second embodiment of an electroacoustic transducer according to the invention
  • FIG. 2b shows a detailed view I of the electroacoustic transducer of FIG. 2a;
  • Figure 3 is a schematic side sectional view of a third embodiment of an electroacoustic transducer according to the invention.
  • Figure 4 is a schematic side sectional view of a fourth embodiment of an electroacoustic transducer according to the invention.
  • FIG. 5 shows a detailed view of an electroacoustic transducer according to a fifth embodiment according to the invention.
  • FIG. 6a shows a plan view of a piezoelectric element in the form of a film strip according to the invention
  • FIG. 6b shows a side view of the film strip of FIG. 6a from direction B;
  • FIG. 6c shows a detailed view of an electroacoustic transducer comprising two foil strips according to FIGS. 6a and 6b;
  • FIG. 6d shows a detailed view of an electroacoustic transducer comprising four foil strips according to FIGS. 6a and 6b;
  • FIG. 7a shows a plan view of a piezoelectric element in the form of a film strip according to the invention
  • Figure 7b is a perspective view of the film strip of Figure 7a;
  • FIG. 7c shows a cross-sectional view of two film strips of FIGS. 7a and 7b in the installed state;
  • FIG. 7d shows a cross-sectional view of four film strips of FIGS. 7a and 7b in the installed state
  • FIGS. 7a and 7b shows a cross-sectional view of six film strips of FIGS. 7a and 7b in the installed state
  • FIG. 8a is a plan view of a combination of piezoelectric elements in the form of a film stack according to a sixth embodiment of an inventive electro-acoustic transducer;
  • FIG. 8b shows a side view of the film stack of FIG. 8a from direction C;
  • FIG. 8 c shows a plan view of a film stack according to a seventh embodiment of an electroacoustic transducer according to the invention.
  • FIG. 8d shows a detailed view II of the film stack of FIG. 8c
  • Figure 9 is a plan view of a film stack according to an eighth embodiment of an electroacoustic transducer according to the invention.
  • FIG. 10 shows a schematic side sectional view of a ninth embodiment of an inventive electroacoustic transducer.
  • FIG. 11 shows a schematic side sectional view of a tenth embodiment of an electroacoustic transducer according to the invention.
  • FIGS. 1a and 1b show an electroacoustic transducer 10 according to a first embodiment of the invention.
  • the electroacoustic transducer 10 comprises a first piezoelectric element in the form of a cellular piezoelectric polymer film 12 and a second piezoelectric element in the form of a cellular piezoelectric polymer film 14.
  • layered films may also be used as piezoelectric elements.
  • the piezoelectric films 12, 14 are fi xed by means of a first holding device in the form of a clamping device 16 on a board 18 fi ⁇ .
  • the first film 12 is fixed in a first holding region 20 and the second film 14 is fixed in a first holding region 22.
  • the board 18 carries the electrical circuit of the electro-acoustic transducer 10.
  • Both the surfaces of the piezoelectric films 12 and 14 facing the printed circuit board 18 and the the board 18 facing away from the surfaces Piezoelectric films 12 and 14 are metallized.
  • the surface of the film 12 facing away from the printed circuit board 18 is connected to the circuit located on the printed circuit board 18 via an unillustrated contacting.
  • the surface of the film 14 facing the printed circuit board 18 is likewise connected to the circuit of the electroacoustic transducer 10 located on the printed circuit board by means of an unillustrated electrical connection, which may in particular be encompassed by the clamping device 16.
  • the clamping device 16 is electrically non-conductive, so that the films 12, 14, in order to increase the voltage applied to the circuit board 18 located circuit, are electrically connected in series.
  • the electroacoustic transducer 10 is characterized in that the two piezoelectric foils 12, 14 in respective decoupling regions 24, 26 are acted upon by sound waves on both surfaces.
  • the piezoelectric films 12, 14 can be used independently of vibrate each other, in particular in their thickness direction, so that the electroacoustic transducer 10 due to the low masses of the piezoelectric films 12 and 14 and the associated relatively high resonant frequency of the individual piezoelectric films 12 and 14 has a large frequency range with a uniform sensitivity als ⁇ .
  • the films 12 and 14 are electrically connected in series, so that the potential differences generated on the surfaces of the films 12, 14 add up and thus a In comparison to the use of a single piezoelectric film increased output voltage of the elec ⁇ cal circuit of the electro-acoustic transducer can be supplied.
  • the electroacoustic transducer 10 has a high sensitivity over a wide frequency range.
  • FIG. 2 a shows a second embodiment of an electroacoustic transducer according to the invention in the form of a microphone 50.
  • the microphone 50 includes a base plate 52 which is particularly formed as a circuit board having an electrical circuit such as an amplifier circuit.
  • the microphone 50 further comprises a clamping device 54 which serves as first and second holding device for piezoelectric elements in the form of cellular piezoelectric polymer films 56, 58, 60, 62. Layered foils can also be used in this embodiment as an alternative to cellular polymer films.
  • the clamping device 54 can extend over the entire side length of the foils 56, 58, 60, 62 or, similar to the electroacoustic transducer 10 shown in FIG. 1b, only a part of the side edge of the foils 56, 58, 60, 62 fix.
  • FIG. 2 b shows a detailed view of the detail I of the microphone 50 of FIG. 2 a.
  • the clamping device 54 has clamping elements 54a and 54b.
  • the piezoelectric films 56, 58, 60, 62 each have a first holding region 56a, 58a, 60a, 62a, and a first decoupling region 56b, 58b, 60b and 62b.
  • the piezoelectric films 56, 58, 60, 62 are respectively metallized on their lower and upper sides.
  • the clamping element 54b kontak- The surface of the foil 56 facing away from the clamping element 54b is in direct contact with the surface of the foil 58 facing the clamping element 54b in the first holding region 58a , This results in an electric series connection between the films 56 and 58.
  • an electrically conductive spacer 64 is arranged, on the side facing away from the film 58, the first holding portion 60a of the film 60 rests.
  • the first holding portion 62a of the film 62 is placed on the first Halte ⁇ area 60a of the film 60.
  • the clamping element 54a of the clamping device 54 is grounded.
  • the clamping device 54 thus on the one hand leads to a mechanical fastening of the foils 56, 58, 60, 62 on the base plate 52.
  • the foils 56, 58, 60, 62 are loosely placed on top of one another via the clamping device 54 Haltebe ⁇ rich 56a, 58a, 60a, 62a fixed.
  • the spacer 64 also ensures that the foils 58 and 60, in particular outside the holding regions 58a, 60a, ie in the first decoupling regions 58b, 60b, are spaced apart from one another or only slightly in these regions 58b, Touch 60b.
  • Figures 2a and 2b are not to scale the relative position of the films 56, 58, 60, 62 represent ins ⁇ particular the fanning of the films 56, 58, 60, 62 is greatly exaggerated, wo ⁇ in in reality the foils 56, 58, 60, 62 are relatively close together.
  • a spacer 66 is arranged on the upper side of the film 56 in the first decoupling region 56b.
  • a similar spacer 68 is also arranged on the film 60 in the first decoupling region 60b.
  • the spacers 66, 68 ensure that the foils 56, 58, in the decoupling regions 56b, 58b, and the foils 60 and 62 in the decoupling regions 60b and 62b are at least partially spaced apart from one another.
  • the films 56, 58, 60, 62 outside the holding areas 56a, 58a, 60a and 62a touch only slightly and are vonein ⁇ other spaced, whereby air between the films 56, 58, 60, 62 in the Ent ⁇ coupling areas 56b, 58b, 60b, 62b is located.
  • At least one spacer is present in the decoupling region or holding region between each pair of foils, without corresponding spacers being provided in the respective holding region or decoupling region. If a sound wave hits the microphone 50, then each film 56, 58, 60, 62 is exposed to the changes in sound pressure, at least in the decoupling region 56b, 58b, 60b, 62b. Due to the changes in sound pressure, there is a change in the geometry of the films 56, 58, 60, 62, in particular in the decoupling regions 56b, 58b, 60b, 62b.
  • This geometry change is in particular a change in the film thickness D, so that due to a high piezo constant d 33 of the films 56, 58, 60, 62 charges are generated on the respective surfaces of the films 56, 58, 60, 62. Due to the electrical series connection of the foils 56, 58, 60, 62, the voltages generated by the foils 56, 58, 60, 62 are added. This results in a high sensitivity of the microphone 50, up to high frequencies.
  • the resonance frequency of the piezoelectric elements of the microphone 50 is hardly changed, at least in the decoupling areas 56b, 58b, 60b, 62b, compared with the use of a single foil.
  • the sensitivity of the four-foil microphone 50 is significantly increased, namely approximately four times as high, without the useful frequency range of the microphone 50 being reduced compared to a single-microphone .
  • the spacers 66, 68 are, in particular, a lacquer layer which is applied to the foil 56 or 60 before the foils 56, 58, 60, 62 are stacked on one another.
  • the thickness of the same and thus the height of the spacer 66 and 68 and thus the distance of the films with each other can be adjusted well.
  • the lacquer layer it is also possible to apply a plastic coating or an adhesive agent layer which is dried before the films are applied to one another.
  • the films are submerged in a lacquer in regions before depositing the films, whereby a substantially continuous layer is formed, which in particular is a fraction of a millimeter thick and thus the mechanical properties of the films is not affected.
  • the lacquer applied in this way has a certain, easily adjustable thickness and leads to a spacing of the foils from one another so that air and thus sound waves can pass between the foils.
  • the first holding regions 56a, 58a, 60a, 62a are as small as possible in relation to the first decoupling regions 56b, 58b, 60b, 62b.
  • FIG. 3 shows a third embodiment of an electroacoustic transducer according to the invention in the form of a microphone 100.
  • the structure of the microphone 100 is similar to that of the microphone 50.
  • the microphone 100 has a base plate 102 on which a clamping device 104 is arranged.
  • piezoelectric elements in the form of piezoelectric, in particular cellular or layered films 106, 108, 110 and 112 are fixed locally such that an electrical Rei ⁇ henscaria between the piezoelectric films 106, 108, 110 and 112 is achieved and simultaneously Using spacers similar to those used in the microphone 50, a fanning of the films 106, 108, 110 and 112 is achieved so that air and thus sound waves can pass between the individual films 106, 108, 110 and 112. In this case, a fixing of the films by means of the Haltvor ⁇ direction 104 over the entire depth of the films or only in partial areas. In contrast to the film microphone 50 shown in FIGS.
  • the films 106, 108, 110, 112 of the microphone 100 have second decoupling regions 106c in addition to first holding regions in the region of the clamping device 104 and first decoupling regions 106b, 108b, HOb, 112b. 108c, 110c and 112c.
  • the piezoelectrically active area of the films 106, 108, 110, 112 is increased in comparison to the films 56, 58, 60, 62 of the microphone 50, whereby the sensitivity of the microphone 100 is further increased compared to the microphone 50 without causing it to malfunction of the microphone 100 due in particular by vibrations from the outside Bending vibrations of the films 106, 108, 110, 112 in the decoupling areas 106b, 106c, 108b, 108c, HOb, HOc, 112b, 112c can come.
  • FIG. 4 shows a fourth embodiment of an electroacoustic transducer according to the invention in the form of a microphone 150.
  • the microphone 150 has a base plate 152, which in particular at least partially carries the electrical circuit of the microphone 150, wherein on the base plate 152 and no electrical component can be located.
  • Foils, in particular cellular or layered piezoelectric foils 156, 158, 160, 162, are mechanically fastened to the base plate 152 by means of a holding device 154, and the foils 156, 158, 160, 162 metallized on both sides are electrically connected in series via the clamping device 154.
  • the films 156, 158, 160, 162 are in particular fanned out by the spacers described above, so that they are spaced von ⁇ and air and thus sound waves in the spaces zwi ⁇ tween the films 156, 158, 160, 162 can occur.
  • the microphone 150 provision is made in particular for sound waves to occur on the microphone 150 from a direction from above in FIG.
  • the microphone 150 comprises a shielding device 164 in the form of an air and sound-permeable metal grid, the grid being grounded, as can be seen in the figure.
  • the piezoelectric elements are loosely stacked in the form of cellular piezoelectric polymer films 202, 204, 206, 208 metallized on both sides each fixed in a holding region 202a, 204a, 206a, 208a by means of a holding device 210 and at the same time electrical are contacted so that the piezoelectric films 202, 204, 206, 208 are connected in series.
  • Layered films can also be used instead of piezoelectric cellular films.
  • the films 202, 204, 206, 208 have a rough surface, so that air is between the respective films 202, 204, 206, 208, and sound waves between the respective films 202, 204, 206th 208 can occur and independent vibrations of each foil 202, 204, 206, 208, in particular thickness vibrations, can take place in the decoupling regions 202b, 204b, 206b, 208b.
  • the spacing of the foils 202, 204, 206, 208 is achieved in particular by the fact that they only contact one another selectively at the elevations caused by the surface roughness and thus have a spacing in the remaining regions.
  • a spacing between the individual piezoelectric elements can also be achieved by a suitable design of the shape of the piezoelectric elements, in particular by forming at least one spacer element.
  • a piezoelectric element in the form of a cellular piezoelectric polymer film strip is shown 250 shown in supervision.
  • the foil strip can also consist of layered foils.
  • Fig. 5b of the film strip 250 is shown in side view from direction B in Fig. 6a.
  • the foil strip 250 has a spacer element in the form of a bend 252. This kink 252 is perpendicular to a longitudinal axis x of the foil strip 250.
  • the longitudinal kink 252 By the longitudinal kink 252, as can be seen from FIGS. 6c and 6d, it is achieved that in the case of incorporation of a plurality of foils which have a shape analogous to the foil strip 250 in an electroacoustic transducer a spacing between individual piezoelectric films 254, 256 or 262, 264, 266 and 268 can be achieved.
  • two piezoelectric films 254, 256 are fixed by means of a holding device 258.
  • the film 254 has a fold or a bend 255 and the film 256 has a fold or a bend 257.
  • piezoelectric films 254, 256 in respective decoupling regions 254a and 256a are spaced apart so that sound waves between the films 254, 256 can occur and so the two films 254, 256 when excited by sound waves independently of each other, especially in their thickness direction.
  • piezoelectric sheets 262, 264, 266, and 268 having creases 263, 265, 267, and 269, respectively are fixed by means of a retainer 260. As can be seen from FIG.
  • the formation of the creases 263, 265, 267, 269 results in the films 262, 264, 266, 268 being at least partially spaced from each other in such a manner that sound waves are between two each The films can occur and so vibration excitation of the individual films can be achieved independently of the respective other ren films for generating an electrical voltage.
  • Such a spacing of individual piezoelectric elements, in particular in the form of cellular piezoelectric polymer films or layered films can also be achieved by a folding or folding of the corresponding piezoelectric element take place along a longitudinal direction of the piezoelectric element.
  • FIGS. 7 a, 7 b a piezoelectric element in the form of a cellular piezoelectric polymer film strip 300, which has a bend 302 along a longitudinal direction x 'of the film strip 300, is shown.
  • FIG. 7c shows a combination of two films 304 and 308 bent or folded analogously to the film strip 300.
  • the film 304 has a bend 306, while the film 308 has a bend 310.
  • FIG. 7c shows a sectional view of the films 304, 308 in a decoupling region.
  • the longitudinal bend 306 of the film 304 and the longitudinal crease 310 of the film 308 ensure that the films 304, 308 are spaced apart from one another in this decoupling region 50 so that sound waves can enter between the films 304, 308 and a piezoelectric activity of the films 304, 308 can be produced.
  • FIGS. 7d and 7e such an arrangement of piezoelectric films or film strips is not restricted to two films, but by forming a longitudinal bend along the respective films, film stacks can be constructed in which each is ensured in that a spacing between each two adjacent foils is achieved in such a way that sound waves can pass between the foils in order to achieve a corresponding excitation of the piezoelectric effect in the individual foils independently of one another.
  • a film stack is shown consisting of four piezoelectric films 312, 314, 316 and 318
  • FIG. 7e shows a film stack consisting of six films 320, 322, 324, 326, 328 and 330.
  • FIGS. 8a to 9 show embodiments of corresponding piezoelectric elements which make it possible to arrange a large piezoelectrically active area in the smallest possible space when using, in particular cellular, piezoelectric polymer films or layered films and thus a high film capacity to reduce the necessary space of an electroacoustic transducer.
  • FIG. 8 a shows a first stack of piezoelectric films of a sixth embodiment of an electronic acoustic transducer according to the invention, comprising three film strips 400, 402, 404 shown.
  • the film 400 is a polymer film that has no piezoelectric properties and serves as insulation while the films 402, 404 are cellular piezoelectric polymer films.
  • FIG. 8b shows a side view of the film stack of FIG. 8a from direction C.
  • FIG. A sound or air inlet or outlet into or out of the foil stack of FIG. 8a takes place in the direction of the arrows 414, 416.
  • FIG. 8c shows a further embodiment of a film stack 450 of a seventh embodiment of an electroacoustic transducer according to the invention. Similar to the film stack shown in FIG. 8a, in the film stack 450 of FIG. 8c, the stack 450 is wrapped around it after being mounted in a fixture 452. In contrast to the film stack shown in FIG. 8 a, however, the end of the film stack 450 opposite that of the holding device 452 is clamped in a holding device 454. As can be seen from FIG. 8d, which shows a section of the film stack 450 of FIG. 8c corresponding to the detail II, the film stack 450 consists of individual films 456, 458, 460 and 462.
  • the films 456, 458 , 460 are piezoelectric films
  • the film 462 is an insulation of a polymer film having no piezoelectric properties.
  • the foils 456, 458, 460 are metallized on both sides and via the holding device 452 or 454 it is achieved that the foils 456, 458, 460 contact each other in such a way that they are electrically connected in series.
  • FIG. 9 shows a foil stack 450 according to an eighth embodiment of an electroacoustic transducer according to the invention, comprising the piezoelectric foils 502, 504 and 506.
  • the film stack 500 is clamped in via clamping devices 508, 510 in such a way that the piezoelectric films 502, 504, 506 metallized on both sides contact each other and are electrically connected in series.
  • the clamping device 508, 510 By appropriate interconnection of the clamping device 508, 510, the use of an insulating film, as is necessary in the film stack shown in FIGS. 7a to 7d, can be dispensed with. As can be seen from FIG.
  • the superimposed individual foils 502, 504, 506 are folded in a zigzag shape in such a way that corresponding free spaces form between the foils 502, 504, 506, into which sound waves can enter and a respective independent oscillation of the films 502, 504, 506 can effect.
  • a sound or air inlet or outlet occurs in the film stack 500 in a direction perpendicular to the plane of the drawing of FIG. 9.
  • FIG. 10 shows a ninth embodiment of an electroacoustic transducer in the form of a microphone 1200.
  • the microphone 1200 has a base plate 1202 on which clamping devices 1204 and 1206 are arranged.
  • clamping devices 1204 and 1206 By means of the clamping devices 1204, 1206, piezoelectric elements in the form of the foils 1208, 1210, 1212, 1214, 1216 are held.
  • the foils 1208, 1210, 1212, 1214, 1216 have first holding regions 1208a, 1210a, 1212a, 1214a and 1216a as well as second holding regions 1208d, 121Od 3 1212d, 1214d, 1216d.
  • the foils 1208, 1210, 1212, 1214, 1216 have, between the first holding regions 1208a, 1210a, 1212a, 1214a, 1216a and the second holding regions 1208d, 121Od, 1212d, 1214d, 1216d, first decoupling regions 1208b, 1210b, 1212b, 1214b, 1216b.
  • the foils 1208, 1210, 1212, 1214, 1216 have different lengths, so that by fixing the foils 1208, 1210, 1212, 1214, 1216 by the clamping devices 1204, 1206 to a spacing of the foils 1208, 1210, 1212, 1214, 1216 comes without the use of Abstandshal ⁇ tern is necessary.
  • FIG. 11 shows an inventive electroacoustic transducer in the form of a microphone 1250.
  • the microphone 1250 has a baseplate 1252 that carries the electrical circuit of the microphone 1250.
  • the microphone 1250 comprises a first holding device 1254 and a second holding device 1256.
  • piezoelectric elements in the form of the films 1258, 1260, 1262, 1264, 1266, 1268, 1270 are arranged.
  • the slides of the microphone 1250 have substantially equal lengths.
  • FIG. 11 shows an inventive electroacoustic transducer in the form of a microphone 1250.
  • the microphone 1250 has a baseplate 1252 that carries the electrical circuit of the microphone 1250.
  • the microphone 1250 comprises a first holding device 1254 and a second holding device 1256.
  • the Haltevor ⁇ devices 1254, 1256 piezoelectric elements in the form of the films 1258, 1260, 1262, 1264, 1266, 1268, 1270 are arranged.
  • the slides of the microphone 1250
  • the holding devices 1254, 1256 are formed in a V-shaped manner in regions, so that the points at which the film 1258 is fastened to the holding devices 1254, 1256 have a smaller distance from each other than the ones In this way, a spacing of the films 1258, 1260, 1262, 1264, 1266, 1268, 1270 is achieved in the respective decoupling regions, whereby if air and thus sound waves can pass between the foils 1258, 1260, 1262, 1264, 1266, 1268, 1270.
  • electroacoustic transducers have been described in the exemplary embodiments whose piezoelectric elements have cellular piezoelectric polymer films or 147 ⁇ th films, the invention is not limited to the use of films or Ver ⁇ use of these materials.
  • other, in particular cellular or porous materials, such as Teflon or the like, as piezo ⁇ electrical material or other geometries of the piezoelectric elements can be used.
  • the invention provides an electroacoustic transducer, in particular in the form of a microphone, whose frequency range can be extended far beyond the usual range of 20 kHz at high sensitivity, if desired, and is structurally simple and inexpensive to produce.
  • the microphone thus fulfills requirements in order to also use DVDs in the audio sector, in particular in order to exploit the high storage capacities of this medium in order to be able to record frequency ranges outside the audible range, in particular in the ultrasound range.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)

Abstract

L'invention concerne un transducteur électroacoustique comprenant au moins un premier élément piézoélectrique et au moins un deuxième élément piézoélectrique couplé électriquement au premier élément piézoélectrique en série, la géométrie du premier et du deuxième élément piézoélectrique pouvant être modifiée par une application d'ondes sonores au moins locale afin de générer des signaux électriques. Selon l'invention, le premier et le deuxième élément piézoélectrique présentent chacun au moins une première zone de découplage et le premier élément piézoélectrique est découplé mécaniquement au moins de la première zone de découplage du deuxième élément piézoélectrique au moins dans sa première zone de découplage au moins localement de sorte que les éléments piézoélectriques puissent osciller séparément indépendamment l'un de l'autre ou que la géométrie du premier élément piézoélectrique et la géométrie du deuxième élément piézoélectrique puissent être modifiées sensiblement indépendamment l'une de l'autre, le premier et le deuxième élément piézoélectrique pouvant être exposés directement à des ondes sonores dans au moins leur première zone de découplage au moins localement.
PCT/DE2005/002030 2004-11-22 2005-11-11 Transducteur electroacoustique Ceased WO2006053528A1 (fr)

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DE200410056200 DE102004056200A1 (de) 2004-11-22 2004-11-22 Elektroakustischer Wandler
DE102004056200.8 2004-11-22

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EP2286988A1 (fr) 2008-12-13 2011-02-23 Bayer MaterialScience AG Composite ferroélectrique à deux et plusieurs couches et son procédé de fabrication
EP2328360A1 (fr) 2009-11-12 2011-06-01 Bayer MaterialScience AG Composite ferroélectrique à deux et plusieurs couches et son procédé de fabrication
EP2439000A1 (fr) 2010-10-05 2012-04-11 Bayer MaterialScience AG Composite en couche polymère doté de propriétés ferroélectriques et son procédé de fabrication
EP2450974A1 (fr) 2010-11-03 2012-05-09 Bayer MaterialScience AG Composite en couche polymère doté de propriétés ferroélectriques et son procédé de fabrication
US8446080B2 (en) 2008-12-13 2013-05-21 Bayer Materialscience Ag Ferroeletret multilayer composite and method for producing a ferroelectret multilayer composite with parallel tubular channels
US11438703B2 (en) * 2019-06-27 2022-09-06 Qualcomm Incorporated Ultrasonic sensor array

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2286988A1 (fr) 2008-12-13 2011-02-23 Bayer MaterialScience AG Composite ferroélectrique à deux et plusieurs couches et son procédé de fabrication
US8446080B2 (en) 2008-12-13 2013-05-21 Bayer Materialscience Ag Ferroeletret multilayer composite and method for producing a ferroelectret multilayer composite with parallel tubular channels
EP2328360A1 (fr) 2009-11-12 2011-06-01 Bayer MaterialScience AG Composite ferroélectrique à deux et plusieurs couches et son procédé de fabrication
EP2339869A1 (fr) 2009-11-12 2011-06-29 Bayer MaterialScience AG Composite ferroélectrique à deux et plusieurs couches et son procédé de fabrication
EP2439000A1 (fr) 2010-10-05 2012-04-11 Bayer MaterialScience AG Composite en couche polymère doté de propriétés ferroélectriques et son procédé de fabrication
EP2450974A1 (fr) 2010-11-03 2012-05-09 Bayer MaterialScience AG Composite en couche polymère doté de propriétés ferroélectriques et son procédé de fabrication
WO2012059437A1 (fr) 2010-11-03 2012-05-10 Bayer Materialscience Ag Composite polymère stratifié possédant des propriétés de ferro-électret et son procédé de fabrication
CN103460423A (zh) * 2010-11-03 2013-12-18 拜耳知识产权有限责任公司 具有铁电驻极体特性的聚合物复合层及其制造方法
US11438703B2 (en) * 2019-06-27 2022-09-06 Qualcomm Incorporated Ultrasonic sensor array

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