EP0180518A1 - Elektroakustischer Wandler mit piezoelektrischer Membran - Google Patents

Elektroakustischer Wandler mit piezoelektrischer Membran Download PDF

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Publication number
EP0180518A1
EP0180518A1 EP85402071A EP85402071A EP0180518A1 EP 0180518 A1 EP0180518 A1 EP 0180518A1 EP 85402071 A EP85402071 A EP 85402071A EP 85402071 A EP85402071 A EP 85402071A EP 0180518 A1 EP0180518 A1 EP 0180518A1
Authority
EP
European Patent Office
Prior art keywords
diaphragm
spacer
electroacoustic transducer
printed circuit
transducer according
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.)
Withdrawn
Application number
EP85402071A
Other languages
English (en)
French (fr)
Inventor
Jean-Paul Morgand
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
Original Assignee
Thomson CSF SA
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.)
Filing date
Publication date
Application filed by Thomson CSF SA filed Critical Thomson CSF SA
Publication of EP0180518A1 publication Critical patent/EP0180518A1/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R7/00—Diaphragms for electromechanical transducers; Cones
    • H04R7/16—Mounting or tensioning of diaphragms or cones
    • H04R7/18—Mounting or tensioning of diaphragms or cones at the periphery
    • H04R7/22—Clamping rim of diaphragm or cone against seating
    • 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
    • H04R17/005—Piezoelectric transducers; Electrostrictive transducers using a piezoelectric polymer
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2499/00—Aspects covered by H04R or H04S not otherwise provided for in their subgroups
    • H04R2499/10—General applications
    • H04R2499/11—Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's

Definitions

  • the present invention relates to electroacoustic transducers for converting an acoustic pressure into an electrical voltage. It relates more particularly to microphones in which the conversion of an acoustic vibration into an electrical voltage is ensured by a vibrating element made of piezoelectric polymer.
  • This transducer uses an elastic structure in the form of a recessed plate having at least one curvature and covered on its two faces with electrodes connected to an electrical impedance adapter circuit. It is composed of a set of elements arranged according to an original principle which gives it excellent qualities. However, the relatively large number of these elements and their method of assembly do not satisfy a mass production of these transducers, at high speed and at low cost.
  • the invention provides an electroacoustic transducer with a piezoelectric diaphragm, the main elements of which are designed in an original way which makes it possible to avoid the use of an insulating jacket and to efficiently perform the embedding functions vibrating element, electrical connection and acoustic filtering.
  • the subject of the invention is therefore an electroacoustic transducer whose vibrating element consists of a piezoelectric diaphragm subjected to acoustic pressure on at least one of its faces, each face being covered with an electrode connected to an electrical circuit arranged on a printed circuit, the diaphragm and the electrical circuit being enclosed in a housing constituted by a tubular body whose bottom is a perforated wall corresponding to the front face of the transducer, said body and a spacer ensuring the embedding of the diaphragm, said printed circuit ensuring the closing of the transducer along the rear face of said body and the positioning of the spacer, the electrical connection means being provided by the body and the spacer, characterized in that the spacer is a hollow structure of form flared whose large crown-shaped base presses the diaphragm against a shoulder of the body to ensure its embedding and whose small b ase is fixed on the center of the printed circuit.
  • Microphone capsules or headphones generally include a piezoelectric diaphragm which can be deformed under the action of the acoustic pressure applied to it and the periphery of which is fixed to at least a rigid piece surrounding it and forming the support. Under the action of an acoustic pressure, the diaphragm deforms and a potential difference appears between its main faces which are provided with electrodes. This potential difference is then amplified to provide the output signal from the device.
  • the diaphragm generally consists of a sheet of piezoelectric polymer such as vinylidene bifluoride (PVF 2 ), or of copolymer.
  • This sheet is embedded by its periphery in the upper part of a housing whose lower part is closed by a printed circuit supporting a preamplifier.
  • Acoustic damping means make it possible to correct the frequency response by avoiding the resonance peaks of the first natural modes of the diaphragm.
  • Figure 1 is a meridian sectional view of a microphone capsule according to the prior art.
  • the active part of the capsule consists of the piezoelectric diaphragm 1 covered on its upper and lower faces with metallizations serving as electrodes.
  • the diaphragm 1 is clamped along its periphery between the body 2 and the spacer 3 which play the role of embedding parts.
  • Parts 2 and 3 are metallic and also provide electrical connection functions between the diaphragm electrodes and the double-sided printed circuit 4.
  • Body 2 forms the upper part and the sides of the capsule.
  • the printed circuit forms the bottom of the capsule. It supports on its internal face electronic components 5 constituting a preamplifier and on its external face pins not shown making it possible to connect the capsule to a connection cable.
  • the upper electrode of the diaphragm, the body 2 and the external face of the printed circuit 4 form a first equipotential which provides the shielding of the diaphragm and of the components 5.
  • the lower electrode of the diaphragm, the spacer 3 and the internal face of the circuit printed form the second equipotential.
  • the annular jacket 6 ensures the electrical isolation of the body 2 with respect to the spacer 3.
  • the body 2 and the spacer 3 can be used advantageously to delimit on either side of the diaphragm cavities and walls pierced with orifices so as to synthesize acoustic components capable of regularizing the microphone response curve.
  • These acoustic components are materialized by the wall 7 of the body 2, this wall being pierced with holes 8, and by the wall 10 of the spacer 3, this wall being pierced by the hole 9.
  • the assembly of the capsule is facilitated by the fact that the symmetry of revolution is everywhere preserved: the relative positioning of the different parts constituting the capsule is thus simply ensured by their stacking and their concentricity.
  • the body 2 initially has, in its lower part, the tubular geometry indicated in dotted lines.
  • the order of assembly operations is as follows: the body first receives the annular insulating jacket 6 which then allows the centering of the diaphragm 1 and of the spacer 3.
  • the printed circuit 4 with its soldered components is then put in components inside the capsule.
  • the stacking and the embedding are tightened by crimping the body 2 on the external face of the printed circuit.
  • the diaphragm must be curved to provide a concave or convex dome.
  • the embedding plane is in this case inclined according to a preset slope calculated according to the arrow-diameter ratio to be given in order to obtain a sensitivity as little dependent on temperature as possible.
  • the lateral part of the body 2 and the spacer 3 are coaxial over a large part of the height of the housing, which requires the presence of the insulating jacket 6 made of a material having a low dielectric constant.
  • the choice of this material thus reduces the parasitic capacity between the body and the spacer. It is also possible to make recesses in the insulating jacket, which makes it possible to reduce the parasitic capacity existing between the body and the spacer, but this complicates the production of the jacket and increases the cost price of the capsule.
  • the transducer according to the invention does not use an insulating jacket.
  • the fact of not using an insulating jacket poses the problem of the electrical insulation of the body and of the spacer and of the shape that must be given to it so that the mounting of the capsule makes it possible to obtain both electrical insulation, sound absorption and tolerance to temperature variations sufficient to meet the required performance.
  • FIG. 2 represents a first embodiment of the capsule according to the invention. It is a view in sectional meridian.
  • the capsule comprises, in addition to the piezoelectric diaphragm 20, three main parts: a body metal 21 forming the housing and the ground electrode, a metal cup 22 forming the spacer and transmitting the electrical signal induced in the diaphragm by an incident acoustic pressure, a printed circuit 23 forming the bottom of the housing.
  • the diaphragm is metallized on its two main faces. One of its electrodes comes into contact with the housing 21 while the other is in contact with the cup 22.
  • the spacer has a large base in contact with the diaphragm and a small base in contact with the printed circuit.
  • the spacer or cup 22 has been given the form of a funnel which allows to leave between the lateral parts of the body 21 and said spacer, sufficient air space to obtain acceptable electrical isolation and reduced parasitic capacity.
  • the cup is mounted so as to be clamped, after crimping the body on the printed circuit, between a shoulder 211 of the body and the printed circuit on which it is supported along the axis of symmetry of the capsule.
  • the cup is made integral with the printed circuit, for example by an assembly of the tenon and mortise type.
  • the pin 222 and the mortise 230 can be cylindrical in shape to respect the overall symmetry of the capsule.
  • the spacer 22 expands or contracts which can cause disturbing stresses at the diaphragm.
  • the wall of the spacer can be profiled so as to have at least one inflection 220. The mechanical effects due to temperature variations will then manifest themselves mainly in the inflection zone.
  • the wall can also be drilled in certain places with holes 221. The number, the distribution and the diameter of these holes make it possible to synthesize an acoustic filter between the two cavities 24 and 29 so as to correct the frequency response of the transducer.
  • the front part of the body is pierced with holes 210 and constitutes, with the cavity 30 formed by this front part and the diaphragm, another acoustic filter. It is advantageous to glue a protective film or fabric 31 to the front of the housing in order to avoid the introduction of dust or moisture inside the capsule.
  • an annular cushion 28 shown in dotted lines in the figure and made of flexible and insulating material can be placed between the parts closest to the body and the cup.
  • the printed circuit 23 can support on its internal face the components of the preamplifier, essentially the input resistance 26 of several megohms and the microbattery 27 containing a Darlington circuit with 2 transistors or a field effect transistor.
  • the diaphragm 20 is preferably rounded either before or at the time of mounting so as to increase the sensitivity of the transducer.
  • the thickness of the diaphragm is chosen to be at the maximum of sensitivity for a given diameter which determines its active capacity.
  • the shoulder 211 and the edge of the spacer 22 facing each other are inclined to form a conical bearing surface in order to pinch the diaphragm at the desired angle. Maintaining the diaphragm is ensured by machining the parts concerned of the elements 21 and 22 at a sharp angle.
  • the volume limited by the diaphragm, the body and the printed circuit is closed. In order to avoid an increase in the pressure of the air enclosed in this volume, it is necessary to cause leaks equalizing static pressure. Instead of drilling an orifice passing right through the printed circuit, it is possible to make radial capillary leaks or vents breaking the tightness of the tightening of the body crimped on the printed circuit.
  • the etching on both sides of the circuit is such that air passages are created in the thickness of the copper layer of the printed circuit.
  • the rear cavity of the microphone is thus connected to atmospheric pressure.
  • An alternative embodiment would consist in having a cup 22 made of insulating material and of which certain parts would be metallized (the crown in contact with the diaphragm, the zone of contact with the printed circuit) in order to ensure the electrical connection between the diaphragm and the printed circuit. Electrical continuity could be ensured by metallization of the holes 221.
  • This variant has the advantage of reducing the parasitic capacity present between the body and the spacer. In this case, the cushion 28 can be omitted.
  • the transducer according to the invention has electro-acoustic characteristics equivalent to the transducer of the known art represented in FIG. 1 but saves on one element, namely the insulating jacket.
  • the acoustic means which allow the shaping of the response curve and in particular the damping of the first resonance are simplified.
  • FIG 3 is a meridian sectional view of a second embodiment of the capsule according to the invention.
  • This capsule differs from that shown in Figure 2 by the shape of the spacer which is made in two parts and by the way it rests on the printed circuit.
  • the body 41 is identical to that of FIG. 2. Its front part is pierced with holes 410 and is covered with a protective fabric 51.
  • the body has a shoulder 411 intended to receive the diaphragm 40.
  • the diaphragm is metallized on its two main faces.
  • One of its electrodes is in contact with the housing or body 41 while the other is in contact with the upper part of the spacer or cup 42.
  • the housing is closed by crimping the body on the printed circuit double-sided 43 which supports the components 46 and 47 of the preamplifier.
  • There is also shown one of the output lugs 45 which are plugged into the printed circuit 43.
  • the capsule differs from that of FIG. 2 by the presence of an additional element, the support 52 formed of a metal part mounted on the printed circuit along the axis of revolution of the capsule and constituting the lower part of the spacer. .
  • the support 52 presses on the cup 42, which in turn rests on the diaphragm according to its peripheral crown.
  • the cup and the support 52 being made of conductive material, the electrical connection between the diaphragm and the printed circuit is ensured.
  • the center of the cup 42 has a re-entrant shape 422 which matches the shape of the upper part of the support 52. Holes 421 have been drilled in the cup in order to form an acoustic filter.
  • the re-entrant shape 422 of the cup contributes to reducing the harmful influence of the stresses due to temperature variations on the part of the cup towards the diaphragm.
  • the assembly of the capsule is carried out as follows.
  • the electronic elements 46 and 47 are welded to the printed circuit on which the support 52 is also fixed, for example by crimping or soldering.
  • the different elements are stacked in the body 41 in the following order: diaphragm, cup, printed circuit equipped with the support 52.
  • the diaphragm centers itself automatically thanks to the shoulder 411.
  • the crimping of the rim of the body on the printed circuit ensures the assembly by clamping of the assembly.
  • the cup 42 may be metallic or made of a dielectric material metallized on certain parts so as to ensure both electrical continuity and a reduction in the stray capacitance.
  • the center of the cup 42 can be pierced with a circular hole.
  • the support 52 can have a pyramid-shaped end whose dimensions are such that the support fits into the central hole of the cup and presses the latter on the diaphragm. In this case, there is an air leak between the interior and the exterior of the cup and the holes 421 no longer have any reason to be.
  • FIG. 4 is a diagram representing the response curve obtained by such a capsule.
  • the ordinate axis represents the sensitivity S in decibels whose origin is chosen arbitrarily.
  • the abscissa axis represents the frequency in hertz on a logarithmic scale.
  • the curve obtained has the reference 60.
  • the sensitivity at 1000 Hz is equal to 1 / uV / Pa.
  • the invention allows the production in large series and at low cost of microphone capsules having the performance required by generally accepted standards and in particular those in force in France.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)
EP85402071A 1984-10-30 1985-10-25 Elektroakustischer Wandler mit piezoelektrischer Membran Withdrawn EP0180518A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8416594A FR2572616A1 (fr) 1984-10-30 1984-10-30 Transducteur electro-acoustique a diaphragme piezoelectrique
FR8416594 1984-10-30

Publications (1)

Publication Number Publication Date
EP0180518A1 true EP0180518A1 (de) 1986-05-07

Family

ID=9309144

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85402071A Withdrawn EP0180518A1 (de) 1984-10-30 1985-10-25 Elektroakustischer Wandler mit piezoelektrischer Membran

Country Status (4)

Country Link
US (1) US4692942A (de)
EP (1) EP0180518A1 (de)
JP (1) JPS61108300A (de)
FR (1) FR2572616A1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0325805A2 (de) * 1987-12-31 1989-08-02 Jochen Heimann Messwertaufnehmer zur nichtinvasiven Messung von Schall, Druck und Vibrationen am menschlichen Körper

Families Citing this family (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4979220A (en) * 1988-05-05 1990-12-18 Audiovox International Limited Integral body speaker with detachable terminal plate
US5168527A (en) * 1990-06-14 1992-12-01 Lzr Electronics, Inc. Miniature speaker variable standoff mount
JPH04259099A (ja) * 1991-02-13 1992-09-14 Kobishi Denki Kk 警報器及び集音検知器
JPH0759184A (ja) * 1993-03-05 1995-03-03 Matsushita Electric Ind Co Ltd 筐体と音響・映像機器とその製造方法
US5684884A (en) * 1994-05-31 1997-11-04 Hitachi Metals, Ltd. Piezoelectric loudspeaker and a method for manufacturing the same
US5805726A (en) * 1995-08-11 1998-09-08 Industrial Technology Research Institute Piezoelectric full-range loudspeaker
US5828765A (en) * 1996-05-03 1998-10-27 Gable; Tony L. Audio loudspeaker assembly for recessed lighting fixture and audio system using same
US6347147B1 (en) * 1998-12-07 2002-02-12 The United States Of America As Represented By The Sceretary Of The Navy High noise suppression microphone
JP2002171594A (ja) * 2000-11-30 2002-06-14 Citizen Electronics Co Ltd スピーカ
JP3797916B2 (ja) * 2001-10-30 2006-07-19 シチズン電子株式会社 スピーカーおよびその製造方法
US8265291B2 (en) * 2005-11-15 2012-09-11 Active Signal Technologies, Inc. High sensitivity noise immune stethoscope
US8003878B2 (en) * 2008-08-05 2011-08-23 Gaynier David A Electroacoustic transducer system
US11413653B2 (en) 2010-06-24 2022-08-16 Cvr Global, Inc. Sensor, sensor pad and sensor array for detecting infrasonic acoustic signals
US9101274B2 (en) * 2010-06-24 2015-08-11 Cvr Global, Inc. Sensor, sensor pad and sensor array for detecting infrasonic acoustic signals
EP2860988A4 (de) * 2012-06-06 2016-01-27 Nec Corp Lautsprechervorrichtung und elektronische vorrichtung
CN109069029A (zh) * 2016-04-28 2018-12-21 太阳诱电株式会社 振动波形传感器和脉搏波检测装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1276729B (de) * 1963-09-04 1968-09-05 Northern Electric Co Mikrofoneinheit aus einem Kondensatormikrofon und einem Transistorverstaerker
US3816671A (en) * 1972-04-06 1974-06-11 Thermo Electron Corp Electret transducer cartridge and case
GB2064264A (en) * 1979-11-30 1981-06-10 Pye Electronic Prod Ltd Microphone unit
EP0118356A1 (de) * 1983-03-07 1984-09-12 Thomson-Csf Elektroakustischer Wandler mit piezoelektrischer Membran

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3660602A (en) * 1970-06-01 1972-05-02 Conrac Corp Microphone cartridge with amplifier
JPS5221823A (en) * 1975-08-12 1977-02-18 Nippon Telegr & Teleph Corp <Ntt> Piezo electric type electric sound exchanger
US4409441A (en) * 1981-07-02 1983-10-11 Polaroid Corporation Ultrasonic transducer for use in a vibratory environment

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1276729B (de) * 1963-09-04 1968-09-05 Northern Electric Co Mikrofoneinheit aus einem Kondensatormikrofon und einem Transistorverstaerker
US3816671A (en) * 1972-04-06 1974-06-11 Thermo Electron Corp Electret transducer cartridge and case
GB2064264A (en) * 1979-11-30 1981-06-10 Pye Electronic Prod Ltd Microphone unit
EP0118356A1 (de) * 1983-03-07 1984-09-12 Thomson-Csf Elektroakustischer Wandler mit piezoelektrischer Membran

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENTS ABSTRACTS OF JAPAN, vol. 1, no. 86, 11 août 1977, page 1901 E 77; & JP - A - 52 21 823 (NIPPON DENSHIN DENWA KOSHA) 18-02-1977 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0325805A2 (de) * 1987-12-31 1989-08-02 Jochen Heimann Messwertaufnehmer zur nichtinvasiven Messung von Schall, Druck und Vibrationen am menschlichen Körper
EP0325805A3 (de) * 1987-12-31 1989-09-06 Jochen Heimann Messwertaufnehmer zur nichtinvasiven Messung von Schall, Druck und Vibrationen am menschlichen Körper

Also Published As

Publication number Publication date
FR2572616A1 (fr) 1986-05-02
US4692942A (en) 1987-09-08
JPS61108300A (ja) 1986-05-26

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