EP0005409B1 - Piezoelektrischer Wandler mit mechanischer Verstärkung für sehr niedrige Frequenzen und akustische Antenne - Google Patents

Piezoelektrischer Wandler mit mechanischer Verstärkung für sehr niedrige Frequenzen und akustische Antenne Download PDF

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Publication number
EP0005409B1
EP0005409B1 EP79400291A EP79400291A EP0005409B1 EP 0005409 B1 EP0005409 B1 EP 0005409B1 EP 79400291 A EP79400291 A EP 79400291A EP 79400291 A EP79400291 A EP 79400291A EP 0005409 B1 EP0005409 B1 EP 0005409B1
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EP
European Patent Office
Prior art keywords
base plate
fact
piezoelectric
lateral plates
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.)
Expired
Application number
EP79400291A
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English (en)
French (fr)
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EP0005409A3 (en
EP0005409A2 (de
Inventor
Bernard Tocquet
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Direction General de lArmement DGA
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Delegation Generale pour lArmement
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Publication of EP0005409A2 publication Critical patent/EP0005409A2/de
Publication of EP0005409A3 publication Critical patent/EP0005409A3/fr
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/08—Non-electric sound-amplifying devices, e.g. non-electric megaphones
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K9/00—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers
    • G10K9/12—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers electrically operated
    • G10K9/121—Flextensional transducers

Definitions

  • the invention relates to piezoelectric transducers, for very low frequencies, between a few Hz and 500 Hz, which comprise a mechanical amplifier and antennas constructed with such transducers.
  • the technical sector of the invention is that of the construction of acoustic devices used in particular in underwater acoustics.
  • the objective of the present invention is to overcome this difficulty by mechanically amplifying the deformations of the piezoelectric transducers, so that it is possible to construct piezoelectric transducers of high power for very low frequencies.
  • each stack of piezoelectric elements comprises a central fixed point and two half stacks located on either side of said fixed point.
  • a transducer according to the invention comprises two identical sub-assemblies located on either side of the same base plate and symmetrical with respect thereto.
  • the invention results in new piezoelectric transducers, transmitters or receivers, making it possible to obtain large amplitudes and therefore high powers in very low frequencies between a few Hz and 500 Hz, while using transducers having relatively small dimensions.
  • the amplitude of the deformations of the piezoelectric stacks is multiplied by the mechanical amplifier associated with these stacks.
  • This amplifier is constituted on the one hand by the two levers which multiply the amplitude of the oscillations by a coefficient equal to the ratio between the two lever arms and, on the other hand, by the elastic membrane which serves as a flag and which connects between them the free ends of the two levers so that when the spacing between the ends of the two levers varies in one direction or the other, this variation results in flexural deformations of the membrane and the amplitude of the deformations at center of the membrane is greater than the amplitude of the variations in spacing of the ends of the two levers.
  • the elastic membrane constitutes a pavilion which can be placed in contact with water and which can therefore transmit water or pick up large amplitude acoustic waves while the deformations of the piezoelectric elements are much smaller than the deformations of the membrane flexible.
  • the flexible membrane can be flat or, preferably, curved.
  • the bending of the flexible membrane is obtained by means of a bending prestress of said plate, so that the latter remains constantly compressed even when the spacing between the two ends of the levers is maximum.
  • the embodiment comprising two identical sub-assemblies arranged symmetrically with respect to the same base plate has the advantage of making it possible to reduce the thickness of this base plate.
  • the transducers according to the invention make it possible to construct antennas comprising a base plate, flat or cylindrical, on which is arranged a network of transducers aligned along lines and / or columns.
  • An advantage of the devices according to the invention lies in the fact that they are mechanical devices having several natural resonant frequencies including certain very low frequencies between a few Hertz and 500 Hz, which makes it possible to choose the lowest of these resonant frequencies and get a sensi curve SV bility measured in decibels with a pronounced peak, located in the very low frequency band.
  • FIGS. 1, 2 and 3 show a piezoelectric transducer intended either to emit or to pick up acoustic waves in water.
  • This transducer comprises one or more stacks 1 of piezoelectric elements.
  • each stack is composed of piezoelectric elements 2, for example plates of piezoelectric ceramic, between which electrodes 3 are inserted.
  • the electrodes 3 are connected alternately on one or the other of two electrical conductors 4a and 4b, of opposite polarity.
  • the elements 2 and the electrodes 3 are held tight by a central prestressing rod 5, of axis x x1 which is threaded at its two ends and by two nuts 6a, 6b which are screwed on the two threaded ends in order to put the rod 5 in tension.
  • Such a stack of piezoelectric elements and electrodes is well known and we know that it deforms parallel to the axis x x1 if a sinusoidal voltage is applied between the conductors 4a and 4b and that reciprocally, a sinusoidal voltage between conductors 4a and 4b if the transducer serves as a receiver of acoustic waves.
  • each piezoelectric element is limited by the nature of the materials. If one wants to emit or pick up very low frequency acoustic waves with sufficient power, it is necessary to use stacks comprising a very large number of elements, but then the transducers become very bulky.
  • a submerged transducer makes it possible to obtain large amplitudes of deformation of the horn, that is to say of the active surface which is in contact with water and which transmits the acoustic waves to the water in the case of a transmitter or which receives the acoustic waves in the case of a receiver, and this result is achieved by means of a transducer whose dimensions remain relatively small, if we compare them to those which would be necessary to obtain the same amplitudes in the case of a traditional transducer comprising only a stack of piezoelectric elements.
  • a transducer according to the invention comprises a very rigid base plate 7. It comprises two flat side plates 8a and 8b which are identical and perpendicular to the base plate 7, on the same side thereof. These side plates have, for example, a rectangular shape.
  • the lower edge of each plate 8a and 8b is connected to the base plate, for example by means of plates 9a and 9b which are each composed of two half plates which are fixed to the base plate 7 by screws 10 and which enclose between them the lower edge of the plates 8a and 8b.
  • Each plate 8a, 8b comprises, along its lower edge, immediately above the plates 9a and 9b, a thinning 11, constituted for example by two grooves 11a and 11b, located on either side of the plate such that the plates 8a and 8b can deform by pivoting around the thinning 11.
  • the plates 8a and 8b are fixed in console on the plate 7 by semi-recesses.
  • this semi-embedding can be replaced by an articulation around an axis parallel to the lower edge of each plate.
  • each side plate such as 8a comprises, along its lower edge, a bead 12 of circular section, which is engaged in a groove 13 of circular section, hollowed out in the base plate 7.
  • Two half plates 14a and 14b are screwed onto the plate 7 and maintain the bead 12 in its housing while allowing it to pivot.
  • this articulation can be replaced by any other equivalent type of articulation.
  • the stacks 1a and 1b extend above the base plate 7, perpendicular to the two plates 8a and 8b.
  • the two axially opposite ends of the stack 1 are pressed against the internal faces of the two plates 8a and 8b slightly above the thinning 11.
  • the support is produced by means of an intermediate support piece 15a, 15b .
  • a support piece 15 is shown in perspective in FIG. 5. This piece has a first flat side face 16 which is pressed against one of the side plates 8 and a second side face 17, opposite to the face 16, which is pressed against one end of the stack 1.
  • the face 17 is a portion of cylindrical surface, in an arc of a circle, so that the support of the stack on the support face is along a line which is the median generatrix 18 of the face 17.
  • Each part 15 has two holes 19a and 19b for the passage of the extensions of the rod 5 which pass through the plates 8a and 8b. Nuts 20a and 20b are screwed onto these extensions to keep the stacks 1a and 1b in place.
  • the cylindrical shape of the faces 17 of the support piece 15 makes it possible to precisely determine the support line 18 and therefore the distance which separates it from the line around which the plates 8a and 8b can pivot, that is ie thinning 11 or the center of the bead 12.
  • the plates 8a and 8b act as levers, the thinning 11 or the beads 12 of which constitute the fulcrum, while the distance separating this fulcrum 18 constitutes the small arm of the lever. It is specified that the support pieces 15a and 15b can be reversed, so that their cylindrical face 17 is placed in contact with a side plate 8a or 8b.
  • each stack 1a, 1b is made up of two symmetrical half stacks with respect to a central fixed point 21 which is constituted for example by a plate fixed to the base plate 7 by screws 22.
  • the transducer shown in Figures 1, 2 and 3 further comprises a horn 23 which is the active surface, in acoustic contact with the water.
  • This pavilion is constituted by an elastic and flexible membrane, for example a thin plate of spring steel having a thickness of a few millimeters.
  • This plate is fixed by any means along each of its two lateral edges to an upper edge of one of the lateral plates 8a and 8b.
  • the two lateral edges of the plate 23 are folded back to form folds 23a and 23b and these folds are held pinched between a plate 8a or 8b and a fixing plate 24a, 24b fixed to the plate 8a or 8b by screws 25. Screws 26 screwed into the thickness of the plates 8a and 8b can reinforce this fixing.
  • the plate 23 is curved, the convex face being turned, preferably, on the side opposite to the base plate 7.
  • a plate is used having a width in the direction parallel to the axis xx1 slightly greater than the spacing between the two side plates 8a and 8b and it is slightly compressed in the direction parallel to the axis x x1 before fixing it along the two upper edges of the plates 8a and 8b.
  • the transducer according to FIGS. 1 to 3 comprises a sealed housing composed of two flanges 27a and 27b parallel to the plates 8a and 8b and of two lateral flanges 28a and 28b, visible in FIG. 3 and a flexible membrane 29, forming a skin of sealing, which envelops the flanges 27a, 27b, 28a, 28b and the roof 23.
  • the skin 29 is made of a material having an acoustic impedance close to that of water so that it is acoustically transparent and that it does not disturb the transmission of waves between the water and the active surface of the roof 23. It is glued to the pavilion 23, so that it follows the movements thereof.
  • the skin 29 is for example a thin skin of rubber or flexible plastic. A slight clearance exists between, on the one hand, the plates 8a, 8b and the roof 23 and on the other hand, the lateral faces 27a, 27b, 28a, 28b of the housing, so that the housing does not hinder movement flag and side plates 8a, 8b.
  • the inside of the waterproof case is filled with gas. If the transducer is to be used in immersion, this gas is maintained in equilibrium with the outside, for example by means of a source of compressed gas provided with a regulator which is adjusted according to the depth.
  • the two walls 27a and 27b of the housing can be eliminated and the membrane 29 can be glued directly to the two external faces 8a and 8b.
  • the plates 8a and 8b constitute acoustically active surfaces.
  • Figures 1 and 3 show a sealed connector 30 through which the electrical conductors 4a and 4b pass through the wall 28b.
  • this transducer is as follows.
  • the stack 1 deforms longitudinally along the axis x x1
  • the deformations are communicated to the two levers 8a and 8b which deform by pivoting around their fulcrum.
  • the displacements of the upper ends of the levers 8a and 8b are multiplied by the ratio between the two lever arms.
  • the variations in spacing between the two upper edges of the two levers 8a and 8b produce flexural deformations of the elastic membrane 23.
  • the displacements at the center of the membrane in the direction perpendicular to the base plate 7 are greater than the displacements of the ends upper two levers 8a and 8b.
  • FIG. 6 represents measurements of the sensitivity SV of a transducer according to the invention as a function of the frequency. It is recalled that the sensitivity SV measured in decibels corresponds to 20 times the logarithm of the ratio between the acoustic pressure measured either in micro bar or in micro pascal and the voltage in volts.
  • FIG. 6 shows on the abscissa a frequency range between 80 Hz and 180 Hz.
  • the sensitivity measured according to the reference ⁇ bar per volt is represented on the left and on the right according to the reference ⁇ pascal / volt.
  • a maximum sensitivity is obtained for a resonance frequency of the order of 125 Hz.
  • FIG. 7 represents a longitudinal section of an alternative embodiment of a transducer according to the invention.
  • An advantage of this embodiment is that it makes it possible to use a less rigid base plate 7 since it is bi-symmetrically stressed by the two half transducers.
  • a transducer according to Figure 7 is very omnidirectional.
  • the figures schematically represent an embodiment of an acoustic antenna comprising 25 transducers according to the invention, arranged in an array along five lines L1 to L5 and five columns C1 to C5.
  • Each transducer is represented diagrammatically by a square whose two sides are in double line and represent the two side plates 8a and 8b of a transducer.
  • All the transducers are fixed on the same rigid plate 31 which serves as a common base plate for all the transducers.
  • the plate 31 can be flat, curved or cylindrical depending on the shape of the antenna.
  • Two networks of transducers can be arranged symmetrically on either side of the plate 31.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Transducers For Ultrasonic Waves (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)

Claims (10)

1. Piezoelektrischer Wandler für sehr niedrige Frequenzen, dadurch gekennzeichnet, dass er umfasst:
- mindestens einen Stapel (1) piezoelektrischer Elemente mit zwei achsrecht entegengesetzten Enden ;
- zwei Hebel (8a, 8b), die jeweils and den Enden besagter Stapel (1) so angeordnet sind, dass jedes der beiden Enden eines jeden Stapels sich auf einem der beiden Hebel in dem Nähe des Stützpunktes (11) desselben abstützt ;
- und einen Schalltrichter (23), der von einer elastischen schwingungsfähigen Membran gebildet wird, die die Enden der beiden Hebel miteinander verbindet.
2. Piezoelektrischer Wandler nach Anspruch 1, dadurch gekennzeichnet, dass er umfasst :
- eine starre Basiplatte (7) ;
- zwei glatte Seitenplatten (8a, 8b), die auf der gleichen Seite von besagter Basisplatte angeordnet sind und die mit Letzterer durch eine Halbeinbettung (11) oder durch ein Gelenk (12) entlang einer ihrer Kanten verbunden ist ;
- mindestens einen Stapel (1) piezoelektrischer Elemente mit zwei achsgerecht entgegengesetzten Enden (6), die jeweils mit jeder der besagten Seitenplatten in der Nähe der Kante derselben verbunden sind, die mit der Basisplatte verbunden ist ;
- einen Schalltrichter (23), der von einer elastischen schwingungsfähigen Membran gebildet wird, die die beiden Kanten der beiden Seitenplatten untereinander verbindet, die den beiden Kanten gegenüberliegen, die mit der Basisplatte verbunden sind ;
- und ein Gehäuse, mit Gas gefüllt, das besagte piezoelektrische Stapel umschliesst und dessen eine Seite von besagtem Schalltrichter gebildet wird, dieses Gehäuse ist dicht von einer akustisch verformbaren und transparenten Membran (29) umgeben, die ebenfalls besagten Schalltrichter (23) umgibt.
3. Piezoelektrischer Wandler nach Anspruch 1, dadurch gekennzeichnet, dass er umfasst :
- eine starre Basisplatte (7) ;
- zwei glatte Seitenplatten (8), die auf der gleichen Seite von besagter Basisplatte angeordnet sind und die mit letzterer durch eine Halbeinbettung (11) oder durch ein Gelenk (12) entlang einer ihrer Kanten verbunden ist ;
- mindestens einen Stapel (1) piezoelektrischer Elemente mit zwei achsgerecht entgegengesetzten Enden (6), die jeweils mit jeder der besagten Seitenplatten (8) in der Nähe der Kante derselben in Kontakt sind, die mit besagter Basisplatte verbunden ist;
- einen Schalltrichter, der von einer elastischen und schwingungsfähigen Membran (23) gebildet wird, die die beiden Kanten der beiden Seitenplatten untereinander verbindet, die den beiden Kanten gegenüberliegen, die mit besagter Basisplatte verbunden sind ;
- und ein mit Gas gefülltes Gehäuse, das besagte piezoelektrische Stapel umschliesst und dessen Wände von besagtem Schalltrichter und von besagten Seitenplatten gebildet werden, dieses Gehäuse ist dicht von einer akustisch verformbaren und transparenten Membran (29) umgeben, diese Membran umgibt besagten Schalltrichter und besagte Seitenplatten.
4. Wandler nach einem beliebigen der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass besagte Stapel (1) piezoelektrischer Elemente einen zentralen Festpunkt (21) und zwei im Verhältnis zu besagtem Festpunkt symmetrische Halbstapel aufweisen.
5. Piezoelektrischer Wandler für sehr niedrige Frequenzen, dadurch gekennzeichnet, dass er auf jeder Seite einer gemeinsamen Basisplatte (7) zwei im Vergleich zur besagten Basisplatte symmetrische Wandler umfasst, wobei jeder der besagten Wandler mit einem Wandler nach einem der Ansprüche 2 bis 4 identisch ist.
6. Wandler nach einem beliebigen der Ansprüche 2 bis 5, dadurch gekennzeichnet, dass er zwei Untereinheiten (1a, 1b) umfasst, von denen jede aus zwei identischen Stapeln piezoelektrischer Elemente besteht, die untereinander parallel sind, von denen jeder einen zentralen Festpunkt hat, der mit besagter Basisplatte verbunden ist.
7. Wandler nach einem beliebigen der Ansprüche 1 bis 6, dadurch gekennzeichnet, dass besagte elastische und schwingungsfähige Membran (23) gewölbt ist.
8. Wandler nach einem beliebigen der Ansprüche 1 bis 6, dadurch gekennzeichnet, dass besagte elastische und schwingungsfähige Membran (23) in der Biegung vorgespannt ist.
9. Wandler nach einem beliebigen der Ansprüche 2 bis 8, dadurch gekennzeichnet, dass jedes Ende (6) der besagten Stapel piezoelektrischer Elemente auf besagten Seitenplatten (8) vermittels einer Zwischenstütze (15) aufliegt.
10. Schallantenne bestehend aus Wandlern nach einem beliebigen der Ansprüche 2 bis 9, dadurch gekennzeichnet, dass sie eine gemeinsame Basisplatte aufweist, auf der eine oder mehrere Reiben und/oder Säulen von elementaren Wandlern angeordnet sind.
EP79400291A 1978-05-08 1979-05-08 Piezoelektrischer Wandler mit mechanischer Verstärkung für sehr niedrige Frequenzen und akustische Antenne Expired EP0005409B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR7813466A FR2425785A1 (fr) 1978-05-08 1978-05-08 Transducteurs piezo-electriques a amplification mecanique pour tres basses frequences et antennes acoustiques
FR7813466 1978-05-08

Publications (3)

Publication Number Publication Date
EP0005409A2 EP0005409A2 (de) 1979-11-14
EP0005409A3 EP0005409A3 (en) 1979-11-28
EP0005409B1 true EP0005409B1 (de) 1981-04-15

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EP79400291A Expired EP0005409B1 (de) 1978-05-08 1979-05-08 Piezoelektrischer Wandler mit mechanischer Verstärkung für sehr niedrige Frequenzen und akustische Antenne

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US (1) US4287582A (de)
EP (1) EP0005409B1 (de)
DE (1) DE2960263D1 (de)
FR (1) FR2425785A1 (de)

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Also Published As

Publication number Publication date
FR2425785B1 (de) 1981-05-29
EP0005409A3 (en) 1979-11-28
EP0005409A2 (de) 1979-11-14
DE2960263D1 (en) 1981-05-07
US4287582A (en) 1981-09-01
FR2425785A1 (fr) 1979-12-07

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