EP0799097A1 - Acoustic transducer shaped as a prestressed ring - Google Patents

Acoustic transducer shaped as a prestressed ring

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Publication number
EP0799097A1
EP0799097A1 EP95942751A EP95942751A EP0799097A1 EP 0799097 A1 EP0799097 A1 EP 0799097A1 EP 95942751 A EP95942751 A EP 95942751A EP 95942751 A EP95942751 A EP 95942751A EP 0799097 A1 EP0799097 A1 EP 0799097A1
Authority
EP
European Patent Office
Prior art keywords
ring
sectors
segments
clamping
clamping means
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.)
Granted
Application number
EP95942751A
Other languages
German (de)
French (fr)
Other versions
EP0799097B1 (en
Inventor
Marc Edouard
Bernard Loubieres
Pascal Bocquillon
Olivier Lacour
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
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Filing date
Publication date
Application filed by Thomson CSF SA filed Critical Thomson CSF SA
Publication of EP0799097A1 publication Critical patent/EP0799097A1/en
Application granted granted Critical
Publication of EP0799097B1 publication Critical patent/EP0799097B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0644—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element
    • B06B1/0655—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element of cylindrical shape

Definitions

  • the present invention relates to piezoelectric transducers having the shape of a ring and which are provided with means making it possible to prestress this ring to apply to it a constraint of determined value. It also relates to the methods which make it possible to use these means for applying said prestress to the ring.
  • Piezoelectric transducers are frequently used in underwater acoustics which make it possible to obtain acoustic waves, more particularly low frequency acoustic waves, from an electrical excitation signal.
  • a particular form of such a transducer, more particularly adapted to the emission of low frequency waves is that of a toroid with rectangular section, formed of a set of ceramic segments polarized head to tail and assembled by gluing with interposition an electrode between each segment.
  • the segments thus excited contract and expand at the rate of the electrical signals which are applied by the electrodes, and this tangential movement of the segments results in an extension and a radial contraction of the ring. This movement therefore results in the production of acoustic waves which are emitted with radial symmetry around the axis of the ring in the medium, generally the sea, in which the transducer is immersed.
  • the rings are subjected to piezoelectric stresses of high amplitude and this effect is all the more marked when the frequency of the acoustic waves to be emitted is low.
  • the ring would tend to disjoin, first at the interfaces between the different segments and then by outright rupture of piezoelectric ceramics from a certain level of emission.
  • it is necessary to prestress the ring by compressing it using means which apply to it radial forces directed towards the center and distributed uniformly over the external surface of the ring.
  • the final value of the prestress thus obtained fluctuates within large limits in an uncontrollable manner.
  • the different means making it possible to pull on the strap, as well as the friction of the latter on the surface of the segments the stresses which are thus generated are not distributed uniformly and they generally concentrate at a particular point. corresponding to the stacking of the ribs.
  • Such an irregularity is a significant source of discomfort, taking into account the radial isotropy which it is sought to obtain for the acoustic radiation.
  • the invention provides a prestressed ring acoustic transducer, of the type comprising a set of piezoelectric segments arranged in the form of a ring, mainly characterized in that its segments are grouped to form substantially identical sectors, and in that that it further comprises end pieces fixed to the ends of these sectors to delimit between them wedge-shaped intervals, the most narrow is directed towards the inside of the ring, wedge-shaped clamps adapted to these intervals and placed in them, a shaping ring making it possible to hold all the sectors, and clamping means making it possible to slide the shims towards the inside of the ring to prestress the segments by the shaping ring.
  • the transducer further comprises strain gauges fixed on the inner face of the sectors to allow the stresses applied to the segments to be measured.
  • the clamping means are formed of screws fixed in holes made in the internal face of the clamping shims and provided with washers which come to bear on the end pieces of the sectors to allow traction to be exerted on the shims when the screws are tightened.
  • the intervals remaining on the one hand between the clamping wedges and the shaping ring and on the other hand between these same clamping wedges and the clamping means are plugged with a filling product when the adjustment is obtained .
  • the dynamic stiffness of the shaping ring is substantially ten times lower than that of the piezoelectric segments.
  • the invention further provides a method of adjusting such a transducer mainly characterized in that the clamping means are gradually tightened by monitoring the indications given by the strain gauges to obtain stresses identical and equal to each sector. the desired value.
  • the piezoelectric ring forming the transducer is produced by assembling a set of elementary segments 101 having the shape of prisms with trapezoidal cross section quite similar to those used in the art known.
  • the ring is divided into a set of substantially identical sectors 102 joining together subsets of segments.
  • the diameter of the ring is of the order of 20 cm and it is divided into 5 sectors each comprising 8 segments.
  • One of these isolated sectors is shown in FIG. 3. It is formed by 8 elementary segments 101 in piezoelectric ceramic, for example PZT.
  • These segments are bonded to each other with the interposition of electrodes 103 which make it possible to apply the electrical excitation voltages.
  • the segments are polarized tangentially alternately in opposite directions.
  • the electrodes 103 are joined alternately to connections 104 and 105 which make it possible to apply these electrical voltages to the electrodes.
  • ends of the sector are provided with metal parts glued to the outer faces of the end segments.
  • These metal parts are wedge-shaped and their external lateral faces form an angle ⁇ with the direction of the radius of the ring, as shown in FIG. 1. This angle ⁇ is such that the width of the corner is greater on the surface inner ring than on the outer surface thereof.
  • At least one strain gauge 107 has been placed on the inner face of the sector, which makes it possible to measure the stresses applied to the sectors at the level of this inner face.
  • This strain gauge is for example produced in the known form of a film supporting metal electrodes arranged in such a way that the extension or the contraction of the surface on which the gauge is stuck causes a variation in resistance of these electrodes according to a known law.
  • the set of 5 sectors is arranged inside a shaping ring 108 and which makes it possible to define the shape and the dimensions of the piezoelectric ring.
  • This ring is for example made of epoxy glass with a carefully polished inner surface.
  • the dimensions of the sectors are provided so that there is a clearance between the metal parts of the ends of two adjacent sectors. This clearance is filled by adjustment shims having the form of wedges 109. These shims, a copy of which is shown in FIG. 2, are therefore placed between the sectors and allow these sectors to be blocked inside the ring. shaping device 108.
  • the angle between the two lateral faces of these shims is designed to correspond to the angle alpha of the end pieces of the sectors, so that when the shims are in position these external faces are applied to the outer faces of these end pieces with as little angular play as possible, to avoid excessive stresses at the points of contact between the wedges and the end pieces.
  • the faces of the shims 109 oriented towards the inside of the ring are provided with tapped holes 110, here 3 in number, which make it possible to receive clamping members which are screwed into these holes based on the faces of the end pieces 106 themselves oriented towards the inside of the ring.
  • These clamping parts may be more or less complicated, but in the embodiment shown they are composed of screws 111 on which are threaded washers 112. These screws are screwed into the tapped holes, then on the washers, they -same supported on the pieces 106.
  • the invention proposes to use the strain gauges 107 described above. For this, they will be connected to measuring means 113 which make it possible to determine the stress at these gauges.
  • the stress at the places where these gauges are placed indicates, to a near known multiplying coefficient, the global stress applied to the ceramics forming each sector.
  • the sectors are small enough so that the stresses thus obtained and measured are uniformly distributed. In the case of a larger ring, we would eventually have to use a larger number of sectors.
  • the tightening of the screws will be done gradually by constantly checking the evolution of the stresses, so as to obtain the desired global stress and to minimize the deviations between the stresses measured locally.
  • the final adjustment it is possible optionally to fill the gap e between the shims 109 and the shaping ring 108, as well as the possible residual gap between the clamping means and these same shims, with a filling material.
  • This filling material will preferably be relatively elastic, polyurethane for example, so as to be able to allow possible subsequent adjustments.
  • the shaping ring 108 is of course involved in the acoustic characteristics of the transducer thus produced, as is also the case in the other already known prestressing systems. It has been determined that to obtain correct results, in particular not excessively disturbing the operation of the piezoelectric ring, it was preferable to use a shaping ring whose dynamic stiffness is approximately ten times lower than that of the piezoelectric ceramic ring. Compared to known prestressing systems, this device is particularly easy to implement and therefore inexpensive. In addition it is modular, which allows if necessary to replace only one segment in the event of damage to it. The stresses are distributed in a remarkably uniform manner, and their variations over time are very small. We can completely adjust this preload, either by depending on operational conditions, ie to correct drift over time. Furthermore the assembly is removable, which allows the repairs mentioned above. Finally, the metal parts 106 and 109 promote, if necessary, thermal drainage, especially when the ring is stressed by very high electrical powers.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Measuring Fluid Pressure (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)
  • Transducers For Ultrasonic Waves (AREA)

Abstract

Acoustic ring-shaped transducers comprising a set of piezoelectric prestressed segments are described. According to the invention, said segments (101) are grouped to form a set of sectors (102) separated by clamping wedges (109). The set of sectors is placed in a forming ring (108) and the wedges are drawn towards the centre by screws (111) so as to urge the sectors against said forming ring and to prestress the segments. Stress gauges (107) are used to control and adjust the resulting stress to a required value while minimising dispersion between sectors. The invention is useful for producing low frequency, powerful, detachable acoustic transducers.

Description

TRANSDUCTEUR ACOUSTIQUE EN ANNEAU PRECONTRAINT ACOUSTIC TRANSDUCER IN PRE-STRESSED RING
La présente invention se rapporte aux transducteurs piézoélectriques présentant la forme d'un anneau et qui sont munis de moyens permettant de précontraindre cet anneau pour lui appliquer une contrainte de valeur déterminée. Elle concerne également les procédés qui permettent de mettre en oeuvre ces moyens pour appliquer ladite précontrainte à l'anneau.The present invention relates to piezoelectric transducers having the shape of a ring and which are provided with means making it possible to prestress this ring to apply to it a constraint of determined value. It also relates to the methods which make it possible to use these means for applying said prestress to the ring.
On utilise fréquemment en acoustique sous-marine des transducteurs piézoélectriques qui permettent d'obtenir des ondes acoustiques, plus particulièrement des ondes acoustiques basse fréquence, à partir d'un signal électrique d'excitation. Une forme particulière d'un tel transducteur, plus spécialement adaptée à l'émission des ondes basse fréquence, est celle d'un tore à section rectangulaire, formé d'un ensemble de segments en céramique polarisés tête-bêche et assemblés par collage avec interposition d'une électrode entre chaque segment. Les segments ainsi excités se contractent et se dilatent au rythme des signaux électriques qui sont appliqués par les électrodes, et ce mouvement tangentiel des segments se traduit par une extension et une contraction radiale de l'anneau. Ce mouvement entraîne donc la production d'ondes acoustiques qui sont émises avec une symétrie radiale autour de l'axe de l'anneau dans le milieu, la mer généralement, dans lequel le transducteur est plongé.Piezoelectric transducers are frequently used in underwater acoustics which make it possible to obtain acoustic waves, more particularly low frequency acoustic waves, from an electrical excitation signal. A particular form of such a transducer, more particularly adapted to the emission of low frequency waves, is that of a toroid with rectangular section, formed of a set of ceramic segments polarized head to tail and assembled by gluing with interposition an electrode between each segment. The segments thus excited contract and expand at the rate of the electrical signals which are applied by the electrodes, and this tangential movement of the segments results in an extension and a radial contraction of the ring. This movement therefore results in the production of acoustic waves which are emitted with radial symmetry around the axis of the ring in the medium, generally the sea, in which the transducer is immersed.
Pour obtenir une puissance acoustique importante, les anneaux sont soumis à des contraintes piézoélectriques de forte amplitude et cet effet est d'autant plus marqué que la fréquence des ondes acoustiques à émettre est basse. Sous l'effet de ces contraintes, l'anneau tendrait à se disjoindre, tout d'abord au niveau des interfaces entre les différents segments et ensuite par rupture pure et simple des céramiques piézoélectriques à partir d'un certain niveau d'émission. Pour pallier cet inconvénient, on est amené à précontraindre l'anneau en le comprimant à l'aide de moyens qui lui appliquent des forces radiales dirigées vers le centre et réparties uniformément sur la surface extérieure de l'anneau. Ces contraintes radiales induisent des contraintes tangentielles qui tendent à maintenir les segments solidarisés entre eux et s'opposent à ce que naissent au sein des céramiques des contraintes de traction, auxquelles on sait que ce type de matériau est particulièrement fragile. On a imaginé différentes sortes de dispositifs pour obtenir de telles contraintes. Ces méthodes consistent généralement à enrouler une sangle d'un matériau adéquat autour de l'anneau en tirant très fort sur les extrémités de cette sangle pour obtenir un frettage convenable. On trouvera des exemples de ces méthodes par exemple dans les brevets français N° 2 346 862 et 2463 979.To obtain a significant acoustic power, the rings are subjected to piezoelectric stresses of high amplitude and this effect is all the more marked when the frequency of the acoustic waves to be emitted is low. Under the effect of these constraints, the ring would tend to disjoin, first at the interfaces between the different segments and then by outright rupture of piezoelectric ceramics from a certain level of emission. To overcome this drawback, it is necessary to prestress the ring by compressing it using means which apply to it radial forces directed towards the center and distributed uniformly over the external surface of the ring. These radial stresses induce tangential stresses which tend to keep the segments secured to one another and oppose the emergence within ceramics of tensile stresses, which we know that this type of material is particularly fragile. We have imagined different kinds of devices to obtain such constraints. These methods generally consist in wrapping a strap of a suitable material around the ring by pulling very hard on the ends of this strap to obtain a suitable hooping. Examples of these methods can be found, for example, in French Pat. Nos. 2,346,862 and 2,463,979.
Les méthodes ainsi utilisées présentent toutefois divers inconvénients.The methods thus used however have various drawbacks.
En particulier la valeur finale de la précontrainte ainsi obtenue fluctue dans de grandes limites de manière incontrôlable. Dans ces conditions, et comme le système n'est ni démontable ni réglable, on est conduit à mettre au rebut l'anneau en cours de construction alors qu'il en est à un stade très avancé de sa fabrication, ce qui entraîne une perte importante. Par ailleurs, compte tenu des différents moyens permettant de tirer sur la sangle, ainsi que de la friction de celle-ci sur la surface des segments, les contraintes qui sont ainsi générées ne sont pas réparties uniformément et elles se concentrent généralement en un point particulier correspondant à l'empilage des côtes. Une telle irrégularité est une source de gêne importante, compte tenu de l'isotropie radiale que l'on cherche à obtenir pour le rayonnement acoustique.In particular, the final value of the prestress thus obtained fluctuates within large limits in an uncontrollable manner. Under these conditions, and as the system is neither removable nor adjustable, we are led to discard the ring during construction while it is at a very advanced stage of its manufacture, which leads to a loss important. Furthermore, taking into account the different means making it possible to pull on the strap, as well as the friction of the latter on the surface of the segments, the stresses which are thus generated are not distributed uniformly and they generally concentrate at a particular point. corresponding to the stacking of the ribs. Such an irregularity is a significant source of discomfort, taking into account the radial isotropy which it is sought to obtain for the acoustic radiation.
D'autre part ces inconvénients sont d'autant plus importants que le diamètre de l'anneau est plus grand. Or le diamètre de l'anneau est directement relié à la fréquence d'émission souhaitée. Plus la fréquence désirée est basse, plus l'anneau doit être grand, et comme dans ce cas plus la puissance d'émission souhaitée est grande, plus la nécessité de la précontrainte est importante, et donc plus les inconvénients cités plus hauts prennent de l'importance.On the other hand, these drawbacks are all the more important the larger the diameter of the ring. However, the diameter of the ring is directly related to the desired transmission frequency. The lower the desired frequency, the larger the ring must be, and as in this case the greater the desired transmit power, the greater the need for prestressing, and therefore the more the disadvantages mentioned above take on greater importance. 'importance.
Pour pallier ces inconvénients, l'invention propose un transducteur acoustique en anneau précontraint, du type comprenant un ensemble de segments piézoélectriques disposés en forme d'anneau, principalement caractérisé en ce que ses segments sont groupés pour former des secteurs sensiblement identiques, et en ce qu'il comprend en outre des pièces d'extrémité fixées aux extrémités de ces secteurs pour délimiter entre eux des intervalles en forme de coin dont l'extrémité la plus étroite est dirigée vers l'intérieur de l'anneau, des cales de serrage en forme de coin adaptés à ces intervalles et placées dans ceux-ci, un anneau conformateur permettant de maintenir l'ensemble des secteurs, et des moyens de serrage permettant de faire glisser les cales de serrage vers l'intérieur de l'anneau pour précontraindre les segments par l'anneau conformateur.To overcome these drawbacks, the invention provides a prestressed ring acoustic transducer, of the type comprising a set of piezoelectric segments arranged in the form of a ring, mainly characterized in that its segments are grouped to form substantially identical sectors, and in that that it further comprises end pieces fixed to the ends of these sectors to delimit between them wedge-shaped intervals, the most narrow is directed towards the inside of the ring, wedge-shaped clamps adapted to these intervals and placed in them, a shaping ring making it possible to hold all the sectors, and clamping means making it possible to slide the shims towards the inside of the ring to prestress the segments by the shaping ring.
Selon une autre caractéristique, le transducteur comprend en outre des jauges de contrainte fixées sur la face intérieure des secteurs pour permettre de mesurer les contraintes appliquées aux segments. Selon une autre caractéristique, les moyens de serrage sont formés de vis fixées dans des trous ménagés dans la face interne des cales de serrage et munies de rondelles venant s'appuyer sur les pièces d'extrémité des secteurs pour permettre d'exercer une traction sur les cales lorsqu'on visse les vis. Selon une autre caractéristique, les intervalles subsistant d'une part entre les cales de serrage et l'anneau conformateur et d'autre part entre ces mêmes cales de serrage et les moyens de serrage sont bouchés avec un produit de remplissage lorsque le réglage est obtenu.According to another characteristic, the transducer further comprises strain gauges fixed on the inner face of the sectors to allow the stresses applied to the segments to be measured. According to another characteristic, the clamping means are formed of screws fixed in holes made in the internal face of the clamping shims and provided with washers which come to bear on the end pieces of the sectors to allow traction to be exerted on the shims when the screws are tightened. According to another characteristic, the intervals remaining on the one hand between the clamping wedges and the shaping ring and on the other hand between these same clamping wedges and the clamping means are plugged with a filling product when the adjustment is obtained .
Selon une autre caractéristique la raideur dynamique de l'anneau conformateur est sensiblement dix fois plus faible que celle des segments piézoélectriques.According to another characteristic, the dynamic stiffness of the shaping ring is substantially ten times lower than that of the piezoelectric segments.
L'invention propose en outre un procédé de réglage d'un tel transducteur principalement caractérisé en ce que l'on serre progressivement les moyens de serrage en surveillant les indications données par les jauges de contrainte pour obtenir sur chaque secteur des contraintes identiques et égales à la valeur souhaitée.The invention further provides a method of adjusting such a transducer mainly characterized in that the clamping means are gradually tightened by monitoring the indications given by the strain gauges to obtain stresses identical and equal to each sector. the desired value.
D'autres particularités et avantages de l'invention apparaîtront clairement dans la description suivante, faite à titre d'exemple non limitatif en regard des figures annexées qui représentent: - la figure 1 , une vue en perspective cavalière d'un transducteur en anneau selon l'invention;Other features and advantages of the invention will appear clearly in the following description, given by way of nonlimiting example with reference to the appended figures which represent: - Figure 1, a perspective view of a ring transducer according to the invention;
- la figure 2, une vue en perspective cavalière d'un coin de réglage de cet anneau; et- Figure 2, a perspective view of an adjustment corner of this ring; and
- la figure 3, une vue en perspective cavalière d'un secteur de l'anneau compris entre deux coins tels que ceux de la figure 2. Dans l'exemple de réalisation représenté sur la figure 1 , l'anneau piézoélectrique formant le transducteur est réalisé par assemblage d'un ensemble de segments élémentaires 101 ayant la forme de prismes à section trapézoïdale tout à fait semblables à ceux utilisés dans l'art connu. Toutefois, selon l'invention, l'anneau est divisé en un ensemble de secteurs 102 sensiblement identiques réunissant des sous-ensemble de segments. A titre d'exemple, dans une réalisation pratique le diamètre de l'anneau est de l'ordre de 20 cm et il est divisé en 5 secteurs comportant chacun 8 segments. On a représenté sur la figure 3 l'un de ces secteurs isolés. Il est formé de 8 segments élémentaires 101 en céramique piézoélectrique, du PZT par exemple. Ces segments sont collés entre eux avec interposition d'électrodes 103 qui permettent d'appliquer les tensions électriques d'excitation. Selon une technique connue, les segments sont polarisés tangentiellement alternativement dans des sens opposés. Les électrodes 103 sont réunies alternativement à des connexions 104 et 105 qui permettent d'appliquer aux électrodes ces tensions électriques.- Figure 3, a perspective view of a sector of the ring between two corners such as those of Figure 2. In the exemplary embodiment represented in FIG. 1, the piezoelectric ring forming the transducer is produced by assembling a set of elementary segments 101 having the shape of prisms with trapezoidal cross section quite similar to those used in the art known. However, according to the invention, the ring is divided into a set of substantially identical sectors 102 joining together subsets of segments. By way of example, in a practical embodiment the diameter of the ring is of the order of 20 cm and it is divided into 5 sectors each comprising 8 segments. One of these isolated sectors is shown in FIG. 3. It is formed by 8 elementary segments 101 in piezoelectric ceramic, for example PZT. These segments are bonded to each other with the interposition of electrodes 103 which make it possible to apply the electrical excitation voltages. According to a known technique, the segments are polarized tangentially alternately in opposite directions. The electrodes 103 are joined alternately to connections 104 and 105 which make it possible to apply these electrical voltages to the electrodes.
En outre les extrémités du secteur sont munies de pièces métalliques collées sur les faces extérieures des segments extrêmes. Ces pièces métalliques sont en forme de coin et leurs faces latérales extérieures font un angle α avec la direction du rayon de l'anneau, comme représenté sur la figure 1. Cet angle α est tel que la largeur du coin soit plus grande sur la surface intérieure de l'anneau que sur la surface extérieure de celui-ci.In addition, the ends of the sector are provided with metal parts glued to the outer faces of the end segments. These metal parts are wedge-shaped and their external lateral faces form an angle α with the direction of the radius of the ring, as shown in FIG. 1. This angle α is such that the width of the corner is greater on the surface inner ring than on the outer surface thereof.
Par ailleurs, on a en outre disposé sur la face intérieure du secteur au moins une jauge de contrainte 107, qui permet de mesurer les contraintes appliquées aux secteurs au niveau de cette face intérieure. Cette jauge de contrainte est par exemple réalisée sous la forme connue d'un film supportant des électrodes métalliques disposées de telle manière que l'extension ou la contraction de la surface sur laquelle la jauge est collée provoque une variation de résistance de ces électrodes selon une loi connue.Furthermore, at least one strain gauge 107 has been placed on the inner face of the sector, which makes it possible to measure the stresses applied to the sectors at the level of this inner face. This strain gauge is for example produced in the known form of a film supporting metal electrodes arranged in such a way that the extension or the contraction of the surface on which the gauge is stuck causes a variation in resistance of these electrodes according to a known law.
L'ensemble des 5 secteurs est disposé à l'intérieur d'un anneau conformateur 108 et qui permet de définir la forme et les dimensions de l'anneau piézoélectrique. Cet anneau est par exemple fabriqué en verre époxy avec une surface intérieure soigneusement polie. Les dimensions des secteurs sont prévus pour qu'il subsiste un jeu entre les pièces métalliques des extrémités de deux secteurs adjacents. Ce jeu est comblé par des cales de réglage ayant la forme de coins 109. Ces cales, dont un exemplaire est représenté sur la figure 2, viennent donc se placer entre les secteurs et permettent de bloquer ces secteurs à l'intérieur de l'anneau conformateur 108. L'angle entre les deux faces latérales de ces cales est étudié pour correspondre à l'angle alpha des pièces d'extrémités des secteurs, de telle manière que lorsque les cales sont en position ces faces extérieures viennent s'appliquer sur les faces extérieures de ces pièces d'extrémités avec un jeu angulaire aussi minime que possible, pour éviter des contraintes excessives aux points de contact entre les cales et les pièces d'extrémité.The set of 5 sectors is arranged inside a shaping ring 108 and which makes it possible to define the shape and the dimensions of the piezoelectric ring. This ring is for example made of epoxy glass with a carefully polished inner surface. The dimensions of the sectors are provided so that there is a clearance between the metal parts of the ends of two adjacent sectors. This clearance is filled by adjustment shims having the form of wedges 109. These shims, a copy of which is shown in FIG. 2, are therefore placed between the sectors and allow these sectors to be blocked inside the ring. shaping device 108. The angle between the two lateral faces of these shims is designed to correspond to the angle alpha of the end pieces of the sectors, so that when the shims are in position these external faces are applied to the outer faces of these end pieces with as little angular play as possible, to avoid excessive stresses at the points of contact between the wedges and the end pieces.
Pour assurer l'assemblage de l'ensemble, les faces des cales 109 orientées vers l'intérieur de l'anneau sont munies de trous taraudés 110, ici au nombre de 3, qui permettent de recevoir des organes de serrage venant se visser dans ces trous en s'appuyant sur les faces des pièces d'extrémité 106 elles-mêmes orientées vers l'intérieur de l'anneau. Ces pièces de serrage peuvent-être plus ou moins compliquées, mais dans l'exemple de réalisation représenté elles sont composées de vis 111 sur lesquelles sont enfilées des rondelles 112. Ces vis viennent se visser dans les trous taraudés, puis sur les rondelles, elles-mêmes appuyées sur les pièces 106. On exerce ainsi sur les cales en coin 109 une traction vers l'intérieur de l'anneau ce qui tend, compte tenu des angles α, à écarter les secteurs 101 et à agrandir l'anneau formé par l'ensemble de ces secteurs et des cales. Sous cet effet d'élargissement l'anneau piézoélectrique vient appuyer fermement sur l'intérieur de l'anneau conformateur 108, ce qui, dans un premier temps, maintient l'ensemble des pièces en position.To ensure the assembly of the assembly, the faces of the shims 109 oriented towards the inside of the ring are provided with tapped holes 110, here 3 in number, which make it possible to receive clamping members which are screwed into these holes based on the faces of the end pieces 106 themselves oriented towards the inside of the ring. These clamping parts may be more or less complicated, but in the embodiment shown they are composed of screws 111 on which are threaded washers 112. These screws are screwed into the tapped holes, then on the washers, they -same supported on the pieces 106. There is thus exerted on the wedges 109 a traction towards the inside of the ring which tends, taking into account the angles α, to spread the sectors 101 and to enlarge the ring formed by all of these sectors and holds. Under this widening effect the piezoelectric ring comes to press firmly on the inside of the shaping ring 108, which, at first, keeps all the parts in position.
L'assemblage ainsi obtenu ayant été vérifié, on peut, dans un deuxième temps, procéder à sa mise en précontrainte en serrant plus fort les vis. Sous cet effet, les cales de réglage 109 progressent vers le centre de l'anneau en augmentant l'écart e entre celles-ci et l'anneau conformateur et donc en augmentant l'effort de pression des secteurs sur l'anneau conformateur. Par réaction ceci entraîne une précontrainte de ces secteurs par cet anneau conformateur. Le serrage se fait de manière classique en serrant progressivement les vis selon un ordre croisé jusqu'à ce que l'on obtienne la précontrainte voulue.The assembly thus obtained having been verified, we can, in a second step, proceed to its prestressing by tightening the screws more tightly. Under this effect, the adjustment shims 109 progress towards the center of the ring by increasing the difference e between them and the shaping ring and therefore by increasing the pressure force of the sectors on the shaping ring. By reaction this causes these sectors to be prestressed by this shaping ring. The clamping is done in a conventional way in gradually tightening the screws in a cross order until the desired preload is obtained.
Pour s'assurer de la valeur et de l'uniformité de la précontrainte, l'invention propose d'utiliser les jauges de contrainte 107 décrites plus haut. Pour cela, celles-ci seront reliées à des moyens de mesure 113 qui permettent de déterminer la contrainte au niveau de ces jauges. La contrainte aux endroits ou sont placés ces jauges indique, à un coefficient multiplicateur près connu, la contrainte globale appliquée aux céramiques formant chaque secteur. Les secteurs sont suffisamment petits pour que les contraintes ainsi obtenues et mesurées soient uniformément réparties. Dans le cas d'un anneau plus grand, on serait éventuellement amené à utiliser un nombre de secteurs plus important. Bien entendu le serrage des vis sera fait progressivement en vérifiant en permanence l'évolution des contraintes, de manière à obtenir la contrainte globale souhaitée et à minimiser au maximum les écarts entre les contraintes mesurée localement.To ensure the value and uniformity of the prestress, the invention proposes to use the strain gauges 107 described above. For this, they will be connected to measuring means 113 which make it possible to determine the stress at these gauges. The stress at the places where these gauges are placed indicates, to a near known multiplying coefficient, the global stress applied to the ceramics forming each sector. The sectors are small enough so that the stresses thus obtained and measured are uniformly distributed. In the case of a larger ring, we would eventually have to use a larger number of sectors. Of course, the tightening of the screws will be done gradually by constantly checking the evolution of the stresses, so as to obtain the desired global stress and to minimize the deviations between the stresses measured locally.
Lorsque le réglage définitif est obtenu, on peut éventuellement combler l'intervalle e entre les cales 109 et l'anneau conformateur 108, ainsi que l'intervalle résiduel éventuel entre les moyens de serrage et ces mêmes cales, avec un matériau de remplissage. Ce matériau de remplissage sera de préférence relativement élastique, du polyuréthane par exemple, de manière à pouvoir permettre des ajustements ultérieurs éventuels.When the final adjustment is obtained, it is possible optionally to fill the gap e between the shims 109 and the shaping ring 108, as well as the possible residual gap between the clamping means and these same shims, with a filling material. This filling material will preferably be relatively elastic, polyurethane for example, so as to be able to allow possible subsequent adjustments.
L'anneau conformateur 108 intervient bien entendu dans les caractéristiques acoustiques du transducteur ainsi réalisé, comme c'est d'ailleurs le cas dans les autres systèmes de précontrainte déjà connu. On a déterminé que pour obtenir des résultats corrects, en particulier ne pertubant pas de manière excessive le fonctionnement de l'anneau piézoélectrique, il était préférable d'utiliser un anneau conformateur dont la raideur dynamique soit environ dix fois plus faible que celle de l'anneau piézoélectrique en céramiques. Par rapport aux systèmes connus de mise en précontrainte, ce dispositif est particulièrement facile à mettre en oeuvre et donc peu coûteux. En outre il est modulaire, ce qui permet le cas échéant de ne remplacer qu'un seul segment en cas d'avarie à celui-ci. Les contraintes sont réparties d'une manière remarquablement uniforme, et leurs variations au cours du temps est très faible. On peut tout à fait ajuster cette précontrainte, soit en fonction des conditions opérationnelles, soit pour corriger la dérive dans le temps. Par ailleurs l'assemblage est démontable, ce qui permet les réparations citées plus haut. Enfin les pièces métalliques 106 et 109 favorisent, le cas échéant, le drainage thermique, surtout lorsque l'anneau est sollicité par de très fortes puissances électriques. The shaping ring 108 is of course involved in the acoustic characteristics of the transducer thus produced, as is also the case in the other already known prestressing systems. It has been determined that to obtain correct results, in particular not excessively disturbing the operation of the piezoelectric ring, it was preferable to use a shaping ring whose dynamic stiffness is approximately ten times lower than that of the piezoelectric ceramic ring. Compared to known prestressing systems, this device is particularly easy to implement and therefore inexpensive. In addition it is modular, which allows if necessary to replace only one segment in the event of damage to it. The stresses are distributed in a remarkably uniform manner, and their variations over time are very small. We can completely adjust this preload, either by depending on operational conditions, ie to correct drift over time. Furthermore the assembly is removable, which allows the repairs mentioned above. Finally, the metal parts 106 and 109 promote, if necessary, thermal drainage, especially when the ring is stressed by very high electrical powers.

Claims

Revendications claims
1. Transducteur acoustique en anneau précontraint, du type comprenant un ensemble de segments piézoélectriques (101) disposés en forme d'anneau, caractérisé en ce que ses segments sont groupés pour former des secteurs (102) sensiblement identiques, et en ce qu'il comprend en outre des pièces d'extrémité (106) fixées aux extrémités de ces secteurs pour délimiter entre eux des intervalles en forme de coin dont l'extrémité la plus étroite est dirigée vers l'intérieur de l'anneau, des cales de serrage (109) en forme de coin adaptés à ces intervalles et placées dans ceux-ci, un anneau conformateur (108) permettant de maintenir l'ensemble des secteurs, et des moyens de serrage (110-112) permettant de faire glisser les cales de serrage vers l'intérieur de l'anneau pour précontraindre les segments par l'anneau conformateur.1. Acoustic transducer in a prestressed ring, of the type comprising a set of piezoelectric segments (101) arranged in the form of a ring, characterized in that its segments are grouped to form substantially identical sectors (102), and in that it further comprises end pieces (106) fixed to the ends of these sectors to delimit between them wedge-shaped intervals, the narrowest end of which is directed towards the inside of the ring, clamps ( 109) in the form of a wedge adapted to these intervals and placed therein, a shaping ring (108) making it possible to hold all of the sectors, and clamping means (110-112) making it possible to slide the clamping wedges towards the inside of the ring to prestress the segments by the shaping ring.
2. Transducteur selon la revendication 1 , caractérisé en ce qu'il comprend en outre des jauges de contrainte (107) fixées sur la face intérieure des secteurs pour permettre de mesurer les contraintes tangentielies appliquées aux segments. 2. Transducer according to claim 1, characterized in that it further comprises strain gauges (107) fixed on the inner face of the sectors to allow the tangential stresses applied to the segments to be measured.
3. Transducteur selon l'une quelconque des revendications 1 et 2, caractérisé en ce que les moyens de serrage sont formés de vis (111 ) fixées dans des trous ménagés dans la face interne des cales de serrage3. Transducer according to any one of claims 1 and 2, characterized in that the clamping means are formed of screws (111) fixed in holes made in the internal face of the clamping wedges
(109) et munies de rondelles (112) venant s'appuyer sur les pièces d'extrémité (106) des secteurs pour permettre d'exercer une traction sur les cales lorsqu'on visse les vis.(109) and provided with washers (112) which come to bear on the end pieces (106) of the sectors to allow traction to be exerted on the wedges when the screws are tightened.
4. Transducteur selon l'une quelconque des revendications 1 à 3, caractérisé en ce que les intervalles subsistant d'une part entre les cales de serrage (109) et l'anneau conformateur (108) et d'autre part entre ces mêmes cales de serrage et les moyens de serrage (110-112) sont bouchés avec un produit de remplissage lorsque le réglage est obtenu.4. Transducer according to any one of claims 1 to 3, characterized in that the intervals remaining on the one hand between the clamping shims (109) and the shaping ring (108) and on the other hand between these same shims the clamping means and the clamping means (110-112) are blocked with a filling product when the adjustment is obtained.
5. Transducteur selon l'une quelconque des revendications 1 à 4, caractérisé en ce que la raideur dynamique de l'anneau conformateur (208) est sensiblement dix fois plus faible que celle des segments piézoélectriques (101 ). 5. Transducer according to any one of claims 1 to 4, characterized in that the dynamic stiffness of the shaping ring (208) is substantially ten times lower than that of the piezoelectric segments (101).
6. Procédé de réglage d'un transducteur selon l'une quelconque des revendications 2 à 5, caractérisé en ce que l'on serre progressivement les moyens de serrage (110-112) en surveillant les indications données par les jauges de contrainte (107) pour obtenir sur chaque secteur des contraintes identiques et égales à la valeur souhaitée. 6. A method of adjusting a transducer according to any one of claims 2 to 5, characterized in that the clamping means (110-112) are gradually tightened by monitoring the indications given by the strain gauges (107 ) to obtain identical constraints equal to the desired value on each sector.
EP95942751A 1994-12-23 1995-12-15 Acoustic transducer shaped as a prestressed ring Expired - Lifetime EP0799097B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9415587 1994-12-23
FR9415587A FR2728755B1 (en) 1994-12-23 1994-12-23 ACOUSTIC TRANSDUCER IN PRE-STRESSED RING
PCT/FR1995/001676 WO1996020046A1 (en) 1994-12-23 1995-12-15 Acoustic transducer shaped as a prestressed ring

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EP0799097A1 true EP0799097A1 (en) 1997-10-08
EP0799097B1 EP0799097B1 (en) 1998-09-23

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EP (1) EP0799097B1 (en)
JP (1) JP3653733B2 (en)
AU (1) AU695815B2 (en)
DE (1) DE69505014T2 (en)
FR (1) FR2728755B1 (en)
WO (1) WO1996020046A1 (en)

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Publication number Priority date Publication date Assignee Title
FR2776161B1 (en) * 1998-03-10 2000-05-26 Thomson Marconi Sonar Sas REMOVABLE ANNULAR ACOUSTIC EMISSION ANTENNA
FR2826828B1 (en) * 2001-06-29 2003-12-12 Thomson Marconi Sonar Sas ACOUSTIC TRANSDUCER WITH PRESTRESSED RING
EP1583941B1 (en) * 2003-01-17 2011-12-28 Kistler Holding AG Prestressing element for sensors
US8854923B1 (en) * 2011-09-23 2014-10-07 The United States Of America As Represented By The Secretary Of The Navy Variable resonance acoustic transducer
FR3015785B1 (en) * 2013-12-20 2015-12-25 Thales Sa COMPACT OMNIDIRECTIONAL ANTENNA FOR SONAR TEMP
CN109633614B (en) * 2018-11-29 2023-08-01 哈尔滨工程大学 Low-post-radiation high-frequency transducer linear array

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US3043967A (en) * 1960-01-13 1962-07-10 Walter L Clearwaters Electrostrictive transducer
US3230505A (en) * 1963-06-27 1966-01-18 David E Parker Reinforced ceramic cylindrical transducers
US4313510A (en) * 1980-11-24 1982-02-02 General Electric Company Weighing scale with dynamic zero error correction
US4546459A (en) * 1982-12-02 1985-10-08 Magnavox Government And Industrial Electronics Company Method and apparatus for a phased array transducer
DE3542741A1 (en) * 1985-12-03 1987-06-04 Taga Electric Co Ltd Torsional oscillation device
GB9409133D0 (en) * 1994-05-09 1994-11-30 Secr Defence Sonar ring transducer

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See references of WO9620046A1 *

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EP0799097B1 (en) 1998-09-23
JPH10511523A (en) 1998-11-04
DE69505014T2 (en) 1999-05-06
AU4393496A (en) 1996-07-19
WO1996020046A1 (en) 1996-07-04
FR2728755A1 (en) 1996-06-28
JP3653733B2 (en) 2005-06-02
AU695815B2 (en) 1998-08-20
US6065349A (en) 2000-05-23
DE69505014D1 (en) 1998-10-29
FR2728755B1 (en) 1997-01-24

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