EP0403378B1 - Omnidirectional loudspeaker with spherical diaphragm using a two-layer magnetostrictive ribbon - Google Patents

Omnidirectional loudspeaker with spherical diaphragm using a two-layer magnetostrictive ribbon Download PDF

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Publication number
EP0403378B1
EP0403378B1 EP90401637A EP90401637A EP0403378B1 EP 0403378 B1 EP0403378 B1 EP 0403378B1 EP 90401637 A EP90401637 A EP 90401637A EP 90401637 A EP90401637 A EP 90401637A EP 0403378 B1 EP0403378 B1 EP 0403378B1
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EP
European Patent Office
Prior art keywords
strip
sphere
face
directed towards
membrane
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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.)
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EP90401637A
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German (de)
French (fr)
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EP0403378A1 (en
Inventor
Siegfried Klein
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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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
    • H04R15/00—Magnetostrictive transducers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/02—Details
    • H01H37/32—Thermally-sensitive members
    • H01H37/52—Thermally-sensitive members actuated due to deflection of bimetallic element
    • H01H2037/523—Thermally-sensitive members actuated due to deflection of bimetallic element using a corrugated bimetal

Definitions

  • the present invention relates to an omnidirectional speaker with a spherical membrane using a magnetostrictive bimetallic strip.
  • This invention is applicable to the omnidirectional broadcasting of sound waves by means of a high performance loudspeaker, with wide bandwidth, extending throughout the range of audible frequencies.
  • An omnidirectional loudspeaker is known, with a spherical membrane, having a wide bandwidth and using the phenomenon of magnetostriction.
  • This loudspeaker is described for example in European patent application No. 0 177 383, filed on August 22, 1985 in the names of the same applicants.
  • This patent application describes an omnidirectional elastic wave transducer with a large passband, and more precisely a spherical speaker using the phenomenon of magnetostriction.
  • the omnidirectional loudspeaker of spherical shape, consists of a ribbon; of a magnetostrictive material wound in a spiral, an elastic seal joining the turns of the ribbon the two ends of this ribbon are connected to means for applying to the loudspeaker thus obtained, which forms a spherical pulsating membrane, a corresponding electrical control signal sound waves to broadcast.
  • the two ends of the ribbon are located in two areas diametrically opposite of the pulsating membrane.
  • This loudspeaker also comprises means of continuous and permanent magnetic polarization, for polarizing the pulsating membrane so that the acoustic wave has an amplitude proportional to the control signal applied to the ends of the ribbon.
  • the loudspeaker described in this patent has the drawback, however, of having only a low power at low frequencies; this imperfection is mainly due to the difficulty of obtaining a large amplitude of the pulsations of the spherical membrane at low frequencies.
  • the object of the invention is to remedy this drawback and in particular to produce a loudspeaker with a spherical pulsating membrane, ensuring sufficient acoustic power in all frequencies and more particularly at low frequencies.
  • a magnetostrictive tape having at least one of its faces completely or partially covered by a thin layer of a material, such as copper, ceramic, etc..
  • This rigid thin layer gives the ribbon, as will be seen in detail below, the properties of a bimetallic strip, the deformations of which are not controlled by variations in temperature, but by the application of a current modulated electric control.
  • This current causes variations in the length of the magnetostrictive tape which, subject to the stresses of the rigid thin layer, the length of which does not vary, deforms substantially at the rate of the variations in amplitude of the modulation current.
  • FIGS. 1a and 1b will make it possible to better understand the phenomenon of magnetostrictive bimetal strip used in the loudspeaker of the invention.
  • FIG. 1a is a side view of a portion of a magnetostrictive tape M, surrounded by a coil B. In the absence of electric current in the coil B, the tape M has a length L.
  • the coil B When a current is applied to the coil B, and in the absence of a permanent continuous magnetic field, the coil induces a magnetic field in the ribbon which shrinks and then has a length L1, very little less than L.
  • Figure 1b shows laterally the magnetostrictive ribbon M, surrounded by the coil B.
  • This ribbon is here covered, on one of its faces, by a thin layer of a rigid material such as copper or ceramic for example.
  • the ribbon M and the layer R have a length L.
  • the invention uses this bimetallic strip in a spherical loudspeaker having sufficient acoustic power throughout the range of acoustic frequencies and in particular at low frequencies.
  • the invention relates to an omnidirectional loudspeaker comprising a spherical membrane, which comprises turns formed of a ribbon of a magnetostrictive material wound in a spiral according to a sphere, these turns being held by an elastic support, so that they form with said support said spherical membrane, this ribbon having two opposite faces, one of which is directed towards the inside of the sphere and the other towards the outside, and two ends situated in two diametrically opposite zones of the sphere, to be connected to an electrical control means supplying a signal corresponding to sound waves to be reproduced, and a means for continuous polarization of the membrane, characterized in that at least one of the faces of the ribbon is at least partially covered with a thin layer of rigid material.
  • the ribbon is covered by the rigid thin layer on its face directed towards the outside of the sphere.
  • the ribbon has over its entire length transverse corrugations, each corrugation having on the face of the ribbon, directed towards the inside of the sphere, a concave zone and a zone convex and, on the face of the ribbon directed towards the outside of the sphere, a concave zone and a convex zone, the rigid layer being located at least partially on the face of the ribbon directed towards the outside of the sphere, opposite the convex areas of this face.
  • the ribbon has transverse undulations over its entire length, each undulation having on the face of the ribbon directed towards the interior of the sphere, a concave zone and a convex zone and, on the face of the ribbon directed towards the outside of the sphere, a concave zone and a convex zone, the rigid layer being located partially on each face of the strip, opposite the concave zones or opposite the convex zones.
  • the means for continuous polarization of the membrane is a permanent magnet located inside said membrane.
  • the DC biasing means is a DC voltage source connected to the ends of said strip.
  • said membrane is formed of two hemispheres joined to one another.
  • FIG. 2 schematically represents a first embodiment of an omnidirectional loudspeaker, according to the invention.
  • This loudspeaker comprises a spherical membrane which comprises turns (2) of a magnetostrictive tape, wound in a spiral according to a sphere. These turns are held by an elastic support 1 which can be either a hollow sphere of an insulating and elastic material, on which the turns are glued, or a strip of an elastic material wound helically according to a sphere, this strip being located between the turns and being made integral with these.
  • the tape 2 of magnetostrictive material forms with the support 1 a spherical membrane.
  • the ribbon has two opposite faces, one of which is directed towards the inside of the sphere, and the other towards the outside of the sphere.
  • the tape 2 of magnetostrictive material comprises on at least one of its faces an at least partial coating of a thin layer of a rigid material such as copper , ceramic ... etc. It also has two ends 3, 4, located in two diametrically opposite zones of the spherical shell 1. These ends are connected to a control means 5 providing a modulation signal corresponding to sound waves to be reproduced.
  • This control means can be constituted for example, in this embodiment, by a transformer, a primary winding 6 of which receives the output signal from an amplifier.
  • the secondary winding 7 of this transformer applies this signal to the ends 3, 4, of the ribbon 2.
  • the loudspeaker also comprises a means of continuous polarization constituted here by an electric source 8 of direct voltage, one of the terminals of which is connected to the end 4 of the ribbon 2 and the other terminal of which is connected to the end 3 of this ribbon, via a choke L.
  • a decoupling capacitor 9 also appears in the figure. This capacitor is conventional in the connection of a loudspeaker to the output of an amplifier.
  • the DC voltage source induces a continuous and permanent magnetic field in the ribbon.
  • At least one of the faces of the tape 2 has a rigid thin layer completely or partially covering this face. This layer does not appear in this figure and will be described later.
  • FIG. 3 schematically represents another embodiment of the loudspeaker of FIG. 1.
  • the means for continuous polarization of the ribbon is here constituted by a permanent magnet 10 situated inside the spherical membrane.
  • This permanent magnet of cylindrical shape for example, has an axis common to the axis X of the loudspeaker.
  • the DC voltage source 8, the choke L and the decoupling capacitor 9, are not necessary and the secondary winding of the transformer 5 is directly connected to the ends of the strip 2.
  • at least l 'One of the faces of the tape 2 here also has a rigid thin layer completely or partially covering this face. This layer does not appear in this figure and will be described later.
  • FIG 4 is a schematic transverse view of an alternative embodiment of the magnetostrictive tape covered with a rigid thin layer, used in the loudspeaker of the invention.
  • the magnetostrictive tape 2 which has two opposite faces 11, 12, one (face 12) directed towards the inside I of the sphere and the other (face 11) directed towards the outside E of the sphere, is completely covered on its face 11, directed towards the outside of the sphere, by a thin layer 13 of rigid material.
  • the magnetostrictive tape can be constituted for example by a colbalt / nickel alloy, while the rigid thin layer 13 can be a layer of copper or a ceramic for example.
  • this ribbon undergoes deformations whose amplitudes are proportional to the variations in amplitude of the current. Due to the presence of the rigid layer, the ribbon undergoes deformations which are amplified in the same way as in a thermal bimetallic strip where it is temperature variations which cause such deformations. It follows that the speaker formed using such a ribbon has a very wide bandwidth in the range of audible frequencies, including for low frequencies or its power is much greater than for the speakers state of the art spherical.
  • FIG. 5 schematically represents a side view of another variant of a magnetostrictive tape used in the loudspeaker of the invention.
  • the ribbon here has undulations over its entire length transverse.
  • Each corrugation has on the face 12 of the ribbon, directed towards the interior I of the sphere, a concave zone 14A and a convex zone 14B.
  • Each corrugation also has on the face 11 of the ribbon, directed towards the outside E of the sphere, a concave zone 15A and a convex zone 15B.
  • the rigid thin layer does not extend over the whole of one of the faces of the ribbon, but it is located at least partially opposite the convex zones 15B of the face 11 of the ribbon, directed towards the outside. E of the sphere. This rigid thin layer is shown at 16 in the figure.
  • FIG. 6 schematically represents a side view of another variant of the magnetostrictive tape.
  • the magnetostrictive ribbon has transverse undulations over its entire length.
  • Each corrugation has, as in the previous embodiment, on its face 12 directed towards the interior I of the sphere, a concave zone 14A, and a convex zone 14B and on its face 11, directed towards the exterior of the sphere , a concave zone 15A and a convex zone 15B.
  • the rigid layer is here partially located opposite the zones concaves 14A and 15A on each side of the ribbon. These localized rigid thin layers are shown at 19, 20 in the figure.
  • the passage of electric current through the ribbon here causes the edges of the corrugations to spread apart.
  • FIG. 7 schematically represents a side view of another variant of a magnetostrictive tape used in the loudspeaker of the invention.
  • the rigid thin layer is here partially deposited on each of the faces of the ribbon, facing the convex zones 14B, 15B of the corrugations. These localized rigid thin layers are shown at 21, 22 in the figure.
  • the amplitude of the deformations of the ribbon in particular at low frequencies, is very large due to the bimetal effect of the structure of the ribbon described.
  • the passage of electric current through the ribbon brings the edges of the corrugations together.
  • the membrane constituted by the ribbon 2, partially covered with rigid material, and by the elastic support 1 can be formed of two hemispheres, such as represented in 23 , 24, in FIG. 1. These two hemispheres are made integral, for example by gluing the support and by welding two half-ribbons, each corresponding to one of the hemispheres.
  • the preferred embodiments of the loudspeaker which has just been described are those which use the magnetostrictive ribbon with bimetal effect, of wavy shape. It is indeed this wavy shape which provides the best acoustic performance and which ensures the simplest manufacture of the spherical loudspeaker.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)

Description

La présente invention concerne un haut-parleur omnidirectionnel à membrane sphérique utilisant un ruban bilame magnétostrictif. Cette invention s'applique à la diffusion omnidirectionnelle d'ondes sonores grâce à un haut-parleur à hautes performances, à large bande passante, s'étendant dans tout le domaine des fréquences audibles.The present invention relates to an omnidirectional speaker with a spherical membrane using a magnetostrictive bimetallic strip. This invention is applicable to the omnidirectional broadcasting of sound waves by means of a high performance loudspeaker, with wide bandwidth, extending throughout the range of audible frequencies.

On connaît un haut-parleur omnidirectionnel, à membrane sphérique, présentant une large bande passante et utilisant le phénomène de la magnétostriction. Ce haut-parleur est décrit par exemple dans la demande de brevet européen N° 0 177 383, déposée le 22 août 1985 aux noms des mêmes demandeurs.An omnidirectional loudspeaker is known, with a spherical membrane, having a wide bandwidth and using the phenomenon of magnetostriction. This loudspeaker is described for example in European patent application No. 0 177 383, filed on August 22, 1985 in the names of the same applicants.

Cette demande de brevet décrit un transducteur omnidirectionnel d'ondes élastiques à large bande passante, et plus précisément un haut-parleur de forme sphérique utilisant le phénomène de la magnétostriction.This patent application describes an omnidirectional elastic wave transducer with a large passband, and more precisely a spherical speaker using the phenomenon of magnetostriction.

Dans un mode de réalisation particulier décrit dans ce brevet, le haut-parleur omnidirectionnel, de forme sphérique, est constitué par un ruban ; d'un matériau magnétostrictif enroulé en spirale, un joint élastique réunissant les spires du ruban les deux extrémités de ce ruban sont reliées à des moyens pour appliquer au haut-parleur ainsi obtenu, qui forme une membrane pulsante sphérique, un signal électrique de commande correspondant à des ondes sonores à diffuser. Les deux extrémités du ruban sont situées en deux zones diamétralement opposées de la membrane pulsante. Ce haut-parleur comporte aussi des moyens de polarisation magnétique continue et permanente, pour polariser la membrane pulsante de sorte que l'onde acoustique ait une amplitude proportionnelle au signal de commande appliqué aux extrémités du ruban.In a particular embodiment described in this patent, the omnidirectional loudspeaker, of spherical shape, consists of a ribbon; of a magnetostrictive material wound in a spiral, an elastic seal joining the turns of the ribbon the two ends of this ribbon are connected to means for applying to the loudspeaker thus obtained, which forms a spherical pulsating membrane, a corresponding electrical control signal sound waves to broadcast. The two ends of the ribbon are located in two areas diametrically opposite of the pulsating membrane. This loudspeaker also comprises means of continuous and permanent magnetic polarization, for polarizing the pulsating membrane so that the acoustic wave has an amplitude proportional to the control signal applied to the ends of the ribbon.

Le haut-parleur décrit dans ce brevet a cependant pour inconvénient de ne présenter qu'une faible puissance aux basses fréquences ; cette imperfection est due essentiellement à la difficulté d'obtenir une amplitude importante des pulsations de la membrane sphérique aux basses fréquences.The loudspeaker described in this patent has the drawback, however, of having only a low power at low frequencies; this imperfection is mainly due to the difficulty of obtaining a large amplitude of the pulsations of the spherical membrane at low frequencies.

L'invention a pour but de remédier à cet inconvénient et notamment de réaliser un haut-parleur à membrane pulsante sphérique, assurant une puissance acoustique suffisante dans toutes les fréquences et plus particulièrement aux basses fréquences. Ces buts sont atteints notamment grâce à l'utilisation d'un ruban magnétostrictif ayant au moins l'une de ses faces recouverte totalement ou partiellement par une couche mince d'un matériau, tel que du cuivre, une céramique...etc. La présence de cette couche mince rigide confère au ruban, comme on le verra plus loin en détail, les propriétés d'un bilame, dont les déformations sont, non pas commandées par des variations de température, mais par l'application d'un courant électrique modulé de commande. Ce courant provoque des variations de longueur du ruban magnétostrictif qui, soumis aux contraintes de la couche mince rigide dont la longueur ne varie pas, se déforme sensiblement au rythme des variations d'amplitude du courant de modulation.The object of the invention is to remedy this drawback and in particular to produce a loudspeaker with a spherical pulsating membrane, ensuring sufficient acoustic power in all frequencies and more particularly at low frequencies. These aims are achieved in particular through the use of a magnetostrictive tape having at least one of its faces completely or partially covered by a thin layer of a material, such as copper, ceramic, etc.. The presence of this rigid thin layer gives the ribbon, as will be seen in detail below, the properties of a bimetallic strip, the deformations of which are not controlled by variations in temperature, but by the application of a current modulated electric control. This current causes variations in the length of the magnetostrictive tape which, subject to the stresses of the rigid thin layer, the length of which does not vary, deforms substantially at the rate of the variations in amplitude of the modulation current.

Les figures 1a et 1b vont permettre de mieux comprendre le phénomène de bilame magnétostrictif utilisé dans le haut-parleur de l'invention.FIGS. 1a and 1b will make it possible to better understand the phenomenon of magnetostrictive bimetal strip used in the loudspeaker of the invention.

La figure 1a est une vue latérale d'une portion d'un ruban magnétostrictif M, entouré d'une bobine B. En l'absence de courant électrique dans la bobine B, le ruban M a une longueur L.FIG. 1a is a side view of a portion of a magnetostrictive tape M, surrounded by a coil B. In the absence of electric current in the coil B, the tape M has a length L.

Lorsqu'un courant est appliqué à la bobine B, et en l'absence de champ magnétique continu permanent, la bobine induit un champ magnétique dans le ruban qui se rétrécit et présente alors une longueur L1, très peu inférieure à L.When a current is applied to the coil B, and in the absence of a permanent continuous magnetic field, the coil induces a magnetic field in the ribbon which shrinks and then has a length L1, very little less than L.

La figure 1b représente latéralement le ruban magnétostrictif M, entouré de la bobine B. Ce ruban est ici recouvert, sur l'une de ses faces, par une couche mince d'un matériau rigide tel que du cuivre ou une céramique par exemple. En l'absence de courant dans la bobine B, le ruban M et la couche R présentent une longueur L.Figure 1b shows laterally the magnetostrictive ribbon M, surrounded by the coil B. This ribbon is here covered, on one of its faces, by a thin layer of a rigid material such as copper or ceramic for example. In the absence of current in the coil B, the ribbon M and the layer R have a length L.

Lorsqu'un courant est appliqué à la bobine B, et en l'absence de champ magnétique permanent et continu, le ruban magnétostrictif M se rétrécit, mais les contraintes mécaniques dues à la présence de la couche mince rigide R solidaire du ruban M provoquent la courbure de l'ensemble qui présente alors une longueur L2. La différence de longueurs L-L2 est bien plus importante que la différence L-L1. Ce phénomène est comparable à celui d'un bilame thermique dont la courbure est provoquée par la température. Ici la courbure est due au rétrécissement du ruban magnétostrictif, soumis aux contraintes du matériau rigide et non magnétostrictif de la couche R. La disposition de la figure 1b peut être qualifiée de "bilame magnétostrictif".When a current is applied to the coil B, and in the absence of a permanent and continuous magnetic field, the magnetostrictive tape M shrinks, but the mechanical stresses due to the presence of the rigid thin layer R secured to the tape M cause the curvature of the assembly which then has a length L2. The difference in length L-L2 is much larger than the difference L-L1. This phenomenon is comparable to that of a thermal bimetallic strip whose curvature is caused by temperature. Here the curvature is due to the narrowing of the magnetostrictive tape, subjected to the constraints of the rigid and non-magnetostrictive material of the layer R. The arrangement of FIG. 1b can be qualified as "magnetostrictive bimetal strip".

L'invention met en oeuvre ce bilame dans un haut-parleur sphérique présentant une puissance acoustique suffisante dans toute la gamme des fréquences acoustiques et notamment aux basses fréquences.The invention uses this bimetallic strip in a spherical loudspeaker having sufficient acoustic power throughout the range of acoustic frequencies and in particular at low frequencies.

L'invention a pour objet un haut-parleur omnidirectionnel comportant une membrane sphérique, qui comprend des spires formées d'un ruban d'un matériau magnétostrictif enroulé en spirale selon une sphère, ces spires étant maintenues par un support élastique, de sorte qu'elles forment avec ledit support ladite membrane sphérique, ce ruban ayant deux faces opposées dont l'une est dirigée vers l'intérieur de la sphère et l'autre vers l'extérieur, et deux extrémités situées en deux zones diamétralement opposées de la sphère, pour être reliées à un moyen de commande électrique fournissant un signal correspondant à des ondes sonores à reproduire, et un moyen de polarisation continue de la membrane, caractérisé en ce que au moins l'une des faces du ruban est au moins partiellement recouverte d'une couche mince d'un matériau rigide.The invention relates to an omnidirectional loudspeaker comprising a spherical membrane, which comprises turns formed of a ribbon of a magnetostrictive material wound in a spiral according to a sphere, these turns being held by an elastic support, so that they form with said support said spherical membrane, this ribbon having two opposite faces, one of which is directed towards the inside of the sphere and the other towards the outside, and two ends situated in two diametrically opposite zones of the sphere, to be connected to an electrical control means supplying a signal corresponding to sound waves to be reproduced, and a means for continuous polarization of the membrane, characterized in that at least one of the faces of the ribbon is at least partially covered with a thin layer of rigid material.

Selon un premier mode de réalisation du haut-parleur de l'invention, le ruban est recouvert par la couche mince rigide sur sa face dirigée vers l'extérieur de la sphère.According to a first embodiment of the loudspeaker of the invention, the ribbon is covered by the rigid thin layer on its face directed towards the outside of the sphere.

Selon un autre mode de réalisation du haut-parleur de l'invention, le ruban présente sur toute sa longueur des ondulations transversales, chaque ondulation présentant sur la face du ruban, dirigée vers l'intérieur de la sphère, une zone concave et une zone convexe et, sur la face du ruban dirigée vers l'extérieur de la sphère, une zone concave et une zone convexe, la couche rigide étant localisée au moins partiellement sur la face du ruban dirigée vers l'extérieur de la sphère, en regard des zones convexes de cette face.According to another embodiment of the loudspeaker of the invention, the ribbon has over its entire length transverse corrugations, each corrugation having on the face of the ribbon, directed towards the inside of the sphere, a concave zone and a zone convex and, on the face of the ribbon directed towards the outside of the sphere, a concave zone and a convex zone, the rigid layer being located at least partially on the face of the ribbon directed towards the outside of the sphere, opposite the convex areas of this face.

Selon un autre mode de réalisation, le ruban présente sur toute sa longueur des ondulations transversales, chaque ondulation présentant sur la face du ruban dirigée vers l'intérieur de la sphère, une zone concave et une zone convexe et, sur la face du ruban dirigée vers l'extérieur de la sphère, une zone concave et une zone convexe, la couche rigide étant localisée partiellement sur chaque face du ruban, en regard des zones concaves ou en regard des zones convexes.According to another embodiment, the ribbon has transverse undulations over its entire length, each undulation having on the face of the ribbon directed towards the interior of the sphere, a concave zone and a convex zone and, on the face of the ribbon directed towards the outside of the sphere, a concave zone and a convex zone, the rigid layer being located partially on each face of the strip, opposite the concave zones or opposite the convex zones.

Selon une autre caractéristique de l'invention, le moyen de polarisation continue de la membrane est un aimant permanent situé à l'intérieur de ladite membrane.According to another characteristic of the invention, the means for continuous polarization of the membrane is a permanent magnet located inside said membrane.

Selon une autre caractéristique, le moyen de polarisation continue est une source de tension continue reliée aux extrémités dudit ruban.According to another characteristic, the DC biasing means is a DC voltage source connected to the ends of said strip.

Selon une autre caractéristique, ladite membrane est formée de deux hémisphères réunis l'un à l'autre.According to another characteristic, said membrane is formed of two hemispheres joined to one another.

Les caractéristiques et avantages de l'invention ressortiront mieux de la description qui va suivre, donnée en référence aux dessins annexés, dans lesquels :

  • les figures 1a et 1b ont déjà été décrites et permettent de mieux comprendre le principe du bilame magnétostrictif ;
  • la figure 2 représente schématiquement un premier mode de réalisation d'un haut-parleur conforme à l'invention ;
  • la figure 3 représente schématiquement un autre mode de réalisation de ce haut-parleur ;
  • la figure 4 représente schématiquement une vue transversale d'une première variante d'un ruban magnétostrictif utilisé dans le haut-parleur de l'invention ;
  • les figures 5, 6 et 7 représentent schématiquement des vues latérales de différentes autres variantes du ruban magnétostrictif utilisé dans le haut-parleur de l'invention.
The characteristics and advantages of the invention will emerge more clearly from the description which follows, given with reference to the appended drawings, in which:
  • FIGS. 1a and 1b have already been described and allow a better understanding of the principle of the magnetostrictive bimetal strip;
  • FIG. 2 schematically represents a first embodiment of a loudspeaker according to the invention;
  • FIG. 3 schematically represents another embodiment of this loudspeaker;
  • FIG. 4 schematically represents a transverse view of a first variant of a magnetostrictive tape used in the loudspeaker of the invention;
  • Figures 5, 6 and 7 schematically show side views of different other variants of the magnetostrictive tape used in the loudspeaker of the invention.

La figure 2 représente schématiquement un premier mode de réalisation d'un haut-parleur omnidirectionnel, conforme à l'invention.FIG. 2 schematically represents a first embodiment of an omnidirectional loudspeaker, according to the invention.

Ce haut-parleur comporte une membrane sphérique qui comprend des spires (2) d'un ruban magnétostrictif, enroulées en spirale selon une sphère. Ces spires sont maintenues par un support élastique 1 qui peut être, soit une sphère creuse d'un matériau isolant et élastique, sur laquelle les spires sont collées, soit une bande d'un matériau élastique enroulé en hélice selon une sphère, cette bande étant située entre les spires et étant rendue solidaire de celles-ci.This loudspeaker comprises a spherical membrane which comprises turns (2) of a magnetostrictive tape, wound in a spiral according to a sphere. These turns are held by an elastic support 1 which can be either a hollow sphere of an insulating and elastic material, on which the turns are glued, or a strip of an elastic material wound helically according to a sphere, this strip being located between the turns and being made integral with these.

Le ruban 2 de matériau magnétostrictif forme avec le support 1 une membrane sphérique.The tape 2 of magnetostrictive material forms with the support 1 a spherical membrane.

Le ruban présente deux faces opposées dont l'une est dirigée vers l'intérieur de la sphère, et l'autre vers l'extérieur de la sphère. Selon l'invention, et comme on le verra plus loin en détail, le ruban 2 de matériau magnétostrictif comporte sur l'une au moins de ses faces un revêtement au moins partiel d'une couche mince d'un matériau rigide tel que le cuivre, une céramique...etc. Il comporte également deux extrémités 3, 4, situées en deux zones diamétralement opposées de la coque sphérique 1. Ces extrémités sont reliées à un moyen de commande 5 fournissant un signal de modulation correspondant à des ondes sonores à reproduire. Ce moyen de commande peut être constitué par exemple, dans ce mode de réalisation, par un transformateur dont un enroulement primaire 6 reçoit le signal de sortie d'un amplificateur. L'enroulement secondaire 7 de ce transformateur applique ce signal aux extrémités 3, 4, du ruban 2. Le haut-parleur comporte aussi un moyen de polarisation continue constitué ici par une source électrique 8 de tension continue, dont l'une des bornes est reliée à l'extrémité 4 du ruban 2 et dont l'autre borne est reliée à l'extrémité 3 de ce ruban, par l'intermédiaire d'une self L. Un condensateur de découplage 9 apparaît également sur la figure. Ce condensateur est classique dans le branchement d'un haut-parleur à la sortie d'un amplificateur. La source de tension continue permet d'induire dans le ruban un champ magnétique continu et permanent.The ribbon has two opposite faces, one of which is directed towards the inside of the sphere, and the other towards the outside of the sphere. According to the invention, and as will be seen below in detail, the tape 2 of magnetostrictive material comprises on at least one of its faces an at least partial coating of a thin layer of a rigid material such as copper , ceramic ... etc. It also has two ends 3, 4, located in two diametrically opposite zones of the spherical shell 1. These ends are connected to a control means 5 providing a modulation signal corresponding to sound waves to be reproduced. This control means can be constituted for example, in this embodiment, by a transformer, a primary winding 6 of which receives the output signal from an amplifier. The secondary winding 7 of this transformer applies this signal to the ends 3, 4, of the ribbon 2. The loudspeaker also comprises a means of continuous polarization constituted here by an electric source 8 of direct voltage, one of the terminals of which is connected to the end 4 of the ribbon 2 and the other terminal of which is connected to the end 3 of this ribbon, via a choke L. A decoupling capacitor 9 also appears in the figure. This capacitor is conventional in the connection of a loudspeaker to the output of an amplifier. The DC voltage source induces a continuous and permanent magnetic field in the ribbon.

Selon l'invention, et comme on le verra plus loin en détail, au moins l'une des faces du ruban 2 présente une couche mince rigide recouvrant totalement ou partiellement cette face. Cette couche n'apparaît pas sur cette figure et sera décrite plus loin.According to the invention, and as will be seen below in detail, at least one of the faces of the tape 2 has a rigid thin layer completely or partially covering this face. This layer does not appear in this figure and will be described later.

La figure 3 représente schématiquement un autre mode de réalisation du haut-parleur de la figure 1. Le moyen de polarisation continue du ruban est ici constitué par un aimant permanent 10 situé à l'intérieur de la membrane sphérique. Cet aimant permanent, de forme cylindrique par exemple, présente un axe commun à l'axe X du haut-parleur. Dans ce cas, la source de tension continue 8, la self L et le condensateur de découplage 9, ne sont pas nécessaires et l'enroulement secondaire du transformateur 5 est directement relié aux extrémités du ruban 2. Selon l'invention, au moins l'une des faces du ruban 2 présente ici aussi une couche mince rigide recouvrant totalement ou partiellement cette face. Cette couche n'apparaît pas sur cette figure et sera décrite plus loin.FIG. 3 schematically represents another embodiment of the loudspeaker of FIG. 1. The means for continuous polarization of the ribbon is here constituted by a permanent magnet 10 situated inside the spherical membrane. This permanent magnet, of cylindrical shape for example, has an axis common to the axis X of the loudspeaker. In this case, the DC voltage source 8, the choke L and the decoupling capacitor 9, are not necessary and the secondary winding of the transformer 5 is directly connected to the ends of the strip 2. According to the invention, at least l 'One of the faces of the tape 2 here also has a rigid thin layer completely or partially covering this face. This layer does not appear in this figure and will be described later.

La figure 4 est une vue schématique transversale d'une variante de réalisation du ruban magnétostrictif recouvert d'une couche mince rigide, utilisé dans le haut parleur de l'invention. Selon cette variante, le ruban magnétostrictif 2, qui comporte deux faces opposées 11, 12, l'une (face 12) dirigée vers l'intérieur I de la sphère et l'autre (face 11) dirigée vers l'extérieur E de la sphère, est totalement recouvert sur sa face 11, dirigée vers l'extérieur de la sphère, par une couche mince 13 de matériau rigide. Le ruban magnétostrictif peut être constitué par exemple par un alliage de colbalt/nickel, tandis que la couche mince rigide 13 peut être une couche de cuivre ou une céramique par exemple.Figure 4 is a schematic transverse view of an alternative embodiment of the magnetostrictive tape covered with a rigid thin layer, used in the loudspeaker of the invention. According to this variant, the magnetostrictive tape 2, which has two opposite faces 11, 12, one (face 12) directed towards the inside I of the sphere and the other (face 11) directed towards the outside E of the sphere, is completely covered on its face 11, directed towards the outside of the sphere, by a thin layer 13 of rigid material. The magnetostrictive tape can be constituted for example by a colbalt / nickel alloy, while the rigid thin layer 13 can be a layer of copper or a ceramic for example.

Selon la polarité du courant appliqué au ruban constitué du matériau magnétostrictif 2 recouvert de la couche rigide 13, ce ruban subit des déformations dont les amplitudes sont proportionnelles aux variations d'amplitude du courant. Du fait de la présence de la couche rigide, le ruban subit des déformations qui sont amplifiées de la même manière que dans un bilame thermique où ce sont des variations de température qui provoquent de telles déformations. Il en résulte que le haut-parleur constitué à l'aide d'un tel ruban présente une bande passante très large dans le domaine des fréquences audibles, y compris pour les basses fréquences ou sa puissance est bien plus importante que pour les haut-parleurs sphériques de l'état de la technique.According to the polarity of the current applied to the ribbon made up of the magnetostrictive material 2 covered with the rigid layer 13, this ribbon undergoes deformations whose amplitudes are proportional to the variations in amplitude of the current. Due to the presence of the rigid layer, the ribbon undergoes deformations which are amplified in the same way as in a thermal bimetallic strip where it is temperature variations which cause such deformations. It follows that the speaker formed using such a ribbon has a very wide bandwidth in the range of audible frequencies, including for low frequencies or its power is much greater than for the speakers state of the art spherical.

La figure 5 représente schématiquement une vue latérale d'une autre variante d'un ruban magnétostrictif utilisé dans le haut-parleur de l'invention. Le ruban présente ici sur toute sa longueur des ondulations transversales. Chaque ondulation présente sur la face 12 du ruban, dirigée vers l'intérieur I de la sphère, une zone concave 14A et une zone convexe 14B. Chaque ondulation présente aussi sur la face 11 du ruban, dirigée vers l'extérieur E de la sphère, une zone concave 15A et une zone convexe 15B. Dans cette variante, la couche mince rigide ne s'étend pas sur la totalité de l'une des faces du ruban, mais elle est localisée au moins partiellement en regard des zones convexes 15B de la face 11 du ruban, dirigée vers l'extérieur E de la sphère. Cette couche mince rigide est représentée en 16 sur la figure.FIG. 5 schematically represents a side view of another variant of a magnetostrictive tape used in the loudspeaker of the invention. The ribbon here has undulations over its entire length transverse. Each corrugation has on the face 12 of the ribbon, directed towards the interior I of the sphere, a concave zone 14A and a convex zone 14B. Each corrugation also has on the face 11 of the ribbon, directed towards the outside E of the sphere, a concave zone 15A and a convex zone 15B. In this variant, the rigid thin layer does not extend over the whole of one of the faces of the ribbon, but it is located at least partially opposite the convex zones 15B of the face 11 of the ribbon, directed towards the outside. E of the sphere. This rigid thin layer is shown at 16 in the figure.

La présence d'ondulations augmente notablement les amplitudes des déformations auxquelles est soumis le ruban magnétostrictif 2, lorsqu'un courant électrique d'amplitude et de fréquence variables lui est appliqué. En effet, les bords tels que 17, 18 de la zone convexe 15B de l'ondulation se rapprochent de manière importante, proportionnellement à l'amplitude du courant électrique appliqué, du fait de la présence de couche de cuivre 16 qui provoque l'effet bilame décrit plus haut.The presence of undulations significantly increases the amplitudes of the deformations to which the magnetostrictive tape 2 is subjected, when an electric current of variable amplitude and frequency is applied to it. In fact, the edges such as 17, 18 of the convex zone 15B of the corrugation approach significantly, in proportion to the amplitude of the electric current applied, due to the presence of copper layer 16 which causes the effect bimetallic strip described above.

La figure 6 représente schématiquement une vue latérale d'une autre variante du ruban magnétostrictif. Dans cette variante, et afin d'accroître encore l'amplitude des déformations du ruban, notamment aux basses fréquences, le ruban magnétostrictif présente sur toute sa longueur des ondulations transversales. Chaque ondulation présente, comme dans le mode de réalisation précédent, sur sa face 12 dirigée vers l'intérieur I de la sphère, une zone concave 14A, et une zone convexe 14B et sur sa face 11, dirigée vers l'extérieur de la sphère, une zone concave 15A et une zone convexe 15B. La couche rigide est ici partiellement localisée en regard des zones concaves 14A et 15A de chaque face du ruban. Ces couches minces rigides localisées sont représentées en 19, 20 sur la figure. Le passage du courant électrique dans le ruban provoque ici un écartement des bords des ondulations.FIG. 6 schematically represents a side view of another variant of the magnetostrictive tape. In this variant, and in order to further increase the amplitude of the deformations of the ribbon, in particular at low frequencies, the magnetostrictive ribbon has transverse undulations over its entire length. Each corrugation has, as in the previous embodiment, on its face 12 directed towards the interior I of the sphere, a concave zone 14A, and a convex zone 14B and on its face 11, directed towards the exterior of the sphere , a concave zone 15A and a convex zone 15B. The rigid layer is here partially located opposite the zones concaves 14A and 15A on each side of the ribbon. These localized rigid thin layers are shown at 19, 20 in the figure. The passage of electric current through the ribbon here causes the edges of the corrugations to spread apart.

La figure 7 représente schématiquement une vue latérale d'une autre variante d'un ruban magnétostrictif utilisé dans le haut-parleur de l'invention. La couche mince rigide est ici déposée partiellement sur chacune des faces du ruban, en regard des zones convexes 14B, 15B des ondulations. Ces couches minces rigides localisées sont représentées en 21, 22 sur la figure. Comme dans le mode de réalisation précédent, l'amplitude des déformations du ruban, notamment aux basses fréquences, est très importante du fait de l'effet bilame de la structure du ruban décrit. Le passage du courant électrique dans le ruban provoque ici un rapprochement des bords des ondulations.FIG. 7 schematically represents a side view of another variant of a magnetostrictive tape used in the loudspeaker of the invention. The rigid thin layer is here partially deposited on each of the faces of the ribbon, facing the convex zones 14B, 15B of the corrugations. These localized rigid thin layers are shown at 21, 22 in the figure. As in the previous embodiment, the amplitude of the deformations of the ribbon, in particular at low frequencies, is very large due to the bimetal effect of the structure of the ribbon described. The passage of electric current through the ribbon here brings the edges of the corrugations together.

Pour faciliter la réalisation et notamment lorsque la source de polarisation continue est constituée par un aimant permanent, la membrane constituée du ruban 2, recouvert partiellement du matériau rigide, et du support élastique 1, peut être formée de deux hémisphères, tels que représentés en 23, 24, sur la figure 1. Ces deux hémisphères sont rendus solidaires, par exemple par collage du support et par soudure de deux demi-rubans, correspondant chacun à l'un des hémisphères.To facilitate the realization and in particular when the source of continuous polarization is constituted by a permanent magnet, the membrane constituted by the ribbon 2, partially covered with rigid material, and by the elastic support 1, can be formed of two hemispheres, such as represented in 23 , 24, in FIG. 1. These two hemispheres are made integral, for example by gluing the support and by welding two half-ribbons, each corresponding to one of the hemispheres.

Les modes préférés de réalisation du haut-parleur qui vient d'être décrit, sont ceux qui utilisent le ruban magnétostrictif à effet bilame, de forme ondulée. C'est en effet cette forme ondulée qui procure le meilleur rendement acoustique et qui assure la fabrication la plus simple du haut-parleur sphérique.The preferred embodiments of the loudspeaker which has just been described are those which use the magnetostrictive ribbon with bimetal effect, of wavy shape. It is indeed this wavy shape which provides the best acoustic performance and which ensures the simplest manufacture of the spherical loudspeaker.

Claims (7)

  1. Omnidirectional loudspeaker comprising a spherical membrane which includes spires formed by a strip (2) made of a magnetostrictive strip, said spires being spiral-wound according to a sphere and kept in place by an elastic support (1) so that, along with said support, they form said spherical membrane, this strip having two opposing faces (11, 12), one of said faces being directed towards the inside (I) of the sphere and the other towards the outside (E) of said sphere, and two extremities (3, 4) situated in two diametrically opposing zones of the sphere so as to be connected to an electric control device (5) supplying a signal corresponding to sound waves to be reproduced, and a device to continuously polarize the membrane, characterized in that at least one of the faces (11) of the strip (2) is at least partly coated with a thin coating (13) made of a rigid material.
  2. Loudspeaker according to claim 1, characterized in that the strip (2) is coated by the thin rigid coating (13) on its face (11) directed towards the outside (E) of the sphere.
  3. Loudspeaker according to claim 1, characterized in that the strip (2) has over its entire length transversal undulations, each undulation having on the face (12) of the strip directed towards the inside (I) of the sphere one concave zone (14A) and one convex zone (14B), and on the face (11) of the strip directed towards the outside (E) of the sphere one concave zone (15A) and one convex zone (15B), the rigid coating (16) being localized at least partly on the face (11) of the strip directed towards the outside (E) of the sphere opposite to the convex zones (15B) of this face.
  4. Loudspeaker according to claim 1, characterized in that the strip (2) has over its entire length transversal undulations, each undulation having on the face (12) of the strip directed towards the inside of the sphere one concave zone (15A) and one convex zone (15B), and on the face (11) of the strip directed towards the outside of the sphere one concave zone (15A) and one convex zone (15B), the rigid coating (19, 20 or 21, 22) being localized partly on each face of the strip opposite the concave zones (14A, 15A) or opposite the convex zones (14B, 15B).
  5. Loudspeaker according to any one of the claims 1 to 4, characterized in that the device to continuously polarize the membrane is a permanent magnet (10) situated inside said membrane.
  6. Loudspeaker according to any one of claims 1 to 4, characterized in that the continuous polarization device is a d.c. voltage source (8) connected to the extremities of said strip.
  7. Loudspeaker according to any one of claim 1 to 4, characterized in that said membrane is formed of two hemispheres (23, 24) joined to each other.
EP90401637A 1989-06-15 1990-06-13 Omnidirectional loudspeaker with spherical diaphragm using a two-layer magnetostrictive ribbon Expired - Lifetime EP0403378B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8907960A FR2648664A1 (en) 1989-06-15 1989-06-15 OMNIDIRECTIONAL SPHERICAL MEMBRANE SPEAKER USING A MAGNETOSTRICTIVE RIBBON
FR8907960 1989-06-15

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EP0403378A1 EP0403378A1 (en) 1990-12-19
EP0403378B1 true EP0403378B1 (en) 1993-12-29

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US (1) US5103483A (en)
EP (1) EP0403378B1 (en)
JP (1) JPH0332200A (en)
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5396266A (en) * 1993-06-08 1995-03-07 Technical Research Associates, Inc. Kinesthetic feedback apparatus and method
CN100375307C (en) * 1999-12-21 2008-03-12 1...有限公司 Electro-active device
AUPR317901A0 (en) 2001-02-16 2001-03-15 Arnstein, Barry Electro-acoustic converter

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2761077A (en) * 1952-03-27 1956-08-28 Harris Transducer Corp Magnetostrictive ceramic transducer
DE1157266B (en) * 1961-01-11 1963-11-14 Sennheiser Electronic Magnetostrictive transducer element
FR2503515B1 (en) * 1981-04-01 1985-12-27 Klein Siegfried OMNIDIRECTIONAL SPEAKER FOR ACUTE SOUND SPECTRUM FREQUENCIES
DE3405635A1 (en) * 1984-02-17 1985-08-22 Rainer J. 5000 Köln Haas ELECTRODYNAMIC SPEAKER WITH ALL-ROUND SOUND EMISSION
US4782471A (en) * 1984-08-28 1988-11-01 Commissariat A L'energie Atomique Omnidirectional transducer of elastic waves with a wide pass band and production process
FR2619481B1 (en) * 1987-08-14 1989-11-17 Commissariat Energie Atomique WIDE BANDWIDTH ELASTIC WAVES OMNIDIRECTIONAL TRANSDUCER
US4843275A (en) * 1988-01-19 1989-06-27 Pennwalt Corporation Air buoyant piezoelectric polymeric film microphone
DE8803776U1 (en) * 1988-03-19 1988-05-11 Klein, Siegfried, Dr. Prof., Paris Acoustoelectric transducer

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FR2648664A1 (en) 1990-12-21
DE69005537T2 (en) 1994-06-23
JPH0332200A (en) 1991-02-12
US5103483A (en) 1992-04-07
EP0403378A1 (en) 1990-12-19
DE69005537D1 (en) 1994-02-10

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