EP0518747B1 - Electrical heating resistance with resistant elements out of carbon/carbon composite materials - Google Patents

Electrical heating resistance with resistant elements out of carbon/carbon composite materials Download PDF

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Publication number
EP0518747B1
EP0518747B1 EP92401581A EP92401581A EP0518747B1 EP 0518747 B1 EP0518747 B1 EP 0518747B1 EP 92401581 A EP92401581 A EP 92401581A EP 92401581 A EP92401581 A EP 92401581A EP 0518747 B1 EP0518747 B1 EP 0518747B1
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EP
European Patent Office
Prior art keywords
strips
carbon
bars
resistance according
connection pieces
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EP92401581A
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German (de)
French (fr)
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EP0518747A1 (en
Inventor
Jean-Pierre Maumus
Henri Gaston Giret
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Safran Aircraft Engines SAS
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Societe Europeenne de Propulsion SEP SA
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/62—Heating elements specially adapted for furnaces
    • H05B3/64—Heating elements specially adapted for furnaces using ribbon, rod, or wire heater

Definitions

  • the present invention relates to an electrical resistance heater using resistive elements made of carbon / carbon composite material (C / C).
  • the field of application of the invention is more particularly that of high power heating resistors, typically 100 kW or more, such as, for example, those used for the heating of industrial ovens.
  • C / C composite material that is to say a material comprising a fibrous carbon reinforcement texture densified by a matrix also made of carbon.
  • C / C composites combine high mechanical resistance with thermal characteristics close to those of graphite; they can be used at relatively high temperatures, for example up to around 1300 ° C.
  • C / C materials are relatively expensive to develop.
  • the object of the invention is to provide an electrical heating resistance using resistive elements made of C / C composite material and the design of which is optimized to reduce the manufacturing cost as much as possible.
  • the resistive elements consist of bars of carbon / carbon composite material connected together by connecting pieces also of carbon / carbon composite material which ensure both the connections electrical and mechanical connections between the bars, the bars and the connecting parts being made of a composite material comprising a fibrous carbon reinforcement texture densified by a carbon matrix.
  • the assembly between the bars and the connecting pieces is made at least in part by the shape. It can be completed by means of fastening elements such as screws or screw-nut systems also made of carbon / carbon composite material.
  • the bars are arranged parallel to an axis around which they are distributed.
  • the connecting pieces comprise first pieces, or bars, intended to connect ends of bars diametrically opposite with respect to the axis, second pieces, or connecting blocks, intended to connect ends of adjacent bars, third pieces, or strips intended to connect neighboring ends of aligned bars, and fourth pieces, or current inlets, intended to connect ends of bars to current supply terminals.
  • the electrical resistance according to the invention can be adapted to different powers using the same basic elements.
  • the C / C composite materials are capable of supporting, without embrittlement, machining of shapes, such as dovetails, allowing assembly at least in part by shape between the bars and the connecting pieces. Such an assembly provides good quality mechanical and electrical connections.
  • the mechanical properties of C / C composite materials are such that the elements of the resistance constitute both heating resistive elements and structural elements capable of giving the desired mechanical strength to the resistance without requiring a supporting structure.
  • the reinforcement texture is of two-dimensional (2D) or three-dimensional (3D) type.
  • a 2D texture is formed of superimposed strata. These can be unidirectional strata, for example layers of wires or cables parallel to each other, or bidirectional strata, for example layers of fabric.
  • a 3D texture has fibers oriented in at least three different non-coplanar directions.
  • a 3D reinforcement texture can be formed by three-dimensional weaving, or by superimposition of two-dimensional layers linked together by needling or by implantation of threads.
  • the densification of the reinforcing texture by the carbon matrix is carried out in a manner known per se by the liquid or gas route.
  • Liquid densification consists in impregnating the fibrous texture with a carbon precursor, such as a resin which is polymerized and pyrolyzed. Several impregnation-polymerization-pyrolysis cycles may be necessary to obtain the desired degree of densification.
  • Densification by gas consists in forming the carbon matrix by chemical vapor infiltration.
  • the resistive bars can be cut from prefabricated C / C composite material plates, while the connecting pieces are machined in blanks or in a solid block of carbon / carbon composite material.
  • the reinforcing texture of the composite material constituting the bars is formed of superimposed strata, these are arranged parallel to the faces of the plates from which the bars are cut.
  • the bars and connecting parts forming a resistance are advantageously coated with a layer of pyrocarbon. This is formed by chemical vapor deposition on the bars and the connecting parts, preferably before they are assembled.
  • the resistive elements coated with pyrocarbon have an improved behavior and a longer service life.
  • the resistive elements not coated with pyrocarbon deteriorate more quickly.
  • the operation of the resistive elements is affected by the presence of fingerprints due to their handling; this is no longer the case with a coating of pyrocarbon.
  • the heating resistance represented by FIGS. 1 to 3 comprises twelve elementary bars 10 1 to 10 12 dishes with rectangular section (partially cut away in FIG. 1).
  • the bars 10 1 to 10 12 are identical and are distributed between a first group of bars 10 1 to 10 6 and a second group of bars 10 7 to 10 12 . In the two groups, the bars are distributed angularly around the same axis 14 to which they are all parallel.
  • Each of the bars 10 1 to 10 6 of the first group is aligned with a respective bar 10 7 to 10 12 of the second and connected electrically to it by means of a respective connecting strip 12 1 to 12 6 .
  • two (10 1 and 10 4 ) of the bars of the first group are connected to respective current inlets 20 1 and 20 2 and the other four are connected two by two by means of respective radial bars 16 1 and 16 2 while, at their other ends, the bars of the second group are connected two by two by means of connection blocks 18 1 to 18 3 .
  • Each bar 10 has a constant width over its entire length with the exception of its ends 10a and 10b which are cut identically into dovetails.
  • Figure 5 shows in exploded form the connecting pieces of the ends - in Figure 1, the upper ends - of the bars 10 1 to 10 6 between them and with the current inlets.
  • Each current supply 20 comprises: a first part 21 secured to a terminal 22 allowing the connection of an electrical conductor by means of a terminal, and a second part 23 provided with a housing 24 in the form of a dovetail of form complementary to that of the dovetail formed at each end of a bar 10.
  • the part 21 is connected to the part 23 by means of screws 25 passing through the holes formed in an insulating disc 26.
  • the latter is interposed between parts 21 and 23 of each current supply.
  • the assembly between one end of a bar and the housing 24 is produced by interlocking in a radial direction relative to the axis 14. This assembly by form is completed by a fixing by means of a screw (not shown) passing through the end of the bar and screwed into a threaded hole formed in the center of the housing 24.
  • the bars 16 have at their opposite ends housings 16a, 16b similar to the housings 24 so as to allow the ends of the bars to be connected 10.
  • the fixing of these ends to the bars is completed by means of screws 17 similar to the screws 27, each screw 17 passing through the end of a bar and being screwed into a threaded hole formed in the center of a housing 16a or 16b.
  • An insulating washer 29 is interposed between the bars 16 1 and 16 2 in order to prevent any contact between them.
  • the insulating washer 29 is provided with a centering pin 29a which penetrates into one of two orifices formed in the middle of the bars 16 1 , 16 2 .
  • the bars 16 1 , 16 2 have a greater thickness at their ends where the housings are formed allowing, in combination with the screws 17, the connection of the ends of the bars.
  • FIG. 6 shows one of the connecting strips 12 and a support piece 30 of insulating material used for connecting the ends of the bars 10 1 to 10 6 adjacent to the corresponding ends of the bars 10 7 to 10 12 .
  • Each connecting strip 12 has, on one side, two dovetail housings 12a, 12b offset in the axial direction and, symmetrically, on the other side, two other housings 12c, 12d also offset in the axial direction.
  • Each of the housings 12a, 12b, 12c, 12d has a shape complementary to that of the end of a bar 10.
  • the support piece 30 has a hexagonal shape and has at its periphery housings 31 regularly distributed and each receiving a strip link 12.
  • Each strip 12 is engaged in its respective housing 31 with the housings 12a to 12d facing outwards.
  • the upper ends of the bars 10 7 to 10 12 are connected to the strips 12 1 to 12 6 and to the insulating piece 30 by engagement in the housings 12c or 12d and by screws 37 ( Figures 1 and 3) which pass through the ends of the bars , pass through a hole formed in the center of the corresponding housing 12c or 12d and are screwed into threaded holes formed in the part 30 in the center of the housings 31.
  • the lower ends of the bars 10 1 to 10 6 are connected to the strips 12 1 to 12 6 by engagement in the housings 12a or 12b and by screws 35 (FIG. 1) which pass through the ends of the bars, pass through a hole formed in the center of the corresponding housing 12a or 12b and are immobilized by nuts 36 (FIG. 1 ).
  • the lower ends of the bars 10 1 and 10 6 are at three different levels.
  • the upper ends of the bars 10 7 to 10 12 are at the same level, that of the support piece 30.
  • the strips 12 1 to 12 6 make it possible to make up for the different distances between the opposite ends of the bars which they connect .
  • a first offset can be made up by placing the strip with its housing 12c or its housing 12d at the level of the part 31 (as is the case respectively for the strips 12 2 , 12 3 , 12 5 , 12 6 and the strips 12 1 , 12 2 ).
  • a second offset can be made up by engaging the lower end of the bars 10 1 to 10 6 in a housing 12a or in a housing 12b (as is the case, respectively, for the bars 10 1 , 10 2 , 10 4 , 10 5 , and the bars 12 3 , 10 6 ).
  • FIG. 7 shows one of the connection blocks 18 and a support piece of insulating material 40 used to connect two by two and assemble the lower ends of the bars 10 7 to 10 12 .
  • the part 40 comprises a base 41 from which project walls 42 which delimit three housings 43 1 , 43 2 , 43 3 distributed angularly around axis 14 and isolated from each other.
  • Each housing 43 1 , 43 2 , 43 3 receives a respective connection block.
  • Each connecting block is intended to connect the lower ends of two adjacent bars.
  • a block 18 has two housings 18a, 18b having a shape of dovetail complementary to that of the end of a bar.
  • the assembly between one end of a bar and a block 18 is produced by engaging this end in a housing 18a or 18b, in the radial direction, and fixing by means of a screw 47 which passes through the end of the bar and is screwed into a threaded hole formed in the center of the housing.
  • connection between the ends of the bars and the various connecting pieces using a dovetail assembly makes it possible to maintain satisfactory electrical contact even in the event of loosening of the screws which complete the assembly.
  • the various insulating parts - disc 26, washer 19, support parts 30 and 40 - are for example made of ceramic.
  • the bars as well as the various parts ensuring the connections between them are made of carbon / carbon composite material.
  • Carbon / carbon composite materials are known and used in particular for their thermostructural properties, that is to say their capacity to constitute structural elements, due to their good mechanical properties, and to preserve these properties up to relatively temperatures. high.
  • Carbon / carbon composite materials consist of a carbon reinforcement texture densified by a carbon matrix.
  • a two-dimensional (2D) reinforcing texture made from carbon fibers and formed of unidirectional or bidirectional layers stacked flat parallel to the faces of the bars.
  • Unidirectional strata are, for example, plies of wires or cables parallel to one another; in this case, the longitudinal direction of the bars is parallel to wires or cables.
  • Bidirectional strata are, for example, layers of fabric.
  • the densification of the fibrous reinforcement texture is carried out by liquid or by gaseous route. These two methods are well known per se.
  • Liquid densification consists in impregnating the fibrous texture by means of a carbon precursor, such as a resin or a pitch leaving a carbon residue after polymerization and pyrolysis.
  • a carbon precursor such as a resin or a pitch leaving a carbon residue after polymerization and pyrolysis.
  • the impregnation can be carried out on the layers (layers of yarns or fabric) before they are superimposed.
  • the pre-impregnated layers can be shaped in press, in order, by compacting, to obtain a desired fiber content (the fiber content being the percentage actually occupied by the fibers within the material).
  • several successive cycles of impregnation -polymerization -pyrolysis may be necessary.
  • Densification by gas consists of forming the matrix by chemical vapor infiltration.
  • the texture is placed in an oven in which a gas flow is admitted which, under determined conditions of temperature and pressure leaves a carbon deposit within the accessible porosity of the texture.
  • the gas flow typically consists of a hydrocarbon or a mixture of hydrocarbons.
  • the fibrous texture at least until consolidation, can be maintained in shape in a tool which also ensures the degree of compaction necessary to obtain the desired fiber content. The tool is dismantled when the texture is consolidated, that is to say when the pyrocarbon deposit is sufficient to bind the fibers together. Chemical vapor infiltration is continued until the desired degree of densification is reached.
  • the bars are coated with a layer of pyrolytic or pyrocarbon carbon. This is formed by deposit chemical vapor phase under conditions similar to that of chemical vapor infiltration of carbon.
  • the thickness of the pyrocarbon layer is for example approximately equal to 100 microns.
  • a carbon / carbon material is used, preferably comprising a three-dimensional (3D) reinforcement texture.
  • a texture is obtained for example by three-dimensional weaving of carbon threads, or by superposition of unidirectional or bidirectional strata and bonding of the strata together.
  • unidirectional strata such as layers of cables are superimposed, the directions of the cables are different from one layer to another.
  • the connection between superimposed strata can be achieved by needling or by implantation of wires. When needling is used, the fibers entrained by the needles can be taken from fiber veils interposed between the strata.
  • the densification of the three-dimensional texture is carried out by the liquid or gaseous route as indicated above.
  • the connecting parts are machined from blocks of carbon / carbon material. After machining, they can be coated with a layer of pyrocarbon, like bars.
  • carbon / carbon composite material is particularly advantageous because it makes it possible to produce an electric heating device in which the resistive elements, in particular the bars, are also structural elements due to their mechanical properties and their non-brittleness.
  • carbon / carbon composite materials are light - their density is generally about 1.7 - and can withstand high temperatures, for example up to 2500 ° C in a non-oxidizing atmosphere.
  • the connections between the resistive elements are produced by means of parts which provide not only the electrical connection but also the mechanical connection.
  • the connections between the resistive elements are produced by means of parts which provide not only the electrical connection but also the mechanical connection.
  • the pyrocarbon coating formed on the resistive elements and the connecting parts makes it possible to improve the service life and the functioning of the resistance.
  • the coating can be renovated after a certain period of use.
  • a heating device intended for use under a power of 250 kW and as illustrated in FIG. 1 has been produced.
  • the bars 10 were cut from a plate of composite material comprising a fibrous texture formed by stacking layers of carbon fabric with a fiber content of 25% and a carbon matrix formed by chemical vapor infiltration. The infiltration was continued until leaving a residual porosity of the order of 15%. The material obtained has a density of about 1.7.
  • Each bar 10 has a thickness of 5 mm, a width of 50 mm and a length of 750 mm. The dimensions are adapted to the desired power.
  • the connecting pieces (current inlets, rods, bars, blocks, screws and nuts) were machined in blocks of composite material comprising a fibrous texture formed by stacking and needling layers of carbon fabric alternating with veils of fiber fibers carbon, with a fiber content of around 25%.
  • the texture was densified by infiltration of pyrocarbon in the vapor phase until a residual porosity of the order of 15% was reached.
  • the material obtained has a density of about 1.7.
  • the resistive elements are formed by twelve bars distributed in two groups of six.
  • the heating device can be adapted to different powers or different configurations of use, by providing for a greater or lesser number of bars.
  • one or more additional groups of six bars can be added to the device of FIG. 1 using one or more additional sets of strips and insulating piece such as the set constituted by strips 12 1 to 12 6 and piece 30 .
  • the resistive elements consist of a group of bars 10 ′ 1 to 10 ′ 6 each extending from one end to the other of the device. If using at the ends of the bars, connecting pieces identical to those used at the ends of the heating device of FIG. 1, it is then necessary to provide bars having different lengths to take account of their offset to their upper end.
  • the offset between the positions of the upper ends of the bars 10 ′ 1 to 10 ′ 6 can be made up, not by giving the bars different lengths, but by using connection blocks 18 ' offering, for each end of a bar, three possibilities of assembly at different levels.

Description

La présente invention concerne une résistance électrique chauffante utilisant des éléments résistifs en matériau composite carbone/carbone (C/C).The present invention relates to an electrical resistance heater using resistive elements made of carbon / carbon composite material (C / C).

Le domaine d'application de l'invention est plus particulièrement celui des résistances chauffantes de forte puissance, typiquement 100 kW ou plus, comme, par exemple, celles utilisées pour le chauffage de fours industriels.The field of application of the invention is more particularly that of high power heating resistors, typically 100 kW or more, such as, for example, those used for the heating of industrial ovens.

Actuellement, les dispositifs de chauffage électrique de puissance élevée utilisent des éléments résistifs métalliques ou en graphite. Les résistances métalliques sont relativement lourdes et ne peuvent être utilisées à des températures très élevées. Les résistances en graphite sont plus légères et ont une meilleure tenue en température, mais sont très fragiles. Le document FR-A-2 385060 divulge un élément de chauffage électrique de carbone.Currently, high power electric heaters use metallic or graphite resistive elements. The metallic resistors are relatively heavy and cannot be used at very high temperatures. The graphite resistors are lighter and have better temperature resistance, but are very fragile. Document FR-A-2 385060 discloses an electric carbon heating element.

Pour remédier à ces inconvénients, il a été proposé de réaliser des éléments résistifs en matériau composite C/C, c'est-à-dire un matériau comprenant une texture fibreuse de renfort en carbone densifiée par une matrice également en carbone. En effet, les composites C/C allient une résistance mécanique élevée à des caractéristiques thermiques voisines de celles du graphite ; ils peuvent être utilisés à des températures relativement élevées, par exemple jusqu'à environ 1300°C. Toutefois, les matériaux C/C sont relativement coûteux à élaborer.To overcome these drawbacks, it has been proposed to produce resistive elements from C / C composite material, that is to say a material comprising a fibrous carbon reinforcement texture densified by a matrix also made of carbon. Indeed, C / C composites combine high mechanical resistance with thermal characteristics close to those of graphite; they can be used at relatively high temperatures, for example up to around 1300 ° C. However, C / C materials are relatively expensive to develop.

Aussi, l'invention a pour but de fournir une résistance électrique chauffante utilisant des éléments résistifs en matériau composite C/C et dont la conception soit optimisée pour réduire autant que possible le coût de fabrication.Also, the object of the invention is to provide an electrical heating resistance using resistive elements made of C / C composite material and the design of which is optimized to reduce the manufacturing cost as much as possible.

Ce but est atteint du fait que, conformément à l'invention, les éléments résistifs sont constitués par des barreaux en matériau composite carbone/carbone reliés entre eux par des pièces de liaison également en matériau composite carbone/carbone qui assurent à la fois les liaisons électriques et les liaisons mécaniques entre les barreaux, les barreaux et les pièces de liaison étant réalisés en un matériau composite comprenant une texture fibreuse de renfort en carbone densifiée par une matrice en carbone.This object is achieved by the fact that, in accordance with the invention, the resistive elements consist of bars of carbon / carbon composite material connected together by connecting pieces also of carbon / carbon composite material which ensure both the connections electrical and mechanical connections between the bars, the bars and the connecting parts being made of a composite material comprising a fibrous carbon reinforcement texture densified by a carbon matrix.

L'assemblage entre les barreaux et les pièces de liaison est réalisé au moins en partie par la forme. Il peut être complété au moyen d'éléments de fixation tels que des vis ou des systèmes vis-écrou réalisés également en matériau composite carbone/carbone.The assembly between the bars and the connecting pieces is made at least in part by the shape. It can be completed by means of fastening elements such as screws or screw-nut systems also made of carbon / carbon composite material.

Selon un mode préféré de réalisation de l'invention, les barreaux sont disposés parallèlement à un axe autour duquel ils sont répartis. Les pièces de liaison comprennent des premières pièces, ou barrettes, destinées à relier des extrémités de barreaux diamétralement opposés par rapport à l'axe, des deuxièmes pièces, ou blocs de liaison, destinées à relier des extrémités de barreaux adjacents, des troisièmes pièces, ou réglettes destinées à relier des extrémités voisines de barreaux alignés, et des quatrièmes pièces, ou arrivées de courant, destinées à relier des extrémités de barreaux à des bornes d'alimentation en courant.According to a preferred embodiment of the invention, the bars are arranged parallel to an axis around which they are distributed. The connecting pieces comprise first pieces, or bars, intended to connect ends of bars diametrically opposite with respect to the axis, second pieces, or connecting blocks, intended to connect ends of adjacent bars, third pieces, or strips intended to connect neighboring ends of aligned bars, and fourth pieces, or current inlets, intended to connect ends of bars to current supply terminals.

Du fait de sa conception modulaire, la résistance électrique conforme à l'invention peut être adaptée à différentes puissances en utilisant des mêmes éléments de base.Due to its modular design, the electrical resistance according to the invention can be adapted to different powers using the same basic elements.

En outre, les matériaux composites C/C sont aptes à supporter sans fragilisation des usinages de formes, telles que des queues d'aronde, permettant un assemblage au moins en partie par la forme entre les barreaux et les pièces de liaison. Un tel assemblage assure des liaisons mécaniques et électriques de bonne qualité.In addition, the C / C composite materials are capable of supporting, without embrittlement, machining of shapes, such as dovetails, allowing assembly at least in part by shape between the bars and the connecting pieces. Such an assembly provides good quality mechanical and electrical connections.

Enfin, les propriétés mécaniques des matériaux composites C/C sont telles que les éléments de la résistance constituent à la fois des éléments résistifs chauffants et des éléments structuraux aptes à donner la tenue mécanique souhaitée à la résistance sans nécessiter de structure porteuse.Finally, the mechanical properties of C / C composite materials are such that the elements of the resistance constitute both heating resistive elements and structural elements capable of giving the desired mechanical strength to the resistance without requiring a supporting structure.

La texture de renfort est de type bidimensionnel (2D) ou tridimensionnel (3D).The reinforcement texture is of two-dimensional (2D) or three-dimensional (3D) type.

Une texture 2D est formée de strates superposées. Celles-ci peuvent être des strates unidirectionnelles, par exemple des nappes de fils ou de câbles parallèles entre eux, ou des strates bidirectionnelles, par exemple des couches de tissu.A 2D texture is formed of superimposed strata. These can be unidirectional strata, for example layers of wires or cables parallel to each other, or bidirectional strata, for example layers of fabric.

Une texture 3D présente des fibres orientées dans au moins trois directions différentes non coplanaires. A titre d'exemples, une texture de renfort 3D peut être formée par tissage tridimensionnel, ou par superposition de strates bidimensionnelles liées entre elles par aiguilletage ou par implantation de fils.A 3D texture has fibers oriented in at least three different non-coplanar directions. By way of examples, a 3D reinforcement texture can be formed by three-dimensional weaving, or by superimposition of two-dimensional layers linked together by needling or by implantation of threads.

La densification de la texture de renfort par la matrice en carbone est réalisée de façon connue en soi par voie liquide ou par voie gazeuse. La densification par voie liquide consiste à imprégner la texture fibreuse par un précurseur du carbone, tel qu'une résine qui est polymérisée et pyrolysée. Plusieurs cycles d'imprégnation-polymérisation-pyrolyse peuvent être nécessaires pour obtenir le degré de densification souhaité. La densification par voie gazeuse consiste à former la matrice carbone par infiltration chimique en phase vapeur.The densification of the reinforcing texture by the carbon matrix is carried out in a manner known per se by the liquid or gas route. Liquid densification consists in impregnating the fibrous texture with a carbon precursor, such as a resin which is polymerized and pyrolyzed. Several impregnation-polymerization-pyrolysis cycles may be necessary to obtain the desired degree of densification. Densification by gas consists in forming the carbon matrix by chemical vapor infiltration.

Les barreaux résistifs peuvent être découpés dans des plaques de matériau composite C/C préfabriquées, tandis que les pièces de liaison sont usinées dans des ébauches ou dans un bloc massif de matériau composite carbone/carbone. Lorsque la texture de renfort du matériau composite constitutif des barreaux est formée de strates superposées, celles-ci sont disposées parallèlement aux faces des plaques dans lesquelles les barreaux sont découpés.The resistive bars can be cut from prefabricated C / C composite material plates, while the connecting pieces are machined in blanks or in a solid block of carbon / carbon composite material. When the reinforcing texture of the composite material constituting the bars is formed of superimposed strata, these are arranged parallel to the faces of the plates from which the bars are cut.

Après usinage, les barreaux et pièces de liaison formant une résistance sont avantageusement revêtus d'une couche de pyrocarbone. Celle-ci est formée par dépôt chimique en phase vapeur sur les barreaux et les pièces de liaison, de préférence avant leur assemblage.After machining, the bars and connecting parts forming a resistance are advantageously coated with a layer of pyrocarbon. This is formed by chemical vapor deposition on the bars and the connecting parts, preferably before they are assembled.

En effet, il a été montré par des essais que les éléments résistifs revêtus de pyrocarbone ont un comportement et une durée de vie améliorés. En particulier, les éléments résistifs non-revêtus de pyrocarbone se détériorent plus rapidement. En outre, en l'absence de revêtement de pyrocarbone, le fonctionnement des éléments résistifs est affecté par la présence de traces de doigts dues à leurs manipulations ; il n'en est plus ainsi avec un revêtement de pyrocarbone.In fact, it has been shown by tests that the resistive elements coated with pyrocarbon have an improved behavior and a longer service life. In particular, the resistive elements not coated with pyrocarbon deteriorate more quickly. In addition, in the absence of a pyrocarbon coating, the operation of the resistive elements is affected by the presence of fingerprints due to their handling; this is no longer the case with a coating of pyrocarbon.

L'invention sera mieux comprise à la lecture de la description faite ci-après, à titre indicatif mais non limitatif, en référence aux dessins annexés, sur lesquels :

  • la figure 1 est une vue en perspective d'une résistance électrique chauffante selon un premier mode de réalisation de l'invention,
  • la figure 2 est une vue en coupe suivant le plan II-II de la figure 1,
  • la figure 3 est une vue en coupe suivant le plan III-III de la figure 1,
  • la figure 4 illustre schématiquement les liaisons électriques entre les barreaux de la résistance chauffante,
  • la figure 5 montre, de façon éclatée, les éléments permettant de relier des extrémités de barreaux entre eux et à des arrivées de courant, à une extrémité de la résistance,
  • la figure 6 montre, de façon éclatée, un support isolant et une réglette de liaison permettant de relier des barreaux mutuellement alignés,
  • la figure 7 montre, de façon éclatée, un support isolant et un bloc de liaison permettant de relier des extrémités de barreaux adjacents à une autre extrémité de la résistance,
  • la figure 8 est une vue schématique en perspective montrant un deuxième mode de réalisation d'une résistance selon l'invention, et
  • la figure 9 est une vue schématique en perspective montrant un troisième mode de réalisation d'une résistance selon l'invention.
The invention will be better understood on reading the description given below, by way of indication but not limitation, with reference to the appended drawings, in which:
  • FIG. 1 is a perspective view of an electric heating resistor according to a first embodiment of the invention,
  • FIG. 2 is a sectional view along the plane II-II of FIG. 1,
  • FIG. 3 is a sectional view along the plane III-III of FIG. 1,
  • FIG. 4 schematically illustrates the electrical connections between the bars of the heating resistor,
  • FIG. 5 shows, in an exploded manner, the elements making it possible to connect the ends of bars to each other and to current inlets, at one end of the resistance,
  • FIG. 6 shows, in an exploded manner, an insulating support and a connecting strip making it possible to connect mutually aligned bars,
  • FIG. 7 shows, in an exploded manner, an insulating support and a connection block making it possible to connect the ends of adjacent bars to another end of the resistor,
  • FIG. 8 is a schematic perspective view showing a second embodiment of a resistor according to the invention, and
  • Figure 9 is a schematic perspective view showing a third embodiment of a resistor according to the invention.

La résistance chauffante représentée par les figures 1 à 3 comprend douze barreaux élémentaires 101 à 1012 plats à section rectangulaire (partiellement arrachés sur la figure 1). Les barreaux 101 à 1012 sont identiques et sont répartis entre un premier groupe de barreaux 101 à 106 et un deuxième groupe de barreaux 107 à 1012. Dans les deux groupes, les barreaux sont répartis angulairement autour d'un même axe 14 auquel ils sont tous parallèles. Chacun des barreaux 101 à 106 du premier groupe est aligné avec un barreau respectif 107 à 1012 du deuxième et relié électriquement à celui-ci au moyen d'une réglette de liaison respective 121 à 126. A leurs autres extrémités, deux (101 et 104) des barreaux du premier groupe sont reliés à des arrivées de courant respectives 201 et 202 et les quatre autres sont reliés deux à deux au moyen de barrettes radiales respectives 161 et 162 tandis que, à leurs autres extrémités, les barreaux du deuxième groupe sont reliés deux à deux au moyen de blocs de liaison 181 à 183.The heating resistance represented by FIGS. 1 to 3 comprises twelve elementary bars 10 1 to 10 12 dishes with rectangular section (partially cut away in FIG. 1). The bars 10 1 to 10 12 are identical and are distributed between a first group of bars 10 1 to 10 6 and a second group of bars 10 7 to 10 12 . In the two groups, the bars are distributed angularly around the same axis 14 to which they are all parallel. Each of the bars 10 1 to 10 6 of the first group is aligned with a respective bar 10 7 to 10 12 of the second and connected electrically to it by means of a respective connecting strip 12 1 to 12 6 . At their other ends, two (10 1 and 10 4 ) of the bars of the first group are connected to respective current inlets 20 1 and 20 2 and the other four are connected two by two by means of respective radial bars 16 1 and 16 2 while, at their other ends, the bars of the second group are connected two by two by means of connection blocks 18 1 to 18 3 .

Comme le montre la figure 4, entre les arrivées de courant 201 et 202, le courant circule successivement dans le barreau 101, le barreau 107 aligné avec le précédent et relié à celui-ci par la réglette 121, le barreau 108 adjacent au barreau 107 et relié à celui-ci par le bloc de liaison 181, le barreau 102 aligné avec le barreau 108 et relié à celui-ci par la réglette 122, le barreau 105 opposé au barreau 102 et relié à celui-ci par la barrette 161, le barreau 1011 aligné avec le barreau 105 et relié à celui-ci par la réglette 125, le barreau 1012 adjacent au barreau 1011 et relié à celui-ci par le bloc de liaison 183, le barreau 106 aligné avec le barreau 1012 et relié à celui-ci par la réglette 126, le barreau 103 opposé au barreau 106 et relié à celui-ci par la barrette 162, le barreau 109 aligné avec le barreau 103 et relié à celui-ci par la réglette 123, le barreau 1010 adjacent au barreau 109 et relié à celui-ci par le bloc de liaison 182, et le barreau 104 aligné avec le barreau 1010 et relié à celui-ci par la réglette 124.As shown in Figure 4, between the current arrivals 20 1 and 20 2 , the current flows successively in the bar 10 1 , the bar 10 7 aligned with the previous one and connected to the latter by the strip 12 1 , the bar 10 8 adjacent to the bar 10 7 and connected to the latter by the connecting block 18 1 , the bar 10 2 aligned with the bar 10 8 and connected to the latter by the strip 12 2 , the bar 10 5 opposite the bar 10 2 and connected to it by the bar 16 1 , the bar 10 11 aligned with the bar 10 5 and connected to it by the strip 12 5 , the bar 10 12 adjacent to the bar 10 11 and connected to it ci by the connecting block 18 3 , the bar 10 6 aligned with the bar 10 12 and connected to the latter by the strip 12 6 , the bar 10 3 opposite the bar 10 6 and connected to the latter by the bar 16 2 , the bar 10 9 aligned with the bar 10 3 and connected to the latter by the strip 12 3 , the bar 10 10 adjacent to the bar 10 9 and connected to the latter by the connecting block 18 2 , and the bar 10 4 aligned with the bar 10 10 and connected to the latter by the strip 12 4 .

Chaque barreau 10 présente une largeur constante sur toute sa longueur à l'exception de ses extrémités 10a et 10b qui sont taillées de façon identique en queues d'aronde.Each bar 10 has a constant width over its entire length with the exception of its ends 10a and 10b which are cut identically into dovetails.

La figure 5 montre sous une forme éclatée les pièces de liaison des extrémités - sur la figure 1, les extrémités supérieures - des barreaux 101 à 106 entre elles et avec les arrivées de courant.Figure 5 shows in exploded form the connecting pieces of the ends - in Figure 1, the upper ends - of the bars 10 1 to 10 6 between them and with the current inlets.

Chaque arrivée de courant 20 comprend : une première pièce 21 solidaire d'une borne 22 permettant le raccordement d'un conducteur électrique au moyen d'une cosse, et une deuxième pièce 23 munie d'un logement 24 en forme de queue d'aronde de forme complémentaire à celle de la queue d'aronde formée à chaque extrémité d'un barreau 10. La pièce 21 est reliée à la pièce 23 au moyen de vis 25 passant à travers les trous formés dans un disque isolant 26. Ce dernier est interposé entre les pièces 21 et 23 de chaque arrivée de courant. L'assemblage entre une extrémité d'un barreau et le logement 24 est réalisé par emboîtement en direction radiale par rapport à l'axe 14. Cet assemblage par la forme est complété par une fixation au moyen d'une vis (non représentée) traversant l'extrémité du barreau et vissée dans un trou fileté formé au centre du logement 24.Each current supply 20 comprises: a first part 21 secured to a terminal 22 allowing the connection of an electrical conductor by means of a terminal, and a second part 23 provided with a housing 24 in the form of a dovetail of form complementary to that of the dovetail formed at each end of a bar 10. The part 21 is connected to the part 23 by means of screws 25 passing through the holes formed in an insulating disc 26. The latter is interposed between parts 21 and 23 of each current supply. The assembly between one end of a bar and the housing 24 is produced by interlocking in a radial direction relative to the axis 14. This assembly by form is completed by a fixing by means of a screw (not shown) passing through the end of the bar and screwed into a threaded hole formed in the center of the housing 24.

Les barrettes 16 présentent à leurs extrémités opposées des logements 16a, 16b analogues aux logements 24 afin de permettre le raccordement d'extrémités de barreaux 10. La fixation de ces extrémités sur les barrettes est complétée au moyen de vis 17 analogues aux vis 27, chaque vis 17 traversant l'extrémité d'un barreau et étant vissée dans un trou fileté formé au centre d'un logement 16a ou 16b.The bars 16 have at their opposite ends housings 16a, 16b similar to the housings 24 so as to allow the ends of the bars to be connected 10. The fixing of these ends to the bars is completed by means of screws 17 similar to the screws 27, each screw 17 passing through the end of a bar and being screwed into a threaded hole formed in the center of a housing 16a or 16b.

Une rondelle isolante 29 est interposée entre les barrettes 161 et 162 afin d'empêcher tout contact entre celles-ci. La rondelle isolante 29 est munie d'un pion de centrage 29a qui pénètre dans l'un de deux orifices formés au milieu des barrettes 161, 162. Dans l'exemple illustré, les barrettes 161, 162 présentent une plus grande épaisseur à leurs extrémités où sont formés les logements permettant, en combinaison avec les vis 17, le raccordement des extrémités des barreaux.An insulating washer 29 is interposed between the bars 16 1 and 16 2 in order to prevent any contact between them. The insulating washer 29 is provided with a centering pin 29a which penetrates into one of two orifices formed in the middle of the bars 16 1 , 16 2 . In the example illustrated, the bars 16 1 , 16 2 have a greater thickness at their ends where the housings are formed allowing, in combination with the screws 17, the connection of the ends of the bars.

La figure 6 montre une des réglettes de liaison 12 et une pièce support 30 en matériau isolant utilisées pour le raccordement des extrémités des barreaux 101 à 106 adjacentes aux extrémités correspondantes des barreaux 107 à 1012. Chaque réglette de liaison 12 présente, d'un côté, deux logements en queue d'aronde 12a, 12b décalés en direction axiale et, symétriquement, de l'autre côté, deux autres logements 12c, 12d également décalés en direction axiale. Chacun des logements 12a, 12b, 12c, 12d a une forme complémentaire de celle de l'extrémité d'un barreau 10. La pièce support 30 a une forme hexagonale et présente à sa périphérie des logements 31 régulièrement répartis et recevant chacun une réglette de liaison 12. Chaque réglette 12 est engagée dans son logement 31 respectif avec les logements 12a à 12d tournes vers l'extérieur.FIG. 6 shows one of the connecting strips 12 and a support piece 30 of insulating material used for connecting the ends of the bars 10 1 to 10 6 adjacent to the corresponding ends of the bars 10 7 to 10 12 . Each connecting strip 12 has, on one side, two dovetail housings 12a, 12b offset in the axial direction and, symmetrically, on the other side, two other housings 12c, 12d also offset in the axial direction. Each of the housings 12a, 12b, 12c, 12d has a shape complementary to that of the end of a bar 10. The support piece 30 has a hexagonal shape and has at its periphery housings 31 regularly distributed and each receiving a strip link 12. Each strip 12 is engaged in its respective housing 31 with the housings 12a to 12d facing outwards.

Les extrémités supérieures des barreaux 107 à 1012 sont reliées aux réglettes 121 à 126 et à la pièce isolante 30 par engagement dans les logements 12c ou 12d et par des vis 37 (figures 1 et 3) qui traversent les extrémités des barreaux, passent à travers un trou formé au centre du logement 12c ou 12d correspondant et sont vissées dans des trous filetés formés dans la pièce 30 au centre des logements 31. Les extrémités inférieures des barreaux 101 à 106 sont reliées aux réglettes 121 à 126 par engagement dans les logements 12a ou 12b et par des vis 35 (figure 1) qui traversent les extrémités des barreaux, passent à travers un trou formé au centre du logement 12a ou 12b correspondant et sont immobilisées par des écrous 36 (figure 1).The upper ends of the bars 10 7 to 10 12 are connected to the strips 12 1 to 12 6 and to the insulating piece 30 by engagement in the housings 12c or 12d and by screws 37 (Figures 1 and 3) which pass through the ends of the bars , pass through a hole formed in the center of the corresponding housing 12c or 12d and are screwed into threaded holes formed in the part 30 in the center of the housings 31. The lower ends of the bars 10 1 to 10 6 are connected to the strips 12 1 to 12 6 by engagement in the housings 12a or 12b and by screws 35 (FIG. 1) which pass through the ends of the bars, pass through a hole formed in the center of the corresponding housing 12a or 12b and are immobilized by nuts 36 (FIG. 1 ).

Du fait du décalage en direction axiale entre les pièces 23 des arrivées de courant reliées aux barreaux 101 et 104, la barrette 161 reliée aux barreaux 102 et 105 et la barrette 162 reliée aux barreaux 103 et 106, les extrémités inférieures des barreaux 101 et 106 se trouvent à trois niveaux différents. Par contre, les extrémités supérieures des barreaux 107 à 1012 se trouvent au même niveau, celui de la pièce support 30. Les réglettes 121 à 126 permettent de rattraper les distances différentes entre les extrémités en regard des barreaux qu'elles relient. Un premier décalage peut être rattrape en disposant la réglette avec son logement 12c ou son logement 12d au niveau de la pièce 31 (comme c'est le cas respectivement pour les réglettes 122, 123, 125, 126 et les réglettes 121, 122). Un deuxième décalage peut être rattrapé en engageant l'extrémité infèrieure des barreaux 101 à 106 dans un logement 12a ou dans un logement 12b (comme c'est le cas, respectivement, pour les barreaux 101, 102, 104, 105, et les barreaux 123, 106).Due to the offset in the axial direction between the pieces 23 of the current inlets connected to the bars 10 1 and 10 4 , the bar 16 1 connected to the bars 10 2 and 10 5 and the bar 16 2 connected to the bars 10 3 and 10 6 , the lower ends of the bars 10 1 and 10 6 are at three different levels. On the other hand, the upper ends of the bars 10 7 to 10 12 are at the same level, that of the support piece 30. The strips 12 1 to 12 6 make it possible to make up for the different distances between the opposite ends of the bars which they connect . A first offset can be made up by placing the strip with its housing 12c or its housing 12d at the level of the part 31 (as is the case respectively for the strips 12 2 , 12 3 , 12 5 , 12 6 and the strips 12 1 , 12 2 ). A second offset can be made up by engaging the lower end of the bars 10 1 to 10 6 in a housing 12a or in a housing 12b (as is the case, respectively, for the bars 10 1 , 10 2 , 10 4 , 10 5 , and the bars 12 3 , 10 6 ).

La figure 7 montre un des blocs de liaison 18 et une pièce support en matériau isolant 40 utilisés pour relier deux à deux et assembler les extrémités inférieures des barreaux 107 à 1012. La pièce 40 comporte une embase 41 de laquelle font saillie des parois 42 qui délimitent trois logements 431, 432, 433 répartis angulairement autour de l'axe 14 et isolés les uns des autres. Chaque logement 431, 432, 433 reçoit un bloc de liaison respectif. Chaque bloc de liaison est destiné à relier les extrémités inférieures de deux barreaux adjacents. A cet effet, un bloc 18 présente deux logements 18a, 18b ayant une forme de queue d'aronde complémentaire de celle de l'extrémité d'un barreau. L'assemblage entre une extrémité d'un barreau et un bloc 18 est réalisé par engagement de cette extrémité dans un logement 18a ou 18b, en direction radiale, et fixation au moyen d'une vis 47 qui traverse l'extrémité du barreau et est vissée dans un trou fileté formé au centre du logement.FIG. 7 shows one of the connection blocks 18 and a support piece of insulating material 40 used to connect two by two and assemble the lower ends of the bars 10 7 to 10 12 . The part 40 comprises a base 41 from which project walls 42 which delimit three housings 43 1 , 43 2 , 43 3 distributed angularly around axis 14 and isolated from each other. Each housing 43 1 , 43 2 , 43 3 receives a respective connection block. Each connecting block is intended to connect the lower ends of two adjacent bars. To this end, a block 18 has two housings 18a, 18b having a shape of dovetail complementary to that of the end of a bar. The assembly between one end of a bar and a block 18 is produced by engaging this end in a housing 18a or 18b, in the radial direction, and fixing by means of a screw 47 which passes through the end of the bar and is screwed into a threaded hole formed in the center of the housing.

On notera que la liaison entre les extrémités des barreaux et les différentes pièces de liaison en utilisant un assemblage en queue d'aronde permet de maintenir un contact électrique satisfaisant même en cas de desserrage des vis qui complètent l'assemblage.It will be noted that the connection between the ends of the bars and the various connecting pieces using a dovetail assembly makes it possible to maintain satisfactory electrical contact even in the event of loosening of the screws which complete the assembly.

Les différentes pièces isolantes - disque 26, rondelle 19, pièces support 30 et 40 - sont par exemple en céramique.The various insulating parts - disc 26, washer 19, support parts 30 and 40 - are for example made of ceramic.

Les barreaux ainsi que les différentes pièces assurant les liaisons entre ceux-ci sont réalisés en matériau composite carbone/carbone.The bars as well as the various parts ensuring the connections between them are made of carbon / carbon composite material.

Les matériaux composites carbone/carbone sont connus et utilisés en particulier pour leurs propriétés thermostructurales, c'est à dire leur capacité à constituer des éléments de structure, en raison de leurs bonnes propriétés mécaniques, et à conserver ces propriétés jusqu'à des températures relativement élevées.Carbon / carbon composite materials are known and used in particular for their thermostructural properties, that is to say their capacity to constitute structural elements, due to their good mechanical properties, and to preserve these properties up to relatively temperatures. high.

Les matériaux composites carbone/carbone sont constitués d'une texture de renfort en carbone densifiée par une matrice en carbone.Carbon / carbon composite materials consist of a carbon reinforcement texture densified by a carbon matrix.

En l'espèce, pour la réalisation des barreaux 10, on peut utiliser une texture de renfort bidimensionnelle (2D) réalisée à partir de fibres de carbone et formée de strates unidirectionnelles ou bidirectionnelles empilées à plat parallèlement aux faces des barreaux. Des strates unidirectionnelles sont par exemple des nappes de fils ou de câbles parallèles entre eux ; dans ce cas, la direction longitudinale des barreaux est parallèle aux fils ou câbles. Des strates bidirectionnelles sont par exemple des couches de tissu.In this case, for the production of the bars 10, one can use a two-dimensional (2D) reinforcing texture made from carbon fibers and formed of unidirectional or bidirectional layers stacked flat parallel to the faces of the bars. Unidirectional strata are, for example, plies of wires or cables parallel to one another; in this case, the longitudinal direction of the bars is parallel to wires or cables. Bidirectional strata are, for example, layers of fabric.

La densification de la texture de renfort fibreuse est réalisée par voie liquide ou par voie gazeuse. Ces deux procédés sont bien connus en soi.The densification of the fibrous reinforcement texture is carried out by liquid or by gaseous route. These two methods are well known per se.

La densification par voie liquide consiste à imprégner la texture fibreuse au moyen d'un précurseur du carbone, tel qu'une résine ou un brai laissant un résidu en carbone après polymérisation et pyrolyse. L'imprégnation peut être réalisée sur les strates (nappes de fils ou tissu) avant superposition de celles-ci. Les strates préimprégnées peuvent être mises en forme sous presse, afin, par un compactage, d'obtenir un taux de fibres désiré (le taux de fibres étant le pourcentage effectivement occupé par par les fibres au sein du matériau). Afin d'obtenir un degré de densification suffisant, plusieurs cycles successifs d'imprégnation -polymérisation -pyrolyse peuvent être nécessaires.Liquid densification consists in impregnating the fibrous texture by means of a carbon precursor, such as a resin or a pitch leaving a carbon residue after polymerization and pyrolysis. The impregnation can be carried out on the layers (layers of yarns or fabric) before they are superimposed. The pre-impregnated layers can be shaped in press, in order, by compacting, to obtain a desired fiber content (the fiber content being the percentage actually occupied by the fibers within the material). In order to obtain a sufficient degree of densification, several successive cycles of impregnation -polymerization -pyrolysis may be necessary.

La densification par voie gazeuse consiste à former la matrice par infiltration chimique en phase vapeur. A cet effet, la texture est placée dans un four dans lequel un flux gazeux est admis qui, dans des conditions déterminées de température et de pression laisse un dépôt en carbone au sein de la porosité accessible de la texture. Le flux gazeux est typiquement constitué par un hydrocarbure ou un mélange d'hydrocarbures. La texture fibreuse, au moins jusqu'à consolidation, peut être maintenue en forme dans un outillage qui assure également le degré de compactage nécessaire pour obtenir le taux de fibres désiré. L'outillage est démonté lorsque la texture est consolidée, c'est à dire lorsque le dépôt de pyrocarbone est suffisant pour lier les fibres entre elles. L'infiltration chimique en phase vapeur est poursuivie jusqu'à atteindre le degré de densification souhaité.Densification by gas consists of forming the matrix by chemical vapor infiltration. To this end, the texture is placed in an oven in which a gas flow is admitted which, under determined conditions of temperature and pressure leaves a carbon deposit within the accessible porosity of the texture. The gas flow typically consists of a hydrocarbon or a mixture of hydrocarbons. The fibrous texture, at least until consolidation, can be maintained in shape in a tool which also ensures the degree of compaction necessary to obtain the desired fiber content. The tool is dismantled when the texture is consolidated, that is to say when the pyrocarbon deposit is sufficient to bind the fibers together. Chemical vapor infiltration is continued until the desired degree of densification is reached.

Par souci évident d'économie, pour la fabrication des barreaux 10, on réalise des plaques de matériau carbone/carbone dans lesquelles les barreaux sont ensuite découpés.For obvious reasons of economy, for the production of the bars 10, carbon / carbon material plates are produced in which the bars are then cut.

Après usinage, les barreaux sont revêtus d'une couche de carbone pyrolytique ou pyrocarbone. Celle-ci est formée par dépôt chimique en phase vapeur dans des conditions similaires à celles de l'infiltration chimique de carbone en phase vapeur. L'épaisseur de la couche de pyrocarbone est par exemple environ égale à 100 microns.After machining, the bars are coated with a layer of pyrolytic or pyrocarbon carbon. This is formed by deposit chemical vapor phase under conditions similar to that of chemical vapor infiltration of carbon. The thickness of the pyrocarbon layer is for example approximately equal to 100 microns.

Pour la réalisation des pièces de liaison - barrettes 161, 162, réglettes 121 à 126, blocs 181 à 183 - ainsi que des arrivées de courant - pièces 21 et 23 - et des vis 17, 27, 35, 37, 47 et écrous 36, on utilise un matériau carbone/carbone comprenant de préférence une texture de renfort tridimensionnelle (3D). Une telle texture est obtenue par exemple par tissage tridimensionnel de fils de carbone, ou par superposition de strates unidirectionnelles ou bidirectionnelles et liaison des strates entre elles. Dans le cas où des strates unidirectionnelles, telles que des nappes de câbles sont superposées, les directions des câbles sont différentes d'une nappe à une autre. Comme connu en soi, la liaison entre strates superposées peut être réalisée par aiguilletage ou par implantation de fils. Lorsque l'aiguilletage est utilisé, les fibres entrainées par les aiguilles peuvent être prélevées dans des voiles de fibres interposés entre les strates.For the production of connecting pieces - bars 16 1 , 16 2 , strips 12 1 to 12 6 , blocks 18 1 to 18 3 - as well as current inlets - pieces 21 and 23 - and screws 17, 27, 35, 37, 47 and nuts 36, a carbon / carbon material is used, preferably comprising a three-dimensional (3D) reinforcement texture. Such a texture is obtained for example by three-dimensional weaving of carbon threads, or by superposition of unidirectional or bidirectional strata and bonding of the strata together. In the case where unidirectional strata, such as layers of cables are superimposed, the directions of the cables are different from one layer to another. As known per se, the connection between superimposed strata can be achieved by needling or by implantation of wires. When needling is used, the fibers entrained by the needles can be taken from fiber veils interposed between the strata.

La densification de la texture tridimensionnelle est réalisée par voie liquide ou par voie gazeuse comme indiqué plus haut.The densification of the three-dimensional texture is carried out by the liquid or gaseous route as indicated above.

Les pièces de liaison sont usinées dans des blocs de matériau carbone/carbone. Après usinage, elles peuvent être revêtues d'une couche de pyrocarbone, comme les barreaux.The connecting parts are machined from blocks of carbon / carbon material. After machining, they can be coated with a layer of pyrocarbon, like bars.

Il est également possible d'utiliser une texture de renfort 3D pour la réalisation des barreaux et une texture de renfort 2D pour la réalisation des pièces de liaison.It is also possible to use a 3D reinforcement texture for the production of the bars and a 2D reinforcement texture for the production of the connecting pieces.

L'utilisation du matériau composite carbone/carbone est particulièrement avantageuse car elle permet de réaliser un dispositif de chauffage électrique dans lequel les éléments résistifs, en particulier les barreaux, sont également des éléments de structure du fait de leurs propriétés mécaniques et leur non-fragilité. De plus, les matériaux composites carbone/carbone sont légers - leur densité est généralement d'environ 1,7 - et peuvent supporter des températures élevées, par exemple jusqu'à 2 500°C en atmosphère non-oxydante.The use of the carbon / carbon composite material is particularly advantageous because it makes it possible to produce an electric heating device in which the resistive elements, in particular the bars, are also structural elements due to their mechanical properties and their non-brittleness. . In addition, carbon / carbon composite materials are light - their density is generally about 1.7 - and can withstand high temperatures, for example up to 2500 ° C in a non-oxidizing atmosphere.

Selon une autre caractéristique du dispositif selon l'invention, et grâce aux propriétés mécaniques du matériau utilisé, les liaisons entre les éléments résistifs sont réalisées au moyen de pièces qui assurent non seulement la liaison électrique mais également la liaison mécanique. En particulier, comme décrit plus haut, il est possible de réaliser un assemblage par la forme qui assure ces deux fonctions électrique et mécanique.According to another characteristic of the device according to the invention, and thanks to the mechanical properties of the material used, the connections between the resistive elements are produced by means of parts which provide not only the electrical connection but also the mechanical connection. In particular, as described above, it is possible to produce an assembly by the form which ensures these two electrical and mechanical functions.

Enfin, comme déjà indiqué, le revêtement de pyrocarbone formé sur les éléments résistifs et les pièces de liaison permet d'améliorer la durée de vie et le fonctionnement de la résistance. Le revêtement peut être rénové au bout d'une certaine durée d'utilisation.Finally, as already indicated, the pyrocarbon coating formed on the resistive elements and the connecting parts makes it possible to improve the service life and the functioning of the resistance. The coating can be renovated after a certain period of use.

ExempleExample

Un dispositif de chauffage prévu pour une utilisation sous une puissance de 250 kW et tel qu'illustré par la figure 1 a été réalisé.A heating device intended for use under a power of 250 kW and as illustrated in FIG. 1 has been produced.

Les barreaux 10 ont été découpés dans une plaque de matériau composite comprenant une texture fibreuse formée par empilement de couches de tissu de carbone avec un taux de fibres de 25 % et une matrice en carbone formée par infiltration chimique en phase vapeur. L'infiltration a été poursuivie jusqu'à laisser une porosité résiduelle de l'ordre de 15 %. Le matériau obtenu a une densité d'environ 1,7. Chaque barreau 10 a une épaisseur de 5 mm, un largeur de 50 mm et une longeur de 750 mm. Les dimensions sont adaptées à la puissance désirée.The bars 10 were cut from a plate of composite material comprising a fibrous texture formed by stacking layers of carbon fabric with a fiber content of 25% and a carbon matrix formed by chemical vapor infiltration. The infiltration was continued until leaving a residual porosity of the order of 15%. The material obtained has a density of about 1.7. Each bar 10 has a thickness of 5 mm, a width of 50 mm and a length of 750 mm. The dimensions are adapted to the desired power.

Les pièces de liaison (arrivées de courant, réglettes, barrettes, blocs, vis et écrou) ont été usinées dans des blocs de matériau composite comprenant une texture fibreuse formée par empilement et aiguilletage de couches de tissu de carbone alternant avec des voiles de fibres de carbone, avec un taux de fibres de l'ordre de 25 %. La texture a été densifiée par infiltration de pyrocarbone en phase vapeur jusqu'à atteindre une porosité résiduelle de l'ordre de 15 %. Le matériau obtenu a une densité d'environ 1,7.The connecting pieces (current inlets, rods, bars, blocks, screws and nuts) were machined in blocks of composite material comprising a fibrous texture formed by stacking and needling layers of carbon fabric alternating with veils of fiber fibers carbon, with a fiber content of around 25%. The texture was densified by infiltration of pyrocarbon in the vapor phase until a residual porosity of the order of 15% was reached. The material obtained has a density of about 1.7.

Dans le mode de réalisation décrit plus haut, les éléments résistifs sont formés par douze barreaux répartis en deux groupes de six.In the embodiment described above, the resistive elements are formed by twelve bars distributed in two groups of six.

Par sa conception modulaire, le dispositif de chauffage peut être adapté à différentes puissances ou à différentes configurations d'utilisation, en prévoyant un nombre de barreaux plus ou moins grand.By its modular design, the heating device can be adapted to different powers or different configurations of use, by providing for a greater or lesser number of bars.

En particulier, un ou plusieurs groupes supplémentaires de six barreaux peuvent être ajoutés au dispositif de la figure 1 en utilisant un ou plusieurs ensembles supplémentaires de réglettes et pièce isolante tel que l'ensemble constitué par les réglettes 121 à 126 et la pièce 30.In particular, one or more additional groups of six bars can be added to the device of FIG. 1 using one or more additional sets of strips and insulating piece such as the set constituted by strips 12 1 to 12 6 and piece 30 .

Il est également possible, comme le montre la figure 8, de réaliser un dispositif de chauffage dans lequel les éléments résistifs sont constitués par un groupe de barreaux 10′1 à 10′6 s'étendant chacun d'une extrémité à l'autre du dispositif. Si l'on utilise, aux extrémités des barreaux, des pièces de liaison identiques à celles utilisées aux extrémités du dispositif de chauffage de la figure 1, il est alors nécessaire de prévoir des barreaux ayant des longueurs différentes pour tenir compte de leur décalage à leur extrémité supérieure.It is also possible, as shown in FIG. 8, to produce a heating device in which the resistive elements consist of a group of bars 10 ′ 1 to 10 ′ 6 each extending from one end to the other of the device. If using at the ends of the bars, connecting pieces identical to those used at the ends of the heating device of FIG. 1, it is then necessary to provide bars having different lengths to take account of their offset to their upper end.

En variante, comme le montre la figure 9, le décalage entre les positions des extrémités supérieures des barreaux 10′1 à 10′6 peut être rattrapé, non pas en donnant aux barreaux des longueurs différentes, mais en utilisant des blocs de liaisons 18' offrant, pour chaque extrémité d'un barreau, trois possibilités d'assemblage à des niveaux différents.As a variant, as shown in FIG. 9, the offset between the positions of the upper ends of the bars 10 ′ 1 to 10 ′ 6 can be made up, not by giving the bars different lengths, but by using connection blocks 18 ' offering, for each end of a bar, three possibilities of assembly at different levels.

Claims (10)

  1. High power electrical heating resistance comprising resistive elements made of carbon/carbon composite material, characterized in that the resistive elements are constituted by strips (10) interconnected by connection pieces (12, 16, 18) providing both electrical connections and mechanical connections between the strips, the strips and connection pieces being made of a carbon/carbon composite material comprising a fibrous reinforcing texture densified by a carbon matrix.
  2. Resistance according to claim 1, characterized in that the strips (10) and the connection pieces (12, 16, 18) are assembled together, at least in part, by their shape.
  3. Resistance according to any one of claims 1 and 2, characterized in that the resistive elements (12) are coated with a layer of pyrocarbon.
  4. Resistance according to claim 3, characterized in that the connection pieces (12, 16, 18) are coated with a layer of pyrocarbon.
  5. Resistance according to any one of claims 1 to 4, characterized in that the strips and the connection pieces are assembled together, at least in part, by their shape, and are further assembled together by fasteners (17, 36, 37, 47) made of carbon/carbon composite material.
  6. Resistance according to any one of claims 1 to 5, characterized in that the strips (10) are disposed parallel to an axis (14) about which they are distributed.
  7. Resistance according to claim 6, characterized in that the connections between the strips (10) at one end of the resistance, are made by connection pieces (16) which extend radially to interconnect the ends of strips that are diametrically opposite about the axis (14).
  8. Resistance according to any one of claims 6 and 7, characterized in that the connections between the strips (10) at one end of the resistance, are made by means of connection pieces (18) which interconnect the ends of adjacent strips.
  9. Resistance according to any one of claims 6 to 8, characterized in that it includes connection pieces (16) interconnecting the adjacent ends of strips that are in alignment.
  10. Resistance according to claim 9, characterized in that each connection piece (12) for interconnecting the adjacent ends of aligned strips includes a plurality of recesses (12a - 12d) suitable for receiving the end of a strip, which recesses are spaced apart from one another parallel to the axis (14) in order to accommodate at least one of the strips connected to said connection piece in different longitudinal positions.
EP92401581A 1991-06-11 1992-06-09 Electrical heating resistance with resistant elements out of carbon/carbon composite materials Expired - Lifetime EP0518747B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9107093A FR2677840B1 (en) 1991-06-11 1991-06-11 ELECTRIC HEATING RESISTANCE USING RESISTIVE ELEMENTS OF CARBON / CARBON COMPOSITE MATERIAL.
FR9107093 1991-06-11

Publications (2)

Publication Number Publication Date
EP0518747A1 EP0518747A1 (en) 1992-12-16
EP0518747B1 true EP0518747B1 (en) 1996-09-11

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Application Number Title Priority Date Filing Date
EP92401581A Expired - Lifetime EP0518747B1 (en) 1991-06-11 1992-06-09 Electrical heating resistance with resistant elements out of carbon/carbon composite materials

Country Status (7)

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US (1) US5233165A (en)
EP (1) EP0518747B1 (en)
JP (1) JP3015806B2 (en)
CA (1) CA2070860C (en)
DE (1) DE69213571T2 (en)
ES (1) ES2092073T3 (en)
FR (1) FR2677840B1 (en)

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CN1325841C (en) * 2004-07-20 2007-07-11 董礼 High efficiency low consumption electric stove
US20100170625A1 (en) * 2007-07-04 2010-07-08 Hunan Kingbo Carbon-Carbon Composites Co. Ltd. Fastener and a manufacture process thereof
US8463113B2 (en) * 2010-12-20 2013-06-11 Gyu Eob HWANG Fan heater applying a carbon fiber ribbon secured in each heating cartridge
JP2018195425A (en) * 2017-05-16 2018-12-06 イビデン株式会社 Resistance heating element

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Also Published As

Publication number Publication date
ES2092073T3 (en) 1996-11-16
FR2677840A1 (en) 1992-12-18
US5233165A (en) 1993-08-03
FR2677840B1 (en) 1993-10-15
JP3015806B2 (en) 2000-03-06
JPH05182747A (en) 1993-07-23
EP0518747A1 (en) 1992-12-16
CA2070860A1 (en) 1992-12-12
DE69213571D1 (en) 1996-10-17
CA2070860C (en) 1997-09-30
DE69213571T2 (en) 1997-02-06

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