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EP1815570A1 - Radiofrequency plasma spark plug - Google Patents

Radiofrequency plasma spark plug

Info

Publication number
EP1815570A1
EP1815570A1 EP05815563A EP05815563A EP1815570A1 EP 1815570 A1 EP1815570 A1 EP 1815570A1 EP 05815563 A EP05815563 A EP 05815563A EP 05815563 A EP05815563 A EP 05815563A EP 1815570 A1 EP1815570 A1 EP 1815570A1
Authority
EP
European Patent Office
Prior art keywords
base
spark plug
electrode
annular
central electrode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP05815563A
Other languages
German (de)
French (fr)
Other versions
EP1815570B1 (en
Inventor
Xavier Jaffrezic
André AGNERAY
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Renault SAS
Original Assignee
Renault SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Renault SAS filed Critical Renault SAS
Priority to PL05815563T priority Critical patent/PL1815570T3/en
Publication of EP1815570A1 publication Critical patent/EP1815570A1/en
Application granted granted Critical
Publication of EP1815570B1 publication Critical patent/EP1815570B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/50—Sparking plugs having means for ionisation of gap
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/52—Sparking plugs characterised by a discharge along a surface

Definitions

  • the present invention relates, in general, radiofrequency plasma candles. More particularly, the invention relates to a spark plug, referred to as a radiofrequency plasma, intended to equip a combustion chamber of an internal combustion engine, and comprising:
  • annular base of main axis D formed in a first conducting material and having first and second ends, and an extreme circular surface having a principal axis of symmetry D located at the first end of the base; a central electrode formed in a second conductive material, extending along the main axis D and having an inner portion disposed within said annular base and an outer portion disposed outside said annular base, to a larger extent; near the first extremity of the base of the second; an electrically insulating piece of annular shape extending at least around the inner portion of the central electrode so as to be interposed between the base and the electrode, this insulating part covering only a part of the outer portion of the central electrode so that the portion of the outer portion not covered is in contact with a gas mixture surrounding the candle.
  • the ignition of gasoline internal combustion engines consisting of initiating the combustion of an air-fuel mixture in a combustion chamber of said engine, is relatively well controlled in current engines.
  • the car manufacturers have developed spark ignition engines capable of operating with poor carbide mixtures, that is to say having an excess of air relative to the amount of fuel injected.
  • Ignition of a fuel-poor mixture is, however, difficult to control. For this, and in order to increase the probability of successful ignition, it is necessary to have more fuel-rich mixtures around the candle at the moment the spark occurs.
  • Such candles are described in particular in patent applications FR97-14799, FR99-09473 and FR00-13821. Such candles generate sparks of large sizes from reduced potential differences.
  • the surface spark plugs have a dielectric (insulating part) separating the electrodes (one electrode being the annular base and the other electrode being the central electrode) in the zone where the distance separating them is the lowest; the sparks formed between the electrodes are thus guided on the surface of the dielectric.
  • These candles amplify the inter-electrode field on the surface of the dielectric.
  • the elementary capacities are progressively formed by the dielectric and an underlying electrode.
  • the candles generate a spark propagating along the surface of the insulator in areas where the electric field in the air / gas mixture is the strongest.
  • the present invention therefore aims to provide a spark plug which when assembled in a combustion chamber increases the probability of ignition of the mixture surrounding the candle.
  • the spark plug of the invention which is also in accordance with the generic definition given in the preamble defined above, is essentially characterized in that the insulating piece has an annular shoulder concealing the entire circular end surface of the base relative to the uncoated portion of the electrode.
  • the central electrode (following a path passing to the surface of the insulating part) is particularly important since it is greater than the minimum dimension of the extreme circular surface (ie the diameter of this circular surface); - And secondly the central electrode and the base are separated by the insulating part and are not in relation to one another.
  • the spark plug according to the invention when the spark plug according to the invention is assembled in a vehicle combustion chamber, with the part of the central electrode not covered by the insulator, arranged inside the chamber, and with the base assembled in the thickness of the chamber wall, no electric arc can occur between the base and the central electrode. Indeed access to the base from the uncoated portion of the central electrode is prevented by the presence of 1 'insulator.
  • the spark plug according to the invention when subjected to a radio frequency excitation, ie an alternating voltage between the base and the central electrode (for example said alternating voltage being greater than 5kV and having a frequency higher than 1 MHz) forms a branched plasma near the central electrode and not an electric arc. It is understood that this given voltage and frequency is suitable for creating a plasma in a gaseous mixture having a molar density greater than 5 * 10 -2 mol / L.
  • plasma or branched plasma refers to the simultaneous generation of at least several lines or ionization paths in a given gaseous volume, their branches being moreover omnidirectional.
  • volume plasma involves heating up the entire volume in which it is to be generated
  • the branched plasma only requires the heating in the path of the sparks formed.
  • the energy required for a branched plasma is significantly less than that required by a volume plasma.
  • the branched plasma generated by the candle according to the invention is generated at a distance from the insulating part, towards the walls of the chamber which are opposite the central electrode, which makes it possible to reduce the probability of generation of an arc with the base and allows correlatively reduce the wear of the electrodes.
  • the plasma has the advantage of having a large number of ionization paths or sparks in a large volume of gas located around the central electrode which increases the probability of ignition of the mixture containing oxidant.
  • a difference between an electric arc and a branched plasma is that: the arc consists of a single chain of ionized gas molecules extending directly between the electrodes and allows electrons to be transferred from one electrode to the other to reduce the difference in electrical potential existing between these electrodes energized while; the plasma produced according to the invention is a set of multiple chains of ionized molecules of gas extending disorderedly around the exciter electrode and issuing from said electrode. These multiple chains can alternately transfer electrons between said electrode and the air located nearby and vice versa.
  • the formation of a spark is initiated by the tearing out of the middle (gas mixture) of a few electrons subjected to a large electric field.
  • electrons of an electrode are accelerated by the electrostatic forces generated between the electrodes and collide with the gaseous mixture containing air.
  • the portion of the electrode that experiences the largest electrostatic field (usually an angle of one electrode or tip near the other electrode) is the starting point of the first avalanche.
  • the molecules of the air are heated and release an electron and a photon ionizing in their turn other molecules of air.
  • a chain reaction ionizes the air when applying a large voltage between electrodes separated by an insulator.
  • the ionized air around the central electrode has a potential close to this central electrode and behaves as an extension of it.
  • the electric field is amplified upstream of the front and promotes the creation of new avalanches.
  • the phenomenon tends to self-maintain to create around the central electrode a conductive ionized gaseous mass in the direction of the walls of the chamber.
  • the candle of the invention is put under AC voltage which makes it possible to vary the potential existing between the central electrode and the base / chamber, this potential being reversible. At each alternation of potential / polarity, the electrons are more and more accelerated in opposite directions.
  • a polarization wave thus propagates oscillatoryly at the frequency of the excitation, recovering at each period the expenses deposited in the previous period. Each alternation then produces a propagation of the wave greater than the preceding one; it is thus possible with the candle of the invention thus fed to obtain relatively large spark amplitudes with voltages between electrode and relatively large cap.
  • the radiofrequency excitation of such a candle makes it possible moreover by avoiding the arcs to suppress the breakdown voltage variations between successive cycles.
  • the extreme circular surface of the base to bear against a complementary bearing surface of the shoulder of the insulating part.
  • This feature makes it possible to eliminate the space between the insulating part and the base, so the heat associated with the presence of a flame triggered by the plasma can be dissipated to the base which prevents overheating of the ceramic.
  • the insulating part has a minimum thickness located inside said base, and the shoulder of the insulating part has a shoulder thickness greater than or equal to half of said minimum thickness.
  • This feature prevents the junction between the uncovered portion of the central electrode and therefore the air / ceramic / central electrode junction is too close to the base. If this part not covered with the electrode or more precisely this junction was too close to the base it could constitute a surface spark emission zone.
  • the base, the electrically insulating part, and the electrode central are parts of revolution having as axis of common symmetry the main axis D.
  • the relative positioning accuracy of the constituents of the candle with respect to a common axis of symmetry makes it possible to center the branched plasma around this axis D and the central electrode, which facilitates the location of the zone of the combustion chamber in which sparks occur.
  • the annular base is in the form of a cylindrical tube comprising at the first end of the base an internal chamfer coming into contact with the extreme circular surface, this internal chamfer being in contact with a complementary chamfer formed on a portion of the insulating part.
  • the inner chamfer has a cross section, in a plane parallel to the main axis D, of rounded shape. It is also possible to ensure that the annular shoulder has an end remote from the annular base at the outer periphery of which is formed a rounded peripheral chamfer, coaxial with the main axis D. This peripheral chamfer reduces or eliminates the presence of sharp angle, at the outer periphery of the annular piece, at the end of the annular shoulder.
  • Figure 1 shows a candle described in the applications for French patents FR03-10766, FR03-10767, FR03-10768 filed by the Applicant and not yet published;
  • Figures 2A, 2B and 2C show embodiments of the candle according to the invention.
  • the candle 1 of Figure 1 is a candle developed by the applicant to be used as plasma generation candle. This candle is the subject of patent applications not yet published at the filing date of this application.
  • This candle comprises a central cylindrical electrode 7 having an axis of symmetry D, a portion of which, said internal portion, is disposed inside and at a distance an annular base 3 which in the form of a cylindrical tube of axis D.
  • An insulating piece of annular shape is also arranged partly inside the annular base, around the central electrode, so as to separate the base of the central electrode 7.
  • the insulating part, the central electrode and the base 3 are parts of revolution oriented along the axis D.
  • the central electrode 7 has an uncoated portion 16 that is not surrounded by the electrically insulating piece 10 and not surrounded by the base 3, this uncovered portion 16 being disposed inside the combustion chamber 2 of the engine.
  • the base 3 has an outer circular surface in the form of a flat disk perforated at its center and having the axis of symmetry axis D and being arranged perpendicular to this axis D.
  • the base 3 has a connection with the wall of the chamber 2 which is usually a thread of the base in a hole made through the wall.
  • the base of the candle thus assembled with the wall of the chamber 2 is at iso electric potential with this wall, that is to say at an electric potential of mass.
  • the central electrode When the central electrode is supplied with AC voltage centered around the ground potential, this voltage being of a frequency between 1 and 1 MHz, the electrons located near the tip 17 of the central electrode move either from the electrode to the walls of the chamber through the gaseous mixture surrounding the chamber, or the gas mixture to the electrode. In both cases, the electrical alternation is such that an electron does not have time to go from the central electrode to the wall of the chamber.
  • the air can thus be ionized without there being a real electric discharge between the two electrical terminals constituted by the central electrode 7 and the wall of the chamber 2. This ionization creates a plasma located around the tip 17 of the central electrode which concentrates the electric charges in movement around a small volume of exchange.
  • the candles of these figures have all the characteristics described for the candle with reference to Figure 1, but also have a shoulder 11 formed on the insulating part 10 and obscuring the outer circular surface 6 of the base 3.
  • This shoulder 11 increases the distance, passing through the gaseous mixture, between the electrode and the base, thereby avoiding the creation of arcs between the central electrode 17 and the base 3.
  • the shoulder of the insulating part 10 of Figure 2A is a shoulder having in longitudinal section right angles which can create concentrations of loads and mechanical stresses.
  • the candles of Figures 2B and 2C have at the first end 4 of base 3, an inner bevel 13.
  • the insulating part 10 has a complementary chamfer 14 coming into contact against the inner bevel 13. This important contact surface allows to evacuate the heat of the insulating part towards the base which prolongs the average life of the candle.
  • the spark plug according to the invention of FIG. 2C has a rounded peripheral chamfer 15 formed on the annular shoulder 11, at the location of the shoulder which is the furthest axially distant from the base 3.
  • This shoulder makes it possible to avoid a right angle at the shoulder, on the path passing through the gaseous mixture, between the tip 17 and the annular base 3. This rounding reduces the risk of creating an arc.
  • the first and second conductive materials which are the respective materials of the central electrode and the base 3 are, according to a particular embodiment of the invention, identical to each other. These materials are metallic materials such as copper alloys. According to a particular embodiment of the invention, the end of the central electrode 7 may consist of a copper core surrounded by a nickel sheath.
  • the insulation material is preferably a ceramic having a breakdown voltage greater than 20 Kv / mm.

Landscapes

  • Spark Plugs (AREA)
  • Ignition Installations For Internal Combustion Engines (AREA)
  • Coating By Spraying Or Casting (AREA)
  • Percussion Or Vibration Massage (AREA)
  • Absorbent Articles And Supports Therefor (AREA)
  • Plasma Technology (AREA)

Abstract

A radiofrequency plasma spark plug configured to equip a combustion chamber including: an annular shell with a main axis; a central electrode made of a conductive material, extending along the main axis and including an inner portion arranged inside the annular shell and an outer portion arranged outside the annular shell; an annular electrically insulating part extending at least about the inner portion of the central electrode so as to be interposed between the shell and the electrode, the insulating part only covering part of the outer portion of the central electrode. The insulating part includes an annular flange concealing the entire circular terminal surface of the shell relative to the uncovered part of the electrode.

Description

BOUGIE A PLASMA. RADIOFREQUENCE PLASMA CANDLE. RADIO FREQUENCY

La présente invention concerne, de façon générale, les bougies à plasma radiofréquence. Plus particulièrement, l'invention concerne une bougie d'allumage, dite plasma à radiofréquence, destinée à équiper une chambre de combustion d'un moteur à combustion interne, et comportant :The present invention relates, in general, radiofrequency plasma candles. More particularly, the invention relates to a spark plug, referred to as a radiofrequency plasma, intended to equip a combustion chamber of an internal combustion engine, and comprising:

- un culot annulaire d'axe principal D formé dans un premier matériau conducteur et possédant des première et seconde extrémités, et une surface circulaire extrême d'axe principal de symétrie D située à la première extrémité du culot ; une électrode centrale formée dans un second matériau conducteur, s'étendant le long de l'axe principal D et comportant une portion interne disposée à l'intérieur dudit culot annulaire et une portion externe disposée à l'extérieur dudit culot annulaire, à plus grande proximité de la première extrémité du culot que de la seconde ; une pièce isolante électriquement de forme annulaire s'étendant au moins autour de la portion interne de l'électrode centrale de façon à s'interposer entre le culot et l'électrode, cette pièce isolante ne recouvrant qu'une partie de la portion externe de l'électrode centrale de façon à ce que la partie de la portion externe non recouverte soit en contact avec un mélange gazeux environnant la bougie.an annular base of main axis D formed in a first conducting material and having first and second ends, and an extreme circular surface having a principal axis of symmetry D located at the first end of the base; a central electrode formed in a second conductive material, extending along the main axis D and having an inner portion disposed within said annular base and an outer portion disposed outside said annular base, to a larger extent; near the first extremity of the base of the second; an electrically insulating piece of annular shape extending at least around the inner portion of the central electrode so as to be interposed between the base and the electrode, this insulating part covering only a part of the outer portion of the central electrode so that the portion of the outer portion not covered is in contact with a gas mixture surrounding the candle.

L'allumage des moteurs à combustion interne essence, consistant à initier la combustion d'un mélange air-essence dans une chambre de combustion dudit moteur, est relativement bien maîtrisé dans les moteurs actuels. Toutefois, pour satisfaire les normes de pollution, les constructeurs automobiles ont développé des moteurs à allumage commandé aptes à fonctionner avec des mélanges carbures pauvres, c'est-à-dire présentant un excès d'air par rapport à la quantité de carburant injectée.The ignition of gasoline internal combustion engines, consisting of initiating the combustion of an air-fuel mixture in a combustion chamber of said engine, is relatively well controlled in current engines. However, to meet the pollution standards, the car manufacturers have developed spark ignition engines capable of operating with poor carbide mixtures, that is to say having an excess of air relative to the amount of fuel injected.

L'allumage d'un mélange pauvre en carburant est toutefois difficiles à maîtriser. Pour cela, et afin d'augmenter la probabilité d'allumage réussi, il est nécessaire d'avoir des mélanges plus riches en carburant autour de la bougie au moment où l'étincelle se produit.Ignition of a fuel-poor mixture is, however, difficult to control. For this, and in order to increase the probability of successful ignition, it is necessary to have more fuel-rich mixtures around the candle at the moment the spark occurs.

Toujours pour augmenter la probabilité d'allumage du mélange par la bougie, de nouvelles bougies à étincelle de surface ont été développées afin de produire des étincelles plus grandes pour traiter le problème du rendez-vous spatio-temporel entre le mélange de carburant et l'étincelle. On allume ainsi un volume de mélange supérieur et la probabilité d'initiation de la combustion est alors très largement augmentée.To further increase the likelihood of the candle igniting the mixture, new surface spark plugs were developed to produce larger sparks to deal with the problem of spatio-temporal rendezvous between the fuel mixture and the spark plug. spark. Thus, a higher mixing volume is ignited and the probability of initiation of combustion is then greatly increased.

De telles bougies sont notamment décrites dans les demandes de brevet FR97-14799, FR99-09473 et FR00-13821. De telles bougies génèrent des étincelles de tailles importantes à partir de différences de potentiel réduites.Such candles are described in particular in patent applications FR97-14799, FR99-09473 and FR00-13821. Such candles generate sparks of large sizes from reduced potential differences.

Les bougies à étincelles de surface présentent un diélectrique (pièce isolante) séparant les électrodes (une électrode étant le culot annulaire et l'autre électrode étant l'électrode centrale) dans la zone où la distance les séparant est la plus faible; on guide ainsi les étincelles formées entre les électrodes sur la surface du diélectrique. Ces bougies amplifient le champ inter-électrode à la surface du diélectrique. On charge pour cela progressivement les capacités élémentaires formées par le diélectrique et une électrode sous- jacente. Les bougies génèrent une étincelle se propageant le long de la surface de 1 ' isolant dans les zones où le champ électrique dans l'air/mélange gazeux est le plus fort .The surface spark plugs have a dielectric (insulating part) separating the electrodes (one electrode being the annular base and the other electrode being the central electrode) in the zone where the distance separating them is the lowest; the sparks formed between the electrodes are thus guided on the surface of the dielectric. These candles amplify the inter-electrode field on the surface of the dielectric. For this purpose, the elementary capacities are progressively formed by the dielectric and an underlying electrode. The candles generate a spark propagating along the surface of the insulator in areas where the electric field in the air / gas mixture is the strongest.

Dans ce contexte, la présente invention à donc pour objet de fournir une bougie d'allumage qui une fois assemblée dans une chambre de combustion permette d'augmenter la probabilité d'allumage du mélange environnant la bougie.In this context, the present invention therefore aims to provide a spark plug which when assembled in a combustion chamber increases the probability of ignition of the mixture surrounding the candle.

A cette fin, la bougie d'allumage de l'invention, par ailleurs conforme à la définition générique qu'en donne le préambule défini précédemment, est essentiellement caractérisée en ce que la pièce isolante possède un épaulement annulaire occultant toute la surface circulaire extrême du culot par rapport à la partie non recouverte de l'électrode. Avec une telle bougie :To this end, the spark plug of the invention, which is also in accordance with the generic definition given in the preamble defined above, is essentially characterized in that the insulating piece has an annular shoulder concealing the entire circular end surface of the base relative to the uncoated portion of the electrode. With such a candle:

- d'une part la distance séparant le culot de la bougie, de l'électrode centrale (en suivant un chemin passant à la surface de la pièce isolante) est particulièrement importante puisqu'il est supérieur à la dimension minimale de la surface circulaire extrême (c'est à dire le diamètre de cette surface circulaire) ; - et d'autre part l'électrode centrale et le culot sont séparés par la pièce isolante et ne sont donc pas en vis à vis l'un de l'autre.- firstly the distance between the base of the candle, the central electrode (following a path passing to the surface of the insulating part) is particularly important since it is greater than the minimum dimension of the extreme circular surface (ie the diameter of this circular surface); - And secondly the central electrode and the base are separated by the insulating part and are not in relation to one another.

Ces deux raisons font que lorsque l'électrode et le culot sont alimentés pour créer entre eux une différence de potentiel électrique importante (généralement variant de 5kV à 35KV en valeurs crêtes absolues) aucun arc électrique ne peut apparaître entre la surface circulaire extrême de la bougie et l'électrode centrale.These two reasons mean that when the electrode and the base are energized to create between them a significant electric potential difference (generally ranging from 5kV to 35KV in absolute peak values) no arc No electrical power can appear between the extreme circular surface of the spark plug and the center electrode.

Plus généralement lorsque la bougie selon l'invention est assemblée dans une chambre de combustion de véhicule, avec la partie de l'électrode centrale non recouverte par l'isolant, disposée à l'intérieur de la chambre, et avec le culot assemblé dans l'épaisseur de la paroi de la chambre, aucun arc électrique ne peut se produire entre le culot et l'électrode centrale. En effet l'accès au culot en partant de la partie non recouverte de l'électrode centrale est empêché par la présence de 1' isolant .More generally, when the spark plug according to the invention is assembled in a vehicle combustion chamber, with the part of the central electrode not covered by the insulator, arranged inside the chamber, and with the base assembled in the thickness of the chamber wall, no electric arc can occur between the base and the central electrode. Indeed access to the base from the uncoated portion of the central electrode is prevented by the presence of 1 'insulator.

Dans ces conditions, la bougie selon l'invention, lorsque soumise à une excitation radiofréquence, c'est à dire une tension alternative entre le culot et l'électrode centrale (par exemple ladite tension alternative étant supérieure à 5kV et ayant une fréquence supérieure à 1 MHz) forme un plasma ramifié à proximité de l'électrode centrale et non un arc électrique. Il est bien entendu que cette tension et fréquence donnée est adaptée pour créer un plasma dans un mélange gazeux présentant une densité molaire supérieure à 5*10"2 mol/L.Under these conditions, the spark plug according to the invention, when subjected to a radio frequency excitation, ie an alternating voltage between the base and the central electrode (for example said alternating voltage being greater than 5kV and having a frequency higher than 1 MHz) forms a branched plasma near the central electrode and not an electric arc. It is understood that this given voltage and frequency is suitable for creating a plasma in a gaseous mixture having a molar density greater than 5 * 10 -2 mol / L.

Le terme plasma ou plasma ramifié utilisé par la suite désigne la génération simultanée d'au moins plusieurs lignes ou chemins d'ionisations dans un volume gazeux donné, leurs ramifications étant en outre omnidirectionnelles.The term "plasma or branched plasma" used hereinafter refers to the simultaneous generation of at least several lines or ionization paths in a given gaseous volume, their branches being moreover omnidirectional.

Alors qu'un plasma de volume implique le réchauffement de tout le volume dans lequel il doit être généré, le plasma ramifié ne nécessite que le chauffage sur le trajet des étincelles formées. Ainsi, pour un volume donné, l'énergie requise pour un plasma ramifié est nettement inférieure à celle requise par un plasma de volume.While a volume plasma involves heating up the entire volume in which it is to be generated, the branched plasma only requires the heating in the path of the sparks formed. Thus, for a given volume, the energy required for a branched plasma is significantly less than that required by a volume plasma.

Le plasma ramifié généré grâce à la bougie selon l'invention est généré à distance de la pièce isolante, en direction des parois de la chambre qui sont en vis à vis de l'électrode centrale ce qui permet de réduire la probabilité de génération d'un arc avec le culot et permet corrélativement de réduire l'usure des électrodes.The branched plasma generated by the candle according to the invention is generated at a distance from the insulating part, towards the walls of the chamber which are opposite the central electrode, which makes it possible to reduce the probability of generation of an arc with the base and allows correlatively reduce the wear of the electrodes.

Par rapport à l'arc électrique, le plasma possède l'avantage de comporter un grand nombre de chemins d'ionisations ou d'étincelles dans un volume de gaz important situé autour de l'électrode centrale ce qui augmente la probabilité d'allumage du mélange contenant du comburant . Une différence entre un arc électrique et un plasma ramifié est que : l'arc est constitué d'une seule chaîne de molécules de gaz ionisées s'étendant directement entre les électrodes et permet de transférer des électrons d'une électrode vers l'autre pour réduire la différence de potentiel électrique existante entre ces électrodes mises sous tension alors que ; le plasma produit selon l'invention est un ensemble de multiples chaînes de molécules ionisées de gaz s'étendant de façon désordonnée autour de l'électrode excitatrice et issue de ladite électrode. Ces multiples chaînes permettent de transférer alternativement des électrons entre ladite électrode et l'air situé à proximité et réciproquement . La formation d'une étincelle est initiée par l'arrachement au milieu (mélange gazeux) de quelques électrons soumis à un champ électrique important. Lors de l'application d'une tension importante entre les électrodes, des électrons d'une électrode sont accélérés par les forces électrostatiques générées entre les électrodes et heurtent le mélange gazeux contenant de l'air. La portion de l'électrode qui subit le champ électrostatique le plus important (généralement un angle d'une électrode ou une pointe proche de l'autre électrode) constitue le lieu de départ de la première avalanche. Les molécules de l'air sont chauffées et libèrent un électron et un photon ionisant à leur tour d'autres molécules d'air. Ainsi, une réaction en chaîne ionise l'air lors de l'application d'une tension importante entre des électrodes séparées par un isolant.With respect to the electric arc, the plasma has the advantage of having a large number of ionization paths or sparks in a large volume of gas located around the central electrode which increases the probability of ignition of the mixture containing oxidant. A difference between an electric arc and a branched plasma is that: the arc consists of a single chain of ionized gas molecules extending directly between the electrodes and allows electrons to be transferred from one electrode to the other to reduce the difference in electrical potential existing between these electrodes energized while; the plasma produced according to the invention is a set of multiple chains of ionized molecules of gas extending disorderedly around the exciter electrode and issuing from said electrode. These multiple chains can alternately transfer electrons between said electrode and the air located nearby and vice versa. The formation of a spark is initiated by the tearing out of the middle (gas mixture) of a few electrons subjected to a large electric field. During the application of a large voltage between the electrodes, electrons of an electrode are accelerated by the electrostatic forces generated between the electrodes and collide with the gaseous mixture containing air. The portion of the electrode that experiences the largest electrostatic field (usually an angle of one electrode or tip near the other electrode) is the starting point of the first avalanche. The molecules of the air are heated and release an electron and a photon ionizing in their turn other molecules of air. Thus, a chain reaction ionizes the air when applying a large voltage between electrodes separated by an insulator.

L'air ionisé autour de l'électrode centrale, possède un potentiel proche de cette électrode centrale et se comporte comme un prolongement de celle-ci. Lors de la propagation du front d'avalanche (nom donné à une vague de migration massive de charges électriques dans le mélange gazeux) , le champ électrique est amplifié en amont du front et favorise la création de nouvelles avalanches. Ainsi le phénomène à tendance à s'auto- entretenir pour créer autour de l'électrode centrale une masse gazeuse ionisée conductrice en direction des parois de la chambre. Comme précédemment précisé la bougie de l'invention est mise sous tension alternative ce qui permet de faire varier le potentiel existant entre l'électrode centrale et le culot/chambre, ce potentiel pouvant être inversé. A chaque alternance de potentiel/polarité, les électrons sont de plus en plus accélérés dans des sens inverses. Une onde de polarisation se propage ainsi de manière oscillatoire à la fréquence de l'excitation, récupérant à chaque période les charges déposées à la période précédente. Chaque alternance produit alors une propagation de l'onde plus importante que la précédente ; il est ainsi possible avec la bougie de l'invention ainsi alimentée d'obtenir des amplitudes d'étincelles relativement importante avec des tensions entre électrode et culot relativement importantes. L'excitation radiofréquence d'une telle bougie permet de plus en évitant les arcs de supprimer les variations de tension de claquage entre des cycles successifs.The ionized air around the central electrode, has a potential close to this central electrode and behaves as an extension of it. During the propagation of the avalanche front (name given to a wave of mass migration of electrical charges in the gas mixture), the electric field is amplified upstream of the front and promotes the creation of new avalanches. Thus, the phenomenon tends to self-maintain to create around the central electrode a conductive ionized gaseous mass in the direction of the walls of the chamber. As previously stated, the candle of the invention is put under AC voltage which makes it possible to vary the potential existing between the central electrode and the base / chamber, this potential being reversible. At each alternation of potential / polarity, the electrons are more and more accelerated in opposite directions. A polarization wave thus propagates oscillatoryly at the frequency of the excitation, recovering at each period the expenses deposited in the previous period. Each alternation then produces a propagation of the wave greater than the preceding one; it is thus possible with the candle of the invention thus fed to obtain relatively large spark amplitudes with voltages between electrode and relatively large cap. The radiofrequency excitation of such a candle makes it possible moreover by avoiding the arcs to suppress the breakdown voltage variations between successive cycles.

On peut par exemple faire en sorte que la surface circulaire extrême du culot soit en appui contre une surface complémentaire d'appui de l'épaulement de la pièce isolante. Cette caractéristique permet de supprimer l'espace entre la pièce isolante et le culot, ainsi la chaleur liée à la présence d'une flamme déclenché par le plasma peut être dissipée vers le culot ce qui évite une surchauffe de la céramique.For example, it is possible for the extreme circular surface of the base to bear against a complementary bearing surface of the shoulder of the insulating part. This feature makes it possible to eliminate the space between the insulating part and the base, so the heat associated with the presence of a flame triggered by the plasma can be dissipated to the base which prevents overheating of the ceramic.

On peut également faire en sorte que la pièce isolante possède une épaisseur minimale située à l'intérieur dudit culot, et l'épaulement de la pièce isolante possède une épaisseur d'épaulement supérieure ou égale à la moitié de ladite épaisseur minimale.It can also be ensured that the insulating part has a minimum thickness located inside said base, and the shoulder of the insulating part has a shoulder thickness greater than or equal to half of said minimum thickness.

Cette caractéristique permet d'éviter que la jonction entre la partie non recouverte de l'électrode centrale et donc la jonction air/céramique/électrode centrale ne soit trop proche du culot. Si cette partie non recouverte de l'électrode ou plus précisément cette jonction se trouvait trop proche du culot elle pourrait constituer une zone d'émission d'étincelle de surface.This feature prevents the junction between the uncovered portion of the central electrode and therefore the air / ceramic / central electrode junction is too close to the base. If this part not covered with the electrode or more precisely this junction was too close to the base it could constitute a surface spark emission zone.

Il est également possible de faire en sorte que le culot, la pièce isolante électriquement, et l'électrode centrale soient des pièces de révolution ayant pour axe de symétrie commun l'axe principal D.It is also possible to make the base, the electrically insulating part, and the electrode central are parts of revolution having as axis of common symmetry the main axis D.

La précision de placement relatif des constituants de la bougie par rapport à un axe de symétrie commun permet de centrer le plasma ramifié autour de cet axe D et de l'électrode centrale, ce qui facilite la localisation de la zone de la chambre de combustion dans laquelle se produisent les étincelles.The relative positioning accuracy of the constituents of the candle with respect to a common axis of symmetry makes it possible to center the branched plasma around this axis D and the central electrode, which facilitates the location of the zone of the combustion chamber in which sparks occur.

On peut également faire en sorte que le culot annulaire ait la forme d'un tube cylindrique comportant à la première extrémité du culot un chanfrein interne venant en contact avec la surface circulaire extrême, ce chanfrein interne étant en contact contre un chanfrein complémentaire formé sur une portion de la pièce isolante.It can also be ensured that the annular base is in the form of a cylindrical tube comprising at the first end of the base an internal chamfer coming into contact with the extreme circular surface, this internal chamfer being in contact with a complementary chamfer formed on a portion of the insulating part.

Cet assemblage de la pièce isolante contre le culot à l'aide de chanfrein complémentaires permet de mieux répartir les contraintes mécaniques existantes entre culot et pièce isolante en réduisant, voir en supprimant complètement les angles vis du culot en contact contre la pièce isolante. Des contraintes mécaniques trop importantes ou mal réparties peuvent conduire à une rupture de la céramique et un endommagement de la bougie. Ainsi cette caractéristique de chanfreins complémentaires l'un de l'autre permet d'augmenter la longévité de la bougie et sa capacité de résistance aux hautes températures et variations de températures.This assembly of the insulating part against the base with the aid of complementary chamfer makes it possible to better distribute the existing mechanical stresses between the base and the insulating part by reducing or even completely eliminating the screw angles of the base in contact against the insulating part. Too great or poorly distributed mechanical stresses can lead to a rupture of the ceramic and a damage of the candle. Thus this characteristic of chamfers complementary to each other increases the longevity of the candle and its ability to withstand high temperatures and temperature variations.

Ce mode de réalisation permet également d'augmenter la surface de contact entre la pièce isolante et le culot ce qui facilite le transfert de chaleur de la pièce isolante vers le culot et permet d'éviter une surchauffe de cette pièce isolante. De façon optimale, afin de répartir les contraintes mécaniques entre la pièce isolante et le culot, le chanfrein interne à une section transversale, selon un plan parallèle à l'axe principal D, de forme arrondie. II est également possible de faire en sorte que l'épaulement annulaire comporte une extrémité distante du culot annulaire à la périphérie extérieure de laquelle est réalisé un chanfrein périphérique arrondi, coaxial par rapport à l'axe principal D. Ce chanfrein périphérique réduit ou supprime la présence d'angle vif, à la périphérie extérieure de la pièce annulaire, au niveau de l'extrémité de l'épaulement annulaire.This embodiment also makes it possible to increase the contact surface between the insulating part and the base, which facilitates the transfer of heat from the insulating part to the base and makes it possible to avoid overheating of this insulating part. Optimally, in order to distribute the mechanical stresses between the insulating part and the base, the inner chamfer has a cross section, in a plane parallel to the main axis D, of rounded shape. It is also possible to ensure that the annular shoulder has an end remote from the annular base at the outer periphery of which is formed a rounded peripheral chamfer, coaxial with the main axis D. This peripheral chamfer reduces or eliminates the presence of sharp angle, at the outer periphery of the annular piece, at the end of the annular shoulder.

D'autres caractéristiques et avantages de 1 ' invention ressortiront clairement de la description qui en est faite ci-après, à titre indicatif et nullement limitatif, en référence aux dessins annexés, dans lesquels : la figure 1 représente une bougie décrite dans les demandes de brevets français FR03-10766, FR03-10767, FR03-10768 déposées par la demanderesse et non encore publiées ; les figures 2A, 2B et 2C représentent des modes de réalisation de la bougie selon l'invention. La bougie 1 de la figure 1 est une bougie développée par la demanderesse pour être utilisée comme bougie de génération de plasma. Cette bougie fait l'objet de demandes de brevets non encore publiées à la date de dépôt de la présente demande . Cette bougie comporte une électrode centrale 7 cylindrique d'axe de symétrie D dont une portion, dite portion interne est disposée à l'intérieur et à distance d'un culot annulaire 3 qui à la forme d'un tube cylindrique d'axe D.Other features and advantages of the invention will emerge clearly from the description which is given below, for information only and in no way limitative, with reference to the accompanying drawings, in which: Figure 1 shows a candle described in the applications for French patents FR03-10766, FR03-10767, FR03-10768 filed by the Applicant and not yet published; Figures 2A, 2B and 2C show embodiments of the candle according to the invention. The candle 1 of Figure 1 is a candle developed by the applicant to be used as plasma generation candle. This candle is the subject of patent applications not yet published at the filing date of this application. This candle comprises a central cylindrical electrode 7 having an axis of symmetry D, a portion of which, said internal portion, is disposed inside and at a distance an annular base 3 which in the form of a cylindrical tube of axis D.

Une pièce isolante de forme annulaire est également disposée en partie à l'intérieur du culot annulaire, autour de l'électrode centrale, de manière à séparer le culot de l'électrode centrale 7. La pièce isolante, l'électrode centrale et le culot 3 sont des pièces de révolution axées selon l'axe D. L'électrode centrale 7 possède une partie non recouverte 16 c'est à dire non entourée par la pièce isolante électriquement 10 et non entourée par le culot 3, cette partie non recouverte 16 étant disposée à l'intérieur de la chambre 2 de combustion du moteur.An insulating piece of annular shape is also arranged partly inside the annular base, around the central electrode, so as to separate the base of the central electrode 7. The insulating part, the central electrode and the base 3 are parts of revolution oriented along the axis D. The central electrode 7 has an uncoated portion 16 that is not surrounded by the electrically insulating piece 10 and not surrounded by the base 3, this uncovered portion 16 being disposed inside the combustion chamber 2 of the engine.

Le culot 3 possède une surface circulaire externe en forme de disque plan perforé en son centre et ayant pour axe de symétrie l'axe D et étant disposé perpendiculairement à cet axe D. Le culot 3 possède une liaison avec la paroi de la chambre 2 qui est généralement un filetage du culot dans un trou pratiqué au travers de la paroi. Le culot de la bougie ainsi assemblée avec la paroi de la chambre 2 est donc à iso potentiel électrique avec cette paroi, c'est à dire à un potentiel électrique de masse.The base 3 has an outer circular surface in the form of a flat disk perforated at its center and having the axis of symmetry axis D and being arranged perpendicular to this axis D. The base 3 has a connection with the wall of the chamber 2 which is usually a thread of the base in a hole made through the wall. The base of the candle thus assembled with the wall of the chamber 2 is at iso electric potential with this wall, that is to say at an electric potential of mass.

Lorsque l'électrode centrale est alimentée en tension alternative centrée autour du potentiel de masse, cette tension étant d'une fréquence comprise entre 1 et lOMhz, les électrons situés à proximité de la pointe 17 de l'électrode centrale se déplacent soit de l'électrode vers les parois de la chambre en passant par le mélange gazeux entourant la chambre, soit du mélange gazeux vers l'électrode. Dans les deux cas, l'alternance électrique est telle qu'un électron n'a pas le temps de passer de l'électrode centrale à la paroi de la chambre. L'air peut être ainsi ionisé sans qu'il n'y ait de réelle décharge électrique entre les deux bornes électriques constituées par l'électrode centrale 7 et par la paroi de la chambre 2. Cette ionisation crée un plasma localisé autour de la pointe 17 de l'électrode centrale qui concentre les charges électriques en mouvement autour d'un faible volume d'échange.When the central electrode is supplied with AC voltage centered around the ground potential, this voltage being of a frequency between 1 and 1 MHz, the electrons located near the tip 17 of the central electrode move either from the electrode to the walls of the chamber through the gaseous mixture surrounding the chamber, or the gas mixture to the electrode. In both cases, the electrical alternation is such that an electron does not have time to go from the central electrode to the wall of the chamber. The air can thus be ionized without there being a real electric discharge between the two electrical terminals constituted by the central electrode 7 and the wall of the chamber 2. This ionization creates a plasma located around the tip 17 of the central electrode which concentrates the electric charges in movement around a small volume of exchange.

Toutefois il a été constaté qu'avec ce type d'électrode, des décharges électriques entre la pointe et le culot peuvent apparaître dans le domaine de fréquence compris entre IMHz et 10MHz. Ces décharges partent du culot annulaire et se propagent le long de la pièce isolante en suivant l'axe de l'électrode centrale. Ce mode d'obtention de l'étincelle n'est pas souhaité car il maintient l'étincelle près de la pièce isolante et favorise ainsi le refroidissement de la flamme ainsi créée.However, it has been found that with this type of electrode, electric discharges between the tip and the base can occur in the frequency range between 1 MHz and 10 MHz. These discharges start from the annular base and propagate along the insulating part along the axis of the central electrode. This method of obtaining the spark is not desired because it keeps the spark near the insulating part and thus promotes the cooling of the flame thus created.

Afin de palier à cet inconvénient, les bougies des types présentés aux figures 2A, 2B, 2C ont été développées .In order to overcome this drawback, the candles of the types shown in FIGS. 2A, 2B, 2C have been developed.

Les bougies de ces figures possèdent l'ensemble des caractéristiques décrites pour la bougie en référence à la figure 1, mais possèdent en outre un épaulement 11 pratiqué sur la pièce isolante 10 et occultant la surface circulaire externe 6 du culot 3.The candles of these figures have all the characteristics described for the candle with reference to Figure 1, but also have a shoulder 11 formed on the insulating part 10 and obscuring the outer circular surface 6 of the base 3.

Cet épaulement 11 augmente la distance, en passant par le mélange gazeux, entre l'électrode et le culot, permettant ainsi d'éviter la création d'arc entre l'électrode centrale 17 et le culot 3.This shoulder 11 increases the distance, passing through the gaseous mixture, between the electrode and the base, thereby avoiding the creation of arcs between the central electrode 17 and the base 3.

Grâce à cette configuration les électrodes des figures 2A, 2B et 2C, une fois disposées avec la pointe à l'intérieur de la chambre 2 et alimentées en courant alternatif par un générateur de haute tension alternative, créent un plasma au niveau de leurs pointes 17. L'épaisseur minimale « e » de la pièce isolante est située à l'intérieur du culot 3 et son épaisseur maximale « E » est au niveau de l'épaulement 11.With this configuration the electrodes of Figures 2A, 2B and 2C, once arranged with the tip to inside the chamber 2 and supplied with alternating current by an alternating high voltage generator, create a plasma at their points 17. The minimum thickness "e" of the insulating part is located inside the base 3 and its maximum thickness "E" is at the shoulder 11.

L'épaulement de la pièce isolante 10 de la figure 2A est un épaulement possédant en section longitudinale des angles droits qui peuvent créer des concentrations de charges et de contraintes mécaniques.The shoulder of the insulating part 10 of Figure 2A is a shoulder having in longitudinal section right angles which can create concentrations of loads and mechanical stresses.

Pour cela, les bougies des figures 2B et 2C possèdent au niveau de la première extrémité 4 de culot 3, un chanfrein interne 13. La pièce isolante 10 possède un chanfrein complémentaire 14 venant en contact contre le chanfrein interne 13. Cette surface de contact importante permet d'évacuer la chaleur de la pièce isolante vers le culot ce qui prolonge la durée de vie moyenne de la bougie. Egalement la bougie selon l'invention de la figure 2C possède un chanfrein périphérique arrondi 15 formé sur l'épaulement annulaire 11, à l'endroit de l'épaulement qui est le plus éloigné axialement du culot 3.For this, the candles of Figures 2B and 2C have at the first end 4 of base 3, an inner bevel 13. The insulating part 10 has a complementary chamfer 14 coming into contact against the inner bevel 13. This important contact surface allows to evacuate the heat of the insulating part towards the base which prolongs the average life of the candle. Also the spark plug according to the invention of FIG. 2C has a rounded peripheral chamfer 15 formed on the annular shoulder 11, at the location of the shoulder which is the furthest axially distant from the base 3.

Cet épaulement permet d'éviter un angle droit au niveau de l'épaulement, sur le chemin passant par le mélange gazeux, entre la pointe 17 et le culot annulaire 3. Cet arrondi réduit le risque de création d'arc.This shoulder makes it possible to avoid a right angle at the shoulder, on the path passing through the gaseous mixture, between the tip 17 and the annular base 3. This rounding reduces the risk of creating an arc.

Le premier et le second matériau conducteur qui sont les matériaux respectifs de l'électrode centrale et du culot 3 sont, selon un mode particulier de l'invention, identiques entre eux. Ces matériaux sont des matériaux métalliques tels que des alliages cuivrés. Selon un mode de réalisation particulier de l'invention, l'extrémité de l'électrode centrale 7 peut être constituée d'une âme en cuivre entourée d'une gaine en nickel .The first and second conductive materials which are the respective materials of the central electrode and the base 3 are, according to a particular embodiment of the invention, identical to each other. These materials are metallic materials such as copper alloys. According to a particular embodiment of the invention, the end of the central electrode 7 may consist of a copper core surrounded by a nickel sheath.

Le matériau d' isolation est préférentiellement une céramique présentant une tension de claquage supérieure à 20Kv/mm. The insulation material is preferably a ceramic having a breakdown voltage greater than 20 Kv / mm.

Claims

REVENDICATIONS 1. Bougie d'allumage (1) , dite plasma à radiofréquence, destinée à équiper une chambre de combustion (2) d'un moteur à combustion interne, et comportant :1. Spark plug (1), called radiofrequency plasma, intended to equip a combustion chamber (2) of an internal combustion engine, and comprising: - un culot annulaire (3) d'axe principal D formé dans un premier matériau conducteur et possédant des première et seconde extrémités (4, 5) , et une surface circulaire extrême (6) d'axe principal de symétrie D située à la première extrémité (4) du culot (3) ;- an annular base (3) of main axis D formed in a first conductive material and having first and second ends (4, 5), and an extreme circular surface (6) of main axis of symmetry D located at the first end (4) of the base (3); - une électrode centrale (7) formée dans un second matériau conducteur, s'étendant le long de l'axe principal D et comportant une portion interne (8) disposée à l'intérieur dudit culot annulaire (3) et une portion externe (9) disposée à l'extérieur dudit culot annulaire (3) , à plus grande proximité de la première extrémité (4) du culot que de la seconde (5) ;a central electrode (7) formed in a second conductive material, extending along the main axis D and having an inner portion (8) disposed inside said annular base (3) and an outer portion (9); ) disposed outside said annular base (3), closer to the first end (4) of the base than the second (5); - une pièce isolante électriquement (10) de forme annulaire s'étendant au moins autour de la portion interne (8) de l'électrode centrale (7) de façon à s'interposer entre le culot (3) et l'électrode (7) , cette pièce isolante (10) ne recouvrant qu'une partie de la portion externe (9) de l'électrode centrale (7) de façon à ce que la partie de la portion externe non recouverte (16) soit en contact avec un mélange gazeux environnant la bougie ; caractérisée en ce que la pièce isolante (10) possède un épaulement annulaire (11) occultant toute la surface circulaire extrême (6) du culot par rapport à la partie non recouverte (16) de l'électrode (7) . an annular electrically insulating piece (10) extending at least around the inner portion (8) of the central electrode (7) so as to be interposed between the base (3) and the electrode (7); ), this insulating piece (10) covering only a portion of the outer portion (9) of the central electrode (7) so that the portion of the outer portion not covered (16) is in contact with a gaseous mixture surrounding the candle; characterized in that the insulating piece (10) has an annular shoulder (11) obscuring the entire extreme circular surface (6) of the base relative to the uncoated portion (16) of the electrode (7). 2. Bougie (1) selon la revendication 1, caractérisée en ce que la surface circulaire extrême (6) du culot est en appui contre une surface complémentaire d'appui (12) de l'épaulement (11) de la pièce isolante (10) .2. Spark plug (1) according to claim 1, characterized in that the end circular surface (6) of the base is in abutment against a complementary bearing surface (12) of the shoulder (11) of the insulating piece (10). ). 3. Bougie (1) selon l'une quelconque des revendications 1 ou 2, caractérisée en ce que la pièce isolante (10) possède une épaisseur minimale (e) située à l'intérieur dudit culot (3) , et l'épaulement (11) de la pièce isolante (10) possède une épaisseur d' épaulement (E) supérieure ou égale à la moitié de ladite épaisseur minimale (e) .3. Spark plug (1) according to any one of claims 1 or 2, characterized in that the insulating part (10) has a minimum thickness (e) located inside said base (3), and the shoulder ( 11) of the insulating piece (10) has a shoulder thickness (E) greater than or equal to half of said minimum thickness (e). 4. Bougie (1) selon l'une quelconque des revendications 1 à 3, caractérisée en ce que la surface circulaire extrême (6) a la forme d'un disque plan percé en son centre.4. Spark plug (1) according to any one of claims 1 to 3, characterized in that the extreme circular surface (6) has the shape of a flat disk pierced at its center. 5. Bougie (1) selon l'une quelconque des revendications 1 à 4, caractérisée en ce que le culot (1) , la pièce isolante électriquement (10) , et l'électrode centrale (7) sont des pièces de révolution ayant pour axe de symétrie commun l'axe principal D.5. Spark plug (1) according to any one of claims 1 to 4, characterized in that the base (1), the electrically insulating part (10), and the central electrode (7) are parts of revolution having for common axis of symmetry the main axis D. 6. Bougie (1) selon la revendication 5, caractérisée en ce que le culot annulaire (3) a la forme d'un tube cylindrique comportant à la première extrémité (4) du culot un chanfrein interne (13) venant en contact avec la surface circulaire extrême (6) , ce chanfrein interne (13) étant en contact contre un chanfrein complémentaire (14) formé sur une portion de la pièce isolante (10) . 6. Spark plug (1) according to claim 5, characterized in that the annular base (3) has the shape of a cylindrical tube having at the first end (4) of the base an internal chamfer (13) coming into contact with the extreme circular surface (6), this inner bevel (13) being in contact against a complementary chamfer (14) formed on a portion of the insulating part (10). 7. Bougie (1) selon la revendication 6, caractérisée en ce que le chanfrein interne (13) à une section transversale, selon un plan parallèle à l'axe principal D, de forme arrondie.7. Spark plug (1) according to claim 6, characterized in that the internal chamfer (13) has a cross section, in a plane parallel to the main axis D, of rounded shape. 8. Bougie (1) selon l'une quelconque des revendications 5 à 7, caractérisée en ce que l'épaulement annulaire (11) comporte une extrémité distante du culot annulaire à la périphérie extérieure de laquelle est réalisé un chanfrein périphérique arrondi (15) , coaxial par rapport à l'axe principal D.8. Spark plug (1) according to any one of claims 5 to 7, characterized in that the annular shoulder (11) has an end remote from the annular base at the outer periphery of which is formed a rounded peripheral chamfer (15). , coaxial with respect to the main axis D. 9. Bougie (1) selon l'une quelconque des revendications 1 à 8, caractérisée en ce que la partie non recouverte (16) de l'électrode comporte une pointe (17) .9. Candle (1) according to any one of claims 1 to 8, characterized in that the uncoated portion (16) of the electrode comprises a tip (17). 10. Bougie (1) selon l'une quelconque des revendications 1 a 9, caractérisée en ce que la pièce isolante est en céramique. 10. Spark plug (1) according to any one of claims 1 to 9, characterized in that the insulating part is ceramic.
EP05815563A 2004-11-16 2005-10-27 Radiofrequency plasma spark plug Expired - Lifetime EP1815570B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PL05815563T PL1815570T3 (en) 2004-11-16 2005-10-27 Radiofrequency plasma spark plug

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR0412153A FR2878086B1 (en) 2004-11-16 2004-11-16 PLASMA RADIOFREQUENCY CANDLE
PCT/FR2005/050909 WO2006054009A1 (en) 2004-11-16 2005-10-27 Radiofrequency plasma spark plug

Publications (2)

Publication Number Publication Date
EP1815570A1 true EP1815570A1 (en) 2007-08-08
EP1815570B1 EP1815570B1 (en) 2010-03-31

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EP05815563A Expired - Lifetime EP1815570B1 (en) 2004-11-16 2005-10-27 Radiofrequency plasma spark plug

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US (1) US7741761B2 (en)
EP (1) EP1815570B1 (en)
JP (1) JP5062629B2 (en)
KR (1) KR101110436B1 (en)
CN (1) CN101057379B (en)
AT (1) ATE463062T1 (en)
DE (1) DE602005020345D1 (en)
ES (1) ES2343362T3 (en)
FR (1) FR2878086B1 (en)
PL (1) PL1815570T3 (en)
RU (1) RU2352041C1 (en)
WO (1) WO2006054009A1 (en)

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Also Published As

Publication number Publication date
US7741761B2 (en) 2010-06-22
CN101057379A (en) 2007-10-17
FR2878086B1 (en) 2007-03-09
KR101110436B1 (en) 2012-02-15
CN101057379B (en) 2012-04-25
JP2008521164A (en) 2008-06-19
JP5062629B2 (en) 2012-10-31
ATE463062T1 (en) 2010-04-15
DE602005020345D1 (en) 2010-05-12
FR2878086A1 (en) 2006-05-19
PL1815570T3 (en) 2010-08-31
RU2352041C1 (en) 2009-04-10
US20090146542A1 (en) 2009-06-11
EP1815570B1 (en) 2010-03-31
ES2343362T3 (en) 2010-07-29
RU2007122515A (en) 2008-12-27
WO2006054009A1 (en) 2006-05-26
KR20070085431A (en) 2007-08-27

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