EP3560049A1

EP3560049A1 - Spark plug with electrode-shuttle

Info

Publication number: EP3560049A1
Application number: EP17825896.8A
Authority: EP
Inventors: Vianney Rabhi
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-12-09
Filing date: 2017-12-07
Publication date: 2019-10-30
Anticipated expiration: 2037-12-07
Also published as: CN110168825A; AU2017371533A1; CA3046393A1; CN110168825B; WO2018104681A1; KR20190091332A; JP7132923B2; JP2020501323A; ES2858457T3; FR3060222B1; FR3060222A1; AU2017371533B2; KR102588000B1; EP3560049B1

Abstract

The spark plug with electrode-shuttle (1) is intended for an internal combustion engine which has a combustion chamber (11) in which a main charge diluted with a neutral gas is ignited (12), said spark plug (1) including a stratification cavity (15) into which a central electrode (6) projects and in which a stratification injector (17) can inject, under pressure, a pilot charge consisting of an easily flammable oxidiser-fuel AF mixture, said cavity (15) being connected to the combustion chamber (11) by a stratification duct (16) while an electrode-shuttle (20) is located between the central electrode (6) and an earth electrode (7) and can move in translation in the stratification duct (16).

Description

ELECTRODE-NAVETTE IGNITION CANDLE

The subject of the present invention is a spark plug with a shuttle electrode which makes it possible to ignite a main charge introduced into the combustion chamber of an internal combustion engine either by means of a spark alone or by means of a a pilot charge known per se and ignited by a spark, said spark plug being designed to optimize the efficiency of said pilot charge to ignite said main charge. The maximum and average efficiency of reciprocating internal combustion engines according to the state of the art is relatively low. In automobiles, the maximum efficiency is of the order of thirty-five percent for Otto-cycle spark ignition engines, and of the order of forty percent for Diesel cycle engines. With regard to the average efficiency in current use of automobile engines, it is most often less than twenty percent for spark ignition engines, and twenty-five percent for diesel engines.

In said engines, the fraction of the energy released by the combustion of the fuel and which is not transformed into useful work is mainly dissipated in the form of heat in the cooling system and the exhaust of said engines.

In addition to poor performance, alternative internal combustion engines used in automobiles produce polluting gases and particles that are harmful to the environment and to health.

Despite these unhelpful features, for lack of other solutions offering a better energy, environmental, functional, and economical compromise, Otto or Diesel internal cycle combustion engines equip almost all the motor vehicles in circulation in the world. world.

This situation explains the significant research and development efforts made by the engine manufacturers to improve by all means the energy and environmental balance of internal combustion engines. These efforts are aimed in particular at perfecting the technologies that constitute said engines, and adding to these new features that allow the implementation of new strategies.

Among these strategies is the dilution of the air and fuel load of the reciprocating internal combustion engines with either a neutral gas or fresh air rich in oxygen.

It is to this dilution that the present invention is addressed which is particularly intended for internal combustion engines with spark-ignition internal combustion that most often consume either gasoline or natural gas. Diluting the charge of spark ignition engines with fresh air or with previously cooled exhaust gas can increase the efficiency average and / or maximum thermodynamics of said engines. The result is reduced fuel consumption at the same job.

When spark ignition engines operate in partial torque, introducing a dilute load into their cylinder (s) produces less pumped losses than introducing an undiluted charge. The reduction of said losses results from the fact that the diluted load is larger with the same energy content. Thus, to introduce the same amount of energy in said cylinder (s), the throttling at the intake of said engines usually performed by means of a throttle is less pronounced, and the pressure of the gases that occur at said admission is higher.

In addition, the same energy introduced into the cylinder (s) of spark ignition engines, dilute the load increases the mass and the total heat capacity of the latter. Thus, all things being equal, the combustion of said charge takes place at a lower temperature. In addition to reducing the amount of nitrogen oxides produced by the combustion, said low temperature reduces heat losses to the walls of the cylinder (s) resulting from the transfer by said load of a portion of its heat to said walls. Finally, particularly if the feedstock is diluted with a neutral gas that is low in oxygen or even free of oxygen, the said feedstock is less sensitive to the uncontrolled self-ignition of the air-fuel mixture. This self-ignition is responsible for rattling, an undesirable phenomenon characterized by a detonating combustion that deteriorates the efficiency of spark ignition engines and damages the mechanical components that constitute them. The desensitization to rattling that provides the dilution of the load allows said engines to either operate at higher compression ratio, or to operate with ignition that is triggered at the most favorable time possible performance, or both.

In this particular context of diluted air and fuel charges, there are spark ignition engines operating stoichiometry of said engines operating in excess air also called "lean".

The engines operating with stoichiometry are only compatible with a three-way catalyst, a device known per se that post-processes the pollutants resulting from combustion. Said catalyst is responsible for burning hydrocarbons that have not been burned in the combustion chamber of the engine. The products of this combustion are water vapor and carbon dioxide already present in the atmosphere. Said three-way catalyst also finalizes the oxidation of notoriously polluting carbon monoxide to also convert it to carbon dioxide, and reduces the nitrogen oxides to convert them into atmospheric dinitrogen which constitutes about seventy-eight percent of the carbon dioxide. terrestrial atmosphere, and which is by nature non-polluting.

The reduction of nitrogen oxides by three-way catalysis requires that the charge introduced into the engine be stoichiometric, that is to say that it contains the right amount of oxygen necessary for the combustion of hydrocarbons contained in said charge. An excess of oxygen makes it impossible to reduce the oxides of nitrogen by the three-way catalyst. It is therefore not possible to post-treat the nitrogen oxides contained in the exhaust gases of the engines operating in excess of air by means of a three-way catalyst. This explains why - in response to ever more stringent environmental regulations - engines operating in excess of air now receive a device specifically designed to reduce nitrogen oxides such as a nitrogen oxide trap or a catalytic reduction device selective oxides of nitrogen to urea. This apparatus is generally placed at the outlet of a two-way oxidation catalyst which has previously burned unburnt hydrocarbons and which has completed the oxidation of carbon monoxide, and more and more often, of a particulate filter.

Diesel engines operating naturally in excess of air, since the entry into force of the Euro VI standard in Europe, almost all European diesel cars are equipped with a device that post-processes nitrogen oxides to transform them in dinitrogen.

The problem of these devices is that they are expensive, complex, and that their size and maintenance requirements are high to the point that said devices are almost used only on diesel engines that can in practice operate only in excess of 'air.

As far as spark ignition engines are concerned, engine manufacturers strive by all means to make them work with stoichiometry so that they remain compatible with a three-way catalytic converter which is simply and inexpensively.

To benefit from the reduction in fuel consumption induced by the dilution of the charge of spark-ignition engines without having to suffer the particular economic drawbacks of a nitrogen oxide trap or a selective catalytic reduction device for oxides from nitrogen to urea, it is therefore necessary to dilute said charge of said engines not with air rich in oxygen, but with a neutral gas devoid of oxygen.

This latter gas is usually provided by the recycling of the exhaust gas of the engine itself, said gases no longer containing oxygen and being available and abundant. This strategy is known under the name of "recirculation of exhaust gas" and more precisely under the acronym "EGR" for "Exhaust Gas Recirculation".

Said gas exiting at high temperature at the exhaust of the spark ignition engine, to prevent them from overheating the load introduced into said engine, it is necessary to reduce the temperature before mixing with the fresh gas.

This strategy is known as the Anglo-Saxon "Cooled EGR", which specifies that the recirculated exhaust gas is cooled prior to mixing with the fresh gas admitted by said engine. The French engine manufacturers finally use the term "franglais" of "cooled EGR", easily understandable and easy to use. Prior cooling of the EGR gases is required for at least two purposes.

First, it is necessary that the temperature of the gas-EGR / gas-fresh mixture admitted by the spark ignition engine remains low so that the volumetric efficiency of said engine remains high when operating at full torque. Indeed, for a given intake pressure, the mass of said mixture introduced into the cylinder (s) of said engine is all the more important that said mixture is cold. Prior cooling of the EGR gas is made even more essential if said engine is supercharged by a turbocharger or by any other means.

Second, the hotter the gas-EGR / gas-fresh mixture, the more it favors the occurrence of rattling which is unfavorable to the performance of said engine.

The problem is that the diluted charge to the cooled EGR is low in oxygen. This is paradoxical since it is also the aim sought in particular for the charge to remain stoichiometric and resistant to rattling. This oxygen depletion results in a combustion initiation that is more difficult to obtain and a slower combustion development than when said charge is undiluted at the cooled EGR. In a spark ignition engine, the initialization of the combustion occurs by creating a high temperature electric arc between two electrodes distant from each other by a few tenths of a millimeter.

When the air-fuel charge is heavily diluted with cooled EGR, the electric arc passes through a globally poor mixture of oxygen and fuel. The risk of a misfire increases if, by accident, the space of a few tenths of a millimeter separating the cathode from the anode of the spark plug does not contain a gas-EGR / gas-charge mixture sufficiently burnable because indeed heterogeneities are inevitably created in the three-dimensional space of the combustion chamber, with pockets richer in oxygen and / or fuel than others.

If combustion is initiated as desired, the fuel energy in the charge begins to release as heat and the flame begins to expand. For this, by successive approaches, said flame communicates its heat to the surrounding gas-EGR / gas-fresh mixture, burnable layer after burnable layer. Each layer is brought to its ignition temperature by the previous layer, burns, and releases heat that it communicates to the next layer and so on. According to the principle of the chain reaction, the flame propagates in the three-dimensional space of the combustion chamber of the spark ignition engine.

The main problem of cooled EGR is that it makes the initialization of combustion difficult, and then considerably slows the development of the latter both because of the overall reduction of its temperature, and because of the heterogeneities of oxidant and / or fuel found in the volume of the combustion chamber and therefore, on the path of the flame. Moreover, it is found experimentally that the higher the cooled EGR charge content, the more unstable the engine becomes. From a certain content, misfires occur and the efficiency - which hitherto tended to increase with the cooled EGR content of the charge - decreases. Beyond a certain content of said EGR, the spark ignition engine stops, the combustion is unable to initialize.

Note also that the content of the exhaust gas in unburned hydrocarbons and carbon monoxide increases in parallel with the cooled EGR content of the load. This is due to both pockets of mixture too poor to burn properly encountered by the flame on its path, and the thickening of the boundary layer flame jam near the cold internal walls of the combustion chamber of the engine.

Still experimentally, it is also found that the higher the ignition power is, the more it is possible to increase the cooled EGR content of the load without greatly altering the stability of the engine.

As such, many research laboratories - such as the South West Research Institute in the United States - have developed increasingly powerful electric ignition devices to push back the accessible limits of cooled EGR content in the United States. load. The purpose of this strategy is of course to improve the efficiency of the spark ignition engine.

The problem of overbidding the power of electric ignitions is that their performance decreases rapidly with their power. Therefore, more electrical power is needed to get less and less additional ignition power.

In addition, high electrical power is of interest only if the electrodes of the candle are moved away from each other to give more chances to the spark to cross a burnable pocket, or while the The duration of the spark is increased, or the spark is repeated. This leads to increasingly higher voltages and electrical powers which make it more difficult to achieve the electrical insulation of the spark plug while drastically reducing the life of the spark plug. The difficulty in igniting the charge also stems from the fact that the cooled EGR is all the more interesting on supercharged spark ignition engines which are sought by all means to reduce the sensitivity to rattling. However, the higher the supercharging pressure, the greater the density of the gas-EGR / gas-fresh mixture is important between the electrodes of the spark plug at the moment of the spark, and more voltage is required to cause said spark.

From this point of view, the cooled EGR does not go in the right direction because at the same energy introduced into the cylinder of the engine, the mass of gas which is between the electrodes increases as well as the resistance of said gas to the ignition. It is noted that the patent No. FR 2 986 564 belonging to the applicant is a robust response to these problems. The spark ignition and high pressure lamination device for an internal combustion engine referred to in said patent proposes to inject under high pressure, in the center of the spark plug and shortly before the triggering of the spark, an approximately stoichiometric pilot charge, highly burnable because undiluted with cooled EGR, and potentially slightly rich in fuel.

Once injected by said device, said pilot charge bathing the electrodes of the candle, as soon as an electric arc is formed between said electrodes, said charge ignites immediately and releases the energy it contains. Thus, said load itself is the ignition means in itself whose power is several hundred to several thousand times greater than that of the electric arc that allowed to ignite. It is practically impossible to obtain such ignition power with electric means alone.

Experience has shown that cooled EGR rates of the order of fifty percent are possible with such a device against of the order of thirty percent only with the single most powerful electric ignition devices that are.

It will be noted that the approach adopted in the patent No. FR 2 986 564 is found in related forms in US Pat. No. 4,319,552 of the inventors Fred N. Sauer and J. Brian Barry, or in the patent No. DE 41 40 962 A1 belonging to the company "Bosch".

In any case, the patent No. US6564770 of the company "Orbital" does not fall into this category because it is according to this patent to ensure at relatively low pressure the constitution of a main load as homogeneous as possible and not to form a pilot charge for ignition of a highly diluted main charge at the EGR.

The problem of the device described by the patent No. FR 2 986 564 and in related patents as they have just been listed is not in the initialization of the combustion which is very efficient, but in the development of said combustion . In particular, when the burned fraction of the fuel contained in the main charge reaches about fifty percent, the combustion hardly progresses so that the total time required to burn the entire main charge is greater than the time required to burn the fuel. whole of an undiluted main charge to the cooled EGR. As a result, part of the potential energy gain of the cooled EGR is lost due to a combustion that develops too slowly.

However, the maximum benefit of the cooled EGR would be found if it were possible to operate a spark ignition engine simultaneously with a main charge whose cooled EGR content is of the order of fifty percent on the one hand , and with a stability and a total combustion time comparable to those found on the same said engine when the latter burns an undiluted charge on the other hand.

The solution could come from the use of a prechamber into which the pilot charge would be introduced, said prechamber being able to house the electrodes of the spark plug and even to be an integral part of said spark plug as proposed in US Pat. No. 4,319,552. The first advantage of such a prechamber is that it potentially maintains the pilot charge as close as possible to the electrodes of the spark plug, which can limit the dispersion of said charge in the main combustion chamber of the spark ignition engine before the fire of said charge.

The second advantage of said antechamber is that once ignited, the pilot charge pressurizes said prechamber which sends hot gas torches at high speed in the main combustion chamber of the spark ignition engine via orifices that includes said prechamber.

This firing of the main charge by means of torches is very effective because instead of starting from the center of the combustion chamber as is the case with an ordinary spark plug, the flame is initialized in multiple places of the combustion chamber, and develops radially from the periphery of the chamber to the center of the chamber, and tangentially between each torch.

The fuel energy is released in a very short time, which is favorable to the thermodynamic efficiency of the spark ignition engine because not only the relaxation is more productive in work, but the slightest sensitivity to rattling that results from a Such rapid combustion makes it possible to operate the engine with a significantly higher volumetric ratio.

In any event, the patent US Pat. No. 4,319,552 or the solution proposed in patent FR 2,986,564 belonging to the applicant or in the related patents previously mentioned can not be compared to the multitude of patents which inject fuel alone into a prechamber or not, and not a mixture of air and fuel.

Among these patents, mention will be made, for example, of those known under No. GB 2 31 1 327 A of "Fluid Research Limited", No. US 4,864,989 to "Tice Technology Corp.", No. 4,124,000 of "General Motors", No. 4,239,023 to "Ford Motor Company", US 4,892,070 inventor Dieter Kuhnert, No. US 2001/0050069 A1 inventors Radu Oprea and Edward Rakosi, or patent US 2012/0103302 A1 of the inventor William Attard on the principle of which is based the ignition system "Turbulent Jet Ignition" developed by the German company "Mahle" for engines of Formula 1.

There is indeed a fundamental difference between the solutions disclosed in these patents which are intended for so-called "lean-burn" spark ignition engines whose sole purpose is to enrich the fuel charge around the point of ignition. ignition on the grounds that the load as a whole is low in fuel but rich in oxygen, and the solutions set forth in patent FR 2 986 564 and related patents, which are mainly directed to positive-ignition engines operating with a heavy load. diluted with cooled EGR, which is intended to provide a fuel-rich AND oxygen-rich mixture around the ignition point, on the grounds that the fuel as a whole is low in fuel AND oxygen. At this stage, it has been seen that injecting a highly burnable pilot charge consisting of air and fuel to envelop the electrodes of the spark plug with said charge as proposed in patent No. FR 2 986 564 makes it possible to effectively light a charge. principal strongly diluted with EGR.

It has also been seen that once the main charge has been ignited, the combustion proceeds rapidly until about fifty percent of the total quantity of fuel contained in the charge has been burned. Beyond the so-called fifty percent, the combustion develops more slowly, so that from a certain EGR content of the main charge, the thermodynamic efficiency of the spark-ignition engine decreases instead of increasing as expected. .

It has been assumed that if - as proposed in US Pat. No. 4,319,552 - the pilot charge is injected into a prechamber in which the electrodes of the candle are housed, the latter problem of combustion development beyond fifty percent. would be fully or partially resolved.

In fact, said prechamber would eject through its orifices flares of hot gas with a high speed that both initialize the combustion over a great radial length around the ignition point, but also, would squint the flame front which would favor the development of the flame perpendicular to said torches.

However, this last solution is not fully satisfactory for a large number of reasons, some of which have led to abandon ignition devices based on a prechamber, particularly in the context of spark ignition engines.

Indeed, to be effective, the prechamber must have a sufficiently protruding dome so that the holes through which the hot gases are ejected to form torches do not lick the cold internal walls of the engine. By passing at high speed through said holes, said gases heat said dome which - from a certain temperature - behaves like a "hot ball" like the ignition system of the internal combustion engine invented by Stuart Herbert -Akroyd and described in the patent CHD4226 of December 4, 1891. Such a hot spot then potentially leads to inadvertent ignitions of the non-spark-controlled main charge. The rattling that may follow is likely to damage or even destroy the spark ignition engine.

One solution may be to intensively cool said dome to prevent it from constituting a hot spot. However, the resulting heat export is to the detriment of the efficiency of hot gas torches whose temperature and velocity are reduced when they pass through the holes in said dome, and on the other hand, the thermodynamic efficiency of the spark ignition engine.

In other words, either the dome is too hot or too cold and most importantly, the ignition of the main load becomes too dependent on the prechamber and the pilot load. This dependency is a handicap when the spark ignition engine requires little or no dilution of its main charge with EGR, which occurs in many cases. Indeed, the constitution of an air-fuel pilot load carried at high pressure is not energy free. It must first compress air, which requires a compressor driven by the spark ignition engine itself, and then inject fuel into said air. Another strategy may consist in directly compressing an air-fuel mixture previously constituted.

Note that because of its non-negligible energy cost, with same ignition efficiency, the smaller the mass of the pilot load compared to that of the main load, the better the final energy balance of the spark ignition engine when it operates under a high rate of EGR. It is therefore necessary to do everything possible to give the pilot load a specific efficiency to turn on the largest possible main load, relative to the mass of said pilot load. In other words, at the same ignition efficiency, the pilot load must lead to the compression of the smallest amount of air-fuel mixture possible, under the lowest pressure possible.

However, the energy expenditure related to the compression of the pilot load is not always justified, especially when the main load is little or not diluted at the EGR. However, at partial loads - which characterize the operation of a motor vehicle in the majority of its time of use - pumping losses can be reduced by means of a flexible control of the intake valves. At partial loads, this strategy known as the Anglo-Saxon variable valve actuation advantageously replaces the EGR and leads to spark ignition engine yields similar to those allowed by said EGR without having to resort to a load Expensive pilot in energy. High loads under strong turbocharging may also be another case where the pilot load is not needed.

Indeed, the EGR increases the boost pressure required at the same energy introduced into the cylinder (s) of the spark ignition engine. At very high loads and while the load of said engine is diluted with the EGR, to obtain the desired power for the spark ignition engine, the supercharger must provide more work than if the load was not diluted. Beyond a certain rate of EGR, the turbine placed at the exhaust of the engine no longer has enough power to drive said compressor. The rate of accessible EGR is so limited that the pilot load is no longer needed to ensure the initialization and development of combustion.

In sum, the ideal situation would be to ignite the main charge by means of a conventional spark plug when said charge is little or not diluted to the EGR, and by means of a pilot charge ignition device if possible. with prechamber when said charge is highly diluted with EGR. A second candle could eventually overcome this need. However, it is almost impossible to accommodate said second spark plug in the cylinder head of a modern automobile engine equipped with four valves per cylinder and an injector that opens directly into the combustion chamber.

So, if one wanted to benefit at the same time from the advantages of first part, of a prechamber such as described for example in the patent US 4,319,552 when one resorts to an injection of pilot charge according to the principles stated in the patent FR 2 986 564 and secondly, a conventional ignition with a conventional spark plug, it should be possible to retract said prechamber when operates the conventional spark plug and vice versa.

In addition, when the prechamber is used, the prechamber should not behave like a "hot-ball" ignition device as previously mentioned or at least that the initialization of the combustion of the main charge is well triggered at the time chosen, and not undergone at an uncontrolled time.

This involves cooling the hot parts of the prechamber capable of triggering a self-ignition without decreasing the efficiency of said prechamber to diffuse hot gas torches into the three-dimensional space of the combustion chamber of the engine that contains the main charge.

However, insofar as modern supercharged engines almost always receive a direct fuel injection, the adoption of a prechamber in which are housed the electrodes of the spark plug for the purpose of igniting a pilot load is almost impossible. if you want with the same means to turn on the main charge without resorting to the pilot load.

Indeed, greatly dilute the charge cooled EGR is very advantageous on this type of engines. However, the electrodes of the spark plug engines supercharged direct injection must be protruding so that the highly burnable fuel mixture formed by the fuel injector bathing said electrodes. Now, if said electrodes are inside a pre-chamber provided with holes, this condition is not fulfilled and the initialization of the combustion can no longer be guaranteed. To circumvent this problem, it would always be necessary to resort to ignition by pilot charge whose energy cost is not marginal.

The difficulty of reaching the electrodes of the spark plug with the fuel mixture if said electrodes are housed in a prechamber is particularly addressed for example in the patent No. EP 1 464 804 A1 of the company "Peugeot Citroën Automobiles" in which is claimed a direct injection pressure important to promote the penetration of a portion of the air-fuel mixture inside the prechamber via the orifices passing through the wall of said prechamber. Moreover, the latter patent inherits the principles of the patent No. EP 1 41 1 221 A2 of the same applicant in which is implicitly addressed the effect of "hot ball" potentially produced by the antechamber and dreaded by motorists for its triggering effect of rattling.

Indeed, in claim No. 10 of said patent, it is proposed to make the wall of the prechamber with an alloy having a thermal conductivity at 20 ° C of at least 10W / K / m and preferably at least 30W / K m. It is understood that this feature is sought so that the wall of the antechamber is cooled as quickly as possible to avoid the effect of "hot ball". In claim 13 of the same patent, it is also found that the walls and orifices of the antechamber can be coated with a refractory material, this being indicative of the need to keep a material also hot enough not to reduce too much. temperature of hot gas torches, and to avoid excessive heat export to the cold parts of the engine. However, such a refractory material would not fail to promote the "hot ball" effect, which is unacceptable.

It is also readily understood that the potential problems disclosed in the aforementioned patents EP 1 464 804 A1 and EP 1 41 1 221 A2 are found in a different form in many patents which describe candles. ignition in which is arranged a prechamber. Among these patents, it will be noted that known under the number DE 0 675 272 A1 and its variant WO 03/071644 A1, and those published under the numbers EP 1 143 126 A2 or EP 1 701 419 A1.

It will be noted that the idea of producing candles with an integrated prechamber is old, as attested by the patent US Pat. No. 2,047,575 of July 14, 1936.

Moreover, the candles exhibited in these patents have a prechamber that is "passive" which consists of a simple cap with orifices. This type of prechamber is mainly used in engines operating at steady state. Indeed, the section of the orifices of said prechamber are provided so that a sufficient differential pressure is obtained at the time of ignition of the load fraction contained in the antechamber so that the hot gas torches reach an ejection speed sufficient through said orifices. The problem is that if the prechamber empties via said orifices, it also fills via the same orifices. Consequently, the use of such spark plugs results from a precise balance between the section of the holes and the speed of rotation of the engine. This helps to explain why this type of spark plug is not used in cars where the spark ignition engine speed varies constantly.

In addition to the problems posed by the high temperature of the prechamber and its filling and emptying, it should be noted that in the particular context of the injection of a pilot charge consisting of a mixture of air and fuel as proposed in Patent No. FR 2 986 564 also raises the problem of the dispersion of said pilot charge in the main charge, before the firing of said pilot charge. Any such dispersion reduces the specific efficiency of the pilot charge to ignite the main charge. This can only be compensated by increasing the mass of said pilot load which is done to the detriment of the final energy efficiency of the spark ignition engine.

The problem arises from the fact that the injector which introduces the pilot charge into the main charge needs time to inject said pilot charge under a pressure necessarily greater than that of the main charge.

It should also be noted that the injection pressure of the pilot charge remains approximately constant while the pressure of the main charge increases as a result of its compression following the raising of the piston of the spark ignition engine towards its top dead center. . The beginning of the injection of the pilot load therefore takes place under a differential pressure greater than the end of said injection. As a result, the ejection speed of the gases constituting the pilot charge is greater at the beginning of the injection than at the end of the injection.

Except for having an antechamber of large volume which is not possible, part of the pilot load will inexorably go out through the orifices of the prechamber and mix with the main charge which has a high EGR content. The mixture between pilot and main charge will be particularly pronounced at the beginning of the injection. The flammability of the mixture thus constituted of air, fuel and EGR will therefore necessarily be heterogeneous in the volume of the prechamber and out of the prechamber. The efficiency of the pilot charge to ignite as quickly as possible will be reduced as well as the effectiveness of the flaming gas torches to ignite the main charge. This decrease in efficiency can only be offset by an increase in the air and fuel mass of the pilot load, this to the detriment of the overall energy efficiency of the spark ignition engine.

Ideally, it should therefore be avoided by any means to disperse the pilot charge in the main charge before the ignition of said pilot charge.

Always ideally and as we have seen previously, it would be necessary to inject the air-fuel pilot charge in a pre-chamber only when the spark ignition engine operates under a high rate of EGR whereas when said engine operates only under low EGR even no, a conventional spark plug would be used to ignite the main charge.

This would always be in line with the objective - the engine operating at a high rate of cooled EGR - to limit the mass of the pilot load as much as possible in order to minimize the energy cost of compression, and to increase efficiency as much as possible. said pilot charge to turn on the main charge.

When only a conventional spark plug is used to ignite the main charge it would be - ideally - that the prechamber disappear so that it can not behave in any way like a "hot ball".

Ultimately, it would be very advantageous to confer the device described by the patent FR 2 986 564 which has proved effective to initiate combustion in very strong cooled EGR rate and develop said combustion until a fraction of about fifty percent of the fuel contained in the main charge is burned, the ability to develop said combustion very rapidly until a fraction of at least ninety or one hundred percent of said fuel is burned.

This could be achieved by means of a prechamber as suggested by US Pat. No. 4,319,552, but with the sole condition of circumventing the usual crippling defects of said prechamber, and significantly improving its efficiency. All of these objectives are addressed by the spark plug-electrode shuttle according to the invention which - according to a particular embodiment - allows:

• To benefit from a single spark plug the advantages of a prechamber in which is injected then fired a pilot charge to ignite a main charge by means of hot gas torches, and advantages of protruding electrodes not enclosed in a prechamber, compatible with the direct injection of gasoline, and for directly igniting the main charge by means of an electric arc formed between said electrodes; · To prevent the prechamber from generating any hot spot that may cause the unintentional self-ignition of the main charge;

• To minimize the mass of the pilot charge necessary not only to initialize the combustion of highly diluted main charges at the EGR, but also to ensure a rapid development of said combustion until all of said main charges are burned.

• In the latter objective, to avoid the dispersion of the pilot load in the main load during the injection of said pilot load in said main load.

To achieve these objectives, the spark plug with shuttle electrode according to the invention provides:

• Retract the prechamber when it is useless, said prechamber then being replaced by protruding electrodes;

• The antechamber being retracted, to actively cool the surface of said antechamber exposed to hot gases, between two combustion cycles; · Keep the prechamber closed during most of the injection time of the pilot load which is carried out in an enclosed space in which the gases of the pilot charge can not mix with the gases of the main charge.

It should be noted that the spark plug with a shuttle electrode according to the invention does not involve significantly increasing the electrical voltage across said spark plug to cause the ignition spark, said voltage remaining in the vicinity of the voltages usually retained. for ordinary spark plugs. Said spark plug electrode shuttle is expected inexpensive to manufacture in large series to remain compatible with the economic constraints of most applications for which it is intended, including automobiles. In addition, the life of said spark plug is assumed to be similar to that of a conventional spark plug.

It is understood that the shuttle electrode spark plug according to the invention can be applied to any internal combustion spark ignition engine of any type, whatever the gas, liquid or solid fuel that it consumes, and its main charge is diluted with EGR cooled or not, with a neutral gas of any kind whatsoever, or with a gas rich in oxygen or any other oxidant.

It is also understood that the pilot charge that the pre-chamber of the shuttle electrode spark plug according to the invention receives may contain a fuel and / or an oxidant different from the fuel and / or oxidant which constitutes the main charge of the engine with controlled ignition.

The spark plug ignition electrode according to the present invention is provided for an internal combustion engine which comprises at least one cylinder in which can translate a piston to form - with a cylinder head - a combustion chamber in which can be set fire a main charge the latter consisting of a fuel-fuel mixture on the one hand, and being more or less diluted with air rich in oxygen or with a neutral gas on the other hand, said internal combustion engine also comprising a intake duct and an exhaust duct opening into said chamber.

The spark plug ignition electrode according to the present invention comprises at least electrodes and a ceramic insulator housed in a metal base which has a base thread, and at least one central electrode, and at least one ground electrode, said candle also receiving a lamination cavity connected to the combustion chamber that the internal combustion engine comprises by a lamination duct while a lamination injector can directly or indirectly inject into said cavity a pilot load previously pressurized, said charge consisting of a fuel-burning AF-fuel mixture that is highly flammable by means of a spark, said shuttle-electrode ignition plug comprising according to the invention:

At least one central electrode which opens into the lamination cavity;

At least one shuttle electrode which is wholly or partly made of an electrically conductive material and which is partially or entirely housed with a small clearance in the lamination duct, said shuttle electrode interposed between the central electrode and a ground electrode and having firstly, a chamber-side end facing the ground electrode and being exposed to the pressure in the combustion chamber and secondly a cavity-side end facing the central electrode and which is exposed to the pressure prevailing in the lamination cavity, said shuttle electrode being able to translate in said duct under the effect of the pressure of the gases towards the lamination cavity when the pressure prevailing therein is less than the pressure prevailing in the chamber of combustion, either towards the combustion chamber when the pressure in the latter is lower than the pressure in the lamination cavity;

At least one cavity-side shuttle electrode abutment which determines the position of the shuttle electrode closest to the lamination cavity;

• At least one chamber-side shuttle electrode stop that determines the position of the shuttle electrode closest to the combustion chamber. The shuttle electrode spark plug according to the present invention comprises a shuttle electrode which closes all or part of the lamination duct when it is closer to the lamination cavity while it opens said duct on a more large section when positioned closer to the combustion chamber. The shuttle electrode spark plug according to the present invention comprises all or part of the lamination duct which comprises an insulating sleeve consisting of an electrically insulating and / or thermally insulating and / or refractory material, which is integral with said duct, and which is inserted radially and / or axially between the shuttle electrode and said conduit, said shuttle electrode being able to translate inside said sleeve.

The shuttle electrode spark plug according to the present invention comprises an insulating sleeve which comprises at least one longitudinal gas passage channel which allows the gases to pass from the lamination cavity to the combustion chamber or vice versa, said channel being able to be arranged inside and / or internal or external surface of said sleeve.

The shuttle electrode spark plug according to the present invention comprises a shuttle electrode which consists of an insulating shuttle body made of an electrically insulating material, said body being traversed right through in the direction of its length. by a conductive core of which it is integral, said core being made of an electrically conductive material, a first end of said core facing the ground electrode while a second end of said core faces the electrode Central. The shuttle electrode spark plug according to the present invention comprises a cavity-side shuttle-electrode abutment which consists of a shuttle electrode closure seat provided in the lamination duct or any one of ends of said conduit, said seat cooperating with a shuttle electrode sealing flange that has the shuttle electrode in its periphery and / or at its end.

The shuttle electrode spark plug according to the present invention comprises a shuttle electrode sealing seat and a shuttle electrode sealing flange which provide a seal when in contact with one of the other, said sealing preventing any gas from passing at said contact when the pressure in the combustion chamber is greater than the pressure in the lamination cavity. The shuttle electrode spark plug according to the present invention comprises a chamber-side shuttle electrode stop which consists of a shuttle electrode opening seat arranged in the lamination duct or any one of ends of said conduit, or in the metal base, said seat cooperating with a shuttle electrode opening collar that has the shuttle electrode in its periphery and / or at its end.

The shuttle electrode spark plug according to the present invention comprises a shuttle electrode opening seat and a shuttle electrode opening flange which provide a seal when in contact with one of the other so as to prevent any gas from passing at the level of said contact.

The shuttle electrode spark plug according to the present invention comprises a shuttle electrode which has at its periphery guide means which maintain said shuttle electrode approximately centered in the lamination duct, and approximately in the same longitudinal orientation as said conducted and this, regardless of the axial position of said shuttle electrode relative to said conduit. The shuttle electrode spark plug according to the present invention comprises a shuttle electrode which has at least one longitudinal gas passage channel which allows gases to pass from the lamination cavity to the combustion chamber or vice versa, said channel it can be arranged inside and / or on the surface of said shuttle electrode and can be made either over the entire length of said shuttle electrode while the two ends of said channel open respectively at the at the end of the chamber side and at the end of the cavity side, ie only a portion of said length while at least one of said two ends of said channel opens radially from the outer surface of the shuttle electrode .

The shuttle-electrode ignition plug according to the present invention comprises a shuttle electrode closure flange and a shuttle electrode opening flange which commonly form a single shutter-opening flange which defines with the lamination duct - when said shutter-opening flange is in contact with the shuttle-electrode opening seat - a torch prechamber which communicates simultaneously with the lamination cavity on the one hand, and with the combustion chamber via at least one gas ejection port on the other hand. The shuttle electrode spark plug according to the present invention comprises a torch prechamber which is provided inside the insulating sleeve.

The spark plug ignition electrode according to the present invention comprises an insulating sleeve which protrudes from the metal base to have an ejection dome protruding from which opens the gas ejection port. The shuttle-electrode ignition plug according to the present invention comprises a protruding ejection dome which is an insert on the insulating sleeve.

The shuttle electrode spark plug according to the present invention comprises a shuttle electrode opening seat which is arranged in the protruding ejection dome.

The spark plug ignition electrode according to the present invention comprises an inner peripheral wall of the ignition prechamber torch which is cylindrical while the shutter-opening flange is housed at low radial clearance in said prechamber.

The spark plug with a shuttle electrode according to the present invention provides that when the shuttle electrode is positioned close to the combustion chamber, that is to say either in the vicinity or in contact with the chamber-shuttle electrode stop with which it cooperates, the shutter-shuttle electrode flange discovers at least one gas ejection port which connects the lamination cavity with the combustion chamber.

The shuttle electrode spark plug according to the present invention comprises a lamination injector which can directly or indirectly via an injector outlet conduit, inject the pilot charge into the lamination cavity via a chamber. annular pilot charge injection which is arranged either in a threaded candle well in which is screwed the metal base by means of the base threading, or on the outer periphery of said metal base, or both in said well and on said periphery of said base, said annular chamber communicating with the lamination cavity via at least one gas injection channel arranged approximately radially in the metal base.

The shuttle electrode spark plug according to the present invention comprises a lamination cavity which is arranged inside the ceramic insulator.

The description which follows with reference to the appended drawings and given by way of non-limiting examples will make it possible to better understand the invention, the characteristics that it presents, and the advantages that it is likely to provide: FIG. schematic section of the spark plug electrode shuttle according to the invention as it can be installed in the cylinder head of an internal combustion engine.

FIG. 2 is a schematic sectional view of the shuttle-electrode ignition plug according to the invention, the shuttle electrode of which is made of a single piece of electrically conductive material that can translate into an insulating sleeve that comprises the lamination duct, a shuttle electrode sealing seat forming the cavity-side shuttle electrode abutment, while a shuttle-electrode opening seat forms the chamber-side shuttle electrode abutment; two so-called stops cooperating with a shutter-opening collar that presents the shuttle electrode. Figures 3 to 8 are partial close-up views in schematic section of the spark plug electrode shuttle according to the invention and in the particular configuration shown in Figure 2, said close views illustrating various phases of operation of said candle.

FIG. 9 is a three-dimensional view of the shuttle-electrode ignition spark plug according to the invention and according to the alternative embodiment shown in FIG. 2. FIG. 10 is a three-dimensional view in broken longitudinal section of the electrode ignition plug. shuttle according to the invention and according to the embodiment variant shown in FIG.

FIG. 11 is an exploded three-dimensional view of the shuttle electrode spark plug according to the invention and according to the embodiment variant shown in FIG. 2.

FIG. 12 is a schematic sectional view of the shuttle-electrode ignition plug according to the invention, the shuttle electrode of which consists of an insulating shuttle body traversed from one end to the other by its length by a conductive core of which it is integral, the cavity-side shuttle-electrode abutment being constituted by a shuttle electrode sealing seat arranged at the end of the lamination duct, said seat cooperating with a sealing flange of the shuttle electrode that the shuttle electrode has at its end. Figures 13 to 18 are partial close-up views in schematic section of the spark plug electrode shuttle according to the invention and in the particular configuration shown in Figure 12, said close-up views illustrating various phases of operation of said candle. FIG. 19 is a three-dimensional view of the shuttle-electrode ignition plug according to the invention and according to the embodiment variant shown in FIG. 12.

FIG. 20 is a three-dimensional view in broken longitudinal section of the shuttle-electrode ignition plug according to the invention and according to the variant embodiment shown in FIG. 12.

FIG. 21 is an exploded three-dimensional view of the shuttle-electrode spark plug according to the invention and according to the embodiment variant shown in FIG. 12. DESCRIPTION OF THE INVENTION

FIGS. 1 to 21 show the shuttle-electrode spark plug 1, various details of its components, variants and accessories. As illustrated in FIG. 1, the spark plug with a shuttle electrode 1 is provided for an internal combustion engine 2 which comprises at least one cylinder 8 in which a piston 9 can be translated to form - with a cylinder head 10 - a chamber of combustion 1 1 wherein a main charge 12 can be ignited, the latter consisting of an oxidant-fuel mixture on the one hand, and being more or less diluted with an air rich in oxygen or with a neutral gas on the other hand. The internal combustion engine 2 for which the spark plug with shuttle electrode 1 is provided further comprises an intake duct 13 and an exhaust duct 14 opening into the combustion chamber January 1 while said candle 1 comprises a ceramic insulator 3 housed in a metal base 4 which has a base thread 5.

The spark plug with shuttle electrode 1 also comprises at least one central electrode 6 and at least one ground electrode 7 while it also receives a lamination cavity 15 connected to the combustion chamber 11 by a lamination duct 16 while a lamination injector 17 can directly or indirectly inject into said cavity 15 a pilot charge 18 previously pressurized by a lamination compressor 19, said load 18 consisting of an AF fuel-oxidant mixture that is highly flammable by means of a spark.

FIGS. 1 to 21 show that the spark plug with a shuttle electrode 1 differs from the state of the art in that the central electrode 6 opens into the lamination cavity 15.

In addition, FIGS. 1 to 21 illustrate that the shuttle electrode ignition plug 1 comprises a shuttle electrode 20 which is wholly or partly made of an electrically conductive material and which is partially or entirely housed at a low level. play in the lamination duct 16.

It will be noted in FIGS. 1 to 21 that the shuttle electrode 20 is inserted between the central electrode 6 and the ground electrode 7 and has, on the one hand, a chamber-side end 21 which faces the ground electrode. 7 and which is exposed to the pressure prevailing in the combustion chamber 1 1 and secondly, a cavity-side end 22 which faces the central electrode 6 and which is exposed to the pressure prevailing in the lamination cavity 15.

It should be noted that, according to the shuttle-electrode ignition plug 1 according to the invention, the shuttle electrode 20 can translate in the lamination duct 16 under the effect of the pressure of the gases either towards the lamination cavity 15 when the pressure in the latter is lower than the pressure in the combustion chamber 1 1, or towards the combustion chamber January 1 when the pressure in the latter is lower than the pressure in the lamination cavity 15 .

It may be noted that the shuttle electrode 20 can also move in the lamination duct 16 under the effect of gravity or acceleration, which can not be interpreted as any advantage or a desired mode of operation. The shuttle-electrode ignition plug 1 according to the invention further comprises at least one cavity-side shuttle electrode abutment 23 which determines the position of the shuttle-electrode 20 closest to the lamination cavity 15. Finally, said spark plug 1 according to the invention comprises at least one chamber-side shuttle electrode stop 24 which determines the position of the shuttle electrode 20 closest to the combustion chamber 11.

Note that according to a particular embodiment of the spark plug-electrode shuttle 1 according to the invention, the cavity-side shuttle electrode stop 23 and / or the chamber-side shuttle electrode stop 24 can be respectively consisting of the central electrode 6 and / or the ground electrode 7.

Alternatively, the shuttle electrode 20 may comprise means of indexing in rotation along its longitudinal axis which prevent it from rotating along said axis without preventing it from translating into the lamination duct 16. It will be noted that advantageously, the shuttle electrode 20 and / or the lamination duct 16 in which it translates may be coated with an anti-friction material known per se and / or non-adherent and / or refractory.

In addition, the shuttle electrode 20 can be hollow or have lightening means while all types of electrodes known to those skilled in the art can be applied to the central electrode 6, to the ground electrode 7, at the chamber end 21 or at the cavity-side end 22.

According to a particular embodiment of the spark plug with a shuttle electrode 1 according to the invention particularly visible in FIGS. 2 to 21, the shuttle electrode 20 can seal all or part of the lamination duct 16 when it is closest to the lamination cavity 15 while it can open said duct 16 on a wider section when it is positioned closer to the combustion chamber 1 1. As illustrated in Figures 2 to 1 1, all or part of the lamination duct 16 may comprise an insulating sleeve 25 made of an electrically insulating material and / or thermally insulating and / or refractory, which is integral with said duct 16, and which is radially and / or axially interposed between shuttle electrode 20 and said conduit 16, said shuttle electrode 20 being able to translate inside said sleeve 25.

It will be noted that according to a particular embodiment of the spark plug with electrode-shuttle 1 according to the invention, the insulating sleeve 25 may be integral with the ceramic insulator 3 and be arranged in the same piece of material as this latest.

Alternatively, an air gap may be left between at least a portion of the insulating sleeve 25 and the laminating duct 16 so as to limit the heat exchange between said sleeve 25 and said duct 16.

FIGS. 3 to 8 and FIG. 11 show that, as an alternative embodiment of the shuttle-electrode ignition plug 1 according to the invention, the insulating sleeve 25 may comprise at least one longitudinal channel for passing gases. Which allows the gases to pass from the lamination cavity 15 to the combustion chamber 11 or vice versa, said channel 35 being able to be arranged inside and / or on the inner or outer surface of said sleeve 25. FIGS. 12 to 21 show in particular that the shuttle electrode 20 may consist of an insulating shuttle body 26 itself made of an electrically insulating material, said body 26 being traversed right through in the direction of its length by a conductive core 27 of which it is integral, said core 27 being made of an electrically conductive material, a first end 28 of said core 27 facing the ground electrode 7 while a second end 29 of said core 27 faces the central electrode 6. FIGS. 3 to 8, FIG. 11, FIGS. 13 to 18 and FIGS. 20 and 21 clearly show that the cavity-side shuttle electrode abutment 23 can be constituted by a shuttle electrode sealing seat 30 arranged in the lamination duct 16 or at any of the ends of said duct 16, said seat 30 cooperating with a shut-off pad of electrode-nav 31 is the shuttle electrode 20 at its periphery and / or at its end.

Note that if the lamination duct 16 houses an insulating sleeve 25, the shutoff electrode seat 30 may be arranged in said sleeve 25 or at any end of said sleeve 25.

It should also be noted that the shuttle electrode closure flange 31 may be made of a thermally insulating and / or refractory material to be attached to the shuttle electrode 20 made of electrically conductive material. As a particular embodiment of the spark plug with shuttle electrode 1 according to the invention, the shuttle-shutter sealing seat 30 and the shuttle-electrode sealing flange 31 may constitute a seal when they are in contact with each other, said sealing preventing any gas from passing at said contact when the pressure in the combustion chamber 1 1 is greater than the pressure prevailing in the lamination cavity 15.

FIGS. 2 to 8 clearly show that the chamber-side shuttle-electrode stop 24 may consist of a shuttle-electrode opening seat 32 provided in the laminating duct 16 or at any one of the ends of said conduit 16, or in the metal base 4, said seat 32 cooperating with a shuttle-electrode opening flange 33 that the shuttle electrode 20 presents at its periphery and / or at its end.

Note that if the lamination duct 16 houses an insulating sleeve 25, the shuttle electrode opening seat 32 may be arranged in said sleeve 25 or at any end of said sleeve 25.

It should also be noted that the shuttle electrode opening flange 33 may be made of a thermally insulating and / or refractory material and be attached to the shuttle electrode 20, the latter being made of an electrically conductive material. It will also be appreciated that the shuttle electrode aperture seat 32 and the shuttle electrode aperture flange 33 may provide a seal when in contact with each other so as to prevent any gas from flowing. move to the level of said contact. FIG. 21 clearly shows that the shuttle electrode 20 may comprise in its periphery guide means 34 which hold said shuttle electrode 20 approximately centered in the lamination duct 16, and approximately in the same longitudinal orientation as said duct 16 and this, regardless of the axial position of said shuttle electrode 20 with respect to said conduit 16.

FIGS. 2 to 21, excluding FIGS. 9 and 19, show that the shuttle electrode 20 may comprise at least one longitudinal gas passage channel 35 which allows the gases to pass from the laminating cavity 15 to the chamber of FIG. combustion 1 1 or conversely, said channel 35 being able to be arranged inside and / or on the surface of said shuttle electrode 20 and can be made over the entire length of said shuttle electrode 20 whereas the two ends of said channel 35 open respectively at the chamber-side end 21 and at the cavity-side end 22, or only at a portion of said length while at least one of said two ends said channel 35 opens radially from the outer surface of the shuttle electrode 20.

As shown in FIGS. 2 to 8 and FIGS. 10 and 11, the shuttle electrode sealing flange 31 and the shuttle electrode opening flange 33 can commonly form one and the same sealing flange. aperture 36 which defines with the lamination duct 16 - when said shutter-opening flange 36 is in contact with the shuttle-electrode opening seat 32 - a flashing prechamber 37.

Note that in this case, the prechamber ignition torch 37 communicates simultaneously with the lamination cavity 15 on the one hand, and with the combustion chamber 1 1 via at least one ejection port gas 38 on the other hand which can for example be arranged approximately radially, in the metal base 4 or in the insulating sleeve 25.

It will be noted that the gas ejection orifice 38 may be more or less oriented towards the combustion chamber 1 1 and exit more or less tangentially to the circumference of the metal base 4. In addition, the geometry of the orifice of FIG. gas ejection 38 may vary depending on whether the jet of gas leaving said orifice 38 is provided rather directed, or rather diffuse.

For example, the gas ejection orifice 38 may be cylindrical, conical, or form a convergent or a divergent. In addition, the shutter-opening flange 36 may be made of a thermally insulating material and / or refractory to be reported on the shuttle electrode 20 made of electrically conductive material.

FIGS. 3 to 8 and FIGS. 10 and 11 show that the torch prechamber 37 can be arranged inside the insulating sleeve 25. In this case, the insulating sleeve 25 may protrude from the metal base 4 to present a protruding ejection dome 47 which opens the gas ejection orifice 38, said dome 47 being able for example to be held in position in said base 4 by legs or by a crimp collar.

Moreover and as illustrated in Figures 2 to 1 1, the protruding ejection dome 47 may be an insert on the insulating sleeve 25 which is also made of an electrically insulating material and / or thermally insulating and / or refractory.

This particular configuration makes it possible, in particular, to assemble the spark plug with the shuttle electrode 1 according to the invention and, in particular, to install the shutter-opening flange 36 constituting the shuttle electrode 20 in the ignition pre-chamber. by torch 37.

FIGS. 3 to 8 show that the shuttle electrode opening seat 32 can be arranged in the protruding ejection dome 47.

As is particularly visible in FIGS. 10 and 11, the inner peripheral wall of the flare prechamber 37 may be cylindrical while the flange-opening flange 36 can be accommodated with a small radial clearance in said prechamber 37 of FIG. so as to leave a small radial clearance between said flange 36 and said wall regardless of the position of shuttle electrode 20 with respect to the lamination duct 16, said small radial clearance constituting a restricted passage which slows the passage of gases between the cavity of stratification 15 and the combustion chamber 1 1.

Moreover, FIGS. 13, 16, 17 and 18 show that when the shuttle electrode 20 is positioned close to the combustion chamber 11, ie either in the vicinity or in contact with the electrode stop a shuttle chamber side 24 with which it cooperates, the shuttle electrode closure flange 31 can discover at least one gas ejection orifice 38 which connects the lamination cavity 15 with the combustion chamber 1 1, said orifice 38 may for example be arranged approximately radially in the metal base 4 and be more or less oriented towards the combustion chamber January 1 out more or less tangentially to the circumference of the metal base 4.

In addition, the geometry of the gas ejection orifice 38 may vary depending on whether the jet of gas leaving said orifice 38 is provided rather directed, or rather diffuse. For example, the gas ejection orifice 38 may be cylindrical, conical, or form a convergent or a divergent.

According to a particular variant of the shuttle-electrode ignition plug 1 according to the invention particularly shown in FIGS. 2 and 12, the stratification injector 17 can directly, or indirectly via an injector outlet conduit, inject the charge. 18 in the lamination cavity 15 via an annular pilot charge injection chamber 39. In this case, the annular pilot charge injection chamber 39 is arranged either in a threaded candle well 40 in which the metal base 4 is screwed by means of the base threading 5, or, on the outside periphery of said metal base 4, that is, both in said well 40 and on said periphery of said base 4, said annular chamber 39 communicating with the lamination cavity 15 via at least one gas injection channel 41 arranged approximately radially in the metal base 4 or possibly tangentially to the latter.

It will be noted that, as another variant of the spark plug with shuttle electrode 1 according to the invention, the lamination cavity 15 is arranged inside the ceramic insulator 3. Alternatively, said cavity It may be coated with a thermally insulating and / or refractory material.

It should be noted that the main innovative components of the shuttle electrode ignition plug 1 according to the invention, such as the shuttle electrode 20, the cavity-side shuttle electrode abutment 23 or the shuttle-side electrode abutment chamber 24, can be housed in a base reported in the cylinder head 10 in which is screwed the metal cap of a conventional spark plug devoid of a ground electrode facing its central electrode.

OPERATION OF THE INVENTION:

The operation of the spark plug electrode-shuttle 1 according to the invention is easily understood in the view of Figures 1 to 21.

FIG. 1 illustrates that the spark plug with shuttle electrode 1 is here mounted on an internal combustion engine 2, its metal base 4 being screwed into the cylinder head 10 of said engine 2. To detail said operation, we will retain here the embodiment of the spark plug with a shuttle electrode 1 according to the invention as illustrated in FIGS. 2 to 11 on which it can be seen that the shuttle electrode 20 is made of a single piece of material electrically conductive which in this case is a metal. According to this example, the shuttle electrode 20 can translate in an insulating sleeve 25 that comprises the lamination duct 16, which is radially interposed between the shuttle electrode 20 and the lamination duct 16, and which consists of an electrically and thermally insulating material such as a ceramic or the like.

It may be noted that the insulating sleeve 25 has three longitudinal channels for the passage of large section gases which allow the gases to pass from the lamination cavity 15 to the combustion chamber 11 or vice versa. Said channels 35 are arranged inside said sleeve 25.

Note in this non-limiting embodiment of the spark plug-electrode shuttle 1 according to the invention that the cavity-side shuttle electrode stop 23 consists of a shutter-shuttle electrode seat 30 at the end of the insulating sleeve 25, said seat 30 cooperating with a shuttle electrode sealing collar 31 that presents the shuttle electrode 20 at its periphery.

It should be understood that the shuttle electrode closure seat 30 and the shuttle electrode closure flange 31 provide a seal when in contact with each other so as to prevent any gas from passing through the seal. level of said contact when the pressure in the combustion chamber January 1 is greater than that prevailing in the lamination cavity 15. Still according to this embodiment, it is also noted that the chamber-side shuttle electrode stop 24 consists of a shuttle electrode opening seat 32 also arranged in the insulating sleeve 25, said seat 32 cooperating with a shuttle-electrode opening flange 33 which the shuttle electrode 20 presents at its periphery and / or at its end.

It should be noted that the shuttle electrode opening seat 32 and the shuttle electrode opening flange 33 form a seal when in contact with each other so as to prevent any gas from passing through. level of said contact. Note that according to the particular embodiment of the spark plug-electrode shuttle 1 according to the invention taken here to illustrate the operation, the shuttle shutter sealing collar 31 and the opening flange The shuttle-electrode 33 are combined to form one and the same blank-opening flange 36. This is particularly visible in FIGS. 2 to 8 and in FIGS. 10 and 11.

Moreover, it can be seen in FIG. 3, in FIGS. 6 to 8, and in FIG. 10, that when the closure-opening flange 36 is in contact with the shuttle-electrode opening seat 32 with which it co-operates, it defines with the insulating sleeve 25 a flare pre-ignition chamber 37 which communicates simultaneously with the lamination cavity 15 on the one hand, and with the combustion chamber 1 1 via eight gas ejection orifices 38 'somewhere else.

According to the example taken here, we will consider that the diameter of said orifices 38 is worth fifteen hundredths of a millimeter.

As particularly illustrated in Figures 2 to 1 1, to receive the ignition prechamber torch 37, the insulating sleeve 25 is extended by a protruding ejection dome 47 within which is arranged said prechamber 37. On note that said dome 47 protrudes from the metal base 4 and that it is from said dome 47 that open the gas ejection ports 38.

As seen in FIGS. 2 to 11, the protruding ejection dome 47 is an insert on the insulating sleeve 25 which is also made of thermally insulating and refractory material, while the electrode opening seat -navette 32 is actually arranged in said dome 47. It will be noted that the inner peripheral wall of the ignition prechamber by torch 37 is cylindrical while the shutter-opening flange 36 is housed with a small radial clearance in said prechamber 37 - for example five hundredths of a millimeter - so as to leave a small radial clearance between said flange 36 and said wall regardless of the position of the shuttle electrode 20 with respect to the lamination duct 16.

Said low radial clearance forces the majority of the gases transferred from the combustion chamber 1 1 to the lamination cavity 15 or vice versa to pass via the gas ejection ports 38 rather than between the inner peripheral wall of the ignition prechamber by flare 37 and the shutter-opening flange 36.

Note that depending on whether the pressure in the lamination cavity 15 is less than or greater than the pressure in the combustion chamber 1 1, the shuttle electrode 20 can be made to position itself either on its electrode stop cavity-side shuttle 23 as illustrated in FIGS. 4 and 5, or on its chamber-side shuttle electrode abutment 24 as illustrated in FIGS. 2 and 3, FIGS. 6 to 8, and FIG.

In the present case and as just described, the cavity-side shuttle-electrode abutment 23 is none other than the shuttle electrode closure seat 30 while the chamber-side shuttle electrode abutment 24 consists of the shuttle electrode opening seat 32.

When the shuttle electrode 20 is in contact with the cavity-side shuttle-electrode abutment 23, the space left between its chamber-side end 21 and the ground electrode 7 is in this illustrative example of seven tenths of a millimeter while that the space left between its cavity-side end 22 and the central electrode 6 is one-tenth of a millimeter.

In contrast and as is readily conceivable, when the shuttle electrode 20 is in contact with the chamber-side shuttle-electrode stop 24, the space left between its chamber-side end 21 and the ground electrode 7 is one-tenth of a millimeter while the space left between its cavity-side end 22 and the central electrode 6 is seven tenths of a millimeter.

Thus, the total length of the electric arc - or otherwise named, spark - to be produced between the ground electrode 7 and the center electrode 6 is constant, eight tenth of a millimeter, while the distance to to travel through the shuttle electrode 20 to go from one stop 23, 24 to the other is six tenths of a millimeter.

Thus, and advantageously, the electrical voltage to be produced to create said electric arc remains constant and close to the values usually used in the spark plugs of spark ignition engines, while the greatest length of said arc occurs in the combustion chamber. 1 1 when the shuttle electrode 20 is in contact with the cavity-side shuttle electrode abutment 23, and in the lamination cavity 15 when the shuttle electrode 20 is in contact with the shuttle-side electrode abutment room 24. To understand the operation of the spark plug-electrode electrode 1 according to the invention, it is useful to break down the operation during the four stages of the internal combustion engine 2.

In a first step, we consider that said engine 2 burns a main charge 12 substantially undiluted and therefore highly burnable. The use of a pilot load 18 is not necessary which saves the compression of said pilot load 18 and to give the engine 2 maximum performance in this context.

With the shuttle electrode 20 in contact with the cavity-side shuttle-electrode abutment 23, during the intake phase of the internal combustion engine 2, the piston 9 descends into the cylinder 8. The volume of the combustion chamber 1 1 increases and the pressure in said chamber 1 1 drops. A main charge 12 is introduced into the cylinder 8 via the intake duct 13 of the internal combustion engine 2 via an intake valve 45.

Thus, the pressure in the combustion chamber 1 1 becomes momentarily lower than that prevailing in the lamination cavity 15. As a result, the gases contained in the lamination cavity 15 exert a force on the sealing flange. opening 36 which hitherto formed a sealed contact with the shuttle shutter seat 30 with which it cooperates. Such a situation is illustrated in Figure 6.

Subsequent to said force, the contact between the shutter-opening flange 36 and the shuttle electrode sealing seat 30 is broken and the shuttle electrode 20 moves towards the combustion chamber 1 1 to that the shutter-opening flange 36 comes into contact with the shuttle-electrode opening seat 32, which is also shown in FIG. 6. In the event of this, burned or non-flared gases from the preceding cycle still contained in the cavity of FIG. lamination 15 escape from the latter to go to the combustion chamber 1 1 mainly and respectively via the three longitudinal passageways of the gas 35 that includes the insulating sleeve 25, the ignition prechamber torch 37, and orifices ejection of gases 38.

It will also be noted that during its run, the shutter-opening flange 36 will have progressively opened the gas passage via the longitudinal passageways of the gases 35 by discovering the gas ejection orifices 38 first partially, then more and more and until completely as it advances towards the shuttle electrode opening seat 32.

The sequence which has just been described makes it possible to find the spark plug with shuttle electrode 1 according to the invention in the situation illustrated in FIG.

As the piston 9 has reached its low dead point and the intake valve 45 has closed, said piston 9 begins to rise in the cylinder 8 and compress the main charge 12. The volume of the combustion chamber 1 1 decreases and the pressure that prevails in the said chamber 1 1 increases to the point of becoming higher than that prevailing in the lamination cavity 15.

As a result, the gases contained in the combustion chamber 1 1 exert a force on the closure-opening flange 36 which until now formed a sealed contact with the shuttle-electrode opening seat 32 with which it co-operates . As a result, the shuttle electrode 20 moves until the shutter-aperture flange 36 abuts the shuttle electrode shutter seat 30 to form a sealed contact therewith again. This leads to the situation shown in FIG.

Note that in all cases, except during the brief moment during which the shutter-opening flange 36 forms a sealed contact with the shutoff electrode seat 30, it is mainly the dynamic pressure of the gas bound the displacement of the latter from the lamination cavity 15 to the combustion chamber 1 1 or vice versa, which acts on said flange 36 to maneuver the shuttle electrode 20 in translation.

It will be understood that the amount of gas passing through the shut-off collar 36 to pass from the combustion chamber 11 to the lamination cavity 15 or vice versa depends on the movement of the piston 9 but also on the ratio between first part, the total volume of said gas contained in the cylinder 8 and the combustion chamber 1 1, and secondly, the total volume of said gas contained in the pre-ignition chamber by torch 37, the longitudinal channels of passage of gas 35, the lamination cavity 15, the gas injection channels 41, the pilot charge injection annular chamber 39, and the injector outlet duct 42.

It will also be noted that when the shutter-opening flange 36 forms a sealed contact with the shuttle-electrode opening seat 32 and while the pressure in the combustion chamber 1 1 rises, the total cross-sectional area exerted by said flange 36 to the gas pressure contained in said chamber 1 1 is significantly greater than the total section of the gas ejection orifices 38. This allows to produce a sufficient force on the shuttle electrode 20 to push it towards the lamination cavity 15 during the ascent of the piston 9 in the cylinder 8, at a sufficiently high speed. The piston 9 continuing its ascent in the cylinder 8, it compresses the main load 12, which increasingly plates the shutter-opening flange 36 on the shutter-shutoff seat 30.

When the main charge 12 is to be fired, a high-voltage current is applied to the center electrode 6 so that a one-tenth of a millimeter electric arc is produced between said central electrode 6 and the cavity-side end 22. of the shuttle electrode 20, while a second electric arc of seven tenths of a millimeter is produced between the ground electrode 7 and the chamber-side end 21 of the shuttle electrode 20. This situation is shown in FIG. 5.

The burnable gases that may be present in the lamination cavity 15 are not ignited because the distance between the central electrode 6 and the cavity-side end 22 of the the shuttle electrode 20 is insufficient. Indeed, said distance is less than the thickness of the flame-sealing layer known per se lining the inner surface of the lamination cavity 15. The main charge 12 is itself fired under conditions similar to those found in any spark ignition engine operating with a main load 12 substantially undiluted and highly burnable.

The piston 9 having crossed its top dead center, it goes down into the cylinder 8 to relax the constituent gases of the main charge 12 now hot. Said piston 9 operates this descent while producing work on a crankshaft 43 that has the internal combustion engine 2, via a connecting rod 44 with which cooperates said crankshaft 43. The piston 9 arriving near its dead point Bottom, the exhaust valve 46 of the internal combustion engine 2 opens and the flue gases start to escape from the combustion chamber 1 1 via the exhaust pipe 14. The pressure in said chamber 1 1 decreases abruptly to the point of rapidly becoming smaller than that prevailing in the lamination cavity 15.

The gases contained in the laminating cavity 15 then exert a force on the closure-opening flange 36 which previously formed a sealing contact with the shuttle-electrode sealing seat 30 with which it co-operates. As a result of this effort and as shown in FIG. 6, the shuttle electrode 20 moves towards the combustion chamber 1 1 until the closure-opening flange 36 comes into contact with the opening seat. or shuttle electrode 32, or not if the time left to this movement is too short because in fact, the piston 9 having exceeded its low dead point, it begins to expel the flue gases from the combustion chamber 1 1 via the conduit of exhaust 14.

During the exhaust stroke of the piston 9, it is understood that the pressure of the gases will substantially go up in the combustion chamber 1 1 to the point that the shuttle electrode 20 can start towards the lamination cavity 15 and this, until the shutter-opening flange 36 does or does not come into contact with the shut-off electrode-shutoff seat 30. This situation which can in all or in part occur is illustrated in FIG. 4.

Once the piston 9 has reached its high dead point at the end of the exhaust stroke, the internal combustion engine 2 can perform a new four-stroke thermodynamic cycle which we understand that the ignition can be operated by the candle ignition electrode shuttle 1 according to the invention under conditions similar to those found in all said spark ignition engine 2 equipped with a conventional spark plug, and operating a main charge 12 little or not diluted and therefore highly burnable. The advantages of the spark-plug ignition electrode 1 according to the invention are effectively noticeable only when the main charge 12 is highly diluted for example with cooled recirculated exhaust gas called "cooled EGR". Indeed, the resulting gas mixture is more resistant to ignition and is in no way conducive to rapid development of its combustion in the three-dimensional space of the combustion chamber 1 January.

Under such conditions, the use of a pilot charge 18 is recommended provided that said charge 18 is effective not only in initiating the combustion, but also in developing said combustion in the shortest possible time, both objectives being directly served by the spark plug electrode-shuttle 1 according to the invention.

According to the non-limiting embodiment of the shuttle-electrode ignition plug 1 taken here to illustrate its operation, we will assume that the pilot charge 18 contains one percent of the fuel contained in the main charge 12.

As previously, the shuttle electrode 20 being in contact with the cavity-side shuttle electrode abutment 23 during the intake phase of said motor 2, the piston 9 descends into the cylinder 8.

The volume of the combustion chamber 1 1 increases and the pressure in said chamber 1 1 drops. A main charge 12 strongly diluted with the cooled EGR is introduced into the cylinder 8 by the intake valve 45 via the intake duct 13 of the internal combustion engine 2.

As previously, the pressure in the combustion chamber 1 1 becomes momentarily lower than that prevailing in the lamination cavity 15. As a result, the gases contained in the lamination cavity 15 exert a force on the sealing flange -opening 36 which previously formed a sealed contact with the shuttle electrode sealing seat 30 with which it cooperates.

As a result of this effort and as illustrated in FIG. 6, the contact between the shutter-opening flange 36 and the shut-off electrode sealing seat 30 is broken and the shuttle electrode 20 moves towards the combustion chamber 1 1 until the shutter-opening flange 36 comes into contact with the shuttle electrode opening seat 32.

In doing so, burned gases or not of the previous cycle still contained in the lamination cavity 15 escape from the latter to go to the combustion chamber 1 1 respectively through the three longitudinal channels of the gas 35 that includes the sleeve 25, the ignition prechamber 37, and the eight gas ejection ports 38.

The piston 9 having reached its Low Dead Point and the inlet valve 45 having closed, said piston 9 begins to rise in the cylinder 8 and to compress the main charge 12 strongly diluted with the cooled EGR. The volume of the combustion chamber 1 1 decreases and the pressure prevailing in said chamber 1 1 rises to the point of becoming higher than that prevailing in the lamination cavity 15.

As a result, the gases contained in the combustion chamber 1 1 exert a force on the closure-opening flange 36 which until now formed a sealed contact with the shuttle-electrode opening seat 32 with which it co-operates . As a result and as illustrated in FIG. 4, the shuttle electrode 20 moves rapidly until the closure-closure flange 36 abuts the shuttle electrode closure seat 30 to form an electrode. with the latter a new waterproof contact.

The piston 9 continues to rise in the cylinder 8, the pressure in the combustion chamber January 1 continues to rise while the pressure in the lamination cavity 15 no longer rises and retains the value it had when the shutter-opening flange 36 abuts on the shuttle electrode sealing seat 30 to form with it a sealed contact.

The lamination cavity 15 now forms a protected volume in which the gases contained in the combustion chamber January 1 can no longer penetrate. It is from this moment that the lamination injector 17 begins to inject a pilot charge 18 consisting of a highly flammable AF-fuel oxidant mixture into the lamination cavity 15, via the injector outlet duct, and through the annular pilot charge injection chamber 39 arranged in the threaded candle well 40.

As can be seen in FIGS. 2 to 12, this is made possible by the fact that the annular pilot charge injection chamber 39 communicates with the laminating cavity 15 by means of - according to this nonlimiting example - eight channels of injection of gases 41 arranged radially in the metal base 4 at the level of the annular pilot charge injection chamber 39.

The lamination cavity 15 initially forming a closed and protected volume, the highly flammable AF combustion-fuel mixture that makes up the pilot charge 18 is not diluted with the low-flammability gases because it is highly diluted with cooled EGR which consists of the main load 12.

Only the residual EGR diluted gases that have been introduced into the lamination cavity 15 remain before the closure-closure flange 36 has come into abutment on the shuttle-electrode sealing seat 30, said gases diluted only a few percent of the pilot charge.

It will be noted that the beginning of the injection of the pilot charge 18 into the stratification cavity 15 by the stratification injector 17 was triggered on the order of a non-represented management computer of the internal combustion engine 2, taking into account the dynamics and the flow rate of said injector 17, and so that the pressure in said cavity 15 becomes greater than that prevailing in the combustion chamber 1 1 only a few degrees of rotation of the crankshaft 43 before the main load has to be ignited 12.

When effectively, the pressure prevailing in the lamination cavity 15 becomes greater than that prevailing in the combustion chamber 1 1, a force is exerted on the shutter-opening flange 36 by the gases mainly consisting of AF fuel-fuel mixture mixture easily. flammable.

As a result, said flange 36 moves rapidly towards the combustion chamber January 1 to abut on the shuttle electrode opening seat 32 and to form a tight contact therewith. This situation is clearly illustrated in Figure 7.

During its displacement, the shutter-opening flange 36 has left a small part of the easily flammable fuel-combustion mixture AF which constitutes the pilot charge 18 to escape mainly via the gas ejection orifices 38.

Once in contact with the shuttle electrode aperture seat 32, said flange 36 effectively moved the cavity-side end 22 of the shuttle electrode 20 to seven tenths of a millimeter from the center electrode 6 so that a high voltage current can now be applied to the central electrode 6 so that a seven tenths of a millimeter electric arc is produced between said central electrode 6 and the cavity-side end 22 of the shuttle electrode 20 while a second electric arc of one-tenth of a millimeter is produced between the ground electrode 7 and the chamber-side end 21 of the shuttle electrode 20. This situation is illustrated in FIG. 8.

Since the pilot charge 18 is locally subjected to the heat of the spark thus created and because it consists mainly of a highly flammable AF comburent-fuel mixture, it ignites rapidly while the pressure rises violently in the lamination cavity. 15 and in the annular pilot charge injection chamber 39 at several bars above the pressure that prevails at the same time in the combustion chamber 1 January.

As a result, an additional unburned fraction of the pilot charge 18 is ejected into the combustion chamber 11 via the eight gas ejection orifices 38, the said fraction being immediately followed by flaming gas torches. ignite, said torches also igniting the part of the gases constituting the pilot charge 18 which was ejected via the gas ejection orifices 38 before the spark is triggered, as shown in FIG. 7 .

This particular configuration has several advantages all in the service of the most effective firing of the main charge 12 with the pilot charge 18, the latter being the smallest possible to minimize the energy cost of compression including the compressor compressor. stratification 19.

Firstly and as we have seen, the spark plug electrode-shuttle 1 according to the invention avoids excessive dispersion of the pilot load 18 in the load main 12 during the injection of said pilot charge 18 and before the firing of the latter.

Then, the spark plug-electrode shuttle 1 according to the invention allows a few microseconds to a portion of the pilot charge 18 to enter the main charge 12 to enrich it very locally fuel-fuel mixture AF easily flammable before to ignite said part by means of hot gas torches. This feature makes it possible to prevent too much heat being transferred by pure loss by the hot gases to the internal walls of the lamination cavity 15 and to those including the longitudinal channels for the passage of gases 35, from the ignition prechamber to a torch. 37 and gas ejection ports 38.

Furthermore, as clearly shown in FIG. 8, the hot gases expelled by the eight gas ejection orifices 38 arranged radially in the protruding ejection dome 47 form flaming gas torches which ignite the main charge 12 by multiple locations of the combustion chamber 1 1, the combustion of said load 12 then developing radially from the periphery of said chamber 1 1 to the center of said chamber 1 1, and tangentially between each said torch. The strong local turbulence resulting from the penetration of said torches into the volume of the combustion chamber 1 1 also promotes the folding of the flame front generated by each said torch, which further increases their effectiveness in promoting a rapid combustion of the main charge 12. It will be noted in passing that the greater the volume of gas between the central electrode 6 and the gas ejection orifices 38 is large relative to the volume of gas between the output of the lamination injector 17 and said central electrode 6, plus the mass of non-combusted AF combustion-fuel mixture expelled by the gas ejection ports 38 before the formation of the torches is large. It is thus possible for engine engineers to choose this ratio by appropriately adapting the relative positions and volumes of the various components of the ignition spark plug electrode 1 according to the invention.

It may also be noted that the shuttle-electrode ignition plug 1 according to the invention makes it easy to ensure the cleanliness of the protruding ejection dome 47 even when the internal combustion engine 2 is operating for a long time with a main charge 12 diluted and therefore without resorting to a pilot charge 18.

Indeed, it is well known that the ceramic insulator head of the candles which is introduced into the combustion chamber 1 1 spark ignition engines must maintain a temperature ideally between about four hundred degrees Celsius to burn all deposits of carbon or carbonized oil, and eight hundred degrees Celsius temperature beyond which appear serious risks of uncontrolled self-ignition of the main charge 12.

It can thus be seen that according to the particular configuration of the spark plug electrode-shuttle 1 according to the invention which has just been taken as an example to illustrate the operation, it is the protruding ejection dome 47 which can become fouled due to lack of temperature, or cause the uncontrolled self-ignition of the main charge 12 due to excess temperature. Clogging of the closure-opening flange 36 does not pose any particular problem in that said flange 36 rises at high temperature when it is licked by the hot gases leaving the lamination cavity 15 or entering this chamber. last, and then cools once the combustion of the main charge 12 has been done by resting several times on the shuttle electrode sealing seat 30 with which it co-operates.

When the combustion of the main charge 12 does not require a pilot charge 18, the spark-plug ignition electrode 1 according to the invention behaves rather like a "cold" candle, the protruding ejection dome 47 being directly in position. contact with the metal base 4 which is in contact with the cylinder head 10 which is usually maintained at around one hundred and ten degrees Celsius when the internal combustion engine 2 has reached its nominal operating temperature.

It will be noted that an air gap may be left between a portion of the insulating sleeve 25 and the laminating duct 16 so as to limit heat exchanges between said sleeve 25 and said duct 16. This allows in particular to adjust the average temperature protruding ejection dome 47.

Alternatively, it is possible to thermally clean the protruding ejection dome 47 by regularly injecting pilot charges 18 by means of the laminating injector 17 which increases the temperature of said dome 47 until the cleaning is obtained. research.

In contrast, and if this is justified, it is also possible to reduce the temperature of the protruding ejection dome 47 by, for example, carrying out air injections alone in the lamination cavity 15, for example during the admission phase. or exhaust of the internal combustion engine 2.

Note the decisive role of the shuttle electrode 20 in limiting the ignition voltage. Indeed, a high ignition voltage greatly reduces the life of the candles including corrosion of the electrodes they contain. In addition, such a voltage calls for massive insulators which are difficult to store and which are prone to break under the effect of temperature. Now, other things being equal, the necessary ignition voltage is approximately proportional to the length of the inter-electrode space, whereas the said voltage must be higher the higher the density of the gas between said electrodes. . It is therefore clear all the difficulty related to the strategy of cooled EGR which is particularly recommended for supercharged spark ignition engines, for example by turbocharger, and which advantageously makes it possible to increase the ratio volumetric said engines and therefore their average efficiency, with the counterpart of increasing the pressure of the main load 12 at the time of its ignition.

This leads to a high density of gas between the electrodes which pleads in favor of the approximation of the latter to avoid using a too high ignition voltage.

However, since the shuttle electrode 20 moves to alternatively leave the greatest length of spark either in the lamination cavity 15 or in the combustion chamber 11, the total length of said spark remains invariably limited to eight tenths of millimeter according to the example taken here to illustrate the operation of the spark plug ignition electrode 1 according to the invention.

The resulting inter-electrode space is always sufficient since if the engine operates a main charge 12 that is highly diluted with the cooled EGR, the spark plug with shuttle electrode 1 according to the invention uses a pilot charge 18 consisting of a highly burnable AF oxidizer / fuel mixture, while if the main charge 12 is not diluted, the inter-electrode gap remains in accordance with the rules of the trade usually retained by those skilled in the art.

Thus, the shuttle electrode 20 makes it possible to have two distinct ignition locations - in this case the lamination cavity 15 and the combustion chamber 1 1 - without the need to provide either a double ignition system with its own ignition system. coil and its conductive son that would become difficult to accommodate, or an increased total inter-electrode space that would require a high ignition voltage.

The choice of one or the other said place takes place automatically depending on whether or not the lamination injector 17 injects a pilot charge 18 into the lamination cavity 15.

It will also be noted that the shuttle-electrode ignition plug 1 enables the internal combustion engine 2 to operate normally, as all said engine 2 operating a main charge 12 undiluted at the cooled EGR in the event of a compressor failure. lamination 19, the lamination injector 17 or any member that would supply the lamination cavity 15 combusted fuel-AF mixture highly burnable. In this case, the firing of the main load 12 no longer passes through any "passive" prechamber whatsoever - this type of prechamber not being suitable for automobile engines operating at infinitely variable speed and load - but by means of protruding electrodes compatible with the direct injection of gasoline, and whose operation is similar to that of ordinary spark plugs as massively produced and marketed in automobile.

The variant illustrated in FIGS. 2 to 1 1 of embodiment of the spark plug with shuttle electrode 1 according to the invention has been chosen by way of example to illustrate the operation thereof. It will be noted that another embodiment of said candle 1 illustrated in FIGS. 12 to 21 is based on similar principles and that the explanation that has just been given can easily be adapted to said FIGS. 12 to 21 which are classified in the same relative order vis-à-vis said operation. The possibilities of the spark plug with electrode-shuttle 1 according to the invention are not limited to the applications which have just been described and it must also be understood that the foregoing description has been given only By way of example, and in no way limits the scope of said invention which would not be overcome by replacing the execution details described by any other equivalent.

Claims

Spark plug with shuttle electrode (1) for internal combustion engine

(2), said spark plug (1) comprising at least electrodes (6, 7) and a ceramic insulator

(3) housed in a metal base (4) which has a base thread (5), said plug (1) also receiving a lamination cavity (15) connected to a combustion chamber (1 1) that comprises the motor internal combustion (2) by a lamination duct (16) while a lamination injector (17) can directly or indirectly inject into said cavity (15) a pilot charge (18) previously pressurized, said load (18) being composed of a fuel-burning AF-fuel mixture that is highly flammable by means of a spark, characterized in that it comprises:

At least one central electrode (6) which opens into the lamination cavity (15);

At least one shuttle electrode (20) which is wholly or partly made of an electrically conductive material and which is partially or fully housed with a small clearance in the lamination duct (16), said shuttle electrode (20) interposing between the central electrode (6) and a ground electrode (7) and having, on the one hand, a chamber end (21) facing the ground electrode (7) and being exposed to pressure prevailing in the combustion chamber (1 1) and secondly, a cavity-side end (22) which faces the central electrode (6) and is exposed to the pressure in the lamination cavity (15), said shuttle electrode (20) being able to translate in said duct (16) under the effect of the gas pressure to the lamination cavity (15) when the pressure in the latter is lower than the pressure prevailing in the combustion chamber (1 1), s oit towards the combustion chamber (1 1) when the pressure in the latter is lower than the pressure prevailing in lamination cavity (15);

At least one cavity-side shuttle electrode abutment (23) which determines the position of the shuttle electrode (20) closest to the lamination cavity (15);

• At least one chamber-side shuttle electrode stop (24) which determines the position of the shuttle electrode (20) closest to the combustion chamber (1 1).

Shuttle-electrode spark plug according to Claim 1, characterized in that the shuttle electrode (20) closes all or part of the lamination duct (16) when it is closest to the lamination cavity ( 15) while it opens said duct (16) on a wider section when it is positioned closer to the combustion chamber (1 1).

A shuttle electrode spark plug according to claim 1, characterized in that all or part of the lamination duct (16) comprises an insulating sleeve (25) made of an electrically insulating and / or thermally insulating and / or refractory material which is integral with said duct (16) and which is radially interposed and / or axially between the shuttle electrode (20) and said conduit (16), said shuttle electrode (20) being translatable within said sleeve (25).

4. Shuttle electrode spark plug according to Claim 3, characterized in that the insulating sleeve (25) has at least one longitudinal gas passage (35) which allows the gases to pass from the lamination cavity ( 15) to the combustion chamber (1 1) or vice versa, said channel (35) being able to be arranged inside and / or on the inner or outer surface of said sleeve (25).

5. Shuttle electrode spark plug according to claim 1, characterized in that the shuttle electrode (20) consists of an insulating shuttle body (26) made of an electrically insulating material, said body ( 26) being traversed throughout its length by a conductive core (27) of which it is integral, said core (27) consisting of an electrically conductive material, a first end (28) of said core (27) facing the ground electrode (7) while a second end (29) of said core (27) faces the central electrode (6).

A shuttle-electrode spark plug according to claim 1, characterized in that the cavity-side shuttle-electrode abutment (23) is comprised of a shuttle electrode closure seat (30) provided in the lamination duct (16) or at any of the ends of said duct (16), said seat (30) cooperating with a shuttle electrode closure flange (31) which the shuttle electrode (20) has. ) at its periphery and / or at its end.

A shuttle electrode spark plug according to claim 6, characterized in that the shuttle electrode sealing seat (30) and the shuttle electrode sealing collar (31) provide a seal when they are in contact with each other, said sealing preventing any gas from passing at said contact when the pressure prevailing in the combustion chamber (1 1) is greater than the pressure prevailing in the lamination cavity (15 ).

A shuttle electrode spark plug according to claim 1, characterized in that the chamber-side shuttle electrode abutment (24) consists of a shuttle electrode opening seat (32) provided in the lamination duct (16) or at either end of said duct (16), or in the metal base (4), said seat (32) cooperating with a shuttle electrode opening flange (33) that presents the shuttle electrode (20) at its periphery and / or at its end.

A shuttle electrode spark plug according to claim 8, characterized in that the shuttle electrode opening seat (32) and the shuttle electrode opening flange (33) provide a seal when they are in contact with each other so as to prevent any gas from passing at the level of said contact.

A shuttle electrode spark plug according to claim 1, characterized in that the shuttle electrode (20) has at its periphery guide means (34) which hold said shuttle electrode (20) approximately centered in the lamination duct (16), and approximately in the same longitudinal orientation as said duct (16) and this, regardless of the axial position of said shuttle electrode (20) relative to said duct (16).

1 1. Shuttle-electrode spark plug according to Claim 1, characterized in that the shuttle electrode (20) has at least one longitudinal gas channel (35) which allows the gases to pass from the lamination cavity ( 15) to the combustion chamber (1 1) or vice versa, said channel (35) being able to be arranged inside and / or on the surface of said shuttle electrode (20) and can be made either on the the entire length of said shuttle electrode (20) while both ends of said channel (35) open respectively at the chamber-side end (21) and at the cavity-side end (22), or on only a portion of said length while at least one of said two ends of said channel (35) opens radially from the outer surface of the shuttle electrode (20).

A shuttle electrode spark plug according to claims 6 and 9, characterized in that the shuttle electrode closure flange (31) and the shuttle electrode opening flange (33) form commonly a single shutter-opening flange (36) which defines with the lamination duct (16) - when said shutter-opening flange (36) is in contact with the shuttle electrode opening seat (32) - a torch prechamber (37) which communicates simultaneously with the lamination cavity (15) on the one hand, and with the combustion chamber (1 1) via at least one orifice of ejecting gases (38) on the other hand.

13. Spark plug electrode plug according to claims 3 and 12, characterized in that the ignition prechamber torch (37) is arranged inside the insulating sleeve (25).

14. spark plug with shuttle electrode according to claim 13, characterized in that the insulating sleeve (25) protrudes from the metal base (4) to present a protruding ejection dome (47) which opens the orifice of ejection of gases (38).

15. Shuttle electrode spark plug according to claim 14, characterized in that the protruding ejection dome (47) is an insert on the insulating sleeve (25).

16. A shuttle electrode spark plug according to claim 14, characterized in that the shuttle electrode opening seat (32) is arranged in the protruding ejection dome (47).

17. Shuttle electrode spark plug according to claim 12, characterized in that the inner peripheral wall of the ignition prechamber torch (37) is cylindrical while the shutter-opening flange (36) is housed with low radial clearance in said antechamber (37).

18. Spark plug with shuttle electrode according to claim 6, characterized in that when the shuttle electrode (20) is positioned close to the combustion chamber (1 1), ie either in the vicinity or at the contacting the chamber-side shut-off electrode abutment (24) with which it cooperates, the shuttle-electrode sealing flange (31) discovers at least one gas ejection orifice (38) which connects the lamination cavity (15) with the combustion chamber (1 1).

A shuttle electrode spark plug according to claim 1, characterized in that the lamination injector (17) can directly or indirectly via an injector outlet conduit (42) inject the pilot charge (18). ) in the lamination cavity (15) via an annular pilot charge injection chamber (39) which is arranged either in a threaded candle well (40) into which the metal base (4) is screwed. ) by means of the base threading (5), either on the outer periphery of said metal base (4), or both in said well (40) and on said periphery of said base (4), said annular chamber (39) ) communicating with the lamination cavity (15) via at least one gas injection channel (41) arranged approximately radially in the metal base (4).

20. Shuttle electrode spark plug according to Claim 1, characterized in that the lamination cavity (15) is arranged inside the ceramic insulator.

(3).