EP1515408B1 - Plasma generating spark plug with integrated inductance - Google Patents
Plasma generating spark plug with integrated inductance Download PDFInfo
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- EP1515408B1 EP1515408B1 EP04292188A EP04292188A EP1515408B1 EP 1515408 B1 EP1515408 B1 EP 1515408B1 EP 04292188 A EP04292188 A EP 04292188A EP 04292188 A EP04292188 A EP 04292188A EP 1515408 B1 EP1515408 B1 EP 1515408B1
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- plug according
- resonator
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Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
- F02P23/00—Other ignition
- F02P23/04—Other physical ignition means, e.g. using laser rays
- F02P23/045—Other physical ignition means, e.g. using laser rays using electromagnetic microwaves
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
- H01T13/00—Sparking plugs
- H01T13/40—Sparking plugs structurally combined with other devices
- H01T13/44—Sparking plugs structurally combined with other devices with transformers, e.g. for high-frequency ignition
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
- F02P3/00—Other installations
- F02P3/01—Electric spark ignition installations without subsequent energy storage, i.e. energy supplied by an electrical oscillator
Definitions
- the present invention relates generally to the generation of plasma in a gas, and more particularly to the plasma generation candles with integrated inductance.
- Plasma generation is used in particular for the controlled ignition of internal combustion engines by the electrodes of a candle.
- the ignition of gasoline internal combustion engines consisting of initiating the combustion of an air-fuel mixture in a combustion chamber of said engine, is relatively well controlled in current engines.
- spark-ignition engines with indirect injection conventionally, a spark plug and an upstream electronic device make it possible to generate a spark capable of transmitting to the mixture sufficient energy for its combustion.
- the formation of this discharge requires high breakdown voltages (of the order of 30 kV per mm), so that the inter-electrode space of the candles is limited to about 1 mm, a relatively unfavorable distance to the initiation of combustion.
- spark ignition engines capable of operating with poor fuel mixtures, that is to say having an excess of air relative to the amount of fuel injected.
- stratified mixtures In contrast to a homogeneous mixture where the richness is globally the same in every respect, a stratified mixture presents a richness which decreases as one moves away from the candle.
- the stratification of the mixture in the combustion chamber is for example obtained by guiding the jet of fuel so that the jet meets the candle at the time of the production of the spark.
- the guidance of the jet is obtained in particular by aerodynamic phenomena, generated for example by a suitable shape of the piston.
- New spark plugs on the surface produce larger sparks to deal with the problem of spatio-temporal rendezvous. Thus, a higher mixing volume is ignited. The probability of initiation of combustion is then greatly increased in a direct injection engine spark ignition and stratified mixture.
- Such candles are notably described in the applications for FR 2771558 , FR 2796767 and FR 2816119 . Such candles generate large sparks from reduced potential differences.
- Surface spark plugs have a dielectric separating the electrodes in the zone where the distance separating them is the lowest; we guide sparks formed between the electrodes on the surface of the dielectric. These candles amplify the inter-electrode field on the surface of the dielectric.
- the elementary capacitances formed by the dielectric and an underlying electrode are gradually charged.
- Candles generate a spark propagating along the surface of the insulation in areas where the electric field in the air is strongest.
- a conventional engine ignition device, coupled with such spark plugs typically generates sparks having a length of 4 mm with breakdown voltages of between 5 and 25 kV.
- the discharge has a probability of appearance substantially identical anywhere around the insulation.
- conventional candles generate an electric arc occurring systematically in the same extremely small volume.
- This method of ignition by plasma generation still has disadvantages. It occurs in particular a passage to the arc following a single line. The initiation of combustion is not optimal.
- branched plasma used in the following refers to the simultaneous generation of at least several lines or ionization paths in a given volume, their branches being moreover omnidirectional.
- volume plasma involves heating up the entire volume in which it is to be generated
- the branched plasma only requires the heating in the path of the sparks formed.
- the energy required for a branched plasma is much lower than that required by a volume plasma.
- the invention makes it possible to reduce the internal parasitic capacitances of a plasma generation candle and thus to obtain a spark plug forming a series resonator having a high overvoltage coefficient.
- This candle makes it possible to maintain a radiofrequency voltage between its electrodes for the generation of a plasma.
- Combustion density will be called any molar density of gas greater than 5 * 10 -2 mol / L.
- a stream of positive ionization propagating from the anode will be referred to as a streamer.
- the invention proposes to integrate a series resonator having a resonance frequency greater than 1 MHz in a candle.
- the electrodes of the spark plug are connected to the terminals of this series resonator.
- the figure 1 illustrates details of the structure of a surface spark spark plug for which the application of a radiofrequency excitation is particularly advantageous. We will first detail the operation of such a candle.
- the surface effect candle 110 comprises a spark plug head for opening into the combustion chamber in the lower wall of the cylinder head of an engine.
- the spark plug comprises a low-voltage cylindrical electrode which serves as a metal base 103 intended to be screwed into a recess made in the cylinder head of the engine and opening inside the combustion chamber.
- the base 103 is intended to be electrically connected to ground.
- the base 103 surrounds a cylindrical high voltage electrode 106 arranged in a central position.
- the electrode 106 is intended to be connected to a generator of a high ignition voltage.
- the electrode 106 is isolated from the base 103 via an insulating sleeve 100.
- the insulating sleeve consists of a material whose relative permittivity is greater than 3, for example a ceramic.
- the spark plug has a gap 105 between the dielectric 100 and one end of the electrode 103.
- the electrode 106 and the insulating sleeve 100 protrude by a length 1 outside the base 103.
- This length 1 substantially corresponds to the length of the spark generated when a high voltage is applied between the electrodes 106 and 103.
- the base or low-voltage electrode 103 comprises in one piece a body and a connecting piece supporting a flanged flange 101.
- the flange 101 has a beveled edge extending in the immediate vicinity of the surface of the insulator 100.
- the dielectric 100 creates an electrostatic field amplification in the air in its vicinity.
- the spark generated between the beveled edge of the flange 101 of the base 103 and a free end 104 of the central electrode 106 is propagated on the surface of the insulator 100, where the electric field in the air is the strongest. .
- the formation of a spark is initiated by tearing in the middle of a few electrons subjected to a large electric field.
- electrons of the collar are accelerated by the generated electrostatic forces and hit molecules of the air.
- the end of the flange is the area that undergoes the most important electrostatic field, and is therefore the starting point of the first avalanche.
- the molecules of the air release an electron and an ionizing photon in turn from other molecules of air.
- a chain reaction ionizes the air in the space 105 between the electrode 103 and the dielectric 100.
- the gas space 105 allows for prior ionization with a relatively small potential difference between the electrodes 103 and 106.
- a conductive channel is thus created, as shown in FIG. figure 2 .
- the discontinuous lines represent equipotentials of the electrostatic field when a high voltage is applied between the electrodes 103 and 106.
- the figure 3 represents an example of an electrostatic field amplitude between the end of the flange 101 and the end of the electrode 106, A designating the end of the flange, B denoting the end 104 of the electrode 106.
- the insulator is separated from the electrode 103 by an air space.
- This space is not essential for the operation of the candle but facilitates the manufacture of the candle with a flange with a very sharp angle near the surface of the insulation. It also reduces the influence of fouling phenomena.
- the physical phenomenon implemented thanks to radiofrequency excitation has similarities with the propagation described above but makes it possible to considerably improve the effects thereof.
- the figure 4 schematically represents the electrostatic field during the departure of an avalanche. It can be noted that the propagation of the avalanche is limited by the local field due to the separation of atoms and their electrons. This local field limits in particular the propagation of the discharge over long lengths.
- the present invention proposes, among other things, an electrical excitation capable of inverting the polarity of the imposed global field before the electrons have been able to recombine with the atoms present in the medium. At each alternation of the polarity, the electrons are more and more accelerated in the opposite direction.
- a polarization wave is thus propagated in an oscillatory manner at the frequency of the excitation, recovering at each period the charges deposited in the previous period. Each alternation then produces a propagation of the wave greater than the preceding one; it is thus possible to obtain sparks of very long lengths with voltage amplitudes between the relatively limited electrodes. Radio frequency excitation also suppresses the breakdown voltage variations between successive cycles.
- Electrodes and insulation having materials and geometry adequate to initiate combustion in a mixture at a combustion density and to resist the plasma thus formed.
- Plasma thus formed has many advantages in the context of automotive ignition: significant reduction in the rate of misfires in a stratified lean mixture system, reduction of wear of the electrodes and adaptation of the ignition initiation volume to density function. It is found that the excitation described is adapted to achieve ignition of a mixture having a density greater than 5 * 10 -2 mol / L. For this ignition application, the generator applies the excitation between 1.5 and 200 times per second, with an application duty ratio of between 10 and 1000, and preferably between 72 and 720.
- the radiofrequency excitation described is also adapted to a plasma deposition application in a gas having a density of between 10 -2 mol / L and 5 * 10 -2 mol / L.
- the gas used in this application may typically be nitrogen.
- the radiofrequency excitation is further adapted to an application for the depollution of a gas having a density of between 10 -2 mol / L and 5 * 10 -2 mol / L.
- the radio frequency excitation is furthermore suitable for a lighting application using a gas having a molar density of between 0.2 mol / l and 1 mol / l.
- the alternating voltage of the amplifier 5 is applied to the resonator LC 6.
- the resonator LC 6 applies the alternating voltage according to the invention between the electrodes 103 and 106 of the candle head.
- the voltage supplied by the power supply 3 is less than 1000V and the power supply preferably has a limited power. It can thus be provided that the energy applied between the electrodes is limited to 300mJ by ignition, for safety reasons. This also clamps the intensity in the voltage generator 2 and its power consumption.
- the power supply 3 may include a 12 Volt to Y Volt converter, where Y is the voltage supplied by the power supply to the amplifier. It is thus possible to generate the desired DC voltage level from a battery voltage.
- the stability of the DC voltage generated is not a priori a decisive criterion, it can be expected to use a switching power supply to power the amplifier, for its qualities of robustness and simplicity.
- This voltage generator makes it possible to concentrate the highest voltages on the resonator 6.
- the amplifier 5 thus deals with much lower voltages than the voltages applied between the electrodes: it is therefore possible to use an amplifier 5 of a reasonable cost and presenting characteristics similar to conventional components for automotive mass production, the reliability of which is furthermore proven.
- such a voltage generator has a relatively small number of components. There is thus a voltage generation system having a reliability, volume, weight and ease of production of interest, especially for large series in an automotive application.
- the amplifier 5 accumulates energy in the resonator 6 at each alternation of its voltage.
- a class E amplifier 5 will preferably be used as detailed in FIG. U.S. Patent 5,187,580 .
- Such an amplifier makes it possible to maximize the overvoltage factor.
- Such an amplifier performs out of phase switching with respect to the amplifier described in FIG. U.S. Patent 3,919,656 which aims at making commutations with voltage and / or zero intensities and does not optimize the overvoltage factor of the amplifier.
- Those skilled in the art will of course associate a switching device adapted to the chosen amplifier, to support the requirements of voltage increases and to have an adequate switching speed.
- the preferred class E amplifier comprises a parallel resonator 62.
- This parallel resonator 62 is preferably made on the same card as the amplifier 5 and its switching control 4.
- the parallel resonator 62 temporarily stores energy supplied by the amplifier 5, and periodically supplies this energy to the series resonator 61.
- an amplifier 5 having an overvoltage coefficient of This overvoltage coefficient corresponds to the ratio between the voltage supplied by the low voltage supply 3 and the amplitude between peaks of the voltage applied to the series resonator.
- the overvoltage coefficient of the associated series resonator 61 is then between 40 and 200.
- the overvoltage coefficient of the series resonator is notably limited by its loss angle.
- figure 6 illustrates an electric model of this resonator.
- the inductance series 65 has in series an inductance L and a resistor Rs taking into account the skin effect in the radiofrequency domain.
- the capacitor 119 has in parallel a capacitance C and a resistor Rp.
- the resistor Rp corresponds, if appropriate, to the dissipation in the ceramic of the spark plug.
- the maximization of the overvoltage coefficient Q is then equivalent to the minimization of The VS .
- a high capacitance C and a reduced inductance L are then preferably selected.
- amplifiers 5 will now be described.
- an amplifier having a power MOSFET transistor will preferably be used as a switch 51 controlling the commutations across the resonator 6.
- Figures 7 and 8 illustrate two embodiments of amplifiers 5 including MOSFETs M4, as switches 51.
- the amplitude and frequency constraints on the voltage to be generated between the electrodes can be solved with a power MOSFET having the following characteristics: greater than 500 V, a drain current capacity greater than 30 A, a switching time of less than 20 ns (and preferably of the order of 10 ns when using a control loop) and a capacitance in grid current up to 10A.
- This MOSFET transistor will also preferably have an inductance of less than 7 nH on its connections between its active silicon surface and the printed circuit on which it is implanted. This avoids transients during high voltage peaks that would be detrimental to the fast switching of the transistor.
- the figure 7 represents a first embodiment of an amplifier 5 having such a switching control transistor M4.
- a midpoint transformer 56 is interposed between the control 4 and the power MOSFET M4.
- the M4 power MOSFET can thus be controlled very quickly with a symmetrical voltage able to block it effectively. Indeed, the application of a negative voltage on the gate of the MOSFET M4 transistor makes it possible to compensate for the overvoltages caused by the linkage inductance of M4 with the rest of the circuit. The blocking the transistor is thus facilitated, especially since a negative voltage makes it possible to discharge the gate-drain capacitor particularly rapidly.
- the amplifier 5 shown comprises two intermediate transistors M1 and M2 arranged to alternately feed the coils L11 and L12 of the primary of the midpoint transformer.
- a control circuit 57 applies respective control signals to the transistors M1 and M2.
- the control signals do not overlap temporally to avoid a short circuit in the primary.
- the control signals also advantageously have substantially equal activation times to limit the magnetizing current in the transformer 56. It is also possible to compensate for an inequality of the activation times by a high value of the magnetising inductance of the transformer 56.
- the chronogram of the figure 9 illustrates various signals during the excitation of the series resonator 61.
- the curve 91 represents the current flowing through the series resonator 61.
- the curve 92 illustrates the gate voltage of the MOSFET M4.
- Curve 93 illustrates the voltage at the input of the series resonator 61.
- the amplifier 5 is advantageously integrated on one and the same printed circuit board 8. It is thus possible to integrate the transformer 56, the transistors M1 to M4 and the control circuit 57 on the same printed circuit board, according to the diagram represented in FIG. figure 10 . This gives a very low power amplifier 5 compact. The leakage inductance of the transformer and the overvoltages at the terminals of the intermediate transistors M1 and M2 are also minimized.
- the left part of the figure 10 represents several elements of the amplifier 5 and their connections.
- the central part of the figure 10 represents the transistors M1 and M2 and their respective windings L11 and L12.
- the right part of the figure 10 schematically represents the various elements integrated on the printed circuit 8.
- the assembly formed by the transistors M1 to M4, the coils L11, L12 and L2, is preferably arranged on an edge of the printed circuit 8. The coils can thus be arranged in the air gap of a split torus 81.
- the figure 8 represents a second embodiment of an amplifier 5 having a MOSFET switching control transistor M4.
- the gates of the transistors M1 and M2 are linked. Transistors M1 and M2 thus switch simultaneously.
- the bipolar transistor M3 is therefore mounted as a follower. When M1 and M2 conduct, the bipolar transistor M3 is off, and therefore the MOSFET transistor M4 is also blocked.
- Intermediate transistors M1 and M2 having the following characteristics are preferably used: a control voltage of 5V, a nominal intensity of 8A at this voltage, a resistance R on less than 150 milliOhm and a response time of less than 20ns.
- a servo-control of the amplifier 5 is carried out on the load current applied to the resonator 6.
- the amplifier 5 thus has a measuring device 54 of the current applied to the input of the resonator 6.
- the setpoint is applied to an input 58 of a comparator.
- the output signal of the comparator is applied to an amplification device 53 shown schematically. This optimizes the overvoltage factor of the amplifier 5 by driving the resonator 6 at its own frequency despite behavioral drifts of the components. This avoids the use of components whose cost and complexity are inappropriate for mass production.
- the slaving is for example carried out by re-injecting into the amplifier 5 a voltage proportional to the current flowing in the load. Phase correction can also be applied to the measured signal via the phase shift module 55.
- the parallel resistor R2 of the secondary of the transformer preferably fulfills two functions of the servocontrol: the feedback of a signal proportional to the current in the load, and the phase shift of the intensity crossing the load according to its resistance value.
- the figure 14 thus presents an example of transformer made on a printed circuit, facilitating the obtaining of such characteristics.
- the left part of the figure 14 independently represents the useful layers of the printed circuit.
- the right part of the figure represents these superimposed and assembled layers.
- the conductive element 151 forms the primary of a transformer, and is disposed on a first face of the substrate 152. This conducting element 151 is in the example realized in substantially wire form.
- the conductive elements 153 and 154 form the secondary of the transformer.
- These conductive elements 153 and 154 are arranged on a second face of the substrate 152, vis-à-vis the conductive element 152.
- the elements 153 and 154 are electrically connected firstly along the dotted line, and other
- the resistor 155 can thus be used to measure the current flowing through the conductive element 151 and to form the phase shift module 55 described above.
- the resonator LC 6 comprises a series resonator 61 and a parallel resonator 62.
- the series resonator 61 has a series capacitance 119 and a series inductor 65.
- the servocontrol structure comprises an astable oscillator 52 (for example a generator of crenellations) to generate the first alternations in the series 119 capacitance and to stabilize the oscillations under steady state conditions. It is expected that the frequency of the oscillator is close to the frequency of the excitation generated between the electrodes.
- the servo structure adds the current measurement signal and the signal of the astable oscillator 52 and thus enables the class E amplifier to perform the switching at the most favorable moments.
- the first slot generated by the oscillator 52 is approximately twice as short as the following: thus, the current in the series inductance 65 can be initialized to the value of this current under steady state conditions.
- the parallel resonator 62 comprises an inductor 621 and a capacitor 622 arranged in parallel. All pulses across inductance 621 and capacitance 622 are then equal. It is thus possible to avoid oversizing the switch 51 and exploit it optimally.
- the figure 12 represents a second variant.
- the control signal applied to the switch 51 generates a voltage slot of short duration, that is to say of the order of 5 ⁇ s, initiating the first alternation in the resonator 6.
- the servocontrol signal then controls the Switch 51.
- the feedback loop of the servo structure has a high gain. Thus, the initial pulse making the servocontrol operational is sufficiently short, and the current flowing through the switch 51 remains reasonable. It is thus not necessary to over-size the switch 51 to start the servocontrol, in particular when the switch is formed of a power MOSFET transistor.
- An advantageous combination of the parallel resonator 62 and the series resonator 61 optimizes the operation of the system when the natural frequency of the parallel resonator 62 is slightly greater than that of the series resonator 61.
- the voltage pulse generated by the closing of the switch transistor M4 has a duration less than the half-period of the series resonator 61.
- the pulse during the closing of the switch transistor M4 is anticipated by the internal reverse diode of the transistor M4 when the voltage of its drain returns to a zero value. It is then expected that the ratio between the impedances respective characteristics of the parallel resonator 62 and the series resonator 61 is less than 100 greater than 40. The lower value guarantees a good overvoltage coefficient.
- the upper value limits the currents in the transistor M4.
- a capacitance of 1 nF and an inductance of 1 ⁇ H are typically used for the parallel resonator 62.
- the characteristic impedance of the parallel resonator 62 is then approximately 32 ohms.
- the capacitances between the turns of the inductor 621 will be negligible with respect to the capacitance of the capacitor 622. It is therefore possible to realize the inductance 621 in the form of a superposition of tracks. substantially circular conductors 623 formed on the superposed layers of a printed circuit. Examples of printed circuit inductance structures 621 are shown in FIGS. Figures 15 and 16 . The embodiments of these figures thus make it possible to produce an inductor 621 without a ferrite core. This reduces the cost and improves the performance of the inductor 621.
- each track 623 is surrounded by a closed loop 625, in order to reduce the radiation of the inductance 621 formed by the tracks.
- the scheme of the figure 15 represents a variant having an upper layer and a lower layer having no coil track.
- the upper layer and the lower layer each have a connection terminal 624 of the inductor 621.
- the scheme of the figure 16 represents a variant, wherein the lower layer and the upper layer each have a coil track and a connection terminal.
- the curved lines 626 joining a connection pad to a connection terminal 624 represent an electrical connection reported on these printed circuit layers.
- the losses are significant.
- the presence of magnetic material in the series resonator 61 is preferably minimized.
- a variant can be envisaged, in which a common power supply and amplifier are used for two resonators 6 arranged in parallel.
- This variant reduces the weight, cost and overall complexity of the voltage generation system 1 for a spark ignition engine.
- Each resonator 6 corresponds to a respective combustion chamber 141 and 142, the two combustion chambers being in phase opposition.
- the amplifier 5 is controlled so that the ignition voltage is generated both during compression and during expansion for each combustion chamber. Indeed, the compression in a chamber 141 is synchronized with the trigger 142 in the other.
- the breakdown in the expansion chamber 142 is much faster than in the compression chamber 141. Indeed, the gas density in the expansion chamber is much lower than the density in the chamber in compression.
- the equivalent discharge resistance of the expansion chamber 142 is thus much higher than that of the compression chamber.
- the candle present in the compression chamber then continues to rise in voltage until breakdown.
- the density of the gas in the expansion chamber is low enough not to disturb the coefficient of overvoltage in the compression chamber; the generation of the spark in the chamber in compression is thus undisturbed by the generation of the voltage in the other chamber.
- the figure 18 represents a sectional view of a spark plug advantageously integrating a series resonator 61.
- the spark plug 110 has a connection terminal 131, connected to a first end of an inductive winding 112.
- the second end of the inductive winding 112 is connected to one end. of the high voltage electrode 106. This end is also in contact with an insulating element 111 forming the capacitor.
- the electrodes 103 and 106 are in this example separated by the dielectric material 100 for guiding sparks between these electrodes.
- the series resonator 61 integrated in the spark plug 110 comprises the inductive winding 112 and the insulating element 100 also forming the capacitor between the electrodes 103 and 106.
- the capacitor and the inductive winding 112 are arranged in series.
- the series capacitance of the series 61 resonator is formed of the capacitor and internal parasitic capacitances of the spark plug.
- This capacitor 119 is arranged in series with an inductor 65 to form the series resonator 61. The length of the connection between the inductor and the capacitor being thus reduced, the parasitic capacitances in the spark plug are reduced. It is thus easy to obtain an overvoltage coefficient of the series resonator in the range of 40 to 200 described above.
- the candle 110 is thus used to maintain the alternating voltage between the electrodes 103 and 106, in the desired frequency range.
- the integrated series resonator in the candle preferably has a single coil 112, facilitating the manufacture of such a candle.
- the only inductive coil 112 preferably has an axis (identified by the dashed line) and consists of a plurality of turns superimposed along its axis. It is thus understood that the projection of a turn is identical to the projection of all the turns along this axis. The parasitic capacitances are then limited by not superimposing turns radially.
- the spark plug furthermore advantageously comprises a shield 132 connected to a ground and surrounding the inductive winding 112.
- the field lines are thus closed inside the shielding 132.
- the shielding 132 thus reduces the parasitic electromagnetic emissions of the spark plug 110.
- coil 112 can indeed generate intense electromagnetic fields with the radiofrequency excitation that is intended to apply between the electrodes. These fields may notably disrupt embedded systems of a vehicle or exceed thresholds defined in emission standards.
- the shield 132 is preferably made of a non-ferrous material of high conductivity, such as copper. It is possible in particular to use a conductive loop as shielding 132.
- the optimum ratio between their diameter is equal to the Euler number, or approximately 2.72, if it is desired to minimize the maximum electric field generated at the surface. turns. This avoids breakdown phenomena at the origin of energy dissipations in the candle. We will then preferably choose a ratio between their diameter of between 2.45 and 3.
- the use of two coils 112 wound on one another and connected in parallel makes it possible to reduce the resistance of the winding formed.
- the skin effect significantly increasing the resistance of the winding in the radio frequency range, is minimized by the winding one over the other of these two windings.
- the optimum ratio between the diameter of the shield 132 and the coil 112 is 2 by winding on one another two windings 112 connected in parallel by their ends.
- the two coils wound on one another have slightly different winding diameters and therefore slightly different inductances, which can disturb the operation of the candle in the radio frequency range. It has been determined that for the value 2 mentioned above, the difference of the inductances did not disturb the operation of the candle in the radiofrequency domain. In this case, a ratio of diameters between 1.35 and 1.5 will preferably be chosen.
- the winding 112 and the shield 132 are preferably separated by an insulating sleeve 133 of a suitable dielectric material, in order to further reduce the risk of breakdown or corona discharge, causing energy dissipation.
- a suitable dielectric material may for example be one of the silicone resins sold under the references Elastosil M4601, Elastosil RTV-2 or Elastosil RT622 (the latter having a breakdown voltage of 25 kV / mm and a dielectric constant of 2.8). It can be provided that the outer surface of the sleeve 133 is metallized to form the shielding 132 above.
- winding 112 around a solid element 134 made of insulating and non-magnetic material. This further reduces the risk of breakdown and parasitic capacitances.
- the set of dielectric materials is preferably strongly debulled, to further reduce the risk of breakdown. All the dielectric materials of the candle preferably have melting temperatures above 150 ° C.
- the coil-candle comprises several insulating elements contiguous, there is a significant risk of creating air inclusions at the interface between these elements, especially when made of ceramic.
- the coil-candle in most cases comprises several insulating elements contiguous.
- the connection between the insulation 134 of the coil and the insulator 111 of the candle head is also, for the same reasons corona, a very important source of dissipation.
- the aforementioned technique can, according to a new embodiment, be used in the ceramic to create equipotentials preventing the formation of electrical discharges.
- the figure 19 represents a section of an insulating element 111 of candle head, also solving this problem.
- This insulating element 111 is intended to be associated with an insulating element 133 in the form of a silicone resin.
- This insulating element 111 has a non-circular section and is included in a circular part 136 belonging to the cathode 103. Thus, this element forms passages intended to let the silicone resin flow during its injection. The silicone resin can thus remove most of the air inclusions from the surface of the insulating elements.
- the dielectric material used for the insulator 100 may for example be a ceramic based on alumina, aluminum nitride, aluminum oxide or silicon carbide.
- the spark plug 110 furthermore has a current measurement winding 139 fulfilling the function of the module 54.
- This winding 139 comprises several turns surrounding the winding 112.
- the winding 139 is preferably arranged to proximity of the connector 131 and remote from the candle head, in an area where the voltages are relatively low.
- the candle of the invention can incorporate a number of other features, such as the seat seal 130 of the invention. figure 18 disposed against a shoulder of the cathode 103, and for sealing the cylinder head at the candle light.
- the candle head is the part of the candle that is placed in the gas in which the plasma must be formed.
- This candle head preferably comprises three elements: a central electrode 106, a ground electrode 103 and an insulator 100.
- the geometry of these elements is decisive for ensuring the formation of the volume plasma or branched plasma at the desired location of the chamber, with optimal properties, especially for ignition (large volume, optimal energy transfer to the gas, etc ).
- the Figures 20 to 27 illustrate various configurations of candle heads, advantageously included in candles adapted to generate a plasma between their electrodes and adapted to be powered by a radio frequency excitation.
- the figure 20 presents a first group of variants of candle heads, which will be called candles with capacitive propagation.
- These geometries of candle heads have a cathode 103 partially covered by the insulation 100 in the axis of the candle. This geometry generates a capacitive propagation of the spark on the surface of the insulator 100.
- the figure 20.I represents a candle head geometry known per se.
- the cathode 103 protrudes axially beyond the insulator 100.
- An electric arc can to form following this direct path.
- Figures 20.II and 20.III generate a better distribution of the plasma on the surface of the insulator 100.
- the probability of formation of an arc is reduced. This creates multidirectional discharges between the electrodes.
- the plasma is distributed more evenly around the candle and the volume of gas affected is increased.
- the capacitive propagation effect between the electrodes is also reduced; the plasma can thus be generated at a greater distance from the surface of the insulator.
- the cathode 103 is no longer protruding axially with respect to the insulator 100.
- the insulator 100, the cathode 103 and the anode 106 form substantially a flat surface, avoiding the formation of an electric arc between the anode 106 and the cathode 103.
- the insulator 100 projects axially with respect to the ends of the electrodes 103 and 106. extend the air path between the electrodes 103 and 106.
- the protrusion of the insulator 100 forms a rounded boss.
- the variant of the figure 21 proposes to reduce the capacitive effect.
- the cathode 103 does not extend radially under the insulator 100.
- the cathode 103 of this variant is arranged axially recessed relative to the insulator.
- the central electrode or anode 106 is arranged flush with the insulation.
- the figure 22 proposes to make a cavity or a recess 120 in the insulator in order to amplify the phenomenon of depolarization.
- the anode 106 also has an increasing section at its end, at the recess 120. Thus, in the recess, the final section of the anode 106 is greater than its intermediate section. Thus, a vacuum 121 is created axially between the end of the anode and the insulator 100, which locally amplifies the electric field.
- the variants to avoid the formation of a direct arc between the electrodes operate optimally in combination with the radiofrequency excitation.
- Radiofrequency excitation makes it possible to extend and curve the trajectory of the sparks.
- the figure 23 represents a preferred embodiment of a peak effect candle head.
- the anode 106 consists of a core 1061 and a sheath 1062.
- the core 1061 is for example made of copper in order to promote the evacuation of heat along the anode 106. electrochemical erosion of the end of the anode.
- the sheath 1062 can be made of any suitable material, such as nickel.
- the figure 24 represents several examples of peak effect candle heads. These candles thus have a ground electrode 103 recessed axially with respect to the insulator 100, in order to reduce the capacitive effect.
- the projecting end of the anode 106 also has a pointed shape.
- Examples 24.II to 24.IV each have a cathode 103 forming an axial recess 122 near the insulator 100.
- This recess 122 has a rounded shape. This increases the ability of the candle to generate a branched spark. This reduces the probability that a plasma will only propagate on the surface of the insulation. The plasma thus tends to be distributed in a volume remote from the surface of the insulation 100.
- Examples 24.III and 24.IV have an insulator 100 whose end has a rounded shape 123, in order to reduce its internal stresses. These constraints are related to the high levels of electric fields and temperature gradients near the end of the insulator 100.
- figure 24.IV comprises an anode 106 whose axial end 1063 has several points. A greater number of sparks are thus generated during the excitation and the erosion of the anode 106 is distributed over all the tips used.
- the spark plugs may accidentally generate arcing between the anode 106 and the piston when the distance between the piston and the spark plug head is small. These arcs prematurely erode the tip of the anode 106 and prevent the formation of plasma volume or branched plasma.
- the candle head of the figure 25 thus presents a solution to this problem.
- the tip of the anode 106 is thus disposed in a counterbore 124 formed in the insulator 100.
- a countersink and a recess are preferably provided in order to reduce the electric field at the interface between the anode 106 and the insulator 100.
- the insulator 100 protrudes axially from the tip of the anode 106.
- the insulation 100 is also an edge 125 projecting axially with respect to the cathode 103.
- the Figures 26 and 27 illustrate dielectric barrier candle heads which will later be referred to as blind candles.
- the anode 106 is completely covered by the insulator 100.
- Such candles make it possible in particular to eliminate the formation of an electric arc between the anode and a piston, and to eliminate the erosion of the anode. The life of the spark plug is thus greatly increased, and can equal the life of a heat engine without requiring maintenance. Such candles only work because of the capacitive nature of the insulation 100.
- the operation of a blind candle is made possible by the use of radiofrequency excitation.
- the application of radiofrequency excitation between the electrodes of a blind candle is also particularly advantageous.
- Electrode excitation forms space charges on the outer surface of the insulation.
- the insulator 100 then behaves as an anode and a volume plasma or a branched plasma is generated on its surface. Although the insulation has a relatively low charge, the radio frequency excitation generates a very large number of sparks on the surface of the insulation in a very short time. In this variant, it is possible for the insulator 100 to form the capacitor of the resonator. This reduces the energy dissipated in the candle.
- the heads of the candles shown have a symmetry of revolution about their axis, it is also possible to provide candle heads having other geometries, within the scope of the invention.
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Abstract
Description
La présente invention concerne de façon générale la génération de plasma dans un gaz, et plus particulièrement les bougies de génération de plasma à inductance intégrée. La génération de plasma est notamment utilisée pour l'allumage commandé de moteurs à combustion interne par les électrodes d'une bougie.The present invention relates generally to the generation of plasma in a gas, and more particularly to the plasma generation candles with integrated inductance. Plasma generation is used in particular for the controlled ignition of internal combustion engines by the electrodes of a candle.
L'allumage des moteurs à combustion interne essence, consistant à initier la combustion d'un mélange air-essence dans une chambre de combustion dudit moteur, est relativement bien maîtrisé dans les moteurs actuels. Dans les moteurs à allumage commandé à injection indirecte, classiquement, une bougie et un dispositif électronique en amont permettent de générer une étincelle capable de transmettre au mélange une énergie suffisante à sa combustion. La formation de cette décharge nécessite des tensions de claquage élevées (de l'ordre de 30 kV par mm), si bien que l'on limite l'espace inter-électrodes des bougies à environ 1 mm, distance relativement peu favorable à l'initiation de la combustion.The ignition of gasoline internal combustion engines, consisting of initiating the combustion of an air-fuel mixture in a combustion chamber of said engine, is relatively well controlled in current engines. In spark-ignition engines with indirect injection, conventionally, a spark plug and an upstream electronic device make it possible to generate a spark capable of transmitting to the mixture sufficient energy for its combustion. The formation of this discharge requires high breakdown voltages (of the order of 30 kV per mm), so that the inter-electrode space of the candles is limited to about 1 mm, a relatively unfavorable distance to the initiation of combustion.
Pour satisfaire les normes de dépollution, les constructeurs automobiles ont développé des moteurs à allumage commandé aptes à fonctionner avec des mélanges carburés pauvres, c'est-à-dire présentant un excès d'air par rapport à la quantité de carburant injectée. Ces développements ont été appliqués en particulier aux moteurs à injection directe, dans lesquels l'injection de carburant se fait directement dans la chambre de combustion.To meet the standards of depollution, the car manufacturers have developed spark ignition engines capable of operating with poor fuel mixtures, that is to say having an excess of air relative to the amount of fuel injected. These developments have been applied in particular to direct injection engines, in which injection fuel is done directly in the combustion chamber.
Les dispositifs d'allumage classiques s'appliquent assez mal sur les moteurs à mélange pauvre et à injection directe. En effet, les dispositifs d'allumage sont alors très ardus à mettre au point. Un front de flamme se propage correctement dans un mélange très pauvre (richesse inférieure à 0,3) mais l'initiation de la combustion nécessite généralement des richesses supérieures à 0,7, et de préférence pour des richesses proches de la stoechiométrie. Il est donc primordial de maintenir une richesse suffisamment élevée au niveau de l'espace inter-électrode.Conventional ignition devices do not apply well on lean-burn and direct injection engines. Indeed, the ignition devices are then very difficult to develop. A flame front propagates correctly in a very poor mixture (richness lower than 0.3) but the initiation of the combustion generally requires wealth higher than 0.7, and preferably for richness close to stoichiometry. It is therefore essential to maintain a sufficiently high richness in the inter-electrode space.
La génération de mélanges stratifiés à donc été développée. Par opposition à un mélange homogène où la richesse est globalement la même en tout point, un mélange stratifié présente une richesse qui décroît au fur et à mesure que l'on s'éloigne de la bougie. La stratification du mélange dans la chambre de combustion est par exemple obtenue en guidant le jet de carburant de sorte que le jet rencontre la bougie au moment de la production de l'étincelle. Le guidage du jet est notamment obtenu par des phénomènes aérodynamiques, générés par exemple par une forme appropriée du piston.The generation of stratified mixtures has therefore been developed. In contrast to a homogeneous mixture where the richness is globally the same in every respect, a stratified mixture presents a richness which decreases as one moves away from the candle. The stratification of the mixture in the combustion chamber is for example obtained by guiding the jet of fuel so that the jet meets the candle at the time of the production of the spark. The guidance of the jet is obtained in particular by aerodynamic phenomena, generated for example by a suitable shape of the piston.
Les mélanges stratifiés posent plusieurs problèmes. Il est délicat de faire coïncider l'instant d'étincelle et la présence au voisinage de l'espace inter-électrodes d'un nuage de mélange présentant une richesse proche de 1, dans un environnement de mélange globalement pauvre. De plus, le mélange situé autour de la bougie au moment de l'étincelle présente d'importantes inhomogénéités de richesse, variables dans le temps, qui ne garantissent pas l'initiation de la combustion au moment du développement de l'étincelle. La taille et la durée d'étincelle des bougies classiques impliquent alors un taux de ratés d'allumage incompatible avec les exigences de rendement et de pollution actuels. Par ailleurs, le jet de carburant frappe souvent directement la bougie, ce qui entraîne un encrassement de l'isolant de la bougie. Cet encrassement favorise les courants de fuites entre l'électrode centrale et la masse. La génération des étincelles est affectée car l'étincelle est court-circuitée par un chemin carboné de faible impédance qui réduit la différence de potentiel entre les électrodes de la bougie.Stratified mixtures pose several problems. It is difficult to coincide the moment of spark and the presence in the vicinity of the inter-electrode space of a mixture cloud with a richness close to 1, in a globally poor mixing environment. In addition, the mixture around the candle at the moment of the spark has significant inhomogeneities of richness, variable in time, which do not guarantee the initiation of combustion at the time of development of the spark. The size and duration of spark of conventional candles then imply a misfire rate incompatible with the current performance and pollution requirements. In addition, the jet of fuel often strikes directly the candle, resulting in fouling of the insulation of the candle. This fouling promotes leakage currents between the central electrode and the mass. The generation of sparks is affected because the spark is short-circuited by a low impedance carbon path that reduces the potential difference between the spark plug electrodes.
De nouvelles bougies à étincelle de surface produisent des étincelles plus grandes pour traiter le problème du rendez-vous spatio-temporel. On allume ainsi un volume de mélange supérieur. La probabilité d'initiation de la combustion est alors très largement augmentée dans un moteur à injection directe à allumage commandé et mélange stratifié. De telles bougies sont notamment décrites dans les demandes de
Il existe donc un besoin, que l'invention vise à satisfaire, pour une bougie de génération de plasma résolvant un ou plusieurs de ces inconvénients.There is therefore a need, which the invention aims to satisfy, for a plasma generation candle solving one or more of these disadvantages.
L'invention porte ainsi sur une bougie comprenant:
- deux électrodes de génération de plasma,
- un condensateur muni de deux bornes, et
- un bobinage inductif, le condensateur et le bobinage étant disposés en série,
- two plasma generation electrodes,
- a capacitor with two terminals, and
- an inductive winding, the capacitor and the winding being arranged in series,
Le terme plasma ramifié utilisé par la suite désigne la génération simultanée d'au moins plusieurs lignes ou chemins d'ionisation dans un volume donné, leurs ramifications étant en outre omnidirectionnelles.The term branched plasma used in the following refers to the simultaneous generation of at least several lines or ionization paths in a given volume, their branches being moreover omnidirectional.
Alors qu'un plasma de volume implique le réchauffement de tout le volume dans lequel il doit être généré, le plasma ramifié ne nécessite que le chauffage sur le trajet des étincelles formées. Ainsi, pour un volume donné, l'énergie requise pour un plasma ramifié est nettement inférieure à celle requise par un plasma de volume.While a volume plasma involves heating up the entire volume in which it is to be generated, the branched plasma only requires the heating in the path of the sparks formed. Thus, for a given volume, the energy required for a branched plasma is much lower than that required by a volume plasma.
L'invention permet de réduire les capacités parasites internes d'une bougie de génération de plasma et ainsi d'obtenir une bougie formant un résonateur série présentant un coefficient de surtension élevé. Cette bougie permet d'entretenir une tension radiofréquence entre ses électrodes pour la génération d'un plasma.The invention makes it possible to reduce the internal parasitic capacitances of a plasma generation candle and thus to obtain a spark plug forming a series resonator having a high overvoltage coefficient. This candle makes it possible to maintain a radiofrequency voltage between its electrodes for the generation of a plasma.
De façon générale, on entendra par la suite par haute densité, toute densité molaire supérieure à 2,5 * 10-3 mol/L. On appellera densité de combustion toute densité molaire de gaz supérieure à 5* 10-2 mol/L. On désignera par streamer une pointe d'ionisation positive se propageant depuis l'anode.In a general manner, the following will be understood by high density, any molar density greater than 2.5 * 10 -3 mol / L. Combustion density will be called any molar density of gas greater than 5 * 10 -2 mol / L. A stream of positive ionization propagating from the anode will be referred to as a streamer.
D'autres particularités et avantages de l'invention apparaîtront clairement à la lecture de la description suivante qui est donnée à titre d'exemple non limitatif et en regard des figures. Ces figures montrent:
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Figure 1 , un schéma de fonctionnement d'une bougie d'allumage à étincelle de surface; -
Figure 2 , la représentation de champs appliqués et de l'étincelle générée entre les électrodes de la bougie durant l'initiation de l'allumage; -
Figure 3 , un diagramme du champ électrostatique entre les deux électrodes de la bougie durant l'initiation de l'allumage; -
Figure 4 , une représentation schématique du développement d'un streamer pour une unique montée en tension (champ local et champ global); -
Figure 5 , une représentation schématique d'un mode de réalisation du système de génération de plasma selon l'invention ; -
Figure 6 , un modèle électrique utilisé pour le dimensionnement du résonateur série; -
Figure 7 , une variante dans laquelle l'amplificateur comprend un transformateur à point milieu; -
Figure 8 , une autre variante du système dans laquelle l'amplificateur comprend une commande de transistor de puissance par un transistor bipolaire; -
Figure 9 , des chronogrammes de signaux durant l'excitation du résonateur de lafigure 7 ; -
Figure 10 , les différents éléments de l'alimentation de lafigure 7 intégrés sur un même circuit; -
Figure 11 , une représentation schématique d'une boucle d'asservissement incluse dans l'amplificateur; -
Figure 12 , une variante du système comprenant une boucle d'asservissement et des circuits de génération des premières oscillations de tension; -
Figure 13 , une autre variante de système comprenant une boucle d'asservissement et des circuits de génération des premières oscillations de tension; -
Figure 14 , un exemple de transformateur formant une sonde de courant de l'amplificateur, réalisé sur un circuit imprimé; -
Figure 15 , un mode de réalisation d'une inductance parallèle sur un circuit imprimé; -
Figure 16 , un autre mode de réalisation d'une inductance parallèle sur un circuit imprimé; -
Figure 17 , une variante d'un système présentant une alimentation et un amplificateur communs pour deux résonateurs; -
Figures 18 et19 , des représentations schématiques en coupe d'un exemple de bougie utilisable dans le système de génération de plasma; -
Figures 20 à 27 , différentes configurations de têtes de bougie adaptées pour une excitation radiofréquence.
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Figure 1 , an operating diagram of a surface spark spark plug; -
Figure 2 , the representation of applied fields and the spark generated between the electrodes of the candle during ignition initiation; -
Figure 3 a diagram of the electrostatic field between the two electrodes of the candle during ignition initiation; -
Figure 4 , a schematic representation of the development of a streamer for a single voltage rise (local field and global field); -
Figure 5 a schematic representation of an embodiment of the plasma generating system according to the invention; -
Figure 6 , an electric model used for the design of the series resonator; -
Figure 7 a variant in which the amplifier comprises a mid-point transformer; -
Figure 8 another variant of the system in which the amplifier comprises a power transistor control by a bipolar transistor; -
Figure 9 , timing of signals during the excitation of the resonator of thefigure 7 ; -
Figure 10 , the different elements of the diet of thefigure 7 integrated on the same circuit; -
Figure 11 , a schematic representation of a control loop included in the amplifier; -
Figure 12 a variant of the system comprising a control loop and generation circuits of the first voltage oscillations; -
Figure 13 another system variant comprising a servo loop and generation circuits of the first voltage oscillations; -
Figure 14 an example of a transformer forming a current probe of the amplifier, produced on a printed circuit; -
Figure 15 , an embodiment of a parallel inductance on a printed circuit; -
Figure 16 another embodiment of a parallel inductance on a printed circuit; -
Figure 17 a variant of a system having a common power supply and amplifier for two resonators; -
Figures 18 and19 schematic sectional representations of an example of a candle that can be used in the plasma generation system; -
Figures 20 to 27 , different configurations of candle heads adapted for radio frequency excitation.
L'invention propose d'intégrer un résonateur série présentant une fréquence de résonance supérieure à 1 MHz dans une bougie. Les électrodes de la bougie sont connectées aux bornes de ce résonateur série.The invention proposes to integrate a series resonator having a resonance frequency greater than 1 MHz in a candle. The electrodes of the spark plug are connected to the terminals of this series resonator.
La
La bougie à effet de surface 110 comprend une tête de bougie destinée à déboucher dans la chambre de combustion ménagée dans la paroi inférieure de la culasse d'un moteur. La bougie comprend une électrode cylindrique basse tension qui sert de culot métallique 103 destiné à se visser dans un évidement réalisé dans la culasse du moteur et débouchant à l'intérieur de la chambre de combustion. Le culot 103 est destiné à être connecté électriquement à la masse.The
Le culot 103 entoure une électrode haute tension cylindrique 106 disposée en position centrale. L'électrode 106 est destinée à être reliée à un générateur d'une haute tension d'allumage. L'électrode 106 est isolée du culot 103 par l'intermédiaire d'un manchon isolant 100. Le manchon isolant est constitué d'une matière dont la permittivité relative est supérieure à 3, par exemple une céramique. La bougie présente un espace 105 séparant le diélectrique 100 et une extrémité de l'électrode 103.The base 103 surrounds a cylindrical
L'électrode 106 et le manchon isolant 100 débouchent en saillie d'une longueur 1 à l'extérieur du culot 103. Cette longueur 1 correspond sensiblement à la longueur de l'étincelle générée lorsqu'une haute tension est appliquée entre les électrodes 106 et 103.The
Le culot ou électrode basse tension 103 comprend de façon monobloc un corps et une pièce de liaison supportant une collerette rabattue 101. La collerette 101 présente un bord biseauté s'étendant à proximité immédiate de la surface de l'isolant 100.The base or low-
Le diélectrique 100 crée une amplification de champ électrostatique dans l'air à son voisinage. L'étincelle générée entre le bord biseauté de la collerette 101 du culot 103 et une extrémité libre 104 de l'électrode centrale 106 se propage à la surface de l'isolant 100, là où le champ électrique dans l'air est le plus fort.The dielectric 100 creates an electrostatic field amplification in the air in its vicinity. The spark generated between the beveled edge of the
La formation d'une étincelle est initiée par l'arrachement au milieu de quelques électrons soumis à un champ électrique important. Lors de l'application d'une tension importante entre les électrodes, des électrons de la collerette sont accélérés par les forces électrostatiques générées et heurtent des molécules de l'air. L'extrémité de la collerette est la zone qui subit le champ électrostatique le plus important, et constitue donc le lieu de départ de la première avalanche. Les molécules de l'air libèrent un électron et un photon ionisant à leur tour d'autres molécules d'air. Une réaction en chaîne ionise l'air dans l'espace 105 entre l'électrode 103 et le diélectrique 100. L'espace de gaz 105 permet de réaliser une ionisation préalable avec une différence de potentiel entre les électrodes 103 et 106 relativement limitée.The formation of a spark is initiated by tearing in the middle of a few electrons subjected to a large electric field. When applying a large voltage between the electrodes, electrons of the collar are accelerated by the generated electrostatic forces and hit molecules of the air. The end of the flange is the area that undergoes the most important electrostatic field, and is therefore the starting point of the first avalanche. The molecules of the air release an electron and an ionizing photon in turn from other molecules of air. A chain reaction ionizes the air in the
Un canal conducteur est ainsi créé, comme illustré à la
La
Dans la bougie de la
Le phénomène physique mis en oeuvre grâce à l'excitation radiofréquence présente des similitudes avec la propagation décrite précédemment mais permet d'en améliorer considérablement les effets. La
Pour une application à l'allumage automobile, l'homme de métier utilisera des électrodes et un isolant présentant des matériaux et une géométrie adéquats pour initier une combustion dans un mélange à une densité de combustion et pour résister au plasma ainsi formé.For automotive ignition applications, those skilled in the art will utilize electrodes and insulation having materials and geometry adequate to initiate combustion in a mixture at a combustion density and to resist the plasma thus formed.
Un plasma ainsi formé présente de nombreux intérêts dans le cadre de l'allumage automobile: diminution sensible du taux de ratés dans un système à mélange pauvre stratifié, réduction de l'usure des électrodes et adaptation du volume d'initiation de l'allumage en fonction de la densité. On constate que l'excitation décrite est adaptée pour réaliser l'allumage d'un mélange présentant une densité supérieure à 5*10-2 mol/L. Pour cette application d'allumage, le générateur applique l'excitation entre 1,5 et 200 fois par secondes, avec un rapport cyclique d'application compris entre 10 et 1000, et de préférence compris entre 72 et 720.Plasma thus formed has many advantages in the context of automotive ignition: significant reduction in the rate of misfires in a stratified lean mixture system, reduction of wear of the electrodes and adaptation of the ignition initiation volume to density function. It is found that the excitation described is adapted to achieve ignition of a mixture having a density greater than 5 * 10 -2 mol / L. For this ignition application, the generator applies the excitation between 1.5 and 200 times per second, with an application duty ratio of between 10 and 1000, and preferably between 72 and 720.
L'excitation radiofréquence décrite est également adaptée à une application de dépôt plasma, dans un gaz présentant une densité comprise entre 10-2 mol/L et 5*10-2 mol/L. Le gaz utilisé dans cette application peut typiquement être de l'azote.The radiofrequency excitation described is also adapted to a plasma deposition application in a gas having a density of between 10 -2 mol / L and 5 * 10 -2 mol / L. The gas used in this application may typically be nitrogen.
L'excitation radiofréquence est encore adaptée à une application de dépollution d'un gaz présentant une densité comprise entre 10-2 mol/L et 5*10-2 mol/L.The radiofrequency excitation is further adapted to an application for the depollution of a gas having a density of between 10 -2 mol / L and 5 * 10 -2 mol / L.
L'excitation radiofréquence est en outre adaptée à une application d'éclairage faisant appel à un gaz présentant une densité molaire comprise entre 0,2 mol/L et 1 mol/L.The radio frequency excitation is furthermore suitable for a lighting application using a gas having a molar density of between 0.2 mol / l and 1 mol / l.
Un système de génération de plasma envisagé comprend principalement trois sous-ensembles fonctionnels:
- un générateur capable de faire résonner une structure L-C à une fréquence supérieure à 1MHz avec une tension aux bornes du condensateur supérieure à 5kV, de préférence supérieure à 6kV.
- un résonateur connecté en sortie du générateur et présentant un facteur de surtension compris entre 40 et 200 et présentant une fréquence de résonance supérieure à 1 MHz.
- une tête de bougie comprenant deux électrodes séparées par un isolant, permettant de générer un plasma lors de l'application de l'excitation radiofréquence.
- a generator capable of resonating an LC structure at a frequency greater than 1 MHz with a voltage across the capacitor greater than 5 kV, preferably greater than 6 kV.
- a resonator connected at the output of the generator and having an overvoltage factor between 40 and 200 and having a resonance frequency greater than 1 MHz.
- a candle head comprising two electrodes separated by an insulator, for generating a plasma during the application of the radiofrequency excitation.
La
- une alimentation basse tension 3 (générant une tension continue inférieure à 1000 V);
un amplificateur radiofréquence 5, amplifiant la tension continue et générant une tension alternative à la fréquence commandée par la commande decommutation 4.
- a low voltage supply 3 (generating a DC voltage of less than 1000 V);
- a
radio frequency amplifier 5, amplifying the DC voltage and generating an AC voltage at the frequency controlled by the switchingcontrol 4.
La tension alternative de l'amplificateur 5 est appliquée sur le résonateur LC 6. Le résonateur LC 6 applique la tension alternative selon l'invention entre les électrodes 103 et 106 de la tête de bougie.The alternating voltage of the
La tension fournie par l'alimentation 3 est inférieure à 1000V et l'alimentation présente de préférence une puissance limitée. On peut ainsi prévoir que l'énergie appliquée entre les électrodes soit limitée à 300mJ par allumage, pour des raisons de sécurité. On bride ainsi également l'intensité dans le générateur de tension 2 et sa consommation électrique. Pour générer des tensions continues supérieures à 12 V dans une application automobile, l'alimentation 3 peut comprendre un convertisseur 12 Volt vers Y Volt, Y étant la tension fournie par l'alimentation à l'amplificateur. On peut ainsi générer le niveau de tension continue souhaitée à partir d'une tension de batterie. La stabilité de la tension continue générée n'étant a priori pas un critère déterminant, on peut prévoir d'utiliser une alimentation à découpage pour alimenter l'amplificateur, pour ses qualités de robustesse et de simplicité.The voltage supplied by the
On peut également envisager, selon une variante, d'appliquer aux bornes de l'amplificateur une tension de 42 V prélevée sur le circuit électrique du véhicule. Il s'agit en effet du niveau de tension qui sera en vigueur dans de futures normes applicables aux futurs véhicules automobiles. Cette variante, évitant la conversion de tension par l'alimentation 3, réduit sensiblement le coût et la complexité du générateur de tension 2.One can also consider, according to one variant, to apply across the amplifier a voltage of 42 V taken from the electrical circuit of the vehicle. This is the level of tension that will prevail in future standards for future motor vehicles. This variant, avoiding the voltage conversion by the
Ce générateur de tension permet de concentrer les tensions les plus élevées sur le résonateur 6. L'amplificateur 5 traite ainsi des tensions beaucoup plus réduites que les tensions appliquées entre les électrodes: on peut donc utiliser un amplificateur 5 d'un coût raisonnable et présentant des caractéristiques voisines de composants usuels pour la production automobile de masse, dont la fiabilité est en outre éprouvée. De plus, un tel générateur de tension présente un nombre de composants relativement réduit. On dispose ainsi d'un système de génération de tension présentant une fiabilité, un volume, un poids et une facilité de production intéréssants, en particulier pour de grandes séries dans une application automobile.This voltage generator makes it possible to concentrate the highest voltages on the
L'amplificateur 5 permet d'accumuler de l'énergie dans le résonateur 6 à chaque alternance de sa tension. On utilisera de préférence un amplificateur 5 en classe E, tel que détaillé dans le
L'amplificateur en classe E préférentiel comporte un résonateur parallèle 62. Ce résonateur parallèle 62 est de préférence réalisé sur la même carte que l'amplificateur 5 et sa commande 4 de commutation. Le résonateur parallèle 62 stocke temporairement de l'énergie fournie par l'amplificateur 5, et fournit périodiquement cette énergie au résonateur série 61. Avec les valeurs de tension d'alimentation précisées par ailleurs, on utilisera un amplificateur 5 présentant un coefficient de surtension de l'ordre de 3. Ce coefficient de surtension correspond au rapport entre la tension fournie par l'alimentation basse tension 3 et l'amplitude entre crêtes de la tension appliquée sur le résonateur série. Le coefficient de surtension du résonateur série 61 associé est alors compris entre 40 et 200. Le coefficient de surtension du résonateur série est notamment limité par son angle de perte.The preferred class E amplifier comprises a
On va exposer un dimensionnement préférentiel des éléments inductifs et capacitifs du résonateur série 61. La
De l'équation ω0 2=(2π*f0)2=1/(L*C), on déduit que l'équation suivante doit être vérifiée pour obtenir la valeur maximale de Q:
On va prendre en compte les conditions suivantes:
- f0 est de l'ordre de 5MHz;
- les valeurs Rs et Rp sont constantes;
- Rp est principalement induite par l'encrassement de la tête de bougie et vaut en moyenne 50 kΩ;
- Rs vaut approximativement 10 Ω en prenant en compte l'effet de peau.
- f 0 is of the order of 5 MHz;
- the values Rs and Rp are constant;
- Rp is mainly induced by fouling of the candle head and is worth on average 50 kΩ;
- Rs is approximately 10 Ω taking into account the skin effect.
On déduit alors
Une autre modélisation permet également de déterminer ces caractéristiques. La résistance de la capacité est modélisée par le facteur de dissipation diélectrique (tan (δ)=1/(Rp*C)) dans le matériau isolant de la tête de bougie, que l'on considère constant et uniquement dépendant du matériau choisi.Another modeling also makes it possible to determine these characteristics. The resistance of the capacitance is modeled by the dissipation factor dielectric (tan (δ) = 1 / (Rp * C)) in the insulating material of the candle head, which is considered constant and solely dependent on the chosen material.
Le coefficient de surtension est alors défini comme suit:
La maximisation du coefficient de surtension Q est alors équivalente à la minimisation de
Ces règles de détermination s'appliquent quel que soit le type de résonateur série utilisé et s'appliquent donc également à la bobine-bougie décrite ultérieurement.These determination rules apply regardless of the type of series resonator used and therefore also apply to the coil-candle described later.
Un compromis dans le choix des valeurs est cependant nécessaire pour la variante utilisant un transistor MOS de puissance comme interrupteur, comme décrit ci-après. En effet, le courant traversant l'interrupteur MOS croit alors avec la capacité C. La valeur de la capacité C doit donc être fixée en fonction du courant nominal de l'interrupteur MOS.A compromise in the choice of values is however necessary for the variant using a power MOS transistor as a switch, as described below. Indeed, the current flowing through the switch MOS then increases with the capacitance C. The value of the capacitance C must therefore be set as a function of the nominal current of the switch MOS.
On va maintenant décrire plusieurs variantes d'amplificateurs 5. De façon générale, on utilisera de préférence un amplificateur présentant un transistor MOSFET de puissance comme interrupteur 51 commandant les commutations aux bornes du résonateur 6. Les
Ce transistor MOSFET présentera également de préférence une inductance inférieure à 7 nH sur ses liaisons entre sa surface active de silicium et le circuit imprimé sur lequel il est implanté. On évite ainsi des transitoires lors de pics de tension élevés qui seraient préjudiciables aux commutations rapides du transistor.This MOSFET transistor will also preferably have an inductance of less than 7 nH on its connections between its active silicon surface and the printed circuit on which it is implanted. This avoids transients during high voltage peaks that would be detrimental to the fast switching of the transistor.
La
L'amplificateur 5 représenté comprend deux transistors intermédiaires M1 et M2 disposés pour alimenter en alternance les bobines L11 et L12 du primaire du transformateur à point milieu. Un circuit de pilotage 57 applique des signaux de commande respectifs sur les transistors M1 et M2. Les signaux de commande ne se recouvrent pas temporellement pour éviter un court-circuit dans le primaire. Les signaux de commande présentent également avantageusement des durées d'activation sensiblement égales pour limiter le courant magnétisant dans le transformateur 56. On peut également compenser une inégalité des temps d'activation par une valeur élevée de l'inductance magnétisante du transformateur 56.The
Le chronogramme de la
On intègre avantageusement l'amplificateur 5 sur un même circuit imprimé 8. On peut ainsi intégrer le transformateur 56, les transistors M1 à M4 et le circuit de pilotage 57 sur le même circuit imprimé, selon le schéma représenté à la
La partie gauche de la
La
Comme représenté aux
Dans un tel transformateur 54, combiné à une boucle d'asservissement, la résistance parallèle R2 du secondaire du transformateur remplit préférentiellement deux fonctions de l'asservissement: la rétroaction d'un signal proportionnel au courant dans la charge, et le déphasage de l'intensité traversant la charge en fonction de sa valeur de résistance.In such a
On utilise avantageusement un transformateur 54 présentant une valeur d'inductance très réduite (par exemple comprise entre 10 et 20 nH) et dont les enroulements supportent un courant de l'ordre de 10A. La
On adapte avantageusement l'asservissement de l'interrupteur 51 commandant les commutations aux bornes du résonateur 6 décrit précédemment aux modes de réalisations présentant un transistor de commande de commutation MOSFET de puissance comme interrupteur. On peut ainsi commuter le transistor MOSFET M4 aux instants optimaux.Advantageously adapts the servocontrol of the
Afin que la structure d'asservissement produise rapidement des oscillations, malgré un courant de charge initial nul, on dispose de plusieurs variantes avantageuses du système.In order for the servo structure to produce oscillations rapidly, despite an initial zero load current, several advantageous variants of the system are available.
Le résonateur LC 6 comprend un résonateur série 61 et un résonateur parallèle 62. Le résonateur série 61 présente une capacité série 119 et une inductance série 65. Selon une première variante, la structure d'asservissement comprend un oscillateur astable 52 (par exemple un générateur de créneaux) pour générer les premières alternances dans la capacité série 119 et stabiliser les oscillations en régime entretenu. On prévoit que la fréquence de l'oscillateur soit proche de la fréquence de l'excitation générée entre les électrodes. La structure d'asservissement additionne le signal de mesure de courant et le signal de l'oscillateur astable 52 et permet ainsi à l'amplificateur en classe E de réaliser les commutations aux moments les plus favorables.The
Par ailleurs, le premier créneau généré par l'oscillateur 52 est approximativement deux fois plus court que les suivants : ainsi, on peut initialiser le courant dans l'inductance série 65 à la valeur de ce courant en régime entretenu. Le résonateur parallèle 62 comprend une inductance 621 et une capacité 622 disposées en parallèle. Toutes les impulsions aux bornes de l'inductance 621 et de la capacité 622 sont alors égales. On peut ainsi éviter de sur-dimensionner l'interrupteur 51 et l'exploiter de façon optimale.Moreover, the first slot generated by the
La
Une combinaison avantageuse du résonateur parallèle 62 et du résonateur série 61 optimise le fonctionnement du système lorsque la fréquence propre du résonateur parallèle 62 est légèrement supérieure à celle du résonateur série 61. Ainsi, l'impulsion de tension générée par la fermeture du transistor interrupteur M4 a une durée inférieure à la demi-période du résonateur série 61. Ainsi, l'impulsion lors de la fermeture du transistor interrupteur M4 est anticipée par la diode inverse interne du transistor M4 lorsque la tension de son drain repasse par une valeur nulle. On prévoit alors que le rapport entre les impédances caractéristiques respectives du résonateur parallèle 62 et du résonateur série 61 soit inférieur à 100 supérieur à 40. La valeur inférieure garantit un bon coefficient de surtension. La valeur supérieure limite les courants dans le transistor M4. On utilise typiquement une capacité de 1 nF et une inductance de 1 µH pour le résonateur parallèle 62. L'impédance caractéristique du résonateur parallèle 62 vaut alors approximativement 32 ohms.An advantageous combination of the
Par ailleurs, dans le résonateur parallèle 62, on peut considérer que les capacités entre les spires de l'inductance 621 seront négligeables par rapport à la capacité du condensateur 622. On peut donc réaliser l'inductance 621 sous forme d'une superposition de pistes conductrices 623 sensiblement circulaires, réalisées sur les couches superposées d'un circuit imprimé. Des exemples de structures d'inductances 621 sur circuit imprimé sont représentés aux
Sur les
Le schéma de la
Le schéma de la
Aux fréquences de travail du résonateur 6, les pertes sont importantes. Afin de limiter ces pertes, on limite de préférence au maximum la présence de matériau magnétique dans le résonateur série 61.At the working frequencies of the
Il est à noter dans ce qui précède que la mention d'un résonateur série n'implique pas forcément que le résonateur inclut également un résonateur parallèle.It should be noted in the foregoing that the mention of a series resonator does not necessarily imply that the resonator also includes a parallel resonator.
Comme illustré à la
La
Les électrodes 103 et 106 sont dans cet exemple séparées par le matériau diélectrique 100 destiné au guidage des étincelles entre ces électrodes. Le résonateur série 61 intégré dans la bougie 110 comprend le bobinage inductif 112 et l'élément isolant 100 formant également le condensateur entre les électrodes 103 et 106. Le condensateur et le bobinage inductif 112 sont disposés en série. La capacité série du résonateur série 61 est formée du condensateur et des capacités parasites internes de la bougie. Cette capacité 119 est disposée en série avec une inductance 65 pour former le résonateur série 61. La longueur de la connexion entre l'inductance et le condensateur étant ainsi réduite, on réduit les capacités parasites dans la bougie. Il est ainsi aisé d'obtenir un coefficient de surtension du résonateur série compris dans la plage de 40 à 200 décrite précédemment. La bougie 110 est ainsi utilisée pour entretenir la tension alternative entre les électrodes 103 et 106, dans le domaine de fréquence souhaité.The
Le résonateur série intégré dans la bougie présente de préférence un bobinage unique 112, facilitant la fabrication d'une telle bougie.The integrated series resonator in the candle preferably has a
Un nombre important de spires dans le bobinage unique 112 est nécessaire pour obtenir une inductance de l'ordre de 50 µH (ordre de grandeur détaillé par la suite). Or, un nombre de spires important génère des capacités parasites. L'unique bobinage inductif 112 présente de préférence un axe (identifié par la ligne en trait mixte) et est constitué d'une pluralité de spires superposées suivant son axe. On entend ainsi que la projection d'une spire est identique à la projection de toutes les spires suivant cet axe. On limite alors les capacités parasites en ne superposant pas des spires radialement.A large number of turns in the single winding 112 is necessary to obtain an inductance of the order of 50 μH (order of magnitude detailed later). However, a large number of turns generates parasitic capacitances. The only
La bougie comprend en outre avantageusement un blindage 132 connecté à une masse et entourant le bobinage inductif 112. Les lignes de champ sont ainsi refermées à l'intérieur du blindage 132. Le blindage 132 réduit ainsi les émissions électromagnétiques parasites de la bougie 110. Le bobinage 112 peut en effet générer des champs électromagnétiques intenses avec l'excitation radiofréquence qu'il est envisagé d'appliquer entre les électrodes. Ces champs peuvent notamment perturber des systèmes embarqués d'un véhicule ou dépasser des seuils définis dans des normes d'émission. Le blindage 132 est de préférence constitué d'un matériau non ferreux à conductivité élevée, tel que le cuivre. On peut notamment utiliser une boucle conductrice comme blindage 132.The spark plug furthermore advantageously comprises a
Pour un blindage 132 et un bobinage unique 112 présentant chacun une forme globalement cylindrique, le rapport optimal entre leur diamètre vaut le nombre d'Euler, soit approximativement 2,72, si l'on veut minimiser le champ électrique maximal, généré à la surface des spires. On évite ainsi des phénomènes de claquage à l'origine de dissipations d'énergie dans la bougie. On choisira alors de préférence un rapport entre leur diamètre compris entre 2,45 et 3.For a
L'utilisation de deux bobinages 112 enroulés l'un sur l'autre et connectés en parallèle permet de réduire la résistance du bobinage formé. L'effet de peau, augmentant de façon importante la résistance du bobinage dans le domaine radiofréquence, est minimisé par l'enroulement l'un sur l'autre de ces deux bobinages. Si l'on veut minimiser la longueur du bobinage 112 pour une inductance prédéterminée, le rapport optimal entre le diamètre du blindage 132 et le bobinage 112 vaut
Le bobinage 112 et le blindage 132 sont de préférence séparés par un manchon d'isolation 133 en un matériau diélectrique approprié, afin de réduire encore le risque de claquage ou d'effluve, à l'origine de dissipations d'énergie. Bien entendu, plus les dissipations d'énergie sont faibles, plus l'amplitude de la tension appliquée entre les électrodes est élevée et plus la durée de vie de la bougie est élevée. Le matériau diélectrique peut par exemple être une des résines silicones commercialisées sous les références Elastosil M4601, Elastosil RTV-2 ou Elastosil RT622 (cette dernière présentant une tension de claquage de 25 kV/mm et une constante diélectrique de 2,8). On peut prévoir que la surface extérieure du manchon 133 soit métallisée pour constituer le blindage 132 précité.The winding 112 and the
De façon générale, on privilégiera un enroulement du bobinage 112 autour d'un élément plein 134 réalisé en matériau isolant et amagnétique. On réduit ainsi encore les risques de claquage et les capacités parasites.In general, it will be preferred to wind the winding 112 around a
L'ensemble des matériaux diélectriques est de préférence fortement débullé, afin de réduire encore les risques de claquage. L'ensemble des matériaux diélectriques de la bougie présente de préférence des températures de fusion supérieures à 150 °C.The set of dielectric materials is preferably strongly debulled, to further reduce the risk of breakdown. All the dielectric materials of the candle preferably have melting temperatures above 150 ° C.
De façon générale, lorsque la bobine-bougie comprend plusieurs éléments isolants accolés, il existe un risque non négligeable de créer des inclusions d'air à l'interface entre ces éléments, notamment lorsqu'ils sont réalisés en céramique. Or, pour des raisons constructives, il est envisagé que la bobine-bougie comprenne dans la plupart des cas plusieurs éléments isolants accolés. En particulier, la liaison entre l'isolant 134 de la bobine et l'isolant 111 de la tête de bougie constitue également, pour les mêmes raisons d'effluve, une source de dissipation très importante. La technique précédemment citée peut, selon un nouveau mode de réalisation, être mise à profit au niveau de la céramique pour créer des équipotentielles prévenant la formation de décharges électriques.In general, when the coil-candle comprises several insulating elements contiguous, there is a significant risk of creating air inclusions at the interface between these elements, especially when made of ceramic. However, for constructive reasons, it is envisaged that the coil-candle in most cases comprises several insulating elements contiguous. In particular, the connection between the
La
Le matériau diélectrique utilisé pour l'isolant 100 peut par exemple être une céramique à base d'alumine, de nitrure d'aluminium, d'oxyde d'aluminium ou de carbure de silicium.The dielectric material used for the
Aux fréquences de travail du résonateur série, les pertes sont importantes. Afin de limiter ces pertes, l'homme de métier limitera au maximum la présence de matériau magnétique dans le résonateur série.At the working frequencies of the series resonator, the losses are significant. In order to limit these losses, those skilled in the art will limit as much as possible the presence of magnetic material in the series resonator.
Selon une variante particulièrement avantageuse illustrée à la
La bougie de l'invention peut intégrer un certain nombre d'autres caractéristiques, comme le joint de siège 130 de la
La tête de bougie est la partie de la bougie qui est placée dans le gaz dans lequel le plasma doit être formé. Cette tête de bougie comprend préférentiellement trois éléments: une électrode centrale 106, une électrode de masse 103 et un isolant 100. La géométrie de ces éléments est déterminante pour assurer la formation du plasma de volume ou du plasma ramifié à l'emplacement souhaité de la chambre, avec les propriétés optimales, notamment pour l'allumage (volume important, transfert d'énergie optimal vers le gaz, etc...).The candle head is the part of the candle that is placed in the gas in which the plasma must be formed. This candle head preferably comprises three elements: a
Les
La
La
Les géométries des
Dans la variante de la
Dans la variante de la
La variante de la
Pour rallonger le chemin d'air entre la cathode et l'anode, la cathode 103 de cette variante est disposée axialement en retrait par rapport à l'isolant. L'électrode centrale ou anode 106 est disposée affleurante avec l'isolant.To lengthen the air path between the cathode and the anode, the
La
De façon générale, les variantes visant à éviter la formation d'un arc direct entre les électrodes fonctionnent de façon optimale en combinaison avec l'excitation radiofréquence. L'excitation radiofréquence permet en effet de rallonger et de courber la trajectoire des étincelles.In general, the variants to avoid the formation of a direct arc between the electrodes operate optimally in combination with the radiofrequency excitation. Radiofrequency excitation makes it possible to extend and curve the trajectory of the sparks.
Les
La
La
Les exemples 24.II à 24.IV présentent chacun une cathode 103 formant un retrait axial 122 à proximité de l'isolant 100. Ce retrait 122 présente en outre une forme arrondie. On augmente ainsi la capacité de la bougie à générer une étincelle ramifiée. On réduit en effet la probabilité qu'un plasma se propage uniquement à la surface de l'isolant. Le plasma a ainsi tendance à se répartir dans un volume distant de la surface de l'isolant 100.Examples 24.II to 24.IV each have a
Les exemples 24.III et 24.IV présentent un isolant 100 dont l'extrémité présente une forme arrondie 123, afin de réduire ses contraintes internes. Ces contraintes sont liées aux niveaux élevés des champs électriques et des gradients de température à proximité de l'extrémité de l'isolant 100.Examples 24.III and 24.IV have an
L'exemple de la
Les bougies à effet de pointe peuvent accidentellement générer des arcs électriques entre l'anode 106 et le piston, lorsque la distance entre le piston et la tête de bougie est faible. Ces arcs érodent prématurément la pointe de l'anode 106 et empêchent la formation du plasma de volume ou du plasma ramifié. La tête de bougie de la
Les
Le fonctionnement d'une bougie borgne est rendu possible par l'utilisation de l'excitation radiofréquence. L'application d'une excitation radiofréquence entre les électrodes d'une bougie borgne est en outre particulièrement avantageuse. L'excitation des électrodes forme des charges d'espace sur la surface extérieure de l'isolant. L'isolant 100 se comporte alors comme une anode et un plasma de volume ou un plasma ramifié est généré à sa surface. Bien que l'isolant présente une charge relativement réduite, l'excitation radiofréquence permet de générer un très grand nombre d'étincelles à la surface de l'isolant en un temps très réduit. On peut prévoir dans cette variante que l'isolant 100 forme le condensateur du résonateur. On réduit ainsi l'énergie dissipée dans la bougie.The operation of a blind candle is made possible by the use of radiofrequency excitation. The application of radiofrequency excitation between the electrodes of a blind candle is also particularly advantageous. Electrode excitation forms space charges on the outer surface of the insulation. The
Selon une variante illustrée à la
On peut également intégrer la bougie dans la culasse du moteur thermique, en utilisant encore la culasse comme cathode de la bougie. L'homme de métier prendra alors toute mesure adéquate pour que la durée de vie de la bougie soit au moins égale à la durée de vie du moteur thermique.It is also possible to integrate the candle in the cylinder head of the engine, still using the cylinder head as the cathode of the candle. The skilled person will then take any appropriate measure so that the life of the spark plug is at least equal to the life of the engine.
Par ailleurs, bien que les têtes des bougies représentées présentent une symétrie de révolution autour de leur axe, on peut également prévoir des têtes de bougie présentant d'autres géométries, dans le cadre de l'invention.Moreover, although the heads of the candles shown have a symmetry of revolution about their axis, it is also possible to provide candle heads having other geometries, within the scope of the invention.
Claims (15)
- Spark plug (110) comprising:• two plasma generating electrodes (103, 106),• a series resonator (61) with a resonant frequency higher than 1 MHz, comprising:• a capacitor (111) with two terminals, and• an inductive coil (112),the capacitor and the coil being arranged in series and the electrodes being connected to the respective terminals of the capacitor, which spark plug is characterized in that said resonator also has a quality factor of between 40 and 200.
- Spark plug according to Claim 1, characterized in that the series resonator comprises a single inductive coil (112).
- Spark plug according to Claim 2, characterized in that the inductive coil has an axis and consists of a plurality of turns superposed along this axis.
- Spark plug according to any one of the preceding claims, characterized in that it also comprises a probe (139) for measuring the current flowing through the coil comprising a winding radially around the coil.
- Spark plug according to any one of the preceding claims, characterized in that it also comprises shielding (132) connected to an earth and surrounding the inductive coil (112).
- Spark plug according to Claim 5, characterized in that the shielding and the inductive coil are of generally cylindrical shape and in that the ratio between their respective diameters is between 2.45 and 3.
- Spark plug according to Claim 5 or 6, characterized in that the shielding and the inductive coil are separated by an insulating sleeve (133) made of a material with a dielectric coefficient of greater than 1.
- Spark plug according to any one of Claims 5 to 7, characterized in that the outer surface (132) of the insulating sleeve is metallized and forms the shielding.
- Spark plug according to any one of Claims 5 to 7, characterized in that the shielding comprises a conducting loop.
- Spark plug according to any one of the preceding claims, characterized in that the inductive coil (112) is wound around a solid component (134) consisting of a material having a dielectric coefficient of greater than 3.
- Spark plug according to Claim 7 or Claim 10, characterized in that one of said insulating materials has a breakdown voltage of greater than 20 kV/mm.
- Point-effect spark plug according to any one of the preceding claims, characterized in that it comprises an insulator (100) separating the two electrodes, one of the electrodes (106) being a central electrode, the second electrode being an earth electrode (103), and in that the central electrode (106) comprises a pointed part projecting axially from an axial end of the insulator (100) and from the earth electrode (103).
- Plasma generating system characterized in that it comprises:• a spark plug according to at least one of the preceding claims;• a generator capable of causing resonance in a structure comprising an inductance (L) and a capacitance (C) at a frequency greater than 1 MHz with a voltage across the terminals of the capacitor greater than 5 kV, said spark plug resonator being connected to the output of said generator and the electrodes of said spark plug being separated by an insulator.
- Plasma generating system according to Claim 13, characterized in that the voltage generator comprises:• a low-voltage power supply (3) generating a direct-current voltage of less than 1000 V;• a radiofrequency amplifier (5) which amplifies the direct-current voltage and generates an alternating-current voltage at the frequency commanded by the switch command (4).
- Method for generating plasma between the electrodes of a spark plug according to any one of Claims 1 to 12, comprising a step of applying an alternating-current voltage with a frequency of greater than 1 MHz, and a peak-to-peak amplitude of greater than 5 kV between the electrodes of the spark plug.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP10012339.7A EP2273632B1 (en) | 2003-09-12 | 2004-09-13 | Plasma generating spark plug with integrated inductance |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0310766A FR2859830B1 (en) | 2003-09-12 | 2003-09-12 | PLASMA GENERATION CANDLE WITH INTEGRATED INDUCTANCE. |
FR0310766 | 2003-09-12 |
Related Child Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP10012339.7A Division EP2273632B1 (en) | 2003-09-12 | 2004-09-13 | Plasma generating spark plug with integrated inductance |
EP10012339.7 Division-Into | 2010-09-30 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP1515408A2 EP1515408A2 (en) | 2005-03-16 |
EP1515408A3 EP1515408A3 (en) | 2006-11-15 |
EP1515408B1 true EP1515408B1 (en) | 2010-11-24 |
Family
ID=34130809
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP04292188A Active EP1515408B1 (en) | 2003-09-12 | 2004-09-13 | Plasma generating spark plug with integrated inductance |
EP10012339.7A Not-in-force EP2273632B1 (en) | 2003-09-12 | 2004-09-13 | Plasma generating spark plug with integrated inductance |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP10012339.7A Not-in-force EP2273632B1 (en) | 2003-09-12 | 2004-09-13 | Plasma generating spark plug with integrated inductance |
Country Status (5)
Country | Link |
---|---|
EP (2) | EP1515408B1 (en) |
AT (1) | ATE489751T1 (en) |
DE (1) | DE602004030195D1 (en) |
ES (2) | ES2354155T3 (en) |
FR (1) | FR2859830B1 (en) |
Families Citing this family (31)
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FR2878086B1 (en) | 2004-11-16 | 2007-03-09 | Renault Sas | PLASMA RADIOFREQUENCY CANDLE |
FR2884365B1 (en) | 2005-04-08 | 2013-10-11 | Renault Sas | MULTI-SPARK CANDLE WITH OPEN BEDROOM |
FR2887083B1 (en) * | 2005-06-08 | 2007-08-10 | Renault Sas | RADIOFREQUENCY PLASMA CANDLE FOR IGNITION CONTROL OF INTERNAL COMBUSTION ENGINES |
FR2887696B1 (en) * | 2005-06-23 | 2007-08-24 | Renault Sas | IGNITION CANDLE FOR INTERNAL COMBUSTION ENGINE |
FR2890248B1 (en) | 2005-08-25 | 2007-09-28 | Renault Sas | PLASMA IGNITION CANDLE FOR AN INTERNAL COMBUSTION ENGINE |
FR2890247B1 (en) * | 2005-08-25 | 2007-09-28 | Renault Sas | PLASMA IGNITION CANDLE FOR AN INTERNAL COMBUSTION ENGINE |
FR2892240B1 (en) | 2005-10-18 | 2010-10-22 | Renault Sas | IGNITION CANDLES FOR THE INTERNAL COMBUSTION ENGINE OF A MOTOR VEHICLE |
FR2893455B1 (en) * | 2005-11-14 | 2007-12-14 | Renault Sas | IGNITION CANDLE FOR INTERNAL COMBUSTION ENGINE |
FR2894034B1 (en) * | 2005-11-28 | 2008-01-18 | Renault Sas | MEASUREMENT DEPORTEE CURRENT CROSSING A LOAD |
FR2899393B1 (en) * | 2006-04-04 | 2008-05-09 | Renault Sas | RADIOFREQUENCY PLASMA GENERATION CANDLE FOR AN INTERNAL COMBUSTION ENGINE |
FR2905538B1 (en) * | 2006-08-30 | 2008-10-31 | Renault Sas | PSEUDOPERIODIC LOGIC SIGNAL GENERATOR. |
FR2907269B1 (en) * | 2006-10-17 | 2009-01-30 | Renault Sas | DEVICE FOR GENERATING RADIOFREQUENCY PLASMA. |
FR2913297B1 (en) * | 2007-03-01 | 2014-06-20 | Renault Sas | OPTIMIZING THE GENERATION OF A RADIO FREQUENCY IGNITION SPARK |
FR2919343B1 (en) * | 2007-07-25 | 2013-08-16 | Renault Sas | COMBUSTION ENGINE AND METHOD FOR CONTROLLING A COMBUSTION ENGINE. |
JP4924275B2 (en) * | 2007-08-02 | 2012-04-25 | 日産自動車株式会社 | Non-equilibrium plasma discharge ignition system |
FR2919901B1 (en) * | 2007-08-08 | 2010-02-26 | Renault Sas | RADIOFREQUENCY PLASMA GENERATION DEVICE |
FR2935759B1 (en) | 2008-09-09 | 2010-09-10 | Renault Sas | DEVICE FOR MEASURING THE IONIZATION CURRENT IN A RADIOFREQUENCY IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE |
EP2342789B1 (en) * | 2008-10-13 | 2012-08-15 | Delphi Technologies, Inc. | Internal combustion engine having a spark plug with an improved firing face |
BRPI1014115B1 (en) * | 2009-05-04 | 2020-02-27 | Tenneco Inc. | IGNITOR, INTERNAL COMBUSTION ENGINE, AND, METHOD FOR FORMING AN IGNITOR |
FR2955710B1 (en) * | 2010-01-22 | 2012-01-13 | Renault Sa | CANDLE, IGNITION SYSTEM, ENGINE AND IGNITION METHOD FOR THE ENGINE. |
FR2964803B1 (en) | 2010-09-10 | 2012-08-31 | Renault Sa | IGNITION CANDLE FOR INTERNAL COMBUSTION ENGINE |
CN102155344B (en) * | 2011-01-21 | 2012-07-04 | 电子科技大学 | Slot coupling micro-wave plasma igniter for internal-combustion engine |
FR2975863B1 (en) | 2011-05-25 | 2013-05-17 | Renault Sa | POWER SUPPLY FOR RADIOFREQUENCY IGNITION WITH DOUBLE-STAGE AMPLIFIER |
DE102012108251B4 (en) * | 2011-10-21 | 2017-12-07 | Borgwarner Ludwigsburg Gmbh | Corona ignition device |
FR2982711B1 (en) * | 2011-11-16 | 2014-01-10 | Renault Sas | IGNITION CANDLE |
CN102518541B (en) * | 2011-12-27 | 2015-05-20 | 成都集思科技有限公司 | Solid state microwave source for ignition of internal combustion engine |
US10056738B2 (en) | 2012-03-23 | 2018-08-21 | Federal-Mogul Llc | Corona ignition device with improved electrical performance |
US9088136B2 (en) | 2012-03-23 | 2015-07-21 | Federal-Mogul Ignition Company | Corona ignition device with improved electrical performance |
US10056737B2 (en) | 2012-03-23 | 2018-08-21 | Federal-Mogul Llc | Corona ignition device and assembly method |
FR3001601B1 (en) | 2013-01-29 | 2015-02-13 | Renault Sa | PLASMA GENERATING DEVICE WITH OVERVOLTAGE REDUCTION TO THE TERMINALS OF THE SWITCHING TRANSISTOR, AND CORRESPONDING CONTROL METHOD |
JP7058084B2 (en) * | 2017-06-14 | 2022-04-21 | 株式会社Soken | Ignition system |
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GB859956A (en) * | 1957-12-12 | 1961-01-25 | Napier & Son Ltd | Spark producing apparatus and adaptors therefor |
US3919656A (en) | 1973-04-23 | 1975-11-11 | Nathan O Sokal | High-efficiency tuned switching power amplifier |
FR2649759B1 (en) * | 1989-07-13 | 1994-06-10 | Siemens Bendix Automotive Elec | IGNITION DEVICE FOR INTERNAL COMBUSTION ENGINE |
US5187580A (en) | 1991-02-04 | 1993-02-16 | Advanced Energy Industries, Inc. | High power switch-mode radio frequency amplifier method and apparatus |
DE19723784C1 (en) * | 1997-06-06 | 1998-08-20 | Daimler Benz Ag | Circuit for ignition system of IC engine supplying high voltage to spark plug electrodes |
DE19840765C2 (en) * | 1998-09-07 | 2003-03-06 | Daimler Chrysler Ag | Method and integrated ignition unit for the ignition of an internal combustion engine |
-
2003
- 2003-09-12 FR FR0310766A patent/FR2859830B1/en not_active Expired - Fee Related
-
2004
- 2004-09-13 DE DE602004030195T patent/DE602004030195D1/en active Active
- 2004-09-13 ES ES04292188T patent/ES2354155T3/en active Active
- 2004-09-13 EP EP04292188A patent/EP1515408B1/en active Active
- 2004-09-13 EP EP10012339.7A patent/EP2273632B1/en not_active Not-in-force
- 2004-09-13 ES ES10012339.7T patent/ES2455742T3/en active Active
- 2004-09-13 AT AT04292188T patent/ATE489751T1/en not_active IP Right Cessation
Also Published As
Publication number | Publication date |
---|---|
DE602004030195D1 (en) | 2011-01-05 |
FR2859830A1 (en) | 2005-03-18 |
FR2859830B1 (en) | 2014-02-21 |
ES2455742T3 (en) | 2014-04-16 |
EP2273632A2 (en) | 2011-01-12 |
EP1515408A3 (en) | 2006-11-15 |
EP2273632A3 (en) | 2013-03-13 |
EP1515408A2 (en) | 2005-03-16 |
ES2354155T3 (en) | 2011-03-10 |
ATE489751T1 (en) | 2010-12-15 |
EP2273632B1 (en) | 2014-02-26 |
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