Classifications

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

Definitions

• the invention relates to a spark plug for a confined gaseous medium present, for example, in a motor vehicle and, in particular, in an internal combustion engine disposed on the motor vehicle.
• the invention relates, according to a first of its aspects, a candle 1 illustrated in Figure 1 and adapted to ignite a confined gaseous medium, the candle 1 having a longitudinal axis AB and comprising:
• an electrode 5 having a tip projecting axially 6 of the insulator toward the second end (31) of the outer shell 3,
• the electrode 5 ionizes the gaseous medium 2 when the series resonator 7 delivers an overvoltage V to the output terminal 72,
• the series resonator furthermore advantageously comprises: as an output terminal, a terminal merged with the tip electrode 6, and / or a ground terminal 71 electrically isolated from the supply terminal 70 and merged with the envelope external 3, a capacitor 74 arranged in series with the inductive coil 73 between the output terminal 72 and the ground terminal 71.
• a candle 1 is known to those skilled in the art as shown, for example, in French patent application FR 2,859,830. The latter describes an internal combustion engine comprising a cylinder head, a piston and a cylinder which form between them. a combustion chamber.
• the known spark plug 1 is actuated by excitation means which supply alternating current to the series resonator via the power supply terminal 70.
• the known spark plug 1 is used to ignite the confined gaseous medium which is contained in the combustion chamber.
• the present invention which is based on this original observation, is primarily intended to provide a candle at least to reduce at least one of the limitations mentioned above.
• the candle which is also in accordance with the generic definition given in the preamble above, is essentially characterized in that several of the following characteristics are verified:
• the axial distance (L1, fig.2) between the inductive winding and a free end of the tip is between 2 cm and 6 cm, said free end comprises at least a first head having a radius of curvature (R1) equal to or less than 250 ⁇ ,
• the series resonator has a natural frequency (F) of between 3 MHz and 10 MHz.
• the candle will be such that all four characteristics above will be verified Thanks to these arrangements, the candle according to the invention is able to generate, from the first head of the tip, at least one branched multifilament spark in the gaseous environment.
• This branched multifilament spark comprises a plurality of filaments which occupy a volume in the extension of the longitudinal axis outside the first head.
• the filaments can ignite the gaseous medium confined almost instantly volumetrically, that is to say, in several places at once, which contributes to increase the spark efficiency of the candle according to the invention.
• the filaments have temperatures ranging from about 1000 ° C to about 1500 ° C. This tends to increase the ignition reliability of the gaseous medium confined by the candle according to the invention.
• the invention relates to an ignition system comprising at least one spark plug according to the invention and to excitation means adapted to supply, via the power supply terminal, the AC series series resonator. excitation.
• the invention relates to an internal combustion engine comprising:
• the invention relates to a method for igniting a gaseous mixture confined, by the ignition system according to the invention, in the internal combustion engine according to the invention.
• the ignition process comprises:
• FIG. 1 a step for exciting the series resonator by the excitation means for a period of excitation between 20 ⁇ and ⁇ 2.10 3 (20 ms), and ⁇ a step rise of the amplitude of the selective voltage supplied by the series resonator to the output terminal with an upshift between 2.5 * 10 9 V / s and 5.0 * 10 9 V / s, during a rise time between 10 ⁇ and 20 ⁇ .
• FIG. 1 schematically represents a simplified view in longitudinal section a known plug described in the French patent application FR 2,859,830 adapted to be installed in an internal combustion engine
• Figure 2 schematically shows a simplified view in longitudinal section an ignition system according to the invention equipped of a spark plug according to the invention installed in an internal combustion engine according to the invention
• FIG. 3 schematically shows in enlarged simplified view a tip (comprising a first head) of the spark plug illustrated in FIG.
• FIG. 4 schematically shows in partial simplified side view an embodiment of the spark plug according to the invention, the tip of which comprises a first, a second and a third head
• FIG. 5 schematically represents a voltage curve between two electrodes arranged at a distance from each other in the confined gaseous medium. as a function of current between these electrodes, said voltage curve illustrating several possible operating conditions of the spark plug according to the invention
• FIG. 6 schematically represents a succession of the steps of an alternative ignition method according to FIG. invention.
• Figure 1 shows a known candle described in the French patent application FR 2 859 830 and commented above. As a result, it is not described below.
• the invention relates to a candle 1 adapted to ignite a gaseous medium 2 confined.
• the candle 1 has a longitudinal axis AB and comprises:
• an outer envelope 3 (for example, formed by a sleeve) elongated along the axis AB and having an inlet 30 and an outlet end 31 axially opposite to each other, the outer casing 3 ensuring a function of fixing of the candle 1 in the gaseous medium 2 confined,
• an insulator 4 made of electrically insulating material disposed axially in the outer casing 3 and adapted to seal the outlet 31 of the outer shell 3,
• a series resonator 7 comprising: o a power supply terminal 70 AC excitation, where an output terminal 72 coincides with the electrode tip 5 to 6, and o an inductive coil 73 (having a given inductance) housed in the outer casing 3 between the output terminal 72 and the power supply terminal 70. o a ground terminal 71 electrically isolated from the power supply terminal 70 and merged with the outer casing 3, o a capacitor 74 arranged in series with the inductive winding 73 between the output terminal 72 and the ground terminal 71.
• the tip electrode 6 is adapted to ionize, by an induced electric field E, the gaseous medium 2 confined when the series resonator 7 delivers at its output terminal 72 a selective overvoltage V.
• the series resonator 7 has the more compact geometry.
• the distance between the inductive coil 73 and the tip 6 is reduced, which contributes, for the inductance given by the inductive coil 73, to reducing the capacitance 74 of the series resonator 7.
• the latter has an inversely proportional natural frequency F, for the inductance given by the inductive winding 73, to the square root of the capacitor 74. Consequently, the reduction of the capacitance 74 is reflected, for the given inductance of the winding.
• the compact geometry of the series resonator 7 with the inductive winding 73 housed in the outer envelope 3 makes it possible, for the inductance given by the inductive winding 73, to increase the natural frequency F of the series resonator 7 and, therefore, its overvoltage coefficient.
• the compact geometry of the series resonator 7 tends to reduce the electrical consumption of the candle 1.
• the lower voltage of the alternating excitation current at the power supply terminal 70 of the series resonator 7 contributes to reducing the risk of electrical losses in electrical circuits upstream of the spark plug 1.
• the distance between the inductive winding 73 and the tip 6 is between 2 cm and 6 cm.
• the selective overvoltage V at the output terminal 72 is equal to or less than 30 KV AC.
• the tip 6 has at its end 60 opposite the outlet 31 of the outer casing 3 at least a first head 61 having a first radius Ri of curvature equal to or less than 250 ⁇ .
• the resonator 7 series has the natural frequency F between 3 MHz and 10 MHz.
• the candle 1 is able to generate at least one branched multifilament spark 600 generated from the first head 61 of the tip 6 and comprising a plurality of filaments 601 occupying a volume ⁇ in the extension of the longitudinal axis AB outside the first head 61.
• the volume ⁇ occupied by the filaments 601 can be inserted in a cone ⁇ (preferably in a cone of revolution with an axis of revolution coinciding with, for example, the longitudinal axis AB) presenting a opening angle ⁇ of the cone ⁇ less than 180 ° ( ⁇ ⁇ 180 °) and a vertex M coincides with the first head 61.
• the filaments 601 make it possible to ignite the gaseous medium 2 confined almost instantaneously volumetrically, that is to say, in several places at the same time, which increases the efficiency of the ignition by the candle 1 and contributes to choke detonations (breakdowns) that may accompany the ignition.
• the filaments 601 have temperatures ranging from about 1000 ° C to about 1500 ° C. This tends to increase the ignition reliability of the gaseous medium 2 confined by the candle 1.
• the axial distance L1 between the inductive winding 73 (lower end 730) and the free end 60 of the tip 6 between 2 cm and 6 cm contributes to making the resonator 7 series and, in fine, the outer envelope 3 (and , therefore, the candle 1 as a whole) more compact.
• the tip 6 is of frustoconical shape presenting:
• ⁇ at its base 610, a transverse dimension L section (typically a diameter, for its cylindrical base), and ⁇ a height H measured along the axis (AB) between said free end 60 and the base 610 (here at the lower end of the isolator 4),
• the ratio between the height H and the transverse dimension L of the tip 6 is between 4.5 and 5.5.
• the height H can be between about 5 mm and about 12 mm (5 mm ⁇ H ⁇ 12 mm); the transverse dimension L (diameter) can be between about 1 mm and about 5 mm (1 mm H H 5 5 mm).
• the first head 61 is disposed axially on the tip 6.
• the latter has at its end 60 opposite the outlet 31 of the outer casing 3 at least a second head 62 having a second radius R 2 of equal or lower curvature at 250 ⁇ and / or disposed laterally to the axis AB, (approximately) two-thirds of the height H of the tip 6 from the insulator 4, the first and second heads 61, 62 being spaced apart from each other.
• Another angle has between 45 ° and 90 °.
• the invention relates to an ignition system 10 comprising at least one candle 1 according to the invention and excitation means 8 adapted to supply, via the power supply terminal 70, the series resonator 7 AC excitation.
• the duration ⁇ of excitation of the series resonator 7 by the excitation means 8 is between 20 ⁇ and 2.10 3 ⁇ : 20 ⁇ ⁇ ⁇ 20 ms.
• the rise speed ⁇ of the amplitude of the selective overvoltage V delivered by the series resonator 7 to the output terminal 72 is between 2.5 * 10 9 V / s and 5.0 * 10 9 V / s: 2 , 5 * 10 9 V / s ⁇ ⁇ ⁇ 5.0 * 10 9 V / s.
• the rise time T of the amplitude of the selective overvoltage V delivered by the series resonator 7 to the output terminal 72 is between 10 ⁇ and 20 ⁇ : 10 ⁇ T ⁇ 20 ⁇ .
• the series resonator 7 has a narrower resonance peak around its resonant frequency. Therefore, any dielectric disturbance around the tip 61 due, for example, to the production by the spark plug 1 (and, therefore, by the ignition system 10) of the branched multifilament spark 600, removes almost immediately the the resonator 7's natural frequency F series of its resonant frequency at which it is controlled.
• the selective overvoltage V delivered by the series resonator 7 to the output terminal 72 and thus on the tip 61 is immediately reduced, which prevents any spatial extension of the filaments 601 of the branched multifilament spark 600, especially in the prolongation of the longitudinal axis AB.
• this self-regulating mechanism it is possible to adjust (by attributing the quality coefficient predefined to the candle 1 during its manufacture), the volume ⁇ occupied by the filaments 601 (and, in particular, the extent of the 600 branched multifilament spark in the extension of the longitudinal axis AB) without resorting to complex systems for the real-time management of the selective overvoltage V at the output terminal 72 of the candle 1.
• control of the spatial extent of the filaments 601 in the prolongation of the longitudinal axis AB outside the spark plug 1 ensures controlled ignition of the gaseous medium 2 confined by the ignition system 10.
• the invention relates to an internal combustion engine 9 comprising: ⁇ a cylinder head 90, a piston 91 and a cylinder 92 adapted to form an inner casing 93 with a combustion chamber 94, and
• a channel 95 arranged for connection in the inner shell 93 and adapted to bind the combustion chamber 94 with the outside 96 of the engine 9, said motor 9 using the ignition system 10 according to the invention wherein the gaseous medium 2 confined is contained in the combustion chamber 94 and wherein the outer casing 3 of the candle 1 is housed in the connecting channel 95.
• the outer casing 3 and the connecting channel 95 each have a thread.
• the outer casing 3 can be screwed into the connecting channel 95.
• the reduced linear dimensions of the series resonator 7 make the spark plug 1 (and, therefore, the ignition system 10) more compact and thus contribute to decluttering the engine 9 and making it lighter. These measures ultimately contribute to increasing the efficiency of the engine 9 by providing equal power for a lower weight of the latter to meet the increasingly stringent requirements of anti-pollution standards. In addition, this makes it easier to mount the spark plug 1 (and, therefore, the ignition system 10) on the engine 9.
• the connecting channel 95 can be arranged in the cylinder head 90, and at least the piston 91 is connected to the ground terminal 71.
• the spark plug 1 (and, therefore, the ignition system 10) can be mounted on the cylinder head 90 almost without encumbering the latter.
• This meets an industrial need for miniaturization of 9 engines to make them comply with anti-pollution standards more stringent. Binding the piston 91 to the ground terminal 71 makes it possible to orient the induced electric field E in a preferred manner, for example, along the longitudinal axis AB, directly in the combustion chamber 94, without calling upon any other specific electrical means (for example, without using any other specific electrode disposed at a distance from the tip 6).
• the absence of said specific electrical means contributes to make the spark plug 1 (and, therefore, the ignition system 10) more compact and to de-clutter the cylinder head 90. Therefore, the spark plug 1 (and, therefore, the ignition system 10) is better adapted to the cylinder heads 90 (and ultimately to the engines 9) of small sizes.
• the piston 91 and the tip 6 are, along the axis AB, spaced from each other by at least 0.5 cm, as illustrated with the aid of FIG. a reference gap ⁇ referenced between the piston 91 and the first head 61 of the tip 6 in Figure 3: ⁇ > 0.5 cm. This should be checked under all circumstances of engine operation.
• FIG. 5 illustrates an example of a voltage curve U between two electrodes, for example, between the tip 6 of the spark plug 1 and the piston 91. disposed at a distance ⁇ from each other in the gaseous medium 2 confined, for example, in an air-fuel mixture, as a function of current between these electrodes 6, 91 ( Figure 3).
• Said curve U presents:
• the spark plug 1 during its operation has only the second discharge, suitable for the third zone III in FIG. 5, with the branched multifilament spark 600 that evolves in the volume ⁇ in the immediate vicinity of the tip 61 so that the filaments 601 remain confined in said volume ⁇ , at a distance ⁇ from the piston 91.
• the threshold difference ⁇ between the tip 6 of the spark plug 1 and the piston 91 greater than 0.5 cm makes it possible to avoid, a priori, the spark plug 1 (and, consequently, the spark plug system 1). ignition 10 and, more generally, the motor 9) operate:
• the third discharge does not ensure the ignition of certain gaseous medium 2 confined especially when starting the engine 9 cold: the substantially monofilament nature, unbranched electric arc can heat a volume (middle gaseous 2 confined) sufficient to ignite cold said gaseous medium 2 confined.
• the unbranched monofilament arcing from the third discharge tends to ignite the gaseous medium 2 confined by non-volumetric manner but only in the immediate vicinity of the arc.
• the third discharge eventually leads to a certain erosion of the piston 91 by the electric arc (short circuit) which makes the motor 9 inoperative.
• the invention relates to a method of igniting Z a gaseous mixture 2 confined, by the ignition system 10 according to the invention, in the internal combustion engine 9 according to the invention.
• the ignition process comprises (FIG. 6):
• ⁇ at least one step mounted Z1 of the amplitude of the selective voltage V output from the resonator R7 to the output terminal 72 with a ⁇ upshift between 2.5 0 9 V / s and 5.0 * 10 9 V / s: 2.5 * 10 9 V / s ⁇ ⁇
• This operating mode contributes to increasing the quality coefficient of the series resonator 7 and, as already mentioned above, to make self-regulating the mechanism for maintaining the second discharge (regime specific to the third zone III in FIG. use of complex systems for real-time management of the selective overvoltage V at the output terminal 72 of the candle 1. This ultimately contributes to further control the ignition of the gaseous medium 2 confined by the spark plug 1 according to the invention (and, consequently, by the ignition system 10 according to the invention).
• the ignition process comprises, during a compression cycle C of the motor 9, at least two stages of delivering the selective overvoltage V by the series resonator 7 to the output terminal 72.
• This operating mode contributes to reliability of the ignition by the spark plug 1 according to the invention (and, consequently, by the ignition system 10 according to the invention) of the gaseous medium 2 confined (air-fuel mixture) in the combustion chamber 94 of the engine 9 regardless of the operating mode of the latter and, in particular, during a cold start of said engine 9 .

Landscapes

• Ignition Installations For Internal Combustion Engines (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=43062723

Family Applications (1)

Country Status (4)

Cited By (1)

Families Citing this family (1)

Citations (2)

Family Cites Families (5)

• 2010
  • 2010-01-22 FR FR1050434A patent/FR2955710B1/fr not_active Expired - Fee Related
• 2011
  • 2011-01-20 EP EP11704661.5A patent/EP2526595B1/de not_active Not-in-force
  • 2011-01-20 CN CN201180014219.1A patent/CN102804527B/zh not_active Expired - Fee Related
  • 2011-01-20 WO PCT/FR2011/050103 patent/WO2011089360A1/fr active Application Filing

Patent Citations (2)

Also Published As

Similar Documents

Legal Events