Ignition system having a high-frequency plasma-enhanced ignition spark of a spark plug, including an antechamber, and a method associated therewith

Abstract

An ignition system and a method for a spark-ignition combustion engine having a high-frequency plasma-augmented ignition spark, the spark ignition of the fuel being realized by at least one spark plug associated with a combustion chamber of the combustion engine. The spark plug has a prechamber having at least one opening via which the prechamber communicates with the combustion chamber on the fuel side, so that the ignition spark in the prechamber, into which the high-frequency plasma can be injected, induces the plasma-augmented spark ignition of the fuel in the prechamber.

Claims

1. An ignition system for a spark-ignition combustion engine, comprising: at least one spark plug configured to provide the spark ignition of fuel, the at least one spark plug being associated with a combustion chamber of the combustion engine; a first electrode of the spark plug that is electrically connected to a high-voltage output of a high-voltage source; a second electrode of the spark plug that is configured as a grounding contact; wherein the first electrode of the spark plug is coupled to an ignition installation that has a high-frequency output to which a high-frequency voltage is applied; wherein the high-voltage output of the high-voltage source of the spark plug and the high-frequency output are electrically interconnected, so that, in a voltage circuit that includes the high-voltage source of the spark plug, the high-voltage output of the high-voltage source is amplified by the high-frequency voltage applied to the high-frequency output to generate a spark discharge between the first electrode and the second electrode of an ignition spark in response to the high-frequency voltage being injected via the high-frequency output into the voltage circuit of the high-voltage source, whereby, at/in the ignition spark, a high-frequency plasma can be injected, thereby enhancing the ignition reliability of the fuel in the combustion chamber by an additional energy input into the ignition spark and an increased ignition spark volume, wherein the spark plug has a prechamber having at least one opening via which the prechamber communicates with the combustion chamber on the fuel side, so that the ignition spark in the prechamber, into which the high-frequency plasma can be injected, induces the plasma-assisted spark ignition of the fuel in the prechamber.

2. The ignition system as recited in claim 1, wherein the ignition installation includes a high-frequency generator and a power amplifier.

3. The ignition system as recited in claim 1, wherein at least one sensor, which acquires at least one ignition parameter of the fuel, is located in the combustion chamber.

4. An ignition method for a spark-ignition combustion engine, comprising: providing the spark ignition of the fuel by at least one spark plug associated with a combustion chamber of the combustion engine, wherein a first electrode of the spark plug is electrically connected to a high-voltage output of a high-voltage source and a second electrode is configured as a grounding contact; applying a high-frequency voltage to a high-frequency output, wherein the first electrode of the spark plug is coupled to an ignition installation that has the high-frequency output, and wherein the high-voltage output of a high-voltage source of the spark plug and the high-frequency output are electrically interconnected, so that, in a voltage circuit, which includes the high-voltage source of the spark plug, the high-voltage output of the high-voltage source is amplified by the high-frequency voltage applied to the high-frequency output to generate a spark discharge between a first electrode and second electrode of an ignition spark in response to the high-frequency voltage being injected via the high-frequency output into the voltage circuit of the high-voltage source, injecting a high-frequency plasma at/in the ignition spark, which enhances the ignition reliability of the fuel in the combustion chamber by an additional energy input into the ignition spark and an augmented ignition spark volume, wherein the spark plug has a prechamber having at least one opening via which the prechamber communicates with the combustion chamber on the fuel side, allowing the ignition spark to be formed in the prechamber, into which the high-frequency plasma is injected, thereby inducing a plasma-augmented spark ignition of the fuel in the prechamber.

5. The ignition method as recited in claim 4, further comprising forming a high-voltage pulse in response to injection of the high-frequency voltage into the voltage circuit of the high-voltage source at the output of the ignition installation, wherein the high-voltage pulse has a high-frequency voltage superimposed thereon.

6. The ignition method as recited in claim 5, wherein the high-frequency plasma is generated at a predefinable initiation instant prior to, concurrently with, or subsequently to ignition of the ignition spark, and is injected thereinto.

7. The ignition method as recited in claim 6, further comprising sustaining the high-frequency plasma, starting at the initiation instant, for a predefinable burning duration of up to 2.5 ms.

8. The ignition method as recited in claim 7, wherein the burning duration of the high-frequency plasma is variable, and wherein the method further comprises varying the burning duration as a function of sensor-acquired ignition parameters of the fuel in the combustion chamber.

9. The ignition method as recited in claim 7, further comprising: lengthening the burning duration as a function of the sensor-acquired ignition parameters in response to poor ignition parameters, and shortening the burning duration in response to good ignition parameters; wherein, in response to good ignition parameters, a burning duration of the high-frequency plasma of <1 ms is set, or the generation of the high-frequency plasma is set.

10. The ignition method as recited in claim 8, further comprising acquiring a magnitude of the charge dilution of the fuel as an ignition parameter, which is present due to enleanment or due to external or internal residual gas recirculation of the fuel in the combustion chamber at the time of ignition of the ignition spark of the spark plug.

11. The ignition method as recited in claim 5, further comprising adapting the ignition installation for initiating, generating and injecting the high-frequency plasma: at the latest 0.5 ms prior to ignition of the ignition spark, or at the latest, 0.5 ms subsequently to ignition of the ignition spark.

12. The ignition method as recited in claim 5, wherein the injected high-frequency voltage at the high-frequency output of the power amplifier has a frequency of 1 to 20 MHz, and a voltage within a voltage amplitude of between 0.1 kV and 30 kV.

13. The ignition method as recited in claim 12, wherein the frequency of the power amplifier is 8 to 12 Mhz.

14. The ignition method as recited in claim 12, wherein the voltage amplitude of the power amplifier is between 0.4 kV and 1 kV.

15. The ignition method as recited in claim 5, further comprising: superimposing a voltage ramp at the high-voltage output of the high-voltage source on the high-frequency voltage of the high-voltage source generated by the high-frequency generator via the power amplifier at the high-frequency output upon injection into the voltage circuit to create a constructive effect on the ignition voltage demand of the high-voltage source, and reducing the ignition voltage demand of the high-voltage source at the high-voltage output of the high-voltage source.

16. The ignition method as recited in at least one of the claim 4, further comprising: acquiring, via at least one sensor, at least one ignition parameter of a fuel-air mixture or of a fuel-air-exhaust gas mixture in the combustion chamber, wherein the spark plug is ignited and the high-frequency plasma is generated as a function of at least one of the acquired ignition parameters; and generating the high-frequency plasma by adapting at least one actual operating variable to at least one predefinable nominal-actual operating variable by an additional energy input into the ignition spark and/or an ignition spark volume augmented by the injected high-frequency plasma, as a function of the magnitude of the at least one acquired ignition parameter, wherein the at least one actual operating variable is the frequency of the high-frequency voltage and/or the voltage amplitude and/or the initiation instant, being adapted.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is clarified in the following with reference to the accompanying drawings, in which:

(2) FIG. 1A shows, in a first specific embodiment, a cylinder of a combustion engine in which a spark plug having a prechamber, in particular a prechamber spark plug, is located, which is connected to an ignition installation and which, together with an ignition coil functioning as a high-voltage source, a high-frequency generator and a power amplifier, makes up the ignition system according to the present invention;

(3) FIG. 1B shows, in the first specific embodiment, the prechamber spark plug (without a cylinder of the combustion engine), including the ignition installation, which, together with the ignition coil, the high-frequency generator and the power amplifier makes up the ignition system according to the present invention;

(4) FIG. 2A shows, in a second specific embodiment, a cylinder of a combustion engine in which a spark plug having a prechamber, in particular a top electrode spark plug, is configured and connected to an ignition installation, and which, together with an ignition coil, a high-frequency generator, and a power amplifier, makes up the ignition system according to the present invention;

(5) FIG. 2B shows, in the second specific embodiment, the prechamber spark plug (without cylinders of the combustion engine), including the ignition installation, which, together with the ignition coil, the high-frequency generator and the power amplifier, makes up the ignition system according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

First Specific Embodiment

(6) In an overall view, FIGS. 1A and 1B show a prechamber spark plug 18 of an ignition system 10, which is configured in a combustion chamber 16 of combustion engine 12, and which, besides prechamber spark plug 18, includes as the ignition installation for spark ignition, in particular an ignition coil 24, a high-frequency generator 32 and a power amplifier 40.

(7) Prechamber spark plug 18 includes a first electrode 20, in particular in the form of a center electrode, and a prechamber 18 and a second electrode 26 as a ground electrode.

(8) Spark plug 18, in particular the prechamber spark plug, has at least one opening 46 in a cap 42, so that a prechamber 18 of prechamber spark plug 18 is disposed between cap 42 and first electrode 20. Via the at least one opening 46, prechamber 18, which forms a prechamber ignition space, communicates with main combustion chamber 16 (compare FIG. 1A).

(9) Injector 52 performs the injection of a fuel into main combustion chamber 16 (compare FIG. 1A). In response to the injection of the fuel into the air induced by intake manifold 50 or in response to an air-exhaust-gas mixture enriched by an exhaust gas recirculation, a fuel-air mixture or a fuel-air-exhaust-gas mixture is produced in combustion chamber 16, which, in a generally known manner, is compressed by the upward movement of piston 54. During the compression stroke of piston 54, the fuel-air mixture or a fuel-air-exhaust gas mixture enters into prechamber 18 of prechamber spark plug 18.

(10) The ignition of the fuel-air mixture or of the fuel-air-exhaust gas mixture is initiated by ignition spark 34 in prechamber 18, in particular in the prechamber ignition space of prechamber 18.

(11) To this end, the appropriate high ignition voltage is fed from high-voltage output 22 of ignition coil 24 via an electrical line realized as an ignition cable 56 to center electrode 20 of prechamber spark plug 18.

(12) Ignition spark 34 is initiated in the intended manner to ignite the fuel-air mixture or the fuel-air-exhaust gas mixture.

(13) Prior to or concurrently with the formation of ignition spark 34 or subsequently to the already formed ignition spark 34, a high-frequency voltage produced by high-frequency generator 32 and fed, and thus amplified, by power amplifier 40 is conducted from high-frequency output 30 to center electrode 20 of prechamber spark plug 18; therefore, injected into high-voltage output 22 of ignition coil 24 at a predefinable initiation instant (prior to, concurrently with, or subsequently to the formation of ignition spark 34).

(14) The conductive channel realized by ignition spark 34 is consequently acted upon by the generated and injected high-frequency plasma 36, and the thus formed ignition spark 34 is charged with higher energy, as well as preferably sustained for a longer period of time, and becomes more voluminous than conventional ignition sparks in response to injected high-frequency plasma 36.

(15) High-frequency plasma 36 advantageously produces more radicals from the molecular compounds of the particular mixture in addition to a conventional ignition spark, thereby leading to a more stable and more rapid inflammation.

(16) In combination, the higher-energy charging of ignition spark 34, the sustaining of ignition spark 34 for a longer period of time, and the larger volume of ignition spark 34 advantageously result in increased ignition energy, leading to more reliable ignition of less flammable fuel-air mixtures, respectively fuel-air-exhaust gas mixtures. Accordingly, even leaner fuel-air mixtures, respectively diluted fuel-air-exhaust gas mixtures having partially charged/compressed combustion air recirculation are more reliably and more completely ignited.

(17) The more reliable initiation (ignition) results in a more complete combustion of the fuel-air mixture or of the fuel-air-exhaust gas mixture, whereby vehicle emissions are reduced. In addition, the specific fuel consumption is reduced, and damage to combustion engine 12 and prechamber spark plug 18 is prevented.

(18) A cylinder of an engine block 48 of a combustion engine 12, shown in FIG. 1A, is designed in a conventional manner to include control valves 60, in particular intake and exhaust valves, in the area of an intake manifold 50 and in the area of an exhaust manifold 62.

Second Specific Embodiment

(19) In an overall view, FIGS. 2A and 2B show a top electrode spark plug 44 of an ignition system 10, which is configured in a combustion chamber 16 of combustion engine 12 and which, analogously to the first specific embodiment, besides top electrode spark plug 44, includes an ignition coil 24, a high-frequency generator 32 and a power amplifier 40 as the ignition installation for spark ignition of top electrode spark plug 44.

(20) Top electrode spark plug 44 includes a first electrode 20, in particular in the form of a center electrode, and a prechamber 44 and a second electrode 26 as a ground electrode.

(21) Top electrode spark plug 44 is equipped with prechamber 44 having at least one opening 44-1. Prechamber 44, which forms a prechamber ignition space, communicates via the least one opening 44-1 with main combustion chamber 16 (compare FIG. 2A).

(22) Injector 52 performs the injection of a fuel into main combustion chamber 16 (compare FIG. 1A). In response to the injection of the fuel into the air induced by intake manifold 50 or in response to air-exhaust-gas mixture enriched by an exhaust gas recirculation (EGR), a fuel-air mixture or a fuel-air-exhaust-gas mixture is produced in combustion chamber 16 and, in a generally known manner, is compressed by the upward movement of piston 54. During the compression stroke of piston 54, the fuel-air mixture or a fuel-air-exhaust gas mixture enters into prechamber 44 of top electrode spark plug 44.

(23) Ignition spark 34 in prechamber 44, in particular in the prechamber ignition space of prechamber 44, advantageously initiates the ignition of the fuel-air mixture or of the fuel-air-exhaust gas mixture and provides the described effects.

(24) The description of the inventive method that is valid for the first specific embodiment and for the design of the ignition installation and for ignition system 10 as a whole also applies to the second specific embodiment, which is shown in FIGS. 2A and 2B analogously to the first specific embodiment.

(25) Differences in the use of a prechamber spark plug 18 having a prechamber 18 and a top electrode spark plug 44 having a prechamber 44 are that top electrode spark plug 44 having a prechamber 44 has two parts, i.e., top electrode spark plug 44 and prechamber 44 are two individual components, whereby, structurally, the space requirements are somewhat greater, but the components may be individually replaced. This difference is especially advantageous for the replacement interval for the spark plugs since, generally, a spark plug does not function for the entire service life of the vehicle.

REFERENCE NUMERAL LIST

(26) 10 ignition system 12 internal combustion engine, combustion engine 16 combustion chamber 18 prechamber spark plug 18 prechamber of the prechamber spark plug 20 first electrode, center electrode 22 high-voltage output 24 high-voltage source, ignition coil 26 second electrode; ground electrode 30 high-frequency output 32 high-frequency generator 34 ignition spark 36 high-frequency plasma 40 power amplifier 42 cap 44 top electrode spark plug 44 prechamber of the top electrode spark plug 44-1 openings in the prechamber of the top electrode spark plug 46 openings in the cap of the prechamber spark plug 48 engine block 50 intake manifold 52 injector 54 piston 56 ignition cable 58 insulator 60 control valve 62 exhaust manifold