Apparatus for igniting a fuel mixture, transmission element for transmitting an ignition signal, ignition device and circuit device

Abstract

The invention relates to an apparatus for igniting a fuel mixture. Set apparatus comprises an ignition system for generating a high-voltage ignition voltage as well as a circuit device comprising a circuit for superimposing a high-frequency signal on to the high-voltage ignition voltage. The apparatus further comprises a spark plug in an engine block as well as a transmission element for transmitting the ignition voltage, onto which the high-frequency signal has been superimposed, to the spark plug. The transmission element includes a contact element which is provided with an electrically conductive coating along at least one portion of the longitudinal axis of the contact element, the impedance of the coding being lower than the impedance of the contact element.

Claims

1. An apparatus for igniting a fuel mixture comprising: an ignition system for generating a high ignition voltage; a circuit device having a circuit for superimposing a high-frequency signal on the high ignition voltage; a spark plug arranged in an engine block; a transmission element for transmitting the high ignition voltage on which the high-frequency signal is superimposed to the spark plug and wherein the transmission element has a contact element that has an electrically conductive coating, at least along a section of the contact element's longitudinal axis, and the electrically conductive coating has an impedance that is lower than an impedance of the contact element.

2. The apparatus as claimed in claim 1 and wherein, magnetic permeability of the electrically conductive coating is lower than magnetic permeability of the contact element.

3. The apparatus as claimed in claim 2 and wherein the magnetic permeability of the electrically conductive coating is lower than the magnetic permeability of steel.

4. The apparatus as claimed in claim 2 and wherein the magnetic permeability of the electrically conductive coating is lower than the magnetic permeability of steel; and the electrical conductivity of the electrically conductive coating is higher than the electrical conductivity of stainless steel.

5. The Apparatus of claim 2 and wherein the electrically conductive coating has both a magnetic permeability that is lower than a magnetic permeability of the contact element and the electrically conductive coating has an electrical conductivity that is higher than an electrical conductivity of the contact element which causes the electrically conductive coating to have a lower impedance than the contact element.

6. The apparatus as claimed in claim 1 and wherein the electrically conductive coating has an electrical conductivity of at least 1.4×10.sup.8 Siemens per meter, and preferably at least of 10×10.sup.6 Siemens per meter.

7. The apparatus as claimed in claim 1 and wherein the electrically conductive coating has several layers.

8. The apparatus as claimed in claim 7 and wherein the first layer is an adhesive layer of copper; and the second layer is a diffusion layer of nickel; and the third layer is a corrosion protection layer of gold or silver or tin.

9. The apparatus as claimed in claim 1 and wherein the electrically conductive coating is at least partially formed from metal.

10. The apparatus as claimed in claim 1 and wherein the electrically conductive coating is at least partially formed of a metal selected from the group consisting of silver, copper, gold, tin, aluminium, tungsten, molybdenum, titanium, zirconium, niobium, tantalum, bismuth, palladium, lead, and an alloy.

11. The apparatus as claimed in claim 1 and wherein the electrically conductive coating has a thickness of between approximately 1.0 μm to 30 μm, and preferably between approximately 2.0 μm to 25 μm.

12. The apparatus as claimed in claim 1 and wherein the contact element is made of metal.

13. The apparatus as claimed in claim 1 and wherein the contact element is a spring.

14. The apparatus as claimed in claim 1 and wherein the contact element is formed, at least partially, of a resilient material.

15. The apparatus as claimed in claim 1 and further comprising: an insulation element which surrounds the contact element.

16. The apparatus as claimed in claim 1 and further comprising: an electrically conductive shielding element which surrounds the contact element in an electromagnetically shielding manner at least along a section of the longitudinal axis, and wherein the electrically conductive shielding element is electrically conductively connected to a ground potential of the circuit device and the electrically conductive shielding element establishes a connection between a ground potential of the circuit device and a ground electrode of the spark plug.

17. The apparatus as claimed in claim 16, and further comprising: a circuit housing which electromagnetically shields the circuit wherein the electrically conductive shielding element is connected to at least one of a ground potential of the circuit housing and a ground potential of the circuit.

18. The apparatus as claimed in claim 1 and wherein, electrical conductivity of the electrically conductive coating is higher than electrical conductivity of the contact element.

19. The apparatus as claimed in claim 1 and wherein electrical conductivity of the electrically conductive coating is higher than electrical conductivity of at least one of stainless steel and iron.

20. The apparatus as claimed in claim 1 and wherein the electrically conductive coating has a thickness of between approximately 3.0 μm to 25 μm and preferably a thickness between approximately 4.0 μm to 25 μm.

21. The apparatus as claimed in claim 1 and wherein the contact element is formed, at least partially, as a spring arm.

22. The apparatus as claimed in claim 1 and wherein the electrically conductive coating is formed from material which has a lower magnetic permeability than the material from which the contact element is made and which has a higher electrical conductivity than the material from which the contact element is made.

23. A transmission element for transmitting an ignition signal from an ignition system to a spark plug, the transmission element comprising: a contact element defining a longitudinal axis and having an electrically conductive coating at least along a section of the longitudinal axis, and wherein the electrically conductive coating has an impedance, and the impedance of the electrically conductive coating is lower than an impedance of the contact element.

24. The transmission element as claimed in claim 23, and wherein magnetic permeability of the electrically conductive coating is lower than magnetic permeability of the contact element.

25. The transmission element as claimed in claim 24, and wherein the magnetic permeability of the electrically conductive coating is lower than the magnetic permeability of steel.

26. The transmission element as claimed in claim 23 and wherein the electrically conductive coating has several layers.

27. The transmission element as claimed in claim 23 and wherein the electrically conductive coating is at least partially formed from metal.

28. The transmission element as claimed in claim 23 and wherein the electrically conductive coating is at least partially formed of a metal selected from the group consisting of silver, copper, gold, tin, aluminium, tungsten, molybdenum, titanium, zirconium, niobium, tantalum, bismuth, palladium, lead, and an alloy.

29. The transmission element as claimed in claim 23 and wherein the contact element is made of metal.

30. The transmission element as claimed in claim 23 and further comprising: an insulation element which surrounds the contact element having the electrically conductive coating.

31. The transmission element as claimed in claim 30, and further comprising: an electrically conductive shielding element which surrounds the insulation element at least along a section of a longitudinal axis of the insulation element, and on an outside of the insulation element.

32. The transmission element of claim 23 and wherein the contact element is at least partially at least one of a contact spring and a spring arm.

33. The transmission element of claim 23 and wherein the contact element is made of a resilient material.

34. The transmission element as claimed in claim 23, and wherein electrical conductivity of the electrically conductive coating is higher than electrical conductivity of the contact element.

35. The transmission element as claimed in claim 24, and wherein electrical conductivity of the electrically conductive coating is higher than electrical conductivity of at least one of stainless steel and iron.

36. An ignition device comprising: an ignition system for generating an ignition signal; and a transmission element having, a contact element that is formed of metal and defines a longitudinal axis and has an electrically conductive coating at least along a section of the longitudinal axis, and wherein the electrically conductive coating has an impedance that is lower than an impedance of the contact element, and wherein the contact element is at least partially, at least one of a contact spring and a spring arm, and is at least partially formed of resilient material, and wherein electrical conductivity of the electrically conductive coating is higher than electrical conductivity of the contact element, and wherein the electrically conductive coating has several layers, and wherein the electrically conductive coating is at least partially formed of a metal selected from the group consisting of silver, copper, gold, tin, aluminium, tungsten, molybdenum, titanium, zirconium, niobium, tantalum, bismuth, palladium, lead, and an alloy, comprising at least one of these materials, and an insulation element which surrounds the contact element that has the electrically conductive coating, and an electrically conductive shielding element surrounds the insulation element at least along a section of a longitudinal axis of the insulation element, and on an outside of the insulation element; and the transmission element transmits the ignition signal to a spark plug.

37. A circuit device for superimposing a high-frequency signal on a high ignition voltage, comprising: a transmission element having, a contact element that is formed of metal and defines a longitudinal axis and has an electrically conductive coating at least along a section of the longitudinal axis, and wherein the electrically conductive coating has an impedance that is lower than an impedance of the contact element, and wherein the contact element is at least partially, at least one of a contact spring and a spring arm, and is at least partially formed of resilient material, and wherein electrical conductivity of the electrically conductive coating is higher than electrical conductivity of the contact element, and wherein the electrically conductive coating has several lavers, and wherein the electrically conductive coating is at least partially formed of a metal selected from the group consisting of silver, copper, gold, tin, aluminium, tungsten, molybdenum, titanium, zirconium, niobium, tantalum, bismuth, palladium, lead, and an alloy, comprising at least one of these materials, and an insulation element which surrounds the contact element that has the electrically conductive coating, and an electrically conductive shielding element surrounds the insulation element at least along a section of a longitudinal axis of the insulation element, and on an outside of the insulation element; and the transmission element transmits the high ignition voltage, on which the high-frequency signal is superimposed, to a spark plug.

Description

BRIEF DESCRIPTIONS OF THE FIGURES

(1) An exemplary embodiment of the invention is described in more detail below with reference to the drawings.

(2) The figures each show preferred exemplary embodiments, in which individual features of the present invention are illustrated in combination with one another. However, the features of the exemplary embodiment can also be implemented separately from the other features of the exemplary embodiment and can accordingly be easily combined by a person skilled in the art to form further useful combinations and subcombinations.

(3) In the figures:

(4) FIG. 1 is a cross-section illustration of the device according to the invention showing a circuit housing of a circuit device and of a transmission element.

(5) FIG. 2 is an orthographic side view of a contact element embodied as a contact spring.

(6) FIG. 3 is a cross section view of the contact element taken through a turn of the contact spring.

(7) FIG. 4 is a cross section view of the contact element taken through a turn of the contact spring, and showing the coating which is made up of three layers.

DETAILED WRITTEN DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) The basic principle and the basic functioning of an internal combustion engine, in particular an internal combustion engine of a motor vehicle, and the associated apparatus for igniting a fuel-air mixture in a combustion chamber, in particular a cylinder of the engine, are well known from the general prior art. Internal combustion engines with external ignition by spark plugs, so-called Otto engines, and in particular also with direct injection, are in particular also known.

(9) Their mode of operation is therefore not discussed in more detail below.

(10) The generation of a high ignition voltage by means of an ignition system 1, which transforms a battery voltage to a required ignition voltage, is also known in principle. The generation of a high-frequency signal, in particular a high-frequency plasma ignition apparatus for igniting a fuel-air mixture in a combustion chamber of an internal combustion engine, is also known in principle, for which reference is also made to DE 20 2012 004 602 U1. This is also not discussed in more detail below.

(11) The exemplary embodiment is described on the basis of the transmission of a high ignition voltage (HV signal or HV pulse) on which a high-frequency signal is superimposed. However, the superimposition element according to the invention is also suitable for the transmission of another ignition signal, for example based on a high ignition voltage or a high-frequency signal. The transmission element according to the invention is not limited to the transmission of a specific ignition signal, but is particularly suitable for the transmission of a high ignition voltage on which a high-frequency signal is superimposed. Furthermore, the ignition device shown in the exemplary embodiment is not limited to the generation of a high ignition voltage on which a high-frequency signal is superimposed. The ignition signal which the ignition device generates can be any ignition signal, as already explained with regard to the transmission element.

(12) The apparatus shown in FIG. 1 shows a particularly suitable structure. However, the use of the transmission element is not limited to a specific structure of an apparatus for igniting a fuel mixture, but can be used in any desired structure. The exemplary embodiment is therefore also isolated as a disclosure of a transmission element, without being restricted to the features of the apparatus shown for igniting a fuel mixture, wherein the use of the transmission element is particularly suitable for the illustrated apparatus.

(13) FIG. 1 shows an apparatus for igniting a fuel mixture, in particular a fuel-air mixture, with an ignition system 1, shown only in principle, for generating a high ignition voltage (HV pulse) and a circuit device 2.

(14) In the exemplary embodiment, the circuit device 2 comprises a circuit housing 3 and a circuit 4 for superimposing a high-frequency signal (HF signal) on the high ignition voltage. In the exemplary embodiment, the high-frequency signal is generated by means of a high-frequency generator 5. The high-frequency signal generated by the high-frequency generator 5 is fed to the circuit 4 via a high-frequency lead 5a. Correspondingly, the high ignition voltage generated by the ignition system 1 is also fed to the circuit 4 via a high-voltage lead 1a.

(15) Alternatively, the ignition system 1 and/or the high-frequency generator 5 and/or another apparatus for generating the high ignition voltage or the high-frequency signal can also be integrated into the circuit device 2, in particular into the circuit housing 3 and possibly also into the circuit 4.

(16) The generation of the high ignition voltage or a corresponding high-voltage pulse and the high-frequency signal can in principle take place in any known manner within the scope of the invention.

(17) A transmission element 6 is also provided, which has a contact element 7 which is guided in an insulation element 8.

(18) As can be seen from FIG. 1, the transmission element 6 extends as far as a spark plug 10 arranged in an engine block 9.

(19) The spark plug 10 can have any suitable structure for igniting a fuel-air mixture. As can be seen from the basic illustration of FIG. 1, the spark plug 10 in the exemplary embodiment has a metallic connection part 11, a ceramic part 12, a flange 13 with an integrated crimped ring for holding the ceramic part 12 in place, a screw-in thread 14, a center electrode 15 and a ground electrode 16.

(20) The structure of the spark plug 10 can also differ; in particular, instead of a center electrode 15 insulated by means of a ceramic part 12, some other type of insulation can optionally also be provided.

(21) The structure of spark plugs and the different variants are known from the prior art.

(22) The spark plug 10 is located in a shaft of the engine block 9. The shaft in the engine block 9 does not have to run at an angle, as shown in the exemplary embodiment, (FIG. 1), but can have any desired course, possibly also a non-angled course.

(23) In the exemplary embodiment, it is provided that the spark plug 10 is connected to the engine block 9 in an electrically conductive manner via the screw-in thread 14.

(24) The circuit housing 3 is designed to be electrically conductive in the exemplary embodiment according to FIG. 1, so that the circuit 4 is electromagnetically shielded. The circuit 4 can be connected to the circuit housing 3 via a ground line 17, so that the circuit housing 3 and the circuit 4 have the same ground potential.

(25) In the exemplary embodiment, the contact element, as shown in more detail in FIG. 2, is embodied as a contact spring 7, preferably as a spiral spring. However, the exemplary embodiment is not restricted to this. The embodiment of the contact element as a contact spring 7 is also particularly suitable, however, in particular to compensate for tolerances.

(26) The contact element 7 can optionally also be embodied such that it is embodied as a spring only over a portion of its longitudinal axis A or (axial) length.

(27) In the exemplary embodiment (see FIG. 1) it is also optionally provided that the insulation element 8 encompasses or encases the contact spring 7. This can preferably be achieved in that the insulation element 8 has a central hole, which may be a drilled hole for receiving the contact spring 7.

(28) The insulation element 8 can be embodied as part of the transmission element 6.

(29) The insulation element 8 is preferably made of rubber or a rubber-like material, but the exemplary embodiment is not limited to this.

(30) In the exemplary embodiment, the insulation element 8 also fulfils the function of a sealing part or takes on a sealing function. In the exemplary embodiment, it is provided that the insulation element 8 seals both the junction with the circuit housing 3 and the junction area with the engine block 9, so that no moisture can penetrate. For this purpose, the insulation element 8 can be designed accordingly, preferably having grooves, for example, for positively locking accommodation, a wall of the circuit housing 3 and/or annular extensions, as shown in principle in FIG. 1.

(31) As can be seen from FIG. 1, an electrically conductive shielding element 18 is also (optionally) provided or formed. The electrically conductive shielding element 18 comprises and shields the contact spring 7 here at least along a section of the longitudinal axis A of the contact spring 7.

(32) The shielding element 18 can be embodied as part of the transmission element 6.

(33) In FIG. 1 it is shown that the shielding element 18 encompasses the contact spring 7 in an electromagnetic shielding manner only over part of the contact elements 7 axial length or the longitudinal axis A. The shielding element 18 is preferably embodied here in such a way that the shielding element 18 encompasses the contact spring 7 to such an extent that the distance d between the circuit housing 3 and the engine block 9 is shielded.

(34) In an embodiment not shown, it can be provided that the shielding element 18 encompasses the contact spring 7 outside the circuit housing 3 up to the spark plug 10. That is to say the contact spring 7 is surrounded almost over its entire length by the shielding element 18 outside the circuit housing.

(35) The shielding element 18 is connected in an electrically conductive manner to a ground or to the ground potential of the circuit device 2. The shielding element 18 establishes a connection between the ground of the circuit device 2 and the ground electrode 16 of the spark plug 10.

(36) In the exemplary embodiment, the shielding element is connected to the circuit housing 3 of the circuit device 2 in an electrically conductive manner. The circuit housing 3 is connected here to the circuit 4 via the ground line 17, as already described, so that the circuit 4, the circuit housing 3 and also the shielding element 18 have the same ground or the same ground potential.

(37) In the exemplary embodiment, the shielding element 18 is embodied in such a way that it encompasses the insulation element 8 on the outside at least along a section of its longitudinal axis A.

(38) FIG. 1 shows that the shielding element 18 encompasses the insulation element 8 over a portion of the longitudinal axis A thereof. As already described, the contact spring 7 is thus accordingly encompassed and shielded by the shielding element 18.

(39) In the exemplary embodiment, it is provided that the shielding element 18 extends as far as the engine block 9 in order to establish an electrical connection between the ground of the circuit device 2 and the ground electrode 16 via the engine block 9. Alternatively, (not shown), the shielding element 18 can extend as far as the spark plug 10 in order to establish an electrically conductive connection to the ground electrode 16 of the spark plug 10 directly via the spark plug 10. The shielding element 18 is preferably connected here to the crimped ring 13 and this in turn is connected to the ground electrode 16 via the screw-in thread 14.

(40) As can be seen from FIG. 1, it can be provided that the circuit housing 3 is fixed on the engine block 9. The area of the engine block 9 on which the circuit housing 3 is secured can be, but is not limited to, a cylinder head of the cylinder into which the spark plug 10 is inserted.

(41) A fastening 19 for securing the circuit housing 3 is shown in principle in FIG. 1.

(42) According to the invention, for the transmission of the ignition signal, which in the exemplary embodiment is a high ignition voltage on which a high-frequency signal is superimposed, it is provided that the contact element 7 is provided with a coating 20 of an electrically conductive material at least along a section of its axial length A. The electrically conductive material for forming the coating 20 is selected here in such a way that the impedance of the coating 20 is lower than the impedance of the contact element 7. The lower impedance of the coating 20 compared to the contact element 7 results in the exemplary embodiment from the fact that the magnetic permeability of the coating 20 is lower than the magnetic permeability of the contact element 7 and/or the electrical conductivity of the coating 20 is higher than the electrical conductivity of the contact element 7.

(43) In the exemplary embodiment it is provided that the magnetic permeability of the coating 20 is lower than the magnetic permeability of steel and that the electrical conductivity of the coating 20 is higher than that of stainless steel.

(44) In FIG. 2, a coated contact element 7 is illustrated in a preferred embodiment as a contact spring 7 with the coating 20 applied on the outside. FIG. 3 shows the cross section through one turn of the contact spring 7. In the exemplary embodiment, the material of the coating 20 is selected such that the electrical conductivity of the material is higher than the electrical conductivity of iron. The electrical conductivity σ of the material of the coating 20 is at least 1.4×10.sup.6 Siemens per meter (S/m), preferably 10×10.sup.6 Siemens per meter (S/m). The coating 20 is formed from metal in the exemplary embodiment.

(45) In one configuration, the transmission element 6 can be composed only of the contact element 7, in particular embodied as a contact spring 7, and of the coating 20. The transmission element 6 can, however, also have the insulation element 8 and/or the shielding element 18 or can be composed of these four components.

(46) In the exemplary embodiment according to FIG. 3, it is provided that the coating 20 is formed from copper, silver, gold or tin.

(47) In the exemplary embodiment, the coating 20 has a thickness of 1.0 μm to 30 μm, preferably 2.0 μm to 25 μm, more preferably 3.0 μm to 25 μm and very particularly preferably 4.0 μm to 25 μm.

(48) In the exemplary embodiment it is also provided that the contact spring 7 is made of metal, preferably steel or stainless steel.

(49) In the exemplary embodiment, the coating 20 is formed from a material which has a lower magnetic permeability than the material from which the contact element 7 is made and which has a higher electrical conductivity than the material from which the contact element 7 is made.

(50) The contact spring 7 with the coating 20 can also be referred to as a hybrid spring.

(51) Like FIG. 3, FIG. 4 shows a cross section through one turn of the contact spring 7. The exemplary embodiment according to FIG. 4 differs from FIG. 3 here in the structure of the coating 20. According to FIG. 4, it is provided that the coating 20 is formed by several layers 21, 22, 23 which together constitute the coating 20. In the exemplary embodiment it is provided that all the layers 21, 22, 23 are formed from metal. This is not absolutely necessary, however. In the exemplary embodiment it is further provided that the layers 21, 22, 23 together have the properties that have already been described above with regard to the formation of the coating 20 from only one material. However, it can also be provided that only one layer or a majority of the layers have the properties that were presented above with regard to the coating 20 as a whole. In this case, the other layers that do not have these properties, in particular the lower impedance compared to the contact element 7, can have other functions, for example they can serve as corrosion protection, diffusion protection or as an adhesive layer.

(52) In the exemplary embodiment, it is provided that all layers 21, 22, 23 individually and in their entirety, satisfy the aforementioned properties, in particular have a lower impedance than the contact element 7.

(53) In principle, more or fewer than three layers can also be provided in the context of the exemplary embodiment according to FIG. 4.

(54) In the exemplary embodiment it is provided that the first layer 21 is embodied as an adhesive layer, preferably as a copper layer. In the exemplary embodiment it is also provided that the second layer 22 is embodied as a diffusion layer, preferably as a nickel layer. In the exemplary embodiment it is further provided that the third layer 23 also assumes the function of corrosion protection and for this purpose is preferably embodied as a gold layer, silver layer or tin layer. The second layer 22, which is embodied as a diffusion layer, preferably as a nickel layer, takes on the function here of avoiding or reducing diffusion of the gold, silver or tin in the direction of the copper layer.

(55) In principle, the various layers 21, 22, 23 can be made of any suitable material.

(56) An apparatus for igniting a fuel mixture with an ignition system (1) for generating a high ignition voltage and a circuit device (2), comprising a circuit (4) for superimposing a high-frequency signal on the high ignition voltage, and with a spark plug (10) arranged in an engine block (9) and a transmission element (6) for transmitting the high ignition voltage on which the high-frequency signal is superimposed to the spark plug (10), the transmission element (6) having a contact element (7) which is provided, at least along a section of its longitudinal axis (A), with an electrically conductive coating (20), wherein the impedance of the coating (20) is lower than the impedance of the contact element (7).

(57) An apparatus characterized in that the lower impedance of the coating (20) compared to the contact element (7) results from the fact that the magnetic permeability of the coating (20) is lower than the magnetic permeability of the contact element (7) and/or the electrical conductivity of the coating (20) is higher than the electrical conductivity of the contact element (7).

(58) An apparatus characterized in that the magnetic permeability of the coating (20) is lower than the magnetic permeability of steel and/or in that the electrical conductivity of the coating (20) is higher than that of stainless steel, preferably higher than the electrical conductivity of iron.

(59) An apparatus characterized in that the electrical conductivity of the coating (20) is at least 1.4×10.sup.6 Siemens per meter (S/m), preferably at least 10×10.sup.6 Siemens per meter (S/m).

(60) An apparatus characterized in that the coating (20) has several layers (21,22,23).

(61) An apparatus characterized in that the coating (20) is formed from metal, or at least one, two, three or more or all of the layers (21,22,23) of the coating is/are formed from metal or metals.

(62) An apparatus characterized in that the coating (20) or at least one, two, three or more or all of the layers (21,22,23) of the coating is/are formed from silver, copper, gold, tin, aluminium, tungsten, molybdenum, titanium, zirconium, niobium, tantalum, bismuth, palladium, lead, an alloy, mainly comprising one or more of these materials, or from a composite material composed of one of these materials.

(63) An apparatus characterized in that the coating (20) has a thickness of 1.0 μm to 30 μm, preferably 2.0 μm to 25 μm, more preferably 3.0 μm to 25 μm and very particularly preferably 4.0 μm to 25 μm.

(64) An apparatus characterized in that the contact element (7) is made of metal, preferably steel or stainless steel.

(65) An apparatus characterized in that the contact element (7) is embodied at least in certain sections as a contact spring, preferably as a spiral spring.

(66) An apparatus characterized in that the contact element (7) is at least in certain sections formed from a resilient material and/or at least in certain sections as a spring arm.

(67) An apparatus characterized in that the transmission element (6) has an insulation element (8) which surrounds the contact element (7).

(68) An apparatus characterized in that an electrically conductive shielding element (18) is provided which surrounds the contact element (7) in an electromagnetically shielding manner at least along a section of its longitudinal axis (A), wherein the shielding element (18) is electrically conductively connected to a ground potential of the circuit device (2) and the shielding element (18) establishes a connection between the ground potential of the circuit device (2) and a ground electrode (16) of the spark plug (10).

(69) An apparatus characterized in that the circuit device (2) comprises a circuit housing (3) which electromagnetically shields the circuit (4), wherein the shielding element (18) is connected to a ground potential of the circuit housing (3) and/or to a ground potential of the circuit (4).

(70) A transmission element (6) for transmitting an ignition signal from an ignition system to a spark plug (10), having a contact element (7), characterized in that the contact element (7) is provided with an electrically conductive coating (20) at least along a section of its longitudinal axis (A), wherein the impedance of the coating (20) is lower than the impedance of the contact element (7), and wherein the contact element (7) is at least in certain sections embodied as a contact spring and/or as a spring arm and/or made from a resilient material.

(71) A transmission element (6) characterized in that the lower impedance of the coating (20) compared to the contact element (7) results from the fact that the magnetic permeability of the coating (20) is lower than the magnetic permeability of the contact element (7) and/or the electrical conductivity of the coating (20) is higher than the electrical conductivity of the contact element (7).

(72) A transmission element (6) characterized in that the magnetic permeability of the coating (20) is lower than the magnetic permeability of steel and/or in that the electrical conductivity of the coating (20) is higher than that of stainless steel, preferably higher than the electrical conductivity of iron.

(73) A transmission element (6) characterized in that the coating (20) has several layers (21,22,23).

(74) A transmission element (6) characterized in that the coating (20) is formed from metal, or at least one, two, three or more or all of the layers (21,22,23) of the coating is/are formed from metal or metals.

(75) A transmission element (6) characterized in that the coating (20) or at least one, two, three or more or all of the layers (21,22,23) of the coating is/are formed from silver, copper, gold, tin, aluminium, tungsten, molybdenum, titanium, zirconium, niobium, tantalum, bismuth, palladium, lead, an alloy, mainly comprising one or more of these materials, or from a composite material composed of one of these materials.

(76) A transmission element (6) characterized in that the contact element (7) is made of metal, preferably steel or stainless steel.

(77) A transmission element (6) characterized in that the transmission element (6) has an insulation element (8) which surrounds the contact element (7) provided with the coating.

(78) A transmission element (6) characterized in that the transmission element (6) has an electrically conductive shielding element (18) which surrounds the insulation element (8) on the outside at least along a section of its longitudinal axis (A).

(79) An ignition device, with an ignition system (1) for generating an ignition signal, and with a transmission element (6) in order to transmit the ignition signal to a spark plug (10).

(80) A circuit device (2) for superimposing a high-frequency signal on a high ignition voltage, and with a transmission element (6) as claimed in one of claims 15 to 23, in order to transmit the high ignition voltage on which the high-frequency signal is superimposed to the spark plug (10).

(81) An apparatus for igniting a fuel mixture comprising: an ignition system (1) for generating a high ignition voltage; a circuit device (2), having a circuit (4) for superimposing a high-frequency signal on the high ignition voltage; a spark plug (10) arranged in an engine block (9); a transmission element (6) for transmitting the high ignition voltage on which the high-frequency signal is superimposed to the spark plug (10), and wherein the transmission element (6) has a contact element that has an electrically conductive coating (7), at least along a section of the contact element's longitudinal axis A, and the electrically conductive coating 20 has an impedance that is lower than an impedance of the contact element (7).

(82) An apparatus wherein, magnetic permeability of the electrically conductive coating (20) is lower than magnetic permeability of the contact element (7).

(83) An apparatus wherein the magnetic permeability of the electrically conductive coating (20) is lower than the magnetic permeability of steel.

(84) An apparatus wherein the electrically conductive coating has an electrical conductivity of at least 1.4×10.sup.6 Siemens per meter (S/m), and preferably at least of 10×10.sup.6 Siemens per meter (S/m).

(85) An apparatus wherein the electrically conductive coating (20) has several layers (21,22,23).

(86) An apparatus wherein the electrically conductive coating is at least partially formed from metal.

(87) An apparatus wherein the electrically conductive coating is at least partially formed of a metal selected from the group consisting of silver, copper, gold, tin, aluminium, tungsten, molybdenum, titanium, zirconium, niobium, tantalum, bismuth, palladium, lead, and an alloy, mainly comprising one or more of these materials, or from a composite material composed of one of these materials.

(88) An apparatus wherein the electrically conductive coating (20) has a thickness of between approximately 1.0 μm to 30 μm, and preferably between approximately 2.0 μm to 25 μm.

(89) An apparatus wherein the contact element (7) is made of metal.

(90) An apparatus wherein the contact element 7 is a spring.

(91) An apparatus wherein the contact element is formed, at least partially, of a resilient material.

(92) An apparatus further comprising: an insulation element (8) which surrounds the contact element (7).

(93) An apparatus further comprising: an electrically conductive shielding element (18) which surrounds the contact element (7) in an electromagnetically shielding manner at least along a section of the longitudinal axis (A), and wherein the electrically conductive shielding element (18) is electrically conductively connected to a ground potential of the circuit device (2) and the electrically conductive shielding element (18) establishes a connection between a ground potential of the circuit device (2) and a ground electrode (16) of the spark plug (10).

(94) An apparatus further comprising: a circuit housing (3) which electromagnetically shields the circuit (4), and wherein the electrically conductive shielding element (18) is connected to at least one of a ground potential of the circuit housing (3) and a ground potential of the circuit (4).

(95) A transmission element (6) for transmitting an ignition signal from an ignition system to a spark plug, the transmission element comprising: a contact element 7 defining a longitudinal axis and having an electrically conductive coating (20) at least along a section of the longitudinal axis (A), and wherein the electrically conductive coating has an impedance, and the impedance of the electrically conductive coating (20) is lower than an impedance of the contact element (7).

(96) A transmission element (6) wherein magnetic permeability of the electrically conductive coating (20) is lower than magnetic permeability of the contact element (7).

(97) A transmission element (6) wherein the magnetic permeability of the electrically conductive coating (20) is lower than the magnetic permeability of steel.

(98) A transmission element (6) wherein the electrically conductive coating (20) has several layers (21,22,23).

(99) A transmission element (6) wherein the electrically conductive coating (20) is at least partially formed from metal.

(100) A transmission element (6) wherein the electrically conductive coating is at least partially formed of a metal selected from the group consisting of silver, copper, gold, tin, aluminium, tungsten, molybdenum, titanium, zirconium, niobium, tantalum, bismuth, palladium, lead, and an alloy.

(101) A transmission element (6) wherein the contact element (7) is made of metal, and preferably steel or stainless steel.

(102) A transmission element (6) and further comprising: an insulation element (8) which surrounds the contact element (7) having the electrically conductive coating.

(103) A transmission element (6) and further comprising: an electrically conductive shielding element (18) which surrounds the insulation element (8) at least along a section of a longitudinal axis (A) of the insulation element, and on an outside of the insulation element.

(104) An ignition device comprising: an ignition system 1 for generating an ignition signal; and a transmission element 6 having, a contact element 7 that is formed of metal and defines a longitudinal axis A and has an electrically conductive coating 20 at least along a section of the longitudinal axis A, and wherein the electrically conductive coating 20 has an impedance that is lower than an impedance of the contact element 7, and wherein the contact element 7 is at least partially, at least one of a contact spring and a spring arm, and is at least partially formed of resilient material, and wherein electrical conductivity of the electrically conductive coating 20 is higher than electrical conductivity of the contact element 7, and wherein the electrically conductive coating 20 has several layers, and wherein the electrically conductive coating 20 is at least partially formed of a metal selected from the group consisting of silver, copper, gold, tin, aluminium, tungsten, molybdenum, titanium, zirconium, niobium, tantalum, bismuth, palladium, lead, and an alloy, comprising at least one of these materials, and an insulation element 8 which surrounds the contact element 7 that has the electrically conductive coating 20, and an electrically conductive shielding element 18 surrounds the insulation element 8 at least along a section of a longitudinal axis A of the insulation element 8, and on an outside of the insulation element 8; and the transmission element 6 transmits the ignition signal to a spark plug 10.

(105) A circuit device 2 for superimposing a high-frequency signal on a high ignition voltage, comprising: a transmission element 6 having, a contact element 7 that is formed of metal and defines a longitudinal axis A and has an electrically conductive coating 20 at least along a section of the longitudinal axis A, and wherein the electrically conductive coating 20 has an impedance that is lower than an impedance of the contact element 7, and wherein the contact element 7 is at least partially, at least one of a contact spring and a spring arm, and is at least partially formed of resilient material, and wherein electrical conductivity of the electrically conductive coating 20 is higher than electrical conductivity of the contact element, 7 and wherein the electrically conductive coating 20 has several layers, and wherein the electrically conductive coating 20 is at least partially formed of a metal selected from the group consisting of silver, copper, gold, tin, aluminium, tungsten, molybdenum, titanium, zirconium, niobium, tantalum, bismuth, palladium, lead, and an alloy, comprising at least one of these materials, and an insulation element 8 which surrounds the contact element 7 that has the electrically conductive coating 20, and an electrically conductive shielding element 18 surrounds the insulation element 8 at least along a section of a longitudinal axis A of the insulation element 8, and on an outside of the insulation element 8; and the transmission element 6 transmits the high ignition voltage, on which the high-frequency signal is superimposed, to a spark plug 10.

(106) An apparatus wherein, electrical conductivity of the electrically conductive coating 20 is higher than electrical conductivity of the contact element 7.

(107) An apparatus wherein electrical conductivity of the electrically conductive coating 20 is higher than electrical conductivity of at least one of stainless steel and iron.

(108) An apparatus wherein the electrically conductive coating 20 has a thickness of between approximately 3.0 μm to 25 μm and preferably a thickness between approximately 4.0 μm to 25 μm.

(109) An apparatus wherein the contact element 7 is formed, at least partially, as a spring arm.

(110) A transmission element 6 wherein the contact element 7 is at least partially at least one of a contact spring and a spring arm.

(111) A transmission element 6 wherein the contact element 7 is made of a resilient material.

(112) A transmission element 6 wherein electrical conductivity of the electrically conductive coating 20 is higher than electrical conductivity of the contact element 7.

(113) A transmission element 6 wherein electrical conductivity of the electrically conductive coating 20 is higher than electrical conductivity of at least one of stainless steel and iron.

(114) An apparatus wherein the magnetic permeability of the electrically conductive coating 20 is lower than the magnetic permeability of steel; and the electrical conductivity of the electrically conductive coating 20 is higher than the electrical conductivity of stainless steel.

(115) An apparatus wherein the electrically conductive coating 20 is formed from material which has a lower magnetic permeability than the material from which the contact element 7 is made and which has a higher electrical conductivity than the material from which the contact element 7 is made.

(116) An apparatus wherein the first layer is an adhesive layer of copper layer; and the second layer is a diffusion layer of nickel; and the third layer is a corrosion protection layer of gold or silver or tin.

(117) An apparatus wherein the electrically conductive coating 20 has both a magnetic permeability that is lower than a magnetic permeability of the contact element 7 and the electrically conductive coating 20 has an electrical conductivity that is higher than an electrical conductivity of the contact element 7 which causes the electrically conducive coating 20 to have a lower impedance than the contact element 7.