This application claims priority to DE 10 2015 101 374.6, filed Jan. 30, 2015, and also claims priority to DE 10 2015 101 568.4, filed Feb. 4, 2015, both of which are hereby incorporated herein by reference in their entireties.
The invention refers to a corona ignition device. Corona ignition devices are known, e.g., from DE 10 2013 104 643 B3 and are used for igniting fuel in an internal combustion engine. In motor vehicles, corona ignition devices are exposed not only to thermal stresses by the operation of the engine, but also to considerable mechanical stresses, which occur from shocks and vibrations during the journey.
This disclosure teaches how a mechanically robust corona ignition device can be manufactured in a cost-efficient manner.
In the housing of a corona ignition device according to this disclosure, a spring is arranged between coil and cover. This spring is a compression spring which presses the coil towards the central electrode and therefore compensates manufacturing tolerances in the length of the housing, the length of the coil or the central electrode. Advantageously, therefore, a compression spring mounted between cover and coil, despite length- and position tolerances, can fix the coil in the housing. The corona ignition device can therefore better withstand the mechanical stresses occurring during the driving operation.
An advantageous further refinement of this disclosure makes provision that the compression spring is a metal plate having spring lugs. The metal plate has an opening through which an electrical connection of the coil is directed. Such a metal plate with spring lugs can be stamped out from sheet metal in a cost-efficient manner, wherein the spring lugs are bent out from the plane of the plate. The spring lugs can rest on the cover or can face the coil.
An additional advantage of a compression spring in the form of a metal plate with spring lugs is that the metal plate can complete a shielding of the coil in the axial direction, which can be, for example a radial sheet metal casing of the coil. For this, it is advantageous if the metal plate has a high electrical conductivity, for example by being produced from copper, aluminium or silver, or carries a highly conductive coating, for example of copper, aluminium, gold or silver, on its side facing the coil. Such a coating is preferably at least 0.1 mm thick. A coating can be applied for example by electroplating or by roll cladding on sheet metal, for example sheet steel.
This disclosure also shows how a corona ignition device can be provided economically with an electromagnetic shield. The function of an electromagnetic shield is to reduce eddy current losses.
This is achieved by arranging a shield that comprises several shell elements around the coil. Shell elements can be made from sheet metal at low cost. Such shell elements can be arranged around the coil. Such shell elements are cheaper than a tube. The shell elements may be made of aluminium, copper, silver or gold, for example.
The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:
The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.
The corona ignition device shown in
The central electrode 3 is connected in series with a coil 7. The coil 7 is wound onto a coil former 8, which is plugged together with the central electrode 3. This plug connection between coil former 8 and central electrode 3 can have a shield cap 9, which surrounds the electrical connection site between coil 7 and central electrode 3. In addition to the mechanical connection of coil former 8 and central electrode 3, the plug connection also brings about an electrical connection between the coil former 8 and the central electrode 3.
A front housing part 1a, which holds the insulator 2, is welded to a housing part 1b adjoining thereon, and the coil 7 with its coil former 8 is connected by inserting into one another with the central electrode 3. The front housing part 1a forms a stop, on joining together of the two housing parts 1a and 1b, for example by the front housing part 1a having an annular shoulder, onto which a tubular housing part 1b is placed. The coil former 8, on joining onto the central electrode 3, can likewise be mounted in abutment, wherein the stop can be formed for example by the central electrode 3 or the insulator 2.
The tolerances which are adding together during assembly are compensated by a compression spring 10, which is mounted between the coil 7 and the cover 5. An example embodiment of such a compression spring is illustrated in
The compression spring can be, for example, a metal plate having spring lugs 10a, which has an opening 11 through which an electrical connection 12 of the coil 7 is directed. The metal plate with spring lugs 10a can be produced as a stamped-bent part of sheet metal. In the illustrated example embodiment, the spring lugs 10a rest on the cover 5, whilst the metal plate itself lies against a flange 8a of the coil former 8. An extension 8b of the coil former 8 projects through the opening of the metal plate 11. This extension 8b can carry an electrical connection of the coil 7, for example a contact pin 13 of the plug connector 6.
The compression spring 10 can be produced for example from steel or bronze and can be provided with a highly conductive coating, for example of copper, gold, silver or aluminium, in order to reduce eddy current losses. It is sufficient here to apply the coating on the side of the compression spring 10 which faces the coil 7. When the coating is applied by electroplating, it can be advantageous from the manufacturing point of view to apply the coating on both sides. The coating can also be applied for example by roll cladding onto a metal sheet from which then the compression spring 10 is produced.
For the reduction of eddy current losses, the inner side of the housing 1 can be provided with a conductive layer, for example of copper, silver, aluminium or gold. As an alternative to a coating of the housing 1, the coil can be surrounded in the housing 1 radially by a shield of sheet metal, for example of copper or aluminium. The shield 12 is shown in
The shell elements 12 are made of sheet metal. A gap may be present between neighbouring shell elements 12 in order to reduce eddy current losses even more. The corona ignition device may comprise three shell elements 12 so that the shield has three gaps that extend in longitudinal direction of the coil 7.
The shell elements 12 can be carried by the coil former 8. For example the coil former 8 may comprise a flange 8a on which the shell elements 12 may be fixed, e.g., by an adhesive.
The coil 7 has a smaller radius at its end facing the insulator 2 than at its end facing away from the insulator. The shell elements 12 have a larger circumferential width at their end facing away from the insulator 2 than at their end facing the insulator 2.
While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
Number | Date | Country | Kind |
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10 2015 101 374 | Jan 2015 | DE | national |
10 2015 101 568 | Feb 2015 | DE | national |
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Entry |
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20160226226 A1 | Aug 2016 | US |