Ignition coil for internal combustion engines

Information

  • Patent Grant
  • 6352069
  • Patent Number
    6,352,069
  • Date Filed
    Tuesday, April 4, 2000
    24 years ago
  • Date Issued
    Tuesday, March 5, 2002
    22 years ago
Abstract
Ignition coil for internal combustion engines with two or more transformer stages connected in a cascade arrangement one behind another.
Description




BACKGROUND OF THE INVENTION




The invention relates to an ignition coil for internal combustion engines.




In the case of ignition coils, a high voltage of up to 50 kV must be produced in a very limited space.




In order to obtain a long useful life, the coil must be insulated as well as possible, a construction not producing partial discharges being ideal. Because of the electrical insulation, a coil with low partial discharges is very bulky. The magnetic leakage fields are large with conventional solutions, and the magnetic coupling between the primary and secondary coil is poor.




BRIEF SUMMARY OF THE INVENTION




The object of the invention is to provide a coil improved with respect to useful life and to a compact construction.




According to the invention, this is obtained by means of an ignition coil for internal combustion engines that is characterised by two or more transformer stages connected in a cascade arrangement one behind another, wherein the secondary windings of all the transformer stages are connected in series onto a spark plug.




With such a construction, the individual transformer stages can be constructed more compactly, as the high voltage required is produced in several stages, wherein the individual stages can easily be insulated one from another. In the respective stages themselves, the voltages are lower with respect to one another, whereby the gaps between the windings can be minimised. As a result, a better magnetic coupling is obtained. Leakage fields can be reduced. With this multiple stage construction, the required insulation gaps are smaller, which allows a closed iron core, or respectively a general ferromagnetic core, to be used in each individual transformer stage, while at the same time preserving a relatively compact construction. In this way the magnetic flux can be better controlled.




In addition to a more compact construction, the ignition coil according to the invention is also characterised by a longer useful life, in particular as, due to lower voltages, it is easier to prevent partial discharges via the insulator.




Furthermore, the cascade arrangement allows a large degree of freedom in the sizing of the ignition coil, both from the electrical point of view and from the point of view of the mechanical construction. It is thus possible, for example, to arrange the individual transformer stages geometrically in almost any arrangement with respect to one another. An arrangement in which the individual transformer stages are “threaded” one behind another on a common imaginary axis is advantageous. There are, however, other possibilities for arrangement. From the electrical point of view, an adaptation to the prevailing conditions can be made, for example, by different transformation ratios in the individual transformer stages. It is also possible to size the input side transformer stages with respect to the volume of the core and the wire thickness of the windings smaller than the output side stages, which allows a more compact and slimmer mode of construction in the output area.




It is also possible to feed the primary winding of the transformer stages using separate voltage sources, for example, by means of a capacitor circuit or a high-frequency ignition circuit. Essentially, the ignition coil according to the invention is suitable in the most different of configurations, both for capacitor ignition circuits and for high-frequency ignition circuits, wherein there is particular suitability for high-frequency ignition circuits, which can transmit frequencies up to the 100 kHz range. Further advantages and details of the invention will be explained with reference to the following description of the drawings.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

shows schematically the electrical construction of an embodiment of an ignition coil according to the invention,





FIG. 2

shows an embodiment for a mechanical construction of an ignition coil according to the invention in a central longitudinal section, wherein the lines according to the invention connecting the individual windings according to

FIG. 1

are not shown in

FIG. 2

for reasons of clarity, or respectively lie outside the sectional plane,





FIG. 3

shows a partly cut-away representation in perspective of the schematic construction of an embodiment of a transformer stage of an ignition coil according to the invention,





FIG. 4

shows the electrical construction of a further embodiment with two separate voltage sources,





FIG. 5

shows the assembly of an ignition coil according to the invention in a cylinder head.











DETAILED DESCRIPTION OF THE INVENTION




The ignition coil


1


shown in

FIG. 1

has a primary side terminal


2


and a secondary side terminal


3


, on which the high voltage is present. On the primary side there can be connected, for example, a capacitor ignition circuit or a high-frequency ignition circuit, known per se, which results in a voltage pulse in the first primary winding


4


of the first transformer stage


5


. In this embodiment there are altogether three transformer stages


5


,


6


, and


7


connected in a cascade arrangement one behind another, wherein the secondary windings


8


,


9


and


10


of the transformer stages


5


,


6


and


7


are connected in series behind one another, so that the voltages induced in the individual secondary windings


8


,


9


and


10


add together to form the output voltage on the terminals


3


.




On the primary side the individual transformer stages


5


,


6


and


7


are coupled respectively via connected primary windings


11


,


12


and respectively


13


,


14


, wherein the transformation ratios in the individual transformer stages can be equal, or, in order to adapt to particular requirements, different.




The ferromagnetic core of each transformer stage


5


,


6


, and


7


is labelled


15


, and is shown only schematically in FIG.


1


.





FIG. 2

shows an embodiment for an actual construction with three transformer stages


6


,


7


, connected one behind another, wherein it is particularly clear that the ferromagnetic core


15


is configured as a closed core. In the embodiment shown, each stage is configured as a shell-type transformer, in which the secondary winding and the primary windings are wound concentrically about the same leg of the ferromagnetic core


15


. This can be seen particularly well in

FIG. 3

, in which this leg is labelled with the reference sign


16


. The secondary winding


8


is wound on the inside about this leg, the primary windings


4


and


11


are wound around concentrically on the outside. On each side of this leg


16


there project two yokes


17


, which are each connected via a non-wound leg


18


into a closed ferromagnetic circuit with the wound leg


16


. Altogether, there is thus produced a doubly closed ferromagnetic core


15


.




As the rear transformer stages no longer have to transmit the whole of the energy, these can be configured smaller, on the one hand with respect to the volume of the ferromagnetic core, but also the load-carrying capacity of the primary winding. This is indicated in FIG.


2


. Such a structure allows, inter alia, saving of material and where needed a more compact external measurement, and offers more possibilities for design in the construction of the ignition coil. This can result in the ignition coil being at least partially inserted into the free space


23


between the inlet and outlet valves


24


of a cylinder head


22


, whereby accommodation in a space-saving manner is possible, and moreover, the gap to the spark plug


25


is reduced (see FIG.


5


). The ignition coil


1


in this case has three housing sections


1




a


,


1




b


and


1




c


of different diameters.




In the embodiment shown in

FIG. 2

, the primary windings


4


,


11


,


12


,


13


and


14


, and the secondary windings


8


,


9


and


10


of all the transformer stages


5


,


6


and


7


are wound about a common imaginary axis


19


, wherein the individual transformer stages


5


,


6


and


7


are each arranged at a distance apart along this axis. The terminal


3


for picking up the high voltage can then still be arranged on this axis.




The embodiment shown in

FIG. 4

shows a version with two voltage sources, which are separated from one another. One is configured as a high-frequency ignition circuit


20


, the other as a capacitor ignition circuit


21


. There are respectively provided separated primary side terminals


2




a


and


2




b


. The ignition coil itself is in turn provided with three transformer stages


5


,


6


and


7


connected in a cascade arrangement one behind another, wherein the secondary windings are connected in series. On the primary side, the voltage source


20


feeds the primary winding


4


of the first stage


5


, while the voltage source


21


feeds the primary winding


12


of the second stage


6


. This second stage


6


is coupled via the primary windings


13


and


14


to the third stage


7


. The high-frequency ignition circuit


12


and respectively the capacitor ignition circuit


21


do not need to be described in more detail. These circuits can be constructed according to the state of the art.




The invention is naturally not limited to the embodiments shown, for example, two or more than three cascade type transformer stages can be used. The spatial arrangement of the transformer stages with respect to one another can also differ from the linear orientation thereof as provided in FIG.


2


.



Claims
  • 1. An Ignition coil for internal combustion engines comprising:two or more transformer stages connected in a cascade arrangement one behind another, the secondary windings of all the transformer stages being connected in series to a spark plug, wherein at least one transformer stage is provided with two primary windings, one of which is connected to an ignition coil input or a primary winding of a preceding transformer stage, and the second of which is connected to the primary winding of a subsequent transformer stage.
  • 2. An ignition coil for internal combustion engines comprising:two or more transformer stages connected in a cascade arrangement one behind another, the secondary windings of all the transformer stages being connected in series to a spark plug, wherein the primary windings and secondary windings of the transformer stages are respectively arranged in a closed magnetic core.
  • 3. The ignition coil according to claim 2, wherein at least one transformer stage is configured having the secondary winding and the primary winding wound concentrically about the same leg of a ferromagnetic core, wherein on both sides of this leg two yokes project which each are connected to the wound central leg via a non-wound leg forming a closed ferromagnetic circuit.
  • 4. An ignition coil for internal combustion engines comprising:two or more transformer stages connected in a cascade arrangement one behind another, the secondary windings of all the transformer stages being connected in series to a spark plug, wherein the transformation ratios of the individual transformer stages are different.
  • 5. An ignition coil for internal combustion engines comprising:two or more transformer stages connected in a cascade arrangement one behind another, the secondary windings of all the transformer stages being connected in series to a spark plug, wherein at least a subsequent transformer stage is sized smaller than the preceding transformer stage with respect to the volume of the ferromagnetic core or the wire thickness of matching primary windings.
  • 6. An ignition coil for internal combustion engines comprising:two or more transformer stages connected in a cascade arrangement one behind another, the secondary windings of all the transformer stages being connected in series to a spark plug, wherein the primary windings and secondary windings of all the transformer stages are wound concentrically about a common imaginary axis, wherein the individual transformer stages are respectively arranged at a distance apart along this axis.
Priority Claims (1)
Number Date Country Kind
623/99 Apr 1999 AT
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Number Date Country
2154792 Nov 1972 DE
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