GB2339973A

GB2339973A - Electrical rod-type ignition coil

Info

Publication number: GB2339973A
Application number: GB9914844A
Authority: GB
Inventors: Friedhelm Rosemann
Original assignee: BREMICKER AUTO ELEKTRIK
Current assignee: BREMICKER AUTO ELEKTRIK
Priority date: 1998-07-21
Filing date: 1999-06-24
Publication date: 2000-02-09
Anticipated expiration: 2019-06-24
Also published as: GB9914844D0; FR2781600A1; GB2339973B; FR2781600B1

Description

2339973 Electrical rod-type ignition coil The invention relates to an

electrical rod-type ignition coil after the fashion of an energy store for supplying with high voltage a spark plug or an ignition means of that type of an internal-combustion engine, in particular an internal-combustion engine employing the Otto principle, comprising a soft-magnetic core made of core parts having a main core, return-path limbs and yokes, comprising an air gap in or at the main core having or not having a permanent magnet in the air gap and also a primary winding and secondary winding surrounding the centrally disposed main core, the primary winding having a primary terminal for the connection to the electrical supply, the secondary winding being magnetically coupled to the primary winding via the core so that a high voltage is induced in the secondary winding by switching off the primary current of the primary winding, and the secondary winding having a secondary terminal for the connection to the spark plug or the ignition means, the main core being surrounded by an internal encasing cylinder made of insulating material, the first winding, in partioular the primary winding, being mounted on the encasing cylinder, an external encasing cylinder made of insulating material being mounted on the first winding on which the second winding, in particular the secondary winding, is mounted, and a casing being provided which surrounds the second winding, the gaps between main core, internal encasing cylinder, external encasing cylinder and casing being filled in with an electrically insulating injection compound or embedding compound, connecting means for the connection of connection leads to the windings furthermore being formed at the one end of the ignition coil and a spark plug connection being formed at the other end of the ignition coil.

High-performance rod-type ignition coils of this type are known in the prior art. Basically, ignition coils are known in which the soft-magnetic core is formed as an Etype core, in particular also with an air gap in or at the main core. Such standard ignition cores are, however, of relatively large volume so that they cannot be used as electrical rod- type ignition coils.

Rod-type ignition coils are known which have an open magnetic circuit, which has the disadvantage, in particular in the case of rod-type ignition coils, that the power of the coil is dependent on the diameter of the spark-plug hole in the cylinder head into which the rodtype ignition coil is plugged. Closed magnetic circuits would also be preferred in the case of rod-type ignition coils, but such designs are not standard in the prior art or, alternatively, are associated with high cost.

Proceeding from this prior art, an aim of the invention is to provide an electrical rod-type ignition coil- of the generic kind which is simply constructed and which has a closed magnetic circuit so that it is independent of the diameter of the spark-plug hole in the cylinder head of the internal-combustion engine into which the rod-type ignition coil is plugged.'

To achieve this aim, the invention proposes that the core is a core of the double-E type which has an air gap in its main core and in its limbs, the main core being situated in the longitudinal axis of the ignition coil and the return-path limbs being situated parallel to the longitudinal axis of the ignition coil.

As a result of the fact that a core of the double-E type is used, a closed,magnetic circuit with the air gap is produced, with the result that the power of the rod-type ignition coil is independent of the diameter of the sparkplug hole into which the rod-type ignition coil is plugged at the cylinder head of the internal-combustion engine because the gap size between ignition coil and spark-plug hole is not of significance for the power of the ignition coil. As a result of the fact that the main core and the return-path limbs are situated in the axis or parallel to the axis of the ignition coil, a compact elongated construction is achieved which makes it possible to insert the rod-type ignition coil into a corresponding spark-plug hole, it nevertheless being possible to achieve a high power from the rod-type ignition coil.

Preferably, provision is additionally made that the return-path limbs are formed in step fashion in cross section at their side surface remote from the main core so that the external contour approaches a circular envelope surface whose central axis is situated in the cenfral axis of the main core.

As a result of this, the cross section of the return-path limbs is increased to such an extent that the overall external contour of the ignition coil has an approximately circular cross section, which corresponds in turn to the cross section which is formed by the sparkplug hole. In this way, a higher power can be generated with the rodtype ignition coil.

In addition, provision can also be made that the side surfaces of the main core which are adjacent to the return-path limbs are widened centrally to form a step so that a cross-sectional shape in the form of a cross is formed.

As a result of this, the cross section of the main core is, on the one hand, increased and, on the other hand, the shaping achieves a guide for the main core in the internal cylinder sleeve which has an identical contour shape in cross section.

Incidentally, the core is assembled in the standard method from laminated metal sheets.

In order to be able to insulate such an ignition coil as simply as possible with embedding compound or injection compound with respect to the interior, provision is preferably made that the casing is closed on all sides or has closed wall parts, in that only the connecting means for the connection of the connecting leads and/or the spark-plug connection has an open communication to the casing interior and/or to the interior of the Ignitioncoil parts inserted into the casing, and in that the outlet of a filling device, in particular a filling funnel, can be inserted into the opening or the like forming the open communication so that the plug region or terminal region is protected by the filling device against embedding compound supplied by means of the filling device and is separated from the latter.

At the same time, provision is preferably made that only the space in the casing or in the ignition-coil parts can be filled with embedding compound in which the highvoltage elements of the ignition coil are disposed.

In addition, provision is preferably made that at least the high-voltage winding is enveloped with embedding compound or injection compound.

According to the invention, a communication with the cavity or interior of the coil can be made via a filling device, in particular a filling funnel with venting facility, for example, via the plug connection of the connecting leads or via the spark-plug connection, the actual plug region being protected by funnel parts or other parts of the filling device. The embedding compound can be cast using the appropriately disposed filling device. After curing, the filling device, in particular the filling funnel, can be pulled off and separated from the embedding compound, possibly by rotation. The plug region is then free of funnel parts and embedding compound so that the corresponding connecting plug of the connecting leads or even the spark plug can be appropriately mounted. The coil cavity or at least the region of the coil whose cavity is to be filled is completely filled with embedding compound. At 'the same time, the feed mark is always at the highest point of the casting (at one of the two ends of the rod-type ignition coil). No feed mark is visible and, in particular, also no surface disturbance due to a lateral feed mark or other feed mark which could be a high-voltage defect.

6 Furthermore provision is preferably made that the length of the core is at least twice as long as the diameter of the core or of the ignition coil.

An appropriate length is necessary for the windings, namely the primary winding and secondary winding of the coil in the case of the desired, slim construction since otherwise poorer and possibly unusable electrical values would be achieved in relation to the high voltage to be generated and the breakdown strength. The specified minimum length is necessary for this reason.

In order to be able to assemble such a rod-type ignition coil from simple parts and also to be able to make the assembly simple and, consequently, inexpensive, provision is preferably made that the internal encasing cylinder carrying the first winding has a rectangular crosssectional shape, the receiving duct for the main core being closely matched to the cross-sectional shape of the latter, in that there is formed onto that end of the internal encasing cylinder which is remote from the sparkplug connection a first linking piece which can be plugged by means of a sealing collar into the one opening of the casing and which has two plugin ducts which are spaced apart from one another by closed base wall parts directed transversely with respect to the coil lon itudinal direction and which are open on both sides in the coil longitudinal direction so that that part of the linking piece adjoining the receiving duct is encompassed or formed by wall parts of the base wall parts and of the plug-in ducts, in that the connection for the connecting leads is formed by a plug well which encompasses a base part which is 7 closed towards the linking piece and from which two plug parts project which are each plugged by means of a circumferential sealing collar into the plug-in ducts of the linking piece in a liquid-tight fashion, the electrical connecting means projecting out of the plug parts in the direction of the linking piece, projecting in the desired position beyond the linking piece in the direction of the internal encasing cylinder and being connected, in particular plug-connected, to the connecting ends of the first winding and one connecting end of the second winding, in that the external encasing cylinder with the second winding is pushed onto the internal encasing cylinder and the casing is fitted over the external encasing cylinder, the casing having, at that end which is remote from the first linking piece two plug-in stubs spaced apart from one another by closed transverse wall parts and open on both sides in the longitudinal direction of the coil, in that the double-E core part is fitted with one E-type core part onto the casing plug-connected to the linking piece and is fitted onto end of the other casing end with the second E-type core part so that the main core passes axially through the casing, the external circumferential contour of the casing with the external surfaceg of the return-path limb forming a cross-sectional shape largely approximated to a circular form, in that a second linking piece having a closed base plate and open connection plug regions which can be tightly plugged into the plug-in stubs by means of a circumferential sealing edge is plugged into the plug- in stubs of the casing, the second linking piece having an 8 externally circumferential collar on the side remote from the casing, in that the spark-plug connection is formed by a cap which is passed through by the connecting plug and electrical connecting parts and which is tightly inserted into the collar of the second linking piece by means of a collar having sealing rim, a connecting lead passing through a plug- in stub and being connected, in particular plugconnected, to the second end of the second winding, in that the component thus formed is a unit which tightly terminates the casing interior and the connecting plug for the spark plug being formed in such a way that there is a passage to the casing interior, and in that the casing interior between the plug well and the connecting plug for the spark plug (including the cap) is filled with insulating embedding compound, the filling and venting openings being formed by the connecting plug for the spark plug.

With the exception of the windings and with the exception of the core of the ignition coil, and also with the exception of the connecting contacts, all the components are preferably made of plastics material, it being possible under some circumstances to use an electrically and/or magnetically conductive plastics material also for the casing. The individual parts of the rod-type ignition coil are all of simple design so that they can be made with relatively simple inject ion-moul ding tools. The parts are matched to one another in such a way that they can be assembled by means of plug assembly so that the final rodtype ignition coil can be installed in a simple manner. At 9 the same time, the sealing collars and the like form, at the separating points, sealing points which make it possible for the plug-connected assembled unit to be subsequently filled with insulating compound in liquid form without said insulating compound being able to leak at the separating joints or the like. Plastics resin is normally used as insulating compound.

At the same time, provision is preferably made that the connecting plug for the spark plug is a cylindrical socket which is held in the cap so that the plug-in end is accessible and the base part is situated inside the cap cavity, the socket wall in the vicinity of the base and/or the base having at least one passage opening or one passage slot which is an open communication between the internal region of the socket and the cap cavity.

In this way, the connecting plug for the spark plug can serve in a particularly favourable way as filling point for injecting the embedding compound, the injection point being at the same time the ventilation for the air escaping during casting.

For example, a filling funnel through which the embedding compound is then introduced into the interior of the casing can be plugged into the connecting plug. - A preferred development is perceived in that there is formed at the return-path limbs or at least one of the return-path limbs of a core part a narrow protuberance which rests against the end face of the connected core part so that the core parts are assembled with the formation of an air gap.

- As a result of this design, it is possible to produce an adjustable air gap which is readily reproducible, in particular, even in the case of industrial manufacture. To hold the individual parts together, the core is welded to the return-path limbs in the region of the narrow protrusions so that an inseparable unit is formed.

The welding point is situated relatively externally with respect to the coil longitudinal centre at the return-path limb core parts so that the welding point is readily accessible.

In addition, provision is preferably made that the plug parts and the plug-in ducts and also the plug-in stubs and connecting plug regions have equal dimensioning only in pairs so that they are pluggable only in a particular position.

As a result of this design, an interchange- free assignment of the connecting plug regions and plug-in stubs and the like is possible so that errors are already avoided during the assembly by the structural design of the individual parts.

An exemplary embodiment of the invention is described hereunder, by way of example only, with referencg to the accompanying drawings, in which:Figure 1 shows an ignition coil according to an embodiment of the invention in side view; Figure 2 shows the same in a position rotated through 900 around the vertical axis; Figure 3 shows the ignition coil in accordance with Figure 2 viewed in longitudinal central section; Figure 4 shows the ignition coil in accordance with Figure 1 viewed in longitudinal central section; Figure 5 shows a detail in the view in accordance with Figure 3; Figure 6 shows the detail in the view in accordance with Figure 4; Figures 7 to 9 show an E-type core in different views; Figure 10 shows a first detail in an isometric representation; Figure 11 shows the part viewed in longitudinal central section; Figure 12 shows the same viewed in the section XII-XII of Figure 11; Figure 13 shows a further detail in side view; Figure 14 shows the same viewed from an end face; Figure 15 shows a further detail in an isometric representation; 12 - Figure 16 shows the detail viewed in central longitudinal section; Figures 17 to 19 show a further detail in different views; Figures 20 and 21 show a further detail in different views; Figures 22 and 23 show a further detail in different views; Figures 24 to 26 show a further detail in different views; Figure 27 shows an auxiliary part viewed in central longitudinal section.

Figures 1 to 4 show an electrical high-power rod-type ignition coil. The rod-type ignition coil serves as energy store for supplying a spark plug or an ignition means of this type of an internal-combustion engine, in particular an internal-combustion engine employing the Otto principle, with high voltage. It has a soft-magnetic core 1 made of core parts comprising a main core, return-path limbs and yokes with an air gap in the main core. Furthermore, a primary winding and secondary wirrding are provided which surround the centrally disposed main core, the primary winding having a primary connection for the connection to the electrical supply, the secondary winding being magnetically coupled to the primary winding via the core so that a high voltage is induced in the secondary winding by switching off the primary current of the primary winding, and the secondary winding having a secondary connection to the connection to the spark plug 13 or the ignition means. The main core is surrounded by an internal encasing cylinder made of insulating material on which the first winding (the primary winding in the exemplary embodiment) is mounted. Mounted on the first winding is an external encasing cylinder made of insulating material on which the second winding, the secondary winding in the exemplary embodiment, is mounted. Furthermore, a casing is provided which surrounds the second winding, the gaps between main core, internal encasing cylinder, external encasing cylinder and casing being filled with an electrically insulating injection compound or embedding compound. Furthermore, connecting means 2 for the connection of connecting leads to the windings are formed at one end of the ignition coil and a spark plug connection 3 is formed at the other end of the ignition coil. All in all, the rod-type ignition coil is of such slim design that it can be inserted into the spark-plug hole in the cylinder head of an internalcombustion engine. As can be seen, in particular, from the comparison of the diagrams in Figures 3 and 4 and also Figures 7 to 9, the core 1 is a core of the double-E type which has an air gap 6, 7 in its main core 4 and in its return-path limbs 5. The main core 4 is situated in the longitudinal axis of the ignition coil, while the returnpath limb 5 is aligned parallel to the longitudinal axis of the ignition coil. The core 1 is made up of two parts in accordance with Figures 7 to 9, which are joined together in opposite orientation.

The return-path limbs 5 are of stepped design in cross section at their side surfaces remote from the main core 4. The steps are denoted by 8. This results in an external contour which approximates to a circular enveloping surface whose central axis is situated in the central axis of the main core 4. In addition, the side surfaces of the main core 4 adjacent to the return-path limbs 5 are also slightly widened to form a step 9 so that a crosssectional shape in the form of a cross is formed. Figure 10 shows the internal encasing cylinder 10 which carries the first winding and which has a rectangular cross-sectional shape with rounded corners in the region in which the winding is mounted. The receiving duct 11 for the main core 4 is closely matched to the cross-sectional shape of the latter, in particular likewise of stepped design, so that guides are formed between main core and receiving duct 11 when the core is inserted. At that end of the internal encasing cylinder 10 which is remote from the spark plug connection, a first linking piece 12 is formed which can be plugged by means of a sealing collar 13 into an opening in the casing 14, which is shown in Figures 15 and 16. The opening into which the part 13 can be plugged is visible on the left in Figure 16. The linking piece 12 has two plug-in ducts 16 spaced apart from one another by closed base walls 15 which extend transversely with respect to the coil longitudinal direction and are open on both sides in the coil longitudinal direction so that that part of the linking piece 12 adjacent to the receiving duct 11 is encompassed or formed by wall parts of the base wall parts 155- and the plug-in ducts 16.

The terminal 2 for the connecting conductors is formed by a plug well which has a base part 17 which is closed with respect to the linking piece 12 and from which two plug parts 18, 19 project, each of which are plugged in a liquid-tight manner into the plug-in ducts 16 of the linking piece 12 by means of a circumferential sealing collar 20, 21. The electrical connecting means 22, 23 project out of the plug parts 18, 19 in the direction of the linking piece 12. In the desired position, they project beyond the linking piece 12 in the direction of the internal encasing cylinder 10 parallel to the wall of the latter and are connected, in particular plugconnected, to the connecting ends of the first winding (the connecting means 22) or to a connecting end of the second winding (connecting means 23), respectively. The external encasing cylinder 24, which is shown in Figures 13 and 14, is pushed onto the internal encasing cylinder 10 with the second winding, which is mounted on the outside of the external encasing cylinder 24 and the casing 14 is fitted over the external encasing cylinder 24. The external encasing cylinder 24 is open at both ends. The casing 14 has at the end remote from the first linking piece 12 in the desired assembled position, two plug-in stubs 26 which are spaced apart from one another by closed transverse wall parts 25 and are open on both sides in the coil longitudinal direction. The double-Etype core is fitted onto the one end of the casing 14 plug-connected to the linking piece 12 by means of an Etype core part and onto the other casing end by means of the second E- type core part so that the main core 4 passes axially through the casing. The casing has side surfaces which are flattened to match the insides of thL- returnpath limbs 5 and against which the return-path limbs rest, while the connecting plug regions merge into rounded outside surfaces of the casing. In this way, the external circumferential contour of the casing 14 is largely approximated to a circular shape in cross section by means of the external surfaces of the return-path limbs 5. A second linking piece 27 having a closed base plate 28 and open connecting regions 30 which can be tightly plugged into the plug-in stubs 26 by means of a circumferential sealing edge 29 is plugged into the plug-in stubs 26 of the casing 14, the second linking piece 27 having an externally circumferential collar 31 on the side remote from the casing 14.

The spark plug connection is formed by a cap 33 which is passed through by the connecting plug 32 and electrical connecting parts and which is shown in Figures 24 to 2.6. The cap 33 is tightly plugged into the collar 31 of the second linking piece 27 by means of a collar 34 having a sealing rim 35, a connecting lead at 35 passing through a connecting stub 35 and being connected, in particular plug-connected, to the second end of the second winding. The connecting lead 36 is shown in Figures 5 and 6. This is an exemplary embodiment in which a resistor 37 is plugged into the connecting contact 33 and leads via a diode 38 to the connecting lead 36.

The connecting plug 32 for the spark plug is formed in such a way that a passage to the casing interior continues to exist. In this connection, the connecting plug 32 for the spark plug is formed as a cylindrical socket which is held in the cap 33 at 36 so that the plug-in end 37 is accessible from the outside for inserting the spark plug connecting pin. The socket has a base part 38 'Which is situated inside the cavity of the cap 33 in the intended assembled position. The socket wall and the base are provided with passage slots 39 which represent an open communication between the internal region of the socket and the cap cavity of the cap 33.

The ignition coil can be assembled as follows.

17 - The primary coil winding is first mounted on the primary coil body (internal encasing cylinder 10). It is onto this part, which is shown in Figures 10 to 12, that the external encasing cylinder 24 wound with the secondary winding can be fitted. This detail is shown in Figures 13 and 14. The casing 14, which is shown in Figures 15 and 16 can then be pushed on. The two E-type cor e parts, of which one is shown in Figures 7 to 9, are then pushed onto the casing in opposite orientation so that the main core passes centrally through the casing and the encasing cylinder. In this position, the core parts terminate flushly with the casing or with the first linking piece at the end. The second linking piece can then be fitted onto the free casing end. Said linking piece is shown in Figures 20 and 21. The plug well, which is shown in Figures 17 to 19, can be fitted onto the other end of the assembly. In this situation, the corresponding connecting contacts, which are formed as plug or fork contacts, make contact with the corresponding conductors. The spark plug terminal, in particular the socket, which is shown in Figures 22 and 23, is preassembled with the electrical component and terminal, as is shown in Figures 5 and 6. This unit is then pulled into the cap 33 in accordance with Figures 24 to 26 in the drawing view from below and held at 36. The cap is then fitted onto the linking piece with the component 32. A tight plug connection is consequently created between the individual parts.

The core parts are welded together with the formation of a gap, for which purpose the return-path limbs 5 of each core part is formed in each case with a projecting stud which serves as spacer for the formation of a gap and, in addition, is formed as welding point. The complete, prefabricated unit can then be sealed with embedding 18 - compound. For this purpose, the filling funnel 40 shown in Figure 27 can be plugged by means of its thin end into the corresponding plug region in the socket 32. The embedding compound can then be fed via the funnel 40, the embedding compound filling all the cavities inside the casing and the connecting elements. In this process, the filling compound is able to flow in through the slots 39, the slots 39 serving, in addition, as venting. The filling funnel can then be removed from the socket 32 and the ignition coil is complete.

In order to make possible an interchange- free assembly, the regions 18, 19, 30 and also the corresponding plug-in regions at 16 and at 26 are each differently dimensioned in pairs so that the parts can be fitted into one another only in a certain position, which is conducive to the correct assembly.

The invention is not limited to the exemplary embodiment, but can be varied in many various ways within the scope of the disclosure.

19 -

Claims

Claims:

1. An electrical rod-type ignition coil for supplying with high voltage a spark plug or an ignition means of that type of an internal-combustion engine, in particular an internal-combustion engine employing the Otto principle, said electrical rod-type ignition coil comprising a softmagnetic core made of core parts having a main core, return-path limbs and yokes, comprising an air gap in or at the main core having or not having a permanent magnet in the air gap and also a primary winding and a secondary winding surrounding the centrally disposed main core, the primary winding having a primary terminal for connection to the electrical supply, the secondary winding being magnetically coupled to the primary winding via the core so that a high voltage is induced in the secondary winding by switching off the primary current of the primary winding, and the secondary winding having a secondary terminal for connection to the spark plug or the ignition means, the main core being surrounded by an internal encasing cylinder made of insulating material, one of the primary and secondary windings, in particular the primary winding, being mounted on the internal encasing cylinder, an external encasing cylinder made of insulating material being mounted on said one of the primary and secondary windings and on which the'other of the primary and secondary windings, in particular the secondary winding, is mounted, and a surrounding casing being provided which surrounds the other of the primary and secondary windings, gaps between the main core, the internal encasing cylinder, the external encasing cylinder and the surrounding casing being filled in with an electrically insulating injection compound or embedding compound, with at least the secondary winding being enveloped in an insulating manner, or the ignition coil being formed without the surrounding casing and the injection compound itself forming the external skin of the element or the insulating envelope; connecting means for the connection of connection leads to the windings furthermore being formed at one end of the ignition coil and a spark plug connection being formed at the other end of the ignition coil, wherein the core is a core of the double-E-type which has an air gap in its main core and/or in its limbs, the main core being situated in the longitudinal axis of the ignition coil and the return-path limbs being situated parallel to the longitudinal axis of the ignition coil; and the connecting means and the sparkplug terminal axially adjoin (in spatial assignment) the lower or upper transverse yoke of the core.

2. An electrical rod-type ignition coil according to Claim 1, wherein the return-path limbs are formed in step fashion in cross section at their side face remote from the main core so that the external contour approaches a circular envelope surface whose central axis is situated in the central axis of the main core.

3. An electrical rod-type ignition coil according to Claim 1 or 2, wherein the side surfaces of the main core which are adjacent to the return-path limbs are widened centrally to form a step so that a cross- sectional shape in the form of a cross is formed.

4. An electrical rod-type ignition coil according to any one of Claims 1 to 3, wherein the surrounding casing is closed on all sides or has closed wall parts, only the 21 - connecting means for the connection of connecting leads and/or the spark- plug connection has an open communication to the casing interior and/or to the interior of the ignition-coil parts inserted into the casing, and the outlet of a filling device, in particular a filling funnel, can be inserted into the opening or the like forming the open communication so that the plug region or terminal region is protected by the filling device against embedding compound supplied by means of the filling device and is separated from the latter.

5. An electrical rod-type ignition coil according to Claim 4, wherein only that space in the casing or in the ignition-coil parts in which the high-voltage elements of the ignition coil are disposed can be filled with embedding compound.

6. An electrical 'rod-type ignition coil according to Claim 4 or 5, wherein at least the high-voltage winding is enveloped with embedding compound or injection compound.

7. An electrical rod-type ignition coil according to one of Claims 1 to 6, wherein the length of the core is at least twice as long as the diameter of the core or of the ignition coil.

B. An electrical rod-type ignition coil according to any one of Claims 1 to 3, wherein the internal encasing cylinder has a rectangular crosssectional shape, the receiving duct for the main core being closely matched to the cross-sectional shape of the latter, in that there is formed onto that end of the internal encasing cylinder which is remote from the spark-plug connection a first 22 - linking piece which can be inserted by means of a sealing collar into the one opening of the casing and which has two plug-in ducts which are spaced apart from one another by closed base wall parts directed transversely with respect to the coil longitudinal direction and which are open on both sides in the coil longitudinal direction so that, that part of the linking piece adjoining the receiving duct is encompassed or formed by wall parts of the base wall parts and of the plug-in ducts; the connection for the connecting leads is formed by a plug well which encompasses a base part which is closed towards the linking piece and from which two plug parts project which are each inserted by means of a circumferential sealing collar into the plug-in ducts of the linking piece in a liquid-tight fashion, the electrical connecting means projecting out of the plug parts in the direction of the linking piece, projecting in the desired position beyond the linking piece in the direction of the internal encasing cylinder and being connected, in particular plug-connected, to the connecting ends of said one of the primary and secondary windings and one connecting end of said other of the primary and secondary windings, preferably directly or indirectly with the insertion of electronic elements for controlling and/or evaluating the combustion process; the external encasing cylinder with the said other of the primary and secondary windings is pushed onto the internal encasing cylinder and the casing is- fitted over the external encasing cylinder, the casing having, at that end which is remote from the first linking piece two plug-in stubs spaced apart from one another by closed transverse 23 - wall parts and open on both sides in the longitudinal direction of the coil; the double-E-type core with one E-type core part is fitted by means of one E-type core part onto one end of the casing plug-connected to the linking piece and is fitted onto, the other casing end by means of the second E-type core part so that the main core passes axially through the casing, the external circumferential contour of the casing with the external surfaces of the return-path limb forming a cross-sectional shape largely approximated to a circular form; a second linking piece having a closed base plate and open connection plug regions which can be tightly plugged into the plug-in stubs by means of a circumferen tial sealing edge is plugged into the plug-in stubs of the casing, the second linking piece having an externally circumferential collar on the side remote from the casing; the spark-plug connection is formed by a cap which is passed through by the connecting plug and electrical connecting parts and which is tightly inserted into the collar of the second linking piece by means of a collar having sealing rim, a connecting lead passing through a plug-in stub' and being connected, in particular plugconnected, to the second end of said other of the primary and secondary windings; the component thus formed is a unit which tightly terminates the casing interior and which has - a filling and/or venting opening for supplying embedding compound, the connecting plug preferably for the spark plug being 24 formed in such a way that there is a passage to the casing interior; and the casing interior between the plug well and the connecting plug for the spark plug (including the cap) is filled with insulating embedding compound, the filling and venting openings preferably being formed by the connecting plug for the spark plug.

9. An electrical rod-type ignition coil according to Claim 8, wherein the connecting plug for the spark plug is a cylindrical socket which is held in the cap so that the plug-in end is accessible and the base part is situated inside the cap cavity, the socket wall in the vicinity of the base and/or the base having at least one passage opening or one passage slot which is an open communication between the internal region of the socket,and the cap cavi-ty.

10. An electrical rod-type ignition coil according to one of Claims 1 to 9, wherein there is formed at the return-path limbs or at least one of the return-path limbs of a core part a narrow protuberance which rests against the end f ace of the connected core part so that the core parts are assembled with the formation of an air gap.

11. An electrical rod-type ignition coil according to Claim 10, wherein the core parts are materially joined together, in particular welded, in the region of the projection.

12. An electrical rod-type ignition coil according to one of Claims 8 to 11, wherein the plug parts and the plug-in ducts and also the plug-in stubs and the connecting plug - regions have equal dimensioning only in pairs so that they are pluggable only in a particular position.

13. An electrical rod-type ignition coil according to any preceding claim, wherein the ignition coil contains electronics for the control and/or the evaluation of the combustion process of the internal combustion engine equipped therewith at one or both ends in the axial direction.

14. An electrical rod-type coil according to any preceding claim, wherein parts of the ignition coil, in particular the casing, are provided at least partially with a conductive coating, preferably the casing at the surfaces against which parts of the core rest or which are adjacent to parts of the core or are situated opposite the latter.

15. An electrical rod-type ignition coil as substantially hereinbefore described with reference to any one or more of the accompanying drawings.