GB2277836A

GB2277836A - Ignition coil for internal combustion engines

Info

Publication number: GB2277836A
Application number: GB9407746A
Authority: GB
Inventors: Horst Behnke
Original assignee: Daimler Benz AG; Mercedes Benz AG
Current assignee: Daimler Benz AG
Priority date: 1993-05-03
Filing date: 1994-04-19
Publication date: 1994-11-09
Also published as: ITRM940238A1; GB9407746D0; ITRM940238A0; FR2706219A1; DE4314444A1

Description

2277836 1 Ignition coil f or internal combustion engines The invention

relates to an ignition coil for a fully electronic ignition system with solid-state high-voltage distribution for internal combustion engines having a coil core around whose central core leg a coil former with one internal primary winding and one external secondary winding is arranged,having a primary winding connection part and at least one highvoltage connection dome, which are partially encapsulated in insulating resin.

Ignition coils of this type are known as single-spark coils (DE-Z.: KRAFT HAND, 26.03.1988, Issue 6, pages 398 to 403, in particular page 400; DE 37 27 458 Al) or also as multi-spark coils with high-voltage connection domes which exit perpendicularly with respect to the surface of the coil core (DE-Z.: KRAFT HAND; DE 37 30 291 A) or with highvoltage connection domes which exit in the direction of the axis of the coil former (EP 388 146 Al) and which are usually constructed according to the applicable ISO standard.

All known ignition coils share the feature that their constructional dimensions are relatively large, in particular as a result of the highvoltage connection domes with their high-voltage seal, in the form of a flexible rubber cap, which is required by the standard, with the result that considerable problems arise with respect to positioning them in the engine area.

Furthermore, a cylindrical ignition coil is known (abstract of JP 52-131 117 A2) in which the high-voltage connection dome which is constructed as part of the insulation housing extends approximately over the length of the encapsulated coil former.

The present invention seeks therefore to construct an ignition coil more compactly whilst ensuring the highvoltage strength.

According to the invention, there is provided an ignition coil for a fully electronic ignition system with solid-state 2 high-voltage distribution f or internal combustion engines having a coil core around whose central core leg a coil f ormer with one internal primary winding and one external secondary winding is arranged, having a primary winding connection part and at least one high-voltage connection dome, which are partially encapsulated in insulating resin, wherein the high-voltage connection dome is arranged essentially in a peripheral quadrant between the coil f ormer and the coil core and is bounded by their external dimensions and extends at least over the external dimension of the encapsulated coil former.

Preferably, a contact part which is arranged in the base of the highvoltage connection dome is adjacent to the highvoltage-side end of the secondary winding and is connected thereto. The primary winding connection part may be arranged in a further peripheral quadrant between the coil former and the coil core.

Preferably, the high-voltage connection dome and/or the primary winding connection part is integrated into the coil former by means of the insulating resin. In this case, the radial high-voltage strength may be determined - starting from the contact part - by the high-voltage connection dome and the insulating resin surrounding it.

A further high-voltage connection dome may be arranged in another peripheral quadrant between the coil former and the coil core, in which case, the two high-voltage connection domes may be located on the same side or on different sides of the coil core. A plurality of ignition coils may be connected to form a compact block and are encapsulated together with insulating resin.

The high-voltage connection dome and/or the primary winding connection part may be part of a separate cup-shaped plastic insulating part in which the winding terminals, the primary and secondary winding and the coil core are encapsulated with insulating resin.

An exemplary embodiment of the invention is illustrated 3 in the drawings and described in greater detail below. The following diagrammatic views are shown:

Fig. la an ignition coil in a front view, Fig. lb in a plan view, Fig. lc in a side view and Pigs. 2-5 alternative designs of an ignition coil.

According to Figs. la to lc, an ignition coil 1 consists of a coil former 8 with a primary winding 2 and a secondary winding 3 and a ferro-magnetic coil core 4. The primary winding 2 has a winding layer structure in which a varnished wire with a diameter of approximately 0.7 mm is wound in several layers onto a primary coil former 2.1 which is cast for example from thermoplastic plastics and is arranged on the central core leg 4.5, each winding layer consisting of several tens of turns and the winding structure comprising in total approximately 100-200 turns. The secondary winding 3 is provided on the external circumference of the primary winding 2 and has a winding structure in which a varnished wire with a diameter of approximately 0.06 to 0.1 mm. is wound with approximately 10, 000 turns onto a secondary coil former 3.1 which also consists of thermoplastic plastics. The secondary winding 3 is divided serially from the start of the winding into 5-15 sections and wound onto the secondary coil former 3.1 which is divided into chambers.

In this ignition coil, which is constructed as a singlespark coil, a start 3.2 of the secondary winding 3 is connected to earth or alternatively to the end 2.3 of the primary winding 2, whilst the end 3.3 of the secondary winding 3 is electrically connected to a contact part 5. 2 which is arranged in the base 5.1 of the high-voltage connection dome 5, an ignition cable being placed in contact with the said contact part 5.2. The start 2.2 and the end 2.3 of the primary winding 2 are connected to a primary winding connection part 6. Both the winding terminals, the primary and secondary winding, the coil core and the highvoltage connection dome and the primary winding connection part are encapsulated with insulating resin 7 and insulated 4 with respect to one another but in such a way that the outer legs 4.1 to 4.4 of the coil core 4 remain free of the insulating resin casting compound.

Alternatively, the winding terminals, the primary and secondary winding and the coil core can be placed in a cupshaped plastic insulating part which constitutes the outer shape of the ignition coil, and then be encapsulated, the high-voltage connection dome and the primary winding connection part then being parts of the plastic insulating part and being moulded thereon.

It is clear that the high-voltage connection dome 5 is arranged in a peripheral quadrant I between the coil former 8 and the coil core 4, specif ically in such a way that it extends along the coil former 8 parallel to the coil axis in the exemplary embodiment - at its highvoltage-side end (indicated by 5.1) terminates approximately flush with the coil former 8 and protrudes with its open end 5.3 beyond the coil f ormer 8, the high-voltage connection dome 5 still being spaced from the surface of the coil core 4 in such a way that a rubber cap which simply serves sealing purposes can be f itted onto the open end 5.3. The primary winding connection part 6 is arranged opposite the high-voltage connection dome 5 in a further peripheral quadrant II. Both the said primary winding connection part 6 and the highvoltage connection dome are integrated here into the coil f ormer 8 by means of the insulating resin 7 without them requiring a separate attachment to the coil former or coil core.

With respect to the high-voltage strength, the embodiment described above has the following particular features: as a result of the fact that the high-voltage connection dome 5 can extend at least over the entire length of the coil former 8 and the contact part 5.2 is arranged directly in the base 5.1 of the connection dome 5, a very large insulation distance L for ensuring high-voltage strength is produced in such a way that the open end 5.3 of the connection dome 5 can end approximately with the external contour of the ignition coil 1, that is. to say protrudes, if at all, only slightly beyond the coil core 4; as a result of the fact that the high-voltage-conducting winding end 3.3 is connected directly to the adjacent contact part 5.2 of the connection dome 5, in comparison with the other components of the ignition coil an increased high-voltage strength and insulation strength are produced; as a result of the fact that the primary winding connection part 6 is located on the side of the start 3.2 of the secondary winding 3, it lies on the side with low voltage potential; as a result of the fact that the connection dome 5 is also surrounded on its external circumference by the insulating resin 7, the radial high-voltage strength is determined by the quantity R resulting from the material strength of the connection dome plus the layer of insulating resin so that the diameter of the connection done can also be kept smaller.

It is therefore clear that a very compact ignition coil is provided whose external dimensions are not increased, or only increased insignificantly, by the primary winding connection part and the high-voltage connection dome.

Of course, the embodiment is not restricted to a singlespark coil, rather a multi-spark coil can also be constructed in this way, in which case, as a departure from Fig. la, the start 3.2 of the secondary winding 3 is then also connected as a winding end to a contact part of a second highvoltage connection dome 5.0.

Thus, Fig. 2 shows a high-voltage connection dome 5 and 5.0 arranged in the I and II quadrants, Fig. 3 shows a high-voltage connection dome 5 and 5.0 arranged in the I and V quadrants, Fig. 4 shows a high-voltage connection dome 5 and 5.0 arranged in the I and II1 quadrants and Fig. 5 shows a high-voltage connection dome 5 and 5.0 arranged in the I and M' quadrants, the quadrants I, etc. lying on the side of the coil core opposite the quadrant 1, etc. and it also being possible for the connection domes to be located with their open end in 6 the same direction or in opposite directions.

In a further design, a plurality of ignition coils can also be connected as 2 x or 3 x multi-spark coils to form a compact block and be encapsulated together with insulating resin.

7

Claims

1. An ignition coil for a fully electronic ignition system with solidstate high-voltage distribution for internal combustion engines having a coil core around whose central core leg a coil f ormer with one internal primary winding and one external secondary winding is arranged, having a primary winding connection part and at least one high-voltage connection done, which are partially encapsulated in insulating resin, wherein the high-voltage connection dome is arranged essentially in a peripheral quadrant between the coil former and the coil core and is bounded by their external dimensions and extends at least over the external dimension of the encapsulated coil former.

2. An ignition coil according to Claim 1, wherein a contact. part which is arranged in the base of the high-voltage connection done is adjacent to the high-voltage-side end of the secondary winding and is connected thereto.

3. An ignition coil according to Claim 1, wherein, in addition, the primary winding connection part is arranged in a further peripheral quadrant between the coil former and the coil core.

4. An ignition coil according to Claim 1 or 3, wherein the high-voltage connection dome and/or the primary winding connection part is integrated into the coil former by means of the insulating resin.

5. An ignition coil according to Claim 4, wherein the radial high-voltage strength is determined - starting from the contact part - by the highvoltage connection done and the insulating resin surrounding it.

8

6. An ignition coil according to Claim 1, wherein a further high-voltage connection dome is arranged in another peripheral quadrant between the coil former and the coil core.

7.

An ignition coil according to Claim 6, wherein the two high-voltageconnection domes are located on the same side or on different sides of the coil core.

8. An ignition coil according to Claim 1 or 6, wherein a plurality of ignition coils are connected to form a compact block and are encapsulated together with insulating resin.

9. An ignition coil according to Claim I or 3, wherein the high-voltage connection dome and/or the primary winding connection part are part of a separate cup-shaped plastic insulating part in which the winding terminals, the primary and secondary winding and the coil core are encapsulated with insulating resin.

1O.An ignition coil for a fully electronic ignition system with solidstate high-voltage distribution for internal combustion engines, substantially as described herein with reference to and as illustrated in the accompanying drawings.