WO2012084313A1 - Ignition coil having a coupling device - Google Patents

Abstract

The invention relates to an ignition coil for an internal combustion engine, comprising a housing (2), a coil assembly (3), a connection assembly (4) for connecting the ignition coil, and a coupling device (5) for coupling the ignition coil in a motor block (M), wherein the coupling device (5) is formed at least partially of an electrically conductive plastic composite material and is designed to connect the ignition coil to a motor block (M) in an electrically conductive manner.

Description

 description

title

 Ignition coil with attachment device prior art

The present invention relates to an ignition coil for internal combustion engines with a device for connecting the ignition coil to an engine block and / or a spark plug well and a method for producing an ignition coil.

Ignition coils in internal combustion engines in conjunction with spark plugs through a spark ensure that combustible gas or gas mixture is ignited at a predefined time. For this purpose, generally arranged at a certain distance from each other electrodes are arranged in the combustion chamber and this at a given time with a

Potential difference applied, due to which the spark traverses the free path between the electrodes and thereby ignites the gas or gas mixture. The interface between the ignition coil and the engine block and / or the ignition coil and the spark plug well in this case is exposed to many challenging conditions that are characterized by thermal, chemical and mechanical stress both by the operation of the

Internal combustion engine as well as by the Wtterungsbedingungen result. In particular, the changing temperatures should be mentioned, which can be several hundred degrees Celsius within a few seconds.

An ignition coil is also challenging among the above

Conditions to fulfill various functions permanently and reliably. This includes on the one hand a reliable ignition of the gas or gas mixture in the combustion chamber at the ignition. However, it is at least equally important to ensure that ignition at no other time takes place through the ignition coil, as this leads to considerable loads on the ignition coil Internal combustion engine and in extreme cases can lead to their destruction. Therefore, highest demands are placed on the electrical function of the ignition coil and thus also on its permanently perfect connection to its electrically relevant peripherals. In addition, the require in one

Internal combustion engine pressures a very high mechanical strength of the ignition coil and absolute tightness of the connection between the ignition coil and the engine block. In addition, however, a certain elasticity within this compound is required, since due to extreme temperature changes and thermal expansion otherwise a permanently tight fit the

Ignition coil in the engine block is not guaranteed. Moreover, the chemical stress by lubricants and fuel gases, but also environmental influences and cleaning agents limit the selection of suitable materials for the production of ignition coils, in particular their housings. So far, in the case of ignition coils, electrical contacting of wires, busbars, electronic components and shielding plates by welding, soldering,

Insulation displacement connection, clamp connection, crimp connection,

Pressure connection made between metallic contacts and conductive bonding. There is therefore a need in the art for ignition coils whose

Functional reliability is ensured by successfully coping with the above-mentioned problems and tasks permanently and inexpensively.

Disclosure of the invention

The ignition coil according to the invention with the features of claim 1 has the advantage that they provide a simple, cost-effective and permanently reliable solution for connecting an ignition coil in one

Engine block provides. According to the invention, a chip-free connection between the ignition coil and the engine block by means of an electrically conductive

Plastic-made attachment device provided which is also permanently elastic, low-resistance and electrically durable. The installation of the ignition coil by means of the connection device according to the invention is also particularly simple, since the electrical connection already takes place by the insertion of the ignition coil in the engine block and thus requires no additional steps for making the electrical connection. The inventive In addition, the connection between the ignition coil and the engine block is protected against ambient media and environmental influences and serves to protect against electromagnetic compatibility (EMC) by means of a

reliable ground connection of the ignition coil.

In the context of the present invention, "electrically conductive plastic is understood to mean a material based on a plastic, to which electrically conductive components (for example metal chips) are mixed in such a way that a required degree of charge exchange by the plastic composite can take place via this , Beyond a reliable electrical contact addition, the ignition coil according to the invention can also be effectively secured by the connection device against rotation in the engine block and "wandering" from the engine block by the elasticity of the plastic composite for a corresponding normal force between the ignition coil and the

 Connecting device and between the wall of the spark plug shaft and the attachment device provides, the normal force in conjunction with the surface textures (in particular the friction coefficient) of both elements provides a suitable frictional engagement. In addition, by the area in the circumferential direction for attachment between attachment device and

Spark plug shaft wall and / or biasing device between the connecting device and ignition coil also a permanent and reliable sealing of the respective annular gap against the

Alternating pressure differences ensured during operation of the internal combustion engine.

The dependent claims show preferred developments of the invention

According to a preferred embodiment, the electrically conductive plastic from which the connection device of the ignition coil is made, elastic. In this way, a particularly reliable biasing force between the ignition coil and the wall of a spark plug shaft of an engine block can be ensured. Moreover, different thermally induced expansions of the individual parts involved in the connection do not have such a detrimental effect on the stability of the connection, in particular the electrical contacting. According to another preferred embodiment, the

Connection device arranged to establish the electrical ground contact between the ignition coil and an engine block (M) and / or to seal a gap between the ignition coil and the wall (90) of a spark plug well (9) of the engine block (M) fluid-tight. By the engine and / or the

Engine block of a vehicle usually corresponds electrically to the vehicle mass, in particular the contacting of the ignition coil mass with the vehicle mass via the attachment device according to the invention and the engine block is easily and reliably possible. In addition, through the

Tying device made of elastic plastic composite also a permanent and reliable sealing of the respective annular gap against the

Alternating pressure differences ensured during operation of the internal combustion engine.

In the context of the present invention, the term "engine" and / or "engine block" is understood to mean that usually metallic engine periphery, in which the

Ignition coil and / or the spark plug are arranged, so a solid body between the combustion chamber on the one hand and the outside with atmospheric pressure on the other. Preferably, the connection device surrounds the housing of the ignition coil at least in sections, in particular completely, in the circumferential direction.

Additionally or alternatively, the attachment device is attached by means of electrically conductive adhesive to the ignition coil and / or in the engine block. Beyond a reliable electrical contacting of the ignition coil is thus also a permanent and reliable sealing of the spark plug shaft against the

Alternating pressure differences between the combustion chamber and the outside and / or the atmospheric pressure ensured.

Advantageously, the connection device has several in

Longitudinal direction (X-X) of the ignition coil one behind the other

 On sealing lips. These are preferably designed to be in insertion into a substantially cylindrical cavity, in particular a

To deform the spark plug shaft of an engine block elastically. Thus, a permanent bias of the connection device on the one hand with respect to the ignition coil housing and on the other hand against the wall of the

Spark plug shaft ensured in the engine block. This also results a permanent and reliable sealing of the spark plug shaft against the alternating pressure differences between the combustion chamber and the outside and / or the atmospheric pressure. More preferably, the attachment device is adjacent to one

 High voltage output of the ignition coil arranged. In the context of the present invention, "adjacent" means a spatial and functional proximity

Attachment device and high voltage outlet are made, which further by mediating the contact force when inserting the ignition coil in the

Engine block ensures a secure electrical connection.

According to yet another preferred embodiment, the

Tying device manufactured as a two-component injection-molded part with the housing. Either you can first in a first step, the

 Tying device itself be made and in a second

In the first step, the housing of the ignition coil can be manufactured and, in a second step, the connection device (e.g.

Overmolding). In particular, however, a combined (ie simultaneous) injection process of both components in only one mold can also be used with suitable process control. A two-component process results in a particularly effective positive connection between the components housing and connection device. In particular, but not only in the variant in which a combined (ie simultaneous) injection process of both components is used in only one form, also an effective material bond is brought about by diffusion of the substances of the components into one another.

Preferably, the plastic composite of the attachment device largely comprises silicone and / or ethylene-propylene-diene monomer (EPDM) and / or a thermoplastic elastomer (TPE) and / or synthetic resin and also comprises electrically conductive constituents, in particular metal particles or graphite. The aforementioned plastics have been found to be suitable to provide a durable and reliable seal by an adequate degree of bias the gap between the wall of the spark plug duct and the ignition coil against the alternating pressure differences between the combustion chamber and the outside and / or the atmospheric pressure to ensure. In order to achieve a suitable degree of elasticity of the plastic composite and still produce the required electrical conductivity, the plastic can be mixed in the granular state prior to processing on the one hand a certain elasticity ensuring particles and on the other hand electrically conductive particles. According to still another embodiment, the ignition coil further includes an external magnetic core, preferably in C-shape ("C-core"), and the attachment device is configured to electrically connect the magnetic core to an engine block, whereby the electrical connection can be preferably made thereby in that a section of the attachment device is brought into contact with the C-core

Connecting device relative to the other attachment device in the direction of the coil assembly are extended to the level of the C-core, so that the attachment device receives an asymmetrical shape. This results in a simple to manufacture and reliable connection without the need for additional parts and manufacturing steps.

The inventive method for producing an ignition coil having the features of claim 9 provides a simple, inexpensive, permanently reliable connectable in an engine block ignition coil ready. On the housing of the ignition coil, the connection device by coating, in particular

Dipping, shrinking, mounting, e.g. by means of glue, or one

Injection process, in particular by means of an injection molding, applied. In particular, in multi-layered processes for the construction of

Tying device can also be the conductivity of the outside of the

Attaching device take a higher degree than the Grundköper (the inner layers) of the connection device.

In the case of multi-layered construction, the main body, that is to say the inner layers, of the connection device can also be designed without compromise with regard to a suitable preload between ignition coil housing and engine block. by its elasticity is not affected by the addition of electrically conductive particles.

If contacting of contact surfaces located on the surface of the housing of the ignition coil is to be produced by the connection device, the first layer of the connection device (viewed from the inside) can preferably be made electrically conductive, on which a plurality of non-conductive layers are applied and, if necessary the outside again by eg a conductive layer for contacting further contacts are formed.

Of course, a conductive layer in the longitudinal direction of the ignition coil may also be made by having conductive circumferentially distributed portions (e.g., in the form of longitudinal stripes) on the surface of the ignition coil

Connection device are arranged.

drawing

Hereinafter, a preferred embodiment of the invention will be described in detail with reference to the accompanying drawings. In the drawing is:

Figure 1 is a side view of an ignition coil according to a first

 Embodiment of the present invention;

Figure 2 is a sectional view of an ignition coil according to the

 Embodiment of the present invention; and

Figure 3 is a further sectional view of an ignition coil according to the

 Embodiment of the present invention.

Preferred embodiment of the invention

Hereinafter, an ignition coil 1 and its underlying manufacturing method will be described with reference to FIGS. FIG. 1 shows a section of an ignition coil 1 according to the invention, in whose upper region the so-called ignition coil head is located in a housing 2. This one hand, the electrical connection to the periphery (control cable) of the ignition coil and on the other hand, the internal electrical

 Connection to a coil assembly 3 for generating the spark is (coil assembly not shown in detail). The ignition coil head contains in this case the ground connection with a first contact zone 6, which is guided to the outside. Approximately at the upper edge of the first contact zone 6 and the upper edge of the connection device 5 is arranged, which is the

Housing 2 of the ignition coil 1 completely surrounds. While the surface of the attachment device 5 is designed to be substantially cylindrical in its upper region, a seal 50 with sealing lips 51 adjoins downward. Of the illustrated three sealing lips 51, the upper has a larger flank on its (in the picture) lower side a larger cross-sectional area by a much flatter edge. This gives it a higher bending stiffness than that of the two lower sealing lips, which are first introduced during assembly in the spark plug shaft of the engine block. A second contact zone 7 is via the conductive portions of

 Tying device 5 is electrically connected to the first contact zone 6. The second contact zone furthermore has strips extending parallel to the longitudinal axis X-X of the ignition coil and which are in contact with the connection device 5.

FIG. 2 shows a sectional view along the longitudinal axis X-X through an ignition coil 1 according to the invention. The coil assembly 3 is equipped with an outer core 30, which, because of its shape, is also called a C core. Correspondingly, the C-core 30 is cut only on the right-hand side and on a C-core contacting 8 with the connection device

5 connected. The interface of the C-core contact 8 with the

Attachment device 5 is arranged on the lower side of the C-core 30, where a portion of the attachment device 5 between the housing 2 and the C-core 30 is braced. The attachment device 5 comprises the seal 50 with the sealing lips 51 and thus provides both the electrical and mechanical

Connection to the spark plug shaft wall 90 of the igniter plug shaft 9, which is arranged in an engine block M. For this purpose, the lower two sealing lips are pressed considerably opposite the wall 90 of the spark plug shaft 9. Since the attachment device 5 is elastic, a corresponding normal force results on the braced components, which electrically connects them to one another and mechanically holds them in position relative to one another, thus ensuring against rotation, and additionally seals them hydraulically.

Figure 3 shows an enlarged sectional view according to the

Embodiment through the first contact zone. The first contact zone 6 is connected inter alia via the seal 50 of the connection device 5 on the one hand electrically connected to the wall 90 of the spark plug well 9, on the other hand with a second contact zone 7. As a result, the grounding of the coil assembly 3 with the engine block M advantageous over the

Tying device 5 of the ignition coil 1 according to the invention take place and is performed simultaneously with the assembly of the ignition coil.

Alternatively, in addition, a clamping connection via an additional component, e.g. an engine-side valve cover, be provided. The contact force between the attachment device 5 and the spark plug well 9 can also be a bias voltage between the two components by appropriate selection of the material properties, in particular the

Material properties of the attachment device, e.g. whose elasticity, can be adjusted. As an alternative, an electrically conductive adhesive may additionally be provided between connection device 5 and spark plug shaft 9.

Thus, according to the invention, the electrical connection device 5 simultaneously also fulfills a holding function of the ignition coil in the plug shaft as well as a sealing function of the plug shaft.

The connection device 5 according to the invention can be applied very simply and inexpensively and is therefore very good for a

Series production suitable.

Claims

Ignition coil for an internal combustion engine comprising: a housing (2), a coil assembly (3), a connection assembly (4) for connecting the ignition coil, and a connecting device (5) for connecting the ignition coil in an engine block (M), characterized, that the connection device (5) is at least partially formed from an electrically conductive plastic composite and is designed to electrically conductively connect the ignition coil to an engine block (M). Ignition coil according to claim 1, wherein the electrically conductive plastic is elastic. Ignition coil according to claim 1 or 2, wherein the connection device (5) is set up to produce an electrical ground contact between the ignition coil (1) and the engine block (M) and / or a gap between the ignition coil and a wall (90) of a spark plug shaft (9) of an engine block (M) to seal fluid-tight. Ignition coil according to one of the preceding claims, wherein the Connection device (5) surrounds the housing (2) at least in sections, in particular completely, in the circumferential direction and / or is attached to the ignition coil and / or in an engine block (M) by means of electrically conductive adhesive. Ignition coil according to one of the preceding claims, wherein the The connecting device (5) has a plurality of sealing lips (51) lying one behind the other in the longitudinal direction (XX) of the ignition coil and surrounding the ignition coil housing, which are designed to open when inserted into a to elastically deform a substantially cylindrical cavity, in particular a spark plug shaft of an engine block (M). Ignition coil according to one of the preceding claims, wherein the Connection device (5) is arranged adjacent to a high-voltage outlet of the ignition coil. Ignition coil according to one of the preceding claims, wherein the Connection device (5) and the housing (2) are manufactured as a two-component injection molded part. Ignition coil according to one of the preceding claims, wherein the ignition coil further contains an external magnetic core (30), and the Connection device is set up to electrically connect the magnetic core to an engine block (M). Method for producing an ignition coil with a connecting device (5) made at least partially, in particular completely, from electrically conductive plastic, the connecting device (5) being applied to a housing (2) of the ignition coil in one of the following methods: - coating, especially dipping, - shrinking, - Assembling, especially gluing, - Spraying and/or overmolding, in particular by means of a Injection molding process. 10. A method for producing an ignition coil according to claim 9, wherein the Connection device (5) is applied as an electrically conductive lateral surface.