Spark plug and ignition assembly comprising an ignition coil and spark plug

Abstract

Spark plug comprising a contact area (30) for contacting a spring (15) of an ignition coil (2), wherein the contact area (30) has a recess (31) for receiving a contact section (15.3) of the spring of the ignition coil, and wherein the recess (31) has a circular base area (33) and a wall area (32) surrounding the base area (33) in an annular manner, which surrounds the recess (31) as a closed, annular wall area (32), wherein the recess (31) is conically tapered from the opening of the recess (31) towards the base area (33), such that the shape of the recess (31) is complementary to a frustoconical surface.

Description

State of the art

[0001] The present invention relates to a spark plug and an ignition arrangement with an ignition coil and a spark plug.

[0002] Ignition coils, spark plugs, and ignition assemblies consisting of them are known in various designs from the prior art. For example, DE 10 2007 026 669 A1 describes an ignition coil with a high-voltage terminal and a spring for electrically connecting the high-voltage terminal to a spark plug, wherein the spring is surrounded by a protective sheath. Contact between the spring and a contact area of ​​the spark plug is therefore designed such that the spring has a conically widening contact section that is placed over a contact area of ​​the spark plug. Such spark plugs have generally proven themselves, but the installation spaces in modern engines are becoming increasingly tight. One possibility would therefore be to reduce the diameter of a spark plug shaft. However, the sharp-edged spring end disadvantageously leads to an increase in the field strength between the spring end and the spark plug shaft.This could lead to electrical failures due to the higher voltage requirements at this point, which must be avoided at all costs. It would therefore be desirable to have an improved connection between a spark plug and an ignition coil, particularly with a reduced installation space.

[0003] An ignition arrangement with a spark plug and an ignition coil is known, for example, from US 6 668 810 B1, DE 19 611 220 A1 and US 2 266 614 A and US 5 487 676 A.

[0004] Spark plugs with a recess at their high-aperture contact section are known, for example, from US 1 996 421 A and DE 691 14 806 T2. Disclosure of the invention

[0005] An ignition coil with a high-voltage terminal and a spring for electrically connecting the high-voltage terminal to a spark plug, wherein a contact section of the spring directed towards the spark plug has a reduced outer circumference compared to an outer circumference of other sections of the spring, has the advantage that it enables simple and reliable contact with a spark plug and is particularly simple and cost-effective to manufacture. Furthermore, the ignition coil ensures that only a very small installation space is required, particularly in the area of ​​contact with the spark plug, especially in the radial direction of a spring of the ignition coil. Furthermore, reliable shielding of a contact section at the end of the spring of the ignition coil is enabled.This is achieved by the ignition coil having a contact section of the spring directed toward the spark plug, which has a reduced outer circumference compared to the remaining outer circumference of the spring. The reduced outer circumference of the contact section can thus be very effectively shielded in the radial direction from the cylinder head, which is connected to ground. Shielding is preferably achieved by means of a recess provided in a contact area of ​​the spark plug, which has an annular, circumferential wall area that accommodates and shields the reduced-circumference contact section of the spring when the ignition coil is installed.

[0006] Preferably, the contact section of the spring with a reduced outer diameter is tapered, in particular conically tapered. This achieves an additional centering effect during assembly of the ignition coil on a spark plug due to the tapered contact section of the spring. Furthermore, the tapered region additionally ensures good fixation of the spring in the assembled state, so that, for example, when vibrations occur in the engine, reduced wear occurs due to reduced movement of the tapered contact section of the spring. If the contact section of the spring is conical, the contact section has a substantially frustoconical envelope surface, wherein the frustoconical envelope surface is preferably formed with an opening angle between 40° and 60°, particularly preferably 50°.

[0007] Alternatively, the circumferentially reduced contact section of the spring is formed substantially cylindrically with a smaller outer diameter than the outer diameter of the other sections of the spring. This also allows for improved shielding of the contact section of the spring and, furthermore, a particularly secure fit of the contact section in a correspondingly designed recess of the spark plug.

[0008] In order to have as little room for movement as possible in the contact section of the spring, the contact section of the spring is preferably arranged in a block, i.e. adjacent windings at the contact section of the spring touch each other.

[0009] The present invention relates to a spark plug with the features of claim 1, comprising a contact region for contact with a spring of an ignition coil. The contact region of the spark plug has a recess with a circular base region and a wall region surrounding the base region in an annular manner, which wall region surrounds the recess as a closed, annular wall region. The recess tapers conically from the opening of the recess towards the base region, so that the shape of the recess is complementary to a frustoconical envelope surface. The recess serves to accommodate a contact portion of the spring of the ignition coil, and the wall region provides radial shielding of the contact portion of the spring. An opening of the recess on the spark plug is preferably directed perpendicular to a central axis of the spring in order to enable secure and easy accommodation of the spring in the recess.Thus, according to the invention, the provision of the recess allows for very cost-effective and reliable shielding of the spring end, preventing undesirable electrical field strength peaks at the end of the spring. In particular, space can be saved in the radial direction of the spark plug, allowing, for example, a bore in a cylinder head for the spark plug to be designed with a smaller diameter.

[0010] Preferably, the recess tapers toward a central axis of the spark plug to facilitate easy location of a contact portion of the ignition coil spring. The taper of the recess has an opening angle of 40° to 60°, and more preferably an opening angle of 50°.

[0011] Further preferably, the recess has a depth equal to or greater than the diameter of a spring wire of the ignition coil spring. This ensures that at least one complete turn of the spring end is arranged in the recess of the spark plug. However, the depth of the recess is preferably selected such that at least two complete turns of the spring can be accommodated. Further preferably, the wall region surrounding the recess has a minimum thickness corresponding to the wire diameter of the spring.

[0012] In order to enable particularly secure contact between the spring of the ignition coil and the spark plug, the recess according to the invention has a circular base region. This allows the last turn of the spring to rest securely on the base region of the recess. More preferably, a transition from the base region to the wall region of the recess is formed with a rounded portion. Particularly preferably, the rounded portion is selected with a radius that corresponds to a radius of the wire of the spring of the ignition coil. The radius is preferably between 0.3 and 0.5 mm, particularly preferably 0.4 mm. More preferably, the depth of the recess is smaller than a radius of the base region. This ensures that the contact area of ​​the spark plug does not become too long in the axial direction. Alternatively, the transition between the base region and the wall region could also be sharp-edged.

[0013] The present invention further relates to an ignition arrangement comprising a spark plug according to the invention and an ignition coil. The spark plug has a contact region with a recess which is surrounded by a ring-shaped, closed wall region. The ignition coil comprises a spring with a contact portion which is arranged in the recess of the spark plug. As a result, the ignition arrangement according to the invention has excellent contact between the spring end and the spark plug, and furthermore, the contact portion of the spring is securely received in the recess. Contact between the spring end and the spark plug can be established both via a base region of the recess and the surrounding wall region. This achieves improved contact, and on the other hand, the wall region of the spark plug surrounding the spring end ensures shielding.The ignition assembly according to the invention does not have an increased installation space in the radial direction of the spark plug, but can preferably be designed even smaller. This allows, in particular, compliance with the more stringent installation space requirements of modern engines and, accordingly, the necessary bores in a cylinder head for the spark plug and ignition coil to be reduced in size.

[0014] The ignition assembly according to the invention is preferably designed such that a shape of the recess in the spark plug is complementary to an envelope surface of the contact portion of the spring of the ignition coil. As a result, the shape of the recess and the shape of the contact portion of the spring correspond, so that the two contact areas of the spark plug and the ignition coil are designed to match each other. This not only simplifies assembly but also facilitates contact between the two components.

[0015] Preferably, the depth of the recess in the axial direction is at least equal to or greater than the wire diameter of the ignition coil spring. The depth of the recess is preferably two to three times greater than the wire diameter of the spring. Further preferably, the thickness of the wall region is equal to or greater than the wire diameter of the spring. The depth of the recess in the axial direction is preferably between 1.2 mm and 1.6 mm, particularly preferably 1.5 mm. The diameter of the spring wire is preferably between 0.5 and 0.8 mm, and particularly preferably 0.6 mm.

[0016] According to a further preferred embodiment of the invention, the contact portion of the spring contacts exclusively the wall area of ​​the spark plug. This ensures minimal abrasion and allows contact to be made at a single point. drawing

[0017] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing: Fig. 1 is a schematic sectional view of an ignition arrangement according to a first embodiment of the invention, Fig. 2 an enlargement of a contact area between an ignition coil and a spark plug of the ignition arrangement of Fig. 1, Fig. 3 an enlargement of a contact area of ​​the spark plug, and Fig. 4 a schematic sectional view of a contact region between an ignition coil and a spark plug according to an embodiment not according to the invention. Preferred embodiments of the invention

[0018] The following is based on the Fig. 1 to 3 an ignition arrangement 1 with an ignition coil 2 and a spark plug 3 according to a first embodiment of the invention is described.

[0019] As from Fig. As can be seen in Figure 1, the ignition coil 2 comprises a coil housing 5 in which a primary coil 6 and a secondary coil 7 interact such that a high voltage for the spark plug 3 is generated from a low direct voltage of a battery 4. The primary coil 6 is electrically connected to the battery 4 via a low-voltage connection 8 and to the spark plug 3 via a high-voltage connection 9. The spark plug 3 is arranged in a shaft 10 of a cylinder head 11 of an internal combustion engine. A central axis of the spark plug and the ignition coil is designated by reference numeral 12.

[0020] The ignition coil 2 further comprises a spring 15 as a contact element, which is surrounded by an insulating protective sheath 16. The insulating protective sheath surrounds both the high-voltage terminal 9 and a contact area 30 of the spark plug 3. The contact area 30 is the area of ​​the spark plug 3 which is directed in the direction of the longitudinal axis 12 towards the ignition coil 3. As can be seen from the Fig. 2 and Fig. 3, the contact area 30 of the spark plug has a recess 31, which is arranged at the outermost end of the contact area 30. The recess 31 has a bottom area 33 and a wall area 32 that completely surrounds the bottom area 33 in an annular manner. As can be seen from Fig. As can be seen in Figure 3, the wall region 32 is tapered from the opening of the recess 31 toward the base region 33. More precisely, the recess 31 tapers conically, with an opening angle α of the taper being 50°. Furthermore, a radially outwardly directed support shoulder 34 is formed on the contact region 30 of the spark plug, which forms a support for the protective sheath 16, as can be seen in Figure 3. Fig. 2 can be seen.

[0021] How further from the Fig. 1 and Fig. As can be seen in Figure 2, the spring 15 has three main sections, namely a first block section 15.1, a spring section 15.2, and a contact section 15.3. The block section 15.1 is several times longer than the spring section 15.2 and the contact section 15.3 combined. Alternatively, the block section 15.1 can be omitted and the section can instead be designed entirely as a spring section. In this case, the pitch of the spring section can also change over its length. The contact section 15.3, as can be seen from Fig. 2, is also tapered towards its end. In this exemplary embodiment, the tapered contact section 15.3 comprises exactly three turns of the spring 15. The contact section 15.3 thus forms a substantially frustoconical end of the spring, which is designed for contact with the spark plug 3. An opening angle of the taper of the contact section 15.3 corresponds to the opening angle α of the wall region 32 of the recess 31 on the spark plug. The last turn of the contact section 15.3 of the spring can touch the bottom region 33, but the contact section rests securely on the circumferential wall region 32 of the recess 31. A single contact point between the contact section and the wall region is sufficient. In the exemplary embodiment, the second and third turns of the contact section 15.3 touch the wall region 32. This ensures particularly good contact between the contact section 15.3 and the contact area 30 of the spark plug. Furthermore, the windings of the contact section 15.3 are formed in a block, i.e., touching one another, which provides improved contact and leads to a certain increase in the stability of the contact section 15.3 of the spring. Furthermore, the wall area 32 provides circumferential shielding for the spring end, so that excellent shielding against excessive electric field strength increases is present in the area of ​​the sharp-edged end of the spring. The outer circumference of the contact area 30 is not larger than in conventional spark plugs, but can, on the contrary, be made smaller. This saves installation space for shielding the spring end, and thus the shaft 10 can have a reduced diameter.

[0022] According to the invention, the spark plug, or more precisely the wall region 32, provides the shielding for the spring end at the contact region 30 of the spark plug, so that no further additional components are necessary. Furthermore, the length of the contact region 30 of the spark plug can be reduced in the axial direction, thus also resulting in a reduction in installation space in the axial direction. Furthermore, material savings result at the contact region 30 of the spark plug. This leads to a further cost reduction for the spark plug. Alternatively, this region can be used for an extended insulator region. Furthermore, the conical recess 31 ensures that the contact section 15.3 is easier to locate during assembly and additionally enables improved fixation of the contact section 15.3 in the recess 31 in the event of vibrations of the internal combustion engine.This results in reduced wear and thus an extended service life of the contact between the ignition coil and the spark plug. The contact solution according to the invention between the spark plug and the ignition coil thus provides a significant improvement that can be implemented in a simple and cost-effective manner. Furthermore, the provision of the support shoulder 34 also enables easy attachment of the protective cover 16 to the spark plug 3.

[0023] Fig. 3 shows in detail the contact area 30 of the spark plug 3, wherein a depth T of the recess 31 is approximately three times a wire diameter D ( Fig. 2). In this exemplary embodiment, the depth is 1.5 mm, with the contact region 30 having a total thickness A of 2.8 mm in the axial direction. A maximum outer diameter B at the support shoulder 34 is 7.7 mm, an outer diameter C of the wall region 32 is 6.4 mm, and a diameter E at the opening of the recess 31 is 5 mm. Furthermore, a transition between the inner wall surface of the wall region 32 and the base region 33 with a radius R is provided, with the wall region 32 also having rounded portions at the opening of the recess 31, so that in particular the contact section 15.3 of the spring can be easily inserted and the protective sheath 16 can also be easily slipped over the wall region 32. This enables particularly simple assembly.

[0024] The following is based on reference to Fig. 4 a second embodiment is described in detail, wherein identical or functionally identical parts are designated by the same reference numerals as in the first embodiment.

[0025] As from Fig.4, the non-inventive embodiment essentially corresponds to the first embodiment, wherein, in contrast to the first embodiment, in the non-inventive embodiment the recess 31 is not conical but cylindrical. Accordingly, the contact section 15.3 of the spring 15 is also designed such that the coils of the spring of the contact section 15.3 form a cylindrical envelope. The contact section 15.3 thus has a cylindrical envelope with a diameter D1 which is smaller than a diameter D2 of the remaining sections of the spring 15. A diameter of the recess 31 is selected such that the contact section 15.3 sits relatively firmly and securely in the recess 31. The wall region 32, in turn, provides shielding for the spring end without the need for additional installation space.The recess 31 of the second embodiment can be manufactured particularly easily and cost-effectively. By rounding the edges of the wall region 32, which face the ignition coil, a certain degree of assistance can be achieved with centering during assembly. The windings of the contact section 15.3 of the spring are also provided in a block configuration, thus achieving particularly good contact. Otherwise, this embodiment corresponds to the previous embodiment, so reference can be made to the description given there.

Claims

[1] Spark plug, comprising a contact region (30) for contacting a spring (15) of an ignition coil (2), wherein the contact region (30) has a recess (31) for receiving a contact section (15.3) of the spring of the ignition coil, and wherein the recess (31) has a circular base region (33) and a wall region (32) which surrounds the base region (33) in an annular manner and which surrounds the recess (31) as a closed, annular wall region (32), wherein the recess (31) is conically tapered starting from the opening of the recess (31) in the direction up to the base region (33), so that the shape of the recess (31) is complementary to a frustoconical envelope surface. [2] Spark plug according to claim 1, characterized by that the recess (31) has an opening angle (α) between 40° and 60° and particularly preferably an opening angle (α) of 50°. [3] Spark plug according to one of claims 1 to 2, characterized bythat the recess (31) is concentric to a central axis (12) of the spark plug. [4] Ignition arrangement, comprising an ignition coil (2) and a spark plug (3) according to one of claims 1 to 3, wherein the ignition coil has a high-voltage terminal (9) and a spring (15) for electrically connecting the high-voltage terminal (9) to the spark plug (3), wherein a contact section (15.3) of the spring (15) directed towards the spark plug (3) has a reduced outer circumference compared to an outer circumference of further sections (15.1, 15.2) of the spring (15), and the contact section (15.3) of the spring (15) of the ignition coil (2) is arranged in the recess (31) of the contact region (30) of the spark plug, wherein a shape of the recess (31) is complementary to an envelope surface of the contact section (15.3) of the spring of the ignition coil (2). [5] Ignition arrangement according to claim 4, characterized bythat the contact section (15.3) of the spring has an opening angle (α) between 40° and 60° and particularly preferably an opening angle (α) of 50°. [6] Ignition arrangement according to claim 4 to 5, characterized by that a depth (T) of the recess (31) of the spark plug (3) is equal to or greater than a diameter (D) of the spring wire of the spring (15), preferably two or three times greater than the diameter (D) of the spring wire. [7] Ignition arrangement according to claims 4 to 6, characterized by that the contact section (15.3) of the spring (15) of the ignition coil contacts exclusively the wall area (32) of the recess (31). [8] Ignition arrangement according to one of the preceding claims 4 to 7, characterized by that the contact section (15.3) of the spring (15) is arranged on a block. [9] Ignition arrangement according to one of the preceding claims 4 to 8, characterized bythat the contact section (15.3) of the spring (15) comprises exactly two turns or exactly three turns.

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