Spark plug having an introduction assistance structure for side

Abstract

The invention relates to a spark plug (1) having a longitudinal axis X, comprising: a housing (2); an insulator (3) arranged inside the housing (2); -a central electrode (4) arranged inside the insulator (3); -a ground electrode (5), the ground electrode (5) being rod-shaped and having a radially inner end (51) and a radially outer end (52); -a hole (20) in which the ground electrode (5) is inserted, the hole having a radially outer end (21) and a radially inner end (22); and-an ignition gap (45) formed between the ground electrode (5) and the central electrode (4), the ground electrode (5) having an introduction aid (60) at its radially inner end (51) and / or the hole (20) at its radially outer end (21).

Description

Technical Field

[0001] The invention relates to a spark plug according to the preamble of claim 1 . Background Art

[0002] In recent years, there has been increasing interest in new spark plug designs in which the ignition gap is formed within the housing. In one design, a ground electrode is inserted into a hole in the housing wall and extends laterally from the wall into the housing interior. For example, DE 10 2017 221 517 A discloses a pre-chamber spark plug in which the ground electrode is arranged in a hole in the housing wall and extends laterally into the interior.

[0003] A ground electrode inserted sideways into a spark plug presents new challenges regarding proper alignment of the ground electrode with the center electrode and adjustment of the ignition gap. In pre-chamber spark plugs, this challenge stems from the fact that a cover placed on the housing can obstruct the view of the electrode and ignition gap, making it more difficult to monitor the ground electrode during assembly.

[0004] For spark plugs with an open combustion chamber-side housing end, while there is no challenge of obstruction of the electrode and ignition gap, the challenge is that the ignition gap is at least partially formed within the housing, so there is little room for post-processing of the electrodes to adjust the electrode spacing after the ground electrode is placed. Summary of the Invention

[0005] The object of the present invention is to provide a spark plug in which reliable and correct assembly of the ground electrode can be achieved, thereby minimizing the need for cumbersome monitoring procedures during ground electrode assembly and post-processing of the electrode after assembly of the ground electrode.

[0006] This object is achieved by the spark plug according to the invention.

[0007] The spark plug according to the present invention has a longitudinal axis X, a housing, and an insulator arranged in the housing. A center electrode is arranged in the insulator. The spark plug has a rod-shaped ground electrode, which has a radial inner end and a radial outer end with respect to the longitudinal axis X of the spark plug. In addition, the spark plug has a hole into which the ground electrode is inserted, so that the spark plug has a laterally inserted ground electrode. The hole has a radial inner end and a radial outer end with respect to the longitudinal axis X of the spark plug. An ignition gap is formed between the ground electrode and the center electrode. The ground electrode has an introduction auxiliary structure at its radial inner end. Additionally or alternatively, the hole has an introduction auxiliary structure at its radial outer end.

[0008] The ground electrode assembly process is simplified by the introduction aid on the ground electrode and / or the hole. This is particularly true when the ground electrode and the hole are dimensioned so that the ground electrode is secured in the hole with an interference fit. The introduction aid ensures that the ground electrode does not tilt during insertion into the hole, but remains straight, allowing the ground electrode to be inserted into the hole with uniform pressure and movement. This prevents the generation of unnecessary stresses between the ground electrode and the hole, which could be released slowly after the ground electrode is installed in the hole and could cause the ground electrode to shift in position.

[0009] The respective radially inner ends of the bore and the ground electrode are spatially closer to the longitudinal axis X of the spark plug than the respective radially outer ends.

[0010] Advantageous developments of the invention are the subject matter of the dependent claims.

[0011] In an advantageous development of the present invention, the introduction aid on the ground electrode is a tapering of the outer diameter of the ground electrode in the direction of the longitudinal axis X of the spark plug. Additionally or alternatively, the introduction aid on the hole is a tapering of the inner diameter of the hole in the direction of the longitudinal axis X. The advantage of designing the introduction aid as a diameter taper is that it can be easily implemented during the production of the spark plug or its components without significantly lengthening or complicating the overall production process. For example, the introduction aid or taper can be implemented by rounding the edges of the ground electrode or the wall delimiting the hole, or by providing chamfers on these edges.

[0012] In one advantageous embodiment of the spark plug according to the present invention, the introduction aid is a rounded portion. The radius R of the rounded portion is advantageously greater than or equal to 0.05 mm and less than or equal to 1 mm. This dimensioning ensures that the rounded portion is large enough to fulfill its introduction aid function while not being too large to ensure that the ground electrode remains securely fixed in the hole and does not shift position over time.

[0013] In another advantageous embodiment of the spark plug according to the present invention, the insertion aid is a chamfer. The length L of the chamfer is measured parallel to the longitudinal direction of the hole or the ground electrode, which corresponds to the insertion direction of the ground electrode. The length L of the chamfer is greater than or equal to 0.1 mm and less than or equal to 1 mm. This dimensioning ensures that the chamfer is large enough to perform its insertion aid function while being small enough to ensure that the ground electrode remains securely fixed in the hole and does not shift position over time.

[0014] Furthermore, it has been found that for the chamfered portion, angle α is advantageously greater than or equal to 5° and less than or equal to 45°. Angle α lies between the chamfered portion surface and the ground electrode insertion direction. When the chamfered portion is formed on the ground electrode, angle α greater than or equal to 10° and less than or equal to 45° has proven particularly advantageous. When the chamfered portion is formed on a hole, angle α greater than or equal to 5° and less than or equal to 35° has proven particularly advantageous.

[0015] Whether it is a design scheme in which only the ground electrode or the hole in the spark plug according to the present invention has an introduction auxiliary structure, or a scheme in which the ground electrode and the hole in the spark plug according to the present invention each have an introduction auxiliary structure, both are advantageous. Of course, when both the ground electrode and the hole have an introduction auxiliary structure, the expected technical effect will be further enhanced. If the hole and the ground electrode both have an introduction auxiliary structure at their respective ends, these introduction auxiliary structures can be implemented in different or identical forms. For example, the hole can have a rounded portion and the ground electrode can have a chamfered portion, or vice versa. Alternatively, the hole and the ground electrode can also have chamfered portions of the same or different sizes, or rounded portions of the same or different sizes.

[0016] In addition, the spark plug may further have a second introduction auxiliary structure on the ground electrode and / or the hole. The second introduction auxiliary structure is, for example, a groove on one or two contact surfaces of the corresponding contact surfaces of the ground electrode and the hole. The groove extends parallel to the insertion direction of the ground electrode. The contact surface of the hole and the ground electrode forms a wall that delimits the hole. On the one hand, the groove acts as an introduction auxiliary structure when the ground electrode is inserted into the hole, and ensures that the ground electrode is inserted into the hole with uniform pressure and uniform speed. In addition, the stress that may be generated during the insertion of the ground electrode can be directly released by the deformation of the groove. The groove can be produced during the manufacturing process of the ground electrode, for example, by punching (Flieβpressen), drawing or calibrating the shape.

[0017] In one design of a spark plug according to the present invention, a ground electrode comprises a base body and an ignition element forming an ignition surface. The ignition element is secured to the base body and has a smaller diameter than the base body. A lead-in aid is formed on the base body. Since the lead-in aid is typically formed by removing material, and the material cost of the ignition element is higher than that of the base body, this design avoids the waste of expensive material due to removal during the formation of the lead-in aid while maintaining the functionality of the lead-in aid.

[0018] In an advantageous design of the present invention, a hole for inserting the ground electrode is formed on the housing.

[0019] In another advantageous embodiment of the invention, the spark plug has a cap fastened to the combustion chamber-side end of the housing, and the spark plug is a pre-chamber spark plug, wherein the hole for inserting the ground electrode is formed in the cap or the housing.

[0020] In other designs, it may be combined or alternatively provided that the ignition gap between the center electrode and the ground electrode is a radial ignition gap, and / or the ignition gap is at least partially, in particular completely, formed in the housing inner cavity.

[0021] The ground electrode may be fixed in the hole by crimping and / or soldering or welding.

[0022] The housing typically has a longitudinal bore parallel to the longitudinal axis X of the spark plug, so that the housing comprises a housing wall and an interior cavity. The hole for inserting the ground electrode is, for example, formed in the housing wall. Thus, the ignition gap is at least partially, and in particular completely, formed within the housing interior cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 An example of a spark plug with an inserted ground electrode is shown;

[0024] Figure 2 A first example of a hole and ground electrode designed according to the present invention is shown;

[0025] Figure 3 A second example of an aperture and ground electrode designed according to the present invention is shown. DETAILED DESCRIPTION

[0026] Figure 1 Spark plug 1 is shown in a half-section. Spark plug 1 has a longitudinal axis X, which extends from the combustion chamber-side end of spark plug 1 to the end facing away from the combustion chamber. Spark plug 1 has a housing 2 with a longitudinal bore parallel to longitudinal axis X of spark plug 1, resulting in housing 2 having a housing wall 26 and an interior cavity 23. Housing 2 typically has threads on its outer surface, which allow spark plug 1 to be screwed into the cylinder head. An outer seal 6 is typically arranged on the outer surface of housing 2, sealing the transition area between housing 2 and the cylinder head.

[0027] An insulator 3 is arranged and fastened within the housing 2. The gap between the housing 2 and the insulator 3 is sealed by an inner seal 10. Connecting screws 8, a resistor element 7, and a center electrode 4 are arranged in the insulator 3, extending from its end facing away from the combustion chamber, and are in electrical contact with one another. The center electrode 4 typically projects from the combustion chamber-facing end of the insulator 3 and, in this example, into the interior 23 of the housing 2.

[0028] In this example, a ground electrode 5 is inserted into a hole 20 formed in the housing wall 26. The ground electrode 5 is rod-shaped and has a radially inner end 51 and a radially outer end 52. The radially inner end 51 of the ground electrode 5 extends laterally into the inner cavity 23 of the housing. The radially inner end 51 of the ground electrode 5, together with the center electrode 4, forms an ignition gap 45. In this example, the two electrodes 4 and 5 form a radial ignition gap 45. The ground electrode 5 and the center electrode 4 can also be arranged relative to each other to form an axial ignition gap.

[0029] The center electrode 4 and / or the ground electrode 5 can each have an ignition element 54 containing precious metal at their ends delimiting the ignition gap 45. In the case of the ground electrode 5, the ignition element 54 containing precious metal is arranged at the radially inner end 51 of the ground electrode 5.

[0030] In an alternative design, a cover can be arranged on the combustion chamber-side end face of the housing 2. The housing 2 and the cover together form a pre-combustion chamber having a pre-combustion chamber volume. The hole 20 for inserting the ground electrode 5 can be formed in the housing wall 26 or the cover wall.

[0031] Figure 2 and Figure 3 The enlarged images are shown Figure 1 In the area marked as circle A, for the sake of convenience, the ground electrode 5 is not yet in its final position in the hole 20, but rather shows the instantaneous state during the process of introducing the ground electrode 5 into the hole 20. Figure 2 and Figure 3 A first example and a second example of realizing the introduction aid 60 on the hole 20 and the ground electrode 5 are shown, respectively.

[0032] Unless otherwise specified, the following descriptions apply to Figure 2 and Figure 3 .

[0033] The wall 26 of the housing 2 or the cover delimits the hole 20 from the side along its longitudinal extension. The hole 20 has a radially outer end 21 and a radially inner end 22. The diameter of the hole 20 at its radially inner end 22 is D BI The diameter of the hole 20 at its radially outer end 21 is D BA The diameter D of the hole 20 at its radially inner end 22 is BI smaller than the diameter D of the hole 20 at its radially outer end 21 BA The diameter taper of the hole 20 in the direction of the longitudinal axis X of the spark plug 1 is produced by the introduction auxiliary structure 60 formed at the radial outer end 21 of the hole 20. Figure 2 In the example of FIG. 1 , the introduction auxiliary structure 60 at the radially outer end 21 of the hole 20 is configured as a rounded portion. The radius R of the rounded portion is 0.05 to 1.0 mm. Figure 3In the example of FIG, the introduction auxiliary structure 60 at the radial outer end 21 of the hole 20 is configured as a chamfer. The length L of the chamfer is, for example, 0.1 to 1 mm, and the angle α is 5° to 35°.

[0034] In a further development, the hole 20 may have grooves as second insertion aids on the contact surface 25 with the ground electrode 5. These grooves preferably extend parallel to the insertion direction of the ground electrode 5. For example, these grooves are formed over the entire length of the contact surface 25 of the hole 20 and / or along the entire circumference.

[0035] The ground electrode 5 is rod-shaped and has a radially inner end 51 and a radially outer end 52. In these examples, the ground electrode 5 has a base 53 and an ignition element 54 arranged and fastened at the radially inner end 51 of the base 53. The diameter of the ignition element 54 is D z The diameter of the base 53 at the radial inner end 51 of the base 53 is D MI , and the diameter at the radially outer end 51 of the base 53 is D MA The diameter satisfies the following relationship:

[0036] D z ≤D MI

[0037] D MI <D MA

[0038] The diameter taper of the base body 53 in the direction of the longitudinal axis X of the spark plug 1 is produced by an introduction auxiliary structure 60 formed at the radial inner end 51 of the base body 53. Figure 2 and Figure 3 In the embodiment shown, the introduction aid 60 at the radially inner end 51 of the base body 53 is configured as a chamfer. The length L of the chamfer is, for example, 0.1 to 1 mm, and the angle α is 10° to 45°. These examples do not show the case where the introduction aid 60 is implemented as a rounded portion on the ground electrode 5.

[0039] If ground electrode 5 does not have ignition element 54 , base body 53 is ground electrode 5 .

[0040] In a further development, the ground electrode 5 or the base body 53 of the ground electrode 5 may have grooves as second insertion aids on the contact surface 55 with the hole 20. These grooves preferably extend parallel to the insertion direction of the ground electrode 5. For example, they may be formed over the entire length and / or along the entire circumference of the contact surface 55 of the ground electrode 5 or its base body 53.

Claims

1. A spark plug (1) having a longitudinal axis X, said spark plug comprising: Housing (2); An insulator (3) arranged in the housing (2); A central electrode (4) arranged within the insulator (3); A ground electrode (5), wherein The ground electrode (5) is rod-shaped and has a radially inner end (51) and a radially outer end (52); a hole (20) into which the ground electrode (5) is inserted, wherein the hole has a radially outer end (21) and a radially inner end (22); and an ignition gap (45) formed between the ground electrode (5) and the center electrode (4), It is characterized in that the ground electrode (5) has an introduction aid structure (60) at its radial inner end (51) and / or the hole (20) has an introduction aid structure (60) at its radial outer end (21).

2. Spark plug (1) according to any one of the preceding claims, characterized in that The introduction auxiliary structure (60) is a tapered portion of the outer diameter of the ground electrode (5) or the inner diameter of the hole (20) along the longitudinal axis X direction of the spark plug (1), such as a rounded portion or a chamfered portion.

3. The spark plug (1) according to claim 1 or 2, characterized in that The introduction auxiliary structure (60) is a rounded portion, and the radius R of the rounded portion is 0.05 to 1.0 mm.

4. Spark plug (1) according to any one of the preceding claims 1 or 2, characterized in that The introduction auxiliary structure (60) is a chamfered portion, and a length L of the chamfered portion measured parallel to the insertion direction of the ground electrode (5) is 0.1-1 mm.

5. The spark plug (1) according to claim 4, characterized in that An angle α of the chamfered portion is greater than or equal to 5° and less than or equal to 45°, in particular 5° to 35° or 10° to 45°, wherein α is an angle between the insertion direction of the ground electrode (5) and the chamfered portion.

6. Spark plug (1) according to any one of the preceding claims, characterized in that The hole (20) and the ground electrode (5) form the same or different introduction auxiliary structures (60) at their respective ends (21, 51), and in particular, the introduction auxiliary structure (60) is a rounded portion or a chamfered portion.

7. Spark plug (1) according to any one of the preceding claims, characterized in that The ground electrode (5) and / or the hole (20) have grooves on their respective contact surfaces (55, 25) as second introduction aids (61), in particular the grooves extend parallel to the insertion direction of the ground electrode (5).

8. Spark plug (1) according to any one of the preceding claims, characterized in that The ground electrode (5) comprises a base body (53) and an ignition element (54) forming an ignition surface, wherein the ignition element (54) is fastened to the base body (53) and has a smaller diameter than the base body (53), wherein the introduction auxiliary structure (60) is formed on the base body (54).

9. Spark plug (1) according to any one of the preceding claims, characterized in that A hole (20) into which the ground electrode (5) is inserted is formed on the housing (2).

10. Spark plug (1) according to any one of the preceding claims 1 to 8, characterized in that The spark plug (1) has a cover fastened to the combustion chamber side end of the housing (2), and the spark plug (1) is a pre-combustion chamber spark plug, wherein a hole (20) into which the ground electrode (5) is inserted is formed on the cover or the housing (2).

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