Method for manufacturing a spark plug having a lateral electrode, and corresponding spark plug

Abstract

The invention relates to a method for producing a spark plug having a laterally inserted electrode, comprising the following steps: • providing a spark plug blank with a housing and optionally a cap, wherein a through-hole is formed in the housing or in the optional cap, which through-hole extends from the outer side to the inner side of the housing or the optional cap, wherein the through-hole is designed to receive an electrode; • inserting an electrode into the through-hole, wherein the electrode has a smaller diameter Dm than the through-hole Db such that a radial gap S is produced between the electrode and the through-hole; • fastening the electrode in the through-hole by means of an integrally bonded connection, characterised in that the radial gap S has a value of at least 0.01 mm and at most 0.5 mm, wherein the value for the radial gap is measured at the greatest distance between the outer side of the electrode and the inner side of the through-hole, and in that, during the production of the integrally bonded connection, a connecting seam is formed which completely fills the radial gap between the electrode and the through-hole radially with respect to the electrode.

Description

[0001] Description

[0002] Title of a spark plug with side electrode and e

[0003] State of the art

[0004] The invention relates to a manufacturing method for a spark plug with a lateral electrode and to a spark plug with such an electrode.

[0005] There are spark plugs in which the ground electrode is arranged in a through-hole. The through-hole can be formed in the housing or in a section of the cap in the case of pre-chamber spark plugs. Typically, the ground electrode is pressed and / or welded into the through-hole to secure it. Such spark plugs are known, for example, from DE 10 2017 221 517 A.

[0006] When the ground electrode is pressed into the through-hole, very high requirements are placed on the accuracy of the through-hole diameter and the ground electrode diameter to ensure stable attachment of the ground electrode while simultaneously implementing a manufacturing process with a high cycle rate and a low failure rate. Achieving and ensuring this is a correspondingly challenging task.

[0007] The object of the present invention is to provide a simple manufacturing method and a spark plug that is easier to manufacture. Advantage of the invention / Disclosure of the invention

[0008] This object is achieved by the manufacturing method according to the invention and the corresponding spark plug.

[0009] The manufacturing method according to the invention for a spark plug with a side electrode comprising the following steps:

[0010] • Providing a spark plug blank with a housing and optionally a cap, wherein a through-hole is formed in the housing or in the optional cap, which through-hole extends from the outside to the inside of the housing or the optional cap, wherein the through-hole is designed to receive an electrode

[0011] • Inserting an electrode into the through-hole, whereby the electrode has a smaller diameter Dm than the through-hole Db, so that a radial gap S is created between the electrode and the through-hole (clearance fit)

[0012] • Fastening the electrode in the through-hole by means of a material-to-material connection, wherein the radial gap S has a value of at least 0.01 mm and a maximum of 0.5 mm, wherein the value for the radial gap is measured at the greatest distance between the outside of the electrode and the inside of the through-hole, and that when the material-to-material connection is produced, a connecting seam is formed which completely fills the radial gap between the electrode and the through-hole radially to the electrode.

[0013] In the method according to the invention, a clearance fit is selected for the electrode in the through-hole instead of a press fit. This results in a gap being formed between the component in which the through-hole is formed, the housing or the cap, and the electrode. By selecting a clearance fit, the requirements for the accuracy of fit of the joining partners are lower. The material connection creates a connecting seam that closes the gap between the component and the electrode, so that the electrode is attached in the spark plug with sufficient mechanical stability and also provides good electrical and thermal conduction to the spark plug. Advantageous developments of the invention are the subject of the dependent claims.

[0014] In an advantageous further development of the method, the through-bore has a length L1 and the connecting seam has a length L2, wherein the lengths L1 and L2 are measured parallel to one another and wherein a ratio of L2 to L1 is not greater than 90% and not less than 10%, in particular not less than 30% or not greater than 70%. For example, the length L2 of the through-bore is equal to the wall thickness of the component, housing or cap in which the through-bore is formed. The fact that the length L1 of the connecting seam is shorter than the length of the through-bore ensures that no material from the connecting seam gets into the interior of the spark plug, for example the inside of the housing or the cap, and contaminates other components of the spark plug already located there or disrupts the desired geometry of the inside.

[0015] In an advantageous further development, the connecting seam is formed, in particular completely, around the electrode between the electrode and the through-hole. This ensures that the electrode has a stable, material-to-material connection with appropriate mechanical strength to the surrounding component along its circumference, so that the electrode has good thermal and electrical conduction to the rest of the spark plug.

[0016] Optionally, the method may include the step of providing the spark plug blank with a center electrode and adjusting the electrode gap between the electrode and the center electrode prior to securing the electrode in the through-hole. This ensures that the correct electrode gap is set, since changing the electrode gap after the inserted electrode is secured is very difficult and only possible within a narrow range.

[0017] For example, the material-to-material joining process is a welding process, specifically a laser welding process. In a further development, the welding beam is guided circumferentially around the electrode during the welding process, particularly in a serpentine or zigzag pattern. This is also called wobbling. This guidance of the welding beam has the advantage that the gap can be better bridged and closed with the weld seam.

[0018] The invention further relates to a spark plug, in particular produced by the method according to the invention, with a longitudinal axis X, which has:

[0019] • a housing,

[0020] • an insulator arranged inside the housing,

[0021] • a central electrode arranged within the insulator,

[0022] • an electrode with a diameter DM as a ground electrode,

[0023] • a through-hole with an outer end, an inner end and a diameter DB, in which the ground electrode is inserted and secured by means of a material connection and protrudes from the through-hole at the inner end thereof, and

[0024] • an ignition gap formed between the ground electrode and the center electrode, wherein a gap S is formed at the inner end of the through-hole between the through-hole and the ground electrode, in particular which is formed circumferentially between the through-hole and the ground electrode.

[0025] This spark plug has the advantage that the electrode can be inserted with a clearance fit, thus simplifying the manufacturing process.

[0026] In a further development of the spark plug, the gap at the inner end of the through-hole has a width B of less than or equal to 0.25 mm, in particular less than 0.05 mm and at least 0.01 mm. This value range for the gap ensures that the gap is not too large, so that a large amount of material is required from the joining partners to create the connecting seam.

[0027] Furthermore, at the outer end of the through-hole, the electrode can be integrally connected to the spark plug element in which the through-hole is formed by means of a connecting seam, and the connecting seam can be formed completely circumferentially around the electrode. For example, in one further development, the connecting seam has a length L2 that extends from the outer end of the through-hole toward the inner end of the through-hole, wherein the connecting seam does not extend to the inner end of the through-hole. In particular, the through-hole has a length L1 and a ratio of L2 to L1 is not greater than 90% and not less than 10%, in particular not greater than 70% and / or not less than 30%.

[0028] In a further embodiment, the ground electrode has an outer side that is at a distance D from the outer end of the through-hole, wherein the distance D is not greater than 0.4 mm, in particular not greater than 0.2 mm. This ensures that the outer end of the ground electrode is not too far away from the outer end of the through-hole, which would complicate the production of the connecting seam and the bridging of the gap.

[0029] In one possible embodiment, the through-bore has a first and a second section, wherein the diameter of the through-bore is smaller in the first section than in the second section.

[0030] In a possible further development of this embodiment, the second section is arranged at the outer end of the through-hole and the first section is arranged at the inner end of the through-hole, wherein the ground electrode is not arranged in the second section.

[0031] In two possible further developments of this embodiment, the second section has a conical shape or a cylindrical shape with a stepped transition to the first section. The conical shape of the second section can be formed, for example, by a chamfer.

[0032] The second section of the through-hole offers the advantage that any raised seams that may arise during manufacturing are located in the second section and thus no longer cause interference on the outside of the spark plug. The through-hole is formed, for example, in the housing or in an optional cap, with the length L1 of the through-hole corresponding to the wall thickness of the housing or cap.

[0033] drawing

[0034] Figure 1 shows two process steps of the process according to the invention

[0035] Figure 2 shows an example of the positioning of the electrode in the through hole

[0036] Figure 3 shows examples of the length of the connecting seam

[0037] Figure 4 shows a third example of the electrode according to the invention

[0038] Figure 5 shows two examples of beam guidance during the production of the connecting seam

[0039] Figure 6 shows two examples of the positioning of the electrode end

[0040] Figure 7 shows an example of a spark plug with a plugged-in ground electrode

[0041] Description of the embodiment

[0042] Figure 1 shows two steps of the manufacturing method according to the invention. Figure 1 a) shows a sectional view of how the electrode 5 is inserted into a through-bore 20. This through-bore 20 is formed in a component 100 of the spark plug 1, for example in the housing 2 or in a cap if the spark plug 1 is a pre-chamber spark plug. A gap 30 exists between the electrode 5 and the component 100 because the electrode 1 is inserted into the through-bore 20 with a clearance fit. Figure 1 b) shows the electrode 5 and the component 100 in a view rotated by 90° to the view in Figure 1 a). Figures 1 c) and 1 d) show the second method step in the same views.The connecting seam 35 between electrode 5 and component 100 is formed and the gap 30 around the electrode 5 is filled with the connecting seam 35, so that a mechanically stable fastening is achieved and the electrode 5 is simultaneously well connected thermally and electrically.

[0043] Figure 2 a) shows the diameter Dm for the electrode 5 and the diameter Db of the through-hole 20. Figure 2 b) shows that the width S of the gap 30 is always measured at the point where the gap 30 is largest.

[0044] Figure 3 shows the length L1 of the through-hole 20 and the length L2 of the connecting seam 35. The length L1 of the through-hole 20 corresponds to the wall thickness of the component 100 in which the through-hole 20 is formed. Figure 3 clearly shows that the connecting seam 35 does not extend to the inner end 21 of the through-hole 20, but rather ends within the through-hole 20. The ratio of L1 to L2 is not greater than 90% and not less than 10%.

[0045] In Figure 4, the dashed line 36 represents the path of the welding beam, by means of which the connecting seam 35 is created to bridge the gap 30. In one example, the welding beam can be guided in a circular path around the electrode 5. In another example, the welding beam is guided in a wobbling motion around the electrode 5, making it easier to form a connecting seam 35 that reliably bridges even a larger gap 30. The wobbling motion can also be described as a zigzag or serpentine line.

[0046] Figure 5 shows how the distance D is measured from the outer end 22 of the through-bore 20 on the outside of the spark plug 1 and the outer end 52 of the electrode 5. The electrode 5 can either protrude from the through-bore 20 on the outside of the spark plug 1 or end within the through-bore 20.

[0047] Figure 6 shows two examples of a through-hole 20 with two sections 23, 24. The first section 23 is cylindrical, and the electrode 5 is placed therein. The second section 24 is arranged at the outer end 22 of the through-hole 20 and has a larger diameter than the first section 23. The second section 24 can, for example, also have a cylindrical shape, with the transition between the first section 23 and the second section 24 being stepped. Alternatively, the second section 24 can also be conical and have a chamfer.

[0048] Figure 7 shows a spark plug 1 in a half-section. The spark plug 1 has a longitudinal axis X that extends from the end closest to the combustion chamber to the end of the spark plug 1 facing away from the combustion chamber. The spark plug 1 has a housing 2 that has a longitudinal bore parallel to the longitudinal axis X of the spark plug 1. On its outer side, the housing 2 typically has a thread with which the spark plug 1 can be screwed into a cylinder head. Typically, an outer seal 10 is arranged on the outer side of the housing 2, sealing a transition between the housing 2 and the cylinder head.

[0049] The insulator 3 is arranged and secured within the housing 2. The air gap between the housing 2 and the insulator 3 is sealed by an internal seal 11. Arranged in the insulator 3, starting from its end facing away from the combustion chamber, are a connecting bolt 8, a resistance element 7, and a center electrode 4, which are electrically connected to one another. The center electrode 4 typically protrudes from the insulator 3 at the combustion chamber end and, in this example, into the interior of the housing 2.

[0050] In this example, the ground electrode 5 is inserted into a bore 20 formed in the housing wall. The bore 20 is a through-bore that extends from the outside to the inside of the housing 2. The ground electrode 5 is rod-shaped and has an inner end 51 and an outer end 52. The inner end 51 of the ground electrode 5 projects into the interior of the housing. The inner end 51 of the ground electrode 5, together with the center electrode 4, forms the ignition gap 45. In this example, the two electrodes 4, 5 form a radial ignition gap 45. The ground electrode 5 and the center electrode 4 can also be arranged relative to one another such that they form an axial ignition gap. The center electrode 4 and / or the ground electrode 5 can each have a precious metal-containing ignition element 53 at one of their ends delimiting the ignition gap 45.In the case of the ground electrode 5, the ignition element 53 containing precious metal is then arranged at the inner end 51 of the ground electrode 5.

[0051] Not shown here is the prechamber spark plug design, in which the spark plug has a cap at the combustion chamber end of the housing. The through-hole for the electrode can be formed in the housing or in the cap.

Claims

Claims 1 . A method for producing a spark plug with a laterally inserted electrode comprising the following steps: • Providing a spark plug blank with a housing and optionally a cap, wherein a through-bore is formed in the housing or in the optional cap, which through-bore extends from the outside to the inside of the housing or the optional cap, wherein the through-bore is designed to receive an electrode • Inserting an electrode into the through-hole, the electrode having a smaller diameter Dm than the through-hole Db, so that a radial gap S is created between the electrode and the through-hole, • Fastening the electrode in the through-hole by means of a material-to-material connection, characterized in that the radial gap S has a value of at least 0.01 mm and a maximum of 0.5 mm, the value for the radial gap being measured at the greatest distance between the outside of the electrode and the inside of the through-hole, and that when the material-to-material connection is produced, a connecting seam is formed which completely fills the radial gap between the electrode and the through-hole radially to the electrode.

2. Method according to claim 1, characterized in that the through-bore has a length L1 and the connecting seam has a length L2, wherein the lengths L1 and L2 are measured parallel to one another and wherein a ratio of L2 to L1 is not greater than 90% and not less than 10%, in particular not less than 30% or not greater than 70%.

3. Method according to claim 1 or 2, characterized in that the connecting seam is formed, in particular completely, circumferentially around the electrode between the electrode and the through-bore.

4. Method according to one of the preceding claims, characterized in that the spark plug blank has a center electrode and that before fastening the electrode in the through-bore, the electrode distance between the electrode and the center electrode is adjusted.

5. Method according to one of the preceding claims, characterized in that the material-to-material joining method is a welding method, in particular a laser welding method.

6. Method according to claim 5, characterized in that the welding beam is guided around the electrode during the welding process and is guided in a serpentine line or a zigzag line.

7. Spark plug (1) with a longitudinal axis X, comprising • a housing (2), • an insulator (3) arranged within the housing (2) • a central electrode (4) arranged within the insulator (3), • an electrode with a diameter DM as a ground electrode (5), • a through-hole (20) with an outer end, an inner end and a diameter DB, in which the ground electrode (5) is inserted and protrudes from the inner end of the through-hole, and • an ignition gap (45) formed between the ground electrode (5) and the center electrode (4), characterized in that a gap S is formed at the inner end of the through-hole between the through-hole and the ground electrode.

8. Spark plug (1) according to claim 7, characterized in that the gap at the inner end of the through-bore has a width B of less than or equal to 0.25 mm, in particular less than 0.05 mm and at least 0.01 mm.

9. Spark plug (1) according to claim 7 or claim 8, characterized in that at the outer end of the through-bore, the electrode is integrally connected to the spark plug element in which the through-bore is formed by means of a connecting seam, and the connecting seam is formed completely circumferentially around the electrode.

10. Spark plug (1) according to claim 9, characterized in that the connecting seam has a length L2 which extends from the outer end of the through-bore in the direction of the inner end of the through-bore and the connecting seam does not reach as far as the inner end of the through-bore, in particular the through-bore has a length L1 and a ratio of L2 to L1 is not greater than 90% and not less than 10%, in particular not greater than 70% and / or not less than 30%.

11. Spark plug according to one of claims 7 to 10, characterized in that the ground electrode has an outer side which is at a distance D from the outer end of the through-bore, the distance D being not greater than 0.4 mm, in particular not greater than 0.2 mm.

12. Spark plug according to one of claims 7 to 11, characterized in that the through-bore has a first and a second section, the diameter of the through-bore being smaller in the first section than in the second section.

13. Spark plug according to claim 12, characterized in that the second section is arranged at the outer end of the through-bore and the first section is arranged at the inner end of the through-bore, wherein the ground electrode is not arranged in the second section.

14. Spark plug according to claim 13, characterized in that the second section has a conical shape or a cylindrical shape with a step-shaped transition to the first section.

15. Spark plug (1) according to one of the preceding claims 10 to 14, characterized in that the through-bore is formed in the housing or in an optional cap, the length L1 of the through-bore corresponding to the thickness of the housing or the cap.

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