Electrode with elongated elevation or groove, and spark plug comprising such an electrode as a ground electrode
Patent Information
- Application Number
- EP2023828162
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-20
- Filing Date
- 2023-12-11
- Publication Date
- 2025-10-29
AI Technical Summary
The existing manufacturing process for spark plugs with a ground electrode inserted into a housing wall is complex and expensive due to high demands on manufacturing accuracy for correct alignment and reliable fastening, leading to potential component failures if precision is not maintained.
The electrode features an elongated elevation or groove on its base body, allowing for plastic deformation during assembly, which simplifies the manufacturing process and ensures secure attachment with lower precision requirements, reducing frictional resistance and enabling controlled insertion.
This design allows for reliable and cost-effective manufacturing of spark plugs by absorbing assembly forces through plastic deformation, ensuring precise gap settings and preventing component failures, thus simplifying the manufacturing process and reducing costs.
Smart Images
Figure 1.1
Abstract
Description
[0001] Description
[0002] title
[0003] Electrode with elongated elevation or groove and spark plug with such an electrode as ground electrode
[0004] State of the art
[0005] The invention relates to an electrode for a spark plug and a spark plug with such an electrode as a ground electrode.
[0006] For some time now, new spark plug designs have been increasingly pursued in which the ignition gap is formed within the housing. In one of these designs, the ground electrode is inserted into a hole in the housing wall and protrudes laterally from the housing wall into the interior of the housing. For example, DE 10 2017 221 517 A discloses a prechamber spark plug in which the ground electrode is located in a hole in the housing wall and protrudes laterally into the interior.
[0007] When a ground electrode is inserted laterally into the spark plug, new challenges arise with regard to the correct alignment of the ground electrode to the center electrode and adjustment of the ignition gap, as well as reliable fastening of the electrode in the bore. One possible fastening method is to press the ground electrode into the bore. This technology requires very high manufacturing precision of the components to ensure that the electrode is pressed sufficiently firmly into the bore for the service life of the spark plug and can be inserted in a controlled manner during assembly, allowing the electrode gap to be adjusted as precisely as possible. Failure to maintain the necessary manufacturing precision can lead to component failures during production. These high demands on manufacturing precision make the manufacturing process complex and expensive.It is the object of the present invention to provide an electrode and a spark plug in which a reliably correct assembly of the ground electrode is enabled, so that the manufacturing process is simplified.
[0008] Advantage of the invention / Disclosure of the invention
[0009] This problem is solved by the electrode and spark plug according to the invention.
[0010] The electrode according to the invention for a spark plug has a base body and a longitudinal axis E that extends from an inner end to an outer end of the base body and the electrode. The ignition surface of the electrode is arranged at the inner end of the electrode and the base body. Accordingly, the inner end faces an ignition gap when the electrode is mounted in a spark plug. The outer end is the end of the electrode opposite the inner end and accordingly faces away from an ignition gap. The base body has a diameter DG. Furthermore, the electrode has at least one elongated elevation and / or a groove on its base body.
[0011] The at least one elongated elevation or at least one groove has the advantage that the manufacturing tolerance increases and the requirement for manufacturing accuracy decreases, thus simplifying the manufacturing process. When the electrode is pressed into a bore on a spark plug, the electrode can undergo plastic deformation; more precisely, the elevation on the base body or the base body with the groove can undergo plastic deformation, so that even with lower manufacturing accuracy, the electrode can be pressed sufficiently firmly into the bore. If excessive force is applied to the electrode during the pressing-in process, this force can be absorbed in the electrode by plastic deformation without damaging the electrode itself or the bore.
[0012] The groove can also be understood as an elongated recess. The base body is, for example, cylindrical or conical. For example, the electrode can have an element at the inner end of the base body on which an ignition surface is formed.
[0013] Advantageous developments of the invention are the subject of the dependent claims. In one development, the base body has at least two or three or four or five elongated elevations and / or grooves which are arranged evenly along the circumference of the base body. This results in the plastic deformation on the electrode being evenly distributed over the circumference of the base body. For example, the electrode has at least two sections along its circumference. In the first section, the electrode has the diameter DG of the base body. In the second section of the electrode, the base body has an elevation or a groove and a diameter DR which differs accordingly from DG in the case of an elevation and DK in the case of a groove. Measured along the circumference of the base body, the first section is longer than the second section. According to the number of elevations and / or grooves, there are also second sections. There are the same number of first sections as second sections.As the number of second sections increases, the length of the first sections approaches the length of the second section. At the maximum number of second sections, the first and second sections are equal in length.
[0014] In a further development, the at least one elevation and / or the at least one groove extend parallel to a longitudinal axis E of the electrode. Alternatively, the at least one elevation and / or the at least one groove extend at an angle of greater than 0° and less than 90°, in particular less than 45° and further in particular less than 30°, to the longitudinal axis E of the electrode. The formation of the elevation or the groove at an angle to the longitudinal axis E of the electrode results in a slight spiral on the surface of the electrode, thereby reducing the frictional resistance when the electrode is inserted into the bore.
[0015] In an advantageous embodiment, the at least one elevation has a height H relative to the base body of the electrode. The diameter DG of the base body at its outer end is smaller than the diameter D of a circumcircle around the at least one elevation with the longitudinal axis E of the electrode as the center point at the outer end. In particular, the ratio of height H to diameter DG of the base body is less than 0.04% and greater than 0.015%, in particular less than 0.036% and greater than 0.02%. The height H has, for example, a value of less than 0.05 mm and greater than 0.02 mm, in particular 0.03 mm.
[0016] Additionally, the height H of the protrusion can increase from the inner end of the base body toward the outer end. This allows at least one protrusion to serve as an insertion aid when the electrode is inserted into the hole, and the force with which the electrode is inserted into the hole can be continuously increased. The process of inserting the electrode into the hole is thus more controllable.
[0017] Additionally or alternatively, the at least one groove can have a depth T relative to the base body of the electrode. The diameter DG of the base body at its outer end is greater than the diameter DK of an inner circle within the at least one groove with the longitudinal axis E of the electrode as the center point at the outer end.
[0018] In an advantageous embodiment, the base body has elongated elevations and grooves arranged alternately along the circumference of the base body. In this example, the base body no longer necessarily has a first section.
[0019] If the protrusions are triangular and the grooves are notched, the arrangement and design of the protrusions and grooves results in the outer face of the base body being star-shaped. This reduces the frictional resistance of the electrode when inserting it into a hole. Furthermore, the protrusions can easily deform plastically and fill the volume of the grooves.
[0020] The invention further relates to a spark plug with a longitudinal axis X. The spark plug comprises a housing, an insulator arranged within the housing, a center electrode arranged within the insulator, an electrode according to the invention as a ground electrode, a bore with a diameter DB into which the ground electrode is inserted, and an ignition gap formed between the ground electrode and the center electrode. The spark plug has the advantage that the use of the electrode according to the invention as the ground electrode allows for easy and cost-effective production.
[0021] In a further development of the spark plug, it is provided that the ground electrode is inserted into the bore and the at least one elevation and / or at least one groove are at least partially plastically deformed by the insertion, so that the ground electrode is pressed into the bore.
[0022] In a further development, the ground electrode is additionally welded in the bore.
[0023] This prevents the ground electrode from becoming accidentally loose. In an alternative embodiment, the spark plug has a cap attached to the combustion chamber end of the housing. The spark plug is a prechamber spark plug, with the hole into which the ground electrode is inserted formed on the cap or the housing.
[0024] The spark plug or the pre-chamber spark plugs, for example, have an M10 or M12 thread on the outside of the housing, which is designed to screw the spark plug or the pre-chamber spark plug into a cylinder head.
[0025] The hole is typically a through hole and can be formed on the housing of the spark plug, for example.
[0026] drawing
[0027] Figure 1 shows an example of a spark plug and an example of a pre-chamber spark plug, each with an inserted ground electrode
[0028] Figure 2 shows a first example of the electrode according to the invention
[0029] Figure 3 shows a second example of the electrode according to the invention
[0030] Figure 4 shows a third example of the electrode according to the invention
[0031] Figure 5 shows two steps of a manufacturing process for a spark plug according to the invention.
[0032] Description of the embodiment
[0033] Figure 1a) 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 22 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 and seals a transition between the housing 2 and the cylinder head.
[0034] The insulator 3 is arranged and secured within the housing 2. The gap between the housing 2 and the insulator s is sealed by an internal seal 11. Arranged within 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.
[0035] In this example, the ground electrode 5 is inserted into a bore 20 formed in the housing wall. The bore 20 is a through-hole 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.
[0036] 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 precious metal-containing ignition element 53 is then arranged at the inner end 51 of the ground electrode 5.
[0037] In an alternative embodiment, shown in Figure 1 b), a cap 6 can be arranged on the housing 2 on its combustion chamber-side end face. The housing 2 and the cap 6 together form a prechamber with a prechamber volume. The bore 20, into which the ground electrode 5 is inserted, can be formed in a housing wall or in a cap wall.
[0038] Figures 2 and 3 show exemplary embodiments of the electrode according to the invention. Figure 2 a) shows a 3D view of a first exemplary embodiment of an electrode 5 according to the invention. The electrode 5 has a base body 50, on which at least two elongated elevations 55 are arranged along its circumference. The elongated elevations 55 run parallel to the longitudinal axis E of the electrode 5 and the base body 50. The elongated elevations 55 are made of the same material as the base body 50 and are formed on the base body 50 by appropriately forming a base body blank. The elongated elevations 55 are formed over at least a partial length of the base body 50. Preferably, they extend over the entire length of the base body 50.
[0039] In this example, an element 53 is arranged at the inner end 51 of the electrode 5, forming the ignition surface of the electrode 5. The element 53 can be made of the same material as the base body 50 or of a different material, for example, a precious metal or a precious metal alloy.
[0040] At the outer end 52 of the electrode 5, the elongated elevation 55 has a height H relative to the surface of the base body 50. The height H can be constant over the entire length of the elevation 55. Alternatively, the height H can increase continuously from the inner end 51 of the elevation 55 to the outer end 52 of the elevation 55. In another alternative, the elevation 55 can have a first region at its inner end 51, at which the height H increases and to which a second region with a constant height H adjoins. The second region then extends from the first region to the outer end 52 of the elevation 55. If, as in this example, the electrode 5 has more than one elongated elevation 55, all elevations 55 are preferably designed the same.
[0041] Figure 2 b) shows a section of the outer end face 52a of the electrode 55 and two side views of the electrode 5. The two side views show two possible configurations for the elongated elevation 55. In both examples, the elongated elevation 55 extends parallel to the longitudinal axis E. The elongated elevation 55 ends at the outer end 52 of the electrode 5 and the base body 50. In the first example, the elongated elevation 55 has a first region with an increasing height H and a second region with a constant height H. In the second example, the elongated elevation 55 has only a first region with an increasing height H.
[0042] The illustration of the outer end face 52a of the electrode 5 shows the resulting shape of the end face 52a. In this example, four elongated elevations 55 with a width BR and a height H are arranged evenly along the circumference of the base body 50. In this example, the electrode 5 has a diameter DR at the elevations and a diameter DG at the base body. D > DG and, in particular, D = DG+2*H. For example, DG has a value of 1.4 mm and D a value of 1.48 mm.
[0043] As can be seen in the illustration of the outer end face 52a of the electrode 5, the electrode 5 has at least two sections along its circumference. In the first section, the electrode 5 has the diameter DG of the base body 50. In the second section of the electrode 5, the base body 50 has a protrusion 55 and a diameter DR that differs accordingly from DG, which is the diameter of a circumference 55U around the at least one protrusion 55. Measured along the circumference of the base body 55, the first section, with its length BG, is longer than the second section. The length of the second section is the width BR of the protrusion 55.
[0044] The elevations 55 shown here are rectangular. Other shapes, such as triangular ones, are also possible.
[0045] Figure 3 also shows the outer end face 52a of the electrode 5 as well as two side views of the electrode 5 in section for a design of the electrode 5 with grooves 56. The side view shows two exemplary embodiments.
[0046] In the first embodiment, the groove 56 extends from the inner end 51 of the base body 50 to approximately half of the base body 50. The groove 56 has a first region in which the depth T increases, a second region with a constant depth T, and a third region in which the depth T decreases. In this example, the outer end face 52a has the diameter DG of the base body, or the radius RG of the base body 50 is shown.
[0047] In the second embodiment, the groove 56 extends from the inner end 51 of the electrode 5 to the outer end 52 of the electrode 5. The groove 56 has a first region in which the depth T increases and a second region with a constant depth T. The outer end face 52a of the electrode 5 according to this example corresponds to the representation of the outer end face 52a shown here.
[0048] As can be seen in the illustration of the outer end face 52a of the electrode 5, the
[0049] Electrode 5 has at least two sections along its circumference. In the first section, electrode 5 has the diameter DG of the base body. In the second section of electrode 5, base body 50 has a groove and a diameter DK that differs from DG, which is the diameter of an inner circle 561 within groove 56. Diameter DK is smaller than diameter DG, in particular, DG = DK + 2 * T.
[0050] Measured along the circumference of the base body 50, the first section, with its length BG, is longer than the second section. The length of the second section is the width BK of the groove 56.
[0051] The grooves 56 shown here are rectangular. Other shapes, such as triangular ones, are also possible.
[0052] Figure 4 shows a sectional view of the combustion chamber-side end region of a spark plug 1 according to the invention. The electrode 5 is partially inserted into a bore 20 formed in the housing 2. According to a further embodiment, the electrode 5 has elongated elevations 55 and grooves 56 in the form of notches, which are arranged alternately along the circumference of the base body 50, so that the outer end face 52a of the electrode 5 has the shape of a multi-pointed star. During the insertion and pressing of the electrode 5 into the bore 20, the elevations 55 plastically deform and reduce the volume of the grooves 56. This results in a secure fastening of the electrode 5 in the bore 20.
[0053] Figure 5 shows two steps of a manufacturing method for a spark plug 1 according to the invention. In Figure 5 a), a spark plug 1 is provided without a ground electrode. Furthermore, an electrode 5 according to the invention is provided, which is inserted into the bore 20 formed in the housing 2. The bore 20 has a diameter DB at its outer end.
[0054] If the electrode has 5 elevations 55, then the electrode 5 has a diameter DG at the base body 50 and a diameter DR at the elevations 55. For example, the relationship that D > DG,
[0055] DG < DB and / or DR > DB. If the electrode has 5 grooves 56, then the electrode 5 has a diameter DG at the base body 50 and a diameter DK within the grooves 56. For example, the relationship that
[0056] DK < DG, DG > DB and / or
[0057] DK < DB.
[0058] If the electrode 5 has elevations 55 and grooves 56, then the electrode 5 has a diameter DR for the elevations 55 and a diameter DK in the grooves 56. The following relationship then applies: DK < DB < D .
[0059] In Figure 5 b), the electrode 5 is mounted in the spark plug 1. The elevations 55 and / or grooves 56 have at least partially or completely disappeared due to the plastic deformation during insertion. In particular, the elevations 55 and the grooves 56 are twisted on at least the area of the base body 50 that protrudes from the bore 20 into the interior of the housing 2. Elevations 55 and / or grooves 56 may still be visible on the outer end face 52a of the electrode 5.
Claims
Claims 1 . Electrode (5) for a spark plug with a base body (50) and a longitudinal axis E and an inner end (51) on which an ignition surface is arranged, and an outer end (52) opposite the inner end, wherein the base body (50) has a diameter DG, characterized in that the electrode (5) has at least one elongated elevation (55) and / or at least one groove (56) on its base body (50).
2. Electrode (5) according to claim 1, characterized in that the base body (50) has at least two or three or four or five elongated elevations (55) and / or grooves (56) which are arranged uniformly along the circumference of the base body (50).
3. Electrode (5) according to claim 1 or 2, characterized in that - the at least one elevation (55) and / or the at least one groove (56) extends parallel or at an angle of greater than 0° and less than 90°, in particular less than 45°, to a longitudinal axis E of the electrode (5).
4. Electrode (5) according to one of the preceding claims, characterized in that the at least one elevation (56) has a height H with respect to the base body (50) of the electrode (5), and in that the diameter DG of the base body (50) at its outer end (52) is smaller than the diameter DR of a circumcircle (55U) around the at least one elevation (55) with the longitudinal axis E of the electrode (5) as the center point at the outer end (52).
5. Electrode (5) according to claim 4, characterized in that the height H of the elevation (55) increases from the inner end (51) of the base body (50) towards the outer end (52) of the base body (50).
6. Electrode (5) according to one of the preceding claims, characterized in that the at least one groove (56) has a depth T in relation to the base body (50) of the electrode (5), and in that the diameter DG of the base body (50) at its outer end (52) is greater than the diameter DK of an inner circle (56I) within the at least one groove (56) with the longitudinal axis E of the electrode (5) as the center point at the outer end (52).
7. Electrode (5) according to one of the preceding claims, characterized in that the elongated elevations (55) and grooves (56) are arranged alternately on the base body (50) along the circumference of the base body (50).
8. Electrode (5) according to claim 7, characterized in that due to the arrangement and design of the elevations (55) and the grooves (56), the outer end face (52a) of the base body (50) is star-shaped.
9. 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 according to one of claims 1 to 7 as a ground electrode (5), • a hole (20) with a diameter DB, in which the ground electrode (5) is inserted, and • an ignition gap (45) formed between the ground electrode (5) and the center electrode (4), 10. Spark plug (1) according to claim 9, characterized in that the ground electrode (5) is inserted into the bore (20) and the at least one elevation (55) and / or at least one groove (56) are at least partially plastically deformed by the insertion, so that the ground electrode (5) is pressed into the bore (20).
11. Spark plug (1) according to one of the preceding claims 9 to 10, characterized in that the ground electrode (5) is welded in the bore (20).
12. Spark plug (1) according to one of the preceding claims 9 to 11, characterized in that the spark plug (1) has a cap (6) which is fastened to the combustion chamber end of the housing (2) and the spark plug (1) is a pre-chamber spark plug, the bore (20) into which the ground electrode (5) is inserted being formed on the cap (6) or on the housing (2).