Electrode having elongated ridge or groove, and spark plug having such electrode as ground electrode

Abstract

In an electrode (5) for a spark plug, the electrode (5) has a body (50) and a major axis E, an inner end (51) on which a spark surface is disposed, and an outer end (52) facing away from the inner end, the body (50) having a diameter D G and the electrode (5) has at least one elongated ridge (55) and / or at least one groove (56) on its body (50).

Description

[Technical Field]

[0001] The present invention relates to an electrode for a spark plug, as well as to a spark plug having such an electrode as a ground electrode. [Background technology]

[0002] In recent years, new spark plug concepts have been increasingly pursued in which the spark gap is formed inside the housing. In such concepts, the ground electrode is inserted into a hole in the housing wall and projects laterally from the housing wall into the interior space of the housing. For example, Patent Document 1 discloses a pre-chamber spark plug in which the ground electrode is arranged in a hole in the housing wall and projects laterally into the interior space.

[0003] Ground electrodes inserted laterally into spark plugs present new challenges with regard to the precise alignment of the ground electrode relative to the center electrode, the adjustment of the spark plug, and the secure installation of the electrode in the bore. One possible installation method is to press the ground electrode into the bore. This technique requires extremely high manufacturing precision for each component, on the one hand to ensure that the electrode is pressed securely into the bore throughout the life of the spark plug, and on the other hand to allow for controlled insertion during assembly so that the electrode spacing can be adjusted as precisely as possible. If the required manufacturing precision is not observed, component failures may occur during production. Such high demands on manufacturing precision make the manufacturing process costly and expensive. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] German Patent Application Publication No. 102017221517 Summary of the Invention [Problem to be solved by the invention]

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide an electrode and a spark plug that can reliably assemble a ground electrode correctly, thereby simplifying the manufacturing method. [Means for solving the problem]

[0006] This problem is solved by the electrode and spark plug according to the present invention.

[0007] The electrode for a spark plug according to the invention has a body and a longitudinal axis E extending from the inner end to the outer end of the body and electrode. The sparking face of the electrode is located at the inner end of each of the electrode and body. Accordingly, the inner end faces the spark gap when the electrode is assembled in the spark plug. The outer end is the end of the electrode facing away from the inner end and, accordingly, faces away from the spark gap. The body has a diameter D G The electrode further has at least one elongated ridge and / or groove on its body.

[0008] The at least one elongated ridge or at least one groove provides the advantage of wider manufacturing tolerances and lower manufacturing precision requirements, thereby simplifying the manufacturing method. When the electrode is pressed into the spark plug hole, the electrode, or more precisely, the body with the ridge or groove thereon, can be plastically deformed, so that the electrode can be pressed into the hole sufficiently securely even with relatively low manufacturing precision. If too much force is applied to the electrode during the press-fitting process, the electrode can withstand this force through plastic deformation, and the electrode itself or the hole will not be damaged.

[0009] A groove may also be understood to be an elongated recess. The body may be, for example, cylindrical or conical. For example, the electrode may have a member at the inner end of the body on which the spark surface is formed.

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

[0011] In one development, the body has at least two, three, four or five elongated ridges and / or grooves evenly distributed around the circumference of the body, so that the plastic deformation in the electrode is evenly distributed around the circumference of the body. For example, the electrode has at least two zones around its circumference. In the first zone, the electrode is located at a diameter D of the body. G In the second region of the electrode, the body has a ridge or groove, and accordingly D G Diameter D in the case of a ridge, which is different from R and diameter D in the case of a groove K The first region is longer than the second region when measured around the circumference of the body. There are also a number of second regions depending on the number of ridges and / or grooves. There are an equal number of first regions as there are second regions. As the number of second regions increases, the length of the first regions approaches the length of the second regions. When the number of second regions is at its maximum, the first and second regions are the same length.

[0012] In another development, the at least one ridge and / or the at least one groove extends parallel to the longitudinal axis E of the electrode. Alternatively, the at least one ridge and / or the at least one groove extends at an angle to the longitudinal axis E of the electrode that is greater than 0° and less than 90°, in particular less than 45°, and even more in particular less than 30°. The configuration of the ridges or grooves at an angle to the longitudinal axis E of the electrode results in a slight spiral on the surface of the electrode, which reduces the frictional resistance when the electrode is inserted into the hole.

[0013] In a preferred embodiment, the at least one ridge has a height H relative to the body of the electrode. The diameter D of the body at the outer end G is the diameter D of the circumscribed circle around at least one ridge having the major axis E of the electrode as its center point at the outer end R In particular, the height H and the diameter D of the body GThe ratio is lower than 0.04% and higher than 0.015%, in particular lower than 0.036% and higher than 0.02%. The height H has a value of, for example, lower than 0.05 mm and higher than 0.02 mm, in particular 0.03 mm.

[0014] Additionally, the height of the protuberances can increase from the inner end of the body to the outer end of the body, so that the at least one protuberance can additionally serve as an insertion aid when inserting the electrode into the hole, and can continuously increase the force with which the electrode is inserted into the hole. In this way, the process of inserting the electrode into the hole can be better controlled.

[0015] Additionally or alternatively, the at least one groove may have a depth T relative to the body of the electrode. G is the diameter D of the inscribed circle inside at least one groove having the major axis E of the electrode as its center point at the outer end K is greater than.

[0016] In a preferred embodiment, the body has elongated ridges and grooves arranged on the body in alternating fashion around the circumference of the body, in this example the body no longer necessarily having a first region.

[0017] When the ridges have a triangular shape and the grooves have a notched shape, the arrangement and configuration of the ridges and grooves results in a star-shaped outer end surface of the body, which on the one hand reduces the frictional resistance of the electrode when it is inserted into the hole, and on the other hand allows the ridges to slightly plastically deform to fill the volume of the groove.

[0018] The present invention further relates to a spark plug having a longitudinal axis X. The spark plug comprises a housing, an insulator arranged inside the housing, a center electrode arranged inside the insulator, an electrode according to the present invention as a ground electrode, and a diameter D into which the ground electrode is inserted. Band a spark gap formed between the ground electrode and the center electrode. This spark plug has an advantage that the electrode according to the present invention is used as the ground electrode, thereby enabling the spark plug to be manufactured easily and at low cost.

[0019] In a development of the spark plug, it is contemplated that the ground electrode is inserted into the hole and the at least one ridge and / or the at least one groove are at least partially plastically deformed by the insertion, thereby press-fitting the ground electrode into the hole.

[0020] In one development, the ground electrode is additionally welded in the hole, thereby preventing the ground electrode from accidentally loosening.

[0021] In an alternative embodiment, the spark plug has a cap attached to the combustion chamber end of the housing, the spark plug is a pre-chamber spark plug, and the cap or housing has a hole through which the ground electrode is inserted.

[0022] The spark plug or pre-chamber spark plug has, for example, M10 or M12 threads on the exterior surface of the housing set up for screwing the spark plug or pre-chamber spark plug into the cylinder head.

[0023] The hole is typically a through hole, and in the case of a spark plug, is formed in, for example, the housing. [Brief explanation of the drawings]

[0024] [Figure 1] 1 shows an example of a spark plug and an example of a pre-chamber spark plug, each with an inserted ground electrode. [Figure 2] 1 shows a first example of an electrode according to the present invention. [Figure 3] 2 shows a second example of an electrode according to the present invention. [Figure 4] 3 shows a third example of an electrode according to the present invention. [Figure 5]1 illustrates two steps of a method for manufacturing a spark plug according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] FIG. 1a) shows a spark plug 1 in half cross section. The spark plug 1 has a longitudinal axis X that extends from the end of the spark plug 1 facing the combustion chamber to the end 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. The housing 2 typically has a thread 22 on its outer surface, which allows the spark plug 1 to be screwed into a cylinder head. An outer seal 10 is typically arranged on the outer surface of the housing 2, sealing the transition between the housing 2 and the cylinder head.

[0026] An insulator 3 is disposed and attached inside the housing 2. The gap between the housing 2 and the insulator 3 is sealed by an inner sealant 11. A connecting bolt 8, a resistance member 7, and a center electrode 4, which are electrically connected to one another, are disposed inside the insulator 3, starting from its end facing away from the fuel chamber. The center electrode 4 typically protrudes from the end of the insulator 3 on the combustion chamber side and extends into the interior space of the housing 2 in this example.

[0027] In this example, the ground electrode 5 is inserted into a hole 20 formed in the housing wall. The hole 20 is a through hole that reaches from the outer surface to the inner surface 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 space of the housing. The inner end 51 of the ground electrode 5 forms a spark gap 45 together with the center electrode 4. In this example, these two electrodes 4, 5 form a radial spark gap 45. The ground electrode 5 and the center electrode 4 may also be arranged relative to each other so that they form an axial spark gap.

[0028] The center electrode 4 and / or the ground electrode 5 may each have a noble metal-containing ignition element 53 at the ends that define the spark gap 45. In the ground electrode 5, the noble metal-containing ignition element 53 is disposed at the inner end 51 of the ground electrode 5.

[0029] In an alternative embodiment shown in FIG. 1b), a cap 6 may be arranged on the combustion chamber-side end face of the housing 2. The housing 2 and the cap 6 together form a prechamber having a prechamber volume. A hole 20 for inserting the ground electrode 5 may be formed in the housing wall or in the cap wall.

[0030] 2 and 3 show an embodiment of an electrode according to the invention.

[0031] 2a) shows a first embodiment of an electrode 5 according to the invention in a 3D view. The electrode 5 has a body 50 on which at least two elongated ridges 55 are arranged along its circumference. The elongated ridges 55 extend parallel to the longitudinal axis E of the electrode 5 and of the body 50. The elongated ridges 55 are made of the same material as the body 50 and are formed on the body 50 by corresponding shaping of a body blank. The elongated ridges 55 are formed over at least a partial length of the body 50, and preferably extend over the entire length of the body 50.

[0032] At the inner end 51 of the electrode 5, in this example, an element 53 is arranged which forms the spark surface of the electrode 5. The element 53 may be made of the same material as the body 50 or may be made of another material, for example a precious metal or a precious metal alloy.

[0033] At the outer end 52 of the electrode 5, the elongated ridge 55 has a height H relative to the surface of the body 50. The height H may be constant throughout the length of the ridge 55. Alternatively, the height H may increase continuously from the inner end 51 of the ridge 55 to the outer end 52 of the ridge 55. As yet another option, the ridge 55 may have a first region at its inner end 51 where the height H increases, followed by a second region where the height H is constant. The second region then extends from the first region to the outer end 52 of the ridge 55. In this example, if the electrode 5 has more than one elongated ridge 55, it is preferred that all of the ridges 55 have the same configuration.

[0034] FIG. 2b) shows the outer end surface 52a of the electrode 55, as well as two side views of the electrode 50 in cross section. Both side views show two possible configurations of the elongated ridge 55. In both examples, the elongated ridge 55 extends parallel to the longitudinal axis E. The elongated ridge 55 terminates at the outer end 52 of the electrode 5 and the body 50. In the first example, the elongated ridge 55 has a first region of increasing height H and a second region of constant height H. In the second example, the elongated ridge 55 has only the first region of increasing height H.

[0035] The drawing of the outer end face 52a of the electrode 5 shows the shape that occurs at the end face 52a. R Four elongated ridges 55 having a diameter D and a height H are evenly distributed around the circumference of the body 50. In this example, the electrode 5 has a diameter D at the ridges. R and the body has a diameter D G D R >D G and especially D R =D G +2 * H holds. For example, D G has a value of 1.4 mm, and D R has a value of 1.48 mm.

[0036] As can be seen in the drawing 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 is located at a diameter D G In the second region of the electrode 5, the body 50 has a protuberance 55, and the diameter of the circumscribed circle 55U around at least one protuberance 55 is correspondingly D G Diameter D is different from R When measured around the circumference of the body 55, the first section has a length B G The length of the second region is equal to the width B of the protrusion 55. R is.

[0037] The ridges 55 shown here have a rectangular shape, although other shapes are possible, such as a triangular shape.

[0038] 3 also shows the outer end face 52a of the electrode 5 and two side views of the electrode 5 in cross section for an embodiment of the electrode 5 having grooves 56. The side views show two examples.

[0039] In a first embodiment, groove 56 extends from inner end 51 of body 50 approximately halfway through body 50. Groove 56 has a first region of increasing depth T, a second region of constant depth T, and a third region of decreasing depth T. In this example, outer end surface 52a is 1 / 3 of the diameter D of the body. G or the radius R of the body 50 G is illustrated.

[0040] In a second embodiment, the groove 56 extends from the inner edge 51 of the electrode 5 to the outer edge 52 of the electrode 5. The groove 56 has a first region with an increasing depth T and a second region with a constant depth T. The outer edge 52a of the electrode 5 according to this embodiment corresponds to the view of the outer edge 52a shown here.

[0041] As can be seen in the drawing 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 a diameter D G In the second region of the electrode 5, the body 50 has a diameter D , which is the diameter of the inscribed circle 56I inside the groove 56. G Diameter D is different from K Diameter D K is the diameter D G Smaller than D G =D K +2 * T holds.

[0042] The first section has a length B as measured around the circumference of the body 50. G The length of the second section is equal to the width B of the groove 56. K is.

[0043] The grooves 56 shown here have a rectangular shape, although other shapes are possible, such as a triangular shape.

[0044] 4 shows a cross-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 the bore 20 formed in the housing 2. According to yet another configuration option, the electrode 5 has elongated ridges 55 and grooves 56 in the form of indentations arranged alternately along the circumference of the body 50, so that the outer end face 52a of the electrode 5 has a jagged star shape. During the insertion and press-fit of the electrode 5 into the bore 20, the ridges 55 undergo plastic deformation, narrowing the volume of the grooves 56. This ensures a secure fit of the electrode 5 in the bore 20.

[0045] Figure 5 shows two steps of a method for manufacturing a spark plug 1 according to the invention. In Figure 5a) a spark plug 1 without a ground electrode is provided. Further, an electrode 5 according to the invention is provided and inserted into a hole 20 formed in the housing 2. The hole 20 has a diameter D at its outer end. B It has the following characteristics.

[0046] If the electrode 5 has a protuberance 55, the electrode 5 has a diameter D G and the diameter D at the protrusion 55 R For example, the following relationship holds: D R >D G and D G <D B and / or D R >D B is.

[0047] If the electrode 5 has a groove 56, the electrode 5 has a diameter D G and the diameter D inside the groove 56 K For example, the following relationship holds: D K <D G and D G >D B and / or D K <D B is.

[0048] If the electrode 5 has a ridge 55 and a groove 56, the electrode 5 has a diameter D R and the diameter D in the groove 56 K Here, the following relationship holds: K <D B <D R

[0049] In FIG. 5b), the electrode 5 is assembled in the spark plug 1. The ridges 55 and / or grooves 56 have disappeared at least partially or entirely due to plastic deformation during insertion. In particular, the ridges 55 and grooves 56 are overcome at least in the region of the body 50 that protrudes from the bore 20 into the interior space of the housing 2. Optionally, the ridges 55 and / or grooves 56 may still be visible on the outer end face 52a of the electrode 5. [Explanation of symbols]

[0050] 1 spark plug 2. Housing 3. Insulators 4 Center electrode 5 Ground electrode 6 Caps 20 holes 45 Spark Gap 50 main unit 51 Inner end 52 Outer edge 52a Outer end face 55 Ridge 55U Circumscribed Circle 56 Groove 56I Inscribed Circle E Long axis of ground electrode H Height T Depth D G Body diameter D R circumscribed circle diameter D K Diameter of the inscribed circle X Spark plug long axis

Claims

1. The body (50) has a longitudinal axis E, an inner end (51) at which the spark surface is located, and an outer end (52) facing away from the inner end, the body (50) having a diameter D Ｇ 1. An electrode (5) for a spark plug, characterized in that the electrode (5) has at least one elongated ridge (55) and / or at least one groove (56) on the body (50) of the electrode.

2. 2. The electrode (5) of claim 1, wherein the body (50) has at least two, three, four, or five elongated ridges (55) and / or grooves (56) evenly distributed around the circumference of the body (50).

3. 3. The electrode (5) according to claim 1 or 2, characterized in that at least one of the ridges (55) and / or at least one of the grooves (56) extend parallel to the longitudinal axis E of the electrode (5) or at an angle greater than 0° and less than 90°, in particular less than 45°.

4. At least one of the ridges (56) has a height H relative to the body (50) of the electrode (5) and a diameter D of the body (50) at the outer end (52). Ｇ is the diameter D of a circumscribing circle (55U) around at least one of the protuberances (55) having the major axis E of the electrode (5) as its center point at the outer end (52). Ｒ Electrode (5) according to any one of claims 1 to 3, characterized in that it is smaller than

5. 5. The electrode (5) according to claim 4, characterized in that the height H of the ridge (55) increases in the direction from the inner end (51) of the body (50) to the outer end (52) of the body (50).

6. At least one of the grooves (56) has a depth T with respect to the body (50) of the electrode (5) and a diameter D of the body (50) at the outer end (52). Ｇ is the diameter D of the inscribed circle (56I) inside at least one of the grooves (56) having the major axis E of the electrode (5) as its center point at the outer end (52). Ｋ Electrode (5) according to any one of claims 1 to 5, characterized in that it is greater than

7. 7. The electrode (5) according to any one of claims 1 to 6, characterized in that the elongated ridges (55) and grooves (56) are arranged on the body (50) in an alternating pattern along the circumference of the body (50).

8. 8. The electrode (5) according to claim 7, characterized in that the outer end surface (52a) of the body (50) is star-shaped due to the arrangement and configuration of the ridges (55) and the grooves (56).

9. A spark plug (1) having a major axis X, a housing (2); an insulator (3) disposed inside the housing (2); a central electrode (4) disposed inside the insulator (3); an electrode according to any one of claims 1 to 7 as a ground electrode (5); The ground electrode (5) is inserted into the diameter D Ｂ a hole (20) having a spark gap (45) formed between the ground electrode (5) and the center electrode (4); A spark plug having:

10. 10. The spark plug (1) according to claim 9, characterized in that the ground electrode (5) is inserted into the hole (20) and the at least one ridge (55) and / or the at least one groove (56) are at least partially plastically deformed by the insertion, whereby the ground electrode (5) is press-fit into the hole (20).

11. Spark plug (1) according to claim 9 or 10, characterized in that the ground electrode (5) is welded in the hole (20).

12. 12. The spark plug (1) according to claim 9, wherein the spark plug (1) has a cap (6) attached to an end of the housing (2) on the combustion chamber side, the spark plug (1) is a pre-chamber spark plug, and the hole (20) into which the ground electrode (5) is inserted is formed in the cap (6) or the housing (2).

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