Manufacturing process for a pre-chamber spark plug with a conical end face on the housing or cap

Abstract

Manufacturing method for a pre-chamber spark plug (1) with a longitudinal axis X, wherein the pre-chamber spark plug (1) has a housing (2) with a combustion chamber-side end face (20) and a cap (6) with an end face (60) facing the housing (2), wherein at least one of the two end faces (20, 60) is angled to a plane E perpendicular to the longitudinal direction X, comprising the method steps: • Placing the cap (6) with its end face (60) on the end face (20) of the housing (2), so that a contact surface (26) is formed at least partially between the end faces (20, 0), • Material connection of the cap (6) and the housing (2) at the contact surface (26) by welding. and prechamber spark plug

Description

State of the art

[0001] The present invention relates to a manufacturing method for pre-chamber spark plugs having at least one end face angled to a plane E on the housing or on the cap, as well as a pre-chamber spark plug.

[0002] Pre-chamber spark plugs are known in various designs from the prior art. Pre-chamber spark plugs typically have a cap defining a pre-chamber, with the cap having so-called cap holes that establish a connection between the pre-chamber and a combustion chamber of an internal combustion engine. The cap is arranged on the end face of the housing facing the combustion chamber. There are various designs for the common contact surface between the housing and cap, such as a stepped contact surface, which offers the advantage of a large contact surface, or a so-called butt-to-butt contact surface, in which the cap and the housing have a flat end face that is typically perpendicular to the longitudinal axis of the pre-chamber spark plug. The butt-to-butt contact surface has the advantage of being easy to manufacture.However, the challenge of placing and attaching the cap to the housing is that the cap can easily slip during this process. This challenge does not exist with a pre-chamber spark plug with a stepped contact surface between the housing and cap.

[0003] Typically, the cap and housing are joined together by welding, with a weld being formed at the contact surface between the cap and housing. With a stepped contact surface, the weld is typically formed perpendicular to the section of the stepped contact surface that runs parallel to the longitudinal axis of the pre-chamber spark plug. With a butt-to-butt contact surface, this is typically perpendicular to the longitudinal axis of the pre-chamber spark plug, and the weld is also typically formed perpendicular to the longitudinal axis of the pre-chamber spark plug. The welding beam is directed onto the cap, the housing, and the small gap between the cap and the housing to form the weld. This small gap occurs because the cap and housing may have small dimensional tolerances during the manufacturing process. These tolerances are compensated for during the material-to-material connection.However, due to this small gap, there is a risk that the welding beam, weld material, or splashes during welding could enter the interior of the pre-chamber spark plug and contaminate the interior or other components within it. Accordingly, with a butt-to-butt contact surface, there is a great need to closely control the welding process to prevent contamination while still achieving a good and robust weld between the housing and cap.

[0004] It is an object of the invention to provide a manufacturing method for a pre-chamber spark plug with a butt-to-butt contact surface, in which the cap can be easily attached to the housing and at the same time there is a stable and robust connection. Disclosure of the invention

[0005] The problem is solved by the method according to the invention.

[0006] The manufacturing method according to the invention is for a prechamber spark plug. The prechamber spark plug has a longitudinal axis X, a housing with an end face facing the combustion chamber, and a cap with an end face facing the housing. The two end faces together form the contact surface between the housing and the cap. This contact surface lies at least partially in an imaginary plane E that is perpendicular to the longitudinal axis X of the prechamber spark plug. According to the invention, at least one of the end faces of the cap or the housing is angled to the plane E. The manufacturing method comprises the following process steps: • Placing the cap with its end face on the end face of the housing so that a contact surface is formed at least partially between the end faces and • Material connection of the cap and the housing at the contact surface by welding.

[0007] According to the invention, at least one of the end faces of the cap or of the housing is angled to the imaginary plane E, in particular before the welded joint is formed. In this case, the inside or the outside of the end face can be closer to the combustion chamber in the axial direction of the longitudinal axis of the pre-chamber ignition than the other side, accordingly resulting in a gap on the inside of the contact surface or on the outside of the contact surface. The contact surface is referred to as a concave contact surface if the at least one angled end face is angled in such a way that the gap is formed on the inside of the contact surface. Accordingly, the contact surface is referred to as a convex contact surface if the at least one angled end face is angled in such a way that the gap is formed on the outside of the contact surface.

[0008] This reduces residual welding stress and pore formation in the weld structure, i.e., the weld seam. This leads to a reduced susceptibility to cracking of the weld seam and increased thermal robustness of the weld seam, thus extending the service life of the prechamber spark plug. This also expands the application range for the prechamber spark plug. Furthermore, this modification of the component geometry reduces the risk of weld spatter in the interior of the prechamber spark plug, thus lessening the requirements for the welding process and expanding the window for process parameters.

[0009] In particular, a concave contact surface has the advantage of reducing residual welding stress and porosity in the weld seam. The weld seam is formed from the outside in. The selected geometry of the end face, with at least one angled end face and the resulting gap on the inside of the contact surface, means that the weld structure has space through the gap toward the interior to expand during the welding process, thereby reducing residual stress or preventing it from building up in the first place.

[0010] In particular, a convex contact surface has the advantage of preventing weld spatter from accumulating inside the chamber. The weld seam is formed from the outside in. Due to the selected geometry of the end face, with at least one angled end face and the resulting gap on the outside of the contact surface, the component with the angled end face represents an obstacle to weld spatter, similar to a stepped contact surface, preventing it from traveling along the contact surface into the interior of the prechamber spark plug.

[0011] In an optional process step, the cap is pressed against the housing during the formation of the material bond between the cap and the housing, increasing the contact area. This reduces any possible gap between the cap and the housing.

[0012] In an advantageous design, the weld seam at the contact surface does not extend to the inside of the cap and / or housing. The weld seam ends within the contact surface or in the wall of the cap or housing. This measure reduces the risk of weld spatter in the interior.

[0013] In an advantageous embodiment of the invention, the angled end face has an angle α to plane E. The angle α is greater than 0° and less than or equal to 30°. In particular, the angle α is less than or equal to 15°. This has the advantage that, on the one hand, the technical advantages described above are achieved and, on the other hand, the advantages of an end-to-end contact surface are still retained. If the angle α is too large, the advantages of an end-to-end contact surface are increasingly lost. A larger gap also results at the contact surface between the cap and housing if the two end faces have too great a difference in their alignment to one another and to plane E. This gap must be at least partially bridged by the weld seam.

[0014] In a further development, the end face angled to plane E has a conical shape along the longitudinal axis towards the combustion chamber end of the pre-chamber spark plug, whereby the shape can narrow conically or widen conically. The shape is viewed in a section of the end face parallel to the longitudinal axis. Looking towards the combustion chamber, the end face narrows conically or widens conically. The end face of the housing is conically narrowed when the inside of the end face is closer to the combustion chamber than the outside of the end face. Correspondingly, the end face of the housing is conically widened when the outside of the end face is closer to the combustion chamber than the inside of the end face. The end face of the cap is conically narrowed when the inside of the end face is closer to the combustion chamber than the outside of the end face.Accordingly, the end face of the cap is conically widened if the outside of the end face is closer to the combustion chamber than the inside of the end face.

[0015] In one embodiment, the end face of the cap and the end face of the housing are each an end face angled to plane E.

[0016] The end face of the cap and the end face of the housing can be angled in different directions relative to plane E. This deliberately creates a gap with increasing distance between the cap and the housing, with the gap being greatest on the inside or outside of the contact surface, depending on the angle of the end faces. The gap is open either towards the inside or the outside.

[0017] Alternatively, the end face of the cap and the end face of the housing can be angled in the same direction to plane E. This has the advantage that the cap and the housing are self-centering and reduces the risk of the cap and the housing slipping relative to each other during the formation of the weld seam.

[0018] The invention also relates to a prechamber spark plug, which is produced in particular using the method according to the invention. The prechamber spark plug according to the invention has a longitudinal axis X and comprises a housing with a combustion chamber-side end face and a cap with an end face facing the housing, which is arranged at the combustion chamber-side end of the housing, wherein at least one of the two end faces is angled to a plane E perpendicular to the longitudinal direction X, and wherein a weld seam is formed at least partially on the contact surface between the cap and the housing.

[0019] This pre-chamber spark plug is easy to manufacture and has a robust cap-to-body connection.

[0020] According to the invention, at least one of the two end faces of the cap or the housing is angled to the imaginary plane E. In this case, the inside or the outside of the end face can be closer to the combustion chamber in the axial direction of the longitudinal axis of the pre-chamber ignition than the other side, accordingly resulting in a gap on the inside of the contact surface or on the outside of the contact surface. The contact surface is referred to as a concave contact surface if the at least one angled end face is angled in such a way that the gap forms on the inside of the contact surface. Accordingly, the contact surface is referred to as a convex contact surface if the at least one angled end face is angled in such a way that the gap forms on the outside of the contact surface.

[0021] This reduces residual welding stress and pore formation in the weld structure, i.e., the weld seam. This leads to a reduced susceptibility to cracking of the weld seam and increased thermal robustness of the weld seam, thus extending the service life of the prechamber spark plug. This also expands the application range for the prechamber spark plug. Furthermore, this modification of the component geometry reduces the risk of weld spatter in the interior of the prechamber spark plug, thus lessening the requirements for the welding process and expanding the window for process parameters.

[0022] In particular, a concave contact surface has the advantage of reducing residual welding stress and porosity in the weld seam. The weld seam is formed from the outside in. The selected geometry of the end face, with at least one angled end face and the resulting gap on the inside of the contact surface, means that the weld structure has space through the gap toward the interior to expand during the welding process, thereby reducing residual stress or preventing it from building up in the first place.

[0023] In particular, a convex contact surface has the advantage of preventing weld spatter from accumulating inside the chamber. The weld seam is formed from the outside in. Due to the selected geometry of the end face, with at least one angled end face and the resulting gap on the outside of the contact surface, the component with the angled end face represents an obstacle to weld spatter, similar to a stepped contact surface, preventing it from traveling along the contact surface into the interior of the prechamber spark plug.

[0024] In an advantageous embodiment of the invention, the angled end face has an angle α to plane E. The angle α is greater than 0° and less than or equal to 30°. In particular, the angle α is less than or equal to 15°. This has the advantage that, on the one hand, the technical advantages described above are achieved and, on the other hand, the advantages of an end-to-end contact surface are still retained. If the angle α is too large, the advantages of an end-to-end contact surface are increasingly lost. A larger gap also results at the contact surface between the cap and housing if the two end faces have too great a difference in their alignment to one another and to plane E. This gap must be at least partially bridged by the weld seam.

[0025] In a further development, the end face angled to plane E has a conical shape along the longitudinal axis towards the combustion chamber end of the pre-chamber spark plug, whereby the shape can narrow conically or widen conically. The shape is viewed in a section of the end face parallel to the longitudinal axis. Looking towards the combustion chamber, the end face narrows conically or widens conically. The end face of the housing is conically narrowed when the inside of the end face is closer to the combustion chamber than the outside of the end face. Correspondingly, the end face of the housing is conically widened when the outside of the end face is closer to the combustion chamber than the inside of the end face. The end face of the cap is conically narrowed when the inside of the end face is closer to the combustion chamber than the outside of the end face.Accordingly, the end face of the cap is conically widened if the outside of the end face is closer to the combustion chamber than the inside of the end face.

[0026] In one embodiment, the end face of the cap and the end face of the housing are each an end face angled to plane E.

[0027] The end face of the cap and the end face of the housing can be angled in different directions relative to plane E. This deliberately creates a gap with increasing distance between the cap and the housing, with the gap being greatest on the inside or outside of the contact surface, depending on the angle of the end faces. The gap is open either towards the inside or the outside.

[0028] Alternatively, the end face of the cap and the end face of the housing can be angled in the same direction to plane E. This has the advantage that the cap and the housing are self-centering and reduces the risk of the cap and the housing slipping relative to each other during the formation of the weld seam.

[0029] The angled end face and the weld seam are always formed along the circumference of the pre-chamber spark plug, the end face, or the contact surface. Short description of the drawings

[0030] Embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing: Fig. 1 a schematic view of a pre-chamber spark plug according to the invention, Fig. 2 a schematic partial sectional view of the end faces of the cap and the housing according to a first embodiment in three variants, Fig. 3 a schematic partial sectional view of the end faces of the cap and the housing according to a second embodiment in three variants Fig. 4 a schematic partial sectional view of the end faces of the cap and the housing according to a third embodiment in two variants Fig. 5 shows schematically the manufacturing process according to the invention Preferred embodiments of the invention

[0031] Fig. Figure 1 schematically shows the prechamber spark plug 1 according to the invention. The prechamber spark plug 1 has a housing 2 and an insulator 3 arranged at least partially in the housing 2. A center electrode 4 is arranged in the insulator 3 and protrudes from the insulator 3 at the combustion chamber end. In these examples, the housing 2 has a bore in its housing wall. A ground electrode 5 is arranged in this bore. The housing 2 has a thread 22 on its outside, which is designed to screw the prechamber spark plug 1 into a cylinder head.

[0032] The housing 2 has an end face 20 facing the combustion chamber. A cap 6 is arranged and fastened to this end face 20. The cap 6 has an end face 60 facing the housing 2. The end face 60 of the cap 6 and the end face 20 of the housing 2 together form the contact surface 26 between the cap 6 and the housing 2. In the prechamber spark plug 1 according to the invention, the contact surface 26 is a butt-to-butt contact surface. This means that the two end faces 20, 60 forming the contact surface 26 are flat and not stepped. A weld seam is formed on the contact surface 26, which firmly connects the cap 6 and the housing 2. The weld seam does not extend to the inner side 6b, 2b of the cap or the housing, but ends within the contact surface 26.

[0033] In the Fig. Figures 2 to 4 show three examples of the design of the end faces 20, 60. The cap 6 and the housing 2 are shown slightly spaced apart from each other so that the respective end faces 20, 60 can be better represented.

[0034] In part a) of the Fig. Figure 2 shows an enlarged view of the area around the end faces 20, 60 of the cap 6 and the housing 2, wherein the end face(s) 20, 60 are each angled to plane E such that a gap 62 forms on the inner side 2b, 6b of the cap 6 or the housing 2. This is the concave configuration of the end faces 20, 60.

[0035] Parts b), c) and d) show the three possible variants for this concave design of the end face 20, 60.

[0036] The presentation in part b) corresponds to the presentation in part a) of the Fig. 2. Both end faces 20, 60 form an angle α to plane E, with the end faces 20, 60 being angled in different directions to plane E. If plane E is drawn through the outermost point of the outer side 20a, 60a of the respective end face 20, 60, then the end face 60 of the cap 6 is angled from plane E towards the combustion chamber, and the end face 20 of the housing 2 is angled in the opposite direction. The outer side 20a of the end face 20 of the housing 2 is axially closer to the combustion chamber than the inner side 20b of the end face 20. In section, the end face 20 on the housing 2 has a conical shape that widens towards the combustion chamber. The inner side 60b of the end face 60 of the cap 6 is axially closer to the combustion chamber than the outer side 60a of this end face 60. In section, the end face 60 on the cap 6 has a conical shape that narrows.

[0037] In part c) of the Fig. 2, only the end face 60 of the cap 6 has an angle α to the plane E. The end face 20 of the housing 2 is parallel to the plane E.

[0038] In part d) of the Fig. 2, only the end face 20 of the housing 2 has an angle α to the plane E. The end face 60 of the cap 6 is parallel to the plane E.

[0039] In part a) of the Fig. Figure 3 shows an enlarged view of the area around the end faces 20, 60 of the cap 6 and the housing 2, wherein the end face(s) 20, 60 are each angled to the plane E such that a gap 62 forms on the outer side 2a, 6a of the cap 6 or the housing 2. This is the convex configuration of the end faces 20, 60.

[0040] Parts b), c) and d) show the three possible variants for this convex design of the front surface 20, 60.

[0041] The presentation in part b) corresponds to the presentation in part a) of the Fig. 3. Both end faces 20, 60 have an angle α to plane E, with the end faces 20, 60 being angled in different directions to plane E. If plane E is placed through the outermost point of the outer side 20a, 60a of the respective end face 20, 60, then the end face 20 of the housing 2 is angled from plane E towards the combustion chamber, and the end face 60 of the cap 6 is angled in the opposite direction. The inner side 20b of the end face 20 of the housing 2 is axially closer to the combustion chamber than the outer side 20a of the end face 20. In section, the end face 20 on the housing 2 has a conical shape that narrows towards the combustion chamber. The outer side 60a of the end face 60 of the cap 6 is axially closer to the combustion chamber than the inner side 60b of this end face 60. In section, the end face 60 on the cap 6 has a conical shape that widens.

[0042] In part c) of the Fig. 3, only the end face 20 of the housing 2 has an angle α to the plane E. The end face 60 of the cap 6 is parallel to the plane E.

[0043] In part d) of the Fig. 3, only the end face 60 of the cap 6 has an angle α to the plane E. The end face 20 of the housing 2 is parallel to the plane E.

[0044] In Fig. 4 shows two variants for a third design of the end faces 20, 60. Both end faces 20, 60 have an angle α to the plane E, whereby the end faces 20, 60 are angled in the same direction to the plane E. This results in the end faces 20, 60 having a conical shape in section, which is as in Fig. 4 a) extended or as in Fig. 4 b). Both variants of the third design have the advantage that the cap 6 centers itself on the housing 2.

[0045] In Fig.Figure 5 shows a schematic representation of the manufacturing process. In the first step S1, the cap is placed with its end face against the end face of the housing so that a contact surface is formed at least partially between the two end faces. In the second, optional step S2, the cap is pressed against the housing to prevent the cap from slipping. In the third step S3, the material connection between the cap and housing is formed by welding. This creates a weld seam at the contact surface between the cap and housing, although the weld seam does not extend to the inside of the cap and the housing.

[0046] At the portion of the contact surface 26 where the weld seam is not formed, it can be seen on the end face 20, 60 of the cap 6 and / or the housing 2, even after the end of the manufacturing process, that at least one end face 20, 60 has an angle α to the plane E.

Claims

[1] Manufacturing method for a pre-chamber spark plug (1) with a longitudinal axis X, wherein the pre-chamber spark plug (1) has a housing (2) with a combustion chamber-side end face (20) and a cap (6) with an end face (60) facing the housing (2), wherein at least one of the two end faces (20, 60) is angled to a plane E perpendicular to the longitudinal direction X, comprising the method steps: • Placing the cap (6) with its end face (60) on the end face (20) of the housing (2), so that a contact surface (26) is formed at least partially between the end faces (20, 0), • Material connection of the cap (6) and the housing (2) at the contact surface (26) by welding. [2] Manufacturing method according to claim 1, characterized by that during the formation of the material connection between the cap (6) and the housing (2), the cap (6) and the housing (2) are pressed against each other. [3] Manufacturing method according to one of the preceding claims, characterized by that the weld seam does not reach the inside (2b, 6b) of the cap (6) and / or the housing (2). [4] Manufacturing method according to one of the preceding claims, characterized by that the angle α between the end face (20, 60) and the plane E has a value greater than 0° and less than or equal to 30°, in particular the angle α is less than or equal to 15°. [5] Manufacturing method according to one of the preceding claims, characterized by that the end face (20, 60) angled to the plane E has a conical shape in the direction of the combustion chamber end of the prechamber spark plug (1) along the longitudinal axis X and narrows or widens conically. [6] Manufacturing method according to one of the preceding claims, characterized by that the end face (60) of the cap (6) and the end face (20) of the housing (2) are each an end face (20, 60) angled to plane E. [7] Manufacturing method according to claim 6, characterized by that the end face (60) of the cap (6) and the end face (20) of the housing (2) are angled in different directions to the plane E. [8] Manufacturing method according to claim 6, characterized by that the end face (60) of the cap (6) and the end face (20) of the housing (2) are angled in the same direction to plane E. [9] Prechamber spark plug (1), in particular produced according to the method according to one of the preceding claims 1 to 8, with a longitudinal axis X, wherein the prechamber spark plug (1) has a housing (2) with a combustion chamber-side end face (20) and a cap (6) with an end face (60) facing the housing (2), characterized bythat at least one of the two end faces (20, 60) is angled to a plane E perpendicular to the longitudinal direction X and that a weld seam is formed at least partially on the contact surface (26) between the cap (6) and the housing (6).

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