Pre-chamber spark plug with conical contact surface between housing and cap

Abstract

Pre-chamber spark plug (10) having a longitudinal axis X - a housing (2) with an inner side (22) and an outer side (23) and - a cap (1) with an inner side (13) and an outer side (14), - wherein the cap (1) has at least one cap hole (15) which establishes a connection between a pre-chamber (16) inside the cap (1) and an area outside the cap (1), and - wherein the cap (1) and the housing (2) each have a mutually facing flat end face (12, 21), wherein the end face (12) of the cap (1) has an angle A° of not equal to 90° to the inside (13) of the cap (1) and the end face (21) of the housing (2) has an angle B° of not equal to 90° to the inside (13) of the cap (1), wherein both end faces (12, 21) have an angle of either greater than or less than 90° to the inside (13) of the cap (1).

Description

Prior ArtThe present invention relates to a pre-chamber spark plug having a conical contact surface between the housing and the cap, thereby simplifying the placement of the cap on the housing.Prechamber spark plugs are known from the prior art in different configurations. Pre-chamber spark plugs usually have a cap which defines a pre-chamber, wherein the cap has so-called cap holes which establish a connection between the pre-chamber and a combustion chamber of an internal combustion engine. The cap is arranged on the combustion chamber-side end face of the housing. There are various configurations for the common contact surface between the housing and the cap, such as a stepped contact surface which enables the advantage of a large contact surface, or a so-called impact-on-impact contact surface, in which the cap and the housing have a planar end face which is perpendicular to the longitudinal axis of the pre-chamber spark plug. The impact-on-impact contact surface has the advantage that it can be easily produced. However, when placing and fastening the cap on the housing, the challenge arises that the cap can easily slip during the method step. This challenge does not exist in the case of a pre-chamber spark plug with a stepped contact surface between the housing and the cap.It is an object of the invention to provide a pre-chamber spark plug with a shock-to-shock contact surface in which the risk of the cap slipping is minimized.Disclosure of the InventionThe pre-chamber spark plug according to the invention having a longitudinal axis X has a housing having an inner side and an outer side and a cap having an inner side and an outer side. The cap has at least one cap hole which establishes a connection between a pre-chamber inside the cap and a region outside the cap. Furthermore, the cap and the housing each have a flat end face facing each other. The end face of the cap has an angle A° of not equal to 90° with respect to the inner side of the cap. Furthermore, the end face of the housing to the inside of the cap also has an angle B° of not equal to 90°, wherein both end faces either have an angle of greater than or less than 90° to the inside of the cap.This has the result that the end faces of cap and housing form a conical, planar contact surface with respect to one another, which has a self-centring effect when the cap is placed on the housing, with the result that the cap no longer slips after the placement and during the fastening. Furthermore, the contact surface is enlarged in comparison to a resulting contact surface in the case of end faces formed perpendicularly to the longitudinal axis.The dependent claims show preferred developments of the invention.In one embodiment of the invention, the angle A° is equal to or less than the angle B°.In a further development, it is provided that the end faces of the cap and of the housing abut against one another on the inner side of the cap and on the inner side of the housing, and the end faces of the cap and of the housing are spaced apart on the outer side of the cap and on the outer side of the housing, such that a gap is formed. This allows a greater manufacturing tolerance at the angles.Furthermore, it is possible for the gap between the cap and the housing to be at least partially filled by a weld seam. This achieves a fixed mechanical connection and good thermal and electrical contacting of the cap with the housing. In particular, if the weld seam is formed circumferentially and additionally still completely fills the gap.In a further embodiment and further development of the pre-chamber spark plug according to the invention, it is provided that the inner sides of the cap and of the housing in the region of the end faces lie in an alignment parallel to the longitudinal axis of the pre-chamber spark plug and / or that the outer side of the cap and of the housing in the region of the end faces lie in an alignment parallel to the longitudinal axis. This has the result that there are no edges within the prechamber that are detrimental to the flow.In one configuration of the pre-chamber spark plug according to the invention, a radially inner section of the end face of the housing is arranged axially closer to the combustion chamber than a radially outer section of the end face of the housing and in particular as a radially outer section of the end face of the cap. Looking along the longitudinal axis of the pre-chamber spark plug in the direction of the combustion chamber, a conically narrowing end face is produced on the housing. The end face of the housing is radially surrounded by the end face of the cap.In an alternative configuration of the pre-chamber spark plug according to the invention, a radially outer portion of the end face of the housing is arranged axially closer to the combustion chamber than a radially inner portion of the end face of the housing and in particular as a radially inner portion of the end face of the cap. Looking along the longitudinal axis of the pre-chamber spark plug in the direction of the combustion chamber, a conically widening end face is produced on the housing. The end face of the cap is radially surrounded by the end face of the housing.Both have the effect that the cap centers itself when it is placed on the housing and slipping is prevented.Brief Description of the DrawingsHereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawing, the following is: FIG. 1 shows a schematic view of a pre-chamber spark plug according to the invention, FIG. 2 shows a schematic partial sectional view of a cap of the pre-chamber spark plug according to a first exemplary embodiment, FIG. 3 shows a schematic partial sectional view of a cap of the pre-chamber spark plug according to a second exemplary embodiment,Preferred Embodiments of the InventionAs shown in FIG. 1, the pre-chamber spark plug 10 includes a metallic housing 2 and an insulator 4. Typically, the pre-chamber spark plug has a central electrode, which lies in a central axis X-X of the pre-chamber spark plug, and at least one ground electrode set laterally, which are not shown here.An external thread is formed on the housing 2, which is configured to screw the pre-chamber spark plug 10 into a cylinder head of an internal combustion engine.The pre-chamber spark plug 10 further comprises a cap 1 which, together with a part of the housing 2, defines a pre-chamber 16. The center electrode and the ground electrode are arranged in the prechamber 16.The cap 1 has a plurality of cap holes 15 which enable a fluid connection between the prechamber 16 and a combustion chamber of an internal combustion engine.FIG. 2 shows a first exemplary embodiment of the contact surface according to the invention between cap 1 and housing 2.The housing 2 has an inner side 22, an outer side 23 and a combustion chamber-side flat end face 21, wherein the combustion chamber-side end face 21 faces the cap 1 and has an angle B° to the inner side 13 of the cap 1. The angle B° is not equal to 90°. In this exemplary embodiment, less than 90°, so that the end face 21 has a conical shape which widens in the direction of the combustion chamber. This has the result that the radially outer section 21 bof the end face 21 is axially closer to the combustion chamber-side end of the pre-chamber spark plug 10 than the radially inner section 21 aof the end face 21.In this example, the cap 1 has an inner side 13, an outer side 14 and a planar end face 12 on the combustion chamber side, wherein the end face 12 faces the housing 2 and has an angle A° to the inner side 13 of the cap 1. The angle A° is not equal to 90°. In this exemplary embodiment, the angle A° is less than 90°, so that the end face 12 has a conical shape which widens in the direction of the combustion chamber. This results in the end face 12 of the cap 1 being radially surrounded by the end face 21 of the housing 2.FIG. 3 shows a second example of the contact surface according to the invention between cap 1 and housing 2. the second exemplary embodiment differs from the first exemplary embodiment in that the angles A° and B° are greater than 90° and the contact surface between cap 1 and housing 2 therefore tapers conically in the direction of the end of pre-chamber spark plug 10 on the combustion chamber side. The cap 1 with its end face 12 is arranged radially on the outside around the end face 21 of the housing 2. The radially inner end 21 aof the end face 21 of the housing 2 is axially closer to the combustion chamber-side end of the pre-chamber spark plug 10 than the radially outer end 21 bof the end face 21 of the housing 2 and also than the radially outer end 12 bof the end face 12 of the cap 1.An extension E of the inner side 13 of the cap 1 in the region of the transition from the cap 1 to the housing 2 is drawn in FIGS. 2 and 3. In these examples, the extension E is parallel to the longitudinal axis X of the pre-chamber spark plug 10. This also applies to the outer sides 23, 14.

Claims

A pre-chamber spark plug (10) having a longitudinal axis X, comprising - a housing (2) having an inner side (22) and an outer side (23), and - a cap (1) having an inner side (13) and an outer side (14), - wherein the cap (1) comprises at least one cap hole (15) which establishes a connection between a pre-chamber (16) within the cap (1) and a region outside the cap (1), and - wherein the cap (1) and the housing (2) each have flat end faces (12, 21) facing one another, characterized in that the end face (12) of the cap (1) has an angle A° of not 90° with respect to the inner side (13) of the cap (1) and the end face (21) of the housing (2) has an angle B° of not 90° with respect to the inner side (13) of the cap (1), wherein both end faces (12, 12, 21) are either at an angle of greater than or less than 90° with respect to the inner side (13) of the cap (1).Pre-chamber spark plug (10) according to Claim 1, characterized in that the angle A° is equal to or less than the angle B°.Pre-chamber spark plug (10) according to one of the preceding claims, characterized in that the end faces (12, 21) of the cap (1) and of the housing (2) on the inner side (13) of the cap and the inner side (22) of the housing bear against one another, and the end faces (12, 21) of the cap (1) and of the housing (2) on the outer side (14) of the cap (1) and the outer side (23) of the housing (2) are spaced apart, such that a gap (3) is formed.Pre-chamber spark plug (10) according to Claim 3, characterized in that the gap (3) between the cap (1) and the housing (2) is at least partially filled by a welded seam.Pre-chamber spark plug (10) according to one of the preceding claims, characterized in that the inner sides (13) of the cap (1) and the inner sides (22) of the housing (2) in the region of the end faces (12, 21) are aligned parallel to the longitudinal axis X of the pre-chamber spark plug (10), and / or in that the outer side (14) of the cap and the outer side (23) of the housing (2) in the region of the end faces (12, 21) are aligned parallel to the longitudinal axis X.Pre-chamber spark plug (10) according to one of the preceding claims, characterized in that a radially inner section (21a) of the end face (21) of the housing (2) is arranged axially closer to the combustion chamber than a radially outer section (21b) of the end face (21) of the housing (2) and in particular as a radially outer section (12b) of the end face (12) of the cap (1).Pre-chamber spark plug (10) according to one of the preceding claims 1 to 6, characterized in that a radially outer section (21b) of the end face (21) of the housing (2) is arranged axially closer to the combustion chamber than a radially inner section (21a) of the end face (21) of the housing (2) and in particular as a radially inner section (12a) of the end face (12) of the cap (1).

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