Pre-chamber spark plug with precisely adjustable electrode spacing and method therefor

Abstract

The present invention relates to a pre-chamber ignition plug comprising a center electrode (2) and a ground electrode (3) arranged in a pre-chamber (7) and a housing (4) having a lateral bore (40), the ground electrode (3) being arranged in the lateral bore (40) such that there is a gap region (8) and a fixing region (9) between the ground electrode (3) and the housing (4).

Description

[Technical Field]

[0001] The present invention relates to a pre-chamber spark plug having a precisely adjusted electrode spacing between the center electrode and the ground electrode and a method for adjusting the precise electrode spacing between the ground electrode and the center electrode of a pre-chamber spark plug. [Background technology]

[0002] Pre-chamber spark plugs of various designs are known from the prior art. In the prior art, pre-chamber spark plugs have primarily been used in stationary gas engines, which typically operate only at a single operating point at a relatively high load. In this case, each pre-chamber spark plug is designed for this operating point. In the case of mobile internal combustion engines, such as those for vehicles, ignition must be ensured in various load ranges, especially in the partial load range. This requires precise adherence to the electrode spacing between the center electrode and the ground electrode. Furthermore, in the case of pre-chamber spark plugs for vehicles, it should be noted that they can be mass-produced. Until now, pre-chamber spark plugs manufactured for stationary gas engines have been produced in small quantities, which, however, results in extremely high costs. Therefore, there is a need to mass-produce pre-chamber spark plugs suitable for use in mobile internal combustion engines for vehicles. Summary of the Invention [Effects of the Invention]

[0003] The pre-chamber spark plug according to the present invention, which has the features of claim 1, has the advantage that the electrode gap between the center electrode and the ground electrode can be precisely adjusted. The electrode gap adjustment process is also suitable for mass production of pre-chamber spark plugs. This significantly reduces the manufacturing costs for the pre-chamber spark plug according to the present invention, making the pre-chamber spark plug particularly suitable for vehicle internal combustion engines. In particular, the cap and housing of the pre-chamber spark plug can be constructed as a single component without weld seams. This is achieved according to the present invention by the pre-chamber spark plug having a center electrode and a ground electrode arranged in the pre-chamber. The ground electrode is arranged in a lateral bore in the housing. A clearance region and a sealing fastening region exist between the lateral bore and the ground electrode.

[0004] The dependent claims indicate preferred developments of the invention.

[0005] The gap area between the ground electrode and the side hole is preferably a clearance fit.

[0006] The fastening region between the ground electrode and the side hole is preferably a welded joint, and is more preferably located radially outward of the gap region, preferably formed outside the pre-chamber spark plug between the outer wall of the housing and the back side of the ground electrode.

[0007] More preferably, the ground electrode is disposed at an angle of 90° relative to the center electrode.

[0008] The ground electrode is preferably cylindrical. Particularly preferably, the ground electrode is a polygonal prism, in particular a triangular prism, a quadrangular prism, a pentagonal prism, or a hexagonal prism. When the ground electrode is formed as a polygonal prism, it is possible to prevent the ground electrode from rotating during adjustment of the electrode spacing. This allows particularly precise adjustment of the electrode spacing between the center electrode and the ground electrode.

[0009] More preferably, the housing has a very small maximum roughness R max The outer surface of the housing has a roughness R max is in this case 10 μm or less, so that the cup or another sealing component can abut reliably and sealingly against the outer surface of the housing, particularly during the process of adjusting the electrode spacing.

[0010] Preferably, the cap and the housing are formed in one piece, i.e. the cap no longer has to be separately fixed to the housing, but the cap and the housing form one common component, so that a welded joint or other type of joint between the cap and the housing can be omitted.

[0011] The present invention also relates to a method for adjusting the electrode spacing between the center electrode and the ground electrode during the manufacture of a pre-chamber spark plug. The method includes the step of positioning the ground electrode in a lateral bore provided in the housing of the pre-chamber spark plug, whereby the ground electrode is freely movable within the lateral bore. Preferably, a loose fit is formed between the ground electrode and the lateral bore. In a next step, the ground electrode is positioned at a predetermined electrode spacing relative to the fixed center electrode. This is possible because the ground electrode is slidably positioned within the lateral bore. In a final step, after the predetermined electrode spacing has been adjusted, the ground electrode is fixed to the housing, thereby maintaining the predetermined electrode spacing between the center electrode and the ground electrode. This completes the accurate setting of the spacing between the center electrode and the ground electrode. Furthermore, the method of the present invention provides the possibility of adjusting the electrode spacing after the pre-chamber cap is installed or after the plug is assembled. This opens up new design possibilities, such as constructing the cap and housing as a single component (without a weld seam).

[0012] The ground electrode is preferably fixed to the housing with the correct electrode spacing by a welded joint, which is particularly preferably formed on the outside of the pre-chamber spark plug between the housing and the ground electrode, and more preferably formed by laser.

[0013] Particularly simple and inexpensive manufacture is ensured if the pre-chamber spark plug is first inserted into a side hole in the housing and then moved downward under gravity into contact with the center electrode. Starting from this state of contact between the ground electrode and the center electrode, the ground electrode is then moved radially outward from the center electrode until the desired, defined electrode spacing is reached. The ground electrode is then fixed to the housing.

[0014] The step of moving the ground electrode away from the center electrode is particularly preferably carried out using air pressure. For this purpose, the prechamber of the prechamber spark plug is preferably placed under pressure, so that the ground electrode moves away from the center electrode in the side bore due to the increasing pressure. The ground electrode is then slowly pushed out of the side bore at the outer surface of the housing, for example, with its back surface, through a predetermined stroke. The distance of the pushed-out path of the ground electrode can be measured, and from this value, the electrode spacing between the center electrode and ground electrode, which were previously in contact, can be estimated. If the desired electrode spacing is achieved, the ground electrode can be fixed to the housing.

[0015] The ground electrode is preferably cylindrical in this case or, more preferably, formed as a polygonal prism. The use of a polygonal ground electrode has the advantage that it is prevented from rotating when pressure is applied to the ground electrode from the inside of the pre-chamber. In order to ensure that a cup or the like that applies pressure to the pre-chamber can be attached to the pre-chamber spark plug, the maximum roughness R in the wall region of the housing is set to 0.05 mm. maxis preferably very small, in particular less than 10 μm.

[0016] Additionally, adjustment of the electrode spacing between the center electrode and the ground electrode can be performed as the final step during manufacture of the pre-chamber spark plug, i.e., while the cap is already secured to the housing. Alternatively, adjustment of the electrode spacing can be performed before securing the cap to the housing, and the cap can then be placed on the housing in a further step after the ground electrode has been secured to the housing with the correct electrode spacing.

[0017] Preferably, the cap is fixed to the housing, particularly by a welded or press joint, before the electrode spacing is adjusted. This allows the electrode spacing to be adjusted as a final step. This prevents thermal distortion of the electrode spacing that would occur if the cap were subsequently fixed to the housing. Alternatively, the cap and housing can be formed as a single unit, which provides cost advantages during the manufacture of the pre-chamber spark plug.

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic cross-sectional view of a pre-chamber spark plug according to a first preferred embodiment of the present invention; [Figure 2] 2 is a schematic cross-sectional view illustrating a method for adjusting the electrode gap between the center electrode and the ground electrode of FIG. 1. FIG. [Figure 3] 2 is a schematic partial cross-sectional view illustrating a method according to the present invention for adjusting electrode spacing of the pre-chamber spark plug of FIG. 1. FIG. [Figure 4] 2 is a schematic partial cross-sectional view illustrating a method according to the present invention for adjusting electrode spacing of the pre-chamber spark plug of FIG. 1. FIG. [Figure 5]2 is a schematic partial cross-sectional view illustrating a method according to the present invention for adjusting electrode spacing of the pre-chamber spark plug of FIG. 1. FIG. [Figure 6] FIG. 2 is a schematic cross-sectional view of a pre-chamber spark plug according to a second preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] A pre-chamber spark plug 1 according to a first embodiment and a method for adjusting the electrode spacing between the center electrode 2 and the ground electrode 3 will now be described in detail with reference to FIGS.

[0021] This pre-chamber spark plug 1 is particularly suitable for mobile internal combustion engines.

[0022] As can be seen in Figure 1, the pre-chamber spark plug 1 comprises a center electrode 2 and a lateral ground electrode 3. The ground electrode 3 is disposed at a 90° angle to the center electrode 2. The center electrode 2 extends within a central axis XX of the pre-chamber spark plug 1. The center electrode 2 is at least partially disposed within an insulator 5. The insulator 5 serves to electrically isolate the center electrode 2 from the housing 4.

[0023] The pre-chamber spark plug 1 further comprises a housing 4 having a lateral bore 40 in which the ground electrode 3 is located.

[0024] The housing 4 and cap 6 define a pre-chamber 7, in this case of a pre-chamber spark plug.

[0025] As can further be seen from FIG. 1, the cap 6 has a plurality of cap holes 60 configured for fluid connection between the pre-chamber 7 and a combustion chamber 80 of the internal combustion engine.

[0026] Between the lateral hole 40 and the ground electrode 3 there are further formed a fastening region 9 and a gap region 8. The fastening region 9 is in this case a welded connection between the rear side of the ground electrode and the housing 4.

[0027] 1, there is an electrode gap 14 between the center electrode 2 and the ground electrode 3. In this case, the electrode gap 14 is the shortest connection between the center electrode 2 and the ground electrode 3.

[0028] 1, the center electrode 2 has a noble metal pin 20 on its end face, and the ground electrode 3 has a noble metal pin 30 on its end face. An electrode gap 14 exists between the noble metal pins 20, 30 in this case.

[0029] In this case, the ground electrode 3 is formed as a polygonal pillar, but may also be cylindrical.

[0030] The method of the present invention for adjusting the electrode spacing 14 between the center electrode 2 and the ground electrode 3 will now be described in detail with reference to FIGS.

[0031] As can be seen from Figure 2, which shows a structure for carrying out the method, the adjustment of the electrode spacing 14 is carried out by a pneumatic pressure generating unit 10. The pressure generating unit 10 comprises a pressure generator 11, e.g., a compressor, and a cup 12. The cup 12 is sealingly arranged on the outer surface 41 of the housing 4 or cap 6 in a sealing region 13. This results in a sealed space substantially outside the cap 6 and pre-chamber 7.

[0032] In this embodiment, the cap 6 is fixed to the housing 4 by a welded joint 15. Alternatively, the cap is directly integrated into the housing. The ground electrode 3 is cylindrical in this case and is arranged with play S in the lateral bore 40. This play S ensures a gap region 8 between the ground electrode 3 and the housing 4 after manufacturing of the pre-chamber spark plug.

[0033] In this embodiment, precise adjustment of the electrode spacing 14 between the center electrode 2 and the ground electrode 3 is the final step in the manufacture of the pre-chamber spark plug.

[0034] 2 and 3, to adjust the electrode spacing 14, according to the method of the present invention, air pressure is first generated by the pressure generator 11. As shown schematically by arrow A in FIG. 2, this pressure is applied to the inner region 12a of the cup 12 of the pressure generating unit 10. Since the cup 12 is sealingly arranged on the outer surface 41 of the housing 4, this pressure is further applied through the cap hole 60 into the pre-chamber 7, as shown schematically by arrow B in FIG. 2.

[0035] The ground electrode 3, which is loosely arranged in the lateral bore 40, is now in contact with the center electrode 2, since the not-yet-complete pre-chamber spark plug 1 is positioned so that the ground electrode 3 is guided downwards by gravity until it comes into contact with the center electrode 2. This position is shown in Figures 2 and 3.

[0036] Due to the air pressure that rises in the pre-chamber 7 and that is significantly higher than the ambient pressure prevailing outside the pre-chamber spark plug, this pressure also acts on the end face, more precisely on the end face of the noble metal pin 30 of the ground electrode 3. This is indicated diagrammatically by arrow C in Figures 2 and 3.

[0037] Since the ground electrode 3 is arranged in the lateral bore 40 with a clearance fit S, the ground electrode 3 now moves radially outward due to the prevailing pressure difference. This can be seen in detail in FIG. 4 (arrow D). The back surface 31 of the ground electrode 3 then exits the lateral bore 40. This is shown diagrammatically in FIG. 4 by the distance H. In this embodiment, the back surface 31 of the ground electrode 3 was flush with the outer surface 41 of the housing 4 when the center electrode 2 and the ground electrode 3 were in contact, so that the distance H is equal to the electrode distance 14 between the center electrode 2 and the ground electrode 3 in this embodiment.

[0038] The electrode spacing 14 can thus be determined simply by measuring the distance H between the rear surface 31 of the ground electrode emerging from the housing and the outer surface 41 of the housing from the outside of the pre-chamber spark plug. If the distance H is equal to the desired electrode spacing 14 between the center electrode 2 and the ground electrode 3, the ground electrode 3 is then fixed in this position. In this case, a welded joint is formed between the ground electrode 3 and the housing 4 from the outside of the pre-chamber spark plug, which then forms the fixing area 9 between the ground electrode 3 and the housing 4 in the lateral bore 40. This is shown in FIG. 5.

[0039] Since the back surface 31 of the ground electrode 3 was flush with the center electrode 2 in the initial state when the ground electrode 3 was in contact with the center electrode 2, the distance H was equal to the electrode spacing 14. Additionally, the ground electrode may be recessed in the housing or may protrude from the housing in the initial state. In this case, a clearance region 8 exists between the ground electrode 3 and the housing 4, radially inside the fixing region 9, in the lateral bore 40, which forms a clearance fit S between the ground electrode 3 and the housing 4 when the electrode spacing is adjusted.

[0040] The invention thus has the advantage that the electrode spacing 14 can be adjusted very precisely, with simple measurement of the electrode spacing 14 being possible from outside the pre-chamber spark plug.

[0041] It should be noted that the rear surface 31 of the ground electrode 3 does not necessarily have to end flush with the outer surface 41 when in contact with the center electrode 2. It is also possible for the rear surface to already slightly protrude from the lateral hole 40 when in contact with the ground electrode 3 and the center electrode 2. This protrusion can also be easily measured, and the electrode spacing adjustment according to the present invention is then carried out using this protrusion as a starting point. This does require two measurement steps to be carried out on the ground electrode 3, but this is easily possible since it can be carried out from outside the pre-chamber spark plug.

[0042] This makes the method of adjusting the electrode spacing 14 according to the invention suitable for mass production, so that the pre-chamber spark plug 1 can also be used in mobile internal combustion engines that are manufactured in high numbers.

[0043] Another major advantage of the method according to the present invention is that the fixing of the ground electrode 3 can be performed as the last step in the manufacture of the pre-chamber spark plug. This means that, for example, welding the cap to the housing 4 after adjusting the electrode spacing is no longer necessary. This prevents the welding heat generated when fixing the cap 6 to the housing 4 from affecting the electrode spacing 14. This makes it possible to ensure that the electrode spacing 14 is exactly the desired spacing.

[0044] 6 shows a pre-chamber spark plug 1 according to a second preferred embodiment of the present invention. The same or functionally the same parts are given the same reference numerals as in the first embodiment.

[0045] Unlike the first embodiment, in this second embodiment, the housing 4 and the cap 6 are formed as a single component. This eliminates the need for a welded or other type of connection between the cap and the housing. This significantly reduces manufacturing costs, among other things. During the manufacture of the pre-chamber spark plug, the electrode spacing adjustment can be performed as the final step in the manufacture of the pre-chamber spark plug. The electrode spacing measurement can be performed from the outside of the pre-chamber spark plug using the method according to the present invention. The ground electrode can be fixed to the single-piece housing-cap component from the outside of the pre-chamber spark plug by a welded connection. In this case, the heat input to the ground electrode is minimal, so that the adjusted electrode spacing 14 does not change. If fixing the ground electrode without a thermal method is desired, the ground electrode can be implemented in the single-piece housing-cap component, for example, by a crimping process or similar process. This embodiment otherwise corresponds to the first embodiment, and therefore the description of the first embodiment is to be referred to. [Explanation of symbols]

[0046] 1 Pre-chamber spark plug 2 center electrode 3 Ground electrode 4. Housing 5. Insulators 6 Caps 7 Pre-chamber 8 Interstitial area 9 Fixed area 10 Pressure generating unit 11 Pressure generator 12 cups 12a Inner area 13 Sealing area 14 Electrode Spacing 15 Welded joints 20 Precious Metal Pins 30 Precious Metal Pins 31 Back 40 Lateral foramen 41 Exterior 60 cap holes 80 Combustion chamber A arrow B arrow C arrow D arrow H interval S Play, play fit XX Center axis

Claims

1. A pre-chamber spark plug, a central electrode (2) disposed within a pre-chamber (7); a housing (4) having a lateral hole (40); a ground electrode (3) disposed in the lateral hole (40); Equipped with Within the side hole (40), there is a gap area (8) and a fixing area (9) between the ground electrode (3) and the housing (4), a first end surface of the ground electrode (3) located within the pre-chamber (7), the first end surface being parallel to a direction intersecting the direction in which the side holes (40) extend, the first end surface having a portion facing the center electrode (2) and a remaining portion not facing the center electrode (2); Pre-chamber spark plug.

2. 2. A pre-chamber spark plug according to claim 1, wherein the gap area (8) is a clearance fit (S) between the ground electrode (3) and the lateral hole (40).

3. 3. A pre-chamber spark plug according to claim 1, wherein the fastening region (9) is a welded joint.

4. 4. A pre-chamber spark plug according to claim 1, wherein the fixing region (9) is arranged radially further outward than the gap region (8).

5. 5. A pre-chamber spark plug according to claim 1, wherein the center electrode (2) is disposed perpendicular to the ground electrode (3).

6. 6. A pre-chamber spark plug according to claim 1, wherein the ground electrode (3) is cylindrical or polygonal.

7. 7. The pre-chamber spark plug according to claim 1, wherein the housing has an outer surface (41) with a specified maximum roughness Rmax of Rmax≦10 μm configured for sealing with the pressure generating unit (10).

8. 8. A pre-chamber spark plug according to claim 1, wherein the cap (6) and the housing (4) are formed as one piece.

9. A method for adjusting an electrode spacing (14) between a center electrode (2) and a ground electrode (3) during manufacture of a pre-chamber spark plug, comprising: Slidably positioning the ground electrode (3) in a lateral hole (40) in the housing (4); measuring the electrode spacing (14) between the ground electrode (3) and the center electrode (2) fixed in a pre-chamber (7); determining a position of the ground electrode (3) relative to the center electrode (2) by sliding the ground electrode (3) within the side hole (40) so that the electrode spacing (14) is a predetermined electrode spacing; When the electrode spacing (14) is equal to the predetermined electrode spacing, fixing the ground electrode (3) in the side hole (40) so that the electrode spacing (14) is maintained; Including, a first end surface of the ground electrode (3) located within the pre-chamber (7), the first end surface being parallel to a direction intersecting the direction in which the side holes (40) extend, the first end surface having a portion facing the center electrode (2) and a remaining portion not facing the center electrode (2); The method comprises fixing the ground electrode (3) to the housing (4) by a welding process, in particular on the outer surface of the housing (4), in such a way that a fixing area (9) and a gap area (8) exist between the ground electrode (3) and the lateral hole (4).

10. A method as described in claim 9, wherein the gap region (8) is a clearance fit (S) between the ground electrode (3) and the lateral hole (40) to ensure mobility of the ground electrode (3) within the lateral hole (40).

11. 11. The method according to claim 9, wherein the positioning of the ground electrode (3) in the lateral hole (40) is carried out in such a way that first there is contact between the ground electrode (3) and the central electrode (2), and then the ground electrode (3) is slid radially outward starting from this contact state between the central electrode (2) and the ground electrode (3).

12. 12. The method according to claim 9, wherein the movement of the ground electrode (3) in the lateral hole (40) is performed pneumatically.

13. 13. The method according to claim 9, wherein the electrode spacing (14) is determined by measuring the distance of a rear surface (31) of the ground electrode (3) from an outer surface (41) of the housing (4).

14. Before adjusting the electrode spacing (14), the cap (6) is fixed to the housing (4), in particular by a welded joint (15), or The cap (6) and the housing (4) are integrally formed.

14. The method according to any one of claims 9 to 13.

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