Spark plug comprising an extended resistance element, and manufacturing method therefor

Abstract

The present invention relates to a spark plug comprising an insulator on which a spark electrode and a terminal stud are arranged. A resistor element made of a ceramic composite material is arranged in a bore in the insulator between the spark electrode and the terminal stud. The terminal stud comprises a sleeve with a through-bore and a closure pin. The closure pin is designed to close, in particular with a force-fit, the through-bore of the sleeve at a first axial end of the spark plug, wherein the insulator has a widened portion at the first axial end, in which widened portion the sleeve is at least partially arranged.

Description

[0001] Description

[0002] title

[0003] Spark plug with extended resistance element and manufacturing process for it

[0004] The following invention relates to a spark plug and a method for manufacturing a spark plug.

[0005] In state-of-the-art spark plugs, a high voltage is applied to the spark plug's terminal pin during operation. This voltage induces a current through the terminal pin, a ceramic composite material (CCM) resistive element, and a center electrode, ultimately resulting in a spark between the center and ground electrodes. The external geometry of the terminal pin head is specified in ISO standard 28741, and the terminal pin itself can be threaded or formed as part of a solid bolt geometry. The resistive element acts as an internal seal to prevent gas leakage through the insulator's internal bore and is designed to have a specific electrical resistance optimized for the internal combustion engine's ignition system with regard to electrode wear and electromagnetic emissions.

[0006] During assembly, after the center electrode is inserted into the insulator, the powdered CCM raw material is filled into the insulator's inner bore. In a second step, the CCM raw material is melted at high temperature, and the bolt is pressed in under high force, compressing the resistive element. The resulting length of the resistive element is shorter than the original raw material length.

[0007] The development of resistance elements for spark plugs for modern internal combustion engines aims at large lengths of the resistance element, which are particularly advantageous for low electromagnetic emissions, resulting in no interference with other electronic circuits of, for example, engine control or entertainment systems.

[0008] The longer the final lengths of the resistive element, the more material must be filled into the insulator bore. A primary limit to the amount of material to be filled is the maximum bore length of the insulator. Furthermore, the connecting bolt must be able to be inserted sufficiently into the insulator bore (minimum bolt guide length) to prevent the bolt from falling out during transport between a bolt feeding station and the furnace for melting the CCM raw material, and to ensure proper bolt guidance during the pressing process.

[0009] It would be desirable to provide a spark plug with an increased length of the resistive element, while the external shape of the spark plug remains unchanged, in particular the insulator head length and the external geometry of the terminal bolt head.

[0010] Disclosure of the invention

[0011] The spark plug according to the invention, with the features of claim 1, has the advantage that the length of the resistance element in the spark plug can be increased while the external geometry of the spark plug can remain unchanged. This is achieved according to the invention by the spark plug having an insulator on which an ignition electrode and a connecting pin are arranged. A resistance element made of a ceramic composite material is arranged in a bore in the insulator between the ignition electrode and the connecting pin. The connecting pin comprises a sleeve with a through-hole and a sealing pin, which is configured to close the through-hole of the sleeve at its end facing away from the combustion chamber. In particular, the sealing pin is configured to close the through-hole in a force-fit manner.The insulator has an extension at the end of its bore facing away from the combustion chamber, in which the sleeve is at least partially arranged. This increases the receiving area for the resistive element within the insulator. The two-part connecting bolt allows more ceramic composite material to be introduced into the spark plug, thus enabling longer resistive elements. This can result in a spark plug with reduced electromagnetic emissions and reduced electrode wear. The through-holes of the sleeve and the bore in the insulator are preferably aligned coaxially with a longitudinal axis of the spark plug. The ignition electrode is preferably designed as a center electrode. Furthermore, the insulator is preferably arranged in a metal housing to which a ground electrode is attached.

[0012] The dependent claims describe preferred embodiments of the invention.

[0013] Preferably, the locking bolt is cylindrical. This means the locking bolt has no stop and can be inserted into the through-hole of the sleeve regardless of fluctuations in the fill level of the ceramic composite material. Thus, different lengths of the resistance element can be used with a single, consistent connecting bolt. Particularly preferably, the length of the locking bolt is selected such that the receiving area is partially formed within the sleeve.

[0014] According to a further preferred embodiment of the invention, the locking bolt comprises a head section and a cylindrical shaft section, the diameter of which corresponds to the diameter of the through-hole in the sleeve. An interference fit is preferably present between the cylindrical shaft section and the through-hole. The head section can serve as a stop for the locking bolt against the sleeve. This results in a defined length of the resistance element.

[0015] The length of the cylindrical shaft section is preferably shorter than the length of the through-hole in the sleeve. In particular, the length of the shaft section is selected such that the receiving area is partially formed within the sleeve. This allows the length of the resistive element to be increased and the electromagnetic emissions of the spark plug to be reduced.

[0016] Preferably, the head of the locking bolt is countersunk. This allows the locking bolt to sit flush with the sleeve even with tolerance-related variations in the fill level of the ceramic composite material. Even more preferably, the head of the locking bolt has a plug-in area on an outer surface, which is configured to form a plug connection with an electrical connector. Thus, the sleeve can have a simple geometry, while the locking bolt is adapted to the geometry of the plug connection.

[0017] Preferably, the diameter of the insulator bore corresponds to the diameter of the sleeve's through-hole. This allows the ceramic composite material to be reliably inserted into the bore in the insulator. Furthermore, the sealing bolt can uniformly compact the ceramic composite material in the bore of the insulator to create the resistive element during the melting process.

[0018] The through-hole of the sleeve is preferably funnel-shaped at the first axial end of the spark plug. The funnel shape can simplify the filling of the ceramic composite material for the resistive element.

[0019] The sleeve preferably has a stop on its outer side, which is designed to contact the insulator. This allows the sleeve to be inserted into the extension in the insulator at a defined length.

[0020] The sleeve is preferably connected to the insulator by means of an adhesive bond and / or a screw connection and / or a force-fit connection. This prevents liquid composite material from escaping laterally between the insulator and the sleeve during the manufacturing process. Furthermore, the penetration depth of the sleeve into the enlarged bore of the insulator can be reduced.

[0021] Preferably, the sleeve is a cast component. This can be manufactured cost-effectively in large quantities. In particular, the sleeve has uniform wall thicknesses and rounded edges.

[0022] Furthermore, the invention relates to a method for manufacturing a previously described spark plug. The method comprises the step of arranging an ignition electrode and a sleeve with a through-hole on the insulator. In a further step, the ceramic composite material is filled into the insulator through the through-hole of the sleeve. In a further step, the sealing pin is inserted into the sleeve. In a final step, the ceramic composite material is melted, with the sealing pin being pressed into the through-hole of the sleeve to compact the ceramic composite material. During the melting process, the ceramic composite material is heated. By attaching the sleeve to the insulator and filling the composite material through the through-hole of the sleeve, more ceramic composite material can be added, thereby increasing the length of the resistive element.The locking bolt can also pre-press the ceramic composite material before heating and / or press it in after heating to improve the melting process.

[0023] Preferably, the sleeve is installed by pressing, screwing, and / or gluing it into an extension within the insulator. This ensures a permanently tight and leak-proof connection between the sleeve and the insulator, even with a small extension. Gluing can be carried out as a separate process or in combination with pressing or screwing.

[0024] Brief description of the drawings

[0025] Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings. The drawing shows

[0026] Figure 1 shows a schematic sectional view of a spark plug according to a first embodiment of the invention,

[0027] Figure 2 shows the spark plug according to the first embodiment of the invention after attaching a sleeve to an insulator and filling it with a ceramic composite material.

[0028] Figure 3 shows the spark plug according to the first embodiment of the invention after the insertion of a locking bolt into the sleeve,

[0029] Figure 4 shows the spark plug according to the first embodiment of the invention after the ceramic composite material has been melted in. Figure 5 shows a schematic sectional view of a spark plug according to a second embodiment of the invention.

[0030] Figure 6 shows a schematic detail view of a spark plug in the area of ​​the connecting bolt according to a third embodiment of the invention and

[0031] Figure 7 shows a schematic detail view of a spark plug in the area of ​​the connecting bolt according to a fourth embodiment of the invention.

[0032] Embodiments of the invention

[0033] Preferably, all identical components, elements and / or units in all figures are provided with the same reference numerals.

[0034] The following section describes in detail a spark plug and a method for its manufacture with reference to Figures 1 to 7.

[0035] Figure 1 shows a spark plug 1 according to the first embodiment of the invention. The spark plug 1 comprises an insulator 20 on which an ignition electrode 2 and a connecting pin 10 are arranged. The connecting pin 10 is arranged at a first axial end 4 of the spark plug 1. The ignition electrode 2 is arranged at a second axial end of the spark plug 1 and is designed as a center electrode. The spark plug 1 is designed as a hook spark plug, with the insulator 20 arranged in a metal housing 5, which is connected to a hook-shaped ground electrode 6. The spark plug 1 is configured to generate an ignition spark between the ignition electrode 2 and the ground electrode 6. In a variant of the spark plug according to the invention (not shown), the ground electrode can also be arranged laterally to the ignition electrode, so that a radial ignition gap is formed.

[0036] The insulator 20 is an elongated ceramic component with a bore 21 along a longitudinal axis XX. The bore 21 forms a receiving area 24 for a resistive element 3, which is made of a ceramic composite material. The resistive element 3 has a specific electrical resistance that is optimized for the ignition system of the internal combustion engine with regard to electron wear and electromagnetic emissions. At the first axial end 4, the insulator 20 has an extension 22 in which the connecting bolt 10 is at least partially arranged. The resistive element 3 is preferably cylindrical.

[0037] The connecting bolt 10 comprises a sleeve 12 with a through-hole 14 and a locking bolt 16. The through-hole 14 in the sleeve 12 and the bore 21 in the insulator 20 are arranged coaxially with the longitudinal axis XX of the spark plug 1. Furthermore, the through-hole 14 and the bore 21 have the same diameter. If the bore 21 has several different diameters, its diameter is measured in the area of ​​the resistance element 3, particularly adjacent to the sleeve 12.

[0038] The locking bolt 16 is mushroom-shaped and has a head region 17 and a cylindrical shaft region 18. The diameter of the cylindrical shaft region 18 corresponds to the diameter of the through-hole 14 of the sleeve 12 or is smaller than the diameter of the through-hole 14 of the sleeve 12.

[0039] The combustion chamber-facing end of the locking bolt 16 can be designed such that it forms a positive-locking connection with the hardened composite material of the resistance element 3 and cannot be pulled out again. The force / form fit that holds the locking bolt 16 in the spark plug 1 is preferably formed between the resistance element 3 and the locking bolt. Additionally or alternatively, the locking bolt 16 can also be materially bonded to the sleeve 12.

[0040] The head section 17 of the locking bolt 16 has a stop against which the locking bolt 16 rests against the sleeve 12. At the stop, the outer diameter of the head section 17 corresponds to the outer diameter of the sleeve 12.

[0041] The sleeve 12 has a plug-in area 19 on its outer surface, which is designed to form a plug connection with an electrical terminal. Furthermore, the sleeve can be connected to the insulator 20 by a screw connection 23. The screw connection 23 is located in the extension 22 of the bore 21 of the insulator 20. Additionally, the screw connection can be bonded or a purely adhesive connection (without a screw connection) can be used to improve the durability and tightness of the connection.

[0042] Furthermore, the sleeve has a stop 11 which is designed to contact the insulator 20. The stop 11 has a surface that is arranged perpendicular to the longitudinal axis XX. A small gap may be provided between the stop 11 and the insulator 20 to compensate for different thermal expansions.

[0043] In Figure 1, the length L1 of the cylindrical shaft section is longer than the length L2 of the through-hole 14, so that the receiving area 24 is not formed in the sleeve 12. Nevertheless, the receiving area for the resistance element 3 could be enlarged compared to the prior art. Due to the two-part design of the connecting bolt 10, the ceramic composite material can be arranged in the through-hole 14 of the sleeve 12 before the resistance element 3 is melted in, which is not possible in the prior art, thus increasing the receiving area for the resistance element 3 according to the invention.

[0044] Figure 2 shows the spark plug 1 according to the first embodiment, after the sleeve 12 has been attached to the insulator 20 and the ceramic composite material has been introduced through the sleeve 12 into the insulator 20.

[0045] The sleeve 12 was fastened in the bore 21 of the insulator 20 by the screw connection 23. The screw connection 23 is located on the extension 22 at the first axial end 14 of the insulator 20.

[0046] The ceramic composite material was injected through the through-hole 14 of the sleeve 12 into the bore 21 of the insulator 20. Sufficient ceramic composite material was introduced to fill the bore 21 of the insulator 20 and part of the through-hole 14 of the sleeve 12.

[0047] The ceramic composite material has a fine-grained structure. Figure 3 shows the spark plug 1 according to the first embodiment, after the locking bolt 16 has been partially inserted into the sleeve 12.

[0048] The locking bolt 16 contacts the ceramic composite material in the through-bore 14 of the sleeve 12, since the volume of the resistance element 3 before melting is larger than after melting due to the spaces in the fine-grained structure of the ceramic composite material.

[0049] Figure 4 shows the spark plug 1 after the ceramic composite material of the resistance element 3 has been melted.

[0050] During the melting process, the ceramic composite material of the resistance element 3 is heated and compressed using the locking bolt 16. The locking bolt 16 is pressed into the sleeve 12 along its longitudinal axis XX. This compacts the fine-grained ceramic composite material, causing air to escape from the spaces within the fine-grained structure, resulting in a resistance element 3 with homogeneous material properties. The locking bolt 16 penetrates the sleeve 12 to such an extent that the head 17 of the locking bolt makes contact with the sleeve 12. To ensure the dimensional accuracy of the resistance element 3, the locking bolt 16 can be further compressed during the cooling of the resistance element 3. During the melting process, the displaced air preferably escapes between the locking bolt 16 and the sleeve 12.

[0051] Thus, the two-part design of the connecting bolt 10, consisting of the locking bolt 16 and the sleeve 12, allows for a spark plug 1 with an enlarged receiving area for the resistance element 3. This enables optimization of the ignition system with regard to electrode wear and electromagnetic emissions.

[0052] Figure 5 shows the spark plug 1 according to a second embodiment of the invention. The features of the second embodiment essentially correspond to those of the first embodiment, but differ from the first embodiment particularly in the shape of the connecting bolt 10. In the second embodiment, the sleeve 12 has a simple shape with flat and cylindrical surfaces. The sleeve 12 is attached to the extension 22 of the insulator 20 by an adhesive bond 25. However, the sleeve 12 is installed deeper in the insulator 20 than in the first embodiment.

[0053] The head region 17 of the locking bolt 16 has a curved outer surface with a plug-in area 19, which can form a plug connection with an electrical terminal. The sleeve 12 also has the stop 11.

[0054] Figure 6 shows the spark plug 1 according to a third embodiment in the area of ​​the connecting bolt 10. The third embodiment differs essentially from the first and second embodiments in the features of the connecting bolt 10.

[0055] The locking bolt 16 is cylindrical and is completely located in the through-bore 14 of the sleeve 12. The locking bolt 16 has no head 17 and corresponds to the cylindrical shaft 18 of the first and second embodiments.

[0056] The length L1 of the locking bolt according to the third embodiment is shorter than the length L2 of the through-hole 14 of the sleeve 12. As a result, the resistance element 3 projects into the sleeve 12, so that its length exceeds the length of the bore 21 in the insulator 20. Thus, the receiving area 24 for the resistance element 3 is partially formed within the sleeve.

[0057] By using locking bolts 16 of different lengths L1, the length of the resistance element 3 in the spark plug 1 can be easily varied. Furthermore, the length of the resistance element 3 can be adjusted by the insertion depth of the cylindrical locking bolt 16 in the sleeve 12.

[0058] In the third embodiment, the sleeve 12 is designed similarly to the sleeve 12 in the first embodiment, with the outer surface of the sleeve 12 having a plug-in area 19. In contrast to the first embodiment, the sleeve in Figure 5 is fastened in the extension 22 of the insulator 20 by a force-fit connection 26. The diameter of the through-hole 14 is identical to the diameter of the bore 21 in the insulator. As a result, the resistance element 3 also has a constant diameter and transitions flush from the bore in the insulator 20 into the through-hole 14 of the sleeve 12.

[0059] Figure 7 shows a fourth embodiment of the spark plug 1 in the area of ​​the connecting bolt 10. The fourth embodiment differs from the third embodiment only in the shape of the connecting bolt 10.

[0060] The through-bore 14 of the sleeve 12 has a funnel-shaped opening 13 at its first axial end. This facilitates the insertion of the ceramic composite material into the bore 21 of the insulator 20. The funnel-shaped opening 13 can also have a curved cross-section along the longitudinal axis XX.

[0061] The locking bolt 16 has a countersunk head section 17, which is adapted to the funnel-shaped opening of the through-bore 14. This allows the locking bolt 16 to close the sleeve 12 flush.

[0062] The connecting bolt 10 made of sleeve 12 and locking bolt 16 has a connecting bolt geometry according to ISO 28741 and can form a plug connection with an electrical connection.

Claims

Claims 1. Spark plug comprising an insulator (20) on which an ignition electrode (2) and a connecting bolt (10) are arranged, wherein a resistance element (3) made of a ceramic composite material is arranged in a bore (21) in the insulator between the ignition electrode (2) and the connecting bolt (10), wherein the connecting bolt (10) comprises a sleeve (12) with a through-bore (14) and a closing bolt (16), wherein the closing bolt (16) is configured to close the through-bore (14) of the sleeve (12) at its combustion chamber-side end (4), in particular by frictional locking, wherein the insulator (20) has an extension (22) at the combustion chamber-side end of its bore (21) in which the sleeve (12) is at least partially arranged.

2. Spark plug according to claim 1, wherein the locking bolt (16) is cylindrical.

3. Spark plug according to claim 1, wherein the locking bolt (16) comprises a head region (17) and a cylindrical shaft region (18), wherein the diameter of the cylindrical shaft region (18) corresponds to the diameter of the through-bore (14) of the sleeve (12).

4. Spark plug according to claim 3, wherein a length (L1) of the cylindrical shaft section (18) is shorter than a length (L2) of the through-bore (14) of the sleeve (12), in particular such that a receiving area (24) for the resistance element (3) is partially formed in the sleeve (12). 5 Spark plug according to one of claims 3 or 4, wherein the head region (17) is countersunk.

6. Spark plug according to one of claims 3 to 5, wherein the head area (17) has a plug area (19) on an outer surface which is configured to form a plug connection with an electrical connection.

7. Spark plug according to one of the preceding claims, wherein the diameter of the bore (21) of the insulator (20) corresponds to the diameter of the through-bore (14) of the sleeve (12).

8. Spark plug according to one of the preceding claims, wherein the through-bore (14) of the sleeve (12) at the first axial end (4) of the spark plug (1) is funnel-shaped.

9. Spark plug according to one of the preceding claims, wherein the sleeve (12) has a stop (11) which is designed to contact the insulator (20).

10. Spark plug according to one of the preceding claims, wherein the sleeve (12) is connected to the insulator (20) by means of an adhesive connection (25) and / or a screw connection (23) and / or a force-fit connection (26).

11. Method for manufacturing a spark plug according to any one of the preceding claims, comprising the steps of: Arranging an ignition electrode (2) and a sleeve (12) with a through-hole (14) on the insulator (20), Pouring the ceramic composite material through the through-hole (14) of the sleeve (12) into the insulator (20), Melting of the ceramic composite material, wherein the locking bolt (16) is pressed into the through-hole (14) of the sleeve (12) to compact the ceramic composite material.

12. Method according to claim 11, wherein the sleeve is arranged in an extension (22) in the insulator (20) by pressing or screwing and / or gluing.

Images