Thermally optimized pre-chamber spark plug

Abstract

The present invention relates to a pre-chamber spark plug (1) including a center electrode (2), a ground electrode (3), a housing (4) having external threads (40), a cap (6) disposed on the housing (4) and defining a pre-chamber (7) together with the housing (4), and an insulator (5) electrically insulating the center electrode (2) from the housing (4). [Solution] The present invention relates to a pre-chamber ignition plug (1) including a center electrode (2), a ground electrode (3), a housing (4) with an external thread (40), a cap (6) disposed on the housing (4) and defining a pre-chamber (7) together with the housing (4), and an insulator (5) electrically insulating the center electrode (2) from the housing (4). The external thread (40) of the housing (4) has a thread length (11) in the axial direction (XX) of the pre-chamber ignition plug (1). The housing (4) is fixed to the insulator (5) at a first fastening region (41) and a second fastening region (42) such that a first clamping force (F1) acts from the housing (4) to the insulator (5) at the first fastening region (41) and a second clamping force (F2) acts from the housing (4) to the insulator (5) at the second fastening region (42), the first and second clamping forces (F1, F2) acting in opposite directions in the axial direction (XX). The distance between the first and second fastening regions (41) and (42) in the axial direction (XX) defines a clamping length (12). The ratio of the thread length (11) to the clamping length (12) is in the range of 0.7 to 1.3.

Description

[Technical Field]

[0001] The present invention relates to a robust, thermally optimized pre-chamber spark plug that significantly reduces the risk of thermal damage during operation. Furthermore, the present invention relates to an internal combustion engine equipped with such a pre-chamber spark plug. [Background technology]

[0002] Pre-chamber spark plugs are known in various configurations from the prior art. They are often used in internal combustion engines powered by a gaseous medium. These types of pre-chamber spark plugs typically have a pre-chamber, within which a center electrode and a ground electrode are located. The pre-chamber is defined by a cap and a portion of the housing. In this case, excessive temperatures in the cap and / or electrodes can result in undesirable, uncontrollable glow ignition. This is undesirable because it increases wear and, on the other hand, can result in more harmful exhaust emissions from the internal combustion engine. In the worst case scenario, substantial damage to the internal combustion engine can occur. Therefore, improving heat removal in pre-chamber spark plugs is essential. Summary of the Invention

[0003] In contrast, the pre-chamber spark plug according to the present invention, which has the features of claim 1, has the advantage that excessive temperatures, particularly in the pre-chamber region, can be avoided. This, in particular, allows for lower electrode temperatures, which in turn reduces electrode wear and thus extends the service life of the pre-chamber spark plug. Furthermore, the lower temperatures allow greater freedom in selecting materials for the electrodes, for example, allowing for the selection of materials with lower thermal conductivity, thereby significantly reducing the cost of the electrodes. Furthermore, the pre-chamber spark plug has improved internal sealing throughout its service life. Furthermore, the present invention also provides greater robustness against improper operation, such as screwing in the pre-chamber spark plug with excessive torque, which could reduce or completely destroy the sealing function of the pre-chamber spark plug and potentially allow gases from the combustion chamber to reach the atmosphere through the non-sealed region of the pre-chamber spark plug. This is achieved by the pre-chamber spark plug according to the present invention having a center electrode, a ground electrode, and a housing with an external thread. A cap is also provided, which is disposed on the housing and, together with a portion of the housing, defines a pre-combustion chamber. The pre-combustion chamber spark plug further includes an insulator that electrically insulates the center electrode from the housing. The housing has a thread extending in the axial direction and is fastened to the insulator via first and second fastening regions. The fastening at the first and second fastening regions is performed so that a first clamping force acts from the housing to the insulator at the first fastening region and a second clamping force acts from the housing to the insulator at the second fastening region. The two clamping forces are directed oppositely in the axial direction of the pre-combustion chamber spark plug. The axial distance between the first and second fastening regions defines a clamping length. Thus, the two opposing prestressing forces achieve prestressing of the housing in the insulator. The ratio between the thread length and the clamping length is selected so that this ratio is within the range of 0.7 to 1.3.By selecting the thread length and the clamping length in this way in relation to the prestress of the housing, improved sealing can be achieved over a wide temperature range, so that even the most stringent requirements for the sealing performance of the pre-chamber spark plug can be met. Furthermore, the location of the fastening area obtained by selecting the thread length and the clamping length in accordance with the invention ensures that the inner sealing element of the pre-chamber spark plug is located as far away as possible from the combustion chamber, in the cooler area of ​​the cylinder head, and therefore ensures that particularly favorable conditions for heat removal from the pre-chamber spark plug prevail. This makes it possible to avoid thermal damage to the components of the pre-chamber spark plug, in particular the electrodes. Furthermore, selecting the thread length and the clamping length in accordance with the invention helps to maintain the prestress in the housing throughout the life of the pre-chamber spark plug. This allows the improved sealing to be maintained throughout the life of the pre-chamber spark plug.

[0004] The dependent claims show advantageous further configurations of the invention.

[0005] Further improvement of the pre-chamber spark plug is preferably achieved if the ratio of thread length to clamp length is within the range of 0.8 to 1.2. Even more advantageously, the ratio of thread length to clamp length is within the range of 0.8 to 1.

[0006] In order to achieve as uniform a prestress as possible for the housing, the first clamping force is preferably the same as the second clamping force, thereby achieving a uniform prestress of the housing.

[0007] It is further preferred that the pre-chamber spark plug has a first and a second fastening region each having an inclined surface, i.e., a surface disposed at an angle to the central axis of the pre-chamber spark plug. This allows for excellent adjustment of the prestressing forces at the first and second fastening regions. It is particularly preferred that the second fastening region, located on the side of the pre-chamber spark plug facing away from the combustion chamber, is formed on the insulator by flanging. It is also preferred that the first and second fastening regions are disposed on different diameters. It is particularly preferred that the second fastening region be disposed on a larger diameter than the first fastening region. This reduces the area of ​​the housing facing the pre-chamber, resulting in less heat penetrating into the housing.

[0008] Furthermore, the pre-chamber spark plug preferably includes a sealing element between the housing and the insulator. The sealing element is preferably a sealing disk. In this case, it is particularly preferred that the sealing element is arranged on the first fastening region. By applying a prestressing force to the first fastening region, the sealing element is preferably deformed, particularly preferably plastically deformed. In this case, it is particularly preferred that the sealing element is arranged on the side of the housing facing radially inward, facing away from the combustion chamber, thereby providing protection against high temperatures and particularly hot gases.

[0009] Preferably, the sealing element is arranged in the first fastening region, so that when the housing is fastened to the insulator, the sealing element can also be elastically deformed and seal the gap between the housing and the insulator. According to a further advantageous embodiment of the invention, the first fastening region is in a first half of the thread length in the axial direction, which is located starting from the pre-chamber.

[0010] The first fastening area is preferably arranged on the inner periphery of the housing, and the second fastening area is preferably arranged on the end of the housing facing away from the pre-chamber.

[0011] The first fastening region is preferably provided by an annular ridge formed on the inner periphery of the housing.

[0012] More preferably, the thread length extends from the fastening region between the cap and the housing, i.e., from the combustion chamber end of the housing, to the abutment surface of the housing. The abutment surface is configured to abut against an external component. The abutment surface is preferably perpendicular to the central axis of the pre-chamber spark plug. In this case, the abutment surface is configured to abut, for example, directly against the cylinder head or indirectly by means of a packing ring or the like.

[0013] The pre-chamber spark plug is preferably installed for use in an internal combustion engine.

[0014] The invention further relates to an internal combustion engine, in particular a mobile internal combustion engine, which is preferably used in a vehicle, equipped with a pre-chamber spark plug according to the invention.

[0015] The use of pre-chamber spark plugs in motorsports is also specifically contemplated. [Brief explanation of the drawings]

[0016] An advantageous embodiment of the invention will now be described in detail with reference to the accompanying drawings, in which:

[0017] [Figure 1] 1 is a schematic diagram, partially in cross section, of a pre-chamber spark plug in accordance with an advantageous embodiment of the present invention; [Figure 2] FIG. 2 is a partial cross-sectional schematic view of the pre-chamber spark plug of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0018] Next, a pre-chamber spark plug 1 according to a first embodiment of the present invention will be described in detail with reference to FIGS.

[0019] The pre-chamber ignition plug 1 includes a center electrode 2 and a ground electrode 3. A noble metal pin 20 is disposed on the center electrode 2. It should be noted that a noble metal pin may also be disposed on the ground electrode 3.

[0020] The pre-chamber spark plug 1 further comprises a housing 4, in particular made of a metallic material, and an insulator 5. The insulator 5 is provided to electrically insulate the central electrode 2 from the housing 4.

[0021] The housing 4 is further provided with an external thread 40. The external thread 40 has a thread length 11, which extends from a first end 4a facing the combustion chamber of the internal combustion engine to an abutment surface 10 provided on the housing 4 (see FIG. 2). The abutment surface 10 is perpendicular to the central axis XX of the pre-chamber spark plug. To prevent damage to the external thread, a circumferentially extending groove 10a is provided between the external thread 40 and the abutment surface 10.

[0022] Furthermore, the pre-chamber ignition plug 1 includes a cap 6 (see FIG. 1). A plurality of cap holes 60 are formed in the cap 6 to enable gas exchange within the pre-chamber 7, on the one hand, and to eject a torch flame stream from the pre-chamber 7 into the combustion chamber of the internal combustion engine for main ignition of the mixture, on the other hand. The pre-chamber 7 is defined by the cap 6 and a plurality of portions of the housing 4. The center electrode 2 and the ground electrode 3 are disposed within the pre-chamber 7.

[0023] 2, the housing 4 is fixed to the insulator 5 at a first fastening region 41 and a second fastening region 42. The housing 4 is fixed in such a way that a first clamping force F1 acts from the housing 4 to the insulator 5 at the first fastening region 41, and a second clamping force F2 acts from the housing 4 to the insulator 5 at the second fastening region 42. In this case, the two clamping forces F1, F2 are directed in opposite directions in the axial direction XX of the pre-chamber spark plug 1. The two clamping forces F1, F2 are preferably equal in magnitude.

[0024] Furthermore, the first fixing area 41 has a first inclined portion 5a on the insulator, and the second fixing area 42 has a second inclined portion 5b on the insulator, which are opposite each other, preferably at an angle of 45°, as can be seen in Figure 2 .

[0025] In this way, the two clamping forces F1, F2 prestress the housing 4 on the insulator 5, which tends to expand radially outward. This results in an improved seal between the outer periphery of the pre-chamber spark plug 1 and the cylinder head when the pre-chamber spark plug 1 is screwed into the cylinder head in its assembled state. Furthermore, due to the stiff spring characteristics of the housing, a high surface pressure acts on the sealing element 9, which is arranged between the housing 4 and the insulator 5, even with a short clamping length. The sealing element 9 is protected from the extremely hot gases by a flange 44, which is arranged on the side of the housing 4 facing away from the combustion chamber and is directed radially inward.

[0026] Furthermore, the distance between the first fastening region 41 and the second fastening region 42 defines the clamping length 12 of the housing. Thus, prestress occurs in the region of the clamping length 12 of the housing. Furthermore, the ratio V of the thread length 11 to the clamping length 12 is in the range of 0.7 to 1.3. Particularly preferably, the ratio of the thread length 11 to the clamping length 12 is in the range of 0.8 to 1.2, and even more preferably in the range of 0.8 to 1. In this case, it is even more advantageous if the ratio of the thread length 11 to the clamping length 12 is less than 1, i.e., the thread length 11 is shorter than the clamping length 12, with the lower limit being approximately 0.7.

[0027] The first fastening region 41 is arranged on the first diameter D1 and the second fastening region 42 is arranged on the second diameter D2, where the first diameter D1 is smaller than the second diameter D2.

[0028] Thus, by combining the measures of selecting the thread length 11 and the clamping length 12 with the measures of prestressing the housing 4, improved robustness, and in particular sealing, of the pre-chamber spark plug 1 can be achieved. Furthermore, the judicious selection of the thread length 11 and the clamping length 12 allows a significantly improved heat removal of the pre-chamber spark plug 1 during operation, resulting in a longer service life due to moderate electrode temperatures.

[0029] Since the temperature at the electrodes is significantly reduced compared to conventional pre-chamber spark plugs, greater freedom is afforded in the selection of materials for the electrodes, which can result in reduced costs. Furthermore, prestressing the first and second fastening regions between the housing 4 and the insulator 5 results in improved internal sealing of the pre-chamber spark plug 1 over its entire lifespan. Furthermore, the selection of the thread length 11 and the tightening length 12 has a positive effect on assembly errors, such as when the pre-chamber spark plug 1 is tightened with excessive torque, since a judicious length selection can prevent damage to the pre-chamber spark plug 1 in the event of excessive tightening torque.

[0030] For example, depending on the thread diameter of the male thread 40, particularly advantageous ratios V of thread length to tightening length can be obtained, as set out in the following table:

[0031] TIFF0007776508000001.tif20149

[0032] In this way, the treatment according to the invention in the pre-chamber spark plug 1 makes it possible to achieve a significantly improved service life and reduced temperatures during operation for the components of the pre-chamber spark plug 1, in particular for the electrodes, and the pre-chamber spark plug 1 is therefore particularly suitable for internal combustion engines in the stationary or mobile field and in the field of motorsport. [Explanation of symbols]

[0033] 1 Pre-chamber spark plug 2 center electrode 3 Ground electrode 4. Housing 4a end 5. Insulators 5a First slope of insulator 5b Second inclined portion of insulator 6 Caps 7 Pre-combustion chamber 9 Sealing Elements 10 Contact surface 11 Male thread length 11a First half of the thread length of the male screw 12 Fastening length 40 male thread 41 First Fixed Area 42 Second Fixed Area 44 flange F1 First clamping force F2 Second clamping force XX Axial direction

Claims

1. In the pre-chamber spark plug (1), A central electrode (2), A ground electrode (3), a housing (4) with an external thread (40); a cap (6) disposed on the housing (4) and defining a pre-combustion chamber (7) together with the housing (4); an insulator (5) electrically insulating the central electrode (2) from the housing (4); The male thread (40) of the housing (4) has a thread length (11) in the axial direction (X-X) of the pre-chamber ignition plug (1), The housing (4) is fixed to the insulator (5) at a first fixing area (41) and a second fixing area (42) having an inclined portion formed by an end of the housing (4) facing away from the pre-combustion chamber (7), in such a way that a first clamping force (F1) acts from the housing (4) to the insulator (5) at the first fixing area (41) and a second clamping force (F2) acts from the housing (4) to the insulator (5) at the second fixing area (42), the first and second clamping forces (F1, F2) being directed in opposite directions to each other in the axial direction (X-X); the distance between the first fastening region (41) and the second fastening region (42) in the axial direction (X-X) defines a clamping length (12); The ratio of the thread length (11) to the clamping length (12) is in the range of 0.8 to 1.

2. Pre-chamber spark plug (1).

2. 2. A pre-chamber spark plug (1) according to claim 1, wherein the ratio between the thread length (11) and the clamping length (12) is in the range of 0.8 to 1.

0.

3. A pre-chamber spark plug (1) according to claim 1 or 2, wherein the first clamping force (F1) is the same magnitude as the second clamping force (F2).

4. 4. The pre-chamber ignition plug (1) according to claim 1, wherein the insulator (5) has a first inclined portion (5a) in the first fixing region (41) and a second inclined portion (5b) in the second fixing region (42).

5. A pre-chamber spark plug (1) according to any one of claims 1 to 4, wherein the first fastening area (41) is arranged on a smaller diameter than the second fastening area (42).

6. A pre-chamber spark plug (1) according to any one of claims 1 to 5, further comprising a sealing element (9) between the housing (4) and the insulator (5).

7. The pre-chamber spark plug (1) according to any one of claims 1 to 6, further comprising a sealing element (9) arranged between the housing (4) and the insulator (5) near the pre-chamber (7).

8. 8. A pre-chamber spark plug (1) according to claim 6 or 7, characterized in that the sealing element (9) is arranged on the side of the flange (44) directed radially inwards, facing away from the combustion chamber.

9. A pre-chamber spark plug (1) according to any one of claims 6 to 8, wherein the sealing element (9) is arranged in the first fastening area (41).

10. 10. A pre-chamber spark plug (1) according to any one of claims 1 to 9, wherein the first fastening region (41) is located in a first half (11a) of the thread length (11) in the axial direction (X-X), the half being located starting from the pre-chamber (7).

11. 11. A pre-chamber spark plug (1) according to claim 1, wherein the thread length (11) extends from a first end (4a) of the housing (4) at which the cap (6) is fixed to the housing (4) to an abutment surface (10) of the housing (4), the abutment surface being configured for abutment against an external component.

12. 9. A pre-chamber spark plug (1) according to claim 8, wherein the abutment surface of the flange (44) is inclined towards the end of the pre-chamber spark plug facing away from the combustion chamber.

13. An internal combustion engine comprising a pre-chamber spark plug (1) according to any one of claims 1 to 12.

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