Spark plug with tapered scavenging chamber

Abstract

A spark plug (1) with a longitudinal axis X, comprising: a housing (2) with a longitudinal bore, whereby the housing (2) has a housing wall (20) with an inner surface (21); an insulator (3) arranged inside the housing (2) and having an insulator tip (30) facing the combustion chamber, which is flush with a plane E1 extending perpendicularly to the longitudinal axis X; a center electrode (4) arranged at least partially inside the insulator (3); and a ground electrode (5) arranged inside the housing (2), wherein the ground electrode (5) and the center electrode (4) define an ignition gap (55). In the spark plug (1) having the ground electrode (5), the ground electrode (5) and the center electrode (4) are arranged so that the ground electrode (5) and the center electrode (4) are arranged so that the spark gap (55) is formed inside the housing (2), the housing (2) has a first inner diameter D1 at its combustion chamber side end and a second inner diameter D2 inside the housing (2) in the plane E1, where the first diameter D1 is larger than the second diameter D2, so that a scavenging chamber (50) formed inside the housing (2) tapers from its combustion chamber side end (51) to its end (52) opposite the combustion chamber.

Description

[Technical field]

[0001] The invention relates to an ignition plug according to claim 1. [Background technology]

[0002] In most spark plugs used today, the ground electrode is located on the end face of the housing facing the combustion chamber, and the spark gap is formed on the outside of the housing. The center electrode also often protrudes from the housing and into the combustion chamber. This allows these electrodes and the insulator to receive a lot of heat from the combustion chamber. Furthermore, the scavenging chamber extending between the housing and the insulator with the center electrode is usually cylindrical in shape and plays a secondary role in spark plugs with a spark gap formed on the outside of the housing.

[0003] These spark plugs are optimized for use in gasoline-powered internal combustion engines. Summary of the Invention [Problem to be solved by the invention]

[0004] The increasing use of hydrogen as a fuel in internal combustion engines presents new challenges in the construction and design of spark plugs. Hydrogen burns very quickly and as a result is ignited later and at higher combustion chamber pressures than other fuels. This creates high temperatures in the combustion chamber.

[0005] Also, hydrogen is already prone to self-ignition at relatively low temperatures, and to avoid this, all components of the spark plug must be as cold as possible.

[0006] An object of the present invention is to provide an ignition plug having low component temperatures. [Means for solving the problem]

[0007] This object is achieved in an ignition plug according to the invention of the type mentioned at the beginning in that the housing has a first inner diameter D1 at its combustion chamber end and a second inner diameter D2 inside the housing in plane E1, the first inner diameter D1 being greater than the second inner diameter D2, so that the scavenging chamber formed inside the housing tapers from its combustion chamber end to its end facing away from the combustion chamber.

[0008] The spark plug according to the invention with a longitudinal axis comprises a housing with a longitudinal bore, whereby the housing has a housing wall with an inner surface, an insulator arranged inside the housing and with an insulator tip facing the combustion chamber, which is flush with a plane E1 extending perpendicular to the longitudinal axis, a central electrode arranged at least partially inside the insulator, and a ground electrode arranged inside the housing, the ground electrode and the central electrode being arranged such that the ground electrode and the central electrode form an ignition gap, the ignition gap being formed inside the housing.

[0009] According to the invention, it is provided that the housing has a first inner diameter D1 at its combustion chamber end and a second inner diameter D2 inside the housing in the plane E1, the first inner diameter D1 being greater than the second inner diameter D2, so that the scavenging chamber formed inside the housing tapers from its combustion chamber end to its end facing away from the combustion chamber. The scavenging chamber is a space inside the spark plug housing and is bounded by the housing wall and the insulator. The area of ​​the scavenging chamber from its end facing away from the combustion chamber to the ignition gap is called dead space, since the flow of the fuel-air mixture into and out of this area can be poor. The tapering of the scavenging chamber reduces the dead space and the amount of fuel-air mixture in the area of ​​the insulator and the electrode is reduced, so that less heat energy is transferred to the electrode, the insulator and the housing by convection and radiation after ignition. The housing volume is additionally enlarged, which further reduces the temperature in the scavenging chamber and its components. The resulting lower temperature load reduces electrode wear and the risk of pre-ignition or glow ignition. In addition, it offers the possibility to configure the geometry of the scavenge air chamber in such a way that the flow of the fuel-air mixture within it is properly guided.

[0010] Furthermore, arranging the electrodes inside the housing has the advantage that the insulator, the ground electrode and the central electrode can be made shorter, which causes them to protrude much less into the combustion chamber. On the one hand, the components receive less heat from the combustion chamber, and on the other hand, the heat is dissipated more efficiently from the components through the housing into the cylinder head, in which the spark plug according to the invention is mounted. Within the scope of this application, the term "combustion chamber" means the combustion chamber of an internal combustion engine cylinder, in whose cylinder head the spark plug according to the invention can be mounted. The scavenging chamber of the spark plug is not considered to be part of the "combustion chamber" within the scope of this application.

[0011] Further advantageous configurations of the invention are the subject of the dependent claims.

[0012] In an advantageous embodiment, it is provided that the second inner diameter D2 corresponds to 35% to 80% of the first inner diameter D1. The second inner diameter D2 also determines the space provided for the insulator in the housing, in particular for the insulator tip. The insulator tip has a diameter D3 smaller than the second inner diameter D2. Due to the tapered shape of the scavenge air chamber, the insulator tip has a smaller surface area capable of absorbing heat from the scavenge air chamber. Furthermore, said smaller surface area of ​​the insulator protruding into the scavenge air chamber results in less loading of the insulator and the central electrode due to the pulsating pressures generated during combustion. This reduces the load of the mechanical fixation of the insulator in the spark plug housing and makes the spark plug more robust.

[0013] In a further development, it is provided that the insulator tip at least partially defines the scavenging chamber at its end facing away from the combustion chamber. The scavenging chamber is defined by the housing and the insulator. In the direction of the combustion chamber, the housing and the scavenging chamber are open. For example, the insulator tip is flush with the surface of the housing that defines the scavenging chamber at its end facing away from the combustion chamber. For example, only the insulator tip may define the scavenging chamber at its end facing away from the combustion chamber, and the inner surface of the housing wall defines the scavenging chamber in the radial direction. This achieves that the scavenging chamber has no dead space or only a small dead space. Furthermore, the surface of the insulator that is in contact with the scavenging chamber and absorbs heat is limited to a minimum. Furthermore, the insulator tip does not protrude into the inside of the scavenging chamber, so that the flow of the fuel-air mixture in the scavenging chamber is not hindered by possible edges of the insulator tip.

[0014] In a further development, it is provided that a housing wall of the housing laterally defines the scavenging chamber, resulting in a tapered shape of the scavenging chamber.

[0015] In a further development, it is provided that the shape of the scavenging chamber results from a straight surface of the housing, in particular in that a first transition from the inner surface of the housing wall to the end surface of the housing facing the combustion chamber and / or a second transition from the inner surface of the housing wall to the surface of the housing defining the scavenging chamber at its end facing away from the combustion chamber is chamfered, which has the advantage that the surfaces defining the scavenging chamber do not have edges that could stimulate the flow of the fuel-air mixture.

[0016] In an alternative embodiment of a further development, it is provided that the shape of the scavenging chamber is made up of a number of partial surfaces arranged side by side parallel to the longitudinal axis, the individual partial surfaces being capable of being straight or curved and different partial surfaces being capable of having different radii of curvature, so that a contour having an overall curved shape results, which results in the above-mentioned advantages.

[0017] In a further alternative embodiment of the invention, the shape of the scavenging chamber is made up of a conical section and a cylindrical section with a constant diameter. In particular, the conical section is arranged closer to the combustion chamber than the cylindrical section. This results, for example, in the shape of the scavenging chamber being the divergent section of a Laval nozzle. This has the advantage that a larger part of the escaping and combusted fuel-air mixture is guided parallel to the longitudinal axis of the spark plug and thus penetrates the cylinder into the combustion chamber to a greater depth.

[0018] In one embodiment of the spark plug according to the invention, it is provided that the contour is rotationally symmetrical and / or mirror symmetrical, with the longitudinal axis of the spark plug being the axis of symmetry, which results in a simple manufacture of the spark plug housing.

[0019] In another embodiment of the spark plug according to the invention, it is provided that the contour is rotationally and / or mirror-symmetrical, with the axis of symmetry being spaced apart from the longitudinal axis of the spark plug. The axis of symmetry of the scavenging chamber is spaced apart from the longitudinal axis of the spark plug, so that the flow of the fuel-air mixture can be directed in a targeted manner.

[0020] A further embodiment of the spark plug according to the invention provides for an asymmetrical contour, which likewise allows the flow of the fuel-air mixture to be directed in a targeted manner.

[0021] In an advantageous further development of the configuration of the spark plug according to the invention, the spark gap has a distance T from the combustion chamber end face of the housing, where T=0.1 mm or more and / or T=15 mm or less. The distance T extends from the combustion chamber end face of the housing to the combustion chamber end of the spark gap. This results in the spark gap being arranged inside the housing. This negative ignition position makes it possible to configure the center electrode and the insulator shorter than usual, so that on the one hand the center electrode and the insulator do not protrude as deeply into the combustion chamber and the distance for heat dissipation is shorter and therefore more efficient.

[0022] Advantageously, for example, the width of the ignition gap is not greater than 0.5 mm, in particular not greater than 0.2 mm. The smaller the ignition gap, the less voltage is required to generate an ignition spark.

[0023] It is also advantageous that the width of the spark gap is at least 0.05 mm, in particular not smaller than 0.1 mm. This ensures that the spark gap is not too small. A very small spark gap places special demands on the precision during spark plug production. With small spark gaps, deviations from the most parallel possible orientation of the electrodes and spark surfaces have greater effects than with larger spark gaps, such as uneven wear of these spark surfaces. A lower limit for the spark gap width is therefore a good compromise between a small spark gap in order to limit the required ignition voltage and wear, on the one hand, and the justifiable costs for a uniform and good quality orientation of the spark surfaces relative to one another during spark plug production, on the other hand.

[0024] The spark plug according to the invention and further developments thereof are hydrogen spark plugs arranged for use in hydrogen-powered engines to ignite a fuel-air mixture containing ignitable hydrogen. The fuel may contain up to 100% hydrogen, i.e. the fuel may be hydrogen or a hydrogen gas mixture.

[0025] However, the spark plug according to the invention is not limited to operation with hydrogen: it can also be used in natural gas or gasoline internal combustion engines, although it is optimized for operation with hydrogen.

[0026] For example, the spark plug may have a cap that is disposed at the combustion chamber end of the housing such that the spark plug is a pre-chamber spark plug. [Brief description of the drawings]

[0027] [Figure 1] FIG. 2 shows a first embodiment of a tapered scavenging chamber of an ignition plug according to the present invention. [Diagram 2] FIG. 13 shows a second embodiment for a tapered scavenging chamber of an ignition plug according to the present invention. [Diagram 3] FIG. 11 shows a third embodiment of a tapered scavenging chamber of an ignition plug according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] 1 to 3 each show a schematic representation of the combustion chamber side half of an ignition plug 1 according to the invention. The ignition plug 1 has a housing 2 which has a longitudinal bore such that the housing 2 has a housing wall 20 with an inner surface 21. The ignition plug 1 further has an insulator 3 which is arranged inside the housing 2 and which has an insulator tip 31 on the combustion chamber side. The insulator tip 31 is flush with a plane E1 which extends perpendicularly to the longitudinal axis X of the ignition plug 1. The insulator tip 31 has a diameter D3.

[0029] A central electrode 4 is arranged inside the insulator 3, and a ground electrode 5 is arranged inside the housing 2. The ground electrode 5 is here configured as a side electrode. It may also be configured as a roof electrode. The ground electrode 5 may be arranged, for example, in a cutout in the inner side 21 of the housing wall 20, or may be inserted in a bore through the housing wall 20, or may be arranged on a protrusion on the inner side 21 of the housing wall 20. This local cutout or this local protrusion on the inner side 21 of the housing wall 20 can be ignored when considering the shape of the scavenging chamber 50. The central electrode 4 and the ground electrode 5 together form, for example, a radial ignition gap 55. The ignition gap 55 is arranged inside the housing 2 at a distance T from the combustion chamber-side end face 27 of the housing 2.

[0030] The scavenging chamber 50 is a space at the combustion chamber end of the spark plug 1, which is bounded in the radial direction by the housing 2 and in the axial direction by the insulator 3 and possibly by the housing part 22 with respect to the longitudinal axis X of the spark plug. The housing 2 has an opening at its combustion chamber end based on a longitudinal hole. Correspondingly, the scavenging chamber 50 also opens at its combustion chamber end 51. The plane of the combustion chamber end face 27 of the housing bounds the scavenging chamber 50 at its combustion chamber end 51. The housing 2 has a first inner diameter D1 at its combustion chamber end and a second inner diameter D2 inside the housing 2 in the plane E1. The first inner diameter D1 is greater than the second inner diameter D2, so that the scavenging chamber 50 formed inside the housing 2 tapers from its combustion chamber end 51 to its end 52 facing away from the combustion chamber. The second inner diameter D2 of the housing 50 is larger than the diameter D3 of the insulator tip 31. The scavenging chamber 50 is defined in the radial direction by the housing wall 20. The housing wall 20 has an increasing wall thickness corresponding to the tapering of the scavenging chamber 50.

[0031] Between the insulator 3 and the housing 2, a sealing element 10 is arranged which seals the intermediate space between the housing 2 and the insulator 3. Thus, gas cannot flow from the scavenging chamber 50 along the longitudinal bore of the housing 2 to the end of the housing 2 and the spark plug 1 facing away from the combustion chamber.

[0032] 1, the scavenging chamber is defined at its end 52 facing away from the combustion chamber by the surface 22 of the housing 2 and the insulator tip 31 of the insulator 3. The insulator tip 31 is flush with the housing surface 22, so that at the end 52 of the scavenging chamber 50 facing away from the combustion chamber, only the central electrode 4 projects into the scavenging chamber 50.

[0033] The shape of the scavenging chamber 50 results from the straight surface of the inner side 21 of the housing wall 20. A first transition 17 from the inner side 21 of the housing wall 20 to the end face 27 of the housing 2 facing the combustion chamber can be chamfered. The chamfer radius of the first transition 17 is R1. Additionally or alternatively, a second transition 18 from the inner side 21 of the housing wall 20 to the face 22 of the housing 2, which defines the scavenging chamber 50 at its end 52 facing away from the combustion chamber, can be chamfered. The chamfer radius of the second transition 18 is R2. The chamfer radii R1 and R2 can be the same or different.

[0034] The other figures show further embodiments for the spark plug 1 according to the invention. The same components are provided with the same reference numbers. In the following, mainly the differences between the embodiments will be described.

[0035] Figure 2 shows a second embodiment for the tapered scavenging chamber of a spark plug 1 according to the invention. In contrast to the first embodiment according to Figure 1, only an insulator tip 31 defines the scavenging chamber at its end facing away from the combustion chamber. The inner surface of the housing wall defines the scavenging chamber in the radial direction relative to the longitudinal axis of the spark plug. The inner surface of the housing wall is made up of a number of sections aligned parallel to the longitudinal axis. These sections may have straight surfaces or curved surfaces with different radii of curvature, resulting in a corrugated shape of the inner surface of the housing wall.

[0036] Figure 3 shows a third embodiment for a tapered scavenging chamber of a spark plug 1 according to the invention. In contrast to the first embodiment according to Figure 1, only the insulator tip 31 defines the scavenging chamber at its end facing away from the combustion chamber. The inner surface of the housing wall defines the scavenging chamber in the radial direction relative to the longitudinal axis of the spark plug. The shape of the scavenging chamber (50) consists of a conical part (53) and a cylindrical part (54) with a constant diameter. Overall, a nozzle shape results, for example like the divergent part of a Laval nozzle. The ground electrode and the central electrode are arranged, for example, in the cylindrical part of the scavenging chamber. [Explanation of symbols]

[0037] 1 Spark plug 2. Housing 3. Insulators 4 Center electrode 5 Ground electrode 17 First Transition 18 Second Transition Section 20 Housing Wall 21 Inner surface of housing wall 27 Combustion chamber side end face of housing 31 Insulator tip 50 Scavenging chamber 51 Combustion side end of scavenging chamber 52 End of the scavenging chamber opposite the combustion chamber 53 Cone-shaped part of the scavenge air chamber 54 Cylindrical part of the scavenge air chamber 55 Spark Gap D1 Housing first inner diameter D2 Second inner diameter of the housing E1 A plane extending parallel to the longitudinal axis of the spark plug X: longitudinal axis of spark plug

Claims

1. A spark plug (1) having a longitudinal axis X, a housing (2) with a longitudinal bore, whereby said housing (2) has a housing wall (20) with an inner surface (21); an insulator (3) arranged inside the housing (2) and having an insulator tip (31) on the combustion chamber side, which is flush with a plane E1 extending perpendicularly to the longitudinal axis X; a central electrode (4) arranged at least partially inside said insulator (3); a ground electrode (5) disposed inside the housing (2), the ground electrode (5) and the central electrode (4) forming an ignition gap (55), the ground electrode (5) and the central electrode (4) being disposed such that the ignition gap (55) is inside the housing (2); In the spark plug (1), The spark plug (1) is characterized in that the housing (2) has a first inner diameter D1 at its combustion chamber side end and a second inner diameter D2 inside the housing (2) within the plane E1, the first inner diameter D1 being larger than the second inner diameter D2, so that a scavenging chamber (50) formed inside the housing (2) tapers from its combustion chamber side end (51) to its end (52) opposite the combustion chamber.

2. 2. The spark plug (1) according to claim 1, characterized in that the second inner diameter D2 corresponds to 35% to 80% of the first inner diameter D1.

3. 3. The spark plug (1) according to claim 1 or 2, characterized in that the insulator tip (31) at least partially defines the scavenging chamber (30) at its end (52) facing away from the combustion chamber.

4. 4. The spark plug (1) according to claim 1, wherein the housing wall (20) of the housing (2) laterally defines the scavenging chamber (50), resulting in a tapered shape of the scavenging chamber (50).

5. 5. The spark plug (1) according to claim 4, characterized in that the shape of the scavenging chamber (50) results from a straight surface of the inner side (21) of the housing wall (20), in particular in that a first transition (17) from the inner side (21) of the housing wall (20) to the end face (27) of the housing (2) facing the combustion chamber and / or a second transition (18) from the inner side (21) of the housing wall (20) to the face (22) of the housing (2) which defines the scavenging chamber (50) at its end (52) facing away from the combustion chamber is chamfered.

6. 5. The spark plug (1) according to claim 4, characterized in that the shape of the scavenging chamber (50) is composed of a plurality of partial surfaces of the inner side (21) of the housing wall which are arranged parallel to the longitudinal axis, the individual partial surfaces being straight or curved, different partial surfaces having different radii of curvature, resulting in an overall curved shape of the scavenging chamber (50).

7. 5. The spark plug (1) according to claim 4, characterized in that the shape of the scavenging chamber (50) is composed of a conical portion (53) and a cylindrical portion (54) having a constant diameter.

8. 8. Spark plug (1) according to any one of claims 4 to 7, characterized in that the shape of the transfer chamber (50) is rotationally symmetrical and / or mirror symmetrical and the longitudinal axis of the spark plug is an axis of symmetry.

9. 8. The spark plug (1) according to claim 4, wherein the shape of the scavenging chamber (50) is rotationally symmetrical and / or mirror symmetrical, the axis of symmetry being spaced apart from the longitudinal axis of the spark plug.

10. 8. The spark plug (1) according to any one of claims 4 to 7, characterized in that the shape of the scavenging chamber (50) is asymmetric.

11. 11. The spark plug (1) according to claim 1, characterized in that a cap is arranged on the combustion chamber side end of the housing (2), so that the spark plug (1) is a pre-chamber spark plug.

12. 12. The spark plug (1) according to any one of claims 1 to 11, characterized in that the spark plug is a hydrogen spark plug, the hydrogen spark plug being installed for use in a hydrogen-powered prime mover to ignite a fuel-air mixture containing ignitable hydrogen.

Images