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 present invention relates to a spark plug according to claim 1.

Background Art

[0002] In the case of many spark plugs currently in use, the ground electrode is disposed on the combustion chamber side end face of the housing, and the spark gap is formed outside the housing. The center electrode also often protrudes from the housing and penetrates into the combustion chamber. As a result, these electrodes and the insulator can receive a lot of heat from the combustion chamber. Further, the scavenging chamber extending between the housing and the insulator provided with the center electrode is usually formed in a cylindrical shape and serves a secondary role in the case of a spark plug in which the spark gap is formed outside the housing.

[0003] These spark plugs are optimized for use in internal combustion engines operating on gasoline.

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is an increasing design concept of using hydrogen as a fuel in internal combustion engines, which has posed new challenges in the structure and design of spark plugs. Hydrogen burns very rapidly and as a result is ignited at a later time and at a higher combustion chamber pressure than in the case of other fuels. At that time, high temperatures occur in the combustion chamber.

[0005] Also, hydrogen has a tendency to auto-ignite at relatively low temperatures. To avoid this auto-ignition, all components of the spark plug must be cooled as much as possible.

[0006] An object of the present invention is to provide a spark plug with low component temperatures.

Means for Solving the Problems

[0007] This problem is solved by the spark plug of the type according to the present invention described at the beginning, wherein the housing has a first inner diameter D1 at its combustion chamber side end and a second inner diameter D2 in a plane E1 inside the housing, in which case the first inner diameter D1 is larger than the second inner diameter D2, and as a result the scavenging chamber formed inside the housing tapers from its combustion chamber side end to the end on the opposite side of the combustion chamber.

[0008] The spark plug having a vertical axis according to the present invention comprises a housing having a vertical hole, thereby the housing having a housing wall with an inner surface, an insulator disposed inside the housing and having a combustion chamber side insulator tip that is flush with a plane E1 extending perpendicular to the vertical axis, a center electrode at least partially disposed inside the insulator, and a ground electrode disposed inside the housing, wherein the ground electrode and the center electrode are arranged as follows, that is, the ground electrode and the center electrode are arranged to form an ignition gap, and the ignition gap is formed inside the housing.

[0009] According to the present invention, the housing has a first inner diameter D1 at its combustion chamber side end and a second inner diameter D2 within the plane E1 inside the housing, where the first inner diameter D1 is larger than the second inner diameter D2, and as a result the scavenging chamber formed inside the housing tapers from its combustion chamber side end to the end opposite the combustion chamber. The scavenging chamber is a space inside the spark plug housing, defined by the housing wall and the insulator. The region of the scavenging chamber from the end opposite the combustion chamber to the ignition gap is called the dead space, because the inflow and outflow of fuel, air, and mixture into this region can be poor. The tapering of the scavenging chamber reduces the dead space, decreasing the amount of fuel, air, and mixture in the region of the insulator and electrode, thereby reducing the thermal energy transferred to the electrode, insulator, and housing by convection and radiation after ignition. The housing volume is additionally increased, further reducing the temperature inside the scavenging chamber and its components. The resulting lower temperature load reduces electrode wear and the risk of premature ignition or glow ignition. Furthermore, it becomes possible to configure the shape of the scavenging chamber so that the flow of fuel, air, and mixture within the chamber is properly guided.

[0010] Furthermore, arranging the electrodes inside the housing has the advantage of allowing the insulator, ground electrode, and center electrode to be formed in a shorter length. This allows them to protrude much less into the combustion chamber. On the one hand, less heat is received by the components from the combustion chamber, and on the other hand, heat dissipation from the components through the housing into the cylinder head (in which the spark plug according to the present invention is installed) becomes more efficient. Within the scope of this application, the concept of “combustion chamber” means the combustion chamber of an internal combustion engine cylinder (in which the spark plug according to the present invention can be installed in the cylinder head). The scavenging chamber of the spark plug is not considered part of the “combustion chamber” within the scope of this application.

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

[0012] In an advantageous embodiment, the second inner diameter D2 is intended to be 35% to 80% of the first inner diameter D1. The second inner diameter D2 also determines the space provided for the insulator within the housing, particularly for the insulator tip. The insulator tip has a smaller diameter D3 than the second inner diameter D2. Due to the tapered shape of the scavenging chamber, the insulator tip has a smaller surface area that can absorb heat from the scavenging chamber. Furthermore, the smaller surface area of ​​the insulator protruding into the scavenging chamber reduces the load on the insulator and center electrode due to the pulsating pressure generated during combustion. This reduces the load on the mechanical fixation of the insulator within the spark plug housing, making the spark plug more robust.

[0013] In further developments, the insulator tip is intended to define a scavenging chamber at least partially at the end opposite 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 housing surface that defines the scavenging chamber at the end opposite the combustion chamber. For example, only the insulator tip may define the scavenging chamber at the end opposite the combustion chamber, and the inner surface of the housing wall defines the scavenging chamber radially. This achieves that the scavenging chamber has no dead space, or only a small amount of dead space. Furthermore, the surface of the insulator that comes into contact with the scavenging chamber and absorbs heat is minimized. Also, the insulator tip does not protrude into the scavenging chamber, and as a result, the flow of fuel, air, and mixture within the scavenging chamber is not obstructed by any possible edges of the insulator tip.

[0014] In a further developmental form, the housing walls of the housing define the scavenging chamber from the side, resulting in a tapered shape for the scavenging chamber.

[0015] In a further developed configuration, the shape of the scavenging chamber arises from a straight surface of the housing, and in particular, the first transition from the inner surface of the housing wall to the combustion chamber side end of the housing, and / or the second transition from the inner surface of the housing wall to the surface of the housing that defines the scavenging chamber at its end opposite the combustion chamber, is intended to be chamfered. This has the advantage that the surface defining the scavenging chamber does not have edges that could stimulate the flow of fuel, air, and mixture.

[0016] In a further developmental alternative configuration, the shape of the scavenging chamber is composed of multiple sub-faces arranged parallel to the longitudinal axis, where each sub-face may be straight or curved, and different sub-faces may have different radii of curvature, resulting in a contour with an overall curved shape. This provides the advantages mentioned above.

[0017] In a further alternative configuration of a more advanced form, the scavenging chamber is intended to consist of a conical portion and a cylindrical portion with a certain diameter. In particular, the conical portion is positioned closer to the combustion chamber than the cylindrical portion. This results in the scavenging chamber having the shape of the flared portion of a Laval nozzle. This has the advantage that a larger portion of the fuel-air-combustion mixture is guided parallel to the longitudinal axis of the spark plug, and therefore the depth of the cylinder's entry into the combustion chamber is increased.

[0018] In one configuration of the spark plug according to the present invention, the profile is rotationally symmetric and / or mirror-symmetric, in which case the longitudinal axis of the spark plug is intended to be the axis of symmetry. This results in a simple manufacturing of the spark plug housing.

[0019] In other configurations of the spark plug according to the present invention, the profile is rotationally symmetric and / or mirror-symmetric, in which case the axis of symmetry is intended to be spaced away from the longitudinal axis of the spark plug. By having the axis of symmetry of the scavenging chamber spaced away from the longitudinal axis of the spark plug, the flow of fuel, air, and mixture can be guided for purpose.

[0020] In further configurations of the spark plug according to the present invention, the contour is intended to be asymmetric. This allows for the equally purposeful guidance of the flow of fuel, air, and mixture.

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

[0022] In a favorable configuration, for example, the ignition gap width is not greater than 0.5 mm, and especially not greater than 0.2 mm. The smaller the ignition gap, the less voltage is required to generate the ignition spark.

[0023] It is also advantageous that the width of the ignition gap is at least 0.05 mm, particularly not less than 0.1 mm. Thereby, it is ensured that the ignition gap is not too small. If the ignition gap is very small, special requirements will be imposed on the accuracy during the production of the spark plug. When the ignition gap is small, if the directions of a plurality of electrodes and ignition surfaces deviate from the parallel orientation as much as possible, there is a greater influence than in the case of a larger ignition gap, for example, effects such as uneven wear of these plurality of ignition surfaces. Therefore, the lower limit value for the width of the ignition gap is, on the one hand, an excellent compromise for a small ignition gap for limiting the required ignition voltage and wear, and on the other hand, an excellent compromise for the cost that can be recognized for uniformly and excellently performing the orientation between a plurality of ignition surfaces during the production of the spark plug.

[0024] The spark plug according to the present invention and its further developed forms are hydrogen spark plugs installed for igniting a fuel-air mixture containing ignitable hydrogen when used in a prime mover operating with hydrogen. The fuel may contain up to 100% hydrogen, that is, the fuel may be hydrogen or a hydrogen-gas mixture.

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

[0026] For example, the spark plug may have a cap, and the cap is arranged at the combustion chamber side end of the housing, and as a result, the spark plug is a pre-chamber spark plug.

Brief Description of the Drawings

[0027] [Figure 1] It is a diagram showing a first embodiment of the tapered scavenging chamber of the spark plug according to the present invention. [Figure 2] It is a diagram showing a second embodiment of the tapered scavenging chamber of the spark plug according to the present invention. [Figure 3] FIG. 1 is a view showing a third embodiment of the tapered scavenging chamber of the spark plug according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0028] In FIGS. 1 to 3, there are shown schematically the combustion chamber side half portions of a spark plug 1 according to the present invention. The spark plug 1 has a housing 2, which has a longitudinal hole, and as a result, the housing 2 has a housing wall 20 provided with an inner surface 21. The spark plug 1 further has an insulator 3 disposed inside the housing 2 and having an insulator tip portion 31 on the combustion chamber side. The insulator tip portion 31 is flush with a plane E1 extending perpendicular to the longitudinal axis X of the spark plug 1. The insulator tip portion 31 has a diameter D3.

[0029] A center electrode 4 is disposed inside the insulator 3, and a ground electrode 5 is disposed inside the housing 2. The ground electrode 5 is formed here as a side electrode. The ground electrode 5 may be formed as a roof electrode. The ground electrode 5 may be disposed, for example, within a recessed portion of the inner surface 21 of the housing wall 20, or may be inserted into a through-hole penetrating the housing wall 20, or may be disposed on a protruding portion provided on the inner surface 21 of the housing wall 20. This local recessed portion or this local protruding portion provided on the inner surface 21 of the housing wall 20 can be ignored when considering the shape of the scavenging chamber 50. The center electrode 4 and the ground electrode 5 cooperate to form, for example, a single radial ignition gap 55. The ignition gap 55 has a spacing T from the combustion chamber side end face 27 of the housing 2 and is formed inside the housing 2.

[0030] The scavenging chamber 50 is a space provided at the combustion chamber side end of the spark plug 1. This space is defined radially by the housing 2 with respect to the spark plug's vertical axis X, and axially by the insulator 3 and, in some cases, the housing portion 22. The housing 2 has an opening at its combustion chamber side end, based on a vertical hole. Correspondingly, the scavenging chamber 50 also opens at its combustion chamber side end 51. The plane of the combustion chamber side end face 27 of the housing defines the scavenging chamber 50 at its combustion chamber side end 51. The housing 2 has a first inner diameter D1 at its combustion chamber side end and a second inner diameter D2 within the plane E1 inside the housing 2. The first inner diameter D1 is larger than the second inner diameter D2, and as a result, the scavenging chamber 50 formed inside the housing 2 tapers from its combustion chamber side end 51 towards the end 52 on the opposite side 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 radially by the housing wall 20. The thickness of the housing wall 20 increases in accordance with the tapering of the scavenging chamber 50.

[0031] A sealing element 10 is positioned between the insulator 3 and the housing 2 to seal the intermediate space between the housing 2 and the insulator 3. Therefore, gas cannot flow from the scavenging chamber 50 along the vertical hole in the housing 2 to the end of the housing 2 and the spark plug 1 on the side opposite to the combustion chamber.

[0032] In the embodiment shown in Figure 1, the scavenging chamber is defined at its end 52 opposite to 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, and as a result, at the end 52 opposite to the combustion chamber of the scavenging chamber 50, only the central electrode 4 protrudes into the scavenging chamber 50.

[0033] The shape of the scavenging chamber 50 is derived from the straight surface of the inner surface 21 of the housing wall 20. In this case, the first transition portion 17 from the inner surface 21 of the housing wall 20 to the combustion chamber side end surface 27 of the housing 2 may be chamfered. The chamfer radius of the first transition portion 17 is R1. Additionally or alternatively, the second transition portion 18 from the inner surface 21 of the housing wall 20 to the surface 22 of the housing 2 that defines the scavenging chamber 50 at its end 52 opposite to the combustion chamber may be chamfered. The chamfer radius of the second transition portion 18 is R2. The chamfer radii R1 and R2 may be the same or different.

[0034] Other figures show other embodiments of the spark plug 1 according to the present invention. The same components are denoted by the same reference numerals. The differences between the embodiments will be described below.

[0035] Figure 2 shows a second embodiment of the spark plug 1 according to the present invention for a tapered scavenging chamber. Unlike the first embodiment shown in Figure 1, only the insulator tip 31 defines the scavenging chamber at the end opposite to the combustion chamber. The inner surface of the housing wall defines the scavenging chamber radially with respect to the longitudinal axis of the spark plug. The inner surface of the housing wall is composed of multiple parts that are parallel to the longitudinal axis. These parts 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 of the spark plug 1 according to the present invention for a tapered scavenging chamber. Unlike the first embodiment shown in Figure 1, only the insulator tip 31 defines the scavenging chamber at its end opposite to the combustion chamber. The inner surface of the housing wall defines the scavenging chamber radially with respect to the vertical axis of the spark plug. The shape of the scavenging chamber (50) consists of a conical portion (53) and a cylindrical portion (54) with a constant diameter. Overall, a nozzle shape is created, for example, similar to the flared portion of a Laval nozzle. The ground electrode and the center electrode are located, for example, within the cylindrical portion of the scavenging chamber. [Explanation of Symbols]

[0037] 1 Spark plug 2 Housing 3. Insulator 4 Center electrode 5 Ground electrode 17. First Transition 18 Second Transition 20 Housing Walls 21. Inner surface of housing wall 27 End face of the housing on the combustion chamber side 31 Insulator tip 50 Evacuation Chamber 51 Combustion-side end of the scavenging chamber 52 The end of the scavenging chamber on the side opposite to the combustion chamber. 53 Conical portion of the scavenging chamber 54. Cylindrical section of the scavenging chamber 55 ignition gap D1 First inner diameter of the housing D2 Second inner diameter of the housing E1 A plane extending parallel to the vertical axis of the spark plug. X Vertical axis of the spark plug

Claims

1. A spark plug (1) having a vertical axis X, - A housing (2) having a vertical hole, thereby the housing (2) having a housing wall (20) with an inner surface (21), - An insulator (3) is disposed inside the housing (2) and has an insulator tip (31) on the combustion chamber side that is flush with a plane E1 that extends perpendicular to the vertical axis X, - A central electrode (4) is located at least partially inside the insulator (3), - The ground electrode (5) is located inside the housing (2), and the ground electrode (5) and the center electrode (4) form an ignition gap (55), and the ground electrode (5) and the center electrode (4) are arranged such that the ignition gap (55) is located inside the housing (2), In the spark plug (1) having, 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, wherein the first inner diameter D1 is larger than the second inner diameter D2, and as a result the scavenging chamber (50) formed inside the housing (2) tapers from its combustion chamber side end (51) towards the end (52) on the opposite side from the combustion chamber. The housing (2) has an opening at the combustion chamber side end (51) based on a vertical hole, The spark plug (1) is characterized in that the scavenging chamber (50) is open at the combustion chamber side end (51).

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. The spark plug (1) according to claim 1 or 2, characterized in that the insulator tip (31) defines the scavenging chamber (50) at least partially at the end (52) on the side opposite to the combustion chamber.

4. The spark plug (1) according to claim 1 or 2, characterized in that the housing wall (20) of the housing (2) defines the scavenging chamber (50) from the side, resulting in a tapered shape of the scavenging chamber (50).

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

6. 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 surface (21) of the housing wall that are arranged in parallel with respect to the vertical axis, and each partial surface is straight or curved, and different partial surfaces have different radii of curvature, resulting in an overall curved shape of the scavenging chamber (50).

7. 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 certain diameter.

8. The spark plug (1) according to claim 4, characterized in that the shape of the scavenging chamber (50) is rotationally symmetric and / or mirror-symmetric, and the vertical axis of the spark plug is the axis of symmetry.

9. The spark plug (1) according to claim 4, characterized in that the shape of the scavenging chamber (50) is rotationally symmetric and / or mirror symmetric, and the axis of symmetry is spaced apart from the vertical axis of the spark plug.

10. The spark plug (1) according to claim 4, characterized in that the shape of the scavenging chamber (50) is asymmetrical.

11. The spark plug (1) according to claim 1 or 2, characterized in that a cap is disposed at the combustion chamber side end of the housing (2), and as a result the spark plug (1) is a pre-combustion chamber / spark plug.

12. The spark plug (1) according to claim 1 or 2, characterized in that the spark plug is a hydrogen spark plug, and the hydrogen spark plug is used in a prime mover that operates on hydrogen and is installed to ignite a mixture of fuel, air, and ignitable hydrogen.

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