Abstract
An internal combustion engine. The internal combustion engine includes: at least one cylinder in which a combustion chamber is formed, the combustion chamber being delimited by side walls of the cylinder and a combustion chamber roof, which is formed by a cylinder head of the cylinder, and a piston that can move in the cylinder; and a spark plug with a longitudinal axis including: a housing with a combustion chamber-facing end face, an insulator disposed in the housing, a center electrode disposed in the insulator, and at least one ground electrode disposed on or in the housing and, together with the center electrode, forms at least one spark gap. The spark plug is mounted in a bore formed in the cylinder head and is designed to ignite a fuel/air mixture in the combustion chamber. The spark gap of the spark plug is located outside the combustion chamber.
Claims
1-14. (canceled)
15. An internal combustion engine, comprising: at least one cylinder in which a combustion chamber is formed, wherein the combustion chamber is delimited by side walls of the cylinder and a combustion chamber roof, which is formed by a cylinder head of the cylinder, and a piston that can move in the cylinder; and a spark plug with a longitudinal axis, the spark plug including: a housing with an end face which faces the combustion chamber, an insulator which is disposed in the housing, a center electrode which is disposed in the insulator, and at least one ground electrode which is disposed on or in the housing and together with the center electrode forms at least one spark gap, wherein the spark plug is mounted in a bore formed in the cylinder head and is configured to ignite a fuel/air mixture in the combustion chamber; wherein the spark gap of the spark plug is located outside the combustion chamber.
16. The internal combustion engine according to claim 15, wherein the spark gap has a distance to the combustion chamber roof of the cylinder of at least 0 mm and at most-15 mm, wherein a contour of the combustion chamber roof is continued by an imaginary line at the bore and the imaginary line is a reference plane having a value of 0 mm.
17. The internal combustion engine according to claim 15, wherein the combustion chamber-facing end face of the housing is disposed outside the combustion chamber, inside the bore for the spark plug.
18. The internal combustion engine according to claim 15, wherein the combustion chamber-facing end face of the housing is at least partly flush with the combustion chamber roof.
19. The internal combustion engine according to claim 15, wherein the spark plug is disposed within a region, wherein the region is a circular area with a midpoint of the combustion chamber roof as a center of the circular areas and has a radius f 15% of an inner cylinder radius.
20. The internal combustion engine according to claim 15, wherein the spark plug is not disposed outside a region, wherein the region is a circular area with a midpoint of the combustion chamber roof as a center of the circular area and has a radius of 15% of an inner cylinder radius.
21. The internal combustion engine according to claim 15, wherein the combustion chamber-facing end face of the housing includes a surface, wherein a shape of the surface corresponds to a contour of the combustion chamber roof.
22. The internal combustion engine according to claim 21, wherein the surface is a flat surface perpendicular to the longitudinal axis of the spark plug.
23. The internal combustion engine according to claim 21, wherein the surface is a flat surface that includes an angle of less than 90? and greater than 30?, with the longitudinal axis of the spark plug, wherein in each case a smaller included angle between the surface and the longitudinal axis is considered.
24. The internal combustion engine according to claim 22, wherein the surface is a curved surface that includes an angle of 90? and greater than 30?, with the longitudinal axis X of the spark plug, wherein in each case the smaller included angle between the surface and the longitudinal axis is considered.
25. The internal combustion engine according to claim 24, wherein the cylinder head (and/or the spark plug each have a mark, so that the spark plug can be mounted in the cylinder in an aligned manner.
26. The internal combustion engine according to claim 15, wherein the spark plug includes a thread on an outer side of the housing, with which the spark plug is screwed into the bore formed in the cylinder head, and an outer sealing surface, wherein, between the outer sealing surface and an end of the thread facing away from the combustion chamber, the housing includes a non-threaded region which is longer in the longitudinal axis of the spark plug than a thickness of an outer seal disposed on the outer sealing surface.
27. The internal combustion engine according to claim 15, wherein a width of the spark gap is specified by an electrode spacing between the center electrode and the at least one ground electrode, wherein the electrode spacing between the center electrode and the at least one ground electrode is not greater than 0.4 mm and not less than 0.05 mm.
28. The internal combustion engine according to claim 15, wherein the internal combustion engine can be operated with hydrogen or a hydrogen mixture as a fuel at least within a partial operating range with a lambda number of at least 1.8.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 shows a first example of the internal combustion engine according to the present invention with a spark plug with a negative spark position in the cylinder head.
[0034] FIG. 2 shows a second example of the internal combustion engine according to the present invention with a spark plug with a negative spark position in the cylinder head.
[0035] FIG. 3 shows a third example of the internal combustion engine according to the present invention with a spark plug with a negative spark position in the cylinder head.
[0036] FIG. 4 shows a fourth example of the internal combustion engine according to the present invention with a spark plug with a negative spark position in the cylinder head.
[0037] FIG. 5 shows an example of a spark plug that can be used in the internal combustion engine according to the present invention and comprises a flat combustion chamber-facing end face which is aligned at an angle to the spark plug longitudinal axis.
[0038] FIG. 6 shows an example of a spark plug that can be used in the internal combustion engine according to the present invention and comprises a curved combustion chamber-facing end face which is aligned at an angle to the spark plug longitudinal axis.
[0039] FIG. 7 shows an example of a spark plug that can be used in the internal combustion engine according to the present invention.
[0040] FIG. 8 shows another example of a spark plug that can be used in the internal combustion engine according to the present invention.
[0041] FIG. 9 shows an internal combustion engine according to the related art, in which the spark plug is disposed in the cylinder head with a positive spark position.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0042] FIG. 1 shows a simplified sectional view of an internal combustion engine 1 according to a first embodiment example of the present invention. The internal combustion engine 1 can comprise a plurality of cylinders 10, wherein only one of the cylinders 10 is shown in FIG. 1. The cylinder 10 comprises a combustion chamber 15, which is delimited by a piston that can move in the cylinder, the side walls 11 of the cylinder and, at its upper end, by a combustion chamber roof 13. The combustion chamber roof 13 is formed by a cylinder head 12 of the internal combustion engine 1. The combustion chamber roof 13 is preferably conical or configured such that it tapers toward the top, wherein in particular a peak of the roof forms the midpoint of the combustion chamber roof 13. The midpoint is in the center, in particular on a central axis 16, of the, preferably circular, cylinder 10. The cylinder has an inner radius R.sub.B, which extends from the central axis 16 of the cylinder to a side wall 11 of the cylinder.
[0043] Not shown here, the cylinder 10 can comprise charge exchange openings, such as at least one inlet opening, through which fresh air can flow into the combustion chamber 15 and at least one outlet opening, through which exhaust gases can flow out of the combustion chamber 15 after combustion. For each cylinder 10, the internal combustion engine 1 can also comprise a combustion chamber fuel injector which is configured to inject fuel directly into the combustion chamber 15, or an intake manifold fuel injector which is configured to inject fuel into an intake manifold that is connected to the combustion chamber 15 via the inlet opening.
[0044] The internal combustion engine 1 further comprises one spark plug 20 per cylinder 10. The spark plug 20 comprises a housing 21, an insulator 22, a center electrode 23 and a ground electrode 24. The center electrode 23 is disposed at least partly in the insulator 22, which in turn is disposed at least partly inside the housing 21. The ground electrode 24 is disposed on or in housing 21. The spark plug 20 is a spark plug which is configured to ignite a fuel/air mixture in the combustion chamber 15 by means of an electric spark. For this purpose, the spark plug 20 comprises a center electrode 23 and a ground electrode 24, which together form a spark gap 25. The ignition spark can be produced between the two electrodes 23, 24. The spark gap 25 can be located radially or axially with respect to a longitudinal axis X of the spark plug 20. The spark gap 25 has a volume that is delimited on the one hand by the oppositely disposed surfaces of the electrodes 23, 24 and by the overlapping projections of these surfaces onto one another.
[0045] The spark plug 20 further comprises a housing 21, which comprises a thread 211 on its outer side, for example, with which the spark plug 20 can be screwed into the bore 14. As shown in FIG. 1, the spark plug 20 can be disposed in a bore 14 inside the cylinder head 12, wherein the bore 14 opens into the combustion chamber 15.
[0046] In the first embodiment example shown in FIG. 1, the spark plug 20 is disposed within a region 40. The region 40 results as a circular area on the combustion chamber roof 13, wherein the circular area has the midpoint of the combustion chamber roof 13 as the center of the circle. In this example, the midpoint of the combustion chamber roof 13 and the central axis 16 of the cylinder 10 coincide. The circular area of the region 40 has a radius R.sub.M which is 15% of the inner cylinder radius R.sub.B. When assessing whether the spark plug 20 is disposed within the region 40, the longitudinal axis X of the spark plug 20 is considered. If the longitudinal axis X is within the region 40, the spark plug 20 is deemed to be disposed within the region 40. The spark plug 20 is in particular disposed at the midpoint of the combustion chamber roof 13. In other words, the longitudinal axis X of the spark plug 20 and the midpoint of the combustion chamber roof 13 coincide.
[0047] The spark plug 20 is disposed in the bore 14 such that its combustion chamber-facing end face 210 of the housing 21 is flush with the combustion chamber roof 13. The combustion chamber-facing end face 210 of the housing 21 is moreover a flat surface which is aligned perpendicular to the longitudinal axis X of the spark plug 20.
[0048] The combustion chamber roof 13 can be a curved surface as shown in FIG. 1. The combustion chamber roof 13 can alternatively also be composed of a plurality of flat surface segments that meet in the midpoint of the combustion chamber roof 13.
[0049] The cylinder head 12 comprises a bore 14 that penetrates the combustion chamber roof 13. The spark plug 20 is mounted in the bore 14, for example screwed in. To assess whether the spark gap 25 of the spark plug 20 is disposed outside the combustion chamber, the contour of the combustion chamber roof is continued by an imaginary line 15a in the region of the bore. This imaginary line 15a serves as the reference plane with the value 0 mm. The distance A 30 between the spark gap 25 and the reference plane is greater than 0 mm, wherein the sign indicates the direction of the distance A 30. A + sign means that the distance extends from the reference plane into the combustion chamber. A ? sign means that the distance extends from the reference plane outside and away from the combustion chamber. The spark gap 25 advantageously has a distance 30 of at least 0 mm and up to ?15 mm from the reference plane. The distance is from ?1 mm to ?4 mm, for instance.
[0050] In the following figures, identical parts of the figures have identical designations and identical reference signs. For the sake of simplicity, the differences to the previous figures are described in the subsequent figures.
[0051] FIG. 2 shows a simplified sectional view of an internal combustion engine 1 according to the present invention according to a second embodiment example. The second embodiment example differs from the first embodiment example in that the combustion chamber-facing end face 210 of the housing 21 of the spark plug 20 ends inside the bore 14. In this example, the ground electrode 24 is disposed in a bore 214 in the housing 21 and as a side electrode forms a radial spark gap 25 together with the center electrode 23. The ground electrode 24 could alternatively be disposed inside the housing 21 such that it is a roof electrode and together with the center electrode 23 forms an axial spark gap 25. In another alternative, the ground electrode 24 can also be disposed on the combustion chamber-facing end face 210 of the housing 21, so that the spark gap 25 is not formed inside, as in FIG. 2, but outside the housing 21. It is important here that the electrodes 23, 24 are disposed in such a way that the spark gap 24 is formed inside the bore 14 in the cylinder head 12, so that the spark plug 20 mounted in the cylinder 10 has a negative spark position.
[0052] FIG. 3 shows a simplified sectional view of the internal combustion engine 1 according to the present invention according to a third embodiment example. The third embodiment example differs from the first and the second embodiment examples in that the combustion chamber-facing end face 210 of the housing 21 of the spark plug 20 ends in the combustion chamber 15. The ground electrode 24 is disposed inside the housing 21, so that the spark gap 25 is also formed inside the housing 21 and outside the combustion chamber 15. As shown, the ground electrode 24 can be disposed as a side electrode, which together with the center electrode 23 forms a radial spark gap 25, or as a roof electrode, which together with the center electrode 23 forms an axial spark gap 25.
[0053] FIG. 4 shows a simplified sectional view of the internal combustion engine 1 according to the present invention according to a fourth embodiment example. The fourth embodiment example differs from the first embodiment example in that the bore 14 in the cylinder head 12 and thus also the spark plug 20 are disposed decentrally, i.e., outside the circular region 40, which has the midpoint of the combustion chamber roof as the center of the circle. The spark plug 20 is disposed inside the bore 14 such that the combustion chamber-facing end face 210 is at least partly flush with the combustion chamber roof 15. In particular if the combustion chamber-facing end face 210 of the housing 21 is a flat surface and the combustion chamber roof 13 has a non-straight contour in the region around the bore 14, the combustion chamber-facing end face 210 of the housing can only be partly flush with the combustion chamber roof 13.
[0054] FIGS. 5 and 6 show respective sectional views of the combustion chamber-side end region of the spark plug 20. Sections of the housing 21, the insulator 22 and the center electrode 23 can be seen. The inner radius RI of the housing in the breathing space and the outer radius RA of the housing are shown. The outer radius RA extends from the longitudinal axis X of the spark plug 20 to the threaded tip of the thread 211 formed on the outer side of the housing 21. The inner radius RI extends from the longitudinal axis X of the spark plug 20 to the inside of the housing 21 in the breathing space. In this example, the ground electrode 24 is disposed in a bore 214 in the region of the thread 211 and together with the center electrode 23 forms a radial spark gap 25. The spark gap 25 is delimited radially by the oppositely disposed surfaces of the electrodes 23, 24 and delimited axially by the volume 251 of the projection of the oppositely disposed surfaces of the electrodes 23, 24. The boundaries of the projection are indicated with a broken line. The distance A 30 between the spark gap 25 and the combustion chamber roof 15 is measured from the combustion chamber-side end of the spark gap. The dashed lines illustrate the boundaries of the spark gap volume 251.
[0055] The combustion chamber-facing end face 210 of the housing 21 in FIGS. 5 and 6 differs from the combustion chamber-facing end face 210 of the housing 21 shown in the first four figures in that the combustion chamber-facing end face 210 is not a surface aligned perpendicular to the longitudinal axis X of the spark plug 20. In FIG. 5, the combustion chamber-facing end face 210 is a flat surface that is aligned at an angle to the longitudinal axis X of the spark plug 20. The surface of the end face 210 and the longitudinal axis X include an angle a. In FIG. 6, the combustion chamber-facing end face 210 is a curved surface that is aligned at an angle to the longitudinal axis X of the spark plug 20. A tangent 210T is applied to the curved surface, which together with the longitudinal axis X includes an angle a. Spark plugs 20 comprising combustion chamber-facing end faces 210 of the housing 21 that are aligned at an angle to the longitudinal axis X of the spark plug are particularly advantageous in a decentralized arrangement of the spark plug 20 in the cylinder head 12, wherein the combustion chamber-facing end face 210 of the spark plug housing 21 is flush with the combustion chamber roof 13.
[0056] FIG. 7 and FIG. 8 show two alternative spark plugs 20 that can be used in the internal combustion engine 1 according to the present invention. FIG. 7 shows a spark plug 20 comprising a plurality of ground electrodes 24. The ground electrodes 24 each form a spark gap 25 with the center electrode 23. The ground electrodes 24 are configured here as side electrodes, which respectively form radial spark gaps 25 together with the center electrode 23.
[0057] In FIG. 8, the ground electrode 24 is configured as a roof electrode, which together with the center electrode 23 forms an axial spark gap 25. The spark plug 20 can, of course, also comprise a roof electrode in combination with one or more side electrodes as ground electrodes.
[0058] FIGS. 7 and 8 show the entire length of the spark plug 20. An outer sealing surface 281 formed on the outer side of the housing 21 above the end of the thread facing away from the combustion chamber 211 can be seen as well. A sealing ring 28 is disposed on the outer sealing surface 281 as an outer seal which seals the transition between the spark plug 20 and the cylinder head 12 when the spark plug 20 is mounted in the cylinder head 12. Between the outer sealing surface 281 and the end of the thread facing away from the combustion chamber, the housing 21 comprises a non-threaded region 212. This region in particular has a length which, measured parallel to the longitudinal axis X of the spark plug 20, is longer than a thickness of the outer seal 28 disposed on the outer sealing surface 281.
[0059] FIG. 9 shows an internal combustion engine with a conventional arrangement of the spark plug in the cylinder head. The spark plug is configured and disposed in the cylinder head such that the electrodes 23, 24 and the spark gap 25 are inside the combustion chamber. This spark plug has a positive spark position.
