PRE-CHAMBER SPARK PLUG WITH IMPROVED HEATING BEHAVIOR

Abstract

A pre-chamber spark plug. The pre-chamber spark plug includes a housing, a pre-chamber, a cap that closes the pre-chamber on the housing and that has one or more through-openings, and an ignition device situated in the pre-chamber. The cap has a cap base and a cap jacket. The cap jacket and a housing inner wall of the housing defines a pre-chamber inner wall. The pre-chamber is defined by the pre-chamber inner wall and the cap base. At least one rib projects into the pre-chamber is formed in the region of the pre-chamber inner wall.

Claims

1-11. (canceled)

12. A pre-chamber spark plug, comprising: a housing; a pre-chamber; a cap that closes the pre-chamber on the housing and that has one or more through-openings; and an ignition device situated in the pre-chamber; wherein the cap has a cap base and a cap jacket, the cap jacket and a housing inner wall of the housing defining a pre-chamber inner wall, and the pre-chamber being defined by the pre-chamber inner wall and the cap base; and wherein at least one rib projecting into the pre-chamber is formed in an area of the pre-chamber inner wall.

13. The pre-chamber spark plug as recited in claim 12, wherein the rib is situated on the cap jacket, and/or the rib is situated on the housing.

14. The pre-chamber spark plug as recited in claim 12, wherein the through-opening in the cap is situated such that a gas flow of inflowing gas through the through-opening is directed onto the rib.

15. The pre-chamber spark plug as recited in claim 14, wherein the rib runs non-parallel to a center axis of the pre-chamber spark plug.

16. The pre-chamber spark plug as recited in claim 14, wherein the rib has a bevel on a region on which the gas flow from the through-opening impinges when flowing into the pre-chamber.

17. The pre-chamber spark plug as recited in claim 12, wherein the rib is made of a different material from the cap and of a different material from the housing.

18. The pre-chamber spark plug as recited in claim 12, wherein the at least one rib includes a plurality of ribs which have the same geometrical dimensions.

19. The pre-chamber spark plug as recited in claim 18, wherein the ribs run in a straight line, and/or the ribs run in a curve.

20. The pre-chamber spark plug as recited in claim 12, wherein the rib has a reduced width at a fixing region at which a fixing to the pre-chamber inner wall takes place.

21. The pre-chamber spark plug as recited in claim 12, wherein the cap base has no rib, and/or the cap is cup-shaped in section and/or the at least one through-opening is formed in the cap base.

22. An internal combustion engine of a vehicle, comprising: a pre-chamber spark plug, including: a housing, a pre-chamber, a cap that closes the pre-chamber on the housing and that has one or more through-openings, and an ignition device situated in the pre-chamber, wherein the cap has a cap base and a cap jacket, the cap jacket and a housing inner wall of the housing defining a pre-chamber inner wall, and the pre-chamber being defined by the pre-chamber inner wall and the cap base, and wherein at least one rib projecting into the pre-chamber is formed in an area of the pre-chamber inner wall.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In the following, preferred exemplary embodiments of the present invention are described in detail with reference to the figures.

[0017] FIG. 1 is a schematic sectional view of a pre-chamber spark plug according to a first preferred example embodiment of the present invention.

[0018] FIG. 2 is a schematic sectional view of a pre-chamber area of the pre-chamber spark plug of FIG. 1.

[0019] FIG. 3 is a schematic sectional view of a pre-chamber area of a pre-chamber spark plug according to a second exemplary embodiment of the present invention.

[0020] FIG. 4 is a schematic sectional view of a pre-chamber area of a pre-chamber spark plug according to a third exemplary embodiment of the present invention.

[0021] FIG. 5 is a schematic sectional view of a pre-chamber area of a pre-chamber spark plug according to a fourth exemplary embodiment of the present invention.

[0022] FIG. 6 is a schematic sectional view of a pre-chamber area of a pre-chamber spark plug according to a fifth exemplary embodiment of the present invention.

[0023] FIG. 7 is a schematic sectional view of a pre-chamber area of a pre-chamber spark plug according to a sixth exemplary embodiment of the present invention.

[0024] FIG. 8 is a schematic sectional view of a pre-chamber area of a pre-chamber spark plug according to a seventh exemplary embodiment of the present invention.

[0025] FIG. 9 is a schematic sectional view of a pre-chamber area of a pre-chamber spark plug according to an eighth exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0026] In the following, a pre-chamber spark plug according to a preferred first exemplary embodiment of the present invention is described in detail with reference to FIGS. 1 and 2.

[0027] As can be seen from FIG. 1, the pre-chamber spark plug 1 has a cap 2 which, together with a housing 4, forms a pre-chamber 3 at an end of the pre-chamber spark plug directed towards a combustion chamber 8. The pre-chamber spark plug 1 is shown schematically in FIG. 1 and further comprises an insulator 5 and an electrical terminal 7. An ignition device 6 with a center electrode and a ground electrode is situated in the pre-chamber 3.

[0028] As can be seen further from FIG. 1, pre-chamber spark plug 1 is screwed in in a cylinder head 9 in such a way that the cap 2 projects into a combustion chamber 8. As a result, cap 2 is directly exposed to high temperatures in the combustion chamber.

[0029] The cap 2 can be seen in detail in FIG. 2. In section, cap 2 has a substantially cup-shaped structure and includes a cap base and a cylindrical cap jacket 21. Multiple through-openings 10 are formed in cap base 20. In FIG. 2 only one through-opening is shown.

[0030] During operation, there is a gas flow 13 into pre-chamber 3 through the through-openings 10, by which an ignitable mixture is fed into pre-chamber 3.

[0031] The cap jacket 21 and a housing inner wall 40 define a pre-chamber inner wall. The pre-chamber 3 is then defined by the pre-chamber inner wall and cap base 20.

[0032] As can be seen in particular from FIG. 2, on the inside of cap jacket 21 an elongated rib 11 is formed, which projects into pre-chamber 3. Here rib 11 has a bevel 12 at an end oriented toward cap base 20. Cap base 20 is free of ribs and has a constant thickness.

[0033] Rib 11 is an elongated component having a longitudinal dimension greater than a height, i.e. the region of the rib projecting into pre-chamber 3, and a width of the rib. The height and width of the rib are preferably the same.

[0034] Rib 11 is connected to cap jacket 21, for example by welding, at its entire rib foot, which forms a fixing region 14 of the rib.

[0035] During operation, a gas flow 13 from combustion chamber 8 is fed through the

[0036] through-opening 10 in the direction onto rib 11. Gas flow 13 is an ignitable mixture that should move as closely as possible into the region of ignition device 6. As can be seen in FIG. 2, gas flow 13 impinges directly on bevel 12. This results in a

[0037] deflection 13 of the gas flow in the direction of ignition device 6. In this way it can be ensured that the ignitable mixture is as close as possible to the region of ignition device 6 in order to enable a reliable ignition in pre-chamber 3.

[0038] In addition, rib 11 enlarges a cap surface of pre-chamber 3, as well as a cap volume. Heat of the cap 2 resulting from the combustion process is therefore also transferred to rib 11 via cap jacket 21. This increases a temperature at rib 11. The higher temperatures at rib 11 cause a heat input into the inflowing gas flow 13, which results in a more stable combustion in pre-chamber 3 and thus in an improved ignition in combustion chamber 8.

[0039] In addition, a flow path of gas flow 13 can be influenced by the situation of rib 3, thereby improving an optimized residual gas purging and also fresh gas replenishment of pre-chamber 3.

[0040] In this embodiment, rib 11 runs parallel to a center axis of pre-chamber spark plug 1. The rib 11 is preferably made of a material that has a poorer thermal conductivity than the material of cap 2. This allows rib 11 to be kept at a relatively high temperature compared to cap 2.

[0041] In this way, through the pre-chamber spark plug according to the present invention a heating behavior of a gas flow 13 flowing into pre-chamber 3 can be significantly improved. As a result, pre-chamber spark plug 1 is designed in particular for use in mobile internal combustion engines, for example in vehicles, and has advantages in particular for cold starting and in partial load operation of the internal combustion engine.

[0042] In the following, further preferred embodiments of the present invention are described in detail with reference to FIGS. 3 through 9. In the Figures described below, identical or nearly identical parts are designated as in the first exemplary embodiment.

[0043] FIG. 3 shows a schematic sectional view of a pre-chamber spark plug 1 according to a second exemplary embodiment of the present invention. As can be seen from FIG. 3, in the second embodiment a plurality of ribs 11 are situated along the inner circumference of the cap jacket 21. Here ribs 11 run parallel to the center axis. On the inside of cap base 20, no rib or other type of raised part is provided.

[0044] FIG. 4 shows a fourth embodiment of the present invention that substantially corresponds to the embodiment shown in FIG. 3. In contrast to the embodiment of FIG. 3, in the third exemplary embodiment ribs 11 are not oriented parallel to the center axis X-X of the pre-chamber spark plug. Furthermore, the ribs running in a straight line are also formed without a bevel 12. Through-opening 10 is here preferably parallel to the ribs. Ribs 11 here ensure a stabilization of the flow in pre-chamber 3.

[0045] The fourth embodiment shown in FIG. 5 corresponds substantially to the third embodiment, but differing therefrom the ribs 11 are curved. This makes it possible for gas flow 13 to undergo a deflection at ribs 11, for example in order to impose a swirl on the gas flow inside pre-chamber 3.

[0046] FIG. 6 shows a pre-chamber spark plug according to a fifth exemplary embodiment of the present invention. Differing from the above-described exemplary embodiments, in the fifth embodiment a fixing of ribs 11 is different. As shown in FIG. 6, rib 11 is not fixed to cap jacket 21 over its entire length, as in the above-described embodiments, but has a smaller fixing area 14.

[0047] In the assembled state, as shown in FIG. 6, this results in an intermediate space 15 between rib 11 and cap jacket 21. As can be seen from FIG. 6, in this embodiment rib 11 is fixed to the inside of the housing 4. Here rib 11 runs in the direction to cap base 20 parallel to the center axis X-X. This embodiment is advantageous in that no temperature increase occurs directly at cap 2 due to rib 11, because rib 11 is fixed only to housing 4. Thus, rib 11 has no effect on a temperature of cap 2.

[0048] FIG. 7 shows a sixth exemplary embodiment that is similar to the embodiment shown in FIG. 6. The rib 11 also has a fixing region 14 having a small surface. However, rib 11 of the sixth embodiment is fixed to cap 2, more precisely to cap jacket 21. The reduced connection of the rib 11 here reduces a dissipation of heat to the cap. An intermediate space 15 is formed here between rib 11 and housing 4.

[0049] FIG. 8 shows a seventh exemplary embodiment of the present invention. As can be seen from FIG. 8, in the seventh embodiment rib 11 is connected to cap jacket 21 at a plurality of individual small fixing areas 14. Intermediate spaces 15 are provided between each of the individual fixing areas 14. Fixing areas 14 can be, for example, point-like connections or line-like connections. As a result, a heat input into cap 2 can be further reduced.

[0050] FIG. 9 shows a pre-chamber spark plug having a rib 11 according to an eighth exemplary embodiment of the present invention. As can be seen from FIG. 9, rib 11 has a first width B1 on a main body of the rib. Rib 11 is connected to cap jacket 21 at a fixing area 14. As shown in FIG. 9, at fixing area 14 rib 11 has a second width B2 that is smaller than first width B1. This reduces a contact area between rib 11 and cap jacket 21, so that a heat transfer from rib 11 to cap 2 is reduced. This can prevent high temperatures of cap 2 due to the provision of ribs 11.

[0051] For all the described embodiments, it is to be noted that the described, different ribs 11 can each be fixed either to cap 2 or to housing 4 and project into pre-chamber 3. It is also possible for a plurality of geometrically differently shaped ribs 11 to be used on one pre-chamber spark plug. Here, any desired combinations of the different ribs 11 shown in embodiments 1 through 8 are possible. For all the embodiments, it should further be noted that ribs 11 are preferably made of a different material from cap 2 and housing 4, preferably of a nickel-containing alloy. Ribs 11 can be welded or soldered to cap 2 or housing 4 or fixed to these components by some other connection technique. Alternatively, ribs 11 are manufactured by an additive manufacturing process or MIM manufacturing process.