PRECHAMBER SPARK PLUG WITH IMPROVED CAP

Abstract

A prechamber spark plug. The prechamber spark plug includes a housing and a cap, which is arranged at a combustion-chamber end of the prechamber spark plug. The cap has, on the combustion-chamber side, a recess in an outer side.

Claims

1-11. (canceled)

12. A prechamber spark plug, comprising a housing; and a cap arranged at a combustion-chamber end of the prechamber spark plug, wherein the cap has, on a combustion-chamber side, a recess in an outer side.

13. The prechamber spark plug as recited in claim 12, wherein a first passage opening is provided in the cap which opens into the recess in the cap.

14. The prechamber spark plug as recited in claim 13, wherein a plurality of passage openings open into the recess in the cap.

15. The prechamber spark plug as recited in claim 12, wherein an inner side of the cap is of concave configuration.

16. The prechamber spark plug as recited in claim 12, wherein the recess is of concave configuration.

17. The prechamber spark plug as recited in claim 12, wherein the housing has an external thread, and the recess in the cap is positioned as a function of a start and/or end of the external thread.

18. The prechamber spark plug as recited in claim 17, wherein a center of the recess and a thread start lie on the housing in a plane which is arranged in a center axis of the prechamber spark plug.

19. The prechamber spark plug as recited in claim 12, wherein the recess is a trough of symmetrical configuration.

20. The prechamber spark plug as recited in claim 12, wherein the cap has at least one further passage opening, which runs through the cap outside the recess, and wherein a first angle of a first midline of the first passage opening relative to a center axis of the prechamber spark plug differs from a second angle of the further passage opening relative to the center axis of the prechamber spark plug.

21. The prechamber spark plug as recited in claim 12, wherein the cap has precisely one single recess.

22. The prechamber spark plug as recited in claim 12, wherein the cap is an MIM component or a sintered component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] A preferred exemplary embodiment of the present invention is described in detail below with reference to the figures.

[0016] FIG. 1 is a schematic side view of a prechamber spark plug according to an exemplary embodiment of the present invention.

[0017] FIG. 2 is a schematic, enlarged sectional detail view of the cap of the prechamber spark plug of FIG. 1.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0018] A prechamber spark plug 1 according to a preferred exemplary embodiment of the present invention is described in detail below with reference to FIGS. 1 and 2.

[0019] As is shown in FIG. 1, the prechamber spark plug 1 comprises a prechamber 2 which is defined by a cross-sectionally substantially U-shaped cap 3. The cap 3 is fixed to a housing 6 of the prechamber spark plug, for example by way of a welded joint 9. The cap 3 is arranged at an installation-space end 10 of the prechamber spark plug.

[0020] The prechamber spark plug 1 further comprises a center electrode 5 and an insulator 7.

[0021] The housing 6 has an external thread 4, which is arranged at the combustion-chamber end of the housing 6. The cap 3 adjoins the housing 6.

[0022] The external thread 4 serves to fix the prechamber spark plug in a cylinder head or the like.

[0023] A plurality of passage openings 31, 32 are furthermore provided in the cap 3. On ignition in the prechamber 2 of the prechamber spark plug, “torch jets” are delivered through the passage openings 31, 32 into a combustion chamber of an internal combustion engine, in which a mixture of fuel and air is then ignited. The number and position of the passage openings 31, 32 may vary.

[0024] Since every internal combustion engine has different conditions with regard to the position of the prechamber spark plug 1 relative to an injector jet and the position of the injector and further geometric constraints, such as for example the geometry of a piston and the arrangement of further components on the installation space, individual adaptation of the prechamber spark plug is desirable for optimized flow control. This is achieved in that the cap 3 is of asymmetric configuration.

[0025] The cap 3 has, on the combustion-chamber side, a recess 8, in this exemplary embodiment a trough-shaped recess, in an outer side 34. The recess 8 here has the geometric shape of part of the surface of a sphere.

[0026] As is shown in the detail view of FIG. 2, a first passage opening 31 here opens into the recess 8. The first passage opening 31 is here of linear configuration and has a midline M1. The midline M1 is arranged at a first angle α to a center axis X-X of the prechamber spark plug 1.

[0027] FIG. 2 additionally has a second passage opening 32 with a second midline M2, which is arranged at a second angle β to the center axis X-X of the prechamber spark plug. The angle β is here greater than the angle α.

[0028] Furthermore, the cap 3 has an inner side 33 which is concave throughout.

[0029] Due to the asymmetric configuration of the cap 3 with the recess 8 into which the first passage opening 31 opens, optimized gas flow can now be achieved on the one hand during a gas change to exchange the gas in the prechamber 2 and also during the exit of torch jets from the prechamber 2 via the first passage opening 31. For example, the torch jets exiting from the first passage opening 31 are directed such that they are directed onto a region of high ignitability in the combustion chamber.

[0030] Furthermore, the first midline M1 of the first passage opening 31 and a start 40 of the external thread 4 lie in one plane (in the section plane shown in FIG. 2), wherein the plane also encompasses the center axis X-X of the prechamber spark plug 1. In this way, precise positioning of the recess 8 in the asymmetrically configured cap 3 may be achieved when mounting the prechamber spark plug 1 on a cylinder head or the like. In this way, mounting errors may in particular be avoided which would not lead to the desired optimized gas flow control in the event of incorrect positioning of the recess 8 on the combustion chamber.

[0031] It is thus possible to achieve a predetermined orientation of the recess 8 relative to a thread start 40 as well as a predetermined orientation of the first passage opening 31 relative to the thread start 40.

[0032] Thus, by way of the clever feature according to the present invention of providing at least one recess 8 in an outer side of the cap 3, targeted gas flow can be achieved both during outflow of gas out of the prechamber 2 and during inflow of gas into the prechamber 2. The geometric shape of the recess 8 can here in each case be adapted to the prevailing circumstances in a combustion chamber. The cap 3 may for example be produced inexpensively by MIM methods or by sintering.

[0033] It should be noted that it is also possible for a plurality of recesses 8 to be provided on the outer side 34 of the cap 3. A plurality of passage openings may also open into one recess in the cap 3.