US 12,031,474 B2
Prechamber spark plug having an optimized cap, and internal combustion engine
Matthias Blankmeister, Heiligenhaus (DE); Stephan Kaske, Sternenfels Diefenbach (DE); and Thomas Steidten, Ludwigsburg (DE)
Assigned to ROBERT BOSCH GMBH, Stuttgart (DE)
Appl. No. 18/003,468
Filed by Robert Bosch GmbH, Stuttgart (DE)
PCT Filed Jun. 23, 2021, PCT No. PCT/EP2021/067099
§ 371(c)(1), (2) Date Dec. 27, 2022,
PCT Pub. No. WO2022/008242, PCT Pub. Date Jan. 13, 2022.
Claims priority of application No. 10 2020 208 578.1 (DE), filed on Jul. 8, 2020.
Prior Publication US 2023/0235695 A1, Jul. 27, 2023
Int. Cl. F02B 19/12 (2006.01); F02B 19/18 (2006.01)
CPC F02B 19/12 (2013.01) [F02B 19/18 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A prechamber spark plug arrangement that includes a prechamber spark plug, the prechamber spark plug comprising:
a housing; and
a cap, which defines a prechamber at least partially, and which includes a plurality of through holes that are configured to produce a connection between the prechamber and a combustion chamber of a cylinder of an internal combustion engine, the through holes each having a hole center line;
wherein:
the cap includes a recess at a region forming a surface of the cap that (a) faces towards the housing and that (b) abuts the housing at a combustion-chamber-side end of the housing; and
the prechamber spark plug includes at least one of the following features (I)-(IV):
(I) at least one of the following features (i) and (ii) is provided for one of the through holes:
(i) a distance from (a) an exit point of the one of the through holes that lies on the hole center line of the one of the through holes to (b) the surface of the recess is in a range of 2 mm to 7 mm; and
(ii) the hole center line of the one of the through holes lies on a same plane as (a) a beginning of an external thread of the housing at a combustion-chamber-side end of the housing facing the combustion chamber and (b) a center axis of the prechamber spark plug, when the housing is completely screwed into a cylinder head of the cylinder;
(II) the recess is formed by a radially inward step of an exterior surface of the cap;
(III) the prechamber spark plug is arranged relative to the combustion chamber and to a fuel injector in the cylinder head such that a center axis of a conical spray of fuel, when generated by the fuel injector into the combustion chamber, is, relative to the center axis of the prechamber spark plug, at an angle that is within a range of 30° to 70°; and
(IV) the through holes are oriented relative to the combustion chamber such that a direction of a stream of a tumble flow of the fuel, generated by a movement of a piston in the cylinder, is parallel to and in line with the hole center line of at least one of the through holes for direct reception therein of the stream.