Auto-ignition gasoline engine combustion chamber and method
View Patent ↗A combustion chamber for an internal combustion engine includes a closed end cylinder having an axis. A piston is reciprocable in the cylinder and includes a generally flat rim having an inner edge surrounding a recessed bowl into which the fuel is primarily injected, the bowl having a floor and a surrounding side formed by an arcuate surface connecting tangentially with the floor and extending to the rim inner edge. A spark plug has a centerline through the spark gap and is offset to one side of the cylinder axis with the spark gap extending into the combustion chamber toward the axis. A fuel injector is offset to an opposite side of the axis with the spray tip aimed to direct a generally conical fuel spray into the piston bowl with a portion of the fuel spray passing near the spark gap. Various dimensional characteristics are disclosed.
1. A combustion chamber for an internal combustion engine comprising:
a closed end cylinder having an inlet port and an exhaust port formed therein with valve members disposed in the ports for controlling the flow of air and products of combustion to and from the combustion chamber, a gasoline fuel injector having a spray tip and a spark ignition source having a spark gap, the cylinder having an axis and positioned to receive air and fuel injected directly from the fuel injector; and
a piston mounted for reciprocation in the cylinder, the piston including a generally flat rim having an inner edge surrounding a recessed bowl into which the fuel is primarily injected, the bowl having a floor and a surrounding side formed by an arcuate surface connecting tangentially with the floor and extending to the rim inner edge;
the spark plug having a centerline through the spark gap and being offset to one side of the cylinder axis with the spark gap extending into the combustion chamber toward the axis; and
the injector being offset to an opposite side of the axis with the spray tip aimed to direct a generally conical fuel spray into the piston bowl with a portion of the fuel spray passing near the spark gap;
wherein the spark plug centerline is spaced inward from the bowl side arcuate surface by a minimum distance in a range of 6 to 10 mm.
2. A combustion chamber as in claim 1 including:
said arcuate surface having a radius in a range of three to twelve millimeters.
3. A combustion chamber as in claim 1 including:
said piston bowl being generally circular and the volume of the bowl being determined by a prescribed compression ratio of the combustion chamber.
4. A combustion chamber as in claim 1 including:
said spray tip forming a spray cone angle in a range of 50 to 90 degrees.
5. A combustion chamber as in claim 1 including:
said spark gap being spaced a dimension in a range of 10 to 20 mm from the injector tip.
6. A combustion chamber as in claim 1 including:
said spark gap extending a dimension in a range of 3 to 9 mm into the combustion chamber.
7. A combustion chamber as in claim 1 including:
the valve members being controllable for variable timing in a range from a normal amount of valve overlap to a substantial amount of negative overlap.
8. A combustion chamber as in claim 1 wherein the inner edge of the piston rim defines an outer circumference of the recessed bowl.
9. A combustion chamber as in claim 8 wherein the recessed bowl is generally centered on said cylinder axis.
10. A combustion chamber as in claim 9 wherein the spark gap and the injector are both positioned near the cylinder axis with the spark gap located below the injector and at least near the path of the conical fuel spray.
11. A combustion chamber as in claim 10 wherein said portion of the fuel spray passes at least closely adjacent to the spark gap.