PURPOSE: To form a sufficiently carbureted mixture around a spark plug irrespective of an injection quantity.
CONSTITUTION: A spark plug is set up in the central part of a cylinder head inner wall surface, and two swirl type fuel injection valves 14a, 14b, whose spray angle becomes larger if the injection quantity goes beyond the constant value, is set up in a peripheral edge of the cylinder head inner wall surface. A recess groove 15, partitioned off by a pair of side wall surfaces 15b extending as gradually spreading toward these fuel injection valves 14a, 14b, is formed on top of a piston 2. Each recess groove side wall surface 15b is provided with a concave curved section while a radius of curvature in a cross section of each recess groove side wall surface 15b is gradually made larger toward each side of these fuel injection valves 14a, 14b. In succession, fuel is sprayed to one side of the paired recess groove side wall surfaces 15b from the fuel injection valve 14a while injection timing at a time when an injection quantity is less than a specified value is more delayed than that at a time when the injection quantity is much more than the specified value as well as when the injection quantity is less than the specified value, the fuel is sprayed toward the recess groove side wall surface 15b large in the radius of curvature being situated at each side of these fuel injection valves as compared with that when the injection quantity is larger than the specified value.
NAKAMURA NORIHIKO
NOMURA KENICHI
NIHEI HIROAKI
NAKADA KOICHI
