To provide a combustion chamber structure in which unburnt fuel does not remain in a multiple ignition engine.
The combustion chamber structure of the engine in which an air flow sucked in from two intake ports 11 becomes a tumble flow, and a twin swirl is generated from the tumble flow such that the twin swirl flows to swirl in the opposite direction to each other, includes a center ignition plug 15a arranged in the vicinity of a center line CL passing through between two intake valves 13 and between two exhaust valves 14, and a circumference ignition plugs 15b arranged in the vicinity of the circumference of the combustion chamber, when viewed in the cylinder axis direction. A size relationship between a width of an inlet-side squish area 20a and a width of an exhaust-side squish area 20b in the vicinity of the center line CL, and a size relationship between the width of the inlet-side squish area 20a and the width of the exhaust-side squish area 20b in the vicinity of a linear line parallel to the center line CL and passing through the center of circumference ignition plugs 15b become opposite to each other when viewed in the cylinder axis direction.
KONISHI YASUHIRO
Masahiro Fujii
Masaaki Iida
Yasunari Mita