Internal-combustion engine

An internal-combustion engine comprising:

• a cylinder including a combustion chamber;
• a piston provided in the cylinder to reciprocate in the cylinder and including a top surface and a cavity provided in the top surface and having a front half and a rear half, the cavity comprising:
• a bottom surface;
• a vertical wall at the front half of the cavity provided near a center of the top surface and standing substantially perpendicularly from the bottom surface, the vertical wall extending from the bottom surface to the top surface;
• a first sidewall extending toward a first end of the vertical wall and extending from the bottom surface to the top surface;
• a second sidewall extending toward a second end of the vertical wall, the second end being opposite to the first end in the vertical wall, the second sidewall extending from the bottom surface to the top surface;
• a first curved transition wall portion between the first sidewall and the vertical wall;
• and
• a second curved transition wall portion between the second sidewall and the vertical wall;
• a spark plug provided above the combustion chamber to generate a spark that ignites a mixture of fuel and air in the cylinder and to face toward a position close to a center of the combustion chamber;
• and
• a fuel injection valve facing the combustion chamber and including a plurality of injection ports from which a plurality of fuel mists are to be obliquely injected toward the top surface of the piston in respectively different directions at a predetermined crank angle in a compression stroke, the cavity extending from a position close to a center of the piston toward the fuel injection valve when viewed from above the top surface of the piston, the first and second sidewalls extending toward the fuel injection valve when viewed from above the top surface of the piston, the plurality of injection ports comprising:
• a first injection port from which a first fuel mist is to be injected at the predetermined crank angle toward the vertical wall and an adjoining portion adjoining the vertical wall, the adjoining portion being provided in the top surface of the piston;
• second injection ports from which a pair of second fuel mists are to be injected at the predetermined crank angle to respectively collide with the first and second sidewalls, the first and second sidewalls being provided to guide the second fuel mists to flow along the first and second sidewalls toward the vertical wall, the first and second curved transition wall portions being provided to guide the second fuel mists to flow from the first and second side walls toward the vertical wall;
• and
• a third injection port from which a third fuel mist is to be injected to collide with the bottom surface of the cavity, the bottom surface being provided to lift the first fuel mist and the second fuel mists to flow toward the spark plug,
• wherein the plurality of injection ports further comprises a pair of fourth injection ports from which a pair of fourth fuel mists are to be injected at the predetermined crank angle from the fourth injection ports such that an entirety of each of the pair of fourth fuel mists each respectively collide with portions other than the cavity in the top surface of the piston,
• wherein the pair of fourth fuel mists are injected toward a position closer to the fuel injection valve than corresponding positions to which the pair of second fuel mists are injected as measured in a direction parallel to a center axis of the piston, and
• wherein a distance between the first and second sidewalls continuously reduces beginning within the rear half of the cavity and continuing to the first curved transition wall portion along a direction toward the vertical wall.

An internal-combustion engine comprising:

• a cylinder including a combustion chamber;
• a piston provided in the cylinder to reciprocate in the cylinder and including a top surface and a cavity provided in the top surface and having a front half and a rear half, the cavity comprising:
• a bottom surface;
• a vertical wall at the front half of the cavity and provided near a center of the top surface and standing substantially perpendicularly from the bottom surface, the vertical wall extending from the bottom surface to the top surface;
• a first sidewall extending toward a first end of the vertical wall and extending from the bottom surface to the top surface;
• a second sidewall extending toward a second end of the vertical wall, the second end being opposite to the first end in the vertical wall, the second sidewall extending from the bottom surface to the top surface;
• a first curved transition wall portion between the first sidewall and the vertical wall;
• and
• a second curved transition wall portion between the second sidewall and the vertical wall;
• a spark plug provided above the combustion chamber to generate a spark that ignites a mixture of fuel and air in the cylinder and to face toward a position close to a center of the combustion chamber;
• and
• a fuel injection valve facing the combustion chamber and including a plurality of injection ports from which a plurality of fuel mists are to be obliquely injected toward the top surface of the piston in respectively different directions at a predetermined crank angle in a compression stroke, the cavity extending from a position close to a center of the piston toward the fuel injection valve when viewed from above the top surface of the piston, the first and second sidewalls extending toward the fuel injection valve when viewed from above the top surface of the piston, the plurality of injection ports comprising:
• a first injection port from which a first fuel mist is to be injected at the predetermined crank angle;
• second injection ports from which a pair of second fuel mists are to be injected at the predetermined crank angle;
• and
• a third injection port from which a third fuel mist is to be injected,
• wherein a distance between the first and second sidewalls continuously reduces beginning within the rear half of the cavity and continuing to the first curved transition wall portion along a direction toward the vertical wall.