Direct injection type internal combustion engine

A device for stratifying an intake gas charge within a combustion chamber of a direct-injection type internal combustion engine in which a plurality of intake ports are provided to form a plurality of swirl flows of intake gases in a same direction of rotation in the combustion chamber and in which a fuel is injected into the combustion chamber, from a center portion of a top surface of the combustion chamber opposed to a top face of a piston, toward a peripheral part of a cavity formed in a central portion of the top face of the piston, said device comprising:

• an arrangement for forming, in an intake stroke, a swirl flow of a first intake gas in an upper portion of the combustion chamber, along a cylindrical wall of the combustion chamber, and a swirl flow of a second intake gas in a lower portion of the combustion chamber, along the cylindrical wall of the combustion chamber, and for maintaining a state of vertical stratification of the intake gas charge consisting of the swirl flows of the first and second intake gases within the combustion chamber, up to a point of time within an intermediate period of a compression stroke;
• an arrangement for causing the first intake gas to flow into a central region of the cavity in the central portion of the top face of the piston, while the second intake gas remains in a peripheral region and a bottom region of the cavity, in a latter half of a compression stroke in which a squish flow is created;
• and
• an arrangement for stratifying the intake gas charge within the combustion chamber at a point of time near a terminal period of the compression stroke in which the combustion of the fuel is initiated, such that the first intake gas exists primarily in a region inside a generally hemispherical or generally flat hemispherical plane having its center at a position of injection of the fuel into the combustion chamber, while the second intake gas exists primarily in a region outside the generally hemispherical or generally flat hemispherical plane.

A direct-injection type internal combustion engine in which a plurality of intake ports are provided to form a plurality of swirl flows of intake gases in a same direction of rotation in a combustion chamber and in which a fuel is injected into the combustion chamber, from a center portion of a top surface of the combustion chamber opposed to a top face of a piston, toward a peripheral part of a cavity formed in a central portion of the top face of the piston, said engine comprising:

• an arrangement for forming, in an intake stroke, a swirl flow of a first intake gas not containing a recirculated exhaust gas, along an upper portion of a cylindrical wall of the combustion chamber, and a swirl flow of a second intake gas containing the recirculated exhaust gas, along a lower portion of the cylindrical wall of the combustion chamber;
• an arrangement for causing the first intake gas to flow into a central region of the cavity in the central portion of the top face of the piston, while the second intake gas remains in a peripheral region and a bottom region of the cavity, in a latter half of a compression stroke in which a squish flow is created;
• and
• an arrangement for stratifying an intake gas charge within the combustion chamber at a point of time near a terminal period of the compression stroke in which the combustion of the fuel is initiated, such that the intake gas not containing the recirculated exhaust gas or having a low concentration of the recirculated exhaust gas exists in a region inside a generally hemispherical or generally flat hemispherical plane having its center at a position of injection of the fuel into the combustion chamber, while the intake gas containing the recirculated exhaust gas or having a high concentration of the recirculated exhaust gas exists in a region outside the generally hemispherical or generally flat hemispherical plane.

A direct-injection internal combustion engine of compression-ignition or spark-ignition type in which a plurality of intake ports are provided to form a plurality of swirl flows of intake gases in a same direction of rotation in the combustion chamber and in which a premixing amount of a fuel is injected into the combustion chamber or an intake passage, at a premixing fuel-injection timing before 30° BTDC in an intake or compression stroke, and in which combustion of the fuel is initiated at a point of time near a terminal period of a compression stroke, said engine comprising:

• a cavity formed in a central portion of a top face of a piston;
• a squish area over a peripheral portion of the top face of the piston;
• an arrangement for injecting the premixing amount of the fuel into a swirl flow of a specific intake gas within the combustion chamber, or into an intake gas in a specific intake port or an intake passage including the specific intake port,
• and an arrangement for stratifying an intake gas charge within the combustion chamber upon initiation of combustion of the fuel, such that an intake gas containing the fuel or having a high concentration of the fuel exists in a central portion of the combustion chamber including a center portion of a top surface of the combustion chamber, while an intake gas not containing the fuel or having a low concentration of the fuel exists in the squish area and near wall surfaces of the cavity.