Exhaust emission control apparatus and method for internal combustion engine

An exhaust emission control apparatus for an internal combustion engine, comprising:

• a fuel injection valve placed substantially at a midpoint above a combustion chamber of the engine;
• a piston having
• an outer cavity formed substantially in a midsection of an upper surface of the piston and
• an inner cavity formed in a bottom surface of the outer cavity;
• an ignition plug placed in a region right above the outer cavity;
• an exhaust purifying catalyst provided in an exhaust passage of the engine;
• and
• a controller configured to carry out a stratified charge combustion when a temperature rise for the exhaust purifying catalyst is required, by
• forming an air-fuel mixture within the outer cavity and in an area substantially right above the outer cavity from a fuel injected through the fuel injection valve and
• allowing the ignition plug to ignite the air-fuel mixture after a compression top dead center of the piston.

An exhaust emission control apparatus for an internal combustion engine, comprising:

• injection means for injecting fuel, being placed substantially at a midpoint above a combustion chamber of the engine;
• a piston having
• an outer cavity formed substantially in a midsection of an upper surface of the piston and
• an inner cavity formed in a bottom surface of the outer cavity;
• ignition means for igniting an air-fuel mixture, being placed in a region right above the outer cavity;
• an exhaust purifying catalyst provided in an exhaust passage of the engine;
• and
• control means for carrying out a stratified charge combustion when a temperature rise for the exhaust purifying catalyst is required, by
• forming the air-fuel mixture which is richer than stoichiometric ratio and is able to be ignited by the ignition means, within the outer cavity and in an area substantially right above the outer cavity, from the fuel injected through the injection means.

An exhaust emission control method for an internal combustion engine including

• a piston having
• an outer cavity formed substantially in a midsection of an upper surface of the piston and
• an inner cavity formed in a bottom surface of the outer cavity,
• an ignition plug placed in a region right above the outer cavity, and
• an exhaust purifying catalyst provided in an exhaust passage of the engine, the exhaust emission control method comprising:
• carrying out a stratified charge combustion when a temperature rise for the exhaust purifying catalyst is required, by forming an air-fuel mixture which is richer than stoichiometric ratio and is able to be ignited by the ignition plug within the outer cavity and in an area substantially right above the outer cavity.