Exhaust gas recirculation system for an internal combustion engine

An exhaust gas recirculation system for an internal combustion engine, comprising:

• means for changing a period of time for which an open state of an intake valve for the engine overlaps with an open state of an exhaust valve therefor;
• an outside exhaust gas recirculation duct connected to an exhaust system of the engine and an intake system thereof for recirculating a portion of exhaust gases into the intake system thereof while forcibly cooling the portion of the exhaust gases;
• an exhaust gas recirculation control valve disposed at said outside exhaust gas recirculation duct;
• load detecting means for detecting a load of the engine;
• control means for generating a control signal to said means for changing said period of time in response to a signal from said load detecting means so as to extend said period of time when the engine exists in a low-load driving state and so as to shorten said period of time when the engine exists in a high-load driving state;
• and
• exhaust gas recirculation controlling means for closing said exhaust gas recirculation control valve when the engine exists in the low-load driving state and for opening said exhaust gas recirculation control valve when the engine is in the high-load driving state, in response to a signal from said load detecting means.

An exhaust gas recirculation system for an internal combustion engine, comprising:

• a supercharger disposed at an intake system of the internal combustion engine;
• means for changing a period of time for which an open state of the intake system thereof overlaps with an open state of the exhaust system thereof;
• an outside exhaust gas recirculation duct connected to an intake system thereof and an exhaust system thereof for recirculating a portion of exhaust gases into the intake system thereof, while cooling forcibly;
• an exhaust gas recirculation control valve disposed at said outside exhaust gas recirculation duct;
• load detecting means for detecting a load of the engine;
• control means for generating a control signal to said means for changing said period of time in response to a signal from said load detecting means so as to shorten said period of time when the engine exists in an extremely low-load driving state and so as to extend said period of time when the engine exists in a light-load or high-load driving state;
• and
• exhaust gas recirculation controlling means for closing said exhaust gas recirculation control valve when the engine exists in the extremely low-load driving state or in the light-load driving state and for opening said exhaust gas recirculation control valve when the engine is in the high-load driving state, in response to a signal from said load detecting means.

An exhaust gas recirculation system for an internal combustion engine which is so arranged as to extend a period of time during which an open state of an intake valve overlaps with an open state of an exhaust valve by putting forward a timing at which the intake valve of the engine is opened, comprising:

• a second throttle valve disposed in the vicinity of an intake port of the engine;
• an actuator for driving said second throttle valve;
• an outside exhaust gas recirculation duct connected to the intake system thereof and the exhaust system thereof for recirculating a portion of exhaust gases while forcibly cooling into the intake system thereof;
• an exhaust gas recirculation control valve disposed at said outside exhaust gas recirculation duct;
• load detecting means for detecting a load of the engine;
• throttle valve controlling means for controlling said second throttle valve in a direction of closing said second throttle valve when the engine exists in an extremely low-load driving state and for opening said second throttle valve to a full extent when the engine exists in a light-load driving region or in a high-load driving state;
• and
• exhaust gas recirculation controlling means for closing said exhaust gas recirculation control valve when the engine exists in the extremely low-load driving state or in the light-load driving state and for opening said exhaust gas recirculation control valve when the engine is in the high-load driving state, in response to a signal from said load detecting means.

An exhaust gas recirculation system for an internal combustion engine, comprising:

• a mechanism for changing a timing at which an intake valve of the engine is closed;
• an outside exhaust gas recirculation duct connected to an intake system thereof and an exhaust system thereof for recirculating a portion of exhaust gases while forcibly cooling into the intake system thereof;
• an exhaust gas recirculation control valve disposed at said outside exhaust gas recirculation duct;
• load detecting means for detecting a load of the engine;
• control means for generating a control signal to said mechanism for changing said timing in response to a signal from said load detecting means so as to delay the timing of closing said intake valve when the engine exists in a low-load driving state and so as to put forward said timing of closing said intake valve when the engine exists in a high-load driving state;
• and
• exhaust gas recirculation controlling means for closing said exhaust gas recirculation control valve when the engine exists in the low-load driving state and for opening said exhaust gas recirculation control valve when the engine is in the high-load driving state, in response to a signal from said load detecting means.

An exhaust gas recirculation system for an internal combustion engine, comprising:

• a first outside exhaust gas recirculation duct connected to an exhaust system of the internal combustion engine and an intake system thereof for recirculating a portion of exhaust gases into the intake system thereof;
• a second outside exhaust gas recirculation duct connected to the exhaust system of the internal combustion engine and the intake system thereof for recirculating a portion of exhaust gases into the intake system thereof while forcibly cooling said portion of exhaust gases;
• a first exhaust gas recirculation control valve disposed at said first outside exhaust gas recirculation duct;
• a second exhaust gas recirculation control valve disposed at said second outside exhaust gas recirculation duct;
• load detecting means for detecting a load of the engine;
• and
• exhaust gas recirculation controlling means for controlling exhaust gas recirculation in a direction of closing said first exhaust gas recirculation control valve while in a direction of opening said second exhaust gas recirculation control valve in accordance with a magnitude of the load, in response to a signal from said load detecting means, when the engine exists in a high-load driving state.