Sequential turbocharger system for an internal combustion engine

An internal combustion engine, comprising:

• an engine body;
• an intake line for introducing a combustible mixture into the engine body;
• an exhaust line for removing exhaust gas from the engine body;
• a first, large-volume turbocharger having a turbine thereof arranged in the exhaust line, and a compressor thereof arranged in the intake line;
• a second, small-volume turbocharger having a turbine thereof arranged in the exhaust line, at a position upstream of the turbine of the large-volume turbocharger in a direction of the flow of the exhaust gas, and a compressor thereof arranged in the intake line at a position downstream of the compressor of the large-volume turbocharger in the direction of the flow of the intake air;
• a bypass passageway connected to the exhaust line so as to bypass the turbine of the small-volume turbocharger;
• exhaust switching valve means for controlling the flow of the exhaust gas in said bypass passageway;
• means, responsive to engine operating conditions, for controlling a two-stage operation of the exhaust switching valve means in such a manner that the exhaust switching valve is gradually opened when a preset pressure of the intake air at a position downstream of the small-volume turbocharger in the intake line is obtained, and is quickly opened when the preset pressure is obtained in the intake line at the position downstream of the compressor of the large-volume turbocharger, and;
• exhaust gas recirculation means for taking out an amount of exhaust gas from the exhaust line at a position located between the turbine of the large-volume turbocharger and the turbine of the small-volume turbocharger and for introducing the taken out exhaust gas into the intake line.

An internal combustion engine, comprising:

• an engine body;
• an intake line for introducing a combustible mixture into the engine body;
• an exhaust line for removing the exhaust gas from the engine body;
• a first, large-volume turbocharger having a turbine thereof arranged in the exhaust line, and a compressor thereof arranged in the intake line;
• a second, small-volume turbocharger having a turbine thereof arranged in the exhaust line at position upstream of the turbine of the large-volume turbocharger in the direction of the flow of the exhaust gas, and a compressor thereof arranged in the intake line at a position downstream of the compressor of the large-volume turbocharger in the direction of the flow of the intake air;
• a bypass passageway connected to the exhaust line so as to bypass the turbine of the small turbocharger;
• exhaust switching valve means for controlling the flow of the exhaust gas in said bypass passageway;
• a first pressure sensor arranged in the intake line at a position downstream of the compressor of the large-volume turbocharger;
• a second pressure sensor arranged in the intake line at a position downstream of the compressor of the small-volume turbocharger;
• actuator means for obtaining a two-stage operation of the exhaust switching valve;
• step operation control means for operating the actuator in such a manner that the actuator controls the exhaust switching valve so that said valve is gradually opened when the second sensor detects a preset value of the intake pressure and is quickly opened when the first sensor detects the preset value of the intake pressure, and;
• exhaust gas recirculation means for taking out an amount of exhaust gas from the exhaust line at a position located between the turbine of the large-volume turbocharger and the turbine of the small-volume turbocharger and for introducing the taken out exhaust gas into the intake line.