Turbocharger control system for turbocharged internal combustion engines equipped with exhaust-gas recirculation control system

A turbocharger control system for a turbocharged internal combustion engine equipped with an exhaust-gas recirculation control system recycling part of inert exhaust gas back through the engine under predetermined operating conditions of the engine, comprising:

• a variable-displacement turbocharger variably adjusting a turbo-charging state;
• sensors detecting operating conditions of the engine;
• a turbocharger control unit configured to be electronically connected to said sensors and said variable-displacement turbocharger for automatically regulating the turbo-charging state;
• said turbocharger control unit comprising
• (1) a desired EGR rate arithmetic-calculation section arithmetically calculating a desired EGR rate (MEGRM) as a function of a first predetermined engine operating condition of the operating conditions detected by said sensors,
• (2) a desired turbo-charging controlled quantity arithmetic-calculation section arithmetically calculating a desired turbo-charging controlled quantity of said variable-displacement turbocharger as a function of the first predetermined engine operating condition,
• (3) a desired EGR-rate correction section correcting the desired EGR rate (MEGRM), and
• (4) a desired turbo-charging controlled quantity correction section correcting the desired turbo-charging controlled quantity in response to correction made to the desired EGR rate by said desired EGR-rate correction section.

In an internal combustion engine equipped with an exhaust-gas recirculation control system recycling part of inert exhaust gas back through the engine under predetermined operating conditions of the engine, and a variable-displacement turbocharger variably adjusting a turbo-charging state, comprising:

• a sensor means for detecting operating conditions of the engine;
• a turbocharger control means configured to be electronically connected to said sensor means and said variable-displacement turbocharger for automatically regulating the turbo-charging state;
• said turbocharger control means comprising
• (1) a desired EGR rate arithmetic-calculation means for arithmetically calculating a desired EGR rate (MEGRM) as a function of a first predetermined engine operating condition of the operating conditions detected by said sensors,
• (2) a desired turbo-charging controlled quantity arithmetic-calculation means for arithmetically calculating a desired turbo-charging controlled quantity of said variable-displacement turbocharger as a function of the first predetermined engine operating condition,
• (3) a desired EGR-rate correction means for correcting the desired EGR rate (MEGRM), and
• (4) a desired turbo-charging controlled quantity correction means for correcting the desired turbo-charging controlled quantity in response to correction made to the desired EGR rate by said desired EGR-rate correction section.

A method for controlling a variable-displacement turbocharger employed in an internal combustion engine, wherein the engine includes an exhaust-gas recirculation control system recycling part of inert exhaust gas back through the engine and having sensors detecting operating conditions of the engine, an air-flow meter detecting an actual intake-air flow rate (QAVNT), and an electronic control unit configured to be electronically connected to the sensors, the air-flow meter and the variable-displacement turbocharger for automatically regulating a turbo-charging state of the variable-displacement turbocharger, the method comprising:

• arithmetically calculating a desired EGR rate (MEGRM) as a function of a first predetermined engine operating condition of the operating conditions detected by the sensors,
• arithmetically calculating a desired turbo-charging controlled quantity of the variable-displacement turbocharger as a function of the first predetermined engine operating condition,
• correcting the desired EGR rate (MEGRM),
• correcting the desired turbo-charging controlled quantity in response to correction made to the desired EGR rate, said correction, which is made to the desired turbo-charging controlled quantity in response to the correction made to the desired EGR rate, is executed as a correcting action made to a feedforward controlled quantity,
• estimating a desired value (QCSSP2) of the turbo-charging state,
• arithmetically calculating a feedback correction value (DUTS) by comparing the desired value (QCSSP2) of the turbo-charging state with the actual intake-air flow rate (QAVNT),
• executing feedback correction with respect to the feedforward controlled quantity, using the feedback correction value (DUTS) under a predetermined operating condition of the engine.