Method for controlling a turbocharger system of an internal combustion engine, and turbocharger system

#This application claims priority to German Patent Application No. 102010037368.0, filed on Sep. 7, 2010, the entire contents of which being incorporated herein by reference.

#The disclosure relates to a method for controlling a turbocharger system of an internal combustion engine, and to a turbocharger system.

#Internal combustion engines, in particular diesel and spark-ignition engines, are increasingly provided with turbochargers. A turbocharger serves to compress the air supplied to the engine, whereby an increase in power can be achieved. Conversely, a predefined power output can be achieved by a turbocharged engine of smaller cubic capacity, whereby a smaller and lighter construction and more fuel-saving propulsion can be attained.

#FIG. 1 is a simplified block diagram of an internal combustion engine with a turbocharger system according to an embodiment of the present disclosure.

#FIG. 2 shows an example graph illustrating turbine efficiency as a function of the pressure ratio.

#FIG. 3 is a flow diagram showing the sequence of an exemplary embodiment of the method according to the disclosure.

#According to the exemplary embodiment of the disclosure represented in FIG. 1, an internal combustion engine 1, which may be, for example, a spark-ignition or a diesel engine, has a turbocharger system 2 comprising a high pressure turbocharger 3 and a low pressure turbocharger 4. A high pressure turbine 6, which drives a high pressure compressor 8 in the charge air system 9 of the internal combustion engine 1 via a shaft 7, is arranged in the exhaust system 5 of the internal combustion engine 1. A low pressure turbine 10, which drives a low pressure compressor 12 via a shaft 11, is arranged in the exhaust system 5 downstream of the high pressure turbine 6. In the embodiment depicted in FIG. 1, the turbine and compressor of the high pressure turbocharger 3 are dimensioned smaller than the turbine and compressor of the low pressure turbocharger 4. A first bypass valve 13 (also referred to as a turbine valve, TBV) is associated with the high pressure turbine 6, the complete or partial opening of which bypass valve 13 produces a bypass through which the exhaust gas flow bypasses the high pressure turbine 6 completely or partially. The drive of the high pressure turbine 6, and therefore of the high pressure turbocharger 3, can therefore be controlled via the position of the first bypass valve 13. Correspondingly, a second bypass valve 14 (wastegate, WG), by which the low pressure turbocharger 4 can be controlled, is associated with the low pressure turbine 10. The exhaust gas flow therefore passes first through the high pressure turbine 6 or the first bypass valve 13, then through the low pressure turbine 10 or the second bypass valve 14, and is then conducted into further devices of the exhaust system (indicated in FIG. 1 by the arrow pointing downwards), for example into an exhaust gas after-treatment system.

#The charge air first flows through the low pressure compressor 12, in the direction of the arrow pointing upwards. The charge air can then flow through the high pressure compressor 8 or bypass the latter via a bypass opened or closed by a third bypass valve 15 (compressor bypass valve, CBV), before being cooled by an intercooler 16 and then supplied to the internal combustion engine 1. The third bypass valve may be actuated passively, in particular by a pressure in the charge air system 9, or may be activated actively. The charge air flow or the charge pressure may be measured by a sensor 17 symbolically represented in FIG. 1. An optionally present exhaust gas recirculation (EGR) system is depicted in FIG. 1. The EGR system diverts a portion of the exhaust gases back to the intake. In one embodiment, the EGR system may include an EGR passage 20 arranged to divert the exhaust after traveling by the high and low pressure turbines and inject it into the intake passage prior to the low pressure compressor. In other embodiments, an EGR passage may be arranged before either the high or low pressure turbines and inject the exhaust into the intake passage after the high and low pressure compressors. However, any suitable EGR arrangement is within the scope of this disclosure.

#A control system 22 may activate the turbocharger system. The control system 22 includes, in particular, a processor 24 for determining the positions of the bypass valves according to a turbine model, a memory 26 for storing the turbine model, and a control unit 28 for activating the bypass valves according to the positions determined, the processor 24 being set up to execute the methods described herein. In addition, the control system 22 includes suitable inputs 30 for capturing input variables, such as the rotational speed and the load of the internal combustion engine, the inlet and outlet pressures of the high pressure and the low pressure turbine and/or the rotational speeds of the high pressure and the low pressure turbine. Furthermore, the control system 22 includes outputs 32 for activating the bypass valves of the high pressure and the low pressure turbine, and optionally of a third bypass valve and/or further actuating elements. The control system 22 may be, in particular, a part of an electronic engine management system.