Control of supercharged engine with variable geometry turbocharger and electric supercharger

Abstract

There is provided a method of controlling an engine system comprising an internal combustion engine, a supercharging system having at least one supercharger to boost intake air to the internal combustion engine, a turbine, and a motor. The turbine receives an exhaust gas flow through flow restriction and is capable of at least partly driving the supercharging system. The motor is capable of at least partly driving the supercharging system. The method comprises reducing the flow restriction and increasing power to drive the motor as a desired intake airflow of the engine increases. By reducing the flow restriction, such as increasing nozzle opening of a variable geometry turbine (VGT), as desired intake airflow of the engine increases, such as when the engine speed increases, an excessively high pressure in the exhaust passage may be prevented. Therefore, the residual gas in the combustion chamber may be decreased so that the knocking may be prevented without retarding the ignition timing or enriching the air-fuel ratio while more air is charged into the engine. At the same time, by increasing the power to drive the motor, such as increasing electricity supplied to an electric motor to drive a compressor, desired amount of the intake air may be charged into the engine even when the flow restriction is decreased and the turbine efficiency may be decreased accordingly. Consequently, the engine can output more torque without degrading the engine fuel economy.

Dependencies are inferred from the claim text.