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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by reading an example of embodiments in which the above aspects are used to advantage, referred to herein as the Detailed Description, with reference to the drawings wherein:

FIG. 1 is a schematic view showing an engine system according to a first embodiment of the present description;

FIG. 2 is a more detailed diagram showing the engine system according to the first embodiment;

FIG. 3 shows a sectional view of a turbine of a turbocharger of the engine system according to the first embodiment;

FIG. 4 shows a flowchart illustrating a control routine of a supercharging system of the engine system according to the first embodiment;

FIG. 5 shows control maps used in the control routine shown in FIG. 4;

FIG. 6 is a diagram showing operating regions of the engine system according to the first embodiment;

FIG. 7 shows graphs of intake manifold pressure and exhaust manifold pressure for engine systems in accordance with the first embodiment and first and second comparative examples;

FIG. 8 shows graphs of maximum torque curves for engine systems in accordance with the first embodiment, a second embodiment and the first and second comparative examples; and

FIG. 9 is a schematic view of the engine system in accordance with the second embodiment of the present description.

Claims

1. 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 said internal combustion engine, a turbine, and a motor, wherein said turbine receives an exhaust gas flow from said internal combustion engine through flow restriction and is capable of at least partly driving said supercharging system, and wherein said motor is capable of at least partly driving said supercharging system, the method comprising: reducing said flow restriction of said turbine and increasing power to drive said motor as a desired intake airflow of said engine increases.

2. The method as described in claim 1, wherein said flow restriction is decreased by opening a nozzle arranged upstream of a turbine wheel of said turbine.

3. The method as described in claim 2, wherein said nozzle is closed to increase flow rate of the exhaust gas through said turbine wheel.

4. The method as described in claim 1, wherein said supercharging system has a first compressor driven by said turbine and a second compressor driven by said motor.

5. The method as described in claim 4, wherein said motor is an electric motor to drive said second compressor.

6. The method as described in claim 1, wherein said motor is an electric motor.

7. The method as described in claim 1, further comprising reducing said power to drive said motor as desired torque of said engine decreases.

8. The method as described in claim 1, further comprising reducing said flow restriction as desired torque of said engine decreases.

9. The method as described in claim 8, further comprising reducing said flow restriction as desired torque of said engine decreases.

10. 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 said internal combustion engine, a turbine, and a motor, wherein said turbine receives an exhaust gas flow from said internal combustion engine through flow restriction and is capable of at least partly driving said supercharging system, and wherein said motor is capable of at least partly driving said supercharging system, the method comprising: reducing said flow restriction of said turbine and increasing power to drive said motor as a speed of said engine increases.

11. The method as described in claim 10, wherein said flow restriction is decreased by opening a nozzle upstream of a turbine wheel of said turbine.

12. The method as described in claim 11, wherein said nozzle is closed to increase flow rate of the exhaust gas through said turbine wheel.

13. The method as described in claim 10, further comprising reducing said power to drive said motor as desired torque of said engine decreases.

14. The method as described in claim 13, further comprising reducing said flow restrictions desired torque of said engine decreases.

15. The method as described in claim 10, further comprising reducing said flow restriction and as desired torque of said engine decreases.

16. An engine system comprising: an internal combustion engine;a supercharging system having at least one supercharger to boost intake air to said internal combustion engine;a turbine configured to receive exhaust gas flow from said internal combustion engine through a flow restrictor and capable of at least partly driving said supercharging system;a flow restrictor actuator capable of changing flow restriction caused by said flow restrictor;a motor capable of at least partly driving said supercharging system;a power source capable of supplying power to drive said motor; anda controller configured to control said flow restrictor actuator to reduce the flow restriction and said power source to supply more power to said motor as a desired airflow of said engine increases.

17. The engine system as described in claim 16, wherein said supercharging system comprises a first supercharger driven by said turbine and a second supercharger driven by said motor.

18. The engine system as described in claim 17, wherein said motor is an electric motor to drive said second supercharger.

19. The engine system as described in claim 17, wherein said first supercharger is arranged upstream of said second supercharger in an intake air passage of said internal combustion engine.

20. The engine system as described in claim 17, wherein said first supercharger is arranged downstream of said second supercharger in an intake air passage of said internal combustion engine.