METHOD FOR CHARGE PRESSURE CONTROL OF AN INTERNAL COMBUSTION ENGINE

Abstract

A method for charge pressure control of an internal combustion engine that is an integral part of a drive train, wherein the drive train comprises at least the internal combustion engine, an intake line, an exhaust gas line, and an exhaust gas turbocharger. The internal combustion engine has at least one intake valve that fluidically connects the intake line to a combustion chamber of the internal combustion engine, and at least one exhaust valve that fluidically connects the combustion chamber to a first section of the exhaust gas line. The exhaust gas line has a first section between the combustion chamber and the exhaust gas turbocharger, and a second section downstream from the exhaust gas turbocharger. The exhaust gas turbocharger and/or a bypass that bypasses the exhaust gas turbocharger are/is adjustable. In the method, an opening point in time of the at least one intake valve and a closing point in time of the at least one exhaust valve are taken into account.

Claims

1. A method for charge pressure control of an internal combustion engine that is an integral part of a drive train, wherein the drive train comprises at least the internal combustion engine, an intake line, an exhaust gas line and an exhaust gas turbocharger; wherein the internal combustion engine has at least one intake valve that fluidically connects the intake line to a combustion chamber of the internal combustion engine, and has at least one exhaust valve that fluidically connects the combustion chamber to a first section of the exhaust gas line; wherein the exhaust gas line has a first section between the combustion chamber and the exhaust gas turbocharger, and has a second section downstream from the exhaust gas turbocharger; wherein an overall cross-sectional area between the first section and the second section through which an exhaust gas may flow is adjustable via an adjustable bypass and/or an adjustable exhaust gas turbocharger between a first position having a smallest flow cross section for an exhaust gas and a second position having a largest flow cross section for the exhaust gas; the method comprising at least the following steps: a) detecting a load requirement for the drive train; b) determining a position of the exhaust gas turbocharger (and/or of the bypass for providing turbine power of the exhaust gas turbocharger, wherein, in step b), an opening point in time of the at least one intake valve and a closing point in time of the at least one exhaust valve are taken into account.

2. The method according to claim 1, wherein during operation of the internal combustion engine, a time overlap of the opening point in time and of the closing point in time occurs, so that the first section is fluidically connected, at least temporarily, to the intake line via the combustion chamber.

3. The method according to claim 1, wherein at least one of the following parameters is additionally taken into account in step b): a cylinder air mass, a speed of the internal combustion engine, an air mass flow, an exhaust gas mass flow, a first pressure in the first section, a second pressure in the second section, a third pressure in the intake line, and a temperature of the exhaust gas.

4. The method according to claim 1, wherein the position determined in step b) is iteratively determined.

5. The method according to claim 4, wherein, within the scope of the iterative step b), a profile (of the turbine power at least as a function of a first pressure in the first section is determined.

6. The method according to claim 5, wherein, based on the profile of the turbine power, a specific first pressure (is iteratively determined for which the turbine power is at a maximum.

7. The method according to claim 5, wherein, starting from the first position, the profile of the turbine power is iteratively determined in a stepwise manner toward the second position.

8. The method according to claim 4, wherein an increment of the iteration is selected as a function of an available computing power of a control unit.

9. The method according to claim 8, wherein the increment is varied during the method.

10. The method according to claim 1, wherein the method is carried out only when a sudden change in load is present.

11. A motor vehicle comprising: a drive train that comprises at least an internal combustion engine, an intake line, an exhaust gas line and an exhaust gas turbocharger, wherein the internal combustion engine has at least one intake valve that fluidically connects the intake line to at least one combustion chamber of the internal combustion engine and has at least one exhaust valve that fluidically connects the combustion chamber to a first section of the exhaust gas line; wherein the exhaust gas line has a first section between the combustion chamber and the exhaust gas turbocharger and has a second section downstream from the exhaust gas turbocharger, wherein an overall cross-sectional area between the first section and the second section through which an exhaust gas may flow is adjustable via an adjustable bypass and/or via an adjustable exhaust gas turbocharger between a first position having a smallest flow cross section for an exhaust gas and a second position having a largest flow cross section for the exhaust gas, and at least one control unit configured for carrying out a method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The invention and the technical context are explained in greater detail below with reference to the appended figures. It is pointed out that the invention is not to be construed as being limited by the illustrated exemplary embodiments. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the information shown in the figures and combine them with other components and findings from the present description. In particular, it is noted that the figures and in particular the illustrated proportions are only schematic. In the figures:

[0054] FIG. 1: shows a motor vehicle 2 having a drive train 1;

[0055] FIG. 2: shows a first flow chart;

[0056] FIG. 3: shows a first diagram;

[0057] FIG. 4: shows a second flow chart together with a second diagram; and

[0058] FIG. 5: shows a further motor vehicle having a drive train.

DETAILED DESCRIPTION OF THE INVENTION

[0059] FIG. 1 shows a motor vehicle 32 having a drive train 2. The drive train 2 comprises an internal combustion engine 1, an intake line 3, an exhaust gas line 4, and an exhaust gas turbocharger 5. The internal combustion engine 1 has an intake valve 7 that fluidically connects the intake line 3 to a combustion chamber 6 of the internal combustion engine 1, and an exhaust valve 9 that fluidically connects the combustion chamber 6 to a first section 8 of the exhaust gas line 4. The exhaust gas line 4 has a first section 8 between the combustion chamber 6 and the exhaust gas turbocharger 5, and a second section 10 downstream from the exhaust gas turbocharger 5. The exhaust gas turbocharger 5 is adjustable between a first position 11 having a smallest flow cross section for an exhaust gas 12, and a second position 13 having a largest flow cross section for the exhaust gas 12 (for example, continuously or in specific steps). In addition, a control unit 28 is provided that is suitably designed for carrying out the described method and/or that carries out or can carry out the method.

[0060] The control unit 28 utilizes models 29, 30, 31 that are stored in the control unit 28. The models 29, 30, 31 comprise a first model 29 via which a cylinder air charge (i.e., a cylinder air mass 19) is determinable as a function of parameters, a second model 30 via which an exhaust gas mass flow 22 is determinable as a function of parameters, and a third model 31 via which the turbine power 16 of the exhaust gas turbocharger 5 is determinable as a function of parameters.

[0061] The first model 29 is provided for controlling the internal combustion engine 1 (for example, for controlling the intake valve 7, the exhaust valve 9, the ignition times, the mixture formation), and the third model 31 is provided for controlling the exhaust gas turbocharger 5 (for example, for changing the turbine geometry, i.e., for adjusting the position 15).

[0062] Within the scope of step a), the presence of a load requirement 14 for the drive train 2 is recognized; i.e., in step a) a load requirement 14 is present that is to be implemented by the control unit. A position 15 of the exhaust gas turbocharger 5 for providing the greatest possible, i.e., maximum, turbine power 16 of the exhaust gas turbocharger 5 is determined in step b). An opening point in time 17 of the intake valve 7 and a closing point in time 18 of the exhaust valve 9 are taken into account in step b).

[0063] The following parameters are additionally taken into account in the method: a cylinder air mass 19, a speed 20 of the internal combustion engine 1, an air mass flow 21 (in the intake line 3), an exhaust gas mass flow 22 (in the exhaust gas line 4), a first pressure 23 in the first section 8 of the exhaust gas line 4, a second pressure 24 in the second section 10 of the exhaust gas line 4, a third pressure 25 in the intake line 3, and a temperature 26 of the exhaust gas 12.

[0064] FIG. 2 shows a first flow chart that illustrates the relationships of the individual parameters utilized by the present method. The first pressure 23 (exhaust gas back pressure in the first section 8), the third pressure 25 in the intake manifold 3, the opening point in time 17 of the intake valve 7, the closing point in time 18 of the exhaust valve 9, the speed 20 of the internal combustion engine 1, the second pressure 24 in the second section 10, and the temperature 26 of the exhaust gas 12 are used as input variables.

[0065] Different values of the first pressure 23 are used as an input variable within the scope of an iteration.

[0066] The parameters comprising the first pressure 23, third pressure 25, opening point in time 17 of the intake valve 7, closing point in time 18 of the exhaust valve 9, and speed 20 of the internal combustion engine 1 are used as input variables for the first model 29 for determining the resulting cylinder air mass 19.

[0067] The cylinder air mass 19 determined within the scope of the particular iteration, together with the speed 20, is used as an input variable for the second model 30 for determining the resulting exhaust gas mass flow 22 (or the air mass flow 21 corresponding thereto).

[0068] The exhaust gas mass flow 22 determined within the scope of the particular iteration, together with the value of the first pressure 23, the second pressure 24, and the temperature 26 of the exhaust gas 12 utilized for the particular iteration, is used as an input variable for the third model 31 for determining the resulting turbine power 16.

[0069] As a result of the iteration, a profile 27 of the turbine power 16 over the various values of the first pressure 23 may be (computationally) determined (see FIG. 3).

[0070] The iteration is carried out in particular solely by computation; i.e., none of the parameters used within the scope of the iteration are actually set in the drive train 2.

[0071] FIG. 3 shows a first diagram with the first pressure 23 plotted on the horizontal axis and the turbine power plotted on the vertical axis. FIG. 3 shows the profile 27 of the turbine power 16, determined within the scope of the method or within the scope of an iteration, over the various values of the first pressure 23. A maximum in the profile 27 is present, so that it is apparent that the described second situation is present.

[0072] The iteration explained with reference to FIG. 2 takes place starting from a first position 11 of the exhaust gas turbocharger 5 (smallest flow cross section, i.e., maximum generatable pressure difference between the first pressure 23 and the second pressure 24), and is iteratively determined in a stepwise manner toward the second position 12.

[0073] FIG. 4 shows a second flow chart together with a second diagram. For the second flow chart, the value of the first pressure 23 for which a maximum turbine power 16 is present from the first flow chart according to FIG. 1 is used as an input variable.

[0074] Thus, the first pressure 23 (the exhaust gas back pressure in the first section 8 for which a maximum of the turbine power 16 in the present operating point has been determined), the third pressure 25 in the intake manifold 3, the opening point in time 17 of the intake valve 7, the closing point in time 18 of the exhaust valve 9, the speed 20 of the internal combustion engine 1, and the second pressure 24 in the second section 10 are used as input variables.

[0075] The parameters comprising the first pressure 23 (with the value for which the maximum of the turbine power 16 in the present operating point has been determined), the third pressure 25, the opening point in time 17 of the intake valve 7, the closing point in time 18 of the exhaust valve 9, and the speed 20 of the internal combustion engine 1 are used as input variables for the first model 29 for determining the resulting cylinder air mass 19.

[0076] The cylinder air mass 19 thus determined, together with the speed 20, is used as an input variable for the second model 30 for determining the resulting exhaust gas mass flow 22 (or the air mass flow 21 corresponding thereto).

[0077] The exhaust gas mass flow 22 thus determined, together with the value of the first pressure 23 and the second pressure 24 utilized here, is used as an input variable for the third model 31 for determining the position 15 of the exhaust gas turbocharger 5 necessary for generating the maximum turbine power 16.

[0078] FIG. 5 shows a further motor vehicle 2 having a drive train 1. Reference is made to the discussion for FIG. 1. In the present case, the drive train 2 comprises a bypass 33 which bypasses the exhaust gas turbocharger 5 and which controllably connects the first section 8 to the second section 10. The bypass 33 (or the flow cross section of the bypass 33 and/or the overall cross-sectional area of the bypass 33 and the exhaust gas turbocharger 5) is adjustable between a first position 11 having a smallest flow cross section for an exhaust gas 12, and a second position 13 having a largest flow cross section for the exhaust gas 12 (for example, continuously or in specific steps).

LIST OF REFERENCE NUMERALS

[0079] 1 internal combustion engine [0080] 2 drive train [0081] 3 intake line [0082] 4 exhaust gas line [0083] 5 exhaust gas turbocharger [0084] 6 combustion chamber [0085] 7 intake valve [0086] 8 first section [0087] 9 exhaust valve [0088] 10 second section [0089] 11 first position [0090] 12 exhaust gas [0091] 13 second position [0092] 14 load requirement [0093] 15 position [0094] 16 turbine power [0095] 17 opening point in time [0096] 18 closing point in time [0097] 19 cylinder air mass [0098] 20 speed [0099] 21 air mass flow [0100] 22 exhaust gas mass flow [0101] 23 first pressure (exhaust gas back pressure) [0102] 24 second pressure (downstream from the turbine) [0103] 25 third pressure [0104] 26 temperature [0105] 27 profile [0106] 28 control unit [0107] 29 first model (cylinder air charge) [0108] 30 second model (exhaust gas mass flow) [0109] 31 third model (turbine power) [0110] 32 motor vehicle [0111] 33 bypass