Power-Neutral Exhaust Gas Temperature Reduction Using an Exhaust Gas Turbine Bypass

Abstract

A method for controlling an internal combustion engine having an exhaust gas turbocharger and an exhaust gas aftertreatment device, includes determining a catalytic converter temperature, comparing the determined catalytic converter temperature with an upper temperature threshold, and, if the comparison determines that the threshold has been exceeded, reducing a proportion of the exhaust gases of the internal combustion engine which are guided through a turbine bypass of the exhaust gas turbocharger.

Claims

1-11. (canceled)

12. A method for controlling an internal combustion engine, the method comprising: determining a catalytic converter temperature; comparing the catalytic converter temperature with an upper temperature threshold value; identifying an overshooting of the threshold value in the comparison; reducing a fraction of the exhaust gases of the internal combustion engine that are conducted through a turbine bypass of an exhaust-gas turbocharger of the internal combustion engine in response to identifying the overshooting; and reducing a supply of fresh air to the cylinders of the internal combustion engine in response to identifying the overshooting.

13. The method according to claim 12, comprising: reducing the supply of fresh air to an extent that is dependent on an extent of the reduction of the fraction of the exhaust gas in the turbine bypass.

14. The method according to claim 12, comprising: ending both the reducing of the fraction of the exhaust gasses that are conducted through the turbine bypass and the reducing of the supply of fresh air to the cylinders in response to undershooting a lower temperature threshold value of the catalytic converter temperature.

15. The method according to claim 12, comprising: increasing both the reducing of the fraction of the exhaust gasses that are conducted through the turbine bypass and the reducing of the supply of fresh air to the cylinders in response to overshooting the upper temperature threshold value by a greater degree.

16. The method according to claim 12, comprising: determining the catalytic converter temperature repeatedly; and determining a temperature gradient and/or a temperature prediction from the catalytic converter temperature repeatedly determined.

17. The method according to claim 12, comprising: determining a temperature gradient and/or a determined temperature prediction; determining, based on the temperature gradient and/or the determined temperature prediction, that an overshoot of the threshold value is to be expected and/or is unavoidable; reducing the fraction of the exhaust gases that are conducted through the turbine bypass in response to determining that the overshoot is to be expected and/or is unavoidable; and reducing the supply of fresh air to the cylinders in response to determining that the overshoot is to be expected and/or is unavoidable.

18. The method according to claim 12, wherein reducing the fraction of the exhaust gases that are conducted through the turbine bypass comprises reducing a degree of opening of a bypass exhaust-gas regulating device.

19. The method according to claim 12, wherein reducing the supply of fresh air to the cylinders comprises reducing a degree of opening of an air regulating device of an intake system of the internal combustion engine.

20. The method according to claim 12, comprising: reducing to a lesser degree both the reducing of the fraction of the exhaust gasses that are conducted through the turbine bypass and the reducing of the supply of fresh air to the cylinders in response to an operating state being present which requires a fast and/or immediate response of the internal combustion engine.

21. The method according to claim 12, comprising: ending both the reducing of the fraction of the exhaust gasses that are conducted through the turbine bypass and the reducing of the supply of fresh air to the cylinders in response to an operating state being present which requires a fast and/or immediate response of the internal combustion engine.

22. An engine controller of an internal combustion engine, wherein the engine controller is configured to: determine a catalytic converter temperature; compare the catalytic converter temperature with an upper temperature threshold value; identify an overshooting of the threshold value in the comparison; reduce a fraction of the exhaust gases of the internal combustion engine that are conducted through a turbine bypass of an exhaust-gas turbocharger of the internal combustion engine in response to identifying the overshooting; and reduce a supply of fresh air to the cylinders of the internal combustion engine in response to identifying the overshooting.

23. The engine controller according to claim 22, wherein the engine controller is configured to: reduce the supply of fresh air to an extent that is dependent on an extent of the reduction of the fraction of the exhaust gas in the turbine bypass.

24. The engine controller according to claim 22, wherein the engine controller is configured to: end both the reduction of the fraction of the exhaust gasses that are conducted through the turbine bypass and the reduction of the supply of fresh air to the cylinders in response to the catalytic converter temperature undershooting a lower temperature threshold value of the catalytic converter temperature.

25. The engine controller according to claim 22, wherein the engine controller is configured to: increase both the reduction of the fraction of the exhaust gasses that are conducted through the turbine bypass and the reduction of the supply of fresh air to the cylinders in response to the catalytic converter temperature overshooting the upper temperature threshold value by a greater degree.

26. The engine controller according to claim 22, wherein the engine controller is configured to: determine the catalytic converter temperature repeatedly; and determine a temperature gradient and/or a temperature prediction from the catalytic converter temperature repeatedly determined.

27. The engine controller according to claim 22, wherein the engine controller is configured to: determine a temperature gradient and/or a determined temperature prediction; determine, based on the temperature gradient and/or the determined temperature prediction, that an overshoot of the threshold value is to be expected and/or is unavoidable; reduce the fraction of the exhaust gases that are conducted through the turbine bypass in response to determining that the overshoot is to be expected and/or is unavoidable; and reduce the supply of fresh air to the cylinders in response to determining that the overshoot is to be expected and/or is unavoidable.

28. The engine controller according to claim 22, wherein the engine controller is configured to: reduce the fraction of the exhaust gases that are conducted through the turbine bypass by reducing a degree of opening of a bypass exhaust-gas regulating device.

29. The engine controller according to claim 22, wherein the engine controller is configured to: reduce the supply of fresh air to the cylinders by reducing a degree of opening of an air regulating device of an intake system of the internal combustion engine.

30. The engine controller according to claim 22, wherein the engine controller is configured to: reduce to a lesser degree or end both the reduction of the fraction of the exhaust gasses that are conducted through the turbine bypass and the reduction of the supply of fresh air to the cylinders in response to an operating state being present which requires a fast and/or immediate response of the internal combustion engine.

31. A vehicle drive comprising: an internal combustion engine; an intake system with an air regulating device; an exhaust-gas turbocharger with an exhaust-gas turbine and with an exhaust-gas turbine bypass that has a bypass exhaust-gas regulating device; an exhaust-gas aftertreatment device with a temperature determining device; and the controller according to claim 22.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 shows a vehicle drive according to the invention having a controller according to an exemplary embodiment of the invention.

[0042] FIG. 2 shows various diagrams, each with a course of different variables with respect to time, for the purposes of illustrating a method according to a first exemplary embodiment, implemented on the vehicle drive from FIG. 1.

[0043] FIG. 3 shows various diagrams, each with a course of different variables with respect to time, for the purposes of illustrating a method according to a second exemplary embodiment, implemented on the vehicle drive from FIG. 1.

DETAILED DESCRIPTION

[0044] FIG. 1 shows a vehicle drive 1 having an internal combustion engine 2. The internal combustion engine 2 is configured in the exemplary embodiment as a four-cylinder diesel engine. The internal combustion engine 2 is connected to an intake system 4 for a supply of oxygen and to an exhaust-gas system 6 for purification of the exhaust gases.

[0045] The intake system 4 has a fresh-air conduit 8, a charge-air cooler 10, an air regulating device 12 configured as a throttle flap, and an air manifold 14.

[0046] Along an exhaust-gas conduit 16, the exhaust-gas system 6 has an exhaust manifold and an exhaust-gas aftertreatment device 20 which has at least one three-way catalytic converter, and in particular further aftertreatment devices such as at least one particle filter and/or at least one SCR catalytic converter.

[0047] To increase the power of the internal combustion engine 2, a two-stage exhaust-gas turbocharger 22 is arranged in the fresh-air conduit 8 of the intake system 4 and in the exhaust-gas conduit 16 of the exhaust-gas system 6, wherein the compressors of the exhaust-gas turbocharger 22 are arranged in the fresh-air conduit 8 and the turbines of the exhaust-gas turbocharger 22 are arranged in the exhaust-gas conduit 16.

[0048] The high-pressure compressor and the high-pressure turbine 26 of the exhaust-gas turbocharger 22 are each configured in the exemplary embodiment such that they can be circumvented by way of a switchable bypass, wherein the exhaust-gas turbine bypass configured as a high-pressure turbine bypass is denoted by the reference designation 28.

[0049] The exhaust-gas turbine bypass 28 has a bypass exhaust-gas regulating device 18 which is configured as a flap or valve and by means of which a fraction of the exhaust gases that is guided through the turbine bypass can be adapted in multi-stage or continuously variable fashion.

[0050] The intake system 4 and the exhaust-gas system 6 are connectable by means of a switchable high-pressure EGR line 24, such that hot exhaust gas can be guided from the exhaust-gas manifold 17 into the air manifold 14 and mixed there with the fresh air. In the exemplary embodiment, the exhaust gases in the EGR line 24 can be switchably guided through an EGR cooler and/or past same.

[0051] A hot film air mass sensor HFM for measuring an air mass flow mHFM, and a temperature sensor for measuring a fresh-air temperature T10, are arranged at a fresh-air inlet 7 of the fresh-air conduit 8. A pressure sensor for measuring a compressor pressure p12 in the fresh-air conduit is arranged between the two compressors 8. A temperature sensor for measuring a pre-throttle temperature T21 in the fresh-air conduit is arranged between the charge-air cooler 10 and the throttle flap 12. A pressure sensor for measuring a charge pressure p22 is arranged in the air manifold 14. A temperature sensor for measuring an EGR mixture temperature T-nEGR at the inlet into the air manifold 14 is arranged in the EGR line 24. A pressure sensor for measuring a pre-turbine pressure p31 is arranged in the exhaust-gas manifold.

[0052] A temperature sensor 29 for measuring a catalytic converter temperature T of the exhaust gases before they enter the exhaust-gas aftertreatment arrangement 20 is arranged between the low-pressure turbine of the exhaust-gas turbocharger 22 and the exhaust-gas aftertreatment arrangement 20.

[0053] The vehicle drive 1 furthermore has an engine controller 30 that is configured to actuate the vehicle drive 1, and all components thereof, in accordance with the operating requirements of the motor vehicle. For optimum actuation of the vehicle drive and of the components thereof, the engine controller 30 is also configured to take into consideration measured values from all of the abovementioned sensors and to access conventional operation models, lookup tables etc., optionally using the detected and/or processed sensor values.

[0054] The engine controller 30 has a controller 32 that is configured to carry out an exemplary method for controlling the internal combustion engine 2. In particular, the controller 32 is configured to determine the catalytic converter temperature T and compare same with a threshold value Tg and, if the threshold value Tg is overshot, to actuate the throttle flap 12 and the bypass exhaust-gas regulating device 18.

[0055] To perform these tasks, the engine controller 30 and/or the controller 32 is configured to use operation models 34 of the vehicle, of the vehicle drive and/or of the at least one drive engine such as are typically stored in current motor vehicles, that is to say in particular to use data, sensor values, lookup tables 36 and/or model predictions that can be accessed in said operation models, for the purposes of the present disclosure.

[0056] The execution of the exemplary method will be described in detail below on the basis of explanations relating to the illustration of FIG. 2 for a first exemplary method. In FIG. 3, a description will subsequently given as to the manner in which a second example of the method differs from the first according to FIG. 2.

[0057] In the diagrams of FIG. 2, the following are plotted, in each case versus the time: [0058] a) The temperatures T, measured continuously by means of the temperature sensor 29, of the exhaust gases in the exhaust-gas conduit 16 directly upstream of the inlet to the exhaust-gas aftertreatment device 20. [0059] b) A degree of opening A.sub.W of the bypass exhaust-gas regulating device 18. [0060] c) A degree of opening A.sub.D of the throttle flap 12.

[0061] The first exemplary method can thus be discussed on the basis of the diagrams of FIG. 2:

[0062] In full-load operation of the internal combustion engine 2, the temperature T increases ever further until, at the point in time t1, it reaches the upper critical temperature threshold value T.sub.G, above which there is the risk of damage to the exhaust-gas aftertreatment device 20.

[0063] In the exemplary embodiment, as a result of the threshold value T.sub.G being reached (or overshot), the controller 32 in the engine controller 30 intervenes by reducing the degree of opening A.sub.W of the bypass exhaust-gas regulating device 18 and the degree of opening A.sub.D of the throttle flap 12.

[0064] This firstly has the result that, owing to the reduction of the degree of opening A.sub.W of the bypass exhaust-gas regulating device 18, a greater fraction of the exhaust gases is conducted via the high-pressure turbine 26 than is actually required for this operating state of the internal combustion engine 2. The entirety of the exhaust gases at the inlet into the exhaust-gas aftertreatment device 20 thus loses more enthalpy and thus temperature than before.

[0065] Consequently, the measured temperature T firstly falls below the upper threshold value T.sub.G, and later decreases further as far as a lower threshold value T.sub.OK.

[0066] At the same time, however, an increased charge pressure would build up, which, owing to the influence on the behavior of the compressor of the exhaust-gas turbocharger, has an undesired influence on the power of the internal combustion engine.

[0067] To compensate for or avoid this effect of the reduction of the degree of opening A.sub.W, at the same time as this reduction the degree of opening A.sub.D of the throttle flap 12 is also correspondingly reduced proceeding from the time t1.

[0068] If, at the time t2, the lower threshold value T.sub.OK of the measured temperature Tthat is to say a non-critical temperature rangehas been reached, the degrees of opening A.sub.W and A.sub.D are set again to the value actually intended for this operating state of the internal combustion engine 2.

[0069] If this has the result that, after a further time interval (for example at the time t3), the temperature T reaches or overshoots the upper threshold value T.sub.G again, then the same measures according to the present disclosure are implemented again.

[0070] FIG. 3 illustrates the same diagrams as FIG. 2, but for a different, second exemplary method. The second exemplary method differs from the first as per FIG. 2 in particular by the fact that the temperature T is regulated not by a digital, on/off implementation of the present disclosure, but by way of a continuous and gradual adaptation of the degrees of opening A.sub.W and A.sub.D.

[0071] This makes it possible in particular for the temperature T to be regulated in a narrow temperature band, which can furthermore be further removed from the critical value T.sub.G. It can thus be ensured that the temperature-critical components exhibit a longer service life.

LIST OF REFERENCE DESIGNATIONS

[0072] 1 Vehicle drive [0073] 2 Internal combustion engine [0074] 4 Intake system [0075] 6 Exhaust-gas system [0076] 8 Fresh-air conduit [0077] 10 Charge-air cooler [0078] 12 Air regulating device, e.g. throttle flap [0079] 14 Air manifold [0080] 16 Exhaust-gas conduit [0081] 18 Bypass exhaust-gas regulating device, e.g. wastegate valve [0082] 20 Exhaust-gas aftertreatment arrangement [0083] 22 Exhaust-gas turbocharger [0084] 24 High-pressure EGR line [0085] 26 High-pressure exhaust-gas turbine [0086] 28 High-pressure turbine bypass [0087] 29 Temperature sensor [0088] 30 Engine controller [0089] 32 controller [0090] t Points in time during an execution of the method [0091] T Catalytic converter temperature [0092] T.sub.G Upper, critical threshold value of the catalytic converter temperature [0093] T.sub.OK Lower threshold value of the catalytic converter temperature [0094] A.sub.W Degree of opening of the bypass exhaust-gas regulating device [0095] A.sub.D Degree of opening of the air control device