Power-neutral exhaust temperature reduction by utilizing exhaust turbine bypass

Abstract

The invention relates to a method for controlling an internal combustion engine having an exhaust turbocharger and an exhaust aftertreatment device, comprising at least the following steps: determining a catalytic converter temperature; comparing the determined catalytic converter temperature with an upper temperature limit value; and, when the comparison identifies an exceedance of the limit value, reducing the share of exhaust gas from the internal combustion engine that is directed through the turbine bypass of the exhaust turbocharger. Furthermore, the invention relates to a control mechanism and a vehicle drive system.

Description

Technical Field

[0001] The present invention relates to a method for controlling an internal combustion engine having an exhaust turbocharger and an exhaust aftertreatment device, a control mechanism for implementing the method, and a vehicle drive device having such a control mechanism. Background Technology

[0002] The increasingly stringent requirements regarding exhaust aftertreatment systems and emission regulations mean that known measures for protecting exhaust aftertreatment systems by reducing or maintaining temperatures are insufficient when disadvantages regarding engine power and / or fuel consumption during high-load operation cannot be tolerated simultaneously. Furthermore, the increased demands on the service life or durability of exhaust aftertreatment systems and the fact that known measures for reducing temperatures in exhaust aftertreatment systems include enriching the air-fuel mixture or the Miller / Atkinson combustion method.

[0003] The principle of concentration—especially due to legal or other standardized regulations—will always disappear further in the future because sufficient concentration will no longer be permitted.

[0004] Furthermore, under demanding boundary conditions for vehicle operation—especially at full load—the Miller / Atkinson combustion method reaches its limits in terms of the system and can no longer be used for exhaust temperature reduction in exhaust aftertreatment systems under such circumstances.

[0005] Therefore, it may be necessary to reduce / limit the power of the internal combustion engine in order to maintain or, where necessary, lower the temperature level in the exhaust system. However, such intervention is undesirable because it is difficult to communicate to vehicle users. Summary of the Invention

[0006] In this context, the objective of the present invention is to improve, particularly when it is necessary to influence the operation of the internal combustion engine and components of the vehicle drive system by affecting the temperature of the exhaust aftertreatment device.

[0007] This task is accomplished by a method having the features of the present invention, a control mechanism having the features of the present invention, and a vehicle drive device having the features of the present invention.

[0008] According to one aspect, a method for controlling an internal combustion engine, particularly an internal combustion engine having an exhaust turbocharger and an exhaust aftertreatment device, is disclosed. This control method comprises at least the following method steps, which may be performed in the given order or another order that is technically appropriate:

[0009] (1) Determine, in particular, measure, read and / or simulate catalyst temperature, especially the catalyst temperature that is critical to the functional realization of the exhaust aftertreatment device in terms of its service life.

[0010] (2) Compare the determined catalyst temperature with the upper temperature limit value above which exhaust gas purification failure and / or an intolerably shortened service life of exhaust gas purification components can be expected.

[0011] If a threshold value is identified during the comparison in step (2), the following additional method steps are performed:

[0012] (III) Reduce the share of exhaust gas from the internal combustion engine that is directed through the turbine bypass of the exhaust turbocharger, especially by direct or more direct reduction, i.e., by having a smaller enthalpy loss to the exhaust aftertreatment device than when the corresponding share of exhaust gas is directed through the turbine.

[0013] (IV) Reduce the supply of fresh air to the cylinder block of the internal combustion engine.

[0014] By directing a smaller portion of the hot exhaust gas directly to the exhaust aftertreatment unit, it is possible to reduce the temperature of the exhaust streams that need to recombine at the aftertreatment unit, since a larger portion is directed through the turbine. This is because the enthalpy loss and associated temperature drop of the exhaust gas in the turbine are greater compared to when it is directed through a turbine bypass.

[0015] However, due to the increased loading on the turbine—especially exceeding what is actually required for the corresponding operating conditions of the internal combustion engine—the boost pressure in the cylinder block increases; this results in an undesirable power increase during combustion.

[0016] By reducing the supply of fresh air, undesirable power gains can be compensated for or avoided by increasing boost pressure, without requiring Miller / Atkinson operation with reduced valve lift, which, in one embodiment, can be achieved by using a smaller throttle opening. This is particularly advantageous when, based on the further improvements required for emissions management in modern internal combustion engines for motor vehicles, reduced valve lift is no longer kinematically feasible, especially on the camshaft, above certain speed limits.

[0017] The method steps (III) of reducing the share of exhaust gas directed through the turbine bypass of the exhaust turbocharger and (IV) of reducing the supply of fresh air to the cylinder block of the internal combustion engine are currently collectively referred to, in particular, as “fluid flow guidance intervention” of the internal combustion engine. That is, the term “intervention” specifically refers to interventions that are functionally, at least primarily, for implementing the method according to the invention.

[0018] According to another aspect, a control mechanism is disclosed, which is particularly configured on the engine controller of an internal combustion engine and designed to implement the method according to the embodiments of the present invention.

[0019] According to another aspect, a vehicle drive system is disclosed. The vehicle drive system has at least:

[0020] (a) Internal combustion engines, especially gasoline or diesel engines.

[0021] (b) Includes the intake equipment of an air conditioning device for regulatedly supplying fresh air to an internal combustion engine.

[0022] (c) At least one or two, particularly in series, exhaust turbochargers for supercharging fresh air for an internal combustion engine, the exhaust turbochargers having an exhaust turbine including an exhaust turbine bypass, the exhaust turbine bypass having a bypass exhaust regulation device.

[0023] (d) An exhaust aftertreatment device including a temperature determination device. The exhaust aftertreatment device has at least one three-way catalytic converter, wherein when the exhaust gas being directed into the catalytic converter is so hot and, if necessary, introduced for such a long time that it exceeds the upper temperature limit of the exhaust aftertreatment device, the catalytic coating of the three-way catalytic converter is damaged directly or indirectly by a shortened service life.

[0024] (e) A control mechanism according to an embodiment of the present invention.

[0025] This invention is also based on the consideration that, in modern internal combustion engines used in passenger cars, the intake valve lift should not be below its minimum level in the higher speed range, as this would otherwise cause component damage. Therefore, the possibility of Miller / Atkinson operation is severely limited in this speed range, and known methods can only maintain exhaust temperatures upstream and within the catalytic converter by enriching the exhaust in a damage-free region. However, this is increasingly being prohibited by law in the future.

[0026] The invention is now further based on the concept (especially in this critical speed range) of allowing more exhaust mass to flow through the exhaust turbine of the exhaust turbocharger in order to achieve a greater temperature reduction. The excess boost pressure generated here is then adjusted downwards again to the value required for this operating point via a limiting mechanism on the guide air side.

[0027] That is, especially when the exhaust aftertreatment system reaches its system limits, the exhaust valve is further closed, particularly more than actually required for that operating state. The resulting increase in boost pressure is suppressed or again limited to the level required for that operating state by the throttle valve (or another air conditioning device (rotary slide valve, etc.)) on the guide air side, which will help the overall system have more power (but usually undesirable). Power is thus kept constant and the exhaust aftertreatment system is relieved of its temperature burden by the additional enthalpy reduction through the turbine. In addition, general cooling of the exhaust aftertreatment system is also achieved, thus resulting in longer durability based on a smaller temperature input.

[0028] In one embodiment, the fresh air delivery is reduced to a degree related to the reduction in the exhaust volume in the turbine bypass. This allows the compensation level to be coordinated with the additionally introduced boost pressure.

[0029] According to one embodiment, the intervention in guiding the combustion fluid—air or a mixture before combustion and exhaust gas after combustion—especially according to the method (particularly method step (III): reducing the share of exhaust gas from the internal combustion engine guided through the turbine bypass of the exhaust turbocharger; method step (IV): reducing the supply of fresh air to the cylinder block of the internal combustion engine), aims to achieve, in particular regulate and / or maintain, a predetermined boost pressure as accurately as possible. In particular, the predetermined boost pressure corresponds to a boost pressure set for the current operating state of the internal combustion engine without neglecting the necessity of cooling the exhaust gas.

[0030] According to one embodiment, intervention in guiding the combustion fluid, particularly according to the method, is terminated when the temperature falls below a lower temperature limit of the catalyst temperature. This clearly defines the scope of operation of the internal combustion engine using the present invention.

[0031] According to one implementation, the stronger the upper temperature limit is exceeded, the stronger the control intervention, especially the intervention according to the method (i.e., especially the further closure of the exhaust valve according to method step III and the further restriction of fresh air supply to the combustion chamber according to method step IV). This enables the continuous and / or sustained and / or finely coordinated implementation of the method.

[0032] According to one implementation, when and / or whenever there is an operating condition requiring a rapid and / or direct response from the internal combustion engine, then particularly temporary, weak control or no control intervention, especially intervention according to the method, is employed. This can be achieved, in particular, by performing a pre-adjustment and then not performing any further readjustment.

[0033] In one embodiment, the catalytic converter temperature is repeatedly determined at short (especially millisecond) time intervals, thereby determining the temperature gradient and / or temperature prediction. The temperature prediction can, for example, be based on analysis of the determined temperature values ​​and temperature gradients, thus allowing for stronger countermeasures in the sense of the invention when temperatures rise rapidly. This enables full utilization of the heat resistance of critical components of the exhaust aftertreatment system without being exposed to temperature inputs that are critical to its service life due to adjustment delays.

[0034] How the catalyst temperature is determined is irrelevant to the implementation of this invention. In particular, the catalyst temperature can be measured and / or simulated using an operating model and / or read using a lookup table, especially when using an engine controller.

[0035] In one implementation, when the determined temperature gradient and / or the determined temperature prediction is expected and / or no longer unavoidable to exceed, intervention, particularly according to the method, is carried out before the upper temperature limit is reached.

[0036] This assists in adjusting the temperature of the exhaust aftertreatment device within a relatively narrow temperature range and thereby assists in the operation of the protective components of the internal combustion engine or exhaust aftertreatment device.

[0037] According to one embodiment, particularly indirectly or directly, the proportion of exhaust gas from the internal combustion engine that is directed through the turbine bypass of the exhaust turbocharger is reduced by decreasing the opening of bypass exhaust regulation devices, such as bypass valves and / or bypass gates and / or bypass throttle valves. Thus, the invention can also be implemented without hardware adaptation to the invention, for example, by using standard components for guiding air and exhaust in internal combustion engines in motor vehicles.

[0038] According to one embodiment, particularly indirectly or directly, the supply of fresh air to the cylinder block of the internal combustion engine is reduced by decreasing the opening of the air conditioning devices of the engine's intake system, such as throttle valves and / or throttle gates and / or throttle valves. Thus, the invention can be implemented on the hardware side using components also installed in systems without the invention. Attached Figure Description

[0039] Other advantages and application possibilities of the invention will become apparent from the following description taken in conjunction with the accompanying drawings.

[0040] Figure 1 A vehicle drive device with a control mechanism is shown according to an exemplary embodiment of the present invention;

[0041] Figure 2 Different graphs showing the time-varying curves with different parameters are presented to illustrate the effect of... Figure 1The method implemented on the vehicle drive device according to the first exemplary embodiment;

[0042] Figure 3 Different graphs showing the time-varying curves with different parameters are presented to illustrate the effect of... Figure 1 The method implemented on the vehicle drive device according to the second exemplary embodiment. Detailed Implementation

[0043] Figure 1 A vehicle drive system 1 with an internal combustion engine 2 is shown. In this embodiment, the internal combustion engine 2 is configured as a four-cylinder diesel engine. The internal combustion engine 2 is connected to the intake system 4 for oxygen supply and to the exhaust system 6 for exhaust purification.

[0044] The intake device 4 includes a fresh air guide section 8, a booster air cooler 10, an air conditioning device 12 configured as a throttle valve, and an air collector 14.

[0045] The exhaust device 6 has an exhaust bend and an exhaust aftertreatment device 20 along the exhaust guide 16, the exhaust aftertreatment device having at least one three-way catalytic converter, but in particular having other aftertreatment devices, such as at least one particulate filter and / or at least one SCR catalytic converter.

[0046] In order to increase the power of the internal combustion engine 2, a two-stage exhaust turbocharger 22 is provided in the fresh air guide section 8 of the intake device 4 and in the exhaust guide section 16 of the exhaust device 6. The compressor of the exhaust turbocharger 22 is provided in the fresh air guide section 8 and the turbine of the exhaust turbocharger 22 is provided in the exhaust guide section 16.

[0047] In this embodiment, the high-pressure compressor and high-pressure turbine 26 of the exhaust turbocharger 22 are respectively configured to bypass by means of switchable bypasses, wherein the exhaust turbine bypass configured as a high-pressure turbine bypass is indicated by reference numeral 28.

[0048] The exhaust turbine bypass 28 has a bypass exhaust regulating device 18 configured as a valve or valve, by means of which the exhaust volume guided through the turbine bypass can be adapted in multiple stages or steplessly.

[0049] The intake device 4 and the exhaust device 6 can be connected via a switchable high-pressure AGR line 24, so that hot exhaust gas can be directed from the exhaust bend 17 into the air collector 14 and mixed there with fresh air. In this embodiment, the exhaust gas in the AGR line 24 can be switched to pass through the AGR cooler and / or be directed past the AGR cooler.

[0050] A hot-film air flow meter (HFM) for measuring air mass flow rate (mHFM) and a temperature sensor for measuring fresh air temperature (T10) are installed on the fresh air inlet 7 of the fresh air guide section 8. A pressure sensor for measuring compressor pressure (p12) in the fresh air guide section 8 is installed between the two compressors. A temperature sensor for measuring the limit valve temperature (T21) in the fresh air guide section is installed between the boost air cooler 10 and the throttle valve. A pressure sensor for measuring boost pressure (p22) is installed in the air collector 14. A temperature sensor for measuring the AGR mixture temperature (t-nAGR) entering the air collector 14 is installed in the AGR line 24. A pressure sensor for measuring the front turbine pressure (p31) is installed in the exhaust bend.

[0051] A temperature sensor 29 is provided between the low-pressure turbine of the exhaust turbocharger 22 and the exhaust aftertreatment device 20 to measure the catalytic converter temperature T of the exhaust before it enters the exhaust aftertreatment device 20.

[0052] The vehicle drive unit 1 further includes an engine control unit 30, which is designed to operate the vehicle drive unit 1 and all its components according to the operational needs of the motor vehicle. The engine control unit 30 is also designed to optimize the operation of the vehicle drive unit and its components by taking into account the measurements of all the aforementioned sensors and accessing common operating models, lookup tables, etc., and using the detected and / or processed sensor values ​​when necessary.

[0053] The engine control unit 30 has a control mechanism 32 designed to exemplarily implement a method for controlling the internal combustion engine 2. In particular, the control mechanism 32 is designed to determine the catalytic converter temperature T and compare it with a threshold value Tg, and to operate the throttle valve and bypass exhaust regulating device 18 if the threshold value Tg is exceeded.

[0054] To accomplish this task, the engine control unit 30 and / or control mechanism 32 are designed to use the operating model 34 typically stored in current motor vehicles, the vehicle, the vehicle drive equipment, and / or at least one driving engine, that is, especially in the sense of the present invention, the data, sensor values, lookup table 36, and / or model predictions that are accessible therein.

[0055] Then, by using the Figure 2 The explanation of the diagrams used for the first exemplary method is used to illustrate the implementation of the exemplary method in detail. Figure 3 The second example of the method is then explained in the following section. Figure 2 The first example shows the difference.

[0056] exist Figure 2 The chart records the time period separately:

[0057] a) The temperature T of the exhaust gas in the exhaust guide section 16 upstream of the input end of the exhaust aftertreatment device 20 is continuously measured by temperature sensor 29.

[0058] b) Opening A of the bypass exhaust regulating device 18 W .

[0059] c) Throttle opening A D .

[0060] In this way, by means of Figure 2 The diagram illustrates the first exemplary method:

[0061] During full-load operation of internal combustion engine 2, temperature T always increases further until it reaches the critical upper temperature limit value T at time t1. G Starting from this upper temperature limit, the exhaust aftertreatment device 20 will be damaged.

[0062] In this embodiment, due to reaching (or exceeding) the threshold value T G The control mechanism 32 in the engine control unit 30 intervenes by reducing the opening A of the bypass exhaust regulating device 18. W And throttle opening A D .

[0063] Therefore, on the one hand, by reducing the opening A of the bypass exhaust regulating device 18 W A larger proportion of exhaust gas is directed via the high-pressure turbine 26 than is actually required for the operation of the internal combustion engine 2. As a result, the exhaust gas loses more enthalpy and thus more temperature at the input end of the exhaust aftertreatment device 20 compared to before.

[0064] As a result, the measured temperature T first drops to the upper limit value T0. G Below and then further down until the lower bound value T OK .

[0065] However, this also creates increased boost pressure, which has an undesirable impact on the power of the internal combustion engine by affecting the characteristics of the compressor in the exhaust turbocharger.

[0066] To compensate for or avoid opening A W This reduction effect, along with the reduction in throttle opening A, also corresponds to a reduction in throttle opening A starting from time t1. D .

[0067] When the lower limit value T of the measured temperature T is reached at time t2 OK - That is, for non-critical temperature ranges, the opening degree A will be... W and AD Adjust it again to the size set for the actual operating state of the internal combustion engine 2.

[0068] If this causes the temperature T to reach or exceed the upper limit value T again after another time interval (e.g., at time t3), G Then the same measures according to the present invention are used again.

[0069] exist Figure 3 The middle shows with Figure 2 The same diagram, but used for a different second exemplary method. This second exemplary method is particularly distinguished from the method described below. Figure 2 The first exemplary method is, not by applying the digital ON / OFF of the present invention, but by the opening degree A. W and A D The temperature T is adjusted by continuous and gradual adaptation.

[0070] This is particularly effective in enabling temperature T regulation within a smaller temperature band, which can also be correlated with the key value T. G It has a large distance. This ensures that temperature-critical components have a long service life.

[0071] List of reference numerals

[0072] 1. Vehicle drive equipment

[0073] 2 Internal Combustion Engines

[0074] 4. Suction equipment

[0075] 6. Exhaust equipment

[0076] 8 Fresh Air Guiding Section

[0077] 10-Pressure Air Cooler

[0078] 12. Air conditioning devices, such as throttle valves

[0079] 14 air collectors

[0080] 16 Exhaust Guide Section

[0081] 18. Bypass exhaust regulation devices, such as wastegate valves

[0082] 20 Exhaust Aftertreatment Device

[0083] 22 exhaust turbocharger

[0084] 24 High-pressure AGR pipeline

[0085] 26 High-pressure exhaust turbine

[0086] 28 High-pressure turbine bypass

[0087] 29 Temperature Sensors

[0088] 30 Engine Control Unit

[0089] 32 control mechanisms

[0090] t at the moment the method is implemented

[0091] T catalyst temperature

[0092] T G The critical upper limit of catalyst temperature

[0093] T OK Lower limit of catalyst temperature

[0094] A W Bypass exhaust regulating device opening

[0095] A D Air conditioning unit opening

Claims

1. A method for controlling an internal combustion engine (2), the method having at least the following method steps: (I) determining a catalyst temperature (T), (II) comparing the catalyst temperature (T) with an upper temperature limit value, (III) reducing the proportion of exhaust gas of the internal combustion engine which is directed through a turbine bypass (28) of an exhaust-gas turbocharger (22) of the internal combustion engine, (IV) reducing the delivery of fresh air to the cylinder volume of the internal combustion engine, when an exceeding of the limit value is identified in the comparison, and (V) reducing the delivery of fresh air to the cylinder volume of the internal combustion engine, when and / or as long as an operating state requiring a rapid and / or direct response of the internal combustion engine is present, the interventions (III, IV) according to the method not being actuated. The delivery of fresh air is reduced to the extent that the reduction in the proportion of exhaust gas in the turbine bypass is related to. The interventions (III, IV) are actuated the more strongly the upper temperature limit value is exceeded. The catalyst temperature is determined repeatedly and from this a temperature gradient and / or a temperature prediction is determined. The interventions according to the method are actuated before the upper temperature limit value is reached when, on the basis of the determined temperature gradient and / or the determined temperature prediction, an exceeding can be expected and / or is no longer avoidable. The control mechanism is designed to carry out the method according to one of claims 1 to 8.

10. A vehicle drive apparatus (1) having: an internal combustion engine (2), an air intake apparatus (4) comprising an air conditioning device (12), an exhaust-gas turbocharger (22) comprising an exhaust-gas turbine (26) and an exhaust-gas turbine bypass (28) having a bypass exhaust-gas conditioning device (18), an exhaust-gas aftertreatment device (20) comprising a temperature determination device (29), and a control mechanism (32) according to claim 9. (II) comparing the determined catalytic converter temperature to the upper temperature limit value (T G ), characterized in that ​ ​ ​ ​ 2. The method of claim 1, wherein, ​ 3. The method according to claim 1 or 2, characterized in that When the lower temperature limit value (T OK ) is undershot, the intervention according to the method (III, IV) on the guiding of the combustion fluid is ended.

4. The method according to claim 1 or 2, characterized in that ​ 5. The method according to claim 1 or 2, characterized in that, ​ 6. The method of claim 5, wherein, ​ 7. The method according to claim 1 or 2, characterized in that By reducing the opening degree (A W ) of the bypass exhaust gas regulating device, the proportion of the exhaust gas of the internal combustion engine that is guided through the turbine bypass of the exhaust gas turbocharger is reduced.

8. The method according to claim 1 or 2, characterized in that By reducing the opening degree (A D ) of an air adjusting device of an intake apparatus of an internal combustion engine to reduce the delivery of fresh air to a cylinder of the internal combustion engine.

9. A control mechanism (32) constituted on an engine control device (30) of an internal combustion engine, characterized by, ​ ​ ​ ​ ​ ​ characterized in that ​

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