Method and system for exhaust aftertreatment for hybrid vehicles

Abstract

Exhaust aftertreatment method for a diesel-powered hybrid vehicle, in which - a control unit (90) of the diesel-powered hybrid vehicle by actuating components of an exhaust aftertreatment system (1) of the hybrid vehicle during a standstill of a diesel-powered internal combustion engine (170) of the hybrid vehicle, the exhaust aftertreatment system (1) for an increased NO x -turnover rate prepared, wherein the components of the exhaust aftertreatment system (1) are actuated with electrical recuperation energy provided by the electric motor (150) during braking of the hybrid vehicle, - the control unit (90) adjusts at least one operating parameter of the internal combustion engine (170) in such a way as to reduce soot emissions from the internal combustion engine (170) and NO x -Emission from the internal combustion engine (170) corresponding to the increased NO x -Sales rate is increased.

Description

[0001] The invention relates to a method for exhaust aftertreatment for a diesel-powered hybrid vehicle. Furthermore, the invention relates to a control unit for exhaust aftertreatment for a diesel-powered hybrid vehicle, a system for exhaust aftertreatment for a diesel-powered hybrid vehicle, and a diesel-powered hybrid vehicle.

[0002] A hybrid vehicle (Hybrid Electric Vehicle, HEV), which can also be designed as an externally chargeable plug-in hybrid vehicle (Plugin Hybrid Electric Vehicle, PHEV), comprises a powertrain with an internal combustion engine and an electric motor, which together or alternatively can provide torque to propel the hybrid vehicle. The internal combustion engine is usually powered by a fossil fuel, and the electric motor by electrical energy from the hybrid vehicle's traction battery. The electric motor can also operate as a generator to recuperate kinetic energy during braking, i.e., convert it into electrical energy that is stored in the traction battery. Furthermore, the hybrid vehicle includes a hydraulic friction braking system, which, alternatively or additionally, dissipates the hybrid vehicle's kinetic energy during braking.transformed into heat energy.

[0003] Every hybrid vehicle with a diesel-powered combustion engine, or diesel engine for short, that meets an emissions standard such as Euro 6, necessarily includes an exhaust aftertreatment system with multiple components for treating the exhaust gas emitted by the diesel engine. This aftertreatment is aimed at reducing pollutants in the exhaust gas emitted by the combustion engine, the so-called raw emissions, in accordance with the standard, and in particular at reducing the concentration of soot particles, or soot, and nitrogen oxides, or NOₓ. x This process involves converting the raw emissions of the diesel engine into reduced exhaust emissions (end-of-pipe emissions) released from the exhaust pipe of the hybrid vehicle, which are subsequently referred to as hybrid vehicle emissions.

[0004] To reduce the raw soot concentration, the exhaust aftertreatment system typically includes a diesel particulate filter (DPF), also known as a soot filter or simply a particulate filter, as a key component. During operation of the hybrid vehicle, the diesel particulate filter gradually becomes clogged with soot as it is deposited from the exhaust gas. Therefore, the diesel particulate filter must be regenerated at regular intervals, meaning it must be cleaned of the accumulated soot.

[0005] German patent application DE 10 2016 218 858 A1 discloses a method for regenerating a diesel particulate filter in a hybrid vehicle. In this method, the hybrid vehicle's combustion engine also drives an electric generator. The electrical energy generated by the electric generator is stored in a battery after it has been charged less intensely by purely hydraulic braking instead of regenerative braking. The additional torque provided to drive the electric generator increases the enthalpy of the exhaust gas from the combustion engine. This increased enthalpy leads to greater heat input into the diesel particulate filter, causing the accumulated soot particles to burn off.

[0006] German patent application DE 10 2017 101 181 A1 discloses a further method for regenerating a diesel particulate filter integrated into a four-way catalytic converter. In this method, oxygen is supplied to the four-way catalytic converter of an exhaust aftertreatment system via a secondary air device of the exhaust aftertreatment system, and the four-way catalytic converter is electrically heated. Thanks to the increased temperature, soot particles deposited in the four-way catalytic converter combust with the supplied oxygen.

[0007] To reduce the concentration of NO x The exhaust aftertreatment system also typically includes a so-called SCR (Selective Catalytic Reduction) catalyst as another essential component. The SCR catalyst can also be combined with the diesel particulate filter to form an integrated device (SCR@DPF). In the SCR catalyst, the NOₓ is reduced. x-Concentration of the exhaust gas containing a reducing agent is reduced by the fact that NO contained in the exhaust gas x It is reduced to nitrogen, forming water. A urea solution known as AdBlue™ is usually used as the reducing agent; the urea in this solution is thermolytically broken down into ammonia (NH3) and isocyanic acid.

[0008] German patent DE 10 2017 204 972 A1 discloses such an exhaust aftertreatment system comprising an exhaust stream, two SCR catalysts arranged in series within the exhaust stream, an AdBlue™ dosing unit arranged upstream of each SCR catalyst and connected to a feed pump, and a control unit for controlling the feed pump and the two AdBlue™ dosing units. During operation of the exhaust aftertreatment system, the two AdBlue™ dosing units are actuated alternately.

[0009] The effectiveness of the exhaust aftertreatment system, in particular the conversion rate for soot removal in a diesel particulate filter or the conversion rate for reducing NOₓ x The coefficient of thermal conductivity (CTC) in an SCR catalyst is temperature-dependent and usually increases with increasing temperature of exhaust aftertreatment system components and / or the exhaust gas. Therefore, heating exhaust aftertreatment system components and / or the exhaust gas is desirable for meeting emissions standards if the exhaust aftertreatment system or its components are not sufficiently heated by the combustion engine alone.

[0010] US patent 9,975,543 B1 discloses an exhaust aftertreatment system for a hybrid vehicle comprising an internal combustion engine, an electric motor, an electric generator, a plurality of electrical resistors connectable to the electric generator, and a control unit. The exhaust aftertreatment system is configured to supply at least some of the electrical energy generated by the electric generator to the electrical resistors. Heat generated by the electrical resistors from the supplied electrical energy is used to heat the exhaust gas from the internal combustion engine and / or components of the exhaust aftertreatment system. German patent DE 10 2018 107 743 A1 describes an exhaust aftertreatment system that is heated before the internal combustion engine is started.

[0011] Another method for effective exhaust gas aftertreatment is disclosed in DE 10 2018 102 490 A1. In this method, the SCR catalyst with the most favorable NOₓ output is always selected from two SCR catalysts of an exhaust gas aftertreatment system, depending on a determined or calculated temperature in the exhaust gas channel. x -sales rate.

[0012] In light of increasingly stringent emissions standards, there remains a need for systems and methods for more effective exhaust aftertreatment. Effective exhaust aftertreatment proves particularly problematic when the combustion engine of a diesel-powered hybrid vehicle is engaged after a standstill during an electric drive.

[0013] It is known that in diesel engines, low emissions of particulate matter are associated with high emissions of nitrogen oxides, and vice versa. This inverse relationship is described, for example, in the textbook "Fundamentals of Combustion Engines" by Merker et al., 6th revised edition, pp. 43, 45, published in 2012 by Vieweg+Teubner-Verlag, ISBN 978-3-8348-1987-1, and in a journal article entitled "Particulate Matter-NOx." x "Scissors: Professor advocates for higher particulate matter limit" by Rebecca Eisert, published online on 29.08.2017 in "Automobilwoche", described,

[0014] The invention is therefore based on the objective of proposing an improved method for exhaust aftertreatment for a diesel-powered hybrid vehicle, which produces particularly low soot and NO emissions. x-emissions of the hybrid vehicle. Furthermore, it is an object of the invention to provide an improved control unit for exhaust aftertreatment and an improved exhaust aftertreatment system for a diesel-powered hybrid vehicle as well as a diesel-powered hybrid vehicle.

[0015] One aspect of the invention is a method for exhaust aftertreatment for a diesel-powered hybrid vehicle. The exhaust aftertreatment method is suitable for a variety of hybrid vehicles.

[0016] In the method according to the invention, a control unit of a diesel-powered hybrid vehicle prepares the exhaust aftertreatment system of the hybrid vehicle for increased NO by actuating components of an exhaust aftertreatment system of the hybrid vehicle during a standstill of a diesel-powered internal combustion engine (internal combustion engine, ICE). x-sales rate and the control unit adjusts at least one operating parameter of the combustion engine in such a way that soot emissions from the combustion engine are reduced and NOₓ is reduced. x -Emission from the combustion engine corresponding to the increased NO x -turnover rate is increased. In other words, the combustion engine is controlled in such a way that its raw emissions of soot are reduced and its raw emissions of NO are increased. x is increased. The increased raw emission of NO x The combustion engine's performance is affected after the combustion engine has been started by the electric drive of the hybrid vehicle with regard to the subsequent NOₓ. x -The sales rate of the optimized exhaust aftertreatment system up to the end-of-pipe emission of the hybrid vehicle is reduced to at least a standard-compliant level thanks to the preparation immediately, i.e. without start-up time with non-compliant exhaust emission.

[0017] In advantageous embodiments, the control unit actuates an electrically driven compressor (EAV), an exhaust gas recirculation valve (EGR valve), and an electric oxidation catalyst (E-cat) as components of the exhaust aftertreatment system. The electrically driven compressor, in conjunction with the exhaust gas recirculation valve, allows air to flow through the exhaust aftertreatment system even when the combustion engine is off. This air is heated in the electric oxidation condenser. The heated air then heats downstream components of the exhaust aftertreatment system, such as an SCR catalyst. Upon starting the combustion engine, the preheated components of the exhaust aftertreatment system immediately reduce NO emissions. x -Sales rates achieved.

[0018] In preferred embodiments, the control unit predicts the increased NO x- Conversion rate of the exhaust aftertreatment system based on a temperature-dependent model of the exhaust aftertreatment system. Based on the forecast, operating parameters of the combustion engine can be adjusted, particularly before the combustion engine is started.

[0019] In other embodiments, the control unit sets at least one operating parameter based on a Design of Experiments (DoE) model of the internal combustion engine. The DoE model, which relies on statistical procedures performed before the engine is started, allows for a reliable prediction of the engine's raw emissions.

[0020] In particularly advantageous embodiments, the control unit minimizes the soot emissions of the combustion engine while making maximum use of the predicted NOₓ. x -Sales rate at the expense of a correspondingly increased NO x -Emission. In other words, the NOx -Raw emissions from the combustion engine in favor of the lowest possible raw soot emissions by utilizing the increased NO x -Sales rate chosen to be so maximum that a NO x -Exhaust emission (end-of-pipe emission) remains within the standard.

[0021] According to the invention, the components of the exhaust aftertreatment system are actuated using electrical recuperation energy from the hybrid vehicle. This is particularly advantageous when the electrical recuperation energy cannot be stored. In this case, it prevents the kinetic energy of the vehicle from being dissipated in a hydraulic braking system of the hybrid vehicle. This results in a higher efficiency of the hybrid vehicle, i.e., a greater driving range.

[0022] The invention also relates to a control unit for exhaust aftertreatment in a diesel-powered hybrid vehicle. Exhaust aftertreatment systems for diesel-powered hybrid vehicles generally include a control unit for controlling the exhaust aftertreatment process. Therefore, the control unit can be used in a large number of diesel-powered hybrid vehicles.

[0023] The control unit according to the invention is configured to carry out a method according to the invention. Accordingly, the control unit allows the combustion engine to be adjusted in such a way that raw soot emissions are reduced and NO is reduced. x -raw emissions from the combustion engine are increased, and a corresponding optimization of the exhaust aftertreatment system is required to ensure that NO x -The turnover rate of the exhaust aftertreatment system is increased.

[0024] In preferred embodiments, the control unit is configured to control an exhaust aftertreatment system of a diesel-powered hybrid vehicle based on a temperature-dependent model of the exhaust aftertreatment system and / or a diesel-powered internal combustion engine of the hybrid vehicle based on a DoE model of the internal combustion engine. In other words, the control unit models both the exhaust aftertreatment system and the internal combustion engine. In this way, the control unit can control operating parameters of the internal combustion engine and an increased NOₓ level. x -Optimally coordinate the conversion rate of the exhaust aftertreatment system.

[0025] A further aspect of the invention is an exhaust aftertreatment system for a diesel-powered hybrid vehicle, comprising a diesel-powered internal combustion engine (ICE), an exhaust gas recirculation valve (EGR valve), a first AdBlue™ dosing unit, a first SCR-coated diesel particulate filter, and a control unit operationally connected to these components. Such exhaust aftertreatment systems are installed in a large number of diesel-powered hybrid vehicles, resulting in numerous possible applications for the exhaust aftertreatment system.

[0026] The system according to the invention comprises an electrically driven compressor (EAV), an electric oxidation catalyst (E-cat), a second AdBlue™ dosing unit, and a second SCR catalyst, each of which is operationally connected to the control unit. With the combustion engine at rest, air can flow through the exhaust aftertreatment system via the electrically driven compressor, the electric oxidation catalyst, and the exhaust gas recirculation valve. This air is heated in the electric oxidation catalyst to heat downstream components of the exhaust aftertreatment system, in particular the SCR-coated diesel particulate filter and the second SCR catalyst.

[0027] Furthermore, according to the invention, the system comprises a control unit according to the invention. The control unit controls the exhaust aftertreatment system such that the exhaust aftertreatment system carries out the method according to the invention.

[0028] The invention also relates to a diesel-powered hybrid vehicle with a control unit according to the invention for exhaust aftertreatment or with a system according to the invention for exhaust aftertreatment. The hybrid vehicle emits little soot and / or NO. x and thus meets increasingly stringent emissions standards.

[0029] A significant advantage of the inventive method for exhaust aftertreatment of a hybrid vehicle is that NO x- and / or soot emissions from the hybrid vehicle (end-of-pipe emissions) are reduced. Thanks to lower soot emissions from the combustion engine, diesel particulate filters in the exhaust aftertreatment system can be regenerated at relatively long intervals, resulting in increased efficiency for the hybrid vehicle. Furthermore, it is advantageous that the electrical energy required for this process can be recuperated from the kinetic energy of the hybrid vehicle, which would otherwise be lost through dissipation in the hybrid vehicle's hydraulic braking system. Consequently, the efficiency of the hybrid vehicle is further improved.

[0030] The invention is schematically illustrated with reference to embodiments in the drawings and is further described with reference to the drawings. It shows: Fig. 1. A schematic representation of a block diagram of a powertrain of a hybrid vehicle according to the state of the art; Fig. 2 in a schematic representation a block diagram of an exhaust aftertreatment system according to an embodiment of the present invention.

[0031] Fig. Figure 1 shows a schematic block diagram of a powertrain 100 of a hybrid vehicle according to the state of the art. The powertrain 100 comprises a diesel-powered internal combustion engine (ICE) 170, a belt-driven starter generator (BSG) 190, and a belt 180 which rotaryally couples the belt-driven starter generator 190 to the diesel-powered internal combustion engine 170.

[0032] Furthermore, the drive train 100 includes an electric motor 150 and a disconnect coupling 160, by which the electric motor 150 can be selectively coupled to the diesel-powered combustion engine 170 or decoupled from the diesel-powered combustion engine 170.

[0033] The drive train 100 further comprises two parallel sub-gearboxes 130 and a drive clutch 140 for each sub-gearbox 130, by which the respective sub-gearbox 130 can be selectively coupled to the electric motor 150 or decoupled from the electric motor 150.

[0034] Furthermore, the drive train includes 100 driven wheels 100 and a differential 120, which distributes a driving torque provided by the diesel engine 170 and / or the electric motor 150 and translated or reduced by the partial transmissions 130 to the driven wheels 110.

[0035] The powertrain 100 is merely an example and does not limit the invention. The invention is readily applicable to any alternative powertrain of a hybrid vehicle, provided that it comprises a diesel engine and an electric motor.

[0036] Fig. Figure 2 shows a schematic block diagram of a system 1 for exhaust aftertreatment according to an embodiment of the present invention. The system 1 is intended for a hybrid vehicle with a diesel-powered combustion engine and can be installed in the diesel-powered hybrid vehicle.

[0037] The exhaust aftertreatment system 1 comprises the diesel-powered combustion engine 170, an exhaust gas recirculation valve (EGR valve) 20, a first AdBlue™ dosing unit 50 and a first SCR-coated diesel particulate filter (SCR@DPF) 60 and a control unit 90 operationally connected with these components.

[0038] The control unit 90 is configured to control the exhaust aftertreatment system 1 based on a temperature-dependent model of the exhaust aftertreatment system 1 and the diesel-powered combustion engine 170 of the hybrid vehicle based on a DoE model of the combustion engine 170. In particular, the control unit 90 is configured to execute the exhaust aftertreatment procedure described below.

[0039] Furthermore, the system 1 includes an electrically driven compressor (EAV) 10, a second AdBlue™ dosing unit 70 and a second SCR catalyst 80 in the form of an underfloor SCR catalyst, each of which is also operationally connected to the control unit 90.

[0040] During the operation of the exhaust aftertreatment system 1, the control unit 90 prepares the exhaust aftertreatment system 1 for increased NO by actuating components of the exhaust aftertreatment system 1 while the diesel-powered combustion engine 170 is stationary. x -Sales rate. The control unit 90 also predicts the increased NOₓ. x -Transmission rate of exhaust aftertreatment system 1 based on a temperature-dependent model of exhaust aftertreatment system 1.

[0041] Specifically, the control unit 90 actuates the electrically driven compressor 10, the exhaust gas recirculation valve 20, and the electric oxidation catalyst 40. The components of the exhaust aftertreatment system 1 are actuated with recuperation energy provided by the electric motor 150 during braking of the hybrid vehicle in order to increase the range of the hybrid vehicle.

[0042] Then the control unit 90 adjusts at least one operating parameter of the internal combustion engine 170 based on the DoE model of the internal combustion engine 170 in such a way that soot emissions from the internal combustion engine 170 are reduced and NOₓ is reduced. x -Emission of the combustion engine 170 corresponding to the increased NO x -Sales rate is increased.

[0043] Ideally, the control unit 90 minimizes the soot emission of the combustion engine 170, i.e., the raw soot emission, by making maximum use of the predicted NO x -Sales rate at the expense of a correspondingly increased NO x -Emission from the internal combustion engine 170, i.e. NO x -Raw emission, to comply with standard NO x -Emission of the hybrid vehicle to result in reduced soot emissions from the hybrid vehicle (end-of-pipe emission in each case). REFERENCE MARK LIST: 1 Exhaust gas aftertreatment system 10 electrically driven compressors (EAV) 20 Exhaust gas recirculation valve (EGR valve) 30 exhaust gas turbochargers 40 electrical oxidation catalyst (E-cat) 50 first AdBlue™ dosing units 60 SCR-coated diesel particulate filter (SCR@DPF) 70 second AdBlue™ dosing unit 80 second SCR catalyst (underfloor SCR) 90 Control unit 100 Powertrain 110 wheel 120 Differential 130 partial gearboxes 140 drive clutch 150 electric motor 160 Disconnect coupling 170 diesel engine (VKM) 180 belts 190 Belt starter generator (BSG)

Claims

[1] Method for exhaust aftertreatment for a diesel-powered hybrid vehicle, wherein - a control unit (90) of the diesel-powered hybrid vehicle by actuating components of an exhaust aftertreatment system (1) of the hybrid vehicle during a standstill of a diesel-powered internal combustion engine (170) of the hybrid vehicle, the exhaust aftertreatment system (1) for an increased NO x -turnover rate prepared, wherein the components of the exhaust aftertreatment system (1) are actuated with electrical recuperation energy provided by the electric motor (150) during braking of the hybrid vehicle, - the control unit (90) adjusts at least one operating parameter of the internal combustion engine (170) in such a way as to reduce soot emissions from the internal combustion engine (170) and NO x -Emission from the internal combustion engine (170) corresponding to the increased NO x -Sales rate is increased. [2] Method according to claim 1, wherein the control unit (90) actuates an electrically driven compressor (10), an exhaust gas recirculation valve (20) and an electric oxidation catalyst (40) as components of the exhaust aftertreatment system (1). [3] Method according to one of claims 1 or 2, wherein the control unit (90) increases the NO x -Transmission rate of the exhaust aftertreatment system (1) is predicted based on a temperature-dependent model of the exhaust aftertreatment system (1). [4] Method according to any one of claims 1 to 3, wherein the control unit (90) sets the at least one operating parameter based on a DoE model of the internal combustion engine (170). [5] Method according to any one of claims 1 to 4, wherein the control unit (90) controls the soot emission of the internal combustion engine (170) by making maximum use of the predicted NO x -Sales rate at the expense of a correspondingly increased NO x -Emission minimized. [6] Control unit (90) for exhaust aftertreatment for a diesel-powered hybrid vehicle, which is configured to perform a method according to any one of claims 1 to 5. [7] Exhaust aftertreatment system (1) for a diesel-powered hybrid vehicle, comprising a diesel-powered internal combustion engine (170), an exhaust gas recirculation valve (20), a first AdBlue dosing unit (50) and a first SCR-coated diesel particulate filter (60) and a control unit (90) operationally connected to these components according to claim 6, and comprising an electrically driven compressor (10), an electric oxidation catalyst (40), a second AdBlue dosing unit (70) and a second SCR catalyst (80), each of which is operationally connected to the control unit (90). [8] Diesel-powered hybrid vehicle with a control unit (90) for exhaust aftertreatment according to claim 6 or with a system (1) for exhaust aftertreatment according to claim 7.

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