Method for determining a hybrid drive torque threshold, for operating a hybrid drive device and hybrid vehicle

Abstract

Method (75) for determining a hybrid drive torque threshold (95, 97, 99) for operating a hybrid drive device (5, 7) below which an electric drive takes place, wherein the method comprises: Receipt of a pollutant signal (43, 44, 45) which is indicative of a pollutant load of an exhaust gas reduction device (31, 33); and Determining the hybrid drive torque threshold (95, 97, 99) based on the pollutant signal (43, 44, 45) and a lower regeneration torque threshold (58, 60, 67) of the exhaust gas reduction device (31, 33).

Description

[0001] The present invention relates to a method for determining a hybrid drive torque threshold for operating a hybrid drive device, a method for operating a hybrid drive device, an engine control unit and a hybrid vehicle with the engine control unit.

[0002] A hybrid drive system comprises, for example, an internal combustion engine, such as a diesel or gasoline engine, and an electric motor, which can be operated in both drive mode and generator mode. The hybrid drive system, which may be used, for example, in a hybrid vehicle, can, within an operating strategy, have, for example, a hybrid drive mode in which both the internal combustion engine and the electric motor are used for propulsion, and an electric drive mode in which (in particular, exclusively) the electric motor is used for propulsion.

[0003] In normal operation of the internal combustion engine, the following premises are typically assumed: 1. Conversion of CO and HC emissions via an oxidation catalyst 2. Storage of NO X -Emissions in NO X -storage catalyst 3. Storage of soot particles in the diesel particulate filter

[0004] One approach to determining a fuel-efficient and customer-optimized operating strategy for a hybrid drive system can be, for example, conventionally described as follows. The development of a fuel-efficient hybrid operating strategy is based on a comparison of the conventional, purely combustion engine drive with intermittent electric-combustion engine operation. In hybrid mode, in addition to recuperation, the increased fuel consumption due to load point increases, as well as the energy input for electric driving and engine start-up processes, must be taken into account. Electric driving is then only permitted within an energetically efficient operating range, where the overall efficiency is higher than in purely combustion engine operation, despite the multiple, lossy energy conversions.This approach conventionally results in a fuel-efficient torque threshold within the combustion engine's fuel consumption map. Typically, the fuel consumption map of the combustion engine during normal operation is considered. Below this torque threshold, electric driving is permitted, while above it, the vehicle switches to hybrid driving mode (with load point increase). The fuel-efficient torque threshold is generally dependent on engine speed.

[0005] The transition from electric to hybrid-combustion engine driving mode (with load point increase) can occur when the driver's requested torque exceeds the predetermined torque threshold. This torque threshold, which also depends on the engine speed (and vehicle speed), can be determined for optimal fuel consumption for various driving cycles using a mathematical optimization method. This allows for significant proportions of purely electric driving in urban areas, while outside urban areas, the combustion engine is predominantly used in hybrid mode. In the New European Driving Cycle (NEDC), for example, this operating strategy results in hybrid-combustion engine driving mode (with load point increase) at the end of the acceleration phases to 32, 50, and 70 km / h, as well as for speeds above 50 km / h. During the remaining phases, driving is purely electric.During deceleration phases, the vehicle's kinetic energy is converted into electrical energy through recuperation (generator-like operation of the electric machine).

[0006] The current state of the art describes, in various forms, the use of the electric motor in a hybrid vehicle as an additional torque source or torque sink in order to influence the operating point of the internal combustion engine by selectively increasing or decreasing the load point with regard to a desired activity of the catalyst system (better conversion, faster warm-up, more favorable temperature level, etc.).

[0007] DE 10 2013 220 349 A1 discloses a regeneration process and a motor vehicle for regenerating an adsorber downstream of an internal combustion engine, wherein the internal combustion engine is operated in a rich combustion phase during regeneration of the adsorber. For the rich combustion, the engine speed or engine load is influenced by means of an electric motor mechanically coupled to the internal combustion engine.

[0008] US 2007 / 0204601A1 concerns a hybrid vehicle with an internal combustion engine and an electric motor. The hybrid vehicle includes an exhaust aftertreatment system located in an exhaust duct of the engine to treat the components contained in the exhaust gas. A control unit is configured to selectively regenerate the exhaust aftertreatment system to burn off and remove deposits within the system. The control unit is further configured to regulate the internal combustion engine and the electric motor so that the exhaust aftertreatment system does not reach an excessively high temperature during regeneration.

[0009] DE 10 2008 004 209 A1 discloses a method for operating a powertrain of a vehicle with an internal combustion engine in whose exhaust system an exhaust gas purification device is arranged. In predefinable operating states of the internal combustion engine, a correction torque is applied to a desired torque generated by an engine control unit, such that an output torque is generated over a predefinite time interval, the value of which lies outside a low-load range.

[0010] DE 10 2005 003 628 A1 describes a method for operating a drive train with a switchable electric machine, wherein the electric machine can be connected to a motor in whose exhaust system an exhaust gas purification device is arranged. It is proposed that a torque supplied or received by the electric machine is superimposed on a torque of the motor requested by a motor control device, depending on an operating state of the exhaust gas purification device.

[0011] US 2014 / 0074386A1 concerns a method for controlling a hybrid vehicle. The vehicle has a compression-ignition engine with an exhaust aftertreatment system and an engine control unit (ECU). The ECU is configured to (i) operate the engine based on an engine start request and (ii) perform exhaust aftertreatment for the vehicle when a portion of the engine's operating time exceeds an aftertreatment threshold over a specified period.

[0012] US Patent 2011 / 0257821A1 discloses a method for regenerating a diesel particulate filter in a vehicle equipped with a hybrid engine, in which the temperature of the exhaust gas exiting the diesel engine is increased above a predetermined value by increasing the engine load. This is achieved by optimizing the interaction between the diesel particulate filter aftertreatment system and the hybrid engine control unit via message transmission over a communication bus. The engine load can be increased with or without the support of the hybrid engine's electric motor / generator and has no effect on the required acceleration / deceleration of the vehicle.

[0013] However, it has been observed that in conventional hybrid drive systems, setting a torque threshold or a hybrid drive torque threshold does not lead to satisfactory results under all operating conditions (of the internal combustion engine). In particular, it has been observed that it is difficult to determine the hybrid drive torque threshold while also requiring the reliable operation of an exhaust gas reduction device.

[0014] One object of the present invention is therefore to provide a method for determining a hybrid drive torque threshold and a corresponding engine control unit that at least partially overcomes the aforementioned disadvantages. A further object is to provide a method for operating a hybrid drive device, in particular a diesel hybrid drive device, and a corresponding engine control unit that operate on the basis of the determined hybrid drive torque threshold.

[0015] The problem is solved by the subject matter of the independent claims, which are directed to a method for determining a hybrid drive torque threshold, to a method for operating a hybrid drive device, to an engine control unit and to a hybrid vehicle, in particular a diesel hybrid vehicle.

[0016] A first aspect of the present invention relates to a method for determining a hybrid drive torque threshold for operating a hybrid drive device, below which an electric drive takes place, wherein the method comprises: Receiving a pollutant signal that is indicative of pollutant loading in an exhaust gas reduction device; and Determining the hybrid drive torque threshold based on the pollutant signal and a lower regeneration torque threshold of the exhaust gas reduction device.

[0017] A second aspect of the present invention relates to a method for operating a hybrid drive device, comprising: Determining a hybrid drive torque threshold according to one of the preceding claims; Activating the electric drive while simultaneously deactivating the combustion engine drive when torque requirements are below the hybrid drive torque threshold; and Regenerating the exhaust gas reduction device if the pollutant load has exceeded a pollutant load threshold by controlling the hybrid drive device in such a way that a torque generated by the internal combustion engine is above the lower regeneration torque threshold.

[0018] A third aspect of the present invention relates to an engine control unit for determining a hybrid drive torque threshold for operating a hybrid drive device, below which an electric drive takes place, wherein the engine control unit comprises: an input module which is designed to receive a pollutant signal which is indicative of a pollutant load of an exhaust gas reduction device; and a processor which is designed to determine the hybrid drive torque threshold based on the pollutant signal and a lower regeneration torque threshold of the exhaust gas reduction device.

[0019] A fourth aspect of the present invention relates to a hybrid vehicle with an engine control unit according to the third aspect, wherein the engine control unit is further configured to control the hybrid drive device of the hybrid vehicle based on the determined hybrid drive torque threshold.

[0020] Further embodiments of the present invention are specified in the dependent claims.

[0021] In a method according to the invention for determining a hybrid drive torque threshold for operating a hybrid drive device, a pollutant signal is obtained which is indicative of a pollutant load in an exhaust gas reduction device (in particular in an exhaust stream of the internal combustion engine of the hybrid drive device). Furthermore, based on the pollutant signal (e.g. an electrical, optical, wirelessly transmitted or wired signal) and a (e.g. predetermined) lower regeneration torque threshold (of the exhaust gas reduction device), the hybrid drive torque threshold is determined.

[0022] The hybrid drive system can be a diesel hybrid drive system comprising both a diesel engine and an electric motor. In other embodiments, the hybrid drive system can also comprise a gasoline or natural gas engine and an electric motor.

[0023] As a rule, when torque is requested (e.g., by the driver of a vehicle equipped with a hybrid drive system) below a specific hybrid drive torque threshold, only the electric motor within the hybrid drive system is used for propulsion, without the internal combustion engine being used. When torque is requested below the hybrid drive torque threshold, the internal combustion engine, particularly a diesel or gasoline engine, may be switched off or at least operated at a low speed. However, if the battery or electrical energy storage system supplying power to the electric motor has a charge level below a certain threshold, the internal combustion engine (e.g., a diesel or gasoline engine) may also be used in a situation where the torque is requested below the hybrid drive torque threshold.in addition to the electric motor) for propulsion.

[0024] The exhaust gas reduction device can reduce the release into the environment of products resulting, for example, from incomplete combustion of fuel and air, and / or lead to or contribute to more complete combustion. The exhaust gas reduction device can be arranged in the exhaust system of the internal combustion engine.

[0025] The complete combustion of diesel fuel, which consists solely of carbon and hydrogen, produces carbon dioxide (CO2) and water (H2O). Diesel engine exhaust also contains hydrogen (H2), carbon monoxide (CO), partially or incompletely combusted hydrocarbons (HC), and soot as products of incomplete combustion. Furthermore, the exhaust contains nitrogen oxides (NOx). X) as oxidation products of nitrogen as well as other oxidation products formed from fuel components (especially sulfur).

[0026] In diesel engine combustion, nitrogen oxides, soot (particles), carbon monoxide, and unburned hydrocarbons are the most important pollutant components in the exhaust gas. Due to the increasingly low sulfur content in diesel fuel (especially in the EU), the oxidation products of sulfur are of minor importance with regard to exhaust emissions, but even at low concentrations they can cause lasting damage to components in the exhaust system. Under certain conditions, compliance with current emission standards (e.g., EU6, Tier 2 BIN5) may no longer be achievable through in-engine measures alone and may therefore require suitable exhaust aftertreatment (e.g., an exhaust gas reduction system) to reduce the emission of the pollutant components (NOx). X, soot, CO and HC) reduced in accordance with the legal limits.

[0027] In a modular diesel engine system, the exhaust aftertreatment for EU6 or Tier 2 BlN5 applications can either use a NOₓ x - Storage catalyst with oxidation catalyst coating and a diesel particulate filter ("engine-mounted exhaust gas purification with NO") X -storage catalyst and diesel particulate filter") or an oxidation catalyst, an SCR dosing module and a diesel particulate filter with SCR coating ("engine-mounted exhaust gas purification with SCR system and diesel particulate filter").

[0028] Carbon monoxide and unburned hydrocarbons can be oxidized to carbon dioxide in the oxidation catalyst, for example, during normal operation with an air-fuel ratio (λ) > 1 (lean, excess air, λ denotes the ratio of fuel particles to oxygen particles (in air)) from a temperature level of approximately 170°C upstream of the oxidation catalyst.

[0029] Soot particles can be deposited / filtered in the diesel particulate filter (DPF) during normal operation with a flow rate (λ > 1). To regenerate the DPF when the maximum permissible soot load is exceeded, soot oxidation by oxygen (O2) can be carried out during engine operation with a flow rate (λ > 1) and an elevated temperature of approximately 450 to 650°C upstream of the DPF. This may require an adjustment to the engine control unit (ECU) to provide the necessary temperature and soot oxidation (C + O2 => CO2).

[0030] Once the diesel particulate filter's maximum soot load is exceeded, regeneration can be initiated. This results in a change in the engine's operating mode from normal operation to DPF heating or DPF regeneration. The DPF heating mode can be temperature-controlled. A late post-injection with a correspondingly delayed heat release (still in the combustion chamber) initially provides the temperature level required for DPF regeneration in the oxidation catalyst (approximately 350°C).

[0031] In DPF regeneration mode, the actual soot oxidation in the diesel particulate filter can then take place, provided sufficient oxygen is supplied and the required temperature level is maintained as much as possible (very late post-injection with heat release in the oxidation catalyst from 350°C). Soot oxidation can occur in two stages: first, oxidation of the first third of the absolute soot load at approximately 550°C upstream of the diesel particulate filter, then oxidation of the last two-thirds of the absolute soot load at approximately 650°C upstream of the diesel particulate filter.

[0032] At a temperature level of 550°C upstream of the oxidation catalyst, soot oxidation is thermally controllable, i.e., during idling or deceleration, or when the internal combustion engine is off, an immediate temperature drop can occur upstream of the diesel particulate filter, which leads to a cessation of soot oxidation (component protection).

[0033] Should the temperature drop in front of the diesel particulate filter (DPF) become too great during DPF regeneration, the engine can briefly switch back to DPF heating mode. In both DPF heating and DPF regeneration modes, any operation with the internal combustion engine (ICE) off (e.g., start-stop during idling) can be suppressed to ensure a consistently high temperature level in front of the DPF and the shortest possible overall DPF regeneration time.

[0034] The diesel engine combustion process can restrict the map range usable for the regeneration of the diesel particulate filter.

[0035] The lower regeneration torque threshold refers to the torque generated by the internal combustion engine below which regeneration of the exhaust gas reduction device is no longer possible or can only be carried out very ineffectively.

[0036] For example, if the internal combustion engine generates a torque that is below the lower regeneration torque threshold, an insufficiently high temperature level may be provided to effectively carry out regeneration of the exhaust gas reduction device.

[0037] In general, regeneration of the exhaust gas reduction system requires the operation of the internal combustion engine to supply combustion products from the engine, which have a suitable temperature, pressure, and composition, to the exhaust gas reduction system via the exhaust system. Additional substances can be added to the exhaust gas reduction system during regeneration. For example, if the engine generates torques above an upper regeneration torque threshold, the oxygen content in the exhaust gas can decrease due to full-load operation, which can reduce the effectiveness of the regeneration, for example, by lowering the diesel particulate filter conversion rate.

[0038] The deposition of nitrogen oxides in the NO X-The storage catalyst can, for example, be used in normal engine operation of the internal combustion engine with λ > 1 according to the following reactions: 2NO + O2 => 2NO2 4NO2 + O2 + 2BaCO3 => 2Ba(NO3)2 + 2CO2

[0039] The reactions can occur particularly in the temperature range of 150 to 450°C. At the lower temperature limit, the oxidation of NO to NO₂ may be limiting. At the upper temperature limit, the thermal stability of Ba(NO₃)₂ may be limiting.

[0040] A regeneration of NO X -storage catalyst (DeNO₂) X (Fat operation) can include, for example: • Release of nitrogen oxides and their reduction to nitrogen • Fuel as a reducing agent for NO X -Reduction, engine operation with λ < 1

[0041] Regeneration can occur particularly with a rich mixture (lack of air, i.e., excess fuel) and a temperature level of approximately 250 to 450°C upstream of the NOₓ.X -storage catalyst.

[0042] During regeneration, the following reactions, for example, can occur: Ba(NO3)2 + CO => BaCO3 + 2NO + O2 2NO + O2 + 4CO => N2 + 4CO2 Σ Ba(NO3)2 + 5CO => BaCO3 + N2 + 4CO2

[0043] Even small amounts of sulfur in diesel fuel (sulfur-free fuel < 50 ppm) can lead to sulfurization of NO. X -storage catalyst, which leads to the NO X -conversion of NO X -storage catalyst reduced. Therefore, regular desulfurization of NO is not necessary. X A storage catalyst may be required, which also necessitates an intervention in the engine application to implement the corresponding functionality.

[0044] The desulfurization of NO X -Storage catalyst is sometimes called DeSO₄ X -Operation or DeSO X-Regeneration is called.

[0045] The desulfurization of NO X -The storage catalyst can operate via alternating operation ("wobble") between a temperature-increasing DeSO₄. X -lean operation (similar to DPF heating operation) and a sulfur-reducing DeSO X -Fat operation will be implemented.

[0046] The diesel engine combustion process can be used for the regeneration or desulfurization of NO. X -Restrict the usable map range of the storage catalyst. The restriction of the regeneration of the exhaust gas reduction device can be achieved, for example, by a map range for NO regeneration. X -storage catalyst. If, for example, the torque generated by the internal combustion engine drops below the lower regeneration torque threshold, a lower fuel consumption may occur, which could result in an insufficient temperature level upstream of the NOₓ. X -storage catalyst can lead to this.

[0047] If the torque generated by the internal combustion engine, in particular a diesel engine, is above an upper regeneration torque threshold (in particular the NOₓ) X -storage catalyst), so the fuel flow rate is prioritized to represent the full load demand by the driver and not to represent a DeNOx X - or DeSO X -Fat operation.

[0048] The oxidation catalyst functionality, the incorporation of nitrogen oxides into the NO X The storage catalyst and the storage of soot particles in the diesel particulate filter can be integrated into the normal operation of the combustion engine, in particular the diesel engine, according to embodiments of the present invention.

[0049] The regeneration of the diesel particulate filter, the regeneration of the NO X -storage catalyst and the desulfurization of NO X-Storage catalyst or the provision of the required temperature levels and / or the required special physicochemical boundary conditions, on the other hand, must each be implemented via separate engine operating modes, which are supported by embodiments of the invention.

[0050] The engine operating modes for normal engine operation and exhaust aftertreatment can be configured as follows, for example, according to the preceding explanations: Normal operation including oxidation of CO and HC, deposition of soot particles and deposition of nitrogen oxides: Exhaust gas: λ > 1, temperature: > 170°C before oxidation catalyst, 150 to 450°C before NOX storage catalyst.

[0051] The following engine operating modes for exhaust aftertreatment for the regeneration of the diesel particulate filter (DPF regeneration) and for the regeneration of the NOx storage catalyst (DeNOx) X , DeSO X ) may be provided for: DPF heating operation: Exhaust gas: λ > 1 (temperature controlled) DPF regeneration: Exhaust gas: λ > 1, Temperature: 450 to 650°C before diesel particulate filter DeNO X -Fat operation: Exhaust gas: λ < 1 (λ-controlled, rich), temperature: 250 to 450°C before NO X -storage catalyst DeSO X -lean: Exhaust gas: λ > 1, Temperature: (temperature-controlled) DeSO X -Fat operation: Exhaust gas: λ < 1 (λ-controlled, rich), temperature: 600 to 750°C before NO X -storage catalyst

[0052] Typically, DPF regeneration can occur approximately every 300 to 500 km and last up to 15 minutes, although the exact timing, frequency and duration of DPF regeneration depend on driving conditions and the driving cycle.

[0053] The DeNO X Regeneration can be a very short but frequently occurring engine operating mode.

[0054] Generally, desulfurization of NO can X -Storage catalyst regeneration, for example, takes place approximately every 700 to 1000 km with a duration of up to 20 minutes, whereby the exact time, frequency and duration also depend on the driving conditions and the driving cycle.

[0055] By determining the hybrid drive torque threshold according to the invention, taking into account (at least) a lower regeneration torque threshold, an advantageous transition point between hybrid drive and (exclusive) electric drive can be defined. This reliably supports the integration and / or assistance of regeneration of the exhaust gas reduction device and, in particular, achieves coordination with any necessary regeneration of the exhaust gas reduction device. Thus, the integration of exhaust gas reduction device regeneration into the operation of a hybrid drive vehicle is enabled or improved.

[0056] According to one embodiment, the hybrid drive torque threshold is determined such that the deviation from the lower regeneration torque threshold decreases with increasing pollutant load. This ensures that, when regeneration of the exhaust gas reduction device becomes necessary, the hybrid drive torque threshold is defined in such a way as to enable reliable and effective regeneration.

[0057] In particular, the hybrid drive torque threshold can be determined as speed-dependent. Furthermore, the hybrid drive torque threshold can be determined as a function of energy efficiency, especially to minimize energy consumption (at least in the case where there is no pollutant load in the exhaust gas reduction device).

[0058] According to one embodiment, the hybrid drive torque threshold can be determined such that it increases with increasing pollutant load (e.g., with increasing pollutant signal) and approaches the lower regeneration torque threshold from below, particularly linearly with regard to pollutant load or pollutant signal. In other embodiments, the hybrid drive torque threshold can be decreased with increasing pollutant load and approach the lower regeneration torque threshold from above, particularly linearly with regard to pollutant load or pollutant signal.

[0059] The hybrid drive torque threshold can be set to the same as the lower regeneration torque threshold when a pollutant load threshold is reached, above which regeneration of the exhaust gas reduction device is necessary. The pollutant load threshold can, for example, correspond to a maximum pollutant load, above which regeneration is required. Thus, it is advantageous to determine precisely the hybrid drive torque threshold that reliably and effectively supports the regeneration of the exhaust gas reduction device when regeneration is required.

[0060] The hybrid drive torque threshold can depend on the pollutant load in a linear, quadratic, or other manner.

[0061] The hybrid drive torque threshold can be determined according to the following equation: H_DMS=H_DMS_0+SB*(uR_DMS−H_DMS_0), where H_DMS is the specific hybrid drive torque threshold, H_DMS_0 is a hybrid drive torque threshold at vanishing pollutant loading of the exhaust gas reduction device, e.g. determined according to the conventional procedure described above for determining a consumption- and customer-optimized operating strategy of a hybrid drive device, SB the pollutant load in percent, uR_DMS is the lower regeneration torque threshold is.

[0062] Further terms can be added to this equation. For example, a compromise can be found between approaching the lower regeneration torque threshold and minimizing energy consumption. Thus, a simple algorithm or mathematical relationship is provided to determine the hybrid drive torque threshold. This threshold is therefore linearly dependent on the pollutant load, particularly the pollutant signal. The determination can therefore be carried out in a straightforward manner.

[0063] The exhaust gas reduction device can include a particulate filter, in particular a diesel particulate filter, and the pollutant load can include soot buildup in the particulate filter. This supports a conventional exhaust gas reduction device.

[0064] The exhaust gas reduction device can (further or exclusively) produce a NOₓ X -storage catalyst and the pollutant load can be NOX -loading and / or a sulfur loading. Therefore, in some embodiments, the process is applicable and designed for conventionally available exhaust gas reduction components or exhaust gas reduction devices.

[0065] The pollutant load can be measured, for example by one or more pressure sensors and / or can be determined from simulations.

[0066] The exhaust gas reduction device can have at least two (or three, four, or even more) exhaust gas reduction components, and the lower regeneration torque threshold can be an average (especially a weighted average) of the lower regeneration torque thresholds of the at least two exhaust gas reduction components. This allows for a favorable compromise to be found for determining the hybrid drive torque threshold in order to support different exhaust gas reduction components during required regeneration.

[0067] Furthermore, the hybrid drive torque threshold can be determined as a function of speed, in order to ensure energy consumption and coordination with the lower regeneration torque threshold, which can also be speed-dependent.

[0068] According to one embodiment of the present invention, a method for operating a hybrid drive device (in particular a hybrid diesel-electric drive device) is provided, which first determines a hybrid drive torque threshold according to one of the embodiments described above. Furthermore, the electric drive is activated when torque demands (e.g., from a driver) fall below the hybrid drive torque threshold, while the combustion engine is simultaneously deactivated. Activating or deactivating a specific drive, i.e., the electric drive or the combustion engine, can, in some embodiments, mean supplying a corresponding torque provided by the respective engine to a drivetrain, so that actual propulsion occurs based on this torque.The respective engine does not necessarily have to be completely switched off if the respective drive is deactivated. Furthermore, the procedure includes regenerating the exhaust gas reduction device if the pollutant load has exceeded a certain threshold. In this process, the hybrid drive system is controlled in such a way that the torque generated by the combustion engine is above the lower regeneration torque threshold.

[0069] According to embodiments of the present invention, the hybrid drive torque threshold is determined such that it does not fall below the lower regeneration torque threshold. This ensures that, when regeneration is required, the hybrid drive device operates at least partially when the internal combustion engine is activated, particularly in a range that reliably supports regeneration.

[0070] The hybrid drive system can, in particular, comprise a diesel hybrid drive system with a diesel engine and an electric motor. The exhaust gas reduction device can, in particular, include at least one diesel particulate filter and a NOₓ reducer. X -storage catalyst, wherein the NO X -Storage catalyst, especially NO X -loading and sulfur loading may each (independently of each other) require regeneration.

[0071] In a process step according to the invention, the electric motor can be operated in drive mode (i.e., in a mode in which the electric motor generates torque) if, during the generation of the exhaust gas reduction device, the torque generated by the internal combustion engine is above an upper regeneration torque threshold, in order to reduce the load point of the internal combustion engine so that the torque generated by the internal combustion engine falls below the upper regeneration torque threshold. This allows effective regeneration to continue.

[0072] Furthermore, during the process, a battery or energy storage device used to supply power to the electric motor can be charged when torque demands exceed the hybrid drive torque threshold. This charging time and / or charging power depends on the pollutant load of the exhaust gas reduction device, with the charging time and / or charging power increasing with increasing pollutant load. If the hybrid drive torque threshold increases with increasing pollutant load, this results in an increasing proportion of electric drive operation. Consequently, the battery may discharge more quickly, which may necessitate an increase in charging time to maintain a battery charge level within a specified range.

[0073] Charging can be achieved, for example, by increasing the load point of the internal combustion engine when the electric motor is operating in generator mode, with the load point increase decreasing, particularly gradually, as the charge level increases. As the charge level increases, further charging to reach a target state of charge becomes less and less necessary. By increasing the load point (especially when the charge level falls below a certain target state of charge), the battery charge can be maintained within a preferred range, thus ensuring reliable operation of the electric motor.

[0074] According to one embodiment of the present invention, an engine control unit is further provided for determining a hybrid drive torque threshold for operating a hybrid drive device. The engine control unit includes an input module configured to receive a pollutant signal indicative of a pollutant load in an exhaust gas reduction device. Furthermore, the engine control unit includes a processor configured to determine the hybrid drive torque threshold based on the pollutant signal and a lower regeneration torque threshold of the exhaust gas reduction device.

[0075] The engine control unit can be included, for example, in a diesel hybrid vehicle, wherein the engine control unit is further configured to control the hybrid drive device of the diesel hybrid vehicle based on the determined hybrid drive torque threshold. If, for example, a torque demand is below the hybrid drive torque threshold, an electric drive (in particular, exclusively) can be engaged. The engine control unit can be configured to execute or control embodiments of a method for determining a hybrid drive torque threshold, as described above.

[0076] The person skilled in the art will understand that features which have been described, disclosed or provided individually or in any combination in connection with a method for determining a hybrid drive torque threshold can likewise be applied or used in an engine control unit according to an embodiment of the present invention and vice versa.

[0077] The diesel hybrid vehicle can, for example, have a diesel particulate filter and a NOₓ filter. X -Feature storage catalyst with oxidation catalyst coating.

[0078] Embodiments of the present invention will now be explained with reference to the accompanying drawings. The invention is not limited to the embodiments described or illustrated. Fig. Figure 1 shows a schematic representation of a diesel hybrid vehicle according to an embodiment of the present invention with an engine control unit according to an embodiment of the present invention, which is configured to perform a method for determining a hybrid drive torque threshold according to an embodiment of the present invention; Fig. Figure 2 illustrates the operating ranges of the diesel hybrid vehicle, which is located in [location], using graphs. Fig. 1 is illustrated; Fig. 3 illustrates, using graphs, operating ranges for regeneration / desulfurization of an NOₓ X -storage catalyst; Fig. 4 illustrates an operating range for diesel particulate filter regeneration; Fig. 5 illustrates a method for controlling a hybrid drive device according to an embodiment of the present invention; Fig. 6 illustrates hybrid drive torque thresholds which are determined according to embodiments of the present invention; Fig. Figure 7 illustrates methods for charging the electric battery of the diesel hybrid vehicle, which is located in Fig. 1 is illustrated; and Fig. Figure 8 schematically illustrates the process steps for operating an electric accumulator in the Fig. 1 illustrated hybrid vehicle.

[0079] The in Fig. Figure 1, a diesel hybrid vehicle 1, illustrated schematically in one embodiment of the present invention, comprises an engine control unit 3, which is configured to control an internal combustion engine 5 and an electric motor 7, both of which are included in the diesel hybrid vehicle 1. For this purpose, the engine control unit 3 outputs control signals 9 and 11, respectively, to the internal combustion engine 5 and the electric motor 7. The internal combustion engine 5 can, in particular, be a diesel engine. The electric motor 7 can be operated in both a drive mode and a generator mode. The electric motor 7 is supplied with electrical energy by an electric battery 13. A rectifier component 15 is optionally provided to supply a suitable transformed voltage and current to the electric motor 7.The rectifier component 15 is formed by power electronics 17, which includes, for example, power transistors.

[0080] The engine control unit 3 has an input module 2 to supply the pollutant signals 43 and 45. Furthermore, the engine control unit has a processor 4 which determines the hybrid drive torque threshold and derives the control signals 9 and 11 from it.

[0081] A mechanical torque, generated by the internal combustion engine 5 and / or the electric motor 7, is transmitted via a transmission with drive clutches 19 to the drive wheels (not illustrated) of the diesel hybrid vehicle 1. A disconnect clutch 21 is arranged between the internal combustion engine 5 and the electric motor 7, which can selectively engage and disengage the two drive units. An (optional) starter 23 is provided for starting the internal combustion engine 5. An electric air conditioning compressor 25 is connected to the accumulator (or battery) 13 via the rectifier component 15. A low-voltage battery 27, which can provide a voltage of, for example, 12 V, is also connected to the drive units 5 and 7.

[0082] The combustion of fuel (especially diesel) and air in the internal combustion engine 5 produces exhaust gas, which is directed into an exhaust system 29. The exhaust system 29 includes a NOₓ X - Storage catalyst 31 with oxidation catalyst coating, and downstream of it a diesel particulate filter 33. Upstream of the NO X A lambda sensor 35 and a temperature sensor 37 are arranged in the storage catalyst 31. Downstream of the NO X A further temperature sensor 37 and a relative pressure sensor 39 are arranged at the storage catalyst 31. A further temperature sensor 37 and a further lambda sensor 35 are also arranged downstream of the diesel particulate filter 33.

[0083] Measurement signals from the various sensors 35, 37, 39 can be supplied to the engine control unit 3 as measurement signals 41. The engine control unit 3 also receives, in particular via an input module 2, a first pollutant signal 43, which is used for the NO loading. X -storage catalyst 31 is indicative. The first pollutant signal 43 can, for example, be the amount of NO. X show which ones are in the NO X -storage catalyst 31. As a further input signal, the engine control unit 3 receives a second pollutant signal 45, which is indicative of the soot loading of the diesel particulate filter 33. As a further input signal, the engine control unit 3 receives a third pollutant signal 44, which indicates the sulfur loading of the NOₓ. X -Storage catalyst is displayed. Further pollutant signals could be supported.

[0084] Fig. 2 shows operating areas of the in Fig. Figure 1 illustrates a diesel hybrid vehicle using boundary curves 47 and 49 in a coordinate system, where the rotational speed of the internal combustion engine 5 is plotted on the abscissa 51 and a requested torque, requested, for example, by a driver using an accelerator pedal, is plotted on the ordinate 53. The contour lines 48 show operating points of the internal combustion engine 5 with the same specific fuel consumption.

[0085] Below a speed-dependent hybrid drive torque threshold 49 (here: full load of the internal combustion engine 5), the diesel hybrid vehicle 1, which is in Fig. 1 is shown, driven (in particular exclusively) by the electric motor 7, while the internal combustion engine 5 is deactivated, in particular switched off. If the torque 53 requested by the driver, for example, is above the hybrid drive torque threshold 49, then the electric motor 7 is used to drive the vehicle shown in the diagram. Fig. In the diesel hybrid vehicle 1 illustrated in Figure 1, the internal combustion engine 5 (or, at times, both the electric motor 7 and the internal combustion engine 5) is used (in particular, exclusively), while the electric motor 7 is deactivated, in particular switched off. Above an upper hybrid drive torque threshold 47 (here: full load of the internal combustion engine 5), both the internal combustion engine 5 and the electric motor 7 can be used to drive the diesel hybrid vehicle 1 (at least temporarily and depending on the state of charge of the electric battery 13). Within curves 49 and 47, however, the electric motor 7 can also be operated, for example, in generator mode, whereby it is mechanically driven by the internal combustion engine 5 and can itself generate electrical energy to supply to the electric battery 13 in order to charge the electric battery 13.

[0086] Fig. Figure 3 illustrates operating areas for regenerating / desulfurizing NOₓ X -storage catalyst 31, wherein the rotational speed of the internal combustion engine 5 is plotted on an abscissa 55 and the torque generated by the internal combustion engine 5 is plotted on an ordinate 57. The area within the curves 58, 59 is used for the regeneration of NO. X -storage catalyst 31 is suitable. The regeneration of NO X -Storage catalyst 31 can, for example, lead to a release of nitrogen oxides or a reduction of NO. X as explained in greater detail above. The area within the dashed lines of curves 60 and 61 represents an operating range used for desulfurizing the NO. X -storage catalyst 31 is suitable. During this desulfurization process, sulfur can be broken down, which is contained in the NO X -storage catalyst 31 has accumulated.

[0087] In Fig. 3 represents curve 60, a lower regeneration torque threshold for NO desulfurization. X -Storage catalyst 31. Curve 58 in Fig. Figure 3 illustrates a lower regeneration torque threshold for NO regeneration. X -Storage catalyst 31.

[0088] Fig. Figure 4 illustrates an operating range which is used for the regeneration of the diesel particulate filter 33 (see Fig. 1) is suitable, wherein the rotational speed of the internal combustion engine 5 is plotted on an abscissa 63 and the torque generated by the internal combustion engine 5 is plotted on an ordinate 65. The (open) curve 67 represents a lower regeneration torque threshold of the diesel particulate filter 33. The curve 69 in Fig. Figure 4 illustrates an upper regeneration torque threshold of the diesel particulate filter 31. Effective and reliable regeneration of the diesel particulate filter 31 can be carried out in the operating range 71 between curves 67 and 69.

[0089] Fig. Figure 5 illustrates process steps 73 of a method for operating a hybrid drive device according to an embodiment of the present invention, which initially comprises a method 75 for determining a hybrid drive torque threshold. In step 77, the method 75 comprises obtaining a pollutant signal, for example, the first pollutant signal 43 and / or the second pollutant signal 45 and / or the third pollutant signal 44 (see Figure 5). Fig. 1), which is for pollutant loading of an exhaust gas reduction device (e.g. the NOₓ) X-storage catalyst 31 and / or the diesel particulate filter 33) is indicative. In a further process step 79, the process 75 comprises determining the hybrid drive torque threshold based on the pollutant signal and a lower regeneration torque threshold (e.g., one or more of the lower regeneration torque thresholds 58, 60, or 67, which are in Fig. 3 and Fig. 4 are shown).

[0090] After the determination of the hybrid drive torque threshold according to procedure 75 is completed, the operating procedure 73 is continued by activating the electric drive while simultaneously deactivating the internal combustion engine when torque requirements are below the hybrid drive torque threshold in procedure step 81. In the further procedure step 83, the exhaust gas reduction device is regenerated if the pollutant load has exceeded a pollutant load threshold by controlling the hybrid drive device (e.g., internal combustion engine 5 and electric motor 7) such that a torque generated by the internal combustion engine (e.g., internal combustion engine 5) above the lower regeneration torque threshold (see, e.g., Fig. 6 below).

[0091] Further process steps may follow, for example charging the electrical accumulator 13, as described in greater detail below.

[0092] Fig. Figure 6 illustrates, by way of example, three graphs 85, 87 and 89, each showing the rotational speed of the internal combustion engine 5 on an abscissa 91 and the torques generated by the internal combustion engine 5 on a respective ordinate 93, hybrid drive torque thresholds 95, 97 and 99, which, according to embodiments of the present invention, are determined for different pollutant loads, in particular for a soot load of 0%, a soot load of 50% and a soot load of 100%. Graphs 85, 87 and 89, which are shown in Fig. 6 are illustrated, in addition the lower regeneration torque threshold 67 of the diesel particulate filter 31 (see Fig. 1), as well as its upper regeneration torque threshold 69 illustrated.

[0093] As shown in graphs 85, 87, and 89, the hybrid drive torque threshold 95, 97, and 99, respectively, approaches the lower regeneration torque threshold 67 of the diesel particulate filter 31 from below with increasing soot loading. Instead of the hybrid drive torque threshold approaching the lower regeneration torque threshold 67 of the diesel particulate filter alone with increasing soot loading, in other embodiments the hybrid drive torque threshold could, for example, approach the lower regeneration torque threshold 58 and / or 60 of the NOₓ filter. X -storage catalyst 31 approximate or a combination, in particular an average value, of the various lower regeneration torque thresholds 58, 60 and 67.

[0094] According to the invention, a method for customer- and consumption-optimized integration of the regeneration of the diesel particulate filter and / or the regeneration of the NO is provided. X-storage catalyst and / or the desulfurization of NO X The integration of a storage catalyst into the operating strategy of a diesel hybrid vehicle has been proposed. The starting point for this is the limited functionality of the regeneration modes for low engine load requirements and the associated low torque requirements.

[0095] The in Fig. The fuel-efficient hybrid operating strategy for normal engine operation, as outlined in section 2, is extended to include a dependency of the torque threshold for hybrid operation 49 on the exhaust gas loading of one or more exhaust system components (e.g., the soot loading of the diesel particulate filter and / or the NOₓ). X -Loading of the NO X -storage catalyst and / or the sulfur loading of the NO X -storage catalyst). Depending, for example, on the soot load of the diesel particulate filter 33 and / or the NO X -Loading of the NO X-storage catalyst 31 and / or the sulfur loading of the NO X -Storage catalyst 31 successively lowers the torque threshold for hybrid operation 95, 97, 99 to the lower torque threshold 67 for the regeneration of the diesel particulate filter and / or the lower torque threshold 58 for the regeneration of the NO X -storage catalyst and / or the lower torque threshold 60 of NO desulfurization X -storage catalyst approximated. At full exhaust gas loading, both torque thresholds are identical.

[0096] The following mathematical relationship could (for example) be applied: Torque threshold hybrid operation (n, exhaust gas load (en)) = fuel consumption-optimized torque threshold hybrid operation for normal engine operation (n) + (exhaust gas load or weighted exhaust gas loads in percent / 100) x [lower torque threshold regeneration operation exhaust system component or weighted lower torque thresholds exhaust system components (n) - fuel consumption-optimized torque threshold hybrid operation for normal engine operation (n)] with n as the speed of the internal combustion engine.

[0097] Fig. 7 and Fig. Figure 8 illustrates graphs 101, 103 and a charge state 105 of an accumulator 13 (see Fig. 1) to illustrate charging methods according to embodiments of the present invention. The abscissa 107 represents time in seconds, the ordinate 109 of graph 101 represents the speed profile of the New European Driving Cycle (NEDC), whereas the ordinate 111 of graph 103 represents the state of charge of the accumulator 13 in percent.

[0098] In graph 101, curve sections 113 illustrate electric driving, curve sections 115 illustrate recuperation, and curve sections 117 illustrate internal combustion engine operation, possibly with a load point increase.

[0099] In graph 103, curve 119 illustrates the state of charge of the battery 13 and curve 121 the speed of the diesel hybrid vehicle 1 according to the speed profile of the New European Driving Cycle (NEDC), which is in Fig. 1 is illustrated.

[0100] As shown in graphs 101 and 103, electric driving, combustion engine operation (possibly with load point increase) and recuperation are carried out alternately over time, whereby load point increases are intensified when the battery charge level is low, i.e., carried out particularly over longer periods of time.

[0101] A target state of charge 123 can be approximately 59% of the maximum charging capacity of the accumulator 13 or the HV battery, as shown in Fig. Figure 8 is illustrated. At lower charge levels, charging processes are carried out stepwise, i.e., charging 3 125, charging 2 127, and charging 1 129. According to embodiments of the present invention, the charging times and charging capacities of the various charging processes can be extended as the exhaust gas regeneration device becomes increasingly loaded.

[0102] The usable state of charge (SOC) range of battery 13 is typically between 20% and 80%. For a hybrid operating strategy, the target state of charge for battery 13 can be 59%. This comparatively high target state of charge ensures, on the one hand, low internal resistance of the battery and thus low high-voltage battery power losses, and on the other hand, it also allows for recuperation at the target state of charge. If the battery's state of charge is above the target state of charge, no load point increase is performed during hybrid-combustion engine operation; that is, the battery is not charged (maintaining the SOC). If the state of charge is below the target state of charge, a load point increase is performed in three stages during hybrid-combustion engine operation, depending on the state of charge; that is, the battery is actively charged (approx. 9 kW in charge 1, approx. 20 kW in charge 2, and 30 kW in charge 3).In the NEDC, this interpretation results in the battery's state of charge being balanced over the entire cycle.

[0103] During the gradual transition from the hybrid operating torque threshold to the DPF regeneration torque threshold, the charging power for charging 1, charging 2 and charging 3 may need to be adjusted in parallel (see Fig. 8) be slightly adjusted to continue ensuring a balanced charge level of the battery 13 throughout the driving cycle. In the example shown above, raising the torque threshold for hybrid operation leads to a slight extension of electric driving operation under higher loads, which may necessitate a slight increase in the charging power for charging 1, charging 2, and charging 3.

[0104] Furthermore, an upper torque threshold 69 is defined during the regeneration of the diesel particulate filter 31 (see Fig. 4) As soon as the operating point of the internal combustion engine 5 is above the upper torque threshold, a load point reduction is carried out by means of the electric motor in order to return the operating point of the internal combustion engine 5 to a map range usable for diesel particulate filter regeneration. For the intended load point reduction when the upper torque threshold for DPF regeneration is exceeded, the charging powers for charging 1, charging 2, and charging 3 may also need to be slightly increased to provide the necessary electrical energy.

[0105] Once the diesel particulate filter regeneration is complete, the engine can return to normal operation. The torque threshold for hybrid operation will then also be reset to its initial value when the diesel particulate filter is at 0% soot load, as shown, for example, in... Fig. 2, Curve 49 is illustrated.

[0106] The successive modification of the torque threshold for hybrid operation depending on the soot load of the diesel particulate filter (and / or the NOₓ) X -Loading of the NO X -storage catalyst and / or the sulfur loading of the NO X -storage catalyst) will regenerate the diesel particulate filter (and / or the NO regeneration) X -storage catalyst and / or the desulfurization of NO X -storage catalyst) is meaningfully integrated into the intermittent hybrid-internal combustion engine driving operation. At the time of diesel particulate filter regeneration (and / or NO regeneration) X -storage catalyst and / or the desulfurization of NO X -storage catalyst) are the torque threshold for hybrid operation and the lower torque threshold for diesel particulate filter regeneration (and / or for NO regeneration). X-storage catalyst and / or for the desulfurization of NO X -storage catalyst) identical.

[0107] The electric driving mode (or the transition from electric driving mode to combustion engine driving mode) is thus displayed reproducibly for the customer, regardless of the engine operating mode. The regeneration of the diesel particulate filter (and / or the regeneration of the NOₓ) is also shown. X -storage catalyst and / or the desulfurization of NO X The storage catalyst then has no feedback on the vehicle's hybrid driving behavior. Additionally, the introduction of the upper torque threshold prevents regeneration of the diesel particulate filter (and / or NOₓ regeneration). X -storage catalyst and / or desulfurization of NO X -storage catalyst) consistently favorable conditions for the regeneration of the diesel particulate filter (and / or the regeneration of the NO) X-storage catalyst and / or the desulfurization of NO X -storage catalyst) so that in some embodiments a fast and efficient execution of the fuel-inefficient engine operation regeneration of the diesel particulate filter (and / or regeneration of the NO) is always possible. X -storage catalyst and / or desulfurization of NO X -storage catalyst) with subsequent return to the more fuel-efficient normal engine operation can be ensured.

[0108] Furthermore, a method is provided for controlling the operation of a powertrain of a diesel hybrid vehicle, which has an electric motor that can be operated singly below a first speed-dependent torque threshold and a diesel engine that can be switched on and off, which has an operating mode for regenerating a nitrogen oxide storage catalyst that can be operated above a second speed-dependent torque threshold, wherein the first speed-dependent torque threshold is reversibly approximated to the second speed-dependent torque threshold depending on the nitrogen oxide loading of the nitrogen oxide storage catalyst, and wherein, during the operating mode for regenerating the nitrogen oxide storage catalyst, an upper torque threshold for a purely combustion engine operating mode is activated, thereby enabling the regeneration of the nitrogen oxide storage catalyst to be optimally integrated into hybrid driving operation. Reference symbol list 1 diesel hybrid vehicle 2 Input module 3 Engine control unit 4 processors 5 Internal combustion engine 7 Electric motor 9, 11 Control signals 13 Accumulator 15 rectifiers or converters 17 Power Electronics 19 gearboxes 21 Disconnect coupling 23 starters 25 electric air conditioning compressor 27 Low-voltage battery 29 Exhaust system 31 NO X -storage catalyst 33 Diesel particulate filters 35 Lambda sensor 37 temperature sensors 39 pressure sensors 41 measurement signals 43, 44, 45 Pollutant signals 47 upper hybrid drive torque threshold and full load of the internal combustion engine 5 48 contour lines 49 Hybrid drive torque threshold 51 Abscissa 53 ordinates 55 Abscissa 57 ordinates 59, 61 upper regeneration torque threshold for regeneration or desulfurization 58, 60 lower regeneration torque threshold for regeneration or desulfurization 63 Abscissa 65 ordinates 67 Lower regeneration torque threshold for diesel particulate filters 69 upper regeneration torque threshold for diesel particulate filters 71 Operating range for DPF regeneration 73 Methods for operating a hybrid drive device 75 Methods for determining a hybrid drive torque threshold 77, 79, 81, 83 Procedural steps 91 Abscissa 93 ordinates 95, 97, 99 Hybrid drive torque threshold 107 abscissas 109, 111 ordinates 113, 115, 117 electric driving, recuperation, combustion engine operation, possibly with load point increase 119 Accumulator charge level 121 Speed 123 Target charge state 125 stores 3 127 Store 2 129 Store 1

Claims

[1] Method (75) for determining a hybrid drive torque threshold (95, 97, 99) for operating a hybrid drive device (5,7) below which an electric drive takes place, wherein the method comprises: Receipt of a pollutant signal (43, 44, 45) which is indicative of a pollutant load of an exhaust gas reduction device (31, 33); and Determining the hybrid drive torque threshold (95, 97, 99) based on the pollutant signal (43, 44, 45) and a lower regeneration torque threshold (58, 60, 67) of the exhaust gas reduction device (31, 33). [2] Method according to claim 1, wherein the hybrid drive torque threshold (95, 97, 99) is determined such that a deviation from the lower regeneration torque threshold (58, 60, 67) becomes smaller with increasing pollutant load. [3] Method according to claim 1 or 2, wherein the hybrid drive torque threshold is determined such that the hybrid drive torque threshold (95, 97, 99) is increased with increasing pollutant load and approaches the lower regeneration torque threshold (58, 60, 67) from below. [4] Method according to one of the preceding claims, wherein the hybrid drive torque threshold (95, 97, 99) is determined to be equal to the lower regeneration torque threshold (58, 60, 67) at a pollutant loading threshold above which regeneration of the exhaust gas reduction device is necessary. [5] Method according to any one of the preceding claims, wherein: H_DMS=H_DMS_0+SB*(uR_DMS−H_DMS_0), where H_DMS is the specific hybrid drive torque threshold, H_DMS_0 is a hybrid drive torque threshold at vanishing pollutant load of the exhaust gas reduction device, SB the pollutant load in percent, uR_DMS is the lower regeneration torque threshold. [6] Method according to one of the preceding claims, wherein the exhaust gas reduction device comprises a particulate filter (33) and wherein the pollutant loading comprises a soot loading of the particulate filter. [7] Method according to one of the preceding claims, wherein the exhaust gas reduction device has a NO X -storage catalyst (31) and wherein the pollutant loading is a NO X -loading and / or a sulfur loading. [8] Method according to one of the preceding claims, wherein the exhaust gas reduction device has at least two exhaust gas reduction components (31, 33) and wherein the lower regeneration torque threshold is an average of the lower regeneration torque thresholds of the at least two exhaust gas reduction components. [9] Method according to one of the preceding claims, wherein the hybrid drive torque threshold (95, 97, 99) is determined as a function of speed. [10] Method (73) for operating a hybrid drive device comprising: Determining (75) a hybrid drive torque threshold (95, 97, 99) according to one of the preceding claims; Activating (81) the electric drive while simultaneously deactivating the internal combustion engine when torque requirements are below the hybrid drive torque threshold; and Regenerating (83) the exhaust gas reduction device (31, 33) if the pollutant load has exceeded a pollutant load threshold by controlling the hybrid drive device such that a torque generated by the internal combustion engine (5) is above the lower regeneration torque threshold (95, 97, 99). [11] Method according to claim 10, further comprising: Operating the electric motor (7) in drive mode if, during the regeneration of the exhaust gas reduction device (31, 33), the torque generated by the internal combustion engine (5) is above an upper regeneration torque threshold (59, 61, 69) in order to reduce the load point of the internal combustion engine (5) so that the torque generated by the internal combustion engine (5) falls below the upper regeneration torque threshold (59, 61, 69). [12] Method according to claim 10 or 11, further comprising: Charging (125, 127, 129) of an accumulator (13) used to supply energy to the electric motor (7) when torque requirements are above the hybrid drive torque threshold via a charging time and / or charging power which depends on the pollutant loading of the exhaust gas reduction device, wherein a charging time and / or charging power is increased with increasing pollutant loading. [13] Method according to the preceding claim, wherein charging is achieved by increasing the load point of the internal combustion engine (5) when operating the electric motor (7) in generator mode, wherein the load point increase decreases with increasing charge content. [14] Engine control unit (3) for determining a hybrid drive torque threshold (95, 97, 99) for operating a hybrid drive device below which an electric drive takes place, wherein the engine control unit comprises: an input module (2) configured to receive a pollutant signal (43, 44, 45) indicative of pollutant loading of an exhaust gas reduction device (31, 33); and a processor (4) which is configured to determine the hybrid drive torque threshold (95, 97, 99) based on the pollutant signal (43, 44, 45) and a lower regeneration torque threshold (58, 60, 67) of the exhaust gas reduction device (31, 33). [15] Hybrid vehicle (1) with an engine control unit (3) according to the preceding claim, wherein the engine control unit is further configured to control the hybrid drive device of the hybrid vehicle based on the determined hybrid drive torque threshold.

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