AT522990B1 - Hybrid motor vehicle and operating method for operating a hybrid vehicle - Google Patents

Abstract

The invention relates to a hybrid motor vehicle with a drive system (1) having an internal combustion engine (2) and an electric motor (3), comprising an exhaust gas cleaning system connected to the internal combustion engine (2) of the vehicle and arranged one behind the other as seen in the flow direction of the exhaust gas emitted by the internal combustion engine (2). arranged has an electric heating element (22), a first oxidation-catalytically active exhaust-gas cleaning component (23) designed as a NOx storage catalytic converter and at least one SCR-catalytically active exhaust-gas cleaning component, and a control unit for controlling an operation of the drive system (1) and exhaust-gas cleaning system (10), wherein the control unit is designed to control the operation of the drive system (1) in such a way that, during heating operation with energization of the electric heating element (22) for heating the exhaust gas, an exhaust gas mass flow emitted by the internal combustion engine (2) does not exceed a predeterminable upper exhaust gas mass flow limit tet and/or does not fall below a specifiable lower exhaust gas mass flow limit, with the upper exhaust gas mass flow limit and the lower exhaust gas mass flow limit being specifiable as a function of a temperature and/or a capacity of at least one of the exhaust gas components and a heating output of the electric heating element (22) as a function of the temperature and the NOx loading of the NOx storage catalytic converter (23) can be adjusted. The invention also relates to an operating method for operating a hybrid vehicle with an internal combustion engine (2) and an electric motor (3).

Description

description

HYBRID VEHICLE AND OPERATING METHOD OF OPERATING A HYBRID VEHICLE

The invention relates to a hybrid vehicle with a drive system having an internal combustion engine and an electric motor according to the preamble of claim 1 and an operating method for operating such a hybrid vehicle according to the preamble of claim 10.

[0002] Hybrid vehicles with a drive system having an internal combustion engine and an electric motor are generally distinguished by comparatively low fuel consumption. Nevertheless, exhaust aftertreatment is indispensable for low emissions of pollutants, especially nitrogen oxides (NOx). However, when operating the hybrid vehicle, the problem of temperature control of the exhaust gas aftertreatment components to be provided for this purpose arises to a particular extent, since due to the internal combustion engine being switched off at times, less exhaust gas is provided in comparison to vehicles with purely combustion engine drive, which could serve to control the temperature of the exhaust gas aftertreatment system. In addition, a purely electric motor drive leads to the exhaust gas cleaning components cooling down, which must be brought back up to operating temperature as quickly as possible when the combustion engine is restarted in order to keep pollutant emissions low. To solve these problems, various proposals have been made to integrate an electrical heating element into the exhaust gas cleaning system, which is energized as required and thus at least supports heating of the exhaust gas aftertreatment components to operating temperature. For example, DE 10 2014 223 490 A1 discloses an exhaust gas aftertreatment device for a vehicle with a diesel engine, which may be designed as a hybrid vehicle, which device has an SCR catalytic converter for NOx reduction and a NOx storage catalytic converter that can be heated by an electric heating device. A control unit can control the heating device in such a way that the NOx storage catalytic converter can be heated independently of an exhaust gas temperature specified by the diesel engine.

Other hybrid vehicles with an exhaust aftertreatment system and methods for operating the same are known for example from DE 102017130695 A1, EP 2803831 A1, US 8883102 B1 and DE 102013203580 A1.

However, this measure is often not sufficient to operate a hybrid vehicle with the lowest possible emission of pollutants, in particular NOx, and with the lowest possible fuel consumption. In particular, an interaction between the heating effects of the exhaust gas and the electric heating device can be advantageous.

The object of the invention is therefore to specify a hybrid vehicle and an operating method for operating a hybrid vehicle, which enable a further improvement in terms of pollutant emissions and fuel consumption.

This object is achieved by a hybrid motor vehicle having the features of claim 1 and by a method having the features of claim 10. Advantageous refinements and developments of the invention are the subject matter of the respective dependent claims.

The hybrid vehicle according to the invention has a drive system with an internal combustion engine and an electric motor. It also includes an exhaust gas purification system connected to the internal combustion engine of the vehicle, which, viewed in the flow direction of the exhaust gas emitted by the internal combustion engine, has an electric heating element arranged one behind the other, a first oxidation-catalytic exhaust gas purification component designed as a NOx storage catalytic converter and at least one SCR catalytically active exhaust gas purification component, and a control unit for Control of an operation of the drive system and the exhaust gas cleaning system, the control unit being designed to control the operation of the drive system in such a way that during a heating operation with energization of the electric heating element for heating the exhaust gas, an exhaust gas mass

flow does not exceed a specifiable upper exhaust gas mass flow limit and/or does not fall below a specifiable lower exhaust gas mass flow limit, the upper exhaust gas mass flow limit and the lower exhaust gas mass flow limit being specifiable as a function of a temperature and/or a performance of at least one of the exhaust gas purification components and a heating output of the electric heating element as a function of the temperature and the NOx loading of the NOx storage catalytic converter can be adjusted.

By limiting or restricting the exhaust gas mass flow, raw emissions and fuel consumption can be kept low on the one hand. On the other hand, by limiting or delimiting the exhaust gas mass flow according to the invention as a function of a temperature and/or an efficiency of at least one of the exhaust gas cleaning components, the total amount of pollutants released into the environment can be kept low. In this context, the performance of an in particular catalytically active exhaust gas cleaning component is to be understood as its ability to catalytically convert a respective pollutant, in particular NOx, or its ability to remove the pollutant from the exhaust gas. This ability is strongly dependent on temperature and throughput, especially at low temperatures. The invention therefore makes it possible to exploit a catalytic exhaust gas cleaning effect of the exhaust gas cleaning components as far as possible in operating areas that are critical with regard to exhaust gas cleaning, in which additional heating takes place by energizing the heating element to heat up or maintain an operating temperature. The measure according to the invention is therefore preferably taken in connection with a cold start or a restart of the internal combustion engine. However, it can also be taken in operating ranges with a critically low temperature for one or more of the emission control components.

The internal combustion engine of the drive system is preferably formed from a diesel engine. However, a design as a gasoline engine is also possible. The electric motor can be designed, for example, as a direct current motor or as a synchronous or asynchronous three-phase motor. In order to deliver drive power, it is supplied by a rechargeable storage device for electrical energy, which is generally referred to as a battery or traction battery. The electric motor can preferably also be operated as a generator and can convert mechanical power taken up by the drive wheels or by the internal combustion engine in order to charge the battery.

As a hybrid vehicle, an embodiment as a so-called serial or parallel or power-split hybrid comes into question. The drive system is preferably designed in such a way that a drive torque can be applied to the driven wheels of the vehicle either solely by the internal combustion engine or solely by the electric motor or by both at the same time. In order to limit or limit the exhaust gas mass flow, the combustion engine and the electric motor are operated in combination, if necessary. In order to avoid exceeding the upper exhaust gas mass flow limit when there is a corresponding power requirement, it is provided that the electric motor is also used to deliver drive power. Conversely, if necessary, to avoid falling below the lower exhaust gas mass flow limit, the drive power of the electric motor can be correspondingly reduced and that of the internal combustion engine can be increased. The control for this is taken over by the control unit. The exhaust gas mass flow limits are preferably taken from stored characteristic curves or characteristic diagrams for the at least one exhaust gas cleaning component.

In addition to the design of the control unit for controlling the drive system, the control unit can also control the operation of the emission control system and in particular the heating element. In order to carry out the control functions, the control device is connected to corresponding sensors for detecting operating states or operating parameters, such as sensors for detecting exhaust gas or operating medium temperatures, pollutant concentrations or operating medium throughputs. The control device is also connected to actuators for influencing the operating states or the operating parameters in order to control them as intended. Actuators can be, for example, a fuel injection system of the internal combustion engine, flaps, valves or pumps for setting loading

be fuel throughput. The sensor signals received by the control unit are converted into control signals for the actuators by hardware and/or software implemented in the control unit and are output to the actuators. For this purpose, the control device can include several control modules, which are integrated into a single device or are designed as separate modules.

In an embodiment of the invention, the exhaust gas cleaning system has the electric heating element, arranged as a NOx storage catalytic converter, arranged one behind the other as seen in the direction of flow of the exhaust gas emitted by the internal combustion engine, a first oxidation-catalytic exhaust gas cleaning component, a first SCR catalytically active exhaust gas cleaning component, a second SCR catalytic effective exhaust gas cleaning component and a second oxidation-catalytically active exhaust gas cleaning component, wherein a dosing device for introducing an ammonia-containing reducing agent into the exhaust gas is provided on the input side of the first and the second SCR-catalytically active exhaust gas cleaning component.

In principle, the elements in the emission control system can also be arranged in a different order. For example, several heating elements, which are designed in particular as heating discs, can be provided. In addition, an SCR-catalytically active exhaust gas cleaning component can also be combined with a diesel particulate filter and/or an SCR-catalytically active exhaust gas cleaning component can be arranged upstream of an SDPF.

The heating element, first oxidation-catalytic exhaust gas cleaning component, first SCR catalytic exhaust gas cleaning component, second SCR catalytic exhaust gas cleaning component and second oxidation-catalytic exhaust gas cleaning component are thus flowed through in this order by the exhaust gas emitted by the internal combustion engine.

The electrical heating element is preferably designed as a resistance heater and can be powered by the vehicle battery. An embodiment as a foil body with a wound or folded metal foil structure that can be heated by current application and through which exhaust gas can flow is preferred. A rated power consumption of several kW, for example about 4 kW, can be provided. Although an embodiment without a coating is preferred, a catalytic coating, in particular an oxidation-catalytic coating, can be provided.

The first oxidation-catalytically effective emission control component can be designed, for example, as a classic diesel oxidation catalyst. However, an embodiment as a NOx storage catalytic converter is preferred. For this purpose, channels of a ceramic honeycomb body are provided with a coating which on the one hand has an oxidation-catalytic effect with regard to the oxidation of hydrocarbons (HC) and carbon monoxide (CO) in particular, and on the other hand can store NOx specifically under oxidizing conditions. In a regeneration process, these can be released again, especially under reducing conditions, and at least partially converted into harmless nitrogen with catalytic support. Storage of NOx can also take place at comparatively low temperatures of around 150° C. or less. This enables NOx to be removed from the exhaust gas even when the exhaust gas cleaning system has been heated up comparatively little.

The SCR-catalytically active exhaust gas purification components are preferably likewise ceramic honeycomb bodies through which exhaust gas can flow, but which are provided here with a coating which can catalyze a selective reduction of NOx by means of a reducing agent, in particular ammonia (NH3). An embodiment as a so-called full catalytic converter is also possible. These exhaust gas cleaning components preferably also have a certain NH3 storage capacity. The SCR catalytically active exhaust gas cleaning components typically allow NOx to be removed from the exhaust gas from around 150 °C.

[0017] The second emission-catalytically active emission control component is preferably an oxidation catalyst, also referred to as a blocking catalyst, which can in particular catalyze an oxidation of ammonia. As a result, an unwanted slippage of odorous and harmful ammonia can be avoided.

The metering devices are preferably designed as metering valves with which NHz or a NH; reducing agent containing in free or bound form, in particular an aqueous urea solution, can be metered into the exhaust gas. The fact that two SCR catalytic exhaust gas cleaning components are provided, each with upstream metering devices that can be actuated as desired, further improved NOx removal is made possible. For example, with a temperature gradient occurring along the exhaust gas purification system, NOx removal can already take place when the first component has reached its operating temperature but not the second.

In a further embodiment of the invention, the control unit is designed to control the operation of the drive system in such a way that an exhaust gas mass flow emitted by the internal combustion engine during normal operation without energizing the heating element does not exceed a predeterminable upper exhaust gas mass flow limit and/or does not fall below a predeterminable lower exhaust gas mass flow limit. if the temperature and/or the performance of one or more of the emission control components effective in relation to NOx reduction fall below a respectively predefinable value. This can be the NOx storage catalytic converter and/or the first SCR-catalytically active exhaust gas cleaning component and/or the second SCR-catalytically active exhaust gas cleaning component. By limiting the exhaust gas mass flow to an upper limit value, it can be avoided, particularly at comparatively low temperatures, that the NOx storage catalytic converter or one of the SCR catalytically active exhaust gas cleaning components lose their cleaning effect in an undesired manner as a result of an excessive exhaust gas mass flow. This extends effective NOx reduction to comparatively low temperatures, at which the full cleaning effect of the corresponding catalysts is not yet achieved. On the other hand, further cooling is prevented if the exhaust gas mass flow does not fall below a lower limit.

Similarly, in a further embodiment of the invention, it is provided that the control unit is designed to control the operation of the drive system in such a way that an exhaust gas mass flow emitted by the internal combustion engine during normal operation without energizing the heating element does not exceed a predeterminable upper exhaust gas mass flow limit if the temperature of the NOx storage catalytic converter and/or the first SCR-catalytically active exhaust gas cleaning component and/or the second SCR-catalytically active exhaust gas cleaning component exceed a respectively predefinable value. In this way, a thermal overload of one of the emission control components can be avoided.

[0021] The limitation or delimitation of the exhaust gas mass flow takes place, as described above, preferably by an interaction of the internal combustion engine and the electric motor controlled by the control unit.

In a further embodiment of the invention, the electric heating element, the NOx storage catalytic converter and the first SCR catalytically active exhaust gas cleaning component are arranged in an engine compartment for the internal combustion engine, in particular close to the internal combustion engine, and the second SCR catalytic exhaust gas cleaning component and the second oxidation catalytically active exhaust gas cleaning component are Far from the combustion engine, in particular in an underbody area of the hybrid motor vehicle. By arranging the NOx storage catalytic converter and the first SCR catalytically active exhaust gas cleaning component close to the combustion engine, they can be warmed up particularly quickly by hot engine exhaust gas. An arrangement in which the NOx storage catalytic converter is arranged directly behind the heating element and together with it in a common housing is particularly preferred. The housing is preferably connected directly to the outlet of an exhaust gas turbocharger turbine.

In a further embodiment of the invention, the first SCR catalytically active exhaust gas cleaning component is designed as a particle filter with an SCR catalytically active coating. In this way, a filter function and a NOx removing function are combined in a space-saving manner. The particle filter is preferably designed as a so-called wall-flow filter with channels that are alternately closed on the inlet and outlet sides.

In a further embodiment of the invention, the first SCR catalytically active exhaust gas cleaning component can also have a particle filter with an SCR catalytically active coating and an additional SCR catalytic converter, these two components being arranged directly one behind the other in a common housing. Viewed in the direction of the exhaust gas flow, the particle filter can be arranged directly in front of or also directly behind the SCR catalytic converter. Provision can also be made for the SCR catalytic converter to be arranged in front of the particle filter.

In a further embodiment of the invention, a first coolant circuit for controlling the temperature of the internal combustion engine and a separate second coolant circuit for controlling the temperature of the electric motor are provided, with a first electric coolant pump being provided for the first coolant circuit and a second electric coolant pump being provided for the second coolant circuit, with the first coolant pump is connected to a first power supply and the second coolant pump is connected to a second power supply, and the first power supply provides a greater electrical voltage than the second power supply. This enables targeted temperature control of both the internal combustion engine and the electric motor in an energy-saving manner. The first coolant pump is preferably more powerful and designed for larger throughputs than the second coolant pump. The voltages of the power supplies can be 48 V and 12 V, for example. The first voltage supply is preferably implemented by the traction battery. Provision can also be made for the second coolant pump to be more powerful or the same powerful as the first coolant pump.

In a further embodiment of the invention, the control unit is designed to operate the first and/or the second coolant pump in a reduced-power operation with an adjustable reduced speed compared to normal operation. Operation at reduced speeds and thus with reduced power consumption is preferably carried out when it is determined, for example based on the power output by the internal combustion engine or by the electric motor, that a full coolant throughput is not absolutely necessary. This can be done in particular by a model-based determination of the required heat dissipation or cooling capacity. If the first or the second coolant pump is then operated at reduced speeds, a further reduction in consumption is achieved overall.

The method according to the invention is characterized by a heating-up operation for heating up the emission control system to the operating temperature, the heating-up operation comprising a first and a subsequent second heating-up phase. In the first heating-up phase, with an unfired internal combustion engine, the electric heating element is energized in such a way that a temperature of an exhaust gas cleaning component arranged downstream of the heating element in the exhaust gas cleaning system reaches or exceeds a predefinable temperature limit. In the second heating-up phase with fired operation of the internal combustion engine, the electrical heating element continues to be energized and, if there is excess oxygen in the exhaust gas emitted by the internal combustion engine, early and/or late fuel post-injection is provided for the internal combustion engine. Furthermore, in the second heating-up phase, the operation of the drive system is controlled such that an exhaust gas mass flow emitted by the internal combustion engine does not exceed a predeterminable upper exhaust gas mass flow limit and/or does not fall below a predeterminable lower exhaust gas mass flow limit. Furthermore, according to the invention, normal operation is provided with exhaust gas cleaning components heated at least approximately to operating temperature, in which the internal combustion engine, depending on a determined NOx emission total value for exhaust gas released to the environment, operates in a first operating mode with minimized raw NOx emissions or in a second operating mode with minimized specific Fuel consumption is operated. The ma-

Maximum efficiency of the exhaust aftertreatment maintained in order to always be able to ensure a minimum possible overall level of emissions emitted to the environment.

Because the electrical heating element is energized in the first heating phase, the exhaust gas cleaning system and in particular an exhaust gas cleaning component arranged close behind the heating element, such as a NOx storage catalytic converter, can be preheated before the internal combustion engine is started. This can be done both when the vehicle is stationary and when it is moving. If the internal combustion engine is started and thus changes from an unfired to a fired operation, at least partial cleaning of the discharged exhaust gas is made possible as soon as the exhaust gas begins to be emitted by the internal combustion engine.

In order to heat up the exhaust gas purification system further, in the second heating-up phase following the first heating-up phase, the heating element can be operated with a reduced heating output that can be predetermined compared to the nominal output. In this case, the heating output is preferably reduced as a function of a temperature for an exhaust gas cleaning component arranged close behind the heating element, such as for example a NOx storage catalytic converter or also the first or second SCR. This temperature can be determined metrologically by means of a sensor or by a calculation model.

As far as the fuel post-injections are concerned, provision is preferably made for an early post-injection of fuel, which is also burning, to be carried out in at least one combustion chamber of the internal combustion engine. As a result, comparatively hot exhaust gas is emitted and the exhaust gas purification system is rapidly further heated. The late fuel post-injection is then switched on, preferably also controlled by a temperature in the exhaust gas purification system. This is preferably designed as a post-injection that does not burn at the same time, with which the emitted exhaust gas is enriched with unburned fuel components. The unburned fuel components are at least partially oxidized with the release of heat in an oxidation-catalytic exhaust gas purification component that is already at least approximately heated to the operating temperature, for example in a NOx storage catalytic converter arranged behind the heating element. In this way, the exhaust gas purification system is quickly further heated. With regard to the limitation or delimitation of the exhaust gas mass flow carried out in the second heating-up phase, reference is made to the conditions already described above.

If the exhaust gas purification components are at least approximately heated to the operating temperature as a result of the heating operation, the heating measures, i.e. the energization of the heating element, and the early and late fuel post-injection are terminated. Optionally, in particular depending on the raw NOx emissions released into the environment, the internal combustion engine is then operated either in an operating mode with minimized NOx emissions or in an operating mode with minimized fuel consumption. In particular, the maximum efficiency of the exhaust aftertreatment is always maintained in order to always be able to guarantee a minimum possible overall emission level, which is emitted to the environment.

In a refinement of the operating method according to the invention, in an exhaust gas cleaning system which, seen in the direction of flow of the exhaust gas emitted by the internal combustion engine, has the electric heating element arranged one behind the other, a first exhaust gas cleaning component which is active in terms of oxidation catalysis, in particular designed as a NOx storage catalytic converter, and at least one SCR catalytically active exhaust gas cleaning component, the current supply for heating the heating element is set at least in the second heating-up phase as a function of a temperature and a NOx loading of the NOx storage catalytic converter. The NOx storage catalytic converter is preferably arranged directly behind the heating element placed close to the combustion engine.

Because the heating of the NOx storage catalytic converter takes into account both its temperature and its loading with stored NOx, one

be achieved that the NOx storage catalytic converter is further heated as required. On the other hand, with a high NOx load, reduced heating by the heating element can prevent stored NOx from being thermally desorbed and released into the environment when the SCR catalytically active exhaust gas cleaning element is not yet ready for operation.

In a further embodiment of the method, the NOx storage catalytic converter is regenerated during the second heating-up phase. For this purpose, the internal combustion engine is operated at least at times with a rich air-fuel ratio and the operation of the drive system is controlled with the aid of the electric motor in such a way that an exhaust gas mass flow rate emitted by the internal combustion engine is between a specifiable upper and a specifiable lower exhaust gas mass flow limit.

During the regeneration of the NOx storage catalytic converter, stored NOx is released and at the same time reduced to harmless nitrogen. Enriching the fuel-air ratio (A) to a value of X<1.0, which is preferably carried out for a comparatively short time, causes the NOx storage catalytic converter and downstream exhaust gas purification components to heat up further. In addition, the NOx storage catalytic converter is returned to a state with high NOx absorption capacity. Since regeneration of the NOx storage catalytic converter always consumes energy, it is particularly efficient to carry out this in the second heating-up phase when the heating element is energized anyway. Limiting the exhaust gas mass flow ensures that regeneration runs optimally.

In a further embodiment of the method, the heating element is heated immediately after switching off the internal combustion engine in such a way that the NOx storage catalytic converter is raised to a temperature at which stored nitrogen oxides are at least partially thermally desorbed. The thermal desorption of previously stored NOx restores or at least improves the NOx storage capacity. This also regenerates the NOx storage catalytic converter. When the combustion engine is restarted, it is therefore able to remove NOx from the exhaust gas. It is advantageous if a so-called low-temperature storage catalytic converter is used, which can adsorb NOx at low temperatures of 150° C. or less.

In a further embodiment of the method, an ammonia-containing reducing agent is fed to the exhaust gas cleaning system during thermal desorption of nitrogen oxides from the NOx storage catalytic converter after the internal combustion engine has been switched off in the exhaust gas flow direction upstream of the at least one SCR catalytically active exhaust gas cleaning component. In this way, NOx desorbed from the NOx storage catalytic converter can be converted to harmless N; reduced and their discharge into the environment avoided. It is preferably provided that at the start of the heating of the heating element, air is blown into the exhaust gas cleaning system by means of a conveying device in front of the heating element. This prevents the heating element from overheating and ensures that desorbing NOx is conveyed to the SCR catalytic emission control component.

In a further embodiment of the method, a maintenance heating operation is provided for at least approximately maintaining the operating temperatures of the emission control components, in which, if necessary, at least one heating measure for heating the emission control system is taken in a definable manner from a selection list of heating measures.

In normal operation without heating measures, it is preferably continuously checked whether there is a critical condition in that one of the emission control components threatens to cool down undesirably. In order to continue to keep the exhaust gas cleaning components, which are typically at least approximately at operating temperature during normal operation, in this state, a heating measure is selected from a selection list stored in the control unit in a predeterminable manner and taken. The selection is preferably made on the basis of an associated increase in fuel consumption and/or on the basis of a possibly related

associated increase in emissions, in particular raw NOx emissions, with the focus always being on the minimum possible total emissions.

In a further advantageous embodiment of the method, the heating measure is selected in such a way that, especially during normal operation, it is continuously determined for what period of time from the current point in time operation of the exhaust gas cleaning system with exhaust gas cleaning components heated at least approximately to the operating temperature is likely to be possible without taking an additional heating measure is. If this time span falls below a predefinable time limit value, that heating measure is selected from the selection list of heating measures or those heating measures are selected with which or with which the time span for the operation of the exhaust gas cleaning system with exhaust gas cleaning components heated at least approximately to the operating temperature is expected to be at least by a predeterminable value extended. The predictions are made using a prediction model stored in the control unit. It is thus possible to react in a foresighted manner to operating conditions that are changing or developing, in particular in an unfavorable manner, and to ensure at least adequate exhaust gas cleaning.

In yet another embodiment of the invention, the heating measure or measures are selected from the selection list as a function of the state of charge of a battery coupled to the electric motor and as a function of an estimated resulting additional fuel consumption and/or an estimated resulting increase in untreated pollutant emissions such that the smallest possible increase in fuel consumption and/or the smallest possible increase in raw pollutant emissions result. This enables fuel consumption and emission behavior to be optimized so that the minimum possible total emissions are always displayed.

In a further embodiment of the method, a first coolant circuit for temperature control of the internal combustion engine is operated with a first electric coolant pump and a separate second coolant circuit for temperature control of the electric motor is operated with a second electric coolant pump, the first coolant pump having a compared to the second Coolant pump higher electrical operating voltage is operated. The first coolant pump is preferably designed to be more powerful and throughput than the second coolant pump. A power-adapted voltage supply enables an optimal component design. The first coolant pump is preferably connected to the traction battery, while the second coolant pump is connected to an on-board battery for the operation of small consumers.

In a further embodiment of the method, a minimum coolant throughput is determined for the first and/or the second coolant circuit and, in order to set the minimum coolant throughput, a speed of the first and/or the second coolant pump is compared to a respective nominal speed as a function of operating parameters of at least the drive system possibly reduced. A speed reduction preferably takes place mainly as a function of the speed of the internal combustion engine or of the electric motor and/or as a function of the respective coolant temperature. Any speed reduction that may be carried out can also take place as a function of one or more of the following variables: ambient temperature, Ooil sump temperature, a temperature in the low-pressure exhaust gas recirculation branch, a cylinder head temperature, the operation of an interior air conditioning system, a temperature of a reducing agent metering valve that may be connected to one of the coolant circuits.

The above and other features and advantages of the invention result from the following description of preferred, non-limiting exemplary embodiments of the invention with reference to the accompanying drawings. Show in it:

1 shows a schematic representation of a drive system with a connected exhaust gas cleaning system for the hybrid vehicle according to the invention,

2 shows a schematic representation of a first advantageous embodiment of an exhaust gas cleaning system for the hybrid vehicle according to the invention,

3 shows a schematic representation of a second advantageous embodiment of an exhaust gas cleaning system for the hybrid vehicle according to the invention,

4 is a schematic representation of a coolant circulation system for the hybrid vehicle according to the invention, and

5 shows a block diagram for the schematic representation of the main features of the operating method according to the invention.

The drive system of the hybrid vehicle according to the invention, which is shown overall in FIG. 1 with the reference numeral 1 and is shown only as an example and schematically, comprises an internal combustion engine 2 and an electric motor 3 as drive units. The internal combustion engine 2, which is preferably designed as a diesel engine, is connected to a transmission via a clutch 4 5 connected. The electric motor 3 is also connected to the transmission 5 and, like the internal combustion engine 2, can deliver drive power to the wheels of the hybrid vehicle via the transmission 5 and an outgoing drive shaft 6. For this purpose, in the case of the internal combustion engine 2, fuel is fed into its combustion chambers (also not shown) via a fuel supply system (not shown), where it is burned and mechanical energy is generated in the process. The electric motor 3 is connected to a traction battery (not shown) in order to generate kinetic energy or drive power.

When the clutch 4 is disengaged, only the electric motor 3 can deliver drive power via the transmission 5 and the outgoing drive shaft 6 to the wheels of the hybrid vehicle. Conversely, when the hybrid vehicle is coasting, its kinetic energy can be converted into electrical energy by the electric motor 3, which can also be operated as a generator, and fed into the traction battery, which is thus charged.

When the clutch 4 is closed, the internal combustion engine 2 can also deliver drive power via the transmission 5 and the outgoing drive shaft 6 to the wheels of the hybrid vehicle. When the hybrid vehicle is overrun, the internal combustion engine 2 can be dragged and can thus absorb the kinetic energy of the hybrid vehicle. On the other hand, it can also be provided that mechanical energy emitted by the internal combustion engine 2 is transmitted to the electric motor 2 and used by it in generator mode to charge the traction battery.

Due to the functional connections provided for the hybrid vehicle according to the invention between the motors 2, 3 on the one hand and between the drive wheels of the hybrid vehicle and the motors 2, 3 on the other hand, the hybrid vehicle can be powered both by the internal combustion engine 2 alone and by the electric motor 3 alone, as well as are driven by both engines 2.3 in definable power distribution. It is also possible that when the hybrid vehicle is coasting, its kinetic energy is partially transferred to the internal combustion engine 2 alone or to the electric motor 3 alone or in a predeterminable distribution to both engines 2, 3.

For the combustion of fuel, the internal combustion engine 2 draws combustion air from the environment via an air supply line 11. The throughput of the combustion air can be throttled by means of an adjustable intake air throttle 14 arranged in the air supply line 11, if necessary. The exhaust gas produced during fuel combustion is discharged via an exhaust pipe 20 and an exhaust gas cleaning system 10 arranged therein. The exhaust gas cleaning system 10 has an electric heating element and, connected downstream, several exhaust gas cleaning components that serve to clean the exhaust gas, in particular to remove NOx, which will be discussed in more detail below.

A turbine 9 of an exhaust gas turbocharger 7 , which can drive an associated compressor 8 in the air supply line 11 , is arranged in front of the exhaust gas cleaning system 10 , viewed in the exhaust gas flow direction. In the present case, the turbine 9 is designed as a turbine with a variably adjustable blade position.

Exhaust gas can be mixed with the combustion air via a low-pressure exhaust gas recirculation line (NDAGR line) 12 and via a high-pressure exhaust gas recirculation line (HP-EGR line) 15 . The LP EGR line branches off from the exhaust gas cleaning system 10 , the HPAGR line 15 branches off from the exhaust gas line 20 before the turbine 9 .

The quantity of exhaust gas mixed in via the LP EGR line 12 can be adjusted via an adjustable LP EGR valve 13 arranged between the intake air throttle 14 and the compressor 8 . The quantity of exhaust gas mixed in via the HP-EGR line 15 can be adjusted via an adjustable HP-EGR valve 16 arranged behind the compressor 8 in the air supply line 11 . However, a common EGR valve for the HP-EGR line 15 and the LP-EGR line 12 can also be provided. Preferably, both the NDAGR line 12 and the HP-EGR line 15 each have a cooler for recirculated exhaust gas, which may also be designed to be bypassable, which is not shown separately here. However, the LP EGR valve 13 is not absolutely necessary.

To control the operation of the internal combustion engine 2 and the electric motor 3 and to control the EGR valves 13, 16, the intake air throttle 14 and the turbine 9, a control unit is provided which is connected to the components to be controlled by control lines, which is not described in detail is shown. Also not shown is a gas conveying device, which can supply a gas, in particular air, to the exhaust gas cleaning system 10 upstream of the heating element, particularly when the internal combustion engine 2 is stationary and the heating element is energized.

With regard to the emission control system 10, a first advantageous embodiment is shown schematically in FIG. This exhaust gas cleaning system 10 has in the exhaust gas line 20 seen in the main exhaust gas flow direction 21 one behind the other in this order an electric heating element 22 and as exhaust gas cleaning components a NOx storage catalytic converter as a first oxidation-catalytically active exhaust gas cleaning component 23, a first SCR-catalytically active exhaust gas cleaning component, a second SCR-catalytically active exhaust gas cleaning component 25 , and an oxidation catalytic converter as the second oxidation-catalytically active exhaust gas cleaning component 26 . The electric heating element 22 and the NOx storage catalytic converter 23 are arranged closely adjacent to one another in a common housing, with this housing being mounted close to the combustion engine, preferably flanged directly to the turbine 9 (FIG. 1). The second SCR-catalytically active exhaust gas cleaning component 25 and the oxidation catalytic converter 26 are also arranged in close proximity in a common housing, but preferably remote from the internal combustion engine in an underbody area of the hybrid vehicle. In the present case, the first SCR-catalytically active exhaust gas purification component is also close to the combustion engine in a separate housing.

Seen in the exhaust gas flow direction 21 upstream of the second SCR-catalytically active exhaust gas cleaning component 25, a LP-EGR line 12 branches off, via which exhaust gas is discharged from the exhaust gas line 20 and the combustion air for the internal combustion engine 2 can be mixed.

The electric heating element 22 designed as a resistance heater preferably has a winding or folding of metal foils through which exhaust gas can flow. If the heating element 22 is supplied with current from the traction battery, the metal foils and the exhaust gas flowing around them heat up. As a result, heat can in turn be transferred to the downstream exhaust gas cleaning components 24, 25, 26 and in particular to the NOx storage catalytic converter 23.

The NOx storage catalytic converter 23 is presently designed as a ceramic honeycomb body with a coating (but can also be a metallic honeycomb body) which, on contact with lean exhaust gas in particular, binds the NOx contained therein by chemisorption and/or physisorption and thus removes it from the exhaust gas can. In addition, the coating has an oxidation-catalytic effect. The process of NOx uptake begins at around 150 °C with a noticeable speed and proceeds steadily faster with increasing temperature up to around 350 °C. With an increasing amount of absorbed NOx, the storage

However, the effectiveness of NOx decreases. NOx then increasingly slips through the NOx storage catalytic converter 23, with more or less large proportions of the NOx contained mostly as nitrogen monoxide (NO) in the exhaust gas of the internal combustion engine 2 being oxidized to nitrogen dioxide (NO»2) depending on the temperature. However, this typically improves the NOx conversion by the downstream SCR catalytically active exhaust gas cleaning components, which typically can convert NOx with larger NO » portions particularly efficiently. In order to restore the NOx absorption capacity of the NOx storage catalytic converter 23 when saturation has occurred, it can be regenerated, for which purpose it is charged by the internal combustion engine with rich, i.e. reducing exhaust gas. Stored NOx is desorbed by reduction to form nitrogen (N2) and discharged with the exhaust gas. However, stored NOx can also be thermally desorbed at high temperatures of more than about 400°C to 450°C.

The first SCR-catalytically active exhaust gas cleaning component is presently designed as a particle filter 24 with an SCR-catalytically active coating, simply referred to below as SDPF. Due to this design, the SDPF 24 can both filter out particles, in particular soot particles, from the exhaust gas and also catalytically reduce NOx contained in the exhaust gas to harmless N2 by reduction with ammonia (NHs) contained in the exhaust gas. This SCR catalytic effectiveness begins at around 150 °C and continues to increase rapidly as the temperature rises.

The second SCR-catalytically active exhaust gas cleaning component 25 is presently designed as an SCR catalytic converter in the form of a honeycomb body. With regard to the SCR catalytic effectiveness, reference is made to the SDPF 24 described above.

The oxidation catalytic converter 26 is mainly used for the oxidative removal of NHs, which may slip through the SCR catalytic converter 25 . However, other components with a reducing effect, such as HC or CO, can also be catalytically oxidized.

In order to supply the SDPF 24 and the SCR catalytic converter 25 with NHs3 to develop their SCR catalytic effect, a first metering valve 29 is installed on the input side of the SDPF 24 and a second metering valve 32 on the input side of the SCR catalytic converter 25 in the exhaust pipe 20 . With these metering valves 29, 32, which can be operated independently of one another, a reducing agent contained in free or bound form of NH3 can be metered into the exhaust gas. In the present case, aqueous urea solution is used as the reducing agent (but can also be gaseous NH 2 ), which can be supplied to metering valves 29, 32 from a tank via separate pumps, which is not shown in detail.

Various sensors are installed in the exhaust pipe 20 to measure temperatures and pollutant concentrations in the exhaust gas. In the present case, a first temperature sensor 27 is provided on the input side of the electrical heating element 22 and a second temperature sensor 30 is provided on the input side of the SDPF 24 . Furthermore, a third temperature sensor 33 is provided on the input side of the SCR catalytic converter 25 and a fourth temperature sensor 34 is provided on the output side of the oxidation catalytic converter 26 . Furthermore, a first NOx sensor 28 is provided on the inlet side of the SDPF 24 and a second NOx sensor 31 on the outlet side of the SDPF 24 and before the branch of the LP-EGR line 12 . However, the second NOx sensor 31 can also be installed behind the branch of the LP EGR line 12 and in front of the SCR catalytic converter 25, but it must be positioned in front of the second urea dosing point. A further, third NOx sensor 35 is provided on the output side of the oxidation catalytic converter 26 . The temperature sensors 27, 30, 33, 34 and the NOx sensors 28, 31, 35 enable comprehensive monitoring of the temperature and NOx content of the exhaust gas within the exhaust gas cleaning system 10 and the performance of the exhaust gas cleaning components installed therein. For this purpose, the sensors are connected to a control unit, not shown, which can evaluate the corresponding signals.

3 shows a further advantageous embodiment of the exhaust gas purification system 10, with the corresponding components being identified by the same reference symbols insofar as they correspond to the parts of FIG. 1 or FIG. 2. The exhaust gas cleaning system shown in FIG. 3 is constructed similarly to the exhaust gas cleaning system 10 of FIG. 2, which is why only the differences are discussed below.

In contrast to the embodiment shown in FIG. 2, the exhaust gas cleaning system of FIG. 3 has a combination of an SDPF 24 and an SCR catalytic converter 36 as the first SCR-catalytically active exhaust gas cleaning component, which are arranged in close proximity in a common housing . In the present case, the SDPF 24 is arranged in front of the SCR catalytic converter 36 as viewed in the exhaust gas flow direction 21 . However, the reverse order can also be provided.

In Fig. 4, a preferred coolant circuit system of the hybrid vehicle according to the invention is shown only schematically. Insofar as components shown therein match those of the preceding figures, the same reference numbers are used. The coolant circuit system of FIG. 4 has a first coolant circuit 40 and a second coolant circuit 47 separate therefrom. The first coolant circuit 40 mainly serves to cool the internal combustion engine 2 , whereas the second coolant circuit 47 mainly serves to cool the electric motor 3 . The coolant heated by the internal combustion engine 2 can be cooled by a first heat exchanger 54 through which air can flow, which is arranged in the first coolant circuit 40 . Analogously, a second heat exchanger 57 in the second coolant circuit 47 serves to cool coolant that has been heated by the electric motor 3 . As explained in more detail below, the coolant circuits 40, 47 have branch circuits which serve to cool or control the temperature of other components. In addition, equalizing or degassing tanks 58, 59 are provided, which in particular can absorb temperature-related volume fluctuations of the coolant in the coolant circuits 40, 47.

A first electric coolant pump 50 is provided for conveying the coolant in the first coolant circuit 40; the second coolant circuit 47 has a second electric coolant pump 51 for this purpose. The first coolant pump 50 is connected to the traction battery with a nominal voltage of 48 V, for example, while the second coolant pump 51, which is designed to be less powerful and throughput, is connected to a 12 V on-board battery. The coolant pumps 50, 51 can be operated with speed control in a predetermined manner, for example by reducing the operating voltages. As a result, the coolant flow rates in the coolant circuits 40, 47 can be adjusted as required.

Coolant supplied to the internal combustion engine 2 in the first coolant circuit 40 is discharged from the latter and can flow through a third heat exchanger 56 serving to heat the interior in a first branch circuit 41 . Furthermore, in a second branch circuit 44, the HP-EGR valve 16 can be flowed through and the temperature can thus be controlled. A third branch circuit 45 serves to regulate the temperature of the lubricant, for which purpose coolant flows through an oil cooler 53 . Furthermore, a fourth branch circuit 42 identified by a dashed line is provided, in which a fourth heat exchanger 55 is arranged, which is used for tempering exhaust gas recirculated via the LP-EGR line 12 . Another fifth branch circuit 43 of the first coolant circuit 40, identified by a dashed line, is used for temperature control of the first metering valve 29. A separate third coolant pump 60 is provided for this fifth branch circuit 43. This enables the coolant throughput in the fifth branch circuit 43 to be set largely independently of the coolant throughput of the first coolant circuit 40. The third coolant pump 60 is preferably connected to the 12 V vehicle battery. By means of a bypass line 46 bypassing the first heat exchanger 54 and a control valve 61 preferably designed as a three-way valve, the coolant throughput through the first heat exchanger 54 and thus the cooling effect brought about by it can be influenced in a targeted manner. In addition, the coolant throughput can be influenced in particular by the first branch circuit 41 , the second branch circuit 44 and the third branch circuit 45 .

A branch circuit is also provided in the second coolant circuit 47 for the electric motor 3 . This sixth branch circuit 48 serves to control the temperature of exhaust gas recirculated via the HP-EGR line 15, for which purpose a fifth heat exchanger 52 is provided.

The main features of the operating method according to the invention are discussed below with reference to FIG. Reference is also made to the previous figures. In the block diagram of FIG. 5, solid connecting lines identify transitions from operating states shown in the form of blocks. Dashed connecting lines identify data and active connections of control unit function blocks. In order to explain the operating method, it is assumed below, without restricting the generality, that the internal combustion engine 2 of the hybrid vehicle is switched off or is in an unfired state with no fuel supply. The previous shutdown is represented by state block 65 . In this state, the vehicle can either be stationary or in motion.

[0075] If it is determined that the internal combustion engine 2 will be started shortly, temperatures in the exhaust gas cleaning system 10 are determined. When the vehicle is parked, it can be determined, for example by detecting a door lock actuation, that the internal combustion engine 2 will start shortly. In this case, temperatures in the exhaust gas cleaning system 10 are preferably determined after an initialization of the control unit. When driving and during brief interruptions in start-stop operation, the temperatures in the exhaust gas purification system 10 are preferably continuously determined anyway when the internal combustion engine 2 is switched off. The temperature can be determined, for example, by evaluating measured values from the sensors installed there. If it is established that one or more predeterminable temperature limit values have not been reached, a preheating operation identified by status block 66 is set as the first heating phase of a general heating operation. A temperature limit value can be fallen below, for example, if the temperature of the NOx storage catalytic converter 23 is below a predefinable temperature of 150° C., for example. In the preheating mode, the heating element 22 is energized, preferably starting with a rated current. At the same time, air is blown into the exhaust pipe 20 in front of the heating element 22 . The air can be blown in by a suitable conveying device such as, for example, a secondary air pump. Depending on the temperature profile over time in the exhaust gas purification system 10, a continuous or other decrease in the heating output of the heating element 22, for example by a pulse-width modulated power supply, can be provided especially in the preheating mode 66. In the present case, the settings of the preheating mode 66 are made by a first control module 71 of the control unit, which is provided in particular for controlling the heating of the exhaust gas cleaning system 10 . An interruption of the preheating operation can also be provided, for example when a secondary air pump for blowing in air has reached a predetermined limit running time and there is a risk of overheating. After the secondary air pump has cooled down sufficiently, the preheating operation can be resumed by energizing the heating element 22 and blowing in air. If possible, the preheating operation 66 is continued at least until the NOx storage catalytic converter 23 has reached a predeterminable temperature of approximately 200° C. or at least approximately its light-off temperature, at least on the inlet side.

If, before starting the internal combustion engine 2, it is determined that the temperature has not fallen below a lower limit that is decisive for starting the preheating operation 66, the operating state of the preheating operation 66 can be skipped and the internal combustion engine 2 can be started without preheating the exhaust gas purification system 10.

[0077] When the internal combustion engine 2 is started, it changes to a fired operation, which is identified by the status block 67 . If the preheating mode 66 was active beforehand, the heating of the heating element 22 is preferably not interrupted by the starting of the internal combustion engine 2 . Preferably, the heating element 22 is energized with rated current until a predefinable temperature is reached in the exhaust gas cleaning system 10 and then the heating power is reduced in a predefinable manner. It has proven to be advantageous to heat the heating element 22 with rated output until at least a first zone of the NOx storage catalytic converter 23 has reached a predeterminable temperature of 200° C., for example. However, another temperature in the exhaust gas cleaning system 10 can also be used as a decisive factor.

After reaching a stable running of the internal combustion engine 2 and preferably a

definable speed limit, the air injection can be ended by the conveyor and it is characterized by the block 68 heating started as a second heating phase, provided that one or more predeterminable temperature limits specifically in the exhaust gas cleaning system 10 are undershot. This is particularly the case when one or more of the emission control components 23, 24, 25, 26, 36 are below their operating temperature. If this is not the case, the heating operation 68 can be skipped. If the heating operation 68 is carried out, then this is also controlled by the first control module 71 of the control unit with its settings explained in more detail below.

In the heating-up mode 68, the heating element 22 is preferably heated with a fraction of the rated output, and the exhaust gas purification system 10 is thus further heated. The heating output is preferably initially adjusted as a function of the temperature and the NOx loading of the NOx storage catalytic converter 23. These can be determined on a model basis, taking into account the temperature value provided by the first temperature sensor 27 and the operating conditions of the internal combustion engine 2. If the NOx storage catalytic converter 23 has reached a predeterminable temperature, which can be based on the ability to store NOx or NO> formation, it is preferably provided to increase the heating output of the heating element 22 as a function of the temperature of the first SCR catalytic Emission control component 24 set. Once this has reached its operating temperature, the heating output is preferably adjusted as a function of the temperature of the second SCR catalytically active exhaust gas cleaning component 25.

[0080] On the other hand, the internal combustion engine 2 is first operated in a first heating operation mode. In this first heating operating mode, an early post-injection of fuel into the combustion chambers of internal combustion engine 2 is carried out in addition to the main injection. This preferably takes place at such an early point in time after the main injection that the post-injected fuel at least largely burns in the respective combustion chamber. It is therefore a so-called co-burning post-injection with torque generation. It preferably takes place in a crank angle range of 20° to 40° after top dead center. As a result, particularly hot exhaust gas is generated, as a result of which the exhaust gas cleaning system 10 can be heated up quickly in conjunction with the heating effect applied by the heating element 22 . In the first heating operating mode, the internal combustion engine is operated without low-pressure exhaust gas recirculation. A predefinable exhaust gas recirculation rate is set in a controlled manner for the high-pressure exhaust gas recirculation. Likewise, the blade positions of the turbocharger turbine 9 and the intake air throttle 14 are adjusted in a controlled manner. In the first heating operating mode, the internal combustion engine 2 is also operated in such a way that the exhaust gas mass flow emitted by it does not exceed a definable upper exhaust gas mass flow limit. In this way, more or less catalytically active exhaust gas purification components are protected from being overloaded with pollutants to be removed. Provision is therefore made for specifying the upper exhaust gas mass flow limit as a function of a temperature and/or an already achieved performance of one or more of the exhaust gas purification components 23, 24, 25, 26, 36. Provision can also be made to control the internal combustion engine 2 in such a way that the exhaust gas mass flow does not fall below a specifiable lower limit. An exhaust gas mass flow range is preferably specified, which is increased as the exhaust gas cleaning system 10 heats up. It is also advantageous if the upper exhaust gas mass flow limit is set as a function of an upper temperature limit and/or the lower exhaust gas mass flow limit is set as a function of a lower temperature limit for one or more of the exhaust gas cleaning components 23, 24, 25, 26, 36.

The respective exhaust gas mass flow limit is preferably set by setting a torque delivered by the internal combustion engine 2 . If an upper exhaust gas mass flow limit is provided, the torque delivered by internal combustion engine 2 is limited to a value that corresponds to the upper exhaust gas mass flow limit. If the driver of the vehicle requests a torque that exceeds this torque limit, the electric motor 3 is accordingly used to deliver the additionally requested torque

Torque energized. If a lower exhaust gas mass flow limit is not to be undershot and the driver only requests a correspondingly low torque, the excess torque delivered by the internal combustion engine 2 can be used to charge the traction battery. For this purpose, the internal combustion engine 2 correspondingly drives the electric motor 3, which is switched to generator operation.

If the light-off temperature of the SDPF 24 or the light-off temperature of the SCR catalytic converter 36 of typically around 150° C. is reached or exceeded in the heating-up operation 68, the first metering valve 29 is actuated to release a predeterminable quantity of reducing agent.

If a predetermined temperature limit is reached for one or more of the emission control components 23, 24, 25, 26, 36, the operation of the internal combustion engine 2 is switched to a second heating mode while the heating element 22 continues to be energized. A temperature limit that is decisive for this can be given, for example, by a temperature of the NOx storage catalytic converter 23 of approximately 200.degree. Switching to the second heating operating mode can also take place when the NOx storage catalytic converter has reached a temperature at which efficiency for NOx storage or for NO2 formation is at least approximately maximum.

In the second heating operating mode, a late fuel post-injection is provided in addition to or instead of the early fuel post-injection. This is carried out as a so-called non-combusting post-injection with at most a low torque effect at a crank angle of around 150 °C after top dead center. In this case, an excess of oxygen in the exhaust gas emitted by the internal combustion engine 2 preferably remains. In this way, the exhaust gas of the internal combustion engine 2 is enriched with unburned fuel components. These can be oxidized at the NOx storage catalytic converter 23, which is already active in terms of oxidation catalysis, due to the lean exhaust gas, with further release of heat. Accordingly, the heat output of the heating element 22 can be reduced to a lower, predefinable value.

A limitation or delimitation of the exhaust gas mass flow is preferably retained. However, values for the upper and/or lower exhaust gas mass flow limit can be changed in comparison to the first heating operating mode. The same applies to the high-pressure exhaust gas recirculation, the turbocharger and intake air throttle settings. As described above, the exhaust gas mass flow limit values are set as a function of a temperature and/or an already achieved performance of one or more of the exhaust gas purification components 23, 24, 25, 26, 36.

[0086] When the second SCR catalytically active emission control component 25 reaches or exceeds a predeterminable temperature of approximately 150° C. in the heating-up operation 68, the second metering valve 32 is actuated to release a predeterminable quantity of reducing agent.

Once the exhaust gas cleaning components 23, 24, 25, 26, 36 have reached their operating temperature, the metering valves 29, 32 inject urea solution into the exhaust gas in a quantity-controlled manner. In this case, normal operation 69 is started.

In normal operation 69, the heating measures of the heating operation 68 are deactivated. This means that the heating element 22 is switched off and there is no early or late fuel post-injection. In addition to the controlled high-pressure exhaust gas recirculation, a controlled low-pressure exhaust gas recirculation is activated. Furthermore, the blade position of the exhaust gas turbocharger turbine 9 is adjusted in a controlled manner. In the present case, a second control module 72 of the control device, provided in particular for normal operation 69, takes over the control and setting of the operating parameters. The second control module 72 can control the internal combustion engine 2 in such a way that it is operated either in an operating mode that is minimized in terms of specific fuel consumption or in an operating mode in terms of raw NOx emissions in order to always be able to ensure the minimum possible total emissions. According to the invention, this takes place as a function of determined NOx emission values for the

exhaust gas emitted to the environment over a past period or a past route, or as a function of estimated NOx emission values for an upcoming period or an upcoming route. The decisive NOx emission value or the decisive NOx emission values are preferably determined in a separate NOx emission determination module 73. In the NOx emission determination module 73, for example, using a calculation model or using measured values of the third NOx sensor 35 at the end, NOx emission sum values for the environment emitted exhaust gas is determined in a predetermined distance and/or travel time past the current point in time. For example, the last 3 km or 6 km or the distance traveled since the combustion engine was last started can be taken into account as the distance traveled. If a calculation model is used to determine a mileage or time-related total NOx emission value, the determination is carried out, for example, using stored characteristic curves or characteristic maps for the NOx conversion efficiencies of the NOx storage catalytic converter 23 and the SCR catalytically active exhaust gas cleaning components of the exhaust gas cleaning system 10, the total exhaust gas mass flow and the operating point-dependent NOx Raw emissions of the internal combustion engine 2. It is preferably provided in the characteristic curves or characteristic diagrams that the NOx conversion efficiencies depend on temperature, exhaust gas throughput and aging condition. Total NOx emission values determined on the basis of a model can be corrected or made plausible by comparison with the measured values of the third NOx sensor 35 at the end.

In the present case, the NOx emissions determination module 73 sends the determined NOx total value or the determined NOx total values to the second control module 72. If a specifiable NOx emission limit is reached or exceeded for one or more of the determined NOx total values, the second switches Control module 72 the internal combustion engine 2 in a normal operating mode with minimized raw NOx emissions in order to always be able to ensure the minimum possible total emissions. In the other case, a normal operating mode with minimized specific fuel consumption is set.

The temperatures of the exhaust gas cleaning components are continuously monitored by means of the temperature sensors 27, 30, 33, 34 installed in the exhaust gas cleaning system 10, particularly during normal operation. In the present case, this takes place in a temperature determination module 75 assigned to the control device. According to the invention, the monitoring includes a model-based computational evaluation with regard to an expected further future temperature profile. If it is determined that one or more of the exhaust gas cleaning components 23, 24, 25, 26, 36 has fallen below its operating temperature or temperature-related performance within a specifiable period of time from the current point in time, this is transmitted to the second control module 72 of the control device. The second control module 72 then sets operating conditions of a sustain heating mode 70 .

In maintenance heating mode 70, one or more heating measures are selected and set from a selection list of possible heating measures. In this case, the selection of the heating measure or measures takes place under the proviso that when they are taken, the operation of the emission control components with at least an approximate operating temperature is extended by at least a specifiable period of time. Furthermore, from the possibly resulting possible combinations of heating measures, that one is selected which results in the smallest possible increase in fuel consumption and/or the NOx emissions released into the environment. If a predeterminable total NOx emission value is exceeded for a certain distance traveled or driving time, that heating measure is preferably selected which results in the smallest possible increase in NOx emissions. In this context, it is advantageous if the total NOx values determined in the NOx emission determination module 73 are also transmitted to the third control module 74 that controls the maintenance mode 70 . On the other hand, it is preferably provided that the results of the continuous temperature monitoring determined in the temperature determination module 75 are also transmitted to the third control module 74 . In this way it can be determined whether the heating measure or measures taken have the desired effect

achieve, in particular with regard to a longer stay of the emission control components at operating temperature. If a further drop in temperature or performance of one or more of the emission control components 23, 24, 25, 26, 36 is determined or predicted, a further heating measure can be selected from the selection list and switched on. On the other hand, the heating measure can be scaled back or switched off if it is determined that the emission control components can probably be kept at the operating temperature long enough anyway.

When selecting a heating measure, the state of charge of the traction battery is preferably also taken into account. A heating measure that reduces the state of charge of the battery is not taken if the state of charge falls below a predefinable lower limit value or if it would fall below this as a result of the heating measure. On the other hand, when the battery is already fully or nearly fully charged, a heating measure increasing the state of charge of the battery is not taken.

The selection list for the measures to be taken in the maintenance heating mode 70 can include at least the following heating measures.

- Energization of the heating element 22 with definable heating power

- Early post fuel injection

- Late post fuel injection

- Increase in the mechanical power delivered by the internal combustion engine.

In the latter case, the drive power output by the electric motor 3 can be reduced in favor of the drive power output by the internal combustion engine 2 . If the electric motor 3 does not contribute to the vehicle drive, a portion of the drive power generated by the internal combustion engine 2 that is not required for the vehicle drive can be transmitted to the electric motor 3 running in generator mode and used to charge the traction battery.

If, after the heating measure or measures have been taken, it is determined, for example in the temperature determination module 75, that the temperatures of the exhaust gas cleaning components have risen again to such an extent that normal operation without additional heating measure is likely to be possible again for a specifiable period of time, the state of maintenance -Heating operation 70 ended and returned to normal operation 69.

A further measure that reduces the overall energy consumption of the hybrid vehicle can be that an energy-consuming regeneration of the NOx storage catalytic converter 23, which is necessary from time to time anyway, is carried out during the heating-up operation 68 or inserted into it. For this purpose, the operation of the internal combustion engine 2 is controlled in such a way that at least temporarily an exhaust gas that has an overall reducing effect is emitted. This can be done by means of a late post fuel injection. An early fuel post-injection can also be provided. At the same time, the internal combustion engine 2 is operated in such a way that the exhaust gas mass flow emitted by it lies between a definable upper and a definable lower exhaust gas mass flow limit. The exhaust gas mass flow limits are preferably stored in a characteristic diagram as a function of one or more temperatures in the exhaust gas cleaning system 10 . Provision is also made for the internal combustion engine 2 to be operated with a minimum load of approximately 3 bar mean pressure. If necessary, the internal combustion engine 2 can be operated for this purpose in such a way that excess mechanical power, which is not required for driving the vehicle, is generated, which is used via the electric motor 3 running in generator mode to charge the traction battery. Conversely, if necessary, the drive power output by the internal combustion engine 2 can be reduced in favor of a drive power applied by the electric motor 3 .

Provision can also be made for at least partial regeneration of the NOx storage catalytic converter 23 to be carried out after the internal combustion engine 2 has been switched off. For this purpose, immediately after the combustion engine has been switched off, the heating element 22

energized, so that the NOx storage catalyst 23 is heated and stored NOx can thermally desorb. For this purpose, the NOx storage catalytic converter 23 is typically heated to a temperature of 400° C. to 450° C. by means of the heating element 22 . As a result of the desorption of previously stored NOx, an at least partially regenerated NOx storage catalytic converter 23 is available when the internal combustion engine 2 is restarted. This enables NOx to be removed from the exhaust gas very quickly after a restart or cold start.

Simultaneously with the energization of the heating element after the internal combustion engine 2 has been switched off, air is blown upstream of the heating element 22 into the exhaust pipe 20 by a gas conveying device such as, for example, a secondary air pump. This prevents the heating element 22 from burning out and desorbing NOx is promoted by the downstream SCR catalytically active exhaust gas cleaning components. So that NOx is not released into the environment, provision is made for the first metering valve 29 and/or the second metering valve 32 to be actuated to release urea solution into the exhaust gas. With the air blown in by the secondary air pump to the SDPF 24 or SCR catalytic converter 25, NOx can thus be converted into harmless N; be reduced. If one or all of these components are not at operating temperature, the addition of urea solution can also be omitted. In this case, provision can also be made for dispensing with the regeneration of the NOx storage catalytic converter 23 by thermal NOx desorption after the internal combustion engine 2 has been switched off.

A comparatively short duration of less than approximately 30 s may be sufficient for the run-on phase with regeneration of the NOx storage catalytic converter 23 after the internal combustion engine 2 has been switched off.

A reduction in fuel consumption can also be achieved by operating the coolant pumps 50, 51 at reduced power. In order to explain a preferred procedure, reference is again made to FIG. 4 below.

In order to achieve a reduction in the power consumption of the first coolant pump 50 and/or the second coolant pump 51, these are optionally operated at a speed that is reduced compared to the nominal speed. This is preferably done as a function of one or more of the following recorded operating variables (or others):

- Ambient temperature

- Lubricant or oil sump temperature

- Temperature in the low-pressure exhaust gas recirculation branch

- cylinder head temperature

- Interior air conditioning adjustable ameter

- Temperature of first dosing valve 29

- Speed combustion engine 2

- Electric motor speed 3

- Coolant temperature in the first coolant circuit 40

- Coolant temperature in the second coolant circuit 47.

A minimum coolant throughput for the first coolant circuit 40 and/or the second coolant circuit 47 is preferably determined as a function of at least one of the listed operating variables. This can be done, for example, by resorting to previously stored characteristic diagrams, in which a relevant influence of the operating variables listed above is shown. If the determined minimum coolant throughput is lower than the current throughput, the speed of the corresponding coolant pump is reduced. This results in a lower coolant throughput and a reduced need for electrical power.

A regulation of the coolant throughput and a control of its distribution to the branch circuits by actuating the three-way valve 61 can also be provided specifically for the first coolant circuit 40 . In particular, if the temperature of the coolant in the first coolant circuit 40 is still below a target temperature or if the internal combustion engine 2 has not yet been sufficiently warmed up, the three-way valve 61 is actuated in such a way that the first heat exchanger 54 is not, or only to a reduced extent, flowed through with coolant. Coolant is routed via the bypass line 46 instead.

As can be seen from the above description, a particularly energy-saving and low-emission operation of the hybrid vehicle is made possible due to the embodiment and mode of operation according to the invention.

Austrian

REFERENCE LIST

10 11 12 13 14 15 16 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 40 41

Drive system combustion engine electric motor

coupling

transmission

Drive shaft turbocharger compressor

Turbine Emission control system Air supply line LP EGR line LP EGR valve Intake air throttle HP EGR line HP EGR valve Exhaust line Main exhaust flow direction Heating element NOx storage catalyst First SCR catalytic emission control component Second SCR catalytic emission control component Oxidation catalyst First temperature sensor First NOx sensor

First metering valve Second temperature sensor Second NOx sensor Second metering valve Third temperature sensor Fourth temperature sensor Third NOx sensor SCR catalyst

First coolant circuit First branch circuit

AT 522 990 B1 2022-07-15

42 Fourth Branch Circuit

43 Fifth Branch Circuit

44 Second branch circuit

45 Third branch circuit

46 bypass line

47 Second coolant circuit

48 Sixth branch circuit

50 First coolant pump

51 Second coolant bp pump

53 oil cooler

54 First heat exchanger

55 Fourth heat exchanger

56 Third heat exchanger

57 Second heat exchanger

58 expansion tank

59 expansion tank

60 Third coolant pump

61 control valve

65 status block shutting down combustion engine 66 status block preheating

67 status block start combustion engine 68 status block heating mode

69 Normal operation status block

70 Sustain heating mode status block 71 First control module

72 Second control module

73 NOx emission determination module

74 Third control module

75 temperature determination module

Claims (1)

patent claims 1. Hybrid motor vehicle, with an internal combustion engine (2) and an electric motor (3) on pointing drive system (1), comprising - An exhaust gas cleaning system (10) connected to the internal combustion engine (2) of the vehicle, which, viewed in the direction of flow of the exhaust gas emitted by the internal combustion engine (2), is arranged one behind the other: an electric heating element (22), a first exhaust gas cleaning component (23) designed as an oxidation-catalytic active and has at least one SCR catalytically active exhaust gas cleaning component, and - a control unit for controlling the operation of the drive system (1) and the exhaust gas cleaning system (10), the control unit being designed to control the operation of the drive system (1) in such a way that during heating operation with energization of the electric heating element (22) for heating the exhaust gas - an exhaust gas mass flow emitted by the internal combustion engine (2) does not exceed a predeterminable upper exhaust gas mass flow limit and/or does not fall below a predeterminable lower exhaust gas mass flow limit, the upper exhaust gas mass flow limit and the lower exhaust gas mass flow limit being predeterminable as a function of a temperature and/or a performance of at least one of the exhaust gas components, and - A heat output of the electrical heating element (22) depending on the temperature and the NOx loading of the NOx storage catalytic converter (23) can be adjusted. 2. Hybrid motor vehicle according to claim 1, characterized in that the exhaust gas purification system (10) is arranged one behind the other as viewed in the flow direction of the exhaust gas emitted by the internal combustion engine (2). - the electric heating element (22), - the first exhaust gas cleaning component (23) designed as a NOx storage catalyst with an oxidation-catalytic effect, - a first SCR-catalytically active emission control component, - A second SCR-catalytic effective emission control component (25) and - A second oxidation-catalytically active exhaust gas cleaning component (26), wherein the inlet side of the first and the second SCR catalytically active exhaust gas cleaning component each have a metering device (29, 32) for introducing an ammonia-containing reducing agent into the exhaust gas. 3. Hybrid motor vehicle according to claim 1 or 2, characterized in that the control unit is designed to control the operation of the drive system (1) in such a way that an exhaust gas mass flow emitted by the internal combustion engine (2) during normal operation (69) without energizing the heating element (22) does not exceed a predeterminable upper exhaust gas mass flow limit and/or a predeterminable lower one exhaust gas mass flow limit if the temperature and/or the performance of the NOx storage catalytic converter (23) and/or the first SCR catalytically active exhaust gas cleaning component and/or the second SCR catalytically active exhaust gas cleaning component (25) fall below a respectively specifiable value. 4. Hybrid motor vehicle according to one of claims 1 to 3, characterized in that the control unit is designed to control the operation of the drive system (1) in such a way that an exhaust gas mass flow emitted by the internal combustion engine (2) during normal operation (69) without energizing the heating element (22) does not exceed a predefinable upper exhaust gas mass flow limit if the temperature of the NOx - Storage catalytic converter (23) and/or the first SCR-catalytically active exhaust-gas cleaning component and/or the second SCR-catalytically active exhaust-gas cleaning component (25) exceed a respectively predeterminable value. 10 Austrian AT 522 990 B1 2022-07-15 Hybrid motor vehicle according to one of claims 2 to 4, characterized in that the electric heating element (22), the NOx storage catalytic converter (23) and the first SCR catalytically active exhaust gas cleaning component are arranged in an engine compartment for the internal combustion engine (2), in particular close to the internal combustion engine, and the second SCR catalytic exhaust gas cleaning component (25) and the second oxidation-catalytically effective exhaust gas cleaning component (26) away from the internal combustion engine, in particular in an underbody area of the hybrid motor vehicle. Hybrid motor vehicle according to one of claims 2 to 5, characterized in that the first SCR catalytically active exhaust gas cleaning component is designed as a particle filter (24) with an SCR catalytically active coating. Hybrid motor vehicle according to one of claims 2 to 5, characterized in that the first SCR-catalytically active exhaust gas cleaning component has a particle filter (24) with an SCR-catalytically active coating and an SCR catalytic converter (36), which are arranged directly one behind the other in a common housing. Hybrid motor vehicle according to one of claims 1 to 7, characterized in that a first coolant circuit (40) for controlling the temperature of the internal combustion engine (2) and a separate second coolant circuit (47) for controlling the temperature of the electric motor (3) are provided, with a first electric coolant pump (50) for the first coolant circuit (40) and a first electric coolant pump (50) for the second coolant circuit (47), a second electric coolant pump (51) is provided, the first coolant pump (50) being connected to a first power supply and the second coolant pump (51) being connected to a second power supply, and the first power supply being greater than the second power supply provides electrical voltage. Hybrid motor vehicle according to claim 9, characterized in that the control unit is designed to operate the first and/or the second coolant pump (50, 51) in reduced-power operation at an adjustable speed that is reduced compared to normal operation. Operating method for operating a hybrid vehicle with a drive system (1) comprising an internal combustion engine (2) and an electric motor (3) and an exhaust gas cleaning system (10) connected to the internal combustion engine (2) of the vehicle and having an electric heating element (22) and a plurality of exhaust gas cleaning devices , in particular with regard to NOx reduction catalytically active exhaust gas cleaning components and a control unit for controlling operation of the drive system (1) and exhaust gas cleaning system (10), wherein - a heating operation for heating the exhaust gas cleaning system (10) to the operating temperature is provided, comprising a first heating-up phase (66), in which, when the internal combustion engine is not fired, the electric heating element (22) is energized in such a way that a temperature of an exhaust gas cleaning component arranged downstream of the heating element (22) in the exhaust gas cleaning system (10) reaches or exceeds a predeterminable temperature limit and a time after de r first heating-up phase (66) running second heating-up phase (68) with fired operation of the internal combustion engine, in which the electrical heating element (22) is still energized and with an excess of oxygen in the exhaust gas emitted by the internal combustion engine (2) for the internal combustion engine (2) an early and / or late fuel post-injection is provided and the operation of the drive system (1) is controlled in such a way that an exhaust gas mass flow emitted by the internal combustion engine (2) does not exceed a predeterminable upper exhaust gas mass flow limit and/or a predeterminable lower exhaust gas mass flow limit is not 11. 12. 13. 14th 15th 16 Austrian AT 522 990 B1 2022-07-15 transcends, - normal operation (69) is provided with exhaust gas purification components heated at least approximately to the operating temperature, in which the internal combustion engine (2) operates in a first operating mode with minimized raw NOx emissions or is operated in a second operating mode with a minimized specific fuel consumption. Operating method according to claim 10, characterized in that in an exhaust gas cleaning system (10) which is installed in the direction of flow of the combustion tion engine (2) exhaust gas seen arranged one behind the other - the electric heating element (22), - a first exhaust gas cleaning component (23) which is active in terms of oxidation catalysis and is in particular designed as a NOx storage catalytic converter, and - Has at least one SCR-catalytically active exhaust gas cleaning component, the power supply for heating the heating element (22) at least in the second heating-up phase (68) depending on a temperature and a NOx loading of the NOx storage catalytic converter (23) is adjusted. Operating method according to Claim 11, characterized in that during the second heating-up phase (68) the NOx storage catalytic converter (23) is regenerated, the internal combustion engine (2) being operated at least at times with a rich fuel/air ratio and the operation of the drive system ( 1) is controlled in such a way that an exhaust gas mass flow emitted by the internal combustion engine (2) lies between a predeterminable upper and a predeterminable lower exhaust gas mass flow limit. Operating method according to claim 11 or 12, characterized, that immediately after the internal combustion engine (2) is switched off, the heating element (22) is heated in such a way that the NOx storage catalytic converter (23) is raised to a temperature at which stored nitrogen oxides are at least partially thermally desorbed. Operating method according to claim 13, characterized, that during thermal desorption of nitrogen oxides from the NOx storage catalytic converter (23) after the internal combustion engine (2) has been switched off in the exhaust gas flow direction (21) upstream of the at least one SCR catalytically active exhaust gas cleaning component, an ammonia-containing reducing agent is fed to the exhaust gas cleaning system (10). Operating method according to one of Claims 10 to 14, characterized in that furthermore, a maintenance heating mode (70) is provided for at least approximately maintaining the operating temperatures of the exhaust gas cleaning components, in which at least one heating measure for heating the exhaust gas cleaning system (10) in a predeterminable manner is taken from a selection list of heating measures. Operating method according to claim 15, characterized in that it is determined for which period of time from the current point in time operation of the exhaust gas cleaning system (10) with exhaust gas cleaning components heated at least approximately to the operating temperature without taking an additional heating measure is likely to be possible and if the time falls below a specifiable time limit value, that heating measure is selected from the selection list of heating measures or those heating measures are selected with which the period of time for the operation of the exhaust gas cleaning system (10) with exhaust gas cleaning components heated at least approximately to the operating temperature is expected to be extended by at least a predeterminable value. 24/30 17. Operating method according to claim 15 or 16, characterized in that the heating measure or measures are selected depending on the state of charge of a battery coupled to the electric motor (3) and depending on an estimated resulting additional fuel consumption and/or an estimated resulting increase in pollutant emissions for the heating measures from the selection list in such a way that the smallest possible additional fuel consumption and /or result in the smallest possible increase in pollutant emissions. 18. Operating method according to one of claims 10 to 17, characterized in that a first coolant circuit (40) for controlling the temperature of the internal combustion engine (2) is operated with a first electric coolant pump (50) and a second coolant circuit (47) separate therefrom for controlling the temperature of the electric motor (3) is operated with a second electric coolant pump (51), wherein the first coolant pump (50) is operated with a higher electrical operating voltage than the second coolant pump (51). 19. Operating method according to claim 18, characterized in that a minimum coolant throughput is determined for the first and/or the second coolant circuit (40, 47) and a speed of the first and/or the first and/or or the second coolant pump (50, 51) may be reduced in comparison to a respective rated speed. 5 sheets of drawings