DE102018208980A1 - Process for heating a catalyst - Google Patents

Abstract

The invention relates to a method for operating a drive train (1) which comprises an internal combustion engine (2), an exhaust gas aftertreatment device with at least one catalytic converter (3, 4) and at least one device for heating a catalytic converter. The method comprises the following steps: a) determining a catalyst (4) whose temperature is below a predetermined temperature threshold value; b) determining a plurality of possible measures for heating the catalyst (4), each measure having a maximum heating power; c) detecting at least one parameter of the current operating state of the drive train (1); d) determining the efficiency of the individual possible measures for heating the catalytic converter (4) taking into account the at least one detected parameter of the current operating state of the drive train (1); e) arranging the number of possible measures for heating the catalytic converter (4) depending on the specific efficiency and determining an order starting with the measure with the highest efficiency; and f) performing the measures for heating the catalyst (4) in the specified sequence until the temperature of the catalyst reaches at least the temperature threshold, wherein in each case when reaching the maximum heat output of a measure, the next measure is additionally performed.

Description

The present invention relates to a method of operating a powertrain, which comprises an internal combustion engine, for example an internal combustion engine, an exhaust aftertreatment device with at least one catalyst and at least one device for heating a catalytic converter. The present invention also relates to a control device for operating a drive train, a motor vehicle, a computer program product and a computer-readable storage medium.

As part of the exhaust aftertreatment of internal combustion engines, in particular internal combustion engines, various catalysts are usually used. To operate certain catalysts, it is necessary that they first identify a specific light-off temperature. It is also advantageous to operate the respective catalyst at an optimum operating temperature for the chemical reactions taking place in this catalyst. The heating of a catalyst can be done in various ways. For example, catalysts may be heated by the exhaust gas and / or by an exothermic chemical reaction taking place in the catalyst and / or by special heaters and / or by post-injection of fuel into the exhaust gas line.

In the document US 9,708,945 B2 For example, a method for heating exhaust gas from an exhaust aftertreatment system is disclosed wherein the heating mode is selected based on engine load and condition of the exhaust after-treatment system components. In particular, an electric heater is used.

Against the background described, it is an object of the present invention to provide an advantageous method for operating a drive train and its execution suitable devices available, which optimizes the existing possibilities for heating catalysts to be used.

This object is achieved by a method for operating a drive train according to claim 1, a control device according to claim 11, a motor vehicle according to claim 11, a computer program product according to claim 13 and a computer-readable storage medium according to claim 14. The dependent claims contain further advantageous embodiments of the invention.

The method according to the invention for operating a drive train relates to a drive train which comprises an internal combustion engine, for example an internal combustion engine, an exhaust aftertreatment device with at least one catalytic converter and at least one device for heating a catalytic converter. The method according to the invention comprises the following steps: a) determining a catalyst whose temperature is below a defined temperature threshold, b) determining a plurality of possible measures for heating the catalyst, each measure having a maximum heat output, c) detecting at least one parameter of the current operating state the drive train, d) determining the efficiency, in particular the heating efficiency, of the individual possible measures for heating the catalyst, taking into account the at least one detected parameter of the current operating state of the drive train, e) arranging the number of possible measures for heating the catalyst depending on determining the specific efficiency and establishing an order starting with the most efficient measure, in other words defining a hierarchical sequence, and f) performing the measures for heating the catalyst in the fixed order until the temperature of the catalyst reaches at least the specified temperature threshold, in each case when a maximum heating power is reached, a measure the next measure is additionally performed.

The specified temperature threshold may be the light-off temperature or the operating temperature of the catalyst. In the context of the present invention, efficiency is understood as meaning the consumption, in particular the fuel or fuel consumption and / or the energy consumption, per temperature increase (ΔT). Preference is given to the fuel efficiency.

The method according to the invention has the advantage that the overall efficiency of the heating process is increased and, at the same time, the consumption in this context is reduced. The increase in efficiency also ensures that the at least one catalyst is heated up in a very short time and thus made available for operation. In this way, the pollutant emissions are reduced.

In an advantageous variant, the at least one parameter of the current operating state of the drive train is detected continuously. At a fixed change of at least one Parameters or a specified change in the operating state, the process continues at step d). This procedure ensures that at a specified or specific change at least one parameter or at a specified change in operating condition, the available measures for heating the catalyst again in terms of their efficiency, taking into account the current operating state of the drive train and arranged in a appropriate sequence are performed. For example, as the load increases, the exhaust gas temperature may have increased, so further heating of the catalyst by the exhaust may prove more efficient in this situation than the use of an electric heater.

The at least one parameter of the current operating state of the drive train may include the temperature of the exhaust gas and / or the temperature of the engine and / or the temperature of at least one catalyst and / or the aging state of at least one catalyst and / or at least one exhaust emission value, such as carbon monoxide (CO ), Hydrocarbon (HC) or nitrogen oxide (NOx) emissions. Additionally or alternatively, the at least one parameter of the current operating state of the drive train, the battery state of charge and / or the performance of the internal combustion engine and / or the load of the internal combustion engine and / or the speed of the internal combustion engine and / or the torque of the internal combustion engine and / or the extent of Throttling the internal combustion engine, in particular the degree of throttling of the fuel supply and / or the charge air supply and / or the power supply include. Additionally or alternatively, the at least one parameter of the current operating state of the drive train, the post-injection of fuel and / or the oil dilution and / or the operating state of an evaporator and / or the current heating power of an electrically heatable catalyst and / or the maximum heating power of an electrically heatable catalyst include. The consideration of one or more of the mentioned parameters in the context of determining the efficiency of a possible measure for heating the catalyst has the advantage that the respective efficiency for the actual situation can be realistically determined, in particular calculated or estimated. It is thus possible to adapt to the respective operating situation.

The at least one device for heating a catalyst may comprise an electrically heatable catalyst and / or an exothermic catalyst. The exhaust aftertreatment device may include a diesel oxidation catalyst (DOC) and / or a lean NOx trap (LNT-Iean NOx trap) and / or an SCR (SCR) catalytic converter (SCR) and / or a diesel particulate filter (DPF) and / or a Include diesel particulate filters with SCR coating (SDPF). In a preferred variant, at least one exothermic catalyst, for example a diesel oxidation catalyst and / or a lean NOx trap, is arranged upstream of a further catalyst, for example an SCR catalytic converter and / or a diesel particle filter. Such an arrangement has, inter alia, the advantage that the heat released by the exothermic catalyst can be used to heat the downstream further catalyst.

The heating measures may include, in particular, operating an electrically heatable catalyst and / or increasing the load of the internal combustion engine and / or increasing the amount of post-injected fuel and / or operating an evaporator.

The powertrain may be configured, for example, as a hybrid powertrain, in particular as a full hybrid powertrain or as a partial hybrid powertrain. The hybrid drive can be designed as a serial hybrid drive or parallel hybrid drive or power-split hybrid drive. In this case, in the case of a parallel hybrid powertrain, an electric machine, in particular an electric motor, may be arranged at different positions of the drive train, in particular at the positions P1 . P2 . P3 or P4 , Of the P1 Hybrid power train is characterized by an attached directly to an internal combustion engine and fixedly connected to the crankshaft electric machine. In a P2 arrangement, the electric machine is located at the transmission input, wherein a clutch is arranged between the internal combustion engine and the electric machine. In a P3 arrangement, the electric machine is arranged at the transmission output, and in a P4 arrangement, the internal combustion engine and the electric machine act on different axes.

In a further variant, a turbine can be arranged downstream of the internal combustion engine with respect to the exhaust gas flow. It can be an electric turbine or a supercharger, for example a turbocharger. In particular, the loader may comprise the turbine. By operating the turbine, for example, the exhaust gas temperature can be at least partially controlled, in particular regulated.

The control device according to the invention for operating a drive train, which comprises an internal combustion engine, in particular an internal combustion engine, an exhaust gas aftertreatment device with at least one catalyst and at least one device for heating a catalytic converter, is adapted to a previously described inventive method perform. The control device according to the invention has the features and advantages already mentioned in connection with the method according to the invention.

The motor vehicle according to the invention comprises a drive train. The drive train comprises an internal combustion engine, in particular an internal combustion engine, an exhaust gas aftertreatment device with at least one catalyst and at least one device for heating a catalytic converter. The motor vehicle according to the invention comprises a control device according to the invention. It is thus designed to carry out a method according to the invention described above.

The powertrain may be, for example, a hybrid powertrain, in particular a full or partial hybrid powertrain. The hybrid powertrain can be configured serially, in parallel or with power branching. In the case of a parallel hybrid powertrain, an electric machine, in particular an electric motor, at the above-mentioned positions P1 . P2 . P3 or P4 be arranged. There may also be several electric motors.

The computer program product according to the invention comprises instructions which, during the execution of the program by a computer, cause it to carry out a method according to the invention described above. The computer-readable storage medium includes instructions that, when executed by a computer, cause it to execute an inventive method as described above.

The motor vehicle according to the invention, the computer program product and the computer-readable storage medium have the advantages already mentioned above. The present invention has the overall advantage that the existing measures for heating a catalyst can be used efficiently. The efficiency of heating a catalyst or a number of catalysts is significantly improved by the present invention.

• 1 zeigt schematisch einen Antriebsstrang.
• 2-4 zeigen schematisch verschiedene Antriebsstrangvarianten.
• 5 zeigt schematisch eine Variante eines erfindungsgemäßen Verfahrens in Form eines Flussdiagramms.
• 6 zeigt schematisch das erfindungsgemäße Vorgehen in Schritt e) des erfindungsgemäßen Verfahrens bzw. in Schritt 15 der 5 anhand eines Blockdiagramms.
• 7 zeigt schematisch eine beispielhafte Reihenfolge der durchzuführenden Maßnahmen.
• 8 zeigt schematisch ein erfindungsgemäßes Kraftfahrzeug.

The invention will be explained in more detail below with reference to embodiments with reference to the accompanying figures. Although the invention is further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

• 1 schematically shows a drive train.
• 2-4 show schematically different powertrain variants.
• 5 schematically shows a variant of a method according to the invention in the form of a flow chart.
• 6 schematically shows the inventive method in step e) of the method according to the invention or in step 15 of the 5 using a block diagram.
• 7 schematically shows an exemplary sequence of actions to be performed.
• 8th schematically shows a motor vehicle according to the invention.

The 1 schematically shows a drive train. The powertrain 1 includes an internal combustion engine 2 , an upstream of which is arranged with respect to the flow direction of the exhaust gas exothermic catalyst 3 and one downstream of the exothermic catalyst 3 arranged further catalyst 4 , For the exothermic catalyst 3 it may be, for example, a diesel oxidation catalyst and / or a lean NOx trap. In the further catalyst 4 it may be, for example, an SCR catalyst and / or a diesel particulate filter with SCR coating.

Examples of concrete arrangements of catalysts in the context of an exhaust aftertreatment device are exemplary in the 2 . 3 and 4 shown. In the 2 to 4 is in each case downstream of the internal combustion engine 2 a turbine 5 arranged. The turbine 5 may be part of a supercharger, such as a turbocharger. In the 2 downstream of the turbine are a diesel oxidation catalyst 6 and downstream of it, a diesel particulate filter with SCR coating 7 arranged. In the 3 is downstream of the turbine 5 a lean NOx trap 8th and downstream of the lean NOx trap 8th a diesel particulate filter 9 arranged. In the in the 4 variant shown is downstream of the turbine 5 a lean NOx trap 8th , Downstream of the lean NOx trap 8, a diesel particulate filter with SCR coating 7 and downstream of the diesel particulate filter 7 an SCR catalyst 10 arranged.

To operate the SCR catalyst or a diesel particulate filter with SCR coating, it is necessary that these catalysts have a certain minimum temperature, for example, a certain light-off temperature or a certain operating temperature. After starting the internal combustion engine 2 is therefore usually first a heating of the catalyst 4 required.

The 5 schematically shows a variant of a method according to the invention in the form of a flow chart. In a first step 11 a catalyst is determined whose temperature T is below a predetermined temperature threshold T _min is. In this context, it can be determined in particular whether the temperature T of the catalytic converter is less than a defined light-off temperature or a defined operating temperature of the catalytic converter (T <T _min ). If the temperature of the catalyst is below the specified temperature threshold, then in a next step 12 possible measures for heating the catalyst determined. Each measure has a maximum heating power. In a further step 13 At least one parameter of the current operating state of the drive train is detected. The steps 12 and 13 can also be done in reverse order.

In one of the steps 12 and 13 subsequent further step 14 is the efficiency, ie the consumption per temperature increase, the individual possible measures for heating the catalyst determined taking into account the at least one parameter of the current operating state of the drive train. Subsequently, in step 15 the number of possible measures for heating the catalyst is ordered depending on the specific efficiency and an order is set starting with the measure with the highest efficiency. The measures are thus brought into a hierarchical order or sequence.

Subsequently, in step 16 Initially, the measure performed with the highest efficiency. When the maximum heat output of the measure is reached, the next step is carried out in accordance with the specified sequence. In step 17 it is checked whether the temperature of the catalyst is below the specified temperature threshold (T <T _min ?). If this is the case, then the method with step 16 continue or it may become one of the steps 12 or 13 recapture and recapture the available measures and / or the current operating state, and then update the efficiency of the available measures and their order. Is at step 17 the temperature of the catalyst is equal to or above the operating temperature (T≥T _min ), the process in step 18 completed.

The catalyst to be heated may be, for example, one in the 1 shown further catalyst 4 , or one in the 2 and 4 shown diesel particulate filter with SCR coating 7 and / or one in the 3 shown diesel particulate filter 9 and / or one in the 4 shown SCR catalyst 10 act.

In the following, individual example scenarios are described. In a first application example, in step 11 the temperature T are below the operating temperature Tmin of a catalyst. As possible measures for heating the catalyst, the heating by means of an electrically heatable catalyst, the increase of the load and the post-injection of fuel into the exhaust gas line are available. When selecting and setting an order, it can be considered that the electrically heatable catalyst allows emission-free heating. Taking into account the efficiency and the current operating state, the measures can be carried out as follows, for example. First, the catalyst can be heated up to its maximum electrical power by means of the electrically heatable catalyst. If the battery state of charge is low or if the electrically heatable catalyst can not provide enough heat to heat up, an increase in the load of the internal combustion engine may occur. Increasing the load will produce additional exhaust heat and charge the battery at the same time.

If the battery state of charge reaches a lower limit, for example because the energy required by the electrically heatable catalyst is greater than the energy charged by the increase in load, the power of the electrically heatable catalyst or its heating power can be limited and by injecting fuel into the fuel Exhaust gas flow channel additional heat can be generated. If the battery state of charge reaches an upper limit, for example, in that the energy required by the electrically heatable catalyst is smaller than the charging power by the load increase, the energy generated by load increase, can be limited and additional heat can be generated by post-injection.

In a second example of application, the catalyst temperature, for example the temperature of an exothermic catalyst, is above the fixed light-off temperature, for example above 180 ° C., and there is little oil dilution. In this variant are available as measures, in particular for further heating of a downstream catalyst, for example, an SCR catalyst, post-injection of fuel and the use of an electrically heatable catalyst available, optionally in connection with a load increase. If the catalyst temperature is above the light-off temperature, post-injection is the most efficient way to heat the catalyst since the fuel is burned immediately where the heat generated thereby is needed. In This case is therefore first nacheingespritzt and then further heated by means of an electrically heatable catalyst optionally with simultaneous increase in load, the catalyst. This can be done in particular as described in the first embodiment.

In a third embodiment, the temperature of the catalyst is higher than the light-off temperature and there is a high oil dilution. As measures for heating, the use of an electrically heatable catalyst, a load increase and a post-injection are available. If the oil dilution is high, if no evaporator is present, the use of an electrically heatable catalyst is the most compatible in terms of oil dilution Heizmaßnahme. In this variant, therefore, as described in the first embodiment, proceed. If an evaporator is present, fuel can first be evaporated in the second and third examples, then heated by means of an electrically heatable catalyst and, if necessary, the load increased.

If an electric turbine or an electric compressor is present, its efficiency must be taken into account and, in particular, set in relation to the heat to be generated and the associated emission effects. The order of execution of the various measures mentioned thus varies depending on the operating conditions considered or the detected current operating state.

In the 6 the procedure of the invention in step e) of the method or step 15 of the 5 illustrated by a block diagram. In block 21 the emission values, in particular the hydrocarbon and carbon monoxide emission values are determined. At this time, the catalyst temperature and the catalyst aging state become inputs 22 considered. In block 23 is based on the current oil dilution and the operating conditions of the internal combustion engine as inputs 24 be taken into account, the oil dilution currently determined and in particular in the case of post-injection their possible change, in particular increase, estimated. In block 25 the fuel efficiency is determined for each device for heating or for each measure. As inputs 26 Here, in particular, the efficiency of the electrical equipment, in particular the battery, a converter, etc., and the efficiency of the catalyst are taken into account.

The in the blocks 21 . 23 and 25 determined results and input 27 , which includes whether an evaporator is present, in block 28 and used to assess current operating conditions with respect to specified limits. In block 28 In particular, the steps d) and e) of the method according to the invention are carried out. As a result, in block 29 issued an optimal order of application of the heating measures. The inventive method can by means of a control device 30 be implemented in the 6 a section of the functions is shown.

The 7 illustrates an exemplary sequence of actions to be performed 29 , In the example shown, starting from the catalyst temperature 31 in block 32 monitoring the temperature gradient with respect to a target temperature and maintaining the target temperature.

To heat up in block 33 initially used an electrically heated catalyst. The maximum power and the current power of the electrically heated catalyst are used as input variables 34 supervised.

When the maximum power is reached, a power request may be issued 35 , In this case, at block 36 increased the load of the internal combustion engine. The inputs are the maximum and the current power of the electric motor 37 considered. If necessary, a power requirement of the internal combustion engine 38 output. If this is the case, then in block 39 went to the post-injection. At this time, the amount of post-injection is output 40.

In the order specified after the post-injection 39 throttling takes place in block 41 , It is in this case a control of the heating by means of the throttle 42 performed. In the specified order after throttling is done in block 43 adjusting the rotational speed of the electric turbine or the electric compressor. This takes place up to a setpoint speed 44 ,

The measures 33 . 36 . 39 . 41 and 43 So they are done in this order, each time until you reach through the expenses 35 . 38 40 . 42 and 44 marked limit or a corresponding restriction. Upon reaching the respective limit values or restriction of the individual measure, a subsequent measure in the sequence is additionally performed. As a result, the first most efficient measure is begun, when the limit values are reached, the next-efficient measure is added and the heating is continued with further measures until the desired operating temperature of the catalytic converter is reached.

The 8th schematically shows a motor vehicle according to the invention 50 , which may be, for example, a passenger car, a truck or a motorcycle. The motor vehicle includes a drive train 1 and a control device 51 , which is designed for carrying out a method according to the invention. The control device may be a cutout in the 6 shown control device 30 act.

LIST OF REFERENCE NUMBERS

1

powertrain

2

internal combustion engine

3

exothermic catalyst

4

further catalyst

5

turbine

6

Diesel oxidation catalyst

7

Diesel particulate filter with SCR coating

8th

Lean NOx trap

9

diesel particulate Filter

10

SCR catalyst

11

Determining a catalyst whose temperature is below a specified temperature threshold

12

Determining a plurality of possible measures for heating the catalyst

13

Detecting at least one parameter of the current operating state of the drive train

14

Determining the efficiency of the individual possible measures for heating the catalyst taking into account the at least one detected parameter of the current operating state of the drive train

15

Arrange the number of possible measures to heat the catalyst depending on the specific efficiency and set an order starting with the measure with the highest efficiency

16

Performing the measures for heating the catalyst in the specified order until the temperature of the catalyst reaches at least the temperature threshold, in each case when the maximum heating power of a measure, the next measure is additionally performed

17

Temperature of the catalyst below the specified temperature threshold?

18

The End

21

Determining emission values

22

Catalyst temperature and catalyst aging state

23

Estimation of the development of the oil dilution

24

Oil dilution and operating conditions of the internal combustion engine

25

Determine fuel efficiency for each action

26

Determining the efficiency of electrical appliances

27

Evaporator available

28

Implementation of steps d) and e)

29

Issue of an order of application of the heating measures

30

control device

31

catalyst temperature

32

Monitoring the temperature gradient

33

Heating by means of electrically heatable catalyst

34

Monitoring the current performance of the electrically heated catalyst

35

Output performance requirement

36

Load increase of the internal combustion engine

37

maximum and current power of the electric motor

38

Output performance requirement

39

injection

40

Output extent of post-injection

41

throttle

42

Control of heating by means of a throttle

43

Adjusting the speed of the electric turbine

44

Adjust up to set speed

50

motor vehicle

51

control device

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 9708945 B2 [0003]

Claims (14)

Method for operating a drive train (1) which comprises an internal combustion engine (2), an exhaust aftertreatment device with at least one catalytic converter (3, 4) and at least one device for heating a catalytic converter, characterized in that the method comprises the following steps: a) determining b) determining a plurality of possible measures for heating the catalytic converter (4), each measure having a maximum heating power, c) detecting at least one parameter of the current operating state of the drive train (FIG. 1), d) determining the efficiency of the individual possible measures for heating the catalytic converter (4), taking into account the at least one detected parameter of the current operating state of the drive train (1), e) arranging the number of possible measures for heating the catalytic converter (4) from the specific E and f) performing the steps of heating the catalyst (4) in the specified order until the temperature of the catalyst reaches at least the temperature threshold, each time a maximum heat output is reached the next measure will be carried out additionally. Method according to Claim 1 characterized in that the predetermined temperature threshold value is the light-off temperature or the operating temperature of the catalytic converter (4). Method according to Claim 1 or Claim 2 , characterized in that the at least one parameter of the current operating state of the drive train (1) is detected continuously and at a fixed change in the operating state of the drive train (1), the method is continued at step d). Method according to one of Claims 1 to 3 , characterized in that the at least one parameter of the current operating state of the drive train (1) the temperature of the exhaust gas and / or the temperature of the engine and / or the temperature of at least one catalyst and / or the aging state of at least one catalyst and / or at least one exhaust emission value and / or the battery state of charge and / or the power of the internal combustion engine and / or the load of the internal combustion engine and / or the speed of the internal combustion engine and / or the torque of the internal combustion engine and / or the degree of restriction of the internal combustion engine and / or the post-injection of fuel and / or the oil dilution and / or the operating state of an evaporator and / or the current heat output of an electrically heatable catalyst and / or the maximum heat output of an electrically heatable catalyst. Method according to one of Claims 1 to 4 , characterized in that the at least one device for heating a catalyst comprises an electrically heatable catalyst and / or an exothermic catalyst (3). Method according to one of Claims 1 to 5 characterized in that the exhaust aftertreatment device comprises a diesel oxidation catalyst (6) and / or a lean NOx trap (8) and / or an SCR catalyst (10) and / or a diesel particulate filter (9) and / or a diesel particulate filter with SCR Coating (7). Method according to one of Claims 1 to 6 , characterized in that at least one exothermic catalyst (3) upstream of another catalyst (4) is arranged. Method according to one of Claims 1 to 7 characterized in that the means for heating comprises operating an electrically heatable catalyst and / or increasing the load of the internal combustion engine (2) and / or increasing the amount of post-injected fuel and / or operating an evaporator. Method according to one of Claims 1 to 8th , characterized in that the drive train (1) is designed as a hybrid drive train. Method according to one of Claims 1 to 9 , characterized in that with respect to the exhaust gas stream downstream of the internal combustion engine (2), a turbine (5) is arranged. Control device (30, 51) for operating a drive train (1) comprising an internal combustion engine (2), an exhaust aftertreatment device with at least one catalytic converter (3, 4) and at least one Means for heating a catalytic converter, characterized in that the control device (30, 51) is adapted to a method according to one of Claims 1 to 10 perform. Motor vehicle (50) with a drive train (1) comprising an internal combustion engine (2), an exhaust aftertreatment device with at least one catalyst (3, 4) and at least one device for heating a catalytic converter, characterized in that the motor vehicle (50) is a control device (30, 51) Claim 11 includes. A computer program product comprising instructions which, upon execution of the program by a computer, cause it to perform the method according to any one of Claims 1 to 10 perform. A computer-readable storage medium comprising instructions which, when executed by a computer, cause it to perform the method according to any one of Claims 1 to 10 perform.

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