CN111120058A

CN111120058A - Method for operating an exhaust gas aftertreatment device

Info

Publication number: CN111120058A
Application number: CN201911016336.6A
Authority: CN
Inventors: 罗伯特·屋罗佩茨; 马里奥·贝尔诺维奇; 简·哈尔姆森; 玛丽亚·阿尔米恩多; 叶夫根尼·斯米尔诺夫
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2018-10-30
Filing date: 2019-10-24
Publication date: 2020-05-08
Also published as: DE102018218522A1

Abstract

The invention relates to a method for operating an exhaust gas aftertreatment device (6) for purifying an exhaust gas flow of an internal combustion engine (4) of a motor vehicle (2), wherein the exhaust gas aftertreatment device (6) comprises at least one catalytic converter, wherein at least one thermoelectric generator (18) is associated with the catalytic converter, wherein the thermoelectric generator (18) is connected to the catalytic converter in order to transfer thermal energy, comprising the following steps: the value (W1) representing the temperature of the catalytic converter is compared with a limit value (G2), and when the value (W1) representing the temperature of the catalytic converter is greater than the limit value (G2), electric power is generated by the thermoelectric generator (18).

Description

Method for operating an exhaust gas aftertreatment device

Technical Field

The invention relates to a method for operating an exhaust gas aftertreatment device for purifying an exhaust gas flow of an internal combustion engine of a motor vehicle.

Background

Once the combustion gases leave the combustion space or combustion chamber of an internal combustion engine driving a motor vehicle, the combustion gases are cleaned mechanically, catalytically or chemically using an exhaust-gas aftertreatment device in order to be able to comply with legal emission limits in this way.

In order to obtain stricter emission conditions, such exhaust aftertreatment devices comprise a plurality of different catalytic converters, which may be arranged at the bottom of the vehicle close to the engine and/or further away from the engine.

In practice, all catalytic converters include an optimum temperature range in which the efficiency of the respective catalytic converter is optimum.

However, each catalytic converter includes a different best operating temperature window. For example, the overlap of the operating temperature windows of identically designed catalytic converters (one disposed close to the engine and the other disposed away from the engine) provides a widened temperature mode window.

However, it is practically impossible to maintain optimum operating temperature conditions for all operating catalytic converters and at the same time obtain a high level of efficiency in removing emissions at different temperatures that occur under various driving conditions, such as in the case of cold starts, when driving on towns and highways, or under other engine operating conditions.

Different operating conditions may result in different temperatures, which leads to non-optimal operating conditions and higher emissions, to unexpectedly higher emissions from the internal combustion engine and/or the catalytic converter, which cannot be treated with a further catalytic converter arranged downstream, by-products build up as secondary emissions, and may also lead to deactivation of the catalytic converter due to chemical and structural changes.

Without a durable catalytic converter with a wide operating temperature window, without a very efficient catalytic converter at low and very high temperatures, and without effective thermal management, undesirable events, such as higher exhaust emissions or secondary emission products, are more likely to occur. In addition, the service life of the exhaust gas aftertreatment device may be shortened.

Disclosure of Invention

It is therefore an object of the present invention to indicate a way in which it is possible to avoid the occurrence of unexpectedly high emissions when switching off the internal combustion engine and when starting the internal combustion engine. In addition, emissions will also decrease when the temperature of the catalytic converter decreases (cold start) or the engine load increases directly after start-up.

The object of the invention is achieved by a method for operating an exhaust gas aftertreatment device for purifying an exhaust gas flow of an internal combustion engine of a motor vehicle, wherein the exhaust gas aftertreatment device comprises at least one catalytic converter, wherein at least one thermoelectric generator is assigned to the catalytic converter, wherein the thermoelectric generator is connected to the catalytic converter in order to transfer thermal energy, having the following steps:

the value representing the temperature of the catalytic converter is compared with a limit value,

when the value representing the temperature of the catalytic converter is greater than a limit value, electric energy is generated using a thermoelectric generator.

Thermal energy can be converted directly into electrical energy using a thermoelectric generator (TEG). Here, a semiconductor material is used instead of a metal, whereby efficiency can be significantly improved compared to a metal thermocouple. Thermoelectric generators are characterized by simple design, high reliability levels and long service life.

The thermoelectric generator additionally comprises one or more peltier elements, which then form a thermopile for providing electrical energy. The peltier element is an electrothermal converter that generates a temperature difference based on the peltier effect when a current flows therethrough, or generates a current when there is a temperature difference (seebeck effect). The peltier element can be used both for cooling and for heating when the direction of the current is reversed.

Thus, for example at the end of a stop stroke of the internal combustion engine, excess thermal energy can be converted directly into electrical energy and stored, for example, intermediately in a battery of the motor vehicle. At the same time, overheating of the catalytic converter beyond its operating temperature window can thus be counteracted in operation. The electrical energy intermediately stored in the battery can then be used again to heat the catalytic converter in order to raise the temperature to the operating temperature window, if necessary.

Thus, by maintaining the temperature in and/or reaching the operating temperature window in a faster manner, emissions of the internal combustion engine may be reduced.

According to one exemplary embodiment, the catalytic converter is assigned at least one thermoelectric heating element, wherein the thermoelectric heating element is connected to the catalytic converter in order to transfer thermal energy. Then the following steps are additionally performed:

a value indicative of the activation state of the internal combustion engine is determined,

when the value indicates an activated internal combustion engine, the thermoelectric heating element is acted upon with electrical energy.

The thermoelectric heating element may be a further heating resistor capable of providing a greater heating output than the thermoelectric generator. In other words, the auxiliary electrical heating is assigned to the catalytic converter, i.e. the catalytic converter is realized as e-cat. Thus, when needed, faster heating can be achieved.

According to another embodiment, the catalytic converter is NO_xThe catalytic converter is stored. Thus, the catalytic converter allows NO_x(storage of nitrogen oxides). To this end, it includes designs with suitable supports having a noble metal catalyst (e.g., platinum) and NO_xA storage component (e.g., an alkaline earth metal such as barium).

According to another embodiment, the catalytic converter is a Selective Catalytic Reduction (SCR) catalytic converter. Thus, the SCR catalytic converter 14 is implemented to selectively catalytically reduce nitrogen oxides using urea, which is injected into the exhaust stream at a urea injection point.

In addition, the invention also comprises a computer program product, a control device, an exhaust gas aftertreatment device and a motor vehicle with such an exhaust gas aftertreatment device.

Drawings

The invention will now be explained with the aid of the accompanying drawings, in which:

FIG. 1 shows an internal combustion engine and an exhaust aftertreatment device of a motor vehicle for carrying out an exemplary embodiment of a method according to the invention;

FIG. 2 illustrates a flow chart of operation of the exhaust aftertreatment device shown in FIG. 1;

fig. 3 shows another flow chart of the operation of the exhaust gas aftertreatment device shown in fig. 1.

Detailed Description

Reference is first made to fig. 1.

Fig. 1 shows an internal combustion engine 4 and an exhaust gas aftertreatment device 6 of a motor vehicle 2.

In the present exemplary embodiment, the internal combustion engine 4 is a diesel engine, i.e., the diesel engine is operated in a lean burn mode with an excess of oxygen (λ > 1) in normal operation. In contrast, the internal combustion engine 4 may also be realized as a gasoline engine in a lean burn mode to improve engine efficiency.

In the present exemplary embodiment, the internal combustion engine 4 is turbocharged such that the turbine of the exhaust turbocharger is connected downstream of the exhaust flow of the internal combustion engine 4.

In the present exemplary embodiment, an exhaust aftertreatment device 6 is connected downstream of the internal combustion engine 4 in the exhaust gas flow direction, which exhaust aftertreatment device 6 comprises a plurality of catalytic converters arranged one after the other in the exhaust gas flow direction. In the present exemplary embodiment, these are NO_xA storage catalytic converter 10, a diesel particulate filter 12 and an SCR catalytic converter 14.

NO_xStorage catalytic converter 10 is implemented to store NO_x(nitrogen oxide). Including designs with suitable supports having a noble metal catalyst (e.g., platinum) and NO_xA storage component (e.g., an alkaline earth metal such as barium).

The diesel particulate filter 12 is implemented for reducing particulates present in the exhaust stream.

The SCR catalytic converter 14 is implemented to selectively catalytically reduce nitrogen oxides using urea, which is injected into the exhaust stream at a urea injection point.

In contrast to the exemplary embodiment, the number of catalytic converters can be varied, i.e. for example two NO's can also be provided_xThe catalytic converter is stored. Multiple SCR catalytic converters may also be provided. It may also be provided that the SCR catalytic converter 14 comprises a coating, in order to realize it as a diesel particle filter with an SCR coating or for reducing the particles and NO present in the exhaust gas stream_xDiesel particulate filter (DPF or SDPF).

The internal combustion engine 4 is provided with a control device 8 which, for example, causes a change from operation with excess oxygen to sub-stoichiometric operation and vice versa in order to cause NO_xRegeneration of the catalytic converter 10 is stored. The control device comprises hardware and/or software components for this purpose and for the tasks and functions described below.

Further, in the present exemplary embodiment, the thermoelectric generator 18 is connected downstream of the internal combustion engine in the exhaust gas flow direction, while the thermoelectric generator 8 and the thermoelectric heating element 20 are connected in each case in the exhaust gas flow direction at NO_xUpstream of the storage catalytic converter 10 and the SCR catalytic converter 14.

Referring now additionally to FIG. 2, there is shown an exhaust aftertreatment device 6 (in particular NO)_xStoring a first flowchart of the operation of the catalytic converter 10).

The method starts in step S1100.

In a further step S1200, a reading is made which indicates the catalytic converter temperature (NO in the present exemplary embodiment)_xThe inlet temperature of the catalytic converter 10) is stored and compared with a first limit value G1. In the present exemplary embodiment, the first limit value G1 includes a value of 200 ℃.

If the first value W1 is not less than the first limit value G1, the method continues with a further step S1300.

In step S1300, the first value W1 representing the catalytic converter temperature is compared with the second limit value G2. In the present exemplary embodiment, the second limit value G2 includes a value of 300 ℃.

If the first value W1 is greater than the second limit value G2, the method continues with a further step S1400.

The thermoelectric generator 18 is activated in step S1400 such that in the generator mode, the thermoelectric generator 18 converts thermal energy into electrical energy, which is then intermediately stored in the battery 16.

This has always been applied to the first value W1 being again equal to or less than the second limit value G2.

In contrast, if the first value W1 is at least equal to the second limit value G2, the method continues to a further step S1500.

In step S1500, a second value W2 is determined, which indicates the activation state of the internal combustion engine 4. In the present exemplary embodiment, for an active or running internal combustion engine 4, the second value W2 is a logical variable 1, while a logical variable 0 represents an inactive or stopped internal combustion engine 4.

If the internal combustion engine 4 is active, the method continues with a further step S1600.

In step S1600, electrical energy is applied to the thermoelectric heating element 20, for example, from the battery 16, so that the thermoelectric heating element 20 heats NO_xThe catalytic converter 10 is stored. Conversely, the thermoelectric generator 18 is inactive (i.e., it does not provide any electrical energy). However, it is also possible to provide that the thermoelectric generator 18 operates in a heating mode and thus supports the heating element 20 in operation in order to accelerate the heating process again.

The method then continues with step S1200.

If, on the other hand, the internal combustion engine 4 is inactive, the method continues with a further step S1700.

In step S1700, a first value W1 representing the catalytic converter temperature is compared with a third limit value G3. In the present exemplary embodiment, the third limit value G3 includes a value of 50 ℃.

If the first value W1 is not greater than the third limit value G3, the method continues with step S1400.

In contrast, if the first value W1 is at least equal to the third limit value G3, the method continues with a further step S1800.

In step S1800, both the thermoelectric generator 18 and the thermoelectric heating element 20 are inactive, i.e., the thermoelectric generator 18 does not supply any electrical energy, and the thermoelectric heating element 20 is not applied with electrical energy.

The method ends with step S1900.

Unlike the present exemplary embodiment, the process of the method may include a different sequence of steps. Multiple steps may also be performed simultaneously or together. In addition, for example, individual steps may also be skipped or omitted.

Referring now additionally to fig. 3, a first flowchart of the operation of the exhaust aftertreatment device 6, in particular the SCR catalytic converter 14, is shown. The SCR catalytic converter 14 may include a structure to implement it as a diesel particulate filter with an SCR coating or a Diesel Particulate Filter (DPF) that reduces particulates present in the exhaust stream.

The method starts in step S2100.

In a further step S2200 a first value W1 representing the catalytic converter temperature (in this exemplary embodiment the inlet temperature of the SCR catalytic converter 14) is read and compared with a first limit value G1. In the present exemplary embodiment, the first limit value G1 includes a value of 180 ℃.

If the first value W1 is not less than the first limit value G1, the method continues with a further step S2300.

In step S2300, a first value W1 representing the catalytic converter temperature is compared with a second limit value G2. In the present exemplary embodiment, the second limit value G2 includes a value of 300 ℃.

If the first value W1 is greater than the second limit value G2, the method continues with a further step S2400.

The thermoelectric generator 18 is activated in step S2400, so that in the generator mode, the thermoelectric generator 18 converts thermal energy into electrical energy, and then the electrical energy is intermediately stored in the battery 16.

In contrast, if the first value W1 is at least equal to the second limit value G2, the method continues with a further step S2500.

In step S2500, a second value W2 is determined, which indicates the activation state of internal combustion engine 4. In the present exemplary embodiment, for an active or running internal combustion engine 4, the second value W2 is a logical variable 1, while a logical variable 0 represents an inactive or stopped internal combustion engine 4.

If the internal combustion engine 4 is active, the method continues with a further step S2600.

In step S2600, electrical energy is applied to the thermoelectric heating element 20, for example from the battery 16, such that the thermoelectric heating element 20 heats the SCR catalytic converter 14. In contrast, the thermoelectric generator 18 is inactive, i.e. it does not supply any electrical energy. However, it is also possible to provide that the thermoelectric generator 18 operates in a heating mode and thus supports the heating element 20 in operation in order to accelerate the heating process again.

The method then continues to step S2200.

If the internal combustion engine 4 is inactive, the method continues with a further step S2700.

In step S2700, the first value W1 representing the catalytic converter temperature is compared with the third limit value G3. In the present exemplary embodiment, the third limit value G3 includes a value of 50 ℃.

If the first value W1 is not greater than the third limit value G3, the method continues with step S2400.

In contrast, if the first value W1 is at least equal to the third limit value G3, the method continues with a further step S2800.

In step S2800, both the thermoelectric generator 18 and the thermoelectric heating element 20 are inactive, i.e., the thermoelectric generator 18 does not supply any electrical energy, and the thermoelectric heating element 20 is not applied with electrical energy.

The method ends with step S2900.

In the two exemplary embodiments explained with reference to fig. 2 and 3, three different situations are considered which occur as a result of the cold start process, the start-stop process and the process at the end of the journey.

In the case of a cold start process, the temperature represented by the first value W1, which is represented by the second limit value G2 in the present exemplary embodiment, is below the limit temperature during the starting operation. The electrical heating is then activated.

In the case of a start-stop procedure, the electrical heating is switched off, but the heat dissipation can continue as long as the temperature is above the limit temperature represented by the first limit value G1. In contrast, if the temperature is lower than the limit temperature during the starting operation, the electric heating is started.

In the case of the process at the end of the stroke, the electrical heating is also switched off, but the heat dissipation can continue depending on the state of the battery 16. This means that heat dissipation can continue as long as there is a significant temperature difference, which is represented by the third limit value G3 in the present exemplary embodiment. It is assumed here that the battery 16 still has free capacity for storing electrical energy.

Unlike the present exemplary embodiment, the method process can include a different sequence of steps. Multiple steps may also be performed simultaneously or together. In addition, for example, individual steps may also be skipped or omitted.

The temperature within the operating temperature window can be maintained and/or reached in a faster manner, which reduces emissions of the internal combustion engine 4.

List of reference numerals

2 Motor vehicle

4 internal combustion engine

6 exhaust gas aftertreatment device

8 control device

10 NO_xStorage catalytic converter

12 diesel particulate filter

14 SCR catalytic converter

16 cell

18 thermoelectric generator

20 thermoelectric heating element

First limit value of G1

Second limit value of G2

G3 third limit value

W1 first value

Second value of W2

S1100 step

S1200 step

Step S1300

S1400 step

S1500 step

S1600 step

S1700 step

S1800 step

S1900 step

S2100 step

S2200 step

S2300 step

S2400 step

S2500 step

S2600 step

S2700 step

S2800 step

S2900 step

Claims

1. Method for operating an exhaust gas aftertreatment device (6) for purifying an exhaust gas flow of an internal combustion engine (4) of a motor vehicle (2), wherein the exhaust gas aftertreatment device (6) comprises at least one catalytic converter, wherein the catalytic converter is assigned at least one thermoelectric generator (18), wherein the thermoelectric generator (18) is connected to the catalytic converter for transferring thermal energy, having the following steps:

the value representing the temperature of the catalytic converter (W1) is compared with a limit value (G2),

generating electrical energy with the thermoelectric generator (18) when the value (W1) indicative of catalytic converter temperature is greater than the limit value (G2).

2. Method according to claim 1, wherein the catalytic converter is assigned at least one thermoelectric heating element (20), wherein the thermoelectric heating element (20) is connected to the catalytic converter in order to transfer thermal energy, the method having the following steps:

determining a value (W2) indicative of the activation state of the internal combustion engine (4),

-acting the thermoelectric heating element (20) with electrical energy when the value (W2) indicates an activated internal combustion engine (4).

3. The method of claim 1 or 2, wherein the catalytic converter is NO_xA catalytic converter (10) is stored.

4. A method according to claim 1 or 2, wherein the catalytic converter is an SCR catalytic converter (14).

5. A computer program product being implemented for carrying out the method according to one of claims 1 to 4.

6. A control device (8) for operating an exhaust gas aftertreatment device (6) for purifying an exhaust gas flow of an internal combustion engine (4) of a motor vehicle (2), wherein the exhaust gas aftertreatment device (6) comprises at least one catalytic converter, wherein the catalytic converter is assigned at least one thermoelectric generator (18), wherein the thermoelectric generator (18) is connected to the catalytic converter in order to transfer thermal energy, wherein the control device (8) is realized for comparing a value (W1) representing a catalytic converter temperature with a limit value (G2) and for generating electrical energy with the thermoelectric generator (18) when the value (W1) representing a catalytic converter temperature is greater than the limit value (G2).

7. The control device (8) as claimed in claim 6, wherein the control device (8) is realized for determining a value (W2) which is indicative of an activation state of the internal combustion engine (4), and for acting on the thermoelectric heating element (20) with electrical energy when the value (W2) is indicative of an activated internal combustion engine (4).

8. The control device (8) according to claim 6 or 7, wherein the catalytic conversionDevice is NO_xA catalytic converter (10) is stored.

9. The control device (8) according to claim 6 or 7, wherein the catalytic converter is an SCR catalytic converter (14).

10. An exhaust-gas aftertreatment device (6) for purifying an exhaust-gas flow of an internal combustion engine (4) of a motor vehicle (2), the exhaust-gas aftertreatment device (6) having at least one catalytic converter, wherein the catalytic converter is assigned at least one thermoelectric generator (18), wherein the thermoelectric generator (18) is connected to the catalytic converter for the purpose of transferring thermal energy.

11. Exhaust gas aftertreatment device (6) according to claim 10, wherein the catalytic converter is provided with at least one thermoelectric heating element (20), wherein the thermoelectric heating element (20) is connected to the catalytic converter for transferring thermal energy.

12. The exhaust gas aftertreatment device (6) of claim 10 or 11, wherein the catalytic converter is NO_xA catalytic converter (10) is stored.

13. The exhaust gas aftertreatment device (6) according to claim 10 or 11, wherein the catalytic converter is an SCR catalytic converter (14).

14. A motor vehicle (2) having an exhaust gas aftertreatment device (6) according to one of claims 10 to 13.