DE102013000247A1 - Exhaust gas system for internal combustion engine e.g. diesel engine of motor car, has screen-like filter element that is formed between motor-side end and exhaust gas recirculation (EGR) valve - Google Patents

Abstract

The exhaust system (14) has a main exhaust path (16) in which a motor-side end (18) for connection to the internal combustion engine (12) and a outlet end (20) for discharging exhaust gases from the internal combustion engine to the environment are extended. A fork (23) from the main exhaust path and an inlet-side end (24) for connection to an air supply (26) of the engine is provided in an exhaust gas recirculation (EGR) path (22). An EGR valve (28) is provided in the EGR path. A screen-like filter element (30) is formed between the motor-side end and the EGR valve. An independent claim is included for a motor car.

Description

The invention relates to an exhaust system for an internal combustion engine. The exhaust system has a main exhaust path, which extends between an engine-side end for connection to the internal combustion engine and an outlet end for discharging exhaust gases of the internal combustion engine to the environment. Furthermore, the exhaust system has an EGR path which extends between a branch from the main exhaust path and an inlet end for connection to an air supply of the internal combustion engine. The exhaust system includes an EGR valve in the EGR path and a mesh-like filter element between the engine-side end and the EGR valve. The sieve-like filter element is designed to retain solids. In addition, the invention relates to a motor vehicle with the exhaust system.

In order to reduce the emission of internal combustion engines and to comply with current exhaust gas legislation, exhaust gas recirculation (EGR) systems are used. To meter in a recirculated exhaust gas flow to an intake air of the internal combustion engine, an EGR valve is used. To protect the EGR valve, as well as the internal combustion engine and its air supply from contamination, in particular by soot (or soot particles), a filter element upstream of the EGR valve can be used. At this filter element settle during operation of the internal combustion engine soot particles.

The US 2001/0042372 A1 discloses a high pressure EGR system that includes an EGR filter system, an EGR cooler, and an EGR valve from an exhaust tract to an intake tract. The EGR filter system includes a particulate filter and a non-thermal plasma generator disposed upstream of the particulate filter. The plasma generator generates NO ₂ , which is used for regeneration of the particulate filter.

The US 6,625,978 B1 discloses an EGR system having a particulate filter at the beginning of an EGR passage. The particulate filter of the EGR system is regenerated by means of waste heat from an exhaust aftertreatment component which serves to purify the main exhaust stream. In addition, the particulate filter comprises an electrical heating element. The exhaust gas flowing through the particulate filter flows to the particulate filter through an EGR cooler and an EGR valve.

The invention is based on the object to provide an exhaust system with a simplified structure available.

This object is achieved by an exhaust system with the features of claim 1.

The exhaust system according to the invention for an internal combustion engine has a main exhaust path, which extends between an engine-side end for connection to the internal combustion engine and an outlet end for discharging exhaust gases of the internal combustion engine to the environment. The exhaust system further includes an EGR path extending between a branch from the main exhaust path and an inlet side end for connection to an air supply of the internal combustion engine. The exhaust system includes an EGR valve in the EGR path and a mesh-like filter element between the engine-side end and the EGR valve. The sieve-like filter element is designed to retain solids. Characteristically, the sieve-like filter element is designed for electrical heating.

The filter element is designed such that an exhaust gas flowing through the EGR path during operation of the internal combustion engine flows through the filter element. During operation of the internal combustion engine, soot (or its soot particles), that is to say soot particles, which can be burnt off by means of the electrical heating, settles on the filter element - the filter element is regenerated, ie, cleaned. Thus, the sieve-like filter element is configured for electrical heating, that the sieve element reaches a predefined temperature by means of electric heating, which corresponds to at least a minimum temperature for the oxidation of soot particles. This is due to the higher soot emissions of particular advantage when the internal combustion engine is a diesel engine. By electrically heating the filter element, a flexibly feasible and optimally controllable regeneration of the filter element is made possible.

Preferably, the electrical heating comprises an electrical resistance heating element, by means of which the filter element is electrically heated. Electric resistance heating elements are inexpensive and proven components to heat the filter element.

In particular, the electrical resistance heating element is arranged upstream of the filter element. Thus, the electrical resistance heating element heats an exhaust gas stream, which then flows through the filter element and thereby heated.

It is preferably provided that the electrical resistance heating element is thermally conductive connected to the filter element. Due to the thermally conductive compound, the resistance heating element directly heat the filter element and does not first heat an exhaust stream, which then in turn heats the filter element. Thus, an increased efficiency of the electrical heating is realized by the thermally conductive compound.

According to a preferred embodiment of the invention it is provided that the filter element is formed as an electrical resistance heating element. Thus, the filter element itself (or even a part of the filter element) is the resistance heating element and can be acted upon for heating with electricity. In this case, a material of the filter element is directly traversed by current and heats up due to its electrical resistance.

Preferably, the sieve-like filter element is essentially made of a metal. By means of a metal as material for the filter element, the sieve-like structures can be realized under the expected exhaust gas temperatures and have a desired durability. In addition, metal is suitable for the realization of the resistance heating element.

Preferably, the filter element is formed substantially two-dimensional. In particular, the expansion of the filter element is perpendicular to an exhaust gas flow direction at least 5 times, preferably at least 10 times, in particular 20 times its extent in the exhaust gas flow direction.

Preferably, the sieve-like filter element has a mesh-like structure, in particular formed by a plurality of wires. Further preferably, the sieve-like filter element to a fabric or a perforated plate. The mesh size, the distance of fabric threads of the fabric or the size of the perforations is preferably at most 0.5 mm, further preferably at most 0.25 mm, in particular at most 0.15 mm. This achieves a desired filtering effect. Preferably, the mesh size, the distance of fabric threads or the size of the perforations is at most 0.5 mm and at least 0.01 mm, further preferably at most 0.25 mm and at least 0.025 mm, in particular at most 0.15 mm and at least 0.05 mm (50 μm to 150 μm). This provides a good compromise between filter action and flow resistance. The mesh size indicates the size of the openings in the sieve-like filter element. By means of the mesh size, it can be determined above which size of the soot particles the soot particles are to be screened out. The mesh size can also be chosen so large that only larger soot particles are screened out, whereby the flow resistance through the filter element decreases.

It is preferably provided that the filter element is arranged in the EGR path. As a result of this embodiment, the filter element merely filters the exhaust gas flow to be recirculated, the residual exhaust gas stream thus experiences no flow resistance through the filter element.

According to a preferred embodiment of the invention it is provided that the exhaust system between the engine-side end and the filter element comprises a turbine of a turbocharger, a catalyst and / or a particulate filter in the main exhaust path. When using a diesel engine as an internal combustion engine, the catalyst used is preferably an oxidation catalytic converter and, as a particle filter, a diesel particulate filter (DPF). When driving, the particle filter is loaded with soot particles. So that an exhaust gas pressure level (upstream of the particulate filter) does not rise too far, the particulate filter is regenerated continuously or periodically. For this purpose, at a sufficient temperature, a thermal oxidation of the soot particles is carried out with oxygen. The presence of a sufficient temperature can be effected in a known manner by influencing motor parameters. Both in the regeneration of the particulate filter, as well as in a conversion of pollutants in the catalyst heat is released. Due to this released heat, the exhaust gas stream is heated, whereby, depending on the operating state, a partial or complete cleaning of the sieve-like filter element is effected. This reduces energy consumption for the electric heating. Since the turbine of the turbocharger is disposed between the filter element and the engine-side end, it is a low-pressure EGR system.

Preferably, the exhaust system comprises a control device, wherein the control device is adapted to control the electrical heating of the filter element in response to a differential pressure upstream and downstream of the filter element. In particular, the electrical heating takes place at a differential pressure greater than a differential pressure threshold. Thus, a needs-based cleaning of the filter element is effected.

Furthermore, a motor vehicle is provided which comprises the exhaust system according to the invention and an internal combustion engine, which is connected on the outlet side with the engine-side end of the exhaust system and on the inlet side with the inlet-side end of the exhaust system fluidically.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

1 a schematic partial view of a motor vehicle,

2 a schematic representation of a filter element and a resistance heating element,

3 a schematic representation of a designed as a resistance heating element filter element,

4 an isometric partial representation of a motor vehicle,

5 an isometric partial representation of an exhaust system,

6 a motorized heating of the filter element,

7 an improved, motorized heating of the filter element and

8th an electric heating of the filter element.

1 schematically shows a partial view of a motor vehicle 10 , The car 10 includes an internal combustion engine 12 , z. B. a diesel engine and an exhaust system 14 , The exhaust system 14 has a main exhaust path 16 on. The main exhaust path 16 extends between an engine-side end 18 , which (by means of an exhaust manifold 48 ) to the internal combustion engine 12 is connected, and an outlet end 20 , which for the discharge of exhaust gases of the internal combustion engine 12 serves to the environment. The exhaust system 14 also has an EGR path 22 (for exhaust gas recirculation), which is located between a branch 23 from the main exhaust path 16 and an inlet end 24 extends. The inlet end is connected to an air supply 26 the internal combustion engine 12 connected. The exhaust system 14 also includes in the EGR path 22 an EGR valve 28 , Furthermore, the exhaust system includes 14 between the engine end 18 and the EGR valve 28 (In the example shown also in the EGR path) a sieve-like filter element 30 , The sieve-like filter element 30 is designed to retain solids. For example, the filter element 30 a closely meshed metal screen. The filter element 30 serves as a protective filter for the EGR valve 28 and the internal combustion engine 12 , as well as for the air supply 26 , The filter element 30 thus prevents penetration of larger particles, which contamination of the EGR valve 28 and cylinders of the internal combustion engine 12 can cause.

The sieve-like filter element 30 is equipped for electric heating. In other words, the exhaust system 14 for electrically heating the filter element 30 set up. For this purpose, upstream of the filter element 30 and / or heat-conducting with the filter element 30 connected, an electrical resistance heating element 31 be provided. Furthermore, the filter element 30 as an electrical resistance heating element 31 be formed, whereby the filter element 30 even the task of the resistance heating element 31 takes over. The filter element 30 can therefore be supplied directly with electricity, causing it to heat due to its electrical resistance.

For controlling the electrical heating of the filter element 30 can the exhaust system 14 a control device 32 include, which next to the filter element 30 z. B. also with a lambda probe 34 , z. B. a broadband lambda probe 34 and a NO _x sensor 36 can be connected.

In the main exhaust path upstream of the filter element 30 can a particle filter 38 and a catalyst 40 be arranged. In addition, in the main exhaust duct 16 upstream of the filter element 30 a turbine 42 be arranged a turbocharger. The turbocharger includes next to the turbine 42 another wave 44 , by means of which a compressor 46 mechanically connected. The compressor 46 is part of the air supply 26 the internal combustion engine 12 and downstream of the inlet end 24 arranged. In addition, the compressor 46 via an intake manifold 50 with the internal combustion engine 12 connected. Because the EGR path 22 in the case shown is arranged on the low pressure side of the turbocharger, it is also called a low pressure EGR system.

The internal combustion engine 12 produces soot particles of different sizes during operation. The particle filter 38 has the task, the soot particles from the exhaust stream of the internal combustion engine 12 to filter. However, the particle filter has 38 In practice, usually a slip (particle slippage), whereby a small proportion of the soot particles, the particulate filter 38 happens. To the EGR valve 28 To protect against contamination by especially larger soot particles, so soot particles or soot, filters the filter element 30 these soot particles in the EGR path 22 from the exhaust stream. The soot particles are thus deposited on the filter element 30 which reduces its permeability in operation increasingly.

Also, the permeability of the particulate filter 38 worsens with increasing soot Loading the particle filter 38 why the particle filter 38 is regenerated continuously or only when needed. This is done for example by means of a targeted influencing engine operating parameters, whereby the exhaust gas temperature before entering the particle filter 38 is raised and also the particulate filter 38 heated. After exceeding a minimum temperature for the oxidation of the soot particles, the soot particles burn in the particulate filter 38 , whereby the soot loading of the particulate filter 38 sinks. As a result of this exothermic combustion, the exhaust gas temperature also rises downstream of the particle filter 38 and thus also heats the filter element 30 , As a result, as a side effect of the regeneration of the particulate filter 38 also the filter element 30 partially or completely regenerated.

Should this described motor regeneration not sufficient regeneration quality of the filter element 30 lead, comes the electric heating of the filter element 30 used for its regeneration. The electrical heating of the filter element 30 can also be used, for example, when a regeneration of the particulate filter 38 (still) not necessary or intended.

The electrical heating of the filter element 30 takes place according to a preferred embodiment of the invention as follows:
First, the controller recognizes 32 a need for regeneration of the filter element 30 , For this purpose, the control unit 32 an increase in a differential pressure upstream and downstream of the filter element 30 (EGR filter differential pressure). The regeneration of the filter element 30 takes place, for example, at a differential pressure greater than a differential pressure threshold.

For electrical heating and thus regeneration of the filter element 30 sets the controller 30 a current flow through the resistance heating element 31 in progress, which heats up due to its electrical resistance. This will result in the filter element 30 heated to a sufficient temperature for oxidation of the soot particles, whereby the filter element 30 Burn off accumulated soot particles. Since the sieve-like filter element has only a very small thickness, this is cleaned by the electric heating (or support) very efficiently and quickly from soot deposits.

The described event-controlled electrical regeneration leads to a significantly higher safety of the regeneration quality of the filter element 30 , Various possible carrier types, which for the diesel particulate filter 38 come into question, can cause a different levels of particle slippage (soot slippage). Even with different types of support can be maintained safely by the invention, a required Regenerationsgüte. Especially with an addition of critical driving conditions, this improved regeneration quality is of significant advantage.

2 shows a schematic representation of a filter element 30 and a resistance heating element 31 , At least the filter element 30 is substantially two-dimensional, whereby its extension in the exhaust gas flow direction with respect to its extension transverse to the exhaust gas flow direction is very small. The filter element 30 has a plurality of meshes and can - as shown - have substantially the shape of a disc. By varying the mesh size, the filtration of the exhaust gas flow can be influenced.

3 shows a schematic representation of a resistance heating element 31 formed filter element 30 , Even as a resistance heating element 31 trained filter element 30 may have a plurality of stitches, not shown, or a cross-over structure. It is also conceivable that only a part of the filter element 30 as a resistance heating element 31 is formed, for. B. by only individual wires are supplied with power.

The in the 2 and 3 imaged electrical conductors (eg, wires) of the resistance heating element 31 (or the filter element 30 in 3 ) can also have a form of wavy lines, which are arranged offset in particular parallel to each other to extend their conductor length.

4 shows an isometric partial representation of a motor vehicle 10 , The individual elements have already been discussed in the preceding description of the figures, some in 1 apparent components, including the internal combustion engine 12 and a connection channel between two terminals 52 of the EGR valve 28 and the air supply 26 are not shown in the interest of clarity. The catalyst 40 and the particulate filter 38 are by means of a space-saving shaped exhaust duct 54 connected with each other. The illustrated exhaust system, or the illustrated low-pressure EGR system is suitable, inter alia, for use in the so-called "modular transverse modular system".

5 shows an isometric partial representation of the in 4 apparent exhaust system 14 , wherein the components in the main exhaust path 16 upstream of the NOx sensor 36 and the components in the EGR path 22 downstream of the filter element 30 are not shown. As a result, a possible construction of the sieve-like filter element 30 seen. Accordingly, the filter element 30 a carrier structure 58 with a variety of webs and a screen applied to it 56 include. The support structure 58 has the purpose of the fine mesh screen 56 to support. In addition, between the sieve 56 and the support structure 58 another supporting material may be arranged which is stronger than the sieve 56 is trained.

6 to 8th show respective courses of temperatures T over time t. In each of these figures are seven temperature curves 62 the sieve-like filter element 30 shown. Each of the seven temperature gradients 62 sets a temperature profile 62 the sieve-like filter element 30 at a different location of the filter element 30 represents.

In detail shows 6 a motorized heating of the filter element 30 , Except for the seven temperature gradients 62 the sieve-like filter element 30 is also a temperature history 60 in front of the particle filter 38 , ie immediately upstream of the particle filter 38 shown. The temperature profile 60 approaching from a common starting point for the temperature gradients 60 . 62 to a plateau whose temperature value is above a minimum temperature for the oxidation of soot particles. It can be seen that the temperature gradients 62 the sieve-like filter element 30 in this case with a certain temperature difference the temperature profile 60 consequences. Thus, a regeneration of the filter element 30 (if at all) only partially given.

7 shows in contrast to 6 an improved, motorized heating of the filter element 30 , It can be seen that the temperature gradients 62 the temperature profile 60 Already much better follow, so less of the temperature profile 60 differ.

As a result, at least in some places of the filter element 30 a regeneration of the filter element 62 given.

8th shows the temperature curves 62 in an inventive electrical heating of the filter element 30 , Again starting from a common starting temperature are the seven temperature gradients 62 almost identical due to the electrical heating. The small deviations between the seven temperature gradients 62 result z. B. from different heat capacities at different points of the filter element 30 or from different flow rates of the exhaust gas flow through the filter element 30 , It's the temperature gradients 62 It can be seen that, due to the electrical heating, starting from the common starting temperature, a steep rise up to a predefined temperature can be achieved. The predefined temperature corresponds at least to the minimum temperature for the oxidation of soot particles, ie in particular greater than 600 ° C. After reaching the predefined temperature, this can be kept constant over a desired period of time, for. B. to a desired regeneration quality of the filter element 30 is reached. This can be z. B. also by means of a, in the control unit 32 implemented temperature control can be realized. After regeneration, the electric heating can be stopped, causing the temperature gradients 62 each fall to a, determined by an exhaust gas temperature.

In summary, it can be stated that by means of the electrical heating of the filter element 30 in an energy-efficient and simple manner, a desired regeneration quality of the filter element 30 can be achieved. In addition, greater safety is achieved even in critical driving profiles and in component variations.

LIST OF REFERENCE NUMBERS

10

motor vehicle

12

Internal combustion engine

14

exhaust system

16

Main exhaust path

18

engine-side end

20

outlet end

22

EGR path

23

diversion

24

inlet end

26

air supply

28

AGR valve

30

sieve-like filter element

31

electrical resistance heating element

32

control device

34

lambda probe

36

NOx sensor

38

particulate Filter

40

catalyst

42

turbine

44

wave

46

compressor

48

exhaust manifold

50

intake manifold

52

connection

54

exhaust duct

56

scree

58

support structure

60

Temperature profile in front of the particle filter

62

Temperature profile of the sieve-like filter element

t

Time

T

temperature

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 2001/0042372 A1 [0003]
• US 6625978 B1 [0004]

Claims (10)

Exhaust system ( 14 ) for an internal combustion engine ( 12 ), the exhaust system ( 14 ) a main exhaust path ( 16 ), which extends between a motor-side end ( 18 ) for connection to the internal combustion engine ( 12 ) and an outlet end ( 20 ) for discharging exhaust gases of the internal combustion engine ( 12 ) extends to the environment, and the exhaust system ( 16 ) also an EGR path ( 22 ), which extends between a branch ( 23 ) from the main exhaust path ( 16 ) and an inlet end ( 24 ) for connection to an air supply ( 26 ) of the internal combustion engine ( 12 ), wherein the exhaust system ( 14 ) in the EGR path ( 22 ) an EGR valve ( 28 ) and between the engine end ( 18 ) and the EGR valve ( 28 ) a sieve-like filter element ( 30 ), designed to retain solids, characterized in that the sieve-like filter element ( 30 ) is set up for electrical heating. Exhaust system according to claim 1, wherein the electric heating comprises an electrical resistance heating element ( 31 ), by means of which the filter element ( 30 ) is electrically heated. Exhaust system according to claim 2, wherein the electrical resistance heating element ( 31 ) with the filter element ( 30 ) is thermally conductive connected. Exhaust system according to claim 1, wherein the filter element ( 30 ) as an electrical resistance heating element ( 31 ) is formed. Exhaust system according to one of the preceding claims, wherein the sieve-like filter element ( 30 ) is essentially made of a metal. Exhaust system according to one of the preceding claims, wherein the filter element ( 30 ) is formed substantially two-dimensionally. Exhaust system according to one of the preceding claims, wherein the filter element ( 30 ) in the EGR path ( 22 ) is arranged. Exhaust system according to one of the preceding claims, wherein the exhaust system between the engine-side end ( 18 ) and the filter element ( 30 ) a turbine ( 42 ) of a turbocharger, a catalyst ( 40 ) and / or a particulate filter ( 38 ) in the main exhaust path ( 23 ). Exhaust system according to one of the preceding claims, wherein the exhaust system comprises a control device ( 32 ), wherein the control device is adapted to the electrical heating of the filter element ( 30 ) depending on a differential pressure upstream and downstream of the filter element ( 30 ) to control. Motor vehicle ( 10 ), comprising the exhaust system ( 14 ) according to one of the preceding claims and an internal combustion engine ( 12 ), which on the outlet side with the engine-side end of the exhaust system ( 18 ) and inlet side with the inlet end ( 24 ) of the exhaust system ( 14 ) is fluidically connected.

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