DE102016009905A1 - Exhaust system of a motor vehicle with an air guide - Google Patents

Abstract

The invention relates to an exhaust system (1) with at least one air guide (23, 23a, 23b, 23c, 23d, 31, 38), in particular with at least one air baffle, for influencing an air flow acting at least on a part of the exhaust system, wherein the at least one Air guide (23, 23a, 23b, 23c, 23d, 31, 38) by means of an actuator (32) is adjustable, wherein by adjusting the Luftleitmittels (23, 23a, 23b, 23c, 23d, 31, 38), the air flow is variable. The heat dissipation of the exhaust system (1) is improved in that the actuator (32) has a body with a Formgedächnislegierung, by a change in temperature of the body, the air guide (23, 23a, 23b, 23c, 23d, 31, 38) is adjustable.

Description

The invention relates to an exhaust system of a motor vehicle having an air-guiding means according to the features of the preamble of claim 1. The invention relates in particular to an exhaust system with an exhaust gas condenser for obtaining a condensate from an exhaust gas stream of an internal combustion engine.

It is known to inject water into the intake tract of an internal combustion engine to increase performance. The evaporating water has a cooling effect and reduces the compression work. The injected into the air intake tract water causes by the applied heat of vaporization an effective intercooler and also allows internal cooling of the engine. Due to the colder combustion air and thus their higher density results in an increase in performance. The additional intercooling reduces the knock tendency in gasoline engines and opens up new possibilities for increasing or downsizing performance.

In order to avoid replenishment of a water tank by the user of a motor vehicle, it has already been proposed in the prior art to recover condensate from the exhaust gas flow of the internal combustion engine and to use this condensate, which is composed of water, for water injection. By recovering the water from the exhaust stream, regardless of refilling a water tank, a water feed is also suitable for a motor vehicle mass market.

In order to obtain condensate from the exhaust gas during condensation by condensation, the exhaust gas must be cooled at least below the dew point of approx. 53 ° C. It is advantageous to arrange the exhaust gas condenser under the vehicle as far back as possible in order to achieve a low exhaust gas temperature when entering the exhaust gas condenser. The exhaust gas condenser is preferably an exhaust gas-to-air heat exchanger, through which a part of the exhaust gas flows and is cooled by the ambient air flowing along the exhaust gas condenser during the drive.

From the generic DE 101 25 989 A1 For example, a method for cooling automobile exhaust gases in an exhaust gas heat exchanger through which the exhaust gases pass is known. The air flow of the ambient air which acts while driving in the underbody area of the motor vehicle is conducted at an acute angle of 20 to 70 ° C. with respect to the exhaust gas flow direction through an exhaust gas heat exchanger in order to selectively reduce the low temperature level of the incoming air to dissipate excess heat energy and to cool the exhaust gas flowing through use. Thereby, the temperature of the downstream catalyst device can be adjusted as needed. To increase the cooling capacity can be attached to the heat exchanger air guide. In addition, the air inflow can be controlled by adjusting the air guide by a controller. The air guiding means are designed as flaps or fins arranged close to the exhaust gas heat exchanger. The inclination of the slats with respect to the longitudinal direction results in a better flow through the exhaust gas heat exchanger. The lamellae are formed by a plurality of layers of a smooth or corrugated sheet, the lamellae are provided to increase turbulence with indentations or Versickungen. To increase the air flow, improve the flow behavior and increase the ground clearance, if necessary, the distance and / or the inclination of the slats with respect to the exhaust gas heat exchanger is adjusted as needed. In order to achieve optimum cooling, the lamellae are selectively activated individually or in groups as needed.

From the EP 2 993 437 A1 For example, a heat transfer tube having a plurality of circumferentially spaced ribs is known. The ribs extend in the longitudinal direction of the tube. The ribs are formed by U-shaped profiles which are each welded to the outside of the otherwise cylindrical tube. As a result, the surface available here for heat exchange is increased.

The weight and the size and thus the cost of the exhaust gas condenser are determined by the heat energy contained in the exhaust gas and thus also by the exhaust gas temperature when entering the exhaust gas condenser. The cooler the exhaust gas is at the inlet of the exhaust gas condenser, the smaller and lighter the exhaust gas condenser can be carried out. The prior art known air conduction are not yet optimally formed.

The invention is therefore based on the object to design the exhaust system such and further, so that the heat dissipation of the exhaust system is improved.

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

The exhaust system has at least one air guide for cooling the exhaust system namely the exhaust gas flow. The air guiding means is adjustable by means of an actuator. The actuator now has a body of a shape memory alloy. The body may be formed in particular as a wire. Molded-alloy bodies can assume two stable states through Temperature change can be converted into each other. The length of the body and the length of the wire changes. The body can be transferred by means of a change in temperature from a long form into a short form and back. The actuator has a body with a shape-memory alloy, wherein the air-conducting means is adjustable by a temperature change of the body. The adjustability of the air-guiding means allows a needs-based adaptation of the air mass flow required for cooling the exhaust system. One advantage is that there the drawbacks of an air resistance increase can be reduced to a minimum. The advantage of using a shape memory alloy actuator is that the actuator is very compact, lightweight, and allows great forces and can be tailored to the design requirements of the application.

The actuator for Luftleitmittelverstellung can be configured either active or passive. Active shape memory alloy actuators require electrical energy to generate heat necessary for deformation. The temperature increase is brought about in the active embodiment in that the body, in particular the wire, flows through current and is thereby heated. By changing the length large forces can be generated. As a result, electrically heated shape-memory alloy bodies are well suited as compact drives in actuators for adjusting air-conducting means. The body can be acted upon by a current, which can be heated by energizing the body and thus the employment or shape of the lube can be changed as needed by energizing.

In passive shape memory alloy actuators, heat from the environment of the actuator is utilized. When a passive shape memory alloy actuator is used, the shape memory alloy body is preferably deformable by the heat of the exhaust system. Similar to a thermostat, when the temperature threshold of the exhaust system or the ambient temperature is exceeded, a deformation of the actuator is triggered and thus an adjustment of the conductive agent. The body is arranged such that the body can be heated by the heat of the exhaust system and thereby deformed. This has the advantage that it can be dispensed with a current supply and the system is self-regulating.

The exhaust system extends at least partially below the bottom of the vehicle and can be partially flowed there by the wind. There, an exhaust gas condenser is now arranged, wherein the exhaust gas condenser can be flown with ambient air while driving. The air flow acting on the exhaust gas condenser can be changed by adjusting the at least one air guiding means.

In a preferred embodiment, the air guiding means below the bottom of the motor vehicle in the direction of travel and in the air flow direction or longitudinal direction of the vehicle is at least partially disposed in front of the exhaust gas condenser. The air guiding means is designed as an air guide plate arranged below the floor of the vehicle, wherein the angle of attack of the air guide plate relative to the arranged also below the bottom of the vehicle exhaust gas condenser by the actuator or a curvature of the air guide plate is changed by the actuator. In a rest position, the lube is arranged horizontally. In the rest position, the actuator is de-energized. In the energized position, the shape memory alloy body in particular shortens the shape memory alloy wire and preferably bends the air conduction upward, so that the air flowing in under the vehicle is directed upward toward the exhaust gas condenser. The air guide is arranged in a plane below the exhaust gas condenser. The elastic air baffle may in particular be arranged partially in the region of a tank. If the air baffle is rigidly formed, it can be rotated by the actuator about a pivot point.

Preferably, a bypass branches off upstream of the exhaust gas condenser in the exhaust system, wherein the bypass is arranged downstream of a catalytic converter and upstream of a muffler, wherein the muffler is arranged upstream of the exhaust gas condenser.

The exhaust system has at least one exhaust pipe with a non-cylindrical shape to increase the heat dissipation. At least one exhaust pipe has inner ribs and / or outer ribs for increasing the heat dissipation. Due to the non-cylindrical cross-sectional shape and / or the ribs, the heat dissipation can be increased.

In order to further increase the heat dissipation, the exhaust system may have transverse to the longitudinal direction of the vehicle extending portions. As a result, the length of the exhaust system is increased, thus also the distance to be covered by the exhaust gas flow, whereby more heat is released until the exhaust gas condenser is reached. The areas may extend in a zigzag pattern under the floor, whereby the areas are well flown by the driving air and thus better cooled.

There are now a variety of ways to design and further develop the exhaust system according to the invention in an advantageous manner. For this purpose, reference may first be made to the claims subordinate to claim 1. In the following, several preferred embodiments of the invention with reference to the drawing and the associated description explained in more detail. In the drawing shows:

1 2 is a schematic representation of an internal combustion engine with an intake system and an exhaust system, wherein the exhaust system can be flown with ambient air as required by means of an air-guiding means,

2 in a schematic representation of a plurality of embodiments of adjustable air guiding means with different pivot points,

3 in a schematic representation of an elastic air guiding means and a centrally deformable air guiding means,

4 in a schematic, side view of a motor vehicle with an elastic air guide and with an exhaust gas condenser,

5 in cross-section different exhaust pipes,

6 in a schematic plan view of another exhaust system, which is arranged in regions transverse to the longitudinal direction of the motor vehicle and thus transversely to the air flow, and

7 in a schematic plan view of another exhaust system, for the cooling air guide means are arranged in the region of a center tunnel.

In 1 is an exhaust system 1 , an internal combustion engine 2 as well as an intake system 3 to recognize a motor vehicle.

By means of the intake system 3 Air is the combustion engine 2 fed. The intake system 3 has an air filter 4 , an air filter 4 downstream compressor 5 an exhaust gas turbocharger 6 , one to the compressor 5 downstream throttle 7 and a charge air cooler 8th on.

From the intercooler 8th the sucked fresh air is in a suction pipe 9 of the internal combustion engine 2 directed. From the intake manifold 9 The sucked fresh air enters the combustion chamber 10 ,

The exhaust gas is the exhaust system 1 , preferably via an exhaust manifold 11 , a turbine 12 , as well as a catalyst 13 , a silencer 14 and an exhaust gas condenser 15 derived. The silencer 14 and the exhaust gas condenser 15 are by means of a bypass 16 bridgeable, including upstream of the muffler 14 an exhaust flap 17 is arranged.

With the exhaust flap 17 the exhaust gas mass flow through the exhaust gas condenser 15 controlled. The exhaust flap 17 is not directly in front of the exhaust gas condenser 15 arranged but in front of the muffler 14 , This reduces the risk that, at low ambient temperatures or unfavorable boundary conditions, condensation of the water contained in the exhaust gas upstream of the exhaust gas condenser 15 comes. At ambient temperatures below 0 degrees Celsius is thus a freezing of the condensed water, especially in the muffler 14 effectively avoided. The exhaust flap 17 is here from the exhaust gas condenser 15 arranged spatially separated and moved as far forward as possible, for example, here directly behind the catalyst 13 , In the control of the exhaust flap 17 can then be considered that at low ambient temperatures, the exhaust gas mass flow at the muffler 14 passed through and thereby the risk of clogging of the muffler 14 is prevented.

The exhaust gas condenser 15 is used for condensate recovery, the condensate one of a cleaning device 18 is fed and finally in a reservoir 19 is stored before there is water injection into the internal combustion engine 2 is used. By means of a pump 20 The condensate with the fuel becomes an emulsion at the site 21 mixed and in the suction tube 9 by means of the nozzle 22 injected.

In the following, various options are explained, such as the heat dissipation of the exhaust system 1 can be increased.

To increase the heat dissipation is now first an airlift 23 intended. Through the airlubber 23 is the corresponding at the exhaust system 1 passing air 24 If necessary, it is easier to stream into. The airlubber 23 is arranged adjustable for this purpose. In particular, the air guiding means 23 by means of an actuator 32 adjustable.

In 2 and 3 are shown very schematically several possibilities, the corresponding air conduction 23a to 23d for deflecting the air flow to the exhaust system 3 embody. In the 2 illustrated embodiment, the substantially rigid air guide 23a . 23b . 23c each at different pivot points 25a . 25b . 25c rotatably arranged. The fulcrum 25a is in the flow direction at the front end of the Luftleitmittels 23a educated. The fulcrum 25b is between the two ends of the louver 23b arranged approximately in the middle. The airlubber 23c is about a rear end seen in the flow direction, namely about the pivot point 25c arranged pivotally.

Furthermore, there is the possibility in addition to rotatable louvers also elastic or to use deformable airlubber, as in 3 is shown. In 3 is shown that the airlaid 23d is fixedly mounted or fixed at its front end substantially, but the rear end seen in the flow direction rear end elastically by an actuator (not shown here), spatially shown, can be deformed. In 3 is further shown that an air guide 23e is fixedly disposed at its front or at its rear end and, however, can be deformed in the middle by an actuator.

4 shows a highly schematic view of a motor vehicle 26 with front wheels 27 and rear wheels 28 , The silencer is very schematically below a floor 14 the exhaust system 1 as well as a tank 30 and an elastic air guiding means 31 arranged. The airlubber 31 is by means of an actuator 32 deformable. As a result, in each case more or less air to the corresponding behind and above the Luftleitmittels 31 arranged exhaust gas condenser 15 directed. The exhaust gas condenser 15 is here below the boot floor 33 arranged.

The actuator 32 comprises a body of a shape memory alloy. The actuator 32 is designed in particular as a shape-memory alloy wire. By means of the Formgedächnislegierungsdrahtes can now the air conduction 31 be bent upwards. The airlubber 31 is designed as a baffle plate. It can be seen that when the exhaust gas condenser 15 behind the tank 30 and the muffler 14 is arranged, the exhaust gas condenser 15 basically only a little air is flown. This can be achieved by using the airlubber 31 be significantly improved. However, since there are Bertriebszustände in which an additional heat dissipation of disadvantage, for example in winter, when there is a risk that the condensed water freezes, it makes sense to regulate the air mass flow and / or can control.

This is now with the actuator 32 in the form of a shape memory alloy wire possible. The actuator 32 is actively trained. The shape memory alloy wire can be traversed by a current. At rest, when the shape-memory alloy wire is de-energized, the louver is 31 horizontal. In the energized position, the shape-memory alloy wire shortens and bends the air-conduction agent 31 upward, so that the air flowing under the vehicle is directed upward. As a result, the exhaust gas condenser 15 additionally cooled.

In 5 are other possibilities represented the heat dissipation of the exhaust system 1 to increase. They are different cross-sectional shapes 34a to 34d and 35a to 35d shown. The design 34a shows the conventional cylindrical cross-sectional shape. It is possible to increase the surface area in relation to the volume or the cross-sectional area in that of this round cross-sectional shape 34a is deviated and an additional heat dissipation is generated by the thus enlarged surface. The cross-sectional shape 34b has an angular shape, in particular a rectangular, preferably a square shape. The cross-sectional shape 34c has a star shape with in particular four unspecified spikes. Furthermore, it is possible that instead of a single tube, several tubes are used, so that a cross-sectional shape in the form of a matrix 34d results. The cross-sectional shapes 35a and 35b characterized by the fact that the surfaces by internal ribs 36a or outer ribs 36b are enlarged.

In the in 6 illustrated exhaust system 1 It can be seen that these sections are inclined, in particular transversely to the longitudinal direction of the vehicle extending areas 37a . 37b . 37c having. The areas 37a to 37c are arranged in a zigzag shape. As a result, the length of the exhaust system is increased, thus also the distance covered by the exhaust gas flow. Furthermore, the exhaust system in the areas 37a to 37c from a larger airflow 24 flowed on, so that the heat dissipation is increased.

In the 7 illustrated exhaust system 1 has additional airflow 38 in the area of the unspecified center tunnel on. The airlubber 38 are in particular by means of the Formgedächnislegierungaktuatoren 32 adjustable.

LIST OF REFERENCE NUMBERS

1

exhaust system

2

internal combustion engine

3

intake system

4

air filter

5

compressor

6

turbocharger

7

throttle

8th

Intercooler

9

suction tube

10

combustion chamber

11

exhaust manifold

12

turbine

13

catalyst

14

silencer

15

flue gas condenser

16

bypass

17

exhaust flap

18

cleaning device

19

reservoir

20

pump

21

emulsion place

22

jet

23

air guide

23a

air guide

23b

air guide

23c

air guide

23d

air guide

23e

air guide

24

air

25a

pivot point

25b

pivot point

25c

pivot point

26

motor vehicle

27

front

28

rear wheel

29

ground

30

tank

31

air guide

32

actuator

33

Boot floor

34a

Cross-sectional shape

34b

Cross-sectional shape

34c

Cross-sectional shape

34d

Cross-sectional shape

35a

Cross-sectional shape

35b

Cross-sectional shape

36a

inner ribs

36b

outer ribs

37a

obliquely arranged areas of the exhaust system

37b

obliquely arranged areas of the exhaust system

37c

obliquely arranged areas of the exhaust system

38 air conduction

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

• DE 10125989 A1 [0005]
• EP 2993437 A1 [0006]

Claims (10)

Exhaust system ( 1 ) with at least one air-conveying means ( 23 . 23a . 23b . 23c . 23d . 31 . 38 ), in particular with at least one air guide plate, for influencing an air stream acting at least on a part of the exhaust system, wherein the at least one air guiding means ( 23 . 23a . 23b . 23c . 23d . 31 . 38 ) by means of an actuator ( 32 ) is adjustable, whereby by adjusting the Luftleitmittels ( 23 . 23a . 23b . 23c . 23d . 31 . 38 ) the air flow is variable, characterized in that the actuator ( 32 ) a body with a shape memory alloy ( 23 . 23a . 23b . 23c . 23d . 31 . 38 ), wherein by a change in temperature of the body, the air guiding means ( 23 . 23a . 23b . 23c . 23d . 31 . 38 ) is adjustable. Exhaust system according to claim 1, characterized in that an exhaust gas condenser ( 17 ) is present, wherein the exhaust gas condenser ( 15 ) with ambient air during driving is flowed, wherein the exhaust gas on the condenser ( 15 ) acting air flow by adjusting the at least one Luftleitmittels ( 23 . 23a . 23b . 23c . 23d . 31 . 38 ) is changeable. Exhaust system according to claim 2, characterized in that the air guiding means ( 23 . 23a . 23b . 23c . 23d . 31 . 38 ) than under a floor ( 29 ) of the vehicle arranged air guide plate is formed, wherein the angle of attack of the air guide plate relative to the likewise under the ground ( 29 ) of the vehicle arranged exhaust gas capacitor ( 15 ) by the actuator ( 32 ) or a curvature of the air baffle by the actuator ( 32 ) is changeable. Exhaust system according to one of the preceding claims, characterized in that the body is designed as a wire. Exhaust system according to one of the preceding claims, characterized in that the body can be acted upon by a current, which can be heated by energizing the body and thereby the shape of the body is variable. Exhaust system according to one of the preceding claims, characterized in that the body is arranged such that the body by the heat of the exhaust system ( 1 ) and thus deformable. Exhaust system according to one of the preceding claims, characterized in that a bypass ( 16 ) upstream of the exhaust gas condenser ( 15 ) in the exhaust system ( 1 ), whereby the bypass ( 16 ) downstream of a catalyst ( 13 ) and upstream of a muffler ( 14 ), wherein the silencer ( 14 ) upstream of the exhaust gas condenser ( 15 ) is arranged. Exhaust system according to one of the preceding claims, characterized in that the exhaust system has at least one exhaust pipe with a non-cylindrical shape to increase the heat dissipation. Exhaust system, characterized in that at least one exhaust pipe inner ribs ( 36a ) and / or outer ribs ( 36b ) have to increase the heat dissipation. Exhaust system according to one of the preceding claims, characterized in that the exhaust system ( 1 ) areas extending transversely to the longitudinal direction of the vehicle ( 37a . 37b . 37c ) having.

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