DE10228619A1 - Exhaust pipe for the exhaust system of a motor vehicle - Google Patents

Abstract

In an exhaust pipe (1) for the exhaust system of a motor vehicle, the exhaust pipe, which leads between an exhaust gas-generating internal combustion engine and an exhaust gas into the environment, in particular between a three-way catalytic converter near the engine and a NO¶x¶ absorber arranged in front of the exhaust pipe If the size is small, the temperature of the exhaust gas emerging from the pipe should be able to be optimally controlled. The exhaust pipe has an inner pipe (2) which conducts the exhaust gas (AG) and a second pipe (3) which surrounds the inner pipe (2) at a distance and which forms an annular gap (4) which conducts an exhaust gas (AG) with the inner pipe (2). The annular gap (4) can be blocked by means of a flap (14). The pivot axis (13) of the flap (14) is arranged along the inner tube wall (15). In the pivoting area of the flap (14) there is a passage opening (12) in the inner tube wall (15) for the exhaust gas of the annular gap (4), the flap (14) between a blocking position of the passage opening (12) and a blocking position of the inner ear (2 ) including intermediate positions is pivotable.

Description

The invention relates to an exhaust pipe for the exhaust system of a motor vehicle, the exhaust pipe which transfers an exhaust gas-producing internal combustion engine and an exhaust gas into the environment, and here in particular between a three-way catalytic converter near the engine and a NO _x adsorber which is located in front of the exhaust pipe. is arranged. The exhaust pipe has an exhaust pipe which conducts exhaust gas and a second pipe which surrounds the inner pipe at a distance and which forms an exhaust gas-conducting annular gap with the inner pipe, the annular gap being lockable by means of a flap.

To reduce the NO _x emissions of direct-injection gasoline engines, for example, cooled exhaust gas recirculation systems, such as those from the DE 19841927 A1 are known, or catalysts with a NO _x adsorber used. The use of catalysts requires a certain temperature window for the exhaust gases. A conversion of the pollutant components such as hydrocarbon (HC), carbon monoxide (CO) and nitrogen oxides (NO _x ) into the compounds carbon dioxide (CO ₂ ), nitrogen (N ₂ ) or water ( H ₂ O) instead. Reaching the light-off temperature after the cold start can be significantly shortened, for example, by air-gap-insulated exhaust manifolds or exhaust pipes. Although rapid heating of the catalytic converter is achieved in this way, temperatures can arise during continuous operation, in particular in high-load or high-speed operation, that the catalytic converter and in particular the thermally sensitive NO _x adsorber are permanently damaged and are therefore no longer effective , In order to bring the NO _x adsorber up to operating temperature as quickly as possible and to set and maintain the temperature within the desired temperature window of 250–450 ° C, the hot exhaust gas that emerges from the engine must be insulated as well as possible in the start-up phase. be cooled during longer operation.

Exhaust systems are known which solve this problem in that the exhaust gas flows through a system with a plurality of parallel tubes. Some of the pipes are thermally insulated and some are not. The exhaust gas is cooled by ambient air in the non-insulated pipes. The control of the proportion of the exhaust gases that flow through the insulated or the non-insulated pipes is carried out either by a plurality of actuators or by omitting actuators, taking advantage of the fact that with increasing the exhaust gas velocity, a larger part of the exhaust gases through the non-insulated pipes flows like in the US 5,979,159 described. The known multi-channel system with parallel tubes requires a relatively large amount of space.

There are also exhaust systems with air-gap-insulated exhaust pipes. From the DE 198 54 095 A1 a device for the aftertreatment of the exhaust gases of internal combustion engines with an exhaust gas line is known, in which a separate line is integrated and thus an annular gap to the outer tube is formed. On the input side, the annular gap, but not the separate line, is closed by a flap. For this purpose, a corresponding recess should be provided in the flap. When the flap is closed, the exhaust gas flows in an air-gap-isolated manner only through the separate line. When the flap is opened, most of the exhaust gas flows into the annular gap due to the lower flow resistance and is cooled by ambient air.

The invention is based on this the task is based on an exhaust pipe for an exhaust system mentioned type so that the temperature is small of the exhaust gas emerging from the pipe can be optimally controlled.

This task is accomplished by means of a Exhaust pipe with the features of claim 1 solved. advantageous Further developments are described in the subclaims.

The core idea of the invention is by means of a flap as an adjusting means either the inner tube against flow through the To block the exhaust gas or the annular gap from flowing through the exhaust gas, intermediate positions in the pivoting area of the flap are also possible. For this purpose, the pivot axis of the flap is along the circumferential direction arranged the inner tube wall. The flap surface is cut so that in the locked position for the inner tube covers the entire cross section of the inner tube. A passage opening is in the pivoting area of the flap the pipe wall for the introduction or discharge of the exhaust gas into or out of the annular gap intended. To prevent the exhaust gas from entering or exiting or restrict this passage opening is blocked by means of the flap which is then pivoted.

The advantage of the invention is that the flap as the active adjusting means can be used to set precisely whether and in what amount the exhaust gas flows through the inner tube or the annular gap. As a result, the optimal working temperature of the NO _x adsorber can be set. Due to the intermediate positions, exact temperature control of the entire exhaust gas emerging is possible in all operating states. With the proposed multi-channel system, which is very compact and effective, the desired exhaust gas temperature window can be optimally regulated. The control of the flap can be selected according to individual requirements.

In order to achieve a complete blocking effect of the passage opening, the flap must have at least the size of the passage opening. If the flap area is larger than the passage area, the flap comes into contact with the inner tube wall. Already shows in this state the flap only has a slight exhaust gas back pressure compared to gas flowing past.

The exhaust back pressure can also be minimized by moving the pivot axis of the flap into the inner tube wall is integrated and the flap area corresponds to the passage area. Then closes the flap is flush when locked with the inner tube wall. Due to the flush conclusion, this can Exhaust gas when the opening is closed Flow through the inner tube without obstacle.

For a complete blocking effect of the inner tube to achieve, the flap has the cross-sectional shape of the inner tube on. Since the pivot axis is straight, the inner tube is adjusted in the swivel area by a corresponding flat wall formed. For reasons of simplification the inner tube can also be produced over its entire length be formed on a flat wall.

The flap with a straight swivel axis is preferably tongue-shaped or semicircular educated. It is preferably arranged on the inlet or outlet side. It is also possible that Flap for example in the middle of the inner tube in the overlap area from the second to the inner tube. To fulfill their Double function or double locking function of the flap only has to guaranteed be that the passage opening is arranged in the swivel area or effective area of the flap. Since the second tube is closed on the input or end side is streaming the exhaust gas on this side is not concentric in or out of the pipe, but in or out of the passage opening.

Because the exhaust gas passes through the annular gap the passage opening enters or exits, the second is recommended for better gas flow Pipe with a slant To connect the wall to the inner tube. The passage opening is within by the slant extended Pipe section arranged. This way the exhaust gas is at the inlet from one side aerodynamically in the Annular gap directed or aerodynamically at the outlet to one side of the inner tube towards the passage opening diverted. A connection with a right-angled wall would also be possible, but meant a higher one Pressure loss.

The proposed multi-channel system can consist of two pipes and the cooling of the exhaust gas in the annular gap due to ambient air unless the second pipe is too thick-walled. To the cooling effect of the exhaust gas flows through the annular gap, to increase the exhaust pipe is advantageously designed with three walls. The second Pipe is surrounded by a casing tube, which is between itself and the second tube a second, outer, annular gap forms. A coolant, for example water, flows through this annular gap. The annular gap described above thus becomes the inner annular gap.

Multi-walled duct systems of this type can be implemented inexpensively by means of internal high-pressure technology, and even complex-shaped cross sections, for example on the inner tube, can be easily formed. A particularly inexpensive manufacturing process is in the DE 40 19 899 C1 described what is also suitable for producing a three-walled tube. Then, in a first step, the inner annular gap is widened in a first tool. Then, in a second step, the outer annular gap is shaped in a second tool with the appropriate engraving.

The flap itself is easy to cut. For your arrangement there are no additional cast and mechanically machined along the inner tube wall casing necessary.

The invention is described below of exemplary embodiments illustrated in the drawings: Here demonstrate:

1 a longitudinal section of an exhaust pipe with the flap in the insulating position;

2 the same longitudinal section of an exhaust pipe with the flap in the cooling position;

3 the sectional view XX from 1 ;

4 the sectional view YY 1 ;

5 a schematic view of an exhaust pipe with a flap which is arranged on the outlet side.

1 shows the exhaust pipe 1 , which is integrated into an exhaust system (not shown) of a motor vehicle between an exhaust gas-generating internal combustion engine and an exhaust pipe that transports exhaust gas into the environment. Here, the exhaust gas first reaches a three-way catalytic converter via a manifold and, via an exhaust pipe, a NO _x adsorber arranged in front of the exhaust pipe. The exhaust pipe 1 as a multi-channel system includes an inner tube 2 as a direct connection between the three-way catalytic converter and the NO _x adsorber. The inner tube 2 is from a second pipe 3 surrounded, causing between the inner tube 2 and the second pipe 3 an inner annular gap 4 is formed. In addition is around the second pipe 3 an outer jacket tube 5 spaced apart, the resulting outer annular gap 6 is flowed through by a coolant KM, which through a feed (not shown) or discharge nozzle 7 enters or exits. These socks 7 are connected to a cooling unit (not shown).

In the embodiment shown, the second tube is 3 closed on the inlet side and with a sloping wall 8th to the outer wall 9 of the inner tube 2 connected. In addition, the second pipe 3 an oblique bleed 10 on. This will make an extended pipe section 11 on one side of the inner tube 2 educated. Within this extended pipe section 11 and in the area of overlap between the second tube 3 and the inner tube 2 is a passage opening 12 , here an inlet opening, for the exhaust gas AG in the inner annular gap 4 brought in. This passage opening 12 can also can be referred to as a recess or window. The shape of the passage opening 12 is from the 4 seen. The straight pivot axis 13 the control or switching flap 14 runs along the inner tube wall 15 and is in the example shown in the inner tube wall 15 integrated. 1 shows the flap 14 in the complete blocking position for the passage opening 12 , This corresponds to the preferred position in the starting phase of the engine, in which the exhaust gas gap is to be kept at a temperature insulated. 100% of the exhaust gas AG flows through the air-gap insulated inner tube 2 , In order to achieve a very quick start ("light often") of the NO _x adsorber, the inner tube is 2 thin-walled. It therefore absorbs little heat and heats up quickly, which is due to the insulation through the inner annular gap 4 is supported.

2 sets the cooling position of the flap 14 With the dash-dotted line is the pivoting area of the flap 14 shown, wherein the cooling position is already reached at a pivot angle less than 90 °. In this position, the exhaust gas AG only flows into the inner annular gap 4 and cools down in the outer annular gap 6 flowing coolant KM.

The section XX of the 1 shows 3 , from which it can be seen that the pivot axis 13 , the flap surface and the inner tube wall 15 lie in one plane. The straight flap end 16 is with a wave 17 connected, which is pivotable at the end in, for example, a plain bearing 18a . b is stored. At one end of the shaft 19 is a - here rod-shaped - actuator 20 welded, via which the pivoting angle of the flap can be adjusted. The control of the actuator 20 and thus the flap is variable and can be realized purely mechanically, pneumatically or also by a force-generating temperature sensor, such as a bimetal. The folding axis also offers itself as a location for a temperature measurement, since exhaust gas constantly flows around it. The bearings 18a . b are welded to the pipe walls ( 21 ).

The flap 14 itself is tongue-shaped, as from the 4 which shows the section YY of the 1 shows. It can be clearly seen that the flap area corresponds to the area of the passage opening. The cut 22 the flap 14 enables a flush immersion of the flap 14 into the average opening 12 , The second pipe 3 is, starting approximately at the end of the passage opening 12 all around, to the outer wall of the inner tube 2 welded on ( 23 ).

With the help of 5 becomes an alternative arrangement of the passage opening 12 ' shown at the end of the exhaust pipe. The second pipe 3 binds at the end to the inner tube 2 on. The dual function of the flap 14 the pivot axis is to enable 13 in the flow direction in front of the passage opening 12 ' arranged. The cut 22 the flap 14 is approximately semicircular, which is the cross section of the inner tube 2 equivalent. That through the inner tube 2 flowing exhaust gas AG is caused by standing exhaust gas in the inner annular gap 4 thermally insulated. This example shows how the diagonal connection of the second pipe works 3 to the inner tube 2 clear. The exhaust gas AG is aerodynamically favorable from the complete annular gap cross section at the oblique gate 10 along the inner tube outside in the part below the opening 12 ' out and then radially emerges from the passage opening 12 ' into the inner tube 2 out.

1

exhaust pipe

2

inner tube

3

second pipe

4

internal annular gap

5

casing pipe

6

outer annular gap

7

Ausführstutzen

8th

sloping wall

9

outer wall of the inner tube

10

oblique gate

11

extended pipe section

12

Passage opening (12 'on the outlet side)

13

pivot

14

flap

15

internal tube wall,

16

flap end

17

wave

18a, b

bearings

19

shaft end

20

actuator

21

WeldingSpot

22

cut the flap

23

Weld

KM

coolant

AG

exhaust

Claims (8)

Exhaust pipe ( 1 ) for the exhaust system of a motor vehicle, which is arranged between an exhaust gas-producing internal combustion engine and an exhaust pipe that transports exhaust gas into the environment, in particular between a three-way catalytic converter near the engine and a NO _x adsorber arranged in front of the exhaust pipe, with an exhaust gas ( AG) conductive inner tube ( 2 ) and the inner tube ( 2 ) with a second pipe surrounding it ( 3 ) with the inner tube ( 2 ) an exhaust gas (AG) conductive ring gap ( 4 ) forms by means of a flap ( 14 ) can be locked, characterized in that the pivot axis ( 13 ) the flap ( 14 ) along the inner tube wall ( 15 ) is arranged and that in the pivoting area of the flap ( 14 ) a passage opening ( 12 ) in the inner tube wall ( 15 ) for introducing or discharging exhaust gas into or out the annular gap ( 4 ) is provided, the flap ( 14 ) between a blocked position of the passage opening ( 12 ) and a locked position of the inner tube ( 2 ) including intermediate positions is pivotable. Exhaust pipe according to claim 1, characterized in that the pivot axis ( 13 ) the flap ( 14 ) in the inner tube wall ( 15 ) is integrated and the flap ( 14 ) in the blocked position of the passage opening ( 12 ) is flush with the inner tube wall. Exhaust pipe according to claim 1 or 2, characterized in that the inner pipe ( 2 ) at least in the swivel area of the flap ( 14 ) the course of a straight swivel axis ( 13 ) corresponding flat wall ( 15 ) having. Exhaust pipe according to one of claims 1 to 3, characterized in that the flap ( 14 ) is tongue-shaped. Exhaust pipe according to one of claims 1 to 4, characterized in that the second pipe ( 3 ) is closed on the inlet side that the passage opening ( 12 ) in the overlap area of the inner tube ( 2 ) and the second pipe ( 3 ) on the inlet side into the inner tube wall ( 15 ) is introduced and that the pivot axis ( 13 ) the flap ( 14 ) in the flow direction behind the passage opening ( 12 ) is arranged. Exhaust pipe according to one of claims 1 to 4, characterized in that the second pipe ( 3 ) is closed on the outlet side that the passage opening ( 12 ' ) in the overlap area of the inner tube ( 2 ) and the second pipe ( 3 ) on the outlet side into the inner tube wall ( 15 ) is introduced and that the pivot axis ( 13 ) the flap ( 14 ) in the flow direction in front of the passage opening ( 12 ' ) is arranged. Exhaust pipe according to claim 5 or 6, characterized in that the second pipe ( 3 ) with a sloping wall ( 8th ) to the inner tube ( 2 ), whereby the passage opening ( 12 . 12 ' ) within the pipe section extended by the slope ( 11 ) is located. Exhaust pipe according to one of the preceding claims, characterized in that the second pipe ( 3 ) from a casing tube ( 5 ) is surrounded and with the casing tube ( 5 ) an outer annular gap carrying a coolant (KM) ( 6 ) forms.