EXHAUST SYSTEM FOR DIESEL VEHICLES

Abstract

An exhaust system for diesel vehicles is described, which includes at least one metering device for introducing and metering a pollutant-reducing medium into an exhaust gas flowing through a flow pipe of an exhaust tract of an internal combustion engine, in particular for the purpose of introducing a reduction agent and/or a reduction agent precursor, for example urea and/or an aqueous urea solution, the exhaust tract having at least one flexible flange connection.

Description

This claims the benefit of German Patent Application DE 10 2013 016 235, filed Oct. 1, 2013 and hereby incorporated by reference herein.

The present invention relates to an exhaust system for diesel vehicles, which includes a flexible flange. Flanges are used in a method for connecting pipe sections or air ducts to each other tightly yet detachably. The contact pressure of the ring-shaped sealing surfaces on the intermediate seal is crucial for the tightness. The contact pressure is applied with the aid of screws which are inserted into the flange faces through bores. These flanges are generally welded to the pipe. They belong to the pipeline parts or fittings. For example, flanges of this type are cast onto fittings and measuring devices. For example, steel flanges, cast iron flanges, flanges made of copper alloys and flanges made of aluminum alloys are known. Flanges made of high grade steel or carbon steel types are also known.

BACKGROUND

The word flange means “to project from a surface.” Pipeline flanges project from a pipeline. However, another explanation is that a tradesman is able to flange something onto a wall. The term also refers to flanges (chords) which form the upper and lower ends of a steel H beam (previously: double T beam).

There are different types of flanges, which are used for different areas of application. For example, flanges may be welded or screwed onto the pipe. Some types of flanges offer better stability, e.g., little face deformation under high screw forces to meet special tightness requirements.

Welding neck flanges are flanges with a neck for welding onto a pipe, for example. They are preformed from a steel blank by forging and subsequently finished by turning and drilling. Larger flanges are also bent into rings from profile steels and then welded. This type of flange is particularly structurally stable and is also used under high pressures.

Slip-on weld flanges with a neck are pushed onto the pipe and then welded to the pipe. The term slip-on flange is used under the ANSI standard.

Smooth flanges are pushed onto the pipe and then welded to the pipe. They are usually manufactured from a metal sheet. Larger flanges are also bent into rings from flat steel and then welded.

Blind flanges have no central bore and are used for sealing, for example, additional connecting pieces on pressure tanks or the ends of pipelines.

Threaded flanges have an inner thread into which the pipe is screwed, instead of a neck for welding.

Loose flanges are pushed loosely onto the pipe. The actual fastening to the pipe is handled by the welding neck ring or welding neck collar to be welded on. They are also used for integrally molded flanges. This design is used if the position of the pitch circle of the mating flange cannot be defined until final assembly.

Block flanges include a forged or a cast block. The associated screw holes have an inner thread. Flanges of this type are primarily welded onto pressure tanks as pipe sockets and used to attach inspection glasses.

Vessel flanges have the same function as normal flanges but are preferably used on boilers, pressure tanks and similar vessels. They can therefore have different dimensions of the flange face thickness, e.g., in the case of cast housings.

SAE flanges are used in various designs in oil hydraulics. These flange fittings are also known as CAT flanges, since they were developed by Caterpillar in the United States. SAE flanges are divided into pressure levels of 3,000, 6,000 and 9,000 PSI.

Vacuum flanges are used for the detachable connection of vacuum chambers. They are available as small flanges, clamp flanges and CF flanges.

In exhaust systems having SCR technology, the pipe connections are generally designed as screw connections or welded connections after metering of the reduction agent (AdBlue/DEF/AUS32). These connections have the disadvantage that the torsion of the two pipe sides with respect to each other is not possible at all (welded connection) or is possible only in keeping with the flange pattern (screw connection).

Known 6-hole flanges permit a torsion of an SCR catalytic converter with respect to the mixing line in 60° increments. This is unsuitable when there is limited installation space.

SUMMARY OF THE INVENTION

It is an object of the present invention to avoid the aforementioned disadvantages.

The present invention provides an exhaust system for diesel vehicles, which includes at least one metering device for introducing and metering a pollutant-reducing medium into an exhaust gas flowing through a flow pipe of an exhaust tract of an internal combustion engine, in particular for the purpose of introducing a reduction agent and/or a reduction agent precursor, for example urea and/or an aqueous urea solution, the exhaust tract having at least one flexible flange connection.

It is advantageous that the flange torsion may occur flexibly, the axial compression of the seal taking place in such a way that an optimum contact pressure is implemented as well as a sealing of the system against AdBlue and exhaust gas.

A further advantage in the case of loose flanges and blind flanges exists if, instead of the standard flange face thickness, a face thickness which meets the particular requirements, i.e., a reduced face thickness, is used. A uniform force distribution/precisely defined introduction of force on the sealing area is possible.

The flexible flange connection is suitable for any type of exhaust system and not only for SCR applications.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional important features and advantages are derived from the subclaims, from the drawings and from the following description of one preferred exemplary embodiment on the basis of the drawings.

FIG. 1 shows an exploded drawing of a screw flange;

FIG. 2 shows a top view and a side view of the screw flange from FIG. 1;

FIG. 3 shows sectional representation A-A of the screw flange from FIG. 2;

FIG. 4 shows an exhaust system of an internal combustion engine.

DETAILED DESCRIPTION

The present invention illustrates a screw connection, which facilitates the adjustment of the two pipes with respect to each other prior to tightening the screws, in any arbitrary angular position and thus independently of the hole pattern of the screw flange.

Flexible flange connection 9 (FIG. 4) is “AdBlue-tight”; tight against DEF, AUS 32 according to ISO 22241, and tight against all common fuels and their condensates as well as tight against all exhaust gases from internal combustion engines.

The flange connection illustrated in FIG. 1 is a screw connection between two pipes 1, 8. One pipe side 8 is fixedly welded to a flange or flange face 4. The mating side permits the free torsion of pipe 1, due to a loose flange 2, and thus a variable adjustment independently of the hole pattern of the flange. Following the desired adjustment of the two pipes 1, 8 with respect to each other, flanges 2, 4 or flange faces are screwed to each other. Seal 3 is pressed between the flanged front surface of pipe 1 and mating flange 4 with the aid of screws 5, spacer sleeves 6 and nuts 7.

FIG. 2 shows a top view and a side view of the screw flange from FIG. 1. The flange connection is a screw connection between two pipes 1 and 8. One pipe side 8 is fixedly welded to a flange or flange face 4. The mating side permits the free torsion of pipe 1, due to a loose flange 2, and thus a variable adjustment independently of the hole pattern of the flange. Following the desired adjustment of the two pipes 1, 8 with respect to each other, flanges 2, 4 or flange faces are screwed to each other. Seal 3 described in FIG. 1 is pressed between the flanged front surface of pipe 1 and mating flange 4 with the aid of screws 5, spacer sleeves 6 and nuts 7.

A sectional view along section line A-A of the screw flange from FIG. 2 is shown in FIG. 3.

The described flange connection is a screw connection between two pipes 1 and 8. Pipe side 8 is fixedly welded to a flange or flange face 4. The mating side permits the free torsion of pipe 1, due to a loose flange 2, and thus a variable adjustment independently of the hole pattern of the flange. Following the desired adjustment of the two pipes 1 and 8 with respect to each other, flanges 2, 4 or flange faces are screwed to each other. Seal 3 is pressed between the flanged front surface of pipe 1 and mating flange 4 with the aid of screws 5, spacer sleeves 6 and nuts 7.

FIG. 4 shows a schematic representation of an exhaust system of an internal combustion engine, which includes an engine 14 from which an exhaust tract 13 extends in the flow direction of the exhaust gas of engine 14. Following exhaust tract 13, a pipe 1, which is used as a mixing line for exhaust gas and urea metering device 11 integrated into pipe 1 extends in the flow direction of the exhaust gas of engine 14. Exhaust tract 13 and pipe 1 are connected gas-tight with the aid of a flange 12. An SCR catalytic converter is situated at the end—in the flow direction of the exhaust gas of engine 14—of pipe 1 used as the mixing line. Pipe 1 and SCR catalytic converter 10 are connected to each other with the aid of gas-tight and liquid-tight flexible flange connection 9, which is illustrated in FIGS. 1, 2 and 3.

Embodiments of the flange in accordance with the present invention may be used, in principle, for all exhaust gas-tight or liquid-tight piping in exhaust systems or gas-conducting, i.e., hot gas-conducting, piping/pipe screw connections.

In particular, and in the case implemented herein, embodiments of the flange in accordance with the present invention are used to seal the exhaust gas piping of an SCR catalytic converter against the AdBlue reduction agent (AUS 32; DEF) in the exhaust gas.

LIST OF REFERENCE NUMERALS

1 pipe (flanged on the outlet side)/mixing line

2 Flange (loose)

3 Seal (AdBlue-resistant)

4 Flange (equivalent part to reference numeral 2)

5 Screws

6 Spacer sleeve

7 Nut

8 pipe (welded onto flange reference numeral 7 [sic; 4])

9 Flexible flange connection

10 SCR catalytic converter

11 Metering device/urea metering

12 Flange

13 Exhaust tract

14 Engine

Claims

1. An exhaust system for diesel vehicles comprising:

an exhaust tract of an internal combustion engine including a flow pipe; and

at least one metering device for introducing and metering a pollutant-reducing medium into an exhaust gas flowing through the flow pipe of the exhaust tract, the exhaust tract having at least one flexible flange connection.

2. The exhaust system for diesel vehicles as recited in claim 1 further comprising a SCR catalytic converter, the flexible flange connection being situated upstream from the SCR catalytic converter.

3. The exhaust system for diesel vehicles as recited in claim 1 wherein the flow pipe is a mixing line for the pollutant-reducing medium and the exhaust gas, the flexible flange connection being situated in the area of the mixing line and in a flow direction of the exhaust gas.

4. The exhaust system for diesel vehicles as recited in claim 1 wherein the flexible flange connection has at least two flanges.

5. The exhaust system for diesel vehicles as recited in claim 1 wherein the flexible flange connection has at least one loose flange.

6. The exhaust system for diesel vehicles as recited in claim 1 wherein the flexible flange connection has at least one flanged pipe at a flow-side outlet side.

7. The exhaust system for diesel vehicles as recited in claim 1 wherein the flexible flange connection includes a flange and at least one pipe attached to the flange.

8. The exhaust system for diesel vehicles as recited claim 1 wherein the at least one metering device introduces at least one of a reduction agent and a reduction agent precursor.

9. The exhaust system for diesel vehicles as recited claim 8 wherein the at least one metering device introduces at least one of urea and an aqueous urea solution.