DE102021112401A1 - Exhaust system for a motor vehicle, and a manufacturing method for an exhaust system of a motor vehicle - Google Patents

Abstract

The invention relates to an exhaust system (1) for a motor vehicle (2), having at least the following components: - a system element (3) made of titanium or a titanium alloy; - a functional unit (4) with a line connection (5) made of an austenitic Stainless steel; and - a connecting element (6) which is arranged between the system element (3) and the line connection (5) of the functional unit (4) and by means of which these are connected to one another. The exhaust system (1) is primarily characterized in that the system element (3) and the connecting element (6) are connected to one another in a gas-tight manner by means of a brazed seam (7). Titanium component that conducts exhaust gases can be connected to a functional unit made of austenitic stainless steel.

Description

The invention relates to an exhaust system for a motor vehicle, a manufacturing method for an exhaust system of a motor vehicle, and a motor vehicle with such a manufacturing method.

Lightweight construction is one of the most effective measures to reduce carbon dioxide emissions and increase vehicle performance. Conventional materials are often substituted by high-performance materials with a lower density.

The use of titanium alloys instead of stainless steel in the exhaust systems of high-performance vehicles has been state of the art for several years. Due to increasingly strict noise emission regulations, electrically actuated, infinitely variable exhaust gas flaps made of stainless steel are used in series production in many applications. The development of these exhaust flaps, including their actuators, represents a considerable development effort, especially for high-performance vehicles with a correspondingly high power density and the associated high exhaust gas temperatures. These components made of stainless steel have been standard for years and are therefore widely available in large series. Due to the manufacturing process of the corrugated pipes in the hydroforming process [IHU] with very high degrees of deformation, titanium alloys are not suitable for this application.

If you combine these requirements, the problem arises that the titanium silencer housing cannot be connected gas-tight to the mass-produced steel exhaust flaps or decoupling elements by welding, which is common practice in exhaust system construction.

Various approaches are already known for this. The obvious first approach is an additional mountable separation point between the stainless steel component and the titanium silencer body, for example with a pipe clamp. The disadvantage is the additional effort and the additional weight for flanges, seals and clamps for the separation point, which then partially compensate for the lightweight construction advantage of the titanium silencer.

Furthermore, for ultra-high-performance vehicles, exhaust gas flaps made of a titanium alloy are also occasionally available, but these are usually developed explicitly for a special application with a great deal of effort. Due to the considerable additional effort and the small quantities, they are often not designed in such a way that they meet the comfort requirements (e.g. freedom from rattling, squeaking) of a mass-produced vehicle, and often have to be provided with additional cooling measures in order to ensure the corresponding long-term stability. The reason for this is that the existing titanium alloys are only suitable to a limited extent as materials for the mechanically moving parts such as the shaft and flap leaf, which are functionally directly in the gas flow and withstand temperatures of up to around 1,000 °C [one thousand degrees Celsius ] have to endure permanently. In addition, the titanium alloys usually used are only suitable to a limited extent as bearing materials for the shaft bearing, which can lead to undesirable noise development during operation.

Welding processes are also being developed that connect stainless steel directly to titanium alloys, but up to now there has been practically no series experience with regard to their strength properties under cyclic thermal plus superimposed vibration loads and their long-term stability, especially with regard to corrosion.

The aim of the invention described below is to provide a construction and a manufacturing method by which stainless steel components can be connected to titanium components (referred to as titanium silencers for short) in a simple manner.

Proceeding from this, the object of the present invention is to at least partially overcome the disadvantages known from the prior art. The features according to the invention result from the independent claims, for which advantageous configurations are shown in the dependent claims. The features of the claims can be combined in any technically meaningful way, whereby the explanations from the following description and features from the figures can also be used for this purpose, which include additional configurations of the invention.

• - ein Anlagenelement aus Titan oder einer Titan-Legierung;
• - eine Funktionseinheit mit einem Leitungsanschluss aus einem austenitischen Edelstahl; und
• - ein Verbindungselement, welches zwischen dem Anlagenelement und dem Leitungsanschluss der Funktionseinheit angeordnet ist und mittels dessen diese miteinander verbunden sind.

The invention relates to an exhaust system for a motor vehicle, having at least the following components:

• - a plant element made of titanium or a titanium alloy;
• - a functional unit with a line connection made of an austenitic stainless steel; and
• - A connecting element, which is arranged between the system element and the line connection of the functional unit and by means of which these are connected to one another.

The exhaust system is primarily characterized in that the system element and the connecting element are connected to one another in a gas-tight manner by means of a brazed seam.

Unless explicitly stated otherwise, ordinal numbers used in the description above and below only serve to clearly distinguish them and do not reflect any order or ranking of the components referred to. An ordinal number greater than one does not mean that another such component must necessarily be present.

The exhaust system proposed here is designed for an internal combustion engine in a motor vehicle for discharging and usually treating exhaust gas from the internal combustion engine with as little resistance as possible (e.g. by means of an exhaust gas catalytic converter), with this exhaust system preferably being completely or at least partially suitable for permanently high exhaust gas temperatures, for example continuously above 800 °C [eight hundred degrees Celsius] to 1,000 °C or higher.

The system element is, for example, a line element, for example an inlet pipe or outlet pipe related to the functional unit and/or to a silencer. In one embodiment, the system element is a component of a silencer, for example a floor panel, an outer wall element or a partition. In one embodiment, the system element is a socket into which a line element and a line connection of a functional unit are inserted, in one embodiment the socket does not come into contact with the exhaust gas to be conducted (apart from leaks) and in another embodiment it comes into contact with the socket Line element is formed for conducting exhaust gas. A socket is preferably used for fluidic connection (particularly preferably within a silencer), the line element and/or the line connection of the functional unit being held displaceably relative to the axis of the socket to compensate for thermal expansion, for example.

The system element, and preferably a muffler, of the exhaust system is preferably made partially or entirely of titanium or a titanium alloy, with the system element being made of titanium or a titanium alloy in the area of the connection (brazed seam) of the system element and the connecting element.

The functional unit is a component which, due to its function in the exhaust system, can be produced more cost-effectively and/or solely from austenitic stainless steel. For example, the functional unit is an exhaust gas flap for (preferably continuously) controlling a (controllable) proportion of the exhaust gas flow through a bypass and/or an exhaust gas catalytic converter. The included line connection is already joined to the other components of the functional unit in advance. The line connection is, for example, functional and therefore cannot be separated from the other components of the functional unit in terms of design, for example the jacket in an exhaust gas catalytic converter, in which the catalytically active (ceramic or metallic) honeycomb material is attached. For example, the functional unit together with its line connection is a structurally uniform purchased component.

The connecting element is, for example, a line element, for example an inlet pipe or outlet pipe related to the functional unit and/or to a muffler. In one embodiment, the connecting element is a component of a silencer, for example a floor panel, an outer wall element or a partition. In one embodiment, the connecting element is a socket into which a line element and a line connection of a functional unit are inserted, in one embodiment the socket does not come into contact with the exhaust gas to be conducted (apart from leaks) and in another embodiment it comes into contact with the socket Line element is formed for conducting exhaust gas. For example, a shaped piece of pipe is formed by the connecting element at the same time, for example a corner connection. The connecting element is at least long enough for the thermal influence of the brazing and/or welding not to impair the respective other (previously formed) connection point.

Instead of a welded connection between an austenitic stainless steel component, i.e. the functional unit including its line connection, and a line element made of titanium or a titanium alloy, for example a titanium silencer, the approach presented here provides for a soldered connection using a hard solder. Due to the very different thermal expansion coefficients of austenitic stainless steel and titanium (alloy) and consequently different radial expansion, a direct soldered connection would be a supercritical thermomechanical one subjected to high stress loads. In order to solve this problem, according to the invention, the connecting element made of a different material with a thermal expansion more similar to titanium is introduced. This connecting element with very similar coefficients of expansion is connected gas-tight to the line element by means of hard soldering.

The connection between the connecting element and the line connection of the functional unit is preferably implemented as a welded connection and corresponds, for example, to the prior art.

In a preferred embodiment, the exhaust system includes a plurality of system elements, connecting elements and functional units.

It is further proposed in an advantageous embodiment of the exhaust system that the connecting element is made of a ferritic high-grade steel.

It has been shown that a ferritic stainless steel is a particularly suitable material for connecting to titanium or a titanium alloy by means of brazing. In an advantageous embodiment, the connecting element is formed entirely from a ferritic high-grade steel. Such a connecting element is very inexpensive to produce and can be easily brought into a desired shape, preferably cold-formable. A ferritic stainless steel also has the advantage that a conventional welded joint with austenitic stainless steel is possible, for example by means of metal inert gas welding [MIG], metal active gas welding [MAG] or tungsten inert gas welding [TIG]. Welding is also possible after the brazing seam has been formed, because the thermally affected zone can be made sufficiently small so that the brazing seam is not adversely affected by the formation of the weld seam. This enables, for example, the sequence in which the system element is introduced together with the connecting element (and, for example, together with an already welded titanium (alloy) silencer) into a soldering furnace before the weld seam is formed between the connecting element and the line connection of the functional unit. The functional unit is thus not exposed to the high temperatures in the soldering furnace for forming the brazing seam. In addition, the cost of the soldering material is not significant, especially in comparison to the previously known solutions with clamps or special welding processes with welding additives containing silver.

• - eine Abgasklappe;
• - ein Entkopplungselement;
• - ein Abgas-Katalysator, wobei bevorzugt das Verbindungselement der Mantel des Abgas-Katalysators ist; und
• - ein Sensorelement.

It is also proposed in an advantageous embodiment of the exhaust system that the functional unit is at least one of the following elements:

• - an exhaust flap;
• - a decoupling element;
• - An exhaust gas catalytic converter, wherein the connecting element is preferably the jacket of the exhaust gas catalytic converter; and
• - a sensor element.

It should be pointed out that the functional units mentioned here do not represent an exhaustive list of possible functional units. Furthermore, it should be pointed out that although the line connection is preferably a component of the functional unit that is formed in one structural unit, in one embodiment it is only subsequently joined to the other components of the functional unit. For example, the functional unit, for example together with the line connection, is a purchased component for the exhaust system, preferably an exhaust gas catalytic converter together with an (austenitic or preferably ferritic) jacket. In an embodiment with the jacket made of a ferritic stainless steel, the jacket is to be regarded as the connecting element or preferably used as such, ie connected directly to the system element by means of a brazed seam.

It is also proposed in an advantageous embodiment of the exhaust system that the connecting element and the line connection of the functional unit are connected to one another in a gas-tight manner by means of welding.

A weld seam, formed, for example, by one of the welding methods mentioned above, can be produced in a particularly cost-effective manner. For example, the weld seam can be produced in a production plant or production line by a production robot in a matter of seconds and with high precision. The thermal influence zone is so small that the connecting element can be made sufficiently short for most drop positions. The benefit of making the system element from titanium (-alloy) is by no means offset by the additional connecting element made from ferritic stainless steel.

In an advantageous embodiment of the exhaust system, it is also proposed that the functional unit is an exhaust gas valve and that a bypass can thus be flown through in a switchable manner.

For some applications, a large number of functional units directly connected to components, i.e. system elements, are made of titanium (-alloy) required. The exhaust system proposed here or its subassembly(s), comprising (each) the functional unit and the (at least one) connecting element, can be integrated particularly easily into a manufacturing process and, when weighing up the costs and the desired lightweight construction of the exhaust system using titanium, is advantageous low mass.

• - ein Leitungselement zum Leiten von Abgas;
• - ein Bodenblech eines Schalldämpfers; oder
• - eine Steckhülse zum Aufnehmen des Verbindungselements,

wobei bevorzugt die Abgasanlage eine Mehrzahl von Anlagenelementen, Verbindungselementen und Funktionseinheiten umfasst.It is also proposed in an advantageous embodiment of the exhaust system that the system element is one of the following elements of the exhaust system:

• - a duct element for conducting exhaust gas;
• - a bottom plate of a muffler; or
• - a socket for receiving the connecting element,

the exhaust system preferably comprising a plurality of system elements, connecting elements and functional units.

An exhaust system with at least one line element and/or a muffler, wherein the line element or the muffler is formed at least partially, preferably at least the pipes and sheets completely, from titanium (alloy), is exposed to high exhaust gas temperatures, especially in high-performance applications, with high demands at the same time the (minimum possible) space requirement and/or the total length of the exhaust pipe (adjustable exhaust flap and bypass) that can be regulated depending on the operating state is required.

1. a. Bereitstellen des Anlagenelements, des Verbindungselements und der Funktionseinheit;
2. b. zueinander Positionieren des Anlagenelements und des Verbindungselements; und
3. c. Bilden einer gasdichten Verbindung mittels Hartlöten zwischen dem Anlagenelement und dem Verbindungselement.

According to a further aspect, a manufacturing method for an exhaust system of a motor vehicle is proposed, wherein an exhaust system according to an embodiment according to the above description is manufactured with the following steps:

1. a. providing the system element, the connection element and the functional unit;
2. b. relative to each other positioning the plant element and the connecting element; and
3. c. Forming a gas-tight connection by means of brazing between the plant element and the connection element.

An exhaust system according to an embodiment according to the above description is manufactured using the manufacturing method proposed here, specifically in advance or in parallel or as intermediate steps in the manufacturing method of the muffler or the entire exhaust system.

The steps mentioned here a. to c. are performed in alphabetical order. Nevertheless, in one embodiment, further steps are carried out in parallel or in between, which relate to the same or other (for example already joined) components. For example, during step c. at the same time, a weld seam can be formed on the connecting element (in a step d.) with the line connection of the functional unit, with preferably before or at the same time as step a. and/or step b. these components are provided or positioned. In one embodiment, a muffler is formed from two housing halves, with the components of the exhaust system being inserted into a (lower) housing half, and after completion of at least part of the manufacturing method proposed here (in step e.), the (upper) housing half is placed and thus a chamber formed by the muffler is closed. It should be noted that the terms below and above are chosen according to a simple embodiment of the method, but not to an orientation in use (e.g. in a motor vehicle) or even (at least not permanently) the orientation during all steps of a method in a Restrict production line.

• - mittels Induktionslöten; und/oder
• - im Lötofen.

It is also proposed in an advantageous embodiment of the manufacturing method that the brazing is carried out:

• - by means of induction brazing; and or
• - in the soldering oven.

The soldering furnace has the advantage that the process reliability is very high, especially with regard to the desired gas tightness, and that the same soldering furnace can always be used for the most diverse dimensions. A disadvantage is that the process takes a long time. In contrast, induction soldering offers a time advantage, with locally limited heating for melting the brazing material being effected by means of an alternating magnetic field. In this case, the induction coil must be precisely adapted to the dimensions of the brazing seam and the process reliability (especially with regard to gas tightness) for the respective dimensions must be individually ensured before series production. Another advantage of induction soldering is that other process steps can be carried out concurrently, such as forming a weld seam (see above).

It is further proposed in an advantageous embodiment of the manufacturing method that in step b. the system element and the connecting element are pre-fitted together,
preferably also the line connection of Functional unit and the connecting element are pre-fitted together.

A plug-in connection between the components mentioned is particularly advantageous, with this plug-in connection particularly preferably being formed with sufficient strength for easy and position-safe handling in the production plant or in a production line. Alternatively or additionally, soldering points or welding points are formed (for example by hand) in order to prefix the named components to one another, with gas-tightness not yet being or not having to be established here. Alternatively or additionally, the components mentioned are mechanically positioned in relation to one another in a temporary holding device.

According to a further aspect, a motor vehicle is proposed, having at least one internal combustion engine for indirect and/or direct propulsion of the motor vehicle and an exhaust system according to an embodiment according to the above description for discharging exhaust gas from the internal combustion engine.

In the embodiment proposed here, the internal combustion engine proposed here is set up to propel the motor vehicle. The motor vehicle and its components are described here only in rudimentary form and are otherwise of conventional design, for example. The drive wheels are, for example, two wheels on a common vehicle axle, for example the rear wheel axle of a four-wheel motor vehicle, and are connected to the internal combustion engine in a torque-transmitting manner by means of a drive train, preferably in a separable manner. The exhaust gases of the internal combustion engine are discharged into the environment via the exhaust system, with the lowest possible back pressure (i.e. resistance) and nowadays at the same time a large number of exhaust gas treatments and soundproofing having to be achieved. Increasingly, the silencing has to be regulated depending on the operating state of the internal combustion engine, for which purpose, for example, a (preferably infinitely variable) controllable exhaust gas valve together with a bypass to lengthen the path of the exhaust gas through a muffler is a suitable measure.

With the exhaust system proposed here, in consideration of the costs and the desired lightweight construction of the exhaust system, an advantageously low mass can be achieved by using titanium.

• 1: ausschnittsweise eine Abgasanlage in einer Schnittansicht;
• 2: ausschnittsweise eine Abgasanlage in einer anderen Ausführungsform in einer Schnittansicht;
• 3: eine Detailansicht eines Ausschnitts einer Abgasanlage gemäß 1;
• 4: eine Detailansicht eines Ausschnitts einer Abgasanlage in einer weiteren Ausführungsform;
• 5: eine Detailansicht eines Ausschnitts einer Abgasanlage in einer weiteren Ausführungsform;
• 6: eine Detailansicht eines Ausschnitts einer Abgasanlage in einer weiteren Ausführungsform;
• 7: eine Detailansicht eines Ausschnitts einer Abgasanlage in einer weiteren Ausführungsform;
• 8: eine Detailansicht eines Ausschnitts einer Abgasanlage mit einem Abgas-Katalysator;
• 9: eine Detailansicht eines Ausschnitts einer Abgasanlage mit einer Steckhülse;
• 10: ein Flussdiagramm eines Fertigungsverfahren für zwei Abgasleitungsabschnitte gemäß 2;
• 11: ein Ausschnitt einer Fertigungsanlage zum induktiven Hartlöten; und
• 12: ein Kraftfahrzeug mit einer Abgasanlage in einer schematischen Draufsicht.

The invention described above is explained in detail below against the relevant technical background with reference to the accompanying drawings, which show preferred embodiments. The invention is in no way restricted by the purely schematic drawings, it being noted that the drawings are not true to scale and are not suitable for defining size relationships. It is presented in

• 1 : detail of an exhaust system in a sectional view;
• 2 1: a detail of an exhaust system in another embodiment in a sectional view;
• 3 : a detailed view of a section of an exhaust system according to FIG 1 ;
• 4 1: a detailed view of a section of an exhaust system in a further embodiment;
• 5 1: a detailed view of a section of an exhaust system in a further embodiment;
• 6 1: a detailed view of a section of an exhaust system in a further embodiment;
• 7 1: a detailed view of a section of an exhaust system in a further embodiment;
• 8th : a detailed view of a section of an exhaust system with an exhaust gas catalytic converter;
• 9 : a detailed view of a section of an exhaust system with a socket;
• 10 : a flow chart of a manufacturing method for two exhaust pipe sections according to FIG 2 ;
• 11 : a section of a production line for inductive brazing; and
• 12 : a motor vehicle with an exhaust system in a schematic plan view.

In 1 shows a section of an exhaust system 1 in a sectional view. The exhaust system 1 shown as an example comprises a muffler 15 with an inlet pipe 18, an outlet pipe 19 and a floor panel 14, with the inlet pipe 18 and the outlet pipe 19 leading through the floor panel 14 into a chamber 20 and exhaust gases from the inlet pipe 18 to the outlet pipe 19 Internal combustion engine 17, for example, of a motor vehicle 2 (cf 12 ) are dissipated and a sound level is attenuated by the chamber 20 and/or dampening material in the chamber 20. The exhaust gas thus flows (according to the illustration) from the right into the inlet pipe 18 and (according to the illustration) flows out downstream to the right via the outlet pipe 19 . It should be noted that the direction of flow is irrelevant for the details described here and, in principle, the silencer 15 can also be operated in reverse.

A connecting element 6 and, in turn, a functional unit 4 are connected to the outlet pipe 19, from which a system element 3 or, more precisely, a line element 13 is formed. The outlet pipe 19 (and preferably also the inlet pipe 18 and/or the silencer 15 enclosing the chamber 20 together with the base plate 14) is made of titanium or a titanium alloy. The outlet pipe 19 protrudes from the floor panel 14 (to the right as shown) in the manner of a socket. The connecting element 6 is inserted into the outlet pipe 19 (alternatively vice versa or with abutment) and by means of a brazed seam 7 (for example after a manufacturing step according to 11 ) connected gas-tight. The connecting element 6 is formed, for example, from a ferritic high-grade steel and is therefore suitable for the formation of the brazed seam 7 with the line element 13 due to a similar thermal expansion behavior. On the other side, a functional unit 4 , here an exhaust flap 8 , connects to the connecting element 6 with its line connection 5 . The line connection 5 of the functional unit 4 is inserted here into the connecting element 6 (alternatively vice versa or butting) and connected in a gas-tight manner, for example by means of a weld seam 21 . The functional unit 4 or the line connection 5 or a part of the line connection 5, with which the gas-tight connection (for example weld seam 21) to the connecting element 6 is formed, is formed from an austenitic stainless steel. The pairing of materials is therefore suitable for a weld seam 21 without special (and above all without expensive) additives.

In 2 shows a detail of an exhaust system 1 in another embodiment in a sectional view. The muffler 15 comprises a purely optional two-part or multi-part housing, with a lower housing half 22 being shown here, for example, into which the exhaust gas-conducting components (inlet pipe 18, secondary pipe 23 and outlet pipe 19) and intermediate walls 24, 25 are inserted during pre-positioning. A (purely optionally branched) tailpipe connection 26 is connected to the outlet pipe 19 . The secondary pipe 23 has a reduced flow cross section compared to the inlet pipe 18 and outlet pipe 19 and thus forms an increased flow resistance. The secondary pipe 23 has a permanent flow. The bypass 12 can be flowed through by means of an exhaust flap 8 (preferably steplessly), so that the length of the flow path and/or the flow cross section is increased, and thus forms a section for controlling the damping efficiency of the exhaust noise. It should be pointed out that the direction of flow is also irrelevant for the details described here and that, in principle, the silencer 15 can also be operated in the opposite direction compared to the following description.

Here the muffler 15 of the exhaust system 1 now has a cut-out (top left according to the illustration) with a first outer wall element 27 and a second outer wall element 28 . The functional unit 4, two connecting elements 6 and two system elements 3 are arranged in this excavation. A connecting element 6 is provided on both sides (that is to say upstream and downstream) of the functional unit 4 (an exhaust gas flap 8 here purely as an option). The system element 3 (here a line element 13) is arranged upstream of the functional unit 4 and is formed by the inlet pipe 18 purely optionally. Here, too, the line element 13 (as in 1 ) Guided through the first outer wall element 27 in the manner of a socket. The other system element 3 (likewise a line element 13) is arranged downstream of the functional unit 4 and formed purely optionally by the outlet pipe 19, this line element 13 also being guided through the second outer wall element 28 in the manner of a socket. Alternatively, at least one of the system elements 3 is formed by the respective outer wall element 27,28. At the respective passage through the outer wall element 27,28 with the respective system element 3 (ie the outer wall element 27,28 or with the inlet pipe 18 or outlet pipe 19) a brazing seam 7 is formed with the connecting element 6. The functional unit 4 is welded with its line connection 5 on both sides (in the direction of flow) to the respective connecting element 6 (not shown here).

A further connecting element 6 and a further functional unit 4 are provided here upstream of the inlet pipe 18 and outside of the silencer 15 . Without excluding the general public and purely for the sake of clarity, this arrangement is largely identical to that in 1 embodiment shown is identical, so that reference is made to the description there. In contrast to this, a decoupling element 9 is provided here as a purely optional functional unit 4 and the system element 3 is purely optionally the base plate 14 for the gas-tight connection to the connecting element 6.

In 3 is a purely schematic detailed view of a section of an exhaust system 1 (for example a silencer 15 according to 1 or 2 ) shown, so that reference is made to the description there. It follow up here 9 one Series of embodiments, this also represents only an exemplary selection and at least the respective features can be used in addition to the particularly emphasized aspects for further combinations. The gas-tight connections between titanium parts and between the (ferritic) connecting element 6 and the functional unit 4, for example the (austenitic) line connection 5, are always referred to here as a weld seam 21. This is purely optional and must be determined from the point of view of costs and the sequence of the production steps. For example, a brazing seam 7 is also particularly optimal in terms of weight and can be produced (at least almost) cost-neutrally in comparison to a weld seam 21 during production, for example using a soldering furnace. Connections which are not gas-tight are usually to be arranged within a gas-tight container, for example in the chamber 20 of a silencer 15 . In all other cases, the floor panel 14 shown, if formed as an outer wall element, can also be used mirrored to the vertical plane of the drawing. It should be pointed out that the floor panel 14 shown can also be designed as an intermediate wall in one embodiment.

Here it can be clearly seen how the line element 13 (for example an outlet pipe 19) protrudes like a socket from the base plate 14 (to the right according to the illustration) from the chamber 20 and forms the system element 3. The outlet pipe 19 itself is gas-tightly connected to the base plate 14 (purely optionally by means of a weld seam 21). In order to accommodate the connecting element 6 in the line element 13, the diameter of the outlet pipe 19 is increased in this area, for example by means of hydroforming. The connecting element 6 is inserted into the outlet pipe 19 . A hard soldering seam 7 is formed in the overlapping area and the system element 3 and the connecting element 6 are thus connected to one another in a gas-tight manner. The line connection 5 of the functional unit 4 is now plugged downstream onto the connecting element 6 and connected to one another in a gas-tight manner (purely optionally by means of a weld seam 21).

In 4 is a similar detailed view of a section of an exhaust system 1 as in FIG 3 shown in another embodiment. In this respect, reference is made to the description there. In contrast to the embodiment shown there, two system elements 3 are connected gas-tight to the (single) connecting element 6 by means of two brazed seams 7 . Namely, a system element 3 is formed by the attached bottom plate 14 and the other by the inserted line element 13 (for example, an outlet pipe 19).

In 5 is a similar detailed view of a section of an exhaust system 1 as in FIG 3 and 4 shown in another embodiment. In this respect, reference is made to the description there. In contrast to the embodiment shown there, the line element 13 (for example an outlet pipe 19) is connected to the system element 3 and thus to the connecting element 6 in a gas-tight manner by means of a brazed seam 7 . The floor panel 14 is therefore not a system element 3 here, i.e. it is not connected to the connecting element 6 in a gas-tight manner by means of a hard soldering seam 7, but purely optionally by means of a welded seam 21.

In 6 is a similar detailed view of a section of an exhaust system 1 as in FIG 4 shown in another embodiment. In this respect, reference is made to the description there. In contrast to the embodiment shown there, the connecting element 6 is guided in the manner of a socket through the passage in the floor panel 14 into the chamber 20 of the silencer 15 and, within the chamber 20, the line element 13, for example an outlet pipe 19, is purely optional, merely on the connecting element 6 attached. The system element 3 is formed by the base plate 14 in this embodiment. The floor panel 14 and the connecting element 6 are therefore connected to one another in a gas-tight manner by means of the brazing seam 7 .

In 7 is a similar detailed view of a section of an exhaust system 1 as in FIG 6 shown in another embodiment. In this respect, reference is made to the description there. In contrast to the embodiment shown there, the line element 13 (for example an outlet pipe 19) is inserted into the connecting element 6 here. The line element 13 is therefore not a system element 3 here either, that is to say it is not connected to the connecting element 6 in a gas-tight manner by means of a hard soldering seam 7 .

In 8th is a similar detailed view of a section of an exhaust system 1 as in FIG 3 shown in an embodiment with an exhaust gas catalyst 10. In this respect, reference is made to the description there. In contrast to the embodiment shown there, the functional unit 4 is an exhaust gas catalytic converter 10 (body) which is designed with a jacket 11 . The connection between the exhaust gas catalytic converter 10 and the jacket 11 is formed, for example, as is known from the prior art, purely optionally in advance. The connecting element 6 is formed by the jacket 11 . A line element 13 (for example an outlet pipe 19) is formed by the system element 3, which is thus connected in a gas-tight manner to the connecting element 6 (jacket 11) by means of a brazed seam 7. The floor panel 14 is purely optional by means a weld 21 gas-tight with the system element 3 (line element 13) connected. In an alternative embodiment, the system element 3 is formed by the base plate 14, for example as in FIG 4 , 6 or 7 shown.

In 9 is a similar detailed view of a section of an exhaust system 1 as in FIG 7 shown in another embodiment. In this respect, reference is made to the description there. In contrast to the embodiment shown there, the line connection 5 of the functional unit 4 is also plugged into the connecting element 6 and (purely optionally by means of a weld seam 21) connected to the connecting element 6 in a gas-tight manner. The connecting element 6 is connected to the floor panel 14 by means of a brazed seam 7, from which the system element 3 is formed here. Here, too, the line element 13 is not a system element 3, that is to say it is not connected to the connecting element 6 in a gas-tight manner by means of a hard soldering seam 7, but is merely optionally inserted on its own. It should also be pointed out that the connecting element 6 is not a line element 13 here, but a socket 16, which is shielded from direct contact with the exhaust gas to be conducted (from the outlet pipe 19 and the line connection 5). In an alternative embodiment, the outlet pipe 19 is also a system element 3 and is connected to the socket 16 in a gas-tight manner by means of a hard soldering seam 7, and possibly the bottom plate 14 is not a system element 3 but is connected in a gas-tight manner to the outlet pipe 19 (for example by means of welding).

In 10 a flowchart of an exemplary manufacturing method for an exhaust system 1 with two functional units 4 and a corresponding number of connecting elements 6 and system elements 3 is shown. Here, a muffler 15 is viewed as a section of an exhaust system 1, such as in 2 shown, to which reference is made below. In a first step a1. the two connecting elements 6 and the functional unit 4, for example the exhaust flap 8 (as in 2 shown above left) and in sub-step b1. positioned to each other. Subsequently, in step d. the functional unit 4 is connected gas-tight on both sides to the connecting elements 6 by forming a weld seam 21, for example by means of MIG/MAG or TIG welding processes (preferably by means of a welding robot). In a sub-step a2. the connecting elements 6 and the associated line elements 13 are now provided. In a purely optional parallel (represented by a dashed line) executable partial step a2'. another connecting element 6 and an associated system element 3 (e.g. a line element 13 as in 2 shown below right). Then in sub-step b2. and purely optionally in a parallel sub-step b2'. positioned these provided components. Purely optionally, in sub-step b2. one before, after or during sub-step a2'. provided (lower) housing half 22 of the muffler 15 is positioned relative to the connecting elements 6 and system elements 3 by the components being inserted into the housing half 22, for example.

In a (purely optionally executable in parallel) step c. and step c', for example in a soldering furnace, a gas-tight connection is formed between the mentioned system elements 3 and connecting elements 6. In a subsequent step e. the chamber 20 of the silencer 15 is closed, for example by placing an upper half of the housing, and the components that were previously only pre-positioned relative to one another are joined by welding. These components are preferably all made of titanium or a titanium alloy. In one embodiment, exhaust-gas-conducting elements, the lower housing half 22 and/or intermediate walls 24, 25 for connection to the housing are already in place before step c. joined together (e.g. welded). In the following step a1'. will be in accordance with 2 Components shown below right, the connecting element 6, which is already connected to the system element 3 (according to 2 the line element 13) by means of a brazing seam 7 from step c'. is connected, and the functional unit 4 (according to 2 the decoupling element 9] provided. Subsequently, in step b1'. the connecting element 6 and the functional unit 4 are positioned relative to each other and in step d'. connected gas-tight by welding.

In 11 a section of a production plant 29 for inductive brazing to form a gas-tight connection between the plant element 3 (here a floor panel 14 of a silencer 15) and the connecting element 6 is shown. This production system 29 can be integrated into a (for example conventional) production line for an exhaust system 1 and can be used to carry out step c. of a manufacturing process (cf 10 ) for an exhaust pipe section, for example as in 1 shown, furnished. Here the system element 3 (floor plate 14) and the connecting element 6 are initially pre-positioned relative to one another, for example by means of a plug connection, together with a solder ring (solder material). An induction coil 30, which is purely optionally U-shaped here, is placed directly around the solder ring or the plug-in connection. When an AC voltage is applied to the induction coil 30, the locally narrowly limited electromagnetic induction effect is used to generate heat in order to Melt solder material and heat the system element 3 and the connecting element 6 at the point of the plug connection, whereby the system element 3 (bottom plate 14) and the connecting element 6 are connected gas-tight.

In 12 a motor vehicle 2 with an exhaust system 1 is shown in a schematic plan view. An internal combustion engine 17 arranged here in the rear of the four-wheeled motor vehicle 2 is connected in a torque-transmitting manner to a left-hand drive wheel 31 and a right-hand drive wheel 32 (here on a common vehicle axle). During operation of the internal combustion engine 17, the exhaust gases produced in the internal combustion engine 17 are removed by means of an exhaust system 1, for example according to the embodiment in 1 , derived into the environment.

With the exhaust gas line section proposed here and the associated manufacturing method, an exhaust gas conducting titanium component can be connected to a functional unit made of austenitic stainless steel in a simple and cost-effective manner.

Reference List

1

exhaust system

2

motor vehicle

3

plant element

4

functional unit

5

line connection

6

fastener

7

braze seam

8th

exhaust flap

9

decoupling element

10

Exhaust catalyst

11

a coat

12

bypass

13

line element

14

floor pan

15

silencer

16

receptacle

17

internal combustion engine

18

inlet pipe

19

outlet pipe

20

chamber

21

Weld

22

lower half of the case

23

secondary pipe

24

first partition

25

second partition

26

tailpipe connection

27

first outer wall element

28

second outer wall element

29

manufacturing plant

30

induction coil

31

left drive wheel

32

right drive wheel

Claims (10)

Exhaust system (1) for a motor vehicle (2), having at least the following components: - a system element (3) made of titanium or a titanium alloy; - A functional unit (4) with a line connection (5) made of an austenitic stainless steel; and - a connecting element (6) which is arranged between the system element (3) and the line connection (5) of the functional unit (4) and by means of which these are connected to one another, characterized in that the system element (3) and the connecting element (6 ) are connected to one another in a gas-tight manner by means of a brazing seam (7). Exhaust system (1) after claim 1 , wherein the connecting element (6) is formed from a ferritic stainless steel. Exhaust system (1) after claim 1 or claim 2 , wherein the functional unit (4) is at least one of the following elements: - an exhaust flap (8); - a decoupling element (9); - An exhaust gas catalytic converter (10), the connecting element (6) preferably being the casing (11) of the exhaust gas catalytic converter (10); and - a sensor element. Exhaust system (1) according to one of the preceding claims, wherein the connecting element (6) and the line connection (5) of the functional unit (4) are connected to one another in a gas-tight manner by means of welding. Exhaust system (1) according to one of the preceding claims, wherein the functional unit (4) is an exhaust gas flap (8) and a bypass (12) can thus be flown through in a switchable manner. Exhaust system (1) according to one of the preceding claims, wherein the system element (3) is one of the following elements of the exhaust system (1) is: - a duct element (13) for conducting exhaust gas; - A floor panel (14) of a muffler (15); or - a socket (16) for receiving the connecting element (6), the exhaust system (1) preferably comprising a plurality of system elements (3), connecting elements (6) and functional units (4). Manufacturing method for an exhaust system (1) of a motor vehicle (2), wherein an exhaust system (1) according to one of the preceding claims is manufactured with the following steps: a. providing the system element (3), the connecting element (6) and the functional unit (4); b. relative to each other positioning the plant element (3) and the connecting element (6); and c. Forming a gas-tight connection by means of brazing between the system element (3) and the connecting element (6). manufacturing process claim 7 , wherein the brazing is carried out: - by means of induction brazing; and/or - in the soldering oven. manufacturing process claim 7 or claim 8 , where in step b. the system element (3) and the connecting element (6) are pre-fitted with one another, with the line connection (5) of the functional unit (4) and the connecting element (6) preferably also being pre-fitted with one another. Motor vehicle (2), having at least one internal combustion engine (17) for indirect and/or direct propulsion of the motor vehicle (2) and an exhaust system (1) according to one of claim 1 until claim 6 for discharging exhaust gas from the internal combustion engine (17).

Images