EP1774147B1 - Exhaust system and method for joining components of an exhaust system - Google Patents

Description

The invention relates to an exhaust system, in particular for a motor vehicle, and to a method for connecting two components of an exhaust system, in particular for a motor vehicle.

The components to be joined together are, in particular, the pipes of the exhaust system, through which the exhaust gas flow is guided, for example, from the exhaust manifold to a catalytic converter or a silencer. In view of the high temperatures and the high dynamic loads that are exposed to the components of an exhaust system, such components have always been connected by a weld. Although there are some disadvantages when the components of an exhaust system are welded together. On the one hand, comparatively much base area for, for example, an automatic welding machine or a welding robot is required for carrying out the method. In both cases, the components to be welded must be moved relative to the welding head. Therefore, expensive devices for fixing the components to be welded at high dynamic load are required. These devices have a relatively large footprint in the welding booth and for their storage. In addition, many devices must be kept in stock, as a new device is usually required for each type. In addition, it has been found that a weld affects adversely on the strength. Namely, the weld leads to an abrupt change in the cross-section of the connected components and, correspondingly, to a change in the rigidity of the exhaust system, which leads to a stress concentration in the region of the weld seam. In particular, the area of the weld root or Einbrandkerbe may be the starting point for cracking. Finally, when welding in the two components introduced heat to a welding delay, which may need to be corrected individually after welding on a bench. Despite all these disadvantages, it has become generally accepted in the field of exhaust systems to weld components together; In the prior art, there is the conviction that only so a connection of components can be created that withstands the occurring temperature loads and dynamic loads.

The EP 1 061 240 A2 describes a method for joining components of exhaust systems by arc brazing. It is stated there that induction soldering of exhaust systems is disadvantageous.

The object of the invention is to connect two components of an exhaust system in a different way than by welding in order to avoid the above-mentioned disadvantages during welding.

To achieve this object erfingdungsgemäß an exhaust system is provided with a first component and a second component, which is characterized in that between the two components, an induction soldering is present, which consists of a high-temperature solder material. This object is also achieved by a method for connecting a first component of a motor vehicle exhaust system to a second component, in which the two assembled and provided with a high-temperature solder material components are heated in the region of the solder material by means of an inductor to a temperature above the melting point of the solder material lies. The invention is based on the surprising finding that, contrary to the prejudices in the art, a high-temperature solder joint withstands the stresses that act on a motor vehicle exhaust system. So far, it has generally been assumed that alone due to the temperatures occurring at the components of the exhaust system, which may be above 600 ° C, a solder joint is out of the question. The maximum allowable operating temperature of soldered components has generally been considered to be around 200 ° C, even when working with a high temperature solder (see, for example, the Draft Specification DVS 938-2 "Arc Soldering" of the German Welding Association of October 2002, which describes exhaust systems an operating temperature for soldered connections up to 180 ° C is specified and a use of solder joints at temperatures of over 180 ° C is expressly not recommended). The invention overcomes this prejudice, as the Applicant has found in experiments that soldered components can be exposed to temperatures of over 600 ° C for longer periods without affecting the mechanical stability of the solder joint. Favorable to the high temperature strength of the solder joint has the additional effect that sets after the solidification of the soldering material, a reflow temperature, which is higher than the initial melting temperature. The reason for this has not yet been finally clarified. One reason could be that certain alloys evaporate when the solder material melts. Another reason could be the diffusion of atoms of the base material into the solder material.

By using a solder joint instead of a welded joint, there are a number of advantages. On the one hand, the two components can be connected to one another with less effort and less space requirement than is the case when using a welding method. It is not necessary that the two components are bypassed in the region of their connection by a robot in the circumferential direction. Instead, the connection area between the two components can be accommodated in a compact protective gas chamber. The dynamic strength of the solder joint is higher up to a certain temperature, which is lower than the operating temperature occurring at exhaust systems, as compared to a welded joint, since no abrupt changes in stiffness are produced. Also, the two components can be formed with a smaller wall thickness, if they are soldered together instead of being welded. The wall thickness of components to be welded together in the field of exhaust systems namely in some cases not be designed in view of the necessary strength of the components, but in view of the risk of burn-through during welding. This risk is eliminated if the two components are soldered together, so that in the future alone the occurring loads are decisive for the dimensioning. Finally, with a solder joint and flange and clamp connections between individual components can be replaced. Such Connections are becoming more and more disadvantageous due to their high assembly costs and due to tightness problems, so that it is passed to produce all components of the exhaust system materially interconnected.

According to a preferred embodiment of the invention it is provided that one of the components has a support surface for solder. This makes it possible to arrange the solder in the vicinity of the soldering gap, so that the solder material, once it has melted, is drawn into the soldering gap by capillary forces. The support surface prevents the solder material from running away from the soldering gap and towards other areas of the component. On the one hand, the solder material would be undesirable there for optical reasons, and on the other hand, this solder material would no longer be available for the actual solder joint.

The bearing surface on the component can be formed with little effort by a circumferential bead, on which the solder ring can be arranged.

According to an alternative embodiment, it may be provided to arrange a solder support in the region of the solder joint which has the support surface for the solder material. This embodiment has the advantage that the component itself does not have to be reshaped to form the support surface. Preferably, the Lotstütze consists of a material which is electrically non-conductive, for example of a ceramic material. This has the consequence that the solder support is not inductively heated during induction soldering, so that the solder material does not connect to the Lotstütze. This can therefore be easily removed after soldering the two components.

According to an alternative embodiment of the invention, an outlet region is provided between the two components, in which excess solder is received without having connected to the two components. The discharge area thus acts in the manner of an overflow container, which is then filled when the soldering gap is completely filled with the solder material. It is envisaged that the outlet area does not heat to soldering temperature during soldering so that the solder material begins to solidify as soon as it enters the outlet area. This ensures that the solder material does not escape again on the side facing away from the soldering gap and leads to undesirable solder drops in the interior of the two components. Such a drop of solder could lead to damage during operation of the exhaust system inside.

Advantageous embodiments of the invention will become apparent from the dependent claims.

• Figur 1 schematisch zwei miteinander zu verlötende Bauteile gemäß einer ersten Ausführungsform der Erfindung, die in einer Lötvorrichtung angeordnet sind;
• Figur 2 in vergrößertem Maßstab den Ausschnitt II von Figur 1, nachdem die beiden Bauteile miteinander verlötet wurden;
• Figur 3 schematisch zwei miteinander zu verlötende Bauteile gemäß einer zweiten Ausführungsform der Erfmdung;
• Figur 4 die beiden Bauteile von Figur 3 im miteinander verlöteten Zustand;
• Figur 5 in vergrößertem Maßstab den Ausschnitt V von Figur 4;
• Figur 6 schematisch zwei miteinander zu verlötende Bauteile gemäß einer dritten Ausführungsform der Erfindung;
• Figur 7 die beiden Bauteile von Figur 6 im miteinander verlöteten Zustand;
• Figur 8 in vergrößertem Maßstab den Ausschnitt VIII von Figur 7;
• Figur 9 schematisch zwei miteinander zu verlötende Bauteile gemäß einer vierten Ausführungsform;
• Figur 10 die Bauteile von Figur 9 im miteinander verlöteten Zustand;
• Figur 11 schematisch zwei miteinander zu verlötende Bauteile gemäß einer fünften Ausführungsform;
• Figur 12 die Bauteile von Figur 11 in einer anderen Lötposition; und
• Figur 13 schematisch zwei miteinander zu verlötende Bauteile gemäß einer sechsten Ausführungsform.

The invention will be described below with reference to various embodiments, which are illustrated in the accompanying drawings. In these show:

• Figure 1 schematically shows two components to be soldered together according to a first embodiment of the invention, which are arranged in a soldering device;
• Figure 2 on an enlarged scale the detail II of Figure 1 after the two components have been soldered together;
• 3 shows schematically two components to be soldered together according to a second embodiment of the invention;
• FIG. 4 shows the two components of FIG. 3 in a state soldered together;
• Figure 5 on an enlarged scale the detail V of Figure 4;
• Figure 6 schematically shows two components to be soldered together according to a third embodiment of the invention;
• Figure 7 shows the two components of Figure 6 in the soldered together state;
• Figure 8 on an enlarged scale the detail VIII of Figure 7;
• Figure 9 schematically shows two components to be soldered together according to a fourth embodiment;
• FIG. 10 shows the components of FIG. 9 in a state soldered together;
• Figure 11 schematically shows two components to be soldered together according to a fifth embodiment;
• FIG. 12 shows the components of FIG. 11 in a different soldering position; and
• Figure 13 schematically shows two components to be soldered together according to a sixth embodiment.

In Figure 1, two components 10, 12 are shown, which are here two tubes of an exhaust system for motor vehicles. It should be noted at this point, however, that in principle also components other than tubes can be interconnected, e.g. Funnels with tubes, funnels with housings, etc.

The first component 10 is designed with a constant cross-section, while the second component 12 at the end, which faces the first component 10, on the one hand with an outwardly facing bead 14 and then to the bead 14 with a male portion 16 is executed. The insertion portion 16 has an outer diameter that is slightly smaller than the inner diameter of the first component 10.

The component 10 facing, aligned perpendicular to the central axis M surface of the bead 14 forms a bearing surface 18 on which a ring of solder material 20 is arranged. The solder material thus lies in the region of a soldering gap, which is formed between the insertion section 16 of the second component 12 and the first component 10. The solder material 20 is a copper-based or nickel-based high temperature solder.

Although in the embodiments, a solder ring is shown, the solder can of course be provided in other forms, such as sheet metal strip, paste, etc.

Around the area to be soldered of the two components 10, 12 around a soldering device 22 is arranged, which consists essentially of two shells 24, 26th exists, which enclose the area to be soldered approximately gas-tight. Within the shells 24, 26, a protective gas atmosphere can be generated by a suitable device (not shown). Extending around the two shells 24, 26 is an inductor 28 which generates eddy currents in the region of the portions of the two components 10, 12 to be soldered together and in the solder material 20, which are converted into heat due to the electrical resistance.

In order to solder the two components 10, 12 together, the ring of solder material 20 is arranged on the bead 14 of the second component 12 in a first step. Then, the second component 12 is inserted with the insertion portion 16 in the first component 10. Subsequently, the two shells 24, 26 closed around the portion to be soldered of the two components 10, 12, and in the interior of the two shells, a protective gas atmosphere is formed. Then, the portions to be soldered together of the two components 10, 12 and the solder material 20 are heated by means of the inductor 28 to a temperature which is of the order of 1000 ° C. In this case, the solder material 20 melts, so that it is drawn by capillary forces against gravity in the soldering gap between the two components 10, 12 and completely fills it. This can be seen in FIG. The support surface 18 on the bead 14 ensures that the solder material 20, when it melts, does not run away from the soldering gap, but is drawn into the soldering gap. Alternatively, it could also be soldered lying or at an angle.

After the two components 10, 12 have cooled so far that no more scaling takes place in the air, the two shells 24, 26 can be opened, and the now interconnected components can be removed. The soldering device is ready to receive the next components. The particular advantage of the soldering device and the induction soldering process carried out with it is that very short processing times are possible. The achievable process time for welding two components, including heating and cooling, is on the order of 40 seconds unlike welding, regardless of the seam length. Thus, with a small footprint, a high output can be achieved.

A second embodiment is shown in FIGS. For the components known from the first embodiment, the same reference numerals are used, and reference is made to the above explanations in this respect.

The difference from the first embodiment is that the bearing surface 18 is not formed on one of the components themselves, but on a Lotstütze 30, which is here designed as a closed ring. The solder support is made of an electrically non-conductive material, such as a ceramic material, and surrounds the second component 12 adjacent to the soldering gap. In other words, the first component 10 is pushed onto the second component 12 until it bears against the solder support 30. This makes it possible to use the solder support 30 as a reference in the positioning of the two components 10, 12 relative to each other. The surface of the solder support 30 facing the first component 10 then forms the contact surface 18 on which the ring of solder material 20 is arranged. At the Lotstütze, if this is designed as a closed ring, waves, noses or grooves may be provided, which facilitate the solder to flow under the end face of the component 10 into the soldering gap.

The area to be soldered together of the two components 10, 12 is then heated by the soldering device, not shown here, as in the first embodiment, so that the solder material 20 melts and is drawn into the soldering gap between the two components 10, 12 (see FIGS and 5). In this case, a small part of the solder material flows past the Lotstütze 30 down. But since the Lotstütze 30 is made of electrically non-conductive material, it is not heated by the inductor 28, so that the solder solidifies in this area. As a result, only a very small part of the solder material is lost for the actual solder joint. In Figure 5, the solder joint between the two components 10, 12 can be seen after the Lotstütze 30 has been removed. This is easily possible because the solder support 30 is not so far heated during soldering that the soldering temperature is reached. Consequently, that connects Solder material 20 not with the surface of Lotstütze. Clearly the "impression" of the Lotstütze 30 can be seen.

In FIGS. 6 to 8, a third embodiment is shown. Again, the same reference numerals are used for the components known from previous embodiments.

The difference from the first embodiment is that in the third embodiment, the support surface 18 is formed on a funnel-shaped flared end portion of the second component 10. The ring of solder material 20 thus lies directly between the first component 10 and the second component 12. Another difference is that the soldering gap between the first and the second component 10, 12 is formed so that a discharge region 32 for the liquid solder material is trained. The outlet area is determined by the fact that it lies outside the area of the two components 10, 12 heated by the inductor 28 and therefore also remains during the actual soldering process at a temperature which is below the solidification temperature of the solder material 20.

When the two components 10, 12 are soldered together, the area of the soldering gap is heated by the inductor. As soon as the solder material 20 has melted, it is drawn into the soldering gap by the capillary forces, in which it wets the surface of the two components 10, 12. As soon as the solder material reaches the lower section of the soldering gap with respect to FIG. 7, it emerges from the actual soldering gap and enters the outlet region 32. Since this is at a temperature which is lower than the solidification temperature of the solder material 20, the solder material solidifies in the outlet region 32. The outlet region 32 is chosen to be sufficiently long to prevent the solder material from the lower side of the soldering and / or into the interior of the two components 10, 12 occurs. In Figure 8 it can be seen that the solder material 20 in the outlet region 32, the surface of the two components 10, 12 is not wetted, since they are at a relatively low temperature. Accordingly is the front side of the solder material 20 is not concave, as can be seen at the upper end of the soldering gap, but convex.

FIGS. 9 and 10 show a fourth embodiment of the invention. The difference from the preceding embodiments is that here a receiving chamber 34 is provided, within which the solder material 20 is arranged. In contrast to the previous embodiments, the solder material 20 does not have to be arranged here as a completely circumferential ring. It is sufficient that the solder material, for example, extends only along half of the circumference of the annular receiving chamber 34. Once the solder has melted, it spreads due to the capillary forces along the entire circumference of the solder gap, so that a circumferential and gas-tight connection between the two components is made.

If the region of the components 10, 12 to be soldered together is heated to a temperature above the melting temperature of the solder material 20, then the liquid solder material is pulled by capillary forces into the gap between the two components 10, 12. In this case, two separate solder joints, namely a first solder joint between the end face of the second component 12 and the outer surface of the first component 10, ie based on Figure 10 on the left side of the receiving chamber, and a second solder joint between the insertion portion 16 of the first component 10th and the second component 12.

FIG. 11 shows a fifth embodiment of the invention. The difference from the previous embodiments is that the first component 10 is provided with a frustoconical constriction at the end, while the second component is provided with a funnel-shaped extension at the end. The constriction of the first component is arranged in the extension of the second component. The solder material 20 abuts directly on the end face of the extension of the second component 12. As soon as the solder material melts, it is drawn into the soldering gap by the capillary forces, so that a uniform connection between the first and the second component is obtained.

FIG. 12 shows the components known from FIG. 11, wherein, in contrast to FIG. 11, the longitudinal axis of the two components 10, 12 is arranged vertically instead of horizontally. Therefore, the end face of the extension of the second component 12 serves as a support surface 18 for the solder material 20th

In Fig. 13, a sixth embodiment is shown. The difference from the preceding embodiments is that no tubes are soldered together, but two housing parts of a muffler, a catalyst or other component of an exhaust system. The first component 10 forms the upper shell of the housing, and the second component 12 forms the lower shell of the housing. Both components are provided with a circumferential edge, wherein the edge of the second component is provided with a circumferential bead, so that together with the edge of the first component, a chamber for receiving the solder material 20 is formed.

The edges of the first and second components 10, 12 and the solder material 20 are inductively heated, so that the solder material melts and the two components are connected together. It is noteworthy that even with this type of components with a very large seam length, the process time does not increase; If the two components were welded together, the process would take several minutes due to the large seam length.

In principle, all components of an exhaust system can be connected to each other with the method according to the invention. It is irrelevant whether the components are soldered successively, in groups at the same time or all at the same time. It is also possible to solder different materials together. For example, end pipes, which are made of non-ferrous metals and thus made of a different material than the actual exhaust pipes, are soldered to the exhaust pipes.

Claims (18)

1. An exhaust gas system comprising a first component and a second component, characterized in that an induction solder joint consisting of high temperature solder material is present between the two components (10, 12).
2. The exhaust gas system according to claim 1, characterized in that the two components (10, 12) are connected with each other through a push fit connection.
3. The exhaust gas system according to claim 1 or claim 2, characterized in that at least one of the components (10, 12) is a pipe.
4. The exhaust gas system according to any of the preceding claims, characterized in that one of the components (10, 12) has a support surface (18) for a solder ring (20).
5. The exhaust gas system according to claim 4, characterized in that the support surface (18) is formed by a surrounding bead (14).
6. The exhaust gas system according to claim 4 or claim 5, characterized in that the component (10, 12) provided with the support surface (18) is received within the other component (12, 10).
7. The exhaust gas system according to any of the preceding claims, characterized in that a runout region (32) is provided between the two components (10, 12), which receives excessive solder (20) without the latter having made a connection with the two components (10, 12).
8. The exhaust gas system according to any of the preceding claims, characterized in that one of the components (10, 12) is provided with a surrounding receiving chamber (34) for solder material.
9. The exhaust gas system according to claim 8, characterized in that the receiving chamber (34) is formed by a bead.
10. A method of connecting a first component of an exhaust gas system with a second component, in particular for a vehicular exhaust gas system, characterized in that the two components (10, 12), which are put together and provided with a high temperature solder material (20), are heated up in the region of the solder material (20) by means of an inductor (28) to a temperature which lies above the melting temperature of the solder material (20).
11. The method according to claim 10, characterized in that the solder material (20) is arranged on a support surface (18).
12. The method according to claim 11, characterized in that a solder support (30) is arranged in the region of the solder joint, which solder support comprises the support surface for the solder material (20).
13. The method according to claim 12, characterized in that the solder support (30) consists of a material which is electrically non-conductive.
14. The method according to claim 13, characterized in that the solder support (30) consists of a ceramic material.
15. The method according to any of claims 12 to 14, characterized in that the solder support (30) is arranged underneath the solder joint.
16. The method according to any of claims 10 to 15, characterized in that the amount of the solder material (20) is matched with the solder gap between the two components (10, 12) such that the solder material completely fills out the solder gap and excessive solder material is received in a runout region.
17. The method according to any of claims 10 to 16, characterized in that a nickel base solder is used as solder material (20).
18. The method according to any of claims 10 to 16, characterized in that a copper base solder is used as solder material (20).

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