DE102022126974A1 - Rivet connection - Google Patents

Abstract

The invention relates to a rivet connection with at least two joining partners (1, 2, 3) that can be connected to one another in the setting process, in which a rivet element (7) with its rivet shaft (13) can be driven in the setting direction through the at least one setting-side joining partner (2, 3) into the joining partner (1) facing away from the setting side, specifically with the rivet shaft (13) spreading out, so that the joining partners (1, 2, 3), viewed in the setting direction, are clamped under compressive stress between a rivet head (9) and a shaft tip of the rivet element (7). According to the invention, the setting-side joining partner (2, 3) is clamped in a floating position between the rivet head (9) of the rivet element (7) and the joining partner (1) facing away from the setting side.

Description

The invention relates to a rivet connection according to the preamble of claim 1 or according to the preamble of claim 19 and a rivet element according to claim 20.

The starting point of the invention is a generic setting process in which at least two joining partners can be connected to one another. In the setting process, a rivet element can be driven in by spreading its rivet shaft in the setting direction through at least one joining partner on the setting side into the joining partner facing away from the setting side. After the setting process has taken place, the joining partners are clamped under compressive stress between a rivet head and a shaft tip of the rivet element, viewed in the setting direction. In the setting process, the rivet element is driven in with a high setting force (e.g. 50 kN) that is usual in the prior art, whereby the rivet foot tip expands radially outwards over an expansion path. This results in an undercut between the rivet head and the expanded rivet foot tip, which is filled with component material. The rivet foot tip is framed by component material in a form-fitting manner. In this way, a relative movement, for example caused by springback of the rivet foot after spreading, is prevented because this would require a deformation of the component.

• Zum einen weist Metalldruckguss im Vergleich zu einem Metallblech eine sehr geringe Duktilität auf. Bei Verwendung eines Metalldruckgussteil als von der Setzseite abgewandten Fügepartner ist daher das oben beschriebene formschlüssige Umfassen der Nietfußspitze - aufgrund der geringen Duktilität - nur eingeschränkt möglich, so dass es nach dem Setzvorgang zu einer Rückfederung des Nietfußes (nach dem Spreizen) kommen kann. Von daher ist das Nietelement nicht ausreichend gegen ein Lösen gesichert. Zudem besteht bei Metalldruckguss aufgrund der geringen Duktilität die Gefahr von Kerbbildung, die zu einem frühzeitigen Bauteilriss oder -bruch führen kann.

The following problem arises especially in the case of a joining partner combination consisting of a plastic component, an aluminum component or a steel component as the joining partner on the setting side and a metal die-cast part as the joining partner facing away from the setting side:

• On the one hand, metal die casting has very low ductility compared to sheet metal. When using a metal die casting part as a joining partner facing away from the setting side, the form-fitting grip of the rivet foot tip described above is only possible to a limited extent due to the low ductility, so that after the setting process the rivet foot can spring back (after spreading). The rivet element is therefore not sufficiently secured against loosening. In addition, with metal die casting, there is a risk of notching due to the low ductility, which can lead to premature component cracking or breakage.

On the other hand, the metal die-cast component has a very pronounced thermal expansion compared to the plastic component and can have a different thermal expansion than other aluminum components or steel components. A joining partner combination of a metal die-cast part and a plastic component is therefore more susceptible to component stresses that are aligned transversely to the setting direction compared to a joining partner combination of sheet metal parts, which are caused by different thermal expansions of the joining partners. Due to the high setting force that is usual in the state of the art (e.g. 50 kN), such a high connection strength is achieved that no relative movement within the rivet connection is permitted in order to enable stress compensation.

From the EN 10 2018 122 200 A1 A joint connection is known. From the WO95/35174 A1 A punch riveting process is known. From the EN 10 2015 014 941 A1 A method for producing a connection between a functional element and a plate-shaped component is known.

The object of the invention is to provide a riveted connection which, in comparison to the prior art, is structurally simple and reliable and in which, in particular, component stresses caused by different thermal expansions and/or the risk of notching are reduced.

The object is solved by the features of claims 1, 19 or 20. Preferred developments of the invention are disclosed in the subclaims.

The invention is based on a rivet connection with at least two joining partners that can be connected to one another in the setting process. In the setting process, a rivet element with its rivet shaft can be driven in the setting direction through the at least one joining partner on the setting side into the joining partner facing away from the setting side while spreading the rivet shaft. As a result, the joining partners, viewed in the setting direction, are clamped under compressive stress between a rivet head and a shaft tip of the rivet element. According to the characterizing part of claim 1, the joining partner on the setting side is clamped in a floating position between the rivet head of the rivet element and the joining partner facing away from the setting side. In this way, a shear stress transverse to the setting direction, in particular caused by different thermal expansion of the joining partners, can be reduced or eliminated by a transverse movement of the joining partner on the setting side.

To support the floating bearing, a sliding element, in particular a plastic intermediate layer, can be arranged between the bottom of the rivet head and the joining partner on the setting side, by means of which a friction coefficient between the bottom of the rivet head and the joining partner on the setting side can be reduced. The sliding element can preferably be pre-assembled as a washer on the rivet element. In this case, a one-piece pre-assembly unit consisting of a rivet element and a washer can be provided. The washer can preferably be pushed onto the rivet shaft with a slight press fit. Alternatively, the sliding element can be designed as a plastic coating injected onto the underside of the rivet head.

The sliding element made of plastic ensures easy processing. In addition, the processing is gentle on the surface and electrically insulating. Furthermore, contact corrosion can be prevented.

The floating bearing according to the invention is particularly preferred in a joining partner combination in which the joining partner on the setting side is a plastic component, aluminum component or steel component and/or the joining partner facing away from the setting side is a metal component, which has a very pronounced or at least different thermal expansion compared to the plastic component, aluminum component or steel component. According to the invention, the different thermal expansions can be compensated by the transverse mobility of the joining partner on the setting side.

The joining partner on the setting side can have a through-hole. During the setting process, the rivet element can be driven through the through-hole into the joining partner facing away from the setting side. In this way, a build-up of tension in the joining partner on the setting side across the setting direction can be reduced or eliminated entirely. To support the floating support of the joining partner on the setting side, the rivet shaft is preferably guided with hole clearance through the through-hole of the joining partner on the setting side, so that the compensating movement of the joining partner on the setting side across the setting direction is possible, particularly within the hole clearance.

The joining partner facing away from the setting side can particularly preferably be manufactured as a metal die-cast component, in particular aluminum die-cast. The metal die-cast component not only has a very pronounced thermal expansion, but also a low ductility compared to a sheet metal part. In the metal die-cast component, due to the low ductility, there is a risk of notching, which can lead to a component crack or breakage in a conventional setting process.

Against this background, it is preferred if, in contrast to a conventional setting process, a form-fitting grip on the expanded rivet shaft tip is dispensed with and instead the following operating principle is used to secure the rivet element to the joining partner facing away from the setting side: The rivet shaft forms a bistable spring section that has two equilibrium states. A first equilibrium state corresponds to the cross-section-reduced, undeformed rivet shaft state. When the setting force is applied, the rivet shaft changes to the second equilibrium state in which the rivet shaft is expanded with an expanded cross-section in the pre-hole of the first joining partner. The change to the expanded state takes place essentially without the build-up of a spring-back force that prestresses the rivet element towards the undeformed state.

According to the invention, the deformation of the rivet element in the setting process takes place using the so-called spring-buckling effect (also known as the cracking frog effect). The spring-buckling effect is a physical effect in which the shape of the rivet element has two stable states that can be converted into one another by applying a suitable force.

A particular advantage of this new operating principle is the following: The setting force required to transfer to the spreading state is much lower than the setting force required in the conventional setting process. Due to the lower setting force compared to the state of the art, the joining partner on the setting side is subjected to significantly lower compressive stress than would be the case with a conventional setting process. This makes a setting process of the assembly consisting of rivet element and sliding element possible. Only due to this lower compressive stress - in interaction with the sliding element - is the compensating movement of the two upper joining partners possible to equalize the stress. In contrast, in the conventional setting process the rivet element is driven into the joining partners with such a high setting force that there is no transverse movement of the joining partner on the setting side with respect to the joining partner facing away from the setting side.

As mentioned above, the joining partner facing away from the setting side is not completely free of pre-holes in the undeformed state, but rather has a pre-hole at the joining point to be created. In the assembled state, the rivet shank of the rivet element is spread against the inner circumference of the pre-hole.

The rivet element can be designed to be rotationally symmetrical with respect to a rivet element longitudinal axis. In addition, the rivet element can have an expanded rivet head that merges into the rivet shaft in the axial direction. A further functional element can also be provided on the top of the rivet head. element, for example a threaded bolt. The rivet shaft can have an inner curvature that is open towards the rivet shaft tip; in addition, the rivet shaft can end at the shaft tip with a ring-shaped cutting edge.

In the expanded state, the rivet shank wall can be folded over in the opposite direction to the setting direction, i.e. in the direction of the rivet head. In this case, the cutting edge can be in expanding engagement with the inner circumference of the component's pilot hole. In addition, the rivet shank wall surrounds the solid material section of the rivet shank in a plate shape and in the circumferential direction without interruption or continuously.

In a preferred technical implementation, the first joining partner can be a metal die-cast part, for example an aluminum die-cast part, while the rivet element can be made of a cold-forming material. In this case in particular, the rivet connection according to the invention is advantageous because the first joining partner is stressed during the setting process essentially without plastic deformation, i.e. in particular only elastically. According to the invention, the first joining partner remains largely undeformed after the setting process has taken place.

In order to ensure that the rivet element is transferred smoothly from the undeformed state to the expanded state, it is advantageous if the component pre-hole has a corresponding activation contour. The activation contour can be used to ensure that the rivet element is transferred reliably from the undeformed state to the expanded state during the setting process.

According to a first embodiment, the activation contour can be implemented as an expansion cone protruding from the base of the pilot hole. With the help of the activation contour, the base-side shaft section of the rivet shaft can be folded into the expanded state in the opposite direction to the setting direction during the setting process. After folding into the expanded state, a radially inner head-side shaft section of the rivet shaft merges at a folding edge remote from the rivet head into the base-side shaft section protruding in the direction of the rivet head, which surrounds the head-side shaft section radially on the outside.

The activation contour formed in the component pilot hole can also have a ring groove that surrounds the expansion cone at its cone base. The ring groove can merge radially outwards into the pilot hole peripheral wall at a particularly rounded inner corner area. In particular, the expansion cone in combination with the ring groove and the pilot hole inner corner area lead to a folding of the base-side shaft section of the rivet shaft, as described above.

A setting process that can be carried out using the activation contour specified above is described below: At the start of the setting process, the rivet element can sit with its cutting edge on the conical surface of the expansion cone. By applying the setting force, the rivet element can slide with its cutting edge along the conical surface in the direction of the ring groove without penetrating the material of the joining partner. In this way, the base-side shaft section of the rivet shaft is pre-expanded while the material is thinned. As the setting process continues, the material-thinned, base-side shaft section of the rivet shaft is guided by the expansion cone into the ring groove. At the end of the setting process, the base-side cutting edge of the rivet element is driven into the material on the pre-hole peripheral wall.

As mentioned above, the rivet shaft is pre-expanded on the expansion cone during the setting process. The pre-expanding causes the rivet shaft to expand conically from its dimensionally stable, cylindrical, undeformed state. The conical expansion of the rivet shaft takes place while reducing the wall thickness of the shaft wall. This reduces the dimensional stability of the rivet shaft. As the setting process continues, the rivet shaft can therefore reliably change to its expanded state.

To ensure that the setting process runs reliably, it is important that the rivet element with its cutting edge does not penetrate the material of the first joining partner at the expansion cone at the start of the setting process. Against this background, a cutting flank on the cutting edge can have a cutting angle that roughly corresponds to a cone angle that is spanned between the conical surface of the expansion cone and a rectangular plane. This ensures that the rivet element with its cutting edge can slide along the conical surface of the expansion cone in the direction of the ring groove without penetrating the material of the first joining partner.

The pilot hole peripheral wall can merge into a setting-side surface of the first joining partner at a pilot hole opening edge. The pilot hole peripheral wall can expand conically from the bottom-side pilot hole inner corner area to the pilot hole opening edge or can run in a cylindrical shape. The pilot hole diameter is preferably larger than the rivet shaft outer diameter. In this way, the rivet element can be easily pre-positioned in the pilot hole of the first joining partner with hole clearance in preparation for the setting process.

In a further design variant, the activation contour can be designed as follows: The blind hole-like pre-hole of the first joining partner can have a large-diameter insertion section. This transitions into a small-diameter depression on a circumferential ring shoulder. The cutting edge of the still undeformed rivet element can lie on a diameter that is larger than the inner diameter of the ring shoulder. This allows the rivet element to be positioned with its cutting edge on the ring shoulder of the component pre-hole (in preparation for the setting process).

When the setting force is applied, the rivet element with its cutting edge can expand radially outwards until a maximum outer diameter is reached. As the setting process continues, the rivet shank can be driven into the pre-hole countersink by an additional over-center stroke. This causes the rivet shank to over-expand, which causes the rivet shank to switch to the expanded state.

The rivet element can preferably be made from a cold-forming material in which a deformation limit is exceeded, particularly during over-expansion, at which a hardening of the rivet element material occurs, which is advantageous with regard to increased connection strength between the rivet element and the component. Therefore, according to the invention, a die can be dispensed with, the die shape of which supports the spreading of the rivet shaft. Instead, the first joining partner can be clamped between a hold-down device and a flat anvil.

The setting process according to the invention can be part of a fully automatic process chain in which a setting device is attached to the distal end of a robot arm of an industrial robot that works autonomously using a program control. In order to ensure a flawless setting process, it is preferred if the rivet shaft outer diameter is smaller than the ring shoulder outer diameter. In this way, the still undeformed rivet element can be positioned with its cutting edge in a floating position, i.e. with transverse play, on the ring shoulder, whereby component and/or manufacturing tolerances can be compensated.

If the joining partner facing away from the setting side is designed as a die-cast part, the pilot hole can be created in the first joining partner during the casting process. In this case, the pilot hole can have a conical inner circumference that serves as a draft angle. The conical inner circumference also acts as an insertion angle during the setting process to ensure that the rivet element is positioned correctly on the ring shoulder of the component pilot hole.

In a specific embodiment, the rivet element can have a rivet element length of, for example, 2 to 5 mm in the undeformed state. The wall thickness of the shaft wall of the rivet shaft can be in a range between 0.3 and 0.7 mm in the undeformed state, in particular 0.5 mm. In addition, depending on the application, the rivet element can be made from a wire material suitable for welding, for example, or from a conventional cold-forming steel, in which a deformation limit is exceeded, in particular during over-expansion, i.e. when turning over during the setting process, at which a hardening of the rivet element material occurs, which is advantageous with regard to increased connection strength between the rivet element and the component. According to the invention, a die can be dispensed with during the setting process, the die engraving of which supports the spreading of the rivet shaft. Instead, the component can be clamped between a hold-down device and a flat anvil during the setting process.

In an embodiment specified above, the two joining partners can be connected to one another directly in the setting process, in which the rivet element with its rivet shank can be driven in the setting direction through the joining partner on the setting side into the joining partner facing away from the setting side. As a result, the two joining partners, viewed in the setting direction, are clamped under compressive stress between a rivet head and a cutting edge of the rivet shank of the rivet element.

In a second embodiment, the rivet element can only be driven into a first joining partner with its rivet shaft in the setting direction during the setting process. The second joining partner, however, can be fastened to the rivet element independently of the setting process, in particular in a clip, screw, snap-in or welded connection.

To implement the above second embodiment, it is advantageous if the pilot hole diameter at the pilot hole opening edge of the blind hole-like pilot hole of the first joining partner (corresponds to the joining partner facing away from the setting side) is smaller than a head diameter of the rivet head, so that after the setting process has been completed, the rivet head underside is in contact with the opening edge area of the component pilot hole. A bolt for connecting the second joining partner, in particular a threaded bolt or welding bolt, can be formed on the rivet head top of the rivet element. In the assembled state, the Bolts must be guided through a through hole in the second joining partner. A clip, locking, screw or welding element can be attached to the threaded bolt tip protruding from the through hole in the second joining partner. In this case, the second joining partner can be clamped between the clip, locking, screw or welding element and the first joining partner.

When welding, the welding stud can be guided through a through hole in the second joining partner in the assembled state. A third joining partner or a head element, such as a welding cap, to which a sliding element (for example a sliding element ring disk) is firmly connected, can be welded onto the welding stud tip protruding from the through hole in the second joining partner using resistance spot welding. The second joining partner can therefore be clamped between the third joining partner or the welding cap and the rivet head.

According to the invention, the second joining partner is clamped in a floating position between the rivet head of the rivet element and the second joining partner. In this way, a shear stress transverse to the setting direction, in particular caused by different thermal expansion of the joining partners, can be reduced or eliminated by a transverse movement of the second joining partner. To support the floating position between the top of the rivet head and the second joining partner, a sliding element, in particular a plastic intermediate layer, can be arranged - analogous to the first embodiment - by means of which a coefficient of friction between the top of the rivet head and the second joining partner can be reduced. The clip, locking, screw or welding element can also be designed, for example, with a collar to which a plastic intermediate layer, such as a plastic disk, is attached or a plastic ring is molded on, by means of which a coefficient of friction between the clip, locking, screw or welding element and the second joining partner can be reduced.

• 1 bis 5 Ansichten einer Nietverbindung gemäß einem ersten Ausführungsbeispiel;
• 6 bis 9 Ansichten einer Nietverbindung gemäß einem zweiten Ausführungsbeispiel; und
• 10 bis 12 Ansichten einer Nietverbindung gemäß weiteren Ausführungsbeispielen.

Exemplary embodiments of the invention are described below with reference to the accompanying figures. They show:

• 1 to 5 Views of a riveted connection according to a first embodiment;
• 6 to 9 Views of a riveted connection according to a second embodiment; and
• 10 to 12 Views of a riveted connection according to further embodiments.

In 1 is a riveted joint with a lower first joining partner 1, a middle second joining partner 2 and a third joining partner 3 facing the setting side. The riveted joint is shown in a 4 The rivet element 7 is produced by means of the setting process indicated with the aid of a rivet element 7 designed as a semi-tubular rivet, which has a large-diameter rivet head 9 that is implemented as a flat head. The rivet head 9 merges at its rivet head underside into a small-diameter rivet shaft 13 that terminates at a circumferential cutting edge 15. In the undeformed state, the rivet element 7 is implemented as a component that is rotationally symmetrical about a longitudinal axis L and is shown in the figures in a cross-section view.

In the, in the 1 In the rivet connection shown, the rivet element 7 is driven through the joining partner 3 on the setting side and through the middle joining partner 2 into the joining partner 1 facing away from the setting side, while maintaining a residual base thickness in the joining partner 1. In the 1 the rivet shank 13 is spread open. The three joining partners 1, 2 and 3 are therefore clamped together under a compressive stress acting in the setting direction S.

In the present exemplary embodiment, a mixed construction connection is realized in which the joining partner 1 facing away from the setting side is an aluminum die-cast part, while the setting-side joining partner 3 and the middle joining partner 2 are each a plastic component, for example a thermoplastic plastic part, or a CFRP component. In an alternative embodiment, the setting-side joining partner 3 and/or the middle joining partner 2 can also be a steel component or aluminum component.

In comparison to a conventional joining partner combination of sheet metal parts, such a joining partner combination of aluminum die-cast part and plastic component is susceptible to component stresses that are directed transversely to the setting direction and are caused by different thermal expansions of the joining partners 1, 2, 3. In addition, the joining partner 1 facing away from the setting side (i.e. the aluminum die-cast part) has very low ductility compared to conventional metal sheets. A conventional setting process in which the rivet shaft is completely enclosed in a form-fitting manner by the die-cast material of the joining partner 1 facing away from the setting side cannot therefore be carried out reliably. In addition, with metal die casting, due to the low ductility, there is a risk that notches will form during the setting process, which can lead to premature component cracking or breakage.

A core of the invention is that the two upper joining partners 2, 3 are clamped in a floating position between the rivet head 9 of the rivet element 7 and the joining partner 1 facing away from the setting side. In this way A component stress transverse to the setting direction S, which is caused, for example, by different thermal expansion of the joining partners 1, 2, 3, can be reduced or eliminated by a transverse compensating movement of the upper joining partners 2, 3.

To support the floating bearing between the bottom of the rivet head and the top joining partner 3, a sliding element 6 is arranged, by means of which a coefficient of friction between the bottom of the rivet head and the top joining partner 3 can be reduced. The sliding element 6 is, for example, a plastic washer that can be pre-assembled on the rivet element 7.

To further support the floating bearing, the two upper joining partners 2, 3 each have a through hole 17 through which the rivet element 7 can be driven into the joining partner 1 facing away from the setting side. The rivet shaft 13 is guided through the through holes 17 of the joining partners 2, 3 with a hole clearance Δx, so that the compensating movement B of the upper joining partners 2, 3 transverse to the setting direction is possible within the hole clearance Δx.

In this way, stress compensation between the joining partners 1, 2, 3 can take place in the event of thermal stress.

In the setting process ( 3 to 5 ), the rivet element 7 is guided stress-free through the pilot hole 17 of the two joining partners 2, 3 and is then driven into the first joining partner 1 facing away from the setting side.

• Gemäß der 1 ist das Nietelement 7 in ein Vorloch 5 des von der Setzseite abgewandten ersten Fügepartners 1 eingetrieben, das sich konusartig bis zu einer Vorlochtiefe t erstreckt und dort mit einem Vorloch-Boden abschließt.

A significant advantage of the invention is that the rivet connection can be realized with a joining partner 1 facing away from the setting side, whose flowability or ductility is reduced compared to the prior art (for example a component made of die-cast aluminum). According to the invention, the securing of the rivet element 7 is not carried out by a complete form-fitting enclosing of the rivet shaft 13 in the material of the first joining partner 1, but by the following based on the 1 to 5 described security mechanism:

• According to the 1 the rivet element 7 is driven into a pre-hole 5 of the first joining partner 1 facing away from the setting side, which extends conically to a pre-hole depth t and ends there with a pre-hole bottom.

In the pre-hole 5 of the first joining partner 1 an activation contour 31 ( 3 or 4 ) which controls the transfer of the rivet element 7 from the undeformed state to the expanded state during the setting process. The activation contour 31 has an expansion cone 33 protruding from the pre-hole base, which is surrounded at its cone base by an annular groove 35 formed in the pre-hole base. The annular groove 35 extends radially outwards at a rounded inner corner area 37 into a pre-hole peripheral wall 39 ( 4 or 5 ) over. In the 1 to 5 the smooth-surfaced pre-hole peripheral wall 39 extends from the pre-hole inner corner area 37 to a pre-hole opening edge 41 ( 2 ) on the setting-side surface of the first joining partner 1 is slightly conically expanded.

According to the 1 a base-side shaft section 43 of the hollow rivet shaft 13 is driven with its cutting edge 15 at the pre-hole peripheral wall 39 into the material of the first joining partner 1.

As from the 2 As can be seen from the drawing, the pre-hole diameter dv is larger than the rivet shaft outer diameter d _A , so that the rivet element 7 can be pre-positioned in preparation for the setting process with a hole clearance in the pre-hole 5 of the first joining partner 1. The pre-hole diameter dv is also smaller than a head diameter d _K of the rivet head 9. After the setting process has been completed, the underside of the rivet head 9 is in contact with the opening edge area of a through-hole 17 of the upper setting-side joining partner 3. As can be seen from the drawing, 2 As can be seen further, the rivet shaft 13 is cylindrical on the outside in the undeformed state. The inner curvature 14 of the rivet shaft 13 is hollow-cylindrical, which results in a constant wall thickness w of the shaft wall over the rivet element longitudinal axis L. The rivet element 7 is designed to be rotationally symmetrical to the rivet element longitudinal axis L.

The following is based on the 3 to 5 a setting process is described: At the beginning of the setting process ( 3 ), the rivet element 7 (guided by the joining partners 2, 3) is brought with its cutting edge 15 into contact with the conical surface of the expansion cone 33. The rivet element 7 is aligned coaxially to the expansion cone 33. When the setting force F is introduced, the rivet element 1 slides with its cutting edge 15 along the conical surface in the direction of the ring groove 35. In this way, the base-side shaft section 43 of the rivet shaft 11 is pre-expanded. On the one hand, the pre-expanding causes the cylindrical rivet shaft 13 to expand conically. On the other hand, the conical expansion of the rivet shaft 13, especially on the base-side shaft section 43, reduces the wall thickness w. Due to the conical expansion and the reduced wall thickness w, the activation contour 31 can reliably transfer the rivet shaft 13 into the expanded state in the further setting process. At the end of the setting process ( 5 ) the cutting edge 15 of the rivet elements 7 are driven into the material of the first joining partner 1 at the pilot hole peripheral wall 39.

In the 2 Two cutting flanks 45, 47 converge on the rivet shaft 13 to form the cutting edge 15. The radially inner cutting edge 45 spans a cutting angle β with a plane perpendicular to the rivet element's longitudinal axis L. This corresponds to a cone angle γ that is spanned between the conical surface of the expansion cone 33 and a plane perpendicular to the rivet element's longitudinal axis L. This ensures that the cutting edge 15 slides reliably in the direction of the ring groove 35 during the setting process without penetrating the material.

With the help of the activation contour 31, the base-side shaft section 43 of the rivet shaft 11 is folded over in the setting process against the setting direction S. In the finished rivet connection, a head-side shaft section 49 therefore merges at a folding edge 51 remote from the rivet head into the base-side shaft section 43 protruding in the direction of the rivet head 9. The folded-over base-side shaft section 43 extends continuously in the circumferential direction and in a plate shape around the head-side shaft section 49. It should be emphasized that only the folded-over base-side shaft section 43 with its cutting edge 15 of the rivet shaft 11 penetrates into the material of the first joining partner 1 on the pre-hole peripheral wall 39, while the head-side shaft section 49 remains without material engagement with the first joining partner 1.

The rivet shaft 11 thus acts like a bistable spring section, which changes into the expanded expansion state during the setting process. The expansion state ( 1 or 5 ) is characterized in that, in contrast to the prior art, essentially no spring-back force is built up in the rivet shaft 13, which prestresses the rivet element 7 in the direction of the undeformed state. Therefore, according to the invention, an almost completely form-fitting enclosing of the rivet shaft 11 in the material can be dispensed with.

According to the 3 to 5 The setting tool according to the invention does not have a die with die engraving as the counterholder 30, but rather a flat anvil.

A particular advantage of this new operating principle is the following: The setting force F required to transfer to the spreading state is much lower than the setting force required in the conventional setting process. Due to the lower setting force F compared to the state of the art, the rivet element 7 with the sliding element 6 and the two upper joining partners 2, 3 are subjected to a much lower compressive stress than would be the case in a conventional setting process. It is only due to this lower compressive stress - in interaction with the sliding element 6 - that the transverse compensation movement of the two upper joining partners 2, 3 to compensate for the stress is possible. In contrast, in the conventional setting process the rivet element is driven into the joining partners with such a high setting force that there is no transverse mobility of the joining partners 2, 3 with respect to the joining partner 1 facing away from the setting side.

In the 6 to 9 a rivet connection according to a second embodiment is shown, the structure of which essentially corresponds to the structure of the first embodiment of the 1 to 5 As in the first embodiment, in the second embodiment the rivet shaft 13 also acts as a bistable spring section, which has the two equilibrium states, namely the undeformed cross-section-reduced state ( 7 ) and an extended spread state ( 6 or 9 ).

The following are based on the 6 to 9 the pre-hole geometry of the first joining partner 1, the rivet element geometry and the setting process according to the invention are described: According to the 7 the still undeformed rivet element 7 is rotationally symmetrical with respect to its longitudinal axis L. The rivet shaft 13 is in the 6 or 7 divided into a head-side shaft section 49 and an adjoining foot-side shaft section 43, which delimits an inner curvature 14 that is open at the rivet shaft tip. The inner curvature 14 ends at an annular circumferential cutting edge 15 of the rivet element 7.

The turning of the rivet shaft 13, which acts as a bistable spring section, is carried out by means of an activation contour 31 ( 7 ) in the pilot hole 5 of the first joining partner 1, which is designed as follows: Thus, the pilot hole 5 of the first joining partner 1 in the 7 a large diameter insertion section 21. This gradually changes in the direction of the pilot hole base 22 on a circumferential annular shoulder 23 into a small diameter pilot hole depression 25. When the rivet element 7 is still undeformed, the cutting edge 15 runs on a diameter d ₁ that is larger than the inner diameter d ₂ of the annular shoulder 23. In addition, the rivet shaft outer diameter is smaller than the annular shoulder outer diameter d ₃ .

The setting process is carried out with a setting tool that is inserted into the 7 to 9 the hold-down device 27, in which a setting piston 29 is guided with an adjustable stroke. The three joining partners 1, 2, 3 are clamped between the hold-down device 27 and a flat anvil 30.

When the setting force F is applied, the rivet shaft 13 with its cutting edge 15 expands radially outwards until a setting stroke dead point T ( 8th ). At the setting stroke dead center T, the cutting edge 15 of the rivet element 1 is expanded with a maximum diameter d _max and in spreading engagement with the inner circumference of the large-diameter insertion section 21 of the component pilot hole 5. In addition, the front side of the rivet shaft tip is in contact with the ring shoulder 23 over a large area.

According to the invention, the setting stroke is extended beyond the dead center T with an over-dead center stroke s ( 8th ). In the further course of the setting process, the head-side shaft section 49 is therefore driven into the pre-hole countersink 25 by the over-dead-center stroke distance s. In this way, an over-expansion of the foot-side shaft section 43 occurs, in which the foot-side shaft section 43 turns into the expanded state. The foot-side shaft section 43 is therefore turned over in the opposite direction to the setting direction, i.e. in the direction of the rivet head 9. The foot-side shaft section 43 extends in the circumferential direction continuously and in a plate shape around the head-side shaft section 49 of the rivet element 7.

As from the 7 As can be seen further, the inner circumference of the large diameter insertion section 21 of the component pre-hole 5 is designed in a conical manner, so that the inner circumference acts as an insertion bevel, by means of which the rivet element 7 can be easily inserted into the pre-hole 5 of the first joining partner 1. In addition, the rivet element 7 is positioned on the ring shoulder 23 in a floating bearing ( 7 ), i.e. positioned with transverse play, whereby component and/or manufacturing tolerances can be compensated.

In the 10 another rivet connection is shown in which the first joining partner 1 can be connected to the second joining partner 2 with the help of the rivet element 7. Analogous to the previous embodiments, the rivet element 7 is driven into the first joining partner 1 in a setting process with its rivet shaft 13 in the setting direction. The second joining partner 2, however, is fastened to the rivet element 7 independently of the setting process in a separate assembly process. For this purpose, the rivet element 7 is formed on its upper side with a threaded bolt 53. In the assembled state, the threaded bolt 53 is guided through a through hole 55 of the second joining partner 2. At the 10 A collar screw nut 57 can be screwed onto the threaded bolt tip protruding from the through hole 55 of the second joining partner 2, so that the second joining partner 2 can be clamped between the collar screw nut 57 and the rivet head 9.

The second joining partner 2 is in the 10 - analogous to the previous embodiment - in a floating position, clamped between the rivet head 9 of the rivet element 7 and the second joining partner 2. As a result, a shear stress transverse to the setting direction, for example caused by different thermal expansion of the joining partners 1, 2, can be reduced or eliminated by a transverse movement of the second joining partner 2.

To support the floating bearing, a sliding element 6 is arranged between the top of the rivet head and the second joining partner 2, by means of which a coefficient of friction between the top of the rivet head and the second joining partner 2 is reduced. The sliding element 6 is, for example, a plastic washer that can be pre-assembled on the threaded bolt 53 of the rivet element 7.

To further support the floating bearing, a sliding element 6 is also arranged between the second joining partner 2 and the facing underside of the collar screw nut 57, by means of which a coefficient of friction between the rivet head top and the second joining partner 2 is reduced. The sliding element 6 is, for example, a plastic coating sprayed onto the underside of the collar screw nut 57 or a permanently mounted plastic disk.

In addition, the second joining partner 2 has a through hole 17 to support the floating bearing, through which the threaded bolt 53 is guided with a hole clearance Δx, so that the compensating movement B of the second joining partner 2 transverse to the setting direction is possible within the hole clearance Δx.

In the 11 another rivet connection is shown in which the first joining partner 1 can be connected to the second joining partner 2 with the help of the rivet element 7. Analogous to the previous embodiments, the rivet element 7 is driven into the first joining partner 1 in a setting process with its rivet shaft 13 in the setting direction. The second joining partner 2, however, is fastened to the rivet element 7 independently of the setting process in a separate welding process. For this purpose, the rivet head 9 of the rivet element 7 is formed on its upper side with a welding bolt 53 which can be guided through a through hole 55 of the second joining partner 2. At the 11 The third joining partner 3, which is formed as a sheet metal component, can be welded onto the welding stud tip protruding from the through hole 55 of the second joining partner 2 by means of resistance spot welding, so that the second joining partner 2 together with the plastic washer 6 can be clamped between the third joining partner 3 and the rivet head 9.

Alternatively, in the 12 a welding cap 56 is welded onto the welding stud tip protruding from the through hole 55 of the second joining partner 2 by means of resistance spot welding, so that the second joining partner 2 is clamped between the welding cap 56 and the rivet head 9. In order to ensure a floating bearing, a further sliding element 6 is arranged between the second joining partner 2 and the welding cap 57, by means of which a coefficient of friction between the welding cap 57 and the second joining partner 2 can be reduced. The further sliding element 6 is in the 12 For example, it is designed as a plastic coating ring sprayed onto the underside of the welding cap 56 or as a firmly connected sliding element ring disk.

In a further embodiment, the sliding element 6 can be applied as a foil on the rivet head 9, the joining partner 3 (in 11 ) and/or the collar screw nut 57, which may have a corresponding material recess 58 for the welding or threaded bolt 53 of the rivet element 7.

List of reference symbols

1

first joining partner

2

second joining partner

3

third joining partner

5

Pre-hole

6

Sliding element

7

Rivet element

5

blind hole-like pre-hole in the first joining partner 1

9

Rivet head

13

Rivet shank

14

Inner curvature

15

Cutting edge

17

Through hole

22

Pre-hole floor

21

large diameter insertion section

23

Ring shoulder

25

Pre-hole countersinking

27

Hold-down clamp

29

Setting piston

30

anvil

31

Activation contour

33

Expansion cone

35

Ring throat

37

Inner corner area

39

Pre-hole perimeter wall

41

Pre-hole opening edge

43

foot-side shaft section

45.47

Cutting edges

49

head-side shaft section

51

Envelope edge

53

bolt

55

Through hole

56

Head element or welding cap

58

Material recess

57

Clip, snap, screw or weld element

there

Shaft outer diameter

dK

Head diameter

dv

Pre-hole diameter

w

Wall thickness

F

Setting force

S

Setting direction

L

Rivet element longitudinal axis

β

Cutting angle

γ

Cone angle

t

Pre-hole depth

Δx

Match play

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 102018122200 A1 [0005]
• WO 9535174 A1 [0005]
• DE 102015014941 A1 [0005]

Claims (20)

Rivet connection with at least two joining partners (1, 2, 3) that can be connected to one another in the setting process, in which a rivet element (7) with its rivet shaft (13) can be driven in the setting direction through the at least one setting-side joining partner (2, 3) into the joining partner (1) facing away from the setting side, specifically by spreading the rivet shaft (13), so that the joining partners (1, 2, 3), viewed in the setting direction, are clamped under compressive stress between a rivet head (9) and a shaft tip of the rivet element (7), characterized in that the setting-side joining partner (2, 3) is clamped in a floating position between the rivet head (9) of the rivet element (7) and the joining partner (1) facing away from the setting side, so that a component stress transverse to the setting direction, in particular caused by different thermal expansion the joining partner (1, 2, 3) can be reduced or removed by a transverse movement of the setting-side joining partner (2, 3). Rivet connection according to Claim 1 , characterized in that to support the floating bearing between the underside of the rivet head and the joining partner on the setting side (2, 3) a sliding element (6), in particular a plastic intermediate layer, is arranged, by means of which a friction value between the underside of the rivet head and the joining partner on the setting side (2, 3) can be reduced. Rivet connection according to Claim 2 , characterized in that the sliding element (6) can be pre-assembled as a washer on the rivet element (7), or that the sliding element (6) is designed as a plastic coating injection-molded onto the underside of the rivet head. Rivet connection according to Claim 1 , 2 or 3 , characterized in that the joining partner (2, 3) on the setting side is a plastic component and/or the joining partner (1) facing away from the setting side is a metal component which has a very pronounced thermal expansion compared to the plastic component. Rivet connection according to one of the preceding claims, characterized in that the setting-side joining partner (2, 3) has a through-hole (17) through which the rivet element (7) can be driven into the joining partner (1) facing away from the setting side, and that in particular to support the floating mounting of the setting-side joining partner (2, 3) the rivet shaft (13) is guided with hole clearance (Δx) through the through-hole (17) of the setting-side joining partner (2, 3), so that a compensating movement of the setting-side joining partner (2, 3) transverse to the setting direction is possible, in particular within the hole clearance (Δx). Rivet connection according to one of the preceding claims, characterized in that the joining partner (1) facing away from the setting side is a die-cast metal component, in particular die-cast aluminum, which not only has a very pronounced thermal expansion, but also has a low ductility compared to a sheet metal part, and that in particular in the die-cast metal component, due to the low ductility, there is a risk of notch formation, which can lead to premature component cracking or breakage. Rivet connection according to one of the preceding claims, characterized in that the rivet shaft (13) is designed as a bistable spring section which has two equilibrium states, namely the undeformed state with a reduced cross-section and the expanded spread state, and that through the action of the setting force (F) the rivet element (7) changes from the undeformed state to the spread state in which the rivet shaft (13) with the expanded cross-section is spread in the joining partner (1) facing away from the setting side, in particular without a spring-back force being built up in the rivet element (7) when changing to the spread state, which prestresses the rivet element (7) in the direction of the undeformed state. Rivet connection according to one of the preceding claims, characterized in that the joining partner (1) facing away from the setting side has, in the undeformed state, a pre-hole (6), in particular a blind hole-like pre-hole, at the joint to be produced, and that in the expanded state a foot-side shaft section (43) of the rivet shaft (13) is driven with its cutting edge (15) into the material of the first joining partner (1) on a pre-hole peripheral wall (39). Rivet connection according to one of the preceding claims, characterized in that the rivet element (7) is rotationally symmetrical with respect to a rivet element longitudinal axis (L), and/or that the rivet element (7) has an expanded rivet head (9) which merges in the axial direction into the rivet shaft (13), which terminates at the shaft tip with the preferably annular circumferential cutting edge (15) and/or delimits an inner curvature (14) which is open at the rivet shaft tip. Rivet connection according to one of the preceding claims, characterized in that in the setting process a foot-side shaft section (43) of the rivet shaft (13) turns over against the setting direction (S), so that in particular a radially inner head-side shaft section (49) on a turning edge (51) remote from the rivet head turns over in the direction of the rivet head (9) protruding radially outer foot-side shaft section (43) which surrounds the head-side shaft section (49) in a plate-like manner, and in particular that only the folded-over foot-side shaft section (43) of the rivet shaft (13) penetrates into the material of the first joining partner (1) with its cutting edge (15) on the pre-hole peripheral wall (39), while preferably the head-side shaft section (49) and/or the folded-over edge (51) remain without material engagement with the material of the first joining partner (1). Riveted joint according to one of the Claims 8 until 10 , characterized in that an activation contour (31) is formed in the pre-hole (6) of the joining partner (1) facing away from the setting side, which activation contour controls a change of the rivet element (7) from the undeformed state to the expanded state during the setting process. Rivet connection according to Claim 11 , characterized in that the activation contour (31) has an expansion cone (33) protruding from the pre-hole bottom of the joining partner (1) facing away from the setting side, and in particular that the activation contour (31) has an annular groove (35) formed in the pre-hole bottom, which surrounds the expansion cone (33) at its conical foot, and in particular that the annular groove (35) merges radially outwards into the pre-hole peripheral wall (39) at a particularly rounded inner corner region (37). Rivet connection according to Claim 12 , characterized in that at the beginning of the setting process the rivet element (7) sits with its cutting edge (15) on the conical surface of the expansion cone (33) and then slides along the conical surface in the direction of the annular groove (35) so that the base-side shaft section (43) of the rivet shaft (13) expands while thinning the material, and that in particular in the further course of the setting process the material-thinned base-side shaft section (43) of the rivet shaft (11) can be guided from the expansion cone (33) into the annular groove (35) so that the rivet element (7) changes into the expanded state due to the action of the setting force (F), in which the base-side cutting edge (15) of the rivet element (7) is driven into the material of the first joining partner (1) on the pre-hole peripheral wall (39). Rivet connection according to Claim 13 , characterized in that in the undeformed state of the rivet element (7) on the rivet shaft (13) two cutting flanks (45, 47) converge to form the cutting edge (15), and that one of the cutting edges (45) spans a cutting angle (β) with a plane perpendicular to the rivet element longitudinal axis (L), and that the cutting angle (α) corresponds to a cone angle (γ) which is spanned between the conical surface and the perpendicular plane. Rivet connection according to one of the preceding claims, characterized in that the pilot hole peripheral wall (39) merges at a pilot hole opening edge (41) into a surface of the joining partner (1) facing away from the setting side, and in particular that the pilot hole peripheral wall (39) widens conically from the pilot hole inner corner region (37) towards the pilot hole opening edge (41) or runs cylindrically between the pilot hole inner corner region (37) and the pilot hole opening edge (41). Rivet connection according to one of the preceding claims, characterized in that the pilot hole diameter (dv) is larger than the rivet shaft outer diameter (d _A ), so that the rivet element (1) can be pre-positioned with hole play in the component pilot hole (6). Rivet connection according to Claim 11 , characterized in that , in order to form the activation contour (31), the pre-hole (6) of the first joining partner (1) has a large-diameter insertion section (21) which, on a circumferential annular shoulder (23), gradually transitions into a small-diameter pre-hole countersink (25), and in that in particular the cutting edge (15) of the still undeformed rivet element (7) lies on a diameter (d ₁ ) which is larger than the inner diameter (d ₂ ) of the annular shoulder (23), so that in preparation for the setting process the rivet element (7) can be positioned with its cutting edge (15) on the annular shoulder (23) of the component pre-hole (6). Rivet connection according to Claim 17 , characterized in that during a setting stroke the rivet element (7) can be driven into the component pilot hole (6) up to a dead center (T), and that at the dead center (T) the rivet element (7) is expanded radially outwards with its cutting edge (15) until a maximum diameter (d _max ) is reached, and that the setting stroke is extended by an over-dead center stroke (s) with which the rivet shaft (13) can be driven into the pilot hole countersink (25), so that an over-expansion of the base-side shaft section (43) takes place, during which it changes over to the expanded state. Riveted connection, in which a rivet element (7) with its rivet shaft (13) can be driven into at least one joining partner (1) in a setting process, namely by spreading the rivet shaft (11), wherein the rivet foot (11) has a reduced cross-section in the still undeformed state and has an expanded cross-section in the driven-in state, wherein a bolt is provided on an upper side of a rivet head (9) of the rivet element (7). zen (53) for connecting a second joining partner (2), in particular a threaded bolt or a welding bolt, wherein in the assembled state the bolt (53) is guided through a through hole (55) of the second joining partner (2), and wherein a further element (3, 56, 57) is fastened to the bolt tip protruding from the through hole (55) of the second joining partner (2), so that the second joining partner (2) can be clamped between the further element (3, 56, 57) and the rivet head (9), characterized in that the second joining partner (2) is clamped in a floating bearing, in particular according to one of the preceding claims, between the rivet head (9) of the rivet element (7) and the further element (3, 56, 57), so that a component tension transverse to the setting direction, in particular caused by different thermal expansion of the joining partners (1, 2), by a transverse movement of the second joining partner (2) can be reduced or eliminated, and that a sliding element (6), in particular a plastic intermediate layer, is arranged between the rivet head top side and the second joining partner (2, 3) in particular to support the floating support, and/or that a sliding element (6), in particular a plastic intermediate layer, is arranged between the second joining partner (2, 3) and the further element (3, 56, 57) in particular to support the floating support. Rivet element for a riveted connection according to one of the preceding claims.

Images