WO2023025535A1

WO2023025535A1 - Riveted connection

Info

Publication number: WO2023025535A1
Application number: PCT/EP2022/071658
Authority: WO
Inventors: Jochen Rintelmann; Jan-Oliver Brassel
Original assignee: Audi Planung GmbH
Priority date: 2021-08-26
Filing date: 2022-08-02
Publication date: 2023-03-02
Also published as: DE102021122064A1; DE102021122064B4

Abstract

The invention relates to a riveted connection, wherein a hollow rivet shank (11) of a rivet element (1) is driven into a component (3), more particularly exactly one component, in a setting direction (S), such that the rivet shank (11) expands. In the undeformed state, the component (3) has a blind-hole-type pre-hole (5) at the joint to be produced. In the expanded state, a cutting edge (15) of a bottom wall portion (43) of the hollow rivet shank (11) is driven into the component material at a pre-hole peripheral wall (39). According to the invention, an activation contour (31) is formed in the component pre-hole (5); in the setting process, the activation contour controls a transformation of the rivet element (1) from the undeformed state into the expanded state. The activation contour (31) has an expansion cone (33) protruding from the pre-hole bottom.

Description

rivet connection

The invention relates to a riveted connection according to the preamble of claim 1 and a component with a pilot hole with an activation contour for producing such a riveted connection according to claim 10.

In a riveted joint of this type, a rivet element is driven into a component with its shank, while maintaining a residual base thickness in the component and expanding the rivet shank. The cross-section of the rivet shank is reduced in the undeformed state. When driven in, the shank of the rivet has an expanded cross-section.

In the prior art, such a rivet connection is produced in a setting process, in which the rivet element has an expanded rivet head and a rivet shank with an open inner curvature at the rivet shank tip. During a setting process, the component without a pre-hole is clamped between a die and a holding-down device of a setting device. The rivet element is driven in with a predefined setting force, as a result of which the rivet shank tip expands radially outwards over an expansion distance. This creates an undercut between the rivet head and the flared shank tip, which is filled with component material. The rivet shank tip is framed by the component material in a form-fitting manner. This causes a relative movement, for example caused by springback of the rivet shank after spreading, because this causes a deformation of the

component would be required.

When using component material with low ductility, such as die-cast aluminum, such a form-fitting gripping of the rivet shank tip is only possible to a limited extent, so that the rivet shank springs back after the setting process (after spreading). Therefore, the rivet element is not adequately secured against loosening. In addition, with component material with low ductility, there is a risk of notch formation, which can lead to premature component cracking or fracture.

A joint connection is known from DE 10 2018 122 200 A1. A punch riveting process is known from WO 95/35174 A1. DE 10 2015 014 941 A1 discloses a method for producing a connection between a functional element and a plate-shaped component.

The object of the invention is to provide a rivet connection in which the rivet element is secured in a simple manner against unintentional detachment from the component.

The object is solved by the features of claim 1 or 10. Preferred developments of the invention are disclosed in the dependent claims.

The invention is based on a rivet connection in which a rivet element with its hollow rivet shank is driven into, in particular precisely one component in a setting direction, specifically with the rivet shank being spread open. In the non-deformed state, the component has a blind hole-like pilot hole at the joint to be produced. In the expanded state, a base-side wall section of the hollow rivet shank element is at a Circumferential wall of the pilot hole driven into the component material. According to the characterizing part of claim 1, an activation contour is formed in the component pilot hole, which controls a transfer of the rivet element from the undeformed state to the expanded state in the setting process. The activation contour is implemented as an expanding cone protruding from the bottom of the pre-hole.

In a preferred embodiment variant, the foot-side wall section of the rivet shank can turn over counter to the setting direction with the help of the activation contour. A head-side wall section of the rivet shank therefore merges at a fold-over edge remote from the rivet head into the base-side wall section protruding in the direction of the rivet head. In this case, the following principle is used to secure the rivet element on the component: The rivet shank acts as a bistable spring section that has two states of equilibrium. A first state of equilibrium corresponds to the cross-sectionally reduced, non-deformed rivet element state. The effect of the setting force causes the rivet shank to switch to the second state of equilibrium, in which the rivet shank is braced with an expanded cross-section in the pre-hole in the component. The transition to the expanded state takes place essentially without the build-up of a restoring force that prestresses the rivet element in the direction of the non-deformed state. With this active principle, there is no need for a form-fitting, complete enclosing of the expanded rivet shank, as would be the case in a conventional setting process. Rather, preferably only the folded-over foot-side wall section of the rivet shank can penetrate into the component material on the pre-hole peripheral wall, while the head-side wall section and/or the folded-over edge remain without material contact with the component material. The activation contour formed in the pre-hole in the component can also have an annular groove, which surrounds the expansion cone at its cone base. The ring groove can merge radially outwards into the peripheral wall of the pre-hole at an inner corner area, in particular a rounded area. In particular, the expansion cone in combination with the ring groove and the pre-hole inner corner area lead to a foldover of the foot-side wall section of the rivet shank, as described above.

A setting process that can be carried out with the activation contour according to the invention is described below: At the beginning of the setting process, the rivet element can sit with its cutting edge on the cone surface of the expanding cone. When the setting force is applied, the rivet element can slide with its cutting edge along the cone surface in the direction of the ring groove without penetrating the component material. In this way, the base-side wall section of the rivet shank is pre-expanded with thinning of the material. In the further course of the setting process, the material-thinned, foot-side wall section of the rivet shank is guided from 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 component material on the peripheral wall of the pre-hole.

As mentioned above, a pre-expansion of the rivet shank takes place in the setting process at the expansion cone. Due to the pre-expansion, the rivet shank is conically expanded from its dimensionally stable, cylindrical undeformed state. The conical widening of the rivet shank takes place while reducing the wall thickness of the shank wall. This reduces the dimensional stability of the rivet shank. In the further course of the setting process, the rivet shank can therefore be transferred to its expanded state in a process-reliable manner. For a process-reliable course of the setting process, it is important that the rivet element does not penetrate the component material with its cutting edge at the expansion cone at the beginning of the setting process. Against this background, a cutting flank on the cutting edge can have a cutting edge angle that corresponds approximately to a cone angle that is spanned between the cone surface of the expanding cone and a right-angled plane. This ensures that the cutting edge of the rivet element can slide along the lateral surface of the expanding cone in the direction of the ring groove without penetrating into the component material.

The peripheral wall of the preliminary hole can merge into a component surface on the setting side at a preliminary hole opening edge. The peripheral wall of the pre-hole can expand conically from the bottom-side pre-hole inner corner area to the pre-hole opening wheel or run in a cylindrical shape. The pilot hole diameter is preferably dimensioned larger than the outside diameter of the rivet shank. In this way, the rivet element can be easily pre-positioned in the pre-hole in the component in preparation for the setting process with hole play.

The rivet element has a rivet head, the underside of which rests on the opening edge area of the pilot hole opening of the component after the setting process has taken place. Therefore, the pre-hole diameter at the pre-hole opening edge is smaller than a head diameter of the rivet head.

With regard to cost-effective production, it is preferred if the rivet element is designed to be rotationally symmetrical to a longitudinal axis of the rivet element. In the non-deformed state, the rivet shank can have a cylindrical shape on the outside. In addition, the rivet shank can be implemented as a hollow cylinder, resulting in a constant wall thickness of the shank wall along the longitudinal axis of the rivet element. In a specific embodiment, the rivet element can have a rivet element length of 2 to 5 mm, for example, in the non-deformed state. The wall thickness of the shank wall of the rivet shank in the non-deformed state can be in a range between 0.3 and 0.7 mm, in particular 0.5 mm. In addition, depending on the application, the rivet element can be made, for example, from a wire material suitable for welding, or from a conventional cold-forming steel, in which a deformation limit is exceeded, in particular during overspreading, i.e. when folding over during the setting process, at which the rivet element hardens. Material occurs, which is advantageous in terms of 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 shank. Instead, the component can be clamped between a hold-down device and a planar anvil during the setting process.

The component can preferably be made of a material that is softer than tool steel, for example, such as a die-cast material, that is to say, for example, die-cast aluminum.

An exemplary embodiment of the invention is described below with reference to the accompanying figures. Show it:

1 shows a rivet connection in a cross section view;

2 shows an exploded view of the rivet element and the component, each in the un-deformed state;

Figs. 3 to 5 are views showing a setting process; and 6 and 7 are views of a conventional setting process, respectively.

With a view to a simpler understanding of the invention, reference is first made to FIGS. 6 and 7, on the basis of which a riveted connection known from the prior art is described. The rivet connection shown in FIG. 6 consists of a rivet element 1 and a component 3. The rivet element 1 is rotationally symmetrical with respect to a longitudinal axis L of the rivet element. In addition, the rivet element 1 has an expanded rivet head 9, on the upper side of which a functional section 19, e.g. a coarse thread, is formed. The rivet head 9 merges into a rivet shank 11 in the axial direction. The rivet shank 11 is divided into a head-side solid rivet shank section 13 and an adjoining hollow-cylindrical rivet shank wall 17. This ends at an annular circumferential cutting edge 15 and delimits an inner curvature 14 open at the rivet shank tip.

The setting process takes place with the aid of a setting device, which in FIGS. The matrix engraving is designed in such a way that the rivet shank 11 is supported to spread radially outwards during the setting process. During a setting process, the component 3 without a pre-hole is clamped between the die 30 and the hold-down device 27 . The rivet element 1 is driven in by the setting piston 29 with a predefined setting force F, as a result of which the rivet shank tip expands radially outwards over an expansion path. The setting force F introduced into the rivet element 3 is divided at a crest point above the inner curvature 14 into load paths, which in FIG. 6 or 7 extend along imaginary expansion lines 16 (indicated by dashed lines). The spreading lines 16 span a spreading angle a. During the setting process (FIG. 7), the rivet element 1 is driven in by a setting stroke up to a bottom dead center T (FIG. 7). At bottom dead center T is the end face of The rivet shank tip is in contact with the component material and the spread angle a is increased (compared to FIG. 6). This results in an undercut between the rivet head 9 and the widened tip of the rivet shank, which is almost completely filled with component material.

In the setting process (FIGS. 6 and 7), the rivet element 1 is not only deformed plastically but also elastically, specifically with the build-up of a restoring force that prestresses the rivet element 1 in the direction of the non-deformed state. In order to prevent springing back into the non-deformed state, the rivet shank 11 in FIG. 7 is surrounded almost completely by component material in a form-fitting manner. As a result, a relative movement, for example caused by the resilience of the rivet shank 11 after spreading, is prevented, because this would require a deformation of the component 3 . In this way, the rivet element 1 is reliably secured against loosening. In order to bring about such a form-fitting enclosing of the rivet shank by means of the component material, the component material must have sufficiently high flowability or ductility.

In contrast to this, the rivet connection according to the invention can also be realized with a component 3 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 rivet element 3 is not secured by a complete form-fit enclosing of the rivet shank 11 by means of the component material, but by the securing mechanism described below with reference to Figures 1 to 5:

According to FIG. 1, the rivet element 1 is driven into a component pre-hole 5, which extends conically to a pre-hole depth t and terminates there with a pre-hole bottom. The essence of the invention is that an activation contour 31 is formed in the component pilot hole 5, which controls the transfer of the rivet element 1 from the undeformed state to the expanded state in the setting process. The activation contour 31 has an expanding cone 33 protruding from the bottom of the pre-hole, which is surrounded at its cone foot by an annular groove 35 formed in the bottom of the pre-hole. The ring groove 35 merges radially outwards at a rounded inner corner area 37 into a peripheral wall 39 for the pre-hole. In FIGS. 1 to 5, the smooth-surfaced peripheral wall 39 of the pre-hole extends slightly conically from the inner corner region 37 of the pre-hole to a pre-hole opening edge 41 on the component surface on the setting side.

According to FIG. 1, a base-side wall section 43 of the hollow rivet shank 11 is driven into the component material with its cutting edge 15 on the peripheral wall 39 of the pre-hole.

As can be seen from FIG. 2, the pilot hole diameter dv is dimensioned larger than the rivet shank outer diameter dA, so that the rivet element 1 can be prepositioned with a hole clearance in the component pilot hole 5 in preparation for the setting process. The pre-hole diameter dv is also dimensioned smaller than a head diameter dK of the rivet head 9. Its underside is in contact with the opening edge area of the component pre-hole 5 after the setting process has taken place cylindrical. The inner curvature 14 of the rivet shank 11 is implemented as a hollow cylinder, resulting in a constant wall thickness w of the shank wall along the longitudinal axis of the rivet element. The rivet element 1 is designed overall to be rotationally symmetrical to the longitudinal axis L of the rivet element.

An inventive

Setting process described: At the beginning of the setting process (Figure 3) the Riveting element 1 brought with its cutting edge 15 in contact with the cone surface of the expanding cone 33. The rivet element 1 is aligned coaxially with the expansion cone 33 . With the introduction of the setting force F, the rivet element 1 slides with its cutting edge 15 along the cone surface in the direction of the ring groove 35. In this way, the foot-side wall section 43 of the rivet shank 11 is pre-expanded. Due to the pre-expansion, on the one hand, the cylindrical rivet shank 11 expands conically. On the other hand, the conical widening of the rivet shank 11 reduces the wall thickness w, especially on the wall section 43 on the foot side. Due to the conical widening and the reduced wall thickness w, the activation contour 31 can reliably transfer the rivet shank 11 to the spread state in the further setting process. At the end of the setting process (FIG. 5), the cutting edge 15 of the rivet element 1 is driven into the component material on the circumferential wall 39 of the preliminary hole.

As can be seen from FIG. 2, two cutting flanks 45, 47 converge on the rivet foot, forming the cutting edge 15. The radially inner cutting edge 45 spans a cutting edge angle β with a plane perpendicular to the longitudinal axis L of the rivet element. This corresponds to a cone angle γ, which is spanned between the cone surface of the expansion cone 33 and a plane perpendicular to the longitudinal axis L of the rivet element. This ensures that the cutting edge 15 reliably slides in the direction of the annular groove 35 during the setting process without penetrating the component material.

With the help of the activation contour 31 according to the invention, the foot-side wall section 43 of the rivet shank 11 is turned over counter to the setting direction S in the setting process. In the finished rivet connection, a head-side wall section 49 therefore merges at a fold-over edge 51 remote from the rivet head into the base-side wall section 43 protruding in the direction of the rivet head 9 . The turned-up foot-side wall section 43 extends in the circumferential direction continuous and plate-shaped around the head-side wall section 49. It should be emphasized that only the folded-over foot-side wall section 43 penetrates the component material with its cutting edge 15 of the rivet shank 11 on the pre-hole peripheral wall 39, while the head-side wall section 49 remains without material contact with the component material.

The rivet shank 11 thus acts like a bistable spring section, which changes over to the expanded spread state during the setting process. The expanded state (FIG. 1 or FIG. 5) is characterized in that, in contrast to the prior art, essentially no springback force is built up in the rivet shank 11, which prestresses the rivet element 1 in the direction of the non-deformed state. Therefore, according to the invention, an almost completely form-fitting enclosing of the rivet shank 11 in the component material can be dispensed with.

According to FIGS. 3 to 5, the setting device according to the invention does not have a die with die engraving as counter-holder 30, but rather a planar anvil.

Reference character list

1 rivet element

3 component

5 preliminary hole

9 rivet head

11 rivet foot

13 rivet foot solid section

14 inner bulge

15 positioning edge

16 spreading lines

17 rivet foot wall

19 function section

27 hold-down

29 setting pistons

30 anvil

31 Activation Contour

33 expansion cone

35 ring throat

37 inside corner area

39 pre-hole perimeter wall

41 pre-hole opening edge

43 foot-side wall section

45, 47 cutting flanks

49 end wall section

51 Cover edge d _A Shank outside diameter d _K head diameter d _v pilot hole diameter w wall thickness F setting force S setting direction

L Longitudinal axis of the rivet element a Spread angle ß Cutting edge angle

Y taper angle t pilot hole depth

Claims

Claims Riveted joint, in which a rivet element (1) with its hollow shank (11) is driven into, in particular precisely one component (3) in the setting direction (S), specifically with the rivet shank (11) being spread open, the component

(3) in the non-deformed state at the joint to be produced has a blind hole-like pilot hole (5), and in the expanded state a foot-side wall section (43) of the hollow rivet shank (11) with its cutting edge (15) on a pilot hole peripheral wall (39) is driven into the component material, characterized in that an activation contour (31) is formed in the component pilot hole (5), which controls a transfer of the rivet element (1) from the undeformed state to the expanded state in the setting process, and in that the activation contour (31) has an expanding cone (33) protruding from the bottom of the pre-hole. Riveted connection according to Claim 1, characterized in that the activation contour (31) has an annular groove (35) formed in the bottom of the preliminary hole, which surrounds the expansion cone (33) at its cone base, and in that in particular the annular groove (33) radially outwards on a particularly rounded inner corner area (37) merges into the pre-hole peripheral wall (39). Riveted connection according to Claim 1 or 2, characterized in that at the beginning of the setting process the rivet element (1) sits with its cutting edge (15) on the cone surface of the expanding cone (33). and then slides along the lateral surface of the cone in the direction of the ring groove (35), so that the base-side wall section (43) of the rivet shank (1 1) pre-expands while the material is thinned, and that in particular in the further course of the setting process the material-thinned base-side wall section (43) of the rivet shank ( 11) can be guided from the expansion cone (33) into the annular groove (35), and that at the end of the setting process the cutting edge (15) of the rivet element (1) on the base side can be driven into the component material on the peripheral wall (39) of the pre-hole.

4. Riveted connection according to one of the preceding claims, characterized in that in the non-deformed state of the rivet element (1) two cutting flanks (45, 47) converge on the rivet foot to form the cutting edge (15), and that one of the cutting edges (45) has a Rivet element longitudinal axis (L) spans a cutting edge angle (ß) perpendicular plane, and that the cutting edge angle (a) corresponds to a cone angle (y) which is spanned between the cone surface and the perpendicular plane.

5. Riveted connection according to one of the preceding claims, characterized in that by means of the activation contour (31), in particular by means of the annular groove (35) and the pre-hole inner corner area (37), the foot-side wall section (43) of the rivet shank (11) in the setting process in the setting direction (S), so that in particular a head-side wall section (49) merges at a fold-over edge (51) remote from the rivet head into the base-side wall section (43) protruding in the direction of the rivet head (9), and that in particular only the folded-over base-side wall section (43) of the rivet shank (1 1) on the pre-hole peripheral wall (39) with its cutting edge (15) penetrates into the component material, while the 16 remain head-side wall section (49) and / or the cover edge (51) without material contact with the component material. Rivet connection according to one of the preceding claims, characterized in that the peripheral wall (39) of the pre-hole merges into a component surface at a edge (41) of the opening in the pre-hole, and in that in particular the peripheral wall (39) of the pre-hole extends from the inner corner area (37 ) widens conically in the direction of the pre-hole opening edge (41) or runs in a cylindrical shape between the pre-hole inner corner area (37) and the pre-hole opening edge (41). Riveted connection according to one of the preceding claims, characterized in that the pilot hole diameter (dv) is dimensioned larger than the rivet shank outside diameter (dA), so that the rivet element (1) can be prepositioned with hole play in the component pilot hole (5). Riveted connection according to one of the preceding claims, characterized in that the pre-hole diameter (dv) at the pre-hole opening edge (41) is dimensioned smaller than a head diameter (di<) of the rivet head (9), so that after the setting process has taken place the underside of the rivet head is in contact with the opening edge area of the component pilot hole (5). Riveted connection according to one of the preceding claims, characterized in that in the undeformed state the rivet shank (11) is cylindrical on the outside and preferably has a constant wall thickness and/or is rotationally symmetrical to a longitudinal axis (L) of the rivet element. 17 component with a pilot hole (5) with activation contour (31) for the production of a riveted connection according to any one of the preceding claims.