Method for joining at least two structural parts

Abstract

A method for joining at least two structural parts includes a fitting step in which a joining element is driven into the first structural part while a residual material thickness is maintained, and a joining step in which the joining element driven into the first structural part is connected to the second structural part. The joining element has a hollow element shaft, which is driven into the first structural part, and an element head, which is welded or adhesively bonded to the second structural part.

Claims

1. A method for joining at least two components, comprising: providing an auxiliary joining element having a hollow shaft and a head; in a setting step driving the shaft of the auxiliary joining element into a first component so as to maintain a residual material thickness of the first component; and in a joining step materially bonding the head of the auxiliary joining element with a second component, wherein the head of the auxiliary joining element at a topside thereof has an at least partially upward bulged dome-shaped material thickening extending over a planar parallel circumferential ring shoulder spaced apart from an outer rim of the head, wherein at an element base of the auxiliary joining element which faces away from the head, the auxiliary joining element has a ring contour which is adapted for placement on the first component so as to form a ring shaped contact zone for preparation of the setting step, said ring contour configured as an annular circumferential acute-angle contact edge, said annular circumferential acute-angle contact edge being radially inwardly offset from an outer wall of the hollow shaft and defining an opening of a hollow dome shaped space of the hollow shaft.

2. The method of claim 1, wherein the head of the auxiliary joining element is materially bonded with the second component by welding or gluing.

3. The method of claim 1, wherein a material thickness of the head of the auxiliary joining element is increased relative to a material thickness of a walling of the shaft of the auxiliary joining element so as to form a material thickening for providing welding material for a weld nugget between the head of the auxiliary joining element and the second component.

4. The method of claim 3, wherein the auxiliary joining element is rotation symmetric about a longitudinal axis, and wherein the material thickness of the head of the auxiliary joining element at the longitudinal axis is 1.5-4 times greater than the material thickness of the shaft of the auxiliary joining element.

5. The method of claim 1 wherein a diameter of the head of the auxiliary joining element is 1.25 to 1.5 times greater than an outer diameter of the shaft of the auxiliary joining element.

6. The method of claim 2, wherein a material thickness of the head of the auxiliary joining element is between 1 and 1.5 mm.

7. The method of claim 2, wherein a diameter of the head of the auxiliary joining element is between 5 and 7 mm.

8. The method of claim 2, wherein an outer diameter of the shaft of the auxiliary joining element is between 3.0 and 6.5 mm.

9. The method of claim 2, wherein a length of the auxiliary joining element is between 2.0 and 4.0 mm.

10. The method of claim 1, wherein the auxiliary joining element has an anti-corrosion layer, which is adapted for avoiding corrosion of a joint formed by the first and second component and the auxiliary joining element, and wherein a base material of the anti-corrosion layer is in particular zinc, ZnNi or Almac.

11. The method of claim 10, wherein a thickness of the anti-corrosion layer is 5 m.

12. The method of claim 10, wherein the base material of the auxiliary joining element is a welding-capable wire material.

13. The method of claim 12, wherein the base material is a cold extruded steel or a cold upset steel, and has a material strength of 950 to 1100 N/mm.sup.2.

14. The method of claim 1, wherein after the setting step, the head of the auxiliary joining element protrudes with a head projection from a surface of the first component.

15. The method of claim 14, wherein the head projection is between 0.1 to 0.5 mm.

16. The method of claim 3, wherein the walling of the shaft of the auxiliary joining element in the setting step is widened radially outwardly by a spread path which is perpendicular to a riveting direction so as to form an undercut.

17. The method of claim 16, wherein the spread path is greater than 0.1 mm.

18. The method of claim 14, further comprising applying adhesive between the first and second components, with the head projection locally displacing the adhesive.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The advantageous embodiments and/or refinements of the invention explained above and/or set forth in the dependent claims can be used individually or in any combinationexcept for example in cases of clear dependencies or irreconcilable alternatives.

(2) In the following the invention and its advantageous embodiments and refinements and their advantages are explained in more detail by way of drawings.

(3) It is shown in:

(4) FIG. 1 in a partial sectional view a component connection;

(5) FIG. 2 in a partial side sectional view an auxiliary joining element by itself;

(6) FIG. 3 a detail view of FIG. 2

(7) FIG. 4 a view corresponding to FIG. 2 a further exemplary embodiment of the auxiliary joining element;

(8) FIGS. 5 and 6 respective views, which illustrate the process steps for producing the component connection shown in FIG. 1;

(9) FIGS. 7 and 8 respective views of an auxiliary joining element according to a further exemplary embodiment, which compared to the exemplary embodiments of FIGS. 2 and 4, is the most preferred exemplary embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(10) FIG. 1 shows a finished component connection in which an aluminum sheet as a first joining partner is connected with a steel sheet 3 as a second joining partner. The two joining partners 1, 3 are connected with each other via an auxiliary joining element 5. In addition an adhesive layer 7 is provided between the joining partners 1, 3. The above material pairing is purely exemplary. As an alternative also any other materials are conceivable, for example magnesium and potentially also plastic materials.

(11) According to the figures the auxiliary joining element 5 is formed with a hollow element shaft 9 and an element head 11. In FIG. 1 the element shaft 9 is driven into the material of the aluminum sheet (first joining partner) 1 in a setting step I described below while maintaining a residual material thickness r. The element head 11 of the auxiliary joining element 5 on the other hand is welded with the second component (steel sheet part) 3 so as to form a weld nugget 13.

(12) The above-mentioned setting step I is conceivable in an upstream process step. As an alternative the setting step is also conceivable in the pressing tool of the component forming shortly thereafter or shortly prior to the welding process. A suitable system would be a robot or a fixed setting device for the parallel setting of multiple elements. This leads to a higher accuracy and faster cycle times.

(13) FIG. 2 shows the auxiliary joining element 5 by itself in a finished state. Accordingly the auxiliary joining element 5 is for example configured rotation symmetric about a longitudinal axis L, wherein a walling 15 of the element shaft 9 delimits a hollow dome shaped space 17, which is open towards the bottom, and which in axial direction is worked into the element shaft 9 with a material depth t. The element shaft walling 15 has a material thickness m.sub. which in FIG. 2 exemplarily is only one third of the element head material thickness m.sub.K which results along the longitudinal axis L. In this way the element head 11 is formed with an additional material thickening 21, which provides a sufficiently great amount of welding material for the formation of the weld nugget 13. This material thickening 21 is hereby dimensioned so that after the welding step II (FIG. 6) a sufficiently material thickness m (FIG. 1) remains in the element head 11 without change of microstructure.

(14) In FIG. 2 the head diameter d.sub.K is 5.5 mm, while the outer diameter d.sub.S of the shaft is 3.35 mm. The length l of the auxiliary joining element 5 in FIG. 2 is 2.8 mm, wherein a side height l.sub.K of the head is about 0.3 mm.

(15) As can be further seen from FIGS. 2 and 3, the auxiliary joining element 5 has at its side, which faces away from the element head 11, an element base 19 with a ring contour, which is configured as a circular circumferential acute angle contact edge. During the setting step (FIG. 5) the contact edge 19 acts as a base cutting edge with which a premature deformation of the auxiliary joining element 5 in the setting step I is prevented and at the same time a spreading apart of the element shaft 9 by a predetermined spread path y (FIG. 1) radially outwardly is controlled. Preferably the spread path y (FIG. 1) should be greater than 0.1 mm. In addition the undercut can be greater than 0.1 mm, preferably 0.3 mm, prior to the welding so that after the welding a sufficient strength of the element in the joining part 1, preferably aluminum part, is present.

(16) The geometry of the contact edge (base cutting edge) 19, which is required therefore can be seen in FIG. 3. According to this the contact edge 19 is radially inwardly offset by a radial offset r from the outer wall of the element shaft, wherein the radial offset r is about 0.15 mm. According to FIG. 3 the height h of the ring contour 19 is about 0.35 mm. The measurements stated herein are to be understood as merely exemplary and do not limit the general inventive idea.

(17) FIG. 4 shows a view according to FIG. 2 of a further auxiliary joining element, which has substantially the same geometry as in FIG. 2 with the exception of the element head 11. In FIG. 4 the topside of the element head 11 is not configured plan parallel but rather with a dome shaped material thickening 21 (welding buckle) upwards bulged. The dome shaped material thickening 21 extends not directly up to the outer rim of the element head 11 but rather over a planar parallel circumferential ring shoulder 23 spaced apart from the outer rim 20 of the element head 11. In this way a central configuration of the weld nugget 13 with respect to the longitudinal axis L is ensured.

(18) FIGS. 5 and 6 show the setting step I and the subsequent welding step II. According to this the auxiliary joining element 5 is first driven into the first component (aluminum sheet) 1 in a joining direction i.e., while maintaining the residual material thickness r. After the setting step I the element head 11 of the auxiliary joining element 5 protrudes with its head projection u from the surface of the first component 1 with a head projection u of 0.33 mm.

(19) Subsequently for preparing the welding step the second joining partner 3 is placed on the topside of the auxiliary joining element 5, optionally with the adhesive layer 7 provided between the two joining partners 1, 2. The electrodes 25 are pushed together, wherein the auxiliary joining element 5 is oriented aligned with the two electrodes 25 and a spot welding process is performed so as to form the weld nugget 13 between the element head 11 and the second joining partner 3.

(20) FIGS. 7 and 8 show in a view according to FIG. 2 an auxiliary joining element 5, which compared to the exemplary embodiments of FIG. 2 and FIG. 4 is the most preferred variant.

(21) The auxiliary joining element 5 shown in FIGS. 7 and 8 has substantially the same geometry as the auxiliary joining element 5 shown in FIG. 2. Correspondingly in FIG. 7 the topside of the element head 11 is also configured flat.

(22) In contrast to FIGS. 2 and 4, in FIGS. 7 and 8 the element base 19 of the auxiliary joining element 5 has no ring shaped circumferential acute angle contact edge (as in FIGS. 2 to 4) but rather a rounded contact edge. Its contact vertex S (FIG. 8) is inwardly offset by a radial offset with respect to the outer circumference of the element shaft 9.

(23) In FIGS. 7 and 9 the head diameter d.sub.K is 5.5 mm while the shaft outer diameter d.sub.S is 3.35 mm. The length l of the auxiliary joining element 5 in FIG. 7 is 2.5 mm, wherein the head side height of l.sub.K is 0.3 mm. The material thickness m.sub.K (FIG. 7) along the longitudinal axis L is 1.3 mm. The here stated measurements are purely exemplary and do not limit the general inventive idea.