SELF-PIERCING RIVET

Abstract

Self-piercing rivet joint and self-piercing rivet for producing a joining connection between at least two components comprising a rivet head and a rivet shank having a central shank bore comprising a base, the rivet shank comprises a cylindrical shank outer surface and a shank inner surface limiting the central shank bore, the rivet shank comprises an annular piercing end facing away from the rivet head, the shank outer surface has a first diameter (Ds), the central shank bore comprises a bore depth (T) between the base of the central shank bore and the annular piercing end, wherein a ratio of the first diameter (Ds) to the bore depth (T) is in the range of 0.50Ds/T0.67.

Claims

1. A self-piercing rivet for use in forming a joining connection between at least two components; the self-piercing rivet comprising: a rivet head and a rivet shank partially defining a central shank bore including a base, the rivet shank includes a cylindrical shank outer surface and a shank inner surface partially defining the central shank bore, the rivet shank includes an annular piercing end facing away from the rivet head, the shank outer surface has a first diameter, the central shank bore defines a bore depth between the base of the central shank bore and the annular piercing end, and a ratio of the first diameter (Ds) to the bore depth (T) is in the range of 0.50Ds/T0.67.

2. A self-piercing rivet according to claim 1, wherein the ratio of the first diameter to the bore depth is in the range of 0.58Ds/T0.63.

3. A self-piercing rivet according to claim 1, wherein the first diameter is of 5.3 mm.

4. A self-piercing rivet according to claim 1, wherein the base is conical or frustoconical and there is an arcuate transition of a radius R2 between the periphery of the base and the shank inner surface.

5. A self-piercing rivet according to claim 4, wherein the radius R2 is in the range of 0.35 to 0.4 mm.

6. A self-piercing rivet according to claim 1, wherein at the annular piercing end between the shank outer surface and the shank inner surface is located a shank end face radially outward of a shank end radius R3.

7. A self-piercing rivet according to claim 6, wherein the shank end radius R3 is in the range of 1.2 to 1.4 mm.

8. A self-piercing rivet according to claim 7, wherein the shank end radius R3 is of 1.3 mm.

9. A self-piercing rivet according to claim 6, and further including a conical taper surface located between the shank end radius and the shank end face, and wherein the conical taper surface has an inclusive angle of 90 degrees.

10. A self-piercing rivet according to claim 6, wherein the shank end face is arcuate, and the arcuate shank end face includes a radius of curvature R4 in the range of 0.15 to 0.3 mm.

11. A self-piercing rivet according to claim 1, wherein the head incudes an upper portion and a transition region between the upper portion and the shank outer surface, the transition region having a radius of curvature R1 in the range of 2.1 to 2.3 mm.

12. A self-piercing rivet according to claim 1, wherein the head includes an upper surface opposite the base and a thickness between the base and the upper surface is in the range of 1.5 to 3.5 mm.

13. A self-piercing rivet according to claim 1, wherein the annular piercing end has a length along the longitudinal axis of less than 0.3 mm.

14. A riveted joint comprising: an upper workpiece; a lower workpiece formed from a brittle material; and a self-piercing rivet including: a rivet head and a rivet shank partially defining a central shank bore including a base, the rivet shank includes a cylindrical shank outer surface and a shank inner surface partially defining the central shank bore, the rivet shank further includes an annular piercing end facing away from the rivet head, the shank outer surface has a first diameter (Ds), the central shank bore comprises a bore depth (T) between the base of the central shank bore and the annular piercing end, and before deformation during joint formation, a ratio of the first diameter to the bore depth is in the range of 0.50Ds/T0.67.

15. A riveted joint according to claim 14, wherein the self-piercing rivet the first diameter is of 5.3 mm.

16. A riveted joint according to claim 14, wherein the self-piercing rivet the base is conical or frustroconical and there is an arcuate transition of a radius R2 between the periphery of the base and the shank inner surface, and the radius R2 is in the range of 0.35 to 0.4 mm.

17. A riveted joint according to claim 14, wherein at the annular piercing end of the self-piercing rivet between the shank outer surface and the shank inner surface is located a shank end face radially outward of a shank end radius R3, and the shank end radius R3 is in the range of 1.2 to 1.4 mm.

18. A riveted joint according to claim 17, wherein the self-piercing rivet further including a conical taper surface located between the shank end radius R3 and the shank end face, and wherein the conical taper surface has an inclusive angle of 90 degrees.

19. A riveted joint according to claim 14, wherein the self-piercing rivet the shank end face is arcuate, and the arcuate shank end face includes a radius of curvature R4 in the range of 0.15 to 0.3 mm.

20. A riveted joint according to claim 14, wherein the self-piercing rivet the annular piercing end has a length along the longitudinal axis of less than 0.3 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0029] FIG. 1 shows a sectioned view of a first embodiment of a self-piercing rivet according to the present invention.

[0030] FIG. 2 is a close-up view of the area of the rivet labelled II in FIG. 1.

[0031] FIG. 3 shows a sectioned view of a second embodiment of a self-piercing rivet according to the present invention.

[0032] FIG. 4A and FIG. 4B show sectioned views through two riveted joints prepared for comparative purposes: one using a prior art self-piercing rivet (FIG. 4A) and the other using a self-piercing rivet in accordance with the present invention (FIG. 4B).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] On the different figures, the same reference signs designate identical or similar elements.

[0034] FIG. 1 and FIG. 3 show a self-piercing rivet 10 comprising a rivet head 12 and a rivet shank 14 extending along a longitudinal axis. The self-piercing rivet 10 is suitable for producing a joining connection between at least two components, and notably between three components C1, C2, C3, such as aluminium components or sheets of aluminium, as shown on FIG. 4B.

[0035] The rivet shank 14 comprises a central shank bore 16 having a base 17. The rivet shank 14 further comprises a cylindrical shank outer surface 18 and a shank inner surface 20 limiting the central shank bore. The shank outer surface has a first diameter Ds. The shank inner surface 20 has a second diameter Di. The rivet shank 14 further comprises an annular piercing end 22 facing away from the rivet head 12. The central shank bore comprises a bore depth T between the base of the central shank bore and the annular piercing end. More particularly the bore depth T is the greatest distance along the longitudinal axis between the base 17 and the annular piercing end 22. For instance, the bore depth T is the distance between the most upper point of the surface of the base (in other words the point of the base situated the nearest of the upper surface of the head) and the lowest point of the annular piercing end 22.

[0036] The geometry of the self-piercing rivet is such that a ratio of the first diameter Ds to the bore depth T is in the range of 0.50Ds/T0.67. More particularly, the ratio can be in the range of 0.58 or 0.59 to 0.67 or to 0.66. Thus, the geometry of the rivet is defined through the ratio of the outside diameter Ds to the bore depth T and not through other parameters like the rivet length L.

[0037] The rivet head 12 extends radially outward from the rivet shank 14. The rivet head 12 has an upper portion 24 and a transition region defined between the upper portion 24 and the rivet shank 14. The transition region has a radius of curvature R1 in the range 2.1 to 2.3 mm, and in particular of 2.2 mm. The upper portion 24 has an upper surface 26 opposite the base 17. The thickness tbu between the base 17 and the upper surface 26 is comprised between 1.5 and 3.5 mm. The upper portion 24 of the rivet head 12 has a height h along the longitudinal axis.

[0038] As illustrated in the drawings, the base 17 can be conical or frustoconical. The base can also be rounded. The base can be provided with an arcuate transition of radius R2 between the periphery of the base and the shank inner surface. The radius R2 is between 0.35 and 0.4 mm.

[0039] The shank inner surface 20 extends parallel to the longitudinal axis from the base until the annular piercing end 22. The shank outer surface 18 and the shank inner surface 20 are connected at the annular piercing end by a shank end face 28 and a shank end radius R3, as illustrated in FIG. 2 and FIG. 3. The shank end radius R3 is between 1.2 and 1.4 millimeters (mm). For example, the shank end radius is of 1.3 mm.

[0040] The shank end face can be a flat shank end face, as depicted on FIG. 3. The flat shank end face has a width w along an axis perpendicular to the longitudinal axis. The shank end face may also be an arcuate shank end face with a radius R4, as illustrated in FIG. 1. The radius R4 may be between 0.15 and 0.3 mm. A conical taper surface is arranged between the shank end radius R3 and the shank end face. The conical taper surface has an inclusive angle of 90 degrees.

[0041] The annular piercing end has a length Lap along the longitudinal axis of less than 0.3 mm.

[0042] As described above, in the first embodiment represented in FIG. 1 and FIG. 2, the self-piercing rivet has an arcuate shank end face with a radius of curvature R4.

[0043] In a first alternative, the self-piercing rivet according to the first embodiment has the following dimensions:

TABLE-US-00001 Ds 5.3 mm Di 3.2 mm 90 Deg. T 9 mm h 0.3 mm tbu 2 mm R1 2.20 mm R2 0.35 mm R3 1.25 mm R4 0.3 mm

[0044] In a second alternative, the self-piercing rivet according to the first embodiment has the following dimensions:

TABLE-US-00002 Ds 5.3 mm Di 3.2 mm 90 Deg. T 9 mm h 0.3 mm tbu 2 mm R1 2.2 mm R2 0.4 mm R3 1.3 mm R4 0.15-0.3 mm

[0045] In a third alternative, the self-piercing rivet according to the first embodiment has the following dimensions:

TABLE-US-00003 Ds 5.3 mm Di 3.26 mm 90 Deg. T 8.5 mm h 0.3 mm tbu 2.5 mm R1 2.2 mm R2 0.35 mm R3 1.25 mm R4 0.15 mm

[0046] In the second embodiment, represented in FIG. 3, the self-piercing rivet has a flat shank end face.

[0047] In an alternative, the self-piercing rivet according to the second embodiment has the following dimensions:

TABLE-US-00004 Ds 5.3 Di 3.3 90 Deg. T 8.5 mm h 0.3 mm tbu 2.5 mm R1 2.2 mm R2 0.4 mm R3 1.3 mm w 0.3 mm

[0048] In a further alternative, the self-piercing rivet according to the second embodiment has the following dimensions:

TABLE-US-00005 Ds 5.3 Di 3.3 90 Deg. T 8.5 mm h 0.3 mm tbu 3.5 mm R1 2.2 mm R2 0.4 mm R3 1.3 mm w 0.3 mm

[0049] Referring now to FIG. 4A and FIG. 4B of the drawings, there is shown a joint formed in a stack of three sheets of brittle aluminium alloy by a self-piercing rivet. FIG. 4A represents a joint formed in a stack of three sheets of aluminium by a self-piercing rivet of the prior art. FIG. 4B represents a joint formed in a stack of three sheets of aluminium by a self-piercing rivet according to the present invention.

[0050] On FIG. 4A, the prior art self-piercing rivet has a first diameter to the bore depth ratio higher than 0.7. The joint section in FIG. 4A reveals that such a structure with new relatively brittle aluminum alloys cannot be jointed with self-piercing riveting with rivets from the state of the art. Indeed, with such rivets, the remaining bottom sheet material thickness is too thin which causes cracks in a serial production environment. Additionally, the setting force is very high and exceeds the upper force tolerance of currently known and used self-piercing riveting equipment, and without this high force the interlock would be too small.

[0051] The self-piercing rivet of FIG. 4B is according to the present invention. In contrast to FIG. 4A, FIG. 4B shows a well-performed joint. Through the shaft diameter to the bore depth ratio according the present invention, the remaining material thickness is significantly higher (no risks of cracks) and the setting forces are significantly lower. This allows reducing the die volume and thus reducing the deformation in the lower sheet material (also even less ductile materials can be jointed).

[0052] Thus, the self-piercing rivet according to the invention allows the self-piercing riveting assembly range to be increased.

[0053] Although exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.