Assembly for minimizing the overlap of a composite element riveted to another element

Abstract

Assembly (10), comprising: a first element (12) with a first overlap area (24); a second element (14) with a second overlap area (26), wherein the first overlap area (24) is in direct contact with the second overlap area (26) to form an overlapped area (28), and wherein the second element (14) includes an end that defines a plurality of projections (52) in the overlapped area (28), and a rivet (15) which is arranged by the first element (12), and at least partially by the second element (14) in one of the plurality of projections (52), whereby the second element (14) is locked to the first element (12), wherein one of the multiple projections (52) includes a body (52A) defining a vertex (52B), and wherein the rivet (15) extends through the body (52A) such that a line extending from the central axis of the rivet (15) is perpendicular to a tangent extending through the vertex (52B), wherein each of the multiple projections (52) is a curved symmetrical structure that defines a wave-shaped distal end, wherein the distal end of the second element (14) further defines curved recesses (62) that separate adjacent curved symmetrical structures; thereby defining an undulating wavy end, wherein the first element (12) has a plurality of adjacent curved projections (68) with curved recesses (70) corresponding to those of the second element (14).

Description

TECHNICAL FIELD

[0001] The invention relates to an assembly for joining a composite member to another member using a rivet, and more particularly to an assembly for minimizing overlap of a composite member joined to another member using a self-piercing rivet. BACKGROUND

[0002] The manufacture of automobiles often requires metal elements to be fastened together. Self-piercing riveting is one possible method for fastening such elements, particularly steel or aluminum sheets. Self-piercing riveting typically requires a sharpened end portion of a rivet to penetrate a first of two stacked metal sheets and at least a portion of the second of the stacked sheets. During such penetration, the sharpened end portion of the rivet is typically deformed or bent to secure the rivet to the metal sheets, thereby locking the metal sheets into an assembly.

[0003] For improved weight savings, non-structural metal parts can be replaced with a composite material, such as a thermoplastic. Thermoplastics are a polymer material that becomes flexible and moldable above a specific temperature, which would be ideal in the manufacture of automotive components such as door panels, fender bodies, bumper covers, and the like. Thermoplastics can be formed by heating and molded into automotive components using various polymer processing techniques, such as injection molding, compression molding, and extrusion. However, below their glass transition temperature (Tg), thermoplastic composites commonly used in automotive applications, such as fiber-reinforced thermoplastics (e.g., polystyrenes, polycarbonates, and polyvinyl chlorides), are less ductile and more brittle than metal elements.

[0004] Self-piercing rivets can be used to join a thermoplastic composite element to a metal element, or a thermoplastic composite element to another thermoplastic composite element. However, when a rivet is pierced close to an edge of the thermoplastic element, the amount of impact force required to drive the rivet through the elements and to deform the sharpened end of the rivet to lock the two elements together can cause microcracks between the rivet and the edge of the less ductile and brittle thermoplastic element, weakening the riveted joint. To compensate for this, the edge of the thermoplastic element can be extended to increase the overlap between the composite element and the other element.This increased overlap provides sufficient clearance between the rivet and the edge of the thermoplastic element to ensure the structural integrity necessary to prevent cracking. However, the increase in the length of the thermoplastic element results in increased material consumption, weight, and overall size of the final assembly, necessitating a redesign of the component's form factor.

[0005] A panel assembly is known from US 2013 / 0 084 422 A1. A functional element assembly is described in DE 100 15 239 A1. DE 10 2013 217 640 A1 discloses a method for attaching a fastener to a workpiece. US 2007 / 0 016 336 A1 describes a method and system for reducing stress concentrations in a lap joint.

[0006] Thus, there is a need for improved self-pierce riveting techniques to achieve high integrity attachments of a thermoplastic element to a thermoplastic or non-thermoplastic element while minimizing the overlap of the thermoplastic element with the other element.

[0007] It is an object of the present invention to provide an improved assembly. SUMMARY

[0008] This object is achieved by the subject matter of claim 1. Advantageous further developments are specified in the dependent claims.

[0009] In another aspect, each of the adjacent curved symmetrical structures includes a first radius and the curved recess includes a second radius, wherein the first radius is greater than the second radius.

[0010] In another aspect, the rivet has an outer tube diameter, wherein the center axis of the rivet is at least 2.0 tube diameters from the apex of the curvature.

[0011] In another aspect, the assembly may further include a washer in contact with the second surface of the second member in the overlapped region. The rivet may be deformable radially outward from the center axis of the rivet and axially toward the second surface of the second member, thereby locking the washer against the second surface of the second member.

[0012] In another aspect, the first element includes a first element thickness and the second element includes a second element thickness, and the overlapped region may include an overlapped region thickness equal to the sum of the thicknesses of the first and second elements.

[0013] In another aspect, the second element is a polymer material comprising a thermoplastic selected from the group consisting of polypropylene (PP), polyurethane (PUR), polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyamide (PA, nylon 6 / 6 and nylon 6), polystyrene (PS), polyethylene (PE), polyoxymethylene (POM), polycarbonate (PC), polyethylene polyethylene terephthalate (PET) and acrylonitrile styrene acrylate (ASA).

[0014] An alternative, unclaimed embodiment of an assembly is also provided. The assembly includes a first member having a first surface and an opposite second surface defining an inverted beveled segment; a second member having a first surface defining an inverted beveled segment and an opposite facing second surface, wherein the inverted beveled segment of the first member overlaps the inverted beveled segment of the second member, thereby forming an overlapped region; and at least one rivet extending through the first member and at least partially through the second member in the overlapped region, thereby locking the second member to the first member. The inverted beveled segment of the first member is complementary to the inverted beveled segment of the second member.

[0015] In one aspect, the first element includes a first element thickness and the second element includes a second element thickness, and the overlapped region may include an overlapped region thickness that is greater than the sum of the thicknesses of the first and second elements.

[0016] In another aspect, the second member has a distal end defining a plurality of adjacent curved symmetrical structures and a curved recess separating immediately adjacent curved symmetrical structures, thereby defining an undulating undulating distal end

[0017] In another aspect, a washer may be disposed in the overlapped region on the second surface of the second member. The at least one rivet may extend through the second member and deforms against the washer, thereby locking the washer against the second surface of the second member.

[0018] A non-claimed method for joining two elements is also described. The method comprises the following steps: (a) placing a first element having a first surface and an opposite facing second surface defining an overlap region on a second element having a first surface defining an overlap region and an opposite facing second surface, such that the overlap region of the first element is in direct contact with the overlap region of the second element, thereby forming an overlapped region; (b) driving at least one rivet through the first element and at least partially through the second element in the overlapped region, the at least one rivet having a head portion defining a bottom surface and a tubular portion extending outwardly from the bottom surface of the head along a central axis,and wherein the tubular portion includes a tapered edge; and (c) deforming the tubular portion and the tapered edge radially outward from the central axis of the rivet, thereby locking the second member to the first member, wherein the second member includes a distal end in the overlapped region defining at least one curved protrusion. The second member includes a polymeric material selected from the group consisting of polypropylene (PP), polyurethane (PUR), polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyamide (PA, Nylon 6 / 6, and Nylon 6), polystyrene (PS), polyethylene (PE), polyoxymethylene (POM), polycarbonate (PC), polyethylene terephthalate (PET), and acrylonitrile styrene acrylate (ASA). The second member includes a distal end in the overlapped region defining at least one curved protrusion, which may be a curved symmetrical structure.which defines a curvature apex. The rivet can be driven into the overlapped region where a radius extending from the rivet's central axis is perpendicular to a tangent extending through the curvature apex and at a distance from the curvature apex such that the curved symmetrical structure provides sufficient structural integrity to prevent breakage of the second element in the overlapped region resulting from driving and deforming the rivet.

[0019] In one aspect, a washer can be placed against the second surface of the second member in the overlapped region. The rivet can be driven through the second member in the overlapped region such that the tapered edge extends over the second surface of the second member and through the washer. The tapered edge of the rivet can be deformed radially outward from the central axis of the rivet and axially contact the washer toward the second surface of the second member, thereby locking the washer against the second surface of the second member. The overlap region of the second surface of the first member can define an inverted chamfered segment, and the overlap region of the second member can define an inverted chamfered segment complementary to the inverted chamfered segment of the first member.The thickness in the overlapped region is greater than the sum of the thickness of the first element and the second element immediately before the overlapping regions of each of the respective elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The foregoing and other aspects will become clearer and more easily understood from the following description of exemplary embodiments in conjunction with the accompanying drawings, in which: Fig. 1 is an exploded perspective view of a first embodiment of the invention; Fig. 2 the bottom view of the first embodiment of the invention of Fig. 1 represents; Fig. 3A is a cross-sectional view of the first embodiment along section line 3-3 of Fig. 2 with a first example of a rivet; Fig. 3B is a cross-sectional view of the first embodiment along section line 3-3 of Fig. 2 with a second example of a rivet; Fig. 4 is an exploded perspective view of a second embodiment of the invention; Fig. 5 a cross section of the second embodiment along the section line 5-5 of Fig. 4 represents; Fig. 6 is an exploded perspective view of a third embodiment of the invention; Fig. 7 shows a cross section of the third embodiment along section line 7-7 of Fig. 6; and Fig. 8 is an exploded perspective view of a fourth embodiment of the invention incorporating the features of the first three embodiments. DESCRIPTION

[0021] The following description is merely exemplary in nature and is not intended to limit the present invention. With reference to Fig. 1 to 3, in which like reference numerals correspond to the same or similar elements throughout the figures, an assembly 10 is illustrated having a first member 12 connected to a second member 14 by one or more self-piercing rivets 15. In general, the first member 12 and the second member 14 may be any two components within a motor vehicle, including, for example, body panels, support members, trim strips, etc. Thus, the first and second members 12, 14 may be a sheet of material or a flange extending from an automotive component. The first member 12 may typically be formed from a metallic material found in automotive components, such as steel, copper, magnesium, aluminum, or a polymeric material, such as a thermoplastic or a thermoplastic composite.The second element 14 is formed from a polymer composite, such as a thermoplastic composite. Exemplary thermoplastic composites used in automotive applications include fiber-reinforced thermoplastics (e.g., polypropylene (PP), polyurethane (PUR), polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyamide (PA, Nylon 6 / 6, and Nylon 6), polystyrene (PS), polyethylene (PE), polyoxymethylene (POM), polycarbonate (PC), polyethylene terephthalate (PET), and acrylonitrile styrene acrylate (ASA)).

[0022] The first member 12 includes a first or outer surface 16 and an opposite, facing second or inner surface 18. Similarly, the second member 14 has a first or inner surface 20 and an opposite, facing second or outer surface 22. A portion of the inner surface 18 of the first member 12 defines an overlap region 24. Similarly, a portion of the inner surface 20 of the second member 14 defines an overlap region 26. The first member 12 and the second member 14 are positioned such that the inner surface 18 of the first member 12 continuously contacts the inner surface 20 of the second member 14 across the overlap regions 24, 26 to form an overlapped region 28 of the assembly 10.

[0023] The punch rivets 15 firmly fasten the first element 12 to the second element 14. Each of the punch rivets 15, which are best used in Fig. 1, includes a head portion 30 and a body portion 32. The head portion 30 is generally disc-shaped having a substantially flat top surface 34 and a bottom surface 36. The body portion 32 is generally tubular and extends outwardly along a central axis 38 away from the bottom surface 36 of the head portion 30. The body portion 32 has a distal end 40 defining a tapered edge 42. The bottom surface 36 of the head portion 30 extends radially outwardly away from the central axis 38 farther than the body portion 32 to thereby define an annular or flat surface 44. The self-piercing rivets 15 may be formed from a variety of metals having a high strength-to-weight ratio, such as steel, aluminum, or magnesium alloys.The self-piercing rivets 15 may be coated with a suitable protective coating, such as a corrosion inhibitor, or may be selectively coated at a specific portion to achieve a hardness gradient within the self-piercing rivet 15. It should also be noted that the self-piercing rivets 15 may have various other shapes and configurations.

[0024] The self-piercing rivets 15 are used to fasten the first member 12 to the second member 14 when the head portions 30 of the rivet 15 are subjected to a driving force. The process begins by clamping the first and second clamping members 12, 14 together between a binder (not shown) and a die (not shown). The rivets 15 are then driven into the first and second members 12, 14. The rivets 15 pierce the first member 12, and the shape of the die causes the tapered edges 42 of the rivet 15 to expand in the second member 14 to form a mechanical detent 46, which can be clearly seen in Fig. 3A. Alternatively, the rivets 15 can be driven into the first member 12 and through the second member 14 until the tapered edge 42 is driven through the outer surface 22 of the second member 14. The die causes the rivets 15 to expand outwardly and upwardly toward the outer surface 22 of the second member 14 to form a rivet flange 48 abutting the second member 14, as shown in Fig. 3B.

[0025] With reference to Fig. 2, the second member 14 includes a distal end surface 50 having a distal end surface 51 connecting the inner and outer surfaces 20, 22. The distal end surface 50 defines a plurality of protrusions 52 along an axis 53 in a direction extending away from the main body of the second member 14. In the example provided, the protrusions 52 are curved protrusions adjacent to one another, thereby defining a wave-shaped distal end 54. Each of the protrusions 52 includes a body 52A having a distal geometric center or apex 52B. In the example provided, the body 52A is a curved symmetrical structure having a center point 55 with a radius 58. Although the body 52A is described as a curved protrusion in Fig. 2, it should be understood that the body 52A may be a rectangle, square, triangle, oval, or other shape extending longitudinally from the distal end surface 50. The projections 52 may be molded into the second member 14. Likewise, the first member 12 may include a plurality of projections 68 (shown in Fig. 1) complementary to those of the second element 14, or may alternatively have a flat, planar distal end or other shape.

[0026] The rivets 15 are punched into the overlapped portion 28 of the assembly 10 such that each of the rivets 15 is disposed within one of the bodies 52A of the plurality of projections 52. Preferably, the rivet 15 extends through the body 52A at a position where a radial line 56 extending from the central axis 38 of the rivet 15 is perpendicular to a tangent 59 through the apex 52B.

[0027] In Fig. 1 and Fig. 2, each of the rivets 15 is centered within the body 52A such that the central axis 38 of the rivet 15 coincides with the center point 55 of the radius 58 of the body 52A. Preferably, the minimum distance from the apex 52B of the body 52A to the central axis 38 of the rivet 15 is at least 2 times the outer tubular diameter 61 of the body portion 32 of the rivet 15. The projections 52 provide sufficient additional material between the rivet 15 and the distal end surface 50 of the second member 14 to extend the structural integrity of the overlapped region 28 while eliminating non-essential material between adjacent rivets 15. The curvature of the projection 52 helps to disperse the impact forces when the rivet 15 is driven into the second member 14 and deformed to lock the first and second members 12, 14.

[0028] Adjacent bodies 52A are separated by a semicircular recess 62. A radius 64 of the semicircular recess 62 is smaller than the radius 58 of the body 52A. The semicircular recesses 62 help disperse the impact forces when the rivet 15 is driven into the second member 14 and distribute the load to adjacent projections 52 to prevent cracking or breakage of the second member 14. Likewise, the first member 12 may include a plurality of complementary semicircular recesses 70 (in Fig. 1), in addition to that of the second element 14

[0029] With reference to Fig. 3A and Fig. 3B, it should be noted that the first member 12 includes a first member thickness 74 and the second member 14 includes a second member thickness 76. The thickness 78 of the overlapped region 28 is the sum of the thickness 74 of the first member 12 and the thickness 76 of the second member 14. The thicknesses of the members 12, 14 do not need to be increased in the overlapped region 28 to accommodate the loads induced by the rivet 15 being punched through the members 12, 14 during the assembly process. In other words, the thicknesses 74, 76 are constant along the longitudinal extent of the members 12, 14.

[0030] With reference now to Fig. 4 and Fig. 5, another embodiment of an assembly is shown and identified by reference numeral 110. The assembly 110 includes a first member 112 and a second member 114 connected by one or more of the self-piercing rivets 15. The distal end 150 of the second member 114 includes a planar surface having a thickness 172 that is greater than the thickness 176 of the second member 114 immediately prior to transitioning into the overlapped region 128, thereby providing an inclined upper surface defining a chamfered segment 180. In other words, a portion of the inner surface 120 of the second member 114 defines a chamfered segment 180. Similarly, the inner surface 118 of the first member 112 defines an inverted chamfered segment 182. The pitch, or angle α, of the chamfered segment 180 of the second member 114 is complementary to the slope, or angle β, of the inverted chamfered segment 182 of the first member 112.

[0031] The first member 112 is disposed on the second member 114 such that the overlap region 124 of the first member 112 is in direct contact with the overlap region 126 of the lower member 114, thereby forming an overlapped region 128. The thickness 178 of the joined members 112, 114 in the overlapped region 128 is greater than the sum of the thickness 174 of the first member 112 and the thickness 176 of the second member 114. The increased thickness 178 in the overlapped region 128 provides the additional structural integrity necessary to accommodate the stresses induced by the rivet 15 piercing the members 112, 114.

[0032] The self-piercing rivet 15 is disposed through the first member 112 and at least partially through the second member 114 in the overlapped region 128. The tapered edge 42 is deformed radially outward from the central axis 38 of the rivet 15 into a portion of the second member 114, thereby locking the first member 112 to the second member 114. Alternatively, the sharpened tapered edge 42 may be deformed radially outward from the central axis 38 of the rivet 15 and upward toward the outer surface 122 of the second member 114 to form a rivet flange 48, thereby locking the first member 112 to the second member 114 between the head portion 30 of the rivet 15 and the rivet flange 48.

[0033] With reference now to Fig. 6 and Fig. 7, another embodiment of an assembly is shown and identified by reference numeral 210. A washer 84 is disposed against the bottom surface 222 of the second member 214 and is configured to receive the rivet 15. The rivet 15 is punched through the members 212, 214, and the tapered edge 42 deforms radially outward from the central axis 38 of the rivet 15 and upward toward the washer 84 to form a rivet flange 48. The first member 212 is locked to the second member 214 between the head portion 30 of the rivet 15 and the rivet flange 48. Alternatively, a workpiece or blank may be placed against the bottom surface 222 of the second member 214, and the rivet 15 is punched through the members 212, 214 and the workpiece, forming the equivalent of a washer 84 surrounding the rivet 15.

[0034] It should be noted that the second member 214 includes a lower member thickness 274 and the first member 212 includes an upper member thickness 276. The thickness 278 of the overlapped region 228 is the sum of the thickness 276 of the second member 214 and the thickness 274 of the first member 212. The thicknesses of the members 212, 214 do not need to be increased in the overlapped region 228 to accommodate the loads induced by the rivet 15 being punched through the members 212, 214 during the assembly process.

[0035] With reference now to Fig.8, another embodiment of an assembly is shown and identified by reference numeral 310. The assembly 310 includes the features of the first three embodiments of the assemblies 10, 110, 210. The second member 314 of the assembly 310 includes a distal end 350 having a plurality of curved protrusions 352 defining a wave-shaped distal end 354. The first member 312 may also include a plurality of adjacent curved protrusions 368 complementary to those of the second member 314 and a semicircular recess 370 between adjacent curved protrusions 368.

[0036] The second member 314 defines a chamfered segment 380. Similarly, the first member 312 defines an inverted chamfered segment 382. The slope, or angle α, of the chamfered segment 380 of the second member 314 is complementary to the slope, or angle β, of the inverted chamfered segment 382 of the first member 312. A rivet 15 is driven through the first member 312 and through the second member 314 in the overlapped area 328. A washer 84 is positioned under the second member 314 and is configured to receive the rivet 15. The combined functions of the undulating distal end 354, the beveled segments 380, 382 and the washer 84 provide the additional structural integrity required to accommodate the loads induced by the rivet 15 piercing the members 312, 314 during the punching operation.

[0037] The assembly with a self-piercing rivet joining a composite component and a joining method for a composite component as described above can be used to fasten a variety of automotive components formed from metallic or polymeric materials. Exemplary automotive components include various vehicle panels such as body panels, door panels, trunk lids, hoods, door frames, sunroof applications, or the like. Resulting joints are also considered part of the present invention.

Claims

[1] Assembly (10) comprising: a first element (12) having a first overlap region (24); a second member (14) having a second overlap region (26), wherein the first overlap region (24) is in direct contact with the second overlap region (26) to thereby form an overlapped region (28), and wherein the second member (14) includes an end defining a plurality of projections (52) in the overlapped region (28), and a rivet (15) disposed through the first element (12) and at least partially through the second element (14) in one of the plurality of projections (52), whereby the second element (14) is locked to the first element (12), wherein one of the plurality of projections (52) includes a body (52A) defining an apex (52B), and wherein the rivet (15) extends through the body (52A) such that a line extending from the central axis of the rivet (15) is perpendicular to a tangent extending through the apex (52B), wherein each of the plurality of projections (52) is a curved symmetrical structure defining a wave-shaped distal end, wherein the distal end of the second member (14) further defines curved recesses (62) separating adjacent curved symmetrical structures; thereby defining an undulating wave-shaped end, wherein the first element (12) has a plurality of adjacent curved projections (68) with curved recesses (70) corresponding to those of the second element (14). [2] The assembly (10) of claim 1, wherein the rivet (15) includes a tube diameter (61), and wherein the center axis of the rivet is spaced at least 2.0 tube diameters (61) from the apex. [3] The assembly (10) of claim 1, wherein the assembly (10) further includes a washer (84) in contact with a bottom surface of the second member (14) of the overlapped portion (28), the rivet (15) locking the washer (84) against the bottom surface of the second member (14). [4] The assembly (10) of claim 1, wherein the first member (12) includes a first member thickness (74) and the second member (14) includes a second member thickness (76), and the overlapped region (28) includes an overlapped region thickness equal to the sum of the thicknesses of the first and second members (12, 14). [5] The assembly (10) of claim 1, wherein the second element comprises a polymer material comprising a thermoplastic. [6] The assembly (10) of claim 1, wherein the second element (14) comprises a polymer composite material selected from the group consisting of polypropylene (PP), polyurethane (PUR), polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyamide (PA, nylon 6 / 6, nylon 6), polystyrene (PS), polyethylene (PE), polyoxymethylene (POM), polycarbonate (PC), polyethylene terephthalate (PET) and acrylonitrile styrene acrylate (ASA).

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