Functional element

Abstract

The present invention relates to a self-piercing functional element which is configured to be pierced into a workpiece, in particular into a sheet metal part, and comprises: a head which forms a flange; and a piercing part which extends away from the head and is arranged, in particular, coaxially with the central longitudinal axis of the functional element and has a peripheral piercing edge, wherein the head has: a contact surface for contacting the workpiece, the contact surface at least partially surrounding the piercing part radially on the outside; and a boundary part which at least partially defines the contact surface radially on the outside and extends away from the contact surface in the same direction as the piercing part; and wherein the inner wall of the boundary part facing the piercing part and the outer wall of the piercing part facing the boundary part are arranged at least partially inclined to the longitudinal axis of the functional element such that the inner wall and the outer wall each form an undercut in at least one plane including the longitudinal axis.

Description

Field of the Invention

[0001] The present invention relates to a self-piercing functional element which is configured to be pierced into a workpiece, in particular into a sheet metal part. The element includes a head forming a flange; and a piercing portion which extends away from the head and is arranged, in particular, coaxially with a central longitudinal axis of the functional element and has a peripheral piercing edge. Background Art

[0002] In the field of connection elements or functional elements which are mechanically attached to a workpiece such as a sheet metal part during production, there is a distinction between press-fit elements on the one hand and rivet elements on the other hand. Press-fit elements are characterized in that they are at least not intentionally deformed when attached to the workpiece, but rather the workpiece itself is deformed and engages with the shape features of the press-fit element, whereby the press-fit element is fastened to the sheet metal part in a manner that is resistant to being pressed out. In the case of a rivet element, the element is intentionally deformed when attached to the sheet metal part, typically to form a rivet curl, whereby the sheet metal part is captured between the rivet curl and a flange portion in order to also achieve a connection that is resistant to being pressed out here.

[0003] Furthermore, both press-fit elements and rivet elements are referred to as self-piercing elements. The name self-piercing is to be understood such that the corresponding element pierces its own hole in the workpiece during the fastening process. The force required for this is generated, for example, by a press, a robot or a power-operated pair of pliers. In this regard, the self-piercing element is pressed against the workpiece while the workpiece is supported on a corresponding die on the side remote from the element. Self-piercing elements are associated with a cost advantage since the workpiece does not have to be pre-pierced.

[0004] Functional elements of the type described above are used in particular in automotive engineering, but not only in automotive engineering to date. As the range of use of such functional elements has expanded, the requirements they must meet have also increased.

[0005] Therefore, there is a need for a self-piercing functional element which can be reliably fastened to a workpiece in a simple manner and can withstand high pressing forces or tensile forces as well as torques. Summary of the Invention

[0006] The present invention provides such a functional element. According to the present invention, the head has: a contact surface for contacting the workpiece, the contact surface at least partially surrounding the piercing portion radially on the outside; and a boundary portion which at least partially defines the contact surface radially on the outside and extends away from the contact surface in the same direction as the piercing portion. The boundary portion is particularly continuous in the circumferential direction. The inner wall of the boundary portion facing the piercing portion and the outer wall of the piercing portion facing the boundary portion are arranged at least partially inclined to the longitudinal axis of the functional element such that the inner wall and the outer wall each form an undercut in at least one plane including the longitudinal axis.

[0007] The inner wall, the contact surface, and the outer wall thus form an annular space which, due to the at least partial inclination of the inner wall and the outer wall relative to the longitudinal axis, has an undercut and is thus suitable for form-fitting with the material of the workpiece pressed into the annular space during the fastening process.

[0008] At this point, the term "inclined" should also be understood as referring to at least partially curved designs of the walls. Due to the at least partial undercuts provided at both the inner wall and the outer wall, a particularly good resistance against the pressing out or pulling out of the resistance element is achieved. The undercuts do not have to be continuous in the circumferential direction. In many embodiments, it may be sufficient if at least the respective peripheral segments of the outer wall and the inner wall each form an undercut. The two peripheral segments are particularly arranged opposite one another when viewed radially.

[0009] The outer wall preferably has an undercut that is continuous in the circumferential direction, while the inner wall has a plurality of undercut segments distributed particularly in a uniform manner.

[0010] Further embodiments of the invention are set forth in the description, the drawings, and the claims.

[0011] According to an embodiment, the inner wall has a polygonal contour in an axial end view, which results in increased safety against rotation of the element. This means that the fastened element can withstand a larger torque because a circumferentially effective form fit can be established between the workpiece and the element.

[0012] An increased safety against rotation is also achieved when the boundary part has an axial end face facing the workpiece and the inner edge and / or the outer edge has a polygonal contour in the axial end view.

[0013] The boundary part can have an axial end face that faces the workpiece and the plane of which is arranged between the plane spanned by the contact surface and the plane spanned by the stamping edge. These three planes are particularly arranged parallel to one another.

[0014] The head and / or the stamping part preferably have a circular basic shape when viewed axially - i.e., in a plane perpendicular to the longitudinal axis. However, different basic shapes can also be envisaged, such as an oval, rectangular, or polygonal basic shape. The stamping edge of the stamping part and / or the outer wall particularly have a polygonal contour in the axial end view. In certain applications, it can be advantageous if the head and the stamping part have different basic shapes.

[0015] The above-mentioned greater geometric design freedom of the inner wall, the outer wall, and the stamping edge, the inner edge, and the outer edge results in the annular space being able to have a complex shape. Thus, in the context of the present invention, the meaning of this term is not limited solely to a circular ring.

[0016] To further improve the safety against rotation, the outer wall and / or the inner wall and / or the contact surface and / or the axial end faces may be provided with at least one feature that provides safety against rotation, in particular with at least one projection and / or recess extending axially and / or radially. The number, positioning and shape of the features can be selected as required.

[0017] For example, at least one rib extends radially from the inner wall towards the stamping portion and axially away from the contact surface. In particular, the axial extent of the rib decreases from the outside towards the inside. The rib may extend into the stamping portion. However, the rib may also only span a part of the gap between the boundary portion and the stamping portion or a part of the annular space (e.g., less than 80% of the gap, less than 70% of the gap, less than 60% of the gap or less than 50% of the gap). The end face of the rib may have a circular shape to minimize its notch effect and thus not reduce the fatigue resistance of the workpiece in the element area.

[0018] Additionally or alternatively, at least one base extending axially away from the contact surface may extend radially from the outer wall towards the boundary portion. The base may extend all the way to the boundary portion. However, the base may also only span a part of the gap between the boundary portion and the stamping portion or a part of the annular space (e.g., less than 80% of the gap, less than 70% of the gap, less than 60% of the gap or less than 50% of the gap). The base may have a substantially planar end face that is arranged perpendicular or inclined to the longitudinal axis. The base not only serves to improve the safety against rotation but also contributes to the displacement and distribution of the workpiece material pressed into the annular space during the fastening process. Among other things, a beneficial result is an improved tightness of the connection between the element and the workpiece.

[0019] The ribs and the bases may be arranged offset circumferentially along the contact surface. In particular, a plurality of ribs and bases are provided, which are arranged evenly distributed circumferentially and offset from each other. An alternating arrangement of ribs and bases that preferably overlap radially provides particularly good results with regard to the reliability and tightness of the connection between the element and the workpiece.

[0020] According to an embodiment, the functional element is a nut element having a hole with an internal thread. The functional element may also be a bolt element having a bolt portion extending from the head on the side remote from the stamping portion, in particular, wherein the bolt portion is at least partially provided with an external thread.

[0021] The invention further relates to a component assembly, which comprises a functional element according to at least one of the foregoing embodiments; and a workpiece, in particular a sheet metal part, wherein the workpiece is at least partially pushed into an annular space formed by an inner wall, a contact surface and an outer wall, and is pushed into an undercut in a region surrounding a hole punched out by a punching part, so that the functional element is connected to the workpiece in a form-fitting manner.

[0022] According to an embodiment of the component assembly, a circumferentially continuous or segmented recess, in particular an annular recess, is provided on a side of the workpiece remote from the contact surface in a region adjacent to or directly adjacent to the hole. In particular, at least part of the material of the workpiece in the region of the recess is arranged in the annular space. The geometric basic shape of the recess is preferably complementary to the geometric basic shape of the annular space. However, it can also deviate. The recess is in particular rotationally symmetric.

[0023] The recess can be produced during the process of fastening the element to the workpiece, for example by means of a die which presses the material of the workpiece adjacent to the hole produced by the punching part into the annular space.

[0024] When manufacturing the component assembly, the element must be coordinated with the thickness and design of the workpiece in the region of the hole to be produced. In many cases, the length of the punching part, i.e. its axial extent starting from the head, is advantageously less than the depth of the recess. In other words, in this embodiment of the component assembly, the axial extent of the punching part is selected such that the punching part does not protrude from the recess, in order to obtain as compact a component assembly as possible. Thus, in particular, it is ensured that there is a flat fastening plane on the side of the workpiece remote from the head of the functional element.

[0025] It can also be provided that, in order to simplify the punching of the hole, the thickness of the workpiece in the hole region substantially corresponds to or is less than the axial extent of the punching part. However, the workpiece can also have a thickness greater than the axial extent of the punching part.

[0026] If the functional element has ribs and a base for providing anti-rotation security, the component assembly is produced by attaching the functional element to the workpiece, and the component assembly is characterized in that both the ribs and the base are engaged with the workpiece in a form-fitting manner. In other words, the workpiece extends into the annular space in a form-fitting manner, since it extends around the ribs and the base and engages behind the undercut. In addition, the material that engages around and / or engages into the undercut of the punching part, i.e. the material in the wall region of the hole in the workpiece, is substantially elastically pressed against the punching part, and a compressive ring stress exists in the workpiece material around the punching part. The corresponding binding between the workpiece material and the punching part results in high-quality fatigue resistance of the joint connection.

[0027] The component assembly is preferably formed by means of a die which has an annular projection such that on the side of the workpiece remote from the element head there is provided an annular recess extending around the stamping edge. This annular recess produced by the annular projection of the die is particularly important when the thickness of the workpiece is greater than the axial extent of the stamping portion. That is, the recess then ensures that the workpiece is completely punched through by the stamping portion. For example, the stamping portion is shorter than the workpiece thickness by an amount up to 0.04 mm, preferably up to 0.02 mm. Description of the Drawings

[0028] Preferred embodiments of the functional element or the corresponding component assembly according to the invention can be seen from the following description of the dependent claims and the examples with reference to the drawings. They show:

[0029] Figure 1 is a perspective view of an embodiment of a functional element according to the invention;

[0030] Figure 2 is according to Figure 1 end view of the functional element;

[0031] Figure 3 is according to Figure 1 cross-sectional view of the functional element;

[0032] Figure 4 、 Figure 5 is an embodiment of a fastening process for fastening a functional element according to Figure 1 to a workpiece; and

[0033] Figure 6 、 Figure 7 is a partial cross-section of the component assembly obtained by the fastening process. Detailed Description

[0034] Figures 1 to 3 An embodiment of the nut element 10 is shown in perspective view, end view and cross-sectional view in two sections A, B, Figure 2 in which the position of the nut element is indicated. The nut element 10 is configured for fastening to a sheet metal part. The element 10 has a head 12 which forms a flange for contact with the workpiece. The element 10 includes a central bore 14 having an internal thread 16 along a longitudinal axis L. The element designed according to the invention can also be a bolt element instead of the bore 14, in which the bolt extends from the head 12.

[0035] The element 10 is a self-piercing press-fit element. The element obtains its self-piercing characteristic from a stamping portion 18 which extends from a sheet metal contact surface 20 remote from the head 12. The stamping portion 18 has a peripheral stamping edge 22 which cooperates with a die to be described below to punch a hole in a sheet metal part (or any other desired workpiece) of the receiving portion 18. As can be seen particularly fromFigure 3 As can be seen, the outer wall 24 of part 18 is not arranged to be completely parallel to the longitudinal axis L. Only the part 22a directly adjacent to the stamping edge 22 extends parallelly to stabilize the stamping edge 22. The outer wall 24 is arranged obliquely between the part 22a and the sheet metal contact surface 20, such that it forms an undercut through which the element 10 can be fixed to the sheet metal part in the direction opposite to the pressing-in direction of the element 10. That is, the edge of the hole produced by part 18 engages behind this undercut, thus fixing the element 10 to the sheet metal part. The angle between the inclined part of the outer wall 24 and the longitudinal axis is several degrees, particularly less than 15°, preferably less than 10°. When manufacturing the element 10, the undercut can be produced by axially extruding the initially cylindrical stamping part.

[0036] To improve the fixing, the element 10 has a circumferentially continuous edge 26 which defines the contact surface 20 at the radially outer side. The edge 26 includes an inner wall 28 which faces the stamping part 18 and is arranged at least partially obliquely to the longitudinal axis L. Thus, the wall 28 also partially forms an undercut which increases the resistance to being extruded or pulled out. The angle between the inclined part of the inner wall 28 and the longitudinal axis is several degrees. In this embodiment, this angle is greater than the angle between the outer wall 24 and the longitudinal axis L. The edge 26 also has an axial end face 26a which is arranged parallel to the sheet metal contact surface 20 and is arranged on the sheet metal part in the assembled state of the element 10.

[0037] The walls 24, 28 and the sheet metal contact surface 20 define an annular space 30 into which the material of the sheet metal part is pressed during the pressing-in of the element 10, whereby a form-fit acting axially is produced. A form-fit acting radially is produced by a plurality of features, and this form-fit prevents the element 10 from rotating by means of a torque acting on the element 10.

[0038] On the one hand, the inner wall 28 of the edge 26 does not have an annular design but a polygonal design. This shape is achieved in a simple manner by radially pressing part of the circular edge 26 inwards in an intermediate state during the manufacturing process - the cold impact process - of the element 10. In this embodiment, eight segments S have been pushed inwards. If necessary, the number of segments S can be adapted to the corresponding application. Due to the treatment of the edge 26, the end face 26a of the edge has an overall polygonal shape, that is, both the inner edge and the outer edge of the end face 26a have a polygonal profile.

[0039] On the other hand, ribs 32 and bases 34 extend radially from the inner wall 28 or the outer wall 24 into the annular space 30. They are evenly distributed and arranged offset in the circumferential direction. Since their radial extent is greater than 50% of the width of the annular space, they overlap in the circumferential direction, such that a particularly good anti-rotation safety effect is produced.

[0040] The ribs 32 communicate with the inner wall portions that do not slope radially inward (see Figure 3 section B in

[0041] ). These portions are not pressed inward during manufacturing because the adjacent segments S abut against each other here.

[0042] In the present embodiment, the upper edges of the ribs 32 extending from the contact surface 20 are circular and are designed to slope radially inward and downward. In the assembled state of the element 10, the ribs 32 penetrate into the material of the sheet metal part pressed into the annular space 30.

[0043] Figure 4 Illustrated is the process of fastening the element 10 to an unprepunched sheet metal part 36. The element 10 is arranged in the recess of the mounting device 38. The stamping portion 18 projects slightly from this recess. During fastening, the sheet metal part 36 is arranged on a die 40 having an annular projection 42. The annular projection 42 has a central recess 44 defined by a die edge 46. When the element 10 is pressed against the sheet metal part 36 with a sufficient force by the mounting device 38, the edge 46 and the stamping edge 22 finally cause the separation of the scrap from the sheet metal part 36. The scrap is guided downward and away.

[0044] During the installation process, the annular projection 42 has the following effect: The sheet metal part 36 is pressed into the annular space 30 in the region around the punching 52, as can be clearly seen in Figure 5 . The material of the sheet metal part 36 is pushed behind the undercuts of the walls 24, 28 in this regard. The material of the sheet metal part 36 is distributed by the ribs 32 protruding into the annular space 30 and in particular by the bases 34, such that a reliable form fit is produced between the element 10 and the sheet metal part 36, which is effective both axially and circumferentially of the element 10. The element 10 and the sheet metal part 36 now form a component assembly 50 (see Figure 5 ).

[0045] Figure 6 and Figure 7 each show the component assembly 50 in a perspective view from obliquely above or obliquely below. Partial segments are cut away to illustrate the nature of the connection between the element 10 and the sheet metal part 36. Figure 6 A part of the left cross-section inFigure 2 and Figure 3 in cross-section B), whereby a downward inclination in the radial direction of its upper edge is recognizable.

[0046] Likewise, it can be seen from Figure 6 that the stamping part 18 does not protrude from the resulting annular recess 48. Thus, it does not prevent the tight contact fastening of a further workpiece to the sheet metal part 36.

[0047] In Figure 7 it is possible to recognize the circular-ring-shaped annular recess 48 produced by the annular projection 42. The geometric basic shape of the annular recess 48 is not actually formed to be completely complementary to the shape of the annular space 30, since the annular space is delimited on the radially outer side by the polygonal inner wall 28. However, due to the features 32, 34 for providing anti-rotation security and the shape of the annular projection 42, the material of the sheet metal part 36 is distributed well enough in the annular space 30.

[0048] List of reference numerals

[0049] 10 Nut element

[0050] 12 Head

[0051] 14 Hole

[0052] 16 Internal thread

[0053] 18 Stamping part

[0054] 20 Sheet metal contact surface

[0055] 22 Stamping edge

[0056] 22a Stamping edge part

[0057] 24 Outer wall

[0058] 26 Edge

[0059] 38A End face

[0060] 28 Inner wall

[0061] 30 Annular space

[0062] 32 Rib

[0063] 34 Base

[0064] 36 Sheet metal part

[0065] 38 Mounting device

[0066] 40 Die

[0067] 42 Annular projection (nose)

[0068] 44 Concave part

[0069] 46 Mold edge

[0070] 48 Annular concave part

[0071] 50 Component assembly

[0072] 52 Hole

[0073] Cross-sections A and B

[0074] L Longitudinal axis

[0075] S Segment

Claims

1. A self - punching functional element configured to be punched into a workpiece, comprising: - a head (12) forming a flange; and - a punching portion (18) extending away from the head, arranged coaxially with the central longitudinal axis (L) of the self - punching functional element, and having a peripheral punching edge (22), wherein the head has: a contact surface (20) for contacting the workpiece, the contact surface (20) at least partially surrounding the punching portion radially outside; and a boundary portion at least partially defining the contact surface radially outside and extending away from the contact surface in the same direction as the punching portion; and wherein the inner wall (28) of the boundary portion facing the punching portion and the outer wall (24) of the punching portion facing the boundary portion are at least partially inclined with respect to the central longitudinal axis of the self - punching functional element such that each of the inner wall and the outer wall forms an undercut in at least one plane including the central longitudinal axis; wherein the inner wall (28), the contact surface (20) and the outer wall (24) form an annular space (30); at least one rib (32) extends radially from the inner wall (28) towards the punching portion (18) and axially away from the contact surface (20) of the self - punching functional element, wherein the axial extent of the rib decreases from outside to inside; at least one base (34) extends radially from the outer wall (24) towards the boundary portion and axially away from the contact surface (20); a plurality of ribs and bases are provided, the plurality of ribs and bases being arranged evenly distributed in the circumferential direction of the contact surface (20) and offset from each other; the radial extent of the rib (32) and the base (34) is greater than 50% of the width of the annular space such that the rib (32) and the base (34) overlap in the circumferential direction; the rib (32) communicates with a portion of the inner wall (28) that does not incline radially inwards; wherein each rib (32) has an end face with a circular shape, and each base (34) has a plane arranged parallel to the contact surface (20).

2. The self - punching functional element according to claim 1, Among them, wherein the workpiece is a sheet metal part (36).

3. The self - punching functional element according to claim 1, Among them, wherein the inner wall (28) has a polygonal profile in an axial end view.

4. The self - punching functional element according to any one of claims 1 - 3, Among them, wherein the boundary portion has an axial end face (26a) facing the workpiece, and the inner edge and / or outer edge of the axial end face (26a) has a polygonal profile in an axial end view.

5. The self - punching functional element according to any one of claims 1 - 3, Among them, The boundary portion has an axial end face (26a) that faces the workpiece, and the plane of the axial end face (26a) is arranged between the plane spanned by the contact surface (20) and the plane spanned by the stamping edge (22).

6. The self-stamping functional element according to claim 5, Among them, The three planes are arranged parallel to each other.

7. The self-stamping functional element according to any one of claims 1-3, Among them, The stamping edge (22) and / or the outer wall (24) of the stamping portion (18) has a circular or polygonal profile in an axial end face view.

8. The self-stamping functional element according to claim 4, Among them, The outer wall (24) and / or the inner wall (28) and / or the contact surface (20) and / or the axial end face (26a) is provided with at least one feature (32, 34) that provides anti-rotation security, wherein the at least one feature (32, 34) is at least one protrusion and / or recess.

9. The self-stamping functional element according to any one of claims 1-3, Among them, The self-stamping functional element is a nut element (10) having a hole (14) with an internal thread (16).

10. The self-stamping functional element according to any one of claims 1 to 3, Among them, The self-stamping functional element is a bolt element having a bolt portion extending from the head (12) on a side away from the stamping portion (18).

11. The self-stamping functional element according to claim 10, Among them, The bolt portion is at least partially provided with an external thread.

12. A component assembly, the component assembly comprising a self-stamping functional element according to any one of claims 1-11; and a workpiece, Among them, The workpiece is at least partially pushed into the annular space (30) and is pushed into the undercut in the region around the hole (52) punched by the stamping portion (18), so that the self-stamping functional element is connected to the workpiece in a form-fitting manner.

13. The component assembly according to claim 12, Among them, The workpiece is a sheet metal part (36).

14. The component assembly according to claim 12, Among them, A recess (48) is provided on a side of the workpiece away from the contact surface (20) in a region adjacent to the hole (52) or directly adjacent to the hole.

15. The component assembly according to claim 14, Among them, The recess (48) is an annular recess.

16. The component assembly according to claim 14, Among them, The axial extent of the stamping portion (18) is selected such that it does not protrude from the recess (48).

17. The component assembly according to any one of claims 12-16, Among them, The thickness of the workpiece in the region of the hole (52) corresponds to or is less than the axial extent of the stamping portion (18).

Images