DE102020118262A1 - functional element - Google Patents

Abstract

The present invention relates to a self-punching functional element which is designed for punching into a workpiece, in particular into a sheet metal part. It comprises a head part forming a flange with a contact surface for contact with the workpiece and a head part, in particular from the contact surface, away from it extending punching section, which is in particular arranged coaxially to a central longitudinal axis of the functional element. At its free end, the punching section has a peripheral punching edge for punching through the workpiece and surrounds a cavity in the peripheral direction, which has an opening defined by the punching edge. An inner wall of the punched section facing the cavity has at least one slug securing elevation projecting radially inwards into the cavity, in particular the elevation having the shape of a rib running in the axial direction.

Description

The present invention relates to a self-piercing functional element which is designed for stamping into a workpiece, in particular into a sheet metal part. The element comprises a head part forming a flange and a punched section, which extends away from the head part and is in particular arranged coaxially to a central longitudinal axis of the functional element, with a peripheral punched edge.

In the field of connecting elements or functional elements, which are mechanically attached to workpieces, such as sheet metal parts, when they are produced, a distinction is made between press-in elements on the one hand and rivet elements on the other. Press-in elements are characterized in that they are at least not intentionally deformed when attached to a workpiece, but the workpiece is deformed and brought into engagement with shape features of the press-in element, whereby the press-in element is secured to the sheet metal part in a press-proof manner. In the case of rivet elements, the element is intentionally deformed when it is attached to the sheet metal part, mostly in order to form a rivet bead, whereby the sheet metal part is caught between the rivet bead and a flange part in order to achieve a connection that is safe from being pressed out.

Both press-in elements and rivet elements are also known as self-piercing elements. The term self-piercing means that the element in question punches 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 power-operated tongs. The self-piercing element is pressed against the workpiece, while this is supported on a corresponding die on the side facing away from the element. Self-punching elements are associated with cost advantages since the workpiece does not have to be pre-punched.

Functional elements of the type described above are used, among other things - but by no means only - in automobile construction. With the expansion of the areas of application of self-punching functional elements, the requirements for the safety of the corresponding process, by means of which the elements are attached to a workpiece, also increase. One of the problems is the whereabouts of the slug punched out during the fastening process. If this is not reliably dissipated, it can damage the fastening tool and/or the workpiece. In some applications, ensuring reliable slug removal is complex and therefore expensive.

With some elements of the conventional type, the slug remains in the stamping section. When the slug is punched out, it expands in it. However, it cannot be ruled out that it will come loose under heavy loads or vibrations.

There is therefore a need for self-piercing functional elements that can be reliably attached to a workpiece in a simple manner and with which the disadvantages described above can be avoided.

The present invention provides a self-piercing functional element that satisfies this need. According to the invention, it is provided that the functional element comprises a head part forming a flange with a contact surface for contact with the workpiece and a punched section extending away from the head part, in particular from the contact surface, which is in particular arranged coaxially to a central longitudinal axis of the functional element. At its free end, the punching section has a peripheral punching edge for punching through the workpiece. It circumferentially surrounds a cavity having an opening defined by the punched edge. Furthermore, an inner wall of the punched section facing the cavity has at least one slug securing elevation projecting radially inwards into the cavity. The elevation can, for example, have the form of a rib running in the axial direction.

With the slug securing elevation, a possibility is provided of simply and reliably securing a slug punched out of the workpiece in the element—more precisely in the cavity defined at least in sections by the punched section.

The element can be made of metal and can be produced, for example, by a conventional cold forging process. The slug securing elevation can be formed at the same time. In principle, however, the element can also be made (partially or entirely) from a different material, for example from a plastic.

The element is suitable for use with a wide variety of workpieces. It is preferably used on a metal sheet metal part. However, fiber-reinforced plastic or composite material can also be provided with an element according to the invention.

Further embodiments of the invention are indicated in the description, the claims and the accompanying drawings.

According to one embodiment of the self-piercing functional element, the punching section is designed as a rivet section that can be deformed to produce a form fit with the workpiece. In principle, however, the present invention can also be implemented with a press-in element.

In an axial end view, the contact surface can surround the punched section in the circumferential direction, in particular with the contact surface being designed in the shape of a ring. The stamped section and/or the head part can also be designed in the shape of a ring. Basic shapes of the contact surface, of the punched section and/or of the head part deviating from rotational symmetry are also conceivable, for example oval or polygonal basic shapes.

In order to make the connection between the workpiece and the functional element particularly reliable - especially if this comprises two layers to be connected - the contact surface and an outer wall section of the punched section, which is arranged parallel to the longitudinal axis, can be connected to one another via a transition section. The transition section is curved at least in sections and/or configured and arranged obliquely to the longitudinal axis.

This configuration is particularly advantageous for a workpiece or a combination of workpieces that comprises two or more layers and, above all, in which different materials are used, for example in the case of a two-layer workpiece in which the component facing the element is a sheet steel part and the component facing away from the element is an aluminum sheet part. The lower sheet metal part is clamped between the upper sheet metal part and an inlet radius of the comparatively hard die by the stamping and subsequent deep-drawing of the sheet metal materials. The run-in radius is the curvature of the die shape at its transition/edge to a support surface for the workpiece.

It was recognized that the lower sheet metal part is (too) severely squeezed at the inlet radius of the die if the inlet radius of the die is (too) small. Therefore, the inlet radius of the die should be large enough, taking into account the properties of the components involved. In order to avoid the formation of cavities between the layers of the workpiece and/or between the layers and the element, the transition section of the element, which according to the invention functions as a stamping and deep-drawing tool, can have a curvature and/or a bevel. The transition section can have a shape complementary to the entry radius of the die. However, it is not absolutely necessary for the transition radius and the inlet radius to have the same radii of curvature.

According to one embodiment, the contact surface, the transition section and/or the outer wall section are provided with at least one anti-rotation feature, in particular with the anti-rotation feature being an elevation or a depression. For example, the at least one anti-rotation feature is a rib or groove extending in the axial or radial direction. In a fastened state of the element, the anti-rotation feature interacts with the workpiece via a form fit, so that the element can withstand greater torques. Various anti-rotation features can be combined with one another as desired in order to achieve the protection required in a specific application against the element rotating due to torques acting on it.

The slug securing elevation can be arranged in an axial end area of the cavity that faces away from the opening of the cavity. The end region preferably comprises less than 50%, preferably less than 40%, of an axial extension of the cavity. In particular, at least one section of the slug securing elevation is further away from an end section, which delimits the cavity in the axial direction on a side facing away from the opening, than a thickness of the workpiece to be punched through. In the area of the opening of the cavity and in the areas adjoining it, the inner wall of the punched section is preferably free of elevations in order to optimize the punching process.

It can be provided that the end section has a stepped depression.

The functional element can be a bolt element which has a bolt section which extends from the head part on the side facing away from the punched section. In particular, the bolt section is provided with an external thread at least in sections. When fixed to a workpiece, such bolt elements serve, for example, as attachment points with the aid of which objects can be attached to the workpiece. The bolt element can, for example, be a centering bolt, a ground bolt, a ball bolt or the like. But it is also conceivable that the element is a blind nut.

The present invention also relates to an assembly component comprising a functional element according to one of the embodiments described above and a workpiece, in particular at least one sheet metal part, with a slug punched out by the punching section being arranged in the cavity, which slug is held in the cavity with a friction fit and/or a form fit by the slug securing elevation.

According to one embodiment of the assembly component, the slug can be held in the hollow space in a form-fitting manner by a deformed section of the slug securing elevation. In particular, the reshaping of said section takes place during the manufacture of the assembled component, that is to say when the element is fastened to the workpiece. The formed section of the elevation reliably secures the slug (possibly in addition to a friction fit) in the cavity, so that the problems described above are avoided. In particular, the formed section engages behind the slug on a side facing away from the head part.

The slug can be deformed in a region adjacent to the slug securing elevation, in particular in the radial direction. For example, it has a notch which is produced by a rib-like slug securing elevation when the slug is separated. This contributes to an improvement in frictional engagement between the element and the slug.

In order to avoid potentially disturbing contours, it can be provided that the slug and the formed section of the slug securing elevation terminate flush with one another on a side facing away from the head part. If a reshaping of the slug securing elevation is provided, material of the elevation can be pressed in sections in the axial direction into the material of the slug, so that this engages behind the slug but does not protrude appreciably beyond it in the axial direction.

The functional element of the assembly component can have a stamped section which is designed as a rivet section, with a section of the rivet section being shaped in such a way that it engages behind the workpiece on a side remote from the head part. As a result, the connection between the functional element and the workpiece is particularly reliable. However, it is also conceivable for the assembly component to comprise a press-in element and a workpiece, in particular the workpiece being deformed in order to create a form-fitting connection with the element.

The workpiece of the assembly component may comprise at least two components which are punched through by the punching section, thereby connecting them together. For example, the workpiece has two or more layers and/or comprises different materials in the area where the components are connected.

• - Bereitstellung des Werkstücks und des Funktionselements,
• - Durchstanzen des Werkstücks mittels des Stanzabschnitts des Funktionselements und Heraustrennen eines Stanzbutzens derart, dass sich dieser in dem Hohlraum des Funktionselements befindet,

wobei der Butzen derart in Eingriff mit der Butzensicherungserhebung gebracht wird, dass der Butzen von der Butzensicherungserhebung reibschlüssig und/oder formschlüssig in dem Hohlraum gehalten ist.A further aspect of the present invention relates to a method for fastening a self-piercing functional element according to at least one of the embodiments described above to a workpiece with the steps:

• - Provision of the workpiece and the functional element,
• - Punching through the workpiece using the punching section of the functional element and cutting out a punched slug in such a way that it is located in the cavity of the functional element,

wherein the slug is brought into engagement with the slug securing ridge such that the slug is frictionally and/or positively retained in the cavity by the slug securing ridge.

In particular, the slug is brought into engagement with the slug securing elevation only after the workpiece has been punched through, so that the forces occurring during the engagement do not counteract the punching through, as a result of which the process forces to be applied are minimized.

According to one embodiment of the method, the slug securing elevation is deformed at least in sections in such a way that the slug is held in a form-fitting manner in the cavity by a deformed section of the slug securing elevation, in particular such that the deformed section engages behind the slug on a side facing away from the head part.

In particular, this method creates an assembly according to one of the embodiments described above.

According to a further embodiment of the method, when the functional element is being fastened, the workpiece is supported on a die which has a die punch which is inserted into the cavity of the functional element and by means of which the slug securing elevation is formed at least in sections after the punching, in particular with the section Reshaping includes at least partially scraping the slug securing elevation from the inner wall of the stamping section.

One embodiment of the method provides that the punched section of the functional element is designed as a rivet section, which is shaped by the die in such a way that it forms the workpiece engages behind on a side facing away from the headboard.

• 1 eine Ausführungsform des erfindungsgemäßen Funktionselements,
• 2 eine Stirnansicht des Elements gemäß 1,
• 3 eine Schnittansicht des Elements gemäß 1,
• 4 eine Teilschnittansicht der bei einer Befestigung des Elements gemäß 1 an einem Werkstück beteiligten Komponenten zu Beginn des Befestigungsprozesses,
• 5 eine Schnittansicht der Komponenten gemäß 4 nach Abschluss der Befestigungsbewegung der beteiligten Komponenten,
• 5A eine Vergrößerung eines Details der 5,
• 6 eine Stirnansicht des erhaltenen Zusammenbauteils,
• 7 eine Schnittansicht des Zusammenbauteils gemäß 6 und
• 7A eine Vergrößerung eines Details der 7.

The present invention is explained below purely by way of example using advantageous embodiments with reference to the accompanying drawings. These show:

• 1 an embodiment of the functional element according to the invention,
• 2 an end view of the element according to FIG 1 ,
• 3 a sectional view of the element according to FIG 1 ,
• 4 a partial sectional view in accordance with an attachment of the element 1 components involved in a workpiece at the beginning of the fastening process,
• 5 a sectional view of the components according to FIG 4 after completion of the fastening movement of the components involved,
• 5A an enlargement of a detail of the 5 ,
• 6 an end view of the assembly component obtained,
• 7 a sectional view of the assembly according to FIG 6 and
• 7A an enlargement of a detail of the 7 .

1 shows a self-piercing element 10 with a head part 12 that is designed to be introduced into a workpiece. As a rule, the workpiece is a sheet metal part, in particular a metal sheet metal part. In principle, however, it is also possible to introduce the element 10, for example, into a workpiece made of a composite material or on a fiber-reinforced plastic component. The shape of the workpiece can be freely selected. The element is preferably made of metal, but may be formed in whole or in part from another material, for example a plastic.

As will be shown below, the element 10 in the present example serves to connect two layers of a workpiece. However, it is also conceivable that the head part 12 is provided with functional components that are used, for example, for fastening purposes. In particular, the head part 12 is provided with a bolt section which extends from a side of the head part 12 which is remote from a contact surface 14 . The bolt portion may have an external thread. Alternatively, the head part 12 can also be provided with a component of a latching connection or the like. In principle, the basic idea of the invention can be used with any self-piercing functional element.

A punched section 16, which is formed by an annular wall 18 that is closed in the circumferential direction, extends from the head part 12 or the contact surface 14. The wall 18 defines a cavity 20 at least in sections. The essentially circular head part 12 , the ring-shaped contact surface 14 and the punching section 16 are arranged coaxially to a longitudinal axis A of the element 10 . Deviating from the embodiment shown, the components mentioned can also be non-rotationally symmetrical, for example oval or polygonal.

The punching section 16 serves to punch through the non-pre-punched workpiece. It thus forms the hole required for fastening the element 10 itself, with a slug being cut out of the workpiece. In order to optimize the stamping process, the section 16 has a stamping edge 22 on its free end facing away from the head part 12 , which in turn defines an opening 24 of the cavity 10 . The punching edge 22 transitions—seen in the axial direction—curved and/or inclined surfaces into an outer wall 18a or an inner wall 18i of the wall 18 .

The dashed lines in 1 indicate aspects of element 10 that would not actually be seen in the perspective view. It can thus be seen that axial ribs 26 which are distributed uniformly in the circumferential direction are arranged on the inner wall 18i, which rise from this wall and protrude into the cavity 20 in the radial direction.

2 shows the element 10 in an axial view, whereby the ribs 26 on the inner wall 18i can be seen. Sectional planes S1, S2 are also indicated. The corresponding sectional views are in 3 shown.

The left side of the 3 shows a section through the element 10 in the plane S1 arranged so that an axial rib 26 is intersected. It can thus be seen that the rib 26 extends in the axial direction from a base section 28 which delimits the cavity 20 in the axial direction on the head part side, up to approximately 33% of the axial extent of the cavity 20 . The free end of the rib 26 is rounded or chamfered in order to be able to penetrate more easily into the slug to be punched out. The axial and radial extent of the ribs 26 can in principle be freely selected. As will become clear from the following explanations, their axial extent is at least slightly greater than the thickness of the slug or the thickness of the workpiece in the fastening area.

In order to simplify the punching process, there is an area starting from the punching edge 22 the inner wall 18i free of ribs 26 or other projections. This elevation-free area preferably comprises more than 20%, more than 30%, more than 50% or more than 60% of the axial extension of the cavity 20. In particular, the axial extension of the elevation-free area 30 is at least slightly larger than the thickness of the slug or of the workpiece, so that the cutting out of the slug is not hindered by elevations. The axial extent of the area 30 without elevation is preferably more than 120% of the thickness of the slug or the workpiece.

The right side of the 3 shows a section that does not go through a rib 26. However, it can be seen from both sections that the outer wall 18a does not merge directly into the contact surface 14 . A transition section 32 is provided between them, which is curved in the present example, the radius of curvature being essentially constant. In addition, the geometry of the transition section 32 does not change in the circumferential direction. However, it is entirely conceivable that the transition section 32—alternatively or additionally—is configured at least in sections obliquely to the longitudinal axis A and/or its geometry varies in the circumferential direction and/or in the axial direction. The geometry of the peripheral section 32 can be completely adapted to the respective requirements. A variation in the circumferential direction can, for example, lead to an improvement in the anti-twist protection of the element 10 .

Basically, i. H. Irrespective of other aspects of the respective embodiment, the contact surface 14 and/or the outer wall 18a can be provided with elevations and/or depressions (e.g. ribs or grooves) which act as anti-twist features. For example, the outer wall 18a can have ribs running in the axial direction. Additionally or alternatively, the contact surface 14 can be provided with radial ribs.

4 shows the element 10 as it is arranged in a setting head 34 of a setting device. By means of the setting head 34, the element 10 is to be introduced into a non-pre-punched workpiece 36, which in the present exemplary embodiment has two layers 36a and 36b. The setting device also includes a die 38 which is arranged on the side of the workpiece 36 opposite the setting head 34 . During the fastening process, the workpiece 36 is supported on a bearing surface 38a of the die 38 and the setting head 34 presses the element 10 against the workpiece 36. A separating edge 40 of a die punch 42 of the die 38 and the punching edge 22 of the element 10 act together and separate a slug 43 (see 5 ) out of the workpiece 36.

The outer radius of the ram 42 is slightly smaller than the inner diameter of the area 30 without elevation, so that the ram 42 can penetrate into the cavity 20, the slug 43 that has been severed being pushed into its interior.

After the slug 43 has been separated, the wall 18 is bent radially outwards by a U-shaped curved section 44 of the die 38 as the movement of the setting head 34 continues. As a result of this reshaping, the reshaped section of the punched section 16 engages behind the workpiece 36. The punched section 16 thus also has the function of a rivet section, which is why the element 10 can also be referred to as a self-piercing rivet element.

When the workpiece 36 is punched through, the lower workpiece layer 36b is clamped between the upper workpiece layer 36a and an inlet radius 39 of the die 38 . If the radius 39 is too small, the sheet 36b will be overstressed in the stamping process. It is therefore to be suitably adjusted taking into account the properties of the layers 36a, 36b.

The condition described above is in 5 shown. The contact surface 14 rests against the layer 36a. It can also be seen that the design of the transition section 32 has resulted in good contact between the hole edge sections of the workpiece 36 bent downwards and the element 10 . The transition section 32 has a somewhat larger radius of curvature than the inlet radius 39 in order to take account of the geometric relationships and the properties (eg material properties, thickness) of the layers 36a, 36b.

When inserting the element 10 - as described above - the slug 43 is pushed into the cavity. As soon as the slug 43 enters the area of the cavity 20 which is provided with the axial ribs 26, these dig into the outside of the slug 43. Since the axial ribs 26 are longer in the axial direction than the thickness of the slug 43, the free ends of the ribs 26 at a certain point in time from the side of the slug 43 facing the die punch 42 .

They then come into contact with the plunger 42, the outer radius of which is only slightly smaller than the inner radius of the cavity 20. Consequently, the ribs 26 are scraped from the inner wall 18i and pressed into the layer 36b of the workpiece 36 by the action of the punch 42, as well the 5A It is easy to see that an enlargement of the part of the diagram marked with a dashed circle 5 is. This creates an undercut H, which reliably secures the slug 43 in the cavity 20 .

This process continues until the jig is closed. With a suitable configuration of the plunger 42 the slug then strikes the base section 28 . In the present example, the bottom section 28 comprises a slightly conical section 28k and a central cylindrical depression 28z.

The assembly component Z obtained is in the 6 , 7 and 7A (Partial enlargement of 7 ) shown. 6 shows an axial view from below so that the undercuts H pressed into the layer 36b of the slug 43 can be seen, which were formed by the scraped portions of the ribs 26. 7 shows sections through the assembly component Z along the cutting planes S1a, S2a (see 6 ).

Deviating from the embodiment of the invention described above by way of example, it is also possible to dispense with a reshaping of the axial ribs 26 . The slug 43 is then held in the cavity only by friction. The frictional connection between the inner wall 18i and the radial outside of the slug 43 is reinforced by the interaction of the ribs 26 with the slug 43 .

Reference List

10

functional element

12

headboard

14

contact surface

16

punching section

18

wall

18a

outer wall

18i

inner wall

20

cavity

22

punching edge

24

opening

26

axial rib

28

bottom section

28k

conical section

28z

cylindrical depression

30

survey-free area

32

transition section

34

setting head

36

workpiece

36a, 36b

workpiece position

38

die

38a

bearing surface

39

inlet radius

40

separation edge

42

die punch

43

hickeys

44

curved die section

A

longitudinal axis

S1, S2, S1a, S2a

cutting plane

H

undercut

Z

assembly part

Claims (19)

Self-punching functional element, which is designed for punching into a workpiece (36), in particular into a sheet metal part, comprising - A head part (12) forming a flange with a contact surface (14) for contact with the workpiece and - a punching section (16) extending away from the head part, in particular from the contact surface, which is arranged in particular coaxially to a central longitudinal axis (A) of the functional element, the punching section having a peripheral punching edge (22) at its free end for punching through the workpiece and circumferentially surrounding a cavity (20) having an opening (24) defined by the punching edge, and an inner wall (18i) of the punched section facing the cavity having at least one slug securing elevation (26) projecting radially inwards into the cavity, in particular the elevation having the form of a rib running in the axial direction. Self-piercing functional element claim 1 , wherein the stamping section is configured as a rivet section that can be deformed to produce a form fit with the workpiece. Self-piercing functional element claim 1 or 2 , wherein the contact surface surrounds the punching section in the circumferential direction in an axial end view, in particular wherein the contact surface is configured annularly. Self-piercing functional element claim 1 , 2 or 3 , wherein the contact surface and an outer wall section (18a) of the punched section, which is arranged parallel to the longitudinal axis, are connected to one another via a transition section (32), the transition section being curved at least in sections and/or being designed and arranged at an angle to the longitudinal axis. Self-punching functional element according to one of the preceding claims, wherein the contact surface, the transition section and/or the outer wall section is provided with at least one anti-rotation feature, in particular wherein the anti-rotation feature comprises an elevation or a depression. Self-punching functional element according to one of the preceding claims, wherein the slug securing elevation is arranged in an axial end region of the cavity which faces away from the opening of the cavity, in particular wherein the end region comprises less than 50%, preferably less than 40%, of an axial extension of the cavity. Self-piercing functional element according to one of the preceding claims, in which the cavity is delimited in the axial direction on a side facing away from the opening by an end section (28) which has a stepped depression (28z). Self-punching functional element according to one of the preceding claims, wherein the functional element is a bolt element which has a bolt section extending from the head part on the side facing away from the punching section, in particular the bolt section being provided with an external thread at least in sections. Assembly component comprising a functional element according to one of the preceding claims and a workpiece, in particular at least one sheet metal part, wherein a slug (43) punched out by the punching section is arranged in the cavity, which is held in the cavity by the slug securing elevation with a friction fit and/or a form fit. assembly component claim 9 , wherein the slug is held positively in the cavity by a formed section (H) of the slug securing elevation, in particular wherein the formed section engages behind the slug on a side facing away from the head part. assembly component claim 9 or 10 , wherein the slug is deformed in a region adjacent to the slug securing elevation, in particular in the radial direction. assembly component claim 9 , 10 or 11 , wherein the slug and the formed section of the slug securing elevation terminate flush with one another on a side facing away from the head part. Assembly according to at least one of claims 9 until 12 , wherein one of the punching section is designed as a rivet section and a section of the rivet section is deformed in such a way that it engages behind the workpiece on a side facing away from the head part. Assembly according to at least one of claims 9 until 13 , wherein the workpiece comprises at least two components (36a, 36b), in particular at least two layers, which are punched through by the punching section. Method for fastening a self-piercing functional element according to at least one of Claims 1 until 8th on a workpiece with the steps: - providing the workpiece and the functional element, - punching through the workpiece using the punching section of the functional element and cutting out a punched slug in such a way that it is located in the cavity of the functional element, the slug being brought into engagement with the slug securing elevation in this way is that the slug is held by the slug securing elevation in a frictional and/or positive manner in the cavity. procedure after claim 15 wherein the slug is brought into engagement with the slug locking boss after punching through the workpiece. procedure after claim 15 or 16 wherein the slug securing elevation is formed at least in sections such that the slug is held in a form-fitting manner in the cavity by a formed section of the slug securing elevation, in particular the formed section engages behind the slug on a side facing away from the head part. procedure according to Claim 17 , wherein the workpiece is supported during the attachment of the functional element on a die (38) having a die stamp (42) which is inserted into the cavity of the functional element and through which the slug securing survey after Punching is at least partially formed, in particular wherein the sectional forming includes an at least partial scraping of the slug securing survey. Method according to at least one of Claims 15 until 18 , wherein the punched section of the functional element is designed as a rivet section, which is formed by the die in such a way that it engages behind the workpiece on a side facing away from the head part.

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