DE102014218193A1 - Expandable connecting element for joining at least two parts to be joined - Google Patents

Abstract

To propose a connecting element for joining at least two joining parts by means of a mechanical joining method, wherein at least one joining part comprises a fiber-reinforced plastic, whereby the strength and thus the life is increased and at the same time a good automation in the manufacturing process is possible, is proposed on or in pin-shaped portion of the connecting element to arrange at least one cavity, wherein in at least one cavity a heat-expandable material is arranged.

Description

The invention relates to a connecting element for joining at least two joining parts by means of friction nails or punch rivets or semi-punched rivets or bolt sets, wherein at least one joining part thereof is formed as a fiber-reinforced plastic and wherein the connecting element as Reibnagel or punch rivet or Halbhohlstanzniet or setting bolts.

Furthermore, the invention relates to an assembled component (= body component or attachment) for a motor vehicle and a method for joining at least two joining parts by means of a connecting element.

State of the art

In the development of motor vehicles, e.g. lighter structures in the body shop increasingly important. For this purpose, a wide variety of material pairings allow a variety of body structures that make a motor vehicle lighter despite increasing demands for vehicle safety and occupant comfort. Prerequisite for this are specially adapted connection techniques for connecting the body parts consisting mostly of different materials. For example, it is known to produce bodies in mixed construction of steel, aluminum, thermoplastics, magnesium and fiber-reinforced plastics (FRP). Carbon fiber reinforced plastics (CFRP) or glass fiber reinforced plastic (GRP) are mainly used as fiber composites.

Steel body panels are commonly joined together using classical welding techniques such as resistance spot welding and MIG (metal-inert gas welding) welding. Joining technologies for the connection of different material pairings, for example of steel-containing parts with aluminum-containing parts, are based on mechanical and thermal joining methods in a known manner. For example, it is known to connect steel-containing parts with aluminum-containing parts by means of punch rivets, nails, screws and clinching with each other. These methods require, in part, the introduction of previous holes or auxiliary feet elements. Furthermore, it is known to connect steel-containing parts with aluminum-containing parts by means of additional connecting elements by means of resistance welding. Again, the introduction of holes is necessary to use the fasteners in the aluminum-containing part. FVK components are usually connected to each other by means of screws, punch rivets or by friction nailing. When Reibnageln penetrates a rotating Reibnagel through the components to be joined and generated by the friction heat occurring and the high axial pressure a cohesive connection of the joining partners.

When using such methods for connecting metal-containing parts to be joined with parts made of fiber reinforced plastic (FRP) or when connecting two FRP components, the fiber structures of the FRP component are at least partially destroyed by the introduction of holes, rivets or screws. Furthermore, multi-material joining processes, for example by the prior introduction of holes, make the automation of the manufacturing process more difficult. The use of friction nails, rivets and bolts to join FRP components also causes damage to FRP. In the FRP material itself, especially by delamination microcavities, which lead to a reduction in the strength of the compound.

In the DE 10 2009 013 200 A1 the use of an assembly of assembled components in the vehicle or body construction is described with connecting means for connecting the components, wherein a first connection of the components is provided by means of a mechanical connection technology and wherein a second connection of the components is provided by means of a cohesive joining technique.

In the US 2010/0088880 A1 and the US 2003/0167620 A1 Rivet connectors are described for connecting flat components, wherein the rivet connectors have a cavity in which an adhesive is arranged. The adhesive may exit through openings in the rivets and bond to the sheet members.

DESCRIPTION OF THE INVENTION: Problem, Solution, Advantages

The object of the present invention is to provide a connecting element for joining at least two joining parts, wherein at least one joining part has a fiber-reinforced plastic (FRP), whereby the strength and service life of the resulting components is increased compared to a use of known connecting elements, and At the same time the automation of the manufacturing process is further improved.

For this purpose, a connecting element for joining at least two joining parts by means of friction nails or punch rivets or semi-hollow punch rivets or bolt set is proposed according to the invention. A first joining part has one fiber reinforced plastic (FRP). The connecting element is embodied as a friction nail or stamped rivet or semi-hollow punch rivet or setting bolt and has a head part at a first front end, wherein a pin-shaped section of the connecting element protrudes from the head part, or the pin-shaped section adjoins the head part of the connecting element. According to the invention, at least one cavity is arranged on or in the pin-shaped section of the connecting element, wherein a material that is expandable upon heat development is arranged in at least one cavity.

The two joining parts are substantially flat, at least partially planar, formed. The first joining part is designed as a FKV component and thus has an FRP, for example carbon fiber reinforced plastic or glass fiber reinforced plastic. The second joining part may also be formed as FKV component or have metal, in particular aluminum.

The at least one cavity on or in the connecting element (Reibnagel or punch rivet or Halbhohlstanzniet or setting bolts) is open, so that the expandable material can escape during the joining. By exerting an axially directed force on the connecting element or on the head part of the connecting element and rotating the connecting element, the connecting element is driven into the two joining parts and thus pierces at least one joining part. Preferably, the connecting element is arranged such that this completely pierces the second joining part or at least deeply penetrates into this. In this process frictional heat is generated, which ensures that thermally expandable material, which is located on or within the connecting element, expands. In the FRP material caused by joining processes according to the prior art, such as the Reibnageln delaminations of the fiber composite material. The delaminations mechanically weaken the FRP material. For the purposes of the invention, however, a mechanical weakening of the FRP material is largely avoided, since the material expanded by the heat development penetrates from or away from the connecting element into the microvoids of the FRP material of the first joining part and / or the second joining part formed by delamination processes, to restore adhesion between fibers and plastic matrix. According to the invention, the expandable material is designed such that it irreversibly expands when heat is generated.

The provision of the expandable material in a cavity on or in the connecting element as well as the joining by means of friction nails or punch rivets or half-hollow punch rivets or bolting with such a connection element can be easily applied in a simple manner in a manufacturing process. The micro-cavities usually produced by delamination processes when introducing a connecting element into an FRP material are refilled by the expandable material, which considerably improves the strength of the connection and thus also the service life of the connection.

Preferably, a plurality of mutually separate cavities are arranged on or in the pin-shaped portion of the connecting element, wherein in at least one cavity a material which is expandable upon exposure to heat is arranged.

Preferably, the connecting element is designed as Reibnagel. However, other mechanical fasteners, such as in particular punch rivets, semi-punched rivets or setting bolts in the context of the invention can be modified. The friction nail is provided at the upper end with a Reibnagelkopf. A second end face of the connecting element is substantially pointed. The diameter of the pin-shaped portion is preferably smaller than the diameter or the width of the head part at any point. The diameter of the pin-shaped portion decreases at least in the lower region, that is, in the region of the second end face, and runs essentially pointed, that is, at an acute angle. The area between the two front ends may be substantially cylindrical.

The expandable material preferably comprises epoxy resin or a suitable thermoplastic material, such as e.g. a polyamide, on. Since the invention can be used in particular for body parts and resulting body parts are usually processed by means of a cathodic dip painting process (KTL process) and have to go through temperatures of up to 195 degrees Celsius, the use of epoxy resin has proven to be particularly advantageous. Particularly preferably, the expandable material can comprise blowing agent-filled hollow microspheres. The shell of the hollow microspheres may comprise or consist of polyacrylonitrile or polyacrylate. In the interior of the hollow microspheres, a readily evaporable liquid, for example isobutane, is preferably arranged. Furthermore, the expandable material is preferably designed such that the hollow microspheres do not shrink on cooling and thus the expansion is irreversible when exposed to heat. When using such particularly preferred hollow microspheres, an expansion can be achieved by forty times.

Furthermore, it is preferably provided that at least one cavity is left free and has no expandable material. This is to be understood that this at least one cavity is empty, or has air or another gas. By providing at least one empty cavity, the softened matrix material of the FVK joining part, for example of the first joining part, can penetrate into the released cavity, whereby an additional solidification is achieved. When providing a changing arrangement of empty and filled cavities in or on the pin-shaped portion of the connecting element, the attachment of the connecting element in the matrix of the FKV joining part is further increased.

The cavities are preferably designed as recesses and arranged in sections in a wall of the pin-shaped portion. The recesses are outside, that is circumferentially distributed, arranged on the pin-shaped portion of the connecting element. Outwardly, the recesses are open, so that the expandable material can escape and so softened FRP material of the joining part can enter in a particularly preferred manner in designated empty recesses. The recesses may be formed as blind holes. The recesses preferably have a flat or curved bottom. The bottom of the recesses thus preferably has a blunt and no acute angle.

Preferably, both filled with the expandable material as well as empty recesses are arranged in sections in the wall of the pin-shaped portion. In this case, the empty and filled recesses can be substantially circumferentially distributed outside provided on the pin-shaped portion. Furthermore, the recesses filled with expandable material could be arranged substantially in the lower region, that is to say in the region directed towards the second end-side end. The empty recesses are arranged in the region of the head part or between the middle and the head part of the connecting element.

It is also preferably provided that at least one cavity is formed as a cavity arranged in the interior of the pin-shaped section. In this case, at least one opening for the passage of the expandable material is arranged on expansion through a wall of the pin-shaped portion. For this purpose, the pin-shaped portion is at least partially hollow in the interior. The formed inside cavity is closed at the top and bottom and is accessible only through the openings in the wall of the pin-shaped portion. These openings through the wall may be holes, for example. The head part is preferably screwed to the pin-shaped portion to fill the expandable material in the cavity. Also, a plurality of mutually separate cavities may be provided in the interior of the pin-shaped portion. For example, two separate cavities may be provided in the interior of the pin-shaped portion, wherein a first cavity is filled with the expandable material and the second cavity is empty, or has no expandable material. Empty and filled cavities may be alternately arranged in the pin-shaped portion along the length of this portion. Furthermore, the filled cavity could be arranged in the lower region, that is to say in the region facing the second end-side end, and the empty cavity in the upper region, that is to say in the region facing the head part.

It is also preferably provided that at least one cavity is formed as a tubular cavity formed through the pin-shaped portion therethrough. The pin-shaped portion is formed solid at least in the region of the tubular cavity. The tubular cavity preferably extends along the width or diameter and extends substantially parallel to the head portion through the entire width of the pin-shaped portion. In this case, the tubular cavity has two openings at its end in the wall of the pin-shaped portion for passage of the expandable material. More preferably, a plurality of tubular cavities may be disposed through the pin-shaped portion. In this case, preferably at least two tubular cavities are oriented differently or directed in different directions. Further filled or empty tubular cavities filled with the expandable material may be alternately arranged along the length of the pin-shaped portion or filled with expandable material, tubular cavities formed at the bottom and empty tubular cavities formed at the top of the pin-shaped portion.

In a wall of the pin-shaped portion incisions are preferably arranged, whereby at least one expansion part is formed, which is expandable upon expansion of the expandable material to the outside and pushes into the first joining part. These cuts are preferably arranged such that the spreading parts are tine-like or as tine-like tabs, so-called expansion tabs are formed. The openings through the wall of the pin-shaped portion may be arranged behind the expansion part or be concealed by this. Preferably, the cuts are completely through the wall of the pin-shaped Section arranged therethrough. The expansion parts thus preferably form a kind of barbs whereby a dowel effect is created and the attachment is further increased.

According to the invention, a joined component is furthermore provided for a motor vehicle, wherein the joined component has at least two joining parts connected to one another by means of a connecting element and wherein at least one joining part consists of fiber-reinforced plastic. The connecting element is designed according to one of claims 1 to 8.

• a) Anordnen eines bei Wärmeeinwirkung expandierbaren Materials in zumindest einer Kavität des Verbindungselements, wobei die Kavität an oder in einem stiftförmigen Abschnitt des Verbindungselements angeordnet ist;
• b) Ausüben einer axialgerichteten Kraft auf das Verbindungselement;
• c) Ausüben einer Drehbewegung bzw. einer anderen Bewegung auf das Verbindungselement, derart, dass das Verbindungselement in die Fügeteile getrieben wird und so eine stoffschlüssige Verbindung mit mindestens einem Fügeteil aufgrund der erzeugten Reibwärme entsteht und dass sich das expandierbare Material aufgrund der erzeugten Reibwärme ausdehnt.

For joining at least two parts to be joined by means of the connecting element according to the invention, a method is furthermore provided according to the invention which has at least the following steps:

• a) arranging a heat-expandable material in at least one cavity of the connecting element, wherein the cavity is arranged on or in a pin-shaped portion of the connecting element;
• b) applying an axially directed force to the connecting element;
• c) exerting a rotational movement or another movement on the connecting element, such that the connecting element is driven into the joining parts and so a cohesive connection with at least one joining part due to the frictional heat generated and that the expandable material expands due to the frictional heat generated.

The abovementioned steps b) and c) can be provided successively, alternately or particularly preferably simultaneously.

Brief description of the drawings

The invention is explained below by way of example with reference to preferred embodiments.

They show schematically:

1a to 1c FIG. 2: a sectional view through a connecting element, wherein the cavities are formed as recesses in the wall of the connecting element, FIG.

2a to 2 B FIG. 2 is a sectional view through a connecting element, wherein the cavities are formed like a tube through the pin-shaped section of the connecting element, FIG.

3a to 3b 3: sectional views of a connecting element, wherein the cavities are formed as a cavity in the pin-shaped section,

4 a sectional view of a connecting element with cuts in the wall of the pin-shaped portion of the connecting element, and

5a to 5d : A schematic representation of a joint with two by a connecting element interconnected joining parts and the introduction of the connecting element.

Preferred embodiments of the invention

1a to 1c show a sectional view through a connecting element 100 , where the cavities 16 as recesses in the wall 20 of the pin-shaped section 13 of the connecting element 100 are formed.

The connecting element 100 has at its first front end 14 a headboard 12 on. At the headboard 12 includes an elongated pin-shaped portion 13 of the connecting element 100 on or stands from the headboard 12 from. In the area of the second front end 15 of the connecting element 100 has the connecting element 100 or its pin-shaped section 12 a peak 24 on. The connecting element 100 is designed as a friction nail, which with simultaneous exercise of compressive force and rotational movement (rotational movement) in the Fügeteile 10 . 11 (in the 1a to 1c not shown) can be driven in and thus by means of friction element welding the joining parts 10 . 11 can be connected to the connecting element.

In 1a are all formed as recesses cavities 16 filled and thus have an expandable material 17 on. In 1b are empty cavities 16a and filled cavities 16b circumferentially distributed and arranged in alternation. In 1c are in the upper area of the pin-shaped section 13 that is in the headboard 12 facing area, empty cavities 16a arranged. In the lower area, that is in the second end face 14 facing area, are filled cavities 16b comprising the expandable material 17 arranged.

During the friction nailing or the driving in of the connecting element 100 in the two parts to be joined 10 . 11 the expandable material expands 17 In doing so, it fills out the micro-cavities created during the friction nailing by delamination processes, whereby the strength of the connection is considerably increased.

In the 2a to 2 B are the cavities 16 tubular through the pin-shaped section 13 of the connecting element 100 arranged therethrough. The tubular cavities 16 are in the area of the wall 20 of the pen-shaped section 13 open formed, so that in the cavities 16 arranged expandable material 17 during the joining process.

In 2a are all cavities 16 as filled cavities 16b trained and thus have the expandable material 17 on. In 2 B is at least a tubular cavity 16 as empty cavity 16a formed and has no expandable material 17 on. Basically, several empty cavities could 16a be provided.

In 3a and 3b are the cavities 16 as voids in the interior of the pin-shaped section 13 arranged. So that the expandable material 17 from the cavity or the filled cavity 16b when joining can escape, are in the wall 20 of the pin-shaped section 13 perforations 19 arranged in the form of holes.

In 3a indicates the pin-shaped section 13a a single cavity arranged inside and thus a single cavity 16 on. This cavity 16 is as a filled cavity 16b trained and thus has the expandable material 17 on. In contrast, the pin-shaped section 13 of the connecting element 100 according to 3b two separate cavities and thus two separate cavities 16 on. The top, that is the headboard 14 facing cavity 16 , is doing as an empty cavity 16a educated. The lower, that is the second end face 15 of the connecting element 100 facing cavity 16 , is as a filled cavity 16b formed and has the expandable material 17 on. Both in the area of the empty cavity 16a as well as in the area of the filled cavity 16b shows the wall 20 of the pin-shaped section 13 perforations 19 on.

This in 4 shown connecting element 100 points in the wall 20 of the pin-shaped section 13 cuts 22 on. Through these cuts 22 become spreading parts 23 which through wall areas of the wall 20 of the pin-shaped section 13 are formed formed. These are each incisions 22 arranged at a point or an angle less than or equal to 90 degrees to each other. The cuts 22 are through the wall 20 of the pin-shaped section 13 completely arranged through. The pen-shaped section 13 is at least partially hollow in the interior, creating at least one cavity 16 is formed. The pen-shaped section 13 could, as well as in 3b , inside several separate cavities 16 or cavities. Thus, for example, empty cavities 16a as well as filled cavities 16b be provided.

In the 5a to 5d are examples of a joined component (eg body part or attachment) 200 as well as the joining of two parts to be joined 10 . 11 by means of a connecting element 100 according to the 1 to 4 shown in sections. This is the connecting element 100 by applying an axially directed force 18 and a simultaneous rotational movement 19 or rotational movement through the second joining part 11 completely through to the first joining part 10 driven in. This creates frictional heat, creating a cohesive connection between the connecting element 100 and a FKV joining part, for example the second joining part. During joining, the expandable material expands due to frictional heat 17 off and displaces the FRP material of a joining part 10 . 11 or fills the resulting during Reibnagelns by Delaminationsprozesse microcavities in the adherend 10 . 11 out.

In 5a is an example of the connecting element 100 in the form of a Reibnagels according to 1b shown. In 5b is an example of a connecting element 100 in the form of a Reibnagels according to 2 B shown. In 5c is an example of a connecting element 100 in the form of a Reibnagels according to 3b shown. In 5d is an example of a connecting element 100 in the form of a Reibnagels according to 4 shown.

LIST OF REFERENCE NUMBERS

100

 connecting element

200

 Joined component

10

 first joining part

11

 second joining part

12

 Head part of the connecting element

13

 pin-shaped portion of the connecting element

14

 first end face of the connecting element

15

 second end face of the connecting element

16

 cavity

16a

 empty cavity

16b

 filled cavity

17

 expandable material

18

 axially directed force

19

 rotary motion

20

 Wall of the pin-shaped section

21

 perforation

22

 incision

23

 spreading

24

 top

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009013200 A1 [0006]
• US 2010/0088880 A1 [0007]
• US 2003/0167620 A1 [0007]

Claims (10)

Connecting element ( 100 ) for joining at least two parts to be joined ( 10 . 11 ) by means of a mechanical joining process, in which heat is generated by friction, wherein at least one joining part ( 10 . 11 ) comprises a fiber-reinforced plastic, wherein the connecting element ( 100 ) is designed as a friction nail or punch rivet or semi-hollow punch rivet or setting bolt, wherein the connecting element ( 100 ) at a first end ( 14 ) a headboard ( 12 ), wherein from the headboard ( 14 ) a pin-shaped section ( 13 ) of the connecting element ( 100 ), characterized in that on or in the pin-shaped section ( 13 ) of the connecting element ( 100 ) at least one cavity ( 16 ), wherein in at least one cavity ( 16 ) a heat-expandable material ( 17 ) is arranged. Connecting element ( 100 ) according to claim 1, characterized in that at least one second end face ( 15 ) of the connecting element ( 100 ) is substantially pointed. Connecting element ( 100 ) according to one of claims 1 and 2, characterized in that the expandable material ( 17 ) thermosetting or thermoplastic material with expandable hollow microspheres or other blowing agents. Connecting element ( 100 ) according to one of the preceding claims, characterized in that at least one cavity ( 16 ) and is not an expandable material ( 17 ) having. Connecting element ( 100 ) according to one of the preceding claims, characterized in that a plurality of cavities ( 16 ) formed as recesses and sections in a wall ( 20 ) of the pin-shaped portion ( 13 ) are arranged. Connecting element ( 100 ) according to one of the preceding claims, characterized in that at least one cavity ( 16 ) as one inside the pin-shaped portion ( 13 ) arranged cavity, wherein by a wall ( 20 ) of the pin-shaped portion ( 13 ) at least one opening ( 21 ) is arranged for passage of the expandable material upon expansion. Connecting element ( 100 ) according to one of the preceding claims, characterized in that at least one cavity ( 16 ) as a tubular cavity formed by the pin-shaped portion ( 13 ) is formed therethrough. Connecting element ( 100 ) according to one of the preceding claims, characterized in that in a wall ( 20 ) of the pin-shaped section incisions ( 22 ), whereby through the cuts ( 22 ) at least one expansion part ( 23 ) is formed, which expands outward upon expansion of the expandable material and into the first or second joining part ( 10 . 11 ). Joined component ( 200 ) for a motor vehicle, the joined component ( 200 ) at least two by means of a connecting element ( 100 ) joined parts ( 10 . 11 ), wherein at least one joining part ( 10 ) comprises a fiber-reinforced plastic, characterized in that the connecting element ( 100 ) is formed according to one of the preceding claims. Method for joining at least two parts to be joined ( 10 . 11 ) by means of at least one connecting element ( 100 ), at least one adherend ( 10 ) comprises a fiber-reinforced plastic, the method comprising the following steps: a) arranging a material which can be expanded under the action of heat ( 17 ) in at least one cavity ( 16 ), wherein the cavity ( 16 ) on or in a pin-shaped section ( 13 ) of the connecting element ( 100 b) exerting an axially directed force ( 18 ) on the connecting element ( 100 ), c) applying a rotational movement ( 19 ) or other movement on the connecting element ( 100 ), such that the connecting element ( 100 ) into the parts to be joined ( 10 . 11 ) and that a cohesive connection with at least one adherend ( 10 . 11 ) arises due to the frictional heat generated, and that the expandable material ( 17 ) expands due to the frictional heat generated.

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