DE102014204778A1 - Method for joining a steel part with a fiber-reinforced plastic part by means of a connecting element - Google Patents

Abstract

In order to further improve a joining method for joining two joining parts, wherein a first joining part comprises steel and a second joining part has a fiber-reinforced plastic, the fiber-reinforced plastic material of the second joining part is destroyed as little as possible during the joining of the two joining parts and the joining process becomes suitable It can be used in an automated manufacturing process, it is proposed to use a connecting element with at least two arms and to heat it before welding the connecting element with the metallic joining part.

Description

The invention relates to a method for joining a steel-containing joining part with a fiber-reinforced plastic-containing joining part by means of a connecting element.

Furthermore, the invention relates to a body part for a motor vehicle and a connecting element for joining a steel-bearing joining part with a fiber-reinforced plastic-containing joining part.

State of the art

In the development of motor vehicles lighter structures in the body shop are becoming 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. This requires specially adapted connection techniques for connecting the body parts made of different materials. For example, it is known to produce bodies in mixed construction of steel, aluminum, thermoplastics, magnesium and fiber composites. As fiber composites find fiber-plastic composite (FRP), or fiber reinforced plastic, application. For example, in this regard carbon fiber reinforced plastic (CFRP), or carbon, to call.

Steel body panels are commonly joined together using standard welding techniques such as resistance spot welding and MIG welding. Joining technologies for the connection of different material pairings, for example of steel-containing parts with aluminum-containing parts are based on known mechanical and thermal joining methods. 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 procedures require, in part, the introduction of previous drilling. 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.

When using such methods for joining steel-containing joining parts with FVK-containing joining parts, the fiber structures of the FVK-containing joining part are at least partially destroyed by the introduction of holes, rivets or screws. Furthermore, multi-stage joining processes, for example due to the previous introduction of holes, make the automation of the manufacturing process more difficult.

In the DE 100 60 390 A1 a punch riveting method is described. In this case, a punch rivet is driven through a first material by means of a punch and connected to a second, resting on a die material. After driving the punch rivet through the first material, the die-side material can be selectively heated.

In the DE 423 7 361 A1 For example, a connection auxiliary part for the resistance-electric welding of aluminum sheet to steel will be described. It is proposed that the shaft end of the connecting auxiliary part is formed as a cutting edge for punching the own passage opening.

The DE 10 2004 025 492 A1 describes a method for joining two joining parts, for example a steel sheet with a light metal sheet or a plastic component, by means of mechanical driving and welding of a joining element. The joining element is designed for this purpose as a rivet or bolt with a cutting edge.

DESCRIPTION OF THE INVENTION: Problem, Solution, Advantages

The object of the present invention is to further improve a method for joining a steel-containing joining part with a fiber-reinforced plastic-containing joining part in such a way that the fiber structure is not or only slightly destroyed and the automation of the manufacturing process is further improved.

Furthermore, it is an object of the invention to propose a body part for a motor vehicle, wherein the body part has at least one steel-containing joining part and a fiber-reinforced plastic-containing joining part and the fiber-reinforced plastic joining part would not or only slightly destroyed when joining the two parts.

It is another object of the invention to provide a connecting element for joining at least two joining parts, wherein the first joining part comprises steel and the second joining part has a fiber-reinforced plastic to further improve such that the fiber-reinforced plastic-containing joining part by the connecting element when connecting the two joining parts only slightly destroyed.

• a) Anordnen der beiden Fügeteile aneinander. Dabei werden die beiden Fügeteile derart aneinander angeordnet, dass eine erste Seitenfläche des ersten Fügeteils zumindest bereichsweise in direktem Kontakt mit einer ersten Seitenfläche des zweiten Fügeteils steht oder dass die beiden Fügeteile über ein zwischen den beiden Fügeteilen angeordnetes Klebemittel miteinander verbunden sind;
• b) Aufsetzen des Verbindungselements auf eine zweite Seitenfläche des zweiten Fügeteils;
• c) Wärmen des Fügeelementes;
• d) Ausüben einer Kraft auf das Verbindungselement bis mindestens zwei Ärmchen des Verbindungselements das zweite Fügeteil durchdrungen haben und in Kontakt mit der ersten Seitenfläche des ersten Fügeteils stehen;
• e) Verschweißen des Verbindungselements mit dem ersten Fügeteil.

For this purpose, a method for joining at least two joining parts by means of at least one connecting element is proposed according to the invention. A first joining part has steel or is made of steel. A second adherend comprises a fiber reinforced plastic, such as a carbon fiber reinforced plastic. The method according to the invention has the following steps, wherein no compelling sequence of the steps is specified by these method steps:

• a) arranging the two joining parts together. In this case, the two joining parts are arranged in such a way that a first side surface of the first joining part is at least partially in direct contact with a first side surface of the second joining part or that the two joining parts are connected to one another via an adhesive arranged between the two joining parts;
• b) placing the connecting element on a second side surface of the second joining part;
• c) heating the joining element;
• d) exerting a force on the connecting element until at least two arms of the connecting element have penetrated the second joining part and are in contact with the first side surface of the first joining part;
• e) welding the connecting element with the first joining part.

By joining the two joining parts, a firm connection between the two parts to be joined, for example, a force and / or positive connection is made. The first joining part has steel or is made of steel. For example, the first joining part could be formed as a steel sheet. The second joining part has a fiber-reinforced plastic. Preferably, the second joining part consists of a fiber-plastic composite (FKV). A fiber-reinforced plastic is understood as meaning a material consisting of reinforcing fibers and a plastic matrix. The matrix surrounds the fibers, which are bonded to the matrix by adhesive or cohesive forces. As a result, the FKV receives a direction-dependent elasticity behavior. The first joining part preferably has a carbon fiber-reinforced plastic (CFRP), or carbon, on.

The two joining parts can have any suitable shape. Preferably, the first joining part and / or the second joining part is at least partially formed as a flat material, for example as a sheet metal. For example, the joining parts may represent parts of a vehicle body, for example a side part or a roof.

The connecting element has a suitable material for welding. Furthermore, the connecting element according to the invention has at least two arms. The two arms of the connecting element may protrude from a head of the connecting element, or a side surface of the head of the connecting element. The arms are essentially elongated. Under an elongated training is to be understood that the arms have a greater length than maximum width or maximum diameter. The front ends of the arms are designed for connection to the metallic material of the first joining part. Preferably, the front ends of the arms are formed as attachment surfaces. Due to the elongated design of the arms penetrate the arms while exerting a force on the previously heated connecting element, the fiber material of the second joining without destroying it significantly. After the arms of the connecting element have penetrated the second joining part, they are in contact with the metallic material of the first joining part or the first side face of the first joining part with their front ends, or the connecting surfaces. After welding of the connecting element with the first joining part, a welded connection is formed in the region of the connecting surface, or in the region of the contact point between the connecting surface and the first side surface of the first joining part.

For heating the connecting element in step c), a heat source may be provided. Furthermore, the connecting element can be heated inductively in step c). The welding of the connecting element to the first joining part in step e) can be carried out by means of a suitable welding method, for example by means of resistance welding. Furthermore, the connecting element can be welded to the first joining part by inductive heating.

Due to the special design of the connecting element, or the arms of the connecting element, no pre-drilling, in particular no pre-drilling by the fiber-reinforced plastic-containing second joining part, is necessary for the method according to the invention for joining the first joining part to the second joining part. Thus, due to the special design of the connecting element or the arms of the connecting element, the fiber material of the second joining part is only slightly or not destroyed on the one hand. Furthermore, the manufacturing process is easier and less expensive to automate.

Furthermore, it is preferably provided that in step d) a force is exerted on the connecting element, such that thus the Arms of the connecting element can easily penetrate the second joining part without further destroying the fiber material of the second joining part.

The order of the process steps essential to the invention can vary at least partially. For example, the heating of the invention element in step c) can also be carried out before placing the connecting element on the second joining part in step b). Preferably, the connecting element is heated in step c) before and / or during the application of the force in step d).

Furthermore, it is preferably provided that the connecting element is welded in step e) by means of resistance welding with the first joining part. For this purpose, to apply an electrical voltage or welding voltage, a first electrode of a welding device is connected to the first joining part and a second electrode of the welding device is connected to the connecting element. Preferably, the second electrode of the welding device is applied to the head of the connecting element. After applying the electrical voltage, the welding current flows through the head of the connecting element through the arms of the connecting element and the first joining part. Thus, between the connection surface of the arms and the first side surface of the first joining part is formed a welded joint.

Furthermore, in step c), the connecting element is preferably heated prior to the application of the voltage for resistance welding. Thus, the heating of the connecting element in step c) is a separate process step. This is preferably not to be understood as meaning heating by the welding current during welding of the connecting element to the first joining part. The connecting element is thus heated to a predetermined temperature prior to the beginning of the welding.

Furthermore, it is preferably provided that the force in step d) is exerted on the connecting element by means of a welding device. For example, the force can be exerted on the connecting element by means of welding tongs. Thus, preferably, no separate pressure means, or no separate pressure device, for exerting the force in step d) on the connecting element necessary. The welding device to be used in step e), for example welding tongs, can thus also be provided as a pressure device for exerting the force on the connecting element and for pressing in the connecting element or the arms of the connecting element into the second joining part.

According to the invention, a body part is further proposed for a motor vehicle, wherein the body part has at least two by means of at least one connecting element interconnected joining parts. A first joining part has steel or is made of steel. A second joining part has a fiber-reinforced plastic. According to the invention, the two joining parts of the body part are connected to one another by means of a method described above.

Furthermore, according to the invention, a connecting element for connecting, or joining, at least two joining parts is provided. A first joining part has steel, or consists of steel. A second adherend comprises a fiber reinforced plastic, such as a carbon fiber reinforced plastic. The connecting element has a head and at least two arms protruding from the head.

Preferably, the connecting element is integrally formed. For example, the connecting element can be produced in one piece from a semi-finished sheet metal in a simple manner by means of a stamping-forming process.

The head of the connecting element forms the upper part of the connecting element. The head is preferably flat. The protruding from the head arms of the connecting element are elongated. By this is meant that the arms of the fastener have a greater length than maximum width or maximum diameter. Preferably, both arms essentially have an identical length. The arms of the connecting element are also preferably substantially perpendicular from a side surface of the preferably flat-shaped head of the connecting element. Thus, the arms of the connecting element preferably extend vertically directed from a side surface of the head of the connecting element. Preferably, the transition between the head and the respective arms of the connecting element is arranged at a distance from the outer edge of the head of the connecting element.

Furthermore, it is preferably provided that the arms at their front ends have attachment surfaces for connection to the second joining part. The attachment area of a sleeve preferably corresponds to 20% to 100%, more preferably 30% to 90%, and most preferably 40% to 80%, of the cross-sectional area of the sleeve in the widest range. Furthermore, it is preferably provided that the connection surface is formed flat and the arms thus in the region of the front side Ends have no tip and no cutting edge.

Preferably, the connecting element has at least three arms. By providing more than two arms, for example, three arms, tilting of the connecting element after placing the connecting element on the second joining part before exerting a force on the connecting element can be avoided. The preferred connecting element with more than two arms thus provides better stability, or safer support on the surface of the second joining part.

Short descriptions of the drawings

The invention is explained below by way of example with reference to preferred embodiments. They show schematically:

1 a perspective view of two parts to be joined and a connecting element for connecting the two joining parts, and

2a to b a method for joining two parts to be joined by means of a connecting element.

Preferred embodiments of the invention

1 shows a perspective view of two adjoining parts to be joined 10 . 11 , The first joining part 10 has a metallic material. The second joining part 11 has a fiber reinforced plastic. The two parts to be joined 10 . 11 are parts of a body part 100 , It is in 1 only a section shown.

To connect the two parts to be joined 10 . 11 is a connecting element 12 intended. The connecting element 12 is integrally formed from a suitable material for welding, namely steel. The connecting element 12 has a substantially flat plate-shaped head 13 with a top and a bottom on. From the bottom extending substantially perpendicular to the underside of the head 13 three little arms 13a . 13b . 13c , The little arms 13a . 13b . 13c are elongated with a polygonal cross-section. The length 27 the little one 13a . 13b . 13c corresponds approximately to the thickness of the second joining part 11 , The width 26 the little one 13a . 13b . 13c is over most of the length 27 the little one 13a . 13b . 13c constant. Only in the frontal end of the arms 13a . 13b . 13c are the arms 13a . 13b . 13c bevelled and have a slightly smaller width 26 on. The front ends of the arms 13a . 13b . 13c form the connection surface 23 for connection to the metallic material of the first part to be joined 10 ,

In the 2a and 2 B are the individual process steps for joining a first joining part 10 with a second joining part 11 shown. Both show 2a and also 2 B each several steps.

As in 2a shown are the two parts to be joined 10 . 11 arranged in such a way to each other that this one between the two parts to be joined 10 . 11 arranged adhesive 18 connected to each other. Thus, the respective first side surfaces 14 . 16 the two parts to be joined 10 . 11 over the adhesive 18 glued together.

After arranging the two parts to be joined 10 . 11 together, becomes the connecting element 12 on the second side surface 17 of the second joining part 11 put on and the connecting element 12 by means of a heat source 26 heated. After placing the connecting element 12 on the second side surface 17 of the second joining part 11 lies the connecting element 12 with the connection surfaces 23 the little one 13a . 13b . 13c on the second side surface 17 of the second joining part 11 on.

In 2 B this is the second part of the joining 11 indented connector 12 shown. This was done by the welding device 20 namely, a welding gun, a force 19 on the connecting element 12 exercised until the arms 13a . 13b . 13c the second joining part 11 have penetrated. The connecting element 12 stands with the connection surfaces 23 the little one 13a . 13b . 13c in contact with the first side surface 14 of the first part to be joined 10 ,

Due to the special, especially elongated design of the arms 13a . 13b . 13c as well as the heated before impressions connecting element 12 becomes the fiber-reinforced plastic of the second joining part 11 not significantly damaged.

After pressing in the connecting element 12 lies the connecting element 12 with his head 13 , or the bottom of the head 13 , on the second side surface 17 of the second joining part 11 on. Subsequently, by means of resistance welding, a welded joint between the connecting element 12 and the first joining part 10 produced. This is a tension 25 to the two welding electrodes 21 . 22 created. By the flow of current through the connecting element 12 and the metallic first joining part 10 becomes a welded joint in the contact area between the bonding surfaces 23 the sleeve13a, 13b . 13c and the first side surface 14 of the first part to be joined 10 produced.

Both for pressing in the connecting element 12 in the second joining part 11 and also for welding, the welding device 20 used. Thus, no separate devices are necessary for these two process steps. The power 19 for pressing in the connecting element 12 in the second joining part 11 is exercised with the welding tongs. For this purpose, the first electrode of the welding gun is on the underside of the composite, or on the second side surface 15 of the first part to be joined 10 placed. Opposite is the second electrode 22 the welding device 20 on the top of the head 13 of the connecting element 12 placed. The two electrodes 21 . 22 become the exercise of power 19 on the connecting element 12 pressed together.

LIST OF REFERENCE NUMBERS

100

 body part

10

 first joining part

11

 second joining part

12

 connecting element

13

 Head of the connecting element

13a, 13b, 13c

 Arm of the connector

14

 first side surface of the first joining part

15

 second side surface of the first joining part

16

 first side surface of the second joining part

17

 second side surface of the second joining part

18

 adhesive

19

 force

20

 welder

21

 first electrode

22

 second electrode

23

 bonding surface

24

 heat source

25

 voltage source

26

 Width of the arms

27

 Length of the arms

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 10060390 A1 [0006]
• DE 4237361 A1 [0007]
• DE 102004025492 A1 [0008]

Claims (9)

Method for joining at least two parts to be joined ( 10 . 11 ) by means of at least one connecting element ( 12 ), wherein a first joining part ( 10 ) Steel and wherein a second joining part ( 11 ) comprises a fiber-reinforced plastic, the method comprising the following steps: a) arranging the two parts to be joined ( 10 . 11 ) to each other, such that these with their two first side surfaces ( 14 . 16 ) are at least partially in direct contact with each other or via one between the two parts to be joined ( 10 . 11 ) arranged adhesive ( 18 ) are connected to each other, b) placing the connecting element ( 12 ) on a second side surface ( 17 ) of the second joining part ( 11 ), c) heating the connecting element ( 12 d) exerting a force ( 19 ) on the connecting element ( 12 ) to at least two arms ( 13a . 13b ) of the connecting element ( 12 ) the second joining part ( 11 ) and in contact with the first side surface ( 14 ) of the first part to be joined ( 10 ), e) welding the connecting element ( 12 ) with the first joining part ( 10 ). Method according to claim 1, characterized in that the connecting element ( 12 ) in step c) before and / or while exerting the force ( 19 ) is heated in step d). Procedure ( 100 ) according to claim 1 or 2, characterized in that in step e) the connecting element ( 12 ) by means of resistance welding with the first joining part ( 10 ) is welded, wherein for applying an electrical voltage, a first electrode ( 21 ) a welding device ( 20 ) with the first joining part ( 10 ) and a second electrode ( 22 ) of the welding device ( 20 ) with the connecting element ( 12 ) is connected Procedure ( 100 ) according to claim 3, characterized in that the connecting element ( 12 ) is heated in step c) prior to application of the voltage for welding in step e). Procedure ( 100 ) according to one of the preceding claims, characterized in that the force ( 19 ) in step d) by means of a welding device ( 20 ) on the connecting element ( 12 ) is exercised Body part ( 100 ) for a motor vehicle, wherein the body part ( 100 ) at least two by means of at least one connecting element ( 12 ) joined parts ( 10 . 11 ), wherein a first joining part ( 10 ) Steel and wherein a second joining part ( 11 ) has a fiber-reinforced plastic, characterized in that the two joining parts ( 10 . 11 ) were joined together by means of a method according to one of the preceding claims. Connecting element ( 12 ) for connecting at least two parts to be joined ( 10 . 11 ), wherein a first joining part ( 10 ) Steel and wherein a second joining part ( 11 ) comprises a fiber-reinforced plastic, characterized in that the connecting element ( 12 ) a head ( 13 ) and at least two from the head ( 13 ) protruding arms ( 13a . 13b ) having. Connecting element ( 12 ) according to claim 7, characterized in that the connecting element ( 12 ) at least three arms ( 13a . 13b . 13c ) having. Connecting element ( 12 ) according to claim 7 or 8, characterized in that the arms ( 13a . 13b ) at the front ends of a connection surface ( 23 ) for connection to the second joining part ( 11 ) exhibit.

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