Method for joining at least two parts to be joined which are arranged so as to overlap at least in a joining zone using a joining element

#This application is the U.S. National Stage of International Application No. PCT/EP2014/003182, filed Nov. 27, 2014, which designated the United States and has been published as International Publication No. WO 2015/106780 and which claims the priority of German Patent Application, Serial No. 10 2014 000 624.7, filed Jan. 18, 2014, pursuant to 35 U.S.C. 119(a)-(d).

#The invention relates to a method for joining at least two parts to be joined that are arranged so as to overlap at least in a joining zone using a joining element according to the preamble of claim 1.

#From DE 103 29 447 A1 a joining method for joining parts that are to be joined and are arranged so as to overlap each other is known which uses a joining element having a shaft region that is free of undercuts. In this disclosed joining method material of a first joining part is urged during the joining process through a punch recess of the second joining part, which recess is generated during the joining method, wherein an undesired punch piece is generated. After urging material of the first joining part through the generated punch opening of the second joining part the material of the first joining part is compressed relative to the second joining part so that a form fit is generated is between the first and second joining part. A disadvantage of this method is that an undesired slug is generated that has to be reliably removed from the joining site. In addition uncoated border regions are generated when urging the first material through the just generated punch opening in the second joining part, which may lead to undesired corrosion.

#In the following the invention is explained in more detail by way of the drawings.

#It is shown in:

#FIG. 1: a cross section through a joining part arrangement, which is to be joined with the method according to the invention;

#FIG. 1 shows an exemplary joining part arrangement, which is suitable for the joining method according to the invention. The joining part arrangement has a first joining part 1, a second joining part 2 and optionally a third joining part 3. The joining parts 1, 2, 3 for example form a first joining flange 4 and a second joining flange 5. In the region of the joining flanges 4 and 5, joining elements are inserted with the joining method according to the invention for example in joining directions F. the joining directions F are hereby preferably perpendicular to the joining flanges 4, 5. In the shown example according to FIG. 1, the second and the third joining parts 2, 3 are for example made of a metal material, wherein the second and the third joining part 2, 3 in the region of the joining flanges 4, 5 are connected with each other by means of spot welding. With the method according to the invention the first joining part 1 is to be connected in the region of the joining flanges 4, 5 with the already joined second and third joining part 2, 3. The first joining part 1 can hereby also be made of a steel material or a different metal material for example aluminum or plastic.

#In the following the method according to the invention is exemplary explained by way of FIG. 2, wherein FIG. 2 shows a joining flange 4, 5 into which a joining element 6 is inserted. The joining element 6 was pressed into the joining flange 4, 5 by means of a punch 7 along the joining direction F. During the pressing in of the joining element 6 along the joining direction F the joining element 6 first comes into contact with the first joining part 1. Further movement of the punch 7 causes the first joining part 1 to be punched through so that a slug 8 is generated. The slug 8 together with a terminal free end 9 of the joining element 6 is pressed onto the second joining part 2 in joining direction F, wherein—importantly—the second joining part 2 is not completely punched through but is only partially deformed in the joining direction F. As a result the slug 8 is embedded between the joining element 6, in particular the free end 9, and the non-punched through remainder of the second joining part 2. When a third joining part 3 is involved in the formation of the joining flange 4, 5, the third joining part is locally deformed optionally in a recess region 10 of the die 11 by urging in the joining element 6 in the joining direction F. Surprisingly, urging in the joining element 6 in joining direction F results in radial forces R that are sufficient to interact with an outer surface 12 of a shaft 13 of the joining element 6. Due to these radial forces friction forces R are generated that act in opposition to pulling the joining element 6 out of the joining parts 1, 2 against the joining direction F. These friction forces are sufficient to achieve a sufficient removal force at which the joining parts would be released from each other. Advantageously a down holder 14 can be arranged which surrounds the die 7, wherein of course after insertion of the joining element 6 into the joining flange 4, 5 the die 7 as well as the down holder 14 and also the die 11 are removed again. In case of a three-layered construction of the joining flange 4, 5 as shown in FIG. 2 it may be advantageous to connect the joining parts 2 and 3 to each other already prior to the insertion of the joining element 6. For example spot welding may be used for this purpose, which is schematically indicated by a spot welding lens 15. The down holder 14 and the die 11 each have contact surfaces 20 or 21 which are in contact with the joining flanges 4, 5 during insertion of the joining element 6 in the region of a joining zone 22. Via these contact surfaces 20, 21 heat may be introduced into the joining zone if desired. For this purpose it may be advantages to heat the down holder 14 and the die 11 in the region of the contact surfaces 20, 21 by means of heating devices (not shown).

#As a result the joining element 6 sits after performance of the joining method according to the invention undercut-free and at least viewed in joining direction F in the absence of a form fit with its shaft 13 in the joining parts 1, 2.