Method for creating a connection between a functional element and a thin sheet metal as well as a connection structure

Abstract

Method for producing a connection between a functional element (1) having a head section (2) and a cutting edge (3) and a thin sheet (10) with a thickness (S), wherein: - the head section (2) of the functional element (1) is formed with a cutting edge foot (4) having a foot length (F) and a predetermined foot diameter (E), - the cutting edge foot (4) is pressed into a recess (31) of a die (30) by means of a tool (20) acting on the functional element (1) with an axial feed movement under its radial expansion to form an undercut (5) in the thin sheet (10), without penetrating the thin sheet (10), - the recess (31) of the die (30) is formed with a die depth (C) and a die diameter (D), and - a bottom surface (31).2) the recess (31) of the die (30) is formed with a dome-shaped elevation (32), characterized in that: - the head section (2) is formed on one side with a bolt section (6) and on the opposite side with the cutting foot (4), wherein, in order to form a collar (2.2) surrounding the cutting foot (4) and the bolt section (6), the cutting foot (4) and the bolt section (6) are formed with a smaller diameter than the head section (2); - in order to form the cutting foot (4), the end face (2.1) of the head section (2) opposite the bolt section (6) is formed with a convex recess (4.1), wherein at a transition of the recess (4.1) to a cylindrical surface (4.2) the cutting edge (3) is formed at the cutting foot (4), and a circumferential gap (7) is formed around the cutting foot (4) in the transition to the head section (2), by selecting the foot length (F) of the cutting foot (4) as well as the die diameter (D) and the die depth (C) of the die (30) depending on the given thickness (S) of the thin sheet (10) according to the following specifications: - F ≤ 2.2xS - D ≤ 2xS+E - C ≤ S.

Description

[0001] The invention relates to a method for creating a connection between a functional element and a plate-shaped component according to the preamble of claim 1. Furthermore, the invention relates to a device for carrying out the method according to the invention.

[0002] A generic method for producing a connection between a functional element designed as a self-piercing rivet and a single sheet metal part is known from DE 43 33 052 A1. Two or more metal sheets can also be joined together with such a self-piercing rivet. This functional element consists of a rivet head to which a rivet shank designed as a hollow cylinder is attached. The end face of the shank facing away from the rivet head is conical, with its conical flanks being slightly curved, thus creating a cutting edge. This cutting edge allows the rivet, for example when joining two metal sheets, to penetrate the upper metal sheet and enter the lower metal sheet.

[0003] To produce such a joint consisting of two metal sheets using this type of rivet, a tool designed as an upper tool and a die designed as a lower tool are provided. To join the two metal sheets, they are placed on the die and held in place by a clamping device of the tool. They are then fed to the rivet by a ram and pressed towards a recess in the die. This recess in the die has a dome-shaped protrusion which, during the setting process, is pressed into the hollow cylindrical shank section of the rivet, thereby widening this shank section and forming an undercut.

[0004] DE 10 2012 003 819 A1 also describes a method for creating a connection between a functional element designed as a self-piercing rivet and a single sheet metal part. This functional element comprises a head section with a cutting edge foot, the cutting edge foot being designed for punching into the sheet metal part without creating a puncture. The cutting edge foot is designed as a hollow cylinder with ribs extending parallel to the longitudinal direction on its outer surface. The inner surface of the cutting edge foot tapers at its free end into a diverging truncated cone shape, which serves to widen the cutting edge foot when punching into the sheet metal part.

[0005] Furthermore, EP 1 533 054 A2 describes a method for creating a connection between a functional element designed as a self-piercing rivet nut and a single sheet metal part. This functional element is cylindrical with a section having an internal thread and another section designed as a cutting foot. When punched into the sheet metal part, this cutting foot is expanded radially outwards without punching through the component.

[0006] Furthermore, DE 199 49 161 A1 describes a functional element designed as a rivet for fastening to a plate-shaped component. This functional element is provided with a functional projection in the form of a threaded bolt and consists of a stub-shaped joining section and a collar section located between the joining section and the functional projection. The joining section has an undercut on its circumference into which material from the plate-shaped component flows during the setting process, thus creating a connection between the functional element and the component. During the setting process, the functional element remains undeformed. The joining section and part of the collar section penetrate the plate-shaped component, but without penetrating or punching through the material. Only displacement and deformation of the material occur, leaving a residual base of nearly uniform thickness around the joining section.

[0007] The disadvantage of these methods is that using different materials to connect the functional element and the plate-shaped component leads to material stresses under temperature loads due to differing coefficients of thermal expansion. This is because the component material forms a positive fit around the cutting edge and also forms a positive fit against the underside of a head section of the functional element. This effect occurs particularly when, for example, the functional element is made of steel and the plate-shaped component is made of aluminum.

[0008] From DE 10 2011 109 815 A1, a bolt for connecting two adjacent components is known. To create the connection, the bolt is driven into the components at high speed under pressure and rotation using a tool, resulting in a strong connection through frictional heating and local deformation of the component materials. In a section of the bolt's shank, raised areas and / or recesses are provided, which, through the flow of the heated material, create a positive fit between the bolt and the components. A cylindrical section adjoins the head of the bolt, the diameter of which is reduced compared to the diameter of the subsequent cylindrical section.This cylindrical section with a reduced diameter causes a small circumferential gap to form between this cylindrical section and the surrounding component after the bolt is driven into the components, which is intended to reduce material stresses and temperature loads in this area.

[0009] However, a disadvantage of such a bolt according to DE 10 2011 109 815 A1 is the local weakening of the bolt in the area of ​​the cylindrical section with reduced diameter.

[0010] Based on this prior art, the object of the invention is to provide a method, as mentioned above, by which a stress-free connection is created between a functional element and a plate-shaped component under temperature loads. Furthermore, it is an object of this invention to provide a device for creating a connection between a functional element and a plate-shaped component.

[0011] The first problem is solved by a method having the features of claim 1.

[0012] Such a method for generating a connection between a functional element having a head section and a cutting edge and a plate-shaped component with a thickness S, in which – the head section of the functional element is formed with a cutting edge foot having a foot length F and a predetermined foot diameter E, – the cutting edge is pressed into a recess of a die by means of a tool engaging the functional element with an axial feed movement under radial spreading to form an undercut in the component, without penetrating the component, and – the recess of the die is formed with a die depth C and a die diameter D, is characterized according to the invention in that – to realize a circumferential gap around the cutting edge at the transition to the head section, the cutting edge length F, the die diameter D, and the die depth C of the die are selected according to the following specifications depending on the given thickness S: – F ≤ 2.2 × S – D ≤ 2 × S + E – C ≤ S.

[0013] These specifications regarding the cutting edge foot length, the die diameter, and the die depth result in a defined circumferential gap. Such a circumferential gap, resembling an air pocket, has a positive effect on the strength of a steel-aluminum sheet joint, for example, when the functional element is made of steel and an aluminum sheet is used as the component.

[0014] Particularly high pull-out strength is achieved when, according to further refinement, the die cavity, especially the bottom surface of the cavity, is provided with a dome-shaped protrusion. Preferably, this dome-shaped protrusion is designed such that, during the axial feed movement, the component material is inserted over the protrusion, and the end face of the die head section facing the component digs into the component with the cutting edge and is displaced radially outwards. Because such a dome-shaped protrusion in the die cavity achieves radial outward material displacement right from the start of the setting process, extremely thin components, such as thin sheets of ductile material, can be used as plate-shaped components.

[0015] Furthermore, according to one embodiment of the invention, it is provided that, for the formation of the cutting edge foot, the end face of the head section facing the component is formed with a convex depression and its transition to the outer surface of the cutting edge foot is designed as a cutting edge.

[0016] This results in a structurally simple contour of the functional element and can therefore be manufactured cost-effectively.

[0017] According to a further embodiment of the invention, the head section of the functional element is formed with at least one anti-rotation nub facing the component, which does not interrupt the circumferential gap. Such anti-rotation nubs engage with the component after the functional element is pressed in, resulting in optimal anti-rotation protection.

[0018] The second problem is solved by a device having the features of claim 5.

[0019] Such a device for generating a connection between a functional element having a head section and a cutting edge and a plate-shaped component with a thickness S, wherein – the head section of the functional element is designed with a cutting edge foot having a foot length F and a predetermined foot diameter E, – the cutting edge is pressed into a recess of a die by means of a tool engaging the functional element with an axial feed movement under radial spreading to form an undercut in the component, without penetrating the component, and – the recess of the die is formed with a die depth C and a die diameter D, is characterized according to the invention in that – to realize a circumferential gap around the cutting edge in the transition to the head section, the cutting edge length F, the die diameter D, and the die depth C are selected according to the following specifications depending on the given thickness S: – F ≤ 2.2 × S – D ≤ 2 × S + E – C ≤ S.

[0020] With such a device according to the invention, a connection between the functional element and the plate-shaped component with a defined circumferential gap can be realized.

[0021] Advantageous embodiments of the device according to the invention are given by the features of dependent claims 6 to 8.

[0022] The invention is described in detail below with reference to an exemplary embodiment and the accompanying figures. These show:

[0023] Fig. 1 a schematic representation of a functional element for carrying out the method according to the invention,

[0024] Fig. 2 a schematic representation of a die for carrying out the method according to the invention, and

[0025] Fig. 3 a schematic representation of a completed setting process for connecting the functional element according to Fig. 1 with a plate-shaped component using a setting tool.

[0026] Fig. Figure 1 shows a functional element designed as an expansion rivet bolt. 1 , which is a head section 2 has a bolt section on one side 6 transitions and on the opposite side with a cutting foot 4 is formed. This cutting foot 4 as well as the bolt section 6 is with a opposite to the head section 2smaller diameter, so that the cutting edge 4 and the bolt section 6 circumferential band 2.2 is formed. The cutting edge foot 4 has a foot height F and a foot diameter E.

[0027] The bolt section 6 of the functional element 1 It serves as a functional component and is, for example, equipped with an external thread. This bolt section could also 6 It must be spherical in shape to form a ball joint with another component.

[0028] On the underside 2.3 of the federal government 2.2 of the functional element 1 There is at least one anti-rotation stud 2.4 , which leads to an anti-rotation device for the component 10 molded functional element 1 leads.

[0029] To form the cutting foot 4 is the bolt section 6 opposite front2.1 of the head section 2 with a convex depression 4.1 trained so that at the transition of this specialization 4.1 to the surface 4.2 of the cutting foot a cutting edge 3 is formed. This cutting edge 3 is formed by an outer chamfer 3.1 and an inner chamfer 3.2 This process creates a particularly sharp cutting edge. 3 .

[0030] The production of a connection of such an expansion rivet bolt 1 with a thin and plate-shaped component 10 with a thickness S, e.g. a thin sheet metal shows Fig. 3 after completion of a setting process carried out using a setting device.

[0031] After Fig. 3. The setting device consists of a tool designed as an upper tool. 20 with a plunger that can be subjected to pressing force 21 and a die designed as a sub-tool30 A hold-down device for the upper tool 20 to hold the thin sheet metal 10 on the die 30 is in Fig. 3 not shown. This matrix 30 indicates according to Fig. 2 a more in-depth look 31 with an inner perimeter wall 31.1 and a floor area 31.2 on, centered on this floor surface 31.2 a dome-shaped elevation 32 is arranged so that the floor area 31.2 forms a ring groove. This die 30 is in the Fig. 2 and Fig. 3 with a matrix depth C and a matrix diameter D of the depression 31 depicted.

[0032] During the setting process, the cutting foot is used. 4 with one of the upper tool 20 according to Fig. 3 generated axial feed movement the material of the thin sheet. 10 into this depth 31 the die 30deformed inwards, so that under radial spreading G of the cutting edge foot 4 an undercut on the outside 5 forming a residual soil 10.1 in thin sheet metal 10 This occurs. The cutting foot is formed during this process. 4 only into the material of the thin sheet metal 10 molded, without this thin sheet metal 10 to punch through or perforate.

[0033] During this setting process, a [missing information] occurs in the transition area of ​​the cutting edge foot. 4 to the adjacent subpage 2.3 of the federal government 2.2 of the head section 2 a cutting foot 4 circumferential gap 7 in the manner of an air pocket, which compensates for the different thermal expansions when the functional element 1 consists of a steel material and is used for thin sheet metal 10 An aluminum alloy is used. This circumferential gap 7is in the axial direction of the functional element 1 through the process of setting the functional element 1 resulting undercut 5 defined. The distance of this undercut 5 in the axial direction of the functional element 1 to the subpage 10.2 of the thin sheet metal 10 is referred to as height B, while the distance starting from the undercut 5 to the top 10.3 This is referred to as height A. The sum of the two values ​​for height A and B gives the thickness S of the thin sheet. 10 .

[0034] To this perimeter gap 7 To achieve this in a targeted and defined way, the values ​​for the foot length F of the cutting foot are determined. 4 as well as the values ​​for the matrix depth C and the matrix diameter D of the depression 31 the die 30 depending on the thickness S of the thin sheet 10 determined according to the following provisions: – F ≤ 2.2 × S, – D ≤ 2 × S + E, and – C ≤ S,

[0035] Where the value for the foot diameter E of the cutting foot 4 is predetermined.

[0036] Will the functional element 1 as well as the associated die 30 The functional element is implemented according to these values ​​for the quantities F, D and C, and according to the described procedure. 1 into the sheet metal 10 A corresponding shape is formed when molded. Fig. 3 Connection structure shown, in which the circumferential gap described above 7 in a defined manner. This results in undercutting for the values ​​of height A. 5 to the top 10.3 of the thin sheet metal 10 and the height B of undercut 5 to the subpage 10.2 of the thin sheet metal 10 The following relationship depends on the thickness S of the thin sheet metal. 10 : – A ≥ 0.7 × S, and – B ≤ 0.3 × S.

[0037] For example, the following results are obtained for a thickness S of the thin sheet metal. 10 The following values ​​apply from 1 mm: – F = 2.2 mm or smaller – D = 6.6 mm or smaller if E = 4.4 mm, – C = 1 mm or smaller.

[0038] This results in the following for height A and height B: – A = 0.7 mm or larger – B = 0.3 mm or smaller.

[0039] In the Fig. 3 shown in the thin sheet metal 10 molded state of the functional element 1 The anti-rotation nubs grip securely 2.4 into the top 10.3 of the thin sheet metal 10 and therefore provide optimal protection against twisting. Several such anti-twist nubs 2.4 are circular around the cutting edge 4 on the underside 2.3 of the federal government 2.2 of the head section 2 arranged.

[0040] The expansion rivet bolt used for the described procedure 1 It could also be designed as an expansion rivet bolt, an expansion ball bolt, an expansion thread bolt, or an expansion coarse thread bolt. Reference symbol list 1 Functional element 2 Head section 2.1 Frontal face of the head section 2 2.2 Bund of the head section 2 2.3 Underside of the Federal Government 2.2 2.4 Anti-rotation stud 3 cutting edges 3.1 outer chamfer 3.2 inner phase 4 cutting feet 4.1 convex depression 4.2 Surface area of ​​the cutting edge foot 4 5. Undercut. 6 Bolt section of the functional element 1 7 Circumferential gap 10 plate-shaped components 10.1 Remaining floor of the component 10 20 Upper tool, tool 21. Plunger of the upper tool 20 30 Lower tool, die 31. Deepening of the die 30 31.1 inner perimeter wall of the depression 31 31.2 Floor area of ​​the depression 31 32 dome-shaped elevations QUOTES INCLUDED IN THE DESCRIPTION

[0041] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0042] DE 4333052 A1

[0002] DE 102012003819 A1

[0004] EP 1533054 A2

[0005] DE 19949161 A1

[0006] DE 102011109815 A1 [0008, 0009]

Claims

[1] Method for creating a connection between a head section ( 2 ) and a cutting edge ( 3 ) exhibiting functional element ( 1 ) and a plate-shaped component ( 10 ) with a thickness (S), at which – the head section ( 2 ) of the functional element ( 1 ) with a cutting edge ( 3 ) having cutting foot ( 4 ) is designed with a foot length (F) and a predetermined foot diameter (E), – the cutting foot ( 4 ) by means of a functional element attached to the functional element ( 1 ) attacking tool ( 20 ) into a depression ( 31 ) a die ( 30 ) with an axial feed movement under radial spreading to form an undercut ( 5 ) into the component ( 10 ) is pressed in without the component ( 10 to penetrate, and – the deepening ( 31 ) the die (30 ) is formed with a matrix depth (C) and a matrix diameter (D), characterized by that – to realize a cutting edge foot ( 4 ) in the transition to the head section ( 2 ) circumferential gap ( 7 ) the foot length (F) of the cutting foot ( 4 ) as well as the die diameter (D) and the die depth (C) of the die ( 30 ) depending on the specified thickness (S) of the component ( 10 ) are selected according to the following criteria: – F ≤ 2.2 × S – D ≤ 2 × S + E – C ≤ S. [2] Method according to claim 1, characterized by that the floor area ( 31.2 ) the deepening ( 31 ) the die ( 30 ) with a dome-shaped elevation ( 32 ) is trained. [3] Method according to claim 1 or 2, characterized by that to form the cutting foot ( 4 ) which belongs to the component ( 10) facing front side ( 2.1 ) of the head section ( 2 ) with a convex depression ( 4.1 ) and their transition to the lateral surface ( 4.2 ) of the cutting foot ( 4 ) as a cutting edge ( 3 ) is trained. [4] Method according to any one of the preceding claims, characterized by that the head section ( 2 ) with at least one of the component ( 10 ) facing anti-rotation studs ( 2.4 ) is trained. [5] Device for creating a connection between a head section ( 2 ) and a cutting edge ( 3 ) exhibiting functional element ( 1 ) and a plate-shaped component ( 10 ) with a thickness (S), wherein – the head section ( 2 ) of the functional element ( 1 ) with a cutting edge ( 3 ) having cutting foot ( 4) is designed with a foot length (F) and a predetermined foot diameter (E), – the cutting foot ( 4 ) by means of a functional element attached to the functional element ( 1 ) attacking tool ( 20 ) into a depression ( 31 ) a die with an axial feed movement under radial spreading to form an undercut ( 5 ) into the component ( 10 ) is pressed in, without the component ( 10 to penetrate, and – the deepening ( 31 ) the die ( 30 ) is designed with a matrix depth (C) and a matrix diameter (D), characterized by that to realize a cutting edge foot ( 4 ) in the transition to the head section ( 2 ) circumferential gap ( 7 ) the foot length (F) of the cutting foot ( 4 ) as well as the die diameter (D) and the die depth (C) of the die ( 30) depending on the specified thickness (S) of the component ( 10 ) are selected according to the following criteria: – F ≤ 2.2 × S – D ≤ 2 × S + E – C ≤ S. [6] Device according to claim 5, characterized by that the floor area ( 31.2 ) the deepening ( 31 ) the die ( 30 ) with a dome-shaped elevation ( 32 ) is trained. [7] Device according to one of claims 5 or 6, characterized by that to form the cutting foot ( 4 ) which belongs to the component ( 10 ) facing front side ( 2.1 ) of the head section ( 2 ) with a convex depression ( 4.1 ) and their transition to the lateral surface ( 4.2 ) of the cutting foot ( 4 ) as a cutting edge ( 3 ) is trained. [8] Device according to any one of claims 5 to 7, characterized by that the head section with at least one component ( 10) facing anti-rotation studs ( 2.4 ) is trained.

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