CN104815912A - Method of bonding and embossing device - Google Patents

Abstract

The invention relates to a method for connecting a steel inner panel (14, 14a) and a soft metal outer panel (16) by means of an undercut flange (12). It is provided that after the outer panel (16) is folded, punching is carried out in the region of the undercut roll (20) of the undercut flange (12), so that the outer panel (16) is prevented in the direction of the inner panel (14, 14a) ( Y) slide up. The invention also relates to a stamping device (30) for stamping an undercut flange (12) of an inner panel (14) made of steel and an outer panel (16) of soft metal.

Description

Method and stamping device for joining

technical field

The invention relates to a method for joining steel inner panels and soft metal outer panels by means of undercut flanges and a stamping device for stamping the undercut flanges.

Background technique

Hybrid constructions consisting of high-strength and very high-strength steel inner panels and soft metal outer panels, such as aluminum outer panels, are increasingly being used for weight reduction purposes in the automotive industry and elsewhere. This requires entirely new or optimized connection technologies. One possibility is a riveted connection, but this is only possible with soft metal and very wide flanges. Another possible solution is folding, specifically rolling folding. Here, an aluminum outer panel is formed on a hot-formed steel inner panel or similar very high-strength inner panel. For a hermetic connection of two boards, an adhesive, such as an epoxy adhesive, is used between the two boards. This epoxy adhesive hardens at approximately 170° C. during the subsequent cathodic electrocoating process. Due to the different coefficients of thermal expansion of aluminum and steel, aluminum migrates into the undercut of the steel inner panel in the drying unit of the cathodic electrocoating process. The adhesive hardens in this state, thereby securing the moved position. This leads to bending deformations between the parts which are moreover irreversible due to hardening of the adhesive. This bending deformation makes this method difficult or impossible for certain applications, such as door frame flanges.

DE 10 2004 047 229 A1 discloses a connection between two adjacent identical parts of a support profile. In order that this type of component connection can simultaneously transmit high forces and torques, the components are partially and form-fittingly encircled around one another. Furthermore, the parts are connected at least partially by force-fitting or friction-fitting in the overlap region by stamping. The special connection case between the steel inner plate and the soft metal outer plate is not covered here.

Contents of the invention

The technical problem to be solved by the present invention is to improve the connection method between the steel inner plate and the soft metal outer plate.

The technical problem is solved by a method for connecting a steel inner panel and a soft metal outer panel by means of an undercut flange, wherein, after folding the outer panel, punching is carried out in the area of the undercut roll of the undercut flange, Thereby, the upward sliding of the outer plate in the direction of the inner plate is prevented. The technical problem is also solved by a stamping device.

The method according to the invention for connecting an inner steel panel with an outer panel of soft metal by means of an undercut flange comprises, after folding the outer panel, stamping in the area of the undercut roll of the undercut flange, thereby avoiding the Swipe up in direction. With the aid of the method according to the invention, it is now possible to realize, for example, a connection between a steel inner panel and a soft metal outer panel for the side panels of a motor vehicle. The costs of the aluminum-steel manufacturing technology can be reduced here by eliminating riveting operations. Furthermore, the undercut flange can be reduced by using, for example, a width of 12 mm instead of a width of 15 mm. This reduces weight and improves comfort. In addition, an efficient tool can be obtained by means of punching positioned after folding, so that thermal bending deformations are counteracted by very short quality control loops.

One of the six degrees of freedom can be precisely locked by the punching process, which prevents an undesired upward sliding (Aufgleiten) or upward movement (Aufschieben) of the outer panel in the direction of the inner panel. In addition, other movements are possible during the production process, that is, to compensate for tolerances. This may be a movement of the end face of the inner panel in a lateral direction, or a movement of the end face of the inner panel in a vertical direction, as well as a movement away from the end face of the inner panel. Thus only one undesired direction of movement is blocked, while the remaining five directions of movement are otherwise permitted.

In a preferred configuration of the invention it is provided that the stamping takes place between the end face of the inner sheet and the bend of the undercut roll. Stamping at this point has the advantage that, on the one hand, the inner panel is not or hardly damaged, and on the other hand, the partially visible bend of the undercut roll is likewise not damaged.

Provision is made here to provide at least two inner panels which are planar in the region of the end faces and lie one above the other. The method according to the invention is particularly suitable for producing a connection between steel inner panels and a soft metal outer panel, which has hitherto been very difficult. The possible freedom of movement for moving or sliding increases with the number of inner plates. By means of the purposeful stamping of the outer panels, it is now also possible to connect several, preferably two to four inner panels, with an outer panel made of a soft metal, for example aluminum.

In a further preferred embodiment of the invention it is provided that the inner plate is made of extremely high-strength steel. Very high-strength steels, such as through-hardened hot-formed steel, are particularly suitable for the method according to the invention, since until now it was almost impossible to connect them to an outer plate of a soft metal.

In yet another preferred embodiment of the invention it is provided that the outer pane comprises aluminum or an aluminum alloy material. Likewise, other soft metals, such as magnesium or titanium, can also advantageously be used. Although the demand for the use of aluminum material for the purpose of reducing weight in the field of automobile manufacturing has increased significantly, the manufacturing technology behind this desire has so far been no progress. With the aid of the invention, a cost-effective and efficient production of aluminum-steel hybrid structures is now possible.

It is advantageously provided that a factor of from 2 to 6, preferably from 3 to 4, is formed between the tensile strengths of the two sheets. The method according to the invention is particularly suitable for plates with significantly different tensile strengths, since they also have significantly different coefficients of thermal expansion. The connection between inner and outer panels has hitherto not been easy to achieve. The method according to the invention is used to join different materials by purposeful punching.

Stamping units may have sizes or gauges or ranges in undercut rolls extension within. The ideal size of the stamping device may depend on the material and quantity of the inner panels, the material of the outer panels, the application, and other factors. It has been shown that embossing within the size of the undercut roll, ie within the height of the undercut roll, achieves very good results. The height of the undercut roll here is substantially equal to the total height of the individual panels. It is also possible for the embossing to have an extension over the height or thickness of the individual plates.

In a preferred embodiment of the invention it is provided that a plurality of embossments are arranged along the undercut flange at intervals of three to ten times, preferably four to six times the size of the undercut roll. The number and location of impressions can have an effect on thermal bending deformation. The position and/or number of embossings can thus also be adjusted during the process, for example in a control loop. This can make the machining process more stable.

In a further preferred embodiment of the invention it is provided that the undercut flange is formed by roll folding. Roll folding is a fast and thus cost-effective joining method which is well matched to the proposed stamping process. Roll folding and subsequent stamping of the rolled undercut flanges allow a fast and versatile production method.

A punching device according to the invention for punching undercut flanges of steel inner panels and soft metal outer panels comprises that the punching device comprises a side with flat or flat sides for aligning the end faces of the inner panels and a A punch aimed at the inclined side of the bend of the undercut roll of the undercut flange, wherein the punch is designed for punching to be embedded between the end face and the bend, so as to avoid sliding of the outer plate towards the inner plate. The same advantages and modifications are also as described above. The punching device and the punch enable targeted punching without damage to the inner sheet and the undercut roll. The flat sides increase tolerances and sensitivity in the punching unit, while the sloped sides ensure minimal influence on the undercut roll.

The different embodiments of the invention mentioned in this patent application can be advantageously combined with each other, provided that no other explanation is given in individual cases.

Description of drawings

The invention will be explained in the structural example below with the aid of the accompanying diagrams:

Figure 1 shows a schematic view of the side of a car body;

Figure 2 shows a cross-sectional view of the folded and then stamped undercut flange of the side;

Figure 3 shows a schematic perspective view of a stamped undercut flange;

Figure 4 shows a schematic diagram of the stamping process;

Figure 5 shows another schematic diagram of the stamping process and

Figure 6 shows a detailed view of the stamping tool.

Detailed ways

In FIG. 1 a side part 10 of a motor vehicle is shown schematically, here using the method for connecting a steel inner panel with a soft metal outer panel by means of an undercut flange. The glue in the undercut flange can be hardened after punching, but this is not necessary for the method according to the invention. The side part 10 has one or more undercut flanges 12 in the region of the door frame. The undercut flange 12 can be produced by means of a roll-folding device which is guided here by a robot or which is fed laterally to the roll-folding device by an automatic machine or the like.

The undercut flange 12 has six degrees of freedom on the end face of the inner panel. Include two tangential movements in tangential X. This movement is allowed and not fixed by the method according to the invention. The two degrees of freedom of movement in the vertical direction Z are generally determined by the undercut and are likewise unimpeded. The movement in the plane normal direction Y of the end surface of the inner plate is treated differently. While sliding the scroll fold up into a position below it is not permitted and is prevented by embossing, sliding down from a position below does not occur and thus does not need to be prevented. Swipe up from the paper according to Figure 1, and slide down from the paper according to Figure 1. The overall movement or direction of movement corresponds to the relative movement between the outer plate made of soft metal and the inner plate made of steel.

FIG. 2 shows two schematic or cut sections through the folded door frame flange 12 (shown at the top) and the folded and subsequently stamped door frame flange 12 (shown at the bottom).

Shown is a first inner panel 14 of very high strength steel, and a second inner panel 14a of the same material or another steel. The flat arcs of the two inner panels 14 and 14a overlap. The two inner panels 14 and 14a again lie flat on the outer panel 16 made of aluminum or an aluminum alloy. The outer panel 16 is folded around the two inner panels 14 and 14 a in the region of the end face 18 of the inner panel 14 . This process is carried out, for example, by means of a rolling and folding device.

The undercut flange 12 has a curved undercut roll 20 which is the curvature of the outer panel 16 around the inner panels 14 and 14a, and a flange portion 22 which is the connection between the panel end of the outer panel 16 and the inner panel 14 and 14a overlap area. The flange portion 22 may have a width of 12 mm, for example. Individual plates have a thickness in the range of 0.1 to about 1.5 mm.

The adhesive 24 is, for example, an epoxy adhesive, which is arranged between the inner panel 14 and the outer panel 16 . Furthermore, provision can be made for an adhesive 24 or a similar adhesive to be arranged between the inner panel 14 and the second inner panel 14 a. The upper illustration in FIG. 2 shows the undercut flange 12 after the folding has been completed.

The lower illustration in FIG. 2 shows the punched undercut flange 12 after folding. The embossed or stamped part 26 is located in the outer panel 16 , more precisely in the region between the end face 18 of the inner panel 14 and the undercut roll 20 . The embossing 26 is arranged here at the top, ie in the end region 28 of the outer panel 16 . The embossing 26 can also be realized in the central region of the outer panel 16 shown below. Furthermore, it is also conceivable for the outer panel 16 to be stamped on both sides of the undercut flange 12 , here the upper side and the lower side. This can be done, for example, by means of a pliers-like stamping device.

The undercut flange 12 is again shown schematically in a three-dimensional illustration in FIG. 3 . As can be seen, the two inner panels 14 and 14 a are mechanically engaged to a certain extent with the outer panel 16 by means of embossing 26 , which prevents the outer panel 16 from sliding onto the two inner panels 14 and 14 a in the y direction. Relative tangential movement of the plate in the tangential y direction is still possible. The embossing 26 has an extent, ie a spatial extent, approximately in the x-direction and/or y-direction of a dimension approximately the height of the undercut roll 20 .

Along the undercut flange 12 , ie tangentially to the opposite end face 18 , a plurality of preferably identical embossments are provided. These other embossings are not shown here for the sake of clarity. Thermal bending deformation can be prevented or reduced by means of the position and number of embossing. The impressions 26 have, for example, a distance of several or several centimeters.

The partial embossing of the undercut flange 12 creates a mechanical connection between the inner panels 14 , 14 a and the outer panel 16 . As a result, during the subsequent cathodic electrocoating process, relative sliding or movement, ie upward sliding, of the components relative to one another due to the different thermal deflection coefficients of aluminum and steel can be prevented in a targeted manner.

FIG. 4 shows the punching process and a punching device 30 is shown schematically. The stamping device 30 has a punch 32 which here has a prismatic shape. An undercut flange 12 rests on a planar counter-support 34 of the stamping device 30 . Rather, the outer panel 16 is located in the middle region on the counter-carrier 34 . The punch 32 is pressed from above at an angle of approximately 10 to 45°, preferably between 10 and 25°, against the end face 18 on the end region 28 of the outer plate 16 . The punch 32 comes into contact with the outer plate 16 in the region of the end face 18 of the inner plate 14 . The stamping process here achieves the connection between the outer panel 16 and the cut edge of the inner panel 14a. The cut edge corresponds to the end face 18 .

FIG. 5 shows a further stamping process by means of a stamping device 30 . The punch 32 here punches on the plane normal Y of the outer panel 16 . The embossing 26 produced here also produces a connection between the outer panel 16 and the inner panels 14 and 14a. The punches 32 shown in FIGS. 4 and 5 have a spatial extension in the plane normal Y, which enables large-area embossing 26 .

A further stamping device 30 with a further punch 32 is shown in FIG. 6 . There is only a small extension in the plane normal Y, for example a tip 36 or a circle radius. A gently sloped side 38 and a sloped side 40 extend from the peak 36 . The flat side 38 faces the end face 18 or the inner panels 14 and 14a. The flat side 38 has an angle of approximately 45° with respect to the upper surface of the plate and, not shown here, with respect to the support 34 . The flat sides 38 serve to produce a larger stamping area in the region of the end face 18 and thus greater tolerance insensitivity in the embossing 26 . The inclined side 40 faces the undercut roll 20 and has an angle between 50 and 80°, preferably between 60 and 70°, on the upper surface of the plate or opposite the upper surface of the support 34 . The sloped sides 40 serve to have a smaller impact on the undercut roll 20 . The punch 32 is pressed onto the outer panel 16 in the vertical direction Z so that the impression 26 is produced. The outer plate 16 is clamped or fixed with the inner plate 14 or the inner plates 14 and 14a, so as to enter the next electrophoretic painting process and drying process, so as not to make the outer plate 16 undesirably slide up to the inner plate 14 or the inner plate 14. boards 14 and 14a.

list of reference signs

10 side

12 undercut flange

14 inner panel

14a Second inner panel

16 outer panel

18 end face

20 undercut rolls

22 flange part

24 adhesive

26 embossing

28 end area

30 stamping device

32 punch

34 relative support

36 tip

38 flat sides

40 sloped sides

X Tangential direction

Y plane normal

Z vertical direction

Claims (10)

1. A method for connecting a steel inner panel (14, 14a) and a soft metal outer panel (16) by means of an undercut flange (12), characterized in that after folding the outer panel (16) Stamping is carried out in the area of the undercut roll (20) of the flange (12), so that the outer panel (16) is prevented from sliding upwards in the direction (Y) of the inner panel (14, 14a). 2. The method according to claim 1, characterized in that the embossing is provided between the end face (18) of the inner panel (14) and the bend of the undercut roll (20). 3. The method according to claim 1, characterized in that at least two flat inner panels (14, 14a) are formed in the region of the end face (18) one above the other. 4. A method according to claim 1, characterized in that the inner panel (14, 14a) is made of very high strength steel. 5. The method according to claim 1, characterized in that the outer plate (16) is made of aluminum or an aluminum alloy. 6. The method according to claim 1, characterized in that the embossing (26) has an extension within the dimensions of the undercut roll (20). 7. The method according to claim 1, characterized in that a plurality of impressions (26) are provided along the undercut flange (12) at intervals of three to ten times, preferably four to six times, the size of the undercut roll (20) . 8. The method according to claim 1, characterized in that the undercut flange (12) is formed by rolling folding. 9. The method according to claim 1, characterized in that a factor of 2 to 6, preferably from 3 to 4, is formed between the tensile strengths of the two plates (14, 16). 10. A stamping device (30) for stamping an undercut flange (12) of a steel inner panel (14) and a soft metal outer panel (16), characterized in that the stamping device (30) comprises a punch (32), which has a flat side (38) for alignment with the end face (18) of the inner panel (14) and a slope for alignment with the bend of the undercut roll (20) of the undercut flange (12) The side ( 40 ), here the punch ( 32 ) designed for punching, is inserted between the end face ( 18 ) and the bend, so as to prevent the outer panel ( 16 ) from sliding up towards the inner panel ( 14 ).