DE10348427A1 - Direct screwing process for joining two or more components involves pressing components together by holding-down force during screwing - Google Patents

Abstract

The direct screwing process involves joining two or more components (7, 8), which are locally warmed in the screw position until they are deformable, after which they are pierced by a screw (9). The components are held down by a holding-down force (FNH) and pressed together by a holding-down plate (17) while they are being screwed to each other.

Description

The The invention relates to a method for directly screwing several joining partner without pre-punching, in which the joining partners locally heated at the screw position be until the joining partners are deformable and then a screw the joining partners penetrates. Furthermore, the invention relates to a device for execution of the procedure.

Either through the increased use of comfort and performance enhancing Technology as well as through the efforts to increase the active and passive Safety is one to increase the weight of motor vehicles to record. Opposite is the demand to protect the Resources that require a reduction in vehicle weight.

to Reduction of body weight become modern lightweight concepts considered with new materials in new construction methods. Increasing importance attains the mixed construction of space-frame structures. An essential requirement for the realization of these methods of construction are appropriate for material and construction Joining processes. Space-frame hybrid structures that are additionally used by flangeless profiles can be characterized in particular due to the one-sided accessibility the joints a challenge for the mechanical joining technique represents.

A possibility at your disposal is the direct screwing, which although with one-sided accessibility the joint can be used, the pre-punching but at least the setting side joining Partners requires. Part of the joint partner material - metallic Materials approx. 1/3 of the joining partner thickness - the screwing direction flows against, becomes the conventional one Directly screw the bolt-side joining partner with a through hole provided this increase receives. By the opening provided by the through hole or through the available standing space is a generation of a gap-free connection possible. Next the effort for the pre-hole operation is the positioning of the screw in the pre-hole to ensure, what in the plant planning for an automated serial solution also to be considered Against this background, the invention is based on the object a method and an apparatus for direct screwing the beginning mentioned type to create such a connection by the joining partner is improved.

These Task is solved with a method according to the features of the patent claim 1 and with a device according to the features of Claim 6. The dependent claims relate to particularly expedient developments the invention.

According to the invention is thus a method for direct screwing provided in which multiple joint partners be connected without pre-punching. The joining partners are heated locally at the screwing position until they become deformable are and then A screw penetrates the deformable joining partners. According to the invention while screwing together the joining partners pressed together by a hold-down force. By the acting Hold-down force prevents the formation of a gap between the joining partners. As preparatory process steps, for example, pre-piling the Joining partners, not done will need, can the process costs and the time for the connection production can be significantly reduced.

A Advantageous embodiment of the method according to the invention comprises the following steps: Heat the joining partner by frictional heat the rotating screw until the joining partners in the area of the connection fluently deformable due to the increased Temperature are. Subsequently Penetration of the joining partners with a conical tip of the screw and forming a cylindrical Passage through the joint partners. After the molding of the passage immediately follows a non-cutting Furrows of a gauge nut thread. In the formed thread can now by screwing the screw through the joining partners the connection will be made. Finally, by putting on the screw with an adjustable torque the procedure for Direct screwing completed. When cooling the joining zone, the passage shrinks and fits around the screw thread of the flow forming screw without play. This will be the release torque the screw in addition elevated and achieved a seal of the connection. This screw connection is always solvable again and can be replaced by a metric screw.

at an advantageous embodiment of the method according to the invention The hold-down force is between about 100 and 1000 N up. The order of magnitude the power is dependent the type of material and or material thickness adjustable.

Prefers acts in the inventive method the hold down force in a substantially annular area around the Screwing position on the joining partners one. This results in a uniform force distribution on the joining partners guaranteed.

The joining partners are preferably metallic for the process according to the invention. This will just for metalworking productions, for example, the motor vehicle manufacturing an advantageous joining method provided.

According to the invention is a Apparatus for carrying out the method provided, a screw and a hold-down includes. The hold-down has in the middle a receptacle for the screw on. The screw spindle serves to hold the introduced Screw while the Hold down the for the inventive method provides the intended hold-down force.

The Hold-down force can by any active principles, for example be applied by means of pneumatic pressure cylinder. At a advantageous embodiment the device according to the invention is the hold-down force by a spring, in particular a spiral spring, provided. Particularly preferably, an adjustment device is also provided is with which the hold-down force of the spring is adjustable. By the adjustable hold-down force can be different types of materials and / or material thicknesses are optimally interconnected.

Prefers In one embodiment of the Device according to the invention for direct screwing of the hold-down a sleeve and a replaceable tail on. This allows for different screw sizes be reacted flexibly to a simple assembly effort.

Farther is a screw according to the invention intended for use in the process of direct screwing, when the screw is in an area where the threaded shaft adjacent to the underside of the screw head, having a recess.

In The recess may be material of the joining partner during the deformation process be picked up that towards the top of the formed draft flows.

The Invention leaves numerous embodiments to. To further clarify its basic principle is one of them illustrated in the drawings and will be described below. These show in

1 a simplified representation of the different stages of the process of screwing with a time course of the process parameters;

2 a comparison of the torque-time curves for direct screwing with and without pre-punching;

3a . 3b . 3c Cross-section examples of direct screwed aluminum-steel connections with and without pre-punching;

4 a schematic diagram of the device according to the invention;

5 an exemplary structure of a blank holder according to the invention

6 An embodiment of a screw according to the invention.

1 shows a simplified representation of the different stages 1 to 6 the sequence of screwing two join partners 7 . 8th and a diagram of the process parameters torque M, path s and speed n over time t. Dashed lines indicate at what point in the parameter diagram which of the stages 1 to 6 takes place. For simplicity, no device according to the invention for providing the hold-down force is shown in this figure.

In the direct screw connection, a high frictional heat is required for the flow hole formation, which is realized depending on the material type and thickness by a high speed in the range of 1000 to 5000 1 / min and a contact pressure of 0.3 to 1.5 kN. For an optimum joining result, the process parameters are to be adapted to the type of material and the joining partner thickness, resulting in several process stages or stages 1 to 6. Compared to the process sequence for direct bolting with pre-punching, the process stage is in progress 1 the joining partners 7 and 8th by a higher contact pressure and a higher speed n of the screw 9 heated. In the process stage 2 the temperature required for plasticization is reached. Through the two joining partners 7 . 8th is now in the process stage 3 a draft 10 formed with steadily increasing Furchmoment and then in the process stage 4 in the passage 10 a thread 11 fearless. The length of the molded passage 11 is the joining partner depending on the material 7 . 8th and the process parameter is about three times the thickness of the joining partners 7 . 8th , When threading the furrow torque increases to a peak value, and then fall off again when screwing through.

After the forming process steps have been completed, it is in the process stage 5 the speed n of the screw 9 reduced, so that the thread 11 when screwing in the screw 9 not damaged. Furthermore, the predetermined tightening torque is more precisely adjustable. Once the head of the screw 9 on the upper joining partner 7 touches, rises in the process stage 6 the insertion torque up to the intended tightening torque and the joining process is completed. When cooling the joining zone, the passage shrinks 11 and fits around the thread of the screw without play 9 , This will cause the loosening moment of the screw 9 additionally increased and achieved a sealing of the connection. This screw is at any time detachable and can be replaced by a metric screw (not shown).

2 shows a diagram in which the curves of the torques M of the variants with and without pre-punching are shown comparatively. In the diagram, the torque M is plotted over the time t, thereby designated 12 the torque when direct screwing with pre-punching and 13 the torque without pre-punching. The entire joining process without pre-punching of the upper joining partner 7 (out 1 ) requires a little more time compared to screwing with Vorlochen, since in the process according to the invention both joining partners 7 . 8th by means of the contact pressure and the speed n of the screw 9 must be heated. Furthermore, the passage 10 through both joining partners 7 . 8th formed through.

The tightening torque is to be selected between the insertion torque M _E and the over-torque M _Ü , wherein the distance to the aforementioned characteristic values should be as large as possible. The distance between the respective characteristic values is called process window. In the 4 is with 14 a first process window for the case of Direktver screws with pre-holes and with 15 a second process window for direct screwing according to the invention without pre-punching called. When direct screwing with and without pre-punching, the insertion torques M _{E are} at about the same level. The over torque M _Ü, however, where the grooved thread 11 in the joining partners 7 . 8th is destroyed in direct screwing without pre-punching (course of the line 13 ) significantly higher, since the screw thread 11 both in the upper joining partner 7 and in the lower joining partner 8th engaged. Although in this case two nut threads with a single screw 9 be bolted, a biasing force is applied. Because the process window 15 For the tightening torque for direct screwing without pre-punching is larger, this process variant offers greater process reliability. In addition, when direct screwing without pre-punching, line 13 , higher tightening torque can be set, which also lead to higher release torque of the screw without pre-punching.

In the 3a . 3b . 3c are cross-section profiles of direct screwed connections shown. All three examples are aluminum-steel compounds. However, the necessary pressure forces when performing the method for direct screwing can cause undesirable deformations in joining zones with low rigidity. The part of the total length of the screw which is used for flow-hole forming and threading, protrudes relatively far out of the compound and is no longer needed for the connection. For these reasons, an application of direct screw, for example, in closed profiles, advantageous that apply sufficient rigidity and can accommodate the protruding screw tips.

In 3a shows a cross-section of a direct screwed aluminum-steel connection, in which the upper joining partner was pre-punched. Clearly the game between the bore wall of the clamping part and the screw shaft can be seen, wherein the upper passage of the screw is received.

In contrast, screwed without Vorloch, as in 3b is shown, the clamping part is directly on the screw shaft and is reinforced by the displaced material, which increases the sheet metal thickness on the screw shaft. However, a gap arises between the two sheet metal layers, since on the one hand the material of the upper layer flows downwards between the two components and also a smaller part of the lower layer. Here by the dimensional accuracy of the components is adversely affected. Furthermore, this allows crevice corrosion and reduces the torsional rigidity of the components.

By the holding-down device according to the invention, which will be described in more detail below and presses the two joining partners in the region of the screw head, the material flow, however, can be controlled so that a gap-free connection is formed and the two joining partners lie flat on each other. This is in the 3c shown. The hold-down force can vary from 100N to 1000N, depending on the material type and thickness. The hold-down preferably presses the sheets together with a circular ring surface around the screw head.

Although in the 3 not shown, the mechanical joining method can also be combined with a hybrid joining method, for example gluing. This is particularly advantageous for joining dissimilar materials that have a large difference in their electrochemical voltage potential. In addition to the avoidance of contact corrosion and crevice corrosion, the mechanical properties of the compound can be significantly improved in comparison to elementary mechanical joining. The combination of both joining methods leads to higher strength of the connection and to a clean gap filling due to a lower adhesive displacement. Since there is no pre-hole in the upper sheet metal layer, no adhesive can escape and soil the component surface. By means of the hold-down and a corresponding hold-down force, a defined adhesive layer thickness can be set.

In the 4 is a schematic diagram of the device according to the invention shown. The joining partners 7 and 8th lie in this figure unconnected plan on each other. On the upper joining partner 7 is the screw 9 through a screw spindle 16 can be rotated with the torque M and the speed n. On the screw 9 acts by means of the screw spindle 16 a contact force F _A down.

Laterally next to the screw 9 in the two-dimensional representation, but annular in the three-dimensional design, is a hold-down 17 arranged, which exerts on the joining partner, the hold-down force F _NH . The hold down 17 presses the joining partners during the entire process 7 . 8th together, allowing a flow of the material between the joining partners 7 . 8th and thus a gap formation is avoided.

In the 5 is an embodiment of the blank holder according to the invention 17 shown in more detail. In the example of 5 is the lower joining partner 8th a hollow profile. Above the upper joining partner 7 is the screw 9 arranged. The hold down 17 has a conventional screw 16 and a hold-down sleeve 18 on. At the top of the hold-down sleeve 18 There is a replaceable tail 19 , Through the exchangeable tail 19 is the hold-down 17 adaptable to different diameters of screw heads. The hold-down force is in this example by a compression spring 20 provided. The hold-down force of the compression or spiral spring 20 can by means of the mother 21 be set.

A screw according to the invention 9 is in the 6 shown enlarged. The screw 9 has a specially shaped tip 22 on, the conical in the thread 23 passes. On the top 22 four circumferentially distributed, raised edges are arranged, which generates during the setting process in conjunction with the contact pressure and the spindle speed, the required frictional heat to the passage 11 (out 1 ). The heated material flows axially around the mold tip 22 the screw 9 , The lower part of the thread in the figure 23 is called thread forming zone. This area fearlessly cuts the thread into the deformable material. The overlying area of the thread 23 is the load-bearing area, ie the area that holds the screw connection. At the bottom of the screw head 24 is a recess 25 intended. As something of the material of the upper joining partner 7 the screw head 24 flows counter, this proportion can in the recess 25 flow. The outer edge of the screw head 24 can then be gap-free on the upper joining partner 7 issue.

At It should be noted that all of the above Parts for seen alone and in any combination, especially those in the drawing shown details claimed as essential to the invention become. amendments this is familiar to the person skilled in the art.

1 until 6

stadiums

7

first joining partner

8th

second joining partner

9

screw

10

Draft

11

thread

12

torque with pre-holes

13

torque without pre-punching

14

process window without pre-punching

15

process window with pre-holes

16

screw

17

Stripper plate

18

Down sleeve

19

tail

20

compression spring

21

mother

22

V-point

23

thread

24

screw head

25

recess

F _A

pressing force

F _NH

Hold down force

M

torque

n

rotation speed

s

path

t

Time

Claims (10)

Method for directly screwing together several joining partners ( 7 . 8th ) without pre-punching, in which the mating partners ( 7 . 8th ) are locally heated at the screw position until the joining partners ( 7 . 8th ) are deformable and then a screw ( 9 ) the joining partners ( 7 . 8th ) penetrates, characterized in that the joining partners ( 7 . 8th ) are pressed together by a hold-down force (F _NH ) during screwing. Method according to claim 1, characterized by the following steps: - heating of the joining partners ( 7 . 8th ) by frictional heat of the rotating screw ( 9 ); - penetration of the joining partners ( 7 . 8th ) with a conical tip ( 22 ) of the screw ( 9 ); - forming a cylindrical passage ( 10 ) by the joining partners ( 7 . 8th ); - chipless furrowing of a gauge-containing nut thread ( 11 ); - Screw through the screw ( 9 ) by the joining partners ( 7 . 8th ); and - tightening the screw ( 9 ) with an adjustable torque. Method according to claims 1 or 2, characterized in that the hold-down force (F _NH ) has a value between about 100 and 1000 N. Method according to at least one of the preceding claims, characterized in that the hold-down force (F _NH ) in a substantially annular area around the screwing position on the joining partners ( 7 . 8th ) acts. Method according to at least one of the preceding claims, characterized in that the joining partners ( 7 . 8th ) are metallic. Device for carrying out the method according to at least one of the preceding claims, characterized in that the device comprises: - a screw spindle ( 16 ); and - a hold-down ( 17 ), the center of a receptacle for the screw ( 16 ) having. Apparatus according to claim 6, characterized in that the hold-down force (F _NH ) by a spring ( 20 ), in particular a spiral spring is provided. Apparatus according to claim 7, characterized in that an adjusting device ( 21 ) is provided, with which the hold-down force (F _NH ) of the spring ( 20 ) is adjustable. Device according to at least one of claims 6 to 8, characterized in that the hold-down ( 17 ) a sleeve ( 18 ) and a replaceable tail ( 19 ) having. Screw ( 9 ) for use in a method according to at least one of claims 1 to 5, characterized in that the screw ( 9 ) in the area in which the threaded shaft ( 23 ) to the underside of the screw head ( 24 ) borders, a recess ( 25 ) is provided.