WO2006045787A1

WO2006045787A1 - Riveted joint

Info

Publication number: WO2006045787A1
Application number: PCT/EP2005/055515
Authority: WO
Inventors: Erich Palm
Original assignee: Sfs Intec Holding Ag
Priority date: 2004-10-28
Filing date: 2005-10-25
Publication date: 2006-05-04
Also published as: DE102005048863A1; DE102005048863B4

Abstract

The invention relates to a riveted joint consisting of at least one thin plate (2) and a punching rivet (1) comprising a shaft (3) and a closing head (6) formed on the penetrating end of the shaft following the penetration of the thin plate (2). Said thin plate (2) consists of a high-strength material having a tensile strength of at least 560 N/mm2, preferably at least 800 N/mm2, and at least the shaft (3) of the punching rivet (1) has approximately the same tensile strength as the thin plate (2). In this way, a riveted joint consisting of a high-strength material can be produced in an exceptionally cost-effective manner.

Description

description

The invention relates to a rivet connection of a workpiece comprising at least one thin plate, and a punch rivet with a shank and a closing head formed on the penetrating end thereof after the penetration of the thin plate.

A rivet connection of this type is known from the utility model DE 93 04 797 U1. This known rivet connection is od for the mechanical elements of ring binders, letter folders. Like. Provided. The punch rivet is made of plastic. It is obvious that such a riveted joint would not be producible without pre-drilling if the thin plate were made of a material much stronger than plastic.

So-called high-strength materials such. As steel with a tensile strength (yield strength) of at least 560 N / mm ² and preferably of at least 800 N / mm ² can not yet connected to a rivet without pre-drilling wer¬, ie not by a direct fastening method such as clinching, punch rivets or solid punch rivets. Generally, it has been heretofore assumed in the art that punching with a die of reasonably high life is feasible only if the punch has significantly greater strength than the workpiece to be punched. The experts assume that workpieces can not be punched with a "soft" punch, ie with a punch whose strength is similar to that of the workpiece to be punched The same reasoning has led to the fact that it has hitherto been customary in the state of the art for producing a riveted joint between a rivet and a high-strength workpiece to either pre-drill the hole for the rivet or, similar to the stamping mentioned above, by punching out the punch rivet a material whose strength is much higher than that of the workpiece. Thus, from the utility model DE 203 19 610 U1 a punch rivet for high-strength sheets be¬ known, which has a tensile strength of 1800 N / mm ² , compared to a Zugfes¬ activity of the high-strength sheets of more than 600 N / mm ² . The punch rivet has a ring-shaped rivet cutting edge and is processed without cutting. For this purpose, the rivet blade has a wedge angle, which is of crucial importance. This punch rivet usually does not completely separate the last plate and fixes itself by being forced into it. Although the workpiece is likewise made of high-strength material, the value of the tensile strength at the lower limit is high-strength, so that between the tensile strength of sheet metal and punch rivet remains a sufficient distance. Otherwise, a punch rivet would have to be used with much higher tensile strength, which would be correspondingly more expensive. However, if a "soft" stamped rivet were to be used, premature deformation of the stamped rivet would occur during production of the riveted joint, which could hinder or prevent the production of the riveted joint.

High-strength materials, such as are increasingly used, for example, in the automotive industry represent an enormous challenge for stamped rivet joints according to the current state of the art. Because of the enormous forces that are necessary for the processing, the processing plants must be massively dimensioned , The self-piercing rivet joints themselves are highly susceptible to cracking and pose a safety risk. The cracks are in the plates, sheets or the like to be joined. In addition to the question of a secure connection, the question of corrosion protection also arises, in particular at the locations subject to cracking. The detection of these cracks is hardly possible with today's metrological possibilities, for example with eddy current testing devices, since there are too many interfering signals at the location of the punched rivet connection. The object of the invention is to make a riveted joint of the type mentioned above so that the riveted joint can be produced much more economically.

This object is achieved according to the invention in a rivet connection of the type mentioned initially in that the thin plate consists of a high-strength material having a strength of at least 560 N / mm ² and preferably of at least 800 N / mm ² and at least the shaft of the Punch rivet has approximately the same high strength as the thin plate.

The lower limit value of at least 560 N / mm ² assumed here for the range of the tensile strength of high-strength material results from a graph in the article "Is Wear Protection Simulatable? Software-supported wear recommendation for the press shop "by C. Jarms, Proceedings of the 4th Tribology Forum at TU Darmstadt on September 24 and 25, 2003 in Darmstadt The upper limit value is likely to be around 3000 N / mm ² .

The rivet connection according to the invention can be produced much more economically, because in one operation the rivet can be punched through the thin plate and subsequently the closing head can be formed. This is achieved as with a "soft" stamp, because the punch rivet has approximately the same high tensile strength as the thin plate.

The invention is thus based on the surprising finding that with a "soft" stamped rivet whose tensile strength approximately corresponds to that of the thin plate, very well punched and a riveted joint of the type mentioned can be produced without causing premature deformation of the Punching rivet comes, and that then a secure plastic deformation to An¬ forms the closing head is possible. Advantageous embodiments of the invention form the subject of Unteran¬ claims.

In one embodiment of the rivet connection according to the invention, if the punch rivet has a circumferentially closed punching edge whose length is dimensioned so that the carrying force F _{N of} the punch rivet is greater than the punching force Fs required for punching through the thin plate, the condition F _N > Fs fulfilled, so that the above-mentioned advantages can be achieved even safer with the rivet connection according to the invention.

If, in a further embodiment of the rivet connection according to the invention, the punching edge on the end face of the shaft forms approximately an angle of 90 degrees, compliance with the aforementioned condition can be calculated in a simple manner, as given below in the description of the embodiments an¬ is.

In a further embodiment of the rivet connection according to the invention, if the closing head has a diameter which is approximately equal to or greater than a punch rivet head formed at the other end of the shank, a well-durable riveted joint is produced.

If, in a further embodiment of the rivet connection according to the invention, the punched rivet head is countersunk in the punched-through thin plate, the rivet connection meets aesthetically higher requirements. By subsequent Ober¬ surface treatment such. B. painting can be such a rivet z. B. on Auto¬ body parts od. Like. Be completely laminated.

If, in a further embodiment of the rivet connection according to the invention, the punch rivet is made of stainless steel, a workpiece which consists of at least one thin plate of stainless steel can be securely connected to the punch rivet. If, in a further embodiment of the rivet connection according to the invention, the punch rivet and the thin plate consist of different materials, the rivet connection to be produced according to the invention can be adapted more easily to certain conditions.

If, in a further embodiment of the rivet connection according to the invention, the shaft has an axial countersinking at its penetration end, it can be achieved when the closing head is pushed up that the material flow takes place more rapidly from the axial to the radial direction.

If, in a further embodiment of the rivet connection according to the invention, the shaft has an axial bore at least at its penetration end, a reduction of the compression surface and thus also a reduction of the compression forces result.

If, in a further embodiment of the rivet connection according to the invention, the axial bore extends continuously over the length of the shank, material and weight of the punch rivet can be saved and thus the economic producibility of the riveted joint can be further improved.

If, in a further embodiment of the rivet connection according to the invention, the shaft has axially extending notches, slots or the like, this can achieve an anti-rotation of the punch rivet.

If, in a further embodiment of the rivet connection according to the invention, the shank has a trilobular cross-section, in addition to the effect of the anti-rotation device, the production of the self-piercing rivet can be carried out with a low-wear tool and thus cost-effectively.

If, in a further embodiment of the rivet connection according to the invention, the shaft has an arbitrary non-circular cross section, an anti-twist device can also be achieved in a simple manner. If in a further embodiment of the rivet connection according to the invention, the product of the ratio of tensile strength of the punch rivet to tensile strength of the thin plate and the ratio of diameter of the closing head to Durch¬ diameter of the shaft is at least approximately between 0.8 and 2, can be due the occurring fastening forces producing processing equipment of good hand¬ habbarer size.

If, in a further embodiment of the rivet connection according to the invention, a punched rivet punched out of the punch hole formed thereby is fixed in the axial bore at the penetration end of the punch rivet, no material part is eliminated which, depending on the application, causes mechanical or electrical damage or at least the removal of this material part or Butzens would make necessary.

Embodiments of the invention are explained in more detail below with reference to the drawings. Show it:

1 shows a rivet connection with a sleeve-shaped punch rivet with Senk¬ head.

FIG. 2 shows a riveted connection with a compressed hollow closing head; FIG.

FIG. 3 shows a riveted connection with a full compressed closing head; FIG.

4 shows a riveted connection with a splayed closing head;

5 shows a rivet connection with a splayed closing head;

Fig. 5a in a cross-sectional view along the line V - V in Figure 5 a shaft with axial notches ..;

Fig. 5b in a cross-sectional view as along the line V - V in Fig. 5 a

Shaft with a trilobular cross-section; FIG. 6 shows a riveted connection with a countersink on the shank and a mandrel for riveting; FIG.

7 shows a riveted connection with a small countersink after punching through a workpiece which comprises two thin plates;

8 shows a punch rivet variant in a conventional form;

9 shows a punch rivet variant with a through bore;

FIG. 10 shows a self-piercing riveted connection on the punch rivet head; FIG.

11 shows a punch rivet for double-sided closing head after punching;

12 a punch rivet for double-sided closing head with recess for the

Workpiece positioning after punching;

FIG. 13 shows a riveted connection with a punch rivet for a closing head on both sides after the upset of both closing heads; FIG.

FIG. 14 shows a riveted connection with a punch rivet for a double-sided closing head after the clamping heads have been spread open; FIG. and

Fig. 15 is an illustration for explaining dimensions of punch rivet and workpiece, which are ver¬ used in the calculation of the load capacity of the punch rivet and the punching force necessary for punching sheet metal.

In a rivet connection shown in FIG. 1, at least the shank 3 of a punch rivet 1 has approximately the same tensile strength as a workpiece consisting of two thin plates 2 to be joined together, wherein the shank 3 of the punch rivet 1 deformed into a closing head 6 cooperates with a Punching rivet head 5 fixed the rivet connection. The punch rivet 1 and the thin plates 2 consist of the same high-strength material with a tensile strength of at least 560 N / mm ² . If the material is a special steel such as stainless steel, the tensile strength is about 2080 N / mm ² . This is explained in detail below.

The punch rivet 1 has a circumferentially closed punching edge 4 whose length is dimensioned such that the carrying force F _{N of} the punch rivet 1 is greater than the punching force Fs necessary for punching the thin plate 2. The punching edge 4 forms approximately one on the end face of the shaft 3 Angle of 90 °. The calculation of the load capacity F _N and the punching force Fs is described below with reference to FIG. 15. At the end remote from the punch rivet head 5, the shank 3 of the punch rivet 1 has an axial bore 11 in the end face. With this axial bore 11, ie through a sleeve-like design of the punched rivet 1, the cross-sectional area of the shaft 3 is reduced, without reducing the punching force Fs required for punching through the sheet. On the other hand, this reduces the deformation force necessary for reshaping the punch rivet 1 to such an extent that it lies only slightly above the punching force Fs for punching through the thin plates 2 made of sheet metal. The closing head 6 is formed by the application of the punching force Fs, wherein the deformation with or without axial bore 11 is usually barrel-shaped. The punch rivet head 5 is countersunk in the punched-through thin plates 2, wherein the punched-thin plates 2 are deformed conically in the region of the punch rivet head 5. The punch rivet 1 is thus not protruding from the upper thin plate 2 at the end of the punch rivet head 5.

The carrying force F _{N of} the rivet and the punching force Fs necessary for punching sheet metal are calculated as follows with reference to FIG.

F _s = D _a -π -B -σ _sheet where is true

Dj = inner diameter of the shank 3 of the punch rivet 1

D ₃ = outer diameter of the shank 3 of the punch rivet 1

B = thickness of the workpiece (consisting of the two plates 2) erNiet = yield stress of the rivet

CTßiech = shear stress of the sheet

The thin plates 2 usually each have a thickness of 0.5 to 1, 5 mm.

A typical tensile strength R _{m of} both the thin plates 2 and the punching rivet 1 is 1600 N / mm ² .

For the shear strength Os, the following applies:

O ₃ = Ic R _n

The factor k depends on the respective alloy.

For carbon steel is typical

Jt = 0.7 to 1

For special steel (for example stainless steel) applies

Jt = 1.3

Thus, the shear strength is Os

from carbon steel 1120 to 1600 N / mm ² and

- of special steel about 2080 N / mm ² . With these shear strengths and an outer diameter D _{3 of} the 5 mm punch rivet, it is possible to produce processing tools of a readily manageable size on account of the attachment forces that occur.

In an embodiment variant according to FIG. 2, the punch rivet 1, which has a hollow hollow closing head 6 which is compressed, can be made of a stainless material, ie of a high-strength material. The choice of material in the rivet connection according to the invention is adjusted so that the load capacity F _{N of} the punch rivet 1 is greater than the punching force Fs, which is necesary for punching through the thin plates 2, so that applies

F _N > F _S

The circumference D ₃ π (and thus the surface) of the punch rivet 1 is therefore designed so that the permissible surface pressure of the punch rivet 1 is not exceeded during the punching operation.

In a further embodiment, FIG. 3 shows that the punch rivet 1 has a fully compressed closing head 6 with a diameter D, such as the punch rivet head formed on the other end of the shaft 3. By increasing the Trag¬ force F _{N of} the punch rivet 1, the closing head 6 can be increased as far as the degree of deformation of the material allows. By attaching predetermined breaking points on the punch rivet 1, the closing head can be upset beyond the permissible degree of deformation of the material. By this measure, the height of the Niet¬ connection can be reduced. The punch rivet 1 is thus only minimally in front of the connected thin plates 2. The upsetting of the closing head 6 with a diameter which is greater than the diameter of the punch rivet head 5 hardly makes sense in conventional applications, since the weak point of the riveted joint would then lie in the punch rivet head 5.

In a further embodiment variant, FIG. 4 shows a rivet connection made of high-strength material, in which the closing head 6 is spread in contrast to the full closing head 6 in FIG. 3. In a further embodiment according to FIG. 5, the shank 3 of the punched rivet 1 has axially extending notches 14, slots or the like. Further embodiments are possible with a trilobular or any non-circular cross-section. In addition to the barrel-shaped shape of the closing head 6, it is also possible by spreading to reach an outwardly opening shape of the closing head, as shown in Fig. 5. Appropriately, for this purpose, the shaft 3 of the punch rivet 1 at the end at which the closing head 6 is formed, provided with a countersink.

In the illustration in Fig. 5a, the cross section of a shaft 3 in a view along the line VV in Fig. 5, the notches 14, slots od. Like. Has, so as to prevent a rotation of the punch rivet 1 in the plates 2 , Securing against rotation is necessary in particular when additional functions are attached to the punch rivet head.

In the further illustration in Fig. 5b, the cross section of a shaft 3 is shown in a view along the line V-V in Fig. 5, which has a trilobular shape. An anti-rotation of the punch rivet 1 is guaranteed with this shape. The production of the trilobular shape of the shaft 3 is very economical, since this shape is widely used in the cold forming technique, especially in the production of threads.

In a further embodiment, the punching rivet head 5 in FIG. 6 is shaped like a lense. With a mandrel 9, the closing head 6 is spread on the punch rivet 1. The Aufspreizvorgang allows forming the closing head with lower Um¬ forming forces. In this case, the mandrel 9 can also have a lateral surface which is formed by a generatrix which is formed by a section of an ellipse and has a steeper tip than a comparable cone tip. Such a tip engages aggressively on the front side of the shaft 3 and displaces the material more radially. Due to the elliptical shape of the surface of the tip of the mandrel 9 is deeper penetration into the shaft 3, the shaped closing head 6 pressed with a higher force to the thin plate 2. In a further embodiment according to FIG. 7, the shank 3 of the punch rivet 1 has an axial countersink 10 in the end face on the end facing away from the punch rivet head 5. Even a small countersink is sufficient to swell a closing head with a mandrel, which is spread outwards as in the case of the rivet connection according to FIG. 5.

In a further embodiment according to FIG. 8, the shank 3 has a punched edge 4 on the face side which forms an angle of approximately 90 degrees. The radius at the punched edge 4 plays a subordinate role and is within the range that is not critical for mass production. A grinding od. Like. The end face of the shaft 3 is therefore not necessary. At best, the properties can be further optimized by suitable heat treatment processes, such as case hardening or the like.

In a further embodiment according to FIG. 9, the shank 3 of the punch rivet 1 has a continuous axial bore 11. Depending on the choice of material, the manufacture of a blind hole can be more costly than a through hole. Also, a through hole can be used to save weight or material savings.

In a further embodiment according to FIG. 10, the punching rivet head 5 is provided with an internal thread 12. The punch rivet head 5 allows in this form any additional functions. Thus, it is conceivable that hooks, clip closures or the like can be screwed to the punched rivet 1 with a threaded bolt. Such or similar functions can also be provided directly on the punch rivet head 5. Instead of the internal thread, an external thread can be provided.

In a further embodiment, a punch rivet 1 is shown in FIG. 11, the shaft of which at least partially has a roughened surface 15 in the form of a knurling or the like. The punch rivet 1 is formed here without the punch rivet head 5. The punch rivet 1 of this type preferably has a roughened surface, since the position after stamping and before swaging is not fixed to a stop for a short time, as is possible, for example, by a punch rivet head. This punch rivet shape also requires that the rivet 1 during assembly must be provided from both sides with a closing head (not shown).

In a further embodiment according to FIG. 12, the shank 3 has a groove 13 in which the two punched thin plates 2 are clamped. After punching, the punch rivet 1 is fixed in the punched thin plates 2 in the groove 13. In this case, the groove 13 od also as a puncture. Like. Be configured. It is sufficient if the depth of the groove 13 is a few centimeters. Thus, the function is ensured and still prevents the punch rivet 1 wobble in the be¬ written position. On the attachment of the closing heads 6, the groove 13 has no negative influence. At best, it can be achieved that the punching rivet 1 is pressed radially in a form-fitting manner before forming the closing head 6 or the closing heads 6 on the punched edge of the two plates 2.

A rivet connection according to the invention is also fully functional when the punch rivet 1 is executed fully or tubular and without a punch rivet head 5. This simple cylindrical shape of the punch rivet 1 can be upset after punching with two closing heads 6. In a further embodiment according to FIG. 13, a closing head 6 is attached to each shaft end.

As a further embodiment, FIG. 14 shows a connection with a punch rivet 1, which has a closing head 6 on both sides, which has been shaped by spreading with a mandrel 9 or the like. In this case, the cylindrical or tubular punch rivet 1 can also be fixed in the punched hole by spreading on both ends of the punch rivet 1. The release of such a connection is only possible by Ab¬ separate one of the closing heads 6 or by drilling the punch rivet 1.

In the embodiments described above, it has been assumed that the punch rivet 1 and the thin plates 2 are made of the same high-strength material. However, it is also possible to produce the thin plates 2 and the punch rivet 1 from different high-strength materials. The materials only have to be suitable for being punched through or deformed at least in the region of the shank 3. The rivet connection can be configured appropriately be that the product of the ratio of tensile strength of the punch rivet 1 to tensile strength of the thin plates 2 and the ratio of diameter of the closing head 6 to diameter of the shaft 3 is at least approximately between 0.8 and 2.

It is also possible to design the riveted joint in such a way that a slug punched out of the punch hole formed during the penetration of the punch rivet 1 is fixed in the axial bore 11 at the penetration end of the punch rivet 1.

Claims

claims

1. Rivet connection of a workpiece, which comprises at least one thin plate (2), and a punch rivet (1) with a shank (3) and a closing head (6) formed on its penetration end after penetration of the thin plate (2). , characterized in that the thin plate (2) consists of a high strength material having a tensile strength of at least 560 N / mm ^2, and preferably of at least 800 N / mm ² , and that at least the shank (3) of the punch rivet (1) is approximately equal to has the same tensile strength as the thin plate (2).

2. rivet connection according to claim 1, characterized in that the punch rivet (1) has a circumferentially closed punching edge (4) whose length is dimensioned so that the carrying force F _{N of} the punch rivet (1) is greater than that for punching through the thin plate (2) necessary punching force F ₅ .

3. rivet connection according to claim 2, characterized in that the punching edge (4) on the end face of the shank (3) approximately forms an angle of 90 degrees.

4. Rivet connection according to one of claims 1 to 3, characterized gekennzeich¬ net, that the closing head (6) has a diameter (D) which is about as large as or larger than a at the other end of the shank (3) formed punch rivet head (5 ).

5. rivet connection according to claim 4, characterized in that the punching rivet head (5) in the punched thin plate (2) is recessed.

6. Rivet connection according to one of claims 1 to 5, characterized gekennzeich¬ net, that the punch rivet (1) consists of stainless steel.

7. Rivet connection according to one of claims 1 to 6, characterized gekennzeich¬ net, that the punch rivet (1) and the thin plate (2) consist of different materials.

8. rivet connection according to one of claims 1 to 7, characterized gekennzeich¬ net, that the shaft (3) has an axial countersink (11) at its penetration end.

9. Rivet connection according to one of claims 1 to 7, characterized gekennzeich¬ net, that the shaft (3) has at least at its penetration end an axial bore.

10. Rivet connection according to claim 9, characterized in that the axial bore (11) extends continuously over the length of the shank (3).

11. rivet connection according to one of claims 1 to 10, characterized gekenn¬ characterized in that the shaft (3) has axially extending notches (14), slots od. Like.

12. Rivet connection according to one of claims 1 to 11, characterized gekenn¬ characterized in that the shank (3) has a trilobular cross-section (8).

13. Rivet connection according to one of claims 1 to 11, characterized gekenn¬ characterized in that the shank (3) has an arbitrary non-circular cross-section (8).

14. rivet joint according to one of claims 1 to 13, characterized gekenn¬ characterized in that the product of the ratio of tensile strength of the punch rivet (1) to tensile strength of the thin plate (2) and the ratio of diameter of the closing head (6) to diameter of Shank (3) is at least approximately between 0.8 and 2.

15. rivet connection according to claim 9 or 10, characterized in that at the penetration of the punch rivet (1) from the punch hole thereby formed punched hole at the penetration end of the punch rivet (1) in the axial bore (11) is fixed.