WO2003013759A1

WO2003013759A1 - Method and device for producing a form-fit cold joining connection

Info

Publication number: WO2003013759A1
Application number: PCT/DE2002/002668
Authority: WO
Inventors: Dieter Mauer
Original assignee: Newfrey Llc
Priority date: 2001-07-20
Filing date: 2002-07-19
Publication date: 2003-02-20
Also published as: DE10135488A1

Abstract

The invention relates to a device for producing a form-fit cold joining connection between layers (4, 5) on work pieces, comprising a matrix (3) and a holding down element (1), between which the layers are disposed, and a die (2) that is axially guided in said holding down element (1). In order to produce a clamping force, the holding down element (1) is actuated by a liquid (10). The invention further relates to a device and to a method by which the viscosity and thus the flowing properties of the liquid (10) can be actively influenced so that the clamping force exerted on the layers (4, 5) by the holding down element (1) can be specifically varied.

Description

Method and device for producing a positive-fit cold joint connection

The subject of the invention is a method and a device for producing a positive cold-joint connection.

Especially in the automotive industry connections established, winning by cold joints are becoming increasingly important since they can form an alternative to the conventional ^welded joint. In particular in the case of material pairings that are difficult to weld due to the material, cold joint connections represent a more than suitable alternative. For example, in the cold joint process of punch riveting, the parts to be connected, for example metal sheets, are connected to a punch rivet from two sides without prepunching. In this case, the pre-punching of the joint parts required in a conventional riveting process is replaced by a corresponding cutting process caused by the self-piercing rivet itself.

In punch riveting, for example with a semi-hollow rivet, the sheet metal components to be connected are placed on a die. The sheet metal components are pressed against the die by a hold-down device and thus fixed. Then the semi-tubular rivet punches through the layers facing it and then this is plastically deformed in the lower, die-side layer to form a closing head with radial expansion, the shape of the closing head inevitably being essentially determined by the shape of the die. The material punched out of the upper layer fills the hollow rivet shank of the semi-hollow rivet and is thereby captively enclosed. In the following, the semi-tubular rivet is compressed, which leads to the closing head and the head being further developed of the semi-tubular rivet is essentially flush with the upper layer of the sheet metal components.

It is of crucial importance for a high-quality punch rivet connection with a semi-tubular rivet that the positioned parts are held firmly ^¬ so that the position of the components cannot change due to a post-flow movement that occurs during the punching process. Furthermore, it is important to make a joint-specific selection of the material and the geometry of the punch rivet based on the material-specific composition of the components to be connected.

For example, from WO 94/14554 a device with a holding-down device is known which can be moved via a piston-cylinder unit in such a way that the clamping force of the holding-down device, by means of which the layers are fixed on the die, counteracts End of the punch riveting process increases significantly. This ensures that there is no subsequent flow during punching. In addition, such a method for producing a punch rivet connection ensures that no annular depressions or distortions occur in the region of the head of the punch rivet.

A similar piston-cylinder unit for generating a necessary clamping force of the hold-down device is known from WO 93/24258. In this device, the generation of different clamping forces is achieved during the punch riveting process by means of a correspondingly varying pressure control.

In general, the mechanical properties of a punch rivet connection, in particular the strength behavior the punch rivet connection depending on the design of the closing head. The strength behavior is essentially influenced by the configuration of the area of the components between the head and the closing head of the punch rivet.

From the German published patent application DE 197 52 367 AI a method is also known by means of a device for producing a punch rivet connection, in which the clamping force exerted by the hold-down device during the punch riveting process corresponds to a predetermined course depending on at least one of the punch path and one derived from the punch path Characteristic size is varied. The variation takes place in such a manner that the clamping force is reduced at least to such an extent that movement of at least one layer of the sheet metal components towards the semi-hollow rivet is made possible. Using a hydraulic work fluid, controlled accordingly by a control device, hydraulic pressure is exerted on the hold-down device with a pressure curve that changes depending on the circumstances.

In practice, however, it has been found that such a device has the disadvantage that the damping effect of the hydraulic pressure can be controlled only in an extremely complicated manner, in particular via a proportional valve which is possibly very susceptible to faults. In addition, this device, which is known from the prior art, involves a large outlay on equipment, which is associated with increased costs.

Proceeding from this, the present invention is based on the object of developing the known method for producing a cold joint connection in such a way that precise and functionally reliable control of the clamping force with simultaneous production of such a Chen cold joint connection is guaranteed with a higher strength. Another object of the invention is to provide a device for carrying out such a method.

These objects are solved are gen by a device having the features of claim 1 and by a method having the features of claim 5. Advantageous Weiterbildun ^¬ subject of the respective dependent claims.

The device according to the invention for producing a cold joint connection is characterized in that during the joining process a clamping force exerted by a hold-down device on at least two layers of workpieces is varied in that the viscosity of a working fluid acting on the hold-down device and thereby its flow properties can be actively influenced.

According to the invention, an electro-rheological fluid is used as the working fluid in an embodiment of the device.

Electro-rheological liquids are dispersions of finely divided, electrically polarizable particles in hydrophobic, highly electrically insulating oils which, under the influence of an electric field with a sufficiently strong electric field strength, quickly and reversibly change their flow limit or their shear or shear modulus over several orders of magnitude , The electro-rheological fluid may change from a low viscosity to a plastic to almost a solid state. The response time is in the range of a few milliseconds. This makes it possible, for example, to provide an excellently actively controllable mechanism if such an electro-rheological fluid is within a Piston-cylinder unit is used, as is already known, for example, from German Offenlegungsschrift DE 197 35 898 AI. Of course, a change in viscosity is also associated with a corresponding change in the vaporization behavior of such a device.

In another embodiment of the device according to the invention, a so-called magneto-rheological fluid is used as the working fluid.

Magneto-rheological liquids are suspensions of finely divided magnetic particles with a particle size of a few mm to a few μm in suitable liquids, such as mineral or silicone oils, the solids content of the suspension typically being about 20 to 60% by volume. Magneto-rheological liquids change their flow resistance under the influence of a strong magnetic field depending on the magnetic field strength. Depending on the type, they reach shear stress values of up to 100 kPa.

The rheological properties of the respective fluids can thus be steplessly controlled via an electrical or magnetic field.

Due to the use of an electro-rheological fluid or a magneto-rheological fluid according to the invention instead of a hydraulic oil, a proportional valve in connection with a hydraulic oil is no longer required, which means that the pulsating impact effect of the oil pressure can also be excluded.

Further advantages associated with the use of such liquids are the possibility of direct activation by an electrical or magnetic signal that responds within a millisecond range. Furthermore, different properties can be set during the compression phase of the liquid on the one hand and the expansion phase of the liquid on the other hand, so that the properties can be varied accordingly in both phases. For example, such a targeted variation can cause the deep-drawn, die-side layer to flow radially into the die in order to form a desired thick-walled counter head.

When an electric or magnetic field is applied, these liquids also show a degressive behavior with regard to the damping force compared to a piston controlled by these liquids. Another advantage associated with the use of such liquids lies in the fact that the proportion of components to be moved mechanically, for example in a piston-cylinder unit, can be considerably reduced within a device making use of these liquids.

The device according to the invention has a, preferably cylindrical, piston which is arranged concentrically around the punch which forms the cold joint connection between the components. Like the plunger, this piston is guided in a hollow cylindrical hold-down device in which the electro-rheological or magneto-rheological fluid is received.

The piston separates two liquid chambers which, according to the invention, are connected by at least one, preferably annular, traversing channel for guiding the respective liquid during the axial movement of the piston within the housing of the hold-down device. In one embodiment of the invention, in the case of using an electro-rheological liquid in the region of the channel walls, electrodes which are insulated from one another are arranged for applying an electrical high voltage to be varied in a targeted manner.

Similarly, if a magneto-rheological fluid is used in the vicinity of the channel, at least one magnetic coil is provided to generate a magnetic field that can be varied in a targeted manner.

In a further advantageous embodiment of the invention, such magnetic coils can also be arranged outside the piston, preferably in the housing wall of the hold-down device.

According to the invention, the electrical signal or the magnetic signal for the targeted influencing of the flow properties of the respective liquids is generated in a corresponding manner via a control device, the control taking place as a function of the relative position of the plunger and the hold-down device. Depending on the level of the voltage at the electrodes or at the magnetic coil, the viscosity of the respective type of liquid and thus its flow through the channel when the piston is displaced relative to the hold-down device is specifically adjusted. In other words, the electrical or magnetic field generated by the high voltage in the channel increases the viscosity of the electro- or magneto-rheological fluid within the channel in such a way that, against the flow resistance caused thereby, only a fraction of that when moving away the amount of liquid required by the piston can pass through the channel. This increases the pressure in the lower liquid chamber and thus the pressure exerted on the hold-down by the piston, which acts as a clamp. transferred force to the layers of the components to be connected.

Since the viscosity of both forms of liquid can be continuously and specifically adjusted, the clamping force exerted by the hold-down device can thus be continuously and specifically influenced according to the invention.

In a further development of the invention, the method that can be carried out by the device according to the invention is characterized in that the course of the clamping force during the cold joining process is varied according to a predetermined course depending on the stamp path or advantageously a characteristic quantity derived from the stamp path. For example, the acceleration and / or the speed of the stamp can be used as parameters here. When using a joint element, for example when using the device for punch riveting, the stamp path in turn corresponds absolutely to the path covered in the layers or the penetration depth of the joint element.

According to the invention, several different program profiles for controlling or for calling up possible variation courses are stored in the control device. For example, a call can be made by comparing, preferably in real time, the stamp path and the pressure prevailing in the liquid with predetermined values.

In order to rule out the undesired afterflow effect, the course of the variation according to the invention can also take place in terms of control technology as a function of the workpiece properties of the layers of components to be joined together and / or the workpiece properties and / or the shape of the joint element. The device and the method which can be carried out according to the invention for producing a cold joint connection can not only be limited to the cold joint process of punch riveting, but also allow use in the connecting method of so-called clinching through several layers of workpieces which does not require a joint element and which are punched through the layers and clamped to one another via the flow of the punched-through material areas that occurs.

Further features and advantages of the method and the device result from the description of several exemplary embodiments shown in the drawings. Show it:

Figure 1 shows schematically and in section a first embodiment of the inventive device for producing a punch rivet connection.

2 shows schematically and in section a second embodiment of the device according to the invention for producing a punch rivet connection;

3 schematically and in section a third embodiment of the device according to the invention for producing a punch rivet connection; and

Fig. 4 shows schematically and in section a fourth embodiment of the device according to the invention for producing a clinching connection.

In the figures, identical components are shown with the same reference numerals. Figure 1 shows schematically a section through a device for producing a punch rivet connection.

The device has a hold-down device 1, a punch 2 and a die 3. The hold-down device 1 can be moved toward and away from the die 3.

Two layers 4, 5 of components are arranged between the die 3 and the holding-down device 1. These layers 4, 5 are clamped between the hold-down device 1 and the die 3. The punch 2 is actuated by a device F, not shown, with a force F and thus drives a schematically illustrated punch rivet 6 through the layers 4, 5 of the workpieces for their connection.

The hold-down device 1 is in one piece and cylindrical and surrounds the punch 2 so that it is guided axially.

A piston 7, which surrounds the punch 2 concentrically, is also guided axially in the cylindrical housing of the hold-down 1. The piston 7 separates two liquid chambers 8 and 9, each of which contains an electro-rheological liquid 10.

A second piston 11, which is freely movable around the plunger 2 m in the longitudinal direction thereof, delimits the upper liquid chamber 9 and thus forms a compensation chamber 12 filled with a gas.

The piston is penetrated by an annular channel 13 which connects the two liquid chambers 8 and 9 to one another, so that the electro-rheological liquid 10 can flow between these liquid chambers 8 and 9. The channel walls of the channel 13 are formed by high-voltage electrodes 14 and 15, which are spaced apart from one another by non-illustrated, non-conductive webs. The high-voltage electrodes 14 and 15 are embedded in the piston 7 in insulators 16 and 17, respectively.

The high-voltage electrode 14 is supplied with the necessary current via a power line 18, which runs inside the stamp 2.

The power line 18 is connected to a control device 19. This control device 19 is again informed from a measuring device 20 via the positional state of the slide 2 so that its linear motion with regard to the prevailing clamping force and the penetration ^¬ or moving speed of the punch rivet 6 can be controlled.

In the operation of the device according to the invention, the plunger 2 moves the piston downward within the hold-down device 1 as long as no high voltage is applied to the high-voltage electrodes 14 and 15, because at this point in time the viscosity of the electro-rheological liquid 10 flows freely through the annular channel 13 in the piston 7.

If the device now comes into contact with the upper layer 4 of the two layers 4, 5, a high voltage is applied to the high-voltage electrodes 14 and 15 within a millisecond range. As a result, the viscosity of the electro-rheological fluid 10 changes suddenly, so that it is no longer sufficiently flowable and consequently the piston 7 can no longer be displaced by the annular channel 13 m. This increases the compression in the lower liquid chamber 8, so that a force is transmitted to the hold-down device 1 and thereby increasing the clamping force on the two layers 4, 5 in a corresponding manner.

2 shows a further embodiment of the device according to the invention, in which a magneto-rheological liquid 21 is used instead of an electro-rheological liquid.

The magneto-rheological fluid 21 is controlled via a magnetic field in order to influence its viscosity in a targeted manner. Accordingly, magnetic coils are used instead of high-voltage electrodes.

In the embodiment shown in FIG. 2, a magnet coil 22 as the one pole and a magnet coil 23 as the other pole are integrated in the wall of the hold-down device 1, all the way around it. The magnet coils 22 and 23 are located essentially at the height of the piston 7. A power line 24 supplies the magnet coils 22 and 23 with a current to be varied accordingly by the control device 19, on the basis of which the generated magnetic field also varies and thus the viscosity of the magneto-rheological fluid 21 actively influenced.

In the embodiment shown in FIG. 3, the magnet coils 22 and 23 are arranged inside the piston 7 and form the channel wall there, the power line 24 then being routed again inside the stamp 2.

The devices according to the invention, as shown in FIGS. 1 to 3, can also be used for the method of clinching, in which the layers 4 and 5 are "punched" together directly by the punch 2 without using a joint element. Fig. 4 shows this exemplarily for the device already described in connection with FIG. 1.

According to the invention, the supply of the high-voltage electrodes 14 and 15 or the magnetic coils 22 and 23 with voltages in the range of a few milliseconds can be varied, so that the clamping force exerted by the hold-down device 1 can also be varied inevitably.

Reference character list:

1 hold-down device

2 stamps

3 die

4, 5 layers of components

6 punch rivet

7 pistons

8 Lower liquid chamber

9 Upper liquid chamber

10 electro-rheological fluid

11 2nd piston

12 compensation chambers

13 Annular channel

14 high voltage electrode

15 high voltage electrode

16 isolator

17 isolator

18 power line

19 control device

20 measuring device

21 Magneto-rheological fluid

22 solenoid

23 solenoid

24 power line

Claims

Expectations

1. Device for producing a form-fitting cold joint connection between layers of workpieces with a die and a hollow cylindrical hold-down device, which presses the layers against the die, and with a punch which is guided coaxially in the hold-down device and passes through it and which holds a piston axially guided in the hold-down device carries a fixed connection, the piston in the hold-down device separating two liquid chambers which are each filled with a working fluid, delimited by a bottom and closed off, and are connected by a channel which is adjustable in terms of its permeability by means of a control device, characterized in that the Arbeitsflussigkeit an electro-rheolo ^¬ cal liquid (10), and that the channel (13) passes through the piston (7) to whose leadership, wherein opposite channel walls mutually insulated high-voltage electrodes (14,15) form, which has a in the die (2) axially guided supply line (18) from the control device (19) are supplied with an electrical voltage which can be set by the control device (19) depending on the relative position of the punch (2) and hold-down device (1) and, depending on the magnitude of the voltage, the viscosity of the electro-rheological Liquid (10) and thus its flow through the channel (13) when the piston (7) is displaced relative to the hold-down device (1).

2. Device for producing a form-fitting cold joint connection between layers of workpieces with a die and a hollow cylindrical hold-down device, which presses the layers against the die, and with a die that is guided coaxially in the hold-down device and that - solve

sen penetrating punch, which carries a piston axially guided in the hold-down device in a fixed connection, the piston in the hold-down device separating two liquid chambers, each filled with a working fluid and delimited by a base, which is permeable by means of a Control device adjustable channel are connected, characterized in that the working fluid is a magneto-rheological liquid (21) and that the channel (13) passes through the piston (7), the channel (13) by a solenoid (22, 23) is enclosed, which is supplied via a supply line (24) from the control device (19) with an electrical voltage from the control device

(19) depending on the relative position of the stamp

(2) and hold-down device (1) is adjustable and in

Depending on the magnitude of the voltage, the viscosity of the magneto-rheological liquid (21) and thus its flow through the channel (13) is adjusted when the piston (2) is moved relative to the hold-down device (1).

3. Apparatus according to claim 2, characterized in that the magnet coil (22, 23) is arranged in the cylindrical region of the hold-down device (1) and the feed line (24) from the outside via the wall of the hold-down device (1) to the magnet coil (22, 23) is performed.

4. The device according to claim 2, characterized in that the magnet coil (22, 23) is arranged in the piston (7) and the feed line (24) is guided axially in the stamp (2).

5. Process for producing a form-fitting cold joint connection between layers of workpieces, in particular with a device according to claim 1 or 2, in which at least two layers of workpieces are printed against the die by a hold-down device which can be controlled via a working fluid and between which a positive cold-joint connection is formed by means of a stamp guided axially in the hold-down device, wah ^¬ During the cold joint, a clamping force exerted by the hold-down device on the two layers is varied, characterized in that the variation takes place via a targeted adjustment of the viscosity of the working fluid (10, 21) and thus of its flow ^behavior .

6. The method according to claim 5, characterized in that the variation takes place according to a predetermined course depending on a stamp path or a derived from the stamp path characteristic, in particular ^¬ such as the acceleration and / or the speed of the stamp (2).

7. The method according to claim 5 or 6, characterized in that the stamp (2) a joint element (6), in particular a punch rivet, in the layers (4,5) prints.

8. The method according to claim 5 or 6, characterized in that the stamp (2) by means of clinching the layers (4,5) clamped together.

9. The method according to claim 7 or 8, characterized in that the stamp path and the pressure prevailing in the work flow are measured, compared with a stored profile for the variation and this is called up in real time.

0. The method according to claim 9, characterized in that the course is determined depending on the workpiece properties of the layers (4,5) and / or the joint element (6).