Clamping device and joining method with clamping device

Abstract

A joining method for joining at least two workpieces using a joining device (10) for joining workpieces, the joining device comprising a joining head having: - a holding device (14) for joining elements (20) such that the joining elements can be guided along or arranged on the joining axis (X); - a punch (16) such that installation movement of the joining elements can be performed, the punch being movable along the joining axis by a first drive unit (18); and - a clamping device (22) such that one or more workpieces are pressed in the joining direction, wherein the clamping device (22) is movable by a second drive unit (24) different from the first drive unit (18).

Description

Technical Field

[0001] This disclosure relates to a joining device, and more particularly to a joining device suitable for joining workpiece assemblies (e.g., at least two sheets or workpieces stacked vertically) together using joining elements without requiring one or more pre-formed holes (e.g., pre-drilled holes or pre-punched holes) to be formed on the parts prior to joining, the joining device including a clamping device. The invention also relates to a joining procedure for workpiece assemblies. Background Technology

[0002] The above-mentioned joining methods and joining devices are well known, especially in fields such as stamping riveting or direct screwing, for example, in automotive engineering.

[0003] A joining device with a punch and clamping mechanism is known to be used in mechanical joining processes. The punch enables setting movements. The clamping mechanism ensures several functions, such as pressing the components of the workpiece assembly together to avoid any gaps between the workpieces, thereby preventing or affecting possible adhesive displacement between the workpieces and reducing workpiece deformation during the joining process.

[0004] Document DE102005031917A1 discloses a joining method in which, in the first step, the main piston and clamping device press against the workpiece with a relatively small force, so that the workpieces maintain fixed contact with each other and with the die.

[0005] Document CH689299 discloses a coupling device including a clamping mechanism having a probe for checking the position of a rivet or workpiece.

[0006] Document DE102017106449 discloses, for example, a coupling device with a hydraulic system, comprising: a punch capable of performing linear, non-rotational mounting movements; a clamping device capable of clamping one or more components along the coupling direction; and a drive unit that operates in at least two steps, by which the punch and clamping device are movable via a motor and several gearboxes.

[0007] DE102012019809A1 discloses a method for stamping and riveting two sheets, which are stacked one on top of the other on the base of a stamping and riveting device, with an adhesive introduced between the two sheets. The joining device for performing the method includes a C-shaped frame with a die, a punch, and a clamping device. An electric motor is arranged to drive the punch and the clamping device.

[0008] JP2007203307 discloses a joining device including a punch and a holding device, the holding device having a clamping shaft adapted to apply a clamping force to the materials to be joined. A servo motor controls the movement of the punch. In addition to a servo motor, a cylinder or a hydraulic cylinder can also be used as the moving mechanism for moving the clamping shaft.

[0009] DE102016007332A1 and DE10319411 disclose an installation tool having a receiver (or retaining device) adapted to apply a clamping force to the workpiece to be engaged.

[0010] DE19905527A1 discloses a joining device having a punch and a clamping device. To join a workpiece, the piston-cylinder unit of the clamping device is first actuated until the nozzle rests against the upper side of the workpiece, and the workpiece is pressed against the die with a controllable force. During adjustment movement, a slider drives the entire joining tool downwards, so that the piston-cylinder unit of the joining tool only needs to perform the remaining feed and joining movements.

[0011] Known mechanical joining processes typically employ spring-loaded hydraulic or pneumatic clamping devices. The clamping force curve of the clamping device is estimated considering the characteristics of the spring, or is a constant of the hydraulic and pneumatic system. The total force applied to the workpiece assembly by the joining device is formed by the superposition of the clamping force and the force generated by the punch. For joining devices that allow for a single-sided joining process, the total force acts on the robot supporting the joining device and / or the workpiece assembly, resulting in the need for robust, bulky, and space-consuming equipment. For double-sided joining, the total force causes the frame used to bend. For example, in self-piercing riveting (as an illustrative example only), the total force causes the C-shaped frame used to bend. This bending causes lateral and angular misalignment and affects the joint quality. Larger robots or equipment that avoid these drawbacks are expensive, space-consuming, and less flexible. Summary of the Invention

[0012] Therefore, one object of the present invention is to provide a flexible and compact joining device, and a joining method that can better control and thus more effectively perform the joining process.

[0013] Accordingly, the present invention provides a joining device and a joining method. More specifically, the joining device for joining workpieces includes a joining head having:

[0014] - A retaining device for the engaging element, which enables the engaging element to be guided along the engaging axis or arranged on the engaging axis.

[0015] - A punch, which enables the installation movement of the engaging element to be performed, and the punch can be driven by a first drive unit to move along the engaging axis.

[0016] - A clamping device that utilizes the force of pressing one or more workpieces together in the engagement direction.

[0017] The clamping device can be moved by a second drive unit that is different from the first drive unit.

[0018] Adding a second drive unit to control the clamping device allows for independent or punch-based control. The second drive unit can be controlled independently of the first drive unit. The clamping device can be controlled and / or monitored in terms of force and / or displacement, and time delays are possible. The clamping device can apply different clamping forces or displacements to the workpiece during the mounting step of installing the engagement element using the punch. The clamping device can ultimately be rigidly attached to the second drive unit (without stiffness reduction measures such as springs or dampers), and therefore precise displacement or force can be applied without correction measures. Adding another drive unit to the engagement device has always been considered a problem because it increases the weight of the device and complicates control commands. However, in the current case, when a dedicated drive unit is connected to the clamping device, space requirements, price, and the weight of the holding components supporting the engagement device are reduced. In fact, because the second drive unit is connected to the clamping device, the size of the holding components of the engagement device (robot arms, etc.) can be reduced without compromising the performance of the engagement device. Furthermore, engagement time can be shortened due to the more flexible movement of the punch and clamping device during the mounting step. Finally, this coupling device with independently controlled clamping mechanism can be used to join several different materials and workpieces, especially brittle casting materials.

[0019] In one embodiment, the second drive unit is a servo electric drive with a spindle. Servo electric drives are lightweight and easy to control. No hydraulic or pneumatic connection is required. In another embodiment, the first drive unit is a servo electric drive with a spindle. Alternatively, the first and / or second drive units can also be hydraulic and / or pneumatic and / or electric drive units. Linear or rotary drive units are also considered.

[0020] In this embodiment, the second drive unit moves the clamping device along a clamping axis that is parallel to but does not coincide with the engagement axis. In other words, the clamping axis extends parallel to the engagement axis at a non-zero distance. This improves the movement flexibility of the clamping device relative to the holding mechanism of the punch. The clamping force is still applied at or near the engagement point.

[0021] In one embodiment, the second drive unit is oriented at an angle relative to the first drive unit, the angle being between 0 and 90 degrees. This improves the compactness or space requirements of the engagement device.

[0022] In one embodiment, the heating device is arranged on the clamping device and moves together with it. In another embodiment, the heating device may be a plasma torch or laser heating system, as well as an induction heating system, an electric arc, or similar equipment. Therefore, the joining device can be used to perform heat-assisted joining processes, such as plasma joining or joining processes utilizing plasma cleaning. The presence of an independently controlled clamping device is advantageous for such a heating device. In fact, the precise force applied to the workpiece can be controlled, and therefore, the heat transfer between the workpieces caused by the heating device can be easily controlled or adjusted. More specifically, the clamping device allows the workpiece to be clamped during the use of the heating device and before the retaining device (also called the receiver) contacts the workpiece. Therefore, the heating device does not damage the front end of the retaining device (or receiver), but heat treatment can still be achieved in a controlled manner using the correct clamping force applied to the workpiece, even before the retaining device has contacted the workpiece.

[0023] In this embodiment, the clamping device includes a surface detection unit adapted to detect the surface of the workpiece. Therefore, the clamping device performs several functions. Surface detection can be performed with or without contact. For example, laser distance measurement can be implemented, or inductive or capacitive sensors can be used. Mechanical contact measurement can also be implemented. Surface detection of the workpiece can help determine optimal engagement parameters (displacement, etc.) during the installation process, or ultimately detect potential errors (absence of the workpiece).

[0024] In this embodiment, the engagement device is adapted to measure temperature. It is noteworthy that the engagement device is adapted to measure the temperature of the workpiece with or without contact.

[0025] In one embodiment, the clamping device includes a hollow cylindrical clamp adapted to be arranged around the punch and retaining device. Therefore, the clamping device does not interfere with the punch or retaining device, but acts directly on the area of ​​the workpiece to be joined. In an alternative embodiment, the clamping device includes a clamp having a C-shaped or U-shaped cross-section. For example, the clamping device or clamp is two-part, with a first part having a C-shaped or U-shaped cross-section and a second part being cylindrical and hollow. The first part is adapted to face the workpiece assembly. The second part is adapted to connect to the remainder of the joining device.

[0026] In this embodiment, the outer diameter of the clamp is between 10 mm and 30 mm. This allows for precise clamping of the designated area without interfering with the punch or retaining device. Alternatively, the clamping device may have a C-shaped, U-shaped, annular shape with holes or slots arranged at different angles, or a parallelepiped or composed of two or more parallelepipeds. In other embodiments, clamping pins or rods may be used. For example, one, two, three, or more clamping pins may be used. The shape of the clamp may vary along its length. For example, three or more pins may be connected to a ring.

[0027] In one embodiment, the engagement device includes a load measurement system. For example, the load measurement system is a load sensor. The load measurement system may be integrated within the engagement device, or more specifically, within the clamping device (internal system), or it may be located externally. The load sensor measures the clamping force, thus enabling precise control and command of the clamping force profile. In another embodiment, clamping force measurement can be achieved via motor current or a central load sensor mounted on the engagement and clamping axes. The punch may also include its own load measurement system.

[0028] The present invention also relates to a joining method for joining at least two workpieces using a joining device, comprising the following steps:

[0029] - Provides a workpiece device including an upper workpiece surface and a lower workpiece surface.

[0030] - Provide a joining device as described above, which is arranged at a non-zero distance above the workpiece device.

[0031] - Move the clamping device along the clamping axis until the clamping device contacts the surface of the workpiece.

[0032] - Apply the first predetermined clamping force

[0033] - Apply a second predetermined clamping force

[0034] - The engaging element is moved into the workpiece device by moving the punch along the mounting device, thereby mounting the engaging element in the workpiece device.

[0035] This method allows for better control of the joining process. For example, the clamping device can apply a high, predetermined first clamping force to the workpieces to close any gaps that may exist between them, or to optimize heat transfer between the first and second workpieces during a heat-assisted joining process. Due to the design of the two axes (clamping axis and joining axis), the clamping force can therefore be reduced (or even eliminated) as needed by the installation force, or replaced by the installation force. The clamping force and installation force can be freely set according to the process parameters, the materials to be joined, and the joining elements.

[0036] In one embodiment, the clamping device includes a sensor unit that provides force, displacement, and time data. In another embodiment, clamping force curves and clamping device displacement curves and / or clamping force curves and engagement element displacement curves and / or clamping force and time curves are recorded. Therefore, all data or values ​​related to force or displacement can be evaluated. This data can be used by the control unit to determine optimal engagement parameters. Attached Figure Description

[0037] A better understanding of the invention and its advantages can be achieved by reading the following description, which is given by way of example only and with reference to the accompanying drawings, in which:

[0038] Figure 1 A perspective view of an engagement device according to the present invention, comprising a clamping drive, a punch, and a retaining device, is shown.

[0039] Figure 2A and Figure 2B A perspective view of a cylindrical clamp included in a clamping device of a coupling device according to the invention is shown;

[0040] Figure 3 A cross-sectional view of the front end of the coupling device according to the present invention is shown;

[0041] Figures 4A to 4G Different possible steps of the joining process according to the present invention are shown, wherein the clamping force curve corresponding to each step is shown;

[0042] Figures 5A to 5G Different possible embodiments of the clamping device of the coupling device according to the present invention are shown in cross section. Detailed Implementation

[0043] Embodiments of this disclosure will be best understood by referring to the accompanying drawings, in which like reference numerals indicate like or similar elements. It will be readily understood that the components of the embodiments of this disclosure generally described and illustrated in the accompanying drawings may also be arranged and designed in various different configurations. Therefore, the following detailed description of embodiments of the systems and methods of this disclosure is not intended to limit the scope of the claimed disclosure, but merely represents possible embodiments of this disclosure.

[0044] Figure 1 A perspective view of the joining device 10 is shown. The joining device 10 is adapted to perform a method of joining a workpiece assembly W, comprising at least first and second workpieces W1, W2 (or sheets) stacked vertically, together with joining elements. The joining device includes a joining head 12, which is freely movable in space by a robot (not shown). Finally, as an alternative, the joining device can be fixed to a structure, and the workpieces to be joined can be moved toward the joining device when needed. The joining head 12 is, for example, mounted on an arm of a robot. The joining device 10 or the joining head 12 includes a holding device 14, a punch 16, and a first drive unit 18. The holding device 14, the punch 16, and the first drive unit 18 are arranged longitudinally along the joining axis X.

[0045] The retaining device 14 is adapted to retain the engaging element 20. The engaging element 20 may be, for example, a pin, screw, rivet, etc. More specifically, the engaging element 20 may be similar to or substantially similar to the engaging element described in the applicant's EP22165638.2 of this application. The retaining device 14 guides or arranges the engaging element 20 along the engagement axis X. The punch 16 is adapted to drive or actuate the engaging element 20 toward the workpiece device W for engagement. Both the retaining device 14 and the punch 16 may be arranged coaxially with the engagement axis X. The punch 16 may be adapted to penetrate the retaining device 14 to push the engaging element 20 toward and into the workpiece device W. The punch 16 allows the engaging element 20 to be moved during installation. Notably, the punch 16 allows for linear installation movement. The punch 16 is movable along the engagement axis X by a first drive unit 18. The first drive unit 18 is an operating module including a motor, particularly a servo motor, or a servo drive adapted to move to a specific position, speed, or torque based on input signals from a controller. The first drive unit 18 controls the punch 16 along the engagement axis X. In other embodiments, the first drive unit 18 may also be a hydraulic and / or pneumatic and / or electric drive unit. Linear or rotary drive units may also be considered.

[0046] The joining device 10 also includes a clamping device 22 adapted to compress or clamp the workpiece device along the joining direction. The clamping device 22 is movable and controlled by a second drive unit 24. The second drive unit 24 differs from the first drive unit 18. For example, the power of the second drive unit may be lower than that of the first drive unit 18. In other embodiments, the second drive unit and the first drive unit may be similar drive units with similar power, depending on the joining process. The second drive unit 24 includes a servo electric driver, thus the clamping device 22 is controlled by its own servo electric driver. In possible alternative embodiments, the second drive unit 24 may also be a hydraulic and / or pneumatic and / or electric drive unit. Linear or rotary drive units are also contemplated. The second drive unit 24 moves and controls the clamping device 22 along the clamping axis Y. In a first embodiment, the clamping axis Y may be parallel to the joining axis X, but extends a non-zero distance from the joining axis. In a second embodiment, the clamping axis Y may be coaxial with the joining axis (in which case, for example, the first and second drive units may be stacked on top of each other, or arranged concentrically with each other, for example, using hollow motors). The first drive unit can be arranged at a 24-degree angle relative to the second drive unit. This angle can be between 0 and 90 degrees. In an embodiment, the clamping device can be driven by its own robot. In this case, commands can be sent from control commands to the robot controlling the clamping device. The robot executes commands and performs the clamping process independently of the engagement device and the rest of the installation equipment. The installation process using the first drive and the punch can then begin (e.g., the robot can send a signal to start the installation process, or the integrated system can automatically send commands to initiate the installation process of the engagement element). The installation and clamping steps can also occur simultaneously.

[0047] The control commands can control the first drive unit 18 and the second drive unit 24 independently and / or in relation to each other, according to the requirements of the engagement process.

[0048] The clamping device 22 may include a clamp 26. For example... Figures 5A to 5G As shown, clamps of different shapes are possible. For example, such as Figure 5C As shown (same as above) Figure 2A and Figure 2B As shown), the clamp 26 may have a portion forming a U-shape in the cross-sectional view. The outer diameter of the clamp is between 10 mm and 30 mm. The clamp 26 defines a recess, and the engaging element 20 is adapted to move within the recess for mounting. More specifically, at least a portion of the punch 16 and the retaining device 14 can be guided within the recess. Figure 2A and Figure 2B As shown, the clamping device or fixture consists of two parts. The first part has a C-shaped or U-shaped cross-section, and the second part is directly connected to the first part and is cylindrical and hollow. Figure 5AAs shown, the clamp can also be a hollow cylindrical clamp 26'. In another embodiment, the clamp 26'' can be C-shaped in cross-sectional view, such as... Figure 5B As shown. The fixture 26''' can also be bent in the cross-sectional view, as... Figure 5D As shown, or as Figure 5E 26 clamps （4） The diagram shows two curved portions defining a recess. In another embodiment, the pin may also... Figure 5F The clamp 26 shown （5） or Figure 5G The two straight columns shown are 26 （6） The implementation defines an area within which the engagement element 20 can be moved and is set by the punch.

[0049] Fixtures 26, 26', 26''', 26 （4） 26 （5） 26 （6） Extending longitudinally along the engagement axis X between the first end 28 and the second end 30. A chamfer may be provided at the first end 28. The first end 28 includes a contact surface 32 adapted to contact the workpiece device W. Fixtures 26, 26', 26'', 26''', 26 （4） 26 （5） 26 （6） A window 34 may be included on its lateral side. An attachment portion 38 is arranged on the second end 30 for attaching the hollow cylindrical clamp 26 to the remainder of the clamping device 22.

[0050] exist Figures 5A to 5G In all embodiments, the attachment portion 38 extends from the clamps 26, 26', 26'', 26''', 26 （4） 26 （5） 26 （6） Extending to the rest of the clamping device. For example... Figure 3 As better illustrated, the attachment portion may extend at least partially parallel to the engagement axis X at a non-zero distance from the outer surface of the clamp to avoid any interference with the punch or retaining device.

[0051] The clamping device 22 may include a surface detection unit 40 adapted to detect the upper surface of the workpiece device W. The surface detection unit 40 may include a laser, a capacitive or inductive sensor, or any other non-contact proximity sensor adapted to non-contactly measure the distance to the workpiece. Alternatively, the surface detection unit 40 may include means for mechanical or contact measurement to perform tactile surface identification. Surface detection may be performed with or without additional components.

[0052] The clamping device 22 may include a load measuring system or an integrated load sensor 54 suitable for directly measuring the clamping force F applied by the clamping device 22 to the workpiece device W. The load measuring system 54 will measure the clamping force and send it to the control unit to monitor and / or control the proper implementation of the installation steps (which will be better described below).

[0053] The clamping device 22 includes a recess or portion adapted to receive the heating device 56 or to directly connect the heating device 56 to the clamping device. In other words, the heating device is arranged on the clamping device. The heating device 56 is, for example, a plasma torch. The plasma torch provides thermal assistance to the bonding process. The applicant's patent publication EP3515632A1 explains, for example, how a plasma torch can assist in the bonding process. In other embodiments, the heating device may be a laser heating system and an induction heating system, an electric arc, or a similar device.

[0054] Figures 4A to 4G Different possible steps of the joining method according to the present invention are shown. The clamping force (F) versus time (t) curves are associated with schematic diagrams of each process step.

[0055] First step, such as Figure 4A As shown, the joining device 10 (e.g., by the robot described above) is positioned above the workpiece assembly W. The joining device 10 does not contact the workpiece assembly W. The workpiece assembly includes at least two workpieces (or sheets) W1, W2 stacked vertically. In other embodiments, more than two workpieces may be used. The workpieces may be made of high-strength materials or brittle cast or extruded materials. Optionally, an adhesive may be provided between the two workpieces.

[0056] The second step is to move the clamping device 22 toward the workpiece device W until the clamping device contacts the upper surface of the workpiece device (see [link]). Figure 4B The upper surface can be identified by the surface detection unit 40 described above. The surface detection unit 40 can be implemented through a function integrated into existing components, or it can be an additional component. For example, a resistance signal can be sent to a controller to determine the contact with the upper surface of the workpiece. If the bonding process is, for example, thermally assisted by a plasma torch 56, the plasma torch 56 can heat the workpiece assembly, such as... Figure 4B It is shown schematically.

[0057] The gap between the workpieces (not shown) can be detected by the clamping device 22 by analyzing the force / time or force / displacement curves of the clamping device, particularly by a load measurement system or load sensor. If a gap is detected, the clamping device 22 is controlled by the control unit to close the gap by applying, for example, a larger clamping force (see, for example, [link to relevant documentation]). Figure 4C In an alternative embodiment, this gap may also have been closed by an initial predetermined clamping force. Therefore, any adhesive remaining in the gap will be displaced to the side.

[0058] Then, to the workpiece device W (see...) Figure 4D Apply a first predetermined clamping force F1. Figure 4D In the figure, the clamping force versus time curve shows a fairly important first predetermined clamping force F1. In the case of heat-assisted joining processes, a large clamping force may be advantageous for allowing heat transfer between the first workpiece and at least the second workpiece. In another alternative, the clamping force can be kept very limited to avoid or restrict heat transfer between the two workpieces.

[0059] exist Figure 4E During the installation process, the clamping force F is reduced to prevent heat transfer to the lower workpiece. Excess heat is generated in the upper workpiece compared to the lower workpiece. The heat flow between the workpieces can be specifically controlled by changing the clamping force during installation. For example, when the clamping force is reduced, the total force (including the clamping force and the installation force) is reduced. When the clamping force is reduced during the heat-assisted joining process, the upper workpiece can be heated, and the heat transfer from the upper workpiece to the lower workpiece is reduced, causing a localized reduction in the material's strength or flow stress, for example, in the case where the upper workpiece is made of high-strength steel, thereby allowing for a reduction in the installation force as well.

[0060] exist Figure 4F During the installation step, the clamping force F reaches a second predetermined clamping force F2 corresponding to the installation step. Once the clamping force reaches the second predetermined value, the engaging element 20 can be installed in the workpiece device W by means of the punch 16. The engaging element 20 can also be pre-installed. A defined installation force presses the engaging element 20 through at least two workpieces W1, W2. The force applied to the engaging device during the installation step corresponds to the superposition of the installation force and the clamping force. The clamping force during the installation step can be controlled at a low or high level depending on the installation parameters. It should be noted that the installation force can also be reduced by a heating device, as described in more detail in EP3515632A1.

[0061] In the final step, move the clamping device 22 back to the retracted position (see...). Figure 4G By recording force / displacement or force / time curves, conclusions can be drawn about the potential springback of the workpiece after installation.

[0062] Connecting device 10

[0063] Workpiece device W

[0064] First workpiece W1 and second workpiece W2

[0065] Connector 12

[0066] Holding device 14

[0067] Punch 16

[0068] First drive unit 18

[0069] Joining axis X

[0070] Connecting element 20

[0071] Clamping device 22

[0072] Second drive unit 24

[0073] Clamping axis Y

[0074] Fixtures 26, 26', 26'', 26''', 26 （4） 26 （5） 26 （6）

[0075] First end 28

[0076] Second end 30

[0077] Contact surface 32

[0078] Window 34

[0079] Appendix 38

[0080] Surface detection unit 40

[0081] Sensor unit 42 (temperature)

[0082] Load measurement system or load sensor 54

[0083] Clamping force F

[0084] Heat device 56

[0085] First predetermined clamping force F1

[0086] Second predetermined clamping force F2

Claims

1. A joining device (10) for joining workpieces, the joining device comprising a joining head having: - A retaining device (14) for the engaging element (20), which enables the engaging element to be guided along the engaging axis (X) or arranged on the engaging axis (X); - A punch (16) that enables the installation movement of the engagement element to be performed, the punch being movable along the engagement axis by a first drive unit (18); and - Clamping device (22), which allows one or more workpieces to be pressed in the engagement direction; Its features are, The clamping device (22) can be moved by the second drive unit (24).

2. The coupling device (10) according to claim 1, wherein, The second drive unit (24) is a servo electric drive with a spindle.

3. The coupling device (10) according to claim 1 or 2, wherein, The second drive unit (24) causes the clamping device (22) to move along the clamping axis (Y), which is parallel to the engagement axis (X) but does not merge with the engagement axis (X).

4. The coupling device (10) according to claim 1 or 2, wherein, The second drive unit (24) is oriented at an angle between 0 degrees and 90 degrees relative to the first drive unit (18).

5. The coupling device (10) according to any one of the preceding claims, wherein, The heating device (56) is arranged on the clamping device and moves together with the clamping device.

6. The coupling device (10) according to any one of the preceding claims, wherein, The heating device is a plasma torch.

7. The coupling device (10) according to any one of the preceding claims, wherein, The clamping device includes a surface detection unit (40) adapted to detect the surface of the workpiece.

8. The coupling device (10) according to any one of the preceding claims, wherein, The first drive unit is a servo electric drive with a spindle.

9. The coupling device (10) according to any one of the preceding claims, wherein, The clamping device includes a clamp (26) having a U-shaped cross-section perpendicular to the engagement axis and adapted to be arranged around the punch and the retaining device.

10. The coupling device (10) according to claim 9, wherein, The outer diameter of the clamp (26) is between 10 mm and 30 mm.

11. The coupling device (10) according to any one of the preceding claims, wherein, The clamping device (22) includes an integrated load measurement system (54).

12. A joining method using a joining device to join at least two workpieces, comprising the following steps: - Provides a workpiece device (W) including an upper workpiece and a lower workpiece. - Provide a joining device (10) according to any one of claims 1 to 11, the joining device being arranged at a non-zero distance above the workpiece device, the joining device being loaded with a joining element; - Move the clamping device (22) along the clamping axis until the clamping device contacts the surface of the upper workpiece. - Apply the first predetermined clamping force (F1). -The engaging element (20) is moved into the workpiece device by moving the punch and / or the holding device along the mounting device, thereby mounting the engaging element in the workpiece device.

13. The joining method according to claim 12, wherein, The clamping device (22) includes a sensor unit that provides force, displacement and time data.

14. The joining method according to claim 12 or 13, wherein, Record the clamping force curve and the clamping device displacement curve and / or the clamping force curve and the engagement element displacement curve and / or the clamping force and time curve.

Images