Method for joining at least two components using a punch riveting device, punch riveting device and manufacturing equipment

Abstract

Method for joining at least two components (11, 12) by means of a punch riveting device (10), wherein the at least two components (11, 12) are arranged between a punch (15) and a counterholder (18), wherein a rivet (20) arranged between the punch (15) and a component (11) of the at least two components (11, 12) facing the punch (15) is pressed into the at least two components (11, 12) by means of the punch (15) by applying a force (F) to the punch (15), wherein at least one component (11, 12, 15, 18, 20) involved in pressing the rivet (20), in particular the punch (15), is set into vibration by means of a vibration generator (30) during pressing, characterized in that a contact profile between the punch (15) and the rivet (20) is determined during pressing.

Description

[0001] The present invention relates to a method for joining at least two components by means of a punch riveting device, a computing unit for carrying out this method, a punch riveting device and a manufacturing device with such a punch riveting device. State of the art

[0002] Punch riveting methods are used to join at least two components (joining partners) that are particularly flat in a joint area. A punch riveting method is characterized by the fact that pre-drilling of the components to be joined is not required. Instead, a rivet is pressed into the at least two components using a punch or punching tool. A suitably shaped counter-holder, e.g., in the form of a die, which interacts with the punching tool, ensures that the rivet deforms in a specific way within the components to be joined, in order to create a force-fit and form-fit connection between the components and simultaneously prevent penetration of the component opposite the rivet.

[0003] DE 199 05 527 A1 discloses a device for joining, for example by punch riveting or clinch joining, workpieces made of ductile material, while US 2006 / 0 230 609 A1 relates to a system and method for punch riveting.

[0004] Furthermore, so-called ultrasonic self-piercing riveting methods are known, for example, from EP 2 318 161 B1 or DE 10 2014 203 757 A1, in which a vibration generator, such as an ultrasonic generator, is used to vibrate one or more components during the joining of the parts. This vibration reduces, for example, the force required to drive in the rivet. Disclosure of the invention

[0005] According to the invention, a method for joining at least two components using a self-piercing riveting device, a computing unit for carrying out this method, a self-piercing riveting device, and a manufacturing device with the features of the independent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description. Advantages of the invention

[0006] A method according to the invention serves to join at least two components using a self-piercing riveting device. The at least two components are arranged between a punch and a counter-holder. A rivet, arranged between the punch and a component of the at least two components facing the punch, is pressed into the at least two components by means of the punch by applying a force to the punch. At least one component involved in pressing the rivet, in particular the punch, is set into vibration by means of a vibration generator during the pressing process. The contact profile, in particular the time profile, between the punch and the rivet during pressing is thereby determined. Both a so-called semi-tubular rivet and a so-called solid rivet can be used as the rivet.

[0007] In conventional self-piercing riveting processes, the force as a function of the punch's position can be used to assess the quality of the process. For example, it can be examined whether the force curve remains within certain limits, such as an envelope. However, in self-piercing riveting processes where vibration is introduced into the joint area, for example, by setting the punch into vibration, such a force curve can usually no longer be used for quality assessment because the force on the punch oscillates due to the vibration. Depending on the force measurement position, the type of measurement, and the sampling rate or sensitivity of the measuring device, the force curve can oscillate to a greater or lesser degree. This prevents the quality assessment necessary for many industrial applications, as the commonly used limits are not appropriate in these cases.

[0008] By recording the contact pattern between the punch and the rivet during the riveting process, a method for quality assessment can be provided even for self-piercing riveting processes with vibration coupling. This is because this contact pattern provides information about the riveting process, as a defined contact pattern is a prerequisite for proper riveting, and this can be determined by measuring the contact pattern. For example, an efficient riveting process can be ensured by checking the contact pattern for optimal performance. If this is not the case, corrective measures can be taken. Furthermore, it can also be determined whether the frequency at which the contact opens and closes corresponds to the frequency of the vibration or whether, for example, harmonics are present.Furthermore, various relevant points during the riveting process can be identified. It is advantageous if the process is monitored online or in real time, as this allows for corrective action to be taken even during the riveting process itself.

[0009] Generally applicable process and quality assessment criteria, such as those that can be provided with a method according to the invention, are also often a basic requirement for the introduction of a new technology into series production.

[0010] Advantageously, the contact path between the punch and the rivet is electrically determined during the pressing process by means of an area comprising at least one contact point between the punch and the rivet. Preferably, the contact path between the punch and the rivet can be determined by detecting a contact voltage drop across the area and / or a current flowing in the area. For example, the electrical voltage across the area can be generated by connecting a voltage source to the area and a resistor in series with it. The contact voltage drop across the area then corresponds approximately to the voltage value of the voltage source when there is no contact between the punch and the rivet, and is determined by the ratio of the resistance of the punch to the resistance of the area when there is contact between the punch and the rivet. For example, if...If an additional resistor is connected in parallel to the section, the contact voltage across the section (and the additional resistor) is approximately zero when there is contact between the punch and rivet. Without contact, the voltage is determined by the ratio of the resistance of the punch to the additional resistor. The current is zero, for example, when there is no contact between the punch and rivet. Instead of a voltage source, a current source with adjustable current can also be used. In this way, the contact behavior can be easily determined.

[0011] Preferably, an electrical voltage and / or current can be applied between the punch and the rivet, one of the components, or the counterholder. In each of these cases, the relevant contact point between the punch and the rivet is captured. The most suitable points for applying the voltage or current can be selected, for example, depending on the specific design of the self-piercing riveting device. A voltage / current contact at the counterholder can, for instance, be maintained permanently, while a voltage / current contact at a component might offer lower resistance.

[0012] Advantageously, at least one of the at least two components is electrically conductive. It is understood that, depending on the position where the voltage or current is applied, none, one, or all components need to be electrically conductive. For example, when the voltage or current is applied between the punch and the rivet, none of the components need to be electrically conductive; however, when the voltage or current is applied between the punch and the counter-holder, all components must be electrically conductive. When the voltage or current is applied between the punch and the component facing the rivet, for example, only this component needs to be electrically conductive. Depending on how the voltage or current is applied, even non-electrically conductive components can be joined using this method, and the riveting process can be monitored. Examples of suitable component materials include...Suitable materials include aluminum sheet, aluminum castings, steel sheet, hot-formed steel, magnesium alloys, and even carbon fiber reinforced plastic. It should be noted that even low electrical conductivity can be sufficient.

[0013] Advantageously, the contact path between the punch and the rivet can be determined by optically measuring the transmittance of the contact point during the insertion process. Specifically, the optical transmittance can be determined by detecting an optical signal directed at the contact point. Such optical detection can be used as an alternative or supplement to electrical detection of the contact path. This method allows for very simple recording of the contact path. In particular, qualitative analysis is possible, as, for example, the amount of light detected can be used as a measure of the distance between the punch and the rivet. Furthermore, even non-electrically conductive components can be joined using this method.

[0014] It is advantageous if the sampling rate for recording the contact behavior is at least five times, and in particular at least ten times, the frequency of the vibration generated by the vibration source, which corresponds, for example, to between 15 and 35 kHz. In this way, for example, additional harmonics can be detected, which can also be used to evaluate the riveting process.

[0015] Preferably, the contact pattern between the punch and the rivet is used to determine the number of contacts between the punch and the rivet during the riveting process, the duration of the contacts, the time between two contacts, and / or the percentage of contact. These values ​​allow for a further or better evaluation of the riveting process.

[0016] Advantageously, the contact progress is displayed on a display device, particularly graphically. This can preferably be, for example, a display on which the progress is shown graphically. This allows for a particularly simple and clear representation of the progress, for example, for an operator of the punch riveting device, who can thus assess the riveting process very quickly.

[0017] It is advantageous to link the contact process to the corresponding riveting operation and save it to a storage medium. This allows for documentation of the riveting process and its quality. For example, faulty rivet connections can be easily identified or explained later. Furthermore, such documentation is often mandatory for industrial applications. This documentation can be done via data cable or wirelessly, for example, via Wi-Fi.

[0018] Preferably, the contact pattern is used for a quality assessment of the vibration behavior of the self-piercing riveting device, the clamping behavior of the self-piercing riveting device, the associated self-piercing riveting process, and / or the joint produced in this self-piercing riveting process between the at least two components. Such a quality assessment can, for example, be at least partially automated, so that an operator of the self-piercing riveting device is automatically notified if a poor or defective rivet joint has been produced. By evaluating the vibration behavior and / or the clamping behavior, i.e., the clamping forces applied to hold the components and / or the force on the rivet, the settings of the self-piercing riveting device can be corrected. Evaluating the vibration behavior and / or the clamping behavior is therefore possible because an incorrect setting of the self-piercing riveting device, for example,This can lead to changes in contact times (duration with contact in relation to duration without contact) and thus also in the percentage of contact and the number of contacts, or to the rivet and the stamp oscillating in opposite or the same direction.

[0019] Advantageously, a sound generator, particularly an ultrasonic generator, such as an analog or digital generator, is used as the vibration source. This is a simple method for generating vibrations. Furthermore, power measurement is straightforward with a sound or ultrasonic generator.

[0020] A computing unit according to the invention, e.g., a control unit or a control device for a self-piercing riveting device, is configured, particularly in terms of programming, to carry out a method according to the invention. Such a computing unit can preferably also be configured to control the necessary detection means or even at least partially include them. A computing unit is typically connected to a power supply anyway, which can then be used, for example, for other purposes.

[0021] A self-piercing riveting device according to the invention comprises a punch, a counter-holder, a vibration generator, and a hold-down device for pressing the at least two components against the counter-holder during the riveting process. Furthermore, the self-piercing riveting device includes sensing means by which the contact path between the punch and the rivet can be determined during the riveting process. In this way, when using the self-piercing riveting device with suitable sensing means, it is possible to determine the contact path between the punch and the rivet during the riveting process. For further advantages of a self-piercing riveting device according to the invention, reference is made to the above descriptions of the method according to the invention to avoid repetition.

[0022] Advantageously, the detection means include an electrical voltage or current source and a voltage measuring device and / or an ammeter, wherein an electrical voltage or current can be applied to an area comprising at least one contact point between the punch and the rivet by means of the voltage or current source.

[0023] Preferably, the hold-down device and / or the counter-holder are electrically insulated from the holding device of the self-piercing riveting tool in which they are arranged. For this purpose, suitable electrically insulating materials, such as plastic or ceramic, can be applied to the relevant points. This prevents voltage or current leakage through the holding device or, furthermore, through the entire production setup to which the self-piercing riveting tool may be attached. This enables improved measurement results.

[0024] Advantageously, the detection means have an optical signal source and an optical sensor which are arranged such that a contact point between the punch and the rivet is located between the optical signal source and the optical sensor.

[0025] A manufacturing device according to the invention comprises a punch riveting device according to the invention and a calculating unit according to the invention, and preferably further display means which are configured to represent the course of the contact between the punch and the rivet, in particular graphically.

[0026] To avoid repetition, reference is made to the above explanations of the inventive method and the inventive punch riveting device with regard to further advantages of a manufacturing device according to the invention.

[0027] Implementing the process as a computer program is also advantageous, as this incurs particularly low costs, especially if the executing control unit is already used for other tasks and is therefore already present. Suitable data carriers for providing the computer program include magnetic, optical, and electrical storage devices, such as hard drives, flash memory, EEPROMs, DVDs, etc. Downloading the program via computer networks (Internet, intranet, etc.) is also possible.

[0028] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.

[0029] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0030] The invention is schematically illustrated in the drawing using an exemplary embodiment and is described in detail below with reference to the drawing. Character description Fig. Figure 1 shows a simplified and schematic representation of a manufacturing device according to the invention in a preferred embodiment. Fig. Figures 2a to 2d show a punch riveting device at different phases of carrying out a punch riveting process. Fig. Figure 3 schematically shows a punch riveting device according to the invention in a preferred embodiment, which is suitable for carrying out a method according to the invention. Fig. Figure 4 schematically shows a punch riveting device according to the invention in a further preferred embodiment, which is suitable for carrying out a method according to the invention. Fig. Figure 5 schematically shows a punch riveting device according to the invention in a further preferred embodiment, which is suitable for carrying out a method according to the invention. Detailed description of the drawing

[0031] In Fig. Figure 1 shows a simplified and schematic representation of a manufacturing device 100 according to the invention in a preferred embodiment. The manufacturing device 100 could, for example, be an industrial robot in a production hall, e.g., for automotive body manufacturing. However, a stationary manufacturing device is also conceivable, e.g., with a stationary frame without movable or adjustable robot arms.

[0032] The manufacturing device 100 comprises a support structure 3 arranged on a base and two interconnected and movable arms 4 and 5 attached to it. A punch riveting device 10 is arranged at the end of arm 5, which is Fig. 3 is described in more detail.

[0033] Furthermore, a computing unit 80 is shown, which is, for example, a control unit for the self-piercing riveting device 10. The computing unit 80 can also be used as a control unit for the entire production facility, i.e., in addition to the self-piercing riveting device, also for controlling the movable arms. Display means 90, e.g., a display, are also provided, on which, for example, current operating parameters of the self-piercing riveting device can be displayed.

[0034] In the Fig. Figures 2a to 2d show the self-piercing riveting device 10 in various phases of the self-piercing riveting process. The self-piercing riveting device 10 has a punch 15, which, by way of example, has a round cross-section.

[0035] The punch 15 is radially surrounded by a sleeve-shaped retainer 16 and is arranged to be movable relative to it in the longitudinal direction. In particular, the punch 15 is coupled to a drive (not shown here), e.g. a hydraulic or pneumatic drive, which serves to apply a force F required to press a rivet 20 into the two components 11, 12.

[0036] The hold-down device 16 is also designed to press against the surface of the component 11 facing the punch 15 with a holding force. For this purpose, a separate drive can be provided, for example. However, the hold-down device can also be coupled to the drive of the punch 15, for example by means of a spring.

[0037] On the side of the two components 11, 12 opposite the punch 15 and the hold-down 16, a die 18 is arranged, acting as a counter-holder. The die 18 is also movably raising and lowering along a longitudinal axis 19, in the direction of which the punch 15 and the hold-down 16 are also movably arranged. The hold-down 16 and the die 18 serve to clamp or compress the two components 11, 12 between the hold-down 16 and the die 18 during machining by the punch 15 and to hold their predetermined position. The die 18 has a flat upper surface 21 on the side facing the component 12, from which a trough- or depression-shaped recess 22 extends.

[0038] The rivet 20, here exemplified as a semi-tubular rivet, preferably consists of a material harder than the materials of the two components 11, 12, at least in the area of ​​the rivet shank 24. The flat upper surface 26 facing away from component 11 is arranged in operative connection with the punch 15, which bears flat against the upper surface 26 of the rivet 20. Thus, the upper surface 26 of the rivet constitutes a contact point 27 between the rivet and the punch.

[0039] The piston 15 is operatively connected to a vibration generator 30 for generating vibrations. In particular, ultrasonic vibrations with a amplitude (distance between the maximum positive and negative amplitude of a vibration) between 10 µm and 110 µm (i.e., an amplitude of 5 µm to 55 µm) and a frequency between 15 kHz and 35 kHz are generated by means of the vibration generator 30.

[0040] These vibrations 15 are coupled into the rivet 20 by the vibration generator 30 via the punch 15. The coupling direction of the vibrations from the vibration generator 30 can be, for example, parallel to the longitudinal axis 19 (longitudinal), that is, parallel to the joining direction of the rivet 20 into the rivet 20 or the components 11, 12. Torsional sound coupling into the rivet 20 or the components 11, 12 is also possible. The vibration generator 30 is connected to the processing unit 80 and can be controlled by it.

[0041] The in Fig. Phase 2a shown represents the beginning of the self-piercing riveting process, in which the rivet shank 24 comes into operative contact with the top surface of the component 11. The punch 15 is pressed against the component 11 facing the punch 15 with the force F.

[0042] In a Fig. In the further phase shown in 2b, i.e., during the further course of the riveting process and with the support of the vibrations coupled into the components 11, 12, the rivet shank 24 first cuts or punches its way into the component 11. In doing so, the two components 11, 12 are plastically deformed, whereby the component 12 facing the recess 22 is pressed into the recess 22 in the corresponding areas.

[0043] During the further movement path or further downward movement of the rivet 20 according to the Fig. 2c the rivet 24 is spread outwards in the area of ​​the recess 22, whereby the two components 11, 12 are securely connected to each other in the axial direction in a form-fit and force-fit manner.

[0044] The essential point is that, according to the Fig. 2d, which shows the final position of the rivet 20, where the rivet shaft 24 does not protrude from or completely penetrate the component 12.

[0045] After the rivet 20 the in the Fig. Once the end position shown in 2d has been reached, in which the top surface 26 of the rivet 20 is at least approximately flush with the top surface of the component 11 (this is common for metal riveting with countersunk rivet elements; for plastic riveting, elements with a flat round head are usually used), the punch 15 is then moved upwards again by the components 11, 12 in the opposite direction.

[0046] In Fig. Figure 3 shows a punch riveting device 10' according to the invention in a preferred embodiment. The punch riveting device 10' differs from the one shown in the Fig. The feature of the punch riveting device 10 shown in Figures 2a to 2d is that an inner surface of the retainer 16' is spaced apart from the outer surface 15 of the punch 15. This ensures that no electrical contact occurs between the punch 15 and the retainer 16'.

[0047] Furthermore, the hold-down device 16' has an insulating ring 41 made of electrically insulating or non-conductive material. An insulating ring 42, also made of electrically insulating or non-conductive material, is also incorporated on the underside of the die 18. This electrically insulates the area of ​​the punch riveting device 10' located between insulating ring 41 and insulating ring 42, including the punch 15, against a support (not shown) to which the die 18 is attached on the underside of the die 18. Fig. 3 shown view and the hold-down 16' on the top side of the in Fig. 3 shown in the illustration, they can be attached, electrically insulated.

[0048] Furthermore, a circuit arrangement 81 is shown, comprising a voltage source 50 connected to the punch 15 and the die 18. A resistor R1 is arranged in series between the punch 15 and the voltage source 50, across the area encompassing the punch 15, the rivet 20, components 11 and 12, and the die 18. This area includes the contact point 27 between the punch 15 and the rivet 20 and forms a resistance designated R3. A resistor R2 is also arranged in parallel with resistor R3. The voltage drop across this area, i.e., across R3 and the parallel resistor R2, can be determined using a voltmeter 51.

[0049] The circuit arrangement 81 can be part of the computing unit 80. Thus, the voltage source 50, which preferably provides a constant voltage, and the voltage measuring device 51 can also be part of the computing unit 80. The computing unit 80 can therefore be connected, for example, simply via two wires to the die 15 and the mold 18. It is understood that suitable contact points are provided on the die 15 and the mold 18 for this purpose.

[0050] A method according to the invention in a preferred embodiment with the in Fig. The punch riveting device 10 shown in Figure 3 and the circuit arrangement 81 will now be described below.

[0051] The riveting process itself, i.e., the pressing of the rivet 20 into the components 11, 12, proceeds in the same or a similar way as in the Fig. 2a to 2d are explained for a conventional punch riveting process with a vibration generator.

[0052] During the riveting process, however, the voltage provided by the voltage source 50 and dropping across the resistor R2 is constantly present between the punch 15 and the die 18.

[0053] When an electrical contact exists between the punch 15, the rivet 20, the components 11, 12 and the die 18, the value of the resistance R3 approaches zero. This means that no voltage is measured by the voltmeter 51, as the voltage collapses.

[0054] It should also be mentioned here that the components involved in the voltage measurement are advantageously electrically conductive. This is generally the case for the punch 15, the rivet 20, and the die 18 anyway. The components to be joined, here components 11 and 12, should therefore also be electrically conductive in the embodiment shown here. The electrical conductivity of the components does not necessarily have to be very high, since low conductivity, i.e., a non-negligible resistance R3, only results in a finite, but low, voltage. This is the case, for example, with carbon fiber reinforced plastics (CFRP).

[0055] If, however, there is no continuous electrical contact between the punch 15, the rivet 20, the components 11, 12, and the die 18, the value of resistance R3 approaches infinity. This means that a voltage measured by the voltmeter 51 corresponds to the voltage drop across resistance R2. If resistances R1 and R2 are equal, for example, i.e., if R1 = R2, then half of the voltage supplied by the voltage source 50 will be measured.

[0056] In the case of a non-negligible resistance R3, i.e. poorly electrically conductive components 11, 12, the resistors R1 and R2 can be chosen so that the voltage values ​​are still distinguishable when the contact between the punch and rivet is open and closed.

[0057] The electrical contact between the punch 15 and the rivet 20 is typically interrupted. This interruption of contact is caused by the punch 15 being set into vibration by the vibration generator 30, while the rivet 20 is usually firmly seated in at least one of the components 11, 12. Thus, the contact history between the punch and the rivet can be determined from the voltage profile measured by the voltage measuring device 51.

[0058] For example, a touch frequency can be derived from the contact history for an evaluation.

[0059] For a preferred representation, for example, the contact frequency relative to a position of the punch during rivet insertion can be displayed, provided this position is also recorded by suitable means. This allows for a simple and quick evaluation of the riveting process.

[0060] It should also be noted that if the voltage is applied differently, e.g. between the hold-down device 16' and the component 11, the component 12 does not need to be electrically conductive.

[0061] In Fig. Figure 4 shows a punch riveting device 10' according to the invention in a further preferred embodiment. The punch riveting device 10' can be, for example, like the one shown in Figure 4. Fig. The punch riveting device shown in Figure 3 is constructed as follows. However, instead of the circuit arrangement with voltage source and voltmeter, a circuit arrangement 82 with current source 60 and current meter 61 is provided here. The circuit arrangement 82 can also be part of the computing unit 80.

[0062] In a preferred embodiment of a method according to the invention, a current is supplied by the current source 60 during the riveting process. When a conductive connection or contact is established between the punch 15 and the die 18, the current begins to flow. An existing current flow can then be monitored by a suitable electronic evaluation circuit or a current measuring device 61 and supplied to the measurement system as a digital or analog signal. Furthermore, reference should be made to the aspects relating to Fig. Reference is made to the 3 statements made.

[0063] In Fig. Figure 5 shows a punch riveting device 10' according to the invention in a further preferred embodiment. The punch riveting device 10' differs here from the one shown in the Fig. 3 and Fig.The 4 punch riveting devices shown are characterized in that an optical signal source 70, e.g. a laser or a high-power LED, and an optical sensor 71, e.g. a photodiode, possibly with an amplifier with rise times e.g. in the ns range, are provided.

[0064] Signal source 70 and sensor 71 are, for example, arranged on opposite sides of the punch 15 outside the hold-down 16' and at the level of the contact area between the punch 15 and the rivet 20. The hold-down 16' can, for example, have recesses 72, e.g., in the form of slots, so that the contact area between the punch and the rivet can be illuminated by the signal source 70. If there is no contact between the punch and the rivet, the optical signal or light from the signal source 70 reaches the sensor 71. By connecting the sensor 71 to the processing unit 80, the contact history can, for example, be determined.

[0065] Care should be taken to account for the relative movement between the punch or contact point and the hold-down device. For example, the signal source and sensor can be elongated and / or planar, particularly rectangular. Alternatively, the signal source and sensor can be arranged to move along with the punch.

Claims

[1] Method for joining at least two components (11, 12) using a self-piercing riveting device (10), wherein the at least two components (11, 12) are arranged between a punch (15) and a counter-holder (18), wherein a rivet (20) arranged between the punch (15) and a component (11) of the at least two components (11, 12) facing the punch (15) is pressed into the at least two components (11, 12) by means of the punch (15) by applying a force (F) to the punch (15), wherein at least one component (11, 12, 15, 18, 20) involved in pressing the rivet (20), in particular the punch (15), is set into vibration by means of a vibration generator (30) during pressing. characterized by , that a course of contact between the stamp (15) and the rivet (20) is determined during the pressing process. [2] Method according to claim 1, wherein the course of the contact between the punch (15) and the rivet (20) in an area comprising at least one contact point (27) between the punch (15) and the rivet (20) is electrically determined during the pressing of the rivet (20). [3] Method according to claim 2, wherein the course of the contact between the punch (15) and the rivet (20) is determined by detecting a contact voltage falling over the area and / or a current flowing over the area. [4] Method according to claim 2 or 3, wherein an electrical voltage and / or an electric current is applied between the punch (15) and the rivet (20), one of the components (11, 12) or the counterholder (18). [5] Method according to one of the preceding claims, wherein at least one of the at least two components (11, 12) is an electrically conductive component. [6] Method according to one of the preceding claims, wherein the course of the contact between the punch (15) and the rivet (20) is determined by detecting an optical permeability of a contact point (27) between the punch (15) and the rivet (20) during the pressing process. [7] Method according to claim 6, wherein the optical transmittance is determined by detecting an optical signal directed at an area encompassing the contact point (27). [8] Method according to one of the preceding claims, wherein a sampling rate for determining the course of the contact is at least five times, in particular at least ten times, a frequency of the vibration generated by the vibration generator (30). [9] Method according to one of the preceding claims, wherein a number of contacts between the punch (15) and the rivet (20) during the pressing process, a duration of the contacts, a duration between two contacts and / or a percentage contact profile is determined from the course of the contact between the punch (15) and the rivet (20). [10] Method according to one of the preceding claims, wherein the course of the contact is displayed on display means (90), in particular graphically. [11] Method according to one of the preceding claims, wherein the progress of the contact is linked to an associated punch riveting process and is stored on a storage medium. [12] Method according to one of the preceding claims, wherein the course of the contact is used for a quality assessment of a vibration behavior of the punch riveting device (10), a clamping behavior of the punch riveting device (10), an associated punch riveting process and / or a connection of the at least two components (11, 12) produced in this punch riveting process. [13] Method according to one of the preceding claims, wherein a sound generator, in particular an ultrasonic generator, is used as the vibration generator (30). [14] Computing unit (80) for a punch riveting device (10) which is configured to carry out a method according to one of the preceding claims. [15] Punch riveting device (10) with a punch (15), a counter-holder (18), a vibration generator (30) and a hold-down device (16') for pressing the at least two components (11, 12) against the counter-holder (18) during the insertion of the rivet (20), characterized byDetection means by which the course of a contact between the punch (15) and the rivet (20) during the pressing process can be determined. [16] Punch riveting device (10) according to claim 15, wherein the detection means comprise an electrical voltage or current source (50, 60) and a voltage measuring device (51) and / or an ammeter (61), wherein an electrical voltage or current can be applied to an area comprising at least one contact point (27) between the punch (15) and the rivet (20) by means of the voltage or current source (50, 60). [17] Punch riveting device (10) according to claim 15 or 16, wherein the hold-down device (16') and / or the counter-holder (18) are electrically insulated from a holding device of the punch riveting device (10) in which holding device they are arranged. [18] Punch riveting device (10) according to one of claims 15 to 17, wherein the detection means comprise an optical signal source (70) and an optical sensor (71) arranged such that a contact point (27) between the punch (15) and the rivet (20) is located between the optical signal source (70) and the optical sensor (71). [19] Manufacturing device (100) comprising a punch riveting device (10) according to one of claims 15 to 18, and a calculating unit (80) according to claim 12, and preferably further comprising display means (90) which are configured to display the course of the contact between the punch (15) and the rivet (20), in particular graphically. [20] Computer program that causes a computing unit (80) to perform a method according to any one of claims 1 to 13 when executed on the computing unit (80). [21] Machine-readable storage medium with a computer program stored thereon according to claim 20.

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