Device and method for setting a joining element on a workpiece or for clinching the workpiece

Abstract

Device (1) for setting a joining element (8) on a workpiece (19) or for clinching the workpiece (19), comprising a punch unit (2) and an opposite die unit (3), between which the workpiece (19) that can be machined with the device (1) can be clamped, wherein the punch unit (2) comprises a punch (4) that is movable along a joining direction and a hold-down device (5) that can be pressed against the workpiece (19), and wherein the die unit (3) has contact means (9) for contacting the workpiece (19) and a die section (10) with a functional area (11, 29) that is designed in the joining direction opposite the punch (4) on the die section (10) for interaction with the punch (4), characterized in that in a disengaged position of the die unit (3), the contact means (9) protrude beyond the die section (10) in the direction of the punch unit (2) and in a Lowering position of the die unit (3),in which a workpiece (19) can be acted upon by the hold-down device (5) on the punch side, a workpiece side on the die side can be supported on the contact means (9) and on the die section (10), wherein in the disengaged position of the die unit (3) the die section (10) is rotatable.

Description

State of the art:

[0001] Joining tools for joining processes must regularly meet complex and diverse joining requirements. If joining requires various sequential work steps, for example, repositioning or changing parts of the tool during the joining process must be considered. In order to work in short cycle times with high process reliability and, at the same time, to use the joining device flexibly and cost-effectively, modern joining tools must be adapted accordingly.

[0002] WO 2012 / 113463 A1, DE 10259369 B3 and DE 102010027195 A1 are cited as prior art. Object and advantages of the invention:

[0003] The object of the present invention is to provide a joining device, such as a setting tool for joining elements or a clinching joining tool, which can be used variably and effectively for various joining tasks or joining processes. In particular, the device should be advantageously designed for setting a functional or joining element on a workpiece or for clinching the workpiece, in particular for various riveting processes and / or for clinching.

[0004] This problem is solved by independent claim 1.

[0005] The dependent claims relate to advantageous developments of the invention.

[0006] The invention is based on a device for placing a joining element on a workpiece or for clinching the workpiece, comprising a punch unit and an opposing die unit, between which the workpiece to be machined with the device can be clamped, wherein the punch unit comprises a punch movable along a joining direction and a hold-down device pressed against the workpiece, and wherein the die unit has contact means for contact with the workpiece and a die section with a functional area which is designed in the joining direction opposite the punch on the die section for interaction with the punch. The punch of the punch unit is, in particular, driven for linear movement, for example hydraulically, pneumatically, hydropneumatically and / or electrically, for example with an electric drive. The device according to the invention is preferably designed as a joining and / or clinching tool and can be used variably.

[0007] The term workpiece generally refers to a single-layer workpiece, for example made from exactly one sheet of metal, or to a multi-layer workpiece that comprises two or more than two superimposed workpiece layers, such as sheet metal layers.

[0008] In addition to clinching, the proposed device is used, in particular, for attaching a joining element to a workpiece. The term "joining element" is used below to represent either a functional element or a rivet element. A functional element is preferably attached to a single-layer workpiece, in particular to provide a functionality to the workpiece.

[0009] A rivet element is particularly used on a multi-layer workpiece, in particular to join the workpiece layers together. A self-piercing rivet, a self-piercing upset rivet, a solid punch rivet, a semi-tubular self-piercing rivet, or a clinch rivet can be used as the rivet element. The device according to the invention is also advantageously suited for clinching or through-hole joining, in which no joining element is processed. During the joining process, a deformation or partial or complete punching out of an area of ​​the workpiece regularly occurs. The joining or rivet elements in question and / or the workpiece are regularly deformed during setting or through-hole joining. In solid punch riveting and the related self-piercing upset riveting, a hole is punched through the non-pre-punched workpiece with the joining element or rivet.In punch-surge riveting, the rivet is additionally compressed, i.e., deformed to anchor it in the workpiece while the rivet is still present in the punched hole, which is not the case with self-pierce riveting. In the following, the device according to the invention will be referred to synonymously with the tool according to the invention.

[0010] A first essential aspect of the invention is that in a disengaged position of the die unit, the contact means protrude beyond the die section in the direction of the punch unit and in a lowered position of the die unit, in which a workpiece can be acted upon by the hold-down device on the punch side, a die-side workpiece side can be supported on the contact means and on the die section, wherein in the disengaged position of the die unit, the die section is rotatable.

[0011] This advantageously allows the die unit to be adjusted during the process. In particular, by rotating the die section, a first portion of the die section can be moved away from the joining axis, while simultaneously moving another portion of the die section toward the joining axis or under the punch.

[0012] A further aspect of the invention can be seen in the fact that in a disengaged position of the die unit, the contact means protrude beyond the die section in the direction of the punch unit and in a lowered position of the die unit, in which a workpiece can be acted upon by the hold-down device on the punch side, a workpiece side on the die side can be supported on the contact means and on the die section, wherein the punch unit and the die unit are coordinated with one another in such a way that a clamping effect on a workpiece that can be positioned between the hold-down device and the die unit is maintained when the die unit moves from the lowered position into the disengaged position, wherein a support contact that can be provided between the workpiece and the die section in the lowered position of the die unit can be canceled.

[0013] The upward displacement of the support means or a die hold-down device, for example, or its stroke, must be at least as large as the die-side projection or the penetration depth of a punching element punched through the workpiece into a channel for slug removal in the die section. This ensures that the workpiece is completely separated from the die section.

[0014] The device according to the invention advantageously enables permanent or uninterrupted clamping of the joining or workpiece assembly, which comprises the workpiece, in particular consisting of two or more workpiece layers, and the inserted joining element or rivet, throughout the joining process. This allows a rivet to be tensioned in the workpiece assembly after the joining process is completed. This leads to the advantageous or desired connection state with a workpiece assembly under pressure or clamping after the joining process is completed.

[0015] With the device according to the invention, it is also advantageous that, during the joining process, a clamping effect on the workpiece, established once or for the first time with the device, with which the position of the workpiece relative to the device is initially determined, is maintained in a subsequent work step. It is often necessary for the punch to act on the workpiece twice, moving away from it in between.

[0016] The device according to the invention is advantageous for such and related processes, in particular when, in a later work step, a previously determined exact positioning of the joining axis on the workpiece must also be precisely achieved for a subsequent work step. For precise and correct machining of the workpiece, the alignment of the workpiece must then be such that the central punch axis passes through exactly the same point on the workpiece in the subsequent work step as in the previous work step in which the punch acted on the workpiece. In punch upset riveting, for example, the rivet is first punched through the clamped workpiece by the advancing punch. For this purpose, the die section forms an opening in a first functional area into which the punch slug is pressed.After a short retraction of the punch, the die unit is moved from the lowered position to the disengaged position and then the punch is moved forward again and the rivet is again pressed against a fixed support of another functional area of ​​the die section and thereby compressed.

[0017] Otherwise, it would be disadvantageous if the workpiece clamping between the hold-down device and the support means had to be interrupted during the process, particularly in order to be able to adjust the die unit. Even a brief suspension of the clamping effect can lead to a relative movement between the workpiece and the tool, which means that in the subsequent upsetting process the punch is not exactly in line with the previous relative position or position of the joining axis. The punch is then slightly offset from the original joining point on the workpiece, which must be reached exactly in order to complete the joining process as desired. If the punch moves even slightly offset or inclined to the joining axis in the subsequent work step according to the previous work step, this can lead to an inferior or even faulty overall process.

[0018] Such a scenario is excluded by the invention because, once established, the clamping effect of the workpiece relative to the tool is not canceled or maintained throughout the entire machining time. The tool, and thus the punch, remains exactly in the original joining axis relative to the workpiece.

[0019] The clamping effect is established on the workpiece from both sides, i.e., the punch and die sides. On the die side, support devices such as a die hold-down clamp are provided for this purpose. On the punch side, this is achieved by the hold-down clamp, as the punch releases from the workpiece when retracting after the first work step. Since the die unit moves from the lowered position to the disengaged position after a process step, the die unit is released from contact with the workpiece and can be easily adjusted before the punch advances and becomes active again in the subsequent work step.

[0020] The protrusion of the contact means means a protrusion of the free end toward the punch unit, such that a front end of the contact means facing the punch unit protrudes beyond a frontmost section facing the punch unit or a frontmost contour of the die section. The frontmost end of the contact means extends closer to the punch unit than the frontmost section of the die section.

[0021] Removing the support contact with the die unit means that relevant support forces for the workpiece are absorbed only via the support elements, but no support forces are transferred from the workpiece to the die section. This allows the die section to be adjusted, for example, by a rotary movement, a tilting movement, a pivoting movement, and / or a linear movement of the die section on the die unit, or by exchanging the die section for another die section. During the adjustment time required for this, the workpiece remains clamped between the hold-down device and the support elements or fixed to the tool.

[0022] By maintaining the clamping effect on the workpieces to be joined or the workpiece layers of the workpiece, it is also advantageously achieved that during punch-up riveting, after the punching process of the joining element through the workpiece layers, whereby the joining element has not yet been compressed or pre-stamped, the position of the joining element in the workpiece assembly or the punched hole in the workpiece layers is maintained. As explained above, the joining element also remains under tension in the workpiece assembly until the end of the joining process, which is also due to the permanently established clamping connection according to the invention.

[0023] Furthermore, in practice, with the device according to the invention, the entire device, such as a press or a corresponding joining tong, moves relative to the workpiece. This may require a corresponding compensating movement, e.g., with a compensating slide.

[0024] According to an advantageous variant of the invention, the clamping effect can be configured to a clamped assembly, wherein the clamped assembly comprises a multi-layer workpiece with a joining element, in particular a rivet element, present on the multi-layer workpiece. This allows a defined and mechanically stable connection point to be created after the joining process is complete by the rivet element under tension.

[0025] Furthermore, it is advantageous for the die section to be located between sections of the support means. Preferably, the die section is positioned within the support means.

[0026] The contact means can be designed as a hollow profile, in the cavity of which the die section, such as a die base, is located. The contact means can, for example, enclose the die section like a sleeve. For example, the contact means are located radially outward on the die section relative to the joining axis. The die section preferably has two or more useful areas or functional areas on its upper side facing the punch unit, each of which is individually designed to interact with the punch when the punch acts on the clamped workpiece or the joining element. By adjusting the die section to a respective predeterminable position on the die unit, which occurs in the disengaged position, exactly one of the several useful areas can be brought or positioned exactly under the front end of the punch or its front face.in alignment with the joining axis, which runs through the punch and the die unit in the respective useful area. The respective functional area located in the joining axis influences the type of machining of the workpiece when the punch acts on the clamped workpiece. A functional area can, for example, provide a defined deformation contour, a recess, an opening or a discharge channel. The channel makes it possible, for example, to punch the workpiece, whereby the punch pushes a self-piercing rivet through the workpiece from above and the self-piercing rivet punches out a material area of ​​the workpiece. This is possible because the opening of the functional area or the channel is positioned as an extension of the piercing rivet. After punching, the self-piercing rivet usually protrudes beyond the underside of the workpiece or into the opening of the functional area of ​​the die section.

[0027] For other shaping steps of die-side areas of the workpiece or rivet, for example for an upsetting process of the punched rivet, a further or different functional area of ​​the die section may be provided on the die section if necessary.

[0028] Preferably, the usable areas can be optionally adjusted by adjusting the die section or brought into an exact position under the punch or the joining axis of the tool with repeatable accuracy.

[0029] Furthermore, it is advantageous that the hold-down device is movably mounted on the punch, with adjusting means being provided between the punch and the hold-down device such that a pressing force that can be applied to the workpiece with the hold-down device depends on the relative position between the punch and the hold-down device. The adjusting means are preferably coordinated such that the pressing force of the hold-down device pressing on the workpiece increases when the punch moves forward relative to the hold-down device in the direction of the die unit, i.e. in the direction of the workpiece. The punch itself is spaced from the workpiece or comes into contact with the workpiece or a joining element later than the hold-down device. The punch is preferably guided through a through-opening in the hold-down device located around the joining axis. The hold-down device preferably surrounds the punch in a sleeve-like manner over at least part of the length of the punch.

[0030] It is also advantageous for the support means and the die section to be movable relative to one another in a first direction. Preferably, the movement occurs along the joining axis. The support means are preferably sleeve-like on the die section, for example, linearly movable in the first direction. The movement according to the first direction of movement is configured for changing from the lowered position to the disengaged position and back.

[0031] It is also advantageous to have spring means acting between the punch and the hold-down device. These are preferably mechanical springs such as compression springs, for example, coil springs.

[0032] Alternatively, a spring package or other force application is also conceivable.

[0033] The spring means preferably form the adjusting means, in particular for applying a compressive force from the hold-down device to the workpiece side facing the punch. As the punch moves forward, the springs clamped between the punch and the hold-down device are compressed, increasing the spring force on the hold-down device and thus the workpiece. As the punch retracts, the springs automatically relax again, and the pressure force decreases again.

[0034] According to a further advantageous variant, a first spring means and a second spring means act between the punch and the hold-down device. This allows the spring forces provided by the spring means to be advantageously coordinated depending on the relative position between the punch and the hold-down device. Both spring means preferably provide compressive forces. In punch-up riveting, for example, it is advantageous if, in an initial forward movement phase of the punch, starting from the retracted position of the punch, a comparatively lower spring force acts on the hold-down device and thus the workpiece. In a later orIn a second forward movement phase following the first forward movement phase, preferably shortly before the punch presses against the workpiece in direct workpiece contact or via the joining element, it is advantageous if the spring force is greater than the spring forces provided by the first spring means, in that the second spring means also act.

[0035] By specifying the graduated or staggered spring forces that act from the punch unit onto the workpiece and thus onto the die unit, it is also specified whether the die unit is in the disengaged or lowered position. This allows the position of a moving part of the die unit, such as the support means, to be influenced. Since the position of the support means on the die unit depends on the force acting against it, the position of the support means can be specified with the first and second spring means and thus the disengaged or lowered position. In this interaction, the force acting on the support means on the die side, which counteracts the force acting on the punch side, must be taken into account.

[0036] The spring means can be, for example, coil springs. Preferably, the first spring means are designed as pneumatic air springs. A pneumatic air spring advantageously provides an approximately constant force. Thus, the same force ratios prevail for different stroke lengths or piston lengths.

[0037] An advantageous modification of the invention provides that the first spring means are effective over the entire, or at least almost the entire, movement path of the punch relative to the blank holder. This allows a comparatively low minimum force to be specified with which the blank holder presses after being placed on the workpiece. Only later in the process does the force of the second spring means come into play, thereby increasing the total compressive force acting on the workpiece on the punch side.

[0038] Furthermore, it is advantageous that the second spring means are effective over a partial path of the total possible movement path of the punch relative to the hold-down device. The second spring means only come into effect in the phase of the process in which a higher pressing force from the punch unit on the workpiece is required, for example, during punching or to press the workpiece against the die section against the action of a counterforce provided by the die unit, i.e., to push the support means back from the protruding position.

[0039] Advantageously, the spring forces provided by the second spring means are greater than the spring forces provided by the first spring means. This allows a force effect on the punch side that can be adapted to the process sequence. Preferably, the spring forces provided by the first spring means are permanently effective, regardless of the relative position of the punch and the hold-down device.

[0040] When the punch moves forward toward the die unit from a position that is fully retracted relative to the blank holder, the blank holder is driven forward with it. When the punch unit is not in contact with the workpiece, the first spring elements push the blank holder into a defined position at the front of the punch. If the blank holder encounters the top side of the workpiece on the punch side as the punch advances further, the first spring elements are compressed, and the punch advances further. The workpiece is supported on the opposite side by the support elements on the die side.

[0041] The punch, still at a distance from the top side of the workpiece, continues to move in the hold-down device towards the workpiece. The first spring means are compressed even further, whereby the pressure on the hold-down side on the workpiece increases. Shortly before the front of the punch hits a joining element previously placed in the punch path, or in a process without a joining element, hits the top side of the workpiece, the second spring means come into effect. For example, the second spring means can be clamped between a collar of the punch and the hold-down device so that at that moment a front end of the second spring means hits the hold-down device as the punch continues to advance. The second spring means between the punch and the hold-down device are then also compressed, and the pressure on the hold-down device due to the added second spring force increases suddenly.

[0042] The now correspondingly increased pressure force from the hold-down device on the workpiece is absorbed by the support elements, which themselves are spring-loaded and / or spring-loaded. Since the spring force exerted by the hold-down device on the workpiece and thus on the protruding support elements, resulting from the addition of the first and second spring elements, exceeds the spring force that brings the support elements into the protruding position on the die section, the support elements, with the supported workpiece, retract from the disengaged position of the die unit to the lowered position of the die unit.

[0043] With a clamped workpiece, which connects the punch unit and the die unit, the die unit is in the disengaged position or the lowered position, depending on whether the second spring means on the punch side are acting on the hold-down device or not. This applies to situations in which the punch is not acting on the workpiece or a joining element adjacent to it, since the punch force is always greater than the force that moves the die unit into the disengaged position, in particular the spring force that disengages the contact means from the die section toward the punch unit.

[0044] It is also advantageous if the spring means include coil springs. This is simple and cost-effective.

[0045] A further alternative modification of the invention is characterized in that adjusting means, preferably third spring means, act between the contact means and the die section. The relationship between the respective position of the die unit, i.e., disengaged position or lowered position, is thus dependent on a force interplay in which the force acting on the die unit via the workpiece on the punch side and the force of the third spring means contribute. Preferably, the adjusting means provide a die-side supporting force for a workpiece in the disengaged position. The adjusting means also ensure that the die unit is in the disengaged position when unloaded. If a counterforce on the protruding contact means exceeds the supporting force of the adjusting means, the contact means or the die section are relatively adjusted into the lowered position of the die unit.This is preferably done by the contact means on the die section moving back against the spring force of the third spring means.

[0046] In an advantageous alternative of the invention, the contact means and the die section are movable relative to one another via adjustment means such that a functional area of ​​the die unit present on the die section can be moved away from the region of the joining axis. The adjustment means are preferably designed such that, as the functional area is moved away, another functional area of ​​the same die unit can be moved precisely into a functional position in the region of the joining axis. Advantageously, this allows the die section with a first functional area to be adjusted in the joining axis with a simple adjustment process such that a second functional area subsequently lies in the joining axis. The prerequisite for this is that the die section has at least two functional areas located on a common adjustment path.If more than two different functional areas are present on a die section, the adjustment means preferably also enable an optional adjustment of exactly one functional area from the several existing functional areas on the die section, each in a precisely aligned position in the area of ​​the joining axis.

[0047] The adjustment means preferably comprise a drive to enable the movement of the die section, in particular in an automated manner, for example pneumatically, hydraulically or electrically.

[0048] The adjustment means advantageously also allow for the replacement of part of the die section or the entire die section on the die unit. This involves setting up a different functional area exactly below the joining axis, which is possible during a joining process. If necessary, the die section can be removed from the die unit and replaced with another die section. The other die section preferably differs from the removed die section only in that it has a different functional area.

[0049] The adjustment devices also make it possible to convert a tool for a different joining task by selecting a different die section or a different functional area of ​​the die section. However, the corresponding adjustment is usually not made within or during a work process, but rather before the work process when the tool is converted.

[0050] Preferably, the adjustment means are designed as a rotating, pivoting, folding or sliding device, so that the die section can be rotated, pivoted, folded away or moved away linearly relative to the rest of the die unit or to the support means such as a die hold-down device.

[0051] It is also particularly advantageous for the die section to be rotatably mounted on the die unit. Preferably, the die section is rotatable about an axis that is parallel to the joining axis or coincides with the joining axis.

[0052] Furthermore, it is advantageous that the die section can be rotated into various predeterminable functional positions relative to the support means.

[0053] If the rotational axis of the die section is offset parallel to the joining axis, it is also advantageous for the die section or its upper side to have two or more functional areas arranged coaxially to the rotational axis. The respective multiple rotational positions, in which a functional area is located exactly in the joining axis or below the punch face, can be precisely specified and set up with repeatable accuracy using, for example, stop devices. This allows the desired functional area to be reliably and precisely positioned in a respective predefined rotational position of the die section, in an extension of the punch or the joining axis, or beneath the workpiece.

[0054] For a tool according to the invention designed for self-piercing riveting, a functional area of ​​the die section can be prepared for a punching process. During punching, a self-piercing rivet is moved on the punch side by the punch towards the die unit. The punch acts with its front side on the upper side of a rivet head of the self-piercing rivet placed in front of the punch. The self-piercing rivet strikes the non-pre-punched workpiece with a shank section at a joint and is pressed through the workpiece by punching. The workpiece is formed, for example, by two sheets lying flat on top of one another. For punching, it is necessary that the workpiece is clamped between the hold-down device and the support means and that areas of the workpiece underside on the die side are supported laterally around the joint by the die section.However, an opening must be provided centrally at the joint so that the rivet shank can punch through the workpiece. This opening accommodates the punched-out workpiece part or the punching slug and allows a front end section of the rivet shank to protrude slightly beyond the underside of the workpiece on the die side. This ensures that the part of the workpiece to be punched out can be safely separated from the workpiece along its entire edge.

[0055] The functional area must therefore have an opening with an adjoining channel for the rivet shank to reach in and for receiving and removing the punching slug, which is surrounded on the workpiece side by fixed areas of the die section.

[0056] For a subsequent upsetting process of the rivet or a widening of the protruding end section of the rivet, a solid counter surface must be provided under the end section by another functional area of ​​the die section. This allows the upsetting to occur by the punch pressing on the rivet head from above, and the rivet is pressed against the solid counter surface at the bottom, which causes the deformation and widening of the end section of the rivet.

[0057] To do this, the die section must be adjusted using the adjustment tools after the punching process. Since the underside of the workpiece is pressed onto the top side of the die section during punching, the workpiece must first be lifted off the die section. To do this, the punch moves slightly upwards or away from the die unit. The effect of the second spring on the hold-down device is canceled out and only the weaker first spring acts downwards on the hold-down device and thus on the workpiece. In contrast, the third spring on the contact tools, which are larger than the first spring, act on the workpiece on the die side. The workpiece is then moved towards the punch unit, supported on the contact tools, whereby the underside of the workpiece is lifted off the die section. The upward displacement or the stroke of the contact tools must be at least as large as the die-side projection or extension.the penetration depth of the rivet shank into the channel or punch slug discharge channel.

[0058] Now the die section is free from the previously pressed workpiece, which means that the die section can be adjusted.

[0059] After adjustment, the relevant functional area on the die section forms a counter-stop for upsetting the self-piercing rivet. During adjustment of the die section, the workpiece remains advantageously clamped between the hold-down device, via which the first spring means act on the workpiece on the punch side, and the contact means, via which the third spring means act on the workpiece on the die side. During the subsequent upsetting process, the punch hits exactly the same point on the workpiece, i.e. centrally from above onto the rivet head of the self-piercing rivet, which is necessary for the secure formation of the self-piercing rivet connection. If the clamp had to be released after the punching process, relative movement between the workpiece and the tool or the punch axis could not be ruled out, which would then be disadvantageous for the subsequent upsetting process or could even result in the formation of the connection being faulty.

[0060] Finally, it is also advantageous for the die section to have a channel for removing a portion of material through the interior of the die section. The channel advantageously does not need to be offset, interrupted, or shifted when adjusting the die section, but rather runs continuously up to a transfer or coupling point of the channel to the outside. The material section is the part of the workpiece that is punched out during the punching process, for example, two punched slugs from two punched sheets. The channel is preferably continuous without interruptions and / or significant changes in direction. This prevents the material section from jamming in the channel and thus blocking the channel.

[0061] The channel is preferably arranged at an angle to a longitudinal axis of the die section. The channel preferably has an opening on the upper side of the die section facing the punch side. In a rotational position of the die section, in which the functional area for punching lies in the joining axis on the side of the die section facing the punch unit, the opening of the channel is arranged in an axial extension of the punch axis or the joining axis. The channel runs through the component that forms the die section to an outer side, preferably an underside of the component, which is opposite the upper side with the functional area of ​​the die section. On the underside, the channel ends with an opening that runs centrally to the rotational axis of the die section, which lies parallel to the joining axis.

[0062] This advantageously ensures that, regardless of the rotational position of the die section, the opening on the underside always connects to a transfer point through which a punched-out slug of material from the workpiece can be removed. The channel does not need to be interrupted in any rotational position of the die section, which could otherwise lead to a blockage of the rotational movement due to a slug present in the interruption point, which could result in the tool's loss of function.

[0063] The inclined discharge channel is advantageously provided on the rotatable die section, which is preferably rotatable about an axis parallel to the joining axis, wherein turning away or towards a workpiece-side punching opening of the channel on a discharge side for discharging a punching slug simultaneously enables unproblematic inward rotation of the slug channel at the discharge-side opening of the channel.

[0064] The invention also extends to a method for placing a joining element on a workpiece or for clinching the workpiece using a device as described above. Advantageously, according to the invention, a single-layer or multi-layer workpiece is positioned between a punch unit and a die unit, and then a first work step is carried out during a punch movement, with the workpiece being clamped between the punch unit and the die unit. This can, for example, involve placing a joining element designed as a functional element on a workpiece with exactly one workpiece layer, or clinching a multi-layer workpiece, or placing a joining element such as a rivet in a multi-layer workpiece. For this purpose, a first region of the die section on the workpiece on the die side is effective as an extension of the punch.In a subsequent work step, the die section is adjusted so that it is not in contact with the workpiece. To do this, the first section is moved away, for example, by twisting, moving linearly, and / or exchanging the die section. Subsequently, instead of the first section of the die section, another die section or a second section of the die section is moved beneath the workpiece in an extension of the punch. This is followed by a further work step involving a punch movement, e.g., a compression process of the joining element. The workpiece is clamped between the punch and the other section of the die section. Character description:

[0065] Further advantages and features of the invention are explained in more detail using a highly schematic embodiment of the invention.

[0066] The Fig. 1 to 11 each show a corresponding, highly schematically illustrated section of a device according to the invention in different work or operating steps with a workpiece to be machined by the device. The work steps each represent momentary situations of the entire process, starting with Fig. 1 the other Fig. 2 to 11 in the order of ascending numbering refer to later or subordinate work steps.

[0067] Further units of the device according to the invention, such as drive and control devices as well as sensor means, are not shown.

[0068] The figures show a section of a device according to the invention, which is designed, for example, as a joining tool for punch-riveting a workpiece 19 or as a punch-riveting tool 1. The tool 1 can be used in any spatial orientation, whereby a vertical orientation of a joining axis F is assumed in the figures.

[0069] The workpiece 19 can be, for example, a single-piece or single-layer material such as sheet metal or several layers of sheet metal and / or other materials.

[0070] The joining tool 1 according to the invention is designed for punch-riveting a punch-rivet 8 onto the two-layer sheet metal workpiece 19.

[0071] The tool 1 comprises, for example, a C-frame with a punch unit 2 and a die unit 3, which are arranged opposite one another and have a free space between them for the workpiece 19. In addition to being used as a fixed joining tool, the joining tool 1 according to the invention can also be used in a mobile manner, for example, on a robotic device. This allows different spatial positions to be reached in order to quickly perform the joining work at different locations on a workpiece. This is important, for example, in the automated processing of body parts in motor vehicle manufacturing.

[0072] In the figures, a bilateral extension of the workpiece 19 is indicated by a line representation.

[0073] The punch-swivel riveting tool 1 according to the invention shown in the figures is used to set a punch-swivel rivet 8 on the workpiece 19, wherein this is a two-layer workpiece 19 consisting of an upper sheet 19a and a lower sheet 19b, which can be connected with the punch-swivel rivet 8 at a joint FS of the workpiece 19, through which the joining axis F runs. The sheets 19a, 19b are sheets with comparatively low ductility, i.e. with little plastic deformation under load. Therefore, after punching the workpiece 19, the necessary deformation in the area of ​​the joint FS for fixing the two sheets 19a and 19b must be introduced via the punch-swivel rivet 8, which is plastically deformable by an upsetting process. This procedure makes it unnecessary to change a functional area on the die side orthe adjustment of a die section of a die during a machining operation is necessary, which increases the demands on tool 1.

[0074] Of the tool 1, only a portion of the highly simplified punch unit 2 and the die unit 3 is shown. The punch unit 2 comprises a punch 4, a hold-down device 5, and adjusting means located between the punch 4 and the hold-down device 5, which are designed, for example, as two helical springs 16 and 17.

[0075] The spring force F3 of the longer, narrower coil spring 16 is noticeably lower than the spring force F1 of the shorter, wider coil spring 17. The coil spring 16 holds the hold-down device 5 in a pre-tensioned position in the basic position of the tool 1 ( Fig. 1).

[0076] The punch 4 can be driven linearly along or parallel to the joining axis F, or can be moved forward in the direction S1 and backward in the opposite direction, or in the direction S2. The punch is driven, for example, hydropneumatically with pressure boosting or with an electric motor drive unit. Fig. 1 to 3, the punch is completely retracted in direction S2. The joining axis F is extended by a central vertical axis or cylinder axis of the punch 4, which is, for example, cylindrical. At a rear end region of the punch 4 facing away from the die unit 3, the punch has a projection 14 that projects radially toward the outer surface of the remaining part of the punch 4.

[0077] In front of the punch 4 is the hold-down device 5 with a sleeve part 5a, which has a through-opening 5b adapted to the punch diameter. The front part of the punch 4 extends more or less deeply into the through-opening 5b depending on its relative position to the hold-down device 5 or the movement position of the punch 4.

[0078] One end of a feed arrangement 6 with an internal, free feed channel 7 is laterally connected to the hold-down device 5 or the sleeve part 5a. From a supply area (not shown) for a plurality of joining elements, the feed arrangement 6 can be used to move joining elements or the individually illustrated punch rivet 8 one after the other through the feed channel 7 in the conveying direction R to the punch 4. Fig. 1 therefore relates to the work step “loading rivet” in the basic position of the tool 1. The feed R of the punch rivet 8 is, for example, pneumatically assisted. The fed punch rivet 8 is Fig. 2 is transported to below a front punch face 4a of the punch 4 and held there by means not visible in a desired template position, for example such that the longitudinal axis of the punch rivet 8 coincides with the joining axis F. In the Fig. 1, with the die unit 3 free, the punch 4 is in a position retracted on the hold-down device 5, so that the feed channel 7 on the hold-down device 5 below the punch front side 4a is not obstructed by the punch 4 or is open, and thus a joining element can be transported up to the punch 4.

[0079] The die unit 3, with a central longitudinal axis L, is slightly offset laterally to the joining axis F and comprises, among other things, a die section designed as a die 10 and contact means, which are formed, for example, as a die hold-down device 9. The sleeve-shaped die hold-down device 9 surrounds the die 10 in the region of approximately half the upper length of the die 10. The die hold-down device 9 is preferably pre-tensioned and guided in a sliding manner on the die 10 and can be moved back and forth relative to the die 10 parallel to the joining axis F. During joining operation of the tool 1, the movement path of the die hold-down device 9 relative to the die 10 is generally only a few millimeters, in particular according to a minimum dimension a (see Fig. 1 and Fig. 2), which is explained below.

[0080] In principle, a reverse arrangement with a die hold-down device fixed to tool 1 and a die that can be moved linearly back and forth is not excluded.

[0081] Preloading means, for example a compression or helical spring 18, are provided between a collar 21 projecting radially to the longitudinal axis L on a lateral surface of the die 10 at the lower end of the die 10 and an underside of the die blank holder 9. The spring force F2 of the helical spring 18 is higher than the spring force F3 of the weaker helical spring 16 and lower than the spring force F1 of the stronger helical spring 17.

[0082] In the unloaded case without force applied to the workpiece 19 or in the basic position according to Fig. 1, the coil spring 18 presses the die retainer 9 upward or toward the punch unit 2, so that a front end portion of the die retainer 9 protrudes slightly, or for example, a few millimeters, axially beyond a die base 10a by the dimension a. The die base 10a forms an axial upper or front side of the die 10, which faces the punch unit 2.

[0083] Fig. 2 shows a work step in which the die hold-down device 9 is applied to the workpiece 19, with an annular end face 9a of the die hold-down device 9 being in contact with the lower sheet 19b on the underside.

[0084] In the work step according to Fig. 3 "Holder sets up" places a flat, annular end face 5c of the hold-down device 5 on top of the upper sheet 19a by moving the punch unit 2 downwards in the direction of the die unit 3. With the further punch movement forward in the direction S1, the punch 4 moves further into the through-opening 5b of the hold-down device 5 and slightly compresses the coil spring 16. The force F3 of the coil spring 16 acts via the hold-down device 5 onto the workpiece 19, which is subsequently held or clamped between the hold-down device 5 and the die hold-down device 9 ( Fig. 3). The die hold-down device 9 remains in its protruding position relative to the die 10, since the spring force F2 of the coil spring 18 is greater than the spring force F3 of the coil spring 16.

[0085] The punch 4 continues to move in the direction S1, whereby a front side of the coil spring 17 is Fig. 4 is placed straight on top of the sheet 19a. The coil spring 17 is compressed between the projection 14 and the hold-down device 5 and thus begins to act. In addition to the spring force F3, the spring force F1 then acts on the workpiece 19 in the direction S1. The punch unit 2 is designed in such a way that this, i.e. the increase in force due to the additional spring force F1 from the punch unit 2 on the workpiece 19, takes place shortly or immediately before the punch rivet 8 is placed on the upper side of the upper sheet 19a (see Fig. 4). The Fig. 4 small discernible distance between the punch face 4a and an upper side of the punch rivet 8 does not reflect the actual relationships exactly or not to scale.

[0086] When the compressed coil spring 18 on the hold-down device 5 becomes effective, the drive of the punch 4 providing the necessary force, the workpiece 19 is pressed against the die hold-down device 9, which according to Fig. 5 in the direction S1 or downwards, since the sum of the spring forces F1 and F3 causes a force directed downwards in the direction S1 on the sleeve part 5a of the blank holder 5, which exceeds the counterforce on the die blank holder 9 due to the spring force F2. Therefore, the die blank holder 9 dives downwards with the workpiece 19 by compressing the helical spring 18. The lowering of the die blank holder 9 ends when the underside of the lower sheet 19b rests on the die bottom 10a. In the illustrated case of the flat underside of the lower sheet 19b, the flat die bottom 10a and the likewise flat front side 9a of the die blank holder 9 are flush (see Fig. 5). The die 10 is placed on the workpiece 19.

[0087] In the next step after Fig. 6, the punching process step begins, and the self-piercing rivet 8 is pressed against the upper sheet 19a by the punch 4, which continues to move downward in the direction S1 and which, under power, acts with its punch face 4a on an upper side of a rivet head 25 of the self-piercing rivet 8. The punch 4 is driven in the direction S1 until it reaches a predeterminable end position and is then stopped. The self-piercing rivet 8, pushed forward by the punch 4, is matched in terms of its shape and material properties to the sheets 19a, 19b to be punched in such a way that the self-piercing rivet 8, with the underside of a rivet shank 26 leading and along an edge of the rivet shank underside, punches a punch hole 27 into the two sheets 19a and 19b. The lower sheet 19b is supported both on the annular end face 9a of the die hold-down device 9 and on the die bottom 10a of the die 10.For the punching function, an end opening 12 of a slug removal channel 13 is formed in a functional area 11 of the die base 10a, directly below the punch face 4a. In the predeterminable die rotational position of the die 10, which is explained further below, the opening 12 is located exactly concentrically to the joining axis F or the punch longitudinal axis, with the diameter of the opening 12 or the slug removal channel 13 being slightly larger than the diameter of the rivet shank 26 or larger than the slugs 23 and 24 punched out of the workpiece 19.

[0088] The punched slug 23 of the upper sheet 19a and the punched slug 24 of the lower sheet 19b are pushed into the slug discharge channel 13 by the rivet shaft 26. The punch rivet 8 is positioned at the end of the punching step according to Fig. 7 with the rivet head 25 resting on the underside of the upper sheet 19a. The lower part of the rivet shank 26 projects slightly downwards over the underside of the lower sheet 19b and can, if necessary, protrude slightly through the opening 12 into the slug discharge channel 13. The loose punched slugs 23, 24 are discharged through the slug discharge channel 13 or the die 10 toward an outlet opening 28. The slug discharge channel 13 extends from the die base 10a with the opening 12 of the slug discharge channel 13, which is radially offset from the central longitudinal axis L of the die 10, over a short section parallel to the longitudinal axis L and then linearly obliquely to the longitudinal axis L through the interior of the otherwise solid die 10. The slug discharge channel 13 ends at the outlet opening 28 of a bottom side 15 of the die 10. The outlet opening 28 is concentric with the longitudinal axis L of the die 10.

[0089] In the next step, the stamp 4 moves according to Fig. 8 again slightly upwards or in the direction S2, whereby the helical spring 17 attached to the projection 14 is taken along and lifts off the hold-down device 5. The punch 4 moves at least far enough in the direction S2 until the helical spring 17 comes out of contact with the top side of the hold-down device 5. As a result, the pressure or spring force F1 no longer acts on the top of the hold-down device 5, but only the spring force F3 of the helical spring 16, whereby the counterforce F2 applied to the die side on the hold-down device 5 by the helical spring 18 is again the determining force or becomes effective and presses the die hold-down device 9 relative to the die 10 upwards in the direction S2, together with the workpiece 19 and the hold-down device 5. (see Fig. 8). The tool 1 is adjusted in such a way that the lifting of the workpiece 19 with the die hold-down device 9 in the direction S2 takes place to a minimum extent, preferably by slightly more than the dimension a, whereby the underside of the lower sheet 19b and the downwardly projecting part of the rivet shank 26 of the punch rivet 8 come out of contact with the die bottom 10a or the opening 12 of the die 10, which in Fig. 8 is evident.

[0090] To anchor the self-piercing rivet 8 inserted into the punch hole 27 of the joint FS on the workpiece 19 and thus to connect the two sheets 19a and 19b at the joint FS, the self-piercing rivet 8 is plastically deformed, which occurs through a compression or squeezing process. During the compression process, the part of the rivet shank 26 protruding from the underside of the sheet 19b is compressed. For this purpose, the punch 4 advances again in the direction S1 and presses from above onto the rivet head 25 of the self-piercing rivet 8. The underside of the rivet shank 26 is supported on a fixed counter or contact surface 20 of a functional area 29 of the die base 10a, which serves as a counterbearing. Therefore, the die 10 must be adjusted before the upsetting process step in such a way that the functional area 11 with the opening 12 is moved from the position in the joining axis F according to the Fig. 1 to 8, in which the joining axis F passes through the opening 12, is moved away, so that the other functional area 29 lies on the die base 10a with the fixed contact surface 20 in the joining axis F.

[0091] In the present embodiment of the invention, the adjustment of the die 10 is realized by a die pivot bearing or by rotation, for which purpose the die 10 is rotatable about its longitudinal axis L, whereby by a defined rotary movement D of the die 10 clockwise or counterclockwise about the longitudinal axis L, one of the functional areas 11 and 29 can be brought into coaxiality with the joining axis F. The rotary adjustment of the die 10 from one position to the other position with respective exact coaxiality of one of the functional areas 11 or 29 with the joining axis F must be possible selectively and with repeatable accuracy or reversibly.For this purpose, for example, preferably milled stops (not shown) can be provided on the outside of the die 10, for example on a collar 21, which allow a rotational movement of the die through precisely defined, predetermined angular dimensions until a stop comes into contact with a counter-stop on a stationary component surrounding the die 10 and is blocked there against further rotation. The die 10 is rotated back until another stop of the die contacts another counter-stop. The rotational movement of the die 10 in both directions of rotation about the longitudinal axis L can, for example, be carried out using a drivable, reversibly reciprocating drive element which is coupled, for example, in an approximately tangentially aligned manner to the preferably cylindrical die 10, for example engaging an opening in the collar 21.When the drive element moves from a starting position, in which the die 10 is in a first position, to an end position of the drive element, the die 10 rotates by a predeterminable angle. The die 10 is located exactly in a second position. By moving the drive element back from the end position, in which the functional area 29 is located in the joining axis F, to the starting position, the die 10 is rotated back with precise positioning to the first position, in which the functional area 11 is located exactly in the joining axis F.

[0092] In principle, more than two functional areas 11, 29 can be present on the die base 10a and can be adjusted with repeatable accuracy, for example three, four or five functional areas.

[0093] In order to maintain the position of the workpiece 19 with the punch rivet 8 placed at the joint FS during rotation or adjustment of the die 10 relative to the tool 1, the workpiece 19 remains clamped between the blank holder 5 and the die blank holder 9 during the adjustment of the die 10. This ensures that the punch axis hits the joint FS or the previously placed punch rivet 8 exactly centrally during upsetting. This is advantageously possible with the tool 1 according to the invention. For the adjustment of the die 10, this or the die base 10a must be removed from contact with the workpiece 19, whereby the upper and lower clamping of the workpiece 19 between the blank holder 5 and the die blank holder 9 is maintained permanently or continuously, which is the transition from the state according to Fig. 7 in the state according to Fig. 8 shows. The workpiece 19 is lifted out without losing the clamping on tool 1.

[0094] In a single step, which is carried out according to the Fig. 8, the die 10 is rotated about its longitudinal axis L according to the arrow D by a defined angle of rotation in one or the other direction of rotation.

[0095] In the achieved rotational position with the joining area 29 in the joining axis F according to Fig. 9, the punch 4 moves downwards again in the direction S1, whereby the helical spring 17 again rests on the hold-down device 5, so that the force effective in the direction S1 from the sum of the spring forces F1 and F3 is greater than the spring force F2 of the helical spring 18 on the die hold-down device 9, whereby the die hold-down device 9 with the workpiece 19 moves downwards until the underside of the rivet shaft 26 rests on the functional area 29 of the die base 10a of the die 10. With the further driven movement of the punch 4 in the direction S1, the punch 4 presses with its punch force onto the punch rivet 8. Between the punch end face 4a and the functional area 29, the part of the rivet shank 26 projecting at the bottom of the sheet 19b is squeezed or pressed flat, whereby a bead 22 is formed which is radially expanded to the remaining rivet shank 26.As a result, the two sheets 19a and 19b are firmly pressed together between the rivet head 25 and the bead 22 at the lower end of the rivet shaft 26 (see . Fig. 10).

[0096] After the punch and upset riveting at the joint FS of the two sheets 19a and 19b with the punch and upset rivet 8 has been completed, the punch unit 2 and the punch 4 are moved in the direction S2 or the die unit 3 is moved downwards away from the workpiece 19.

[0097] The punch is retracted far enough so that the next punch rivet can be transported via the feed channel 7 and placed in front of the punch face 4a.

[0098] The coil spring 18 pushes the die hold-down device 9, which is again unloaded on the top, upwards, so that the front side 9a projects beyond the die base 10a of the die 10 with the projection a. The tool 1 is again in the basic position according to Fig. 1. List of reference symbols: 1 punch riveting tool 2 stamp units 3 die unit 4 stamps 4a Stamp front side 5 hold-down clamps 5a Sleeve part 5b Passage opening 5c front side 6 Feed arrangement 7 Feed channel 8 punch rivet 9 die hold-down device 9a front side 10 die 10a Die bottom 11 Functional area 12 Opening 13 Sludge discharge channel 14 Overhang 15 Bottom 16 coil spring 17 coil spring 18 coil spring 19 Workpiece 19a sheet metal 19b sheet metal 20 contact surface 21 Bund 22 bulge 23 punching slugs 24 punching slugs 25 rivet head 26 rivet shank 27 punch hole 28 Outlet opening 29 Functional area

Claims

[1] Device (1) for placing a joining element (8) on a workpiece (19) or for clinching the workpiece (19), comprising a punch unit (2) and an opposing die unit (3), between which the workpiece (19) that can be machined with the device (1) can be clamped, wherein the punch unit (2) comprises a punch (4) that can be moved along a joining direction and a hold-down device (5) that can be pressed onto the workpiece (19), and wherein the die unit (3) has contact means (9) for contacting the workpiece (19) and a die section (10) with a functional area (11, 29) that is designed in the joining direction opposite the punch (4) on the die section (10) for interaction with the punch (4), characterized byin a disengaged position of the die unit (3), the contact means (9) protrude beyond the die section (10) in the direction of the punch unit (2), and in a lowered position of the die unit (3), in which a workpiece (19) can be acted upon by the hold-down device (5) on the punch side, a die-side workpiece side can be supported on the contact means (9) and on the die section (10), wherein in the disengaged position of the die unit (3), the die section (10) is rotatable. [2] Device (1) according to the preamble of claim 1, in particular according to claim 1, wherein in a disengaged position of the die unit (3), the contact means (9) protrude in the direction of the punch unit (2) over the die section (10) and in a lowered position of the die unit (3), in which a workpiece (19) can be acted upon by the hold-down device (5) on the punch side, a die-side workpiece side can be supported on the contact means (9) and on the die section (10), wherein the punch unit (2) and the die unit (3) are coordinated with one another in such a way that a clamping effect on a workpiece (19) positionable between the hold-down device (5) and the die unit (3) is maintained when the die unit (3) moves from the lowered position into the disengaged position, wherein a support contact that can be provided in the lowered position of the die unit (3) between the workpiece (19) and the die section (10) can be revoked, characterized bythat the contact means (9) and the die section (10) are movable relative to one another via adjusting means in such a way that a functional area (11, 29) of the die unit (3) present on the die section (10) can be moved away from the area of ​​the joining axis. [3] Device (1) according to one of claims 1 and 2, characterized by that the clamping effect can be set up on a clamping assembly, wherein the clamping assembly comprises a multi-layer workpiece (19) with a joining element present on the multi-layer workpiece (19), in particular a rivet element (8). [4] Device (1) according to one of the preceding claims, characterized by that the matrix section (10) is present between sections of the investment means (9). [5] Device (1) according to one of the preceding claims, characterized byin that the hold-down device (5) is movably received on the punch (4), wherein adjusting means (16, 17) are provided between the punch (4) and the hold-down device (5) in such a way that a pressing force which can be applied to the workpiece (19) by means of the hold-down device (5) depends on the relative position between the punch (4) and the hold-down device (5). [6] Device (1) according to one of the preceding claims, characterized by that the contact means (9) and the die section (10) are movable relative to each other in a first direction. [7] Device (1) according to one of the preceding claims, characterized by that first spring means (16) and second spring means (17) are effective between the punch (4) and the hold-down device (5). [8] Device (1) according to one of the preceding claims, characterized by that the first spring means (16) are effective over an entire or at least almost entire path of movement of the punch (4) relative to the hold-down device (5). [9] Device (1) according to one of the preceding claims, characterized by that the second spring means (17) are effective over a partial path of an entire possible path of movement of the punch (4) relative to the hold-down device (5). [10] Device (1) according to one of the preceding claims, characterized by that the spring forces that can be provided by the second spring means (17) are greater than the spring forces that can be provided by the first spring means (16). [11] Device (1) according to one of the preceding claims, characterized by that adjusting means, preferably third spring means (18), act between the contact means (9) and the die section (10). [12] Device (1) according to one of the preceding claims 1 and 3 to 11, characterized bythat the contact means (9) and the die section (10) are movable relative to one another via adjusting means in such a way that a functional area (11, 29) of the die unit (3) present on the die section (10) can be moved away from the area of ​​the joining axis. [13] Device (1) according to one of the preceding claims, characterized by that the die section (10) is rotatably mounted on the die unit (3). [14] Device (1) according to one of the preceding claims, characterized by that the die section (10) can be rotated into various predeterminable functional positions relative to the contact means (9). [15] Device (1) according to one of the preceding claims, characterized by that the die section (10) has a channel (13) for removing a material section (23, 24) through the interior of the die section (10). [16] Method for setting a joining element (8) on a workpiece (19) or for clinching the workpiece (19) with a device (1) according to one of the preceding claims.

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