EP1034055B1 - Process and device for joining by punching and riveting - Google Patents

Description

The object of the invention relates to a method and to a Device for producing a punch rivet connection according to the preamble of claims 1 and 20 (see, for example, WO-A-94/14554).

In the automotive industry in particular, riveted joints always win more important as they can be an alternative to the welded joint. In the case of poorly weldable material pairings, riveted joints create a suitable alternative. The parts to be connected are riveted without Punched together. The prepunching required for conventional riveting Joined parts are replaced by a corresponding cutting process of the punch rivet.

In the case of punch riveting with a semi-hollow rivet, the components to be connected are opened laid a matrix. These are fixed on the die by a hold-down device. The semi-tubular rivet cuts through the layer facing the semi-tubular rivet. After that the semi-tubular rivet in or in the lower layers to form a Closing head plastically deformed. The shape of the closing head is in essentially determined by the shape of a die. That from the top layer and material punched out from other layers may fill the hollow one Rivet shaft of the semi-tubular rivet and is locked captive. After that the semi-tubular rivet compressed, so that on the one hand further training of the Closing head takes place and the head of the semi-tubular rivet essentially is flush with the top layer.

Through the essay by L. Budde and W. Lappe "Rivets without prepunching - Punch rivets are promising in sheet metal processing ", published in the Journal bands tapes tubes 5-1991, pages 95-100, is known to be from crucial for a high quality punch rivet connection with a half-hollow rivet on the one hand the perfect holding of the positioned Components so that the position of the Components are not changed to each other, and on the other hand the joining-specific choice a suitable punch rivet with regard to the material-specific composition and its rivet geometry is.

To ensure that a post-flow movement does not occur during punching known from WO 94/14554 that the clamping force of the hold-down, by the the components are fixed on the die towards the end of the punch riveting process increases significantly. This configuration of the method for producing a Punch rivet connection should also be achieved that in the area of the head of the Punch rivets no annular depressions or distortions arise.

To implement the method, WO 94/14554 proposes a device which has a die, a hold-down and a stamp. Between the The hold-down device and the die can be clamped to at least two layers of components. The hold-down device can be moved via a first piston-cylinder unit. A second Piston-cylinder unit is provided as the drive unit for the stamp. The first and second piston-cylinder units are independent of each other actuated.

A similar embodiment of a device for producing a Punch rivet connection is known from WO 93/24258. This device too has a piston-cylinder unit through which the necessary clamping force of the Hold-down can be generated on. By appropriate pressure control different clamping forces can be generated. The device after the WO 93/24258 has a second piston-cylinder unit as the drive unit of the Stamp on.

The mechanical properties of a punch riveted joint, especially that The strength behavior of the punch rivet connection depends on the design of the Closing head. The strength behavior is also determined by the design of the Area of the components between the head and the closing head of the punch rivet affected.

Proceeding from this, the present invention has the object that further develop known methods for producing a punch rivet connection, that on the one hand a gentle production of a punch rivet connection and on the other hand, a punch rivet connection with higher strength is achieved. On Another object of the invention is an apparatus for producing a Specify punch rivet connection that is suitable for protecting the material Make rivet connection. The device is also intended to achieve that the punch rivet connection produced by the device is high Strength values reached.

This objective is achieved by a method with the features of claim 1 or a device with the features of claim 20 solved. advantageous Further training is the subject of the respective subclaims.

By the method according to the invention for producing a punch rivet connection is achieved that one of the hold-down on the at least two layers of clamping force exerted according to a predetermined one Course is varied. A variation of the hold down on the at least two layers of clamping force is achieved in that the Hold-down device can be connected to the stamp via a coupling unit so that during a punch riveting process a coupling of the hold-down with the Stamp between a substantially rigid coupling state and one decoupled state can be changed. Through this invention Procedure is achieved that the rigid coupling state Hold-down device synchronized with the stamp, especially in the direction of the die is movable. In the decoupled state, while maintaining or varying the a movement of the clamping force acting on the components Stamp are carried out.

Because the clamping force acting on the components from the hold-down device is changeable, since this depends on the movement of the stamp achieved that the sufficient for individual sections of the punch riveting process necessary clamping force is applied. The measure by which the clamping force is changed depends on the coupling status. In particular suggested that the coupling state depending on the stamp path or a parameter derived from the stamp path is changed.

Depending on material pairings and mechanical properties the materials of the layers, it may be appropriate that the layers first with a reduced clamping force can be pressed against the die. After that you can the layers with a varying compared to the reduced clamping force Clamping force against the die. In particular, the Clamping force can be increased during the upsetting process. This has the advantage that in the case of a formation of the head of the hollow rivet at least partially surrounding bead, this is compressed by the hold-down device so that the head of the hollow rivet is flush with the layer. The clamping force can also be significantly higher than the usual clamping force.

The variation of the coupling state depending on the stamp path can be carried out continuously or discontinuously. A continuous change in the Coupling state is preferred because it does not change the Clamping force occurs. Even if there is a discontinuous change in the Coupling state, the jumps in the clamping force can be selected so that there is no pronounced sudden change in the process parameters.

By rigidly coupling the hold-down with the stamp, the Hold down the same movement as the stamp. The hold-down brings in essentially the same force as the stamp. According to one predetermined course of the clamping force can be controlled by controlling the coupling unit the hold-down device can be uncoupled from the punch. The further application of clamping force the hold-down device is controlled via the coupling unit. Should after a given punch path of the hold-down device a higher force on the layers exercise, the hold-down device can be connected to the Stamp can be coupled.

In particular, it is proposed that the hold-down device with the stamp should be too connecting layers is moved so that the hold-down the layers with a predetermined clamping force presses against the die. The hold-down is from that Stamp decoupled and the stamp for severing at least that Half-rivet facing position, a training of a closing head Move the compression of the semi-hollow rivet further, the holder if necessary a predetermined stamp path is coupled to the stamp.

The clamping force varies depending on the stamp path preferably according to a predetermined course of the clamping force in Dependence on the stamp path. The specified clamping force-stamp path curve is a target profile, which is preferably continuous with the actual profile of the Clamping force depending on the stamp path is compared. To do this suggested that a stamp path be measured or one from the stamp path derived parameter is compared with a predetermined target size.

Depending on the comparison result, the hold-down device is preferably of Stamp decoupled or coupled to the stamp.

The process according to the invention also makes it gentle plastic deformation of the punch rivet ensured in at least one position without that this layer or these layers is excessively weakened. A Excessive weakening of the layer or layers can lead to an unwanted Punch through this layer or layers. A punching through of the situation or the layers would become one depending on the material pairings Cause corrosion. This problem arises with the method according to the invention however not on.

According to an advantageous development of the method, it is proposed that the Coupling state depending on the material properties, in particular of the strength, at least one layer is changed. This beneficial Further training is based on the idea that the locations are different Flow behavior or deformation behavior can have. In particular proposed that a clamping force-stamp path course depending on the Properties of the pairing of layers made of different materials changed becomes. For example, if you want a layer of aluminum or an aluminum alloy with a second layer of aluminum or an aluminum alloy by means of a Punch rivets are connected, the coupling state is changed differently than for an aluminum / steel connection. It can also be taken into account here that the coupling state can also depend on which one Material properties, the layer to be punched or the layer to be formed having.

To further improve the formation of a punch rivet connection suggested that the coupling state depending on a thickness changed at least one position, in particular the position facing the punch rivet becomes. This is to take into account the fact that Flow behavior of the layer (s) also depends on the thickness of the layer (s). At a relatively thin position there is more of a risk that the position in the area of the head of the punch rivet is overstressed, causing textures or cracks can. This can be avoided by moving this layer to flow Semi-tubular rivet at least during part of the punch riveting process, the Coupling state from a rigid to a less rigid connection between the hold-down device and the stamp is changed. With relative thick layers, the clamping force can be compared to layers with a relatively small thickness, be chosen higher, because thick layers have a different stress behavior exhibit. The thick layer is overstressed compared to a thin one Position much later because there is enough material for a flow movement in the Matrix and to the semi-tubular rivet is available.

According to a further advantageous embodiment of the method, it is proposed that that the coupling state depending on the material properties of the Punch rivets is changed. In particular, the criterion for changing the Coupling state suggested the hardness of the punch rivet.

The geometry of the punch rivet, in particular the design of the free one End face of the punch rivet, as well as the recess of the semi-tubular rivet plays for the Design of the rivet connection a role. The geometry of the punch rivet influences the stamping and forming process. It is therefore proposed that the coupling state depending on a geometry of the punch rivet is changed. The geometry of the punch rivet can also be individual Geometric sizes of the punch rivet can be used as a criterion. Here, for example, the cross section of the punch rivet, the length of the Punch rivets can be used as factors. The other geometrical ones too Sizes of a punch rivet can be used as criteria for choosing a suitable one Coupling status curve can be used.

In particular, the coupling state can be at least during at least one Part of an upsetting process can be reduced to such an extent that it is essentially transverse movement of at least one layer to the semi-tubular rivet is made possible. This ensures that a material flow during the formation of the Closing head occurs so that the layers in the area of the punch rivet connection less mechanical stress, especially tensile stress, get abandoned

A stamping force of the Stamp are determined and compared with a predetermined target size, the hold-down device preferably depending on the stamping force and / or the stamp path is decoupled from the stamp or with the stamp is coupled.

Additionally or alternatively, the clamping force of the hold-down can be during the Punch riveting process determined and compared with a predetermined target size become. By comparing the clamping force depending on Stamp path can be varied.

A target characteristic curve of a clamping force-stamp path can be determined by tests be determined. Here it can be assumed that such a target characteristic for the particular one trained during the experiment, Punch rivet connection is valid. For self-piercing rivet connections that differ in terms of Material properties of the layers, their geometry, etc. change, are corresponding to determine further target characteristics. In a first approximation, the Determination of a target characteristic curve for a given punch riveting task Extrapolation of the known target characteristics an assumed target characteristic are determined as the basis for the comparison with the clamping force-stamp path can serve.

In view of the fact that the layers within the manufacturing tolerances can be of different thickness, it is proposed that the hold-down to the Stamp is coupled depending on a stamp force. It can also be one Coupling of the hold-down device to the stamp take place when the stamp force and the The path of the stamp lies within a certain tolerance range.

According to a further advantageous embodiment of the method, it is proposed that that a clamping force of the hold-down device is measured directly or indirectly. The Hold-down devices can be used depending on the clamping force and / or the punch force and / or the travel path of the stamp decoupled from the stamp or to the Stamp can be coupled.

It is particularly expedient if the Hold-down devices have a piston and the plunger has a pressure piston, the Piston and the pressure piston relative to each other within a common Chamber are movable, with a between the piston and the pressure piston Fluid, preferably an essentially incompressible fluid, is provided, the distance between the piston and the pressure piston relative to each other in is essentially changed by the fluid, in particular the fluid volume. The Chamber with the fluid as well as the piston and the pressure piston form the Coupling unit. By changing the volume or pressure of the fluid between the piston and the pressure piston, the coupling state between Hold-down device and stamp can be varied. If the fluid volume is constant, especially with an essentially incompressible fluid, there is between the stamp and the hold-down device a rigid connection. The hold-down executes a movement corresponding to the stamp path when the stamp is moved Change in position. The fluid volume is changed during the stamp movement in such a way that this is reduced, the stamp carries out a larger one Stamp movement as the hold-down. The hold-down can with appropriate Change in the fluid volume to be stationary, the force with which the Hold-down acts on the components, variable or constant depending can be changed by the fluid volume. In a corresponding manner, the Fluid pressure of the coupling state can be influenced.

Preferably, at least a portion of the fluid from the chamber is in a Compensating chamber passed, whereby the relative position of the piston and the Pressure piston is changed to each other. The speed at which one Change in position of the piston and the pressure piston can occur through the Flow rate of the fluid from the chamber can be influenced. Through the Flow rate is thus also the rate of change of Clamping force influenced.

The fluid flowing out of the chamber into a reservoir is used to form a Another punch rivet connection from the compensation chamber into the chamber returned, whereby a closed fluid flow is achieved.

According to a further advantageous embodiment of the method proposed that the hold-down device is connected to a piston which in a double-acting cylinder is arranged, through which the stamp passes extends. The stamp has a pressure piston which is in a preferably incompressible, fluid-loaded chamber is guided. The Chamber is connected to a volumetrically variable reservoir. The Chamber is rigidly connected to the cylinder and slidably in a housing guided.

The change in fluid pressure is preferably dependent on Stamp path and / or the travel path of the hold-down device and / or the clamping force and / or the stamp force. A fluid pressure is preferably dependent on the Stamp path determined and the fluid pressure-stamp path course with a predetermined target course compared. Depending on the comparison, a pressure-regulating valve fluidically connected to the chamber. By the Pressure control valve controls the fluid pressure in the chamber.

The fluid removal is preferably dependent on the clamping force and / or the stamp force and / or the travel path of the stamp and / or the Controlled travel of the hold-down device.

If there is no fluid withdrawal from the chamber, the pressure piston causes one Pressure build-up of the fluid in the chamber, causing the fluid to pressure the The hold-down piston exerts and the hold-down moves in the direction of the layers becomes. Has the hold-down device for clamping the layers between the hold-down device and the matrix has the necessary force, for example, by suitable Fluid removal from the chamber of the stamp continues to move, the The clamping force between the hold-down device and the die is retained. Is a stronger one Volume change due to fluid withdrawal from the chamber as the conditional Volume change due to the change in stamp travel, so the clamping force of the Hold-down device, the punch performing the actual punch riveting process.

If the layers are initially to be applied with a reduced clamping force against the die and then with a higher clamping force compared to the reduced clamping force can be pressed against the die, so this can be done by no or only a minor one Fluid is withdrawn from the chamber.

According to a further inventive idea, a device for Production of a punch rivet connection with a die, a hold-down and proposed a stamp. The stamp and the hold-down are for the die movable to and from this. Between the hold-down device and a die At least two layers of components can be clamped. A punch rivet that is for example, a half-rivet, a full rivet, can be done by means of Stamp to connect the layers at least through the hold-down driven adjacent position of the components. The invention The device is characterized in that a coupling unit is provided, which connects the hold-down and the stamp so that during a Punch riveting a coupling of the hold-down with the punch between an essentially rigid coupling state and a decoupled state can be changed. The stamp is driven by a drive unit.

An advantage of this embodiment of the device can be seen in that the hold-down device is moved depending on the stamp. The fact that the Hold-down with the stamp is essentially rigidly coupled, also becomes a Clamping force reached relatively quickly.

According to a further advantageous embodiment of the device proposed that the hold-down device a piston crown and the punch one Have pressure pistons. The piston and the pressure piston are in one with one, preferably incompressible, fluid-filled chamber of the coupling unit movable relative to one another, the fluid pressure in the chamber being variable.

According to a further advantageous embodiment of the device proposed that a control device is provided which is used to control the Coupling unit is used. The control unit can be used to achieve that Coupling unit during a punch riveting process from the hold-down to the at least two layers of clamping force exerted according to a predetermined one Course depending on at least the stamp path or one from the Stamp path derived parameter is varied.

Fluid pressure can be controlled by withdrawing fluid from the chamber, so that the relative position of the piston with respect to the pressure piston by volume of the removed fluid is dependent.

If no fluid is removed, there is between the piston and the Pressure piston a substantially rigid connection, so that the hold-down is moved synchronously with the stamp. By appropriately removing the fluid the clamping force can be maintained or changed even though the stamp is used the plunger moves in the direction of the layers. The fluid withdrawal can also are controlled such that suitable clamping force profiles of the hold-down device can be realized.

The device preferably has a compensation chamber into which at least a line conducts at least a portion of the fluid during a punch riveting operation conductive from the chamber, and for a renewed punch riveting process from the Compensating chamber can be returned to the chamber.

Preferably, there is at least one line between the compensation chamber and the Chamber provided in which a pressure control valve is arranged. By the Pressure control valve can control the fluid pressure in the chamber. to Automatic control of the device suggests that a pressure sensor is provided for measuring the fluid pressure with the control device connected is. With the control device is also the pressure control valve connected. A fluid pressure is preferably dependent on the stamp path determined and a fluid pressure stamp path curve or a characteristic curve determines this by means of the control device with a predetermined target course compared and the pressure valve depending on the comparison accordingly driven. This ensures that the clamping force is essentially above the Fluid pressure control is controlled.

According to a further advantageous embodiment of the device proposed that the hold-down device is connected to a piston which in a double-acting cylinder is arranged. The extends through the cylinder Stamp through. The stamp has a pressure piston which is in one with a incompressible fluid acted chamber is guided. The chamber is with connected to a variable-volume reservoir. The chamber is with the Cylinder rigidly connected and slidably guided in a housing.

In order to achieve a high quality punch rivet connection proposed that the device has a path measuring device through which at least a stroke of the punch is measured, and the hold-down is dependent is decoupled from the travel of the stamp or is coupled to the stamp. The course of the path change of the stamp can lead to a quality statement about the punch rivet connection to be achieved are used. A quality check the punch rivet connection can already during the training of Punch rivet connection can be made. The measuring device is preferably arranged on the stamp.

Alternatively or additionally, it is proposed that the device be a Has measuring device through which a stamp force of the stamp is measured or is determined, the hold-down depending on the punch force and / or the stamp path decoupled from the stamp or with the stamp is coupled.

The measurement of the clamping force of the hold-down can also be used for quality assurance be used. In particular, by measuring the path of the Stamp, the force of the stamp or the clamping force of the hold-down suitable time of decoupling or coupling the hold-down device with the Stamp can be determined.

The path of the hold-down device can also be measured with suitable means. The distance measurement of the hold-down device can provide information about the thickness of the connecting layers of the components are used, so that the path of Stamp with knowledge of the thickness of the layers can be determined. This is particularly important if the thickness of the layers is due to manufacturing tolerances is within a tolerance range. hereby is also avoided, for example, by means of a punch rivet connection self-piercing punch rivets do not cut through the lowest layer through the punch rivet becomes. The layers can also be pressed against each other by the hold-down device be that they lie against each other before the actual punch riveting process is triggered.

The stamp can be driven by means of a hydraulic drive unit. Instead of a hydraulic drive unit, it is also proposed that the stamp by means of a motor, in particular an electromotive, drive unit is driven. Through the drive unit, the stamp performs an im essential linear motion.

Fig. 1

schematisch und im Schnitt ein erstes Ausführungsbeispiel einer Vorrichtung zur Herstellung einer Stanznietverbindung,

Fig. 2

schematisch und im Schnitt ein zweites Ausführungsbeispiel einer Vorrichtung zur Herstellung einer Stanznietverbindung,

Fig. 3 - 8

Momentaufnahmen während eines Stanznietvorgangs der Vorrichtung nach Figur 2 und

Fig. 9

schematisch ein Diagramm einer Klemmkraft in Abhängigkeit vom Verfahrweg des Stempels.

Further details and advantages of the method and the device are explained on the basis of a preferred exemplary embodiment. Show it:

Fig. 1

schematically and in section a first embodiment of a device for producing a punch rivet connection,

Fig. 2

schematically and in section a second embodiment of a device for producing a punch rivet connection,

3 - 8

Snapshots during a punch riveting process of the device according to Figures 2 and

Fig. 9

schematically a diagram of a clamping force as a function of the travel of the punch.

Figure 1 shows schematically and in section a device for producing a Punch rivet. The device has a hold-down device 1, a stamp 2 and a die 3. The hold-down device 1 is towards the die 3 and away from it movable. In the illustration of Figure 1 are between the die 3 and the Hold-down 1 two layers 4, 5 of components shown. The layers 4, 5 are clamped between the hold-down device 1 and the die 3. Schematic is one Punch rivet 8 shown, which rests on the layer 4.

The hold-down device 1 surrounds the punch 2. The punch 2 is also toward the die 3 and movable away from it.

The device has a coupling unit 6, which the hold-down device 1 and the Stamp 2 connects so that a coupling of the Hold-down 1 with the stamp 2 between a substantially rigid Coupling state and a decoupled state can be changed. For this the coupling unit 6 has a piston 9 connected to the hold-down device 1 A plunger 10 is connected to the plunger 2. The piston 9 and the Pressure pistons 10 are displaceable relative to one another within a chamber 11. The chamber 11 is delimited by a housing 12. The chamber 11 is equipped with a preferably substantially incompressible, fluid 7 filled. The fluid pressure inside the volume-variable chamber 11 through the housing 12, the Piston 9 and the pressure piston 10 is limited, is changeable.

The piston 9 has a circumferential groove 13 in which a sealing ring 14 is arranged is. This results in a seal of the piston 9 with respect to the inner jacket of the Housing 12 reached. A through opening 15 is located within the piston 9 formed, through which the stamp 2 extends. Also between the The outer surface of the through opening 15 and the stamp 2 is fluid-tight Connection provided by a sealing ring 16 which in a groove 17 of the Piston 9 is arranged, is formed.

On the outer casing of the housing 12, a housing part 18 is provided, in which one Return spring 19 is arranged. The housing part 18 is connected to the housing 12 connected. The housing part 18 is preferably screwed to the housing 12. The return spring 19 is at one end with the hold-down 1 and with opposite end connected to the housing 12. With a movement of the Retaining spring 19 is tensioned in the direction of layers 4, 5. By the hold-down device 1 can retract the pretension of the return spring 19 become.

On the chamber 11 opposite end face of the pressure piston 10 is a Compensation chamber 20 formed. The compensation chamber 20 has a connection 22 through which an elastic compensating element 21 can be pressurized is. The stamp 2 extends through an end plate 23. In the End plate 23, a sealing element 24 is arranged, which seals on the Outer jacket of the stamp 2 is applied.

The housing 12 is connected to a frame 25. Figure 1 shows one Path measuring device 26 through which the stamp path can be measured. The Displacement measuring device 26 is connected to a control device 27. The Control device 27 is connected to a pressure sensor 28 via a sensor line 36 connected. The pressure sensor 28 is arranged in a line 29, which via a Port 30 is connected to the chamber 11. A line 35 leads to the Compensation chamber 20. In line 35 is a pressure control valve 31, which has a Control line 32 is connected to the control device 27.

Via a drive unit, not shown, the stamp 2 and thus also the Pressure piston 10 in the direction of the die 3 and movable away from this. Is this Pressure control valve 31 closed and the chamber 11 with a substantially filled incompressible fluid, so there is between the stamp 2 and Hold-down device 1 is an essentially rigid coupling.

Due to the rigid coupling and the movement of the stamp 2 also moves the hold-down device 1 in the direction of the die 3. The hold-down device 1 is with for as long the punch 2 rigidly coupled until the hold-down 1 has a predetermined clamping force on layers 4, 5.

The clamping force is dependent on the pressure of the fluid in the chamber 11 determined by the pressure sensor 28.

The stamp 2 with the rivet 8 is positioned on the layer 4. This position forms for example a reference position from which a path measurement of the stamp 2 he follows. Then the punch 2 drives the punch rivet 8 into at least the position 4. Here, the path of the stamp 2 through the path measuring device 26 measured. The path measuring device 26 transmits an output signal to the Control device 27. Has it been specified that the hold-down 1 after a Cut at least the layer 4 with a reduced clamping force on the Layers 4, 5 presses, depending on the travel path of the punch 2 through the control device 27 controls the pressure regulating valve 31. By the Pressure control valve 31, line 29 is at least partially released, so that a fluid 7 can flow out of the chamber 11 via the line 29. simultaneously the pressure piston 10 moves in the direction of the die 3 without the Clamping force of the hold-down 1 is changed.

The fluid flowing out of the chamber 11 becomes the compensation chamber 20 fed. The pressure sensor 28 measures the pressure throughout the process within the chamber 11 and transmits this to the control device 27. If the First hold down the layers with a reduced clamping force and then with a higher clamping force than the current clamping force press against the die, the control device 27 will Pressure control valve 31 is at least partially closed. When closed Pressure control valve 31 is again a quasi-rigid connection between the stamp 2 and the hold-down 1 manufactured.

During a punch riveting process, at least part of the fluid flows out of the Chamber 11 in the compensation chamber 20. It is for a new punch riveting process necessary that the fluid from the compensation chamber 20 into the chamber 11th flowing back. This can be done via line 35. To be as quick as possible Backflow of the fluid from the compensation chamber 20 into the chamber 11 reach, a channel 33 is provided within the piston 10, in which a Check valve 34 is arranged. The check valve 34 is designed such that this a return flow of the fluid from the compensation chamber 20 into the chamber 11 allows. This will cause a possible foaming if it is in the fluid is a pneumatic oil prevented.

Due to the compensating element 21, a change in volume of the fluid can occur foaming of the fluid in the reservoir can be compensated.

The drive unit of the device is preferably an electric motor. The Electromotive drive unit is connected to the transmission unit Stamp connected. This ensures that a rotational movement of the electromotive drive unit via the transmission unit in a Translational movement of the stamp is achieved. This avoids that an abrupt load on the device occurs, as is the case, for example, with known hydraulic devices is the case. At the transmission unit it is preferably at least one gear. The gear is preferably a reduction gear. This has the advantage that a drive unit can be used with a relatively low torque. The relatively minor Torque of the drive unit through the reduction gear depending on Reduction ratio in a correspondingly higher torque or force on the Transfer stamp.

The electromotive drive unit is preferably with the control device connected.

The course of the clamping force of the hold-down device can be controlled via the control device 27 be specified. The control device 27 preferably comprises at least one electronic data processing device.

Figure 2 shows a second embodiment of an apparatus for manufacturing a punch rivet connection.

The device has an essentially cylindrical housing 12. By doing A stamp 2 is arranged in the housing. The stamp 2 is at one end with a setting spindle 53 connected. The setting spindle 53 is with a not shown Drive connected. The setting spindle 53 extends through a spindle nut 38. Between an end face of the housing 12 and the spindle nut 38 is a Thrust bearing 37 arranged.

A cylinder 39 is arranged inside the housing 12. It is preferably the cylinder 39 is a hydraulic synchronous cylinder The cylinder 39 has a chamber 40 and a chamber 11. The chambers 11, 40 are through a pressure piston 10 separated from each other. This is with the stamp 2 connected.

A further cylinder 41 is arranged in the housing 12 and is connected to the cylinder 39 is firmly connected. The cylinders 39 and 40 are axial within the housing 12 Slidably mounted towards the housing.

The cylinder 41 delimits a chamber 42 in which a piston 9 is arranged. The Piston 9 is connected to a hold-down device 1. The stamp 2 extends through the piston 9 and by the hold-down 1, which preferably the stamp 2 all around. The exemplary embodiment shows that a punch rivet 8 is arranged within the hold-down 1.

The cylinder 39 has two connections 30, 43. The connection 30 is via a Line 44 connected to a compensation unit 45. Compensation unit 45 has a reservoir 46 into which the line 44 opens. Inside the reservoir 46, a piston 47 is arranged. The piston 47 is connected to a spindle 48 Drive 50 connected. The spindle 48 and the piston 47 are designed such that the piston 47 at least partially moved out of the reservoir 46 or can be driven into this, so that the volume of the Chamber 46 changes depending on the position of the piston 47. The chamber 40 can be supplied with air via the connection 43.

The cylinder 41 has two connections 51, 52, through which air preferably flows in the chamber 42 of the cylinder 41 can be introduced, so that the piston 9 and thus also the hold-down device 1 can be moved to the layers 4, 5 and away from them.

The mode of operation of the device according to FIG. 2 is described below with reference to FIGS Figures 3 to 8 illustrated snapshots explained.

Figure 3 shows the device 2 in an initial position. The piston 10 is located itself in a middle position within the cylinder 39. The piston 47 of the Compensation unit 45 has assumed an end position in which the volume of the Chamber 46 is the lowest. The piston 9 has reached an end position in which the hold-down device 1 can be equipped with a punch rivet 8. In the hold-down 1 is a punch rivet 8 introduced.

The chamber 42 is supplied with compressed air via the connection 52, so that the Piston 9 is moved into its second end position. This also moves the Hold-down device 1 away from layers 4, 5. The stamp 2 is not in its position changed so that the punch rivet 8 in a joining position within the holding-down device 1 brought. FIG. 4 shows the position of the punch rivet described above 8 within the hold-down device 1.

The hold-down 1 with the punch rivet are spaced apart from those to be connected Components, as can be seen from Figure 4. By interaction of the Setting spindle 53 with the spindle nut 38, the punch 2 in the direction of the components method. The volume of the chamber 11 remains unchanged. The cylinder 39 and the Cylinder 41 are moved with the hold-down device 1 in the direction of the layers 4, 5. The hold-down device 1 exerts a clamping force on the layers 4, 5.

With a further movement of the stamp 2 in the direction of the layers 4, 5, the Stamp 2 a force on the punch rivet 8, thereby forming a Punch rivet connection. During the movement of the stamp for training the punch rivet connection is via the drive 50 of the piston 47 Compensating unit 45 move so that the volume of the chamber 46 increases is so that the fluid can flow from the chamber 11 into the chamber 46. (Fig. 6).

After a punch rivet connection has been formed, the hold-down device 1 and the stamp 8 lifted from the layers 4, 5. Withdrawal takes place via the Setting spindle 53, the pressure of the fluid in chamber 40 preferably is kept constant so that the cylinders 39, 41 simultaneously with the movement of the stamp can be moved, as shown in Figure 7.

To re-equip the device with a punch rivet, the stamp is in move its end position further. That passed from chamber 11 into chamber 46 Fluid volume during the formation of the punch rivet connection is from the Chamber 46 returned to chamber 11 This is done by the fact that Drive 50 of the piston 47 is stirred into the chamber 46. The chamber 42 will acted on with a fluid so that the piston 9 in its lower end position is proceeded. Another punch rivet can be inserted into the hold-down. The punching device is provided for a new punch riveting process. It can a new punch riveting process can be carried out accordingly.

A clamping force-stamp path diagram is shown schematically in FIG.

The production of a punch rivet connection with a hollow rivet can be done in the Sections cutting, spreading and upsetting can be divided. The form of the individual sections can have different strengths.

From the course of the clamping force over the stamp path it can be seen that the Clamping force increases relatively quickly and essentially throughout Cutting process is kept constant. The course shows that the clamping force during the spreading process and essentially during the upsetting process compared to the clamping force during the cutting process is lower. Through the Reduction of the clamping force is achieved that one towards the semi-tubular rivet directional movement of at least one layer is made possible.

The clamping force-stamp path diagram shows that shortly before the end of the Upsetting the clamping force of the hold-down compared to the reduced Clamping force increases. This should allow any training of beads or Warps that rise above the head of the punch rivet into the upper position be pushed in.

The course of the clamping force as a function of the stamp travel is shown in FIG. 9 shown schematically. It can be adapted to different punch riveting tasks become. In particular, the course of the clamping force can be a function of the connecting components, as well as the punch rivet.

A further course of a clamping force as a function of is dashed Stamp path shown. The course shows that the clamping force initially up to a predetermined value increases and is held at this value. In particular during an upsetting process, the clamping force is given for a given one Stamp stroke increased and then decreased again.

The device according to the invention is also suitable for other designs of Suitable rivet connections, in particular by means of hollow rivets, full rivets and like. It is not imperative that self-piercing be carried out by a rivet.

LIST OF REFERENCE NUMBERS

1

down device

2

stamp

3

die

4

location

5

location

6

coupling unit

7

fluid

8th

rivet

9

piston

10

pressure piston

11

chamber

12

casing

13

groove

14

seal

15

Through opening

16

seal

17

groove

18

casing

19

return spring

20

compensation chamber

21

compensation element

22

Connection

23

end plate

24

sealing element

25

frame

26

displacement measuring device

27

control device

28

pressure sensor

29

management

30

Connection

31

actuator

32

control line

33

channel

34

check valve

35

management

36

sensor line

37

camp

38

spindle nut

39

cylinder

40

chamber

41

cylinder

42

chamber

43

Connection

44

management

45

compensation unit

46

reservoir

47

piston

48

spindle

49

camp

50

drive

51

Connection

52

Connection

53

setting spindle

Claims (31)

1. Method for the production of a punch riveted joint, wherein at least two layers (4, 5) are pressed by means of a holding-down device (1) against the bottom die (3), and a rivet, especially a semi-hollow rivet (8), for the joining of the layers (4, 5) by means of a punch (2), cuts through at least the layer (4) facing the semi-hollow rivet (8), is deformed in the lower layer or layers (5) with formation of a closing head and is then upset, characterised in that the holding-down device (1) is connected by way of a coupling unit (6) to the punch (2), and that during a punch riveting operation a coupling of the holding-down device (1) to the punch (2) is varied between a substantially rigid coupling state and an uncoupled state.
2. Method according to claim 1, characterised in that the coupling state is varied in dependence on the punch travel or a characteristic magnitude derived from the punch travel.
3. Method according to claim 1 or 2, characterised in that the coupling state is varied in dependence on material properties, especially on the stability, of at least one layer.
4. Method according to claim 1, 2 or 3, characterised in that the coupling state is varied in dependence on the properties of a pairing of the layers (4, 5) of different materials.
5. Method according to one of claims 1 to 4, characterised in that the coupling state is varied in dependence on the number of the layers (4, 5).
6. Method according to one of claims 1 to 5, characterised in that the coupling state is varied in dependence on a thickness of at least one layer (4, 5), especially the layer (4, 5) facing the punch rivet (8).
7. Method according to one of claims 1 to 6, characterised in that the coupling state is varied in dependence on the material properties of the punch rivet (8).
8. Method according to one of claims 1 to 8, characterised in that the coupling state is varied in dependence on the hardness of the punch rivet (8).
9. Method according to claim 7 or 8, characterised in that the coupling state is varied in dependence on the geometry of the punch rivet (8).
10. Method according to one of claims 1 to 9, characterised in that the coupling state is varied at least in an end section of the upsetting operation in such a manner that the clamping force exerted by the holding-down device (1) is increased.
11. Method according to claim 10, characterised in that the coupling state of the holding-down device (1) is varied in such a manner that the clamping force is increased such that the head finishes substantially flush with the layer (4) facing the punch rivet (8).
12. Method according to one of claims 1 to 11, characterised in that the holding-down device (1) is moved with the punch (2) to the layers (4, 5) and the holding-down device (1) presses the layers (4, 5) with a predetermined clamping force against a bottom die (3), in that the holding-down device (1) is at least partially uncoupled from the punch (2), and the punch (2) for cutting through at least the layer (4) facing the semi-hollow rivet (8) for the formation of a closure head and for upsetting of the semi-hollow rivet (8) is moved further, the holding-down device (1) optionally being coupled to the punch (2) after a predetermined punch travel or a characteristic magnitude derived from the punch travel.
13. Method according to claim 12, characterised in that a punch travel is measured and the punch travel or a characteristic magnitude derived from the punch travel is compared with a predetermined desired magnitude, the coupling state being varied in dependence on the comparison result of the punch (2).
14. Method according to claim 12 or 13, wherein a punch force of the punch (2) is determined and compared with a predetermined desired magnitude, the coupling state being varied in dependence on the punch force and/or the punch travel (2).
15. Method according to claim 12, 13 or 14, wherein a clamping force of the holding-down device (1) is determined and compared with a predetermined desired magnitude, the coupling state being varied in dependence on the clamping force and/or the punch force and/or the punch travel (2).
16. Method according to one of claims 1 to 15, wherein the holding-down device (1) comprises a piston (9) and the punch (2) comprises a pressure piston (10), the piston (9) and the pressure piston (10) are movable relative to each other in a chamber (11), filled with a preferably incompressible fluid, of the coupling unit (6), the fluid pressure in the chamber (11) being varied and the punch (2) being driven by a drive unit.
17. Method according to one of claims 1 to 15, wherein the holding-down device (1) is connected to a piston (9) which is arranged in a cylinder (41) through which the punch (2) extends, the punch (2) has a pressure piston (10) which is guided in a cylinder (39) to which an incompressible fluid can be applied and which is connected to an equalising chamber (46), the cylinders (39, 41) being rigidly connected and slidably guided in a housing (12).
18. Method according to claim 16 or 17, wherein a fluid pressure is controlled in dependence on the clamping force and/or the punch force and/or the punch travel and/or the travel of the holding-down device (1).
19. Method according to claim 17, wherein in dependence on the clamping force and/or the punch force and/or the punch travel and/or the travel of the holding-down device (1), or in dependence on a desired-versus-actual comparison, an adjusting member (31) fluidly connected to the chamber (11) is triggered.
20. Apparatus for the production of a punch riveted joint having a bottom die (3), a holding-down device (1) and a punch (2), the punch (2) and the holding-down device (1) being movable towards and away from the bottom die (3), at least two layers (4, 5) of components being able to be clamped between the holding-down device (1) and the bottom die (3), and a punch rivet (8), for joining the layers (4, 5) by means of the punch (2), being able to be driven into at least the layer (4) adjacent to the holding-down device (1), characterised by a coupling unit (6) which connects the holding-down device (1) and the punch (2) in such a manner that during a punch riveting operation a coupling of the holding-down device (1) to the punch (2) can be varied between a substantially rigid coupling state and an uncoupled state, and by a drive unit which drives the punch (2).
21. Apparatus according to claim 20, characterised in that the holding-down device (1) comprises a piston (9) and the punch (2) comprises a pressure piston (10), in that the piston (9) and the pressure piston (10) are movable relative to each otherin a chamber (11), filled with a preferably incompressible fluid, of the coupling unit (6), the fluid pressure in the chamber (11) being variable.
22. Apparatus according to claim 21, characterised in that a control device (27) is provided for triggering the coupling unit (6), a clamping force exerted by the holding-down device (1) on the at least two layers (4, 5) being varied, during a punch riveting operation, according to a predetermined curve in dependence at least on the punch travel or a characteristic magnitude derived from the punch travel.
23. Apparatus according to claim 21 or 22, characterised in that at least one equalising chamber (20) is provided into which, by way of at least one line (29, 35), at least a part of the fluid can be led out of the chamber (11) and led back out of the latter.
24. Apparatus according to claim 23, characterised in that in at least one line (29) a pressure control valve (31) or a proportional control valve is provided.
25. Apparatus according to claim 22, 23 or 24, characterised in that a pressure sensor (28) for measuring a fluid pressure is provided.
26. Apparatus according to claim 25, characterised in that the control device (27) is connected to the pressure sensor (28) and to at least one pressure control valve (31).
27. Apparatus according to claim 26, characterised in that means are provided by which a fluid pressure is determined in dependence on the punch travel and a fluid pressure-versus-punch travel curve or a characteristic magnitude curve is derived, this is compared by means of the control device (27) with a predetermined desired curve, and the pressure control valve (31) is triggered accordingly in dependence on the comparison.
28. Apparatus according to claim 20, characterised in that the holding-down device (1) is connected to a piston (9), which is arranged in a cylinder (41) through which the punch (2) extends, in that the punch (2) comprises a pressure piston (10) which is guided in a cylinder (39) to which an incompressible fluid can be applied, and in that the cylinder (39) is connected to a reservoir (46) the volume of which is variable, the cylinders (39, 41) being rigidly connected to each other and being slidably guided in a housing (12).
29. Apparatus according to claims 20 to 28, characterised by a path-measuring device (26) for measuring a punch travel of the punch (2), the coupling state being varied in dependence on the punch travel.
30. Apparatus according to one of claims 20 to 29, characterised by a measuring device by means of which a punch force of the punch (2) is measured or determined, the coupling state being varied in dependence on the punch force and/or the punch travel.
31. Apparatus according to one of claims 20 to 30, characterised by a measuring device by means of which a clamping force of the holding-down device (1) is measured or determined, the coupling state being varied in dependence on the clamping force and/or the punch force and/or the punch travel.

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