GB2524654A

GB2524654A - Method for connecting at least two components by the punch riveting method, device for carrying out the method, production apparatus and use of the method

Info

Publication number: GB2524654A
Application number: GB1503009.1A
Authority: GB
Inventors: Jens Koenig; Harald Lukosz; Florian Woelke; Sebastian Engler
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-02-28
Filing date: 2015-02-23
Publication date: 2015-09-30
Anticipated expiration: 2035-02-23
Also published as: GB2524654B; SE540747C2; DE102014203757A1; SE1550163A1; DE102014203757B4; GB201503009D0

Abstract

A method for connecting at least two components 11, 12 by punch riveting, in which the components are arranged between a punch 15 and a die or holder-up 18. A rivet 20 is pushed by the punch 15 into the components 11, 12 to connect them in a force- and form-locking manner. During pushing-in, the rivet 20 and/or the at least two components 11, 12 are caused to oscillate by apparatus 30. The oscillations may be ultrasonic, preferably at a frequency of 15-40kHz and a stroke of 10-100 micro metres. The oscillations may be coupled parallel to, perpendicular to or at an oblique angle to the joining direction or in the circumferential direction of the rivet. The frequency and/or stroke may be altered during riveting. The apparatus 30 may be located on the side of the punch facing away from the rivet. The method may be used to join brittle materials such as light metals or composite fibre materials.

Description

Method for connecting at least two components by the punch riveting method, device for carrying out the method, production apparatus and use of the method

Prior art

The invention relates to a method for connecting at least two components by the punch riveting method according to the preamble of Claim 1. The invention further relates to a device for carrying out the punch riveting method, to a production apparatus having a device according to the invention and to the use of a method according to the invention.

A method according to the preamble of Claim 1 is already known from practice and serves to connect at least two components, in particular of plane form, in a connecting region. The punch riveting method is distinguished in that it is not necessary to prepunch the components to be connected to one another. Rather, a rivet is pushed into the at least two components by means of a punching tool, during which a correspondingly shaped holder-up in the form of a die, which cooperates with the punching tool, ensures that the rivet is deformed in a specific manner within the components to be connected to one another, in order to produce a force-and form-locking connection between the components and at the same time avoid a penetration of the component facing away from the rivet. The punch riveting method has the advantage, for example over a welding method, that materials of different types can be connected to one another and that the connection is relatively insensitive to corrosion, because it enables a tight component connection. Typical applications of the punch riveting method are found, for example, in body making, in which a device for carrying out the punch riveting method is fastened, for example, to a movably designed robot arm.

Owing to the fact that no prepunching of the components is required, relatively high pushing-in forces for the rivet are required, and the rivet must be composed of special materials, in particular exhibiting relatively high strength values. Furthermore, although in principle components of different types can be connected to one another, in particular the application in fibre-reinforced, relatively brittle components using the known punch riveting method is, however, problematic, since these components tend to tear or tear out when the rivet is pushed in. Furthermore, it is considered disadvantageous that, owing to the relatively large pushing-in forces required, the drives for the punching tool are of relatively large and costly design and therefore also tend to have a relatively high weight. This results in disadvantages regarding the structure on which a device for carrying out the punch riveting method is arranged, for example a robot arm. The latter then has to be of correspondingly stable or costly design, in order to be able to carry the relatively heavy device. The relatively high weight of the structure results, in turn, in a relatively costly drive also being required for moving the robot arm. Overall, therefore, relatively high investments costs result for a corresponding production apparatus.

Furthermore, the so-called ultrasonic welding method, in which components composed of thermoplastic plastics or metallic materials are connected to one another, is known from the prior art. The metallic materials used are, especially, aluminium, copper and their alloys. The heat required in ultrasonic welding is generated by a high-frequency mechanical oscillation arising between the components due to molecular and interfacial friction.

Disclosure of the invention

Starting from the prior art described, the object on which the invention is based is to develop a method for connecting at least two components by the punch riveting method according to the preamble of Claim 1 in such a way that the above-mentioned disadvantages can be at least partly overcome. This object is achieved according to the invention in a method having the features of Claim 1 in that, during the pushing-in of the rivet, the rivet and/or the at least two components are caused to oscillate by means of a (vibration) apparatus, preferably in the form of a power ultrasonic system. Such a method according to the invention result in a large number of advantages. In particular, the required pushing-in or setting forces for the rivet are thereby reduced. As explained above, a series of advantages result therefrom, in particular a drive of reduced size or weight for the punching tool. This has, in turn, in the use on an industrial robot, the result that the industrial robot or its carrying structure can be equipped more simply and thus lighter and with low drive-related cost. The arm of the industrial robot which is simpler and has, for example, a smaller cross-section then, in turn, has the result that regions of the components which hitherto were not accessible to the punch riveting method with conventional industrial robots can likewise be connected to one another using the punch riveting method.

With regard to the actual connection, the use of a vibration apparatus has, in dependence on the amplitude and its frequency, the result that, in addition to the force-and form-locking connection forming the connection, optionally a material-locking connection in the manner of an ultrasonic welding connection between the rivet and the joining partners can be formed. It is considered a further advantage that, for example, a rivet excited to oscillate contributes to an improved and friction-reduced material separation. This is advantageous in the cutting or shearing phase of the punch riveting process, in particular in the case of brittle light metals, fibre reinforced plastics, but also in the case of traditional steel or aluminium materials. In addition, it is known that in the case of an ultrasonic superposition, which is preferably employed as vibrational oscillations, a reduction of the yield stresses during the forming leads. This effect also results in a reduction of the setting or pushing-in forces of the rivet and optionally in an improved spreading behaviour of the rivet. In addition, for example, also brittle materials which are difficult to rivet can be connected to one another by means of the method according to the invention.

Here, possible tears in the punch-or die-side joining partners (component) of the riveted connection owing to the increase of the plastic deformation properties of the materials can be avoided by the oscillations. A reduction of the required pushing-in force for the rivet has, moreover, the result that new rivet materials can be used which may exhibit lower strengths and/or novel rivet geometries. It is thereby possible, for example, to use corrosion-resistant special steel punch rivets which have markedly lower yield points than heat-treated tempering steel.

Advantageous developments of the method according to the invention are recited in the subclaims.

It has proved particularly preferable when the oscillations have a stroke (by this is understood the sum of the height of the amplitude in the positive and negative oscillation direction) between 10 pm and 100 pm, at a frequency of the oscillations of between 15 kHz and 40 kHz. The frequency range is thus a range which typically corresponds to ultrasonic oscillations.

With regard to the coupling-in direction of such (ultrasonic) oscillations into the rivet or the components, various variations are conceivable: In a first configuration of the method, it is provided that the oscillations are coupled, at least substantially parallel to the joining direction of the rivet, into the rivet and/or the at least two components. In this case, particularly low pushing-in or pressing-in forces are required for the rivet.

Depending on the components or rivet geometry used, it can, however, also be advantageous when the oscillations are coupled, at least substantially perpendicularly to the joining direction of the rivet, into the rivet and/or the at least two components.

In an alternative configuration, it can be provided that the oscillations are coupled, at an oblique angle to the joining direction of the rivet, into the rivet and/or the at least two components.

In a further alternative configuration, it can be provided that the oscillations are coupled, at least substantially in the circumferential direction of the rivet, into the rivet and/or the at least two components.

A further advantageous configuration of the method according to the invention provides that the stroke and/or the frequency of the oscillations are/is altered during the joining process. For example, at the start of the joining process, a relatively large stroke can be provided, which reduces with increasing pushing-in or pressing-in depth of the rivet.

The invention also comprises a device for connecting at least two components by the punch riveting method, in particular by means of the method according to the invention described above. The device comprises a punch element for pushing a rivet into at least two components and a holder-up arrangeable with the punch element with interposition of the at least two components. According to the invention, it is provided that the device has an apparatus for generating oscillations, which is arranged in operative connection with the punch and/or the at least two components.

In a preferred configuration of the device, which is aimed at the provided stroke or frequency range of the vibrations, it is provided that the vibration apparatus is formed as an ultrasonic oscillation generator.

Preferably, it is provided that the vibration apparatus is arranged on the side of the punch facing away from the rivet. Such an arrangement of the vibration device on the punch has, in particular, the advantage that the vibrations can be directly introduced into the connecting region of the components via the rivet, and that the device can be configured particularly simply.

Furthermore, the invention comprises a production apparatus, comprising a carrier structure having a device according to the invention arranged on the carrier structure. By a production apparatus in the meaning of the invention there is understood, by way of example, and in a non-limiting manner, an industrial robot having a robot arm which forms the carrier structure on which the device according to the invention is arranged. As a result of the use of the vibration apparatus, it is made possible here, owing to reduced setting or pushing-in forces for the rivet, that the required drive for the punch has a relatively low mass, so that the carrier structure too can be designed structurally relatively simply or with small cross-sections. This results, in particular, in relatively low investment or manufacturing costs for the production apparatus. In the case of a robot, it is thereby possible to use, for example, constructions with lower ultimate loads, also because lower joining forces have tc be transmitted or taken up.

B

Lastly, the invention comprises the use of a method according to the invention for connecting components composed of brittle material, in particular light metals or composite fibre materials.

Further advantages, features and details of the invention

emerge from the following description of preferred

exemplary embodiments and with reference to the drawing.

In the drawing: Fig. 1 shows a simplified illustration of an industrial robot having a device according to the invention, arranged on a carrier arm, for connecting at least two components by the punch riveting method and Fig. 2 to Fig. 5 show a partial region of the device according to the invention during different, successive steps in the punch riveting of two components, each in longitudinal section.

Like elements or elements with the same function are provided with the same reference numbers in the figures.

Fig. 1 illustrates, in a highly simplified manner, a production apparatus 100 in the form of an industrial robot 1. The industrial robot 1 comprises a carrier structure 2 having a column 3 and two arms 4, 5 articulatedly connected to one another, a device 10 according to the invention for connecting at least two components 11, 12 by the punch riveting method being arranged on the side of the arm 5 facing away from the arm 4. As a result of the articulated connection of the arms 4, 5 on the column 3, it is possible, in customary fashion, for the production apparatus 100 or the industrial robot 1 to be able to reach with the device 10 substantially any point in space located within the range of the arms 4, 5.

The two components 11, 12 which can be seen in Figs. 2 to 5 are, in particular, but not in a limiting way, components such as those used in automotive body making. Possible materials for the components 11, 12 here are, in particular, metallic components or sheets or else composite fibre materials.

The device 10 has a punch 15 which, in the illustrated exemplary embodiment, has a round cross-section. The punch is radially surrounded by a sleeve-shaped hold-down 16 and is arranged so as to be movable in the longitudinal direction relative to the latter. In particular, the punch is coupled to a drive (not illustrated), preferably a hydraulic or pneumatic drive, which serves to apply a pressing-in force F required for pushing a rivet 20 into the two components 11, 12. Likewise, the hold-down 16 is coupled to a drive (likewise not illustrated) which serves to press the hold-down 16 against the surface of the component 11 facing the punch 15 with a holding-down force.

Alternatively, it is also conceivable to realise the function of the hold-down 16 by a mechanical spring. In this case, the holding-down force is diverted from the punching force of the punch 15. As a result, no separate drive is required for the hold-down 16.

On the side of the two components 11, 12 lying opposite the punch 15 and the hold-down 16, there is arranged a die 18 acting as a holder-up. The die 18 is likewise liftable and lowerable in the direction of a longitudinal axis 19, in the direction of which the punch 15 and the hold-down 16 are also movably arranged. In particular, it can be provided that the drive of the hold-down 16 and of the die 18 are coupled to one another. The hold-down 16 and the die 18 serve to clamp in or press together the two components 11, 12 between the hold-down 16 and the die 18 during the machining by the punch 15.

The die 18 has, on the side facing the component 12, a plane upper side 21, from which two trough-or pit-shaped recesses 22, 23 originate. In particular, the recesses 22, 23 are arranged in alignment with projections 24, 25 which are arranged on the rivet 20 and are pin-shaped in the exemplary embodiment illustrated.

It can also be provided that a single, ring-shaped recess originates from the upper side 21 of the die 18, and that a plurality of projections arranged at uniform angular distances from one another are formed on the rivet 20, the projections being aligned with the corresponding recess.

The rivet 20 is composed of a material harder than the materials of the two components 11, 12, at least in the region of the projections 24, 25. The plane upper side 26 facing away from the component 11 is arranged in operative connection with the punch 15, which bears in a planar manner against the upper side 26 of the rivet 20.

According to the invention, it is provided that the punch is arranged in operative connection with an apparatus 30 for generating oscillations or vibrations. In particular, ultrasonic oscillations with a stroke (distance between maximum positive and negative amplitude of an oscillation) between 10 pm and 100 pm and a frequency between 15 kf-{z and kHz are generated by means of the device 30. These oscillations are coupled into the rivet 20 by the apparatus via the punch 15. The coupling-in direction of the vibrations of the apparatus 30 can be either parallel to the longitudinal axis 19, i.e. parallel to the direction of joining the rivet 20 to the components 11, 12, perpendicular to the longitudinal axis 19 in the circumferential direction of the longitudinal axis 19, or else at an oblique angle to the longitudinal axis 19.

In addition, it is mentioned that in an alternative configuration of the invention it can be provided that the apparatus 30 (or an additional apparatus 30) is arranged either additionally in operative connection with the two components 11, 12, in order to transmit corresponding oscillations into the two components 11, 12, preferably only in the connecting region of these components, or else that the apparatus 30 couples exclusively corresponding oscillations into the components 11, 12.

Fig. 2 shows the start of the punch riveting method, when the projections 24, 25 come into operative connection with the upper side of the component 11. In doing so, the punch is pressed with the pressing-in force F against the component 11 facing the punch 15. In the further course of the method and with assistance of the oscillations coupled into the components 11, 12, the projections 24, 25 firstly cut or punch into the component 11. In doing so, the two components 11, 12 are plastically deformed, the component 12 facing the recesses 22, 23 being pressed in the corresponding regions into the recesses 22, 23. During the further movement path or the further downward movement of the rivet 20 in accordance with Fig. 4, the projections 24, are spread outwards in the region of the recesses 22, 23, whereby the two components 11, 12 are connected to one another in the axial direction securely in a force-locking manner. It is essential here that, in accordance with Fig. 5, which shows the end position of the rivet 20, the projections 24, 25 do not protrude from the component 12 or completely penetrate the latter.

After the rivet 20 has reached the (axial) end position illustrated in Fig. 5, in which the upper side 26 of the rivet 20 ends at least approximately flush with the upper side of the component 11, the punch 15 is subsequently moved upwards again in the opposite direction away from the components 11, 12. Furthermore, the hold-down 16 and the die 18 are moved away from one another, in order to free the two components 11, 12 connected to one other.

The method described so far for punch riveting at least two components 11, 12 and the production apparatus 100 can be modified in various ways, without departing from the inventive concept.