Abstract:
A method for joining, by adhesive bonding, at least two large joining partners in vehicle construction, in particular in aircraft construction, comprises the following steps:
       detecting the geometric data of the joining partners in an automated manner,   detecting the joint gap dimensions of the joining partners from the geometric data,   applying adhesive to one or both joint faces of the two joining partners to be joined as a function of the joint gap dimensions,   joining the joining partners in the joining position, and   sequentially applying joining pressure to the joint faces along the joint gap to bring the joining partners into the final joining position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of and claims priority to PCT/EP2010/053523 filed Mar. 18, 2010 which claims the benefit of and priority to German Patent Application No. 10 2009 013 540.5 filed Mar. 19, 2009 and German Patent Application No. 10 2010 010 686 filed Mar. 8, 2010, the entire disclosures of which are herein incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a method for joining, by adhesive bonding, large components in vehicle construction, in particular in the construction of aircraft fuselages for large aircraft. 
         [0003]    In recent years, modern lightweight constructions have significantly changed vehicle construction, whether of ships, aircraft, cars or railway vehicles. Thus, the use of suitable materials leads to improvements in terms of weight, safety and comfort, with cost savings also being possible at the same time. In addition to the use of suitable materials, this progress has been achieved through the intelligent use of modern adhesive technology, it being possible to combine the adhesive technology with the conventional joining technologies such as riveting, screwing or spot welding. 
         [0004]    Meanwhile, the adhesive technology has also found its way into aircraft construction. Thus, the fuselage of large aircraft is joined substantially manually in a shell construction. In correspondingly large devices, the fuselage of an aircraft is equipped with stringers, formers, passenger and cargo floors, door and freight door frames and window frames in partially mechanised and in part in manual assembly steps, before the outer skin is closed. In this case the fuselage, which consists of CFRP, light metal alloys and/or Glare®, consists of a barrel-shaped segment or of partial shells. 
         [0005]    Structural connections are joined by riveting or by a combination of riveting and adhesive bonding, also referred to as rivet-bonding. Panels and fuselage segments and the inserted components are interconnected by riveting, liquid shim materials which fill the slightly irregular gap remaining between the joining parts during riveting being applied before joining. The shim materials are generally two-component epoxy resins which have a gap-filling capacity of approximately 2-3 mm and a curing time of 8 h at room temperature. 
         [0006]    Larger gaps are compensated manually in a time-consuming manner by means of solid shim made of fibre composite material. A combination of liquid and solid shim materials can also be used. As a whole, the processing of the shim materials is carried out substantially manually and is very time-consuming, in particular since the joining partners are temporarily joined to determine the gap dimensions and the joining partners must then be moved apart from one another again. 
         [0007]    An example of the construction of large aircraft in shell construction can be derived from DE 10 2007 061 429 A1, from which a fuselage structure of an aircraft is known. In this case, the fuselage structure comprises an outer skin, structural components such as stringers and formers which are connected to the outer skin, and an inner lining. The structural components are adhesively bonded, riveted and/or welded to the outer skin, and the inner lining and the outer skin and the structural components thereof together form a carrying connection. In this case, the inner lining can also be connected to the structural components and/or the outer skin by means of an adhesive joint. 
         [0008]    The adhesion systems and adhesion technologies which have so far been used in the aviation field do not allow rapid, automated joining by adhesion of the fuselage and fitted components. Furthermore, automated pressing of the components to be adhesively bonded is difficult to control in the case of large joint faces, since very high joining forces would be required for pressing and ensuring complete wetting of the joint faces of the joining partners. 
       SUMMARY OF THE INVENTION 
       [0009]    The object of the invention is therefore to provide a method and a corresponding device for automated joining, by adhesive bonding, of large components in vehicle construction, in particular in aircraft construction. 
         [0010]    This object is achieved by a method with the features of claim  1  and/or by a device with the features of claim  10 . Preferred embodiments of the invention are the subject-matter of the dependent claims. 
         [0011]    The method according to the invention for joining, by adhesive bonding, at least two large joining partners in vehicle construction, in particular in aircraft construction, comprises the following steps:
       detecting the geometric data of the joining partners in an automated manner,   detecting the joint gap dimensions of the joining partners from the geometric data,   applying adhesive to one or both joint faces of the two joining partners to be joined as a function of the joint gap dimensions,   joining the joining partners in the joining position thereof, and   sequentially applying joining pressure to the joint faces along the joint gap to bring the joining partners into the final joining position.       
 
         [0017]    The sequential application of the joining pressure preferably takes place in a predetermined region which is shifted along the joint gap of corresponding joining partners, the joining partners being brought into the final joining position by the joining pressure in the predetermined region. 
         [0018]    More preferably, the position of the predetermined region in which the sequential pressure is applied is shifted continuously along the joint gap. 
         [0019]    In a further preferred embodiment of the invention, the position of the predetermined region in which the sequential pressure is applied is shifted piecewise along the joint gap. In other words, the sequential pressure is applied discontinuously in a predetermined cycle. 
         [0020]    In aircraft construction, the joining partners, such as fuselage elements and fuselage segments, and the components to be fitted are subject to tolerances. The geometries of the joining partners can be detected by modern measuring methods and the gap dimensions for adhesive joining can be determined from the detected digital data with sufficient accuracy. Applying the adhesive in the joint gap after or during joining of the joining partners makes it possible to join the joining partners in an automated manner. Further, since temporary joining of the joining partners for determining the gap dimensions is omitted, a high production rate is possible. 
         [0021]    The amount of adhesive to be applied is preferably determined on the basis of the joint gap dimensions. It is thus ensured that the adhesive joint is sufficient for the desired stability conditions and that adhesive is used economically. 
         [0022]    The adhesive can be applied in a region of the joint gap which is located directly in front of the predetermined region of the joint gap which is to be joined by sequential pressure. However the adhesive can also be applied at a time before the joining partners are joined. 
         [0023]    The flow required for this purpose of the adhesive can be achieved by means of its composition, gravitational force, centrifugal force, magnetic and/or electrical fields, low pressure in the joint, temperature control of the joining partners and/or the adhesive or a combination of the mentioned parameters. 
         [0024]    More preferably, the joint gap can comprise lateral or surface-edge limiting elements in order to prevent the adhesive applied in the joint gap from escaping. As a result, uncontrolled leakage of adhesive from the bonding gap is avoided. These limiting elements can remain at the bonded joint after curing or can be removed once a sufficient mechanical stability of the bonded joint has been reached. In the case that the elements remain, they can consist of a second adhesive. This second adhesive can be applied to one or both of the adherend surfaces at a time before, while or after the joining partners are brought into the final joining position. This second adhesive can be cured together with the adhesive applied in the joint gap or separately therefrom. In the case that the limiting elements are removed, they can comprise a non-adhesive surface, which for example can be obtained by means of the material used or a laminated film. 
         [0025]    Before the joining partners are joined together, the joint faces of the joint gaps or joints are preferably subjected to an automated pretreatment to optimise the quality in terms of adhesion and the quality thereof in terms of adhesion is determined. An optimum bonding result is thus achieved. 
         [0026]    In particular, in aircraft construction the joining partners are formed by fuselage segments and structural components such as formers, stringers, etc. for constructing a fuselage structure. 
         [0027]    The device according to the invention for carrying out the above-described method comprises:
       a component carrier comprising a component seat for receiving a first joining partner,   a central carrier for receiving at least an integration tool,   an integration tool for receiving and introducing the further joining partner to be introduced into the first joining partner,   a measuring system for detecting the geometric data of the joining partners and for calculating the joint gaps,   at least a modular tool for applying the adhesive,   at least a pressure tool for applying the joining pressure along the joint gap to be adhesively bonded,   a control system for controlling the device.       
 
         [0035]    The pressure tool can preferably apply the joining pressure to the joint gap sequentially on one side or on each side. 
         [0036]    More preferably, the device comprises further tools for surface treatment and/or for surface monitoring and/or for curing the adhesive. In this case, individual tools can be used for processing the components to be fitted, while further tools are designed to be received on the central carrier, in order to be able to process and/or measure the first joining partner arranged on the component carrier. These tools can be designed as robots which, according to requirements, have corresponding spatial degrees of freedom. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]    A preferred embodiment of the invention will be described below with reference to the drawings, in which: 
           [0038]      FIG. 1  is a first perspective view of the device according to the invention comprising a tool for fitting formers which is guided via a central carrier, 
           [0039]      FIG. 2  is a second perspective view of the device comprising a further tool, 
           [0040]      FIG. 3  is a view of a detail of the device according to  FIG. 1 , 
           [0041]      FIG. 4  is a schematic view of the continuous sequential application of a joining pressure, and 
           [0042]      FIG. 5  is a schematic view of the piecewise sequential application of a joining pressure. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0043]      FIG. 1  is a schematic view of the device according to the invention for the structural completion of fuselage segments based on the central carrier principle, the device holding ready technologies and systems for largely parallelised fitting of formers, passenger and cargo floors, door and freight door frames and window frames in the fitted fuselage segment. A fuselage segment  1  is mounted on a movable component carrier  2 , the component carrier  2  comprising an automated component seat and systems for correcting shape and position (not shown). A central carrier  3 , which is supported on each side by rigid and lowerable supports  4 ,  5 , extends inside the fuselage segment  1  when the fuselage segment  1  is in the fitted state. 
         [0044]    Depending on the fitting operation, different integration tools  6  are guided on the central carrier  3 , which is supported by the rigid and lowerable supports  4 ,  5  and can for example have a length of approximately 22 m. The central carrier  3  can be retracted telescopically to bring the barrel-shaped fuselage segment  1  shown in  FIG. 1  into the device. The fuselage segment  1  is brought into the device lying on the movable component carrier  2 . The component carrier  2  has a functionality for correcting the position of the fuselage segment  1  and tensioning devices with which the shape of the fuselage segment  1  can be fixed and optionally corrected. Once the fuselage segment  1  has been introduced, the central carrier  3  can be moved back out to the rear support  5 . The respectively required integration tool  6 , which is already prefitted outside the system and in the example is equipped with formers  7  to be fitted, is then mounted. 
         [0045]    In order to achieve a high level of parallelisation of assembly steps, as many of the above-mentioned components as possible per process step and per tool are to be fitted simultaneously. 
         [0046]    The integration tool  6  equipped with the components to be introduced is moved into the fuselage segment  1  via the central carrier  3  as a guide means and orientates itself optically in space, in such a way that the former flange surface  8  later represents the zero reference point. 
         [0047]    The components to be fitted, in this case the formers  7 , are then brought simultaneously into their precise joining positions by folding, placing or radial expansion processes of the integration tool  6 . A possible combination is for example the simultaneous introduction of formers  7  and floor (not shown). 
         [0048]    The device further comprises modular tools  9 ,  10 ,  11 , known as end effectors, which are movably arranged on a rail system  12 , are used for surface treatment, surface monitoring, adhesive application and for curing the adhesive and for these tasks can be equipped with the corresponding tools, the corresponding equipment taking place automatically. 
         [0049]      FIG. 2  shows the device of  FIG. 1 , a modular tool  13  being arranged on the central carrier  3 , which tool is used to treat the joint faces in the fuselage segment  1  automatically to achieve an optimum bonding result. The modular tool  13  is also used to assess the pretreated joint faces with regard to the quality thereof in terms of adhesion. The modular tool  13  is moved into the fuselage segment  1  to pretreat and assess the joint faces. 
         [0050]    As explained above, the approach in terms of joining is based on the use of adhesive bonding technology, without additional riveting being used for fixing. Should rivets be required at selected points, these are introduced later in another system. The function of the adhesive bonding during assembly is thus to fix the introduced components rapidly and compensate tolerances on the inner surface of the fuselage, which depending on the production technology may be subject to tolerances of varying strengths. 
         [0051]    In addition to the fulfilment of a compensating and sealing function, the basic requirements placed on a CFRP structural adhesive for aviation applications include good processibility, which in particular is defined by long open times and assembly-compatible rheology, rapid curing and high pressure resistance, in order to avoid loosening in the cured joint owing to flow processes. 
         [0052]    Therefore, the joint faces in the fuselage and on the components such as the exemplary formers are firstly pretreated automatically, in this case by the tool  13 , and then tested by an automated monitoring method with regard to the quality thereof in terms of adhesion. As a result, the required pretreatment time is considerably reduced with substantially improved reproducibility in comparison to manual execution. 
         [0053]      FIG. 3  shows the process of the preparatory surface treatment of the formers  7  by means of the modular tools  9  and  10 . In this case, the formers  7  are arranged on schematically shown receivers  14 . After the preparatory surface treatment, the integration tool  6  together with the fitted formers is brought into the fuselage structure  1  and the formers  7  are brought automatically into the joining position by means of the receiver  14  of the integration tool  6 . The adhesive is then introduced into the respective joint gaps through application openings  15  arranged in the fuselage structure. 
         [0054]      FIG. 4  is a schematic cross-sectional view of the process of continuous joining with sequential pressurisation. A first, outer joining partner  20  and a second, inner joining partner  21  are shown. The outer joining partner  20  can for example be a fuselage segment in which a former is to be introduced as an inner joining partner  21 . The two joining partners are brought into a temporary joining position (not shown) by corresponding tools of the device, i.e. the component carrier  1  and the integration tool  6  described in the preceding figures, i.e. the receivers  14  thereof. After a preparatory treatment and inspection of the joint faces, the required adhesive  22  is applied. In  FIG. 4 , the adhesive  22  is applied only to the inner joining partner  21 , but this is not obligatory. The adhesive  22  can be applied to the two joining partners  20 ,  21  or only to one, depending on the application. An inner pressure tool  24  and an outer pressure tool  25  are shown, which exert a predetermined pressure P on to the outer joining partner  20  and inner joining partner  21  within a joint region  26 , which results in a joint gap  23  of a predetermined thickness. The outer and inner pressure tools  20 ,  21  are moved at a predetermined speed V along the joint gap  23 , in such a way that continuous sequential joining of the joining partners  20 ,  21  results. The adhesive  22  can be introduced in a region  27  directly in front of the current joint region  26 , or else the adhesive  22  can be introduced before joining of the joining partners in the temporary joining position. In other words, on the basis of the example of  FIGS. 1 to 3 , the adhesive  22  can be applied to the joint faces of the formers  7  before the integration tool  6  with the fitted formers  7  is moved into the fuselage segment  1 . In this case, the inner pressure tool can be a component of the receivers  14  of the integration tool  6 , while the outer pressure tool  25  can be an exchangeable tool of the modular tools  9 ,  10 ,  11  designed as a robot. As a result of the pressure being applied sequentially and thus locally, the required high pressure can be provided locally and does not need to be provided over the entire joint gap simultaneously, which is hardly expedient technically in the case of the large components. 
         [0055]      FIG. 5  is a schematic cross-sectional view of the process of joining with sequential pressurisation in pieces or portions, i.e. discontinuously. An outer joining partner  20  and an inner joining partner are joined together by means of an adhesive  22  in such a way a joint gap  23  of predetermined thickness is formed. In this case, the sequential pressurisation for joining the joining partners takes place in cycles using an inner and an outer pressure tool  28 ,  29 . In other words, at a time t a pressure P is exerted on the joining partners in the current joint region  30  and the joining partners  20 ,  21  are brought into the final joining position. Dashed lines show the pressure tools at the previous time t−1, where they joined the joining partners  20 ,  21  in the preceding joint region  32 . At the next time t+1, the pressure tools are brought along the joint gap  23  into the next joint region  31  and then join the joining partners  20 ,  21  therein. In other words, the pressure tools are removed from the current pressure region  30  on each side and brought into the next joint region  31  where the next joining operation is carried out by means of pressurisation. 
         [0056]    At the current time t, the next joint region  31  can be used as a region in which the adhesive  22  is introduced. However, this is not obligatory, but rather the adhesive  22  can also be applied at a time before the introduction of the formers  7  into the fuselage segment  1 , as in the description of  FIG. 4 . 
         [0057]    In the described exemplary methods for sequential pressurisation it is possible for the pressure to be applied from only one side. If, for example, the outer joining partner  20  has a sufficient strength, the pressurisation can take place by means of only an inner pressure tool either continuously or in portions. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
         
           
               1  fuselage segment 
           
         
           2  component carrier 
           3  central carrier 
           4  front support 
           5  rear support 
           6  integration tool 
           7  formers 
           8  former flange surface 
           9  modular tool 
           10  modular tool 
           11  modular tool 
           12  rail system 
           13  modular tool 
           14  receiver 
           15  application opening 
           20  first joining partner 
           21  second joining partner 
           22  adhesive 
           23  joint gap 
           24  inner pressure tool 
           25  outer pressure tool 
           26  joint region 
           27  region in front of the joint region 
           28  inner pressure tool 
           29  outer pressure tool 
           30  joint region 
           31  next joint region 
           32  previous joint region 
         P pressure 
         V speed along the joint gap 
         t time