Abstract:
A folding top for a cabriolet vehicle, that includes a first roof part which is embodied as a rigid shell element, a second roof part which is embodied as a rigid shell element, and a forced control unit. The first roof part and the second roof part are pivotable relative to a body of the vehicle, are driven by a common force-introducing unit, and are movable by means of the forced control unit. The forced control unit includes a mechanical control device, by means of which movement of the second roof part can be delayed from movement of the first roof part.

Description:
The invention relates to a folding top for a cabriolet vehicle. 
     BACKGROUND 
     The modern construction of folding cabriolet tops which consists of a plurality of solid roof parts, and can be stowed automatically in a rear region of the vehicle, is generally accompanied by the problem of rigid parts which can be moved extensively in relation to one another. In respect of the configuration of the relative sizes of the roof parts, of the movement sequence of the roof parts in relation to one another, of the dimensions of the collapsed and stowed roof and of the outlay in relation to the drive devices which are to be provided, in terms of the number and associated costs thereof, a set of simultaneously fulfillable boundary conditions is often desirable. Thus, in the case of a number of particularly preferred embodiments of multi-part hard-shell tops, the overlapping of the movements of different roof parts in space results, for example, in it only being possible for these roof parts to be pivoted sequentially, or quasi-sequentially, without colliding with one another. 
     It is known, from the construction of hard-shell tops, to provide separate drive devices for different roof parts in order to achieve sequential pivoting of the different roof parts in each case. 
     In order to release a stowage space for the folding top in the rear region during an opening movement, use is often made of a rear element which can be pivoted open counter to the direction of travel, possibly for a rear-window shelf arranged in front of the rear element being provided in a separately pivotable manner in order to achieve a collision-free movement sequence. The pivoting of the rear-window shelf here allows the rear roof part to move into the stowage space. 
     DE 44 35 222 C1 describes a folding top in which the rear roof part is pivoted open, in the first instance, in the direction of travel, whereupon the rear element can be opened counter to the direction of travel without a separately pivotable rear-window shelf necessarily having to be provided. The disadvantage with the solution presented here is that both the rear roof part and a central roof part, which adjoins the rear roof part in the direction of travel, are articulated separately in each case on the bodywork of the vehicle. In order not to collide with the central roof part during pivoting in the direction of travel, the articulations of the rear roof part comprise extendable hydraulic cylinders in order to raise the rear roof part over the central roof part. Such activation is not just complex and costly, but also susceptible to malfunctioning. In addition, it is necessary to have further means for fixing the rear roof part when the folding top is closed since the hydraulic cylinders which, at the same time, form bearing links of the roof part, are not readily routed in their longitudinal direction. In order to do away with an even greater number of drive arrangements, it is proposed to lock the rear roof part to the central roof part in a position in which it has been pivoted over the central roof part. In respect of automated folding-top opening, however, it is also necessary to have high-outlay hydraulic or electromechanical means for this purpose. 
     DE 100 06 296 C1 describes a three-part hard-shell top for a cabriolet vehicle in which a central roof part is connected to a bodywork of the vehicle by means of a link mechanism, both a front roof part and a rear roof part being mounted on the central roof part in each case via link mechanisms, and it being possible for the front roof part to be moved over the central roof part and for the rear roof part to be moved beneath the front roof part and over the central roof part. Such an arrangement provides for unfavorable stacking of the roof parts and, if at all, can only be realized in the manner presented, with essentially planar roof parts. If, for example, the rear roof part comprises C-pillars of the vehicle, or if the roof parts are to be stacked in a different order, then the technical realization quickly comes up against limitations, at least when as large a proportion of the roof-part movements as possible take place in a positively controlled manner in relation to one another. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a folding top for a cabriolet vehicle according to the preamble of claim  1  and/or claim  17  in the case of which the flexibility of the positively controlled movement of roof parts in relation to one another is increased. 
     The present invention provides a folding top for a cabriolet vehicle that includes a first roof part including a rigid shell part and being pivotable with respect to a bodywork of the vehicle; a second roof part including a rigid shell part and being pivotable with respect to the bodywork; a positive control means including a mechanical control device; and a common-force-introduction unit configured to driveably move the first and second roof parts using the positive control means, wherein the control device is configured to enable a delay a movement of the second roof part with respect to a movement of the first roof part. 
     A mechanical control device is advantageously provided here in a positively controlled connection of a first and a second roof part, with the result, that on the one hand, the roof parts can be moved simultaneously by means of just a single drive device and, on the other hand, the mechanical control device allows coordination of the movement of the roof parts, in particular a temporal sequential or quasi-sequential sequence of the individual movements without any additional drives being required. In particular, doing away with additional drives, in addition to reducing costs, ensures that the mechanics of the folding top as a whole are less susceptible to malfunctioning. 
     A folding top according to the invention additionally achieves the situation where an opening movement of a front or central roof part can begin before the first roof part has moved all the way over the front or central roof part, with the result that a particularly time-saving opening movement can be realized overall. 
     In a preferred embodiment of a folding top according to the invention, the control device comprises a rotary link. A single force-introduction unit particularly preferably drives the rotary link, and the rotary link is connected to the first roof part via a first linkage and to the second roof part via a second linkage. It is thus possible to transmit a given way of the force-introduction unit in accordance with the principle of a projected circular movement onto the first and the second linkages, with a phase shift in each case. Starting from a closed folding-top position, it is thus possible to drive, in the first instance, the first linkage and thus the first roof part, whereas the second linkage, and thus the second roof part, is noticeably driven only once the rotary link has been rotated. If the angular position alpha of the rotary link in the starting position is called zero degrees, then, in a first approximation, it is possible for a factor which can be achieved in the transmission of the displacement for the first linkage to be proportional to sine (alpha+delta) and for the factor for the transmission of the displacement of the second linkage to be proportional to sine (alpha+delta+phi), where the phase shift phi is preferably in the order of magnitude of ninety degrees and delta is a constant, predetermined angle of origin. Delta can preferably differ from zero and, in particular, be somewhat smaller than zero, in order that there is a large transmission factor for the first linkage for as long as possible at the start of the movement operation. 
     The first roof part is particularly preferably a front roof part, and the second roof part is a rear roof part, of the folding top, a central roof part being arranged between the first roof part and the second roof part when the folding top is closed. It is preferable here for the first roof part to be connected to the central roof part via a front four-bar mechanism, and for the second roof part to be connected to the central roof part via a rear four-bar mechanism. 
     In particular in the case of the first roof part moving in the opposite direction in relation to the second roof part here, this movement, in addition, being particularly extensive as a result of the four-bar mechanisms, the fact that the invention provides the mechanical control device is advantageous since this makes it possible to achieve a particularly large degree of freedom in the dimensioning of the roof parts and the design of the paths of motion of the roof parts. 
     The central roof part may advantageously be connected to the bodywork of the vehicle via a main four-bar mechanism, with the result that, during or after pivoting of the first and of the second roof parts over the central roof part, it is possible for the roof parts arranged in a stack to be pivoted together into a rear stowage region by means of the main four-bar mechanism. 
     At least one link of the front four-bar mechanism particularly advantageously is arranged adjacent the outside of the central roof part when the folding top is closed. This advantageously achieves the situation, in respect of space-saving stowage of the open folding top, where a link which bears the means for activating the first, front roof part may be of particularly short configuration, since the outside link of the front four-bar mechanism allows the front four-bar mechanism to be largely set back relative to the central roof part. In particular, however, this provision of the outside link also results in very advantageous use of the control device, since the outside link ultimately gives rise to particularly space-consuming pivoting of the first roof part which, without the control device, would, in the case of a preferred folding top, result in a collision with the second, rear roof part. 
     The object of the invention is additionally achieved, for a folding top which is mentioned in the introduction and is in accordance with the preamble of claim  17 , by the characterizing features of claim  17 . 
     The present invention additionally provides a folding top that includes a first roof part; a second roof part, the first roof part disposed in front of the second roof part when relative to a direction of travel when the folding top is closed; an openable rear element, the second roof part resting on the rear element from above when the folding top is closed; and a main-link mechanism mounted in a movable manner on the bodywork, wherein the first roof part and the second roof part are mounted on the main-link mechanism and wherein the first roof part is displaceable relative to the main link mechanism. 
     The second roof part advantageously rests on the rear element with sealing action from above when the folding top is closed and, in a first stage of a folding-top opening movement, can be raised up from the rear element, with the result that, on the one hand, straightforward sealing of the folding top in its rear region is made possible and, on the other hand, it is possible to utilize early release of the rear element for simultaneous movement of the folding-top parts and of the rear element. The rear element can be pivoted open counter to the direction of travel in a particularly straightforward manner here in order to release a rear stowage region for the folding top. 
     In an advantageous further development of a folding top according to the invention, at least one of the roof parts, but preferably both roof parts, can be displaced in relation to the main-link mechanism. In this way, inter alia, it is possible for the roof parts to form a stack before the stack of roof parts is pivoted into the stowage region by means of the main-link mechanism. 
     It is advantageous here for the first roof part and the second roof part to be mounted on the main-link mechanism by means of a first and a second link mechanism in each case, with the result that the roof parts can be pivoted in relation to the main-link mechanism and toward one another. 
     In a particularly straightforward realization of a folding top according to the invention, which is stable in respect of kinematics, at least one of the roof parts is, or also both roof parts are, mounted on a carrying link of the main-link mechanism. Such a carrying link may be, for example, the connecting rod of a straightforward main four-bar mechanism. Depending on the desired folding-top movement, however, it is also possible for the main-link mechanism to be of more complex design, for example to be designed as a seven-bar mechanism. It is possible here for the roof parts, as proposed, to be fitted on a common carrying link at the base or also to be articulated on different links of the main-link mechanism. In the latter case, pivoting of the main-link mechanism, at least to a slight extent, will also give rise to pivoting of the roof parts relative to one another, which, depending on the respective demands, may be desirable. 
     The roof parts are particularly advantageously connected to one another by a positive control means, with the result that the movement of one roof part gives rise to a movement of the other roof part. The total number of driving devices necessary for the folding top can thus be kept small. 
     The first roof part can advantageously be moved over the second roof part, for example by virtue of the link mechanisms of the roof part being configured correspondingly, in order to allow a favorable stowage position and stacking sequence of the folding-top parts in the rear region of the vehicle. As an alternative, however, it is also possible for the second roof part to be moved over the first roof part. Which of the possible stacking sequences, which can be realized by just slight modifications, are optimal in each case depends, in particular, on the design-related shape of the bodywork and the folding-top parts. 
     A folding top according to the invention which is particularly advantageous in respect of stability is one in which a first roof part and a second roof part are mounted on the main-link mechanism in each case via a first and a second link mechanism, it being possible for the roof parts to be moved relative to one another and, in each case, relative to the main-link mechanism. In such a combination, the total displacement which is necessary in the overlapping of the roof parts is distributed fairly uniformly between the two roof parts, with the result that each of the link mechanisms of the roof parts can be kept relatively small. Large link mechanisms in particular have the disadvantage of a lack of stability, which generally has to be compensated for by an undesirably solid configuration of the link parts and articulations. 
     An additional, third roof part may advantageously also be provided in order to cover over the passenger compartment of large vehicles. Such a third roof part may be arranged, as a central roof part, between the first roof part and the second roof part. In this case, it can be fixed particularly straightforwardly to the abovementioned preferred carrying link.  
     As an alternative to this, which may be advantageous depending on the desired stacking sequence and predetermined dimensioning of the roof parts, it is also possible, however, for the third roof part to be provided as the front roof part, in which case it can be mounted, in particular, on the first roof part. It can thus be ensured, for example, that, even in the case of a three-part folding top, the second, rear roof part may be arranged as the lowermost roof part of the stacking sequence when the folding top is open. 
     The positive control means, which couples the movements of the first roof part and the second roof part, can particularly preferably be equipped with a previously described mechanism for delaying the movement of the roof parts in relation to one another. As far as the advantages of such a delaying mechanism are concerned, it is referred to the description above. 
     Further advantages and features of the folding top according to the invention can be gathered from the exemplary embodiments described hereinbelow and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Two preferred exemplary embodiments of a folding top according to the invention are described hereinbelow and explained in more detail with reference to the attached drawings, in which: 
         FIG. 1  shows a schematic partial view, from the side, of a first exemplary embodiment of a folding top according to the invention in a closed position, 
         FIG. 2  shows the folding top from  FIG. 1  in a basic illustration depicting the interaction of the components, 
         FIG. 3  shows a schematic partial view, from the side, of a first exemplary embodiment of a folding top according to the invention in a first step of an opening movement, 
         FIG. 4  shows the folding top from  FIG. 3  in a basic illustration depicting the interaction of the components, 
         FIG. 5  shows a schematic partial view, from the side, of a first exemplary embodiment of a folding top according to the invention in a second step of an opening movement, 
         FIG. 6  shows the folding top from  FIG. 5  in a basic illustration depicting the interaction of the components, 
         FIG. 7  shows a schematic partial view, from the side, of a first exemplary embodiment of a folding top according to the invention in a third step of an opening movement, 
         FIG. 8  shows the folding top from  FIG. 7  in a basic illustration depicting the interaction of the components, 
         FIG. 9  shows a schematic partial view, from the side, of a first exemplary embodiment of a folding top according to the invention in a fourth step of an opening movement, 
         FIG. 10  shows the folding top from  FIG. 9  in a basic illustration depicting the interaction of the components, 
         FIG. 11  shows a lateral overall view of the folding top from  FIG. 1 , 
         FIG. 12  shows a lateral overall view of the folding top from  FIG. 9 , 
         FIG. 13  shows the folding top from  FIG. 12  in a further step of an opening movement, 
         FIG. 14  shows the folding top from  FIG. 12  in a state in which it has been opened fully and stowed in a rear region of the vehicle, 
         FIG. 15  shows a view, in detail form, of an outside link of the first exemplary embodiment of a folding top according to the invention in a closed position, 
         FIG. 16  shows the view, in detail form, from  FIG. 15  in a partially open position, 
         FIG. 17  shows the view, in detail form, from  FIG. 15  in a fully open position, with the outside link pivoted to the maximum extent, 
         FIG. 18  shows a schematic view, from the side, of a second exemplary embodiment of a folding top according to the invention, 
         FIG. 19  shows the folding top from  FIG. 18  following a first step of a folding-top opening movement, 
         FIG. 20  shows the folding top from  FIG. 18  following a second step of a folding-top opening movement, 
         FIG. 21  shows the folding top from  FIG. 18  following a third step of a folding-top opening movement, 
         FIG. 22  shows the folding top from  FIG. 18  following a fourth step of a folding-top opening movement, 
         FIG. 23  shows the folding top from  FIG. 18  following a fifth step of a folding-top opening movement, 
         FIG. 24  shows the folding top from  FIG. 18  following a sixth step of a folding-top opening movement, 
         FIG. 25  shows the folding top from  FIG. 18  in a fully open state, the folding top having been stowed in a rear stowage region of the vehicle, 
         FIG. 26  shows the folding top from  FIG. 25  with the rear element closed, and 
         FIG. 27  shows the folding top from  FIG. 18 , a trunk lid which is integrated in the rear element having been opened. 
     
    
    
     DETAILED DESCRIPTION 
     The first exemplary embodiment of a folding top of the invention according to  FIGS. 1 to 17  comprises a first, front roof part  1 , a second, rear roof part  2  and a central roof part  10  which, in the closed state, is arranged between the first and the second roof parts  1 ,  2 . The central roof part  10  is fixed to a central link  10   a , with the result that the central roof part  10  and the central link  10   a  may be regarded as a structural unit. 
     The first roof part  1  is connected to the central roof part  10  via a front four-bar mechanism  11 , a front link  11   b  of the front four-bar mechanism being connected in an articulated manner to the central link  10   a , and an outside link  11   a  of the front four-bar mechanism  11  being articulated on the central roof part  10  from the outside. In the closed state according to  FIGS. 1 ,  2  and  11 , the outside link is arranged adjacent the outside of the central roof part  10 , the outside link being located in a roof-rail or rain-channel recess of the central roof part  10 . 
     The second, rear roof part  2  is articulated on the central link  10   a  by means of a rear four-bar mechanism  12 . The rear roof part  2  comprises C-pillars of the folding top and a solid rear window. The rear four-bar mechanism  12  comprises a first rear link  12   a  and a second rear link  12   b.    
     Overall, the first roof part  1  and the second roof part  2  can thus be pivoted over the central roof part  10  in each case, it being possible for the rear roof part  2  additionally to be pivoted over the front roof part  1 . 
     The front four-bar mechanism  11  and the rear four-bar mechanism  12  are connected to one another via a drivable positive control means  4 , with the result that a position of the first roof part  1  is clearly associated in each case, in mechanical terms, with a position of the second roof part  2 . 
     The positive control means  4  comprises a first linkage  8 , which activates the front four-bar mechanism  11 , a second linkage  9 , which activates the rear four-bar mechanism  12 , and a rotary link  7 . The rotary link is connected to the central link  10   a  such that it can be rotated at a first articulation  7   a . The rotary link  7 , in addition, can be rotated for driving action by means of a force-introduction unit  5 , which is designed as a linear hydraulic cylinder and is supported against the central link  10   a . In this case, the rotary link is designed as three-arm link. However, it is also possible, in particular, for a rotary link to be understood, in the sense of the invention, as a rotary plate or control plate. In particular a universally usable perforated plate can also be utilized as a control plate, with the result that, by virtue of articulations being fitted in a variable manner on the perforated plate, it is possible, using standard components, to provide a deceleration-control means which can be adapted to different folding tops. 
     The first linkage  8  comprises a first, front control link  8   a  and two front links  8   b ,  8   c , it being possible to achieve a particularly large pivoting angle for the front four-bar mechanism  11  by virtue of the front link  11   b  being connected to the first control link  8   a  by means of the two front links  8   b ,  8   c . The first control link  8   a  is connected to the rotary link  7  at a second articulation  7   b  of the rotary link  7 . 
     The second linkage  9  comprises a second, rear control link  9   a , which is guided in relation to the central link  10   a  via a small supporting link  9   b . The second control link  9   a  is articulated on an extension of the second rear link  12   b , with the result that the rear four-bar mechanism  12  is articulated on the second control link  9   a  and can be activated via the latter. 
     The central roof part  10  or the central link  10   a  is connected to a bodywork-mounted main-bearing unit  14  via a main four-bar mechanism  13 , the main four-bar mechanism  13  comprising a first main link  13   a  and a second main link  13   b.    
     A rear stowage region  16  of the vehicle can be covered over by means of a rear element  15 , it being possible for the rear element  15  to be pivoted open counter to the direction of travel in order to release a through-passage space for the folding top which is to be stowed. 
     As a particularly advantageous detailed solution for the folding top according to the invention which is illustrated in detail, in particular, in  FIGS. 15 to 17 , the outside link  11   a  is not articulated on the central roof part  10  via a conventional rotary articulation. Rather, the articulation arrangement comprises a small four-bar mechanism  20 , the central roof part  10  forming the base of the small four-bar mechanism  20  and the outside link  11   a  forming the connecting rod of the small four-bar mechanism  20 . A first link  20   a  and a second link  20   b  of the small four-bar mechanism  20  cross over one another. A short covering plate  21  can be pivoted along essentially parallel to the links  20   a ,  20   b  of the small four-bar mechanism  20  about a dedicated articulation arrangement  21   a , the covering plate  21  being guided with sliding action in the region of its end located opposite its articulation arrangement  21   a.    
     In the case of a link being configured as an outside link, account should be taken of a series of special features. As is also the case in the exemplary embodiment shown, an outside link  11   a  is advantageously arranged in a roof-rail recess  10   b , which is provided in any case in most modern folding vehicle tops. The roof-rail recess  10   b  is laminated with a roof-rail covering  10   c  outside the region of the link  10   a . The outside link  11   a  expediently comprises a corresponding lamination  22  positioned on the actual link, with the result that, when the folding top is closed, the link is able to give the appearance of a continuous drip molding  10   c ,  22 . Such an arrangement, however, is accompanied by the problem that, on account of being accommodated in a sunken manner in the roof-rail recess  10   b , the link  11   a  would strike against the roof-rail covering  10   c  during a pivoting movement, at least when a large pivoting angle of the link  11   a  is necessary. As a result of the advantageous detailed solution for the articulation arrangement of the link in the small four-bar mechanism  20 , however, the link  11   a , together with its roof-rail cover  22 , passes out of the roof-rail recess  10   b  over its entire length even as it begins to pivot, with the result that a particularly large pivoting angle is made possible.  FIGS. 15 to 17  show that a free pivoting angle of the outside link of more or less 180 degrees is thus made possible. 
     The short covering plate  21 , which can be pivoted along with the four-bar mechanism  20 , merely serves for covering over the roof-rail region above the small four-bar mechanism  20  when the folding top is closed. 
     It should be mentioned that the prior art has disclosed solutions in which a recessed, outside link can be covered by means of a strip-like flap which is fitted in a pivotable manner on a roof part and forms a roof-rail cover. In contrast, the solution described has considerable advantages since, for example, the roof-rail cover can be secured directly on the link. 
     The invention functions, then, as follows: 
     Starting from the closed state of the folding top according to  FIGS. 1 ,  2  and  11 , in the first instance, a first part of a folding-top opening movement is initiated. The force-introduction unit  5  is actuated for this purpose, as a result of which the rotary link  7  is rotated, according to the illustrations, in the counterclockwise direction. A comparison of  FIGS. 1 to 10  clearly shows that, in the first instance here, it is predominantly the first linkage  8  which is actuated by the rotary link, whereas, on account of the position of the third articulation  7   c  in relation to the second linkage  9 , the second linkage  9  is barely actuated in the first instance, in particular in the relevant longitudinal direction of the second, rear control link  9   a.    
     In the first instance, it is thus predominantly the case that the front roof part  1  pivots over the central roof part  10 . The pivoting of the front roof part  1  prevails in the movement sequence approximately up to the position which is illustrated in  FIGS. 5 and 6 . 
     The relative movement of the front roof part  1 , which has already been pivoted to a significant extent over the central roof part  10 , subsequently slows down. At the same time, the movement of the rear roof part  2  increases since (for example from the position which is shown in  FIGS. 5 and 6 ) a very direct conversion of the rotary movement of the rotary link  7  into a longitudinally directed movement of the rear control link  9   a  then takes place. The abovedescribed movement sequence of the two roof parts may thus be referred to as quasi-sequential. 
     The first part of the folding-top opening movement is at an end when the three roof parts  1 ,  2  and  10  are arranged entirely in the form of a stack (see  FIGS. 9 ,  10  and  12 ). 
     A second part of the folding-top opening movement is illustrated in the overall views of the folding top according to  FIGS. 12 to 14 . In this case, pivoting of the main four-bar mechanism  13  driven by a second drive device displaces the previously formed stack of roof parts  1 ,  2 ,  10  into a rear stowage region  16  of the vehicle. For this purpose, the rear element  15  is first of all pivoted open counter to the direction of travel and then pivoted closed again. 
     A second exemplary embodiment of a folding top according to the invention is described hereinbelow: 
     The second exemplary embodiment of the folding top according to the invention comprises a first, front roof part  101  and a second, rear roof part  102 . The second roof part  102  rests on a rear element  115  with sealing action from above when the folding top is closed, according to  FIG. 18 , and comprises a rear window and pillars of the folding-top located alongside the rear window. The rear element  115  comprises a front region  115   a , as seen in the direction of travel, which is arranged within the passenger compartment, and thus beneath the second roof part  102 , when the folding top is closed. The region  115   a  essentially corresponds to a rear-window shelf, arranged beneath a rear window, in a conventional sedan with a solid roof. 
     The first, front roof part is connected in a releasable manner to a windshield frame  130  of the vehicle when the folding top is closed. 
     A main-link mechanism  113  is mounted on the bodywork of the vehicle by means of a main-bearing unit  114 . This makes it possible, in particular, to construct the folding top as a module which can be prefabricated separately, since the main-bearing unit essentially constitutes the only connection between the movable roof parts and the rest of the vehicle which is to be fitted. 
     The main-link mechanism is designed as a four-bar mechanism, the main-bearing unit  114  or the bodywork of the vehicle forming the base of the four-bar mechanism. A first main link  113   a  and a second main link  113   b  form the links of the main-link mechanism or four-bar mechanism  113 . A carrying link  110   a  forms the connecting rod of the main-link mechanism  113 . The carrying link  110   a  extends both to the front and rear over the distance which is necessary for coupling the four-bar mechanism  113 , and serves as a carrier for the roof parts  101  and  102 . The carrying link  110   a  thus essentially corresponds to the central link  10   a  of the first exemplary embodiment. It can be seen from this that it is also possible for a central roof part to be additionally mounted on the carrying link  110   a.    
     The first roof part  101  is mounted on the carrying link  110   a  in its front region by means of a first link mechanism  111 , the first link mechanism being designed here as a four-bar mechanism and comprising a first front link  111   a  and a second front link  111   b . The first roof part  101  or a link which is fixed to the first roof part  101  forms the connecting rod of the first link mechanism  111 . 
     The second roof part  102  is mounted on the carrying link  110   a  in its rear region by means of a second link mechanism  112 , the second link mechanism  112  being designed here as a four-bar mechanism and comprising a first rear link  112   a  and a second rear link  112   b . The second roof part  102  or a link which is fixed to the second roof part  102  forms the connecting rod of the second link mechanism  112 . 
     A control link  104  is articulated in each case on the first front link  111   a  and the second rear link  112   b . This produces a positive control means  104  which connects the first link mechanism  111  and the second link mechanism  112  to one another in a positively controlled manner. A positively controlled link chain is thus formed overall, this chain comprising the first and the second front links  111   a ,  111   b , the first roof part  101 , the first and the second rear links  112   a ,  112   b , the second roof part  102 , the carrying link  110   a  and the positive control means  104 . As an alternative to the positive control means  104  being designed as a straightforward control link  104 , it is also possible to provide a more complex mechanism according to the first exemplary embodiment as the positive control means, for example the positive control means  4 , which is shown in the first exemplary embodiment, with the integrated control device  6  for delaying the movement of the roof parts  101 ,  102 , relative to one another. 
     A drive arrangement (not illustrated) for moving the roof parts  101 ,  102  relative to one another can easily be provided as a linear force-introduction unit which is supported against two suitable links of the previously described positively controlled link chain. 
     In the present exemplary embodiment, the rear element is designed in two parts, an articulation being provided between the rear-window-shelf region  115   a  and the rest of the rear element  115 . A particularly large trunk lid which can be pivoted open in the direction of travel is thus formed, as can be seen from  FIG. 27  in particular. This practice of dividing up the rear element in the region of the rear-window shelf, however, does not in any way correspond with the separately pivotable rear-window shelf which is known from the prior art for the purpose of releasing a space for the movement of the folding top. In the closed folding-top arrangement according to  FIGS. 18 and 27 , the rear-window-shelf region  115   a  cannot be pivoted. 
     The invention functions, then, as follows: 
     Starting from the closed folding-top position according to  FIG. 18 , in the first instance, a first stage of movement of the roof opening is initiated by means of a first force-introduction unit (not illustrated), the main-link mechanism  113  staying in the same position. It can be seen from  FIGS. 19 to 21  that the second roof part  102  is pivoted in the direction of travel in the first instance by the driven movement of the previously described positively controlled link chain, the second roof part raising up from the rear element and being moved away upward, and in the direction of travel, from the rear element. 
     At the same time, the first roof part  101  is pivoted rearward, counter to the direction of travel, away from the windshield frame, with the result that the roof parts  101 ,  102  move toward one another, in which case they essentially maintain their spatial orientation. The first, front roof part  101  here is pivoted over the second, rear roof part  102  until a stacked position of the roof parts according to  FIG. 21  has been reached. The stack of roof parts is connected to the vehicle via the main-link mechanism  113 . 
     The rear element  115  is then pivoted open counter to the direction of travel (see  FIG. 22 ), in which case in particular the region  115   a  of the rear element  115  is pivoted along integrally. This is made possible by the previously described movement of the second roof part  102 , as a result of which the movement space for the rear element  115  has been released. 
     Once a rear stowage region  116  for the folding top has thus been released, the main-link mechanism  113  is moved by means of a second drive device (not illustrated). According to the movement steps shown in  FIGS. 23 to 25 , the stack of roof parts here is displaced over an arcuate path of motion into the rear stowage region  116 . 
     The rear element  115  is then closed again (see  FIG. 26 ), in which case it covers over the stowed roof. In particular, the front region  115   a  of the rear element  115  adjoins a rear seat back  131 , as is also the case when the folding top is closed. 
     It can be seen from the open state of the folding top according to  FIG. 26  that a useful trunk volume remains beneath the lowermost, second roof part  102 . 
     For the closing operation of the folding top, the previously described kinematics take place in reverse order.