Patent Publication Number: US-2021178447-A1

Title: Vehicle panel roller hemming device and processing method using the same

Description:
TECHNICAL FIELD 
     The present invention relates to a vehicle panel roller hemming device and a processing method using the same. 
     BACKGROUND ART 
     A member having a gently curved surface, such as a vehicle door panel or hood panel, typically includes an outer panel on the front side and an inner panel on the back side provided for reinforcing the outer panel. The outer panel and the inner panel are joined together by hemming by bending a flange formed on the peripheral edge part of the outer panel. 
     When the outer panel and the inner panel are joined together by roller hemming, an adhesive is first applied to the peripheral edge parts of the panels, and the panels as a workpiece in a temporarily assembled state are set on a hemming die. At this time, the workpiece is accurately positioned and set by a plurality of locators which are disposed around the hemming die. Then, in this state, the flange on the peripheral edge part of the outer panel is bent inward by a roller which is disposed on the tip of an arm of a roller hemming robot to wrap the peripheral edge part of the inner panel. Accordingly, joining of the peripheral edge parts of the outer panel and the inner panel by hemming is completed. 
     As described above, in setting of the workpiece on the hemming die, the workpiece is positioned by the locators disposed on the peripheral edge part of the hemming die and fixed by clamping. During roller hemming, each locator is located on a path of the roller which moves on the peripheral edge part of the workpiece. Thus, an operation of temporarily retracting the locator from the path of the roller in response to the movement of the roller and returning the locator again to its original position after the passage of the roller is typically repeated. 
     However, an operation of constructing a control program for causing the roller, which moves corresponding to the shape of the workpiece, and the locators to move in cooperation with each other with no three-dimensional interference and incorporating the control program into the roller hemming device is extremely complicated. Thus, various fixing means other than fixation by clamping have been proposed until now. 
     For example, Patent Literature 1 proposes a method in which a plurality of openings which are disposed a plurality of suction tools, which come into surface contact with the lower face of a workpiece, are formed, and the lower face of the workpiece is sucked and fixed using rubber vacuum pads as the suction tools to perform roller hemming. Specifically, the lower face of the workpiece is sucked and fixed using a multistage bellows type rubber pad having a circular sectional shape as the vacuum pad. This eliminates the necessity to temporarily release the fixation by the locators. 
     However, in the proposal of Patent Literature 1, since the lower part of the workpiece is fixed using the multistage bellows type rubber pad as the suction tool, it is considered that a rubber part of the vacuum pad is deformed along with pressing-rotation of the roller during roller hemming, and the workpiece is displaced from a predetermined disposing position. 
     Further, Patent Literature 2 discloses a roller hemming method in which a peripheral edge part of a workpiece (an outer panel of a door panel) is positioned by a plurality of claw portions, and further fixed by clamping and vacuum cups. However, in such a configuration of positioning by the claw portions, it is necessary to prevent interference between the claw portions and a roller on the tip of a robot arm during roller hemming, and incorporating a control program for preventing the interference is an essential configuration. Further, although the shape, the size, the number of vacuum cups and the like are not specified, it is estimated from the drawings or the like that the vacuum cup is a conical cup. Thus, also in the proposal of Patent Literature 2, there is a possibility that a rubber part of the vacuum cup is deformed by pressing-rotation of the roller, and the workpiece is displaced from a predetermined disposing position, for example, during hemming after the claw portions are retracted from the path of the roller. 
     Further, Patent Literature 3 discloses a configuration in which, when a workpiece is hemmed by a hemming robot after the workpiece is aligned by means of auxiliary clamping means, an inner panel and an outer panel of the workpiece are sucked by a vacuum suction force of a suction unit, which enables the restriction force to be ensured. 
     However, in the configuration of Patent Literature 3, since a pressing unit and the auxiliary clamping means are located on a path of a roller of the hemming robot, it is considered that the pressing unit and the auxiliary clamping means constitute a hindrance to the movement of the roller. Thus, there is still a problem similar to the conventional problem in measures when the pressing unit and the auxiliary clamping means are retracted from the path of the roller. 
     Further, in the suction unit used in Patent Literature 3, a conical vacuum cup having a structure similar to the structure of the vacuum pad used in Patent Literature 1 is illustrated ( FIG. 8 ), and the occurrence of displacement caused by deformation of the pad during roller hemming is assumed. Further, some of a plurality of suction units are disposed along the peripheral edge of a restriction pad to vacuum-suck the inner panel of the workpiece, and the other suction units are disposed inside a die body to vacuum-suck the outer panel. Thus, it is considered that the structure of the pressing unit may become complicated. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2010-240708 A 
     Patent Literature 2: JP 5288047 B2 
     Patent Literature 3: JP 2013-86181 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     As described above, although the workpiece fixing means in the roller hemming device proposed until now has a certain degree of outer panel fixing effect by suction by the vacuum pad, such as a multistage bellows type vacuum pad, deformation caused by shrinkage of the pad under reduced pressure is large and the workpiece is displaced from a predetermined position due to a shearing force caused by the pressing-rotation of the roller, which disables accurate roller hemming. Further, when the workpiece cannot be fixed at the predetermined position as described above, a defective piece in which a part of the entire peripheral edge part of each of the inner panel and the outer panel is not hemmed is produced, which largely deteriorates productivity and quality. 
     Further, when only the lower face of the outer panel is fixed by suction, since the outer panel and the inner panel are temporarily assembled with a viscous adhesive applied to the peripheral edge part of each of the outer panel and the inner panel, which is an incomplete state, the inner panel is lifted during roller hemming, and the inner panel is also displaced from a predetermined position. 
     The present invention has been made to solve the above problems, and an object thereof is to provide a vehicle panel roller hemming device and a processing method using the same that make it possible, in manufacture of a vehicle panel, to accurately set a workpiece, which includes an outer panel and an inner panel, at a predetermined position on a hemming die in roller hemming and reliably fix the panels when moving a roller during hemming, and have techniques for reducing the number of programming processes for automating roller hemming, improving the product quality, reducing the defective rate, and achieving excellent mass production. 
     Solution to Problem 
     The present invention is characterized by the following in order to solve the above problems. 
     &lt;1&gt; A vehicle panel roller hemming device for hemming a peripheral edge part of an outer panel of a vehicle panel, the vehicle panel including the outer panel and an inner panel, by a roller of a roller hemming robot, the vehicle panel roller hemming device including: 
     a positioning mechanism configured to position the outer panel on a hemming die by a locator; 
     a suction and fixing mechanism configured to suck and fix a lower face of the outer panel by a plurality of vacuum pads; and 
     a locator retracting mechanism configured to retract the locator from a path of the roller of the roller hemming robot during roller hemming, wherein 
     each of the vacuum pads of the suction and fixing mechanism includes:
         a pad base part;   a skirt part continuously rising with a predetermined thickness from an edge of the pad base part and including an opening on an end edge of the skirt part;   a decompression space formed by an inner wall of the pad base part and an inner wall of the skirt part; and   a suction through pipe penetrating the pad base part and communicating with the decompression space, and configured to suck air inside the decompression space, and       

     a top-view shape of the opening of the skirt part is an ellipse, and a longer axis of the ellipse is substantially parallel to a direction in which a curvature of the vehicle panel is smaller. 
     &lt;2&gt; The vehicle panel roller hemming device according to &lt;1&gt;, in which a rise height of the skirt part from a surface of the pad base part is within a range of 3 to 5 mm. 
     &lt;3&gt; The vehicle panel roller hemming device according to &lt;1&gt; or &lt;2&gt;, further including a swing arm device including a swing arm capable of turning, bending, and moving up and down in a space above the hemming die, in which 
     an inner panel fixing pad is disposed facing downward on a tip part of the swing arm, and 
     the swing arm lowers the inner panel fixing pad at a predetermined position to hold down an upper face of the inner panel with the inner panel fixing pad to prevent displacement and lift of the inner panel. 
     &lt;4&gt; A vehicle panel processing method including performing roller hemming while maintaining a state where the outer panel and the inner panel are fixed at a predetermined position on the hemming die by sucking and fixing the lower face of the outer panel by the vacuum pads and holding down an upper face of the inner panel by the inner panel fixing pad of the swing arm and a state where the locator for positioning the outer panel is retracted from the path of the roller. 
     Advantageous Effects of Invention 
     The vehicle panel roller hemming device and the processing method using the same according to the present invention provide a vehicle panel roller hemming device and a processing method using the same that make it possible, in manufacture of a vehicle panel, to accurately set a workpiece, which includes an outer panel and an inner panel, at a predetermined position on a hemming die in roller hemming and reliably fix the panels when moving a roller during hemming, and have techniques for reducing the number of programming processes for automating roller hemming, improving the product quality, reducing the defective rate, and achieving excellent mass production. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic sectional view illustrating an embodiment of a roller hemming device according to the present invention. 
         FIG. 2  is a schematic perspective view illustrating an embodiment of a hemming die according to the present invention. 
         FIG. 3  is a schematic view illustrating an embodiment of a vacuum pad used in the present invention, in which (A) is a top view and (B) is a sectional view. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinbelow, a vehicle panel roller hemming device of the present invention will be described with reference to the drawings.  FIG. 1  is a schematic side view illustrating an embodiment of the roller hemming device according to the present invention.  FIG. 2  is a schematic perspective view illustrating an embodiment of a hemming die according to the present invention. 
     A vehicle panel roller hemming device  1  (hereinbelow, also merely referred to as the roller hemming device) of the present invention is a roller hemming device for hemming a peripheral edge part  210  of an outer panel  21  of a vehicle panel  2 , which includes the outer panel  21  and an inner panel  22 , by a roller of a roller hemming robot. 
     The roller hemming device  1  includes a positioning mechanism which positions the outer panel  21  on a hemming die  10  by a locator  12 , a suction and fixing mechanism which sucks and fixes a lower face of the outer panel  21  by a vacuum pad  3 , and a locator retracting mechanism which retracts the locator  12  from a path  11  of the roller of the roller hemming robot during the roller hemming. 
     The positioning mechanism of the roller hemming device  1  of the present invention is a mechanism which positions a workpiece  2 , which includes the outer panel  21  and the inner panel  22 , when the workpiece  2  is set on the hemming die  10 . A plurality of locators  12 , each of which moves up and down, is disposed around the hemming die  10 . The workpiece  2  is set at an accurate position on the hemming die  10  by the locators  12  lifted with respect to the hemming die  10 . 
     As described above, the workpiece  2  set on the hemming die  10  is previously temporarily assembled with an adhesive applied to a peripheral edge part  220  of the inner panel  22  and the peripheral edge part  210  of the outer panel  21  which includes a flange  211  having a predetermined dimension and a predetermined angle on the peripheral edge part  210 . In other words, the outer panel  21  and the inner panel  22  are temporarily assembled with the adhesive applied to the peripheral edge parts  210 ,  220 . Note that the above adhesive is either a thermoplastic resin or a thermosetting resin, and preferably a high-viscosity mixture containing at least one kind of filler selected from the group consisting of inorganic or metal powder and an inorganic or metal spherical particle. 
     The suction and fixing mechanism of the present invention is a mechanism which supports, and sucks and fixes the lower face of the outer panel  21  of the workpiece  2  by the vacuum pad  3  in a state where the workpiece  2  is accurately set at the predetermined position on the hemming die  10  in the positioning mechanism. As illustrated in  FIGS. 3(A) and 3(B) , the vacuum pad  3  includes at least a pad base part  30 , a skirt part  31 , a decompression space  32 , and a suction through pipe  33 . The pad base part  30  is a member which fixes and supports the workpiece  2  together with the skirt part  31  and the suction through pipe  33 , and the material thereof is not particularly limited to any material as long as it is not easily deformed. 
     The skirt part  31  is a member which comes into contact with the lower face of the outer panel  21  of the workpiece  2  to suck and fix the lower face. The skirt part  31  continuously rises with a predetermined thickness from the edge of the pad base part  30 , and includes an opening  34  on the upper end edge thereof. The skirt part  31  may be integrally formed with the pad base part  30 , or may be formed separately from the pad base part  30  and joined to the pad base part  30 . Further, the decompression space  32  is formed in a part surrounded by the pad base part  30  and an inner wall of the skirt part  31 . 
     The material of the skirt part  31  is not particularly limited to any material as long as it is not easily deformed with the workpiece  2  sucked thereto, but preferably a thermoplastic elastomer. Examples of the thermoplastic elastomer include styrene-butadiene rubber, butyl rubber, nitrile rubber, ethylene-propylene rubber, acrylic rubber, silicone rubber, and fluorine rubber. Among these materials, nitrile rubber is particularly preferably used. Further, the Shore hardness of the skirt part  31  is 40 to 90 HS, preferably 45 to 85 HS, and more preferably 60 HS. 
     Further, the rise height of the skirt part  31  from the pad base part  30  is within the range of 3 to 5 mm, and preferably within the range of 3.5 to 4.5 mm. The rise height of the skirt part  31  within the above range prevents displacement of the workpiece  2  even when the fixation by the locators  12  is released and roller hemming is performed on the workpiece  2  in a sucked state. Further, the thickness of the skirt part  31  can be appropriately set according to, for example, the hardness of the material, and is not particularly limited to any thickness. However, typically, the thickness of the skirt part  31  is preferably within the range of 1.5 to 3.5 mm. 
     Further, the top-view shape of the opening  34  is an ellipse. Preferably, the longer axis of the ellipse is within the range of 50 to 125 mm, and the shorter axis thereof is within the range of 15 to 70 mm. 
     The suction through pipe  33  is a member for sucking air inside the decompression space  32  to suck the workpiece  2 , and penetrates the pad base part  30  and communicates with the decompression space  32 . The material of the suction through pipe  33  is not particularly limited to any material as long as it is capable of fixing and supporting the workpiece  2  together with the pad base part  30  and the skirt part  31  and not easily deformed, and is preferably metal. 
     Further, a method for joining the pad base part  30  and the suction through pipe  33  is not particularly limited to any method as long as they are joined together so as not to be easily detached. For example, the pad base part  30  and the suction through pipe  33  may be joined together as illustrated in  FIG. 3(B) . Specifically, an insertion hole is formed on the central part of the pad base part  30 . A metal reinforcement member  37 , which includes a female thread on the inner face thereof, is fitted inside the insertion hole. A male thread is formed on one end part of the suction through pipe  33 . The male thread on the tip part of the suction through pipe  33  and the female thread of the metal reinforcement member  37  are screwed with each other. Alternatively, in a case where the pad base part  30  is made of a hard material, a female thread may be formed on the inner face of the insertion hole formed on the pad base part  30  to directly screw the female thread with the male thread on the suction through pipe  33 . 
     Further, in the vacuum pad  3  used in the present invention, a projection and a recess are preferably formed on the surface of the pad base part  30 , the surface facing the decompression space  32 , except a part having the opening  34  of the suction through pipe  33 . In the case where the projection and the recess are formed on the surface of the pad base part  30 , the surface facing the decompression space  32 , a projection  35  comes into intimate contact with the surface of the workpiece  2  when the workpiece  2  is sucked. Thus, it is possible to more stably tightly fix the workpiece  2 . 
     Specifically, air inside the decompression space  32  passes through a gap between the projection  35  and a recess  36  by suction and is discharged through the suction through pipe  33 , which penetrates the pad base part  30 , so that the volume of the decompression space  32  is reduced. Along with this, the projection  35  comes into contact with the lower face of the outer panel  21  of the workpiece  2 . Accordingly, the vacuum pad  3  is not excessively shrink-deformed, which reliably prevents displacement of the outer panel  21  caused by the suction. 
     Note that, in a case where a plurality of projections  35  is formed, the surfaces of the projections  35  are preferably flush with each other. Further, a height difference between the recess  36  and the projection  35  is not particularly limited to any height difference as long as air can flow during suction. The shape and the hardness of the projection  35  are not particularly limited to any shape and hardness as long as the projection  35  is not so deformed as to obstruct the flow of air in the recess  36  during the suction. 
     Further, in the suction and fixing mechanism of the roller hemming device  1  of the present invention, the vacuum pad  3  is disposed inside the peripheral edge of the hemming die  10 , and the longer axis of the elliptical skirt part  31  is substantially parallel to a direction in which the curvature of the vehicle panel  2  set on the hemming die  10  is smaller. 
     For example, the curvature of an outer plate surface of a vehicle door is typically designed in such a manner that the curvature in the front-rear direction is smaller than the curvature in the up-down direction. Thus, setting all the vacuum pads  3  to be disposed with their longer axes substantially parallel to the front-rear direction of the door as illustrated in  FIG. 2  makes it possible to suck the workpiece  2  on the hemming die  10  so as to be brought into intimate contact with the vacuum pads  3  with no displacement, thereby accurately and reliably fixing the workpiece  2 . 
     Further, the roller hemming device  1  of the present invention may be provided with a swing arm device  4  as illustrated in  FIG. 1  which includes a swing arm  43  which is capable of turning, bending, and moving up and down in a space above the hemming die  10 . 
     The swing arm device  4  of the embodiment illustrated in  FIG. 1  includes a strut  41  which is disposed outside the hemming die  10 , the swing arm  43 , and a support part  42  which is disposed on the tip part of an upper part of the strut  41  to turnably support the swing arm  43 . Further, an inner panel fixing pad  44  is disposed facing downward on the tip part of the swing arm  43 . Note that the material of the inner panel fixing pad  44  is not particularly limited to any kind and performance as long as it is a solid of one kind selected from the group consisting of a metal material, a high molecular material, and a rubber material or a composite material thereof. Further, the shape of the inner panel fixing pad  44  is not particularly limited to any shape as long as the inner panel fixing pad  44  is capable of coming into contact with a flat surface of the inner panel. However, the shape of the inner panel fixing pad  44  is preferably a circular plate shape or a columnar shape having a diameter within the range of 10 to 40 mm. 
     The swing arm device  4  is capable of holding down the upper face of the inner panel  22  from above by the inner panel fixing pad  44  by operating the support part  42  to lower the swing arm  43  at a predetermined position above the inner panel  22 . Accordingly, it is possible to reliably prevent displacement and lift of the inner panel  22 . 
     Note that the swing arm  43  may be further provided with an inner panel reference pin on the tip part thereof to enable accurate and reliable positioning of the inner panel  22 . Further, in the case where the swing arm device  4  is formed in an arch shape illustrated in  FIG. 1 , it is possible to prevent the operation of the roller of the roller hemming robot from being obstructed. 
     Next, an embodiment of a vehicle panel processing method using the roller hemming device  1  of the present invention will be specifically described. The vehicle panel processing method of the present embodiment executes at least a workpiece positioning step, a workpiece fixing step, a workpiece upper face holding step, and a hemming step. 
     First, in the workpiece positioning step, the workpiece  2  of the vehicle panel with the outer panel  21  and the inner panel  22  previously temporarily assembled with the adhesive is set on the hemming die  10  with the surface of the outer panel  21  facing downward. At this time, the workpiece  2  is accurately positioned by the locators  12  which are disposed around the hemming die  10 . 
     In the next workpiece fixing step, the lower face of the outer panel  21  of the workpiece  2  is sucked and fixed by the vacuum pads  3  described above. Then, in this state, the locators  12  are retracted from the path  11  of the roller of the roller hemming robot. In this state, the outer panel  21  of the workpieces  2  is strongly sucked and fixed by the vacuum pads  3 . Thus, retracting the locators  12  does not cause displacement of the position of the workpiece  2 . 
     In the next workpiece upper face holding step, the arch-shaped swing arm  43  supported by the support part  42  is moved by the operation of the support part  42 , which is disposed on the strut  41  of each of the two swing arm devices  4  installed outside the hemming die  10 , to bring the inner panel fixing pad  44  disposed on the tip part of the swing arm  43  into contact with the upper face of the inner panel  22 . Note that, at this time, the inner panel reference pin on the tip part of the swing arm  43  enables accurate and reliable positioning of the inner panel  22 . 
     According to the upper face holding step described above, since the inner panel fixing pad  44  on the tip part of the swing arm  43  is in contact with the surface of the inner panel  22  substantially perpendicularly thereto, it is possible to reliably prevent displacement and lift of the inner panel  22  even in the workpiece  2  in an incomplete joined state with the outer panel  21  and the inner panel  22  temporarily assembled. 
     In the next hemming step, hemming is performed by the roller of the roller hemming robot in a state where the lower face of the outer panel  21  of the workpiece  2  is sucked and fixed by the plurality of vacuum pads  3  and the locators  12  are retracted, and a state where the inner panel fixing pad  44  of the swing arm  43  is in contact with the upper face of the inner panel  22  of the workpiece  2 . Note that the arch shape of the swing arm device  4  enables the roller of the roller hemming robot to pass under the arch-shaped swing arm  43  and perform hemming without interference. 
     As described above, according to the vehicle panel processing method of the present invention, the lower face side of the outer panel  21  of the workpiece  2  is strongly sucked and fixed by the vacuum pads  3 , and the upper face side of the inner panel  22  is pressed from above by the inner panel fixing pad  44  of the swing arm  43 . Thus, even when the locators  12  are in a retracted state, displacement and lift are prevented, and roller hemming can be performed at an accurate set position. 
     The vehicle panel roller hemming device and the processing method using the same according to the present invention have been described above based on the embodiment. However, the present invention is not limited to the embodiment described above, and can be variously modified and changed without departing from the gist thereof. 
     For example, although, in the above embodiment, the inner panel  22  is pressed from above using the two swing arm devices  4 , one or two or more swing arm devices  4  may be used as long as the path  11  of the roller of the roller hemming robot is not obstructed. 
     EXAMPLES 
     Hereinbelow, the vehicle panel roller hemming device and the processing method using the same according the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples. 
     Example 1 
     A solventless and one-pack type thermosetting epoxy resin adhesive containing 1 mass % of glass beads having an average particle diameter of 200 μm and being of a uniform paste form having a viscosity of 300 Pa·s was applied to an inner peripheral edge part of an outer panel which is made of a hot-dip galvanized steel sheet and includes a flange having a width of 8 mm and an angle of 90° on the peripheral edge part thereof and a peripheral edge part of an inner panel, and the outer panel and the inner panel were temporarily assembled by a robot to prepare a vehicle panel workpiece. Next, the above workpiece was automatically set at a predetermined position on a hemming die in accordance with a program of the roller hemming device by another robot, and positioned by a locator. 
     As illustrated in  FIG. 2 , twelve vacuum pads were disposed at predetermined positions inside the hemming die with the longer axis of each of the vacuum pads substantially parallel to the front-rear direction of the vehicle, that is, the direction in which the curvature of a curved surface of the outer panel is smaller. The vacuum pad which includes a skirt part having a thickness of 3 mm, has an elliptical shape having a longer-axis length of 94 mm and a shorter-axis length of 34 mm, is made of oil-proof nitrile rubber, and has a Shore hardness of 60 HS was used. Note that, at the point when the workpiece was set on the hemming die, it was confirmed that the upper ends of the skirt parts of all the twelve vacuum pads were in contact with the lower surface of the outer panel. 
     Next, in a state where the workpiece was positioned by the locator, all the vacuum pads were sucked to fix the outer panel. Then, the locator used for the positioning was automatically retracted from the path of the roller. At this point, it was confirmed that the position of the peripheral edge part of the outer panel coincided with the predetermined disposing position, and the workpiece as the vehicle panel was set on the hemming die within the range of the assembly accuracy. 
     Next, pre-hemming was performed using four roller hemming robots whose operation has been previously programmed to further bend the flange formed on the peripheral edge part of the outer panel of the workpiece and bent at 90° up to 145° by the rollers of the roller hemming robots. 
     After the pre-hemming, roller hemming, which is programmed 180° bending, was further performed on the workpiece. As a result, it was confirmed that the roller hemming was performed without a hindrance to the movement of the roller, and the position of the peripheral edge part of the outer panel of the workpiece was not displaced at all and coincided with the predetermined disposing position. 
     Example 2 
     The workpiece and the hemming die that are the same as those of Example 1 were used, and the workpiece was sucked and fixed on the hemming die on the same condition as Example 1. 
     Next, an inner panel fixing pad disposed on the tip of a swing arm was brought into contact with the flat part of the surface of the inner panel substantially perpendicularly thereto, and the inner panel was pressed from above to perform lift prevention and fixation. At this stage, there was no displacement of the peripheral edge part of the outer panel and the peripheral edge part of the inner panel. 
     At the same time, while the outer panel was sucked and fixed by the vacuum pads, the swing arm disposed on the strut of each of the two swing arm devices installed outside the hemming die was automatically extended through the support part to form an arch, and the inner reference pin of each swing arm was brought into contact with the surface of the inner panel substantially perpendicularly thereto to position the inner panel. 
     That is, at this point, in a state where the outer panel and the inner panel were temporarily assembled with the adhesive applied to the peripheral edge part of the outer panel and the peripheral edge part of the inner panel, the outer panel side was fixed by the vacuum pads, and the inner panel was fixed at the predetermined position by the swing arms. 
     Next, in the same manner as Example 1, pre-hemming was performed using four roller hemming robots whose operation has been previously programmed to further bend the flange formed on the peripheral edge part of the outer panel of the workpiece and bent at 90° up to 145° by the rollers of the roller hemming robots. Further, after the pre-hemming, roller hemming, which is programmed 180° bending, was performed on the workpiece. 
     In the above roller hemming, the tip part and the roller of each roller hemming robot passed under the swing arm, and the swing arm was able to hem the entire peripheral edge part of the panel without obstructing the movement on the path of the roller. Further, in the above hemming, there was no hindrance to the back and forth movement of the roller. 
     That is, in the method of Example 2, it was confirmed that pre-hemming was performed with no hindrance to the movement of the roller, and the position of the peripheral edge part of the outer panel coincided with the predetermined disposing position. Further, the peripheral edge part (hemmed part) of the vehicle panel after the hemming was cut at a plurality of positions, and displacement from the initial predetermined position of the peripheral edge part of each of the outer panel and the inner panel was checked. As a result, it was confirmed that there was completely no displacement in the fixed position of the outer panel with respect to the inner panel of the present invention. 
     It was confirmed from the above results that the swing arm device of the present invention is effective in accurate positioning and fixation of the inner panel and precise roller hemming. 
     Comparative Example 1 
     The adhesive was applied to the outer panel and the inner panel, and the temporarily-assembled vehicle panel workpiece was set at the predetermined position on the hemming die by the locator in the same manner as Example 1 except that a bellows vacuum pad which is made of oil-proof nitrile rubber, has a Shore hardness of 60 HS, has a circular bottom face, and includes a rubber part having a bottom face radius of 50 mm and a height of 42 mm was used as a vacuum pad for fixing the outer panel of the workpiece. 
     Next, the bellows vacuum pad was sucked to fix the outer panel. In this state, it was confirmed that the pad was crushed by pressure reduction, and the height of the rubber part became substantially half the initial height. 
     Next, in the same manner as Example 1, pre-hemming was performed using four roller hemming robots whose operation has been previously programmed to further bend the flange formed on the peripheral edge part of the outer panel of the workpiece and bent at 90° up to 145° by the rollers of the roller hemming robots. Further, after the pre-hemming, roller hemming, which is programmed 180° bending, was performed on the workpiece. 
     At this stage, the hemmed state of the workpiece was observed by visual check, and it was confirmed that there was displacement of the workpiece caused by displacement of the bellows vacuum pad, and there was a part into which the inner panel was not inserted in the outer panel bent to 180° at the final hemming. 
     Further, the peripheral edge part (hemmed part) of the vehicle panel after the hemming was opened at a plurality of positions, and displacement from the initial predetermined position of the peripheral edge part of each of the outer panel and the inner panel was checked. As a result, it was confirmed that there was a displacement of approximately 0.5 mm from the predetermined position of the peripheral edge part of each of the outer panel and the inner panel. 
     Accordingly, it was confirmed that, when the conventional vacuum pad is used, the disposing position of the outer panel is displaced, and the inner panel is also displaced.