Patent Abstract:
The present invention relates to a press die set for forming a flange that bends an edge of a part, such as a door panel and a hood panel, at a right angle in a press-forming direction and bends an edge adjacent to the edge at a negative angle, and a flange forming method. The press die set for forming a flange according to the present invention can accomplish the flange formation described above in one step, has a simple structure, and is easy to maintain.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a press die set for forming a flange that bends an edge of a panel at a right angle in a press-forming direction and an edge adjacent to the edge at a negative angle and a flange forming method. 
     2. Description of the Related Art 
     Many automobile parts are formed by press working. Such parts include door parts that have a flange formed along the edge thereof. In many cases, the flange of the door part or the like is formed by right-angle bending, which is a technique of bending an edge of a panel at approximately a right angle in the press-forming direction. However, negative-angle bending is sometimes used, which is a technique of bending a panel at an angle greater than a right angle to cover the expanded portion of the lower die. In general, the panel bent at a negative angle is difficult to eject from the die set. Thus, in flange formation involving the negative-angle bending, a rotary cam type press die set, a double cam type press die set or the like, from which the panel can be easily ejected, is often used for press working. However, for press working of door panels, hood panels or the like that have an edge bent at a right angle in the press-forming direction and an edge adjacent to the edge bent at a negative angle, there are proposed working apparatus or methods that do not use the rotary cam type press die set, the double cam type press die set or the like, which are complicated and expensive. 
     For example, in Japanese Utility Model Publication No. 6-49375, there is proposed a composite pressing apparatus that can perform right-angle bending and negative-angle bending of an automobile hood panel at the same time in one step and has a mechanism for ejecting the worked panel from the lower die. It is described that the part of the composite pressing apparatus that is responsible for flange formation is movable, so that the panel can be easily released. In order to appropriately bend the boundary part between the negative-angle part and the right-angle part, many composite pressing apparatus including the apparatus described above have a cam bending blade for negative-angle bending having a substantially L-shaped profile and is configured so that a part of the edge bent at a right angle by a press bending blade is bent at a right angle by the cam bending blade, and the operation of the press bending blade slightly lags behind the operation of the cam bending blade. The term “one step” indicates the operation of the upper die which lowers to the lower die and then rises to the original position. 
     However, such composite pressing apparatus have a problem that deformation, such as strain and fracture, due to the difference in timing between the operation of the press bending blade and the cam bending blade is likely to occur. Japanese Patent No. 3013684 proposes a composite pressing apparatus that solves the problem. More specifically, Japanese Patent No. 3013684 proposes a composite pressing apparatus comprising a press bending blade that bends one of two adjacent edges of a curved workpiece in the same direction as the direction of pressing of an upper die and a cam bending blade that bends the other of the adjacent two edges at a negative angle inwardly with respect to the pressing direction of the upper die, in which the press bending blade has a movable bending blade at a part that overlaps with the cam bending blade during press working, and the adjacent two edges are bent at the same time by avoiding interference between the cam bending blade and the press bending blade by retracting the movable bending blade when the cam bending blade moves downward. 
     SUMMARY OF THE INVENTION 
     However, the composite pressing apparatus proposed in Japanese Patent No. 3013684 has a problem that the apparatus requires a specially designed component, such as the movable bending blade, and therefore the structure of the die set is complicated, although the apparatus can advantageously perform negative-angle bending and right-angle bending at the same time in one step and prevent deformation, such as strain and fracture, of the transitional part between the negative-angle part and the right-angle part in press working of a part, such as a door panel and a hood panel. 
     The present invention has been devised in view of such problems with the related art, and an object of the present invention is to provide a press die set for forming a flange that bends an edge of a panel, such as a door panel and a hood panel, at a right angle in a press-forming direction, bends an edge adjacent to the edge at a negative angle, has a simple structure and can accomplish the bendings in one step, and a flange forming method. 
     A press die set for forming a flange according to an aspect of the present invention is a press die set for forming a flange that bends an edge of a panel at a right angle in a press-forming direction and an edge adjacent to the edge at a negative angle, comprising: an upper die having a fixed die used for right-angle bending and a slide cam that slides in a direction perpendicular to the press-forming direction to perform negative-angle bending; and a lower die having a fixed punch associated with the fixed die, a fixed punch associated with the slide cam and a driver cam for guiding the slide cam, in which a bending blade of the slide cam has a right-angle bending forming portion provided at the top thereof and a negative-angle bending forming portion immediately following the right-angle bending forming portion. 
     In the aspect of the present invention described above, the slide cam preferably has a resilient body that urges the slide cam into a rest position, and the driver cam is preferably provided so that the slide cam slides in the direction perpendicular to the press-forming direction to perform negative-angle bending after the fixed die and the slide cam perform right-angle bending of the respective edges of the panel. Furthermore, a parting line between the bending blade of the slide cam and a bending blade of the fixed die is preferably intrudes into the edge to be bent at a negative angle from the edge to be bent at a right angle. 
     Furthermore, the press die set for forming a flange according to the aspect of the present invention described above preferably further comprises a panel lifter that abuts against an end face of a negative-angle flange to release the panel from the lower die. Furthermore, the panel lifter can have a plurality of ejectors that abut against the end face of the negative-angle flange of the panel, a coupling board to which the ejectors are integrally attached, a plurality of pressing means that operate within a predetermined range in a releasing direction in which the negative-angle flange is released from the lower die and urge the coupling board in the releasing direction, and a cam follower that abuts against the slide cam to maintain the coupling board in a predetermined position when the negative-angle flange is being worked. 
     A flange forming method according to another aspect of the present invention is a flange forming method of bending an edge of a panel at a right angle in a press-forming direction and an edge adjacent to the edge at a negative angle, in which a part bent at a right angle and a part bent at a negative angle are adjacent to each other at a parting line. 
     In the flange forming method described above, the parting line is preferably intrudes into the edge bent at a negative angle from the edge bent at a right angle. 
     A press die set for forming a flange according to an aspect of the present invention has a simple structure, is easy to maintain, and can perform press working to form an edge of a part, such as a door panel and a hood panel, into a continuous flange including a portion bent at a negative angle in one step. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross-sectional view of a part of a press die set for forming a flange according to an embodiment of the present invention that is used for right-angle bending; 
         FIG. 2  is a partial cross-sectional view of a part of the press die set for forming a flange according to the embodiment of the present invention that is used for negative-angle bending; 
         FIG. 3  is a partial cross-sectional view showing attachment of a slide cam shown in  FIG. 2  to an upper die holder; 
         FIG. 4  is an enlarged perspective view showing the slide cam shown in  FIG. 1  or  2 , a driver cam associated with the slide cam, and a panel lifter; 
         FIG. 5  is a diagram for illustrating attachment of bending blades of a fixed die and a bending blade of the slide cam to an upper die holder; 
         FIG. 6  includes diagrams showing a panel yet to be worked (shown by the alternate long and short dash line) and a panel after right-angle bending and negative-angle bending (shown by the solid line), in which  FIG. 6(A)  is a plane view, and  FIG. 6(B)  is a cross-sectional view taken along the line pOq; 
         FIG. 7  includes diagrams for illustrating different steps in a process of bending the panel; and 
         FIG. 8  includes diagrams for illustrating different steps in a process of releasing the panel from a lower die. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, a press die set for forming a flange according to an embodiment of the present invention will be described with reference to the drawings.  FIGS. 1 and 2  are partial cross-sectional views showing a configuration of a press die set for forming a flange according to an embodiment of the present invention.  FIG. 1  shows a portion of the press die set used for right-angle bending, and  FIG. 2  shows a portion of the press die set used for negative-angle bending. As shown in  FIGS. 1 and 2 , an upper die  10  of the press die set for forming a flange has an upper die holder  11  and a pad  13 , and a fixed die  15  and a slide cam  20  are attached to the upper die holder  11 . The fixed die  15  has a bending blade  16 , and the slide cam  20  has a bending blade  21 . The bending blade  21  has a right-angle bending forming portion  21   a  at the top thereof and a negative-angle bending forming portion  21   b  immediately following the right-angle bending forming portion. The bending blade  21  enables easy negative-angle bending as described later. On the other hand, the lower die  30  of the press die set for forming a flange has a lower die holder  31  and fixed punches  33  and  35 , and the lower die holder  31  has a driver cam  40 . 
     In the press die set for forming a flange, the fixed die  15  is associated with the fixed punch  33  as shown in  FIG. 1 , and the slide cam  20  is associated with the fixed punch  35  as shown in  FIG. 2 . As described later, the driver cam  40  makes the slide cam  20  slide in a direction perpendicular to a press-forming direction (in the rightward direction in  FIG. 2 ). Arranged in this way, the bending blade  16  of the fixed die  15  and the fixed punch  33  cooperate to bend a panel  80  at a right angle to form a flange, and the bending blade  21  of the slide cam  20  and the fixed punch  35  cooperate to bend the panel  80  at a negative angle to form a flange. 
     As shown in  FIG. 3 , the slide cam  20  is attached to the upper die holder  11  with an attachment bolt  25 . A through-hole  26  for the attachment bolt  25  formed in the bending blade  21  of the slide cam  20  is an elongate hole or unloaded hole, so that the slide cam  20  is free to slide within a predetermined range. In addition, sliding members  28  and  29  are provided to allow the slide cam  20  to smoothly slide with respect to the upper die holder  11 . 
     As shown in  FIG. 4 , the bending blade  21  of the slide cam  20  has the shape of a rectangular column with one ridge trimmed off. The top flat portion thereof forms the right-angle bending forming portion  21   a,  and the inclined portion abutting on the right-angle bending forming portion  21   a  forms the negative-angle bending forming portion  21   b.  The inclination angle of the inclined portion depends on the angle of the negative-angle bending. 
     In addition, as shown in  FIG. 4 , the bending blade  21  has guide grooves  22  at predetermined intervals into which driver cams  40  are fitted. The driver cam  40  has a sliding member  45  on an inclined surface of a driver portion  41  thereof. As described later, the driver portion  41  of the driver cam  40  is fitted into the guide groove  22  to make the slide cam  20  smoothly slide in a direction perpendicular to the press-forming direction. The driver cam  40  further has a sliding member  46  at the rear thereof, which allows the driver cam  40  to smoothly slide on the upper die holder  11 . In addition, the bending blade  21  has a roll-off  21   c  to avoid interference or the like with the panel  80 . 
     The slide cam  20  is connected to stoppers  23  connected to the upper die holder  11  at predetermined intervals via a resilient body  24 , and as described later, the resilient bodies  24  urge the slide cam  20  into a rest position. As a result, play of the slide cam  20  is removed, and the quality of the press forming is improved. The resilient body  24  can be a resilient material, such as a spring and urethane rubber. 
       FIG. 5  shows a layout of the bending blade  16  of the fixed die  15  and the bending blade  21  of the slide cam  20 . As shown in  FIG. 5 , in this embodiment, three edges of the panel  80  adjacent to each other are surrounded by the bending blades  16  and the bending blade  21 . More specifically, bending blades  16 A and  16 B are disposed on the left and right of the panel  80  to be worked, and the bending blade  21  is disposed below the panel  80 . The bending blade  16 A,  16 B has a protrusion  17  at an end thereof. The protrusions  17  slightly intrude into the bending blade  21  and are in contact with the bending blade  21  in such a manner that the protrusions  17  do not interfere with the bending blade  21  during operation. Thus, the peripheral edges of the panel  80  can be simultaneously worked to form a flange. As described above, the associated fixed punches  33  and  35  are provided for the bending blades  16  and  21 . 
     Using such a press die set for forming a flange, the panel  80  can be bent at a right angle and at a negative angle to form a flange as described later.  FIG. 6  includes diagrams for illustrating a panel worked using the press die set for forming a flange according to an embodiment of the present invention. In  FIG. 6 , the alternate long and short dash line indicates the shape of the panel  80  yet to be worked, and the solid line indicates the shape of the panel  80  worked. Left and right edges (right-angle flanges  83 ) and a corner (a corner  85 ) of a panel-main body  81  of the panel  80  are portions to be bent at a right angle (P regions), and a lower edge (a negative-angle flange  84 ) of the panel-main body  81  is a portion to be bent at a negative angle (an F region). The boundary between the P region and the F region is the boundary between the bending blade  21  and the bending blade  16 , which is generally referred to as parting line. As shown in  FIG. 6(B) , the portion to be bent at a negative angle is shaped to cover the expanded portion of the fixed punch  35 . 
     In working the panel  80 , first, as shown in  FIGS. 1 and 2 , the panel  80  is placed on the upper surface of the fixed punches  33  and  35 , and then the pad  13  is lowered and pressed against the panel  80  to secure the panel  80  between the pad  13  and the fixed punches  33  and  35 . Then, the upper die holder  11  is lowered to bend the left, right and lower edges of the panel  80  at a right angle between the bending blades  16  of the fixed die  15  and the fixed punch  33  and between the bending blade  21  of the slide cam  20  and the fixed punch  35  as described above. In this step, the bending blade  21  of the slide cam  20  first comes into contact with the panel  80  at the right-angle bending forming portion  21   a  at the top thereof, so that the panel  80  is bent at a right angle between the right-angle bending forming portion  21   a  and the fixed punch  35 .  FIG. 7(A)  illustrates this step. The down arrow in  FIG. 7(A)  indicates the direction of lowering of the upper die holder  11  (the press-forming direction). 
     As the upper die holder  11  is lowered, when right-angle bending of the left, right and lower edges of the panel  80  is completed, negative-angle bending of the panel  80  is then carried out. As shown in  FIG. 7(B) , at the lower edge of the panel  80  to be bent at a negative angle, the surface of the sliding member  45  of the driver portion  41  of the driver cam  40  comes into contact with the guide groove  22  in the bending blade  21  of the slide cam  20  ( FIG. 4 ). As the upper die holder  11  is further lowered, the slide cam  20  slides in the direction of the right arrow in  FIG. 7(B)  by being guided by the driver portion  41  of the driver cam  40 . As a result, the lower edge of the panel  80  bent at a right angle as described above is further bent at a negative angle by the negative-angle bending forming portion  21   b  of the bending blade  21 . Although the driver portion  41  is fitted between the upper die holder  11  and the guide groove  22  as shown in  FIG. 7 , the driver portion  41  has the sliding members  45  and  46  on the surfaces to come into contact therewith, so that the driver portion  41  smoothly slides between the upper die holder  11  and the guide groove  22 . 
     In such right-angle bending and negative-angle bending of the panel  80 , the slide cam  20  (the bending blade  21 ) is pulled toward the stopper  23  fixed to the upper die holder  11  by the action of the resilient body  24  as shown in  FIG. 7(C) . In other words, the slide cam  20  is urged by the resilient body  24  to come into contact with a surface of the stopper  23 , and the position is the rest position of the slide cam  20 . Thus, play of the slide cam  20  in the right-angle bending and the negative-angle bending is removed, and highly precise working is achieved. 
     When the right-angle bending and the negative-angle bending are completed, then, the bent panel  80  is released from the fixed punches  33  and  35  (the lower die  30 ). The panel  80  is preferably released using a panel lifter  50  as shown in  FIG. 8 .  FIG. 8(A)  shows the panel  80  at the time when the bending is completed.  FIG. 8(B)  shows the bent panel  80  released from the lower die  30  using the panel lifter  50 . 
     As shown in  FIG. 8(A) , when the bending is completed, a cam follower  55  of the panel lifter  50  abuts against the bending blade  21 , and an ejector  53  is positioned below the panel  80 . Then, the upper die holder  11  and the pad  13  are first raised. As the upper die holder  11  is raised, the slide cam  20  slides in the left direction in  FIG. 8(A)  by the action of the driver cam  40  and the resilient body  24  while moving upward. Thus, as shown in  FIG. 8(B) , the cam follower  55  is released from the bending blade  21 , and by the action of pressing means  57 , the ejector  53  abuts against an end face of a negative-angle flange  84  to press the panel  80 , thereby releasing the panel  80  from the lower die  30  (the fixed punches  33  and  35 ). 
     To release the panel  80  from the lower die  30 , the ejector  53  preferably exerts a uniform pressing force to the end face of the negative-angle flange  84 . Therefore, for example, as shown in  FIG. 4 , the panel lifter  50  preferably has a plurality of pressing means  57  and a plurality of ejectors  53  with a coupling board  51  interposed therebetween as required. For the panel lifter  50 , in order that the pressing means  57  is effective only within a predetermined distance, a stopper  58  or the like is used to limit the movement of the pressing means  57  after the panel  80  is released from the lower die  30 . In addition, in order to effectively exert the pressing force to the end face of the negative-angle flange  84 , the panel lifter  50  is disposed at the same angle as the bending angle of the negative-angle bending. For the panel lifter  50 , as shown in  FIG. 4 , the pressing means  57  is housed in a case  56 , and the cam follower  55  is rotatably coupled to the coupling board  51  via a bracket  54 . The pressing means  57  can be a coil spring. 
     Right-angle bending and negative-angle bending of the panel  80  using the press die set for forming a flange according to an embodiment of the present invention have been described above. As described above, the bending blade  21  and the protrusions  17  of the bending blades  16  are in contact with each other at the respective parting lines. That is, a flange forming method according to an embodiment of the present invention differs from conventional flange forming methods in that the bending blade used for right-angle bending and the bending blade used for negative-angle bending do not overlap. In addition, as shown in  FIG. 6 , the parting line between the bending blades intrudes into the edge bent at a negative angle from the edge to be bent at a right angle. Thus, a strain or damage that is likely to occur in the transitional part between the right-angle part and the negative-angle part (the area indicated by a character s in  FIG. 6 ) in conventional flange forming methods can be prevented. Furthermore, in the case where the parting line is positioned at the transition point from the corner  85  to the negative-angle flange  84  as shown in  FIG. 6 , the range of the transition part can be advantageously reduced. 
     The corner  85  is subject to drawing, and this makes it difficult to release the panel  80  from the lower die  30 . Therefore, at the corner  85 , the flange preferably has a height that prevents drawing of the flange and occurrence of overlapping wrinkles, for example, a height of 5 mm or less. 
     Description of Symbols 
     
         
           10  upper die 
           11  upper die holder 
           13  pad 
           15  fixed die 
           16  bending blade 
           17  protrusion 
           20  slide cam 
           21  bending blade 
           22  guide groove 
           23  stopper 
           24  resilient body 
           25  attachment bolt 
           26  hole 
           28 ,  29  sliding member 
           30  lower die 
           21  lower die holder 
           33 ,  35  fixed punch 
           40  driver cam 
           41  driver portion 
           45 ,  46  sliding member 
           50  panel lifter 
           51  coupling board 
           53  ejector 
           54  bracket 
           55  cam follower 
           56  case 
           57  pressing means 
           80  panel 
           81  panel-main body 
           83  right-angle flange 
           84  negative-angle flange 
           85  corner

Technology Classification (CPC): 1