Patent Publication Number: US-11660650-B2

Title: Apparatus for and method of manufacturing roll-formed component

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a Continuation of application Ser. No. 16/215,761 filed Dec. 11, 2018, which claims the benefit of priority to Japanese Patent Application No. 2017-236670 filed on Dec. 11, 2017 to the Japan Patent Office. The disclosures of the prior applications are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates to an apparatus for and a method of manufacturing a roll-formed component, capable of continuously adjusting or controlling curvature of the roll-formed component along its longitudinal direction. 
     (2) Description of Related Art 
     Frame components used for manufacturing of an aircraft include a stringer, a stiffener, a spar, a floor beam, a rib, a frame, a doubler, and the like, for example. Examples of a method of manufacturing the frame components include roll forming. In the roll forming, a flat metal material is formed in a shape with a predetermined cross-sectional shape by a plurality of roll members. A contour (bent shape) is provided to a frame component formed in a shape with a cross section as described above, in many cases. Performing roll bending after roll forming enables a frame component provided with a contour with a predetermined cross-sectional shape to be manufactured. In the following description, roll bending is also included in “roll forming”. 
     Examples of a method of manufacturing a frame component using roll forming include a roll assembly disclosed in U.S. Pat. No. 4,080,815, for example. It is disclosed that this roll assembly enables a contour to be provided to a frame component with a cross-sectional shape, such as a T shape, an L shape, a Z shape, or a hat shape. 
     For example, Japanese Unexamined Patent Publication No. 2001-047260 discloses a manufacturing method for forming a component with a cross-sectional shape changing in its longitudinal direction, used for wings of an aircraft, so as to change its curvature. In this manufacturing method, at least one of side portions of an extruded molded material or the like is cut out and then the side portions are joined to each other by friction stir welding to form an integral component. When forming is performed so as to change curvature of the integral component, the integral component is formed by plastic forming after being joined. Examples of a method of the plastic forming include press forming, shot peening forming, creep forming, and the like. 
     SUMMARY OF THE INVENTION 
     The component with a cross-sectional shape changing in its longitudinal direction, disclosed in Japanese Unexamined Patent Publication No. 2001-047260, is used for wings or the like as described above. The component is manufactured using friction stir welding, and plastic forming is used to change curvature of the component. 
     In manufacturing of a frame component for an aircraft by roll forming, there has not been known a technique for continuously changing curvature of the frame component steplessly in a longitudinal direction of the frame component (providing continuous change in curvature). In particular, the frame component for an aircraft has a cross-sectional shape in which a side edge portion in the width direction is bent, such as an L shape, a hat shape, an S shape, or a Z shape, for example. It has been substantially difficult to appropriately adjust or control curvature of the frame component along its longitudinal direction so as to provide continuous curvature change to the frame component having a complicated cross-sectional shape as described above, for example. 
     The present invention is made to solve a problem as described above, and an object thereof is to provide an apparatus for and a method of manufacturing a roll-formed component, capable of favorably changing, adjusting, or controlling curvature of the roll-formed component along its longitudinal direction in the manufacturing of the roll-formed component. 
     An apparatus for manufacturing a roll-formed component, according to the present invention, manufactures a roll-formed component with curvature continuously changing along its longitudinal direction by applying roll bending to an elongated sheet or an elongated extrusion material, being a workpiece, along its longitudinal direction, to solve the problem described above. The apparatus includes a fulcrum roll that is provided upstream of the workpiece in a bending path to support the workpiece during bending, or to serve as a fulcrum of bending, a bending roll positioned downstream of the fulcrum roll in the bending path to apply bending to the workpiece, a roll moving unit that moves at least one of the fulcrum roll and the bending roll so as to relatively change a position of the bending roll with reference to a position of the fulcrum roll, and a control unit. Under the following conditions: a position allowing the fulcrum roll to be brought into contact with the workpiece is set as a fulcrum roll contact position; a position allowing the bending roll to be brought into contact with the workpiece is set as a bending roll contact position; when the roll-formed component is divided into a plurality of unit intervals in its longitudinal direction, a design value of a curvature radius of an unit portion corresponding to each of the unit intervals in the roll-formed component is set as a design curvature radius; a curvature radius applied to the workpiece at the fulcrum roll contact position is set as an initial curvature radius; and a curvature radius remaining in the workpiece when the workpiece is fed out from the bending roll contact position to achieve the design curvature radius in the roll-formed component is set as a final curvature radius, the initial curvature radius is set as a curvature radius to be applied to the workpiece before spring back occurs by applying bending to the workpiece. Under the following conditions: the unit portion positioned at the fulcrum roll contact position at the time when the workpiece is fed to a nip between the fulcrum roll and the bending roll is set as a fulcrum roll unit portion; the unit portion positioned at the bending roll contact position is set as a bending roll unit portion; and the unit portion positioned between the unit portions above, corresponding to each of the unit intervals, is set as an intermediate unit portion, the control unit integrates an amount of change in bending position in each of the intermediate unit portion and the bending roll unit portion when an intermediate curvature radius set so as to continuously change curvature of the intermediate unit portion from the initial curvature radius to the design curvature radius is applied to the intermediate unit portion, and the design curvature radius is applied to the bending roll unit portion, to apply the initial curvature radius corresponding to the unit portion to the fulcrum roll unit portion and apply the design curvature radius corresponding to the unit portion to the bending roll unit portion. The control unit causes the roll moving unit to be driven to move at least one of the fulcrum roll and the bending roll on the basis of an integrated value. 
     A method of manufacturing a roll-formed component, according to the present invention, is configured to manufacture a roll-formed component with curvature continuously changing along its longitudinal direction by applying roll bending to an elongated sheet or an elongated extrusion material, being a workpiece, along its longitudinal direction, to solve the problem described above. The method may include the steps of: supporting the workpiece during bending by a fulcrum roll provided upstream of the workpiece in a bending path, or allowing the fulcrum roll to serve as a fulcrum of bending; applying bending to the workpiece by a bending roll positioned downstream of the fulcrum roll in the bending path; moving at least one of the fulcrum roll and the bending roll so as to relatively change a position of the bending roll with reference to a position of the fulcrum roll by using a roll moving unit; setting a position allowing the fulcrum roll to be brought into contact with the workpiece as a fulcrum roll contact position; setting a position allowing the bending roll to be brought into contact with the workpiece as a bending roll contact position; setting a design value of a curvature radius of each of the unit intervals in the roll-formed component as a design curvature radius when the roll-formed component is divided into a plurality of unit intervals in its longitudinal direction; setting a curvature radius applied to the workpiece at the fulcrum roll contact position as an initial curvature radius; setting a curvature radius remaining in the workpiece when the workpiece is fed out from the bending roll contact position to achieve the design curvature radius in the roll-formed component as a final curvature radius; setting the initial curvature radius as a curvature radius to be applied to the workpiece before spring back occurs by applying bending to the workpiece; setting the unit portion positioned at the fulcrum roll contact position at the time when the workpiece is fed to a nip between the fulcrum roll and the bending roll as a fulcrum roll unit portion; setting the unit portion positioned at the bending roll contact position as a bending roll unit portion; setting the unit portion positioned between the unit portions above, corresponding to each of the unit intervals, as an intermediate unit portion; applying an intermediate curvature radius set so as to continuously change curvature of the intermediate unit portion from the initial curvature radius to the design curvature radius to the intermediate unit portion, to apply the initial curvature radius corresponding to the unit portion to the fulcrum roll unit portion and apply the design curvature radius corresponding to the unit portion to the bending roll unit portion; applying the design curvature radius to the bending roll unit portion; integrating an amount of change in bending position in each of the intermediate unit portion and the bending roll unit portion; and moving the roll moving unit, and at least one of the fulcrum roll and the bending roll using the roll moving unit on the basis of this integrated value. 
     According to the above configuration, a design curvature radius is preset for a position of the roll-formed component manufactured in its longitudinal direction, and the initial curvature radius being a curvature radius before spring back occurs is preset for the design curvature radius to form a database. The control unit integrates a relative amount of change in position of the bending roll based on an individual design curvature radius in each unit interval in a period from the fulcrum roll contact position to the bending roll contact position when a workpiece is fed out from the fulcrum roll, with reference to the database. The control unit controls the roll moving unit such that a relative positional change of the bending roll with respect to the fulcrum roll becomes an amount of change in position based on this integrated quantity. 
     In this configuration, not only the initial curvature radius is set by paying attention to the fulcrum roll contact position, but also a position of the bending roll with respect to the fulcrum roll is determined such that a workpiece advanced from the fulcrum roll contact position toward the bending roll contact position has a shape formed by accumulating a bending shape. This enables a relative position of the bending roll to the fulcrum roll to be gradually changed to provide a continuous curvature change to the workpiece. Thus, a portion with curvature continuously changing can be formed at a desired position in the roll-formed component obtained, in its longitudinal direction. As a result, a roll-formed component can be adjusted or controlled to have favorable curvature along its longitudinal direction in manufacturing thereof. 
     The present invention achieves an effect that enables providing an apparatus for and a method of manufacturing a roll-formed component, capable of favorably changing, adjusting, or controlling curvature of the roll-formed component along its longitudinal direction in the manufacturing of the roll-formed component, by using the above configuration. 
     The following detailed description of a preferred embodiment of the present invention, with reference to accompanying drawings, will reveal the above object, other objects, features, and advantages of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram comparing a schematic plan view illustrating an example of a representative configuration of a roll-formed component according to the present disclosure with a change in curvature of the roll-formed component in its longitudinal direction; 
         FIG.  2    is a diagram comparing a schematic plan view illustrating an example of another representative configuration of the roll-formed component according to the present disclosure with a change in curvature of the roll-formed component in its longitudinal direction; 
         FIG.  3    is a diagram comparing a schematic plan view illustrating an example of yet another representative configuration of the roll-formed component according to the present disclosure with a change in curvature of the roll-formed component in its longitudinal direction; 
         FIGS.  4 A to  4 E  are each a schematic cross-sectional view illustrating a typical example of a transverse cross section of each of the roll-formed components illustrated in  FIGS.  1  to  3   ; 
         FIG.  5 A  is a schematic view illustrating an example of an apparatus for manufacturing a roll-formed component according to an embodiment of the present disclosure, and  FIG.  5 B  is a schematic view illustrating an example of a moving direction of a roll moving unit of the apparatus for manufacturing a roll-formed component illustrated in  FIG.  5 A ; 
         FIG.  6 A  is a schematic view for illustrating an absolute position of a roll-formed component and a workpiece, and  FIG.  6 B  is a schematic view for illustrating a relative position and a relative section between a support roll and a bending roll in the apparatus for manufacturing a roll-formed component illustrated in  FIG.  5 A ; 
         FIG.  7    is a schematic view illustrating an example of control by a control unit in the apparatus for manufacturing a roll-formed component illustrated in  FIG.  5 A ; 
         FIG.  8    is a schematic view illustrating an example of calculation of the amount of change in position of the bending roll under control of the control unit in the apparatus for manufacturing a roll-formed component illustrated in  FIG.  5 A ; 
         FIG.  9 A  is a graph illustrating a relationship between change in a curvature radius of a roll-formed component and change in a stroke of the bending roll in the apparatus for manufacturing a roll-formed component illustrated in  FIG.  5 A , and  FIG.  9 B  is a graph for illustrating a deviation between the change in a curvature radius and the change in a stroke in the graph illustrated in  FIG.  9 A ; 
         FIG.  10    is a schematic view illustrating another example of the apparatus for manufacturing a roll-formed component according to the embodiment of the present disclosure; 
         FIG.  11    is a schematic view illustrating yet another example of the apparatus for manufacturing a roll-formed component according to the embodiment of the present disclosure; and 
         FIG.  12    is a schematic view illustrating yet another example of the apparatus for manufacturing a roll-formed component according to the embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, a representative embodiment of the present invention will be described with reference to the drawings. In the following description, the same or corresponding element is designated by the same reference numeral throughout the drawings to eliminate a duplicated description of the element. 
     [Workpiece and Roll-Formed Component] 
     First, a roll-formed component manufactured according to the present disclosure and a workpiece as a raw material before being formed into the roll-formed component will be specifically described with reference to  FIGS.  1  to  3   , and  FIGS.  4 A to  4 E . 
     In the present embodiment, a frame used in an aircraft fuselage in its cross-sectional direction (lateral direction) of various frame components used for manufacturing the aircraft fuselage is exemplified as a roll-formed component, for example. As illustrated in  FIG.  1 ,  2  or  3   , roll-formed components  20 A to  20 C (frames) each have a generally curved shape, and have a portion with curvature continuously changing in its longitudinal direction (a longitudinal direction of each of the roll-formed components  20 A to  20 C, or an axial direction of a material). 
     Specifically, the roll-formed component  20 A illustrated in the upper diagram of  FIG.  1    is provided in its both longitudinal end portions with constant-curvature portions  20   a  and  20   c  each curved with constant curvature. Between the constant-curvature portions  20   a  and  20   c , there is provided a curvature-changing portion  20   b  that is curved such that its curvature continuously changes in its longitudinal direction from the constant curvature in the constant-curvature portion  20   a.    
     The lower diagram of  FIG.  1    is a graph illustrating change of a curvature radius corresponding to a position in the longitudinal direction of the roll-formed component  20 A illustrated in the upper diagram of  FIG.  1   . The horizontal axis of this graph represents a distance from one end of the roll-formed component  20 A, i.e., a longitudinal position of the roll-formed component  20 A, and the vertical axis represents curvature radius at the position. In addition, each portion constituting the roll-formed component  20 A illustrated in the upper diagram of  FIG.  1    and a position (distance) on the horizontal axis in the graph illustrated in the lower diagram of  FIG.  1    are associated with each other by a dotted line (the same applies to  FIGS.  2  and  3    described below). The roll-formed component  20 A illustrated in the upper diagram of  FIG.  1    is configured such that the curvature radius in the curvature-changing portion  20   b  gradually decreases from the curvature radius of the constant-curvature portion  20   a  to connect to the constant-curvature portion  20   c  as illustrated in the lower diagram of  FIG.  1    by a graph with a dashed line. 
     The roll-formed component  20 B illustrated in the upper diagram of  FIG.  2    is provided in its both longitudinal end portions with constant-curvature portions  20   d  and  20   f . Between the constant-curvature portions  20   d  and  20   f , there is provided a curvature-changing portion  20   e  that is curved such that its curvature continuously changes in its longitudinal direction from the constant curvature in the constant-curvature portion  20   d . The roll-formed component  20 B illustrated in the upper diagram of  FIG.  2    is configured such that the curvature radius in the curvature-changing portion  20   e  gradually increases from the curvature radius of the constant-curvature portion  20   d  to connect to the constant-curvature portion  20   f  as illustrated in a graph of the lower diagram of  FIG.  2   . 
     In addition, the roll-formed component  20 C illustrated in the upper diagram of  FIG.  3    is provided in its both longitudinal end portions with constant-curvature portions  20   g  and  20   k . A portion between the constant-curvature portions  20   g  and  20   k  is composed of a curvature-changing portion  20   h , a constant-curvature portion  20   i , and a curvature-changing portion  20   j . For convenience of description, the curvature-changing portion  20   h  is referred to as a first curvature-changing portion  20   h , and the curvature-changing portion  20   j  is referred to as a second curvature-changing portion  20   j.    
     The roll-formed component  20 C illustrated in the upper diagram of  FIG.  3    is curved such that curvature radius of the first curvature-changing portion  20   h  continuously changes in its longitudinal direction from constant curvature in the constant-curvature portion  20   g , and the second curvature-changing portion  20   j  is curved such that curvature thereof continuously changes in its longitudinal direction from constant curvature in the constant-curvature portion  20   i , as illustrated in a graph of the lower diagram of  FIG.  3   . Thus, as viewed from the constant-curvature portion  20   g  constituting one end portion of the roll-formed component  20 C, the roll-formed component  20 C is formed by connecting the constant-curvature portion  20   g , the first curvature-changing portion  20   h , the constant-curvature portion  20   i , the second curvature-changing portion  20   j , and the constant-curvature portion  20   k , in this order. 
     The curvature-changing portion  20   b  of the roll-formed component  20 A illustrated in  FIG.  1    and the curvature-changing portion  20   e  of the roll-formed component  20 B illustrated in  FIG.  2    have respectively curvature change gradually increasing along a longitudinal direction of the curvature-changing portion  20   b  and curvature change gradually decreasing along a longitudinal direction of the curvature-changing portion  20   e  (refer to the lower diagram of  FIG.  1    and the lower diagram of  FIG.  2   ). In contrast, as illustrated in graph of the lower diagram of  FIG.  3   , the first curvature-changing portion  20   h  in the roll-formed component  20 C illustrated in  FIG.  3    has a curvature radius that changes so as to once decrease along its longitudinal direction and then increase after reaching the minimum, and the second curvature-changing portion  20   j  has a curvature radius that changes so as to once increase along its longitudinal direction and then decrease after reaching the maximum. 
     The change in the curvature radius in each of the curvature-changing portions  20   b ,  20   e ,  20   h , and  20   j  is not limited to the corresponding one of the examples illustrated in  FIGS.  1  to  3    described above. Likewise, a specific configuration of each of the constant-curvature portions  20   a ,  20   c ,  20   d ,  20   f ,  20   g ,  20   i , and  20   k  is also not particularly limited. While any of the examples illustrated in  FIGS.  1  to  3    is formed in a curved (curved) shape having a constant curvature, a curvature radius may be infinite, i.e., linear, for example. In this case, the “constant-curvature portion” may be referred to as a “straight portion”. 
     The position in the longitudinal direction of each of the roll-formed components  20 A to  20 C is referred to as a “component position”, for convenience. As described below, the component position can be defined as an absolute position in the longitudinal direction (a length or a distance from one end) with respect to one end of each of the roll-formed components  20 A to  20 C (e.g., 0 mm). 
     When the roll-formed components  20 A to  20 C are collectively referred to as a roll-formed component  20 , the cross-sectional shape of the roll-formed component  20  is not particularly limited, and may be a predetermined shape. Examples of a cross-sectional shape using a feature of roll forming include a shape in which both edges in a cross-sectional direction are bent in directions different from each other, i.e., a shape of “Z” in the alphabet (Z type), as illustrated in  FIG.  4 A , for example. 
     Alternatively, examples of the cross-sectional shape of the roll-formed component  20  may include the following: a shape in which one edge portion in a cross-sectional direction is bent, i.e., a shape of “L” in the alphabet (L type) as illustrated in  FIG.  4 B ; a shape in which both edges in a cross-sectional direction is bent in the same direction, i.e., a shape of “C” in the alphabet (C type) as illustrated in  FIG.  4 C ; a shape obtained by combining C types in directions opposite to each other (a shape in which both edges in a cross sectional direction are bent in directions opposite to each other and a central portion in the cross sectional direction is bent so as to face both edges), i.e., a shape of “S” in the alphabet (S type) as illustrated in  FIG.  4 D ; and a shape obtained by protruding (or depressing) a central portion with respect to both edge portions in a cross sectional direction, i.e., a hat type (or a S2 type) as illustrated in  FIG.  4 E . 
     In other words, examples of a cross-sectional shape using a feature of roll forming include a shape (Z type, L type, C type or the like) in which at least one edge portion in a cross sectional direction is bent, or a shape bent at a central portion in the cross sectional direction (e.g., a hat type), or a combination thereof (S type or the like). As a matter of course, it is needless to say that the cross-sectional shape of the roll-formed component  20  may be other than the shapes illustrated in  FIGS.  4 A to  4 E . 
     Further, while only one edge portion (upper side in the drawing) of both edge portions in the cross-sectional direction is bent inward further in the Z type cross-sectional shape illustrated in  FIG.  4 A , a cross-sectional shape of the Z type roll-formed component  20  is not limited thereto. For example, only the other edge portion may be further bent, or the outer edges of respective both edge portions may be bent. Likewise, a further bent portion may or may not be formed in the edge portion of the L type illustrated in  FIG.  4 B , the C type illustrated in  FIG.  4 C , or the S type illustrated in  FIG.  4 D . 
     In addition, when the cross-sectional shape of each of the roll-formed components  20 A to  20 C illustrated in  FIGS.  1  to  3    is a Z type, for example, any portion in the longitudinal direction may have a cross-sectional shape of the same Z type (refer to  FIG.  4 A ), for example. However, the roll-formed component  20  manufactured according to the present disclosure is not limited to this, and may have a different sectional shape (having a flexible cross-sectional shape) for each portion in the longitudinal direction. For convenience of description, the former is referred to as a “uniform cross-section molded component”, and the latter is referred to as a “flexible cross-section molded component”. 
     In addition, a material of the roll-formed component  20  is also not particularly limited. When the roll-formed component  20  is an aircraft component such as a frame, examples of the material of roll-formed component  20  include aluminum and an alloy thereof (aluminum-based material). When it is a component used in other fields, the examples thereof include an iron-based material such as steel or the like (iron or an alloy containing iron). 
     When the roll-formed component  20  has a flexible cross-sectional shape, cross-sectional rigidity may be different depending on a cross-sectional shape. In addition, when the same curvature is formed in the roll-formed component  20  in the same shape using the same roll bending apparatus, a different material causes a difference in section rigidity even in the same shape and curvature. Examples of a difference in the material include a difference in a metal material serving as a main component, such as a difference between an aluminum-based material and an iron-based material, for example. In addition, even a plurality of alloy materials each classified as an aluminum-based material may cause different sectional rigidity depending on a kind of alloy or the like. As described above, the roll-formed component  20  manufactured according to the present disclosure has different cross-sectional rigidity, such as caused by a different cross-sectional shape from the middle in the longitudinal direction of the roll-formed component  20 , or a different material used from the middle therein. 
     When the roll-formed component  20  is a component for an aircraft, a specific example of the roll-formed component  20  is not limited to the frame, and examples thereof include a stringer, a stiffener, a spar, a floor beam, a rib, a frame, and the like. While these components are each a frame component of the aircraft, the roll-formed component  20  is not limited to such a frame component, and may be another aircraft component. In addition, the roll-formed component  20  manufactured according to the present disclosure is not limited to an aircraft component, and can also be suitably used for a component having curvature used in another field such as the automobile field or the building material field. 
     In the present disclosure, the roll-formed component  20  may be manufactured by forming curvature (providing curvature) to an elongated extrusion (long extrusion) material in which a predetermined cross-sectional shape is previously formed, or a flat elongated sheet (long sheet) before a predetermined cross-sectional shape is formed may be subjected to a step of forming a predetermined cross-sectional shape followed by continuously a step of forming curvature, for example. In the present disclosure, when the “roll-formed component  20 ” as illustrated in  FIGS.  1  to  3    is defined as a “component (or member) provided with curvature”, a “component (or member) before curvature is formed)” is referred to as a “workpiece”, for convenience. 
     When other known processing is performed on the roll-formed component  20  in addition to forming of a cross-sectional shape and forming of curvature, the “workpiece” includes not only a sheet material (or raw material) that is not subjected to any processing, but also a sheet material that is already subjected to processing other than curvature-forming processing. Forming of a cross-sectional shape or another processing other than this may be performed by a known method. In particular, the forming of a cross-sectional shape can be performed by known roll forming along with the forming of curvature in the present disclosure. 
     [Apparatus for Manufacturing Roll-Formed Component] 
     Next, an apparatus for manufacturing a roll-formed component according to the present embodiment will be described in detail with reference to  FIGS.  5 A and  5 B . 
     As illustrated in  FIG.  5 A , a roll-formed component manufacturing apparatus  10 A (hereinafter simply referred to as a “manufacturing apparatus  10 A”) according to the present embodiment includes a fulcrum roll  11 , a bending roll  12 , a feeding roll  13 , a control unit  30 , a curvature-radius database  31 , a roll moving unit  32 , and the like. The manufacturing apparatus  10 A includes at least the fulcrum roll  11  and the bending roll  12 , and manufactures the roll-formed component  20  described above by applying roll bending to an elongated extrusion material  21 , for example, being a workpiece along its longitudinal direction. In the manufacturing apparatus  10 A, a path through which the elongated extrusion material  21  is fed (conveyed) and subjected to roll bending is referred to as a bending path. 
     The fulcrum roll  11  is positioned upstream of the bending roll  12  in the bending path, and supports the elongated extrusion material  21  during bending or serves as a fulcrum of bending of the elongated extrusion material  21 . The bending roll  12  is positioned downstream of the fulcrum roll  11  in the bending path, and is configured to be movable with respect to a position of the fulcrum roll  11 . Moving the bending roll  12  enables bending to be applied to the elongated extrusion material  21  at a position of the fulcrum roll  11 . 
     The feeding roll  13  is positioned upstream of the fulcrum roll  11  in the bending path, and feeds out (conveys) the elongated extrusion material  21  toward the fulcrum roll  11 . Thus, in the manufacturing apparatus  10 A, the feeding roll  13 , the fulcrum roll  11 , and the bending roll  12  are positioned in this order from upstream of the bending path. The bending path between the fulcrum roll  11  and the bending roll  12  is referred to as an “inter-roll path”, for convenience of description. 
     A specific configuration of each of the fulcrum roll  11 , the bending roll  12 , and the feeding roll  13  is not particularly limited, and various forming rolls known in the field of a roll bending apparatus can be used. For example, while any one of the fulcrum roll  11 , the bending roll  12 , and the feeding roll  13  is a single roll in the configuration illustrated in  FIG.  5 A , at least one of the rolls may be a pair of rolls composed of two rolls facing each other as illustrated in a modified example described below. 
     The control unit  30  controls operation of the manufacturing apparatus  10 A. In particular, operation of the roll moving unit  32  is controlled with reference to the curvature-radius database  31  in the present embodiment, as described below. The curvature-radius database  31  stores a design value of a curvature radius (or curvature) and the like as a database to apply a desired curvature radius (or curvature) to the elongated extrusion material  21  being a workpiece. The roll moving unit  32  moves at least one of the fulcrum roll  11  and the bending roll  12  so as to relatively change a position of the bending roll  12  with reference to a position of the fulcrum roll  11 . 
     In the present embodiment, the fulcrum roll  11  is fixed in position, and only the bending roll  12  is configured to be moved by the roll moving unit  32 . The bending roll  12  is configured to be moved by stroke movement in a direction (e.g., a vertical direction) intersecting a bending path (a feeding (conveying) direction or a feeding-out direction of a workpiece). 
     The movement of the bending roll  12  is not limited to one-dimensional movement such as the stroke movement, and may be two-dimensional movement. Even when the fulcrum roll  11  is movable, its movement may be stroke movement or two-dimensional movement, like the movement of the bending roll  12 . In addition, when the bending roll  12  is a pair of rolls composed of two rolls facing each other as in a modification described below, it is preferable that this pair of rolls includes a rotating shaft for rotating the pair of rolls itself so as to always be a direction (e.g., a substantially vertical direction) intersecting the bending path (workpiece) even with a stroke. 
     In  FIG.  5 A , a position at which the fulcrum roll  11  is brought into contact with the elongated extrusion material  21  (workpiece) is defined as a fulcrum roll contact position  11   a , for convenience. Likewise, a position at which the bending roll  12  is brought into contact with the elongated extrusion material  21  is defined as a bending roll contact position  12   a , for convenience. Each of the fulcrum roll contact position  11   a  and the bending roll contact position  12   a  is illustrated in  FIG.  5 A  as a region surrounded by a short broken line. 
     A specific configuration of each of the control unit  30 , the curvature-radius database  31 , and the roll moving unit  32  is not particularly limited, and a control configuration or a moving mechanism well-known in the field of a roll bending apparatus can be suitably used. For example, the control unit  30  may be composed of a microcomputer, or a CPU of a microcontroller. The curvature-radius database  31  may be configured as a storage unit that can be read out by a microcomputer or a microcontroller. The storage unit may be built in the manufacturing apparatus  10 A or may be externally connected. 
     The roll moving unit  32  may be a known actuator or the like capable of changing a position of the forming roll, or may be configured to be capable of moving the roll  12  along a known linear guide or the like. For example, a direction in which bending is applied to the elongated extrusion material  21  by the bending roll  12  is defined as a first direction. At this time, the roll moving unit  32  can move the bending roll  12  in X-X direction by providing a linear guide or the like along X-X direction being the first direction as illustrated in  FIG.  5 B . 
     When the bending roll  12  is in contact with the elongated extrusion material  21  during forming, a substantially normal direction at the contact portion, i.e., a substantially normal direction at the roll contact position  12   a  is defined as a second direction. At this time, the roll moving unit  32  can move the bending roll  12  in not only X-X direction but also Y-Y direction by providing a linear guide or the like along Y-Y direction being the second direction as illustrated in  FIG.  5 B . 
     In addition, when a distance between the fulcrum roll contact position  11   a  and the bending roll contact position  12   a  is changed, setting of an unit interval or calculation of a curvature radius may be complicated to divide the roll-formed component  20  into a plurality of unit intervals in its longitudinal direction, or to calculate the curvature radius to be applied to the elongated extrusion material  21 , for example, as described below. Thus, to adjust a distance between the fulcrum roll contact position  11   a  and the bending roll contact position  12   a , the roll moving unit  32  may be configured so as to move the bending roll  12  in its rotation direction. 
     For example, when the roll moving unit  32  is configured to be capable of moving the bending roll  12  in X-X direction being the first direction and Y-Y direction being the second direction, the roll moving unit  32  may be configured to be capable of further moving the bending roll  12  in Z-Z direction, as illustrated in  FIG.  5 B . This Z-Z direction may be a direction (rotation direction) in which the bending roll  12  is rotated to move its position (this rotation direction is not a direction of rotation of the bending roll  12 ). 
       FIG.  5 A  illustrates the roll moving unit  32  as a functional block.  FIG.  5 A  also illustrates the block of the roll moving unit  32  and the bending roll  12  while they are connected by a solid line segment. This schematically shows that the roll moving unit  32  is configured to be capable of moving the bending roll  12 . In addition,  FIG.  5 A  illustrates the block of the control unit  30  and a block of each of the curvature-radius database  31  and the roll moving unit  32  while they are connected by dotted line segments. This schematically shows that the control unit  30  reads out data from the curvature-radius database  31 , and controls the roll moving unit  32 . 
     In the present embodiment, the curvature-radius database  31  stores at least three kinds of curvature radius data on the design curvature radius, the initial curvature radius, and the intermediate curvature radius, based on a component position (a position of the roll-formed component  20  in its longitudinal direction). The curvature-radius database  31  may also store another data on a curvature radius. These curvature radii are each set to a portion corresponding to a predetermined component position of the roll-formed component  20 . 
     First, the design curvature radius will be described. For example, it is assumed that the roll-formed component  20  is divided into a plurality of unit intervals D in its longitudinal direction as illustrated in  FIG.  6 A . In  FIG.  6 A , one end of the roll-formed component  20  on its downstream side in a feeding direction (indicated by a block arrow in  FIG.  6 A ) is defined as a “reference end  20   p ”. The reference end  20   p  is 0 mm as a component position. The unit interval D is set as a constant distance between the corresponding component positions at d1 mm, d2 mm, d3 mm, d4 mm, d5 mm, . . . . The design curvature radius is a design value of curvature radius of a unit portion  20   q  corresponding to each unit interval D in the roll-formed component  20 . 
     The “unit portion  20   q ” means a portion (part) corresponding to each unit interval in the roll-formed component  20 . While setting of the unit portion  20   q  is not particularly limited, a component position on an upstream side in the feeding direction (an opposite side to the reference end  20   p , or the other end side) of component positions at respective opposite ends of the unit interval D is set as the unit portion  20   q  of the unit interval D in the example illustrated in  FIG.  6 A . Specifically, in the first unit interval D from the reference end  20   p , a portion corresponding to a component position at d1 mm corresponds to the unit portion  20   q  of the unit interval, as illustrated in  FIG.  6 A . In the second unit interval D from the reference end  20   p , a portion corresponding to a component position at d2 mm corresponds to the unit portion  20   q  of the unit interval D. The design curvature radius of each unit interval D is set for the corresponding one of the unit portions  20   q.    
     While the roll-formed component  20  is a member (a formed member, or a formed product) subjected to bending by the manufacturing apparatus  10 A, the unit interval D can be set to not only the roll-formed component  20 , but also the elongated extrusion material  21  that is a “workpiece (or raw material)” before the bending is applied, as illustrated in  FIG.  6 A . Thus, the reference end  21   p  is defined also in the elongated extrusion material  21 , as with the roll-formed component  20 . An absolute position from the reference end  21   p  is a component position, a portion  21   q  corresponding to an appropriate component position is defined as a unit portion  21   q , and a unit interval D is set as a constant distance between the corresponding component positions. 
     Thus, in the description below, terms (definitions) of the “component position”, the “unit interval D”, and the “unit portion  20   q ” are applied to not only the roll-formed component  20  that is a formed member, but also the elongated extrusion material  21  in the middle of bending with the manufacturing apparatus  10 A. 
     Here, a predetermined distance (interval) is formed between the fulcrum roll  11  and the bending roll  12  as illustrated in  FIG.  5 A . The elongated extrusion material  21  during the bending is fed in the inter-roll path between the fulcrum roll  11  and the bending roll  12 . To apply a predetermined curvature radius to an appropriate component position  20   q , it is necessary to define not only an absolute position (component position  20   q ) of the elongated extrusion material  21  (roll-formed component  20 ) in its longitudinal direction, but also a relative position between the fulcrum roll  11  and the bending roll  12 . 
     When a distance between the fulcrum roll contact position  11   a  and the bending roll contact position  12   a  (i.e., the length of the inter-roll path) is abbreviated as a “roll interval” for convenience of description, an ideal contact point at which the fulcrum roll  11  is in contact with the elongated extrusion material  21 , in the fulcrum roll contact position  11   a , can be defined as a “start position Rs” (a black block arrow Rs) of the roll interval as illustrated in  FIG.  6 B . In addition, an ideal contact point at which the bending roll  12  is in contact with the elongated extrusion material  21 , in the bending roll contact position  12   a , can be defined as an “end position Rt” (a black block arrow Rt) of the roll interval. 
     A distance (roll interval) from the start position Rs to the end position Rt is divided into a plurality of intervals (lower intervals) each of which is the same as the unit interval D. The number of divisions of the roll interval (the number of lower intervals) is not particularly limited, and the roll interval is divided into four lower intervals in the example illustrated in  FIG.  6 B . Specifically, the start position Rs is set as a “relative position n 0 ” and the end position Rt is set as a “relative position n 4 ”, and “relative positions n 1  to n 3 ” at equal intervals are set between them. An interval (lower interval) between the corresponding adjacent relative positions n 0  to n 4  may be the same as the unit interval D of the elongated extrusion material  21  (roll-formed component  20 ). 
     In other words, the inter-roll path between the fulcrum roll  11  and the bending roll  12  is divided at equal intervals of an integer to set the plurality of relative positions, for example, on the basis of a specific configuration of the manufacturing apparatus  10 A, and the unit interval D of each of the roll-formed component  20  and the elongated extrusion material  21  can be set to be identical to the interval between the adjacent relative positions. While the reference sign of “ 20   q ” is attached in  FIG.  6 A  for convenience of description of the “unit portion”, the unit portion of the elongated extrusion material  21  is not illustrated in  FIGS.  6 B and  7    and the like referred to in the description below, for convenience of illustrating the relative positions n 0  to n 4 . In the description with reference to  FIG.  7    and the like, the “unit portion” is not designated by the reference sign “ 20   q”.    
     Here, the relative positions n 0  to n 4  are set with respect to the ideal contact point at which the fulcrum roll  11  and the bending roll  12  are brought into contact with the elongated extrusion material  21 . However, in the actual bending, the fulcrum roll  11  and the bending roll  12  are required to be brought into contact with the elongated extrusion material  21  in a “line” or a predetermined “section” (or a part of the section) instead of at a “point”. Thus, as illustrated in  FIG.  6 B , the division of the roll interval can also be set as each of “relative sections z 0  to z 4 ” (corresponding to the lower intervals), surrounded by dotted lines in  FIG.  6 B , instead of each of the relative positions n 0  to n 4 , being an ideal “point”. 
     The relative section z 0  is set as a section having the center point of the start position Rs of the roll interval, and a distance of this section may be the same as the unit interval D of the elongated extrusion material  21  (roll-formed component  20 ). Likewise, in the example illustrated in  FIG.  6 B , the relative sections z 1  to z 4  having the relative positions n 1  to n 4  as the center points, respectively, can be set (thus, the relative section z 4  is set as a section having the end position Rt of the roll interval as its center point). The relative sections z 1  to z 4  each may have the same distance as the unit interval D, as with the relative section z 0 . 
     Next, the initial curvature radius will be described. The initial curvature radius is a value of a curvature radius to be applied to a workpiece such as the elongated extrusion material  21  at the fulcrum roll contact position  11   a . Specifically, the initial curvature radius is preliminarily calculated to be a desired curvature radius (i.e., the same value of the design curvature radius) after the elongated extrusion material  21  passes through the bending roll contact position  12   a , i.e., after being spring-backed or after bending moment is released. The initial curvature radius is set as a value of a curvature radius to be applied to a workpiece before spring back is caused by bending applied to the workpiece or before strain is reduced. 
     In addition, a curvature radius remaining in the workpiece when the workpiece such as the elongated extrusion material  21  or the like is fed out from the bending roll contact position  12   a  is defined as a final curvature radius. As described above, a specific design curvature radius is preset in each unit portion in the roll-formed component  20 , so that a specific value of a design curvature radius is achieved in each unit portion in the roll-formed component  20  actually manufactured. Thus, the design curvature radius ideally may be substantially the same as the final curvature radius, or the final curvature radius may be approximate to the design curvature radius within a range of accuracy of the curvature radius required for the roll-formed component  20 . 
     When the workpiece such as the elongated extrusion material  21  is fed out from the fulcrum roll  11 , the curvature radius of the elongated extrusion material  21  smoothly changes in the section from the fulcrum roll contact position  11   a  to the bending roll contact position  12   a . Specifically, the curvature radius applied to the elongated extrusion material  21  smoothly changes from the initial curvature radius at the time when the elongated extrusion material  21  passes through the fulcrum roll  11  to the final curvature radius at the time when it passes through the bending roll  12 , as described later, in the same unit portion of the roll-formed component  20 . Thus, in consideration of this smooth change in the curvature radius, an individual value of the design curvature radius is set in each unit portion. 
     Specific values of the design curvature radius are set in all unit portions of the roll-formed component  20 , so that specific values of the initial curvature radius corresponding to the specific values of the design curvature radius are also set. A set of these specific values of the curvature radius is prepared in the curvature-radius database  31 . 
     Next, the intermediate curvature radius will be described. As described above, bending is applied to the elongated extrusion material  21  at the fulcrum roll contact position  11   a  by movement of the bending roll  12 . However, a predetermined distance (roll interval) is formed between the fulcrum roll  11  and the bending roll  12  as described above, and the elongated extrusion material  21  is fed from the fulcrum roll contact position  11   a  to the bending roll contact position  12   a . Thus, in the inter-roll path of the bending path, a stress is also applied from the bending roll  12  to a portion to which bending is applied at the fulcrum roll contact position  11   a.    
     As described above, the fulcrum roll  11  and the bending roll  12  are positioned at a predetermined roll interval. Thus, as described below, an arbitrary portion of the elongated extrusion material  21  to which bending is applied by the fulcrum roll  11  gradually changes in strain or bending moment acting, while the elongated extrusion material  21  is fed along the inter-roll path to travel toward the bending roll contact position  12   a . This requires the “intermediate curvature radius” in consideration of change in strain or bending moment to be set for the unit portion positioned in the inter-roll path. 
     The intermediate curvature radius may be set such that a curvature radius continuously changes from the initial curvature radius to the design curvature radius in each of the unit portions, from the fulcrum roll contact position  11   a  to the bending roll contact position  12   a . While a specific method of setting the intermediate curvature radius is not particularly limited, the intermediate curvature radius can be set from a value of the initial curvature radius applied to an arbitrary unit portion when it is at the fulcrum roll contact position  11   a , and strain or bending moment that changes until the unit portion reaches the bending roll contact position  12   a , in the present embodiment. 
     Typically, strain or bending moment in a unit portion of the elongated extrusion material  21  decreases gradually (temporarily) toward a unit portion closer to the bending roll contact position  12   a . Thus, the intermediate curvature radius may be set on the basis of the initial curvature radius applied at the fulcrum roll contact position  11   a  and a degree of reduction in strain or bending moment. 
     The control unit  30  integrates the amount of change in bending position of each unit portion from the fulcrum roll contact position  11   a  to the bending roll contact position  12   a  when a workpiece such as the elongated extrusion material  21  is fed out from the fulcrum roll  11 , with reference to the curvature-radius database  31 , to calculate “the amount of roll movement” as the amount of movement of the bending roll  12 . The amount of change will be described below. The control unit  30  causes the roll moving unit  32  to move at least one of the fulcrum roll  11  and the bending roll  12  on the basis of this integrated quantity (the amount of roll movement). In the configuration illustrated in  FIG.  5 A , only the bending roll  12  is moved on the basis of the integrated quantity. This enables the roll-formed component  20  obtained to be provided at a desired position in its longitudinal direction with a portion where curvature changes continuously. 
     [Example of Control of Roll Moving Unit with Control Unit] 
     Next, with reference to  FIGS.  7  and  8   , there is specifically described a configuration formed by the manufacturing apparatus  10 A according to the present embodiment, in which the control unit  30  causes the roll moving unit  32  to change a relative position of the bending roll  12  with respect to the fulcrum roll  11  to form the curvature-changing portion  20   b  (refer to  FIG.  1   ), the curvature-changing portion  20   e  (refer to  FIG.  2   ), the first curvature-changing portion  20   h , or the second curvature-changing portion  20   j  (refer to  FIG.  3   ) in the roll-formed component  20  obtained. 
     For example, it is assumed that the elongated extrusion material  21  being a workpiece is fed out from the fulcrum roll  11  toward the bending roll  12  (toward the feeding direction indicated by the block arrow F) as illustrated in  FIG.  7    (the same as the state illustrated in  FIG.  5 A ). At this time, the relative positions n 0  to n 4  are set between the fulcrum roll contact position  11   a  and the bending roll contact position  12   a  so that the roll intervals are equally divided as described above. A distance between the corresponding adjacent relative positions n 0  to n 4  is the same distance (interval) as the unit interval D as described above. Instead of the relative positions n 0  to n 4 , the relative sections z 0  to z 4  may be set (refer to  FIG.  6 B ). 
     As described above, a plurality of unit intervals D is each set for the elongated extrusion material  21  so as to be the same distance as the distance between the corresponding adjacent relative positions n 0  to n 4  set by equally dividing the roll interval (refer to  FIG.  6 A ). As described above, a setting curvature radius, the initial curvature radius, and the intermediate curvature radius are set in the corresponding unit portions (refer to  FIG.  6 A ) each corresponding to the unit interval D. 
     In the example illustrated in  FIG.  7   , the roll interval is divided into four portions in a schematic manner with the same interval as the unit interval D. Thus, a total of five relative positions including the fulcrum roll contact position  11   a  and the bending roll contact position  12   a  are schematically set in this roll interval. In  FIG.  7   , when the fulcrum roll contact position  11   a  is set as the relative position n 0 , the relative position n 1 , the relative position n 2 , the relative position n 3 , and the relative position n 4  are set for each unit interval D toward a downstream side of the bending path, in the roll interval. The relative position n 4  corresponds to the bending roll contact position  12   a.    
     For the roll-formed component  20 , the design curvature radius is set in the unit portion for each unit interval D. While a specific numerical value of the unit interval D is not particularly limited, one unit interval D is set to 10 mm, for example, in the present embodiment. In the lower diagram of  FIG.  7   , an example of data such as a design curvature radius, an initial curvature radius, and an intermediate curvature radius, stored as the curvature-radius database  31  is shown as a table T 0 . 
     As illustrated in  FIG.  7   , at an arbitrary point in time when the elongated extrusion material  21  is fed to the inter-roll path, an arbitrary unit portion is positioned at the fulcrum roll contact position  11   a , and another unit portion positioned downstream in the feeding direction F is positioned at the bending roll contact position  12   a . In addition, a plurality of unit portions (three unit portions in  FIG.  7   ) is positioned between the fulcrum roll contact position  11   a  and the bending roll contact position  12   a  (inter-roll path). 
     Then, for the convenience of description, a unit portion positioned at the fulcrum roll contact position  11   a  is defined as a “fulcrum roll unit portion”, and a unit portion positioned at the bending roll contact position  12   a  is defined as a “bending roll unit portion”. In addition, unit portions each corresponding to a unit interval, positioned between the fulcrum roll unit portion and the bending roll unit portion, are referred to as an “intermediate unit portion”. In the example illustrated in  FIG.  7   , the unit portion positioned at the relative position n 0  is the “fulcrum roll unit portion”, the unit portion positioned at the relative position n 4  is the “bending roll unit portion”, and the unit portions positioned at the respective relative position n 1  to n 3  are each the “intermediate unit portion”. 
     As described above, the roll interval is divided into a plurality of intervals each having the same length as the unit interval D. Thus, the intermediate unit portion positioned at the relative position n 1  corresponds to the first unit interval D as viewed from the relative position n 0 , the intermediate unit portion positioned at the relative position n 2  corresponds to the second unit interval D as viewed from the relative position n 0 , and the intermediate unit portion positioned at the relative position n 3  corresponds to the third unit interval D as viewed from the relative position n 0 . 
     In the course of being fed to the inter-roll path, arbitrary unit portions of the elongated extrusion material  21  become the fulcrum roll unit portion, the plurality of intermediate unit portions, and the bending roll unit portion. In other words, it can be considered that the same unit portion sequentially is moved to the fulcrum roll unit portion, the intermediate unit portion, and the bending roll unit portion during conveyance (feed) of the elongated extrusion material  21 . When an arbitrary unit portion is the fulcrum roll unit portion, an initial curvature radius having a value corresponding to the component position of the unit portion is applied, and when the unit portion is the bending roll unit portion, the design curvature radius having a value corresponding to the component of the unit portion is applied. 
     In addition, when an arbitrary unit portion is the intermediate unit portion, its curvature radius is an intermediate curvature radius having a value continuously changing from the value of the initial curvature radius when the arbitrary unit portion is the fulcrum roll unit portion to the value of the design curvature radius when the arbitrary unit portion is bending roll unit portion. In Table T 0  exemplified in  FIG.  7   , the initial curvature radius, the design curvature radius, and the intermediate curvature radius at an arbitrary unit portion (component position) of the elongated extrusion material  21  (roll-formed component  20 ) are summarized. 
     Specifically, Table T 0  exemplifies a total of six component positions for every 10 mm from the component position of 1000 mm (1000 mm, 1010 mm, 1020 mm, 1030 mm, 1040 mm, and 1050 mm), so that a total of five unit intervals D 1  to D 5  are each exemplified as the unit interval D.  FIG.  7    illustrates the unit intervals D 5 , D 4 , D 3 , D 2 , and D 1  from the downstream side in the feeding direction F (a side with a smaller numerical value of the component position). 
     In the present embodiment, the unit portions corresponding to the unit intervals D 1  to D 5  are set to the component positions on the respective downstream sides of the corresponding unit intervals D 1  to D 5  as described above. For example, the unit interval D 1  in Table T 0  is between component positions of 1040 mm and 1050 mm, and the component position of the elongated extrusion material  21  corresponding to the unit interval D 1  is the unit portion of 1040 mm on the downstream side. 
     Table T 0 , in order from the left in  FIG.  7   , includes a column (“component” in  FIG.  7   ) of the component position (unit portion), a column (“RO” in in  FIG.  7   ) of the design curvature radius set for the component position, a column (“n 0 ” in  FIG.  7   ) of the initial curvature radius set for the component position, a column of the intermediate curvature radius set for the component position when the component position reaches each of the relative positions n 1  to n 3  (“n 1  to n 3 ” in  FIG.  7   ), and a column (“n 4 ” in  FIG.  7   ) of the curvature radius set for the component position when the component position reaches the relative position n 4 . 
     In the present embodiment, an intermediate curvature radius is set for each of the columns of the respective relative positions n 1  to n 3 . These intermediate curvature radiuses are each an estimated value that is estimated by the initial curvature radius applied when an arbitrary unit portion reaching these relative positions is the fulcrum roll unit portion, and strain or bending moment that changes until the arbitrary unit is moved to the bending roll unit portion from the fulcrum roll unit portion. 
     Curvature radii set to the relative position n 4  are the same values as the respective design curvature radii (refer to numerical values in the column of RO and the column of n 4 ). The relative position n 4  corresponds to an arbitrary unit portion that is a bending roll unit portion. Thus, when an arbitrary unit portion is a bending roll unit portion (when it reaches the relative position n 4 ), a design curvature radius of a value corresponding to a component position of the arbitrary unit portion is applied. 
     Here, the relative position n 4  is the bending roll contact position  12   a  as well as the end position Rt of the roll interval. This enables the curvature radius set for the component position reached the relative position n 4  to be referred to as an “end position curvature radius”. The end position curvature radius is the same value as the design curvature radius as described above. In addition, the relative position n 0  is the fulcrum roll contact position  11   a  as well as the start position Rs of the roll interval. Thus, the curvature radius set for the component position reached the relative position n 0  is the initial curvature radius as described above, and can be referred to as a “start position curvature radius”. In other words, it can be expressed that the same value as the initial curvature radius is set as the “start position curvature radius”. 
     For convenience of making it easier to understand that the intermediate curvature radius is set to continuously change from the initial curvature radius to the design curvature radius, Table T 0  shows the intermediate curvature radius such that it continuously changes by an equal amount of 10 mm. In practice, however, the curvature radius in the section from the relative position n 1  to the relative position n 4  also changes exponentially such that strain changes exponentially. Accordingly, the intermediate curvature radius to be set may also be set as a value that exponentially changes. 
     The unit portion at a component position of 1010 mm will be described, for example, as an example of the design curvature radius, the initial curvature radius, the intermediate curvature radius, and the ending position curvature radius, at an arbitrary unit portion. As shown in Table T 0 , the design curvature radius is set to 2000 mm in the unit portion of the component position of 1010 mm. When this unit portion reaches the fulcrum roll contact position  11   a  (when it is moved to the fulcrum roll unit portion or reaches the relative position n 0 ), the initial curvature radius to be applied to the elongated extrusion material  21  by the fulcrum roll  11  is set to 1960 mm. 
     After that, when this unit portion advances from the fulcrum roll contact position  11   a  to the downstream relative position n 1  (when it moves to a first intermediate unit portion), its intermediate curvature radius is set to 1970 mm. When this unit portion further advances to the relative position n 2  on the downstream side (when it moves to a second intermediate unit portion), its intermediate curvature radius is set to 1980 mm. When this unit portion further advances to the relative position n 3  on the downstream side (when it moves to a third intermediate unit portion), its intermediate curvature radius is set to 1990 mm. 
     When this unit portion further advances to the relative position n 4  on the downstream side, its end position curvature radius is set to 2000 mm that is the same value as the design curvature radius. The relative position n 4  is the final position of the inter-roll path (the end position Rt of the roll interval) as well as the bending roll contact position  12   a . Thus, the unit portion at the component position of 1010 mm has moved to the bending roll unit portion, and a design curvature radius corresponding to the component position is applied. 
     The number of intermediate unit portions in the inter-roll path is not particularly limited. In the example illustrated in  FIG.  7   , the roll interval is equally divided into four sections, and the five relative positions n 0  to n 4  are set. This causes the unit portions positioned at the respective relative positions n 1  to n 3  to be intermediate unit portions, so that three intermediate unit portions are set in  FIG.  7   . As described above, the number of relative positions (or relative sections) acquired by dividing the roll interval is not particularly limited, so that the number of intermediate unit portions is a number corresponding to the number of divisions of these relative positions. Thus, the number of intermediate unit portions may be one or more. 
     It is assumed that the same value as the design curvature radius (e.g., a curvature radius of 2000 mm at a component position of 1010 mm) is applied to the elongated extrusion material  21  at the fulcrum roll contact position  11   a , i.e., at the relative position n 0 . According to the studies of the inventors of the present invention, it becomes clear that when the elongated extrusion material  21  is fed out from the fulcrum roll contact position  11   a , the maximum strain is applied to the elongated extrusion material  21  at the relative position n 0 , and that at the time point when it reaches each of the relative positions n 1  to n 4  on the downstream side, strain at the same component position exponentially decreases and strain remaining when it passes through the relative position n 4  forms a final shape as a permanent deformation. This can be said to be the shape after so-called spring back. 
     More specifically, according to the studies by the inventors of the present invention, it becomes clear that even when a conventional apparatus for manufacturing a roll-formed component causes a relative change in position of the bending roll  12  with respect to the fulcrum roll  11  to be applied by the roll moving unit  32  so as to be simply proportional to the curvature at a predetermined position of a workpiece, to manufacture a roll-formed component  20  having curvature continuously changing, the roll-formed component  20  cannot obtain a desired curvature change and may be bend or have no bending. 
     In addition, according to the studies of the inventors of the present invention, it becomes clear that (1) when bending is applied by the bending roll  12 , a desired continuous change in curvature cannot be obtained unless the relative position of the bending roll  12  with respect to the fulcrum roll  11  is gradually changed as described below, and that (2) when bending is applied by the bending roll  12 , spring back occurs in a workpiece, and only changing a position of the bending roll  12  so as to correspond to application of the initial curvature radius, with respect to a unit portion positioned at the relative position n 0 , in consideration of influence of the spring back, cannot obtain a desired change in curvature. 
     This is because (1) the maximum bending strain is actually applied to the workpiece at the fulcrum roll contact position  11   a , and (2) between the fulcrum roll  11  and the bending roll  12 , the workpiece has already passed through the fulcrum roll  11  to become a bent state. Thus, only changing the relative position of the bending roll  12  with respect to the fulcrum roll  11  at a value proportional to a continuous change in curvature cannot obtain a desired continuous change in a roll-formed member finally obtained. 
     Thus, in the present disclosure, an initial curvature radius in consideration of reduction in strain, and spring back (or apparent bending degree due to application of bending moment) is applied at the fulcrum roll contact position  11   a , i.e., at the relative position n 0 , instead of the same value as the design curvature radius. For example, when a unit portion at a component position of 1010 mm in the elongated extrusion material  21  is defined as an “attention portion” for convenience, an initial curvature radius of 1960 mm with respect to a design curvature radius of 2000 mm is applied to the attention portion. 
     After that, when the elongated extrusion material  21  is fed out to cause the attention portion to reach the relative position n 1 , the curvature radius of the attention portion changes to the intermediate curvature radius having a value of 1970 mm at the relative position n 1 . Likewise, when the attention portion reaches the relative position n 2 , the curvature radius of the attention portion changes to the intermediate curvature radius having a value of 1980 mm at the relative position n 2 , when it reaches the relative position n 3 , the curvature radius of the attention portion changes to the intermediate curvature radius having a value of 1990 mm at the relative position n 3 , and when it reaches the relative position n 4 , i.e., the bending roll contact position  12   a , the curvature radius of the attention portion changes to the end position curvature radius having a value of 2000 mm at the relative position n 4 , i.e., a value that is the same as the design curvature radius in the attention portion (unit portion to be a component position of 1010 mm). Thus, the curvature radius at the bending roll contact position  12   a  is the final curvature radius, and in the example illustrated in  FIG.  7   , the final curvature radius coincides with the design curvature radius. 
     In the schematic state illustrated in  FIG.  7   , five unit portions ranging from a component position of 1010 mm to a component position of 1050 mm are positioned in the inter-roll path. In the five unit portions, the design curvature radius changes from 2000 mm to 1800 mm. In other words, a part of the roll-formed component  20  corresponding to the five unit portions corresponds to the curvature-changing portion  20   b , the curvature-changing portion  20   e , the first curvature-changing portion  20   h , or the second curvature-changing portion  20   j  (or a part of these portions), described above. Thus, bending is applied to each unit portion fed out to the fulcrum roll contact position  11   a  so that an initial curvature radius in consideration of strain reduction or spring back is applied to each unit portion. 
     In the schematic state illustrated in  FIG.  7   , it is assumed that the unit portion of 1050 mm at the component position in the elongated extrusion material  21  is fed to the fulcrum roll contact position  11   a , i.e., the relative position n 0 , the design curvature radius for the unit portion of 1050 mm is 1800 mm, and an initial curvature radius of 1760 mm is applied to the unit portion of 1050 mm. At this time, when the unit portion at the component position of 1040 mm to which bending is applied just before is defined as an attention portion, the attention portion is fed out the relative position n 0  to the relative position n 1 . The attention portion (the unit portion at the component position of 1040 mm) having reached the relative position n 1  has a curvature radius having changed from the applied initial curvature radius of 1810 mm to the intermediate curvature radius at the relative position n 1 , having a value of 1820 mm. 
     Likewise, a unit portion at a component position of 1030 mm to which the bending is applied prior to the unit portion at the component position of 1040 mm is fed out from the relative position n 0  to the relative position n 2 . When the unit portion at the component position of 1030 mm is defined as an attention portion, the attention portion having reached the relative position n 2  has a curvature radius that has changed from the applied initial curvature radius of 1860 mm to the intermediate curvature radius at the relative position n 2 , having a value of 1880 mm. 
     Likewise, a unit portion at a component position of 1020 mm to which the bending is applied prior to the unit portion at the component position of 1030 mm is fed out from the relative position n 0  to the relative position n 3 . When the unit portion at the component position of 1020 mm is defined as an attention portion, the attention portion having reached the relative position n 3  has a curvature radius that has changed from the applied initial curvature radius of 1910 mm to the intermediate curvature radius at the relative position n 3 , having a value of 1940 mm. 
     Likewise, a unit portion at a component position of 1010 mm to which the bending is applied prior to the unit portion at the component position of 1020 mm is fed out from the relative position n 0  to the relative position n 4 , i.e., the bending roll contact position  12   a . When the unit portion at the component position of 1010 mm is defined as an attention portion, the attention portion having reached the bending roll contact position  12   a  has a curvature radius that has changed from the applied initial curvature radius of 1960 mm to the end position curvature at the radius relative position n 4 , having a value of 2000 mm, i.e., the same value as the design curvature radius. Thus, as illustrated by the dotted line in  FIG.  7   , Table T 0  shows that the curvature radius of each unit portion at the same time is a numeric value along the diagonally upper right direction. 
     As described above, to achieve a predetermined design curvature radius at a predetermined component position, an initial curvature radius in consideration of reduction in strain or spring back (or apparent bending degree) at the fulcrum roll contact position  11   a  is applied at the component position. In addition, as described above, the unit interval of the elongated extrusion material  21  and the lower interval of the roll interval are set to the same length (distance). Thus, it is necessary that the control unit  30  causes the roll moving unit  32  to move the bending roll  12  (move at least one of the fulcrum roll  11  and the bending roll  12 ) such that when an arbitrary component position at the same time is positioned at the relative position n 0  to enable the initial curvature radius to be applied at the fulcrum roll contact position  11   a , component positions positioned (a reference end  21   p  side) ahead the component position are positioned at the respective relative positions n 1  to n 4 , i.e., a numeric value along the diagonally upper right direction in Table T 0  is achieved. 
     As illustrated in  FIG.  5 A  (and  FIG.  7   ), a predetermined initial curvature radius is applied to a unit portion of the elongated extrusion material  21  (workpiece), having reached the relative position n 0 , and to a unit portion having reached each of the relative positions n 1  to n 4 , it is necessary to apply a predetermined bending (a value of the intermediate curvature radius or the end position curvature radius at each of the relative positions). Then, the control unit  30  calculates the amount of change in position of the bending roll  12  by integrating the bending position of each of unit portions having reached the respective relative positions n 0  to n 4 , and controls the roll moving unit  32  on the basis of the integrated quantity, i.e., the amount of roll movement. 
     The amount of change in position of the bending roll  12  in the roll interval can be calculated on the basis of a specific value of an individual initial curvature radius set for a unit portion for each unit interval of the elongated extrusion material  21 . For example, based on a bending state of the elongated extrusion material  21  illustrated in  FIG.  7   ,  FIG.  8    represents a schematic state of the elongated extrusion material  21 , the fulcrum roll  11 , and the bending roll  12 . The state illustrated in each of  FIGS.  7  and  8    corresponds to a state at the time when arbitrary unit intervals D 1  to D 5  of the elongated extrusion material  21  (roll-formed component  20 ) coincide with the relative positions n 0  to n 4  of the inter-roll path, respectively. 
       FIG.  8    schematically illustrates not only the elongated extrusion material  21  with a thick line, but also each of the fulcrum roll  11  and the bending roll  12  with a block arrow, and sets a two-dimensional plane PL (indicated by a dotted line) in XY-direction, including a bending direction of the elongated extrusion material  21 . In  FIG.  8   , unit portions corresponding to the unit interval D 1  to D 4  are designated by reference signs  21 - 1  to  21 - 4 , respectively, for convenience of description. The unit portions  21 - 1  to  21 - 4  of the elongated extrusion material  21  each have a component position coinciding with the corresponding one of the relative positions n 1  to n 4 . 
     The unit interval D 1  of the elongated extrusion material  21  corresponds to the interval between the relative position n 0  and the relative position n 1 . As described above, a predetermined initial curvature radius shown in Table T 0  is applied to the unit portion  21 - 1  corresponding to the unit interval D 1 . At this time, as illustrated in  FIG.  8   , a distance from a start point A 0  of the unit interval D 1  corresponding to the relative position n 0  to an end point A 1  of the unit interval D 1  corresponding to the relative position n 1  can be calculated as a distance X 1  in X-direction and a distance Y 1  in Y-direction. 
     In the unit interval D 2  downstream of the unit interval D 1 , a value of an initial curvature radius corresponding to the relative position n 2  is applied to an end point A 2  corresponding to the relative position n 2 , i.e., the unit portion  21 - 2  corresponding to the unit interval D 2 . A start point A 1  of the unit interval D 2  is the end point of the unit interval D 1 , and corresponds to the relative position n 1  as described above. At this time, a distance between the start point A 1  of the unit interval D 2  and the end point A 2  of the unit interval D 2  can be calculated as a distance X 2  in X-direction and a distance Y 2  in Y-direction. 
     Likewise, a value of an initial curvature radius corresponding to the relative position n 3  is applied to an end point A 3 , i.e., the unit portion  21 - 3 , also in the unit interval D 3 . Thus, a distance from the start point A 2  to the end point A 3  of the unit interval D 3  can be calculated as a distance (X 3 ) in X-direction and a distance (Y 3 ) in Y-direction. Likewise, a value of an initial curvature radius (the same value as the design curvature radius) corresponding to the relative position n 4  is applied to an end point A 4 , i.e., the unit portion  21 - 4 , also in the unit interval D 4 . Thus, a distance from the start point A 3  to the end point A 4  of the unit interval D 4  can be calculated as a distance (X 4 ) in X-direction and a distance (Y 4 ) in Y-direction. 
     With reference to the curvature-radius database  31 , the control unit  30  integrates distances X 1  to Xn, and Y 1  to Yn of the corresponding unit intervals D 1  to Dn of an elongated extrusion material  21 , positioned from the fulcrum roll contact position  11   a  to the bending roll contact position  12   a  (roll interval), when the elongated extrusion material  21  (workpiece) is fed out from the fulcrum roll  11 , thereby acquiring the amount of roll movement. While the amount of roll movement (integrated value) may be calculated every time from a shape of the roll-formed component  20 , a pre-calculated value may be stored in the curvature-radius database  31 , or a pre-calculated value converted into an NC program may be registered in the control unit  30  or the like. 
     In the example illustrated in each of  FIGS.  7  and  8   , the five relative positions n 0  to n 4  are set in the roll interval, and four equal intervals (lower intervals) are set between the corresponding adjacent positions, as described above. A distance between the corresponding adjacent relative positions n 0  to n 4  is the same as a distance of the unit interval D, so that there are four unit intervals D 1  to D 4  in the roll interval. Thus, the control unit  30  may integrate the distances of the four unit intervals D 1  to D 4  at the time when a start point of an arbitrary unit portion reaches the relative position n 0  (X 1 +X 2 +X 3 +X 4 , and Y 1 +Y 2 +Y 3 +Y 4 ). The control unit  30  causes the roll moving unit  32  to change a relative position of the bending roll  12  with respect to the fulcrum roll  11  on the basis of the integrated quantity (amount of roll movement). When the roll interval is divided into “n” relative positions (or relative sections), there are “n” unit intervals D 1  to Dn in the roll interval. Thus, distances of “n” unit intervals D may be integrated. 
     In other words, the control unit  30  sets a two-dimensional plane PL including a bending direction of a workpiece (refer to  FIG.  8   ), and may integrate the amount of change in position using two-dimensional coordinates in the two-dimensional plane PL. Setting the two-dimensional plane PL including the bending direction enables obtaining a two-dimensional coordinate (a distance from a start point to an end point) based on an initial curvature radius at each relative position, as described above. Then, integrating absolute values of distances based on numerical values of the two-dimensional coordinates enables obtaining a two-dimensional coordinate corresponding to a position of the bending roll  12 . The control unit  30  may cause the roll moving unit  32  so as to position the bending roll  12  at the obtained two-dimensional coordinate. 
     It is needless to say that specific control of the roll moving unit  32  by the control unit  30  is not limited to integration of distances, or control using two-dimensional coordinates, as described above. The control unit  30  can control the roll moving unit  32  using various other control methods. 
     [Relationship Between Change in Curvature Radius and Change in Relative Position of Bending Roll] 
     Next, a relationship between change in a curvature radius of the roll-formed component  20  and change in relative position of the bending roll  12  will be specifically described with reference to  FIGS.  9 A and  9 B . In the present embodiment, the bending roll  12  is moved in a stroke direction intersecting (orthogonal) to the bending path, so that a relative position of the bending roll  12  is referred to as a “stroke position”. 
     The graphs illustrated in  FIGS.  9 A and  9 B  show the same change, and the horizontal axis represents a component position of the roll-formed component  20 , the first vertical axis represents a curvature radius of the roll-formed component  20  to a component position, and the second vertical axis represents a stroke position of the bending roll  12 . Each of the graphs corresponds to manufacture of the roll-formed component  20 C illustrated in  FIG.  3   . 
     Each of  FIGS.  9 A and  9 B  shows a stroke position of the bending roll  12  in the second vertical axis, at which an arbitrary component position of a workpiece (elongated extrusion material  21 ), which is to be a roll-formed component  20 , is positioned at the fulcrum roll contact position  11   a . This is for convenience of describing the maximum bending that is applied to the workpiece when an arbitrary component position of the workpiece passes through the fulcrum roll  11 . 
     The stroke position on the second vertical axis is referred to as a stroke position with respect to the fulcrum roll contact position  11   a , for convenience. Then, when a stroke position in the second vertical axis in each of  FIGS.  9 A and  9 B  is indicated with respect to the bending roll contact position  12   a , a graph indicating stroke positions is illustrated while being moved to the right from the positions illustrated in each of  FIGS.  9 A and  9 B . When a stroke position of the bending roll  12  in the second vertical axis is defined as a stroke position at which an arbitrary component position of a workpiece is at the bending roll contact position  12   a , the reference position is changed from the fulcrum roll contact position  11   a  to the bending roll contact position  12   a . Accordingly, the graph indicating the stroke positions in each of  FIGS.  9 A and  9 B  is illustrated while being moved to the right by a distance between the bending roll  12  and the fulcrum roll  11  (i.e., the roll interval). 
     Each of  FIGS.  9 A and  9 B  illustrates the graph of curvature radii indicated by a dashed line, and the graph of stroke positions indicated by a solid line. In  FIG.  9 B , reference signs indicating respective change points, which are not designated in  FIG.  9 A , are designated for convenience of describing a difference between the graph of curvature radii against respective component positions and the graph of stroke positions against respective component positions. 
     As the roll-formed component  20  is fed out to be changed in position in its longitudinal direction (component position), change in a final curvature radius of the roll-formed component  20  and change in a stroke position of the bending roll  12  (a relative position of the bending roll  12  to the fulcrum roll  11 ) show a complicated difference as illustrated in  FIGS.  9 A and  9 B . 
     As described above, the roll-formed component  20  has not only the constant-curvature portions  20   g ,  20   i , and  20   k  in each of which a constant curvature radius is maintained along its longitudinal direction, but also the first curvature-changing portion  20   h  and the second curvature-changing portion  20   j  in each of which a curvature radius changes so as to continuously increase or decrease (refer to  FIG.  3   ). As illustrated in  FIG.  9 A , the control unit  30  may cause the roll moving unit  32  to maintain uniformly a stroke position of the bending roll  12  because a workpiece has portions corresponding to the constant-curvature portions  20   g ,  20   i , and  20   k , the portions each having a constant curvature radius. As illustrated in  FIG.  9 A , the curvature radius and the stroke position are not changed and are constant at the component positions corresponding to the respective constant-curvature portions  20   g ,  20   i , and  20   k.    
     For convenience, a constant curvature radius at each of the constant-curvature portions  20   g ,  20   i , and  20   k  is defined as a “reference curvature radius”, and a constant stroke position of the bending roll  12  corresponding to the reference curvature radius is defined as a “reference position”.  FIGS.  9 A and  9 B  each illustrate curvature radii and reference positions while superimposing them to make it easy to understand a difference between a behavior of change in a curvature radius against a component position (a graph by a dashed line) and a behavior of change in a stroke position of the bending roll  12  (a graph by a solid line). 
     As illustrated in  FIG.  3   , a curvature radius changes against a component position in the first curvature-changing portion  20   h  as follows: it continuously decreases to reach the minimum value; it then increases so as to return to the reference curvature radius; it then continuously increases to reach the maximum value; and it then decreases so as to return to the reference curvature radius. 
     As illustrated in  FIG.  9 B , when the minimum value of the curvature radius in the first curvature-changing portion  20   h  is indicated as Ve 1 , the maximum value of the curvature radius therein is indicated as Ve 2 , and the reference curvature radius therein is indicated as Vb 1  or Vb 2 , a curvature radius changes in the first curvature-changing portion  20   h  as follows: it continuously decreases until it reaches the minimum value Ve 1 ; it then continuously increases to reach the reference curvature radius Vb 1 ; it then further continuously increases to reach the maximum value Ve 2 ; and it then continuously decreases to return to the reference curvature radius Vb 2 . 
     As illustrated in  FIG.  3   , a curvature radius changes against a component position in the second curvature-changing portion  20   j  as follows: it continuously increases to reach the maximum value; it then decreases so as to return to the reference curvature radius; it then further continuously decreases to reach the minimum value; and it then increases so as to return to the reference curvature radius, contrary to the first curvature-changing portion  20   h.    
     As illustrated in  FIG.  9 B , when the maximum value of the curvature radius in the second curvature-changing portion  20   j  is indicated as Ve 3 , the minimum value of the curvature radius therein is indicated as Ve 4 , and the reference curvature radius therein is indicated as Vb 3  or Vb 4 , a curvature radius changes in the second curvature-changing portion  20   j  as follows: it continuously increases until it reaches the maximum value Ve 3 ; it then continuously decreases to reach the reference curvature radius Vb 3 ; it then further continuously decreases to reach the minimum value Ve 4 ; and it then continuously increases to return to the reference curvature radius Vb 4 . 
     In contrast, a stroke position of the bending roll  12  changes against a component position in the first curvature-changing portion  20   h  as follows: it continuously increases to reach the maximum value; it then decreases so as to return to the reference position; it further continuously decreases to reach the minimum value; and it then increases so as to return the reference position. As illustrated in  FIGS.  9 A and  9 B , the component position at which the change in a curvature radius starts is naturally substantially the same as the component position at which the change of a stroke position of the bending roll  12  starts. However, the change in a stroke position against a component position does not completely opposite in direction to the change in a curvature radius, and there is a unique difference between the changes as illustrated in  FIGS.  9 A and  9 B . 
     As illustrated in  FIG.  9 B , the maximum value of a stroke position in the first curvature-changing portion  20   h  is indicated as Pb 1 , and the minimum value of a stroke position is indicated as Pb 2 . In addition, a stroke position at a component position when a curvature radius reaches the minimum value Ve 1  is indicated as Pe 1 , and a stroke position at a component position when a curvature radius reaches the maximum value Ve 2  is indicated as Pe 2 . 
     The change in a stroke position in the first curvature-changing portion  20   h  is as follows: the stroke position Pe 1  at the time when a component position reaches a portion in which a curvature radius becomes the minimum value Ve 1  corresponds to a value within a range of 45% to 55% of an absolute value of the maximum value Pb 1  of the stroke position; and the stroke position Pe 2  at the time when a curvature radius of the first curvature-changing portion  20   h  returns to the reference curvature radius Vb 1  corresponds to a value of 90% or more and less than 100% of an absolute value of the minimum value Pb 2  of a stroke position. 
     A stroke position of the bending roll  12  changes against a component position in the second curvature-changing portion  20   j  as follows: it continuously decreases to reach the minimum value; it then increases so as to return to the reference position; it then continuously increases to reach the maximum value; and it then increases so as to return to the reference position. 
     As illustrated in  FIG.  9 B , the minimum value of a stroke position in the second curvature-changing portion  20   j  is indicated as Pb 3 , and the maximum value of a stroke position is indicated as Pb 4 . In addition, a stroke position at a component position when a curvature radius reaches the maximum value Ve 3  is indicated as Pe 3 , and a stroke position at a component position when a curvature radius reaches the minimum value Ve 4  is indicated as Pe 4 . 
     The change in a stroke position in the second curvature-changing portion  20   j  is as follows: the stroke position Pe 3  at the time when a component position reaches a portion in which a curvature radius becomes the maximum value Ve 3  corresponds to a value within a range of 45% to 55% of an absolute value of the minimum value Pb 3  of the stroke position; and the stroke position Pe 3  at the time when a curvature radius of the second curvature-changing portion  20   j  returns to the reference curvature radius Vb 3  corresponds to a value of 90% or more and less than 100% of an absolute value of the maximum value Pb 4  of a stroke position. 
     In each of the first curvature-changing portion  20   h  and the second curvature-changing portion  20   j , the bending roll  12  is still changing in a stroke position (90% to 100% at the peak time (extreme value)) at a component position at which a curvature radius finally returns to the reference curvature radius (Vb 2  or Vb 4 ), and the stroke position changes to return to the reference position quite a while later in position (quite a while later in time as views as time of bending) after the curvature radius returns to the reference curvature radius. 
     Change in a stroke position against change in a curvature radius as described above can be summarized as follows. 
     In roll forming (bending), bending for determining a shape is applied at the fulcrum roll contact position  11   a  by the fulcrum roll  11 . That is, when a portion of a workpiece (elongated extrusion material  21 ), corresponding to a portion different in curvature in the roll-formed component  20 , passes through the fulcrum roll contact position  11   a , strain (or bending moment in other words) suitable for the curvature needs to be applied. 
     However, the strain applied at the fulcrum roll contact position  11   a  is not applied only by the fulcrum roll  11 , but is applied by relative movement of the fulcrum roll  11  and the bending roll  12 . Thus, when the manufacturing apparatus  10 A is configured such that roll forming and roll bending continue to each other, moving (operating) the bending roll  12  positioned downstream enables strain (or bending moment) to be introduced to a portion reaching the fulcrum roll contact position  11   a.    
     Alternatively, it can be said that a shape of the portion reaching the fulcrum roll contact position  11   a  is determined by a movement position of the bending roll  12 . However, between the fulcrum roll contact position  11   a  and the bending roll contact position  12   a , there is a portion (referred to as a “bent portion” for convenience) bent before reaching there between. Thus, the movement position of the bending roll  12  needs to be in a position in consideration of the bent portion described above (set by reflecting bending of the bent portion). 
     In particular, as the workpiece advances from the fulcrum roll contact position  11   a  to the bending roll contact position  12   a , strain or bending moment acting on an arbitrary portion of the bent workpiece gradually decreases. Thus, in a portion of the workpiece positioned between the fulcrum roll contact position  11   a  and the bending roll contact position  12   a , a degree of influence of bending by the bending roll  12  increases toward the fulcrum roll contact position  11   a . As a result, the change in a stroke position of the bending roll  12  behaves somewhat “behind” the change in a curvature radius. 
     [Modification] 
     While the manufacturing apparatus  10 A described above is configured such that the control unit  30  refers to the curvature-radius database  31  as illustrated in  FIG.  5 A , the present disclosure is not limited to this. For example, a manufacturing apparatus  10 B illustrated in  FIG.  10    is configured without the curvature-radius database  31 . That is, the present disclosure allows the curvature-radius database  31  provided in the manufacturing apparatus  10 A not to be an indispensable configuration, and may allow a manufacturing apparatus to be configured as with the manufacturing apparatus  10 B that includes the control unit  30  and the roll moving unit  32  without including the curvature-radius database  31 . 
     As described above, the control unit  30  may convert an integrated value of distances for each unit interval in a roll interval into an NC program to register the NC program in the control unit  30  or the like. Thus, as illustrated in  FIG.  10   , the control unit  30  may be configured to store a program  30   a  in a storage unit or the like (not shown) to control the roll moving unit  32  according to the program  30   a . This configuration does not require an integrated value to be calculated with reference to the curvature-radius database  31 . Thus, in the present disclosure, the curvature-radius database  31  may not be an indispensable configuration. 
     While the manufacturing apparatus  10 A described above is configured such that the roll moving unit  32  moves only the bending roll  12  as illustrated in  FIG.  5 A , the present disclosure is not limited to this.  FIG.  11    illustrates a manufacturing apparatus  10 C in which the roll moving unit  32  is configured to be capable of moving both the fulcrum roll  11  and the bending roll  12  as described above. While not shown here, the roll moving unit  32  may be configured to move only the fulcrum roll  11 , and the bending roll  12  may be fixed. The other configurations of the manufacturing apparatus  10 C are the same as those of the manufacturing apparatus  10 A, so that description thereof is eliminated. 
     While, in the manufacturing apparatus  10 A described above, a workpiece just before being subjected to bending by the bending roll  12  has a cross-section including a folded portion or a bent portion in its cross-sectional direction, the workpiece being an elongated extrusion material  21 , the workpiece is not limited to this. It may be a plate-shaped elongated sheet material having no predetermined cross-section. 
     In addition, while, in the manufacturing apparatus  10 A described above, the control unit  30  integrates the amount of change in position of the bending roll  12  for each unit interval in a roll interval on the basis of the fact that strain at the same component position exponentially decreases (spring back occurs in an exponential manner like the strain), and controls the roll moving unit  32  on the basis of the integrated quantity, the present disclosure is not limited to this. For example, the amount of change in position for each unit interval may be integrated by approximately substituting a linear (proportional) decrease of strain (or occurrence of spring back) for an exponential decrease of strain (or exponential occurrence of spring back). 
     Further, while, in the manufacturing apparatus  10 A described above, the control unit  30  applies an initial curvature radius at the fulcrum roll contact position  11   a  so that the design curvature radius is substantially the same as the final curvature radius, the present disclosure is not limited to this. As described above, the final curvature radius may be approximate to the design curvature radius within a range of accuracy of a curvature radius required in the roll-formed component  20 , or the final curvature radius may be set to a value different from the design curvature radius in consideration of post-forming to be applied to the roll-formed component  20 , or the like. 
     For example, when an aluminum alloy for an aircraft is forming, artificial aging is performed after forming. Here, it is known that applying artificial aging to a member of an aluminum alloy molded changes a lattice coefficient of the aluminum alloy to cause a molded product to be slightly changed in shape. In such a case, the final curvature radius may be set to a value different from the design curvature radius by the amount of change. 
     While, in the manufacturing apparatus  10 A described above, a single initial curvature radius is set for a design curvature radius for each unit interval (component position) and stored in the curvature-radius database  31 , the present disclosure is not limited to this. As the initial curvature radius, a plurality of different values may be set on the basis of at least physical properties of a workpiece. For example, physical properties such as strength of a workpiece may be changed depending on heat treatment applied to the workpiece or other conditions. Thus, the curvature-radius database  31  may store an initial curvature radius that is set for a design curvature radius for each unit interval in accordance with strength of a workpiece to deal with a difference in physical properties of the workpiece as described above. The control unit  30  may appropriately cause the roll moving unit  32  to change a relative position of the bending roll  12 , according to different values of the initial curvature radius. 
     In addition, while a single roll is exemplified as each of the fulcrum roll  11  and the bending roll  12 , provided in each of the manufacturing apparatus  10 A, the manufacturing apparatus  10 B, and the manufacturing apparatus  10 C, described above, the present disclosure is not limited to this. For example, at least one of the fulcrum roll  11  and the bending roll  12  may be configured as a pair of rolls across the elongated extrusion material  21  (workpiece) as in a manufacturing apparatus  10 D illustrated in  FIG.  12   . In the manufacturing apparatus  10 D illustrated in  FIG.  12   , a pair of fulcrum rolls  15  is substituted for the fulcrum roll  11  in the manufacturing apparatus  10 A or  10 B.  FIG.  12    illustrates a position at which the pair of fulcrum rolls  15  is brought into contact with an elongated extrusion material  21  (workpiece) as a fulcrum roll contact position  15   a . Instead of the fulcrum roll  11 , a pair of rolls may be substituted for the bending roll  12 , or a pair of rolls may be substituted for each of the fulcrum roll  11  and the bending roll  12 . 
     When at least one of the fulcrum roll  11  and the bending roll  12  is a pair of rolls, the manufacturing apparatus  10 D may further include a roll-pair position adjustment unit  33  that adjusts a position of the pair of rolls such that the pair of rolls is perpendicular to a surface of an elongated extrusion material  21  (workpiece) as illustrated in  FIG.  12   . A specific configuration of the roll-pair position adjustment unit  33  is not particularly limited, and a well-known perpendicular-to-surface mechanism or the like in the field of a roll bending apparatus or the like can be suitably used. While the roll-pair position adjustment unit  33  is provided as a separate mechanism from the roll moving unit  32  in  FIG.  12   , the roll-pair position adjustment unit  33  and the roll moving unit  32  may be integrated as a single mechanism. 
     In the present disclosure, a forming roll unit  14  may be provided upstream of the feeding roll  13  in the bending path, as in the manufacturing apparatus  10 C illustrated in  FIG.  11   . Examples of the forming roll unit  14  may include a roll device for imparting a predetermined cross-section to a flat elongated sheet  22 . The forming roll unit  14  may be configured so as to be capable of imparting not only a predetermined cross-section but also a portion where at least one of width and thickness continuously changes along its longitudinal direction. While  FIG.  11    schematically illustrates the forming roll unit  14  as a single pair of rolls, the present disclosure is not limited to this configuration as a matter of course. 
     In other words, the roll-formed component  20  manufactured according to the present disclosure may include not only a portion where a curvature radius continuously changes but also a portion where at least one of width and thickness continuously changes along its longitudinal direction. While the first curvature-changing portion  20   h  and the second curvature-changing portion  20   j  are each a part of the roll-formed component  20  in the roll-formed component  20 C illustrated in  FIG.  3   , the roll-formed component  20  may be continuously changed in a curvature radius throughout its longitudinal direction. 
     In addition, the roll-formed component  20  may include a portion where a curvature radius changes stepwise rather than continuously. In this case, the manufacturing apparatus  10 A or  10 B may be configured such that the control unit  30  causes the roll moving unit  32  to change a relative position (stroke position) of the bending roll  12  so as to impart a change in the curvature radius stepwise. 
     As described above, according to the present disclosure, a design curvature radius is preset for a position of the roll-formed component  20  manufactured in its longitudinal direction, and the initial curvature radius being a curvature radius before spring back occurs or strain is reduced is preset for the design curvature radius to form a database. The control unit  30  integrates the amount of change in position of the bending roll  12  based on an individual design curvature radius in each unit interval in a period from the fulcrum roll contact position  11   a  to the bending roll contact position  12   a  when a workpiece is fed out from the fulcrum roll  11 , with reference to the database. The control unit  30  controls the roll moving unit  32  such that a relative positional change of the bending roll  12  with respect to the fulcrum roll  11  becomes the amount of change in position based on this integrated quantity. 
     In this configuration, not only the initial curvature radius is set by paying attention to the fulcrum roll contact position  11   a , but also a position of the bending roll  12  with respect to the fulcrum roll  11  is determined such that a workpiece advanced from the fulcrum roll contact position  11   a  toward the bending roll contact position  12   a  has a shape formed by accumulating a bending shape. This enables a relative position of the bending roll  12  to the fulcrum roll  11  to be gradually changed to provide a continuous curvature change to the workpiece. As a result, a portion with curvature continuously changing can be formed at a desired position in the roll-formed component  20  obtained, in its longitudinal direction. This enables a molded part including a portion in which curvature is freely changed in at least a part in its longitudinal direction to be manufactured by roll forming. 
     It is needless to say that the present disclosure includes not only an apparatus for manufacturing a roll-formed component, having the above-described configuration, but also a method of manufacturing a roll-formed component. 
     In addition, the present invention is not limited to the description of the embodiment described above, and various modifications are possible within a range shown in the scope of claims, and an embodiment that can be acquired by appropriately combining technical means disclosed in each of different embodiments and a plurality of modifications is also included in the technical scope of the present invention. 
     As described above, an apparatus for manufacturing a roll-formed component, according to the present invention, manufactures a roll-formed component with curvature changing continuously along its longitudinal direction by applying roll bending to an elongated sheet or an elongated extrusion material, being a workpiece, along its longitudinal direction. The apparatus includes a fulcrum roll that is positioned upstream of the workpiece in a bending path to support the workpiece during bending, or to serve as a fulcrum of bending, a bending roll positioned downstream of the fulcrum roll in the bending path to apply bending to the workpiece, a roll moving unit that moves at least one of the fulcrum roll and the bending roll so as to relatively change a position of the bending roll with reference to a position of the fulcrum roll, and a control unit. Under the following conditions: a position allowing the fulcrum roll to be brought into contact with the workpiece is set as a fulcrum roll contact position; a position allowing the bending roll to be brought into contact with the workpiece is set as a bending roll contact position; when the roll-formed component is divided into a plurality of unit intervals in its longitudinal direction, a design value of a curvature radius of an unit portion corresponding to each of the unit intervals in the roll-formed component is set as a design curvature radius; a curvature radius applied to the workpiece at the fulcrum roll contact position is set as an initial curvature radius; and a curvature radius remaining in the workpiece when the workpiece is fed out from the bending roll contact position to achieve the design curvature radius in the roll-formed component is set as a final curvature radius, the initial curvature radius is set as a curvature radius to be applied to the workpiece before spring back occurs by applying bending to the workpiece. Under the following conditions: the unit portion positioned at the fulcrum roll contact position at the time when the workpiece is fed to a nip between the fulcrum roll and the bending roll is set as a fulcrum roll unit portion; the unit portion positioned at the bending roll contact position is set as a bending roll unit portion; and the unit portion positioned between the unit portions above, corresponding to each of the unit intervals, is set as an intermediate unit portion, the control unit integrates the amount of change in bending position in each of the intermediate unit portion and the bending roll unit portion when an intermediate curvature radius set so as to continuously change curvature of the intermediate unit portion from the initial curvature radius to the design curvature radius is applied to the intermediate unit portion, and the design curvature radius is applied to the bending roll unit portion, to apply the initial curvature radius corresponding to the unit portion to the fulcrum roll unit portion and apply the design curvature radius corresponding to the unit portion to the bending roll unit portion. The control unit causes the roll moving unit to be driven to move at least one of the fulcrum roll and the bending roll on the basis of an integrated value. 
     According to the above configuration, a design curvature radius is preset for a position of the roll-formed component manufactured in its longitudinal direction, and the initial curvature radius being a curvature radius before spring back occurs is preset for the design curvature radius to form a database. The control unit integrates a relative amount of change in position of the bending roll based on an individual design curvature radius in each unit interval in a period from the fulcrum roll contact position to the bending roll contact position when a workpiece is fed out from the fulcrum roll, with reference to the database. The control unit controls the roll moving unit such that a relative positional change of the bending roll with respect to the fulcrum roll becomes an amount of change in position based on this integrated quantity. 
     In this configuration, not only the initial curvature radius is set by paying attention to the fulcrum roll contact position, but also a position of the bending roll with respect to the fulcrum roll is determined such that a workpiece advanced from the fulcrum roll contact position toward the bending roll contact position has a shape formed by accumulating a bending shape. This enables a relative position of the bending roll to the fulcrum roll to be gradually changed to provide a continuous curvature change to the workpiece. Thus, a portion with curvature continuously changing can be formed at a desired position in the roll-formed component obtained, in its longitudinal direction. As a result, a roll-formed component can be adjusted or controlled to have favorable curvature along its longitudinal direction in manufacturing thereof. 
     The apparatus for manufacturing a roll-formed component, having the configuration described above, may be configured such that the intermediate curvature radius is set from a value of the initial curvature radius applied when the unit portion is the fulcrum roll unit portion, and strain or bending moment, changing during a period in which the unit portion is the intermediate unit portion. 
     The apparatus for manufacturing a roll-formed component, having the configuration described above, also may be configured such that the intermediate curvature radius is set based on the fact that strain or bending moment at the unit portion decreases gradually as the unit portion is moved from the fulcrum roll unit portion to the bending roll unit portion. 
     The apparatus for manufacturing a roll-formed component, having the configuration described above, also may be configured such that at least the design curvature radius and the initial curvature radius in all the unit portions of the roll-formed component are preliminarily prepared as the curvature-radius database and the control unit calculates the integrated quantity with reference to the curvature-radius database. 
     The apparatus for manufacturing a roll-formed component, having the configuration described above, also may be configured to further include a feeding roll positioned upstream of the fulcrum roll in the bending path to feed the workpiece toward the fulcrum roll. 
     The apparatus for manufacturing a roll-formed component, having the configuration described above, also may be configured such that the fulcrum roll is fixed in position and only the bending roll is moved by the roll moving unit. 
     The apparatus for manufacturing a roll-formed component, having the configuration described above, also may be configured such that a plurality of different values are set as the initial curvature radius constituting the curvature-radius database based on at least physical properties of the workpiece, and the control unit controls the roll moving unit according to the different values of the initial curvature radius. 
     The apparatus for manufacturing a roll-formed component, having the configuration described above, also may be configured such that the workpiece just before being subjected to bend by the bending roll has a cross-section including a folded portion or a bent portion in its cross-sectional direction. 
     The apparatus for manufacturing a roll-formed component, having the configuration described above, also may be configured such that the roll-formed component includes a portion where at least one of width and thickness continuously changes along its longitudinal direction. 
     The apparatus for manufacturing a roll-formed component, having the configuration described above, also may be configured to further include a roll unit for continuously changing at least one of width and thickness of the workpiece in its longitudinal direction. 
     The apparatus for manufacturing a roll-formed component, having the configuration described above, also may be configured such that at least one of the fulcrum roll and the bending roll is configured as a pair of rolls across the workpiece, and configured to further include a roll-pair position adjustment unit that adjusts the pair of rolls such that it is positioned perpendicular to a surface of the workpiece. 
     The apparatus for manufacturing a roll-formed component, having the configuration described above, also may be configured such that the roll-formed component is a frame component for an aircraft. 
     In addition, a method of manufacturing a roll-formed component, according to the present disclosure, is configured to manufacture a roll-formed component including a portion with curvature continuously changing along its longitudinal direction by applying roll bending to an elongated sheet or an elongated extrusion material, being a workpiece, along its longitudinal direction. The method may include the steps of: supporting the workpiece during bending by a fulcrum roll provided upstream of the workpiece in a bending path, or allowing the fulcrum roll to serve as a fulcrum of bending; applying bending to the workpiece by a bending roll positioned downstream of the fulcrum roll in the bending path; moving at least one of the fulcrum roll and the bending roll so as to relatively change a position of the bending roll with reference to a position of the fulcrum roll by using a roll moving unit; setting a position allowing the fulcrum roll to be brought into contact with the workpiece as a fulcrum roll contact position; setting a position allowing the bending roll to be brought into contact with the workpiece as a bending roll contact position; setting a design value of a curvature radius of each of the unit intervals in the roll-formed component as a design curvature radius when the roll-formed component is divided into a plurality of unit intervals in its longitudinal direction; setting a curvature radius applied to the workpiece at the fulcrum roll contact position as an initial curvature radius; setting a curvature radius remaining in the workpiece when the workpiece is fed out from the bending roll contact position to achieve the design curvature radius in the roll-formed component as a final curvature radius; setting the initial curvature radius as a curvature radius to be applied to the workpiece before spring back occurs by applying bending to the workpiece; setting the unit portion positioned at the fulcrum roll contact position at the time when the workpiece is fed to a nip between the fulcrum roll and the bending roll as a fulcrum roll unit portion; setting the unit portion positioned at the bending roll contact position as a bending roll unit portion; setting the unit portion positioned between the unit portions above, corresponding to each of the unit intervals, as an intermediate unit portion; applying an intermediate curvature radius set so as to continuously change curvature of the intermediate unit portion from the initial curvature radius to the design curvature radius to the intermediate unit portion, to apply the initial curvature radius corresponding to the unit portion to the fulcrum roll unit portion and apply the design curvature radius corresponding to the unit portion to the bending roll unit portion; applying the design curvature radius to the bending roll unit portion; integrating an amount of change in bending position in each of the intermediate unit portion and the bending roll unit portion; and moving the roll moving unit, and at least one of the fulcrum roll and the bending roll using the roll moving unit on the basis of this integrated value. 
     The present invention can be widely and suitably used in the field of manufacturing a roll-formed component including a portion in which a curvature radius continuously changes by subjecting a workpiece to roll bending along its longitudinal direction. 
     From the above description, many modifications and other embodiments of the present invention are apparent to a person skilled in the art. Thus, the above description is to be construed only as illustrative examples, and is provided for a purpose of teaching the best mode of practicing the invention to a person skilled in the art. Details of structure and/or function of the present invention can be substantially changed without departing from the spirit of the present invention.