DESCRIPTION Title of Invention: Method of Producing Shaped article, Tooling, and Tubular Shaped article Technical Field [0001] The present invention relates to a method of producing a shaped article using a metal plate, tooling used for that method of production,·. and a tubular shaped 10 article produced by that method ~f production. Background Art [0002] Auto parts and household electric appliances first and foremost and vehicles, building materials, ships, etc. make frequent use of bent tubes having bent 15 shapes, irregular diameter tubes having different outside diameters in the longitudinal direction, irregular crosssection tubes having different cross-sectional shapes in the longitudinal direction, and other tubular products. For this reason, technology for producing such tubular 20 parts is being developed. [0003] In the past, in the production of tubular parts, mainly straight shaped thick wall large diameter tubes have been UO-formed. For example, Japanese Patent Publication No. 58-32010A discloses the art of 25 successively using a C-press, U-press, and 0-press to form a straight shaped steel tube. However, \•lith conventional UO-forming, forming a bent tube, irregular diameter tube, and irregular cross-section tube is difficult. 30 [0004] In recent years, UO-forming has been further improved to develop the art of forming a bent tube, irregular diameter tube, irregular cross-section tube, and other tubular parts having 30 shapes. For example, International Publication No. 2005/002753A proposes a 35 method of using tooling provided with guide blades for edges in the vertical direction for UO-forming and producing straight shaped irregular diameter tubes. - 2 - Further, Japanese Patent No. 3114918 and Japanese Patent Publication No. 2008-80381A propose a method of production of a curved hollow tube comprised of a method of bending the tube in the longitudinal direction at the 5 time of U-forming the tube wherein the U-forming step is made a step including dra~oling process. [0005] However, the method described in International Publication No. 2005/002753A is a method of production of a straight shaped irregular diameter tube. Formation of a 10 bent tube is difficult. Further, the methods described in Japanese Patent No. 3114918 and Japanese Patent Publication No. 2008-80381A have the problems that the numbers of steps are large and the yields are low. Summary of Invention 15 Technical Problem [0006] With the method of bending in the longitudinal direction at the time of U-forming such as described in Japanese Patent No. 3114918 and Japanese Patent Publication No. 2008-80381A, depending on the shape or 20 material of the shaped article, there is the problem of fracture or wrinkling during U-forming, creasing of the vertical 1o1alls, and other shaping defects. [0007] The present invention was made in consideration of the above problem and has as its object the provision 25 of a method of producing a shaped article able to suppress shaping defects 1o1hen bending in the longitudinal direction to produce a shaped article, tooling used for that method of production, and a tubular shaped article obtained by that method of production. 30 Solution to Problem [0008] To achieve the above ob]ect, the gist of the invention perfected by the inventors is as follows: [0009] [1] A method of producing a shaped article comprising: 35 a first step of press-forming a metal plate into a Ushape to obtain a U-shaped article having a bottom part straight extending in a longitudinal direction and 5 - 3 - a second step of press-forming said U-shaped article to bend it in the longitudinal direction so that the bottom part of the U-shaped article projects to an inside and to obtain a U-cross-section bent article. [0010] [2] The method of producing a shaped article according to [1] characterized in that, in said second step, an external force in a·direction connecting an edge and the bottom part is applied to at least a part of a planned bending part of said U-shaped article, at the 10 same time as said bending. [0011] [3] The method of producing a shaped article according to [2] characterized in that said external force is applied by compressing, in in-plane directions, said edge along the longitudinal direction of said U- 15 shaped article toward the outside of the bottom part of said U-shaped article. [0012] [4] The method of producing a shaped article according to any one of [1] to [3] further comprising a third step of shaping said U-cross-section bent article 20 into a closed cross-section to obtain a tubular shaped article. [0013] [5] A tooling for bending a U-shaped article in a longitudinal direction so that the bottom part projects to an inside and for obtaining a U-cross-section bent 25 article, said tooling provided with a die, a punch, and pads arranged at side surfaces of said punch and compressing, in in-plane directions, at least parts of a planned bending part of said U-shaped article in end parts along the longitudinal direction of said U-shaped 30 article. [0014] [6] A tubular shaped article comprised of a metal plate and including only one seam extending in an axial direction, wherein a bottom part positioned at an opposite side to said seam in a peripheral direction 35 includes a bent part projecting to an inside in an axial direction, and a ratio .H1/H2 of a plate thickness H1 of said bent article at said seam and a plate thickness H2 - 4 - of said bent article at said bottom part satisfies a following equation (1): H1/H22Ri/(Ri+D) (1) (wherein in said equation (1), Ri is a radius of curvature of a bottom part side of the bent part, and D is a width of 5 the bent part at a cross-section including a seam and a centerline of the_tubular shaped article) Advantageous Effects of Invention [0015] In the method of producing a shaped article according to the present invention, U-forming and bending 10 in the longitudinal direction are performed separately. Therefore, according to the method of producing a shaped article according to the present invention, it is possible to suppress shaping defects of the U-crosssection. bentarticle and in turn possible to suppress 15 shaping defects even in the shaped article. Note that, according to the tooling according to the present invention, it is possible to efficiently perform the above method of production and in turn possible to obtain a tubular shaped article according to the present 20 invention. Brief Description of Dravlings [0016] FIGS. 1 are process diagrams showing an example of a first step and second step in the method of producing a shaped article according to the present 25 invention. FIGS. 2 are process diagrams shovling an example of a third step in the method of producing a shaped article according to the present invention. FIG. 3 is a schematic plan view showing one example of a 30 metal plate used in the method of producing a shaped article according to the present invention. FIGS. 4 are schematic perspective vie1·1s showing an example of a tubular shaped article according to the present invention. 35 FIGS. 5 are process diagrams showing an example of a first step in the method of producing a shaped article according to the present invention. - 5 - FIGS. 6 are process diagrams showing an example .of a second step in. the method of producing a shaped article according to the present invention. FIGS. 7 are process diagrams shm;ing another example of a 5 first step in the method of producing a shaped article according to the present invention. FIGS. 8 are process diagrams showing another example of a second step in the method of producing a shaped article according to the present invention. 10 FIGS. 9 are process diagrams showing an example qf a third step in the method of producing a shaped article according to the present invention. FIGS. 10 are schematic perspective views showing another example of a tubular shaped article according ~o the 15 present invention. FIGS. 11 are a schematic front view, side view, top view, and cross-sectional view of another example of a tubular shaped article according to the present invention. FIGS. 12 are a schematic front vie~;, side vie"', top vie~;, 20 and cross-sectional vie~; of another example of a tubular shaped article according to the present invention. FIG. 13 is a graph sho,ling a thickness reduction rate at a cross-section at the center of bending of Example 3. FIG. 14 is a graph showing the results of investigation 25 of the ratio (Hl/H2) of Examples 2 and 3. Description of Embodiments [0017] Below, the method of producing a shaped article, tooling, and tubular shaped article according to the present invention Hill be explained in detail. 30 [0018] A. Method of producing Shaped article Basic Embodiment The method of producing a shaped article of the basic embodiment includes a first step of press-forming a metal plate into a U-shape to obtain a U-shaped article having 35 a bottom part straight extending in a longitudinal direction and a second step of press-forming the U-shaped article to bend it in the longitudinal direction so that - 6 - the bottom part of the part projects to the inside and obtain a U-cross-section bent article. Further, in the method of producing a shaped article of the basic embodiment, after the end of the above second step, for 5 example, it is possible to perform a third step of shaping the above U-cross-section bent article into a closed cross-section to obtain a tubular shaped article. Note that, instead of the third step, piercing or burling, trimming, etc. can be performed. Further, 10 piercing etc. can be performed before the first step, before the second step, or before the third step. [0019] The method of producing a shaped article of the basic embodiment v1ill be explained while referring to the drawings. 15 FIGS. 1A to 1F and FIGS. 2A ·to 2C are process diagrams shov1ing one example of the method of producing a shaped article of the basic embodiment. FIGS. 1A and 10 are front views, FIG. 1B is a cross-sectional view along the line A-A of FIG. 1A, FIG. 1E is a cross-sectional view 20 along the line A-A of FIG. 10, FIGS. 1C and 1F are perspective viev1s, FIG. 2A is a front vievl, FIG. 2B is a cross-sectional view along the line A-A of FIG. 2A, and FIG. 2C is a perspective view. [0020] First, at the first step, as shown in FIGS. 1A 25 and 1B, first tooling for U-forming use is prepared. The first tooling for U-forming use has a die 11 and punch 12. The bottom part 11a of the recessed part of the die 11 and the bottom part 12a of the punch 12 both extend straight in the longitudinal direction. Between the die 30 11 and punch 12 of the first tooling for U-forming use, a metal plate 1a is placed. The metal plate 1a is U-formed. Due to this, as shown in FIG. 1C, a U-shaped article 1b having a bottom part 2 extending straight in the longitudinal direction x is obtained. 35 [0021] Next, at the second step, as shown in FIGS. 10 and 1E, second tooling for bending use is prepared. The second tooling for bending use has a die 21 and punch 22. - 7 - The bottom part 2la of the recessed part of the die 21 is formed curved projecting upward in the longitudinal direction. The~ bottom part 22a of the punch 22 is formed curved recessed in the longitudinal direction. Between 5 the die 21 and punch 22 of this second tooling for bending use, the U-shaped article lb is placed and the Ushaped article lb is bent in the longitudinal direction x. Due to this, as shown in FIG. lF, a U-cross-section bent article lc is obtained. The U~cross~section bent 10 article lc is formed with the bottom part 3 curved projecting to the inside in the longitudinal direction. It has a bent part lOa with a bottom part 3 projecting inside in the longitudinal direction and a straight part lOb with a bottom part 3 extending straight in the 15 longitudinal direction and having a total length of the U-shape in the U-cross-section equal along the centerline. [0022] Next, at third step, as shown in FIGS. 2A and 2B, third tooling for 0-forming use is prepared. The 20 third tooling for 0-forming use has a die 31 and punch 32. The bottom part 31a of the recess of the die 31 is formed curved projecting in the longitudinal direction, the bottom part 32a of the recess of the punch 32 is formed curved recessed in the longitudinal direction, and 25 the recess of the die 31 and the recess of the punch 32 both have semicircular cross-sectional shapes. Between the die 31 and punch 32 of this third tooling for 0- forming use, the U-cross-section bent article lc is placed and the U-cross-section bent article lc is 0- 30 formed. Due to this, as shown in FIG. 2C, a tubular shaped article ld is obtained. The tubular shaped article ld has a seam 4 formed curved projecting to the outside and a bottom part 5 positioned at the opposite side from the seam 4 in the peripheral direction formed curved 35 projecting inside in the axial direction. It has a bent part lOa having a bottom part 5 projecting inside in the axial direction and a straight part lOb having a bottom - 8 - part 5 extending straight in the axial direction and 11ith an equal length in the peripheral direction along the centerline. [0023] If, like in the past, performing the U-forming 5 and bending in the longitudinal direction simultaneously, a force in a direction outside the plane easily acts on the vertical walls (straight parts·at the ends of U-shape of worked object seen from side view) and creasing easily occurs at the edges (in particular near final edges of 10 the straight parts) . Further, in this case, the metal plate is bent in the plate 1·Tidth direction and is bent in the longitudinal direction as well, so a compressing force is generated at the bottom part in the substantially flat state and wrinkling easily occurs. 15 [0024] As opposed to this·;- in the basic embodiment according to the present invention, U-forming (first step) and bending in the longitudinal direction (second step) are performed in separate steps, so it is possible to decrease the force acting in the direction outside the 20 plane on the vertical walls (straight parts of the two ends of the U-shaped article in the side view) at the time of bending of the second step and in turn it is possible to suppress the occurrence of creasing at the edges (in particular near final edges of the straight 25 parts). Further, in the basic embodiment, the metal plate is not simultaneously bent in the plate width direction and longitudinal direction like in the past. The metal plate is bent once in the plate width direction to obtain a U-shaped article which is then bent in the longitudinal 30 direction, so when bending in the longitudinal direction, it is possible to maintain the rigidity of the bottom part (U-shaped bottom part) at a high state. For this reason, stable bending in the longitudinal direction becomes possible, occurrence of wrinkling of the bent 35 part at the bottom part can be suppressed, and in turn it is possible to obtain a U-cross-section bent article free of shaping defects and in turn a tubular shaped article. - 9 - [0025] Below, the different steps of the method of producing a shaped article of the basic embodiment will be explained in more detail. [0026] (1) First Step 5 At the first step, the metal plate is press-formed into a U-shape to obtain a U-shaped article having a bottom part extending straight in the longitudinal direction. As the U-forming method, press-forming and roll forming can be employed. 10 [0027] The metal plate is not particularly limited so long as one able to be shaped. For example, a hot rolled steel plate, cold rolled steel plate, plated steel plate, etc. may be used. Further, for the metal plate, one comprised of a plurality of metal plates joined together, 15 a so-called "tailored blank", may a·lso be used. Further, a differential thickness steel plate can also be used. Further, a plate comprised of a plurality of metal plates superposed or a plate comprised of a metal plate >lith which a nonmetal material is superposed, that is, 20 multilayer plates, may also be used. [0028] The material of the metal plate is not particularly limited so long as one able to be shaped. For example, an Fe-based one (for example, carbon steel, stainless steel, etc.), anAl-based one (for example, Al 25 or an alloy including Al and at least one of Cu, Mn, Si, Mg, Zn, etc.), a Cu-based one (for example, Cu or an alloy including Cu and at least one of Al, Ag, As, Be, Co, Cr, Fe, Mn, Ni, P, Pb, S, Se, Sd, Sn, Si, Te, Zn, Zr, etc.), a Ti-based one (for example, Ti or an alloy 30 including Ti and at least one of N, C, H, Fe, o, Al, V, etc.), or other material may be mentioned. [0029] The plate thickness of the metal plate need only be made an extent able to be shaped. While differing according to the material or the shape of the shaped 35 article or the like, for example, it can be made vlithin 0.5 mm to 30 mm in range. However, if the plate thickness is too small, at the time of bending, the bent part .is - 10 - liable.to wrinkle or fracture, while if the plate thickness· is too great, sometimes an excessive ·load· is required for shaping operations, so the plate thickness is preferably made 1.0 rom to 5.0 rom. 5 [0030] The shape of the metal plate is suitably adjusted in accordance with the shape of the shaped article. For example, at the time of bending, the total length of the U-shape at the U-cross-section of the bent article ~ecreases, so the plate width of the region to be 10 the bent part of the metal plate is preferably designed so as to become larger than the targeted length of the ucross- section of the U-cross-section bent article. Specifically", when fabricating the U-cross-section bent article lc having the bent part lOa and straight part lOb · 15 sho~>m in FIG. lF, as sho~>m in FIG. 3, it is preferable to design the plate width d2 of the region to be the bent part of the metal plate la larger than the plate 11idth dl of the region becoming the straight part. [0031] The U-shaped article obtained at the first step 20 has a bottom part extending straight in the longitudinal direction. At the cross-section of the U-shaped article in the longitudinal direction, the bottom part is formed straight. [0032] (2) Second Step 25 At the second step, press-forming is used to bend the above U-shaped article in the longitudinal direction so that the above bottom part projects inside so as to obtain a U-cross-section bent article. As the bending method in this step, press-forming can be employed. 30 [0033] The radius of curvature at the bending differs according to the material, the shape of the shaped article or the like, but for example can be set in the range of 0.5 to 10 times the width of the U-crosssection. If the radius of curvature is small, the bent 35 part is liable to wrinkle or fracture at the time of bending. Further, if the radius of curvature is large, the effect of performing the U-forming and bending in the 5 - 11 - longitudinal 'direction by separate steps (that is, suppress the occurrence of shaping defects) sometimes cannot be sufficiently obtained. Here, the "width of the U-cross-section'' indicates the width w such as shown in FIG. lE. [0034] (3) Third Step At the third step, the U-cross-section bent arti·cl-e ·is press-formed into a closed cross-section to obtain a tubular shaped.article. Here, the "closed cross-section" 10 is a concept including not only a completely closed cross-section but also the case where there is a clearance between the abutting edges. That is, at the seam of the tubular shaped article, the edges may be closely in contact or may be separated. That is, th.e seam 15 may also have clearance. [0035] As the method of forming the closed crosssection, press-forming can be employed. Further, \vhen forming the closed cross-section, it is possible to use a mandrel in accordance \'lith need. By using a mandrel, it 20 is possible to stably form the tubular shaped article even if the cross-sectional shape of the peripheral direction is a complicated shape. [0036] The tubular shaped article obtained at the third step has a bent part v1ith a bottom part positioned 25 at the opposite side from the seam in the peripheral direction and projecting inside in the axial direction. It is formed curved so that the bottom part projects inside in the cross-section of the axial direction. The seam may for example be formed curved so that it projects 30 to the outside and may be formed straight. [0037] The cross-sectional shape of the tubular shaped article in the peripheral direction is not particularly limited. It may be made a round shape, oval shape, square shape, vertically asymmetric shape, or various other 35 shapes. [0038] (4) Other Steps In the basic embodiment, after the third step, it is also - 12 - possible to perform a welding step of 1•/elding the seam of the tubular shaped article. As the welding method, for example, arc welding, laser welding,·· etc. may be mentioned. Further, in the basic embodiment, before the 5 first step, edge bending of the metal plate, so-called curling or other processing may be performed. [0039] (5) Shaped article The shaped article produced by the basic embodiment is a tubular shaped article. Further, the shape of the tubular 10 shaped article is not particularly limited so long as one able to be formed well by the method of the basic embodiment. For example, a bent tube 1·1ith a circular cross-sectional shape in the peripheral direction such as shown in FIG. 4A, a bent tube vii th a vertically 15 asymmetric cross-sectional shape in the peripheral direction such as shown in FIG. 4B, a not shown irregular diameter tube or irregular cross-section tube etc. may be illustrated . [0040] . Due to the above, according to the method of 20 producing a shaped article shovm in FIGS. 1 and FIGS. 2 (basic embodiment), in particular, at the second step, aforming and bending in the longitudinal direction can be separately performed so as to suppress the occurrence of shaping defects. 25 [0041] Applied Embodiments Next, the Applied Embodiments 1 and 2 improved over the above basic embodiment will be explained in detail. [0042] Applied Embodiment 1: Modification Applying to at Least Part of Planned Bending Part of U-Shaped article 30 External Force in Directions Connecting Edges and Bottom Part In the method of producing a shaped article of the Applied Embodiment 1, in the second step explained in the basic embodiment, at the same time as the bending, 35 external force in directions connecting the edges and bottom part is applied to at least part of the planned bending part of the U-shaped article. Here, the "planned - 13 - bending part of the U-shaped article" means the region corresponding to the region to be the bent part in the Ucross- section bent article obtained at the time of end of the second step. Further, the "outside of the bottom 5 part" means the side in the direction of movement of the punch at the time of bending. [0043] As such an example of "at ·the same time as the bending, external force in directions connecting the edges and bottom part is applied to at least parts of the 10 planned bending part of the U-shaped article", the type of "applying the external force by compressing the edges along the longitudinal direction of the U-shaped article toward the outside of the bottom part of the U-shaped article in the planar direction" and the type of 15 "applying the external force by pulling the vertical v1alls of the U-shaped article tm-1ard the inside of the bottom part of the U-shaped article (direction opposite to direction of movement of punch at time of bending) in the planar direction" may be mentioned. 20 [0044] The method of producing a shaped article of the Applied Embodiment 1 v1ill be explained 1vhile referring to the drawings. Note that, below, the type of "applying the external force at the second step by compressing the edges along the longitudinal direction of U-shaped 25 article tov1ard the outside of the bottom part of the Ushaped article in the planar direction" will be explained in detail. [0045] FIGS. 5A to 5D and FIGS. 6A to 6E are process diagrams .showing an example of the method of producing a 30 shaped article of the present embodiment. FIG. 5A is a top view, FIG. 5B is a front view, FIG. 5C is a crosssectional view along the line A-A of FIG. 5B, and FIG. 5D is a perspective vie1v. Further, FIGS. 6A and 6C are front viev1s, FIG. 6B is a cross-sectional viev1 along the line 35 A-A of FIG. 6A, FIG. 6D is a cross-sectional view along the line A-A of FIG. 6C, and FIG. 6E is a perspective view. - 14 - _ [0046] First, as shown ~n FIG. SA, a metal plate la vlith a plate width d2 of the planned bending part (region to be a bent part) larger than the plate width dl of the region becoming the straight part is prepared. 5 [0047] Next, at first step, as shown in FIGS. 5B and 5C, first tooling for U-forming use is prepared. The first tooling for U-forming use has a· die 11 and punch 12. The bottom part lla of the recessed part of the die 11 and the bottom part 12a of the punch 12 both extend 10 straight in the longitudinal direction. The metal plate la is placed between the die 11 and punch 12 of the first tooling for U-forming use and the metal plate 1a is Uformed. Due to this, as shown in FIG. 50, a U-shaped article 1b having a bottom part 2 extending straight in 15 the longitudinal direction x is obtained. [0048] Furthermore, at the second step, as shmm in FIGS. 6A and 6B, second tooling for bending use is prepared. The second tooling for bending use has a die 21, punch 22, and pads 23 arranged at the two side 20 surfaces of the punch 22. The bottom part 2la of the recess of the die 21 is formed curved projecting in the longitudinal direction, while the bottom part 22a of the punch 22 is formed curved recessed in the longitudinal direction. 25 [0049] The pads 23 compress at least parts of the planned bending part (in U-cross-section bent article, region to be a bent part) 7 of the U-shaped article 1b at the edges 6 in the longitudinal direction x of the Ushaped article 1b in the planar direction and can move up 30 and d01m. In the example shovm in FIGS. 6, the pads 23 are a type compressing the entire part of the planned bending part 7, but the pads according to the present invention are not limited to such a type. They may also be a type compressing parts of the planned bending part 35 7. [0050] Next, as shown in FIGS. 6A to 60, the U-shaped article 1b is placed between the die 21 and punch 22 of - 15 - the second tooling for bending use, then the U-shaped article lb is bent in the longitudinal direction x. At this time, at least parts of the planned bending part 7 of the U-cross-section bent article at the edges 6 of the 5 U-shaped article lb in the longitudinal direction x are compressed in the planar direction. Due to this, as shovm in·FIG. 6E, aU-cross-section bent article lc is' obtained. The U-cross-section bent article lc has a bottom part 3 formed curved projecting inside in the_ 10 longitudinal direction. It has a bent part lOa with a bottom part 3 projecting inside in the longitudinal direction and a straight part lOb having a bottom part 3 extending straight in the longitudinal direction and with an equal U-cross-section along the centerline. 15 [0051] Due to the above, according to the method of producing a shaped article shown in FIGS. 5 and· FIGs·. 6 (Applied Embodiment 1), not only the effect exhibited by the above basic embodiment of "suppressing the occurrence of shaping defects", in particular, not only the effect 20 that at the second step, by applying external force to at least parts of the planned bending part of the U-shaped article toward the outside of the bottom part of the Ushaped article, it is possible to suppress local changes in the plate thickness in the U-cross-section bent 25 article, that is, decrease of thickness and increase of thickness, but also it is possible to further suppress the occurrence of wrinkling at the bottom part of the bent part. Further, by going through a third step in the same way as the basic embodiment, a desired tubular 30 shaped article can be obtained. [0052] Here, the specific grounds why it is possible to suppress local changes in the plate thickness, that is, decrease of thickness and increase of thickness, for the v10rked part· lc shm1n in FIG. 6E, are as follm·1s: That 35 is, in Applied Embodiment 1, at the second step, by using the pads 23 to compress at least parts of the planned bending part 7 in the planar direction, at least parts of - 16 - the bottom part·of the planned bending part are pressed against the tooling and the neutral axis of bending (position not stretching or contracting in longitudinal direction) moves to the bottom part side compared Hith 5 the case of not compressing in the planar direction. For this reason, in the worked part lc shm·m in FIG. 6E, not only it is possible to suppress the increase in plate thickness at the bottom part 3 side at the bent part lOa, but also it is possible to suppress the decrease in plate 10 thickness due to material being supplied by compressing to the edge 8 side along the longitudinal direction. Therefore, not only is it possible to suppress the occurrence of fractures at the edge along the longitudinal direc;tion of the bent part lOa and Vlrinkling 15 at the bottom part, but it also pos·sible to make the distribution of plate thickness of the U-cross-section of the U-cross-section bent article uniform. [0053] In this Hay, in the Applied Embodiment 1, it is possible to make the distribution of plate thickness 20 uniform, so it is possible to enlarge the range of possible shaping of the bent part in the longitudinal direction of the U-cross-section bent article lc compared with the basic embodiment. For this reason, for example, a U-cross-section bent article having a bent part Hith 25 the relatively small radius of curvature and a U-crosssection bent article having a taper part also can suppress the occurrence of >lrinkling and fracture Vlhile enabling stable shaping. [0054] Furthermore, when compressing at least parts of 30 the planned bending part at the edges along the longitudinal direction of the U-shaped article (region to be a bent part of U-cross-section bent article) in the planar direction, it is not necessary to constantly apply pressure during bending. It is sufficient to apply 35 pressure at any time during bending. [0055] In addition, as the pressure at the time of compressing at least parts of the planned bending part at - 17 - the edges along the longitudinal direction of the Ushaped article in the planar direction, one of an extent enabling· suppression of the decrease of plate thickness at the edges along the longitudinal direction of the bent 5 part and increase of plate thickness at the bottom part is sufficient. It may be suitably adjusted in accordance vii th the shape of the shaped article, the shape ·of the pads of the bending-use second too'ling, the plate thickness or material of the metal plate, etc. 10 [0056] Applied Embodiment 2: Modification Relating to Shape of Tubular Shaped article The method of producing a shaped article of the Applied Embodiment 2 is a method of production improving ·the shape of the shaped article obtained in the basic 15 embodiment and Applied Embodiment 1. [0057] FIGS. 7A to 7F and FIGS. SA to SF are process diagrams shm1ing an example of the method of producing a shaped article of the Applied Embodiment 2. FIG. 7A is a top vie~<, FIG. 7B is a perspective vie1·1, FIG. 7C is a 20 front vie1'1, FIG. 70 is a left side vie~< of FIG. 7C, FIG. 7E is a right side vievl of FIG. 7C, and FIG. 7F is a top viev1 of FIG. 7C. Further, FIG. SA is a perspective vie~<, FIG. SB is a front view, FIG. SC is a front view, FIG. SO is a left side view of FIG. SC, FIG. BE is a right side 25 view of FIG. SC, and FIG. SF is a top view of FIG. SC. [0058] First, the metal plate la such as shown in FIG. 7A is prepared. [0059] Next, at a first step, as shown in FIG. 7B, first tooling for U-forming use is prepared. The first 30 tooling for U-forming use has a die 11 and punch 12. The bottom part lla of the recessed part of the die 11 and the bottom part 12a of the punch 12 both extend straight in the longitudinal direction. A metal plate la is placed bet1-1een the die 11 and punch 12 of the first tooling for 35 U-forming use, then the metal plate la is U-formed. Due to this, as shown in FIGS. 7C to 7F, a U-shaped article lb having a bottom part 2 extending straight in the - 18 - longitudinal direction x is obtained. [0060] Further, in the second step, as shmvn .. in FIGS. SA and SB, second tooling for bending use is prepared. The second tooling for bending use has a die 21, punch 5 22, and pads 23 arranged at the two side surfaces of the punch 22. The bottom part 21a of the recessed part of the die 21 is formed curved projecting in the longitudinal direction, 1·1hile the bottom part 22a of the punch 22 is formed curved recessed in the longitudinal direction. The 10 pads 23 compress the region to be the bent part 7 of the U-cross-section bent article of the edge 6 along the longitudinal direction x of the U-shaped article lb in the planar direction and can move up and down.· [0061] Next, as shmm in FIG. SB, the U-shaped article 15 lb is placed bet1o1een the die 21 and punch 22 of the second tooling for bending use and the U-shaped article lb is bent in the longitudinal direction x. At this time, the region to be the bent part 7 of the U-cross-section bent article of the edge 6 along the longitudinal 20 direction x of the U-shaped article lb is compressed in the planar direction. Due to this, as shovm in FIGS. 8C to SF, a U-cross-section bent article lc is obtained. The U-cross-section bent article lc has a bottom part 3 formed curved projecting inside in the longitudinal 25 direction. It has a bent part lOa 1vith a bottom part 3 projecting inside in the longitudinal direction, a straight part lOb having a bottom part 3 extending straight in the longitudinal direction and having an equal length of the U-cross-section along the centerline, 30 and a taper part lOc having and a bottom part 3 extending straight in the longitudinal direction and having a length of the U-cross-section increasing along the centerline. [0062] In the Applied Embodiment 2, in the same v1ay as 35 the Applied Embodiment 1, Hhen bending the U-shaped article at the second step to obtain the U-cross-section bent article, the U-shaped article is bent and at least - 19 - part of the planned bending part (region to be a bent part) of the above U-cross-section bent article is compressed in the planar direction. [0063] Due to the above, according to the method of 5 producing a shaped article shown in FIGS. 7 and FIGS. 8 (Applied Embodiment 2), in the same way as the Applied Embodiment 1, not only is there the effect exhibited by the basic embodiment of "suppressing the occurrence of shaping defects", in particular, at the secondstep, by 10 applying external force to at least parts of the planned bending part of the U-shaped article toward the outside of the bottom part of the U-shaped article, it is possible to suppress local changes in the plate thickness in the U-cross-section bent article, that is, decrease of 15 thickness. Further, by going through a third step in the same "'ay as the basic embodiment and Applied Embodiment 1, a desired tubular shaped article can be obtained. [0064] Here, the third step in the Applied Embodiment 2 will be explained in detail. That is, in the above 20 formed U-cross-section bent article (FIG. 8C to FIG. SF), further, as shown in FIG. 9, the U-cross-section bent article is shaped to a closed cross-section. [0065] FIG. 9A is a perspective vie•1, FIG. 98 is a front view, FIG. 9C is a front view, FIG. 9D is a left 25 side view of FIG. 9C, and FIG. 9E is a right side vie1·1 of FIG. 9C. [0066] At the third step, as shmm in FIGS. 9A and 98, third tooling for a-forming use is prepared. The third tooling for 0-forming use has a die 31 and punch 32, the 30 bottom part 31a of the recessed part of the die 31 is formed curved projecting in the longitudinal direction, the bottom part 32a of the recessed part of the punch 32 is formed curved recessed in the longitudinal direction, and both the recessed part of the die 31 and the recessed 35 part of the punch 32 have semicircular cross-sectional shapes. [0067] A U-cross-section bent article 1c is placed - 20 - between the die.31 and punch 32 of the third tooling for 0-forming use, and the U-cross~section bent article 1c is 0-formed. Due to this, as shown in FIGS. 9C to 9E, a tubular shaped article ld is obtained. The tubular shaped 5 article ld has a seam 4 formed curved projecting inside and has a bottom part 5 positioned at the opposite side from the seam 4 in the peripheral direction and formed curved projecting inside in the axial direction. It has a bent part lOa having a bottom part 5 projecting inside in 10 the axial direction, a straight part lOb having a bottom part 5 extending straight in the axial direction and having an equal length in the peripheral direction along the centerline; and a taper part lOc having a bottom part 5 extending straight in the axial direction and having a 15 length in the peripheral direction increasing alorig the centerline. [0068] Due to the basic embodiment and Applied Embodiments 1 and 2 shmm above, various shaped articles are obtained. That is, as the obtained shaped articles, 20 there are various shapes of tubular shaped articles obtained through various shapes of U-cross-section bent articles. These are suitably selected in accordance with the presence/absence of the third step, Helding step, etc. 25 [0069] Further, as the shape of the shaped article, for example, in the case of the tubular shaped article ld, a bent tube such as sho>m in FIGS. lOA and lOB having a cross-sectional shape in the peripheral direction of a circular shape and having a bent part lOa and straight 30 part lOb, a trumpet-shaped irregular diameter tube such as shoHn in FIG. lOC having a cross-sectional shape in the peripheral direction of a circular shape and having a bent part lOa, straight part lOb, and taper part lOc, a trumpet-shaped irregular diameter tube such as shmm in 35 FIG. lOD having a cross-sectional shape in the peripheral direction changing from a circular shape to a square shape and having a bent part lOa, straight part lOb, and - 21 - taper part lOc, a bent tube such as shown in FIG. lOE having a cross-sectional shape in the peripheral direction of a vertically asymmetrical shape and having a bent part lOa and straight part lOb, an irregular 5 diameter tube such as shm-m in FIG. lOF having pluralities of bent parts lOa, straight parts lOb, and taper parts lOc can be mentioned. [0070] B. Tooling The tooling according to the present invention is .for 10 bending a U-shaped article in the longitudinal direction so that the bottom part projects inside so as to obtain a U-cross-section bent article and is characterized by the provision of a die, a punch, and pads arranged at side surfaces of the above punch and compressing at least 15 parts of the planned bending part of the U-shaped article at the edged along the longitudinal direction of the Ushaped article in the planar direction. That is, the tooling according to the present invention is used in the second step of the method of producing a shaped article 20 in the above Applied Embodiments 1 and 2. [0071] FIGS. 6A and 6B show an example of tooling according to the present invention, while FIGS. BA and BB shov1 another example of tooling according to the present invention. As shm-m in FIGS. 6A and 6B (FIGS. BA and 88), 25 the tooling has a die 21, punch 22, and pads 23 arranged at the two side surfaces of the punch 22. The bottom part 21a of the recessed part of the die 21 is formed curved projecting in the longitudinal direction, v1hile the bottom part 22a of the punch 22 is formed curved recessed 30 in the longitudinal direction. The pads 23 compress at least parts of the planned bending part 7 of the U-shaped article at the edges 6 along the longitudinal direction x of the U-shaped article lb in the planar direction and can move up and do\•ln. 35 [0072] In the tooling according to the present invention, by having the above such predetermined pads, at the time of bending using the tooling, the pads can - 22 - compress at least parts of the planned bending part at the edges along the longitudinal direction of the Ushaped article in the planar direction. For this reason, in the U-cross-section bent article lc shown in FIG. 6E 5 and FIGS. 8C to SF, it is possible to suppress the decrease in plate thickness at the bent part lOa at the edges 8 along the longitudinal direction and the increase in plate thickness at the bottom part 3. Therefore, by using the tooling according to the present invention, it 10 is possible to suppress the occurrence of wrinkling at the bottom part of the bent part and fracture at the edges along the longitudinal direction to a high level. Not only that, it is possible to make the distribution of plate thickness at the U-cross-section. of the U-cross- 15 sect.ion bent article uniform. Due to this, by using the tooling according to the present invention, it is· possible to suitably enlarge the possible range of shaping of the bent article in the longitudinal direction of the U-cross-section bent article lc (number of types 20 of shapes and extent of complexity of parts which can be formed) compared with the past. Due to this, for example, even "'i th a U-cross-section bent article having a bent part with a relatively small radius of curvature or a Ucross- section bent article having a taper part, it is 25 possible to suppress the occurrence of wrinkling or fracture and in turn possible to suppress the occurrence of shaping defects at a high level. [0073] Below, the different components in the tooling according to the present invention will be explained. 30 [0074] 1. Pads The pads are arranged at the two side surfaces of the punch and compress at least parts of the planned bending part at the edges along the longitudinal direction of ushaped article in the planar direction. 35 [0075] The parts where the pads abut against the Ushaped article arc made at least parts of the planned bending part (that is, region to be a bent part in u- 23 - cross-section bent article) of the edges. along the longitudinal direction of the U-shaped article; If the planned bending part is too broad, even untargeted regions end up being compressed in the planar direction 5 and shaping defects are liable to occur. Further, if the planned bending part is too narrow, the reduction of plate thickness at the edges along the longitudinal direction of the bent part and increase of plate thickness at the bottom part could .not·be sufficiently 10 suppressed. Not only cannot shaping defects be suppressed to a high level, but also it becomes difficult to make the distribution of plate thickness of the U-crosssection uniform. [0076] The shapes of the parts of the pads abutting 15 against the shaped article need only be shapes enabling at least parts of the planned bending part at the edges along the longitudinal direction of the U-shaped article to be compressed in the planar direction. It is possible to suitably design them in accordance with the shapes 20 etc. of the U-shaped article. Along with the bending of the U-shaped article, the U-shaped article changes in shape and the edges along the longitudinal direction of the U-shaped article also change in shape. For this reason, for example, if assuming the shapes of the edges 25 along the longitudinal direction of the U-shaped article at the initial stage, middle stage, and later stage of bending, the shapes of the parts of the pads abutting against the U-shaped article are preferably shapes corresponding to the shapes of the edges along the 30 longitudinal direction of the U-shaped article at the initial stage or middle stage of bending. If the shapes of the parts of the pads abutting against the U-shaped article are shapes corresponding to the shapes .of the edges along the longitudinal direction of the shaped 35 articles at the later stage of bending, due to the pads, sometimes it becomes difficult to compress at least parts of the planned bending part of the edges along the - 24 - longitudinal direction of the U-shape-d article in the planar direction. [0077] Further, the pads may be divided into pluralities of blocks along the direction of advance of 5 the pads. In this case, by making the individual blocks forming the pads move up and dmIing equation ( 2) : Hl/H22':Ri/ (Ri+D) (2) (>Iherein in the above equation (2), Ri is the radius of curvature of the bottom part side of the bent part and D 25 is the width of the bent part of the cross-section including the seam and centerline of the tubular shaped article) [0084] FIGS. llA to llE are vie>Is sho>Iing one example of a tubular shaped article according to the present 30 invention, 11herein FIG. llA is a front view, FIG. llB is a left side view, FIG. llC is a right side view, FIG. llD is a top view, and FIG. llE is a cross-sectional view along the line C-C of FIG. llA. The tubular shaped article ld shmm in FIGS. llA to llE is comprised of a 35 metal plate. It has only one seam 4 extending in the axial direction and is comprised of a single metal plate formed into a tubular shape. The tubular shaped article - 26 - ld has a bent part lOa having a bottom part 5 positioned at the opposite side to the seam 4 in the peripheral direction projecting inside in the axial direction and a straight part lOb having a bottom part 5 extending 5 straight in the axial direction and having an equal length in the peripheral direction along the centerline S. Further, the ratio Hl/H2 of the plate thickness Hl at the seam 4 of the bent part lOa and the plate thickness H2 at the bottom part 5 of the bent part lOa is a 10 predetermined range. [OOBS] FIGS. 12A to 12E are views showing another example of a tubular shaped article according to the present invention, wherein FIG. 12A is a front vie1-1, FIG. 128 is a left side view, FIG. 12C is a right side view, 15 FIG. 120 is a top view, and FIG. 12e is a cross-sectional vie1-1 along the line C-C of FIG. 12A. The tubular shaped article ld shown in FIGS. 12A to 12E is comprised of a metal plate. It has only one seam 4 extending in the axial direction. A single metal plate is formed into a 20 tubular shape. The tubular shaped article ld has a bent part lOa having a bottom part 5 positioned at the opposite side to the seam 4 in the peripheral direction and projecting inside in the axial direction, a straight part lOb having a bottom part 5 extending straight in the 25 axial direction and having an equal length in the peripheral direction along the centerline s, and a taper part lOc having a bottom part 5 extending straight in the axial direction and increasing in length in the peripheral direction along the centerline s. There are 30 pluralities of the bent part lOa, straight part lOb, and taper part lOc. Further, in the bent part lOa, in any case, the ratio Hl/H2 of the plate thickness Hl at the seam 4 of the bent part lOa and the plate thickness H2 at the bottom part 5 of the bent part lOa is a predetermined 35 range. [0086] Here, when bending the U-shaped article, 1-1ith a tubular shaped article obtained 1-1ithout compressing the - 27 - planned bending part of the edge along the longitudinal direction of the U-shaped article at all in the planar ~direction, usually, Hl/H2 becomes less than Ri/(Ri+D) and the above equation (2) is not satisfied. This is because 5 in general, at the time of bending, at the seam of the bent part (outside of bending), a tensile stress acts, so the plate thickness easily decreases and at the bottom part of the bent part (inside of bending), compressive stress acts, so~the plate thickness easily increases. As 10 opposed to~ this, in a tubular shaped article according to the present invention, H1/H2 satisfies the above equation (2), so at the bent part, a uniform distribution of plate thickness can be obtained. Therefore, according to the tubular shaped article according to the present 15 invention, not only is it possible to suppress the occurrence of fractures at the seam and IYrinkling at the bottom part of the bent part to a high level and eliminate shaping defects, but also it is possible to make the distribution of plate thickness in the 20 peripheral direction uniform. [0087] BeloVI, the components of the tubular shaped article according to the present invention vlill be explained. [0088] 1. Seam 25 The tubular shaped article according to the present invention has only one seam extending in the axial direction. Here, the fact that the tubular shaped article has only one seam extending in the axial direction means that one metal plate is shaped into a tubular shape. 30 Therefore, a tubular shaped article obtained by shaping a metal plate in advance into a tubular shape to fabricate a plurality of tubular members and vlelding the tubular members not only has a plurality of seams in the longitudinal direction, but also has seams in the 35 peripheral direction, so is not included in a tubular shaped article according to the present invention. [0089] At the seam, the edges may be in close contact - 28 - with each other or may be separated. That is, there may be clearance in the seam. Further, the seam may also be vlelded. If the edges of the seam are separated, the degree of separation may be made a distance (shortest) 5 between the edges of 1 mm to 100% of the total length of the cross-sectional U-shape. [0090] When viewing the tubular shaped article so that the seam is positioned right above, the seam and centerline are preferably straight since there is 10 resistance to shaping defects, but these may also be slightly curved. [0091] Further, the tubular shaped article need only be one formed by shaping a single metal plate into a tubular shape. For example, it may be comprised of a 15 single tailored blank shaped into a tubular shape. [0092] 2. Bent Part The bent part is a part l·lith a bottom part positioned at the opposite side from the above seam in the peripheral direction and projecting to the inside in the axial 20 direction. Here, the bottom part of the tubular shaped article means a part positioned at the opposite side from the seam at the cross-section including the seam and centerline. The tubular shaped article may have a single bent part or may have several. 25 [0093] The ratio H1/H2 of the plate thickness H1 at the seam of the bent part and the plate thickness H2 at the bottom part of the bent part satisfies the follovling equation (3): H1/H2~Ri/ (Ri+D) ( 3) 30 {where in the above equation (3), Ri is the radius of curvature at the bottom part side of the bent part, Hhile D is the Hidth of the bent part of a cross-section including the seam and centerline of the tubular shaped article) 35 [0094] The plate thickness Hl at the seam of the bent part and the plate thickness H2 at the bottom part of the bent part may be distributed in the longitudinal 5 - 29 - direction or peripheral direction, but preferably. is uniform in the longitudinal direction or peripheral direction. Here, the plate thickness Hl at the seam of the bent part is made a plate thickness of the seam at the center of bending in the longitudinal direction of the tubular shaped article. Similarly, the plate thickness H2 at the bottom part of the bent part is made the plate thickness of the bottom part at the center of bending in the longitudinal direction .of the tubular 10 shaped article. [0095] Further, in the cross-section including the seam and centerline of the tubular shaped article, the vlidth D of the bent part (for example, see FIG. 11) ·is made the width at the center of bending. Similarly, the 15 radius of curvature Ri at the bottom part si'de of the bent part (for example, see same figure) is made the radius of curvature of the intersection between the bottom part of the bent part and the plane including the seam and bending centerline. 20 [0096] Next, the rate of reduction of plate thickness T of the seam of the bent part preferably satisfies the following equation (4): Tlard the outside of the bottom part of said U-shaped article. Claim 4. The method of producing a shaped article 25 according to any one of claims 1 to 3 further comprising a third step of shaping said U-cross-section bent article into a closed cross-section to obtain a tubular shaped article. Claim 5. A tooling for bending a U-shaped article in 30 a longitudinal direction so that the bottom part projects to an inside and for obtaining a U-cross-section bent article, said tooling provided with a die, a punch, and 35 pads arranged at side surfaces of said punch and compressing, in in-plane directions, at least parts of a planned bending part of said U-shaped article in - 39 - edges along the longitudinal direction of said U-shaped article. Claim 6. A tubular shaped article comprised of a metal plate and including only one seam extending in an 5 axial direction, wherein a bottom part positioned at an opposite side to said seam in a peripheral direction includes a bent part projecting to an inside in an axial direction, and a ratio H1/H2 of a plate thickness· Hl .0f said 10 bent article at said seam and a plate thickness H2 of said bent article at said bottom part satisfies a folloHing equation (1}: H1/H2?Ri/ (Ri+D} (1} .(wherein in said equation (1}, Ri is a radius 15 ·of curvature of a bottom part side of the bent part, and D is a width of the bent part at a cross-section including a seam and a centerline of the tubular shaped article}.