Patent Publication Number: US-2021180377-A1

Title: Method for producing structure

Description:
TECHNICAL FIELD 
     The present invention relates to a structure body having a resin molded body (resin panel for example) which can be used as a bath lid or as a floor board installed in a luggage compartment of a vehicle. 
     BACKGROUND 
     Patent Literature 1 discloses a resin molded body having a hinge portion. 
     CITATION LIST 
     Patent Literature 
     
         
         [Patent Literature 1] JP 2013-067148A 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     When the resin molded body of Patent Literature 1 is bent at its hinge portion, a folded line is formed at the hinge portion. When the resin constituting the resin molded body does not contain inorganic fiber, the folded line would be formed linearly as shown in  FIG. 15A , and thus no problem would occur with the external appearance. On the other hand, when the resin constituting the resin molded body contains inorganic fiber, the folded line formed would meander as shown in  FIG. 15B , thereby deteriorating the external appearance. 
     The present invention has been made by taking the afore-mentioned circumstances into consideration. The present invention provides a structure body having a resin molded body which can suppress deterioration of external appearance due to meander of the folded line formed in the hinge portion even when the resin constituting the resin molded body contains inorganic fiber. 
     Solution to Problem 
     According to the present invention, a structure body having a resin molded body; the resin molded body comprising: a first main body portion and a second main body portion; and a hinge portion; wherein the first main body portion and the second main body portion are connected at the hinge portion with each other so as to be rotatable with respect to each other; the hinge portion comprises a first thin portion, a second thin portion, and a thick portion; the thick portion is a portion being larger in thickness than the first thin portion and the second thin portion; the first thin portion, the second thin portion, and the thick portion elongate in a longitudinal direction of the hinge portion; and the thick portion is sandwiched by the first thin portion and the second thin portion in a width direction of the hinge portion, is provided. 
     In the hinge portion of the resin molded body, a thick portion is sandwiched by a first and second thin portion, and the hinge portion is ben at the thin portion, easily forming a folded line. Since the width of the thin portion is smaller than the width of the entire hinge portion, the folded line formed in the thin portion would not be prominent even if it is meandered. Therefore, according to the present invention, deterioration of the external appearance due to meander of the folded line formed in the hinge portion can be suppressed. 
     Hereinafter, various embodiments of the present invention will be described. The embodiments described hereinafter can be combined with each other. 
     Preferably, the thick portion does not reach an end portion of the hinge portion in a longitudinal direction of the hinge portion. 
     Preferably, a width of the hinge portion decreases towards the end portion of the hinge portion in the longitudinal direction of the hinge portion, in a vicinity of the hinge portion in the longitudinal direction of the hinge portion. 
     Preferably, at least one of thickness or width of the thick portion becomes gradually smaller towards the end portion of the hinge portion in the longitudinal direction in a vicinity of an end portion in a longitudinal direction of the thick portion. 
     Preferably, when a width of the hinge portion at a portion in which the width of the hinge portion is constant and a width of the thick portion at the portion in which the width of the hinge portion is constant are taken as Wh and Wc, respectively, relation of Wc/Wh=0.2 to 0.8 is satisfied. 
     Preferably, a thickness of the thick portion decreases gradually towards an end of a width direction of the thick portion. 
     Preferably, the structure body further comprises: an outer surface material provided so as to extend over the first main body portion, the hinge portion, and the second main body portion; wherein: the outer surface material is integrally molded with the resin molded body. 
     Preferably, the resin molded body contains inorganic fiber; and the inorganic fiber is orientated in a direction not parallel with a longitudinal direction of the hinge portion. 
     According to another aspect of the present invention, a method for manufacturing a structure body mentioned above, comprising the steps of: an extruding step, a shaping step, and a clamping step; wherein: in the extruding step, a first resin sheet and a second resin sheet are extruded in between a first mold and a second mold; each of the first mold and the second mold is provided with a cavity; in the shaping step, the first resin sheet and the second resin sheet are shaped along an inner surface of the cavity of the first mold and the second mold; in the clamping step, the first mold and the second mold are clamped; the first resin sheet and the second resin sheet contain inorganic fiber; at least one of the first mold and the second mold is provided with a protrusion to form the hinge portion; and a longitudinal direction of the protrusion is not parallel with an extrusion direction of the first resin sheet and the second resin sheet, is provided. 
     Preferably, the longitudinal direction of the protrusion is orthogonal with the extrusion direction of the first resin sheet and the second resin sheet. 
     According to another aspect of the present invention, a method for manufacturing a structure body mentioned above, comprising the steps of: an extruding step, a shaping step, and a clamping step; wherein: in the extruding step, a first resin sheet and a second resin sheet are extruded in between a first mold and a second mold; each of the first mold and the second mold is provided with a cavity; in the shaping step, the first resin sheet and the second resin sheet are shaped along an inner surface of the cavity of the first mold and the second mold in a condition where an outer surface material is arranged in between the first resin sheet and the first mold; in the clamping step, the first mold and the second mold are clamped; the second mold is provided with a protrusion to form the hinge portion; and a groove facing the thick portion is provided at a tip of the protrusion, is provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of the structure body according to the first embodiment of the present invention. 
         FIG. 2  shows an enlarged view of region A in  FIG. 1 . 
         FIG. 3  shows a cross-sectional view cut at the center in a longitudinal direction of the hinge portion  5  of  FIG. 1 . 
         FIG. 4  shows an enlarged view of region B in  FIG. 3 . 
         FIG. 5  shows an enlarged view of region C in  FIG. 3 . 
         FIG. 6  shows a cross-sectional view of the same cross-section as  FIG. 3 , in a condition where the main body portions  2   a  and  2   b  are bent at the hinge portion  5 . 
         FIG. 7A  shows an enlarged view of region D in  FIG. 6 , in a condition where the thin portions  5   a  and  5   b  are bent evenly. 
         FIG. 7B  shows an enlarged view of region D in  FIG. 6 , in a condition where the thin portions  5   a  and  5   b  are bent unevenly. 
         FIG. 8  shows an enlarged view of a cross-section of a vicinity of the hinge portion  5  crossing the thin portion  5   e , at a vicinity of the end portion  5   d  in the longitudinal direction of the hinge portion  5 . 
         FIG. 9  shows a structural diagram (a longitudinal cross-sectional view with respect to molds  21  and  31 , and components in the vicinity thereof) of a molding machine  10  which can be used for manufacturing a structure body according to the first embodiment of the present invention. 
         FIG. 10  shows a cross-sectional view in which resin sheets  23  and  33  are extruded in between the molds  21  and  31 . 
         FIG. 11  shows a cross-sectional view in which the resin sheets  23  and  33  are shaped along the inner surface of the cavity of molds  21  and  31 , from the condition shown in  FIG. 10 . 
         FIG. 12  shows a cross-sectional view in which an insert component  7  is adhered onto the resin sheet  23  from the condition shown in  FIG. 11 . 
         FIG. 13  shows a cross-sectional view in which the molds  21  and  31  are clamped from the condition shown in  FIG. 12 . 
         FIG. 14  shows a picture of a resin molded body  1  having glass fibers aligned in a direction orthogonal with the longitudinal direction of the hinge portion  5 , the width of each of the thin portions  5   a  and  5   b  being 1 mm, the width of the thick portion  5   c  being 2 mm, wherein the resin molded body  1  is being bent at the hinge portion  5 . 
         FIG. 15A  shows a picture of a resin molded body containing no inorganic fiber, the width of the hinge portion being 4 mm, wherein the resin molded body is being bent at the hinge portion. 
         FIG. 15B  shows a picture of a resin molded body having glass fiber aligned in a direction orthogonal with the longitudinal direction of the hinge portion, the width of the hinge portion being 4 mm, wherein the resin molded body is being bent at the hinge portion. 
         FIG. 16  shows a perspective view of a structure body  100  according to the second embodiment of the present invention, corresponding to  FIG. 4 . 
         FIG. 17A  shows a picture in which the structure body  100  according to the present embodiment is observed from the outer surface material  8  side. 
         FIG. 17B  shows a picture in which a conventional structure body  100  is observed from the outer surface material  8  side. 
         FIG. 18A  to  FIG. 18D  show a cross-sectional view of the manufacturing process of the structure body  100  of  FIG. 16 . 
         FIG. 18A  corresponds to  FIG. 11  and  FIG. 18B  corresponds to  FIG. 13 ,  FIG. 18C  shows the structure body  100  taken out from the molds  21  and  31 , and  FIG. 18D  shows an enlarged view of region D in  FIG. 18C . The insert component  7  is omitted in  FIG. 18A  to  FIG. 18D . 
         FIG. 19A  to  FIG. 19D  show a cross-sectional view of the manufacturing process of a conventional structure body  100 . 
         FIG. 19A  corresponds to  FIG. 11  and  FIG. 19B  corresponds to  FIG. 13 ,  FIG. 19C  shows the structure body  100  taken out from the molds  21  and  31 , and  FIG. 19D  shows an enlarged view of region D in  FIG. 19C . The insert component  7  is omitted in  FIG. 19A  to  FIG. 19D . 
         FIG. 20  shows a figure corresponding to  FIG. 5  of an alternative example of the first embodiment. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, various embodiments of the present invention will be described. 
     Various distinctive features shown in the following embodiments can be combined with each other. In addition, an invention can be established independently for each of the distinctive features. 
     1. FIRST EMBODIMENT 
     1-1. Structure of Structure Body 
     As shown in  FIG. 1  and  FIG. 2 , the structure body according to the first embodiment of the present invention has a resin molded body  1 . The resin molded body  1  comprises a first and second main body portions  2   a  and  2   b , and a hinge portion  5 . The main body portions  2   a  and  2   b  are connected at the hinge portion  5  with each other so as to be rotatable with respect to each other. 
     In the present embodiment, the resin molded body  1  is a resin panel, and the main body portions  2   a  and  2   b  are molded bodies having a panel shape. 
     The resin molded body  1  comprises a front wall  3  and a back wall  4 . The front wall  3  and the back wall  4  face each other with a gap. The surroundings of the front wall  3  and the back wall  4  are connected by a surrounding wall  6 . 
     As shown in  FIG. 3  and  FIG. 4 , the insert component  7  is provided in between the front wall  3  and the back wall  4 . The insert component  7  is a component arranged for the purpose of providing a space in between the front wall  3  and the back wall  4 , and for improving strength and heat resistance of the resin molded body  1 . Preferably, the insert component  7  is constituted with a foam body. 
     The hinge portion  5  comprises a first and second thin portions  5   a  and  5   b , and a thick portion Sc. The thick portion  5   c  is a portion having a larger thickness than the thin portions  5   a  and  5   b . The thin portions  5   a  and  5   b  and the thick portion  5   c  have an elongated shape, and elongates along the longitudinal direction of the hinge portion  5 . The thick portion  5   c  is sandwiched by the thin portions  5   a  and  5   b  in the width direction of the hinge portion  5 . 
     As shown in  FIG. 4  and  FIG. 7 , the thick portion  5   c  has an approximately triangle-shaped cross-section. The thickness of the thick portion  5   c  decreases gradually towards the end of the thick portion  5   c  in the width direction. Accordingly, the thick portion  5   c  is connected with the thin portions  5   a  and  5   b  smoothly. 
     The thickness of the thin portions  5   a  and  5   b  is, for example, 0.001 to 0.5 mm, and is specifically for example, 0.001, 0.01, 0.1, 0.2, 0.3, 0.4, or 0.5, and can be in the range between the two values exemplified herein. The thickness of the thickest portion of the thick portion  5   c  is 0.1 to 3 mm, and is specifically for example, 0.1, 0.5, 1, 1.5, 2, or 3 mm, and can be in the range between the two values exemplified herein. 
     The thickness of the thin portions  5   a  and  5   b  is smaller than the thickness of the thick portion  5   c . Therefore, when the main body portions  2   a  and  2   b  are bent at the hinge portion  5 , as shown in  FIG. 7A , the thin portions  5   a  and  5   b  tend to be bent selectively. The width of the thin portions  5   a  and  5   b  are smaller than the entirety of the hinge portion  5 . Therefore, even when the folded line formed in the thin portions  5   a  and  5   b  is meandered, it would not be prominent. Thus, according to the present embodiment, deterioration of the external appearance due to meander of the folded line formed in the hinge portion  5  is suppressed. 
     For example, in the conventional technique, where the width of the entirety of the hinge portion  5  is 4 mm and the thickness of the hinge portion  5  is uniform, the folded line would meander throughout the width of 4 mm, resulting in large amplitude. Accordingly, as shown in  FIG. 15B , the meander of the folded line would be prominent. On the other hand, in the present embodiment having a constitution in which the thick portion  5   c  is sandwiched by the thin portions  5   a  and  5   b , the width of each of the thin portions  5   a  and  5   b  being 1 mm and the width of the thick portion  5   c  being 2 mm, the folded line would be formed in each of the thin portions  5   a  and  5   b . Therefore, the meandering range of each of the folded line would be restricted within 1 mm. Accordingly, the amplitude of the meander would be reduced largely compared with the conventional technique, and thus the meander of the folded line would not be prominent as shown in  FIG. 14 . Therefore, deterioration of external appearance due to meander of the folded line would be suppressed. 
     Here, when the main body portions  2   a  and  2   b  are bent at the hinge portion  5 , the thin portions  5   a  and  5   b  are not always bent uniformly, and the thin portions  5   a  and  5   b  can be bent ununiformly as shown in  FIG. 7B . In the case shown in  FIG. 7B , the radius of curvature of the thin portion  5   b  is significantly smaller than the radius of curvature of the thin portion  5   a . In such case, cracks easily occur at the thin portion  5   b , which can be problematic. 
     In order to prevent such cracks, in the present embodiment, as shown in  FIG. 2  and  FIG. 5 , the thick portion  5   c  is provided so as not to reach the end portion  5   d  of the hinge portion  5  in the longitudinal direction. Accordingly, the thick portion  5   c  do not exist in the vicinity of the end portion  5   d , and only one thin portion Se is provided. When the main body portions  2   a  and  2   b  are bent at the hinge portion  5 , they would provide a condition shown in  FIG. 8 . Since cracks of the thin portion tend to occur at the end portion  5   d , by preventing the thin portion from being divided by the thick portion at the end portion  5   d , occurrence of cracks at the thin portion can be suppressed. 
     On the other hand, when the thick portion is not provided in the vicinity of the end portion  5   d , the meander of the folded line in the vicinity of the end portion  5   d  would become prominent, which can be problematic. Accordingly, in order to alleviate the influence of such problem, in the present embodiment, as shown in  FIG. 2  and  FIG. 5 , the width of the hinge portion  5  decreases towards the end portion  5   d  in the vicinity of the end portion  5   d . Here, when the width of the hinge portion  5  is made small in the vicinity of the end portion  5   d , the meander would be less prominent, however, the radius of curvature when bent at the hinge portion  5  would become small, thereby raising the possibility of cracks at the hinge portion  5 . When secure prevention of cracks at the hinge portion  5  is given priority, it is preferable not to make the width of the hinge portion  5  small in the vicinity of the end portion  5   d . For example, as shown in  FIG. 20 , the width of the hinge portion  5  is made the same as the width of the entirety of the hinge portion  5  at the portion where the thick portion  5   c  is provided, even in the vicinity of the end portion  5   d.    
     When the width of the hinge portion  5  at the portion in which the width of the hinge portion  5  is constant (herein after referred to as “constant width portion”) is taken as Wh, and the width of the hinge portion  5  at the end portion  5   d  is taken as We, relation of We/Wh=0.2 to 0.8 is preferably satisfied. When this value is too large, the meander of the folded line tends to become prominent. When this value it too small, it becomes difficult to bend at the hinge portion  5 . The value of We/Wh is, specifically for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8, and can be in the range between the two values exemplified herein. 
     In addition, when the width of the thick portion  5   c  at the constant width portion is taken as Wc, relation of Wc/Wh=0.2 to 0.8 is preferably satisfied. When this value is too large, the width of the thin portions  5   a  and  5   b  would be too small, and thus it becomes difficult to bend at the hinge portion  5 . When this value is too small, the width of the thin portions  5   a  and  5   b  would be too large, and thus the meander of the folded line tends to become prominent. The value of Wc/Wh is, specifically for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8, and can be in the range between the two values exemplified herein. 
     Wh is, for example, 2 to 10 mm, preferably 3 to 6 mm. When this value is too large, the hinge portion  5  would become too prominent, thereby deteriorating the external appearance. When this value is too small, it becomes difficult to bend at the hinge portion  5 . Wh is, specifically for example, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mm, and can be in the range between the two values exemplified herein. 
     The distance L from the end portion  5   d  to the constant width portion is, for example, 5 to 30 mm, and is specifically for example, 5, 10, 15, 20, 25, or 30 mm, and can be in the range between the two values exemplified herein. When this value is too large, the meander of the folded line tends to become prominent. When this value is too small, it becomes difficult to bend at the hinge portion  5 . The distance Lc from the end portion  5   d  from the end portion  5   c   1  of the thick portion in the longitudinal direction is, for example, 3 to 15 mm, specifically for example, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 mm, and can be in the range between the two values exemplified herein. When this value is too large, the meander of the folded line tends to become prominent. When this value is too small, cracks of the hinge portion  5  tend to occur at the end portion  5   d.    
     At least one of the thickness or the width of the thick portion  5   c  becomes gradually smaller towards the end portion  5   d  in the vicinity of the end portion  5   c   1  in the longitudinal direction of the thick portion  5   c . With such constitution, the thick portion  5   c  fades smoothly at the vicinity of the end portion  5   d.    
     The length of the section (gradually changing section) V in which at least one of the thickness or the width of the thick portion  5   c  becomes gradually smaller is, for example, 3 to 25 mm, and is specifically for example, 3, 5, 10, 15, 20, or 25 mm, and can be in the range between the two values exemplified herein. When this value is too large, the meander of the folded line tends to become prominent. When this value is too small, cracks tend to occur at the boundary of the thick portion  5   c  and the thin portion  5   e.    
     The resin molded body  1  preferably contains inorganic fiber. In addition, the inorganic fiber is preferably orientated in a direction not parallel with the longitudinal direction of the hinge portion  5 , and is further preferably orientated in a direction orthogonal with the longitudinal direction of the hinge portion  5 . The meander of the folded line is especially prominent in such case, and thus technical significance of adopting the constitution of the present invention is especially large. As the inorganic fiber, glass fiber and carbon fiber can be mentioned. The phrase “inorganic fiber is orientated” refers to a condition in which a plurality of inorganic fiber are oriented in approximately the same direction. For example, when the resin molded body  1  is formed by using a resin sheet formed by extruding a molten resin containing the inorganic fiber, a plurality of inorganic fiber would be orientated approximately in the extrusion direction of the resin sheet. Accordingly, the extrusion direction of the resin sheet would be the orientation direction of the inorganic fiber. Content of inorganic fiber in the resin molded body  1  is preferably 1 to 40 mass %, more preferably 5 to 30 mass %, and further preferably 10 to 25 mass %. The content is, specifically for example, 1, 5, 10, 15, 20, 25, 30, 35, or 40 mass %, and can be in the range between the two values exemplified herein. When the content is too small, rigidity of the resin molded body  1  would be insufficient, and when the content is too large, the moldability of the resin molded body  1  would deteriorate and the resin molded body  1  would be cracked easily. 
     1-2. Molding Machine  10   
     Next, referring to  FIG. 9  and  FIG. 10 , the molding machine  10  which can be used in implementation of the manufacturing method of the structure body according to the first embodiment of the present invention will be explained. The molding machine  10  comprises a pair of resin sheet forming machine  20 , and a first and second molds  21  and  31 . Each of the resin sheet forming machine  20  comprises a hopper  12 , an extruder  13 , an accumulator  17 , and a T-die  18 . The extruder  13  and the accumulator  17  are connected via a connecting tube  25 . The accumulator  17  and the T-die  18  are connected via a connecting tube  27 . 
     Hereinafter, each of the constitution will be explained in detail. 
     &lt;Hopper  12 , Extruder  13 &gt; 
     The hopper  12  is used for charging a raw material resin  11  into the cylinder  13   a  of the extruder  13 . The form of the raw material resin  11  is not particularly limited, however, it is usually in a pellet form. The raw material resin is a thermoplastic resin such as polyolefin for example. As the polyolefin, low density polyethylene, straight chain low density polyethylene, high density polyethylene, polypropylene, ethylene-propylene copolymer, and mixtures thereof can be mentioned. The raw material resin  11  is charged into the cylinder  13   a  from the hopper  12 , and is heated in the cylinder  13   a , thereby being melt to a molten resin. Then, by the rotation of the screw arranged in the cylinder  13   a , the molten resin is transferred towards the tip of the cylinder  13   a . The screw is arranged in the cylinder  13   a , and its rotation kneads and transfers the molten resin. At the rear anchor of the screw, a gear device is provided, and the screw is rotated by the gear device. 
     When the inorganic fiber is contained in the resin sheets  23  and  33 , the inorganic fiber is preferably contained in the raw material resin. 
     &lt;Accumulator  17 , T-Die  18 &gt; 
     The molten resin is extruded from the resin extruding outlet of the cylinder  13   a , and is injected into the accumulator  17  via the connecting tube  25 . The accumulator  17  is provided with a cylinder  17   a  and a piston  17   b  which is slidable within the cylinder  17   a . The molten resin can be stored in the cylinder  17   a . By moving the piston  17   b  after a predetermined amount of the molten resin is stored in the cylinder  17   a , the molten resin is extruded from the slit provided in the T-die  18  via the connecting tube  27 , thereby forming the first and second resin sheets  23  and  33  in a molten condition. When the inorganic fiber is contained in the raw material resin the inorganic fiber is orientated in the extrusion direction of the resin sheets  23  and  33 . 
     &lt;Molds  21  and  31 &gt; 
     The resin sheets  23  and  33  are extruded in between the molds  21  and  31 . As shown in  FIG. 10 , the molds  21  and  31  have cavities  21   a  and  31   a , and pinch off portions  21   b  and  31   b  are provided so as to surround the cavities  21   a  and  31   a , respectively. In the cavities  21   a  and  31   a , reduced pressure suction holes (not shown) are provided, and the resin sheets  23  and  33  are suctioned by reduced pressure via the reduced pressure suction holes, thereby being shaped into a shape following the inner surface of the cavities  21   a  and  31   a  of the molds  21  and  31 . The reduced pressure suction holes are minute holes, and one end thereof is communicated with the inner surface of the cavities  21   a  and  31   a  by penetrating through the molds  21  and  31 , and the other end thereof is connected to the pressure reducing device. 
     The mold  31  is provided with a protrusion  31   c  for forming the hinge portion  5 . The protrusion  31   c  is an elongated protrusion, and the longitudinal direction of the protrusion  31   c  is preferably not parallel with the extrusion direction of the resin sheets  23  and  33 . The longitudinal direction of the protrusion  31   c  is preferably orthogonal with the extrusion direction of the resin sheets  23  and  33 . In such case, the change in the thickness of the resin sheets  23  and  33  along the longitudinal direction of the hinge portion  5  is suppressed. As shown in  FIG. 10 , at the tip of the protrusion  31   c , a tip surface  31   c   1  corresponding to the thin portions  5   a  and  5   b , and a groove  31   c   2  corresponding to the thick portion  5   c  are provided. 
     1-3. Manufacturing Method of Structure Body 
     Here, referring to  FIG. 9  to  FIG. 13 , the manufacturing method of the structure body according to the first embodiment of the present invention will be explained. The method of the present embodiment comprises an extruding step, a shaping step, an inserting step, and a clamping step. Hereinafter, detailed explanation will be provided. 
     (1) Extruding Step 
     In the extruding step, as shown in  FIG. 9  and  FIG. 10 , the resin sheets  23  and  33  are extruded in between the molds  21  and  31 . 
     (2) Shaping Step 
     In the shaping step, as shown in  FIG. 10  and  FIG. 11 , the resin sheets  23  and  33  are subjected to reduced pressure suction by the molds  21  and  31 , thereby shaping the resin sheets  23  and  33  into a shape following the inner surface of the cavities  21   a  and  31   a . In the present embodiment, other component such as outer surface material is not arranged in between the resin sheet  23  and the mold  21 , and in between the resin sheet  33  and the mold  31 . Accordingly, each of the resin sheets  23  and  33  is shaped so as to come directly into contact with the molds  21  and  31 , respectively. Here, the outer surface material can be integrally molded on the resin sheet  23  side. In such case, the resin sheet  23  is shaped in a condition where the outer surface material is arranged in between the mold  21  and the resin sheet  23 . 
     (3) Inserting Step 
     In the inserting step, as shown in  FIG. 11  and  FIG. 12 , the insert component  7  is welded on the resin sheet  23 . When the insert component  7  is constituted with a foam body, the foam body melts by the heat of the resin sheet  23 , and thus one surface  7   d  of the insert component  7  is welded on the resin sheet  23 . The other surface  7   e  of the insert component  7  is welded on the resin sheet  33  when clamping shown in  FIG. 13  is performed. The insert component  7  is constituted by connecting the first and second main body portions  7   a  and  7   b  with the connecting portion  7   c . The main body portions  7   a  and  7   b  are each housed in the main body portions  2   a  and  2   b  of the resin molded body  1 , respectively. The connecting portion  7   c  corresponds to the hinge portion  5 . The connecting portion  7   c  can be omitted, and in such case, two insert components corresponding to each of the main body portions  7   a  and  7   b  can be inserted. 
     (4) Clamping Step 
     In the clamping step, as shown in  FIG. 12  and  FIG. 13 , the molds  21  and  31  are subjected to clamping. Accordingly, the resin sheets  23  and  33  are welded with each other along the pinch off portions  21   b  and  31   b , thereby obtaining a resin molded body  1  having a shape following the inner surface of the cavity formed by a pair of molds  21  and  31 . In between the protrusion  31   c  and the mold  21 , the resin sheets  23  and  33  and the connecting portion  7   c  are compressed to form the hinge portion  5 . The portion compressed by the tip surface  31   c   1  of the protrusion  31   c  would be the thin portions  5   a  and  5   b , and the portion facing the groove  31   c   2  would be the thick portion  5   c . The outer side of the pinch off portions  21   b  and  31   b  would be burr  41 . Thereafter, the molds  21  and  31  are opened to take out the resin molded body  1 , followed by removal of the burr  41 , thereby obtaining the structure body having the resin molded body  1  shown in  FIG. 1 . The tip surface  31   c   1  can be a planar surface of a curved surface. 
     2. SECOND EMBODIMENT 
     The second embodiment of the present invention will be explained with reference to  FIG. 16  to  FIG. 19 . The present embodiment is similar to the first embodiment, and the major difference is that the structure body  100  is constituted with the resin molded body  1  and the outer surface material  8 . Hereinafter, such difference will be mainly explained. 
     The hinge portion  5  is formed by denting the back wall  4  side of the resin molded body  1 . The thick portion  5   c  is protruded towards the back wall  4  side, thereby allowing to have a larger thickness than the thin portions  5   a  and  5   b . The hinge portion  5  has a flat surface at the front wall  3  side. At the front wall  3  side of the resin molded body  1 , a flat surface is provided so as to extend over the main body portion  2   a , the hinge portion  5 , and the main body portion  2   b.    
     The outer surface material  8  is provided on the front wall  3  side of the resin molded body  1 , so as to extend over the main body portion  2   a , the hinge portion  5 , and the main body portion  2   b . The outer surface material  8  is preferably constituted with a carpet-like component having air permeability like a non-woven cloth, and is preferably integrally molded with the resin molded body  1  when the resin molded body  1  is molded. Accordingly, the structure body  100  having the resin molded body  1  and the outer surface material molded integrally is obtained. 
     Here, as in the present embodiment, when the hinge portion  5  is constituted with the thin portions  5   a  and  5   b , and with the thick portion  5   c  between thereof, as shown in  FIG. 17A , the external appearance of the portion  8   a  which face the hinge portion  5  hardly differs from the other portions of the outer surface material  8 . On the other hand, in the conventional case where the hinge portion  5  is constituted with only the thin portion, as shown in  FIG. 17B , the portion  8   a  which face the hinge portion  5  shines, thereby deteriorating the external appearance of the outer surface material  8 . 
     As described, according to the present embodiment, an effect of improving the external appearance of the portion  8   a  which face the hinge portion  5  can be achieved. 
     The principle of achieving such effect with be explained with reference to  FIG. 18A  to  FIG. 18D  and  FIG. 19A  to  FIG. 19D .  FIG. 18A  to  FIG. 18D  are related to the present embodiment in which the tip surface  31   c   1  and the groove  31   c   2  are provided on the tip of the protrusion  31   c  of the mold  31 , and  FIG. 19A  to  FIG. 19D  are related to a conventional technique in which the groove  31   c   2  is not provided. Here, a case where the outer surface material  8  is a carpet-like component like a non-woven cloth is explained for example. 
       FIG. 18A  and  FIG. 19A  correspond to the condition shown in  FIG. 11 . The resin sheet  23  is shaped along the inner surface of the cavity of the mold  21  in a condition where the outer surface material  8  is arranged in between the mold  21  and the resin sheet  23 . As shown in  FIG. 18A  and  FIG. 19A , in a condition where the molds  21  and  31  are spaced, the outer surface material  8  is not compressed. 
     As shown in  FIG. 18B  and  FIG. 19B , when the molds  21  and  31  are closed, the tip surface  31   c   1  of the protrusion  31   c  of the mold  31  comes substantially in contact with the inner surface of the mold  21 . In this condition, the entirety of the outer surface material  8  is compressed, and the portion sandwiched by the tip surface  31   c   1  of the protrusion  31   c  and the mold  21  is especially strongly compressed. In addition, in this portion, the resin of the resin sheets  23  and  33  are also compressed, and are impregnated into the outer surface material  8 . As shown in  FIG. 18B , when there is a groove  31   c   2  at the tip of the protrusion  31   c , the outer surface material  8  is hardly compressed at the portion facing the groove  31   c   2 , and the resin is hardly impregnated into the outer surface material  8 . 
     The structure body  100  taken out from the molds  21  and  31  after cooling the resin is shown in  FIG. 18C  and  FIG. 18D , and in  FIG. 19C  and  FIG. 19D . In both structure body  100 , the outer surface material  8  at the portion other than the hinge portion  5  is returned to an uncompressed condition. 
     In the conventional structure body  100  shown in  FIG. 19D , the outer surface material  8  is kept compressed in the entirety of the portion  8   a  facing the hinge portion  5 . The reason for such phenomena is that since the molten resin is impregnated into the entirety of the portion  8   a , the molten resin would solidify in such condition. In addition, since the outer surface material  8  is compressed in such a large area, in the conventional structure body  100 , as shown in  FIG. 17B , the portion  8   a  shines, thereby deteriorating the external appearance. 
     On the other hand, in the structure body  100  according to the present embodiment shown in  FIG. 18D , the portion facing the thin portions  5   a  and  5   b  among the portion  8   a  facing the hinge portion  5  are kept compressed as in the case of the conventional structure body  100 , however, the portion facing the thick portion  5   c  has low degree of compression of the outer surface material  8  and a low degree of resin impregnation, and thus when the structure body  100  is taken out of the molds  21  and  31 , the outer surface material  8  would substantially recover its original condition. Accordingly, in the structure body  100  according to the present embodiment, the region in which the outer surface material  8  is compressed would have a smaller width compared with the case of the conventional structure body  100 , and thus the portion  8   a  would be less prominent as shown in  FIG. 17A . 
     3. OTHER EMBODIMENT 
     The insert component  7  can be omitted. 
     The resin molded body  1  can be constituted with one foam resin sheet or non-foam resin sheet. 
     EXPLANATION OF SYMBOLS 
     
         
           1 : resin molded body,  2   a : first main body portion,  2   b : second main body portion,  3 : front wall,  4 : back wall,  5 : hinge portion,  5   a : first thin portion,  5   b : second thin portion,  5   c : thick portion,  5   c   1 : end portion,  5   d : end portion,  5   e : thin portion,  6 : surrounding wall,  7 : insert component,  7   a : first main body portion,  7   b : second main body portion,  7   c : connecting portion,  7   d : one surface,  7   e : other surface,  8 : outer surface material,  8   a : portion,  10 : molding machine,  11 : raw material resin,  12 : hopper,  13 : extruder,  13   a : cylinder,  17 : accumulator,  17   a : cylinder,  17   b : piston,  18 : T-die,  20 : resin sheet forming machine,  21 : first mold,  21   a : cavity,  21   b : pinch off portion,  23 : first resin sheet,  25 : connecting tube,  27 : connecting tube,  31 : second mold,  31   a : cavity,  31   b : pinch off portion,  31   c : protrusion,  33 : second resin sheet,  41 : burr,  100 : structure body