Patent Publication Number: US-2021188364-A1

Title: Automobile part

Description:
TECHNICAL FIELD 
     The present invention relates to an automobile part using a composite of thermoplastic resin and a metal plate, and further more specifically, relates to an automobile part in which the thermoplastic resin is directly adhered to the metal plate. 
     BACKGROUND ART 
     With automobile parts, reduction in vehicle weight has been aimed for by using a composite of resin and metal members, and adhesives have been used often for the adhesion of the resin and the metal material. 
     Although many adhesives for adhering resin and metal material have been developed, since thermal shrinkage is different between the metal member and the resin, residual shear stress is generated on the adhesive sandwiched between the metal member and the resin; this causes the adhesive to break, and peeling will occur easily. 
     JP5523849B2 (Patent Document 1) discloses a frame side component of bodywork of a motor vehicle in which voids formed between an outer frame and an inner frame produced from a metal sheet is reinforced by reinforcement structures composed of molded-on plastic. 
     This further discloses that by providing perforations to the frame made from the metal sheet and passing plastic pegs through the perforations and extending them over the surfaces of the perforations, it is possible to achieve a secure and discontinuous interlock bond between the frame made from the metal sheet and the plastic. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: JP5523849B2 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the frame side component disclosed in Patent Document 1, stress may easily concentrate on the discontinuous interlock bond, and peeling occurs since the area that the metal frame is adhered to the plastic is small. 
     The present invention has been made in view of such problem in the prior art, and an object thereof is to provide an automobile part in which peeling of the thermoplastic resin from the metal plate is prevented. 
     Solution to Problem 
     As a result of diligent study to achieve the above object, the inventors of the present invention found that the above object can be achieved by providing a liner layer on a metal plate side of a reinforcing member, the liner layer coating the metal plate, and closely and directly adhering the entirety of one surface of the liner layer to the metal plate. The inventors thus completed the present invention. 
     Namely, an automobile part of the present invention includes a metal plate, and a reinforcing member including thermoplastic resin disposed on one surface of the metal plate. 
     The reinforcing member has a liner layer which coats the metal plate, and a reinforcement structure portion which is provided upright on the liner layer, and reinforces the metal plate, and 
     The entirety of one surface of the liner layer is directly adhered to the metal plate. 
     Advantageous Effects of Invention 
     According to the present invention, a reinforcing member having a liner layer that coats the metal plate is provided, and one surface of the liner layer is closely and directly adhered to the metal plate in the entirety of the surface. Therefore, it is possible to provide an automobile part in which peeling of the reinforcing member from the metal plate is prevented. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view of an automobile part viewed from a reinforcing member side thereof. 
         FIG. 2  is a cross-sectional view of a part shown by line A-A′ in  FIG. 1 . 
         FIG. 3  is a cross-sectional view schematically enlarging an adhesion interface of the metal plate with the thermoplastic resin. 
         FIG. 4  is a cross-sectional view showing an adhesion state of the reinforcing member (thermoplastic resin) formed with a reinforcement structure portion alone, and the metal plate. 
         FIG. 5  is a cross-sectional view showing a state in which the liner layer is continuously provided from one surface to the other surface of the metal plate. 
         FIG. 6  is a cross-sectional view of a surface along the reinforcement structure portion shown by line B-B′ in  FIG. 1 . 
         FIG. 7  is a cross-sectional view showing a state in which an exposed portion and the metal plate of the automobile part are welded to each other. 
         FIG. 8  is a cross-sectional view showing a state in which two automobile parts are welded to each other at the exposed portions. 
         FIG. 9  is an SEM image of an aluminum plate surface of Example 1. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An automobile part of the present invention comprises a metal plate, and a reinforcing member including thermoplastic resin disposed on one surface of the metal plate. 
     The thermoplastic resin may contain a reinforcing fiber, such as carbon fiber and glass fiber. In particular, carbon fiber is preferably used since an automobile part with lightweight and high rigidity can be obtained. 
     The automobile part of the present invention is described below based on an example of a case in which the thermoplastic resin is carbon fiber-reinforced thermoplastic resin (hereinafter may be referred to as CFRTP) containing carbon fiber. 
       FIG. 1  shows a plan view of the automobile part of the present invention viewed from a reinforcing member (CFRTP) side thereof, and  FIG. 2  shows a cross-sectional view of a part shown by line A-A′ in  FIGS. 1 . 
     The automobile part  1  has a reinforcing member  3  formed of a metal plate  2  and CFRTP, as shown in  FIG. 1 . The reinforcing member  3  has, not only a reinforcement structure portion  31 , such as a rib or bead, but a continuous liner layer  32  that coats the metal plate  2 , and the liner layer  32  covers an interval between the reinforcement structure portion  31  and the reinforcement structure portion  31  provided upright on the liner layer  32  without any gap. 
     That is to say, as shown in  FIG. 1 , a projected area of the liner layer  32 , when viewing the reinforcing member  3  from its thickness direction, is a projected area of the entire reinforcing member  3 , and as shown in  FIG. 2 , the reinforcement structure portions  31  are connected to each other and provided upright on the continuous substantially planar liner layer  32 . 
     One surface of the liner layer  32  is closely adhered to the metal plate  2  in the entirety of the surface, and the metal plate  2  is directly adhered on the reinforcing member  3 . 
     In the automobile part  1 , the entirety of one surface of the liner layer  32  having a large projected area as described above serves as an adhesion surface; since an adhesion area of the reinforcing member  3  with the metal plate  2  is large, the reinforcing member  3  can be firmly adhered to the metal plate  2  without an adhesive or the like intervening therebetween, and peeling can be prevented. 
     Moreover, in the automobile part  1 , the liner layer  32  is adhered to the metal plate  2 , and where the liner layer  32  is adhered, the liner layer  32  supports the metal plate  2 , thus allowing for achieving sufficient rigidity. Accordingly, it is possible to reduce the thickness of the metal plate  2 . 
     More specifically, although depending on the required strength, it is possible to make the thickness of the metal plate  2  be 0.5 mm or more and 2.5 mm or less, thus allowing for a significant reduction in weight. 
     The automobile part  1  may be produced by injection pressing or press molding method. 
     The injection pressing is a method in which injection material is injected in a state in which a mold is slightly open, and then the mold is closed completely, the injected material is pressed, to spread the injection material throughout a cavity to effect molding. 
     In the injection pressing, since the cavity is filled with molten thermoplastic resin, the thermoplastic resin closely adheres to the metal plate  2  without any gap and thus firm adhesion can be effected. Hence, it is preferably used. 
     More specifically, a molded metal plate is disposed inside the mold and pressed by an upper mold, and in a state in which the mold is slightly open, injection material containing thermoplastic resin is injected towards the metal plate from a lower mold side. The mold is then closed completely, and the injection material is pressed together with the metal plate, to spread the injection material throughout the cavity, while the thermoplastic resin is closely adhered to the metal plate, to produce the automobile part. 
     The metal plate  2  is preferably roughened on at least one surface thereof. By having the surface adhering to the reinforcing member  3  roughened, it is possible to adhere firmly furthermore. 
     Examples of the roughening process include mechanical roughening processes, such as sandblasting, liquid honing, buffing, and polishing using a polishing sheet, as well as acid treatment, chemical etching, Laseridge and the like. 
     Among these, unlike the mechanical roughening processes, chemical etching and Laserige can effect the roughening by forming pores having an internal diameter greater than an opening diameter. Therefore, by filling the thermoplastic resin inside the pores by injection pressing, an anchor effect is obtained, and the thermoplastic resin can be firmly adhered to the metal plate. 
     Furthermore, chemical etching can form a porous structure  23  of an ant&#39;s nest form, as shown in  FIG. 3 , having voids connected to each other by tunnels; this allows for achieving a large anchor effect, thus achieving a further firm adhesion. Since the voids within the porous structure  23  are connected to each other by tunnels, even if one opening is blocked by carbon fibers  33  during the injection pressing, the thermoplastic resin  3  can be filled into all of the voids in the porous structure  23 , because the thermoplastic resin  3  enter from the other openings, and it is not likely that defects in filling occur. Hence, the chemical etching is preferably used in particular. 
     The chemical etching may be performed by immersing the metal plate in an aqueous solution of ammonium, hydrazine, and/or water-soluble amine compound. More specifically, roughening having a minute unevenness is possible by immersing the metal plate in 3% to 10% hydrazine monohydrate aqueous solution that is warmed to 40° C. to 70° C. for several minutes and then rinsing with water. 
     As the metal plate, other than metal sheets, such as aluminum, steel, stainless steel, copper, titanium, magnesium, or brass, metal sheets coated with the above metals may be used, for example. 
     Surface roughness (Ra) of the roughened metal plate is preferably 5 μm or less, further preferably 1.2 μm or less. 
     By having the surface roughness (Ra) of the metal plate be 5 μm or less, it is possible to configure a design plane without the unevenness standing out even if the other surface is also roughened, and further by having the surface roughness be 1.2 μm or less, a smooth painting plane can be formed. 
     The thermoplastic resin preferably contains carbon fibers whose average fiber diameter is 7 μm or more and 15 μm or less, and whose average length is 0.1 mm or more and 1 mm or less. 
     By containing carbon fibers of the above range, molding by injection pressing is possible, and an automobile part with high rigidity can be obtained. 
     Moreover, the thermoplastic resin preferably contains the carbon fibers in an amount of 30 mass % or more and 40 mass % or less. By having the carbon fiber content which satisfies the above range, the rigidity of the automobile part can be improved. 
     Namely, if the carbon fiber content exceeds 40 mass %, kneaded material (injection material) of the thermoplastic resin and the carbon fibers cools down and increases in viscosity since the material contains many carbon fibers that has high heat conductivity; this makes the thermoplastic resin difficult to enter inside the porous structure, thus causing filling defects and easy peeling, and may cause a decrease in the rigidity of the automobile part. 
     Moreover, when the carbon fiber content is less than 30 mass %, reinforcement effect by the carbon fibers will be small, thus causing the rigidity of the automobile part to decrease. 
     The viscosity of the injection material when performing the injection pressing, although depending on the thermoplastic resin, injection pressure or the like, is preferably 30 Pa·s or more and 200 Pa·s or less, and preferably 30 Pa·s or more and 50 Pa·s or less. 
     When the viscosity of the injection material is low, the thermoplastic resin easily enters the inside part of the porous structure, however at a temperature, at which the viscosity is less than 30 Pa·s, the thermoplastic resin thermally decomposes and the adhesive strength may easily decrease. 
     As the thermoplastic resin, a thermoplastic resin that can be molded by the injection pressing may be used. Examples thereof include, nylon 6, nylon 66, polyphenylene sulfide, polybutylene terephthalate, and polyphthalamide. 
     In the automobile part 1, when viewed from the thickness direction shown in  FIG. 1 , the projected area of the liner layer  32 , that is the reinforcing member  3 , is preferably 50% or more of the projected area of the metal plate  2 . 
     In the automobile part  1  of the present invention, the metal plate  2  may be made thin and can cool easily, whereas the reinforcement structure portion  31  formed by CFRTP to which the metal plate  2  is adhered is thick and is difficult to cool; this thus causes a large difference in cooling speed. 
     Accordingly, shear force is generated due to the difference in heat contraction amount after the injection pressing, thus easily causing deformation of the metal plate  2  and peeling of the metal plate  2  from the reinforcing member  3 . 
     By having the projected area of the liner layer  32  of 50% or more of the projected area of the metal plate  2 , the cooling speed of the metal plate  2  slows down while thermal strain is dispersed, thus enabling the prevention of deformation of the metal plate  2  and the peeling of the metal plate  2  from the reinforcing member  3 . Furthermore, with the liner layer  32  having an even thickness, the thermal strain is reduced. 
     Moreover, in the injection pressing, the injection material is injected in a state in which the mold is slightly open; this causes the injection material to leak and cause application of the thermoplastic resin on a region outside a desired region. 
     In the automobile part  1  of the present invention, the liner layer  32  is formed continuously, and a length of a border  5  between a location where the liner layer  32  is formed and a location where the liner layer  32  is not formed, shown in  FIG. 2 , is shorter than the length of the aforementioned border  5 ′ of the reinforcing member  3  formed by the reinforcement structure portion  31  alone, shown in  FIG. 4 . 
     Therefore, in the automobile part  1  of the present invention, since the length of the border  5  is short and there is a small risk that the thermoplastic resin will leak, injection press molding is possible with a reduced amount of sealing structure of the mold for preventing the leakage of thermoplastic resin, thus enabling cost effective molding. 
     In the reinforcing member  3 , when viewed from the thickness direction shown in  FIG. 1 , the projected area of the reinforcement structure portion  31  is preferably 30% or less with respect to the projected area of the liner layer  32 .
         By having the projected area of the reinforcement structure portion  31  of 30% or less, it is possible to prevent local deformation of the metal plate  2  that generates around the reinforcement structure portion  31  due to sink marks at ribs.       

     From the viewpoint of preventing local deformation of the metal plate  2 , there is no lower limit in the projected area of the reinforcement structure portion  31  with respect to the projected area of the liner layer  32 . However, since the rigidity of the automobile part  1  will improve with more of the reinforcement structure portions  31 , it is preferably 5% or more, although depending on the required rigidity. 
     Moreover, the thickness of the liner layer  32  is preferably 1 mm or more and 3 mm or less. When the thickness is less than 1 mm, the cavity will become narrow and a filling distance will become long, thus causing difficulty in molding by the injection pressing, and when exceeding 3 mm, the effect of weight reduction will decrease. 
     The automobile part  1  preferably has, at an end portion of the other surface of the metal plate  2 , a coated portion  21  coated by the liner layer  32  continuing from the one surface side. As shown in  FIG. 5 , by having the liner layer  32  provided continuously from one surface to the other surface of the metal plate  2 , a physical engagement is formed, and thus falling off of CFRTP3 can be prevented. 
     By forming the coated portion  21 , the thermoplastic resin will be exposed on the other surface side that serves as a design plane. However, when this is an automobile part, in which the exposed thermoplastic resin can be coated by door molding, such as a door frame of a body side panel, designability thereof will not decrease. 
     The metal plate  2  preferably has a bent portion  24  at its end portion that is bent towards the liner layer  32  side. The bent portion  24  improves the strength of the metal plate  2  itself, and together with the reinforcing member  3 , can improve the strength of the automobile part  1 . 
     Furthermore, it is preferable that the metal plate  2  includes the bent portion  24  at both of its end portions, that the cross section of the surface along the reinforcement structure portions  31  shown by line B-B′ in  FIG. 1  is as shown in  FIG. 6 , and that the reinforcement structure portions  31  are provided upright continuously from the bent portion  24  at one end to the bent portion at the other end. 
     With such reinforcement structure portion  31  provided upright between the two bent portions, it is possible to further improve the strength of the automobile part  1  against stress from a direction intersecting with the bent portion  24 , which makes the interval between the both end portions of the metal plate  2  narrow. 
     Moreover, the automobile part  1  preferably has an exposed portion  22  at an end portion of one surface of the metal plate  2 , which is exposed from the liner layer  32 . By forming a flange and making it exposed from the liner layer  32 , welding between metals become possible; as shown in  FIGS. 7 and 8 , it is possible to bond on the reinforcement member  3  side a further other metal plate  2 ′ or another automobile part  1 ′, by welding. 
     The bent portion  24  may include a flange portion  25  at its end portion that is further bent towards a planar direction end portion side of the metal plate. By providing the metal plate  2  with a hat shape having the flange portion  25 , it is possible to further improve the strength of the automobile part  1 . 
     In addition, by making the flange portion  25  be the exposed portion  22  exposed from the liner layer  32 , it is possible to bond another metal plate  2 ′ or another automobile part  1 ′ by welding, as shown in  FIG. 8 . 
     The length of the exposed portion  22 , namely, the length from the edge portion of the metal plate  2  to the edge portion of the liner layer  32  is preferably 5 mm or more and 30 mm or less. 
     When the length of the exposed portion  22  is less than 5 mm, not only will the welding margin be short thus causing difficulty in welding, the thermoplastic resin will thermally decompose by the heat of the welding, thus generating a void inside the porous structure; this void will serve as a starting point for peeling, and cause a decrease in adhesive strength. Moreover, when outer force is applied, the stress will concentrate on a border between a part on which the liner layer  32  is adhered and the exposed portion  22 , thus making the reinforcing member  3  to easily peel off. 
     Moreover, in the automobile part  1  of the present invention, since the liner layer  32  and the metal plate  2  together support the part as one, when the length of the exposed portion  22  exceeds 30 mm and a portion with the metal plate  2  alone increases, outer force will concentrate on that portion and would make the part break more easily. 
     The automobile part  1  is preferably of a sandwich structure that sandwiches the reinforcing member  3  with the metal plates  2 ,  2 ′, as shown in  FIGS. 7 and 8 . 
     The edge portion of the liner layer  32  and the reinforcement structure portion  31  of the reinforcing member  3  abuts the other metal plate  2 ′ or the reinforcing member  3 ′ provided on the other metal plate  2 ′ to form a hollow structure; and the reinforcement structure portion  31  serve as a partition that divides the hollow structure. Therefore, the automobile part  1  can be increased in strength while being reduced in weight. 
     The automobile part  1  may be suitably used for a framework member, such as a body side panel, a rear fender and a dash panel, as well as for a door panel and a back door panel. 
     EXAMPLES 
     Hereinafter, the present invention will be described in more detail with examples. However, the present invention is not limited to the following examples. 
     Example 1 
     A press molded aluminum plate of a thickness of 1 mm is immersed in alkaline liquid to degrease, and then was immersed in acidic liquid to neutralize. After immersing the aluminum plate in 5% hydrazine monohydrate aqueous solution heated to 50° C. for five minutes, the aluminum plate was washed with water and dried to obtain a surface-roughened aluminum plate. 
     In this aluminum plate, a porous structure layer having an average aperture diameter of 10 nm was formed to a depth of 100 nm, and its surface roughness (Ra) was 0.3 μm. 
     An SEM image of the aluminum plate surface is shown in  FIG. 9 . 
     The aluminum plate was disposed in the mold, was pressed with the upper mold, and, kneading material of carbon fibers and nylon 6 that contains 35 mass % of carbon fibers having an average fiber diameter of 10 μm and an average length of 0.5 mm was injected in a state in which the mold was slightly open, while being heated to 280° C. The mold was then closed completely and pressed at 10 MPa, to obtain an automobile part having a liner layer of a thickness of 2 mm. 
     The cross section of this automobile part was observed, and it was confirmed that the thermoplastic resin was filled in all voids in the porous structure formed in the aluminum plate as shown in  FIG. 3 , and that there were no filling defects. 
     Example 2 
     An automobile part was obtained as with Example 1 except that the surface was roughened by sandblasting, and that an aluminum plate having a surface roughness (Ra) of 7 μm was used. 
     Example 3 
     An automobile part was obtained as with Example 1 except that no roughening process was carried out to the aluminum plate. 
     &lt;Evaluations&gt; 
     Adhesion strength of the aluminum plate with the carbon fiber-reinforced thermoplastic resin was measured for the automobile parts of Examples 1 to 3 described above. The measurement results are shown in Table 1. 
     The adhesion strength was measured by cutting out the automobile part so that an adhesion area is 0.5 cm 2 , actually measuring this with a tension testing machine, then converting this to an area strength of 1.0 cm 2 . 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Example 1 
                 Example 2 
                 Example 3 
               
               
                   
               
             
            
               
                 Bonding strength 
                 42 
                 5 
                 2 
               
               
                 (MPa) 
               
               
                   
               
            
           
         
       
     
     From Table 1, it can be seen that the automobile part of the present invention has strong adhesion strength between the metal plate and the reinforcing member containing the thermoplastic resin, and that peeling can be prevented. 
     In particular, Example 1, in which a metal plate roughened by forming pores having an internal diameter greater than the opening diameter was used, has an adhesion strength 8.4 times stronger than Example 2, which was roughened by a mechanical process. Therefore, it was confirmed that by roughening by chemical etching, the adhesion strength becomes dramatically high, and by reinforcing with the reinforcing member, an automobile part of high rigidity can be obtained. 
     REFERENCE SIGNS 
       1  Automobile part 
       2  Metal plate 
       21  Coated portion 
       22  Exposed portion 
       23  Porous Structure 
       24  Bent portion 
       25  Flange portion 
       3  Reinforcing member (Carbon fiber-reinforced thermoplastic resin) 
       31  Reinforcement structure portion 
       32  Liner layer 
       33  Carbon fiber 
       4  Welded portion 
       5  Border