Patent Publication Number: US-9428225-B2

Title: Vehicle panel joint structure

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 USC 119 from Japanese Patent Application, No. 2014-135060 filed Jun. 30, 2014, the disclosure of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a vehicle panel joint structure. 
     2. Related Art 
     Japanese Patent Application Laid-Open (JP-A) No. 2009-178750 describes technology relating to a method of configuring a vehicle body member in which an end edge portion of an inner panel and an end edge portion of an outer panel are joined together by hemming. In this technology, by sandwiching a resilient adhesive into a hemming join portion, stress is absorbed by resilient deformation of the adhesive, even when distortion stress, due to a difference in linear expansion coefficients of both panels, is imparted to the hemming join portion by heat input during curing of the adhesive. 
     Thus in cases in which the outer panel and the inner panel with different linear expansion coefficients are joined by hemming, there is a possibility of the panels distorting due to a difference in expansion or contraction displacement, that may occur due to the difference in the linear expansion coefficients of both panels, when there is a change in temperature during a paint drying process or the like after joining by hemming (after the adhesive has cured). Thus there is room for improvement with respect to a joint structure of vehicle panels with different linear expansion coefficients. 
     Note that other related technology is described in JP-A No. S58-067566, JP-A No. 2007-118852, and JP-A No. 2009-126481. 
     SUMMARY 
     In consideration of the above circumstances, a subject of the present invention is to provide a vehicle panel joint structure capable of effectively suppressing distortion of vehicle panels with different linear expansion coefficients due to a change in temperature. 
     A vehicle panel joint structure of a first aspect of the present invention includes a pair of vehicle panels formed of a first vehicle panel and a second vehicle panel that have different linear expansion coefficients to each other, a hemming portion that is formed by folding over an end portion at an outer edge portion of the first vehicle panel, a rib portion that is formed at a leading end of an end portion at an outer edge portion of the second vehicle panel, that projects out toward the hemming portion of the first vehicle panel, and that contacts the hemming portion, and an adhesive layer that is formed between the outer edge portions of the pair of vehicle panels, and that joins the outer edge portions together. 
     In the vehicle panel joint structure of the first aspect, the adhesive layer formed between the outer edge portions of the pair of vehicle panels joins the outer edge portions together. Thus the difference in expansion or contraction displacement, which may occur due to the difference in the linear expansion coefficients of the pair of vehicle panels during a change in temperature, is absorbed by the adhesive layer stretching, whereby distortion of the vehicle panels is suppressed. 
     The outer edge portions are joined together by the adhesive layer in a state in which the rib portion, formed at the leading end of the end portion at the outer edge portion of the second vehicle panel, contacts the hemming portion of the end portion at the outer edge portion of the first vehicle panel. 
     Thus the layer thickness of the adhesive layer can easily be made thicker than in a case in which the rib portion is not formed, such that distortion, due to a change in temperature, of vehicle panels with different linear expansion coefficients is effectively suppressed. 
     A vehicle panel joint structure of a second aspect of the present invention is the structure of the first aspect, wherein a contact position where the rib portion contacts the hemming portion is set such that a distance from a leading end of the hemming portion to the contact position is a displacement difference or greater, wherein the displacement difference is generated at the pair of vehicle panels due to the difference in the linear expansion coefficients of the pair of vehicle panels. 
     In the vehicle panel joint structure of the second aspect, the contact position at which the rib portion contacts the hemming portion is changed due to the displacement difference of the vehicle panels during a change in temperature. However, the contact position where the rib portion contacts the hemming portion is set such that the distance from the leading end of the hemming portion to the contact position is the displacement difference or greater, which displacement difference is generated due to the difference in the linear expansion coefficients of the pair of vehicle panels. This prevents the rib portion from detaching from the folded-over portion, and the rib portion and the hemming portion from separating. 
     A vehicle panel joint structure of a third aspect of the present invention is the structure of the first aspect or the second aspect, wherein the adhesive layer is formed in a gap between the hemming portion of the first vehicle panel and the end portion at the outer edge portion of the second vehicle panel. 
     In the vehicle panel joint structure of the third aspect, the adhesive layer is formed not only between the outer edge portions of the pair of vehicle panels, but also in the gap between the hemming portion of the first vehicle panel and the end portion at the outer edge portion of the second vehicle panel, such that water ingress into the gap is prevented. Thus water resistance performance of the outer edge portions of the vehicle panels is improved. 
     A vehicle panel joint structure of a fourth aspect of the present invention is the structure of any one of the first aspect to the third aspect, wherein the pair of vehicle panels is formed by an outer panel that is disposed at an vehicle outside and formed of a metal material, and an inner panel that is disposed at an vehicle inside of the outer panel and formed of a resin material. 
     In the vehicle panel joint structure of the fourth aspect, the outer panel is formed of a metal material, and the inner panel is formed of a resin material. Creep is more liable to occur in the inner panel formed of resin material than in the outer panel formed of metal material. However, the displacement difference occurring due to the difference in linear expansion coefficients between the outer panel and the inner panel is absorbed by the adhesive layer stretching, such that creep in the inner panel formed of resin material is prevented or suppressed from occurring. 
     A vehicle panel joint structure of a fifth aspect of the present invention is the structure of any one of the first aspect to the fourth aspect, wherein the outer edge portion of the first vehicle panel and the outer edge portion of the second vehicle panel face each other through mutual faces, and a distance between outer edge portions of the facing pair of vehicle panels is determined by the displacement difference generated at the pair of vehicle panels due to the difference in the linear expansion coefficients of the pair of vehicle panels, and by a stretch ratio of the adhesive layer due to a change in temperature. 
     In the vehicle panel joint structure of the fifth aspect, the distance between outer edge portions of the pair of vehicle panels that face each other through mutual faces is determined by the displacement difference generated at the pair of vehicle panels due to the difference in the linear expansion coefficients of the pair of vehicle panels, and by the stretch ratio of the adhesive layer due to a change in temperature, such that the difference in expansion or contraction displacement occurring at the pair of vehicle panels due to the difference in the linear expansion coefficients of the pair of vehicle panels is absorbed by the adhesive layer stretching. Distortion of the vehicle panels is accordingly suppressed. 
     A vehicle panel joint structure of a sixth aspect of the present invention is the structure of the fifth aspect, wherein the distance between outer edge portions of the facing pair of vehicle panels is determined by a distance by which the rib portion formed at the leading end of the end portion at the outer edge portion of the second vehicle panel projects out toward the hemming portion of the first vehicle panel. 
     In the vehicle panel joint structure of the sixth aspect, the distance between outer edge portions of the facing pair of vehicle panels is determined by the distance by which the rib portion formed at the second vehicle panel projects out toward the hemming portion of the first vehicle panel, such that the difference in expansion or contraction displacement occurring at the pair of the vehicle panels due to the difference in the linear expansion coefficients of the vehicle panels is absorbed by the adhesive layer stretching. Distortion of the vehicle panels is accordingly suppressed. 
     The vehicle panel joint structure of the first aspect enables distortion of vehicle panels with different linear expansion coefficients occurring due to a change in temperature to be effectively suppressed. 
     The vehicle panel joint structure of the second aspect enables the rib portion to be prevented from separating from the hemming portion due to a change in temperature. 
     The vehicle panel joint structure of the third aspect improves the water resistance performance of the outer edge portions of the vehicle panels. 
     The vehicle panel joint structure of the fourth aspect enables the occurrence of creep in the inner panel formed of a resin material to be prevented or suppressed. 
     The vehicle panel joint structure of the fifth aspect enables distortion of vehicle panels with different linear expansion coefficients occurring due to a change in temperature to be more effectively suppressed. 
     The vehicle panel joint structure of the sixth aspect enables distortion of vehicle panels with different linear expansion coefficients occurring due to a change in temperature to be more effectively suppressed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a cross-section of relevant portions of an engine hood applied with a vehicle panel joint structure according to an exemplary embodiment of the present invention; 
         FIG. 2  is an enlarged cross-section of relevant portions in  FIG. 1 ; 
         FIG. 3A  is an explanatory drawing to explain a displacement difference between an inner panel and an outer panel due to a change in temperature, and stretching of an adhesive layer; and 
         FIG. 3B  is an explanatory drawing to explain a displacement difference between an inner panel and an outer panel due to a change in temperature, and stretching of an adhesive layer. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Explanation follows regarding a vehicle panel joint structure according to an exemplary embodiment of the present invention, with reference to  FIG. 1  to  FIG. 3B . 
     Joint Structure 
       FIG. 1  illustrates relevant portions of an engine hood  12  applied with a vehicle panel joint structure  10  of the present exemplary embodiment. The engine hood  12  is formed including an inner panel  20  disposed at the vehicle inside, and an outer panel  30  that is disposed at the vehicle outside and has a larger external profile than the inner panel  20 . 
     The inner panel  20  and the outer panel  30  are formed of materials with different linear expansion coefficients to each other. In the present exemplary embodiment, the inner panel  20  is made by a material that has a smaller linear expansion coefficient than the outer panel  30 . Specifically, a resin material (such as carbon fiber reinforced plastic (CFRP)) is employed for the inner panel  20 , and a metal material (such as aluminum alloy or steel plate) is employed for the outer panel  30 . 
     As illustrated in  FIG. 1  and  FIG. 2 , a hemming portion  36 , formed by folding over an end portion  34 , is provided at an outer edge portion  32  of the outer panel  30 . The hemming portion  36  of the present exemplary embodiment is configured by a hemming end portion  37  rounded into a hollow shape protruding toward the vehicle inside, and a folded-over portion  38  at which the panels overlap each other. 
     An end portion  24  of an outer edge portion  22  of the inner panel  20  is disposed at the outside (the vehicle inside) of the folded-over portion  38  of the hemming portion  36  of the outer panel  30 . A rib portion  26 , which projects out toward the folded-over portion  38  of the hemming portion  36  and contacts the folded-over portion  38 , is formed at a leading end of the end portion  24  at the outer edge portion  22  of the inner panel  20 . 
     As illustrated in  FIG. 2 , a contact position (leading end position)  26 A of the rib portion  26  is set at a distance M from a leading end  38 A of the folded-over portion  38  of the hemming portion  36 . In other words, a width of overlap between the end portion  24  of the inner panel  20  and the folded-over portion  38  of the outer panel  30  is M. The distance M is set at a displacement difference ΔL or greater, which displacement difference ΔL is generated due to the difference in linear expansion coefficients of the inner panel  20  and the outer panel  30 , described later, (see  FIG. 3B ). 
     As illustrated in  FIG. 1  and  FIG. 2 , an adhesive layer  52  is formed by an adhesive  50  filled between the outer edge portion  32  of the outer panel  30  and the outer edge portion  22  of the inner panel  20 , such that the outer edge portion  32  of the outer panel  30  is joined together with the outer edge portion  22  of the inner panel  20 . To explain from a different perspective, the outer edge portion  32  of the outer panel  30  and the outer edge portion  22  of the inner panel  20  are joined together by the adhesive  50  (adhesive layer  52 ), in a state in which the rib portion  26  of the outer edge portion  22  of the inner panel  20  abuts the folded-over portion  38  of the hemming portion  36  of the outer panel  30 . 
     Note that, as illustrated in  FIG. 2 , a gap  40 , this being a location at which the end portion  24  of the outer edge portion  22  of the inner panel  20  and the folded-over portion  38  of the outer panel  30  overlap, is also filled with the adhesive  50 , such that the adhesive layer  52  is also formed in the gap  40 . 
     Operation and Advantageous Effects 
     Explanation follows regarding operation and advantageous effects of the present exemplary embodiment. 
     As illustrated in  FIG. 1  and  FIG. 2 , the end portion  24  of the outer edge portion  22  of the inner panel  20  is disposed at the outside (the vehicle inside) of the folded-over portion  38  of the hemming portion  36  of the outer panel  30 . Moreover, the outer edge portion  32  of the outer panel  30  and the outer edge portion  22  of the inner panel  20  are joined together by the adhesive layer  52  (adhesive  50 ), in a state in which the rib portion  26  of the inner panel  20  abuts the folded-over portion  38  of the hemming portion  36  of the outer panel  30 . 
     Since the inner panel  20  is formed of a resin material, and the outer panel  30  is formed of a metal material, the inner panel  20  has a smaller linear expansion coefficient than the outer panel  30 . Thus a difference in expansion or contraction displacement occurs between the outer panel  30  and the inner panel  20  due to the difference in linear expansion coefficients, when the temperature changes in a paint drying process or the like after the adhesive  50  has cured. However, the difference in expansion or contraction displacement between the outer panel  30  and the inner panel  20  is absorbed by the adhesive layer  52  (adhesive  50 ) stretching. 
     As illustrated in  FIG. 2 , since joining is made in a state in which the rib portion  26  abuts the folded-over portion  38 , a necessary layer thickness T 0  of the adhesive layer  52  is easily secured by the rib portion  26  such that the adhesive layer  52  is stretched and absorbs the difference in expansion or contraction displacement between the outer panel  30  and the inner panel  20 . Thus distortion of the outer panel  30  and the inner panel  20  is effectively suppressed. 
     Moreover, the adhesive layer  52  is formed between the outer edge portion  22  of the inner panel  20  and the outer edge portion  32  of the outer panel  30 , such that corrosion of the outer edge portion  32  of the outer panel  30  is prevented or suppressed. 
     Furthermore, the gap  40 , this being the location at which the end portion  24  of the outer edge portion  22  of the inner panel  20  and the folded-over portion  38  of the hemming portion  36  of the outer panel  30  overlap each other, is also filled with the adhesive  50 , forming the adhesive layer  52 , such that ingress of water into the gap  40  is prevented. Thus corrosion of the outer panel  30  due to water ingress into the gap  40  is prevented or suppressed. 
     Creep is, for example, more liable to occur within hot atmosphere, such in a paint drying process or the like, in the inner panel  20  formed of resin material than in the outer panel  30  formed of metal material. However, the displacement difference between the outer panel  30  and the inner panel  20  is absorbed by the adhesive layer  52  (adhesive  50 ) stretching as described above, such that creep in the inner panel  20  formed of resin material is prevented or suppressed from occurring. 
       FIG. 3A  and  FIG. 3B  are explanatory drawings (model drawings) illustrating models of the join location of the inner panel  20  to the outer panel  30 , in order to explain the displacement difference between the inner panel  20  and the outer panel  30 , and the stretching of the adhesive layer  52  (adhesive  50 ). Note that the hemming portion  36 , the rib portion  26 , and so on are not shown in  FIGS. 3A and 3B , in order to simplify the explanation. 
     A stretch ratio S of the adhesive layer  52  due to change in temperature is shown in Equation 1, where T 0  is the layer thickness of the adhesive layer  52  in an initial state, T 1  is a layer thickness of the adhesive layer  52  in a stretched state (envisaged maximum value) due to change in temperature, and ΔL is the displacement difference between the inner panel  20  and the outer panel  30  (envisaged maximum value) due to change in temperature. 
     
       
         
           
             
               
                 
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     The adhesive layer  52  needs to stretch up to the layer thickness T 1  in order for the adhesive layer  52  to sufficiently absorb the displacement difference ΔL between the inner panel  20  and the outer panel  30 , which displacement difference ΔL is generated due to the difference in linear expansion coefficients of the inner panel  20  and the outer panel  30 . The possible stretch ratio S is determined according to the type of the adhesive  50 . Thus by determining the layer thickness T 0  in the initial state such that the stretch ratio S is the threshold value of the adhesive  50  or below, the adhesive layer  52  stretches up to the layer thickness T 1 , and the displacement difference ΔL due to the difference in linear expansion coefficients is sufficiently absorbed by the adhesive layer  52 . 
     The layer thickness T 0  of the adhesive layer  52  in the initial state is the sum of a plate thickness t 1  of the folded-over portion  38  of the hemming portion  36 , and a height t 2  of the rib portion  26  (T 0 =t 1 +t 2 , see  FIG. 2 ). Thus the necessary layer thickness T 0  in the initial state can be secured by adjusting the height t 2  of the rib portion  26  whereby the adhesive layer  52  is stretched and absorbs the displacement difference ΔL due to the difference in the linear expansion coefficients between the inner panel  20  and the outer panel  30 . 
     Thus in the present exemplary embodiment, by determining the height t 2  of the rib portion  26  such that the stretch ratio S of the adhesive  50  (see Equation 1) is set at a threshold value of the stretch ratio of the adhesive  50 , or below, the necessary layer thickness T 0  in the initial state (layer thickness T 1  after stretching) is secured, and the displacement difference ΔL between the inner panel  20  and the outer panel  30  due to the difference in the linear expansion coefficients is absorbed by the adhesive layer  52  stretching. 
     The contact position  26 A, at which the rib portion  26  of the inner panel  20  contacts the folded-over portion  38  of the hemming portion  36  of the outer panel  30 , as illustrated in  FIG. 2 , changes by the displacement difference ΔL (see  FIG. 3B ) during a change in temperature. In the present exemplary embodiment, the distance M from the leading end  38 A of the folded-over portion  38  (hemming portion  36 ) to the contact position  26 A of the rib portion  26  is set at the displacement difference ΔL (see  FIG. 3B ) or greater. This prevents the rib portion  26  from detaching from the folded-over portion  38 , and the rib portion  26  and folded-over portion  38  from separating (positional displacement). 
     Other 
     Note that the present invention is not limited to the above exemplary embodiment. 
     For example, the present invention has been applied to the engine hood  12  configured including the inner panel  20  disposed at the vehicle inside and the outer panel  30  disposed at the vehicle outside, however configuration is not limited thereto. The present invention may be applied to joint structures of a pair of vehicle panels, such as in a side door, a back door, or a trunk door. 
     Moreover, there is no limitation to the placement of the pair of vehicle panels, and the placement direction may be set as appropriate. 
     Moreover, the materials configuring the pair of vehicle panels are not limited to a combination of a resin material and a metal material. For example, a pair of vehicle panels formed of two metal materials with different linear expansion coefficients to each other may be employed. 
     It goes without saying that various embodiments may be implemented within a range not departing from the spirit of the present invention.