Abstract:
It is desired to make a shock absorbing structure small in size. The shock absorbing structure includes a beam-like structural member having a concave section; and a shock absorbing member, one end of which is arranged in the concave section to abut to the structural member and the other end of which is arranged outside the structural member. Even in a case of a dead stroke when the shock absorbing member is bottomed out, the concave section overlaps with the structural member supporting the structure, so that there is no wasteful space.

Description:
TECHNICAL FIELD 
       [0001]    The present invention is related to an installation structure of a shock absorbing member. 
       RELATED ART 
       [0002]    A shock absorbing member is known which uses a member exemplified by carbon fiber reinforced plastics. For example, the shock absorbing member of an angular tube shape absorbs an impact while crushing into an axis line direction when the impact is imposed into the axis line direction. As a result, the impact applied to a main body to which the shock absorbing member is attached is reduced. 
         [0003]    As a structure of a navigation body such as an automobile and an aircraft (for example, a helicopter which is a rotary-wing aircraft), a shock absorbing structure is used for shock absorption in case of collision. For example, in the helicopter as the rotary-wing aircraft, an underfloor structure provided with the shock absorbing structure is proposed in order to secure safety of crews at the time of crash landing. 
         [0004]    When the shock absorbing member crushes for a length or more, the fragments of a destructed part of the shock absorbing member fill the inside of the shock absorbing member and the shock absorbing member hardly crush any more, so that the shock absorbing member is bottomed out to lose shock absorbing ability.  FIG. 1  shows an example of a relation between a displacement (crushing length) of the shock absorbing member and load. When the displacement exceeds a point B, the impact load begins to increase rapidly and the shock absorbing ability is lost. 
         [0005]      FIG. 2A  show a reference example of the installation structure of the shock absorbing member.  FIG. 2A  shows an example that the shock absorbing member is installed in a lower portion of the rotary-wing aircraft. A fuselage of the rotary-wing aircraft is formed from a structural beam  102 . The structural beam  102  supports a floor board  101 . A shock absorbing member  103  is attached to the structural beam  102 . It is shown that the thickness of the structural beam  102  is L 11 , the length of the shock absorbing member  103  is L 12 , and the length from the floor board  101  to the shock absorbing member  103  is L 13 . 
         [0006]      FIG. 2B  shows a state that an impact is imposed to an axis line direction of the shock absorbing member shown in  FIG. 2A  so that the shock absorbing member is bottomed out. The length of the shock absorbing member  103   a  when a part  104  crushes so that the shock absorbing member  103  is bottomed out is shown as L 14 . A relation of the bottoming displacement B in  FIG. 1  is L 12 −L 14 =B. The length L 14  of the shock absorbing member in the bottoming state is a dead stroke. 
         [0007]    As a reference example of a technique which deals with the bottoming, Patent Literature 1 is exemplified. A shock enduring structure of a helicopter is described in Patent Literature 1. In this technique, a foaming agent is injected only to a partial space of one of a space between fiber-reinforced composite material hollow tubes and an internal space of each fiber-reinforced composite material hollow tube. Thus, a destruction fragment is set in the foaming agent, or the destruction fragment is housed in a sectional space, so that attainment of rigidity of the whole member due to compaction of the destruction fragment is prevented. An effective stroke is utilized. 
       Citation List: 
       [0008]    [Patent Literature 1]: Japanese Patent No. 3888630 
       SUMMARY OF THE INVENTION 
       [0009]    A part of the shock absorbing member shown in  FIG. 2B  corresponding to the length L 14  is the dead stroke and there is not an ability to absorb the impact. Therefore, in order to secure the enough shock absorbing ability, it is required to use the shock absorbing member of the length L 12  which is obtained by adding the effective stroke to the length L 14  at the time of bottoming out. Moreover, because the thickness L 11  of the structural beam  102  is added, the length L 13  from the floor board  101  to the end of the shock absorbing member  103  is considerably long. The structure provided with the shock absorbing member has difficulty to be made small, because it is necessary to secure the length L 13 . 
         [0010]      FIG. 3  shows an example in which the shock absorbing member  103  is fixed on the floor board  101  at a portion other than the structural beam  102 . In this case, the length from the floor board  101  to the end of the shock absorbing member  103  is the length L 12 , and the structure can be made short by thickness L 11  of the structural beam  102 , compared with a case of  FIG. 2A . However, in such a structure, the floor board  101  must be reinforced so as not for the floor board  101  to be destroyed with the reaction when an impact is imposed to the shock absorbing member  103 . Therefore, the weight increases. 
         [0011]    It is desired to make the shock absorbing structure small in size and light in weight so as to make the structures such as an automobile and an aircraft small in size and light in weight. 
         [0012]    In one aspect of the present invention, the shock absorbing structure includes a beam-like structural member ( 6 ) having a concave section; and a shock absorbing member ( 12 ), one end of which is arranged in said concave section to abut to the structural member and the other end of which is arranged outside the structural member. 
         [0013]    According to such a shock absorbing structure, even when the shock absorbing member is bottomed out while a dead stroke is remained, the region of the concave section overlaps with a region of the structural beam, so that there is no wasteful space. 
         [0014]    In another aspect of the present invention, the beam-like structural member is provided with a first flange; a first web, one end of which is fixed on one surface of the first flange; and a second flange which is fixed on the other end of said first web to be in parallel to the first flange. The concave section is formed form the first web and the one surface of the first flange. 
         [0015]    In further another aspect of the present invention, the beam-like structural member is further provided with: a second web, one end of which is fixed on the one surface of the first flange to be in parallel to the first web; and a third flange which is fixed on the other end of the second web to be in parallel to the first flange and which forms a space between the second flange and the third flange. The concave section is formed by the first web, the second web and the one surface of the first flange. 
         [0016]    In another aspect of the present invention, a through-hole is provided in a portion of the first flange to which the shock absorbing member abuts. 
         [0017]    In another aspect of the present invention, a rotary-wing aircraft is provided with: a floor supported by the first flange; and a bottom plane supported by the beam-like structural member and arranged on a lower-side of the floor. A longitudinal direction of said shock absorbing member is a vertical direction. 
         [0018]    In another aspect of the present invention, in an automobile, the shock absorbing member is arranged such that the other end of the shock absorbing member turns to a front direction of the automobile. 
         [0019]    With the present invention, the shock absorbing structure can be made small. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The above object, other object, effects and features of the present invention would be made clear from the following description made in conjunction with the attached drawings: 
           [0021]      FIG. 1  shows relation between displacement and load of a shock absorbing member; 
           [0022]      FIG. 2A  show an installation structure of the shock absorbing member as a reference example; 
           [0023]      FIG. 2B  shows a condition that the shock absorbing member as the reference example is bottomed out; 
           [0024]      FIG. 3  shows an installation structure of the shock absorbing member as another reference example; 
           [0025]      FIG. 4  is a side view showing a rotary-wing aircraft provided with a shock absorbing structure; 
           [0026]      FIG. 5  is a diagram showing an underfloor structure of the rotary-wing aircraft; 
           [0027]      FIG. 6  is a perspective view showing a structural beam; 
           [0028]      FIG. 7A  is a sectional view showing the shock absorbing structure in an embodiment; 
           [0029]      FIG. 7B  shows a state that the shock absorbing structure in the embodiment is bottomed out; 
           [0030]      FIG. 8  is a floor top view; 
           [0031]      FIG. 9  is a perspective view showing another structural beam; 
           [0032]      FIG. 10  is a sectional view showing the shock absorbing structure in another embodiment; and 
           [0033]      FIG. 11  is a top view of an automobile provided with the shock absorbing structure. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0034]    Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.  FIG. 4  is a sectional view showing a rotary-wing aircraft (especially, a helicopter) provided with a shock absorbing structure according to an embodiment of the present invention when viewed from the side. A rotary-wing aircraft  2  is provided with a fuselage  4 . The fuselage  4  is provided with a floor  10 . The floor  10  supports seats, cargo and so on. A shock absorbing structure is arranged under the floor  10 . The shock absorbing structure is provided with structural beams  6  and shock absorbing members  12 . A bottom plate  8  which is an outer plate of the fuselage  2  on the lower side is supported by the structural beams  6  and arranged in the lower ends of the shock absorbing members  12 . In such a rotary-wing aircraft, when the bottom collides with the ground and an obstacle, the shock absorbing member  12  absorbs an impact while crushing, so as to protect the structure of the fuselage  4  and aircrews inside it. 
         [0035]      FIG. 5  shows a structure under the floor  10  of the rotary-wing aircraft  2 . The structural beams  6 - 1  and  6 - 2  are arranged under the floor. The plurality of structural beams  6 - 1  are arranged in parallel to the longitudinal direction of the rotary-wing aircraft  2 . The plurality of structural beams  6 - 2  are arranged in parallel to the lateral direction of the rotary-wing aircraft  2 . The structural beams  6 - 1  and  6 - 2  are reinforcement members in the longitudinal and lateral directions to the load during the operation of the rotary-wing aircraft  2 . 
         [0036]    Under the floor of the rotary-wing aircraft  2 , webs  14  supported by the structural beams  6 - 1  and extending along the structural beam  6 - 1 , and frames  16  supported by the structural beams  6 - 2  and extending along the structural beams  6 - 2  are arranged. A bottom plate  8  is attached to cover the lower ends of the webs  14  and the frames  16 . 
         [0037]      FIG. 6  is a perspective view showing the structural beam  6 . The structural beam  6  is equivalent to each of the structural beams  6 - 1  and  6 - 2  in  FIG. 5 . The structural beam  6  has flanges  18 ,  22 - 1 , and  22 - 2  and webs  20 - 1  and  20 - 2 . These are members, each of which is a member having a thin, long and tabular shape and has two principal surfaces of a principal surface (upper-side surface) and a principal surface (lower-side surface). The flange  18  and the flanges  22 - 1  and  22 - 2  correspond to the flange on the upper-side and the flange on the lower-side in the I-type structural beam. The webs  20 - 1  and  20 - 2  are connected with the flange  18  on the lower-side surface of the flange  18  and correspond to the web in the I-type structural beam. The structure of the structural beam  6  is different from the I-type structural beam and has the structure shown below when viewing a sectional plane perpendicular to the longitudinal direction. The webs  20 - 1  and  20 - 2  having substantially the same shape are attached to the identical principal surface (lower-side surface) of the flange  18  so as for the principal planes of the two webs to be in parallel to each other. The longitudinal direction of the webs  20 - 1  and  20 - 2  and the longitudinal direction of the flange  18  are the same. The principal surfaces of the webs  20 - 1  and  20 - 2  and the principal surface of the flange  18  are perpendicular. A space  26  exists between the two webs  20 - 1  and  20 - 2  to have a predetermined width and to extend into the longitudinal direction of the structural beam  6  while having a constant shape. The lower end of the first web  20 - 1  is connected with the one end of the first flange  22 - 1 . The first flange  22 - 1  extends into a direction opposite to the space  26  from the one end. The lower end of the second web  20 - 1  is connected with the one end of the second flange  22 - 2 . The second flange  22 - 2  extends into a direction opposite to the space  26  from the one end. The longitudinal directions of the first flange  22 - 1 , the second flange  22 - 2  and the flange  18  are the same and moreover their principal surfaces are parallel to each other. The structural beam  6  is a π type beam having a π type section which is formed from the flange  18  as an upper side, the web  20 - 1  and the flange  22 - 1  as a left leg, and the web  20 - 2  and the flange  22 - 2  as a right leg. 
         [0038]    Through-holes  28  are provided for the flange  18 . The through-hole  28  connects the space  26  on the underside of the flange  18  and a space on the upper side of the flange  18 . A plurality of through-holes  28  are arranged along the longitudinal direction of the structural beam  6 . The position where the through-hole  28  is arranged is a position where the shock absorbing member  12  is arranged. One end of the shock absorbing member  12  is inserted into a concave section which is formed from the lower-side surface of the flange  18 , an inner surface  24 - 1  of the first web  20 - 1  which faces the space  26  and an inner surface  24 - 2  of the second web  20 - 2  which faces the space  26 , and the shock absorbing member  12  is fixed. The installation of the shock absorbing member  12  can be made through gluing to the inner surfaces  24 - 1  and  24 - 2  of the space  26 , the web  14 , and the frame  16  by using adhesive. 
         [0039]      FIG. 7A  is a sectional view showing the shock absorbing structure in the present embodiment. The section of the structural beam  6  which is perpendicular to the longitudinal direction is shown. The flange  18  of the structural beam  6  is attached at the upper surface to an installation surface  11  which is a lower-side surface of the floor board  30  of the rotary-wing aircraft  2 . 
         [0040]    The shock absorbing member  12  is a stick-shaped member. The longitudinal direction of the member  12  is a crush direction in which the shock absorbing member  12  is crushed and compressed, when an impact is imposed. The shock absorbing member  12  is attached at the upper end to the bottom of the concave section of the structural beam  6  when the longitudinal direction of the member  12  is an upper and lower direction (a vertical direction) of the rotary-wing aircraft  2 . When the width of the shock absorbing member  12  is equal to a width when the adhesive is applied to the inner surfaces of the space  26 , the installation is easy and is desirable. In this case, the upper end of the shock absorbing member  12  abuts to the lower-side surface of the flange  18  which faces the space  26  and contacts the inner surfaces  24 - 1  and  24 - 2 . 
         [0041]    The through-hole  28  is provided in a position of the flange  18  where the shock absorbing member  12  abuts to the flange  18 . A through-hole  32  is provided in a portion of the floor board  30  corresponding to an area in which the through-hole  28  is provided. The upper end of the shock absorbing member  12  is exposed on the side of the floor  10  through the through-hole  28  and the through-hole  32 . The area where the through-hole  28  is provided is smaller than the area where the shock absorbing member  12  abuts to the lower-side surface of the flange  18 . Therefore, when an impact is imposed, the shock absorbing member  12  is destroyed from the bottom end in the state that upper end of the member  12  is supported with the flange  18  of the structural beam  6 . 
         [0042]      FIG. 7B  shows the shock absorbing member  12   a  which is crushed with the impact and is bottomed out. The length of a dead stroke on the bottoming of the shock absorbing member  12   a  is shown as L 5 . Of the length L 5  of the shock absorbing member  12   a,  the length L 3  from the underside surface of the flange  18  to the lower-side surfaces of the flanges  22 - 1  and  22 - 2  overlaps with the length of the structural beam  6 . Therefore, the length L 5 −L 3  of the dead stroke outside the structural beam  6  can be made short. 
         [0043]    Comparing with the shock absorbing structure of  FIG. 2A , when the shock absorbing member  103  and the shock absorbing member  12  are formed of the same material, the size which is necessary for the underside of the floor is L 13 =L 11 +L 12  in the structure of  FIG. 2A . On the other hand, in the example of  FIG. 7A , the size which is necessary for the underside of the floor is L 2 =L 4 +(L 1 −L 3 ). When the shock absorbing member and the structural beam of the same size are used, the length L 2  on the underside of the floor can be shortened by the length L 3  while securing the effective stroke (L 4 −L 5 ), in case of  FIG. 7A . Therefore, by using the structural beam  6  of the π type as shown in  FIG. 7A , the equivalent shock absorption effect can be attained in the smaller underfloor structure, compared with the case of  FIG. 2A . Or, in the fuselage with the same overall size, the larger space can be secured above the floor. 
         [0044]    When the shock absorbing member  12  receives the impact and the destruction progresses, a part of the fragment passes through the through-holes  28  and  32  to the space above the floor  10 . As a result, the bottoming of the shock absorbing member  12  can be delayed to reduce the dead stroke. Therefore, the length L 4  of the shock absorbing member  12  which is necessary to attain an identical shock absorption effect can be made small and the size of the structure in the underfloor portion can be made smaller. In order to prevent fragments from scattering onto the floor, a scattering prevention member such as the sheet of the resin is provided on the floor  10  to cover the through-hole  32 . 
         [0045]      FIG. 8  shows a top view showing the shock absorbing member when viewed from the floor  10 . The through-hole  28  is formed in the floor board  30 . The shock absorbing member  12  may has a section of any shape, and in the present embodiment, the section shape is square as shown by a dotted line in  FIG. 8 . In case of such a square column shape, because the inner surfaces  24 - 1  and  24 - 2  of the structural beam  6  of the π-type section and the sides of the shock absorbing member  12  contact in plane, it is easy to fix the shock absorbing member  12 . 
         [0046]    The shape of the structural beam  6  may be another shape if it has a concave section to support the one end of the shock absorbing member  12 . For example, the structural beam  6  may have the π-type structure only in the portion to which the shock absorbing member  12  is attached, and a general I-type structure in the other portion. However, the beam which has a uniform sectional shape as shown in  FIG. 6  is excellent in a point of the manufacturing facility. The π-type beam as shown in  FIG. 6  is excellent especially in the strength and the manufacturing facility. 
         [0047]      FIG. 9  shows another example of the structural beam. The structural beam  6   a  is a J-type beam which has the sectional shape of a J character and in which the second web  20 - 2  and the second flange  22 - 2  are removed, compared with the π-type beam shown in  FIG. 6 .  FIG. 10  is a side view of the shock absorbing structure in which the shock absorbing member  12  is attached to the structural beam  6   a.  In this case, the shock absorbing member  12  is installed in the concave section which is formed from the lower-side portion of the flange  18  and the inner surface  24 - 1  of the web  20 - 1 . In this example, too, the same effect as the effect described by referring to  FIG. 7A ,  FIG. 7B  can be attained. 
         [0048]      FIG. 11  is a top view showing an example in which the shock absorbing structure of the present embodiment is applied to an automobile car. The structural beam  6  is attached to the neighborhood of the front surface  36  of the automobile  34  while the width direction of the automobile is a longitudinal direction of the beam  6 . In the example of the structural beam  6  of  FIG. 6 , as for the direction of the structural beam  6 , the surface of the flange  18  is vertical, the surfaces of the webs  20 - 1  and  20 - 2  are horizontal, and the flange  18  is provided on a back side in a movement direction of the automobile  34  and the opening of the concave section  26  is provided on a front side in the movement direction. The shock absorbing member  12  is inserted into the concave section of the structural beam  6 . The shock absorbing member  12  is fixed in the longitudinal direction which is the movement direction of the automobile  34 . According to such a shock absorbing structure, the high shock absorption effect can be attained while restraining the length of automobile  34 . 
         [0049]    The present invention has been described in the above with reference to the embodiments. However, the present invention is not limited to the embodiments. It is possible to carry out various modifications to the embodiments.