Patent Publication Number: US-11638455-B2

Title: Helmet airflow control member and helmet

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates to a helmet airflow control member arranged on a shell of the helmet and a helmet including the helmet airflow control member. 
     2. Description of Related Art 
     Airflow generated by a helmet greatly affects how a wearer feels in the helmet. For example, airflow directed from the inside of a helmet toward the outside of the helmet greatly improves the ventilation performance of the helmet (for example, refer to Japanese Laid-Open Patent Publication No. 2-26908, Japanese Laid-Open Patent Publication No. 7-3516, and Japanese Laid-Open Patent Publication No. 2000-328343). Changes in airflow generated by the helmet are limited to decrease noise such as wind noise and significantly improve quietness. Disturbance in the airflow generated by the helmet is limited to significantly improve posture stability when traveling straight forward (for example, refer to International Publication No. WO 2007/144937). 
     A change in the shape of a shell of the helmet allows for a new control of the airflow generated by the helmet. However, the shell needs to have mechanical strength, impact resistance, and penetration resistance. This imposes limitations on detailed structures that can be added to control airflow. 
     SUMMARY 
     One object of the present disclosure is to provide a helmet airflow control member and a helmet that allow for a new control of airflow generated by the helmet. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     In one general aspect, a helmet airflow control member includes a plate-like main body and at least one passage formation portion. The main body is arranged on a shell and includes a main body rear surface that covers part of a shell outer surface. The passage formation portion is arranged on the main body rear surface. A periphery of the main body rear surface includes a first peripheral portion and a second peripheral portion. The first peripheral portion is shaped in correspondence with the shell outer surface and closes a space between the main body rear surface and the shell outer surface. The second peripheral portion is spaced apart from the shell outer surface and defines an opening of the space between the main body rear surface and the shell outer surface in cooperation with the shell outer surface. The passage formation portion defines a passage in the space, with the passage extending from the opening into the space and returning from the space to the opening. 
     In another general aspect, a helmet airflow control member includes a plate-like main body and at least one passage formation portion. The main body is arranged on a shell and includes a main body rear surface that covers part of a shell outer surface. The passage formation portion is arranged on the main body rear surface. A periphery of the main body rear surface includes a first peripheral portion and a second peripheral portion. The first peripheral portion is shaped in correspondence with the shell outer surface and closes a space between the main body rear surface and the shell outer surface. The second peripheral portion is spaced apart from the shell outer surface and defines an opening of the space between the main body rear surface and the shell outer surface in cooperation with the shell outer surface. The at least one passage formation portion includes at least one first passage formation portion and at least one second passage formation portion. The first passage formation portion defines a first passage extending from the opening into the space and returning from the space to the opening. The second passage formation portion is located adjacent to the at least one first passage formation portion to define a second passage extending from the space toward the opening and connected to a hole extending through the shell. 
     In one general aspect, a helmet includes a shell and a helmet airflow control member. The helmet airflow control member includes a plate-like main body and at least one a passage formation portion. The main body is arranged on the shell and includes a main body rear surface that covers part of a shell outer surface. The passage formation portion is arranged on the main body rear surface. A periphery of the main body rear surface includes a first peripheral portion and a second peripheral portion. The first peripheral portion is shaped in correspondence with the shell outer surface and closes a space between the main body rear surface and the shell outer surface. The second peripheral portion is spaced apart from the shell outer surface and defines an opening of the space between the main body rear surface and the shell outer surface in cooperation with the shell outer surface. The passage formation portion defines at least part of a passage in the space, with the passage extending from the opening into the space and returning from the space to the opening. 
     Other features and aspects will be apparent from the following detailed description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view showing a helmet taken from a rear upper side. 
         FIG.  2    is a side view showing the helmet of  FIG.  1   . 
         FIG.  3    is a rear view showing the helmet of  FIG.  1   . 
         FIG.  4    is a rear view showing helmet airflow control member of the helmet of  FIG.  1   . 
         FIG.  5    is a perspective view showing the helmet airflow control member of the helmet of  FIG.  1   . 
         FIG.  6    is a plan view showing a rear surface of the helmet airflow control member of  FIG.  5   . 
         FIG.  7    is a rear view showing the structure of a helmet airflow control member in accordance with a modified example. 
         FIG.  8    is a cross-sectional view taken along line  8 - 8  in  FIG.  7   . 
     
    
    
     Throughout the drawings and the detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, and convenience. 
     DETAILED DESCRIPTION 
     This description provides a comprehensive understanding of the methods, apparatuses, and/or systems described. Modifications and equivalents of the methods, apparatuses, and/or systems described are apparent to one of ordinary skill in the art. Sequences of operations are exemplary, and may be changed as apparent to one of ordinary skill in the art, with the exception of operations necessarily occurring in a certain order. Descriptions of functions and constructions that are well known to one of ordinary skill in the art may be omitted. 
     Exemplary embodiments may have different forms, and are not limited to the examples described. However, the examples described are thorough and complete, and convey the full scope of the disclosure to one of ordinary skill in the art. 
     One embodiment of a helmet airflow control member and a helmet will now be described with reference to  FIGS.  1  to  6   . In  FIGS.  1  to  3   , the helmet airflow control member is removed from a shell to facilitate the description of the helmet airflow control member. Further, a vertical plane extending from the center of the helmet with respect to the sideward direction when setting the helmet on a horizontal plane will be referred to as a symmetry plane S. Also, the front side of the helmet when traveling forward will be referred to as the front, and the opposite side of the front will be referred to as the rear. 
     As shown in  FIG.  1   , the helmet includes a shell  10  and an air outlet  20  that is one example of a helmet airflow control member (hereafter, also referred to as airflow control member). 
     The shell  10  forms an outer shell of the helmet. The shell  10  is a semispherical plastic member that is substantially plane-symmetric with respect to the symmetry plane S. The material for the shell  10  is selected from, for example, acrylonitrile-butadiene-styrene copolymer (ABS), polycarbonate (PC), and a thermosetting resin impregnated with reinforcement fibers. 
     The shell  10  may accommodate, for example, an impact absorption liner that is an interior member to absorb impacts. Further, the shell  10  may accommodate various types of pads having a lower repulsion force than the impact absorption liner, for example, to cushion the head. Also, the shell  10  may accommodate, for example, a shield support mechanism and a shield operation mechanism. 
     The shell  10  includes a shell outer surface  10 S, which is an outer surface of the shell  10  and forms the outermost surface of the helmet. The shell outer surface  10 S includes a plurality of ventilation holes  11 . In the present embodiment, the ventilation holes  11  are circular and include air intake holes  11 A and air discharge holes  11 B. The air intake holes  11 A are located in a front portion of the shell  10 , and the air discharge holes  11 B are located in a rear portion of the shell  10 . The shell outer surface  10 S does not have to include the air intake holes  11 A. Further, the air discharge holes  11 B may be located in only the rear portion of the shell  10  or a side portion of the shell  10 . 
     The air intake holes  11 A draw air into the shell  10 . The air intake holes  11 A are covered by a front intake (not shown) or an upper intake (not shown). The front intake or the upper intake is fixed to the shell outer surface  10 S to form an opening directed toward the front of the helmet and guide air to the air intake holes  11 A. 
     The air discharge holes  11 B discharge heat and moisture out of the shell  10 . In a case where the shell  10  accommodates an impact absorption liner, the impact absorption liner may form, for example, a passage that connects the air intake holes  11 A and the air discharge holes  11 B. Further, a passage that connects the inside of the impact absorption liner and the air discharge holes  11 B may be formed in, for example, the impact absorption liner. 
     The air discharge holes  11 B discharge the air drawn in through the air intake holes  11 A or the residual air inside the impact absorption liner out of the shell  10 . The diameter of the air discharge holes  11 B is, for example, 6 mm or greater and 12 mm or less. 
     The air discharge holes  11 B are covered by the air outlet  20 . The air outlet  20  is fixed to the shell outer surface  10 S to form an opening directed toward the rear of the helmet. The air outlet  20  guides the air exiting the air discharge holes  11 B toward the rear of the helmet. 
     In a case where the air discharge holes  11 B are located in the side portion of the shell  10 , an air outlet fixed to the side portion of the shell  10  covers the air discharge holes  11 B. The air outlet fixed to the side portion of the shell  10  also forms an opening directed toward the rear of the helmet to guide the air exiting the air discharge holes  11 B toward the rear of the helmet. 
     As shown in  FIG.  2   , the shell outer surface  10 S includes an outer surface coupling portion  12  used to couple the air outlet  20 . The outer surface coupling portion  12  is a recess located in the shell outer surface  10 S. The outer surface coupling portion  12  is located in the rear portion of the shell  10  at a central part with respect to the sideward direction of the shell  10 . The outer surface coupling portion  12  includes inclined surfaces  12 S, which are gradually inclined, and forms a smoothly curved surface in the shell outer surface  10 S. 
     As shown in  FIGS.  2  and  3   , the outer surface coupling portion  12  includes a bottom surface  12 B that is a three-dimensionally curved surface having a relatively small curvature in a front-rear direction and in the sideward direction. The bottom surface  12 B of the outer surface coupling portion  12  includes two air discharge holes  11 B. The two air discharge holes  11 B are located in end portions of the outer surface coupling portion  12  with respect to the sideward direction. The air outlet  20  is coupled to the outer surface coupling portion  12  by, for example, screws, which extend into the bottom surface  12 B, or an adhesive. 
     The air outlet  20  forms part of the outmost surface of the helmet. The air outlet  20  is a plastic plate member that is substantially plane-symmetric with respect to the symmetry plane S. The material of the air outlet  20  is selected from, for example, acrylonitrile-butadiene-styrene copolymer (ABS), polycarbonate (PC), or polypropylene (PP). 
     The air outlet  20  includes a main body  21  and a passage formation portion  22 . 
     Main Body  21   
     The main body  21  includes a main body front surface  21 S, which is a front surface of the main body  21 . The main body front surface  21 S is a three-dimensionally curved surface having a relatively small curvature in the front-rear direction and in the sideward direction. The main body  21  has the form of a curved plate such that the main body front surface  21 S and the shell outer surface  10 S appear as a continuous surface. The main body front surface  21 S is a surface that regulates the airflow and reduces airflow disturbance in the rear portion of the helmet. Thus, the air outlet  20  functions as a stabilizer. 
     As shown in  FIGS.  4  and  5   , the main body  21  includes a main body rear surface  21 B, which is a rear surface of the main body  21 . The main body rear surface  21 B has a smaller radius of curvature than the bottom surface  12 B of the outer surface coupling portion  12  in the front-rear direction and in the sideward direction of the helmet. The difference in the radius of curvature forms a space between the main body rear surface  21 B and the shell outer surface  10 S. 
     A periphery  21 E of the main body  21  includes a first peripheral portion  21 E 1  and a second peripheral portion  21 E 2 . 
     The first peripheral portion  21 E 1  is shaped in correspondence with part of the shell outer surface  10 S, for example, the inclined surfaces  12 S of the outer surface coupling portion  12  or the bottom surface  12 B of the outer surface coupling portion  12 . The first peripheral portion  21 E 1  forms a front edge and side edges in the periphery  21 E of the main body  21 . 
     The first peripheral portion  21 E 1  closes the space between the main body rear surface  21 B and the shell outer surface  10 S. The first peripheral portion  21 E 1  is in contact with the shell outer surface  10 S or located proximate to the shell outer surface  10 S to close the space between the main body rear surface  21 B and the shell outer surface  10 S. The closing of the space is not limited to sealing the space through touch contact of the first peripheral portion  21 E 1  with the shell outer surface  10 S. The closing of the space allows for the formation of a gap between the first peripheral portion  21 E 1  and the shell outer surface  10 S so that air can flow through the gap and enter the space between the main body rear surface  21 B and the shell outer surface  10 S. 
     The air outlet  20  may be formed so that the first peripheral portion  21 E 1  can slide on the inclined surfaces  12 S and be fitted to the inclined surfaces  12 S. In this case, the air outlet  20  may be configured to be fitted to the shell  10  in a removable manner. This allows the position of the air outlet  20  to be changed relative to the shell  10  and the air outlet  20  to be removed from the shell  10  for replacement. 
     The second peripheral portion  21 E 2  is arcuate and spaced apart from the shell outer surface  10 S. The second peripheral portion  21 E 2  forms the rear edge in the periphery  21 E of the main body  21 . 
     The second peripheral portion  21 E 2  and the bottom surface  12 B of the outer surface coupling portion  12  define an opening  20 P. The opening  20 P is an arcuate slit extending along the shell outer surface  10 S and opens the space between the main body rear surface  21 B and the shell outer surface  10 S. Opening the space means allowing for the generation of a larger amount of air flowing between the space, which extends between the main body rear surface  21 B and the shell outer surface  10 S, and the outside than when the space is closed. 
     The main body  21  may be shaped such that, for example, the radius of curvature of the main body rear surface  21 B is greater than that of the bottom surface  12 B as long as the main body  21  closes the space between the main body rear surface  21 B and the shell outer surface  10 S at the front and the sides and opens the opening  20 P at the rear of the space. Further, the main body rear surface  21 B may have the same shape as part of the shell outer surface  10 S. 
     Passage Formation Portion  22   
     As shown in  FIG.  4   , the passage formation portion  22  is located on the main body rear surface  21 B. The passage formation portion  22  includes left and right first passage formation portions  22 B and left and right second passage formation portions  22 A. The second passage formation portions  22 A are located at opposite ends of the main body rear surface  21 B in the sideward direction. The pair of the first passage formation portions  22 B are located between the pair of the second passage formation portions  22 A in the sideward direction. Specifically, one of the second passage formation portions  22 A is located at the left side of the two first passage formation portions  22 B, and the other one of the second passage formation portions  22 A is located at the right side of the two first passage formation portions  22 B. The two first passage formation portions  22 B are substantially plane-symmetric with respect to the symmetry plane S. Also, the two second passage formation portions  22 A are substantially plane-symmetric with respect to the symmetry plane S. 
     As shown in  FIG.  5   , the second passage formation portions  22 A are formed by ribs projecting from the main body rear surface  21 B toward the shell outer surface  10 S. Each second passage formation portion  22 A includes two open ribs  22 A 1  and one guide rib  22 A 2 . 
     The guide rib  22 A 2  extends from the second peripheral portion  21 E 2 , which defines the opening  20 P, into the space between the main body rear surface  21 B and the shell outer surface  10 S. In a view of the main body rear surface  21 B, the guide rib  22 A 2  is arcuate and protrudes from the second peripheral portion  21 E 2  into the space between the main body rear surface  21 B and the shell outer surface  10 S, that is, toward the front of the helmet. In other words, the guide rib  22 A 2  is U-shaped and is open toward the rear of the helmet. 
     Two ends of the arcuate guide rib  22 A 2  are located proximate to the second peripheral portion  21 E 2 , which defines the opening  20 P. Each guide rib  22 A 2  is disposed so that the guide rib  22 A 2  extends above and around a corresponding air discharge hole  11 B and is open toward the opening  20 P. Thus, each guide rib  22 A 2  defines a passage (second passage) from the air discharge hole  11 B toward the opening  20 P. The guide rib  22 A 2  serves as a boundary of the second passage, which is part of the space, and other portions of the space. In this manner, the guide rib  22 A 2  and the main body rear surface  21 B form the second passage in the space. 
     The two open ribs  22 A 1  are located proximate to the second peripheral portion  21 E 2 , which defines the opening  20 P. The two open ribs  22 A 1  are located between two ends of the corresponding guide rib  22 A 2 . The two open ribs  22 A 1  divide the passage formed by the guide rib  22 A 2  into three passages at the opening  20 P. In other words, the two open ribs  22 A 1  partition the second passage formed by the guide rib  22 A 2  and divide the second passage into three passages at the opening  20 P. 
     Each first passage formation portion  22 B includes two ribs projecting from the main body rear surface  21 B toward the shell outer surface  10 S. In a view of the main body rear surface  21 B, the ribs of the first passage formation portion  22 B are each arcuate and protrude from the second peripheral portion  21 E 2  into the space between the main body rear surface  21 B and the shell outer surface  10 S, that is, toward the front of the helmet. In other words, the ribs of the first passage formation portion  22 B are each U-shaped and open toward the rear of the helmet. In the view of the main body rear surface  21 B, one of the ribs of the first passage formation portion  22 B is located at the inner side of the other one of the ribs. 
     The two ribs of the first passage formation portion  22 B extend from the opening  20 P into the space between the main body rear surface  21 B and the shell outer surface  10 S and define a passage (first passage) returning to the opening  20 P from the space between the main body rear surface  21 B and the shell outer surface  10 S. Thus, the first passage formation portion  22 B includes two ribs that define the first passage. The first passage formation portion  22 B also serves as a boundary between the first passage, which is part of the space, and other portions of the space. The first passage formation portion  22 B is configured to divide the space into the first passage and other portions of the space. In this manner, the first passage formation portion  22 B and the main body rear surface  21 B form the first passage in the space. In the view of the main body rear surface  21 B, the first passage is U-shaped and protrudes from the second peripheral portion  21 E 2  (opening  20 P) toward the inner side of the main body  21  (into the space). In other words, the first passage is U-shaped and open toward the rear of the helmet. 
     Between the adjacent ones of second passage formation portion  22 A and the first passage formation portion  22 B, one end of the guide rib  22 A 2  of the second passage formation portion  22 A is coupled to one end of the outer rib of the first passage formation portion  22 B at the second peripheral portion  21 E 2 . Between the two adjacent first passage formation portions  22 B, one end of the outer rib of one first passage formation portions  22 B is coupled to one end of the outer rib of the other first passage formation portion  22 B at the second peripheral portion  21 E 2 . This increases the mechanical strength of the ribs that form the passage formation portion  22 . 
     Operation 
     As shown in  FIG.  6   , the air inside the shell  10  including hot air or moisture exits the air discharge holes  11 B of the shell outer surface  10 S and flows through the passage defined by the guide ribs  22 A 2 . Then, the hot air or moisture from the inside of the shell  10  is discharged as a discharged airflow FA through the opening  20 P, which is formed by the second peripheral portion  21 E 2  of the air outlet  20  and the shell outer surface  10 S, toward the rear of the helmet. 
     In this case, the step between the shell outer surface  10 S and the main body front surface  21 S generates a turbulent airflow near the opening  20 P. The turbulent airflow includes airflow FB directed toward the opening  20 P. According to experiments conducted by the inventors of the present invention, for example, when the wind velocity is 100 km/h and the diameter of the ventilation holes  11  is 6 mm or greater and 12 mm or less, the pressure distribution in the vicinity of the second peripheral portion  21 E 2  has a tendency to be higher at the central part in the sideward direction and lower toward the opposite ends in the sideward direction. As a result, the airflow FB enters the passage defined by each first passage formation portion  22 B from an entrance close to the central part of the second peripheral portion  21 E 2  and is discharged from an exit that is close to the adjacent passage defined by the guide rib  22 A 2 . 
     More specifically, based on the distribution of the negative pressure at the second peripheral portion  21 E 2 , the first passage formation portion  22 B generates the airflow FB directed from the space between the shell outer surface  10 S and the main body rear surface  21 B toward the rear. Consequently, the airflow FB aids the discharged airflow FA to increase the ventilation efficiency inside the shell  10 . 
     Further, the open ribs  22 A 1  divide and narrow a sideward width WA of the passage defined by the second passage formation portion  22 A at the opening  20 P so that a returning airflow like the airflow FB will not be generated. This regulates the discharged airflow FA and further improves the ventilation efficiency inside the shell  10 . 
     The amount of discharged air can be increased by increasing the number of discharge passages or the cross-sectional flow area of the discharge passages. However, the air discharge holes  11 B, which are part of the discharge passages, extend through the shell  10 . Thus, an increase in the number of the air discharge holes or enlargement of the air discharge holes to increase the cross-sectional flow area of the discharge passages will lower the mechanical strength, the impact resistance, and the penetration resistance of the shell  10 . Further, additional ribs or increased thickness of the shell  10  to raise the mechanical strength, the impact resistance, and the penetration resistance of the shell  10  will increase the weight of the helmet and manufacturing costs. 
     In this respect, the air outlet  20  including the passage formation portion  22  and the passage formation portion  22  configured to improve the ventilation efficiency readily obtain the mechanical strength of the shell  10  and the impact resistance of the shell  10 . 
     In a comparative example, a shutter mechanism that opens and closes the air discharge holes  11 B will prevent rain water from entering the air discharge holes  11 B. However, the addition of a separate shutter mechanism will increase the number of parts of the helmet and the manufacturing cost of the helmet. In this respect, the air outlet  20  of the present embodiment configured to cover the air discharge holes  11 B will limit increases in the number of parts and the manufacturing cost. 
     The above-described embodiment has the following advantages. 
     (1) The distribution of positive pressure and negative pressure occurs at a certain extent in the vicinity of the opening of the space between the shell outer surface and the main body rear surface because of various factors such as the entire shape of the shell outer surface, the shape of part of the shell outer surface, the dimensions of parts of the shell outer surface, and the shapes of accessories attached to the shell outer surface. In the above embodiment, positive pressure and negative pressure may be distributed in the vicinity of the opening  20 P of the space between the shell outer surface  10 S and the main body rear surface  21 B because of the location of the main body  21  on the shell outer surface  10 S, the shape of the shell outer surface  10 S, and the like. In the above-described structure, the passages (first passages) that extend from the opening  20 P through the space and return to the opening  20 P from the space are defined in the space between the shell outer surface  10 S and the main body rear surface  21 B. In this manner, the air drawn from one portion of the opening  20 P into the space flows out of another portion of the opening  20 P. This reduces the difference of the positive pressure and the negative pressure in the vicinity of the opening  20 P. As a result, the structure of the air outlet  20 , which is a member separate from the shell  10 , allows for a new control of the airflow compared to comparative examples lacking the above-described structure of the air outlet  20  and the shell  10 . 
     (2) The passage that extends from the opening  20 P into the space and returns to the opening  20 P from the space is defined by the ribs. This reduces the amount of material used to form the passage as compared with, for example, a structure in which the thickness of the main body  21  is increased from the above embodiment to form a groove defining the passage in the main body rear surface  21 B. 
     (3) In addition to the first passage formation portions  22 B, which define the passages (first passages) that reduce the difference of the positive pressure and the negative pressure in the vicinity of the opening  20 P, the air outlet  20  includes the second passage formation portions  22 A, which define the passages (second passages) that connect the inside and the outside of the shell  10 . The second passage formation portions  22 A extend from the space toward the opening  20 P and are connected to the air discharge holes  11 B, which extend through the shell  10 . The airflow FB generated by each of the first passages, which are defined by the first passage formation portions  22 B, increases the velocity of the discharged airflow FA generated by each of the second passages, which are defined by the second passage formation portions  22 A. This improves the ventilation efficiency inside the shell  10 . 
     (4) The air outlet  20  is located at the center at the rear portion of the shell  10  with respect to the sideward direction, and the first passage formation portions  22 B and the second passage formation portions  22 A are each symmetric in the sideward direction. This increase the stability of the air outlet  20 . Specifically, the air outlet  20  includes the left and right first passage formation portions  22 B and the left and right second passage formation portions  22 A that sandwich the first passage formation portions  22 B in the sideward direction. This reduces the difference of the positive pressure and the negative pressure in the vicinity of the opening  20 P at the left and right sides of the shell  10 . 
     Further, the ventilation performance obtained by the connection between the inside and the outside of the shell  10  can be improved at the left and right sides of the shell  10 . As a result, the air outlet improves airflow controllability at the left and right sides of the shell  10  in the same manner. Since the airflow controllability at the right side is the same as the airflow controllability at the left side, stability is improved, that is, stability is improved in the sideward direction when traveling. 
     (5) In a view of the main body rear surface  21 B, the first passages defined by the first passage formation portions  22 B are U-shaped and protrude from the opening  20 P into the space. In other words, the first passages defined by the first passage formation portions  22 B are U-shaped and protrude toward the front of the helmet. Thus, the airflow directed from the opening  20 P into the space is smoothly returned from the space to the opening  20 P. This also reduces pressure loss in the passages defined by the first passage formation portions  22 B. 
     (6) The air outlet  20  serves as a stabilizer including a surface that regulates the airflow and improves the ventilation performance Thus, airflow disturbances are reduced and the ventilation performance is improved when the single air outlet  20  is used. 
     The above embodiment may be modified as described below. 
     Airflow Control Member 
     The airflow control member is not limited to a top air outlet fixed to the rear portion of the shell  10 . For example, the airflow control member may be changed to, for example, a side air outlet fixed to a side surface of the shell  10 . 
     The airflow control member may be modified as long as it includes at least one first passage formation portion  22 B and at least one the second passage formation portion  22 A adjacent to the first passage formation portion  22 B. For example, an airflow control member that serves as a stabilizer may be arranged on each of the two side surfaces of the shell  10 . In this case, the shell  10  only includes one or more holes extending through the shell  10  and one or more passages for each airflow control member. 
     The passage formation portion of the airflow control member is applicable to a spoiler that serves as a resistance against the airflow and upwardly deflects the airflow. Specifically, the passage formation portion can be arranged on a rear surface of the spoiler facing the shell outer surface  10 S. 
     The passage formation portion of the airflow control member is applicable to a diffuser that diffuses the airflow. Specifically, the passage formation portion can be arranged on a rear surface of the diffuser facing the shell outer surface  10 S. 
     The second passage formation portion  22 A can be omitted from the airflow control member. Even in this structure, when the airflow control member reduces the difference of the positive pressure and the negative pressure, changes and disturbances in the airflow are reduced. This allows for a new control of the airflow that increases quietness or improves posture stability. 
     In the first passage formation portion  22 B of the above embodiment, the two ribs projecting from the main body rear surface  21 B toward the shell outer surface  10 S divide the opening  20 P in the sideward direction. Instead, as shown in  FIG.  7   , the first passage formation portion  22 B can be configured to divide the opening  20 P in a vertical direction. In this case, as shown in  FIG.  8   , the first passage formation portion  22 B defines a passage that extends from the upper side of the opening  20 P into the space and then from the space to the lower side of the opening  20 P. Specifically, the first passage formation portion  22 B divides part of the opening  20 P in the vertical direction to define an upper opening and a lower opening and connect the upper opening and the lower opening in the space between the main body rear surface  21 B and the shell outer surface  10 S. For example, the first passage formation portion  22 B includes a partition plate that divides the opening  20 P in the vertical direction and an outer rib located at the outer side of the partition plate. The partition plate divides the opening  20 P in the vertical direction and extends from the opening  20 P into the space. The partition plate is formed integrally with the outer rib and defines passages that are connected at the inner side of the outer rib. This defines the passage that extends from the upper side of the opening  20 P into the space and from the space to the lower side of the opening  20 P. 
     The air passing by the main body front surface  21 S generates a disturbed airflow at the rear end of the main body front surface  21 S. Thus, in the above modified example vertically connecting the opening  20 P with the passage, the air flowing into the upper opening proximate to the rear end of the main body front surface  21 S is discharged from the lower opening. Further, outer surface shapes of the outer surface coupling portion  12  and the air outlet  20  can be changed to draw air into the lower opening and discharge from the upper opening of the first passage formation portion  22 B. In this manner, the first passage formation portion  22 B formed in the vertical direction decreases the width of the air outlet  20  in the sideward direction. This allows for the helmet airflow control member to be reduced in size and weight. 
     The passage defined by the first passage formation portion  22 B may be V-shaped and protrude toward the front of the helmet or U-shaped to have right-angle corners and protrude toward the front of the helmet. The passage defined by the first passage formation portion  22 B may have any shape as long as airflow is directed from the opening  20 P into the space and returned from the space toward the opening  20 P. 
     The passage that generates the discharged airflow FA may be formed by the airflow control member in cooperation with the shell. For example, the airflow control member may include the open ribs  22 A 1 , and the shell outer surface  10 S may include the guide rib  22 A 2 . This structure also has better mechanical strength and impact resistance in the shell  10  compared to a structure in which the passage formation portion is arranged on the shell outer surface  10 S. 
     The passage that generates the airflow FB may be formed by the airflow control member in cooperation with the shell. For example, the airflow control member may include the inner rib, and the shell outer surface  10 S may include the outer rib. This structure also has better mechanical strength and impact resistance in the shell  10  compared to a structure in which the passage formation portion is arranged on the shell outer surface  10 S. 
     Helmet 
     The helmet is not limited to be of a full face type and can be changed to various types of helmets such as a flip up type helmet, of which a chin portion can be lifted, or an open face type helmet, which does not have a chin portion. 
     Various changes in form and details may be made to the examples above without departing from the spirit and scope of the claims and their equivalents. The examples are for the sake of description only, and not for purposes of limitation. Descriptions of features in each example are to be considered as being applicable to similar features or aspects in other examples. Suitable results may be achieved if sequences are performed in a different order, and/or if components in a described system, architecture, device, or circuit are combined differently, and/or replaced or supplemented by other components or their equivalents. The scope of the disclosure is not defined by the detailed description, but by the claims and their equivalents. All variations within the scope of the claims and their equivalents are included in the disclosure.