Abstract:
An aerodynamic device provided as a plate-shaped body attached to a roof or a side wall of a vehicle includes means configured to selectively raise ribs arranged in two directions from a surface portion of the plate-shaped body in a switching manner between the two directions.

Description:
INCORPORATION BY REFERENCE 
       [0001]    The disclosure of Japanese Patent Application No. 2016-095742 filed on May 12, 2016 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
       BACKGROUND 
     1. Technical Field 
       [0002]    The present disclosure relates to an aerodynamic device. More specifically, the present disclosure relates to a device that optimizes aerodynamic characteristics of a vehicle against a side wind, such as an anti-lift characteristic and an anti-yaw characteristic. 
       2. Description of Related Art 
       [0003]    Published Japanese Translation of PCT Application No. 9-511466 (JP-T 9-5114661 describes as follows: in order to restrain a spin by more strongly pressing a rear part of an automobile against a road surface at the time when the automobile spins out at a high speed, a rear part of a roof of the automobile is configured such that a part of a rectangular shape of a board member forming a contour surface of the roof is raised by a hinge appropriately so as to receive a travel wind as an air deflector to generate a force to press the rear part of the automobile downward. A pair of air deflectors are placed side by side in a vehicle width direction and have such a posture that each of the air deflectors is provided so as to be inclined relative to the vehicle width direction such that its outer end in the vehicle width direction is biased toward a vehicle front side relative to its inner end, so that the pair of air deflectors enclose the travel wind blowing from a front side of the vehicle. Further, Japanese Patent Application Publication No. 2006-168636 (JP 2006-168636 A) describes that a wing member extending in a vehicle width direction on a roof of an automobile and configured to change an angle of attack with respect to a travel wind from a vehicle front side is provided movably in a vehicle longitudinal direction, and a lengthwise position of such a wing member and the angle of attack are controlled depending on a vehicle travel state, so as to achieve improvement of stability of vehicle travel. 
       SUMMARY 
       [0004]    When a side wind blows during travel of a vehicle, a vector of a travel wind and a vector of the side wind are added. On this account, a flow velocity of an air stream flowing along a roof or a side wall of the vehicle with respect to a surface of the roof or the side wall may become very fast. When the air stream with such a fast flow velocity flows along a smooth surface of the roofer the side wall of the vehicle, a negative pressure is generated thereon. Due to the negative pressure applied to the roof or the side wall of the vehicle, a vertical load of the vehicle is reduced or a yawing moment is applied to the vehicle, which may affect traveling characteristics. 
         [0005]    The present disclosure provides an aerodynamic device for aerodynamic characteristics of a vehicle against a side wind, such as an anti-lift characteristic and an anti-yaw characteristic. 
         [0006]    A first aspect of the present disclosure provides an aerodynamic device provided as a plate-shaped body attached to a roof or a side wall of a vehicle. The aerodynamic device includes means configured to selectively raise ribs arranged in two directions from a surface portion of the plate-shaped body in a switching manner between the two directions. 
         [0007]    A second aspect if the present disclosure provides an aerodynamic device. The aerodynamic device includes a body portion provided as a plate-shaped body attached to a roof or a side wall of a vehicle, the body portion including ribs arranged along two directions on a surface portion of the body portion; and means configured to selectively raise the ribs. The ribs may be provided so as to extend from a middle of the roof of the vehicle to a rear part of the roof. A sheet material made of an elastic body may be provided in a stretched manner on surfaces of the ribs. 
         [0008]    As described above, the device provided as the plate-shaped body attached to the roof or the side wall of the vehicle includes the means that selectively raises the ribs arranged in respective directions from the surface portion in a switching manner between the two directions. Accordingly, if such a device is attached to the roof or the side wall of the vehicle so that the ribs are raised appropriately depending on the intensity of the side wind, it is possible to prevent generation of a negative pressure such that an air stream flowing along the roof or the side wall of the vehicle is disturbed by the ribs, thereby making it possible to restrain traveling stability from being unpaired due to a reduction of a vertical load of the vehicle by the side wind or due to application of a yawing moment to the vehicle. In this case, an air stream obtained by adding a vector of the side wind to a vector of the travel wind of the vehicle blows from a diagonal left front side or a diagonal right front side depending on a direction of the side wind. Accordingly, particularly in a roof part of the vehicle, a direction of the air stream flowing along the roof part greatly changes right and left frequently. However, if an arrangement direction of the ribs thus raised is switched between the two directions, it is possible to optimize the arrangement direction of the ribs thus raised according to the direction of the side wind. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
           [0010]      FIG. 1  is a plan view illustrating an example in which an aerodynamic device according to one embodiment of the disclosure is provided on a roof of a vehicle; 
           [0011]      FIG. 2  is a plan view illustrating the aerodynamic device in a state where any ribs in two directions are not raised; 
           [0012]      FIG. 3A  is a plan view illustrating a state where one of the ribs is not raised; 
           [0013]      FIG. 3B  is a side view illustrating a state where one of the ribs is not raised; 
           [0014]      FIG. 4A  is a plan view illustrating a state where one of the ribs is raised; 
           [0015]      FIG. 4B  is a side view illustrating a state Where one of the ribs is raised; 
           [0016]      FIG. 5  is a plan view, similar to  FIG. 2 , illustrating the aerodynamic device in a state where its ribs are raised only in one direction; 
           [0017]      FIG. 6  is a plan view, similar to  FIG. 2 , illustrating the aerodynamic device in a state where its ribs are raised only in the other one direction; 
           [0018]      FIG. 7  is a graph illustrating an example of an experimental result of a lift restraint effect of the aerodynamic device according to the embodiment of the disclosure; and 
           [0019]      FIG. 8  is a graph illustrating an example of an experimental result of a yaw restraint effect of the aerodynamic device according to the embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0020]      FIG. 1  is a plan view illustrating an example in which an aerodynamic device according to one embodiment of the disclosure is provided on a roof of a vehicle. In  FIG. 1 , an aerodynamic device  10  is provided so as to form a plate-shaped body and extend from a middle of the roof of the vehicle to a rear part thereof. 
         [0021]    As illustrated in  FIG. 2 , the aerodynamic device  10  has a structure in which strips  12 ,  14 ,  16 ,  18 ,  20  that form ribs that should be raised when an air stream caused by a vector sum of a travel wind of the vehicle and a side wind blows toward the vehicle from a diagonal left front side and strips  22 ,  24 ,  26 ,  28 ,  30 ,  32 ,  34  that form ribs that should be raised when an air stream caused by a vector sum of the travel wind of the vehicle and a side wind blows toward the vehicle from a diagonal right front side are woven in an intersected manner. One ends of these strips are fixed to a rectangular fixed frame body  36 . 
         [0022]    The other ends of the strips  12 ,  14 ,  16 ,  18 ,  20  are fixed to an L-shaped movable frame body  38 . The other ends of the strips  22 ,  24 ,  26 ,  28 ,  30 ,  32 ,  34  are fixed to an L-shaped movable frame body  40 . The movable flame body  38  can be moved by an actuator  100  in a direction from a state illustrated in  FIG. 2  toward a left upper side in the figure. The movable frame body  40  can be moved by an actuator  200  in a direction from the state illustrated in  FIG. 2  toward a right upper side in the figure. These actuators  100 ,  200  are controlled b a controller  300 . 
         [0023]    The strip is configured such that three rib formation hinges in total are provided in exposed parts of the strip in a distributed manner over an extending direction of the strip. One of the rib formation hinges is indicated by a reference sign  42 . As illustrated in  FIGS. 3 and 4 , the rib formation hinge such as the rib formation hinge  42  is provided so as to include, in part of the strip  26 , for example, one pivot portion  44  to be folded upward and two pivot portions  46 ,  48  provided along both sides of the pivot portion  44  so as to be folded downward. A clip spring  50  configured to bias the rib formation hinge from a non-raised state illustrated in  FIG. 3  toward a raised state illustrated in  FIG. 4  is incorporated into the pivot portion  44 . When the one end of the strip is pushed toward the other end, the rib formation hinge is promoted to be raised by a biasing force of the clip spring  50  as illustrated in  FIG. 4 , so as to form a mound-shaped rib. 
         [0024]      FIG. 5  illustrates a state where the movable frame body  38  is driven toward a left upper direction in the figure relative to the fixed frame body  36  from the state illustrated in  FIG. 2  and the rib formation hinges in the strips  12 ,  14 ,  16 ,  18 ,  20  are accordingly raised in a mound shape. This is an operation state of the device in a case where the air stream caused by the vector sum of the travel wind of the vehicle and the side wind blows toward the vehicle from the diagonal left front side. 
         [0025]      FIG. 6  illustrates a state Where the movable frame body  40  is driven toward a right tipper direction in the figure relative to the fixed frame body  36  from the state illustrated  FIG. 2 , and the rib formation hinges in the strips  22 ,  24 ,  26 ,  28 ,  30 ,  32 ,  34  are accordingly raised in a mound shape. This is an operation state of the device in a case where the air stream caused by the vector sum of the travel wind of the vehicle and the side wind blows toward the vehicle from the diagonal right front side. 
         [0026]    The device may be configured such that the surfaces of the strips woven in an intersected manner are just exposed, or may be configured such that a flexible sheet material, such as a rubber sheet, elastically deformable in longitudinal and width directions may be provided in a stretched manner on the strips thus woven in an intersected manner. In a case where such a sheet material is provided in a stretched manner, when the rib formation hinges are raised to form mound-shaped ribs, the surface of the device is in such a state where parts between adjacent mound-shaped ribs are smoothly recessed in a valley shape with parts corresponding to the mound-shaped ribs being taken as apexes of respective protrusions. 
         [0027]      FIG. 7  illustrates an example of an experimental result of a lift restraint effect (a device effect) of the aerodynamic device according to the present disclosure in terms of a lift coefficient with respect to a deflection angle. The deflection angle is an angle of a direction of the vector sum of the travel wind of the vehicle and the side wind with respect to the vehicle longitudinal direction, and the lift coefficient is a zero-other coefficient obtained by comparing a lift caused by the wind with a geometrically calculated value. A characteristic line indicated by a solid line in the figure shows a value in a case where the device of the present disclosure is not provided, and a characteristic line indicated by a broken line shows an effect of the device of the present disclosure. In this case, a value of the lift coefficient with respect to a positive deflection angle is a value obtained when the ribs of the device are set with respect to a side toward which the side wind blows, and a value of the lift coefficient, indicated by the broken line, with respect to a negative deflection angle is a value obtained when the ribs of the device are set with respect to a side wind toward an opposite side to the above side-wind blowing side. 
         [0028]      FIG. 8  illustrates an example of an experimental result of a yaw restraint effect (a device effect) of the aerodynamic device according to the present disclosure in terms of a yawing moment coefficient with respect to a deflection angle. The yawing moment coefficient is a zero-order coefficient obtained by comparing a yawing moment caused by a side wind with a geometrically calculated value. Similarly, in the figure, a characteristic line indicated by a solid line shows a value in a case where the device of the present disclosure is not provided, and a characteristic line indicated by a broken line shows an effect of the device of the present disclosure. A value of the yawing moment coefficient, indicated by the broken line, with respect to a positive deflection angle is a value obtained when the ribs of the device are set with respect to a side where the side wind blows, and a value of the yawing moment coefficient, indicated by the broken line, with respect to a negative deflection angle is a value obtained when the ribs of the device are set with respect to a side wind toward an opposite side to the above side-wind blowing side. 
         [0029]    The embodiment of the present disclosure has been described above in detail, but it is obvious to those skilled in the art that, the above embodiment is variously modifiable within the scope of the invention.