Abstract:
Disclosed is a length-variable bumper capable of adjusting the length of a vehicle body to lengthen a time interval over which momentum changes upon collision. The length-variable bumper includes a bumper member primarily absorbing collision energy, a collision energy absorbing member foldable in a longitudinal direction, and an operation unit configured to transit the collision energy absorbing member to an unfolded state when a vehicle speed is a predetermined level or more and to transit the collision energy absorbing member to a folded state when the vehicle is the to predetermined level or less. The collision energy absorbing member has one end connected to a frame of the vehicle and the other end connected to the bumper member and configured to be deformed upon collision to secondarily absorb the collision energy.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2009-0076822, filed on Aug. 19, 2009, the disclosure of which is hereby incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a length-variable shock absorbing apparatus for a vehicle, and more particularly, to a length-variable shock absorbing apparatus for a vehicle capable of lengthening the length of a bumper in a longitudinal direction of a vehicle to form a space for absorbing collision energy upon collision of the vehicle to secure safety of a driver when a vehicle speed is more that a predetermined level, and reducing the length of the bumper in the longitudinal direction of the vehicle to readily park the vehicle when the vehicle speed is lower than the predetermined level, and a vehicle employing the same. 
     2. Description of the Related Art 
     In the recent automobile industries, safety regulations for protection of drivers from collisions of vehicles have been further strengthened. There are laws related to automobile safety standards, and the standards have become stricter with development of automobile technologies. Automobile makers are establishing stricter internal standards to compete with other makers, independently from the laws. 
     Such automobile safety apparatus may be generally classified into equipment for preventing occurrence of accidents themselves and equipment for protecting drivers in the case of accidents. 
     In recent times, most automobiles are equipped with electronic control devices for preventing traffic accidents. While the prevention of accidents is the best way of protecting drivers, it is impossible for such apparatus to completely prevent accidents. In addition, such apparatus cannot protect the drivers in the case of accidents. For this reason, various equipment of reducing injury to drivers have been developed. 
     Impulse is change in momentum, and is in proportion to a time interval over which a force is applied. Therefore, when the same impulse is applied, a magnitude of a force is in reverse proportion to a time interval over which the force is applied. That is, if a vehicle collides at a high speed, since change in momentum is large, the magnitude of the force applied to a passenger increases. Therefore, when a vehicle is designed such that a deformation section of the vehicle becomes longer when the vehicle collides at a high speed, the length of a collision energy absorbing section may increase to relatively reduce the force applied to the passenger. On the other hand, since impulse is small when a vehicle collides at a low speed, the length of the collision energy absorbing section may be reduced to consider both driving performance and parking convenience. 
     For example, safety belts, airbags, etc., can protect drivers when vehicles collide. These equipment functions to increase a time interval over which a shock is absorbed to instantly reduce the force applied to the passenger. However, in the case of a small-sized vehicle having a relatively short length, even when the vehicle is provided with the equipment, it is difficult for the vehicle to substantially reduce impulse due to its structural disadvantages as compared with a mid-or large-sized vehicle. In particular, when the small-sized vehicle collides at a high speed, change in acceleration is very large and a time interval for dissipating the colliding energy is insufficient, increasing probability of injury to the passenger. 
     In order to solve the problems, various researches have been performed to improve the structures of vehicles to effectively absorb collision energy or employ novel energy absorbing materials. In relation to improvement of the vehicle structure, a bumper that can project immediately before collision may be used. However, the bumper may project even when there is no collision, possibly causing traffic accidents. Moreover, a hydraulic or pneumatic bumper is very expensive and heavy. 
     SUMMARY OF THE INVENTION 
     The present invention, therefore, solves aforementioned problems associated with conventional devices by providing a length-variable shock absorbing apparatus, which is light and inexpensive, capable of projecting a bumper to form a space for absorbing collision energy upon high speed collision when a vehicle is running at a predetermined speed or more, and retracting the bumper when the vehicle is running at a predetermined speed or less, thereby forming a collision energy absorbing space depending on the vehicle speed. 
     In an exemplary embodiment of the present invention, there is provided a length-variable shock absorbing apparatus for a vehicle comprising: a bumper member disposed in the front of a vehicle and primarily absorbing collision energy upon collision; a collision energy absorbing member foldable in a longitudinal direction thereof, having one end connected to a frame of the vehicle and the other end connected to the bumper member, and configured to be deformed upon collision to secondarily absorb the collision energy; and an operation unit configured to transit the collision energy absorbing member to an unfolded state when a vehicle speed is a predetermined level or more and to transit the collision energy absorbing member to a folded state when the vehicle is the predetermined level or less. 
     The collision energy absorbing member may have grooves longitudinally disposed at predetermined intervals to be entirely collapsed upon collision. 
     The collision energy absorbing member have a cross-sectional area of a portion connected to the bumper member smaller than that of a portion connected to the vehicle frame, and a linear surface with no step in a longitudinal direction thereof. 
     The operation unit may include: a motor; a screw disposed at the vehicle frame in a longitudinal direction of the vehicle and driven by the motor; a linear member projecting from the vehicle frame or retracting toward the vehicle frame by the screw; and a connection member having one end connected to a side surface of the linear member and the other end connected to the collision energy absorbing member to push the collision energy absorbing member to be unfolded when the linear member projects and pull the colliding member absorbing member to be folded when the linear member retracts. 
     The linear member may have grooves longitudinally disposed at predetermined intervals to be entirely collapsed upon collision. 
     The linear member may have a cross-sectional area of a portion connected to the bumper member smaller than that of a portion connected to the vehicle frame. 
     The collision energy absorbing member may have a front end coupled to the bumper member and a rear end coupled to the vehicle frame, the front end being longer than the rear end such that the front end and the rear end forms a predetermined angle to obtain a predetermined space between the bumper member and the frame when the collision energy absorbing member is folded, enhancing absorption of collision energy upon low speed collision. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features of the present invention will be described in reference to certain exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a perspective view of a length-variable bumper in accordance with an exemplary embodiment of the present invention; 
         FIG. 2  is a plan view of the length-variable bumper in accordance with the exemplary embodiment of the present invention shown in  FIG. 1 ; 
         FIG. 3  is a perspective view of the length-variable bumper in accordance with the exemplary embodiment of the present invention having grooves formed in a folded collision energy absorbing member at predetermined intervals; 
         FIG. 4  is a perspective view of the length-variable bumper in accordance with the exemplary embodiment of the present invention having grooves formed at an unfolded collision energy absorbing member at predetermined intervals; 
         FIG. 5  is a plan view of the length-variable bumper in accordance with the exemplary embodiment of the present invention shown in  FIG. 4 ; 
         FIG. 6  is a plan view showing a collision state in which the unfolded collision energy absorbing member is in an offset state; 
         FIG. 7  is a plan view showing a collision state in which the folded collision energy absorbing member is in an offset state; and 
         FIG. 8  is a perspective view of a vehicle on which the length-variable bumper is mounted. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. 
       FIG. 1  is a perspective view schematically showing a frame of a vehicle to which a length-variable shock absorbing apparatus for a vehicle in accordance with an exemplary embodiment of the present invention is mounted.  FIG. 2  is a plan view of the frame of a vehicle shown in  FIG. 1 .  FIG. 3  is a perspective view of a folded collision energy absorbing member  20  having grooves formed at predetermined intervals;  FIG. 4  is a perspective view of the unfolded collision energy absorbing member  20  of  FIG. 3 .  FIG. 5  is a plan view of the length-variable bumper in which the shock absorbing member  20  shown in  FIG. 4  is folded. 
     Referring to  FIG. 1 , the length-variable shock absorbing apparatus for a vehicle in accordance with an exemplary embodiment of the present invention includes a bumper member  10 , a collision energy absorbing member  20 , and an operation unit  30 . 
     In the length-variable shock absorbing apparatus for a vehicle in accordance with the exemplary embodiment of the present invention, the length of the collision energy absorbing member  20  is maximized when a vehicle speed reaches a predetermined speed, which may cause a certain level of impulse or more. That is, the length of the vehicle increases by substantially the length of the collision energy absorbing member  20 . In this state, when head-on collision between vehicles or between a vehicle and an object occurs, the collision energy absorbing member  20  fixed to a frame F is deformed to absorb collision energy, remarkably reducing the collision energy transmitted to the vehicle body. 
     The buffer member  10  shown in  FIGS. 1 to 8  is disposed in the front of the vehicle. The buffer member  10  contacts with an object first upon collision of the vehicle. The bumper member  10  is formed of a material, which is light and can absorb shocks, and absorbs all collision energy when a fender bender occurs. While the bumper member is shown as a plate shape in  FIG. 1 , the bumper member may surround the entire length-variable bumper as shown in  FIG. 8 . 
     As shown in  FIGS. 1 and 3 , the collision energy absorbing member  20  is disposed between the bumper member  10  and the frame F. In this embodiment, the collision energy absorbing member  20  includes two beam members  21  and  22  extending along a longitudinal direction of the vehicle. The respective beam members  21  and  22  are formed of a light and rigid material. While the beam members  21  and  22  have a rectangular column shape, they may have, although not limited thereto, a cylindrical column shape, a polygonal column shape, etc., which may function as a support between the bumper member  10  and the frame F. Each beam member  21  or  22  is configured to connect the front member and the rear member via a hinge, etc., such that the front member and the rear member can be foldable in the longitudinal direction of the vehicle. One ends of front members  21   a  and  22   a  are connected to the bumper member  10  via hinges, etc., and ends of rear members  21   b  and  22   b  are rotatably connected to the frame F via hinges, etc. 
     The respective beam members  21  and  22  of the collision energy absorbing member  20  may have grooves formed at predetermined intervals in a longitudinal direction thereof. As described above, since the collision energy absorbing member  20  is entirely collapsed upon collision, the collision energy is substantially absorbed by the collision energy absorbing member  20  to reduce the collision energy transmitted to the frame F. 
     The respective beam members  21  and  22  of the collision energy absorbing member  20  have a cross-sectional area connected to the bumper member  10  larger than that connected to the frame F. The cross-sectional area may be continuously varied from a portion of each beam member  21  and  22  connected to the frame F to a portion thereof connected to the bumper member  10 . As a result, the front portions of the beam members  21  and  22  are more effectively deformed than the rear portions thereof so that the collision energy absorbed by the collision energy absorbing member  20  increases to reduce the collision energy transmitted to the vehicle body. 
     As shown in  FIG. 5 , the operation unit  30  for controlling movement of the collision energy absorbing member  20  includes a motor  31 , a screw  32 , a linear member  33  and a connection member  34 . 
     The screw  32  is installed in the frame F of the vehicle. The motor  31  is operated to rotate the screw  32 . The motor  31  is controlled by a signal of an external control terminal configured to read change in vehicle speed. The external control terminal drives the motor  31  to lengthen the length-variable shock absorbing apparatus when a vehicle speed is a predetermined level or more, and drives the motor to shorten the length-variable shock absorbing apparatus when the vehicle speed is the predetermined level or less. The signal from the external control terminal increases a speed limit range of a conventional vehicle speed sensor or reads change in acceleration to prevent malfunction of the apparatus due to slide movement, etc., when the vehicle runs on a bad road surface caused by rain or snow. When the speed sensor, which is set as described above, detects that the vehicle speed is the predetermined level or more, the motor  31  is operated to drive the screw  32  so that the linear member  33  moves forward or rearward. 
     As shown in  FIGS. 1 and 2 , the linear member  33  is coupled to the screw  32  to reciprocate forward and rearward depending on a rotational direction of the screw  32 . 
     The linear member  33  may be formed of a light and rigid material. In addition, the linear member  33  may have grooves formed at predetermined intervals in a longitudinal direction thereof to perform a collision energy absorbing function together with the collision energy absorbing member  20 , or may have a trapezoidal structure so that the front part can be readily deformed to effectively absorb collision energy. 
     As shown in  FIGS. 1 and 6 , the connection member  34  completely restrains the linear member  33  and the respective beam members  21  and  22  of the collision energy absorbing member  20  when the linear member  33  is completely moved forward. The linear member  33  and the respective beam members  21  and  22  of the collision energy absorbing member  20  completely restrained by the connection member  34  are not pushed upon collision. 
     As shown in  FIGS. 2 and 5 , one end of the connection member  34  is rotatably connected to a side surface of the linear member  33 . The opposite end of the connection member  34  is also rotatably connected to the collision energy absorbing member  20 . As a result, when the screw  32  moves the linear member  33  forward, the connection member  34  gradually forms an included angle from a state parallel to the linear member  33 . As the included angle increases, the connection member  34  pushes the collision energy absorbing member  20  to form a certain space in the front of the vehicle. At this time, the linear member  33  and the respective beam members  21  and  22  of the collision energy absorption member  20  are parallel to each other, and the connection member  34  is perpendicularly disposed therebetween. In this state, the connection member  34  supports the linear member  33  and the respective beam members  21  and  22  of the collision energy absorbing member  20 . On the contrary, when the linear member  33  is moved backward, the connection member  34  perpendicular to the respective beam members  21  and  22  of the collision energy absorbing member  20  is also moved backward. The connection member  34  is returned back to its original state to fold the respective beam members  21  and  22  of the collision energy absorbing member  20  to reduce the space. 
     Hereinafter, the operation of the length-variable bumper in accordance with an exemplary embodiment of the present invention will be described with reference to the accompanying drawings. 
       FIGS. 4 and 5  show the length-variable bumper before operation. That is, when the vehicle is in a stop state or runs at a low speed, the length-variable bumper has a short length. 
     In the length-variable bumper having the short length, when the vehicle is accelerated to a predetermined speed or more, the motor  31  drives the screw  32 . The screw  32  moves the linear member  33  forward depending on a rotational speed of the screw  32 . The linear member  33  moves forward to push the connection member  34  connected to its side surface in parallel to widen the included angle. 
     The linear member  34  is connected to the collision energy absorbing member  20 . As the linear member  34  moves forward, the connection member  34  pushes the folded collision energy absorbing member  20  to gradually unfold it. The linear member  34  is completely moved forward to be parallel to the collision energy absorbing member  20 , and the connection member  34  is perpendicularly disposed between the linear member  33  and the collision energy absorbing member  20  to support them.  FIGS. 1 and 3  show that the linear member  33  is completely moved forward and the connection member  34  completely unfolds the collision energy absorbing member  20  so that the length-variable bumper is maximally lengthened. 
       FIG. 6  is a plan view showing that collision occurs in an offset state in which the collision energy absorbing member  20  is unfolded. That is, when the length-variable bumper is maximally lengthened and a head-on collision occurs in the offset state, the collision energy absorbing member  20  in a collision state is deformed to absorb a certain amount of collision energy, minimizing collision energy transmitted to the vehicle body. Therefore, passengers can be safely protected from frequent offset collisions. In addition, in the case of the collision accident shown in  FIG. 6 , since the collision energy absorbing member  20 , the bumper member  10 , and the operation unit  30  can be repaired by changing only some components thereof, it is possible to reduce repair costs of the vehicle body. 
     When the vehicle running at the high speed as shown in  FIGS. 1 and 3 , in which the length-variable shock absorbing apparatus is maximally lengthened, is decelerated to a predetermined speed or less, the motor  31  drives the screw  32  in a reverse direction. The screw  32  driven in the reverse direction gradually moves the linear member  33  backward. At this time, the linear member  33  moves backward to pull the connection member  34  perpendicular to the linear member  33 , and the collision energy absorbing member  20  connected to the connection member  34  is gradually folded. When the collision energy absorbing member  20  is completely folded, the length-variable shock absorbing apparatus for a vehicle is minimally shortened to reduce the length of the vehicle. 
       FIG. 7  shows that a collision occurs in an offset state when the collision energy absorbing member  20  is folded. If the front members  21   a  and  22   a  of the collision energy absorbing member  20  are longer than rear members  21   b  and  22   b , even when they are completely folded, the front members  21   a  and  22   a  are not in contact with the rear members  21   b  and  22   b  to form a predetermined angle and thus a predetermined space. Even when the variable length is short as shown in  FIG. 7 , it is possible to obtain a certain space. In this case, while the collision energy absorbing member  20  is folded, collision energy can be absorbed by the obtained space even when another vehicle collides with the member  20  at a high speed. In addition, when the vehicle is damaged to an extent shown in  FIG. 7 , since some components of the length-variable bumper may be exchanged without repair of the vehicle body, repair costs can be reduced. 
       FIG. 8  shows a three-wheel single-seat vehicle on which the length-variable shock absorbing apparatus for a vehicle in accordance with an exemplary embodiment of the present invention is mounted. It is transparently illustrated that the length-variable shock absorbing apparatus for a vehicle is moved forward, and it is translucently illustrated that the length-variable shock absorbing apparatus for a vehicle is in a stop position or moved backward. 
     As can be seen from the foregoing, a length-variable shock absorbing apparatus for a vehicle in accordance with the present invention has the following effects. 
     The length of the vehicle can be varied depending on a vehicle speed to obtain a collision energy absorbing space upon collision at a high speed, making it possible to more safely protect a passenger, and the length of the vehicle can be reduced at a lower speed or upon stop to provide both driving performance and parking convenience. 
     Since the apparatus can be operated using a motor, not a hydraulic or pneumatic pressure, the apparatus is light and inexpensive, and can precisely control a length-variable bumper. 
     In addition, when accidents occur, the vehicle body can be less damaged to protect the engine, reducing repair costs. 
     Although the present invention has been described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that a variety of modifications and variations may be made to the present invention without departing from the spirit or scope of the present invention defined in the appended claims, and their equivalents.