Abstract:
A collision detecting device includes a chamber member providing a chamber, a pressure sensor connected to the chamber member, and a bumper absorber absorbing an impact generated by collision of an object with the vehicle. The bumper absorber has a region, which has a thickness in a front-rear direction of the vehicle. The thickness of the region is equal to or smaller than a predetermined thickness. The region is in contact with at least a portion of the chamber member. The collision is detected based on the pressure of the chamber detected by the pressure sensor. Hereby, a collision detecting device in which the bumper absorber has sufficient rigidity, and the chamber has sufficient deformability in case of collision can be obtained.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based on Japanese Patent Application No. 2007-186107 filed on Jul. 17, 2007, the disclosure of which is incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a collision detecting device for detecting collision of a pedestrian or the like with a vehicle. 
       BACKGROUND OF THE INVENTION 
       [0003]    The conventional obstacle determination device for vehicles is disclosed in JP-A-2006-117157 corresponding to US 2006/0087417 A1 as a pedestrian collision detecting device for detecting collision of a pedestrian or the like with a vehicle. The obstacle determination device includes an absorber, a pressure sensor, a velocity sensor and an airbag ECU device. The absorber is a member for absorbing an impact generated by collision of an object with a vehicle. The absorber includes a chamber member and a connection member. The chamber member is attached to a front surface of a bumper reinforcement by the connection member. Air is filled in a chamber which is provided by the chamber member. The pressure sensor detects a pressure inside the chamber. The pressure sensor is connected to the connection member through a tube. The velocity sensor is a sensor for detecting a velocity of the vehicle and arranged inside the vehicle. The pressure sensor and the velocity sensor are connected to the airbag ECU. The airbag ECU determines based on detecting results of the pressure sensor and the velocity sensor whether collision with a bumper of the vehicle is caused by a pedestrian. Specifically, the airbag ECU determines whether the pressure in the chamber exceeds a threshold value determined by a running velocity of the vehicle. 
         [0004]    Standards of vehicles for North America require to have a structure of vehicles that breakage of the vehicle can be suppressed as much as possible even when the collision is caused. Thus, the absorber is made to be rigid. However, when the absorber is rigid, the chamber member is deformed only a little in case of collision is caused. That is, the deformation of the chamber member is limited. Therefore, it becomes difficult to change the pressure inside the chamber and it is difficult to determine the collision of the object with the vehicle accurately. 
       SUMMARY OF THE INVENTION 
       [0005]    In view of the above-described problem, it is an object of the present disclosure to provide a collision detecting device in which a bumper absorber has sufficient rigidity, and a chamber has sufficient deformability in case of collision. 
         [0006]    According to a first aspect of the present disclosure, a collision detecting device for a vehicle includes: a chamber member providing a space, and arranged in front of a bumper reinforcement extending in a lateral direction of the vehicle; a pressure sensor connected to the chamber member, and detecting a pressure inside the space; and a bumper absorber absorbing an impact generated by collision of an object with the vehicle, and arranged in front of the bumper reinforcement. The bumper absorber has a region, which has a thickness in a front-rear direction of the vehicle. The thickness of the region is equal to or smaller than a predetermined thickness. The region is in contact with at least a portion of the chamber member. The collision is detected based on the pressure of the space detected by the pressure sensor. 
         [0007]    Hereby, a collision detecting device in which a bumper absorber has sufficient rigidity, and a chamber has sufficient deformability in case of collision can be obtained. 
         [0008]    According to a second aspect of the present disclosure, a collision detecting device for a vehicle includes: a chamber member providing a space, and arranged in front of a bumper reinforcement extending in a lateral direction of the vehicle; a pressure sensor connected to the chamber member, and detecting a pressure inside the space; and a bumper absorber absorbing an impact generated by collision of an object with the vehicle, and arranged in front of the bumper reinforcement. The bumper absorber includes at least one of a concave portion and a hollow portion. A portion of the chamber member is accommodated in the at least one of the concave portion and the hollow portion. The collision is detected based on the pressure of the space detected by the pressure sensor. 
         [0009]    Hereby, a collision detecting device in which a bumper absorber has sufficient rigidity, and a chamber has sufficient deformability in case of collision can be obtained. 
         [0010]    According to a third aspect of the present disclosure, a collision detecting device for a vehicle includes: a chamber member providing a space, and arranged in front of a bumper reinforcement extending in a lateral direction of the vehicle; a pressure sensor connected to the chamber member, and detecting a pressure inside the space; and a bumper absorber absorbing an impact generated by collision of an object with the vehicle, and arranged in front of the bumper reinforcement. A rear side end surface of the chamber member is in contact with a front surface of the bumper reinforcement. The bumper absorber includes a main body portion and a deformation portion. A rear side end surface of the bumper absorber is in contact with a front surface of the chamber member. The main body portion extends to a front side of the chamber member and has a predetermined rigidity. The deformation portion extends from a rear side of the main body portion to a rear direction of the vehicle, and a rear side end surface of the deformation portion is in contact with a front surface of the bumper reinforcement. The deformation portion starts to compress and deform the chamber member when a load applied to the main body portion reaches greater than or equal to 2 kN and less than or equal to 6 kN. The collision is detected based on the pressure of the space detected by the pressure sensor. 
         [0011]    Hereby, a collision detecting device in which a bumper absorber has sufficient rigidity, and a chamber has sufficient deformability in case of collision can be obtained. 
         [0012]    According to a fourth aspect of the present disclosure, a collision detecting device for a vehicle includes: a chamber member providing a space, and arranged in front of a bumper reinforcement extending in a lateral direction of the vehicle; a pressure sensor connected to the chamber member, and detecting a pressure inside the space; and a bumper absorber absorbing an impact generated by collision of an object with the vehicle, and arranged in front of the bumper reinforcement. The bumper absorber has a predetermined rigidity. A rear side end surface of the bumper absorber is in contact with a front surface of the chamber member. A rear side end surface of the chamber member is in contact with a front surface of the bumper reinforcement. The chamber member is compressed and deformed when a load applied to the bumper absorber reaches greater than or equal to 2 kN and less than or equal to 6 kN. The collision is detected based on the pressure of the space detected by the pressure sensor. 
         [0013]    Hereby, a collision detecting device in which a bumper absorber has sufficient rigidity, and a chamber has sufficient deformability in case of collision can be obtained. 
         [0014]    According to a fifth aspect of the present disclosure, a collision detecting device for a vehicle includes: a chamber member providing a space, and arranged in front of a bumper reinforcement extending in a lateral direction of the vehicle; a pressure sensor connected to the chamber member, and detecting a pressure inside the space; and a bumper absorber absorbing an impact generated by collision of an object with the vehicle, and arranged in front of the bumper reinforcement. The bumper absorber has a predetermined rigidity. A rear side end surface of the bumper absorber is in contact with a front surface of the bumper reinforcement. A rear side end surface of the chamber member is in contact with a front surface of the bumper absorber. The chamber member is compressed and deformed when a load applied to the chamber member reaches greater than or equal to 2 kN and less than or equal to 6 kN. The collision is detected based on the pressure of the space detected by the pressure sensor. 
         [0015]    Hereby, a collision detecting device in which a bumper absorber has sufficient rigidity, and a chamber has sufficient deformability in case of collision can be obtained. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0016]    The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings: 
           [0017]      FIG. 1  is a view showing a pedestrian collision detecting device according to a first embodiment; 
           [0018]      FIG. 2  is a cross sectional view showing a bumper reinforcement, a chamber member and a bumper absorber of the pedestrian collision detecting device according to the first embodiment; 
           [0019]      FIG. 3  is a cross sectional view showing a bumper reinforcement, a chamber member and a bumper absorber of a pedestrian collision detecting device according to a second embodiment; 
           [0020]      FIG. 4  is a view showing a pedestrian collision detecting device according to a third embodiment; 
           [0021]      FIG. 5  is a cross sectional view showing a bumper reinforcement, a chamber member and a bumper absorber of the pedestrian collision detecting device according to the third embodiment; 
           [0022]      FIG. 6  is a cross sectional view showing a bumper reinforcement, a chamber member and a bumper absorber of a pedestrian collision detecting device according to a modification of the third embodiment; 
           [0023]      FIG. 7  is a view showing a pedestrian collision detecting device according to a fourth embodiment; 
           [0024]      FIG. 8  is a cross sectional view showing a bumper reinforcement, a chamber member and a bumper absorber of the pedestrian collision detecting device according to the fourth embodiment; 
           [0025]      FIG. 9  is a view showing a pedestrian collision detecting device according to a fifth embodiment; and 
           [0026]      FIG. 10  is a cross sectional view showing a bumper reinforcement, a chamber member and a bumper absorber of the pedestrian collision detecting device according to the fifth embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]    It is noted that the front-rear direction and the up-down direction in drawings indicate the front-rear direction and the up-down direction of the vehicle. In all the embodiments, “the front side” indicates a front side with respect to the traveling direction and “the rear side” indicates a rear side with respect to the traveling direction. Moreover, “the front surface” indicates a surface arranged at the front side with respect to the traveling direction and “the rear surface” indicates a surface arranged at the rear side with respect to the traveling direction. 
       First Embodiment 
       [0028]    A structure of a pedestrian collision detecting device for detecting collision with a pedestrian is described with reference to  FIG. 1  and  FIG. 2 . 
         [0029]    As shown in  FIGS. 1 and 2 , a pedestrian collision detecting device  1  (a collision detecting device) includes a chamber member  10 , a pressure sensor  11 , a pedestrian collision determination portion  12  and a bumper absorber  13 . 
         [0030]    The chamber member  10  is an elongated sack-like member made of such as resin, which has a cross section of a square shape, and provides a chamber  100 , which is a sealed space or a substantially sealed space. Air is filled in the chamber  100 . The chamber member  10  is arranged on a bumper reinforcement  14  extending in a lateral direction of the vehicle, which has a cross section that substantially two squares are attached in line, so that a rear surface of the chamber member  10  is attached to an upside front surface of the bumper reinforcement  14 . The bumper reinforcement  14  is attached to front side end portions of a pair of side members  15  and  16 , which extends in the front-rear direction of the vehicle and provides a frame of the vehicle. 
         [0031]    The pressure sensor  11  is connected to the chamber member  10  and detects the pressure inside the chamber  100 . The pressure sensor  11  is included inside of the bumper reinforcement  14  and connected to the chamber member  10  with an end portion of the pressure sensor  11  protruded to the front side. 
         [0032]    The pedestrian collision determination portion  12  determines based on the detecting result of the pressure sensor  11  whether a collided object is a pedestrian and outputs a corresponding signal. For example, the determination portion  12  is a device equipped in a microcomputer. The determination portion  12  is arranged inside the vehicle and connected to the pressure sensor  11 . 
         [0033]    The bumper absorber  13  is an elongated shape member made of resin, for example. The bumper absorber  13  absorbs an impact generated by a collision of an object with the vehicle. The bumper absorber  13  includes a main body portion  130  and a flexible portion  131 . The flexible portion  131 , which is thinner than the main body portion  130  in the front-rear direction of the vehicle, is formed in the bumper absorber  13 . Thus, a concave portion is formed between the bumper reinforcement  14  and the flexible portion  131 . 
         [0034]    The main body portion  130  is arranged under the chamber member  10  with a rear side end surface of the main body portion  130  attached to a downside front surface of the bumper reinforcement  14 . The main body portion  130  arranged in front of the bumper reinforcement  14  has a predetermined rigidity and a cross section of a substantially rectangular shape. A material and a volume of the main body portion  130  are adjusted so that the main body portion  130  has the predetermined rigidity defined by the standard for North America. 
         [0035]    The flexible portion  131  is arranged on a front side end portion of the main body  130  and bends to the rear side according to a load applied to the device at the impact of collision. Specifically, the flexible portion  131  is a plate-like cantilever extending from the front side end portion of the main body portion  130  to an upside of the device. Dimension A of the flexible portion  131  in the up-down direction is set to be greater than or equal to 1/10 and less than or equal to ⅔, more preferably, greater than or equal to 1/10 and less than or equal to ⅕, of Dimension B of the main body portion  130  in the up-down direction. In addition, Dimension C of the flexible portion  131  in the front-rear direction is set to be greater than or equal to 1/10 and less than or equal to ⅔, more preferably, greater than or equal to 1/10 and less than or equal to ⅕, of Dimension D of the main body portion  130  in the front-rear direction. A rear surface of the flexible portion  131  is attached to a front surface of the chamber member  10 . That is, the chamber member  10  is arranged at the rear side of the flexible portion  131 . An elongated plate-like bumper cover  17  is arranged at the front side of the bumper absorber  13 . 
         [0036]    An operation of the pedestrian collision detecting device is described with reference to  FIGS. 1 and 2 . 
         [0037]    Power source is applied to the device  1 , the pressure sensor  11  and the determination portion  12  start to operate. When a pedestrian collides with the bumper cover  17 , the bumper cover  17  deforms to the rear side and the flexible portion  131  of the bumper absorber  13  deforms to the rear side. The main body portion  130  of the bumper absorber  13  absorbs an impact generated by collision by a compressive deformation of the main body portion  130  in the rear direction. The main body portion  130  has the predetermined rigidity defined by the standard or the like. Thus, the bumper absorber  13  can absorb sufficiently the impact without the significant deformation in normal accidents not only in the collision with the pedestrian and a peripheral portion of the bumper is not broken significantly. The bumper absorber  13  includes the flexible portion  131 . The flexible portion.  131  bends to the rear side with the deformation of the bumper cover  17  and the chamber member  10  deforms. The pressure inside the chamber  100  increases with the deformation of the chamber member  10 . The pressure sensor  11  detects the pressure inside the chamber  100 . The determination portion  12  determines based on the detecting result of the pressure sensor  11  whether the collided object is a pedestrian and outputs a corresponding signal. 
         [0038]    The bumper absorber  13  of the device  1  includes the main body portion  130  having the predetermined rigidity and the flexible portion  131  which bends to the rear side by the impact. The chamber member  10  is arranged at the rear side of the flexible portion  131 . The rigidity of the bumper absorber  13  can be ensured by the main body portion  130 . The flexible portion  131  bends to the rear side and the chamber member  10  can deform. Thus, the rigidity of the bumper absorber  13  can be ensured and the chamber member  10  can deform sufficiently by the collision. 
         [0039]    The flexible portion  131  is arranged on a front side end portion of the main body  130 . The flexible portion  131  is a plate-like cantilever extending to the upside of the device. Therefore, when a load generated by an impact is applied to the device, the flexible portion  131  can bend in the front-rear direction. 
         [0040]    In addition, the dimensions of the flexible portion  131 , as the cantilever, in the up-down direction and the front-rear direction are set to be greater than or equal to 1/10 and less than or equal to ⅔, more preferably, greater than or equal to 1/10 and less than or equal to ⅕, of the corresponding dimensions of the main body portion  130  in the up-down direction and the front-rear direction, respectively. Since the chamber member  10  and the bumper absorber  13  are attached to the front surface of the bumper reinforcement  14 , a space for the arrangement is limited. The dimension of the flexible portion  131  in the up-down direction is set to be greater than or equal to 1/10 and less than or equal to ⅔, more preferably, greater than or equal to 1/10 and less than or equal to ⅕, of the dimension of the main body portion  130  in the up-down direction, and the sufficient volume of the main body portion  130  can be ensured. Thus, the sufficient rigidity of the main body portion  130  can be ensured. In addition, the dimension of the flexible portion  131  in the front-rear direction is set to be greater than or equal to 1/10 and less than or equal to ⅔, more preferably, greater than or equal to 1/10 and less than or equal to ⅕, of the dimension of the main body portion  130  in the front-rear direction, and the flexible portion  131  can be thinned as compared with the main body portion  130 . Therefore, the flexible portion  131  can bend sufficiently. 
         [0041]    Moreover, the material and the volume of the main body portion  130  are adjusted so that the main body portion  130  has the predetermined rigidity defined by the standard. Thus, the rigidity of the bumper absorber  13  can be ensured sufficiently. 
         [0042]    Although the first embodiment shows the example that the flexible portion  131  is the plate-like cantilever extending from the front side end portion of the main body portion  130  to the upside of the device, the flexible portion  131  may have a different structure. The flexible portion  131  may extend to the downside of the device. 
       Second Embodiment 
       [0043]    A pedestrian collision detecting device of a second embodiment is described. The second embodiment is a modification of the first embodiment with respect to the structure of the flexible portion. 
         [0044]    A structure of the pedestrian collision detecting device is described with reference to  FIG. 3 . In the second embodiment, only a flexible portion, which has a different structure from the flexible portion of the first embodiment, is described. 
         [0045]    As shown in  FIG. 3 , a pedestrian collision detecting device  2  (a collision detecting device) includes a chamber member  20 , a pressure sensor  21  and a bumper absorber  23 . 
         [0046]    The chamber member  20  is an elongated sack-like member made of such as resin. The chamber member  20  has a cross section of a square shape, which is elongated in the front-rear direction. The chamber member  20  is arranged on the bumper reinforcement  24  so that a rear surface of the chamber member  20  is attached to a front surface of the bumper reinforcement  24  at a substantially center portion of the front surface in the up-down direction. 
         [0047]    The bumper absorber  23  includes a main body portion  230  and a flexible portion  231 . A hollow portion, which has Width E in the up-down direction of the vehicle and Width I in the front-rear direction of the vehicle, is formed in the bumper absorber  23 . Thus, the flexible portion  231  and the main body portion  230  are formed in the bumper absorber  23 . 
         [0048]    The main body portion  230  is divided into two parts, that is, an upside main body portion  230   a  and a downside main body portion  230   b . The upside main body portion  230   a  is arranged on the chamber member  20  with a rear side end surface of the upside main body portion  230   a  attached to an upside front surface of the bumper reinforcement  24 . The upside main body portion  230   a , which extends to a front side of the bumper reinforcement  24 , has a cross section of a substantially rectangle shape. The downside main body portion  230   b  is arranged under the chamber member  20  with a rear side end surface of the downside main body portion  230   b  attached to a downside front surface of the bumper reinforcement  24 . The downside main body portion  230   b , which extends to the front side of the bumper reinforcement  24 , has a cross section of a substantially rectangle shape. A material and a volume of the main body portion  230  are adjusted so that the main body portion  230  has the predetermined rigidity, which is defined by the standard. 
         [0049]    The flexible portion  231  is arranged at a middle portion of the main body portion  230  in the up-down direction and bends to the rear side by being applied a load generated by an impact. Specifically, the flexible portion  231  is arranged between a front side end portion of the upside main body portion  230   a  and a front side end portion of the downside main body portion  230   b , and the flexible portion  231  is a plate-like portion having a bridge-shaped beam extending in the up-down direction. Dimension E of the flexible portion  231  in the up-down direction is set to be greater than or equal to 1/10 and less than or equal to ⅔, more preferably, greater than or equal to 1/10 and less than or equal to ⅕, of Dimension F+G of the main body portion  230  in the up-down direction. In addition, Dimension H of the flexible portion  231  in the front-rear direction is set to be greater than or equal to 1/10 and less than or equal to ⅔, more preferably, greater than or equal to 1/10 and less than or equal to ⅕, of Dimension I of the main body portion  230  in the front-rear direction. A rear surface of the flexible portion  231  is attached to a front surface of the chamber member  20 . That is, the chamber member  20  is arranged at the rear side of the flexible portion  231 . 
         [0050]    The flexible portion  231  of the second embodiment is the bridge-shaped beam, both ends of which are supported by the main body portion  230 . The device  2  can obtain the same effect with the first embodiment. 
       Third Embodiment 
       [0051]    A pedestrian collision detecting device of a third embodiment is described. 
         [0052]    A structure of the pedestrian collision detecting device is described with reference to  FIGS. 4 and 5 . 
         [0053]    As shown in  FIGS. 4 and 5 , a pedestrian collision detecting device  3  (a collision detecting device) includes a chamber member  30 , a pressure sensor  31 , a pedestrian collision determination portion  32  and a bumper absorber  33 . 
         [0054]    The chamber member  30  is an elongated sack-like member made of such as resin, which has a cross section of a square shape and is elongated in the up-down direction. The chamber member  30  provides a chamber  300 . Air is filled in the chamber  300 . The chamber member  30  is arranged on a bumper reinforcement  34  so that a rear surface of the chamber member  30  is attached to an upside front surface of the bumper reinforcement  34 . 
         [0055]    The pressure sensor  31  is connected to the chamber member  30  and detects the pressure inside the chamber  300 . The pressure sensor  31  is included inside of the bumper reinforcement  34  and connected to the chamber member  30  with an end portion of the pressure sensor  31  protruded to the front side. 
         [0056]    The pedestrian collision determination portion  32  determines based on the detecting result of the pressure sensor  31  whether a collided object is a pedestrian and outputs a corresponding signal. For example, the determination portion  32  is a device equipped in a microcomputer. The determination portion  32  is arranged inside the vehicle and connected to the pressure sensor  31 . 
         [0057]    The bumper absorber  33  is an elongated member made of such as resin and absorbs an impact generated by collision of an object with the vehicle. The bumper absorber  33  includes a main body portion  330  and a deformation portion  331 . 
         [0058]    The main body portion  330  is arranged so that a rear side end surface of the main body portion  330  is attached to a front surface of the chamber member  30 . The main body portion  330  arranged in front of the chamber member  30  has a predetermined rigidity and a cross section of a substantially rectangle shape. A material and a volume of the main body portion  330  are adjusted so that the main body portion  330  has the predetermined rigidity, which is defined by the standard. 
         [0059]    The deformation portion  331  extends from a rear and down side end portion of the main body portion  330  to the rear side of the main body portion  330 . A rear end surface of the deformation portion  331  is attached to a downside front surface of the bumper reinforcement  34  and the deformation portion  331  is a portion in which a compressive deformation is caused by an application of a load generated by an impact. The deformation portion  331  is set to compress and deform in the rear direction when the load being applied to the main body portion  330  reaches the predetermined value in the range of greater than or equal to 2 kN and less than or equal to 6 kN, more preferably, greater than or equal to 4 kN and less than or equal to 6 kN, which corresponds to the load when the pedestrian collides with a vehicle. An elongated plate-like bumper cover  37 , which is made of such as resin, is arranged at the front side of the bumper absorber  33 . 
         [0060]    An operation of the pedestrian collision detecting device is described with reference to  FIGS. 4 and 5 . 
         [0061]    When a pedestrian collides with the bumper cover  37 , the bumper cover  37  deforms in the rear direction. The main body portion  330  of the bumper absorber  33  absorbs an impact generated by collision by a compressive deformation of the main body portion  330  in the rear direction. The main body portion  330  has the predetermined rigidity, which is defined by the standard or the like. Thus, the main body portion  330  can absorb sufficiently the impact without the significant deformation in normal accidents not only in the collision with the pedestrian. A peripheral portion of the bumper is not broken significantly. When the load being applied to the main body portion  330  reaches the predetermined load, the deformation portion  331  starts to bend in the rear direction. The compressive deformation of the deformation portion  331  is caused, and the chamber member  30  deforms with the compression of the main body portion  330 . The pressure inside the chamber  300  increases with the deformation of the chamber member  30 . The pressure sensor  31  detects the pressure inside the chamber  300 . The determination portion  32  determines based on the detecting result of the pressure sensor  31  whether the collided object is a pedestrian and outputs a corresponding signal. 
         [0062]    The bumper absorber  33  of the device  3  includes the main body portion  330  having the predetermined rigidity and the deformation portion  331  in which the compressive deformation is caused by the impact. The chamber member  30  is arranged at the rear side of the main body portion  330 . The rigidity of the bumper absorber  33  can be ensured by the main body portion  330 . The compressive deformation of the deformation portion  331  is caused in the rear direction so that the chamber member  30  is deformed by the main body portion  330 . Thus, the rigidity of the bumper absorber  33  can be ensured and the chamber member  30  can deform sufficiently by the collision. Moreover, the deformation portion  331  is set to compress and deform when the load being applied to the main body portion  330  reaches the predetermined value. The predetermined value is set to be in the range of greater than or equal to 2 kN and less than or equal to 6 kN, more preferably, greater than or equal to 4 kN and less than or equal to 6 kN, which corresponds to the load when the pedestrian collides. The pressure in the chamber  300  changes when the pedestrian or the like collides, and the collision with the pedestrian can be detected. 
         [0063]    The deformation portion  331  is arranged under the chamber member  30 . When the pedestrian collides with the vehicle, the deformation portion  331  is compressed and deformed in the rear direction. Thus, the chamber member  30  can be deformed sufficiently. 
         [0064]    Although the third embodiment shows the example that the deformation portion  331  is arranged under the chamber portion  30 , the structure of the deformation portion  331  may have a different structure. For example, deformation portions  332  and  333  may be arranged on and under the chamber member  30 , as shown in  FIG. 6 . A deformation portion may be arranged either on the chamber member  30  or under the chamber member  30 . 
       Fourth Embodiment 
       [0065]    A pedestrian collision detecting device of a fourth embodiment is described. 
         [0066]    A structure of the pedestrian collision detecting device is described with reference to  FIGS. 7 and 8 . 
         [0067]    As shown in  FIGS. 7 and 8 , a pedestrian collision detecting device  4  (a collision detecting device) includes a chamber member  40 , a pressure sensor  41 , a pedestrian collision determination portion  42  and a bumper absorber  43 . 
         [0068]    The chamber member  40  is an elongated sack-like member made of such as resin, which has a cross section of a square shape and is elongated in the up-down direction. The chamber member  40  provides a chamber  400 . Air is filled in the chamber  400 . The chamber member  40  is arranged on a front surface of a bumper reinforcement  44  so that a rear surface of the chamber member  40  is attached to the front surface of the bumper reinforcement  44 . The chamber member  40  is set to be compressed and deformed in the rear direction when the load being applied to the bumper absorber  43  reaches the predetermined value in the range of greater than or equal to 2 kN and less than or equal to 6 kN, more preferably, greater than or equal to 4 kN and less than or equal to 6 kN, which corresponds to the load when the pedestrian collides. 
         [0069]    The pressure sensor  41  is connected to the chamber member  40  and detects the pressure inside the chamber  400 . The pressure sensor  41  is included inside of the bumper reinforcement  44  and connected to the chamber member  40  with an end portion of the pressure sensor  41  protruded to the front side. 
         [0070]    The determination portion  42  determines based on the detecting result of the pressure sensor  41  whether a collided object is a pedestrian and outputs a corresponding signal. For example, the determination portion  42  is a device equipped in a microcomputer. The determination portion  42  is arranged inside the vehicle and connected to the pressure sensor  41 . 
         [0071]    The bumper absorber  43  is an elongated member made of such as resin and absorbs an impact generated by collision of an object with the vehicle. The bumper absorber  43  has a predetermined rigidity and a cross section of a rectangular shape. A rear side end surface of the bumper absorber  43  is attached to a front surface of the chamber member  40 . A material and a volume of the bumper absorber  43  are adjusted so that the bumper absorber  43  has the predetermined rigidity defined by the standard. An elongated plate-like bumper cover  47 , which is made of such as resin, is arranged at the front side of the bumper absorber  43 . 
         [0072]    An operation of the pedestrian collision detecting device is described with reference to  FIGS. 7 and 8 . 
         [0073]    When a pedestrian collides with the bumper cover  47 , the bumper cover  47  deforms in the rear direction. The bumper absorber  43  absorbs an impact generated by collision by a compressive deformation of the bumper absorber  43  in the rear direction. The bumper absorber  43  has the predetermined rigidity, which is defined by the standard or the like. Thus, the bumper absorber  43  can absorb sufficiently the impact without the significant deformation in normal accidents not only in the collision with the pedestrian. A peripheral portion of the bumper is not broken significantly. When the load being applied to the bumper absorber  43  reaches the predetermined load, the chamber member  40  starts to bend in the rear direction. The pressure inside the chamber  400  increases with the deformation of the chamber member  40 . The pressure sensor  41  detects the pressure inside the chamber  400 . The determination portion  42  determines based on the detecting result of the pressure sensor  41  whether the collided object is a pedestrian and outputs a corresponding signal. 
         [0074]    The bumper absorber  43  of the device  4  has the predetermined rigidity. The bumper absorber  43  is arranged on the front surface of the chamber member  40  and the chamber member  40  is arranged on the front surface of the bumper reinforcement  44 . Thus, the rigidity of the bumper absorber  43  can be ensured and the chamber member  40  can be deformed sufficiently by the collision. Moreover, the chamber member  40  is set to be compressed and deformed when the load being applied to the bumper absorber  43  reaches the predetermined value. The predetermined value is set to be in the range of greater than or equal to 2 kN and less than or equal to 6 kN, more preferably, greater than or equal to 4 kN and less than or equal to 6 kN, which corresponds to the load when the pedestrian collides. The pressure in the chamber  400  changes when the pedestrian or the like collides, and the collision with the pedestrian can be detected. 
       Fifth Embodiment 
       [0075]    A pedestrian collision detecting device of a fifth embodiment is described. The fifth embodiment is a modification of the fourth embodiment and the difference from the fourth embodiment is that an arrangement of a chamber member and a bumper absorber are inverted. 
         [0076]    A structure of the pedestrian collision detecting device is described with reference to  FIGS. 9 and 10 . In the fifth embodiment, only an arrangement of a chamber member and a bumper absorber, which has a different structure from the fourth embodiment, is described. 
         [0077]    As shown in  FIGS. 9 and 10 , a pedestrian collision detecting device  5  (a collision detecting device) includes a chamber member  50 , a pressure sensor  51 , a pedestrian collision determination portion  52  and a bumper absorber  53 . 
         [0078]    The chamber member  50  is arranged on a front surface of a bumper absorber  53  so that a rear surface of the chamber member  50  is attached to the front surface of the bumper absorber  53 . The chamber member  50  is set to be compressed and deformed in the rear direction when the load being applied to the chamber member  50  reaches the predetermined value in the range of greater than or equal to 2 kN and less than or equal to 6 kN, more preferably, greater than or equal to 4 kN and less than or equal to 6 kN, which corresponds to the load when the pedestrian collides. A bumper cover  57  is arranged at the front side of the chamber member  50 . 
         [0079]    The pressure sensor  51  is included in a concave portion  530 , which is arranged at a front side end surface of the bumper absorber  53 , and connected to the chamber member  50 . 
         [0080]    The bumper absorber  53  is an elongated member made of such as resin and absorbs an impact generated by collision of an object with the vehicle. The bumper absorber  53  has a predetermined rigidity and a cross section of a rectangular shape. A rear side end surface of the bumper absorber  53  is attached to a front surface of the bumper reinforcement  54 . A material and a volume of the bumper absorber  53  are adjusted so that the bumper absorber  53  has the predetermined rigidity defined by the standard. 
         [0081]    The device  5  of the fifth embodiment is the modification of the device  4  of the fourth embodiment and the difference from the fourth embodiment is that an arrangement of the chamber member and the bumper absorber are inverted. The device  5  can obtain the same effect with the device  4 . 
         [0082]    In each of the first to fifth embodiments, although the example that each of the pedestrian collision detecting device  1  to  5  is arranged on the bumper, which is arranged at the front side of the vehicle, is shown, each of the embodiments may provide different structures, respectively. Each of the device  1  to  5  may be arranged at the bumper, which is arranged at the rear side of the vehicle. 
         [0083]    Moreover, in each of the first to fifth embodiments, although the example that each of the pedestrian collision determination portion  12 ,  32 ,  42  and  52  determines based on the detecting result of each of the pressure sensor  11 ,  21 ,  31 ,  41  and  51  is shown, each of the embodiments may have a different structure. As described above, the pedestrian collision determination portion determines based on the detecting result of the pressure sensor and the velocity sensor. 
         [0084]    While the invention has been described with reference to preferred embodiments thereof, it is to be understood that the invention is not limited to the preferred embodiments and constructions. The invention is intended to cover various modification and equivalent arrangements. In addition, while the various combinations and configurations, which are preferred, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the invention.