Abstract:
A vehicle body side structure is provided to prevent deformation of a structural member due to deformation of a door during a side collision. The vehicle body structure reduces the possibility that the structural member contacts an occupant and obtains an excellent impact absorption effect when the door contacts the occupant. The vehicle body structure has a body side portion with the structural member, and a door coupled to the body side portion to open and close relative to the structural member. An energy absorption member is coupled to the door. A door engagement mechanism is coupled between the door and the side structural member. The door engagement mechanism is arranged to hold the door and the structural member together. A collision sensor generates a collision signal when a side collision is detected by the collision sensor. A door release mechanism is connected to the door engagement mechanism to release the door from the structural member in response to the collision signal. The energy absorption member can be a block of compressible material located in the door, or an air bag, or a frame member with a fragile portion.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to a vehicle body structure. More specifically, the present invention relates to a vehicle body structure for reducing an impact of occupants in a vehicle during a side collision.  
           [0003]    2. Background Information  
           [0004]    A vehicle body structure typically has one or more swingably mounted doors that latch to a center pillar. The upper and the lower ends of the center pillar are welded to a side roof rail and a side sill, respectively. The cross section of the center pillar is formed with a closed cross section over its entire length between the side roof rail and the side sill. When another vehicle collides with the side of a vehicle having this type of side structure, the center pillar and the front and rear doors of the vehicle are compressed by the front portion of the colliding vehicle. More specifically, the center pillar or structural member tends to bend at the center towards the occupant. Since the height of the center portion of the center pillar or structural member is located at almost the same height of the chest of an occupant, the occupant&#39;s chest may contact the center portion of the center pillar or structural member.  
           [0005]    One attempt to solve this phenomenon is disclosed in Japanese Laid-Open Patent Application No. 8-72740. This publication discloses a side structure of a vehicle having a center pillar or structural member that is formed with a closed cross section over its entirety. The center pillar has a strength-discontinuity portion formed at a lower portion of the center pillar. When another vehicle collides against the side of a vehicle having this type of structure, the center or structural member is bent at the strength-discontinuity portion and the upper portion of the center pillar is moved horizontally with respect to the vehicle cabin. Accordingly, the contact degree with occupant and the center pillar will relatively be reduced.  
           [0006]    As mentioned above, in conventional vehicle body structures, an improvement is applied merely to the structure of a center pillar itself.  
           [0007]    In actual side collision cases, however, the front portion of a colliding vehicle hits not only the center pillar but also one or both doors of the vehicle and compresses one or both of the doors. In particular, the center pillar is made of a frame material having a closed cross section that is relatively strong against a bending moment generated during a side collision. The door, on the other hand, generally has a weaker strength than center pillar against an external surface force generated during a side collision, since the door is made of a paneling material with many openings. Accordingly, the front portion of the colliding vehicle tends to be deformed so as to surround the center pillar. Thus, the door moves farther into the cabin of the vehicle as compared with the center pillar. If the door is moved more towards the interior of the vehicle relative to the center pillar or structural member, as mentioned above, the door pulls the center pillar via an engaging mechanism, which results in deformation of the center pillar. Conventionally, this deformation is controlled by increasing the thickness of a door panel or other reinforcement parts. Accordingly, although the above-mentioned deformation of the center pillar will be avoided by using conventional technique, there is a disadvantage in the increase of weight.  
           [0008]    Also, although an energy absorbing member for relieving an impact is often provided with doors as a measure for side collision, the size of the energy absorbing member has to be very large to provide good impact absorption. Specifically, in cases where the door and the center pillar are strongly bound, if the capacity of the energy absorbing member is relatively small, deformation of the energy absorbing member may be over or almost over before the door contacts an occupant. Accordingly, there is a disadvantage in prior art in that the width of a vehicle may be significantly increased.  
           [0009]    Moreover, Japanese Laid-Open Patent Application No. 10-196183 discloses a door lock that is released upon a side collision. The release mechanism of this publication simply releases the door lock. However, the latch of the door is still engaged with a striker on the center pillar. Therefore, the load applied to the door is transmitted to the center pillar and the above-mentioned problem is not solved by this technique.  
           [0010]    In view of the above, there exists a need for a vehicle body side structure which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.  
         SUMMARY OF THE INVENTION  
         [0011]    One object of the present invention is to provide a vehicle body structure which limits deformation of the pillar due to the deformation of a door without increasing the size and the weight of the door.  
           [0012]    Another object of the present invention is to provide a vehicle body structure with a door release mechanism that releases the door from the side structural member upon detection of a side collision.  
           [0013]    The foregoing objects can basically be attained by providing a vehicle body structure comprising a body side portion, a door, an energy absorption member, a door engagement mechanism, a collision sensor and a door release mechanism. The body side portion includes a structural member. The door is coupled to the body side portion to open and close relative to the structural member. The energy absorption member is coupled to the door. The door engagement mechanism is coupled between the door and the structural member and arranged to hold the door and the structural member together. The collision sensor generates a collision signal when a side collision is detected by the collision sensor. The door release mechanism is connected to the door engagement mechanism to release the door from the structural member in response to the collision signal.  
           [0014]    The foregoing objects can basically be attained by providing a vehicle body structure comprising: a body side portion including a structural member; a door coupled to the vehicle body portion to open and close relative to the structural member; energy absorption means for absorbing energy during a side collision being coupled to the door, door engagement means for engaging the door with the structural member of the vehicle body portion in a closed state of the door, collision sensing means for detecting the side collision, and door engagement releasing means for releasing engagement of the door engagement means between the door and the structural member when the side collision is detected by the collision sensing means so that the door will be separated from the structural member.  
           [0015]    These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    Referring now to the attached drawings that form a part of this original disclosure;  
         [0017]    [0017]FIG. 1 is an exploded perspective view of the main parts of the body of a vehicle with a vehicle body structure in accordance with a first embodiment of the present invention;  
         [0018]    [0018]FIG. 2 is a front perspective view of one of the doors in accordance with the first embodiment of the present invention;  
         [0019]    [0019]FIG. 3 is a partial perspective view of the vehicle body structure in the vicinity of the center pillar or side structural member in accordance with the first embodiment of the present invention;  
         [0020]    [0020]FIG. 4 is a rear perspective view of one of the doors in accordance with the first embodiment of the present invention;  
         [0021]    [0021]FIG. 5 is a partial diagrammatic perspective view showing the door engagement mechanism in the engaged state in accordance with the first embodiment of the present invention;  
         [0022]    [0022]FIG. 6 is a partial diagrammatic top plan view showing the door engagement mechanism in the engaged state in accordance with the first embodiment of the present invention;  
         [0023]    [0023]FIG. 7 is a partial diagrammatic perspective view showing the door engagement mechanism in a released state in accordance with the first embodiment of the present invention;  
         [0024]    [0024]FIG. 8 is a partial diagrammatic top plan view showing the door engagement mechanism in a released state in accordance with the first embodiment of the present invention;  
         [0025]    [0025]FIG. 9 is a top plan view showing a side collision of the vehicle with another vehicle in accordance with the first embodiment of the present invention;  
         [0026]    [0026]FIG. 10 is a partial diagrammatic cross sectional view showing deformation of a conventional vehicle in the vicinity of the center pillar at the time of a side collision and as viewed from the top of the vehicle;  
         [0027]    [0027]FIG. 11 is a partial diagrammatic cross sectional view showing deformation of a vehicle in the vicinity of the center pillar having the vehicle body structure according to the first embodiment of the present invention at the time of a side collision, as viewed from the top of the vehicle;  
         [0028]    [0028]FIG. 12 is a partial diagrammatic cross-sectional view showing deformation of a conventional vehicle in the vicinity of the center pillar with the door contacting the occupant at the time of a side collision, as viewed from the front of the vehicle;  
         [0029]    [0029]FIG. 13 a partial diagrammatic cross-sectional view showing deformation of the conventional vehicle in the vicinity of the center pillar at the time of a side collision and as viewed from the front of the vehicle;  
         [0030]    [0030]FIG. 14 is a partial diagrammatic cross-sectional view showing deformation of a vehicle in the vicinity of the center pillar provided with the vehicle body structure according to the first embodiment of the present invention and a contact state of the door with the occupant at the time of a side collision and as viewed from the front of the vehicle;  
         [0031]    [0031]FIG. 15 is a partial diagrammatic cross-sectional view showing deformation of a vehicle in the vicinity of the center pillar having the vehicle body structure according to the first embodiment of the present invention at the time of a side collision and as viewed from the front of the vehicle;  
         [0032]    [0032]FIG. 16 is a graph showing the changes of a load (F) applied to an occupant during period (T) of a side collision;  
         [0033]    [0033]FIG. 17 is a typical graph showing a change of the load (F) applied to the occupant during a side collision using the energy absorption member;  
         [0034]    [0034]FIG. 18 is a flow chart showing an algorithm of a program for the controller for operating the door release mechanism in accordance with the first embodiment of the present invention;  
         [0035]    [0035]FIG. 19 is a front diagrammatic view showing a vehicle with a distance sensor that is detecting an approaching vehicle in accordance with a second embodiment of the present invention;  
         [0036]    [0036]FIG. 20 is a perspective view of the cabin side of the door indicating an air bag packed in the door in accordance with the second embodiment of the present invention;  
         [0037]    [0037]FIG. 21 is a perspective view of the cabin side of the door showing a deployed air bag in accordance with the second embodiment of the present invention;  
         [0038]    [0038]FIG. 22 is a partial diagrammatic cross-sectional view showing deformation of the vicinity of the center pillar and the air bag contacting the occupant during a side collision in accordance with the second embodiment of the present invention;  
         [0039]    [0039]FIG. 23 is a graph showing the changes of a load (F) applied to an occupant during period (T) of a side collision;  
         [0040]    [0040]FIG. 24 is a flow chart showing an algorithm of a program for the controller for operating the door release mechanism and the air bag in accordance with the second embodiment of the present invention;  
         [0041]    [0041]FIG. 25 is an exploded diagrammatic perspective view of a door with frame members having fragile portions exploded outwardly therefrom;  
         [0042]    [0042]FIG. 26 is a perspective view of the cabin side of the door before fragile portions are bent in accordance with a third embodiment of the present invention;  
         [0043]    [0043]FIG. 27 is a perspective view of the cabin side of the door after the fragile portions are bent in accordance with the third embodiment of the present invention;  
         [0044]    [0044]FIG. 28 is a top plan view of the entire vehicle in accordance with the third embodiment of the present invention;  
         [0045]    [0045]FIG. 29 is a diagrammatic top plan view showing the occupant and the door prior to a collision in accordance with the third embodiment of the present invention;  
         [0046]    [0046]FIG. 30 is a diagrammatic top plan view showing the door and the occupant after the side collision in accordance with the third embodiment of the present invention;  
         [0047]    [0047]FIG. 31 is a perspective view of the door and a portion of the vehicle body side structure in the vicinity of the side structural member in accordance with a fourth embodiment of the present invention;  
         [0048]    [0048]FIG. 32 is a partial perspective view showing an unlocked position of a door lock in accordance with the fourth embodiment of the present invention;  
         [0049]    [0049]FIG. 33 is a perspective view showing a locked position of the door lock in accordance with the fourth embodiment of the present invention;  
         [0050]    [0050]FIG. 34 is a partial diagrammatic cross-sectional view showing an unlocked position of the door lock shown in FIG. 32 in accordance with the fourth embodiment of the present invention;  
         [0051]    [0051]FIG. 35 is a partial diagrammatic cross-sectional view showing the locked position of the door lock illustrated in FIG. 33 in accordance with the fourth embodiment of the present invention;  
         [0052]    [0052]FIG. 36 is a diagrammatic top view showing the occupant and the door before a side collision in accordance with the fourth embodiment of the present invention;  
         [0053]    [0053]FIG. 37 is a diagrammatic view showing the occupant and the door after the side collision in accordance with the fourth embodiment of the present invention;  
         [0054]    [0054]FIG. 38 is a flow chart showing an algorithm of a program for the controller for operating the door lock in accordance with the fourth embodiment of the present invention;  
         [0055]    [0055]FIG. 39 is a perspective view of the door and a portion of the vehicle body side structure in the vicinity of the side structural member in accordance with a fifth embodiment of the present invention;  
         [0056]    [0056]FIG. 40 is a partial perspective view showing an unlocked position of the door lock in accordance with the fifth embodiment of the present invention;  
         [0057]    [0057]FIG. 41 is a partial perspective view showing a locked position of the door lock in accordance with the fifth embodiment of the present invention;  
         [0058]    [0058]FIG. 42 is a partial diagrammatic cross-sectional view showing the unlocked position of the door lock illustrated in FIG. 40 in accordance with the fifth embodiment of the present invention;  
         [0059]    [0059]FIG. 43 is a partial diagrammatic cross-sectional view showing the locked position of the door lock illustrated in FIG. 41 in accordance with the fifth embodiment of the present invention;  
         [0060]    [0060]FIG. 44 is a perspective view of the entire vehicle in accordance with a sixth embodiment of the present invention;  
         [0061]    [0061]FIG. 45 is a perspective view of a front door, a portion of the vehicle body structure in the vicinity of the side structural member and a back door in accordance with the sixth embodiment of the present invention;  
         [0062]    [0062]FIG. 46 is a perspective view showing the engaged position of a door hinge release mechanism in accordance with the sixth embodiment of the present invention;  
         [0063]    [0063]FIG. 47 is a perspective view showing the disengaged position of the door hinge release mechanism in accordance with the sixth embodiment of the present invention;  
         [0064]    [0064]FIG. 48 is a diagrammatic top view showing the occupants and doors prior to a collision in accordance with the sixth embodiment of the present invention;  
         [0065]    [0065]FIG. 49 is an enlarged diagrammatic top view showing the doors and the occupants after the collision in accordance with the sixth embodiment of the present invention;  
         [0066]    [0066]FIG. 50 is a flow chart showing an algorithm of a program for the controller for operating the hinge release mechanism in accordance with the sixth embodiment of the present invention;  
         [0067]    [0067]FIG. 51 is a top plan view showing the entire vehicle in accordance with a seventh embodiment of the present invention;  
         [0068]    [0068]FIG. 52 is a top plan view showing a vehicle with another vehicle colliding at the front door in accordance with a seventh embodiment of the present invention;  
         [0069]    [0069]FIG. 53 is a top plan view showing a vehicle with another vehicle colliding at the rear door in accordance with a seventh embodiment of the present invention; and  
         [0070]    [0070]FIG. 54 is a flow chart showing an algorithm of a program for the controller for operating the door release mechanism and the hinge release mechanism in accordance with the seventh embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0071]    Examples of the present invention will now be described in conjunction with attached drawings. Referring initially to FIGS. 1 through 18, a first embodiment of the present invention is illustrated. As shown in FIGS.  1 - 4 , the vehicle has a single door  3  disposed on each of the right and left sides of a vehicle body  1 , respectively, and a door frame  2  provided on each side of the vehicle body  1 , respectively.  
         [0072]    Each of the door frames  2  includes a plurality of frame or structural members. More specifically, the frame or structural members of each of the door frames  2  includes a side sill  4 , a side roof rail  5 , a front pillar  6  and a center pillar (structural member)  7 . The pillars  6  and  7  are structural members that engage the doors  3 , respectively, as explained below. The side sill  4  is a lower frame member (structural member) that is disposed at the lower side of the door  3 . The side roof rail  5  is an upper frame member (structural member) that is disposed at the upper side of the door  3 . The front pillar  6  is a front frame member that is disposed at the front side of the door  3 , and that is welded to the side sill  4  and the side roof rail  5 . The center pillar  7  is a frame or structural member that is disposed at the back side of the door  3 , and that is welded to the side sill  4  and the side roof rail  5 . Each of the structural members has a closed transverse cross section so that it has a strong structure against a bending moment. In other words, structural member is a tubular member.  
         [0073]    Each door  3  is rotatably supported at its front end by the front pillar  6  via door hinges (door engagement mechanism)  8  so that the door  3  can be pivoted between opened and closed states via the door hinges  8 . The door hinges  8  also function to support doors about a corresponding support axis. In this illustrated embodiment, each door  3  is rotatably supported by two door hinges (an upper hinge and a lower hinge)  8  that are provided between the door  3  and the front pillar  6 . The structure of doors  3  is relatively conventional, except as modified in accordance with the present invention as explained hereinafter. In other words, the doors  3  have a power window unit in a hollow door body. The inner side of the door  3  is covered by a paneling member  3   a  that overlies a plurality of openings formed in the hollow door body.  
         [0074]    An energy absorption member  9  is provided inside a portion of the hollow door body behind the paneling member  3   a.  More specifically, the energy absorption member  9  is disposed at the middle portion of the door  3  and forms an energy absorption means. In other words, the energy absorption member  9  is disposed at the height that corresponds to an area between the abdomen and the chest of an occupant. The energy absorption member  9  can be any known type of energy absorbing member. In the first embodiment of the present invention, the energy absorption member  9  is a compressible member such as urethane foam block located within the door  3  as seen in FIGS. 2 and 4.  
         [0075]    As shown in detail in FIGS. 6 and 8, the door engagement mechanism  10  basically includes a striker  11  and a latch  12  that forms a door engagement means. The striker  11  has a U-shaped configuration as viewed from the top. The striker  11  is movably coupled to the center pillar  7  by a door release mechanism  13 . The latch  12  has a pin member that is provided on the backside of the door  3 . The striker  11  is engaged with the latch  12  when the door  3  is closed to prevent the door  3  from moving in its opening direction.  
         [0076]    As shown in FIGS.  5 - 8 , the door release mechanism  13  includes an actuator body  14  with a movable piston  15  that form a door engagement releasing means. The actuator body  14  is fixedly coupled to the center pillar  7  by a mounting bracket or member  14   a.  The actuator body  14  actuates the piston  15  according to a control signal from a controller  18  that will be described below. The end portion of the piston  15  is fixedly coupled to one end of the above-mentioned U-shaped striker  11 . When the door release mechanism  13  is actuated, the piston  15  shifts the position of the striker  11  from the engaged position shown in FIG. 2 to the released position shown in FIG. 3. In the engaged position, the other end of the striker  11  contacts the center pillar  7  so that the latch  12  can be engaged with the striker  11  to maintain the engaged position. In the released position, however, that end of the striker  11  is separated from the center pillar  7  and disengages the latch  12 . In other words, the door  3  can be detached from the center pillar  7 . Under normal conditions, the door release mechanism  13  is set to be at the engaged position as shown in FIGS. 5 and 6.  
         [0077]    A collision sensor  16  is provided in the side sill  4  and detects a side collision by another vehicle  17  from the side direction of the vehicle. In this first embodiment, the collision sensor  16  is an object contacting detection sensor, which outputs a collision signal to the controller  18  when it detects an actual collision caused by the vehicle  17 . Object contacting sensors are well known in the art, and thus, the collision sensor  16  will not be illustrated or discussed in detail. The collision sensor  16  forms a collision sensing means that can be any known object contacting detection sensor that will detect a collision immediately on impact. As explained below, the collision sensing means can also be any known distance detector that detects a collision by detecting a collision expected approach of another vehicle.  
         [0078]    The controller  18  is operatively coupled to the door release mechanism  13  and the collision sensor  16  via a control cable  18   a.  The control cable  18   a  allows signals such as electrical signals to be sent between the controller  18 , the door release mechanism  13  and the collision sensor  16 . The controller  18  outputs a signal to the door release mechanism  13  to release the door  3  from the center pillar member  7  in an instant it receives the collision signal from the collision sensor  16 .  
         [0079]    Next, operation in the above-mentioned configuration will be explained. As shown in FIG. 9, when the vehicle  17  collides with the side of the vehicle  20 , the collision sensor  16  detects the collision. Then, the collision sensor  16  immediately outputs a collision signal to the controller  18 . Next, the controller  18  immediately outputs a signal to the door release mechanism  13  to release the door engagement mechanism  10 . The door release mechanism  13  is actuated by this signal so that the position of the piston  15  is shifted from the engaged position to the released position and the engagement of the striker  11  of the door engagement mechanism  10  with the latch  12  is then disengaged. In other words, the door  3  can be separated from the center pillar  7 .  
         [0080]    Referring now to FIGS.  10 - 15 , the effects of releasing the door  3  from the center pillar  7  during a side collision will be compared with respect to a vehicle without the present invention. In the side collision, the head of the vehicle  17  compresses not only the center pillar but also the door  3  at the same time. The center pillar  7  is relatively strong against a bending moment since it is made of a frame member having a closed cross section. The door  3  generally has a weaker strength than the center pillar  7 . In particular, the door is constructed of thin paneling members having a lot of openings. Accordingly, there is a possibility that the front portion of the vehicle  17  is deformed to surround the center pillar  7  and invades to the cabin side of the vehicle. Since the crash energy is larger than the energy absorbing capacity of the door  3 , the door  3  may farther intrude into the cabin as compared with the center pillar  7 . In conventional vehicles, as shown in FIGS. 10, 12 and  13 , the door  3  pulls the center pillar via the door engagement mechanism  10  resulting in deformation of the center pillar  7 .  
         [0081]    Also, in conventional vehicles, as shown in FIGS. 12 and 13, when the door  3  is forced into the cabin and pulls the center pillar  7  via the door engagement mechanism  10 , the portion of the center pillar  7 , indicated by {circle over (1)} in FIG. 12, touches the chest area of the occupant  19 . Moreover, the latch  12  of the door  3  is normally disposed on the paneling member  3   a,  which is located at the inside of the door  3 . Thus, when the vehicle  17  compresses the outside of the door  3 , the energy absorption member  9 , which is placed inside the door  3  is also compressed, causing an increase in the amount of deformation C 1  shown in FIG. 10. Thus, there is a possibility that the energy absorption member  9  may be completely or almost completely compressed before the door  3  touches the occupant  19 .  
         [0082]    On the other hand, according to the first embodiment of the present invention, as shown in FIGS. 11, 14 and  15 , the door  3  is released from the center pillar  7 . Thus, even if the front portion of the vehicle  17  is deformed to surround the side structural member  7  and pushes the door  3  farther into the cabin as compared with the position of the center pillar  7 , the door  3  does not pull the center pillar  7  because the engagement of the door  3  with the center pillar  7  by the door engagement mechanism  10  has been disengaged. In other words, a deformation of the center pillar  7  is not induced by the deformation of the door  3  and the space for the occupant  19  is assured to limit the possibility that the portion of the center pillar  7 , indicated by {circle over (1)} in FIG. 14, touches the chest of the occupant  19 . Also, since the door  3  is released from the center pillar  7 , the door  3  can move towards the cabin with the energy absorption member  9  remaining substantially undeformed. When the vehicle  17  compresses the door  3 , the amount of deformation C 2  of the energy absorption member  9  is significantly less (as shown in FIG. 11) than the amount of deformation C 1  of a vehicle without the present invention (FIG. 10). As a result, most of the energy absorption member  9  functions after the door  3  contacts the occupant  19 .  
         [0083]    Also, since the door  3 , as indicated by {circle over (2)} in FIG. 14, is moved into the cabin relatively easily when the vehicle  17  compresses the door  3  in the first embodiment, the energy absorption member  9  makes contact with the occupant  19  at an early stage after a side collision occurs as compared with a conventional construction of a door, as indicated by {circle over (2)} in FIG. 12. As seen in FIGS. 12 and 13, when the door  3  is secured to the center pillar  7 , the door can only travel a very small amount as indicated as by D 1 . However, if the door  3  is disconnected from center pillar  7 , the door  3  can travel a larger distance as indicated by D 2  of FIGS. 14 and 15. Thus, the energy absorption member  9  is not completely compressed and it has a larger effective space to absorb the impact as indicated by D 2  of FIGS. 14 and 15. It may appear that the increase in the amount the door  3  intrusion into the cabin in contradiction to the occupant&#39;s impact. However, when the amount that the door  3  moves into the cabin is large as indicated by D 2  of FIGS. 14 and 15, the energy absorption member  9  is not deformed by the door deformation. So more effective impact absorption can be achieved by the door  3 , which is an impact inputting object, contacting the occupant  19  in an early stage and gradually accelerating the occupant  19  while compressing the energy absorption member  9 .  
         [0084]    This principle is indicated by the graph shown in FIG. 16. In FIG. 16, the curve {circle over (1)} shows a case in which a small gap D 1  is present between the impact inputting object (i.e., the door  3 ) and the occupant  19 . The curve {circle over (1)} indicates that a large impact force F is instantly applied to the occupant  19  when the door  3  contacts the occupant  19  after being moved into the cabin, i.e., after time T 1  has elapsed. On the other hand, the curve {circle over (2)} in FIG. 16 shows a case in which a large gap D 2  is present between the impact inputting object (i.e., the door  3 ) and the occupant  19 . Curve {circle over (2)} indicates that an effective impact absorption can be achieved even when the door  3  contacts the occupant  19  after a shorter amount of time T 2 . Since the energy absorption member  9  compresses when the door  3  contacts the occupant  19 , the amount of the impacting force F is smaller than in a conventional vehicle. In other words, as indicated by the curve {circle over (2)} shown in FIG. 16, the early contact of the occupant  19  with the energy absorption member  9  in the first embodiment does not make any wrong affect to the occupant  19 .  
         [0085]    Also, FIG. 17 is a general graph showing a change of the load in the energy absorption member  9 . This graph of FIG. 17 indicates that the deformation of the energy absorption member  9  is over after being compressed in some degree and after that a reaction force increases rapidly. In a conventional vehicle body side structure, as mentioned above, since the energy absorption member  9  has been already deformed, if the thickness of the door plate is insufficient, when it makes contacts with the occupant  19 , there is a possibility that the deformation of the energy absorption member  9  will be completed before the door  3  contacts the occupant  19 .  
         [0086]    According to the first embodiment of the present invention, even if the thickness of plate member in the door  3  is thin and the size of the energy absorption member  9  is small, an effective impact absorbing by the energy absorption member  9  can be obtained. Specifically, the energy absorption member  9  contacts the occupant  19  before any substantial compression has occurred in the energy absorption member  9 . Thus, increase in the thickness of each plate member will be avoided and the size of the energy absorption member  9  will be reduced so that increase in the weight of the vehicle and in the size of the door will be avoided.  
         [0087]    As seen in FIG. 18, a flowchart is shown that represents the algorithm of a program stored in the controller  18 . The controller  18  is preferably a microcomputer that comprises a central processing unit, with input and output interface circuits operatively coupled to the central processing unit, and storage devices such as a read-only memory device and/or a read-access memory device. The algorithm represented by the flowchart of FIG. 18 is stored in the microprocessor based controller  18 .  
         [0088]    As seen in the flowchart of FIG. 18, the algorithm of the controller  18  in step S 1  first determines whether a crash is expected. Specifically, the collision sensor  16  is operatively coupled to the controller  18 , such that the collision sensor  16  outputs a collision signal to the controller  18  upon detecting a crash or an expected crash. If the collision sensor  16  is an object contacting detection sensor, the collision signal is outputted when collision sensor  16  detects an actual collision has occurred. On the other hand, if the collision sensor  16  is a distance detector, the collision sensor  16  outputs a collision signal to the controller  18  when a vehicle is detected on a collision expected approach. If no collision signal is outputted to the controller  18 , the controller  18  proceeds to step S 2 , where the controller outputs a door engagement signal so that the door release mechanism  13  holds the door engagement mechanism  10  in the engaged position. If a collision signal is received by the controller  18 , the controller  18  proceeds to step S 3 , where the controller  18  outputs a door release signal to the door release mechanism  13 . The door release mechanism  13  moves the striker  11  to the released position, as seen in FIG. 8. Next, the controller  18  determines or reaffirms that a crash has actually occurred at step S 4 . If no actual collision has occurred, the controller  18  proceeds to step S 2  so that the door release mechanism  13  moves the striker  11  to the engaged position, as seen in FIG. 6, and the controller  18  returns to the beginning of the algorithm. If the collision is confirmed in step S 4 , the door release mechanism  13  keeps the striker  11  in the released position and the process is terminated.  
       SECOND EMBODIMENT  
       [0089]    A modification of the first embodiment according to the present invention is shown in FIGS.  19 - 24  that indicates a state in which the collision sensor  16  detects the vehicle  17 . In this modified or second embodiment, as shown in FIG. 19, a distance sensor is used as the collision sensor  16 , and as shown in FIGS.  20 - 22 , an air bag  21  is installed in door  3  as the energy absorption member. The collision sensor  16  outputs a collision signal to the controller  18  when it detects the vehicle  17  approaching extraordinarily from the side direction. The air bag  21  replaces the compressible block energy absorption member  9  of the first embodiment. Since other elements of this second embodiment are the same as those in the first embodiment, the explanation thereof is omitted. Note that in FIG. 19 the same numeral is used for an element that is the same in the above-mentioned first embodiment.  
         [0090]    In the second embodiment, explanation of structures that are the same as in the first embodiment are omitted for simplicity and only structures different from the first embodiment will be explained. Also, in the Figures, the same numerals are used for elements that are the same in the above-mentioned first embodiment.  
         [0091]    In this modified embodiment, the collision sensor  16  outputs a collision signal to the controller  18  when the vehicle  17  makes an extraordinary approach from the side direction, and the door release mechanism  13  releases the engagement of the door  3  before the vehicle  17  collides. Accordingly, in this second embodiment, measures can be taken before the collision and can be fully prepared for the collision. However, it is necessary, if an actual collision has not occurred for a few seconds after the actuation of the door release mechanism  13 , that the controller  18  output an engagement signal to the door release mechanism  13  so that the striker  11  returns to a normal engagement state and causes no hindrance for normal operation of the vehicle.  
         [0092]    FIGS.  20 - 22  are diagrams for showing the air bag  21  of the second embodiment of the present invention. FIG. 20 is a perspective view of the door  3  with the air bag  21  packed in the door  3  as viewed from the cabin. FIG. 21 is a perspective view of the door  3  showing the deployed air bag  21  as viewed from the cabin. FIG. 22 is a diagrammatic view showing the deformation of the center pillar  7 , and the air bag  21  and the door  3  contacting the occupant  19  upon a side collision. FIG. 23 is a graph showing the changes of a load or force F applied to the occupant  19  during a side collision versus time T.  
         [0093]    In the second embodiment of the present invention, the energy absorption member is the air bag  21 . As shown in FIG. 20, the air bag  21  is placed inside the paneling member  3   a,  which is located at the cabin side of the door  3 . The part of the paneling member  3   a  is weakened at a position that corresponds to that of the air bag  21  so that the air bag  21  can easily be deployed. As shown in FIG. 21, the air bag  21  expands toward the occupant (i.e., the cabin side). The position of the air bag  21  is predetermined so that the air bag  21  covers the upper half of the occupant  19  when it is deployed. The air bag  21  deploys when an inflator I is actuated in a conventional, well known manner.  
         [0094]    Also, when the controller  18  receives a collision signal from the collision sensor  16 , it immediately outputs an inflate air bag signal to the inflator I for the air bag  21  as well as a door release signal to the door release mechanism  13  to release the door engagement as in the above-mentioned first embodiment.  
         [0095]    Next, the operation of the above-mentioned configuration will be explained with reference to the flow chart in FIG. 24. As seen in FIG. 24, a flowchart is shown that represents an algorithm for a program for the controller  18  when used in connection with the third embodiment of the present invention. In this embodiment, the algorithm of the controller  18  outputs a door release signal and an inflate airbag signal in response to a signal from collision sensor  16 . In step S 11 , the controller  18  determines if a collision or crash is expected. If no collision signal is received by the controller  18  from the collision sensor  16 , the controller proceeds to step S 12 , where the controller  18  outputs a door engagement signal to the door release mechanism  13 . The door release mechanism  13  maintains the striker  11  in the engaged position, as seen in FIG. 6. The controller  18  proceeds back to step S 11  to continue to monitor for a side collision or crash. When the vehicle  17  collides from the side of the collided vehicle  20 , the collision sensor  16 , as shown in FIG. 19, detects the vehicle  17  prior to the collision. Then, the collision sensor  16  immediately outputs a collision signal to the controller  18 .  
         [0096]    The controller  18  in step S 11  proceeds to step S 13 , where the controller  18  immediately outputs a signal to the door release mechanism  13 , as shown in FIGS.  5 - 8  to release the door engagement. Thus, the engagement of the pillar  7  with the door  3  is also disengaged in this second embodiment in the same manner as in the first embodiment mentioned above. Accordingly, deformation of the pillar  7  induced by the deformation of the door  3  can be avoided and the possibility that the pillar  7  contacts the occupant  19  can be reduced.  
         [0097]    The controller  18  then proceeds to step S  14  to determine if a crash actually occurred. If no crash occurred, the controller  18  proceeds to step S 12 , where the controller  18  outputs a door engagement signal to the door release mechanism  13 . The door release mechanism then moves the striker  11  back to the engaged position. If a crash is confirmed, the controller  18  proceeds to step S 15  wherein controller  18  outputs an inflate air bag signal to the inflator I for inflating the air bag  21  as well as a door release signal for releasing the door engagement as mentioned above. Then, the inflator I is instantly actuated and the air bag  21  is deployed to fill the space between the occupant  19  and the door  3  immediately after the side collision. The process of the controller  18  is then terminated.  
         [0098]    Next, the effect of filling the space between the occupant  19  and the door  3  with the air bag  21  immediately after the collision to reduce the degree of the impact on the occupant  19  will be explained using FIG. 16. The curve {circle over (1)} indicates a case of a conventional vehicle in which the space between the occupant  19  and the door  3  is filled after the collision with a delay time T 1 . As shown in the graph, an impact against the occupant  19  increases rapidly when the energy absorption member  9  or the air bag  21  of the door  3  makes contact with the occupant  19  after the collision with the delay time Ti. On the other hand, the curve {circle over (2)} indicates a case of a vehicle in accordance with the second embodiment of the present invention in which the space between the occupant  19  and the door  3  is filled after the collision with almost no delay time T 2 . As shown in this graph, effective impact absorption can be obtained when using the second embodiment of the present invention, since an impact against the occupant  19  gradually increases and the degree of impact is reduced.  
         [0099]    Although the compressible member  9  and the air bag  21  are provided in order to absorb an impact caused by the door  3  against the occupant  19  at a side collision in the above-mentioned first and the second embodiments, respectively, both the compressible member  9  and the air bag  21  can be used in combination to further reduce the impact transmitted against the occupant  19 . This kind of usage is more effective when a sufficient capacity cannot be given to the air bag  21 .  
         [0100]    Also, since the air bag  21  needs to be deployed before the door  3  hits the occupant  19 , the use of a distance sensor, which detects a collision before it actually happens, as a collision sensor  16  is effective as described in this second embodiment. In other words, when the collision sensor  16  is a distance sensor, a preparatory time between the detection of a collision and an actual collision is provided so that the air bag  21  can be completely deployed in this period. Accordingly, a situation in which the air bag  21  is not fully deployed at the time of a collision can be avoided.  
       THIRD EMBODIMENT  
       [0101]    Referring now to FIGS.  25 - 30 , a third embodiment is illustrated according to the present invention. FIG. 26 is an exploded perspective view of the door  3  with a pair of frame members  22  each having a fragile portion  22   a.  FIG. 27 is a perspective view of the door  3  after the fragile portions  22   a  of the frame members  22  are bent as viewed from the interior of the vehicle. FIG. 28 is a partly cut-out plan view of the entire vehicle  20  as viewed from the top of the vehicle. FIG. 29 is a diagrammatic view showing the occupant  19  and the door  3  prior to a collision as viewed from the top of the vehicle  20 . FIG. 30 is a diagrammatic view showing the door  3  and the occupant  19  after the side collision as viewed from the top of the vehicle  20 .  
         [0102]    In this third embodiment, explanation of structures that are the same as in the first embodiment are omitted for simplicity and only structures different from the first embodiment will be explained. Also, in the figures, the same numerals are used for elements that are the same in the above-mentioned first embodiment.  
         [0103]    In the third embodiment, the fragile portions  22   a,  which are weak in strength, are provided in the center portion of the frame members  22  of the door  3  with respect to the front to back direction of the vehicle  20 . More specifically, the fragile portions  22  are formed in the center and lower frame members  22  of the door  3 , which extend horizontally from the front of the vehicle  20  to the rear of the vehicle  20 .  
         [0104]    Next, the operation of the above-mentioned configuration will be explained. In this third embodiment, the controller  18  performs the steps set forth in the flow chart shown in FIG. 24. When another vehicle  17  collides with the vehicle  20  from the side direction, the collision is detected by the collision sensor  16 . Then, the collision sensor  16  immediately outputs a collision signal to the controller  18 . Next, the controller  18  instantly outputs a signal to the door release mechanism  13  to release the door engagement. Accordingly, in this third embodiment, the center pillar  7  is disengaged from the door  3  as in the above-mentioned first embodiment. Thus, deformation of the center pillar  7  that can be induced by the deformation of the door  3  can be avoided and the possibility of the center pillar  7  contacting the occupant  19  can be reduced.  
         [0105]    Also, as shown in FIG. 30, since the door hinges  8  coupled between the door  3  and the front pillar  6  are not released during a side collision, the door  3  moves into the cabin rotating in a counter-clockwise direction in FIG. 30 around the axis of the door hinges  8 . In the third embodiment, since the door  3  is bent at the fragile portions  22   a  of the frame members  22 , the rear portion of the door  3  does not move as far into the cabin  20 . In other words, during a side collision, the front portion of the door  3  with respect to the fragile portions  22   a  moves into the cabin rotating about the axis of the door hinges  8  towards the cabin. The rear portion of the door  3  with respect to the fragile portions  22   a,  on the other hand, is influenced very little by the rotation force of the front portion of the door  3 , and thus, the rear portion of the door  3  moves into the cabin  20  in a direction parallel to the vehicle body  1  mainly due to the impact force from the side direction as indicated by the arrows in FIG. 30. Accordingly, the impact against the occupant  19  becomes small in this embodiment.  
       FOURTH EMBODIMENT  
       [0106]    Referring now to FIGS.  31 - 38 , a fourth embodiment is illustrated according to the present invention. FIG. 31 is an exploded perspective view of the door  3  and a portion of the vehicle in the vicinity of the center pillar  7 . FIG. 32 is a perspective view showing an unlocked position of a door lock  23 . FIG. 33 is a perspective view showing a locked position of the door lock  23 . FIG. 36 is a diagrammatic view showing the occupant  19  and the door  3  before a collision as viewed from the top of the vehicle  20 . FIG. 37 is a diagrammatic view showing the occupant  19  and the door  3  after the side collision as viewed from the top of the vehicle  20 .  
         [0107]    In this fourth embodiment, explanation of structures that are the same as in the first embodiment is omitted for simplicity and only structures different from the first embodiment will be explained. Also, in the figures, the same numerals are used for elements that are the same in the above-mentioned first embodiment.  
         [0108]    In the fourth embodiment, the door lock  23  is provided which, in addition to the door engagement mechanism  10  for the door  3 , locks an under part of the door  3  in a closed state during a side collision. The door lock  23  includes a locking hole  24  and a lock pin actuator  25 . The locking hole  24  is provided in the bottom surface of the door  3 , and is located at the rear portion of the door  3  with respect to the center of the door  3  in the front to rear direction of the vehicle  20 . The lock pin actuator  25  is provided in the side sill  4  at a position corresponding to the locking hole  24  and is mounted to side sill  4  via a mounting member  26  as seen in FIGS. 34 and 35.  
         [0109]    The lock pin actuator  25  operates to move that a lock pin  25   a  between the unlocked position shown in FIG. 32 and locked position shown in FIG. 33. The lock pin  25   a  is not located in the locking hole  24  in the unlocked position, which the lock pin  25   a  is located in the locking hole  24  in the locked position. Under normal conditions, the lock pin  25   a  is located in the unlocked position. A seal member  27  surrounds lock pin  25   a  to seal the lock pin actuator  25 .  
         [0110]    Also, when the controller  18  receives a collision signal from the collision sensor  16 , it outputs a door lock signal to the lock pin actuator  25  of the door lock  23  as well as a signal to the door release mechanism  13  to release the door engagement as in the above-mentioned first embodiment.  
         [0111]    Specifically, upon receiving a collision signal from the collision sensor  16 , the controller  18  outputs a door lock signal to the lock pin actuator  25  of the door lock  23  as well as a door release signal as mentioned above. Then, the lock pin  25   a  is inserted in the locking hole  24  to engage the door  3  with the side sill  4 .  
         [0112]    In other words, at the time of a collision, the door  3  is disengaged with the center pillar  7  while it is engaged with the side sill  4 . Then, as explained in the third embodiment, since the door hinges  8  for engaging the door  3  with the front pillar  6  are not released at the time of a side collision, the door  3  moves into the cabin to rotate counter clockwise around the door hinges  8 , as shown in FIG. 37. However, in the fourth embodiment, since the door  3  is engaged with the side sill  4  by the door lock  23 , a reaction force by the side sill  4  is exerted against the above-mentioned rotational force of the door  3  via the door lock  23 . Accordingly, even if the front portion of the door  3  moves into the cabin so as to rotate towards the cabin thereof, at least the rear portion of the door  3  is forced into the cabin. Thus, the degree of an impact against the occupant  19  is reduced.  
         [0113]    Since the side sill  4  is a frame member stronger than the center pillar  7  and a large external force is not directly applied to it by a colliding vehicle  17  at the time of a side collision, no significant problem is caused when the door  3  pulls the side sill  4 . On the contrary, by engaging the door  3  with the side sill  4 , the moving speed of the door  3  moves into the cabin  20  will be reduced when a colliding vehicle  17  compresses the door  3 . As seen in FIG. 38, a flowchart is shown that represents an algorithm for a program that is stored in the controller  18 , when the controller  18  is used in connection with the fourth embodiment of the present invention. In this embodiment, the algorithm represented by the flow chart of FIG. 18 or  24  is also stored in the controller  18  to operate the door release mechanism  13  and/or inflator I. Thus, the algorithms of the controller  18  output a door unlock signal and a door lock signal in response to a signal from collision sensor  16  in this fourth embodiment.  
         [0114]    When the controller  18  executes the algorithm represented by the flow chart in FIG. 38, the controller first determines whether a crash has occurred or a crash is expected. If no crash has occurred or no crash is expected, the controller  18  proceeds to step S 22 , where the controller outputs a door unlock signal to maintain the lock pin  25   a  in the unlocked position, as shown in FIG. 32. The controller then proceeds back to step S 21  to continue to monitor whether a crash has occurred or is expected.  
         [0115]    Next, operation of the above-mentioned configuration will be explained. When another vehicle  17  collides or is about to collide with the vehicle  20  from the side direction, the collision is detected by collision sensor  16 . Then, the collision sensor  16  immediately outputs a collision signal to the controller  18 . The controller  18  in step S 23  then instantly outputs a door lock signal to the lock pin actuator  25  to insert the lock pin  25   a  into locking hole  24  for locking the door  3 . The controller then proceeds to step S 24 , where the controller  18  confirms that a crash has occurred. If a crash or side collision did not actually occur, the controller proceeds to step S 22 , where the controller  18  outputs a door unlock signal to retract the lock pin  25   a  from the locking hole  24 . The controller then returns to step S 21  to continue to monitor the state of the vehicle  17 . If, on the other hand, a crash is detected at step S 24 , the controller terminates the algorithm and the door  32  remains locked with the door side sill  4  of the body side portion of the vehicle  17 .  
         [0116]    The controller  18  simultaneously executes the algorithm represented by one of the flow charts in FIGS.  18  or  24 , depending upon whether an air bag is used in conjunction with the fourth embodiment. In any event, in this fourth embodiment, the side structural member  7  is also disengaged from the door  3  as in the above-mentioned first embodiment and deformation of the center pillar  7  that can be induced by the deformation of the door  3  will be avoided. Thus, the possibility that the center pillar  7  touches the occupant  19  will be reduced.  
       FIFTH EMBODIMENT  
       [0117]    Referring now to FIGS.  39 - 43 , a fifth embodiment is illustrated according to the present invention. FIG. 39 is an exploded perspective view of the door  3  and the vicinity of the center pillar  7 . FIG. 40 is a perspective view showing another unlocked position of the door lock  23 . FIG. 41 is a perspective view showing another locked position of the door lock  23 . Also, in the figures, the same numerals are used for elements that are the same in the above-mentioned first embodiment.  
         [0118]    The configuration in this fifth embodiment is almost the same as that in the fourth embodiment and only the position of the door lock  23  is different. In other words, in the fifth embodiment, the door lock  23  includes the locking hole  24 , which is provided with the upper surface of the door  3  and it is located at the back thereof with respect to the center of the door  3  in the front to back direction of the vehicle. The lock pin actuator  25  is provided in the side roof rail  5  at a position corresponding to the locking hole  24  and is mounted to side roof rail  5  via mounting member  26 . The lock pin actuator  25  has a lock pin  25   a  that is surrounded by a seal member  27 .  
         [0119]    In the fifth embodiment, the door  3  is disengaged from the center pillar  7  while it is engaged with the side roof rail  5  at the time of a collision side roof rail  5  is a stronger frame member than the center pillar  7 . Thus, as in the above-mentioned fourth embodiment, the rear portion of the door  3 , which is engaged by the door lock  23 , moves into the cabin to be parallel to the vehicle body  1 . Accordingly, the degree of an impact against the occupant  19  is reduced.  
         [0120]    In this embodiment, the controller  18  has the algorithms represented by one of the flow charts of FIGS.  18  or  24 , and the flow chart of FIG. 38 stored therein. Accordingly, controller  18  operates the door release mechanism  13  in accordance with either the flow chart of FIG. 18 or  24 , depending upon whether or not the door includes an air bag or some other type of energy absorption member. In any event, the two algorithms will be operated simultaneously, such that the door  3  is released from pillar  7 , while the door  3  is locked to roof rail  5 .  
       SIXTH EMBODIMENT  
       [0121]    Referring now to FIGS.  44 - 50 , a sixth embodiment is illustrated according to the present invention. FIGS. 44 and 45 are exploded perspective views of vehicle  20  with a front door  30 , a center pillar  7  and a rear door  31  on each side of the vehicle  20 . FIG. 46 is a perspective view showing the engagement state of a door hinge release mechanism  37 . FIG. 47 is a perspective view showing the disengagement state of the door hinge release mechanism  37 . FIG. 48 is a diagrammatic view showing occupants  19   a  and  19   b  and doors  30  and  31  prior to a collision as viewed from the top of the vehicle  20 . FIG. 49 is a magnified diagrammatic view showing the doors  30  and  31  and the occupants  19   a  and  19   b,  respectively, after the collision as viewed from the top of the vehicle  20 .  
         [0122]    As shown in FIG. 44, the vehicle  20  has two pairs of doors  30  and  31  disposed on the right and left sides of the vehicle  20 , respectively, and a pair of door frames  2  are provided on both sides of the vehicle body  1 , respectively. Each of the door frames  2  includes a side sill  4 , a side roof rail  5 , a front pillar  6 , a center pillar  7  and a rear pillar  32 .  
         [0123]    The front door  30  is rotatably supported, at its front end, by the front pillar  6  via a pair of door hinges  8  (shown in FIG. 49), which act as a supporting axis so that the front door  30  can be opened and closed. As in the above-mentioned first embodiment, the door engagement mechanism  10  includes the striker  11  and the latch  12  that are provided in the center pillar  7  and the front door  30 , respectively. Also, the door release mechanism  13  that releases the engagement of the door engagement mechanism  10  is provided in the center pillar  7  as in the first embodiment described above.  
         [0124]    The back door  31  is rotatably supported, at its front end, by the center pillar  7  via a pair of door hinges  33 , which act as a supporting axis so that the back door  31  can be opened and closed.  
         [0125]    On the other hand, a door engagement mechanism (not shown) including the striker  11  and the latch  12  as shown in FIGS. 6 and 8 for the front door  30 , are provided on the rear pillar  32  the rear surface of the rear door  31 , respectively.  
         [0126]    Also, the inner and outer surfaces of the front door  30  and the rear door  31  are covered with paneling members  30   a  and  31   a,  respectively, the energy absorption member  9 , similar to the one shown in FIGS. 2 and 5, is placed inside the respective paneling members  30   a  and  31   a.    
         [0127]    As shown in FIGS. 46 and 47 in detail, each door hinge  33  includes a pillar side shaft bushing  34 , a door side shaft bushing  35  and a supporting shaft  36 . The pillar side shaft bushing  34  is fixedly coupled to the center pillar  7 . The door side shaft bushing  35  is fixedly coupled to the rear door  31 . The supporting shaft  36  is inserted in both the shaft bushings  34  and  35 . Door hinges  33  are provided at upper and lower positions, as seen in FIG. 45.  
         [0128]    As shown in FIGS. 46 and 47 in detail, a door hinge release mechanism  37  is coupled to each supporting shaft  36  and includes an actuator  38  fixedly coupled to the center pillar  7 , which operates so as to move a piston  39  according to a signal from the controller  18  as will be explained below. The piston  39  has substantially a U-shape with one end integrally and fixedly coupled to the above-mentioned supporting shaft  36  of the door hinge  33 . The door hinge release mechanism  37  can change its position from the door engagement position (a state shown in FIG. 46) to the door release position (a state shown in FIG. 47). At the door engagement position, the piston  39  is moved downward so that the supporting shaft  36  is inserted in both the shaft bushings  34  and  35 . At the door release position, the piston  39  is moved upward so that the supporting shaft  36  is pulled up from both the shaft bushings  34  and  35 . Under normal condition, the door hinge release mechanism  37  is positioned at the door engagement position as shown in FIG. 46.  
         [0129]    As shown in FIG. 44, the collision sensor  16  is provided in the side sill  4  below the front door  30  and detects a collision by another vehicle  17  from the side direction. In the sixth embodiment, the collision sensor  16  is preferably an object contacting detection sensor and outputs a collision signal to the controller  18  when it detects an actual collision caused by another vehicle. Of course, the collision sensor  16  of the sixth embodiment can also be a distance sensor, and the doors  30  and  31  can be provided with air bags, as in the second embodiment. Thus, the controller  18  has neither the algorithm represented by the flow chart of FIG. 18 stored therein, or the algorithm represented by the flow chart of FIG. 24 stored therein.  
         [0130]    Controller  18  is operatively coupled to (front door) door engagement release mechanism  13 , collision sensor  16  and door hinge release mechanisms  37  via control cable  18   a.  Control cable  18   a  allows signals such as electrical signals to be sent between collision sensor  16 , controller  18 , door engagement release mechanism  13  and door hinge release mechanisms  37 .  
         [0131]    Upon receiving a collision signal from the collision sensor  16 , the controller  18  instantly outputs a signal to the door hinge release mechanisms  37  to release the engagement of the door hinges  33  as well as a signal to the door release mechanism  13  to release the front door engagement mechanism  10 .  
         [0132]    As seen in FIG. 50, a flowchart is shown that represents an algorithm of a program stored in the controller  18  for operating the door hinge release mechanisms  37  of the sixth embodiment of the present invention. The controller  18  in this embodiment outputs an upper hinge releasing signal and a lower hinge releasing signal for releasing door  31  in the event of a side collision that affects the rear door  30 . Preferably, the algorithm of the controller  18  releases the upper one of the door hinges  33  prior to the crash, while the lower one of the door hinges  33  is not released until after the impact has occurred. This will prevent the door from falling off prior to the actual crash. As mentioned above, it will be apparent to those skilled in the art from this disclosure that the algorithm represented by the flow chart of FIG. 50 is utilized in conjunction with one of the algorithms of FIGS. 18, 24 and  38 , depending upon whether an air bag or a door lock is used.  
         [0133]    Next, operation of the above-mentioned configuration will be explained with reference to the flow charts of FIGS. 18 and 50. The controller  18  has the algorithms represented by the flow chart of FIGS. 18 and 50 stored therein. Accordingly, the controller simultaneously runs the algorithms such that the door release mechanism  13  of the front door  30  and the door hinge release mechanisms  37  of the rear door  31  are disengaged from the center pillar  7  in the event of a side collision.  
         [0134]    As explained in the first embodiment, the algorithm represented by the flow chart of FIG. 18 is processed by the controller  18  such that in step S 1 , the controller first determines whether a crash has actually occurred or is expected to occur. Step S 1  preferably occurs simultaneously with step S 31  of the flow chart shown in FIG. 50. If no crash is detected by the collision sensor  16 , the controller proceeds to steps S 2  and S 32 , where the controller outputs a door engagement signal to maintain the flow release mechanism  13  of the front door  30  in the engaged position, and outputs a hinge engagement signal to maintain the upper and lower door hinge release mechanisms  37  in the engaged positions. The controller then proceeds from steps S 2  and S 32  back to steps S 1  and S 31  to continue to monitor the status of the vehicle. If a crash is detected, the algorithms shown in the flow charts of FIGS. 18 and 50 proceed to steps S 3  and S 33 , where the controller  18  outputs a door release signal and an upper hinge release signal. Accordingly, the door release mechanism  13  moves the striker  11  to a release position and moves the supporting shaft  36  of the upper hinge  33  to a release position.  
         [0135]    The controller  18  then proceeds to steps S 4  and S 34  to confirm that a crash has actually occurred. In the event that no crash has actually occurred, the controller  18  proceeds to steps S 2  and S 32 , where the controller  18  outputs a door engagement signal and a hinge engagement signal to re-engage the striker  11  with latch  12 , and re-engage the upper supporting shaft  36  with bushings  34  and  35 . In the event that a crash is actually confirmed by the controller  18 , the controller  18  then proceeds to step S 35  in the algorithm of the flow chart seen in FIG. 50. In step S 35 , the controller  18  outputs a lower hinge release signal to the lower door hinge release mechanism  37  to move the supporting shaft  36  out of bushings  34  and  35  to release the rear door  31 .  
         [0136]    When another vehicle  17  collides with vehicle  20  from the side direction, the collision sensor  16  detects the collision. Then, the collision sensor  16  immediately outputs a collision signal to the controller  18 . The controller  18  proceeds to steps S 3  and S 43  to output a signal to the door release mechanism  13  (front door) to release the door engagement mechanism  10 . Accordingly, in the sixth embodiment, since the engagement of the center pillar  7  with the front door  3  is released by the same operation as in the above-mentioned first embodiment, deformation of the center pillar  7  that can be induced by the deformation of the front door  30  will also be avoided because of the same reasons explained in the above first embodiment. Thus, the possibility that the center pillar  7  touches the occupant  19   a  in the front seat may be reduced.  
         [0137]    Also, as mentioned above, upon receiving a collision signal from the collision sensor  16 , the controller  18  outputs a signal to the door hinge release mechanisms  37  to release the engagement of the door hinges  33  as well as a signal to release the door engagement mechanism  10  of front door  30 . The door hinge release mechanisms  37  are actuated by the signal such that the pistons  39  are moved from the pulled-down position to the pulled-up position so that the supporting shafts  36  are moved from the engagement position to the disengagement position to release the support by the door hinges  33 . In short, the engagement of the rear door  31  with the center pillar  7  is released. Accordingly, deformation of the center pillar  7  that can be induced by the front door  30  can be avoided by the same reasons explained for the front door  30 . Thus, the possibility that the center pillar  7  contacts occupant  19   b  in the rear seat can be reduced.  
         [0138]    Since the door hinges  33  for the rear door  31  are located at the front end of the door  31 , i.e., far away from the occupant  19  seated at the rear seat, the possibility that this portion, even if largely forced into the cabin will make contact with the occupant  19   b  is relatively low. If, however, this portion touches the occupant  19   b  at the rear seat, most of the energy absorption member  9  will not be compressed prior to contact with the occupant  19   b  when the door contacts the occupant  19   b.  Thus, an excellent impact absorption effect by the energy absorption member  9  is obtained.  
       SEVENTH EMBODIMENT  
       [0139]    Referring now to FIGS.  51 - 54 , a seventh embodiment is illustrated according to the present invention. FIG. 51 is a plan view showing the entire vehicle  20  viewed from the top. FIG. 52 is a diagrammatic view showing the vehicle  20  and another vehicle  17  collided at the front door  31  of the vehicle  20  as viewed from the top of the collision. FIG. 53 is a diagrammatic view showing the vehicle  20  and vehicle  17  collided at the rear door  31  of the vehicle  20  as viewed from the top of the collision.  
         [0140]    In the seventh embodiment, only the configurations of the collision sensors  16   a  and  16   b  and the controller  18  are different from that of the above-mentioned sixth embodiment. Accordingly, only the configurations of the collision sensors  16   a  and  16   b  and the controller  18  will be explained and shown in FIGS.  51 - 54  and the explanations of the structures of the seventh embodiment that are the same as in the sixth embodiment are omitted for simplicity.  
         [0141]    As shown in FIG. 51, the collision sensors  16   a  and  16   b  are provided in the side sill  4  corresponding to the front door  30  and the rear door  31 , respectively. The collision sensor  16   a  located at front mainly detects a side collision against the front door  30  as shown in FIG. 52. The collision sensor  16   b  located at rear side of the body mainly detects a side collision against the rear door  30  as shown in FIG. 53. In other words, the location of the collision by another vehicle  17  with vehicle  20  is detected by using the two collision sensors  16   a  and  16   b.  The collision sensors  16   a  and  16   b  are preferably distance sensors, since airbags  21  are packed into the doors  30  and  31 . Of course, the sensors  16   a  and  16   b  can be object contacting detection sensors, if desired.  
         [0142]    As seen in FIG. 54, a flowchart is shown that represents an algorithm of a program stored in the controller  18  in accordance with the seventh embodiment of the present invention. In this embodiment, the algorithms represented by the flow charts of FIGS. 24 and 50 have been combined into a single algorithm.  
         [0143]    As seen in FIG. 54, the controller  18  determines whether a crash has actually occurred or is expected to occur at steps S 41 . If no crash has been detected or is expected, the controller  18  proceeds to steps S 42   a  and S 42   b  to output an upper hinge engagement signal and a door engagement signal so that the door release mechanism  13  and the upper door hinge release mechanism  37  are both maintained in the engaged positions. The controller then continues to monitor the status of the vehicle  20 . In the event that a crash is detected, the controller proceeds to steps S 43   a  and S 43   b  to determine whether it is a front crash or a rear crash that has occurred or is expected. Of course, if no crash is expected, the algorithm returns to start again.  
         [0144]    In the event that the controller receives a collision signal from collision sensor  16   a,  the controller proceeds to step S 44   a  to output a door release signal to the door release mechanism  13  so that the front door  30  is released from the center pillar  7 . If the collision sensor  16   b  sends a collision signal to controller  18 , the controller proceeds to step S 44   b,  where the controller  18  outputs an upper hinge release signal to the upper door hinge release mechanism  37  to release the upper hinge  33  of the rear door  31 . Of course, it is possible that both collision sensors  16   a  and  16   b  sends collision signals to controllers  18  to simultaneously operate the door release mechanism  13  and the door hinge release mechanisms  37 .  
         [0145]    Next, the controller proceeds to steps S 45   a  and/or step S 45   b  to confirm that a crash has actually occurred. If no crash has occurred, the controller  18  proceeds to either step S 42   a  and/or step S 42   b  depending upon whether the side collision is a front crash or a rear crash. In steps S 42   a  and S 42   b,  the controller outputs an upper hinge engagement signal and a door engagement signal, respectively, so as to maintain the engagement between the center pillar  7  and the front and rear doors  30  and  31 .  
         [0146]    If the controller determines that a crash has actually occurred in step S 45   a  and/or step S 45   b,  the controller proceeds to steps S 46   a  or S 46   b.  In step S 46   a,  the controller  18  outputs an inflate air bag signal to the air bag  21  that is located in the front door  30 . If the controller  18  determines that the crash occurred at the rear door  31 , then the controller  18  proceeds to step S 46   b,  where the controller  18  outputs a lower hinge release signal to the lower door release mechanism  37  to release the lower door hinge  33  of the rear door  31  from the center pillar  7 . Accordingly, now the rear door  31  is completely disengaged from the center pillar  7 . Finally, the controller proceeds from step S 46   b  to step S 47   b,  where the air bag  21  in the rear door  31  is inflated in response to a signal outputted from the controller  18  to an inflator of the air bag  21 . The algorithm represented by the flow chart shown in FIG. 54 is terminated upon the inflation of one or both of the air bags  21 .  
         [0147]    Also, as mentioned above, upon receiving the collision signal from the collision sensor  16   a  located at front, the controller  18  outputs a signal only to the door release mechanism  13  to release the door engagement of front door  30 . Upon receiving the collision signal from the collision sensor  16   b  located at back, the controller  18  outputs a signal only to the door hinge release mechanisms  37  to release the support by the door hinges  33  as shown in FIG. 47. Upon receiving the collision signal from both the collision sensors  16   a  and  16   b,  the controller  18  outputs a signal to the door release mechanism  13  to release the door engagement of front door  30  and a signal to the door hinge release mechanisms  37  to release the support by the door hinge of back door  31 . In other words, releasing operation by the door engagement release mechanism  13  and by the door hinge release mechanism  37  are controlled independently according to the site of the collision.  
         [0148]    As shown in FIG. 52, in the seventh embodiment, the engagement of the front door  30  with the center pillar  7  is released by operation of the door release mechanism  13  when the vehicle  17  collides against the front door  30  from the side direction of the vehicle  20 . Although the front portion of the vehicle  17  may be deformed so as to surround the center pillar  7  at the collision site to force the front door  30  into the cabin, deformation of the center pillar  7  induced by the deformation of the front door  30  is prevented from occurring because the engagement of the front door  30  with the side structural member  7  is released. Accordingly, the possibility that the center pillar  7  hits the occupant  19   a  seated at the front seat may be reduced. Also, since the engagement of the rear door  31  with the center pillar  7  is not released, the strength of the center pillar  7  against a bending moment can be maintained.  
         [0149]    The engagement of the rear door  31  with the center pillar  7  is released by the operation of the door hinge release mechanisms  37  when the vehicle  17  collides against the rear door  31  from the side direction of the vehicle  20 , as seen in FIG. 53. Although the rear portion of the vehicle  17  may be deformed so as to surround the side structural member  7  at the collision site to force the rear door  31  into the cabin  20 , deformation of the center pillar  7  induced by the deformation of the back door  31  is prevented from occurring because the engagement of the rear door  31  with the center pillar  7  is released. Accordingly, the possibility that the center pillar  7  touches the occupant  19   b  seated at the rear seat will be reduced. Also, since the engagement of the front door  30  with the center pillar  7  is not released, the strength of the center pillar  7  against a bending moment can be maintained.  
         [0150]    Also, when the vehicle  17  collides against the vicinity of the center pillar  7  from the side direction of the vehicle  20 , a collision signal is output from the collision sensors  16   a  and  16   b,  respectively, and the engagement of both the front door  30  and the rear door  31  with the center pillar  7  is released by the operation of the door engagement release mechanism  13  and the door hinge release mechanisms  37 , respectively. Accordingly, regardless the deformation of the front and/or rear portions of the vehicle  17  so as to surround the center pillar  7  at the collision site to force the front door  30  and/or the rear door  31  into the cabin, deformation of the center pillar  7  induced by the deformation of the front door  30  and/or rear door  31  is avoided. Accordingly, the possibility that the center pillar  7  touches the occupant  19   a  in the front seat or the occupant  19   b  in the rear seat can be reduced.  
         [0151]    In the above-mentioned embodiments, it will be apparent to those skilled in the art from this disclosure that the energy absorption members (compressible block, air bag or frame members with fragile portions) can be inter-changed between the various embodiments. Thus, it is possible to provide the embodiments that use the compressible member  9  with the air bag  21  instead of the compressible member  9 , or both the compressible member  9  and the air bag  21 . If both are used, it is possible to reduce the impact against the occupants  19 ,  19   a  and/or  19   b.  This type of combined use of energy absorption members is effective for the small sized air bag  21 .  
         [0152]    In the embodiments mentioned above, when the air bag  21  is used as the energy absorption member, the controller  18  outputs a signal to operate the inflators I of the air bag  21  located at the door  3 , the front door  30  and/or the rear door  31 , respectively, as well as a signal to the door release mechanism  13  and the door hinge release mechanisms  37  to release the door engagement and the door hinges  33 , respectively.  
         [0153]    Also, in the seventh embodiment, when the air bag  21  is employed, the controller  18 , upon receiving a collision signal from the front collision sensor  16   a,  outputs an actuation signal to the inflator I for the air bag  21  at the front door  30  as well as a signal to the door release mechanism  13  to release the door engagement. The controller  18 , upon receiving a collision signal from the rear collision sensor  16   b,  outputs an actuation signal to the inflator I for the air bag  21  at the rear door  31  as well as a signal to the door hinge release mechanisms  37  to release the door hinges  33 . The controller  18 , upon receiving collision signals from both the front and rear collision sensors  16   a  and  16   b,  outputs an actuation signal to both the inflators I for the air bags  21  at the front and back doors  30  and  31  as well as a signal to the door release mechanism  13  to release the door engagement (front door) and a signal to the door hinge release mechanisms  37  to release the door hinges  33  (rear door).  
         [0154]    In the above-mentioned embodiments, an object contacting detection sensor or a distance sensor can be used as the collision sensor  16 . If the distance sensor is used, preparation for collision is completed before the actual collision takes place and it is possible to fully prepare for the collision more effectively because the air bag  21  can be fully deployed before for the collision. Especially, when the air bag  21  is used, the use of the distance sensor as a collision sensor is effective.  
         [0155]    Moreover, in the above-mentioned embodiments, although cases in which the present invention is applied to a vehicle having the door  3  on one side of the vehicle or to a vehicle having two doors, i.e. the front door  30  and the back door  31 , is explained herein, it is also possible to apply the present invention to a vehicle having more than two doors on a side of the vehicle such as mini-van or limousine.  
         [0156]    Furthermore, although cases in which the center pillar  7  is the side structural member are described in the aforementioned embodiments, the present invention can be applied to any pillar or other structural member that is engaged with a door.  
         [0157]    This application claims priority to Japanese Application No. H11-076364. The entire disclosure of Japanese Application No. H11-076364 is hereby incorporated herein by reference.  
         [0158]    While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing description of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. Thus, the scope of the invention is not limited to the disclosed embodiments.