Patent Publication Number: US-2007114771-A1

Title: Passenger protecting system for vehicle

Description:
CROSS REFERENCE TO RELATED APPLICATION  
      This application is based on a Japanese Patent Application No. 2005-336099 filed on Nov. 21, 2005, the disclosure of which is incorporated herein by reference.  
     FIELD OF THE INVENTION  
      The present invention relates to a passenger protecting system, which can be suitably used for a vehicle.  
     BACKGROUND OF THE INVENTION  
      Generally, as disclosed in JP-2-249740A, a vehicle can be provided with a pressure sensor for a detection of a collision of the vehicle. Specifically, an air tank which is closed is arranged in a door of the vehicle. The pressure in the air tank is detected by the pressure sensor. In the case where the pressure detected by the pressure sensor is larger than or equal to a predetermined threshold value, it is determined there occurs the collision between the vehicle and an obstacle. Thus, a passenger protection device of the vehicle such as an airbag and the like is actuated.  
      Moreover, as disclosed in JP-2654428B2 (U.S. Pat. No. 5,748,075), a pressure of a predetermined space in the vehicle and an acceleration of the vehicle which will vary due to a collision of the vehicle are detected. Whether or not there occurs the collision of the vehicle is repeatedly determined, respectively based on the pressure and the acceleration. In this case, the passenger protection device is actuated when the collision of the vehicle has been determined.  
      Furthermore, as disclosed in JP-2004-513824A (U.S. Pat. No. 6,725,961), a temperature of a predetermined space defined in the vehicle and the acceleration of the vehicle are detected. The temperature and the acceleration will vary due to the collision of the vehicle. Whether or not there occurs the collision of the vehicle is repeatedly determined, respectively based on the temperature and the acceleration. In this case, the passenger protection device is actuated when the collision of the vehicle has been determined.  
      According to JP-2654428B2 and JP-2004-513824A, the collision determination accuracy is improved because the collision is repeatedly determined.  
      However, according to JP-2654428B2, there is a difference between the time period elapsed from the collision occurrence to the collision detection based on the pressure, and that based on the acceleration. For example, in the case of the collision at the vehicle door, the collision is determined based on the pressure of the inner space of the vehicle door and the acceleration of the vehicle chassis. Generally, the vehicle door has a stiffness which is not so high, to be readily deformed. That is, when there occurs the collision between the door and the obstacle, the door is firstly deformed and then the vehicle chassis moves.  
      Therefore, the acceleration of the vehicle will vary after the pressure increase of the inner space of the vehicle door. Thus, the collision is detected based on the pressure of the inner space, and thereafter the collision is detected based on the acceleration of the vehicle. In this case, the passenger protection device will not be actuated, until the detection (which is later) of the collision based on the acceleration.  
      Similarly, according to JP-2004-513824A, there is a difference between the time period elapsed from the collision occurrence to the collision detection based on the temperature, and that based on the acceleration. In this case, the passenger protection device will not be actuated, until the detection (which is later) of the collision based on the acceleration.  
     SUMMARY OF THE INVENTION  
      In view of the above-described disadvantages, it is an object of the present invention to provide a passenger protecting system, in which a collision of a vehicle is detected at an earlier time with an improved accuracy for an actuation of a passenger protection device.  
      According to the present invention, a passenger protecting system for a vehicle has a space defining member which partially constructs a chassis of the vehicle and defines therein an inner space deformable due to a collision of the vehicle, a pressure detection member which is arranged in the inner space to detect a pressure of air in the inner space, a temperature detection member which is arranged in the inner space to detect a temperature of air in the inner space, a determination unit and a passenger protection device for protecting a passenger in the vehicle. The determination unit determines whether or not there occurs the collision of the vehicle, based on a variation of the pressure detected by the pressure detection member and a variation of the temperature detected by the temperature detection member. The passenger protection device is actuated when the determination unit determines that there occurs the collision of the vehicle.  
      In this case, the collision of the vehicle is repeatedly determined, respectively based on the variation of the pressure and the variation of the temperature in the inner space of the space defining member which is fixed to the vehicle. Because the multiple kinds of information is used for the determination of the vehicle collision, the collision can be detected with an improved accuracy. Thus, an unnecessary actuation of the passenger protection device can be restricted.  
      Moreover, the variations of the pressure and the temperature used for the collision determination are in substantial synchronism with each other. In this case, the pressure and the temperature of the inner space increase substantially simultaneously, corresponding to the collision of the vehicle. That is, the time period elapsed from the occurrence of the collision to the determination (detection) of the collision based on the pressure variation is substantially equal to, the time period elapsed from the occurrence of the collision to the determination (detection) of the collision based on the temperature variation. Therefore, the collision can be detected at an earlier time, even when the collision is determined according to the multiple kinds of information.  
      Preferably, the passenger protecting system has a correction unit which determines a corrected pressure by correcting the pressure corresponding to the temperature. The pressure and the temperature are respectively detected by the pressure detection member and the temperature detection member. The determination unit determines whether or not there occurs the collision of the vehicle based on a variation of the corrected pressure and the variation of the temperature.  
      In this case, the temperature in the inner space detected by the temperature detection member is used for the determination of the collision and for the correction of the pressure in the inner space. Therefore, it is unnecessary to provide an additional temperature detection member for detecting the ambient temperature of the pressure detection member. Thus, the pressure detected by the pressure detection member can be corrected with a reduced cost. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      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 which:  
       FIG. 1  is a schematic view showing a door of a vehicle according to a first embodiment of the present invention;  
       FIG. 2  is an enlarged partial sectional view showing a part II in  FIG. 1  according to the first embodiment;  
       FIG. 3  is a block diagram showing a passenger protecting system according to the first embodiment;  
       FIG. 4  is a flow chart showing a determination process of a determination unit of an airbag ECU according to the first embodiment;  
       FIG. 5A  is a graph showing a change of a corrected pressure variation with the time elapsing in the case of a collision of the door, and  FIG. 5B  is a graph showing a change of a temperature variation with the time elapsing in the case of the collision of the door; and  
       FIG. 6  is a block diagram showing a passenger protecting system according to a second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS  
     First Embodiment  
      A passenger protecting system according to a first embodiment of the present invention will be described with reference to  FIGS. 1-5 . The passenger protecting system can be suitably used for a vehicle, for example. The passenger protecting system is provided with a sensor module  20 , an airbag ECU  30 , a passenger protection device  40  and the like.  
      As shown in  FIG. 1 , the sensor module  20  includes a housing  21 , a pressure detection member  22  (e.g., pressure sensor), a temperature detection member  23  (e.g., temperature sensor) and a communication IC  24 . The sensor module  20  is arranged in an inner space  13 , which is defined in a space defining member (e.g., door  10 ). The space defining member can construct a part of the chassis of the vehicle, and be deformable due to a collision of the vehicle.  
      The door  10  has an inner panel  11  which is arranged at an inner side of a passenger compartment of the vehicle, and an outer panel  12  which is arranged at an outer side of the passenger compartment. The inner space  13  is defined between the inner panel  11  and the outer panel  12 .  
      In this case, a surface (e.g., right side in  FIG. 1 ) of the inner panel  11  and a surface (e.g., left side in  FIG. 1 ) of the outer panel  12  are covered by a heat insulation material. These surfaces of the inner panel  11  and the outer panel  12  are positioned at the inner side of the inner space  13 . That is, the most surfaces for defining the inner space  13  are covered by the heat insulation material.  
      The housing  21  which is hollow is arranged in the inner space  13  and attached to the inner panel  11 . The housing  21  has an opening  21   a  through which the space in the housing  21  is communicated with the inner space  13  of the door  10 . The opening  21   a  can be arranged at an opposite side of the housing  21  to the inner panel  11  (passenger compartment). The pressure and the temperature of air in the inner space  13  will vary due to the collision at the door  10  of the vehicle, and be transferred from the exterior of the housing  21  to the interior thereof through the opening  21   a.    
      The pressure sensor  22  is fixed in the housing  21  to detect a variation of the pressure of air in the inner space  13  of the door  10 . Specifically, the pressure sensor  22  can have a sensor chip  22   a  (i.e., pressure detection portion) and an amplification circuit  22   b  (i.e., pressure correction unit).  
      The sensor chip  22   a  includes a diaphragm which can be constructed of a silicon chip having a thin-walled center portion. A diffusion resistance which constructs a Wheatstone bridge is provided at the diaphragm. In the case where a pressure is applied to the sensor chip  22   a  so that the diaphragm is deformed, a potential difference between two ends (i.e., right end and left end in  FIG. 3 ) of the sensor chip  22   a  varies. Thus, the sensor chip  22   a  outputs a signal of the potential difference between the two ends thereof. Therefore, the variation ΔP (caused by collision at door  10 , for example) of the pressure applied to the sensor chip  22   a  can be detected via the potential difference signal.  
      In this case, the signal of the pressure variation ΔP outputted by the sensor chip  22   a  is related to the ambient temperature T of the sensor chip  22   a  (i.e., temperature T in housing  21 ). That is, the pressure variation ΔP detected by the sensor chip  22   a  has a variability due to the ambient temperature T.  
      The amplification circuit  22   b  is provided, to perform an amplification correction process of the pressure variation ΔP detected by the sensor chip  22   a  so that a corrected pressure variation ΔP 1  is obtained. In this case, the amplification correction process includes an amplification process for proportionally amplifying the pressure variation ΔP outputted by the sensor chip  22   a , and a correction process based on the temperature T detected by the temperature sensor  23 . In the correction process, the pressure variation ΔP having been amplified can be corrected so that the variability thereof due to the ambient temperature T of the sensor chip  22   a  is eliminated. For example, correction amounts (to be used in correction process) corresponding to temperatures can be predetermined. Then, the correction amount corresponding to the temperature T which is practically detected by the temperature sensor  23  is, for example, added to the pressure variation ΔP detected by the sensor chip  22   a . In this case, the correction of the pressure variation ΔP can be also performed before the amplification thereof.  
      According to this embodiment, the temperature sensor  23  is fixed in the housing  21  and positioned near the pressure sensor  22 , to detect the temperature T and the temperature variation ΔT (caused by collision at door  10 , for example) of air in the inner space  13  of the door  10 .  
      The communication IC  24 , which can be arranged in the housing  21 , includes an A/D converter  24   a  and an interface  24   b . The corrected pressure variation ΔP 1  outputted from the pressure sensor  22  and the temperature variation ΔT outputted from the temperature sensor  23  are inputted to the A/D converter  24   a  to be A/D converted. Then, the corrected pressure variation ΔP 1  and the temperature variation ΔT which have been A/D-converted are outputted to the airbag ECU  30  through the interface  24   b.    
      The airbag ECU  30  can have an interface  31  and a determination unit  32 . The information outputted from the interface  24   b  of the communication IC  24  is inputted to the determination unit  32  through the interface  31 . Then, a determination process for determining whether or not actuate the passenger protection device  40  is performed by the determination unit  32 , based on the information inputted thereto through the interface  31 . A pressure threshold Pth and a temperature threshold value Tth which are used in the determination process can be beforehand memorized in the determination unit  32 .  
      The determination process of the determination unit  32  of the airbag ECU  30  will be described with reference to  FIG. 4 . At first, at step S 1 , it is determined whether or not the corrected pressure variation ΔP 1  is larger than the pressure threshold value Pth. In the case where the corrected pressure variation ΔP 1  is smaller than or equal to the pressure threshold value Pth (i.e., S 1 : No), the process shown in  FIG. 4  will be repeated from step S 1 .  
      On the other hand, in the case where the corrected pressure variation ΔP 1  is larger than the pressure threshold value Pth (i.e., S 1 : Yes), it is further determined at step S 2  whether or not the temperature variation ΔT is larger than the temperature threshold Tth.  
      In the case where the temperature variation ΔT is smaller than or equal to the temperature threshold value Tth (i.e., S 2 : No), the process shown in  FIG. 4  will be repeated from step S 1 . On the other hand, in the case where the temperature variation ΔT is larger than the temperature threshold value Tth (i.e., S 2 : Yes), it is determined that there occurs the collision with the door  10  of the vehicle. Then, at step S 3 , the passenger protection device  40  is actuated. Thereafter, the process shown in  FIG. 4  is repeatedly performed from step S 1  when a predetermined time period has elapsed, for example.  
      In this embodiment, the passenger protection device  40  can include airbags, for example. The airbag can be deployed between the door  10  and a passenger when the collision at the door  10  has been determined.  
      Next, the operation of the passenger protecting system according to this embodiment will be described with reference to  FIGS. 5A and 5B .  FIG. 5A  shows the change of the corrected pressure variation ΔP 1  with the time elapsing, in the case of the collision of the door  10 .  FIG. 5B  shows the change of the temperature variation ΔT with the time elapsing, in the case of the collision of the door  10 .  
      Generally, the outer panel  12  of the door  10  has a stiffness which is not so high. Therefore, in the case where there occurs a collision at the outer panel  12 , the outer panel  12  will be deformed to the side of the inner panel  11 . That is, immediately after the occurrence of the collision of the outer panel  12 , the inner space  13  is deformed to become narrow. Thus, the pressure in the inner space  13  increases.  
      Moreover, the temperature in the inner space  13  increases due to an adiabatic change. That is, the pressure variation ΔP and the temperature variation ΔT in the inner space  13  are in substantial synchronism with each other. As described above, because the most surfaces which define the inner space  13  are covered by the heat insulation material, the heat in the inner space  13  is restricted from radiating to the exterior of the inner space  13 . Thus, the temperature of air in the inner space  13  will efficiently and substantially increase corresponding to the increase of the pressure, and be used for the collision determination.  
      In this case, the sensor chip  22   a  of the pressure sensor  22  detects the pressure variation ΔP in the inner space  13 , which is transferred to the sensor chip  22   a  through the opening  21   a . The temperature sensor  23  detects the temperature T and the temperature variation ΔT in the inner space  13  which is transferred thereto through the opening  21   a . Furthermore, the corrected pressure variation ΔP 1  can be obtained via the amplification circuit  22   b  of the pressure sensor  22 , based on the pressure variation ΔP and the temperature T (i.e., ambient temperature of pressure sensor  22 ). That is, the pressure variation ΔP detected by the sensor chip  22   a  (pressure detection portion) is corrected via the temperature information outputted from the temperature sensor  23  (temperature detection member).  
      According to this embodiment, the pressure sensor  22  and the temperature sensor  23  are arranged in the housing  21  and positioned in close proximity to each other. Therefore, the pressure variation ΔP detected by the sensor chip  22   a  of the pressure sensor  22  and the temperature variation ΔT detected by the temperature sensor  23  are in substantial synchronism with each other. Accordingly, as shown in  FIGS. 5A and 5B , the corrected pressure variation ΔP 1  and the temperature variation ΔT are in substantial synchronism with each other.  
      In the case where the corrected pressure variation ΔP 1  is larger than the pressure threshold value Pth with reference to  FIG. 5A  and the temperature variation ΔT is larger than the temperature threshold value Tth with reference to  FIG. 5B , the passenger protection device  40  will be actuated.  
      In this case, because the collision of the outer panel  12  of the door  10  is repeatedly determined according to the corrected pressure variation ΔP 1  and the temperature variation ΔT of the inner space  13  of the door  10 , the determination accuracy can be improved. Furthermore, the corrected pressure variation ΔP 1  and the temperature variation ΔT in the inner space  13  are in substantial synchronism with each other, so that the collision can be determined at an earlier time. Moreover, in this case, the corrected pressure variation ΔP 1  which has been amplified and corrected by the amplification circuit  22   b  is used for the determination of the collision. That is, the variability of the signal outputted from the sensor chip  22   a  due to the ambient temperature T thereof can be eliminated.  
      Moreover, because the pressure sensor  22  and the temperature sensor  23  are arranged in the same housing  21 , the synchronization between the signals from the pressure sensor  22  and the temperature sensor  23  can be improved. Furthermore, the space can be reduced and the cost can be decreased.  
     Second Embodiment  
      A second embodiment of the present invention will be described with reference to  FIG. 6 . In this case, the correction process of the pressure variation ΔP is performed by a correction unit  33  of the airbag ECU  30 . That is, the airbag ECU  30  calculates the corrected pressure variation ΔP 1  based on the pressure variation ΔP and the temperature T.  
      The passenger protecting system is provided with the sensor module  20 , the airbag ECU  30  and the passenger protection device  40 . The sensor module  20  which is arranged in the inner space  13  has the housing  21 , the pressure sensor  22 , the temperature sensor  23  and the communication IC  24 . The pressure sensor  22  having the sensor chip  22   a  and the amplification circuit  22   b  is arranged in the housing  21 , to detect the pressure variation ΔP of air in the inner space  13  of the door  10 . The temperature T and the temperature variation ΔT of the inner space  13  are detected by the temperature sensor  23  which is arranged in the housing  12 .  
      According to the second embodiment, the amplification circuit  22   b  performs the amplification process of the pressure variation ΔP detected by the sensor chip  22   a . At the amplification process, the pressure variation ΔP outputted from the sensor chip  22   a  is proportionally amplified, for example.  
      The airbag ECU  30  has the interface  31 , the determination portion  32 , and the correction unit  33 . The pressure variation ΔP having been amplified, the temperature T and the temperature variation ΔT (which are outputted from interface  24   b  of communication IC  24 ) are inputted to the correction unit  33  through the interface  31 .  
      In this case, the pressure variation ΔP having been amplified is provided with the correction process by the correction unit  33 , based on the temperature T. At the correction process, the pressure variation ΔP having been amplified is processed so that the variability thereof due to the ambient temperature T of the sensor chip  22   a  is eliminated. For example, the correction amounts corresponding to the temperatures can be beforehand set. Then, the correction amount corresponding to the temperature T which is practically detected by the temperature sensor  23  is, for example, added to the pressure variation ΔP having been amplified so that the corrected pressure variation ΔP 1  is calculated.  
      The determination unit  32  performs the determination process for determining whether or not actuate the passenger protection device  40 , based on the temperature variation AT detected by the temperature sensor  23  and the corrected pressure variation ΔP 1  which is calculated by the correction unit  33 . The determination process can be performed similarly to that in the above-described first embodiment with reference to  FIG. 4 . The pressure threshold Pth and the temperature threshold value Tth which are used in the determination process can be beforehand memorized in the determination unit  32 , for example.  
      In the case where the corrected pressure variation ΔP 1  and the temperature variation ΔT are respectively larger than the predetermined threshold values Pth and Tth, it is determined that there occurs the collision at the door  10 . Thus, the passenger protection device  40  is actuated.  
      In this case, because the collision of the door  10  is repeatedly determined according to the pressure variation and the temperature variation of the inner space  13  of the door  10 , the determination accuracy can be improved. Furthermore, the pressure variation and the temperature variation in the inner space  13  are in substantial synchronism with each other, so that the collision can be determined at an earlier time. Moreover, because the corrected pressure variation ΔP 1  which has been amplified and corrected is used for the determination of the collision, the variability of the pressure variation ΔP detected by the sensor chip  22   a  due to the ambient temperature T can be restricted.  
      About the passenger protecting system, what has not been described in the second embodiment is the same with the first embodiment.  
     Other Embodiments  
      Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.  
      For example, the space defining member for defining therein the inner space  13  can be also constructed of a vehicle chassis member (e.g., bumper) other than the door  10 . In this case, the space defining member having the inner space  13  therein is deformable due to the collision of the vehicle.  
      Moreover, the heat insulation material can be also provided for one of the inner surface (at inner side of inner space  13 ) of the outer panel  13  and that of the inner panel  11 .  
      Such changes and modifications are to be understood as being in the scope of the present invention as defined by the appended claims.