Abstract:
A vehicle occupant protection apparatus includes a first collision detection mechanism provided for a vehicle and that detects a collision of the vehicle; a second collision detection mechanism provided closer to a middle of the vehicle than the first collision detection mechanism and that detects a collision of the vehicle; a first protection mechanism that protects an occupant from a collision of the vehicle; a controller that activates the first protection mechanism at the time when the first and second collision detection mechanisms detect a collision of the vehicle; and a collision prediction mechanism that predicts a collision of the vehicle. Every time the collision prediction mechanism predicts a collision of the vehicle in a direction from the first collision detection mechanism toward the middle of the vehicle, the controller activates the first protection mechanism at the time when the first collision detection mechanism detects the collision of the vehicle.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relatesto a vehicle occupant protection apparatus and, more particularly, to a vehicle occupant protection apparatus, such as a vehicle air-bag system. 
         [0003]    2. Description of the Related Art 
         [0004]    A generally known air-bag system provides a technology for deploying an air bag at the time when a main G sensor and a safing G sensor both detect a collision of a vehicle in order to prevent erroneous deployment of the air bag. In regard to the above technology, in recent years, an air-bag system that is able to deploy an air bag even when an abnormal condition, such as a fault or a break, occurs in a safing G sensor, which is, for example, suggested in Japanese Patent Application Publication No. 2005-239059 (JP-A-2005-239059). 
         [0005]    Hereinafter, an air-bag system that is able to deploy an air bag even when an abnormal condition, such as a fault or a break, occurs in a safing G sensor according to a related art will be described with reference to  FIG. 11  and  FIG. 12 .  FIG. 11  is a schematic view of a vehicle equipped with an air-bag system according to the related art.  FIG. 12  is a circuit configuration diagram of the air-bag system according to the related art. 
         [0006]    As shown in  FIG. 11 , the air-bag system according to the related art is mounted on a vehicle  1 , and includes a pre-crash sensor (PCS sensor)  2 , a pre-crash ECU (PCS_ECU)  3 , a main G sensor (MG sensor)  4 , an air-bag ECU (A/B_ECU)  5  and an air-bag device (AB device)  6 . 
         [0007]    The PCS sensor  2  is formed of a radar and is mounted at the front of the vehicle  1 . The PCS_ECU  3  is mounted inside the vehicle  1 . The PCS_ECU  3  estimates the course of a target vehicle on the basis of information acquired by the PCS sensor  2 , and calculates the likelihood of a collision of the host vehicle on the basis of the estimated course of the target vehicle. When the likelihood of a collision of the host vehicle increases, and when the collision will occur at the front of the vehicle  1  (frontal collision), the PCS_ECU  3  predicts a frontal collision of the vehicle  1 . When the PCS_ECU  3  predicts a frontal collision, the PCS_ECU  3  outputs a signal that indicates the prediction of a frontal collision to the A/B_ECU  5 . The MG sensor  4  is mounted at the front of the vehicle  1 , and regularly detects a longitudinal acceleration of the vehicle  1 . The MG sensor  4  regularly outputs a signal that indicates the magnitude of the detected acceleration to the A/B_ECU  5 . 
         [0008]    The A/B_ECU  5  is mounted in the middle of the vehicle  1 , and activates the A/B device  6  on the basis of the signals output from the PCS_ECU  3  and the MG sensor  4 . The A/B device  6  is mounted forward of an occupant A. Specifically, as shown in  FIG. 12 , the A/B_ECU  5  includes a collision determination unit  51 , a safing G sensor (SG sensor)  52 , a collision determination unit  53 , an abnormal condition determination unit  54 , an AND gate  55 , an OR gate  56 , an AND gate  57 , and an air-bag activation unit (A/B activation unit)  58 . 
         [0009]    The collision determination unit  51  regularly receives the signal output from the MG sensor  4 . The collision determination unit  51  regularly monitors the signal output from the MG sensor  4  and, when a rearward acceleration is larger than a predetermined threshold, determines that a frontal collision has occurred. When the collision determination unit  51  determines that a frontal collision has occurred, the collision determination unit  51  outputs a signal that indicates the occurrence of a frontal collision to the AND gate  57 . 
         [0010]    The SG sensor  52  is mounted inside the A/B_ECU  5 , and regularly detects a longitudinal acceleration of the vehicle  1 . The SG sensor  52  regularly outputs a signal that indicates the magnitude of the detected acceleration to the collision determination unit  53  and the abnormal condition determination unit  54 . 
         [0011]    The collision determination unit  53  regularly receives the signal output from the SG sensor  52 . The collision determination unit  53  regularly monitors the signal output from the SG sensor  52  and, when a rearward acceleration is larger than a predetermined threshold, determines that a frontal collision has occurred. When the collision determination unit  53  determines that a frontal collision has occurred, the collision determination unit  53  outputs a signal that indicates the occurrence of a frontal collision to the OR gate  56 . 
         [0012]    The abnormal condition determination unit  54  regularly receives the signal output from the SG sensor  52 . The abnormal condition determination unit  54  regularly monitors the signal output from the SG sensor  52 , and determines whether an abnormal condition, such as a fault or a break, occurs in the SG sensor  52 . When the abnormal condition determination unit  54  determines that an abnormal condition has occurred in the SG sensor  52 , the abnormal condition determination unit  54  outputs a signal that indicates the occurrence of an abnormal condition to the AND gate  55 . 
         [0013]    The AND gate  55  receives the signal output from the PCS_ECU  3  in addition to the signal output from the abnormal condition determination unit  54 . When the AND gate  55  receives both the signal output from the abnormal condition determination unit  54  and the signal output from the PCS_ECU  3 , the AND gate  55  outputs a signal that indicates the reception of both signals to the OR gate  56 . When the OR gate  56  receives at least one of the signal output from the AND gate  55  and the signal output from the collision determination unit  53 , the OR gate  56  outputs a signal that indicates the reception of the at least one of the signals to the AND gate  57 . When the AND gate  57  receives both the signal output from the collision determination unit  51  and the signal output from the OR gate  56 , the AND gate  57  outputs a signal that indicates that the reception of both signals to the A/B activation unit  58 . 
         [0014]    When the A/B activation unit  58  receives the signal output from the AND gate  57 , the A/B activation unit  58  activates the A/B device  6 . The A/B device  6  is activated and then deploys the air bag. 
         [0015]    In this way, the air-bag system according to the related art, shown in  FIG. 11  and  FIG. 12 , determines beforehand whether an abnormal condition occurs in the SG sensor  52 , and, when an abnormal condition has occurred in the SG sensor  52 , activates the A/B device  6  at the time when the MG sensor  4  has detected a collision. By so doing, even when an abnormal condition occurs in the SG sensor  52 , it is possible to deploy the air bag. 
         [0016]    However, in the air-bag system according to the related art, shown in  FIG. 11  and  FIG. 12 , when there is no abnormal condition in the SG sensor  52 , the air bag is deployed only when both the MG sensor  4  and the SG sensor  52  detect a collision of the vehicle  1 . For this reason, there has been a case in which deployment of the air bag delays against required time within which the air bag must be deployed after a collision. 
         [0017]    Hereinafter, the reason why deployment of the air bag delays will be described in detail with reference to  FIG. 13 .  FIG. 13  is a view that schematically shows the operation timings of the MG sensor  4 , SG sensor  52  and A/B activation unit  58 . In  FIG. 13 , it is assumed that the PCS_ECU  3  predicts a frontal collision at time t 1  and the frontal collision actually occurs at time t 2 . Because the MG sensor  4  is mounted at the front of the vehicle  1 , the MG sensor  4  detects the frontal collision at a timing that is substantially the same as the timing of the actual frontal collision, that is, time t 2 . On the other hand, the SG sensor  52  is mounted in the middle of the vehicle  1 . This delays a timing at which the SG sensor  52  detects the frontal collision from the timing at which the MG sensor  4  detects the frontal collision by a period of time (Δt) during which the frontal collision propagates from the MG sensor  4  to the SG sensor  52 . Thus, as shown in  FIG. 13 , the timing at which the SG sensor  52  detects the frontal collision is time t 3  that is delayed by Δt from time t 2 . The A/B activation unit  58  does not activate the A/B device  6  until the SG sensor  52  detects the frontal collision. Thus, a timing at which the A/B device  6  is activated is the same as the timing at which the SG sensor  52  detects the frontal collision, that is, time t 3 . 
         [0018]    In this way, the timing at which the A/B device  6  is activated delays by propagation time Δt. In accordance with this, deployment of the air bag also delays by the propagation time Δt. This has sometimes caused a delay of deployment of the air bag against the time required for deployment. Particularly, when the MG sensor  4  is mounted at the side of the vehicle  1  and then a side air bag is deployed at the time of a side collision, time required for deployment of the air bag is shorter because the distance from a collision location to the occupant A is short. For this reason, when the side air bag is deployed at the time of a side collision, there have been many cases in which deployment of the air bag delays. 
       SUMMARY OF THE INVENTION 
       [0019]    The invention provides a vehicle occupant protection apparatus that is able to advance a timing at which protection means, such as an air-bag device, is activated to thereby prevent a delay of deployment of the protection means. 
         [0020]    An aspect of the invention provides a vehicle occupant protection apparatus. The vehicle occupant protection apparatus includes: first collision detection means that is provided for a vehicle and that detects a collision of the vehicle; second collision detection means that is provided closer to a middle of the vehicle than the first collision detection means and that detects a collision of the vehicle; first protection means that protects an occupant from a collision of the vehicle; control means that activates the first protection means at the time when the first collision detection means and the second collision detection means detect a collision of the vehicle; and collision prediction means that predicts a collision of the vehicle. Every time the collision prediction means predicts a collision of the vehicle in a direction from the first collision detection means toward the middle of the vehicle, the control means activates the first protection means at the time when the first collision detection means detects the collision of the vehicle. Note that the first collision detection means may, for example, correspond to any one of an MG sensor  4 , a right MG sensor  4   a  and a left MG sensor  4   b , which will be described later in embodiments. In addition, the second collision detection means may, for example, correspond to any one of an SG sensor  71 , a right/left SG sensor  91 , a right SG sensor  91   a  and a left SG sensor  91   b , which will be described later in embodiments. 
         [0021]    According to the thus configured vehicle occupant protection apparatus of the aspect of the invention, every time the collision prediction means predicts a collision of the vehicle in a direction from the first collision detection means toward the middle of the vehicle, the first protection means is activated at the time when the first collision detection means detects the collision of the vehicle. By so doing, in terms of a collision of the vehicle in the direction from the first collision detection means, it is possible to advance activation of the first protection means as compared with that of the related art and, as a result, it is possible to prevent a delay of deployment of the first protection means. 
         [0022]    In addition, in the vehicle occupant protection apparatus according to the above aspect, the first collision detection means may be provided at a side of the vehicle. By so doing, at the time of a side collision of which time required for activation of the first protection means (time required for deployment), it is possible to further effectively prevent a delay of activation of the first protection means. 
         [0023]    In addition, in the vehicle occupant protection apparatus according to the above aspect, the first collision detection means may be provided at a front of the vehicle. 
         [0024]    In addition, in the vehicle occupant protection apparatus according to the above aspect, the first protection means may be an air-bag device. 
         [0025]    In addition, the vehicle occupant protection apparatus according to the above aspect may further include first collision detection cancellation means that cancels collision detection by the second collision detection means when the collision prediction means predicts a collision of the vehicle in the direction from the first collision detection means toward the middle of the vehicle. 
         [0026]    In addition, in the vehicle occupant protection apparatus according to the above aspect, the first collision detection means may be a G sensor that detects an acceleration in the direction from the first collision detection means toward the middle of the vehicle. 
         [0027]    In addition, the vehicle occupant protection apparatus according to the above aspect may further include seat adjusting means that adjusts the condition of a seat when the collision prediction means predicts a collision of the vehicle. 
         [0028]    In addition, the vehicle occupant protection apparatus according to the above aspect may further include third collision detection means that is provided at a left side of the vehicle with respect to a direction in which the vehicle travels and that detects a collision of the vehicle; and second protection means that protects an occupant from a collision of the vehicle. The first collision detection means may be provided at a right side of the vehicle with respect to the direction in which the vehicle travels. The second collision detection means may be provided closer to the middle of the vehicle than the first collision detection means and the third collision detection means. The second protection means may be activated by the control means at the time when the second collision detection means and the third collision detection means detect a collision of the vehicle. Every time the collision prediction means predicts a collision of the vehicle from a right side of the vehicle, the control means may activate the first protection means at the time when the first collision detection means detects the collision of the vehicle, and every time the collision prediction means predicts a collision of the vehicle from a left side of the vehicle, the control means may activate the second protection means at the time when the third collision detection means detects the collision of the vehicle. Note that the first collision detection means may, for example, correspond to a right MG sensor  4   a , which will be described later in embodiments. In addition, the second collision detection means may, for example, correspond to any one of a right/left SG sensor  91 , a right SG sensor  91   a  and a left SG sensor  91   b , which will be described later in embodiments. In addition, the third collision detection means may, for example, correspond to a left MG sensor  4   b , which will be described later in embodiments. Thus, the control means separately executes control against a collision of the vehicle from a left side of the vehicle and against a collision of the vehicle from a right side of the vehicle. By so doing, it is possible to prevent erroneous activation of the non-collision-side protection means, and it is possible to prevent erroneous activation of the protection means when right and left multiple collisions occur. 
         [0029]    In addition, in the vehicle occupant protection apparatus according to the above aspect, the second protection means may be an air-bag device. 
         [0030]    In addition, the vehicle occupant protection apparatus according to the above aspect may further include second collision detection cancellation means that cancels collision detection by the second collision detection means when the collision prediction means predicts a collision of the vehicle in a direction from the third collision detection means toward the middle of the vehicle. 
         [0031]    In addition, in the vehicle occupant protection apparatus according to the above aspect, the third collision detection means may be a G sensor that detects an acceleration in a direction from the third collision detection means toward the middle of the vehicle. 
         [0032]    According to the aspect of the invention, it is possible to provide a vehicle occupant protection apparatus that is able to advance a timing at which protection means, such as an air-bag device, is activated as compared with that of the related art to thereby prevent a delay of deployment of the protection means. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]    The features, advantages, and technical and industrial significance of this invention will be described in the following detailed description of example embodiments of the invention with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
           [0034]      FIG. 1  is a schematic view of a vehicle equipped with a vehicle occupant protection apparatus according to a first embodiment of the invention; 
           [0035]      FIG. 2  is a circuit configuration diagram of the vehicle occupant protection apparatus according to the first embodiment of the invention; 
           [0036]      FIG. 3  is a flowchart that shows the process flow of a control unit according to the first embodiment of the invention; 
           [0037]      FIG. 4  is a view that schematically shows the operation timings of an MG sensor, and the like, according to the first embodiment of the invention; 
           [0038]      FIG. 5  is a schematic view of a vehicle equipped with the vehicle occupant protection apparatus, which is further provided with a seat ECU, according to the first embodiment of the invention; 
           [0039]      FIG. 6  is a schematic view of a vehicle equipped with a vehicle occupant protection apparatus according to a second embodiment of the invention; 
           [0040]      FIG. 7  is a circuit configuration diagram of the vehicle occupant protection apparatus according to the second embodiment of the invention; 
           [0041]      FIG. 8  is a flowchart that shows the process flow of a control unit according to the second embodiment of the invention; 
           [0042]      FIG. 9  is a view that schematically shows the operation timings of a right MG sensor, and the like, according to the second embodiment of the invention; 
           [0043]      FIG. 10  is a circuit configuration diagram of the vehicle occupant protection apparatus provided with a right SG sensor and a left SG sensor according to the second embodiment of the invention; 
           [0044]      FIG. 11  is a schematic view of a vehicle equipped with an air-bag system according to the related art; 
           [0045]      FIG. 12  is a circuit configuration diagram of the air-bag system according to the related art; and 
           [0046]      FIG. 13  is a view that schematically shows the operation timings of an MG sensor, and the like, according to the related art. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0047]    The configuration of a vehicle occupant protection apparatus according to a first embodiment of the invention will be described with reference to  FIG. 1  and  FIG. 2 .  FIG. 1  is a schematic view of a vehicle equipped with the vehicle occupant protection apparatus according to the first embodiment.  FIG. 2  is a circuit configuration diagram of the vehicle occupant protection apparatus according to the first embodiment. The following description provides an example in which an air-bag device (A/B device) serves as a protection means and an air bag provided forward of an occupant A is deployed at the time of a frontal collision. 
         [0048]    As shown in  FIG. 1 , the vehicle occupant protection apparatus according to the present embodiment is mounted on a vehicle  1  and includes a PCS sensor  2 , a PCS_ECU  3 , an MG sensor  4 , an A/B_ECU  7 , and an A/B device  6 . Note that components other than the A/B_ECU  7  are similar to the components shown in  FIG. 11  and are assigned with like reference numerals, and the description thereof is omitted. 
         [0049]    The A/B_ECU  7  is mounted in the middle inside the vehicle  1  or near a tunnel of the vehicle  1 , and activates the A/B device  6  on the basis of signals output from the PCS_ECU  3  and the MG sensor  4 . The A/B device  6  is mounted forward of the occupant A of the vehicle  1 . Specifically, as shown in  FIG. 2 , the A/B_ECU  7  includes an SG sensor  71  and a control unit  72 . The control unit  72  includes collision determination units  721  and  722 , a cancellation request unit  723 , an OR gate  724 , an AND gate  725 , and an A/B activation unit  726 . 
         [0050]    The collision determination unit  721  regularly receives the signal output from the MG sensor  4 . The collision determination unit  721  regularly monitors the signal output from the MG sensor  4  and, when a rearward acceleration is larger than a predetermined threshold, determines that a frontal collision has occurred. When the collision determination unit  721  determines that a frontal collision has occurred, the collision determination unit  721  outputs a signal that indicates the occurrence of the frontal collision to the AND gate  725 . 
         [0051]    The SG sensor  71  is mounted inside the A/B_ECU  7 , and regularly detects a longitudinal acceleration of the vehicle  1 . The SG sensor  71  regularly outputs a signal that indicates the magnitude of the detected acceleration to the collision determination unit  722 . 
         [0052]    The collision determination unit  722  regularly receives the signal output from the SG sensor  71 . The collision determination unit  722  regularly monitors the output signal from the SG sensor  71  and, when a rearward acceleration is larger than a predetermined threshold, determines that a frontal collision has occurred. When the collision determination unit  722  determines that a frontal collision has occurred, the collision determination unit  722  outputs a signal that indicates the occurrence of the frontal collision to the OR gate  724 . 
         [0053]    The cancellation request unit  723  receives the signal output from the PCS_ECU  3 . When the cancellation request unit  723  receives the signal output from the PCS_ECU  3 , the cancellation request unit  723  outputs a signal that indicates a request for cancellation of frontal collision detection by the SG sensor  71  to the OR gate  724 . 
         [0054]    When the OR gate  724  receives at least one of the signal output from the collision determination unit  722  and the signal output from the cancellation request unit  723 , the OR gate  724  outputs a signal that indicates the reception of the at least one of the signals to the AND gate  725 . When the AND gate  725  receives both the signal output from the collision determination unit  721  and the signal output from the OR gate  724 , the AND gate  725  outputs a signal that indicates that the reception of both signals to the A/B activation unit  726 . 
         [0055]    When the A/B activation unit  726  receives the signal output from the AND gate  725 , the A/B activation unit  726  activates the A/B device  6 . 
         [0056]    Next, the process flow of the control unit  72  in regard to the thus configured vehicle occupant protection apparatus according to the first embodiment will be described with reference to  FIG. 3 .  FIG. 3  is a flowchart that shows the process flow of the control unit  72 . 
         [0057]    In  FIG. 3 , as the process starts, the processes of steps S 10  to S 12  are executed substantially at the same time. In step S 10 , the collision determination unit  721  regularly monitors the signal output from the MG sensor  4  and, when the collision determination unit  721  determines that a frontal collision has occurred (Yes in S 10 ), outputs a signal that indicates the occurrence of the frontal collision to the AND gate  725 . Note that when the collision determination unit  721  determines that no frontal collision is occurring, the process of step S 10  is repeated. In step S 11 , the collision determination unit  722  regularly monitors the signal output from the SG sensor  71  and, when the collision determination unit  722  determines that a frontal collision has occurred (Yes in S 11 ), outputs a signal that indicates the occurrence of the frontal collision to the OR gate  24 . Note that when the collision determination unit  722  determines that no frontal collision is occurring, the process of step S 11  is repeated. In step S 12 , when the cancellation request unit  723  receives the signal output from the PCS_ECU  3  (Yes in S 12 ), the cancellation request unit  723  outputs a signal that indicates a request for cancellation of frontal collision detection by the SG sensor  71  to the OR gate  724 . Note that when the cancellation request unit  723  receives no signal output from the PCS_ECU  3 , the process of step S 12  is repeated. 
         [0058]    In step S 13 , the OR gate  724  calculates the logical OR of the signal output from the collision determination unit  722  through the process of step S 11  and the signal output from the cancellation request unit  723  through the process of step S 12 . That is, in step S 13 , when the OR gate  724  receives at least one of the signal output from the collision determination unit  722  through the process of step S 11  and the signal output from the cancellation request unit  723  through the process of step S 12 , the OR gate  724  outputs a signal that indicates the reception of the at least one of the signals to the AND gate  725 . In step S 14 , the AND gate  725  calculates the logical AND of the signal output from the collision determination unit  721  through the process of step S 10  and the signal output from the OR gate  724  through the process of step S 13 . That is, when the AND gate  725  receives both the output signal from the collision determination unit  721  through process of step S 10  and the signal output from the OR gate  724  through the process of step S 13 , the AND gate  725  outputs a signal that indicates the reception of both signals to the A/B activation unit  726 . In step S 15 , when the A/B activation unit  726  receives the signal output from the AND gate  725  through the process of step S 14 , the A/B activation unit  726  activates the A/B device  6 . Thus, the process of the control unit  72  ends. 
         [0059]    Next, the advantageous effects of the vehicle occupant protection apparatus according to the first embodiment through the above described configuration and process will be described with reference to  FIG. 4 .  FIG. 4  is a view that schematically shows the operation timings of the MG sensor  4 , cancellation request unit  723  and AB activation unit  726 . In  FIG. 4 , it is assumed that the PCS_ECU  3  predicts a frontal collision at time t 1  and the frontal collision actually occurs at time t 2 . Because the MG sensor  4  is mounted at the front of the vehicle  1 , the MG sensor  4  detects the frontal collision at a timing that is substantially the same as the timing of the actual frontal collision, that is, time t 2 . On the other hand, the SG sensor  71  is mounted in the middle of the vehicle  1 . As described with reference to  FIG. 13 , this delays a timing at which the SG sensor  71  detects the frontal collision from the timing at which the MG sensor  4  detects the frontal collision by a period of time (Δt) during which the frontal collision propagates from the MG sensor  4  to the SG sensor  71 . However, in the present embodiment, when the PCS_ECU  3  predicts a frontal collision, the cancellation request unit  723  unconditionally requests cancellation of frontal collision detection by the SG sensor  71 . Thus, without waiting for frontal collision detection by the SG sensor  71 , the A/B activation unit  726  activates the A/B device  6  at the timing (time t 2 ) at which the MG sensor  4  has detected the frontal collision. Therefore, according to the present embodiment, as compared with the related art, it is possible to reduce a period of time from the occurrence of a frontal collision to completion of deployment of the air bag by the propagation time Δt. 
         [0060]    As described above, according to the vehicle occupant protection apparatus of the first embodiment, at the time of a frontal collision, it is possible to advance the timing at which the forward A/B device is activated as compared with that of the related art and, as a result, it is possible to prevent a delay of deployment of the air bag. 
         [0061]    In addition, according to the vehicle occupant protection apparatus of the first embodiment, only when the PCS_ECU  3  predicts a frontal collision, the cancellation request unit  723  requests cancellation of frontal collision detection by the SG sensor  71 . By so doing, it is possible to prevent erroneous activation of the A/B device due to cancellation of detection by the SG sensor  71  when a frontal collision is not predicted by the PCS_ECU  3 . 
         [0062]    Note that the vehicle occupant protection apparatus according to the first embodiment may further include a seat ECU  8  as shown in  FIG. 5 .  FIG. 5  is a schematic view of a vehicle equipped with the vehicle occupant protection apparatus, which is further provided with the seat ECU  8 , according to the first embodiment. When a frontal collision is predicted by the PCS_ECU  3 , the seat ECU  8  raises the backrest of a seat (not shown), on which the occupant A is seated, to an appropriate position. 
         [0063]    In addition, in the first embodiment, the case in which the air-bag device is used as the protection means is described; however, the protection means is not limited to the air-bag device. The vehicle occupant protection apparatus according to the first embodiment may employ another device that is able to protect an occupant at the time of a collision as the protection means. 
         [0064]    The configuration of a vehicle occupant protection apparatus according to a second embodiment of the invention will be described with reference to  FIG. 6  and  FIG. 7 .  FIG. 6  is a schematic view of a vehicle equipped with the vehicle occupant protection apparatus according to the second embodiment.  FIG. 7  is a circuit configuration diagram of the vehicle occupant protection apparatus according to the second embodiment. The following description provides an example in which an air-bag device (A/B device) serves as the protection means and an air bag provided on each side of occupants A and B is deployed at the time of a side collision. 
         [0065]    As shown in  FIG. 6 , the vehicle occupant protection apparatus according to the second embodiment is mounted on a vehicle  1 , and includes a right PCS sensor  2   a , a left PCS sensor  2   b , a PCS_ECU  3 , a right MG sensor  4   a , a left MG sensor  4   b , an A/B_ECU  9 , a right A/B device  6   a , and a left A/B device  6   b.    
         [0066]    The right PCS sensor  2   a  is formed of a radar and is mounted at the front right of the vehicle  1 . The left PCS sensor  2   b  is formed of a radar and is mounted at the front left of the vehicle  1 . The PCS_ECU  3  is mounted inside the vehicle  1 . The PCS_ECU  3  estimates the course of a target vehicle on the basis of information acquired by the right PCS sensor  2   a  and the left PCS sensor  2   b , and calculates the likelihood of a collision of the host vehicle on the basis of the estimated course of the target vehicle. When the likelihood of a collision of the host vehicle increases, and when the collision will occur at the right side of the vehicle  1  (right-side collision), the PCS_ECU  3  predicts a right-side collision of the vehicle  1 . When the PCS_ECU  3  predicts a right-side collision, the PCS_ECU  3  outputs a signal that indicates the prediction of the right-side collision to the A/B_ECU  9 . On the other hand, when the likelihood of a collision of the host vehicle increases, and when the collision will occur at the left side of the vehicle  1  (left-side collision), the PCS_ECU  3  predicts a left-side collision of the vehicle  1 . When the PCS_ECU  3  predicts a left-side collision, the PCS_ECU  3  outputs a signal that indicates the prediction of the left-side collision to the A/B_ECU  9 . The right MG sensor  4   a  is mounted at the right side of the vehicle  1 , and regularly detects a transverse acceleration of the vehicle  1 . The right MG sensor  4   a  regularly outputs a signal that indicates the magnitude of the detected acceleration to the A/B_ECU  9 . The left MG sensor  4   b  is mounted at the left side of the vehicle  1 , and regularly detects a transverse acceleration of the vehicle  1 . The left MG sensor  4   b  regularly outputs a signal that indicates the magnitude of the detected acceleration to the A/B_ECU  9 . 
         [0067]    The A/B_ECU  9  is mounted in the middle inside the vehicle  1  or near a tunnel of the vehicle  1 , and activates the right A/B device  6   a  on the basis of the signals output from the PCS_ECU  3  and the right MG sensor  4   a  or activates the left A/B device  6   b  on the basis of the signals output from the PCS_ECU  3  and the left MG sensor  4   b.    
         [0068]    The right A/B device  6   a  is mounted on the right side of the occupant A of the vehicle  1 . The left A/B device  6   b  is mounted on the left side of the occupant B of the vehicle  1 . Specifically, as shown in  FIG. 7 , the A/B_ECU  9  includes a right/left SG sensor  91  and a control unit  92 . The control unit  92  includes a right collision determination unit  921   a , a left collision determination unit  921   b , a right/left collision determination unit  922 , a right/left cancellation request unit  923 , OR gates  924   a  and  924   b , AND gates  925   a  and  925   b , a right A/B activation unit  926   a , and a left A/B activation unit  926   b.    
         [0069]    The right collision determination unit  921   a  regularly receives the signal output from the right MG sensor  4   a . The right collision determination unit  921   a  regularly monitors the signal output from the right MG sensor  4   a  and, when a leftward acceleration is larger than a predetermined threshold, determines that a right-side collision has occurred. When the right collision determination unit  921   a  determines that a right-side collision has occurred, the right collision determination unit  921   a  outputs a signal that indicates the occurrence of the right-side collision to the AND gate  925   a.    
         [0070]    The left collision determination unit  921   b  regularly receives the signal output from the left MG sensor  4   b . The left collision determination unit  921   b  regularly monitors the signal output from the left MG sensor  4   b  and, when a rightward acceleration is larger than a predetermined threshold, determines that a left-side collision has occurred. When the left collision determination unit  921   b  determines that a left-side collision has occurred, the left collision determination unit  921   b  outputs a signal that indicates the occurrence of the left-side collision to the AND gate  925   b.    
         [0071]    The right/left SG sensor  91  is mounted within the A/B_ECU  9 , and regularly detects a transverse acceleration of the vehicle  1 . The right/left SG sensor  91  regularly outputs a signal that indicates the magnitude of the detected acceleration to the right/left collision determination unit  922 . Note that the magnitude of the signal output from the right/left SG sensor  91  is positive when the right/left SG sensor  91  has detected a leftward acceleration, and the magnitude of the signal output from the right/left SG sensor  91  is negative when the right/left SG sensor  91  has detected a rightward acceleration. 
         [0072]    The right/left collision determination unit  922  regularly receives the signal output from the right/left SG sensor  91 . The right/left collision determination unit  922  regularly monitors the signal output from the right/left SG sensor  91 , and determines whether the magnitude of the output signal is positive or negative. When the magnitude of the output signal is positive and is larger than a predetermined threshold, the right/left collision determination unit  922  determines that a right-side collision has occurred. When the right/left collision determination unit  922  determines that a right-side collision has occurred, the right/left collision determination unit  922  outputs a signal that indicates the occurrence of the right-side collision to the OR gate  924   a . On the other hand, when the magnitude of the output signal is negative and is smaller than a predetermined threshold, the right/left collision determination unit  922  determines that a left-side collision has occurred. When the right/left collision determination unit  922  determines that a left-side collision has occurred, the right/left collision determination unit  922  outputs a signal that indicates the occurrence of the left-side collision to the OR gate  924   b.    
         [0073]    The right/left cancellation request unit  923  receives the signal output from the PCS_ECU  3 . When the right/left cancellation request unit  923  receives the signal that indicates the prediction of a right-side collision from the PCS_ECU  3 , the right/left cancellation request unit  923  outputs a signal that indicates a request for cancellation of right-side collision detection by the right/left SG sensor  91  to the OR gate  924   a . On the other hand, when the right/left cancellation request unit  923  receives the signal that indicates the prediction of a left-side collision from the PCS_ECU  3 , the right/left cancellation request unit  923  outputs a signal that indicates a request for cancellation of left-side collision detection by the right/left SG sensor  91  to the OR gate  924   b.    
         [0074]    When the OR gate  924   a  receives at least one of the signal output from the right/left collision determination unit  922  and the signal output from the right/left cancellation request unit  923 , the OR gate  924   a  outputs a signal that indicates the reception of the at least one of the signals to the AND gate  925   a . When the AND gate  925   a  receives both the signal output from the right collision determination unit  921   a  and the signal output from the OR gate  924   a , the AND gate  925   a  outputs a signal that indicates the reception of both signals to the right A/B activation unit  926   a . When the right A/B activation unit  926   a  receives the signal output from the AND gate  925   a , the right A/B activation unit  926   a  activates the right A/B device  6   a.    
         [0075]    When the OR gate  924   b  receives at least one of the signal output from the right/left collision determination unit  922  and the signal output from the right/left cancellation request unit  923 , the OR gate  924   b  outputs a signal that indicates the reception of the at least one of the signals to the AND gate  925   b . When the AND gate  925   b  receives both the signal output from the left collision determination unit  921   b  and the signal output from the OR gate  924   b , the AND gate  925   b  outputs a signal that indicates the reception of both signals to the left A/B activation unit  926   b . When the left A/B activation unit  926   b  receives the signal output from the AND gate  925   b , the left A/B activation unit  926   b  activates the left A/B device  6   b.    
         [0076]    Next, the process flow of the control unit  92  in regard to the thus configured vehicle occupant protection apparatus according to the second embodiment will be described with reference to  FIG. 8 .  FIG. 8  is a flowchart that shows the process flow of the control unit  92 . 
         [0077]    In  FIG. 8 , as the process starts, the processes of steps S 20  to S 25  are executed substantially at the same time. In step S 20 , the right collision determination unit  921   a  regularly monitors the signal output from the right MG sensor  4   a  and, when the right collision determination unit  921   a  determines that a right-side collision has occurred (Yes in S 20 ), outputs a signal that indicates the occurrence of the right-side collision to the AND gate  925   a . Note that when the right collision determination unit  921   a  determines that no right-side collision is occurring, the process of step S 20  is repeated. In step S 21 , the right/left collision determination unit  922  regularly monitors the signal output from the right/left SG sensor  91  and, when the right/left collision determination unit  922  determines that a right-side collision has occurred (Yes in S 21 ), outputs a signal that indicates the occurrence of the right-side collision to the OR gate  924   a . Note that when right/left collision determination unit  922  determines that no right-side collision is occurring, the process of step S 21  is repeated. In step S 22 , when the right/left cancellation request unit  923  receives the signal that indicates the prediction of a right-side collision from the PCS_ECU  3  (Yes in S 22 ), the right/left cancellation request unit  923  outputs a signal that indicates a request for cancellation of right-side collision detection by the right/left SG sensor  91  to the OR gate  924   a . Note that when the right/left cancellation request unit  923  receives no signal that indicates the prediction of a right-side collision from the PCS_ECU  3 , the process of step S 22  is repeated. 
         [0078]    In step S 26 , the OR gate  924   a  calculates the logical OR of the signal output from the right/left collision determination unit  922  through the process of step S 21  and the signal output from the right/left cancellation request unit  923  through the process of step S 22 . That is, in step S 26 , when the OR gate  924   a  receives at least one of the signal output from the right/left collision determination unit  922  through the process of step S 21  and the signal output from the right/left cancellation request unit  923  through the process of step S 22 , the OR gate  924   a  outputs a signal that indicates the reception of the at least one of the signals to the AND gate  925   a . In step S 27 , the AND gate  925   a  calculates the logical AND of the signal output from the right collision determination unit  921   a  through the process of step S 20  and the signal output from the OR gate  924   a  through the process of step S 26 . That is, when the AND gate  925   a  receives both the signal output from the right collision determination unit  921   a  through the process of step S 20  and the signal output from the OR gate  924   a  through the process of step S 26 , the AND gate  925   a  outputs a signal that indicates the reception of both signals to the right A/B activation unit  926   a . In step S 28 , when the right A/B activation unit  926   a  receives the signal output from the AND gate  925   a  through the process of step S 27 , the right A/B activation unit  926   a  activates the right A/B device  6   a.    
         [0079]    In addition, in step S 23 , the left collision determination unit  921   b  regularly monitors the signal output from the left MG sensor  4   b  and, when the left collision determination unit  921   b  determines that a left-side collision has occurred (Yes in S 23 ), outputs a signal that indicates the occurrence of the left-side collision to the AND gate  925   b . Note that when the left collision determination unit  921   b  determines that no left-side collision is occurring, the process of step S 23  is repeated. In step S 24 , the right/left collision determination unit  922  regularly monitors the signal output from the right/left SG sensor  91  and, when the right/left collision determination unit  922  determines that a left-side collision has occurred (Yes in S 24 ), outputs a signal that indicates the occurrence of the left-side collision to the OR gate  924   b . Note that when right/left collision determination unit  922  determines that no left-side collision is occurring, the process of step S 24  is repeated. In step S 25 , when the right/left cancellation request unit  923  receives the signal that indicates the prediction of a left-side collision from the PCS_ECU  3  (Yes in S 25 ), the right/left cancellation request unit  923  outputs a signal that indicates a request for cancellation of left-side collision detection by the right/left SG sensor  91  to the OR gate  924   b . Note that when right/left cancellation request unit  923  receives no signal that indicates the prediction of a left-side collision from the PCS_ECU  3 , the process of step S 25  is repeated. 
         [0080]    In step S 29 , the OR gate  924   b  calculates the logical OR of the signal output from the right/left collision determination unit  922  through the process of step S 24  and the signal output from the right/left cancellation request unit  923  through the process of step S 25 . That is, in step S 29 , when the OR gate  924   b  receives at least one of the signal output from the right/left collision determination unit  922  through the process of step S 24  and the signal output from the right/left cancellation request unit  923  through the process of step S 25 , the OR gate  924   b  outputs a signal that indicates the reception of the at least one of the signals to the AND gate  925   b . In step S 30 , the AND gate  925   b  calculates the logical AND of the signal output from the left collision determination unit  921   b  through the process of step S 23  and the signal output from the OR gate  924   b  through the process of step S 29 . That is, when the AND gate  925   b  receives both the signal output from the left collision determination unit  921   b  through the process of step S 23  and the signal output from the OR gate  924   b  through the process of step S 29 , the AND gate  925   b  outputs a signal that indicates the reception of both signals to the left A/B activation unit  926   b . In step S 31 , when the left A/B activation unit  926   b  receives the signal output from the AND gate  925   b  through the process of step S 30 , the left A/B activation unit  926   b  activates the left A/B device  6   b . Thus, the process of the control unit  92  ends. 
         [0081]    Next, the advantageous effects of the vehicle occupant protection apparatus according to the second embodiment through the above described configuration and process will be described with reference to  FIG. 9 .  FIG. 9  is a view that schematically shows the operation timings of the right MG sensor  4   a , right/left cancellation request unit  923 , right A/B activation unit  926   a , left MG sensor  4   b  and left A/B activation unit  926   b . In  FIG. 9 , it is assumed that the PCS_ECU  3  predicts a right-side collision at time t 1 , the right-side collision actually occurs at time t 2 , the PCS_ECU  3  predicts a left-side collision at time t 3 , and the left-side collision actually occurs at time t 4 . 
         [0082]    Because the right MG sensor  4   a  is mounted at the right side of the vehicle  1 , the right MG sensor  4   a  detects the right-side collision at a timing that is substantially the same as the timing of the actual right-side collision, that is, time t 2 . On the other hand, the right/left SG sensor  91  is mounted in the middle of the vehicle  1 . This delays a timing at which the right/left SG sensor  91  detects the right-side collision from the timing, at which the right MG sensor  4   a  detects the right-side collision by a period of time (Δt′) during which the right-side collision propagates from the right MG sensor  4   a  to the right/left SG sensor  91 . However, in the present embodiment, when the PCS_ECU  3  predicts a right-side collision, the right/left cancellation request unit  923  unconditionally requests cancellation of right-side collision detection by the right/left SG sensor  91 . Thus, without waiting for right-side collision detection by the right/left SG sensor  91 , the right A/B activation unit  926   a  activates the right A/B device  6   a  at the timing (time t 2 ) at which the right MG sensor  4   a  has detected the right-side collision. In addition, in the present embodiment, when the PCS_ECU  3  predicts a left-side collision, the right/left cancellation request unit  923  unconditionally requests cancellation of left-side collision detection by the right/left SG sensor  91 . Thus, without waiting for left-side collision detection by the right/left SG sensor  91 , the left A/B activation unit  926   b  activates the left A/B device  6   b  at the timing (time t 4 ) at which the left MG sensor  4   b  has detected the left-side collision. Therefore, according to the present embodiment, as compared with the related art, it is possible to reduce a period of time from the occurrence of a right-side collision or the occurrence of a left-side collision to completion of deployment of the air bag by the propagation time Δt′. 
         [0083]    As described above, according to the vehicle occupant protection apparatus of the second embodiment, at the time of a side collision of which time required for deployment of the A/B device is short, it is possible to advance the timing at which each side A/B device is activated as compared with that of the related art and, as a result, it is possible to further effectively prevent a delay of deployment of the air bag. 
         [0084]    In addition, according to the vehicle occupant protection apparatus of the second embodiment, only when the PCS_ECU  3  predicts, for example, a right-side collision, the right/left cancellation request unit  923  requests cancellation of right-side collision detection by the right/left SG sensor  91 . By so doing, it is possible to prevent erroneous activation of the right A/B device due to cancellation of right-side collision detection by the right/left SG sensor  91  when a right-side collision is not predicted by the PCS_ECU  3 . 
         [0085]    Furthermore, according to the vehicle occupant protection apparatus of the second embodiment, the right/left cancellation request unit  923  separately requests cancellation of right-side collision detection by the right/left SG sensor  91  and cancellation of left-side collision detection by the right/left SG sensor  91  from each other. By so doing, it is possible to prevent erroneous activation of the left (non-collision-side) A/B device due to cancellation of left-side collision detection by the right/left SG sensor  91  when a right-side collision is, for example, predicted by the PCS_ECU  3 . In addition, it is possible to prevent erroneous activation of the A/B devices when right and left multiple collisions occur. 
         [0086]    Note that the vehicle occupant protection apparatus according to the second embodiment includes the single right/left SG sensor  91  and separately detects a right-side collision and a left-side collision; however, the vehicle occupant protection apparatus is not limited to this configuration. As shown in  FIG. 10 , the vehicle occupant protection apparatus may include a right SG sensor  91   a  that detects only a right-side collision and a left SG sensor  91   b  that detects only a left-side collision, in place of the right/left SG sensor  91 . In this case, the vehicle occupant protection apparatus includes a right collision determination unit  922   a  and a left collision determination unit  922   b , in place of the right/left collision determination unit  922 . The right collision determination unit  922   a  regularly monitors the signal output from the right SG sensor  91   a  and determines whether a right-side collision has occurred. The left collision determination unit  922   b  regularly monitors the signal output from the left SG sensor  91   b  and determines whether a left-side collision has occurred. In addition, in this case, the right/left cancellation request unit  923  requests cancellation of detection by any one of the right SG sensor  91   a  and the left SG sensor  91   b  on the basis of the signal output from the PCS_ECU  3 . 
         [0087]    In addition, the vehicle occupant protection apparatus according to the second embodiment may further include a seat ECU  8  as shown in  FIG. 5 . In this case, when a right-side collision is, for example, predicted by the PCS_ECU  3 , the seat ECU  8  raises the backrest of a seat (not shown), on which the occupant A is seated, to an appropriate position, but the seat ECU  8  does not raise the backrest of a seat, on which the occupant B is seated. 
         [0088]    In addition, in the second embodiment, for example, at the time of a right-side collision, the right A/B device  6   a  is activated; however, depending on the type of the protection means, the left A/B device  6   b , which is the non-collision-side A/B device, may be activated. 
         [0089]    The vehicle occupant protection apparatus according to the aspect of the invention is utilized in various protection means, such as an air-bag device, for protecting an occupant at the time of a collision. 
         [0090]    While the invention has been described with reference to example embodiments thereof, it should be understood that the invention is not limited to the example embodiments or constructions. To the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the example embodiments are shown in various combinations and configurations, which are example, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the invention.