Abstract:
A satellite module mounted near the periphery of a vehicle inboard of a body panel such as a bumper or side door panel includes both primary and secondary (safing) sensors. Response time is enhanced by co-locating the sensors in a satellite module, and reliability is enhanced by utilizing different sensing technologies for the co-located sensors. In a preferred embodiment, either the primary or secondary sensor is responsive to airflow inboard of the body panel due to a crash event.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to supplemental restraint systems in motor vehicles, and more particularly to crash sensing apparatus disposed in a satellite module near the periphery of a vehicle.  
       BACKGROUND OF THE INVENTION  
       [0002]     It has been customary in the deployment of vehicular supplemental restraints such as air bags to require both a primary crash sensor for determining whether and when the restraints should be deployed for a detected crash event and a secondary (safing) crash sensor for independently confirming the existence of the crash event. In most system configurations, the primary crash sensor is mounted in a satellite module disposed near the periphery of the vehicle (such as behind the front bumper or in the side door or pillar), while the secondary crash sensor is mounted along with the signal processor in a central module disposed near the center of the vehicle. This configuration is intended to enhance fault tolerance, but can also result in unacceptable deployment delay, particularly in applications such as side impacts and certain frontal impacts where the required deploy time occurs very soon after the onset of the crash. In other words, a primary satellite-mounted sensor may provide timely impact detection, but structural dynamics of the vehicle result in a delayed reaction at the centrally located secondary sensor. Accordingly, what is needed is a fault tolerant crash impact sensing apparatus that detects impacts both quickly and reliably.  
       SUMMARY OF THE INVENTION  
       [0003]     The present invention is directed to an improved and fault tolerant vehicle crash sensing apparatus for a supplemental restraint system in which primary and secondary (safing) sensors are co-located in a satellite module mounted near the periphery of the vehicle inboard of a body panel such as a bumper or side door panel. Fault tolerance is enhanced by utilizing different sensing technologies for the co-located sensors, and in a preferred embodiment, either the primary or secondary sensor is responsive to airflow inboard of a body panel due to impacts with the body panel. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]      FIG. 1  is a diagram of a vehicle equipped with a supplemental restraint system including multiple satellite crash sensing modules according to this invention;  
         [0005]      FIG. 2A  is a block diagram of the side-impact satellite module of  FIG. 1 ;  
         [0006]      FIG. 2B  is a block diagram detailing a portion of the block diagram of  FIG. 2A  pertaining to supplemental restraint deployment logic;  
         [0007]      FIG. 3A  is a diagram of a heated element airflow sensor for the satellite modules of  FIG. 1 ;  
         [0008]      FIG. 3B  is a diagram of a venturi airflow sensor for the satellite modules of  FIG. 1 ; and  
         [0009]      FIG. 3C  is a diagram of a Pitot tube airflow sensor for the satellite modules of  FIG. 1 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0010]     Referring to  FIG. 1 , the reference numeral  10  generally designates a vehicle equipped with a supplemental restraint system including satellite crash sensing modules  12 ,  14 ,  16  for detecting frontal and side impacts. The frontal impact satellite module  12  is located inboard of the front bumper  18 , while the side impact satellite modules  14 ,  16  are located in the front side doors  20 ,  22  inboard of the exterior door panels  20   a ,  22   a . Of course, satellite modules may additionally be placed in the rear side doors  24 ,  26  or in other portions of the vehicle  10  if desired. The satellite modules  12 ,  14 ,  16  include primary and secondary (safing) crash sensors as explained below, and each satellite module  12 ,  14 ,  16  is capable of issuing a deployment command for one or more supplemental restraint devices, designated in  FIG. 1  by the single block (R)  30 . The deployment commands produced by satellite modules  12 ,  14 ,  16  are supplied to a microprocessor-based airbag control module (ACM)  28 , which diagnoses proper operation of the satellite modules  12 ,  14 ,  16  and deploys restraints  30  corresponding to the received deployment commands if the respective satellite module(s) is deemed to be in proper working condition. For example, the ACM  28  may include one or more internal crash sensors such as accelerometers for diagnosing proper operation of the satellite modules  12 ,  14 ,  16 . Alternatively, the crash signals developed by the satellite sensors could be processed by ACM  28 ; in this case, the satellite modules  12 ,  14 ,  16  would supply ACM  28  crash signals instead of deployment commands, and crash signal developed by sensors internal to ACM  28  could be used as additional safing signals.  
         [0011]      FIG. 2A  illustrates a mechanization of the side impact satellite module  14 . In the illustration, the satellite module  14  is mounted on a structural beam  34  in the vehicle side door  20 , inboard of the exterior door panel  20   a . Alternately, the module  14  could be mounted on an inner door panel. The satellite module  14  includes both primary and secondary crash sensors  36 ,  37  and a microprocessor (μP)  38  that receives and processes the crash signals produced by sensors  36  and  37  to detect a crash event and to determine if and when one more of the restraints  30  should be deployed for passenger protection. As explained below in reference to  FIG. 2B , the microprocessor  38  issues a deployment command on line  39  for a side-impact crash event if the primary crash sensor  36  indicates that the crash is sufficiently severe, and the secondary crash sensor  37  confirms the existence of a severe crash. According to this invention, fault tolerance is enhanced because the sensors  36  and  37  utilize different sensing technologies and reliability is enhanced because both sensors produce crash signals that reliably discriminate between crash events and non-crash events. To this end, one of the primary and secondary crash sensors  36 ,  37  is responsive to impact-related airflow inboard of the door panel  20   a , and the other crash sensor  37 ,  36  is responsive to a different impact-related parameter such as lateral acceleration or air pressure in door  20 . In the illustrated embodiment, the primary crash sensor  36  is an airflow sensor (AFS) and the secondary crash sensor  37  is an acceleration sensor or pressure sensor (ACCEL/PR).  
         [0012]     The block diagram of  FIG. 2B  represents deployment logic carried out by the microprocessor  38  of satellite module  14 . In applications where the satellite module  14  does not have signal processing capability, the deployment logic of  FIG. 2B  can be carried out by the ACM  28 . Blocks  38   a  and  38   b  respectively represent various crash discrimination and safing measures or determinations based on the airflow signal produced by sensor  36 . Similarly, blocks  38   e  and  38   f  respectively represent various crash discrimination and safing measures or determinations based on the acceleration or pressure signal produced by sensor  37 . In general, the crash discrimination measures of blocks  38   a  and  38   e  can be sophisticated algorithms designed to discriminate between deployment events and non-deployment events; each block may comprise several different algorithms, as indicated by the multiple outputs. The safing measures of blocks  38   b  and  38   f , on the other hand, are typically less sophisticated than the crash discrimination measures, and are designed primarily to confirm the existence of a crash event. The logic gates  38   c ,  38   h ,  38   i  and  38   k  produce a deployment command on line  39  when at least one of the discrimination measures of block  38   a  indicates the occurrence of a deployment event and at least one of the safing measures of block  38   f  confirms the existence of the crash event. Similarly, the logic gates  38   d ,  38   g ,  38   j  and  38   k  produce a deployment command on line  39  when at least one of the discrimination measures of block  38   e  indicates the occurrence of a deployment event and at least one of the safing measures of block  38   b  confirms the existence of the crash event.  
         [0013]      FIGS. 3A-3C  depict three examples of suitable airflow sensors. When an exterior vehicle body panel such as the bumper  18  or the door panels  20   a ,  22   a  of side doors  20 ,  22  is struck by an object, the body panel deflects inward. The inward deflection produces compression and inward displacement of air inboard of the body panel, and the airflow sensors within the respective satellite modules  12 ,  14 ,  16  produce signals responsive to the airflow.  FIG. 3A  depicts a heated element sensor  40 ;  FIG. 3B  depicts a venturi sensor  50 ; and  FIG. 3C  depicts a Pitot tube sensor  60 .  
         [0014]     Referring to  FIG. 3A , the heated element sensor  40  comprises four resistors  41 ,  42 ,  43 ,  44  configured in a conventional Wheatstone bridge arrangement and a differential amplifier  45  responsive to the potential difference between the bridge nodes  46  and  47 . The amplifier  45  adjusts the bridge voltage (Vout) as required to balance the bridge. The resistors  41 - 44  are selected so that when the bridge is balanced, the resistor  42  (which may be a wire, for example) is maintained at an elevated temperature such as 250° C. The resistor  42  is positioned adjacent to a body panel such as bumper  18  or door panels  20   a ,  22   a  so that transient airflow (as represented by the arrows  48 ) due to deflection of the body panel in a crash event displaces the heated air surrounding the resistor  42  with air at essentially ambient temperature. This cools the resistor  42  and the amplifier  45  responds by increasing the bridge voltage. In this way, the amplifier output voltage Vout provides a measure of the magnitude of the airflow across resistor  42 .  
         [0015]     Referring to  FIG. 3B , the venturi sensor  50  has a sensor body  51  and a differential pressure sensor  52 , such as a silicon diaphragm sensor. The sensor body  51  is located adjacent a body panel (such as bumper  18  or door panels  20   a ,  22   a ) and is configured to define restricted and unrestricted airflow ports  53 ,  54  that are in-line with the transient air airflow (designated by arrows  48 ) produced by a body panel impact. The pressure sensor  52  is disposed in a passage  57  extending between the airflow ports  53 ,  54 , and the difference between the airflow in restricted airflow port  53  (designated by arrow  55 ) and the airflow in unrestricted airflow port  54  (designated by arrows  56 ) produces a corresponding pressure difference across the sensor  52 . The sensor  52  produces a signal corresponding to the pressure difference, which is also an indication of the magnitude of the impact-related transient airflow.  
         [0016]     Referring to  FIG. 3C , the Pitot tube sensor  60  has a sensor body  61 , first and second pressure chambers  62 ,  63  and a differential pressure sensor  64  separating the pressure chambers  62  and  63 . The sensor body  61  is located adjacent a body panel (such as bumper  18  or door panels  20   a ,  22   a ) and defines a central air passage  65  having an inlet  66  that is in-line with the transient air airflow (designated by arrows  48 ) produced by a body panel impact, and one or more static air passages  66 ,  67  having inlets  68 ,  69  that are perpendicular to the impact-related airflow. The central air passage  65  is coupled to the first pressure chamber  62 , while the static air passages  66 ,  67  are coupled to the second pressure chamber  63 . The sensor  64  is responsive to the difference in pressures between the first and second chambers  62 ,  63 , and such difference provides a measure of velocity of the impact-related transient airflow.  
         [0017]     In summary, the present invention provides a novel crash sensing approach that utilizes satellite sensing modules to detect serious vehicle impacts both quickly and reliably, in part by responding to a transient airflow inboard of a vehicle body panel that is struck by an object. Since the airflow sensor is responsive to transient air displacement, it does not need to be located in a closed or sealed cavity such as a door; this broadens the applicability of the sensing approach to different types of impacts and installations. While the present invention has been described with respect to the illustrated embodiments, it is recognized that numerous modifications and variations in addition to those mentioned herein will occur to those skilled in the art. For example, airflow may be sensed differently than described herein, and so on. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.