Abstract:
A vehicle occupant protection apparatus ( 10 ) comprises an inflatable device ( 14 ) for helping to protect an occupant of a vehicle during a crash condition. A support structure ( 18 ) secures a portion of the inflatable device ( 14 ). A plurality of tethers ( 34, 36, 38,  and  40 ) extend between the support structure ( 18 ) and the inflatable device ( 14 ). At least one sensor ( 62, 64, 66,  or  68 ) senses a vehicle occupant condition and generates an occupant condition signal indicative of the sensed condition. A control module ( 72 ) receives the occupant condition signal and determines a preferred inflation volume and shape for the inflatable device ( 14 ). The control module ( 72 ) determines which of the respective tethers ( 34, 36, 38,  and  40 ) to release for inflating the inflatable device ( 14 ) to the preferred inflation volume and shape and initiates the release of the respective tethers ( 34, 36, 38,  and  40 ) from the support structure ( 18 ).

Description:
TECHNICAL FIELD 
     The present invention relates to a vehicle occupant protection apparatus and, more particularly, to a vehicle occupant protection apparatus having an inflatable device. 
     BACKGROUND OF THE INVENTION 
     A known vehicle occupant protection apparatus includes an inflatable device known as an air bag. An air bag may be inflated during a vehicle crash condition to help protect a vehicle occupant. 
     It is desirable to control the inflation volume and shape of an air bag. By controlling the inflation volume and shape, the inflated air bag may be customized for varying conditions, including the size, weight, and Position of the occupant. 
     U.S. Pat. No. 6,076,854 addresses varying conditions of the occupant by providing an air bag assembly in which the inflation volume of the air bag assembly in which the inflation volume of the air bag may be modified from a partially inflated volume to a fully inflated volume. The air bag assembly includes a plurality of tethers that are connected to the air bag. Depending upon the varying conditions, during inflation of the air bag, all of the tethers remain secured so that the air bag is partially inflated or all of the tethers are released so that the air bag is fully inflated. 
     Co-pending application Ser. No. 09/469,053, filed Dec. 21, 1999, which is assigned to the assignee of the present application, also addresses varying conditions of the occupant. In the copending application, the air bag assembly preferably includes four tethers, each of which is attached between the air bag and a tether tension control mechanism. Based on the varying conditions, the tether tension control mechanism may shorten the lengths of the tethers to change the volume and location of the inflated air bag. Shortening some tethers and not shortening others may move the air bag to a desired location with respect to the occupant. 
     SUMMARY OF THE INVENTION 
     The present invention is a vehicle occupant protection apparatus. The vehicle occupant protection apparatus comprises an inflatable device, a support structure, a plurality of tethers, at least one sensor, and a control module. The inflatable device helps to protect an occupant of a vehicle during a crash condition. The support structure secures a portion of the inflatable device. The plurality of tethers extend between the support structure and the inflatable device. The sensor senses a vehicle occupant condition and generates an occupant condition signal indicative of the sensed condition. The control module receives the occupant condition signal and determines a preferred inflation volume and shape of the inflatable device. The control module determines which of the respective tethers to release for inflating the inflatable device to the preferred inflation volume and shape and initiates the release of the respective tethers from the support structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, in which: 
     FIG. 1 is a schematic representation of a vehicle occupant protection apparatus constructed in accordance with the present invention wherein an air bag is inflated to a minimum inflation volume; 
     FIG. 2 is a schematic representation of the vehicle occupant protection apparatus of FIG. 1 wherein an air bag is inflated to a maximum inflation volume; 
     FIG. 3 is an illustration of an inflated air bag of the present invention wherein the air bag is shaped such that an upper portion of the air bag extends farther outward than a lower portion of the air bag; 
     FIG. 4 is an illustration of an inflated air bag of the present invention wherein the air bag is shaped such that a lower portion of the air bag extends farther outward than an upper portion of the air bag; 
     FIG. 5 is a perspective view of a portion of the vehicle occupant protection apparatus of the present invention including a reaction can of an air bag module with release mechanisms securing tethers to the reaction can; 
     FIG. 6 illustrates an air bag module of the vehicle occupant protection apparatus including a second embodiment of a release mechanism; 
     FIG. 7 illustrates an enlarged view of the release mechanism of FIG. 6; 
     FIG. 8 illustrates an alternate tether arrangement for the vehicle occupant protection apparatus of the present invention using the release mechanism of FIG. 6; 
     FIG. 9 illustrates a cross-section of a first end of a tether of the vehicle occupant protection apparatus of the present invention; 
     FIG. 10 illustrates a third embodiment of the release mechanism of the vehicle occupant protection apparatus of the present invention; and 
     FIG. 11 illustrates a fourth embodiment of the release mechanism of the vehicle occupant protection apparatus of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The vehicle occupant protection apparatus  10  illustrated in FIGS. 1 and 2 includes an air bag module  12  mounted in either the instrument panel  13  or the steering wheel (not shown) of a vehicle. The air bag module  12  includes an air bag  14 , an inflator  16  for inflating the air bag  14 , and a reaction can  18  for housing the inflator  16  and the uninflated air bag  14 . 
     With reference to FIG. 5, the reaction can  18  is preferably made from metal. The reaction can  18  includes upper and lower side walls  20  and  22 , respectively. The upper and lower side walls  20  and  22  are interconnected by opposite left and right side walls  24  and  26 , respectively, and a curved front wall  28 . 
     Each of the upper, lower, left, and right side walls  20 ,  22 ,  24 , and  26  has a rear edge surface  30  opposite the front wall  28 . The four rear edge surfaces  30 , collectively, define an opening  32  into the reaction can  18 . When the air bag module  12  is mounted to the instrument panel  13  of the vehicle, the opening  32  of the reaction can  18  is nearest the vehicle occupant compartment  17  (FIG.  1 ). 
     As shown in FIG. 5, four tethers  34 ,  36 ,  38 , and  40  extend from the reaction can  18 . Preferably, one tether extends from each side wall  20 ,  22 ,  24 , and  26  of the reaction can  18 . Thus, an upper tether  34  extends from the upper side wall  20  of the reaction can  18 . A lower tether  36  extends from the lower side wall  22  of the reaction can  18 . A left tether  38  extends from the left side wall  24  of the reaction can  18 . A right tether  40  extends from the right side wall  26  of the reaction can  18 . 
     The tethers  34 ,  36 ,  38 , and  40  initially extend between the reaction can  18  and the air bag  14 , as shown in FIG.  1 . The tethers  34 ,  36 ,  38 , and  40  are attached to the air bag  14  such that when the air bag  14  is inflated, the length of the tethers  34 ,  36 ,  38 , and  40  limits the inflation volume of the air bag  14  and shapes the air bag  14 . Preferably, the upper tether  34  is attached to an upper portion  42  (FIGS. 3 and 4) of the air bag  14 . The lower tether  36  is attached to a lower portion  44  of the air bag  14 . The left tether  38  is attached to a left portion (not shown) of the air bag  14 , and the right tether  40  is attached to a right portion (not shown) of the air bag  14 . 
     As shown in FIGS. 3 and 4 with specific reference to tethers  34  and  36 , each tether  34 ,  36 ,  38 , and  40  includes a first end  46 , a second end  48 , and an intermediate portion  50  that extends between the first and second ends  46  and  48 . The first end  46  of each tether  34 ,  36 ,  38 , or  40  is secured to the reaction can  18  prior to inflation of the air bag  14 . FIG. 9 shows a cross-sectional view of the first end  46  of a tether, for example, tether  34 . Preferably, the tether  34  is woven from a fabric material, such as nylon. The tether  34  is made from a single piece of material that is folded upon itself along its length to form three layers that are sewn together. The first end  46  of the tether  34  also includes a welt  52 . The welt  52  is a {fraction (1/16)} to ⅛ inch plastic or metal cord that surrounds the portion of the first end  46  of the tether  34  that is secured to the reaction can  18 . The welt  52  strengthens the first end  46  of the tether  34  and prevents ripping of the tether  34  when the tether  34  is subjected to a tension. The second end  48  of each tether  34 ,  36 ,  38 , and  40  is attached to the air bag  14  by stitches, adhesive, or the like. 
     As best shown in FIG. 5, the first end  46  of each tether  34 ,  36 ,  38 , and  40  is secured to the reaction can  18  by a release mechanism  54 . Each release mechanism  54  illustrated in FIG. 5 includes an anchoring plate  56  that is connected to a solenoid mechanism  58 . The anchoring plate  56  includes a surface that is contoured to mate with an inner surface of the respective side wall  20 ,  22 ,  24 , or  26  upon which the release mechanism  54  is mounted. Preferably, the surface of the anchoring plate includes a grip (not shown) for holding the first end  46  of the respective tether  34 ,  36 ,  38 , or  40  against the inner surface of the respective side wall  20 ,  22 ,  24 , or  26 . 
     The solenoid mechanism  58  includes an arm (not shown) that extends through the respective side wall  20 ,  22 ,  24 , or  26  and attaches to the anchoring plate  56 . In an unactuated position, the solenoid mechanism  58  presses the anchoring plate  56  against the inner surface of the respective side wall  20 ,  22 ,  24 , or  26  of the reaction can  18 . The first end  46  of the respective tether  34 ,  36 ,  38 , or  40  is clamped between the anchoring plate  56  and the reaction can  18 . In the clamped position, the welt  52  of the first end  46  of the tether  34 ,  36 ,  38 , or  40  surrounds the grip of the anchoring plate  56 . Thus, in addition to preventing ripping of the respective tether  34 ,  36 ,  38 , or  40 , the welt  52  helps to prevent the tether  34 ,  36 ,  38 , or  40  from sliding out from under the anchoring plate  56 , particularly when subjected to a tension. The first end  46  of the tether  34 ,  36 ,  38 , or  40  may be slotted for fitting around the arm of the solenoid mechanism  58  or the anchoring plate  56  may extend to the side of the arm of the solenoid mechanism  58  when clamping the respective tether  34 ,  36 ,  38 , or  40 . 
     As shown in FIGS. 1 and 2, the vehicle occupant protection apparatus  10  also includes at least one sensor for sensing a vehicle occupant condition and for generating an occupant condition signal indicative of the sensed condition. Preferably, the vehicle occupant safety apparatus  10  includes four sensors for sensing vehicle occupant conditions. The four sensors include a seat position sensor  62 , a seat weight sensor  64 , a seat belt usage sensor  66 , and an occupant position sensor  68 . Each of the four sensors  62 ,  64 ,  66 , and  68  is of a known construction. 
     Additionally, the vehicle occupant protection apparatus  10  includes a crash severity sensor  70  for sensing the occurrence and the severity of a vehicle crash condition. The crash severity sensor  70  generates a signal indicative of the crash condition. 
     Each of the sensors  62 ,  64 ,  66 ,  68 , and  70  is electrically connected to an electronic control module  72 . The electronic control module  72  preferably includes a microprocessor. The electronic control module  72  receives power from a power source (not shown), preferably the vehicle battery. The electronic control module  72  is also electrically connected to both the inflator  16  of the air bag module  12  and to the solenoid mechanism  58  of each release mechanism  54 . The electronic control module  72  may include circuitry that would prevent the energization of each solenoid mechanism  58  except upon actuation of the air bag module  12 . 
     Upon the occurrence of a crash condition, the electronic control module  72  receives the signal generated by the crash severity sensor  70  and determines whether or not the air bag module  12  should be actuated. If the air bag module  12  is actuated, the electronic control module  72  uses the occupant condition signals received from the occupant condition sensors  62 ,  64 ,  66 , and  68  to determine a preferred inflation volume and shape for the air bag  14 . The inflation volume of the inflated air bag  14  ranges from a minimum volume when each tether  34 ,  36 ,  38 , and  40  remains attached to the reaction can  18 , as shown in FIG. 1, to a maximum volume when each tether  34 ,  36 ,  38 , and  40  is released from the reaction can  18 , as shown in FIG.  2 . The number of stages between the minimum volume and the maximum volume is dependent upon the number of tethers and the tether arrangement, as will become clearer after reference to the remainder of this description. 
     Two examples of the electronic control module  72  using occupant condition signals to determine the preferred inflation volume and shape for the air bag  14  follow. For simplicity of the description, the examples focus on the upper and lower portions  42  and  44  of the air bag  14 . Those skilled in the art will recognize that similar shaping of the left and right portions of the air bag  14  is within the scope of this invention. 
     In the first example, the occupant is determined to weigh 80 pounds, the seat is in the forwardmost seat position, and the occupant is leaning against the seat back with the seat back reclined slightly. Based on the signals from sensors  62 ,  64 , and  68 , the electronic control module  72  may determine that the preferred inflation of the air bag  14  is low volume with the upper portion  42  of the air bag  14  extending farther outward than the remainder of the air bag  14 . Thus, upon actuation of the air bag  14 , the electronic control module  72  will actuate only the solenoid mechanism  58  on the upper side wall  20 . As a result, during inflation of the air bag  14 , the upper tether  34  will be released and the lower, left, and right tethers  36 ,  38 , and  40  will remain secured to the reaction can  18  and will limit the inflation volume of the air bag  14 . Thus, the air bag  14  will take an inflated shape similar to that shown in FIG.  3 . 
     In the second example, the occupant is determined to weigh 200 pounds, the seat is in the rearmost seat position, and the occupant is leaning forward in the seat. Based on signals from sensors  62 ,  64 , and  68 , the electronic control module  72  may determine that a preferred inflation of the air bag  14  is a high volume with the upper portion  42  of the air bag  14  less inflated than the remainder of the air bag  14 . Upon actuation of the air bag  14 , the electronic control module  72  will energize the solenoid mechanisms  58  on the lower, left, and right side walls  36 ,  38 , and  40 , but will not energize the solenoid mechanism  58  on the upper side wall  20 . As a result, during inflation of the air bag  14 , the lower, left, and right tethers  36 ,  38 , and  40  will be released and the upper tether  34  will remain secured to the reaction can  18 . As a result, the air bag  14  will inflate to a high inflation volume and the air bag  14  will have an inflated shape similar to that shown in FIG.  4 . 
     FIG. 6 illustrates a second embodiment of the release mechanisms  54  of the vehicle occupant protection apparatus  10  of the present invention. The release mechanisms  54  illustrated in FIG. 6 are exploding fasteners  74 . FIG. 7 illustrates an enlarged view of an exploding fastener  74 . The exploding fastener  74  includes an axially extending tubular bolt  76 . The bolt  76  has a length defined as the distance between a first axial end  78  and a second axial end  80 . The bolt  76  has an outer surface  82  and an inner surface  84 . A radially outwardly extending flange  86  extends from the outer surface  82  of the bolt  76  at approximately the middle of the length of the bolt  76 . The outer surface  82  of the bolt  76  is threaded from a first axial end  78  to the outwardly extending flange  86  for receiving a nut  88 . 
     An end wall  90  closes the first axial end  78  of the bolt  76 . A central wall  92  extends inwardly from the inner surface  84  of the bolt  76  at about the middle of the length of the bolt  76  to define a chamber  94  in the first axial end  78  of the bolt  76 . A pyrotechnic charge  96  is located in the chamber  94 . The central wall  92  includes a bore  98  for receiving an initiator  100 . The initiator  100  is electrically connected to the electronic control module  72  by a connector  103  that attaches to terminals  102  of the initiator  100 . Although a bolt-nut combination has been described, those skilled in the art will recognize that an exploding rivet or other fastener may be used. 
     When using the exploding fastener  74  in the vehicle occupant protection apparatus  10 , the reaction can  18  includes a bore  104  for receiving the exploding fastener  74 . The bore  104  is sized so that the threaded outer surface  82  of the bolt  76  will extend through the bore  104  but the radially outwardly extending flange  86  will not extend through the bore  104 . 
     The first axial end  78  of the bolt  76  is received in the bore  104  in the reaction can  18 , and the bolt  76  is moved into the bore  104  until the radially outwardly extending flange  86  of the bolt  76  presses against an outer surface  106  of the reaction can  18 . Preferably, the radially outwardly extending flange  86  is welded to the outer surface  106  of the reaction can  18 . When the radially outwardly extending flange  86  is pressed against the outer surface  106  of the reaction can  18 , the first axial end  78  of the bolt  76  extends into the reaction can  18  beyond an inner surface  107  of the reaction can  18 . 
     The tether  110  of the vehicle occupant protection apparatus  10  also includes a hole  108 . The hole  108  in the tether  110  extends through the first end  112  of the tether  110 . Preferably, a welt  52  (FIG. 9) surrounds the hole  108  in the tether  110 . 
     The first axial end  78  of the bolt  76  extends through the hole  108  of the tether  110  such that the threaded outer surface  82  of the bolt  76  extends through the hole  108  in the tether  110 . Preferably, a washer  109  is placed on the bolt  76  and then the nut  88  is screwed onto the bolt  76 . By tightening nut  88 , the nut  88  and the washer  109  clamp the tether  110  to the reaction can  18 . 
     The exploding fastener  74  is of sufficient strength to retain the tether  110  during inflation of the air bag  14 . If the electronic control module  72  determines that the tether  110  should be released, the electronic control module  72  will send a signal to the initiator  100  causing the initiator  100  to ignite the pyrotechnic charge  96  in the chamber  94  of the respective bolt  76 . The pyrotechnic charge  96  will sever the bolt  76  in a location between the nut  88  and the radially outwardly extending flange  86 . As a result, the tether  110  will be released. Those skilled in the art will recognize that a cage, a retaining wire, or other means may be used to prevent the nut  88  and the washer  109  from projecting into the inflating air bag  14 . 
     The use of the exploding fastener  74  allows an alternate tether arrangement for the vehicle occupant protection apparatus  10  of the present invention. As shown in FIG. 8, the first end  112  of a tether  110  is secured to the reaction can  18  by a first fastener  114 . The intermediate portion  116  of tether  110  is secured to the reaction can  18  by an exploding fastener  74 . A loose portion  118  of tether  110  extends between the first fastener  114  and the exploding fastener  74 . If the exploding fastener  74  is actuated, the loose portion  118  of tether  110  is released from the reaction can  18 . As the air bag  14  inflates, tether  110  becomes taut and limits further inflation of the respective portion of the air bag  14 . To further affect inflation volume and shape of the air bag  14 , the first fastener  114  may also be a release mechanism  54  that can be separately actuated. Thus, release mechanisms  54  may be systematically actuated to control an amount of the tether  110  that is released. This tether arrangement increases the number of stages of inflation volume between the minimum volume and the maximum volume. Those skilled in the art will recognize that additional exploding fasteners  74  and loose portions of the tether  110  may be included to further increase the number of stages. 
     A third embodiment of the release mechanism  54  of the vehicle occupant protection apparatus  10  is illustrated in FIG.  10 . The first end  112  of the tether  110  is permanently secured to the reaction can  18  by a fastener  120 . Near the first end  112  of the tether  110 , a pyrotechnic charge  122  is placed on or is woven into the fabric of the tether  110 . The pyrotechnic charge  122  is electrically connected to the electronic control module  72 . Upon actuation, the pyrotechnic charge  122  burns through the tether  110  to sever the tether  110  into two separate pieces. Preferably, the pyrotechnic charge  122  is a material known by the trademark ITLX, a trademark of Explosive Technology, Inc. 
     A fourth embodiment of the release mechanism  54  is illustrated in FIG.  11 . The release mechanism  54  is a metal or plastic retainer  124  that is fixed to the reaction can  18  by a fastener  120 . The first end  112  of the tether  110  is secured to a stem  126  of the retainer  124 . A pyrotechnic charge  128  is located on the stem  126  of the retainer  124  between the reaction can  18  and the tether  110 . Upon actuation, the pyrotechnic charge  128  severs the stem  126  of the retainer  124  releasing the tether  110 . 
     From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. For example, multiple tethers may be connected to one release mechanism  54 . Those skilled in the art will recognize that the inflatable device may be an air bag mounted in the vehicle steering wheel, an inflatable side curtain, an inflatable knee bolster, or any other inflatable device known in the art. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.