Abstract:
An airbag module has a capacitive vehicle occupant sensor to detect an out-of-position vehicle occupant who is closely spaced from an airbag deployment door. The airbag module incorporates tape sensors, which monitor the rate at which a airbag is deployed, and a vent which can be actuated if the airbag deployment sensor controller or system logic associated with the airbag indicates a premature collision of the airbag with an out-of-position vehicle occupant. A capacitive vehicle occupant sensor is attached to the airbag module, or to the door through which the airbag deploys. In the event a vehicle occupant is closely spaced from the deployment door(s), airbag deployment is inhibited, the airbag module is simultaneously vented, or the airbag deployment profile is otherwise modified.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to airbag modules that employ sensors to monitor the rate at which the airbag is deploying, and which divert inflation gas from the airbag if the airbag deployment slows prematurely, indicating the presence of an out-of-position vehicle occupant.  
         [0002]     Airbags that deploy in the event of a vehicle crash form an important part of the overall safety system of an automobile. Airbags in combination with seatbelts and other safety systems reduce death and injury that can occur during a vehicle crash. However, in certain circumstances an airbag can present a hazard to a vehicle occupant if the vehicle occupant is positioned too close to the airbag as it deploys. In such a circumstance the vehicle occupant is described as out-of-position. If a vehicle occupant is out-of-position with respect to an airbag, it is better if the airbag does not deploy, or if deployment has begun, the deployment may be altered by diverting inflation gas from the airbag such as by venting the airbag module. One known approach is to monitor the position of the vehicle occupant with sensors within the passenger compartment and to use safety system logic to not deploy an airbag in those situations where the vehicle occupant is out-of-position. This approach has several difficulties, including that there is a time delay between when the decision to deploy is made and when the actual deployment takes place, and that during this time delay the vehicle occupant may have moved closer to the airbag, and thus may be out-of-position during actual airbag deployment. Sensors within the passenger compartment must also deal with a crash environment where noise, debris, and electromagnetic interference may make reliable detection of vehicle occupant position difficult. Furthermore, sensors within the passenger compartment are typically required to be on at all times, which consumes power and which might be objected to by the consumer.  
         [0003]     Another approach to dealing with the out-of-position problem is to mount a sensor on the inside or outside of the airbag. One type of sensor is mounted inside the airbag and uses tapes sewn to the inside of the airbag, which are drawn out of tape cartridges such that the tapes pass by sensors which monitor the rate at which the airbag deploys by monitoring the rate at which tape is withdrawn from the cartridges. Examples of such systems are disclosed in EP 0 990 567 A1, EP 0 812 741 A1, US 2004/0174156 A1, U.S. Pat. No. 6,793,243 B2, and U.S. Pat. No. 6,789,819 B1.  
         [0004]     If the rate of tape withdrawal slows down before the airbag has fully deployed, that is an indication that the airbag has collided with an object before full deployment, and that inflation gas can be diverted from the airbag. If the door through which the airbag enters the passenger compartment is formed as part of the vehicle dash or other vehicle structure, the weight of the door will slow the airbag deployment down in a way which can be difficult to distinguish from the situation where an out-of-position vehicle occupant is blocking the door. It is also possible that if the vehicle occupant is too close to the airbag door, the mass and rigidity of the airbag door can cause injury to the vehicle occupant during the initial stages of the airbag deployment, before the tape sensing system has the ability to detect the out-of-position vehicle occupant. What is needed is a means for detecting an out-of-position vehicle occupant closely spaced from an airbag door.  
       SUMMARY OF THE INVENTION  
       [0005]     The airbag module of this invention employs a vehicle occupant sensor, preferably using the capacitive principal, to detect an out-of-position vehicle occupant, who is closely spaced from an airbag deployment door. The airbag module will preferably incorporate tape sensors which monitor the rate at which the airbag is deployed, and a vent which can be actuated in the event it is determined by the airbag deployment sensor controller or system logic associated with the airbag that the airbag has prematurely collided with an object, which may be an out-of-position vehicle occupant. During the opening of the airbag deployment door(s) the weight of the door(s) can cause one or both of the following to occur: 
        1. The rate at which the airbag deploys slows so it cannot readily be determined if the airbag is simultaneously being slowed by the airbag door and by impact with an out-of-position vehicle occupant.     2. Injury to the vehicle occupant during the initial stages of the airbag deployment caused by the mass and rigidity of the airbag deployment door(s).        
 
         [0008]     The vehicle occupant sensor is used to detect, before the airbag is deployed, whether a vehicle occupant is so closely spaced from the deployment door(s), that the opening door(s) will impact the out-of-position vehicle occupant. In the event a vehicle occupant is closely spaced from the deployment door(s), airbag deployment is inhibited. Alternatively the airbag may still be fired, but the airbag deployment may be modified, for example by venting the airbag module at the time of initiation of the airbag inflator igniter, or at a selected time after initiation of the airbag inflator igniter.  
         [0009]     It is a feature of the present invention to provide an airbag module that incorporates an auxiliary sensor or sensing system capable of detecting an out-of-position vehicle occupant that is in very close proximity to the airbag module deployment door.  
         [0010]     It is another feature of the present invention to provide a capacitive sensing system, mounted to or in front of an airbag, which can detect an out-of-position vehicle occupant a short distance in front of the door.  
         [0011]     It is a further feature of the present invention to provide a sensor for use in conjunction with an airbag deployment rate sensor, so that the probability of injury to an out-of-position vehicle occupant is reduced by sensing an out-of-position vehicle occupant, so as to inhibit airbag deployment, or divert inflation gas from the airbag during deployment.  
         [0012]     It is a still further feature of the present invention to provide a sensor which can determine the lateral position of a closely spaced out-of-position vehicle occupant.  
         [0013]     It is yet another feature of the present invention to provide a means of determining differences in various parts of a vehicle occupant&#39;s body e.g., hands vs. head, which have varying masses, and whether such parts are in close proximity to the airbag door(s).  
         [0014]     It is a yet further feature to provides a means of detecting differences in objects that are in close proximity to the airbag door(s) based on material properties, specifically differences in dielectric strength.  
         [0015]     Further features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a schematic, side elevation, cross-section view of the airbag module of this invention positioned behind a vehicle dash, with open airbag doors shown in phantom view.  
         [0017]      FIG. 2  is a schematic view of a capacitive sensor used with the airbag module of  FIG. 1 .  
         [0018]      FIG. 3  is a schematic view of an alternative embodiment capacitive sensor used with the airbag module of  FIG. 1 .  
         [0019]      FIG. 4  is a schematic view of another alternative embodiment capacitive sensor for use with the airbag module of  FIG. 1 .  
         [0020]      FIG. 5  is a schematic view of a further alternative embodiment capacitive sensor for use with the airbag module of  FIG. 1 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     The following commonly owned patent publications teach various aspects of airbag modules and deployment systems and components thereof as well as the manufacture and operation thereof and each is incorporated herein by reference to disclose and teach the present invention: U.S. Pat. No. 6,241,282 B1; U.S. Pat. No. 6,129,379 B; U.S. Pat. No. 6,796,578 B2; US 2004/0178613 A1; US 2004/0178615 A1; U.S. Pat. No. 6,789,818 B2; US 2004/0232673 A1; US 2004/0155442 A1; U.S. Pat. No. 6,793,243 B2; US 2004/0211795 A1; US 2004/0222622 A1; U.S. Pat. No. 6,825,654 B2; US 2004/0207261 A1; US 2004/0251892 A1; US2004/0207388 A1; U.S. Pat. No. 6,789,819 B1; U.S. Pat. No. 6,840,539 B2; and U.S. Pat. No. 6,830,265 B2.  
         [0022]     Referring more particularly to  FIGS. 1-5 , wherein like numbers refer to similar parts, an airbag module  20  is shown in  FIG. 1 . The airbag module  20  has a gas generator module  22  that incorporates a gas generant  24 , and gas vent valves  26 . An airbag  28  is connected to the gas generator module  22  so that initiation of an airbag inflator igniter  30 , by an airbag crash controller  29  causes the gas generant  24  to deploy the airbag  28 . The airbag module  20  has an electronic system  32  in signal receiving relation to a plurality of airbag deployment rate sensors  34 . Each airbag deployment rate sensor  34  monitors airbag deployment by monitoring the rate at which a tape  36  is drawn from a cartridge  38  mounted inside the airbag  28 . When the airbag  28  collides with an out-of-position vehicle occupant  40  the collision is detected by the deployment rate sensors  34  which detect the premature stopping or slowing of airbag deployment. Once premature stopping or slowing of the airbag is detected, the gas valves  26  are opened to vent inflation gas from the airbag module  28 .  
         [0023]      FIG. 1  shows a vehicle occupant  40  positioned immediately in front of the doors  42 , which form part of a vehicle structure  43 , such as a dashboard, and through which the airbag  28  is deployed. If the doors  42 , which open along a tear line  41 , are sufficiently massive because they form part of the vehicle structure  43 , then they will significantly slow the rate of airbag deployment. At the same time, the opening doors  42  can, because of their weight, injure an out-of-position vehicle occupant. This slowing of airbag deployment, whether an out-of-position vehicle occupant is present or not, means that the airbag deployment rate sensors may not be able to detect an impact with a vehicle occupant during a potentially injurious phase of the airbag deployment. Thus the mass of the doors  42  hides the presence of an out-of-position vehicle occupant  40  located immediately in front of the doors  42  because the airbag deployment rate sensors  34  will sense a slowdown caused by impact with the doors  42  whether or not an out-of-position vehicle occupant is present. A capacitive sensor  44  positioned on or within the material making up the door  42  can be designed to detect a large liquid-containing object such as the head or torso of a vehicle occupant. The capacitive sensor  44  may be always active, activated when the onset of a crash event is detected, or activated just before airbag deployment.  
         [0024]     The capacitive sensor  44  may be a single metal plate, or film  46 , which forms a capacitor with the vehicle ground. The out-of-position vehicle occupant  40  functions as a grounded body that affects the potential of the metal film  46  charge in a detectable way, when the head or torso of the vehicle occupant  40  is positioned within a few centimeters, e.g. about 5-15 cm (2-6 inches), of the metal film  46 . As shown in  FIG. 2 , an alternative capacitive sensor  45  may comprise a ground plane  39  and two or more adjacent electrodes  47  separated by a dielectric film to make up a series of capacitors. The presence of the out-of-position vehicle occupant  40  affects the electric field developed on the electrodes  47 . In general, the charge on the capacitive plates is caused to oscillate at one or more selected frequencies and a change in amplitude of the oscillations is measured to detect an out-of-position vehicle occupant. The operation of the sensor  45  is described more fully in U.S. Pat. No. 6,079,738 B and U.S. Pat. No. 6,135,494 B, which are incorporated herein by reference. Because the range of detection needed is relatively short compared to the prior art vehicle occupant position capacitive sensors, the design of the capacitive sensor can be simpler, and the sensor can incorporate lateral position sensing.  
         [0025]     Referring to  FIG. 3 , a capacitive sensor  52  is shown which can detect a lateral, or side to side position, of a vehicle occupant  40 . The alternative sensor  52  is made up of individual capacitive plates  54 , with a floating common ground  56  therebetween. The capacitive plates  54  and the common ground  56  can be made by screen printing or otherwise printing a conductive silver ink on one side of an electrically non-conductive flexible polyester film  58 . The capacitive sensor  52  has nine capacitive plates  54  arranged side-to-side. Each capacitive plate  54  comprises a plurality of connected trace portions which interdigitate with portions of the common ground  56  to increase the capacitance of each formed capacitor. A field is set up between the capacitive plates  54  and the floating ground  56 . An alternating voltage is used to drive the capacitive plates  54  causing the electromagnetic field to expand and collapse between each capacitive plate  54  and the common ground  56 . High dielectric objects, which include the human body which consists mostly of liquid, can be detected by the effect the dielectric object has on the electromagnetic fields formed between the capacitive plates  54  and the common ground  56 . The presence of the high dielectric object in front of the sensor causes a change of the oscillation amplitude. The change in amplitude of the oscillations is identified by a circuit which may be part of the airbag deployment Sensor controller  32 , which may have a single threshold, or may output a varying value which is related to size and distance of the object that changes the output state of the sensor. Each capacitive plate can be driven at the same or a different frequency and individually processed by the circuit. The change in amplitude on each capacitive plate can be monitored, and compared to determine the lateral or side-to-side position of the out-of-position vehicle occupant  40  with respect to the tear line  41 . The tear line  41  defines the line from which the doors  42  open to allow the airbag  28  to pass through the vehicle structure  43 .  
         [0026]     The capacitive plates  54  shown in  FIG. 3  are arranged to maximize the length of the capacitive plate borders  60  by comprising multiple line segments. Increased plate border results in increased capacitance which increases the strength of the electromagnetic field created by the capacitive plates  54 . The capacitive sensor  52 , because it need not sense objects more than a few centimeters from the sensor, is capable of determining the lateral or side-to-side position. The sensor  54  has limited range. This simplifies the location of side-to-side position of an object with respect to the tear line  41  from which the doors  42  open.  
         [0027]     Knowledge of the side-to-side position of the out-of-position vehicle occupant  40  allows the airbag to be deployed even if the vehicle occupant  40  is out-of-position, as long as the vehicle occupant is not immediately in front of the opening doors  42 . The safety advantages of deploying an airbag can, in the right circumstances, be considerable. Therefore a sensor  52  which can provide more information about the out-of-position vehicle occupant is desirable, so that safety system logic can consider the risks of deployment, versus the risks of non-deployment, with knowledge of the specific position of the obstructing out-of-position vehicle occupant  40 . Once the airbag doors  42  are open the airbag deployment rate sensors  34  are effective to detect premature impact with the out-of-position vehicle occupant  40 . Thus the airbag deployment rate sensors  34  in combination with the capacitive sensor  52  allow for the following safety system logic: 
        1. Based on signals from crash sensors, is airbag deployment desirable?; if yes, then:     2. Check the output of the capacitive sensor  52  and determine if airbag deployment through the airbag door(s)  42  can be safely accomplished based on the output of the capacitive sensor  52 . If yes, then deploy airbag; and     3. Monitor the output of the airbag deployment rate sensors  34 . If the airbag  28  prematurely slows down, then divert inflation gas from the airbag using gas valves  26 .        
 
         [0031]     An alternative embodiment capacitive sensor  62  is shown in  FIG. 4 . The capacitive sensor  62  is similar to the sensor  52 , having the same number of capacitive plates  64 , and similarly using a floating common ground  66 . Also the sensor  62  may be manufactured as a silver ink printed on a polyester film  68 . The borders  70  of the capacitive plates  64  are simple straight lines.  
         [0032]     The sensors  62 ,  52  detect a side-to-side positioning of an out-of-position vehicle occupant, but it may be desirable to detect not only side-to-side position, but up-and-down position. The capacitive sensor  72  shown in  FIG. 5  is comprised of eight individual capacitive plates  74 , again surrounded by a floating common ground  76 . The embodiment illustrated in  FIG. 4  uses interdigitating comb like structures for the individual capacitive plates  74 , and the common ground  76 . Again the capacitive plates  74  and common ground  76  may be constructed by printing conductive ink such as a silver-based ink on one side of a flexible polyester film  78 . The capacitive sensor  72  comprises two side-by-side modules, each module being comprised of a two-by-two array of capacitive plates  74 . The two modules together create a four-by-two array, which provides a side-to-side resolution which is about twice the vertical resolution. Each of the sensors  62 ,  52 ,  72  is arranged to extend across the airbag tear line  41  through which the airbag  28  exits. Thus each sensor is arranged to provide highest resolution with respect to the positioning of the vehicle occupant  40  with respect to the opening doors  42  as shown in  FIG. 1 .  
         [0033]     The scale of the capacitive sensors  52 ,  62 ,  72  is selected so the the range which is normally dependent on the area and shape of the individual capacitive plate, and the area and distance to the obstructing dielectric object i.e., the head of an out-of-position vehicle occupant  40 . Typically the detection distance is dependent on the size of the object to be detected, and the size of the plates. In the particular embodiments described, geometry of the plates is also related to the airbag module geometry and/or the airbag door(s) geometry. Based on these and other factors, individual capacitive plates must be no more than 70 percent of the target to be sensed. In the embodiments described, individual plate sizes of the sensor  52  is about 7.6 cm by 1.9 cm (3 inches by 0.75 inches), with interlaced, interdigitated grounds. The individual plate sizes of the sensor  62  are about 0.5 cm by 7.6 cm (0.2 inches by 3 inches). The capacitive plates  74  of the sensor  72  are roughly squares about 3.8 cm (1.5 inch) on each side, arranged in a pattern comprising two rows and four columns. The specific geometry of the capacitive plate  74  in the embodiment described comprises conductive “fingers,” about 3.8 cm long by 0.25 cm wide (1.5 inches long by 0.1 inches wide), with a total of 6 “fingers” per plate. Because the maximum sensing distance from the instrument panel is about 5.1-15.2 cm (2-6 inches), and specific biomass sizes and lateral positions must be determined, the maximum dimensions of the plate should be no more than about 5.1 cm by 7.6 cm (2 inches by 3 inches).  
         [0034]     By incorporating the airbag doors  42  as part of the vehicle structure, integration with the airbag module is simplified, because a single airbag design can be used with a plurality of vehicles. However, incorporating a sensor into the doors  42  may present a problem with the desirable design goal of minimizing the interface between the vehicle design and the airbag module design. As shown in  FIG. 1 , a sensor positioning wrap  48  may surround the airbag  28  so as to position a capacitive sensor  50  which forms a part of the airbag module  20 . Because the capacitor sensor  50  does not need to be integrated with the airbag doors  42 , the same airbag module  20  can simply be reprogrammed to take into account the positioning and door geometry of a particular vehicle model. The capacitor sensor  50  can be similar to the capacitive sensor  44 ,  52 ,  62 , or  72  as described above. A capacitor sensor  51  can be mounted to a retainer ring  53  which holds the airbag  28  to the gas generator module  22  or a housing (not shown) to which the retainer ring  53  is mounted. The sensor  51  thus senses through the airbag  28  in addition to the doors  42 , to the vehicle interior  55 . The retainer ring  53  may be a plate which has openings through which gas enters the airbag  28  to cause inflation of the airbag, portions of the plate may form relatively large flat areas within the confines of the airbag which can be used for mounting sensors such as illustrated in  FIGS. 2-5 .  
         [0035]     It should be understood that the capacitive sensor  50  could be mounted to the airbag such as shown in U.S. Pat. No. 6,796,578, to White et al., or it can be held in place by straps instead of the sensor positioning wrap  48  shown in  FIG. 1 . It should be understood that the capacitive sensors  52 ,  62  and  72 , while described as extending laterally i.e., side-to-side across the tear seam  41 , depending on the design of the tear seam, and whether there is one or two doors, may be variously arranged. For example, if only one door is created by airbag deployment the array of capacitors forming the sensor may be positioned on the door side of the tear seam. Other arrangements of the array of capacitors may be required to optimize the information gathering potential of an array of capacitors and for a particular door/airbag arrangement, which will allow best prediction of the safety of deploying a airbag at least through the door, when an out-of-position vehicle occupant is detected.  
         [0036]     It should be understood that when in the claims the vehicle occupant or capacitive sensor is described as being mounted to the airbag, this includes a physical attachment to the airbag, or being integrally formed with the airbag, or being mounted to a film which surrounds the airbag.  
         [0037]     In general a capacitive sensor  44 ,  45 ,  52 ,  62 ,  72  can be mounted parallel to the airbag door  42  anywhere from a surface  57  of the airbag door facing the vehicle interior, to a position within the door or spaced from the door opposite the vehicle interior  55 , yet within the airbag module so long as the sensor is not blocked by a high dielectric material, and where the sensor has sufficient range to extend at least about 5.1 cm (2 inches) past the surface of the airbag door facing the vehicle interior.  
         [0038]     It should be understood that as used herein and in the claims the word tape when referring to the airbag deployment rate sensor is understood to include cloth tape, film tape, metal tape, string, wire, or other lightweight elongated structure which by being drawn past a sensor can detect the rate at which an airbag is deploying.  
         [0039]     It is understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces all such modified forms thereof as come within the scope of the following claims.