Abstract:
A vehicle seat occupant position sensor has one of four mechanisms to provide input with respect to how a seat occupant is engaged with a seat back. The first mechanism has some of the individual tension wires forming the flexolator pass through magnetostrictive sensors to detect in wire tension. Another mechanism employs a potentiometer geared so that relative deflection between the seat back and the seat recliner is amplified. A further mechanism is a magnetostrictive sensor that senses the stress in a seat back structure that is loaded by the seat occupant leaning against the seat back. Lastly, a bladder filled with a fluid provides pressure measurements as an indicator of the force generated by the vehicle seat occupant leaning against the seat back.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to vehicle safety systems that use deployment logic that takes into account the position of a vehicle occupant.  
           [0002]    It is generally recognized by those in the automobile industry that the decision to deploy an airbag can be improved if the presence and position of the occupant can be determined before bag deployment. If the position of an occupant is known, deployment can be prevented or varied in response to the position of the occupant.  
           [0003]    One known approach to determine the position of a vehicle occupant is to determine the position of the car seat, particularly for the driver&#39;s side seat. Other sensors such as capacitance sensors have been considered for determining the presence of the driver in relation to both the vehicle seat and the seat back. Alternatively, various techniques employing ultrasound have been employed to detect and characterize the occupant&#39;s position on the seat. Sensors, such as rotary potentiometers, have been mounted to a vehicle seat recliner to determine seat back inclination angles. Various sensors have been used to detect and even measure the weight of the occupants in a vehicle seat. Such sensors have included pressure sensors, fluid within a bladder, load cells, and sensors employing the inverse-magnetostrictive effect such as shown in U.S. Pat. No. 5,739,757 which is incorporated herein by reference.  
           [0004]    Many approaches to detecting a seat occupant&#39;s position with respect to a seat back have also been considered, using the capacitance sensor as suggested in U.S. Pat. No. 6,292,727. U.S. Pat. No. 6,302,438 suggests any of a number of rangefinder sensors including capacitance, optical, ultrasonic or radar to detect the distance between the seat occupant&#39;s back and the seat back. U.S. Pat. No. 6,015,163 suggests using flexible potentiometers that are mounted on some sort of deflectable or bendable substrate to which the variable resistant material is applied so that the presence of the person in the seat, the position of the person and the profile of the person may be detected. U.S. Pat. No. 5,074,583 discloses five sets of pressure sensors, where the pressure sensors are comprised of a pair of electrical conductors such as aluminum alloy, and an electrical insulator such as resilient synthetic resin between the conductors so that pressure on the conductors causes a change in the electrostatic capacitance of the sensors. U.S. Pat. No. 6,242,701 suggests the use of motion sensors utilizing a micro-power impulse radar system positioned within the seat back.  
           [0005]    While various approaches have been proposed for deploying an airbag based on greater intelligence concerning the actual position of a vehicle occupant, the importance in terms of possible improved safety makes the development of new approaches for determining the position of a person with respect to a vehicle seat of considerable importance.  
         SUMMARY OF THE INVENTION  
         [0006]    The vehicle seat occupant position sensor of this invention employs one of four mechanisms to determine whether the seat occupant is engaged with a seat back, and the extent of that engagement. The first mechanism employs a vehicle seat back containing a flexolator in which some of the individual tension wires forming the flexolator pass through magnetostrictive sensors such as disclosed in U.S. Pat. No. 5,739,757 which is incorporated herein by reference. The magnetostrictive sensors detect a change in wire tension that provides an indication of the load or force with which the seat occupant&#39;s back engages with the seat back of the vehicle seat.  
           [0007]    A second mechanism employs a potentiometer connected by a gear so that relative movement between the seat back and the seat recliner is amplified. In this way the small elastic deflections of the seat back in response to the seat occupant leaning against the seat back are amplified and made available to the airbag deployment logic.  
           [0008]    A third mechanism is a magnetostrictive sensor that senses the stress in a seat back recliner, or recliner bracket, when the recliner is loaded by the seat occupant leaning against the seat back.  
           [0009]    A fourth mechanism is a bladder filled with a fluid such as air or an ethylene glycol mix. Pressure within the bladder is used as an indicator of the force generated by the vehicle seat occupant leaning against the seat back.  
           [0010]    Each of the foregoing mechanisms provides an indication of the force with which the seat occupant is engaged with the back of the vehicle seat. This information can be correlated with a seat occupant&#39;s position on the seat by comparing the output from the various mechanisms when the seat occupant assumes various positions.  
           [0011]    It is a feature of the present invention to provide input to a safety system deployment logic that is indicative of a vehicle occupant&#39;s position with respect to the seat back of a vehicle seat.  
           [0012]    It is another feature of the present invention to provide a means for sensing stress in the back of a vehicle seat that can be correlated with the seat occupant&#39;s position.  
           [0013]    It is a further feature of the present invention to provide magnetostrictive sensors that can be used to determine a vehicle occupant&#39;s position with respect to the back of a vehicle seat.  
           [0014]    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  
       [0015]    [0015]FIG. 1 is an isometric view partly cutaway of a vehicle seat back showing a flexolator employing magnetostrictive sensors and a fluid bladder contained within the seat back cushion.  
         [0016]    [0016]FIG. 2 is a partial schematic view of a vehicle seat recliner and seat back with a geared mechanism connecting a potentiometer between the seat back recliner and the seat back recliner support.  
         [0017]    [0017]FIG. 3 is a fragmentary, partly cutaway, side elevational view of a magnetostrictive sensor for sensing the stress in a seat back recliner support.  
         [0018]    [0018]FIG. 4 is a block diagram for the vehicle safety systems of this invention.  
         [0019]    [0019]FIG. 5 is an isometric view of the magnetostrictive sensor of FIG. 3 wherein the sensor is shown in an alternative position.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    Referring to FIGS.  1 B 4 , wherein like numbers refer to similar parts, a vehicle seat back  20  is shown in FIG. 1. The seat back  20  has a frame  22  to which is mounted a flexolater  24 . The flexolator  24  has a pair of parallel rods  26 , only one of which is visible in FIG. 1, that are mounted by springs  28  to the sides  30  of the seat back frame  22 . Stretched between the rods  26  are support wires  32 . Resilient foam  34 , which is shown cutaway in FIG. 1, is molded over the seat frame  22  and the flexolator  24 . A seat cover  36  encloses the resilient foam  34 , the seat back frame  22 , and the flexolator  24  to form the vehicle seat back  20 . The support wires  32  are under tension. The level of tension in particular support wires will depend upon how a seat occupant is positioned on the vehicle seat, and more particularly upon how the seat occupant is engaged with the seat back  20 . As disclosed in U.S. Pat. No. 5,739,757, it is possible to use a magnetostrictive sensor  38  to detect the tension in the support wires  32 .  
         [0021]    First reported by Joule in 1847, the magnetostrictive effect describes a small change in physical dimensions of ferromagnetic materials in the presence of a magnetic field. The opposite effect known as the inverse magnetostrictive effect results in the generation of an electromagnetic field when a ferromagnetic material undergoes strain. Sensors capable of detecting stress in materials using the magnetostrictive effect employ a first coil that generates an oscillating magnetic field that produces oscillating stress in a ferromagnetic material, and a second coil that detects the magnetic field produced by the strain in the ferromagnetic material produced by the first coil. Strains in the ferromagnetic material produced by the first coil are modulated by the static stress in the ferromagnetic material and thus can be detected by the second coil. Magnetostrictive sensors have the potential of being reliable and operating over a large temperature range making them suitable for use in automobile applications.  
         [0022]    A second and distinct approach for determining the position of vehicle occupants with respect to the seat back  20  is the use of an fluid bladder  40  which is illustrated in FIG. 1 as being foamed in place. The bladder connects to a pressure sensor  42  such as is well known in the art. The output of the pressure sensor  42  is used as an indicator of the seat occupant&#39;s position relative to the seat back  20 . Although U.S. Pat. No. 5,739,757 describes the use of an air bladder for determining the seat occupant&#39;s weight, and lists various problems encountered in such an application, the use of an air bladder in the seat back is less demanding because absolute accuracy is less necessary. A relative measurement that compares bladder pressure when the seat is unoccupied with a bladder pressure when the seat is occupied is sufficient as an input to an occupant position modeling algorithm.  
         [0023]    A typical car seat  44  structure, as shown in FIG. 2, has a seat bottom  46  that is mounted to a top rail  48  which is laterally adjustable on a bottom rail (not shown) that is structurally mounted to the floor of a vehicle. The car seat  44  has a seat back  50  that is structurally joined to the seat bottom  46  by a recliner  52  mounted to a recliner bracket  54 . The recliner  52  is mounted about a pivot pin  56 , and the recliner bracket  54  is mounted to a top rail  48 . By this arrangement, the structural loading on the seat back  50  is transferred to the top rail  48  and then to a bottom rail mounted to the floor of a vehicle. The car seat  44  illustrated in FIG. 2 has a simplified connection between a seat back  50  and the seat bottom  46 , the actual arrangements are typically more mechanically complex and allow for manual or motorized adjustment between the seat back and the seat bottom. However all car seats require a structure for transferring the loads between the seat back and the seat bottom or seat top rail. The transfer of the load imposed on the seat back to the seat bottom or seat top rail produces a strain or deflection between the seat back and the seat bottom or top rail.  
         [0024]    The third approach to determining a vehicle seat occupant&#39;s position with respect to the vehicle seat back  50  can be accomplished by connecting a potentiometer  58  through a gear train  60  to structural portions of the seat that deflect with respect to one another as the seat back  50  is loaded. The gear train  60  amplifies the deflection of the seat back with respect to the seat bottom and the potentiometer measures the amplified deflection as a changing resistance.  
         [0025]    The gear train  60  illustrated in FIG. 2 has a partial gear  62  formed as part of the recliner structure  52  which engages a small second gear  64 , that is mounted to a larger gear  66  that turns a gear  68  mounted to the potentiometer  58  which is mounted to the recliner bracket  54 . A slight deflection of the recliner structure  52  with respect to the recliner bracket  54  produces a substantial rotation of the potentiometer  58 .  
         [0026]    It will be understood that the gear train  68  illustrated in FIG. 2 will in general be specifically designed to amplify the occupant-induced strains between the seat back and the seat bottom, while accommodating whatever adjustment functions are considered necessary for a particular seat design. Thus the particular arrangement of the gear train will depend upon the design of a particular vehicle seat, but the gearing of a potentiometer to the relative deflection between the seat back and the seat bottom or seat bottom rail will remain a constant.  
         [0027]    [0027]FIG. 3 illustrates portions of a car seat  70  where strains induced in a recliner bracket  72  by loads transmitted from a seat back (not shown) through a recliner  74  are monitored by a magnetostrictive sensor  76 . The recliner bracket  72  is mounted to the top rail  78  of the seat  80 . The recliner  74  is mounted about a pin  82  to the recliner bracket  72  so that backward force indicated by arrow  84  produces elastic strain in the body  86  of the recliner bracket  72 . The recliner bracket  72  has a portion that forms a U-shaped flange  88  such as might be formed by stamping and shearing the recliner bracket  72 . A first coil  90  is formed on one side of the U-shaped flange  88  leading into one side of the body  86  of the recliner bracket  72  and a second coil  92  is formed on the second side of the U-shaped flange  88  leading into a second side of the body  86  of the recliner bracket  72 . The first coil  90  is driven with an alternating current to induce an alternating stress wave that passes through the body  86  and into the second side of the U-shaped flange  88  where the alternating stress wave is detected by the second coil  92 . The magnetostrictive sensor  76  is thus formed between the first coil  90  and the second coil  92  and allows the solid-state monitoring of stress in the recliner bracket  72 . Stress in the bracket  72  is correlated with how the seat back is engaged by the seat occupant because the engagement causes stress in the recliner  74 . An isometric view of the car seat  70  is shown in FIG. 5, wherein the U-shaped flange  88  is shown bent to a greater angle with respect to the recliner bracket  72 .  
         [0028]    It will be understood that a magnetostrictive sensor can be formed in other ways such as by welding or bonding of ferromagnetic cores about which the first and second coils are formed. In general, magnetostrictive sensors can be used with any portion of the seat back and its attachment to the seat bottom or upper rail that experiences a representative stress, i.e., stress that proves useful in determining a vehicle seat occupant&#39;s position relative to the seat back.  
         [0029]    [0029]FIG. 4 shows a simplified diagram for a vehicle safety system  96  having a safety device  97 , a safety device controller  98 , and a seat occupant position sensor  100 . The safety device  97  may be an airbag; either a side impact airbag, or a front airbag. The airbag may be of the two-stage type, or have a variable gas volume deployment capability. The controller  98  determines whether or not to deploy the airbag based on one or more crash sensors  106 . The airbag controller  98  considers the type and severity of the crash as determined by input from the crash sensors and onboard logic. The airbag controller  98 , depending on the functionality of the airbag, makes the decision whether or not to deploy the airbag, and if the airbag is capable of veritable deployment, as to gas pressure, timing, deployment velocity or other factor, the controller uses onboard logic to control one or more deployment variables. In addition to considering attributes of the crash, and other sensors within the vehicle, such as seat occupant weight, seat belt use, radar, ultrasound, or optical sensors, the controller and the onboard logic consider input from the seat occupant position sensors. The seat position sensors described herein can be used to determine through experimentation, modeling, crash testing, and black box monitoring of real world crashes, correlations between the output of the sensors and the optimal method of deploying a safety device so as to minimize the unfavorable results of a vehicle crash. In this way the vehicle occupant sensors disclosed herein can be seen to be tools which can be used to improve vehicle crash outcomes.  
         [0030]    It should be understood that magnetostrictive sensors, while requiring ferromagnetic materials to generate and detect stress waves, can be used to detect stresses in nonferromagnetic materials by joining stress-wave-producing ferromagnetic components to nonferromagnetic structures.  
         [0031]    It should also be understood that more than one type of vehicle occupant seat position sensor could be used on the same vehicle seat. Furthermore, the seat occupant position sensors described herein could be used in conjunction with seat occupant position sensors such as capacitance sensors, or those which utilize ultrasound, radar, or light to directly image or otherwise detect the seat occupant&#39;s position relative to an airbag or other point of reference.  
         [0032]    It is further to be understood that vehicle seats take on a wide variety of structural designs, and that various seat occupant position sensors may be adapted to the various designs within the limitations set forth in the following claims.  
         [0033]    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.