Abstract:
A method of determining the location of a movable seat in a vehicle relative a stationary reference point therein. The method includes the steps of providing a flexible member characterized by electrical resistance as a function of curvature, operationally connecting the flexible member to the seat such that movement of the seat relative the reference point bends the flexible member, moving the seat relative the reference point, measuring the electrical resistance of the flexible member, and determining the location of the seat.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority to U.S. Provisional Application Serial No. 60/287,459 filed Apr. 30, 2001. 
     
    
     
       TECNNICAL FIELD OF THE INVENTION  
         [0002]    The invention relates generally to the field of automotive technology and, more particularly, to an apparatus and method for determining position by means of a flexible resistive circuit.  
         BACKGROUND OF THE INVENTION  
         [0003]    There is a need for detecting the forward/rearward position of a seat in an automobile, so that the seat may be adjusted to accommodate the size of a seated driver relative to the automobile controls and also so that the automobile airbag system can be managed for the size and proximity of an individual sitting in the seat. Deployment of the airbag system can be injurious or even fatal to vehicle occupants positioned too close to the deploying airbag. This is especially true if the passengers are frail, as is common with infants, children, the elderly, and the ill.  
           [0004]    One important criterion of a seat position sensor is that these sensors are required to function equally well if the seat is repositioned hundreds or thousands of times or if years or decades pass between seat repositionings. In other words, the detector must not substantially degrade from either repeated usage or from prolonged disuse.  
           [0005]    Current technologies useful for tracking seat position include magnetic, inductive, ultrasonic, seatbelt spool-out, potentiometer sliding brush, mechanical, microwave and optical devices. While all of these technologies are useful, each suffers from some flaws. For example, optical sensing devices usually include an emitter and a detector positioned with a portion of the movable, perforated seat rail therebetween. The optical sensor system is especially susceptible to interference from dust, dirt, and assorted detritus generated during the operation of the automobile that may partially or completely obstruct the optical path between the emitter and the detector, thereby disabling the optical detector system. This becomes an especially troublesome problem if the sensor is left in disuse for long periods of time, as the optical pathway may become gradually obstructed. The optical system is also subject to errors arising from a misalignment of the emitter and the detector.  
           [0006]    Sonic echo sensors having an active sound emitter and a sound detector may be used to interrogate the position of the seat. The active emitter is positioned to direct a sound beam toward the seat. By detecting the echo, the position of the seat relative the emitter and/or detector may be calculated. This system may also determine the proximity of passengers within the seat to the air bags by direct interrogation. However, this system is susceptible to interference form sound-emitting devices (especially in the ultrasonic range) and cannot distinguish between passengers and inanimate objects on the seat. This system also directs an ultrasound beam at the passengers, which may interfere with such things as hearing aids, and may be blocked and/or deflected. Moreover, this system is bulky and, due to it&#39;s placement within the vehicle, is also readily susceptible to misalignment of the emitter, the detector, or both.  
           [0007]    Sensors utilizing a magnetic element, such as a Hall effect sensor, require the placement of a magnetic strip on or adjacent the seat rail. The placement and length of the strip defines the detectable switchpoints for detection by a magnetic sensor. While not as susceptible to interference from dirt, dust, moisture or the like, the magnetic sensor is susceptible to electromagnetic interference from such items as speakers, metallic objects, and other magnets. The system is also susceptible to damage from repeated use, since repetitive motion of the seat may cause dislodging or misalignment of the sensor and/or magnetic strip.  
           [0008]    An inductive sensor system utilizes an active sensor to detect the presence of metallic objects. The movable seat rail may have a profile cut thereinto, and a stationary sensor can be used to read the profile to determine the position of the rail relative the sensor. However, this system is especially susceptible to interference from foreign metallic objects.  
           [0009]    There is therefore a need for a seat position sensor system that is reliable, is resistant to dust, dirt, interference from metallic and/or magnetic objects, and is positioned away from sources of accidental misalignment and the like. The present invention addresses this need.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention relates to a vehicular seat position detector. The position detector includes a rail having a profile, a seat movable relative to the rail, an elongated member having a first end pivotably connected to the seat and a second end extending to the rail, and a flexible member having electrical resistance and connected between the elongated member and the rail. Moving the seat relative the rail actuates the second end to trace the profile, thereby pivoting the elongated member. Pivoting of the elongated member actuates flexure of the flexible member, wherein the electrical resistance of the flexible member is a known function of the flexure of the flexible member. Flexure of the flexible member changes the electrical resistance of the flexible member, allowing the position of the seat to be calculated by measuring the electrical resistance of the flexible member.  
           [0011]    One object of the present invention is to provide an improved seat position detector for an automobile. Related objects and advantages of the present invention will be apparent from the following description.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a partial schematic diagram of a first embodiment of a position detector having a flexible member of variable resistance attached thereto.  
         [0013]    [0013]FIG. 2A is a partial schematic diagram of the position detector of FIG. 1 wherein the rail includes a plurality of steps.  
         [0014]    [0014]FIG. 2B is a partial schematic diagram of the position detector of FIG. 1 wherein the rail is substantially smoothly sloped.  
         [0015]    [0015]FIG. 3A is a first partial schematic diagram of a second embodiment of a position detector having a flexible member of variable resistance connected between a stationary member and a pivotable armature attached thereto.  
         [0016]    [0016]FIG. 3B is a second partial schematic diagram of the embodiment of FIG. 3A.  
         [0017]    [0017]FIG. 4A is a schematic diagram of a third embodiment of a position detector having a flexible member of variable resistance connected between a pivotable member and a stationary reference member.  
         [0018]    [0018]FIG. 4B is a schematic diagram of the embodiment of FIG. 4A wherein the pivotable member is further pivoted in a first direction.  
         [0019]    [0019]FIG. 4C is a schematic diagram of the embodiment of FIG. 4A wherein the pivotable member is further pivoted in a second direction.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.  
         [0021]    [0021]FIGS. 1, 2A and  2 B illustrate a first embodiment of the present invention, a position detector  10  for measuring the position of a movable component in a vehicle such as an automobile, truck, airplane or the like. The position detector  10  includes a flexible strip or member  12  having an electrical resistance that predictably varies as a function of its flexure or curvature. In other words, as the flexible member  12  is bent, its resistance changes according to known parameters. Examples of such flexible members characterized by electrical resistance as a function of flexure and their manufacture are discussed in U.S. Pat. Nos. 5,086,785 to Gentile et al.; 5,157,372 to Langford; and 5,583,476 to Langford, each incorporated by reference herein in its entirety.  
         [0022]    The exterior of the flexible member  12  is preferably substantially electrically and chemically insulated. The flexible member  12  is connected at one end to a movable vehicular component  14 , such as a seat. The flexible member  12  is connected such that movement of the seat  14  causes the curvature or flexure, and thereby the electrical resistance, of the flexible member  12  to change. The component  14  may move linearly, such as by sliding from front to back, from side to side or up and down, or may move pivotally.  
         [0023]    In this embodiment, the vehicular component  14  may be taken as a car seat that is adapted to slide from front to back. The seat  14  includes an armature member  16  pivotably connected thereto. The seat  14  may be movable relative to a stationary profiled rail  18  connected to the vehicle. The armature  16  extends from the seat  14  to contact the rail  18 . As the seat  14  moves relative the rail  18 , the end of the armature  16  in contact with the rail  18  traces or follows the profile. The rail  18  is preferably profiled such that as the seat  14  moves, the distance between the seat  14  and the rail  18  changes, either discontinuously (i.e., the profile-is stepped, as shown in detail in FIG. 2A) or smoothly (i.e., the profile is inclined, as shown in more detail in FIG. 2B). The flexible member  12  is preferably connected between the pivotable armature  16  and the seat  14 , such that as the seat  14  moves relative the rail  18 , the armature  16  pivots to follow the rail profile and the flexure of the flexible member  12  changes accordingly. The electrical resistance of the flexible member  12  may be measured, such as by an ohmmeter or electronic controller  20  connected thereto. The position of the seat  14  may be calculated by using a known relationship between the resistance of the flexible member  12  and its curvature to determine the curvature, and then by using a known relationship between the curvature of the flexible member  12  and the position of the seat  14  to determine the position of the seat  14 .  
         [0024]    A second embodiment of the present invention is disclosed in FIGS. 3A and 3B. In this embodiment, the vehicular position detector  10 ′ includes a flexible strip  12 ′ connected between a stationary reference point or member  22  and a pivotable armature or member  16 ′. The flexible strip  12 ′ is again characterized as having an electrical resistance that predictably varies as a function of its flexure or curvature. The position detector  10 ′ also includes a movable profiled rail portion  18 ′. The profiled rail portion  18 ′ is connected to a movable member or component  14 ′, taken hereinafter as a slideable car seat. As the seat  14 ′ moves, so does the rail  18 ′. As above, the pivotable member  16 ′ is connected with one end in contact with and following the profile of the rail  18 ′. The end of the pivotable member  16 ′ therefore traces the profile of the rail  18 ′ as the seat  14 ′ and the connected rail  18 ′ move. The flexible member  12  is preferably connected between the pivotable armature  16 ′ and the reference point  22  such that as the seat  14 ′ and rail  18 ′ move past the reference point  22 , the armature  16 ′ pivots to follow the rail profile and the flexure of the flexible member  12 ′ changes accordingly. The electrical resistance of the flexible member  12 ′ may be measured, such as by an ohmmeter or electronic controller  20  connected thereto. The position of the seat  14 ′ may be calculated by using a known relationship between the resistance of the flexible member  12 ′ and its curvature to determine the curvature, and then by using a known relationship between the curvature of the flexible member  12 ′ and the position of the seat  14 ′ to determine the position of the seat  14 ′.  
         [0025]    A third embodiment of the present invention is illustrated in FIGS.  4 A- 4 C, and includes a movable vehicular component  14 ″, wherein at least a portion thereof is adapted pivot or rotate through an arc. As in the previous embodiments, the movable vehicular component may be a seat  14 ″. The seat  14 ″ is at least partially pivotable relative to the vehicle. A flexible member  12 ″ characterized by variable electrical resistance as a function of bend or curvature is connected between the seat  14 ″ and a stationary member  18 ″ connected to the vehicle. The relationship between the curvature and the electrical resistance of the flexible member  12 ″ is preferably stable and more preferably well known. The flexible member  12 ″ is connected such that pivoting the seat  14 ″ through a predetermined arc amount changes the curvature of the flexible member  12 ″ by a predetermined amount, thereby changing its electrical resistance. Since the relationships between the arc traversed by the pivoting seat  14 ″ and the curvature of the flexible member  12 ″ and between the curvature of the flexible member  12 ″ and its electrical resistance are known, it is possible to determine the position of the pivoted seat  14 ″ by measuring the electrical resistance of the flexible member  12 ″. This may be accomplished by connecting an ohmmeter or electronic controller  20  in electric communication with the flexible member  12 ″.  
         [0026]    While the above embodiments contemplate the vehicular component as being a seat  14 , the present invention may be practiced with any moving vehicular component, such as a window, a steering column, the windshield wipers, or the like.  
         [0027]    While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.