Abstract:
A vehicle seat power track for an automobile vehicle seat which includes a sensor arrangement to detect the seat position along the track relative to a front airbag apparatus and generate a signal to control the apparatus of the airbag. The vehicle seat power track also includes brackets configured to reduce horizontal movement of the track components.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 12/677,243, filed Sep. 2, 2010, claiming priority to a U.S. National Stage filing of International Application No. PCT/US2007/019638, filed on Sep. 10, 2007 titled “Vehicle Seat Power Track Enhancements”, the entire contents of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     The present disclosure relates generally to adjustable vehicle seat assemblies utilizing power track systems. More particularly, the present disclosure relates to enhancements to a power track system and its transmission. 
     Vehicle seat assemblies are typically provided with a track system that enables the forward and rearward positioning of the seat assembly. Such adjustment capability is desirable to enable vehicle operators of various sizes to be seated comfortably within the motor vehicle. Such seat assemblies typically include a track assembly including two tracks that move relative to one another and a latching mechanism that retains the tracks (and therefore the seat assembly) in a locked position relative to one another until the latch mechanism is released. The tracks may be moved relative to one another, which allows the occupant of the seat assembly to adjust the seat assembly to a new position. 
     Some vehicle seat assemblies include an electric motor, a transmission and a lead screw positioned within the track assembly for power adjustment of the vehicle seat. In such arrangements, the lead screw may generally be fixed and does not rotate. The transmission includes a worm gear assembly rotatably coupled to the lead screw and the electric motor causes the worm gear to rotate causing the transmission to translate along the fixed non-rotating lead screw to adjust the vehicle seat assembly forward or rearward. 
     In such configuration, the electric motor, mounted on a traverse beam is positioned relative to each of the tracks, for example in the center of the tracks or at one end of the tracks. A transmission mounting bracket couples the transmission, which may float inside of the mounting bracket, and the stationary lead screw to one of the rails. Thus, the strength of the power track is realized through the transmission mounting bracket. In the event of a collision, the load on the bracket could cause the bracket to bend. Using a larger bracket to provide more strength to the power track could be problematic due to space constraints inside the track section that limits the size of the mounting bracket. 
     Occasionally, the movement of the seat forward can place the occupant of the vehicle too close to airbags that are located in front of the occupant. In such arrangement, the power to the air bag could be diminished or turned off. Generally, it is known to provide a seat position sensor for controlling the airbag based upon seat position. However, such known seat position sensors are affected by debris (such as dirt and dust) in the passenger cabin of the vehicle. 
     Therefore there is a need for a stronger transmission mounting bracket that can withstand the extra load encountered in situations such as a vehicle collision. There is also a need for a compact design of a sensor arrangement that can detect the position of the seat in reference to the proximity of an airbag and adjust the airbag power down or off as needed. 
     SUMMARY 
     In one exemplary embodiment, a vehicle seat power track for an automobile vehicle seat includes a lower rail for being fixed to a vehicle floor and an upper rail for having a seat fixed thereto and the upper rail may be mounted and traveled freely with support of the lower rail. The power track system includes a lead screw member which may extend in longitudinal direction of the rails and a transmission member located inside the rails and mounted using a bracket. A motor is provided and may be coupled to the transmission member to cause movement of the transmission along the lead screw in the longitudinal direction of the track. In the exemplary embodiment, the lead screw may be mounted on the upper rail and the transmission and bracket member on the lower rail to enable relative movement of the upper to the lower rails. A position sensor may be mounted at a predetermined position on the top surface of the upper rail to detect a magnet or a plate member (or detecting cell) generating a magnetic field near the sensor. In the one exemplary embodiment, the detecting cell (plate member) is mounted on a surface of the bracket member facing a top surface of the upper rail such that when the vehicle seat is moved to a predetermined position the plate member is aligned with the seat position sensor and affects the signal status of the seat position sensor. 
     In one exemplary embodiment, the bracket member includes flanges extending along the lower rail and the bracket member clip front and back surfaces of the transmission. 
     In one exemplary embodiment, a support member fixedly couples the lead screw to the upper rail. The support member contacts a rear surface of the transmission to form a stop surface and functions to control or limit the seat movement. Further, in the one exemplary embodiment, one end of the detecting cell is aligned at the level of the stop surface of the transmission. Further, in the one exemplary embodiment, another end of the detecting cell extends, or is cantilevered, in one direction from the bracket member. 
     In an exemplary embodiment, the detecting cell is fixed to the bracket member using a welding process and in particular a laser welding process to minimize any welding projections from the resulting combination of the detecting cell and bracket member. 
     In one exemplary embodiment, the seat position sensor includes a magnet and a detection member for detecting a magnetic field. 
     In one exemplary embodiment, the seat position sensor is located toward a rear end of the upper rail and the bracket member and detecting cell are located toward the front end of the lower rail to detect a seat position which is a front most position and to control or prevent deployment of a front airbag. In one exemplary embodiment, the front airbag is deployed with a lower force when the seat is detected as being the front most position. In one exemplary embodiment, the front airbag is not deployed when the seat is detected as being the front most position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a seat assembly according to an exemplary embodiment. 
         FIG. 2  is a top view of a track system as used with a seat assembly shown in  FIG. 1  according to an exemplary embodiment. 
         FIG. 3  is a cross section of a track system of  FIG. 2  along line  3 - 3  according to an exemplary embodiment. 
         FIG. 4  is a magnified view of a track system transmission according to an exemplary embodiment. 
         FIG. 5  is a perspective view of a track system of  FIG. 2  according to an exemplary embodiment. 
         FIG. 6  is a magnified view of a seat position sensor according to an exemplary embodiment. 
         FIG. 7  is a cross section of a track system of  FIG. 2  according to an exemplary embodiment. 
         FIG. 8  is a magnified view of a shunt member according to an exemplary embodiment. 
         FIG. 9  is a cross section of a seat track system of  FIG. 2  according to an exemplary embodiment. 
         FIG. 10  is a magnified view of a seat position sensor according to an exemplary embodiment. 
         FIG. 11  is a perspective view of a lead screw illustrating a spacer between the lead screw bracket and saddle bracket according to an exemplary embodiment. 
         FIG. 12  is a magnified view of the lead screw in  FIG. 11  according to an exemplary embodiment. 
     
    
    
     DESCRIPTION 
     Referring to  FIG. 1 , a seat assembly  10  is shown according to an exemplary embodiment. Seat assembly  10  includes a seat  12  and a track system  14 . Seat  12  generally includes a back portion  16  and a seat cushion portion  18 , which each may take any one of a variety of well known configurations. Track system  14  is generally configured to enable an occupant of seat  12  to adjust the position of seat  12  in forward and/or rearward directions. 
     Referring to  FIG. 2 , a track system  14  is shown according to an exemplary embodiment. Track system  14  includes an inboard track arrangement  20  and an outboard track arrangement  22 . Inboard track arrangement  20  and outboard track arrangement  22  are coupled to seat cushion portion  18  (shown in  FIG. 1 ) of seat  12  in a generally parallel relationship with inboard track arrangement  20  being located proximate the inboard side of seat cushion portion  18  and outboard track arrangement  22  being located proximate the outboard side of seat cushion portion  18 . 
     Referring now to  FIG. 3 , a cross section of track system  14  illustrated in  FIG. 2 , is shown according to an exemplary embodiment. For simplicity, only track arrangement  20  will be described below, it being understood that the description applies equally to track arrangement  22 . Track arrangement  20  includes a lower track (rail)  24  coupled to the vehicle and an upper track (rail)  26  coupled to seat  12 , a lead screw  28  located between lower track  24  and upper track  26  and mounted to the upper track  26 , a transmission  30  rotatably coupled to lead screw  28 , and a transmission mounting bracket  32  partially enclosing the transmission  30  and movably coupled with respect to the lead screw  28  and coupled to the lower track  24 . The track system  14  may also include a motor and flexible drive cables for interconnecting the motor and the transmission. 
     In an exemplary embodiment, a motor turns drive cables which are coupled to transmission  30  which transmits power to the lead screw  28 . The lead screw  28  is fixed and does not rotate. A worm gear assembly  29  within the transmission  30  and coupled with the lead screw  28  causes transmission  30  to translate along the fixed non-rotating lead screw  28  thereby moving the vehicle seat assembly  10  forward or rearward depending upon the rotation direction. 
     Referring now to  FIG. 4 , a magnified view of transmission  30  illustrated in  FIG. 3 , is shown according to an exemplary embodiment. Transmission  30  causes the upper track  26  to move along the lead screw  28 . In this configuration, the upper track  26  and seat  12  move relative to the lower track  26 . The seat  12  may be moved in the opposite direction by reversing the direction that the motor turns. One end of the lead screw  28  is fixedly coupled to upper track  26  through the bracket or support  34  and the other end of the lead screw  28  is coupled to the upper track  26  through the bracket or support  48 . 
     In the event excessive forces are applied to the vehicle, e.g. a vehicle collision, the load path of the force is from the seat  12  to the upper track  26  through the support  34  to the transmission mounting bracket  32 . Excessive loading on the transmission mounting bracket  32  may cause the bracket to bend, putting a high load onto the transmission  30  and potentially causing it to fail. 
     To lessen the bending of the bracket  32 , a brace portion  36  may be utilized to support the transmission mounting bracket  32  at the point of interface between the lead screw  28  and transmission  30 . The brace portion  36  may be located on one or both sides of the transmission mounting bracket  32 . The brace portion  36  may be highly and efficiently achieved utilizing an extension of the head  39  of the fastener  77  used to connect the transmission mounting bracket  32  to the lower track  24  thereby also providing an efficient load path back to lower track  24 . 
     Another exemplary embodiment of track system  14  is illustrated in  FIGS. 5 through 8 . As mentioned above, vehicle seat  12  moves with upper track  26  forward and rearward through track system  14 . Generally, the movement of seat  12  too far forward may cause the occupant of seat  12  to be located close to an airbag (not shown in the FIGURES) situated in front of the occupant, such as a driver&#39;s position in a passenger vehicle. To determine the location of seat  12  relative to an airbag, a seat position sensor  38  may be mounted to the upper track  26  using an attachment nut  40 . The seat position sensor  38  detects the location of the seat  12  relative to a shunt (plate) member or detecting cell  42  affixed to the top of transmission mounting bracket  32 . The shunt (plate) member  42  may be a magnet. Seat position sensor  38  may be affixed to the top of the upper rail of the track assembly and the shunt plate  42  may be coupled to the transmission mounting bracket  32 . The shunt plate  42  may be coupled to the transmission mounting bracket  32  using a laser weld process to prevent weld matter from extending from the laser welded surfaces. Alternatively, the shunt plate  42  may be coupled to the transmission mounting bracket  32  using other appropriate materials such as adhesives or other welding procedures. 
     Referring now to  FIG. 7 , the seat position sensor  38  is located at the rear end of the track system  14  given the particular seat position. In this vehicle seat position, the shunt member  42  is not located near the seat position sensor  38 . Therefore, the seat position sensor  38  is considered “off” in proximity to the shunt plate  42  and the seat position sensor  38  will send a signal to the airbag to remain on or in full power mode or, alternatively, the seat position sensor  38  will not prevent activation of the airbag. 
     As the seat  12  moves forward, the seat position sensor  38  will be positioned aligned over the shunt member  42 , as best illustrated in  FIGS. 9 and 10 . When the seat position sensor  38  is over the shunt member  42 , the seat is considered in full forward position. In this position, the seat position sensor  38  is considered “on” in proximity to the shunt plate and the airbag will receive a signal to power down or turn off due to the close proximity of the occupant. 
     In the exemplary embodiment shown, the seat position sensor  38  and shunt plate  42  located inside the seat rails allow for utilization of a narrow space within the seat rails as well as for sensing of the seat position. With the sensor or shunt  42  located inside of the slide rail, foreign objects may be prevented from entering the seat position sensor thereby improving the accuracy of detection of the full forward seat position and limiting the affects of foreign objects and dirt and dust since the sensor is set on the top surface of the upper rail. The seat position sensor  38  and shunt plate  42  design provide greater flexibility in design for the vehicle seat. 
     In an exemplary embodiment, as illustrated in  FIGS. 11 and 12 , an annular ring, or spacer  46  may be located between the lead screw bracket  48  and transmission mounting bracket  32 . Spacer  46  may function as a stopping member to minimize the force felt by the occupant when the track assembly comes to a stop. Spacer  46  may be comprised of any non-metallic, resilient flexible material such as Acetal (POM) Copoly (Acetal (POM) Copolymer) plastic material available as CELCON™ M90 available from Ticona Company in Florence, Ky., USA. 
     For purposes of this disclosure, the term “coupled” means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two components (electrical or mechanical) and any additional intermediate members being integrally formed as a single unitary body with one another or with the two components or the two components and any additional member being attached to one another. Such joining may be permanent in nature or alternatively may be removable or releasable in nature. 
     It should be noted that the construction and arrangement of the track system as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the various exemplary embodiments.