Abstract:
A position adjusting system for adjusting the position of a seat n a vehicle and preventing movement of the seat resulting from external forces acting on the seat. The system includes a seat track fixable to the vehicle, a motor actuator, and a gear train engaged with the motor actuator. The seat track is adapted to cooperate with the seat track to convert movement of the motor actuator into movement of the seat track and the seat. A non-reversing clutch mechanism is coupled with the gear train and adapted to transfer torque from the motor actuator through the gear train to move the seat upon actuation of the motor actuator but locking upon torque being applied through the seat track, thereby preventing the external forces acting on the seat from moving the seat relative to the vehicle.

Description:
TECHICAL FIELD  
         [0001]    This invention relates generally to a power adjuster system for seats of motor vehicles, and more particularly to a mechanism within such a system that prevents forces applied to the seat in a vehicle collision from being restrained entirely by the drive motor of the system.  
         BACKGROUND  
         [0002]    Automotive power driven seat mechanisms are well known in the art. A typical power adjuster seat mechanism uses a worm gear driven by a motor connected to a rack and pinion to produce fore-and-aft movement of the seat. The typical current design of these systems relies on the geometry and internal friction of the gear drive to maintain the seat set in a desired position when it is not being moved.  
           [0003]    The requirements of these products presents two conflicting design constraints. First, in order to keep an external load on the seat, such as that encountered in a vehicle collision, from moving the seat by “back driving” the worm gear and drive motor, it has been necessary to use a relatively high gear reduction ratio. The high reduction ratio provides a high degree of friction. However, using a high gear ratio causes the rate of powered movement of the seta to be limited. Decreasing the gear tends to increase the speed with which the powered seat is capable of moving, but it also results in undesirable movement of the seat upon application of external forces to the seat. These concerns are especially significant with so-called integrated structural seats, which have belt restraint anchorages on the seat structure, and therefore, the seat which is movable on its tracks absorbs all restraint loadings. In short, past designs have had to sacrifice adjustment speed for rigidity and vice versa. Therefore, there is a need in the automotive industry for a seat power adjuster system that is rigid enough to withstand the application of high external forces, yet is capable of moving the seat relatively rapidly.  
         SUMMARY OF THE INVENTION  
         [0004]    In accordance with the present invention, a power adjuster system is provided with an internal non-reversing clutch mechanism. The clutch mechanism is integrated into the power adjuster dear drive train. When the clutch is driven by the motor actuator to adjust seat position in either the fore or the aft directions, the clutch mechanism allows free rotation and driving engagement with the seat. If however, a high level of external force is acting on the seat, the clutch mechanism locks, transferring these loads directly to the seat track or other mounting structural member. Since the clutch is located between the seat and the drive motor actuator, locking of the clutch transfers forces away from the motor actuator. Since the motor drive system does not have to be designed with sufficient friction to withstand inertial or other external loads applied to the seat, that system can be optimized for its function of allowing position changes for the seat.  
           [0005]    Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a perspective view, of a vehicle showing the seat and the seat track of a prior art design;  
         [0007]    [0007]FIG. 2 is a perspective view of a prior art seat adjuster system;  
         [0008]    [0008]FIG. 3 is a cross-sectional view of a prior art seat adjuster system;  
         [0009]    [0009]FIG. 4 is a plan view of a prior art power seat apparatus equipped to move a seat along two axes;  
         [0010]    [0010]FIG. 5 is a cross-sectional view of a power seat apparatus equipped with a non-reversing clutch mechanism in accordance with this invention;  
         [0011]    [0011]FIG. 6 is a cross-sectional view of a portion of the clutch mechanism taken along line  6 - 6  of FIG. 5;  
         [0012]    [0012]FIG. 7 is a cross-sectional view of the clutch mechanism similar to FIG. 6 showing the clutch actuated in a different mode than shown in FIG. 6;  
         [0013]    [0013]FIG. 8 is a cross-sectional view through a non-reversing clutch assembly in accordance with the second embodiment of this invention;  
         [0014]    [0014]FIG. 9 is a cross-sectional view taken along line  9 - 9  from FIG. 8;  
         [0015]    [0015]FIG. 10 is a cross-sectional view taken along line  10 - 10  from FIG. 8;  
         [0016]    [0016]FIG. 11 is a cross-sectional view of a third embodiment of a non-reversing clutch assembly in accordance with this invention;  
         [0017]    [0017]FIG. 12 is a cross-sectional view taken along line  12 - 12  from FIG. 11;  
         [0018]    [0018]FIG. 13 is a cross-sectional view taken along line  13 - 13  from FIG. 11; and  
         [0019]    [0019]FIG. 14 is a partial cross-sectional view through a representative non-reversing clutch assembly in accordance with this invention showing an alternate configuration of a roller engaging surface. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    The following description of the preferred embodiment of the invention and the preferred method of supplying the invention are not intended to limit the scope of this invention to these preferred embodiments and methods, but rather to enable any person skilled in the art of clutch mechanisms to make and use this invention.  
         [0021]    Now with reference to FIG. 1, the environment of application of the present invention is illustrated. As shown in that figure, seat  12  of vehicle  14  is shown mounted to seat track  16 . These components are in turn mounted to a floor pan  18  of vehicle  14 .  
         [0022]    Now with reference to FIGS. 2 and 3, a power adjuster system  20  in accordance with a prior art design is illustrated for causing fore-and-aft movement of a seat. Power adjuster system  20  includes drive motor  22  which drives worm gear shaft  24 . Worm shaft  24  drives worm wheel  26  which in turn drives worm shaft  28  which meshes with a second worm wheel  30 . Worm wheel  30  in turn drives pinion dear  32  which engages with toothed rack  34 . Actuation of drive motor actuator  22  causes the various components to rotate. As pinion  32  rotates, the engine system advances with respect to toothed rack  34 . Drive motor  22  is bidirectional, enabling the seat position to be adjusted in the fore-and-aft direction. FIG. 3 provides a sectional view illustrating the previously described components held within upper and lower drive cases  36  and  38 . Toothed rack  34  is part of seat track  16 .  
         [0023]    [0023]FIG. 4 is a further illustration of a seat track assembly in accordance with the prior art. As shown, motor  22 , which was previously described, is used to cause fore-and-aft motion of the seat  12  along track rails  40  and  42 . This figure further illustrates that additional motor actuators are provided for causing vertical motion of the front and rear portions of the seat  12 . Motor  44  is coupled with jack screws  46  to elevate the forward portion of the seat  12 , whereas motor  48  is coupled to jack screws  50  which are provided for moving the rear portion of the seat in the vertical direction.  
         [0024]    Now with reference to FIGS. 5, 6, and  7 , a position adjusting system  54  is shown in accordance with a first embodiment of this invention. Elements common to those of the prior art designs described above are hereafter identified by the previously used reference numbers. Like the prior art designs, position adjusting system  54  includes worm  56  which meshes with worm gear  58 . These elements in turn drive shaft  70  and pinion  60  which meshes with toothed rack  34 . These elements are held by housing components  62  and  64  and are mounted to seat frame  66 . Position adjusting system  54  differs from the prior art system described previously in that it incorporates non-reversing clutch assembly  68 . Non-reversing clutch assembly  68  primarily comprises shaft  70 , retainer  72 , rollers  74 , and roller springs  75 . As best shown in FIGS. 6 and 7, shaft  70  has a roughly “D” shape in cross-section in a plane above the plane of rollers  74  (the section line  6 - 6  of FIG. 5 is broken to cut through two parallel planes). Shaft  70  further features a number of flat cam surfaces  76  oriented to engage with each of rollers  74 . Rollers  74  are trapped between shaft  70  and the inside cylindrical surface of outer race  78 . Retainer  72  has an internal cavity  80  which receives shaft  70  and includes a flat abutment surface  82 . Retainer  72  further forms roller tangs  84 . Roller springs  75  act on rollers  74  to bias them to engage with flats  76 . Non-reversing clutch assembly  68  is connected in the drive system such that worm gear  58  directly engages and drives retainer  72 , whereas shaft  70  is engaged with pinion  60 .  
         [0025]    In the ordinary course of operation in moving the seat by actuation of the motor  22 , the source of torque is applied onto retainer  72 , and the torque is transferred to shaft  70  as shown in FIG. 6. Retainer tangs  84  and springs  75  push the rollers  74  against shaft cam surfaces  76 . Rollers  74  are permitted to roll or slide freely. Thus in this operating condition, non-reversing clutch assembly  68  freely allows torque to be transferred worm gear  58  and pinion  60 , and thus fore-and-aft adjustment of the seat is provided. When, however, the source of the torque is “back fed” from an external force acting on the seat, for example due to inertial loads on the seat, toothed rack  34  drives pinion  60  and shaft  70  in the opposite direction, which causes rollers  74  to be frictionally trapped between shaft cam surface  76  and outer race  78 . This direction of force is shown in FIG. 7. This frictional engagement causes the shaft  70  and retainer  72  to “lock up” against outer race  78 . Since outer race  78  is rigidly mounted, this lock up condition prevents further fore-and-aft movement of the seat  12  on seat track  16 . These restraining loads are not born by the motor  22  or its related gear reduction components.  
         [0026]    The interlocking geometry between retainer  72  and shaft  70  is used to transmit the torque between the two components when it is driven by motor  22 . The geometry also provides a means for limiting the degree of angular rotation between retainer  72  and shaft  70  which must be sufficient so that rollers  74  are pushed fully into the position where they can engage between shaft  70  and outer race  78  when torque is applied through shaft  70 . This geometry may take various alternate forms. In the form previously described as shown in FIGS. 5 through 7, the interfitting of shaft  70  and the retainer cavity  80  controls the amount of relative angular rotation.  
         [0027]    Now with reference to FIGS. 8, 9, and  10 , a second embodiment of a non-reversing clutch assembly  88  is described. This embodiment differs in that the shaft  90  geometry is extended and engages with matching geometry with controlled clearance provided in the retainer  96  to transmit torque in the driving direction. As shown in FIGS. 9 and 10, shaft  90  has a regular polygonal shape, here in the form of a hexagon having six cam surfaces  92  which engage with rollers  74 . The shape of shaft  90  is extended into a torque transmitting section  94  of retainer  96 . The inter-engagement between torque transmitting section  94  and shaft  90  provides a means for limiting the degree of angular rotation between these components designated by angle α in FIG. 9. This inter-engagement allows driving torque to be transmitted between these two components when non-reversing clutch assembly  88  is in a disengaged or non-locking condition. Each of retainer tangs  98  are identical for each roller and are distributed around the entire perimeter of shaft  90 . This embodiment operates in a manner consistent with the first embodiment. Accordingly, when torque is transmitted from an actuating motor through retainer  96 , free rotation of clutch assembly  88  is provided. If, however, the shaft  90  is actuated for rotation, rollers  74  are forced into frictional locking engagement with outer race  100 . It should be noted that the interfifting components  94  and  90  do not have to be configured as a polygon, numerous other non-circular shapes could be used so long as they permit limited angular rotation while permitting driving torque to be transmitted.  
         [0028]    Now with reference to FIGS. 11, 12, and  13 , a third embodiment of a non-reversing clutch assembly  104  is described. This embodiment is identical to clutch assembly  88  except with regard to the manner with which torque is transmitted between shaft  106  and retainer  108 . In this instance, shaft  106  has the same six sided hexagonal shape as that of shaft  90 . However, retainer torque transmitting section  110  has a smooth inside cylindrical bore. In this case, pin  112  is pressed into a bore within shaft  106  and protrudes from the shaft and engages with aperture  114  formed by retainer  108 . The aperture  114  is dimensioned to permit the appropriate degree of angular relative rotation designated by angle α as the case of the previously described embodiment. This angle α is selected to allow the locking engagement previously described to occur.  
         [0029]    [0029]FIG. 14 illustrates an alternate embodiment of shaft  116  which could replace shafts  106  or  90 . In this instance, the flat cam surfaces are replaced by surfaces  118  with a concave shape which engage with rollers  74 . By making the surface  118  slightly concave instead of flat, less relative angular rotation (α) is required to engage rollers  74  between the shaft and outer race  100 , thereby reducing the relative rotation of “lash” in the assembly. This geometry also allows rollers  74  to disengage more easily, reducing the response time and torque required when the associated motor starts to drive the system. A further benefit of this configuration is that the slightly higher engagement angle reduces the internal stresses in the clutch. However, the curvature of surface  118  needs to be carefully controlled to keep the contact angle in the proper range where the clutch locks firmly without slipping. Surface  118  may be formed of various shapes including semicircular or a smooth blending of varying radii.  
         [0030]    While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.