Abstract:
A head restraint system for an automotive vehicle seat includes a headrest carried upon eccentric mounting posts which may be extended telescopically from a seatback and rotated about their base axes so as to reposition the headrest not only vertically, but also horizontally. A sensor mounted in the headrest feeds back the location of an occupant&#39;s head to a system controller.

Description:
TECHNICAL FIELD 
   The present invention relates to an automotive head restraint system including a headrest with motor driven adjustments for both the height and the horizontal position of the headrest. 
   BACKGROUND 
   Adjustable headrests have been used for many years in automotive vehicles. For optimum effectiveness, such headrests must be adjusted properly. Because achieving a correct adjustment is more difficult in the case of manually adjustable headrests, motor drive headrests have been offered. U.S. Pat. No. 6,511,130 discloses a headrest which is adjustable both manually, and by means of a motor. The arrangement of the &#39;130 patent is however, very complex, costly, and high in weight. 
   The present head restraint system for an automotive vehicle occupies a package of reasonable volume, with reasonable weight, and low complexity. 
   SUMMARY 
   A head restraint system for an automotive vehicle includes a plurality of mounting posts extending generally vertically from a seatback, with each of the posts having a lower base portion with a longitudinal axis, and an upper eccentric portion. A headrest is carried upon the eccentric portion of each of the posts. A first drive mechanism, which is coupled to the base portion of each of the mounting posts, extends and retracts the posts so as to raise and lower the headrest. A second drive mechanism rotates the mounting posts about their longitudinal axes, so as to move the eccentric portions and the attached headrest fore and aft. The first drive mechanism preferably includes a height control bar having a mounting plate for the base portions of the headrest posts, and a linear actuator coupled to the height control bar. The actuator moves the height control bar and mounting posts vertically. This linear actuator may include a lead screw powered by an electric motor. 
   According to another aspect of the present invention, a second drive mechanism for a head restraint system according to the present invention includes a plurality of linear actuators, with a separate one of the linear actuators being coupled to the base portion of each mounting post, and with the linear actuators being controlled so as to move the mounting posts laterally in opposite directions. Because the mounting posts are connected within the headrest by an indexing mechanism extending between the mounting posts, the lateral movement produced by the linear actuators will cause the mounting posts to rotate equally, but in opposite directions, thereby moving the headrest either fore or aft at a constant attitude, and in a direction depending upon the direction of rotation of the mounting posts. Of course, the direction of rotation depends upon whether the mounting posts have been moved closer to, or farther from, each other by the action of the linear actuators. In a preferred embodiment the indexing mechanism comprises a plurality of secondary gears meshing between primary gears locked rotationally to each of the mounting posts. 
   According to another aspect of the present invention, a controller for operating the first and second drive mechanisms of the headrest mounting system includes either a manual controller or a microprocessor controller having at least a first sensor for determining an operating state of the vehicle, and a second sensor for determining the position of a passenger&#39;s head with respect to the headrest. In a preferred embodiment, a second sensor which may be advantageously mounted within the headrest itself. 
   According to another aspect of the present invention, a seat for an automotive vehicle includes a seat frame, a seat cushion mounted to the seat frame, a seatback mounted to the seat frame, and a plurality of mounting posts extending generally vertically from the seatback, with each of the mounting posts having a lower base portion with a longitudinal axis and an upper eccentric portion. A headrest is mounted to and carried upon the eccentric portions of the posts. A first drive mechanism, coupled to the base portion of each of the mounting posts, extends and retracts the posts so as to raise and lower the headrest. A second drive mechanism moves the posts laterally, so as to cause rotation of the posts and to thereby move the eccentric portions of the posts, and the attached headrest, fore and aft. 
   A seat according to the present invention further includes a sensor for determining the position of a passenger&#39;s head with respect to the headrest and a controller for operating the first and second drive mechanisms so as to adjust the position of the headrest to establish a predetermined spatial relationship between the headrest and the passenger&#39;s head. 
   According to another aspect of the present invention, a method for adjusting a passenger headrest in an automotive vehicle includes the steps of activating a head proximity sensor located in the headrest, activating a first drive mechanism to adjust the vertical position of the headrest based upon a signal from the proximity sensor, and activating a second drive mechanism to adjust the horizontal position of the headrest based upon the signal from the proximity sensor. 
   It is an advantage of a system according to the present invention that a passenger headrest in a vehicle may be adjusted either manually or automatically with precision, so as to achieve a desired position offering enhanced protection for a vehicle occupant. 
   It is a further advantage of the present invention that the present headrest adjusting system provides enhanced functionality with minimum cost and weight. 
   It is a further advantage of a system according to the present invention that the present headrest adjusting system may be fully contained within a seat of a vehicle, without the need for external electronic logic support. 
   Other advantages, as well as features and objects of the present invention will become apparent to the reader of this specification. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic representation of an automotive seat according to the present invention. 
       FIG. 2  is a perspective view of a headrest adjusting mechanism according to the present invention. 
       FIG. 3  is a plan view of the top or upper portion of the present headrest adjusting system, taken in the direction of line  3 - 3  of  FIG. 2 . 
       FIG. 4  is a block diagram of a control system suitable for use with a headrest adjusting system according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As shown in  FIG. 1 , seat  10  has seat cushion  13  and seatback  12 , incorporating a headrest adjustment mechanism which positions headrest  20  upon mounting posts  14 . One such post  14  is shown in  FIG. 1 . 
   As shown in  FIG. 2 , mounting posts  14  provide a foundation for the present headrest adjusting mechanism. Each of posts  14  has a base portion,  14   a , and an eccentric portion,  14   b . Base portions  14   a  extend within seatback  12 . The lowermost portions of mounting posts  14  are attached to height control bar  30 . The attachment of posts  14   a  to height control bar  30  is facilitated by post bushings  40 , which are fitted so as to accommodate movement in a slots  38  which are provided within two portions of height control bar  30 . As explained more fully below, slots  38  allow lateral movement of mounting posts  14 , so as to facilitate fore and aft movement of headrest  20 . 
   The vertical positioning of mounting posts  14  is facilitated by elevation motor  26 , which drives lead screw  28  through nut  34 , which is attached to height control bar  30 . Motor  26  is attached to motor mounting bracket  24 , which extends between sides  22  of the seat frame. As motor  26  turns in response to command from a controller, lead screw  28  will turn within nut  34 , which will cause height control bar  30  to move either up or down, thereby moving mounting posts  14  and headrest  20  up or down as commanded. 
   System controller  90  ( FIG. 4 ) reads the actual height of headrest  20  by means of height control sensor  42 , which may, for example, be a multi-turn potentiometer geared to either motor  26  or to lead screw  28 . Those skilled in the art will appreciate in view of this disclosure that other types of position sensors, such as a linear potentiometer or a linear variable differential transformer may be used with a system according to the present invention. The measured height of headrest  20  is compared with the position of the passenger&#39;s head, which is detected by sensor  18 . Although occupant sensor  18  is preferably of the capacitive type, the present system may utilize other types of sensors known to those skilled in the art and suggested by this disclosure. 
   Mounting posts  14  extend generally vertically through post bearings  46  which are mounted at the upper portion of seat frame  22 . As with the lowermost portions of mounting post  14 , the middle portions of posts  14  extending through post bearings  46  may be displaced laterally in response to the fore and aft adjusting mechanism. This lateral movement is allowed by slots  72  formed in upper angle plate  64  and slots  76  formed in lower angle plate  68 . Fore and aft motor  54  rotates a set of three bevel gears  52 , so as to drive two lead screws  58  which are driven into nuts,  50 , housed within post bearings  46 . 
   When motor  54  rotates, mounting posts  14  will be moved either closer to each other or away from each other by the action of lead screws  58 . In the event that mounting posts  14  are moved closer to each other, headrest  20  will be caused to move closer to the passenger&#39;s head. This results from the kinematics shown in  FIG. 3 , where it is seen that as base portions  14   a  move inwardly in slots  72  formed in upper angle plate  64 , eccentric portions  14   b  are rotated forwardly because of their linkage within headrest  20 . During rotation of mounting posts  14 , primary gears  82 , which are rotationally locked to eccentric portions  14   b  of posts  14 , will rotate with eccentric portions  14   b , and secondary gears  86 , which are imposed between primary gears  82 , will assure that rotation of each of mounting posts  14  is equal. This indexing mechanism will maintain the desired parallel relationship between the seatback and headrest  20 . 
   Controller  90 , which is shown in  FIG. 4 , may be drawn either from a class of microprocessor controllers commonly employed to operate vehicular seating systems, or from other types of controllers known to those skilled in the art and suggested by this disclosure. In any event, operation of controller  90  to adjust headrest  20  may be initiated either by manual switch  92  or by feedback provided by sensor  18 . Sensor  18  may include a proximity sensor, such as a capacitive sensor mounted within headrest  20 . Other sensors useful with the present invention may include sensors measuring vehicle parameters, such as transmission gear selection and occupant sensing. In general, controller  90  will cause headrest  20  to be adjusted only if the seat  10  is occupied and if the vehicle is in a forward drive gear. If, on the other hand, the vehicle is in a reverse drive gear, or in park, headrest  20  may be placed in its lowermost and rearmost position, so as to promote the driver&#39;s ability to view the surrounding landscape through the back window of the vehicle. 
   As further shown in  FIG. 4 , controller  90  operates a plurality of actuators  94 , which include the actuators driven by elevation motor  26  and fore and aft motor  54 . 
   According to a final aspect of the present invention, a method for adjusting a passenger headrest in an automotive vehicle includes the steps of activating a head proximity sensor located in the headrest, and activating a first drive mechanism to adjust the vertical position of the headrest based upon a signal from the proximity sensor. The present method further includes the step of activating a second drive mechanism to adjust the horizontal position of the headrest based upon the signal from the proximity sensor. 
   While particular embodiments of the invention have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.