Abstract:
A seat track assembly includes first and second tracks. The second track includes a detent. A roller engages the first and second tracks for facilitating movement of the first track relative to the second track. Movement of the first track relative to the second track at a predetermined position causes the roller to engage with the detent such that the detent resists rotation of the roller, thereby temporarily retaining the first track relative to the second track at the predetermined position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of German Patent Application No. 102012201274.5 filed Jan. 30, 2012. 
     BACKGROUND OF THE INVENTION 
     This invention relates in general to adjustable seats and in particular to vehicle seats whose position may be adjusted fore and aft. 
     Vehicles, such as passenger cars, typically include seats for the use of a driver and other occupants. In many vehicles, the position of the seats may be adjusted for the comfort of the driver or the occupant. The options to adjust the position of a seat typically include the ability to move the seat fore and aft. 
     Some vehicles include the option of moving the seats in the first row in order to facilitate access to the second row. This is known as an easy entry option and is commonly seen in two-door vehicles having a front row of seats and a second row of seats located behind the front row. The easy entry option allows the generally upright back portion of the front row seat to be pivoted from its normal use position to a more forward position in order to facilitate access to the space behind the seat. Additionally, the entire seat may be unlocked so that it may be moved forward. Often, the seat is moved to its most forward position. This allows a person to more easily gain access to the space located behind the seat to sit in the second row of seats. After the person is seated in the second row of seats, the seat back of the front row seat may be raised to its normal use position, and the front row seat may be moved rearwardly from its most forward position. Some conventional front row seats include a spring mechanism to bias the front seat in its most forward position when the easy entry feature is used to prevent the front row seat from inadvertently moving rearwardly while the second row passenger is entering or exiting the vehicle. 
     SUMMARY OF THE INVENTION 
     This invention relates to vehicle seats and in particular to a vehicle seat having a seat track assembly. The seat track assembly includes first and second tracks. The second track includes a detent. A roller is engaged with the first and second tracks for facilitating movement of the first track relative to the second track. Movement of the first track relative to the second track to a predetermined position causes the roller to engage with the detent such that the detent resists rotation of the roller, thereby temporarily retaining the first track relative to the second track at the predetermined position. 
     In another aspect of the invention, a seat assembly is provided for mounting on a vehicle floor. The seat assembly includes a seat and a track assembly mounted on the seat for movably mounting the seat relative to the floor. The track assembly permits movement of the seat between an aft seating position and a forward easy entry position. The track assembly may include a first track mounted on the seat and a second track for mounting on the vehicle floor. A detent mechanism temporarily retains the seat in the forward easy entry position such that the seat may be released from the forward easy entry position towards the aft seating position by manually pulling or pushing on said the to overcome a retaining force of said detent mechanism. 
     Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side elevational view of a vehicle seat having a track assembly incorporating an easy entry feature. 
         FIG. 2  is a schematic side elevational view of the vehicle seat of  FIG. 1 , wherein the seat is in its forward easy entry position. 
         FIG. 3  is a perspective view of the track assembly of  FIG. 1 . 
         FIG. 4  is a cross-sectional view along lines  4 - 4  in  FIG. 3  of the track assembly. 
         FIG. 5  is a sectional view along lines  5 - 5  in  FIG. 4  through a portion of the track assembly incorporating the detent feature. 
         FIG. 6  is a sectional view of the portion of the track assembly of  FIG. 5 , wherein the track assembly is shown in a forward easy entry position. 
         FIG. 7  is a sectional view of a second embodiment of a track assembly incorporating a detent feature, wherein the track assembly is shown in a forward easy entry position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, there is schematically illustrated in  FIGS. 1 and 2  a vehicle seat  10 . The seat  10  may be in the form of a bucket style seat such that the seat  10  is made for single occupancy, such as a front row driver or passenger seat. However, it should be understood that the seat  10  can be configured other than what is shown and described such as, for example, a bench style seat for supporting multiple occupants. The seat  10  includes a seat bottom  12  and a seat back  14 . The seat bottom  12  and seat back  14  may be cushioned and upholstered for aesthetics and for the comfort of the occupants. The seat portion  12  and the backrest  14  may also be upholstered with leather, fabric, or other desired materials. 
     The seat  10  can include a recliner mechanism (not shown) that permits the seat back  14  to pivot relative to the seat bottom  12  to a desired generally upright normal use position. The recliner mechanism (not shown) can then be operated to a locked position to maintain the seat back  14  at the desired upright position. Thus, the seat back  14  may be moved to one of a plurality of upright normal use positions. As will be discussed below, the seat back  14  may also be pivotally mounted on the seat bottom  12  so that the seat back  14  may be moved from one of the upright normal use positions, as shown in  FIG. 1 , to a forward easy entry position, as shown in  FIG. 2 . In the forward easy entry position, the seat back  14  is positioned generally above the seat bottom  12 . The reason for moving the seat back  14  to its forward easy entry position will be described in detail below. 
     The seat  10  may include a latch assembly, indicated schematically at  16  in  FIGS. 1 and 2 . The latch assembly  16  can be operated to move the seat back  14  between an upright normal use position and the forward easy entry position. For example, the latch assembly  16  may include a lever  17  that is manually operated by the passenger to unlatch the latch assembly  16  so that the seat back  14  can be moved from the upright normal use position to the forward easy entry position. The latch assembly  16  can be integrated with the recliner mechanism (not shown), as described above, or may be separate therefrom. 
     The seat  10  is supported on a vehicle floor  18  by a seat adjustment apparatus, indicated generally at  20 . The seat adjustment apparatus  20  provides support for the seat  10 , as well as enabling the seat  10  to be moved to various longitudinal positions in the passenger compartment of the vehicle relative to the vehicle floor  18 . For example, the seat adjustment apparatus  20  permits movement of the seat  10  in fore and aft longitudinal directions (leftward and rightward, respectively, as viewing  FIGS. 1 and 2 ). The seat adjustment apparatus  20  may include one or more seat track assemblies, indicated generally at  30 . A typically arrangement would include one seat track assembly  30  mounted on an outboard side of the seat  10  and another seat track assembly  30  mounted on an inboard side of the seat  10 . In the embodiment shown in  FIGS. 1 and 2 , only the outboard seat track assembly  30  is shown. The inboard and outboard track assemblies  30  may be similar in structure and function. Therefore, only the structure and function of a single track assembly  30  will be discussed herein. 
     Referring to  FIGS. 3 and 4 , the seat track assembly  30  includes an upper track  32  and a lower track  34 . The tracks  32  and  34  may be formed from elongated sheets of metal, such as steel, that are formed and/or machined to a desired configuration. Of course, the upper and lower tracks  32  and  34  may be formed from any suitably rigid materials and may be formed as a single structure or multiple components attached together. The upper and lower tracks  32  and  34  are slidably mounted to each other such that the upper track  32  can be moved in a longitudinal direction relative to the lower track  34 . For example, in the embodiment of the track assembly  30  shown in  FIG. 4 , a portion of the upper track  32  is telescopically disposed within the lower track  34 . The upper track  32  may be mounted to the seat bottom  12  by any suitable manner. For example, the upper track  32  of the track assembly  30  may include mounting bolts  36  that extend upwardly therefrom for securing the upper track  32  to an underside  38  of the seat bottom  12 . The lower track  34  is preferably fixedly mounted to the vehicle floor  18 . It should be understood that the terms upper and lower as used herein are for reference only and the track assemblies  30  may be oriented differently than what is shown in  FIGS. 1-4 . For example, the track assemblies  30  may be arranged in an angled or sideways manner such that the lower track  34  is mounted to a side wall of the vehicle floor  18  instead of a generally horizontal floor  18  shown in  FIGS. 1 and 2 . 
     The upper track  32  may be configured to slide relative to the lower track  34  with the assistance of multiple rollers disposed between portions of the tracks  32  and  34 . In the embodiment shown in  FIGS. 4 through 6 , there is a lower outboard row of rollers  40 , a lower inboard row of rollers  42 , an upper outboard row of rollers  44 , and an upper inboard row of rollers  46 . Each row of rollers  40 ,  42 ,  44 , and  46  may have a plurality of rollers arranged and spaced from each other along the longitudinal lengths of the tracks  32  and  34 . For example, there are three rollers  40   a  shown in  FIGS. 5 and 6  which illustrate a portion of the upper and lower tracks  32  and  34 . The row of rollers  42 ,  44 , and  46  may have a plurality of rollers  42   a,    44   a,  and  46   a,  respectively. The plurality of rollers within the row of rollers  40 ,  42 ,  44 , and  46  may extend along the entire length of the upper and lower tracks  32  and  34  or may be located only at select portions thereof. For example, it may be sufficient to only include groups of rollers  40   a,    42   a,    44   a,  and  46   a  at end portions of the tracks  32  and  34 . Although the rollers  40   a,    42   a,    44   a,  and  46   a  are shown and described as being spherical in shape, it should be understood that the rollers  40   a,    42   a,    44   a,  and  46   a  may have a shape other than spherical, such as cylindrical. Additionally, the rollers  40   a,    42   a,    44   a,  and  46   a  may be identically shaped and sized or may be sized differently from one another. For example, as shown in  FIG. 4 , the rollers  40   a  and  42   a  of the row of rollers  40  and  42  are larger in diameter than the rollers  44   a  and  46   a  of the row of rollers  44  and  46 . This arrangement of larger diameter rollers  40   a  and  42   a  accommodates the different loads acting on the rollers  40   a,    42   a,    44   a,  and  46   a  due to the specific configuration of the seat track assembly  30 . 
     It may also be desirable to include a cage (not shown) which can be disposed between the upper and lower tracks  32  and  34  and confines the rollers  40   a,    42   a,    44   a,  and  46   a  such that they are secured in a spaced relationship with one another, while still being permitted to roll along the lengths of the upper and lower tracks  32  and  34 . The cage (not shown) may be in the form of an elongated strip having holes formed therein which loosely hold the rollers  40   a,    42   a,    44   a,  and  46   a  in their desired placement. Alternatively, the rollers  40   a,    42   a,    44   a,  and  46   a  may be freely disposed between the upper and lower tracks  32  and  34 . Thus, the rollers  40   a,    42   a,    44   a,  and  46   a  may be permitted to move relative to one another in the longitudinal direction along the upper and lower tracks  32  and  34 . 
     The upper and lower tracks  32  and  34  can have any shape which is suitable to permit the upper track  32  to slide relative to the lower track  34 . Thus, the upper and lower tracks  32  and  34  can have any suitable construction which permits a sliding mounting arrangement. In the embodiment illustrated in  FIG. 4 , the track assembly  30  includes four rows of rollers  40 ,  42 ,  44 , and  46  which roll along adjacent portions of the upper and lower tracks  32  and  34 . To accommodate the rollers  40   a,    42   a,    44   a,  and  46   a,  the upper track  32  includes first and second inner walls  50  and  52  connected together by an upper web  53 . As shown in  FIG. 3 , the mounting bolts  36  are secured to the upper web  53  for attachment of the upper track  32  to the seat bottom  12 . Referring back to  FIG. 4 , the upper track  32  further includes first and second outer walls  54  and  56 . The upper track  32  includes a first generally laterally extending portion  58  that connects the first inner wall  50  with the first outer wall  54 . The upper track  32  also includes a second generally laterally extending portion  60  that connects the second inner wall  52  with the second outer wall  56 . 
     The first extending portion  58  includes a bent portion  62  having an arcuate engagement surface  64 . The rollers  40   a  of the row of rollers  40  engage and roll along the engagement surface  64  as the upper track  32  moves relative to the lower track  34 . The first outer wall  54  includes an end portion  66  having an arcuate engagement surface  68 . The rollers  44   a  of the row of rollers  44  engage and roll along the arcuate engagement surface  68  as the upper track  32  moves relative to the lower track  34 . Similarly, the second extending portion  60  includes a bent portion  70  having an arcuate engagement surface  72 . The rollers  42   a  of the row of rollers  42  engage and roll along the arcuate engagement surface  72  as the upper track  32  moves relative to the lower track  34 . The second outer wall  56  includes an end portion  74  having an arcuate engagement surface  76 . The rollers  46   a  of the row of rollers  46  engage and roll along the arcuate engagement surface  76  as the upper track  32  moves relative to the lower track  34 . 
     The lower track  34  includes first and second outer walls  80  and  82  which are connected together by a generally horizontally extending floor portion  84 . The floor portion  84  may be fixedly attached to the vehicle floor  18  by any suitable manner, such as by mounting bolts (not shown). The lower track  34  includes a first corner portion  86  connecting the first outer wall  80  with the floor portion  84 . The corner portion  86  includes an arcuate engagement surface  88 . The rollers  40   a  of the row of rollers  40  engage and roll along the arcuate engagement surface  88  as the upper track  32  moves relative to the lower track  34 . The lower track  34  also includes a second corner portion  90  connecting the second outer wall  82  with the floor portion  84 . The corner portion  90  includes an arcuate engagement surface  92 . The rollers  42   a  of the row of rollers  42  engage and roll along the arcuate engagement surface  92  as the upper track  32  moves relative to the lower track  34 . 
     The lower track  34  includes first and second inner walls  96  and  98 . The first inner wall  96  is connected to the first outer wall  80  via a first web portion  100  having a corner portion  102 . The corner portion  102  includes an arcuate engagement surface  104 . The rollers  44   a  of the row of rollers  44  engage and roll along the arcuate engagement surface  104  as the upper track  32  moves relative to the lower track  34 . The second inner wall  98  is connected to the second outer wall  82  via a second web portion  106  having a corner portion  108 . The corner portion  108  includes an arcuate engagement surface  110 . The rollers  46   a  of the row of rollers  46  engage and roll along the arcuate engagement surface  110  as the upper track  32  moves relative to the lower track  34 . 
     The track assembly  30  may include a lock assembly, indicated schematically at  120  in  FIGS. 3 and 4 . The lock assembly  120  enables the seat occupant to adjust the fore and aft position of the seat  10  relative the vehicle floor  18  and then retain or lock the seat  10  in a desired position. The lock assembly  120  can be any suitable apparatus which permits the upper and lower tracks  32  and  34  to move relative to one another and then selectively lock the upper and lower tracks  32  and  34  relative to one another once moved to a desired position. In the illustrated embodiment of  FIG. 4 , the locking assembly  120  includes a catch  122  which is movable between a locked position, as indicated by solid lines  122 , and an unlocked position, indicated generally by broken lines  122   a.  The catch  122  may be moved by any suitable manner. For example, the lock assembly  120  may include a handle  121 , as shown in  FIG. 3 , which extends outwardly from between the upper and lower tracks  32  and  34  such that movement of the handle  121  caused the catch  122  to move between its locked and unlocked positions. The catch  122  includes ends  124  which are moved vertically within slots  126  formed in the inner walls  50  and  52  of the upper track  32 . The ends  124  of the catch  122  also extend through slots  128  formed in the outer walls  54  and  56  of the upper track  32 . The lock assembly  120  and the catch  122  are mounted on the upper track  32  and thus move with the upper track  32  as the upper track  32  moves relative to the lower track  34 . The lower track  34  includes a plurality of slots  130  formed in the inner walls  96  and  98 . The plurality of slots  130  extend along the longitudinal length of the lower track  34  and may be equally spaced from one another. 
     When the catch  122  of the lock assembly  120  is in its locked position, each of the ends  124  of the catch  122  extend through an associated one of the slots  130 . The slot  130  may be sized to have the same width or slightly wider than the ends  124  of the catch  122 , so that the ends  124  of the catch  122  are trapped within the respective slots  130 , thereby preventing movement of the upper track  32  relative to the lower track  34 . When the seat occupant wants to adjust the position of the seat  10  relative to the vehicle floor  18 , the occupant manipulates the handle  121  to cause the catch  122  to be moved to its unlocked position  122   a,  as shown in  FIG. 4 . In the unlocked position, the ends  124  of the catch  122  extend downwardly and out from the slots  130 . The upper track  32  can then be moved relative to the lower track  34  to a desired position. The handle  121  is then moved to cause the ends  124  of the catch  122  to move upwardly into different slots  130  of the inner walls  96  and  98  of the lower track  34 . The catch  122  can be a single member which moves into a single pair of opposed slots  130  or may include multiple members or ends  124  which simultaneously extend into multiple slots  130  along the length of the lower track  34 . As stated above, the lock assembly  120  can be any suitable apparatus other than that illustrated to selectively lock the upper track  32  relative to the lower track  34  in a desired position. 
     The seat  10  may be configured such that it includes an easy entry feature. An easy entry feature enables the seat  10  to be moved from an upright normal use position, as shown in  FIG. 1 , to a forward easy entry position, as shown in  FIG. 2 . In the forward easy entry position, the seat  10  is moved forward in the vehicle and the seat back  14  is pivoted to a forward position above the seat bottom  12 . When the seat  10  is in the forward easy entry position, a passenger can more easily enter and exit the rear of the vehicle. For example, if the seat  10  is installed as a front row seat in a two door coupe vehicle, the easy entry feature would permit the seat  10  to be moved forward to expand the room within the passenger compartment so that a passenger could more easily enter through the respective door to get to a second row seat located behind the front row seat  10 . Once the passenger is seated in the second row seat, the seat  10  can be moved back to its upright normal use position. 
     The seat  10  can be operated by any suitable manner to move it between the upright normal use position and the forward easy entry position. For example, as described above, the seat  10  may include a latch assembly  16  for locking and releasing the seat back  14  from its upright normal use position. To initiate the easy entry mode, the lever  17  of the latch assembly  16  is operated, thereby unlatching the seat back  14  from the seat bottom  12 . The seat back  14  can then be pivoted to its forward easy entry position above the seat bottom  12 . The seat  10  may also be slid forward to a forward easy entry position, as shown in  FIG. 2 , such that the upper track  32  is moved forward relative to the lower track  34 . To permit the sliding movement of the seat  10  relative to the vehicle floor  18 , the seat  10  may include an actuator, indicated schematically at  140  in  FIGS. 1 and 2 , that actuates the lock assembly  120  to release the catch  122  from the slots  130 . The actuator  140  may be automatically actuated upon movement of the seat back  14  to its forward easy entry position above the seat bottom  12 . Thus, when the seat back  14  is pivoted forward to a sufficient angle relative to the seat bottom  12 , the actuator  140  operates the lock assembly  120  to move the catch  122  from out of the slots  130 . When the catch  122  is withdrawn from the slots  130 , the upper track  32  is free to move relative to the lower track  34 . Thus, the seat  10  can then be pushed or pulled to its forward easy entry position, as shown in  FIG. 2 . The actuator  140  can include any suitable mechanism, such as a cable (not shown), that operates the catch  122  upon the pivoting motion of the seat back  14 . After the passenger has entered or exited the second row seat, the seat  10  can be slid rearwardly back to its upright normal use position, as shown in  FIG. 1 . 
     The actuator  140  and the lock assembly  120  can be configured such that when the seat back  14  is pivoted upward and the seat  10  is slid rearwardly to its normal use position, the actuator  140  actuates the lock assembly  120  so that the catch  122  reengages with the slots  130 . The lock assembly  120  may include a memory feature (not shown) which enables the lock assembly  120  to remember the position that the seat  10  was in when the easy entry feature is used so that the seat  10  is returned automatically to that specific seat position after being moved from the forward easy entry position. Alternatively, the lock assembly  120  may be configured such that when the seat  10  is slid rearwardly after the easy entry mode, the lock assembly  120  is actuated at a specific location to lock the seat  10  back to the same position after every easy entry mode regardless of the position that the seat  10  was in prior to engaging the easy entry mode. 
     To help prevent the seat  10  from moving once it is in the forward easy entry position after initiating an easy entry mode, the seat  10  preferably includes a detent mechanism, such as indicated generally at  150  in  FIGS. 5 and 6 . The detent mechanism  150  retains the seat  10  in its forward easy entry position. Once the passenger is seated in the second row seat, the detent mechanism  150  can be operated to release the seat  10  from its forward easy entry position so that the seat  10  can be slid back to one upright normal use positions. An advantage of the detent mechanism  150  is that that the seat  10  will generally not move from its forward easy entry position until it is desired to move the seat  10 . If the seat  10  were mounted at an incline, for example, the detent mechanism  150  may prevent the seat  10  from moving backwards before the user wants to move the seat  10 . 
     In the illustrated embodiment of the detent mechanism  150  shown in  FIGS. 5 and 6 , the detent mechanism  150  is defined as formations formed in the lower track  34  that interact with the rollers  40   a  to retain the rollers  40   a  from moving, thereby preventing the upper track  32  from moving relative to the lower track  34 . More specifically, the lower track  34  includes one or more slots or holes  152  formed therein. The spacing between the holes  152  may be the same as the spacing between the associated ones of the plurality of rollers  40   a.    FIG. 5  illustrates a portion of the track assembly  30  when the seat  10  is not in the forward easy entry position. For example, the track assembly  30  may be in one of the plurality of upright positions set by the occupant of the seat  10 . In this position, the rollers  40   a  are spaced from the holes  152 . The rollers  40   a  are engaged with the engagement surfaces  64  and  88  of the upper and lower tracks  32  and  34 , respectively. As shown in  FIG. 5 , the portions of the engagement surfaces  64  and  68  which are contacted by the rollers  40   a  are preferably continuous arcuate surfaces to permit smooth rolling when the seat is moved between its plurality of upright positions. However, when the seat  10  is moved to its forward dumped position, such as during an easy entry mode, the rollers  40   a  engage with the holes  152  of the detent mechanism  150 , as shown in  FIG. 6 . Once seated, the holes  152  mechanically resist rotation of the rollers  40   a  along the length of the upper and lower tracks  32  and  34 . Note that if multiple rollers  40   a  and holes  152  are used for the detent mechanism  150 , the rollers  40   a  may move over one or more holes  152 . Thus, the detent mechanism  150  may have more than one position. Alternatively, the rollers  40   a  and the holes  152  may be spaced such that each roller  40   a  will only engage with one corresponding hole  152 . 
     The holes  152  may have a width W which is less than the diameter of the rollers  40   a.  This prevents the rollers  40   a  from falling therethrough, while permitting the rollers  40   a  to be retained within the holes  152 . Note that the load acting on the upper track  32  from the weight of the seat  10  acts to push the rollers  40   a  downwardly into the holes  152 . The rollers  40   a  and the holes  152  are preferably sized so that the seat  10  can be manually pushed or pulled by a user to unseat the rollers  40   a  from the holes  152 , thereby permitting the upper track  32  to be freely moved in a rearward direction relative to the lower track  34 . This unseating force slightly raises the rollers  40   a  from out of the respective holes  152  to a position such that the rollers  40   a  are on top of the engagement surface  88  of the lower track  34 , as shown in  FIG. 5 . Thus, a user can simply push or pull on the seat  10  in a generally horizontally longitudinal direction to unseat the rollers  40   a  from the holes  152 . The dimensions of the rollers  40   a  and the holes  152 , along with the weight of the seat  10 , generally determine the force necessary to unseat the rollers  40   a.  Generally, the force required to unseat the rollers  40   a  will be reduced with a smaller width W of the hole  152  compared to the widths or diameters of the rollers  40   a.  The seat track assembly  30  may also include a stop (not shown) which prevents the upper track  32  from moving beyond a furthermost forward position and a furthermost rear position relative to the lower track  34 . The stop can be any suitable mechanism or feature, such as an interference (not shown) formed in the upper and/or lower tracks  32  and  34  that prevents the further relative movement of the upper and lower tracks  32  and  34 . 
     It should be understood that the fit and assembly of the upper and lower tracks  32  and  34  and the rollers  40   a,    42   a,    44   a,  and  46   a  may be sized to accommodate clearance between these components. Thus, the seat track assembly  30  may have some “play” to accommodate vertical and lateral movement between the upper track  32 , lower track  34 , and the rollers  40   a,    42   a,    44   a,  and  46   a.  Thus,  FIG. 4  schematically illustrates the generally placement of the rollers  40   a,    42   a,    44   a,  and  46   a  relative to their respective engagement surfaces. This clearance or “play” permits the rollers  40   a,    42   a,    44   a,  and  46   a  to be seated and unseated from the holes  152  even when a generally vertical load or force is applied to the seat track assembly  30 . 
     It should be understood that the detent mechanism  150  may be placed anywhere along the length of the upper and lower tracks  32  and  34  so that the seat  10  may be retained in a desired position. For seats  10  having easy entry features, it may be desirable to locate the detent mechanism  150  such that the rollers  40   a  are retained when the seat  10  is in its furthermost forward position. However, the forward easy entry position may not necessarily be the furthermost possible forward position of the seat  10  relative to the vehicle floor  18 . The seat track assembly  30  may also include a stop (not shown) which prevents the upper track  32  from moving beyond the furthermost possible forward position and/or the forward easy entry position. 
     An advantage of the use of the detent mechanism  150  over conventional seats that they use separate locking mechanisms to maintain the seat  10  in its forward easy entry position is that the user need not activate a release handle or switch but simply instead moves the seat rearwardly. The detent mechanism  150  simply temporarily retains the seat  10  in a forward easy entry position until a user moves the seat  10 . The detent mechanism  150  also provides a relatively low cost in the manufacture and assembly cost of the seat  10  compared to conventional seats with separate easy entry locking mechanisms. Although the seat  10  has been described to be in a forward and dumped position as shown in  FIG. 5 , it should be understood that the seat back  14  does not necessarily have to be pivoted forward to a position above the seat bottom  12  as shown in  FIG. 2 , but may simply remain in its upright position. An advantage of the seat back  14  being moved to its forward position is that more space is generated to permit the passenger to move through the door opening of the vehicle. 
     Although  FIGS. 5 and 6  illustrate three rollers  40   a  seating in three holes  152 , it should be understood that any number of holes  152  may be used for seating any suitable number of rollers  40   a.  It should also be understood that the detent mechanism  150  may be located at any suitable location along the length of the upper and lower tracks  32  and  34 . The detent mechanism  150  may be used with just one row of rollers  40 ,  42 ,  44 , or  46  or with any combination thereof. For example, holes (not shown) similar to the holes  152  can be formed in other portions of the lower track  34  to interact with the rollers  42   a,    44   a,  and/or  46   a.  Alternatively, the holes  152  may be formed in the upper track  32  or in both the upper and lower tracks  32  and  34 . 
     Although the detent mechanism  150  has been described above with respect to holes  152  formed through the lower track  24 , it should be understood that other types of detent mechanisms may be employed. For example, there is schematically illustrated in  FIG. 7  a second embodiment of a seat track assembly, indicated generally at  160 , which may be mounted to the seat  10 . The seat track assembly  160  includes an upper track  162  and a lower track  164 . A plurality of rollers  166  are disposed between the upper and lower tracks  162  and  164 . A detent mechanism, indicated generally at  170  interacts with the rollers  166  disposed between the upper and lower tracks  162  and  164 . The detent mechanism  170  includes formations formed in the lower track  164  but in the form of depressions or raised portions  172 . To retain the seat  10  in a forward easy entry position, one or more of the rollers  162  is trapped or prevented from longitudinal movement along an engagement surface  174  of the lower track  164 . As with the holes  152  of the detent mechanism  150  described above, the raised portions  172  of the detent mechanism  170  resist rotation of the rollers  166  when trapped within the raised portions  172 . The raised portions  172  can have any suitable profile or shape to retain or resist movement of the rollers  166  in the longitudinal direction. For example, the raised portions  172  may have abrupt or steep inclines or may include a more gradual incline. As shown in  FIG. 7 , each side of the raised portions  172  may have different incline profiles  174  and  176 . 
     The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.