WO2009003282A1

WO2009003282A1 - Off-set seat track assembly

Info

Publication number: WO2009003282A1
Application number: PCT/CA2008/001222
Authority: WO
Inventors: David J. Wrong; James E. Basley; Rick J. Kalaska; Laura Vujovich
Original assignee: Intier Automotive Inc.
Priority date: 2007-07-03
Filing date: 2008-06-30
Publication date: 2009-01-08

Abstract

A seat track assembly is adapted to mount a seat to a floor of an automotive vehicle and provide selective forward and rearward adjustment of the seat among a plurality of seating positions. The seat track assembly includes a first track and a second track that is slidably coupled to the first track. A first rolling element is positioned between the first and second tracks on a first side of the seat track assembly. The first rolling element is only vertically constrained between the first and second tracks, thereby allowing lateral alignment of the first rolling element between the first and second tracks. Second and third rolling elements are positioned between the first and second tracks on a second side of the seat track assembly. The second rolling element is vertically and laterally constrained between the first and second tracks.

Description

OFF-SET SEAT TRACK ASSEMBLY

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to a seat track assembly for a vehicle seat assembly.

More particularly, the invention relates to a seat track assembly having rolling elements on one side of the seat track assembly which are vertically and laterally constrained and rolling elements on another side of the seat track assembly which are only vertically constrained.

2. Description of Related Art

[0002] Automotive vehicles include seats for supporting occupants within the vehicle.

Vehicle seats typically include a pair of seat track assemblies interconnecting the seat to a floor of the vehicle to allow selective locking and adjustment of the seat along the floor of the vehicle among a plurality of fore and aft seating positions. Each seat track assembly typically includes a fixed track that is fixedly secured to the floor of the vehicle and a movable track that is slidably coupled to the fixed track and fixedly secured to the bottom of the seat.

[0003] It is well known to provide a plurality of rolling elements or bearings between the fixed track and the movable track to reduce friction and facilitate movement of the movable track relative to the fixed track. One example of such a seat track assembly is disclosed in United States Patent 5,741,000 ("the OOO reference"), which issued to Goodbred on April 21, 1998. The OOO reference discloses a seat track assembly 10 including an elongated fixed track structure 12 and a cooperating movable track structure 14. The seat track assembly 10 also includes a plurality of rolling elements 16, which are mounted in a pair of rolling assemblies 18, and a plurality of guide elements 20. More specifically, each side of the seat track assembly 10 includes a rolling assembly 18 disposed between the fixed track 12 and the movable track 14. The guide elements 20 are mounted along both sides of the movable track 14 and cooperate with portions of the fixed track 12 to prevent vertical separation of the fixed 12 and movable 14 tracks.

[0004] The rolling elements on both sides of a conventional seat track assembly are vertically and laterally constrained when the fixed track and the movable track are mated to each other. As such, variation in the profiles of the fixed and movable tracks from manufacturing can greatly increase or decrease the interference with the rolling elements and as a result can increase the level of effort required to adjust the seat fore and aft. In order to establish an acceptable level of effort adjustment must be made to account for any manufacturing variations to maintain a repeatable interference between the rolling elements and the tracks for each seat track assembly. Plastic guide elements are often provided to prevent relative vertical movement between the fixed and movable tracks in a direction tending to separate them vertically. To adjust the vertical interference between the rolling elements and the tracks the guide elements are shaved using a broaching tool. In other instances, different sizes of rolling elements or ball bearings can be maintained such that when the fixed and movable tracks are assembled suitably sized rolling elements can be selected depending on the desired amount of interference. Changing the size of the rolling elements will adjust both the vertical and lateral interferences.

[0005] Adjusting the interferences as set forth above by shaving plastic guide elements or maintaining various sizes of rolling elements is time consuming and costly. It therefore remains desirable to provide a seat track assembly having rolling elements on one side of the seat track assembly which are vertically and laterally constrained and rolling elements on another side of the seat track assembly which are only vertically constrained.

SUMMARY OF THE INVENTION

[0006] According to one aspect of the invention, a seat track assembly is adapted to mount a seat to a floor of an automotive vehicle and provide selective forward and rearward adjustment of the seat relative to the floor among a plurality of seating positions. The seat track assembly includes a first track that is adapted to be fixedly secured to the floor of the vehicle and a second track that is adapted to be fixedly secured to the seat and slidably coupled to the first track. The seat track assembly also includes a first rolling element that is positioned between the first and second tracks on a first side of the seat track assembly. The first rolling element is only vertically constrained between the first and second tracks, thereby allowing lateral alignment of the first rolling element between the first and second tracks. The seat track assembly further includes second and third rolling elements that are positioned between the first and second tracks on a second side of the seat track assembly. The second and third rolling elements are vertically and laterally constrained between the first and second tracks. [0007] According to a another aspect of the invention, a seat track assembly is adapted to mount a seat to a floor of an automotive vehicle and provide selective forward and rearward adjustment of the seat relative to the floor among a plurality of seating positions. The seat track assembly includes a first track that is adapted to be fixedly secured to the floor of the vehicle and a second track that is adapted to be fixedly secured to the seat and slidably coupled to the first track. The seat track assembly also includes first and fourth rolling elements that are positioned between the first and second tracks on a first side of the seat track assembly. The first and fourth rolling elements are only vertically constrained between the first and second tracks, thereby allowing lateral alignment of the first and fourth rolling elements between the first and second tracks. The seat track assembly further includes second and third rolling elements that are positioned between the first and second tracks on a second side of the seat track assembly. The second and third rolling elements are vertically and laterally constrained between the first and second tracks.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

[0009] Figure 1 is a cross-sectional view of a seat track assembly according to a first embodiment of the invention;

[0010] Figure 2 is a cross-sectional view of a seat track assembly with a narrower profile relative to the seat track assembly of Figure 1;

[0011] Figure 3 is a cross-sectional view of a first seat track assembly according to a second embodiment of the invention;

[0012] Figure 4 is a cross-sectional view of a second seat track assembly according to the second embodiment of the invention;

[0013] Figure 5 is a cross-sectional view of a third seat track assembly according to the second embodiment of the invention;

[0014] Figure 6 is a cross-sectional view of a fourth seat track assembly according to the second embodiment of the invention; [0015] Figure 7 is a cross-sectional view of a fifth seat track assembly according to the second embodiment of the invention;

[0016] Figure 8 is a cross-sectional view of a sixth seat track assembly according to the second embodiment of the invention;

[0017] Figure 9 is a cross-sectional view of a first seat track assembly according to the third embodiment of the invention;

[0018] Figure 10 is a cross-sectional view of a second seat track assembly according to the third embodiment of the invention;

[0019] Figure 11 is a cross-sectional view of a first seat track assembly according to a fourth embodiment of the invention; and

[0020] Figure 12 is a cross-sectional view of a second seat track assembly according to the fourth embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0021] Referring to Figure 1, a seat track assembly, generally shown at 10, is provided for slidably interconnecting a vehicle seat 12 to a floor 14 of an automotive vehicle. Typically, a pair of seat track assemblies 10 is disposed between the seat 12 and the floor 14, however, for simplicity only one seat track assembly 10 is shown in the Figures. The seat track assembly 10 allows selective forward and rearward adjustment of the seat 12 among a plurality of seating positions along the floor 14 of the vehicle.

[0022] The seat track assembly 10 includes a fixed or inner track, generally indicated at 18, that is typically formed from sheet steel and adapted to be fixed to the floor 14 of the vehicle. The fixed track 18 has a U-shaped cross-section defined by a generally horizontal lower portion 20 having first 22 and second 24 laterally spaced upstanding sides extending upwardly therefrom and terminating at distal ends 26, 28, respectively. A generally horizontal first outer flange 30 extends laterally outward from the distal end 26 of the first side 22. Top and bottom sides of the first outer flange 30 define first 32 and second 33 flat bearing surfaces, respectively. The first 32 and second 33 flat bearings surfaces extend longitudinally with respect to the fixed track 18. A depending free end portion 34 extends downwardly from the first outer flange 30 and is spaced laterally outward from the first side 22. A second outer flange 36 includes a generally horizontal first portion 38 extending laterally outward from the second side 24 and a second portion 40 extending downwardly at an angle relative to the first portion 38. In the embodiment shown, the second portion 40 extends downwardly from the first portion 38 at an angle of approximately forty-five degrees (45°). Top and bottom sides of the second portion 40 define third 42 and fourth 44 flat bearing surfaces, respectively. The third 42 and fourth 44 flat bearing surfaces extend longitudinally with respect to the fixed track 18. A depending free end portion 46 extends downwardly from the second portion 40 of the second outer flange 36 and is spaced laterally outward from the second side 24.

[0023] The seat track assembly 10 also includes a movable or outer track, generally indicated at 48, that is typically formed from sheet steel and adapted to be fixedly secured to the seat 12 and slidably coupled to the fixed track 18. The movable track 48 has a U-shaped cross-section that is inverted relative to the fixed track 18 and defined by a generally horizontal upper portion 50 having first 52 and second 54 laterally spaced depending sides extending downwardly therefrom and terminating at downwardly facing convex portions 56, 58, respectively. Upstanding free end portions 60, 62 that are spaced laterally inward relative to the first 52 and second 54 sides extend upwardly from the respective convex portions 56, 58. The upper portion 50 defines a first concave bearing surface 64 adjacent the first side 52 of the movable track 48 which corresponds to or is aligned with the first flat bearing surface 32 of the fixed track 18. The first concave bearing surface 64 extends longitudinally with respect to the movable track 48. The upstanding free end portion 60 of the first side 52 includes a plurality of plastic guide elements 66 mounted thereto. Each of the guide elements 66 includes an upwardly facing surface 68 that is engaged with the second flat bearing surface 33 of the fixed track 18 to prevent vertical separation of the movable track 48 from the fixed track 18. A corner portion 72 between the upper portion 50 and the second side 54 of the movable track 48 defines a second concave bearing surface 74 that corresponds to or is aligned with the third flat bearing surface 42 of the fixed track 18. The second concave bearing surface 74 extends longitudinally with respect to the movable track 48. The upstanding free end portion 62 of the second side 54 includes an arcuate portion 75 that defines a third concave bearing surface 76 that corresponds to or is aligned with the fourth flat bearing surface 44 of the fixed track 18. [0024] The seat track assembly 10 can be utilized with a power-actuating mechanism

(not shown), in which the power-actuating mechanism serves as a means for adjusting the movable track 48 relative to the fixed track 18 and for retaining the movable track 48 in any position of adjustment. In the alternative, when manual operation is contemplated, a releasable latching mechanism (not shown) may be utilized. As is well known in the art, the releasable latching mechanism is operable between an unlocked position for allowing selective adjustment of the movable track 48 relative to the fixed track 18 and a locked position for retaining the movable track 48 in any position of adjustment.

[0025] On a first side of the seat track assembly 10, generally indicated at 78, a plurality of first rolling elements or ball bearings 80 is positioned between the first concave bearing surface 64 of the movable track 48 and the first flat bearing surface 32 of the fixed track 18. On a second side of the seat track assembly 10, generally indicated at 82, a plurality of second rolling elements or ball bearings 84 is positioned between the second concave surface 74 of the movable track 48 and the third flat bearing surface 42 of the fixed track 18. Also on the second side 82 of the seat track assembly 10, a plurality of third rolling elements or ball bearings 86 is positioned between the third concave bearing surface 76 of the movable track 48 and the fourth flat bearing surface 44 of the fixed track 18. In the embodiment shown, the line of contact between the second bearings 84 and the third flat bearing surface 42 and the line of contact between the third bearings 86 and the fourth flat bearing surface 44 are directly opposing. The first 80, second 84, and third 86 bearings reduce friction between the fixed 18 and movable 48 tracks during sliding movement of the movable track 48 relative to the fixed track 18.

[0026] Typically, in the prior art, rolling elements on both sides of a seat track assembly are subject to vertical and lateral compression, or in other words, the rolling elements are vertically and laterally constrained between a fixed track and a movable track. Therefore, any variations in the profile of either the fixed track or the movable track that arise during the manufacturing process can greatly increase or decrease the amount of interference with the rolling elements, which in turn can increase the travel effort required to adjust the seat fore and aft.

[0027] The second 84 and third 86 bearings on the second side 82 of the seat track assembly 10 are vertically and laterally constrained between the fixed 18 and movable 48 tracks. It is appreciated, however, that the upstanding free end portion 62 of the second side 54 of the movable track 48 is springingly flexible to allow for lateral alignment of the movable track 48 relative to the fixed track 18. Such lateral alignment reduces variation to travel efforts due to variations in the profile of either the fixed track 18 or the movable track 48 that arise during the manufacturing process. Such bearing compliance also reduces the wear to the seat track assembly 10.

[0028] In order to allow the lateral alignment of the movable track 48 relative to the fixed track 18, the first bearings 80 and the guide elements 66 on the first side 78 of the seat track assembly 10 are only vertically constrained between the fixed 18 and movable 48 tracks. The first bearings 80 and the guide elements 66 have the ability to move laterally due to contact with the first 32 and second 33 flat bearing surfaces, respectively. The first bearings 80 are preferably made of hardened steel or a material that is harder than the material of the fixed track 18 with which the first bearings 80 rollingly engage so that the first bearings 80 will burnish a groove into the first flat bearing surface 32. Therefore, the first bearings 80 and the guide elements 66 will self-locate laterally and any manufacturing variation in the profile of either the fixed track 18 or the movable track 48 will not contribute to a high travel effort to adjust the seat 12 fore and aft. The interference in a vertical direction is controlled by using a broaching tool to shave or remove excess material from the upwardly facing surface 68 of each of the guide elements 66. It is appreciated that the guide elements 66 normally have more material on the upwardly facing surface 68 than would be needed so as to ensure that there will be material removed during the broaching operation.

[0029] The first side 78 of the seat track assembly 10 normally corresponds to the non-latching side and the second side 80 of the seat track assembly 10 normally corresponds to the latching side, i.e., the side of the seat track assembly 10 with the latching mechanism. It is appreciated, however, that either the first 78 or second 80 side of the seat track assembly 10 may correspond to the latching side, without varying from the scope of the invention.

[0030] Referring to Figures 2 through 12, it is appreciated that any number of track profiles may be used for the fixed track 18 and the movable track 48 without varying from the scope of the invention. For example, referring to Figure 2, the second portion 40 of the fixed track 18 extends downwardly from the first portion 38 at an angle of approximately twenty-two and a half degrees (22.5°), rather than forty-five degress (45°), such that the overall packaging width of the track assembly 10 is reduced. Top and bottom sides of the second portion 40 define fourth 88 and fifth 90 concave bearing surfaces, respectively. The fourth 88 and fifth 90 concave bearing surfaces extend longitudinally with respect to the fixed track 18.

[0031] On the first side 78 of the seat track assembly 10, the first bearings 80 are positioned between the first concave bearing surface 64 of the movable track 48 and the first flat bearing surface 32 of the fixed track 18. Thus, the first bearings 80 on the first side 78 of the seat track assembly 10 are only vertically constrained between the fixed 18 and movable 48 tracks. On the second side 82 of the seat track assembly 10, the second bearings 84 are positioned between the second concave bearing surface 74 of the movable track 48 and the fourth concave bearing surface 88 of the fixed track 18. Also on the second side 82 of the seat track assembly 10, the third bearings 86 are positioned between the third concave bearing surface 76 of the movable track 48 and the fifth concave bearing surface 90 of the fixed track 18. Thus, the second 84 and third 86 bearings on the second side 82 of the seat track assembly 10 are vertically and laterally constrained between the fixed 18 and movable 48 tracks. The fourth 88 and fifth 90 concave bearing surfaces are oriented such that the line of contact between the second bearings 84 and the fourth concave bearing surface 88 and the line of contact between the third bearings 86 and the fifth concave bearing surface 90 are not directly opposing, which reduces the amount of wear to the fixed 18 and movable 48 tracks.

[0032] Referring to Figures 3 through 8, wherein like primed reference numerals represent similar elements as those described above, in a second embodiment of the invention the guide elements 66 have been replaced with a plurality of fourth rolling elements or ball bearings 92. While it is appreciated that the particular profiles of the fixed 18' and movable 48' tracks are different in Figures 3 through 8, it is apparent that the first 80' and fourth 92 rolling elements on the first side 78' of the seat track assembly 10' are only vertically constrained between the fixed 18' and movable 48' tracks. In contrast, the profiles of the fixed 18' and movable 48' tracks on the second side 82' of the seat track assembly 10' are substantially the same as that shown in Figure 2, and as such, the second 84' and third 86' bearings are vertically and laterally constrained between the fixed 18' and movable 48' tracks.

[0033] More specifically, referring to Figure 3, the first bearings 80' are positioned between the first concave bearing surface 64' of the movable track 48' and the first flat bearing surface 32' of the fixed track 18'. Further, a corner portion 94 between the first side 22' and the first outer flange 30' of the fixed track 18' defines a sixth concave bearing surface 96. Additionally, the upstanding free end portion 60' of the first side 52' of the movable track 48' is formed to include a lateral portion 98 at the distal end that extends laterally inward toward the first side 22' of the fixed track 18'. The lateral portion 98 defines a fifth flat bearing surface 100 which corresponds to the sixth concave bearing surface 96 of the fixed track 18'. The fourth bearings 92 are positioned between the fifth flat bearing surface 100 of the movable track 48' and the sixth concave bearing surface 96 of the fixed track 18'.

[0034] Referring to Figure 4, the first bearings 80' are positioned between the first concave bearing surface 64' of the movable track 48' and the first flat bearing surface 32' of the fixed track 18'. Further, the depending free end portion 34' of the first side 22' of the fixed track 18' is formed to include a lateral portion 102 at the distal end that extends laterally inward back toward the first side 18' thereof. The lateral portion 102 defines a sixth flat bearing surface 104. Additionally, the first side 52' of the movable track 48' is formed having an arcuate profile and the downwardly facing convex portion 56' defines a seventh concave bearing surface 106 which corresponds to the sixth flat bearing surface 104. The fourth bearings 92 are positioned between the seventh concave bearing surface 106 of the movable track 48' and the sixth flat bearing surface 104 of the fixed track 18'.

[0035] Referring to Figure 5, the first concave bearing surface 64' of the movable track 48' is replaced with a seventh flat bearing surface 108 and the first flat bearing surface 32' of the fixed track 18' is replaced with a first convex bearing surface 110 which corresponds to the seventh flat bearing surface 108. Thus, the first rolling elements 80' are positioned between the seventh flat bearing surface 108 of the movable track 48' and the first convex bearing surface 110 of the fixed track 18'. The second flat bearing surface 33' of the fixed track 18' is replaced with an eighth concave bearing surface 112. The distal end of the upstanding free end portion 60' of the first side 52' of the movable track 48' includes the lateral portion 98 defining the fifth flat bearing surface 100 which corresponds to the eighth concave bearing surface 112 of the fixed track 18'. The fourth bearings 92 are positioned between the fifth flat bearing surface 100 of the movable track 48' and the eighth concave bearing surface 112 of the fixed track 18'.

[0036] Referring to Figure 6, the first rolling elements 80' are positioned between the seventh flat bearing surface 108 of the movable track 48' and the first flat bearing surface 32' of the fixed track 18'. The first side 52' of the movable track 48' includes a lower portion 116 extending laterally toward the first side 22' of the fixed track 18" and defining a ninth concave bearing surface 118. The ninth concave bearing surface 118 corresponds to the second flat bearing surface 33' of the fixed track 18'. Thus, the fourth rolling elements 92 are positioned between the ninth concave bearing surface 118 of the movable track 48' and the second flat bearing surface 33' of the fixed track 18'.

[0037] Referring to Figure 7, the first bearings 80' are positioned between the first concave bearing surface 64' of the movable track 48' and the first flat bearing surface 32' of the fixed track 18'. Further, the lower portion 116 of the first side 52' of the movable track 48' defines a second convex bearing surface 120 which corresponds to the second flat bearing surface 33' of the fixed track 18'. Thus, the fourth rolling elements 92 are positioned between the second convex bearing surface 120 of the movable track 48' and the second flat bearing surface 33' of the fixed track 18'.

[0038] Referring to Figure 8, the first rolling elements 80' are positioned between the sixth flat bearing surface 108 of the movable track 48' and the first flat bearing surface 32' of the fixed track 18'. Further, the lower portion 116 of the first side 52' of the movable track 48' defines an eighth flat bearing surface 122 which corresponds to the second flat bearing surface 33' of the fixed track 18'. Thus, the fourth rolling elements 92 are positioned between the eighth flat bearing surface 122 of the movable track 48' and the second flat bearing surface 33' of the fixed track 18'.

[0039] Referring to Figures 9 and 10, wherein like double-primed reference numerals represent similar elements as those described above, in a third embodiment of the invention the profiles of the fixed 18" and movable 48" tracks are generally reversed from that which is described above. While it is appreciated that the particular profiles of the fixed 18" and movable 48" tracks are different in Figures 9 and 10, it is apparent that the first 80" and fourth 92" bearings on the first side 78" of the seat track assembly 10" are only vertically constrained between the fixed 18" and movable 48" tracks. In contrast, the second 84" and third 86" bearings on the second side 82" of the seat track assembly 10" are vertically and laterally constrained between the fixed 18" and movable 48" tracks.

[0040] In the third embodiment, the fixed track 18" is now the outer track and the movable track 48" is now the inner track. The lower portion 20" of the fixed track 18" defines the first concave bearing surface 64" adjacent the first side 22" and the first side 52" of the movable track 48" extends downwardly to a lateral portion 124 that extends outwardly toward the first side 22" of the fixed track 18". The lateral portion 124 defines the first flat bearing surface 32" which corresponds to the first concave bearing surface 64". Thus, the first bearings 80" are positioned between the first concave bearing surface 64" of the fixed track 18" and the first flat bearing surface 32" of the movable track 48". Further, the distal end 26" of the first side 22" of the fixed track 18" defines a tenth concave bearing surface 126. A distal end of the upstanding free end portion 60" of the first side 52" of the movable track 48" includes a lateral portion 128 that extends laterally outward toward the first side 22" of the fixed track 18". The lateral portion 128 defines a ninth flat bearing surface 130 which corresponds to the tenth concave bearing surface 126. The fourth bearings 92" are positioned between the ninth flat bearing surface 130 of the movable track 48" and the tenth concave bearing surface 126 of the fixed track 18".

[0041] Finally, referring to Figures 11 and 12, wherein like triple-primed reference numerals represent similar elements as those described above, in a fourth embodiment of the invention the plastic guide elements 66 and fourth rolling elements or ball bearings 92 have been replaced with an upwardly facing convex portion 132. The upwardly facing convex portion 132 is engaged with the second flat beating surface 33'" of the fixed track 18'" to prevent vertical separation of the movable track 48'" from the fixed track 18'" on the first side 78'" of the seat track assembly 10'".

[0042] Additionally, in Figure 12, the first concave bearing surface 64'" of the movable track 48"', shown in Figure 11, is replaced with the seventh flat bearing surface 108'". Thus, the first rolling elements 80'" are positioned between the seventh flat bearing surface 108'" of the movable track 48'" and the first flat bearing surface 32'" of the fixed track 18'".

[0043] The invention has been described here in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of words of description rather than limitation. Many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically enumerated within the description.

Claims

What is claimed:

1. A seat track assembly adapted to mount a seat to a floor of an automotive vehicle and provide selective forward and rearward adjustment of the seat relative to the floor among a plurality of seating positions, said seat track assembly comprising:

a first track;

a second track slidably coupled to said first track;

a first rolling element positioned between said first and second tracks on a first side of said seat track assembly, wherein said first rolling element is only vertically constrained therebetween, thereby allowing lateral alignment of said first rolling element between said first and second tracks; and

second and third rolling elements positioned between said first and second tracks on a second side of said seat track assembly, wherein said second and third rolling elements are vertically and laterally constrained therebetween.

2. A seat track assembly as set forth in claim 1 wherein said first track includes a first flat bearing surface and said second track includes a first concave bearing surface facing said first flat bearing surface and said first rolling element is disposed between said first concave bearing surface and said first flat bearing surface.

3. A seat track assembly as set forth in claim 2 wherein said first flat bearing surface is oriented generally horizontally relative to the floor of the vehicle.

4. A seat assembly as set forth in claim 3 wherein said first track includes a second flat bearing surface facing in an opposite direction of said first flat bearing surface and said second track includes a guide element slidably engaging said second flat bearing surface to prevent vertical separation of said first and second tracks on said first side of said seat track assembly.

5. A seat track assembly as set forth in claim 4 wherein the height of said guide element is adjustable thereby providing vertical compliance between said first and second tracks.

6. A seat track assembly as set forth in claim 5 wherein said first track includes third and fourth flat bearing surfaces, said third and fourth flat bearing surfaces oriented to face in opposite directions, and wherein said second track includes a second concave bearing surface facing said third flat bearing surface and said second rolling element is disposed between said second concave bearing surface and said third flat bearing surface, and wherein said second track includes a third concave bearing surface facing said fourth flat bearing surface and said third rolling element is disposed between said third concave bearing surface and said fourth flat bearing surface.

7. A seat track assembly as set forth in claim 6 wherein said third and fourth flat bearing surfaces are disposed at an angle relative to said first flat bearing surface.

8. A seat track assembly as set forth in claim 7 wherein said third and fourth flat bearing surfaces are oriented at approximately forty-five degrees relative to said first flat bearing surface.

9. A seat track assembly as set forth in claim 3 wherein said second track includes second and third concave bearing surfaces and said first track includes fourth and fifth concave bearing surfaces oriented to face in opposite directions, wherein said second concave bearing surface is facing said fourth concave bearing surface and said second rolling element is disposed between said second and fourth concave bearing surfaces, and wherein said third concave bearing surface is facing said fifth concave bearing surface and said third rolling element is disposed between said third and fifth concave bearing surfaces.

10. A seat track assembly as set forth in claim 9 wherein said fourth and fifth concave bearing surfaces are disposed at an angle relative to said first flat bearing surface.

11. A seat track assembly as set forth in claim 10 wherein a portion of said second track including said third concave bearing surface is springly flexible thereby providing lateral compliance between said first and second tracks.

12. A seat assembly as set forth in claim 11 wherein said first track includes a second flat bearing surface facing in an opposite direction of said first flat bearing surface and said second track includes a guide element slidably engaging said second flat bearing surface to prevent vertical separation of said first and second tracks on said first side of said seat track assembly.

13. A seat assembly as set forth in claim 12 wherein said guide element is an upwardly facing convex portion.

14. A seat track assembly adapted to mount a seat to a floor of an automotive vehicle and provide selective forward and rearward adjustment of the seat relative to the floor among a plurality of seating positions, said seat track assembly comprising:

a first track;

a second track slidably coupled to said first track;

first and fourth rolling elements positioned between said first and second tracks on a first side of said seat track assembly, wherein said first and fourth rolling elements are only vertically constrained therebetween, thereby allowing lateral alignment of said first and fourth rolling elements between said first and second tracks; and

15. A seat track assembly as set forth in claim 14 wherein said first rolling element is disposed between a first concave bearing surface and a first flat bearing surface, said second rolling element is disposed between a second concave bearing surface and a fourth concave bearing surface, said third rolling element is disposed between a third concave bearing surface and a fifth concave bearing surface, and said fourth rolling element is disposed between a sixth concave bearing surface and a second flat bearing surface.

16. A seat track assembly as set forth in claim 15 wherein said first and second flat bearing surfaces are oriented generally horizontally relative to the floor of the vehicle.

17. A seat track assembly as set forth in claim 16 wherein said first track includes said fourth concave bearing surface and said fifth concave bearing surface and said second track includes said second concave bearing surface and said third concave bearing surface.

18. A seat track assembly as set forth in claim 17 wherein said first track includes said first flat bearing surface and said sixth concave bearing surface, said first flat bearing surface and said sixth concave bearing surfaces oriented to face in opposite direction, and wherein said second track includes said first concave bearing surface and said second flat bearing surface.

19. A seat track assembly as set forth in claim 17 wherein said first track includes said first flat bearing surface and said second flat bearing surface, said first and second flat bearing surfaces oriented to face in opposite directions, and wherein said second track includes said first concave bearing surface and said sixth concave bearing surface.

20. A seat track assembly as set forth in claim 14 wherein said first rolling element is disposed between a first concave bearing surface and a first flat bearing surface, said second rolling element is disposed between a second concave bearing surface and a fourth concave bearing surface, said third rolling element is disposed between a third concave bearing surface and a fifth concave bearing surface, and said fourth rolling element is disposed between a first convex bearing surface and a second flat bearing surface.

21. A seat track assembly as set forth in claim 20 wherein said first track includes said fourth concave bearing surface and said fifth concave bearing surface, said fourth and fifth concave bearing surfaces oriented to face in opposite directions, and wherein said second track includes said second concave bearing surface and said third concave bearing surface.

22. A seat track assembly as set forth in claim 21 wherein said first track includes said first flat bearing surface and said second flat bearing surface, said first and second flat bearings surfaces oriented to face in opposite directions, and wherein said second track includes said first concave bearing surface and said first convex bearing surface.

23. A seat track assembly as set forth in claim 14 wherein one of said first and second tracks includes a first flat bearing surface and a second flat bearing surface, wherein said first rolling element is disposed between said first flat bearing surface and the other of said first and second tracks and said second rolling element is disposed between said second flat bearing surface and the other of said first and second tracks.

24. A seat track assembly as set forth in claim 14 wherein said first rolling element is disposed between a first flat bearing surface and a first convex bearing surface, said second rolling element is disposed between a second concave bearing surface and a fourth concave bearing surface, said third rolling element is disposed between a third concave bearing surface and a fifth concave bearing surface, and said fourth rolling element is disposed between a sixth concave bearing surface and a second flat bearing surface.

25. A seat track assembly as set forth in claim 24 wherein said first track includes said second concave bearing surface and said third concave bearing surface, and wherein said second track includes said fourth concave bearing surface and said fifth concave bearing surface, said fourth and fifth concave bearing surfaces oriented to face in opposite directions.

26. A seat track assembly as set forth in claim 25 wherein said first track includes said first convex bearing surface and said sixth concave bearing surface, and wherein said second track includes said first flat bearing surface and said second flat bearing surface, said first and second flat bearing surfaces oriented to face in opposite directions.