WO2011150489A1

WO2011150489A1 - Power drive assembly for a seat track assembly featuring compressible ribs

Info

Publication number: WO2011150489A1
Application number: PCT/CA2010/000841
Authority: WO
Inventors: David J. Wrong
Original assignee: Magna Seating Inc.
Priority date: 2010-05-31
Filing date: 2010-05-31
Publication date: 2011-12-08

Abstract

An adjustment mechanism includes a movable member slidably interconnected with a fixed member for linear movement relative to the fixed member. A threaded lead screw is fixedly secured to the movable member. A housing includes a gear threadably engaging the lead screw and a worm threadably engaging the gear. The housing is fixedly secured to the fixed member by a mounting bracket. The housing includes a plurality of crush ribs compressingly engaging the mounting bracket to prevent fore and aft chuck of the housing. Rotation of the worm in a clockwise direction rotates the gear in a first direction which urges the movable member linearly in a forward direction relative to the fixed member and rotation of the worm in a counterclockwise direction rotates the gear in a second direction which urges the movable member linearly in a rearward direction relative to the fixed member.

Description

POWER DRIVE ASSEMBLY FOR A SEAT TRACK ASSEMBLY FEATURING COMPRESSIBLE RIBS

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to a seat assembly for an automotive vehicle. More particularly, the invention relates to a power drive assembly for a seat track assembly for providing fore and aft movement of a seat assembly along a floor of an automotive vehicle.

2. Description of Related Art

[0002] Automotive vehicles include seat assemblies for supporting seat occupants within a passenger compartment of the vehicle. Typically, seat assemblies include a generally horizontal seat cushion spaced above a floor of the vehicle and a generally vertical or upright seat back. The seat back is commonly operatively coupled to the seat cushion to allow for selective pivotal adjustment of the seat back relative to the seat cushion between a plurality of reclined seating positions. [0003] Many seat assemblies also include a seat track assembly coupled between the seat cushion and the floor to provide fore and aft movement of the seat assembly within the vehicle. Typically, the seat track assembly includes a lower track fixedly secured to the floor of the vehicle and an upper track slidably engaging the lower track. The upper track is fixedly secured to a bottom surface of the seat cushion to allow for sliding movement of the seat assembly along the lower track.

[0004] It is well known in the vehicle seating art to provide a power seat track assembly driven by an electric motor for moving the upper track, and thus the seat assembly, relative to the lower track. Many such power seat track assemblies include a conventional drive assembly comprised of a gearbox and lead screw operatively coupled in a longitudinal channel between the upper and lower tracks for converting rotational input of the motor into linear movement of the seat assembly. Several such examples are described in U.S. Patent Nos. 6,915,998; 6,575,421 ; 6,322,146; 6,260,922; 5,816,555; 5,314,158; 4,790,202; and U.S. Patent Application Nos. 2006/0213302 and 2005/0082890. Typically, a threaded spindle or lead screw is fixedly secured to the lower track and the gearbox is operatively coupled between the lead screw and the upper track. The gearbox includes a housing having through holes or bores that are offset ninety (90) degrees to align and retain a worm and a gear or worm wheel. The gear includes a threaded internal bore for threadably engaging the lead screw and a geared outer surface for meshing with the worm. In an arrangement of this kind the worm is driven by a shaft extending from the motor which in turn causes the gear to rotate. Rotation of the gear causes the gear to move in a longitudinal direction along the fixed lead screw which causes the desired movement of the upper track relative to the lower track. [0005] Because the longitudinal channel between the upper and lower tracks is limited, packaging of the gearbox is an important issue. Therefore, it is desirable to provide a drive assembly incorporated into a power seat track assembly wherein the drive assembly has a simple and robust design that is cheap to manufacture and easy to assemble. SUMMARY OF THE INVENTION

[0006] According to one aspect of the invention, an adjustment mechanism is provided for selectively adjusting a movable member or upper seat track forward and rearward in a linear direction relative to a fixed member or lower seat track. A threaded lead screw extends in the linear direction and is fixedly secured to the upper seat track. A housing includes a primary bore and a secondary bore that are oriented generally perpendicular and are at least partially interconnected. The housing also includes at least one end having a plurality of first crush ribs protruding therefrom. The housing is disposed between two spaced apart sides of a generally U-shaped mounting bracket, which fixedly secures the housing to the lower seat track. The first crush ribs compressingly engage with one of the two spaced apart sides of the mounting bracket to prevent fore and aft chuck of the housing. A gear is rotatably disposed within the primary bore and includes a threaded internal bore threadably engaging the lead screw and a geared outer surface. A rotatably driven worm is disposed within the secondary bore and includes a threaded outer surface threadably engaging the geared outer surface of the gear. Rotation of the worm in a clockwise direction rotates the gear in a first direction which urges the upper seat track forward in the linear direction relative to the lower seat track. Alternatively, rotation of the worm in a counterclockwise direction rotates the gear in a second direction which urges the upper seat track rearward in the linear direction relative to the lower seat track.

BRIEF DESCRIPTION OF THE DRAWINGS [0007] 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:

[0008] Figure 1 is a perspective view of a seat track assembly for a vehicle seat according to the invention; [0009] Figure 2 is a perspective view of one seat track of the seat track assembly including a power lead screw;

[0010] Figure 3 is a cross-section view taken along line 3-3 of Figure 2;

[0011] Figure 4 is an exploded view of the gearbox;

[0012] Figure 5 is an outboard perspective view of the gearbox and lead screw; and

[0013] Figure 6 is an inboard perspective view of the gearbox and lead screw.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] Referring to Figure 1 , a seat assembly 10 for an automotive vehicle is shown. The seat assembly 10 includes a generally horizontal seat cushion 12 and a generally upright seat back 14 for supporting a seat occupant above a floor 16 within the vehicle. The seat cushion 12 includes an upward- facing seating surface 18 and a downward- facing mounting surface 20. A power seat track assembly or adjustment mechanism 22 is positioned between the mounting surface 20 of the seat cushion 12 and the floor 16 of the vehicle. As is well known in the art, the seat track assembly 22 provides fore and aft adjustment of the seat assembly 10 within the vehicle.

[0015] Referring to Figures 1 and 2, the seat track assembly 22 includes a pair of laterally spaced apart seat tracks 24, one of which will now be described in detail. Each seat track 24 includes a lower track or fixed member 26 extending longitudinally between a first or forward end 28 and a second or rearward end 30. The lower track 26 has a generally U-shaped cross-section defined by a horizontal lower wall 32 extending between a pair of spaced apart inner side walls 34, 36. A riser bracket 38 is fixedly secured to each of the forward and rearward ends 28, 30 of the lower track 26 and is adapted to mount the lower track 26 to the floor 16 of the vehicle. Each seat track 24 also includes an upper track or movable member 40 slidably engaging the lower track 26 and extending longitudinally between a first or forward end 42 and a second or rearward end 44. The upper track 40 has an inverted, generally U-shaped cross-section defined by a horizontal upper wall 46 extending between a pair of spaced apart outer side walls 48, 50. The upper track 40 is slidably coupled to the lower track 26 and the lower and upper tracks 26, 40 fit together such that their inward and/or outward bent marginal areas form a closed track profile.

[0016] The lower and upper tracks 26, 40 define a channel 52 extending longitudinally therebetween. The channel 52 extends vertically between the lower wall 32 of the lower track 26 and the upper wall 46 of the upper track 40. In addition, the channel 52 extends laterally between the inner side walls 34, 36 of the lower track 26. A drive assembly includes a horizontal lead screw 54 that is disposed longitudinally within the channel 52 and extends between a first end 56 and a second end 58. The first and second ends 56, 58 of the lead screw 54 are adapted to be fixedly secured to the upper wall 46 of the upper track 40 near the forward and rearward ends 42, 44, respectively. The drive assembly also includes a gearbox, generally shown at 60. The gearbox 60 is disposed within the channel 52 and operatively couples the lead screw 54 to the lower track 26 such that the gearbox 60 remains stationary with the lower track 26 and drives the upper track 40 linearly fore and aft relative to the lower track 26 in response to a rotary input. The rotary input is provided by an electric motor 62 that is mounted to a support bracket 64 that is fixedly secured between the lower tracks 26 of the pair of seat tracks 24.

[0017] Alternatively, it is appreciated that the lead screw 54 could be fixedly secured to the lower track 26 and the gearbox 60 operatively coupled between the lead screw 54 and the upper track 40. In this instance, the lead screw 54 would remain stationary and the gearbox 60 would move with and drive the upper track 40 linearly fore and aft in response to the rotary input. In addition, the support bracket 64 for the motor 62 would be fixedly secured between the upper tracks 40 of the pair of seat tracks 24.

[0018] Referring to Figures 3-6, the gearbox 60 includes a cube-shaped housing 66 having a primary bore 68 and a secondary bore 70, which are oriented generally perpendicular to one another. The primary bore 68 and the secondary bore 70 are at least partially interconnected. The primary bore 68 extends between a first end 72 that is sized for inserting a gear or worm wheel 74 into the primary bore 68 and a second end 76. The gear 74 is rotatably disposed in the primary bore 68 and includes a threaded internal bore 78 and a geared outer surface 80. The internal bore 78 threadably receives the lead screw 54 therethrough. Each end of the gear 74 includes a recessed lip 82 extending circumferentially therearound. The recessed lip 82 at one end of the gear 74 is rotatably supported at the second end 76 of the primary bore 68. A first bushing 84 is disposed between the gear 74 and a thrust bearing surface 86 at the second end 76 of the primary bore 68. A primary end cover 88 is attached to the housing 66 for rotatably supporting the other end of the gear 74 at the first end 72 of the primary bore 68. A second bushing 90 is disposed between the gear 74 and a thrust bearing surface 92 on the primary end cover 88. The first and second bushings 84, 90 and the thrust bearing surfaces 86, 92 prevent the gear 74 from moving longitudinally within the primary bore 68.

[0019] The lead screw 54 extends through an opening 94 in the primary end cover 88 and an opening 96 in the housing 66 at the second end 76 of the primary bore 68. The end of the housing 66 adjacent the second end 76 of the primary bore 68 defines an outer surface 98 including a plurality of crush ribs 100 protruding therefrom. In the embodiment shown, the crush ribs 100 extend generally horizontally and help prevent fore/aft chuck or play of the gearbox 60, as will be described in further detail below.

[0020] The secondary bore 70 extends between a first end 102 that is sized for inserting a worm 104 into the secondary bore 70 and a second end 106. The worm 104 is rotatably disposed in the secondary bore 70 and includes a helically threaded outer surface 108 for meshingly engaging the geared outer surface 80 of the gear 74. Each end of the worm 104 includes a recessed lip 1 10 extending circumferentially therearound. The recessed lip 110 at one end of the worm 104 is rotatably supported at the second end 106 of the secondary bore 70. A thrust bearing surface 112 at the second end 106 of the secondary bore 70 engages the worm 104. A secondary end cover 114 is attached to the housing 66 for rotatably supporting the other end of the worm 104 at the first end 102 of the secondary bore 70. The secondary end cover 114 includes a thrust bearing surface 116 that engages the worm 104 at the first end 102 of the secondary bore 70. The thrust bearing surfaces 112, 116 prevent the worm 104 from moving laterally within the secondary bore 70.

[0021] The housing 66 includes laterally opposing sides defining an inboard surface 1 18 adjacent to the first end 102 of the secondary bore 70 and an outboard surface 120 adjacent to the second end 106 of the secondary bore 70. The inboard surface 118 of the housing 66 and an outer surface 122 of the secondary end cover 114 include a plurality of crush ribs 124 protruding therefrom. Similarly, the outboard surface 120 of the housing 66 includes a plurality of crush ribs 126 protruding therefrom. In the embodiment shown, the crush ribs 124, 126 extend generally horizontally and compressingly engage with the inner side walls 34, 36 of the lower track 26 to help control lateral chuck or play of the gearbox 60 therebetween. The housing 66 also includes a plurality of grease injection ports 127 for injecting grease into the gearbox 60 after it is assembled. [0022] A generally U-shaped gearbox mounting bracket 128 is provided to attach the gearbox 60 to the lower track 26. More specifically, the mounting bracket 128 includes a cover 130 and two spaced apart sides 132 to partially surround the gearbox 60. One side 132 is disposed adjacent to and engages the primary end cover 88 and one side 132 is disposed adjacent to and engages the plurality of crush ribs 100 protruding from the outer surface 98 of the housing 66. The crush ribs 100 compressingly engage with one side 132 of the mounting bracket 128 to provide a snug fit between the gearbox 60 and the mounting bracket 128 to prevent fore/aft chuck of the gearbox 60. The lead screw 54 extends through an opening 134 in each side 132 of the mounting bracket 128. A distal end of each one of the sides 132 includes an outwardly projecting flange 136 for securing the mounting bracket 128 to the lower wall 32 of the lower track 26. Each flange 136 includes an aperture 138 through which a bolt, screw, rivet or other attachment means extends to fixedly secure the mounting bracket 128 to the lower track 26. In the event of a crash the mounting bracket 128 will deform in the manner of a parallelogram such that the openings 134 in the sides 132 of the mounting bracket 128 move into engagement with and jam against the lead screw 54 to prevent the seat assembly 10 from moving fore or aft. [0023] A drive shaft 140 extends between the motor 62 and the gearbox 60.

The drive shaft 140 is operatively coupled to the motor 62 and extends through an aperture 142 in the lower track 26 and an opening 144 in the secondary end cover 114 and drivingly engages a recess 146 in the worm 104. Operation of the motor 62 turns the drive shaft 140 in either a clockwise or counterclockwise direction which creates a torque input to the worm 104, thereby causing the worm 104 to rotate in the clockwise or counterclockwise direction. Rotation of the worm 104 in the clockwise direction drives rotation of the gear 74 in a first direction and rotation of the worm 104 in the counterclockwise direction drives rotation of the gear 74 in a second direction. Because the gearbox 60 is fixedly secured to the lower track 26 by the mounting bracket 128, rotation of the gear 74 in the first and second directions urges the lead screw 54 in either a fore or aft direction. The fore and aft movement of the lead screw 54 in turn moves the upper track 40, and thus, the entire seat assembly 10 in the fore and aft directions.

[0024] The invention has been described 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. An adjustment mechanism comprising: a fixed member; a movable member slidably interconnected with said fixed member for linear movement in forward and rearward directions relative to said fixed member; a threaded lead screw extending linearly and fixedly secured to one of said fixed and movable members; a housing including a primary bore and a secondary bore oriented generally perpendicular to said primary bore, said primary and secondary bores are at least partially interconnected, said housing further including at least one end having a plurality of first crush ribs protruding therefrom; a generally U-shaped mounting bracket fixedly securing said housing to the other of said fixed and movable members, said mounting bracket having two spaced apart sides, and said housing is disposed between said two spaced apart sides with said plurality of first crush ribs compressingly engaging one of said two spaced apart sides to prevent fore and aft chuck of said housing; a gear rotatably disposed within said primary bore, said gear including a threaded internal bore and a geared outer surface, said threaded internal bore threadably engaging said lead screw; and a rotatably driven worm disposed within said secondary bore, said worm including a threaded outer surface threadably engaging said geared outer surface of said gear; wherein rotation of said worm in a clockwise direction rotates said gear in a first direction which urges said movable member linearly in said forward direction relative to said fixed member and wherein rotation of said worm in a counterclockwise direction rotates said gear in a second direction which urges said movable member linearly in said rearward direction relative to said fixed member.

2. The adjustment mechanism as set forth in claim 1 wherein said fixed and movable members define a channel therebetween and said lead screw and said housing are disposed in said channel.

3. The adjustment mechanism as set forth in claim 2 wherein said housing includes opposing lateral sides, at least one of said opposing lateral sides including a plurality of second crush ribs protruding therefrom, said plurality of second crush ribs compressingly engaging one of said fixed and movable members to prevent lateral chuck of said housing.

4. The adjustment mechanism as set forth in claim 3 wherein said lead screw extends through said two spaced sides of said mounting bracket.

5. The adjustment mechanism as set forth in claim 4 further including primary and secondary end covers, said primary end cover attached to said housing and retaining said gear in said primary bore, and said secondary end cover attached to said housing and retaining said worm in said secondary bore.

6. The adjustment mechanism as set forth in claim 5 wherein an outer surface of said secondary end cover includes a plurality of third crush ribs protruding therefrom, said plurality of third crush ribs compressingly engaging one of said fixed and movable members to prevent lateral chuck of said housing.

7. The adjustment mechanism as set forth in claim 6 wherein said secondary end cover includes an opening therethrough, said worm is rotatably driven through said opening.

8. The adjustment mechanism as set forth in claim 7 wherein said primary bore of said housing extends between a first primary end adapted for receiving said gear into said primary bore and a second primary end, said primary end cover including a first thrust bearing surface engaging one end of said gear and said second primary end of said primary bore including a second thrust bearing surface engaging the other end of said gear.

9. The adjustment mechanism as set forth in claim 8 wherein said secondary bore of said housing extends between a first secondary end adapted for receiving said worm into said secondary bore and a second secondary end, said secondary end cover including a third thrust bearing surface engaging one end of said worm and said second secondary end of said secondary bore including a fourth thrust bearing surface engaging the other end of said worm.

10. The adjustment mechanism as set forth in claim 9 further including a first bushing disposed between said first thrust bearing surface and one end of said gear and a second bushing disposed between said second thrust bearing surface and the other end of said gear.

1 1. The adjustment mechanism as set forth in claim 1 wherein said lead screw is fixedly secured to said movable member and said mounting bracket fixedly secures said housing to said fixed member.

12. The adjustment mechanism as set forth in claim 11 wherein said housing includes opposing lateral sides, each of said opposing lateral sides including a plurality of second crush ribs protruding therefrom, said plurality of second crush ribs compressingly engaging said fixed member to prevent lateral chuck of said housing.

13. The adjustment mechanism as set forth in claim 12 further including primary and secondary end covers, said primary end cover attached to said housing and retaining said gear in said primary bore, and said secondary end cover attached to said housing and retaining said worm in said secondary bore.

14. The adjustment mechanism as set forth in claim 13 wherein an outer surface of said secondary end cover includes a plurality of third crush ribs protruding therefrom, said plurality of third crush ribs compressingly engaging said fixed member to prevent lateral chuck of said housing.