WO2000035706A1

WO2000035706A1 - Power recliner mechanism for a seat assembly

Info

Publication number: WO2000035706A1
Application number: PCT/CA1999/001078
Authority: WO
Inventors: Roger Freund
Original assignee: Dura Global Technologies, Inc.
Priority date: 1998-12-17
Filing date: 1999-11-16
Publication date: 2000-06-22
Also published as: AU1254200A

Abstract

A vehicle seat assembly (10) includes a seat bottom (12) and a seat back (14) supported for pivotal movement relative to the seat bottom to allow adjustment of the seat back between a variety of reclined positions. The seat includes a power adjustment mechanism (16) that pivots the seat back with respect to the seat bottom. The adjustment mechanism includes a threaded shaft (36) pivotally supported at one end such that the shaft moves with the seat back as the seat back pivots with respect to the seat bottom. A gearbox assembly (38) is mounted to the seat back and includes a housing (56) that substantially encloses a gear (42) and drive nut (44) assembly. The threaded shaft defines a longitudinal axis along which the gearbox assembly moves as the seat pivots. An electric motor (40) is used to drive the gear and drive nut assembly along the threaded shaft causing the seat back to pivot relative to the seat bottom. A pair of thrust bearings are mounted on opposite sides of the gear and drive nut assembly, and a spacer is used to properly locate the bearings within the housing. The housing is electromagnetically formed around the spacer to fix the spacer with respect to the housing and to eliminate free play along the longitudinal axis.

Description

POWER RECLINER MECHANISM FOR A SEAT ASSEMBLY

BACKGROUND OF THE INVENTION This application relates to an adjustment mechanism that moves a seat member between a plurality of angular positions. The adjustment mechanism includes a threaded shaft and gearbox assembly that is driven up and down along the threaded shaft by an electπc motor resulting in pivotal movement of the seat member. An electromagnetic forming process is used to eliminate free play between components of the gearbox assembly. The electromagnetic forming process also eliminates the need for fasteners, such as screws or πvets, used for attaching a cover to enclose the adjustment mechanism.

Adjustment mechanisms are often used in seat assemblies for controlling movement between seat members. Typically a first seat member, such as a seat bottom, is fixed to seat track assembly, and a second seat member, such as a seat back, is supported with respect to the seat bottom for pivotal movement relative to the seat bottom. Adjustment mechanisms are used to selectively control pivotal movement of the seat back and allow the seat back to be moved between a plurality of reclined positions relative to the seat bottom. Some adjustment mechanisms for rechners use dπve assemblies with gear components that are often complex, requiπng a great number of parts which subsequently increases assembly time. Also, these dπve assemblies often have axial free play between the gears and other drive assembly components, which leads to looseness in the seat back. This looseness can cause a rattling noise in an empty passenger seat, for example. Set screws or shims are typically used to reduce free play between drive assembly components. However, these methods require additional components for the adjustment mechanism and are time consuming to install.

Thus, it is desirable to have an adjustment mechanism for reclining a seat back that has a simplified gear dπve that reduces the number of components and assembly ti e as compared to known mechanisms. It is also desirable to eliminate axial free play in the adjustment mechanism without the use of additional components.

SUMMARY OF THE INVENTION In a disclosed embodiment, a vehicle seat assembly includes a seat bottom member and a seat back member supported for pivotal movement relative to the seat bottom member. The seat includes an adjustment mechanism powered by an electric motor to move the seat back between a variety of reclined positions. The adjustment mechanism includes a threaded shaft and a gearbox assembly that is driven up and down the threaded shaft by the electric motor. The gearbox assembly has a housing that is mounted to the seat back and a drive gear that is driven by the electric motor longitudinally along the threaded shaft.

In a preferred embodiment, the adjustment mechanism includes at least one thrust bearing that is supported by the gear assembly for accommodating axial loads that occur during adjustment. A spacer is used to properly locate the thrust bearing within the housing. The housing is electromagnetically formed around the spacer to fix the spacer with respect to the housing resulting in the elimination of undesirable free play between the bearing and the gear assembly.

The subject adjustment mechanism provides a simplified seat adjuster that requires few parts, is easy to assemble, and reduces cost. The adjustment mechanism also eliminates free play between adjustment mechanism components without additional parts. These and other features can be understood from the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of a seat assembly incorporating the subject adjustment mechanism.

Figure 2 is perspective view of the adjustment mechanism. Figure 3 is an exploded view of the adjustment mechanism shown in Figure 2. Figure 4A is a partial cross sectional view of the gearbox before assembly.

Figure 4B is a partial cross sectional view of the gearbox after assembly. Figure 5 is a side view of the seat assembly with the seat back in the full upright position.

Figure 6 is a side view of -the seat assembly with the seat back in the fully reclined position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A vehicle seat assembly is shown generally at 10 in Figure 1. The seat assembly 10 includes a first seat member 12, such as a seat bottom or a seat-pan and a second seat member 14, such as a seat back or seat back frame member, supported with respect to the seat bottom 12. The seat bottom 12 and seat back 14 are shown as frames so that the present invention can be easily visualized. The seat back 14 is supported for pivotal movement relative to the seat bottom 12 such that the position of the seat back 14 can be adjusted to a variety of angular positions with respect to the seat bottom 12. An adjustment mechanism 16 is used to move the seat back 14 between various angular seat positions relative to the seat bottom 12. The seat 10 includes a first mount 18 and a second mount 20 that pivotally attach the seat back 14 to the seat bottom 12. Each of the mounts 18, 20 includes a bracket member 22 and a first pivot

24. The bracket member 22 is supported on the seat bottom 12. The seat back 14 is attached to the bracket member 22 at the first pivot 24.

The adjustment mechanism 16 is mounted to the seat bottom 12 adjacent to one of the mounts 18 and is selectively controlled by a seat occupant to adjust the position of the seat back 14 between a variety of reclined positions. The seat back 14 pivots about the first pivot 24 when actuated by the adjustment mechanism 16. Preferably a single adjustment mechanism 16 is used to pivot the seat back 14 with respect to the seat bottom 12, however, a second adjustment mechanism could be mounted adjacent to the other of the mounts 20 to assist in seat adjustment.

A third mount 30 is used to support the adjustment mechanism 16 with respect to the seat 10. The third mount 30 is preferably mounts the adjustment mechanism 16 to the seat bottom 12, however, the third mount 30 could also mount the adjustment mechanism 16 to the seat slides or tracks that move the seat forward and rearward. The third mount 30 includes a bracket 32 with a pivot 34 that pivotally supports a component of the adjustment mechanism at one end, which will be discussed in further detail below. While a separate third mount 30 is shown for supporting the adjustment mechanism, it should be under stood that the third mount 30 could be formed as part of either of the other mounts 18, 20.

The adjustment mechanism 16 is shown in greater detail in Figure 2. The adjustment mechanism includes a threaded rod 36, a gearbox assembly 38 mounted to the seat back 14 at a second pivot 28, and an electric motor 40. The motor 40 is selectively powered by a seat occupant to drive the gearbox assembly 38 along the threaded rod 36 to bring the seat back 14 to a desired angular position with respect to the seat bottom 12. In the preferred embodiment, the gearbox assembly 38 is driven along the threaded shaft 36, however, the gearbox assembly 38 could be fixed with the threaded rod 36 moving with respect to the gearbox assembly 38 to recline the seat back 14. An exploded view of the adjustment mechanism 16 is shown in Figure 3. The gearbox assembly 38 is comprised of a drive gear 42, a drive nut 44, an upper thrust bearing 46 and a lower thrust bearing 48. The drive gear 42 is supported on the drive nut 44 and the upper 46 and lower 48 thrust bearings are supported on opposite sides of the drive gear 42. The thrust bearings 46, 48 take the axial forces or axial loading that occurs in both directions as the gearbox assembly 38 moves up and down the threaded rod 36.

The drive nut 44 includes an internal threaded bore 50 that is received on the threaded rod 36. The drive nut 44 and the drive gear 42 are preferably integrally formed as a single piece such that the gear 42 and nut 44 are concentric. The electric motor 40 includes an output shaft 52 that engages teeth 54 on the drive gear 42. The output shaft 52 preferably has a rollformed thread that matingly engages the gear teeth 54. The output shaft 52 drives the gear 42 and drive nut 44 causing the gear 42 and nut 44 to rotate about the threaded rod 36 resulting in transnational movement of the gearbox assembly 38 along the rod 36. The gearbox assembly 38 includes a housing 56 that is preferably attached to a seat back member at pivot 28. The housing 56 substantially encloses the gear 42, nut 44, and thrust bearings 46, 48 such that dirt and other contaminants are prevented from interfering in the operation of the gearbox assembly 38.

The threaded rod 36 defines a longitudinal axis 58, shown in Figure 2, along which the gearbox assembly 38 travels. The threaded rod 36 has one end 60 pivotally attached to the third mount 30 at pivot 34. Thus, as the seat back 14 moves between reclined positions, the threaded rod 36 pivots with the seat back 14 about pivot 34.

The gearbox assembly also includes a sleeve 62 located between the lower thrust bearing 48 and the gear 42 and a spacer 64 located above the upper thrust bearing 46. The spacer 64 is used to properly locate the upper bearing 46 in the axial direction within the housing 56, and also acts as a cover, which closes the housing 56.

The housing is electromagnetically formed around the spacer 64 for fixing the spacer 64 with respect to the housing 56, as shown in Figures 4A and 4B. Electromagnetically forming the housing 56 into engagement with the spacer 64 also eliminates free play between the bearings 46, 48 and the drive gear/nut 42,44 along the longitudinal axis 58.

Figure 4 A shows the gearbox assembly 38 before the Electromagnetic Forming Process (EMF) has been performed. The housing 56 includes a lip 66 that locates the lower bearing 48 within the housing 56. The lower thrust bearing 48 is placed on one side of the gear 42 and the upper thrust bearing 36 is placed on an opposite side of the gear 42. The spacer 64 is installed on top of the upper thrust bearing 46. Before the

EMF process has been performed, a gap 68 exists between the exterior surface of the spacer 64 and the interior surface of the housing 56. The spacer 64 also preferably includes a groove 70 around the circumference of the spacer 64.

One the EMF process has been performed, as shown in Figure 4B, the housing 56 has been collapsed around the spacer 64 such that the gap 68 and the groove 70 are filled with housing material. This fixes the spacer 64 with respect to the housing 56, properly locates the upper bearing 46 within the housing 56, and eliminates axial free play along the longitudinal axis 58.

The EMF process is a high rate metal forming process. Kinetic energy is imparted to the electrically conductive workpiece, i.e. the housing 56, by means of an electromagnetic pulse. The EMF process is performed by placing part of the gearbox housing 56 inside a forming coil, shown schematically at 72 in Figure 4B. Preferably, the forming coil 72 is placed around the part of the housing that surrounds the spacer 64. An electric current is sent through the forming coil 72, which generates an electronic pressure pulse to collapse the walls of the gearbox housing 56 into the spacer 64 located inside the housing 56.

Once the EMF process has been performed on the gearbox assembly 38, the adjustment mechanism 16 is mounted to a seat back member 14. When the seat back 14 is in the full upright position as shown in Figure 5, the threaded rod 36 is generally vertical and the gearbox assembly 38 and motor 40 are located away from end 60 of the threaded rod 36. As the motor 40 drives the gear/nut 42, 44 along the threaded rod

36, the gearbox assembly 38 moves downwardly toward end 60 of the threaded rod 36 causing the seat back 14 to eventually move to the fully reclined position shown in Figure 6. In this position, the threaded rod 36 has also been moved from the vertical position to a reclined position. Preferred embodiments of this invention have been disclosed, however, a worker of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. For that reason the following claims should be studied to determine the true scope and content of this invention.

Claims

CLALMSWe claim:

1. A vehicle seat assembly comprising: a first seat member; a second seat member supported for pivotal movement relative to said first seat member; and an adjustment mechanism mounted to a vehicle structure for selectively moving said second seat member between a plurality of angular positions with respect to said first seat member, said adjustment mechanism including a threaded rod, a gearbox assembly mounted to said second seat member and having a drive gear, and a motor having an output shaft for driving said drive gear along said threaded rod to bring said second seat member to a desired angular position with respect to said first seat member.

2. An assembly as recited in claim 1 wherein said threaded rod is pivotally mounted to said adjustment mechanism at one end such that said rod moves with said second seat member between various angular positions during adjustment.

3. An assembly as recited in claim 2 wherein said gearbox assembly includes a housing mounted to said second seat member for movement relative to said threaded rod as said motor drives said drive gear along said threaded rod.

4. An assembly as recited in claim 3 wherein said output shaft includes a roll-formed thread for engaging gear teeth on said drive gear to drive said drive gear along said threaded rod.

5. An assembly as recited in claim 4 including a drive nut supported on said drive gear having a threaded internal bore received on said threaded shaft wherein said drive gear provides rotational input to said drive nut for moving said drive nut along said threaded shaft.

6. An assembly as recited in claim 5 wherein said drive nut and said drive gear are integrally formed as a single piece with said drive gear surrounding said drive nut such that said drive gear and said drive nut are concentric.

7. An assembly as recited in claim 5 including a pair of thrust bearings supported on either side of said drive gear for accommodating axial loading occurring during adjustment.

8. An assembly as recited in claim 7 including at least one spacer installed within said housing and supported by one of said bearings for properly locating said bearing within said housing.

9. An assembly as recited in claim 8 wherein said housing is electromagnetically formed around said spacer for fixing said spacer with respect to said housing.

10. An adjustment mechanism for selectively controlling angular position of a first seat member with respect to a second seat member comprising: a threaded rod defining a longitudinal axis and pivotally mounted at one end for movement with the second seat member between a plurality of angular positions; a gearbox assembly having a housing mounted to the second seat member and a drive nut for driving said gear box assembly along said longitudinal axis; and a motor having an threaded output shaft for providing input to said drive nut to drive said motor and said gearbox assembly along said threaded rod causing the second seat member to pivot with respect to the first seat member.

11. An assembly as recited in claim 10 including upper and lower thrust bearings supported on opposite sides of said drive nut for accommodating axial forces occurring during adjustment.

12. An assembly as recited in claim 10 including at least one spacer for locating said upper thrust bearing within said housing.

13. An assembly as recited in claim 12 wherein said housing is electromagnetically formed into engagement with said spacer to eliminate free play along said longitudinal axis.

14. A method for assembling a seat adjustment mechanism comprising the steps of: providing a threaded shaft defining a longitudinal axis and a gearbox including a housing and a drive mechanism for driving the gearbox along the threaded shaft; and electromagnetically forming the housing around the drive mechanism to eliminate free play along the longitudinal axis.

15. A method as recited in claim 14 further including the steps of installing an upper thrust bearing on one side of the drive mechanism and installing a lower thrust bearing on an opposite side of said drive mechanism before electromagnetically forming the housing.

16. A method as recited in claim 15 further including the step of installing at least one spacer within the housing to properly locate the upper bearing before electromagnetically forming the housing.

17. A method as recited in claim 16 further including the steps of providing a groove around the spacer, and electromagnetically forming the housing such that housing material is received in the groove.

18. A method as recited in claim 16 wherein the step of electromagnetically forming the housing around the dπve mechanism further includes the steps of surrounding part of the housing with a forming coil and generating an electronic pulse to cause the housing to collapse around the dπve mechanism.

19. A method as recited in claim 18 wherein the step of surrounding part of the housing with a forrmng coil further includes the step of placing the forming coil around a housing portion that surrounds the spacer.