# Patent

## Title
Overload protection for belt drive mechanism

## Abstract

An assembly includes a steering shaft and a primary drive system eccentrically coupled to the steering shaft and configured to transfer a torque applied to the steering shaft to a vehicle steering system. The assembly also includes a secondary drive system coupled to the steering shaft and configured to transfer the torque applied to the steering shaft if the primary drive system is inactive and substantially unable to transfer the torque.

## Background
FIELD OF THE INVENTION
The following description relates to steering column assemblies and, more specifically, to an overload protection system for a steering column assembly.
BACKGROUND
Some known steering columns may include a belt drive mechanism to allow eccentric attachment to a vehicle steering system. However, the belt drive mechanism may experience a failure mode if a belt of the belt drive mechanism is disabled or broken, which may result in loss of steering.
Accordingly, it is desirable to provide steering column having a flexible element drive mechanism with a secondary drive transmitting mechanism.
SUMMARY OF THE INVENTION
In an exemplary embodiment of the present invention, an eccentric power transfer system for a steering column assembly is provided. The power transfer system includes a primary drive system configured to transfer a torque applied to the steering column assembly to a vehicle steering system, and a secondary drive system configured to transfer the torque applied to the steering column when the primary drive system is inactive and unable to transfer the torque.
In another exemplary embodiment of the present invention, a steering column assembly for a vehicle is provided. The assembly includes a steering shaft and a primary drive system eccentrically coupled to the steering shaft and configured to transfer a torque applied to the steering shaft to a vehicle steering system. The assembly also includes a secondary drive system coupled to the steering shaft and configured to transfer the torque applied to the steering shaft if the primary drive system is inactive and substantially unable to transfer the torque.
In yet another exemplary embodiment of the invention, a method of assembling a steering column assembly for a vehicle is provided. The method comprises providing a steering shaft rotatable about an axis and eccentrically coupling a primary drive system to the steering shaft to transfer a torque applied to the steering shaft. A secondary drive system is coupled to the steering shaft to transfer the torque applied to the steering shaft if the primary drive system is inactive and substantially and unable to transfer the torque.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 illustrates an exemplary steering column assembly according to one embodiment of the disclosure;
FIG. 2 is a plan view of a power transfer system of the invention;
FIG. 3. is an elevation view of the power transfer system of FIG. 2; and
FIG. 4 illustrates an alternative embodiment of a power transfer system.



DETAILED DESCRIPTION
Referring now to the Figures, where the invention will be described with reference to specific embodiments, without limiting same, FIG. 1 illustrates an exemplary steering column assembly 10 that generally includes a steering column shaft 12, a column jacket 14, a hub support 16, a stationary steering wheel hub 18, and a steering wheel rim 20. In an exemplary embodiment, steering column assembly 10 is adjustable in a rake direction and a telescope direction. The steering column assembly provides an eccentric power transfer system 60, 160 that translates rotation of the steering column shaft 12 eccentrically through the power transfer system 60, 160 to the vehicle steering gear system (not shown).
Steering shaft 12 extends along an axis ‘A’ and includes a lower shaft 22 and an upper shaft 24. Lower shaft 22 includes a first end 26 and an opposite second end 28. Upper shaft 24 includes a first end 30 and an opposite second end 32. Upper shaft first end 30 is disposed within lower shaft 22 such that upper shaft 24 is telescopically and slidingly disposed within lower shaft 22. Upper shaft second end 32 is coupled to steering wheel rim 20, and steering shaft 12 is rotatable about axis ‘A’ and is configured to transmit torque from wheel 20 to vehicle road wheels (not shown). Alternatively, upper shaft 24 may be slidingly disposed about lower shaft 22.
Column jacket 14 extends along axis ‘A’ and includes a lower jacket 34 and an upper jacket 36. Jacket 14 surrounds and supports shaft 12 via upper bearings 38 and lower bearings 40 disposed between shaft 12 and jacket 14. In the exemplary embodiment, jacket 14 extends coaxially with steering shaft 12, which is rotatably connected to upper jacket 36. Lower jacket 34 is coupled to a stationary part of the vehicle such as the vehicle chassis (not shown), and upper jacket 36 is telescopically and slidingly disposed at least partially within lower jacket 34. Alternatively, upper jacket 36 may be slidingly disposed about lower jacket 34.
Hub support 16 extends along axis ‘A’ and includes a lower hub support 42 and an upper hub support 44 surrounded by steering shaft 12. In the exemplary embodiment, hub support 16 extends coaxially with steering shaft 12 and column jacket 14. Lower hub support 42 is coupled to a stationary part of the vehicle such as the vehicle chassis, and upper hub support 44 is telescopically and slidingly disposed at least partially about lower hub support 42. As such, upper hub support 44 includes a first end 46 disposed about lower hub support 42, and a second end 48 coupled to stationary hub 18. A bearing 50 is disposed between stationary hub 18 and upper shaft 24 to facilitate rotation of shaft 12 about axis ‘A’. Alternatively, upper hub support 44 may be slidingly disposed within lower hub support 42. In some embodiments, hub support 16 may be pivotally mounted to the vehicle to facilitate raking movement of steering column assembly 10.
In the illustrated embodiment, stationary hub 18 is coupled to upper hub support second end 48. Because lower and upper hub supports 42, 44 are fixed from rotation about axis ‘A’, stationary hub 18 is fixed from rotation about axis ‘A’. However, due to telescoping movement, upper hub support 44 and thus stationary hub 18 may be translated a predefined distance along axis ‘A’. As such, stationary hub 18 is non-rotatably attached to telescoping hub support 16.
One or more switches 52 may be coupled to stationary hub 18 to provide control of various functions of the vehicle. For example, switches 52 may be a wiper control stalk, a vehicle light control stalk, a turn signal stalk, a power telescope/rake switch, or the like. Switches may be in electrical and/or signal communication with a vehicle controller 54 via a conduit 56 (e.g., electrical wire, optical, etc.) or other mode (e.g., wireless). As used herein, the term controller refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
In the illustrated embodiment, conduit 56 is disposed within hub support 16, which provides a direct pathway for communication with switches 52. A cord reel 58 may be provided to take up slack of conduit 56 during telescoping movement of column assembly 10. Moreover, electrical devices (e.g., video screen, computer, device charger, etc.) may be disposed on or within stationary hub 18 and connected to conduit 56.
With reference to FIGS. 1-3, steering column assembly 10 includes an eccentric power take-off or power transfer system 60 that generally includes a primary drive system 62 and a secondary drive system 64. Torque and rotation by the driver to steering shaft 12 may be maintained by secondary drive system 64 in the event of failure of primary drive system 62, such as due to belt or chain breakage. Accordingly, primary drive system will be substantially inactive and unable to transfer the torque.
In the exemplary embodiment, primary drive system 62 generally includes a drive pulley 66, a driven pulley 68, and a toothed belt 70. Drive pulley 66 is coupled to shaft 12 and transmits torque to driven pulley 68 via belt 70 coupled therebetween. In alternative embodiments, belt 70 may be a chain or other continuous loop flexible element. Driven pulley 68 is coupled to an output shaft 72 and transmits torque to an intermediate shaft (not shown), for example, via a yoke 74 coupled to shaft 72 (see FIG. 3).
In the exemplary embodiment, secondary drive system 64 generally includes a drive overload gear 80, a driven overload gear 82, and an idler gear 84. Drive overload gear 80 is coupled to steering shaft 12 and/or drive pulley 66, and driven overload gear 82 is coupled to shaft 72 and/or driven pulley 68.
Idler gear 84 is supported for rotation on a shaft 86, which is rotatably coupled to a housing (not shown) or other portion of system 60. Idler gear 84 is disposed between and meshingly engages drive overload gear 80 and driven overload gear 82. However, the teeth of idler gear 84 are loosely meshed with the teeth of gears 80, 82. As such, gears 80, 82, 84 are not tightly meshed and rotate with a predetermined small clearance in the tooth mesh. This enables belt 70 to be adjusted tightly to provide lash-free rotation without conflict from gears 80, 82, 84. As such, in the event that belt 70 is damaged (e.g., broken, worn teeth) and primary drive system 62 is substantially disabled or inoperable, idler gear 84 transfers torque and rotation from drive overload gear 80 to driven overload gear 82.
FIG. 4 illustrates a dual-belt eccentric power take-off or power transfer system 160 that is similar to system 60 and like reference numerals indicate like parts. System 160 generally includes a primary drive system 162 and a secondary drive system 164. Torque and rotation by the driver to steering shaft 12 may be maintained by secondary drive system 164 in the event of failure of primary drive system 162, such as due to belt or chain breakage. Accordingly, primary drive system will be substantially inactive and unable to transfer the torque.
In the exemplary embodiment, primary drive system 162 includes a dual belt system that generally includes drive pulleys 166a and 166b, driven pulleys 168a and 168b, and belts 170a and 170b. Drive pulleys 166a, 166b are coupled to an input shaft 171 and transmit torque to respective driven pulleys 168a, 168b via respective belts 170a, 170b. Alternatively, drive pulleys 166a, 166b may be coupled directly to shaft 12 rather than through input shaft 171. Driven pulleys 168a, 168b are coupled to shaft 72 and transmit torque to the intermediate shaft via yoke 74.
In the illustrated embodiment, secondary drive system 164 includes drive overload gear 80, driven overload gear 82, and idler gear 84. Drive overload gear 80 is coupled to input shaft 171 (or steering shaft 12) and/or one or both drive pulleys 166a, 166b. Driven overload gear 82 is coupled to shaft 72 and/or one or both driven pulleys 168a, 168b. 
Idler gear 84 is supported for rotation on shaft 86, which is rotatably coupled to a housing (not shown) or other portion of system 160. Idler gear 84 is disposed between and meshingly engages drive overload gear 80 and driven overload gear 82. However, the teeth of idler gear 84 are loosely meshed with the teeth of gears 80, 82. As such, gears 80, 82, 84 are not tightly meshed and rotate with a predetermined small clearance in the tooth mesh. This enables belts 170a, 170b to be adjusted tightly to provide lash-free rotation without conflict from gears 80, 82, 84. As such, in the event that belts 170a, 170b are damaged (e.g., broken, worn teeth) and primary drive system 162 is inoperable, idler gear 84 transfers torque and rotation from drive overload gear 80 to driven overload gear 82.
A method of assembling power take-off system 60, 160 includes coupling drive pulley 66, 166a, 166b and drive overload gear 80 to shaft 12, 171, coupling driven pulley 68, 168a, 168b and driven overload gear 82 to shaft 72, and rotatably coupling the drive pulley and driven pulley with belt 70, 170a, 170b. Idler gear 84 is rotatably disposed between and meshingly engages the drive pulley and the driven pulley to transfer torque and rotation therebetween.
Described herein are systems and methods providing an overload protection system for a power transfer system of a steering column assembly. The power transfer system includes a primary drive system to transfer steering motion through a drive pulley, a driven pulley, and a belt. A secondary drive system transfers steering motion through a drive overload gear, a driven overload gear, and an idler gear disposed therebetween. The idler gear is loosely meshed between the drive/driven overload gears. As such, the secondary drive system transfers steering motion in the steering column assembly in the event the primary drive system is disabled or inoperable.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description.

## Claims

1. An eccentric power transfer system for a steering column assembly, the system comprising:
a primary drive system configured to transfer a torque applied to the steering column assembly to a vehicle steering system; and
a secondary drive system in parallel with the primary drive system and configured to transfer the torque applied to the steering column assembly when the primary drive system is inactive and substantially unable to transfer the torque, the primary drive system further comprising:
a drive pulley configured to couple to a steering shaft of the steering column assembly;
a driven pulley configured to couple to an output shaft; and
a drive belt engaging the drive pulley and the driven pulley to transfer a torque therebetween.

2. The system of claim 1, wherein the drive pulley comprises a first drive pulley and a second drive pulley, the driven pulley comprises a first driven pulley and a second driven pulley, and the drive belt comprises a first drive belt and a second drive belt.

3. The system of claim 1, further comprising a yoke coupled to the output shaft, the yoke configured to couple to an intermediate shaft.

4. An eccentric power transfer system for a steering column assembly, the system comprising:
a primary drive system configured to transfer a torque applied to the steering column assembly to a vehicle steering system; and
a secondary drive system configured to transfer the torque applied to the steering column assembly when the primary drive system is inactive and substantially unable to transfer the torque, the secondary drive system further compromising:
a drive overload gear configured to couple to a steering shaft of the steering column assembly;
a driven overload gear configured to couple to an output shaft; and
an idler gear disposed between and meshingly engaged with the drive overload gear and the driven overload gear to transfer a torque therebetween.

5. The system of claim 4, wherein the idler gear is loosely meshed to the drive overload gear and the driven overload gear.

6. A steering column assembly for a vehicle, the assembly comprising:
a steering shaft;
a primary drive system eccentrically coupled to the steering shaft and configured to transfer a torque applied to the steering shaft to a vehicle steering system; and
a secondary drive system in parallel with the primary drive system and coupled to the steering shaft and configured to transfer the torque applied to the steering shaft if the primary drive system is inactive and substantially unable to transfer the torque, the primary drive system further comprising:
a drive pulley configured to couple to the steering shaft;
a driven pulley configured to couple to an output shaft; and
a drive belt engaging the drive pulley and the driven pulley to transfer a torque therebetween.

7. The assembly of claim 6, wherein the drive pulley comprises a first drive pulley and a second drive pulley, the driven pulley comprises a first driven pulley and a second driven pulley, and the drive belt comprises a first drive belt and a second drive belt.

8. The assembly of claim 6, further comprising a yoke coupled to the output shaft, the yoke configured to couple to an intermediate shaft.

9. A steering column assembly for a vehicle, the assembly comprising:
a steering shaft;
a primary drive system eccentrically coupled to the steering shaft and configured to transfer a torque applied to the steering shaft to a vehicle steering system; and
a secondary drive system coupled to the steering shaft and configured to transfer the torque applied to the steering shaft if the primary drive system is inactive and substantially unable to transfer the torque, the secondary drive system further compromising:
a drive overload gear configured to couple to the steering shaft;
a driven overload gear configured to couple to an output shaft; and
an idler gear disposed between and meshingly engaged with the drive overload gear and the driven overload gear to transfer a torque therebetween.

10. The assembly of claim 9, wherein the idler gear is loosely meshed to the drive overload gear and the driven overload gear.

11. A steering column assembly for a vehicle, the assembly comprising:
a steering shaft;
a primary drive system eccentrically coupled to the steering shaft and configured to transfer a torque applied to the steering shaft to a vehicle steering system; and
a secondary drive system in parallel with the primary drive system and coupled to the steering shaft and configured to transfer the torque applied to the steering shaft if the primary drive system is inactive and substantially unable to transfer the torque, the steering shaft is rotatable about an axis and is configured to couple to a steering wheel rim, the steering column assembly further comprising:
a hub support configured to be non-rotatably coupled to a support structure of the vehicle; and
a stationary hub coupled to the hub support, the steering wheel rim rotatable relative to the stationary hub.

12. The assembly of claim 11, wherein the hub support is disposed about the axis and is concentric with the steering shaft.

13. The assembly of claim 11, wherein the steering shaft includes a first shaft slidingly disposed within a second shaft, the steering shaft configured for telescopic movement.

14. The assembly of claim 11, wherein the hub support includes a first hub support slidingly disposed within a second hub support, the hub support configured for telescopic movement.

15. A method of assembling a steering column assembly for a vehicle, the method comprising:
providing a steering shaft rotatable about an axis;
eccentrically coupling a primary drive system to the steering shaft to transfer a torque applied to the steering shaft;
coupling a secondary drive system to the steering shaft to transfer the torque applied to the steering shaft if the primary drive system is inactive and substantially unable to transfer the torque, wherein coupling a primary drive system comprises:
coupling a drive pulley to the steering shaft;
coupling a driven pulley to an output shaft; and
coupling a drive belt to the drive pulley and the driven pulley to transfer a torque therebetween; and coupling a secondary drive system comprises:
coupling a drive overload gear to at least one of the steering shaft and the drive pulley;
coupling a driven overload gear to at least one of the output shaft and the driven pulley; and
meshingly disposing an idler gear between the drive overload gear and the driven overload gear to transfer a torque therebetween.

16. The method of claim 15, further comprising:
coupling a steering wheel rim to the steering shaft;
non-rotatably coupling a hub support to a support structure of the vehicle; and
coupling a stationary hub to the hub support, the steering wheel rim rotatable relative to the stationary hub.