Telescopic Steering Column Assembly

Abstract

A telescopic steering column assembly comprises an upper and a lower shroud portion able to move relatively during telescopic adjustment, a telescopic steering shaft that passes through and is supported by the shroud portions through at least one support bearing assembly that acts between an upper portion of the telescopic steering shaft and a lower portion of the shroud that move relative to one another axially during telescopic adjustment. The at least one support bearing assembly comprises a first bearing race which is separate from the shroud portions and the steering shaft, a resilient spacer that applies a biasing force that is directed in a radial direction from the axis of the shaft and that is located between the first race and an adjacent face of one of the lower shroud portion and the upper shaft portion; a set of bearings, and a cage that locates the bearings relative to the first bearing race. The bearings bear onto a second bearing race that is defined by a surface of the other one of the lower shroud portion and the upper shaft portion, the second bearing face permitting the bearings to slide or roll in the direction of adjustment of the steering column assembly when it is adjusted for reach.

Claims

1. A telescopic steering column assembly comprising an upper shroud portion, a lower shroud portion, the two shroud portions being able to move relatively along a common linear path during telescopic adjustment, a telescopic steering shaft that passes through the upper and lower shroud portions and is supported by the shroud portions through at least one support bearing assembly that acts between an upper portion of the telescopic steering shaft and a lower portion of the shroud that move relative to one another axially during telescopic adjustment of the steering column assembly for reach, the support bearing assembly in use removing free play between the telescopic steering shaft and the shroud portions that would otherwise occur in at least one direction orthogonal to the telescopic adjustment, in which the at least one support bearing assembly comprises: a first bearing race which is separate from the shroud portions and the steering shaft, a resilient spacer that applies a biasing force that is directed in a radial direction from an axis of the steering shaft and that is located between the first bearing race and an adjacent face of one of the lower shroud portion and the upper shroud portion; a set of bearings, and a cage that locates the bearings relative to the first bearing race, wherein the bearings bear onto a second bearing race that is defined by a surface of the other one of the lower shroud portion and the upper shroud portion, the second bearing race permitting the bearings to slide or roll in the direction of telescopic adjustment of the steering column assembly when adjusted for reach.

2. The telescopic steering column assembly according to claim 1 in which the resilient spacer is axially fixed relative to the one of the lower shroud portion and upper shroud portion by frictional engagement of the contacting surfaces.

3. The telescopic steering column assembly according to claim 1 in which the first bearing race comprises an inner bearing race that is located radially inside the bearings and cage, which are arranged around a common axis, and the resilient spacer is located between the inner race and the upper shroud portion.

4. The telescopic steering column assembly according to claim 1 in which the second bearing race comprises an inner surface of the lower shroud portion.

5. The telescopic steering column assembly according to 1 claim in which the resilient spacer comprises an annular ring.

6. The telescopic steering column assembly according to claim 5 in which the annular ring comprises an interlinked set of circumferentially extending arcuate portions that together form a ring including at least three circumferentially extending arcuate portions that are spaced apart from each other around an axis of the ring and that provide a majority or all of a compressive preload between the first bearing race and the one of the lower shroud portion and the upper shroud portion.

7. The telescopic steering column assembly according to claim 6 in which the three arcuate portions are each thicker as measured in a radial direction than the portions that interconnect them so that in use the portions that interconnect them apply substantially no preload to the first bearing race.

8. The telescopic steering column assembly according to claim 6 in which the three arcuate portions are spaced substantially evenly around the ring, so that there is a spacing of approximately or precisely 120 degrees between the centres of adjacent portions.

9. The telescopic steering column assembly according to claim 6, in which at least two of the three arcuate portions that carry the majority of the preload comprise relatively rigid, incompressible, portions.

10. The telescopic steering column assembly according to claim 9 in which a third of the three arcuate portions comprises one or more radially extending resiliently compressible elements that are supported by an arcuate portion so that the compressible elements and supporting portion together have a radial thickness at rest that is greater than the average spacing between the first bearing race and the one of the upper and lower shroud portions.

11. The telescopic steering column assembly according to claim 10 in which the third of the three arcuate portions is integrally formed with the arcuate portions that interconnect the other two arcuate portions.

12. The telescopic steering column assembly according to claim 1 in which the first bearing race comprises a ring with a slit that extends from one side to the other so that the ring is not continuous but has two adjacent ends, the ends being spaced apart slightly to enable the diameter of the first bearing race to vary as the force is applied by the resilient spacer.

13. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 is a vertical cross sectional view of a part of an embodiment of a steering column assembly of the present invention;

[0036] FIG. 2 is a first angle projection view of the bearing assembly that sits between the inner and outer shrouds along with a view of the adjacent part of the shrouds;

[0037] FIG. 3 is a view in the first angle projection of the split inner bearing race;

[0038] FIG. 4 is a view in the first angle projection of an exemplary resilient spacer assembly that secures the inner race to the inner shroud portion.

DETAILED DESCRIPTION OF THE INVENTION

[0039] FIG. 1 provides a view of a steering column assembly which includes a telescopic arrangement within the scope of one aspect on the present invention. The steering column assembly comprises a shroud 1, 2 which comprises a tubular upper shroud portion 1 and a tubular lower shroud portion 2, each of which comprises a cylindrical tube. The shroud portions 1, 2 are moveable relative to each other with the end of the upper shroud portion 1 being a sliding fit within an end of the lower shroud portion 2. The shroud 1, 2 surrounds a telescopic steering column shaft 3, 4. The shaft comprises an upper shaft portion 3 that at least partially surrounds a lower shaft portion 4, the two portions being connected through complimentary axially extending splines 5. The opposite end of the upper shaft is tapered so that it can be secured to a steering wheel (not shown). The lower shaft portion 4 is connected to an optional electric power steering gearbox which in turn connects to the road wheels of the vehicle.

[0040] The upper shaft fits over the lower shaft and the upper shaft portion 3 moves whilst the lower shaft portion 4 does not move axially. Similarly, the upper, outer, shroud portion 1 is located towards the steering wheel and slides over the lower, inner, shroud portion 2. The lower shroud portion 2 is axially fixed to a gearbox (not shown). The tubular upper shroud portion 1 may be secured to a fixed part of the vehicle using a clamp mechanism (of which only a clamp bolt 5 is shown) that clamps onto a rail 6 on the upper shroud portion 1. A slit is provided in the outer shroud that is closed up as the clamp assembly is closed to cause the outer shroud portion 1 to grip the inner shroud portion 2.

[0041] An upper column bearing assembly 7 is located between the upper shaft 3 and the inner surface of the upper shroud portion 1. This snugly fills the space and ensures that the shaft 3 is located securely within the shroud 1.

[0042] An extra column bearing assembly 8 is provided between the inner shroud portion and the upper shaft 3, in the region where they overlap, providing support for the shaft 3, 4 close to the joint between the two shaft portions. In use the extra support bearing assembly 8 removes the free play that would other exist and this increases the minimum resonant natural frequency of the whole assembly compared with the same assembly without the support bearing assembly 8. This can provide a welcome improvement in the levels of NVH (noise, vibration and harshness) perceived by a user when the vehicle is travelling along a rough surface. The outer shroud portion 2, support bearing assembly 7 and shaft 3, 4 together form a telescopic assembly within the scope of the first aspect of the invention.

[0043] To allow the length of the shroud to be adjusted, the inner shroud must be free to move axially relative to the outer shroud. To this end, the support bearing assembly 8 is fixed axially only to the outer surface of the shaft 3 and is able to slide axially relative to the inner surface of the lower shroud portion 2.

[0044] The support bearing assembly 8 is shown in more detail in FIG. 2 and parts of the bearing assembly 8 are shown separately in FIGS. 3 and 4 of the drawings.

[0045] The extra bearing assembly 8 comprises an inner bearing race 9 through which the shaft 3 passes. A set of roller bearings 11 run in a track formed in an outwardly facing surface of the inner race and are held in position by a bearing cage 10. There is no discrete outer bearing race and instead the roller bearings roll on the inner surface of the inner shroud potion 2. The roller bearings are free to slide axially along this surface as required, with the surface being given a smooth finish to reduce friction during this sliding motion.

[0046] The inner race 9 of the bearing assembly comprises a strip of steel which is formed into a ring and whose ends are mitred 9a so that they come together to form a narrow split line which was angled relative to the bearing axis. This enables the inner race to expand or contract slightly while allowing the rollers to still progress around it noiselessly. The bore of the Lower shroud portion is smooth and accurate within conventional manufacturing tolerances. Because the radial forces acting on this bearing are generally small in relation to its overall size, there is no need to specially harden the surface of the said bore. This bore therefore acts as the bearing's outer race, proving suitable for both rolling contact and axial sliding contact of the rollers without damage.

[0047] The inner race 9 is fixed to the outer surface of the upper shaft portion 1 by a resilient spacer 12. The spacer could be a simple elastic ring which has an inner diameter, in a relaxed state before assembly that is slightly less than the outer diameter of the corresponding section of the upper shaft 1, and also an outer diameter when relaxed that is slightly greater than the inner diameter of the inner race. Thus when in the assembled position this ring presses the inner race away from the shaft 1 and thereby presses the rollers into contact with the inner shroud portion 2.

[0048] However, in this embodiment the resilient spacer comprises a ring structure that includes a number of discrete, yet interconnected, arcuate portions that have differing properties. The function of the different portions it to provide a controlled preload of the inner race at a reduced number of locations, giving a higher degree of performance in managing preload and also abuse loads applied to the steering shaft, for instance when a driver pulls heavily down on the steering wheel.

[0049] The resilient spacer 12 is shown in FIG. 4. It includes three arcuate portions 13, 14 that are equally spaced apart from each other around the axis of the ring and that provide the path across which in normal use all of the compressive preload between the first bearing race and the upper shaft portion passes.

[0050] The three arcuate portions 13, 14 are each radially wider than portions that interconnect them so that in use the portions that interconnect them apply substantially no preload to the bearing race. As shown in FIG. 2 a small gap is present between the outer face of these interconnecting portions and the inner race, so their sole function in this example is to locate the three load bearing portions relative to one another.

[0051] Two portions 13 of the three portions that carry the majority of the preload comprise relatively rigid, incompressible, metal pads. Of course other materials could be used.

[0052] The third of the portion 14 comprises a compressible rubber or elastomeric pad that has a radial thickness at rest that is greater than the average spacing between the first race and the one of the upper shaft and lower shroud portion. This third portion 14 includes a set of radially extending ridges, or spines, on the surface that engages the inner race that both resiliently compress and deflect so as to produce a force that ensures the two relatively incompressible portions are always in contact with and applying a preload to the bearings. The radial ridges extend around the circumference of the third portion.

[0053] In this example the third portion is integrally formed with the interconnecting portions that connect the two metal pads together.

[0054] By choosing the total of the radial thickness of the ribbed third portion, the inner race, and the roller bearings to be slightly greater than the radius of the bore of the Lower shroud portion the ribs of the rubber ring are put into compression when the bearing is assembled to the column. This compression provides a radial preload.

[0055] In this example there are two solid arcuate inserts 13 located in the rubber ring whose centres are approximately 120 degrees apart. The wall thickness of the rubber ring is reduced for most of its circumference so as to ensure that only the said solid inserts provide the radial support between the shaft and the inner race, rather than the rubber. The ribs of the third portion preload the shaft into contact with the two solid inserts and, in turn, onto the inside surface of the inner race. The Inner race, in trying to expand as a result of this, exerts a radial preload on the rollers which are in the vicinity of the inserts. Likewise, the inner race is urged against the rollers which are in the vicinity of the compression ribs. It now requires a considerable radial force acting on the shaft in a direction towards the arc of ribs to further compress them are cause the shaft to lose contact with the two solid inserts. Such a magnitude of radial force is well in excess of that which would be encountered in a steering wheel natural frequency test or in circumstances which are likely to excite the natural vibration modes of the steering wheel. For small radial disturbances in any direction, the shaft behaves as though it is rigidly connected to the shroud.

[0056] In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.