GB2463137A

GB2463137A - Steering column assembly

Info

Publication number: GB2463137A
Application number: GB0914328A
Authority: GB
Inventors: Niclas Davies
Original assignee: TRW Ltd
Current assignee: TRW Ltd
Priority date: 2008-09-06
Filing date: 2009-08-17
Publication date: 2010-03-10
Anticipated expiration: 2029-08-17
Also published as: GB0914328D0; GB2463137B; GB0816351D0

Abstract

A steering column assembly having a steering column shroud which comprises outer (2, Figure 1) and inner (1, Figure 1) members. The outer member (2) includes a first bracket 24 having two walls located on opposing sides of an axial slot (2a, Figure 6). A second bracket 20 is fixed to a part of a vehicle, comprising: two depending arms 22, 23 between which lie the two walls of the first bracket 24; and a clamping mechanism which in a locked position clamps the first 24 and second 20 brackets together and closes the slot (2a) in the outer member (2) preventing movement of the shroud relative to the second bracket 20. The assembly further includes an anti-rotation device 43 fitted to one wall of the first bracket 24 which comprises an arm that extends down below the clamp mechanism so as to contact one of the arms 22 of the second bracket 20 so that during release of the clamp mechanism the interaction between the anti-rotation device and the second bracket 20 prevents any rotation of the shroud.

Description

STEERING COLUMN ASSEMBLY

This invention relates to improvements in steering column assemblies for vehicles.

Steering column assemblies for automotive vehicles and the like are increasingly required to be adjustable for rake and, in many cases, reach.

This requires the column shroud, within which the steering column shaft attached to the steering wheel is rotatably located, to be fixed to the vehicle by a clamp mechanism which can be locked and unlocked to either prevent or permit adjustment of the column shroud position respectively.

One common arrangement uses a telescopic column shroud which comprises an inner member and an outer member-typically two elongate metal tubes of differing diameters-which slide one inside the other to permit reach adjustment. A fixing rail is welded to the top of one of the tubes and is secured to a support bracket by a releasable clamp mechanism. The clamp mechanism typically includes a bolt which is threaded through openings in the fixing rail and support bracket. Rake adjustment can be achieved by providing a support bracket which includes vertically extending slots through which the bolt of the clamp mechanism passes. The clamp bolt can be moved vertically within these slots, taking the column with it to adjust rake. Similarly, horizontal slots can be provided in the fixing rail allowing the rail to move relative to the bolt to permit reach adjustment.

A known arrangement for use in restricted spaces is illustrated in Figures 2(a) and 2(b) of the accompanying drawings. It utilises a support bracket in the form of an inverted U-shape having two arms depending from a base which have the vertical slots formed therein. A further bracket defining the fixing rail comprises two opposing upright walls or rails and is fixed to the top of the outer part of the shroud, usually a tube. The fixing rail has horizontal slots in its sides. The walls are arranged on opposing sides of an axial slot in the top of the outer shroud member. The clamp mechanism includes a bolt which passes through the slots in the two brackets to link the arms together and the column is located between the arms. Tightening the bolt draws the arms of the fixing bracket together to squeeze them onto the sides of the upright rails that are fixed to the top of the column. This action in turn squeezes the sides rails together to close up the slot in the top of the outer tube. This causes the diameter of the outer tube to reduce, squashing the outer tube onto the inner tube to remove any free play between them.

According to a first aspect there is provided a steering column assembly comprising a steering column shroud which comprises an elongate outer member and an elongate inner member which is received within the outer member, the two members supporting a steering shaft for a steering wheel, the outer member including a first bracket having two generally upright opposing walls located on opposing sides of an axial slot in the outer member, a second bracket which is fixed in position relative to a part of vehicle and which comprises a generally U-shaped member with two depending arms of the U-shaped member extending from its base to define a space therebetween within which the walls of the first bracket are located, and a clamp mechanism which includes a first set of teeth fixed to the second bracket and a second set of teeth fixed to the first bracket, the clamp mechanism being movable between a locked position in which the two sets of teeth are engaged and the clamp mechanism clamps the first bracket and the second bracket together by forcing the arms of the second bracket towards one another in turn causing the walls of the inner bracket to be moved towards one another so as to close up the slot in the outer member such that the outer member applies a compressive force onto the inner member, and an unlocked position in which the clamp mechanism permits movement of the shroud relative to the second bracket, characterised in that the assembly further includes an anti-rotation device fixed relative to one wall of the first bracket which comprises an arm that extends downwards below the clamp mechanism so as to contact one of the arms of the second bracket when the clamp mechanism is clamped over a region vertically offset from the region where the two sets of teeth engage so that during release of the clamp mechanism the interaction between the anti-rotation device and the arm prevents any rotation of the shroud which would otherwise tend to occur as the slot in the outer member opens up.

The anti-rotation device prevents the small rotation of the clamp mechanism and/or outer shroud member that the applicant has noticed can occur with the prior art arrangement as the outer tube relaxes during release of the axial slot in the upper member. Because the outer shroud locates parts such as the indicator stalks and steering lock, any slight rotation is undesirable as it can be apparent to a driver and leads to an impression of low quality. The invention can completely, or at least partially, overcome this problem.

One of the walls of the first bracket may carry a toothed rail which defines the first teeth that co-operate with a set of teeth on the inner face of a corresponding arm of the second bracket when in the clamped position, the clamp mechanism applying force to the first bracket through the meshing of these teeth, and the anti-rotation device may comprise a vertically extended lower part of the toothed rail. This toothed rail may be welded to the wall of the first bracket.

By vertically extended we may mean that the lower part of the toothed rail extends downwards beyond the bottom of the walls of the first bracket, and perhaps to the lower most point of the depending arm of the clamp bracket.

The extension portion may comprise a metal extension plate which defines a substantially vertical engagement surface which engages a corresponding substantially vertical engagement surface on the inside of a corresponding arm of the second bracket at least when the clamp mechanism is clamped.

The extension portion may be vertically extended downwards to be level with a horizontal plane that passes through a centre line of the upper shroud. Where the upper member of the shroud is tubular this level will be the level of the axis of the tube. The lower end of the corresponding arm of the second bracket may also depend to this same level.

The lower, otherwise free, end of the anti-rotation device may be secured to the outer member to provide additional rigidity. It may be welded to the outer member.

The first bracket may be fixed to the outside of the outer member of the shroud by welding or other fastening means.

There will now be described, by way of example only, one embodiment of the present invention with reference to the accompanying drawings of which; Figure 1 is a general view in plan of a part of a first embodiment of a steering column assembly that is adjustable for reach and rake; Figure 2(a) and (b) are views of a prior art clamp mechanism in an unclamped position and a clamped position; Figure 3 is a cross section through a clamp assembly of a steering column according to the invention when viewed along the axis of the steering column; Figure 4 is a view of a first arrangement of toothed plate with anti-rotation device as used in the assembly of Figures 1 and 3; Figure 5 is a view of an alternative arrangement of toothed plate and ant-rotation device; and Figure 6 is a perspective view of the shroud part of the assembly of Figure 1 showing the location of the toothed plate and anti-rotation device.

As shown in Figures 1 a steering column assembly comprises a telescopic steering column shroud comprising an inner member 1 and an outer member 2 which receives a portion of the inner member 1. The inner and outer members are metal tubes with the inside diameter of the outer member being only slightly greater than the outside diameter of the inner member so as to permit relative movement between them by sliding. In the example of Figure 1 the inner member 1 passes into a gearbox housing 3 whilst the outer member 2 extends away from that towards a steering wheel. This housing may contain a gearbox in the case of an electric power steering system which is driven by an electric motor to provide an assistance torque.

The wheel (not shown) is supported by a telescopic steering shaft 4 that is free to rotate within the steering column shroud 1,2. A bush 5 (optional) of low friction material such as a soft plastic is located between the inner and outer members to control the friction that is generated when the two are moved over one another to extend or collapse the steering column either when adjusting reach of the steering wheel or in an accident.

The steering column shroud 1,2 is fixed pivotally to a part of the vehicle body at a point 6 and also to a support bracket (not shown in Figure 1) secured to the body of the vehicle by a clamp mechanism. The bracket is typically welded or bolted in place in a region under the dashboard and clamps the shroud at a point somewhere between the pivot and the steering wheel. The clamp mechanism can be locked or unlocked to allow the rake of the steering column to be adjusted by pivoting about the pivot.

When locked the steering column cannot be moved other than in an accident.

The support bracket and the clamping mechanism are shown in detail in Figure 3 of the accompanying drawings. The support bracket 20 is in the form of a metal sheet pressed into an inverted U-shape, with the base 21 of the U lying in a generally horizontal plane above the steering column shroud 1,2. The two arms 22,23 of the U depend downwards in a generally vertical plane and extend down either side of a fixing rail 24 welded to the outer shroud member 2. This rail can be seen in Figure 6 which is a view of the shroud and the rail with the u-shaped bracket removed. It comprises two spaced vertical walls welded to the outer tube 2 on opposing sides of an elongate slot 2a.

A clamp mechanism acts between the two arms 22,23 of the U-shaped bracket 20 to draw them together when locked so that they are squeezed onto the fixing rail 24. It includes a bolt which passes through vertical slots in the arms of the support bracket and horizontal slots in the walls of the rail 24. The purpose of these slots, which extend along in the direction of the long axis of the tubular members 1,2, is to allow the steering column to be telescoped for reach adjustment and moved for rake when the clamp mechanism is unlocked.

The clamp mechanism comprises a shaft 25 which passes through the elongate, substantially vertically extending, slots in the U shaped bracket arms and through the slots in the fixing rail 24. A fixed nut 29 is located on one end of the shaft. The other end of the shaft 25 is secured with a cam mechanism 28 that is provided between an adjustable nut 27 and the outer face of the corresponding arm of the support bracket. The cam comprises a fixed portion 30 that is prevented from rotation and a moving portion 31 that together present cam faces that slide over one another.

The moving portion 31 is operated by a lever 32 as shown or could be operated by an electric motor.

Rotation of the moving cam portion 31 by rotation of the lever 32 to lock the clamp mechanism increases the length of the cam and this pushes the adjustable nut 27 away from the arm 22, causing the shaft 25 to draw the the other arm 23 towards the arm 22. This forces the arms of the support bracket together, in turn pushing the walls of the fixing rail 24 together and closing the slot 2a in the outer tube 2. This reduces the inner diameter of the tube 2 causing it to grip the inner tube 1.

Rotation of the cam to unlock the mechanism has the effect of shortening the length of the cam and thus reduces the tension in the shaft, releasing the grip of the arms on the fixing bracket.

To ensure that the U-shaped bracket and rail cannot slide relative to one another when clamped, a toothed plate 40 carrying two spaced rows of teeth 41,42 is welded to the fixing rail 24 alongside one of the elongate slots, and a complimentary set of teeth are provided on the fixed cam part of the clamp mechanism. The toothed rail includes a slot which lines up with the slot in the fixing rail 24. When clamped the teeth on the clamp mechanism mesh together with some of the facing teeth of the toothed plate 40. When unclamped, the clamp mechanism moves away to allow the teeth to disengage fully.

In the unclamped condition the combined width of the cams of the clamp mechanism has decreased as the moving cam was rotated by the clamp lever, the said rotation having allowed the cams to fully intermesh. The slack thus created in the clamp bolt has allowed the fixed cam to be urged to the right (as drawn) by a spring or springs (not shown) acting horizontally between the fixed cam and the U-bracket. The movement of the fixed cam to the right has been sufficient to release the locking teeth at which are part of the fixed cam from engagement with the locking teeth which are part of the reach tooth plate.40. The clamp bolt tension having been reduced almost to zero, the head of the clamp bolt and the clamp block have been able to move to the left (as drawn) by a small distance having been urged by the inner leaf plate 3$. The inner leaf itself has been urged to the left by the tube bracket itself in turn having been urged by the expansion of the split outer tube as it unwrapped itself from its previously tight contact with the inner tube.

In the said unclamped condition, there is effectively some horizontal free play between the external overall width dimension across the rail and toothed plate and the corresponding internal width dimension between the surface of the inside of the arms of the U-bracket. The said free play could give rise to an excessive feeling of looseness at the steering wheel since the outer tube is no longer rigidly clamped to the stiff vertical leg of the U-bracket. This feeling of looseness can be partly disguised by the biasing effect of tension remaining in the clamp bolt. The said remaining tension is mainly due to residual compression in the springs acting on the fixed cam.

There is also a tendency, when unclamping the column, for the upper end (i.e. the end nearest the steering wheel) of the outer tube to rotate slightly in an anti-clockwise direction. This is due to the aforesaid unwrapping of the split outer tube. Because the steering column multi-function switch (not shown) is usually attached to the upper end of the outer tube, it will also rotate slightly. This rotation could be noticeably to the driver who may observe the resulting vertical movements of the outer ends of the direction indicator and screen wiper control levers The applicant has therefore appreciated that when the clamping force is released and the slot 2a in the top of the outer tube 2 opens, the outer tube 2 will unwind slightly which can cause a small amount of rotation of the outer tube 2.

To restrict this rotation an anti-rotation device is provided as shown in Figures 4 and 5, and visible in its position of use in Figure 6 of the accompanying drawings. This comprises an extension part 43 to the toothed plate 40 that is secured to the upright side wall of the rail 24. The extension part 43 is vertically extended downwards to form an anti-rotation device that provides additional contact with the arm of the U shaped bracket over a much greater vertical distance.

A first arrangement of this plate 40 is shown also shown in detail in Figure 4 of the accompanying drawings. In use, the bottom part of the toothed plate is aligned with the inside wall of the corresponding arm of the U-shaped bracket as shown in Figure 3 and reaches down past the bottom of the rail to be level with a centre line of the outer member. It is welded to the outside of the outer member at this point to give it additional rigidity. Any attempt by the outer member to rotate is resisted by the engagement of this extended portion on the inside of the ti-shaped bracket. Small amounts of horizontal free play between the arms of the u shaped bracket and the rail no longer permit as much rotation as would otherwise be possible.

An alternative arrangement of toothed plate 50 is shown in Figure 5 of the accompanying drawings. This is similar to the toothed plate of Figure 4 but the vertical extension is provided by welding 52 an extension plate 51 onto the bottom of the toothed plate.

Claims

CLAIMS1. A steering column assembly comprising a steering column shroud which comprises an elongate outer member and an elongate inner member which is received within the outer member, the two members supporting a steering shaft for a steering wheel, the outer member including a first bracket having two generally upright opposing walls located on opposing sides of an axial slot in the outer member, a second bracket which is fixed in position relative to a part of vehicle and which comprises a generally U-shaped member with two depending arms of the U-shaped member extending from its base to define a space therebetween within which the walls of the first bracket are located, and a clamp mechanism which includes a first set of teeth fixed to the second bracket and a second set of teeth fixed to the first bracket, the clamp mechanism being movable between a locked position in which the two sets of teeth are engaged and the clamp mechanism clamps the first bracket and the second bracket together by forcing the arms of the second bracket towards one another in turn causing the walls of the inner bracket to be moved towards one another so as to close up the slot in the outer member such that the outer member applies a compressive force onto the inner member, and an unlocked position in which the clamp mechanism permits movement of the shroud relative to the second bracket, characterised in that the assembly further includes an anti-rotation device fixed relative to one wall of the first bracket which comprises an arm that extends downwards below the clamp mechanism so as to contact one of the arms of the second bracket when the clamp mechanism is clamped over a region vertically offset from the region where the two sets of teeth engage so that during release of the clamp mechanism the interaction between the anti-rotation device and the arm of the second bracket prevents any rotation of the shroud which would otherwise tend to occur as the slot in the outer member opens up.
2. A steering column assembly according to claim 1 in which one of the walls of the first bracket carries a toothed rail which defines the first teeth that co-operate with a set of teeth on the inner face of a corresponding arm of the second bracket when in the clamped position, the clamp mechanism applying force to the first bracket through the meshing of these teeth, and in which the anti-rotation device comprise a vertically extended lower part of the toothed rail.
3. A steering column assembly according to claim 2 in which the extended lower part of the toothed rail extends downwards beyond the bottom of the walls of the first bracket.
4. A steering column assembly according to any preceding claim in which the extended portion of the anti-rotation device comprises a metal extension plate which defines a substantially vertical engagement surface which engages a corresponding substantially vertical engagement surface on the inside of a corresponding arm of the second bracket at least when the clamp mechanism is clamped.
5. A steering column assembly according to any preceding claim in which the extended portion is vertically extended downwards to be level with a horizontal plane that passes through a centre line of the upper shroud.
6. A steering column assembly substantially as described herein with reference to and as illustrated in the accompanying drawings.