WO2009007709A1

WO2009007709A1 - A steering column assembly and bracket

Info

Publication number: WO2009007709A1
Application number: PCT/GB2008/002339
Authority: WO
Inventors: Carl Thompson
Original assignee: Trw Limited
Priority date: 2007-07-10
Filing date: 2008-07-09
Publication date: 2009-01-15
Also published as: GB2463595A; GB2463595B; GB0713354D0; GB0922518D0

Abstract

A steering assembly includes a support bracket (20) which comprises a generally U-shaped member with two depending arms (22, 23) of the U extending from its base (21) having a portion of a column shroud located therebetween, and a clamp mechanism which upon locking of the clamp mechanism provides tension between the two arms of the U shaped member together thereby clamping the steering column shroud in position. One arm of the U-shaped member comprises an outer leaf (22b) extending from the base to a free end of the arm and an inner leaf (22a) i having a further flexible tab, said inner leaf being connected to the free end of the arm and extending upwards from the free end towards the base, the inner leaf (22a) being located between outer leaf (22b) and the other arm (23) of the U-shaped member.

Description

A STEERING COLUMN ASSEMBLY AND BRACKET

This invention relates to improvements in steering column assemblies, and to a support bracket for such assemblies.

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 two tubes which slide one inside the other to permit reach adjustment. A fixing rail welded to one of the tubes is secured to a support bracket by the releasable clamp mechanism. Rake adjustment can be achieved by providing a support bracket which includes vertically extending slots through which the clamp mechanism passes. The clamp mechanism, which is secured to the fixing rail, can be moved vertically within these slots, taking the column with it to adjust rake.

A known arrangement for use in restricted spaces utilises a bracket in the form of an inverted U-shape having two arms depending from a base which have the vertical slots formed therein. The clamp mechanism includes a bolt which passes through the slots to link the arms together and the column is located between the arms. Tightening the bolt draws the arms together to squeeze them onto the column. A drawback is that the amount of force needed to apply a consistent clamp load decreases as the clamp moves towards its lowest position towards the free ends of the arms of the brackets. This inconsistency gives an unpleasant feel to the driver. It is also known from WO2007/026224 to provide for a bracket in which one arm comprises inner and outer leaves. The outer leaf extends down from the bracket base as before, and the inner leaf is fixed to the free end of the outer leaf and extends back up towards the base. The clamp acts between the inner leaf and the other arm of the bracket. The function of the inner/outer leaves is to reduce variations in clamping force that arise during rake adjustment due to the clamp acting at different points along the clamp bracket arms. Both the inner and outer leaves can be made to flex such that changes in spring force of one leaf cancel out changes in the other as the clamp mechanism moves up and down.

According to a first aspect there is provided a steering column assembly comprising a steering column shroud which supports a steering shaft for a steering wheel, a support bracket which is fixed in position relative to a part of vehicle, and a clamp mechanism which is movable between a locked position in which the clamp mechanism fixes the shroud in position relative to the support bracket and an unlocked position in which the clamp mechanism permits movement of the shroud relative to the support bracket, in which the support bracket comprises a generally U- shaped member with two depending arms of the U extending from its base having a portion of the column shroud located therebetween, and a clamp mechanism which upon locking of the clamp mechanism provides tension between the two arms of the U shaped member together thereby clamping the steering column shroud in position, characterised in that one arm of the U-shaped member comprises an outer leaf extending from the base to a free end of the arm and an inner leaf connected to the free end of the arm and extending upwards from the free end towards the base, the inner leaf being located between outer leaf and the other arm of the U-shaped member, and further in which the inner leaf is so constructed and arranged as to form a main body portion which is fixed to the outer leaf and a tab which is connected to the main body portion along an upper edge so that it can flex relative to the main body portion, the tab extending from its upper edge towards the other end of the inner leaf, the tab including at least a part of a slot which extends downwards from a point at or adjacent to the top of the tab to a point closer to the bottom of the tab, and in which the clamp mechanism acts to apply tension between the tab of the inner leaf and the other arm.

The inner leaf may include a slot which is wholly located within the tab, the clamp mechanism at least partially extending through the slot to the other arm of the bracket.

By providing an inner leaf that includes a tab which carries at least part of a slot, and preferably all of the slot, the changes in clamp force can be carefully controlled or indeed eliminated. There is no longer a need for the outer leaf to flex, as is required for the bracket disclosed in the earlier application WO2007/026114. This enables a stiffer outer leaf to be used which provides increased consistency in clamp force and greater security of location for the steering column shroud. It may also allow the outer arm and other arm to be formed by simply folding over the ends of a plate which forms the base of the bracket. The base and outer arm may therefore comprise material of the same thickness.

The outer leaf may include a slot which is in register with the slot in the inner leaf but which is wider than the slot in the inner leaf. The purpose is that the clamp mechanism can pass through the slot in the outer leaf to contact a region surrounding the slot in the tab of the inner leaf.

The inner and outer leafs may be formed by folding of a single member back on itself, preferably through 180 degrees so that they overlap. Alternatively, the inner and outer leaves may comprise separate components connected by welding, bonding, riveting or the like.

The tab may be formed by a continuous cut-out region, which may have a U-shape extending around the tab, the top of the arms of the U-shape being joined by a line about which the tab can flex. The tab may therefore lie wholly in the plane of the remainder of the inner leaf.

In an alternative arrangement, the tab may be a separate element which is bonded, welded or otherwise fixed to the main body of the inner leaf. Alternatively it may be formed by folding the free end of the inner leaf back on itself. In the later case three slots may be needed - one in the outer leaf, one in the main body of the inner leaf and one in the tab formed by bending back the inner leaf.

The base of the U shaped bracket is preferably located above a portion of the column assembly, as is the clamp mechanism. Thus, the base may be located horizontally above the portion of the steering column with the arms depending vertically downwards such that the U-shape is inverted.

The inner leaf and outer leaf of the one arm may be integrally formed. Most preferably they are formed by providing an over length arm and bending it back on its self at a point along its length corresponding to the desired length of the outer leaf. This is convenient and relatively inexpensive.

Alternatively, the inner leaf may comprise a separate component which is secured to the outer leaf at or near the free end of the arm. It may be secured by welding, perhaps using two or more spot welds. It could, of course, be fixed by any other known technique depending upon the choice of materials used for the inner and outer leaf. Whilst providing the inner and outer leaf as separate components is more complex and potentially more complex than bending, it may allow the properties of the inner and outer leafs to differ. Different materials or thicknesses of material could be used.

The clamp mechanism may include a clamp bolt that connects the inner leaf and the other arm. The bolt may comprise a shaft which may be provided with a nut or bolt head at one end with the shaft and bolt head/nut passing cleanly through an opening (such as a hole or slit) in the outer leaf yet prevented from passing through an opening in the inner leaf and continuing to pass through an opening in the other arm whereupon a means for drawing the shaft towards the other arm is provided. This may take the form of a cam which acts between the arm and a fixed nut or head fixed to the end of the shaft.

Alternatively, the inner leaf may be provided with a thread which receives a complimentary thread on the shaft to fix the shaft to the inner leaf. In a still further alternative the clamp shaft may be welded or otherwise fixed to the inner leaf. Whatever arrangement is chosen, it is important that when the clamp shaft is pulled towards the other arm it only pulls on the inner leaf and not the outer leaf, with the inner leaf in turn pulling on the outer leaf.

The other arm may be of greater rigidity than the arm with the inner and outer leafs, providing a relatively fixed datum for securing the column and ensuring that overall lateral stiffness remains adequate. The outer arm of the one arm may have the same rigidity as the other arm. The shroud may be telescopic and may comprise an inner member and an outer member, the inner member being at least partially received within the outer member.

The arms of the U-shaped member may clamp on to a portion of the outer or inner members, or to a fixing rail secured thereto. The engagement between the inner leaf and the fixing rail (or other part) is preferably over a smaller vertical distance than the engagement between the fixing rail (or other part) and the more rigid arm. By vertical distance we mean the distance vertically when the arms of the bracket are considered to be aligned vertically. This ensures that small deformations of the inner leaf out of the vertical as the clamp mechanism is locked are absorbed without any significant rotation of the column assembly.

The clamp assembly may be arranged such that when the clamp is in the unlocked position the rake of the steering column can be adjusted whilst the inner and outer members remain fixed relative to one another. This is known as a single adjust mechanism.

Additionally, the clamp when in the unlocked position may permit the inner member to move relative to the outer member to provide for reach adjustment, this movement being prevented when the clamp mechanism is moved to its locked position. This is known as a double adjust mechanism. This arrangement therefore permits both rake and reach adjustment from a single unlocking of the clamp mechanism.

In one embodiment of a double adjust mechanism the outer member, or the fixing rail, may be provided with one or more slits in the region fixed by the clamp such that the action of locking the clamp closes the slits and so deforming the outer member so that it grips the inner member. It may grip it directly or indirectly, e.g. through an intermediate member. The intermediate member may be chosen so as to provide a require friction between the inner and outer members.

The inner and outer members may each be substantially tubular, with the outer member having at least one elongate slit along its length at least in the region clamped by the clamping mechanism whereby the effective diameter of the outer member is reduced upon clamping to grip the inner member.

According to a second aspect the invention provides a support bracket for a steering column assembly which comprises a generally inverted U- shaped member having a base and two arms depending from it; at least one of the arms comprising an outer leaf extending from the base to a free end of the arm and an inner leaf connected to the free end of the arm and extending upwards from the free end towards the base, the inner leaf being located between the outer leaf and the other arm of the U-shaped member and in which the inner leaf is so constructed and arranged as to form a main body portion which is fixed to the outer leaf and a tab which is fixed to the main body portion along an upper edge so that it can flex relative to the main body portion, the tab extending from its upper edge towards the other end of the inner leaf, the tab including a slot which extends downwards from a point at or adjacent the top of the tab to a point closer to the bottom of the tab.

The outer leaf may include a slot which is in register with the slot in the inner leaf but which is wider than the slot in the inner leaf.

The inner and outer leafs may be formed by folding of a single member back on itself, preferably through 180 degrees. The inner and outer leafs may comprise separate components connected by welding, bonding, riveting or the like.

The tab may be formed by a continuous cut-out region, which may have a U-shape extending around the tab, the top of the arms of the U-shape being joined by a line about which the tab can flex.

There will now be described, by way of example only, three embodiments of the present invention of which:

Figure l(a) is a general view in plan of a steering column assembly that is adjustable for reach and rake;

Figure l(b) is a general view of an alternative steering column assembly;

Figure 2(a) is a cross section through a first embodiment of a clamp assembly of a steering column according to the invention when viewed along the axis of the steering column;

Figure 2(b) is an alternative view of the bracket of Figure 2 (a) when viewed from the side;

Figure 3 (a) is a cross section through a first embodiment of a clamp assembly of a steering column according to the invention when viewed along the axis of the steering column;

Figure 3(b) is an alternative view of the bracket of Figure 2 (a) from the side;

Figure 4 is a side view of an inner leaf of the bracket of Figure 2 or 3; Figure 5 (a) and (b) are two views of the bracket of the first embodiment in perspective showing the detail of the tab provided in the inner slot, with figure 5(c) showing the inner leaf separate from the rest of the bracket for clarity; and

Figures 6 and 7 show two alternative arrangements for the inner leaf.

As shown in Figures l (a) and l(b) , a steering column assembly comprises a steering column shroud 1,2 that extends from a gearbox housing 3 that is fixed pivotally to a part of the vehicle body at a point 6 and also releasably fixed to a support bracket 20 (shown in Figure 2) which is secured to the vehicle, typically by welding or bolting it to a region under the dashboard at a point somewhere between the pivot and the steering wheel. The shroud 1,2 is fixed to the bracket by a clamp mechanism. The clamp mechanism 20 can be unlocked and locked to allow the rake of the steering column shroud to be adjusted by pivoting about the pivot point 6. When locked the steering column shroud cannot easily be moved.

A first embodiment of a support bracket 20 and clamp mechanism is shown in Figure 2 (a) and 2(b) of the accompanying drawings. The 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. The two dependent arms 22,23 of the U-shaped bracket extend generally downwards in a vertical plane and extend down either side of a fixing rail 24 welded to the outer portion 2 of the steering column shroud. A clamp mechanism acts between the two arms 22,23 to squeeze them together so that they clamp onto the sides of the fixing rail 24 when the clamp mechanism is in its locked position, thereby holding the shroud in position. The clamp mechanism comprises a shaft or pin 25 which passes through a respective opening 26,27,28 in each arm and openings in each side of the fixing rail 25. The size and shape and location of these openings determines the range of movement that is possible for the steering column shroud. The A head 29 is provided on one end of the shaft, which has an outer dimension greater than the width of the opening in the adjacent arm 22 so that it cannot pass through the opening. Threaded onto the other end of the shaft 25 is an adjustable nut 33, and between that nut 33 and the outside of the outer leaf of the adjacent arm 23 is a cam assembly. The cam assembly comprises a fixed cam 30 carried by the shaft 25 and a moving cam 31 which can be rotated relative to the fixed cam by a locking lever 32. Rotation of the cam 31 varies the length of the cam assembly 30,31.

In the unlocked position, the cam assembly has its shortest length so that the bracket arms 22,23 are not clamped to the fixed rail 24. In the locked position, the cam assembly has its longest length. The cam therefore pushes the adjacent nut away from the adjacent arm 23, which causes the shaft to pull the head on the other end of the shaft towards the cam assembly and so acts to squeeze the arms 22,23 of the bracket onto the fixed rail 24. As this occurs, the force applied by the cam mechanism is opposed by the amount of "spring" in the arms 22,23 of the bracket which resist being bent onto the fixed rail.

As shown in Figure 1 , the steering column shroud comprises an inner part 1 and an outer part 2 which can telescope relative to one another. Located within the shroud is a two-part collapsible steering shaft 4,5. One end of the shaft connects to a gearbox within the gearbox housing, the other to a steering wheel (not shown) . It is not essential to the invention that the shaft connects to a gearbox- it could equally connect directly to a part of a steering rack. The two part shroud and shaft allow the steering wheel to be adjusted for reach, and this can be accommodated by providing elongate slots in the fixing rail which allow the outer tube to be moved relative to the clamp pin. In addition, to allow the steering column to be adjusted for rake (height adjustment) , the arms of the brackets are provided with elongate, generally vertical slots along which the pin can move.

It will be appreciated that with a column assembly that can be adjusted for rake, as the clamp pin moves from the top of the slot to the bottom, corresponding to the steering being moved from its highest position to its lowest position, the clamp mechanism will attempt to bend the ends of the arms onto the rail rather than the part of the arms that join the base. Since the arms effectively act as leaf springs, the result is that the locking forced required at the lowest position might be lower than that needed at the top in order to apply the same amount of clamping force to the fixed rail. The applicants have appreciated that this could be a problem and is so doing having moved to solve this problem as shown in Figure 2 (a) and 2(b) through careful design of the arms of the bracket.

As can be seen in Figures 2(a) and 2(b), one arm 23 of the bracket comprises a single plate with a suitably shaped elongate slot 26. This plate can be relatively thick. The other arm 22 comprises an outer leaf or plate 22b which is fastened to the base 21 of the bracket 20, and an inner leaf or plate 22a which is formed by bending the outer plate back onto its self. The bent back portion forms an inner plate 22a which is located inside the outer plate 22b, and extends upwards towards the base of the bracket to provide- in effect- a double layered arm. The inner plate 22a is not fixed to the outer plate anywhere other than the fold at the free end of the outer plate. Both the inner plate 22a and the outer plate 22b are provided with generally vertically extending slots 27,28, with the slot 28 in the outer plate being wider than the slot 27 in the inner plate. The clamp mechanism is arranged so that as it is moved to the locked position the head 29 does not act on the outer plate but only the inner plate. This means that as the clamp mechanism is locked, the inner plate is forced onto the fixed rail and is doing so applies force to the end of the outer plate.

Because the inner and outer plates are constructed in the way described, a more consistent clamping force is achieved. Whilst the force needed to bend the outer plate is greater when the steering column shroud is in its highest position, the force needed to bend the inner plate is lowest in that position. The opposite is true at the lowest position of the steering column shroud, so the two effects can be made to approximately cancel each other out by selection of material types and thicknesses for the inner and outer plates.

In a further refinement best seen in Figures 4 and 5(a)-(c) of the accompanying drawings, the inner plate 22a is provided with a cut-out 41 which forms a u-shape around the slot 27. The cut-out can be formed by laser cutting a slot in the inner leaf, or the cut-out could be formed by pressing or stamping. The base of the U-shaped cut-out is located below the slot 27 but above the join between the inner plate 22a and the outer plate 22b, and the top point of the upwardly extending arms of the u- shaped cut-out 41 are roughly level with the top of the elongate slot 27 through which the clamp pin 25 passes. The cut-out 41 therefore defines a tab 42 in the centre of the main body of the inner plate which carries the elongate slot, the tab joining the rest of the inner plate at its upper edge along a line which links the two upper points of the cut-out (shown as dotted line 45 in Figure 4) . To reduce localised stresses which could lead to fatigue the top ends of the cut-out are shaped as circular holes of slightly larger width than the remainder of the slot. The corners of the cut-out are also rounded slightly.

The tab 42 can flex relative to the rest of the inner plate 22a as the clamp mechanism is locked, providing an additional spring effect. This additional flexing gives further control over the variation in clamping force for different steering column rake positions. For example, with the rake of the steering column shroud set to its highest position, the clamp shaft will be located at the top end of the inner plate, and the root of the tab 42. Thus, the inner plate 22a will bend relatively a lot and the tab 42 relatively little. With the rake at its lowest position the clamp shaft 25 will be located close to the base of the inner plate 22a and the end of the tab 42. The main body 43 of the inner plate 22a will therefore bend a relatively small amount and the tab by a lot. The two effects can therefore be made to cancel each other out, or the tab can be made to work together with bending of the outer plate to cancel out the bending of the inner plate.

In particular, the tab 42 allows the outer plate 22b to be made relatively stiff because the bending of the main body 43 of the inner plate and the tab 42 can be made to cancel out with rake adjustment to give consistent clamping force. There may, in some cases, be no need for the outer plate to contribute any significant amount of flex. By making the outer plate 22b stiff er the clamping action has been found to be more consistent. Also, it gives more freedom to the design of the outer plate, which could be made by simply folding over a flat sheet to form the base and arms of the bracket without concern about ensuring outer plate has the correct deformation to match the inner plate. It will be appreciated that various modifications can be made without departing from the scope of the present invention and the specific embodiments is not intended to be limiting to the protection provided which is defined by the claims. For example, a second embodiment shown in Figures 3 (a) and 3(b) of the accompanying drawings includes an inner plate 22a which is separate from the outer plate 22b, the two being secured by a pair of spot welds 34,35 towards the free end of the outer plate 22b.

Figures 6 and 7 show two alternative arrangements for an inner leaf of a clamp assembly in accordance with the invention. In figure 6, an inner leaf 60 comprises a main body portion 61 and a tab 62 which is formed by folding the free end of the inner leaf back on itself. The inner leaf therefore comprises two layers, one forming the main body and the other the tab. In figure 7, the tab 72 comprises a separate element which is fastened to the free end of the main body 71 of the inner leaf 70. In the example shown it is fastened by two spot welds.

In each of Figures 6 and 7, the main body must be provided with a slot or opening 64,74 through which the clamp pin shaft can pass so that the clamp mechanism acts on the surrounding edges of the slot 63,73 in the tab only. The slots or openings in the main body of the inner leaf 60,70 must therefore be wider than those in the tab.

Also, where the inner leaf comprises two layers, the tab may be spaced from the main body of the inner leaf as shown in Figure 6 for example or be in contact with the inner leaf as shown in Figure 7.

Claims

1. A steering column assembly comprising a steering column shroud which supports a steering shaft for a steering wheel, a support bracket which is fixed in position relative to a part of vehicle, and a clamp mechanism which is movable between a locked position in which the clamp mechanism fixes the shroud in position relative to the support bracket and an unlocked position in which the clamp mechanism permits movement of the shroud relative to the support bracket, in which the support bracket comprises a generally U-shaped member with two depending arms of the U extending from its base having a portion of the column shroud located therebetween, and a clamp mechanism which upon locking of the clamp mechanism provides tension between the two arms of the U shaped member together thereby clamping the steering column shroud in position, characterised in that one arm of the U-shaped member comprises an outer leaf extending from the base to a free end of the arm and an inner leaf connected to the free end of the arm and extending upwards from the free end towards the base, the inner leaf being located between outer leaf and the other arm of the U-shaped member, and further in which the inner leaf is so constructed and arranged as to form a main body portion which is fixed to the outer leaf and a tab which is connected to the main body portion along an upper edge so that it can flex relative to the main body portion, the tab extending from its upper edge towards the other end of the inner leaf, the tab including at least a part of a slot which extends downwards from a point at or adjacent to the top of the tab to a point closer to the bottom of the tab, and in which the clamp mechanism acts to apply tension between the tab of the inner leaf and the other arm.

2. A steering column assembly according to claim 1 in which the inner leaf includes a slot which is wholly located within the tab, the clamp mechanism at least partially extending through the slot to the other arm of the bracket.

3. A steering column assembly according to claim 1 or claim 2 in which the tab is formed by a continuous cut-out region, which has a U- shape extending around the tab, the top of the arms of the U-shape being joined by a line about which the tab can flex.

4. A steering column assembly according to claim 1,2 or 3 in which the tab lies wholly in the plane of the main body of the inner leaf.

5. A steering column assembly according to claim 1 or claim 2 in which the tab is a separate element which is bonded, welded or otherwise fixed to the main body of the inner leaf.

6. A steering column assembly according to claim 1 or claim 2 in which the tab is formed by folding the free end of the inner leaf back on itself.

7. A support bracket for a steering column assembly which comprises a generally inverted U-shaped member having a base and two arms depending from it; at least one of the arms comprising an outer leaf extending from the base to a free end of the arm and an inner leaf connected to the free end of the arm and extending upwards from the free end towards the base, the inner leaf being located between the outer leaf and the other arm of the U-shaped member and in which the inner leaf is so constructed and arranged as to form a main body portion which is fixed to the outer leaf and a tab which is fixed to the main body portion along an upper edge so that it can flex relative to the main body portion, the tab extending from its upper edge towards the other end of the inner leaf, the tab including a slot which extends downwards from a point at or adjacent the top of the tab to a point closer to the bottom of the tab.

8. The support bracket of claim 7 in which the tab is formed by a continuous cut-out region, which may have a U-shape extending around the tab, the top of the arms of the U-shape being joined by a line about which the tab can flex.

9. A support bracket substantially as described herein with reference to and as illustrated in the accompanying drawings.