GB2463138A

GB2463138A - Steering column assembly

Info

Publication number: GB2463138A
Application number: GB0914334A
Authority: GB
Inventors: Patrick Anthony Duffy; 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: GB0816353D0; GB2463138B; GB0914334D0

Abstract

A shroud comprising a first 1 and second 2 members in which an end portion of the first member 1 fits within an end portion of the second member 2, the members 1, 2 being free to telescope. A clamp mechanism 5 which releasably fixes the members 1, 2 relative to one another and which fixes the shroud in position relative to a vehicle. A sprung support 16 is fixed to thr vehicle in a first region and which has a slide portion 15 at a second region that engages an underside of the shroud to at least partially support the weight of the shroud when the clamp mechanism 5 is released. The second member 2 comprises a main body (21, Figure 3) having an insert (23, Figure 3) secured to it. The insert (23) comprising a first portion that forms a guide bush that extends at least partially around an inner face of the body (21) and provides a sliding support for the end portion of the first member 1. A second portion located on the outside of the body (21) forms a runner 17 between the slide portion 15 and the body (21) and a connecting part (24) which connects the guide bush (23) to the runner 17.

Description

STEERING COLUMN ASSEMBLY

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

It is known to provide a steering column assembly in which the steering shaft is adjustable for steering wheel height known as reach and for steering wheel distance known as rake. Such assemblies are known as double adjust steering columns. A steering column shroud is provided that supports the steering shaft that in turn supports the steering wheel. To permit the rake and reach adjustment the shroud is secured to the vehicle at first point by a pivot and at a second point nearer the steering wheel by a releasable clamp mechanism. When clamped the shroud, and hence shaft and wheel are fixed. When released, the shroud and shaft can be pivoted upwards to provide rake adjustment. The shroud and shaft may also be adjusted for length, typically by telescopic action, which provides for the reach adjustment.

The weight of the steering wheel and shaft can be quite considerable. If the clamp mechanism is released and some additional support of the shroud/shaft/wheel is not present it could fall into a drivers lap with considerable force. The considerable weight of the assembly may inconvenience the driver when raising the wheel to the required position and securing the clamp mechanism. As the driver typically needs one hand free to operate the clamp this adjustment may prove burdensome.

To solve this problem it is common to provide a spring loaded support mechanism which acts between the vehicle and the shroud. The spring mechanism takes some of the weight of the shroud and shaft and wheel when the clamp assembly is released for adjustment. This damps the fall of the assembly and assists the driver when they try to make rake adjustments by taking some of the weight.

In one known example of a possible prior art arrangement for a spring loaded support mechanism, the spring mechanism comprises a sling having a base portion that passes under the shroud and two sprung arms. One arm is provided on each side of the shroud and connects an end of the base portion to the vehicle body above the shroud. The arms comprise coils springs. In adjusting the assembly for reach, the applicant has observed that the base of the sling must slide over the lower surface of the shroud during reach adjustment. This movement can be quite stiff if friction is high and the operation may be noisy.

According to a first aspect the invention provides a steering column assembly for a vehicle, the assembly comprising a shroud comprising an first member and a second member in which an end portion of the first member fits within an end portion of the second member, the first and second members being free to telescope relative to one another such that the overall length of the shroud can be adjusted, a steering shaft which is supported by the shroud, a clamp mechanism which releasably fixes the first member and second member relative to one another and which fixes the shroud in position relative to the vehicle, and a sprung support is fixed to the vehicle in a first region and which has a slide portion at a second region that engages an underside of the shroud to at least partially support the weight of the shroud when the clamp mechanism is released, characterised in that the second member comprises a main body and an insert that is secured to the main body, the insert comprising a first portion that forms a guide bush that extends at least partially around an inner face of the main body and provides a sliding support for the end portion of the first member where it fits within the main body, a second portion which is located on the outside of the main body to form a runner that lies between the slide portion of the sprung support and the main body, and a connecting part which extends through a slot in the main body to connect the guide bush to the runner.

The insert may comprise a molded insert.

The provision of a molded integral guide bush and runner connected by the integral connecting part that passes through the main body offers an especially elegant solution to the problem securing a guide bush and spring runner in place. The spring runner and guide bush provide surfaces across which the first shroud member and spring can slide.

The molded insert may be constructed of plastic material or any other material that has a low coefficient of friction (for instance a coefficient of friction less than say 0.2 or perhaps 0.05 or less) at least in the areas where friction contact with the first member or slide portion occurs.

The element may comprise a part which is molded in situ onto the main body of the outer member of shroud. The plastic element and main body may in this way be arranged in such a manner that they could not be separately produced and later assembled due to mechanical interferences between the parts. This allows the element to be made thinner and yet still secured to the main body.

The main body of the second member may comprise a generally cylindrical tube.

The guide bush may also be generally tubular and conform to a portion of an inner wall of the main body. The guide bush may be relatively thin, by which we mean it may have a thickness less than the wall thickness of the main body.

The end of the guide bush may be aligned with the end of the main body through which the first member is inserted and may be provided with an outwardly extending flange at that end which lies against the radial end face of the main body.

This flange helps prevent the guide bush nicking up as the first member of the shroud is pushed into the main body. The connecting part prevents nicking of the guide bush when the first member is pulled out of the main body.

The spring runner may comprise a relatively thin elongate tongue having a length equal to or greater than the amount of adjustment in length of the shroud due to telescoping. The tongue may be part cylindrical in cross section so that it conforms to the outer wall of the main body of the second member of the shroud.

The sprung support mechanism may be formed from a bent metal rod with a central portion passing under the shroud to provide the support and the ends bent to form arms which include a torsion coil spring part.

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 view of an electric power assisted steering assembly in accordance with a first aspect of the invention; Figure 2 is a perspective view of a complete steering column assembly constructed in accordance with the principles of the schematic of Figure 1; Figure 3 is an enlarged view in cross section along its length of the upper shroud portion of the assembly of Figure 2; and Figure 4 shows the plastic element of the upper shroud portion of Figure 3 in isolation.

A steering column assembly 100 is shown in Figures 1 and 2 of the accompanying drawings. The assembly comprises a shroud 1,2 which is fixed to the vehicle (not shown), a steering shaft 3 supported in bearings joumaled to the shroud, a steering wheel (not shown) connected to one end of the shaft 3, and an electric power assisted steering gearbox 4 connected to the end of the steering shaft 3 furthest from the steering wheel. The gearbox 4 connects the shaft 3 to a motor which provides assistance when the driver tries to turn the wheel by applying a torque of the same sense as that applied by the driver. The gearbox also connects the shaft through further mechanical links such as a steering rack to the road wheels.

The shroud 1,2 is fixed to the vehicle at one point by a pivot (not shown) close to the gearbox and at another point closer to the steering wheel through an adjustable clamp mechanism 5 seen in Figure 2. When released the clamp mechanism 5 enables the shroud 1,2 to tilt up and down about the pivot to provide rake adjustment of the steering wheel.

As can also be seen in Figure 1 the shroud comprises a first member 1 and a second member 2, and end of the first member 1 being received partially within an end of the second member 2 and free to telescope relative to the second member 2 when the clamp mechanism 5 is released. Both members 1,2 are generally cylindrical metal tubes. As can be seen in Figure 1 the inner diameter of the second member 2 is greater than the outer diameter of the first member 1 and so it can slide over the end of the first member 1. The steering shaft 3 is also provided in two parts which can telescope to follow changes in length of the shroud. This movement provides reach adjustment of the steering wheel.

The clamp mechanism 5 comprises a fixed bracket 6 which has an inverted U -shape in cross section (when viewed along the length of the shroud). The base 7 of the U shaped bracket 7 is rigidly fixed to the vehicle body above the shroud 1,2 and has two arms 8,9 that depend down either side of the shroud. A clamp rail 10, visible in Figure 1, which is also of U-shape in cross section, is welded to the top of the shroud along a length of the shroud which is surrounded by the arms of the fixed bracket 7. The clamp rail 10 is a snug fit within the arms of the bracket 7 SO that the side walls of the clamp rail touch the inside of the arms of the bracket 7 and prevent excessive side to side movement of the shroud relative to the bracket 7. As shown the rail 10 is fixed to the top of the second member of the shroud which has the larger diameter.

Each arm 8,9 of the bracket 7 is provided with a vertically extending elongate slot.

One slot 8a in arm 8 can be seen in Figure 2. Each side wall of the clamp rail 10 is provided with a substantially horizontal slot 11 as shown in Figure 1. A clamp bolt 12 passes through the slots in the arms 8,9 and side rails and is provided with a fixed head on one end and an adjustable head on the other operated by a hand lever 13. The driver can rotate the hand lever 13 to move the adjustable head towards the fixed head. This clamps the arms of the bracket to the side walls of the clamp rail and locks the shroud in place. The driver can also move the lever 13 to expand the distance between the fixed head and adjustable head which unclamps the bracket arms and clamp rail. In this condition the clamp bolt can slide up and down the vertical rails to give rake adjustment and along the horizontal slots to give reach adjustment.

It will be appreciated that the weight of the shroud 1,2, the steering shaft 3, the wheel and the moving part of the clamp mechanism 5 is considerable. A sprung support mechanism 14 is therefore provided which is formed from a bent metal wire or rod. It has a lower support portion 15 that passes under the shroud 1,2 and which is connected to the vehicle by two sprung arms, one on each side of the shroud. One of the arms 16 can be seen in Figure 2. Each arm comprises a torsion coil spring with multiple turns forming a right angled connection between the lower support portion and the fixed bracket. If the clamp mechanism 5 is released with the steering wheel at its highest rake position, the sprung support mechanism 14 damps the fall of the shroud. The spring rate of the arms is chosen so that the shroud will fall to its lowest position, albeit in a much slower rate than it would without the spring. It is then easier for the driver to raise the wheel to a desired rake as the spring takes much of the weight. Alternatively the spring rate of the arms may be chosen so that the shroud rises gently to its highest position.

As the second member 2 of the shroud is moved during reach adjustment it must slide over the slide portion 15 of the sprung support mechanism. To make this action smoother, a plastic runner 17 is provided along which the slide portion 15 slides. This runner 17 is an integral part of the shroud member 2 and is shown in more detail in Figures 3 and 4 of the accompanying drawings. It is also shown in place in Figure 2 of the accompanying drawings.

Refering to Figure 3, the second member 2 of the shroud comprises a main body 21 in the form of a cylindrical tube and an integrally molded plastic element 22 that functions as both a guide bush 23 for the end of the first member of the shroud and also a runner 17 for the sprung support mechanism to slide along during reach adjustment. The two parts of the plastic element 22 are connected by an integral connecting part 24 that passes through a slot in the main member 21. Because the guide bush 23, runner 17 and connecting part 24 are all integrally formed as one element they hold one another in place without the need for additional fasteners or adhesive.

The guide bush part 23 of the element 22 is tubular and may have a relatively thin wall. It extends around the entire inner surface of an end section of the main body 21 of the second member 2 except for a narrow slot at its top edge. Although not shown, this slot coincides with a similar axial slot in the upper wall of the main body located inside the clamp rail 10. The provision of this slot allows the main body to close up slightly when the clamp mechanism is clamped. When assembled the guide bush 23 fits between the main body 21 and the end of the first member 1 that is received in the main body 21.

A free end of the guide bush 23 is aligned with the radial end face of the main body and is terminated with an outwardly extending flange 24 that lies against the radial end face of the main body. This prevents the guide bush 23 from nicking up as the shroud is adjusted in length and enables the guide bush to be kept thin.

The runner part 17 of the plastic element 22 comprises a thin curved tongue like strip which conforms to the lower outer surface of the metal tube 21. This can be seen in more detail in Figure 4 which shows the plastic element 22 separate from the metal tube 21. The plastic guide element 22 has a lower friction coefficient than the metal tube.

The runner 17 provides a low friction guide surface for the support portion 15 of the sprung support mechanism 15 to slide upon. The length of this surface is chosen to be a little longer than the range of reach adjustment. This surface reduces wear, lowers the force needed to make reach adjustments and also reduces noise.

The inside part forms a guide bush 23 which provides a low friction sliding engagement between the metal tube 21 of the second member and the end of the first member 1 that slides within it.

Claims

CLAIMS1. A steering column assembly for a vehicle, the assembly comprising a shroud comprising an first member and a second member in which an end portion of the first member fits within an end portion of the second member, the first and second members being free to telescope relative to one another such that the overall length of the shroud can be adjusted, a steering shaft which is supported by the shroud, a clamp mechanism which releasably fixes the first member and second member relative to one another and which fixes the shroud in position relative to the vehicle, and a sprung support is fixed to the vehicle in a first region and which has a slide portion at a second region that engages an underside of the shroud to at least partially support the weight of the shroud when the clamp mechanism is released, characterised in that the second member comprises a main body and an insert that is secured to the main body, the insert comprising a first portion that forms a guide bush that extends at least partially around an inner face of the main body and provides a sliding support for the end portion of the first member where it fits within the main body, a second portion which is located on the outside of the main body to form a runner that lies between the slide portion of the sprung support and the main body, and a connecting part which extends through a slot in the main body to connect the guide bush to the runner.
2. A steering column assembly according to claim 1 in which the insert is a molded insert.
3. A steering column according to claim 1 or claim 2 in which the insert is constructed of plastic material or any other material that has a low coefficient of friction (for instance a coefficient of friction less than say 0.2 or perhaps 0.05 or less) at least in the areas where friction contact with the first member or slide portion occurs.
4. A steering column assembly according to claim 1, 2 or 3 in which the element comprises a part which is molded in situ onto the main body of the outer member of shroud.
5. A steering column assembly according to any preceding claim in which the main body of the second member comprise a generally cylindrical tube, the guide bush also is generally tubular and conforms to a portion of an inner wall of the main body.
6. A steering column assembly according to any preceding claim in which the end of the guide bush is aligned with the end of the main body through which the first member is inserted and isprovided with an outwardly extending flange at that end which lies against the radial end face of the main body.
7. A steering column assembly according to any preceding claim in which the spring runner comprises a relatively thin elongate tongue having a length equal to or greater than the amount of adjustment in length of the shroud due to telescoping.
8. A steering column assembly substantially as described herein with reference to and as illustrated in the accompanying drawings.