GB2586662A

GB2586662A - Steering column assembly

Info

Publication number: GB2586662A
Application number: GB1914361.9A
Authority: GB
Inventors: Wojtalik Artur; Ponikiewski Pawel
Original assignee: TRW Steering Systems Poland Sp zoo
Current assignee: TRW Steering Systems Poland Sp zoo
Priority date: 2019-08-30
Filing date: 2019-10-04
Publication date: 2021-03-03
Anticipated expiration: 2039-10-04
Also published as: DE102020210489A1; GB2586662B; GB201914361D0

Abstract

A steering column assembly 100 for a vehicle is provided, with a support bracket 122 attachable to a vehicle and supporting a shroud 112 which in turn supports a steering shaft 102. A clamp mechanism 134 is provided and is movable between a locked position, where shroud 112 is fixed relative to support bracket 122, and an unlocked position, in which shroud 112 is movable relative to support bracket 122 in a rake direction. A spring support 158, comprising a coil spring which may be coiled around a clamp bolt, is secured to support bracket 122 and at least partially supports shroud 112 when clamp 134 is unlocked. Spring support 158 also provides a force to bias clamp 134 toward the unlocked position.

Description

STEERING COLUMN ASSEMBLY

The present invention relates to an adjustable steering column assembly for a vehicle.

it is known to provide steering column assemblies in which the steering wheel mounted on the column is adjustable for reach -the distance from the driver -and for rake -the vertical height of the steering wheel. Reach adjustment is enabled by providing a steering shaft that is in two parts that can slide telescopically in relation to one another. A shroud is also provided, which supports the steering shaft and is also in two parts that adjust telescopically. Rake adjustment is enabled by allowing the steering shaft and shroud to move relative to a support bracket that is attached to the vehicle.

A clamp assembly is also provided which locks and unlocks the adjustment of the steering column assembly. The clamp assembly is usually locked and unlocked by a lever that is operable by the driver. When unlocked, the steering shaft and shroud may be moved to a desired position by the driver and when locked the steering shaft and shroud are prevented from moving relative to the driver. The clamp assembly may secure the steering shaft and shroud by friction, for example by tightening an outer shroud portion around an inner shroud portion, or by using a positive-lock mechanism such as one or more toothed blocks that lock together with toothed racks on the shroud and support bracket. For each of these types of mechanism, a clamp bolt, which includes a cam assembly, is provided. The lever rotates the cam assembly to adjust the effective length of the clamp bolt. In turn, the shortening or lengthening of the clamp bolt acts to engage and disengage the lock of the steering column assembly. In some cases, a coil spring is wound around the clamp bolt which is compressed in the locked position and therefore helps to disengage the lock when the lever is rotated to the unlocked position.

in order to prevent the steering column dropping during adjustment, and to make the adjustment easier for the driver, it is common to provide a spring that counterbalances the adjustment. The counterbalance spring is most commonly positioned such that it acts as a sling under the shroud and is attached at either end to the support bracket. This can provide issues with packaging of the steering column assembly, as the steering column assembly must be kept compact within tight surrounds of the vehicle, whilst maintaining safe clearances with other components. Moreover, steering column assemblies are required to collapse in a predictable manner during impacts, and counterbalance springs can clash with other components of the steering column assembly during such collapses, often as the counterbalance spring moves towards a power steering gearbox on the end of the steering shaft.

In accordance with an aspect, there is provided a steering column assembly for a vehicle, the steering column assembly comprising: a support bracket configured to provide attachment to a vehicle; a shroud, which is supported by the support bracket; a steering shaft, which is supported by the shroud; and a clamp mechanism which is movable between a locked position where the shroud is fixed relative to the support bracket and an unlocked position where the shroud is movable relative to the support bracket in a rake direction; and a sprung support assembly comprising a coil spring that is secured to the support bracket and is configured to at least partially support a weight of the shroud when the clamp mechanism is in the unlocked position; wherein the coil spring is further configured to provide a biasing force that biases the clamp mechanism towards the unlocked position.

The coil spring therefore has the dual function of both supporting the steering shroud to help assist adjustment of the shroud and of biasing the clamp mechanism to be unlocked, ensuring that the clamp mechanism does not stay locked even when the user attempts to move it to the unlocked position. The assembly can therefore be made more compact and simpler to assemble.

The coil spring may be coiled around a clamp bolt of the clamp assembly. This provides a strong connection to the assembly and may ensure that the coil spring is in a good position to act on the shroud and damp mechanism.

The coil spring may be compressed along its axis by movement of the clamp mechanism from the unlocked position to the locked position.

The coil spring may be compressed between two parts of the clamp mechanism. The two parts of the damp mechanism may be, for example, two spacers between which the coil spring is retained.

The coil spring may therefore act on the two parts of the clamp mechanism in order to bias the clamp mechanism towards the unlocked position. The two parts, for example the spacers, may move closer together when the clamp mechanism is moved to the locked position, increasing the compression of the coil spring, and the coil spring may bias the two parts of the damp mechanism apart such that they move apart automatically or are assisted in moving apart upon the clamp mechanism being moved to the unlocked position.

The coil spring may act to disengage an engagement mechanism of the clamp mechanism. The engagement mechanism may include a positive-locking mechanism or a frictional locking mechanism, such as where the outer shroud frictionally engages with the inner shroud and/or support bracket to provide a lock.

Where the clamp mechanism includes a positive-locking mechanism, such as the engagement of one or more toothed blocks with one or more toothed racks, the coil spring may therefore act on the positive-locking mechanism to encourage it to disengage when the clamp mechanism is moved to the unlocked position, for example by movement of the clamp lever by a user.

Movement of the clamp mechanism between the locked and unlocked positions may be achieved by operation of a clamp lever by a user. The clamp lever may operate a cam mechanism that acts to shorten or lengthen an effective length of the clamp bolt.

A first end portion of the coil spring may be configured to engage with the support bracket at a first reaction point and a second end portion of the coil spring, at an opposite end of the coil to the first end portion, may be configured to engage with the shroud at a second reaction point.

The coil spring may therefore provide a force that acts between the first reaction point and the second reaction point.

The support bracket may include an aperture through which the first end portion of the coil spring passes, the first end portion sliding through the aperture during movement of the shroud in the rake direction, moving the first reaction point along the first end portion.

The aperture may form the first reaction point By moving the first reaction point along the first end portion, the force applied by the coil spring between the shroud and the support bracket will be adjusted depending on the rake position of the steering column assembly, i.e. the further away from an axis of the coiled portion the first reaction point lies, the lower the force provided by the coil spring.

The aperture may include a friction-reducing insert, such as a polymer insert. The insert may reduce the friction between the coil spring and the support bracket. The polymer insert may comprise high-density polyethylene.

The aperture may be sized and/or shaped so as to restrict movement of the first end portion of the coil spring in directions orthogonal to the rake direction. The first end portion will therefore be confined to a single direction of movement, making the biasing force more predictable.

The first end portion may extend in the rake direction or substantially in the rake direction. The first end portion may therefore be able to slide within the aperture without undue difficulty or deformation.

The first reaction point may be configured to rotate relative to the shroud when the shroud is moved towards the rake down position, lowering tension in the coil spring.

The force provided by the coil spring may therefore be greater when the steering column assembly is at a greater height, increasing support to the shroud and preventing unwanted dropping of the shroud. This may also prevent unwanted movement of the shroud upwards during damping when the shroud is in the rake down position.

The support bracket may include a rake slot through which the clamp bolt passes, the rake slot sliding relative to the clamp bolt as the shroud is moved in the rake direction.

The second end portion may be received within a slot in the shroud. The slot may form the second reaction point.

The slot may be sized and/or shaped so as to allow sliding movement of the second end portion of the coil spring in a direction of compression of the coil spring. The slot may therefore allow unimpeded movement of the second end portion during locking or unlocking of the clamp mechanism.

The shroud and steering shaft may be movable relative to the support bracket in a reach direction when the clamp assembly is in the unlocked position. The reach direction may be orthogonal or substantially orthogonal to the rake direction. The assembly may therefore be adjusted for the reach of the driver.

The shroud may be configured to slide along the second end portion of the coil spring during movement of the shroud in the reach direction, moving the second reaction point along the second end portion.

By moving the second reaction point along the second end portion, the force applied by the coil spring between the shroud and the support bracket will be adjusted depending on the reach position of the steering column assembly, i.e. the further away from an axis of the coiled portion the second reaction point lies, the lower the force provided by the coil spring.

The second end portion may extend in the reach direction or substantially in the reach direction. The second end portion may therefore be able to slide within the slot without undue difficulty or deformation.

The second reaction point may be configured to move closer to a coiled portion of the coil spring when the shroud is moved towards a reach-out position. The coiled portion may define a coil axis of the coil spring.

The force provided by the spring may therefore be greater when the steering column assembly has a greater length, increasing the support to the shroud and preventing unwanted dropping of the shroud.

The shroud may include a reach slot through which the damp bolt passes, the reach slot sliding relative to the clamp bolt as the shroud is moved in the reach direction.

The clamp mechanism may be positioned below the steering shaft. The coil spring may therefore be positioned below the steering shaft in order to support the shroud from beneath.

The support bracket may extend underneath the shroud, allowing the coil spring to easily interact with both the shroud and the support bracket.

A non-limiting embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a partially cut-away perspective view of a steering column assembly in accordance with the invention; Figure 2 is a front perspective view of the steering column assembly of Figure 1; Figures 3a and 3b show front perspective views of the damp mechanism in the unclamped position and clamped position, respectively; Figures 4a to 4c show multiple views of the steering column assembly of Figure 1 in the rake-up position -in a reach-out position, reach-middle position, and reach-in position; and Figures 5a to 5c show multiple views of the steering column assembly of Figure 1 in the rake-down position in a reach-out position, reach-middle position, and reach-in position.

Referring firstly to Figures 1 and 2, there is shown a steering column assembly 100 for a vehicle. The steering column assembly 100 is adjustable for both reach and rake. A steering shaft 102 is formed of an upper shaft 104 that slides within a lower shaft 106 by means of a telescopic splined connection 108. The upper shaft 104 is positioned at an end closest to a steering wheel (not shown) and includes an end configured to receive the steering wheel. The lower shaft 106 is connected to a power steering gearbox 110, which provides power assistance to help the driver turn the steering wheel, in use.

A shroud 112 surrounds and supports the steering shaft 102 via two bearing assemblies 114, 116, which are situated at either end of the shaft 102. In order that the reach of the steering column assembly 100 can be adjusted, the shroud 112 is also in two parts. An inner shroud 118 is positioned around the lower shaft 106 and supports the lower shaft 106 by a lower bearing assembly 114. An outer shroud 120 is positioned around the upper shaft 104 and supports the upper shaft 104 by an upper bearing assembly 116. The outer shroud 120 slides over the outer surface of the inner shroud 118 during telescopic adjustment of the steering column assembly 100.

Adjustment of the steering column assembly 100 for reach and rake is achieved through sliding of the shroud 112 relative to a support bracket 122 that is configured to be attached to a fixed part of a vehicle. In the present embodiment the support bracket 122 includes two wings 124, each of which is fixed to the vehicle by a capsule 126 that is configured to rupture in the event that the vehicle is in a collision, allowing the steering column assembly 100 to collapse. However, other methods of attachment may alternatively be used.

The support bracket 122 includes an upper portion 128 that extends over the top of the shroud 112 and interconnects the two wings 124. Two arms 130 depend from the upper portion 128 and extend down the sides of the shroud 112. The arms 130 are joined together by a lower portion 132. The support bracket 122 therefore encircles the shroud 112. By doing so, the support bracket 122 has increased strength, but it is not necessarily required that the support bracket 122 should enclose the shroud 112 around its entire circumference.

A clamp mechanism 134 releasable engages with the shroud 112 and support bracket 122 in order to allow or disallow relative movement. in a locked position of the clamp mechanism 134, the shroud 112 is prevented from moving relative to the support bracket 122 in either a reach or a rake direction. In an unlocked position, the shroud 112 is free to move relative to the support bracket 122 in the reach and rake directions. Operation of a clamp lever 136 by a user moves the clamp mechanism 134 between the locked position and the unlocked position.

The clamp mechanism 134 includes a clamp bolt 138 on which is positioned a cam mechanism 140. The cam mechanism 140 includes a fixed cam 142 and a moving cam 144, which have opposed bearing surfaces. The bearing surfaces are shaped such that, as the moving cam 144 rotates, the cam mechanism 140 lengthens or shortens, dependent on the direction of rotation of the moving cam 144 by the clamp lever 136. This in turn changes the effective length of the clamp bolt 138.

The damp mechanism 134 passes through a reach slot 146 in the outer shroud 120 and a rake slot 148 in the support bracket 122. The reach slot 146 includes a reach toothed rack 150 which extends in the reach direction and engages with a reach toothed block 152 that is threaded onto the clamp bolt 138. With the clamp mechanism 134 in the unlocked position, the reach toothed block 152 is disengaged from the reach toothed rack 150, allowing the shroud 112 and reach slot 146 to slide along the clamp bolt 138 in the reach direction. In the locked position, the reach toothed block 152 engages with the reach toothed rack 150 in order to prevent relative movement. Depending on the reach position of the shroud 112, the reach toothed block 152 engages with the reach toothed rack 150 in different relative positions.

Similarly to the reach adjustment, the rake adjustment utilises the engagement of teeth. The rake slot 148 includes a rake toothed rack 154 that extends in the rake direction and engages with a rake toothed block 156 that is also threaded onto the clamp bolt 138. With the clamp mechanism 134 in the unlocked position, the rake toothed block 156 is disengaged from the rake toothed rack 154, allowing the shroud 112 and clamp bolt 138 to slide along the rake slot 148 in the rake direction. In the locked position, the rake toothed Hock 156 engages with the rake toothed rack 154 in order to prevent relative movement. Depending on the rake position of the shroud 112, the rake toothed block 156 engages with the rake toothed rack 154 in different relative positions.

Although the depicted embodiment includes a damp mechanism 134 that engages using positive-locking -i.e. teeth engage to lock the shroud in both the rake and reach directions, preventing slippage -a clamp mechanism may also be employed that utilises friction to provide the locking. Such mechanisms are well-known in the art and will be implemented readily by the skilled person.

It will be apparent that the rake direction and reach direction will not be absolute directions but will change depending on the position of the steering column assembly 100 at the time. For example, the reach direction will depend on the rake position of the steering column assembly 100 at any time, but will always extend along the longitudinal axis of the steering shaft 102. The rake direction, on the other hand, will extend along an arc defined by the length of the steering shaft 102 between the clamp bolt 138 and a pivot, which is for example defined by the gearbox 110 to which the steering column assembly 100 attaches. The steering column assembly 100 may pivot around different points in order to provide rake adjustment, the options for which will be known to the person skilled in the art.

Without any additional support, it will be apparent that moving the clamp mechanism 134 to the unlocked position will allow the steering shaft 102 and shroud 112 to be freely movable, and therefore if without user input, the rake position of the steering column assembly 100 will be likely to drop due to gravity. The reach position would also be free to move and may therefore change position in response to various external forces.

In order to prevent the free movement of the steering column assembly when the clamp mechanism 134 is in the unlocked position, the steering column assembly 100 therefore includes a sprung support assembly 158. The sprung support assembly 158 includes a coil spring 160 that provides a force to provide at least some force resistive to the dropping of the rake position of the steering shaft 102 and shroud 112. The sprung support assembly 158 also accomplishes the secondary purpose of providing a force to bias the clamp mechanism 134. This force ensures that, upon moving the clamp mechanism 134 to the unlocked position, the engagement mechanism -comprising in the present embodiment the reach and rake toothed blocks 152, 156, but otherwise comprising whatever features lock the shroud 112 in position relative to the support bracket 122 -is pushed out of engagement to make sure that the shroud 112 is free to move relative to the support bracket 122. in the present embodiment, the sprung support assembly 158 therefore acts to bias the reach and rake toothed blocks 152, 156 out of engagement with their respective toothed racks 150, 154.

The coil spring 160, as shown clearly in Figures 3a and 3b, engages with both the support bracket 122 and the shroud 112 in order to provide a force between the two. A first end portion 162 of the coil spring 160 engages with the lower portion 132 of the support bracket 122. The first end portion 162 is received within an aperture 164 in the lower portion 132 of the support bracket 122 and passes through in a direction that is substantially in the rake direction. An insert 166 in the aperture 164, formed here as a polymer insert, decreases the friction between the coil spring 160 and the support bracket 122 such that the first end portion 162 of the coil spring 160 may slide with less resistance through the support bracket 122 during adjustment of the rake position of the shroud 112. The first end portion 162 is snugly received within the aperture 164, i.e. it has limited or no freedom of movement in the directions orthogonal to the rake direction.

A second end portion 168 of the coil spring 160, located towards the end opposite to that of the first end portion 162, engages with the shroud 112. More specifically, the second end portion 168 of the present embodiment engages with a slot 170 on the underside of the shroud 112. The slot 170 provides an area in which the second end portion 168 can be seated and upon which the second end portion 168 can act to apply forces to the shroud 112. It also allows movement of the second end portion 168 in an axial direction of the clamp bolt 138, such that as the clamp mechanism 134 is moved from the unlocked to locked position the second end portion 168 can freely move due to compression of the coil spring 160. The second end portion 168 extends substantially in the reach direction of the steering column assembly 100, i.e. in an axial direction of the steering shaft 102 and shroud 112.

The coil spring 160, due to a coiled portion 172 located between the first end portion 162 and the second end portion 168, therefore acts to exert a force between the support bracket 122 where it engages with the first end portion 162 and the shroud 112 where it engages with the second end portion 168. Of course, in order to ensure that such a force is applied, it may be necessary to tension the coil spring 160 during the manufacture or assembly process. The point of engagement of the first end portion 162 with the support bracket 122 may be termed the first reaction point 174 and the point of engagement of the second end portion 168 with the shroud 112 may be termed the second reaction point 176. The force provided by the coil spring 160 will therefore act between the first reaction point 174 and the second reaction point 176. As the first end portion 162 is effectively restrained due to the support bracket 122 being fixedly attached to the vehicle, the force provided by the coil spring 160 acts to bias the shroud 112 in an upward direction. This therefore opposes the inclination of the shroud 112 to drop in the rake direction when the clamp mechanism 134 is moved to the unlocked position.

As mentioned previously, the coil spring 160 also acts to bias the clamp mechanism 134 towards the unlocked position. This is achieved by the ends of the coiled portion 172 acting upon two parts of the clamp mechanism 134. In the present embodiment, the ends of the coiled portion 172 act on two spacers 178, which are positioned between the cam mechanism 140 and the reach and rake toothed blocked 152, 156. As the clamp mechanism 134 is moved to the locked position, the effective length of the clamp bolt 138, i.e. the length between an end stop 180 of the clamp bolt 138 and the cam mechanism 140, is shortened, causing compression of the coiled portion 172 of the coil spring 160. Energy is therefore stored within the coiled portion 172 such that when the clamp mechanism 134 is moved to the unclamped position the coiled portion 172 pushes against the spacers 178 and acts upon the reach and rake toothed blocks 152, 156 in order to disengage them from their respective toothed racks 150, 154.

Although not necessary for functioning of the sprung support assembly 158, for compactness, the coiled portion 172 of the coil spring 160 is wound around the clamp bolt 138. Not only does this provide a compact arrangement and provides a good position for application of the forces that bias the clamp mechanism 134 towards the open position, but it also acts to retain the coil spring 160 in the assembly. Therefore, additional fixtures to keep the coil spring 160 in position are not necessary. However, where compactness and simplicity is less of an issue, the coil spring 160 may be located in different positions or may be restrained by different or addition& fixtures.

For example, the coil spring may be provided parallel to the axis of the clamp bolt rather than coaxially with it.

Beneficially, the sprung support assembly 158 also varies the force provided by the coil spring 160 based on the rake and reach position of the steering column assembly 100. The force applied differs due to movement of the first and second reaction points 174, 176 during adjustment of the shroud 112. The alteration in the position of the reaction points 174, 176 is shown clearly in Figures 4a to 4c and 5a to 5c. In each of these Figures, three different views of the steering column assembly 100 are shown: the uppermost picture shows a side view; the middle picture shows an enlarged perspective view from the rear left; and the lowermost picture shows an enlarged perspective view from the rear right.

It will be apparent from the above that the coil spring 160 operates in two modes: both torsion and compression. The coil spring 160 is compressed along the axis of the coiled portion 172, providing an axial force to the clamp mechanism 134. in the present embodiment, this axial force is provided as a force acting against the compression of the coil spring 160. In different embodiments, it may be possible to provide the coil spring in a different position such that it is expanded along its axis when the clamp mechanism is moved to the locked position. In such a case, the coil spring would act to recoil back to its original compressed state in order to provide the biasing force to the steering column assembly.

Additionally, the coil spring 160 acts in torsion due to the engagement of the first and second end portions. The coil spring 160 is formed as a helix with the two end portions being straightened and expanding at a tangent to the outer surface of the helix. As such, relative movement of the end portions about the axis of the coil spring increases and decreases tension. The coil spring 160 therefore provides a force resistive to this torsion. The coil spring 160 may also be configured to be tensioned during manufacture or assembly in order that a default torque is applied by the coil spring 160 before any relative movement of the steering shaft 102 and shroud 112.

Referring now to Figures 4a to 4c, the steering column assembly 100 is shown in the rake up position. In this position, the first reaction point 174 is positioned on the first end portion 162 in a position furthest away from the coiled portion 172 of the coil spring 160.

in Figure 4a, the steering column assembly 100 is in the reach out position. This means that the shroud 112 and steering shaft 102 are at their maximum length, such that the clamp bolt 138 is at the furthest right position of the reach slot 146, when considered from the side shown in the uppermost picture. With the shroud 112 in the reach out position, the slot 170 in the shroud 112 that receives the second end portion 168 of the coil spring 160 is positioned closer to the coiled portion 172 of the coil spring 160. As the second reaction point 176 is closer to the coiled portion 172 of the coil spring 160, the force provided by the coil spring 160 to the shroud 112 is higher, as the distance from the axis of the coiled portion 172 is lower. As such, a higher force is provided to help support the steering shaft 102 and shroud 112 in the reach out position. This helps to compensate for the increased length of the steering shaft 102 and shroud 112.

in Figure 4b, the steering column assembly 100 is in a nominal middle position between the reach out position and reach in position. Here, the clamp bolt 138 is midway between the extremes of its movement along the reach slot 146 and the second reaction point 176 is approximately half way along the length of the second end portion 168 of the coil spring 160. The force provided by the coil spring 160 to the shroud 112 is therefore slightly lower than that provided when in the reach out position. However, in the reach middle position, it the length of the steering shaft 102 and shroud 112 will be less than that when in the reach out position and therefore the force required from the sprung support assembly 158 to support the shroud 112 and steering shaft 102 is lower.

In Figure 4c, the steering column assembly 100 is in the reach in position. This means that the shroud 112 and steering shaft 102 are at their minimum length, such that the clamp bolt 138 is at the furthest left position of the reach slot 146, when considered from the side shown in the uppermost picture. With the shroud 112 in the reach in position, the slot 170 in the shroud 112 that receives the second end portion 168 of the coil spring 160 is positioned further from the coiled portion 172 of the coil spring 160. As the second reaction point 176 is further from the coiled portion 172 of the coil spring 160, the force provided by the coil spring 160 to the shroud 112 is lower, as the distance from the axis to the coiled portion 172 is higher. As such, a lower force is provided, as the decreased length of steering shaft 102 and shroud I12 does not require the same level of support.

By adjusting the force provided by the coil spring 160 dependent on the length of the stccring shaft 102 and shroud 112, the provision of a force that is too large or too small is avoided. If a force that is too large were to be provided, the steering shaft 102 would tend to be over-supported and move upwards in the rake direction during locking of the clamp mechanism 134. Conversely, if a force that is too small were to be provided, the steering shaft 102 would tend to be under-supported and move downwards in the rake direction during locking of the clamp mechanism 134. The present assembly therefore adapts the force based on the length of the steering shaft 102 and shroud 112 in order to avoid under-or over-support in any reach position.

Referring now to Figures 5a to 5c, the stccring column assembly 100 is shown in the rake down position. In this position, the first reaction point 174 is positioned on the first end portion 162 in a position closest to the coiled portion 172 of the coil spring 160. Moreover, the rotation of the shroud 112 relative to the support bracket 122 as the shroud 112 moves towards the rake down position unfurls the coiled portion 172 of the coil spring 160. This rotation loosens some of the tension in the coil spring 160, resulting in a lowering of the force applied to the shroud 112 by the spring 160. Of course, when the steering column is moved upwards in the rake direction, this tension will be re-applied, increasing the force delivered to the shroud 112 by the spring 160.

By releasing some of the tension in the coil spring 160 when moving the shroud 112 and steering shaft 102 down in the rake direction, an unwanted movement of the shroud 112 during locking of the clamp mechanism 134 can be avoided. In prior art assemblies, it is known that when moving the clamp mechanism to the locked position with the shroud and steering shaft in the rake down position, the shroud can move upwards slightly in the rake direction, which is undesirable. Such movement is therefore prevented in the present steering column assembly 100.

in Figure 5a, the steering column assembly 100 is in the reach out position. This means that the shroud 112 and steering shaft 112 are at their maximum length, such that the clamp bolt 138 is at the furthest right position of the reach slot 146, when considered from the side shown in the uppermost picture. With the shroud 112 in the reach out position, the slot 170 in the shroud 112 that receives the second end portion 168 of the coil spring 160 is positioned closer to the coiled portion 172 of the coil spring 160. As the second reaction point 176 is closer to the coiled portion 172 of the coil spring 160, the force provided by the coil spring 160 to the shroud 112 is higher, as the distance from the axis of the coiled portion 172 is lower. As such, a higher force is provided to help support the steering shaft 102 and shroud 112 in the reach out position. This helps to compensate for the increased length of the steering shaft 102 and shroud 112.

In Figure 5b, the steering column assembly 100 is in a nominal middle position between the reach out position and reach in position. Here, the clamp bolt 138 is midway between the extremes of its movement along the reach slot 146 and the second reaction point 176 is approximately half way along the length of the second end portion 168 of the coil spring 160. The force provided by the coil spring 160 to the shroud 112 is therefore slightly lower than that provided when in the reach out position. However, in the reach middle position, it the length of the steering shaft 102 and shroud 112 will be less than that when in the reach out position and therefore the force required from the sprung support assembly 158 to support the shroud 112 and steering shaft 102 is lower.

In Figure 5c, the steering column assembly 100 is in the reach in position. This means that the shroud 112 and steering shaft 102 are at their minimum length, such that the clamp bolt 138 is at the furthest left position of the reach slot 146, when considered from the side shown in the uppermost picture. With the shroud 112 in the reach in position, the slot 170 in the shroud 112 that receives the second end portion 168 of the coil spring 160 is positioned further from the coiled portion 172 of the coil spring 160. As the second reaction point 176 is further from the coiled portion 172 of the coil spring 160, the force provided by the coil spring 160 to the shroud 112 is lower, as the distance from the axis to the coiled portion 172 is higher. As such, a lower force is provided, as the decreased length of steering shaft 102 and shroud 112 does not require the same level of support.

Claims

CLAIMS1. A steering column assembly for a vehicle, the steering column assembly comprising: a support bracket configured to provide attachment to a vehicle; a shroud, which is supported by the support bracket; a steering shaft, which is supported by the shroud; and a clamp mechanism which is movable between a locked position where the shroud is fixed relative to the support bracket and an unlocked position where the shroud is movable relative to the support bracket in a rake direction; and a sprung support assembly comprising a coil spring that is secured to the support bracket and is configured to at least partially support a weight of the shroud when the clamp mechanism is in the unlocked position; wherein the coil spring is further configured to provide a biasing force that biases the clamp mechanism towards the unlocked position.
2. A steering column assembly according to claim I, wherein the coil spring is coiled around a clamp bolt of the clamp assembly.
3. A steering column assembly according to claim 1 or claim 2, wherein the coil spring is compressed along its axis by movement of the damp mechanism from the unlocked position to the locked position.
4. A steering column assembly according to claim 3, wherein the coil spring is compressed between two parts of the clamp mechanism, such as two spacers between which the coil spring is retained.
5. A steering column assembly according to any preceding claim, wherein the coil spring acts to disengage an engagement mechanism of the clamp mechanism. 30
6. A steering column assembly according to any preceding claim, wherein a first end portion of the coil spring is configured to engage with the support bracket at a first reaction point and a second end portion of the cod spring, at an opposite end of the coil to the first end portion, is configured to engage with the shroud at a second reaction point.
7. A steering column assembly according to claim 6, wherein the support bracket includes an aperture through which the first end portion of the coil spring passes, the first end portion sliding through the aperture during movement of the shroud in the rake direction, moving the first reaction point along the first end portion.
8. A steering column assembly according to claim 7, wherein the aperture forms the first reaction point.
9. A steering column assembly according to claim 8, wherein the aperture includes a friction-reducing insert, such as a polymer insert.
10. A steering column assembly according to claim 8 or claim 9, wherein the aperture is sized and/or shaped so as to restrict movement of the first end portion of the coil spring in directions orthogonal to the rake direction.
11. A steering column assembly according to any of claims 6 to 10, wherein the first end portion extends in the rake direction or substantially in the rake direction.
12. A steering column assembly according to any of claims 6 to 11, wherein the first end portion is configured to rotate relative to the shroud when the shroud is moved towards the rake down position, lowering tension in the coil spring.
13. A steering column assembly according to any of claims 6 to 12, wherein the support bracket includes a rake slot through which the clamp bolt passes, the rake slot sliding relative to the clamp bolt as the shroud is moved in the rake direction.
14. A steering column assembly according to any of claims 6 to 13, wherein the second end portion is received within a slot in the shroud.
15. A steering column assembly according to claim 14, wherein the slot forms the second reaction point.
16. A steering column assembly according to claim 14 or claim 15, wherein the slot is sized and/or shaped so as to allow sliding movement of the second end portion of the coil spring in a direction of compression of the coil spring.
17. A steering column assembly according to any of claims 6 to 16, wherein the shroud and steering shaft are movable relative to the support bracket in a reach direction when the clamp assembly is in the unlocked position.
18. A steering column assembly according to any of claims 6 to 17, wherein the shroud is configured to slide along the second end portion of the coil spring during movement of the shroud in the reach direction, moving the second reaction point along the second end portion.
19. A steering column assembly according to any of claims 6 to 18, wherein the second end portion extends in the reach direction or substantially in the reach direction, optionally wherein the second reaction point is configured to move closer to a coiled portion of the coil spring when the shroud is moved towards a reach-out position.
20. A steering column assembly according to any of claims 6 to 19, wherein the shroud includes a reach slot through which the damp bolt passes, the reach slot sliding relative to the clamp bolt as the shroud is moved in the reach direction.