GB2575883A

GB2575883A - A steering column assembly

Info

Publication number: GB2575883A
Application number: GB1813000.5A
Authority: GB
Inventors: Pluta Krzysztof; Wojtalik Artur; Ponikiewski Pawel
Original assignee: TRW Steering Systems Poland Sp zoo
Current assignee: TRW Steering Systems Poland Sp zoo
Priority date: 2018-07-25
Filing date: 2018-08-09
Publication date: 2020-01-29
Anticipated expiration: 2038-08-09
Also published as: DE102019210379A1; GB201813000D0; GB2575883B

Abstract

A steering column assembly 100 for a vehicle has a shroud 102 supporting a steering column 104, a support bracket 108, a clamp pin 112 and a clamp mechanism. Bracket 108 is secured to a fixed part of the vehicle and has two arms 110a, 110b embracing shroud 102 and depending from a base 130. Clamp pin 112 extends through an opening 114 in each arm 110a, 110b and a slot in shroud 102. The clamp mechanism is movable between an unclamped position where shroud 102 is adjustable for rake and a clamped position where shroud 102 is secured to arms 110a, 110b. Bracket 108 also has a bridge portion 140, 142 for at least one arm 110a, 110b, connected at one end the arm and at another end to base 130 at a point offset from where the arm depends from the base, providing two discrete paths for transferring load from the clamp mechanism to base 130 and the vehicle body.

Description

A STEERING COLUMN ASSEMBLY

The present invention relates to improvements in steering column assemblies. More particularly, the invention relates to steering column assemblies including a frictional clamping system.

It is known to provide a collapsible steering column assembly comprising a steering shaft that is supported within a steering column shroud. To prevent significant injury to the driver in the event of a crash the steering column should be able to collapse as an axial load is applied through the steering wheel, for instance in a front impact where an unrestrained driver is thrown onto the steering wheel.

A typical collapsible steering column assembly comprises a telescopic shroud, having an outer shroud portion and an inner shroud portion, an end of the inner shroud portion extending into the outer shroud portion. The outer shroud portion may be located closer to the steering wheel, or further from the steering wheel than the inner shroud portion. A telescopic steering shaft, also having an upper and lower shaft part, is supported inside the shroud through one or more bearing assemblies. The steering wheel is fixed to the upper shaft portion. In some cases, the shroud will not include two portions and instead the shroud will simply move relative to the bracket.

The part of the shroud closest to the wheel must be able to move, or collapse, during a crash so as to allow the steering wheel to move forwards relative to the vehicle body but be prevented from moving during normal use. There is also a need to fix the shroud relative to the vehicle body to define the rake position of the steering wheel. This is typically achieved by a clamp mechanism that secures the shroud to a support bracket that is in turn fixed to the vehicle body, perhaps to a cross beam provided behind the dashboard of the vehicle. The clamp mechanism may be adjustable to permit reach adjustment, or rake adjustment, or both, of the steering wheel. In the event of a crash the shroud must be able to move, and this is achieved if it is able to break free of the clamp mechanism, or for the support bracket to be able to break free of the vehicle body, to allow the steering column assembly to collapse telescopically.

A lever may be provided on an end of the a clamp bolt that forms a part of the clamp mechanism that the driver can push or pull to rotate the clamp bolt and thereby operate the clamp mechanism.

Steering column assemblies are known which include a clamp mechanism that relies solely on friction when locked to prevent unwanted movement of the column assembly. The clamp mechanism can be unlocked and locked by movement of a locking lever or, sometimes, electrically using a motor or perhaps hydraulically or pneumatically. These columns can typically resist radial and/or axial forces of 600N applied at the steering wheel before slipping. These radial and axial force largely pass through the support bracket and into the vehicle body.

However, it is increasingly a requirement from car manufacturers that there should be no substantial movement of the steering column assembly when forces of up to 5000N are applied. The objective is to prevent unwanted movements of the steering wheel in a crash so that the deployment of the air bag is ideally controlled. If the bracket is insufficiently rigid it may twist or otherwise deform allowing the shroud to move. To date, this has been prevented using brackets with relatively massive arms to ensure that the arms do not bend or otherwise flex under load.

According to a first aspect, there is provided a steering column assembly for a vehicle, the steering column assembly comprising:

a shroud;

a steering shaft, which is supported by the shroud;

a support bracket configured to be secured to a fixed part of the vehicle and including two arms that depend from a base portion to embrace the shroud;

a clamp pin that extends through an opening in each of the arms of the support bracket and a slot in the shroud; and a clamp mechanism that is movable between an unclamped position in which the shroud can be adjusted for rake relative to the support bracket and a clamped position in which the shroud is fixed relative to the support bracket; and whereby the clamp mechanism in use secures the shroud to the two arms of the bracket;

characterised in that the bracket includes, associated with at least one arm, a bridging portion that is connected at one end to the base portion offset from the region where the arm depends from the base portion and is connected at the opposite end to the bracket arm at a position spaced from the base portion, the configuration of the bridging portion and arm providing two discrete paths for transferring load from the clamp mechanism to the base portion and hence to the vehicle body.

The base portion, bridging portion and arm may form a triangle with a space defined between the three portions.

The bridging portion may be connected to the base portion at a point further form the centreline of the bracket than the point where the arm connects to the base portion. The bracket may be considered to comprise a base portion having a central region and two opposing wings that project away from the central portion and define regions where the bracket is secured to the vehicle body when in use. These wings may extend out in a horizontal direction beyond the shroud giving clearance to access one or more fastenings that pass through the wing to secure the bracket to the vehicle body.

Making the bracket relatively wide by providing the wings allows the fixing locations to be spaced relatively far apart, making the bracket better at resisting any twisting forces that may arise in the event of a crash. This allows the bracket better to transfer horizontal and vertical loads applied to the bracket by the shroud, in particular during a crash.

The bracket arm may be generally J-shaped having a hooked end portion which defines the attachment point for the bridging portion. By providing a J-shape the region of the bracket arm above the bridging portion attachment point is effectively cut-away reducing weight by removing parts that would not carry any significant loads.

The bridging portion may be connected to the bracket arm by one or more welds or other fastening means such as adhesive or rivets or other the like.

The bridging portion may include stiffening ribs along the outer edges to help it resist bending when under compression.

The bridging portion may include one or more cut outs to reduce weight.

Both arms may be provided with bridging portions.

The assembly may be configured such that with the shroud clamped in position in a lowermost rake position the bridging portion carries more load than the arm, and in the uppermost rake position the bridging portion carries less load than the arm.

To achieve this, the region at which the shroud is clamped to the arm when in the lowermost position maybe closer to the region where the bridging portion connected to the arm than it is to the base portion, and when in the uppermost position the region where the shroud is clamped to the arm may be closer to the base portion than to the bridiging porition.

In other words, the distance that the load must pass from the clamp mechanism to the base portion of the bracket through the arm and through the briding porition may be shorter compared to the distance for the load to pass through the arm alone when the steering shroud is in the lowermost position.

When the shroud is clamped in a mid position the load may be shared substantially equal between the arm and the bridging portion.

The bridging portion may be offset laterally from the region where the clamp mechanism connects to the arm. It may be offset so that it is located on the oppporite side of the clamp mechanism to the end of the shroud that connects to the steering wheel.

The base portion, arm and bridign portion may comprise separate elements that are connected together in use by one or more fixings. The fixings may comprise one or more of rivets, welds, adhesive patches or any other fixing means.

The bracket arms may extend substantially vertically, and the briding portion or poritons may extend at an angle inclined between 10 degrees and 50 degrees from the vertical in a preferred arrangement. Other angles may be possible.

In a most preferred arrangement the end of the bridging portion connected to the wing of the base portion may be located inboard of the region where the wing is secured to the vehicle body.

Providing the two load paths enables a very rigid mounting of the shroud to the vehicle body without the need for providing very chunky bracket arms as a single load path. This may beneficially reduce the overall weight and potentially reduce the cost of the bracket. In a vehicle both weight and cost savings are highly beneficial.

The at least one arm of the bracket may be provided with a guide plate that includes a slot along which the clamp mechanism can be moved when adjusting the steering column assembly for rake.

The cam mechanism may include a fixed cam part and a moving cam part. Movement of the lever may act to rotate the moving cam part relative to the fixed cam part. Cam surfaces of the moving cam part and fixed cam part may result in a length of the cam mechanism changing due to this rotation.

The cam mechanism may include a part that fits within one of the slots in the arms of the support bracket. This part may prevent the rotation of a fixed cam part of the cam mechanism and may take the form of a block.

In the clamped position, the two bracket arms may be compressed between the cam mechanism and opposing sides of the shroud

An embodiment of the present invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a cross section view of an embodiment of a steering column assembly in accordance with the first aspect looking along a length of the steering shaft of the assembly;

Figure 2 is a side view of the assembly of Figure 1 with the shroud in a midheight rake position;

Figure 3 is an enlarged perspective view of a portion of the assembly of Figure 1 corresponding to the rake position of Figure 2;

Figure 4 is a side view of the assembly of Figure 1 with the shroud in the lowest height rake position;

Figure 5 is an enlarged perspective view of a portion of the assembly of Figure 1 corresponding to the rake position of Figure 4;

Figure 6 is a side view of the assembly of Figure 1 with the shroud in its heighest rake position; and

Figure 7 is an enlarged perspective view of a portion of the assembly of Figure 1 corresponding to the rake position of Figure 6.

Referring firstly to Figure 1, there is shown a steering column assembly 100 comprising a shroud 102 that houses a shaft 104. The shaft 104 is configured to be attached to a steering wheel (not shown). The shaft 104 is supported by a bearing assembly (not shown) that allows rotation of the shaft 104 relative to the shroud 102. A support bracket 108 includes two arms 110a and 110b that depend in a substantially vertical direction and provide support and stability to the shroud 102.

A clamp pin 112 passes through vertical slots 114 in the support bracket 108 and a horizontal slot 116 in a clamp rail 118 of the shroud 102. The clamp pin 112 has a stop 120 at one end that prevents the clamp pin 112 being drawn through the support bracket 108. At the other end, a cam mechanism 122 that is rotated by use of a lever 124 enables an effective length of the clamp pin 112, i.e. the length of the clamp pin 112 between the cam mechanism 122 and the stop 120, to be varied. The cam mechanism 122 comprises a fixed cam part 126 and a moving cam part 128, the moving cam part 128 being rotated by the rotation of the lever 124, pushing against the fixed cam part 126 and extending the length of the cam mechanism 122. The clamp pin and the cam and end stops together with the bracket arms and rail define a clamp mechanism.

In the unclamped position of the clamp mechanism 130, there is sufficient freedom of movement of the arms to allow adjustment of the reach and rake position of the steering column assembly 100 without undue exertion from a user. The clamping mechanism 130 is shown in the clamped position in all of the accompanying Figures.

To move from the unclamped to the clamped condition the user roates the level 124. Rotation of the lever 124 leads to extension of the cam mechanism 122 along the clamp pin 112 and thus the cam mechanism 122 extends through the slot 114 in the support bracket 108 and presses on the outside of one of the arms 110a. This arm is pressed into contact with the shroud 102. The shroud 102 is thus pushed over towards the right side of the support bracket 108 and presses the other arm 110b onto the end stop 120 on the clamp pin thus locking the shroud 102 in a desired position relative to the support bracket 108.

The bracket comprises a base portion 130 that is generally planar and extends across the top of the shroud 102. Each end of the base portion 130 projects outwards to define awing 132,134 portion. The wings defined outboard fixing points for securing the bracket to the body of the vehicle. In the example shown bolts (not shown) may pass through holes 136,138 in the wings. The bracket also includes, associated with each arm 110a and 110b a respective bridging portion 140,142 that is connected at one end to a wing 132,134 of the base portion so that it is outboard from the region where the arm 110a, 110b depends from the base portion and is connected at the opposite end to the bracket arm 110a, 110b at a position spaced from the base portion. The configuration of the bridging portion and arm provides two discrete paths for transferring load from the clamp mechanism to the base portion and hence to the vehicle body.

Figures 2 and 3 show the assembly with the steering at a mid-point rake position. The large white arrows marked in Figure 3 show the path through which forces transfer from the clamp mechanism through to the vehicle body. The relative size of each arrow indicates the relative proportion of the force flowing in the direction of the arrow (with a larger arrow indicating a larger portion of the force). As can be seen forces flow along two paths, one through the top of the bracket arm and the other through the bridging portion, in roughly equal amounts.

Figures 4 and 5 show the same views as Figures 2 and 3 but with the shroud in a lowermost rake position. In this case it can be seen that the clamp pin is closer to the briding portion than for the mid-position and a larger proportion of the load now flows through the briding portion than does through the top of the bracket arm.

Figures 6 and 7 show the final case where the steering is that the uppermost rake position. In this case, the highest proportion of the load flows up through the top part of the bracket arm to the vehicle body.

By providing two load paths, with the ability to share the forces, the overall stiffness of the bracket assembly for a range of rake positions can be improved with respect to a single bracket arm, giving a good resistance to twisting and other deformation without the need for an excessively thick plate material to be used at any part of the bracket.

Claims

1. A steering column assembly for a vehicle, the steering column assembly comprising:

a shroud;

a steering shaft, which is supported by the shroud;

a clamp pin that extends through an opening in each of the arms of the support bracket and a slot in the shroud; and a clamp mechanism that is movable between an unclamped position in which the shroud can be adjusted for rake relative to the support bracket and a clamped position in which the shroud is fixed relative to the support bracket; and whereby the clamp mechanism in use secures the shroud to the two arms of the bracket; characterised in that the bracket includes, associated with at least one arm, a bridging portion that is connected at one end to the base portion offset from the region where the arm depends from the base portion and is connected at the opposite end to the bracket arm at a position spaced from the base portion, the configuration of the bridging portion and arm providing two discrete paths for transferring load from the clamp mechanism to the base portion and hence to the vehicle body.

2. A steering column assembly according to claim 1 in which the base portion, bridging portion and arm form a triangle with a space defined between the three portions.

3. A steering column assembly according to claim 1 or claim 2 in which the bridging portion is connected to the base portion at a point further from the centreline of the bracket than the point where the arm connects to the base portion.

4. A steering column assembly according to any preceding claim in which both arms are provided with bridging portions.

5. A steering column assembly according to any preceding claim which is configured such that with the shroud clamped in position in a lowermost rake position the bridging portion carries more load than the arm, and in an uppermost rake position the bridging portion carries less load than the arm.

6. A steering column assembly according to any preceding claim in which the

5 bridging portion is offset laterally from the region where the clamp mechanism connects to the arm.

7. A steering column assembly according to any preceding claim in which the base portion, arm and bridging portion comprise separate elements that are connected 10 together in use by one or more fixings.