GB2411156A

GB2411156A - A collapsible steering column with a breakable anchor member

Info

Publication number: GB2411156A
Application number: GB0502489A
Authority: GB
Inventors: Laurie Barton; Mohammed Ali
Original assignee: NSK Steering Systems Europe Ltd
Current assignee: NSK Steering Systems Europe Ltd
Priority date: 2004-02-18
Filing date: 2005-02-07
Publication date: 2005-08-24
Anticipated expiration: 2025-02-07
Also published as: GB2411156B; GB0502489D0; GB0403613D0

Abstract

A collapsible steering apparatus for a motor vehicle is disclosed. The steering apparatus includes main bracket 10 and a skid bracket 12, the skid bracket mounting the steering column 16. In a crash condition, the skid bracket slides relative to the main bracket by sliding of a connecting bolt in a slot 18. The connecting bolt is held in the slot by an anchor member 22 that has projecting arms 44, 46 held in recesses. The anchor member has deformable ribs 50 to ensure a snug fit in the slot. In the crash condition, the projecting arms shear from the anchor member to allow sliding of the anchor member and the connecting bolt along the slot to provide sliding of the skid bracket relative to the main bracket.

Description

no 2411156

STEERING APPARATUS

The present invention relates to steering apparatus of the type in which the steering column assembly is collapsible in a crash condition.

Collapsible steering column assemblies for vehicles are known. Such assemblies are designed to collapse in a controlled manner in the event of a crash condition (e.g. in a road traffic accident). In a crash condition, the driver of a vehicle may be thrown forwards to collide with the steering wheel. In order to minimize driver injuries, some known steering columns are able to collapse away from the driver, along the axis of the steering column, in a manner which absorbs some of the energy of the collision between the driver and the steering wheel. Of course, in a normal driving condition such collapse of the steering column should not be allowed.

Known collapsible steering column assemblies have two components, one of which is a main bracket which is fixed with respect to the vehicle body and the other of which is a skid bracket which is slidable relative to the main bracket. The skid bracket is able to slide relative to the main bracket in a crash condition, but is inhibited from such movement during normal driving. The relative sliding movement in a crash condition is often referred to as 'ride-down' of the component. Typically, To the steering column is attached to the skid bracket, thereby allowing ridedown of the steering wheel and steering column in a crash condition.

US-B-6595079, for example, describes a collapsible steering column assembly in which relative sliding movement between a main bracket and a skid bracket is controlled by means of applying a clamping force between the two components. In that document, a clamping bolt is described extending through a guide slot in the fixed main bracket. The bolt clamps the skid bracket with respect to the main bracket. When the force of impact in a crash condition is sufficient to overcome the clamping force provided by the bolt, sliding of the skid bracket along the guide slot will occur. The bolt clamping force is selected to allow controlled sliding (i.e. ride-down) only in a crash condition.

In known steering apparatus of this type, the condition in which relative sliding occurs between the main bracket and the skid bracket is dependent on the magnitude of the clamping force holding the skid bracket with respect to the main bracket. In other words, the magnitude of the clamping force may determine the impact required in a crash condition to cause ride-down of a component.

However, the bolt clamping force at the time of the crash condition may not necessarily be the same as the original clamping force provided at the time of To manufacture or installation of the steering column assembly. In particular, where a bolt is used as the clamping means, general movement and abuse loads encountered during normal driving may serve to allow the bolt to become loosened or to develop clearance with respect to the clamped components. Consequently, the impact required to overcome the clamping force is also reduced. Thus, known steering apparatus may not provide a reliable and reproducible ride-down of the steering column assembly only in a crash condition.

The present invention aims to address one or more of the above problems, preferably to ameliorate, reduce or even overcome those problems.

In a general aspect, the invention provides a breakable anchor member adapted to break at a threshold load condition corresponding to a crash condition to allow ride-down, at least one deformable protrusion at the periphery of the anchor member ensuring a snug fit for the anchor member within the steering apparatus.

Preferably, in a first aspect of the invention, there is provided a steering apparatus for a vehicle having a first component connected to a second component, the second component being adapted to slide relative to the first component in a crash condition to allow ride down of part of the steering apparatus, at least one guide slot being provided in the first component to guide the sliding of the second component with respect to the second component in said crash condition, the apparatus further having a breakable anchor member retaining the second component against sliding relative to the first component in a normal driving condition and being adapted to break at a threshold load condition corresponding to said crash condition to allow said sliding, wherein the anchor member has at least one deformable protrusion at its periphery for ensuring a snug fit within the slot.

Preferably, in a second aspect of the invention, there is provided a method of managing ride-down of a vehicle steering column in a crash condition, wherein the steering column is mounted with respect to the vehicle via a steering apparatus according to the first aspect, the method including the step of breaking the anchor member to allow relative sliding between the first and second components in the crash condition.

In the context of this invention, "ride-down" is preferably used to mean the sliding movement of a slidable part (e.g. skid bracket) of the steering apparatus relative to a fixed part (e.g. main bracket) of the steering apparatus in a crash condition.

Preferably, the breakable anchor member serves to retain the second component against sliding relative to the first component in a normal driving condition by anchoring the components against relative movement in the sliding direction. In this way, it is possible to avoid the requirement for a clamping bolt to prevent relative sliding. However, one may be provided anyway, to prevent relative movement in other directions than the ride-down direction.

Typically, the anchor member is breakable at a predetermined threshold load. When subjected to a load less than this threshold the anchor member will typically remain intact, thus retaining the components in the same position with respect to one another.

Typically, the threshold load required to break the anchor member is determined at the time of manufacture of the anchor member. Usually, the threshold load to break the anchor member is directed in the same direction as the direction of ride-down of the first component with respect to the second component in the crash condition.

Preferably, the magnitude of the threshold load required to break the anchor member remains constant over an extended period in a normal driving condition.

Typical movement and abuse loads on the steering apparatus encountered during normal driving preferably do not affect that threshold load. Thus, the anchor member preferably always breaks at substantially the same threshold load imposed upon it in a crash condition resulting in the provision of reliable and reproducible ride-down in a crash condition.

Preferably, the present invention allows a snug engagement between the first and second components of the To steering assembly. It may also serve to limit or eliminate loosening and/or the development of clearances between the components. The resulting preferred effect is that the anchor member serves to reduce or eliminate give or rattling between the components during driving which may otherwise be associated with loosely fitting components. Further preferred features that further promote this advantage are mentioned below.

Preferred and/or optional features are described below. These features are applicable to any of the above aspects of the invention and may be combined with one another.

Preferably, the anchor member is breakable by shearing.

The first component is preferably a mounting bracket fixedly mountable with respect to a vehicle.

Preferably, the steering column is mounted with respect to the second component. This is typically the case for a steering apparatus in which the position of the steering column is adjustable by the user.

Alternatively, for a vehicle in which the position of the steering column is not adjustable, the steering column itself may be the second component. In that case, in a crash condition, the steering column itself would slide relative to the fixed mounting bracket.

The anchor member preferably includes a body portion and at least one projecting element. Preferably, in use, the projecting element engages with a corresponding recess in the first component.

Alternatively, the projecting element may make hooked engagement with a corresponding projection on the first component. More preferably, the anchor member has two projecting elements for engagement with corresponding recesses in, or projections on, the first component.

Thus, the engagement of the projecting element with the first component may retain the second component against sliding relative to the first component in a normal driving condition.

The first component is provided with a guide slot which guides the movement of the second component with respect to the first component during ride-down of part of the steering apparatus in a crash condition.

Preferably, the axis of the guide slot is substantially parallel to the direction of the axis of the steering column.

Preferably, the recess that engages with the projecting element of the anchor member is formed in communication with the guide slot in the first component.

In particular, the anchor member may slide along the slot in the crash condition. There may be more than one guide slot for guiding the movement of the second component with respect to the first component, e.g. two.

Preferably, in the anchor member, the projecting element is breakable from the body portion along an interface between the projecting element and the body portion. More preferably, the projecting element is shearable from the body portion along an interface between the projecting element and the body portion.

It is preferred that the body portion of the anchor member is shaped to allow sliding of the body portion along the guide slot after breakage of the projecting element from the body portion. Thus, the body portion may ride-down with the second component.

Preferably, the or each projecting element extends from the body portion in a direction substantially perpendicular to the direction of sliding of the second component in a crash condition. More preferably, when there are two projecting elements, both extend from the body portion in a direction substantially perpendicular to the direction of sliding of the second component during ride-down. Thus, in the crash condition, the projecting elements typically become detached from the body portion. The projecting elements may remain in position with respect to the first component or they may fall away.

In a preferred embodiment, the anchor member further has a head plate portion projecting from the body portion for abutment with a surface of the first component adjacent the slot. The head plate portion preferably has a first substantially flat surface for abutment with said surface adjacent the slot of the first component. This head plate may in effect function as a washer portion between the first component and, e.g. a clamping bolt holding the second component with respect to the first component.

Similarly, the anchor member may additionally have a second head plate portion, preferably having a first substantially flat surface, for abutment with another surface (e.g. an opposite surface) of the first component.

The flat surface of either or both head plate portions may serve to provide a low friction interface between the anchor member and the first component to facilitate controlled sliding in the crash condition.

Preferably, the at least one deformable protrusion is at least one deformable rib. The deformable rib may be on the body portion and/or the projecting element of the anchor member. More preferably, the anchor member has more than one deformable rib. Most preferably, the anchor member has more than one deformable rib on the body portion and on the projecting element.

The deformable rib may serve to ensure that the anchor member fits snugly within the slot or recess in the first component such that there is no give or clearance between the anchor member and the first component. The deformable nature of the rib provides for this in two ways. Firstly, the rib can ensure a snug fit at the outset even where the sizes of the anchor member c) and the slot or recess may not correspond precisely enough to allow a clearance-free fit without the rib.

Secondly, progressive elastic deformation of the rib may be able to accommodate any loosening or development of clearances between the anchor member and the first component which may result from the movement and abuse loads encountered during normal driving.

Preferably, the body portion of the anchor member has a through-passage for a connecting member to connect the first and second components. The connecting member may be a bolt or rivet or similar. The surface of the through-passage preferably has at least one deformable rib, and most preferably, more than one deformable rib.

Thus, the deformable rib may serve to ensure that the connecting member fits snugly in the through-passage of the anchor member and accommodates any loosening or development of clearances between them.

As will be clearly understood, the deformable rib or ribs may be replaced by mechanically equivalent means such as deformable pads, dimples or other protrusions.

The anchor member may include separable portions.

A second anchor portion member may be provided, adapted to engage with a first anchor member portion. The engagement may be through the slot in the first portion component. In that case, typically each anchor member portion has only one head plate, the assembly of the first and second anchor member portions thereby having head plates disposed at either side of the assembly. The two anchor member portions may be attached via a link, which may be between the respective head plates of the anchor member portions. Preferably, the first and second anchor member portions are formed in one piece for ease of manufacture.

In a preferred embodiment, the steering apparatus has two guide slots, each guide slot having its own breakable anchor members.

Preferred embodiments of the invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which: Fig. l shows a plan view engineering drawing of a collapsible steering column assembly in a normal driving condition, incorporating an embodiment of the invention.

Fig. 2 shows the collapsible steering column assembly of Fig. l in a crash condition.

Fig. 3 shows a schematic perspective view of a steering apparatus according to an embodiment of the present invention in a normal driving condition.

Fig. 4 shows an enlarged view of an anchor member, skid bolt and part of the main bracket of the steering apparatus of Fig. 3.

Fig. 5 shows a view corresponding to Fig. 4 but with the skid bolt removed to show the anchor member more clearly.

Fig. 6 shows a view corresponding to Fig. 5 but with the anchor member removed.

Fig. 7 shows a view corresponding to part of Fig. 6 but with one lower part of the anchor member included, the main bracket being shown in part sectional view.

Fig. 8 shows a schematic enlarged view of an anchor member, shown partially in sectional view, for use in an embodiment of the invention.

Figs. 1 and 2 show a schematic view of a collapsible steering column assembly. In a normal driving condition shown in Fig. 1, main bracket 10 is fixed with respect to the cross-beam of a vehicle (not shown). Skid bracket 12 is attached to the main bracket.

In a crash condition shown in Fig. 2, main bracket 10 remains fixed in position with respect to the cross-beam, but skid bracket 12 slides with respect to main bracket along axis 14. Thus, the steering wheel (not shown), attached to steering column 16 (which in turn is attached to the skid bracket), rides-down away from the driver of the vehicle.

Fig. 3 shows an embodiment of the steering apparatus according to the present invention in a normal driving condition. The main bracket 10 (first component) is fixed on the cross-beam of a vehicle (not shown). The skid bracket 12 (second component) has the steering column 16 mounted on it. The main bracket has two elongate guide slots 18, 20, the elongated axes of which are substantially parallel to axis 14. The main bracket and skid bracket are connected to each other by means of an anchor member 22 and a connecting bolt 24 passing through guide slot 18 in the main bracket, the through- passage 26 of the anchor member and an aperture 13 in the skid bracket 12. This arrangement is repeated for guide slot 20. The head of the connecting bolt is in contact with a head plate portion 28 of the anchor member. The direction of sliding of the skid bracket with respect to the main bracket in a crash condition is along the direction of the slot. The engagement of the anchor member with the components of the steering apparatus will now be described in more detail with reference to Figs. 4 to 8.

Fig. 8 shows the anchor member in more detail and in partly cutaway view. The anchor member includes two separable anchor member portions 30, 32. Each anchor member portion has a head plate 34, 36. The two anchor member portions are attached to one another via a link 38 between their respective head plates. Each anchor member portion has a body 40, 42 and two projecting elements 44, 46, 48. The two projecting elements extend from the body on opposite sides of the body. Each body has a through passage 26 perpendicular to the direction of projection of the two projecting elements. The first and second anchor member portions engage with each other as shown directly to attach one body to the other, to define a contiguous through-passage through the assembled anchor To member. Deformable ribs 50 are present on the surface of each body, each of the projecting elements and each through-passage. The deformable ribs (or in the more general sense, the deformable protrusions) extend in a direction generally aligned with the direction in which the anchor member is to be pushed into the slot 18 or 20 and aligned with the axis of the through-passage.

Anchor member 22 is typically formed in one piece from plastics material, e.g. by press moulding or injection moulding.

For ease of assembly, the first and second anchor member portions are only assembled into the anchor member through the guide slot in the main bracket. As shown in Figs. 4 to 7, the body portion of the assembled anchor member is positioned within the guide slot in the main bracket. The projecting elements 44, 46 of the anchor members are in engagement with correspondingly-shaped recesses 52, 54 in communication with the guide slot 18.

The through-passage 26 of the anchor member is in alignment with aperture 13 in the skid bracket. The top head plate 36 of the anchor member has a flat lower surface (not shown) which abuts with the upper surface of the main bracket adjacent the guide slot. The lower head plate 34 of the anchor member has an upper flat surface which abuts the lower surface (not shown) of the main bracket.

The steering apparatus is assembled by attaching To the skid bracket to the main bracket first by inserting and assembling the anchor member in the guide slot of the main bracket, the projecting elements of the anchor member being retained in the recesses provided in communication with the slot. The deformable ribs 50 on the periphery of the body and on the projecting elements deform so as to ensure that there is no freedom of movement of the anchor member in the slot.

Next, the skid bracket is linked through the anchor member to the main bracket via bolt 24. The head of the bolt abuts the upper surface of the upper head plate, optionally via a washer. The bolt is retained via a nut (and optional washer, neither shown) tightly abutting a surface (not shown) of the skid bracket.

Now the operation of the anchor member during a crash condition will be described. The projecting elements and the corresponding recesses that they engage with extend in a direction perpendicular to the direction of ride-down of the skid bracket in a crash condition.

Thus, in a crash condition, the impact of the driver on the steering wheel is transmitted to the skid bracket via the steering column. Furthermore, this impact is transmitted to the anchor member via the bolt. The anchor member is retained in the guide slot by virtue of the projecting elements being retained in their corresponding recesses in the guide slot. However, the shear strength of the interface between the body portion and each projecting element is not sufficient to withstand the load placed on it due to the crash condition. Thus, the projecting elements shear from the body portion. The body portion is then free to slide along the guide slot, allowing ride-down of the skid bracket.

The interfaces 60, 62 along which shearing occurs is shown in the cutaway view of Fig. 7.

Following shear breakage along interfaces 60, 62 in a crash condition, the projecting elements are retained within the recesses in the guide slot, at least for the time when they are still supported from underneath by the skid bracket. Once the skid bracket has moved away from beneath the main bracket, the projecting elements may fall away from the recesses. The body portion of the assembled anchor member slides along the guide slot which the skid bracket.

The lower surface of the upper head plate and the upper surface of the lower head plate slide with respect to the main bracket. Also, the body portion of the anchor member slides within the guide slot. Typically, the anchor member is formed from a relatively low friction plastics material to reduce friction between the anchor member and the main bracket. Note that the energy-absorbing means (not shown) for absorbing the driver impact on the steering column is typically separate from the anchor member and is known to the skilled person.

The embodiment described above is described by way of example. On reading this disclosure, modifications of this embodiment, further embodiments and modifications thereof will be apparent to the skilled person and as such are within the scope of the invention. To

Claims

CLAIMS: 1. A steering apparatus for a vehicle, having a first component

connected to a second component, the second component being adapted to slide relative to the first component in a crash condition to allow ride-down of part of the steering apparatus, at least one guide slot being provided in the first component to guide the sliding of the second component with respect to the first component in said crash condition, the apparatus further having a breakable anchor member retaining the second component against sliding relative to the first component in a normal driving condition and being adapted to break at a threshold load condition corresponding to said crash condition to allow said sliding, wherein the anchor member has at least one deformable protrusion at its periphery for ensuring a snug fit within the slot.
2. A steering apparatus according to claim l, wherein the anchor member has a through-passage for a connecting member to connect the first and second components.
3. A steering apparatus according to claim 2, wherein the anchor member has at least one deformable protrusion at an internal surface of the through-passage.
4. A steering apparatus according to any one of claims 1 to 3, wherein the anchor member is breakable by shearing.
5. A steering apparatus according to any one of claims 1 to 4, wherein the first component is a mounting bracket fixedly mountable with respect to a vehicle and a steering column is mounted with respect to the second component.
6. A steering apparatus according to any one of claims 1 to 5, wherein the anchor member includes a body portion and at least one projecting element for engagement with a corresponding recess in communication with the guide slot of the first component.
7. A steering apparatus according to claim 6, wherein the body portion of the anchor member is slidable along the guide slot in said crash condition.
8. A steering apparatus according to claim 6 or claim 7, wherein the projecting element is breakable from the body portion along an interface between the projecting element and the body portion.
9. A steering apparatus according to claim 8, wherein the body portion is shaped to allow sliding of the body portion along the slot after breakage of the projecting element from the body portion.
10. A steering apparatus according to any one of claims 6 to 9, wherein the projecting element extends from the body portion in a direction substantially perpendicular to the direction of sliding of the second component in said crash condition.
11. A steering apparatus according to any one of claims 6 to 10, wherein the anchor member has a head plate portion projecting from the body portion for abutment with a surface of the first component adjacent the slot.
12. A steering apparatus according to any one of the preceding claims, wherein the anchor member includes first and second anchor member portions, engageable with each other through the guide slot of the first component.
13. A method of managing ride-down of a vehicle steering column in a crash condition, wherein the steering column is mounted with response to the vehicle via a steering apparatus according to any one of the preceding claims, the method including the step of breaking the anchor member to allow relative sliding between the first and second components in the crash To condition.