GB2278580A

GB2278580A - Collapsible steering column assembly.

Info

Publication number: GB2278580A
Application number: GB9311564A
Authority: GB
Inventors: Jean-Luc Renevot
Original assignee: ACG France SAS; General Motors France SA
Current assignee: ACG France SAS; General Motors France SA
Priority date: 1993-06-04
Filing date: 1993-06-04
Publication date: 1994-12-07
Anticipated expiration: 2013-06-04
Also published as: GB2278580B; GB9311564D0

Abstract

The assembly comprises a steering column (10) including a first telescopic element (12) coupled to a vehicle steering wheel and a second telescopic element (14) slidable telescopically within the first telescopic element (12) and coupled to a vehicle steering mechanism. An energy absorber (20) including a tubular support element (22) is disposed over the steering column (10) and a tubular deformable element is disposed in a close fit over the support element (22) so as to be supported by the support element (22). The deformable element (24) is slidable over the support element (22) during its deformation on collapse of the steering column. <IMAGE>

Description

COLLAPSIBLE STEERING COLUMN ASSEMBLY The present invention relates to a collapsible steering column assembly.

GB-A-1,200,437 discloses a telescopically collapsible steering column assembly which includes an energy absorbing portion in the form of a jacket tube adapted to deform during collapse of the column assembly so as to provide resistance to the collapse.

GB-A-1,369,188 discloses an energy absorber for a collapsible steering column assembly which includes an arrangement of deforming balls provided between two telescopic tubular elements of the steering column assembly. On movement of the two telescopic elements within one another during collapse of the steering column, the balls deform the walls of the telescopic elements, thereby absorbing impact energy.

The present invention seeks to provide an improved collapsible steering column assembly.

According to an aspect of the present invention, there is provided a collapsible steering column assembly comprising a steering column including a first telescopic element connectable to a vehicle steering wheel and a second telescopic element slidable telescopically within the first telescopic element and connectable to a vehicle steering mechanism; and an energy absorber including a tubular support element disposed over the steering column and a tubular deformable element disposed over the support element in a close fit so as to be supported by the support element; the deformable element being slidable over the support element during deformation thereof.

The support element provides support for the deformable element both during normal driving conditions and during deformation of the deformable element to ensure that the deformation occurs in a controlled manner.

The support element preferably comprises a first supporting portion of relatively greater axial cross-sectional diameter and a second supporting portion of smaller axial cross-sectional diameter, the first and second supporting portions having substantially the same wall thickness.

The deformable element preferably comprises a first portion of reduced wall thickness and relatively greater axial cross-sectional diameter, and a second portion of relatively greater wall thickness and relatively smaller axial cross-sectional diameter.

These shapes of the support and deformable elements enables the deformable element to fold over itself during deformation.

The first tubular portion of the deformable element may have a wall thickness of substantially 0.25 millimetres. The second tubular portion of the deformable element may have a wall thickness of substantially 1.5 millimetres.

Preferably, the first tubular portion of the deformable element has an axial cross-sectional diameter of substantially 40 millimetres and the second tubular portion an axial cross-sectional diameter of substantially 34 millimetres.

The tubular support element may have a wall thickness of substantially 1.5 millimetres.

These dimensions for the support and deformable elements have been found to produce in some embodiments a retarding force on deformation of around 4000 Newtons.

In an embodiment, the steering column assembly includes adjustment means for adjusting the position of the vehicle steering wheel in an axial direction of the steering column assembly.

Advantageously, the adjustment means comprises an adjustment member lockable to prevent movement of the steering wheel in the axial direction of the steering column and releasable to allow movement of the steering wheel in the axial direction of the steering column, the tubular support element being coupled to the adjustment member.

According to another aspect of the present invention, there is provided an energy absorber for a collapsible steering column assembly including a tubular support element disposable over a steering column of the steering column assembly and a tubular deformable element disposed over the support element in a close fit so as to be supported by the support element; the deformable element being slidable over the support element during collapse of the energy absorber.

An embodiment of the present invention is described below, by way of illustration only, with reference to the accompanying drawings, in which: Figure 1 shows a side elevational view of an embodiment of steering column assembly in which an embodiment of energy absorber is shown in cross-section; and Figure 2 shows a side elevational view of the steering column assembly of Figure 1 in a collapsed stated, the energy absorber being shown in cross-section.

Referring to Figure 1, a collapsible steering column 10 includes a first telescopic member 12 connected to a vehicle steering wheel (not shown). A second telescopic member 14 slidable within the first telescopic member 12 is connected to a steering mechanism (not shown) in conventional manner. Disposed around the first telescopic member 12 is a tubular adjustment element 16 which is coupled to the first telescopic member 12 at an end adjacent the steering wheel by a suitable bearing (not shown) which prevents the first telescopic member 12 from sliding axially relative to the tubular adjustment element 16 but which enables the first telescopic member to rotate in the tubular element 16. The other end of the tubular adjustment element 16 is coupled to an energy absorber 20 through a releasable clamping block 18.

The clamping block 18 can be opened to enable the tubular adjustment element 16 to slide therealong so as to adjust the vehicle steering wheel along the axial direction of the first telescopic member 12. The clamping block 18 can also be closed to fix the tubular adjustment element 16 in the set axial position. An example of a suitable clamping block and tubular adjustment element is disclosed in our co-pending British patent application no. ............ (RJ/549) filed the same day as this application.

The energy absorber 20 is formed from two tubular elements 22,24, one disposed within the other in a relatively close-fitting manner. The first tubular element is a support element 22 having a substantially constant wall thickness of, in this example, approximately 1.5 millimetres. A first end 26 of this support element 22 is fixed to the clamping block 18 in such a manner as to allow the clamping block 18 to open and close. A second end 28 of the support element 22 has a reduced diameter relative to the first end 26. In this embodiment, the first end 26 of the support element 22 has an outer diameter of substantially 39.5 millimetres, while the second end 28 has an outer diameter of substantially 34 millimetres.

On the other hand, the second tubular element of the energy absorber 20 is a deformable element 24 which includes a first end 30 which is a close fit over the first end 26 of the support element 22 and a second end 32 which is a close fit over the second end 28 of the support element 22.

The first end 30 of the deformable element 24 has a relatively greater diameter than the diameter of its second end 32. In this example, the first end 30 of the deformable element 24 has an outer diameter of approximately 40 millimetres and the second end 32 an outer diameter of substantially 37 millimetres.

Relative to the support element 22, the first end 30 of the deformable element 24 has a substantially reduced wall thickness, in this example around 0.25 millimetres. However, the second end 32 of the deformable element 32 has a greater thickness, in this example the same thickness as the support element 22, that is approximately 1.5 millimetres. These thicknesses are chosen to cause only the larger diameter portion 30 of the deformable element 24 to deform during collapse of the energy absorber 20 and in so doing to produce a retarding force of, for example, around 4000 Newtons.

The second end 32 of the deformable element 24 is fixed to a vehicle structure 34, for example a vehicle fire wall, in such a manner that this end 32 of the deformable element 24 does not move relative to the vehicle structure during collapse of the steering assembly.

The support element 22 acts to provide sufficient strength to the steering column assembly during normal use and support during deformation of the deformable element 24 on collapse of the steering column, thereby ensuring that collapse occurs in a controlled manner.

Referring to Figure 2, a force imparted to the steering wheel in a direction towards the steering mechanism (in other words from left to right in the view of Figure 2) which is greater than a predetermined amount will cause deformation of the deformable element 24. Deformation occurs in the reduced thickness portion of the deformable element 24. Since the second end 32 of the deformable element 24 has a significantly greater thickness than the remainder of the deformable element 24 and a smaller diameter, the reduced thickness portion 30 rides over the second end 32 at the neck separating the two portions 30 and 32. The support element 22 and the second end 32 of the deformable element 24 together support the reduced thickness portion 30 during its deformation to ensure that the deformation occurs in a controlled manner and that any lateral forces imparted to the steering column assembly are controlled.

The energy absorber is made of any suitable material which can provide controlled deformation of the deformable element 24 and satisfactory support by the supporting element 22. An example of suitable material is a metal alloy. The support element and the deformable element may each be made of different materials.

The support element 22 and the deformable element 24 are preferably substantially circular in axial cross-section, although may have any other suitable axial cross-sectional shape.

Claims

Claims:

1. A collapsible steering column assembly comprising a steering column including a first telescopic element connectable to a vehicle steering wheel and a second telescopic element slidable telescopically within the first telescopic element and connectable to a vehicle steering mechanism; and an energy absorber including a tubular support element disposed over the steering column and a tubular deformable element disposed over the support element in a close fit so as to be supported by the support element; the deformable element being slidable over the support element during deformation thereof.

2. A collapsible steering column assembly according to claim 1, wherein the supporting element comprises a first supporting portion of relatively greater axial cross-sectional diameter and a second supporting portion of smaller axial cross-sectional diameter, the first and second supporting portions having substantially the same wall thickness.

3. A collapsible steering column assembly according to claim 1 or 2, wherein the deformable element comprises a first portion of reduced wall thickness and relatively greater axial cross-sectional diameter, and a second portion of relatively greater wall thickness and relatively smaller axial cross-sectional diameter.

4. A collapsible steering column assembly according to claim 3, wherein the first tubular portion of the deformable element has a wall thickness of substantially 0.25 millimetres.

5. A collapsible steering column assembly according to claim 3 or 4, wherein the second tubular portion of the deformable element has a wall thickness of substantially 1.5 millimetres.

6. A collapsible steering column assembly according to claim 3, 4 or 5, wherein the first tubular portion of the deformable element has an axial cross-sectional diameter of substantially 40 millimetres and the second tubular portion of the deformable element has an axial cross-sectional diameter of substantially 37 millimetres.

7. A collapsible steering column assembly according to any preceding claim, wherein the tubular support element has a wall thickness of substantially 1.5 millimetres.

8. A collapsible steering column assembly according to any preceding claim, comprising adjustment means for adjusting the position of the vehicle steering wheel in an axial direction of the steering column assembly.

9. A collapsible steering column assembly according to claim 8, wherein the adjustment means comprises an adjustment member lockable to prevent movement of the steering wheel in the axial direction of the steering column and releasable to allow movement of the steering wheel in the axial direction of the steering column, the tubular support element being coupled to the adjustment member.

10. An energy absorber for a collapsible steering column assembly including a tubular support element disposable over a steering column of the steering column assembly and a tubular deformable element disposed over the support element in a close fit so as to be supported by the support element; the deformable element being slidable over the support element during collapse of the energy absorber.

11. A collapsible steering column assembly substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

12. An energy absorber substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.