GB2278321A

GB2278321A - Motor vehicle steering column assemblies

Info

Publication number: GB2278321A
Application number: GB9417117A
Authority: GB
Inventors: Roland John Hayward
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1991-01-25
Filing date: 1994-08-24
Publication date: 1994-11-30
Anticipated expiration: 2011-01-25
Also published as: GB9101717D0; GB2252084A; GB9417117D0; GB2278321B; GB2252084B

Abstract

A motor vehicle steering column assembly includes an inner shaft 11C and an outer column 14C. A bearing bush 39 is located in a bore of the outer column and is combined with a switch housing 20C mounted on the outside of the outer column. The switch housing is retained by a screw 42 and a wedge 41. <IMAGE>

Description

MOTOR VEHICLE STEERING COLUMN ASSEMBLIES The invention relates to motor vehicle steering column assemblies.

According to the invention there is provided a motor vehicle steering column assembly comprising a shaft member for connection to a steering wheel and an outer column rotatably supporting the shaft member by means of a bearing bush located in the bore of the outer column, the bush being combined with a switch housing mounted on the outside of the outer column.

The invention will now be described by way of example and with reference to the accompanying drawings, of which Fig 1 is a side elevation of the upper part of a motor vehicle steering column assembly as described in our copending application No.9101717.8 (GB 2 252 084) from which this application is divided.

Fig 2 is a view corresponding to a cross-section on the line II-II in Fig 1 but showing more detail; Fig 3 is a view on arrow A in Fig 2; Fig 4 is a view in the direction of arrow A in Fig 2 showing one of the components in more detail; Fig 5 is a view on arrow B in Fig 4; Fig 6 is a view similar to Fig 1 showing a first alternative; Fig 7 is a view similar to Fig 1 showing a second alternative; Fig 8 is longitudinal cross-section on the line VIII VIII in Fig 7; Fig 9 is cross-section on the line IX-IX in Fig 8; Fig 10 is a scrap view showing part of Fig 8 during a collision; and Fig 11 is a longitudinal cross-section showing part of a motor vehicle steering column according to the invention.

Referring to Figs 1 to 5, a motor vehicle steering column assembly includes an inner shaft comprising an upper shaft member 11 having means in the form of a taper 12 and splines 13 for connection to a steering wheel. An outer column 14 rotatably supports the upper shaft member 11 and is itself fixed to the vehicle body structure 15 by frangible mounting means 16. A switch assembly 20 is mounted on the outer column 14.

The frangible mounting means 16 comprises a break-out capsule in the form of a zinc or zinc alloy half clamp 17 slotted to receive an arm member 18 of steel strip. The arm member 18 carries bushes 19 which allow it to slide on tubular projections 21 on a bracket 22 in a direction perpendicular to the column axis. The arm member 18 can be clamped to the bracket 22 by a screwed stud 23 and a nut 24 with a handle 25 which gives the driver a means for adjustment of the steering column angle or rake. Bolts 26 (one only shown in Fig 2). are inserted through the tubular projections 21 to secure the bracket 22 and thus the arm member 18 to the vehicle body structure 15.

The arm member 18 has a U shaped cut-out 27 which corresponds to the slot in the half clamp 17, a hot melt plastics adhesive being used to retain the arm member in the slot.

A steering column lock 28 has its main body clamped to the outer column 14 by two bolts 29 inserted through holes 31 in the half clamp 17 so that the frangible mounting means 16 is combined with the steering column lock as well as with steering column rake adjustment means. The lock 28 is generally conventional, a key being used to rotate a lock barrel which allows a plunger to prevent relative rotation of the upper shaft member 11 and the outer column 14.

In the event of a vehicle collision the frangible mounting means 16 allows axial movement of the outer column 14 and the upper shaft member 11 away from the driver by the half clamp 17 shearing away from the arm member 18.

By combining the frangible mounting means 16 and the steering column lock 28, the distance which the column can move away from the driver in the event of a collision is increased compared to the conventional steering column where the lock is mounted separately on the column between the frangible mounting means and the steering wheel.

A further advantage is that the mass of the steering column lock is not carried on the column itself, thus reducing the mass which the column has to carry as a cantilever and improving its vibration characteristics.

In the first alternative shown in Fig 6, the combined frangible mounting means 16A and steering column lock 28A are positioned further up the steering column. This alters the cantilever vibration characteristics still further and allows more distance between the frangible mounting means and the lower end of the steering column for telescopic collapse of the column.

In the second alternative shown in Figs 7 to 10, the switch assembly 20B is located closer to the frangible mounting means 16B. This allows a telescopic joint between the upper shaft member llB and the lower shaft member 32 to be situated above the frangible mounting means.

The connection between the upper and lower shaft members may be conventional, eg the shaft members each have a respective configuration which allows one shaft member to slide telescopically within the other without relative rotation and one shaft member is axially located relative to the other by means of plastics injection.

However, in Figs 8 to 10 axial location is provided by metal location means in the form of U shaped staples 33 and 34. The upper and lower shaft members llB and 32 are of D shaped tubular section in the region where they connect and the staples 33 and 34 are each inserted through a respective pair of holes in the flat portion of the upper shaft member 11. The base of each staple 33 and 34 is thus within the bore of the outer column 14B.

Each staple 33 and 34 extends through a respective axial slot 35 and 36 in the lower shaft member 32 and straddles a respective pin 37 and 38. Each pin 37 and 38 is transverse to the respective staple and is offset from the diameter to give a suitable cantilever offset of the staple leg between the pin and hole in the upper shaft member llB.

In the event of a collision which causes a compressive axial load on the column, the staples are deformed plastically in bending as shown in Fig 10. Once one leg of each staple has been bent back the shaft members can continue to telescope relatively freely up to the limit imposed by the length of the slots 34 and 35.

Although the staples may be an interference fit in the holes in the upper shaft member llB, they are preferably made to grip the respective pin 37 and 38, the outer column 14B preventing the staple from jumping out of the holes in the event of a collision.

The break-out load, ie the load to cause deformation of the staples and allow telescopic movement of the shaft members, can be varied by varying the cross section and material grade of the staples, by varying the number of staples and by selecting the cantilever arm length at which the pin contacts the staple. This load is predictable to closer limits than those achievable using other methods of controlling break-out load, particularly the commonest method of plastics injection which requires very close control of the process parameters for predictable results.

The present design may use plastics injection to keep the shaft members concentric to each other and prevent rattling but this would not contribute to the break-out load significantly.

Where the switch assembly 20A or 20B is very close to the steering column lock and frangible mounting means as in Figs 6 and 7 the switches may be attached to the lock or to the mounting bracket and the cowl or cover attached to any of these components.

Fig 11 shows an arrangement according to the invention where the switch housing 20C is combined with a bearing bush 39 which rotatably supports the upper shaft member llC. A wedge 41 is moved by a screw 42 to hold the housing on the end of the outer column 14C.

The arrangement allows for an axially compact assembly which allows more room for collapse mechanisms elsewhere on the steering column. The invention may be used with the arrangements shown in Fig 1 or Fig 6 or in an otherwise conventional steering column.

Claims

1. A motor vehicle steering column assembly comprising a shaft member for connection to a steering wheel and an outer column rotatably supporting the upper shaft member by means of a bearing bush located in the bore of the outer column, the bush being combined with a switch housing mounted on the outside of the outer column.

2. An assembly according to Claim 1 wherein said shaft member is an upper shaft member and comprising a lower shaft member and a telescopic joint between the shaft members which allows one shaft member to slide axially within the other without relative rotation and which comprises metal location means for axially locating one shaft member relative to the other and arranged for plastic deformation under an axial impact load transmitted from one shaft member to the other.

3. An assembly according to any preceding claims wherein the metal locating means comprises a cantilever extending transversely from one shaft member and arranged to be deformed in bending by the other shaft member.

4. An assembly according to Claim 3 wherein the cantilever forms one arm of a U shaped staple inserted through holes in one shaft member and straddling a pin which extends through the other shaft member, the other shaft member having an axial slot to allow movement relative to the staple and being located radially within the one shaft member in the region of the telescopic joint.

5. An assembly according to Claim 4 wherein the shaft members are of D shaped tubular section in the region of the telescopic joint and the holes for the staple are in the flat of the one shaft member.

6. An assembly according to any preceding claim wherein a wedge is movable by a screw to hold the housing on the outer column.