GB2340086A - A motor vehicle with a collapsible steering column - Google Patents

Description

2340086 A Motor Vehicle This invention relates to a motor vehicle and in

particular to a steering column assembly for a motor vehicle.

It is well known to provide a motor vehicle with a steering wheel connected to a steering apparatus of the motor vehicle by a steering column.

In the event of a front impact the driver is normally thrown forward towards the steering wheel and the windscreen and so it has been the common, practice in recent years to provide an inflatable airbag located within the central portion of the steering wheel.

It is also known from US 5 507 521 to provide 'a rake adjustable steering wheel, which in the event of a frontal impact, tilts the steering wheel so as to improve the orientation of an airbag mounted on the steering wheel.

However, it can be a problem with rake adjustable steering wheels that, when the steering column is not in its straightest position, the energy absorbing collapse of the column is hindered because the column is not collapsing in a straight line.

It is an object of this invention to provide an improved steering assembly for a motor vehicle.

According to the invention there is provided a motor vehicle having a body structure and a steering assembly secured to said structure, the steering assembly including a steering column extending between a steering wheel at its upper end and a flexible joint at its lower end for connecting the steering column to a steering unit, and having a collapsing section between its upper and lower ends arranged to collapse in the event of a vehicle impact, and actuation means arranged, in the event of a vehicle impact, to rotate the column, including the collapsing section, about its lower end, so as to alter the orientation of the steering column whilst maintaining it in a 10 substantially straight condition.

Preferably the actuation means comprises a biasing means arranged to bias the column into a first position and a releasable retaining means arranged to retain the column in a second position, but to be released in the event of a vehicle impact.

Preferably the motor vehicle further comprises an airbag mounted on the steering wheel and arranged to be inflated in the event of a vehicle impact.

Preferably, the securing means is automatically released just prior to inflation of the airbag.

Alternatively, the securing means may be automatically released during inflation of the airbag.

The securing means may include an explosively released member connected to said electronic control means.

The invention will now be described by way of example with reference to the accompanying drawing of which:

Fig. lis a scrap cross-section through part of a motor vehicle according to the invention; and Fig. 2is a cross section through a steering column support bracket forming part of the invention.

With reference to the drawing there is shown a motor vehicle 21 having a body structure 23. A seat 39 for a driver "D" is attached to part of the body structure as is an inertia reel seat belt assembly 2. A windscreen 38 extends upwardly from a bonnet portion of the vehicle body 23.

A steering wheel 24 is provided to permit the driver to steer the motor vehicle by means of a steering unit 9 which is connected to steerable wheels of the motor vehicle by steering arms (not shown). The steering wheel is connected to the steering unit 9 by a steering column assembly. The steering column assembly has an outer non-rotatable sleeve 3 and an inner rotatable shaft 4. The outer sleeve 3 acts as a support for the shaft 4 at its upper end towards the steering wheel 24. The shaft 4 has a universal joint 10 at its lower end to permit the angle of the steering column to be varied between a normal inclined position and a lower, less inclined, i.e. more horizontal position shown by the dotted line on Fig. 1 and the reference numeral 24a for the steering wheel. A collapsible section 30 is also included in the steering column to permit longitudinal collapse of the column if the steering,unit 9 is moved rearwardly in a crash.

The outer sleeve 3 is connected to a column mounting structure 1 forming part of the body structure of the motor vehicle by means of a "U' shaped bracket 12. The bracket 12 being connected to the beam 1 via flexible mountings 13.

The outer sleeve 3 is welded to two support plates 5,6 which are joined together by a cross brace 2. Each of the support plates has a slot 20 therein through which extends a machine bolt 8. The lower end of each of the support plates 5, 6 is turned outwardly to form a spring support 11, 16 for the lower end of a helical coil spring 15.

A pair of spring abutments 14 are located on the bolt 8 and interposed between the support plates 5,6 and the bracket 12. A spacer block 18 is located on the bolt 8 and interposed between the two support plates 5,6. A thick washer 23 is interposed between the bracket 12 and a nut 19 which is in threaded engagement with the bolt 8. At its other end the bolt has a head 17 which in combination with the nut 19 and the bolt 8 forms part of a 5 releasable securing means 25.

The releasable securing means 25 further includes a piston member 31, an end cap 27, a ball bearing assembly 19, a reaction plate 28, a spacer plate 34 and an explosive charge 29.

1 The piston 31 and the end cap 27 form a variable length spacer between the head 17 and the bracket 12.

With particular reference to Fig. 2 the piston 31 has a circumferentially extending chamber formed in one of its ends in which is located the explosive charge 29. Around the outer circumference of the piston 31 adjacent to said chamber there is formed a circumferentially extending recess 32 for co-operation with an inwardly turned lip 33 at one end of the end cap 27. The length of the recess 32 is greater than the thickness of the lip 33. The ball bearing assembly is interposed between the reaction plate 28 and the support plate 34. The support plate 34 is an interference fit in a serrated bore 35 formed within the end cap 27.

The support plate 34 is pressed into the serrated bore 35 by the action of inserting and securing the reaction plate 28 into the end cap 27. The reaction plate 28 being secured in place by the inturned lip 33 of the end cap 27 which is formed by swaging over the end of the end cap 27. The end cap 27 complete with bearing assembly 19 is then located on the bolt 8 and the piston 31 complete with explosive charge is then slid along the bolt 8 so that the recess 32 engages with the inturned lip 33 and the end face of the piston 31 abuts the reaction plate 28.

The bolt 8 complete with the piston and end cap sub-assembly is then engaged with the bracket 12, spring abutments 14, spacer block 18, the two support plates 5,6 and the thick washer 23 and lightly secured in place by the nut 19.

In this state the internal width "W' of the bracket is greater than the total length of the spacer 18, the two spring abutments 14 and the combined thickness of the two support plates 5,6 and so the support plates 5,6 are free to move relative to the bolt 8 within the constraints imposed by the slots 20.

To put the steering column 3,4 into a normal position it is urged upwardly against the action of the helical biasing spring 15 which is interposed between the spring supports 11, 16 and the spring abutments 14 until it is in the position shown in Fig. 2. The nut 19 is then tightened to a pre-determined torque which cause the bracket to be squeezed inwardly to clamp the support plates 5,6 against the spacer 18 thereby securing the steering column 3,4 in its normal operating position.

The explosive charge 29 is connected via an electric cable 7 to an electronic control unit 60 forming part of an airbag system. The electronic control unit 60 is connected to an airbag 61 forming part of an airbag assembly mounted in the centre of the steering wheel 24 and is arranged to receive a signal from a vehicle acceleration sensor 50.

As is well known in the art when the sensor 50 senses that a predetermined deceleration has been reached it sends a signal to the electronic control unit 60 that indicates that the airbag 61 should be inflated and the electronic control unit 60 then sends a signal to an inflator (not shown) to inflate the airbag 61.

However in this case prior to inflation of the airbag the electronic control unit sends a signal to the explosive charge 29 causing it to detonate and release the clamping effect upon the steering column 3,4 which is then rapidly moved downwardly, into a less inclined position by the action of the spring 15. During this downward movement the column 3, 4 rotates as a whole about the joint 10 and therefore remains substantially straight. The collapsible section can therefore subsequently collapse in its intended controlled way in a substantially straight line.

The explosive force causes the reaction plate to be forced away from the end face of the piston 31 and pushes the support plate 34 via the bearing 19 further into engagement with the serrated bore 35. This effectively introduces free play into the securing means which prevents the bolt 8 from providing any clamping force to the bracket 12.

Although it is desirable to have the steering column reach its less inclined position before the airbag 61 is fired it will be appreciated that firing of the airbag 61 could take place simultaneously with the releasing of the steering column.

It will also be appreciated that the clamping force on the steering column could be achieved by other means for example it could be effected by a solenoid operated latch.

Claims (8)

-9CLAIMS

1. A motor vehicle having a body structure and a steering assembly secured to said structure, the steering assembly including a steering column extending between a steering wheel at its upper end and a flexible joint at its lower end for connecting the steering column to a steering unit, and having a collapsing section between its upper and lower ends arranged to collapse in the event of a vehicle impact, and actuation means arranged, in the event of a vehicle impact, to rotate the column, including the collapsing section, about its lower end, so as to alter the orientation of the steering column whilst maintaining it in a substantially straight condition.

2. A motor vehicle according to claim 1 wherein the actuation means comprises a biasing means arranged to bias the column into a first position and a releasable retaining means arranged to retain the column in a second position, but to be released in the event of a vehicle impact.

3. A motor vehicle according to claim 1 or claim 2 further comprising an airbag mounted on the steering wheel and arranged to be inflated in the event of a vehicle impact.

4. A motor vehicle as claimed in claim 3 wherein the actuation means is arranged to be actuated just prior to inflation of the airbag.

5. A motor vehicle as claimed in claim 3 in which the actuation means is arranged to be actuated during inflation of the airbag.

6. A motor vehicle as claimed in claim 2 or any claim dependent thereon in which said biasing means is a spring.

7. A motor vehicle as claimed in claim 2 or any claim dependent thereon in which the retaining means includes an explosively released member.

8. A motor vehicle substantially as described herein with reference to the accompanying drawings.