Land vehicles – Wheeled – Attachment
Reexamination Certificate
1998-10-21
2001-11-06
Swann, J. J. (Department: 3611)
Land vehicles
Wheeled
Attachment
C280S777000, C280S750000
Reexamination Certificate
active
06312011
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a steering wheel having a steering wheel hollow which is fastened by its base to a steering column and in which an airbag, which inflates in the event of a vehicle impact, is accommodated and from its casing spokes lead to a steering wheel rim which, with respect to the steering wheel hollow, is offset axially toward the vehicle interior.
Steering wheels of this type are widely used in today's motor vehicles and are therefore generally known. In the event of an impact accident, the airbag, which is arranged in the steering wheel hollow, is intended to be completely inflated if the driver is flung in the direction of the steering wheel, in order to prevent a hard impact against the steering wheel. Cases may, however, arise in which this protective action of the airbag does not occur. For example, this is the case if in an accident there is an initial impact against a first obstacle and then against a further obstacle which finally brings the vehicle to rest. In such a case, the airbag is inflated in the first impact and may already be discharged again by the second impact. Another occurrence which is most unfavorable for the driver is if he sits too close to the steering wheel and impacts against the airbag which is still inflating and at this time is undesirably hard and initially unyielding. It is therefore desirable for the steering wheel to be deformable in the axial direction in order, independently of the airbag, to be able to yield in the axial direction in the event of the driver impacting against the steering wheel.
It is also already known to connect a vehicle steering to a cable mechanism in such a manner that in the event of a frontal impact, the entire steering wheel is displaced in the direction of the dash-board. This reduces the risk of the driver becoming wedged, but mechanisms of this type are very costly and complex and have therefore not been able to be generally used so far.
SUMMARY OF THE INVENTION
An object of the invention is to provide a steering wheel having an airbag in its steering wheel hollow in such a manner that the steering wheel can be deformed in the axial direction.
According to the invention, the airbag is fastened on a plate which in the rest position bears against the base of the steering wheel hollow and, as the airbag inflates, is displaced within the steering wheel hollow away from the base, the steering wheel having at least one travel limiting means for the maximum possible travel of the plate, and with the airbag released, the space between the plate and the base of the steering wheel hollow being formed to receive end regions of the spokes, which end regions are remote from the steering wheel rim, and/or regions of the casing of the steering wheel hollow.
This formation of the steering wheel produces a free space in the steering wheel hollow after the airbag has been released. As a result, in the event of the driver impacting on the steering wheel rim and/or on the inflated airbag, the steering wheel rim can buckle forward by the ends of the spokes moving into this free space in the steering wheel hollow. The invention thus provides a steering wheel which is able, because of its axial deformability, to mitigate the consequences of an impact independently of the airbag. Furthermore, this deformability in the event of an accident increases the free space for the driver thereby reducing the risk of the driver becoming wedged behind the steering wheel. The inventive formation of the steering wheel can be implemented substantially more cost-effectively than the measures disclosed previously to withdraw the steering wheel in the event of a frontal impact and thus the passive safety of motor vehicles can be increased with relatively little outlay.
According to the invention, a sufficiently large, free space is produced between the base of the steering wheel hollow and the plate after the airbag has been released, into which space the spokes can move. It must, however, be reliably ensured that the airbag cannot be detached from the steering wheel in the event of an accident. These two requirements can be fulfilled in a very simple manner if, in accordance with a development of the invention, the travel limiting means is formed by a bolt which is fastened to the plate, penetrates through a recess in the base and on that side of the base which is remote from the plate, with the plate bearing against the base, has, at a distance from the base, a head which does not fit through the particular recess.
As the plate moves away from the base of the steering wheel hollow after the airbag has been released, it is not braked abruptly, which could result in components being destroyed and thereby in the plate coming free, if, in accordance with a particularly advantageous feature of the invention, the head of the bolt is expanded from its shank with a cross-sectionally conical surface. In such an embodiment, the conical surface is able to slightly widen the recess before the head of the bolt prevents further axial travel. Braking is therefore brought about over a distance defined by the conical surfaces, rather than sudden stopping.
For simple production and easy assembly of the steering wheel, it is of particular advantage if the bolt is a screw which is screwed into the plate.
According to an advantageous feature of the invention, the steering wheel has two travel limiting means. These enable the forces which occur as the airbag is inflating to be particularly readily and uniformly absorbed by the base of the steering wheel hollow.
Wedging of the bolts in the holes, and hence obstruction of the axial travel of the plate as the airbag is being released, can be ruled out in a simple manner by the plate being guided in the hollow by means of a rotation-preventing means, and the bolts in the recesses in the base of the steering wheel hollow have a clearance which cannot be eliminated by the maximum possible rotation of the plate.
The spokes and the steering wheel hollow can differ very widely in design in order to achieve the ability of the spoke ends buckling into the steering wheel hollow. It would be possible, for example, to design the casing surface of the steering wheel hollow such that it can be deformed to the extent that in the event of an accident, the spokes together with the corresponding regions of the steering wheel hollow move into the space behind the plate and in front of the base of the steering wheel hollow. The steering wheel is formed in a particularly simple manner if the spokes, on their side which faces the steering column, each have a web which is directed toward the side of the steering column and leads right against the outer casing surface of the steering wheel hollow, and in the region of each spoke, the casing of the steering wheel hollow is provided with a respective predetermined breaking region. As a result, in the event of a crash the ends of the spokes pivot into the steering wheel hollow.
During normal operation of the motor vehicle, steering wheels are often stressed by high forces. In many cases, steering wheels are of such stable design that the driver is able to support his full weight on the steering wheel without causing it to be deformed. Even in the case of a steering wheel having predetermined breaking points, this high degree of strength can be provided if the webs extend in the axial direction of the steering wheel hollow until they overlap the plate which is arranged in the steering wheel hollow and is in the rest position. By means of this development, the plate prevents the spokes from collapsing into the steering wheel hollow in the rest position by supporting the regions behind the predetermined breaking points. In the event of an accident, this support disappears as the plate moves in the direction of the driver, with the result that the predetermined breaking points can then break, even when forces are relatively low, and the desired axial displaceability of the steering wheel occurs.
REFERENCES:
patent: Re. 36351 (1999-10-01), Yama
Dohring Klaus
Kaufmann Veit
Farber Martin A.
Mannesmann VDO AG
Shriver J. Allen
Swann J. J.
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