Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
1999-05-25
2001-01-30
Hannon, Thomas R. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S517000, C384S538000, C384S539000
Reexamination Certificate
active
06179473
ABSTRACT:
ROLLING BEARING OF A STEERING COLUMN FOR MOTOR VEHICLES
The present invention is in the field of rolling bearings, especially for motor vehicle steering columns.
Steering columns generally comprise a shaft, one end of which is secured to a steering wheel acted upon by the driver of the vehicle, and the other end of which is secured to mechanical components intended to angularly position the wheels of the vehicle. The steering column shaft is mounted in a stationary tubeshaped housing by means of two rolling bearings, generally angular contact ball bearings mounted in opposition.
The outer rings of the rolling bearings are secured to the steering column housing and the inner rings are mounted on the column shaft via a ring known as a tolerance ring.
The assembly runs with zero clearance by virtue of an axial preload exerted on the tolerance rings by an axially elastic member which may, for example, be a spring, a spring washer, etc.
In general, the axial preload is exerted on the tolerance ring of just one of the two rolling bearings, the tolerance ring of the second rolling bearing being axially immobilized in the direction of this preload. As the tolerance ring of the first rolling bearing can slide axially along the shaft, the axial force exerted by the axially elastic member tends to move the inner rings of the two rolling bearings axially closer together.
Internal play in the rolling bearings is thus take up and preloaded clearance-free continuous contact between the rings and the rolling elements of the rolling bearing is ensured.
Document U.S. Pat. No. 5,193,917 (INA) discloses a rolling bearing for a steering column, in which the axially elastic member consists of a part made of plastic which can be made as a single piece with the tolerance ring. The main drawbacks of this rolling bearing lie in the relatively complex shape of this plastic part and in the difficulty in guaranteeing, in the long-term, control over the amount of preload, bearing in mind the aging of the plastic.
Other known rolling bearings for steering columns comprise an additional part in the form of a locking washer for positioning the tolerance ring on the steering column shaft.
These rolling bearings therefore generally comprise an outer ring that is secured to the housing, an inner ring that is in contact with the shaft, a row of rolling elements arranged between the two rings and Ain contact with them, an tolerance ring, generally made of polyamide, which provides the connection between the inner ring and the steering column shaft and is capable of transmitting axial loads to the inner ring in order to keep the rolling bearing under continuous internal preload, and a locking washer which serves to close the rolling bearing assembly and lock it axially on the shaft while at the same time maintaining an axial preload on the tolerance ring so as to achieve playfree running of the rolling bearing.
In the conventional way, the various parts of such a rolling bearing are not joined together until they are mounted in the steering column device. There is therefore a risk that elements will become mislaid during handling and during the mounting of the assembly in the steering column device. Furthermore, it is necessary to perform stock control on numerous different parts.
For these various reasons the search has been on to produce a non-disassemblable assembly comprising the rings, the rolling elements, the tolerance ring and the locking washer so that said assembly can be assembled before it is mounted in the steering column device and thus deliver rolling bearings that are ready to be mounted without the risk of parts being mislaid.
Document DE-A 38 08 556 (FAG) discloses a steering column rolling bearing in which the tolerance ring made of synthetic material comprises a portion arranged radially between the inner ring and the shaft, and which is extended axially on one side, toward a cylindrical end of the outer ring, this axial extension having radial protrusions intended to axially retain the outer ring. The tolerance ring also comprises a cylindrical portion arranged axially on the opposite side to the aforementioned portion, and radially between the outer ring and a locking washer system, the free end of this cylindrical portion also having radial protrusions for axially retaining the locking washer. However, a tolerance ring of this type protrudes radially inwards with respect to the bore of the inner ring, which increases the radial bulk of the rolling bearing and protrudes axially beyond the radial end of the outer ring, which increases the axial bulk of the rolling bearing.
The object of the present invention is to overcome these drawbacks and to use a tolerance ring of simple shape.
Another object of the invention is to provide a rolling bearing which forms a very compact non-disassemblable assembly which can be mounted in the steering column device in a single operation.
A further object of the invention is to provide a rolling bearing which forms a compact non-disassemblable assembly incorporating axially elastic means for exerting a radial preload allowing the assembly comprising the two rolling bearings mounted one at each end of the housing of a steering column to run without play.
The rolling bearing according to the invention is in particular intended for a motor vehicle steering column, and is of the type comprising an outer ring equipped with a raceway, an inner ring equipped with a raceway, a row of rolling elements arranged between the raceways of said rings, a tolerance ring providing the connection between the inner ring and the steering column shaft, and a locking washer for locking the bearing axially on the shaft. The outer ring comprises a means of axially retaining the locking washer.
Thus, at least when the bearing is mounted on the shaft, the tolerance ring need not project either inward with respect to the bore of the inner ring or axially beyond the outer ring. In this case, the dimensions of the two rings essentially define the overall dimensions of the rolling bearing.
In one embodiment of the invention, the outer ring comprises a cylindrical portion surrounding the tolerance ring and the locking washer, and provided with a radial deformation, said radial deformation being capable of cooperating with the periphery of the locking washer, thus axially retaining it. The radial deformation may be arranged at the free end of the outer ring and may form a narrowing. It is very simple and economical to produce such a narrowing.
In one embodiment of the invention, the radial deformation comprises a number of bosses projecting inward with respect to the bore of the cylindrical portion of the outer ring.
In another embodiment of the invention, the radial deformation comprises an annular bulge projecting inward with respect to the bore of the cylindrical portion of the outer ring.
In another embodiment, the deformation comprises a number of tabs projecting with respect to the bore of the cylindrical portion of the outer ring.
In another embodiment of the invention, the deformation comprises an annular slot provided in the bore of the cylindrical portion of the outer ring.
In one embodiment of the invention, the locking washer comprises a cylindrical portion arranged radially between the tolerance ring and the retaining means of the outer ring, said cylindrical portion being extended at its free end by a radial flange facing outward and capable of cooperating with the retaining means.
In another embodiment of the invention, the locking washer is substantially radial near this periphery.
The locking washer may be cut into tabs on its periphery.
In order that the means for exerting an axial preload can also be integrated into the rolling bearing, an axially elastic washer may be inserted axially between the tolerance ring and the locking washer.
In an alternative form, the locking washer is shaped with means that have axial elasticity so that it itself exerts an axial preload on the tolerance ring.
In this case, the locking washer may preferably comprise a radial portion in which the
Arnault Beno{circumflex over (i)}t
Collignon Bertrand
Houdayer Christophe
Ponson Frederic
Poulle Thierry
Hannon Thomas R.
SKF France
Smith , Gambrell & Russell, LLP
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