FR2798170A1 - Ball bearing unit for steering column of a motor vehicle, has a blocking washer to block the bearing on the shaft - Google Patents

Abstract

The ball bearing consists of an outer ring (4) and an inner ring (6) both providing rolling paths for a series of balls (8) placed between them. A tolerance ring (9) is provided to ensure the liaison between the inner ring (6) and the shaft (3) of the steering column. A blocking washer (11) is provided to block the bearing on the shaft and the outer ring (4) contains an inner circumferential groove (13) for the reception of a spring clip (14), which forms an axial stop for the blocking washer. A wavy washer (12) is provided to take up any axial play between the inner and outer rings of the bearing.

Description

Bearing 'steering column bearing for motor vehicles, the present invention relates to the field of rolling bearings in particular for steering columns of' automotive vehicles.

steering columns generally comprise a shaft, one end of which is secured to a drive wheel actuated by the driver of the vehicle and the other end of which is secured to mechanical members intended to ensure the angular positioning of the vehicle wheels. The shaft of the steering column mounted in a fixed tubular housing by means of two rolling bearings, generally with angular contact balls, mounted in opposition.

rolling bearings generally comprise an outer ring integral with the housing, an inner ring in contact with the shaft, each ring being provided with a toroidal raceway, and a row of rolling elements arranged between the two raceways in contact with these. One can also provide a cage to maintain the regular circumferential spacing of the rolling elements. cage is made, for example of molded synthetic material. Given the low speed of rotation of this type of bearing, the presence of a cage is not compulsory, the rolling elements can be provided practically contiguous in the circumferential direction.

The bearing rings are made of pressed sheet metal and undergo a hardening heat treatment.

The outer rings of rolling bearings are secured to the housing of the steering column and inner rings are mounted on the column shaft by means of a so-called radially deformable tolerance ring, for example made of molded synthetic material. The tolerance ring makes it possible to ensure easy mounting of the bearing on the shaft without initial tightening and to be able to then carry out the joining between the inner ring and the shaft, even when their respective sections have very different profiles, for example a inner ring having a shape of revolution and shaft with square section. The tolerance ring also makes it possible to compensate by deforming geometric defects and dimensional dispersions of the rings and of the shaft, and to transmit to the inner ring the axial stressing force.

The tree may have a circular or polygonal cross section, for example square. The bore of the tolerance ring is adapted to the cross section of the shaft. The tolerance ring can be in the form of an elastic ring interrupted by a radial slot.

The assembly operates at zero clearance thanks to an axial prestressing force exerted on the tolerance rings by an axially elastic member which can be, for example, a spring, an elastic washer, etc.

The axial prestressing force can be exerted on the tolerance ring of only one of the two rolling bearings, the tolerance ring of the second rolling bearing being immobilized axially in the direction of this force. Since the tolerance ring of the first rolling bearing can slide axially on the shaft, the axial force tends to bring the inner rings of the two rolling bearings axially together. This axial force can be exerted by an elastic washer, of the wavy type or with tongues with axial elasticity.

This compensates for the internal clearances of the bearings and ensures permanent contact without play and under preload between the rings and the rolling elements of the rolling bearing.

Known rolling bearings for steering columns include an additional piece in the form of a lock washer for positioning the tolerance ring on the shaft of the steering column. The lock washer is used to close the entire rolling bearing and to lock it axially on the shaft while maintaining an axial preload on the tolerance ring in order to obtain a clearance-free operation of the rolling bearing.

conventionally, the different parts such as rolling bearings are only combined qtze when they are mounted in the steering column device. There is therefore a risk of loss of elements during handling and mounting of the assembly in the steering column device. In addition, several different parts stocks must be managed.

For these various reasons, it is sought to constitute a non-removable assembly comprising the rings, the rolling elements, the tolerance ring and the lock washer so as to be able to assemble the said assembly before it is mounted in the steering column device and thus to provide bearings to bearings ready to be mounted without risk of losing parts.

knows from document FR 9705259 a rolling bearing whose outer ring comprises a cylindrical portion provided with a plurality of bosses projecting radially inwardly relative to the bore of said cylindrical portion and arranged axially at a portion cylindrical lock washer. The bosses define a diameter smaller than that of a radial flange of the lock washer and guarantee its retention in the axial direction.

However, obtaining the bosses requires an operation to take up the outer ring, which complicates manufacture and increases costs. The lock washer is forced back into the outer ring with elastic deformation during the passage of the boss or bosses and then resumes its initial shape. It follows that the possibilities of radial interference, and therefore of subsequent axial retention are severely limited under penalty of no longer being able to assemble said parts. Small material tears are, moreover, liable to occur during the reentry and to pollute the interior of the bearing thereafter. After its installation the lock washer can be put in an inclined position relative to the bearing which is detrimental to its retention by the bosses present invention aims to remedy these drawbacks.

The object of the invention is also to propose a rolling bearing forming a very compact removable assembly which can be mounted in a single operation in the steering column device. rolling bearing according to the invention is in particular intended for a steering column of a motor vehicle, is of the type comprising an outer ring provided with a raceway an inner ring provided with a raceway, a row of rolling elements arranged between the raceways of said rings, a tolerance ring ensuring connection of the inner ring with the shaft of the steering column and a lock washer for locking the bearing axially on the shaft. outer ring includes an axial retaining means of the lock washer. The outer ring is provided with a circular groove arranged on its internal surface, the said groove being intended to receive an elastic ring forming an axial stop for the lock washer.

In one embodiment of the invention, the elastic ring is in contact with an external surface of revolution of the lock washer, said surface having a convex profile in axial section. This outer surface can be intermediate between an outer cylindrical surface and a radial surface arranged opposite the rolling elements. Said groove can have a circular arc, V-shaped profile, or have two oblique edges and a flat bottom parallel to the axis of the bearing.

Advantageously, the rolling bearing comprises an axial prestressing means, such as an elastic washer axially disposed between the tolerance ring and the lock washer.

The elastic ring can be of circular or polygonal section.

In one embodiment of the invention, the elastic ring is open. In one embodiment, the groove is arranged towards the end of the outer ring axially opposite the raceway.

The invention also relates to a method of manufacturing a rolling bearing as described above, in which the outer ring provided with said groove is formed by stamping a sheet blank, then by stamping cutting.

Thanks to the invention, an economical rolling bearing is obtained, the outer ring groove being stamped in masked time with other cutting and stamping operations. The assembly being carried out without forcing, the risk of the presence of metal particles torn off which can be harmful to the life of the bearing is reduced. The elastic ring, which is slightly prestressed in its circular groove, constitutes an effective axial retaining element for the lock washer, even if the latter is put in an inclined position relative to the axis of the bearing.

The invention will be better understood on studying the detailed description of a few embodiments taken by way of nonlimiting examples and illustrated by the appended drawings, in which FIG. 1 is seen in axial section of a rolling bearing. according to a first embodiment of the invention; Figure 2 is a detail of Figure 1; Figure 3 is a view similar to Figure 2 showing a rolling bearing according to a second embodiment of the invention; Figure 4 is a view similar to Figure 2 showing a rolling bearing according to a third embodiment of the invention; Figure 5 is an axial sectional view of a stamped sheet blank intended to form the outer ring of a rolling bearing according to the first embodiment of the invention; Figure 6 is a top view in elevation of the sheet blank of Figure 5; and Figure 7 is an axial section of an outer ring of a rolling bearing according to the first embodiment of the invention; As can be seen in Figure 1, rolling bearing 1 is disposed between a fixed housing 2 shown in phantom and comprising a bore 2a and a front surface 2b, and a rotating shaft 3 also shown in phantom.

The rolling bearing 1 comprises an outer ring 4 of pressed sheet metal, defining a raceway 5, an inner ring 6, of pressed sheet metal, defining a raceway 7, and a row of rolling elements 8, for example balls , arranged between the inner race 5 of the outer ring 4 and the outer race 7 of the inner ring 6.

The outer ring 4 comprises a cylindrical portion 4a extending from the raceway 5 and a radial flange 4b extending from the free end of the cylindrical portion 4a, towards the outside. The cylindrical portion 4a is in contact with the bore 2a of the housing 2 and the radial flange 4b is in contact with the front surface 2b of the housing 2 and serves as an axial positioning stop. The inner ring 6 comprises a cylindrical portion 6a fitted onto the shaft 3 with a certain radial clearance and a toroidal portion 6b whose external surface forms the path 7.

The rolling bearing 1 comprises an elastic tolerance ring 9 made of synthetic material, for example polyamide, and forming a ring interrupted by a radial slot 10. The radial slot 10 allows the tolerance ring 9 to adapt to dimensional variations diametral of the shaft 3 and the inner ring 6, due to manufacturing tolerances and thus ensuring by elasticity the connection between the inner ring 6 and the shaft 3. The tolerance ring 9 also makes it possible to compensate for defects of coaxiality of the housing with respect to the shaft. The tolerance ring 9 includes a bore 9a in contact with the shaft 3, a toroidal surface portion 9b of a shape corresponding to and in contact with the toroidal portion 6b of the inner ring 6 the toroidal surface 9b, a radial surface 9c.

The rolling bearing 1 also comprises a lock washer 11 comprising a radial portion 11a, an oblique flange 11b extending from the radial portion 11a radially inward and axially opposite the tolerance ring 9, and a cylindrical portion 11c extending from the periphery of the radial portion 11a towards the rolling elements 8 and disposed radially between the cylindrical portion 4a of the outer ring 4 and the tolerance ring 9.

The radial portion 1a is connected to the cylindrical portion 11c by a rounded portion l 1d of which the external surface has, in axial section, a convex profile.

The oblique flange l lb, which can be cut into tongues clamps on the shaft 3 which makes it possible to move the lock washer 11 in the direction of the rolling elements 8 by sliding on the shaft 3 but prevents reverse axial movement by bracing of the oblique flange 11b on the shaft 3. It is therefore possible, during assembly, to place the lock washer 11 in a determined axial position on the shaft 3 in order to apply an axial prestress to the inner ring 6 by means of the ring tolerance 9. The toroidal surface 9b of the tolerance ring 9 in contact with the inner ring 6 causes a wedge effect between the shaft 3 and the toroidal portion 6b of the inner ring 6 which ensures a satisfactory connection between the shaft 3 and the inner ring 6 and on the other hand prevents any unwanted radial movement of the tolerance ring 9 as long as the rolling bearing is not mounted on the shaft.

The rolling bearing 1 also comprises an elastic preloading washer 12 of wavy type, disposed axially between the radial surface 9c of the tolerance ring and the radial portion 1a of the locking washer, the elastic washer 12 being surrounded radially by the cylindrical portion 11c.

The cylindrical portion 4a of the outer ring 4 is provided with a circular groove 13 formed in the bore of said cylindrical portion 4a towards the end of the cylindrical portion opposite axially to the raceway. The groove 13 is cross section in an arc and is preferably formed by stamping.

The rolling bearing 1 comprises an elastic ring 14 open at a point of its circumference and of toroidal shape. The elastic ring is disposed in the groove 13 and projects from the bore of the cylindrical part 4a radially inwards so that it has a smaller internal diameter than the external diameter of the cylindrical portion llc of the lock washer. 11. The elastic ring 14 thus prevents an axial movement of disassembly of the lock washer 11 retains the parts of the rolling bearing together. The elastic ring can be produced by cutting a metal wire which is then rolled on itself. A hardening heat treatment can be provided to give said ring 14 the desired hardness and elasticity characteristics.

The elastic ring will have diametrical dimensions in the free state such that it is slightly prestressed in the groove 13 once in place therein.

proceeds to the assembly of the rolling bearing 1 as follows: the row of rolling elements 8 is placed on the path 5 of the outer ring 4, the inner ring 7 is brought into contact with the rolling elements 8, the tolerance ring 9 in contact with the inner ring 6, the elastic washer 12 is introduced axially then the lock washer 11 in the outer ring 4, there is the elastic ring 14 in the groove 13. It will be noted that if one exercises on the lock washer an axial force which pushes the latter against the elastic ring, the contact zone was made at the level of the convex external surface of the rounded connection 11 c and an area of the surface of the elastic ring close of the bore of the latter, said axial force tends to increase the tightening of the elastic ring in the groove 13 and to strengthen the retaining power of said elastic ring.

The embodiment illustrated in Figure 3 is similar to that of Figure 1 except that the groove 13 has a V-shaped cross section, in other words with frustoconical edges inclined for example by an angle of 30 with respect to the axis of the rolling bearing.

The embodiment illustrated in FIG. 4 is similar to that of FIG. 1 except that the groove 13 has a cross section with inclined edges and flat bottom, in other words with frustoconical inclined edges for example of a angle of 30 relative to the axis of the rolling and cylindrical bottom bearing.

The elastic ring 15 disposed in the groove 13 is open at a point of its circumference and of polygonal shape. The elastic ring 15 can be produced by injection molding of a synthetic material.

The elastic ring 15 comprises a cylindrical surface 15a in contact with the bottom of the groove 13, an oblique surface 15b adjacent to the cylindrical surface 15a on the side of the rolling elements, in contact with the corresponding inclined edge of the groove 13, and is extending outside said groove 13, an oblique surface 15c adjacent to the cylindrical surface 15a on the side opposite to the rolling elements 8, in contact with the corresponding inclined edge of groove 13, and extending outside said groove 13, a cylindrical surface 15d adjacent to the oblique surface 15c and extending opposite the rolling elements 8, a radial surface 15e adjacent to the cylindrical surface 15d and extending inward, a cylindrical surface 15f adjacent to the radial surface 15e and extending towards the rolling elements 8, and an oblique surface 15g adjacent to the cylindrical surface 15f and to the oblique surface 15b. The oblique surface 15g is capable of coming into contact with the locking washer 11 in a rounded convex zone intermediate between the radial portion 11a and the cylindrical portion 11c to prevent disassembly of said locking washer 11 and to hold the parts of the rolling bearing together. Again, an axial thrust exerted by the lock washer on the elastic ring tends, by wedge effect, to open said ring and to expand it inside the groove.

As can be seen in Figures 5 to 7, an outer ring 4 is obtained by circular cutting of a sheet blank 16 giving it a planar circular shape, stamping forming a circular groove 13 on one of the faces of the blank then stamping and cutting of the central part giving the sheet blank 16 the form of an outer ring. Provision could be made to reverse the circular cutting and stamping operations. In all cases, the stamping operation will be planned to be carried out during idle times of the processes used to date so as not to slow down the production of rolling bearings.

Thanks to the invention, there is obtained a axially and radially compact rolling bearing which can be manipulated by an operator before its final installation without the risk of losing parts. As the elastic ring is mounted last after the lock washer, significant diametral interference is provided between said elastic ring and the lock washer, thereby improving the axial retention. The elastic ring constitutes a retaining member acting over its entire circumference. It will therefore be understood that it remains effective even if the locking washer tends to tilt relative to the axis of the bearing.

Finally, since the contact zones between the elastic ring and the lock washer are designed such that if the lock washer exerts an axial force on the elastic ring, said axial force tends to increase the tightening of the elastic ring in the groove, which enhances the reliability and efficiency of the device.

Claims (10)

1. Rolling bearing (1), in particular for a motor vehicle steering column, of the type comprising an outer ring (4) provided with a raceway, an inner ring (6) provided with a raceway, a row of rolling elements arranged between the raceways of said rings, tolerance ring (9) ensuring the connection of the inner ring with the shaft of the steering column, and a lock washer (11) for locking the bearing axially on the shaft, characterized in that the outer ring (4) is provided with a circular groove (13) arranged on its internal surface, the said groove being intended to receive elastic ring (14) forming an axial stop for the lock washer. 2. Bearing according to claim 1, characterized in that the elastic ring (14) is in contact with an outer surface revolution of the lock washer, said surface having a convex profile in axial section. 3. Bearing according to claim 1 or 2, characterized in that said groove has a profile in an arc. 4. Bearing according to claim 1 or 2, characterized in that said groove is V-shaped. 5. Bearing according to claim 1 or 2, characterized in that said groove has two oblique edges and a flat bottom parallel to the axis of the bearing. 6. Bearing according to any one of the preceding claims, characterized in that the ring (14) elastic is circular section. 7. Bearing according to any one of the preceding claims, characterized in that the elastic ring (15) is of polygonal section. 8. Bearing according to any one of the preceding claims, characterized in that the elastic ring is open. 9. A bearing according to any one of the preceding claims, characterized in that the groove is arranged towards the end of the outer ring axially affixed to the raceway. 10. A method of manufacturing a rolling bearing according to any one of the preceding claims, wherein the outer ring provided with said groove is formed by stamping a sheet blank, then by cutting and stamping.