Rolling bearing with asymmetrical raceway, especially for steering column

Abstract

Rolling bearing with asymmetrical raceway, in particular for a steering column Rolling bearing (1), in particular for a steering column, comprising a first ring (2), a second ring (3) and at least one row of balls (4) arranged between said rings (2, 3), the second ring (3) comprising a casing (8) and at least one insert (9) arranged in the casing (8) to form a raceway of said second ring (3), and at least one prestressing element (11) mounted in the casing (8) and exerting an axial force on said insert (9). The first ring (2) is provided with a raceway (7) for the balls (4) having in cross section a concave internal profile asymmetrical with respect to a plane (P') parallel to a radial plane (P) passing through the center of the balls (4). Reference: Figure 2

Description

Title of the invention: Rolling bearing with asymmetrical raceway, in particular for a steering column Technical field of the invention

[0001] The present invention relates to the field of rolling bearings and in particular those used in the steering columns of motor vehicles. State of the prior art

[0002] Steering columns generally comprise a shaft, one end of which is secured to a drive wheel operated 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's wheels. The shaft of the steering column is rotatably mounted in a tubular housing by means of two rolling bearings.

[0003] A type of rolling bearing for a steering column comprises an inner ring, an outer ring and a row of balls arranged between raceways of said rings, at least one of the rings comprising a casing and inserts arranged in said casing to form raceways of said ring. This produces a rolling bearing with three or four contact points capable of operating under axial and / or radial loads. Generally, such a bearing also comprises an elastic prestressing element mounted inside the casing and bearing axially against one of the inserts so as to obtain operation with limited displacements.

[0004] The architecture of such a rolling bearing makes it possible to avoid the presence of free play in the bearing but does not completely limit the axial and radial movements between the rings even when adjusting the preload of the bearing after assembly.

[0005] The present invention therefore aims to remedy these drawbacks. Summary of the invention

[0006] The subject of the invention is a rolling bearing, in particular for a steering column, comprising a first ring, a second ring and at least one row of balls arranged between said rings, the second ring comprising an envelope, at least one added element arranged in the envelope to form a raceway for said second ring, and at least one prestressing element mounted in the envelope and exerting an axial force on said added element.

[0007] By “added element” is meant an element distinct from the envelope.

[0008] According to a general characteristic, the first ring is provided with a path of bearing for balls having in cross section an internal concave asymmetrical profile metric with respect to a plane parallel to a radial plane passing through the center of the balls.

[0009] Thus, the osculation, which is the ratio between the curvature of the raceway and the diameter of the balls, is of different value on the two sides of the radial plane passing through the center of the balls.

[0010] Advantageously, in cross section, the concave internal profile of the raceway of the first ring comprises a first arc of a circle of a first radius located axially on the side of the prestressing element and a second arc of a circle of a second radius located axially on the side opposite the prestressing element, the first and second arcs of a circle having different centers and the first radius being greater than the second radius.

[0011] Said asymmetrical concave internal profile of the raceway of the first ring makes it possible to limit the relative axial displacement of the rings.

[0012] To the extent that the smallest radius of the raceway is located axially on the side opposite the prestressing element, the balls of said row will tend in operation to rise more quickly on this part of the raceway, which will cause greater compression of the prestressing element and in return a greater prestressing force exerted by said element.

[0013] Thus, the rolling bearing will therefore allow less axial deflection at equivalent prestress without compromising the friction torque. This also makes it possible to increase the axial rigidity of the bearing.

[0014] For information purposes, the radius of the first arc of the circle of the raceway of the first ring is between 110% and 130% of the radius of the second arc of the circle, and in particular equal to 120%.

[0015] Advantageously, the first ring comprises an annular surface from which the raceway is formed, said circular arcs connecting to said annular surface. Alternatively, it is possible to provide a connecting surface between each circular arc and said annular surface.

[0016] Optionally, each circular arc connects to said annular surface via a chamfer.

[0017] In one embodiment, said circular arcs of the concave internal profile of the raceway connect to each other at a point belonging to the plane parallel to the radial plane passing through the center of the balls. Alternatively, it is possible to provide a cylindrical connecting surface between the circular arcs.

[0018] In one embodiment, the second ring comprises two added elements which are arranged in the casing on either side of the radial plane passing through the center of the balls.

[0019] Advantageously, the two added elements of the second ring are identical.

[0020] In one embodiment, the first ring is the inner ring of the bearing bearing and the second ring is the outer ring of the rolling bearing.

[0021] The invention also relates to a steering column comprising a housing, a shaft coaxial with said housing and at least one rolling bearing as defined above, mounted radially between the housing and the shaft. Brief description of the figures

[0022] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0023] [Fig-1] is an axial sectional view of a rolling bearing according to an exemplary embodiment;

[0024] [Fig.2] is a detail view of [Fig.l];

[0025] [Fig.3] is a detailed sectional view of a rolling bearing according to another example of realization; and

[0026] [Fig.4] is a detailed sectional view of a rolling bearing according to yet another exemplary embodiment. Detailed description of the invention

[0027] In [Fig.l], a rolling bearing is illustrated, designated by the reference numeral 1, comprising a first ring 2, a second ring 3, and a row of balls 4 arranged between said rings 2, 3. In this embodiment, the rolling bearing 1 comprises a cage 5 arranged radially between the rings 2, 3 to maintain a regular circumferential spacing between the balls 4. Alternatively, the rolling bearing 1 could be without a cage 5.

[0028] In this embodiment, the first ring 2 is the inner ring of the rolling bearing 1 and the second ring 3 is the outer ring of the rolling bearing 1.

[0029] The inner ring 2 comprises a cylindrical bore delimited axially by opposite radial front faces and an outer axial annular surface 6 from which is formed a toroidal circular groove having in cross section a concave internal profile capable of forming a raceway 7 for the balls 4, said groove being oriented radially outwards.

[0030] As will be described in more detail below, the raceway 7 of the inner ring 2 has in cross section an internal concave profile asymmetrical with respect to a plane P' which is parallel to a radial plane P passing through the center of the balls 4.

[0031] The inner ring 2 is solid. The term “solid ring” means a ring whose shape is obtained by machining with chip removal (turning, grinding) from tubes, bars, forged and / or rolled blanks.

[0032] The outer ring 3 comprises an outer casing 8 and two elements separate inserts 9, 10 forming raceways of said ring 3 for the balls 4. The inserts 9, 10 are here in the form of two separate wires. The outer ring 3 also comprises a prestressing element 11 exerting an axial force on one of said inserts 9, 10. The inserts 9, 10 and the prestressing element 11 are mounted inside the casing 8.

[0033] The casing 8 can advantageously be manufactured by cutting and stamping a sheet of metal. The casing 8, of annular shape, comprises an external axial portion 12a extended, at each end, radially inwards by a radial portion 12b, 12c. The added elements 9, 10 are arranged in radial contact with the bore of the axial portion 12a and are arranged in the casing 8 on either side of a radial plane P passing through the center of the balls 4. The radial portion 12c has a radial dimension smaller than that of the radial portion 12b and also has a reduced thickness to be slightly curved in the direction of the balls 4 so as to come to bear against the added element 10 and axially prestress the bearing 1. The cage 5 is arranged radially between the free edge of the radial portion 12c of the casing 8 and the outer surface of the inner ring 2.

[0034] The casing 8 also comprises an inner axial portion 12d extending axially inwards a small diameter edge of the radial portion 12b. The axial portion 12d is provided for centering the prestressing element 11 inside the casing 8.

[0035] The prestressing element 11, of annular shape, is mounted axially in contact against the radial portion 12b of the casing 8 and the added element 9 and radially between the outer axial portions 12a and 12d inner while remaining at a distance from them. A radial surface of the prestressing element 11 is in axial contact with the inner face of the radial portion 12b and an opposite radial surface is in axial contact with the added element 9. The prestressing element 11 remains at a distance from the balls 4. The prestressing element 11 exerts a permanent axial force on the added element 9 which tends to prestress the balls 4 on the other added element 10 and on the groove of the inner ring 2.

[0036] The prestressing element 11 is advantageously formed from an elastic material, for example an elastomer such as nitrile rubber or polyurethane. In the illustrated embodiment, the prestressing element 11 is in the form of a torus with a square section. Alternatively, it could be possible to provide a prestressing element 11 having a different profile in cross section, for example circular.

[0037] The added elements 9, 10 are in the form of open toroids and are mounted inside the casing 8 in direct contact with it. The balls 4 are arranged between the inserts 9, 10 of the outer ring 3 which form raceways and the raceway 7 of the inner ring 2. This produces a rolling bearing 1 with three contact points. In the illustrated embodiment, the inserts 9, 10 are identical so as to reduce manufacturing costs.

[0038] As illustrated more visibly in Figures 2, 3 and 4, the raceway 7 of the inner ring 2 is provided with a first axial end el and a second axial end e2 which delimit the axial length of said raceway 7. The first and second axial ends el, e2 are connected to the annular surface 6 of the inner ring 2. The first and second axial ends el, e2 are aligned considering the axial direction.

[0039] The first axial end el is located axially on the same side as the prestressing element 11 relative to the radial plane P passing through the center of the balls 4, and the second axial end e2 is located axially on the opposite side.

[0040] As illustrated more visibly in [Fig.2], in cross-section, the raceway 7 of the inner ring 2 has an asymmetrical concave internal profile relative to the plane P' which is parallel to the radial plane P passing through the center of the balls 4.

[0041] The concave internal profile of the raceway 7 comprises a first circular arc 13a of radius rl which is located axially on the side of the prestressing element 11, and a second circular arc 13b of radius r2 which is located axially on the side opposite the prestressing element 11. In the embodiment illustrated in FIGS. 1 and 2, the radius rl is greater than the radius r2. The first and second circular arcs 13a, 13b have different centers C1, C2. The center C1 is located in the radial plane P and the center C2 is located in the plane P' parallel to the radial plane P. The center C1 is offset radially on the side of the outer ring 1 relative to the center C2, and offset axially on the side opposite the prestressing element 11 relative to the center C2. The plane P' is axially offset on the side of the first end el relative to the plane P. The axial offset of the planes P and P' is illustrated by the double arrow referenced d.The arc of a circle 13a extends from the first axial end 11 of the raceway 7 to a radial plane P” parallel to the plane P. In the embodiment illustrated in the figures, the plane P” is axially offset to the side opposite the prestressing element 11 relative to the plane P.

[0042] The arc of a circle 13b extends from the axial end e2 of the raceway 7 to the radial plane P”. The arcs of a circle 13a, 13b therefore connect to each other at a point 14 coinciding with the plane P”.

[0043] For information purposes, for a rolling bearing having a ball diameter equal to 3.969 millimeters, the radius rl of the arc of a circle 13a may be equal to 2.4 millimeters and the radius r2 of the arc of a circle 13b may be equal to 2 millimeters. Preferably, the radius rl is between 110% and 130% of the radius r2, and in particular equal to 120%.

[0044] In this embodiment, the outer ring 3 comprises two elements 9, 10 inserted into the casing in the form of wires to form the raceways of the outer ring.

[0045] Alternatively, other designs of the outer ring may be provided.

[0046] For example, as illustrated in [Fig.3], in which the identical elements bear the same references, the outer ring 3 comprises an added element 9 in the form of a cup which delimits a rolling path for the balls 4.

[0047] In the embodiment illustrated in [Fig. 4], in which identical elements bear the same references, the outer ring 3 comprises a single added element 10 in the form of a cup which delimits a raceway for the balls 4, the casing 8 comprising an oblique extension 12d obliquely extending the inner axial portion 12d and delimiting a raceway for the balls 4. In this example, the prestressing element 11 is arranged axially between the radial portion 12c of the casing and the added element 10.

[0048] As indicated previously, in the illustrated embodiments, the first ring 2 of the bearing is the inner ring and the second ring 3 is the outer ring. Alternatively, it is possible to provide an inverted arrangement in which the first ring 2 is the outer ring and the second ring 3 is the inner ring. In this case, the raceway 7 having in cross section an asymmetrical concave internal profile is formed on the bore of the outer ring which forms an inner surface of said ring.

Claims

Claims

1. Rolling bearing (1), in particular for a steering column, comprising a first ring (2), a second ring (3) and at least one row of balls (4) arranged between said rings (2, 3), the second ring (3) comprising a casing (8) and at least one insert (9) arranged in the casing (8) to form a raceway for said second ring (3), and at least one prestressing element (11) mounted in the casing (8) and exerting an axial force on said insert (9), characterized in that the first ring (2) is provided with a raceway (7) for the balls (4) having in cross section a concave internal profile asymmetrical with respect to a plane (P') parallel to a radial plane (P) passing through the center of the balls (4).

2. Bearing (1) according to claim 1, in which, in cross section, the concave internal profile of the raceway (7) of the first ring comprises a first arc of a circle (13a) of radius (rl) and located axially on the side of the prestressing element (11), and a second arc of a circle (13b) of radius (r2) and located axially on the side opposite the prestressing element (11), the first and second arcs of a circle having different centers (Cl, C2) and the radius (rl) being strictly greater than the radius (r2).

3. Bearing (1) according to claim 2, wherein the radius (rl) is between 110% and 130% of the radius (r2).

4. Bearing (1) according to any one of claims 1 to 3, wherein the first ring (2) comprises an annular surface (6) from which the raceway (7) is formed, said circular arcs (13a, 13b) connecting to said annular surface (6).

5. Bearing (1) according to claim 4, wherein each circular arc (13a, 13b) connects to said annular surface (6) via a chamfer.

6. Bearing (1) according to any one of claims 1 to 5, wherein said circular arcs (13a, 13b) of the concave internal profile of the raceway (7) of the first ring (2) connect together at a point (14) belonging to the plane (P') parallel to the radial plane (P) passing through the center of the balls (4).

7. Bearing (1) according to any one of claims 1 to 6, in which the second ring (3) comprises two inserts (9, 10) which are arranged in the envelope (8) on either side of the radial plane (P) passing through the center of the balls (4).

8. Bearing (1) according to claim 7, in which the two added elements (9, 10) of the second ring (3) are identical.

9. A bearing (1) according to any one of claims 1 to 8, wherein the first ring (2) is the inner ring of the rolling bearing (1) and the second ring (3) is the outer ring of the rolling bearing (1).

10. Steering column comprising a housing, a shaft coaxial with said housing and at least one rolling bearing (1) according to any one of claims 1 to 9, mounted radially between the housing and the shaft.

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