Rolling bearing with asymmetric raceway, especially for a steering column

Abstract

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 the rings (2, 3), wherein the second ring (3) comprises a housing (8) and at least one insert (9) arranged in the housing (8) to form a raceway of the second ring (3), and at least one prestressing element (11) fixed in the housing (8) and exerting an axial force on the insert (9). The first ring (2) is provided with a raceway (7) for the balls (4) which, in cross-section, has a concave internal profile which is asymmetrical with respect to a plane (P') parallel to a radial plane (P) passing through the center of the balls (4).

Description

Technical field of the invention

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

[0002] Steering columns generally consist of a shaft, one end of which is rigidly connected to a steering wheel operated by the vehicle driver, and the other end of which is rigidly connected to mechanical elements that control the angular positioning of the vehicle's wheels. The steering column shaft is rotatably mounted in a tubular housing by means of two rolling bearings.

[0003] One type of rolling bearing for a steering column comprises an inner ring, an outer ring, and a series of balls arranged between the raceways of the rings, with at least one of the rings comprising a housing and inserts arranged within the housing to form raceways of the ring. Thus, a rolling bearing with three or four contact points is produced, suitable for operation under axial and / or radial loads. Generally, such a bearing also includes an elastic preload element mounted inside the housing, which presses axially against one of the inserts to achieve limited-motion operation.

[0004] The architecture of such a rolling bearing makes it possible to prevent free play in the bearing, but does not completely limit the axial and radial movements between the rings, even if the bearing preload is adjusted after assembly.

[0005] The present invention therefore aims to overcome these disadvantages. Summary of the invention

[0006] The invention relates to 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 the rings, the second ring comprising a housing and at least one insert arranged in the housing to form a raceway of the second ring, and at least one preloading element fixed in the housing and exerting an axial force on the insert. “Insert” means an element separate from the housing.

[0007] According to a general feature, the first ring is provided with a raceway for the balls which, in cross-section, has a concave internal profile which is asymmetrical with respect to a plane parallel to a radial plane passing through the center of the balls.

[0008] The osculation, which is the ratio between the curvature of the raceway and the diameter of the balls, therefore has a different value on both sides of the radial plane passing through the center of the balls.

[0009] Advantageously, the concave inner profile of the raceway of the first ring comprises, in cross-section, a first arc having a first radius located axially on the same side as the preloading element and a second arc having a second radius located axially on the opposite side to the preloading element, the first and second arcs having different centers and the first radius being greater than the second radius.

[0010] The asymmetrical concave inner profile of the raceway of the first ring makes it possible to limit the relative axial movement of the rings.

[0011] Insofar as the smallest radius of the raceway is located axially on the side opposite the preload element, the balls of the row tend to rise more quickly on this part of the raceway during operation, causing a greater compression of the preload element and, in turn, a greater preload force exerted by this element.

[0012] The rolling bearing thus allows for less axial deflection at the same preload without compromising the frictional torque. This also makes it possible to increase the axial rigidity of the bearing.

[0013] For example, the radius of the first arc of the raceway of the first ring is between 110% and 130% of the radius of the second arc and, in particular, is equal to 120%.

[0014] Advantageously, the first ring comprises an annular surface from which the raceway is formed, with the arcs adjacent to the annular surface. Alternatively, a connecting surface may be provided between each arc and the annular surface.

[0015] Optionally, each arc borders the annular surface by means of a chamfer.

[0016] In one embodiment, the arcs of the concave inner profile of the raceway adjoin each other at a point belonging to the plane parallel to the radial plane passing through the center of the balls. Alternatively, a cylindrical connecting surface may be provided between the arcs.

[0017] In one embodiment, the second ring comprises two inserts arranged in the housing on either side of the radial plane passing through the center of the balls.

[0018] Advantageously, the two inserts of the second ring are identical.

[0019] In one embodiment, the first ring is the inner ring of the rolling bearing and the second ring is the outer ring of the rolling bearing.

[0020] The invention further relates to a steering column comprising a housing, a shaft coaxial with the housing, and at least one rolling bearing as defined above mounted radially between the housing and the shaft. Short description of the characters

[0021] Further objects, features and advantages of the invention will become apparent upon reading the following description, given purely as a non-limiting example, and with reference to the accompanying drawings in which: [ Fig. 1] is an axial cross-sectional view of a rolling bearing according to an exemplary embodiment; [ Fig. 2] a detailed view of Fig. 1 is; [ Fig. 3] is a detailed cross-sectional view of a rolling bearing according to another exemplary embodiment; and [ Fig. 4] is a detailed cross-sectional view of a rolling bearing according to another exemplary embodiment. Detailed description of the invention

[0022] Fig. Figure 1 shows a rolling bearing, designated by the numerical reference 1, comprising a first ring 2, a second ring 3, and a series of balls 4 arranged between the rings 2, 3. In this embodiment, the rolling bearing 1 includes a cage 5 arranged radially between the rings 2, 3 to maintain a uniform circumferential spacing between the balls 4. Alternatively, the rolling bearing 1 could be without a cage 5.

[0023] 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.

[0024] The inner ring 2 comprises a cylindrical bore axially delimited by opposite radial end surfaces and an outer axial annular surface 6 from which a toroidal circular groove is formed, which in cross-section has a concave internal profile suitable for forming a raceway 7 for the balls 4, the groove being oriented radially outwards.

[0025] As will be described in more detail below, the raceway 7 of the inner ring 2 has, in cross-section, a concave internal profile which is asymmetric with respect to a plane P' which is parallel to a radial plane P passing through the center of the balls 4.

[0026] The inner ring 2 is solid. "Solid ring" refers to a ring whose shape is obtained by machining (turning, grinding) tubes, bars, or forged and / or rolled blanks.

[0027] The outer ring 3 comprises an outer housing 8 and two separate inserts 9, 10, which form raceways of the ring 3 for the balls 4. Here, the inserts 9, 10 are designed as two separate wires. The outer ring 3 also includes a preload element 11, which exerts an axial force on one of the inserts 9, 10. The inserts 9, 10 and the preload element 11 are mounted inside the housing 8.

[0028] The housing 8 can advantageously be manufactured by cutting and forming a metal sheet. The housing 8, which is annular, comprises an outer axial portion 12a extending radially inward at each end through a radial portion 12b, 12c. The inserts 9, 10 are in radial contact with the bore of the axial portion 12a and are arranged in the housing 8 on either side of a radial plane P passing through the center of the balls 4. The radial portion 12c has a smaller radial dimension than the radial portion 12b and also has a reduced thickness, so that it is slightly curved towards the balls 4 to press against the insert 10 and axially preload the bearing 1. The cage 5 is arranged radially between the free edge of the radial portion 12c of the housing 8 and the outer surface of the inner ring 2.

[0029] The housing 8 also includes an inner axial portion 12d extending axially inward from a small-diameter edge of the radial portion 12b. The axial portion 12d is provided for centering the preloading element 11 within the housing 8.

[0030] The preloading element 11, which is annular, is axially in contact with the radial portion 12b of the housing 8 and the insert 9, and is radially fixed between the outer axial portion 12a and the inner axial portion 12d, maintaining a distance therefrom. One radial surface of the preloading element 11 is in axial contact with the inner surface of the radial portion 12b, and an opposite radial surface is in axial contact with the insert 9. The preloading element 11 remains at a distance from the balls 4. The preloading element 11 exerts a permanent axial force on the insert 9, which tends to preload the balls 4 on the other insert 10 and on the groove of the inner ring 2.

[0031] The prestressing element 11 is advantageously made of an elastic material, for example, an elastomer such as nitrile rubber or polyurethane. In the illustrated embodiment, the prestressing element 11 has the shape of a torus with a square cross-section. In a variant, a prestressing element 11 could be provided that has a different cross-sectional profile, for example, circular.

[0032] The inserts 9, 10 are shaped like open tori and are mounted inside the housing 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. Thus, a rolling bearing 1 with three contact points is produced. In the exemplary embodiment shown, the inserts 9, 10 are identical to reduce manufacturing costs.

[0033] As in the Fig. 2, Fig. 3 and Fig. As shown more clearly in Figure 4, the raceway 7 of the inner ring 2 is provided with a first axial end e1 and a second axial end e2, which define the axial length of the raceway 7. The first and second axial ends e1, e2 are adjacent to the annular surface 6 of the inner ring 2. The first and second axial ends e1, e2 are aligned with respect to the axial direction.

[0034] The first axial end e1 is located axially on the same side as the preloading element 11 with respect 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.

[0035] As in Fig. 2 is shown more clearly in cross-section, the raceway 7 of the inner ring 2 has a concave internal profile which is asymmetrical with respect to the plane P' which is parallel to the radial plane P passing through the center of the balls 4.

[0036] The concave inner profile of the raceway 7 comprises a first arc 13a with a radius r1, which lies axially on the same side as the preloading element 11, and a second arc 13b with a radius r2, which lies axially on the side opposite the preloading element 11. In the Fig. 1 and Fig. 2, the radius r1 is greater than the radius r2. The first and second arcs 13a, 13b have different center points C1, C2. The center point C1 lies in the radial plane P and the center point C2 lies in the plane P' parallel to the radial plane P. The center point C1 is radially offset relative to the center point C2 on the same side as the outer ring 3 and axially offset relative to the center point C2 on the side opposite the preload element 11. The plane P' is axially offset relative to the plane P on the same side as the first end e1. The axial offset of the planes P and P' is represented by the double arrow, designated d. The arc 13a extends from the first axial end e1 of the raceway 7 to a radial plane P'' which runs parallel to the plane P. In the embodiment shown in the figures, the plane P'' is axially offset relative to the plane P on the side opposite the preload element 11.

[0037] The arc 13b extends from the axial end e2 of the raceway 7 to the radial plane P''. The arcs 13a, 13b therefore adjoin each other at a point 14 which coincides with the plane P''.

[0038] For example, in a rolling bearing with a ball diameter of 3.969 millimeters, the radius r1 of the arc 13a can be 2.4 millimeters, and the radius r2 of the arc 13b can be 2 millimeters. Preferably, the radius r1 is between 110% and 130% of the radius r2, in particular equal to 120%.

[0039] In this exemplary embodiment, the outer ring 3 comprises two inserts 9, 10 in the form of wires in the housing to form the raceways of the outer ring.

[0040] Alternatively, other designs of the outer ring can be provided.

[0041] For example, as in Fig. 3, in which identical elements have the same reference numerals, the outer ring 3 comprises an insert 9 in the form of a shell which defines a raceway for the balls 4.

[0042] In the Fig. In the embodiment shown in Figure 4, in which identical elements have the same reference numerals, the outer ring 3 comprises a single insert 10 in the form of a cup defining a raceway for the balls 4, and the housing 8 comprises an oblique extension 12d extending obliquely from the inner axial portion 12d and defining a raceway for the balls 4. In this example, the preloading element 11 is arranged axially between the radial portion 12c of the housing and the insert 10.

[0043] As mentioned above, in the exemplary embodiments illustrated, the first ring 2 of the bearing is the inner ring, and the second ring 3 is the outer ring. Alternatively, a reverse arrangement may be provided, 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, which has an asymmetrical concave inner profile in cross-section, is formed on the bore of the outer ring, which forms an inner surface of the ring.

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 the rings (2, 3), the second ring (3) comprising a housing (8) and at least one insert (9) arranged in the housing (8) to form a raceway of the second ring (3), and at least one prestressing element (11) fixed in the housing (8) and exerting an axial force on the insert (9), characterized by that the first ring (2) is provided with a raceway (7) for the balls (4) which, in cross-section, has a concave internal profile which is 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, wherein in cross-section the concave inner profile of the raceway (7) of the first ring comprises a first arc (13a) having a radius (r1) and located axially on the same side as the preloading element (11), and a second arc (13b) having a radius (r2) and located axially on the side opposite the preloading element (11), the first and second arcs having different centers (C1, C2) and the radius (r1) being strictly greater than the radius (r2). [3] Bearing (1) according to claim 2, wherein the radius (r1) is between 110% and 130% of the radius (r2). [4] Bearing (1) according to one of claims 1 to 3, wherein the first ring (2) comprises an annular surface (6) from which the raceway (7) is formed, the arcs (13a, 13b) being adjacent to the annular surface (6). [5] Bearing (1) according to claim 4, wherein each arc (13a, 13b) is adjacent to the annular surface (6) via a chamfer. [6] Bearing (1) according to one of claims 1 to 5, wherein the arcs (13a, 13b) of the concave inner profile of the raceway (7) of the first ring (2) adjoin one another 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 one of claims 1 to 6, wherein the second ring (3) comprises two inserts (9, 10) arranged in the housing (8) on either side of the radial plane (P) passing through the center of the balls (4). [8] Bearing (1) according to claim 7, wherein the two inserts (9, 10) of the second ring (3) are identical. [9] Bearing (1) according to 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 the housing and at least one rolling bearing (1) according to one of claims 1 to 9, which is mounted radially between the housing and the shaft.

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