Cage for a rolling bearing, especially for a bearing for an electric motor vehicle power steering system

Abstract

Cage for a rolling bearing, wherein the cage is intended to ensure the circumferential spacing of a series of rolling elements and comprises pockets (12, 14) for the rolling elements, wherein it comprises connecting lugs (16; 22; 28) that each connect two successive pockets (12, 14), wherein at least one recess (18; 20; 24; 26; 30; 32) is formed in the thickness of at least one of the lugs, characterized in that the recess (18; 20; 24; 26; 30; 32) extends in a first direction from an edge of the connecting lug (16; 22; 28) to an opposite edge, thus leaving a zone of reduced thickness on the lug (16; 22; 28), wherein the recess (18; 20) extends on each side of the connecting lug (16; 22; 28) in a second direction, which is the first direction differs, opens, and wherein the recess (18; 20) extends radially and opens axially on each side of the connecting nose (16; 22; 28).

Description

[0001] The present invention relates to the field of rolling bearings, in particular rolling bearings used in electric motor vehicle power steering systems.

[0002] In particular, the invention relates to retaining cages that ensure circumferential spacing between the rolling elements of the rolling bearings.

[0003] An electric power steering system for motor vehicles generally comprises an electromechanical actuator located on the steering column or on the lower assembly, which includes mechanical components designed to ensure the angular positioning of the vehicle's steered wheels. The electromechanical actuator includes an electric rotary motor whose shaft is supported in at least one rolling bearing, either directly or via a ball screw system. The rolling bearing generally comprises an inner ring, an outer ring, and a series of rolling elements, generally balls, arranged between the rings.

[0004] Document US 4,004,840 A discloses a rolling bearing cage according to the preamble of claim 1. Documents DE 35 26 627 A1 and US 6,843,604 B2 further disclose other cages. Document US 2012 / 0024,618 A1 further describes prior art.

[0005] A retaining cage for a rolling bearing, comprising several pockets for receiving the balls, each partially defined by two claws arranged opposite a shoulder of the cage, is known from FR 2 911 934 A1. Such cages are fully satisfactory in many applications. However, in low-speed applications or applications where the direction of rotation reverses abruptly, this cage presents various difficulties. In particular, the cage can undergo significant deformation under the action of the balls and come into contact with the inner ring, potentially damaging or even destroying it.

[0006] Furthermore, the cage will also be severely deformed or even destroyed if the direction in which the load is applied to the roller bearing changes, as is the case, for example, when the wheels of a vehicle equipped with an electric power steering system are turned, as described above, while the driver maneuvers left and right while parking the vehicle.

[0007] Document FR 2 883 941 A1 also discloses a cage for a rolling bearing, comprising first pockets equipped with axial retaining claws for axially holding the cage to the balls, and second pockets without axial retaining claws.

[0008] In applications with high axial and radial loads and low rotational speeds, for example, between 100 and 300 RPM, the rolling bearing undergoes significant deformation. Such a cage does not provide the balls with sufficient freedom relative to each other, meaning that the cage also deforms considerably when two adjacent balls move in opposite directions. This can lead to cage failure.

[0009] The present invention aims to overcome these disadvantages.

[0010] In particular, the present invention aims to provide a cage for a rolling bearing that offers high reliability.

[0011] Furthermore, the present invention aims to provide a cage that can be deformed with a limited risk of damage.

[0012] Furthermore, the present invention aims to provide a cage that is small in size, has a limited weight and is easy to assemble.

[0013] In one embodiment, the cage for a rolling bearing, wherein the cage is intended to ensure the circumferential spacing of a series of rolling elements, comprises pockets for the rolling elements and connecting lugs that each connect two successive pockets, wherein at least one recess is formed in the thickness of at least one of the lugs.

[0014] The connecting nose can extend around the circumference between the two associated pockets. Advantageously, the connecting nose is offset axially to the inside of the cage with respect to the open free ends of the pockets and axially to the outside with respect to the bottoms of the pockets.

[0015] The recess extends in a first direction from one edge of the connecting nose to the opposite edge, thus creating a zone of reduced thickness on the nose. The recess opens on each side of the connecting nose in a second direction, which differs from the first.

[0016] The recess extends radially and opens axially on each side of the connecting nose. The recess can open radially on the inside or outside of the cage.

[0017] In another embodiment, the recess extends axially or obliquely and opens radially on each side of the connecting nose. The recess can open axially on the same side as the pockets or on the opposite side of the pockets.

[0018] Preferably, each of the connecting lugs comprises at least one recess formed to the thickness of the lug. Advantageously, each recess can form a slot.

[0019] In one embodiment, the cage comprises first pockets for first rolling elements of the series, wherein the pockets are provided with axial retaining means for axially holding the cage to the rolling elements, and second pockets for second rolling elements of the series, wherein the pockets do not have axial retaining means.

[0020] The cage can, for example, be made in one piece from a synthetic material, preferably a polymer material.

[0021] According to a second aspect, the invention relates to a rolling bearing comprising an outer ring, an inner ring, at least one series of rolling elements arranged between the rings, and a cage as defined above.

[0022] According to a third aspect, the invention relates to an electric motor vehicle power steering system comprising at least one rolling bearing as defined above.

[0023] The present invention will be better understood by reading the detailed description of some embodiments, which are only given as non-limiting examples and illustrated by the attached drawings; the drawings show: - Fig. 1 a perspective view of a rolling bearing cage according to a first embodiment of the invention, - Fig. 2 a detailed view of Fig. 1, - Fig. 3 a sectional view along III-III of Fig. 2, - Fig. 4 a detailed view of a cage according to a second embodiment of the invention, - Fig. 5 a detailed view of a cage according to a non-inventive embodiment, - Fig. 6 a sectional view along VI-VI of Fig. 5, - Fig. 7 a detailed view of a cage according to a further non-inventive embodiment, - Fig. 8 a detailed view of a cage according to a further embodiment, - Fig. 9 a sectional view along IX-IX of Fig. 8, - Fig. 10 a detailed view of a cage according to a further embodiment, and - Fig. 11 a detailed view of a cage according to a third embodiment of the invention.

[0024] Fig. Figure 1 represents a cage 10 designed for use in a rolling bearing of the type comprising an outer ring, an inner ring, and several rolling elements manufactured in the form of balls and arranged between the rings. The cage 10 enables a uniform circumferential spacing of the balls between the rings to be maintained. The cage 10 can advantageously be manufactured in one piece by forming a polymer material, such as polyamide, in particular PA 66 or PA 46, or alternatively, a polyetheretherketone (PEEK).

[0025] The cage 10, which has an overall ring shape, comprises several pockets 12, 14, which are evenly distributed in the circumferential direction and are designed to receive the spheres, and lugs 16, which each connect, join, or link two successive pockets together. As will be described in more detail later, each connecting lug 16 is designed to allow relative movement between the two adjacent associated pockets.

[0026] Each pocket 12, 14 is axially open on only one side and radially open to the inside and outside to allow the cage 10 to be attached and positioned over the balls. In the illustrated embodiment, the pockets 14 are provided with axial retaining means for axially holding the cage to the balls, as will be described below, while the pockets 12 do not have such retaining means. In this case, eight pockets 12 are arranged in pairs of immediately adjacent pockets. The pairs of pockets 12 are separated by a pocket 14. In this case, four pockets 14 are evenly distributed circumferentially to ensure uniform axial retention of the cage 10 to the balls.

[0027] As in the Fig. 2 and Fig. As shown more clearly in Figure 3, each pocket 12 comprises two essentially cylindrical side walls 12a, 12b, spaced apart circumferentially, and a bottom wall 12c connecting the side walls 12a, 12b. The walls 12a, 12b, and 12c have a constant thickness. The diameter of the cylinder defining the side walls 12a, 12b of each pocket 12 is larger than that of the spheres, thus providing the spheres with a certain degree of freedom in which they can move radially and circumferentially with respect to the pockets 12. The side walls 12a, 12b cannot provide axial retention of the cage on the spheres. The pockets 12 have no such axial retention means.

[0028] Each pocket 14 comprises a spherical wall 14a that tends to enclose the associated sphere, forming a shell of constant thickness to receive the sphere. Each pocket 14 further comprises two opposing claws 14b, 14c, each extending one end of the spherical wall 14a. Claw 14b extends circumferentially to the opposite claw 14c to delimit the associated pocket 14. The free ends of claws 14b, 14c are spaced apart at a distance smaller than the diameter of the spheres. The claws 14b, 14c of a pocket are able to axially hold the cage 10 by clamping onto the sphere located in the pocket.

[0029] The connecting lugs 16 are identical to each other and extend around the circumference between two adjacent pockets. In the illustrated embodiment, the lugs 16 also extend radially and have a reduced axial thickness compared to the axial dimension of the pockets 12, 14. Each lug 16 extends around the circumference from the wall of one of the two associated pockets and is connected to the circumferentially opposite wall belonging to the other pocket. Each lug 16 connects either one pocket 12 and one pocket 14 or two pockets 12. In the case of each lug 16 connecting two pockets 12, the lug is connected around the circumference on each side to the side wall 12a or 12b of the associated pocket on the opposite side with respect to the opening provided for the ball.In each nose 16, which connects a pocket 12 and a pocket 14, the nose is connected on one side to the side wall 12b of the pocket 12 and on the other side to the spherical wall 14a of the pocket 14, which lies circumferentially on the opposite side from the opening defined for each pocket.

[0030] Each lug 16 is located axially between the bottom wall 12c and the free end of the side wall 12a or 12b of the associated pocket, essentially midway between the free end and the bottom wall. In other words, each lug 16 is offset axially to the inside of the cage with respect to the open free ends of the pockets 12, 14, and axially to the outside with respect to the bottoms of the pockets. Each lug 16 is bounded radially by an inner edge facing the bore of the cage and by an opposing outer edge facing the outer surface of the cage. Each lug 16 is flat.

[0031] Each nose 16 includes a slot 18 extending radially from the inner edge of the nose to the outer edge. The slot 18 extends over most of the nose 16 to near the outer edge, thus leaving a zone of low radial material thickness at the outer edge. The slot 18 is open radially on the inner side and closed radially on the outer side. The slot 18 is open axially on each side of the nose 16. The slot 18 passes axially through the thickness of the nose 16. In the illustrated embodiment, the slot 18 is U-shaped and lies in an axial median plane of the nose.

[0032] During operation, when balls housed in two adjacent pockets move in opposite directions, the connecting lug 16, which has the slot 18, can elastically bend in the radial and / or axial direction to allow relative movement of the balls and pockets, and then return to its initial position when the balls are again caused to move in the same direction. During operation, the lugs 16 can therefore deform, thus greatly reducing the risk of damage to the cage 10. The thinness of the lugs promotes this bending or deformation. The slot 18 forms a zone on each lug 16 where the mechanical strength is locally weakened, further promoting deformation of the lug and movement of the two associated pockets.Furthermore, the provision of thin lugs 16, each encompassing a slot 18, facilitates the attachment of the cage over the balls by axial pressing. In particular, the lugs 16 and the slots 18 increase the flexibility of the cage, thereby preventing localized cracking during attachment. Additionally, the slots 18 form recesses that reduce the weight of the cage 10 by decreasing the amount of material used.

[0033] In the illustrated embodiment, the slots 18 of the noses 16 are open radially on the inside of the cage. Alternatively, each nose 16 comprises, as in the embodiment of Fig. Figure 4, in which identical elements bear the same reference numerals, shows a slot 20 that is radially open on the outside of the cage and opens axially on each side through the thickness of the nose. Each slot 20 extends radially from the outer edge of the nose to near the inner edge, thus leaving a zone of low radial material thickness and opening axially on each side of the nose.

[0034] The in the Fig. 5 and Fig. The embodiment shown in Figure 6, in which identical elements bear the same reference numerals, differs from the previously described embodiments in that the cage 10 comprises lugs 22 extending circumferentially and axially between two adjacent pockets. Each lug 22 extends circumferentially from the wall of one of the two associated pockets and is connected to the circumferentially opposite wall, which is located circumferentially on the opposite side from the opening defined by each pocket to the other pocket. Each lug 22 has a reduced axial dimension compared to the axial dimension of the pockets 12, 14. Each lug 22 is axially offset towards the inside of the cage with respect to the open free ends of the pockets 12, 14 and axially offset towards the outside with respect to the bottoms of the pockets. Each lug 22 has a reduced radial dimension compared to the radial thickness of the pockets 12, 14.Each nose 22 is located radially between the inner and outer edges of the pockets 12, 14 and is aligned with the bore or the outer surface of the cage.

[0035] Each nose 22 includes a slot 24 extending axially on the side opposite the pockets 12, 14. Each slot 24 extends axially from a radial end edge located on the same side as the bottom of the pockets 12 and 14 to the opposite radial end edge. The edges axially bound the nose. The slot 24 extends over most of the nose 22. The slot 24 is open axially on the side opposite the pockets 12, 14 and is not axially open on the same side as the pockets. The slot 24 is open radially on each side of the nose 22. The slot 24 passes radially through the thickness of the nose 22. In this embodiment, the slot 24 is U-shaped and lies in an axial median plane of the nose.

[0036] In this illustrated embodiment, the slots 24 of the noses 22 are open axially on the opposite side with respect to the pockets 12, 14. As in the embodiment of Fig. Figure 7, in which identical elements bear the same reference numerals, shows that each nose 22 alternatively includes a slot 26 which is open axially on the same side as the pockets 12, 14 and opens radially on each side through the thickness of the nose.

[0037] The in the Fig. 8 and Fig. 9, in which identical elements bear the same reference numerals, the embodiment shown differs from the embodiment of the Fig. 5 and Fig. 6 only in that the cage comprises lugs 28 extending around the circumference and obliquely between two adjacent pockets. Each lug 28 extends obliquely to the inside of the cage. Each lug 28 is located radially between the inner and outer edges of the pockets 12, 14 and is aligned with the bore and the outer surface of the cage, respectively. Each lug 28 is axially offset to the inside of the cage with respect to the open free ends of the pockets 12, 14 and axially offset to the outside with respect to the bottoms of the pockets. A slot 30 is formed on each lug 28 in exactly the same way as the slots 24 of the lugs 22 of the third embodiment. In this embodiment, the slots 30 are axially open on the side opposite the pockets 12, 14 and open radially on each side through the thickness of the lug. As in the embodiment of Fig. Figure 10, in which identical elements bear the same reference numerals, shows that each nose 28 alternatively includes a slot 32 which is open axially on the side of the pockets 12, 14 and opens radially on the inside and outside of the cage.

[0038] In all illustrated embodiments, each nose comprises a single slot. Alternatively, it would be possible for one or each nose to provide a large number of slots, for example two, to further increase the cage's flexibility. Such slots could be located on the same edge of the nose or, alternatively, on two opposite edges, as in the embodiment of Fig. 11, which corresponds to the combination of the first and second embodiments, is shown. In this embodiment, the cage for each nose 16 comprises the slot 18 extending from the inner edge of the nose and the slot 20 extending from the outer edge. The slots 18, 20 are positioned facing each other. Similarly, it may be possible to configure the slots of the embodiment of Fig. 5 and Fig. 6 and the embodiment of the Fig. 7 or even the slots of the embodiment of Fig. 8 and Fig. 9 and the embodiment of the Fig. 10 to combine.

[0039] In the illustrated embodiments, the slots form recesses in the noses. Alternatively, it may be possible to provide other types of recesses as replacements or in combination, for example, notches, cutouts, etc. In another alternative embodiment, it might also be possible to provide a cage that includes both noses with recesses and noses without recesses.

[0040] In all of the illustrated embodiments, the noses extend either radially, axially, or obliquely. Alternatively, it might be possible to combine the different nose orientations and the different orientations of the slots on the noses within one and the same cage.

[0041] In the illustrated embodiments, the cage comprises pockets provided with axial retaining means and pockets without such retaining means. Alternatively, the cage could comprise only one type of pocket. In another alternative embodiment, it might even be possible to provide a cage that allows for the circumferential spacing of other types of rolling elements, for example, rollers.

[0042] Thanks to the invention, the pockets that hold the rolling elements can move relative to each other in radial and / or axial directions. Thus, the risk of damage to the cage when two adjacent rolling elements move in opposite directions is greatly reduced, since these rolling elements can move relative to each other.

Claims

[1] Cage for a rolling bearing, wherein the cage is intended to ensure the circumferential spacing of a series of rolling elements and comprises pockets (12, 14) for the rolling elements, wherein it comprises connecting lugs (16; 22; 28) which each connect two successive pockets (12, 14), wherein at least one recess (18; 20; 24; 26; 30; 32) is formed in the thickness of at least one of the lugs, characterized by , that the recess (18; 20; 24; 26; 30; 32) extends in a first direction from one edge of the connecting nose (16; 22; 28) to an opposite edge, thus leaving a zone of reduced thickness on the nose (16; 22; 28), wherein the recess (18; 20) opens on each side of the connecting nose (16; 22; 28) in a second direction different from the first direction, and wherein the recess (18; 20) extends radially and opens axially on each side of the connecting nose (16; 22; 28). [2] Cage according to claim 1, wherein the connecting nose (16, 22; 28) between the two associated pockets (12, 14) extends around the circumference. [3] Cage according to claim 1 or 2, wherein the connecting nose (16; 22; 28) is offset axially to the inside of the cage with respect to the open free ends of the pockets (12, 14) and axially to the outside with respect to the bottoms of the pockets (12, 14). [4] Cage according to one of the preceding claims, wherein each of the connecting lugs (16; 22; 28) comprises at least one recess (18; 20) formed in the thickness of the lug (16; 22; 28). [5] Cage according to any of the preceding claims, wherein each recess (18; 20) forms a slot. [6] Cage according to one of the preceding claims, comprising first pockets (14) for first rolling elements of the series, wherein the pockets (14) are provided with axial retaining means (14b, 14c) for axially retaining the cage on the rolling elements, and second pockets (12) for second rolling elements of the series, wherein the pockets (12) do not have axial retaining means. [7] Rolling bearing comprising an inner ring, an outer ring, at least one series of rolling elements arranged between the rings and a cage according to any of the preceding claims. [8] Electric motor vehicle power steering comprising at least one rolling bearing according to claim 7.

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