Current transfer device between a fixed subassembly and a rotating subassembly

Abstract

A current-passing device (70) comprises two subassemblies (2, 4), at least one of the two subassemblies being capable of rotating about an axis of revolution relative to the other of the two subassemblies. The device includes an annular inner contact track (26) having rotational symmetry about a reference axis (100), oriented radially outwards and extending axially between a first inner end (32) and a second inner end (34); an annular outer contact track (56) having rotational symmetry about the reference axis (100), oriented radially inwards with respect to the inner contact track; and at least one contact ball (35), having a ball diameter DBC, positioned between the inner and outer contact tracks, and capable, in an operational position, of rolling on the frustoconical inner and outer contact tracks. (Shortcut Figure: 2)

Description

Title of the invention: Device for passing current between a fixed subassembly and a rotating subassembly TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a device for passing electric current between a rotating subassembly, supporting, for example, an electric machine rotor, and a fixed subassembly, fixed, for example, to an electric machine stator, and in particular, although not exclusively, when such devices are mounted or intended to be mounted on vehicles, for example, automobiles, railway vehicles, or aircraft, regardless of the nature of the electric current, whether direct or alternating, and whether the current is, for example, leakage current, control current, information transmission current, or power supply current. It also relates to a plain or rolling bearing incorporating such a current-passing device. PREVIOUS STATE OF THE ART

[0002] To ensure electrical conduction between a rotating subassembly and a stationary subassembly, it might be tempting to use rolling bearings, whose primary function is to provide relative rotational guidance between the rotating and stationary subassemblies, since the constituent elements of such bearings—raceways and rolling elements—are made of conductive materials. However, it turns out that the lubrication required for the operation of a bearing does not satisfactorily ensure this current flow at high speeds. Indeed, as the rotational speed increases, a lubricant film forms between the rolling elements and the raceways, and its thickness increases with speed. This effect, desirable for the primary mechanical function of the bearing, is not desirable for electrical conduction, because the lubricant behaves as an electrical insulator.Consequently, a potential difference between the raceways generates electrical arcs which rapidly alter the lubricant and the metallic surface of the raceways and rolling elements, causing heating and spalling of the raceways or rolling elements.

[0003] To overcome this problem, it was proposed in document JP 2022118903 to add to a rolling bearing a current-conducting device comprising contact balls rolling on two attached contact tracks, one on the inner ring and the other on the outer ring. The contact balls are made of a flexible and porous conductive material, which has the dual property of absorbing the lubricant at the contact between the balls and the contact tracks and of compressing slightly to The contact area with the contact tracks is increased as speed increases. This ensures that the electrical current flowing through the bearing rings will preferentially pass through the current-conducting device, whose impedance is significantly lower than that of the bearing. However, this solution is not efficient in terms of friction. Furthermore, it is sensitive to the axial load of the bearing and the resulting axial micro-displacements, and it also generates a higher noise level. Description of the invention

[0004] The invention aims to remedy at least some of the drawbacks of the prior art mentioned above and to propose a current passage device which reduces friction and / or whose impedance does not increase significantly with speed.

[0005] To this end, according to a first aspect of the invention, a current-passing device between two sub-assemblies is proposed, at least one of the two sub-assemblies being capable of rotating about an axis of revolution relative to the other of the two sub-assemblies, the device comprising: • an annular and conductive inner contact track, intended to be integral with a first of the two subassemblies, the inner contact track having a rotational symmetry around a reference axis of the current passage device intended to coincide with the axis of revolution, the inner contact track being radially turned outwards and extending axially at least from a first inner end to a second inner end, further from the reference axis than the first inner end; • an annular and conductive outer contact track, intended to be integral with a second of the two sub-assemblies, the outer contact track having a rotational symmetry around the reference axis, the outer contact track being radially turned inwards and opposite the inner contact track; • at least one conductive contact ball, having a ball diameter DBC, positioned between the inner and outer contact tracks, and capable, in an operational position, of rolling on the inner and outer contact tracks;

[0006] According to the invention, the current-passing device is such that in a cutting plane containing the reference axis, any segment perpendicular to the reference axis, and having a first end belonging to the inner contact track and a second end belonging to the outer contact track, exhibits: • a center which, in an orthonormal coordinate system having an x-axis coinciding with the reference axis and an ordinate axis which passes through the first inner end of the inner contact track, has an x-axis equal to x and an ordinate equal to y, defining a function xy - f(x) which, when x varies between 0 and a positive x-axis of the second end, is strictly increasing continuously; • a length1 defining a function xl = g(x) which, when the abscissa x of the center of the segment varies between 0 and the second endpoint, is strictly decreasing continuously, exhibiting a maximum value greater than the diameter of the balls DBc, and a minimum value less than the diameter of the balls Dbc.

[0007] The inner and outer contact tracks thus allow the contact ball both axially and radially to move. Centrifugal force pushes the contact ball away from the reference axis and therefore, by rolling on the outer contact track, to move axially. Thus, when the rotational speed is sufficient, the contact ball is in contact with both contact tracks simultaneously, with a contact pressure that increases with speed and counterbalances the tendency for the lubricating oil film thickness between the contact ball(s) and the contact tracks to increase with speed. Furthermore, the chosen geometry allows for centrifugal circulation of the lubricating oil present in the device, thereby preventing oil accumulation on the contact tracks, which also contributes to better control of the oil film thickness as speed increases.Finally, this geometry of the contact tracks allows the contact balls to reposition themselves in the event of relative axial and radial micro-displacements between the fixed sub-assembly and the moving sub-assembly.

[0008] According to one embodiment, the inner contact track is frustoconical. Preferably, the inner contact track has, in any cutting plane including the reference axis, a generatrix forming, with the reference axis, an angle Al greater than 2°, preferably greater than 14°, and less than 47°, preferably less than 42°. Larger angles allow for manufacturing with tighter tolerances.

[0009] According to one embodiment, the outer contact track is frustoconical. Preferably, the outer contact track has, in any cutting plane including the reference axis, a generatrix forming, with the reference axis, an angle A2 greater than 1.5°, preferably greater than 12°, and less than 45°, preferably less than 40°.

[0010] According to one embodiment, the outer contact track has, in any cutting plane including the reference axis, a generatrix forming, with a generatrix of the inner contact track, an angle greater than 0.5°, preferably greater than 1°, and less than 30°, preferably less than 15°.

[0011] Such tracks have an osculating circle of infinite radius, which reduces the contact ellipse between the contact ball and the contact track, as well as the viscosity of the lubricant's adhesion to the contact track. The contact ball then more easily breaks the lubricant film on the contact track, thereby reducing the impedance of the current-carrying device and extending the service life of the contact tracks by reducing, and preferably eliminating, electrical arcing. Furthermore, the contact ball can make contact with both contact tracks since angle A2 is strictly less than angle A1, the two contact tracks forming a truncated cone in a plane including the reference axis. Finally, each of these arrangements promotes oil evacuation by centrifugal force.

[0012] According to one embodiment, the current-passing device comprises a guide cage positioned at least partially between the inner and outer contact tracks, the guide cage having at least one recess in which the contact ball is housed, the recess defining a first axial stop for the contact ball, the first axial stop being located between the inner and outer contact tracks and axially closer to the first inner end of the inner contact track than to the second inner end of the inner contact track, the first axial stop being axially oriented towards the second inner end of the inner contact track, the contact ball establishing a point of contact with the inner contact track at abscissa 0 when it is bearing against the axial stop, the recess having two opposing guide facets facing each other in an orthoradial direction,The two guide facets extend axially from the first axial stop towards the second inner end, so as to allow displacement of the contact ball such that the abscissa of the contact point between the contact ball and the inner contact track varies between 0 and the abscissa of the second end. Preferably, the two guide facets are located at a distance from each other greater than the diameter of the balls Dbc, and / or the two guide facets are flat or concave.

[0013] The guide cage thus makes it possible to hold and guide the contact ball(s), regardless of the operating phase of the current-conducting device, i.e., rotating or stationary, between the two contact tracks. Preferably, the current-conducting device comprises three contact balls housed in three recesses of the guide cage, preferably arranged at 120° intervals from each other, so as to be rotationally balanced and not generate excessive vibrations.

[0014] According to one embodiment of the invention, the guide cage comprises at least one centrifugal disengagement device capable of locking the guide cage to a rotating contact track, either the inner or outer contact track, below a predetermined angular velocity threshold for disengagement of the inner or outer contact track, and of releasing the guide cage above the angular velocity threshold for disengagement. The disengagement system differentiates the behavior below and above the angular velocity threshold for disengagement. To this end, the centrifugal disengagement device comprises, for example, a movable portion connected to an annular body of the guide cage by at least one flexible arm, said movable portion comprising a movable pad intended to come into contact with either of the two subassemblies.The flexible arm(s) are designed to allow a rocking motion of the moving portion in order to maintain the moving pad in contact with the rotating contact track in a coupled position below a disengagement angular velocity threshold, and to allow the pad to be disengaged by flexing the flexible arm to an uncoupled position, and the cage to be released, beyond the disengagement angular velocity threshold, by centrifugal force. In practice, the travel between the coupled and uncoupled positions is greater than 0.05 mm, preferably greater than 0.10 mm, for example greater than 0.50 mm. The stop may have an additional function of stiffening the guide cage.

[0015] At low speeds, the ball(s) cannot roll on the rotating contact track relative to which the guide cage remains fixed. Subjected to a low centrifugal force, potential effects of gravity, and possible reaction forces from contact with the external contact track, the positioning of the contact balls is uncertain and may fluctuate. However, this is not a significant issue since, at low speeds, it is possible to pass the current through a roller bearing or a plain bearing guiding the moving subassembly without having to worry about excessive oil film thickness.

[0016] As the rotational speed of the moving sub-assembly increases, the centrifugal force on the balls is sufficient to cause them to migrate into an area of ​​the recesses that imposes simultaneous contact with the inner and outer contact tracks, so that the contact balls slide and roll simultaneously on the contact tracks. This effect is obtained when the centrifugal force exerted on the balls is greater than the gravitational force on the balls, which can be expressed, as a first approximation, by the inequality: [oeni mQi ^

[0018] where m denotes the mass of the ball, denotes the rotational speed of the rotating sub-assembly, DB denotes the diameter of the ball, D CI denotes the diameter of the inner contact track, and g denotes the acceleration due to gravity. We can thus define an angular velocity of change of behavior O / 0 such that:

[0019] o ^10 ~ \ DB+DCI

[0020] As soon as the guide cage reaches the disengagement angular velocity threshold Qs, the cage is released from the rotating ring and driven into rotation by the rolling of the balls on the contact tracks. The cage then rotates at a speed that is lower than the rotational speed of the rotating ring Qj, and, considering a non-slip bearing of the contact ball and the inner and outer rings respectively, defined by the following relation:

[0021] n - Q.......... - ^idci+Dce

[0022] where DCi denotes the diameter of the contact point between the rotating ring and the contact ball and DCE denotes the diameter of the contact point between the fixed ring and the ball contact.

[0023] To ensure the balls rotate when the disengagement angular velocity threshold is exceeded, &c should preferably be greater than the angular velocity at which behavior changes, so that the balls remain, by centrifugal force, in the contact zone with the two contact tracks once the disengagement angular velocity Qs is reached. The disengagement device is therefore preferably calibrated such that:

[0024] Qc>^zo

[0025] i.e.:

[0026] n / 2g (Dç^Dce) LiI>\l(Dcl+DCE) x DCI

[0027] Below the angular velocity threshold for disengagement Q$, Oc = Ob, which leads to preferably defining the angular velocity threshold for disengagement of the cage such that:

[0028] / 2g

[0029] According to one embodiment of the disengagement device, the centrifugal disengagement device comprises a stop rotated radially towards the reference axis opposite the moving portion to limit outward radial displacement of the moving pad. The parameters that will be adjusted to obtain the above inequality will then preferably be the bending stiffness of the flexible arm and the mass of the moving portion.

[0030] Furthermore, it may be provided that the guide cage includes one or more retaining tabs projecting radially towards the rotating guide track or the associated sub-assembly, to ensure that the cage is held in position relative to the rotating guide track. These retaining tabs, preferably arranged in an equidistant manner around the periphery or inside the guide cage, can for example be designed to fit into an annular groove formed on the sub-assembly associated with the rotating guide track.

[0031] According to one embodiment, the guide cage is made of a single piece of plastic material, which minimizes the number of parts and assembly costs.

[0032] According to another aspect of the invention, it relates to a rolling bearing comprising an inner ring including at least one inner raceway; an outer ring including at least one outer raceway; at least two rolling elements having a diameter DBR, positioned so as to roll simultaneously on the inner and outer raceways; the rolling bearing being notable in that it includes a current-conducting device as described above, the inner ring including the annular inner contact track and the outer ring including the annular outer contact track. The rolling elements may be rollers or balls, for example. The rolling elements are distinct from the contact balls and their main function is to ensure the rotational guidance of the rotating subassembly relative to the stationary subassembly.The sizing of rolling elements therefore depends, in particular, on the axial or radial loads to which the bearing is subjected. Preferably, the rolling elements and raceways are made of an electrically conductive material, which ensures current conduction at low rotational speeds, before the centrifugal force of the balls in the current-conducting device establishes the electrical connection. Preferably, the inner ring is a single piece and / or the outer ring is a single piece.

[0033] According to an embodiment, in which the current passage device comprises a guide cage as described above, the guide cage has a guide face oriented predominantly along the radial direction and located opposite and at a distance of less than 0.5 mm and greater than 0.05 mm from a corresponding face of one of the two sub-assemblies, to ensure radial guidance of the cage with respect to said sub-assembly.

[0034] According to one embodiment, the inner raceway is located axially at a distance from the inner contact track, and the outer raceway is located axially at a distance from the outer contact track. These arrangements reduce the number of parts required to manufacture the bearing, assembly costs, and, where applicable, the overall size.

[0035] According to one embodiment, the first inner end of the inner contact track is axially further from the inner raceway than the second inner end of the inner contact track. This arrangement facilitates the assembly operations of the current passage device, and in particular the contact balls.

[0036] In an embodiment where retaining tabs are provided on a guide cage of the current passage device, an annular groove can be formed on one of the bearing rings, the retaining tabs fitting into this annular groove to ensure axial retention of the guide cage of the current passage device.

[0037] Where applicable, the rolling elements are positioned in recesses of a bearing cage. If the current-conducting device itself includes a guide cage, the bearing cage is preferably not fixed to the guide cage. The two cages then rotate at different angular speeds, which contributes to the mixing of the oil within the bearing housing.

[0038] According to another aspect of the invention, it relates to an assembly comprising two sub-assemblies and a bearing to guide at least one of the two sub-assemblies in rotation around an axis of revolution relative to the other of the two sub-assemblies, the bearing being a bearing as described above, the inner ring of which is integral with one of the two sub-assemblies and the outer ring is integral with a second of the two sub-assemblies.

[0039] According to one embodiment, the first subset is able to rotate relative to the second subset around the axis of revolution, the second subset being fixed in rotation in a geostationary frame. BRIEF DESCRIPTION OF THE FIGURES

[0040] Other features and advantages of the invention will become apparent from the following description, with reference to the attached figures.

[0041] [Fig.1] Fig.1 illustrates, in a cross-sectional view, a rolling bearing comprising a passage device according to a first embodiment.

[0042] [Fig.2] Fig.2 illustrates, in a cross-sectional view, the current passage device only according to the first embodiment.

[0043] [Fig.3] Fig.3 illustrates, in an isometric view, a detail of the bearing according to the first embodiment.

[0044] [Fig.4] Fig.4 illustrates, in an isometric view, a cage of the device current passage according to the first embodiment.

[0045] [Fig.5] Fig.5 illustrates a cross-sectional view of the cage according to the first embodiment.

[0046] [Fig.6] The [Fig.6] illustrates a geometric detail of the structure of the contact tracks of the contact device according to the first embodiment.

[0047] [Fig.7] Fig.7 illustrates a detail of the cage cells.

[0048] [Fig-8] Fig.8 illustrates a detail of a cage disengagement device according to the first embodiment.

[0049] [Fig.9] Figure [Fig.9] illustrates, in a cross-sectional view, a ball bearing comprising the current passage device according to a second embodiment.

[0050] [Fig. 10] The [Fig. 10] illustrates in a cross-sectional view, the cage of the current passage device according to the second embodiment.

[0051] [Fig. 11] Fig. 11 illustrates in a cross-sectional view the rolling bearing comprising the passage device according to a third embodiment.

[0052] [Fig. 12] Fig. 12 illustrates a detail of the cage disengagement device according to the third embodiment.

[0053] For clarity, identical or similar elements are identified by identical reference symbols throughout the figures. DETAILED DESCRIPTION OF IMPLEMENTATION METHODS

[0054] Figures 1 to 10 illustrate a bearing 10 between a fixed sub-assembly 2, for example a housing of a motor vehicle and defining a reference axis 100, and a rotating sub-assembly 4, for example a shaft, adapted to rotate about the reference axis 100 inside the fixed sub-assembly 2, the bearing comprising a metallic outer ring 12 integral with the fixed sub-assembly 2, a metallic inner ring 14 integral with the rotating sub-assembly 4, and rolling elements 16 between the inner ring 14 and the outer ring 12. The bearing 10 further comprises a current-passing device 70 illustrated alone in [Fig.2].

[0055] The inner ring 14 is here a solid, one-piece metallic inner ring comprising an inner annular surface 18 rotated radially opposite the reference axis 100 and extending between a first end face 20 and a second end face 22. On the inner annular surface 18 are formed an inner raceway 24 and an inner contact track 26, which are coaxial and are surfaces of revolution about the reference axis 100. For this purpose, the inner ring 14 may undergo heat treatment and machining, both located at the inner raceway 24 and the inner contact track 26. The inner raceway 24 is positioned near the first end face 20, while the inner contact track 26 is positioned near the second end face 22. The inner contact track 26 forms a first element of the current-conducting device 70.

[0056] The inner raceway 24 comprises two flanks 28 located axially on either side of a raceway bottom 30, and is intended to accommodate the rolling elements 16, which here are balls having a diameter D Br, but could alternatively be rollers, cones or barrels. The rolling bodies 16 are composed, preferably made of, metal, and are configured to guide and support external radial and / or axial loads.

[0057] The inner contact track 26 is a frustoconical, preferably ground, annular surface with rotational symmetry about the reference axis 100. The inner contact track 26 extends between a first inner end 32, near the second end face 22, and a second inner end 34 near the inner raceway 24. It is configured to accommodate contact rolling elements, more particularly contact balls 35. The contact balls 35 are made, preferably of metal, and have a diameter DBC. They form an element of the current-conducting device 70. Furthermore, the contact balls 35 are configured to conduct electric current between the fixed outer ring 12 and the rotating inner ring 14, and thus between the fixed subassembly 2 and the rotating subassembly 4.Unlike the rolling elements 16, they are not intended to guide the rotation of the rotating sub-assembly 14. There are three of them here, positioned 120° apart, but alternatively, there may be more or fewer. The diameter DBc of the contact balls 35 is preferably strictly less than the length L of the generatrix of the inner contact track 26, in order to allow movement including an axial component of the contact balls 35 on the inner contact track 26 while reducing the axial size of the inner ring 14. Advantageously, the diameter DBc of the balls should be as small as possible to reduce the size of the current-conducting device 70.

[0058] According to a first embodiment illustrated in Figures 1 to 8, in a section plane including the datum axis 100 (as illustrated in [Fig. 1]), the inner contact track 26 has an inner generatrix 102 forming an angle Al of 17° with the datum axis 100. More generally, this angle Al is greater than 2°, preferably greater than 14°, and less than 47°, preferably less than 42°. The inner generatrix 102 of the inner contact track 26 is such that it moves away from the datum axis 100 as it approaches the inner bearing race 24. The inner bearing race 24 and the inner contact track 26 are separated by an inner separating surface 36.

[0059] On the inner annular surface 18, a receiving portion 38 is further formed, configured to receive on the inner ring 14 a guide cage 40 described later in this application. The receiving portion 38 is positioned between the second end face 22 and the inner contact track 26. As it approaches the second end face 22, it comprises a receiving face 42 cylindrical circularly, an annular groove 44 and a chamfer 46 opening onto the second end face 22.

[0060] The fixed outer ring 12 is here a solid, one-piece metal ring comprising an outer annular surface 48 oriented radially towards the reference axis 100 and extending between a first outer end 50 and a second outer end 52. On the outer annular surface 48 are formed an outer raceway 54 and an outer contact track 56 coaxial, defining the reference axis 100. For this purpose, the outer ring 12 may undergo heat treatment and machining, both located at the outer raceway 54 and the outer contact track 56. The outer contact track 56 forms a second element of the current-passing device 70.

[0061] The outer raceway 54 comprises two flanks 28' situated axially on either side of a raceway bottom 30'. The outer raceway 54 is situated opposite the raceway 24 and is intended to accommodate the rolling bodies 16.

[0062] The outer contact track 56 has a frustoconical annular surface, preferably ground, and exhibits rotational symmetry about the datum axis 100. The outer contact track 56 is located opposite and at a distance from the inner contact track 26 and is configured to accommodate the contact balls 35. In a cross-sectional plane containing the datum axis 100 (as illustrated in [Fig. 1]), the outer contact track 56 has an outer generatrix 104 forming, with the datum axis 100, an angle A2 of 15°. More generally, the angle A2 is greater than 1.5°, preferably greater than 12°, and less than 45°, preferably less than 40°. The outer generatrix 104 of the outer contact track 56 is such that it moves away from the reference axis 100 as it approaches the outer rolling track 54.Furthermore, as it approaches the outer raceway 54, it moves away from the reference axis 100 less rapidly than the inner generatrix 102 of the inner contact track 26. The outer contact track 56 more generally presents, in any cutting plane including the reference axis 100, a generatrix forming, with the generatrix of the inner contact track 26, an angle greater than 0.5°, preferably greater than 1°, and less than 30°, preferably less than 15°. The outer raceway 54 and the outer contact track 56 are separated by an outer separating surface 58.

[0063] The ball bearing 10 further comprises a bearing cage 60, configured to space and maintain the rolling elements 16 in predetermined relative positions, and a guide cage 40, independent of the bearing cage 60 and intended to guide the contact balls 35. The guide cage 40, which belongs to the current-conducting device 70, comprises a ring 62 having a guide face intended to be aligned with the receiving surface. The ring 62 comprises in in addition to the recesses 66 and at least one disengagement device 68, the guide cage 40 comprises three recesses 66 angularly offset from each other by an angle of 2π / 3 so that the current-passing device 70 is statically balanced. The recesses 66 project axially and radially from the ring 62, so as to penetrate without contact between the contact tracks. To achieve this, in the cutting plane comprising the reference axis 100 and the center of a contact ball 35 (illustrated in [Fig. 1]), a recess 66 forms, with the reference axis 100, a mean angle greater than 12°, preferably greater than 14°, and less than 47°, preferably less than 42°. The recesses 66 are defined by rigid recess elements 64.The sockets 66 are equidistant from each other and have an ovoid shape, that is to say, the through hole of the socket element 64 intended to receive the ball has an axial dimension greater than its orthoradial dimension. Thus, the socket element 64 has an axial stop 72 to hold the contact ball 35 between the contact tracks when it moves towards the second end face 22, two orthoradial guide facets 76 to drive the contact ball 35 orthoradially, and an axial linkage 74, opposite the axial stop 72, and linking the two orthoradial guide facets 76 together so as to solidify the structure of the socket.

[0064] The disengagement devices 68 are also three in number and are equidistant from each other. They are also equidistant from the two adjacent associated recesses 66. Such an arrangement ensures the static balance of the cage and minimizes mechanical stresses, thus maximizing the cage's strength. The disengagement devices 68 are configured to drive the guide cage 40 in rotation with the inner ring 14 at low speed, and to disengage them when the angular velocity exceeds a predetermined threshold, called the disengagement angular velocity threshold. To achieve this, each of the disengagement devices 68 comprises at least one movable portion 90 connected to a rigid structure 82, formed here by a protrusion, via a flexible arm 84 capable of elastically deforming according to the centrifugal force induced by the rotational speed of the rotating subassembly 4.The moving portion 90 includes a movable pad 78 configured to come into the coupling position, bearing against the inner ring 14, and more particularly the inner annular surface 18, and preferably on at least a portion of the inner contact track 26 when the mechanism is at rest, and more generally below the disengagement angular velocity threshold. Each flexible arm 84, coupled to the moving portion 90 which includes a mass distribution configured to allow tilting, is configured to deform so as to move the moving portion 90 away from the reference axis 100, lifting the associated movable pad 78 from the inner ring 14 accordingly. that the rotational speed of the rotating sub-assembly 4 increases until it reaches a disengaged position in which it is no longer in contact with said rotating sub-assembly 4 as soon as the rotational speed exceeds the disengagement angular speed threshold.

[0065] The ring 62 also includes radial stops 86, each radial stop 86 being arranged opposite the associated moving portion 90, radially further away from the reference axis 100, so as to limit the centrifugal radial displacement of the moving portion 90.

[0066] The ring 62 further comprises an inner cylindrical annular face 79 facing the reference axis 100. It is intended to be positioned opposite the receiving face 42 of the inner ring 14. The inner annular face 79 comprises at least one retaining tab 80 projecting radially towards the reference axis 100 and intended to penetrate the annular groove 44 of the receiving portion 38. The retaining tab 80 is configured to secure the axial positioning of the guide cage 40 in the ball bearing 10, and is housed without contact in the annular groove 44 of the receiving portion 38. The retaining tabs 80 are preferably flexible, so as to be inserted into the annular groove 44 by elastic deformation.

[0067] The current-passing device 70 comprises, as a reminder, the inner and outer contact tracks, as well as the guide cage 40 and the contact balls 35. The fixed subassembly 2 is radially further from the rotating subassembly 4 at the first inner end 32 than at the second inner end 34. In the cutting plane containing the reference axis 100, any segment S perpendicular to the reference axis 100, and having a first end belonging to the inner contact track 26 and a second end belonging to the outer contact track 56, has: • a center C which, in a direct orthonormal coordinate system having an x-axis coinciding with the reference axis 100 and an ordinate y which passes through the first inner end 32 of the inner contact track 26, has an x-axis equal to x and an ordinate equal to y, defining a function x—>y=f(x) which, when x varies between 0 and the second inner end 34 of the inner contact track 26, is strictly increasing continuously; • a length? defining a function x—> / =g(x) which, when the abscissa x of the center C of the segment S varies between 0 and the second interior endpoint 34, is strictly decreasing continuously, having a maximum value strictly greater than the diameter of the balls D BC, and a minimum value less than or equal to the diameter of the balls D BC.

[0068] When the bearing is stationary, the contact balls 35 position themselves axially between the two contact tracks according to gravity. For example, if the reference axis is horizontal, a contact ball 35 positioned lower than the reference axis will have rolled by gravity along the outer contact track to position itself as close as possible to the raceways 24 and 54. Conversely, a contact ball 35 positioned higher than the reference axis 100 will be pulled by gravity along the inner contact track to position itself as far as possible from the raceways 24 and 54. The contact ball is then held between the two contact tracks by the axial stop 72.

[0069] During operation, when the ball bearing 10 is in motion, the rotating sub-assembly 4 drives the guide cage 40 with it via the movable slides 78. The guide cage 40 then drives the contact balls 35 in rotation via one of the two orthoradial surfaces 76 of each socket 66. Under the effect of centrifugal force, these balls move away from the axis of rotation, which coincides with the reference axis 100. The contact balls 35 then roll on the outer contact track, regardless of their initial position. The contact balls roll so as to move as far away as possible from the reference axis 100 under the influence of the centrifugal force. They then move radially and axially towards the point on the inner contact track 26 that is radially furthest from the reference axis 100, here the second inner end 34.This movement continues until each contact ball 35 reaches a position in which it is in contact with the inner contact track 26 and the outer contact track 56. Each contact ball 35 is then in an extreme axial position, in contact only with the two contact tracks 26, 56.

[0070] The contact ball 35 rolling on the inner contact track 26 has a rotational speed around the reference axis 100 lower than the rotational speed of the rotating sub-assembly 4. The contact ball 35, housed in the socket 66, drives the guide cage 40 which has separated from the faster rotating inner ring 14 into rotation, the flexible arms 84 deforming elastically so that the movable portions 90 tilt, lifting the movable pads 78 from the inner ring 14 so as not to generate friction.

[0071] Such a current-passing device structure 70, comprising frustoconical contact tracks, presents, in a cutting plane including the reference axis, an osculating circle of infinite radius, reducing the contact ellipses between the contact ball 35 and each of the two contact tracks, making it easier to split the lubricant film present in the mechanism, and thus reducing the electrical impedance of the current-passing device 70 at the point of contact, extending the service life of contact tracks and bearing tracks by reducing, and preferably eliminating, electrical arcs.

[0072] According to a second embodiment illustrated in Figures 9 and 10, the inner contact track 26 has an inner generatrix 102 forming an angle A1 of 38° with the reference axis 100, while the outer contact track 56 has an outer generatrix 104 forming an angle A2 of 34° with the reference axis 100. This embodiment is preferred in bearings requiring a smaller axial footprint. The recesses 66 and the disengagement devices 68 then have an angle adapted so as to fit between the two contact tracks.

[0073] Furthermore, according to a third alternative embodiment illustrated in Figures 11 and 12, the outer ring 12 is connected to a rotating subassembly 2, while the inner ring 14 can be connected to a fixed or rotating subassembly. In this scenario, the guide cage 40 is not connected to the inner contact track 26 but to the outer annular surface 48, preferably at least partially to the outer contact track 56. To achieve this, the flexible arm 84 connects the ring 62 to the axially projecting movable portion 90, the movable portion 90 comprising the projecting movable pad 78 of the latter and located in a radial projection of the ring 62. The movable portion 90 has a mass greater than that of the movable pad 78 to which it is connected by a rigid arm 92, understood here as the operating conditions of this part. The movable pad 78 is located radially further from the reference axis 100 than the movable portion 90.In this embodiment, the radial stop 86 is also rotated radially towards the reference axis 100, however, it is opposite the movable portion 90 to limit a radial displacement of said movable portion 90 outwards. During operation, when the rotational speed of the guide cage 40 is sufficiently high, the moving portion 90 moves away from the reference axis 100, a movement made possible by the flexibility of the flexible arm 84 and implemented by the centrifugal force acting on the mass of said moving portion 90. By lever effect, when the moving portion 90 moves away from the reference axis 100, the moving pad 78 is displaced radially in the direction of the reference axis 100, which detaches it from the outer contact track 56. In addition, in this embodiment, the retaining tabs 80 are radially projecting in a centrifugal manner and are housed in an annular groove 44' located on the outer ring 12.

[0074] The examples shown in the figures and discussed above are given for illustrative purposes only. Other embodiments may be considered, in particular by combining the features of the different illustrated embodiments.

[0075] For example, according to an alternative embodiment, the ring 62 can be equipped with a number N, other than three, of 6 6 cavities angularly offset from each other by an angle 2ir / N. Alternatively, the ring 62 can be equipped with a number N', different from three, of disengagement devices 68 angularly offset from each other by an angle 2ji / N'.

[0076] According to another alternative embodiment, the current-conducting device 70 is formed by two rings separate from the two rings forming the bearing raceways. In a variant, the current-conducting device 70 is formed by two separate rings, one of which also forms one of the raceways, the other raceway being formed on a ring separate from the two rings of the current-conducting device. Another feasible variant would be to form the current-conducting device with a ring fixedly mounted on one of the two sub-assemblies 2, 4 of the rotating device, allowing the assembly and fixing of the guide cage and the provision of one of the two contact tracks, the other contact track being formed directly on the other sub-assembly 2, 4, which in this hypothesis constitutes the other ring.

[0077] According to another alternative embodiment, the bearing has rolling bodies 16 which are not balls, but cylindrical or conical rollers, or barrel-shaped for example.

[0078] According to another alternative embodiment, the inner contact tracks 26 and outer contact tracks 56 move away from each other as they approach the guideways. The guide cage 40 then comprises recesses and at least one suitable centrifugal disengagement device 68, inserted between the two contact tracks by deformation.

[0079] According to another alternative embodiment, the current-passing device 70 is mounted on two rings forming a plain bearing.

Claims

1. Demands Current-passing device (70) between two sub-assemblies (2, 4), at least one of the two sub-assemblies being capable of rotating about an axis of revolution relative to the other of the two sub-assemblies, the device comprising: - an annular and conductive inner contact track (26), intended to be integral with a first of the two sub-assemblies (2, 4), the inner contact track (26) having a rotational symmetry about a reference axis (100) of the current-passing device (70) intended to coincide with the axis of revolution, the inner contact track (26) being radially turned outwards and extending axially at least from a first inner end (32) to a second inner end (34), further from the reference axis than the first inner end (32); - an annular and conductive outer contact track (56), intended to be integral with a second of the two sub-assemblies (2, 4), the outer contact track (56) having a rotational symmetry around the reference axis (100), the outer contact track (56) being radially turned inwards and opposite the inner contact track (26); - at least one conductive contact ball (35), having a ball diameter DB c, positioned between the inner and outer contact tracks, and capable, in an operational position, of rolling on the inner and outer contact tracks; the current-passing device (70) being characterized in that, in a cutting plane containing the reference axis (100), any segment perpendicular to the reference axis (100), and having a first end which belongs to the inner contact track (26) and a second end which belongs to the outer contact track (56), has: - a center (C) which, in an orthonormal coordinate system having an x-axis coinciding with the reference axis (100) and an ordinate axis passing through the first inner endpoint (32) of the inner contact track (26), has an abscissa equal to x and an ordinate equal to y, defining a function x - y - f(x) which, as x varies between 0 and a positive abscissa of the second endpoint, is strictly increasing continuously; - a length 1 defining a function xl = g(x) which, as the abscissa x of the center (C) of the segment (S) varies between 0 and the second endpoint, is strictly decreasing continuously, having a maximum value greater than the diameter of the balls DB c, and a minimum value less than the diameter of the balls DB c-

2. Current-passing device (70) according to claim 1, characterized in that the inner contact track (26) is frustoconical.

3. Current passage device (70) according to claim 2, characterized in that the inner contact track (26) has, in any cutting plane including the reference axis (100), a generatrix forming, with the reference axis (100), an angle Al greater than 2°, preferably greater than 14°, and less than 47°, preferably less than 42°.

4. Current-passing device (70) according to any one of claims 1 to 3, characterized in that the outer contact track (56) is frustoconical.

5. Current passage device (70) according to claim 4, characterized in that the outer contact track (56) has, in any cutting plane including the reference axis (100), a generatrix forming, with the reference axis (100), an angle A2 greater than 1.5°, preferably greater than 12°, and less than 45°, preferably less than 40°.

6. Current-passing device (70) according to claim 4 in combination with claim 2, characterized in that the outer contact track (56) has, in any cutting plane including the reference axis (100), a generatrix forming, with a generatrix of the inner contact track (26) an angle greater than 0.5°, preferably greater than 1°, and less than 30°, preferably less than 15°.

7. Current-passing device (70) according to any one of the preceding claims, characterized in that it comprises a guide cage (40) positioned at least partially between the inner and outer contact tracks, the guide cage (40) having at least one recess (66) in which the contact ball (35) is housed, the recess (66) defining an axial stop (72) for the contact ball (35), the axial stop (72) being located between the inner and outer contact tracks and axially closer to the first inner end (32) of the inner contact track (26) than to the second inner end (34) of the inner contact track (26), the axial stop (72) being axially oriented towards the second inner end (34) of the inner contact track (26),the contact ball (35) establishing a point of contact with the inner contact track (26) at abscissa 0 when it is against the axial stop (72), the socket (66) having two opposing guide facets (76) facing each other in an orthoradial direction, the two guide facets (76) extending axially from the axial stop (72) towards the second inner end (34), so as to allow a displacement of the contact ball (35) such that the abscissa of the point of contact between the contact ball (35) and the inner contact track (26) varies between 0 and the abscissa of the second end.

8. Current-passing device (70) according to claim 7, characterized in that - the two guide facets (76) are located at a distance from each other greater than the diameter of the balls DBc; and / or - the two guide facets (76) are flat or concave.

9. Current passage device (70) according to claim 7 or 8, characterized in that the guide cage (40) comprises at least one centrifugal disengagement device (68) capable of securing the guide cage (40) to a rotating contact track among the inner contact track (26) and the outer contact track (56), below a disengagement angular speed threshold of the inner contact track (26) or the outer contact track (56) and of releasing the guide cage (40) beyond the disengagement angular speed threshold.

10. Current passage device (70) according to claim 9, characterized in that the centrifugal disengagement device comprises a movable portion (90) connected to an annular body (62) of the guide cage (40) by at least one flexible arm (84), said movable portion (90) comprising a movable pad (78) intended to come into contact with any one of the two subassemblies (2, 4).

11. Current passage device (70) according to claim 10, characterized in that the centrifugal disengagement device comprises a radial stop (86) opposite the moving portion (90) to limit a radial displacement of the moving portion (90) when it moves away from the reference axis (100).

12. Current passage device (70) according to any one of claims 7 to 11, characterized in that the guide cage (40) has one or more retaining tabs (80) in radial projection.

13. Current passage device (70) according to any one of claims 7 to 12, characterized in that the guide cage (40) is made of a piece of plastic material.

14. A rolling bearing (10) comprising an inner ring (14) including at least one inner raceway (24); an outer ring (12) including at least one outer raceway (54); and rolling bodies (16), positioned so as to roll simultaneously on the inner and outer raceways; the rolling bearing being characterized in that it comprises a current-passing device (70) according to any one of the preceding claims, the inner ring (14) including the annular inner contact track (26) and the outer ring (12) including the annular outer contact track (56).

15. Bearing housing (10) according to claim 14, characterized in that the inner ring (14) is one piece and / or the outer ring (12) is one piece.

16. Bearing bearing (10) according to any one of claims 14 to 15, the current-passing device being according to any one of claims 7 to 13, characterized in that the guide cage (40) has a guide face and is located opposite and at a distance of less than 0.5 mm and more than 0.05 mm from a corresponding face of one of the two subassemblies (2,4).

17. Rolling bearing (10) according to any one of claims 14 to 16 characterized in that the inner raceway (24) is located axially at a distance from the inner contact track (26) and the outer raceway (54) is located axially at a distance from the outer contact track (56).

18. Rolling bearing according to any one of claims 14 to 17, characterized in that the first inner end (32) of the inner contact track (26) is axially further from the inner raceway (24) than the second inner end (34) of the inner contact track (26).

19. Rolling bearing according to any one of claims 14 to 18, the current-passing device being according to any one of claims 7 to 13, characterized in that the rolling bodies (16) are positioned in recesses (64') of a bearing cage (60) not integral with the guide cage (40).

20. Assembly characterized in that it comprises two subassemblies and a rolling bearing according to any one of claims 14 to 19 for guiding at least one of the two subassemblies in rotation about an axis of revolution relative to the other of the two subassemblies, the first subassembly being able to rotate relative to the second subassembly about the axis of revolution, the second subassembly being fixed in rotation in a geostationary frame.

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