ROLLER CAGE ASSEMBLY AND ROTATIONAL GUIDE BEARING COMPRISING AT LEAST ONE SUCH ASSEMBLY

Abstract

The present invention relates to a roller cage assembly (200S) for guiding the rotation of a first bearing ring relative to a second bearing ring and comprising a series of rollers (RS) each having an individual axis of rotation (AS) and a cage (10S) for guiding and positioning the rollers (RS), in which the cage (10S) comprises at least one ring or ring segment (12SA, 12SB) which comprises a series of circumferentially distributed fingers (14SA, 14SB) each of which is received inside an axial hole of an associated roller (RS), characterized in that the ring or ring segment (12SA, 12SB) and the series of fingers (14SA, 14SB) are made in one piece. The invention also provides a bearing integrating at least one roller cage assembly. Figure for abstract: 6

Description

Title of the invention: ROLLER CAGE ASSEMBLY AND ROTATIONAL GUIDE BEARING COMPRISING AT LEAST ONE SUCH ASSEMBLY Technical field of the invention

[0001] The invention relates to a roller cage assembly for guiding in rotation, about a main axis of rotation, a first bearing ring relative to a second bearing ring.

[0002] The invention also relates to a rotational guide bearing capable of being interposed between two elements of a structure which are mounted to rotate relative to each other. Technical background

[0003] The invention relates to a roller cage assembly for guiding in rotation, around a main axis of rotation, a first bearing ring relative to a second bearing ring, this assembly comprising: - a series of rollers each having an individual axis of rotation and which are distributed circumferentially around the main axis; and - and a cage for guiding and circumferential positioning of the rollers.

[0004] For example, one or more cages may be integrated into a rotating guide bearing, or rolling bearing.

[0005] Examples of integration of three roller cages are for example illustrated in documents FR2072552 and EP2503164B1.

[0006] Roller guidance is very important to avoid contact between the rollers, which would cause their wear and premature failure, and to maintain the axis of rotation of each of the rollers in the optimal position, to avoid an increase in torque and premature failure.

[0007] A first problem with this standard guidance is that the number of rollers is limited by the thickness of the cage wall between adjacent rollers.

[0008] In a known manner, it is possible to use cages, or cage segments in which the cage comprises a series of windows in each of which a roller is arranged with play.

[0009] The angular or circumferential gap between the rollers must be large enough to maintain sufficient resistance of the cage wall between the rollers of the same sector, and between the rollers of two neighboring sectors.

[0010] The space between the cage segments must also be sufficient to avoid blockages due to expansion under the effect of heat in particular.

[0011] This limits the number of rollers and therefore the load capacity of the bearing.

[0012] A second problem is that standard guidance from the outside diameter of the rollers leads to removing the lubricant on the outside diameter of the roller, and thus limits the amount of lubricant present at the contact surfaces between the rollers and the raceways or tracks.

[0013] This can cause premature wear during operation.

[0014] A third problem is that conventionally designed cages have a large volume and most of the time there is contact between the cages and the raceways, which limits the circulation of the lubricant inside the bearing and thus prevents uniform lubrication of the bearing.

[0015] One known solution is to guide the rollers using a design in which the cage comprises at least one ring which comprises a series of circumferentially distributed fingers, each of which is received inside an axial hole of an associated roller.

[0016] An example of such a design is illustrated in document EP2172664A1. This design, which involves producing such fingers in the form of pins screwed into two complementary rings, is complex, expensive, heavy and difficult to assemble and integrate into bearing structures.

[0017] Generally speaking, it is also desirable to be able to reduce the weight and manufacturing cost of rollers and cages. Summary of the invention

[0018] The invention provides a roller cage assembly for guiding in rotation, around a main axis of rotation, a first bearing ring relative to a second bearing ring comprising: - a series of rollers each having an individual axis of rotation and which are distributed circumferentially around the main axis; - and a cage for guiding and circumferential positioning of the rollers around the main axis, wherein the cage comprises at least one ring or ring segment which comprises a series of circumferentially distributed fingers each of which is received within an axial hole of an associated roller, characterized in that the ring and the series of fingers are made in one piece.

[0019] According to other characteristics of the invention:

[0020] - the cage comprises two complementary rings or ring segments of which each comprises a series of fingers, made in one piece with the ring or ring segment, which are distributed circumferentially and each of which is received inside an axial hole of an associated roller; and each roller, at at least one of its two opposite axial ends, comprises an axial hole which receives a finger of a of the two complementary rings or ring segments; - the individual axis of rotation of each roller is orthogonal to the main axis of rotation; - the individual axis of rotation of each roller is parallel to the main axis of rotation;

[0021] - the individual axis of rotation of each roller present forms an angle included between 0 and 90 degrees angle relative to the principal axis of rotation; - each ring or ring segment with its fingers is leaf-shaped, flat or curved; - each ring or ring segment with its fingers is made by cutting, in particular by laser cutting, from a metal sheet;

[0022] - each ring or ring segment with its fingers is provided with a coating fa preventing slippage, and therefore limiting wear - at each of its two opposite ends, each roller has a blind axial hole which is capable of receiving a finger; - each roller has an axial through hole, each axial end of which is capable of receiving a finger; - each roll is a cylindrical roll or one of similar shape; - each roller is a conical, truncated conical, or similarly shaped roller - each roll is made by cutting a section of tube or solid bar; - the two complementary rings or ring segments of the cage are integral with each other; - the two rings or ring segments of the cage are independent of each other; - that the end sections of two aligned and opposite fingers received inside the same roller overlap axially; - each cage extends along a specific angular sector and / or is made up of several independent angular sectors.

[0023] The invention also proposes a bearing for guiding rotation, around a main axis of rotation, capable of being interposed between two elements of a structure which are mounted to rotate relative to each other, this bearing comprising: - a first radially inner rolling ring; - a second coaxial, radially outer bearing ring extending around the first bearing ring; - and at least one assembly for guiding the rotation of the first bearing ring relative to the second bearing ring produced according to the invention.

[0024] According to other characteristics of the bearing: - one of the two bearing rings has a housing open radially by relative to the main axis of rotation; the other of the two rolling rings comprises a projecting part which extends radially inside the housing, and it comprises at least two assemblies for guiding the rotation of the first rolling ring relative to the second rolling ring, each of which is produced according to the invention and which comprise two assemblies in each of which the individual axis of rotation of each roller forms a non-zero angle relative to the main axis of rotation and each of which is interposed axially between two opposite annular rolling tracks belonging respectively to the projecting part and to the housing; - the projecting portion extends radially towards the main axis of rotation from the second radially outer bearing ring; - the projecting portion extends radially away from the main axis of rotation from the first radially inner bearing ring. Brief description of the figures

[0025] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0026] [Fig-1] - [Fig.l] is a sectional view through an axial plane of an assembly comprising a guide bearing incorporating three roller cage assemblies;

[0027] [Fig.2] - [Fig.2] is a partial sectional and perspective view of the assembly of [Fig.l];

[0028] [Fig.3] - [Fig.3] is a partial sectional and perspective view similar to that of [Fig.2] in which only the three roller cage assemblies are shown;

[0029] [Fig.4] - [Fig.4] is an exploded perspective detail view of a section of the central roller cage assembly;

[0030] [Fig.5] - [Fig.5] is a perspective view of a section of one of the two upper or lower roller cage assemblies;

[0031] [Fig.6] - [Fig.6] is an exploded perspective view of the section illustrated in [Fig.4];

[0032] [Fig.7] - [Fig.7] is a sectional view through plane 7-7 of [Fig.5];

[0033] [Fig.8] - [Fig.8] is a view similar to that of [Fig.5] illustrating a variant of construction of the cage illustrated in figures 5 to 7. Detailed description of the invention

[0034] For the description of the invention and the understanding of the claims, the vertical orientation according to the orientation of the main axis of rotation AP indicated in [Fig.l] will be adopted as a non-limiting example and without limiting reference to Earth's gravity.

[0035] In the following description, identical, similar or analogous elements will be designated by the same reference numbers or by reference numbers analogous and indexed.

[0036] In [Fig. 1], in section through an axial plane passing through a main axis of rotation AP, an assembly 100 is shown comprising a crown or bearing 106 for guiding the rotation of an upper component 102 relative to a lower component 104.

[0037] The two components 102 and 104 are for example the lower end of a wind turbine blade pivotally assembled on a rotor hub 104.

[0038] The bearing 106 comprises a first rolling ring 108 - radially inner relative to the main axis AP - in two upper 110 and lower parts - on which the component 102 is fixed.

[0039] The assembly of the three components 102, 110 and 112 is carried out by means of a set of axial bolts 114 distributed circumferentially around the main axis AP.

[0040] The first bearing ring 108 comprises a housing 116 which is open radially, here outwards, relative to the main axis of rotation.

[0041] The housing 116 of the bearing ring 108 is formed partly in the lower part 112 and partly in the upper part 110 and it is delimited vertically by two planar and opposite annular faces orthogonal to the main axis AP, including an upper face 122 and a lower face 123.

[0042] Each flat annular face 122, 123 constitutes a flat annular rolling track belonging to the first rolling ring 108.

[0043] The housing 116 is also delimited, radially inwards by a convex cylindrical face of axial orientation 118.

[0044] The face 118 constitutes a cylindrical rolling track belonging to the first rolling ring 108.

[0045] The bearing 106 comprises a second rolling ring 124 - radially external with respect to the main axis AP - in a single part on which the component 104 is fixed.

[0046] The assembly of the two components 104 and 124 is carried out by means of a set of axial bolts 126 distributed circumferentially around the main axis AP.

[0047] The second bearing ring 124 comprises a projecting portion 128 which here extends radially towards the main axis AP inside the housing 116 of the first bearing ring 108.

[0048] The projecting part, or nose, 128 is delimited vertically by two flat and opposite annular faces orthogonal to the main axis AP, including an upper face 132 and a lower face 133.

[0049] Each flat annular face 132, 133 constitutes a flat annular rolling track belonging to the second rolling ring 124.

[0050] The projecting portion 128 is also delimited, radially inwards by a face concave cylindrical with axial orientation 130.

[0051] The face 130 constitutes a cylindrical rolling track belonging to the second rolling ring 124.

[0052] The projecting portion 128 extends radially inwardly from a concave axial cylindrical surface 129 of the body of the second bearing ring 124.

[0053] An upper roller cage assembly 200S is axially interposed between the flat and parallel annular rolling tracks 122 and 132, while a lower roller cage assembly 2001 is axially interposed between the annular and opposed rolling tracks 123 and 133.

[0054] The axes of rotation AS and AI of the rollers of the two roller cage assemblies 200S and 2001 are orthogonal to the main axis of rotation AP.

[0055] The two roller cage assemblies 200S and 2001 of the bearing 106 are capable of supporting axial loads oriented parallel to the main axis AP.

[0056] By way of non-limiting example, the design of the two roller cage assemblies 200S and 2001 of the bearing 106 is identical here.

[0057] A central roller cage assembly 200C is interposed radially between the cylindrical and parallel rolling tracks 118 and 130.

[0058] The axes of rotation of the rollers of the central roller cage assembly 200C are parallel to the main axis of rotation AP.

[0059] The central roller cage assembly 200C is capable of supporting radial loads oriented orthogonally to the main axis AP.

[0060] Traditionally, each series of rollers belonging to a 200S, 2001 or 200C roller cage is arranged in a circle angularly around the main axis AP.

[0061] With particular reference to FIGS. 3 and 4, the design example of the central roller cage assembly 200C will now be described.

[0062] The assembly 200C comprises a series of rollers RC each having an individual axis of rotation AC and which are distributed circumferentially around the main axis AP.

[0063] To guide and position the RC rollers, the assembly 200C here comprises a cage 10C, for guiding and circumferentially positioning the RC rollers, in two complementary parts 10CA and 10CB (See [Fig.4]) each of which comprises a ring 12CA, 12CB.

[0064] Each ring 12CA, 12CB comprises a series of fingers 14CA, 14CB which are distributed circumferentially along the ring 12CA, 12CB.

[0065] Each ring, or ring sector, 12CA, 12CB is made in a single piece with its series of associated fingers.

[0066] Without limitation, each ring 12CA, 12CB is in the form of a sheet or plate which is here curved to adopt a generally cylindrical conformation.

[0067] By way of non-limiting example, each RC roller has an axial through hole 16C which opens at the two opposite axial ends of the RC roller.

[0068] Each finger 14CA, 14CB is received inside an axial hole 16C of an associated RC roller.

[0069] The design of each of the two upper roller cage assemblies 200S and 2001 is identical here.

[0070] With particular reference to FIGS. 3 and 5 to 7, the design example of the upper roller cage assembly 200S will now be described in more detail.

[0071] The assembly 200S comprises a series of rollers RS each having an individual axis of rotation AS which are distributed circumferentially around the main axis AP.

[0072] To guide and position the RS rollers, the assembly 200S here comprises a cage 10S for guiding and circumferentially positioning the RS rollers, in two complementary parts 10SA and 10SB, each of which comprises a ring 12SA, 12SB.

[0073] Each ring 12SA, 12SB comprises a series of fingers 14SA, 14SB which are distributed circumferentially along the ring 12SA, 12SB.

[0074] Each ring, or ring sector, 12SA, is made in one piece with its associated series of fingers.

[0075] Without limitation, each ring 12SA, 12SB is in the form of a flat annular sheet or plate.

[0076] Without limitation, each RS roller has an axial through hole 16S which opens at the two opposite axial ends of the RS roller.

[0077] Each finger 14SA, 14SB is received inside an axial hole 16S of an associated roller RS.

[0078] The corresponding components of the assembly 2001 are designated by the same alphanumeric references indexed “I”, namely RI, AI, 101, 12IA, 12IB, 14IA, 14IB, 161.

[0079] According to one embodiment, each ring 12CA, 12CB, 12SA, 12SB, 12IA, 12IB with its fingers 14CA, 14CB, 14SA, 14SB, 14IA, 14IB is produced by cutting, in particular by laser cutting, in a metal sheet.

[0080] Without limitation, each finger 14CA, 14CB, 14SA, 14SB, 14IA, 14IB here has a rectangular section.

[0081] It is thus possible to produce metal cages at low cost by laser cutting from a standard construction steel sheet. Then, a polyamide (PA) coating similar to that used for coating ball bearing cages can be applied; for example, a polyamide PA11 or PA12 which can be deposited by immersion in a fluidized bath.

[0082] Such a production method is notably more economical than the production of cages molded from plastic material requiring in particular the manufacture of as many molds as necessary.

[0083] Alternatively, the fingers may be of circular section requiring the implementation other manufacturing techniques, or additional manufacturing steps.

[0084] As a non-limiting example, according to one embodiment, when each roller RC, RS, RI is a cylindrical roller of substantially constant section and comprises an axial through hole 16C, 16S, 161 (each axial end of which is capable of receiving a finger 14CA, 14CB, 14SA, 14SB, 14IA, 14IB), each cylindrical roller can be produced by cutting a section of tube.

[0085] Being able to make large diameter axial holes 16C, 16S, 161 makes it possible to significantly reduce the weight of the rollers, which are made from an expensive material, and to produce these rollers from tubes rather than solid bars to reduce weight and costs.

[0086] The maximum hole diameter is defined based on the minimum load capacity of the roller.

[0087] When, in particular due to the desired load level or a reduced external diameter of the roller, the design of a roller with a through axial hole is not possible, the other advantages of the innovative design of the cage remain applicable by using, for example, a roller which has a blind axial hole at each of its two opposite axial ends which is capable of receiving an associated finger.

[0088] Reduced cost and reduced weight are not the only advantages of this design as it is also more reliable than the conventional plastic window cages currently in use.

[0089] Indeed, steel cages are much stronger and less fragile than plastic cages.

[0090] For the assembly and mounting of each roller cage assembly, the procedure is carried out, for example, in the following manner.

[0091] Considering Figures 5 to 7, the fingers 14SA of the radially inner ring 10SA are introduced through the four axial holes 16S of the rollers RS, then the fingers 14SB of the radially outer ring 12SB are introduced into the axial holes 16S of the rollers RS.

[0092] Then, the “pre-assembled” 200S assembly can be placed in position inside the bearing 106 between the bearing rings 108 and 124.

[0093] According to the variant illustrated in [Fig.8], the two complementary rings 12SA and 12SB can be integral with each other.

[0094] For this purpose, by way of example, the free end sections of two aligned and opposite fingers 14SA and 14SB received inside the same roller RS ​​overlap axially and are fixed to each other.

[0095] For the purposes of the invention, each roller cage assembly may be produced in the form of a complete annular assembly extending over 360°, or in the form of a roller cage segment extending over an arc of a circle, several segments being able to be associated along a circumference.

[0096] Depending on the applications, a roller cage assembly, complete or segmental, may comprise only a single ring or a single ring segment with its fingers which are received in the series of associated rollers.

[0097] It is also possible to leave fingers without rollers, the number of rollers equipping a cage being able in particular to be determined according to the loads to be absorbed.

[0098] An assembly according to the invention may comprise only one lateral roller guide cage (in one piece or in several segments) arranged on one side of the rollers. In such a case, a single pierced end of each roller is sufficient.

[0099] Within the meaning of the invention, each cylindrical roller may have a profile approaching that of a cylinder with a rectilinear generator (as illustrated in the figures) and in particular have a barrel-shaped or curved profile.

[0100] The invention also finds application to assemblies comprising conical or truncated conical rollers.

[0101] Each roller can also be made from a section of a solid bar. In this case, the end hole(s) can be made by drilling.

[0102] The rollers of a series may roll on the surface of an associated track or be received in a groove cut into that surface.

[0103] Each bearing ring can be made in one or more parts.

[0104] The invention also finds application to a bearing comprising, for example, only two opposing assemblies similar to the assemblies 200S and 2001 described previously which are received between opposing annular frustoconical rolling tracks each forming an angle relative to the main axis of rotation.

[0105] The invention is applicable to the design of all types of rolling or bearing, including for a linear displacement guide capable of being interposed between two elements of a structure which are mounted to move relative to each other, this bearing comprising a first rolling element, made in one or more parts, a second rolling element, made in one or more parts, extending parallel to the first rolling element, and at least one assembly for guiding the first rolling element relative to the second rolling element made according to the principle of the invention and in which and a cage for guiding and circumferentially positioning the rollers around said main axis, in which the cage comprises at least one rectilinear segment which comprises a series of fingers distributed linearly, each of which is received inside an axial hole of a roller,each straight segment and the series of fingers being made in a single piece. 10

Claims

Claims

1. Roller cage assembly (200C, 2001, 200S) for guiding in rotation, around a main axis (AP) of rotation, a first bearing ring (108) relative to a second bearing ring (124), this assembly comprising: - a series of rollers (RC, RS, RI) each having an individual axis of rotation (AC, AS, AI) and which are distributed circumferentially around said main axis (AP);- and a cage (10C, 10S, 101) for guiding and circumferentially positioning the rollers (RC, RS, RI) around said main axis (AP), in which the cage (10C, 10S, 101) comprises at least one ring or ring segment (12CA, 12CB, 12SA, 12CB, 12IA, 12IB) which comprises a series of fingers (14CA, 14CB, 14SA, 14Sb, 14IA, 14IB) distributed circumferentially, each of which is received inside an axial hole of an associated roller (RC, RS, RI), characterized in that the ring or ring segment (12CA, 12CB, USA, UCB, UIA, 12IB) and the series of fingers (14CA, 14CB, USA, 14Sb, 14IA, 14IB) are made in one piece.;

2. Assembly (200C, 2001, 200S) according to claim 1, characterized in that: - the cage (10C, 10S, 101) comprises two complementary rings or ring segments (12CA, 12CB, USA, 12CB, 12IA, 12IB), each of which comprises a series of fingers (14CA, 14CB, USA, USb, 14IA, 14IB), made in a single piece with the ring or ring segment (12CA, 12CB, USA, UCB, UIA, UIB), which are distributed circumferentially and each of which is received inside an axial hole (16) of an associated roller (RC, RS, RI); and - each roller (RC, RS, RI), at each of its two opposite axial ends, has an axial hole (16C, 16S, 161) which receives a finger (14C, 14S, 141) of one of the two complementary rings or ring segments (UCA, UCB, USA, UCB, UIA, UIB).

3. Assembly (200C, 2001, 200S) according to one of claims 1 or 2, characterized in that the individual axis (AC, AS, AI) of rotation of each roller (RC, RS, RI) is orthogonal to said main axis (AP) of rotation.

4. Assembly (200C, 2001, 200S) according to one of claims 1 or 2, characterized in that the individual axis (AC, AS, AI) of rotation of each roller (RC, RS, RI) is parallel to said main axis (AP) of rotation.

5. Assembly according to one of claims 1 or 2, characterized in that the individual axis of rotation of each roller forms an angle between 0 and 90 degrees of angle relative to said main axis of rotation.

6. An assembly (200C, 2001, 200S) according to any one of the preceding claims, characterized in that each ring or ring segment (12CA, 12CB, 12SA, 12CB, 12IA, 12IB) with its fingers (14CA, 14CB, 14SA, 14Sb, 14IA, 14IB) is in the form of a sheet, flat or curved.

7. Assembly (200C, 2001, 200S) according to the preceding claim, characterized in that each ring or ring segment (12CA, 12CB, 12SA, 12CB, 12IA, 12IB) with its fingers (14CA, 14CB, 14SA, 14Sb, 14IA, 14IB) is produced by cutting, in particular by laser cutting, in a metal sheet.

8. Assembly (200C, 2001, 200S) according to any one of the preceding claims, characterized in that, at at least one of its two opposite ends, each roller (RC, RS, RI) comprises a blind axial hole (16C, 16S, 161) which is capable of receiving a finger.

9. Assembly (200C, 2001, 200S) according to any one of claims 2 to 6, characterized in that each roller (RC, RS, RI) comprises an axial through hole (16C, 16S, 161) each axial end of which is capable of receiving a finger.

10. Assembly (200C, 2001, 200S) according to any one of the preceding claims, characterized in that each roller (RC, RS, RI) is a cylindrical roller, or one of similar shape.

11. Assembly (200C, 2001, 200S) according to any one of claims 1 to 9, characterized in that each roller (RC, RS, RI) is a conical roller, or one of similar shape.

12. Assembly (200C, 2001, 200S) according to one of claims 10 or 11 taken in combination with claim 9, characterized in that each roller (RC, RS, RI) is produced by cutting a section of tube.

13. Assembly (200C, 2001, 200S) according to claim 9, characterized in that the two complementary rings or ring segments (12CA, 12CB, 12SA, 12CB, 12IA, 12IB) of the cage (10C, 10S, 101) are integral with each other.

14. Assembly (200C, 2001, 200S) according to claim 9, characterized in that the two rings or ring segments (12CA, 12CB, 12SA, 12CB, 12IA, 12IB) of the cage (10C, 10S, 101) are independent of each other.

15. Assembly (200C, 2001, 200S) according to claim 9, characterized in that the free end sections of two aligned and opposite fingers (14CA, 14CB, 14SA, 14Sb, 14IA, 14IB) received inside the same roller (RC, RS, RI) overlap axially.

16. Assembly (200C, 2001, 200S) according to any one of the preceding claims, characterized in that each cage (10C, 10S, 101) extends along a determined angular sector and / or is made up of several independent angular sectors.

17. Bearing (106) for guiding rotation, around a main axis (AP) of rotation, capable of being interposed between two elements (102, 104) of a structure which are mounted to rotate relative to each other, this bearing (106) comprising: - a first rolling ring (108), radially inner, made in one or more parts; - a second coaxial rolling ring (124), radially outer, made in one or more parts, extending around the first rolling ring (108); - and at least one assembly (200C, 2001, 200S) for guiding rotation of the first rolling ring (108) relative to the second rolling ring (124) made according to any one of claims 1 to 16.

18. Bearing (106) according to the preceding claim, characterized in that: - one (108) of the two bearing rings comprises a housing (116) open radially relative to the main axis (AP) of rotation;- the other (124) of the two rolling rings comprises a projecting portion (128) which extends radially inside said housing (116), and in that it comprises at least two assemblies (200C, 2001, 200S) for guiding the rotation of the first rolling ring (108) relative to the second rolling ring (124), each of which is produced according to any one of claims 1 to 16 and which comprise two assemblies (2001, 200S) in each of which the individual axis (AS, AI) of rotation of each roller (RS, RI) forms a non-zero angle relative to said main axis (AP) of rotation and each of which is interposed axially between two opposite annular rolling tracks (132-133, 122-123) belonging respectively to said projecting portion (128) and to said housing (116).;

19. Bearing (106) according to one of claims 17 or 18, characterized in that said projecting part extends radially opposite the axis main rotation from the first radially inner bearing ring.

20. Bearing (106) according to one of claims 17 or 18, characterized in that said projecting portion extends radially towards the main axis of rotation from the second radially outer bearing ring.

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