JP6568358B2 - Thrust roller bearing cage and manufacturing method thereof - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a thrust roller bearing retainer (hereinafter sometimes simply referred to as “retainer”) and a method for manufacturing the same, and in particular, a thrust roller bearing retainer manufactured using a press, and It relates to the manufacturing method.

  For example, a thrust roller bearing that receives a thrust load may be disposed at a location where a thrust load is applied in an automatic transmission for an automobile, a compressor for a car air conditioner, or the like. Such thrust roller bearings are desired to reduce the rotational torque of the bearings from the viewpoint of reducing fuel consumption and saving labor. The thrust roller bearing includes a bearing ring disposed in the rotation axis direction, a plurality of needle rollers that roll on the raceway surface of the bearing ring, and a cage that holds the plurality of needle rollers. The cage may be manufactured by bending a steel plate and then removing a pocket to accommodate the rollers.

  For example, Japanese Patent Application Laid-Open No. 10-220482 (Patent Document 1) discloses a technique related to a cage provided in such a thrust roller bearing. The cage for thrust roller bearings of Patent Document 1 is composed of an annular main body having a concavo-convex shape formed in the plate thickness direction and a convex portion provided on the outer diameter side of the annular main body, and the convex portion is an annular main body. The portions located in the respective pockets on the end surface on the outer diameter side that is folded back are protruded in the inner diameter direction so as to protrude near the center of the roller. According to this thrust roller bearing retainer, it is disclosed that the rotational torque of the roller can be kept small because the tip of the convex portion contacts the vicinity of the rotation center of the roller.

Japanese Patent Laid-Open No. 10-220482

  However, the inventors of the present invention have noted that the thrust roller bearing of Patent Document 1 has a problem that the flow of lubricating oil is poor. Then, this invention makes it a subject to provide the cage | basket of the thrust roller bearing which makes the flow of lubricating oil favorable, and its manufacturing method.

  The inventor has found that the problem of poor lubricant flow in the thrust roller bearing of Patent Document 1 is caused by the formation of irregularities in the plate thickness direction on the inner diameter side of the pocket in the annular body. Found. The inventor has completed the present invention as a result of diligent research to improve the flow of the lubricating oil without increasing the amount of the lubricating oil even when the irregular shape is formed on the inner diameter side of the pocket. I let you.

  That is, the cage of the thrust roller bearing of the present invention is a thrust roller bearing cage provided in the thrust roller bearing and provided with a plurality of pockets for accommodating the rollers, and the first cylinder extending in the rotation axis direction. A first cylindrical portion, a first circular cylindrical portion, a first circular cylindrical portion, a first circular cylindrical portion, a first circular cylindrical portion, and a second circular cylindrical portion extending in the rotation axis direction. The plate portion and the second cylindrical portion are formed in a region on the inner diameter side of the pocket, and the height of the first cylindrical portion in the rotational axis direction is smaller than the height of the second cylindrical portion in the rotational axis direction.

  A method for manufacturing a cage for a thrust roller bearing according to the present invention is a method for manufacturing a cage for a thrust roller bearing provided in a thrust roller bearing and provided with a plurality of pockets for accommodating the rollers, and the retainer serves as a cage. In the step of forming the concave and convex shape, the step of forming the concave and convex shape in the plate thickness direction for the cage material, and the step of forming the pocket for the cage material, A first cylindrical portion extending in the rotation axis direction, a disk portion extending in the outer diameter direction and connected to the first cylinder portion, and a second cylinder portion extending in the rotation axis direction and connected to the disk portion. In the step of forming the concavo-convex shape so that the height in the rotation axis direction of the first cylindrical portion is smaller than the height in the rotation axis direction of the second cylindrical portion, and forming the pocket, the second cylindrical portion A pocket is formed on the outer diameter side.

  According to the cage of the thrust roller bearing and the manufacturing method thereof according to the present invention, the first cylindrical portion, the disc portion, and the second cylindrical portion are formed with an uneven shape in the thickness direction on the inner diameter side of the pocket. . Even in the cage having such a concavo-convex shape, the height in the rotation axis direction of the first cylindrical portion located on the inner diameter side is smaller than the height in the rotation axis direction of the second cylinder portion. A gap caused by a difference in height in the rotation axis direction in the cylindrical portion can be formed as a flow path for the lubricating oil. Therefore, the thrust roller bearing retainer and the manufacturing method thereof according to the present invention can improve the flow of the lubricating oil.

  In the cage of the thrust roller bearing of the present invention, preferably, the outer diameter region bent portion formed by bending the region located on the outer diameter side of the pocket toward the inner diameter side, and the outer diameter region at a position aligned with each of the pockets And a protruding portion that is provided at the tip of the bent portion and protrudes toward the inner diameter side from the outer edge of the pocket so as to contact the end face of the roller accommodated in the pocket.

  Preferably, in the method for manufacturing the cage of the thrust roller bearing according to the present invention, the cage material projects from the edge on the outer diameter side of the pocket toward the inner diameter side so as to contact the end surface of the roller accommodated in the pocket. A step of forming an outer shape including a portion to become a protruding portion, and a step of bending an area located on the outer diameter side of the pocket in the cage material to the inner diameter side to form an outer diameter area bent portion. Yes.

  Thereby, since a protrusion part can support the outer diameter side end surface of a roller, the rotational torque of a thrust roller bearing can be reduced.

  Preferably, in the cage of the thrust roller bearing according to the present invention, the height in the rotation axis direction of the outer diameter region bent portion is smaller than the height in the rotation axis direction of the second cylindrical portion.

  Preferably, in the method for manufacturing the cage of the thrust roller bearing according to the present invention, in the step of forming the outer diameter region bent portion, the height in the rotation axis direction of the outer diameter region bent portion is the height in the rotation axis direction of the second cylindrical portion. The outer diameter region bent portion is formed so as to be smaller than this.

  As a result, the height in the rotation axis direction of the outer diameter region bent portion located on the outer diameter side is smaller than the height in the rotation axis direction of the second cylindrical portion. The gap generated by the above can be used as a lubricating oil flow path. Therefore, the flow of the lubricating oil can be improved.

  In the cage of the thrust roller bearing of the present invention, preferably, a region of the projecting portion that comes into contact with the end surface of the roller is subjected to surface pressing.

  Preferably, the method for manufacturing a cage for a thrust roller bearing according to the present invention further includes a step of performing a surface pressing process on a region of the projecting portion that contacts the end surface of the roller.

  Thereby, since the area | region which contacts a roller end surface among protrusions is surface-press-processed, at the time of rotation of a bearing, an oil film is slid by sliding with the area | region which contacts a roller end surface of a roller end surface during a protrusion part. Can be cut off. If it does so, the lubricity of this contact area | region will improve and the aggressiveness to the protrusion part of what is called a holder | retainer of a roller can be relieved. Therefore, such a thrust roller bearing retainer can further reduce the rotational torque of the bearing.

  The above-mentioned “surface pressing process” means that the protruding portion is formed by utilizing the outer diameter surface of the mold that plays a role of a stopper for regulating the amount of collapse in the process of forming the outer diameter region bent portion. By pressing in the diameter expansion direction, it means a process of smoothing the roughness shape of the surface before and after the process. Specifically, the press shear surface or fractured surface formed during the step of forming the outer shape can be smoothed to an arithmetic average roughness Ra (JIS B 0601) of about 2 μm or less by surface pressing.

  Preferably, in the cage of the thrust roller bearing of the present invention, the protruding portion is formed so as to bend the region on the outer diameter side of the cage obliquely to the inner diameter side.

  In the method for manufacturing the cage of the thrust roller bearing according to the present invention, preferably, in the step of forming the outer diameter region bent portion, a region of the cage material located on the outer diameter side from the pocket is bent obliquely toward the inner diameter side.

  Since the outer diameter region bent portion is formed by obliquely bending the region located on the outer diameter side of the pocket toward the inner diameter side, it is not inclined as in Patent Document 1 (inclination angle is 0 °). In comparison with the above, the area in contact with the roller is small in the protrusion provided at the tip of the outer diameter region bent portion. When the roller is urged toward the outer diameter side from the shaft center by the rotational centrifugal force of the roller, the portion that contacts the roller in the protrusion becomes friction, but contacts the roller in the obliquely bent protrusion Since the area is small, the rotational resistance can be reduced. For this reason, rotational torque can be reduced.

  According to the cage of the thrust roller bearing and the manufacturing method thereof according to the present invention, the flow of the lubricating oil can be improved.

It is a figure which shows a part of cage | basket of the thrust roller bearing which concerns on one Embodiment of this invention. It is sectional drawing of the cage | basket of the thrust roller bearing shown in FIG. It is an expanded sectional view which shows a part of cage | basket of the thrust roller bearing shown in FIG. It is a flowchart which shows the typical process of the manufacturing method of the retainer of the thrust roller bearing which concerns on one Embodiment of this invention. It is sectional drawing of the cage | basket material after performing an uneven | corrugated shape formation process. (A) is an expanded sectional view which expands and shows a part of cage material after performing a through hole formation process, and (B) shows a part of cage material after performing a pilot hole formation process. It is an expanded sectional view expanding and showing. It is an expanded sectional view which expands and shows a part of cage material after performing an external shape formation process. It is a figure which shows a part of cage material after performing a pocket formation process. It is an expanded sectional view which expands and shows a part of cage material after performing a pocket formation process. It is an expanded sectional view which expands and shows a part of cage material of the middle stage of an outer diameter area | region bending process. It is an expanded sectional view which shows the state which performs an outer diameter area | region bending process. It is an expanded sectional view which shows the state which performs an outer diameter area | region bending process. It is an expanded sectional view which expands and shows a part of cage material after performing an outer diameter area | region bending process. It is an expanded sectional view which expands and shows a part of cage material after performing an outer diameter area | region bending process. It is an expanded sectional view which shows the state which implements an outer diameter area | region bending process. It is an expanded sectional view which shows the state which performs a surface pressing process. It is an expanded sectional view which expands and shows the front-end | tip part of the outer diameter area | region bending part after performing a surface pressing process. It is sectional drawing which shows a part of cage | basket of the thrust roller bearing which concerns on other embodiment of this invention. It is a figure which shows a part of cage | basket of the thrust roller bearing which concerns on other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

FIG. 1 is a view showing a part of a cage 11 of a thrust roller bearing according to an embodiment of the present invention. FIG. 1 is a view of the cage 11 as seen from the rotation axis direction of the cage 11. FIG. 2 is a sectional view of the cage 11 of the thrust roller bearing shown in FIG. FIG. 2 is a case of cutting along a section indicated by II-II in FIG. Specifically, a cross section of a portion where a pocket described later is formed in the right region of FIG. 2 is shown, and a cross section of a portion where a column portion described later is formed in the left region of FIG. FIG. 3 is an enlarged sectional view showing a part of the cage 11 of the thrust roller bearing shown in FIG. FIG. 3 is an enlarged cross-sectional view of a region indicated by III in FIG. 2 and 3, the rotation axis 12 of the cage 11 is indicated by a one-dot chain line. Further, from the viewpoint of easy understanding, in FIG. 3, one of a pair of track rings 14 and 15 arranged on both sides of the needle roller 13 accommodated in a pocket 21 described later and the rotating shaft direction of the retainer 11. The part is illustrated. Note that the front and back direction of the paper surface in FIG. 1 and the vertical direction of the paper surface in FIG. 2 and FIG. Further, the direction of the direction or vice versa indicated by the arrow A ₁ in FIG. 1, a circumferential direction. From the viewpoint of easy understanding, the upper side in FIG. 2 and FIG. 3 is the upper side in the axial direction. That is, the direction indicated by arrow A ₂ in FIG. 2 and FIG. 3, the upward direction. Further, the horizontal direction in FIG. 2 and FIG. 3 is the radial direction. Direction indicated by arrow A ₃ in FIG. 3, the outer diameter direction.

  With reference to FIGS. 1-3, the structure of the cage | basket 11 of the thrust roller bearing which concerns on one Embodiment of this invention is demonstrated first. The thrust roller bearing retainer 11 according to an embodiment of the present invention has a disk shape, and a through hole 22 is provided in a central region thereof so as to penetrate straight in the thickness direction. A rotation shaft (not shown) is disposed in the through hole 22.

  The retainer 11 is provided at intervals in the circumferential direction so as to form a pair of annular portions 23 and 24 having different diameters and a pocket 21 that accommodates the needle rollers 13. And a plurality of column portions 25 to be connected.

  The pocket 21 has a substantially rectangular shape when viewed from the axial direction. The pockets 21 are arranged radially about the rotation axis 12 of the cage 11. On the side wall surface of the pocket 21, an upper roller stopper 26 that prevents the needle rollers 13 accommodated in the pocket 21 from falling off in the axial direction and an axial direction of the needle rollers 13 accommodated in the pocket 21. Lower roller stoppers 27 and 28 are provided to prevent falling off. The upper roller stopper 26 is provided at the center in the radial direction of the pocket 21. Further, the lower roller stopper 27 is provided on the inner diameter side of the pocket 21, and the lower roller stopper 28 is provided on the outer diameter side of the pocket 21. The upper roller stopper 26 and the lower roller stoppers 27 and 28 are provided on the side wall surfaces on both sides in the circumferential direction of the pocket 21 so as to protrude toward the pocket 21.

  The needle rollers 13 are accommodated so as to be pushed into the pockets 21. The shape of the end face of the needle roller 13, specifically, the end face 16 located on the bearing outer side and the end face 17 located on the bearing inner side is flat.

  The cage 11 is formed with a concavo-convex shape obtained by bending a plate material several times in the plate thickness direction and bending it. Specifically, the retainer 11 includes four disk portions 31, 32, 33, and 34 that extend in the radial direction, and four cylindrical portions 36, 37, 38, and 39 that extend in the axial direction. The four disk parts 31 to 34 have an inner diameter in the order of the first disk part 31, the second disk part 32, the third disk part 33, and the fourth disk part 34 from the inner diameter side. Is configured to be large. The four cylindrical portions 36 to 39 are arranged in the order of the first cylindrical portion 36, the second cylindrical portion 37, the third cylindrical portion 38, and the fourth cylindrical portion 39 from the inner diameter side. The first cylindrical part 36 and the second cylindrical part 37 are configured to extend straight in the axial direction. The third cylindrical portion 38 is configured to be slightly inclined so that the inner diameter side portion is located on the lower side in the axial direction than the outer diameter side portion. On the other hand, the fourth cylindrical portion 39 located on the outermost diameter side is configured to be slightly inclined so that the inner diameter side portion is located on the upper side in the axial direction than the outer diameter side portion.

  More specifically, the first cylindrical portion 36 extends in the axial direction. A first disc portion 31 is formed so as to be continuous with the upper end of the first cylindrical portion 36 and extend in the outer diameter direction. A second cylindrical portion 37 is formed so as to be continuous with the end portion on the outer diameter side of the first disc portion 31 and extend downward in the axial direction. A second disc portion 32 is formed so as to be continuous with the lower end of the second cylindrical portion 37 and extend in the outer diameter direction. A third cylindrical portion 38 is formed so as to be continuous with the end portion on the outer diameter side of the second disc portion 32 and to extend upward in the axial direction. A third disc portion 33 is formed so as to be continuous with the upper end of the third cylindrical portion 38 and extend in the outer diameter direction. A fourth cylindrical portion 39 is formed so as to be continuous with the outer diameter side end portion of the third disc portion 33 and extend downward in the axial direction. A fourth disc portion 34 is formed so as to be continuous with the lower end of the fourth cylindrical portion 39 and extend in the outer diameter direction. The first disc portion 31 and the third disc portion 33 are positioned on substantially the same plane. The second disc portion 32 and the fourth disc portion 35 are positioned on substantially the same plane.

  The above-described upper roller stopper 26 is provided on the third disk portion 33. Further, the lower roller stopper 27 is provided in the second disc portion 32, and the lower roller stopper 28 is provided in the fourth disc portion 34.

  The annular portion 23 on the inner diameter side includes the first disc portion 31, a part of the second disc portion 32, the first cylindrical portion 36, and the second cylindrical portion 37. . Further, the annular portion 24 on the outer diameter side described above includes a part of the fourth disc portion 34, an outer diameter region bent portion 41 described later, and a protruding portion 44 described later. The column 25 described above includes a part of the second disk part 32, a third disk part 33, a part of the fourth disk part 34, a third cylindrical part 38, and a fourth cylindrical part. 39. That is, the first cylindrical portion 36, the first disc portion 31, the second cylindrical portion 37, and a part of the second disc portion 32 are located in a region on the inner diameter side of the pocket 21. A part of the second disk part 32, a third cylindrical part 38, a third disk part 33, a fourth cylindrical part 39, and a part of the fourth disk part 34 are the same as the pocket 21. Located in the radial region. A part of the fourth disc portion 34 and the outer diameter region bent portion 41 are located in the outer diameter side region of the pocket 21.

  As shown in FIG. 3, the axial height H <b> 36 of the first cylindrical portion 36 is smaller than the axial height H <b> 37 of the second cylindrical portion 37. In other words, in the region on the inner diameter side of the pocket 21, a step having a lower inner diameter side in the rotation axis direction is formed. In other words, the other end of the first cylindrical portion 36 opposite to the one end connected to the first disc portion 31 is opposite to the one end connected to the first disc portion 31 in the second cylindrical portion 37. It is positioned so as to recede to one end side from the other end.

  Specifically, the lower end of the first cylindrical portion 36 is located above the lower end of the second cylindrical portion 37. In the first cylindrical portion 36, a gap generated by the difference in height in the axial direction from the second cylindrical portion 37 becomes a flow path for the lubricating oil. In the present embodiment, a gap below the first cylindrical portion 36 located closest to the inner diameter side (below the lower end of the first cylindrical portion 36, the lower end of the first cylindrical portion 36 and the second cylindrical portion 37). The gap between the lower end of the imaginary surface and the imaginary plane is a lubricating oil flow path.

  A through hole 53 is formed in the first disc portion 31. The through hole 53 serves as a flow path for the lubricating oil. The through holes 53 are provided in the first disc portion 31 located on the inner diameter side of the pocket 21 with a gap in the circumferential direction so as to face each of the pockets 21. From the viewpoint of improving the flow of the lubricating oil, it is preferable that the through holes 53 are provided at equal intervals in the circumferential direction and are symmetric with respect to the rotation axis 12. The through holes 53 may be provided at intervals in the circumferential direction so as to face a part of the plurality of pockets 21. The through hole 53 penetrates straight in the plate thickness direction, and is opened in a round hole shape in the present embodiment.

  The retainer 11 includes an outer diameter region bent portion 41 that is formed by bending an outer diameter side region of the retainer 11 toward an inner diameter side. That is, the retainer 11 is provided with an outer diameter region bent portion 41 formed by bending an area located on the outer diameter side of the pocket 21 toward the inner diameter side. The outer diameter region bent portion 41 is an upright wall portion that rises in the axial direction, and is formed to extend in a ring shape.

  The outer diameter region bent portion 41 of the present embodiment is formed by obliquely bending a region located on the outer diameter side of the pocket 21 toward the inner diameter side. Specifically, the outer diameter region bending portion 41 bends the outer diameter side end portion of the fourth disc portion 34 disposed on the outermost diameter side at a predetermined angle toward the upper side in the axial direction. It is formed.

The angle of the outer diameter region bent portion 41, that is, the angle between the surface 42 located on the inner diameter side of the outer diameter region bent portion 41 and the upper surface 43 of the fourth disc portion 34 is shown in FIGS. The angle B ₁ in 3 is 0 and may be 0 °, but is preferably an acute angle.

  The axial height H41 of the outer diameter region bent portion 41 is smaller than the axial height H37 of the second cylindrical portion 37. Specifically, the upper end of the outer diameter region bent portion 41 is positioned below the upper end of the second cylindrical portion 37. In the outer diameter region bent portion 41, the gap generated by the difference in the height in the axial direction from the second cylindrical portion 37 becomes a flow path for the lubricating oil. In the present embodiment, the upper gap of the outer diameter region bent portion 41 (the upper end of the outer diameter region bent portion 41 and the upper end of the second cylindrical portion 37 extend above the upper end of the outer diameter region bent portion 41. The space between the virtual surfaces) is a flow path for the lubricating oil.

  In the present embodiment, the axial height H41 of the outer diameter region bent portion 41 is smaller than the axial height of the third cylindrical portion 38. That is, the axial height H41 of the outer-diameter region bent portion 41 is smaller than the axial height of the third cylindrical portion 38 that is the closest cylindrical portion on the inner diameter side of the outer-diameter region bent portion 41. .

  A protruding portion 44 is provided at the tip of the outer diameter region bent portion 41 at a position aligned with each of the pockets 21. That is, the protrusion 44 is directed radially inward at a position aligned with each pocket 21. The position aligned with the pocket 21 is a position where the outer peripheral edge of the protrusion 44 overlaps the outer peripheral edge of the pocket 21. In other words, the inner edge of the outer diameter region bent portion 41 overlaps the outer edge of the pocket 21.

  The protruding portion 44 protrudes from the edge on the outer diameter side of the pocket 21 toward the inner diameter side so as to contact the end face 16 of the roller 13 accommodated in the pocket 21. That is, each protrusion 44 abuts against the end face of the roller accommodated in each pocket 21 and restricts the movement of the roller in the radially outward direction. Specifically, the protruding portion 44 has a shape extending continuously from the inner peripheral side edge of the outer diameter region bent portion 41 to the inner diameter side. That is, the outer diameter region bent portion 41 and the protruding portion 44 are integrally formed.

  The protruding portion 44 is formed so that the apex of the protruding portion 44 is located at the center in the circumferential direction of the pocket 21 at the circumferential position. Specifically, the corner portion 45 on the surface 42 side (the corner portion 45 located on the innermost diameter side of the protruding portion 44), which is the portion positioned on the innermost diameter side of the protruding portion 44, accommodates the pocket 21. The needle roller 13 is provided so as to contact the center of the end surface 16. The corner portion 45 in this case is a corner located on the fourth disc portion 34 side of the protruding portion 44.

  The cage 11 is provided with three pilot holes 51 and 52. The three pilot holes 51 and 52 serve as alignment engaging portions. In FIG. 1, one of the pilot holes is not shown. The three pilot holes 51 and 52 are provided so as to penetrate straightly in the plate thickness direction at intervals in the circumferential direction. The three pilot holes 51 and 52 are each opened in a round hole shape. The three pilot holes 51 and 52 are provided at approximately equal intervals. In this case, the pilot holes 51 and 52 are provided at intervals of 120 degrees around the rotation axis 12 of the cage 11. Specifically, the pilot holes 51 and 52 are provided at the center in the radial direction in the first disc portion 31 located on the innermost diameter side. As the diameter of the pilot holes 51 and 52, for example, φ2.5 mm or φ3 mm is selected.

  The pilot holes 51 and 52 may be omitted, and the through hole 53 for the lubricating oil flow path may be used as the pilot hole. When the pilot holes 51 and 52 and the through hole 53 are formed, the through hole 53 is preferably smaller than the pilot holes 51 and 52 from the viewpoint of strength.

  The thrust roller bearing 20 provided with such a retainer 11 has, for example, a configuration including a plurality of needle rollers 13, a bearing ring 14 located on the upper side, and a bearing ring 15 located on the lower side. When the thrust roller bearing 20 is in operation, the needle rollers 13 accommodated in the pocket 21 are the raceway surface 18 of the raceway 14 located on the upper side in the axial direction and the raceway ring located on the lower side in the axial direction. Roll on 15 raceway surfaces 19. The cage 11 rotates around the rotation axis 12. Moreover, each needle roller 13 accommodated in the pocket 21 performs a revolving motion while performing a rotation motion. Here, centrifugal force to the outer diameter side acts on the needle rollers 13. The center of the end surface 16 of the needle roller 13 has a protrusion 44 provided on the retainer 11, specifically, a corner 45 positioned on the innermost diameter side of the protrusion 44 provided on the retainer 11. Sliding contact. In other words, the corner 45 of the projecting portion 44 is a region in contact with the end face 16 of the needle roller 13.

  Here, the corner 45 is subjected to surface pressing. By this surface pressing process, the corner portion 45 does not have a sharply pointed portion, and is smoothly connected to the surface constituting the corner portion 45. For this reason, the aggression to the member of the other party which the corner | angular part 45 contacts is relieved.

  Next, a manufacturing method of the thrust roller bearing retainer 11 according to the embodiment of the present invention will be described. The thrust roller bearing retainer 11 is manufactured using a transfer press. The transfer press is a relatively inexpensive press apparatus that is not so complicated in apparatus configuration. FIG. 4 is a flowchart showing typical steps of the method for manufacturing the thrust roller bearing retainer 11 according to the embodiment of the present invention.

  Referring to FIG. 4, first, a cage material that will later become cage 11 is prepared (cage material preparation step: step S1). As this cage material, for example, a thin flat steel plate is used. Here, the cage material is a plate material cut into a substantially rectangular shape at this stage in order to form the final outer shape of the cage in the subsequent outer shape forming step (step S4). Alternatively, it may be a disk-shaped plate material.

  Next, a concavo-convex shape is formed in the thickness direction on such a cage material (concave / convex shape forming step: step S2). As a result, as shown in FIG. 2, the first cylindrical portion 36 extending in the axial direction, the first disc portion 31 extending in the outer diameter direction, connected to the first cylindrical portion 36, and the first A second cylindrical portion 37 that is continuous with the disc portion 31 and extends in the axial direction is formed. In this step (step S2), the first cylindrical portion 36, the first disc portion 31, and the second cylindrical portion 37 are formed on the inner diameter side of the pocket formed in the pocket forming step (step S5) described later. Form in the area. By carrying out this process, even in the case of the thin plate-like cage 11, the length of the cage 11 in the direction of the rotation axis can be ensured and the rollers can be appropriately held.

  In this step, specifically, the drawing is performed on the cage material. In this case, the uneven shape can be formed more efficiently. FIG. 5 is a cross-sectional view of the cage material after performing the uneven shape forming step. The cross section shown in FIG. 5 corresponds to the cross section shown in FIG. Specifically, referring to FIG. 5, the flat retainer material 56 is drawn, and the first to fourth disk portions 61 to 64 and the first to fourth cylindrical portions are formed. 66-69 are formed. And the round hole-like through-hole 57 which penetrates in a plate | board thickness direction is provided in the center. That is, in this case, the cage material 56 has a so-called mountain-valley shape that is bent a plurality of times in the axial direction.

  In this step, the axial height of the first cylindrical portion 66 is made smaller than the axial height of the second cylindrical portion 67. As a result, in the first cylindrical portion 66, the cage that uses the gap (the gap below the first cylindrical portion 66) generated by the difference in the axial height from the second cylindrical portion 67 as a flow path for the lubricating oil. It becomes.

  Next, a through hole is formed in the first disc portion 31 as a flow path for the lubricating oil (through hole forming step: step S3). In this step, a step of forming a pilot hole as an engaging portion (pilot hole forming step) may be performed together.

  FIG. 6 is an enlarged cross-sectional view showing a part of the cage material 56 after through-hole formation, and (A) shows a state in which a through-hole 54 as a lubricating oil flow path is formed. , (B) shows a state in which the pilot hole 71 is formed. The cross section shown in FIG. 6A corresponds to a portion shown in a region III in FIG. 2, and the cross section shown in FIG. 6B corresponds to a portion shown in a region VI in FIG.

  A through hole 54 as a lubricating oil flow path shown in FIG. 6 (A) and a pilot hole 71 as an engaging portion shown in FIG. 6 (B) are arranged at the center in the radial direction of the first disc portion 61. It is provided so as to penetrate straight in the thickness direction. The through holes 54 are provided at substantially equal intervals at intervals in the circumferential direction so as to face the pockets formed in the pocket forming step (step S5) described later. A total of three pilot holes 71 are provided at approximately equal intervals with an interval of 120 degrees in the circumferential direction.

  The through hole forming step for forming the through hole 54 and the pilot hole forming step may be performed at the same time, either one may be performed first, or the pilot hole forming step may be omitted. Further, in the through hole forming step, a plurality of through holes 54 may be formed by punching simultaneously, or the through holes 54 may be formed by punching one by one.

  Thereafter, the outer shape of the cage material 56 is formed (outer shape forming step: step S4). FIG. 7 is an enlarged cross-sectional view showing a part of the cage material 56 after the outer shape forming step is performed. The cross section shown in FIG. 7 corresponds to a portion shown in a region VI in FIG. 2, and is a case where the cross section shown by VII-VII in FIG. 8 is cut. In this case, specifically, the retainer material 56 is straightly punched in the thickness direction so that the final outer shape of the retainer 11 is obtained by an outer diameter region bending step (step S7) to be performed later. To form. In this case, the outer shape of the cage material 56 can be formed relatively easily and accurately. In this manner, the outer end 72 of the retainer 11, specifically, the outer end 72 of the fourth disc portion 64 is formed.

  Here, when forming the outer shape, the cage material 56 is punched out so as to form a portion that will later become the protruding portion 70. That is, in this case, the outer shape forming process is also a protruding part forming process for forming the protruding part. FIG. 8 is a view showing a part of the cage material 56 after the pocket forming step performed after the outer shape forming step. FIG. 8 corresponds to FIG. When punching out so as to form the protruding portion 70, the circumferential positioning is performed using the plurality of pilot holes 71. Specifically, a plurality of guide pins (not shown) serving as a so-called pencil-shaped positioning jig whose tip is sharp and gradually increases in diameter in a tapered shape are provided in a plurality of pilot holes 71. Insert gradually from one side in the thickness direction. Then, positioning is performed using a plurality of guide pins, and the entire outer shape is punched out by a punching device (not shown) in consideration of the position, shape, and the like of the protrusion 70. By doing so, even if the positions of the punching device and the cage material 56 are slightly deviated from the positions where the protrusions 70 are provided, the pencil-shaped guide pins with sharp tips are gradually inserted into the pilot holes 71. In the process of being done, punching can be performed by returning the cage material 56 to the correct position where the protrusion 70 should be provided with respect to the positional relationship with the punching device. In this case, since the three pilot holes 71 are provided, rotation of the cage material 56 and the like can be prevented when positioning is performed, and more reliable positioning can be performed.

  Next, a pocket is formed on the outer diameter side of the second cylindrical portion (pocket formation step: step S5). FIG. 9 is an enlarged cross-sectional view showing a part of the cage material after the pocket forming step is enlarged. The cross section shown in FIG. 9 corresponds to the portion shown in region III in FIG. 2, and is a case where the cross section is shown by IX-IX in FIG. In this case, the pocket 73 extends over a part of the second disk part 62, the third disk part 63, a part of the fourth disk part 64, and the third cylindrical part 68, and the The pocket material is formed so as to penetrate the retainer material 56 straightly in the plate thickness direction over the four cylindrical portions 69. Here, although not shown in FIG. 9, an upper roller stopper and a lower roller stopper having a shape protruding inward in the circumferential direction of the pocket 73 are formed at the same time. That is, the pocket is removed along the outer shape of the needle roller 13 accommodated in the pocket 73 in consideration of the shapes of the upper roller stopper and the lower roller stopper. A plurality of pockets 73 may be formed simultaneously by removing the pockets, or one pocket 73 may be formed one by one.

  Here, also when the pocket 73 is formed in the cage material 56, the pilot hole 71 is used to align the punching device (not shown) for punching the pocket with the cage material 56 to be punched. That is, the pocket 73 is formed with reference to the position where the pilot hole 71 is provided. Also in this case, the circumferential positioning is performed using the plurality of pilot holes 71 in the same manner as in the outer shape forming process described above. Specifically, similarly to the above, a plurality of guide pins as sharp pencil-shaped positioning jigs are prepared, and the tips are gradually inserted into the plurality of pilot holes 71 from one side in the plate thickness direction. Then, positioning is performed by a plurality of guide pins, and the pocket 73 is punched out by a punching device in consideration of the position, shape, etc. of the pocket 73. By doing so, it is possible to make the positional relationship between the formed pocket 73 and the formed protrusion 70 appropriate by aligning the circumferential phases of the provided pocket 73 and the protrusion 70. For this reason, in the positional relationship between the formed projecting portion 70 and the formed pocket 73, the projecting portion 70 can be formed accurately and efficiently, and the projecting portion 44 is accurately formed at an appropriate location. Therefore, the end surface 16 of the needle roller 13 and the protruding portion 44 can be appropriately brought into contact with each other during the operation of the bearing. A plurality of pockets 73 may be formed by punching at the same time, or the pockets 73 may be formed by punching one by one.

  In the present embodiment, a pilot hole 71 is formed in a region on the inner diameter side of the pocket 73. In this case, the pilot hole 71 can be formed by effectively using the space that the cage 11 has.

  Further, in the present embodiment, the pilot hole 71 is formed at a position avoiding the place where the pocket 73 is provided in the circumferential direction. In this case, a local decrease in strength can be avoided in the circumferential direction of the cage 11. The positional relationship with the pilot hole 71 is arbitrarily determined. In this case, specifically, the plurality of pockets 73 are formed such that the pilot hole 71 is disposed at a position corresponding to the center in the circumferential direction between the adjacent pockets 73.

  Next, as shown in FIGS. 8 and 9, an annular groove 79 is formed on the outer diameter side of the pocket 73 in the cage material (groove forming step: step S6). In this step (step S6), in the outer diameter region bending step (step S7), which will be described later, a groove 79 is formed at a position serving as a bending start point in order to form the outer diameter region bent portion 41. By performing the groove forming step (step S6), the outer diameter side region of the cage material 56 can be easily bent inward in the outer diameter region bending step (step S7) described later. (Step S6) may be omitted. Further, the order of steps S4 to S6 is not particularly limited.

  Next, a region located on the outer diameter side of the pocket 73 in the cage material 56 is bent toward the inner diameter side to form an outer diameter region bent portion (outer diameter region bending step: step S7). In this step, the outer diameter region bent portion is formed so that the axial height is smaller than the axial height of the second cylindrical portion 67. In the outer-diameter region bent portion, a cage that uses a gap (above the outer-diameter region bent portion) generated by the difference in height in the axial direction from the second cylindrical portion 67 serves as a lubricant flow path.

  In this step, it is preferable that the outer diameter region bent portion is formed by bending the inner diameter side obliquely at an acute inclination angle. Further, when the groove forming configuration (step S7) is performed, the outer diameter side bent portion is formed by bending the outer diameter side region of the cage material 56 using the groove 79 as a bending start point.

FIG. 10 is an enlarged cross-sectional view showing a part of the cage material in an intermediate stage of the outer diameter region bending process. 11 and 12 are enlarged cross-sectional views showing a state in which the outer diameter region bending step is performed. 13 and 14 are enlarged cross-sectional views showing a part of the cage material 56 after the outer diameter region bending step is enlarged. The cross section shown in FIGS. 10 and 13 corresponds to a portion shown in a region VI in FIG. The cross section shown in FIG. 14 corresponds to the portion shown in region III in FIG. The cross section shown in FIGS. 11 and 12 shows the positional relationship between the holding member 101, 102 and the pressing member 103, the outer diameter side region of the cage material 56 corresponding to the portion shown in the region VI in FIG. Show. Here, as shown in FIG. 10, the end 72 on the outer diameter side of the cage material 56 extending in an annular shape is once bent over the entire region so as to be straight in the thickness direction. That is, the angle B ₂ between the surface 75 located on the inner diameter side of the outer diameter region bent portion 74 and the upper surface 76 of the fourth disc unit 64 is approximately at right angles. Although the method of bending at a right angle is not particularly limited, for example, it is performed as follows. As shown in FIG. 11, a region excluding the region on the outer diameter side of the fourth disc portion 64 in the cage material 56 is sandwiched and held in the vertical direction by the holding members 101 and 102, and the fourth disc portion 64 is held. The pressing member 103 is disposed under the outer diameter side region. Next, as shown in FIG. 12, by pushing up the pressing member 103, the outer diameter region bent portion 74 can be bent at a right angle with respect to the fourth disc portion 64.

Thereafter, as shown in FIGS. 13 and 14, the outer diameter region bent portion 74 is bent toward the inner diameter side to form the outer diameter region bent portion 74. The angle of bending (inclination angle), that is, the angle between the surface 75 located on the inner diameter side of the outer diameter region bending portion 74 and the upper surface 76 of the fourth disc portion 64 is shown in FIGS. represented by an angle _{B 3} in 14. Angle _{B 3} corresponds to the angle _{B 1} described above. That is, the angle B ₁ and the angle B ₃ are in the same relationship. Angle _{B 1} and the angle _{B 3} is preferably an acute angle.

  In this case, since the protrusion 70 is provided at the center in the circumferential direction of the pocket 73 in the circumferential positional relationship, the protrusion 70 is formed at an appropriate location. Specifically, in the protruding portion 70, the corner portion 77 located on the fourth disc portion 64 side comes into contact with the center of the end surface 16 of the needle roller 13. Finally, a surface pressing process is performed on a region of the protrusion 70 that contacts the end surface 16 of the needle roller 13. Thus, the thrust roller bearing retainer 11 having the configuration shown in FIGS. 1 to 3 is manufactured.

  In addition, a step of bending the retainer material 56 bent toward the inner diameter side so that the outer diameter side end 72 of the retainer material 56 extending in an annular shape is straight in the plate thickness direction, and a step of performing a surface pressing process May be carried out continuously. FIG. 15 is an enlarged cross-sectional view illustrating a state in which the outer diameter region bending step is performed. FIG. 16 is an enlarged cross-sectional view illustrating a state in which the surface pressing process is performed. FIG. 17 is an enlarged cross-sectional view showing the distal end of the outer diameter region bent portion after performing the surface pressing process. Specifically, as shown in FIG. 15, in the cage material 56 that is bent so that the outer diameter region bent portion 74 is perpendicular to the fourth disk portion 64, the outer diameter region bent portion 74 Also, the inner diameter side region is sandwiched and held by the dies 104 and 105 in the vertical direction. At this time, the outer diameter side edge of the upper mold 104 is positioned closer to the inner diameter side than the outer diameter side edge of the lower mold 105. Further, the mold 106 that pressurizes the outer diameter region bent portion 74 from the upper side to the lower side is disposed so as to be in contact with the surface 78 located on the outer diameter side of the outer diameter region bent portion 74. The mold 106 is abutted with the upper mold 104 and extends in the vertical direction on the inner diameter side end face 106 a, the horizontal surface 106 b that is continuous with the inner diameter side end face 106 a and extends on the outer diameter side, and the outer diameter area bending portion 74. A portion 106d that has an inner diameter side surface 106c that abuts the outer diameter side surface 78 and extends in the vertical direction has a round (R) shape. In this state, when the mold 106 is moved downward so that the inner diameter side end face 106a is along the outer diameter side end face 104a of the mold 104, the outer diameter area bent portion 74 is guided to the inner diameter side by being guided by the round portion 106d. It can be bent so as to be inclined toward the. Thereafter, as shown in FIG. 16, the mold 104 is moved further downward, the outer diameter side end face 104 a of the mold 104 is smoothed at the corner located on the inner diameter side in the outer diameter region bent portion 74, and the mold 106 is moved. In the horizontal plane 106b, the corner located on the outer diameter side in the outer diameter region bent portion 74 is smoothed. Thereby, as shown in FIG. 17, the protrusion part 70 by which the area | region which contacts the roller end surface is surface-pressed can be formed.

  As described above, according to the thrust roller bearing retainer 11 and the manufacturing method thereof according to the present embodiment, the first cylindrical portions 36 and 66, the first disc portions 31 and 61, and the second cylindrical portion. 37 and 67 form a concavo-convex shape in the thickness direction on the inner diameter side of the pockets 21 and 73. By forming the concavo-convex shape, the strength of the cage 11 can be increased and bending can be prevented. However, the flow of the lubricating oil becomes worse due to the uneven shape. Therefore, in the present embodiment, even in the cage 11 having such a concavo-convex shape, the height H36 in the rotation axis direction of the first cylindrical portions 36, 66 constituting the concavo-convex shape is set to the second cylinder. The gaps caused by the difference in height in the rotation axis direction between the first cylindrical portions 36 and 66 are made smaller than the height H37 in the rotation axis direction of the portions 37 and 67 to serve as a lubricating oil flow path. For this reason, the flow of the lubricating oil can be formed toward the outer diameter side by the centrifugal force, and the circulation of the lubricating oil can be improved. Therefore, it is possible to improve the circulation of the lubricating oil with a small amount of lubricating oil (dilute lubricating state) without increasing the amount of the lubricating oil.

  In the thrust roller bearing retainer and the manufacturing method thereof according to the present embodiment, the rotation axis direction height H41 of the outer diameter region bent portions 41, 74 is greater than the rotation axis direction height H37 of the second cylindrical portions 37, 67. Is preferably small. That is, the rotational axis direction height H36 of the first cylindrical portions 36 and 66 located closest to the inner diameter side and the rotational axis direction height H41 of the outer diameter region bent portions 41 and 74 located closest to the outer diameter side are determined by the cage. Is smaller than the height H37 of the second cylindrical portion 37, 67 constituting the maximum height in the direction of the rotation axis. Thereby, the clearance gap which arises by the difference in the rotating shaft direction height in the outer diameter area | region bending parts 41 and 74 can also be made into the flow path of lubricating oil. Therefore, the circulation of the lubricating oil can be further improved in the lean lubrication state.

  Here, in the above embodiment, the corner portion located on the fourth disc portion side of the projecting portion is in contact with the center of the end face of the needle roller housed in the pocket. It is good also as the following structures. FIG. 18 is a cross-sectional view showing a part of the cage in this case. FIG. 18 corresponds to a cross section of the cage shown in FIG.

  Referring to FIG. 18, a thrust roller bearing retainer 81 according to another embodiment of the present invention is provided with a protruding portion 83 at a position where a pocket 85 is formed in an outer diameter region bent portion 82. ing. The protruding portion 83 is configured to come into contact with the center of the end surface 16 of the needle roller 13 accommodated in the pocket 85 at a corner portion 84 opposite to the fourth disc portion 86 side. The corner portion 84 is subjected to surface pressing. In order to obtain such a configuration, it is preferable to perform processing using a jig having an angle along the corner 84 in the outer diameter region bending step.

  The position where the pilot hole is provided may be a position where the pocket is provided. That is, one of the plurality of pockets may be used as a pilot hole. FIG. 19 is a diagram showing a part of the cage in this case. Referring to FIG. 19, a thrust roller bearing retainer 91 according to still another embodiment of the present invention includes a plurality of pockets 92 and a pillar portion 93 positioned between two adjacent pockets 92. A pilot hole 95 is provided between the pocket 92 and the pocket 92 at the position of the column portion 94 where the pocket 92 is to be formed. The pilot holes 95 have a so-called alternative shape in which one of the plurality of pockets 92 provided at equal intervals in the circumferential direction is replaced with the pilot hole 95.

  Although the pilot hole is provided as the engaging portion, the present invention is not limited to this, and the engaging portion may be configured by another configuration, for example, a notch.

  Further, in the above-described embodiment, the through hole 53 and the pilot hole 51 as the lubricating oil flow path shown in FIG. 1 are configured to penetrate straight in the thickness direction. For example, you may penetrate so that the wall surface of the through-hole 53 and / or the pilot hole 51 may become taper shape. In addition, a rectangular hole, a triangular hole, or the like can be employed regardless of the round hole shape.

  In the above embodiment, the drawing process is performed in the uneven shape forming step. However, the present invention is not limited to this, and the uneven shape may be formed by a process other than the drawing process, for example, a bending process.

  In the above embodiment, the cage is configured to form an uneven shape in the thickness direction, but the first cylindrical portion 36, the first disc portion 31, and the second cylinder If the portion 37 is formed in the region on the inner diameter side of the pocket 21, the region on the same diameter and outer diameter side as the pocket 21 may not have an uneven shape in the plate thickness direction.

  Further, in the above embodiment, the thrust roller bearing provided with such a cage may be configured not to include a race ring. Furthermore, you may decide to use rollers other than a needle roller, for example, a rod-shaped roller.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above-described embodiment but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

  The thrust roller bearing retainer and the manufacturing method thereof according to the present invention are required in the case where a thrust roller bearing retainer having good performance and a more efficient production of such a thrust roller bearing retainer are required. , Effectively used.

  11, 81, 91 Cage, 12 axis of rotation, 13 rollers, 14, 15 raceway, 16, 17 end face, 18, 19 raceway, 20 thrust roller bearing, 21, 73, 85, 92 pocket, 22, 53, 54, 57 Through-hole, 23, 24 annular part, 25, 93, 94 pillar part, 26, 27, 28 roller stopper part, 31, 32, 33, 34, 61, 62, 63, 64, 86 disc part, 36, 37, 38, 39, 66, 67, 68, 69 Cylindrical part, 41, 74, 82 Outer diameter region bent part, 42, 43, 75, 76, 78 surface, 44, 70, 83 Protruding part, 45, 77,84 Corner, 51,52,71,95 Pilot hole, 56 Cage material, 72 End, 79 Groove, 101,102 Holding member, 103 Pressing member, 104,105,106 Mold, 104a Outer diameter side End face, 106a Inner diameter side end face, 106b Horizontal plane, 106c Inner diameter side face, 106d portion.

Claims (8)

A thrust roller bearing retainer provided in a thrust roller bearing and provided with a plurality of pockets for accommodating rollers,
A first cylindrical portion extending in the rotation axis direction;
A disk portion extending in the outer diameter direction, connected to one end portion in the rotational axis direction of the first cylindrical portion;
A second cylindrical portion that is connected to the outer diameter side end of the disc portion and extends to the other side in the rotational axis direction;
The first cylindrical portion, the disc portion, and the second cylindrical portion are formed in a region on the inner diameter side of the pocket,
An outer diameter region bent portion formed by bending an area located on the outer diameter side of the pocket toward the inner diameter side;
It is provided at the tip of the outer diameter region bent portion at a position aligned with each of the pockets, and protrudes from the edge on the outer diameter side of the pocket toward the inner diameter side so as to contact the end face of the roller accommodated in the pocket. And further comprising a protrusion,
The height of the first cylindrical portion in the rotational axis direction is smaller than the height of the second cylindrical portion in the rotational axis direction , and becomes a flow path for lubricating oil on the other side of the first cylindrical portion in the rotational axis direction. A gap is formed,
The disc portion that extends in the outer diameter direction and continues to the one end portion in the rotational axis direction of the first cylindrical portion is provided with a through hole that penetrates straight in the thickness direction and serves as a flow path for the lubricating oil. Thrust roller bearing cage.   2. The thrust roller bearing retainer according to claim 1, wherein a height in the rotation axis direction of the outer diameter region bent portion is smaller than a height in the rotation axis direction of the second cylindrical portion.   The thrust roller bearing retainer according to claim 1 or 2, wherein a region of the protruding portion that contacts the end surface of the roller is subjected to surface pressing.   The thrust roller bearing retainer according to any one of claims 1 to 3, wherein the protrusion is formed so that an outer diameter side region of the retainer is obliquely bent toward an inner diameter side. A method of manufacturing a thrust roller bearing retainer provided in a thrust roller bearing and provided with a plurality of pockets for accommodating rollers,
A step of preparing a cage material to be a cage;
For the cage material, forming a concavo-convex shape in the plate thickness direction;
Forming the pocket with respect to the cage material,
In the step of forming the concavo-convex shape, the first cylindrical portion extending in the rotation axis direction, the disk portion extending in the outer diameter direction, connected to the one end portion in the rotation axis direction of the first cylindrical portion , and the circle contiguous with the outer diameter side end portion of the plate portion, the second forming a cylindrical portion, the first said rotation axis direction height of the cylindrical portion of the second cylindrical portion of the rotary shaft extending in the axial direction other side The concavo-convex shape is formed so that a gap serving as a flow path for the lubricating oil is formed on the other side in the rotation axis direction of the first cylindrical portion, the height being smaller than the direction height.
In the step of forming the pocket, the pocket is formed on the outer diameter side of the second cylindrical portion,
A step of forming an outer shape of the cage material including a portion that becomes a protruding portion that protrudes toward the inner diameter side from an outer edge on the outer diameter side of the pocket so as to contact an end surface of the roller accommodated in the pocket. When,
Bending the region positioned on the outer diameter side of the pocket in the cage material to the inner diameter side to form an outer diameter region bent portion;
A step of forming a through-hole that penetrates straight in the plate thickness direction and serves as a flow path for the lubricating oil in the disc portion that extends in the outer diameter direction and continues to the one end portion in the rotation axis direction of the first cylindrical portion. A method of manufacturing a cage for a thrust roller bearing, further comprising:   In the step of forming the outer diameter region bent portion, the outer diameter region bent portion is formed such that the height in the rotation axis direction of the outer diameter region bent portion is smaller than the height in the rotation axis direction of the second cylindrical portion. The manufacturing method of the cage | basket of the thrust roller bearing of Claim 5 formed.   The method of manufacturing a cage for a thrust roller bearing according to claim 5 or 6, further comprising a step of performing a surface pressing process on a region of the protruding portion that contacts the end surface of the roller.   The thrust according to any one of claims 5 to 7, wherein in the step of forming the outer diameter region bent portion, a region of the retainer material located on the outer diameter side of the pocket is obliquely bent toward the inner diameter side. A method for manufacturing a roller bearing cage.

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