Cage-equipped needle roller

Abstract

A base R section (20) is formed on the axial inner side of the base of a roller stopper piece (10). An inner diameter-side R section (19) is formed at a portion where the radial inner-side surface (17) of a pillar-inclined part (8) and the radial inner-side surface (18) of a pillar edge section (7) intersect. The base R section (20) is formed at a position offset axially outward from the inner diameter-side R section (19) such that the axial range of the base R section (20) and the axial range of the inner diameter-side R section (19) do not overlap.

Description

Needle roller and cage assembly

[0001] The present invention relates to a needle roller and cage assembly and a revolution mechanism using the needle roller and cage assembly.

[0002] The applicant of the present application has already proposed a needle roller with cage for supporting planet gears of a planetary gear mechanism, as described in Patent Document 1.

[0003] The planetary gear mechanism has a sun gear with external teeth, a ring gear with internal teeth formed in an annular shape surrounding the sun gear, multiple planet gears incorporated between the outer periphery of the sun gear and the inner periphery of the ring gear so as to mesh with both the sun gear and the ring gear, and a planet carrier that supports the multiple planet gears so that they can rotate and revolve around their axes.

[0004] The planetary carrier has a carrier body that revolves at a fixed position and multiple planetary shafts attached at positions radially spaced from the center of revolution of the carrier body. The planetary shafts are fixed to the carrier body so as to revolve integrally with the carrier body. Planetary gears are rotatably attached to the outer periphery of the planetary shafts via needle rollers with cages.

[0005] The needle roller and cage assembly that supports the planetary gear includes a plurality of needle rollers spaced apart in the circumferential direction and a cage that holds the plurality of needle rollers. The cage has a pair of annular portions that face each other in the axial direction with the plurality of needle rollers between them, and a plurality of bar portions that pass between circumferentially adjacent needle rollers and connect the pair of annular portions. The pair of annular portions and the circumferentially adjacent bar portions form pockets that house the needle rollers.

[0006] In this planetary gear mechanism, when rotation is input to the sun gear, the planet gears rotate on their axes while revolving together with the planet carrier. Unlike typical needle roller and cage assemblies that rotate at fixed positions, centrifugal force is generated by the orbital motion of the needle rollers of the needle roller and cage assemblies that support the planet gears. The centrifugal force generated by this orbital motion in the needle rollers subjects each column portion of the cage to a load that alternates between being pressed by a needle roller located on one circumferential side of the column portion and being pressed by a needle roller located on the other circumferential side of the column portion. Therefore, tensile stress and compressive stress are repeatedly applied to the corners of the pockets that house the needle rollers, making the cage susceptible to fatigue failure.

[0007] Therefore, in Patent Document 1, in order to prevent fatigue failure of the cage, arc-shaped corner R portions (recessed portions) are formed in the corners of the pockets that house the needle rollers when viewed from the radial direction, and the radius of curvature of these corner R portions is set to be large, thereby alleviating stress concentration in the corners of the pockets.

[0008] JP 2009-68677 A

[0009] The inventors of the present application have investigated ways to further improve the durability of the cage of the needle roller and cage assembly that supports the planet gears of a planetary gear mechanism, as in Patent Document 1. As a result, they have noticed that in the cage of Patent Document 1, there are two other locations besides the corners of the pockets that house the needle rollers where high stress may be generated in the cage when centrifugal force generated in the needle rollers due to revolution acts on the column portions of the cage, and that the proximity of these two locations increases stress, making the cage more susceptible to fatigue failure.

[0010] In other words, in the cage of the needle roller and cage assembly of Patent Document 1, each column portion has a pair of column end portions extending axially inward from a pair of annular portions with a constant outer diameter, a pair of column inclined portions extending axially inward from the pair of column end portions at an angle so that the outer diameter gradually decreases as it extends axially inward, and a column central portion connecting the pair of column inclined portions. The column end portions are formed with roller stop pieces that protrude circumferentially to restrict radial outward movement of the needle rollers.

[0011] In a cage with this configuration, centrifugal force is generated in the needle rollers due to the orbital motion, and when this centrifugal force causes the needle rollers to press against the column portions of the cage, the needle rollers press the column central portions (or column inclined portions) in the circumferential direction of the cage, generating a moment load in the column portions that twists the column inclined portions around the column ends. This moment load then generates high stresses at the intersections of the radially inner surfaces of the column inclined portions and the radially inner surfaces of the column ends, and at the axially inner portions of the bases of the roller stop pieces that protrude circumferentially from the column ends.

[0012] In conventional needle roller and cage assemblies such as those disclosed in Patent Document 1, the axially inner portion of the base of the roller stopper piece and the portion where the radially inner surface of the pillar inclined portion and the radially inner surface of the pillar end intersect are positioned close to each other. Therefore, when a moment load that twists the pillar inclined portion around the pillar end is generated as a result of the needle rollers pressing against the pillar portion of the cage, the high stress generated at the axially inner portion of the base of the roller stopper piece and the high stress generated at the portion where the radially inner surface of the pillar inclined portion and the radially inner surface of the pillar end intersect overlap, and it was noticed that fatigue failure of the cage is likely to occur.

[0013] In the needle roller and cage assembly of Patent Document 1, a root R portion that is arc-shaped when viewed from the radial direction is formed on the axially inner part of the root of the roller stopper piece that protrudes circumferentially from the column end, and this root R portion relieves stress concentration on the axially inner part of the root of the roller stopper piece. However, because the root R portion and the part where the radially inner surface of the column inclined portion and the radially inner surface of the column end intersect are in close proximity to each other, it is ultimately not possible to fundamentally solve the above problem.

[0014] The problem to be solved by this invention is to provide a needle roller and cage assembly that has excellent durability when used in an application where centrifugal force due to revolution motion is generated in the needle rollers.

[0015] In order to solve the above problems, the present invention provides a needle roller and cage assembly having the following configuration. [Configuration 1] A needle roller and cage comprising: a plurality of needle rollers arranged at intervals in the circumferential direction; and a cage for holding the plurality of needle rollers, wherein the cage has a pair of annular portions facing each other in the axial direction with the plurality of needle rollers therebetween, and a plurality of pillar portions passing between the circumferentially adjacent needle rollers and connecting the pair of annular portions, wherein each of the pillar portions has a pair of pillar end portions extending axially inward from the pair of annular portions with a constant outer diameter, a pair of pillar inclined portions extending axially inward from the pair of pillar end portions at an angle such that the outer diameter gradually decreases as it extends axially inward from the pair of pillar end portions, and a pillar central portion connecting the pair of pillar inclined portions, wherein the pillar end portions are formed with roller stop pieces that protrude circumferentially so as to restrict radially outward movement of the needle rollers, wherein a root R portion that is arc-shaped as viewed from the radial direction is formed on the axially inner side of the root of the roller stop piece, and an inner diameter side R portion that is arc-shaped as viewed from the circumferential direction is formed at a portion where the radially inner surface of the pillar inclined portion and the radially inner surface of the pillar end portion intersect, the root R portion is formed axially outward of the inner diameter side R portion so that the axial range in which the root R portion is formed does not overlap with the axial range in which the inner diameter side R portion is formed.

[0016] When this configuration is adopted, a base R portion that is arc-shaped when viewed radially is formed on the axially inside of the base of the roller stop piece that protrudes circumferentially from the pillar end, and an inner diameter side R portion that is also arc-shaped when viewed circumferentially is formed at the portion where the radially inner surface of the pillar inclined portion and the radially inner surface of the pillar end intersect.Therefore, when a moment load is generated that twists the pillar inclined portion around the pillar end as a result of the needle rollers pressing against the pillar portion of the cage, stress concentration is alleviated at the axially inside portion of the base of the roller stop piece (base R portion), and stress concentration is also alleviated at the portion where the radially inner surface of the pillar inclined portion and the radially inner surface of the pillar end intersect (inner diameter side R portion). Furthermore, the root R portion is formed at a position offset axially outward from the inner diameter side R portion so that the axial range where the root R portion is formed does not overlap with the axial range where the inner diameter side R portion is formed. Therefore, when a moment load is generated that twists the column inclined portion around the column end by the needle rollers pressing against the column portion of the cage, it is possible to prevent the high stress generated at the axially inner part of the root of the roller stop piece (root R portion) from overlapping with the high stress generated at the part where the radially inner surface of the column inclined portion and the radially inner surface of the column end intersect (inner diameter side R portion), thereby keeping the maximum stress low. Therefore, when used in applications where centrifugal force due to revolution motion is generated on the needle rollers, the cage is less likely to suffer fatigue failure and has excellent durability.

[0017] [Configuration 2] The needle roller and cage assembly according to Configuration 1, wherein the axially outer ends of the roller stop pieces and the annular portion are connected via rounded corners that are arc-shaped when viewed from the radial direction.

[0018] By adopting this configuration, when a moment load is generated that twists the inclined column portion around the column end portion due to the needle roller pressing against the column portion of the retainer, stress concentration in the portion (corner R portion) where the axially outer end of the roller stop piece and the annular portion are connected can be alleviated.

[0019] [Configuration 3] A needle roller and cage according to Configuration 1 or 2, wherein the annular portion has a cylindrical outer peripheral surface, the column end portion has a partially cylindrical radially outer surface having the same outer diameter as the outer peripheral surface of the annular portion, the roller stop piece has a partially cylindrical radially outer surface formed continuously with the radially outer surface of the column end portion, and the outer peripheral surface of the annular portion, the radially outer surface of the column end portion, and the radially outer surface of the roller stop piece are guided surfaces of the cage.

[0020] When this configuration is adopted, the cage is of an outer diameter guide type.

[0021] [Configuration 4] The needle roller and cage assembly according to any one of Configurations 1 to 3, wherein each of the annular portions has a welded portion joined in the circumferential direction by welding.

[0022] When this configuration is adopted, the cage becomes a welded cage, which is manufactured by bending a steel strip into a ring shape and welding both ends of the steel strip, thereby keeping the manufacturing cost of the cage low.

[0023] [Configuration 5] The needle roller and cage assembly according to Configuration 4, wherein each of the annular portions has a cylindrical portion and an inward flange portion extending radially inward from an axial outer end of the cylindrical portion, and the radial thickness of the column central portion is 0.5 mm to 1.5 mm.

[0024] When this configuration is adopted, the cage becomes an M-shaped cage. In this case, if the radial thickness of the column center portion is set to 0.5 mm or more, the strength of the cage can be ensured, and if the radial thickness of the column center portion is set to 1.5 mm or less, the strip steel, which is the material for the cage, can be easily bent into a ring shape when manufacturing the cage, making it easier to ensure the dimensional precision of the cage.

[0025] The present invention also provides a revolution mechanism using the above-mentioned needle roller and cage assemblies, having the following configuration: [Configuration 6] A revolution mechanism having: a revolution member that revolves at a fixed position, a planetary shaft that is arranged at a position radially spaced from the center of revolution of the revolution member and revolves integrally with the revolution member, and a rotation member that is rotatably attached to the outer periphery of the planetary shaft via the needle roller and cage assemblies described in any one of configurations 1 to 5.

[0026] In the needle roller and cage assembly of this invention, the root R portion is formed at a position offset axially outward from the inner diameter side R portion so that the axial range in which the root R portion is formed does not overlap with the axial range in which the inner diameter side R portion is formed. Therefore, when a moment load is generated that twists the column inclined portion around the column end by the needle roller pressing against the column portion of the cage, it is possible to prevent the high stress generated at the axially inner part of the root of the roller stop piece (root R portion) from overlapping with the high stress generated at the part where the radially inner surface of the column inclined portion and the radially inner surface of the column end intersect (inner diameter side R portion), and it is possible to keep the maximum stress low. Therefore, when used in applications in which centrifugal force due to revolution motion is generated on the needle rollers, fatigue failure of the cage is resistant and it has excellent durability.

[0027] 1. A cross-sectional view taken along line II-II in FIG. 1. A cross-sectional view taken along line III-III in FIG. 1. An enlarged view of the vicinity of the roller stop piece in FIG. 3. An explanatory diagram of a method for identifying the starting position of the base R portion. A perspective view of the vicinity of the roller stop piece shown in FIG. 4. A diagram showing a planetary gear mechanism using the needle roller and cage assembly of FIG. 1. A cross-sectional view of the planet gear portion of FIG. 7.

[0028] 1 and 2 show a needle roller and cage assembly 1 according to an embodiment of the present invention. This needle roller and cage assembly 1 has a plurality of needle rollers 2 and a cage 3 that holds the plurality of needle rollers 2.

[0029] The needle rollers 2 are rollers with a cylindrical outer periphery. The needle rollers 2 are arranged at intervals in the circumferential direction, with the axis of the needle roller 2 parallel to the axis of the cage 3. The diameter of the needle rollers 2 is 6 mm or less, and the axial length of the needle rollers 2 is between three and ten times the diameter of the needle rollers 2. The outer peripheries of the needle rollers 2 may be crowned (the generatrix shape of the outer periphery of the needle rollers 2 is made a convex curve with a slight curvature) to prevent stress concentration on the outer peripheries of the end portions of the needle rollers 2 due to installation errors, etc.

[0030] The cage 3 has a pair of annular portions 4 that face each other in the axial direction with a plurality of needle rollers 2 between them, and a plurality of column portions 5 that connect the pair of annular portions 4 by passing between circumferentially adjacent needle rollers 2. The pair of annular portions 4 and the column portions 5 that are circumferentially adjacent to each other form pockets 6 that accommodate the needle rollers 2.

[0031] 1 and 3 , the column portion 5 has a pair of column end portions 7 extending axially inward with a constant outer diameter from the pair of annular portions 4, a pair of column inclined portions 8 extending axially inward from the pair of column end portions 7 at an angle such that the outer diameter gradually decreases as the column extends axially inward, and a column central portion 9 connecting the pair of column inclined portions 8. The axially inward direction is the direction from the annular portions 4 toward the column portion 5, and the axially outward direction is the direction from the column portion 5 toward the annular portion 4.

[0032] As shown in Figure 3, the outer diameter D2 of the column central portion 9 is smaller than the outer diameter D1 of the column end portion 7. The inner diameter of the column end portion 7 is larger than the diameter of a circle connecting the centers of the needle rollers 2 (the pitch circle diameter of the needle rollers 2). The radial thickness t of the column central portion 9 is set in the range of 0.5 mm to 1.5 mm. As shown in Figure 2, the column central portion 9 has a circumferential width that is larger than the circumferential width of the column inclined portion 8, and the circumferential spacing of the needle rollers 2 is maintained by guiding the needle rollers 2 at both circumferential ends of the column central portion 9.

[0033] As shown in Figure 6, a roller stop piece 10 that protrudes in the circumferential direction is formed on the column end portion 7. As shown in Figure 2, the roller stop piece 10 is formed to extend in the circumferential direction radially outward of the diameter of a circle connecting the centers of each needle roller 2 (the pitch circle diameter of the needle roller 2), so as to restrict radially outward movement of the needle rollers 2 and prevent the needle rollers 2 from falling out radially outward from the pocket 6.

[0034] As shown in Fig. 3, one of the pair of annular portions 4 extends circumferentially along one of both end faces of the plurality of needle rollers 2, and the other annular portion 4 extends circumferentially along the other end faces of the plurality of needle rollers 2. Each annular portion 4 has a cylindrical portion 11 and an inward flange portion 12 extending radially inward from the axial outer end of the cylindrical portion 11. As shown in Fig. 1, each annular portion 4 has a welded portion 13 that is joined circumferentially by welding.

[0035] As shown in Figure 6, the annular portion 4 has a cylindrical outer peripheral surface 14. The column end portion 7 has a partially cylindrical radially outer surface 15 with the same outer diameter as the outer peripheral surface 14 of the annular portion 4. The roller stopper pieces 10 have partially cylindrical radially outer surfaces 16 formed circumferentially continuous with the radially outer surface 15 of the column end portion 7. The outer peripheral surface 14 of the annular portion 4, the radially outer surface 15 of the column end portion 7, and the radially outer surface 16 of the roller stopper pieces 10 form guided surfaces that are guided by the inner periphery of a member (such as the planetary gear 31 in Figure 8) attached radially outside the needle roller and cage assembly 1. The guided surfaces are ground surfaces with a surface roughness of Ra 1.0 µm or less.

[0036] As shown in FIG. 4 , an inner diameter side R portion 19 is formed at the intersection between the radially inner surface 17 of the column inclined portion 8 and the radially inner surface 18 of the column end portion 7. The inner diameter side R portion 19 has a shape curved in a concave arc when viewed from the circumferential direction. Furthermore, a root R portion 20 is formed on the axially inner side of the root of the roller locking piece 10 (on the right side in the figure). The root R portion 20 has a shape curved in a concave arc when viewed from the radial direction, smoothly connecting the axially inner surface 21 of the roller locking piece 10 and the circumferential end face 22 of the column end portion 7. The radius of curvature of the root R portion 20 is set to be equal to or greater than ¼ (preferably equal to or greater than ⅓) of the circumferential length of the roller locking piece 10. Furthermore, the axially outer end (left side in the figure) of the roller locking piece 10 and the annular portion 4 are connected via a corner R portion 23 that is arc-shaped when viewed from the radial direction.

[0037] The root R portion 20 is formed at a position shifted axially outward (to the left in the drawing) from the inner diameter side R portion 19 so that the axial range in which the root R portion 20 is formed does not overlap with the axial range in which the inner diameter side R portion 19 is formed. In other words, the axial end face of the pocket 6 is set as a reference point O, and when an axial distance L1 from the reference point O to the start position of the root R portion 20 and an axial distance L2 from the reference point O to the start position of the inner diameter side R portion 19 are measured, the positional relationship between the root R portion 20 and the inner diameter side R portion 19 is set so that the axial distance L1 is smaller than the axial distance L2.

[0038] Here, when measuring the axial distance L1, as shown in Fig. 5 , a straight line tangent to the root R portion 20 (a straight line along the circumferential end face 22 of the column end portion 7) is assumed, and a position 10 µm circumferentially away from this straight line is taken as the start position S of the root R portion 20. In the figure, the distance of 10 µm is exaggerated for ease of understanding, but the actual 10 µm is much smaller than the distance shown in the figure. Similarly, when measuring the axial distance L2, a straight line tangent to the inner diameter side R portion 19 (a straight line along the radially inner surface 18 of the column end portion 7) is assumed, and a position 10 µm radially inward from this straight line is taken as the start position of the inner diameter side R portion 19.

[0039] As shown in Figure 2, the roller stop piece 10 has a radially inner surface 24 that extends in the circumferential direction and is formed continuously with the radially inner surface 18 of the column end portion 7, and a roller stop surface 25 that slopes radially outward in the circumferential direction from the radially inner surface 24.

[0040] This cage 3 can be manufactured as follows: That is, first, a flat, band-like steel strip is formed into an M-shaped cross section (forming process), pockets 6 for accommodating needle rollers 2 are formed in the steel strip with the M-shaped cross section (pocket punching process), the steel strip with the pockets 6 formed therein is cut to a length corresponding to the circumferential length of the cage 3 (cutting process), the cut steel strip is bent into a cylindrical shape (bending process), both ends of the bent cylindrical steel strip are joined by welding (welding process), and then outer periphery grinding, heat treatment, etc. are performed to manufacture the cage.

[0041] This needle roller and cage assembly 1 can be used as a needle roller and cage assembly that supports a planet gear 31 of a planetary gear mechanism 30 shown in Fig. 7. The planetary gear mechanism 30 is, for example, part of a transmission that changes the rotation speed of a prime mover (engine, electric motor, etc.) for running a vehicle.

[0042] The planetary gear mechanism 30 has an externally toothed sun gear 32, an internally toothed ring gear 33 formed in a ring shape surrounding the sun gear 32, a plurality of planetary gears 31 incorporated between the outer periphery of the sun gear 32 and the inner periphery of the ring gear 33 so as to mesh with both the sun gear 32 and the ring gear 33, and a planetary carrier 34 that supports the plurality of planetary gears 31 so that they can rotate and revolve around their own axes.

[0043] The planetary carrier 34 has a carrier body 35 that revolves at a fixed position, and a plurality of planetary shafts 36 attached at positions radially spaced from the center of revolution of the carrier body 35. The planetary shafts 36 are fixed to the carrier body 35 so as to revolve integrally with the carrier body 35. The planetary gears 31 are rotatably attached to the outer peripheries of the planetary shafts 36 via needle rollers with cages 1.

[0044] As shown in Figure 8, the needle rollers 2 that make up the needle roller and cage assembly 1 are in rolling contact with the outer periphery of the planetary shaft 36 and the inner periphery of the planetary gear 31. In addition, the cage 3 that makes up the needle roller and cage assembly 1 is guided by the inner periphery of the planetary gear 31, thereby being positioned in the radial direction.

[0045] In the planetary gear mechanism 30 shown in Figure 7, when rotation of a prime mover (not shown) is input to the sun gear 32, the planet gear 31 rotates on its axis while revolving integrally with the planet carrier 34. At this time, unlike typical needle rollers with cages that rotate at a fixed position, centrifugal force is generated in each needle roller 2 shown in Figure 2 due to the orbital motion. The centrifugal force generated in the needle rollers 2 by this orbital motion causes each column portion 5 of the cage 3 to be subjected to a load such that it is alternately pressed by needle rollers 2 located on one circumferential side of the column portion 5 and pressed by needle rollers 2 located on the other circumferential side of the column portion 5. At this time, a moment load is generated in the column portion 5 such that it twists the column inclined portion 8 around the column end portion 7, as the needle rollers 2 press the column center portion 9 circumferentially. This moment load generates high stress at the intersection of the radially inner surface 17 of the column inclined portion 8 and the radially inner surface 18 of the column end portion 7 shown in Figure 4, and at the axially inner portion of the base of the roller stop piece 10 that protrudes circumferentially from the column end portion 7.

[0046] In conventional needle roller and cage assemblies, the axially inner portion of the base of the roller stopper piece 10 and the portion where the radially inner surface 17 of the pillar inclined portion 8 and the radially inner surface 18 of the pillar end 7 intersect are in close proximity (their axial positions are nearly aligned). Therefore, when the needle rollers 2 press against the pillar portions 5 of the cage 3, and a moment load is generated that twists the pillar inclined portion 8 around the pillar end 7, the high stress generated at the axially inner portion of the base of the roller stopper piece 10 and the high stress generated at the portion where the radially inner surface 17 of the pillar inclined portion 8 and the radially inner surface 18 of the pillar end 7 intersect overlap, resulting in the problem that fatigue failure of the cage 3 is likely to occur.

[0047] To address this problem, in the needle roller and cage assembly 1 of the above embodiment, as shown in Figure 4, a base R portion 20 that is arc-shaped when viewed from the radial direction is formed on the axially inside of the base of the roller stopper piece 10, and also an inner diameter side R portion 19 that is arc-shaped when viewed from the circumferential direction is formed at the portion where the radially inside surface 17 of the pillar inclined portion 8 and the radially inside surface 18 of the pillar end 7 intersect. Therefore, when a moment load that twists the pillar inclined portion 8 around the pillar end 7 is generated as a result of the needle roller 2 pressing against the pillar portion 5 of the cage 3, stress concentration at the axially inside portion of the base of the roller stopper piece 10 (base R portion 20) is alleviated, and stress concentration at the portion where the radially inside surface 17 of the pillar inclined portion 8 and the radially inside surface 18 of the pillar end 7 intersect (inner diameter side R portion 19) is also alleviated. Furthermore, since root R portion 20 is formed at a position offset axially outward (to the left in the figure) from inner diameter side R portion 19 so that the axial range where root R portion 20 is formed does not overlap with the axial range where inner diameter side R portion 19 is formed, when a moment load is generated that twists column inclined portion 8 around column end 7 by needle roller 2 pressing column portion 5 of cage 3, it is possible to prevent the high stress generated in the axially inner part of the root of roller locking piece 10 (root R portion 20) from overlapping with the high stress generated in the part where radially inner surface 17 of column inclined portion 8 and radially inner surface 18 of column end 7 intersect (inner diameter side R portion 19), and it is possible to keep the maximum stress low. Therefore, as shown in Figures 7 and 8 , when used in applications where centrifugal force due to revolution motion is generated in needle roller 2, fatigue failure of cage 3 is unlikely to occur and it has excellent durability.

[0048] Furthermore, as shown in Figure 6, in this needle roller and cage assembly 1, the axially outer end (left side in the figure) of the roller stop piece 10 and the annular portion 4 are connected via a corner R portion 23 that is arc-shaped when viewed from the radial direction, so that when a moment load is generated that twists the column inclined portion 8 around the column end portion 7 due to the needle roller 2 pressing against the column portion 5 of the cage 3, it is possible to alleviate stress concentration in the portion (corner R portion 23) where the axially outer end of the roller stop piece 10 and the annular portion 4 are connected.

[0049] Furthermore, in this needle roller and cage assembly 1, the radial thickness t of the column center portion 9 shown in Figure 3 is set to 0.5 mm or more, which results in high strength of the cage 3. Furthermore, because the radial thickness t of the column center portion 9 is set to 1.5 mm or less, when manufacturing the cage 3, the strip steel that is the material for the cage 3 can be easily bent into an annular shape, making it easy to ensure the dimensional precision of the cage 3.

[0050] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0051] DESCRIPTION OF SYMBOLS 1 Needle roller and cage assembly 2 Needle roller 3 Cage 4 Annular portion 5 Column portion 7 Column end portion 8 Column inclined portion 9 Column center portion 10 Roller stop piece 11 Cylindrical portion 12 Inward flange portion 13 Welded portion 14 Outer peripheral surface 15 Radial outer surface 16 Radial outer surface 19 Inner diameter side R portion 20 Root R portion 23 Corner R portion 30 Planetary gear mechanism (revolving mechanism) 31 Planet gear (rotating member) 34 Planet carrier (revolving member) 36 Planet shaft t Radial thickness

Claims

1. A needle roller with a cage, comprising a plurality of needle rollers (2) arranged at intervals in the circumferential direction, and a cage (3) for holding the plurality of needle rollers (2), wherein the cage (3) has a pair of annular portions (4) axially opposed with the plurality of needle rollers (2) therebetween, and a plurality of column portions (5) connecting the pair of annular portions (4) through between the circumferentially adjacent needle rollers (2); each of the column portions (5) has a pair of column end portions (7) extending axially inward from the pair of annular portions (4) with a constant outer diameter, a pair of column inclined portions (8) extending obliquely so that the outer diameter gradually decreases toward the axially inner side from the pair of column end portions (7), and a column central portion (9) connecting the pair of column inclined portions (8); in the needle roller with a cage, a roller stopper piece (10) protruding in the circumferential direction is formed on the column end portion (7) so as to regulate the radially outward movement of the needle roller (2), a root R portion (20) having an arcuate shape when viewed in the radial direction is formed on the axially inner side of the root of the roller stopper piece (10), an inner diameter side R portion (19) having an arcuate shape when viewed in the circumferential direction is formed at a portion where the radially inner side surface (17) of the column inclined portion (8) intersects with the radially inner side surface (18) of the column end portion (7), and the root R portion (20) is formed axially outside the inner diameter side R portion (19) so that the axially formed range where the root R portion (20) is formed does not overlap with the axially formed range where the inner diameter side R portion (19) is formed.

2. The needle roller with a cage according to claim 1, wherein an axially outer end portion of the roller stopper piece (10) and the annular portion (4) are connected through an arcuate corner R portion (23) when viewed in the radial direction.

3. The needle roller with a cage according to claim 1 or 2, wherein the annular portion (4) has a cylindrical outer peripheral surface (14), the column end portion (7) has a partial cylindrical radially outer side surface (15) having the same outer diameter as the outer peripheral surface (14) of the annular portion (4), the roller stopper piece (10) has a partial cylindrical radially outer side surface (16) continuously formed on the radially outer side surface (15) of the column end portion (7), and the outer peripheral surface (14) of the annular portion (4), the radially outer side surface (15) of the column end portion (7), and the radially outer side surface (16) of the roller stopper piece (10) are used as a guided surface of the cage (3).

4. The needle roller with cage according to any one of claims 1 to 3, wherein each of the annular portions (4) has a welded portion (13) joined circumferentially by welding.

5. The needle roller with cage according to claim 4, wherein each of the annular portions (4) has a cylindrical portion (11) and an inward flange portion (12) extending radially inward from an axially outer end of the cylindrical portion (11), and the radial thickness (t) of the central portion (9) of the column is 0.5 mm to 1.5 mm.

6. A revolving mechanism having a revolving member (34) revolving at a fixed position, a planet shaft (36) disposed at a position radially away from the center of revolution of the revolving member (34) and revolving integrally with the revolving member (34), and a rotating member (31) rotatably attached to the outer periphery of the planet shaft (36) via the needle roller with cage (1) according to any one of claims 1 to 5.

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