Cages, caged rollers, and thrust roller bearings

Abstract

To allow short and small rollers to be stably held.SOLUTION: A retainer (30) for a thrust roller bearing comprises an annular center region (31) including a pillar part (33) having a hat-shaped cross section. The pillar part includes a center flat part (45) and both end flat parts (41 and 42) whose axial positions are different from each other, a pair of inclined parts (43 and 44) extending in an axial direction between the center flat part and both the end flat parts, and two pairs of bend R parts (R1, R2, R3, and R4) located in boundaries between the inclined parts, and the center flat part and both the end flat parts. Thicknesses (T3 and T4) of the bend R parts are larger than thicknesses (T1 and T2) of the center flat part and both the end flat parts.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a cage for a thrust roller bearing that bears an axial load.

Background Art

[0002] A thrust roller bearing is used in an automotive automatic transmission or a continuously variable transmission for an automobile. The thrust roller bearing includes a cage having a plurality of pockets provided at equal intervals in the circumferential direction, and rollers (needle rollers) accommodated in the pockets. As shown in Japanese Patent Application Laid-Open No. 2000-213546 (Patent Document 1) and Japanese Patent No. 3933336 (Patent Document 2), in the cage of a thrust roller bearing, there is a cage in which a column portion located between circumferentially adjacent pockets has a hat-shaped cross section. That is, there is a so-called W-shaped cage in which the central portion in the radial direction of the column portion protrudes toward one side in the axial direction.

[0003] In Patent Documents 1 and 2, the minimum plate thickness of the bent corner portion of the column portion of the W-shaped cage is set to 75% or more of the stock plate thickness to ensure the rigidity and strength of the cage.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] With the demand for multi-speed and compact automotive transmissions, the roller raceway surface is becoming narrower, and the roller length (length dimension) and roller diameter (diameter dimension) tend to decrease. When such rollers (hereinafter referred to as "short rollers") are held in a W-type cage with a hat-shaped cross-section column, dimensional control is important to prevent the rollers from falling out, and therefore, it is currently difficult to increase the plate thickness of the cage material.

[0006] In light of these circumstances, simply setting the minimum plate thickness of the bent corner portion of the column of the retainer to 75% or more of the material plate thickness, as in Patent Documents 1 and 2, raises concerns about strength when the material plate thickness of the retainer is thin. Therefore, conventional retainers may not be able to stably hold short rollers. As a result, conventional retainers could not be used in a triplicate type consisting of a pair of raceway plates and needle rollers with retainers.

[0007] The present invention was made to solve the above-mentioned problems, and its objective is to provide a cage that can stably hold short rollers, a roller with a cage, and a thrust roller bearing. [Means for solving the problem]

[0008] A cage according to one aspect of this invention is a cage for a thrust roller bearing and comprises an annular central region including a plurality of pockets arranged at equal intervals in the circumferential direction in which rollers are arranged, and columnar portions located between adjacent pockets in the circumferential direction and having a hat-shaped cross-section, and a pair of edge regions located on the inner and outer diameter sides of the central region. The columnar portion includes a central flat portion and end flat portions having different axial positions from each other, a pair of inclined portions extending diagonally along the axial direction between the central flat portion and end flat portions, and two pairs of bent R portions located at the boundary between the inclined portions and the central flat portion and end flat portions, wherein the thickness of the bent R portions is greater than the thickness of the central flat portion and end flat portions.

[0009] Preferably, the thickness of the central flat section and the flat sections at both ends is 80-95% of the thickness of the curved section.

[0010] Preferably, the thickness of the bent R portion is 80% or more of the material thickness.

[0011] The rollers held in the retainer are short rollers, for example, having a diameter of 1.5 mm to 2.5 mm and a length of 3 mm to 5 mm. Alternatively, rollers with a diameter of 1.5 mm to 2.5 mm or a length of 3 mm to 5 mm may also be used.

[0012] Preferably, the retainer is of the roller guide type, and roller stopper protrusions are provided at both circumferential ends of the central flat portion and the flat portions at both ends.

[0013] According to the configuration of the present invention, it is possible to provide a roller with a retainer, comprising the retainer described above and a roller disposed in the pocket of the retainer.

[0014] Furthermore, a thrust roller bearing can be provided that includes a caged roller and a pair of raceway plates that sandwich the caged roller from both axial sides. [Effects of the Invention]

[0015] According to the present invention, it is possible to stably hold short rollers. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic plan view showing a cage for a thrust roller bearing according to an embodiment of the present invention. [Figure 2] This is a partial cross-sectional view of the retainer along the line II-II in Figure 1. [Figure 3] This is a partial cross-sectional view of the retainer along the line III-III in Figure 1. [Figure 4] This is a partially cross-sectional view showing an enlarged view of the structure of a retainer according to an embodiment of the present invention. [Figure 5] This figure schematically shows an example of a mold used in the processing of a retainer according to an embodiment of the present invention. [Figure 6]It is a plan view schematically showing a roller with a cage according to an embodiment of the present invention. [Figure 7] It is a partial cross-sectional view showing a roller with a cage along the line VII-VII of FIG. 6. [Figure 8] It is a partial cross-sectional view showing a thrust roller bearing according to an embodiment of the present invention. [Figure 9] It is a partial cross-sectional view showing a thrust roller bearing according to another embodiment of the present invention. [Figure 10] It is a partial cross-sectional view showing a thrust roller bearing according to still another embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0017] Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their description will not be repeated.

[0018] <Schematic Structure> First, referring to FIGS. 1 to 3, the schematic structure of a cage for a thrust roller bearing according to the present embodiment will be described. FIG. 1 is a plan view schematically showing a cage 30 for a thrust roller bearing according to an embodiment of the present invention. FIG. 2 is a partial cross-sectional view of the cage 30 along the line II-II of FIG. 1. FIG. 3 is a partial cross-sectional view of the cage 30 along the line III-III of FIG. 1. The cross-sections shown in FIGS. 2 and 3 are flat surfaces including the axis O of the thrust roller bearing.

[0019] <S In the following description, the circumferential direction refers to the direction around the axis O, the radial direction refers to the diameter direction or the radius direction of a circle centered on the axis O. The same applies to the inner diameter, outer diameter, inner circumference, and outer circumference. Also, the direction parallel to the axis O is referred to as the axial direction. In the description of the cage 30, for the sake of easy understanding, the upper side (one side in the axial direction) of the paper surface in FIGS. 2 and 3 is described as the upper side of the cage 30, and the lower side (the other side in the axial direction) of the paper surface is described as the lower side of the cage 30.

[0020] The retainer 30 consists of an annular central region 31 and inverted U-shaped folded portions 34 and 35 located at the inner and outer periphery, respectively. The central region 31 includes pockets 32 and columnar portions 33 arranged alternately at equal intervals in the circumferential direction. The folded portions 34 constitute the inner diameter edge region, and the folded portions 35 constitute the outer diameter edge region. Rollers 20 (shown as dashed lines in Figure 3) are placed in each pocket 32. The rollers 20 roll on a raceway surface (not shown).

[0021] As shown in Figure 2, the retainer 30 of this embodiment is a so-called W-shaped retainer, and the column portion 33 (central region 31) has a hat-shaped cross-section. Specifically, the column portion 33 includes a pair of flat portions (hereinafter also referred to as "both end flat portions") 41, 42 that extend radially with one end connected to the folded portions 34, 35, a pair of inclined portions 43, 44 that rise axially from the other ends of the both end flat portions 41, 42, and a flat portion (hereinafter referred to as "central flat portion") 45 that extends radially and is located between the upper ends of the inclined portions 43, 44. The inclined portions 43, 44 and the central flat portion 45 form a peak.

[0022] In this type of W-shaped retainer, as shown in Figure 1, the circumferential ends of the inclined sections 43 and 44 and the bent R sections R1 to R4 are notched. As a result, the circumferential lengths of the flat sections 41, 42, and 45 are longer than the circumferential lengths of the inclined sections 43 and 44 and the bent R sections R1 to R4. This makes the circumferential dimension L3 of the pocket 32 ​​at the positions of the flat sections 41, 42, and 45 smaller than the roller diameter L1 (Figure 3), and the circumferential ends of the flat sections 41, 42, and 45 function as roller stoppers. Specifically, roller stopper protrusions 41a and 41b are formed at both circumferential ends of the flat section 41, roller stopper protrusions 42a and 42b are formed at both circumferential ends of the flat section 42, and roller stopper protrusions 45a and 45b are formed at both circumferential ends of the flat section 45. The retainer 30 is of the roller guide type (rolling element guide type), and the roller stopper protrusions 41a, 41b, 42a, 42b, 45a, and 45b function as axial roller guides.

[0023] The roller 20 in this embodiment is a so-called short roller, and the size of the roller 20 is assumed to be a roller diameter L1 of 1.5 mm or more and 2.5 mm or less (more specifically 2.0 mm or less), and a roller length L2 of 3.0 mm or more and 5.0 mm or less (more specifically 4.0 mm or less). As an example, the size of the roller 20 in this embodiment is a roller diameter L1 of 2 mm and a roller length L2 of 3.5 mm.

[0024] Incidentally, since W-type retainers are manufactured by press-forming materials such as cold-rolled steel sheets, the overall thickness of the product after pressing is thinner. In other words, if the thickness of the material is represented as "T0", the thickness of the product will be less than T0. In a normal press process, the bent R section (rounded bent corner section) of the W-type retainer is also bent, so the thickness of the bent R section is thinner than the thickness of the flat section. Also, a thinner material thickness (T0) for retainers used for short rollers makes dimensional control easier.

[0025] In contrast, the retainer 30 of this embodiment is formed such that the plate thickness in the bent R sections R1 to R4 of the central region 31 is greater than the plate thickness in the flat sections 41, 42, and 45. While the reduction in plate thickness in the bent R sections could conventionally be as much as 75%, in this embodiment it can be limited to 80%, improving strength. Furthermore, conventionally, retainers for short rollers used relatively thin material plates, but since dimensional control has become easier without reducing the material plate thickness, the plate thickness in the bent R sections R1 to R4 has been increased, improving strength. The structure of the retainer 30 of this embodiment will be described in detail below.

[0026] <Specific structural examples of the retainer> Figure 4 is a schematic enlarged view of a portion of the structure of the retainer 30 in this embodiment.

[0027] As described above, the column portion 33 of the retainer 30 includes a central flat portion 45 and two end flat portions 41, 42 whose axial positions are different from each other, and a pair of inclined portions 43, 44 that extend diagonally along the axial direction between the central flat portion 45 and the two end flat portions 41, 42, as well as bent R portions R1, R2 located at the boundary between the two end flat portions 41, 42 and the inclined portions 43, 44, and bent R portions R3, R4 located between the boundary between the central flat portion 45 and the inclined portions 43, 44. In other words, the column portion 33 includes two pairs of bent R portions R1 to R4.

[0028] Referring to Figure 4, the plate thickness T2 of the central flat section 45 is equal to the plate thickness T1 of the flat sections 41 and 42 at both ends. "Equal" means that the difference between the two values ​​is less than or equal to the tolerance. The plate thickness T3 of the lower bent R sections R1 and R2 and the plate thickness T4 of the upper bent R sections R3 and R4 are both greater than the plate thicknesses T1 and T2 of the flat sections 41, 42, and 45. In other words, there is a difference between the two that exceeds the tolerance. Specifically, the plate thicknesses T1 and T2 of the flat sections 41, 42, and 45 are 80-95% of the plate thicknesses T3 and T4 of the bent R sections R1-R4. This improves the strength of the bent R sections R1-R4, which are the weakest parts of the W-shaped retainer.

[0029] The processing method for such a retainer 30 may be basically the same as a known method as described in Patent Document 1. That is, i) an annular blank is punched out from a thin steel sheet having a thickness T0, and ii) the central region of this blank is drawn using a tool with a shoulder radius larger than the cross-sectional radius of curvature of the bending R portions R1 and R3 of the product to form an annular first bent step (corresponding to the inclined portion 43). Next, iii) on the outer circumference of the bent step formed by this drawing process, an annular second bent step (corresponding to the inclined portion 44) is reverse drawn in the opposite direction to the first bent step using a tool with a shoulder radius larger than the cross-sectional radius of curvature of the bending R portions R2 and R4 of the product. In this way, a central region having a hat-shaped cross section larger than the hat-shaped cross section of the product is pre-formed.

[0030] Next, iv) the inner and outer circumferences of the preformed central region are drawn using a tool with a shoulder radius larger than the product's cross-sectional radius of curvature to preform annular third and fourth bend steps (corresponding to parts of the folded sections 34 and 35), and v) the preformed hat-shaped cross section and the third and fourth bend steps are finished to match the product dimensions. In other words, the central region is formed with a hat-shaped cross section throughout the circumferential direction.

[0031] Next, vi) the outer edges of the third and fourth bends are folded back to form the inner and outer folded portions 34 and 35. Finally, vii) pockets 32 are punched out at equal intervals in the circumferential direction in the central region of the hat-shaped cross section. This completes the retainer 30, which has a central region 31 with pockets 32 and column portions 33. As a finishing touch, a soft nitriding treatment is applied to complete the retainer 30 with a surface hardness of 350 HV or higher.

[0032] Figure 5 schematically shows an example of a mold used in step v) above, when pressing the pre-formed hat-shaped central region to form the central region of the product dimensions. The mold 50 has a lower mold 51 and an upper mold 55. The retainer (retainer during molding) 130 that is pressed in the mold 50 has a hat-shaped pre-formed central region 131 and L-shaped bent steps 134 and 135.

[0033] As shown in Figure 5, the distance between the lower mold 51 and the upper mold 55 during pressure molding is not constant, but varies depending on the area being pressed. Specifically, the distance D3 corresponding to the inclined sections 143 and 144 is larger than the distance D1 corresponding to the flat sections 141 and 142 at both ends of the central region 131, and the distance D2 corresponding to the central flat section 145. More specifically, when the material plate thickness T0 is set to 1, the distances D1 and D2 are set in the range of 0.7 to 0.8, and the distance D3 is set in the range of 0.85 to 0.95.

[0034] Thus, by including a process in the manufacturing process of the retainer 30 to form the inclined portions 143 and 144 thicker than the flat portions 141, 142, and 145, the plate thickness T3 and T4 of the bent R portions R1 to R4 of the finished retainer 30 can be made larger than the plate thickness T1 and T2 of the flat portions 41, 42, and 45, and can be made 80% or more of the material plate thickness T0. In addition, the plate thickness of the inclined portions 43 and 44 of the finished retainer 30 may also be larger than the plate thickness T1 and T2 of the flat portions 41, 42, and 45.

[0035] As shown in Figure 5, the lower mold 51 may be formed as a single piece, or it may be divided into multiple (for example, three) lower molds 52-54 along the radial direction. The central lower mold 52 has a size and shape that allows it to support the central region 131 from below. The inner diameter lower mold 53 has a size and shape that allows it to support the folding step 134 from below and from the inner diameter side. The outer diameter lower mold 54 has a size and shape that allows it to support the folding step 135 from below and from the outer diameter side. The upper mold 55 may also be formed as a single piece, or it may be divided into multiple (for example, three) upper molds along the radial direction (not shown).

[0036] Referring again to Figure 2, in the finished cage 30, it is desirable that the height (peak height) H1 of the upper surface of the central flat section 45, relative to the lower surfaces of the flat sections 41 and 42 at both ends, be 65 to 85% of the roller diameter L1. If the height H1 of the central flat section 45 is large (exceeds 85%), the rolling element guidance will no longer be effective when the cage 30 moves significantly in the axial direction.

[0037] Furthermore, in order to stably hold the rollers 20 in the retainer 30, it is desirable that the radial length W1 of the central flat portion 45 be 10 to 25% of the radial length W2 of the pocket 32. The widths of the roller-stopping protrusions 45a and 45b formed at both circumferential ends of the central flat portion 45 are formed to be approximately equal to the radial length W1. The radial lengths of the flat portions 41 and 42 at both ends are similar.

[0038] Furthermore, it is desirable that the inclination angle θ of the inclined portions 43 and 44 with respect to the axis O be 20 degrees or less. If the inclination angle θ of the inclined portions 43 and 44 becomes large (exceeds 20 degrees), it becomes difficult to secure the roller stopper protrusions 41a, 41b, 42a, 42b, 45a, and 45b, and the roller 20 cannot be properly held.

[0039] The material plate thickness T0 of the relatively small retainer that holds the short roller 20 was generally set at less than 0.5 mm. However, by using a mold 50 as shown in Figure 5, for example, and by appropriately modifying the press working process, it is possible to use a material with a plate thickness of 0.5 mm or more. In other words, even if a material with a plate thickness of 0.5 mm or more is used, the dimensions of the retainer for the short roller 20 can be controlled, so the short roller 20 can be held stably without tilting in the pocket 32 ​​or trying to get stuck between the retainer 30 and the raceway (not shown).

[0040] The retainer 30 in this embodiment is formed by press-forming a material with a plate thickness of, for example, 0.5 mm. In this case, the plate thickness T3 and T4 of the bent R portions R1 to R4 of the retainer 30 are 0.4 mm or more (0.400 mm to 0.475 mm), so the strength of the retainer 30 can be significantly improved compared to conventional designs.

[0041] <Roller with retainer> Figure 6 is a schematic plan view showing a retained roller 10 according to an embodiment of the present invention. Figure 7 is a partial cross-sectional view of the retained roller 10 along the line VII-VII in Figure 6. The retained roller 10 comprises a retainer 30 and short rollers 20 incorporated into pockets 32 of the retainer 30. As described above, the retainer 30 has bent R portions R1 to R4 with improved strength, so according to this embodiment, the quality of the retained roller 10 can be improved compared to conventional models.

[0042] <Thrust roller bearings> Figure 8 is a schematic partial cross-sectional view of a thrust roller bearing 10A. The thrust roller bearing 10A comprises a caged roller bearing 10 (Figures 6 and 7) in which short rollers 20 are incorporated into a cage 30, and a pair of raceway plates 61 and 62 that sandwich the caged roller bearing 10 from both axial sides.

[0043] The raceway 61 has a raceway surface 61a facing the flat portions 41 and 42 at both ends of the retainer 30, and a peripheral wall portion 61b that surrounds the retainer 30 from the outer diameter side. The raceway 62 has a raceway surface 62a facing the central flat portion 45 of the retainer 30, and a peripheral wall portion 62b that surrounds the retainer 30 from the inner diameter side.

[0044] The thrust roller bearing 10A, equipped with a pair of raceway plates 61 and 62, can be applied to mating parts with narrow mounting or rolling surfaces, making it effective for multi-stage automotive transmissions. Furthermore, because the cage 30 is of the roller guide type, damage to the raceway surfaces 61a and 62a can be prevented, resulting in lower torque. In addition, since the thrust roller bearing 10A is equipped with a W-shaped cage 30, it has better oil permeability compared to configurations with box-type cages or single-plate cages, offering the advantage of reduced costs.

[0045] Furthermore, as shown in Figure 9, the thrust roller bearing 10B may have only one of the raceway plates 61 and 62 shown in Figure 8 (for example, only raceway plate 62). In addition, in a configuration with only one raceway plate, as shown in Figure 10, the thrust roller bearing 10C may have a raceway plate 63 that has a raceway surface 63a facing the central flat portion 45 of the cage 30, and a peripheral wall portion 63b that surrounds the cage 30 from the outer diameter side.

[0046] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0047] 10 Roller with cage, 10A, 10B, 10C Thrust roller bearing, 20 Roller, 30 Cage, 31 Central area, 32 Pocket, 33 Column section, 34, 35 Folded section (edge ​​area), 41, 42 Flat sections at both ends, 43, 44 Inclined section, 45 Central flat section, 41a, 41b, 42a, 42b, 45a, 45b Roller stopper protrusions, 61, 62, 63 Raceway, R1, R2, R3, R4 Bent radius section.

Claims

1. A cage for a thrust roller bearing, An annular central region including a plurality of pockets arranged at equal intervals in the circumferential direction, on which rollers are positioned, and a columnar portion located between adjacent pockets in the circumferential direction, having a hat-shaped cross-section that is convex in the axial direction, The central region comprises a pair of edge regions located on the inner and outer diameter sides, The column portion includes a central flat portion and flat portions at both ends that are at different axial positions, a pair of inclined portions that extend diagonally along the axial direction between the central flat portion and the flat portions at both ends, and two pairs of curved R portions located at the boundary between the inclined portions and the central flat portion and the flat portions at both ends. A retainer in which the thickness of the bent R portion is greater than the thickness of the central flat portion and the flat portions at both ends.

2. The holder according to claim 1, wherein the plate thickness of the central flat portion and the flat portions at both ends is 80 to 95% of the plate thickness of the curved R portion.

3. The holder according to claim 1 or 2, wherein the thickness of the bent R portion is 80% or more of the thickness of the material plate.

4. The holder according to any one of claims 1 to 3, wherein the plate thickness of the bent R portion is 0.4 mm or more.

5. The retainer according to any one of claims 1 to 4, wherein the roller has a diameter dimension of 1.5 mm or more and 2.5 mm or less, and a length dimension of 3 mm or more and 5 mm or less.

6. The aforementioned retainer is of the roller guide type, The retainer according to any one of claims 1 to 5, wherein roller-stopping protrusions are provided at both circumferential ends of the central flat portion and the two end flat portions.

7. A retainer according to any one of claims 1 to 6, A retained roller having a roller positioned in a pocket of the retainer.

8. A roller with a retainer as described in claim 7, A thrust roller bearing comprising a pair of raceway plates that sandwich the caged roller from both axial sides.

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