Thrust roller bearing with integrated raceway ring holder

Abstract

To facilitate dimension control to realize high dimension accuracy while suppressing an increase in the number of steps, for a thrust bearing 10 having a raceway ring 11 that has a flange part 21 erecting from the entire peripheral edge of a raceway surface 27, and a holder in which a tip of the flange part 21 is held by an edge part 22 bent toward the raceway surface side over the entire circumference.SOLUTION: An edge part 22 is configured so that a tip part 24 is harder than a bend start part 23. A thrust rolling bearing can be manufactured in processes of: after temporarily bending the edge part, hardening the entire raceway ring to ensure hardness; softening only an area near the bend start part 23 leading to the edge part 22; incorporating rollers 13 and a holder 12; and bending the edge part 22 at the softened bend start part 23.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thrust roller bearing in which a raceway ring and a cage are integrated. [Background technology]

[0002] Thrust roller bearings, which have a raceway and cage integrated into one unit, are used in automotive automatic transmissions (ATs), continuously variable transmissions (CVTs), torque converters, air compressors, and other applications.

[0003] Patent Document 1 describes a thrust needle roller bearing in which a cage is fitted to a raceway ring through elastic deformation, and proposes a manufacturing procedure for it. When the raceway ring is press-formed, a latch is formed to catch the cage after fitting. After the latch is formed, heat treatment is performed, and then the roller and cage assembly is assembled.

[0004] Patent Document 2 proposes a method for assembling a non-separable, one-piece thrust bearing. Tabs used for engaging with the cage are preformed in four places on a lip that rises from the edge of the raceway around the entire circumference. After the bearing, with the rollers sandwiched between thrust retainers, is assembled, these tabs are locally heated to bend them and caulked to allow the bearing to rotate freely. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 58-125720 [Patent Document 2] Japanese Patent Application Publication No. 5-180218 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the manufacturing procedure described in Patent Document 1 had the problem of difficulty in controlling the dimensions of the latch. If the latch is large, plastic deformation is likely to occur when the roller and cage assembly is assembled, and conversely, if the latch is small, the cage is likely to come off.

[0007] Furthermore, the assembly method described in Patent Document 2 involves a process of locally heating and bending only the tab portion, which makes it easy for the dimensions of multiple tabs to vary, making it difficult to design jigs and tools, and increasing the amount of work required for actual processing.

[0008] In view of the above background, the problem that the present invention aims to solve is to provide a thrust roller bearing that, when manufactured, allows for easy dimensional control while suppressing an increase in labor costs, achieves high dimensional accuracy, and prevents the retainer from coming off the raceway without impairing the ease with which the retainer can be assembled into the raceway. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides: a bearing ring having a flange portion rising from the entire circumferential edge of the raceway surface, the tip of the flange portion being bent toward the inner diameter side along the entire periphery; At several places, a cage that is held by the flange and holds a plurality of the rollers, the cage has a plurality of holes formed radially, and holds the rollers housed in the holes radially on the raceway surface at equal intervals in the circumferential direction; The edge portion adopts a first configuration of a thrust roller bearing in which the tip portion has a higher hardness than the bending start portion.

[0010] That is, since the structure is such that the flange that rises all around holds the cage with an edge that is bent all around the tip, the edge can be formed by bending the edge all around the circumference, which improves dimensional accuracy compared to Patent Document 2, which forms the tabs locally. Also, since the edge can be formed by bending the flange tip all around the circumference at once, it is possible to manufacture with less increase in man-hours compared to Patent Document 2, which requires the work of bending multiple tabs individually.

[0011] Furthermore, in addition to the first configuration, the thrust roller bearing according to the present invention has: The hardness of the bending starting point is 420 HV or more and 500 HV or less, The hardness of the tip is 500 HV or more, A second configuration can be adopted in which the hardness of the raceway surface is 664 HV or more.

[0012] Furthermore, in addition to the first or second configuration, the thrust roller bearing according to the present invention can employ a third configuration in which the plate thickness of the edge portion is 40% or more and 80% or less of the plate thickness of the flange portion.

[0013] Furthermore, in addition to any one of the first to third configurations, the thrust roller bearing according to the present invention can employ a fourth configuration in which the angle of the edge portion relative to the rib portion is not less than 30 degrees and not more than 95 degrees. [Effects of the Invention]

[0014] In the thrust roller bearing according to the present invention, the edge at the end of the rib is bent all around to form a retainer against the cage, so the retainer can be formed in a single process with fewer steps than forming multiple tabs. Furthermore, because the shape is consistent all around, the rib is less likely to collapse, making it easier to maintain a uniform height. Furthermore, even when the cage and the edge come into active contact, a certain degree of hardness can be ensured at the tip of the edge, thereby suppressing wear.

[0015] Furthermore, this configuration allows for manufacturing by softening the bend start point and bending the edge after assembling the cage. This eliminates the need for forced assembly of the cage, and prevents plastic deformation during assembly. As a result, the cage can be easily assembled into the raceway without compromising its fit, resulting in a bearing in which the cage is less likely to come off the raceway. [Brief explanation of the drawings]

[0016] [Figure 1] (a) is a plan view showing a first embodiment of a thrust roller bearing according to the present invention; (b) is a cross-sectional view taken along the line B-B of (a); [Figure 2] 1 is an enlarged cross-sectional view of the vicinity of a flange and an edge of a bearing ring used in the first embodiment; [Figure 3] FIG. 10 is a cross-sectional view showing a bearing ring before pre-bending for manufacturing the first embodiment; [Figure 4] FIG. 10 is a cross-sectional view showing the dimensions of the raceway ring, cage, and rollers after pre-bending in the manufacturing process of the first embodiment. [Figure 5] Cross-sectional view showing an example of a die for bending the edge [Figure 6] FIG. 10 is a cross-sectional view showing a second embodiment of a thrust roller bearing according to the present invention. [Figure 7] FIG. 10 is a cross-sectional view showing a bearing ring before pre-bending for manufacturing the second embodiment; [Figure 8] FIG. 10 is a cross-sectional view showing the raceway, cage, and rollers after pre-bending in the manufacturing process of the second embodiment. [Figure 9] FIG. 10 is a cross-sectional view showing a third embodiment of a thrust roller bearing according to the present invention. [Figure 10] FIG. 10 is a cross-sectional view showing a fourth embodiment of a thrust roller bearing according to the present invention. [Figure 11] Graph plotting hardness measurement results in Examples DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention relates to a thrust roller bearing 10 in which a raceway ring 11 and a cage 12 are integrated. Fig. 1(a) shows a plan view of a first embodiment as an example of a thrust roller bearing according to the present invention, and Fig. 1(b) shows a cross-sectional view of part BB in Fig. 1(a). The embodiment shown is an example, and the present invention is not limited to the embodiment shown in the figures.

[0018] The raceway ring 11 has a flange 21 that rises from the entire periphery (outer peripheral edge 26) of the raceway surface 27 on which the rollers 13 roll. The entire periphery may be the edge on either the outer diameter side or the inner diameter side of the raceway surface 27. In the embodiment shown in the figures, the flange 21 rises from the outer peripheral edge 26, which is the edge on the outer diameter side. The flange 21 is bent all around to form a cylindrical shape.

[0019] A bent edge 22 is formed around the entire circumference at the tip of flange 21 of bearing ring 11. Edge 22 is bent toward raceway surface 27, and the raceway surface 27 side of edge 22 forms a retaining portion 28 that holds cage 12 and prevents it from falling off.

[0020] The cage 12 has a plurality of radially formed holes 31, which accommodate a plurality of rollers 13 and hold them radially at equal intervals in the circumferential direction. In the thrust roller bearing 10 according to the present invention, the rollers 13 do not fall out toward the raceway surface 27, so it is sufficient that the cage is formed in a way that prevents the rollers 13 from falling out on the side opposite the raceway surface 27. The circumferential width of the holes 31 is smaller than the outer diameter of the rollers 13, and the inner edge of the holes 31 forms an upper surface holding portion 34 that holds down the upper surface side of the rollers 13 (the side opposite the raceway surface 27). Although not shown in the figures, a protrusion that holds down the rollers 13 may be formed as the upper surface holding portion 34.

[0021] In the first embodiment, the outer diameter side and inner diameter side of the cage 12 are bent to form an inner diameter side cylindrical portion 32 and an outer diameter side cylindrical portion 33. The outer diameter side cylindrical portion 33 is pressed by the pressing portion 28 to hold the cage 12, and the cage 12 holds the rollers 13 with the upper surface pressing portion 34.

[0022] As shown in FIG. 1, the cage 12 may be bent partway in the radial direction so that the rollers 13 are also held by lower surface holding portions 35 on the lower surface side of the rollers 13 (the side facing the raceway surface 27).

[0023] Furthermore, although not shown, the cage may not be bent partway in the radial direction, and the entirety of the cage's punch hole 31 may hold down the top side of the rollers 13. This can prevent the cage from tilting and the rollers 13 from easily coming out, particularly when the rollers 13 are short. However, in thrust roller bearing 10 according to the present invention, the holding portion 28 prevents the cage from tilting, making it difficult for the rollers 13 to come out, so there is a certain degree of freedom in selecting the structure of the cage.

[0024] The thrust roller bearing 10 according to the present invention is characterized in that the hardness of the tip 24 of the edge 22 is higher than that of the bend start point 23 of the edge 22 where the tip of the rib 21 is bent. FIG. 2 shows an enlarged cross-sectional view of the rib 21 and the vicinity of the edge 22 of the raceway ring 11. The bend start point 23 specifically refers to the start point of the radius of the bend leading to the edge 22. On the other hand, the tip 24 refers to the tip of the edge 22, and may be on either the outer or inner side, but particularly refers to the tip on the raceway surface 27 side closer to the retaining portion 28 (the inner side in the illustrated embodiment). The angle θ is the angle between an extension line from the outer periphery of the rib 21 and the straight portion beyond the end point of the radius of the edge 22. This angle θ is the angle at which the edge 22 is bent.

[0025] An example of the manufacturing procedure for thrust roller bearing 10 having these characteristics will be described with reference to Figures 3 and 4. First, a disk-shaped material is pressed to form bearing ring 11 as shown in the cross-sectional view of Figure 3. Specifically, the disk-shaped material is bent all around at a position that will become outer peripheral edge 26 of raceway surface 27, so that flange 21 and the portion beyond it that will become edge 22 are raised in a cylindrical shape.

[0026] Furthermore, in this state, it is preferable to perform a pre-bending process by pressing the corner 25 between the flange 21 and the edge 22 where the thickness is reduced, which corresponds to the position of the bend start point 23, to bend the edge 22 toward the raceway surface 27. A cross-sectional view of the pre-bending stage is shown in Figure 4. The inner diameter φX1 of the tip end portion 24 at the pre-bending stage is larger than the outer diameter φX0 of the cage 12 to be assembled. This is to ensure that the cage 12 can be assembled later. By performing the pre-bending process once, the bend start point 23 is formed, allowing for bending at the intended position even if the bending jig after annealing is simplified. In addition, since the bending allowance after annealing is small, cracks are less likely to occur. Furthermore, when the tip end portion 24 is pre-bent and located farther from the bend start point 23, it is less likely to be hit by the high-frequency waves required to soften the bend start point 23, thereby preventing a decrease in the hardness of the tip end portion 24. This makes it difficult for the pressing portion 28 below the tip portion 24 to wear even when it comes into contact with the retainer 12.

[0027] After the press working, the entire raceway is hardened by heat treatment such as carburizing and quenching. At this stage, it is advisable to adjust the hardness of the raceway surface 27 to the desired value.

[0028] Next, the outside of the corner 25, or the entire periphery of the bend starting point 23 if the bend starting point 23 has already been formed by pre-bending, is softened by induction tempering. At this time, the softening range only needs to be the extent necessary for the final bending, and it is desirable to limit the softening range so as not to excessively reduce the hardness of the tip 24. For this reason, when softening with a high-frequency coil or the like, the softening should be performed as close to the bend starting point 23 as possible.

[0029] Next, the rollers 13 with cage 12 are assembled and placed on the raceway surface 27, and the tip end 24 side of the edge 22 is bent to a specified dimension all around so that the bend start point 23 is in the appropriate position, and the cage 12 is integrated so that it does not come off. The cross section at this stage is as shown in Figure 1(b). Bending all around allows for processing with high dimensional accuracy. To prevent the cage 12 from coming off, the inner diameter φX2 of the tip end 24 at this stage must be smaller than the outer diameter φX0 of the cage.

[0030] The tip end portion 24 and the pressing portion 28 that come into contact with the cage 12 are located farther from the bend starting point 23, and therefore softening from the high hardness state hardened by heat treatment such as carburizing is kept to a minimum. As a result, high hardness can be maintained at the bend starting point 23.

[0031] Of these locations, the hardness of the bend start point 23 is preferably 420 HV or more and 500 HV or less, and more preferably 480 HV or less. If the hardness is softened to less than 420 HV, the decrease in hardness may have a significant effect on the raceway surface 27. On the other hand, if the hardness is higher than 500 HV, cracks may easily occur on the outer periphery of the edge portion 22.

[0032] Furthermore, the hardness of tip end portion 24 is preferably 500 HV or more. If it is less than 500 HV, tip end portion 24 is more likely to wear when cage 12 and tip end portion 24 come into contact in the axial direction. However, in the thrust roller bearing according to the present invention, edge portion 22 is formed along the entire circumference, and therefore cage 12 is prevented from coming off around the entire circumference of the raceway compared to conventional configurations in which the cage is held in place by tabs, which has the advantage of being less prone to wear in the first place.

[0033] Furthermore, the hardness of raceway surface 27 is preferably 664 HV or more. If the hardness is less than 664 HV, it becomes difficult to satisfy the bearing's service life. In the thrust roller bearing according to the present invention, the softening point is centered on bend start point 23, which is away from raceway surface 27, so that the reduction in hardness of raceway surface 27 can be minimized.

[0034] A configuration that facilitates the manufacture of such a thrust roller bearing will now be described using the symbols shown in Figure 2. It is preferable that the thickness t1 of edge portion 22 be 40% or more and 80% or less of the thickness t2 of flange portion 21. If edge portion 22 is too thin, it may not have sufficient strength. On the other hand, if edge portion 22 is too thick, it may be difficult to bend it to the appropriate angle.

[0035] Furthermore, when using small diameter rollers (approximately φ2 mm), it is preferable that the length L1 of the edge portion 22 be 1.2 mm or less. If it is too long, not only is it unnecessary from a design perspective, but the force acting on the bend starting point 23 due to the load on the tip portion 24 becomes non-negligible. On the other hand, when using similar small diameter rollers (approximately φ2 mm), it is preferable that the length L2 of the flange portion 21 be 2.0 mm or less. If it is too long, the inclination of the cage 12 becomes too great, making it easier for the rollers 13 to come off.

[0036] Furthermore, the angle θ of edge portion 22 relative to flange portion 21 is preferably between 40 degrees and 95 degrees. If it is less than 40 degrees, the effect of preventing retainer 12 from coming off is insufficient, and even if it does not come off, there is a risk that too much space will be left between retainer 12 and retainer 12, causing retainer 12 to tilt and rollers 13 to come off. On the other hand, if it is 95 degrees or more, the load on the bending allowance will increase, increasing the risk of cracks occurring.

[0037] One method for bending the edge portion 22 at the correct angle θ is to press the bearing ring 11, whose bend starting point 23 has been softened, against a die 61 as shown in FIG. 5 to bend the edge portion 22. A corner 62 having an interior angle (180 degrees - θ) that matches the angle θ is formed inside the die 61, and the edge portion 22 is bent along a plate portion 63 that extends obliquely from this corner 62 toward the center. This allows the edge portion 22 to be bent from the flange portion 21 to the desired angle θ. This bending can be performed both during pre-bending and during final bending. During pre-bending, a die is used in which the angle of the corner 62 is larger than the angle (180 degrees - θ) used for final bending.

[0038] Next, a thrust roller bearing 30 according to a second embodiment of the present invention will be described. An enlarged cross-sectional view of thrust roller bearing 30 is shown in FIG. 6. In this embodiment, the thickness of the bearing ring 11a on the inner diameter side between rib 21 and edge 22 decreases gradually, and unlike corner 25 of the first embodiment, corner 25a does not have any sharp edges. Even with this type of bearing ring 11a with a smooth inner diameter side, the outer peripheral edge of raceway surface 27 can be bent to raise rib 21 and edge 22 into a cylindrical shape (as shown in the cross-sectional view of FIG. 7), as with bearing ring 11 of the first embodiment. Optionally, pre-bending edge 22 can be performed, and then a cage 12 holding rollers 13 can be assembled (as shown in the cross-sectional view of FIG. 8). The absence of sharp edges reduces the load acting between rib 21 and edge 22 during bending, resulting in less cracking than in the first embodiment.

[0039] Furthermore, a thrust roller bearing 40 according to a third embodiment of the present invention will be described with reference to the cross-sectional view of Figure 9. This thrust roller bearing 40 has the same basic configuration as the thrust roller bearing 10 according to the first embodiment. What differs from the first embodiment is that the angle θ of the edge 22 is bent to approximately 90 degrees. By increasing the angle of the edge 22 in this way, the gap between the outer diameter side cylindrical portion 33 of the cage 12 can be reduced, thereby preventing the cage 12 from tilting.

[0040] A thrust roller bearing 50 according to a fourth embodiment of the present invention, which is an application of the thrust roller bearing 30 according to the second embodiment, will be described with reference to the cross-sectional view of FIG. 10 . This thrust roller bearing 50 has the same basic configuration as the thrust roller bearing 30 according to the second embodiment. It differs from the second embodiment in that the edge 22 is bent so that the angle θ is approximately 90 degrees. Increasing the angle of the edge 22 in this manner reduces the gap between the outer diameter side cylindrical portion 33 of the cage 12, thereby preventing tilting of the cage 12. Furthermore, compared to the thrust roller bearing 40 according to the third embodiment, the corner 25 a is smoother, so cracks are less likely to occur even when the cage is bent to approximately 90 degrees.

[0041] 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. [Example]

[0042] The bearing ring used in the thrust roller bearing according to the second embodiment is made of SCM material, and the outer periphery is press-formed to form a cylindrical flange and rim. The flange thickness is 0.7 mm, and the rim thickness is 0.35 mm. The length from the tip of the rim to the corner, i.e., the rim length, is 0.8 mm.

[0043] After hardening the entire bearing by heat treatment, the entire circumference was heated from 2 mm away, starting at a point 0.8 mm from the edge, for 3 seconds using a high-frequency heating device. The entire circumference was then bent at a 50° angle, with the bend starting point 0.8 mm from the edge, to form the bearing ring. The hardness of the bearing ring was measured using a Vickers hardness tester at each location along the circumference from the edge tip to a depth of 0.05 mm from the surface. Figure 11 shows a graph plotting the hardness measurements against the distance from the edge circumference. The edge tip here refers to the outer periphery of the edge tip, corresponding to the outer periphery of tip 24 in the figure above. While the hardness near the edge tip, close to 0 mm, maintained a hardness of over 520 HV, the area around the bend starting point, heated to a distance of 0.8 mm, dropped to approximately 470 HV, where cracks are less likely to occur. It was confirmed that the hardness increased from there toward the raceway surface. In other words, it was possible to manufacture a bearing ring that ensures hardness near the tip and raceway surface while having a soft area around the bend start point. [Explanation of symbols]

[0044] 10, 30, 40, 50 thrust roller bearings 11, 11a Raceway ring 12 Cage Around 13 21 Tsuba 22 Edge 23 Bending start point 24 Tip 25, 25a corner 26 outer edge 27 Raceway surface 28 Retainer 31 Drill holes 32 Inner diameter cylindrical part 33 Outer diameter cylindrical part 34 Upper surface holding part 35 Lower surface holding part 61 Mold 62 Corner 63 Board part

Claims

1. a raceway ring (11) having a flange (21) rising from the entire peripheral edge (26) of a raceway surface (27), the tip of which is bent toward the inner diameter side along the entire circumference to form an edge (22); Multiple koro (13) and a cage (12) that is held by the flange portion (21) and holds a plurality of the rollers (13); and The cage (12) has a plurality of radially formed holes (31), and holds the rollers (13) housed in the holes (31) radially on the raceway surface (27) at equal intervals in the circumferential direction, The edge portion (22) has a tip portion (24) that is harder than a bend starting portion (23).

2. The hardness of the bending starting point (23) is 420 HV or more and 500 HV or less, The hardness of the tip portion (24) is 500 HV or more, 2. A thrust roller bearing according to claim 1, wherein the raceway surface (27) has a hardness of 664 HV or more.

3. 2. A thrust roller bearing according to claim 1, wherein the thickness of the edge portion (22) is 40% to 80% of the thickness of the flange portion (21).

4. 4. A thrust roller bearing according to claim 1, wherein the angle of the edge portion (22) relative to the flange portion (21) is between 30 degrees and 95 degrees.

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