Rolling bearing

Abstract

To provide a rolling bearing restraining excessive temperature rise, stabilizing behaviors of a retainer, and not giving an influence on durability.SOLUTION: A retainer 6 of a rolling bearing has two annular bodies 10, 10 overlaid on each other in an axial direction. Each annular body 10 has plural pocket walls 13 aligned at a constant interval in a circumferential direction, and constituting an inner wall face of a pocket, and plural coupling plate parts 14 coupling the pocket walls 13 adjacent to each other in the circumferential direction. The two annular bodies 10, 10 are overlaid and coupled with each other at each coupling plate part 14. Grease reservoir walls 26, 26 for reserving grease in inner peripheral faces of the coupled plate parts 14, 14 and preventing the grease from being leaked an axial outer side from the inner peripheral faces are provided on the inner peripheral faces of the coupling plate parts 14, 14.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a rolling bearing, and more particularly to a technique that is advantageous against heat generation and vibration and can suppress deterioration in durability in, for example, rolling bearings for motors. [Background technology]

[0002] Synthetic resin cages for use in rolling bearings have been proposed (Patent Documents 1 and 2). These synthetic resin cages are formed by engaging two annular bodies of the same shape.

[0003] In rolling bearings lubricated with grease, it is known that grease adhering to the surfaces of rotating balls is caught in the cage pocket or raceway surface, affecting parameters such as bearing temperature rise, vibration, and noise level, and it can be said that the grease flow inside the bearing affects the performance of the bearing. In recent years, there has been an increasing demand for higher speed bearings, and cages that have a large effect on grease flow are required to be compatible with higher speeds.

[0004] The synthetic resin cage of Patent Document 1 has a notch on the inner or outer diameter surface of the pocket wall to scrape off grease adhering to the balls. In the synthetic resin cage of Patent Document 2, the relief shape in the pocket axial direction is formed as a cylindrical surface extending in the cage radial direction on the inner diameter side of the ball pitch circle, taking into consideration deformation of the cage due to centrifugal force. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-159548 A [Patent Document 2] Patent No. 5876237 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, a notch is provided on the inner or outer diameter surface of the pocket wall to improve the scraping ability of grease adhering to the ball surface and reduce the break-in time. In addition, some of the grease remaining in the stationary space is scraped off by the notch, and base oil is supplied between the ball and the pocket to suppress heat generation. Although the shape of the notch is actually effective, the centrifugal force acting on the cage rotating at high speed may deform the pocket in a direction that reduces the axial clearance between the ball and the pocket, and the ball may interfere with the pocket in the axial direction. This may cause abnormal wear, heat generation, and other deterioration of bearing parameters.

[0007] Patent Document 2 describes a method for preventing interference between the pockets and balls due to deformation of the cage caused by centrifugal force. In this patent document 2, the shape of the pocket's axial relief is a cylindrical surface extending in the cage radial direction on the inner diameter side of the ball pitch circle so that there is no interference between the pockets and balls even if deformation occurs in the axial portion of the cage pocket due to centrifugal force. With this shape, even if the pockets are deformed by centrifugal force, there will be no interference between the pockets and balls, so abnormal wear can be prevented.

[0008] However, the gap between the pocket and the balls becomes larger, and the amount of grease entering the pocket increases when operation starts. This causes problems such as an increase in break-in time, heat generation due to shearing of the grease and balls inside the pocket, and unstable behavior of the cage. One solution to this problem is to reduce the amount of grease packed in, but reducing the amount of grease packed in leads to problems with the durability of the bearing.

[0009] In a sealed bearing, the space inside the bearing can be broadly divided into two: the dynamic space, which is affected by the cage and balls as the bearing rotates, and the static space, which is not affected by the cage and balls. Most of the grease enclosed inside the bearing moves into the static space during rotation. The ratio of this static space to the amount of grease enclosed (static space ratio) affects the bearing parameters. At high speeds, a smaller static space ratio (smaller amount of grease enclosed) is more advantageous in terms of heat generation and vibration, as it reduces the re-entrapment of grease that has migrated to the static space. However, as mentioned above, a smaller static space ratio reduces durability parameters.

[0010] An object of the present invention is to provide a rolling bearing which suppresses excessive temperature rise, stabilizes the behavior of the cage, and does not affect durability. [Means for solving the problem]

[0011] The rolling bearing of the present invention comprises an inner ring, an outer ring, a number of balls interposed between the inner ring and the outer ring, and a cage formed with pockets for holding the balls, the cage having two annular bodies overlapping each other in the axial direction, each annular body having a number of pocket wall portions arranged at regular intervals in the circumferential direction and each constituting an inner wall surface of the pocket, and a number of connecting plate portions connecting adjacent pocket wall portions in the circumferential direction, the two annular bodies being overlapped and connected to each other at the connecting plate portions, and the rolling bearing being lubricated with grease, The inner peripheral surface of the joined plate portions is provided with a grease reservoir wall for storing grease on the inner peripheral surface of the joined plate portions and preventing the grease from flowing outward in the axial direction from the inner peripheral surface.

[0012] With this configuration, while the cage is rotating, the grease reservoir wall collects grease on the inner peripheral surface of the connected connecting plate portion and prevents the grease from flowing outward in the axial direction from the inner peripheral surface. This reduces the actual static space ratio to the amount of grease enclosed. This prevents excessive heating of the bearing caused by re-entrapment of grease that has migrated from the dynamic space to the static space. In particular, the amount of grease flowing out during high-speed rotation is stable, stabilizing the heating characteristics of the bearing. The amount of grease adhering to the inner peripheral surface of the cage can be controlled by the grease reservoir wall, so the amount of imbalance in the cage is smaller than in conventional structures. This stabilizes the behavior of the cage. Compared to conventional structures, this structure suppresses temperature rise and stabilizes the behavior of the cage without reducing the amount of grease filled, which is effective in improving the durability of the bearing.

[0013] The grease reservoir walls may be provided on both axially opposite edge portions of the inner circumferential surface of the joined plate portions. In this case, the amount of grease held in the dynamic space can be increased compared to the conventional structure. Therefore, the amount of grease moving to the static space can be reduced without changing the amount of grease filled, i.e., the static space ratio.

[0014] The minimum diameter of the grease reservoir wall may be larger than the outer diameter of the inner ring and smaller than the inner diameter of the cage, in which case the grease reservoir wall can be easily assembled without interfering with the outer diameter of the inner ring when the two annular bodies are joined by overlapping each other at the joining plate portions to the subassembly of the inner and outer rings and balls.

[0015] The balls may be ceramic balls, which have a smaller specific gravity than steel balls made of bearing steel or the like, allowing the rolling bearing to operate at higher speeds and with improved heat resistance.

[0016] The rolling bearing may be a rolling bearing for a motor. If the rolling bearing for a motor has the effect of suppressing excessive temperature rise, stabilizing the behavior of the cage, and not affecting durability, the rolling bearing can be applied to motors for various applications, and the versatility of the rolling bearing for a motor can be improved. Effect of the Invention

[0017] The rolling bearing of the present invention is a rolling bearing having a cage in which two annular bodies are joined by overlapping each other at each joining plate portion, and the inner peripheral surface of the joining plate portion is provided with a grease reservoir wall that stores grease on the inner peripheral surface of the joined joining plate portion and prevents the grease from flowing outward in the axial direction from the inner peripheral surface. This makes it possible to realize a rolling bearing that suppresses excessive temperature rise, stabilizes the behavior of the cage, and does not affect durability. [Brief description of the drawings]

[0018] [Figure 1] 1 is a vertical sectional view of a rolling bearing according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view of a cage of the rolling bearing. [Diagram 3] FIG. 4 is a front view of the cage as viewed from the axial direction. [Figure 4A] FIG. [Figure 4B] 4B is a cross-sectional view taken along line IVB-IVB of FIG. 4A. [Figure 5A] FIG. 4 is a cross-sectional view taken along line VA-VA in FIG. [Figure 5B] 5B is a diagram for explaining a state in which the amount of grease is controlled in FIG. 5A. FIG. [Figure 6] FIG. 2 is an enlarged perspective view of a main part of the cage. [Figure 7] FIG. 4 is an enlarged cross-sectional view of the axial center portion of the cage. [Figure 8] FIG. 13 is a diagram showing the results of a temperature rise test of the cage and a conventional cage. [Figure 9] 2 is a conceptual diagram showing a rolling bearing for a motor in which the rolling bearing is applied to a motor. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] [First embodiment] A rolling bearing according to an embodiment of the present invention will be described with reference to FIGS. <About rolling bearings> As shown in Fig. 1, the rolling bearing 1 in this example is a grease-lubricated deep groove ball bearing, and includes an inner ring 2, an outer ring 3, balls 5 which are multiple rolling elements interposed between the rolling surfaces 2a, 3a of the inner and outer rings 2, 3, a cage 6 which holds the balls 5, and a seal 4. The balls 5 are steel balls or ceramic balls. In this specification, the "axial direction" refers to the direction along the bearing center line of the rolling bearing 1. The "radial direction" refers to the direction perpendicular to the straight line that forms the "axial direction".

[0020] An annular space is formed between the outer periphery of the inner ring 2 and the inner periphery of the outer ring 3, and openings at both axial ends of this annular space are closed by seals 4, 4. Lubricating grease is sealed in the closed annular space. A seal mounting groove 7 is formed on the inner circumferential surface of the outer ring 3, and an inner ring seal groove 8 is formed on the outer circumferential surface of the inner ring 2. Each seal 4 in this example is a non-contact seal in which the lip does not come into contact with the inner ring seal groove 8. The seal 4 is made of rubber material molded onto a core metal, and the outer circumferential edge of this seal 4 is fitted into and fixed in the seal mounting groove 7 of the outer ring 3.

[0021] <About the cage> The cage 6 in Fig. 2 is of a rolling element guide type and is composed of two synthetic resin annular bodies 10, 10 that overlap each other in the axial direction. As shown in Figs. 2 and 3, when the two annular bodies 10, 10 are joined together, the outer diameter surfaces of the annular bodies 10, 10 form cylindrical surfaces of the same diameter except for the cutout portion 13b, and the inner diameter surfaces of the annular bodies 10, 10 form cylindrical surfaces of the same diameter except for the cutout portion 13a. Each annular body 10 is formed by, for example, injection molding a synthetic resin. The two annular bodies 10, 10 have the same shape and can be molded using the same mold.

[0022] The synthetic resin may be polyolefin resin, thermosetting resin, engineering plastic, super engineering plastic, etc., as long as it is injection moldable and has sufficient heat resistance, oil resistance, mechanical strength, etc., as a cage material. In addition, the cage 6 is preferably made of a resin material with a melting point of 200°C to 360°C, preferably 200°C to 350°C, in consideration of heat resistance. If the melting point is less than 200°C, the resin may melt or wear abnormally due to frictional heat caused by the sliding of the balls and the pocket wall. In order to increase the strength, the resin may contain 15 to 45 mass% of glass fiber, carbon fiber, aramid fiber, etc., but resin without these fibers may also be used.

[0023] 4A and 4B, each annular body 10 has a plurality of semi-cylindrical pocket wall portions 13 and a plurality of connecting plate portions 14. The plurality of pocket wall portions 13 are arranged at regular intervals in the circumferential direction and each constitutes an inner wall surface of a pocket 12 that holds a ball 5. The plurality of connecting plate portions 14 connect the pocket wall portions 13 adjacent to each other in the circumferential direction.

[0024] 4B, the joining plate portion 14 has a mating surface 15 that comes into surface contact when the two annular bodies 10, 10 are joined together. Near the circumferential center of the mating surface 15 of the joining plate portion 14, there are formed a joining claw 16 that protrudes in the axial direction and a joining hole 17 into which the joining claw 16 of the other annular body 10 is inserted. A hook 19 is formed at the axial tip of the connecting claw 16, and the hook 19 of one annular body 10 engages with a step 18 formed on the inner surface of the connecting hole 17 of the other annular body 10. This engagement prevents the connecting claw 16 from slipping out of the connecting hole 17, and the two annular bodies 10, 10 are overlapped and connected to each other.

[0025] The connecting plate portion 14 has a protruding wall portion 20 and a receiving recess 21. The protruding wall portion 20 is provided at one circumferential end of the mating surface 15 of one of the annular bodies 10 so as to protrude in the axial direction. The receiving recess 21 is provided at the other circumferential end of the mating surface 15 of one of the annular bodies 10, and receives the protruding wall portion 20 of the other annular body 10. Since the connecting plate portion 14 has the protruding wall portion 20 and the receiving recess 21, the joint of the two annular bodies 10, 10 when they are connected is located at a position shifted from the axial center of the pocket 12. This can prevent the balls 5 from contacting the connecting plate portion 14 due to the delay or advance of the balls 5 during bearing operation. Therefore, it is possible to stably hold the balls 5. When the two annular bodies 10, 10 are joined together, the space formed by the portions of the pocket walls 13, 13 that face each other in the axial direction and the portions of the connecting plate portions 14, 14 connected to the pocket walls 13, 13 that face each other in the circumferential direction is the pocket 12.

[0026] When the two annular bodies 10, 10 are joined together, the protruding wall portion 20 and the accommodating recess 21 are sized to generate circumferential and axial gaps 22, 23 between the protruding wall portion 20 and the accommodating recess 21. This makes it possible to prevent interference between the protruding wall portion 20 and the accommodating recess 21 due to differential shrinkage after the annular body 10 is injection molded, and makes it possible to reliably bring the mating surfaces 15 of the joining plate portions 14 of the two annular bodies 10, 10 into close contact with each other.

[0027] A partial concave spherical surface 25 is formed on both circumferential ends of each pocket 12, following the outer periphery of the ball 5. The partial concave spherical surfaces 25 are formed facing each other at the front and rear in the traveling direction of the ball 5, sandwiching the ball 5 therebetween. The radius of curvature of the partial concave spherical surface 25 is set slightly larger than the radius of the ball 5.

[0028] <About the cutout> 3, the cage 6 has cutouts 13a, 13b on the inner and outer diameter surfaces of the pocket wall 13 so that the radial dimension of the pocket wall 13, that is, band width W1, is smaller than the radial dimension W2 of the connecting plate 14. The cutouts 13a, 13b on the inner and outer diameter surfaces are curved surfaces that form concave curves when viewed from the bearing axial direction. These cutouts 13a, 13b are formed, for example, during injection molding of the annular body 10, but can also be formed by machining or the like after injection molding.

[0029] In each pocket wall 13, the deepest part of the cutout 13a on the inner diameter surface is provided at the circumferential middle part of the inner diameter surface, and the deepest part of the cutout 13b on the outer diameter surface is provided at the circumferential middle part of the outer diameter surface. In each pocket wall 13, the band width W1 is smallest at the circumferential middle part, and is formed so that the band width W1 gradually increases from the circumferential middle part toward both sides in the circumferential direction along the curved shape.

[0030] <Grease reservoir wall> As shown in Fig. 5A, grease reservoir walls 26, 26 are provided on the inner peripheral surface of the joined joint plate parts 14, 14. As shown in Fig. 6, which is an enlarged view of part VI in Fig. 2, the grease reservoir walls 26, 26 are integrally formed on both axial side edges of the inner peripheral surface of the joined plate parts 14, 14. As shown in Fig. 5B, the grease reservoir walls 26, 26 store grease Gr on the inner peripheral surface of the joined joint plate parts 14, 14 and prevent the grease Gr from flowing out from the inner peripheral surface to the axial outside A1. By adjusting the wall height, i.e., the radial height, of the grease reservoir walls 26, the amount of grease adhering to the inner peripheral surface of the joined plate parts 14, 14 can be adjusted. In other words, when the grease Gr accumulates above the wall height of the grease reservoir wall 26, the grease Gr above the wall height flows out, but a certain amount of grease Gr contained in the grease containing space GS (Figure 6) within the wall height remains attached to the inner circumferential surface of the connecting plate portions 14, 14.

[0031] As shown in FIG. 7, the minimum diameter D 26is larger than the inner ring outer diameter D2 and smaller than the cage inner diameter D6. In other words, (cage inner diameter D6)>(minimum diameter D 26 The relationship was set so that the minimum diameter D of the grease reservoir wall 26 was greater than the outer diameter D of the inner ring. 26 A predetermined radial gap δ is set between the inner ring outer diameter D2 and the inner ring outer diameter D3. The grease reservoir wall 26 has a maximum wall height at a circumferential intermediate portion of the inner peripheral surface of the connecting plate portion 14. The circumferential intermediate portion where the wall height is maximum corresponds to the minimum diameter D 26 The wall height is gradually reduced from the circumferential intermediate portion toward both circumferential sides.

[0032] <Temperature rise test> A temperature rise test was carried out with and without the grease reservoir wall 26. <Test conditions> Testing machine: High-speed testing machine Test bearing: deep groove ball bearing with designation 6312, sealed on both sides, grease lubricated Rotation speed: 3000min -1 From 13500min -1 Step up to Load: Axial load Fa=588.4N Measurement item: Bearing outer ring temperature

[0033] The high-speed testing machine had two of the deep groove ball bearings installed in a housing with a specified distance between them in the axial direction, and the inner rings rotated by driving a motor. Thermocouples for measuring the temperature of the outer rings of each deep groove ball bearing were installed in the housing. The outer ring temperature of the deep groove ball bearing closest to the motor side, which has the most severe temperature conditions, was used for a deep groove ball bearing equipped with a conventional cage without a grease reservoir wall (comparative example) and a deep groove ball bearing equipped with a cage equipped with a grease reservoir wall (embodiment).

[0034] <Temperature rise test results> As shown in FIG. 8, in contrast to the comparative example without a grease reservoir wall, the embodiment with the grease reservoir wall suppresses a sudden rise in temperature and enables high-speed operation.

[0035] <Action and effect> According to the rolling bearing 1 of FIG. 1 described above, during rotation of the cage of FIG. 6, the grease reservoir walls 26, 26 collect grease on the inner peripheral surface of the coupled coupling plate parts 14, 14 and prevent the grease from flowing outward in the axial direction from the inner peripheral surface. This reduces the actual static space ratio to the amount of grease enclosed. This suppresses excessive heating of the bearing caused by re-entrapment of grease that has migrated from the dynamic space to the static space. In particular, the amount of grease flowing out during high-speed rotation is stabilized, stabilizing the temperature rise characteristics of the bearing. The static space refers to the space in the bearing space between the inner and outer rings through which the balls and cage do not pass when the bearing rotates.

[0036] The amount of grease adhering to the inner peripheral surface of the cage 6 can be controlled by the grease reservoir walls 26, 26, so the amount of imbalance in the cage 6 is smaller than in the conventional structure. This stabilizes the behavior of the cage 6. Compared to the conventional structure, this has the effect of suppressing temperature rise and stabilizing the behavior of the cage 6 without reducing the amount of grease filled, which is effective in improving the durability of the bearing.

[0037] Grease reservoir walls 26, 26 are provided on both axial edge portions of the inner circumferential surface of the joined joint plate portions 14, 14. In this case, the amount of grease held in the dynamic space can be increased compared to the conventional structure. Therefore, the amount of grease moving to the static space can be reduced without changing the amount of grease enclosed, i.e., the static space ratio.

[0038] As shown in FIG. 7, the minimum diameter D 26 is larger than the inner ring outer diameter D2 and smaller than the cage inner diameter D6. In this case, when the two annular bodies 10, 10 in Fig. 2 are overlapped and joined at the joining plate portions 14 to the subassembly of the inner and outer rings 2, 3 and balls 5 in Fig. 1, the grease reservoir walls 26, 26 can be easily assembled without interfering with the inner ring outer diameter.

[0039] <Roller bearings for motors> This rolling bearing is used, for example, as rolling bearings 50, 50 for a motor 51 shown generally in Fig. 9. However, this rolling bearing can also be applied to applications other than motors. If the rolling bearing is a rolling bearing for motors which has the effect of suppressing excessive temperature rise, stabilizing the behavior of the cage, and not affecting durability, the rolling bearing can be applied to motors for a variety of applications, thereby increasing the versatility of the rolling bearing as a motor rolling bearing.

[0040] <Other embodiments> Grease reservoir walls 26, 26 may be provided in addition to both axially opposite edge portions of the inner circumferential surface of the connecting plate portions 14, 14 shown in Fig. 5A. For example, a pair of grease reservoir walls may be provided in an axially intermediate portion of the inner circumferential surface. The pocket walls 13 of each annular body 10 in FIG. 2 are not limited to being semi-cylindrical, but may be semi-spherical.

[0041] The seal 4 in FIG. 1 may be a contact seal in which the lip contacts the inner ring seal groove 8 . The seal 4 may be a so-called shield plate made only of a steel plate. An open type rolling bearing without the seal 4 may also be used. Any of the rolling bearings may be applied to machine tools, industrial machines, vehicles, and the like. Each annulus can be formed by 3D printing or machining.

[0042] Although the embodiment of the present invention has been described above, the disclosed embodiment is illustrative in all respects and is not restrictive. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0043] 1... rolling bearing, 2... inner ring, 3... outer ring, 5... ball, 6... cage, 10... annular body, 12... pocket, 13... pocket wall portion, 14... connecting plate portion, 26... grease reservoir wall

Claims

1. A rolling bearing comprising an inner ring, an outer ring, a plurality of balls interposed between the inner ring and the outer ring, and a cage formed with pockets for holding the balls, the cage having two annular bodies overlapping each other in the axial direction, each annular body having a plurality of pocket wall portions arranged at regular intervals in the circumferential direction and each constituting an inner wall surface of one of the pockets, and a plurality of connecting plate portions connecting adjacent pocket wall portions in the circumferential direction, the two annular bodies being overlapped and connected to each other at the connecting plate portions, and lubricated with grease, A rolling bearing comprising a grease reservoir wall on the inner circumferential surface of the connected connecting plate portions, the grease reservoir wall storing grease on the inner circumferential surface of the connected connecting plate portions and preventing the grease from leaking axially outward from the inner circumferential surface.

2. 2. The rolling bearing according to claim 1, wherein the grease reservoir walls are provided on both axially opposite edge portions of the inner circumferential surfaces of the joined connecting plate portions.

3. 3. The rolling bearing according to claim 1, wherein the minimum diameter of the grease reservoir wall is larger than the outer diameter of the inner ring and smaller than the inner diameter of the cage.

4. 3. The rolling bearing according to claim 1, wherein the balls are ceramic balls.

5. 3. The rolling bearing according to claim 1, wherein the rolling bearing is a rolling bearing for a motor.

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