Rolling bearing

Abstract

To provide a rolling bearing stabilizing behaviors of a retainer, and having the retainer for reducing abrasion.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 14. Contact parts P contacting a ball at plural points at an interval in a retainer axial direction C1 are provided at both circumferential ends of each pocket 12.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a rolling bearing, and more particularly to a technique that can stabilize the behavior of a cage in a rolling bearing for a motor, for example, and reduce wear, excessive temperature rise, and the like. [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 that are lubricated with grease, it is known that grease adhering to the surfaces of the rotating balls becomes trapped between the cage pockets or raceway surfaces, affecting parameters such as bearing temperature rise, vibration, and noise levels, and it can be said that grease flow inside the bearing affects bearing performance. In recent years, there has been an increasing demand for higher bearing speeds, and cages, which have a significant impact on grease flow, need to be able to accommodate these high speeds.

[0004] The synthetic resin cage of Patent Document 1 has notches 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, taking into consideration deformation of the cage due to centrifugal force, the relief shape in the pocket axial direction is formed as a cylindrical surface extending in the radial direction of the cage on the inner diameter side of the ball pitch circle. [Prior art documents] [Patent documents]

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

[0006] In Patent Document 1, notches are 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 break-in time. Furthermore, the notches scrape off some of the grease remaining in the stationary space, and base oil is supplied between the ball and the pocket, thereby suppressing heat generation. While the shape of the notches is actually effective, the centrifugal force acting on the cage rotating at high speed can deform the pocket in a direction that reduces the axial clearance between the ball and pocket, which can cause the ball to interfere with the pocket in the axial direction. This can lead to deterioration of bearing parameters such as abnormal wear and heat generation.

[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 axial relief shape of the pocket is a cylindrical surface extending in the radial direction of the cage on the inner diameter side of the ball pitch circle, so that interference between the pocket and the balls does not occur even if deformation occurs in the axial portion of the cage pocket due to centrifugal force. This shape prevents interference between the pocket and the balls even if the pocket is deformed by centrifugal force, thereby preventing abnormal wear and the like. However, this method has the problem of increasing vibration due to the large axial gap between the cage and the balls.

[0008] During high-speed rotation, the influence of centrifugal force becomes greater, making the behavior of the cage more unstable. In particular, the behavior of the cage becomes unstable due to imbalances such as the weight balance of the cage itself or variations in the amount of grease adhering to the cage. Furthermore, when the pocket shape, particularly the portion that comes into contact with the balls in the circumferential direction of rotation, is a partial spherical surface 71 as shown in Figures 11 and 12, as in the conventional cage 70 shown in Figure 10, the following problems arise.

[0009] 13A, when the balls 72 move in the circumferential direction A2 of rotation, the contact position between the cage and the balls 72 in the circumferential direction is one-point contact, as shown in Fig. 13B, and the contact point P changes depending on the quality of the cage pocket, resulting in unstable behavior of the cage 70. When the rotation of the cage 70 becomes unstable, the balls 72 and the cage 70 come into abnormal contact, causing problems such as wear and excessive temperature rise.

[0010] An object of the present invention is to provide a rolling bearing equipped with a cage that stabilizes the behavior of the cage and reduces wear, etc. [Means for solving the problem]

[0011] The rolling bearing of the present invention comprises 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 the pocket, and a plurality of connecting plate portions connecting the pocket wall portions adjacent in the circumferential direction, the two annular bodies overlapping and connected to each other at the connecting plate portions, At both circumferential ends of each pocket, contact portions are provided that come into contact with the balls at a plurality of points spaced apart in the axial direction of the cage.

[0012] With this configuration, contact portions are provided at both circumferential ends of each pocket, which contact the balls at multiple points spaced apart in the axial direction of the cage. Because this cage contacts the balls at multiple points in the circumferential direction, no force is generated that tends to move the cage in the axial direction. As a result, the cage's axial behavior is more stable, especially during high-speed rotation, than conventional cages, which contact the balls at a single point in the circumferential direction of rotation, and the surface pressure at the contact portions is reduced, working more effectively against wear.

[0013] A plurality of tapered surfaces inclined with respect to a plane including the cage axis and passing through the center of the pocket may be formed at both circumferential ends of each pocket, and the contact portion may be provided on each tapered surface. In this case, each tapered surface can be easily formed using a mold or the like, thereby reducing manufacturing costs.

[0014] The tapered surfaces formed at one circumferential end of each pocket may be provided on one of the annular bodies, in which case no force is generated in the direction separating the two annular bodies, thereby preventing abnormalities in the cage.

[0015] The balls may be ceramic balls, which have a lower specific gravity than steel balls made of bearing steel, for example, and thus can increase the speed of the rolling bearing and improve heat resistance.

[0016] The rolling bearing may be a rolling bearing for a motor. When the rolling bearing for a motor includes a cage that stabilizes the behavior of the cage and reduces wear, the rolling bearing can be applied to motors for a variety of applications, thereby increasing the versatility of the rolling bearing for a motor. [Effects of the Invention]

[0017] The rolling bearing of the present invention is equipped with a cage formed by joining two overlapping annular bodies, and contact portions are provided at both circumferential ends of each pocket of the cage that come into contact with the balls at multiple points spaced apart in the axial direction of the cage, thereby stabilizing the behavior of the cage and reducing wear on the cage. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a vertical cross-sectional view of a rolling bearing according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a front view of the cage of the rolling bearing as viewed from the axial direction. [Figure 3A] FIG. 3 is a cross-sectional view taken along line IIIA-IIIA in FIG. 2. [Figure 3B]FIG. 3B is a cross-sectional view taken along line IIIB-IIIB in FIG. 3A. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. [Figure 5A] FIG. [Figure 5B] FIG. 4 is a partially enlarged view showing a contact portion between the cage and the balls. [Figure 6] FIG. 10 is a diagram showing radial vibration results of the rolling bearing and a comparative example equipped with a conventional cage. [Figure 7] FIG. 10 is a diagram showing the results of axial vibration of the rolling bearing and a comparative example equipped with a conventional cage. [Figure 8] FIG. 2 is a conceptual diagram showing a rolling bearing for a motor in which the rolling bearing is applied to a motor. [Figure 9A] FIG. 6 is a partially enlarged view of a cage of a rolling bearing according to a second embodiment. [Figure 9B] FIG. 10 is a partially enlarged view of a cage of a rolling bearing according to a third embodiment. [Figure 9C] FIG. 10 is a partially enlarged cross-sectional view of a cage of a rolling bearing according to a fourth embodiment. [Figure 10] FIG. 10 is a front view of a conventional cage as viewed from the axial direction. [Figure 11] FIG. 11 is a cross-sectional view taken along line XI-XI in FIG. [Figure 12] FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. [Figure 13A] FIG. 10 is a partially enlarged view of a main part of a conventional cage. [Figure 13B] FIG. 10 is a partially enlarged view showing a contact portion between the conventional cage and the balls. DETAILED DESCRIPTION OF THE INVENTION

[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 Figure 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 that holds each ball 5, and a seal 4. The balls 5 are steel balls or ceramic balls. In this specification, "axial direction" refers to the direction along the center line of the rolling bearing 1. "Radial direction" refers to the direction perpendicular to the 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. In this example, each seal 4 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 by molding a rubber material onto a core metal, and the outer periphery 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 annular bodies 10, 10 made of synthetic resin that overlap each other in the axial direction, as shown in Figs. 3A and 3B. When the two annular bodies 10, 10 are joined together, the outer diameter surfaces of the annular bodies 10, 10 have the same diameter except for the cutout portion 13b, and the inner diameter surfaces of the annular bodies 10, 10 have the same diameter except for the cutout portion 13a, as shown in Fig. 2. Each annular body 10 is formed by, for example, injection molding synthetic resin. The two annular bodies 10, 10 have the same shape and can be molded using the same mold.

[0022] The synthetic resin can be injection-moldable and has sufficient heat resistance, oil resistance, and mechanical strength for use as a cage material, and can be selected from polyolefin resins, thermosetting resins, engineering plastics, super-engineering plastics, etc. Furthermore, considering heat resistance, the cage 6 should be made of a resin material with a melting point of 200°C to 360°C, preferably 200°C to 350°C. Materials with a melting point below 200°C may melt or wear abnormally due to frictional heat generated by the sliding of the balls and pocket walls. To increase strength, resins containing 15 to 45 mass% of glass fiber, carbon fiber, or aramid fiber can be used, but resins without these fibers can also be used.

[0023] 3A and 3B, 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 form the 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 that are adjacent in the circumferential direction.

[0024] 3B, the joining plate 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 14, there are formed joining claws 16 that protrude in the axial direction and joining holes 17 into which the joining claws 16 of the other annular body 10 are 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 joined together by overlapping them.

[0025] The connecting plate 14 has a protruding wall 20 and an accommodating recess 21. The protruding wall 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 accommodating recess 21 is provided at the other circumferential end of the mating surface 15 of one of the annular bodies 10 and accommodates the protruding wall 20 of the other annular body 10. Because the connecting plate 14 has the protruding wall 20 and the accommodating recess 21, when the two annular bodies 10 are connected, the seam between the annular bodies 10 is positioned off-center in the axial direction of the pocket 12. When the two annular bodies 10 are connected, the space formed by the axially opposing portions of the pocket walls 13 and the circumferentially opposing portions of the connecting plates 14 connected to the pocket walls 13 defines 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 leave circumferential and axial gaps 22, 23 between the protruding wall portion 20 and the accommodating recess 21. This prevents interference between the protruding wall portion 20 and the accommodating recess 21 due to differential shrinkage after injection molding of the annular body 10, and ensures that the mating surfaces 15 of the joining plate portions 14 of the two annular bodies 10, 10 are tightly attached to each other.

[0027] <Contact parts, etc.> As shown in Figure 4, each pocket 12 has contact portions P at both circumferential ends that contact the outer periphery of the balls 5 (Figure 5A) at multiple points (two points in this example) at a distance δ (Figure 5B) determined in the cage axial direction C1. The "cage axial direction" C1 refers to the direction along the cage axis, which is the rotational axis of the cage 6. The distance δ between the two contact portions P, P shown in Figure 5B is determined appropriately depending on, for example, the bearing size and the results of vibration tests described below.

[0028] At both circumferential ends of each pocket 12 shown in Fig. 4, multiple (two in this example) tapered surfaces P2 are formed that are inclined at a predetermined angle α with respect to a plane P1 that includes the cage axis and passes through the pocket center P0, as shown in Fig. 5A. As shown in Fig. 5B, a contact portion P is provided on each tapered surface P2. A tapered edge P3 at one circumferential end of each pocket 12, where adjacent tapered surfaces P2, P2 are connected, is located at the axial center of the pocket 12. The tapered edge P3 at the other circumferential end of each pocket 12 is also located at the axial center of the pocket 12.

[0029] As shown in FIG. 3A, with respect to the tapered edge P3 of each pocket 12 as a reference, tapered surfaces P2, P2, partial spherical surfaces P4, P4, and stepped flat surfaces P5, P5 are sequentially connected to approximately cylindrical surfaces P6, P6 on both sides of the cage in the axial direction. The partial spherical surface P4 has a partial spherical shape with a spherical surface R that is slightly larger than the diameter of the balls 5. The spherical center of the partial spherical surface P4 is the pocket center P0 (FIG. 4). As shown in FIG. 4, the two tapered surfaces P2, P2 formed at one circumferential end of each pocket 12 are provided on a single annular body 10. The two tapered surfaces P2, P2 formed at the other circumferential end of each pocket 12 are provided on a single annular body 10 that is connected to the annular body 10.

[0030] <About the cutout> 2, the cage 6 has cutouts 13a, 13b formed in the inner and outer diameter surfaces of the pocket wall 13 so that the radial dimension of the pocket wall 13, i.e., band width W1, is smaller than the radial dimension W2 of the connecting plate 14. The cutouts 13a, 13b in the inner and outer diameter surfaces have a concave curved shape when viewed axially of the bearing. 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.

[0031] In each pocket wall 13, the deepest part of the cutout 13a on the inner diameter surface is provided in the circumferential middle part of the inner diameter surface, and the deepest part of the cutout 13b on the outer diameter surface is provided in 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 along the curved surface shape from the circumferential middle part toward both sides in the circumferential direction.

[0032] <Vibration test> Vibration tests were carried out on a deep groove ball bearing (Example) equipped with the cage according to this embodiment and a deep groove ball bearing (Comparative Example) equipped with a conventional cage that makes single-point contact with the ball. <Test conditions> Testing machine: High-speed testing machine Test bearing: Deep groove ball bearing with nominal number 6312, with seals on both sides, grease lubrication Rotation speed: 3000 min -1 From 13,500 min -1 Step up to Load: Axial load Fa=588.4N Measurement items: Radial vibration acting on the bearing outer ring (radial vibration), axial vibration acting on the outer ring (axial vibration)

[0033] The high-speed testing machine is configured so that two deep groove ball bearings are mounted in a housing with a predetermined axial distance between them, and the inner rings are rotated by a motor. A vibration sensor capable of measuring the radial and axial vibrations of the outer rings of each deep groove ball bearing is mounted in the housing. Examples of the vibration sensors used include piezoelectric, electromagnetic, and capacitance vibration sensors. Of the two deep groove ball bearings mounted axially at a predetermined distance, the vibration value of the deep groove ball bearing closest to the motor, which is subject to the most severe vibration conditions, was used.

[0034] <Vibration test results> As shown in Figs. 6 and 7, in contrast to the comparative example, in the example, both radial and axial vibrations are suppressed across the entire rotational speed range, and the behavior of the cage is stabilized.

[0035] <Action and effect> 1 explained above, contact portions P are provided at both circumferential ends of each pocket 12, which make contact with the balls at multiple points spaced apart in the cage axial direction C1, as shown in Figure 4. Because this cage 6 makes two-point contact with the balls in the circumferential direction, no force is generated that tends to move the cage 6 in the axial direction. For this reason, the behavior of the cage 6 in the cage axial direction C1, particularly during high-speed rotation, is more stable than with conventional cages that make contact at a single point in the circumferential direction of rotation, and the surface pressure at the contact portions P is reduced, working more favorably against wear.

[0036] At both circumferential ends of each pocket 12, a plurality of tapered surfaces P2 are formed that are inclined with respect to a plane P1 that includes the cage axis and passes through the pocket center P0, and each tapered surface P2 is provided with a contact portion P. In this case, each tapered surface P2 can be easily formed using a mold or the like, which reduces manufacturing costs.

[0037] The two tapered surfaces P2, P2 formed at one circumferential end of each pocket 12 are provided on one annular body 10. In this case, no force is generated in the direction separating the two annular bodies 10, 10, and stress is generated only on one of the two annular bodies 10, 10. As a result, excessive load is not applied to the coupling claws 16 in FIG. 3B, and abnormalities in the coupling claws 16 can be prevented. This makes it possible to prevent abnormalities in the cage 6.

[0038] <Rolling bearings for motors> This rolling bearing is used, for example, as rolling bearings 50, 50 for a motor 51 shown schematically in Fig. 8. However, this rolling bearing can also be used for purposes other than motors. When the rolling bearing is a rolling bearing for a motor and is equipped with a retainer that stabilizes the behavior of the retainer and can reduce wear, etc., 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.

[0039] <Other embodiments> In the following description, parts corresponding to matters previously described in each embodiment are given the same reference numerals, and duplicated description will be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those in the previously described embodiment unless otherwise specified. The same configuration produces the same effects. It is possible to combine not only the parts specifically described in each embodiment, but also partially combine embodiments as long as there is no particular problem with the combination.

[0040] [Second embodiment: FIG. 9A, three-point contact] 9A, a contact portion P that makes three-point contact may be provided at both circumferential ends of each pocket 12. In this case, the surface pressure at the contact portion P can be further reduced compared to a conventional cage that makes contact at one point in the circumferential direction of rotation, which is more advantageous in terms of wear resistance.

[0041] [Third embodiment: Figure 9B, composite curved surface] At both circumferential ends of each pocket 12, instead of each tapered surface P2 of FIG. 5B, a concave curved surface P7 as shown in FIG. 9B may be applied, and each concave curved surface P7 may be provided with a contact portion P. Each concave curved surface P7 may be, for example, a cylindrical surface extending along the radial direction of each pocket 12. This configuration provides substantially the same effects as the first embodiment.

[0042] [Fourth embodiment: FIG. 9C, tapered surfaces on each annular body] For example, under conditions of use at medium to low rotation speeds, each annular body 10 may be provided with a tapered surface P2, and each tapered surface P2 may be provided with a contact portion, as shown in Fig. 9C. However, this is not suitable for use at high rotation speeds because a force is generated in the direction A1 that separates the two annular bodies 10, 10.

[0043] In the pocket wall portion 13 of FIG. 4, the cylindrical surfaces P6, P6 on both sides in the axial direction of the cage may be partial spherical surfaces. 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 of only a steel plate. An open type rolling bearing without the seal 4 may also be used. Any of the rolling bearings can also be applied to machine tools, industrial machinery, vehicles, and the like. Each annulus can also be formed by 3D printing or machining.

[0044] Although the embodiments of the present invention have been described above, the disclosed embodiments are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0045] 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, P... contact portion, P2... tapered surface

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 having pockets for holding each ball, wherein the cage has two annular bodies that overlap 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 the inner wall surface of the pocket, and a plurality of connecting plate portions connecting adjacent pocket wall portions in the circumferential direction, wherein the two annular bodies are joined together by overlapping each of the connecting plate portions, Each of the aforementioned pockets is provided with contact portions at both circumferential ends that contact the ball at multiple points spaced apart in the direction of the holder axis. Multiple tapered surfaces are formed at both circumferential ends of each pocket, inclined with respect to a plane that includes the retainer axis and passes through the pocket center, and the contact portion is provided on each tapered surface. The multiple tapered surfaces formed at one end of each pocket in the circumferential direction constitute rolling bearings provided on a single annular body.

2. A rolling bearing according to Claim 1, wherein the balls are ceramic balls.

3. A rolling bearing according to claim 1 or claim 2, wherein the rolling bearing is a rolling bearing for a motor.

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