Rolling bearings

Abstract

A rolling bearing capable of reducing the amount of dust generated from inside the bearing. [Solution] The rolling bearing comprises an inner ring 2, an outer ring 3, a plurality of balls interposed between the inner ring 2 and the outer ring 3, and a seal member 6 that seals the bearing space between the inner ring 2 and the outer ring 3. The seal member 6 has a main lip 15 that contacts a seal groove 7 in the inner ring 2, and a secondary lip 16 that protrudes axially inward from its base end and does not contact the seal groove 7, and grease is sealed in the bearing space. The seal member 6 is equipped with grease flow obstruction means Gs that obstructs the flow of grease from the inner circumferential surface 16b of the secondary lip 16 to the inner diameter side tip 15c of the main lip 15. The grease flow obstruction means Gs includes a shape in which the inner circumferential surface 16b of the secondary lip 16 is inclined toward the outer diameter as it extends axially outward.

Description

[Technical Field]

[0001] The present invention relates to a rolling bearing, and to a technique capable of reducing the amount of dust generated from inside the bearing. [Background technology]

[0002] 14, there is a model of rolling bearing 50 for a servo motor in which encoder 52 is located near motor 51. For such models, low dust generation as the rolling bearing 50 is required using a contact seal to prevent malfunction of encoder 52 due to dust generation from inside the bearing and seal wear powder adhering to encoder 52.

[0003] Prior art includes Patent Documents 1 and 2. Both of these documents propose rolling bearings that can reduce the amount of dust generated from inside the bearing even when the internal pressure of the bearing increases during rotation. Specifically, they specify the relative positions of the core and the secondary lip, the shape of the tip of the contact seal lip that comes into contact with the seal groove, and the inclined surface of the seal groove. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-72083 [Patent Document 2] Japanese Patent Publication No. 2022-102580 Summary of the Invention [Problem to be solved by the invention]

[0005] The two prior art documents mentioned above are improvement proposals for preventing dust generation from inside the bearing, and there are no problems with the shape proposals in terms of dust generation. Both prior art documents have a structure in which contact occurs on the axial outer surface of the inner ring seal groove, which is effective in preventing dust generation from inside the bearing due to an increase in internal pressure. However, there are cases where base oil adhering to the bearing side of the seal surface (hereinafter referred to as the "inner seal surface") runs down the seal and reaches the tip of the inner lip. In this case, the base oil that has reached the tip of the inner lip may seep out.

[0006] Specifically, as shown in Figure 15A, the secondary lip 100, which is provided to prevent grease from entering the inner ring seal groove 7 on the inner surface of the seal, protrudes axially inward from the base end. As shown in Figure 15B, when the seal 101 is inserted into the bearing with interference, the secondary lip 100 tilts as the inner lip 102 deforms. The position of the seal 101 changes depending on the mounting state of the bearing. As shown in Figure 16, in a certain seal position, the secondary lip 100 tilts in a direction that directs the base oil Ky toward the inner lip tip 103. Therefore, the base oil Ky that reaches the inner lip tip 103 may seep out when the inner ring 104 rocks.

[0007] An object of the present invention is to provide a rolling bearing that can reduce the amount of dust generated from inside the bearing. [Means for solving the problem]

[0008] The rolling bearing of the present invention comprises an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and a seal member that seals a bearing space between the inner ring and the outer ring, the seal member having a main lip that contacts a seal groove in the inner ring and a sub-lip that protrudes axially inward from a base end portion and does not contact the seal groove, and grease is sealed in the bearing space, The sealing member is provided with a grease flow obstruction means for obstructing the flow of grease from the inner peripheral surface of the secondary lip to the inner diameter side tip of the primary lip.

[0009] With this configuration, the grease flow obstruction means obstructs the flow of grease from the inner circumferential surface of the secondary lip to the inner diameter side tip of the main lip, preventing the base oil of the grease running along the inner surface of the seal from reaching the inner diameter side tip of the main lip, thereby reducing the amount of dust generated from inside the bearing compared to conventional structures.

[0010] The grease flow obstruction means includes a shape in which the inner peripheral surface of the secondary lip is inclined toward the outer diameter side as it goes axially outward. When the axial direction of the rolling bearing is set along the horizontal axis, the base oil of the grease that flows along the inner surface of the seal can be more reliably prevented from accumulating on the inner peripheral surface of the secondary lip and flowing to the tip of the inner diameter side of the primary lip.

[0011] The grease flow obstruction means may have an uneven portion provided between the inner peripheral surface of the secondary lip and the axially inner surface of the primary lip. The surface extending from the inner peripheral surface of the secondary lip to the axially inner surface of the primary lip is referred to as the "seal back surface." In this case, the base oil of the grease running along the inner surface of the seal is blocked by the back surface of the seal and is released in the circumferential direction.

[0012] The seal member may be provided with an air hole on its outer circumferential side for releasing the internal pressure of the rolling bearing. In this case, by releasing the internal bearing pressure through the air hole when the rolling bearing rotates, it is possible to suppress excessive changes in the interference of the seal member and the outflow of grease caused by an increase in the internal bearing pressure.

[0013] The sealing member may be provided on only one axial side of the rolling bearing or on both axial sides. When the sealing member is provided on only one axial side, the number of parts and the number of steps required to process the seal grooves, etc., can be reduced, thereby reducing costs. When the sealing members are provided on both axial sides, it is possible to prevent grease from leaking from inside the bearing and foreign matter from entering from the atmosphere side. [Effects of the Invention]

[0014] The rolling bearing of the present invention comprises an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and a seal member sealing the bearing space between the inner ring and the outer ring, the seal member having a main lip that contacts the seal groove in the inner ring and a secondary lip that protrudes axially inward from its base end and does not contact the seal groove, the bearing space being filled with grease, and the seal member having grease flow obstruction means that obstructs the flow of grease from the inner circumferential surface of the secondary lip to the inner diameter side tip of the main lip, thereby reducing the amount of dust generated from inside the bearing. [Brief explanation of the drawings]

[0015] [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 perspective view of the cage of the rolling bearing. [Figure 3] FIG. 2 is an enlarged cross-sectional view showing a seal member of the rolling bearing. [Figure 4] FIG. 2 is an enlarged cross-sectional view of the lip and other parts of the seal member. [Figure 5A] FIG. 4 is an enlarged cross-sectional view of the grease flow obstruction means of the seal member. [Figure 5B] 4 is an enlarged cross-sectional view of a main part for explaining the effect of the sealing member. FIG. [Figure 6] FIG. [Figure 7] FIG. 6 is an enlarged cross-sectional view of a main portion of a sealing member in a rolling bearing according to a second embodiment of the present invention. [Figure 8] FIG. 10 is an enlarged cross-sectional view of a main part showing a modified example of the seal member. [Figure 9] 10A and 10B are enlarged cross-sectional views of the main part for explaining the effect when the attitude of the sealing member is different. [Figure 10] FIG. 10 is an enlarged cross-sectional view of a main portion of a sealing member in a rolling bearing according to a third embodiment of the present invention. [Figure 11] FIG. 10 is a vertical cross-sectional view of a rolling bearing according to a fourth embodiment of the present invention. [Figure 12]FIG. 10 is a vertical cross-sectional view of a rolling bearing according to a fifth embodiment of the present invention. [Figure 13] FIG. 10 is a vertical cross-sectional view of a rolling bearing according to a sixth embodiment of the present invention. [Figure 14] FIG. 1 is a diagram illustrating a rolling bearing for a servo motor. [Figure 15A] FIG. 10 is an enlarged cross-sectional view of a main part of a conventional seal member showing a state before the seal member comes into contact with a seal groove. [Figure 15B] FIG. 4 is an enlarged cross-sectional view of a main part showing a state after the seal member has come into contact with the seal groove. [Figure 16] FIG. 3 is an enlarged cross-sectional view of a main part of the seal member, showing the flow of base oil adhering to the inner seal surface. DETAILED DESCRIPTION OF THE INVENTION

[0016] [First embodiment] A rolling bearing according to an embodiment of the present invention will be described with reference to Figures 1 to 6. This rolling bearing is applied to, for example, industrial machinery such as servo motors, vehicles, etc. However, the rolling bearing is not limited to these uses and can be applied to various types of machinery, devices, etc.

[0017] <General structure of rolling bearing> 1 is a cross section (longitudinal cross section) of the rolling bearing 1 cut along a plane including the axial direction. The same applies to cross sections of the other embodiments. The rolling bearing 1 is a deep groove ball bearing comprising an inner ring 2, an outer ring 3, balls (rolling elements) 4, a cage 5, and a seal member 6. A plurality of balls 4 are interposed between the raceway surfaces 2a, 3a of the inner and outer rings 2, 3 and are held at regular intervals in the circumferential direction by the cage 5. The seal member 6 is attached to the outer ring 3 and closes the bearing space, which is the annular space between the inner ring 2 and the outer ring 3. In this example, seal members 6, 6 are attached to both axial sides of the inner circumferential surface of the outer ring. Grease, a lubricant, is sealed in the bearing space between the inner and outer rings 2, 3.

[0018] In this specification, a rolling bearing may be simply referred to as a "bearing." In the following description, the direction of the bearing center axis AX, which is the bearing axis, is referred to as the "axial direction," the direction perpendicular to the bearing center axis AX is referred to as the "radial direction," and the direction around the bearing center axis AX is referred to as the "circumferential direction." In addition, the side facing the bearing center axis AX is referred to as the "inner diameter side," and the side away from the bearing center axis AX is referred to as the "outer diameter side."

[0019] <Cage> As shown in FIG. 2, the cage 5 in this example is made of synthetic resin and is a two-piece cage consisting of two identically shaped annular bodies 5a, 5a mated together. This cage 5 holds balls 4 (FIG. 1) in pockets Pt, which have a cylindrical axial shape. Each annular body 5a has multiple semi-cylindrical pocket walls 5c and multiple connecting plates 5b. The two pocket walls 5c, 5c are mated with each other in the axial direction to form pockets Pt. The pockets Pt are evenly spaced around the circumference. The cage 5 has engaging holes Ka and engaging claws Kb that engage with each other on the connecting plates 5b between the pockets Pt. The cage 5 is assembled by engaging the engaging claws Kb with the engaging holes Ka and mating the two identically shaped annular bodies 5a, 5a. The pockets of the cage 5 may also have a spherical shape.

[0020] <Seal structure, etc.> As shown in Figure 1, each seal member 6 is a contact seal in which a main lip 15 contacts a seal groove 7 in the inner ring 2. Seal grooves 7 are formed in the circumferential direction on the outer peripheral surface of the inner ring 2, and seal grooves 9 for fixing the seal member are provided on the inner peripheral surface of the outer ring 3 opposite each seal groove 7. As shown in Figure 3, the seal member 6 is made by molding a rubber material 11 onto a core metal 10, and an outer peripheral portion 8 of the seal member 6 is fitted into and fixed in the seal groove 9 of the outer ring 3.

[0021] <Outer ring seal groove> The seal groove 9 of the outer ring 3 has, in order axially outward, an inner surface 9a, a groove bottom surface 9c, and an outer surface 9b. The inner surface 9a connects to outer ring shoulders provided on both axial sides of the raceway surface 3a (Figure 1).

[0022] The groove bottom surface 9c, which is smoothly connected to the inner surface 9a, is recessed radially outward. The outer surface 9b is smoothly connected to the groove bottom surface 9c and is formed as an inclined surface that slopes inward in the axial direction. In Figures 1 and 3, a portion of the outer peripheral portion of the seal member 6 is shown as being embedded in the seal groove 9 of the outer ring 3, but this portion is an interference, and in reality it is fitted into the seal groove 9 in an elastically deformed state. The same applies to the seal structures in Figures 11 to 13, which will be described later.

[0023] As shown in FIG. 4, the inner peripheral portion 13 of the seal member 6 is provided with a main lip 15 that comes into contact with the outer surface 7c of the seal groove 7 of the inner ring 2. 1 and 3, a portion of the main lip 15 of the seal member 6 is shown as being embedded in the seal groove 7 of the inner ring 3, but this portion is an interference and is actually in contact with the seal groove 7 in an elastically deformed state. The same applies to the seal structures in Figs. 11 to 13, which will be described later.

[0024] <Air vent> As shown in Figure 6, a plurality of air holes 12 for releasing the internal pressure of the rolling bearing are provided in the outer peripheral portion 8 (Figure 3) of the seal member 6. These air holes 12 include radial air holes 12a, 12a formed along the radial direction and axial air holes 12b formed along the axial direction. The air holes 12a, 12b are each formed by grooves provided in the outer peripheral portion 8 (Figure 3) of the seal member 6. The radial air holes 12a, 12a and the axial air hole 12b are provided at different circumferential positions. The number and circumferential positions of the air holes 12a, 12b are not limited to those shown in Figure 6.

[0025] 3 and 6, the radial air holes 12a, 12a and the axial air hole 12b communicate with each other via the groove bottom surface 9c of the seal groove 9. Therefore, when the rolling bearing 1 (FIG. 1) is rotating, the internal bearing pressure can be released to the outside from the two radial air holes 12a, 12a via the axial air hole 12b.

[0026] <Inner ring seal groove> As shown in Figure 1, the seal groove 7 of the inner ring 2 has, in order axially outward, an inner surface 7a, a groove bottom surface 7b, and an outer surface 7c. The inner surface 7a connects to inner ring shoulders provided on both axial sides of the raceway surface 2a and forms an inclined surface that slopes inward toward the inner diameter as it extends axially outward. The groove bottom surface 7b, which smoothly connects to this inner surface 7a, is recessed toward the inner diameter. The outer surface 7c connects smoothly to the groove bottom surface 7b and forms an inclined surface that slopes outward toward the outer diameter as it extends axially outward.

[0027] As shown in FIG. 3, nitrile rubber is typically used as the material for the rubber material 11 in the seal member 6, but other materials such as acrylic rubber, silicone rubber, and fluororubber may also be used depending on the operating temperature.

[0028] <Lip> As shown in Figure 4, the inner peripheral portion 13 of the seal member 6, which extends radially inward beyond the inner diameter of the core metal 10, is made of the rubber material 11. The inner peripheral portion 13 has a constricted portion 14 whose thickness decreases toward the inner diameter, and a main lip 15 and a sub-lip 16 connected to the constricted portion 14. The constricted portion 14, main lip 15, and sub-lip 16 are molded as a single unit. "Molded as a single unit" means that the constricted portion 14, main lip 15, and sub-lip 16 are molded as part or the whole of a single object from a single material, for example by injection molding, rather than being composed of multiple elements joined together.

[0029] A main lip 15 is connected to the inner diameter side end of the constricted portion 14, and a secondary lip 16 protrudes from the inner surface of a base end 15a of the main lip 15. The secondary lip 16 protrudes axially inward from the base end 16a of the secondary lip 16 and, as shown in Figure 1, does not contact the seal groove 7 of the inner ring 2. A labyrinth seal Rs is formed between the tip end of the secondary lip 16 and the inner surface 7a of the seal groove 7. Here, "axially inward" refers to the direction from the base end 16a toward the inside of the bearing.

[0030] As shown in Figure 4, the main lip 15 has a base end 15a that slopes inward in the axial direction, a lip main body 15b that extends inward from the base end 15a, and a tip end 15c that is provided on the outer surface portion of the lip main body 15b on the tip side. The tip end 15c of the main lip 15 is also referred to as the inner diameter side tip end 15c. The inner diameter side tip end 15c contacts the seal groove 7 of the inner ring 2. Specifically, the inner diameter side tip end 15c is formed in an R-shape that abuts the outer surface 7c of the seal groove 7 in the normal direction. The outer diameter surface 15ca of the inner diameter side tip end 15c slopes inward in the axial direction and smoothly connects to the R-shape.

[0031] <Grease flow prevention measures> 5A, the seal member 6 is provided with a grease flow obstruction means Gs that obstructs the flow of grease from the inner circumferential surface 16b of the secondary lip 16 to the inner diameter side tip portion 15c of the primary lip 15. The grease flow obstruction means Gs includes a shape (reverse inclined shape) in which the inner circumferential surface 16b of the secondary lip 16 is inclined toward the outer diameter side as it goes outward in the axial direction. Here, the direction from the secondary lip 16 toward the outside of the bearing is referred to as the axially outward direction.

[0032] As shown in FIG. 4, even when the inner diameter side tip portion 15c is in contact with the seal groove 7, the inner circumferential surface 16b of the secondary lip 16 is configured to be inclined toward the outer diameter side as it moves axially outward. As shown in FIG. 5A, the inclination angle α of the inner circumferential surface 16b with respect to the axial direction is set to, for example, approximately 1° to 20° through testing or simulation. However, the inclination angle α is not limited to this angle. In this example, the entire inner circumferential surface 16b of the secondary lip 16 has a reverse inclined shape, but this shape is not limited thereto. For example, a portion of the inner circumferential surface 16b in the axial direction may have a reverse inclined shape, and the other portion of the inner circumferential surface 16b may have a flat shape that is approximately parallel to the axial direction.

[0033] <Action and effect> As shown in Figure 5B, the grease flow obstruction means Gs has an inverted inclination shape in which the inner circumferential surface 16b of the secondary lip 16 slopes radially outward as it moves axially outward. This inverted inclination shape of the secondary lip 16 obstructs the flow of grease FL from the inner circumferential surface 16b of the secondary lip 16 to the inner diameter side tip 15c of the primary lip 15. In other words, when the axial direction of the rolling bearing is aligned horizontally, the base oil Ky of the grease flowing along the inner seal surface remains on the inner circumferential surface 16b of the secondary lip 16, more reliably preventing it from flowing to the inner diameter side tip 15c of the primary lip 15. This reduces the amount of dust generated from inside the bearing compared to conventional structures.

[0034] 4, the main lip 15 has a base end 15a that slopes axially outward and therefore radially inward, and a lip main body 15b that extends radially inward from the base end 15a. This maintains the ability of the main lip 15 to follow the seal groove 7 of the inner ring 2, and the main lip 15 contacts the outer surface 7c of the seal groove 7 with a desired interference (pressing force). In addition to the base end 15a and lip main body 15b, the inner diameter side tip 15c that connects to the lip main body 15b is formed in an R-shape that contacts the outer surface 7c of the seal groove 7 in the normal direction.

[0035] As a result, even if the internal bearing pressure rises during rotation of the rolling bearing 1 (FIG. 1), the main lip 15 can prevent foreign matter from entering from the atmosphere and suppress changes in the surface pressure distribution of the main lip 15. This makes it possible to prevent undesirable increases in torque and undesirable heat generation by the main lip 15.

[0036] As shown in Figure 6, air holes 12 for releasing the internal pressure of the rolling bearing 1 (Figure 1) are provided in the outer peripheral portion 8 (Figure 3) of the sealing member 6. Therefore, by releasing the internal bearing pressure through the air holes 12 when the rolling bearing 1 (Figure 1) is rotating, it is possible to suppress excessive changes in the interference of the sealing member 6 and the outflow of grease caused by an increase in the internal bearing pressure.

[0037] <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.

[0038] [Second embodiment: Figs. 7 to 9, uneven portion] 7, the grease flow obstruction means Gs may have an uneven portion Un provided between the seal back surface, which is the surface extending from the inner circumferential surface 16b of the secondary lip 16 to the axially inner surface 15d of the primary lip 15. In this example, the area in which the uneven portion Un is provided is the entire inner circumferential surface 16b of the secondary lip 16 and the axially inner surface 15d of the primary lip 15 (the area indicated by the thick line in FIG. 7). As shown in Fig. 8, a protrusion 15ba protruding axially inward may be provided on the inner surface of the lip main body 15b. The seal back surface Sm excluding the protrusion 15ba corresponds to the recess. In the second embodiment, the uneven portion Un (Fig. 7) consisting of the recess and protrusion 15ba constitutes the grease flow obstruction means Gs.

[0039] With this configuration, the grease base oil Ky flowing along the inner seal surface is blocked by the convex portion 15ba of the seal back surface Sm and is released in the circumferential direction, more so than in the first embodiment. Even when the axial direction of the rolling bearing is aligned vertically, that is, even when the seal member 6 is in the position shown in Figure 9, the grease base oil Ky is blocked by the convex portion 15ba of the seal back surface Sm. This makes it possible to reduce the amount of dust generated from inside the bearing compared to conventional structures.

[0040] [Third embodiment: FIG. 10, reverse slope + convex portion] As shown in Figure 10, the inner peripheral surface 16b of the secondary lip 16 may have a reverse inclination shape that slopes outward in the axial direction, combined with the aforementioned protrusion 15ba. In this case, the possibility of the grease base oil flowing onto the seal back surface Sm is reduced. Furthermore, even if base oil does flow onto the seal back surface Sm, it is blocked by the protrusion 15ba, making it difficult for it to reach the inner diameter side tip 15c of the primary lip 15. This reduces the amount of dust generated from inside the bearing compared to conventional structures.

[0041] [Fourth embodiment: FIG. 11, one-sided seal] 11, the seal member 6 may be provided on only one axial side of the rolling bearing 1. In this case, the number of parts can be reduced and the number of steps required to process the seal grooves, etc. can be reduced, resulting in cost savings, compared to a rolling bearing provided with seal members on both axial sides.

[0042] [Fifth embodiment: FIG. 12, crown cage] 12, the cage 5 may be a so-called crown cage having an opening on one axial side of the pocket Pt. In this case, the number of parts of the cage 5 can be reduced compared to the two-piece cage described above, thereby reducing the number of assembly steps.

[0043] [Sixth embodiment: Figure 13, one-sided seal] As shown in FIG. 13, in a rolling bearing 1 having a crown-shaped cage 5, a seal member 6 may be provided on only one axial side of the rolling bearing 1.

[0044] In each embodiment, it is possible to omit or increase the number of air holes in the outer peripheral portion of the seal member. That is, the seal member may be configured to have no air holes or to have multiple air holes. In deep groove ball bearings, a steel plate wave cage may be used. The rolling bearing equipped with the grease flow obstruction means is not limited to deep groove ball bearings, but can be applied to various bearings such as angular contact ball bearings, tapered roller bearings, and cylindrical roller bearings.

[0045] Although the embodiments of the present invention have been described above, the disclosed embodiments are illustrative in all respects and are not limiting. 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 meaning and scope of the claims. [Explanation of symbols]

[0046] 1... rolling bearing, 2... inner ring, 3... outer ring, 4... ball (rolling element), 6... seal member, 7... seal groove, 12a, 12a... air hole, 15... main lip, 15c... inner diameter side tip portion, 15d... axial inner surface, 16... secondary lip, 16b... inner circumferential surface, Gs... grease flow obstruction means, Un... uneven portion

Claims

1. A rolling bearing comprising an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and a seal member that seals a bearing space between the inner ring and the outer ring, the seal member having a main lip that contacts a seal groove in the inner ring and a sub-lip that protrudes axially inward from a base end portion and does not contact the seal groove, and grease is sealed in the bearing space, The sealing member is a rolling bearing provided with a grease flow obstruction means for obstructing the flow of grease from the inner peripheral surface of the secondary lip to the inner diameter side tip of the main lip.

2. 2. The rolling bearing according to claim 1, wherein the grease flow obstruction means includes a shape in which the inner peripheral surface of the secondary lip is inclined toward the outer diameter side as it goes axially outward.

3. 3. The rolling bearing according to claim 1, wherein the grease flow obstruction means comprises an uneven portion provided between the inner peripheral surface of the secondary lip and the axially inner surface of the primary lip.

4. 3. A rolling bearing according to claim 1, wherein an air hole for releasing internal pressure of the rolling bearing is provided on the outer peripheral portion of the seal member.

5. 3. The rolling bearing according to claim 1, wherein the seal member is provided on only one axial side of the rolling bearing or on both axial sides of the rolling bearing.

Images