Bearing with seal

Abstract

To inhibit stick-slip phenomenon of multiple projections of a seal lip in a bearing with a seal which can turn an area between a seal lip and a seal slide surface into a fluid lubrication state with the projections.SOLUTION: A projection 12 has corner parts 12a, 12b which curve from an intermediate portion as seen in a height direction of the projection 12 to a root in a direction such that a circumferential width W of the projection 12 is gradually widened. Thereby, improves the strengh of areas near the root of the projection 12 is improved to inhibit stick-slip phenomenon.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a sealed bearing including a rolling bearing and a seal member. [Background technology]

[0002] To prevent early failure of rolling bearings, sealing members are used. Since foreign matter such as wear powder from gears is present inside the transmissions installed in vehicles such as cars and various construction machines, a seal member is used to prevent wear powder and other foreign matter from entering the inside of the bearing.

[0003] Generally, the seal member has an annular seal lip made of a rubber-like material, etc. A mating component, such as a raceway ring or slinger, which rotates circumferentially relative to the seal member as the bearing rotates, has a seal sliding surface that comes into sliding contact with the seal lip.

[0004] In typical seal materials, the seal lip and seal sliding surface are in sliding contact all around, and microscopically, there is a solid contact area. The drag resistance (seal torque) of the seal lip leads to an increase in bearing torque. This sliding contact is also a factor in the temperature rise of the rolling bearing. Furthermore, because the inside of the bearing is sealed off from the outside by the seal material, the pressure difference between the inside and outside of the bearing can cause an adhesion effect that presses the seal lip against the seal sliding surface, increasing the seal torque. For these reasons, typical seal materials have limitations on the high-speed operation of bearings.

[0005] It is possible to eliminate seal torque by forming a labyrinth seal by positioning the seal lip of the seal member so that it does not come into contact with the mating part, but it is difficult to control the various errors in the size of the gap between the seal member and the mating part so that foreign matter of a specified particle size can be prevented from entering.

[0006] In response to this, a sealed bearing has been proposed in which the seal lip has multiple protrusions arranged circumferentially, and gaps are created between adjacent protrusions in the circumferential direction, connecting the inside and outside of the bearing, and a film of lubricating oil is drawn into the gaps between the protrusions and the seal sliding surface as the bearing rotates, creating a fluid lubrication state between the seal lip and the seal sliding surface (Patent Document 1).

[0007] The sealed bearing of Patent Document 1 allows lubricating oil to flow between the internal space and the outside of the rolling bearing through gaps that can prevent the intrusion of foreign matter of a specified particle size, thereby making the lubricating oil abundant on the seal sliding surface, and the wedge effect created when the lubricating oil is dragged between the protrusions and the seal sliding surface as the bearing rotates forms a thick oil film that completely separates the protrusions from the seal sliding surface, achieving a fluid lubrication state between the seal lip and the seal sliding surface.As a result, the sealed bearing of Patent Document 1 can prevent the intrusion of foreign matter of a specified particle size, can accommodate high-speed operation of the bearing, and can significantly reduce seal torque. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2016 / 143786 Summary of the Invention [Problem to be solved by the invention]

[0009] In the seal lip of Patent Document 1, from the time the bearing stops until the bearing rotation speed reaches a predetermined value (when the relative peripheral speed between the projection and the seal sliding surface is less than a certain value), the space between the projection and the seal sliding surface is not in a fluid lubrication state, but is in a boundary lubrication or mixed lubrication state including a solid contact area. When the bearing starts to rotate after stopping, the protrusions are dragged in the circumferential direction against the seal sliding surface in the solid contact area.

[0010] However, the seal lip of Patent Document 1 has a protrusion whose base forms an angle when viewed from the gap side. Therefore, when the bearing starts to rotate after stopping, the protrusion is dragged in the solid contact area with the seal sliding surface and elastically deforms, which can cause a non-uniform stick-slip phenomenon similar to Charmack waves, which are characteristic of rubber and occur due to static friction.

[0011] In view of the above background, the problem that the present invention aims to solve is to suppress the stick-slip phenomenon of protrusions in a sealed bearing in which a state of fluid lubrication can be established between the seal lip and the seal sliding surface by using multiple protrusions on the seal lip. [Means for solving the problem]

[0012] In order to achieve the above object, the present invention provides a sealed bearing comprising a seal member that seals the internal space of a rolling bearing from the outside, and a seal sliding surface that slides circumferentially against the seal member, wherein the seal member has an annular seal lip, and the seal lip has a plurality of protrusions arranged circumferentially, the plurality of protrusions being formed in such a way that gaps are formed between adjacent protrusions in the circumferential direction, communicating the internal space with the outside, and a film of lubricating oil is drawn from the gaps between the protrusions and the seal sliding surface as the bearing rotates, thereby creating a fluid lubrication state between the seal lip and the seal sliding surface, and wherein the protrusions have corner portions that are curved in such a way that the circumferential width of the protrusions gradually increases from the middle of their height to their base.

[0013] According to the above configuration, the area from the middle of the height of the protrusion to the base has a curved corner portion that widens the circumferential width, thereby improving the strength of the protrusion near the base. This suppresses elastic deformation when the protrusion is dragged circumferentially in the solid contact area with the seal sliding surface at the beginning of rotation after the bearing has stopped, and ultimately suppresses the stick-slip phenomenon of the protrusion.

[0014] The ratio of the corner portion to the height of the protrusion should be 30% or less. To maintain a fluid lubrication state between the protrusion and the seal sliding surface even when the bearing is rotating at low speeds, it is necessary to obtain an appropriate wedge effect in the wedge-shaped gap between the protrusion and the seal sliding surface and to prevent the oil film from being broken at the top of the protrusion. For this reason, a sufficient curved surface that gradually moves away from the seal sliding surface must be formed between the top and the middle part of the protrusion. By setting the ratio of the corner portion's height to the height of the protrusion to 30% or less, a sufficient wedge-shaped gap can be formed without making the corner portion unnecessarily tall.

[0015] The protrusion may have the corner portions on both sides in the circumferential direction of the protrusion, so that the circumferential width of the protrusion near its base can be increased on both sides, thereby improving its strength.

[0016] The corner portions may be formed over the entire length of the projections, thereby making it possible to utilize the entire length of the projections without waste and improving the strength of the bases of the projections.

[0017] The composite roughness σ of the protrusions and the seal sliding surface is preferably 0.9 μm or less, which is suitable for bringing the sliding portion between the protrusions and the seal sliding surface into a fluid lubrication state in which the stick-slip phenomenon does not occur even at extremely low peripheral speeds. [Effects of the Invention]

[0018] By adopting the above-described configuration, the present invention can suppress the stick-slip phenomenon of the protrusions in a sealed bearing in which the multiple protrusions on the seal lip can create a fluid lubrication state between the seal lip and the seal sliding surface. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view showing a sealed bearing according to an embodiment of the present invention; [Figure 2] A partial cross-sectional view showing the natural state of the seal lip of Figure 1. [Figure 3]Enlarged left side view of the protrusion in Figure 2 [Figure 4] Enlarged view of the protrusion in Figure 1 [Figure 5] Enlarged right side view of the protrusion in Figure 1 [Figure 6] Graph showing the results of measuring the coefficient of friction for a test piece with a rubber strength of 70Hs [Figure 7] Graph showing the results of measuring the coefficient of friction for a test piece with a rubber strength of 75Hs DETAILED DESCRIPTION OF THE INVENTION

[0020] A sealed bearing according to an embodiment of the present invention will be described with reference to the accompanying drawings, FIGS. 1 to 6. FIG.

[0021] The sealed bearing shown in FIG. 1 comprises a rolling bearing 1 and two seal members 2 arranged on either side of the rolling bearing 1.

[0022] The rolling bearing 1 is made up of an inner ring 3, an outer ring 4, a predetermined number of rolling elements 5 interposed between the inner ring 3 and the outer ring 4, and a cage 6 that holds the predetermined number of rolling elements 5. The seal member 2 seals the internal space 7 of the rolling bearing 1 from the outside. The purpose of this sealing is to prevent early damage to the rolling bearing 1 by preventing external foreign matter from entering the internal space 7 between the inner and outer rings 3 and 4 around the sealed bearing, and is not to seal the internal space 7 liquid-tight.

[0023] The inner ring 3 and outer ring 4 have raceway surfaces corresponding to the rolling elements 5. The inner ring 3 is attached to a rotating shaft S and rotates integrally with the rotating shaft S. The outer ring 4 is attached to a member such as a housing or gear that bears the load from the rotating shaft. The rolling elements 5 revolve while being interposed between the inner ring 3 and outer ring 4.

[0024] Balls are used as the rolling elements 5. This sealed bearing is a deep groove ball bearing.

[0025] The internal space 7 is lubricated by lubricating oil (not shown; the same applies below) supplied from the outside. Examples of lubrication methods include a splash method in which lubricating oil is poured onto the sealed bearing, or an oil bath method in which the lower part of the sealed bearing is immersed in an oil bath. An appropriate amount of grease may be sealed in the internal space 7 as an initial lubricant.

[0026] The rotating shaft S is provided as a rotating part provided in, for example, any one of a vehicle transmission, a differential, a constant velocity joint, a propeller shaft, a turbocharger, a machine tool, a wind power generator, and a wheel bearing.

[0027] In the following, the direction along the bearing center axis (not shown, same below) of the sealed bearing will be referred to as the "axial direction." The direction perpendicular to the axial direction will be referred to as the "radial direction." The circumferential direction around the bearing center axis will be referred to as the "circumferential direction." In the illustrated example, the bearing center axis is the center axis of the inner ring 3, which serves as the rotating ring, and corresponds to the left-right direction in the same figure.

[0028] A seal groove 8 that holds the seal member 2 is formed at the end of the inner circumference of the outer ring 4. The seal member 2 is attached to the outer ring 4 by press-fitting its outer peripheral edge into the seal groove 8.

[0029] The exterior surrounding this sealed bearing contains foreign matter, such as wear powder from gears and clutches, and tiny crushed stones, depending on the installation location of the sealed bearing. Such powdery foreign matter can reach the vicinity of the seal member 2 due to the flow of lubricating oil or atmosphere. The seal member 2 is designed to prevent foreign matter from entering the internal space 7 from the outside.

[0030] The seal member 2 has a metal core 9 and an annular seal lip 10. The metal core 9 is a pressed part formed into an annular shape that is continuous in the circumferential direction. The seal lip 10 is formed from a vulcanization-molded rubber material. Examples of rubber materials include nitrile rubber (NBR), acrylic rubber (ACM), and fluororubber (FKM).

[0031] A seal sliding surface 11 that slides in the circumferential direction against the seal lip 10 is formed on the outer periphery of the inner ring 3. The seal sliding surface 11 is in the form of a cylindrical surface that is continuous over the entire circumferential direction.

[0032] The seal lip 10 is a radial lip. Here, the radial lip refers to a seal lip that provides a sealing effect with a seal sliding surface along the axial direction or a seal sliding surface that has a gradient at an acute angle of 45° or less with respect to the axial direction, and that has a radial interference with the seal sliding surface.

[0033] 2 shows the cross-sectional shape (shape at the time of molding) of the seal lip 10 alone in its natural state. The seal lip 10 has a waist portion formed in a circular ring shape that continues in the radial direction with a constant width in the axial direction, and a head portion formed in a protruding piece shape that bends outward from the waist portion.

[0034] The head of the seal lip 10 has a leading edge that defines the inner diameter of the seal lip 10 in the state shown in Figure 2. When the seal member 2 is attached in the specified position shown in Figure 1, the seal lip 10 is pressed against the seal sliding surface 11 due to the interference with the seal sliding surface 11, causing a rubber-like elastic deformation that bends outward, generating a tension force on the seal lip 10. Mounting errors, manufacturing errors, etc. of the seal member 2 are absorbed by changes in the degree of deflection of the seal lip 10.

[0035] Fig. 3 shows an enlarged left side view of the vicinity of the head of the seal lip 10 in Fig. 2. Fig. 4 shows an enlarged view of the vicinity of the head of the seal lip 10 in Fig. 1. Fig. 5 shows an enlarged right side view of the vicinity of the head of the seal lip 10 in Fig. 1.

[0036] As shown in FIGS. 3 to 5, the seal lip 10 has a plurality of protrusions 12 arranged in the circumferential direction.

[0037] As shown in Figure 3, the protrusions 12 extend in a direction perpendicular to the circumferential direction. The protrusions 12 are arranged at a constant pitch in the circumferential direction. The total length of the protrusions 12 covers the entire range of the radial interference between the seal sliding surface 11 and the protrusions 12. The overall shape of the seal lip 10 is rotationally symmetrical corresponding to the pitch of the protrusions 12.

[0038] When the seal member 2 is attached to the rolling bearing 1 as shown in FIG. 1 , the multiple protrusions 12 come into contact with the seal sliding surface 11. The protrusions 12 have a height in a direction perpendicular to the seal sliding surface 11 on an imaginary plane including the bearing center axis. The protrusions 12 push against the tension of the seal lip 10. As a result, as shown in FIGS. 4 and 5 , gaps 13 are formed between adjacent protrusions 12 in the circumferential direction and between the seal sliding surface 11 and the seal lip 10, connecting the internal space 7 to the outside. The cross-sectional height of the gaps 13 corresponds to the radial distance between the lip portion connecting the adjacent protrusions 12 and the seal sliding surface 11. The seal lip 10 slides against the seal sliding surface 11 only on the multiple protrusions 12, and the lip portion connecting the adjacent protrusions 12 in the circumferential direction is kept out of contact with the seal sliding surface 11.

[0039] 5, the protrusion 12 is shaped so that it gradually moves away from the seal sliding surface 11 from the circumferential center of the protrusion 12 to both sides in the circumferential direction. Therefore, the protrusion 12 forms a wedge-shaped gap between the seal sliding surface 11 and the protrusion 12, which is larger on the gap 13 side and smaller on the protrusion 12 side.

[0040] The protrusion 12 is composed of a corner portion 12a formed from the base of the protrusion 12 on one circumferential side, a corner portion 12b formed from the base of the protrusion 12 on the other circumferential side, and a top portion 12c that continues from the corner portions 12a and 12b to the tip of the protrusion 12.

[0041] The corner portions 12a, 12b are each formed into a curved surface that gradually widens the circumferential width W of the protrusion 12 from the middle portion in the height direction of the protrusion 12 to the base of the protrusion 12 toward the base.

[0042] Here, the height h1 of the protrusion 12 refers to the difference in height from the lip portion connecting adjacent protrusions 12 in the circumferential direction to the tip of the protrusion 12 on an imaginary plane perpendicular to the bearing center axis, the height direction of the protrusion 12 refers to the linear direction forming the height h1 on the same imaginary plane, and the circumferential width W of the protrusion 12 refers to the circumferential length between both circumferential ends of the protrusion 12 on the same imaginary plane.

[0043] The entire protrusion 12 is solid and has a plane-symmetrical shape with respect to an imaginary plane that is perpendicular to the bearing center axis and passes through a position that bisects the circumferential width W. The height h1 of the protrusion 12 is constant over the entire length of the protrusion 12.

[0044] The corner portions 12a and 12b each have a rounded corner when viewed from the gap 13 side. The apex 12c has an arcuate surface extending between the corner portions 12a and 12b. The radius of curvature R1 of the apex 12c and the radius of curvature R2 of the corner portions 12a and 12b are set so that the proportion of the height h1 of the protrusion 12 that the corner portions 12a and 12b account for is 30% or less. In other words, the value of the height h2 of the corner portions 12a and 12b is 0.3h1 or less.

[0045] The corner portions 12 a and 12 b are each formed over the entire length of the projection 12 .

[0046] The corner portions 12a and 12b are intended to improve the strength of the protrusion 12 so that, when in a lubricated state where a solid contact area exists between the protrusion 12 and the seal sliding surface 11, the top 12c of the protrusion 12 is dragged circumferentially against the seal sliding surface 11, thereby preventing the protrusion 12 from elastically deforming near its base.

[0047] Tests were conducted to determine whether improving the strength of the protrusions 12 is effective in suppressing stick-slip phenomena such as Charmack waves. The tests were conducted according to JIS P8147:2010. In each measurement, the coefficient of friction μ was measured after three consecutive reciprocating motions of a rubber test piece with a given Shore hardness. Figure 6 shows the results for the 70Hs rubber test piece, and Figure 7 shows the results for the 75Hs rubber test piece. In Figures 6 and 7, the reciprocating motion begins approximately 5 seconds into the measurement (horizontal axis). Comparing the changes in the coefficient of friction μ in the graphs of Figures 6 and 7, the change in the coefficient of friction (i.e., the difference between the static and dynamic coefficients of friction) for the 75Hs rubber test piece is significantly smaller than the change in the coefficient of friction for the 70Hs rubber test piece. This indicates that improving the strength of the rubber portion is effective in suppressing stick-slip phenomena.

[0048] The corner portions 12a and 12b illustrated in FIG. 5 are each formed as a single arcuate surface with rounded corners. However, if the circumferential width W of the projection 12 is enlarged near the base while forming a curved shape without corners that alleviates stress concentration at the base, the projection 12 can be made to have a rounded shape without corners in view of the deformation resistance of the projection 12 against drag in the circumferential direction. By improving the strength of 2, the stick-slip phenomenon can be suppressed between the protrusion 12 and the seal sliding surface 11 in a lubricated state where a solid contact area exists, and ideally, a curved shape that does not cause the stick-slip phenomenon should be formed.

[0049] As shown in Figure 4, the top 12c of the protrusion 12 has a region that roughly aligns with the seal sliding surface 11 on an imaginary plane that includes the bearing center axis. This region exists with a certain width in the direction along the seal sliding surface 11 (corresponding to the axial direction in the illustrated example). Therefore, the sliding portion between the protrusion 12 and the seal sliding surface 11 that occurs as the bearing rotates, i.e., the wedge effect created when the protrusion 12 drags the lubricating oil in the gap 13 circumferentially between the protrusion 12 and the seal sliding surface 11, promotes oil film formation, and the region where an oil film is interposed between the top 12c of the protrusion 12 and the seal sliding surface 11 occurs over a finite length L greater than or equal to a predetermined length in the direction along the seal sliding surface 11 on the imaginary plane in the figure. It is thought that such a sliding portion between the protrusion 12 and the seal sliding surface 11 occurs in the shape of a contact ellipse based on Hertz's elastic contact theory.

[0050] In the sliding portion between the protrusions 12 and the seal sliding surface 11, as described above, the shear resistance of the lubricating oil between the rounded tops 12c of the protrusions 12 and the seal sliding surface 11 is suppressed, and the circumferential center of the protrusions 12 is prevented from becoming sharp, preventing the protrusions 12 from cutting the oil film. This wedge effect effectively promotes oil film formation. Therefore, when the peripheral speed of the relative rotation between the protrusions 12 and the seal sliding surface 11 due to bearing rotation exceeds a certain level, the oil film thickness between the protrusions 12 and the seal sliding surface 11 easily exceeds the composite roughness σ between the protrusions 12 and the seal sliding surface 11, resulting in a hydrodynamic lubrication state in which each protrusion 12 and the seal sliding surface 11 are completely separated by an oil film. This allows the seal lip 10 and the seal sliding surface 11 to be completely separated by an oil film and hydrodynamic lubrication state. When such a fluid lubrication state is achieved, the seal torque of the seal member 2 can be reduced to the same level as that of a non-contact seal, which in turn suppresses the temperature rise of the sealed bearing and prevents the adhesion of the seal lip 10. Furthermore, when the peripheral speed is below a certain level after the bearing has stopped, microscopically, a boundary lubrication state or a mixed lubrication state including a solid contact region is achieved.

[0051] For example, in applications supporting rotating parts in a vehicle transmission, sealed bearings are typically lubricated by appropriate methods such as splashing or oil bathing. Therefore, externally supplied lubricant oil is present around the seal lip 10. This lubricant is also used for other lubricating parts, such as gears, within the transmission. The lubricant is circulated by an oil pump and filtered by an oil filter installed in the circulation path. Large foreign particles exceeding 0.05 mm in diameter are thought to adversely affect the bearing's lifespan if they enter the internal space 7. Setting the height of the protrusions 12 to 0.07 mm or less creates a gap 13 that prevents such large foreign particles from easily passing through. When the height h1 of the protrusions 12 is 0.07 mm or less, for example, the spacing between adjacent protrusions 12 in the circumferential direction can be set to 0.3 mm or more and 2.6 mm or less, the circumferential width W of the protrusions 12 can be set to 0.2 mm or more and 1.0 mm or less, and the radius of curvature R1 of the apex 12c of the protrusions 12 can be set to 0.15 mm or more and less than 2.0 mm. In this example, when the oil temperature is 30 to 120°C and the relative peripheral speed of the seal lip 10 and the seal sliding surface 11 is 0.2 m / s or more, it is considered that the lubrication mode will be either the iso-viscosity rigid body region (RI mode) or the iso-viscosity elastic body region (EI mode, soft EHL) in the lubrication region diagram (Johnson chart) based on the dimensionless numbers viscosity parameter gv and elastic parameter ge determined by Greenwood-Johnson, i.e., the aforementioned fluid lubrication state.

[0052] When the aforementioned distance is 2.6 mm, an oil film of approximately 3 μm is formed between the protrusion 12 and the seal sliding surface 11, and when it is less than 2.6 mm, the oil film tends to become thicker. When the aforementioned distance is 2.6 mm or less, the bearing rotation torque tends to decrease (i.e., the seal torque tends to decrease). When the aforementioned distance is less than 0.3 mm, it becomes difficult to process the transfer surface for forming the protrusion 12 in the mold with a ball end mill. When considering molding in a mold, Therefore, it is preferable to set the radius of curvature R1 of the tops 12c of the protrusions 12 to 0.15 mm or more and less than 2.0 mm. Since the circumferential width W of the protrusions 12 correlates with the radius of curvature R1, it is preferable to set the circumferential width W of the protrusions 12 to 0.2 mm or more and 1.0 mm or less.

[0053] Here, if the oil film parameter Λ≧3, the lubrication mode of the sliding part is considered to be in a hydrodynamic lubrication state. The oil film parameter Λ is the ratio of the composite roughness σ to the minimum oil film thickness h in the sliding part, and is Λ=h / σ. The minimum oil film thickness h can be calculated based on the theory of elastohydrodynamic lubrication. Composite roughness σ=√((Rq1 2 +Rq2 2 ) / 2). Rq1 is the root mean square roughness of the seal sliding surface 11 that constitutes the sliding portion described above. Rq2 is the root mean square roughness of the surface of the protrusion 12, where the root mean square roughness is the value (μm) of the root mean square roughness Rq specified in JIS (B0601:2013).

[0054] The oil film parameter Λ depends on the composite roughness σ, and the smaller the composite roughness σ, the thicker the oil film can be. In order to make the sliding portion between the protrusion 12 and the seal sliding surface 11 in a fluid lubrication state even when the peripheral speed is extremely low, it is preferable to make the composite roughness σ at the sliding portion 0.9 μm or less. For example, under the calculation conditions of composite roughness σ of 0.9 μm, lubricating oil is transmission oil (30 cst, 40°C), ambient temperature is 20°C, and peripheral speed is 0.2 m / s, When the lubrication mode was determined, the minimum oil film thickness h was 2.8 μm, the oil film parameter Λ was 3 or more, and the lubrication mode was determined to be EI mode. Therefore, if the composite roughness σ of the protrusions 12 and the seal sliding surface 11 is 0.9 μm or less, it is expected that a fluid lubrication state will be achieved reliably in the actual operating range of the bearing.

[0055] As described above, this sealed bearing is capable of creating a fluid lubrication state between the seal lip 10 and the seal sliding surface 11 by the multiple protrusions 12 of the seal lip 10, and these protrusions 12 have corner portions 12a, 12b that curve in such a way that the circumferential width W of the protrusions 12 gradually widens from the middle of the height of the protrusions 12 to the base, thereby improving the strength near the base of the protrusions 12 and suppressing elastic deformation when the protrusions 12 are dragged circumferentially in the solid contact area with the seal sliding surface 11 when the rolling bearing 1 starts to rotate after coming to a stop, thereby suppressing the stick-slip phenomenon of the protrusions 12.

[0056] As a result, this sealed bearing reduces the static friction coefficient between the seal lip 10 and the seal sliding surface 11 when the transmission is stationary, such as in idle-stop vehicles, which have become more common in recent years, i.e., in locations where the rotating part (rotating shaft S) supported by the sealed bearing is frequently stopped, and can also reduce the starting torque of the sealed bearing.

[0057] Furthermore, in this sealed bearing, the corner portions 12a and 12b account for 30% or less of the height h1 of the protrusion 12, so the height h2 of the corner portions 12a and 12b is not unnecessarily large, and a wedge-shaped gap sufficient to maintain a fluid lubrication state between the tops 12c of the protrusions 12 and the seal sliding surfaces 11 can be formed even when the rolling bearing 1 is rotating at low speeds.

[0058] In addition, in this sealed bearing, the protrusion 12 has corner portions 12a, 12b on both sides of the circumferential direction of the protrusion 12, so that the circumferential width W near the base of the protrusion 12 can be expanded on both sides, thereby improving strength.

[0059] Furthermore, in this sealed bearing, the corner portions 12a, 12b are formed over the entire length of the protrusion 12, so the entire length of the protrusion 12 can be utilized without waste, improving the strength near the base of the protrusion 12.

[0060] In addition, in this sealed bearing, the composite roughness σ of the protrusions 12 and the seal sliding surface 11 is 0.9 μm or less, so that the sliding portion between the protrusions 12 and the seal sliding surface 11 is stuck even at an extremely low peripheral speed. This is suitable for achieving a fluid lubrication state in which the slip phenomenon does not occur.

[0061] In each of the above-described embodiments, examples have been shown in which the protrusions are uniformly arranged in the circumferential direction, but they may also be arranged non-uniformly.

[0062] Furthermore, in each of the above-described embodiments, the sealing member is exemplified as being composed of a core metal and vulcanized rubber material, but the present invention can also be applied to sealing members formed from a single material such as rubber or resin.

[0063] Furthermore, although a radial lip has been exemplified in each of the above-described embodiments, the present invention can also be applied to a seal sliding surface having a gradient of more than 45° relative to the axial direction and a seal lip (axial lip) that provides a sealing effect.

[0064] Furthermore, while the above-described embodiments have been described with reference to radial ball bearings with rotating inner rings, the present invention can also be applied to other suitable types of bearings, such as bearings with rotating outer rings, thrust bearings, roller bearings, etc. Furthermore, while the examples have been described in which the seal sliding surface is formed on the rotating ring, the present invention can also be applied when it is formed on the fixed ring.

[0065] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Therefore, 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]

[0066] 1. Rolling bearings 2. Sealing material 7. Interior Space 10 Sealing Lip 11 Seal sliding surface 12 protrusions 12a, 12b corner parts 13 Gap

Claims

1. The rolling bearing includes a seal member that seals an internal space of the rolling bearing from the outside, and a seal sliding surface that slides in a circumferential direction relative to the seal member, a sealing member having an annular seal lip, the seal lip having a plurality of protrusions arranged in a circumferential direction, the plurality of protrusions being formed in such a manner that gaps are formed between adjacent protrusions in the circumferential direction, the gaps communicating the internal space with the outside, and a film of lubricating oil is drawn into between the protrusions and the seal sliding surface from the gaps as the bearing rotates, thereby creating a fluid lubrication state between the seal lip and the seal sliding surface; A sealed bearing characterized in that the protrusion has a corner portion that is curved in such a way that the circumferential width of the protrusion gradually increases from the middle of the height of the protrusion to the base.

2. 2. The sealed bearing according to claim 1, wherein the height of the projection is accounted for by the corner portion in a proportion of 30% or less.

3. 3. The sealed bearing according to claim 1, wherein the projection has the corner portions on both sides in the circumferential direction of the projection.

4. 4. The sealed bearing according to claim 1, wherein the corner portion is formed over the entire length of the projection.

5. 5. The sealed bearing according to claim 1, wherein a composite roughness σ of the projections and the seal sliding surface is 0.9 μm or less.

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