Sealed bearings

Abstract

To suppress intrusion of foreign matter into a bearing having a seal, the bearing allowing fluid lubrication between a seal lip and a seal sliding surface by a plurality of protrusions of the seal lip.SOLUTION: Projections 12 extend in an oblique direction so as to pressurize in a direction to push lubricant in a gap 13 between the projections 12 to the outside as a bearing rotates. Alternatively, a seal lip has a rib arranged out of phase with the plurality of projections so as to face the gap and spaced from a seal sliding surface. Alternatively, the circumferentially adjacent projections extend in directions inclined so as to be opposite to each other in a circumferential direction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Seals are used to prevent early failure of rolling bearings. For example, the transmissions installed in vehicles such as automobiles and various construction machines contain foreign matter such as gear wear debris, and seals are used to prevent this debris 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] However, because the seal lip in Patent Document 1 has only one row of multiple protrusions extending straight in the radial direction, the gaps between adjacent protrusions in the circumferential direction are linearly connected between the inside and outside of the bearing. Foreign matter with a particle size smaller than the cross-sectional height of the gap is likely to flow linearly through the gap and enter the bearing. Even small foreign matter, if many of them enter the bearing, can cause peeling and surface roughness of the raceway, leading to acoustic degradation and vibration. Therefore, it is preferable to prevent even small foreign matter from entering the bearing. In this respect, the sealed bearing in Patent Document 1 leaves room for improvement.

[0010] In view of the above background, the problem that the present invention aims to solve is to prevent foreign matter from entering the interior of a sealed bearing in which multiple protrusions on the seal lip can create a fluid lubrication state between the seal lip and the seal sliding surface. [Means for solving the problem]

[0011] As a first means for achieving the above-mentioned 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 that communicate the internal space with the outside are formed between adjacent protrusions in the circumferential direction, and a film of lubricating oil that 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 extend in a direction inclined towards one side circumferentially towards the outside.

[0012] According to the first means, in a sealed bearing in which multiple protrusions on the seal lip are capable of maintaining fluid lubrication between the seal lip and the seal sliding surface, the protrusions extend outward in a direction inclined to one side in the circumferential direction, and are therefore arranged in a threaded manner around the seal sliding surface. Therefore, when using the sealed bearing, if the rotation direction of the bearing is selected so that the protrusions pressurize the lubricating oil in the gap in a direction to force it out as the bearing rotates, the protrusions and the seal sliding surface will produce a screw pumping action that prevents foreign matter from entering the bearing through the gap, thereby preventing foreign matter from entering the bearing.

[0013] For example, the protrusion is formed in a linear shape inclined relative to the radial direction.

[0014] Preferably, the protrusions are formed in a curved shape that bends to one side in the circumferential direction, which makes the protrusions longer than straight protrusions, thereby increasing the pressure loss of the lubricating oil flow in the gap (labyrinth effect) and further suppressing the intrusion of foreign matter.

[0015] As a second means for achieving 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 rotates circumferentially relative to 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 manner that gaps that communicate with the internal space and the outside are formed between adjacent protrusions in the circumferential direction, and a film of lubricating oil is drawn into the gaps between the protrusions and the seal sliding surface as the bearing rotates, thereby achieving fluid lubrication between the seal lip and the seal sliding surface. In this sealed bearing, the seal lip has a rib that is arranged out of phase with the plurality of protrusions so as to face the gap, and is arranged at a distance from the seal sliding surface.

[0016] According to the second feature, the seal lip's multiple protrusions create a fluid lubrication state between the seal lip and the seal sliding surface as the bearing rotates. The rib faces the gap out of phase with the multiple protrusions, forming a labyrinth with adjacent protrusions in the circumferential direction, whereby some of the lubricating oil flowing from the gap into the internal space collides with the rib, thereby preventing foreign matter from entering the bearing. The rib is spaced apart from the seal sliding surface, so it is not in contact with the seal sliding surface, and the shear resistance of the lubricating oil between the rib and the seal sliding surface is not increased. This prevents the rib from adversely affecting seal torque reduction.

[0017] For example, the protrusions and the ribs each extend linearly in a direction perpendicular to the circumferential direction.

[0018] Preferably, the protrusions and the ribs are each hemispherical, which reduces the shear resistance of the lubricating oil between the seal sliding surface and the protrusions and ribs compared to linear protrusions and ribs.

[0019] As a third means for achieving the above-mentioned 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 rotates circumferentially relative to 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 manner that gaps that communicate the internal space with the outside are formed between adjacent protrusions in the circumferential direction, and a film of lubricating oil is drawn from the gaps between the protrusions and the seal sliding surface as the bearing rotates, thereby achieving fluid lubrication between the seal lip and the seal sliding surface, and wherein adjacent protrusions in the circumferential direction extend in directions that are inclined in opposite directions relative to each other in the circumferential direction.

[0020] According to the third aspect, the seal lip and the seal sliding surface can be fluidly lubricated by the multiple protrusions on the seal lip as the bearing rotates. Since adjacent protrusions extend in directions inclined in opposite directions in the circumferential direction, the gaps that serve as paths for foreign matter to enter can be reduced, thereby preventing foreign matter from entering the bearing.

[0021] Specifically, among the plurality of protrusions, a first protrusion extending in a direction inclined toward one circumferential side and a second protrusion adjacent to the first protrusion on the other circumferential side and extending in a direction inclined toward the other circumferential side may be contiguous at their ends on the interior space side, which allows the mold transfer surfaces for molding the pair of first protrusions and second protrusions to be processed in a continuous manner, thereby reducing processing costs.

[0022] In each of the first to third means, the protrusion preferably has a streamlined end portion located closer to the internal space than the sliding portion with the seal sliding surface, and the streamlined end portion preferably has a shape in which the circumferential width and height of the protrusion gradually decrease toward the internal space. In this way, the streamlined end portion of the protrusion prevents turbulence of the lubricating oil flowing through the gap along the protrusion toward the internal space, which is suitable for reducing the agitation resistance of the lubricating oil.

[0023] In each of the first to third means, the angle α formed by the seal lip and the seal sliding surface from the sliding portion between the protrusion and the seal sliding surface toward the internal space may be 0°<α≦45°. In this way, a pumping action that discharges lubricating oil to the outside can be generated in the area where the seal lip and the seal sliding surface form angle α, which is advantageous for reducing the stirring resistance of the lubricating oil inside the bearing.

[0024] In each of the first to third means, the composite roughness σ of the projections and the seal sliding surface is preferably 0.9 μm or less, which is suitable for bringing the sliding portion between the projections and the seal sliding surface into a fluid lubrication state even at an extremely low peripheral speed. [Effects of the Invention]

[0025] By adopting a configuration relating to at least one of the first to third means described above, this invention can prevent foreign matter from entering the interior of a sealed bearing in which 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]

[0026] [Figure 1] 1 is a cross-sectional view showing a sealed bearing according to a first 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 gap in Figure 1 [Figure 6] Cross-sectional view of the VI-VI section in Figure 4 [Figure 7] FIG. 4 is a left side view similar to FIG. 3 showing a seal lip according to a second embodiment of the present invention. [Figure 8] FIG. 7 is a cross-sectional view similar to FIG. 6 showing a gap according to a second embodiment of the present invention. [Figure 9] FIG. 6 is a right side view similar to FIG. 5 showing the gap and its vicinity according to the second embodiment of the present invention. [Figure 10] FIG. 10 is a plan view showing a protrusion according to a third embodiment of the present invention; [Figure 11] FIG. 10 is a perspective view of a protrusion according to a third embodiment of the present invention; [Figure 12] FIG. 12 is a cross-sectional view showing a seal lip according to a fourth embodiment of the present invention taken along the XII-XII cutting line in FIG. [Figure 13] FIG. 4 is a left side view similar to FIG. 3 showing a seal lip according to a fourth embodiment. [Figure 14] 14 is a cross-sectional view taken along the line XIV-XIV in the longitudinal direction of the protrusion shown in FIG. 12. [Figure 15] FIG. 5 is a cross-sectional view similar to FIG. 4 showing a seal lip according to a fifth embodiment of the present invention. [Figure 16] 16 is a cross-sectional view taken along the line XVI-XVI in FIG. 15 along the longitudinal direction of the protrusion. [Figure 17] FIG. 10 is a cross-sectional view similar to FIG. 4 showing a seal lip according to a sixth embodiment of the present invention. [Figure 18] 18 is a cross-sectional view taken along the line XVIII-XVIII in the longitudinal direction of the protrusion shown in FIG. 17. [Figure 19] FIG. 10 is a left side view similar to FIG. 3 showing a seal lip according to a sixth embodiment. [Figure 20] 1 is a perspective view of an electric vertical take-off and landing aircraft equipped with a sealed bearing according to the present invention. [Figure 21] A partial cross-sectional view of the motor in the drive unit of the electric vertical take-off and landing aircraft shown in Figure 20. DETAILED DESCRIPTION OF THE INVENTION

[0027] As an example of the invention relating to the first means, a sealed bearing according to a first embodiment will be described with reference to the accompanying drawings, FIGS. 1 to 6. FIG.

[0028] 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.

[0029] The rolling bearing 1 is made up of an inner ring 3, an outer ring 4, a plurality of rolling elements 5 interposed between the inner ring 3 and the outer ring 4, and a cage 6 that holds the plurality 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.

[0030] 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.

[0031] Balls are used as the rolling elements 5. This sealed bearing is a deep groove ball bearing.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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).

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 view of the gap 13 as viewed axially from the outside. Fig. 6 shows a cross section taken along line VI-VI in Fig. 4.

[0043] As shown in FIGS. 3 to 5, the seal lip 10 has a plurality of protrusions 12 arranged in the circumferential direction.

[0044] As shown in FIG. 3, the protrusions 12 are formed linearly inclined relative to the radial direction of the seal lip 10 over their entire length. The inclination direction of the protrusions 12 is set in a direction inclined to one side in the circumferential direction from the outer diameter side to the inner diameter side of the seal lip 10 (corresponding to a linear direction inclined downward and leftward in the same figure). The height of the protrusions 12 is constant over their entire length. The protrusions 12 are arranged at a constant pitch in the circumferential direction. The entire length of the protrusions 12 extends over the entire range of the radial interference between the seal sliding surface 11 and the protrusions 12. The seal lip 10 has only one row of protrusions 12. The overall shape of the seal lip 10 is rotationally symmetrical corresponding to the pitch of the protrusions 12.

[0045] As shown in FIG. 1 , when the seal member 2 is attached to the rolling bearing 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 force of the seal lip 10. As a result, as shown in FIGS. 4 to 6 , gaps 13 that communicate with the internal space 7 and the outside are generated between the circumferentially adjacent protrusions 12 and between the seal sliding surface 11 and the seal lip 10. The cross-sectional height of the flow passage of the gap 13 corresponds to the radial distance between the lip portion connecting the circumferentially 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 circumferentially adjacent protrusions 12 is kept out of contact with the seal sliding surface 11.

[0046] When the seal member 2 is attached to the rolling bearing 1 as shown in Figure 1, the multiple inclined protrusions 12 as shown in Figure 3 are arranged to form a screw thread around the seal sliding surface 11. That is, as can be seen in the circumferential cross section shown in Figure 6, the protrusions 12 extend in the axial direction from the internal space 7 toward the exterior in a direction inclined to one side in the circumferential direction (corresponding to a direction inclined upward toward the right in the figure). For this reason, if the rolling bearing 1 shown in Figure 2 is rotated so that the protrusions 12 pressurize the lubricating oil in the gap 13 in a direction to the outside (to the right in the figure) as the bearing rotates, the protrusions 12 and the seal sliding surface 11 will produce a screw pumping effect that prevents foreign matter from entering the bearing through the gap 13.

[0047] 5, the protrusions 12 are shaped so that they gradually move away from the seal sliding surface 11 from the circumferential center of the protrusions 12 toward both circumferential ends. Therefore, the protrusions 12 form wedge-shaped gaps between themselves and the seal sliding surface 11, which are larger on the gap 13 side and smaller on the protrusion 12 side. In the illustrated example, each protrusion 12 has a semicircular shape when cut along the circumferential direction.

[0048] As shown in Figure 4, 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, that is, 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 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.

[0049] At the sliding portion between the protrusions 12 and the seal sliding surface 11, the shear resistance of the lubricating oil between the rounded protrusions 12 and the seal sliding surface 11 is suppressed as described above. Furthermore, the protrusions 12 are prevented from cutting the oil film by avoiding sharp edges at the circumferential center, thereby effectively promoting oil film formation through a wedge effect. Therefore, when the relative rotational speed of 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. This hydrodynamic lubrication state reduces the seal torque of the seal member 2 to the same level as a non-contact seal, thereby suppressing temperature rise in the sealed bearing and preventing adhesion of the seal lip 10. When the peripheral speed is less than a certain value after the bearing stops, the bearing microscopically enters a boundary lubrication state or a mixed lubrication state including a solid contact region.

[0050] For example, when supporting rotating parts in a vehicle transmission, sealed bearings are typically lubricated by a suitable method, such as splashing or an oil bath. 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 life 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 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 of the protrusions 12 can be set to 0.2 mm or more and 1.0 mm or less, and the radius of curvature of the surface 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.

[0051] When the aforementioned spacing is 2.6 mm, a calculated oil film of approximately 3 μm is formed between the protrusions 12 and the seal sliding surface 11, and when it is less than 2.6 mm, the oil film tends to become thicker. Furthermore, when the aforementioned spacing is 2.6 mm or less, the bearing rotational torque tends to decrease (i.e., the seal torque tends to decrease). When the aforementioned spacing is less than 0.3 mm, it becomes difficult to process the transfer surface for molding the protrusions 12 in the mold with a ball end mill. Considering molding in a mold, it is preferable to set the aforementioned radius of curvature of the protrusions 12 to 0.15 mm or more and less than 2.0 mm. Since the circumferential width of the protrusions 12 correlates with the aforementioned radius of curvature, it is preferable to set the circumferential width of the protrusions 12 to 0.2 mm or more and 1.0 mm or less.

[0052] 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).

[0053] 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. To ensure that the sliding area between the protrusions 12 and the seal sliding surface 11 is in a hydrodynamic lubrication state even at extremely low peripheral speeds, it is preferable to set the composite roughness σ at the sliding area to 0.9 μm or less. For example, when the oil lubrication mode was determined using the Johnson chart under the following calculation conditions: a composite roughness σ of 0.9 μm, transmission oil (30 cst, 40°C) as the lubricant, an ambient temperature of 20°C, and a peripheral speed of 0.2 m / s, the minimum oil film thickness h was 2.8 μm, the oil film parameter Λ was 3 or more, and the lubrication mode was 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 the hydrodynamic lubrication state will be reliably achieved in the actual operating range of the bearing.

[0054] 4, the angle α formed by the seal lip 10 and the seal sliding surface 11 from the sliding portion between the protrusion 12 and the seal sliding surface 11 toward the internal space 7 (in the illustrated example, toward the internal space 7 in the axial direction) is 0°<α≦45°. Within the internal space 7, a spatial region 7a forming the angle α is a wedge-shaped space that narrows toward the outside in the axial direction. The spatial region 7a is open toward the rolling elements 5 and the cage 6.

[0055] The flow of lubricating oil into the internal space 7 is ensured by the gap 13. However, improving the lubricating oil inflow into the internal space 7 comes at the cost of increased bearing torque due to the resistance (stirring resistance) generated when the rolling elements 5 and cage 6 stir the lubricating oil. As the lubricating oil is stirred, it is pushed by the rolling elements 5 and cage 6 toward the wedge-shaped spatial region 7a. Due to the wedge effect, the oil pressure increases as it approaches the sliding portion between the protrusion 12 and the seal sliding surface 11. This creates a pumping action that expels the lubricating oil displaced into the spatial region 7a through the gap 13 to the outside. This improves the lubricating oil discharge from the internal space 7, reduces the stirring resistance, and reduces the torque inside the bearing. This allows the rolling bearing 1 to be used with even lower torque.

[0056] If the angle α exceeds 45°, the tensioning force of the seal lip 10 decreases, and the seal lip 10 becomes too easily separated from the seal sliding surface 11, which may result in a decrease in sealing performance against foreign matter.

[0057] 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 using the multiple protrusions 12 on the seal lip 10, and these protrusions 12 extend in a direction inclined to one side circumferentially toward the outside of the sealed bearing.Therefore, when using this sealed bearing, if the bearing rotation direction is selected so that the protrusions 12 pressurize the lubricating oil in the gap 13 in a direction to force it out as the bearing rotates, the protrusions 12 and the seal sliding surface 11 will produce a screw pumping action that prevents foreign matter from entering the interior of the bearing (internal space 7) through the gap 13, thereby suppressing the intrusion of foreign matter into the interior of the bearing.

[0058] Furthermore, in this sealed bearing, the angle α formed by the seal lip 10 and the seal sliding surface 11 from the sliding portion (region of finite length L) between the protrusion 12 and the seal sliding surface 11 toward the internal space 7 is 0°<α≦45°, so that a pumping action that discharges the lubricating oil to the outside can be generated in the spatial region 7a that forms the angle α. Therefore, this sealed bearing is suitable for promoting the discharge of the lubricating oil from the internal space 7 and reducing the stirring resistance of the lubricating oil caused by the rolling elements 5, etc.

[0059] Furthermore, since the composite roughness σ of the protrusions 12 and the seal sliding surface 11 of this sealed bearing is 0.9 μm or less, it is suitable for bringing the sliding portion between the protrusions 12 and the seal sliding surface 11 into a fluid lubricated state even at extremely low peripheral speeds.

[0060] The second embodiment will be described with reference to Figures 7 to 9 (hereinafter, refer to Figures 1 and 4 as appropriate). The second embodiment is another example of the invention relating to the first aspect. Note that the following description of each embodiment will be limited to describing the differences from the first embodiment.

[0061] The protrusions 21 according to the second embodiment are formed in a curved shape that bends to one side in the circumferential direction from the internal space 7 toward the exterior. As a result, the protrusions 21 are longer than the protrusions of the first embodiment, and therefore the gaps 22 formed between circumferentially adjacent protrusions 21 are also longer and curved than the gaps of the first embodiment, as shown in Figure 8, a cross-sectional view of the second embodiment taken along line VI-VI in Figure 4. As a result, in the sealed bearing according to the second embodiment, the protrusions 21 not only provide a screw pumping effect, but also increase the pressure loss of the lubricating oil flow in the gaps 22 (labyrinth effect) compared to the first embodiment, thereby better suppressing the intrusion of foreign matter.

[0062] The third embodiment will be described with reference to Figures 10 and 11. The third embodiment is yet another example of the invention relating to the first aspect.

[0063] The protrusion 31 according to the third embodiment has a streamlined end 32 located closer to the internal space 7 than the sliding portion with the seal sliding surface 11. The streamlined end 32 has a predetermined length from the end of the protrusion 31 closest to the internal space 7 throughout its entire length, and its circumferential width and height gradually decrease toward the internal space 7. The remaining portion of the protrusion 31 other than the streamlined end 32 has a semicircular cross section with a constant circumferential width and height. The shape change of the streamlined end 32 relative to the remaining portion prevents the lubricating oil flowing through the gap 33 along the protrusion 31 toward the internal space 7 from separating from the protrusion 31 until it passes the protrusion 31 (gap 33), thereby suppressing turbulence. If this flow becomes turbulent and flows out of the gap 33 into the internal space 7, the rolling elements 5 and the cage 6 will come into contact with the turbulent flow and experience increased agitation resistance. Therefore, it is preferable to suppress turbulence.

[0064] If the area of ​​the protrusion 31 that slides against the seal sliding surface 11 is made sharp like the streamlined end 32, the wedge effect between the protrusion 31 and the seal sliding surface 11 will be reduced, which is not preferable.

[0065] Ideally, the streamlined end 32 should have a streamlined shape that does not cause turbulence until the lubricating oil passes the protrusion 31 at a typical speed of the lubricating oil flowing along the protrusion 31 toward the internal space 7. The shape of the streamlined end 32 can be determined based on, for example, Fuhrmann's streamlined body of revolution.

[0066] In this way, in the sealed bearing of the third embodiment, the streamlined end 32 of the protrusion 31 prevents the lubricating oil flowing through the gap 33 along the protrusion 31 toward the internal space 7 from becoming turbulent, thereby reducing the agitation resistance of the lubricating oil in the internal space 7 compared to the first embodiment.

[0067] The fourth embodiment will be described with reference to Figures 12 to 14. The fourth embodiment is an example of the invention relating to the second means.

[0068] The seal lip 41 according to the fourth embodiment has a rib 44 that faces a gap 43 between the projections 42 adjacent to each other in the circumferential direction.

[0069] The protrusions 42 and the ribs 44 each extend linearly in a direction perpendicular to the circumferential direction.

[0070] The protrusions 42 and the ribs 44 are each arranged at a constant pitch angle. Therefore, the row of protrusions 42 aligned in the circumferential direction and the row of ribs 44 aligned in the circumferential direction form two rows with a constant phase difference from each other.

[0071] The rib 44 is located closer to the internal space 7 than the protrusion 42. The rib 44 is arranged with a gap between it and the seal sliding surface 11. It is possible to ensure sufficient oil permeability to create a fluid lubrication state between the protrusion 42 and the seal sliding surface 11 by using lubricating oil supplied from the outside to the gap 43 or lubricating oil flowing from the internal space 7 into the gap 43.

[0072] The rib 44 faces the gap 43 at its outer end 45. The facing direction is the length direction of the projection 42 (length direction of the gap 43) on the aforementioned imaginary plane, the direction along the gap 43 and the seal sliding surface 11, and the axial direction in the illustrated example. A space is formed between the end 45 of the rib 44 and the projection 42.

[0073] Circumferentially adjacent protrusions 42 and the rib 44 nearest to the gap 43 between these protrusions 42 form a labyrinth in which part of the lubricating oil flowing out from the gap 43 into the internal space 7 collides with the end 45 of the rib 44. For this reason, the lubricating oil flowing out from the gap 43 into the internal space 7 generates a pressure loss due to this collision, making it difficult for foreign matter to enter the internal space 7 from the gap 43.

[0074] Furthermore, foreign matter carried by the lubricating oil may become caught between the end 45 of the rib 44 and the nearest protrusion 42, or may be expelled to the outside by the flow of lubricating oil that bounces off the end 45, or by the flow of lubricating oil that is expelled from the internal space 7 to the outside.

[0075] In this way, the sealed bearing according to the fourth embodiment is capable of creating a fluid lubrication state between the seal lip 41 and the seal sliding surface 11 by the multiple protrusions 42 of the seal lip 41, and yet has ribs 44 that are arranged out of phase with the multiple protrusions 42 so that the seal lip 41 faces the gap 43, so that circumferentially adjacent protrusions 42 and the ribs 44 form a labyrinth that can prevent foreign matter from entering the bearing. As a result, the labyrinth prevents external lubricating oil from flowing into the internal space 7, and a reduction in stirring resistance can also be expected.

[0076] Furthermore, since the ribs 44 are disposed with a gap between them and the seal sliding surface 11, they are not in contact with the seal sliding surface 11, and the shear resistance of the lubricating oil between the ribs 44 and the seal sliding surface 11 does not increase. This prevents the ribs 44 from adversely affecting the seal torque reduction performance.

[0077] The shape of a cut surface of the rib 44 along the circumferential direction is the same as the shape of the protrusion 42. Therefore, even if abnormal bending deformation of the seal lip 41 occurs and the gap between the rib 44 and the seal sliding surface 11 disappears, there is no problem because the sliding portion between the rib 44 and the seal sliding surface 11 is in a fluid lubricated state.

[0078] In the illustrated example, the rib 44 is formed discontinuously with the protrusion 42, but the rib may be formed continuous with the protrusion, or the rib may be formed as a connecting portion that connects adjacent protrusions in the circumferential direction into a continuous protrusion.

[0079] The fifth embodiment will be described with reference to Figures 15 and 16. The fifth embodiment is another example of the invention relating to the second aspect. Here, only further changes from the fourth embodiment will be described.

[0080] The protrusions 51 and ribs 52 according to the fifth embodiment are each hemispherical. Here, "semispherical" refers to a surface that is convexly curved when cut along the circumferential direction and also convexly curved when cut perpendicular to the circumferential direction. This convex curve may be an arc of a circle, but is not limited to a case where half of a sphere protrudes. The hemispherical shape has a curvature that ensures a Hertzian contact area necessary to achieve a fluid lubrication state at the sliding portion with the seal sliding surface 11.

[0081] The hemispherical projections 51 have a shape that is more distant from the seal sliding surface 11 than the linear projections of the fourth embodiment, and therefore can reduce the shear resistance of the lubricating oil between the projections 51 and the seal sliding surface 11. In addition, the hemispherical ribs 52 can reduce the shear resistance of the lubricating oil, particularly on the outer side of the ribs 52 that is close to the seal sliding surface 11.

[0082] The sixth embodiment will be described with reference to Figures 17 to 19. The sixth embodiment is an example of the invention relating to the third means.

[0083] As shown in Figures 17 and 18, of the multiple protrusions 62a, 62b of the seal lip 61 according to the sixth embodiment, the protrusions 62a, 62b adjacent to each other in the circumferential direction extend in directions inclined in opposite directions in the circumferential direction.

[0084] As shown in FIG. 19, the protrusions 62a and 62b have a generally rectangular shape with two rounded corners on the seal sliding surface 11 side.

[0085] 18, of the multiple protrusions 62a, 62b, a first protrusion 62a extending in a direction inclined toward one circumferential side and a second protrusion 62b adjacent to the first protrusion 62a on the other circumferential side and extending in a direction inclined toward the other circumferential side are continuous with each other at their end portions 62c on the side of the internal space 7. The pair of first protrusion 62a and second protrusion 62b extends outward from the end portions 62c in a V-shape.

[0086] Because the first protrusions 62a and the second protrusions 62b extend in directions inclined toward opposite sides of the circumferential direction, the gap 63a formed by one pair is wider on the outer side and narrower on the inner space 7 side, and the gap 63b between two circumferentially adjacent pairs is narrower on the outer side and wider on the inner space 7 side. Because the gap 63a formed by the pair of protrusions 62a, 62b narrows toward the inner space 7, some of the lubricating oil flowing toward the inner space 7 collides with it, which can prevent foreign matter from entering in the same way as the rib described above. Because the gap 63b is narrow on the outer side, it is not particularly easy for foreign matter to enter through the gap 63b.

[0087] Furthermore, the first protrusion 62a and the second protrusion 62b extend in directions inclined toward opposite sides of the circumferential direction, and the pair of first protrusion 62a and second protrusion 62b can provide the strength to resist the tensioning force of the seal lip 61 over a wide circumferential range. Therefore, even if the number of circumferentially arranged protrusions 62a, 62b is reduced, that is, even if the number of gaps 63a, 63b is reduced, the rigidity of the seal lip 61 can be ensured so that the lip portion connecting the protrusions 62a, 62b does not come into solid contact with the seal sliding surface 11 due to the tensioning force.

[0088] In this way, the sealed bearing of the sixth embodiment is capable of creating a fluid lubrication state between the seal lip 61 and the seal sliding surface 11 by the multiple protrusions 62a, 62b of the seal lip 61, but since the first protrusions 62a and second protrusions 62b that are adjacent to each other in the circumferential direction extend in directions that are inclined in opposite directions in the circumferential direction, it is possible to reduce the gaps 63a, 63b that serve as routes for foreign matter to enter, and thereby suppress the intrusion of foreign matter into the interior of the bearing.

[0089] Furthermore, in the sealed bearing of the sixth embodiment, of the multiple protrusions 62a, 62b, the first protrusion 62a extending in a direction inclined to one circumferential side and the second protrusion 62b adjacent to the other circumferential side of the first protrusion 62a and extending in a direction inclined to the other circumferential side are continuous with each other at their ends 62c on the internal space 7 side, so that the mold transfer surfaces for molding the pair of first protrusions 62a and second protrusions 62b can be processed in a continuous manner, which in turn reduces processing costs.

[0090] Specifically, the mold transfer surface can be processed by cutting a series of grooves in a V-shaped path into the mold with an end mill. The pair of first and second protrusions can also be formed as discontinuous portions at their ends on the interior space side, but in this case, it is necessary to raise and lower the end mill to switch between cutting the transfer surface for molding the first protrusions and cutting the transfer surface for molding the second protrusions, which is disadvantageous in terms of processing costs.

[0091] In the above-described embodiments, the projections are uniformly arranged in the circumferential direction, but they can also be arranged non-uniformly. Furthermore, in the first, second, and sixth embodiments, as in the fourth and fifth embodiments, it is also possible to lengthen the sliding portion (area of ​​finite length L) between the projection and the seal sliding surface.

[0092] 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.

[0093] Furthermore, in each of the above-described embodiments, a radial lip is exemplified, but 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.

[0094] Furthermore, in the above-described embodiments, an inner ring rotating radial ball bearing has been exemplified, but the present invention can also be applied to appropriate types of bearings, such as an outer ring rotating bearing, thrust bearing, roller bearing, etc. Also, although an example has been shown in which the seal sliding surface is formed on the rotating ring, the present invention can also be applied to cases in which it is formed on the fixed ring.

[0095] In addition, the streamlined end of the protrusion in the third embodiment can also be applied to the protrusions in each of the above-mentioned embodiments, and can be applied as appropriate to any sealed bearing with fluid lubrication specifications that is the premise of this invention.

[0096] In recent years, flying cars, or so-called flying cars, have been attracting attention as an alternative means of transportation to cars. Flying cars are expected to solve the above-mentioned social problems and are expected to be used in a variety of situations, such as intra-regional transportation, inter-regional transportation, tourism and leisure, emergency medical care, and disaster relief.

[0097] Vertical take-off and landing aircraft (VTOL) are attracting attention as flying cars. VTOLs can ascend and descend vertically between the sky and take-off and landing sites, eliminating the need for runways and offering great convenience. In particular, in recent years, due to societal demands for reducing CO2 emissions, electric vertical take-off and landing aircraft (eVTOL), which fly using batteries and motors, have become the mainstream of development. Note that the concept of vertical take-off and landing aircraft here also includes those without wheels.

[0098] As described above, the sealed bearing according to the present invention is suitable for high-speed rotation and has excellent low torque characteristics (energy-saving operation), and therefore is also suitable for the drive unit of an electric vertical take-off and landing aircraft that rotates rotors at high speed using a battery-powered electric motor. As an example, an electric vertical take-off and landing aircraft equipped with a sealed bearing according to the present invention is shown in Figure 20.

[0099] The electric vertical take-off and landing aircraft 101 shown in Fig. 20 is a multicopter having a main body 102 located in the center of the aircraft body and four drive units 103 arranged in the front, rear, left, and right directions. The drive units 103 are devices that generate lift and thrust for the electric vertical take-off and landing aircraft 101, and the electric vertical take-off and landing aircraft 101 flies when driven by the drive units 103. The electric vertical take-off and landing aircraft 101 may have multiple drive units 103, and is not limited to four.

[0100] The main body 102 has a living space large enough to accommodate a crew member (for example, one to two people). This living space is provided with an operating system for determining the direction of travel and altitude, and instruments that indicate altitude, speed, flight position, etc. Four arms 102a extend from the main body 102, and a drive unit 103 is provided at the tip of each arm 102a. In FIG. 20, a circular ring portion that covers the rotating periphery of the rotor 104 is integrally provided on the arm 102a to protect the rotor 104. In addition, a skid 102b that supports the aircraft during landing is provided below the main body 102.

[0101] The driving unit 103 has a rotor 104 and a motor 105 that rotates the rotor 104. In the driving unit 103, a pair of rotors 104 are provided on both axial sides of the motor 105. Each rotor 104 has two blades that extend radially outward.

[0102] The main body 102 is provided with a battery (not shown) and a control device (not shown). The control device is also called a flight controller. The electric vertical take-off and landing aircraft 101 is controlled by the control device, for example, as follows: The control device outputs a command to change the rotation speed to the motor 105, which should adjust lift based on the difference between the current attitude and the target attitude. Based on this command, an amplifier provided in the motor 105 adjusts the amount of power sent from the battery to the motor 105, and the rotation speed of the motor 105 (and the rotor 104) is changed. Furthermore, the adjustment of the rotation speed of the motors 105 is performed simultaneously for multiple motors 105, and the attitude of the aircraft is determined thereby.

[0103] Figure 21 shows a partial cross section of the motor in the drive unit. In Figure 21, the above-mentioned rotor is attached to one end (upper side of the figure) of the rotating shaft 107 of the motor 105, and a rotor is attached to the other end (lower side of the figure). The rotor is disposed opposite a stator fixed to a housing 106 and is rotatable relative to the stator. Note that the motor 105 can be configured as an outer rotor brushless motor or an inner rotor brushless motor.

[0104] The motor 105 includes a housing (device housing) 106, a rotor (not shown), a stator (not shown), an amplifier (not shown), and two rolling bearings 110, 110. The housing 106 has an outer cylinder 106a and an inner cylinder 106b, with a coolant flow path 106c provided between them. By flowing a coolant through this flow path 106c, excessive temperature rise can be prevented. The material of the housing 106 is not particularly limited, and for example, an iron-based material or CFRP (carbon fiber reinforced plastic) can be used.

[0105] The rolling bearing 110 corresponds to any one of the first to sixth embodiments described above. The rolling bearing 110 rotatably supports a rotating shaft 107 within a housing 106. The outer diameter shape of an outer ring 111 of the rolling bearing 110 is the same shape as the fitting portion on the inner periphery of the housing, and the rolling bearing 110 is fitted directly into the housing 106 without an intervening bearing housing or the like. An inner ring spacer 108 is inserted between the inner rings 112 of the rolling bearings 110, 110, and an outer ring spacer 109 is inserted between the outer rings 111, and a preload is applied.

[0106] The bearing configuration in the drive unit is not limited to the configuration in Fig. 21. In Fig. 21, the rotating shaft of the motor and the rotating shaft of the impeller are the same rotating shaft, but the rotating shaft of the motor and the rotating shaft of the impeller may be connected via a transmission mechanism. In this case, the rolling bearing that supports the rotating shaft in the drive unit may be the rolling bearing that supports the rotating shaft of the motor, or may be the rolling bearing that supports the rotating shaft of the impeller.

[0107] 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]

[0108] 1, 110 Rolling bearings 2. Sealing material 3. Inner circle 4, 111 outer ring 5 rolling elements 6 Cage 7. Interior Space 10, 41, 61 Seal lip 11 Seal sliding surface 12, 21, 31, 42, 51, 62a, 62b protrusions 13, 22, 33, 43, 53, 63a, 63b gap 32 Streamlined end 44, 52 Ribs 62c end 101 Electric vertical take-off and landing aircraft 103 Drive unit 104 Rotor 105 Motor 107 Rotational Axis

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; The protrusion extends in a direction inclined toward one side in the circumferential direction toward the outer side, the protrusion has a streamlined end portion located closer to the internal space than the sliding portion with the seal sliding surface, and the streamlined end portion has a shape in which the circumferential width and height of the protrusion gradually decrease toward the internal space, A sealed bearing, characterized in that the protrusion is formed in a curved shape that bends to one side in the circumferential direction.

2. 2. The sealed bearing according to claim 1, wherein an angle α formed between the seal lip and the seal sliding surface from a sliding portion between the protrusion and the seal sliding surface toward the internal space satisfies 0°<α≦45°.

3. 3. 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.

4. 4. The sealed bearing according to claim 1, which supports one rotating part selected from the group consisting 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.

5. The electric vertical take-off and landing aircraft is equipped with a plurality of drive units each having a rotor and a motor for rotating the rotor, and the electric vertical take-off and landing aircraft flies by rotating the rotor, The bearing comprises an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and a cage that holds these rolling elements, The sealed bearing according to claim 1 , wherein the sealed bearing supports a rotating shaft in the drive unit.

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