Sealed bearings

Abstract

To increase an area of a sliding part between protrusions and a seal sliding surface, in a bearing having a seal that allows fluid lubrication between the seal sliding surface and a seal lip of a seal member by a plurality of protrusions of the seal lip.SOLUTION: A protrusion 12 has a flat tip part 12a extending in a tangential direction to a seal sliding surface 11, and formed into a planar shape or the like. The following relation is satisfied: D / R1≥0.00075, where D represents a circumferential width of the tip part 12a, and R1 represents a radius of curvature of the seal sliding surface 11. Consequently, a sliding part between the tip part 12a and the seal sliding surface 11 is enlarged in a circumferential direction.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] Seals are used to prevent early failure of rolling bearings. For example, in the transmissions installed in vehicles such as automobiles and various construction machines, foreign matter such as wear powder from gears is present, and seals are used to prevent the wear powder from entering the inside of the bearing.

[0003] Generally, the seal member has a seal lip formed in an annular shape from an elastic material such as a rubber-like material, and a mating part, such as a raceway ring or a 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. In addition, this sliding contact is one of the causes of temperature rise in rolling bearings. In addition, 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 high-speed operation of bearings.

[0005] It is possible to eliminate the seal torque by forming a labyrinth seal by arranging the seal lip of the seal member so that it does not come into contact with the mating part; however, it is difficult to control various errors in the size of the gap between the seal member and the mating part in order to prevent the intrusion of foreign matter of a specified particle size.

[0006] In response to this, a sealed bearing has been proposed (Patent Document 1) in which the seal lip has multiple protrusions arranged circumferentially, creating gaps between adjacent circumferentially adjacent protrusions that communicate with the inside and outside of the bearing, and in which a film of lubricating oil is drawn from 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.

[0007] The sealed bearing of Patent Document 1 allows the flow of lubricating oil between the internal space and the outside of the rolling bearing through a gap that can prevent the intrusion of foreign matter of a specified particle size, 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, completely separating each protrusion from the seal sliding surface with the oil film, and creating a fluid lubrication state between the seal lip and the seal sliding surface. Therefore, the sealed bearing of Patent Document 1 can significantly reduce seal torque while preventing the intrusion of foreign matter of a specified particle size and allowing the bearing to operate at high speed. [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] When realizing a fluid lubrication state by the wedge effect between the protrusion of the seal lip and the seal sliding surface, as in the sealed bearing of Patent Document 1, forming a convex arc-shaped tip over the entire width of the protrusion can provide an excellent wedge effect and is suitable for transitioning from a low speed to a fluid lubrication state. However, after transitioning to a fluid lubrication state, the area of ​​the sliding part (Hertzian contact area) between the convex arc-shaped tip of the protrusion and the seal sliding surface is relatively small, which is disadvantageous in suppressing the surface pressure at the sliding part and suppressing the shear resistance of the lubricating oil.

[0010] In view of the above background, the problem that this invention aims to solve is to increase the area of ​​sliding between the protrusions and the seal sliding surface in a sealed bearing in which a fluid lubrication state can be established between the seal sliding surface and the seal lip of a seal member by multiple protrusions on the seal lip. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention provides a sealed bearing comprising a seal member which seals the internal space of a rolling bearing from the outside, and a seal sliding surface which slides circumferentially against the seal member, the seal member having a seal lip formed in an annular shape from an elastic material, the seal lip having a number of protrusions arranged in the circumferential direction, the protrusions being formed in such a manner that gaps are generated between adjacent protrusions in the circumferential direction, and the seal lip and the seal sliding surface can be brought into a fluid lubricated state by an oil film of lubricating oil which is dragged between the protrusions and the seal sliding surface from the gaps as the bearing rotates, the protrusions having a tip portion formed in a flat shape extending in a tangential direction to the seal sliding surface, or in a concave curved shape which bends in the same direction as the seal sliding surface and has a curvature equal to or less than that of the seal sliding surface, the circumferential width of the tip portion being D, the radius of curvature of the seal sliding surface being R1, and satisfying D / R1 ≧ 0.00075.

[0012] As in the above configuration, by forming the tip of the protrusion into a flat surface extending tangentially to the seal sliding surface or into a concave curved surface curving in the same direction as the seal sliding surface and having a curvature equal to or less than that of the seal sliding surface, and by making the circumferential width D of the protrusion at least 0.00075 times the radius of curvature R1 of the seal sliding surface, it is possible to expand the sliding portion where an oil film is present between the tip of the protrusion and the seal sliding surface in the circumferential direction, thereby increasing the area of ​​the sliding portion, compared to when the tip of the protrusion is made into a convex arc surface.

[0013] The tip of the protrusion may be formed into a concave curved shape that is curved in the same direction as the seal sliding surface and has a curvature equal to or smaller than the curvature of the seal sliding surface. Such a concave curved tip can enlarge the sliding portion in the circumferential direction more than the flat tip, thereby increasing the area of ​​the sliding portion.

[0014] More preferably, the tip of the protrusion is formed into a concave curved shape having a curvature equal to the curvature of the seal sliding surface, thereby making maximum use of the circumferential width of the tip, thereby increasing the area of ​​the sliding portion mentioned above.

[0015] The projection may have connection portions that bend from both circumferential sides of the tip portion toward the base of the projection, and end portions that continue from the connection portions on both sides to the base of the projection, and the end portions on both sides are formed in an inclined shape that inclines in a direction away from each other in the circumferential direction toward the base of the projection. In this way, a cross section cut across the projection in a direction transverse to the circumferential direction (circumferential cross section) is substantially trapezoidal, so that elastic deformation on the base side of the projection can be suppressed regardless of the direction of relative rotation between the seal sliding surface and the projection, and a series of wedge-shaped gaps can be formed between the seal sliding surface and the projection from the inclined end portion to the tip portion.

[0016] The projection may have connecting portions that bend from both circumferential sides of the tip portion toward the base of the projection, and end portions that continue from the connecting portions on both sides to the base of the projection, and the end portions on both sides may be formed in parallel planes. In this way, the circumferential cross section of the projection is substantially rectangular, which is suitable when the circumferential width of the tip portion of the projection is large.

[0017] The protrusion may have connecting portions that bend from both circumferential sides of the tip portion toward the base side of the protrusion, and each of these connecting portions may be formed into an arcuate surface that continues to the base of the protrusion. In this way, regardless of the direction of relative rotation between the seal sliding surface and the protrusion, elastic deformation at the base side of the protrusion can be suppressed and a continuous wedge-shaped gap can be formed between the seal sliding surface and the protrusion from the connecting portions to the tip portion.

[0018] The sealed bearing according to the present invention is suitable for use in supporting any one of the rotating parts of a vehicle transmission, differential, propeller shaft, turbocharger, machine tool, wind power generator, and wheel bearing. Effect of the Invention

[0019] By adopting the above-mentioned configuration, the present invention makes it possible to increase the area of ​​the sliding portion between the protrusions and the seal sliding surface in a sealed bearing in which the space between the seal sliding surface and the seal lip of the seal member can be fluid-lubricated by multiple protrusions on the seal lip. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a cross-sectional view showing a sealed bearing according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged side view showing a part of the side surface of the seal lip of FIG. 1 on the inner space side in a natural state; [Diagram 3] Cross-sectional view of line III-III in Figure 2 [Figure 4] Enlarged view of the protrusion in Figure 1 [Diagram 5] Cross-sectional view of line VV in Figure 2 [Figure 6] FIG. 6 is a cross-sectional view showing how the protrusion of FIG. 5 slides against the seal sliding surface. [Figure 7] FIG. 1 is a cross-sectional view showing a second embodiment of the present invention. [Figure 8] FIG. 3 is a cross-sectional view showing a third embodiment of the present invention. [Figure 9] FIG. 11 is a cross-sectional view showing a fourth embodiment of the present invention. [Figure 10]FIG. 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 11] A partial cross-sectional view of the motor in the drive unit of the electric vertical take-off and landing aircraft shown in Figure 10. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] As an example of the present invention, a sealed bearing according to a first embodiment will be described with reference to the accompanying drawings, FIGS. 1 to 6.

[0022] 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.

[0023] 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 suppressing the intrusion of external foreign matter around this sealed bearing into the internal space 7 between the inner and outer rings 3 and 4, and is not to liquid-tightly seal the internal space 7.

[0024] The inner ring 3 and the 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 that bears the load from the rotating shaft, such as a housing or a gear. The rolling elements 5 revolve while being interposed between the inner ring 3 and the outer ring 4.

[0025] Balls are used as the rolling elements 5. This sealed bearing is a deep groove ball bearing.

[0026] 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, and 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 enclosed in the internal space 7 as an initial lubricant.

[0027] 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.

[0028] In the following, the direction along the bearing central axis of the sealed bearing (not shown, same below) is referred to as the "axial direction." The direction perpendicular to the axial direction is referred to as the "radial direction." The direction along the circumference around the bearing central axis is referred to as the "circumferential direction." In Figure 1, the bearing central axis is the central axis of the inner ring 3, which serves as the rotating ring, and corresponds to the left-right direction in the figure.

[0029] A seal groove 8 for holding 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.

[0030] The exterior surrounding this sealed bearing contains foreign matter such as wear powder from gears and clutches, tiny crushed stones, etc., depending on the environment in which the sealed bearing is installed. Such powdery foreign matter can reach the vicinity of the seal member 2 due to the flow of lubricating oil and atmosphere. The seal member 2 is intended to prevent foreign matter from entering the internal space 7 from the outside.

[0031] The seal member 2 has a core 9 made of a metal plate and an annular seal lip 10. The core 9 is a pressed part formed into an annular shape that continues in the circumferential direction.

[0032] The seal lip 10 is made of an elastic material. Examples of the elastic material include vulcanized rubber material, elastomer equivalent to rubber material, etc. Examples of the rubber material include nitrile rubber (NBR), acrylic rubber (ACM), fluororubber (FKM), etc.

[0033] The elastic material may have a hardness of, for example, 65 HS or more and 75 HS or less. The Shore hardness (HS) is a value measured by a Shore hardness test method in accordance with JIS K 6301 "Physical test method for vulcanized rubber."

[0034] 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 a cylindrical surface that is continuous all around in the circumferential direction. Therefore, the radius of curvature R1 of the seal sliding surface 11 is constant all around and corresponds to the radius of the seal sliding surface 11.

[0035] 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 has a radial interference with the seal sliding surface.

[0036] FIG. 2 shows a side view of the seal lip 10 alone in its natural state (shape at the time of molding), and FIG. 3 shows a cross section of the seal lip 10 of FIG. 2 cut in the radial direction.

[0037] As shown in Figures 2 and 3, the seal lip 10 has a waist portion formed in a radially continuous annular shape with a constant width in the axial direction, and a head portion formed in a protruding piece shape bent outward from the waist portion.

[0038] The head of the seal lip 10 has a leading edge which defines the inside diameter of the seal lip 10 when in the state shown in Fig. 2. When the seal member 2 is attached in the specified position shown in Fig. 1, the seal lip 10 is pressed against the seal sliding surface 11 due to the interference with the seal sliding surface 11, causing deformation of the rubber-like elasticity bent outward as shown in Fig. 4, generating tension in the seal lip 10. Mounting errors, manufacturing errors, etc. of the seal member 2 are absorbed by changes in the degree of flexure of the seal lip 10.

[0039] As shown in Figures 2 and 3, the seal lip 10 has a plurality of protrusions 12 arranged in the circumferential direction. The protrusions 12 extend in a direction perpendicular to the circumferential direction over their entire length. 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 that has a radial interference with the seal sliding surface 11. The overall shape of the seal lip 10 is rotationally symmetrical corresponding to the pitch of the protrusions 12.

[0040] 5, the projection 12 has a tip portion 12a formed in a flat shape over a circumferential width D including the top of the projection 12, a connection portion 12b bending from an end P1 on one circumferential side of the tip portion 12a toward the base of the projection 12, a connection portion 12b bending from an end P2 on the other circumferential side of the tip portion 12a toward the base of the projection 12, an end portion 12c continuing from the connection portion 12b on one circumferential side to the base of the projection 12, and an end portion 12c continuing from the connection portion 12b on the other circumferential side to the base of the projection 12. Here, the base of the projection 12 refers to a portion where the projection 12 has substantially no protruding height and is connected to another surface portion of the seal lip 10.

[0041] Considering an imaginary circle C tangent to each tip 12a of the multiple protrusions 12, the tip 12a of each protrusion 12 is formed in a plane extending in a direction along a tangent TL to the imaginary circle C. The tangent point between the imaginary circle C and the tip 12a is set at the center that bisects the circumferential width D of the tip 12a. The tangent TL is a tangent to the tangent point at the circumferential center of the tip 12a. The circumferential width D of the tip 12a corresponds to the circumferential length between ends P1 and P2, which are the boundaries between the tip 12a and the connecting portion 12b.

[0042] 1 and 4, the protrusion 12 comes into contact with the seal sliding surface 11 from the center of the circumferential width D of the planar tip portion 12a shown in Fig. 5. That is, the tip portion 12a of the protrusion 12 is formed in a planar shape extending in a tangential direction to the seal sliding surface 11 (a direction along the tangent line TL).

[0043] The relationship between the circumferential width D of the tip portion 12a of the projection 12 shown in FIG. 5 and the radius of curvature R1 of the seal sliding surface 11 shown in FIG. 1 satisfies D / R1≧0.00075.

[0044] 5, the connection parts 12b on both sides of the projection 12 are each formed into a curved surface continuing from the tip 12a to the end 12c. If the radius of curvature of the connection parts 12b is R2, the relationship between the circumferential width D of the tip 12a of the projection 12 and the radius of curvature R2 of the connection parts 12b satisfies R2 / D≧0.03.

[0045] In addition, when D / R1=0.00075 and R2 / D=0.03, it is difficult to form the transfer surface for molding the tip portion 12a and the connection portion 12b of the protrusion 12 in the mold by end mill processing, but it is possible to form them by laser processing.

[0046] Ends 12c on both sides of projection 12 are formed in an inclined shape inclined away from each other in the circumferential direction toward the base side of projection 12. Ends 12c extend from connection portion 12b to the base of projection 12 at a constant incline.

[0047] When the seal member 2 is attached to the rolling bearing 1 as shown in FIG. 1, the tip portions 12a of the multiple protrusions 12 come into contact with the seal sliding surface 11. As shown in FIG. 4, the protrusions 12 have a height in a direction perpendicular to the seal sliding surface 11 on a virtual plane including the bearing center axis, and therefore push against the tension of the seal lip 10. As a result, gaps 13 that communicate with the internal space 7 and the outside are generated between the protrusions 12 adjacent to each other in the circumferential direction and between the seal sliding surface 11 and the seal lip 10. The flow passage cross-sectional height of the gap 13 corresponds to the radial distance between the lip portion connecting the protrusions 12 adjacent to each other in the circumferential direction 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 protrusions 12 adjacent to each other in the circumferential direction is kept in a non-contact state with the seal sliding surface 11.

[0048] The end 12c of the projection 12 forms a wedge-shaped gap between the seal sliding surface 11 and the projection 12, the gap being larger on the gap 13 side and smaller on the projection 12 side. The tip 12a of the projection 12 has a region that is generally along the seal sliding surface 11 on a virtual plane including the bearing center axis. This region has a width in the direction along the seal sliding surface 11 (corresponding to the axial direction in the illustrated example). For this reason, the sliding portion between the projection 12 and the seal sliding surface 11 accompanying the rotation of the bearing, i.e., the wedge effect when the projection 12 drags the lubricating oil in the gap 13 between the seal sliding surface 11 in the circumferential direction, promotes the formation of an oil film, and the region where the oil film is interposed between the projection 12 and the seal sliding surface 11 is generated with a finite length L of a predetermined length or more in the direction along the seal sliding surface 11 on the aforementioned virtual plane. Such a sliding portion between the projection 12 and the seal sliding surface 11 is considered to be generated in the shape of a contact ellipse based on Hertz's elastic contact theory, and the major axis of the contact ellipse corresponds to the finite length L.

[0049] When the bearing stops rotating, the projection 12 generally maintains the cross-sectional shape shown in Fig. 5, but the tension of the seal lip 10 causes the tip 12a and connection part 12b of the projection 12 to be pressed against the seal sliding surface 11. As a result, the projection 12 is elastically deformed, and the tip 12a and connection part 12b are slightly crushed, with a solid contact area with the seal sliding surface 11 being distributed over the entire surface.

[0050] When the bearing starts to rotate from the stopped state, the protrusion 12 and the seal lip 10 rotate relative to each other in the circumferential direction as shown in Fig. 6. Here, it is assumed that the direction in which the seal sliding surface 11 rotates relative to the protrusion 12 is the circumferential direction (clockwise direction) indicated by the arrow in the figure. In the sliding portion between the protrusion 12 and the seal sliding surface 11, the tip 12a and the connection portion 12b of the protrusion 12 are dragged in the clockwise direction in the solid contact area with the seal sliding surface 11, and the lubricating oil in the gap 13 (indicated by a dotted pattern in the figure) is dragged into the wedge-shaped gap between the connection portion 12b and the tip 12a of the protrusion 12 and the seal sliding surface 11. At this time, the drag resistance due to friction between the protrusion 12 and the seal sliding surface 11 in the solid contact area and the shear resistance of the lubricating oil sheared between the protrusion 12 and the seal sliding surface 11 act on the protrusion 12, so that the connection part 12b and the vicinity of the tip part 12a of the protrusion 12 are elastically deformed as shown in FIG. 6, and a series of wedge-shaped gaps are formed from the end part 12c to the connection part 12b and the circumferential center of the tip part 12a (the center in the minor axis direction of the contact ellipse). This prevents the protrusion 12 from cutting the oil film, and the wedge effect effectively promotes the formation of the oil film. When the peripheral speed of the relative rotation between the seal lip 10 and the seal sliding surface 11 is less than a certain value, a boundary lubrication state or a mixed lubrication state including the solid contact area is formed microscopically.

[0051] When the bearing rotation speed increases and the circumferential speed of the relative rotation between the protrusions 12 and the seal sliding surface 11 exceeds a certain level, the oil film thickness between the tip 12a of the protrusions 12 and the seal sliding surface 11 exceeds the composite roughness σ between the protrusions 12 and the seal sliding surface 11 by a large margin, and each protrusion 12 and the seal sliding surface 11 are completely separated by the oil film to create a fluid lubrication state. This allows the seal lip 10 and the seal sliding surface 11 to be completely separated by the oil film to create a fluid lubrication state. When this fluid lubrication state is achieved, the seal torque by 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 suction action of the seal lip 10.

[0052] Here, if the oil film parameter Λ is 3 or more, the lubrication mode of the sliding part is considered to be 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 Λ = h / σ. The minimum oil film thickness h is calculated based on the theory of elastohydrodynamic lubrication. Composite roughness σ = √((Rq 1 2 +Rq 2 2 ) / 2). Rq 1 is the root mean square roughness of the seal sliding surface 11 that constitutes the sliding portion described above. Rq 2 is the root mean square roughness on the surface of the protrusions 12, the root mean square roughness is the value of the root mean square roughness Rq (μm) defined 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. In order to make the sliding part between the protrusion 12 and the seal sliding surface 11 in a fluid lubrication state even when the circumferential speed is extremely low, it is preferable to make the composite roughness σ at the sliding part 0.9 μm or less. For example, when the oil lubrication mode was determined using the Johnson chart under the calculation conditions of a composite roughness σ of 0.9 μm, a lubricant oil of transmission oil (30 cst, 40° C.), an ambient temperature of 20° C., and a circumferential 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 protrusion 12 and the seal sliding surface 11 is 0.9 μm or less, it is expected that the lubrication state will be reliably made fluid lubricated in the actual use range of the bearing.

[0054] For example, in applications that support rotating parts in a vehicle transmission, the sealed bearing is generally lubricated by a suitable method such as splashing or oil bath. Therefore, lubricating oil supplied from the outside is present around the seal lip 10. The lubricating oil is also commonly used for other lubricating parts such as gears in the transmission. The lubricating oil is circulated by an oil pump and filtered by an oil filter installed in the circulation path. It is considered that if large foreign matter with a particle size exceeding 0.05 mm enters the internal space 7, it will have a negative effect on the bearing life. If the height of the protrusions 12 is set to 0.07 mm or less, it is possible to generate a gap 13 through which such large foreign matter cannot easily pass. When the height of the protrusions 12 is 0.07 mm or less, for example, the interval 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 is either the isoviscosity-rigid body region (RI mode) or the isoviscosity-elastic body region (EI mode, soft EHL) in the lubrication region diagram (Johnson chart) based on the viscosity parameter gv and the elasticity parameter ge, which are dimensionless numbers determined by Greenwood-Johnson, that is, the above-mentioned fluid lubrication state. When the above-mentioned interval is 2.6 mm, an oil film of about 3 μm is formed between the protrusion 12 and the seal sliding surface 11, and when it is smaller than 2.6 mm, the oil film tends to become thicker. When the above-mentioned interval is 2.6 mm or less, the bearing rotation torque tends to decrease (i.e., the seal torque tends to decrease). When the above-mentioned interval is less than 0.3 mm, it becomes difficult to form the transfer surface for molding the protrusion 12 in the mold by end mill processing.

[0055] As described above, when the lubrication mode between the protrusion 12 and the seal sliding surface 11 becomes mixed lubrication or fluid lubrication, the solid contact area between the protrusion 12 and the seal sliding surface 11 almost disappears or disappears completely, but the shear resistance of the lubricating oil sheared between the protrusion 12 and the seal sliding surface 11 continues to act on the protrusion 12, so that the elastic deformation of the protrusion 12 as shown in Figure 6 continues.

[0056] When the connection portion 12b of the projection 12 is formed into a small, approximately angular surface shape, as when the above-mentioned D / R1=0.00075 and R2 / D=0.03 are satisfied, when rotation is stopped, a wedge-shaped gap capable of realizing a fluid lubrication state cannot be formed between the connection portion 12b of the projection 12 and the seal sliding surface 11. However, due to the resistance acting on the projection 12 during rotation, the projection 12 is elastically deformed to form a wedge-shaped gap required to realize the fluid lubrication state, so there is no problem in realizing the fluid lubrication state.

[0057] In order to suppress the seal torque when the area between the protrusions 12 and the seal sliding surface 11 is in a fluid lubrication state, it is important to suppress the shear resistance of the lubricant between the protrusions 12 and the seal sliding surface 11. If the surface pressure of the protrusions 12 at the sliding portion between the protrusions 12 and the seal sliding surface 11 is reduced, the shear resistance of the lubricant is lowered, and therefore the seal torque can be suppressed. The surface pressure of the protrusions 12 at the sliding portion depends on the area of ​​the protrusions 12 that form the sliding portion.

[0058] Since the tip 12a of the projection 12 is formed in the above-mentioned flat shape with a circumferential width D that satisfies D / R1≧0.00075 (see FIG. 1 and FIG. 5), the entire area of ​​the above-mentioned contact elliptical area, which is the sliding portion between the projection 12 and the seal sliding surface 11, or a circumferential area including this entire area, can be generated between the tip 12a and the seal sliding surface 11. Therefore, the area of ​​the sliding portion between the tip 12a of the projection 12 and the seal sliding surface 11 shown in FIG. 4 and FIG. 6 is larger than that in the case where the tip of the projection is formed in a convex arcuate shape. This is because the projection 12 having the flat tip 12a is relatively long in the circumferential direction, which constitutes the sliding portion. As a result, the surface pressure of the tip 12a of the projection 12 in the sliding portion can be reduced.

[0059] For example, a comparative model in which the entire width of the protrusion is a convex arc surface is assumed, with the radius of the convex arc surface being 1.5 mm, the height of the protrusion being 40 μm, the circumferential spacing of the protrusions being 2° (the number of protrusions arranged in the circumferential direction being 180), the radius of curvature R1 of the seal sliding surface being 32 mm, the elastic material forming the seal lip being acrylic rubber (Shore hardness: 70 ± 5 HS), and the tension force of the seal lip acting on the protrusion being 1 N. Assuming the operating conditions, the seal member is stationary and the rotation speed of the seal sliding surface is 1500 min -1 , the kinetic viscosity of the lubricating oil (40℃) is 26mm 2 / s, the area of ​​the osculating ellipse is calculated to be 0.0032 mm 2 (The major axis length of the contact ellipse is 0.3 mm, and the minor axis length is 0.15 mm.) On the other hand, when the area of ​​the contact ellipse was calculated for the working model that adopted the protrusion 12 according to the first embodiment while having the same seal sliding surface, overall width and height of the protrusion, circumferential spacing, elastic material, tensioning force, and operating conditions as the comparative model, the minor axis length of the contact ellipse was enlarged and the area was larger than that of the comparative model.

[0060] As described above, the sealed bearing shown in Figs. 1 to 6 comprises the seal member 2 which seals the internal space 7 of the rolling bearing 1 against the outside, and the seal sliding surface 11 which slides in the circumferential direction against the seal member 2, the seal member 2 has the seal lip 10 formed in an annular shape from an elastic material, the seal lip 10 has a plurality of protrusions 12 arranged in the circumferential direction, the plurality of protrusions 12 generate gaps 13 between adjacent protrusions 12 in the circumferential direction, and as the bearing rotates, drag is generated between the protrusions 12 and the seal sliding surface 11 through the gaps 13. The projection 12 has a tip 12a formed in a flat shape extending in a tangential direction relative to the seal sliding surface 11, and the circumferential width of the tip 12a is D and the radius of curvature of the seal sliding surface 11 is R1, satisfying D / R1≧0.00075, so that the sliding portion between the tip 12a of the projection 12 and the seal sliding surface 11 can be expanded in the circumferential direction to increase the area of ​​the sliding portion. This suppresses the surface pressure of the tip 12a in the sliding portion, and thus suppresses the shear resistance of the lubricant between the tip 12a and the seal sliding surface 11, thereby suppressing the seal torque.

[0061] In addition, in this sealed bearing, the protrusion 12 has connection portions 12b that bend from both circumferential sides of the tip portion 12a toward the base of the protrusion 12, and end portions 12c that continue from these connection portions 12b, 12b on both sides to the base of the protrusion 12, and these end portions 12c, 12c on both sides are formed in an inclined shape that inclines circumferentially away from each other toward the base side of the protrusion 12.As a result, the circumferential cross section of the protrusion 12 is approximately trapezoidal (see Figure 5).Therefore, regardless of the direction of relative rotation between the seal sliding surface 11 and the protrusion 12, elastic deformation at the base side of the relatively wide protrusion 12 can be suppressed, and a series of wedge-shaped gaps can be formed between the seal sliding surface 11 and the protrusion 12 from the inclined end portions 12c to the tip portion 12a (see Figure 6).

[0062] In the first embodiment, the tip 12a of the projection 12 is formed flat, but by changing the tip to a concave curved shape, it is possible to increase the area of ​​the sliding portion with the seal sliding surface 11. As an example, a second embodiment is shown in Fig. 7. Note that, below, only the differences from the first embodiment will be described.

[0063] The protrusion 21 of the seal lip 20 according to the second embodiment has a tip portion 21a formed in a concave curved shape that curves in the same direction as the seal sliding surface 11 and has a curvature equal to or smaller than the curvature of the seal sliding surface 11.

[0064] 7, the tip 21a of the projection 21 is formed of an arcuate surface defined by a radius of curvature R3. The radius of curvature R3 of the tip 21a and the radius of curvature R1 of the seal sliding surface 11 are set to be the same. Therefore, the tip 21a is formed into a concave curved surface having the same curvature as the seal sliding surface 11.

[0065] The connecting portion 21b of the projection 21 has an angular shape. By changing the connecting portion 21b to an angular shape, the connecting portion 21b is made smaller than that of the first embodiment, and the end portion 21c of the projection 21 is extended to the vicinity of the tip portion 21a. Even in the projection 21 employing the angular connecting portion 21b in this manner, the resistance acting on the projection 21 causes the projection 21 to be elastically deformed so as to form a wedge-shaped gap required for transition to a fluid lubrication state between the seal sliding surface 11 and the projection 21 (see FIG. 6).

[0066] As described above, in the sealed bearing of the second embodiment, the tip portion 21a of the protrusion 21 is curved in the same direction as the seal sliding surface 11 and is formed into a concave curved shape with a curvature equal to or less than the curvature of the seal sliding surface 11. Therefore, compared to the tip portion of the first embodiment, the sliding portion between the tip portion 21a and the seal sliding surface 11 can be expanded in the circumferential direction, making its area larger.

[0067] Furthermore, in the sealed bearing of the second embodiment, in particular, the tip 21a of the protrusion 21 is formed into a concave curved shape with a curvature equal to the curvature of the seal sliding surface 11, so that the circumferential width of the tip 21a can be made maximum use of to increase the area of ​​the sliding portion between the tip 21a and the seal sliding surface 11, compared to the case where a curvature less than the same is used.

[0068] In the first and second embodiments, the circumferential cross-sectional shape of the protrusion is substantially trapezoidal, but it is also possible to adopt other circumferential cross-sectional shapes. As an example, a third embodiment is shown in Fig. 8. Here, only further differences from the second embodiment will be described.

[0069] In the protrusion 31 of the seal lip 30 according to the third embodiment, both end portions 31c continuing from the connecting portions 31b on both circumferential sides of the tip portion 31a are formed in parallel flat shapes. Therefore, the circumferential cross section of the protrusion 31 is substantially rectangular, which is suitable for making the circumferential width of the tip portion 31a larger than that of the substantially trapezoidal protrusions of the first and second embodiments.

[0070] FIG. 9 shows a fourth embodiment as another example of the circumferential cross-sectional shape of the projection.

[0071] In the protrusion 41 of the seal lip 40 according to the fourth embodiment, the connection parts 41b on both circumferential sides of the tip part 41a are each formed in the shape of an arcuate surface continuing to the base of the protrusion 41. Therefore, the circumferential cross-sectional shape of the protrusion 41 is relatively wide on the base side of the protrusion 41, and the connection parts 41b form a wedge-shaped gap between the seal sliding surface 11 and the protrusion 41. Therefore, the sealed bearing according to the fourth embodiment can form a continuous wedge-shaped gap between the seal sliding surface 11 and the protrusion 41 from the connection parts 41b to the tip part 41a while suppressing elastic deformation on the base side of the relatively wide protrusion 41, regardless of the direction of relative rotation between the seal sliding surface 11 and the protrusion 41.

[0072] In the third and fourth embodiments, the tip portions 31a, 41a of the projections 31, 41 may be either flat or concavely curved as described above.

[0073] In addition, in each of the above-described embodiments, the sealing member is configured from a core metal and a vulcanized rubber material, but the present invention can also be applied to a sealing member formed from a single elastic material.

[0074] In addition, in each of the above-described embodiments, a radial lip has been 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.

[0075] In addition, in each of 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 bearings, roller bearings, 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 the case in which it is formed on the fixed ring.

[0076] In recent years, flying cars, or so-called flying cars, have been attracting attention as an alternative means of transportation to automobiles. Flying cars are expected to solve the above social problems, and are expected to be used in various situations, such as intra-regional transportation, inter-regional transportation, tourism and leisure, emergency medical care, and disaster relief.

[0077] Vertical take-off and landing aircraft (VTOL) are attracting attention as flying cars. VTOL aircraft can ascend and descend vertically between the sky and the landing site, so they do not require runways and are therefore highly convenient. 2 Due to societal demands for reducing energy consumption, electric vertical take-off and landing (eVTOL) aircraft that fly using batteries and motors are becoming mainstream in development. The concept of vertical take-off and landing aircraft here also includes aircraft that do not have wheels.

[0078] As described above, the sealed bearing of the present invention is suitable for high-speed rotation and has excellent low torque characteristics (energy-saving drivability), so it is also suitable for the drive unit of an electric vertical take-off and landing aircraft that rotates the rotor at high speed using a battery-powered electric motor. As one example, an electric vertical take-off and landing aircraft equipped with a sealed bearing of the present invention is shown in Figure 10.

[0079] The electric vertical take-off and landing aircraft 101 shown in Fig. 10 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, back, 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 by being 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.

[0080] The main body 102 has a living space capable of accommodating crew members (for example, about one or two people). This living space is provided with an operating system for determining the direction of travel and altitude, and instruments for indicating altitude, speed, flight position, and the like. 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. 10, a ring portion that covers the rotating periphery of the rotor 104 is integrally provided on the arm 102a in order to protect the rotor 104. In addition, a skid 102b that supports the aircraft when landing is provided below the main body 102.

[0081] 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 extending radially outward.

[0082] 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 the lift based on the difference between the current attitude and the target attitude. Based on the 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.

[0083] Fig. 11 shows a partial cross-sectional view of the motor in the drive section. In Fig. 11, the above-mentioned rotor is attached to one end (upper side of the figure) of a 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 type brushless motor or an inner rotor type brushless motor.

[0084] 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, and a cooling medium flow path 106c is provided between them. By flowing a cooling medium through this flow path 106c, it is possible to prevent an excessive temperature rise. 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.

[0085] The rolling bearing 110 corresponds to any one of the first to fourth 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 a fitting portion on the inner circumference of the housing, and the rolling bearing 110 is directly fitted into the housing 106 without a 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.

[0086] The bearing configuration in the drive unit is not limited to the configuration in Fig. 11. In Fig. 11, the rotating shaft of the motor and the rotating shaft of the rotor are the same rotating shaft, but the rotating shaft of the motor and the rotating shaft of the rotor may be connected via a transmission mechanism. In this case, the rolling bearing supporting the rotating shaft in the drive unit may be the rolling bearing supporting the rotating shaft of the motor, or may be the rolling bearing supporting the rotating shaft of the rotor.

[0087] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. Therefore, the scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0088] 1, 110 Rolling bearings 2. Sealing material 3. Inner Circle 4, 111 Outer ring 5 Rolling elements 6 Cage 7. Interior Space 10, 20, 30, 40 Seal Lip 11 Seal sliding surface 12, 21, 31, 41 protrusions 12a, 21a, 31a, 41a Tip 12b, 21b, 31b, 41b connection 12c, 21c, 31c ends 13. Gap 101 Electric vertical take-off and landing aircraft 103 Drive unit 104 Rotor 105 Motor 107 Rotational Axis

Claims

1. The bearing comprises a seal member that seals an internal space of the rolling bearing against the outside, and a seal sliding surface that slides in a circumferential direction relative to the seal member, a seal member having a seal lip formed in an annular shape from an elastic material, 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 generated between adjacent protrusions in the circumferential direction, 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 enabling a fluid lubrication state between the seal lip and the seal sliding surface; The projection has a tip portion formed in a concave curved shape that is curved in the same direction as the seal sliding surface and has a curvature equal to or smaller than the curvature of the seal sliding surface, A sealed bearing, characterized in that, where D is the circumferential width of the tip portion and R1 is the radius of curvature of the seal sliding surface, D / R1 ≧ 0.00075 is satisfied.

2. 2. The sealed bearing according to claim 1, wherein the tip of the projection is formed into a concave curved shape having a curvature equal to that of the seal sliding surface.

3. 3. A sealed bearing as described in claim 1 or 2, wherein the protrusion has connection portions that bend from both circumferential sides of the tip portion toward the base of the protrusion, and end portions that continue from these connection portions on both sides to the base of the protrusion, and these end portions on both sides are formed in an inclined shape that inclines circumferentially away from each other toward the base of the protrusion.

4. 3. A sealed bearing as described in claim 1 or 2, wherein the protrusion has connection portions that bend from both circumferential sides of the tip portion toward the base of the protrusion, and end portions that continue from the connection portions on both sides to the base of the protrusion, and these end portions on both sides are formed in flat planes that are parallel to each other.

5. 3. A sealed bearing as described in claim 1 or 2, wherein the protrusion has connection portions that bend from both circumferential sides of the tip portion toward the base side of the protrusion, and each of these connection portions is formed into an arcuate surface that continues to the base of the protrusion.

6. 6. 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.

7. The electric vertical take-off and landing aircraft includes a plurality of drive units each having a rotor and a motor for rotating the rotor, and the drive unit is mounted on the electric vertical take-off and landing aircraft that 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 , which supports a rotating shaft in the drive section.

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