Seal member and rolling bearing with seal

Abstract

A large number of fine protrusions (23) are formed on the outer side surface of a seal member (5) so as to form a water-repellent surface having a contact angle (θ) of water of 90° or more.

Description

Seal member and sealed rolling bearing

[0001] The present invention relates to a seal member and a sealed rolling bearing using the seal member.

[0002] Sealed rolling bearings are often used as bearings that support rotating shafts in automobiles, industrial machinery, etc. Sealed rolling bearings have an outer ring, an inner ring disposed radially inward of the outer ring, a plurality of rolling elements incorporated in an annular bearing space formed between the outer ring and the inner ring, and an annular sealing member that closes an axial end opening of the bearing space between the outer ring and the inner ring (see, for example, Patent Documents 1 and 2).

[0003] This sealed rolling bearing has the end openings of the bearing space physically sealed with sealing members, so even when used in an environment exposed to foreign matter such as water or muddy water, it is possible to prevent the foreign matter from entering the bearing space.

[0004] Furthermore, in the sealed rolling bearing of Patent Document 1, in order to improve water resistance and resistance to muddy water in harsh environments, the outer surface of the seal member (the side of the seal member opposite the bearing space side) is coated with a water-repellent film (such as a PTFE film) to prevent water and muddy water from accumulating in the seal lip of the seal member.

[0005] JP 2007-332990 A JP 2020-133770 A

[0006] The sealed rolling bearing of Patent Document 1 has a water-repellent coating (such as a PTFE coating) coated on the outer surface of the sealing member, and therefore exhibits excellent water resistance and muddy water resistance in the early stages of use.

[0007] However, since the water-repellent coating (such as a PTFE coating) gradually peels off and deteriorates over time, the water-repellent properties of the outer surface of the seal member gradually decrease. As a result, the sealed rolling bearing of Patent Document 1 has the problem of difficulty in maintaining water resistance and muddy water resistance over the long term.

[0008] An object of the present invention is to provide a seal member that can maintain excellent water resistance and muddy water resistance for a long period of time.

[0009] In order to solve the above problems, the present invention provides a sealing member having the following configuration: [Configuration 1] A sealing member that prevents foreign matter from entering from the outside to the inside, characterized in that a large number of fine protrusions are formed on the outer side surface of the sealing member so that the outer side surface becomes a water-repellent surface with a water contact angle of 90° or more.

[0010] By adopting this configuration, the outer side surface of the seal member has a water-repellent surface with a water contact angle of 90° or more, which prevents water and muddy water from accumulating in the sealing portion of the seal member, thereby achieving excellent water resistance and muddy water resistance. Here, the water-repellent property of the outer side surface of the seal member is physically imparted by the lotus effect caused by the formation of numerous fine protrusions, so that the water-repellent property is unlikely to decrease over time. Therefore, it is possible to maintain excellent water resistance and muddy water resistance for a long period of time.

[0011] [Configuration 2] The sealing member according to Configuration 1, wherein the value of A / (B×C) is 0.26 or less, where B (μm) is the diameter of the tip surfaces of the numerous fine protrusions, A (μm) is the distance between the tip surfaces of the numerous fine protrusions, and C (μm) is the height of the numerous fine protrusions.

[0012] By adopting this configuration, it is possible to reliably impart water repellency to the outer side surface of the seal member by the lotus effect.

[0013] [Configuration 3] A sealing member according to Configuration 1 or 2, wherein each of the numerous fine protrusions has a circular tip surface, the diameter B (μm) of the tip surface is 80 μm or less, the numerous fine protrusions are uniformly arranged in a square or equilateral triangular lattice pattern, the spacing A (μm) between the tip surfaces of the numerous fine protrusions is 120 μm or less, and the height C (μm) of the numerous fine protrusions is 80 μm or less.

[0014] When this configuration is adopted, the size of the tip surface of each of the fine protrusions formed on the outer side surface of the sealing member is sufficiently smaller than the size of a water droplet, and the fine protrusions are uniformly arranged in a grid of tiny squares or equilateral triangles that are also sufficiently smaller than the size of a water droplet.Furthermore, since the area ratio of the tip surfaces of the fine protrusions is sufficiently small, the contact angle of water on the outer side surface of the sealing member is reliably 90° or more, making it possible to reliably impart water repellency due to the lotus effect.

[0015] [Configuration 4] The sealing member according to any one of Configurations 1 to 3, wherein the sealing member comprises a circular disk-shaped core metal and rubber vulcanization-bonded to the core metal, and the numerous fine protrusions are formed on the surface of the rubber.

[0016] By adopting this configuration, the sealing member can be formed using a molding die in which a large number of micro recesses corresponding to the large number of micro protrusions on the outer side surface of the sealing member are formed on the inner surface of the cavity, making it possible to easily form a large number of micro protrusions. Furthermore, since rubber is generally a hydrophobic material, forming a large number of micro protrusions can impart particularly excellent water repellency.

[0017] [Configuration 5] The sealing member according to any one of Configurations 1 to 3, wherein the sealing member comprises a circular disk-shaped core metal and a resin bonded to the core metal, and the numerous fine protrusions are formed on the surface of the resin.

[0018] By adopting this configuration, a large number of fine protrusions can be easily formed by forming the sealing member using a molding die in which a large number of fine recesses corresponding to the large number of fine protrusions on the outer side of the sealing member are formed on the inner surface of the cavity.

[0019] [Configuration 6] The sealing member according to any one of Configurations 1 to 5, wherein the outer side surface of the sealing member has a non-projection surface between adjacent micro-projections, and the surface roughness Ra of the non-projection surface is set to 0.35 μm or less.

[0020] By adopting this configuration, when a sealing member is formed using a molding die, the non-protruding surfaces between adjacent micro-protrusions on the sealing member correspond to the inner surface of the cavity of the molding die, and since the surface roughness Ra of the inner surface of the cavity of the molding die is 0.35 μm or less, a large number of micro-recesses corresponding to the large number of micro-protrusions on the outer side surface of the sealing member can be formed with precision on the inner surface of the cavity, and as a result, it becomes possible to form a large number of micro-protrusions on the outer side surface of the sealing member with precision.

[0021] [Configuration 7] The sealing member according to any one of Configurations 1 to 6, wherein the numerous fine protrusions are coated with a film made of a water-repellent material.

[0022] The present invention also provides a sealed rolling bearing using the above-mentioned seal member, having the following configuration: [Configuration 8] A sealed rolling bearing comprising an outer ring, an inner ring arranged radially inward of the outer ring, a plurality of rolling elements incorporated in an annular bearing space formed between the outer ring and the inner ring, and the seal member according to any one of configurations 1 to 7 that closes one axial end opening of the bearing space.

[0023] [Configuration 9] A sealed rolling bearing according to Configuration 8, wherein a seal lip that comes into sliding contact with the outer periphery of the inner ring is formed at a radially inner end of the seal member, and a cylindrical surface that extends axially with a constant outer diameter from the location with which the seal lip comes into sliding contact and connects to the axial end face of the inner ring is formed on the outer periphery of the inner ring.

[0024] When this configuration is adopted, a cylindrical surface is formed on the outer circumference of the inner ring that extends axially at a constant outer diameter from the portion where the seal lip slides and connects to the axial end face of the inner ring, and therefore water repelled by the outer side surface of the seal member is less likely to accumulate in the portion of the outer circumference of the inner ring where the seal lip slides, compared to when the portion of the outer circumference of the inner ring where the seal lip slides is formed as a recessed groove, thereby achieving excellent water resistance and muddy water resistance.

[0025] The seal member of this invention has a water-repellent outer side surface with a water contact angle of 90° or more, which prevents water and muddy water from accumulating in the sealing portion of the seal member, thereby achieving excellent water resistance and muddy water resistance. Here, the water-repellent property of the outer side surface of the seal member is physically imparted by the lotus effect caused by the formation of numerous fine protrusions, so that the water-repellent property is unlikely to decrease over time. Therefore, it is possible to maintain excellent water resistance and muddy water resistance for a long period of time.

[0026] 1 is an enlarged view of the vicinity of the seal member; FIG. 2 is an enlarged view of the numerous fine protrusions formed on the axially outer side surface of the seal member; FIG. 3 is a cross-sectional view of a modified example of the fine protrusions shown in FIG. 3; FIG. 3 is a view of the numerous fine protrusions shown in FIG. 3 from the tip side; FIG. 5 is a view of a modified example of the arrangement of the fine protrusions shown in FIG.

[0027] 1 shows a sealed rolling bearing using a seal member 5 according to an embodiment of the present invention. This sealed rolling bearing comprises an outer ring 1, an inner ring 2 arranged coaxially radially inward of the outer ring 1, a plurality of rolling elements 4 incorporated at intervals in the circumferential direction in an annular bearing space 3 formed between the outer ring 1 and the inner ring 2, an annular seal member 5 that closes one axial end opening of the bearing space 3, an annular seal member 6 that closes the other axial end opening of the bearing space 3, and a cage 7 that maintains the circumferential spacing of the plurality of rolling elements 4. A lubricant is sealed in the bearing space 3.

[0028] The inner circumference of the outer ring 1 is formed with an outer ring raceway groove 8 with which the rolling elements 4 roll, a pair of outer ring shoulders 9 located axially outward of the outer ring raceway groove 8, and a pair of seal fixing grooves 10 located axially outward of the outer ring shoulders 9. The pair of outer ring shoulders 9 are bank-shaped portions extending circumferentially on both sides of the outer ring raceway groove 8 in the axial direction. The seal fixing groove 10 is a groove extending circumferentially and formed adjacent to the axially outward side of the outer ring shoulders 9. Seal members 5, 6 are fitted into and fixed in the pair of seal fixing grooves 10, respectively.

[0029] The outer periphery of the inner ring 2 is formed with an inner ring raceway groove 11 with which the rolling elements 4 roll, a pair of inner ring shoulders 12 located axially outward of the inner ring raceway groove 11, and a pair of cylindrical surfaces 13 located axially outward of the inner ring shoulders 12. The pair of inner ring shoulders 12 are bank-shaped portions extending circumferentially on both sides of the inner ring raceway groove 11 in the axial direction. The cylindrical surfaces 13 are formed adjacent to the axially outward sides of the inner ring shoulders 12. Seal lips 14 formed at the radially inner ends of the seal members 5 and 6 are in sliding contact with the cylindrical surfaces 13.

[0030] In this example, the rolling elements 4 are balls. The rolling elements 4 are sandwiched radially between the outer ring raceway groove 8 and the inner ring raceway groove 11. The outer ring raceway groove 8 and the inner ring raceway groove 11 are grooves whose cross sections perpendicular to the circumferential direction are concave arc-shaped.

[0031] The sealing member 5 blocks the end opening of the bearing space 3 between the outer ring 1 and the inner ring 2, thereby preventing foreign matter such as water or muddy water from entering the bearing space 3 from the outside (left side in the figure) to the inside (right side in the figure).

[0032] 2, the seal member 5 is made of an annular plate-shaped core metal 15 and rubber 16 vulcanization-bonded to the core metal 15. The core metal 15 is formed by press-forming a steel plate such as a cold-rolled steel plate or a stainless steel plate. The core metal 15 has an annular plate portion 17 perpendicular to the axial direction, an annular bent-edge portion 18 formed by bending the radially outer end of the annular plate portion 17 inward in the axial direction, and an inclined portion 19 extending radially inward from the radially inner end of the annular plate portion 17 at an inclination inward in the axial direction.

[0033] The rubber 16 is made of a rubber material such as nitrile rubber or acrylic rubber. The rubber 16 is adhered to the surface of the core 15 by vulcanization molding the rubber 16 while the core 15 is placed in a mold for forming the seal member 5. The rubber 16 has an outer rubber portion 20 adhered to the axially outer side surfaces of the annular plate portion 17 and the inclined portion 19 of the core 15, an outer rubber portion 21 extending radially outward from the bent edge portion 18 of the core 15, and a seal lip 14 extending radially inward from the inclined portion 19 of the core 15. The outer rubber portion 21 is fitted into a seal fixing groove 10 on the inner circumference of the outer ring 1. The seal lip 14 is in sliding contact with a cylindrical surface 13 on the outer circumference of the inner ring 2. The cylindrical surface 13 extends axially at a constant outer diameter from the location where the seal lip 14 slides and connects to an axial end face 22 of the inner ring 2.

[0034] As shown in Figures 3 and 5, a large number of fine protrusions 23 are formed on the side surface of the seal member 5 shown in Figure 2 opposite to the bearing space 3 side (axially outer side). These fine protrusions 23 are formed on the surface of the rubber 16. Specifically, as shown by the thick lines in Figure 2, the fine protrusions 23 are formed on the axially outer side surfaces of the outer peripheral rubber portion 21, the outer surface rubber portion 20, and the seal lip 14. In the figure, an example is shown in which a large number of fine protrusions 23 are formed on the axially outer side surfaces of the outer peripheral rubber portion 21, the outer surface rubber portion 20, and the seal lip 14, respectively. However, the large number of fine protrusions 23 may be formed only on the axially outer side surfaces of the outer surface rubber portion 20 and the seal lip 14 out of the outer peripheral rubber portion 21, the outer surface rubber portion 20, and the seal lip 14.

[0035] As shown in Fig. 5, the numerous micro-projections 23 are uniformly arranged in a square lattice pattern. Each of the numerous micro-projections 23 has a circular tip surface 24. Here, the distance A (µm) between the tip surfaces 24 of the micro-projections 23 shown in Figs. 3 and 5 is set to 120 µm or less, the diameter B (µm) of the tip surfaces 24 of the micro-projections 23 shown in Fig. 3 is set to 80 µm or less, and the height C (µm) of the micro-projections 23 shown in Fig. 3 is set to 80 µm or less. Furthermore, when the diameter of the tip surfaces 24 of the micro-projections 23 shown in Fig. 3 is B (µm), the distance between the tip surfaces 24 of the micro-projections 23 is A (µm), and the height of the micro-projections 23 is C (µm), the dimensions of the micro-projections 23 are set so that the value of A / (B x C) is 0.26 or less.

[0036] 3, a flat non-projection surface 25 is formed between adjacent fine projections 23. The surface roughness Ra of the non-projection surface 25 is set to 0.35 μm or less.

[0037] By forming numerous micro-projections 23 as shown in Figures 3 and 5, the side surface of the sealing member 5 shown in Figure 2 becomes a water-repellent surface with a water contact angle θ (see Figure 7) of 90° or more due to the lotus effect. The water contact angle θ can be measured by the sessile drop method specified in Japanese Industrial Standard JIS R3257:1999, "Test Method for Wettability of Substrate Glass Surfaces." The lotus effect refers to the effect that when a surface in contact with water is formed with numerous micro-projections 23 arranged with small gaps that prevent water from penetrating, the water contact state becomes point contact with the tip surfaces 24 of the micro-projections 23, resulting in a large water contact angle θ. The water contact angle θ in this case can be calculated using the Cassie-Baxter equation. Note that in Figure 7, the size of the micro-projections 23 is exaggerated to make them easier to understand, but the actual micro-projections 23 are extremely small.

[0038] The Cassie-Baxter equation is expressed as f １ , the area ratio of material 2 is f ２ , the contact angle of water on the surface of material 1 is θ １ , the contact angle of water on the surface of material 2 is θ ２ Then, cosθ=f １ cosθ １ +f ２ cosθ ２ Here, if the substance 2 is air, the contact angle θ ２ is 180°, and f ２ = 1 - f １ Therefore, by modifying the Cassie-Baxter equation, θ １ The condition for f ≥ 90° is found as follows: １ ≦1 / (1+cosθ １ Furthermore, the rubber material forming the rubber 16 of the sealing member 5 is designated as Substance 1, and the contact angle of water on the surface of Substance 1 is θ １ If f is set to 70°, the above equation becomes as follows: １≦0.745

[0039] In this sealed rolling bearing, the side of the seal member 5 shown in Figure 2 opposite the bearing space 3 (the left side in the figure) is a water-repellent surface with a water contact angle θ (see Figure 7) of 90° or more, which prevents water and muddy water from accumulating in the sealing portion of the seal member 5 and provides excellent water resistance and muddy water resistance. Here, the water repellency of the side surface of the seal member 5 is physically imparted by the lotus effect achieved by forming numerous fine protrusions 23, as shown in Figures 3 and 5, so that the water repellency is unlikely to decrease over time. As a result, excellent water resistance and muddy water resistance can be maintained over the long term.

[0040] As shown in Figures 2 and 3, in this sealed rolling bearing, the size of the tip surface 24 of each of the fine protrusions 23 formed on the side surface of the seal member 5 is sufficiently smaller than the size of a water droplet (usually about several mm), and as shown in Figure 5, the fine protrusions 23 are uniformly arranged in a fine square lattice pattern that is sufficiently smaller than the size of a water droplet, and furthermore, the area ratio f １ Since the ratio (the ratio of the area of ​​the tip surface 24 to the total area of ​​the surface on which the fine protrusions 23 are formed) is sufficiently small, the water contact angle θ of the side surface of the sealing member 5 is reliably 90° or more, making it possible to reliably impart water repellency due to the lotus effect.

[0041] Furthermore, in this sealed rolling bearing, the numerous fine protrusions 23 shown in Figures 3 and 5 are formed on the surface of the rubber 16 shown in Figure 2, so by using a molding die in which numerous fine recesses corresponding to the numerous fine protrusions 23 shown in Figures 3 and 5 are formed on the inner surface of a cavity to form the seal member 5 shown in Figure 2, the numerous fine protrusions 23 shown in Figures 3 and 5 can be easily formed. Furthermore, because the rubber 16 is generally a hydrophobic material, forming the numerous fine protrusions 23 can impart particularly excellent water repellency.

[0042] 2, this sealed rolling bearing is formed with a cylindrical surface 13 on the outer circumference of the inner ring 2 that extends axially at a constant outer diameter from the portion where the seal lip 14 slides and connects to the axial end face 22 of the inner ring 2, and therefore water repelled by the side surface of the seal member 5 is less likely to accumulate in the portion of the outer circumference of the inner ring 2 where the seal lip 14 slides, compared to when the portion on the outer circumference of the inner ring 2 where the seal lip 14 slides is formed as a recessed groove. As a result, excellent water resistance and muddy water resistance can be achieved.

[0043] Furthermore, in this sealed rolling bearing, the surface roughness Ra of the non-projection surface 25 shown in Fig. 3 is set to 0.35 µm or less. That is, when the sealing member 5 shown in Fig. 2 is formed using a molding die, the non-projection surface 25 between adjacent microprojections 23 shown in Fig. 3 corresponds to the inner surface of the cavity of the molding die, and the surface roughness Ra of the inner surface of the cavity of the molding die is set to 0.35 µm or less. Therefore, a large number of microrecesses corresponding to the large number of microprojections 23 shown in Fig. 3 can be formed accurately on the inner surface of the cavity of the molding die, and as a result, the large number of microprojections 23 shown in Fig. 3 can be formed accurately.

[0044] In the sealed rolling bearing of this embodiment, a test was conducted to confirm that when a large number of fine protrusions 23 are formed on the side surface of the seal member 5, the lotus effect results in the side surface of the seal member 5 becoming water-repellent, with a water contact angle θ of 90° or more. The test results are shown in Table 1.

[0045] From the test results, it can be confirmed that a surface having a value of A / (B×C) of 0.26 or less is a water-repellent surface with a water contact angle θ of 90° or more. １ is made of rubber material at 70°.

[0046] In the above embodiment, an example was given in which a large number of micro-protrusions 23 were uniformly arranged in a square lattice pattern as shown in Fig. 5, but a large number of micro-protrusions 23 may also be uniformly arranged in an equilateral triangular lattice pattern as shown in Fig. 6. Furthermore, in the above embodiment, an example was given in which cylindrical micro-protrusions 23 were used as shown in Fig. 3, but truncated cone-shaped micro-protrusions 23 may also be used as shown in Fig. 4. Even in this case, the same effects as those of the above embodiment can be achieved. The shape of the micro-protrusions 23 may also be a triangular truncated pyramid, a quadrangular truncated pyramid, a triangular prism, a quadrangular prism, a hemisphere, or the like.

[0047] Furthermore, in the above embodiment, an example was shown in which the sealing member 5 was formed from a circular plate-shaped core 15 and rubber 16 vulcanization-bonded to the core 15, but the sealing member 5 may also be formed from a circular plate-shaped core 15 and resin bonded to the core 15, with a large number of fine protrusions 23 formed on the surface of the resin. Even in this case, as in the above embodiment, the sealing member 5 can be formed using a molding die in which a large number of fine recesses corresponding to the large number of fine protrusions 23 on the side surface of the sealing member 5 are formed on the inner surface of the cavity, thereby making it possible to easily form a large number of fine protrusions 23.

[0048] It is also possible to coat the fine protrusions 23 with a film made of a water-repellent material.

[0049] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0050] DESCRIPTION OF SYMBOLS 1 Outer ring 2 Inner ring 3 Bearing space 4 Rolling element 5 Seal member 13 Cylindrical surface 14 Seal lip 15 Core metal 16 Rubber 22 Axial end face 23 Fine projection 24 Tip face of fine projection 25 Non-projection face A Distance between tip faces of fine projection B Diameter of tip face of fine projection C Height of fine projection

Claims

1. A sealing member (5) for preventing the intrusion of foreign matter from the outside to the inside, characterized in that a large number of fine protrusions (23) are formed on the outer side surface of the sealing member (5) so that the outer side surface becomes a water-repellent surface with a water contact angle (θ) of 90° or more.

2. A sealing member as described in claim 1, wherein the diameter of the tip surfaces (24) of the numerous fine protrusions (23) is B (μm), the distance between the tip surfaces (24) of the numerous fine protrusions (23) is A (μm), and the height of the numerous fine protrusions (23) is C (μm), the value of A / (B x C) is 0.26 or less.

3. A sealing member as described in claim 1 or 2, wherein each of the numerous fine protrusions (23) has a circular tip surface (24), the diameter B (μm) of the tip surface (24) is 80 μm or less, the numerous fine protrusions (23) are uniformly arranged in a square or equilateral triangular lattice pattern, the spacing A (μm) between the tip surfaces (24) of those fine protrusions (23) is 120 μm or less, and the height C (μm) of the numerous fine protrusions (23) is 80 μm or less.

4. A sealing member as described in any one of claims 1 to 3, wherein the sealing member (5) comprises a circular plate-shaped core metal (15) and rubber (16) vulcanized and bonded to the core metal (15), and the numerous fine protrusions (23) are formed on the surface of the rubber (16).

5. A sealing member according to any one of claims 1 to 3, wherein the sealing member (5) comprises a circular plate-shaped core metal (15) and a resin bonded to the core metal (15), and the numerous fine protrusions (23) are formed on the surface of the resin.

6. A sealing member as described in any one of claims 1 to 5, wherein the outer side surface of the sealing member (5) has a non-projection surface (25) between adjacent fine projections (23), and the surface roughness Ra of the non-projection surface (25) is set to 0.35 μm or less.

7. A sealing member according to any one of claims 1 to 6, wherein the numerous fine projections (23) are coated with a film made of a material having water repellency.

8. A sealed rolling bearing comprising an outer ring (1), an inner ring (2) arranged radially inward of the outer ring (1), a plurality of rolling elements (4) incorporated in an annular bearing space (3) formed between the outer ring (1) and the inner ring (2), and a sealing member (5) as described in any one of claims 1 to 7 that closes one axial end opening of the bearing space (3).

9. A sealed rolling bearing as described in claim 8, wherein a seal lip (14) that slides against the outer periphery of the inner ring (2) is formed at the radially inner end of the seal member (5), and a cylindrical surface (13) is formed on the outer periphery of the inner ring (2) which extends axially with a constant outer diameter from the point where the seal lip (14) slides against the outer periphery of the inner ring (2) and connects to the axial end face (22) of the inner ring (2).

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