Sealing device and sealing device-equipped bearing unit

Abstract

The present invention provides a sealing device-equipped bearing unit that has lubricant retention properties and that lowers torque. A sealing device (15) is constituted by: seal lips (19a, 19b, 19c) composed of an elastic material; and a mating member (slinger 17) with which the seal lips (19a, 19b, 19c) are in sliding contact. A plurality of dimples (20) are formed in the surface of the region of the mating member (slinger 17) that is in sliding contact with at least the seal lips (19a, 19b, 19c), each of the dimples (20) being constituted by a recess (21) further recessed than the surface of the mating member (slinger 17) and a first protrusion (22) protruding from the surface of the mating member (slinger 17) and surrounding the recess (21). Furthermore, a sealing device-equipped bearing unit (10) is provided with the abovementioned sealing device (15).

Description

Sealing device and bearing unit with sealing device

[0001] The present invention relates to a bearing unit (sealed bearing unit) equipped with a sealing device that is interposed in a location where sealing is required between a fixed member and a rotating member, such as a bearing unit in a wheel suspension of an automobile, and also to a sealing device that is incorporated into the sealed bearing unit.

[0002] Conventionally, sealing devices have been known that are interposed between a fixed member and a rotating member, such as a bearing unit, in a wheel suspension of a vehicle such as an automobile to seal in grease or lubricating oil (hereinafter collectively referred to as "lubricant") and prevent water and dust from seeping in. Furthermore, various measures have been taken to improve the fuel efficiency of vehicles today, and there is also a demand for reducing the rotational torque of bearing units.

[0003] For example, Patent Document 1 discloses a sealing device in which a seal lip fixed to a core metal has an uneven surface that slides in contact with a slinger. Also, Patent Document 2 discloses a sealing device in which a separate member is provided on the surface of the slinger on which the seal lip slides, and the separate member forms the sliding surface with the seal lip, and the sliding surface of the separate member that slides in contact with the seal lip is roughened.

[0004] Japanese Patent Publication No. 2012-193835 Japanese Patent Publication No. 2010-107035

[0005] However, in the sealing device described in Patent Document 1, the unevenness is formed on the seal lip rather than the slinger, but the seal lip is made of a soft material and is therefore prone to wear, raising concerns that the unevenness will disappear as it wears away, making it impossible to maintain its effectiveness. Furthermore, in the sealing device described in Patent Document 2, the surface of a separate member on the slinger side rather than the seal lip is roughened, but the depth and size of the recesses in the roughened surface are not uniform, resulting in insufficient lubricant retention and sealing performance, and furthermore, the flow behavior of the lubricant in each recess is different, resulting in uneven torque, raising concerns that torque reduction cannot be achieved sufficiently.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a bearing unit with a sealing device that achieves both good lubricant retention and low torque.

[0007] The above object of the present invention is achieved by the following configuration [1] relating to a sealing device.

[0008] [1] A sealing device that holds a plurality of rolling elements between an outer ring and an inner ring so that they can roll freely, is filled with lubricant, and is incorporated into a bearing unit with a sealing device that is sealed by a sealing device, wherein the sealing device is composed of a seal lip made of an elastic material and a mating member with which the seal lip slides, and wherein a plurality of dimples are formed on the surface of the mating member at least in the sliding contact area with the seal lip, the dimples being composed of a recess that is recessed below the surface of the mating member and a first protrusion that protrudes above the surface of the mating member and surrounds the recess.

[0009] Furthermore, preferred embodiments of the present invention relating to the sealing device relate to the following [2] to [5].

[0010] [2] The sealing device according to [1], characterized in that an average value of the difference in height between the top of the first convex portion and the deepest portion of the concave portion is 25 μm or less. [3] The sealing device according to [1] or [2], characterized in that the area ratio of the opening of the first convex portion to the sliding contact area is 10 to 80%. [4] The sealing device according to any one of [1] to [3], characterized in that a soft coating made of a material having a lower melting point than the mating member is formed on the surface of the mating member on which the dimples are formed. [5] The sealing device according to [4], characterized in that second convex portions made of the material that forms the soft coating are formed.

[0011] The above object of the present invention is achieved by the following configuration [6] relating to a bearing unit with a sealing device.

[0012] [6] A bearing unit with a sealing device, in which a plurality of rolling elements are held between an outer ring and an inner ring so as to be freely rollable, a lubricant is filled, and the bearing unit is sealed with a sealing device, characterized in that the sealing device is the sealing device described in any one of [1] to [5].

[0013] According to the present invention, it is possible to provide a bearing unit with a sealed device that achieves both lubricant retention and low torque.

[0014] FIG. 1 is a cross-sectional view showing one embodiment of a bearing unit with a sealed device according to the present invention. FIG. 2 is an enlarged view showing a sealing device in the bearing unit with a sealed device shown in FIG. 1. FIG. 3 is an enlarged cross-sectional view showing dimples formed in the sliding contact area of ​​a slinger in a sealing device according to the present invention. FIG. 4 is a top view showing an example of the shape of the recesses. FIG. 5 is a top view showing an example of the distribution of the recesses. FIG. 6 is a top view showing another example of the distribution of the recesses. FIG. 7 is an example of a cross-section obtained by linearly scanning the sliding contact area of ​​the slinger using a surface roughness meter. FIG. 8 is a schematic diagram illustrating the height difference of the dimples. FIG. 9 is a schematic diagram illustrating the opening diameter of the dimples. FIG. 10 is a cross-sectional view showing an example of the height difference between the recesses and the soft coating. FIG. 11 is a cross-sectional view showing an example of the height difference between the recesses and the soft coating. FIG. 12 is an enlarged view showing another example of a sealing device. FIG. 13 is a diagram showing the measurement results of a surface roughness meter for Comparative Examples 2 to 5. FIG. 14 is a diagram showing the measurement results of a surface roughness meter for Examples 1 to 4. Fig. 15 is a graph showing the measurement results in Table 1. Fig. 16 is a graph showing the measurement results in Table 2.

[0015] A sealing device and a bearing unit with a sealing device according to one embodiment of the present invention will be described below. Note that this embodiment shows only one example of the present invention, and the present invention is not limited to this embodiment. Furthermore, various modifications and improvements can be made to this embodiment, and such modifications and improvements can also be included in the present invention.

[0016] In this embodiment, the bearing unit with a sealed device in which a plurality of rolling elements are held between an outer ring and an inner ring so that they can roll freely, and which is filled with lubricant and sealed with a sealing device is not limited to this, and an example thereof is a bearing unit with a sealed device 10 shown in Fig. 1. As shown in the figure, the bearing unit with a sealed device 10 includes an outer ring 11 which is a fixed ring, an inner ring 12 which is a rotating ring, balls 13 which are a plurality of rolling elements that are rollably disposed in an annular gap defined by the outer ring 11 and the inner ring 12 and are held at equal intervals in the circumferential direction by a cage 14, and a sealing device 15 disposed at the open end of the annular gap.

[0017] 2, the sealing device 15 comprises a seal member 16 made of an elastic material fixed to the inner peripheral surface of the outer ring 11, and a slinger 17 located further outward from the open end than the seal member 16 and fixed to the outer peripheral surface of the inner ring 12. The sealing device 15 is composed of the seal member 16 and the slinger 17, and the slinger 17 corresponds to the "mating member" in the present invention. The sliding contact between the seal member 16 and the slinger 17 closes the open end of the annular gap, preventing foreign matter such as dust from entering the bearing and preventing the lubricant filled inside the bearing from leaking out of the bearing.

[0018] The sealing member 16 is constructed by reinforcing a rubber seal 19 (elastic material) also formed in an annular shape with a roughly L-shaped cross section with a core metal 18, and the tip portion of the rubber seal 19 branches into multiple seal lips 19a, 19b, 19c, which slide against the surface of the slinger 17.

[0019] The slinger 17 is made of a metal plate such as ferritic stainless steel (e.g., SUS430) or martensitic stainless steel (e.g., SUS410), and has a cylindrical portion 17a fitted onto the inner ring 12, and a brim-like flange portion 17c connected to the axial end of the cylindrical portion 17a via a curved portion 17b and formed to extend radially outward.

[0020] In FIG. 2, the slinger 17 has a substantially L-shaped cross section, but it may have a substantially U-shaped cross section or other cross-sectional shapes.

[0021] 2, there are three seal lips (seal lips 19a, 19b, and 19c), but there is no limit to the number. If there are multiple seal lips, it is preferable to form dimples 20 (described later) on the slinger 17 in all sliding contact areas with the seal lips, as this will increase the torque reduction effect.

[0022] In this embodiment, multiple dimples 20 are formed in the sliding contact area between the slinger 17 (mating member) and the sealing member 16 (here, the surfaces of the sealing lips 19a, 19b, 19c and the sliding contact areas of the cylindrical portion 17a, curved portion 17b, and flange portion 17c that slide against them).As shown in the enlarged cross-sectional view of Figure 3, the dimple 20 is composed of a recess 21 that is recessed below the slinger surface 17A, and a first protrusion 22 that protrudes above the slinger surface 17A and surrounds the recess 21.

[0023] As the bearing rotates, it moves slightly in the width direction (left and right in FIG. 1) and radial direction (up and down in FIG. 1), and the seal member 16 also undergoes elastic deformation and wear, so the sliding contact area of ​​the seal member 16 with the slinger 17 is not a line but a surface, i.e., it has a certain degree of expanse. Therefore, the sliding contact area is the range in which sliding contact between the seal member 16 and the slinger 17 is expected.

[0024] The recesses 21 are individually independent as shown in the figure, and may be formed in a lattice pattern at approximately equal intervals when viewed from above, or may be formed in an irregular (random) distribution. Furthermore, the first protrusions 22 may surround the entire periphery of the recess 21, or may surround it partially.

[0025] 4 illustrates examples of the shape of the recess 21 in a top view, but may be a "circular shape" as shown in (a), an "elliptical shape" as shown in (b), a "triangular shape" as shown in (c), a "square shape" as shown in (d), an "arc shape" as shown in (e), a "L-shaped arrow shape" as shown in (f), a "rectangular shape" as shown in (g), a "wave shape" as shown in (h), a "jagged shape" as shown in (i), or an "irregular shape" (not shown). A combination of these shapes may also be used. These shapes can be easily formed by laser processing, transfer from a mold, or the like.

[0026] 5(a) to 5(c) show examples of the distribution of the recesses 21 from a top view, and all show cases where a plurality of recesses 21 are formed on the surface of the flange portion 17c of the slinger 17. That is, as shown in Fig. 5(a), when a checkerboard-like grid indicated by dotted lines is superimposed on the surface of the flange portion 17c, the recesses 21 may be formed so as to fill all of the grid points, as shown in Fig. 5(b), the recesses 21 may be formed at equal intervals on a circle concentric with the flange portion 17c, or as shown in Fig. 5(c), the recesses 21 may be formed at each of the grid points diagonally opposite the squares in the checkerboard-like grid shown in Fig. 5(a).

[0027] The recesses 21 are preferably arranged at a high density in a top view, and may be formed by combining a plurality of recesses 21 of different diameters. For example, as shown in Fig. 6(a) , a large-diameter recess 21a, a medium-diameter recess 21b, a small-diameter recess 21c, and a minimum-diameter recess 21d are combined, and the medium-diameter recess 21b is arranged at the center of a space formed by stacking four large-diameter recesses 21a in a square shape, and the small-diameter recesses 21c are arranged at equal intervals around the medium-diameter recess 21b, and three minimum-diameter recesses 21d are arranged to fill the space formed by the large-diameter recesses 21a, the medium-diameter recess 21b, and the small-diameter recess 21c. Alternatively, as shown in the same figure (b), a medium-diameter recess 21b may be placed in the center of the space formed by stacking three large-diameter recesses 21a in the shape of an equilateral triangle, small-diameter recesses 21c may be placed at equal intervals around the medium-diameter recess 21b, and a smallest-diameter recess 21d may be placed so as to fill the space formed by the large-diameter recess 21a and the small-diameter recess 21c.

[0028] As shown in Figure 3, the presence of the recess 21 surrounded by the first protrusion 22 allows the lubricant to penetrate the interior 21A of the recess 21, improving lubricant retention. This also causes a pressure change in the lubricant within the interior 21A of the recess 21, resulting in cavitation. In the region where cavitation occurs, shear resistance decreases, resulting in a reduction in torque. Cavitation also occurs on the slope 22a of the first protrusion 22 opposite the recess 21, which, combined with the cavitation within the interior 21A of the recess 21, further reduces torque. This is the torque reduction mechanism of the present invention.

[0029] In order to more effectively exert this torque reduction effect, it is preferable that the average height difference between the deepest part of the recess 21 and the top of the first protrusion 22 be 25 μm or less, more preferably 22 μm or less, and even more preferably 20 μm or less.

[0030] Furthermore, because the first protrusions 22 come into contact with the seal lips 19a, 19b, and 19c, the higher the first protrusions 22 of the dimples 20, the greater the amount of wear on the seal lips 19a, 19b, and 19c. Therefore, it is preferable to set the maximum height of the first protrusions 22 to 1 to 10 μm. If the maximum height of the first protrusions 22 exceeds 10 μm, the seal lips 19a, 19b, and 19c may be severely worn, resulting in a decrease in sealing performance.

[0031] The height difference, its average value, and the maximum height of the first convex portion 22 are determined as follows.

[0032] FIG. 7 shows an example of a cross section obtained by linearly scanning the sliding contact area of ​​the slinger 17 using a surface roughness meter. In this cross section, the large recessed portion is the recess 21 of the dimple 20, and the protruding portions on both sides of it are the first protrusions 22 of the dimple 20. As shown in FIG. 8 , for a certain dimple 20, let a1 be the height difference between the deepest part of the recess 21 and the apex of the first protrusion 22 on the left side of the figure, and a2 be the height difference between the deepest part of the recess 21 and the apex of the first protrusion 22 on the right side of the figure. The height difference (depth) of the dimple 20 is then calculated as "(a1 + a2) / 2." The height differences of each dimple 20 for one scan are then calculated, and their average value is calculated. The maximum value of the protruding portion is defined as the maximum height of the first protrusion.

[0033] Furthermore, the dimples 20 preferably have an area ratio of the opening area of ​​the first protrusions 22 to the sliding contact area of ​​10 to 80%. If the area ratio is less than 10%, torque reduction may not be sufficient. On the other hand, if the area ratio exceeds 80%, the individual first protrusions 22 may overlap with each other, increasing the height of the protrusions and possibly causing wear on the seal lip and reducing sealing performance.

[0034] 9, the above area ratio is determined by finding the distance d1 between the apexes of the first protrusions 22 on the left and right sides of a certain dimple 20 in the cross section shown in FIG. 7, and calculating the circular equivalent area to be the opening area of ​​the dimple 20. The opening areas of the individual dimples 20 for one scan are then found, and the sum of these is calculated, and the area ratio is calculated as the ratio to the area of ​​a square whose sides are the length of one scan.

[0035] As described above, the recesses 21 surrounded by the first protrusions 22 are individually independent, and the recesses 21 may be distributed, for example, as shown in Fig. 5(a) so as to fill all the lattice points when a checkerboard grid indicated by dotted lines is superimposed on the surface of the flange portion 17c, or as shown in Fig. 5(b) so as to be equally spaced on a circle concentric with the flange portion 17c, or as shown in Fig. 5(c) so as to be located at each lattice point diagonally opposite the square in the checkerboard grid shown in Fig. 5(a) , or may be distributed irregularly (randomly). The torque reducing effect of the present invention, which is produced by the combination of the cavitation inside 21A of the recesses 21 and the cavitation occurring on the slope 22a opposite to the recesses 21, does not particularly depend on whether the recesses 21 (dimples) are arranged in a checkerboard pattern, concentric circles, or irregularly (randomly). This point will be explained in detail in (1) to (4) below.

[0036] (1. Explanation of the resistance generated at the seal) The lubrication condition of the hub seal changes depending on the vehicle speed (number of revolutions), but except for very low speeds, it is fluid lubrication at most speed ranges. Therefore, the resistance generated at the seal is dominated by the shear resistance of the lubricant, which is a fluid.

[0037] (2. Explanation of cavitation generation and its effect on seal resistance) When a sliding surface is provided with a spatial expansion in the film thickness direction of the fluid lubricant film, such as a recess or protrusion, a drop in fluid pressure occurs in this expansion gap, causing gas dissolved in the lubricant to precipitate and generate cavitation (gas bubbles) in the sliding part. Because this cavitation is a gas, its viscosity is extremely low compared to lubricants such as oil and grease, so resistance becomes almost zero in the area where cavitation occurs, and the resistance of the seal part can be reduced.

[0038] (3. Explanation of the influence of texture parameters) An investigation into the influence of the shape parameters (dimple diameter, depth, area ratio) of the recesses provided on the sliding surface revealed that the occurrence of cavitation has almost no effect on the dimple diameter, but is strongly influenced by the depth and area ratio. This is because the dimple depth affects the occurrence of cavitation by forming a widening gap and affecting pressure fluctuations, while the dimple area ratio affects the rate at which cavitation occurs on the sliding surface, thereby affecting sliding resistance at the seal section. On the other hand, it has been confirmed that the amount of cavitation generated is the same even for different dimple diameters as long as the area ratio is the same, so the dimple diameter has no effect. This is because the pressure fluctuations change similarly when the diameter is changed, so the rate at which cavitation occurs per dimple is the same.

[0039] (4. Conclusion) In summary, the formation of a spatial expansion in the thickness direction of the fluid lubrication film generates pressure fluctuations, which in turn generates cavitation in the sliding area, thereby reducing the resistance of the seal. In other words, the percentage of dimples present in the sliding area is important. As long as the percentage is the same, it is irrelevant whether the dimples are arranged in a checkerboard pattern, concentric circles, or irregular (random) pattern. Furthermore, because cavitation can also occur behind dimples with protrusions surrounding recesses (i.e., the slope 22a opposite the recesses 21), the amount of cavitation generated is greater than in a simple recess without protrusions. However, the amount of cavitation generated behind the protrusions around the recesses also depends on the percentage of dimples present in the sliding area. Therefore, as mentioned above, it is irrelevant whether the dimples are arranged in a checkerboard pattern, concentric circles, or irregular (random) pattern.

[0040] Next, a method for forming the recess 21 and the first protrusion 22 will be described. Possible methods for forming the recess 21 and the first protrusion 22 include laser processing, plastic processing by transfer from a mold, cutting, low-flow shot blasting, etching, laser cladding, 3D printing, electrical discharge machining, and plating buildup. For example, with laser irradiation, the portion of the slinger surface 17A irradiated with laser light melts to form the recess 21, and the molten material dissolves and solidifies around the opening of the recess 21, forming the first protrusion 22. Furthermore, when transferring a mold, a mold with protrusions is used, and the portion of the slinger surface 17A into which the protrusion is pressed plastically deforms to form the recess 21, and the opening of the recess 21 rises, forming the first protrusion 22. Therefore, the deeper the recess 21 of the dimple 20, the higher the first protrusion 22 is likely to be. Furthermore, the larger the opening area, the higher the first protrusion 22 is likely to be. Therefore, the height difference and opening area can be adjusted within the above range by adjusting the irradiation intensity of the laser light and the pressing force of the mold.

[0041] As shown in FIG. 10 , the slinger surface 17A (i.e., the surface of the mating member on which the dimples 20 are formed) is made of metal, but may be coated with a soft coating 30 made of a material with a lower melting point than the slinger 17 (mating member), such as a resin. Examples of resins include phenolic resin and epoxy resin. When the dimples 20 are formed by laser processing, the soft coating 30 creates double protrusions of the base metal and the soft coating 30 due to the difference in melting points, making cavitation more likely to occur. These protrusions made of the material forming the soft coating 30 are "second protrusions 32." The second protrusions 32 are formed outside the first protrusions 22, i.e., closer to the surface than the first protrusions 22 formed on the slinger 17 (mating member). Furthermore, the soft coating 30 is less aggressive to the seal lips 19a, 19b, and 19c, thereby reducing wear on the seal lips 19a, 19b, and 19c and prolonging the sealing effect.

[0042] As shown in the figure, in order to maximize the effect, it is desirable that the second convex portions 32 of the soft coating 30 have a height approximately equal to that of the first convex portions 22. It is preferable to adjust the film thickness of the soft coating 30 and the laser processing conditions so as to achieve this height relationship.

[0043] 11 , it is possible that the second protrusions 32 are not formed depending on the material and processing method of the soft coating 30. Even in this case, cavitation occurs in the voids 33 formed between the soft coating 30 and the first protrusions 22, improving the low-torque effect compared to when the soft coating 30 is not present.

[0044] Although the above description shows the metallic slinger 17 as the mating member, the mating member is not limited to metal, but may be non-metallic, such as resin or ceramic.

[0045] Grease or lubricating oil can be used as the lubricant, and there are no limitations on the type or properties thereof. However, from the viewpoint of the torque reduction aimed at in the present invention, when grease is used, the following is preferred.

[0046] The base oil of the grease is preferably low in kinematic viscosity, and the kinematic viscosity is preferably 5.0 mm at 40°C. ２ / s or more 460.0mm ２ / s or less, and 1.9 mm at 100 °C ２ / s or more 56.0mm ２ / s or less. When the kinematic viscosity is equal to or greater than the lower limit, the desired heat resistance is obtained, and the base oil can be prevented from volatilizing over time during use, thereby maintaining sealing performance. On the other hand, when the kinematic viscosity is equal to or less than the upper limit, an increase in sliding friction resistance on the sliding surface can be prevented, and low torque can be achieved.

[0047] The kinematic viscosity is preferably 9.0 mm at 40°C. ２ / s or more 75.0mm ２ / s or less, and 2.0 mm at 100°C ２ / s or more 11.0mm ２ More preferably, it can be 9.0 mm / s or less at 40°C. ２ / s or more 30.0mm ２ / s or less, and 2.0 mm at 100°C ２ / s or more 6.0mm ２ / s or less.

[0048] There are no limitations on the type of base oil, and mineral oil, synthetic oil, or natural oil lubricating oils can all be used. Specifically, mineral oil-based lubricating base oils can include those obtained by refining mineral oils through an appropriate combination of vacuum distillation, oil deasphalting, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay refining, and hydrorefining. Synthetic oil-based lubricating base oils can include hydrocarbon oils, aromatic oils, ester oils, ether oils, fluorine-based oils, and silicone oils. Among these, poly-α-olefins (PAO) and gas-to-liquid (GTL) are preferred. Poly-α-olefins have a high viscosity index, so they exhibit little viscosity loss at high temperatures and a high ability to maintain an oil film. Furthermore, they do not become too viscous at low temperatures, maintaining appropriate fluidity, resulting in little loss of lubricity. This excellent low-temperature fluidity is an extremely effective effect when used as a base oil. Examples of natural oil-based lubricating base oils include beef tallow, lard, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, palm kernel oil, and other fat-based oils, as well as hydrogenated products thereof.

[0049] However, when the rubber seal 19 is made of, for example, nitrile rubber, which is the most commonly used material, it is preferable to use mineral oil or synthetic hydrocarbon oil.

[0050] The thickener is not limited, and examples thereof include soap-based thickeners such as Li soap and complex Li soap, urea-based thickeners such as diurea, inorganic thickeners such as organic clay and silica, and organic thickeners such as PTFE. Among these, urea-based thickeners are preferred, as they have excellent resistance to heat generation due to lubrication under high loads and are less expensive than other thickeners. The content of the thickener is selected to achieve an appropriate consistency depending on the application and purpose.

[0051] Furthermore, the sealing device 15 is not limited to the configuration shown in Figures 1 and 2, and can also have, for example, the configuration shown in Figure 12. That is, the seal member 16 is provided with a rubber seal 19 that covers the inner ring 12 side of a core metal 18 with a generally U-shaped cross section that is fixed to the inner peripheral surface of the outer ring 11. The rubber seal 19 branches into three seal lips 19a, 19b, and 19c that slide against the surface of the inner ring 12. Note that Figure 12 shows the shapes of the seal lips 19a, 19b, and 19c in their free states. As with the sealing device shown in Figure 2, the number of seal lips is three (seal lips 19a, 19b, and 19c), but there is no limit to the number.

[0052] In this embodiment, the above-mentioned dimples 20 (not shown) are formed on the raceway surface of the inner ring 12 in the sliding contact areas with the seal lips 19a, 19b, 19c, thereby achieving low torque.

[0053] The effects of the present invention were verified by the following examples.

[0054] (Test 1: Examples 1 to 4 and Comparative Examples 1 to 5) A ball bearing unit equipped with a seal member and a slinger as shown in Figure 1 was fabricated and subjected to a torque test. The seal member was a rubber seal with an outer diameter of 75 mm, an inner diameter of 61 mm, and one seal lip. Urea grease was used as the lubricant.

[0055] The slinger was made of SUS430, and in Examples 1 to 4 and Comparative Examples 2 to 4, 50 μm diameter dimples were formed in a grid pattern at equal intervals with a pitch of 80 μm, as shown in Table 1. In Examples 1 to 4, first convex portions were formed around the concave portions, while in Comparative Examples 2 to 5, only concave portions were formed without first convex portions around the concave portions. The dimple depth and the maximum height of the first convex portions were average values ​​determined with a surface roughness meter. Comparative Example 1 had no dimples.

[0056] FIG. 13 shows the measurement results of the surface roughness meter for Comparative Examples 2 to 5, and FIG. 14 shows the measurement results of the surface roughness meter for Examples 1 to 4.

[0057] The ball bearing was then rotated at a rotation speed of 1000 rpm, and the torque was measured. The results are shown in Table 1 and FIG. 15. Note that, since Comparative Example 1 had no dimples, "dimple diameter (μm)," "dimple depth (μm)," "dimple pitch (μm)," and "maximum height of first convex portion (μm)" are each indicated with "-" in Table 1. Furthermore, since Comparative Examples 2 to 5 did not have first convex portions formed around the concave portions, "maximum height of first convex portion (μm)" is each indicated with "-" in Table 1.

[0058]

[0059] From Table 1 and FIG. 15, it can be seen that by forming the first convex portion around the recessed portion as in Examples 1 to 4, the torque can be reduced compared to when only the recessed portion is simply formed.

[0060] (Test 2: Examples 5 to 7 and Comparative Example 6) A ball bearing unit equipped with a seal member and a slinger as shown in Figure 1 was fabricated. The seal member was a rubber seal with an outer diameter of 75 mm, an inner diameter of 61 mm, and three seal lips. Urea grease was used as the lubricant.

[0061] The slinger was made of SUS430, and in Examples 5 to 8, dimples with a diameter of 65 μm were formed in a lattice pattern at equal intervals with a pitch of 80 μm, as shown in Table 2. The difference in dimple height was the average value determined with a surface roughness meter. Comparative Example 6 had no dimples.

[0062] The ball bearing was then rotated at 1000 rpm, and the torque was measured. The results are shown in Table 2 and Figure 16. Note that, since Comparative Example 6 had no dimples, in Table 2, the "dimple diameter (μm)" and "dimple height difference (μm)" are indicated by "-".

[0063]

[0064] From Table 2 and FIG. 16, it can be seen that by forming first convex portions around the recessed portions and setting the dimple area ratio to 80% or less, as in Examples 5 to 8, the torque can be reduced compared to when only recessed portions are formed.

[0065] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0066] This application is based on a Japanese patent application (Patent Application No. 2024-062729) filed on April 9, 2024, the contents of which are incorporated herein by reference.

[0067] REFERENCE SIGNS LIST 10 Bearing unit with sealing device 11 Outer ring 12 Inner ring 13 Ball (rolling element) 14 Cage 15 Sealing device 16 Seal member 17 Slinger 17a Cylindrical portion (of slinger) 17b Curved portion (of slinger) 17c Flange portion (of slinger) 17A Slinger surface 18 Core metal 19 Rubber seal 19a, 19b, 19c Seal lip 20 Dimple 21 Concave portion 22 First convex portion 30 Soft coating 33 Void

Claims

1. A sealing device that holds multiple rolling elements between an outer ring and an inner ring so that they can roll freely, is filled with lubricant, and is incorporated into a bearing unit with a sealing device that is sealed with a sealing device, wherein the sealing device is composed of a seal lip made of an elastic material and a mating member with which the seal lip slides, and wherein a plurality of dimples are formed on the surface of the mating member, at least in the sliding contact area with the seal lip, and each dimple is composed of a recess that is recessed below the surface of the mating member and a first protrusion that protrudes above the surface of the mating member and surrounds the recess.

2. The sealing device according to claim 1, characterized in that the average difference in height between the top of said first convex portion and the deepest part of said concave portion is 25 μm or less.

3. A sealing device according to claim 1, characterized in that the area ratio of the opening of said first protrusion to said sliding contact area is 10 to 80%.

4. A sealing device according to claim 2, characterized in that the area ratio of the opening of said first protrusion to said sliding contact area is 10 to 80%.

5. A sealing device according to claim 1, characterized in that a soft coating made of a material having a lower melting point than the mating member is formed on the surface of the mating member on which the dimples are formed.

6. A sealing device according to claim 5, characterized in that a second protrusion is formed from the same material as that of the soft coating.

7. A bearing unit with a sealed device, in which a plurality of rolling elements are held between an outer ring and an inner ring so as to be able to roll freely, filled with lubricant, and sealed with a sealing device, characterized in that the sealing device is a sealing device as defined in any one of claims 1 to 6.

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