Sealing device and bearing unit with sealing device

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

[Technical Field]

[0001] The present invention relates to a bearing unit (bearing unit with sealing device) that includes a sealing device interposed in a part where it is necessary to seal the space between a fixed-side member and a rotating-side member, such as a bearing unit in the wheel suspension of an automobile. The present invention also relates to a sealing device incorporated into the above-mentioned bearing unit with sealing device. [Background technology]

[0002] Conventionally, sealing devices have been known that are interposed between fixed and rotating members of bearing units and other components in the wheel suspension of vehicles such as automobiles. These devices seal in grease or lubricating oil (hereinafter collectively referred to as "lubricants") and prevent the ingress of water and dust. Furthermore, various measures are being taken today to improve the fuel efficiency of vehicles, and in bearing units, there is a demand for reducing rotational torque.

[0003] For example, Patent Document 1 discloses a sealing device in which the sliding contact surface between the seal lip fixed to a core metal and the slinger is given an uneven surface. Patent Document 2 also discloses a sealing device in which a separate member is provided on the side of the slinger that the seal lip slides against, the separate member forms the sliding contact surface with the seal lip, and the sliding contact surface of the separate member with the seal lip is roughened. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2012-193835 [Patent Document 2] Japanese Patent Publication No. 2010-107035 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in the sealing device described in Patent Document 1, the irregularities are formed on the seal lip rather than the slinger, but since the seal lip is made of a soft material, it is prone to wear, and there is a concern that the formed irregularities will disappear with wear and the effect will not be maintained. Furthermore, in the sealing device described in Patent Document 2, the surface of a separate component on the slinger side rather than the seal lip is roughened, but because the depth and size of the recesses on the roughened surface are not uniform, the lubricant retention and sealing performance will not be sufficient, and furthermore, the flow behavior of the lubricant in each recess will differ, and the torque will not be uniform, so there is a concern that sufficient torque reduction cannot be achieved.

[0006] This invention has been made in view of these circumstances, and aims to provide a bearing unit with a sealing device that achieves both lubricant retention and low torque. [Means for solving the problem]

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

[0008] [1] A sealing device incorporated into a bearing unit with a sealing device, wherein a plurality of rolling elements are held rotatably between an outer ring and an inner ring, and the unit is filled with lubricant and sealed with a sealing device, The sealing device is composed of a seal lip made of an elastic material and a mating member with which the seal lip slides, A sealing device characterized in that a plurality of dimples are formed on the surface of the mating member, at least in the sliding contact area with the seal lip, each dimple being composed of a recess that is lower than the surface of the mating member and a first protrusion that protrudes from the surface of the mating member and surrounds the recess.

[0009] Furthermore, preferred embodiments of the present invention relating to a sealing device are described in the following [2] to [5].

[0010] [2] The sealing device according to [1], characterized in that the average value of the height difference between the top of the first convex portion and the deepest part 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 region is 10 to 80%. [4] The sealing device according to any one of [1] to [3], characterized in that a soft film made of a material having a lower melting point than the mating member is formed on the surface of the mating member where the dimples are formed. [5] The sealing device according to [4], characterized in that a second convex portion made of the material of the soft film is formed.

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

[0012] [6] A bearing unit with a sealing device that holds a plurality of rolling elements between an outer ring and an inner ring so as to be freely rotatable, fills a lubricant, and seals with a sealing device, The bearing unit with a sealing device, characterized in that the sealing device is the sealing device according to any one of [1] to [5].

Effect of the Invention

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

Brief Description of the Drawings

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

MODE FOR CARRYING OUT THE INVENTION

[0015] The sealing device and the bearing unit with a sealing device according to an embodiment of the present invention will be described below. Note that this embodiment shows an example of the present invention, and the present invention is not limited to this embodiment. Further, various changes or improvements can be made to this embodiment, and forms with such changes or improvements can also be included in the present invention.

[0016] In this embodiment, there are no limitations on the type of bearing unit with a sealing device in which a plurality of rolling elements are held rotatably between the outer ring and the inner ring, a lubricant is filled in, and the unit is sealed with a sealing device. For example, the bearing unit with a sealing device 10 shown in Figure 1 can be cited. As shown in the figure, the bearing unit with a sealing device 10 comprises an outer ring 11 which is a fixed ring, an inner ring 12 which is a rotating ring, a plurality of rolling elements, which are balls 13, are rotatably arranged in the 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] As shown in Figure 2, the sealing device 15 comprises a seal member 16 made of an elastic material fixed to the inner circumferential surface of the outer ring 11, and a slinger 17 positioned outside the opening end of the seal member 16 and fixed to the outer circumferential surface of the inner ring 12. The sealing device 15 is composed of the seal member 16 and the slinger 17, with the slinger 17 corresponding to the "countering member" in this invention. The sliding contact between the seal member 16 and the slinger 17 seals the opening end of the annular gap, preventing foreign matter such as dust from entering the bearing interior, and also preventing the lubricant filled inside the bearing from leaking to the outside of the bearing.

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

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

[0020] In Figure 2, the slinger 17 has a roughly L-shaped cross-section, but it may also have a roughly U-shaped, U-shaped, or other cross-sectional shape.

[0021] Furthermore, although there are three seal lips (seal lips 19a, 19b, 19c) in Figure 2, there is no limit to the number of seal lips. When there are multiple seal lips, it is preferable to form the dimples 20 described later on all sliding contact areas of the slinger 17 that slide against the seal lips, as this will increase the low torque effect.

[0022] In this embodiment, multiple dimples 20 are formed on the sliding contact area of ​​the slinger 17 (the mating member) with 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 in Figure 3, the dimples 20 consist of a recess 21 that is lower than the slinger surface 17A and a first protrusion 22 that protrudes from the slinger surface 17A and surrounds the recess 21.

[0023] Furthermore, as the bearing rotates, it moves slightly in the width direction (left-right direction in Figure 1) and the radial direction (up-down direction in Figure 1), and the seal member 16 also undergoes elastic deformation and wear. Therefore, the sliding contact area of ​​the seal member 16 with the slinger 17 is not a line, but a surface, that is, it has a certain extent of width. For this reason, 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 grid pattern at approximately equal intervals when viewed from above, or they may be formed in an irregular (random) distribution. Furthermore, the first protrusions 22 may surround the entire circumference of the recesses 21, or they may partially surround them.

[0025] Figure 4 illustrates the shape of the recess 21 in a top view. It 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 "bent 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" which is not shown in the figure. Multiple types of these shapes may also be used in combination. These shapes can be easily formed by laser processing or transfer from a mold.

[0026] Furthermore, Figures 5(a) to 5(c) show examples of the distribution of recesses 21 in a top view, all of which show cases where multiple recesses 21 are formed on the surface of the flange portion 17c of the slinger 17. That is, as shown in Figure 5(a), recesses 21 may be formed so as to fill each grid point when a grid-like pattern shown by dotted lines is superimposed on the surface of the flange portion 17c, or as shown in Figure 5(b), recesses 21 may be formed at equal intervals on concentric circles with the flange portion 17c, or as shown in Figure 5(c), recesses 21 may be formed at each grid point on the diagonal corner of the square in the grid-like pattern shown in Figure 5(a).

[0027] The recesses 21 are preferably denser when viewed from above, and may be formed by combining multiple types of recesses 21 with different diameters. For example, as shown in Figure 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, with the medium-diameter recess 21b placed in the center of the space formed by overlapping four large-diameter recesses 21a in a square shape, the small-diameter recesses 21c placed at equal intervals around the medium-diameter recess 21b, and the three minimum-diameter recesses 21d placed to fill the space formed by the large-diameter recesses 21a, medium-diameter recesses 21b, and small-diameter recesses 21c. Alternatively, as shown in Figure (b), a medium-diameter recess 21b may be placed in the center of the space formed by overlapping three large-diameter recesses 21a in an equilateral triangle shape, small-diameter recesses 21c may be placed at equal intervals around the medium-diameter recess 21b, and a minimum-diameter recess 21d may be placed to fill the space formed by the large-diameter recesses 21a and the small-diameter recesses 21c.

[0028] As shown in Figure 3, the presence of the recess 21 surrounded by the first convex portion 22 allows the lubricant to enter the interior 21A of the recess 21, improving the retention of the lubricant. Simultaneously, a pressure change occurs in the lubricant inside the recess 21A, causing cavitation. In the region where cavitation occurs, shear resistance decreases, resulting in a reduction in torque. Furthermore, cavitation also occurs on the slope 22a of the first convex portion 22 opposite to the recess 21, and this, combined with the cavitation inside the recess 21A, further reduces torque. This is the torque reduction mechanism of the present invention.

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

[0030] Furthermore, since the first protrusion 22 comes into contact with the seal lips 19a, 19b, and 19c, the higher the first protrusion 22 of the dimple 20, the greater the wear on the seal lips 19a, 19b, and 19c. Therefore, it is preferable to set the maximum height of the first protrusion 22 to 1 to 10 μm. If the maximum height of the first protrusion 22 exceeds 10 μm, it may cause severe wear on the seal lips 19a, 19b, and 19c, potentially reducing the sealing performance.

[0031] The above-mentioned height difference, its average value, and the maximum height of the first protrusion 22 are determined as follows.

[0032] Figure 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 area is the recess 21 of the dimple 20, and the protruding areas on both sides are the first convex portions 22 of the dimple 20. As shown in Figure 8, in a given dimple 20, if the height difference between the deepest part of the recess 21 and the top of the first convex portion 22 on the left side of the figure is a1, and the height difference between the deepest part of the recess 21 and the top of the first convex portion 22 on the right side of the figure is a2, then the height difference (depth) of the dimple 20 is defined as "(a1 + a2) / 2". The height differences of each individual dimple 20 for one scan are then determined, and their average value is calculated. The maximum value of the protruding portion is defined as the maximum height of the first convex portion.

[0033] Furthermore, the dimple 20 is preferably 10 to 80% of the area ratio of the opening area of ​​the first protrusion 22 to the sliding contact area. If the area ratio is less than 10%, the torque reduction may not be sufficient. On the other hand, if the area ratio exceeds 80%, the individual first protrusions 22 will overlap, which will increase the height of the protrusions and may cause wear on the seal lip, reducing the sealing performance.

[0034] The above area ratio is calculated by determining the distance d1 between the tops of the first protrusions 22 on both the left and right sides of a given dimple 20 in the cross-section shown in Figure 7, calculating the area equivalent to a circle, and using this as the opening area of ​​the dimple 20. Then, the opening area of ​​each individual dimple 20 for one scan is determined, their sum is calculated, and the ratio of this sum to the area of ​​a square with sides equal to the length of one scan is calculated as the area ratio.

[0035] Incidentally, as described above, the recesses 21 surrounded by the first protrusions 22 are individually independent, and the distribution of the recesses 21 may be such that, for example, as shown in Figure 5(a), when a grid-like pattern shown by dotted lines is superimposed on the surface of the flange portion 17c, the recesses 21 fill in each grid point; as shown in Figure 5(b), the recesses 21 may be formed at equal intervals on concentric circles with the flange portion 17c; or as shown in Figure 5(c), the recesses 21 may be formed at each grid point on the diagonal corners of the square in the grid-like pattern shown in Figure 5(a); or they may be formed in an irregular (random) distribution. Furthermore, the torque reduction effect of the present invention, which is caused by the combined cavitation inside the recesses 21A and the cavitation occurring on the slope 22a opposite to the recesses 21, is not particularly related to whether the arrangement of the recesses 21 (dimples) is grid-like, on concentric circles, or irregular (random). This point will be explained in detail in (1) to (4) below.

[0036] (1. Explanation regarding resistance generated in the sealing area) The lubrication state of the hub seal changes with vehicle speed (rotational speed), but fluid lubrication is present in most speed ranges, except at very low speeds. Therefore, the resistance generated at the seal is predominantly due to the shear resistance of the fluid lubricant.

[0037] (2. Explanation of the occurrence of cavitation and its effect on the resistance of the seal) By creating spatial expansions in the direction of the fluid lubrication film thickness, such as recesses or protrusions, on the sliding surface, a pressure drop in the fluid occurs in these expanded gaps. This causes gases dissolved in the lubricant to precipitate, generating cavitation (bubbles) on the sliding surface. Since this cavitation is a gas, its viscosity is extremely low compared to lubricants such as oil or grease. Therefore, the resistance in the region where cavitation occurs becomes almost zero, reducing the resistance of the sealing portion.

[0038] (3. Explanation of the effects of texture parameters) An investigation into the effects of shape parameters (dimple diameter, depth, and area ratio) on recesses created on sliding surfaces revealed that cavitation is hardly affected by the dimple diameter, but is strongly influenced by the depth and area ratio. This is because the dimple depth affects cavitation because it forms a spreading gap and influences pressure fluctuations, while the dimple area ratio affects the cavitation rate on the sliding surface, thus affecting the sliding resistance at the seal. On the other hand, it has been confirmed that the amount of cavitation generated is the same even if the dimple diameter is different, as long as the area ratio is the same, so the dimple diameter has no effect. This is because the pressure fluctuations change similarly as the diameter changes, so the cavitation rate per dimple remains the same.

[0039] (4. Conclusion) In summary, by creating a spatial spread in the film thickness direction of the fluid lubrication film, pressure fluctuations are generated, causing cavitation in the sliding part and thereby reducing the resistance of the seal. In other words, the important factor is the proportion of dimples present in the sliding part, and if that proportion is the same, it can be said that there is no particular difference whether the dimples are arranged in a grid pattern, on concentric circles, or irregularly (randomly). Furthermore, cavitation can also occur behind dimples with protrusions that surround the recesses (i.e., on the slope 22a opposite to the recess 21), so the amount of cavitation generated will be greater than in a simple recess without protrusions. However, the amount of cavitation generated behind the protrusions around the recesses similarly depends on the proportion of dimples present in the sliding part, so as mentioned earlier, it can be said that there is no particular difference whether the dimples are arranged in a grid pattern, on concentric circles, or irregularly (randomly).

[0040] Next, the method for forming the recess 21 and the first protrusion 22 described above will be explained. Possible methods for forming the recess 21 and the first protrusion 22 include laser processing, plastic deformation by transfer from a mold, cutting, low-flow shot blasting, etching, laser cladding, 3D printing, electrical discharge machining, and plating. 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 around the opening of the recess 21 and solidifies to form the first protrusion 22. When transferring from a mold, a mold with protrusions is used, and the portion of the slinger surface 17A into which the protrusions are pressed undergoes plastic deformation to form the recess 21, and the area around the opening of the recess 21 rises to form the first protrusion 22. Therefore, the deeper the recess 21 of the dimple 20, the higher the first protrusion 22 tends to be. Also, the larger the opening area, the higher the first protrusion 22 tends to be. Therefore, the height difference and aperture area can be adjusted to the above range by controlling the laser beam irradiation intensity and the mold pressing force.

[0041] Furthermore, as shown in Figure 10, although the slinger surface 17A (i.e., the surface on the mating member where the dimples 20 are formed) is metal, a soft coating 30 made of a material with a lower melting point than the slinger 17 (matting member), such as a resin, may be present. Examples of resins include phenolic resin and epoxy resin. When the dimples 20 are formed by laser processing, for example, the difference in melting points creates a double protrusion between the base metal and the soft coating 30, making cavitation more likely to occur. This protrusion made of the material forming the soft coating 30 is called the "second convex portion 32". The second convex portion 32 is formed outside the first convex portion 22, that is, on the surface side of the first convex portion 22 formed on the slinger 17 (matting member). In addition, since the soft coating 30 has low aggressiveness towards the seal lips 19a, 19b, and 19c, wear of the seal lips 19a, 19b, and 19c is suppressed, and the sealing effect lasts longer.

[0042] As shown in the figure, the second protrusion 32 formed by the soft coating 30 is preferably about the same height as the first protrusion 22 in order to maximize its effect. It is preferable to adjust the film thickness of the soft coating 30 and the laser processing conditions so that this height relationship is achieved.

[0043] Furthermore, as shown in Figure 11, depending on the material and processing method of the soft coating 30, the second protrusion 32 may not be formed. Even in that case, cavitation occurs in the void 33 formed between the soft coating 30 and the first protrusion 22, thus improving the low torque effect compared to the case without the soft coating 30.

[0044] Although the above example shows a metal slinger 17 as the mating component, the mating component is not limited to metal; it may also be made of non-metallic materials such as resin or ceramics.

[0045] While grease and lubricating oil can be used as lubricants, and there are no restrictions on their type or properties, the following is preferable when using grease, from the viewpoint of reducing torque, which is the objective of this invention.

[0046] The base oil of the grease is preferably low, and the kinematic viscosity can be 5.0 mm 2 / s or more and 460.0 mm 2 / s or less at 40°C, and 1.9 mm 2 / s or more and 56.0 mm 2 / s or less at 100°C. When the kinematic viscosity is not less than the above lower limit value, it has desired heat resistance, can suppress the volatilization of the base oil over time during use, and can maintain the sealing performance. On the other hand, when the kinematic viscosity is not more than the above upper limit value, it can suppress the increase in sliding friction resistance on the sliding surface and achieve low torque.

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

[0048] Furthermore, there are no restrictions on the type of base oil; all mineral oil-based, synthetic oil-based, or natural oil-based lubricants can be used. Specifically, examples of mineral oil-based lubricant base oils include those refined from mineral oil by appropriately combining vacuum distillation, degreasing, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay refining, and hydrorefining. Examples of synthetic oil-based lubricant base oils include hydrocarbon oils, aromatic oils, ester oils, ether oils, fluorinated 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, resulting in less viscosity reduction at high temperatures and a high ability to maintain an oil film. At low temperatures, the viscosity does not become too high, maintaining appropriate fluidity, thus minimizing the reduction in lubricity. This excellent low-temperature fluidity is an extremely effective feature when used as a base oil. Examples of natural oil-based lubricating base oils include fatty oils such as beef tallow, lard, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, and palm kernel oil, as well as their hydrogenated products.

[0049] However, if nitrile rubber, which is the most commonly used rubber, is used as the rubber seal 19, it is preferable to use mineral oil or synthetic hydrocarbon oil.

[0050] There are no restrictions on the thickeners used; examples include soap-based thickeners such as lithium soap and complex lithium 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 because they have excellent resistance to heat generation due to lubrication under high loads and are also less expensive than other thickeners. The amount of 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 configurations shown in Figures 1 and 2, but can also be configured as shown in Figure 12, for example. That is, the sealing member 16 has a rubber seal 19 that covers the inner ring 12 side of a core metal 18 with a substantially U-shaped cross-section that is fixed to the inner circumferential surface of the outer ring 11. The rubber seal 19 branches out and slides against the surface of the inner ring 12 as three seal lips 19a, 19b, and 19c. Note that in this figure, the free-state shapes of the seal lips 19a, 19b, and 19c are shown. Also, as with the sealing device shown in Figure 2, there are three seal lips (seal lips 19a, 19b, and 19c) in Figure 12, but there is no limit to the number of seal lips.

[0052] In this embodiment, the dimples 20 (not shown) are formed in the sliding contact area of ​​the raceway surface of the inner ring 12 with the seal lips 19a, 19b, and 19c to reduce torque. [Examples]

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

[0054] (Test 1: Examples 1-4 and Comparative Examples 1-5) A ball bearing unit, as shown in Figure 1, comprising a sealing member and a slinger, was fabricated and subjected to torque testing. The sealing member used was a rubber seal with an outer diameter of φ75 mm, an inner diameter of φ61 mm, and a single sealing lip. Urea grease was used as the lubricant.

[0055] The slinger is made of SUS430 stainless steel. In Examples 1-4 and Comparative Examples 2-4, 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 1-4, a first convex portion was formed around the recess, while in Comparative Examples 2-5, only the recess was formed without the first convex portion around the recess. The dimple depth and the maximum height of the first convex portion were the average values ​​obtained using a surface roughness meter. Comparative Example 1 had no dimples.

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

[0057] The ball bearing was then rotated at a rotational speed of 1000 rpm and the torque was measured. The results are shown in Table 1 and Figure 15. In Comparative Example 1, since there were no dimples, "dimple diameter (μm)", "dimple depth (μm)", "dimple pitch (μm)", and "maximum height of the first protrusion (μm)" are all indicated with "-" in Table 1. Also, in Comparative Examples 2 to 5, since no first protrusions were formed around the recesses, "maximum height of the first protrusion (μm)" is indicated with "-" in Table 1.

[0058] [Table 1]

[0059] Table 1 and Figure 15 show that, as in Examples 1 to 4, forming a first convex portion around the concave portion reduces torque compared to simply forming a concave portion alone.

[0060] (Test 2: Examples 5-7 and Comparative Example 6) A ball bearing unit comprising a sealing member and a slinger was fabricated as shown in Figure 1. The sealing member was a rubber seal with an outer diameter of φ75 mm, an inner diameter of φ61 mm, and three sealing lips. Urea grease was used as the lubricant.

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

[0062] The ball bearing was then rotated at a rotational speed of 1000 rpm, and the torque was measured. The results are shown in Table 2 and Figure 16. Note that in Comparative Example 6, since there were no dimples, "Dimple diameter (μm)" and "Dimple height difference (μm)" are shown as "-" in Table 2.

[0063] [Table 2]

[0064] Table 2 and Figure 16 show that, as in Examples 5 to 8, forming a first convex portion around the concave portion and reducing the dimple area ratio to 80% or less can reduce torque compared to simply forming a concave portion.

[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 these examples. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any way without departing from the spirit of the invention.

[0066] This application is based on Japanese Patent Application No. 2024-062729 filed on April 9, 2024, and its contents are incorporated herein by reference. [Explanation of symbols]

[0067] 10. Bearing unit with sealing device 11 Outer ring 12 Inner Ring 13 Balls (rolling elements) 14 Cage 15 Sealing device 16. Sealing member 17 Slinger 17a Cylindrical part (of the slinger) 17b (Slinger) curved section 17c (Slinger) flange section 17A Slinger surface 18 Mandrel 19 Rubber seal 19a, 19b, 19c Seal Lip 20 dimples 21 Recess 22 First convex part 30 Soft coating 33 Blanks

Claims

1. The sealing device is incorporated into a bearing unit with a sealing device, which holds a plurality of rolling elements rotatably between an outer ring and an inner ring, fills the unit with lubricant, and seals it with a sealing device, The sealing device is composed of a seal lip made of an elastic material and a mating member with which the seal lip slides, Multiple dimples are formed on the surface of the mating member, at least in the sliding contact area with the seal lip, each dimple being a recess that is lower than the surface of the mating member and a first protrusion that protrudes from the surface of the mating member and surrounds the recess. The recesses are formed independently of each other, The lubricant is grease, The kinematic viscosity of the base oil of the grease is 5.0 mm at 40°C. ２ / s or more 460.0mm ２ It is less than or equal to / s, and 1.9 mm at 100°C. ２ / s or more 56.0mm ２ A sealing device characterized by being / s.

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

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

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

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

6. The sealing device according to claim 5, characterized in that a second protrusion made of the soft coating-forming material is formed thereon.

7. A bearing unit with a sealing device, wherein multiple rolling elements are held movably between the outer ring and the inner ring, and the unit is filled with lubricant and sealed with a sealing device, A bearing unit with a sealing device, characterized in that the sealing device is the sealing device described in any one of claims 1 to 6.

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