Sealing device and bearing unit with sealing device

Abstract

To provide a bearing unit with a sealing device attaining both holding property of a lubricant and reduction in torque.SOLUTION: A sealing device 15 is composed of seal lips 19a, 19b, 19c comprising elastic materials, and a metal mating member (slinger 17) which is brought into slide contact with seal lips 19a, 19b, 19c, and is formed with a plurality of dimples 20 at least on a surface in a slide contact region with the seal lips 19a, 19b, 19c in the mating member (slinger 17), composed of recesses 21 further recessed than the surface of the mating member (slinger 17), and projections 22 further projecting than the surface of the mating member (slinger 17) and surrounding the recesses 21. A bearing unit 10 with a sealing device includes the sealing device 15.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[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, also collectively referred to as "lubricant") and prevent water and dust from entering. Furthermore, various measures are being taken today to improve the fuel efficiency of vehicles, and there is a demand for reducing the rotational torque in the bearing unit as well.

[0003] For example, Patent Document 1 discloses a sealing device in which unevenness is provided on the sliding surface of a seal lip fixed to a core bar that comes into sliding contact with a slinger. 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 comes into sliding contact, the separate member constitutes the sliding surface with the seal lip, and the sliding surface of the separate member with the seal lip is roughened. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-193835 A [Patent Document 2] JP 2010-107035 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the sealing device described in Patent Document 1, the unevenness is formed on the seal lip, not on the slinger, but the seal lip is made of a soft material and is easily worn, so there is a concern that the unevenness formed will disappear as it wears, making it impossible to maintain its effect. Also, in the sealing device described in Patent Document 2, the surface of a separate member on the slinger side, not the seal lip, is roughened, but the depth and size of the recesses in the roughened surface are not uniform, so the lubricant retention and sealing properties are insufficient, and further the flow behavior of the lubricant in each recess is different, and the torque is also not uniform, so there is a concern that the torque cannot be sufficiently reduced.

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

[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 is incorporated into a bearing unit with a sealing device, which holds a plurality of rolling elements between an outer ring and an inner ring so as to be able to roll, is filled with a lubricant, and is sealed by a sealing device, The sealing device is composed of a seal lip made of an elastic material and a metal mating member with which the seal lip is in sliding contact, 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, the dimples being composed of a recess that is recessed below the surface of the mating member and a protrusion that protrudes above the surface of the mating member and surrounds the recess.

[0009] Further, preferred embodiments of the present invention relating to a sealing device relate to the following [2] to [3].

[0010] [2] The sealing device according to [1], wherein the average difference in height between the top of the 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 convex portion to the sliding contact area is 10 to 60%.

[0011] The above object of the present invention can be achieved by the following configuration [4] relating to a bearing unit with a sealing device.

[0012] [4] A bearing unit with a sealed device, which holds a plurality of rolling elements between an outer ring and an inner ring so as to be able to roll, is filled with a lubricant, and is sealed with a sealing device, A bearing unit with a sealing device, wherein the sealing device is the sealing device according to any one of [1] to [3]. Effect of the Invention

[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. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view showing one embodiment of a bearing unit with a sealing device according to the present invention. [Diagram 2] FIG. 2 is an enlarged view showing a sealing device in the bearing unit with a sealing device shown in FIG. [Diagram 3] FIG. 3 is an enlarged cross-sectional view showing a dimple formed in a sliding contact area of ​​a slinger in a sealing device according to the present invention. [Figure 4] FIG. 4 shows an example of a cross section obtained by linearly scanning the sliding contact area of ​​the slinger using a surface roughness meter. [Diagram 5] FIG. 5 is a schematic diagram for explaining the height difference of the dimples. [Figure 6] FIG. 6 is a schematic diagram for explaining the opening diameter of the dimple. [Figure 7] FIG. 7 is a graph showing the results of the examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A sealing device and a bearing unit with a sealing device according to an embodiment of the present invention will be described below. Note that this embodiment shows one example of the present invention, and the present invention is not limited to this embodiment. In addition, 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 sealing device is not limited, and an example of the bearing unit with a sealing device 10 shown in Fig. 1 can be given. As shown in the figure, the bearing unit 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 arranged to roll freely in an annular gap defined by the outer ring 11 and the inner ring 12 and 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 includes 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 outside the open end of 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 inside of the bearing and preventing the lubricant filled inside the bearing from leaking out of the bearing.

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

[0019] 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 brim-shaped flange portion 17c that is connected to the axial end of the cylindrical portion 17a via a curved portion 17b and is formed so as to extend radially outward.

[0020] In this embodiment, a plurality of dimples 20 are formed in the sliding contact area between the slinger 17 and the seal 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 which slide therewith), and as shown in the enlarged cross-sectional view of Figure 3, the dimple 20 is composed of a recessed portion 21 recessed below the slinger surface 17A, and a protruding portion 22 which protrudes above the slinger surface 17A and surrounds the recessed portion 21.

[0021] 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 elastically deforms and wears, so the sliding contact area of ​​the seal member 16 with the slinger 17 is not a point but a surface, i.e., it has a certain degree of spread. Therefore, the sliding contact area is the range where the sliding contact between the seal member 16 and the slinger 17 is expected.

[0022] The recesses 21 are independent from one another as shown in the figure, and may be formed in a lattice shape at approximately equal intervals when viewed from above, or may be formed in an irregular distribution. The protrusions 22 may surround the entire circumference of the recesses 21, or may surround them partially.

[0023] Due to the presence of the recess 21 surrounded by the protrusion 22, the lubricant penetrates into the inside 21a of the recess 21, improving the retention of the lubricant, and a pressure change occurs in the lubricant in the inside 21a of the recess 21, causing cavitation. Then, in the area where cavitation occurs, the shear resistance decreases, resulting in a reduction in torque. Cavitation also occurs on the slope 22a of the protrusion 22 on the opposite side to the recess 21, and together with the cavitation in the inside 21a of the recess 21, the torque is further reduced.

[0024] In order to more effectively exert such a torque reducing effect, the average value of the height difference between the deepest part of the recessed part 21 and the top of the protruding part 22 is preferably set to 25 μm or less, more preferably set to 22 μm or less, and further preferably set to 20 μm or less. The height difference and its average value are determined as follows.

[0025] FIG. 4 is 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 the left and right sides are the protrusions 22 of the dimple 20. As shown in FIG. 5, in a certain dimple 20, the height difference between the deepest part of the recess 21 and the top of the protrusion 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 protrusion 22 on the right side of the figure is a2. The height difference of the dimple 20 is then defined as "(a1+a2) / 2". The height differences of the individual dimples 20 for one scan are then obtained, and their average value is calculated.

[0026] Furthermore, the dimples 20 preferably have an area ratio of the opening area of ​​the protrusions 22 to the sliding contact area of ​​10 to 60%. If the area ratio is less than 10%, there is a risk that torque reduction is not sufficient. On the other hand, if the area ratio exceeds 60%, the opening area of ​​each protrusion 22 becomes large, and the height increases accordingly, which may cause wear of the seal lips 19a, 19b, and 19c and reduce sealing performance.

[0027] As shown in Fig. 6, the above area ratio is calculated by finding the distance d1 between the apexes of the convex portions 22 on the left and right sides of a certain dimple 20 in the cross section shown in Fig. 4, and calculating its equivalent circular area to be the opening area of ​​the dimple 20. The opening areas of each of the dimples 20 in 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 one side is the length of one scan.

[0028] However, since the protrusion 22 contacts the seal lips 19a, 19b, and 19c, the higher the protrusion 22 of the dimple 20, the greater the wear of the seal lips 19a, 19b, and 19c. The recess 21 is formed by laser irradiation or by pressing a mold having a protrusion and transferring it. In laser irradiation, the part of the slinger surface 17A irradiated with the laser light melts to form the recess 21, and the molten material dissolves and solidifies around the opening of the recess 21 to form the protrusion 22. In addition, when a mold having a protrusion is pressed, the part of the slinger surface 17A into which the protrusion is pressed plastically deforms to form the recess 21, and the opening periphery of the recess 21 rises to form the protrusion 22. Therefore, the deeper the recess 21 of the dimple 20, the higher the protrusion 22 is likely to be. Also, the larger the opening area, the higher the protrusion 22 is likely to be. Therefore, the height difference and the opening area can be adjusted to the above range by the irradiation intensity of the laser light and the pressing force of the mold.

[0029] Although the slinger surface 17A is made of metal, a soft coating such as resin may be present. When forming the dimples 20 by laser processing, for example, the soft coating creates double protrusions of the base metal and the soft coating due to the difference in melting points, making cavitation more likely to occur. In addition, the soft coating is less aggressive to the seal lips 19a, 19b, and 19c, so wear of the seal lips 19a, 19b, and 19c is suppressed and the sealing effect lasts longer. EXAMPLES

[0030] The effects of the present invention were verified by the following examples.

[0031] (Examples 1 to 4 and Comparative Example 1) 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 φ75 mm, an inner diameter of φ61 mm, and three seal lips. Urea grease was used as the lubricant.

[0032] The slinger was made of SUS430, and dimples as shown in Table 1 were formed in Examples 1 to 4. The opening diameter and height difference of the dimples were average values ​​determined by a surface roughness meter, and the dimples were formed in a lattice pattern at equal intervals with a pitch of 80 μm. Comparative Example 1 had no dimples.

[0033] The ball bearing was then rotated at a rotation speed of 1000 rpm and the torque was measured.

[0034] The results are shown in Table 1 and FIG. 7. It can be seen that in Examples 1 to 4 in which dimples according to the present invention were formed, the torque was significantly reduced compared to Comparative Example 1.

[0035] [Table 1] [Explanation of symbols]

[0036] 10 Bearing unit with sealed device 11 Outer ring 12 Inner Circle 13 Ball (rolling element) 14 Cage 15 Sealing device 16 Sealing material 17 Slinger 17a (Slinger) cylindrical part 17b (Slinger) curved part 17c (Slinger) flange 17A Slinger Surface 18 Core wire 19 Rubber seal 19a, 19b, 19c Seal lip 20 Dimples 21 Recess 22 Convex

Claims

1. The sealing device is incorporated into a bearing unit with a sealing device, the bearing unit having a plurality of rolling elements between an outer ring and an inner ring so as to be capable of rolling, the bearing unit being filled with a lubricant and sealed by a sealing device, The sealing device is composed of a seal lip made of an elastic material and a metal mating member with which the seal lip is in sliding contact, 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, the dimples being composed of a recess that is recessed below the surface of the mating member and a protrusion that protrudes above the surface of the mating member and surrounds the recess.

2. 2. The sealing device according to claim 1, wherein an average difference in height between the top of the protrusion and the deepest part of the recess is 25 μm or less.

3. 2. The sealing device according to claim 1, wherein an area ratio of the opening of the protrusion to the sliding contact area is 10 to 60%.

4. 3. The sealing device according to claim 2, wherein an area ratio of the opening of the protrusion to the sliding contact area is 10 to 60%.

5. A bearing unit with a sealing device, which holds a plurality of rolling elements between an outer ring and an inner ring so as to be able to roll, is filled with a lubricant, and is sealed by a sealing device, A bearing unit with a sealing device, wherein the sealing device is the sealing device according to any one of claims 1 to 4.

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