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) provided with a sealing device interposed in a portion where it is necessary to seal between a fixed-side member and a rotating-side member, such as a bearing unit in a wheel suspension portion of an automobile. The present invention also relates to a sealing device incorporated in the bearing unit with the sealing device.

Background Art

[0002] Conventionally, a sealing device is known that is interposed between a fixed-side member and a rotating-side member, such as a bearing unit in a wheel suspension portion of a vehicle such as an automobile, seals grease and lubricating oil (hereinafter also collectively referred to as "lubricant"), and prevents the intrusion of water and dust. Also, today, various measures are being taken to improve the fuel efficiency of vehicles, and in the bearing unit as well, reduction of rotational torque is required.

[0003] For example, Patent Document 1 discloses a sealing device in which unevenness is provided on a sliding contact surface with a slinger in a seal lip fixed to a mandrel. Also, Patent Document 2 discloses a sealing device in which a separate member is provided on the surface of a slinger on the side where the seal lip slides, the sliding contact surface with the seal lip is formed by the separate member, and the sliding contact surface of the separate member with the seal lip is roughened.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[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 metal 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 protrusion that extends beyond 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]-[3].

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

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

[0012] [4] 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, A bearing unit with a sealing device, characterized in that the sealing device is the sealing device described in any one of [1] to [3]. [Effects 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 explanation of the drawing]

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

[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 an example of the present invention, and the present invention is not limited to this embodiment. In addition, 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 is no limitation on the bearing unit with a sealing device, and for example, the bearing unit 10 with a sealing device shown in FIG. 1 can be cited. As shown in the figure, an outer ring 11 which is a fixed ring, an inner ring 12 which is a rotating ring, a plurality of rolling elements 13 which are arranged to be freely rollable 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 arranged at an opening end of the annular gap are provided.

[0017] As shown in FIG. 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 arranged outside the opening end portion rather than the seal member 16 and fixed to the outer peripheral surface of the inner ring 12. Note that the sealing device 15 is composed of the seal member 16 and the slinger 17, and the slinger 17 corresponds to the "counter member" referred to in the present invention. And by the sliding contact between the seal member 16 and the slinger 17, the opening end portion of the annular gap is closed, preventing foreign matters such as dust from entering the bearing interior, and preventing the lubricant filled in the bearing interior from leaking to the outside of the bearing.

[0018] The seal member 16 is configured by reinforcing a rubber seal 19 (elastic material) formed in an annular shape with a substantially L-shaped cross section by a core metal 18 formed in an annular shape with a substantially L-shaped cross section. The tip portion of the rubber seal 19 branches to form a plurality of seal lips 19a, 19b, 19c, which are in sliding 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 this embodiment, multiple dimples 20 are formed in the sliding contact area of ​​the slinger 17 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 are composed of recesses 21 that are lower than the slinger surface 17A and protrusions 22 that protrude from the slinger surface 17A and surround the recesses 21.

[0021] 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 point, but a surface, i.e., it has a certain extent of coverage. 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.

[0022] 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 distribution. The protrusions 22 may surround the entire circumference of the recesses 21, or they may partially surround them.

[0023] The presence of a recess 21 surrounded by a convex portion 22 allows the lubricant to penetrate the interior 21a of the recess 21, improving its retention. Simultaneously, pressure changes occur within 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 inclined surface 22a of the convex portion 22 opposite to the recess 21, and this, combined with the cavitation inside the recess 21a, further reduces torque.

[0024] To more effectively achieve 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 convex part 22 to 25 μm or less, more preferably to 22 μm or less, and even more preferably to 20 μm or less. The above height difference and its average value can be determined as follows.

[0025] Figure 4 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 deeply recessed portion is the recess 21 of the dimple 20, and the protruding portions on both sides are the convex portions 22 of the dimple 20. As shown in Figure 5, in a given dimple 20, if the height difference between the deepest part of the recess 21 and the top of the 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 convex portion 22 on the right side of the figure is a2, then the height difference of the dimple 20 is defined as "(a1+a2) / 2". Then, the height differences of each individual dimple 20 for one scan are determined, and their average value is calculated.

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

[0027] The area ratio is calculated as follows: As shown in Figure 6, in the cross-section shown in Figure 4, the distance d1 between the tops of the protrusions 22 on both the left and right sides of a certain dimple 20 is determined, and the area equivalent to that circle is calculated to be 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.

[0028] However, since the protrusions 22 come into contact with the seal lips 19a, 19b, and 19c, the higher the protrusions 22 of the dimple 20, the greater the wear on the seal lips 19a, 19b, and 19c. The recesses 21 are formed by laser irradiation or by pressing a mold with protrusions onto the surface. 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, forming the protrusions 22. When a mold with protrusions is pressed onto the surface, 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 bulges, forming the protrusions 22. Therefore, the deeper the recess 21 of the dimple 20, the higher the protrusions 22 tend to be. Also, the larger the opening area, the higher the protrusions 22 tend to be. Thus, the height difference and opening area can be adjusted within the above range by adjusting the laser irradiation intensity and the pressing force of the mold.

[0029] Furthermore, although the slinger surface 17A is metal, a soft coating such as resin may be present. When forming dimples 20 by laser processing, for example, the difference in melting points of the soft coating creates a double protrusion between the base metal and the soft coating, making cavitation more likely to occur. In addition, since the soft coating is less aggressive to the seal lips 19a, 19b, and 19c, 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 1-4 and Comparative Example 1) 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 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.

[0032] The slinger was made of SUS430 stainless steel, and dimples were formed in Examples 1 to 4 as shown in Table 1. The opening diameter and height difference of the dimples were the average values ​​obtained using a surface roughness meter, and they were formed in a grid pattern at equal intervals with a pitch of 80 μm. Comparative Example 1 did not have dimples.

[0033] Then, the ball bearing was rotated at a speed of 1000 rpm, and the torque was measured.

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

[0035] [Table 1] [Explanation of Symbols]

[0036] 10. Bearing unit with sealing device 11 Outer ring 12 Inner Ring 13 Balls (rolling bodies) 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 Convex part

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 metal 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 composed of a recess that is lower than the surface of the mating member and a protrusion that extends beyond the surface of the mating member and surrounds the recess. A sealing device characterized in that the recesses are formed independently of each other.

2. The sealing device according to claim 1, characterized in that the average value of the height difference between the top of the 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 protrusion to the sliding contact area is 10 to 60%.

4. The sealing device according to claim 2, characterized in that the 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, 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 4.

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