Seal device and hub unit bearing

Abstract

To provide a seal device including a seal lip capable of achieving both sealability and a low torque, and to provide a hub unit bearing including the seal device.SOLUTION: A seal device 5 includes seal lips 27-29 which extend in a direction inclined with respect to a seal slide contact surface 14 of a mating member, and in which tip parts come into a slide contact with the seal slide contact part 14 across the whole circumference. The tip parts of the seal lips 27-29 have a plurality of thick wall parts 30 and thin wall parts 31 arranged side by side alternately in a circumferential direction. The thin wall part 31 exists so as to connect end parts closer to the seal slide contact surface 14 regarding a thickness direction of the seal lips 27-29 out of a pair of thick wall parts 30 adjacent to each other. In a free state of the seal lips 27-29, the thin wall part 31 curves so that a circumferential direction intermediate part protrudes further to the far side from the seal slide contact surface 14, regarding the thickness direction of the seal lips 27-29 than end parts on both sides in the circumferential direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a seal device provided with a seal lip that slidably contacts a seal sliding contact surface at its tip, and a hub unit bearing for rotatably supporting an automobile wheel with respect to a suspension device.

Background Art

[0002] A hub unit bearing is used in an environment where mud and water splash directly. Therefore, the hub unit bearing is provided with a seal device to prevent foreign substances such as mud and water from entering the space where the rolling elements are installed, and to prevent the grease enclosed in the space from leaking to the outside (see, for example, Japanese Patent Application Laid-Open No. 2005-155882). The seal device includes a seal material having a seal lip, and the tip of the seal lip is slidably contacted with a seal sliding contact surface provided on a mating member such as an outer ring or a slinger.

[0003] By the way, in recent years, in order to improve the fuel efficiency and high efficiency of automobiles, the demand for reducing the torque of hub unit bearings has been increasing. As a method for reducing the torque of a hub unit bearing, it is conceivable to reduce the frictional force between the tip of the seal lip and the seal sliding contact surface of the mating member.

[0004] Japanese Patent Application Laid-Open No. 2018-119648 describes a seal device in which protrusions are provided at a plurality of circumferential positions at the tip of a seal lip in order to reduce the frictional force between the tip of the seal lip and the seal sliding contact surface of a mating member. In this seal device, a wedge-shaped gap is formed between the tip of the seal lip and the seal sliding contact surface of the mating member, specifically, between adjacent protrusions in the circumferential direction. When the mating member rotates relative to the seal material, lubricating oil is drawn into the wedge-shaped gap, and the formation of an oil film is promoted by the wedge effect, and the plurality of protrusions slidably contact the seal sliding contact surface of the mating member through a sufficient oil film. For this reason, the frictional force between the tip of the seal lip and the seal sliding contact surface of the mating member is reduced.

[0005] Furthermore, in the sealing device described in Japanese Patent Publication No. 2018-119648, the rigidity of the circumferential portion of the tip of the seal lip where there are no protrusions is increased compared to the circumferential portion where there are protrusions. This prevents the portion of the tip of the seal lip located between adjacent protrusions in the circumferential direction from approaching the sealing sliding surface of the mating member, thus reducing the wedge-shaped gap and preventing the formation of an oil film due to the wedge effect from being impaired. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2005-155882 [Patent Document 2] Japanese Patent Publication No. 2018-119648 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The sealing device described in Japanese Patent Publication No. 2018-119648 is effective in applications where the lubrication in the space to be sealed is oil-lubricated and a small amount of oil leakage is acceptable, such as in transmissions.

[0008] However, in hub unit bearings, since the lubrication within the space to be sealed by the sealing device is grease lubrication, the effect of lubricating oil being drawn into the wedge-shaped gap does not occur. Furthermore, since the foreign matter attempting to enter the space from the outside is muddy water, the intrusion of such foreign matter is unacceptable. Therefore, the sealing device described in Japanese Patent Application Publication No. 2018-119648 cannot be said to be effective for use in hub unit bearings.

[0009] The present invention aims to provide a sealing device equipped with a seal lip that can achieve both airtightness and low torque, and a hub unit bearing equipped with the sealing device. [Means for solving the problem]

[0010] A sealing device according to one aspect of the present invention includes a sealing lip that extends in a direction inclined with respect to the sealing sliding surface of a mating member, and whose tip is in sliding contact with the sealing sliding surface over its entire circumference. The tip of the sealing lip has a plurality of thick and thin portions arranged alternately in the circumferential direction. The thin portions are located such that they connect the ends of a pair of adjacent thick portions in the circumferential direction that are closer to the sealing sliding surface with respect to the thickness direction of the sealing lip. In the free state of the sealing lip, the thin portions are curved such that their circumferential middle portions protrude further from the sealing sliding surface with respect to the thickness direction of the sealing lip than the ends on both sides in the circumferential direction.

[0011] In one embodiment of the present invention, the thickened portion has a shape in which the circumferential width decreases towards the tip.

[0012] A hub unit bearing according to one aspect of the present invention comprises an outer member having double rows of outer ring raceways on its inner circumferential surface, an inner member having double rows of inner ring raceways on its outer circumferential surface, a plurality of rolling elements rotatably arranged between the double rows of outer ring raceways and the double rows of inner ring raceways, and a sealing device that closes the axial end opening of the internal space existing between the inner circumferential surface of the outer member and the outer circumferential surface of the inner member, wherein the sealing device is configured as a sealing device according to one aspect of the present invention. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a sealing device equipped with a seal lip that can achieve both sealing performance and low torque, and a hub unit bearing equipped with the sealing device. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a cross-sectional view of a hub unit bearing according to a first example of an embodiment of the present invention. [Figure 2] Figure 2 is an enlarged view of section A in Figure 1. [Figure 3] Figure 3 is an enlarged view of section B in Figure 1. [Figure 4]FIG. 4 is a perspective view of a circumferential-directional part of the tip of a seal lip constituting the seal device of the first example, as viewed from the radially outer side. [Figure 5] FIG. 5(a) is a view of a circumferential-directional part of the tip of a seal lip constituting the seal device of the first example, as viewed from one side (radially outer side) in the thickness direction of the seal lip; FIG. 5(b) is a view of FIG. 5(a) as viewed from below; and FIG. 5(c) is a cross-sectional view taken along line C-C of FIG. 5(a). [Figure 6] FIG. 6 is a partial cross-sectional view of another example (first example) of a seal device to which the present invention is applicable. [Figure 7] FIG. 7 is a partial cross-sectional view of another example (second example) of a seal device to which the present invention is applicable. [Figure 8] FIG. 8 is a partial cross-sectional view of another example (third example) of a seal device to which the present invention is applicable. [Figure 9] FIG. 9 is a partial cross-sectional view of another example (fourth example) of a seal device to which the present invention is applicable.

MODE FOR CARRYING OUT THE INVENTION

[0015] [First Example] The first example of the embodiment of the present invention will be described with reference to FIGS. 1 to 5.

[0016] The hub unit bearing 1 in this example includes an outer ring 2 corresponding to an outer member, a hub 3 corresponding to an inner member, a plurality of rolling elements 4, and seal rings 5 and combined seal rings 6, each of which is a seal device.

[0017] The hub unit bearing 1 in this example is of an inner-ring rotation type in which the inner member rotates during use. However, the present invention can also be applied to a hub unit bearing of an outer-ring rotation type in which the outer member rotates during use.

[0018] The hub unit bearing 1 in this example has a structure for a driving wheel. However, the present invention can also be applied to a hub unit bearing having a structure for a driven wheel.

[0019] In this example, the axial inner side of the hub unit bearing 1 corresponds to the center side in the width direction of the vehicle when assembled to the vehicle, which is the right side in Figure 1, and the axial outer side corresponds to the outer side in the width direction of the vehicle when assembled to the vehicle, which is the left side in Figure 1.

[0020] The outer ring 2 is made of a hard metal such as medium carbon steel and has double-row outer ring raceways 7a and 7b and a stationary flange 8. The double-row outer ring raceways 7a and 7b are provided on the inner circumferential surface of the outer ring 2. The stationary flange 8 is used to connect and fix the outer ring 2 to the knuckle of the suspension device and protrudes radially outward from the axial middle portion of the outer ring 2.

[0021] The hub 3 is positioned coaxially with the outer ring 2, radially inward of the outer ring 2, and has double-row inner ring raceways 9a and 9b, and a rotating flange 10. The double-row inner ring raceways 9a and 9b are provided on the outer circumferential surface of the hub 3, on the portion facing the double-row outer ring raceways 7a and 7b. The rotating flange 10 is used to connect and fix the wheel and braking rotating member to the hub 3, and protrudes radially outward from the axially outer portion of the hub 3. The rotating flange 10 has an axial sliding contact surface 11 on the radially inner portion of its axially inner surface.

[0022] The hub 3 has a concave curved surface 12 with an arc-shaped cross-section on the portion of its outer circumferential surface adjacent to the axially inward side of the axial sliding surface 11, and a cylindrical radial sliding surface 13 on the portion of its outer circumferential surface adjacent to the axially inward side of the concave curved surface 12. In this example, the axial sliding surface 11, the concave curved surface 12, and the radial sliding surface 13 constitute a sealing sliding surface 14 that brings the sealing lip of the sealing ring 5, i.e., the axial lip 27 and the radial lips 28 and 29, into sliding contact.

[0023] In this example, the hub unit bearing 1 is for a drive wheel, and therefore the hub 3 has a splined hole 15 that penetrates axially through its center. The tip of the drive shaft, which is rotationally driven directly or via the transmission by a drive source such as an engine or electric motor, is spline-engaged into the splined hole 15. When the vehicle is running, the hub 3 is rotationally driven by the drive shaft, thereby rotating the wheel and braking rotating body that are coupled and fixed to the rotation flange 10 of the hub 3.

[0024] In this example, the hub 3 is formed by combining the inner ring 16 and the hub ring 17.

[0025] The inner ring 16 is made of a hard metal such as bearing steel. The inner ring 16 has an inner ring raceway 9a on its outer circumferential surface that is axially inward.

[0026] The hub wheel 17 is made of a hard metal such as medium carbon steel. The hub wheel 17 has an inner ring raceway 9b that is axially outward in the axial middle part of its outer circumference, a rotating flange 10 that protrudes radially outward from the axially outward part, a spline hole 15 that penetrates axially in the center, and a fitting cylinder portion 18 into which the inner ring 16 is fitted on the axially inward part. The hub wheel 17 further has a crimping portion 19 that bends radially outward from the axially inward end of the fitting cylinder portion 18 and presses against the axially inward end face of the inner ring 16. Alternatively, instead of the crimping portion, the axially inward end face of the inner ring can be pressed against by an outer ring for a constant velocity joint fixed to the axially inward end of the drive shaft.

[0027] Multiple rolling elements 4 are arranged to roll freely between the double-row outer ring raceways 7a, 7b and the double-row inner ring raceways 9a, 9b, each held by a cage 20. In this example, balls are used as rolling elements 4, but tapered rollers can be used instead of balls. In this example, the pitch circle diameters of the rolling elements 4 in the axial inner row and the pitch circle diameters of the rolling elements 4 in the axial outer row are the same, but the present invention can also be applied to hub unit bearings of different diameter PCD type in which the pitch circle diameters of the rolling elements in the axial inner row and the pitch circle diameters of the rolling elements in the axial outer row are different.

[0028] Between the inner surface of the outer ring 2 and the outer surface of the hub 3, there is a roughly cylindrical internal space 21 in which the rolling elements 4 are arranged, and grease, which is a lubricant, is sealed in the internal space 21.

[0029] The seal ring 5 closes the axially outer end opening of the internal space 21. This prevents foreign matter such as muddy water from entering the internal space 21 from the external space through the opening, and prevents grease from leaking from the internal space 21 to the external space.

[0030] In this example, the seal ring 5 comprises a core metal 22 and a sealing material 23, as shown in Figure 2.

[0031] The core metal 22 is formed into an annular shape by bending a metal plate such as a mild steel plate. The core metal 22 has a fitting cylinder portion 24 that is fitted and fixed to the axially outer end of the outer ring 2 by interference fit, and a support plate portion 25 that is bent radially inward from the axially outer end of the fitting cylinder portion 24.

[0032] The sealing material 23 is made of rubber and is fixed to the support plate portion 25 of the core metal 22 by vulcanization bonding. The sealing material 23 includes a base portion 26 and sealing lips R (27, 28, 29) whose tips slide in contact with the sealing sliding surface of the mating member. In this example, the sealing lips R include an axial lip 27, a radial lip 28, and a radial lip 29. In Figure 2, the axial lip 27, radial lip 28, and radial lip 29 are shown in their free state.

[0033] The base portion 26 covers the surface of the support plate portion 25, specifically the axial outer surface, the inner circumferential surface, and the radially inner end of the axial inner surface of the support plate portion 25.

[0034] The axial lip 27 extends in a direction inclined with respect to the axial sliding surface 11, specifically extending from the portion of the base 26 that covers the radially intermediate portion of the axially outer surface of the support plate portion 25 in a direction toward both the axially and radially outward direction. The tip of the axial lip 27 slides against the axial sliding surface 11 over its entire circumference. In this example, a clamping allowance is set for the sliding contact portion of the tip of the axial lip 27 with respect to the axial sliding surface 11. This clamping allowance can be set to any size, but for example, it can be set to 0.5 mm to 1.1 mm.

[0035] Radial Lip 28 is a concave curved surface 12 It extends in a direction inclined toward the surface, specifically extending from the portion of the base 26 that covers the radially inner end of the support plate portion 25 in the axially outward and radially inward direction. The tip of the radial lip 28 slides against the concave curved surface 12 over its entire circumference. In this example, a tightening allowance is set for the sliding contact portion of the tip of the radial lip 28 with the concave curved surface 12. This tightening allowance can be set to any size, but for example, it can be set to a radius value of 0.2 mm to 0.8 mm.

[0036] The radial lip 29 extends in a direction inclined with respect to the radial sliding surface 13, specifically extending from the portion of the base 26 that covers the radially inner end of the support plate portion 25 in a direction toward both the axial and radially inward direction. The tip of the radial lip 29 slides against the radial sliding surface 13 over its entire circumference. That is, the radial lip 29 extends toward the internal space 21 as it approaches the tip, and is a grease lip specifically designed to prevent grease leakage from the internal space 21. A tightening allowance is set for the sliding contact portion of the tip of the radial lip 29 with respect to the radial sliding surface 13. This tightening allowance can be set to any size, but for example, it can be set to a radius value of 0.2 mm or less.

[0037] In this example, the tip of the seal lip R (axial lip 27, radial lip 28, and radial lip 29) has multiple (N) thick-walled portions 30 and thin-walled portions 31 arranged alternately in the circumferential direction, as shown in Figures 4 and 5(a) to 5(c). Figure 4 is a perspective view of a portion of the circumferential tip of the seal lip R viewed from the radially outside. Figure 5(a) is a view of the circumferential portion of the tip from one side in the thickness direction (radially outside), and the left-right direction in Figure 5 is the circumferential direction. Figure 5(b) is a view of the circumferential portion of the tip from below (tip side) of Figure 5(a). Figure 5(c) is a cross-sectional view of Figure 5(a). Figures 4 and 5(a) to 5(c) show the seal lip R in a free state.

[0038] In this example, the thickened portion 30 has a shape in which its circumferential width decreases towards the tip side (the lower side in Figure 5(a)). That is, as viewed from the thickness direction of the seal lip R, the thickened portion 30 has a trapezoidal shape in which the circumferential width at the tip side is smaller than the circumferential width at the base end side (the upper side in Figure 5(a)), as shown in Figure 5(a). In this example, by adopting such a shape, mud, water, grease, etc. that hit the circumferential side surface of the thickened portion 30 when the vehicle is in motion can be moved along the circumferential side surface toward the tip side of the thickened portion 30. This point will be discussed further later. Note that when implementing the present invention, the circumferential width of the thickened portion can also be kept constant.

[0039] The thin-walled portion 31 is located between a pair of adjacent thick-walled portions 30 in the circumferential direction, and connects the ends of the portions closest to the seal sliding surface 14 (axial sliding surface 11, concave curved surface 12, and radial sliding surface 13) (the lower side in Figures 4 and 5(b), and the left side in Figure 5(c)) with respect to the thickness direction of the seal lip R (the vertical direction in Figures 4 and 5(b), and the left-right direction in Figure 5(c)). In this example, the thin-walled portion 31 has a shape in which the circumferential width increases towards the tip side when viewed from the thickness direction of the seal lip R, as shown in Figure 5(a).

[0040] In the free state of the seal lip R, the thin-walled portion 31 is curved such that its circumferential middle portion protrudes further from the seal sliding surface 14 in the thickness direction of the seal lip R than the ends on both sides in the circumferential direction (upper side in Figures 4 and 5(b), and right side in Figure 5(c)). In this example, the amount of protrusion increases towards the tip side (lower side in Figure 5(c)), as shown in Figure 5(c).

[0041] The number (N) of the thick-walled portion 30 and the thin-walled portion 31 is not particularly limited, but can be 30 or more and 100 or less, preferably 40 or more and 60 or less.

[0042] The thickness T1 of the thick-walled portion 30 is not particularly limited, but can be 0.5 mm or more and 1.0 mm or less, and preferably 0.6 mm or more and 0.8 mm or less. Also, the ratio of the thickness T2 of the thin-walled portion 31 to the thickness T1 of the thick-walled portion 30 is not particularly limited, but can be 10% or more and 50% or less, and preferably 15% or more and 25% or less.

[0043] In this example, in the free state of the seal lip R, the total circumference of the tip of the seal lip R, that is, the sum of the circumferential lengths L1 of the tips of all (N) thick-walled portions 30 and L2 of the circumferential lengths L2 of the tips of all (N) thin-walled portions 31 (N × (L1 + L2)), is slightly smaller than the total circumference of the portion of the seal sliding surface 14 that the tip of the seal lip R slides against.

[0044] In other words, in this example, with the tip of the seal lip R in sliding contact with the seal sliding surface 14, at least the thin-walled portion 31 of the thick-walled portion 30 is elastically deformed so that it is stretched in the circumferential direction. Then, the amount by which the circumferential middle portion of the thin-walled portion 31 protrudes on the side further away from the seal sliding surface 14 in the thickness direction of the seal lip R becomes zero compared to the ends on both sides in the circumferential direction, and the tip of the seal lip R slides against the seal sliding surface 14 with an overlap over its entire circumference.

[0045] The combination seal ring 6 is fitted between the inner circumferential surface of the axially inner end of the outer ring 2 and the outer circumferential surface of the axially inner end of the hub 3, sealing the axially inner end opening of the internal space 21. This prevents foreign matter such as muddy water from entering the internal space 21 from the external space through the opening, and prevents grease from leaking from the internal space 21 to the external space.

[0046] In this example, the combination seal ring 6 comprises a slinger 32 and a seal ring 33, as shown in Figure 3.

[0047] The slinger 32 is constructed in an annular shape by bending a corrosion-resistant metal plate, such as a stainless steel plate. The slinger 32 has a slinger cylindrical portion 34 that is fitted and fixed to the outer circumference of the axially inner end of the hub 3 by interference fit, and an annular slinger side plate portion 35 that is bent radially outward from the axially inner end of the slinger cylindrical portion 34.

[0048] The slinger side plate portion 35 has an axial sliding contact surface 36 on its axially outer surface. The slinger cylindrical portion 34 has a cylindrical radial sliding contact surface 37 on its outer surface. In this example, the axial sliding contact surface 36 and the radial sliding contact surface 37 constitute a sealing sliding contact surface 38 that slides against the sealing lip of the combined sealing ring 6, i.e., the axial lip 44 and the radial lips 45, 46.

[0049] The seal ring 33 comprises a core metal 39 and a sealing material 40.

[0050] The core metal 39 is formed into an annular shape by bending a metal plate such as a mild steel plate. The core metal 39 has a core metal cylindrical portion 41 that is fitted and fixed to the inner circumferential surface of the axially inner end of the outer ring 2 by interference fit, and a roughly annular core metal side plate portion 42 that is bent radially inward from the axially outer end of the core metal cylindrical portion 41.

[0051] The sealing material 40 is made of rubber and is fixed to the core metal 39 by vulcanization adhesion. The sealing material 40 comprises a base portion 43 and sealing lips R (44, 45, 46) whose tips slide in contact with the sealing sliding surface of the mating member. In this example, the sealing lips R include an axial lip 44, a radial lip 45, and a radial lip 46. In Figure 3, the axial lip 44, radial lip 45, and radial lip 46 are shown in their free state.

[0052] The base portion 43 covers the surface of the core metal 39, specifically the axially inner end, axially inner end face, and inner circumferential surface of the outer circumferential surface of the core metal cylindrical portion 41, and the radially inner end of the axially inner surface, inner circumferential surface, and axially outer surface of the core metal side plate portion 42.

[0053] The axial lip 44 extends in a direction inclined with respect to the axial sliding contact surface 36, specifically extending from the portion of the base 43 that covers the radially intermediate portion of the axially inner surface of the core metal side plate portion 42 in a direction toward both the axially inward and radially outward direction. The tip of the axial lip 44 is in sliding contact with the axial sliding contact surface 36 over its entire circumference. A tightening allowance is set for the sliding contact portion of the tip of the axial lip 44 with respect to the axial sliding contact surface 36. This tightening allowance can be set to any size, but for example, it can be set to 0.5 mm to 1.1 mm.

[0054] The radial lip 45 extends in a direction inclined with respect to the radial sliding surface 37, specifically extending from the portion of the base 43 that covers the radially inner end of the core metal side plate portion 42 in a direction toward both the axial and radially inward direction. The tip of the radial lip 45 slides against the axially inner portion of the radial sliding surface 37 over its entire circumference. A clamping allowance is set at the sliding contact portion of the tip of the radial lip 45 with respect to the radial sliding surface 37. This clamping allowance can be set to any size, but for example, it can be set to a radius value of 0.2 mm to 0.8 mm.

[0055] The radial lip 46 extends in a direction inclined with respect to the radial sliding surface 37, specifically extending from the portion of the base 43 that covers the radially inner end of the core metal side plate portion 42 in a direction toward both the axially outer and radially inner directions. The tip of the radial lip 46 slides against the axially outer portion of the radial sliding surface 37 over its entire circumference. In other words, the radial lip 46 extends toward the internal space 21 as it approaches the tip, and is a grease lip specifically designed to prevent grease leakage from the internal space 21. A tightening allowance is set at the sliding contact portion of the tip of the radial lip 46 with respect to the radial sliding surface 37. This tightening allowance can be set to any size, but for example, it can be set to a radius value of 0.2 mm or less.

[0056] In this example, the combination seal ring 6, like the seal ring 5, has multiple thick-walled portions 30 and thin-walled portions 31 arranged alternately in the circumferential direction at the tips of the seal lips R (axial lip 44, radial lip 45, and radial lip 46), as shown in Figures 4 and 5(a) to 5(c). The overlap and sliding contact characteristics of the tips (thick-walled portions 30 and thin-walled portions 31) of the seal lips R (axial lip 44, radial lip 45, and radial lip 46) with respect to the seal sliding surface 38 (axial sliding surface 36, radial sliding surface 37) are also the same as those of the seal ring 5.

[0057] In the hub unit bearing 1 of this example, the tips of the seal lips R ((axial lip 27, radial lip 28, and radial lip 29), (axial lip 44, radial lip 45, and radial lip 46)) of the seal ring 5 and the combined seal ring 6 slide against the seal sliding surfaces 14 and 38 over their entire circumference. In other words, in the structure of this example, unlike the conventional structure described in Japanese Patent Application Publication No. 2018-119648, a wedge-shaped gap is not formed between the tips of the seal lips R and the seal sliding surfaces 14 and 38. Therefore, it is easier to ensure sealing performance by the seal lips R.

[0058] In this example, of the multiple thick-walled portions 30 and thin-walled portions 31 that constitute the tip of the seal lip R, the thin-walled portions 31 have a smaller wall thickness than the thick-walled portions 30, and in a free state, the circumferential middle portion is curved so that it protrudes further away from the seal sliding surfaces 14 and 38 in the thickness direction of the seal lip R than the ends on both sides in the circumferential direction. Therefore, when the tip of the seal lip R is stretched in the circumferential direction and is in sliding contact with the seal sliding surfaces 14 and 38 over its entire circumference, the sliding pressure, i.e., the frictional force, of the tip of the seal lip R against the seal sliding surfaces 14 and 38 is smaller at the circumferential position where the thin-walled portion 31 is located than at the circumferential position where the thick-walled portion 30 is located. Consequently, the frictional force of the tip of the seal lip R against the seal sliding surfaces 14 and 38 can be reduced. In other words, the torque of both the seal ring 5 and the combined seal ring 6 can be reduced.

[0059] In this example, the thickened portion 30 has a shape in which its circumferential width decreases towards the tip. Therefore, with respect to the seal lip R ((axial lip 27, radial lip 28), (axial lip 44, radial lip 45)) that extends toward the external space towards the tip, when foreign matter such as muddy water that adheres to the seal sliding surfaces 14 and 38 and moves around with the vehicle during driving strikes the circumferential side surface of the thickened portion 30, the foreign matter can be moved along the circumferential side surface toward the tip of the thickened portion 30, that is, moved toward returning to the external space. In contrast, with respect to the seal lip R (radial lip 29, radial lip 46) that extends toward the internal space 21 towards the internal space 21, when the vehicle is driving, the grease present in the internal space 21 can be recirculated along the circumferential side surface of the thickened portion 30 toward the axial center of the internal space 21.

[0060] Furthermore, when implementing the present invention, it is also possible to adopt a configuration in which the tip of the seal lip has a thick-walled portion and a thin-walled portion for only one of the sealing devices, either the seal ring 5 or the combined seal ring 6. In addition, when implementing the present invention, it is also possible to adopt a configuration in which, for each of the seal ring 5 and the combined seal ring 6, the thick-walled portion and the thin-walled portion are adopted for only some of the seal lips among the multiple seal lips.

[0061] The configuration of the sealing device of the present invention is not limited to the sealing device of the embodiment described above, but can also be applied to various sealing devices with structures that have a sealing lip R that slides against the sealing sliding surface of a mating member, such as the sealing devices shown in Figures 6 to 9.

[0062] The sealing device of the present invention is not limited to hub unit bearings, but can be applied to sealing devices incorporated into various types of mechanical devices. [Explanation of Symbols]

[0063] 1 Hub unit bearing 2 Outer ring 3 Hubs 4 Rolling elements 5 Seal ring 6 combination sealing rings 7a, 7b Outer ring track 8. Static flange 9a, 9b Inner ring track 10 Rotating flanges 11 Axial sliding surface 12 Concave curved surface 13 Radial sliding surface 14 Seal sliding surface 15 spline holes 16 Inner circle 17 Hub Wheel 18 Fitting cylinder 19 Crimping part 20 Retainer 21 Interior space 22 Mandrel 23. Sealant 24 Fitting cylinder 25 Support plate part 26 base 27 Axial Lip 28 Radial Lip 29 Radial Lip 30 Thick wall part 31 Thin-walled section 32 Slinger 33 Seal ring 34 Slinger cylindrical section 35 Slinger side plate section 36 Axial sliding surface 37 Radial sliding surface 38 Seal sliding contact surface 39 Mandrel 40 sealing material 41. Core metal cylinder section 42 Core metal side plate 43 Base 44 Axial Lip 45 Radial Lip 46 Radial Lip

Claims

1. It is equipped with a seal lip that extends in a direction inclined with respect to the sealing sliding surface of the mating member, and whose tip portion slides in contact with the sealing sliding surface over its entire circumference, The tip portion of the seal lip has multiple thick and thin sections arranged alternately in the circumferential direction. The thin-walled portion is located in a pair of thick-walled portions adjacent to each other in the circumferential direction, and the ends of these portions that are closer to the seal sliding surface with respect to the thickness direction of the seal lip are connected to each other. In the free state of the seal lip, the thin-walled portion is curved such that its circumferential middle portion protrudes further from the seal sliding surface in the thickness direction of the seal lip than the ends on both sides in the circumferential direction. The aforementioned thickened portion has a shape in which the circumferential width decreases towards the tip. Sealing device.

2. An outer member having double rows of outer ring raceways on its inner circumferential surface, An inner member having double rows of inner ring raceways on its outer surface, A plurality of rolling elements are arranged to roll freely between the double-row outer ring raceway and the double-row inner ring raceway, The system includes a sealing device that closes the axial end opening of the internal space existing between the inner circumferential surface of the outer member and the outer circumferential surface of the inner member, The sealing device is configured as the sealing device described in claim 1. Hub unit bearing.

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