Hub unit bearing

Abstract

To provide a hub unit bearing capable of improving workability of an assembly process.SOLUTION: A combination seal ring 5 has: a slinger 22 having a substantially horizontal U-shaped cross-sectional shape; and a seal ring 23 having only a side lip 24 and a grease lip 25 as a slide contact lip. The slinger 22 has a slinger small diameter cylindrical part 26, a slinger large diameter cylinder part 27, a slinger circular-ring part 28, and a slinger chamfer part 29. The seal ring 23 has a seal cylinder part 37, a seal circular-ring part 38, an auxiliary lip 39, and a rear face lip 40. An axial projection amount A of the rear face lip 40, an axial gap B between a lateral face on one side in an axial direction of the seal circular-ring part 38, and an end face on the other side in an axial direction of the slinger large diameter cylinder part 27, and an axial gap C between the slinger chamfer part 29 and the auxiliary lip 39 satisfy a relation of A>C>B.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a hub unit bearing. [Background technology]

[0002] Hub unit bearings, which are used to support the rotation of automobile wheels relative to the suspension system, are used in an environment where they are directly exposed to muddy water, so they require high-level sealing performance.On the other hand, hub unit bearings are required to keep rotational torque low in order to reduce automobile fuel consumption.

[0003] Hub unit bearings rotatably support a hub, to which a wheel is fixed, via multiple rolling elements inside an outer ring supported by a suspension system. A lubricant such as grease is sealed in the annular space in which the rolling elements are installed, and the opening of the annular space is blocked by a sealing member. For this reason, the performance of the sealing member has a significant impact on the sealing performance and torque reduction required of hub unit bearings.

[0004] FIG. 7 shows a hub unit bearing 100 of a conventional structure described in Japanese Patent Application Laid-Open No. 2023-38063.

[0005] The hub unit bearing 100 has an outer ring 101 and a hub 102. An axially inner opening of an annular space 103 existing between the inner peripheral surface of the outer ring 101 and the outer peripheral surface of the hub 102 is closed by a combination seal ring 104, which is a sealing member.

[0006] The combination seal ring 104 includes a slinger 105 and a seal ring 106 .

[0007] Slinger 105 has a substantially L-shaped cross section and is fixed to hub 102. Slinger 105 has a slinger cylindrical portion 107 fitted onto the outside of hub 102, and a slinger ring portion 108 extending radially outward from the axially inner end of slinger cylindrical portion 107.

[0008] The seal ring 106 is fixed to the outer ring 101. The seal ring 106 has a cylindrical seal portion 109 fitted inside the outer ring 101, and a circular seal portion 110 extending radially inward from the axially outer end of the cylindrical seal portion 109.

[0009] The seal ring 106 has two side lips 111 a and 111 b and one grease lip 112 as sliding contact lips that bring the tip portion of the seal ring 106 into sliding contact with the slinger 105 .

[0010] The seal ring 106 has an auxiliary lip 113 provided at the axially inner end of the seal cylindrical portion 109, and a back lip 114 provided on the axially outer surface of the seal ring portion 110 and protruding axially outward. The auxiliary lip 113 has a substantially J-shaped cross section, and its tip is closely opposed to the radially outer end of the axially inner surface of the slinger ring portion 108 over the entire circumference.

[0011] In the hub unit bearing 100 of the conventional structure, the combined seal ring 104 is provided with two side lips 111a, 111b that can keep the seal torque low, and does not have a dust lip (shaft lip) that is likely to increase the seal torque, so it is possible to ensure both sealing performance and low torque. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2023-38063 Summary of the Invention [Problem to be solved by the invention]

[0013] The combined seal ring 104 mounted on a hub unit bearing 100 of conventional construction has two side lips 111a, 111b that apply a force between the seal ring 106 and the slinger 105 in an axial direction separating them, but does not have a dust lip that can apply a force that prevents the seal ring 106 and the slinger 105 from displacing axially away from each other. For this reason, when the combined seal ring 104 is in a standalone state before being mounted on the hub unit bearing 100, the seal ring 106 and the slinger 105 are likely to separate axially.

[0014] In the process of installing the combination seal rings 104, a plurality of combination seal rings 104 are stacked in a rod shape in a magazine rack of a distributor with their axial directions facing up and down. Then, of the plurality of combination seal rings 104, the combination seal ring 104 arranged at the bottom is pushed out in the radial direction and installed between the outer ring 101 and the hub 102.

[0015] When the combination seal rings 104 described in JP 2023-38063 A are stacked, the engagement between the auxiliary lip 113 of the lowest combination seal ring 104 and the back lip 114 of the second lowest combination seal ring 104 tends to be large.

[0016] For this reason, when the lowest combination seal ring 104 is pushed out radially, the auxiliary lip 113 of the lowest combination seal ring 104 is likely to get caught on the back lip 114 of the second-lowest combination seal ring 104. This changes the posture of the seal ring 106 that constitutes the lowest combination seal ring 104, making it more likely that the seal ring 106 will separate from the slinger 105. Separation of the seal ring 106 from the slinger 105 will lead to a stoppage of the production line and reduce the workability of the assembly process for the hub unit bearing 100.

[0017] An object of the present disclosure is to provide a hub unit bearing that can improve the workability of the assembly process. [Means for solving the problem]

[0018] A hub unit bearing according to one aspect of the present disclosure includes an outer ring, a hub, a plurality of rolling elements, and a combination seal ring. The outer ring has a double-row outer ring raceway on its inner circumferential surface. The hub has a double row inner ring raceway on its outer circumferential surface. The plurality of rolling elements are disposed so as to roll freely between the double row outer ring raceways and the double row inner ring raceways. The combination seal ring closes an opening on one axial side of an annular space that exists between the inner peripheral surface of the outer ring and the outer peripheral surface of the hub.

[0019] The combination seal ring has a slinger having a substantially horizontal U-shaped cross section, and a seal ring having only a side lip and a grease lip as sliding contact lips that bring the tip of the seal ring into sliding contact with the slinger. In other words, the seal ring does not have a dust lip (shaft lip) as the sliding lip.

[0020] The slinger has a slinger small diameter cylindrical portion fitted onto the hub, a slinger large diameter cylindrical portion arranged radially outside the slinger small diameter cylindrical portion, a slinger ring portion connecting one axial end of the slinger small diameter cylindrical portion to one axial end of the slinger large diameter cylindrical portion, and a slinger chamfer portion provided at the connection between the outer surface of the slinger large diameter cylindrical portion and one axial side of the slinger ring portion.

[0021] The seal ring has a sealing cylindrical portion fitted into the outer ring, a sealing ring portion extending radially inward from the other axial end of the sealing cylindrical portion, an auxiliary lip provided on one axial end of the inner surface of the sealing cylindrical portion and protruding radially inward, with its inner surface closely facing the slinger chamfer portion over its entire circumference to form a labyrinth seal between it and the slinger chamfer portion, and a back lip provided on the side surface on the other axial side of the sealing ring portion and protruding toward the other axial side.

[0022] The axial protrusion amount A of the rear lip, the axial gap B between the side surface on one axial side of the seal ring portion and the end face on the other axial side of the slinger large diameter cylindrical portion, and the axial gap C between the auxiliary lip and the slinger chamfered portion satisfy the relationship A>C>B. The axial clearance C refers to the minimum value of the axial clearance between the auxiliary lip and the slinger chamfered portion.

[0023] In a hub unit bearing according to one aspect of the present disclosure, the auxiliary lip has a drainage passage that communicates in the axial direction. [Effects of the Invention]

[0024] According to the hub unit bearing according to one aspect of the present disclosure, the workability of the assembly process can be improved. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a half cross-sectional view showing a hub unit bearing according to a first example of an embodiment of the present disclosure. [Figure 2] FIG. 2 is an enlarged view of the X portion of FIG. [Figure 3] FIG. 3 is a view of a circumferential portion of a cylindrical seal portion of a seal ring constituting a combination seal ring according to the first example, viewed from the axially inner side. [Figure 4] FIG. 4 is a cross-sectional view of the first example showing a state in which combination seal rings are stacked up in the vertical direction. [Figure 5]FIG. 5 is a cross-sectional view showing a state in which the combination seal rings of the comparative example are stacked up in the vertical direction in relation to the first example. [Figure 6] FIG. 6 is a diagram corresponding to FIG. 2 and illustrating a second example of an embodiment of the present disclosure. [Figure 7] FIG. 7 is a partial cross-sectional view of a hub unit bearing of a conventional structure. DETAILED DESCRIPTION OF THE INVENTION

[0026] [Example 1] A first example of an embodiment of the present disclosure will be described with reference to FIGS.

[0027] [Overall structure of hub unit bearing] The hub unit bearing 1 includes an outer ring 2, a hub 3, a plurality of rolling elements 4a, 4b, and a combination seal ring 5. The hub unit bearing 1 is an inner ring rotating type hub unit bearing.

[0028] The hub unit bearing 1 of this example is a so-called third-generation hub unit bearing for a driving wheel. However, a hub unit bearing according to one embodiment of the present disclosure can also be applied to a hub unit bearing for a driven wheel, as well as first- and second-generation hub unit bearings.

[0029] In the following description, unless otherwise specified, the axial direction, radial direction, and circumferential direction of the hub unit bearing 1 refer to the axial direction, radial direction, and circumferential direction of the outer ring 2. The axial direction, radial direction, and circumferential direction of the outer ring 2 coincide with the axial direction, radial direction, and circumferential direction of the hub 3. Additionally, the outer axial direction refers to the outer side in the width direction of the vehicle when the hub unit bearing 1 is assembled to the vehicle, and the inner axial direction refers to the center side in the width direction of the vehicle when the hub unit bearing 1 is assembled to the vehicle.

[0030] The outer ring 2 is made of a hard metal such as medium carbon steel. The outer ring 2 has a generally cylindrical shape and has double-row angular outer ring raceways 7a, 7b on its inner circumferential surface. The outer ring 2 has a stationary flange 8 that protrudes radially outward at an axially intermediate portion. The stationary flange 8 has support holes 9 that penetrate the axial direction at multiple circumferential locations at the radially intermediate portion.

[0031] In this example, the support holes 9 are configured as threaded holes. The outer ring 2 is supported and fixed to the suspension by threading a support bolt, which is inserted through a through hole provided in the knuckle of the suspension, into the support hole 9 of the stationary flange 8 from the inside in the axial direction, so that the outer ring 2 does not rotate even when the wheel rotates.

[0032] The hub 3 is disposed coaxially with the outer ring 2 and radially inward of the outer ring 2. The hub 3 has angular double-row inner ring raceways 10a, 10b on its outer peripheral surface. The hub 3 has a rotating flange 11 that protrudes radially outward at a portion that protrudes axially outward beyond the outer ring 2. The hub 3 has a cylindrical pilot portion 12 at its axially outer end. Furthermore, the hub 3 has a spline hole 13 in its radial center that penetrates the hub 3 in the axial direction.

[0033] The rotating flange 11 has mounting holes 14 that penetrate the axial direction at multiple locations circumferentially in the radially middle portion. Studs 15 for connecting and fixing a braking rotor such as a disc or drum and a wheel that constitutes a wheel to the rotating flange 11 are press-fitted into each mounting hole 14 with serrations. That is, in this example, the mounting holes 14 are cylindrical holes.

[0034] A braking rotating body such as a brake disc and a wheel of a vehicle are connected and fixed to the rotating flange 11 by inserting a pilot portion 12 into a central hole provided in the center of each and inserting studs 15 into through holes provided at multiple locations circumferentially in the radially middle portion of each, and then screwing a hub nut onto the tip of the stud 15.

[0035] The mounting holes of the rotating flange can also be threaded holes. In this case, the braking rotor and wheel are connected and fixed to the rotating flange by threading a hub bolt, which passes through a through hole provided in the braking rotor and a through hole provided in the wheel, into the mounting hole from the outside in the axial direction.

[0036] The tip of a drive shaft that is rotated and driven by an engine or electric motor as a drive source is spline-engaged with the spline hole 13. When the vehicle is running, the hub 3 is rotated by the drive shaft, which rotates and drives the wheels and braking rotors that are coupled and fixed to the rotating flange 11 of the hub 3.

[0037] The hub 3 is configured by combining an inner ring 16 and a hub ring 17 .

[0038] The inner ring 16 is made of a hard metal such as bearing steel and has an annular shape. The inner ring 16 has an inner ring raceway 10b on the axially inner side on its outer circumferential surface.

[0039] The hub ring 17 is made of a hard metal such as medium carbon steel, and includes an inner ring raceway 10a on the axially outer side, a rotation flange 11, a pilot portion 12, and a spline hole 13.

[0040] The hub ring 17 has a small diameter step 18, which has a smaller outer diameter than the adjacent axially outer portion, at a portion located axially more inward than the axially outer inner ring raceway 10a. The hub ring 17 has a step surface 19, facing axially inward, at the axially outer end of the small diameter step 18.

[0041] The inner ring 16 is fitted onto the small diameter step 18 of the hub ring 17 with an interference fit, and its axially outer end face abuts against a step surface 19 of the hub ring 17. In this way, the hub ring 17 and the inner ring 16 are joined and fixed together.

[0042] The hub wheel and inner wheel can also be joined and fixed by clamping the inner wheel from both axial sides between the stepped surface of the hub wheel and a crimping portion provided on the axially inner end of the hub wheel, or by clamping the inner wheel from both axial sides between the stepped surface of the hub wheel and a nut threaded onto the axially inner end of the hub wheel.

[0043] The rolling elements 4a, 4b are made of hard metal such as bearing steel or ceramics. The rolling elements 4a, 4b are arranged between the double-row outer ring raceways 7a, 7b and the double-row inner ring raceways 10a, 10b, with multiple rolling elements in each row spaced apart in the circumferential direction. The rolling elements 4a, 4b are held in a freely rolling manner by cages 20a, 20b. In this example, balls are used as the rolling elements 4a, 4b, but tapered rollers can also be used as the rolling elements. The rolling elements 4a, 4b arranged in double rows are given a back-to-back (DB) type contact angle.

[0044] The hub unit bearing 1 of this example has a so-called equal diameter PCD type structure in which the pitch circle diameter of the rolling elements in the axially outer row and the pitch circle diameter of the rolling elements 4b in the axially inner row are equal. However, a hub unit bearing according to one embodiment of the present disclosure can also be applied to a different diameter PCD type structure in which the pitch circle diameter of the rolling elements 4a in the axially outer row and the pitch circle diameter of the rolling elements 4b in the axially inner row are different.

[0045] The combined seal ring 5 closes the axially inner opening of the annular space 21 that exists between the inner peripheral surface of the outer ring 2 and the outer peripheral surface of the hub 3. Therefore, in the following description of the combined seal ring 5, the axially inner side corresponds to one axial side in the claims, and the axially outer side corresponds to the other axial side in the claims.

[0046] However, when implementing a hub unit bearing according to one aspect of the present disclosure, the combined seal ring can also close the axially outer opening of the annular space in addition to or instead of the axially inner opening of the annular space. In this case, with respect to the combined seal ring closing the axially outer opening of the annular space, the axially outer side corresponds to one axial side in the claims, and the axially inner side corresponds to the other axial side in the claims.

[0047] Hub unit bearing 1 of this example further includes a seal ring 6 that closes the opening on the axially outer side of annular space 21. When implementing a hub unit bearing according to an embodiment of the present disclosure, the structure of the seal ring (seal device) that closes openings other than the openings closed by the combined seal ring according to an embodiment of the present disclosure is not limited to the structure shown in the figure.

[0048] The combined seal ring 5 and the seal ring 6 prevent leakage of grease (not shown) sealed in the annular space 21 and also prevent foreign matter such as muddy water from entering the annular space 21 .

[0049] [Structure of combined seal ring] The combination seal ring 5 has a slinger 22 having a cross-sectional shape that is approximately horizontally U-shaped, and a seal ring 23 that has only a side lip 24 and a grease lip 25 as a sliding lip that slides against the tip of the slinger 22.

[0050] The slinger 22 is fixed to the hub 3 and rotates during use, whereas the seal ring 23 is fixed to the outer ring 2 and does not rotate during use.

[0051] Slinger The slinger 22 has a slinger small diameter cylindrical portion 26 fitted onto the outside of the hub 3, a slinger large diameter cylindrical portion 27 arranged radially outside the slinger small diameter cylindrical portion 26, and a slinger circular ring portion 28 connecting the axially inner end of the slinger small diameter cylindrical portion 26 and the axially inner end of the slinger large diameter cylindrical portion 27.

[0052] In this example, the slinger small diameter cylindrical portion 26 is fitted onto the outer surface of the inner ring 16 that constitutes the hub 3. Specifically, the slinger small diameter cylindrical portion 26 is fitted onto the outer surface of the inner ring 16 by an interference fit.

[0053] The small-diameter cylindrical slinger portion 26 and the large-diameter cylindrical slinger portion 27 are arranged coaxially with each other and each have a cylindrical shape. The axial dimension of the small-diameter cylindrical slinger portion 26 is larger than the axial dimension of the large-diameter cylindrical slinger portion 27. When the combination seal ring 5 is installed, the axially outer end face of the small-diameter cylindrical slinger portion 26 is located axially inward of the end face 40a of the back lip 40, which will be described later.

[0054] The outer peripheral surface of the slinger large-diameter cylindrical portion 27 is cylindrical except for both axial ends. The axially outer end surface of the slinger large-diameter cylindrical portion 27 is flat on an imaginary plane perpendicular to the central axis of the slinger 22 except for the radially outer end.

[0055] The axially inner surface of the slinger ring portion 28 is configured as a flat surface existing on an imaginary plane perpendicular to the central axis of the slinger 22, except for both radially opposite ends.

[0056] Slinger 22 has a slinger chamfered portion 29 provided at a corner (edge) that is the connection between the outer peripheral surface of slinger large-diameter cylindrical portion 27 and the axially inner surface of slinger circular ring portion 28. In this example, slinger chamfered portion 29 is configured as a C-chamfer having a linear cross-sectional shape.

[0057] In this example, the slinger 22 is made up of a core metal (encoder core metal) 30 and an encoder body 31 fixed to the core metal 30.

[0058] The core 30 is made of a magnetic metal plate and has a cross section that is roughly shaped like a horizontal U. The core 30 has a small-diameter cylindrical core portion 32 fitted onto the inner ring 16, a large-diameter cylindrical core portion 33 disposed radially outward of the small-diameter cylindrical core portion 32, and a core ring portion 34 connecting the axially inner end of the small-diameter cylindrical core portion 32 and the axially inner end of the large-diameter cylindrical core portion 33.

[0059] The small-diameter cylindrical core portion 32 and the large-diameter cylindrical core portion 33 are arranged coaxially with each other and each have a cylindrical shape. The axial dimension of the small-diameter cylindrical core portion 32 is larger than the axial dimension of the large-diameter cylindrical core portion 33.

[0060] The encoder body 31 is made of a permanent magnet and has a substantially L-shaped cross section. The encoder body 31 has a disk-shaped cover portion 35 that covers the axially inner surface of the core metal circular ring portion 34, and a cylindrical cover portion 36 that covers the outer peripheral surface of the core metal large-diameter cylindrical portion 33. In this example, the cylindrical cover portion 36 covers not only the outer peripheral surface of the core metal large-diameter cylindrical portion 33, but also the axially outer end face of the core metal large-diameter cylindrical portion 33. The axially inner surface of the disk-shaped cover portion 35 has south poles and north poles arranged alternately in the circumferential direction, and functions as a detection surface.

[0061] In this example, the slinger small diameter cylindrical portion 26 is composed only of a small diameter cylindrical core portion 32. In contrast, the slinger large diameter cylindrical portion 27 is composed of a large diameter cylindrical core portion 33 and a cylindrical cover portion 36, and the slinger circular ring portion 28 is composed of a circular core portion 34 and a disk-shaped cover portion 35. The slinger chamfered portion 29 is provided on the encoder body 31.

[0062] <Seal ring> The seal ring 23 has a cylindrical seal portion 37 fitted inside the outer ring 2, and a circular seal portion 38 extending radially inward from the axially outer end of the cylindrical seal portion 37.

[0063] In this example, the cylindrical seal portion 37 is fitted into the axially inner end portion of the outer ring 2. Specifically, the cylindrical seal portion 37 is fitted into the outer ring 2 by interference fit.

[0064] The axially inner end face of the cylindrical seal portion 37, except for the radially outer end, is configured as a flat surface that exists on an imaginary plane perpendicular to the central axis of the seal ring 23. In this example, when the combination seal ring 5 is installed, the axially inner end face of the cylindrical seal portion 37 and the axially inner side surface of the slinger ring portion 28 are arranged on the same imaginary plane.

[0065] The inner peripheral surface of the cylindrical seal portion 37 is cylindrical except for its axially inner end. The inner diameter of the cylindrical seal portion 37 is slightly larger than the outer diameter of the large-diameter cylindrical slinger portion 27 (cylindrical cover portion 36) that constitutes the slinger 22. The inner peripheral surface of the cylindrical seal portion 37 closely faces the outer peripheral surface of the large-diameter cylindrical slinger portion 27 over the entire circumference. As a result, a labyrinth seal 46a extending in the axial direction is formed between the inner peripheral surface of the cylindrical seal portion 37 and the outer peripheral surface of the large-diameter cylindrical slinger portion 27.

[0066] The axially inner surface of the seal ring portion 38 is configured as a flat surface existing on an imaginary plane perpendicular to the central axis of the seal ring 23. The axially inner surface of the seal ring portion 38 closely faces the axially outer end face of the slinger large-diameter cylindrical portion 27 over the entire circumference, with a sufficiently small axial gap B between them. As a result, a labyrinth seal 46b extending in the radial direction is formed between the axially inner surface of the seal ring portion 38 and the axially outer end face of the slinger large-diameter cylindrical portion 27. Specifically, the size of the axial gap B is approximately 0.2 mm to 0.4 mm. In this example, the axial gap B is smaller than the radial gap between the inner peripheral surface of the seal ring portion 37 and the outer peripheral surface of the slinger large-diameter cylindrical portion 27.

[0067] The seal ring 23 is provided with only a side lip 24 and a grease lip 25 as sliding lips that bring its tip into sliding contact with the slinger 22, and is not provided with a dust lip (axial lip, radial lip) that provides a large radial interference between the seal ring 23 and the slinger. Note that Figures 1, 2, 4, and 5 show the side lip 24 and grease lip 25 in a free state.

[0068] In this example, the seal ring 23 has one side lip 24 and one grease lip 25. However, when implementing a hub unit bearing according to one aspect of the present disclosure, the seal ring can have two or more side lips.

[0069] The side lip 24 has a conical cylindrical shape. The base end of the side lip 24 is connected to the inner circumferential surface of the seal ring portion 38, and extends radially outward as it moves axially inward. The tip of the side lip 24 slides against the axially outer surface of the slinger ring portion 28 that constitutes the slinger 22. Specifically, the tip of the side lip 24 slides against the axially outer surface of the core ring portion 34 that constitutes the slinger ring portion 28.

[0070] The grease lip 25 is thinner than the side lip 24 and has a conical cylindrical shape. The base end of the grease lip 25 is connected to the inner peripheral surface of the seal ring portion 38, and extends axially outward as it moves radially inward. The tip of the grease lip 25 makes sliding contact with the outer peripheral surface of the slinger small-diameter cylindrical portion 26 that constitutes the slinger 22. Specifically, the tip of the grease lip 25 makes sliding contact (light contact) with the outer peripheral surface of the core small-diameter cylindrical portion 32 that constitutes the slinger small-diameter cylindrical portion 26.

[0071] Since the grease lip 25 is a lip specialized for the function of preventing grease leakage from the annular space 21, the clamping margin with respect to the slinger small diameter cylindrical portion 26 (core small diameter cylindrical portion 32) is sufficiently smaller than that of a dust lip, which functions to prevent the intrusion of foreign matter.

[0072] The seal ring 23 has an auxiliary lip 39 and a back lip 40 in addition to the side lip 24 and the grease lip 25 .

[0073] Auxiliary lip 39 is provided at the axially inner end of the inner peripheral surface of cylindrical seal portion 37 and protrudes radially inward, with its inner peripheral surface closely facing slinger chamfered portion 29 over the entire circumference to form a labyrinth seal 46c between it and slinger chamfered portion 29. An axial gap C exists between the inner peripheral surface of auxiliary lip 39 and slinger chamfered portion 29. The size of axial gap C between the inner peripheral surface of auxiliary lip 39 and slinger chamfered portion 29 is sufficiently small because a labyrinth seal 46c is formed between the inner peripheral surface of auxiliary lip 39 and slinger chamfered portion 29, specifically, approximately 0.4 mm to 0.6 mm.

[0074] The auxiliary lip 39 has an inner peripheral surface that slopes radially inward as it extends axially inward. In this example, the auxiliary lip 39 has a triangular cross-sectional shape and an inner peripheral surface that has a linear cross-sectional shape. The inner peripheral surface of the auxiliary lip 39 and the slinger chamfer 29 are arranged substantially parallel to each other. However, when implementing a hub unit bearing according to one aspect of the present disclosure, the inner peripheral surface of the auxiliary lip may have a curved cross-sectional shape. Furthermore, the inner peripheral surface of the auxiliary lip and the slinger chamfer may be arranged non-parallel to each other.

[0075] In this example, the axial dimension of the auxiliary lip 39 is approximately the same as the axial dimension of the slinger chamfered portion 29. The inner diameter of the inner peripheral edge portion (tip edge portion) 39a of the auxiliary lip 39 is smaller than the outer diameter of the slinger large-diameter cylindrical portion 27 (cylindrical covering portion 36).

[0076] As shown in Figure 3, the auxiliary lip 39 has a drainage channel 47 that communicates in the axial direction. The drainage channel 47 is arranged in a portion of the auxiliary lip 39 that is located vertically lower when the hub unit bearing 1 is assembled to the vehicle. Because the drainage channel 47 is provided in the auxiliary lip 39, even if water enters the annular space 21, the water can be discharged to the outside through the drainage channel 47 when the vehicle is stopped. The drainage channel 47 may be provided at one location in the circumferential direction of the auxiliary lip 39, or at multiple locations in the circumferential direction.

[0077] In this example, the drainage channel 47 is configured by a notch having a substantially V-shape. However, the drainage channel is not limited to a notch, and can be configured by a through hole, a slit, or the like.

[0078] The back lip 40 is provided on the axially outer surface of the seal ring portion 38, and protrudes axially outward by a protrusion amount A. An axially outer end face (tip face) 40a of the back lip 40 is positioned axially outermost of the seal ring 23. The axial protrusion amount A of the back lip 40 is specifically about 0.6 mm to 1 mm.

[0079] In this example, the rear lip 40 is provided at a radially intermediate portion of the axially outer surface of the seal ring portion 38. Specifically, as shown in FIG. 4, the rear lip 40 is formed at a position where an end face 40a of the rear lip 40 abuts against the axially inner side surface of the slinger ring portion 28 when the combination seal rings 5 ​​are stacked vertically with the axially inner side facing upward and the axially outer side facing downward. The rear lip 40 has a substantially trapezoidal cross section and a tapered shape. The radial thickness of the rear lip 40 decreases toward the axially outer side. As is clear from FIG. 4, the provision of the rear lip 40 on the seal ring 23 makes it possible to stack multiple combination seal rings 5 ​​at predetermined intervals.

[0080] The axially outer end face 40a of the back lip 40 is formed as a flat surface existing on an imaginary plane perpendicular to the central axis of the seal ring 23. The outer peripheral surface 40b of the back lip 40 is formed as a truncated cone surface that slopes radially outward as it moves axially inward. The inner peripheral surface 40c of the back lip 40 is formed as a truncated cone surface that slopes radially inward as it moves axially inward.

[0081] The end face 40a and the outer peripheral surface 40b of the rear lip 40 are smoothly connected via a connecting portion having an arc-shaped cross section. The end face 40a and the inner peripheral surface 40c of the rear lip 40 are smoothly connected via a connecting portion having an arc-shaped cross section.

[0082] In this example, the seal ring 23 is composed of a seal core metal 41 and a seal material 42 fixed to the seal core metal 41 .

[0083] The seal core metal 41 is made of a metal plate such as a cold-rolled steel plate, and has a substantially L-shaped cross section.

[0084] The seal core 41 comprises a core tube portion 43 fitted into the axially inner end of the outer ring 2, and a core flange portion 44 extending radially inward from the axially outer end of the core tube portion 43.

[0085] The core metal flange portion 44 of this example has a generally crank-shaped cross section in which the axially inner portion is offset axially inward from the axially outer portion.

[0086] The seal material 42 is made of an elastic material such as an elastomer like rubber, and has a seal base 45 , a side lip 24 , a grease lip 25 , an auxiliary lip 39 , and a back lip 40 .

[0087] The seal base 45 covers the surface of the seal core 41. Specifically, the seal base 45 covers the inner peripheral surface, the axially inner end portion of the outer peripheral surface, and the axially inner end face of the core tube portion 43, and also covers the axially inner side surface, the radially inner portion of the axially outer surface, and the inner peripheral surface of the core flange portion 44. In this example, the axially outer side surface of the portion of the seal base 45 that covers the radially inner portion of the axially outer surface of the core flange portion 44 and the axially outer side surface of the radially outer portion of the core flange portion 44 are arranged on the same imaginary plane.

[0088] The portion of the seal base 45 that covers the inner peripheral surface of the core metal tube portion 43 is configured as a cylindrical surface and constitutes the inner peripheral surface of the seal tube portion 37. The portion of the seal base 45 that covers the axially inner surface of the core metal flange portion 44 is configured as a flat surface and constitutes the axially inner surface of the seal ring portion 38. The portion of the seal base 45 that covers the radially inner portion of the axially outer surface of the core metal flange portion 44 constitutes the radially inner portion of the axially outer surface of the seal ring portion 38. In contrast, the radially outer portion of the axially outer surface of the seal ring portion 38 is constituted by the radially outer portion of the axially outer surface of the core metal flange portion 44.

[0089] When the combination seal ring 5 is mounted on the hub unit bearing 1, the axial protrusion amount A of the back lip 40, the axial gap B between the axial inner surface of the seal ring portion 38 and the axial outer end face of the slinger large diameter cylindrical portion 27, and the axial gap C between the auxiliary lip 39 and the slinger chamfered portion 29 satisfy the relationship A>C>B.

[0090] The axial protrusion amount A of the back lip 40 refers to the axial dimension from the portion of the axially outer surface of the seal annular portion 38 where the axially inner end faces of the seal cylindrical portions 37 of axially adjacent combination seal rings 5 ​​face each other when multiple combination seal rings 5 ​​are stacked up and down in the axial direction as shown in Figure 4, to the axially outer end face 40a of the back lip 40. Also, the axial clearance C refers to the minimum value of the axial clearance between the auxiliary lip 39 and the slinger chamfered portion 29.

[0091] According to the hub unit bearing 1 of this embodiment, the workability of the assembly process can be improved. The reason for this will be explained with reference to FIGS.

[0092] Figure 4 shows a state in which combination seal rings 5, in which the axial protrusion amount A of the rear lip 40, the axial gap B between the axial inner surface of the seal circular ring portion 38 and the axial outer end face of the slinger large diameter cylindrical portion 27, and the axial gap C between the auxiliary lip 39 and the slinger chamfered portion 29 satisfy the relationship A>C>B, are stacked in a rod shape with the axial inner side facing upward and the axial outer side facing downward.

[0093] As a comparative example, Figure 5 shows a state in which a combination seal ring 5x is stacked vertically in a rod shape, in which the axial protrusion amount A of the rear lip 40, the axial gap B between the axial inner surface of the seal circular ring portion 38 and the axial outer end face of the slinger large diameter cylindrical portion 27, and the axial gap C between the auxiliary lip 39 and the slinger chamfered portion 29 satisfy the relationship A>B>C.

[0094] When multiple combination seal rings 5, 5x are stacked, the relationship A>B is satisfied, so that the end face 40a of the back lip 40 of the upper combination seal ring 5, 5x abuts against the upper side face (axial inner side face) of the slinger ring portion 28 of the lower combination seal ring 5, 5x of the two combination seal rings 5, 5x stacked vertically, and the axial gap B becomes 0 (zero). As a result, the upper side face of the slinger ring portion 28 moves downward by the amount of the axial gap B relative to the upper end face of the tubular seal portion 37. In addition, a gap is formed between the upper end face (axial inner end face) of the tubular seal portion 37 of the lower combination seal ring 5, 5x of the two combination seal rings 5, 5x stacked vertically and the lower side face (axial outer side face) of the tubular seal portion 38 of the upper combination seal ring 5, 5x.

[0095] To remove the lowest combination seal ring 5, 5x by moving it radially, the end face 40a of the rear lip 40 of the second-lowest combination seal ring 5, 5x must get over the inner peripheral edge 39a of the auxiliary lip 39 of the lowest combination seal ring 5, 5x. In particular, because the mass of the stacked combination seal rings 5, 5x is applied to the end face 40a of the rear lip 40, the end face 40a of the rear lip 40 must get over the inner peripheral edge 39a of the auxiliary lip 39 while elastically deforming.

[0096] Here, comparing Figures 4 and 5, when combined seal rings 5 ​​that satisfy the relationship A>C>B are stacked together, the engagement allowance δ1 (see Figure 4), which corresponds to the height required for the end face 40a of the rear lip 40 to overcome the inner peripheral edge 39a of the auxiliary lip 39, is smaller than the engagement allowance δ2 (see Figure 5), which corresponds to the height required for the end face 40a of the rear lip 40 to overcome the inner peripheral edge 39a of the auxiliary lip 39 when combined seal rings 5x that satisfy the relationship A>B>C are stacked together.

[0097] Therefore, when combination seal rings 5 ​​that satisfy the relationship A>C>B are stacked and the lowest combination seal ring 5 is removed by moving it radially, the inner peripheral edge 39a of the auxiliary lip 39 of the lowest combination seal ring 5 can be prevented from getting caught on the back lip 40 of the second lowest combination seal ring 5.

[0098] Furthermore, when the lowest combination seal ring 5 is removed radially, the amount of elastic deformation and elastic repulsion of the auxiliary lip 39 are kept small, and the radial friction force acting between the auxiliary lip 39 and the back lip 40 is also kept small. Therefore, when the lowest combination seal ring 5 is removed radially, the moment load acting on the seal ring 23 is kept small. Therefore, changes in the posture of the seal ring 23 can be suppressed. In this way, by providing only the side lip 24 and the grease lip 25 as sliding lips, the combination seal ring 5 has a structure in which the seal ring 23 and the slinger 22 are easily separated in the axial direction, but separation of the seal ring 23 and the slinger 22 during the installation process can be suppressed. As a result, the workability of the assembly process of the hub unit bearing 1 can be improved.

[0099] In this example, the auxiliary lip 39 is provided with a drainage channel 47, so that foreign matter such as moisture that has entered between the seal ring 23 and the slinger 22 can be discharged to the outside through the drainage channel 47.

[0100] In this example, an axially long labyrinth seal 46a is provided between the inner peripheral surface of the cylindrical seal portion 37 and the outer peripheral surface of the large-diameter cylindrical slinger portion 27, which sufficiently prevents foreign matter that has entered the labyrinth seal 46c from the external space from reaching the side lip 24. As a result, simply providing one side lip 24 on the seal ring 23 ensures sufficient sealing performance for the combination seal ring 5, thereby enabling low torque. Furthermore, because the inner peripheral surface of the cylindrical seal portion 37 and the outer peripheral surface of the large-diameter cylindrical slinger portion 27 are closely opposed in the radial direction, the amount of relative radial displacement between the seal ring 23 and the slinger 22 is kept small before the seal ring 23 is attached to the hub unit bearing 1.

[0101] In this example, the end face 40a of the back lip 40 is smoothly connected to the outer peripheral surface 40b and the inner peripheral surface 40c via connecting portions that are each arc-shaped in cross section, which effectively prevents the inner peripheral edge 39a of the auxiliary lip 39 of the lowermost combination seal ring 5 from getting caught on the back lip 40 of the second-lowest combination seal ring 5. Therefore, this also improves the workability of the assembly process for the hub unit bearing 1.

[0102] [Example 2] A second example of the embodiment of the present disclosure will be described with reference to FIG.

[0103] In this example, of the slinger 22a and the seal ring 23 that make up the combined seal ring 5a, only the structure of the slinger 22a is changed from the structure of the slinger 22 of the first example. The structure of the seal ring 23 is the same as the structure of the seal ring 23 of the first example.

[0104] Similar to the structure of the first example, the slinger 22a has a slinger small diameter cylindrical portion 26a fitted onto the hub 3, a slinger large diameter cylindrical portion 27a arranged radially outside the slinger small diameter cylindrical portion 26a, and a slinger ring portion 28a connecting the axially inner end of the slinger small diameter cylindrical portion 26a and the axially inner end of the slinger large diameter cylindrical portion 27a.

[0105] The slinger small diameter cylindrical portion 26a is fitted onto the outer surface of the inner ring 16 that constitutes the hub 3. Specifically, the slinger small diameter cylindrical portion 26a is fitted onto the outer surface of the inner ring 16 by interference fit.

[0106] The slinger small-diameter cylindrical portion 26a and the slinger large-diameter cylindrical portion 27a are arranged coaxially with each other and each have a cylindrical shape. The axial dimension of the slinger small-diameter cylindrical portion 26a is larger than the axial dimension of the slinger large-diameter cylindrical portion 27a. When the combination seal ring 5a is installed, the axially outer end face of the slinger small-diameter cylindrical portion 26a is located axially inward of the end face 40a of the back lip 40.

[0107] The outer peripheral surface of slinger large-diameter cylindrical portion 27a is cylindrical except for the inner axial end portion, which is a flat surface that exists on an imaginary plane perpendicular to the central axis of slinger 22a.

[0108] The axially inner surface of the slinger ring portion 28a, except for both radially opposite ends, is configured as a flat surface that exists on an imaginary plane perpendicular to the central axis of the slinger 22a.

[0109] Slinger 22a has slinger chamfered portion 29a provided at the corner (edge) that is the connection between the outer peripheral surface of slinger large-diameter cylindrical portion 27a and the axially inner surface of slinger ring portion 28a. In this example, slinger chamfered portion 29a is configured as an R-chamfer having a curved cross-sectional shape.

[0110] In this example, the slinger 22a is made up of only a core metal 30a.

[0111] The core 30a is made of a rust-resistant metal plate such as a ferritic stainless steel plate (SUS430) or an austenitic stainless steel plate (SUS304), and has a substantially horizontal U-shaped cross section. The core 30a has a small-diameter cylindrical core portion 32a fitted onto the inner ring 16, a large-diameter cylindrical core portion 33a disposed radially outward of the small-diameter cylindrical core portion 32a, and a core ring portion 34a connecting the axially inner end of the small-diameter cylindrical core portion 32a and the axially inner end of the large-diameter cylindrical core portion 33a.

[0112] The small-diameter cylindrical core portion 32a and the large-diameter cylindrical core portion 33a are arranged coaxially with each other and each have a cylindrical shape. The axial dimension of the small-diameter cylindrical core portion 32a is larger than the axial dimension of the large-diameter cylindrical core portion 33a.

[0113] In this example, slinger small-diameter cylindrical portion 26a is composed only of core small-diameter cylindrical portion 32a, slinger large-diameter cylindrical portion 27a is composed only of core large-diameter cylindrical portion 33a, slinger ring portion 28a is composed only of core ring portion 34a, and slinger chamfered portion 29a is provided on core 30a.

[0114] When the combination seal ring 5a is mounted on the hub unit bearing 1, the axial protrusion amount A of the back lip 40, the axial gap B between the axial inner surface of the seal ring portion 38 and the axial outer end face of the slinger large diameter cylindrical portion 27a, and the axial gap C between the auxiliary lip 39 and the slinger chamfered portion 29a satisfy the relationship A>C>B.

[0115] In the case of the hub unit bearing 1 of this example equipped with the above-described combined seal ring 5a, separation of the seal ring 23 and the slinger 22a can be suppressed during the process of attaching the combined seal ring 5a. As a result, the workability of the process of assembling the hub unit bearing 1 can be improved.

[0116] Other configurations and effects of the second example are the same as those of the first example. [Explanation of symbols]

[0117] 1 Hub unit bearing 2 outer ring 3. Hub 4a, 4b rolling elements 5, 5a, 5x combination seal ring 6 Seal ring 7a, 7b Outer ring raceway 8 Stationary Flange 9 Support hole 10a, 10b Inner raceway 11 Rotating flange 12 Pilot Division 13 Spline hole 14 Mounting holes 15 studs 16 Inner Circle 17 Hub wheel 18 Small diameter stepped section 19 Step surface 20a, 20b retainer 21 Annular Space 22, 22a Slinger 23 Seal ring 24 Side lip 25 Grease Lip 26, 26a Slinger small diameter cylinder 27, 27a Slinger large diameter cylinder 28, 28a Slinger ring part 29, 29a Slinger chamfer 30, 30a core metal 31 Encoder body 32, 32a Core metal small diameter cylindrical part 33, 33a Large diameter cylindrical core 34, 34a Core metal ring part 35 Disc-shaped cover 36 Cylindrical covering part 37 Seal cylinder 38 Seal ring 39 Auxiliary Lip 39a Inner edge 40 rear lip 40a end face 40b Outer surface 40c Inner surface 41 Seal core metal 42 Sealing material 43 Core tube part 44 Core flange 45 Seal base 46a~46c Labyrinth seal 47 Drainage Channel 100 Hub unit bearing 101 outer ring 102 Hub 103 Annular Space 104 Combination Seal Ring 105 Slinger 106 Seal ring 107 Slinger tube 108 Slinger circular ring 109 Seal cylinder 110 Seal ring part 111a, 111b side lip 112 Grease Lip 113 Auxiliary Lip 114 Rear lip

Claims

1. an outer ring having a double-row outer ring raceway on its inner circumferential surface; a hub having a double row inner ring raceway on its outer circumferential surface; a plurality of rolling elements disposed between the double row outer ring raceways and the double row inner ring raceways so as to be freely rollable; a combined seal ring that closes an opening on one axial side of an annular space that exists between the inner peripheral surface of the outer ring and the outer peripheral surface of the hub, The combination seal ring has a slinger having a substantially horizontal U-shaped cross section, and a seal ring having only a side lip and a grease lip as sliding contact lips whose tip end is in sliding contact with the slinger, The slinger has a slinger small diameter cylindrical portion fitted onto the hub, a slinger large diameter cylindrical portion arranged radially outward of the slinger small diameter cylindrical portion, a slinger ring portion connecting one axial end of the slinger small diameter cylindrical portion to one axial end of the slinger large diameter cylindrical portion, and a slinger chamfer portion provided at the connection between the outer peripheral surface of the slinger large diameter cylindrical portion and one axial side surface of the slinger ring portion, the seal ring has: a cylindrical seal portion fitted into the outer ring; a circular seal ring portion extending radially inward from the other axial end of the cylindrical seal portion; an auxiliary lip provided on one axial end of the inner peripheral surface of the cylindrical seal portion and protruding radially inward, with its inner peripheral surface closely facing the slinger chamfered portion over the entire circumference to form a labyrinth seal between it and the slinger chamfered portion; and a back lip provided on the side surface on the other axial side of the circular seal ring portion and protruding toward the other axial side. The axial protrusion amount A of the back lip, the axial gap B between the side surface on one axial side of the seal ring portion and the end face on the other axial side of the slinger large-diameter cylindrical portion, and the axial gap C between the auxiliary lip and the slinger chamfered portion satisfy the relationship A>C>B. Hub unit bearing.

2. 2. The hub unit bearing according to claim 1, wherein said auxiliary lip has a drainage passage communicating in the axial direction.

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