Hub unit bearing

Abstract

The present invention provides a hub unit bearing that can suppress the sticking of the first side lip even when negative pressure is generated between the first side lip and the second side lip, thereby reducing torque. [Solution] When the seal ring 5 is cut in a virtual plane containing the central axis of the hub 3, and the first side lip 23 is represented in a free state, the first side lip 23 extends axially beyond the flat portion 12 or the inclined portion 13, and has a tapered tip portion 31 at the tip side with the flat portion 12 or the inclined portion 13 as the boundary. The inner circumferential surface of the first side lip 23 in the range including the tapered tip portion 31 from the tip to the middle portion is a first inner circumferential generatrix G in a straight shape inclined with respect to the central axis of the hub 3. A The outer circumferential surface of the tip section 31 is continuous or stepped toward the tip side of the first side lip 23, and the first inner circumferential generatrix G A Approaching the first tip-side outer perimeter busbar G B It has.

Description

Technical Field

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

Background Art

[0002] A hub unit bearing rotatably supports a vehicle wheel with respect to a suspension device and is used in an environment where mud and water directly splash. Therefore, the hub unit bearing is required to have a high sealing performance. On the other hand, the hub unit bearing is required to keep the rotational torque low from the aspect of suppressing the fuel consumption of the vehicle.

[0003] In a hub unit bearing, a hub to which a wheel is fixed is rotatably supported inside an outer ring supported by a suspension device via a plurality of rolling elements. A lubricant such as grease is enclosed in an annular space where the rolling elements are installed. The opening of the annular space is closed by a sealing member such as a seal ring. Therefore, the performance of the sealing member has a great influence on the performance such as the sealing performance and low torque required for the hub unit bearing.

[0004] FIG. 9 shows a hub unit bearing 100 having a conventional structure described in Japanese Patent Application Laid-Open No. 2016-223453.

[0005] The hub unit bearing 100 has an outer ring 101 and a hub 102. The opening on the axially outer side of the 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 seal ring 104.

[0006] The seal ring 104 is supported and fixed to the outer ring 101. The seal ring 104 has a first side lip 105 extending in the axial direction, a second side lip 106 disposed radially inside the first side lip 105 and extending in the axial direction, and a grease lip 107 extending in the radial direction.

[0007] The hub 102 has a seal sliding contact surface 108 that slidably contacts the tip portions of the first side lip 105, the second side lip 106, and the grease lip 107, respectively.

[0008] The seal sliding contact surface 108 includes a flat portion 109 formed by an annular flat surface orthogonal to the central axis of the hub 102, an inclined portion 110 formed by an inclined surface that curves and slopes radially outward in a direction away from the annular space 103 in the axial direction, and a cylindrical surface portion 111.

[0009] The first side lip 105 mainly plays a role in preventing muddy water from entering the annular space 103, and its tip portion is slidably contacted with the flat portion 109.

[0010] The second side lip 106 mainly plays a role in preventing the movement of the grease enclosed in the space between the second side lip 106 and the first side lip 105 and the grease enclosed in the space between the second side lip 106 and the grease lip 107, and its tip portion is slidably contacted with the inclined portion 110.

[0011] The grease lip 107 mainly plays a role in preventing the grease from leaking from the annular space 103, and its tip portion is slidably contacted with the cylindrical surface portion 111.

[0012] Generally, it is considered that the shape of the seal lip that plays a role in preventing the intrusion of muddy water is preferably a shape in which the peak of the contact surface pressure stands on the side where the muddy water intrudes (radially outer side). On the other hand, the shape of the seal lip that plays a role in preventing the movement of the grease is preferably a shape in which the contact width with respect to the seal sliding contact surface is relatively large and the surface pressure distribution of the contact surface pressure is smooth (no peak).

[0013] In the conventional structure described in Japanese Patent Publication No. 2016-223453, a difference in thickness and intersection angle with respect to the sealing sliding surface 108 is provided between the first side lip 105 and the second side lip 106, thereby obtaining a contact pressure suitable for each of their respective roles. [Prior art documents] [Patent Documents]

[0014] [Patent Document 1] Japanese Patent Publication No. 2016-223453 [Overview of the project] [Problems that the invention aims to solve]

[0015] In recent years, there has been a growing demand for lower torque in hub unit bearings, and this has led to a need to reduce the sealing torque of the seal rings incorporated into hub unit bearings.

[0016] In the conventional hub unit bearing 100 described in Japanese Patent Publication No. 2016-223453, repeated rotation and stopping of the hub 102 causes the annular space 103 to repeatedly expand and contract, changing the internal pressure. When negative pressure is generated between the first side lip 105 and the second side lip 106, the contact area of ​​the first side lip 105 with the flat portion 109 increases, making it easier for the first side lip 105 to stick to the flat portion 109. Therefore, the conventional hub unit bearing 100 still has room for improvement in terms of reducing torque.

[0017] The present disclosure aims to provide a hub unit bearing that can suppress sticking of the first side lip even when negative pressure is generated between the first side lip and the second side lip, thereby reducing torque. [Means for solving the problem]

[0018] Each hub unit bearing according to one aspect of this disclosure comprises an outer ring, a hub, a plurality of rolling elements, and a seal ring. The outer ring has a double row of outer ring raceways on its inner circumferential surface. The hub has a double row of inner ring raceways on its outer surface. The plurality of rolling elements are arranged to be able to roll freely between the double row of outer ring raceways and the double row of inner ring raceways. The seal ring is supported by the outer ring and closes the opening of the annular space that exists between the inner surface of the outer ring and the outer surface of the hub.

[0019] The seal ring has a first side lip that extends in the axial direction and a second side lip that is located radially inward from the first side lip and also extends in the axial direction.

[0020] The hub or the member fixed to the hub is composed of a ring-shaped plane perpendicular to the central axis of the hub and has a flat portion that slides against the tip of the first side lip, and an inclined surface that is curved or linearly inclined in a direction radially outward as it approaches the flat portion in the axial direction and has an inclined portion that slides against the tip of the second side lip.

[0021] In one aspect of the present disclosure, when the first side lip is represented in a free state in a cross-section cut by a virtual plane including the central axis of the hub, The first side lip extends axially beyond the flat portion or the inclined portion, and has a tip-shaped section at the tip end, with the flat portion or the inclined portion as the boundary. Of the first side lip, the inner circumferential surface in the area including the tip portion extending from the tip to the middle portion has a first inner circumferential generatrix that is inclined with respect to the central axis of the hub. The outer circumferential surface of the aforementioned tip section has a first tip-side outer circumferential generatrix that approaches the first inner circumferential generatrix continuously or stepwise as it approaches the tip side of the first side lip.

[0022] In a hub unit bearing according to one aspect of the present disclosure, the first inner circumferential generatrix and the first tip-side outer circumferential generatrix can be directly connected at the tip edge of the first side lip.

[0023] In a hub unit bearing according to one aspect of the present disclosure, the planar portion may have an uneven portion with a maximum height Rz of 3.2 μm or more in the portion that slides against the tip of the first side lip.

[0024] In a hub unit bearing according to one aspect of the present disclosure, the planar portion and the inclined portion can be provided directly on the hub. Alternatively, the flat portion and the inclined portion may be provided on a member fixed to the hub. In this case, the flat portion and the inclined portion may be provided on a slinger fixed to the hub. [Effects of the Invention]

[0025] According to one aspect of the present disclosure, a hub unit bearing can suppress the sticking of the first side lip even when negative pressure is generated between the first side lip and the second side lip, thereby reducing torque. [Brief explanation of the drawing]

[0026] [Figure 1] Figure 1 is a cross-sectional view showing a hub unit bearing according to a first example of an embodiment of the present disclosure. [Figure 2] Figure 2 is an enlarged view corresponding to section X in Figure 1, and shows the first side lip, second side lip, and grease lip provided on the seal ring in a free state. [Figure 3] Figure 3 is a magnified view of a portion of Figure 2. [Figure 4] Figure 4 is an enlarged view corresponding to section X in Figure 1, showing the first side lip, second side lip, and grease lip provided on the seal ring in an elastically deformed state. [Figure 5] Figure 5 is a diagram corresponding to Figure 2, showing a second example of an embodiment of the present disclosure. [Figure 6] Figure 6 is a diagram corresponding to Figure 2, showing a third example of an embodiment of the present disclosure. [Figure 7] Figure 7 is a diagram corresponding to Figure 2, showing a fourth example of an embodiment of the present disclosure. [Figure 8] Figure 8 is a diagram corresponding to Figure 4, showing a fifth example of an embodiment of the present disclosure. [Figure 9] Figure 9 is a partial cross-sectional view showing a conventional hub unit bearing structure. [Modes for carrying out the invention]

[0027] [Example 1] A first example of the embodiment of this disclosure will be explained with reference to Figures 1 to 4.

[0028] This example illustrates an application of a seal ring for a hub unit bearing according to one aspect of the present disclosure to a seal ring that closes an axially outer opening in an annular space.

[0029] [Overall structure of the hub unit bearing] The hub unit bearing 1 comprises an outer ring 2, a hub 3, a plurality of rolling elements 4a, 4b, and a seal ring 5. The hub unit bearing 1 is an inner ring rotating type hub unit bearing.

[0030] The hub unit bearing 1 in this example is a so-called third-generation hub unit bearing for a driven wheel. However, a hub unit bearing according to one aspect of this disclosure can also be applied to a hub unit bearing for a drive wheel, as well as first-generation and second-generation hub unit bearings, etc.

[0031] In the following description, with respect to the hub unit bearing 1, the axial, radial, and circumferential directions refer to the axial, radial, and circumferential directions of the outer ring 2 unless otherwise specified. The axial, radial, and circumferential directions of the outer ring 2 coincide with the axial, radial, and circumferential directions of the hub 3. Furthermore, the axial outer side 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 axial inner side refers to the center side in the width direction of the vehicle when the hub unit bearing 1 is assembled to the vehicle.

[0032] The outer ring 2 is made of a hard metal such as medium carbon steel and has double rows of outer ring raceways 6a and 6b on its inner circumferential surface.

[0033] The outer ring 2 has a stationary flange 7 projecting radially outward from its axial middle section. The stationary flange 7 is used to connect and fix the outer ring 2 to the knuckle of the suspension device. In operation, the outer ring 2 is connected and fixed to the knuckle of the suspension device and does not rotate.

[0034] The hub 3 is made of a hard metal such as medium carbon steel or bearing steel, and has double rows of inner ring raceways 8a and 8b on its outer circumference, and a rotating flange 9 that protrudes radially outward in a portion located axially outward from the outer ring 2, and is positioned radially inward from the outer ring 2 and coaxially with the outer ring 2. The rotating flange 9 is used to connect and fix the wheel and the braking rotating member to the hub 3.

[0035] The hub 3 has a cylindrical pilot portion 10 at its axially outer end. The pilot portion 10 is the part that fits the wheel and braking rotating member, which are coupled and fixed to the rotating flange 9. In operation, the hub 3 rotates together with the wheel and braking rotating member coupled and fixed to the rotating flange 9.

[0036] The hub 3 or a member fixed to the hub 3 has a sealing sliding surface 11 that functions as a sliding surface for the sealing ring 5. In this example, the sealing sliding surface 11 is provided directly on the hub 3.

[0037] However, when implementing a hub unit bearing according to one aspect of this disclosure, the sealing sliding surface may be provided on a member that is fixed to the hub and rotates synchronously with the hub, such as a sliding ring or a slinger.

[0038] The seal sliding surface 11 is composed of a flat portion 12 and an inclined portion 13. Therefore, the flat portion 12 and the inclined portion 13 are directly provided on the hub 3. The seal sliding surface 11 is subjected to grinding as a finishing process, for example, using a full-form grinding wheel.

[0039] The flat portion 12 is composed of a ring-shaped plane perpendicular to the central axis O of the hub 3 (see Figure 1). In this example, the flat portion 12 is provided on the axially inner surface of the radially inner end of the rotating flange 9. The tip of the first side lip 23, which constitutes the seal ring 5 (described later), slides against the flat portion 12. The arithmetic mean roughness Ra of the flat portion 12 is not limited to this, but is, for example, 0.32 μm or less.

[0040] The inclined portion 13 is composed of an inclined surface that is curved or linearly inclined in a direction radially outward as it approaches the flat portion 12 in the axial direction. In this example, the inclined portion 13 is composed of a concave curved surface that is curved in a direction radially outward as it approaches the flat portion 12 (as it approaches the axially outward direction). Therefore, the inclined portion 13 has an arc-shaped cross-section. The axially outward end of the inclined portion 13 is connected to the radially inward end of the flat portion 12. The tip of the second side lip 24, which constitutes the seal ring 5 and will be described later, is in sliding contact with the inclined portion 13. However, when implementing a hub unit bearing according to one aspect of this disclosure, the inclined portion may be composed of a tapered surface that is linearly inclined in a direction radially outward as it approaches the flat portion in the axial direction.

[0041] In this example, the sealing sliding surface 11 further includes a cylindrical surface portion 14.

[0042] The cylindrical surface portion 14 is composed of a cylindrical surface whose outer diameter does not change in the axial direction. The cylindrical surface portion 14 is provided on the outer circumferential surface of the portion of the inner ring raceway 8a adjacent to the axially outer side of the hub 3. The axially outer end of the cylindrical surface portion 14 is connected to the axially inner end of the inclined portion 13. The tip of the grease slip 37, which will be described later and constitutes the seal ring 5, is in sliding contact with the cylindrical surface portion 14.

[0043] In this example, the hub 3 is composed of a hub ring 15 and an inner ring 16. However, when implementing the hub unit bearing of this disclosure, the hub may be composed of a different combination of parts than that in this example.

[0044] The hub wheel 15 comprises an axially outer inner ring raceway 8a, a rotating flange 9, a pilot portion 10, a flat portion 12, an inclined portion 13, and a cylindrical surface portion 14, which constitute the hub 3.

[0045] The hub wheel 15 has a small-diameter stepped portion 17 located axially inward from the inner ring raceway 8a on the axially outer side, which has a smaller outer diameter than the adjacent portion on the axially outer side, and into which the inner ring 16 is fitted. Furthermore, the hub wheel 15 has a stepped surface 18 facing axially inward at the axially outer end of the small-diameter stepped portion 17, and a crimped portion 19 that is bent radially outward from the axially inner end of the small-diameter stepped portion 17.

[0046] The inner ring 16 has an inner ring raceway 8b on its outer surface that is axially inward and forms the hub 3.

[0047] In this example, the hub 3 is constructed by fitting an inner ring 16 onto the axially inner portion of the hub ring 15. More specifically, in this example, the hub 3 is constructed by fitting the inner ring 16 onto the small-diameter stepped portion 17 of the hub ring 15, and by clamping the inner ring 16 from both axial sides between the stepped surface 18 of the hub ring 15 and the crimping portion 19, thereby joining and fixing the hub ring 15 and the inner ring 16. The crimping portion 19 is formed by plastically deforming a cylindrical portion provided at the axially inner end of the hub ring 15 radially outward after fitting the inner ring 16 onto the small-diameter stepped portion 17.

[0048] Alternatively, the hub ring and the inner ring can be joined by screwing a nut onto the axially inward end of the hub ring that protrudes from the axially inward end of the inner ring.

[0049] In this example, the hub unit bearing 1 is a hub unit bearing for the driven wheel, so the hub 3 is solid.

[0050] However, the hub unit bearing of this disclosure can also be applied to a hub unit bearing for a drive wheel. In this case, the hub has a splined hole in its center that penetrates axially. The tip of a drive shaft, which is rotationally driven by an engine or electric motor, is spline-engaged into the splined hole. When the vehicle is running, the hub is rotationally driven by the drive shaft, thereby rotationally driving the wheel and braking rotation member, which are coupled and fixed to the rotation flange of the hub.

[0051] The rolling elements 4a and 4b are made of an iron alloy such as bearing steel or ceramics, and are arranged so as to be able to roll freely between the double-row outer ring raceways 6a and 6b and the double-row inner ring raceways 8a and 8b, with multiple elements of each held by cages 20a and 20b. As a result, the hub 3 is rotatably supported radially inward of the outer ring 2.

[0052] The hub unit bearing 1 in this example has a so-called equal-diameter PCD type structure in which the pitch circle diameter of the rolling elements 4a in the axial outer row is equal to the pitch circle diameter of the rolling elements 4b in the axial inner row. However, the hub unit bearing of this disclosure can also be applied to a so-called different-diameter PCD type hub unit bearing in which the pitch circle diameter of the rolling elements 4b in the axial outer row is different to the pitch circle diameter of the rolling elements 4b in the axial inner row. Furthermore, although balls are used as the rolling elements 4a and 4b in the hub unit bearing 1 in this example, tapered rollers can be used instead of balls.

[0053] The seal ring 5 is supported by the outer ring 2 and closes the opening of the annular space 21 that exists between the inner circumferential surface of the outer ring 2 and the outer circumferential surface of the hub 3. In this example, the seal ring 5 closes the axially outer opening of the annular space 21. This prevents foreign matter from the external space from entering the annular space 21 through the axially outer opening of the annular space 21, and prevents lubricants such as grease sealed in the annular space 21 from leaking into the external space.

[0054] However, when implementing a hub unit bearing according to one aspect of the present disclosure, the seal ring may also close the axially inner opening of the annular space in addition to, or instead of, the axially outer opening of the annular space.

[0055] The hub unit bearing 1 in this example further includes a bearing cap 22 that closes the axially inner opening of the annular space 21. This prevents foreign matter from the external space from entering the annular space 21 through the axially inner opening of the annular space 21, and prevents lubricant sealed in the annular space 21 from leaking into the external space. When implementing a hub unit bearing according to one aspect of this disclosure, openings other than those closed by the seal ring according to one aspect of this disclosure may be closed not only by the bearing cap, but also by sealing devices such as combination seal rings.

[0056] [Structure of the sealing ring] The structure of the seal ring 5 will be explained with reference to Figures 2 to 4.

[0057] Figure 2 shows a cross-section of the hub 3 cut through a virtual plane containing the central axis O, with the first side lip 23, second side lip 24, and grease lip 37 of the seal ring 5 in their free state. Figure 3 is a partially enlarged view of Figure 2. Figure 4 shows a cross-section of the hub 3 cut through a virtual plane containing the central axis O, with the first side lip 23, second side lip 24, and grease lip 37 in their elastically deformed state.

[0058] The seal ring 5 has a first side lip 23 that extends in the axial direction and a second side lip 24 that is located radially inward from the first side lip 23 and also extends in the axial direction. In other words, the seal ring 5 has two side lips 23 and 24.

[0059] When implementing a hub unit bearing according to one aspect of the present disclosure, the seal ring may have two or more side lips. If the seal ring has three or more side lips, the first side lip may consist of at least the radially outermost side lip whose tip slides against the flat surface, preferably all of the side lips whose tip slides against the flat surface.

[0060] In this example, the seal ring 5 is composed of a core metal 25 and a sealing material 26 having a first side lip 23 and a second side lip 24.

[0061] The core metal 25 is made of a metal sheet such as cold-rolled steel sheet and is constructed in a ring shape.

[0062] The core metal 25 has a cylindrical fitting cylinder portion 27, an annular outward-facing flange portion 28 that is bent radially outward from the axially outer end of the fitting cylinder portion 27, and an inward-facing flange portion 29 whose radially outer end is connected to the axially inner end of the fitting cylinder portion 27 and which has a substantially crank-shaped cross-section.

[0063] The core metal 25 is supported and fixed to the outer ring 2 by interlocking the fitting cylinder portion 27 with the axially outer end of the outer ring 2. The axially inner surface of the outward flange portion 28 abuts against the axially outer end surface of the outer ring 2 via a portion of the sealing material 26.

[0064] The sealing material 26 is made of an elastic material such as an elastomer containing rubber, and is configured in an annular shape. The sealing material 26 is bonded and fixed to the core metal 25.

[0065] The sealing material 26 has a sealing base 30 in addition to the first side lip 23 and the second side lip 24.

[0066] The seal base 30 covers the surface of the core metal 25. Specifically, the seal base 30 covers the inner circumferential surface of the fitting cylinder portion 27, the axial outer surface of the outward-facing flange portion 28, the radially outer portion of the axial inner surface, and the outer circumferential surface, as well as the axial outer surface of the inward-facing flange portion 29, the radially inner portion of the axial inner surface, and the inner circumferential surface.

[0067] The first side lip 23 and the second side lip 24 are contact lips whose respective tips come into contact with the sealing sliding surface 11. The first side lip 23 and the second side lip 24 are arranged to overlap radially.

[0068] In the free state of the first side lip 23 and the second side lip 24, the tip of the first side lip 23 is located axially outward than the tip of the second side lip 24. In this example, since the base end of the first side lip 23 and the base end of the second side lip 24 are located at approximately the same axial position, the axial dimension of the first side lip 23 in the free state is larger than the axial dimension of the second side lip 24.

[0069] In the seal ring 5 of this example, the first side lip 23 and the second side lip 24 are configured to extend from the axially inward to the axially outward direction. Therefore, with respect to the first side lip 23 and the second side lip 24, the tip side refers to the axially outward direction, and the base end side refers to the axially inward direction.

[0070] In the free state of the first side lip 23 and the second side lip 24, the inclination angle of the first side lip 23 with respect to the central axis O of the hub 3 is greater than that of the second side lip 24.

[0071] The first side lip 23 is the contact lip on the seal ring 5 that is located furthest to the external space, and its main role is to prevent muddy water from entering the annular space 21.

[0072] The first side lip 23 has a substantially partially conical shape in its free state. The base end of the first side lip 23 is connected to the axially outer surface of the radially inner portion of the seal base 30, and extends radially outward as it moves axially outward. The tip of the first side lip 23 slides against the flat portion 12 provided on the hub 3. As shown in Figure 4, with its tip sliding against the flat portion 12, the first side lip 23 elastically deforms so that its middle portion is convex radially inward.

[0073] When the first side lip 23 is represented in a free state in a cross-section cut by a virtual plane containing the central axis O of the hub 3, it extends axially beyond the flat portion 12 or the inclined portion 13, and has a tapered tip 31 at the tip end, with the flat portion 12 or the inclined portion 13 as the boundary. In this example, the first side lip 23 extends axially beyond the radially outer end of the inclined portion 13, and has a tapered tip 31 at the tip end, with the inclined portion 13 as the boundary.

[0074] The thickness of the tip section 31 decreases continuously or gradually as it approaches the tip of the first side lip 23. In this example, the thickness of the tip section 31 decreases continuously as it approaches the tip of the first side lip 23.

[0075] The first side lip 23 has a root portion 32 connected to the seal base 30. In the free state of the first side lip 23, the root portion 32 has a substantially cylindrical shape.

[0076] The first side lip 23 has an intermediate portion 33 between the tip portion 31 and the root portion 32. In the free state of the first side lip 23, the intermediate portion 33 has a partially conical shape. The thickness dimension of the intermediate portion 33 is approximately constant along the axial direction, or its thickness dimension decreases slightly as it moves outward in the axial direction.

[0077] The first side lip 23 comprises, in order from the base end, a root portion 32, an intermediate portion 33, and a tip portion 31.

[0078] In the free state of the first side lip 23, the inner peripheral surface of the first side lip 23 within the range including the tapered portion 31 extending from the tip portion to the middle portion has a first inner peripheral generatrix G in a linear shape inclined with respect to the central axis O of the hub 3.

[0081] , A , B , B , , B , A , , A , A , Therefore, the inner peripheral surface of the first side lip 23 within the range including the tapered portion 31 extending from the tip portion to the middle portion is configured as a conical surface (tapered surface). The first inner peripheral generatrix G A is inclined in a direction toward the radially outer side as it goes toward the axially outer side. The inclination angle of the first inner peripheral generatrix G with respect to the central axis O of the hub 3 A is set, for example, within a range of 15 degrees to 30 degrees, preferably within a range of 20 degrees to 25 degrees. In the illustrated example, the inclination angle of the first inner peripheral generatrix G with respect to the central axis O of the hub 3 A is approximately 20 degrees.

[0079] In this example, the generatrix of the inner peripheral surface of the tapered portion 31 and the generatrix of the inner peripheral surface of the middle portion 33 are arranged in a straight line and connected to each other, constituting the first inner peripheral generatrix G A .

[0080] <sin000357>The first inner peripheral generatrix G A The intersection angle α (see FIG. 3) between the tangent line of the inclined portion 13 passing through the intersection point of the first inner peripheral generatrix G A and the first inner peripheral generatrix G is set, for example, within a range of 50 degrees to 70 degrees, preferably within a range of 55 degrees to 65 degrees. In the illustrated example, the intersection angle α is approximately 60 degrees.

[0081] The outer peripheral surface of the tapered portion 31 has a first tip-side outer peripheral generatrix G that continuously or stepwise approaches the first inner peripheral generatrix G A toward the tip side of the first side lip 23. In this example, the first tip-side outer peripheral generatrix G B continuously approaches the first inner peripheral generatrix G B toward the tip side of the first side lip 23. Specifically, the first tip-side outer peripheral generatrix G A has a linear shape and linearly approaches the first inner peripheral generatrix G B toward the tip side of the first side lip 23. A

[0082] 1st tip side outer circumferential generatrix G B It is positioned almost parallel to the central axis O of the hub 3. Therefore, the outer circumferential surface of the tip section 31 is configured as a cylindrical surface. However, the first tip side outer circumferential generatrix G B The hub 3 can also be inclined in a direction that moves radially inward as it moves axially outward with respect to the central axis O. In this case, the outer circumferential surface of the tip section 31 is configured as a partially conical cylindrical surface (tapered surface).

[0083] In this example, the first leading edge outer perimeter busbar G B and the first inner circumference busbar G A They are not directly connected. First tip-side outer busbar G B and the first inner circumference busbar G A This is connected via the generatrix of the tip surface of the tip section 31 (the surface connecting the outer and inner surfaces of the tip section 31). The generatrix of the tip surface of the tip section 31 has its radially outer end connected to the first tip-side outer generatrix G B It is connected to the axially outer end, and its radially inner end is the first inner circumferential generator G A It is connected to the axially outer end. The tip section 31 has a certain thickness even at its tip edge and has a roughly trapezoidal cross-sectional shape. The tip section 31 has a first ridge 34 that connects the inner circumferential surface and the tip surface.

[0084] The outer surface of the intermediate section 33 is the first inner circumference busbar G A The first base end outer perimeter busbar G is a straight line extending approximately parallel to the first base end. C It has the following: First base end outer perimeter busbar G C The inclination increases in the direction of radial outward movement as it moves axially outward.

[0085] The first side lip 23, in its free state, has a bending point 35 at a position where it intersects with the inclined portion 13, connecting the outer circumferential surface of the intermediate portion 33 with the outer circumferential surface of the tip portion 31. However, when implementing a hub unit bearing according to one aspect of this disclosure, the bending point may be provided at a position where it intersects with the planar portion in the axial direction.

[0086] In the free state of the first side lip 23, the first base end outer circumference busbar G C Axial dimension L C (See Figure 3) is the first tip-side outer circumference busbar G B Axial dimension L B (See Figure 3) This is approximately 2 to 3 times the size shown. In the illustrated example, the first base end outer perimeter busbar G C Axial dimension L C is the first tip side outer circumferential generatrix G B Axial dimension L B It is approximately 2.5 times that amount.

[0087] The second side lip 24 is a contact lip located radially inward of the first side lip 23, which is the radially outermost contact lip among the contact lips provided on the seal ring 5, and its main role is to prevent the movement of grease. Specifically, the second side lip 24 mainly plays a role in preventing the movement of grease sealed in the space between the second side lip 24 and the first side lip 23 and grease sealed in the space between the second side lip 24 and the grease lip 37, which will be described later.

[0088] The second side lip 24, in its free state, has a substantially cylindrical or substantially partially conical shape. The base end of the second side lip 24 is connected to the inner circumferential surface of the seal base 30, and it extends slightly radially outward as it moves axially outward. The tip of the second side lip 24 slides against the inclined portion 13 provided on the hub 3. As shown in Figure 4, with its tip sliding against the inclined portion 13, the second side lip 24 elastically deforms so that its middle portion is convex radially inward.

[0089] When the second side lip 24 is represented in a free state in a cross-section cut by a virtual plane containing the central axis O of the hub 3, it extends axially beyond the inclined portion 13. In this example, the second side lip 24 extends axially beyond the radially intermediate portion of the inclined portion 13.

[0090] In this example, in the free state of the second side lip 24, the inner circumferential surface of the second side lip 24, extending almost the entire range from the tip to the base, is a linear second inner circumferential generatrix G D It has a second outer surface G, which is a straight shape, and the outer surface of the second side lip 24 extends over almost the entire area from the tip to the base. E It has.

[0091] 2nd inner bus line G D and the second outer busbar G E These are arranged in approximately parallel directions. Therefore, the thickness dimension of the second side lip 24 is almost constant along its entire length. The second side lip 24 has a second ridge portion 36 that connects the inner circumferential surface and the tip surface.

[0092] 2nd inner bus line G D The tangent line of the inclined section 13 passing through the intersection with the inclined section 13, and the second inner circumference generator G D The intersection angle β (see Figure 3) between the two (β < α) is smaller than the intersection angle α, and is set to a range of, for example, 20 to 50 degrees, preferably 30 to 40 degrees. In the illustrated example, the intersection angle β is approximately 30 degrees.

[0093] In this example, the sealing material 26 of the seal ring 5 further includes a grease slip 37 and a weir 38. When implementing a hub unit bearing according to one aspect of this disclosure, it is optional for the seal ring to include a grease slip and a weir.

[0094] The grease lip 37 is the contact lip on the seal ring 5 that is located closest to the annular space 21, and its main role is to prevent grease from leaking out of the annular space 21.

[0095] The grease slip 37 has a substantially partially conical shape in its free state. The base end of the grease slip 37 is connected to the inner circumferential surface of the seal base 30, and it extends radially inward as it moves axially inward. The tip of the grease slip 37 slides against or comes into close proximity with the cylindrical surface portion 14 provided on the hub 3.

[0096] The weir portion 38 has a disc shape, and its radially inner end is connected to the radially outer end of the seal base portion 30. The weir portion 38 has an outer diameter larger than the outer circumferential surface of the axially outer end of the outer ring 2. The weir portion 38 plays a role in preventing foreign matter such as muddy water traveling along the outer circumferential surface of the outer ring 2 from reaching the first side lip 23. When implementing a hub unit bearing according to one embodiment of this disclosure, a non-contact lip (labyrinth lip), a so-called canopy lip, can also be provided on the axially outer surface of the weir portion.

[0097] According to the hub unit bearing 1 in this example, even when negative pressure is generated between the first side lip 23 and the second side lip 24, sticking of the first side lip 23 can be suppressed, thereby reducing torque.

[0098] In other words, as shown in Figure 3, in the seal ring 5 of this example, when the first side lip 23 is represented in a free state in a cross-section cut by a virtual plane containing the central axis O of the hub 3, the first side lip 23 extends axially beyond the flat portion 12 or the inclined portion 13, and has a tapered tip 31 at the tip end, with the flat portion 12 or the inclined portion 13 as the boundary. Therefore, compared to the conventional structure described in Japanese Patent Application Publication No. 2016-223453, the area in which the tapered tip 31 is formed (axial dimension in the free state) of the first side lip 23 is larger, so the excessive volume at the tip of the first side lip 23 is reduced, and the rigidity of the tip of the first side lip 23 is reduced. Therefore, even when the internal pressure of the annular space 21 changes due to the repeated rotation and stopping of the hub 3, and negative pressure is generated between the first side lip 23 and the second side lip 24, the contact area of ​​the tip of the first side lip 23 with the flat portion 12 is suppressed to increase, and the tip of the first side lip 23 is suppressed from sticking to the flat portion 12. As a result, the torque of the hub unit bearing 1 is reduced.

[0099] Furthermore, the inner circumferential surface of the first side lip 23, including the tip section 31 extending from the tip to the middle section, has a straight shape, the first inner circumferential generatrix G, which is inclined with respect to the central axis O of the hub 3. A The outer circumferential surface of the tip section 31 is continuously or stepwise formed towards the tip side of the first side lip 23, and the first inner circumferential generatrix G A Approaching the first tip-side outer perimeter busbar G B This is why the contact pressure peak tends to occur on the side of the sliding contact area between the tip section 31 of the first side lip 23 and the flat section 12, where muddy water enters. Specifically, since the first ridge 34 and the portion of the inner circumferential surface near the first ridge 34 of the tip section 31 slide against the flat section 12, the contact pressure peak tends to occur at the contact point between the first ridge 34 and the flat section 12. Therefore, the first side lip 23 can adequately perform its role in preventing the intrusion of muddy water.

[0100] The second side lip 24 does not have a tapered tip at its end, and its thickness is almost constant along its entire length. As a result, the contact width (contact area) of the second side lip 24 with respect to the inclined portion 13 is relatively large, and the surface pressure distribution of the contact surface pressure becomes smooth. Specifically, the second edge 36 and the portion of the inner circumferential surface of the second side lip 24 that is relatively far from the second edge 36 slide against the inclined portion 13, so the contact width (contact area) between the second side lip 24 and the inclined portion 13 is large, and the surface pressure distribution of the contact surface pressure becomes smooth (trapezoidal, plateau-like). Therefore, the second side lip 24 can adequately perform its role in preventing grease movement.

[0101] As a result, with the hub unit bearing 1 in this example, not only is torque reduced, but the two side lips 23 and 24 of the seal ring 5 can also fully perform their respective roles.

[0102] Furthermore, in this example, since the seal ring 5 is equipped with a weir 38, foreign matter such as muddy water traveling along the outer surface of the outer ring 2 is prevented from reaching the first side lip 23. Therefore, the sealing performance of the seal ring 5 is sufficiently enhanced.

[0103] [Example 2] A second example of the embodiment of this disclosure will be explained with reference to Figure 5.

[0104] The hub unit bearing 1 in this example has the same structure as the hub unit bearing 1 in the first example, except for the tip section 31a of the first side lip 23a. Therefore, the explanation of the parts of the hub unit bearing 1 other than the tip section 31a of the first side lip 23a will be omitted. Also, since the basic structure and function of the first side lip 23a are the same as those of the first side lip 23 in the first example, redundant explanations of these will be omitted, and the explanation will focus on the parts that differ from the first side lip 23 in the first example.

[0105] In this example, with the first side lip 23a in a free state, the first tip-side outer circumference generatrix G of the outer circumference surface of the tip section 31a BHowever, with respect to the central axis O of the hub 3 (see Figure 1), it is linearly inclined radially inward as it moves axially outward. Therefore, the outer circumference G of the first tip side B and the first base end outer perimeter busbar G C Therefore, the inclination direction of the hub 3 with respect to the central axis O is different. In addition, the outer circumferential surface of the tip section 31a is configured in a conical shape.

[0106] In this example, the first leading edge outer perimeter busbar G B And, the first inner circumferential generatrix G of the inner circumferential surface of the first side lip 23a, including the tip portion 31a extending from the tip to the middle portion. A The two are directly connected. That is, at the tip edge of the first side lip 23a, the first tip-side outer circumference busbar G B and the first inner circumference busbar G A These are directly connected. The inner and outer surfaces of the tip section 31a are connected at the first edge 34a.

[0107] The tip section 31a has a roughly triangular cross-sectional shape, and its thickness decreases linearly as it extends outward in the axial direction.

[0108] In this example, the first tip-side outer circumferential generatrix G of the outer circumferential surface of the tip section 31a B and the first inner circumferential generatrix G of the inner circumferential surface of the tip section 31a A Because they are directly connected, the volume of the tip portion of the tip section 31a is further reduced compared to the tip section 31 of the first example. As a result, the contact area of ​​the tip of the first side lip 23a with the flat section 12 is less likely to increase further, and adhesion of the tip of the first side lip 23a is effectively suppressed.

[0109] The other components and effects of the second example are the same as those of the first example.

[0110] [Example 3] A third example of the embodiment of this disclosure will be explained with reference to Figure 6.

[0111] In this example, the hub unit bearing 1 also has the same structure as the hub unit bearing 1 in the first example, except for the tip section 31b of the first side lip 23b. Therefore, the explanation of the part of the first side lip 23b other than the tip section 31b will be omitted.

[0112] In this example, in the free state of the first side lip 23b, the first tip-side outer circumferential generatrix G of the outer circumferential surface of the tip section 31b B However, the hub 3 is curved inward in the radial direction as it moves axially outward with respect to its central axis O (see Figure 1). Therefore, the first tip-side outer circumference generatrix G B It has a curved shape, specifically an arc shape. The outer surface of the tip section 31b is configured as a convex curved surface.

[0113] 1st tip side outer circumferential generatrix G B and the first inner circumference busbar G A This is directly connected. That is, at the tip edge of the first side lip 23b, the first tip-side outer circumference busbar G B and the first inner circumference busbar G A These are directly connected. The inner and outer surfaces of the tip section 31b are connected at the first edge 34b.

[0114] The tip section 31b has a roughly semicircular (fan-shaped) cross-section, and its thickness decreases curvilinearly as it moves outward in the axial direction.

[0115] In this example as well, the first tip-side outer circumferential generatrix G of the outer circumferential surface of the tip section 31b B and the first inner circumferential generatrix G of the inner circumferential surface of the tip section 31b A Because they are directly connected, the volume of the tip portion of the tip section 31b is further reduced compared to the tip section 31 of the first example. As a result, the contact area of ​​the tip of the first side lip 23b with the flat portion 12 does not increase further, and adhesion of the tip of the first side lip 23b is effectively suppressed.

[0116] The other components and effects of the third example are the same as those of the first and second examples.

[0117] [Example 4] A fourth example of the embodiments of this disclosure will be explained with reference to Figure 7.

[0118] The hub unit bearing 1 in this example also has the same structure as the hub unit bearing 1 in the first example, except for the tip section 31c of the first side lip 23c. Therefore, the explanation of the part of the first side lip 23c other than the tip section 31c will be omitted.

[0119] In this example, the outer surface of the tip section 31c gradually changes towards the tip side of the first side lip 23c, and the first inner circumferential generatrix G A Approaching the first tip-side outer perimeter busbar G B It has the first tip-side outer circumference busbar G B It is bent in a roughly triangular wave or sawtooth shape. The outer surface of the tip section 31c is configured as a stepped cone.

[0120] 1st tip side outer circumferential generatrix G B and the first inner circumference busbar G A This is directly connected. That is, at the tip edge of the first side lip 23c, the first tip-side outer circumference busbar G B and the first inner circumference busbar G A These are directly connected. The inner and outer surfaces of the tip section 31c are connected at the first ridge 34c.

[0121] The tip section 31c has a roughly triangular cross-sectional shape, and its thickness gradually decreases as it moves outward in the axial direction.

[0122] In this example as well, the first tip-side outer circumferential generatrix G of the outer circumferential surface of the tip section 31c B and the first inner circumferential generatrix G of the inner circumferential surface of the tip section 31c A Because they are directly connected, the volume of the tip portion of the tip section 31c is further reduced compared to the tip section 31 of the first example. As a result, the contact area of ​​the tip of the first side lip 23c with the flat portion 12 does not increase further, and adhesion of the tip of the first side lip 23c is effectively suppressed.

[0123] The other components and effects of the fourth example are the same as those of the first to third examples.

[0124] [Example 5] A fifth example of the embodiments of this disclosure will be explained with reference to Figure 8.

[0125] The hub unit bearing 1 in this example differs from the hub unit bearing 1 in the first example only in the structure of the flat portion 12a that slides against the tip of the first side lip 23. For this reason, the explanation of parts other than the flat portion 12a will be omitted.

[0126] The flat portion 12a has an uneven portion 39 with a maximum height Rz of 3.2 μm or more in the area where the tip of the first side lip 23 slides against it. The uneven portion 39 may be provided over the entire flat portion 12a, or, as shown in the figure, may be provided only in the area where the tip of the first side lip 23 slides against it.

[0127] The upper limit of the maximum height Rz of the uneven portion 39 is not limited to this, but can be 6.3 μm, preferably 4 μm. If the maximum height Rz of the uneven portion 39 is greater than 6.3 μm, wear of the tip of the first side lip 23 due to the rotation of the hub 3 may become a problem.

[0128] The uneven portion 39 can be formed, for example, by applying a finishing process to the flat portion 12a using a grinding wheel or the like, and then lightly applying a cutting tool to the portion that will become the uneven portion 39. In other words, the uneven portion 39 can be formed by the machined surface.

[0129] In this example, a surface with irregularities 39 having a maximum height Rz of 3.2 μm or more is provided on the portion of the flat portion 12a where the tip of the first side lip 23 (tip section 31) slides against it. Therefore, compared to the structure of the first example where the surface portion 12 does not have irregularities 39, the contact area of ​​the tip of the first side lip 23 with the flat portion 12a is reduced. Consequently, the tip of the first side lip 23 is prevented from sticking to the flat portion 12a.

[0130] The other components and effects of the fifth example are the same as those of the first example.

[0131] The first to fifth examples of the embodiments can be combined as appropriate, as long as no inconsistencies arise. [Explanation of Symbols]

[0132] 1 Hub unit bearing 2 Outer ring 3 Hubs 4a, 4b Rolling elements 5 Seal ring 6a, 6b Outer ring track 7. Stationary flange 8a, 8b Inner ring track 9 Rotating flange 10 Pilot Section 11 Seal sliding surface 12, 12a flat part 13 Slope 14 Cylindrical surface part 15 Hub Wheel 16 Inner circle 17 Small diameter stepped section 18 Step surface 19 Crimping part 20a, 20b retainer 21 Circular Space 22 Bearing cap 23, 23a, 23b, 23c First side lip 24. Second side lip 25 Mandrel 26. Sealant 27 Fitting cylinder 28 Outward-facing flange 29 Inward-facing flange 30 Seal base 31, 31a, 31b, 31c Tapered section 32. Root part 33 Middle section 34, 34a, 34b, 34c 1st ridge 35 Inflection points 36. Second Ridge 37 Grease Lip 38 Weir 39 Uneven part 100 Hub Unit Bearing 101 Outer ring 102 Hub 103 Circular Space 104 Seal ring 105 First side lip 106 Second side lip 107 Grease Lip 108 Seal sliding contact surface 109 Plane section 110 Inclined section 111 Cylindrical surface part

Claims

1. An outer ring having a double row of outer ring raceways on its inner circumference, A hub having double rows of inner ring raceways on its outer surface, Multiple rolling elements are arranged to roll freely between the double-row outer ring raceway and the double-row inner ring raceway, The hub comprises a seal ring supported by the outer ring, which closes the opening of the annular space between the inner surface of the outer ring and the outer surface of the hub, The seal ring has a first side lip that extends in the axial direction and a second side lip that is located radially inward from the first side lip and also extends in the axial direction. The hub or the member fixed to the hub is composed of a ring-shaped plane perpendicular to the central axis of the hub and has a flat portion that slides against the tip of the first side lip, and an inclined surface that is curved or linearly inclined in a direction radially outward as it approaches the flat portion in the axial direction and has an inclined portion that slides against the tip of the second side lip. In a cross-section cut by a virtual plane including the central axis of the hub, when the first side lip is represented in a free state, The first side lip extends axially beyond the flat portion or the inclined portion, and has a tip-shaped section at the tip end, with the flat portion or the inclined portion as the boundary. The inner circumferential surface of the first side lip, including the tip portion extending from the tip to the middle portion, has a first inner circumferential generatrix that is inclined with respect to the central axis of the hub. The outer circumferential surface of the aforementioned tip section has a first tip-side outer circumferential generatrix that approaches the first inner circumferential generatrix continuously or stepwise towards the tip side of the first side lip. Hub unit bearing.

2. The hub unit bearing according to claim 1, wherein the first inner circumferential generatrix and the first tip-side outer circumferential generatrix are directly connected at the tip edge of the first side lip.

3. The hub unit bearing according to claim 1, wherein the flat portion has an uneven portion with a maximum height Rz of 3.2 μm or more in the portion that slides against the tip of the first side lip.

Images