JP2017110786A - Hub unit bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of negative pressure between lips of a sealing device for a long period of time, and to surely prevent a rise of rotation torque, in a hub unit bearing.SOLUTION: A sealing device 30 is composed of a metal-made core grid 27 fixed to an outer ring, and an elastic member 34 which is fixed to the core grid 27, and formed of an elastic body, and the elastic member 34 comprises one lip 35 which extends toward an annular space, and slide-contacts with an inner shaft, and the other lip 36 which extends toward a direction apart from the annular space, and slide-contacts with the inner shaft. A valve 40 extending toward a lip tip in a tongue shape from the core grid 27 is formed at the one lip 35 by forming a notch J which penetrates in a thickness direction. A position of a tip of the valve 40 is apart from the lip tip of the one lip 35 by a prescribed dimension.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a technique for reducing the rotational torque of a hub unit bearing. In particular, it relates to a technique for reducing the rotational torque of a seal.

In vehicles such as automobiles, hub unit bearings are used to rotatably support the wheels. In order to improve the fuel efficiency of a vehicle, a reduction in rotational torque is required for the hub unit bearing.
FIG. 5 shows an example of the hub unit bearing 100. In this hub unit bearing 100, an inner shaft 101 is rotatably supported with respect to an outer ring 102 via a ball 104, and a wheel (not shown) is attached to a flange 103 formed at the shaft end of the inner shaft 101. It is fixed. In order to prevent water or the like from entering the annular space H in which the balls 104 are incorporated, the entire surface of the opening of the outer ring 102 and the inner shaft 101 on the right side of the figure is covered with a cover 106, and the opening on the left side of the figure The sealing device 105 is fixed to the inner periphery of the outer ring 102. The sealing device 105 includes a plurality of lips formed of an elastic body such as rubber. Generally, the sealing device 105 includes a grease lip 107 for preventing the grease enclosed in the annular space H from flowing out, and muddy water from the outside. An axial lip 108 for preventing foreign matter from entering is provided (see FIG. 6).
When the hub unit bearing 100 rotates, the tip of the lip of the sealing device 105 slides on the outer periphery of the inner shaft 101 to generate a sliding resistance. Therefore, the lip shape is appropriately selected to reduce the rotational torque, and the inner shaft 101 The pressure contact force of the lip that contacts the outer periphery of the lip is reduced.

On the other hand, when the vehicle travels and the inner shaft 101 rotates, the temperature of the hub unit bearing 100 increases. By this temperature increase, the air in the lip space (the area indicated by K in FIG. 6) surrounded by the grease lip 107 and the axial lip 108 expands. As shown in FIG. 6, since the grease lip 107 and the axial lip 108 are formed in a direction away from the lip space K, the air in the lip space K easily flows out beyond the sliding contact portions of the lips 107 and 108. To do.
Thereafter, while the temperature of the hub unit bearing 100 is lowered while the vehicle is stopped, the air in the lip space K contracts. However, since it is difficult for air to flow into the lip space K from the outside, the lip space K becomes negative pressure, and the lip is sucked to the raceway surface like a suction cup. For this reason, since the lip is strongly pressed against the outer periphery of the inner shaft 101, the slip resistance of the lip increases and the rotational torque increases when the vehicle travels again.

  In order to eliminate the negative pressure in the lip space K, in Patent Document 1, a protrusion 109 is provided on the inner peripheral side of the grease lip 107. In the structure of Patent Document 1, when the lip space K becomes negative pressure and the grease lip 107 bends toward the lip space K, the lip tip of the grease lip 107 is lifted from the raceway surface with the protrusion 109 as a fulcrum. This facilitates air to flow into the lip space K.

Japanese Patent Laying-Open No. 2015-143564

  In the structure of Patent Document 1, when a negative pressure is generated and the grease lip 107 is pulled inward, the protrusion 109 comes into contact with the inner shaft 101. When the inner shaft 101 rotates in this state, the protrusion 109 makes sliding contact with the outer peripheral surface of the inner shaft 101. For this reason, when the hub unit bearing 100 is used over a long period of time, the protrusion 109 is worn, and when a negative pressure is generated in the lip space K, the tip of the lip cannot be lifted. In this case, since the vehicle travels in a state where the grease lip 107 is attracted to the inner shaft 101 and the lip is strongly pressed against the outer periphery of the inner shaft 101, an increase in the rotational torque of the hub unit bearing 100 is prevented. There is a problem that cannot be done.

  An object of the present invention is to provide a hub unit bearing having a sealing device having a plurality of lips, which prevents an increase in rotational torque by preventing the generation of negative pressure between the lips over a long period of time. That is.

  One form of the hub unit bearing according to the present invention includes an outer ring, an inner shaft, a plurality of rolling elements incorporated in an annular space between an inner periphery of the outer ring and an outer periphery of the inner shaft, and the annular space. A hub unit bearing provided with a sealing device attached to an opening on the vehicle outer side, wherein the sealing device is a metal core fixed to the outer ring, and an elastic body fixed to the core And the elastic member extends toward the annular space and slidably contacts the inner shaft, and extends in a direction away from the annular space. A valve extending in a tongue shape from the cored bar toward the tip of the lip is formed in the one lip by providing a notch penetrating in the thickness direction. The position of the tip of the valve is the lip tip of the one lip It is characterized in that apart Luo predetermined dimension.

  Since the hub unit bearing having a sealing device having a plurality of lips according to the present invention can prevent generation of negative pressure between the lips over a long period of time, it can prevent an increase in rotational torque.

It is an axial sectional view of a hub unit bearing which is one embodiment of the present invention. It is a perspective view in the radial cross section of a sealing device. 3A is a cross-sectional view showing an initial state in which the sealing device is assembled, and FIG. 3B is a cross-sectional view showing a state in which the grease lip is deformed by negative pressure. It is a principal part enlarged view which shows the shape of a valve. It is an axial sectional view of a conventional hub unit bearing. It is explanatory drawing explaining the operation | movement which reduces the negative pressure of the conventional hub unit bearing.

An embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described with reference to the drawings. FIG. 1 is an axial sectional view of a hub unit bearing 10 according to the present embodiment.
The hub unit bearing 10 includes an outer ring 11, an inner shaft 12, and balls 13 that are a plurality of rolling elements. The inner shaft 12 is coaxially disposed radially inward of the outer ring 11 and is supported through a ball 13 so as to be rotatable around the rotation axis m. In the following description, the direction of the rotation axis m is referred to as the axial direction, the direction orthogonal to the rotation axis m is referred to as the radial direction, and the direction of circling around the rotation axis m is referred to as the circumferential direction. The rolling elements of the hub unit bearing 10 are not limited to balls. It may be a tapered roller.

  The outer ring 11 is made of carbon steel and has a substantially cylindrical shape. A double row outer raceway surface 14 is formed on the inner circumference. On the outer periphery, there are integrally formed mounting flanges 15 extending radially outward from a plurality of locations in the circumferential direction. Each mounting flange 15 is provided with a screw hole penetrating in the axial direction, and the outer ring 11 is fixed to a knuckle (not shown) by a bolt (not shown).

The inner shaft 12 is formed by integrally combining a hub shaft 17 and an inner ring member 18.
The hub shaft 17 is made of carbon steel, and a substantially cylindrical shaft portion 19 and a disk-shaped hub flange 16 formed at the shaft end of the shaft portion 19 are integrally formed. A plurality of bolt holes 20 penetrating in the axial direction are formed in the hub flange 16. A wheel is attached to the bolt hole 20 by inserting a bolt (not shown).
The inner ring member 18 is made of bearing steel, and is fitted to the shaft end of the hub shaft 17 opposite to the hub flange 16 by an interference fit. After the inner ring member 18 is fitted, the shaft end portion of the hub shaft 17 protruding from the inner ring member 18 is subjected to plastic working to form a caulking portion 21 that expands radially outward. The inner ring member 18 is firmly fixed to the hub shaft 17 by the caulking portion 21.
Inner raceway surfaces 22 and 22 are formed on the outer periphery of the hub shaft 17 and the outer periphery of the inner ring member 18, respectively. A cylindrical grease lip sliding surface 23 is formed on the outer periphery on the outer side of the inner raceway surface 22 provided on the hub shaft 17. An axial lip sliding surface 24 that extends in the radial direction is formed on the side surface of the hub flange 16 on the shaft portion 19 side. The grease lip sliding surface 23 and the axial lip sliding surface 24 are connected by an R surface having an arcuate cross section in the axial direction.

  A plurality of balls 13 are rotatably incorporated between the outer raceway surfaces 14 and 14 and the inner raceway surfaces 22 and 22 that are opposed to each other in the radial direction. The ball 13 is assembled with the outer raceway surface 14 and the inner raceway surface 22 with a pressure in the direction of the contact angle. The contact angle refers to an angle formed by a direction in which the ball 13 and each raceway surface are in contact with a direction orthogonal to the rotation axis m.

  When the hub unit bearing 10 is mounted on the vehicle, the hub flange 16 is attached toward the outside of the vehicle. For this reason, in the following description, the hub flange 16 side (right side in FIG. 1) of the hub unit bearing 10 is referred to as an outer side, and the inner ring member 18 side (left side in FIG. 1) is referred to as an inner side.

Grease is sealed in the annular space W formed between the inner periphery of the outer ring 11 and the outer periphery of the inner shaft 12, and the rolling contact portions between the balls 13 and the inner and outer raceway surfaces 14 and 22 are lubricated. .
When muddy water or the like enters the annular space W, the raceways 14 and 22 rust, causing problems such as generating abnormal noise when the balls 13 roll. For this reason, the sealing device 30 is incorporated in the opening on the outer side of the annular space W, and the cover 29 is attached to the opening on the inner side.

  The form of the sealing device 30 will be described with reference to FIG. The sealing device 30 is annular, and FIG. 2 is a perspective view of the sealing device 30 cut in a radial direction at one place on the circumference and the vicinity of the cross section viewed from the outside in the radial direction. In the description of the sealing device 30, the direction of the central axis is referred to as the axial direction, and the direction orthogonal to the axial direction is referred to as the radial direction.

  In the sealing device 30, the core metal 27 and the elastic member 34 are integrally molded. The elastic member 34 is formed by vulcanization molding of a rubber material with a mold in which a core metal 27 is inserted in advance, and is bonded to the core metal 27 simultaneously with the vulcanization molding. Nitrile rubber or acrylic rubber is used as the rubber material.

  The core metal 27 is manufactured by press-molding a thin carbon steel plate such as SPCC. The metal core 27 includes a fixing part 31 for fixing the sealing device 30 to the outer ring 11 and a lip holding part 32 for holding the elastic member 34. The fixed part 31 has a cylindrical shape. The lip holding part 32 is formed integrally with the fixing part 31 by bending one end in the axial direction of the fixing part 31 radially inward. Thus, the core bar 27 is formed in a substantially L-shaped axial cross section.

  The elastic member 34 includes three lips, a grease lip 35, a first axial lip 36, and a second axial lip 37.

The grease lip 35 is formed radially inward of the lip holding portion 32, and extends toward the side on which the fixing portion 31 is formed in the axial direction as it goes radially inward. The inner diameter dimension of the lip tip of the grease lip 35 is smaller than the outer diameter dimension of the grease lip sliding surface 23.
The first axial lip 36 is formed radially inward of the lip holding portion 32, extends in the axial direction toward the side opposite to the fixed portion 31, and increases in diameter toward the lip tip. It has become.
The second axial lip 37 is formed on the side surface of the lip holding portion 32, extends in substantially the same direction as the first axial lip 36, and increases in diameter toward the lip tip. In this way, the second axial lip 37 is formed radially outward from the first axial lip 36 and substantially parallel to the first axial lip 36 in the axial sectional shape.

  As shown in FIG. 1, the sealing device 30 is incorporated in a seal mounting portion formed on the outer side end portion of the outer ring 11. The seal mounting portion is formed on the inner circumference of the end portion of the outer ring 11 in the axial direction, and includes a cylindrical fitting surface 25 formed in the axial direction. Since the inner diameter dimension of the fitting surface 25 is slightly smaller than the outer diameter dimension of the fixing portion 31 of the metal core 27, the sealing device 30 is assembled to the outer ring 11 in a state of an interference fit. For this reason, foreign matter such as muddy water does not enter from the fitting surface of the outer ring 11 and the sealing device 30.

  Thus, the grease lip 35 (one lip) is fixed to the metal core 27 and extends toward the annular space W, and the tip of the lip is in sliding contact with the grease lip sliding surface 23 of the inner shaft 12. . The first axial lip 36 (the other lip) and the second axial lip 37 are fixed to the core metal 27 and extend away from the annular space W. The tip of each lip is connected to the inner shaft 12. It is in sliding contact with the axial lip sliding surface 24.

  In the present embodiment, a valve 40 is formed on the grease lip 35. The form of the valve 40 will be described in detail with reference to FIGS. FIG. 3 is a cross-sectional view taken along an axial plane passing through the center of the valve 40 at the position indicated by XX in FIG. FIG. 3A shows an initial state in which the sealing device 30 is assembled. FIG. 3B shows a state where the grease lip 35 is deformed by a negative pressure. Details of the state of occurrence of negative pressure will be described later.

The valve 40 is formed by making a notch J penetrating the grease lip 35 in its thickness direction. In FIG. 3, the shape of the cut J when viewed in the thickness direction of the grease lip 35 as shown by an arrow E is substantially U-shaped.
The start position G1 and the end position G2 of the cut J are formed at the base of the grease lip 35, respectively. The base portion is an area where the grease lip 35 is fixed to the lip holding portion 32. In addition, in this embodiment, although the valve 40 is installed in one place of the circumferential direction, you may install in multiple places.

FIG. 4 is an explanatory diagram for explaining the direction of the cut J. FIG. FIG. 4A shows the shape of the valve 40 viewed in the direction of arrow E in FIG. 4 (b) is a cross-sectional view taken along the direction of the arrow at the position AA in FIG. 4 (a), and FIG. 4 (c) is the position of the arrow at the position BB in FIG. 4 (a). It is sectional drawing seen in direction. Hereinafter, for convenience of explanation, the direction AA is referred to as the width direction of the valve 40, and the direction BB is referred to as the center line direction of the valve 40.
The radially outer surface of the grease lip 35 is referred to as a grease lip outer peripheral surface 35a, and the radially inner surface is referred to as a grease lip inner peripheral surface 35b.

  The incision J proceeds from the start position G1 toward the lip tip, then changes its direction in the circumferential direction while drawing an arc before the lip tip, proceeds again toward the base side, and stops at the end position G2.

The direction of the cut J in the thickness direction of the grease lip 35 is inclined with respect to the direction orthogonal to the grease lip outer peripheral surface 35a.
As shown in FIG. 4B, in the circumferential cross section of the valve 40, the width direction dimension of the valve 40 is inclined to become smaller from the grease lip outer circumferential surface 35 a toward the grease lip inner circumferential surface 35 b. . Further, as shown in FIG. 4C, in the radial cross section of the valve 40, the length in the center line direction of the valve 40 decreases from the grease lip outer peripheral surface 35a toward the grease lip inner peripheral surface 35b. Tilt to the direction.

  Thus, the valve 40 is integrally connected to the grease lip 35 on the base side, and has a shape extending in a tongue shape from the base toward the tip of the lip of the grease lip 35. Further, the tip G3 of the cut J (the point closest to the tip of the grease lip 35) is set at a position separated from the tip of the grease lip 35 by a predetermined dimension La toward the base.

The function of the valve 40 will be described with reference to FIG.
First, an initial state in which the sealing device 30 is assembled will be described with reference to FIG. For convenience of explanation, the surfaces where the valve 40 and the grease lip 35 face each other with the notch J interposed therebetween are referred to as a valve side mating surface 40a and a lip side mating surface 35c, respectively.
In the initial state, since the grease lip 35 is hardly deformed, the valve side mating surface 40a and the lip side mating surface 35c are in contact with each other. For this reason, grease and air do not move through the notch J toward the space surrounded by the grease lip 35 and the first axial lip 36 (hereinafter referred to as “lip space Z”) from the annular space W. .
Thus, the grease lip 35 prevents the grease inside the annular space W from flowing out.

  Next, the operation of the valve 40 when a negative pressure is generated in the lip space Z will be described with reference to FIG. FIG. 3 (b) exaggerates the deformation state of the grease lip 35 and the first axial lip 36 in order to facilitate understanding of the function of the valve 40.

When the hub unit bearing 10 rotates, heat is generated due to rolling friction when the balls 13 roll on the raceway surfaces 14 and 22. For this reason, the air of the lip space Z expands. Since the lip tips of the grease lip 35 and the first axial lip 36 are incorporated in a direction away from the lip space Z, the lip tips are easily pushed up by the expanded air. When the tip of the lip is lifted in this way, a gap is formed between the grease lip sliding surface 23 and the axial lip sliding surface 24, so that the air in the lip space Z easily exceeds the grease lip 35 and the first axial lip 36. leak.
When the air in the lip space Z flows out and the air pressure in the lip space Z returns to the atmospheric pressure, the shapes of the lips 35 and 36 are restored by elasticity, and the tip of each lip is connected to the grease lip sliding surface 23 and the axial. It comes into contact with the lip sliding surface 24 again.

  Thereafter, when the vehicle stops, the temperature of the hub unit bearing 10 decreases, so the volume of air in the lip space Z decreases. Since the lip tips of the grease lip 35 and the first axial lip 36 are incorporated in a direction away from the lip space Z, external air cannot flow beyond the grease lip 35 and the first axial lip 36. For this reason, the air pressure in the lip space Z is lowered, and the differential pressure P between the atmospheric pressure and the air pressure in the lip space Z acts on the outer peripheral surface 35a of the grease lip 35.

  For this reason, in the hub unit bearing 10 when it is assumed that the valve 40 is not provided, the lips 35 and 36 are strongly pressed against the inner shaft 12. For this reason, it becomes more difficult for outside air to flow in over the grease lip 35 and the first axial lip 36. Therefore, since the negative pressure in the lip space Z is not eliminated, the rotational torque of the hub unit bearing 10 increases.

  In the hub unit bearing 10 of the present embodiment, the range of the valve 40 from the start position G1 through the tip G3 to the end position G2 is separated from the cut J grease lip 35. For this reason, when the grease lip 35 is urged toward the lip space Z by the differential pressure P, the valve 40 is separated from the grease lip 35 and individually deformed.

Although illustration of the differential pressure P is omitted, it acts uniformly in the vertical direction on the outer peripheral surface of the grease lip 35 a and the outer peripheral surface of the valve 40. For this reason, as shown in FIG. 3B, in the grease lip 35, the portion between the base and the lip tip is urged toward the lip space Z by the differential pressure P, and is bent into an arc shape. Yes.
On the other hand, the valve 40 has a length in the center line direction, that is, a dimension L1 from the start position G1 (or end position G2) to the tip G3, and a dimension L2 from the start position G1 (or end position G2) to the lip tip. Of 40% or less. For this reason, when the grease lip outer circumferential surface 35 a and the outer circumferential surface of the valve 40 are uniformly subjected to the differential pressure P, the deflection amount of the valve 40 can be made smaller than the deflection amount of the grease lip 35.

The position of the grease lip 35 relative to the valve 40 when the grease lip 35 is deflected more than the valve 40 is indicated by broken lines in FIGS. 4B and 4C. As can be seen from these drawings, when the grease lip 35 is bent, the valve side mating surface 40a and the lip side mating surface 35c are separated from each other, and a clearance S is generated.
Since air flows from the annular space W toward the lip space Z through the gap S, the pressure in the lip space Z is restored to atmospheric pressure. As a result, since the differential pressure P becomes zero, the grease lip 35 and the first axial lip 36 are restored to their original shapes (the state shown in FIG. 3A) by their elasticity.

  Further, when the grease lip 35 is bent, the valve side mating surface 40a on the valve side and the lip side mating surface 35c on the grease lip 35 side that are opposed to each other across the notch J are inclined in directions away from each other. , A clearance S always occurs. For this reason, the valve 40 opens at the moment when negative pressure is generated in the lip space Z, and air flows into the lip space Z. Therefore, in this embodiment, the grease lip 35 is not greatly bent as shown in FIG. 3B, and the lips 35 and 36 are not strongly pressed against the inner shaft 12. Thus, an increase in the rotational torque of the hub unit bearing 10 can be suppressed.

In the present embodiment, the distal end portion G3 of the valve 40 is set at a position separated by a predetermined dimension La from the distal end of the grease lip 35 toward the base portion. Since the grease lip 35 is in sliding contact with the inner shaft 12 at the tip of the lip, the valve 40 does not directly contact the inner shaft 12. Further, when the grease lip 35 is urged toward the lip space Z by the differential pressure P, the amount of bending of the valve 40 is smaller than the amount of bending of the grease lip 35, so that the valve 40 is radially outward from the grease lip 35. Yes (see FIG. 3B). For this reason, when the grease lip 35 is drawn toward the lip space Z and bent into an arc shape, the valve 40 protrudes on the opposite side of the inner shaft 12 with the grease lip 35 interposed therebetween. . For this reason, even when the hub unit bearing 10 is used over a long period of time, the valve 40 does not come into contact with the inner shaft 12 and therefore the valve 40 is not worn.
Thus, the hub unit bearing 10 of the present embodiment can prevent the generation of negative pressure in the lip space Z over a long period of time. As a result, it is possible to reliably prevent an increase in rotational torque.

In the present embodiment, the valve 40 has been described with respect to the case where the shape of the tip portion G3 when viewed from the direction of the arrow E in FIG. 3 is an arc shape, but is not limited to this shape. For example, the cut J may be formed linearly between G1 and G3, and between G2 and G3, and the valve 40 may be formed in a triangular shape. In addition, a cut J at the tip of the valve 40 may be formed in a tangential direction in G3 so that the valve 40 has a rectangular shape.
However, when the lip space Z becomes negative pressure and the grease lip 35 is deformed into an arc shape, stress is generated inside the grease lip 35. And in the part where the shape of the lip side mating surface 35c changes rapidly, a high stress is generated by the stress concentration. For this reason, it is desirable to form the valve 40 in a smooth shape so that the shape of the lip side mating surface 35c does not change abruptly.

  In the present embodiment, the valve 40 is formed in a circular arc shape when viewed from the direction of arrow E in FIG. In this way, the stress concentration is suppressed by forming the lip side mating surface 35c in a smooth shape so that the shape of the lip side mating surface 35c does not change abruptly, and the increase in stress generated in the grease lip 35 can be more effectively suppressed. As a result, even if negative pressure is repeatedly generated in the lip space Z due to running / stopping of the vehicle, the grease lip 35 is not damaged. Thus, the durability of the sealing device 30 can be maintained well.

  Further, since the valve 40 is installed in the grease lip 35, when the negative pressure generated in the lip space Z is eliminated, the air in the annular space W flows into the lip space Z. Since the intrusion of foreign matter is blocked in the annular space W by the sealing device 30 and the cover 29, there is no possibility of sucking foreign matter such as muddy water into the lip space Z. Therefore, the function of the sealing device 30 can be exhibited over a long period of time.

  As described above, in the hub unit bearing 10 having the sealing device 30 having a plurality of lips, generation of negative pressure between the lips can be prevented over a long period of time, so that an increase in rotational torque can be prevented. .

(This embodiment) 10: Hub unit bearing, 11: Outer ring, 12: Inner shaft, 13: Ball, 14: Outer raceway surface, 15: Mounting flange, 16: Hub flange, 17: Hub shaft, 18: Inner ring member, 19: Shaft portion, 21: Caulking portion, 22: Inner raceway surface, 23: Grease lip sliding surface, 24: Axial lip sliding surface, 25: Fitting surface, 27: Core, 29: Cover, 30: Sealing Device: 31: fixing part, 32: lip holding part, 34: elastic member, 35: grease lip, 35a: grease lip outer peripheral surface, 35b: grease lip inner peripheral surface, 35c: lip side mating surface, 36: first axial Lip, 37: second axial lip, 40: valve, 40a: valve side mating surface, W: annular space, J: notch,
(Prior art) 100: hub unit bearing, 101: inner shaft, 102: outer ring, 103: flange, 104: ball, 105: sealing device, 106: cover, 107: grease lip, 108: axial lip, 109: protrusion, H: annular space

Claims (3)

An outer ring, an inner shaft, a plurality of rolling elements incorporated in an annular space between the inner periphery of the outer ring and the outer periphery of the inner shaft, and a sealing device attached to an opening on the vehicle outer side of the annular space A hub unit bearing comprising:
The sealing device includes a metal core fixed to the outer ring and an elastic member formed of an elastic body fixed to the core.
The elastic member includes one lip extending toward the annular space and slidingly contacting the inner shaft, and another lip extending away from the annular space and slidingly contacting the inner shaft. And
The one lip is provided with a notch penetrating in the thickness direction so that a valve extending in a tongue shape from the core metal toward the lip tip is formed, and the position of the tip of the valve is the one lip A hub unit bearing having a predetermined dimension away from the tip of the lip. The direction of the cut in the thickness direction of the one lip is:
When the one lip is urged toward a lip space surrounded by the one lip and the other lip,
2. The hub unit bearing according to claim 1, wherein the valve side surface and the one lip side surface facing each other across the notch are inclined in a direction away from each other.   The hub unit bearing according to any one of claims 1 and 2, wherein a shape of a tip portion of the valve when viewed in a thickness direction of the one lip is an arc shape.

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