Wheel bearing device

Abstract

To provide a wheel bearing device including a seal member capable of suppressing the occurrence of a pressure difference between inside and outside a seal lip, suppressing a reduction of grease sealed therein, and suppressing an increase in the rotation torque while preventing the wear at the front end of the seal lip due to suction-adhesion onto a slide surface.SOLUTION: An outer side seal member 7 includes a core metal 71 fitted to an outer ring 2, and a seal body 72 consisting of an elastic body joined to the core metal 71, the seal body 72 having a seal lip 72b extending in an axial direction and having a front end slidably contacting a slide surface (a flat part 31a, a shaft peripheral face part 31b, and a circular-arc face part 31c) of an inner member. At the front end of the seal lip 72b, a plurality of protruding parts 74a is provided protruding toward the slide surface and arranged along a peripheral edge of the front end.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a wheel bearing device. [Background technology]

[0002] BACKGROUND ART Wheel bearing devices that rotatably support wheels have been known in suspension systems for vehicles such as automobiles. The wheel bearing device has a configuration in which, for example, a hub ring (inner member) connected to a wheel is rotatably supported on an outer member via rolling elements. Furthermore, the wheel bearing device is often disposed in a space surrounded mainly by the suspension device, the tire well of the wheel, the brake rotor, etc., in an exposed state to the outside. For this reason, in order to prevent foreign matter such as muddy water from entering the installation space of the rolling elements from the outside, the wheel bearing device is provided with sealing members at the opening ends of the inner and outer sides of the annular space formed between the outer member and the inner member.

[0003] Incidentally, Figure 7 is a diagram showing an example of an outer-side seal member 107 in a conventional wheel bearing device 101. As shown in this figure, the tip portions of the multiple seal lips 172b·172b·172b (outer axial lip 173, inner axial lip 174, and radial lip 175) of the seal member 107 are all in contact with the sliding surfaces (flat portion 131a, axial circumferential surface portion 131b, and arcuate surface portion 131c) of the hub wheel 103, which is the inner member. Therefore, between these multiple seal lips 172b·172b·172b and the sliding surface of the hub wheel 103, there are formed sealed spaces separated by the inner axial lip 174, i.e., a first lip space P1 separated by the outer axial lip 173 and the inner axial lip 174, and a second lip space P2 separated by the radial lip 175 and the inner axial lip 174.

[0004] When a vehicle equipped with such a wheel bearing device 101 is driven and the temperature inside each of the above-mentioned sealed spaces rises, the air inside these sealed spaces expands and may pass through the sealing member 107 and be discharged to the outside. Specifically, the air in the first lip space P1 is pushed outward in the radial direction (in the direction of arrow B) as the volume increases, passes through the tip end of the outer axial lip 173, and is discharged to the outside. Furthermore, the air in the second lip space P2 is pushed out to one side in the axial direction (the direction of arrow C) as the volume increases, passes through the tip end of the radial lip 175, and is discharged to the outside. After the air is discharged to the outside, the first lip space P1 and the second lip space P2 are sealed again as the tip of the outer axial lip 173 and the tip of the radial lip 175 immediately come into contact with the sliding surfaces.

[0005] Then, when the vehicle stops operating and the temperature in each sealed space drops to near room temperature, the pressure in the first lip space P1 and the pressure in the second lip space P2 drop and become negative pressures relative to the external atmospheric pressure. As a result, a pressure difference occurs between the first lip space P1 and the second lip space P2, and the tip of the inner axial lip 174 may be pulled radially inward (opposite the direction of arrow B) and become adsorbed to the sliding surface (more specifically, the arc surface portion 131c).

[0006] Under such circumstances, when operation of the vehicle equipped with the wheel bearing device 101 is resumed and the relative rotation between the plurality of seal lips 172b·172b·172b and the hub wheel 103 is repeated, the tip of the inner axial lip 174 will wear significantly, not only reducing sealing performance but also increasing the torque required to rotate the hub wheel connected to the wheel, which is uneconomical. Therefore, an example of a technique for solving such problems is disclosed in Patent Document 1. That is, Patent Document 1 discloses a technology relating to a sealing device (corresponding to a sealing member) consisting of a so-called pack seal, which can suppress the pressure difference that occurs between a space portion located radially outside the axial lip (corresponding to the inner axial lip) (a space portion surrounded by the axial lip and the base, corresponding to the first lip space P1; hereinafter referred to as the "outer space portion") and a space portion located radially inside the axial lip (a space portion surrounded by the axial lip and the radial lip, corresponding to the second lip space P2; hereinafter referred to as the "inner space portion"), thereby preventing adhesion of the tip of the axial lip and suppressing wear of the axial lip. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-190323 Summary of the Invention [Problem to be solved by the invention]

[0008] In the sealing device of Patent Document 1, the bent extension portion of the slinger (corresponding to the sliding surface of the hub ring (inner member)) extends radially inward at an angle on the radially outer side of the tip of the axial lip and is arranged to cover the tip of the axial lip. Therefore, when the temperature inside the inner space rises and the air inside expands, the tip of the axial lip will initially rise radially outward, but will come into contact with the bent extension portion, maintaining the inner space in a sealed state, thereby preventing the air inside the inner space from passing through the tip of the axial lip and being discharged to the outside. Therefore, according to the sealing device in Patent Document 1, even if the temperature in the inner space subsequently drops to near room temperature, the pressure in the inner space can be prevented from becoming negative relative to the external atmospheric pressure, and the tip of the axial lip can be prevented from firmly adhering to the bent extension portion of the slinger. Furthermore, the outer space is connected to the outside, and air can freely enter and exit depending on the air pressure within the outer space, so it does not cause a pressure difference between the outer space and the inner space.

[0009] However, in the sealing device of Patent Document 1, when the tip of the axial lip rises radially outward, the grease in the inner space is pushed radially outward together with the air inside, and is pushed near the base of the bent extension portion. As a result, even if the temperature inside the inner space subsequently drops to near room temperature and the tip of the axial lip returns to its normal position, it is difficult for the grease that has been pushed near the base of the bent extension portion to return to the inner space again. Therefore, over time, the grease in the inner space gradually decreases, which accelerates wear at the tip of the axial lip and can cause an increase in torque when rotating the hub wheel connected to the wheel. Furthermore, as described above, the bent extension portion of the slinger is arranged radially outside the tip end of the axial lip, covering the tip end of the axial lip and extending at an angle radially inward. Therefore, when the slinger is moved axially to be assembled during the assembly process of the sealing device, the tip end of the axial lip and the bent extension portion are likely to interfere with each other, making the assembly work difficult.

[0010] The present invention has been made in consideration of the current problems described above, and has an object to provide a wheel bearing device equipped with a sealing member that can suppress the differential pressure generated between the inside and outside of the seal lip, suppress the reduction of the enclosed grease, prevent the tip of the seal lip from adhering to the sliding surface and becoming worn, and suppress an increase in rotational torque. [Means for solving the problem]

[0011] The problem to be solved by the present invention is as described above, and the means for solving this problem will now be described.

[0012] That is, the wheel bearing device according to the present invention comprises an inner member comprising an outer member having a double-row outer raceway surface on its inner circumference, a hub ring having a small-diameter step extending axially on its outer circumference, and at least one inner ring press-fitted into the small-diameter step of the hub ring, the inner member having a double-row inner raceway surface on its outer circumference that faces the double-row outer raceway surface, double-row rolling elements accommodated so as to be able to roll freely between the raceway surfaces of the outer member and the inner member, and a seal member that closes the open end of an annular space formed by the outer member and the inner member, wherein the seal member comprises a core metal fitted into the outer member, and a seal body made of an elastic material joined to the core metal, the seal body extending in the axial direction and having a seal lip at its tip end that is in slidable contact with the sliding surface of the inner member, and the tip end of the seal lip is provided with a plurality of protrusions that protrude toward the sliding surface and are arranged along the periphery of the tip end. [Effects of the Invention]

[0013] The present invention has the following effects. In other words, the wheel bearing device of the present invention can suppress the differential pressure that occurs between the inside and outside of the seal lip and suppress the reduction of the enclosed grease, thereby realizing a sealing member that prevents the tip of the seal lip from adhering to the sliding surface and wearing away, and can suppress an increase in rotational torque. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing the overall configuration of a wheel bearing device according to the present invention. [Figure 2] 2A and 2B are diagrams showing the overall configuration of an outer seal member in a first embodiment of the present invention, in which (a) is a side cross-sectional view thereof, and (b) is a front view seen in the direction of arrow X in FIG. 2A. [Figure 3] 2A and 2B are enlarged views of the portion indicated by area A1 in FIG. 1 in the first embodiment of the present invention, where (a) is an enlarged cross-sectional view seen in the direction of arrow Y1 in FIG. 2, and (b) is an enlarged cross-sectional view seen in the direction of arrow Y2 in FIG. 2. [Figure 4] 3(a) are enlarged views of a portion indicated by region A2 in FIG. 3(a), where (a) is an enlarged cross-sectional view showing the shape of the tip of the inner axial lip in the first embodiment, and (b) is an enlarged cross-sectional view showing the shape of the tip of the inner axial lip in another embodiment. [Figure 5] FIG. 10 is a diagram for explaining a wheel bearing device according to a second embodiment of the present invention, and is a front view showing the overall configuration of an outer seal member. [Figure 6] 1A and 1B are diagrams for explaining wheel bearing devices in the third to fifth embodiments of the present invention, in which (a) is an enlarged cross-sectional view of the portion indicated by area A1 in FIG. 1 in the third embodiment, (b) is an enlarged cross-sectional view of the portion indicated by area A3 in FIG. 1 in the fourth embodiment, and (c) is an enlarged cross-sectional view of the portion indicated by area A3 in FIG. 1 in the fifth embodiment. [Figure 7] 2 is an enlarged cross-sectional view of a portion indicated by an area A1 in FIG. 1 in a conventional wheel bearing device. DETAILED DESCRIPTION OF THE INVENTION

[0015] Next, one embodiment of the present invention will be described with reference to FIGS. For convenience, the description in this specification will be based on the inner side and the outer side defined by the direction of the arrow in FIG. Here, the "inner side" refers to the direction toward the inside of the vehicle body with respect to the wheel bearing device 1 when it is attached to the vehicle body of an automobile or the like. In addition, "outer side" means the side opposite to the inner side of the wheel bearing device 1 when it is attached to the body of a vehicle such as an automobile, i.e., the direction of the wheel side that is rotatably supported by the wheel bearing device 1.

[0016] In addition, in this specification, the direction parallel to the rotation axis G (see Figure 1) of the wheel bearing device 1 is defined as the "axial direction," the direction perpendicular to the rotation axis G of the wheel bearing device 1 is defined as the "radial direction," and the direction along the arc centered on the rotation axis G of the wheel bearing device 1 is defined as the "circumferential direction."

[0017] [Overall configuration of wheel bearing device 1 (first embodiment)] First, the overall configuration of a wheel bearing device 1 according to a first embodiment of the present invention will be described with reference to FIG.

[0018] The wheel bearing device 1 is a device for supporting a wheel rotatably in a suspension system of a vehicle such as an automobile. The wheel bearing device 1 mainly comprises an outer ring 2 which is an example of an outer member, a hub ring 3, an inner ring 4, double-row (two-row in this embodiment) ball rows 5·5 which are rolling elements, and an inner side seal member 6 and an outer side seal member 7 which are examples of seal members.

[0019] The outer ring 2 supports the hub ring 3 and the inner ring 4 . The outer ring 2 is made of a substantially hollow cylindrical member, and its inner end is provided with an inner opening 2a into which an inner seal member 6 can be fitted, and its outer end is provided with an outer opening 2b into which an outer seal member 7 can be fitted.

[0020] The inner circumference of the outer ring 2 is provided with double-row (two-row in this embodiment) outer raceway surfaces 2c·2c that are annular in the circumferential direction and coaxially spaced apart in the axial direction, and the outer circumference of the outer ring 2 is integrally provided with a flange (not shown) that can be attached to a knuckle of a suspension device.

[0021] The hub wheel 3 is a member that constitutes an inner member together with the inner ring 4, and supports a vehicle wheel (not shown) so that it can rotate freely. The hub ring 3 is made of a substantially solid cylindrical member, and on the outer periphery on the inner side thereof, a small diameter stepped portion 3a that extends in the axial direction and has a reduced diameter is provided. A wheel mounting flange 3b, to which the wheel can be mounted, is integrally provided at the outer end of the hub wheel 3 so as to expand in diameter in an arc shape when viewed in radial cross section.

[0022] A plurality of hub bolts 3c for fastening the wheel to the hub wheel 3 are press-fitted into the wheel mounting flange 3b. Additionally, on the outer periphery of the outer hub wheel 3, an inner raceway surface 3d having an annular shape in the circumferential direction is provided opposite the outer raceway surface 2c on the outer side.

[0023] An inner ring 4 is press-fitted into the small diameter step 3 a of the hub wheel 3 . The inner ring 4 is a component that constitutes the inner member together with the hub ring 3, and is made of a substantially hollow cylindrical component, with a circumferentially annular inner raceway surface 4a on its outer periphery, facing the inner-side outer raceway surface 2c described above.

[0024] The inner ring 4 is fixed to the hub wheel 3 by plastically deforming (crimping) the inner end of the hub wheel 3 radially outward. The method of fixing the inner ring 4 to the hub wheel 3 is not limited to this embodiment, and for example, a fastening member such as a nut may be screwed and fixed at the inner end of the hub wheel 3.

[0025] In this way, in the inner member formed by the hub ring 3 and the inner ring 4, the inner raceway surface 4a provided on the inner ring 4 is arranged at the inner end, and the inner raceway surface 3d provided on the hub ring 3 is arranged at the outer end, and these double row (two rows in this embodiment) inner raceway surfaces 3d·4a are arranged opposite the two rows of outer raceway surfaces 2c·2c provided on the outer ring 2 described above.

[0026] The two rows of balls 5 , 5 support an inner member consisting of the hub ring 3 and the inner ring 4 so as to be rotatable relative to the outer ring 2 . Each ball row 5 is made up of a plurality of balls 5a arranged in an annular shape and a cage 5b that holds these balls 5a so that they can roll freely.

[0027] These two rows of balls 5·5 are each housed in a rollable manner within two installation spaces Q1·Q1 formed between two rows of outer raceway surfaces 2c·2c provided at the inner and outer ends of the outer ring 2, respectively, and two rows of inner raceway surfaces 3d·4a provided at the inner and outer ends of the inner member (hub ring 3 and inner ring 4), respectively.

[0028] As described above, the wheel bearing device 1 in this embodiment is configured as a double-row angular contact ball bearing made up of the outer ring 2, hub ring 3, inner ring 4, and two rows of balls 5·5. The configuration of the wheel bearing device 1 is not limited to this embodiment, and may be configured as a double-row tapered roller bearing, for example, using a tapered roller row instead of the ball row 5.

[0029] The inner seal member 6 closes the inner open end of the annular space Q2 formed by the outer ring 2 and the inner member (the hub ring 3 and the inner ring 4). The inner seal member 6 includes a substantially cylindrical seal plate 6a, a substantially cylindrical slinger 6b, and the like.

[0030] The sealing plate 6a is formed by pressing a circular steel plate made of, for example, a ferritic stainless steel plate (JIS standard SUS430 series, etc.), an austenitic stainless steel plate (JIS standard SUS304 series, etc.), or a dustproof treated cold rolled steel plate (JIS standard SPCC series, etc.). The seal plate 6a is annular and bent in an L-shape when viewed in the circumferential direction, and a plurality of seal lips 6a1 made of, for example, synthetic rubber are vulcanized and bonded to the inner side thereof.

[0031] The seal lip 6a1 is formed of an elastic body made of synthetic rubber such as NBR (acrylonitrile butadiene rubber), HNBR (hydrogenated acrylonitrile butadiene rubber) which has excellent heat resistance, EPDM (ethylene propylene rubber), ACM (polyacrylic rubber) which has excellent heat resistance and chemical resistance, FKM (fluororubber), or silicone rubber.

[0032] On the other hand, like the sealing plate 6a, the slinger 6b is formed by pressing a circular steel plate made of, for example, a ferritic stainless steel plate (JIS standard SUS430 series, etc.), an austenitic stainless steel plate (JIS standard SUS304 series, etc.), or a dustproof treated cold rolled steel plate (JIS standard SPCC series, etc.). The slinger 6b is annular and is made of a steel plate or the like bent into an L shape when viewed in the circumferential direction, and an annular magnetic encoder 6b1 is vulcanization-bonded to the inner side thereof.

[0033] The magnetic encoder 6b1 is configured as a rotary encoder for detecting the rotational speed of a wheel, in which magnetic powder such as ferrite is mixed into an elastomer such as rubber, so that N and S magnetic poles are magnetized alternately and at equal intervals in the circumferential direction, thereby changing the magnetic characteristics.

[0034] The seal plate 6a is fitted into the inner opening 2a of the outer ring 2 so as to be coaxial with the outer ring 2 and with the plurality of seal lips 6a1 facing the slinger 6b side. The slinger 6b is fitted onto the outer periphery of the inner ring 4 coaxially with the inner ring 4 and on the inner side of the sealing plate 6a so as to face the sealing plate 6a. As a result, the inner seal member 6 is configured as a pack seal made up of the seal plate 6a and the slinger 6b.

[0035] The outer seal member 7 seals the outer opening end (more specifically, the outer opening 2b of the outer ring 2) of the annular space Q2 formed by the outer ring 2 and the inner member (hub ring 3 and inner ring 4). The configuration of the outer seal member 7 will be described in detail later.

[0036] As described above, the wheel bearing device 1 in this embodiment is configured as a wheel bearing device of a third-generation structure in which the inner raceway surface 3d, on which the outer ball row 5 can roll, is formed directly on the outer periphery of the hub wheel 3, but is not limited to this. For example, the wheel bearing device may be configured as a wheel bearing device of a second-generation structure in which a pair of inner rings are press-fitted and fixed coaxially to each other on the outer periphery of the hub wheel, and an inner raceway surface, on which the ball row can roll, is formed directly on the outer periphery of each inner ring.

[0037] [Configuration of outer seal member 7] Next, the configuration of the outer seal member 7 will be described in detail with reference to FIGS. As shown in FIG. 3(a), the outer seal member 7 includes a core metal 71 fitted to the outer ring 2, and a seal body 72 made of an elastic body joined to the core metal 71.

[0038] The core wire 71 is formed by pressing a circular steel plate made of, for example, a ferritic stainless steel plate (such as JIS standard SUS430 series), an austenitic stainless steel plate (such as JIS standard SUS304 series), or a dustproof treated cold rolled steel plate (such as JIS standard SPCC series). The core metal 71 is mainly composed of a cylindrical portion 71a, a curved portion 71b, a disk portion 71c, and the like.

[0039] The cylindrical portion 71 a is formed in a hollow cylindrical shape extending in the axial direction, and the outer diameter thereof is set to be approximately equal to the inner diameter of the outer side opening 2 b of the outer ring 2 . The curved portion 71b is formed in a circular ring shape that is convex toward the outer side in the axial direction (see Figure 1) when viewed in the circumferential direction, and is provided continuously from the outer end of the cylindrical portion 71a toward the radially inner side. Furthermore, the disk portion 71c is formed in the shape of an upright disk, and is provided continuously from the end of the curved portion 71b toward the inside in the radial direction.

[0040] On the other hand, a seal body 72 is joined to the outer side surface of the core metal 71 so as to wrap around toward the outer circumferential surface of the cylindrical portion 71a, and the outer seal member 7 has a so-called half-metal structure.

[0041] The outer side sealing member 7 is fitted into the outer side opening 2b of the outer ring 2 (i.e., the outer side end of the aforementioned annular space Q2 (see Figure 1), which is the inner circumference of the outer ring 2) via the cylindrical portion 71a of the core metal 71. This increases the airtightness of the annular space Q2 of the wheel bearing device 1, and the outer seal member 7 can protect the inside of the bearing.

[0042] The sealing body 72 is formed from an elastic body made of synthetic rubber such as NBR (acrylonitrile-butadiene rubber), HNBR (hydrogenated acrylonitrile-butadiene rubber) which has excellent heat resistance, EPDM (ethylene propylene rubber), ACM (polyacrylic rubber) which has excellent heat resistance and chemical resistance, FKM (fluororubber), or silicone rubber, and is integrally joined to the core metal 71 by vulcanization bonding. The seal body 72 also has a base 72a that covers the outer side surface of the core metal 71, and a plurality of seal lips 72b, 72b, 72b that extend axially from the base 72a and whose tip ends are in slidable contact with the sliding surfaces (flat surface portion 31a, axial circumferential surface portion 31b, and arc surface portion 31c, which will be described later) of the hub wheel 3, which is the inner member.

[0043] The seal lips 72b are each formed in an annular shape and are composed of an outer axial lip 73, an inner axial lip 74, and a radial lip 75 that are coaxially arranged.

[0044] Here, the outer axial lip 73 is formed so as to be inclined radially outward and extend in one direction in the axial direction (towards the outer side in this embodiment) in a circumferential cross section. The inner axial lip 74 is located radially inward of the outer axial lip 73, and is formed so as to extend in one axial direction (toward the outer side) while inclining radially outward when viewed in a circumferential cross section. Furthermore, the radial lip 75 is located radially inward of the inner axial lip 74, and when viewed in circumferential cross section, is formed so as to incline radially inward and extend in the other axial direction (in this embodiment, toward the inner side (see Figure 1)).

[0045] The outer axial lip 73 , the inner axial lip 74 , and the radial lip 75 are brought into sliding contact with the stepped portion 31 of the hub wheel 3 at their respective tip ends.

[0046] Here, the step portion 31 refers to a portion provided at the base end of the wheel mounting flange 3b of the hub wheel 3 that protrudes toward the inner side. Specifically, the step portion 31 is composed of a flat portion 31a consisting of a plane perpendicular to the rotation axis G (see Figure 1), an axial circumferential surface portion 31b located radially inside the flat portion 31a and extending coaxially with the rotation axis G, and an arc surface portion 31c that smoothly connects the flat portion 31a and the axial circumferential surface portion 31b. Additionally, the outer peripheral surface portion 31d of the step portion 31 is inclined at a predetermined curvature, and smoothly connects from the outer edge of the flat portion 31a to the bearing surface 31e of the hub bolt 3c (see FIG. 1).

[0047] Then, the tip of the outer axial lip 73 contacts the flat surface portion 31a of the stepped portion 31 through the oil film of the grease Z which is a lubricant, and the tip of the inner axial lip 74 contacts the arc surface portion 31c of the stepped portion 31 through the oil film. Further, the tip of the radial lip 75 contacts the axial circumferential surface portion 31b of the stepped portion 31 through the oil film. Thereby, between these plurality of seal lips 72b·72b·72b and the stepped portion 31 of the hub ring 3, a sealed space partitioned by the inner axial lip 74, that is, a first lip space P1 isolated by the outer axial lip 73 and the inner axial lip 74, and a second lip space P2 isolated by the radial lip 75 and the inner axial lip 74 are formed.

[0048] By the way, as shown in Fig. 2(a), in the present embodiment, a plurality of protrusions 74a·74a··· are provided at the tip of the inner axial lip 74 which is an example of the seal lip 72b. Each of the protrusions 74a·74a··· is arranged at a predetermined interval along the circumferential direction. Each protrusion 74a is formed so as to protrude toward the arc surface portion 31c (also refer to Fig. 3(a)) which is a sliding surface provided on the stepped portion 31 (refer to Fig. 3(a)).

[0049] Specifically, as shown in Fig. 2(b), each protrusion 74a is formed as an arc-shaped tongue piece extending along the tip of the inner axial lip 74 in the axial direction view, and the radially inner corners 74a1 at both circumferential ends thereof are formed to have a roundness with a radius R of 3 mm or less (0 mm < R ≤ 3 mm) for the purpose of reducing the contact area between the protrusion 74a and the arc surface portion 31c (refer to Fig. 3) and reducing the sliding resistance when the outer seal member 7 rotates.

[0050] Also, as shown in Fig. 4(a), in the circumferential cross-sectional view, both corner portions 74a2 on the arc surface portion 31c side of each protrusion 74a are also formed to have a rounded shape for the purpose of reducing the sliding resistance when the outer seal member 7 rotates, similar to the corner portion 74a1. In addition, as another embodiment of each protrusion 74a, for example, as shown in Fig. 4(b), for the purpose of further reducing the sliding resistance when the outer seal member 7 rotates, the shape on the arc surface portion 31c side may be formed in a substantially semi-circular shape in the cross-sectional view.

[0051] And, as shown in Fig. 4(a), the thickness from the side surface on the arc surface portion 31c side to the opposite side surface in each protrusion 74a, that is, the height dimension H of each protrusion 74a, is set to be 0.6 mm or less (0 mm < H ≤ 0.6 mm) in consideration of the air permeability between the first lip space P1 and the second lip space P2 between adjacent protrusions 74a·74a and the mud resistance of the inner axial lip 74.

[0052] A plurality of protrusions 74a·74a··· having such a shape are arranged at equal intervals with a predetermined gap along the peripheral edge of the tip of the inner axial lip 74 as shown in Fig. 2(b). And, a virtual circle passing through the central position (center of gravity) in the circumferential direction of each protrusion 74a and centered on the rotation axis G (refer to Fig. 1) is defined as a virtual pitch circle S1, and a virtual circle that is inscribed inside each protrusion 74a in the radial direction and is coaxial with the virtual pitch circle S1 with a radius dimension of r is defined as a virtual inscribed circle S2. When defined in this way, the arc length dimension T of each protrusion 74a on the virtual pitch circle S1 is set to be not more than the length of a semi-circle of the virtual inscribed circle S2 (0 < T ≤ πr). Also, in the gap between adjacent protrusions 74a·74a, the separation dimension L on the virtual pitch circle S1 is also set to be not more than the length of a semi-circle of the virtual inscribed circle S2 (0 < L ≤ πr), similar to the length dimension T.

[0053] Regarding the relationship between the length dimension T and the clearance dimension L, it is desirable to set the clearance dimension L to be smaller than the length dimension T (T>L) in order to minimize the decrease in muddy water resistance of the inner axial lip 74. Furthermore, the fewer the number of protrusions 74a, the higher the muddy water resistance of the inner axial lip 74 can be maintained, and the length dimension T and spacing dimension L described above are set taking this into consideration.

[0054] In this manner, in this embodiment, since multiple protrusions 74a·74a··· are provided at the tip end of the inner axial lip 74, as shown in Figure 3(b), between adjacent protrusions 74a·74a, the tip end of the inner axial lip 74 is in a non-contact state with the sliding surface (arcuate surface portion 31c) of the hub wheel 3, which is the inner member, resulting in multiple gaps D·D···.

[0055] As a result, the first lip space P1 and the second lip space P2 separated by the inner axial lip 74 are connected via the gap D, and the pressure in the first lip space P1 and the pressure in the second lip space P2 are always maintained at an equal level, thereby suppressing the pressure difference that occurs between the first lip space P1 and the second lip space P2.

[0056] Furthermore, by having multiple gaps D·D···, the tip end of the inner axial lip 74 comes into contact with the arc surface portion 31c only via the multiple protrusions 74a·74a···, and as compared to the conventional case in which the entire tip end of the inner axial lip 74 comes into contact with the arc surface portion 31c, the contact area is reduced, thereby enabling to reduce the rotational torque of the wheel bearing device 1.

[0057] Furthermore, even if the grease Z is suddenly pushed radially outward through the tip of the inner axial lip 74 due to, for example, centrifugal force, the pushed-out grease Z will pass through multiple gaps D·D··· due to the influence of gravity, etc., and be pulled back to its original position, i.e., radially inward at the tip of the inner axial lip 74. Therefore, the grease Z at the tip of the inner axial lip 74 does not gradually decrease over time, so that wear at the tip can be suppressed and an increase in the rotational torque of the wheel bearing device 1 can be prevented.

[0058] On the other hand, the occurrence of such multiple gaps D·D··· may reduce the muddy water resistance of the inner axial lip 74, but as shown in Figure 3(a), the tip of the inner axial lip 74 contacts the sliding surface (arcuate surface portion 31c) of the hub wheel 3, which is the inner member, via multiple protrusions 74a·74a···, and the first lip space P1 and the second lip space P2 are maintained in a sealed state at least in the area where the protrusions 74a are provided, so the reduction in the muddy water resistance can be minimized.

[0059] In this embodiment, the grease Z sealed in the gap between the tip of each seal lip 72b and the sliding surface (flat surface portion 31a, axial circumferential surface portion 31b, and arc surface portion 31c) of the inner member, the hub wheel 3, has a mixable consistency range of 175 to 385.

[0060] Generally, the mixed consistency range of the grease sealed in the sealing member is often set to 400 or less, but in the wheel bearing device 1 of this embodiment, the mixed consistency range of the sealed grease Z is lower than that of general grease, and a high-viscosity grease Z is used.

[0061] Therefore, for example, even if the relative rotation between the outer seal member 7 and the hub wheel 3 is repeated during operation of a vehicle equipped with the wheel bearing device 1, centrifugal force, etc., can prevent the grease Z from being discharged radially outward of the inner axial lip 74, i.e., toward the first lip space P1, through the gap D, and can remain so as to block the gap D at least temporarily. As a result, the grease Z can maintain the second lip space P2 in the gap D in a sealed state, and the deterioration of the muddy water resistance of the inner axial lip 74 can be more reliably suppressed.

[0062] As described above, in the wheel bearing device 1 of this embodiment, the tip of the seal lip 72b (more specifically, the inner axial lip 74) is provided with a plurality of protrusions 74a·74a··· that protrude toward the sliding surface of the hub wheel 3, which is the inner member, i.e., the arc surface portion 31c, and are arranged at equal intervals with a predetermined gap along the periphery of the tip. Therefore, the plurality of protrusions 74a form a plurality of gaps D between adjacent protrusions 74a.

[0063] Therefore, for example, as described above, when a vehicle equipped with the wheel bearing device 1 is operated, the air in the first lip space P1 and the second lip space P2 each expands, and even if the air in the first lip space P1 passes through the tip of the outer axial lip 73 and is discharged to the outside, and the air in the second lip space P2 passes through the tip of the radial lip 75 and is discharged to the outside, the differential pressure between the inside and outside of the inner axial lip 74 can be suppressed via the above-mentioned multiple gaps D·D···, which may occur when the temperature then drops to near room temperature.

[0064] Furthermore, the grease Z that has passed through the tip end of the inner axial lip 74 and has been extruded to the outside can be recovered again via the plurality of gaps D·D···. As a result, the tip end of the inner axial lip 74 can be prevented from being attracted to the sliding surface (arcuate surface portion 31c) of the hub wheel 3 and from being worn away.

[0065] Furthermore, since the tip end of the inner axial lip 74 can be prevented from being stuck to the sliding surface (arcuate surface portion 31c) of the hub wheel 3, an increase in rotational torque in the wheel bearing device 1 can be suppressed.

[0066] In this embodiment, multiple protrusions 74a·74a··· are provided only at the tip end of the inner axial lip 74, but this is not limited to this. For example, multiple protrusions 74a·74a··· may be provided at the tip end of the outer axial lip 73 or the radial lip 75, which are other examples of the seal lip 72b.

[0067] By providing multiple protrusions 74a·74a··· at the tip of the outer axial lip 73, the pressure difference that occurs between the external space located outside the outer axial lip 73 and the first lip space P1 located inside can be suppressed through multiple gaps D·D··· formed between adjacent protrusions 74a·74a, and grease Z that has passed through the tip of the outer axial lip 73 and been temporarily pushed out can be recovered again through the multiple gaps D·D···. As a result, it is possible to prevent the tip end of the outer axial lip 73 from being attracted to the sliding surface of the hub wheel 3, which is the inner member, that is, the flat surface portion 31a, and from being worn away. Furthermore, since the tip end of the outer axial lip 73 can be prevented from being stuck to the flat surface portion 31a, an increase in rotational torque in the wheel bearing device 1 can be suppressed.

[0068] Alternatively, by providing multiple protrusions 74a·74a··· at the tip of the radial lip 75, the pressure difference that occurs between the annular space Q2 (see Figure 1) located on the outside of the radial lip 75 and the second lip space P2 located on the inside can be suppressed through multiple gaps D·D··· formed between adjacent protrusions 74a·74a, and the grease Z that has passed through the tip of the radial lip 75 and been temporarily pushed out toward the annular space Q2 can be recovered again through the multiple gaps D·D···. As a result, it is possible to prevent the tip end of the radial lip 75 from being attracted to the sliding surface of the hub wheel 3, which is the inner member, that is, the shaft circumferential surface portion 31b, and from being worn away. Furthermore, since the tip end of the radial lip 75 can be prevented from being stuck to the shaft circumferential surface portion 31b, an increase in rotational torque in the wheel bearing device 1 can be suppressed.

[0069] [Configuration of wheel bearing device 201 (second embodiment)] Next, the configuration of a wheel bearing device 201 according to a second embodiment will be described with reference to FIGS. In Figure 1, the wheel bearing device 201 in the second embodiment has a configuration that is approximately the same as the wheel bearing device 1 in the first embodiment described above, but differs from the wheel bearing device 1 mainly in the positioning of the protrusion 274a (see Figure 5) provided on the outer side seal member 207. Therefore, in the following description, differences from the wheel bearing device 1 described above will be mainly described, and descriptions of configurations equivalent to those of the wheel bearing device 1 will be omitted.

[0070] As shown in FIG. 5, a plurality of protrusions 274a are provided at the tip end of an inner axial lip 274, which is an example of a seal lip 272b. Each protrusion 274a is formed to protrude toward an arcuate surface portion 31c (also see FIG. 3(a)) serving as a sliding surface provided on the hub wheel 3 (see FIG. 3(a)). The details of the shape of each of the protrusions 274a are the same as those of the protrusions 74a of the wheel bearing device 1 described above, and therefore will not be described here.

[0071] The plurality of protrusions 274a are arranged at equal intervals with predetermined gaps between them along the periphery of the tip end of the inner axial lip 274 in the region opposite the road surface side. Here, "road surface side" means the side where the road surface is located (e.g., the lower side) with respect to the wheel bearing device 201 (see Figure 1) when attached to the body of an automobile or the like, and "opposite road surface side" means the side opposite to the road surface (e.g., the upper side).

[0072] Specifically, when viewed in the axial direction, if a virtual circle that passes through the center position (center of gravity) of each protrusion 274a and has its center at the rotation axis G (see Figure 1) is defined as a virtual pitch circle S1, the multiple protrusions 274a·274a··· are arranged in the area on the opposite side of the virtual pitch circle S1 to the road surface, so that the center position (center of gravity) of each protrusion 274 in the circumferential direction is located on a virtual arc S1a whose central angle α is greater than 0° and is 180° or less.

[0073] The tip end of the inner axial lip 274 is in sliding contact with the arc surface portion 31c of the stepped portion 31 via the multiple protrusions 274a·274a··· in the region on the virtual arc S1a, while in the region on the virtual pitch circle S1 excluding the virtual arc S1a where these multiple protrusions 274a·274a··· are not provided, the tip end is in direct sliding contact with the arc surface portion 31c of the stepped portion 31.

[0074] With this configuration, in the area facing the road surface where foreign matter such as muddy water is relatively likely to enter from the outside, the tip of the inner axial lip 274 is brought into contact with the arc surface portion 31c of the hub wheel 3, ensuring high muddy water resistance, while in the area facing the opposite road surface, the differential pressure generated between the inside and outside of the inner axial lip 274 is suppressed via multiple gaps D·D··· (see Figure 3(b)), thereby suppressing wear at the tip of the inner axial lip 274 and an increase in rotational torque in the wheel bearing device 201.

[0075] [Configuration of wheel bearing device 301 (third embodiment)] Next, the configuration of a wheel bearing device 301 according to the third embodiment will be described with reference to FIG. 1 and FIG. 6(a). In Figure 1, the wheel bearing device 301 in the third embodiment has a configuration that is approximately the same as the wheel bearing device 1 in the first embodiment described above, but differs from the wheel bearing device 1 mainly in that the configuration of the outer side seal member 307 is a type that includes a dam portion 376 (see Figure 6(a)). Therefore, in the following description, differences from the wheel bearing device 1 described above will be mainly described, and descriptions of configurations equivalent to those of the wheel bearing device 1 will be omitted.

[0076] As shown in FIG. 6(a), the outer seal member 307 includes a core metal 371 fitted to the outer ring 2, and a seal body 372 made of an elastic body joined to the core metal 371.

[0077] The core metal 371 is mainly composed of a cylindrical portion 371a, a bent portion 371b, a disk portion 371c, a flange portion 371d, and the like. The material of the core metal 371 is the same as that of the core metal 71 of the outer seal member 7 in the wheel bearing device 1 described above, and therefore a description thereof will be omitted.

[0078] The cylindrical portion 371a extends from the end of the outer side (see Figure 1) of the outer ring 2 toward the inner side (also see Figure 1), and its outer diameter is set to be approximately equal to the inner diameter of the outer side opening 2b of the outer ring 2. The bent portion 371b is bent radially inward from the inner end of the cylindrical portion 371a, and then extends radially outward to the middle of the cylindrical portion 371a in the axial direction. Furthermore, the disk portion 371c extends radially inward from the outer end of the bent portion 371b to the vicinity of the outer periphery of the hub wheel 3.

[0079] The flange portion 371d extends radially outward from the outer end of the cylindrical portion 371a. The radially outer end of the flange portion 371d is located radially outward compared to the outer peripheral surface at the outer end of the outer ring 2, and the radially outer end of the flange portion 371d is provided with an outer edge portion 371e that extends toward the inner side while maintaining a predetermined gap with the outer peripheral surface.

[0080] On the other hand, the seal body 372 has a plurality of seal lips 372b·372b·372b provided on the disc portion 371c of the core bar 371, a dam portion 376 provided on the outer edge portion 371e of the core bar 371, and the plurality of seal lips 372b·372b·372b are composed of an outer axial lip 373, an inner axial lip 374, and a radial lip 375. The material of the seal body 372 is the same as that of the seal body 72 of the outer seal member 7 in the wheel bearing device 1 described above, and therefore a description thereof will be omitted.

[0081] The outer axial lip 373 is formed to extend toward the outer side and radially outward. The inner axial lip 374 is provided radially inward relative to the outer axial lip 373 and is formed so as to extend toward the outer side. Furthermore, the radial lip 375 is provided radially inward relative to the inner axial lip 374, and is formed so as to extend toward the inner side and radially inward.

[0082] These outer axial lip 373, inner axial lip 374, and radial lip 375 are arranged coaxially with each other and are in sliding contact with the sliding surfaces (flat surface portion 31a, axial circumferential surface portion 31b, and arc surface portion 31c) provided on the hub wheel 3.

[0083] The dam portion 376 is provided in a generally rectangular shape in a circumferential cross section, and is arranged at the outer end of the outer ring 2 so as to protrude radially outward while contacting the outer peripheral surface. The dam portion 376 is provided on the core metal 371 so as to cover the radially outer end of the flange portion 371d and the outer edge portion 371e.

[0084] In the outer seal member 307 configured as described above, a plurality of protrusions 374a are provided at the tip end of the inner axial lip 374, which is an example of the seal lip 372b. The configuration of the protrusion 374a is the same as that of the protrusion 74a of the outer seal member 7 in the wheel bearing device 1 described above, and therefore a description thereof will be omitted.

[0085] By having such a configuration, the outer seal member 307 in the third embodiment can also suppress the pressure difference that occurs between the first lip space P1 located on the outside of the inner axial lip 374 and the second lip space P2 located on the inside through the multiple gaps D·D··· formed between adjacent protrusions 374a·374a (see Figure 3(b)), and can also recover the grease Z (also see Figure 3(b)) that has passed through the tip end of the inner axial lip 374 and been temporarily extruded to the outside. As a result, it is possible to prevent the tip end of the inner axial lip 374 from being attracted to the sliding surface of the hub wheel 3, which is the inner member, that is, the arcuate surface portion 31c, and from being worn away. Furthermore, since the tip end of the inner axial lip 374 can be prevented from being attracted to the arc surface portion 31c, an increase in rotational torque in the wheel bearing device 301 can be suppressed.

[0086] [Configuration of wheel bearing device 401 (fourth embodiment)] Next, the configuration of a wheel bearing device 401 according to the fourth embodiment will be described with reference to FIG. 1 and FIG. 5(b). In Figure 1, the wheel bearing device 401 in the fourth embodiment has a configuration that is approximately the same as the wheel bearing device 1 in the first embodiment described above, but differs from the wheel bearing device 1 mainly in that the seal lip 406a1 of the inner side seal member 406 is provided with multiple protrusions 474a·474a··· (see Figure 5(b)). Therefore, in the following description, differences from the wheel bearing device 1 described above will be mainly described, and descriptions of configurations equivalent to those of the wheel bearing device 1 will be omitted.

[0087] As shown in FIG. 5(b), the inner seal member 406 includes a substantially cylindrical seal plate 406a, a substantially cylindrical slinger 406b, and the like. The main configurations of the sealing plate 406a and the slinger 406b are the same as those of the sealing plate 6a and the slinger 6b in the wheel bearing device 1 described above, and therefore a description thereof will be omitted.

[0088] The seal lip 406a1 is composed of an outer axial lip 473, an inner axial lip 474, and a radial lip 475, each of which is formed in an annular shape and arranged coaxially.

[0089] The outer axial lip 473 is formed so as to be inclined radially outward and extend axially toward the inner side (see FIG. 1) in the circumferential cross section. The inner axial lip 474 is located radially inward of the outer axial lip 473, and is formed so as to extend axially inward while inclining radially outward in a circumferential cross-sectional view. Furthermore, the radial lip 475 is located radially inward of the inner axial lip 474, and is formed so as to incline radially inward and extend axially outward (see FIG. 1) in a circumferential cross-sectional view.

[0090] The outer axial lip 473 and the inner axial lip 474 are in sliding contact at their respective tip ends with the sliding surface of the inner ring 4, which is the inner member, that is, the flat surface on the outer side of the slinger 406b. Further, the radial lip 475 is in sliding contact at its tip end with the sliding surface of the inner ring 4, which is the inner member, that is, the outer peripheral surface of the slinger 406b.

[0091] In the inner seal member 406 configured as described above, a plurality of protrusions 474a are provided at the tip end of the inner axial lip 474, which is an example of the seal lip 406a1. The configuration of the protrusion 474a is the same as that of the protrusion 74a of the outer seal member 7 in the wheel bearing device 1 described above, and therefore a description thereof will be omitted.

[0092] By having such a configuration, the inner side seal member 406 in the fourth embodiment can also suppress the pressure difference that occurs between the third lip space P3 located on the outside of the inner axial lip 474 and the fourth lip space P4 located on the inside through the multiple gaps D·D··· formed between adjacent protrusions 474a·474a (see Figure 3(b)), and can also recover the grease Z (also see Figure 3(b)) that has passed through the tip end of the inner axial lip 474 and been temporarily extruded to the outside. As a result, it is possible to prevent the tip end of the inner axial lip 474 from being attracted to and wearing down the sliding surface of the inner ring 4, which is the inner member, that is, the flat surface on the outer side of the slinger 406b. Furthermore, since the tip end of the inner axial lip 474 can be prevented from being attracted to the flat surface on the outer side of the slinger 406b, an increase in rotational torque in the wheel support bearing device 401 can be suppressed.

[0093] Furthermore, in the case of the inner side seal member 406 in the fourth embodiment, even if it is configured, for example, by a sealing device consisting of a so-called pack seal, there is no need to provide a curved extension portion on the slinger 406b that extends radially inwardly and inclined to cover the tip end of the axial lip (corresponding to the outer axial lip 473 in this embodiment) radially outside the tip end of the axial lip, as in the conventional case, and assembly work is easy.

[0094] [Configuration of wheel bearing device 501 (fifth embodiment)] Next, the configuration of a wheel bearing device 501 according to the fifth embodiment will be described with reference to FIG. 1 and FIG. 5(c). In Figure 1, the wheel bearing device 501 in the fifth embodiment, like the wheel bearing device 401 in the fourth embodiment, has a configuration that is approximately equivalent to the wheel bearing device 1 in the first embodiment described above, but differs from the wheel bearing device 1 mainly in that the seal lip 506a1 of the inner side seal member 506 is provided with a plurality of protrusions 574a·574a··· (see Figure 5(c)). Therefore, in the following description, differences from the wheel bearing device 1 described above will be mainly described, and descriptions of configurations equivalent to those of the wheel bearing device 1 will be omitted.

[0095] As shown in FIG. 5(c), the inner seal member 506 includes a substantially cylindrical seal plate 506a, a substantially cylindrical slinger 506b, and the like. The main configurations of the sealing plate 506a and the slinger 506b are the same as those of the sealing plate 6a and the slinger 6b in the wheel bearing device 1 described above, and therefore a description thereof will be omitted.

[0096] The seal lip 506a1 is composed of an outer axial lip 573, an inner axial lip 574, and a radial lip 575, each of which is formed in an annular shape and arranged coaxially.

[0097] The outer axial lip 573 is formed so as to be inclined radially outward and extend axially toward the inner side (see FIG. 1) in the circumferential cross section. The inner axial lip 574 is located radially inward of the outer axial lip 573, and is formed so as to extend axially toward the inner side while inclining radially inward in a circumferential cross-sectional view. Furthermore, the radial lip 575 is located radially inward of the outer axial lip 573, and is formed so as to incline radially inward and extend axially outward (see FIG. 1) in a circumferential cross-sectional view. The inner axial lip 574 is designed to have a thickness that increases toward the tip in order to improve rigidity.

[0098] The outer axial lip 573 has a tip end that is in sliding contact with the sliding surface of the inner ring 4, which is the inner member, that is, the flat surface on the outer side of the slinger 506b. Further, the inner axial lip 574 and the radial lip 575 are in sliding contact at their tip ends with the sliding surface of the inner ring 4, which is the inner member, that is, the outer peripheral surface of the slinger 506b.

[0099] In the inner seal member 506 configured as described above, a plurality of protrusions 574a are provided at the tip end of the inner axial lip 574, which is an example of the seal lip 506a1. The configuration of the protrusion 574a is the same as that of the protrusion 74a of the outer seal member 7 in the wheel bearing device 1 described above, and therefore a description thereof will be omitted.

[0100] By having such a configuration, the inner side seal member 506 in the fifth embodiment can also suppress the pressure difference that occurs between the third lip space P3 located on the outside of the inner axial lip 574 and the fourth lip space P4 located on the inside through the multiple gaps D·D··· formed between adjacent protrusions 574a·574a (see Figure 3(b)), and can also recover the grease Z (also see Figure 3(b)) that has passed through the tip end of the inner axial lip 574 and been temporarily extruded to the outside. As a result, it is possible to prevent the tip end of the inner axial lip 574 from being attracted to the sliding surface of the inner ring 4, which is the inner member, that is, the outer peripheral surface of the slinger 506b, and from being worn away. Furthermore, since the tip end of the inner axial lip 574 can be prevented from being attracted to the outer peripheral surface of the slinger 506b, an increase in rotational torque in the wheel support bearing device 501 can be suppressed.

[0101] Furthermore, in the case of the inner side seal member 506 in the fifth embodiment, even if it is configured, for example, by a sealing device consisting of a so-called pack seal, there is no need to provide a curved extension portion on the slinger 506b that extends radially inward at an angle to cover the tip end of the axial lip (corresponding to the outer axial lip 573 in this embodiment) radially outside the tip end of the axial lip, as in the conventional case, and assembly work is easy.

[0102] Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, which are merely examples, and it goes without saying that the present invention can be embodied in various other forms without departing from the spirit of the present invention. The scope of the present invention is indicated by the claims, and further includes the equivalent meanings set forth in the claims, and all modifications within the scope of the claims. [Explanation of symbols]

[0103] 1, 201, 301, 401, 501 Wheel bearing device 2 Outer ring (outer member) 2c Outer raceway surface 3 Hub Wheel 3a Small diameter stepped section 3d, 4a Inner raceway surface (inner member) 31a Flat part (sliding surface) 31b Shaft peripheral surface (sliding surface) 31c Arc surface part (sliding surface) 4. Inner Circle 5 Ball row (rolling element) 6, 406, 506 Inner seal material (seal material) 7, 207, 307 Outer seal material (seal material) 71, 371 Core 72, 372 seal body 72b, 272b, 372b, 406a1, 506a1 seal lip 73, 373, 473, 573 Outer axial lip 74, 274, 374, 474, 573 Inner axial lip 74a, 274a, 374a, 474a, 574a protrusion 75, 375, 475, 575 Radial lip Q2 Annular space S1a Virtual arc Z Grease

Claims

1. an outer member having a double-row outer raceway surface on its inner periphery; an inner member including a hub ring having an axially extending small diameter stepped portion on its outer periphery and at least one inner ring press-fitted into the small diameter stepped portion of the hub ring, the inner member having a double row inner raceway surface on its outer periphery that faces the double row outer raceway surface; double-row rolling elements rollably housed between the raceway surfaces of the outer member and the inner member; a seal member that closes an open end of an annular space formed by the outer member and the inner member, The sealing member is a core metal fitted to the outer member; a seal body made of an elastic body joined to the core metal, the seal body extends in the axial direction and has a seal lip at a tip end thereof that is in slidable contact with a sliding surface of the inner member, The tip end of the seal lip is provided with a plurality of protrusions that protrude toward the sliding surface and are arranged along the periphery of the tip end, Each of the protrusions comprises: In axial view, The radially inner corners at both circumferential ends are formed into a curved shape with a curvature radius of 3 mm or less, In a circumferential cross section, Both corners on the protruding side are formed in an arc shape, The plurality of protrusions are In axial view, The center position of each of the protrusions in the circumferential direction is located on the opposite side to the road surface, on a virtual arc with a central angle α exceeding 0° and not exceeding 180°. A wheel bearing device characterized in that:

2. The seal is sealed in a gap between the tip end of the seal lip and the sliding surface, The grease has a mixed consistency range of 175 to 385.

2. The wheel bearing device according to claim 1, wherein:

3. The sealing lip is an outer axial lip inclined radially outward and extending in one axial direction; an inner axial lip located radially inside the outer axial lip, inclined radially outward, and extending in one axial direction; a radial lip located radially inward of the inner axial lip, inclined radially inward, and extending in the other axial direction, The protrusion is provided at a tip end of the inner axial lip.

3. The wheel bearing device according to claim 1 or 2, wherein:

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