JP7776937B2 - Wheel bearing device - Google Patents

Description

The present invention relates to a wheel bearing device.

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, for example, a configuration in which 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 wheel well, the brake rotor, etc., in an exposed state.
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.

Incidentally, Figure 4 is a diagram showing an example of an outer-side sealing member 107 in a conventional wheel bearing device 101, and as shown in (a) of this figure, the tip portions of the multiple sealing lips 172b, 172b, 172b (outer axial lip 173, inner axial lip 174, and radial lip 175) of the sealing member 107 are all in contact with the sliding surfaces (flat portion 131a, axial circumferential surface portion 131b, and arc 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, an enclosed space separated by the inner axial lip 174 is formed, 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.

In the first lip space P1 and the second lip space P2, the annular gap formed by the tip of each seal lip 172b and the sliding surface is filled with grease Z, a lubricant.

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.
For example, as the volume of the air in the first lip space P1 increases, it is pushed radially outward (toward the direction of arrow B) and discharged to the outside, and as the volume of the air in the second lip space P2 increases, it is pushed axially to one side (toward the direction of arrow C) and discharged to the outside.

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 pressure relative to the external atmospheric pressure, so that, as shown in Figure 4(b), the tip of each seal lip 172b comes into contact with the sliding surface in a sticking manner, and the annular gap described above is crushed.
As a result, the grease Z sealed in the annular gap passes through the tip end of each seal lip 172b and is forced outward.

As a result, when operation of a vehicle equipped with the wheel bearing device 101 is resumed, the amount of grease Z sealed between the tip of each seal lip 172b and the sliding surface will be insufficient, making it impossible to obtain a sufficient oil film effect. This will result in significant wear across the entire tip of each seal lip 172b, not only reducing sealing performance but also increasing the contact area between the tip of each seal lip 172b and the sliding surface, which will increase the torque required to rotate the hub wheel connected to the wheel, potentially resulting in uneconomical operation.

An example of a technique for solving such problems is disclosed in Japanese Patent Application Laid-Open No. 2003-222299.
That is, Patent Document 1 discloses a technique in which a plurality of annular projections or annular grooves are formed continuously in the circumferential direction at the tip end of each seal lip.

Japanese Patent Application Laid-Open No. 2021-1637

According to the technology of Patent Document 1, even if, for example, macroscopically, the tip ends of each seal lip come into contact and stick to the sliding surface, and the enclosed grease is forced outward, microscopically, a predetermined amount of grease can be collected through the gaps between adjacent annular protrusions or annular grooves, and therefore at least the minimum necessary oil film effect can be obtained.
Therefore, it is possible to prevent significant wear across the entire tip of each seal lip, preventing the seal member from needing to be replaced earlier, and it is also possible to prevent the contact area between the tip of each seal lip and the sliding surface from increasing, preventing an increase in torque when rotating the hub wheel connected to the wheel.

However, the multiple annular protrusions or annular grooves are made up of minute protrusion shapes, and their protruding end faces come into contact with the sliding surface. Therefore, the period until the protrusion shapes disappear due to wear, etc. is relatively short, and after the protrusion shapes disappear, the tip portion immediately returns to a state equivalent to that of a conventional seal lip.
Therefore, it has been difficult to maintain at least the minimum necessary oil film effect between the tip end of each seal lip and the sliding surface for a relatively long period of time, to prevent significant progress of wear over the entire surface of the tip end of each seal lip, and to prevent an increase in the contact area between the tip end of each seal lip and the sliding surface.

The present invention was made in consideration of the current problems described above, and aims to provide a wheel bearing device equipped with a sealing member that can maintain at least the minimum necessary oil film effect for a relatively long period of time between the tip of the seal lip and the sliding surface with which the tip makes sliding contact, even if the grease previously sealed between the tip and the sliding surface with which the tip slides is forced out, and that can suppress wear across the entire tip of the seal lip.

The above is the problem that this invention aims to solve, and next we will explain the means for solving this problem.

That is, the bearing device for a wheel according to the present invention is a bearing device for a wheel comprising an outer member having a double-row outer raceway surface on its inner periphery, a hub ring having a small-diameter stepped portion extending axially on its outer periphery, and at least one inner ring press-fitted into the small-diameter stepped portion of the hub ring, an 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 accommodated in a rollable manner between the raceway surfaces of the outer member and the inner member, and a seal member that closes an open end of an annular space formed by the outer member and the inner member, The sealing member comprises a core bar fitted to the outer member and a sealing body made of an elastic material joined to the core bar, the sealing body extending in the axial direction and having a sealing lip at its tip that is in sliding contact with the sliding surface of the inner member, and the tip of the sealing lip is formed with an annular groove portion that, when viewed in circumferential cross section, is composed of a plurality of annular protrusions formed in an approximately triangular shape that continues along the arc shape of the curved surface , and a plurality of approximately inverted triangular grooves each formed between adjacent protrusions.

The present invention has the following effects.
In other words, with the wheel bearing device of the present invention, even if the grease that has been sealed in advance between the tip of the seal lip and the sliding surface with which the tip makes sliding contact is forced out, it is possible to maintain at least the minimum necessary oil film effect for a relatively long period of time, and it is possible to realize a sealing member that can suppress wear across the entire tip of the seal lip.

1 is a cross-sectional view showing the overall configuration of a wheel bearing device according to the present invention. 2 is a circumferential cross-sectional view of the outer seal member and the surrounding structure in the first embodiment of the present invention, and is an enlarged cross-sectional view of a portion indicated by region A1 in FIG. 1. FIG. 3A and 3B are diagrams showing the configuration of an outer seal member in a first embodiment of the present invention, in which FIG. 3A is a perspective view thereof, and FIG. 3B is an enlarged perspective view of a portion indicated by region B in FIG. 3A. 1A and 1B are circumferential cross-sectional views for explaining wheel bearing devices in second to fourth embodiments of the present invention, in which (a) is an enlarged cross-sectional view of a portion indicated by area A1 in FIG. 1 in the second embodiment, (b) is an enlarged cross-sectional view of a portion indicated by area A2 in FIG. 1 in the third embodiment, and (c) is an enlarged cross-sectional view of a portion indicated by area A2 in FIG. 1 in the fourth embodiment. 2A and 2B are enlarged views of a portion indicated by area A1 in FIG. 1 in a conventional wheel bearing device, in which (a) is an enlarged circumferential cross-sectional view showing an outer seal member in a normal state, and (b) is an enlarged circumferential cross-sectional view showing an outer seal member in a state in which the tip of the seal lip is adhered to the sliding surface.

Next, an 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, the "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.

In addition, in this specification, the direction parallel to the rotation axis G of the wheel bearing device 1 (see Figure 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."

[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.

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 sealing member 6 and an outer side sealing member 7 which are examples of sealing members.

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.

The inner circumference of the outer ring 2 is provided with a circumferentially annular double row (two rows in this embodiment) of outer raceways 2c, 2c that are spaced apart axially and coaxially arranged, and the outer circumference of the outer ring 2 is integrally provided with a flange (not shown) that can be attached to the knuckle of a suspension system.

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 has a small-diameter stepped portion 3a on the outer periphery of its inner side, which extends in the axial direction and has a reduced diameter.
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.

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

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.

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.

In this way, the inner member formed by the hub ring 3 and inner ring 4 has the inner raceway 4a provided on the inner ring 4 disposed at its inner end, and the inner raceway 3d provided on the hub ring 3 disposed at its outer end, with these double-row (two-row in this embodiment) inner raceway surfaces 3d and 4a disposed opposite the two-row outer raceway surfaces 2c and 2c provided on the outer ring 2 described above.

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 a ring, and a cage 5b that holds the balls 5a so that they can roll freely.

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

As described above, the wheel bearing device 1 in this embodiment is configured as a double-row angular contact ball bearing comprising the outer ring 2, the hub ring 3, the inner ring 4, and two rows of balls 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.

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 (hub ring 3 and inner ring 4).
The inner seal member 6 includes a substantially cylindrical seal plate 6a, a substantially cylindrical slinger 6b, and the like.

The sealing plate 6a 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 seal plate 6a is annular and bent in an L-shape when viewed in the circumferential direction, and a plurality of seal lips 6a1, 6a1, 6a1 made of, for example, synthetic rubber are vulcanized and bonded to the inner side thereof.

The seal lip 6a1 is formed from an elastic material 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 and chemical resistance, FKM (fluororubber), or synthetic rubber such as silicone rubber.

On the other hand, like the sealing plate 6a, the slinger 6b is also 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 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.

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, thereby magnetizing N and S poles alternately and at equal intervals around the circumference, changing the magnetic properties.

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, 6a1, 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, facing the sealing plate 6a.
As a result, the inner seal member 6 is configured as a pack seal consisting of the seal plate 6a and the slinger 6b.

The outer side sealing member 7 seals the outer side opening end (more specifically, the outer side 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.

As described above, the wheel bearing device 1 in this embodiment is configured as a wheel bearing device with 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. However, this is not limited to this. For example, the wheel bearing device may be configured as a wheel bearing device with a second-generation structure in which a pair of inner rings are press-fitted 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.

[Configuration of outer seal member 7]
Next, the configuration of the outer seal member 7 will be described in detail with reference to FIGS. 2, 3 and 5. FIG.
As shown in FIG. 2, 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 material joined to the core metal 71.

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.

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 an upright disk shape and is provided continuously from the end of the curved portion 71b toward the inside in the radial direction.

Meanwhile, a seal body 72 is joined to the outer side of the core metal 71 so that it wraps around toward the outer periphery of the cylindrical portion 71a, giving the outer seal member 7 a so-called half-metal structure.

The outer seal member 7 is fitted into the outer opening 2b of the outer ring 2 (i.e., the outer end of the annular space Q2 (see Figure 1) mentioned above, which is the inner circumference of the outer ring 2) via the cylindrical portion 71a of the core metal 71.
As a result, the annular space Q2 of the wheel support bearing device 1 is made more airtight, and the outer seal member 7 can protect the inside of the bearing.

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 of the core wire 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, described later) of the hub wheel 3, which is the inner member.

As shown in Figure 3(a), each of these multiple seal lips 72b, 72b, 72b is formed in an annular shape and is composed of an outer axial lip 73, an inner axial lip 74, and a radial lip 75 arranged coaxially.

Specifically, as shown in FIG. 2, the outer axial lip 73 is formed so as to be inclined radially outward and extend axially toward the outer side (see FIG. 1) in the 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 axially outward while inclining radially outward in a circumferential cross-sectional view.
Furthermore, the radial lip 75 is located radially inward of the inner axial lip 74, and is formed so as to extend in the axial inner direction (see Figure 1) while inclining radially inward when viewed in circumferential cross section.

The outer axial lip 73, inner axial lip 74, and radial lip 75 each have their tip portions in sliding contact with the stepped portion 31 of the hub wheel 3.

Here, the step portion 31 refers to a portion provided at the base end of the wheel mounting flange 3 b 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 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).

The tip of the outer axial lip 73 contacts the flat surface 31a of the step portion 31 via an oil film of grease Z, which is a lubricant, and the tip of the inner axial lip 74 contacts the arc surface 31c of the step portion 31 via the oil film, and further, the tip of the radial lip 75 contacts the axial circumferential surface 31b of the step portion 31 via the oil film.
As a result, between these multiple seal lips 72b, 72b, 72b and the step portion 31 of the hub wheel 3, an enclosed space separated by the inner axial lip 74 is formed, i.e., a first lip space P1 separated by the outer axial lip 73 and the inner axial lip 74, and a second lip space P2 separated by the radial lip 75 and the inner axial lip 74.

As shown in FIG. 3(b), in this embodiment, the outer axial lip 73 and the inner axial lip 74, which are examples of the seal lip 72b, are each provided at their tip ends with annular bulges 10, 10 extending circumferentially along the outer edges of the tip ends.
Since these bulge portions 10, 10 have approximately the same configuration, the following explanation will mainly describe the bulge portion 10 provided on the outer axial lip 73, and will omit the description of the bulge portion 10 provided on the inner axial lip 74.

As shown in FIG. 2, the bulging portion 10 is formed so as to bulge in an arc shape toward a flat portion 31a serving as a sliding surface provided on the step portion 31 in a circumferential cross section.
Furthermore, an annular groove 11 extending continuously in the circumferential direction is formed on a curved surface 10a of the bulging portion 10 that faces the sliding surface (flat surface portion 31a) (see FIGS. 3(a) and 3(b)).

The radius of curvature R1 of the bulge portion 10 is not particularly limited. However, even if the bulge portion 10 is provided at the tip of the inner axial lip 74 that contacts the arc surface portion 31c, which is the sliding surface, as will be described later, it is desirable that the radius of curvature R1 of the bulge portion 10 be less than or equal to the radius of curvature R2 of the arc surface portion 31c (R1 < R2) so that the curved surface 10a of the bulge portion 10 and the arc surface portion 31c are in line contact with each other.

The annular groove 11 is formed by a plurality of convex and concave shapes that are continuous along the arc shape of the curved surface 10 a in a circumferential cross section of the bulging portion 10 .
Specifically, the annular groove portion 11 is configured with a plurality of annular protrusions 11a, 11a..., which are formed in an approximately triangular shape when viewed in circumferential cross section, and are arranged coaxially and radially continuous along the curved surface 10a.
In other words, between adjacent protrusions 11a, 11a, grooves 11b having an approximately inverted triangular shape when viewed in circumferential cross section are formed, and the annular groove 11 is configured such that a plurality of protrusions 11a, 11a... constituting the convex portion and a plurality of grooves 11b, 11b... constituting the concave portion are alternately arranged in succession in the radial direction along the curved surface 10a.

The shape of each protrusion 11a is not limited to that of this embodiment, and may be, for example, generally trapezoidal, generally rectangular, or generally arc-shaped when viewed in circumferential cross section.

If an excessive external force is applied to the tip of the outer axial lip 73, for example, bending it radially outward, stress will concentrate in the annular groove 11. Therefore, providing the annular groove 11 in an area larger than necessary can reduce the rigidity of the outer axial lip 73.

In this embodiment, therefore, verification experiments were conducted in advance to determine the formation range that would ensure sufficient rigidity even when such excessive external forces were applied, and based on the results, the annular groove portion 11 was formed within that formation range.

That is, in this embodiment, the radial width dimension P of the annular groove portion 11 and the radial lip length L from the base end to the tip end of the outer axial lip 73 are set to satisfy P≦(3/4)×L.
As a result, even if an excessive external force is applied that tends to bend the tip of the outer axial lip 73 radially outward, such as when the tip of the outer axial lip 73 comes into adhesive contact with the sliding surface (flat surface portion 31a) provided on the step portion 31 due to a pressure difference with the external atmospheric pressure, the outer axial lip 73 can maintain sufficient rigidity.

Similarly, the depth dimension H of each groove portion 11b is also determined by conducting verification experiments in advance to determine the minimum amount of grease Z required to obtain a sufficient oil film effect, and based on the results, the dimension is set to be capable of collecting that predetermined amount of grease Z.
That is, in this embodiment, the depth H of the bottom surface of the groove 11b relative to the tip of the protrusion 11a is set to 1 mm or less in the adjacent protrusion 11a and groove 11b in the annular groove 11. In other words, the depth H of the groove 11b is the depth of the annular groove 11, and the depth of the annular groove 11 is set to 1 mm or less.

With this configuration, even if grease Z sealed between the tip of the outer axial lip 73 and the sliding surface (flat surface portion 31a) provided on the stepped portion 31 passes through the tip and is forced out of the outer axial lip 73, a predetermined amount of grease Z can be collected via the multiple grooves 11b, 11b..., and at least the minimum necessary oil film effect can be obtained.

However, the greater the depth dimension H of each groove portion 11b is set, the greater the risk of reduced rigidity against excessive external forces that tend to bend the tip of the outer axial lip 73 radially outward. However, because the depth dimension H of each groove portion 11b does not exceed 1 mm, sufficient rigidity can be ensured even against such external forces.

In this manner, in this embodiment, a bulge portion 10 that bulges out in an arc shape when viewed in circumferential cross section is formed at the tip of the outer axial lip 73, and the outer axial lip 73 abuts against the sliding surface (flat surface portion 31a) via this bulge portion 10.
Microscopically, the outer axial lip 73 abuts against the sliding surface (flat surface 31a) via the protrusion 11a (protrusion 11a1 in Figure 2) located at the vertex X1 on the curved surface 10a of the bulge portion 10, which is in line contact with the sliding surface (flat surface 31a).

For example, if the tip end is deformed so as to stick to the sliding surface (flat surface 31a) due to a pressure difference with the external atmosphere, the contact point on the curved surface 10a with the sliding surface (flat surface 31a) will shift sequentially from vertex X1 to vertex X2, vertex X3, and so on, which are located radially inward from vertex X1, and the outer axial lip 73 will always abut against the sliding surface (flat surface 31a) via the protrusion 11a provided at the tip end.

As shown in Figure 5(b), for example, the contact area between the tip of the outer axial lip 173 and the sliding surface (flat surface portion 131a) of the hub wheel 103 does not increase due to deformation caused by the pressure difference with the external atmospheric pressure, as is the case with conventional outer axial lip 173.The outer axial lip 73 of this embodiment can therefore suppress an increase in torque when rotating the hub wheel 3 connected to a wheel (not shown).

Furthermore, as shown in Figure 5(a), with the conventional outer axial lip 173, when the seal member 107 is mounted on the wheel bearing device 101, tension force (the force pressing the tip of the outer axial lip 173 against the flat surface 131a, which is the sliding surface) is concentrated at the vertex Y on the outer edge that is farthest from the base end, which accelerates wear at the tip of the outer axial lip 173 due to the relative rotation between the seal member 107 and the hub wheel 103.

However, as shown in FIG. 2, in this embodiment, for example, when the tip end of the outer axial lip 73 abuts against the sliding surface (flat surface portion 31 a) via the protrusion 11 a (protrusion portion 11 a1) located at vertex X1, as the wear of the protrusion 11 a (protrusion portion 11 a1) progresses, the protrusion 11 a will then abut against the sliding surface (flat surface portion 31 a) via the protrusion 11 a located at vertex X2 (protrusion portion 11 a2 in FIG. 2), the protrusion 11 a located at vertex X3 (protrusion portion 11 a3 in FIG. 2), and so on, in that order.
In other words, in this embodiment, even if wear occurs at the tip of the outer axial lip 73, the sealing function (sealing ability) can be restored by the multiple protrusions 11a, 11a... that are continuous radially along the curved surface 10a.

For this reason, in this embodiment, the above-mentioned tension force can be distributed and applied to multiple protrusions 11a, 11a..., making it possible to reduce wear at the tip of the outer axial lip 73 due to relative rotation between the outer seal member 7 and the hub wheel 3.
In addition, it is possible to ensure the initial sealing performance of the outer seal member 7 when it is attached to the wheel bearing device 1, and to maintain and ensure this sealing performance even when wear progresses.

As described above, in the wheel bearing device 1 of this embodiment, the tip portions of the seal lips 72b/72b (more specifically, the outer axial lip 73 and the inner axial lip 74) are provided with bulge portions 10/10 that bulge in an arc shape toward the sliding surface of the inner member, the hub wheel 3, i.e., the flat portion 31a and the axial surface portion 31b, when viewed in circumferential cross section.
In addition, each bulge portion 10 is provided in a circular ring shape along the outer edge of the tip of the outer axial lip 73 (or inner axial lip 74), and its curved surface 10a (the surface opposite the sliding surface) is formed with an annular groove portion 11 consisting of multiple uneven shapes (protrusions 11a and grooves 11b) that are continuous along the curved surface 10a and that are continuous in the circumferential direction.

The tip of the outer axial lip 73 (or inner axial lip 74) contacts the sliding surface (flat surface portion 31a or shaft circumferential surface portion 31b) via the bulge portion 10, and microscopically, it abuts against the sliding surface via a convex portion (e.g., protrusion 11a1) located at the apex (e.g., apex X1) of the bulge portion 10, among the multiple concave-convex shapes that make up the arc-shaped annular groove portion 11 in a circumferential cross-section.

Therefore, even if the protrusion 11a1 disappears due to wear or the like, the entire tip of the outer axial lip 73 (or inner axial lip 74) will not immediately come into contact with the sliding surface. Only a portion of the bulge 10 (the portion where the protrusion 11a1 was located) will come into contact with the sliding surface. This prevents significant wear from progressing across the entire tip of the outer axial lip 73 (or inner axial lip 74), as was the case in the past.

Furthermore, after the protrusion 11a1 disappears due to wear or the like, a new convex portion adjacent to the protrusion 11a1 (for example, the protrusion 11a2 located at the vertex X2) continues to come into contact with the sliding surface.
By having such a configuration, it is possible to ensure the initial sealing performance of the outer seal member 7 when it is attached to the wheel bearing device 1, and to maintain and ensure this sealing performance even when wear progresses.
Furthermore, since it is possible to collect a predetermined amount of grease Z through the recess (groove portion 11b) adjacent to the protrusion portion 11a2, by continuing this action, it is possible to maintain at least the minimum necessary oil film effect for a relatively long period of time.

In this embodiment, the bulges 10 are provided only at the tips of the outer axial lip 73 and the inner axial lip 74, but this is not limited to this. For example, the tip of the radial lip 75, which is another example of the seal lip 72b, may be provided with a bulge that bulges toward the shaft circumferential surface 31b, which is the sliding surface.

[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. 1 and 4(a).
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 that the configuration of the outer side seal member 207 is a type that includes a dam portion 276 (see Figure 4 (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.

As shown in Figure 4(a), the outer seal member 207 includes a core 271 that fits into the outer ring 2, and a seal body 272 made of an elastic material that is bonded to the core 271.

The core metal 271 is mainly composed of a cylindrical portion 271a, a bent portion 271b, a disk portion 271c, and a flange portion 271d.
The material of the core metal 271 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.

The cylindrical portion 271a 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 271b is bent radially inward from the inner end of the cylindrical portion 271a, and then extends axially toward the outer side to the middle of the cylindrical portion 271a.
Furthermore, the disk portion 271 c extends radially inward from the outer end of the bent portion 271 b to the vicinity of the outer periphery of the hub wheel 3 .

The flange portion 271d extends radially outward from the outer end of the cylindrical portion 271a.
In addition, the radially outer end of the flange portion 271d 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 271d is provided with an outer edge portion 271e that extends toward the inner side while having a predetermined gap with the outer peripheral surface.

On the other hand, the seal body 272 has a plurality of seal lips 272b, 272b, 272b provided on the disc portion 271c of the core bar 271, a dam portion 276 provided on the outer edge portion 271e of the core bar 271, and the plurality of seal lips 272b, 272b, 272b are composed of an outer axial lip 273, an inner axial lip 274, and a radial lip 275.
The material of the seal body 272 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.

The outer axial lip 273 is formed to extend toward the outer side and radially outward.
The inner axial lip 274 is provided radially inward relative to the outer axial lip 273 and is formed so as to extend toward the outer side.
Furthermore, the radial lip 275 is provided radially inward relative to the inner axial lip 274 and is formed so as to extend toward the inner side and radially inward.

The outer axial lip 273, inner axial lip 274, and radial lip 275 are arranged coaxially with one another and are in sliding contact with the sliding surfaces (flat surface portion 31a, circumferential shaft surface portion 31b, and arcuate surface portion 31c) provided on the hub wheel 3.

The dam portion 276 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 276 is provided on the core metal 271 so as to cover the radially outer end of the flange portion 271d and the outer edge portion 271e.

In the outer seal member 207 having the above-described configuration, the outer axial lip 273, which is an example of the seal lip 272b, and the inner axial lip 274 each have a circular bulge portion 210/210 at the tip portion along the outer edge of the tip portion.
Furthermore, a circular groove (not shown) that continues in the circumferential direction is formed on the curved surface 210a of each bulging portion 210.
The configurations of the bulge portion 210 and the annular groove portion are the same as those of the bulge portion 10 and the annular groove portion 11 in the wheel bearing device 1 described above, and therefore a description thereof will be omitted.

The outer side seal member 207 of the second embodiment, which has this configuration, can also suppress significant wear over the entire tip end of the outer axial lip 273 (or inner axial lip 274), as was the case with the outer side seal member 7 in the wheel bearing device 1 described above.
In addition, it is possible to ensure the initial sealing performance of the outer seal member 207 when it is attached to the wheel bearing device 201, and to maintain and ensure this sealing performance even when wear progresses.
Furthermore, at the tip of the outer axial lip 273 (or inner axial lip 274), as wear progresses, it is possible to collect a predetermined amount of grease Z through the multiple grooves (not shown) that make up the annular groove portion, and by continuing this action, it is possible to maintain at least the minimum necessary oil film effect for a relatively long period of time.

[Configuration of wheel bearing device 301 (third embodiment)]
Next, the configuration of a wheel bearing device 301 according to a third embodiment will be described with reference to FIGS. 1 and 4B.
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 a bulge portion 310 is provided at the tip of the seal lip 306a1 in the inner side seal member 306.
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.

As shown in FIG. 4B, the inner seal member 306 includes a substantially cylindrical seal plate 306a, a substantially cylindrical slinger 306b, and the like.
The main configurations of the sealing plate 306a and the slinger 306b 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.

The seal lip 306a1 is composed of an outer axial lip 373, an inner axial lip 374, and a radial lip 375, each of which is formed in an annular shape and arranged coaxially.

The outer axial lip 373 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 374 is located radially inward of the outer axial lip 373 and is formed so as to extend axially inward while inclining radially outward in a circumferential cross-sectional view.
Furthermore, the radial lip 375 is located radially inward of the inner axial lip 374, and is formed so as to incline radially inward and extend axially outward (see FIG. 1) when viewed in circumferential cross section.

The outer axial lip 373 and the inner axial lip 374 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 306b.
The radial lip 375 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 outer peripheral surface of the slinger 306b.

In the inner side seal member 306 having the above-described configuration, the outer axial lip 373, which is an example of the seal lip 306a1, and the inner axial lip 374 each have a circular bulge portion 310/310 at the tip portion along the outer edge of the tip portion.
Furthermore, a continuous annular groove (not shown) is formed in the curved surface 310a of each bulging portion 310 in the circumferential direction.
The configurations of the bulge portion 310 and the annular groove portion are the same as those of the bulge portion 10 and the annular groove portion 11 in the wheel bearing device 1 described above, and therefore a description thereof will be omitted.

The inner side seal member 306 of the third embodiment, which has this configuration, can also suppress significant wear over the entire tip end portion of the outer axial lip 373 (or inner axial lip 374), as was the case with the outer side seal member 7 in the wheel bearing device 1 described above.
In addition, it is possible to ensure the initial sealing performance of the inner seal member 306 when it is attached to the wheel bearing device 301, and to maintain and ensure this sealing performance even when wear progresses.
Furthermore, at the tip of the outer axial lip 373 (or inner axial lip 374), as wear progresses, it is possible to collect a predetermined amount of grease Z through the multiple grooves (not shown) that make up the annular groove portion, and by continuing this action, it is possible to maintain at least the minimum necessary oil film effect for a relatively long period of time.

[Configuration of wheel bearing device 401 (fourth embodiment)]
Next, the configuration of a wheel bearing device 401 according to a fourth embodiment will be described with reference to FIGS. 1 and 4C.
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 a bulge portion 410 is provided at the tip of the seal lip 406a1 of the inner side seal member 406, which has a labyrinth structure.
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.

As shown in FIG. 4C, 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.

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

The 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 radial lip 474 is located radially inward of the axial lip 473 and is formed so as to extend axially inward and inclined radially inward in a circumferential cross-sectional view.
Furthermore, the grease lip 475 is located radially inward of the axial lip 473, and is formed so as to incline radially inward and extend axially outward (see FIG. 1) in a circumferential cross-sectional view.
The radial lip 474 is designed to have a thickness that increases toward the tip in order to improve rigidity.

The axial lip 473 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 406b.
Furthermore, the radial lip 474 and the grease lip 475 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 406b.

In the inner side seal member 406 having the above-described configuration, the axial lip 473 and the radial lip 474, which are examples of the seal lip 406a1, each have annular bulge portions 410, 410 provided at the tip portion along the outer edge of the tip portion.
Furthermore, a continuous annular groove (not shown) is formed in the curved surface 410a of each bulging portion 410 in the circumferential direction.
The configurations of the bulge portion 410 and the annular groove portion are the same as those of the bulge portion 10 and the annular groove portion 11 in the wheel bearing device 1 described above, and therefore a description thereof will be omitted.

The inner side seal member 406 of the fourth embodiment, which has this configuration, can also suppress significant wear over the entire tip end of the axial lip 473 (or radial lip 474), as was the case with the outer side seal member 7 in the wheel bearing device 1 described above.
In addition, it is possible to ensure the initial sealing performance of the inner seal member 406 when it is attached to the wheel bearing device 401, and to maintain and ensure this sealing performance even when wear progresses.
Furthermore, at the tip of the axial lip 473 (or radial lip 474), as wear progresses, it is possible to collect a predetermined amount of grease Z through the multiple grooves (not shown) that make up the annular groove portion, and by continuing this action, it is possible to maintain at least the minimum necessary oil film effect for a relatively long period of time.

The above describes the embodiments of the present invention, but 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, as well as all modifications within the scope of the claims.

1, 201, 301, 401 Wheel bearing device 2c Outer raceway surface 2 Outer ring (outer member)
3 Hub ring (inner member)
3a Small diameter step portion 3d, 4a Inner raceway surface 4 Inner ring (inner member)
5 Ball row 6 Inner seal member (seal member)
7 Outer seal member (seal member)
10, 210, 310, 410 Bulging portion 10a, 210a, 310a, 410a Curved surface 11 Annular groove portion 11a Projection portion (convex portion)
11b Groove portion (recess)
31a Plane part (sliding surface)
31b Shaft peripheral surface (sliding surface)
31c Arc surface part (sliding surface)
71, 271 Core metal 72, 272 Seal body 72b, 272b, 306a1, 406a1 Seal lip 306b Slinger (sliding surface)
406b Slinger (sliding surface)
H: Depth dimension of the groove L: Length of the lip in the radial direction from the base end to the tip end of the seal lip P: Width dimension in the radial direction of the annular groove Q2: Annular space

Claims (3)

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 portion of the seal lip is provided with an annular bulging portion that bulges in an arc shape toward the sliding surface in a circumferential cross section and extends in the circumferential direction,
The curved surface of the bulging portion facing the sliding surface has
In a circumferential cross section,
a plurality of annular protrusions formed in a substantially triangular shape that are continuous along the arc shape of the curved surface;
an annular groove portion is formed by a plurality of groove portions each having a substantially inverted triangular shape, the groove portions being respectively formed between the adjacent protrusion portions;
A wheel bearing device characterized in that: a radial width dimension P of the annular groove portion and a radial lip length L from a base end to a tip end of the seal lip satisfy P≦(3/4)×L;
2. The wheel bearing device according to claim 1, wherein: The depth dimension H of the annular groove portion is 1 mm or less.
3. The wheel bearing device according to claim 1 or 2, wherein: