JP2019184043A - Hub unit bearing - Google Patents

Abstract

To suppress a degree of an increase of a fastening margin of a seal lip constituting a sealing device for blocking an end part opening of a bearing internal space in an axial direction accompanied by a pressure change in a sealing space.SOLUTION: A sealing device 4a for air-tightly blocking an end part opening of a bearing internal space 11 in an axial direction comprises a core grid 12a and a seal material 13a fixed to the core grid. The seal material 13 has a plurality of pieces of seal lips 14a, 15a and 16a, and makes tip edges of the seal lips slide-contact with a seal slide-contact face formed on a surface of a hub over the whole periphery. An sublimation substance is sealed into a sealing space which is defined by the adjacent seal lips and the seal slide-contact face.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hub unit bearing used for rotatably supporting a wheel of an automobile with respect to a suspension device.

  Conventionally, various types of hub unit bearings have been used to support automobile wheels on a suspension system. FIG. 4 shows an example of a conventional structure of such a hub unit bearing. The hub unit bearing includes an outer ring 1, a hub 2, a plurality of rolling elements 3, and a pair of sealing devices 4 and 5.

The outer ring 1 has double-row outer ring raceways 6a and 6b on the inner peripheral surface and a stationary flange 7 on the outer peripheral surface. The outer ring 1 does not rotate while being supported by the suspension device by connecting and fixing the stationary flange 7 to a knuckle of the suspension device (not shown) during use. The hub 2 is provided concentrically with the outer ring 1, and has double-row inner ring raceways 8 a and 8 b on the outer peripheral surface facing the outer ring raceways 6 a and 6 b. The hub 2 has a rotation-side flange 9 at a portion protruding outward in the axial direction from the outer ring 1. In use, the hub 2 rotates together with the wheels and the braking rotating member in a state where a braking rotating member such as a wheel and a disc (not shown) is supported and fixed to the rotation side flange 9. Further, since the hub unit bearing shown in the figure is for a drive wheel, a spline hole 10 for engaging a spline shaft as a drive shaft is formed in the central portion in the radial direction of the hub 2.
Note that “outside” in the axial direction refers to the left side of each figure, which is the outer side in the width direction of the vehicle when assembled to the automobile. On the contrary, the right side of each figure, which is the center side in the width direction of the vehicle, is referred to as “inside” in the axial direction.

  A plurality of rolling elements 3 are provided between each of the outer ring raceways 6a and 6b in the double row and the inner ring raceways 8a and 8b in the double row so as to roll freely. In the illustrated example, a ball is used as the rolling element 3, but in the case of a hub unit bearing for an automobile that is heavy in weight, a tapered roller may be used instead of the ball. The sealing devices 4 and 5 hermetically block the axial opening at both ends of the bearing inner space 11 that exists between the inner peripheral surface of the outer ring 1 and the outer peripheral surface of the hub 2. The sealing devices 4 and 5 prevent foreign matters such as muddy water from entering the bearing internal space 11 and prevent the lubricating grease sealed in the bearing internal space 11 from leaking to the outside.

  The sealing devices 4 and 5 have the same structure as the sealing devices that are described in FIGS. That is, the outer (intermediate) seal lip constituting the sealing device is inclined on the seal sliding contact surface in a state in which the outer (intermediate) seal lip is inclined in the direction toward the outside (opposite to the bearing internal space 11) from the base end to the tip edge. In contact. Thereby, the foreign matter intrusion prevention function by the outer (intermediate) seal lip is enhanced. On the other hand, the inner seal lip is inclined in the direction toward the bearing internal space 11 as it goes from the base end to the tip edge. This enhances the grease leakage prevention function by the inner seal lip.

  By the way, in the case of a hub unit bearing, the pressure in the bearing internal space 11 changes as the temperature in the bearing internal space 11 changes as the use environment and the operating state change. The inner seal lips constituting the sealing devices 4 and 5 are provided at a position in contact with the bearing inner space 11, that is, at a position directly receiving the pressure in the bearing inner space 11. For this reason, when the pressure in the bearing internal space 11 changes, the posture of the inner seal lip changes elastically. When the pressure in the bearing inner space 11 suddenly increases, the tip of the inner seal lip receives a force from the bearing inner space 11 toward the outer space and presses against the seal sliding contact surface with a wider contact area. There is a possibility that the inner seal lip may be reversed.

  In Patent Document 2, as shown in FIG. 5, the seal member 13 fixed to the core metal 12 includes a plurality of seal lips (an outer seal lip 14, an intermediate seal lip 15, and an inner seal lip 16). When there is a pressure difference between the internal space 11 side and the external side (the pressure in the bearing internal space 11 increases, or the pressure in the seal sealed space existing between the intermediate seal lip 15 and the inner seal lip 16 decreases) ), The sealing device 4 is disclosed in which the inner seal lip 16 that receives a large force on the outside is not easily reversed to the outside. The inner seal lip 16 of the sealing device 4 has a plurality of protrusions 40 that are adjacent to each other in the radial direction on the surface opposite to the bearing internal space 11. The adjacent protrusions 40 come into contact with each other due to the deformation of the inner seal lip 16 to prevent the inner seal lip 16 from being reversed.

  However, although the sealing device 4 can suppress the generation of excessive torque due to the reversal of the inner seal lip 16, it is more strongly pressed against the seal sliding contact surface than a seal lip without the protrusion 40. As a result, the frictional force acting on the sliding contact portion between the front end portion of the inner seal lip 16 and the seal sliding contact surface is increased, and the wear of the inner seal lip 16 is promoted.

JP 2005-016603 A JP 2011-106617 A

  In view of the circumstances as described above, the present invention can suppress the extent to which the tightening margin of the seal lip constituting the sealing device that closes the axial end opening of the bearing internal space increases with the pressure change in the sealed space. It was invented to realize the structure.

The hub unit bearing of the present invention includes an outer ring having a double row outer ring raceway on an inner peripheral surface, a hub having a double row inner ring raceway on an outer peripheral surface, the double row outer ring raceway and the double row inner ring raceway. A plurality of rolling elements provided between the outer ring and the inner peripheral surface of the outer ring and the outer peripheral surface of the hub, and a sealing device that closes an axial end opening of the bearing internal space. With
The sealing device includes an annular metal core fixed to the axial end of the outer ring, and a seal material fixed to the metal core, and the seal material includes a plurality of seal lips, The leading edge of each seal lip is slidably contacted over the entire circumference with a seal slidable contact surface provided on the hub or the surface of a slinger fixed to the hub.

In particular, in the hub unit bearing of the present invention, a sublimable substance is enclosed in a space defined by the adjacent seal lip and the seal sliding contact surface.
Further, in the hub unit bearing of the present invention, a sublimable substance is sealed in a portion of the sealing device that faces the bearing internal space.

According to the hub unit bearing of the present invention configured as described above, it is possible to suppress the extent to which the tightening margin of the seal lip constituting the sealing device increases with the pressure change in the sealed space.
That is, when the pressure in the seal sealed space (bearing internal space) decreases (increases), the sublimation substance sublimates (solidifies) under the influence of the pressure, so that the pressure change is alleviated and the seal lip tightening allowance is reduced. Can be prevented from increasing. Therefore, an increase in the frictional force acting on the sliding contact portion between the tip end portion of the seal lip and the seal sliding contact surface can be suppressed, and the fuel efficiency of the automobile can be improved. Furthermore, the promotion of wear of the seal lip can be suppressed, and the life of the seal lip can be extended.

The sectional view of the seal ring which shows a 1st embodiment of the present invention. Sectional drawing of the combination seal ring which shows 1st Embodiment of this invention. Sectional drawing of the seal ring which shows 2nd Embodiment of this invention. Sectional drawing of a hub unit bearing which shows an example of the conventional structure. Sectional drawing of the sealing device which shows an example of a conventional structure.

[First Embodiment]
1 and 2 show a first embodiment of the present invention. The feature of the present embodiment is that the structure of a pair of sealing devices 4a and 5a that closes both axial openings of the bearing internal space 11 is devised. Since the structure and operation of the other parts are the same as in the case of the example of the conventional structure shown in FIG. 4 described above, the same parts are denoted by the same reference numerals, and overlapping illustrations and descriptions are omitted or simplified. Hereinafter, the characteristic part of this embodiment will be mainly described.

  The hub unit bearing of this embodiment includes an outer ring 1 having double-row outer ring raceways 6a and 6b on the inner peripheral surface, a hub 2 having double-row inner ring raceways 8a and 8b on the outer peripheral surface, and a double-row outer ring raceway 6a. , 6b and a plurality of inner ring raceways 8a, 8b, a plurality of rolling elements 3 provided in a freely rotatable manner, and a bearing that exists between the inner peripheral surface of the outer ring 1 and the outer peripheral surface of the hub 2. And a pair of sealing devices 4a and 5a for closing the axial end opening of the internal space 11 (see FIG. 4).

  Of the pair of sealing devices 4a and 5a, the axially outer sealing device 4a that closes the axially outer end opening of the bearing inner space 11 includes a cored bar 12a and a sealing material 13a as shown in FIG. The seal ring which comprises is comprised. The cored bar 12a is made of a metal plate and has a substantially L-shaped cross section, and is formed into an annular shape as a whole. The sealing material 13a is formed in an annular shape by an elastic material such as an elastomer such as rubber, and is bonded and fixed to the entire circumference of the core metal 12a. The seal material 13a includes three seal lips, that is, an outer seal lip 14a, an intermediate seal lip 15a, and an inner seal lip 16a. The respective leading edges of the outer and intermediate seal lips 14a, 15a are in sliding contact with the inner peripheral surface of the rotary flange 9, which is the seal sliding contact surface, over the entire circumference. The leading edge of the inner seal lip 16a extends over the entire circumference on the axially outer portion of the outer peripheral surface of the hub 2 (the portion between the rotating flange 9 and the axially outer ring raceway 8a), which is the seal sliding surface. Are in sliding contact.

  On the other hand, the axially inner side sealing device 5a that closes the axially inner end opening of the bearing internal space 11 constitutes a combined seal ring by combining a slinger 17 and a seal ring 21 as shown in FIG. Yes. The slinger 17 is made of a metal plate in an annular shape as a whole, and includes a rotation-side cylindrical portion 18 and a rotation-side annular portion 19 that is bent radially outward from the axial inner end edge of the rotation-side cylindrical portion 18. And. The slinger 17 is supported and fixed to the hub 2 in a state in which the rotation-side cylindrical portion 18 is externally fitted to the inner end of the hub 2 in the axial direction. An annular encoder 20 that constitutes the rotational speed detection device is fixed to the inner surface in the axial direction of the rotation-side annular portion 19.

  The seal ring 21 includes a cored bar 22 and a sealing material 23. The metal core 22 is made of a metal plate in an annular shape as a whole, and includes a stationary side cylindrical portion 24 and a stationary side annular portion bent radially inward from the axial outer end edge of the stationary side cylindrical portion 24. 25. The cored bar 22 is supported and fixed to the outer ring 1 in a state where the stationary side cylindrical part 24 is fitted into the inner end in the axial direction of the outer ring 1 with an interference fit. The sealing material 23 is formed in an annular shape by an elastic material such as an elastomer such as rubber, and is bonded and fixed to the entire circumference of the cored bar 22. The seal material 23 includes three seal lips, that is, an outer seal lip 26, an intermediate seal lip 27, and an inner seal lip 28. And the front-end edge of outer side and intermediate seal lips 26 and 27 is slid over the perimeter to the axial direction outer side surface of the rotation side annular ring part 19, which is a seal sliding contact surface. The leading edge of the inner seal lip 28 is in sliding contact with the outer peripheral surface of the rotation-side cylindrical portion 18, which is a seal sliding contact surface, over the entire periphery.

  In the case of the present embodiment, the sealing device 4a encloses a sublimable substance in a sealed space formed between two seal lips provided in an adjacent state and the seal sliding contact surface. Specifically, the sublimable substance 30a is contained in the seal sealed space 31a defined by the adjacent outer seal lip 14a, intermediate seal lip 15a, and the axially inner side surface of the rotary flange 9 that is the seal sliding contact surface. Is enclosed. The sublimable substance 30a is disposed over the entire circumference on the inner peripheral surface of the base end portion of the outer seal lip 14a. Further, the seal sealing space 31b defined by the adjacent intermediate seal lip 15a and inner seal lip 16a, the inner surface in the axial direction of the rotary flange 9 that is the seal sliding contact surface, and the outer peripheral surface of the hub 2 is sublimated. The substance 30b is enclosed. The sublimable substance 30b is disposed over the entire circumference on the inner peripheral surface of the base end portion of the intermediate seal lip 15a and the inner peripheral surface of the base end portion of the inner seal lip 16a.

  When the pressure inside the sealed seal spaces 31a and 31b decreases, the sublimable substances 30a and 30b change from solid to gas (sublimate). On the other hand, when the pressure inside the sealed seal spaces 31a and 31b increases, the sublimable substances 30a and 30b return from gas to solid (solidify). As the sublimable substances 30a and 30b, for example, benzotriazole, benzophenone, naphthalene, iodine, phenol, and derivatives thereof can be used.

  Similarly, the sealing device 5a encloses a sublimable substance in a sealed space formed between the adjacent seal lip and the seal sliding contact surface. Specifically, sublimation is provided in a seal sealed space 32a defined by the adjacent outer seal lip 26, intermediate seal lip 27, and the axially outer surface of the rotary side ring portion 19 that is the seal sliding contact surface. The active substance 30a is enclosed. The sublimable substance 30 a is disposed over the entire circumference between the inner peripheral surface of the base end portion of the outer seal lip 26 and the outer peripheral surface of the base end portion of the intermediate seal lip 27. Further, the seal sealing defined by the adjacent intermediate seal lip 27 and inner seal lip 28, the axially outer side surface of the rotating side annular portion 19 and the outer peripheral surface of the rotating side cylindrical portion 18 which are seal sliding contact surfaces. A sublimable substance 30b is enclosed in the space 32b. The sublimable substance 30b is disposed on the inner peripheral surface of the base end portion of the intermediate seal lip 27 over the entire circumference.

According to the hub unit bearing of the present embodiment configured as described above, the extent to which the tightening allowance of each seal lip constituting the sealing devices 4a and 5a increases with a change in pressure in the sealed space can be suppressed.
That is, since each seal sealed space 30a, 30b, 31a, 31b is an airtight space, a gas-solid equilibrium is established based on Le Chatelier's principle. Therefore, when the pressure inside the sealed seal space is reduced, the sublimation substance is further sublimated, and when the sublimation substance is vaporized, the volume expands several thousand times, so that the pressure drop is alleviated. Conversely, when the pressure inside the sealed space increases, the sublimable substance solidifies (the volume of the sublimable substance is reduced to a thousandth), and the pressure increase is alleviated. Further, when the pressure inside the sealed seal space does not fluctuate, sublimation and solidification of the sublimable substance are balanced, so that the total amount of sublimable substance enclosed in the sealed seal space does not change.
As a result, the tip of each seal lip can be prevented from elastically deforming (sticking phenomenon) in the direction along the seal sliding contact surface as the internal pressure changes, so that the tightening margin of each seal lip is prevented from increasing. It is done. Therefore, it is possible to suppress an increase in the frictional force acting on the front end portion of each seal lip and the seal sliding contact surface, thereby improving the fuel efficiency of the automobile. Further, the promotion of wear of each seal lip can be suppressed, and the life of each seal lip can be extended.

Since the temperature of the hub unit bearing rises during use, it is preferable that the melting point of the sublimable substance be equal to or higher than the temperature of the hub unit bearing at the time of use to prevent loss of the sublimable substance due to melting.
In general, sublimable substances have a low molecular weight and fine molecules. Therefore, even if the sublimated material solidifies on the seal lip or the seal sliding contact surface, for example, the sublimable material is easily solidified on the sliding contact portion because the sublimation material is easily sublimated by the frictional heat of the sliding contact portion. Hard to seal and does not degrade sealing performance

[Second Embodiment]
FIG. 3 shows a second embodiment of the present invention. The sealing device (seal ring) 4b of the present embodiment is an annular inner surface of the cored bar 12a that is recessed in the axially outer side (opened inward in the axial direction) at a portion facing the bearing internal space 11. A concave groove 33 is provided. Then, the sublimable substance 30 c is enclosed over the entire circumference of the concave groove 33. The bearing inner space 11 is closed in an airtight state by a pair of sealing devices 4b and 5a, and the internal pressure of the bearing inner space 11 is reduced by disposing the sublimable substance 30c in the bearing inner space 11 as well. It is stabilized. Therefore, an increase in rotational torque and an increase in wear of the seal lip due to elastic deformation (sticking) of the inner seal rib 16a (28) toward the seal sliding contact surface due to an increase in pressure in the bearing internal space 11 are suppressed. ing.

  In general, sublimable substances have a low molecular weight and fine molecules. Moreover, the lump which the sublimable substance aggregated is soft. Therefore, even if the sublimated material solidifies on the raceway surface (outer ring raceway 6a, 6b or inner ring raceway 8a, 8b), for example, it easily sublimates again due to the frictional heat of the contact portion between the raceway surface and the rolling element 3, As a result, the sublimable substance is difficult to solidify at the contact portion, and thus does not adversely affect the bearing life or generate abnormal noise.

The present invention is applicable to hub unit bearings having various structures.
For example, in the present invention, only the axial outer end opening of the bearing inner space is closed by a seal ring, and the axial inner end opening is closed by a cover attached to the axial inner end of the outer ring. It can also be applied to hub unit bearings.

DESCRIPTION OF SYMBOLS 1 Outer ring 2 Hub 3 Rolling element 4, 4a, 4b Sealing device (seal ring)
5, 5a Sealing device (combination seal ring)
6a, 6b Outer ring raceway 7 Static flange 8a, 8b Inner ring raceway 9 Rotating flange 10 Spline hole 11 Bearing inner space 12, 12a Core metal 13, 13a Sealing material 14, 14a Outer seal lip 15, 15a Intermediate seal lip 16, 16a Inner seal Lip 17 Slinger 18 Rotating side cylindrical part 19 Rotating side annular part 20 Encoder 21 Seal ring 22 Core 23 Seal material 24 Static side cylindrical part 25 Static side annular part 26 Outer seal lip 27 Intermediate seal lip 28 Inner seal lip 30a, 30b, 30c Sublimable material 31a, 30b Seal sealed space 32a, 32b Seal sealed space 33 Annular groove 40 Projection

Claims (2)

A plurality of outer rings having a double row outer ring raceway on the inner peripheral surface, a hub having a double row inner ring raceway on the outer peripheral surface, and a plurality of rolls each between the double row outer ring raceway and the double row inner ring raceway. A rolling element provided freely, and a sealing device for closing an axial end opening of a bearing internal space existing between an inner peripheral surface of the outer ring and an outer peripheral surface of the hub,
The sealing device includes an annular metal core fixed to the axial end of the outer ring, and a seal material fixed to the metal core, and the seal material includes a plurality of seal lips, A hub unit bearing in which the front end edge of each seal lip is slidably contacted over the entire circumference with a seal slidable contact surface provided on the surface of the hub or slinger fixed to the hub,
A hub unit bearing, wherein a sublimable substance is enclosed in a space defined by the adjacent seal lip and the seal sliding contact surface.   The hub unit bearing according to claim 1, wherein a sublimable substance is sealed in a portion of the sealing device that faces the bearing internal space.

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