JP2023159713A - hub unit bearing - Google Patents

Abstract

To realize a structure capable of securing sufficient sealing performance by a side lip of a seal ring, regardless of inclination of a central axis of a hub to a central axis of an outer ring.SOLUTION: An inclination angle α to a virtual plane P orthogonal to a central axis of a hub 3, of a radial inner face 13a of a projecting portion 13 constituting an axial slide surface 11 is determined to be larger than an inclination angle of a radial outer face 13b of the projecting portion 13 to the virtual plane P over the whole periphery in a circumferential direction.SELECTED DRAWING: Figure 3

Description

The present invention relates to a hub unit bearing for rotatably supporting wheels and braking rotors of an automobile relative to a suspension system.

The wheels and braking rotating body of an automobile are rotatably supported by a hub unit bearing relative to a suspension system. The hub unit bearing has an outer ring having a double-row outer ring raceway on the inner peripheral surface, and a double-row inner ring raceway on the outer peripheral surface, and protrudes radially outward from a portion located axially outer than the outer ring. The vehicle includes a hub having a rotating flange, and a plurality of rolling elements rotatably disposed between the double-row outer ring raceway and the double-row inner ring raceway.

The axially outer side refers to the outer side in the width direction of the vehicle body when the hub unit bearing is assembled to the vehicle, and conversely, the axially outer side refers to the center side in the width direction of the vehicle body when the hub unit bearing is assembled to the vehicle. It's called inside.

The hub unit bearing further includes a seal ring that closes an axially outer opening of the rolling element installation space that exists between the inner circumferential surface of the outer ring and the outer circumferential surface of the hub. Japanese Unexamined Patent Application Publication No. 2010-261598 (Patent Document 1) describes a seal ring having a plurality of seal lips each having a tip end slidably in contact with the surface of a hub. Among the multiple seal lips, the outermost seal lip in the radial direction is called a side lip, and its tip is in axial sliding contact with the radially inner portion of the axially inner surface of the rotating flange. It is in sliding contact with the surface.

As described in Japanese Unexamined Patent Publication No. 2017-180599 (Patent Document 2), a full-sized grinding wheel (rotary grindstone) is used for the portion of the outer peripheral surface of the hub where the tip of the seal lip comes into sliding contact. It has a soft finish. When finishing the outer circumferential surface of the hub using a full-size grinding wheel, concentric grinding marks are formed on the axial sliding surface, with concave portions and convex portions arranged alternately in the radial direction. It is formed.

Japanese Patent Application Publication No. 2010-261598 JP 2017-180599 Publication

By the way, when the moment load acting on the rotating flange changes with changes in driving conditions such as road surface conditions and vehicle speed, the angle of inclination of the central axis of the hub with respect to the central axis of the outer ring changes.

FIG. 4 shows a portion of the hub unit bearing where the seal ring 104 is installed, which is located on the upper side in the vertical direction. When the central axis of the hub 101 is inclined counterclockwise in FIG. The axial sliding surface 103 provided on the inner portion moves axially outward and radially inward, as shown by arrow A in FIG. Therefore, in the vertically upper portion, the interference between the side lip 105 provided on the seal ring 104 and the axial sliding surface 103 becomes small, and the sealing performance of the side lip 105 deteriorates. there is a possibility.

On the other hand, when the central axis of the hub 101 is tilted clockwise in FIG. , it moves axially inward and radially outward. Therefore, the interference between the side lip 105 and the axial sliding surface 103 becomes large in the vertically upper portion. However, in the lower part of the installation part of the seal ring 104, the axial sliding contact surface 103 moves axially outward and radially inward, so that the side lip 105 and the axially sliding contact surface 103 move axially outward and radially inward. There is a possibility that the interference with the contact surface 103 becomes small, and the sealing performance of the side lip 105 deteriorates.

In view of the above-mentioned circumstances, the present invention provides a hub unit bearing structure that can ensure sufficient sealing performance by the side lip of the seal ring, regardless of the inclination of the central axis of the hub with respect to the central axis of the outer ring. The aim is to achieve this goal.

A hub unit bearing according to one aspect of the present invention includes an outer ring, a hub, a plurality of rolling elements, and a seal ring.

The outer ring has a double-row outer ring raceway on its inner peripheral surface.

The hub has a double-row inner raceway and a rotating flange.

The double-row inner ring raceway is provided on the outer peripheral surface of the hub.

The rotating flange has an axial sliding surface on a radially inner portion of the axially inner surface, and projects radially outward.

The plurality of rolling elements are rotatably arranged between the double-row outer ring raceway and the double-row inner ring raceway.

The seal ring has a side lip whose tip portion is in sliding contact with the axial sliding surface.

The axial sliding surface has a line formed by alternately radially arranging concave portions and convex portions, each of which extends in the circumferential direction.

In particular, in the hub unit bearing according to one aspect of the present invention, the inclination angle of the radially inner surface of the convex portion with respect to the virtual plane perpendicular to the central axis of the hub is such that the convex portion with respect to the virtual plane is is larger than the inclination angle of the radially outer surface of.

In the hub unit bearing according to one aspect of the present invention, an inclination angle of a radially inner surface of the convex portion with respect to the virtual plane is less than five times an inclination angle of a radially outer surface of the convex portion with respect to the virtual plane. , preferably greater than 1.5 times and less than 3 times.

According to the hub unit bearing of one aspect of the present invention, sufficient sealing performance by the side lip of the seal ring can be ensured regardless of the inclination of the central axis of the hub with respect to the central axis of the outer ring.

FIG. 1 is a sectional view showing a hub unit bearing as an example of an embodiment of the present invention. FIG. 2 is an enlarged view of the X section in FIG. FIG. 3 is an enlarged view of the Y section in FIG. 2 with the axial direction exaggerated. FIG. 4 is an enlarged sectional view of a main part for explaining a problem caused by a change in the inclination angle of the central axis of the hub with respect to the central axis of the outer ring.

1 to 3 show an example of an embodiment of the present invention. The hub unit bearing 1 of this example includes an outer ring 2, a hub 3, a plurality of rolling elements 4, and a seal ring 5. The hub unit bearing 1 of this example has a structure for a driven wheel, and uses balls as the rolling elements 4.

In the following description, the axial direction, radial direction, and circumferential direction with respect to the hub unit bearing 1 refer to the axial direction, radial direction, and circumferential direction of the outer ring 2 unless otherwise specified. When the central axis of the hub 3 is not tilted with respect to the central axis of the outer ring 2, the axial direction, radial direction, and circumferential direction of the outer ring 2 are the same as the axial direction, radial direction, and circumferential direction of the hub 3. Match. Furthermore, the axially outer side refers to the outer side in the width direction of the vehicle body when the hub unit bearing 1 is assembled to the automobile, and the axially inner side refers to the inner side in the widthwise direction of the vehicle body when the hub unit bearing 1 is assembled to the automobile. say.

The outer ring 2 is made of hard metal such as medium carbon steel. The outer ring 2 has a double-row outer ring raceway 6 on its inner circumferential surface, and has a stationary flange 7 projecting radially outward at an axially intermediate portion. The stationary flange 7 has support holes 8 that penetrate in the axial direction at a plurality of locations in the circumferential direction of the radially intermediate portion.

In this example, the support hole 8 is constituted by a screw hole. The outer ring 2 is supported and fixed to the suspension system by screwing support bolts inserted through holes provided in the knuckles of the suspension system into the support holes 8 of the stationary flange 7 from the inside in the axial direction, and the wheel rotates. It doesn't rotate when you do it.

The hub 3 includes a double-row inner ring raceway 9 and a rotating flange 10, and is disposed coaxially with the outer ring 2 inside the outer ring 2 in the radial direction.

A double-row inner ring raceway 9 is provided on the outer peripheral surface of the hub 3.

The rotating flange 10 is provided at a portion of the hub 3 located axially outer than the axially outer end of the outer ring 2 so as to protrude radially outward. The rotating flange 10 has an axial sliding surface 11 on the radially inner portion of the axially inner surface.

The axial sliding surface 11 has a line 37 formed by alternately radially arranging concave portions 12 and convex portions 13, each of which extends in the circumferential direction and has a substantially triangular cross-sectional shape. The streaks 37 are formed in a logarithmic spiral shape.

Then, in at least a portion in the circumferential direction, the inclination angle α of the radially inner surface 13a of the convex portion 13 with respect to the virtual plane P perpendicular to the central axis O of the hub 3 is set to the radially outer side of the convex portion 13 with respect to the virtual plane P. The inclination angle β of the side surface 13b is made larger (α>β). Therefore, the apex T of each convex portion 13 is located radially inward from the radial center position of the convex portion 13 . In this example, the inclination angle α of the radially inner surface 13a is made larger than the inclination angle β of the radially outer surface 13b of the convex portion 13 with respect to the virtual plane P over the entire circumference.

The inclination angle α of the radially inner surface 13a can be larger than the inclination angle β of the radially outer surface 13b and less than 5 times (β<α<5β), and preferably, the inclination angle α of the radially outer surface 13b can be greater than 1.5 times and less than 3 times the inclination angle β (1.5β<α<3β). If the inclination angle α of the radially inner surface 13a is greater than five times the inclination angle β of the radially outer surface 13b, the radial length of the radially outer surface 13b may become unnecessarily long.

The inclination angle α of the radially inner surface 13a is not particularly limited, but can be 0.01 degrees or more and 0.31 degrees or less, preferably 0.015 degrees or more and 0.25 degrees or less. more preferably 0.02 degrees or more and 0.15 degrees or less.

In this example, the inclination angle α of the radially inner surface 13a is approximately twice the inclination angle β of the radially outer surface 13b. Note that FIG. 3 shows the lines 37 in an exaggerated manner by increasing the magnification in the axial direction by about 30 times as compared to the radial direction.

The hub 3 includes a concave curved surface 14 having an arcuate cross-sectional shape on a portion of the outer circumferential surface adjacent to the axially inner side of the axial sliding surface 11, and a concave curved surface 14 having an arcuate cross-sectional shape. A cylindrical radial sliding surface 15 is provided at a portion adjacent to the inner side in the axial direction. That is, the axial sliding contact surface 11, the concave curved surface 14, and the radial sliding contact surface 15 form a seal sliding contact surface on which the seal lip of the seal ring 5, that is, the side lip 25, the radial lip 26, and the grease lip 27 come into sliding contact. It consists of 16.

The seal sliding contact surface 16 including the axial sliding contact surface 11 is constituted by a ground surface that has been subjected to a grinding process using a grindstone. That is, when manufacturing the hub ring 21 constituting the hub 3, the portion of the intermediate material obtained by forging a metal material where the seal sliding surface 16 is to be formed is subjected to induction hardening or the like. After the hardened layer is formed by heat treatment, the seal sliding contact surface 16 is formed by grinding the part using a full-size grindstone.

Particularly in this example, after the grinding process using the full-form grindstone, additional processes such as laser processing, coining process, or etching process are performed on the portion where the axial sliding surface 11 is to be formed. Thereby, the inclination angle α of the radially inner surface 13a of the convex portion 13 constituting the axial sliding surface 11 is made larger than the inclination angle β of the radially outer surface 13b.

Note that the axial height of the convex portion 13 constituting the axial sliding surface 11, that is, the axial depth h of the recessed portion 12 is not particularly limited, but is set to 0.5 μm or more and 3.2 μm or less. The thickness can be preferably 0.8 μm or more and 2.5 μm or less, more preferably 1.0 μm or more and 2.5 μm or less.

The rotating flange 10 has mounting holes 17 that penetrate in the axial direction at a plurality of locations in the circumferential direction of the radially intermediate portion. A stud 18 is press-fitted into each of the mounting holes 17 with serrations for connecting and fixing a braking rotating body such as a disk or a drum, and a wheel constituting a wheel to the rotating flange 10. That is, in this example, the attachment hole 17 is configured by a cylindrical hole.

The braking rotating body and the wheel have a pilot part 19 provided at the axially outer end of the hub 3 inserted into a center hole provided at the center of each, and a circular hole at the radially intermediate portion of each of the brake rotors and the wheel. The stud 18 is inserted into through holes provided at a plurality of circumferential locations, and a hub nut is screwed onto the tip of the stud 18, thereby being coupled and fixed to the rotating flange 10.

Note that the mounting hole of the rotating flange can also be configured with a screw hole. In this case, the brake rotor and the wheel are attached to the rotating flange by screwing a hub bolt inserted through a through hole in the brake rotor and a through hole in the wheel into the mounting hole. Combine and fix.

In this example, the hub 3 is formed by combining an inner ring 20 and a hub ring 21.

The inner ring 20 is made of hard metal such as bearing steel. The inner ring 20 has an axially inner inner ring raceway 9 on its outer peripheral surface.

The hub ring 21 is made of hard metal such as medium carbon steel. The hub ring 21 includes an axially outer inner ring raceway 9, a rotating flange 10, and a pilot portion 19.

The hub ring 21 has a small-diameter stepped portion 22, which has a smaller outer diameter than the adjacent portion on the axial outer side, and onto which the inner ring 20 is fitted, in a portion located axially inward than the inner raceway 9 on the axially outer side. . Furthermore, the hub ring 21 has a step surface 23 facing axially inward at the axially outer end of the small diameter step 22, and radially outward from the axially inner end of the small diameter step 22. It has a caulked portion 24 bent toward.

The hub 3 is constructed by fitting the inner ring 20 onto the small-diameter stepped portion 22 of the hub ring 21 and sandwiching the inner ring 20 from both sides in the axial direction between the step surface 23 of the hub ring 21 and the caulking portion 24. 20 and a hub ring 21 are coupled and fixed.

Note that the hub ring and the inner ring can also be coupled by screwing a nut to the axially inner end of the hub ring that protrudes from the axially inner end of the inner ring.

In addition, since the hub unit bearing 1 of this example is a hub unit bearing for a driven wheel, the hub 3 is constructed solidly.

However, the hub unit bearing of the present invention can also be applied to a hub unit bearing for a driving wheel. In this case, the hub has a spline hole in the center that extends through the hub in the axial direction. The tip of a drive shaft that is rotationally driven using an engine or an electric motor as a drive source is engaged with the spline hole by a spline. When the automobile is running, the hub is rotationally driven by the drive shaft, thereby rotationally driving the wheels and the braking rotary body that are fixedly connected to the rotating flange of the hub.

A plurality of rolling elements 4 are each disposed between a double-row outer ring raceway 6 and a double-row inner ring raceway 9 so as to be freely rollable while being held by a retainer 38 . Thereby, the hub 3 is rotatably supported inside the outer ring 2 in the radial direction.

The seal ring 5 has a side lip 25 whose tip portion is in sliding contact with the axial sliding surface 11 . The seal ring 5 of this example further includes a radial lip 26 whose tip end is in sliding contact with the concave curved surface 14, and a grease lip 27 whose tip end is in sliding contact with the radial sliding surface 15.

In this example, the seal ring 5 includes a core metal 28 and a sealing material 29.

The core metal 28 is formed entirely into an annular shape by bending and forming a metal plate such as a mild steel plate. The core metal 28 includes a fitting cylinder part 30 that is internally fitted and fixed to the axially outer end of the outer ring 2 by interference fit, and a fitting cylinder part 30 that extends radially inward from the axially outer end of the fitting cylinder part 30. It has a bent support plate part 31.

The sealing material 29 is made of an elastic material such as an elastomer such as rubber, and is bonded and fixed to the surface of the support plate portion 31 of the core bar 28 by vulcanization adhesive. The sealing material 29 has a base 32, a side lip 25, a radial lip 26, and a grease lip 27. In addition, in FIG. 2, each of the side lip 25, the radial lip 26, and the grease lip 27 is shown in a free state. In FIG. 3, the side lip 25 is shown in a state in which it is elastically deformed and in sliding contact with the axial sliding surface 11.

The base portion 32 covers the surface of the support plate portion 31, specifically, the axially outer surface, the inner circumferential surface, and the radially inner end of the axially inner surface of the support plate portion 31.

The side lip 25 has a tip portion slidably in contact with the axial sliding surface 11 over the entire circumference. In this example, the side lip 25 extends from a portion of the base portion 32 that covers a radially intermediate portion of the axially outer surface of the support plate portion 31 in a direction toward the axially outer side and the radially outer side.

Note that the thickness of the tip of the side lip 25 is not particularly limited, but can be 0.2 mm or more and 0.8 mm or less, preferably 0.3 mm or more and 0.6 mm or less. More preferably, it is 0.35 mm or more and 0.45 mm or less.

The radial lip 26 has its tip portion slidably in contact with the concave curved surface 14 over the entire circumference. In this example, the radial lip 26 extends from the portion of the base 32 that covers the radially inner end of the support plate portion 31 in the axially outer direction.

The tip of the grease lip 27 is brought into sliding contact with the radial sliding surface 15 over the entire circumference. In this example, the grease lip 27 extends in a direction axially inward and radially inward from a portion of the base 32 that covers the radially inner end of the support plate portion 31 .

Such a seal ring 5 closes the axially outer opening of the rolling element installation space 33 that exists between the inner circumferential surface of the outer ring 2 and the outer circumferential surface of the hub 3 and in which the rolling elements 4 are arranged. I'm here. This prevents foreign matter such as muddy water from entering the rolling element installation space 33 from the axially outer opening of the rolling element installation space 33, and grease sealed in the rolling element installation space 33 from entering the rolling element installation space 33. This prevents leakage from the axially outer opening of 33 into the external space. In this example, the portion between the side lip 25 and the radial lip 26 and the portion between the radial lip 26 and the grease lip 27 are also filled with grease.

The hub unit bearing 1 of this example further includes a cover 34 that closes an opening on the axially inner side of the rolling element installation space 33. The cover 34 has a cylindrical portion 35 that is internally fitted and fixed to the axially inner end of the outer ring 2 by tight fit, and a bottom plate portion 36 that closes the axially inner end of the cylindrical portion 35 . Such a cover 34 prevents foreign matter from entering the rolling element installation space 33 from the axially inner opening of the rolling element installation space 33, and prevents grease sealed in the rolling element installation space 33 from entering the rolling element installation space 33. This prevents leakage from the axially inner opening of the space 33 to the external space. Note that instead of the cover 34, a combination seal ring may be used to close the opening on the axially inner side of the rolling element installation space.

In addition, in the hub unit bearing 1 of this example, when viewed macroscopically, that is, from the overall sliding contact area between the tip end of the side lip 25 and the axial sliding contact surface 11, the tip end of the side lip 25 and the axial sliding contact surface are The contact surface pressure with 11 increases as it approaches the external space, that is, as it goes radially outward. On the other hand, when viewed microscopically, that is, per one of the protrusions 13, the apex T of the protrusion 13 is located radially inward than the radial center position of the protrusion 13, so the side lip 25 The peak of the contact surface pressure between the tip end portion and the axial sliding surface 11 is located radially inward from the radial center position of the convex portion 13 .

According to the hub unit bearing 1 of this example, the sealing performance by the side lip 25 of the seal ring 5 can be sufficiently ensured regardless of the inclination of the central axis of the hub 3 with respect to the central axis of the outer ring 2.

That is, in this example, the inclination angle α of the radially inner surface 13a of the convex portion 13 with respect to the virtual plane P is made larger than the inclination angle β of the radially outer surface 13b of the convex portion 13 with respect to the virtual plane P over the entire circumference. (α>β). Therefore, the central axis of the hub 3 is inclined with respect to the central axis of the outer ring 2, and the axial sliding surface 11 is axially outward and radially inward (indicated by arrow A in FIG. 2) at one position in the circumferential direction. direction), the tip of the side lip 25 is likely to catch on the radially inner surface 13a of the convex portion 13. When the tip of the side lip 25 is caught on the radially inner surface 13a of the convex portion 13, the relative movement of the tip of the side lip 25 radially outward with respect to the axial sliding surface 11 is inhibited. Then, the base end portion of the side lip 25 is elastically deformed, and the pressing force of the distal end portion of the side lip 25 against the axial sliding surface 11 increases. As a result, the interference between the side lip 25 and the axial sliding surface 11 can be prevented from becoming small.

On the other hand, in a portion located on the radially opposite side of the one position in the circumferential direction, the axial sliding surface 11 moves axially inward and radially outward (in the direction indicated by arrow B in FIG. 2). do. Here, since the inclination angle β of the radially outer surface 13b of the convex portion 13 with respect to the virtual plane P is smaller than the inclination angle α of the radially inner surface 13a of the convex portion 13 with respect to the virtual plane P (β<α), the side Even when the tip of the lip 25 attempts to move radially inward relative to the axial sliding surface 11, the tip of the side lip 25 is unlikely to be caught on the radially outer surface 13b of the convex portion 13. That is, the tip of the side lip 25 can be smoothly moved radially inward relative to the axial sliding surface 11, and the side lip 25 can be moved radially inward relative to the axial sliding surface 11. The interference between the lip 25 and the axial sliding surface 11 can be increased.

As described above, in the hub unit bearing 1 of this example, as the moment load acting on the rotating flange 10 changes with changes in driving conditions such as road surface conditions and vehicle speed, Even if the inclination angle of the central axis of the hub 3 changes, a sufficient interference between the side lip 25 and the axial sliding surface 11 can be ensured over the entire circumference. That is, sufficient sealing performance by the side lip 25 can be ensured.

The hub unit bearing 1 of this example has an equal diameter PCD type structure in which the pitch circle diameter of the rolling elements 4 in the axially inner row is equal to the pitch circle diameter of the rolling elements 4 in the axially outer row. The invention can also be applied to a different diameter PCD type hub unit bearing in which the pitch circle diameter of the rolling elements in the axially inner row is larger or smaller than the pitch circle diameter of the rolling elements in the axially outer row. . Furthermore, although balls are used as the rolling elements 4 in the hub unit bearing 1 of this example, tapered rollers may be used instead of the balls.

1 Hub unit bearing 2 Outer ring 3 Hub 4 Rolling element 5 Seal ring 6 Outer raceway 7 Stationary flange 8 Support hole 9 Inner raceway 10 Rotating flange 11 Axial sliding surface 12 Recess 13 Convex portion 13a Radial inner surface 13b Radial outer surface 14 Concave curved surface 15 Radial sliding surface 16 Seal sliding surface 17 Mounting hole 18 Stud 19 Pilot part 20 Inner ring 21 Hub ring 22 Small diameter stepped part 23 Stepped surface 24 Caulked part 25 Side lip 26 Radial lip 27 Grease lip 28 Core metal 29 Seal material 30 Fitting cylinder part 31 Support plate part 32 Base part 33 Rolling element installation space 34 Cover 35 Cylindrical part 36 Bottom plate part 37 Line 38 Cage 100 Outer ring 101 Hub 102 Rotating flange 103 Axial sliding surface 104 Seal ring 105 Side lip

Claims (3)

an outer ring having a double-row outer ring raceway on the inner peripheral surface;
A hub having a double-row inner ring raceway provided on an outer circumferential surface, and a rotating flange having an axial sliding surface on a radially inner portion of the axially inner surface thereof and protruding radially outward. ,
a plurality of rolling elements rotatably disposed between the double-row outer ring raceway and the double-row inner ring raceway;
a seal ring having a side lip whose tip portion is in sliding contact with the axial sliding contact surface;
Equipped with
The axial sliding surface has a line formed by alternately radially arranging concave portions and convex portions each extending in the circumferential direction,
Over the entire circumference in the circumferential direction, an inclination angle of the radially inner surface of the convex portion with respect to an imaginary plane perpendicular to the central axis of the hub is greater than an inclination angle of the radially outer surface of the convex portion with respect to the imaginary plane.
hub unit bearing. The inclination angle of the radially inner surface of the convex portion with respect to the virtual plane is less than five times the inclination angle of the radially outer surface of the convex portion with respect to the virtual plane.
The hub unit bearing according to claim 1. The inclination angle of the radially inner surface of the convex portion with respect to the virtual plane is greater than 1.5 times and less than 3 times the inclination angle of the radially outer surface of the convex portion with respect to the virtual plane.
The hub unit bearing according to claim 2.

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