JP7487642B2 - Hub unit bearing - Google Patents

Description

The present invention relates to a hub unit bearing for supporting the wheels and braking rotors of an automobile so that they can rotate freely relative to the suspension system.

Automobile wheels and braking rotors such as discs and drums are supported rotatably relative to the suspension by hub unit bearings. Hub unit bearings have an outer member with an outer ring raceway on its inner circumferential surface, an inner member with an inner ring raceway on its outer circumferential surface, and multiple rolling elements arranged to roll freely between the outer ring raceway and the inner ring raceway.

One of the outer member and the inner member is used as a stationary member that is supported by the suspension device and does not rotate when in use. The other of the outer member and the inner member is used as a rotating member that rotates integrally with the wheel and the braking rotor when in use. The rotating member has a rotating flange that protrudes radially outward. The wheel that constitutes the wheel and the braking rotor are fixed to the rotating flange using multiple hub bolts.

A widely known type of hub unit bearing has press-fit holes that penetrate the axial direction at multiple points around the circumference of the rotating flange, and the serrations at the axially inner ends (the base ends of the hub bolts) are press-fitted into each of the press-fit holes from the axially inner side (hereafter referred to as the hub bolt press-fit type).

Note that with respect to hub unit bearings, the axially inner side is the center side of the vehicle in the width direction when assembled to the vehicle, and the axially outer side is the outer side of the vehicle in the width direction when assembled to the vehicle.

In a hub bolt press-in type hub unit bearing, the middle part of the hub bolt is inserted into the through holes provided at multiple points in the circumferential direction of the wheel and the braking rotor, and then a hub nut is screwed onto the male threaded part at the axially outer end of the hub bolt, which is the tip of the hub bolt, and then tightened to connect and fix the wheel and the braking rotor to the rotating flange.

As described in JP 2002-370104 A (Patent Document 1) and JP 2003-175702 A (Patent Document 2), in a hub bolt press-in type hub unit bearing, a structure is known in which an annular groove is formed on the axially outer surface of the rotating flange, the annular groove being centered on the central axis of the rotating member, and the axially outer ends of each press-in hole are open only to the bottom surface of the annular groove.

With this structure, even if the periphery of the axially outer opening of the press-fit hole is plastically deformed and raised as a result of the serration portion of the hub bolt being pressed into the press-fit hole, this bulge can be contained within the annular groove, improving the surface runout accuracy of the portion of the axially outer surface of the rotating flange other than the annular groove. This improves the surface runout accuracy of the braking rotor, and suppresses the occurrence of vibrations accompanied by abnormal noise known as brake judder during braking.

As described in JP 2017-190865 A (Patent Document 3) and elsewhere, there is also a type of hub unit bearing that can be made lighter by omitting the hub nut. In other words, the rotating flange has female threaded holes with open axially outer ends at multiple locations around the circumference, and the male threads at the axially inner ends (the tips of the hub bolts) are screwed into each of the female threaded holes from the axially outer side (hereinafter referred to as the hub bolt screw-in type).

In a hub bolt-threaded hub unit bearing, the hub bolt is inserted into through holes provided at multiple locations in the circumferential direction of the wheel and the braking rotor, and the male threads of the hub bolt are threaded into the female threaded hole of the rotating flange from the outside in the axial direction, and then tightened to connect and fix the wheel and the braking rotor to the rotating flange.

As described in JP 2017-190865 A and other publications, even in this type of hub bolt-threaded hub unit bearing, a structure is known in which an annular groove is formed on the axially outer surface of the rotating flange, the groove being centered on the central axis of the rotating member, and the axially outer ends of each of the female threaded holes are open only to the bottom surface of the annular groove.

With this structure, even if the periphery of the axially outer opening of the female threaded hole deforms and bulges as a result of the male thread of the hub bolt being screwed into the female threaded hole and then tightened, this bulge can be contained within the annular groove.

In some hub unit bearings, a through hole is formed in the rotating flange in the axial direction for the purpose of weight reduction or to allow the insertion of tools during assembly or maintenance. At least a radial portion of the axially outer end of such a through hole opens into the bottom surface of the annular groove, and therefore muddy water or other moisture may enter the gap between the bottom surface of the annular groove and the axially inner surface of the braking rotor from the axially inner side through this through hole.

In this case, for example, if the axially outer end of the through hole opens into the radially middle part of the bottom surface of the annular groove, moisture that has entered the gap between the bottom surface of the annular groove and the axially inner surface of the braking rotor may not be completely discharged from the through hole into the external space, and some of the moisture may remain in the part of the gap that is located radially outer than the through hole. The moisture remaining in the gap may then enter between the axially outer surface of the rotating flange and the axially inner surface of the braking rotor due to the centrifugal force caused by the rotation of the wheel, causing inconvenience such as rusting of the axially outer surface of the rotating flange and the axially inner surface of the braking rotor.

To resolve this problem, JP 2017-190865 A describes a structure in which the diameter of the inscribed circle of the through hole (drain hole) centered on the central axis of the rotating member is made smaller than the outer diameter of the annular groove, and the diameter of the circumscribed circle of the through hole centered on the central axis of the rotating member is made larger than the outer diameter of the annular groove.

With this structure, moisture that has entered the gap between the bottom surface of the annular groove and the axially inner surface of the braking rotor is collected at the radially outer end of the gap by the centrifugal force caused by the rotation of the wheel, and can then be discharged from this end to the external space through the through hole.

JP 2002-370104 A JP 2003-175702 A JP 2017-190865 A

When adopting the structure described above, that is, a structure in which the diameter of the inscribed circle of the through hole centered on the central axis of the rotating member is made smaller than the outer diameter of the annular groove, and the diameter of the circumscribed circle of the through hole centered on the central axis of the rotating member is made larger than the outer diameter of the annular groove, it is believed that in order to efficiently discharge moisture from the gap between the bottom surface of the annular groove and the axial inner surface of the braking rotor through the through hole to the external space, it is effective to increase the axial depth of the annular groove and bring the bottom surface of the annular groove closer to the axial inner opening of the through hole.

However, if the axial depth of the entire annular groove is increased, the axial thickness of the portion of the rotating flange that axially overlaps with the annular groove will be reduced, making it difficult to ensure the strength and rigidity of that portion.

The present invention aims to provide a hub unit bearing that can be easily designed to efficiently discharge moisture from the gap between the bottom surface of the annular groove and the axial inner surface of the braking rotor to the external space through the through hole while ensuring the strength and rigidity of the rotating flange.

A hub unit bearing of one embodiment of the present invention comprises an outer member having an outer ring raceway on its inner surface, an inner member having an inner ring raceway on its outer surface, and a plurality of rolling elements arranged freely rollable between the outer ring raceway and the inner ring raceway.
Of the outer member and the inner member, the rotating member which rotates during use has a rotating flange protruding radially outward.
The rotating flange has, on its axially outer surface, a circular annular groove centered on the central axis of the rotating member, mounting holes at multiple locations in the circumferential direction, extending in the axial direction and whose axially outer ends open only to the bottom surface of the annular groove, and a through hole penetrating in the axial direction at at least one location in the circumferential direction.
The diameter of the inscribed circle of the through hole centered on the central axis of the rotating member is smaller than the outer diameter of the annular groove, and the diameter of the circumscribed circle of the through hole centered on the central axis of the rotating member is larger than the outer diameter of the annular groove.
The axial depth of a portion of the annular groove radially outward from the circumscribing circle of the mounting hole centered on the central axis of the rotating member is greater than the axial depth of a portion of the annular groove radially inward from the circumscribing circle of the mounting hole centered on the central axis of the rotating member.

In one embodiment of the hub unit bearing of the present invention, the bottom surface of the annular groove has a shape in which the axial depth of the annular groove increases toward the radially outward direction.

In one embodiment of the hub unit bearing of the present invention, the portion of the bottom surface of the annular groove that is radially inward from the circumscribing circle of the mounting hole centered on the central axis of the rotating member is configured with a flat surface portion perpendicular to the central axis of the rotating member, and the portion of the bottom surface of the annular groove that is radially outward from the circumscribing circle of the mounting hole centered on the central axis of the rotating member is configured with a groove portion that is recessed axially inward from the flat surface portion.

According to one aspect of the present invention, a hub unit bearing can be provided that can be easily designed to efficiently discharge moisture from the gap between the bottom surface of the annular groove and the axial inner surface of the braking rotor to the external space through the through hole while ensuring the strength and rigidity of the rotating flange.

FIG. 1 is a cross-sectional view of a hub unit bearing according to a first embodiment of the present invention. FIG. 2 is a view of a hub according to a first embodiment of the present invention, as viewed from the outside in the axial direction. FIG. 3 is an enlarged view corresponding to the upper left portion of FIG. 1, showing only the rotating flange. FIG. 4 is an enlarged view corresponding to the lower left portion of FIG. FIG. 5 is a diagram corresponding to FIG. 3 and relating to a second embodiment of the present invention. FIG. 6 is a diagram corresponding to FIG. 4 and relating to a second embodiment of the present invention. FIG. 7 is a diagram corresponding to FIG. 4 and relating to a modified example of the second embodiment of the present invention.

[First embodiment]
A first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG.

The hub unit bearing 1 in this example is for a driven wheel and comprises an outer ring 2, which is an outer member, a hub 3, which is an inner member and a rotating member that rotates during use, and a number of rolling elements 4. Note that the present invention is also applicable to hub units for driving wheels. The present invention is also applicable to hub unit bearings in which the outer member is a rotating member.

In the following description, unless otherwise specified, the axial and radial directions of the hub unit bearing 1 refer to the axial and radial directions of the outer ring 2 and hub 3. Also, with respect to the hub unit bearing 1, the axial inner side is the right side in FIG. 1, which is the center side in the width direction of the vehicle when assembled to the vehicle, and the axial outer side is the left side in FIG. 1, which is the outer side in the width direction of the vehicle when assembled to the vehicle.

The outer ring 2 has double-row outer ring raceways 5a, 5b on its inner circumferential surface, and a stationary flange 6 that protrudes radially outward at the axially intermediate portion. The stationary flange 6 has support holes 7 that penetrate in the axial direction at multiple circumferential locations at the radially intermediate portion. The outer ring 2 is supported and fixed to the suspension by support bolts that are screwed into the support holes 7 of the stationary flange 6, and does not rotate even when the wheel rotates.

The hub 3 is disposed coaxially with the outer ring 2 on the radially inner side of the outer ring 2, and has double row inner ring raceways 8a, 8b facing double row outer ring raceways 5a, 5b on its outer peripheral surface. The hub 3 has a rotating flange 9 that protrudes radially outward in a portion located axially outward from the outer ring 2, and has a cylindrical pilot portion 10 at its axially outer end.

The rotating flange 9 has, on its axially outer surface, a circular annular groove 11 centered on the central axis C of the hub 3, female threaded holes 13 at multiple locations in the circumferential direction, which are mounting holes that extend in the axial direction and whose axially outer ends open only to the bottom surface 12 of the annular groove 11, and a through hole 14 that penetrates in the axial direction at at least one location in the circumferential direction.

That is, in this example, the axially outer surface of the rotating flange 9 has an inner abutment portion 15 provided on the radially inner portion, an outer abutment portion 16 provided on the radially outer portion, and an annular groove 11 provided on the radially intermediate portion, the annular groove 11 being centered on the central axis C of the hub 3.

The inner abutment portion 15 and the outer abutment portion 16 are formed by flat surfaces that exist in the same imaginary plane perpendicular to the central axis C of the hub 3.

The annular groove 11 has an inner peripheral surface 17 facing radially outward, an outer peripheral surface 18 facing radially inward, and a bottom surface 12 facing axially outward.

The axially inner end of the inner peripheral surface 17 is connected to the radially inner end of the bottom surface 12. The axially outer end of the inner peripheral surface 17 is connected to the radially outer end of the inner abutment portion 15.

The axially inner end of the outer peripheral surface 18 is connected to the radially outer end of the bottom surface 12. The axially outer end of the outer peripheral surface 18 is connected to the radially inner end of the outer abutment portion 16.

As shown in Figures 2 and 3, the radial width Wa of the annular groove 11 is larger than the groove bottom diameter Da of the female threaded hole 13 (Wa>Da). Note that the groove bottom diameter Da of the female threaded hole 13 is the diameter of the bottom of the threaded groove of the female threaded hole 13.

Each female threaded hole 13 axially penetrates a plurality of locations (five locations in the illustrated example) that are equally spaced in the circumferential direction of the radially intermediate portion of the rotating flange 9. That is, in this example, the axially inner end of each female threaded hole 13 opens to the axially inner side surface of the rotating flange 9, and the axially outer end opens to the axially outer side surface of the rotating flange 9. However, when implementing the present invention, each female threaded hole can be a bottomed hole in which only the axially outer end opens to the axially outer side surface of the rotating flange, and the axially inner end does not open to the axially inner side surface of the rotating flange. The axially outer end of each female threaded hole 13 opens to the radial center of the bottom surface 12 of the annular groove 11. Therefore, a part of the bottom surface 12 of the annular groove 11 is also present in each of the portions adjacent to both radial sides of the axially outer opening of the female threaded hole 13.

That is, in this example, as shown in FIG. 3, the inner diameter Di of the annular groove 11 is smaller than the diameter di of the inscribed circle of the female screw hole 13 centered on the central axis C of the hub 3 (see FIG. 1 and FIG. 2) (Di<di). The inscribed circle of the female screw hole 13 centered on the central axis C of the hub 3 (hereinafter simply referred to as the "inscribed circle of the female screw hole 13") refers to the imaginary circle with the smallest diameter among the imaginary circles centered on the central axis C of the hub 3 and tangent to the bottom of the thread groove of the female screw hole 13. The outer diameter Do of the annular groove 11 is larger than the diameter do of the circumscribed circle of the female screw hole 13 centered on the central axis C of the hub 3 (Do>do). The circumscribed circle of the female screw hole 13 centered on the central axis C of the hub 3 (hereinafter simply referred to as the "circumscribed circle of the female screw hole 13") refers to the imaginary circle with the largest diameter among the imaginary circles centered on the central axis C of the hub 3 and tangent to the bottom of the thread groove of the female screw hole 13.

Furthermore, in this example, the radial width Wi (=(di-Di)/2) of the portion of the annular groove 11 that is radially inward of the female threaded hole 13, i.e., the portion of the annular groove 11 that is radially inward of the inscribed circle of the female threaded hole 13, and the radial width Wo (=(Do-do)/2) of the portion of the annular groove 11 that is radially outward of the female threaded hole 13, i.e., the portion of the annular groove 11 that is radially outward of the circumscribed circle of the female threaded hole 13, are equal to each other (Wi=Wo).

In addition, in this example, the axial depth of the annular groove 11 does not change in the circumferential direction. In this example, the axial depth of the portion of the annular groove 11 that is radially outward from the circumscribing circle of the female threaded hole 13 (the portion shown by width Wo in FIG. 3) is deeper than the axial depth of the portion of the annular groove 11 that is radially inward from the circumscribing circle of the female threaded hole 13 (the portion shown by width (Da+Wi) in FIG. 3).

For this reason, in this example, the bottom surface 12 of the annular groove 11 has a shape in which the axial depth of the annular groove 11 increases as it moves radially outward. More specifically, in this example, the bottom surface 12 is configured as a partial conical convex surface that is inclined axially inward as it moves radially outward.

In other words, in this example, because the bottom surface 12 has such a shape, the axial depth of the portion of the annular groove 11 that is radially outward of the circumscribing circle of the female threaded hole 13 is greater than the axial depth of the remaining portion of the annular groove 11.

When implementing the present invention, if the shape of the bottom surface of the annular groove is such that the axial depth of the annular groove increases radially outward, a shape different from that of this example, such as a partially spherical convex surface, can be used.

In the illustrated example, the inner peripheral surface 17 and the outer peripheral surface 18 are each formed of a cylindrical surface whose diameter does not change along the axial direction. However, each of the inner peripheral surface and the outer peripheral surface can also be formed of an inclined surface that is inclined in a direction in which the radial width of the annular groove increases as it moves axially outward, or an inclined surface that is inclined in a direction in which the radial width of the annular groove decreases as it moves axially outward.

The through hole 14, which is clear from FIG. 2, is provided in the rotating flange 9 for the purpose of inserting tools during assembly or maintenance, and for weight reduction, etc.

In the present invention, the number of through holes 14 is arbitrary, but in this example, the through holes 14 are provided in the same number as the female threaded holes 13, and are arranged at equal intervals in the circumferential direction. In this example, the phase of the arrangement of the through holes 14 in the circumferential direction is shifted by half a pitch from the phase of the arrangement of the female threaded holes 13 in the circumferential direction. In this example, each of the through holes 14 is composed of a circular hole that penetrates the rotating flange 9 in the axial direction.

As shown in FIG. 4, in this example, the diameter δi of the inscribed circle of the through hole 14 (hereinafter simply referred to as the "inscribed circle of the through hole 14") centered on the central axis C of the hub 3 is smaller than the outer diameter Do of the annular groove 11 (δi < Do), and the diameter δo of the circumscribed circle of the through hole 14 (hereinafter simply referred to as the "circumscribed circle of the through hole 14") centered on the central axis C of the hub 3 is larger than the outer diameter Do of the annular groove 11 (δo > Do).

In this example, the radially outer portion of each of the through holes 14 opens to the outer abutment portion 16, and the radially inner portion opens to the bottom surface 12 of the annular groove 11. In this example, the inner circumferential surface of each of the through holes 14 has a partially cylindrical concave surface portion 19 that is concave toward the radially outward direction in the portion that overlaps radially outward with the annular groove 11. The axial width of the concave surface portion 19 is Wx as shown in FIG. 4, since a chamfered portion 20, which will be described later, is formed.

In this example, the connection between the inner circumferential surface of the through hole 14 and the portion of the axially outer surface of the rotating flange 9 that is radially outer than the annular groove 11, i.e., the connection between the concave surface portion 19 and the outer abutment portion 16, has a chamfered portion 20 that is inclined in a direction toward the radially outer side about the central axis of the through hole 14 as it approaches the axially outer side. The chamfered portion 20 is provided to suppress the generation of burrs when machining the outer abutment portion 16. The axial width of the chamfered portion 20 is Wy as shown in FIG. 4. In the illustrated example, the chamfered portion 20 is configured as a C chamfered portion having a linear cross-sectional shape. However, when implementing the present invention, the chamfered portion can also be configured as an R chamfered portion having a circular arc cross-sectional shape. When implementing the present invention, it is also possible to omit providing a chamfered portion at the connection between the concave surface portion and the outer abutment portion.

In addition, in this example, the axial depth Wz of the radially outer end of the annular groove 11 is greater than the axial width Wy of the chamfered portion 20 (Wz>Wy). That is, in this example, the radially outer end of the bottom surface 12 of the annular groove 11 is located axially inward of the chamfered portion 20. Note that if the chamfered portion 20 is omitted, the axial width Wx of the concave portion 19 will be equal to the axial depth Wz of the radially outer end of the annular groove 11.

In this example, the diameter δi of the inscribed circle of the through hole 14 is larger than the inner diameter Di of the annular groove 11 (δi>Di). However, when implementing the present invention, the diameter of the inscribed circle of the through hole can also be smaller than the inner diameter of the annular groove. In this case, the radially inner end of the through hole opens into the inner abutment portion.

Returning to Figure 1, in this example, the hub 3 is made up of an inner ring 21 and a hub wheel 22.

The inner ring 21 has an inner ring raceway 8a on the outer circumferential surface, which is axially inward.

The hub ring 22 has an axially outer inner ring raceway 8b in the axially middle part of the outer peripheral surface. The hub ring 22 also has a rotating flange 9 that protrudes radially outward in a portion located axially outward of the axially outer inner ring raceway 8b, and has a cylindrical pilot portion 10 at the axially outer end.

The hub 3 is constructed by fitting the inner ring 21 tightly to the axially inner part of the hub wheel 22, and by pressing the axially inner end face of the inner ring 21 with a crimping portion 23 provided at the axially inner end of the hub wheel 22, the inner ring 21 and the hub wheel 22 are fixed together.

The wheel 25 and braking rotor 26 that make up the wheel are fixed to the rotating flange 9 by hub bolts 27 that are screwed into the female threaded holes 13.

Specifically, the inner peripheral surface provided in the radial center of the braking rotor 26 is fitted onto the outer peripheral surface of the axially inner part of the pilot part 10, and the inner peripheral surface provided in the radial center of the wheel 25 is fitted onto the outer peripheral surface of the axially outer part of the pilot part 10. In this state, the hub bolt 27 is inserted into the through holes 28a, 28b provided at multiple circumferential positions in the radial middle parts of the braking rotor 26 and the wheel 25, and the male threaded part 29 provided at the axially inner end, which is the tip part of the hub bolt 27, is screwed into the female threaded hole 13 of the rotating flange 9 from the axially outer side, and further tightened. As a result, the wheel 25 and the braking rotor 26 are firmly clamped from both axial sides by the rotating flange 9 and the head 30 provided at the axially outer end, which is the base end of the hub bolt 27, and the wheel 25 and the braking rotor 26 are fixed to the rotating flange 9.

In this example, the present invention is applied to a hub bolt screw-in type hub unit bearing 1 in which each of the mounting holes provided at multiple circumferential locations on the rotating flange 9 is configured as a female threaded hole 13 into which the male threaded portion 29 of the hub bolt 27 is screwed from the axially outer side. However, the present invention can also be applied to a hub bolt press-in type hub unit bearing in which each of the mounting holes provided at multiple circumferential locations on the rotating flange 9 is configured as a press-in hole into which the serration portion of the hub bolt is press-in from the axially inner side.

The rolling elements 4 are arranged between the double row outer ring raceways 5a, 5b and the double row inner ring raceways 8a, 8b, with multiple rolling elements for each row held by a cage 24, so that they can roll freely. As a result, the hub 3 is supported rotatably on the radial inside of the outer ring 2. In this example, balls are used as the rolling elements 4, but tapered rollers can be used instead of balls. In this example, the pitch circle diameter of the rolling elements 4 in the axially outer row and the pitch circle diameter of the rolling elements 4 in the axially inner row are the same, but the present invention can also be applied to a PCD type hub unit bearing with different diameters, in which the pitch circle diameters of the rolling elements in the axially outer row and the rolling elements in the axially inner row are different from each other.

According to the hub unit bearing 1 of this example as described above, even if the periphery of the axially outer opening of the female threaded hole 13 is deformed and raised as a result of the male threaded portion 29 of the hub bolt 27 inserted into the through holes 28a, 28b of the braking rotor 26 and the wheel 25 being screwed into the female threaded hole 13 of the rotating flange 9 from the axially outer side and then tightened, this bulge is kept within the annular groove 11, thereby improving the surface runout accuracy of the portion of the axially outer surface of the rotating flange 9 other than the annular groove 11. This improves the surface runout accuracy of the portion of the braking rotor 26 at the radially outer end where the brake pads come into contact, and suppresses the occurrence of brake judder during braking.

In addition, the hub unit bearing 1 of this embodiment can be easily designed to efficiently discharge moisture from the gap 31 between the bottom surface 12 of the annular groove 11 and the axial inner surface of the braking rotor 26 through the through hole 14 to the external space while ensuring the strength and rigidity of the rotating flange 9. This point will be explained below.

While the vehicle is running, moisture such as rainwater or muddy water may enter the gap 31 through the through-hole 14. In this example, moisture that enters the gap 31 is less likely to remain in the gap 31 and is more likely to be discharged to the outside space through the through-hole 14.

That is, in this example, the diameter δi of the inscribed circle of the through hole 14 is smaller than the outer diameter Do of the annular groove 11 (δi < Do), and the diameter δo of the circumscribed circle of the through hole 14 is larger than the outer diameter Do of the annular groove 11 (δo > Do). Therefore, when the vehicle is running, the moisture that has entered the gap 31 moves to the radially outer end of the gap 31 due to the centrifugal force caused by the rotation of the wheels, and then is shaken off toward the concave portion 19. Also, when the vehicle is stopped, the moisture that has entered the gap 31 moves to the lower and radially outer end of the gap 31 due to gravity, and then drips toward the concave portion 19. In any case, the moisture that has reached the concave portion 19 is discharged from this concave portion 19 to the outside space through the part of the through hole 14 that is located axially inside the concave portion 19.

In particular, in this example, the axial depth of the portion of the annular groove 11 that is radially outward of the circumscribing circle of the female threaded hole 13 is deeper than the axial depth of the remaining portion of the annular groove 11. For this reason, by making the axial depth of the portion of the annular groove 11 that is radially outward of the circumscribing circle of the female threaded hole 13 sufficiently deep, specifically, by making it deeper than the axial depth of the annular groove of a conventional structure, for example, the concave portion 19, which is the destination of moisture that has migrated to the radially outer end (outer peripheral surface 18) of the gap 31, can be brought closer to the axially inner opening of the through hole 14. Therefore, the moisture that has reached the concave portion 19 can be efficiently discharged to the external space through the portion of the through hole 14 that is axially inward of the concave portion 19.

In this example, the bottom surface 12 of the annular groove 11 has a shape in which the axial depth of the annular groove 11 increases as it moves radially outward. Therefore, moisture that has entered the gap 31 moves in the axially inward direction as it moves radially outward while traveling along the bottom surface 12. Also, in this example, the axial depth Wz of the radially outer end of the annular groove 11 is greater than the axial width Wy of the chamfered portion 20 (Wz>Wy). Therefore, moisture that has moved to the radially outer end of the gap 31 while traveling along the bottom surface 12 can be efficiently sent to the concave portion 19 located axially inward of the chamfered portion 20. Therefore, the moisture that has entered the gap 31 can be efficiently discharged to the external space through the through hole 14.

In addition, in this example, the axial depth of the portion of the annular groove 11 that is radially outer than the circumscribing circle of the female threaded hole 13 is deeper than the axial depth of the remaining portion of the annular groove 11. That is, in the structure of this example, the axial depth of the portion of the annular groove 11 that is radially outer than the circumscribing circle of the female threaded hole 13 can be increased, while the axial depth of the portion of the annular groove 11 that is radially inner than the circumscribing circle of the female threaded hole 13 can be reduced. Therefore, in the portion of the rotating flange 9 that axially overlaps with the annular groove 11, the axial thickness, i.e., the strength and rigidity, of the portion radially inner than the circumscribing circle of the female threaded hole 13 can be sufficiently secured. Therefore, according to the structure of this example, it is easy to design the rotating flange 9 to efficiently discharge moisture from the gap 31 through the through hole 14 to the external space while securing the strength and rigidity.

As described above, the structure of this example allows moisture to be efficiently discharged from the gap 31 through the through hole 14 to the outside space, so that moisture remaining in the gap 31 can be prevented from entering between the inner abutment portion 15 and the outer abutment portion 16 of the rotating flange 9 and the axial inner surface of the braking rotor 26 due to centrifugal force and/or gravity accompanying the rotation of the wheel. This prevents rust from forming between the inner abutment portion 15 and the outer abutment portion 16 of the rotating flange 9 and the axial inner surface of the braking rotor 26. Therefore, the braking rotor 26 can be easily removed from the rotating flange 9 during maintenance. In addition, deterioration of the surface runout accuracy of the braking rotor 26 can be prevented, and brake judder can be prevented during braking.

[Second Example of the Embodiment]
A second embodiment of the present invention will be described with reference to FIGS.

In the hub unit bearing of this example, the axial depth of the portion of the annular groove 11a that is radially outward of the circumscribing circle (diameter do) of the female threaded hole 13 is deeper than the axial depth of the remaining portion of the annular groove 11a, i.e., the portion of the annular groove 11a that is radially inward of the circumscribing circle of the female threaded hole 13.

For this reason, in this example, the portion of the bottom surface 12a of the annular groove 11a that is radially inward from the circumscribing circle of the female threaded hole 13 is configured with a flat surface portion 32 that is perpendicular to the central axis C of the hub 3. In contrast, the portion of the bottom surface 12a of the annular groove 11a that is radially outward from the circumscribing circle of the female threaded hole 13 is configured with a groove portion 33 that is recessed axially inward from the flat surface portion 32.

When carrying out this example, the groove portion 33 can be formed, for example, in the same manner as when a clearance groove is formed by cutting at the connection between the axial side surface and the peripheral surface. Specifically, the entire bottom surface of the annular groove is machined into a flat surface centered on the central axis C of the hub 3 by forging or cutting, and then the groove portion 33 is formed by cutting the radially outer end of this flat surface, and the remaining part of this flat surface becomes the flat surface portion 32. However, the flat surface portion 32 and the groove portion 33 can also be formed simultaneously by forging.

In this example, the outer peripheral surface 18 of the annular groove 11a, adjacent to the radially outer side of the groove portion 33, is configured as a cylindrical surface whose diameter does not change along the axial direction. However, when implementing the present invention, the outer peripheral surface 18a can also be configured as an inclined surface whose diameter increases toward the axially inner side, as in the modified example of the second embodiment shown in FIG. 7.

In the structure of this example, the axially outer ends of each of the female threaded holes 13 open into the flat surface portion 32 of the bottom surface 12a of the annular groove 11a. For this reason, if the flat surface portion 32 is formed and then the female threaded hole 13 is formed using this flat surface portion 32 as the start or end point of processing, the female threaded hole 13 can be formed more easily than if the female threaded hole 13 is formed using an inclined surface inclined with respect to the central axis C of the hub 3 as the start or end point of processing.
The other configurations and effects are the same as those of the first embodiment.

The present invention can be implemented by appropriately combining the structures of each embodiment, so long as no contradiction occurs. For example, the present invention can employ a structure in which the bottom surface of the annular groove, a portion radially inward from the circumscribing circle of the mounting hole centered on the central axis of the rotating member, is configured with an inclined surface in which the axial depth of the annular groove increases radially outward, and the bottom surface of the annular groove, a portion radially outward from the circumscribing circle of the mounting hole centered on the central axis of the rotating member, is configured with a groove portion recessed axially inward from the inclined surface.

REFERENCE SIGNS LIST 1 hub unit bearing 2 outer ring 3 hub 4 rolling elements 5a, 5b outer ring raceway 6 stationary flange 7 support hole 8a, 8b inner ring raceway 9 rotating flange 10 pilot portion 11, 11a annular groove 12, 12a bottom surface 13 female thread hole 14 through hole 15 inner abutment portion 16 outer abutment portion 17 inner circumferential surface 18, 18a outer circumferential surface 19 concave portion 20 chamfered portion 21 inner ring 22 hub ring 23 crimped portion 24 cage 25 wheel 26 braking rotor 27 hub bolt 28a, 28b through hole 29 male thread portion 30 head portion 31 gap 32 flat surface portion 33 groove portion

Claims (2)

an outer member having an outer ring raceway on an inner circumferential surface;
an inner member having an inner ring raceway on an outer circumferential surface;
a plurality of rolling elements disposed between the outer ring raceway and the inner ring raceway for free rolling motion;
A rotating member that rotates during use among the outer member and the inner member has a rotating flange that protrudes radially outward,
the rotating flange has, on its axially outer surface, an annular groove having an annular shape centered on the central axis of the rotating member, mounting holes at a plurality of locations in the circumferential direction, the mounting holes extending in the axial direction and having axially outer ends opening only to a bottom surface of the annular groove, and a through hole penetrating in the axial direction at at least one location in the circumferential direction,
a diameter of an inscribed circle of the through hole centered on a central axis of the rotating member is smaller than an outer diameter of the annular groove, and a diameter of a circumscribed circle of the through hole centered on the central axis of the rotating member is larger than the outer diameter of the annular groove,
an axial depth of a portion of the annular groove that is radially outward from a circumscribing circle of the mounting hole that is centered on the central axis of the rotating member is greater than an axial depth of a portion of the annular groove that is radially inward from a circumscribing circle of the mounting hole that is centered on the central axis of the rotating member,
The bottom surface of the annular groove has a shape in which the axial depth of the annular groove increases toward the radially outward side.
Hub unit bearing. an outer member having an outer ring raceway on an inner circumferential surface;
an inner member having an inner ring raceway on an outer circumferential surface;
a plurality of rolling elements disposed between the outer ring raceway and the inner ring raceway for free rolling motion;
A rotating member that rotates during use among the outer member and the inner member has a rotating flange that protrudes radially outward,
the rotating flange has, on its axially outer surface, an annular groove having an annular shape centered on the central axis of the rotating member, mounting holes at a plurality of locations in the circumferential direction, the mounting holes extending in the axial direction and having axially outer ends opening only to a bottom surface of the annular groove, and a through hole penetrating in the axial direction at at least one location in the circumferential direction,
a diameter of an inscribed circle of the through hole centered on a central axis of the rotating member is smaller than an outer diameter of the annular groove, and a diameter of a circumscribed circle of the through hole centered on the central axis of the rotating member is larger than the outer diameter of the annular groove,
an axial depth of a portion of the annular groove that is radially outward from a circumscribing circle of the mounting hole that is centered on the central axis of the rotating member is greater than an axial depth of a portion of the annular groove that is radially inward from a circumscribing circle of the mounting hole that is centered on the central axis of the rotating member,
a portion of a bottom surface of the annular groove that is radially inward from a circumscribing circle of the mounting hole centered on the central axis of the rotating member is formed by a flat surface portion perpendicular to the central axis of the rotating member, and a portion of the bottom surface of the annular groove that is radially outward from a circumscribing circle of the mounting hole centered on the central axis of the rotating member is formed by a groove portion that is recessed axially inward from the flat surface portion,
a boundary between the flat surface portion and the groove portion is located at the same radial position as a circumscribing circle of the mounting hole centered on a central axis of the rotating member;
Hub unit bearing.

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