JP2022149090A - hub unit bearing - Google Patents

Abstract

To realize a structure capable of sufficiently securing a diameter and a pitch diameter of a rolling body in an axial inside row, regardless of an inner diameter of a knuckle.SOLUTION: An outer ring 2 comprises an outer ring body 13 having double-row outer ring raceways 5a, 5b on its inner peripheral surface, and a pilot member 14 having a knuckle fitting surface part 7 on its outer peripheral surface. The outer ring 2 is configured by connecting and fixing the outer ring body 13 and the pilot member 14, by internally fitting and fixing the pilot member 14 to the axial inside end part of the outer ring body 13 .SELECTED DRAWING: Figure 1

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hub unit bearing for rotatably supporting wheels and braking rotors of an automobile with respect to a suspension system.

A vehicle wheel and a braking rotator are rotatably supported with respect to a suspension system by hub unit bearings. A hub unit bearing includes an outer ring, a hub, and a plurality of rolling elements. In the following description, "outside" with respect to the axial direction refers to the laterally outer side of the vehicle body when the hub unit bearing is assembled to the vehicle. In this state, the center side in the width direction of the vehicle body is referred to as "inside" with respect to the axial direction.

The outer ring has a double-row outer ring raceway on its inner peripheral surface, and a cylindrical knuckle pilot portion protruding axially inward at its axially inner end. The outer ring is supported and fixed to the knuckle in a radially positioned state (centered state) by fitting the outer peripheral surface of the knuckle pilot portion to the knuckle that constitutes the suspension system, Does not rotate when in use.

The hub has a double-row inner ring raceway on its outer peripheral surface and a rotating flange protruding radially outward at its axially intermediate portion. A wheel constituting a wheel and a braking rotating body such as a disk or a drum are supported and fixed to the rotating flange. That is, the hub, in use, rotates with the wheel and the braking rotor.

The plurality of rolling elements are arranged between the double-row outer ring raceway and the double-row inner ring raceway so as to be free to roll.

JP-A-2003-232343

When a moment load based on road surface reaction force is applied to the rotary flange while the vehicle is running, the central axis of the hub is tilted with respect to the central axis of the outer ring. Since the central axis of the hub is inclined with respect to the central axis of the outer ring, the load applied to the rolling elements tends to be greater on the rolling elements in the axially inner row than on the rolling elements in the axially outer row. Therefore, the rolling fatigue life of the axially inner rolling element and the axially inner outer and inner ring raceways is greater than the axially outer rolling element and the axially outer outer and inner ring raceways. also tend to be shorter.

In FIG. 2 of Japanese Patent Application Laid-Open No. 2003-232343 (Patent Document 1), the diameter of the rolling elements (balls) in the axially inner row is larger than the diameter of the rolling elements in the axially outer row, and A hub unit bearing of the reduced PCD type is described in which the pitch diameter (PCD) of the rolling elements in a row is greater than the pitch diameter of the rolling elements in the axially outer row. According to such a different-diameter PCD type hub unit bearing, the load capacity of the rolling contact portions between the axially inner rolling elements and the axially inner outer and inner ring raceways is equal to that of the axially outer rolling elements. Although the load capacity of the rolling contact portions with the outer ring raceway and the inner ring raceway on the axially outer side can be made larger than that, there is room for improvement in the following respects.

The hub unit bearing is arranged radially inwardly of the double-row outer ring raceway of the outer ring with the rolling elements held in the retainer. It is assembled by fitting and fixing the inner ring to the axially inner end of the .

Here, when the rolling elements of the axially inner row are arranged radially inward of the outer ring raceway on the axially inner side, the rolling elements held in the respective pockets of the cage are moved radially inward to The diameter of the circumscribed circle of the rolling element centered on the central axis of the outer ring is made smaller than the inner diameter of the counterbore provided at the axially inner end of the outer ring. In this state, the axially inner row of rolling elements held by the retainer is passed through the radially inner side of the counterbore portion. Therefore, if the inner diameter of the knuckle that constitutes the suspension system is small and the inner diameter of the counterbore portion of the outer ring is small, it may be difficult to increase the diameter of the rolling elements in the axially inner row and the diameter of the pitch circle. be.

SUMMARY OF THE INVENTION In view of the circumstances described above, the present invention realizes a structure of a hub unit bearing that can sufficiently secure the diameter of the rolling elements in the axially inner row and the diameter of the pitch circle regardless of the inner diameter of the knuckle. It is intended to

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

The outer ring has a double-row outer ring raceway on its inner peripheral surface and a knuckle fitting surface portion on its outer peripheral surface at the axially inner end. The outer ring is supported and fixed to the knuckle in a radially positioned state (centered state) by internally fitting the knuckle fitting surface portion to the knuckle that constitutes the suspension system. does not rotate.

The hub has a double-row inner ring raceway on its outer peripheral surface. During use, the hub supports a wheel constituting a wheel and a braking rotating body such as a disk or a drum, and rotates together with the wheel and the braking rotating body.

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

In particular, in the hub unit bearing according to one aspect of the present invention, the outer ring includes an outer ring main body having the double-row outer ring raceway on the inner peripheral surface, and a pilot member having the knuckle fitting surface portion on the outer peripheral surface. The member is coupled and fixed to the axially inner end of the outer ring main body.

In the hub unit bearing of one aspect of the present invention, each of the rolling elements can be composed of a ball. In this case, the diameter (ball diameter) of the rolling elements in the axially inner row of the rolling elements is larger than the diameter of the rolling elements in the axially outer row of the rolling elements, and can be greater than the pitch diameter (PCD) of the rolling elements of said axially outer row.

Alternatively, the diameter of the rolling elements in the axially inner row of the rolling elements and the diameter of the rolling elements in the axially outer row of the rolling elements are equal to each other, and the rolling elements in the axially inner row It is also possible for the pitch diameter and the pitch diameter of the rolling elements of said axially outer row to be equal to each other.

In the hub unit bearing of one aspect of the present invention, the outer diameter of the knuckle fitting surface portion can be made smaller than the groove bottom diameter of the outer ring raceway on the inner side in the axial direction of the double-row outer ring raceway.

According to the hub unit bearing of one aspect of the present invention, it is possible to sufficiently secure the diameter of the rolling elements in the axially inner row and the pitch circle diameter regardless of the inner diameter of the knuckle.

FIG. 1 is a half sectional view showing a hub unit bearing of a first example of the embodiment. FIG. 2 is a half sectional view showing the hub unit bearing of the second example of the embodiment.

[First example of embodiment]
FIG. 1 shows a first example of an embodiment of the invention. A hub unit bearing 1 of this example is for a driven wheel, and includes an outer ring 2, a hub 3, and a plurality of rolling elements 4a and 4b.

The outer ring 2 has double-row outer ring raceways 5a and 5b on its inner peripheral surface, and has a knuckle pilot portion 6 protruding axially inward at its axially inner end. The knuckle pilot portion 6 has, on its outer peripheral surface, a cylindrical knuckle fitting surface portion 7 whose outer diameter does not change in the axial direction.

In the hub unit bearing 1 of this example, the diameter (ball diameter) of the rolling elements 4a in the axially inner row is larger than the diameter of the rolling elements 4b in the axially outer row, and the rolling elements in the axially inner row It has a reduced PCD type structure in which the pitch diameter (PCD) of 4a is greater than the pitch diameter of the rolling elements 4b in the axially outer row. For this reason, the groove bottom diameter (maximum diameter) of the axially inner outer ring raceway 5a is made larger than the groove bottom diameter of the axially outer outer ring raceway 5b.

The outer ring 2 has a cylindrical surface-shaped counterbore portion 34a in a portion of the inner peripheral surface adjacent to the axially inner side of the outer ring raceway 5a on the axially inner side. A cylindrical surface-shaped counterbore portion 34b is provided in a portion adjacent to the outer ring raceway 5b in the axial direction. In this example, the inner diameter of the axially inner counterbore portion 34a is the same as or substantially the same as the groove bottom diameter of the axially inner outer ring raceway 5a (slightly smaller than the groove bottom diameter of the axially inner outer ring raceway 5a). to a lesser or greater extent). In addition, the axially outer counterbore portion is set to the extent that the assembly of the axially outer row of rolling elements 4b and the retainer 31b can be assembled radially inwardly of the axially outer outer ring raceway 5b by the procedure described later. The inner diameter of 34b is made smaller than the groove bottom diameter of the outer ring raceway 5b on the axially outer side.

Furthermore, the outer ring 2 has a stationary flange 8 projecting radially outward at its axially intermediate portion. The stationary flange 8 has axially penetrating support holes 9 at a plurality of locations in the circumferential direction of the radially intermediate portion. Each of the support holes 9 is configured by a female screw hole.

The outer ring 2 is positioned (centered) in the radial direction with respect to the knuckle 10 by fitting the knuckle fitting surface portion 7 into the knuckle 10 constituting the suspension system with clearance. The bolt 12 inserted through the through hole 11 of 10 is screwed into the support hole 9 of the stationary flange 8 from the inside in the axial direction, thereby being supported and fixed to the knuckle 10 . That is, the outer ring 2 does not rotate even when the wheel rotates in use.

In this example, the outer ring 2 is formed by combining an outer ring main body 13 and a pilot member 14 .

The outer ring main body 13 is made of hard metal such as medium carbon steel. The outer ring main body 13 has double-row outer ring raceways 5a, 5b and counterbore portions 34a, 34b on its inner peripheral surface, and a stationary flange 8 protruding radially outward at its axially inner end. have The outer ring main body 13 has, on the inner peripheral surface of the axially inner end portion, a large-diameter surface portion 15 having an inner diameter larger than the groove bottom diameter of the axially inner outer ring raceway 5a located on the axially outer side. A stepped surface 16 facing inward in the axial direction is provided at the axially outer end of the radial surface portion 15 .

The pilot member 14 is made of hard metal such as medium carbon steel. The pilot member 14 has a knuckle fitting surface portion 7 on the axially inner portion of the outer peripheral surface, and has a body fitting surface portion 17 on the axially outer portion of the outer peripheral surface. In this example, the outer diameter of the knuckle fitting surface portion 7 and the outer diameter of the body fitting surface portion 17 are the same. That is, in this example, the outer peripheral surface of the pilot member 14 is configured by a cylindrical surface whose outer diameter does not change in the axial direction except for the axially opposite ends where the chamfered portions are formed. However, male splines (including male serrations) can also be formed on the body fitting surface portion 17 .

The inner peripheral surface of the pilot member 14 connects a small-diameter portion 18 on the axially inner side and a large-diameter portion 19 on the axially outer side by a connecting portion 20 inclined in a direction in which the inner diameter increases toward the axially outer side. It is configured.

The outer ring 2 abuts the axially outer end surface of the pilot member 14 against the stepped surface 16 of the outer ring body 13 and fits the body fitting surface portion 17 into the large-diameter surface portion 15 by interference fit. 13 and the pilot member 14 are connected and fixed. The knuckle pilot portion 6 is configured by an axially inner portion of the pilot member 14 that protrudes axially inward from the axially inner side surface of the outer ring main body 13 (stationary flange 8).

The hub 3 is arranged coaxially with the outer ring 2 radially inside the outer ring 2 . The hub 3 has double-row inner ring raceways 21a and 21b on its outer peripheral surface.

The hub 3 has a cylindrical pilot portion 22 at its axially outer end, and protrudes radially outward at a portion located axially outward from the axially outer end of the outer ring 2 . It has a rotating flange 23 which The rotating flange 23 has mounting holes 24 extending axially through it at a plurality of locations in the circumferential direction of the radially intermediate portion. A stud 25 is press-fitted (serration-fitted) into each of the mounting holes 24 from the inner side in the axial direction. That is, in this example, the attachment hole 24 is configured by a press-fit hole.

Braking rotating bodies such as discs and drums, and wheels constituting wheels are radially positioned with respect to the hub 3 by fitting the pilot portion 22 into a center hole axially penetrating the center portion. be. In this state, the stud 25 is inserted through the through-hole axially penetrating through the plurality of radially intermediate portions of the braking rotator and the wheel in the circumferential direction, and a hub nut is screwed onto the tip of the stud 25. By doing so, the braking rotor and the wheel are connected and fixed to the hub 3 .

It should be noted that the mounting hole of the rotating flange can also be configured by a female screw hole. In this case, by screwing hub bolts inserted through through holes provided in the braking rotor and wheel into the mounting holes, the braking rotor and the wheel are coupled and fixed to the rotating flange. do.

In this example, the hub 3 is formed by combining an inner ring 26 and a hub ring 27 .

The inner ring 26 is made of hard metal such as bearing steel. The inner ring 26 has the axially inner inner ring raceway 21a of the double-row inner ring raceways 21a and 21b on its outer peripheral surface.

The hub wheel 27 is made of hard metal such as medium carbon steel. The hub wheel 27 has an axially outer inner ring raceway 21b of the double-row inner ring raceways 21a and 21b at an axially intermediate portion of the outer peripheral surface. The hub wheel 27 has a rotary flange 23 protruding radially outward at a portion located axially outside the inner ring raceway 21b on the axially outer side, and has a cylindrical shape at the axially outer end. has a pilot portion 22 of .

The hub wheel 27 has a fitting tubular portion 28, which has a smaller outer diameter than the portion adjacent to the axially outer side and into which the inner ring 26 is fitted, at a portion positioned axially inward of the axially outer inner ring raceway 21a. have. Further, the hub wheel 27 has a stepped surface 29 facing inward in the axial direction at the axially outer end of the tubular fitting portion 28 , and has a diameter from the axially inner end of the tubular fitting portion 28 . It has a crimped portion 30 that is bent outward.

In the hub 3, the inner ring 26 is fitted to the fitting cylindrical portion 28 of the hub ring 27 by interference fit, and the inner ring 26 is clamped from both sides in the axial direction between the stepped surface 29 of the hub ring 27 and the crimped portion 30. Thus, the inner ring 26 and the hub ring 27 are connected and fixed.

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

Each of the rolling elements 4a, 4b is composed of a ball, and a plurality of cages 31a, 31b are provided for each row between the double-row outer ring raceways 5a, 5b and the double-row inner ring raceways 21a, 21b. It is rotatably arranged while being held by

In this example, the diameter (ball diameter) of the rolling elements 4a in the axially inner row is made larger than the diameter of the rolling elements 4b in the axially outer row, and the pitch diameter of the rolling elements 4a in the axially inner row ( PCD) is greater than the pitch diameter (PCD) of the rolling elements 4b of the axially outer row. That is, the hub unit bearing 1 of this example is configured by a different diameter PCD type hub unit bearing.

Although the degree to which the diameter of the rolling elements 4a in the axially inner row is larger than the diameter of the rolling elements 4b in the axially outer row is not particularly limited, for example, the diameter of the rolling elements 4a in the axially inner row can be 1.03 times or more and 1.16 times or less, preferably 1.03 times or more and 1.10 times or less, the diameter of the rolling elements 4b in the axially outer row. Also, the extent to which the pitch diameter of the rolling elements 4a in the axially inner row is larger than the pitch diameter of the rolling elements 4b in the axially outer row is not particularly limited. The pitch circle diameter of the rolling elements 4a in the axially outer row can be 1.001 times or more and 1.200 times or less, and 1.001 times or more and 1.050 times or less of the pitch circle diameter of the rolling elements 4b in the axially outer row. is preferred.

The hub unit bearing 1 exists between the inner peripheral surface of the outer ring 2 and the outer peripheral surface of the hub 3, and is located on both axial sides of a cylindrical rolling element installation space 32 in which the rolling elements 4a and 4b are arranged. It further comprises a pair of sealing devices 33a, 33b closing the opening.

Of the pair of seal devices 33a and 33b, the axially inner seal device 33a is composed of a combined seal ring including a slinger and a seal ring. The slinger is formed by bending a metal plate into an L-shaped cross section, and is fitted and fixed to the outer peripheral surface of the axially inner end portion of the inner ring 26 . The seal ring has a seal lip that slides on the surface of the slinger and is internally fitted and fixed to the small diameter portion 18 of the pilot member 14 that constitutes the outer ring 2 .

The axially inner seal device that closes the axially inner opening of the rolling element installation space is a bottomed cylindrical cover that is internally fitted and fixed to the axially inner end of the pilot member that constitutes the outer ring. Can also be configured. In this case, an encoder for detecting the number of rotations (rotational speed) of the wheel can be externally fitted and fixed to the inner end of the inner ring in the axial direction, if necessary.

Of the pair of seal devices 33 a and 33 b , the axially outer seal device 33 b has a seal lip that is in sliding contact with the outer peripheral surface of the hub 3 or the axial inner surface of the rotary flange 23 over the entire circumference. It is internally fitted and fixed to the end on the direction outer side. That is, the axially outer seal device 33b is composed of a seal ring.

When assembling the hub unit bearing 1 of this example, first, a plurality of rolling elements 4a and 4b are inserted into the pockets of a pair of cages 31a and 31b, and the rolling elements 4a and 4b are moved by the cages 31a and 31b. Hold 4b. Next, the rolling elements 4a and 4b held by the retainers 31a and 31b are arranged radially inside the double-row outer ring raceways 5a and 5b of the outer ring main body 13 .

Here, in order to dispose the rolling elements 4b of the axially outer row radially inward of the axially outer outer ring raceway 5b, the rolling elements 4b held in the respective pockets of the retainer 31b are moved radially inward. Thus, the diameter of the circumscribed circle of the rolling element 4b around the central axis of the retainer 31b is made smaller than the inner diameter of the axially outer counterbore portion 34b. In this state, the axially outer row of rolling elements 4b held by the retainer 31b is inserted from the axially outer side of the outer ring main body 13 and passed through the radially inner side of the axially outer counterbore portion 34b. After that, by releasing the force that presses the rolling elements 4b radially inward and placing them in a free state, the diameter of the circumscribed circle of the rolling elements 4b centered on the central axis of the retainer 31b is increased to the axially outer counterbore portion. It is made larger than the inner diameter of 34b. As a result, the assembly of the axially outer row of the rolling elements 4b and the retainer 31b is assembled to the outer ring main body 13 without being carelessly separated.

On the other hand, the inner diameter of the axially inner counterbore portion 34a is the same or substantially the same as that of the outer ring raceway 5a of the axially inner row. Therefore, if the rolling elements 4a held by the cage 31a are arranged radially inward of the outer ring raceway 5a of the axially inner row, the assembly of the rolling elements 4a of the axially inner row and the cage 31a will be damaged. , it cannot be assembled to the outer ring main body 13 without being carelessly separated.

Therefore, after the assembly of the axially inner row of rolling elements 4a and the retainer 31a is arranged radially inward of the axially inner row of the outer ring raceway 5a, the pilot member 14 is attached to the large diameter surface portion 15 of the outer ring main body 13. The outer ring main body 13 and the pilot member 14 are connected and fixed by internally fitting the main body fitting surface portion 17 by an interference fit. As a result, the outer ring 2 is formed, and at the same time, the connection portion 20 of the pilot member 14 is opposed to the axially inner portion of the rolling elements 4a of the axially inner row. This prevents the assembly of the axially inner row of rolling elements 4a and cage 31a from accidentally coming off (separating) from the outer ring 2 .

Next, the axially outer seal device 33 b is internally fitted and fixed to the axially outer end of the outer ring main body 13 .

Next, the previous hub ring 27 forming the caulked portion 30 is inserted from the axial outer side into the radially inner side of the outer ring 2, the plurality of rolling elements 4a, 4b, and the cages 31a, 31b that are combined with each other, and , the inner ring 26 is fitted onto the fitting cylindrical portion 28 of the hub wheel 27 . Then, the inner ring 26 and the hub ring 27 are joined and fixed to form the hub 3 by plastically deforming the axially inner end portion of the hub ring 27 radially outward to form the crimped portion 30 .

Finally, an axially inner seal device 33a is mounted between the axially inner end inner peripheral surface of the outer ring 2 (pilot member 14) and the axially inner end outer peripheral surface of the hub 3 (inner ring 26). do.

The hub unit bearing 1 of this example is assembled as described above. The procedure for assembling the hub unit bearing 1 is to connect the outer ring main body 13 and the pilot member 14 after the rolling elements 4a of the axially inner row are arranged radially inward of the axially inner outer ring raceway 5a. As long as they are performed, the order can be changed or they can be performed at the same time as long as there is no contradiction.

As described above, when assembling the hub unit bearing 1 of this example, the rolling elements 4a of the axially inner row are arranged radially inward of the axially inner outer ring raceway 5a, and then the outer ring raceways 5a and 5b are installed. The outer ring main body 13 and the pilot member 14 having the knuckle fitting surface portion 7 are combined to form the outer ring 2 . That is, when assembling the hub unit bearing, it is not necessary to pass the rolling elements in the axially inner row held by the retainer through the radially inner side of the knuckle pilot portion. Therefore, regardless of the inner diameter of the knuckle 10 that fits into the knuckle fitting surface portion 7, the diameter of the rolling elements 4a in the axially inner row and the pitch circle diameter can be sufficiently secured. In other words, regardless of the diameter and pitch diameter of the rolling elements 4a in the axially inner row, the inner diameter of the knuckle pilot portion 6 (the small diameter portion 18) is such that the axially inner rolling elements are held in the retainer, and It can be made smaller than a structure that needs to pass through the radially inner side of the knuckle pilot portion in a state of being radially inwardly moved.

The knuckle pilot portion 6 is a portion for radially positioning (centering) the hub unit bearing 1 with respect to the knuckle 10 when the hub unit bearing 1 is supported and fixed to the knuckle 10 . A gap is formed between the knuckle fitting surface portion 7 and the inner peripheral surface of the knuckle 10 after the hub unit bearing 1 is supported and fixed to the knuckle 10 by the bolts 12 . Therefore, a large radial load is not applied to the knuckle pilot portion 6 after the hub unit bearing 1 is supported and fixed to the knuckle 10 . Therefore, the fitting force between the large-diameter surface portion 15 of the outer ring main body 13 and the main body fitting surface portion 17 of the pilot member 14 does not need to be so large.

However, in order to reliably prevent water from entering from the fitting portion between the large-diameter surface portion 15 of the outer ring main body 13 and the main-body fitting surface portion 17 of the pilot member 14 , the large-diameter surface portion 15 of the outer ring main body 13 and the pilot member 14 are required to be prevented from entering. A sealing device such as a sealant or an O-ring can also be provided at the fitting portion with the main body fitting surface portion 17 . And/or, the large diameter surface portion 15 of the outer ring main body 13 and the main body fitting surface portion 17 of the pilot member 14 can be adhered with an adhesive or welded with a continuous wave laser.

In the hub unit bearing of the present invention, as in this example, the diameter of the rolling elements 4a in the axially inner row is larger than the diameter of the rolling elements 4b in the axially outer row, and the diameter of the rolling elements 4a in the axially inner row is is larger than the pitch diameter of the rolling elements 4b in the axially outer row, a significant effect can be obtained when applied to the hub unit bearing 1 of the different diameter PCD type.

However, in the hub unit bearing of the present invention, the diameter of the rolling elements in the axially inner row of the rolling elements and the diameter of the rolling elements in the axially outer row of the rolling elements are equal to each other, and It can also be applied to an equal-diameter PCD type hub unit bearing in which the pitch diameter of the rolling elements in the axially inner row and the pitch diameter of the rolling elements in the axially outer row are equal to each other. Alternatively, in the hub unit bearing of the present invention, the diameter of the rolling elements in the axially inner row is smaller than the diameter of the rolling elements in the axially outer row, and the pitch diameter of the rolling elements in the axially inner row is It can also be applied to hub unit bearings of the different diameter PCD type, which are smaller than the pitch circle diameter of the rolling elements in the directionally outer row.

Further, the hub unit bearing of the present invention is not limited to the hub unit bearing 1 for the driven wheel in which the hub wheel 27 is a solid body as in this example, but the hub wheel has a spline that penetrates in the axial direction at the center. It can also be applied to hub unit bearings for driving wheels having holes.

[Second example of embodiment]
FIG. 2 shows a second example of an embodiment of the invention. In the hub unit bearing 1a of this example, similarly to the hub unit bearing 1 of the first example of the embodiment, the diameter of the rolling elements 4a in the axially inner row is larger than the diameter of the rolling elements 4b in the axially outer row. Also, the pitch diameter of the rolling elements 4a in the axially inner row is larger than the pitch diameter of the rolling elements 4b in the axially outer row.

In this example, the outer diameter of the knuckle fitting surface portion 7a is made smaller than the groove bottom diameter of the outer ring raceway 5a on the inner side in the axial direction. To this end, the pilot member 14a has a crank-shaped cross-sectional shape with the axially inner portion offset radially inwardly with respect to the axially outer portion. That is, the outer peripheral surface of the pilot member 14a includes a knuckle fitting surface portion 7a provided in the axially inner portion and a main body having an outer diameter larger than the outer diameter of the knuckle fitting surface portion 7a provided in the axially outer portion. The fitting surface portion 17a is connected to the fitting surface portion 17a by a stepped surface 35a directed inward in the axial direction. On the other hand, the inner peripheral surface of the pilot member 14a is formed by connecting a small-diameter portion 18a on the axially inner side and a large-diameter portion 19a on the axially outer side by a stepped surface 35b facing axially outward.

When assembling the hub unit bearing 1a of this example, similarly to when assembling the hub unit bearing 1 of the first example of the embodiment, the rolling elements 4a of the axially inner row are arranged in the radial direction of the axially inner outer ring raceway 5a. After arranging on the inner side, the outer ring 2a is formed by connecting the outer ring main body 13 having the outer ring raceways 5a and 5b and the pilot member 14a having the knuckle fitting surface portion 7a. Therefore, the outer diameter of the knuckle fitting surface portion 7a can be made smaller than the groove bottom diameter of the outer ring raceway 5a on the inner side in the axial direction.

In this example, the hub wheel 27a forming the hub 3a has a spline hole 36 extending axially through the central portion thereof. A spline shaft portion forming a constant velocity joint is spline-engaged with the spline hole 36 . That is, the hub unit bearing 1a of this example is configured as a hub unit bearing for driving wheels. Other configurations and effects are the same as those of the first embodiment.

Reference Signs List 1, 1a hub unit bearing 2, 2a outer ring 3, 3a hub 4a, 4b rolling element 5a, 5b outer ring raceway 6 knuckle pilot portion 7, 7a knuckle fitting surface portion 8 stationary flange 9 support hole 10 knuckle 11 through hole 12 bolt 13 outer ring Main body 14, 14a Pilot member 15 Large diameter surface portion 16 Step surface 17 Main body fitting surface portion 18, 18a Small diameter portion 19, 19a Large diameter portion 20 Connection portion 21a, 21b Inner ring raceway 22 Pilot portion 23 Rotating flange 24 Mounting hole 25 Stud 26 Inner ring 27, 27a Hub ring 28 Fitting cylindrical portion 29 Stepped surface 30 Crimped portion 31a, 31b Cage 32 Rolling element installation space 33a, 33b Sealing device 34a, 34b Counterbore portion 35a, 35b Stepped surface

Claims (3)

an outer ring having a double-row outer ring raceway on its inner peripheral surface and a knuckle fitting surface portion on its outer peripheral surface at the axially inner end;
a hub having a double-row inner ring raceway on its outer peripheral surface;
a plurality of rolling elements arranged in each row between the double-row outer ring raceway and the double-row inner ring raceway so as to be free to roll;
with
The outer ring includes an outer ring main body having the double-row outer ring raceway on the inner peripheral surface, and a pilot member having the knuckle fitting surface portion on the outer peripheral surface,
The pilot member is coupled and fixed to an axially inner end of the outer ring main body,
hub unit bearings. Each of the rolling elements is composed of a ball,
A diameter of the rolling elements in the axially inner row of the rolling elements is larger than a diameter of the rolling elements in the axially outer row of the rolling elements, and a pitch diameter of the rolling elements in the axially inner row is greater than the pitch diameter of the rolling elements of said axially outer row,
A hub unit bearing according to claim 1. The outer diameter of the knuckle fitting surface portion is smaller than the groove bottom diameter of the axially inner outer ring raceway of the double-row outer ring raceway,
A hub unit bearing according to claim 1 or 2.

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