Hub unit bearing

Abstract

To provide a structure of a hub unit bearing capable of suppressing the amount of change in the inclination angle of an inner ring raceway on the inside in the axial direction provided on an inner ring and the outside surface in the axial direction of a large flange part accompanying assembly.SOLUTION: Hub 3 includes an inner ring 9 and a hub ring 10. The inner ring 9 includes an inner ring raceway 8a on the axially inner side of the double-row inner ring raceways 8a and 8b, and a large flange portion 11 protruding radially outward from a portion adjacent to the axially inner side of the inner ring raceway 8a on the axially inner side. The wheel hub 10 has a fitting shaft portion 18 to which the inner ring 9 is externally fitted. Both axial side portions of the inner peripheral surface of the inner ring 9 deviated in the axial direction from the inner ring raceway 8a on the inner side in the axial direction are externally fitted and fixed to the outer peripheral surface of the fitting shaft portion 18 by press-fitting, and a radial gap is present over the entire circumference between a portion of the inner peripheral surface of the inner ring 9 overlapping the inner ring raceway 8a on the inner side in the axial direction in the radial direction and the outer peripheral surface of the fitting shaft portion 18.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a hub unit bearing for rotatably supporting a wheel of an automobile relative to a suspension system. [Background technology]

[0002] A hub unit bearing for supporting an automobile wheel rotatably relative to a suspension system comprises an outer ring having a double-row outer ring raceway on its inner peripheral surface, a hub having a double-row inner ring raceway on its outer peripheral surface, and a plurality of rolling elements arranged between the double-row outer ring raceway and the double-row inner ring raceway.

[0003] The rolling elements are balls or tapered rollers. Hub unit bearings that use tapered rollers as rolling elements have a higher load bearing capacity than hub unit bearings that use balls as rolling elements, and are used as hub unit bearings for heavy automobiles.

[0004] JP 2013-007441 A describes a hub unit bearing that uses tapered rollers as rolling elements, in which the hub is constructed by combining multiple parts, including an inner ring (second inner ring) having an inner ring raceway on the axially inner side of a double row of inner ring raceways, and a hub ring onto which the inner ring is externally fixed by press-fitting.

[0005] The inner ring has a large rib portion that protrudes radially outward at a portion adjacent to the axially inner side of the inner ring raceway on the axially inner side. The large rib portion has a large rib surface on its axially outer side that inclines axially outward as it moves radially outward. The large diameter side end faces of the tapered rollers slide against the large rib surface. Note that with respect to the hub unit bearing, the axially outer side is the outer side in the vehicle width direction when assembled to the vehicle, and the axially inner side is the center side in the vehicle width direction when assembled to the vehicle. The hub wheel has a fitting shaft portion onto which the inner ring is press-fitted. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-007441 [Patent Document 2] Japanese Patent Application Publication No. 2022-148470 Summary of the Invention [Problem to be solved by the invention]

[0007] In hub unit bearings that use tapered rollers as rolling elements, the radial thickness of the inner ring is smaller at the axially outer portion located on the smaller diameter side of the axially inner inner ring raceway than at the axially inner portion located on the larger diameter side of the axially inner inner ring raceway. In other words, the radial rigidity (resistance to deformation) of the inner ring is lower at the axially outer portion than at the axially inner portion.

[0008] For this reason, when assembling a hub unit bearing that uses tapered rollers as rolling elements, the amount of elastic expansion of the inner ring caused by press-fitting the inner ring onto the mating shaft portion of the hub wheel is greater at the axially outer portion than at the axially inner portion. As a result, the inclination angle of the inner ring raceway on the axially inner side relative to the hub central axis and the inclination angle of the large rib surface relative to the hub central axis each decrease as the inner ring is press-fitted onto the mating shaft portion.

[0009] As described in JP 2022-148470 A (see Fig. 1), in a tapered roller bearing, the inclination angle of the outer ring raceway relative to the central axis and the inclination angle of the inner ring raceway relative to the central axis are set so that an extension of the generatrix of the outer ring raceway and an extension of the generatrix of the inner ring raceway intersect on the central axis, thereby enabling smooth rolling motion of the tapered rollers relative to the outer ring raceway and the inner ring raceway.

[0010] For this reason, when the inclination angle of the axially inner inner ring raceway relative to the central axis of the hub decreases as a result of press-fitting the inner ring onto the mating shaft portion as described above, the extension of the generatrix of the axially inner outer ring raceway and the extension of the generatrix of the axially inner inner ring raceway come to intersect at a position that is shifted radially relative to the central axis of the hub. As a result, not only is there the possibility that edge load will occur at the contact points between the outer circumferential surfaces of the tapered rollers and the axially inner outer ring raceway and the axially inner inner ring raceway, but slippage will also occur at these contact points, causing the tapered rollers to skew, which may impede smooth rolling motion of the tapered rollers relative to the axially inner outer ring raceway and the axially inner inner ring raceway.

[0011] Furthermore, when the inclination angle of the large rib surface relative to the central axis of the hub decreases as the inner ring is press-fitted onto the mating shaft portion as described above, the sliding portion of the large-diameter end face of the tapered roller against the large rib surface moves toward the outer diameter of the hub, which increases the amount of circumferential slip at the sliding portion, potentially increasing the rotational torque.

[0012] The present disclosure aims to provide a hub unit bearing structure that can reduce the amount of change in the inclination angle of the axially inner inner ring raceway and the axially outer surface of the large flange portion provided on the inner ring during assembly. [Means for solving the problem]

[0013] The hub unit bearing of the first aspect of the present disclosure includes: an outer ring having a double row of outer ring raceways on its inner peripheral surface, each of the double row of outer ring raceways being formed by a truncated cone surface inclined in a direction such that the inner diameter increases as the outer ring raceways move away from each other in the axial direction; a hub having double row inner ring raceways on its outer peripheral surface, each of the double row inner ring raceways being formed by a truncated cone surface inclined in a direction such that the outer diameter increases as the raceways move away from each other in the axial direction; and a plurality of tapered rollers arranged between the double row outer ring raceways and the double row inner ring raceways.

[0014] The hub includes an inner ring and a hub ring.

[0015] The inner ring has an axially inner inner ring raceway among the double-row inner ring raceways, and a large flange portion protruding radially outward from a portion adjacent to the axially inner side of the axially inner inner ring raceway.

[0016] The hub wheel has a fitting shaft portion onto which the inner ring is fitted.

[0017] The inner peripheral surface of the inner ring has both axially opposite portions axially deviated from the inner ring raceway on the axially inner side, and is fixed to the outer peripheral surface of the mating shaft portion by press-fitting. A radial gap exists around the entire circumference between the portion of the inner peripheral surface of the inner ring that radially overlaps with the inner ring raceway on the axially inner side and the outer peripheral surface of the mating shaft portion.

[0018] In a hub unit bearing of a second aspect of the present disclosure, in the hub unit bearing of the first aspect of the present disclosure, the hub ring has an axially outer inner ring raceway of the double-row inner ring raceways, and a step surface that connects an axially inner end of the axially outer inner ring raceway to an axially outer end of the outer peripheral surface of the fitting shaft portion, and against which the axially outer end face of the inner ring abuts.

[0019] In a hub unit bearing of a third aspect of the present disclosure, in the hub unit bearing of the first or second aspect of the present disclosure, the inner ring is provided with a small flange portion that protrudes radially outward at a portion adjacent to the axially outer side of the axially inner inner ring raceway and has an outer diameter that is larger than the outer diameter of the axially inner end of the axially outer inner ring raceway.

[0020] In a hub unit bearing of a fourth aspect of the present disclosure, in the hub unit bearing of any one of the first to third aspects of the present disclosure, the hub ring can have a crimping portion at the axially inner end portion that presses against the axially inner end face of the inner ring. [Effects of the Invention]

[0021] According to the hub unit bearing of one aspect of the present disclosure, it is possible to reduce the amount of change in the inclination angle of the inner ring raceway on the axially inner side of the inner ring and the axially outer surface of the large rib portion that occurs during assembly. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a half cross-sectional view showing a hub unit bearing according to a first example of an embodiment of the present disclosure. [Figure 2] FIG. 2 is a half cross-sectional view showing a hub unit bearing according to a second example of an embodiment of the present disclosure. [Figure 3] FIG. 3 is a half cross-sectional view showing a hub unit bearing according to a third example of an embodiment of the present disclosure. [Figure 4] FIG. 4 is a half cross-sectional view showing a hub unit bearing according to a fourth example of an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0023] [Example 1] A first example of an embodiment of the present disclosure will be described with reference to FIG.

[0024] The hub unit bearing of the present disclosure is applicable to both hub unit bearings for driving wheels and hub unit bearings for driven wheels, but in this example, the hub unit bearing of the present disclosure is applied to a hub unit bearing for a driving wheel.

[0025] In the following description of this example, with respect to the hub unit bearing 1, the axially outer side is the widthwise outer side of the vehicle when assembled to the vehicle (left side in Figure 1), and the axially inner side is the widthwise center side of the vehicle when assembled to the vehicle (right side in Figure 1).

[0026] The hub unit bearing 1 of this example comprises an outer ring 2, a hub 3, and a plurality of tapered rollers 4a, 4b.

[0027] The outer ring 2 is made of a hard metal such as medium carbon steel. The outer ring 2 has double-row outer ring raceways 5a, 5b on its inner circumferential surface. Each of the double-row outer ring raceways 5a, 5b is made up of a truncated cone surface that is inclined so that the inner diameter increases as the raceways move away from each other in the axial direction.

[0028] In this example, the outer ring 2 has a stationary flange 6 that protrudes radially outward in an axially intermediate portion. The stationary flange 6 has support holes 7 that penetrate in the axial direction at multiple locations around the circumference of the radially intermediate portion.

[0029] In this example, the support hole 7 is configured as a threaded hole. The outer ring 2 is supported and fixed to the suspension by threading a support bolt, which is inserted through a through hole provided in the knuckle of the suspension, into the support hole 7 of the stationary flange 6 from the inside in the axial direction, so that the outer ring 2 does not rotate even when the wheel rotates.

[0030] The hub 3 is disposed coaxially with the outer ring 2 and radially inward of the outer ring 2. The hub 3 has double-row inner ring raceways 8a, 8b on its outer peripheral surface. Each of the double-row inner ring raceways 8a, 8b is formed by a truncated cone surface that is inclined such that the outer diameter increases as it moves away from the other raceway in the axial direction.

[0031] The hub 3 is configured to include an inner ring 9 and a hub ring 10 .

[0032] The inner ring 9 is made of a hard metal such as quenched and tempered bearing steel. The inner ring 9 has an axially inner inner ring raceway 8a of the double-row inner ring raceways 8a, 8b, and a large rib portion 11 that protrudes radially outward from a portion adjacent to the axially inner side of the axially inner inner ring raceway 8a.

[0033] In this example, the axially inner inner ring raceway 8a is provided in the axially middle portion of the outer peripheral surface of the inner ring 9. Furthermore, the large rib portion 11 protrudes radially outward from the axially inner end portion of the inner ring 9. The large rib portion 11 is provided on its axially outer surface with a large rib surface 12 that inclines axially outward as it extends radially outward. The large diameter side end faces of the axially inner row of tapered rollers 4a are in sliding contact with the large rib surface 12. The axially inner inner ring raceway 8a and the large rib surface 12 are connected via a relief groove 13.

[0034] In this example, the inner ring 9 has, as an optional component, a small rib portion 14 that protrudes radially outward at the axially outer end, which is the portion adjacent to the axially outer side of the axially inner inner ring raceway 8a. The small rib portion 14 has, on its axially inner surface, a small rib surface 15a that inclines axially outward as it extends radially outward. The small rib surface 15a is closely opposed to the small diameter side end faces of the axially inner row of tapered rollers 4a. The axially inner inner ring raceway 8a and the small rib surface 15a are connected via a relief groove 16.

[0035] In this example, the small rib portion 14 has an outer diameter larger than the outer diameter of the axially inner end of the axially outer inner ring raceway 8b of the double-row inner ring raceways 8a, 8b. The small rib portion 14 has a small rib surface 15b on its axially outer surface, in a portion that is positioned radially outward of the axially inner end of the axially outer inner ring raceway 8b. The small rib surface 15b is closely opposed to the small diameter side end faces of the tapered rollers 4b in the axially outer row. In this example, the small rib surface 15b is inclined axially outward as it extends radially outward.

[0036] In this example, the inner ring 9 has an annular recess 17 recessed in the radial direction in a portion of the inner peripheral surface that radially overlaps with the inner ring raceway 8a on the axially inner side.

[0037] The axial range of the annular recess 17 can be determined arbitrarily as long as it is arranged so as to radially overlap with the inner ring raceway 8a on the axially inner side. That is, the annular recess 17 can be arranged in an axial range so as to radially overlap with only a portion of the axially inner inner ring raceway 8a, or can be arranged in an axial range so as to radially overlap with the entire inner ring raceway 8a on the axially inner side.

[0038] The annular recess 17 is provided to prevent changes in the inclination angle of the axially inner inner ring raceway 8a relative to the central axis of the hub 3 and the inclination angle of the axially outer surface (large rib surface 12) of the large rib portion 11 relative to the central axis of the hub 3 when assembling the hub unit bearing 1. From the standpoint of easily preventing changes in these inclination angles, the annular recess 17 is preferably disposed in an axial range that radially overlaps with the entire axially inner inner ring raceway 8a. In this example, the annular recess 17 is disposed in an axial range that radially overlaps with the entire axially inner inner ring raceway 8a. More specifically, the axially inner edge of the annular recess 17 is disposed in a position that radially overlaps with the relief groove 13, and the axially outer edge of the annular recess 17 is disposed in a position that radially overlaps with the relief groove 16.

[0039] The average circumferential value of the radial depth of the annular recess 17 is preferably 0.1 mm or more, and more preferably 0.2 mm or more, although not limited thereto. In this example, the radial depth of the annular recess 17 is approximately 0.2 mm. The bottom surface (inner diameter surface) of the annular recess 17 is a surface that cannot be subjected to finish grinding, i.e., a surface where the black scale is not removed, and therefore heat treatment deformation remains. Therefore, if the average circumferential value of the radial depth of the annular recess 17 is set to less than 0.1 mm, the heat treatment deformation may result in some circumferential areas where the annular recess 17 is not present. Furthermore, considering the impact on the strength and lifespan of the inner ring 9, it is preferable that the average circumferential value of the radial depth of the annular recess 17 be as small as possible while still allowing the annular recess 17 to exist around the entire circumference.

[0040] The hub ring 10 is made of a hard metal such as medium carbon steel. The hub ring 10 has a fitting shaft portion 18 onto which the inner ring 9 is fitted, and the portion from the inner ring raceway 8b to the axially outer side of the fitting shaft portion 18 is induction hardened.

[0041] In this example, the fitting shaft portion 18 is provided on the axially inner side of the hub wheel 10, and the outer peripheral surface of the fitting shaft portion 18 is configured as a cylindrical surface whose outer diameter does not change in the axial direction.

[0042] In this example, hub ring 10 has an inner ring raceway 8b on the axially outer side, and a stepped surface 19 against which the axially outer end face of inner ring 9 abuts. Hub 3 is constructed by externally fitting inner ring 9 onto mating shaft portion 18 of hub ring 10 by press fitting, and then abutting the axially outer end face of inner ring 9 against stepped surface 19 of hub ring 10, thereby joining and fixing inner ring 9 to hub ring 10. In this example, by constructing hub 3 by joining and fixing inner ring 9 to hub ring 10, a predetermined amount of preload is applied to each row of tapered rollers 4a, 4b.

[0043] When implementing the present disclosure, the hub wheel may also have a shaft member and another inner ring having an inner ring raceway on the axially outer side. That is, a structure may be adopted in which the hub is configured by fitting two inner rings onto the shaft member. In this case, the fitting shaft portion is configured by a portion of the shaft member that is located axially inward of the portion onto which the other inner ring is fitted.

[0044] In this example, the axially outer inner ring raceway 8b is provided in the axially middle portion of the outer peripheral surface of the hub ring 10. The hub ring 10 also has a large rib portion 20 that protrudes radially outward from a portion adjacent to the axially outer side of the axially outer inner ring raceway 8b. The large rib portion 20 is provided on its axially inner surface with a large rib surface 21 that slopes axially inward as it extends radially outward. The large diameter side end faces of the axially outer row of tapered rollers 4b come into sliding contact with the large rib surface 21. The axially outer inner ring raceway 8b and the large rib surface 21 are connected via a relief groove 22.

[0045] The step surface 19 extends radially outward from the axially outer end of the outer peripheral surface of the fitting shaft portion 18 and faces axially inward. In this example, the step surface 19 connects the axially inner end of the axially outer inner ring raceway 8b and the axially outer end of the outer peripheral surface of the fitting shaft portion 18. However, when implementing the present disclosure, the step surface 19 can also be positioned at a position spaced axially inward from the axially outer inner ring raceway 8b.

[0046] In this example, the hub wheel 10 has a rotating flange 23 that protrudes radially outward at a portion that protrudes axially outward beyond the outer ring 2, and has a cylindrical pilot portion 24 at the axially outer end.

[0047] The rotary flange 23 has mounting holes 25 penetrating in the axial direction at a plurality of circumferential positions in a radially intermediate portion thereof. Each of the mounting holes 25 is configured as a press-fit hole or a screw hole.

[0048] When each mounting hole 25 is configured as a press-fit hole, a stud is press-fitted from the axially inner side into each mounting hole 25. A braking rotating body such as a brake disc and a wheel of a vehicle wheel are connected and fixed to the rotating flange 23 by inserting the pilot portion 24 into a central hole provided in the center of each and inserting studs into through-holes provided at multiple locations circumferentially in the radially middle portion of each, and screwing a hub nut onto the tip of the stud.

[0049] When each of the mounting holes 25 is configured as a threaded hole, the braking rotating body such as a brake disc and the wheel of the vehicle are connected and fixed to the rotating flange 23 by inserting the pilot portion 24 into the central hole provided in the center of each and threading hub bolts, which have been inserted into through holes provided at multiple locations circumferentially in the radially middle portion of each, into the mounting holes 25 from the outside in the axial direction.

[0050] Because the hub unit bearing 1 of this example is a hub unit bearing for a drive wheel, the hub 3 has a spline hole 26 that penetrates axially in the radial center and is splined to engage with a splined shaft portion of a drive shaft member (not shown). The tip of a drive shaft that is driven to rotate by an engine or electric motor as a drive source is splined to the spline hole 26. When the vehicle is traveling, the hub 3 is driven to rotate by the drive shaft, which in turn drives to rotate the wheel and braking rotor that are coupled and fixed to the rotation flange 23 of the hub 3.

[0051] When the hub unit bearing of the present disclosure is applied to a hub unit bearing for a driven wheel, the spline holes can be omitted and the hub wheel can be constructed as a solid body.

[0052] The inner ring 9 and the hub ring 10 are joined and fixed by externally fitting and fixing both axially opposite portions of the inner peripheral surface of the inner ring 9 that are axially offset from the axially inner inner ring raceway 8a onto the outer peripheral surface of the fitting shaft portion 18 by press fitting. With the inner ring 9 and the hub ring 10 joined and fixed, the axially outer end face of the inner ring 9 abuts against a stepped surface 19.

[0053] In addition, in this example, an annular recess 17 is provided in the portion of the inner surface of the inner ring 9 that radially overlaps with the inner ring raceway 8a on the axially inner side, so that a radial gap 29 exists around the entire circumference between that portion and the outer surface of the mating shaft portion 18.

[0054] The tapered rollers 4a, 4b are arranged between double-row outer ring raceways 5a, 5b and double-row inner ring raceways 8a, 8b, with multiple rollers in each row, with a back-to-back contact angle and preload applied. As a result, the hub 3 is supported radially inside the outer ring 2 so as to be able to rotate freely.

[0055] The tapered rollers 4a, 4b are made of hard metal such as bearing steel or ceramics. The tapered rollers 4a, 4b in each row are held by cages 27a, 27b and are arranged at equal intervals in the circumferential direction.

[0056] In this example, the hub unit bearing of the present disclosure is applied to a so-called equal diameter PCD type hub unit bearing in which the pitch diameter of the axially inner row of tapered rollers 4a is equal to the pitch diameter of the axially outer row of tapered rollers 4b, but the hub unit bearing of the present disclosure can also be applied to a so-called different diameter PCD type hub unit bearing in which the pitch diameter of the axially inner row of tapered rollers is larger or smaller than the pitch diameter of the axially outer row of tapered rollers.

[0057] The hub unit bearing 1 of this example can be assembled, for example, as follows. First, a plurality of tapered rollers 4b are placed radially inside the axially outer outer ring raceway 5b of the outer ring 2, while being held by a cage 27b. Next, the hub ring 10 is inserted radially inside the outer ring 2 from the axially outer side. Next, a plurality of tapered rollers 4a are placed around the axially inner inner ring raceway 8a of the inner ring 9, while being held by a cage 27a. Next, the inner ring 9 is externally fitted onto the fitting shaft portion 18 of the hub ring 10 from the axially inner side. In this way, both axial side portions of the inner peripheral surface of the inner ring 9 that are axially offset from the axially inner inner ring raceway 8a are externally fitted and fixed by press fitting onto the outer peripheral surface of the fitting shaft portion 18, and the axially outer end face of the inner ring 9 is brought into contact with the stepped surface 19 of the hub ring 10, thereby completing the hub 3. The steps for assembling the hub unit bearing 1 can be changed in order or performed simultaneously as appropriate, as long as no contradiction occurs.

[0058] According to the hub unit bearing 1 of this example, the inclination angle of the inner ring raceway 8a on the axially inner side of the inner ring 9 and the axially outer surface (large collar surface 12) of the large collar portion 11 can be reduced by an amount that changes during assembly.

[0059] That is, in the hub unit bearing 1 of this example, a radially recessed annular recess 17 is provided in the inner circumferential surface of the inner ring 9 in a portion that radially overlaps with the axially inner inner ring raceway 8a, thereby providing a radial gap 29 around the entire periphery between the inner circumferential surface of the inner ring 9 and the outer circumferential surface of the fitting shaft portion 18 of the hub ring 10 within the axial range where the annular recess 17 is present. This makes it possible to suppress changes (decreases) in the inclination angle of the axially inner inner ring raceway 8a relative to the central axis of the hub 3 and the inclination angle of the large rib surface 12 relative to the central axis of the hub 3 that occur when the inner ring 9 is press-fitted onto the fitting shaft portion 18, specifically, when both axial side portions of the inner circumferential surface of the inner ring 9 that are axially deviated from the axially inner inner ring raceway 8a are press-fitted onto the outer circumferential surface of the fitting shaft portion 18.

[0060] In particular, in this example, the annular recess 17 is arranged in an axial range that overlaps radially with the entire inner ring raceway 8a on the axial inner side, thereby making it possible to enhance the effect of suppressing the change in the inclination angle described above compared to a configuration in which the annular recess 17 is arranged in an axial range that overlaps radially with only a portion of the axial direction of the inner ring raceway 8a on the axial inner side.

[0061] As described above, in this example, it is possible to suppress changes in the inclination angle of the inner ring raceway 8a on the axially inner side relative to the central axis of the hub 3 that occur when the inner ring 9 is press-fitted onto the fitting shaft portion 18, and therefore it is possible to prevent edge loads from occurring at the contact areas between the outer peripheral surfaces of the tapered rollers 4a and the outer ring raceway 5a and inner ring raceway 8a on the axially inner side, and to prevent skew of the tapered rollers 4a. Therefore, it is easy to achieve smooth rolling motion of the tapered rollers 4a relative to the outer ring raceway 5a and inner ring raceway 8a on the axially inner side.

[0062] In addition, since the change in the inclination angle of the large rib surface 12 relative to the central axis of the hub 3 that occurs when the inner ring 9 is press-fitted onto the mating shaft portion 18 can be suppressed, the amount by which the sliding portion of the large diameter side end surface of the tapered roller 4a against the large rib surface 12 moves toward the outer diameter side of the hub 3 can be suppressed, thereby suppressing an increase in rotational torque.

[0063] In the structure of this example, the presence of the annular recess 17 on the inner surface of the inner ring 9 reduces the fitting force of the inner ring 9 against the fitting shaft portion 18, which raises the concern that the inner ring 9 may creep (rotate relative to the hub ring 10) during use.

[0064] In contrast, in the structure of this example, the axially inner end of the axially outer inner ring raceway 8b and the axially outer end of the outer peripheral surface of the fitting shaft portion 18 are connected by a stepped surface 19 that abuts the axially outer end face of the inner ring 9 of the hub wheel 10. In other words, the stepped surface 19 is located adjacent to the axially inner side of the axially outer inner ring raceway 8b. As a result, in this example, the axial width of the axially outer end of the inner ring 9 is increased compared to when the stepped surface 19 is located axially inwardly separated from the axially outer inner ring raceway 8b, thereby increasing the fitting length of the inner ring 9 relative to the fitting shaft portion 18. This ensures a fitting force of the inner ring 9 relative to the fitting shaft portion 18, improving the creep resistance of the inner ring 9 relative to the fitting shaft portion 18.

[0065] Furthermore, in this example, the outer diameter of the axially outer end of the inner ring 9, i.e., the outer diameter of the small flange portion 14, is larger than the outer diameter of the axially inner end of the axially outer inner ring raceway 8b. As a result, in the structure of this example, the radial thickness of the axially outer end of the inner ring 9 is larger, i.e., the radial rigidity is higher, compared to a structure in which the outer diameter of the axially outer end of the inner ring 9 is equal to or smaller than the outer diameter of the axially inner end of the axially outer inner ring raceway 8b. This ensures the fitting force of the inner ring 9 to the fitting shaft portion 18, thereby improving the creep resistance of the fitting portion between the fitting shaft portion 18 and the inner ring 9.

[0066] In the hub unit bearing 1 of this example, small rib surfaces 15a, 15b are provided in positions facing the small diameter side end faces of the tapered rollers 4a, 4b in each row, making it easier to bring the posture of the tapered rollers 4a, 4b in each row closer to the optimum state when assembly of the hub unit bearing 1 is complete. This makes it possible to shorten the run-in time required to bring the posture of the tapered rollers 4a, 4b in each row into the optimum state. Also, in this example, small rib surfaces 15b that face the small diameter side end faces of the tapered rollers 4b in the axially outer row are not formed on the hub ring 10, so the shape of the hub ring 10 can be simplified and the processing costs of the hub ring 10 can be reduced.

[0067] [Example 2] A second example of the embodiment of the present disclosure will be described with reference to FIG.

[0068] In the hub unit bearing 1a of this example, the annular recess 17a is formed not on the inner peripheral surface of the inner ring 9a but on the outer peripheral surface of the fitting shaft portion 18a of the hub ring 10a.

[0069] That is, in this example, the hub ring 10a has a radially recessed annular recess 17a in the outer peripheral surface of the fitting shaft portion 18a, at a portion that radially overlaps the inner ring raceway 8a on the axially inner side. Because the outer peripheral surface of the fitting shaft portion 18a and the annular recess 17a are subjected to induction heat treatment, there is little deformation due to the heat treatment. Therefore, the average radial depth of the annular recess 17a in the circumferential direction can be made smaller than that of the annular recess 17 (see FIG. 1) provided on the inner peripheral surface of the inner ring 9. More specifically, the average radial depth of the annular recess 17a in the circumferential direction is not limited to, but is preferably 0.05 mm to 1 mm, and more preferably 0.15 mm to 0.5 mm. In this example, the average radial depth of the annular recess 17a in the circumferential direction is approximately 0.15 mm. The axial range of the annular recess 17a is the same as in the first example. The inner peripheral surface of the inner ring 9a does not have an annular recess, and is configured as a cylindrical surface whose inner diameter does not change in the axial direction.

[0070] In this example, a radially recessed annular recess 17a is provided in a portion of the outer peripheral surface of the fitting shaft portion 18a that radially overlaps with the axially inner inner ring raceway 8a, thereby providing a radial gap 29a around the entire periphery within the axial range where the annular recess 17a is present between the inner peripheral surface of the inner ring 9a and the outer peripheral surface of the fitting shaft portion 18a. This makes it possible to suppress changes (decreases) in the inclination angle of the axially inner inner ring raceway 8a relative to the central axis of the hub 3a that occur when the inner ring 9a is press-fitted onto the fitting shaft portion 18a, specifically, when both axially opposite portions of the inner peripheral surface of the inner ring 9a that are axially displaced from the axially inner inner ring raceway 8a are press-fitted onto the outer peripheral surface of the fitting shaft portion 18a.

[0071] This makes it easy to achieve smooth rolling motion of the tapered rollers 4a relative to the axially inner outer ring raceway 5a and inner ring raceway 8a. Also, the amount of movement of the sliding contact portion of the large diameter side end face of the tapered rollers 4a relative to the large rib surface 12 toward the outer diameter side of the hub 3 can be suppressed, thereby suppressing an increase in rotational torque.

[0072] In the structure of this example, annular recess 17a is provided on the outer peripheral surface of fitting shaft portion 18a of hub wheel 10a. Therefore, to manufacture hub wheel 10a, a metal material is forged to form the rough shape of hub wheel 10a, and then when the shape of hub wheel 10a is shaped by turning, annular recess 17a can be formed in the same process as turning the other parts of hub wheel 10a, i.e., without changing turning tools. This reduces the processing costs of the parts that make up hub unit bearing 1a.

[0073] The other configurations and effects of the second example are the same as those of the first example.

[0074] [Example 3] A third example of the embodiment of the present disclosure will be described with reference to FIG.

[0075] Hub unit bearing 1b of this example differs from the structure of the first example in that it has a crimped portion 28 that presses down on the axially inner end face of inner ring 9 at the axially inner end of hub ring 10b that constitutes hub 3b. That is, in this example, hub 3b is constructed by fitting inner ring 9 onto fitting shaft portion 18 of hub ring 10b, and sandwiching inner ring 9 from both axial sides between stepped surfaces 19 of hub ring 10b and crimped portion 28, thereby joining and fixing inner ring 9 to hub ring 10b. In this example, the preload applied to tapered rollers 4a, 4b arranged in double rows can be adjusted by adjusting the magnitude of the force with which crimped portion 28 presses down on the axially inner end face of inner ring 9.

[0076] The crimping portion 28 is formed by fitting the inner ring 9 onto the mating shaft portion 18 of the hub ring 10b, and then plastically deforming the cylindrical portion provided at the axially inner end of the hub ring 10b radially outward.

[0077] There are no particular limitations on the specific method for forming the crimped portion 28. For example, the crimped portion 28 can be formed by a typical forging press process in which a forming die is pressed against the cylindrical portion over the entire circumference. Alternatively, the crimped portion 28 can be formed by orbital forging in which a forming die, supported so as to be rotatable about a central axis inclined with respect to the central axis of the hub ring 10b, is pressed against the cylindrical portion while rotating about the central axis O of the hub ring 10b.

[0078] In either case, when forming the crimped portion 28, material moves (flows) from the crimped portion 28 side to the portion of the fitting shaft portion 18 adjacent to the axially outer side of the crimped portion 28, i.e., the axially inner portion of the fitting shaft portion 18. This increases the radial thickness of the axially inner portion of the fitting shaft portion 18, resulting in a state equivalent to an increase in the fit between the outer peripheral surface of the axially inner portion of the fitting shaft portion 18 and the inner peripheral surface of the inner ring 9. As a result, with the formation of the crimped portion 28, the inclination angle of the large rib surface 12 with respect to the central axis of the hub 3b decreases, and the inclination angle of the inner ring raceway 8a on the axially inner side with respect to the central axis of the hub 3b increases.

[0079] In contrast, in the hub unit bearing 1b of this example, a radially recessed annular recess 17 is provided on the inner circumferential surface of the inner ring 9 at a portion that radially overlaps with the axially inner inner ring raceway 8a. Therefore, when forming the crimped portion 28, material that has migrated from the crimped portion 28 side to the axially inner portion of the fitting shaft portion 18 can be allowed to escape into the annular recess 17. Therefore, a decrease in the inclination angle of the large rib surface 12 relative to the central axis of the hub 3b and an increase in the inclination angle of the axially inner inner ring raceway 8a relative to the central axis of the hub 3b, which are associated with forming the crimped portion 28, can be suppressed. In this example, the average radial depth of the annular recess 17 in the circumferential direction is made larger than in the first example so that material that has migrated from the crimped portion 28 side to the axially inner portion of the fitting shaft portion 18 can be efficiently allowed to escape into the annular recess 17 when forming the crimped portion 28. When the structure of this example is adopted, the average value of the radial depth of the annular recess 17 in the circumferential direction is, but is not limited to, preferably 0.2 mm or more, and more preferably 0.3 mm or more. In this example, the average value of the radial depth of the annular recess 17 in the circumferential direction is about 0.4 mm.

[0080] In this example, the inner ring 9 is press-fitted onto the mating shaft portion 18, specifically, the axially opposite portions of the inner surface of the inner ring 9 that are axially offset from the axially inner inner ring raceway 8a are press-fitted onto the outer surface of the mating shaft portion 18, and the final change in the inclination angle of the axially inner inner ring raceway 8a relative to the central axis of the hub 3b is the difference between the amount by which the inclination angle of the axially inner inner ring raceway 8a relative to the central axis of the hub 3b decreases as a result of the formation of the crimped portion 28. Furthermore, the sum of the amount by which the angle of inclination of large rib surface 12 with respect to the central axis of hub 3b decreases as inner ring 9 is press-fitted onto mating shaft portion 18, and the amount by which the angle of inclination of large rib surface 12 with respect to the central axis of hub 3b decreases as crimped portion 28 is formed, is the final amount of change in the angle of inclination of large rib surface 12 with respect to the central axis of hub 3b. In this example, these final amounts of change can be reduced compared to a structure without annular recess 17.

[0081] Therefore, in this example as well, it is easy to achieve smooth rolling motion of the tapered rollers 4a relative to the axially inner outer ring raceway 5a and inner ring raceway 8a. Also, the amount of movement of the sliding contact portion of the large diameter side end face of the tapered roller 4a relative to the large rib surface 12 toward the outer diameter side of the hub 3 can be suppressed, thereby suppressing an increase in rotational torque.

[0082] The other configurations and effects of the third example are the same as those of the first example.

[0083] [Example 4] A fourth example of the embodiment of the present disclosure will be described with reference to FIG.

[0084] The hub unit bearing 1c of this example differs from the structure of the second example in that the axially inner end of the hub ring 10c that constitutes the hub 3c has a crimping portion 28 that presses down on the axially inner end face of the inner ring 9a.

[0085] In the hub unit bearing 1c of this example, a radially recessed annular recess 17a is provided on the outer peripheral surface of the fitting shaft portion 18a of the hub wheel 10c at a portion that radially overlaps the axially inner inner ring raceway 8a. Therefore, when forming the crimped portion 28, material that has migrated from the crimped portion 28 side to the axially inner portion of the fitting shaft portion 18a can be released into the annular recess 17a. Therefore, a decrease in the inclination angle of the large flange surface 12 relative to the central axis of the hub 3c and an increase in the inclination angle of the axially inner inner ring raceway 8a relative to the central axis of the hub 3c, which would occur when forming the crimped portion 28, can be suppressed. In this example, the average radial depth of the annular recess 17a in the circumferential direction is made larger than that of the second example to efficiently release material that has migrated from the crimped portion 28 side to the axially inner portion of the fitting shaft portion 18a into the annular recess 17a when forming the crimped portion 28. When the structure of this example is adopted, the average value of the radial depth of the annular recess 17a in the circumferential direction is, but is not limited to, preferably 0.15 mm or more, and more preferably 0.25 mm or more. In this example, the average value of the radial depth of the annular recess 17a in the circumferential direction is about 0.3 mm.

[0086] Other configurations and effects of the fourth example are similar to those of the first and third examples.

[0087] The structures of the first to fourth examples of the above-described embodiment can be combined as appropriate within the scope of not causing any contradiction. [Explanation of symbols]

[0088] 1, 1a, 1b, 1c Hub unit bearing 2 outer ring 3, 3a, 3b, 3c Hub 4a, 4b tapered rollers 5a, 5b Outer ring raceway 6 Stationary Flange 7 Support hole 8a, 8b Inner raceway 9, 9a Inner ring 10, 10a, 10b, 10c Hub ring 11 Otsubabe 12 Large Tsuba Face 13 Relief groove 14 Small tsuba 15a, 15b Small tsuba surface 16 Relief groove 17, 17a Annular recess 18, 18a Mating shaft 19 Step surface 20 Otsubabe 21 Large Tsuba Face 22 Relief groove 23 Rotating flange 24 Pilot Division 25 Mounting holes 26 spline holes 27a, 27b retainer 28 Crimping part 29, 29a Radial clearance

Claims

1. an outer ring having a double-row outer ring raceway on its inner circumferential surface; a hub having a double row inner ring raceway on its outer circumferential surface; a plurality of tapered rollers arranged between the double row outer ring raceways and the double row inner ring raceways, The hub includes an inner ring and a hub ring, the inner ring has an axially inner inner ring raceway among the double-row inner ring raceways, and a large rib portion protruding radially outward from a portion adjacent to the axially inner side of the axially inner inner ring raceway, the hub wheel has a fitting shaft portion onto which the inner ring is fitted, a radial gap exists over the entire circumference between a portion of the inner peripheral surface of the inner ring that radially overlaps with the inner ring raceway on the axially inner side and the outer peripheral surface of the fitting shaft portion; Hub unit bearing.

2. 2. The hub unit bearing according to claim 1, wherein the hub ring has an axially outer inner ring raceway of the double-row inner ring raceways, and a stepped surface that connects an axially inner end of the axially outer inner ring raceway to an axially outer end of the outer peripheral surface of the fitting shaft portion, and against which an axially outer end face of the inner ring abuts.

3. 3. The hub unit bearing according to claim 2, wherein the inner ring is provided with a small rib portion that protrudes radially outward at a portion adjacent to the axially outer side of the axially inner inner ring raceway and has an outer diameter that is larger than the outer diameter of an axially inner end portion of the axially outer inner ring raceway.

4. 4. The hub unit bearing according to claim 1, wherein the hub ring has a crimped portion at an end portion on the inner side in the axial direction that presses down on an end face on the inner side in the axial direction of the inner ring.

Images