Wheel support rolling bearing unit

Abstract

To provide a rolling bearing unit for wheel support capable of preventing an overheating state due to high-frequency hardening at a place near an intersection point of an inner ring raceway and a small-diameter step portion formed on a hub ring, even when a small flange portion of an inner ring also serves as a small flange face of the inner ring raceway disposed on the hub ring.SOLUTION: An inner ring 10 has a small flange portion 15 having axial both side faces respectively capable of being kept into contact with tail portions 4a, 4a of a double row conical rollers 4, 4. A hub ring 9 includes a small flange-side connection portion 32 having a cross-sectional shape formed by connecting convex arc 30 disposed at a step face side and a slant face 31 disposed at an inner ring raceway side and crossing the inner ring raceway 12a at an acute angle or the other convex arc having a radius larger than the convex arc 30, between a step face 13a of a small diameter step portion 13 and the inner ring raceway 12a of an axial outer row.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a wheel supporting rolling bearing unit used to rotatably support a wheel of an automobile relative to a suspension system. [Background technology]

[0002] In wheel-supporting rolling bearing units for relatively heavy automobiles such as small trucks and large passenger cars, it has been known to use double-row tapered roller bearings equipped with double rows of tapered rollers as rolling elements (see, for example, Patent Document 1).

[0003] As shown in FIG. 6, the double-row tapered roller bearing unit 100 described in Patent Document 1 comprises a hub ring 102, an inner ring 103, an outer ring 104, a plurality of first tapered rollers 105, a plurality of second tapered rollers 106, a first seal ring 107, and a second seal ring 108.

[0004] The small rib portion 123 formed on the outer peripheral surface of the outer end of the inner ring 103 is formed so that both axial end faces can abut against the small diameter end faces of the first and second tapered rollers 105, 106. This allows both axial end faces of the first and second tapered rollers 105, 106 to abut against the side faces of the large rib portion and the small rib portion, respectively, shortening the run-in time required to align the first and second tapered rollers 105, 106 and simplifying the shape of the hub ring 102. Induction hardening is also performed to form a hardened layer on the outer peripheral surface of the portion of the hub ring 102 spanning from the middle portion to the inner end, and on the inner peripheral surface of the middle portion of the outer ring 104.

[0005] Furthermore, Patent Documents 2 to 4 describe various techniques for suppressing local overheating during induction hardening. For example, in the hub unit described in Patent Document 2, the angle formed between the guide surface of the large flange and the outer peripheral surface is set to an obtuse angle to prevent local overheating during induction hardening. Furthermore, in the hub unit described in Patent Document 3, the angle between the guide surface of the large flange and the outer peripheral surface of the large flange that continues to the guide surface is an obtuse angle, and the large diameter portion that continues to the large flange is a cylindrical portion with a substantially constant outer diameter, thereby suppressing local overheating during induction hardening and ensuring sealing performance. Furthermore, in the hub unit described in Patent Document 4, the hardened layer of the inner ring raceway and the hardened layer of the small diameter step portion formed on the hub ring are provided separately to prevent overheating due to heat treatment. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-113841 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-3111 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-223973 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-138354 Summary of the Invention [Problem to be solved by the invention]

[0007] 6, in a wheel-supporting rolling bearing unit in which the small-diameter end faces of the first and second tapered rollers 105, 106 can freely abut against both axial end faces of the small rib portion 123 of the inner ring 103, an overheating state is likely to occur during induction hardening near the intersection of the inner ring raceway 111 and the small-diameter step portion 112 formed in the hub ring 102, and the overheating can cause the structure to coarsen, resulting in a risk of shortening the bearing life. In particular, in the bearing unit 100 described in Patent Document 1, the inner ring raceway 111 is formed up to the vicinity of the small-diameter step portion 112, so it is not possible to perform induction hardening on the inner ring raceway and the small-diameter step portion separately, as in Patent Document 4.

[0008] Furthermore, in Patent Document 3, the large flange portion formed on the hub wheel is devised to suppress overheating by induction hardening and ensure sealing performance, but because the volume of the intersection between the large flange surface and the outer peripheral surface of the large flange portion is reduced, it is still desirable to increase heat capacity and prevent localized overheating.

[0009] In view of the above circumstances, the present invention aims to provide a wheel support rolling bearing unit that can prevent overheating due to induction hardening near the intersection of the inner ring raceway formed on the hub wheel and the small diameter step portion, even when the small rib portion of the inner ring also serves as the small rib surface of the inner ring raceway provided on the hub wheel. [Means for solving the problem]

[0010] The above object of the present invention can be achieved by the following configuration. (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 and a rotating flange on the outboard side for supporting and fixing a wheel; a plurality of tapered rollers rollably provided between the double row outer ring raceways and the double row inner ring raceways; Equipped with The hub comprises, from the outboard side to the inboard side, a hub wheel having at least the rotating-side flange, one row of the inner ring raceways, and a small diameter stepped portion, and an inner ring having the other row of the inner ring raceways, fitted onto the outer peripheral surface of the small diameter stepped portion with its outboard side end face abutting against a stepped surface of the small diameter stepped portion, and fixed to the hub wheel, the inner ring has small ribs having both axial side surfaces that can come into contact with the tail portions of the double row tapered rollers, The hub wheel is provided with a small flange-side connecting portion between a step surface of the small diameter step portion and the inner ring raceway of one row, the small flange-side connecting portion having a cross-sectional shape that connects a convex arc provided on the step surface side to a slope provided on the inner ring raceway side that intersects with the inner ring raceway at an acute angle or another convex arc with a radius larger than that of the convex arc. Rolling bearing unit for wheel support. (2) The hub ring comprises a large rib portion having a large rib surface capable of coming into contact with the heads of the tapered rollers of one row, and an outer diameter cylindrical surface provided on the outboard side of the large rib portion, The hub wheel is provided with a large rib-side connecting portion between the large rib surface of the large rib portion and the outer diameter cylindrical surface, the large rib-side connecting portion having a cross-sectional shape connecting a convex arc provided on the large rib surface side and a slope provided on the outer diameter cylindrical surface side that intersects with the outer diameter cylindrical surface at an acute angle, or another convex arc having a radius larger than that of the convex arc on the large rib surface side. 2. A wheel supporting rolling bearing unit according to claim 1. (3) 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 and a rotating flange on the outboard side for supporting and fixing a wheel; a plurality of tapered rollers rollably provided between the double row outer ring raceways and the double row inner ring raceways; Equipped with The hub comprises, from the outboard side to the inboard side, a hub wheel having at least the rotating-side flange, one row of the inner ring raceways, and a small diameter stepped portion, and an inner ring having the other row of the inner ring raceways, fitted onto the outer peripheral surface of the small diameter stepped portion with its outboard side end face abutting against a stepped surface of the small diameter stepped portion, and fixed to the hub wheel, the hub ring comprises a large rib portion having a large rib surface capable of coming into contact with the heads of the tapered rollers of one row, and an outer diameter cylindrical surface provided on the outboard side of the large rib portion, The hub wheel is provided with a large rib-side connecting portion between the large rib surface of the large rib portion and the outer diameter cylindrical surface, the large rib-side connecting portion having a cross-sectional shape connecting a convex arc provided on the large rib surface side and a slope provided on the outer diameter cylindrical surface side that intersects with the outer diameter cylindrical surface at an acute angle, or another convex arc having a radius larger than that of the convex arc on the large rib surface side. Rolling bearing unit for wheel support. [Effects of the Invention]

[0011] According to the wheel support rolling bearing unit of the present invention, even when the small flange portion of the inner ring also serves as the small flange surface of the inner ring raceway provided on the hub ring, it is possible to prevent overheating due to induction hardening near the intersection between the inner ring raceway formed on the hub ring and the small diameter step portion. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view of a wheel supporting rolling bearing unit according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing the hub wheel of FIG. [Figure 3] FIG. 3 is an enlarged view of part III in FIG. 2. [Figure 4] FIG. 3 is an enlarged view of part IV in FIG. 2. [Figure 5] FIG. 5 is a cross-sectional view of a wheel supporting rolling bearing unit according to a second embodiment of the present invention. [Figure 6] FIG. 10 is an enlarged view of a main portion of a conventional wheel supporting rolling bearing unit. DETAILED DESCRIPTION OF THE INVENTION

[0013] A wheel-supporting rolling bearing unit according to one embodiment of the present invention will be described in detail with reference to Figures 1 to 4. Throughout this specification and claims, "outside" in the axial direction refers to the left side in Figure 1, which is the outer side in the width direction of the vehicle body when assembled to the automobile, and is also referred to as the "outboard side." Conversely, the right side in Figure 1, which is the center side in the width direction of the vehicle body, is referred to as "inside" in the axial direction and is also referred to as the "inboard side."

[0014] The wheel supporting rolling bearing unit 1 of this embodiment is for a driving wheel, and mainly comprises an outer ring 2, a hub 3, a plurality of tapered rollers 4, 4, a seal ring 5, and an encoder 6.

[0015] The outer ring 2 has a stationary flange 7 on its outer peripheral surface and double-row (two-row) outer ring raceways 8a, 8b on its inner peripheral surface. When in use, the stationary flange 7 is fixed to the knuckle of a suspension device, so that the outer ring 2 does not rotate while supported by the suspension device.

[0016] The hub 3 is composed of a hub ring 9 and an inner ring 10, and is disposed coaxially (concentrically) with the outer ring 2 on the inner diameter side of the outer ring 2.

[0017] The hub wheel 9 is provided with a circular rotating side flange 11 that extends radially outward from a portion that protrudes axially outward from the axially outer (outboard) opening of the outer ring 2 and that supports and fixes wheels (drive wheels) and rotating braking members such as disc rotors. Specifically, the rotating side flange 11 is provided with a plurality of insertion holes 11a, and if each insertion hole 11a is a female thread, a hub bolt (not shown) is threaded into each insertion hole, and if each insertion hole 11a is a cylindrical hole, a stud bolt is serrated and fitted into each insertion hole.

[0018] An inner ring raceway 12a of an axially outer row (one row) is provided on the outer peripheral surface of the hub ring 9 at a portion facing the outer ring raceway 8a of the axially outer row provided on the inner peripheral surface of the outer ring 2. Furthermore, a small diameter step 13 is provided on the outer peripheral surface of the hub ring 9 at an axially inner end portion facing the outer ring raceway 8b of the axially inner (inboard) row provided on the inner peripheral surface of the outer ring 2.

[0019] An inner ring raceway 12b of the axially inner row (the other row) is provided on the outer peripheral surface of the inner ring 10. The inner ring 10 is press-fitted onto the outer peripheral surface of the small diameter step 13 of the hub ring 9 with an interference, with its outboard end face 10a abutting against the step surface 13a of the small diameter step 13, and is fixed to the hub ring 9. The inner ring 10 also has a small rib portion 15 having both axial side surfaces that can come into contact with the tail portions 4a, 4a of the double row tapered rollers 4, 4, respectively.

[0020] A spline hole 17 is formed in the center of the hub ring 9, penetrating it in the axial direction. Although not shown, when the wheel support rolling bearing unit is assembled to the vehicle body, a spline shaft coupled to a constant velocity joint engages with the spline hole 17, and the unit is fixed to the hub 3 by screwing a nut into it. At this time, the axially inner end face of the large rib portion 14 of the inner ring 10 abuts against the end face of the constant velocity joint (not shown) or a step formed on the end of the drive shaft (not shown), and the outboard end face 10a of the inner ring 10 abuts against the step surface 13a of the small diameter step portion 13, thereby positioning and fixing the inner ring 10 to the hub ring 9 in the axial direction, as described above.

[0021] A plurality of tapered rollers 4, 4 are provided in the portion between the outer ring raceway 8a and the inner ring raceway 12a of the axially outer row, and in the portion between the outer ring raceway 8b and the inner ring raceway 12b of the axially inner row, with the tail portions 4a, 4a of the tapered rollers 4, 4 of each row facing each other and held by cages 24, 24 so that they can roll freely.

[0022] The seal ring 5 is supported and fixed to the axial outer end of the outer ring 2, and closes the axial outer end opening of the internal space in which a plurality of tapered rollers 4, 4 are provided, which is located between the inner peripheral surface of the outer ring 2 and an outer diameter cylindrical surface 20 on the outboard side of the large rib portion 19 of the hub ring 9.

[0023] Therefore, in this embodiment, the hub ring 9 has, from the outboard side to the inboard side, a rotating side flange 11, an outer diameter cylindrical surface 20, a large flange portion 19, an inner ring raceway 12a in the axially outer row, and a small diameter step portion 13.

[0024] The encoder 6 is fitted and fixed to the outer peripheral surface of the large flange 14 of the inner ring 10a via a slinger 18 formed with an L-shaped cross section. The encoder 6 is attached to the axially inner surface of the slinger 18 and faces a rotation detection sensor (not shown) to detect the rotation speed of the wheel. A seal member may also be provided at the axially inner end of the outer ring 2 to close the axially inner end opening of the internal space.

[0025] Here, in order to ensure the performance of the axially outer row inner ring raceway 12a, the hub ring 9 is locally induction hardened from near the base of the rotating side flange 11 to the outer diameter cylindrical surface 20, large rib portion 19, the axially outer row inner ring raceway 12a, and small diameter step portion 13, as shown in Fig. 2, to form a surface-hardened layer X in those areas (see the shaded area in Fig. 2). In this embodiment, in order to prevent the occurrence of areas on the surface of the hub ring 9 that become overheated due to induction hardening, the hub ring 9 has the following shape.

[0026] 3, the hub ring 9 is provided with a small flange-side connecting portion 32 having a cross-sectional shape formed by connecting a convex arc 30 of radius r1 provided on the step surface 13a side between the step surface 13a of the small diameter step portion 13 and the inner ring raceway 12a of the axially outer row, and a slope 31 provided on the inner ring raceway side that intersects with the inner ring raceway 12a at an acute angle. In other words, the small flange-side connecting portion 32 is formed by connecting a truncated cone shape formed by the cross-sectional shape made up of the slope 31 and a convex spherical shape formed by the cross-sectional shape made up of the convex arc 30.

[0027] As a result, the area near the intersection between the inner ring raceway 12a formed on the hub ring 9 and the step surface 13a of the small diameter step portion 13 is formed by the small flange side connecting portion 32 which has no corners, thereby ensuring a distance from the high frequency heating coil and preventing overheating due to high frequency hardening of the small flange side connecting portion 32.

[0028] The inclined surface 31 is further inclined at an angle θ of 10° to 20° (17° in this embodiment) relative to the inner ring raceway 12a of the axially outer row. Furthermore, the reason why the lower limit of the angle θ is set to 10° is to keep the small rib side connecting portion 32 within the range t of the sum of the gap g (for example, g = 0.2 mm) between the small rib portion 15 and the tail portion 4a of the tapered roller 4 when the head portion 4b of the tapered roller 4 abuts against the large rib surface 19a of the large rib portion 19, and the axial dimension s (for example, s = 0.6 mm) of the chamfer 4c of the tapered roller 4. Furthermore, the reason why the upper limit of the angle θ is set to 20° is to prevent an overheating state from occurring in the boundary portion between the inner ring raceway 12a and the slant surface 31, and to suppress a sudden change in the hardened layer depth.

[0029] The angle a between the step surface 13a of the small diameter step portion 13 along the radial direction and the slope 31 is set to 57° to 67° (60° in this embodiment) depending on the angle θ, and the axial dimension b is the axial distance from the step surface 13a to the point of contact between the convex arc 30 and the slope 31, and is set from the radius r1 of the convex arc 30 and the angle a so as to ensure a grinding allowance for the step surface 13a. In Fig. 3, c represents the grinding allowance for the step surface 13a and the inner ring raceway 12a.

[0030] Furthermore, instead of the slope 31, the small rib side connecting portion 32 may have the cross-sectional shape of another convex arc having a larger radius than the convex arc 30 on the stepped surface side. In this case as well, the size of the other convex arc may be designed to prevent an overheating state from occurring at the boundary between the inner ring raceway 12a and the other convex arc, and to satisfy the condition that it falls within the range t of the sum of the gap g between the small rib portion 15 and the tail portion 4a of the tapered roller 4 and the axial dimension s of the chamfer 4c of the tapered roller 4.

[0031] 4, the hub ring 9 is provided with a large rib-side connecting portion 42 having a cross-sectional shape connecting a convex arc 40 with a radius r2 provided on the large rib surface side and another convex arc 41 provided on the outer diameter cylindrical surface side and having a larger radius than the convex arc 40 on the large rib surface side (in this embodiment, a radius r3 four times the radius r2 of the convex arc 40), between the large rib surface 19a of the large rib portion 19, which is a conical surface against which the heads 4b of the tapered rollers 4 abut in an assembled state, and the outer diameter cylindrical surface 20. In other words, the large rib-side connecting portion 42 is formed by connecting two convex spherical shapes constituted by the cross-sectional shapes made up of the convex arc 40 and the other convex arc 41.

[0032] As a result, the area near the intersection between the large flange surface 19a of the large flange portion 19 formed on the hub wheel 9 and the outer cylindrical surface 20 is formed by a large flange side connecting portion 42 without corners, which ensures a distance from the high-frequency heating coil and prevents overheating due to high-frequency hardening of the large flange side connecting portion 32.

[0033] The other convex arc 41 may have a radius r3 that is three to five times the radius r2 of the convex arc 40. The reason why the radius r3 of the other arc portion 41 is set to three times or more the radius of the convex arc 40 is to prevent overheating at the boundary between the outer cylindrical surface 20, which forms the seal sliding surface, and the other convex arc 41, and to suppress a sudden change in the hardened layer depth. The reason why the radius r3 of the other convex arc 41 is set to five times or less the radius r2 of the convex arc 40 is to ensure the axial width of the outer cylindrical surface 20.

[0034] The large flange side connecting portion 42 may be a slope that intersects with the outer cylindrical surface 20 at an acute angle, instead of the other convex arc 41. In this case as well, the angle of the slope is preferably set to 10° to 20° in order to ensure the axial width of the outer cylindrical surface 20 and to prevent overheating at the boundary between the outer cylindrical surface 20 and the slope.

[0035] As explained above, in the wheel support rolling bearing unit 1 of this embodiment, the hub ring 9 is provided, between the step surface 13a of the small diameter step 13 and the inner ring raceway 12a of the axially outer row, with a small rib-side connecting portion 32 having a cross-sectional shape that connects the convex arc 30 provided on the step surface side and the slope 31 provided on the inner ring raceway side that intersects with the inner ring raceway 12a at an acute angle, or another convex arc with a larger radius than the convex arc 30. As a result, even when the small rib portion 15 of the inner ring 10 also serves as the small rib surface of the inner ring raceway 12a provided on the hub ring 9, it is possible to prevent overheating due to induction hardening near the intersection of the inner ring raceway 12a formed on the hub ring 9 and the step surface 13a of the small diameter step 13.

[0036] Furthermore, in the wheel support rolling bearing unit 1 of this embodiment, the hub ring 9 is provided with a large rib-side connecting portion 42 between the large rib surface 19a of the large rib portion 19 and the outer diameter cylindrical surface 20, which has a cross-sectional shape that connects a convex arc 40 provided on the large rib surface side and a slope provided on the outer diameter cylindrical surface side that intersects with the outer diameter cylindrical surface 20 at an acute angle, or another convex arc 41 with a larger radius than the convex arc 40 on the large rib surface side. This prevents overheating due to induction hardening and ensures sealing performance, and in particular, because the volume of the intersection between the large rib surface 19a of the large rib portion 19 and the outer diameter cylindrical surface 20 is secured, heat capacity is secured and localized overheating can be prevented.

[0037] The present invention is not limited to the above-described embodiment, and modifications and improvements can be made as appropriate. For example, in the above embodiment, a wheel supporting rolling bearing unit for a driving wheel has been described, but the present invention is not limited to this and can also be applied to a wheel supporting rolling bearing unit for a driven wheel as shown in FIG. In the case of the wheel supporting rolling bearing unit 1a for a driven wheel, an end cap may be used in addition to the seal member as a member for closing the axially inner end of the outer ring 2a.

[0038] That is, in the wheel support rolling bearing unit 1a for a driven wheel, the inner ring 10 is externally fitted and fixed by press fitting onto the small diameter step portion 13 of the hub ring 9 with an interference, and the axial inner end face 14 on the large flange portion 14 side is pressed down by the crimping portion 23 formed on the axial inner end portion of the hub ring 9, thereby positioning and fixing it to the hub ring 9. In such a wheel support rolling bearing unit 1, as in the above embodiment, a small flange side connecting portion 32 and a large flange side connecting portion 42 can be formed on the hub ring 9, and the same effects as in the above embodiment can be achieved. [Explanation of symbols]

[0039] 1,1a Wheel support rolling bearing unit 2 outer ring 3. Hub 4 tapered rollers 5 seal ring 6 Encoders 7 Stationary side flange 8a, 8b Outer ring raceway 9 Hub Wheel 10. Inner Circle 11 Rotating side flange 12a, 12b Inner raceway 13 Small diameter stepped section 14 Otsubabe 15 Small tsuba 23 Crimping part 24 Cage 30 Convex Arc 31 Slope 32 Small flange side joint 40 Convex Arc 41 Other convex arcs 42 Large tsuba side joint

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 and a rotating flange on the outboard side for supporting and fixing a wheel; a plurality of tapered rollers rollably provided between the double row outer ring raceways and the double row inner ring raceways; Equipped with The hub comprises, from the outboard side to the inboard side, a hub wheel having at least the rotating-side flange, one row of the inner ring raceways, and a small diameter stepped portion, and an inner ring having the other row of the inner ring raceways, fitted onto the outer peripheral surface of the small diameter stepped portion with its outboard side end face abutting against a stepped surface of the small diameter stepped portion, and fixed to the hub wheel, the inner ring has small ribs having both axial side surfaces that can come into contact with the tail portions of the double row tapered rollers, The hub wheel is provided with a small flange-side connecting portion between a step surface of the small diameter step portion and the inner ring raceway of one row, the small flange-side connecting portion having a cross-sectional shape that connects a convex arc provided on the step surface side to a slope provided on the inner ring raceway side that intersects with the inner ring raceway at an acute angle or another convex arc with a radius larger than that of the convex arc. Rolling bearing unit for wheel support.

2. the hub ring comprises a large rib portion having a large rib surface capable of coming into contact with the heads of the tapered rollers of one row, and an outer diameter cylindrical surface provided on the outboard side of the large rib portion, The hub wheel is provided with a large rib-side connecting portion between the large rib surface of the large rib portion and the outer diameter cylindrical surface, the large rib-side connecting portion having a cross-sectional shape connecting a convex arc provided on the large rib surface side and a slope provided on the outer diameter cylindrical surface side that intersects with the outer diameter cylindrical surface at an acute angle, or another convex arc having a radius larger than that of the convex arc on the large rib surface side.

2. A wheel supporting rolling bearing unit according to claim 1.

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