JP2018112225A - Rolling bearing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To actualize the construction of a rolling bearing unit to prevent a deterioration in the lifetime of a bearing while securing the strength of a flange piece.SOLUTION: In the axial outside face of a root part of each of a plurality of flange pieces 8a constituting a stationary-side flange 6a, a recessed part 20 recessed axially inward is provided over the whole circumferential width of the flange piece 8a. A constriction part 21 is thereby provided at the radial inner end of the flange piece 8a at its portion adjacent to the axial inside of the recessed part 20. Then, the constriction part 21 is located in an area spaced axially inward from an outer ring raceway 7d without radially overlapping with the outer ring raceway 7d in an inside row.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an improvement of a rolling bearing unit that is used, for example, to rotatably support a vehicle wheel with respect to a suspension device.

  6 and 7 show an example of a conventional structure described in Patent Document 1 as a wheel bearing rolling bearing unit for rotatably supporting a wheel with respect to an automobile suspension system. The rolling bearing unit 1 supports the hub 3 on the inner diameter side of the outer ring 2 through a plurality of rolling elements 4 and 4 so as to be rotatable.

  In the present specification and claims, “outside” in the axial direction means the left side of FIGS. 1, 3, 4, 6, and 7, which is the outer side in the width direction of the vehicle when assembled to the vehicle body. On the other hand, the right side in FIGS. 1, 3, 4, 6, and 7 which is the center side in the width direction of the vehicle when assembled to the vehicle body is referred to as “inside” in the axial direction.

  The outer ring 2 includes an outer ring main body 5 and a stationary side flange 6. Of these, the outer ring main body 5 is formed in a cylindrical shape as a whole, and has double-row outer ring raceways 7a and 7b on the inner peripheral surface. The stationary side flange 6 is provided on the outer peripheral surface of the outer ring main body 5 so as to protrude radially outward from a portion overlapping the outer ring raceway 7b in the inner row in the radial direction. In the illustrated example, the stationary side flange 6 is constituted by a plurality (four in the illustrated example) of flange pieces 8 and 8 provided in a state of being separated in the circumferential direction. Mounting holes 9 and 9 penetrating in the axial direction are provided in portions near the radially outer ends of the flange pieces 8 and 8.

  On the outer peripheral surface of the outer ring main body 5, protrusions 10, 10 that connect the flange pieces 8, 8 adjacent in the circumferential direction are provided between the flange pieces 8, 8. And since such an outer ring | wheel 2 is couple | bonded and fixed to the knuckle which comprises a suspension apparatus with the knuckle bolt screwed in the attachment holes 9 and 9 formed in the flange pieces 8 and 8, it does not rotate at the time of use.

  The hub 3 is configured by coupling a hub main body 11 and an inner ring 12, and has double-row inner ring raceways 13 a and 13 b and a rotation side flange 14 on an outer peripheral surface. Of these, the hub body 11 has a rotation-side flange 14 on the outer peripheral surface near the outer end in the axial direction, an inner ring raceway 13a in the outer row in the middle in the axial direction, and a small-diameter stepped portion near the inner end in the axial direction. 15 are formed directly. The inner ring 12 is configured in a cylindrical shape, and an inner row of inner ring raceways 13b are formed on the outer peripheral surface. The inner ring 12 is externally fitted to the small-diameter step portion 15 of the hub main body 11, and the axial inner end surface is suppressed by a caulking portion 16 formed at the axial inner end portion of the hub main body 11. Such a hub 3 rotates during use because the wheel and the brake rotating member are supported and fixed by the hub bolt 18 inserted through the support hole 17 formed in the rotation side flange 14.

  A plurality of rolling elements 4, 4 are rolled in each row while being held by cages 19, 19 between the double row outer ring raceways 7a, 7b and the double row inner ring raceways 13a, 13b. It is provided freely.

  The above-described rolling bearing unit 1 for supporting a wheel is required to have both high rigidity for improving steering stability and weight reduction for reducing unsprung load and improving riding comfort performance. . In view of such circumstances, in the case of the conventional structure, high rigidity is achieved by increasing the thickness dimension in the axial direction of the flange piece 8 in order to secure the screwing width with the knuckle bolt. The weight of the outer ring main body 5 is reduced by keeping the thickness dimension in the radial direction small.

Japanese Patent Laid-Open No. 2006-168860

  However, in the case of the above-described conventional structure, the flange pieces 8 and 8 are intermittently provided in the circumferential direction, and are provided at positions that overlap with the outer ring raceway 7b in the inner row in the radial direction. Due to this, problems as shown in the following (1) to (3) are likely to occur, which may adversely affect the strength of the flange piece 8 and the bearing life of the rolling bearing unit 1.

(1) The deformation amount of the outer ring 2 generated when the flange piece 8 is coupled and fixed to the suspension device is increased, which may adversely affect the roundness of the outer ring raceway 7b.
In other words, when the flange piece 8 is coupled and fixed to the suspension device, if a radial force is applied to the flange piece 8 from the knuckle bolt, the inner circumference of the outer ring main body 5 configured to be thin for weight reduction. Of the surface, the outer ring raceway 7b provided at a position overlapping the flange piece 8 in the radial direction may be slightly deformed in the radial direction. As a result, the roundness of the outer ring raceway 7b may be reduced, and the life of the rolling bearing unit 1 may be reduced.

(2) The thickness dimension in the radial direction of the heat-treated hardened layer formed on the inner peripheral surface of the outer ring 2 is smaller at the portion where the phase in the circumferential direction coincides with the flange piece 8, whereas the phase in the circumferential direction is smaller. It becomes large in a portion that does not coincide with the flange piece 8 (portion that coincides with the protrusion 10), and the thickness dimension of the heat-treated cured layer becomes nonuniform in the circumferential direction.

The above (2) will be described with reference to FIG. In FIG. 8A, the vertical axis represents the radial dimension, and the horizontal axis represents the circumferential position (phase) of the outer ring 2.
Of the outer ring 2, the portion in which the phase in the circumferential direction coincides with the flange piece 8 has a larger thickness dimension in the radial direction than the portion in which the phase in the circumferential direction does not coincide with the flange piece 8. That's why it gets bigger For this reason, when the heat treatment hardened layer is formed on the inner peripheral surface of the outer ring 2, as shown in FIG. 8A, the thickness dimension in the radial direction of the heat treat hardened layer is such that the phase in the circumferential direction is the flange piece 8. Is smaller than the portion that does not match the flange piece 8.
Here, the thickness dimension of the heat-treated hardened layer related to the outer ring raceway 7b is determined in consideration of the depth at which shear stress (τ0 or τst) generated based on the load applied to the outer ring raceway 7b is taken into consideration. There is a need. For this reason, it is necessary to ensure more than the above-mentioned minimum thickness also about the heat processing hardened layer formed in the part in which the phase regarding the circumferential direction corresponds with the flange piece 8. FIG. For this reason, there is a possibility that the thickness dimension of the heat-treated and hardened layer at a portion where the phase in the circumferential direction does not coincide with the flange piece 8 becomes excessive. As a result, it is difficult to ensure the thickness dimension of the non-cured portion existing on the radially outer side of the heat-treated cured layer, and sufficient compressive stress does not act on the heat-treated cured layer, so metal fatigue is likely to occur in the heat-treated cured layer. Thus, the rolling fatigue life of the outer ring raceway 7b may be reduced.

(3) There is a possibility that the tensile stress acting on the continuous portion (corner R portion) between both circumferential edges of the flange piece 8 and the outer peripheral surface of the outer ring main body 5 may be excessive.
The above (3) will be described by adding (B) to (D) in FIG. 8B to 8D, the vertical axis represents the magnitude of the tensile stress, and the horizontal axis represents the circumferential position (phase) of the outer ring 2.

  As shown in FIG. 8A, in the outer ring 2, the thickness in the radial direction is greater in the portion where the phase in the circumferential direction does not match the flange piece 8 than in the portion where the phase matches the flange piece 8. The ratio of the thickness dimension of the heat-treated cured layer to the dimension increases. For this reason, as shown in FIG. 8B, the outer ring main body 5 caused by the heat treatment hardened layer is formed at a portion where the phase in the circumferential direction does not coincide with the flange piece 8 and at a portion coincident with the flange piece 8. The tensile stress in the circumferential direction of the non-cured portion on the outer peripheral surface side increases. As described above, since the thickness dimension of the heat treatment hardened layer at the portion where the phase in the circumferential direction does not coincide with the flange piece 8 may be excessive, the outer peripheral surface side of the outer ring main body 5 caused by the heat treatment hardened layer. Regarding the tensile stress in the circumferential direction of the non-hardened portion, there is a possibility that the phase in the circumferential direction becomes excessive at a portion where the phase does not coincide with the flange piece 8.

Next, considering a case where a turning outer load as shown by an arrow X in FIG. 6 acts on the hub 3, as shown in FIG. 8C, the non-hardening of the outer peripheral surface side of the outer ring main body 5 is performed. The tensile stress in the axial direction of the portion is larger in the portion where the phase in the circumferential direction coincides with the flange piece 8 than in the portion which does not coincide with the flange piece 8, whereas as shown in FIG. The tensile stress in the circumferential direction of the non-cured portion on the outer peripheral surface side of the outer ring main body 5 is greater in the portion adjacent to both sides in the circumferential direction of the flange piece 8 than in the other portions.
Accordingly, when the vehicle is turning, the tensile stresses in the circumferential direction shown in FIGS. 8B and 8D are respectively applied. Therefore, both circumferential edges of the flange piece 8 and the outer ring main body. The tensile stress acting on the continuous part (corner R part) with the outer peripheral surface of 5 may be excessive. As a result, it may be difficult to ensure the strength of the flange piece 8.

  Furthermore, when the flatness (flatness) of the axially inner side surface of the flange piece 8 abutting against the suspension device is not sufficient, the flange piece 8 is inclined with respect to the flange piece 8 when the knuckle bolt is fastened. Thus, a tensile stress in the circumferential direction further acts on a continuous portion between both circumferential edges of the flange piece 8 and the outer peripheral surface of the outer ring main body 5.

In the case of the rolling bearing unit 1 having the conventional structure, the problem as described in the above (1) to (3) is likely to occur due to the shape and formation position of the stationary side flange 6. It may be difficult to ensure the strength, and the bearing life of the rolling bearing unit 1 may be easily reduced.
In view of the circumstances as described above, the present invention has been invented to realize a structure of a rolling bearing unit that can ensure the strength of the flange piece and prevent a decrease in bearing life.

The rolling bearing unit of the present invention includes an outer ring, a hub, and a plurality of rolling elements.
Of these, the outer ring has an outer ring main body and a plurality of flange pieces. For example, the outer ring is supported and fixed to the suspension device during use and does not rotate. Of these, the outer ring main body is formed in a cylindrical shape, and has an outer ring raceway on the inner peripheral surface. The flange piece protrudes radially outward from a plurality of locations in the circumferential direction of the outer peripheral surface of the outer ring main body and is provided so as to overlap the outer ring raceway in the radial direction, and constitutes a stationary side flange.
The hub is disposed concentrically with the outer ring on the inner diameter side of the outer ring, and has an inner ring raceway on a portion of the outer peripheral surface facing the outer ring raceway. Rotate with.
Each of the rolling elements is, for example, a ball or a tapered roller, and is provided between the outer ring raceway and the inner ring raceway so as to freely roll.
A concave portion that is recessed in the axial direction is provided at a portion that overlaps the outer ring raceway in the radial direction at the radially inner end portion (root portion, proximal end portion) of the flange piece. Thereby, the constriction part is provided in the part adjacent to this recessed part and an axial direction among the radial direction inner ends of this flange piece. And this constriction part is located in the part which remove | deviated from this outer ring track | truck in the axial direction, without overlapping with the said outer ring track | truck.

When implementing this invention, the said recessed part can be provided over the circumferential direction full width of the said flange piece.
In this case, the cross-sectional shape (contour shape) of the portion of the outer peripheral surface of the outer ring that overlaps the outer ring raceway in the radial direction can be made the same without changing over the entire circumference.

  On the other hand, in the case of carrying out the present invention, the concave portion is provided in one or a plurality of circumferential directions of the flange piece in a state where the concave portion is opened only on the axial side surface of the flange piece. A configuration in which a portion adjacent to the concave portion is a reinforcing rib extending in the radial direction may be employed.

  According to the rolling bearing unit of the present invention having the above-described configuration, the strength of the flange piece can be ensured and the bearing life can be prevented from decreasing.

Sectional drawing which shows the rolling bearing unit which shows the 1st example of embodiment of this invention. The schematic diagram which shows the state which looked at the flange piece from the axial direction outer side. FIG. 5 is an enlarged view of a portion corresponding to the portion A in FIG. 1, illustrating the cross-sectional shape of a portion overlapping with the outer ring raceway in the inner row in the radial direction on the outer peripheral surface of the outer ring. The outline of the part removed from the flange piece is indicated by a one-dot chain line. The half part sectional view of the rolling bearing unit which shows the 2nd example of an embodiment of the invention. The figure corresponding to FIG. 2 similarly. Sectional drawing which shows the rolling bearing unit of a conventional structure. The perspective view which takes out an outer ring | wheel similarly and shows. The figure shown in order to demonstrate that the magnitude | size of the heat-treatment hardening layer thickness and the acting tensile stress change according to the circumferential direction position of an outer ring | wheel similarly.

[First example of embodiment]
A first example of the embodiment of the present invention will be described with reference to FIGS. The rolling bearing unit 1a of this example is used for rotatably supporting a wheel (driven wheel) of an automobile with respect to a suspension device, and includes an outer ring 2a, a hub 3a, and a plurality of rolling elements (balls). 4a and 4a.

  The outer ring 2a is made of an iron-based alloy such as medium carbon steel and has a substantially cylindrical shape, and includes an outer ring main body 5a and a stationary side flange 6a. Of these, the outer ring main body 5a is entirely formed in a cylindrical shape, and has double-row outer ring raceways 7c and 7d on the inner peripheral surface. The stationary flange 6a is provided in a state of projecting radially outward from the outer peripheral surface of the outer ring main body 5a, and the outer half in the axial direction overlaps the outer ring raceway 7d in the inner row in the radial direction. In the case of this example, the stationary side flange 6a is constituted by a plurality (four in the illustrated example) of flange pieces 8a provided in a state of being separated in the circumferential direction. The flange piece 8a has a substantially trapezoidal shape when viewed from the axial direction, and is formed in a substantially flat plate shape. A mounting hole (screw hole) 9a penetrating in the axial direction is provided in the radial and circumferential intermediate portions. It has been.

  Particularly in the case of this example, on the axially outer side surface of the radially inner end portion (the root portion, the base end portion) of the flange piece 8a originally having the shape shown by the broken line in FIG. A concave portion (thickening portion) 20 having a semi-elliptical cross section that is recessed inward in the axial direction is provided over the entire circumferential width of the flange piece 8a. In other words, the recess 20 is provided not only on the outer surface in the axial direction of the flange piece 8a but also on both sides in the circumferential direction of the flange piece 8a. Thereby, the constriction part 21 is formed in the part adjacent to the axial direction inner side of the recessed part 20 among the radial direction inner end parts of the flange piece 8a. In other words, by forming the recess 20 at the radially inner end of the flange piece 8a, the remaining part other than the recess 20 of the radially inner end of the flange piece 8a is used as the constricted portion 21. In the case of this example, by adjusting the axial depth dimension of the concave portion 20, the constricted portion 21 is axially inward from the outer ring raceway 7d without overlapping the inner ring outer raceway 7d in the radial direction. It is located in the part which was removed. On the other hand, among the radial direction intermediate part or outer end part of the flange piece 8a, the axial direction outer half part which overlaps with the recessed part 20 is overlapped with the outer ring raceway 7d of the inner row in the radial direction. In addition, the radial intermediate portion or the outer end portion of the flange piece 8a including the attachment hole 9a is sufficiently larger in the axial width than the constricted portion 21 (about twice in the illustrated example). For this reason, the screwing width between the knuckle bolt and the mounting hole 9a is sufficiently secured. Further, the radially inner side surface (inner diameter side end portion) constituting the inner surface of the recess 20 is smoothly (without a step) continuous with the outer peripheral surface of the outer ring body 5a. The radially outer surface (outer diameter side end) constituting the inner surface of the recess 20 is continuous with the axially outer surface of the flange piece 8 via a chamfered portion having an arcuate cross section.

  Also, as shown in FIG. 3, the portion of the outer peripheral surface of the outer ring 2a that overlaps the outer ring raceway 7d in the inner row in the radial direction with the cross-sectional shape (contour shape) of the radially inner side surface constituting the inner surface of the recess 20 In addition, the phase in the circumferential direction is matched with the cross-sectional shape (see contour shape, one-dot chain line) of the portion that does not match the flange piece 8a. As a result, in the case of this example, in the outer peripheral surface of the outer ring 2a, the cross-sectional shape (contour shape) of the portion overlapping the inner ring outer ring raceway 7d in the radial direction is the same without changing over the entire circumference. (Uniform).

  Further, a protrusion 10a that connects the flange pieces 8a adjacent to each other in the circumferential direction is provided on the outer peripheral surface of the outer ring main body 5a between the flange pieces 8a so as to protrude radially outward. Yes. The protrusion 10a is smaller in dimensions in the radial direction and the axial direction than the flange piece 8a. Specifically, when the outer peripheral surface of the fitting cylinder portion 22 provided at the axially inner end of the outer ring main body 5a is used as a reference, the radial protrusion amount of the protrusion 10a is the radial protrusion amount of the flange piece 8a. The axial width dimension of the protrusion 10a is about 1/3 to 2/3 of the axial width dimension of the flange piece 8a. Further, the axial inner surface of the protrusion 10a and the axial inner surface of the flange piece 8a have the same axial position and the same cross-sectional shape. Further, of the outer peripheral surface of the outer ring main body 5a, the outer portion in the axial direction of the stationary flange 6a is a tapered surface whose outer diameter is reduced toward the outer side in the axial direction, and the thickness in the radial direction of the outer ring main body 5a is reduced. It is suppressed.

  Further, as shown by the oblique lattice pattern in FIG. 3, the outer ring main body 5a has an outer ring raceway extending from the outer ring raceway 7c portion of the outer row to the outer ring raceway 7d portion of the inner row, or the outer ring raceway of each row. A heat-treated hardened layer 23 is formed on the entire circumference by induction hardening individually in the vicinity of 7c and 7d.

  The outer ring 2a constituting the rolling bearing unit 1a of this example is formed into a rough shape by subjecting a cylindrical metal material made of an iron-based alloy such as medium carbon steel to forging (hot forging or cold forging). After that, it is manufactured by grinding the outer ring raceways 7c, 7d and the like by cutting and induction heat treatment. And since such an outer ring | wheel 2a is couple | bonded and fixed to the knuckle which comprises a suspension apparatus with the knuckle bolt screwed in the attachment hole 9a formed in the flange piece 8a, it does not rotate at the time of use.

  The hub 3a is configured by connecting the hub body 11a and the inner ring 12a, and is disposed concentrically with the outer ring 2a on the inner diameter side of the outer ring 2a. The hub body 11a is made of an iron-based alloy such as medium carbon steel, for example, and is subjected to hardening heat treatment such as high-frequency heat treatment on the outer peripheral surface extending from the root portion of the rotation side flange 14a described later to the small diameter step portion 15a described later. ing. An annular rotation-side flange 14a for supporting and fixing a wheel and a disk rotor is provided on a portion of the outer peripheral surface of the hub body 11a that protrudes axially outward from the axial outer end opening of the outer ring 2a. . Further, an inner ring raceway 13c having a partial arc shape in cross section is provided in a portion of the outer peripheral face of the hub body 11a facing the outer ring raceway 7c in the outer row provided on the inner peripheral face of the outer ring 2a. Such a hub 3a rotates during use because the wheel and the brake rotating member are supported and fixed by the hub bolt 18a inserted through the support hole 17a formed in the rotation side flange 14a.

  The inner ring 12a that constitutes the hub 3a together with the hub body 11a is made of a high carbon chrome bearing steel such as SUJ2 and has a substantially annular shape, and is subjected to heat treatment such as quenching. Also, an inner row of inner ring raceways 13d having a partial arc shape in cross section is formed on the outer circumferential surface of the inner ring 12a. Such an inner ring 12a is externally fixed to the small-diameter step portion 15a provided at the inner end in the axial direction of the hub body 11a by an interference fit. The inner ring 12a has its axial inner end face held down by a caulking portion 16a formed by plastically deforming the axial inner end of the hub body 11a radially outward. Instead of the structure in which the caulking portion 16a is formed at the inner end portion in the axial direction of the hub main body 11a, a structure in which a nut is screwed onto the inner end portion in the axial direction of the hub main body may be employed.

  The rolling elements 4a and 4a are respectively held by retainers 19a and 19a in a portion between the outer ring raceway 7c and the inner ring raceway 13c in the outer row and a portion between the outer ring raceway 7d and the inner ring raceway 13d in the inner row. It is arranged to roll freely in the state. The rolling elements 4a and 4a are given a contact angle of the rear combination type and an appropriate preload using the pressing force of the caulking portion 16a. In the illustrated example, balls are used as the rolling elements 4a and 4a. However, in the case of a rolling bearing unit for supporting a wheel of an automobile having a heavy weight, a tapered roller can be used instead of the ball. .

  Both ends in the axial direction of the internal space (rolling element installation space) 24, which exists between the inner peripheral surface of the outer ring 2a and the outer peripheral surface of the hub 3a, are covered by a pair of sealing devices 25a and 25b. Yes. As a result, grease (not shown) existing in the internal space 24 is prevented from leaking, and foreign substances such as moisture and dust existing in the external space are prevented from entering the internal space 24. In the illustrated example, a combination seal ring having a seal ring and a slinger is used as the sealing device 25b that closes the axially inner end opening of the internal space 24. And the encoder 26 which comprises a rotational speed detection apparatus with the sensor which is not shown in figure is supported and fixed to the slinger which comprises this combination seal ring.

  Further, a cap 27 for holding the sensor is fitted and fixed to the fitting cylinder portion 22 at the inner end in the axial direction of the outer ring 2a. The cap 27 has a bottomed cylindrical shape as a whole by subjecting a magnetic metal plate having corrosion resistance, such as a galvanized steel plate and a martensitic stainless steel plate, to plastic processing such as drawing. The bottom of the cap 27 is provided with a holding cylinder 28 for inserting the tip of the sensor inside, and a nut 29 for screwing a bolt for fixing the sensor is fixed. ing. In a state in which the sensor is supported and fixed to the cap 27 having such a configuration, the detection unit provided on the front end surface of the sensor is opposed to the encoder 26 in the axial direction inside the cap 27 through a minute gap. . In this state, when the encoder 26 rotates together with the hub 3a, the S pole and the N pole existing on the detection surface of the encoder 26 alternately pass in the vicinity of the detection portion of the sensor, thereby changing the output of the sensor. . Since the frequency of the change is proportional to the rotational speed of the hub 3a and the period of the change is inversely proportional to the rotational speed, the rotational speed of the wheel fixed to the hub 3a can be obtained based on either.

In the case of the rolling bearing unit 1a of the present example having the above-described configuration, the strength of the flange piece 8a is increased while the rigidity can be increased at the same time as the case of the conventional structure described above. It can be ensured and the bearing life can be prevented from decreasing.
That is, in this example, the knuckle bolt and the mounting hole 9a are screwed together by ensuring a large axial width dimension from the radial intermediate part to the outer end part of the flange piece 8a constituting the stationary flange 6a. Since a large width is secured, the support rigidity of the rolling bearing unit 1a with respect to the suspension device can be increased. Further, since the outer circumferential surface of the outer ring main body 5a has a taper surface on the outer side in the axial direction of the stationary flange 6a, the thickness of the outer ring main body 5a in the radial direction is kept small, so that the rolling bearing unit 1a as a whole is provided. Weight reduction can be achieved.

  In addition, in the case of this example, by forming the concave portion 20 at the radially inner end of the flange piece 8a, the constricted portion 21 formed at the radially inner end of the flange piece 8a is replaced with the inner ring outer ring raceway. Without being superimposed on the radial direction of 7d, it is positioned at a portion that is axially inward from the outer ring raceway 7d. Therefore, when the flange piece 8a is coupled and fixed to the suspension device, even when a radial force is applied to the flange piece 8a from the knuckle bolt, this force is axially inward from the outer ring raceway 7d. It is possible to effectively prevent the outer ring raceway 7d from being deformed in the radial direction by acting on the detached portion. For this reason, it is possible to effectively prevent the roundness of the outer ring raceway 7d from being lowered, and to prevent the life of the rolling bearing unit 1a from being reduced.

  Furthermore, in the case of this example, the cross-sectional shape of the radially inner side surface constituting the inner surface of the recess 20 is a portion of the outer peripheral surface of the outer ring 2a that overlaps the outer ring raceway 7d in the inner row in the radial direction, and By making the phase in the circumferential direction coincide with the cross-sectional shape of the portion that does not coincide with the flange piece 8a (the protrusion 10a), the portion of the outer circumferential surface of the outer ring 2a that overlaps the outer ring raceway 7d in the inner row in the radial direction. The cross-sectional shape is the same without changing over the entire circumference. For this reason, among the heat-treated hardened layers 23 formed on the inner peripheral surface of the outer ring 2a, the thickness dimension in the radial direction of the inner hardened layer 30 formed on the inner ring outer ring raceway 7d is constant over the entire circumference. I can do things. Moreover, the thickness dimension in the radial direction of the inner hardened layer 30 is appropriately set to the minimum thickness in consideration of the depth at which shear stress (τ0 and τst) generated based on the load applied to the outer ring raceway 7d is generated. Can be set. For this reason, since the thickness dimension of the non-hardening part 31 which exists in the radial direction outer side of the inner side hardening layer 30 can fully be ensured, it can make it hard to generate | occur | produce a metal fatigue in the inner side hardening layer 30, and an outer ring | wheel track | orbit 7d rolling fatigue life can be prevented from decreasing.

Moreover, since the thickness dimension in the radial direction of the inner hardened layer 30 can be made constant over the entire circumference, the circumferential direction of the non-hardened portion 31 on the outer peripheral surface side of the outer ring main body 5a caused by the inner hardened layer 30 Also, the tensile stress can be constant over the entire circumference. For this reason, even when the vehicle is turning, the tensile stress acting on the continuous portion (corner R portion) between both circumferential edges of the flange piece 8a and the outer peripheral surface of the outer ring main body 5a is excessive. Can be prevented. Accordingly, the strength of the flange piece 8a can be sufficiently ensured.
As a result, according to the rolling bearing unit 1a of the present example, the strength of the flange piece 8a can be ensured and the bearing life can be prevented from decreasing.

  When carrying out the present invention, the shape of the flange piece and the shape of the recess can be appropriately changed according to the shape of the outer ring raceway and the like. Moreover, the formation position of a recessed part can also be formed not only in the axial direction outer side surface of a flange piece but in an axial direction inner side surface.

[Second Example of Embodiment]
A second example of the embodiment of the present invention will be described with reference to FIGS. In the case of the rolling bearing unit 1b of this example, the concave portion 20a formed at the radially inner end of the flange piece 8b constituting the stationary flange 6b is not formed over the entire circumferential width of the flange piece 8b. The flange piece 8b is formed only at the intermediate portion in the circumferential direction. That is, in the case of this example, the recess 20a is provided in a state of opening only on the outer surface in the axial direction of the flange piece 8b. As a result, of the circumferential end portions of the radially inner end portion of the flange piece 8b, the portions overlapping the outer ring raceway 7d in the inner row in the radial direction are left as thin plate-like reinforcing ribs 32 and 32, respectively. Yes. In other words, the portions adjacent to both sides in the circumferential direction of the recess 20a are the reinforcing ribs 32, 32 extending in the radial direction, respectively. The thickness dimension of the reinforcing ribs 32, 32 in the circumferential direction is such that the heat capacity of the outer ring 2b and the radial thickness dimension of the inner hardened layer 30 (see FIG. 3) can be obtained by leaving such reinforcing ribs 32, 32. It is set so thin that it does not affect it. Specifically, the thickness dimension of the reinforcing ribs 32, 32 in the circumferential direction is set to 10% or less of the circumferential length at the radially inner end of the flange piece 8b.

  In the case of this example having the above-described configuration, by providing the reinforcing ribs 32 and 32 as described above, the axially outer portion of the flange piece 8b (a portion overlapping the outer ring raceway 7d in the radial direction). However, since it is possible to effectively prevent deformation (displacement) in the radial direction, it is possible to obtain higher support rigidity (moment rigidity) while ensuring the effect obtained by the structure of the first example of the embodiment described above. it can.

When the present invention is carried out, the formation position of the concave portion formed in the flange piece is not limited to the intermediate portion in the circumferential direction, and can be formed in a state where only one side in the circumferential direction opens to the circumferential side surface of the flange piece. . Further, the number of recesses is not limited to one, and a plurality of recesses can be formed apart from each other in the circumferential direction (with reinforcing ribs sandwiched in the circumferential direction).
About another structure and an effect, it is the same as that of the case of the 1st example of the said embodiment.

  The present invention is not limited to a rolling bearing unit for a driven wheel for rotatably supporting a driven wheel as shown in FIG. 1, but a rolling bearing unit for a driving wheel for rotatably supporting a driving wheel. It can be applied to.

DESCRIPTION OF SYMBOLS 1, 1a, 1b Rolling bearing unit 2, 2a, 2b Outer ring 3, 3a Hub 4, 4a Rolling body 5, 5a Outer ring main body 6, 6a, 6b Static side flange 7a-7d Outer ring track 8, 8a, 8b Flange piece 9, 9a Mounting hole 10, 10a Rib 11, 11a Hub body 12, 12a Inner ring 13a-13d Inner ring raceway 14, 14a Rotating flange 15, 15a Small diameter step 16, 16a Caulking part 17, 17a Support hole 18, 18a Hub bolt 19, 19a Cage 20 Recessed portion 21 Constricted portion 22 Fitting cylinder portion 23 Heat treatment and hardening layer 24 Internal space 25a and 25b Sealing device 26 Encoder 27 Cap 28 Holding cylinder portion 29 Nut 30 Inner hardening layer 31 Non-hardening portion 32 Reinforcement rib

Claims (3)

A cylindrical outer ring main body having an outer ring raceway on the inner peripheral surface, and a radially outer portion of the outer peripheral surface of the outer ring main body that protrudes radially outward and overlaps with the outer ring raceway in a radial direction. An outer ring that has a plurality of flange pieces and does not rotate during use;
A hub that has an inner ring raceway on an outer peripheral surface, is arranged concentrically with the outer ring on the inner diameter side of the outer ring, and rotates during use;
A plurality of rolling elements provided between the outer ring raceway and the inner ring raceway so as to freely roll,
A concave portion recessed in the axial direction is provided at the radially inner end portion of the flange piece, and a constricted portion provided at a portion adjacent to the concave portion in the axial direction of the radially inner end portion of the flange piece. Is located in a portion axially deviated from the outer ring raceway,
Rolling bearing unit.   The recess is provided over the entire circumferential width of the flange piece, and the cross-sectional shape of the portion of the outer circumferential surface of the outer ring that overlaps the outer ring raceway in the radial direction does not change over the entire circumference. The rolling bearing unit according to claim 1, which is the same.   The rolling bearing unit according to claim 1, wherein the concave portion is provided at one or a plurality of circumferential directions of the flange piece in a state where the concave portion is opened only on an axial side surface of the flange piece.

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