JP2014029202A - Rolling bearing unit for wheel support - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain a structure that is a different diameter PCD type, ensures rolling fatigue life and moment rigidity, and ensures durability by suppressing occurrence of an edge load.SOLUTION: The cross sectional shapes of an outside outer ring track 6 and an outside inner ring track 15 are the shapes that in plural kinds of arc with respective different curvature radii, respective edges are smoothly continued in respective tangential directions. The curvature radius of each arc becomes small at width directional center parts 21a, 21b of the outside outer ring track 6 and the outside inner ring track 15, which is a direction of a contact angle of each ball 4a, and becomes large at width directional both end parts 22a, 22b, 22c, 22d.

Description

  The present invention relates to an improvement of a wheel bearing rolling bearing unit for rotatably supporting a vehicle wheel with respect to a suspension device. In particular, the present invention is a rolling bearing unit for supporting a wheel in which pitch circle diameters of balls arranged in a double row are different from each other, and it makes it difficult for the ball rolling surface to ride on the shoulder portion of the raceway surface, thereby ensuring sufficient durability. It is intended to realize an easy structure.

  The wheel of the automobile and the rotating member for braking are rotatably supported with respect to the suspension device by the wheel bearing rolling bearing unit. A large moment is applied to such a wheel-supporting rolling bearing unit when the automobile turns. Therefore, it is necessary to ensure a large moment rigidity in order to ensure traveling stability during turning. For this reason, conventionally, as a rolling bearing unit for supporting a wheel, a structure in which balls are arranged in a double row and a contact angle of a preload and a back combination type (DB type) is given to the balls in both rows is generally used. It is used. Further, in recent years, in order to secure a larger moment rigidity while suppressing an increase in size, a structure in which pitch circle diameters (PCD) of both rows of balls are made different from each other as described in, for example, Patent Document 1 (differentiated). (Diameter PCD structure) has been proposed.

FIG. 1 shows an example of such a different diameter PCD type wheel bearing rolling bearing unit. The wheel support rolling bearing unit 1 includes an outer ring 2, a hub 3, and a plurality of balls 4a and 4b.
Outer ring 2 includes an outer flange-shaped mounting portion 5 on the outer peripheral surface, an outer outer ring raceway 6 positioned on the outer side in the axial direction, and an inner side positioned on the inner side in the axial direction. An outer ring raceway 7 is provided. Among these outer and inner outer ring raceways 6, 7, the inner diameter of the outer outer ring raceway 6 is larger than the inner diameter of the inner outer ring raceway 7. Note that the outside in the axial direction is the side that is the outer side in the width direction when assembled to the vehicle, and refers to the left side of FIG. 1, and the inner side is the side that is the center side in the width direction in the assembled state to the vehicle. The right side of FIG. The mounting portion 5 is a portion for coupling and fixing the outer ring 2 to a knuckle (not shown) constituting a suspension device. Therefore, the outer ring 2 does not rotate during use.

The outer and inner outer raceways 6 and 7 each have an arc shape in cross section. In addition, the cross-sectional shape in the present specification and claims refers to a cross-sectional shape related to a virtual plane including the central axis of the wheel-supporting rolling bearing unit 1 (coincident with the central axis of the outer ring 2 and the hub 3). .
Further, an outer outer ring groove shoulder portion 8 having a reduced inner diameter is formed at the inner end portion in the axial direction of the outer outer ring raceway 6, and an inner outer ring groove shoulder portion 9 having an inner diameter reduced at the outer end portion in the axial direction of the inner outer ring raceway 7. Are formed respectively.

The hub 3 is formed by coupling and fixing the hub body 10 and the inner ring 11 in a non-separable manner. That is, the inner ring 11 is externally fitted to the small-diameter step 12 provided near the inner end of the hub body 10 by an interference fit, and the inner end of the hub body 10 is plastically deformed radially outward. The inner ring 11 is held down by a caulking portion 13 formed as described above. The hub 3 configured in this manner has a mounting flange 14 for supporting a wheel on the outer peripheral portion of the outer peripheral surface in the axial direction and a double row inner ring raceway on the intermediate portion and the inner portion in the axial direction. And an outer inner ring raceway 15 and an inner inner ring raceway 16 each having a circular arc shape are provided. Of these, the outer inner ring raceway 15 is formed on the outer peripheral surface of the intermediate portion of the hub body 10, and the inner inner ring raceway 16 is formed on the outer peripheral surface of the inner ring 11. Of these outer and inner inner raceways 15, 16, the outer diameter of the outer inner raceway 15 is larger than the outer diameter of the inner inner raceway 16.
Further, an outer inner ring groove shoulder 17 having an increased outer diameter is formed at an axially outer end portion of the outer inner ring raceway 15, and an inner inner ring groove shoulder having an outer diameter increased at an axial inner end portion of the inner inner ring raceway 16. Each part 18 is formed.

Of the balls 4a and 4b, the balls 4a and 4a in the outer row are between the outer outer ring raceway 6 and the outer inner raceway 15, and the balls 4b and 4b in the inner row are the inner outer ring raceway 7 and the inner side. It is provided between the inner ring raceway 16 and the inner ring raceway 16 so that it can roll while being held by the cages 19a and 19b. Further, a preload is applied to each of the balls 4a and 4b together with a contact angle of a back contact type. For this purpose, the inner ring 11 is externally fitted to the small-diameter stepped portion 12, and the axially outer end surface of the inner ring 11 and the stepped surface 20 existing at the axially outer end portion of the small-diameter stepped portion 12 are abutted. Thus, the shape and size of each part are regulated so that the rolling contact parts between the rolling surfaces of the balls 4a, 4b and the tracks 6, 7, 15, 16 are slightly elastically deformed. Thus, in the state where the wheel support rolling bearing unit 1 is assembled, the pitch circle diameter PCD _OUT of the balls 4a, 4a in the outer row is larger than the pitch circle diameter PCD _IN of the balls 4b, 4b in the inner row ( PCD _OUT > PCD _IN ). In the illustrated example, the diameter of the balls 4a and 4a in the outer row is made smaller than the diameter of the balls 4b and 4b in the inner row, as in the structure described in FIGS. The number of balls 4a, 4a in the outer row is larger than the number of balls 4b, 4b in the inner row. However, even in the structure in which the diameters (ball diameters) of the balls 4a and 4b in both rows are equal to each other, it is conventionally known as described in FIGS.

The different diameter PCD type wheel bearing rolling bearing unit 1 configured as described above can increase the moment rigidity by increasing the pitch circle diameter PCD _OUT of the balls 4a and 4a in the outer row. In other words, the moment stiffness of the wheel support rolling bearing unit 1 is calculated based on virtual straight lines α and β representing the contact angles of the balls 4a and 4b arranged in double rows, and the central axis X of the wheel support rolling bearing unit 1. The longer the bearing span L, which is the distance between the intersections, the larger the distance. In the case of the rolling bearing unit 1 for supporting wheels of different diameter PCD type, the bearing span L can be lengthened by the larger pitch circle diameter PCD _OUT of the balls 4a, 4a in the outer row, and the moment rigidity can be increased. This is advantageous in terms of improving the running stability of the vehicle.
On the other hand, the pitch circle diameters PCD _IN of the inner rows of balls 4b and 4b are suppressed to be equal to those of a general wheel support rolling bearing unit in which the pitch circle diameters of the balls of the double rows are equal to each other. Therefore, the same knuckle for fixing and fixing the outer ring 2 can be used as the one for assembling this general wheel support rolling bearing unit, and the enlargement of the wheel support portion for the suspension device can be suppressed.

  As described above, the different diameter PCD type wheel support rolling bearing unit 1 can increase the moment rigidity, improve the wheel support rigidity with respect to the suspension device, improve the straight running stability, improve the stability during turning, etc. Although it can contribute to the improvement of the running performance of the vehicle, there is room for improvement in terms of ensuring both rigidity and durability. That is, the moment stiffness of the wheel-supporting rolling bearing unit 1 exists not only in the bearing span L but also in the rolling contact portion between the rolling surfaces of the balls 4a and 4b and the tracks 6, 7, 15 and 16. It is also greatly influenced by the size (area) of the contact ellipse. The larger the contact ellipse (the larger the area) and the lower the surface pressure of each of the rolling contact portions, the lower the surface pressure of each of the rolling contact portions, so that the balls 4a, 4b and the The amount of elastic deformation of each of the tracks 6, 7, 15, 16 can be suppressed to be small, and the moment rigidity of the wheel bearing rolling bearing unit 1 can be increased. In order to enlarge the contact ellipse, the curvature radius of the cross-sectional shape of each of the tracks 6, 7, 15, 16 is in rolling contact with the track 6, 7, 15, 16. That is, the radius of curvature of the cross-sectional shape of each of the tracks 6, 7, 15 and 16 is made close to ½ of the diameter (ball diameter) of each of the balls 4a and 4b (balls). It is effective to make the value slightly larger than 50% of the diameter).

  However, when the radius of curvature of the cross-sectional shape of each of the tracks 6, 7, 15, 16 approaches 50% of the ball diameter of each of the balls 4 a, 4 b, the rolling surface of each of the balls 4 a, 4 b becomes the track 6. 7, 15, 16 can easily ride on the respective groove shoulder portions 8, 9, 17, 18 existing at the end portions in the width direction. When such a ride-up occurs, the rolling surfaces of the balls 4a, 4b come off from the tracks 6, 7, 15, 16 (so-called contact ellipse chipping occurs), and the balls 4a, 4b roll. Excessive surface pressure based on edge load is applied to the moving surface. As a result, damage such as scratches occurs on the rolling surfaces of the balls 4a and 4b, and the durability of the wheel bearing rolling bearing unit 1 is impaired.

  The problem caused by such riding is particularly noticeable in the structure in which the diameters of the balls 4a and 4a in the outer row are smaller than the diameters of the balls 4b and 4b in the inner row. That is, when the diameters of the balls 4a and 4a in the outer row are reduced, the distance from the position where each contact ellipse is present to the groove shoulder at a normal time is shortened. It becomes easy to reach. Increasing the radius of curvature of the cross-sectional shape of each of the tracks 6, 7, 15 and 16 can make it difficult for the above-described disadvantageous riding to occur, but the contact ellipse of each rolling contact portion is reduced (area). Becomes narrower). As a result, not only the rolling fatigue life of each surface constituting each rolling contact portion is reduced, but also the moment rigidity of the wheel supporting rolling bearing unit 1 is lowered, and the meaning of adopting a different diameter PCD type structure is adopted. Because it is damaged, it cannot be adopted as it is.

  In Patent Documents 2 to 4, the outer ring raceway and the inner ring raceway, each of which has a circular arc shape, are in the direction of the contact angle of each ball, and the cross-sectional shape of the portion where the rolling surface of each ball is in rolling contact is normal. A ball bearing with a small radius of curvature (a value that slightly exceeds 50% of the diameter of each ball) and a large radius of curvature at a portion that deviates from this (largely exceeds the diameter of 50% of each ball) An invention relating to structure is described. According to such a structure, the rolling surface of each ball is present at the axial end of each track while making the size of the contact ellipse present at each rolling contact in the normal state appropriate (without making it too small). It is possible to prevent riding on the shoulder of the groove. However, the structures of the inventions described in Patent Documents 2 to 4 are all related to single-row deep groove ball bearings (in the case of the inventions described in Patent Documents 3 and 4) or arranged in double rows. The present invention relates to an equal-diameter PCD type wheel bearing rolling bearing unit in which pitch diameters of the balls are equal to each other (in the case of the invention described in Patent Document 2). In short, the conventional rolling bearing unit for wheel support of different diameter PCD type is particularly considered for ensuring durability by suppressing the occurrence of edge load while ensuring the rolling fatigue life and moment rigidity. It wasn't.

JP 2004-108449 A Japanese Unexamined Patent Application Publication No. 2004-052784 JP 2008-169920 A JP 2009-174691 A

  In view of the circumstances as described above, the present invention is a rolling bearing unit for supporting a wheel of a different diameter PCD type, which ensures the durability by suppressing the occurrence of edge load while ensuring the rolling fatigue life and moment rigidity. Invented to realize the above.

The wheel support rolling bearing unit of the present invention includes an outer ring, a hub, and a plurality of balls.
Outer rings of these are provided with outer and inner outer ring raceways, each with an arc cross section, on the inner peripheral surface near the axially outer end and axially inner end, respectively, and rotate during use. do not do. An outer outer ring groove shoulder having a smaller inner diameter is provided at the inner end in the axial direction of the outer outer ring raceway provided near the outer end in the axial direction. Further, an inner outer ring groove shoulder portion having a smaller inner diameter is provided at an outer end portion in the axial direction of the inner outer ring raceway provided at a portion near the inner end in the axial direction and having a diameter different from that of the outer outer race raceway.
The hub is provided with a mounting flange on the outer peripheral surface near the outer end in the axial direction, an outer inner ring raceway in the middle, and an inner inner ring raceway in the same portion near the inner end in the axial direction. Of these, the mounting flange is for supporting the wheel. The outer inner ring raceway has an arc shape in cross section, and an outer inner ring groove shoulder portion having an outer diameter increased at the outer end portion in the axial direction. The inner inner ring raceway has a circular arc cross section, and has a diameter different from that of the outer inner ring raceway, and an inner inner ring groove shoulder having a larger outer diameter is provided at the inner end in the axial direction.
Each of the balls is provided between the outer and inner outer raceways and the outer and inner inner raceways so as to be able to roll, and preload is applied together with the contact angle of the back contact type. doing.

Further, the cross-sectional shapes of the outer outer ring raceway and the outer inner ring raceway are formed such that a plurality of types of arcs having different radii of curvature are smoothly connected to each other in the tangential direction. And the radius of curvature of each of these arcs is small in the width direction center of the outer outer ring raceway and the outer inner ring raceway, which is the direction of the contact angle, and at least the outer outer ring groove shoulder and It is enlarged on the outer inner ring groove shoulder side.
The direction of the contact angle for restricting the range of the radius of curvature of each arc is the direction when the wheel bearing rolling bearing unit is assembled and no load or moment is applied in each direction. , And throughout the specification and claims.

When the present invention as described above is implemented, preferably, as in the invention described in claim 2, the diameter of the inner outer ring raceway is smaller than the diameter of the outer outer ring raceway, and the diameter of the inner inner ring raceway is The diameter is smaller than the diameter of the outer inner ring raceway.
When the invention described in claim 2 is carried out, the diameter of each ball provided between the outer outer ring raceway and the outer inner ring raceway, as in the invention described in claim 3, The diameter of each ball provided between the inner outer ring raceway and the inner inner ring raceway is made smaller.

When implementing the present invention as described above, specifically, as in the invention described in claim 4, the range of the central portion in the width direction of the outer outer ring race is ± on the basis of the direction of the contact angle. The range is 15 to 25 degrees (angle range of 30 to 50 degrees). The radius of curvature of the central portion in the width direction is set to 52 to 54% of the diameter of each ball provided between the outer outer ring raceway and the outer inner ring raceway, and the outer groove of the outer outer ring raceway is set. Similarly, the radius of curvature of the shoulder portion is 53 to 55%.
Further, the range of the central portion in the width direction of the outer inner ring raceway is set to a range of ± 20 to 30 degrees (an angle range of 40 to 60 degrees) centered on the direction of the contact angle. The radius of curvature of the central portion in the width direction is set to 51 to 53% of the diameter of each ball provided between the outer outer ring raceway and the outer inner ring raceway, and the outer groove shoulder of the outer outer ring raceway is included. Similarly, the radius of curvature of the portion near the portion is set to 52 to 54%.

  When the present invention is implemented, preferably, as in the invention described in claim 5, in addition to the cross-sectional shapes of the outer outer ring raceway and the outer inner ring raceway, cross sections of the inner outer ring raceway and the inner inner ring raceway. The shape is a shape in which a plurality of types of arcs having different radii of curvature are smoothly connected with each other in the tangential direction. And the radius of curvature of each arc is small at the center in the width direction of the inner outer ring raceway and the inner inner ring raceway, which is the direction of the contact angle, and at least the inner outer ring groove shoulder and Enlarge on the inner inner ring groove shoulder side.

Further, according to the present invention, as in the invention described in claim 6, the diameter of the inner outer ring raceway is larger than the diameter of the outer outer ring raceway, and the diameter of the inner inner ring raceway is larger than the diameter of the outer inner ring raceway. It can also be implemented with a large structure.
When carrying out the invention described in claim 6, preferably, as in the invention described in claim 7, the diameter of each ball provided between the outer outer ring raceway and the outer inner ring raceway, The diameter of each ball provided between the inner outer ring raceway and the inner inner ring raceway is made smaller.

According to the present invention configured as described above, a rolling bearing unit for supporting a wheel of a different diameter PCD type is capable of ensuring durability by suppressing the occurrence of edge load while ensuring the rolling fatigue life and moment rigidity. realizable.
For example, according to the invention described in claim 2, by increasing the pitch circle diameter of each ball in the outer row, the bearing span can be lengthened without increasing the mounting portion to the knuckle and the moment rigidity is improved. Be made.
According to the sixth aspect of the present invention, the wheel support rolling bearing unit can be reduced in size and weight by reducing the diameter of the outer ring while suppressing the shortening of the bearing span and suppressing the decrease in moment rigidity.
In addition, since the radius of curvature of the cross-sectional shape of each track is reduced at the center of each track in the width direction, which is the direction of the contact angle, the rolling surface of each track and each ball in a normal state. The contact ellipse existing at the rolling contact portion can be enlarged. Accordingly, it is possible to secure rigidity and rolling fatigue life by suppressing the amount of elastic deformation of each rolling contact portion.
Furthermore, since the radius of curvature of the cross-sectional shape of each track is increased at the end in the width direction on the side of the groove shoulder, the rolling surface of each ball can hardly ride on the groove shoulder, and The edge load can be prevented from acting on the moving surface, and the durability can be prevented from being lowered due to the damage of the rolling surface of each ball.

Sectional drawing which shows the 1st example of the rolling bearing unit for wheel support used as the object of this invention. The A section enlarged view of FIG. 1 which shows the 1st example of embodiment of this invention. Sectional drawing which shows the 2nd example of the rolling bearing unit for wheel support used as the object of this invention.

[First example of embodiment]
A first example of an embodiment of the present invention corresponding to claims 1 to 5 will be described with reference to FIG. In addition, the feature of the present invention including this example is that, by devising the cross-sectional shape of each track, the endurance is ensured by suppressing the occurrence of edge load while ensuring the rolling fatigue life and moment rigidity. . Regarding the present example, the basic structure of the wheel-supporting rolling bearing unit 1 is as shown in FIG. 1 described above. Therefore, the overlapping description is omitted or simplified. 2 will be described with reference to FIG. 1 if necessary.

In the case of the wheel support rolling bearing unit 1 of the present example, the outer outer ring raceway 6 and the outer inner ring raceway 15 are made to have a plurality of types of arcs having different curvature radii r _O1 , r _O2 , r _I1 , r _I2. The composite arc shape is such that the edges of each other are smoothly continuous in the tangential direction of each other. The radius of curvature r _O1 , r _O2 , r _I1 , r _I2 of each arc is a predetermined range centered on the direction of the contact angle of each ball 4a, and the outer outer ring raceway 6 and the outer inner ring raceway 15 The width direction center portions 21a and 21b have relatively small values (r _O1 and r _I1 ). On the other hand, the curvature radii of the width direction both end portions 22a, 22b, 22c, and 22d existing at positions sandwiching the width direction center portions 21a and 21b from both sides in the width direction are relatively large values ( _rO2 , _rI2). (R _O1 <r _O2 , r _I1 <r _I2 ).

Specifically, the range of the central portion 21a in the width direction of the outer outer ring raceway 6 is set to a range of ± 15 to 25 degrees centered on the direction of the contact angle. Then, the curvature radius _{r O1} of the widthwise central portion 21a, is set to 52 to 54% of the diameter of the respective balls 4a. In contrast, sandwiching the widthwise central portion 21a from both sides in the width direction, the both widthwise end portions 22a, the curvature radius _{r O2} in 22b, is set to 53 to 55% of the diameter of the respective balls 4a.

The range of the central portion 21b in the width direction of the outer inner ring raceway 15 is a range of ± 20 to 30 degrees with the direction of the contact angle as the center. Then, the curvature radius _{r I1} of the widthwise central portion 21b, is set to 51 to 53% of the diameter of the respective balls 4a. On the other hand, the curvature radius r _I2 of the width direction both end portions 22c and 22d sandwiching the width direction central portion 21b from both sides in the width direction is set to 52 to 54% of the diameter of each ball 4a. The reason why the curvature radii r _I1 and r _{I2 of the} outer inner ring raceway 15 are smaller in the corresponding portions than the curvature radii r _O1 and r _O2 of the outer outer ring raceway 6 is that the outer outer ring raceway 6 This is because the outer inner ring raceway 15 has a convex shape with respect to the circumferential direction, whereas it has a concave shape with respect to the direction. Corresponding to such a difference in the circumferential shape, a difference is set in the radius of curvature of the plurality of types of arcs of the cross-sectional shape, and the rolling surface of each ball 4a, the outer outer ring raceway 6 and the outer inner ring raceway 15 are set. Thus, there is no significant difference in the size of the contact ellipse existing at the rolling contact portion.

According to the structure of the present example configured as described above, the rolling bearing unit 1 for supporting a wheel of different diameter PCD type ensures durability by suppressing the occurrence of edge load while ensuring the rolling fatigue life and moment rigidity. A structure that can be realized can be realized.
That is, by increasing the pitch circle diameter of each ball 4a in the outer row, the bearing span L can be lengthened without increasing the size of the attachment portion 5 to the knuckle, and the moment rigidity can be improved.
In addition, since the curvature radii of the cross-sectional shapes of the outer outer ring raceway 6 and the outer inner ring raceway 15 are reduced at the central portions 21a and 21b in the width direction, both the tracks 6 and 15 and the balls 4a are in a normal state. The contact ellipse existing at the rolling contact portion with the rolling surface can be enlarged. Accordingly, it is possible to secure rigidity and rolling fatigue life by suppressing the amount of elastic deformation of each rolling contact portion.
Further, the radius of curvature of the cross-sectional shape of the outer outer ring raceway 6 and the outer inner ring raceway 15 includes both the outer outer ring and outer inner ring both groove shoulder portions 8 and 17 side, and both end portions 22a in the width direction of both raceways 6 and 15; 22b, 22c, and 22d, it is difficult to ride the rolling surfaces of the balls 4a onto the groove shoulder portions 8 and 17 even when a large moment is temporarily applied. As a result, it is possible to prevent an edge load from acting on the rolling surfaces of the balls 4a, and it is possible to prevent a decrease in durability due to damage to the rolling surfaces of the balls 4a.

[Second Example of Embodiment]
A second example of the embodiment corresponding to claims 1, 6, and 7 will be described with reference to FIG. In the case of the wheel support rolling bearing unit 1a of this example, the pitch circle diameter PCD _OUT of the balls 4a in the outer row is set to the pitch circle diameter of the balls 4b in the inner row, contrary to the structure shown in FIG. It is smaller than PCD _IN (PCD _OUT <PCD _IN ). Of these, the pitch circle diameter PCD _IN of the balls 4b in the inner row is suppressed to be equivalent to that of a general wheel support rolling bearing unit in which the pitch circle diameters of the balls in the double row are equal to each other. Conversely, in the case of the structure of this example, the pitch circle diameter PCD _OUT of the balls 4a in the outer row is made smaller than that of the general wheel support rolling bearing unit. Since the wheel-supporting rolling bearing unit 1a shown in FIG. 3 is for driving wheels, a spline hole 23 is formed at the center of the hub body 10a constituting the hub 3a.

According to such a structure of this example, the diameter of the outer ring 2a is reduced while suppressing the shortening of the bearing span L and suppressing the decrease in moment rigidity as compared with the general wheel support rolling bearing unit. The wheel support rolling bearing unit 1a can be reduced in size and weight. In other words, to reduce the unsprung load in order to improve the wheel grounding performance and improve the driving performance such as ride comfort and turning performance, to reduce the size and weight of the wheel bearing rolling bearing unit, May be required. In such a case, if the diameter of the outer ring is reduced while maintaining the structure of the general wheel support rolling bearing unit, the bearing span L becomes extremely short, and it becomes difficult to ensure the required moment rigidity. On the other hand, according to the structure of this example shown in FIG. 3, only the pitch circle diameter PCD _OUT of the balls 4a in the outer row is reduced without reducing the pitch circle diameter PCD _IN of the balls 4b in the inner row. doing. For this reason, the diameter of the outer ring 2a is reduced while the shortening of the bearing span L is suppressed and the decrease in moment rigidity is ensured (to ensure the required moment rigidity), and the wheel supporting rolling bearing unit 1a is reduced in size. Weight reduction can be achieved.

  In the case of the present example, the structure of the rolling bearing unit 1a for supporting a wheel that can achieve a reduction in size and weight while ensuring the necessary moment rigidity in this way is the first embodiment described with reference to FIG. Similar to the structure according to one example, the curvature radii of the cross-sectional shapes of the outer outer ring raceway 6 formed on the inner peripheral surface of the outer ring 2a and the outer inner ring raceway 15 formed on the outer peripheral surface of the hub 3a are set to both outer outer ring and outer inner ring. The width is increased at both ends in the width direction of both the tracks 6 and 15 including the groove shoulder portions 8 and 17 side. Accordingly, even when a large moment is temporarily applied, it is difficult to ride the rolling surfaces of the balls 4a on the groove shoulder portions 8 and 17. The edge load is prevented from acting on the rolling surfaces of these balls 4a, and the durability is prevented from being deteriorated due to the damage of the rolling surfaces of these balls 4a. Since the configuration and operation of the other parts are the same as those in the first example of the embodiment shown in FIGS.

  In each example of the embodiment described above, the curvature radii of the cross-sectional shapes of the outer outer ring raceway 6 and the outer inner ring raceway 15 are larger at the width direction end portions 22a, 22b, 22c, and 22d than the width direction center portions 21a and 21b. doing. However, it is mainly the outer outer ring groove shoulder portion 8 and the outer inner ring groove shoulder portion 17 that the edge load is applied to the rolling surfaces of the balls 4a and 4a based on the riding. For example, when the large-diameter side end edge of the outer outer ring raceway 6 and the small-diameter side end edge of the outer inner ring raceway 15 have a counterbore shape that continues in the tangential direction as they are, At the edge and the small-diameter side edge of the outer inner ring raceway 15, no edge load is applied to the rolling surfaces of the balls 4a, 4a. Accordingly, in such a case, if the radius of curvature of the cross-sectional shape of the outer outer ring raceway 6 and the outer inner ring raceway 15 is increased only on the outer outer ring groove shoulder portion 8 and the outer inner ring groove shoulder portion 17 side. It ’s enough. Of course, even in such a case, it is free to make the radius of curvature larger at the width direction end portions 22a, 22b, 22c and 22d than at the width direction center portions 21a and 21b.

  In addition, when a moment is applied to the wheel bearing rolling bearing unit 1 (1a), an edge load is easily applied to the rolling surfaces of the balls 4a and 4b as the balls 4a and 4b ride on the groove shoulders. Are the outer rows of balls 4a, 4a. Accordingly, regarding the cross-sectional shapes of the inner outer ring raceway 7 and the inner inner ring raceway 16, it is not always necessary to make the radius of curvature near the inner outer ring groove shoulder 9 and the inner inner ring groove shoulder 18 larger than the central portion in the width direction. . However, with respect to the cross-sectional shapes of the inner outer ring raceway 7 and the inner inner ring raceway 16, the inner outer ring raceway 7 and the inner outer raceway 7 and The radius of curvature of the cross-sectional shape of the inner inner ring raceway 16 may be made larger than the center portion in the width direction at the end portions near the shoulder portions 9 and 18 (invention according to claim 5).

  Further, the effect of the present invention becomes prominent when applied to a structure in which the diameters of the balls 4a and 4a in the outer row are made smaller than the diameters of the balls 4b and 4b in the inner row (claims 3 and 7). Invention). The reason for this is that, as described above, in the structure in which the diameters of the balls 4a, 4a in the outer row are smaller than the diameters of the balls 4b, 4b in the inner row, the groove shoulder portion starts from the position where each contact ellipse normally exists. This is because each contact ellipse easily reaches the groove shoulder even with a relatively small moment. However, even when the present invention is implemented with a structure in which the diameters of the balls 4a and 4b in both rows are equal to each other, a certain effect can be obtained.

DESCRIPTION OF SYMBOLS 1, 1a Rolling bearing unit for wheel support 2, 2a Outer ring 3, 3a Hub 4a, 4b Ball 5 Mounting portion 6 Outer outer ring raceway 7 Inner outer ring raceway 8 Outer outer ring groove shoulder portion 9 Inner outer ring groove shoulder portion 10, 10a Hub body 11 Inner ring 12 Small diameter step portion 13 Caulking portion 14 Mounting flange 15 Outer inner ring raceway 16 Inner inner ring raceway 17 Outer inner ring groove shoulder portion 18 Inner inner ring groove shoulder portion 19a, 19b Cage 20 Stepped surface 21a, 21b Width direction center portion 22a, 22b, 22c, 22d Width direction end 23 Spline hole

Claims (7)

An outer ring, a hub, and a plurality of balls,
Of these, the outer ring has an outer outer ring raceway having an arc cross section with an outer outer ring groove shoulder having a reduced inner diameter at the inner end in the axial direction, and the outer end in the axial direction at a portion near the outer end in the axial direction of the inner peripheral surface. Inner outer ring groove shoulders with a smaller inner diameter at the inner part, each having an inner outer ring raceway having a circular arc shape and a diameter different from the outer outer ring raceway on the inner peripheral surface of the inner peripheral surface. Sometimes it does not rotate,
The hub has an outer cross-sectional arc shape with a mounting flange for supporting the wheel on the outer peripheral surface near the axial outer end, and an outer outer ring groove shoulder with a larger outer diameter at the outer axial end. The inner ring raceway is provided with an inner inner ring groove shoulder having an outer diameter increased at the inner end portion in the axial direction at the intermediate portion of the outer peripheral surface, and the inner inner ring raceway having a circular arc shape and a diameter different from that of the outer inner ring raceway. At the inner end in the axial direction of
Each ball is provided between the outer and inner outer ring raceways and the outer and inner both inner raceways so as to be capable of rolling.
Preload is applied to each ball together with the contact angle of the back contact type,
In addition, the cross-sectional shapes of the outer outer ring raceway and the outer inner ring raceway are formed by smoothly connecting a plurality of types of arcs having different radii of curvature to each other's edges in the tangential direction, and the curvature of each arc. The radius is small at the width direction central portion of the outer outer ring raceway and the outer inner ring raceway, which is the direction of the contact angle, and at least the outer outer ring groove shoulder portion and the outer inner ring groove shoulder portion side of both ends in the width direction. Rolling bearing unit for wheel support.   The wheel bearing rolling bearing unit according to claim 1, wherein a diameter of the inner outer ring raceway is smaller than a diameter of the outer outer ring raceway, and a diameter of the inner inner ring raceway is smaller than a diameter of the outer inner ring raceway.   The diameter of each ball provided between the outer outer ring raceway and the outer inner ring raceway is smaller than the diameter of each ball provided between the inner outer ring raceway and the inner inner ring raceway. Rolling bearing unit for wheel support described in 2.   The range of the central portion in the width direction of the outer outer ring raceway is a range of ± 15 to 25 degrees centering on the direction of the contact angle, and the radius of curvature of the central portion in the width direction is the outer outer ring raceway and the outer inner ring. 52 to 54% of the diameter of each ball provided between the outer race and the outer outer ring raceway, the radius of curvature of the outer groove shoulder portion is also 53 to 55%. The range of the central portion in the width direction is a range of ± 20 to 30 degrees centered on the direction of the contact angle, and the radius of curvature of the central portion in the width direction is between the outer outer ring raceway and the outer inner ring raceway. The diameter of each said ball provided is 51 to 53%, and the curvature radius of the portion near the outer groove shoulder in the outer outer ring raceway is also 52 to 54%. The rolling bearing unit for wheel support described in item 1.   In addition to the cross-sectional shapes of the outer outer ring raceway and the outer inner ring raceway, the cross-sectional shapes of the inner outer ring raceway and the inner inner ring raceway are a plurality of types of arcs having different radii of curvature. The radius of curvature of each arc is small at the center in the width direction of the inner outer ring raceway and the inner inner ring raceway, which is the direction of the contact angle, and at least the width direction at both ends. The wheel bearing rolling bearing unit according to any one of claims 1 to 4, wherein the wheel bearing rolling bearing unit is enlarged on the inner outer ring groove shoulder and the inner inner ring groove shoulder side.   The wheel bearing rolling bearing unit according to claim 1, wherein a diameter of the inner outer ring raceway is larger than a diameter of the outer outer ring raceway, and a diameter of the inner inner ring raceway is larger than a diameter of the outer inner ring raceway.   The diameter of each ball provided between the outer outer ring raceway and the outer inner ring raceway is smaller than the diameter of each ball provided between the inner outer ring raceway and the inner inner ring raceway. The rolling bearing unit for wheel support described in 6.

Images