Bearing device

Abstract: There is disclosed a bearing device in which a double row angular contact ball bearing is mounted to an outer periphery of a hub wheel, a caulking portion is bent diametrically outward and caulked on an end face of an inner ring of a bearing, thereby preventing the bearing from falling out from the bearing device and to applying a pre-load to the bearing. An axially outer edge of the inner ring is chamfered roundly, the caulking portion is provided at its shaft end with a small-diameter portion, and a starting point of the small-diameter portion is located closer to an axially central portion than a chamfer-starting point of the axially outer edge of the inner ring.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a bearing device such as a hub unit mounted to a vehicle such as an automobile for example. Description of the Related Art In a conventional hub unit for a vehicle as being known from US 5 226 738 A, a rolling bearing of angular contact type is attached to an outer periphery of a hub wheel, a cylindrical shaft end of the hub wheel is bent in diametrically outward direction by rotary forging and caulked on an end face of an inner ring of the rolling bearing, thereby applying a pre-load to the rolling bearing and preventing the rolling bearing from loosing out from the hub unit. When the caulking operation is carried out, in order to inhibit a caulking force from being applied to the inner ring of the rolling bearing and to inhibit a raceway of the inner ring from being deformed, an annular support jig is used. When the shaft end of the hub wheel is bent and caulked in the diametrically outward direction, this support jig restrains an outer periphery of a shoulder portion of the inner ring to inhibit the inner ring from being deformed. This support jig is necessary for improving the performance of the hub unit, but it is troublesome to insert the support jig between the opposed inner ring and outer ring of the rolling bearing so as to bring the support jig into abutment against the outer periphery of the inner ring shoulder portion. Moreover, even if the inner ring shoulder portion is restrained by the support jig, since the inner ring can be deformed by the rotary forging in this structure, it is necessary to carry out, with high precision, the rotary forging operation itself, therefore and there is a limit for speedup thereof. For this reason, the conventional hub unit structure is inferior in mass production performance. SUMMARY OF THE INVENTION Accordingly, it is a main object of the present invention to provide a bearing device suitable for mass production and in which the number of assembling steps and assembling time are reduced by making the inner ring such that it is less prone to be deformed so that the precision of the bearing is not affected even if the support jig is not used. Other objects, features and advantages will be apparent from the following description. According to the invention, there is provided a bearing device comprising a shaft body whose shaft end is formed into a cylindrical shape as a caulking portion; and an angular contact type rolling bearing fitted over an outer periphery of the shaft body; wherein an axially outer edge of an inner ring of the rolling bearing is partially chamfered roundly with a predetermined radius of curvature, the caulking portion comprises a large-diameter portion having an outer diameter substantially coinciding with an inner diameter of an inner periphery of the inner ring and fitted to the inner periphery of the inner ring, and a small-diameter portion having an outer diameter smaller than the inner diameter of the inner ring and extended in axially one direction from the large-diameter portion through a predetermined distance, a starting point of the small-diameter portion is located closer to an axially central portion than a chamfer-starting point of the axially outer edge of the inner ring, and the small-diameter portion of the caulking portion is bent in diametrically outward direction and caulked on an end face of the inner ring of the rolling bearing so as to prevent the rolling bearing from falling out from the bearing device and to apply a pre-load to the rolling bearing. According to the invention, since the small-diameter portion is smaller than the inner diameter of the inner ring, when it is subjected to a rotary forging using a forging tool for example, a force for deforming the inner ring diametrically outward is not applied to the inner ring. In this state, since the starting point of the small-diameter portion is located closer to the axially central portion than the chamfer-starting point of the axially outer edge of the inner ring, when it is subjected to a rotary forging using a forging tool for example, the small-diameter portion is deformed diametrically outward such that it is extended in the vicinity of the starting point. When the outer periphery of the small-diameter portion came into contact with the axially outer edge of the inner ring, the force for deforming the inner ring diametrically outward became smaller, a deforming effort for deteriorating the circularity of the inner ring is not applied to the inner ring, and as a result, the inner ring is not deformed, and the caulking portion is caulked on the end face of the inner ring as a caulked portion. From the above reason, according to the invention, the support jig is unnecessary and thus, the number of assembling steps and assembling time are reduced, and the structure of the hub unit is suitable for mass production. Preferably, in the invention, the shaft body is a hub wheel to which a wheel is mounted, the hub wheel having a shaft portion comprising a small-diameter outer peripheral face and a large-diameter outer peripheral face, a shaft end of the shaft portion is the caulking portion, the rolling bearing is a double row angular contact ball bearing having an inner ring of a single raceway fitted over the small-diameter outer peripheral face of the shaft portion of the hub wheel, a single outer ring having two row raceway grooves, a plurality of balls arranged in two rows, and two crown-like retainers, the large-diameter outer peripheral face of the shaft portion of the hub wheel is one inner ring, the axially outer edge of the inner ring of the rolling bearing is partially chamfered roundly with a predetermined radius of curvature, and the small-diameter portion of the caulking portion is bent in diametrically outward and caulked on an end face of the inner ring of the rolling bearing so as to prevent the rolling bearing from falling out from the bearing device and to apply a pre-load to the rolling bearing. In the invention, further, it is preferable that the small-diameter portion of the caulking portion includes, before the small-diameter portion is caulked, a junction having a tapered face which is reduced in diameter in an axially one direction from a starting point of the small-diameter portion, and a shaft end extending in an axially one direction from the junction. In this case, the small-diameter portion can smoothly extend along an inner periphery of the inner ring in a state in which the small-diameter portion is not in contact with the inner periphery of the inner ring, and it is effective to prevent the inner ring from being warped by the caulking. It is preferable that in the invention, an outer diameter difference between the large-diameter portion and the small-diameter portion of the caulking portion before the small-diameter portion is caulked is 0.1 mm or less. This is preferable because the small-diameter portion can be caulked in a state in which the small-diameter portion is tightly connected to the inner ring without gap in the caulked state. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects as well as advantages of the invention will become clear by the following description of a preferred embodiment of the invention with reference to the accompanying drawings, wherein: Fig.1 is a longitudinal sectional side view of a hub unit for a vehicle before a shaft end is caulked according to a preferred embodiment of the present invention; Fig.2 is a longitudinal sectional side view of the hub unit for the vehicle after the shaft end was caulked in Fig.1. Fig.3 is enlarged view of an essential portion of Fig.1 for explaining the caulking; Fig.4 is a view corresponding to Fig.3 for explaining the caulking; Fig.5 is view corresponding to Fig.3 for explaining the caulking; Fig.6 is enlarged view of an essential portion of Fig.2 for explaining the caulking; and Fig.7 is a view showing steps for explaining a caulking form. In all these figures, like components are indicated by the same numerals. DETAILED DESCRIPTION OF THE INVENTION Referring to Fig.1 to Fig.7, a hub unit for a vehicle which is one example of a bearing device according to a preferred embodiment of the present invention will be explained. A hub unit A includes a hub wheel 1 to which a wheel is mounted as a shaft body, and a double row angular-contact ball bearing 2 (bearing, hereinafter) which is one example of an angular-contact type rolling bearing. The hub wheel 1 includes a shaft portion 12. A shaft end 3a of the shaft portion 12 is formed cylindrically, and is bent from a state shown in Fig.1 diametrically outward to assume a state shown in Fig.2. For convenience of explanation, a shaft end in a state shown in Fig.1 is called a caulking portion 3a, and a shaft end in a state shown in Fig.2 is called a caulked portion 3. The bearing to which the present invention is applied is not limited to the angular-contact ball bearing only, and a rolling bearing such as a counter bore ball bearing, a single row angular contact ball bearing, a double row tapered roller bearing are included. The hub wheel 1 includes an annular flange 11 and a shaft portion 12 provided with a small-diameter outer peripheral face and a large-diameter outer peripheral face in the axial direction. A bearing 2 is fitted over the small-diameter outer peripheral face of the shaft portion 12. The bearing 2 includes an inner ring 21 having a single raceway fitted over the small-diameter outer peripheral face of the shaft portion 12, a single outer ring 22 having raceway grooves in two rows, a plurality of balls 23 as rolling elements disposed in two rows, and two crown-like retainers 24. In the bearing 2, the large-diameter outer peripheral face of the shaft portion 12 of the hub wheel 1 is formed as one inner ring. As the inner ring 21, an inner ring of a general single row angular contact ball bearing is used as it is. A flange 25 directing diametrically outward is provided on an outer periphery of the outer ring 22. The flange 25 is mounted to an axle case (not shown) non-rotatably. In the case of the embodiment according to the present invention, a conventional support jig is unnecessary as will be explained with reference to Figs.3 to 7. As shown in Fig.3, an angled portion 21a of an axially outer edge of the inner ring 21 is rounded. For example, the angled portion 21a in a region from a chamfering-starting point 21b to a chamfering-ending point 21c is chamfered into 1/4 of a circumference of radius of curvature r with respect to the center O or smaller (straight portion may exist). The chamfering-starting point 21b is a point of intersection between a vertical line directing diametrically inward from the center O and the angled portion 21a. The caulking portion 3a is cylindrical in shape, and comprises a large-diameter portion 3b having an outer diameter that substantially coincides with an inner diameter of the inner ring 21 along an inner circumference thereof, and a small-diameter portion 3c having an outer diameter smaller than the inner diameter of the inner ring 21 and extending through a required distance in one of the axial direction from the large-diameter portion 3b. Because the large-diameter portion 3b is fitted over the inner circumference of the inner ring 21, it is preferable that the large-diameter portion 3b is grained to a finish. The small-diameter portion 3c is subjected to turning to have small diameter. The small-diameter portion 3c further comprises a junction 3c1 having a tapered face which is tapered in axially one direction, and a shaft end 3c2 extending in axially one direction. A starting point 3d of the small-diameter portion 3c, i.e., a starting point 3d of the junction 3c1 is positioned closer to the axially center portion of the inner ring 21 than the chamfering-starting point 21b. An outer diameter difference (step) between the large-diameter portion 3b and the small-diameter portion 3c, a step between the inner diameter of inner ring 21 and the shaft end 3c2 of the small-diameter portion 3c is set to 0.1mm or less. If the step is 0.1mm or less, a gap is not generated between the inner ring 21 and the caulked portion 3. If the step exceeds 0.1mm, the probability that the gap is generated is increased. A bending operation of the caulking portion 3a in diametrically outward direction will be explained. In brief, a forging tool 90 in a rotary-forging device C shown in Fig.7 is inclined through a required angle β with respect to the caulking portion 3a and abutted against the caulking portion 3a and rolled. For clarifying the illustration, the forging tool 90 is not illustrated in Figs.3 to 6. The junction 3c1 of the small-diameter portion 3c is extended by the rolling as shown in Fig.4. If further rolled, the junction 3c1 of the small-diameter portion 3c and the shaft end 3c2 are bent along the angled portion 21a as shown in Fig.5. Finally, as shown in Fig.6, the small-diameter portion 3c is elastically bent in diametrically outward direction and pushed against an inner end face of the inner ring 21 as the caulked portion 3. The reason why the support jig is unnecessary will be explained. A caulking force at the time of rolling of the forging tool 90 is expressed by component of force, the caulking force is a sum of a diametrically outward component of force and a component of force in an axially center direction. A caulking force (deformation effort) for deforming a raceway of the inner ring 21 is a diametrically outward component of force. In the case of the rolling of the forging tool 90 in a state shown in Fig.3, the diametrically outward component of force becomes maximum. In the state of Fig.3, the starting point 3d of the small-diameter portion 3c is located closer to the axially center portion than the chamfering-starting point 21b. For this reason, as shown in Figs.3 and 4, the shaft end 3c2 is deformed diametrically outward such that the junction 3c1 of the small-diameter portion 3c is extended. In this case, a diametrically outward component of force is not applied to the inner ring 21 because the small-diameter portion 3c is not in contact with the inner ring 21 and thus, the inner ring 21 is not deformed. In Fig.5, the entire junction 3c1 of the small-diameter portion 3c and a portion of the shaft end 3c2 are in contact with the angled portion 21a of the inner ring 21. At this point of time, the diametrically outward component of force is small and component of force on the axially central side becomes great. This axially central side component of force is not applied to the inner ring 21 as a deformation effort, which impairs the circularity of the inner ring 21. Therefore, the inner ring 21 is not deformed by this caulking, and the caulking portion 3a is caulked on the end face of the inner ring 21 as the caulked portion 3 as shown in Fig.6. As described above, according to the hub unit of the embodiment, the adverse probability that the inner ring 21 is deformed is largely reduced, the number of assembling steps and assembling time are reduced, and the structure of the hub unit is suitable for mass production. The present invention can be applied to a general bearing device in which the hub wheel class is used as a shaft body and the angular contact type rolling bearing is disposed on the outer periphery of the shaft portion of this shaft body. The present invention can be applied to a guide roller of a sliding door of an automobile and a general bearing device. While there has been described what is at present considered to be preferred embodiment of this invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications which fall within the true scope thereof.

Claims: A bearing device (A), having a shaft with a caulked portion (3) formed from a cylindrical shaped caulking portion (3a), comprising a shaft body whose shaft end is formed into a cylindrical shape as a caulking portion (3a); and an angular contact type rolling bearing (2) fitted over an outerperiphery of said shaft body; wherein an axially outer edge of an inner ring (21) of said rolling bearing (2) is partially chamfered roundly with a predetermined radius (r) of curvature, said caulking portion (3a) comprises a large-diameter portion (3b) having an outer diameter substantially coinciding with an inner diameter of an inner periphery of said inner ring (21) and fitted to the inner periphery of said inner ring (21), and a small-diameter portion (3c) having an outer diameter smaller than the inner diameter of said inner ring (21) and extended in axially one direction from said large-diameter portion (3b) through a predetermined distance, a starting point (3d) of said small-diameter portion (3c) is located closer to an axially central portion than a chamfer-starting point (21b) of the axially outer edge of said inner ring (21), and said small-diameter portion (3c) of said caulking portion (3a) is bent in diametrically outward direction and caulked on an end face of said inner ring (21) of said rolling bearing (2) so as to prevent the rolling bearing (2) from falling out of said bearing device (A) and to apply a pre-load to said rolling bearing (2). A bearing device according to claim 1, wherein said shaft body is a hub wheel (1) to which a wheel is mounted, said hub wheel (1) having a shaft portion (12) comprising a small diameter outer peripheral face and a large-diameter outer peripheral face, a shaft end (3a) of said shaft portion is said caulking portion (3a), said rolling bearing (2) is a double row angular contact ball bearing having an inner ring (21) of a single raceway fitted over the small-diameter outer peripheral face of said shaft portion (12) of said hub wheel (1), a single outer ring (22) having two row raceway grooves, a plurality of balls (23) arranged in two rows, and two crown-like retainers (24), said large-diameter outer peripheral face (3b) of said shaft portion (12) of said hub wheel (1) is one inner ring, the axially outer edge of the inner ring (21) of said rolling bearing (2) is partially chamfered roundly with a predetermined radius (r) of curvature, and said small-diameter portion (3c) of said caulking portion (3a) is bent in diametrically outward direction and caulked on the end face of said inner ring (21) of said rolling bearing (2) so as to prevent the rolling bearing (2) from falling out of said bearing device (A) and to apply a pre-load to said rolling bearing (2). A bearing device according to claim 1, wherein said small diameter portion (3c) of said caulking portion (3a) includes, before said small-diameter portion (3c) is caulked, a junction (3c1) having a tapered face which is reduced in diameter in an axially one direction from a starting point (3d) of said small-diameter portion (3c), and a shaft end (3c2) extending in an axially one direction from said junction (3c1). A bearing device according to claim 3, wherein an outer diameter difference between said large-diameter portion (3b) and said small-diameter portion (3c) of said caulking portion (3a) before said small diameter portion (3c) is caulked is 0.1 mm or less. A bearing device according to claim 1, wherein a surface of said large-diameter portion (3b) of said caulking portion (3a) is grained to a finish and fitted to the inner periphery of said inner ring (21) of said rolling bearing (2), and said small-diameter portion (3c) of said caulking portion (3a) is formed small in diameter by turning.

Inventors: ISHII TOMOHIRO, KASHIWAGI SHINICHIROU, MITARAI TADASHI, MIYAZAKI MAKOTO, TODA KAZUTOSHI, ISHII, TOMOHIRO, KASHIWAGI, SHINICHIROU, MITARAI, TADASHI, MIYAZAKI, MAKOTO, TODA, KAZUTOSHI, Ishii, Tomohiro, c/o Koyo Seiko Co., Ltd., Kashiwagi, Shinichirou, c/o Koyo Seiko Co., Ltd., Mitarai, Tadashi, c/o Koyo Seiko Co., Ltd., Miyazaki, Makoto, c/o Toyota Motor Corporation, Toda, Kazutoshi, c/o Koyo Seiko Co., Ltd.
Applicants: KOYO SEIKO CO, KOYO SEIKO CO., LTD.
Application year: 2000
Main classification: F16C35
IPC codes: F16C43, G01L5, B60B27, G01P3, F16C19