Abstract:
An inner ring is fitted on one-end side of an inner shaft and fixed to the inner shaft by caulking. During the caulking, the inner shaft is supported by a caulking receiving jig. A receiving section to which the jig is in contact is provided at a position near the one-end side of the inner shaft, for example, at a position nearer to the inner ring than a raceway section formed on the outer periphery on the other side of the inner shaft. As a result, a caulking load acting from a caulking jig on the inner shaft plastically deforms only a desired portion.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method of producing a rolling bearing device, more particularly to a method of securing an inner ring externally mounted on an inner shaft to the inner shaft by caulking one-end side of the inner shaft. 
     There is such a type that an inner ring is fixed to be externally engaged on one-end side of an inner shaft provided on an inner-diameter side of an outer ring in a rolling bearing device used for supporting a wheel of a motor vehicle. As an example of a method of producing the rolling bearing device of this type, there is a method of securing the inner ring to the inner shaft by caulking the one-end side of the inner shaft onto an outer end surface of the inner ring (see the Patent Literature 1).
     Patent Literature 1: No. 2002-339959 of the Japanese Patent Applications Laid-Open   

     The conventional producing method where the caulking is adopted has such a problem that a raceway section of the inner ring is slightly deformed. 
     SUMMARY OF THE INVENTION 
     The inventors of the present invention found out the following in a process of devising the present invention. More specifically, in the conventional producing method, a wheel mounting surface of a flange part for mounting a wheel and an inner end part of a spigot joint part, which are on another-end side of an inner shaft, are used as receiving sections for receiving a caulking load, the receiving sections are abutted by a caulking receiving jig so that the inner shaft is supported, and then, the one-end side of the inner shaft is caulked. In the rolling bearing device produced by means of the conventional producing method, therefore, a large distance is formed between the one-end side of the inner shaft and the caulking receiving tool. As a result, in the case where the caulking load is increased in order to, for example, obtain an necessary axial force, the caulking load acts on parts which originally do not require the caulking load because the large distance is generated, and thereby, it may generate such an inconvenience that a raceway section of the inner ring is slightly deformed. 
     The present invention solves the foregoing problem by adopting the following constitution based on the knowledge described above. In other words, a method of producing a rolling bearing device according to the present invention is a method wherein one-end side of an inner shaft is caulked onto an end surface of an inner ring externally engaged on the inner shaft, and a receiving section subject to a stress applied to the inner shaft in the caulking is formed in vicinity of the one-end side of the inner shaft so that the caulking is implemented while supporting the receiving section by a caulking receiving jig. 
     According to the foregoing constitution, in the present invention, the stress applied to the inner shaft when the end surface of the inner ring on the one-end side of the inner shaft is caulked can be received at a position in vicinity of the one-end side of the inner shaft, and as a result, a load necessary for the caulking can be transmitted alternatively to a part of the inner shaft which requires the load. Therefore, when a required preload is applied to the bearing part, the inner ring can be secured lest it is slipped out in an axial outward direction. The rolling bearing device can be thereby produced without generating even a slight deformation in a raceway section of the inner shaft, a raceway section of the inner ring and the like. 
     In order to achieve the foregoing effect, the receiving section is preferably provided at an axial position between the raceway section of the inner shaft and the part on which a caulking jig is operated. However, since the part to which the inner ring is secured has a small diameter conventionally, a thickness of the small-diameter part could have been too thin if the receiving section is provided at a position axially corresponding to the small-diameter part. Therefore, it is more preferable that the receiving section is provided, not at any position in the small-diameter part, but at an axial position between the raceway section of the inner shaft and the inner ring. 
     The inner shaft may be solid or hollow with a bearing hole at a central part thereof. In the case where the inner shaft is hollow, it is preferable that the receiving section is formed at an axial position closer to the inner ring than the raceway section of the inner shaft and a radial position facing a region axially rightly opposed to the part on which the caulking jig is operated in an inner periphery of the hollow part. 
     According to the foregoing constitution, the receiving section can be axially and radially close to the inner ring and can thereby receive the caulking load operating from the caulking jig at the position very close to the inner ring. Accordingly, the caulking load transmitted to the part where the caulking load is originally unnecessary can be lessened, which reliably prevents the deformation of the part in which the caulking load is unnecessary. 
     According to the present invention, the caulking can be performed without transmitting the stress applied to the inner shaft to the part in which the caulking load is unnecessary. As a result, a rolling bearing device having a necessary axial force can be produced without any adverse influence such as the slight deformation of the raceway section or the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an axially sectional view showing the state on the way of a process producing a rolling bearing device used for the implementation of the present invention. 
         FIG. 2  is an axially sectional view of a schematic shape of a modified example of the rolling bearing device shown in  FIG. 1 . 
         FIG. 3  is an axially sectional view showing the state on the way of a process producing a rolling bearing device used according to another preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , preferred embodiments of the present invention are described.  FIG. 1  is an axially sectional view of a rolling bearing device according to the present invention, wherein the rolling bearing device on the way of a producing process is shown. 
     The rolling bearing device according to the present preferred embodiment is a type of a double-row angular ball bearing for supporting a driven wheel of a motor vehicle, comprising an outer ring  1 , an inner shaft  2 , an inner ring  3 , a plurality of balls  4  and  5  as rolling bodies, cages  6  and  7  and a seal  8 . 
     The outer ring  1  is secured to a vehicle-body side such as a carrier via a flange part  11  provided on an outer circumferential surface thereof, and raceway sections  1   a  and  1   b  are formed in double rows on an inner circumferential surface thereof. 
     A spigot joint part  21 , a flange part  22  for mounting a wheel and a raceway section  2   a  are formed on a vehicle-outer side of the inner shaft  2  (lower-end side in  FIG. 1 ). Mounting holes  9  axially penetrating through are formed at a plurality of circumferential positions of the flange part  22 , and bolts for securing a disc rotor and a wheel of a disc brake device (not shown) can be pressed into these mounting holes  9  from a vehicle-inner side. A small-diameter part  23  is formed on the vehicle-inner side of the inner shaft  2  (upper-end side in  FIG. 1 ), and a cylindrical part serving as a caulking part (both are shown by  23   a ) is provided at an edge of the small-diameter part  23 . 
     The inner ring  3  comprises a raceway section  3   b  facing the raceway section  1   b  of the outer ring on an outer peripheral surface thereof, and is externally mounted on an outer peripheral surface of the small-diameter part  23  of the inner shaft  2 . The cylindrical part  23   a  of the small-diameter part  23  is caulked radially outward by a caulking jig K so that the inner ring  3  is secured to the inner shaft  2 . 
     The balls  4  and  5  are provided in double rows in a facing space between the raceway pars  1   a,    1   b,    2   a  and  3   b,  and are retained by the cages  6  and  7  so as to freely roll. The seal  8  seals a bearing space between the outer ring  1  and the inner shaft  2 . 
     In the present preferred embodiment, the inner shaft  2  is solid, and a recessed part  10  opened toward the vehicle-outer side is formed on a radially inner side thereof. A caulking receiving jig U abuts a bottom part of the recessed part  10 , and the recessed part  10  (in particular, bottom part thereof) thereby serves as a receiving section  12  subject to a stress applied to the inner shaft  2  at the time of the caulking. The receiving section  12  desirably has a large diameter for receiving a caulking load. Further, it is necessary to set the diameter of the receiving section  12  so that an enough thickness can be provided between the recessed part  10 , and the raceway section  2   a  of the inner shaft  2  and the outer peripheral surface of the small-diameter part  23 . An axial position P of the receiving section  12  may be a position more axially inward of the inner shaft than the raceway section  2   a  of the inner shaft  2  (position axially closer to the inner ring  3 ). In the present preferred embodiment, the axial position P is set to a position before an axial position Q (position axially closer to the raceway section  2   a ) of an inner end surface of the inner ring  3  (small end surface in the example shown in the drawing) based on the following reason. The diameter of the section of the inner shaft  2  where the inner ring  3  is provided is small (small-diameter part  23 ) in comparison to any other axial position of the inner ring. Therefore, the axial position P of the receiving section  12  is set to the position before the axial position Q (position axially closer to the raceway section  2   a,  that is, lower side in  FIG. 1 ) on the inner end surface of the inner ring  3  (small end surface in the example shown in  FIG. 1 ) so that the section where the receiving section  12  is provided does not overlap with the section where the inner ring  3  is provided in order to prevent the thickness of the small-diameter part from becoming too thin. 
     When the caulking process is performed in the producing of the rolling bearing device thus constituted, first, the outer ring  1 , inner shaft  2 , inner ring  3 , balls  4  and  5  and the like are assembled in the state shown in  FIG. 1 . Then, the assembly is set in the upright position so that the flange part  22  for mounting the wheel is at the bottom, and the columnar caulking receiving jig U is made to abut the receiving section  12  of the inner shaft  2  so that the receiving section  12  is supported on a substrate S via the caulking receiving jig U. The caulking jig K is then made to abut the cylindrical part  23   a  of the inner shaft  2  protruding more upward than the inner ring  3  so as to rolling-caulk the cylindrical part  23   a  by rotating the caulking jig K while oscillating it around a vertical axis. Then, the cylindrical part  23   a  of the inner shaft  2  is plastically deformed radially outward so that the inner ring  3  is secured to the inner shaft  2 . 
     In the foregoing case, as shown in outline arrows in  FIG. 1 , the caulking load acting on the cylindrical part  23   a  of the inner shaft  2  and the caulking part  23   a  generated from the cylindrical part  23   a  is received by the caulking receiving jig U via the receiving section  12  (the arrows shown in the caulking receiving jig U denote reactions resulting from the reception of the caulking load. The stress resulting from the caulking is generated mainly in from the cylindrical part  23   a  through to the receiving section  12  among the respective sections of the inner shaft  2 , and rarely generated in any part lower than the receiving section  12 . Therefore, there is no risk of deformation of the raceway section  2   a  of the inner shaft  2  and the like. 
     In addition, when the caulking to the inner shaft  2  is completed, the seal is attached between the inner ring  3  and the outer ring  1 , and the bolts are respectively pressed into the mounting holes  9  of the flange part  22  for mounting the wheel in the inner shaft  2 . 
       FIG. 2  shows a modified embodiment of the preferred embodiment shown in  FIG. 1 . In the case where the recessed part  10  of the inner shaft  2  has such a shape that is recessed in two steps and a shaft step part  24  is present in an inner periphery of the inner shaft  2  as shown in  FIG. 2 , a jig step part Ua is formed in an outer periphery of the caulking receiving jig U so that the caulking receiving jig U has such a shape that protrudes in a step shape corresponding to the shape of the recessed part  10  (shaft step part  24 ). Accordingly, the shaft step part  24  is made to abut the jig step part Ua of the caulking receiving jig U so that the shaft step part  24  of the inner shaft  2  functions as a second receiving section for receiving the caulking load. 
     Next, another preferred embodiment of the present invention is described referring to  FIG. 3 . The inner shaft  2  is hollow and has a bearing hole  13  at the center thereof. In the inner shaft  2  thus constituted, a step-shape receiving section  12  to which the caulking receiving jig U is made to abut is formed across an entire inner periphery of the hollow part. 
     A position of the receiving section  12  is an axial position closer to the inner ring  3  than the raceway section  2   a  of the inner shaft  2 , and set to a radial position R partly or entirely included in a region axially rightly opposed to the section where the caulking jig K of the inner shaft  2  acts (more specifically, the cylindrical part  23   a  of the inner shaft  2  and the caulking part formed from the cylindrical part  23   a ). The region is a region corresponding to a thickness  2   b  of the inner shaft  2  between the raceway section  2   a  of the inner shaft  2  and the inner ring  3 . A spline  2   c  is formed in the inner periphery of the hollow part closer to a caulking part  23   a  than the receiving section  12 . 
     In this constitution, the receiving section  12  can be axially and radially close to the inner ring  3 , and receives the caulking load acting from the caulking jig K at a front position very close to the inner ring  3 , which reliably prevents any undesirable part from being unnecessarily deformed. 
     The producing method according to the present invention is not necessarily limited to the producing of the rolling bearing device wherein the balls are used as the rolling bodies, and can be applied to the producing of rolling bearing devices of various types wherein tapered rollings and cylindrical rollings can used as the rolling bodies as far as these rolling bearing devices are used in such a manner that an inner ring is secured to one end side of an inner shaft by caulking.