Patent Publication Number: US-2021190142-A1

Title: Cage for bearing

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/KR2018/010372 filed on Sep. 5, 2018, the entire contents of which are herein incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a bearing cage. 
     BACKGROUND 
     A bearing is a mechanical element which serves to position a shaft of a rotating machine at a certain position and to rotate the shaft while supporting the weight of the shaft and the load applied on the shaft. When the bearing is used while being mounted to the shaft, it is necessary to reduce the frictional force between the bearing and the shaft in order to facilitate the rotation of the shaft. To do this, lubricant such as oil, grease, or the like is supplied to the bearing. 
       FIG. 1  is a schematic cross-sectional view of a Dual Clutch Transmission (DCT) when viewed in an axial direction. Bearings are coupled to shafts A, B, C and D of the DCT and lubricant is stored in a certain space inside the DCT. The stored lubricant may be supplied to bearings, which are coupled to the shafts A and B located at a height to which the lubricant does not reach, by churning. The shaft A corresponds to an input shaft, the shafts B and C correspond to an output shaft, and the shaft D corresponds to a differential shaft (differential gear shaft). The term “churning” refers to an operation in which elements, which are coupled to the lower shafts C and D located at a height to which the lubricant reaches, splash the lubricant upward while rotating. 
     During the operation of the DCT, the lubricant may also be supplied to bearings coupled to the upper shafts A and B by the churning. However, when the operation of the DCT is resumed after being left in a non-use state for a long time, the lubricant adhered to the bearings coupled to the upper shafts A and B may be completely dried. If the DCT is operated in a state in which the lubricant is completely dried (i.e., dry start), the upper shafts A and B may rotate with no lubricant, and the frictional force between the shafts and the bearings may be increased, which may cause damage to the bearings and/or the shafts. 
     SUMMARY 
     One object of the present disclosure is to provide a bearing cage that enables a bearing coupled to a mechanical device to operate with lubricant even if the mechanical device is operated again after being left in a non-use state for a long time. 
     In one embodiment, a bearing cage comprises: a first circular ring; a second circular ring provided to be spaced apart from the first ring in a coaxial relationship with the first ring; a plurality of pillars provided in a circumferential direction of the first ring and the second ring, one end of the pillar being connected to the first ring and the other end of the pillar being connected to the second ring; a plurality of pockets provided in the circumferential direction and configured to provide a space in which a bearing roller is accommodated, the pocket being formed to be surrounded by the first ring, the pillars and the second ring; and first reservoirs provided in the pillars and comprising a first storage space for storing lubricant. 
     In another embodiment, a bearing cage comprises: a first circular ring; a second circular ring provided to be spaced apart from the first ring in a coaxial relationship with the first ring; a plurality of pillars provided in a circumferential direction of the first ring and the second ring, one end of the pillar being connected to the first ring and the other end of the pillar being connected to the second ring; a plurality of pockets provided in the circumferential direction and configured to provide a space in which a bearing roller is accommodated, the pocket being formed to be surrounded by the first ring, the pillars and the second; and second reservoirs having a second storage space to be opened in a radially outward direction for storing lubricant, the second reservoir being formed to extend in a radially inward direction from an inner surface of the pillar, which is a surface facing inward of the first ring of the second ring, out of the surfaces of the pillar. The second reservoir is formed to be surrounded by: a pair of (2-1)th wall portions formed to extend in the radially inward direction from the inner surface of the pillar and provided to be spaced apart with each other in the circumferential direction; a (2-2)th wall portion configured to connect radially inner ends of the (2-1)th wall portions; and a (2-3)th wall portion formed to extend in the radially outward direction from an end of the (2-2)th wall portion in a direction opposite to a first direction, which extends from the second ring toward the first ring, so as to block at least a portion of an opening formed between the (2-1)th wall portions. 
     According to the present disclosure, lubricant that has been used during an operation of a mechanical device can be stored in a first storage space of a first reservoir provided in the bearing cage, and the lubricant can be supplied to bearing rollers even when the mechanical device is resumed after the operation is stopped for a long time. 
     Further, according to the present disclosure, since the bearing case comprises a first reservoir having a first storage space opened in a radially inward direction and a second reservoir having a second storage space opened in a radially outward direction, when a bearing is coupled to a mechanical device in a state that a shaft direction of the bearing is horizontal to the ground, lubricant can be stored in the first storage space of the first reservoir below the shaft and the lubricant can be stored in the second storage space of the second reservoir above the shaft. Accordingly, a sufficient amount of lubricant can be supplied to bearing rollers even when the mechanical device is reoperated after the operation is stopped for a long time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a Dual Clutch Transmission (DCT) when viewed in an axial direction. 
         FIG. 2  is a perspective view of a bearing cage according to a first embodiment of the present disclosure. 
         FIG. 3  is a longitudinal cross-sectional view showing a state in which rollers and an inner ring of a bearing are coupled to the bearing cage according to the first embodiment of the present disclosure. 
         FIG. 4  is a perspective view specifically showing a first reservoir according to the first embodiment of the present disclosure. 
         FIG. 5A  is a longitudinal cross-sectional view schematically illustrating a process of injection-molding the first reverser according to the first embodiment of the present disclosure. 
         FIG. 5B  is a longitudinal cross-sectional view schematically illustrating a process of injection-molding the first reverser according to the first embodiment of the present disclosure. 
         FIG. 5C  is a longitudinal cross-sectional view schematically illustrating a process of injection-molding the first reverser according to the first embodiment of the present disclosure. 
         FIG. 6  is a longitudinal cross-sectional view showing a state in which rollers and an inner ring of a bearing are coupled to a bearing cage according to a second embodiment of the present disclosure. 
         FIG. 7  is a perspective view specifically illustrating a second reservoir according to the second embodiment of the present disclosure. 
         FIG. 8A  is a longitudinal cross-sectional view schematically illustrating a process of injection-molding the second reservoir according to the second embodiment of the present disclosure. 
         FIG. 8B  is a longitudinal cross-sectional view schematically illustrating a process of injection-molding the second reservoir according to the second embodiment of the present disclosure. 
         FIG. 8C  is a longitudinal cross-sectional view schematically illustrating a process of injection-molding the second reservoir according to the second embodiment of the present disclosure. 
         FIG. 9  is a longitudinal cross-sectional view showing a state in which rollers and an inner ring of a bearing are coupled to a bearing cage according to a third embodiment of the present disclosure. 
         FIG. 10  is a perspective view specifically showing a first reservoir and a second reservoir according to the third embodiment of the present disclosure. 
         FIG. 11A  is a longitudinal cross-sectional view schematically illustrating a process of injection-molding the first reservoir and the second reservoir according to the third embodiment of the present disclosure. 
         FIG. 11B  is a longitudinal cross-sectional view schematically illustrating a process of injection-molding the first reservoir and the second reservoir according to the third embodiment of the present disclosure. 
         FIG. 11C  is a longitudinal cross-sectional view schematically illustrating a process of injection-molding the first reservoir and the second reservoir according to the third embodiment of the present disclosure. 
         FIG. 12A  is a longitudinal cross-sectional view schematically showing a process of assembling the inner ring in the bearing cage according to the third embodiment of the present disclosure. 
         FIG. 12B  is a longitudinal cross-sectional view schematically showing a process of assembling the inner ring in the bearing cage according to the third embodiment of the present disclosure. 
         FIG. 12C  is a longitudinal cross-sectional view schematically showing a process of assembling the inner ring in the bearing cage according to the third embodiment of the present disclosure. 
         FIG. 12D  is a longitudinal cross-sectional view schematically showing a process of assembling the inner ring in the bearing cage according to the third embodiment of the present disclosure. 
         FIG. 13  is a plan view showing a state in which the roller of the bearing is accommodated in the bearing cage according to the third embodiment of the present disclosure. 
         FIG. 14  is a plan view showing a state in which the roller, the inner ring and an outer ring of the bearing are assembled to the bearing cage according to the third embodiment of the present disclosure. 
         FIG. 15  is a perspective view specifically illustrating a pillar according to a fourth embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, some embodiments of the present disclosure will be described in detail through exemplary drawings. It should be noted that, in adding reference numerals to components in the drawings, the same components are made to have the same symbols as possible even if they are illustrated on the other drawings. In addition, if it is determined that detailed descriptions on related known configurations or functions in describing the embodiments of the present disclosure prevent understanding of the embodiments of the present disclosure, detailed descriptions thereof will be omitted. 
     First Embodiment 
       FIG. 2  is a perspective view of a bearing cage according to a first embodiment of the present disclosure.  FIG. 3  is a longitudinal cross-sectional view showing a state in which rollers and an inner ring of a bearing are coupled to the bearing cage according to the first embodiment of the present disclosure.  FIG. 4  is a perspective view specifically showing a first reservoir according to the first embodiment of the present disclosure. The bearing cage according to the first embodiment of the present disclosure will be described below with reference to  FIGS. 2 to 4 . 
     Referring to  FIGS. 2 and 3 , the bearing cage according to the first embodiment of the present disclosure comprises a first ring  1 , a second ring  2 , pillars  3 , pockets  4  and first reservoirs  10 . 
     The second ring  2  is arranged coaxially with the first ring  1 , and is provided spaced apart from the first ring  1 . A diameter of the second ring  2  may be smaller than that of the first ring  1 . In this case, the bearing cage may be used for a tapered roller bearing. 
     Hereinafter, a direction extending from the second ring  2  toward the first ring  1  will be referred to as a first direction. In addition, a direction extending from a central axis of the first ring  1  and the second ring  2  toward the first ring  1  and the second ring  2  will be referred to as a radially outward direction, and a direction extending from the first ring  1  and the second ring  2  toward the central axis of the first ring  1  and the second ring  2  will be referred to as a radially inward direction (see  FIG. 3 ). 
     The pillar  3  is configured such that one end thereof is connected to the first ring  1  and the other end thereof is connected to the second ring  2 . A plurality of pillars  3  are provided in a spaced-apart relationship with each other along a circumferential direction of the first ring  1  and the second ring  2 . The plurality of pillars  3  may be provided to be spaced at equal intervals. 
     The first ring  1 , the second ring  2  and a pair of pillars  3  form a pocket  4 . That is, the pocket  4  is formed to be surrounded by the first ring  1 , the pillars  3  and the second ring  2 , and a plurality of pockets  4  are provided along the circumferential direction. The pocket  4  provides a space in which a roller of the bearing is accommodated. The pillar  3  may function as a partition between one pocket  4  and another pocket  4  adjacent thereto, and may serve to prevent rollers accommodated in adjacent pockets  4  from coming into contact with each other. 
     The first reservoir  10  is provided in the pillar  3 , and has a first storage space  11  for storing lubricant. When the operation of a mechanical device to which the bearing is coupled is stopped, the used lubricant may be stored in the first storage space  11 . When the mechanical device is reoperated, the lubricant stored in the first storage space  11  may be supplied to the roller by virtue of a centrifugal force caused by the rotation of a shaft. 
     That is, when the operation of the mechanical device is resumed in a state in which the mechanical device is left in a non-use state for a long time, the lubricant adhered to the rollers and the bearing cage may be completely dried, and consequently the rotation of the shaft may begin with no lubricant (i.e., dry start). In this case, the frictional force between the rollers and the shaft is increased, which may cause damage to the bearing and the shaft. 
     In particular, in the case of the tapered roller bearing in which the diameter of the second ring  2  is smaller than the diameter of the first ring  1 , the used lubricant may flow downward along inclined surfaces of the pillars  3 . In the bearing cage of the present disclosure, the used lubricant may be stored in the first reservoir  10 , which prevents the mechanical device from operating with no lubricant. 
     Hereinafter, the first reservoir  10  will be described in more detail with reference to  FIG. 4 . The first storage space  11  may be provided on an inner surface  3   a , which faces inward of the first ring  1  or the second ring  2 , out of surfaces of the pillar  3 . The first storage space  11  may be formed to be open in the radially inward direction. 
     For example, the first storage space  11  may be formed to be recessed in the radially outward direction from the inner surface  3   a . Alternatively, the first storage space  11  may be formed to be surrounded by wall portions extending in the radially inward direction from the inner surface  3   a . That is, the first reservoir  10  may further comprise: a pair of (1-1)th wall portions  13  formed to extend in the radially inward direction and provided to be spaced apart from each other along the circumferential direction; and a (1-2)th wall portion  15  formed to extend in the radially inward direction from the inner surface  3   a  and configured to connect the (1-1)th wall portions  13 . The (1-1)th wall portions  13  and the (1-2)th wall portion  15  may form the first storage space  11  therein. Alternatively, the first storage space  11  formed by the (1-1)th wall portions  13  and the (1-2)th wall portion  15  may be formed to be further recessed in the radially outward direction. 
     In this case, as illustrated in  FIG. 4 , one ends of the (1-1)th wall portions  13  may be coupled to the second ring  2 , and the (1-2)th wall portion  15  may connect the other ends (the first direction ends) of the (1-1)th wall portions  13 . Alternatively, when the (1-1)th wall portions  13  are not coupled to the second ring  2 , the (1-2)th wall portion  15  may be provided both at end portions in the first direction and at end portions in the opposite direction to the first direction. 
     Further, even in the case where the diameter of the second ring  2  is set to be smaller than the diameter of the first ring  1 , the (1-2)th wall portion  15  may be provided so as to connect the first direction ends of the (1-1)th wall portions  13 . That is, in the case where the diameter of the second ring  2  is set to be smaller than the diameter of the first ring  1 , the pillar  3  is formed to be inclined in the radially outward direction as it goes from the second ring  2  toward the first ring  1 . Thus, even if the (1-2)th wall portion  15  is formed only at the first direction end, the first storage space  11  may be formed by the inclination of the pillar  3 . 
     In the meantime, the bearing cage according to the first embodiment of the present disclosure may be formed of a plastic material. In this case, the bearing cage may generally be manufactured by injection-molding.  FIG. 5  is a longitudinal cross-sectional view schematically illustrating a process of injection-molding the first reservoir according to the first embodiment of the present disclosure. 
     Since, the first storage space  11  is provided to be recessed in the radially outward direction relative to the (1-2)th wall portion  15 , when separating a mold  70  which has been inserted to form the first storage space  11  from the bearing case, the mold  70  may not be separated because it is locked to the (1-2)th wall portion  15 . 
     To address this, the (1-2)th wall portion  15  may comprise a (1-2)th inclined surface  16  formed to extend from the bottom surface of the first storage space  11  and configured to gradually increase a thickness in the radially inward direction as it goes in the first direction. The (1-2)th inclined surface  16  is an inclined surface formed to extend from the bottom surface of the first storage space  11  and configured to be moved in the radially inward direction as it goes in the first direction. 
     Further, the (1-1)th wall portion  13  may comprise a (1-1)th inclined surface  13   a . The (1-1)th inclined surface  13   a  may be formed to extend from a position spaced apart from the (1-2)th wall portion  15  by a certain distance in a direction opposite to the first direction (see  FIG. 4 ). The (1-1) the inclined surface  13   a  may be formed such that a thickness in the radially inward direction is increased as it goes in the first direction (see  FIG. 4 ). That is, the (1-1)th inclined surface  13   a  is an inclined surface configured to be moved in the radially inward direction as it goes in the first direction. 
     The inserted mold  70  may press the (1-1)th inclined surface  13   a  and the (1-2)th inclined surface  16  when being separated from the bearing cage, so that the first reservoir  10  is elastically deformed in the radially outward direction and thus the inserted mold  70  can be easily separated from the bearing cage (see  FIG. 5B ). 
     In this case, the bearing cage may further comprise a first displacement space  19  to form a space in which the first reservoir  10  is elastically displaced in radially outward direction. The first displacement space  19  may be formed at the rear side of the first reservoir  10  in the direction opposite to the first direction between the (1-2)th wall portion  15  and the inner surface  3   a  of the pillar  3 . When the mold  70  is separated from the bearing cage, the (1-1)th wall portions  13  and the (1-2)th wall portion  15  may be elastically displaced to the first displacement space  19  so that the mold  70  can be easily separated. As described above, since the bearing cage according to the first embodiment of the present disclosure comprises the (1-1)th inclined surface  13   a , the (1-2)th inclined surface  16 , the first displacement space  19 , or the like, the bearing cage according to the first embodiment of the present disclosure can be produced in a simplified manner through a conventional mold. 
     Second Embodiment 
       FIG. 6  is a longitudinal cross-sectional view showing a state in which rollers and an inner ring of a bearing are coupled to a bearing cage according to a second embodiment of the present disclosure.  FIG. 7  is a perspective view specifically illustrating a second reservoir according to the second embodiment of the present disclosure. The bearing cage according to the second embodiment of the present disclosure will be described with reference to  FIGS. 6 and 7 . The bearing cage according to the second embodiment of the present disclosure is different from the bearing cage according to the first embodiment in that the second reservoir is provided instead of the first reservoir. 
     The bearing cage according to the second embodiment of the present disclosure comprises a second reservoir  20  formed to extend in the radially inward direction from the pillar  3 . The second reservoir  20  may comprise a second storage space  21  formed to be open in the radially outward direction for storing lubricant. 
     As illustrated in  FIG. 6 , in a case in which the bearing is coupled to the mechanical device such that the axial direction of the bearing is arranged to be horizontal to the ground, when the operation of the mechanical device is stopped, the lubricant may be stored in the second storage space  21  located above the shaft, and when the operation of the mechanical device is resumed, the lubricant stored in the second storage space  21  may be supplied to the roller by virtue of a centrifugal force caused by the rotation of the shaft. Thus, even if the operation of the mechanical device is resumed after the mechanical device is left in a non-use state for a long time, it possible to prevent the mechanical device from operating with no lubricant by the lubricant stored in the second reservoir  20 . 
     Referring to  FIG. 7 , the second reservoir  20  may further comprise: (2-1)th wall portions  23 ; a (2-2)th wall portion  25 ; and a (2-3)th wall portion  27 . The second storage space  21  may be formed to be surrounded by the (2-1)th wall portions  23 , the (2-2)th wall portion  25  and the (2-3)th wall portion  27 . The second reservoir  20  may further comprise a (2-4)th wall portion  28 , and the second storage space  21  may be further surrounded by the (2-4)th wall portion  28 . 
     First, a pair of (2-1)th wall portions  23  may be formed to extend in the radially inward direction from the inner surface  3   a  of the pillar  3  while being spaced apart from each other along the circumferential direction. Further, the (2-1)th wall portions  23  may comprise a first extended portion  23   a  formed to extend in the radially inward direction from an end of the inner surface  3   a  in the direction opposite to the first direction; and a second extended portion  23   b  formed to extend in the first direction from a radially inward end of the first extended portion  23   a . That is, the (2-1)th wall portions  23  may be formed in an L shape. 
     Next, the (2-2)th wall portion  25  may connect the radially inward ends of the (2-1)th wall portions  23  with each other. The (2-3)th wall portion  27  may extend in the radially outward direction from an end of the (2-2)th wall portion  25  in the direction opposite to the first direction so as to block at least a portion of an opening formed between the (2-1)th wall portions  23 . 
     The (2-4)th wall portion  28  may extend in the radially outward direction from a first direction end of the (2-2)th wall portion  25  so as to block at least a portion of an opening formed between the (2-1)th wall portions  23 . The (2-4)th wall portion  28  may be formed lower than the (2-1)th wall portions  23  with reference to the (2-2)th wall portion  25 . That is, both the (2-4)th wall portion  28  and the (2-1)th wall portions  23  extend in the radially outward direction from the (2-2)th wall portion  25 , but the radially outward end of the (2-4)th wall portion  28  is positioned adjacent to the (2-2)th wall portion  25  relative to the radially outward end of the (2-1)th wall portion  23 . 
     An opening  29  is formed in the (2-4)th wall portion  28 , so that the lubricant stored in the second storage space  21  can be easily discharged to the roller  7  (see  FIG. 7 ). 
     In the meantime, the bearing cage according to the second embodiment of the present disclosure may also be formed of a plastic material. In this case, the bearing cage may generally be manufactured through a mold.  FIG. 8  is a longitudinal cross-sectional view schematically illustrating a process of injection-molding the second reservoir according to the second embodiment of the present disclosure. 
     Since the second storage space  21  is provided to be recessed more radially inwardly than the (2-4)th wall portion  28 , when the mold  70  inserted to form the second storage space  21  is separated from the bearing cage, the mold  70  may not be separated because it is locked to the (2-4)th wall portion  28 . 
     To address this, the (2-4)th wall portion  28  may comprise a (2-4)th inclined surface  281 . The (2-4)th inclined surface  281  may be formed to extend from the bottom surface of the second storage space  21 . Further, The (2-4)th inclined surface  281  may be formed to gradually increase a thickness in the radially outward direction as it goes in the first direction. That is, the (2-4)th inclined surface  281  is a inclined surface configured to be moved in the radially outward direction as it goes in the first direction. 
     When the inserted mold  70  is separated from the bearing cage, the mold  70  may press the (2-4)th inclined surface  281  so that the second reservoir  20  is elastically deformed in the radially inward direction and thus the mold  70  can be easily separated from the bearing cage (see  FIG. 8B ). As described above, since the bearing cage according to the second embodiment of the present disclosure comprises the (2-4)th inclined surface  281 , the bearing cage according to the second embodiment of the present disclosure can be produced in a simplified manner through a conventional mold. 
     Third Embodiment 
       FIG. 9  is a longitudinal cross-sectional view showing a state in which rollers and an inner ring for a bearing are coupled to a bearing cage according to a third embodiment of the present disclosure.  FIG. 10  is a perspective view specifically showing a first reservoir and a second reservoir according to the third embodiment of the present disclosure. The bearing cage according to the third embodiment of the present disclosure will be described below with reference to  FIGS. 9 and 10 . 
     As illustrated in  FIGS. 9 and 10 , the bearing cage according to the third embodiment of the present disclosure may comprise both the first reservoir  10  of the first embodiment and the second reservoir  20  of the second embodiment. In this case, the (2-1)th wall portion  23  may be formed to extend in the radially inward direction from the (1-1)th wall portion  13 . 
     In the present embodiment, the bearing cage comprises both the first reservoir  10  provided with the first storage space  11  opened in the radially inward direction and the second reservoir  20  provided with the second storage space  21  opened in the radially outward direction. Thus, in a case in which the bearing is coupled to the mechanical device such that the axial direction of the bearing is horizontal to the ground, the lubricant may be stored in the first storage space  11  of the first reservoir  10  below the shaft and may be stored in the second storage space  21  of the second reservoir  20  above the shaft, as illustrated in  FIG. 9 . Therefore, even if the operation of the mechanical device is resumed after the mechanical device is left in a non-use state for a long time, a sufficient amount of lubricant may be supplied to the roller  7  for the bearing. 
       FIG. 11  is a longitudinal cross-sectional view schematically illustrating a process of injection-molding the first reservoir and the second reservoir according to the third embodiment of the present disclosure. The first reservoir  10  according to the third embodiment of the present disclosure may also comprise the (1-1)th inclined surfaces  13   a , the (1-2)th inclined surfaces  16  and the first displacement space  19 . The second reservoir  20  according to the third embodiment of the present disclosure may also comprise the (2-4)th inclined surfaces  281 . Accordingly, when the mold  70  is separated from the bearing cage, the first reservoir  10  may be elastically displaced in the radially outward direction, and the second reservoir  20  may be elastically displaced in the radially inward direction. As a result, the mold  70  can be easily separated from the bearing cage (see  FIG. 11B ). 
       FIG. 12  is a longitudinal cross-sectional view schematically showing a process of assembling the inner ring in the bearing cage according to the third embodiment of the present disclosure.  FIG. 13  is a plan view showing a state in which the roller for the bearing is accommodated in the bearing cage according to the third embodiment of the present disclosure.  FIG. 14  is a plan view showing a state in which the roller, the inner ring and an outer ring of the bearing are assembled to the bearing cage according to the third embodiment of the present disclosure. A process of assembling the inner ring and the outer ring in the bearing cage according to the third embodiment of the present disclosure will be described below with reference to  FIGS. 12 to 14 . Hereinafter, descriptions will be mainly made on the bearing cage according to the third embodiment of the present disclosure, however configurations to be described below may be similarly applied to the bearing cage according to the first embodiment or the second embodiment of the present disclosure. 
     First, a bearing cage where rollers  7  are accommodated into a pocket and an inner ring  5  to be assembled to the bearing cage are prepared, as illustrated in  FIG. 12A . Then, as illustrated in  FIGS. 12A to 12C , the inner ring  5  of the bearing may be assembled inside the first ring  1  and the second ring  2  in a second direction extending from the first ring  1  toward the second ring  2 . More specifically,  FIG. 12B  shows a state in which a lower flange  5   b  of the inner ring  5  is in contact with the (2-2)th wall portion  25  in the process of assembling the inner ring  5  in the bearing cage, and  FIG. 12C  shows a state in which the inner ring  5  is coupled to the bearing cage. 
     As illustrated in  FIGS. 13 and 14 , the (2-1)th wall portions  23  may be provided so as to extend in the radially inward direction from the inner surface of the pillar such that the (2-2)th wall portion  25  protrudes more radially inwardly than the second ring  2 . Further, as illustrated in  FIG. 13 , the (2-1)th wall portions ( 23 ) may be provided so as to extend in the radially inward direction from the inner surface such that the (2-2)th wall portion  25  protrudes more radially inwardly than the roller  7  when the roller  7  is accommodated in the pocket ( 24 ). Thus, as illustrated in  FIG. 12B , when the inner ring  5  is assembled to the bearing cage, the lower flange  5   b  of the inner ring  5  may not be brought into contact with the roller  7  and may be brought into contact with the (2-2)th wall portion  25 . When the inner ring  5  continues to move in the second direction after the inner ring  5  is in contact with the (2-2)th wall portion  25 , the inner ring  5  may press the (2-2)th wall portion  25  to elastically deform the (2-2)th wall portion  25  in the radially outward direction, and then may be completely assembled to the bearing cage as illustrated in  FIG. 12C . 
     In this case, the first ring  1  and the second ring  2  may formed of a material such as plastic to be elastically deformable. The (2-2)th wall portion  25  may be configured to be inclined in the radially outward direction along the direction extending from the first ring  1  toward the second ring  2 , so that the (2-2)th wall portion  25  can be easily pressed in the radially outward direction by the inner ring  5  being assembled. 
     As described above, in the course of assembling the inner ring  5  to the bearing cage, the inner ring  5  is coupled to the bearing cage in the state in which the lower flange  5   b  of the inner ring  5  presses the (2-2)th wall portions  23  without coming into contact with the roller  7 . This makes it possible to prevent the roller  7  from being damaged by the inner ring  5  in the course of assembling the inner ring  5  to the bearing cage. 
     After the inner ring  5  is assembled to the bearing cage as illustrated in  FIG. 12C , the outer ring is assembled as illustrated in  FIGS. 12D and 14 . Although, the outer ring is not illustrated in  FIGS. 12D and 14 ,  FIG. 12D  shows a state in which the outer ring is coupled to the bearing cage in the direction extending from the second ring toward the first ring. In  FIG. 14 , a symbol “o” denotes a raceway formed by an inner peripheral surface of the outer ring. 
     In this case, the pocket may have a size to form a clearance s between the pocket and the roller  7  as illustrated in  FIG. 14 , so that the roller accommodated in the pocket can be displaced in the radially inward direction by the assembly of the outer ring. That is, when the outer ring is coupled to the bearing cage, the roller  7  is pressed in the radially inward direction. After the assembling of the outer ring is completed, the roller  7  protrudes more radially inwardly than the (2-2)th wall portion  25 , so that a raceway i in which the roller  7  and the inner ring are in contact with each other may be formed at the radially inward position more than the (2-2)th wall portion  25 . 
     Fourth Embodiment 
       FIG. 15  is a perspective view specifically illustrating a pillar according to a fourth embodiment of the present disclosure. A bearing cage according to the fourth embodiment of the present disclosure differs from the bearing cages according to the first to third embodiments in that the bearing cage according to the fourth embodiment further comprise a third reservoir  30  and/or a fourth reservoir  40 , and the configuration of the pillar  3  of the bearing cage according to the fourth embodiment is different from those of the first to third embodiments 
     Referring to  FIG. 15 , the bearing cage according to the fourth embodiment of the present disclosure may further comprise the third reservoir  30 . The third reservoir  30  may be provided in the pillar  3  to be spaced apart in the first direction from the first reservoir  10 . The third reservoir  30  may be provided with a third storage space  31  as a space for storing lubricant. The third storage space  31  may be formed to be recessed in the radially outward direction from the inner surface  3   a  or may be formed to be surrounded by (3-1)th wall portions  33  and (3-2)th wall portion  35 . The (3-2)th wall portion  35  may also comprise a (3-2)th inclined surface  33   a  formed to extend from the bottom surface of the third storage space  31  and configured to be moved in the radially inward direction as it goes in the first direction. The (3-2)th inclined surface  33   a  may perform a function similar to the (1-2)th inclined surface  16  shown in  FIG. 5 . Further, the third reservoir  30  may comprise a third displacement space  39  in which the third reservoir  30  can be elastically displaced in the radially outward direction. The third displacement space  39  may perform a function similar to the first displacement space  19  shown in  FIG. 5 . The third reservoir  30  has a substantially same configuration with the first reservoir  10 , and thus detailed descriptions thereof will be omitted. 
     Since the bearing cage according to the fourth embodiment of the present disclosure further comprises the third reservoir  30 , in a case in which the bearing is coupled to the mechanical device such that the axial direction of the bearing is horizontal to the ground, when the operation of the mechanical device is stopped, the lubricant may be stored in the third storage space  31  located below the shaft. Further, even if the operation of the mechanical device is resumed after the mechanical device is left in a non-use state for a long time, the mechanical device can be operated in a state where a sufficient amount of lubricant is supplied to the roller. 
     Further, the bearing cage according to the fourth embodiment of the present disclosure may further comprise a fourth reservoir  40  provided with a fourth storage space  41 . The fourth storage space  41  may be formed to be recessed in the radially outward direction on a surface, which faces the center of the first ring  1 , out of surfaces of the first ring  1 . In addition, the fourth reservoir  40  may comprise a fourth inclined surface  43  formed to extend from the bottom surface of the fourth storage space  41  and configured to gradually increase a thickness in the radially inward direction as it goes in the first direction. That is, the fourth inclined surface  43  is an inclined surface configured to be moved in the radially inward direction as it goes in the first direction. Lubricant may also be stored in the fourth storage space  41 . Further, the fourth inclined surface  43  may be pressed when the mold is separated from the bearing cage. 
     In addition, the pillar  3  of the bearing cage according to the fourth embodiment of the present disclosure may comprise a pair of chamfered portions  50 . The chamfered portions  50  may be provided on both sides of the inner surface  3   a  of the pillar  3  in the circumferential direction, and may face the roller accommodated in the pocket  4 . Hereinafter, the chamfered portions  50  will be explained with reference to the bearing cage according to the fourth embodiment. However, the chamfered portions  50  may be provided similarly even in the bearing cages according to the first to third embodiments. 
     The chamfered portion  50  may comprise a contact portion  51  and a non-contact portion  53 . The contact portion  51  refers to a portion which is formed to protrude toward the roller to be in direct contact with the roller, and the non-contact portion  53  refers to a portion which is formed to be recessed more inward than the contact portion  51  and is not in contact with the roller. Since the chamfered portion  50  has the non-contact portion  53  which is not in contact with the roller, it is possible to reduce the frictional force generated between the roller and the chamfered portion  50 . 
     In this case, the contact portion  51  may be arranged close to the second ring  2 , and the non-contact portion  53  may be arranged close to the first ring  1 . Further, a guide surface may be formed as a step portion between the contact portion  51  and the non-contact portion  53  at a boundary between the contact portion  51  and the non-contact portion  53 . 
     Further, in a case where the roller is accommodated in the pocket  4  shown in  FIG. 15 , a space defined by the non-contact portion  53 , the guide surface and the roller may function as a passage through which the lubricant accommodated in each storage space moves. That is, since the chamfered portion  50  has the contact portion  51  and the non-contact portion  53 , even if the bearing cage has a complicated structure comprising the first reservoir  10 , the second reservoir  20  and the third reservoir  30 , the lubricant stored in the first storage space  11 , the second storage space  21  and the third storage space  31  may smoothly flow out to the space defined by the non-contact portion  53 , the guide surface and the roller. Thus, even in the case in which a large amount of lubricant is accommodated in each reservoir, the lubricant can be smoothly discharged to the outside, which makes it possible to prevent agitate resistance from being increased during the drive of the bearing. 
     Further, the guide surface may be formed to be inclined from the second ring  2  toward the first ring  1  as it goes in the radially outward direction. Thus, the guide surface can guide the supply path of the lubricant to be supplied to the roller. That is, it is possible to guide the lubricant in a desired direction by adjusting the inclination angle of the guide surface. 
     Although the above embodiments of the present disclosure are exemplified for the purpose of describing the technical spirit of the present disclosure, it should be noted that various modification and variations can be devised by those skilled in the art to which the present disclosure pertains without departing from the technical spirit and scope of the present disclosure. Accordingly, the embodiments described herein are merely examples for describing the technical sprit of the present disclosure, and the technical sprit of the present disclosure is not limited to the embodiments. Further, the scope of the present disclosure should be construed within the appended claims, and all technical ideas falling within the equivalent scope thereof should be interpreted as being included in the scope of the disclosure.