Patent Publication Number: US-2021172477-A1

Title: Cage, radial-thrust integrated bearing, and planetary gear device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2019-221414 filed on Dec. 6, 2019, incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a cage, a radial-thrust integrated bearing, and a planetary gear device. 
     2. Description of Related Art 
     In the related art, some planetary gear devices used in vehicles are, for example, configured such that a plurality of planetary gears is placed between an external gear and an internal gear, and each of the planetary gears is rotatably supported by a roller bearing. A planetary gear device described in Japanese Unexamined Patent Application Publication No. 7-103320 (JP 7-103320 A) is configured such that a radial roller bearing is placed between an outer peripheral surface of a support shaft (a pinion shaft) of a carrier and an inner peripheral surface of a shaft hole of a planetary gear. 
     Further, the applicants of this application have proposed that a thrust roller bearing is placed between an axial end surface of a planetary gear and a side wall of a carrier in addition to a radial roller bearing so as to further reduce a rotational resistance of the planetary gear (e.g., see Japanese Unexamined Patent Application Publication No. 2012-47225 (JP 2012-47225 A)). The thrust roller bearing described in JP 2012-47225 A includes a plurality of thrust rollers, a thrust cage in which the thrust rollers are held, and a thrust bearing ring including a raceway portion having a raceway surface on which the thrust rollers roll. The thrust bearing ring includes: an attachment portion extending axially outwardly from an outer peripheral portion of the raceway portion and attached to an outer peripheral portion of the carrier; and a cage guide portion extending axially inwardly from the outer peripheral portion of the raceway portion and making sliding contact with an outer peripheral surface of the thrust cage so as to guide the thrust cage in a rotating manner. The thrust cage is supported by the cage guide portion and is placed such that an inner peripheral surface of the thrust cage radially faces, via a gap, an outer peripheral surface of a radial cage of the radial roller bearing. This configuration prevents the radial cage and the thrust cage from being damaged by making contact with each other. 
     SUMMARY 
     In the planetary gear device described in JP 2012-47225 A, in order to prevent contact between the thrust cage and the radial cage, the thrust bearing ring that supports the thrust cage is required, and this accordingly increases the number of components and the number of man-hours for assembly. 
     The present disclosure provides a cage in which a plurality of radial rollers and a plurality of thrust rollers are held, the cage being able to restrain an increase in the number of components and the number of man-hours for assembly, a radial-thrust integrated bearing including the cage, and a planetary gear device including the radial-thrust integrated bearing. 
     A first aspect of the present disclosure relates to a cage including a first holding portion, a second holding portion, and a connecting portion. A plurality of radial rollers is held in the first holding portion. A plurality of thrust rollers is held in the second holding portion. The first holding portion is connected to the second holding portion via the connecting portion. The first holding portion, the second holding portion, and the connecting portion are molded integrally by a resin member. 
     Further, a second aspect of the present disclosure relates to a radial-thrust integrated bearing including the cage, the radial rollers held in the first holding portion, and the thrust rollers held in the second holding portion. 
     Further, a third aspect of the present disclosure relates to a planetary gear device including a sun gear, an internal gear, a plurality of planetary gears, and a carrier. The sun gear has external teeth provided on an outer peripheral surface of the sun gear. The internal gear has internal teeth provided on an inner peripheral surface of the internal gear. The planetary gears are placed between the sun gear and the internal gear. The carrier is configured to support the planetary gears. The planetary gears are supported by the radial-thrust integrated bearing such that the planetary gears are rotatable to the carrier. 
     With the cage, the radial-thrust integrated bearing, and the planetary gear device according to the above aspects of the present disclosure, it is possible to restrain an increase in the number of components and the number of man-hours for assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
         FIG. 1  is an exploded perspective view illustrating a planetary gear device using a radial-thrust integrated bearing including a cage according to an embodiment of the present disclosure; 
         FIG. 2A  is a sectional view illustrating a section of the radial-thrust integrated bearing together with its peripheral portion; 
         FIG. 2B  is a sectional view taken along a line II-II in  FIG. 2A ; 
         FIG. 3  is a side view illustrating the radial-thrust integrated bearing; 
         FIG. 4A  is a sectional view taken along a line IVA-IVA in  FIG. 3 ; 
         FIG. 4B  is a sectional view taken along a line IVB-IVB in  FIG. 3 ; and 
         FIG. 5  is a perspective view illustrating the cage of the radial-thrust integrated bearing. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiment 
     An embodiment of the present disclosure will be described below with reference to  FIGS. 1 to 5 . Note that the embodiment described below indicates a preferred concrete example on performing the present disclosure. There are some parts that specifically show various technical matters that are technically preferable, but a technical scope of the present disclosure is not limited to such a concrete example. 
     Overall Configuration of Planetary Gear Device 
       FIG. 1  is an exploded perspective view illustrating a planetary gear device using a radial-thrust integrated bearing including a cage according to an embodiment of the present disclosure.  FIG. 2A  is a sectional view illustrating a section of the radial-thrust integrated bearing together with its peripheral portion, and  FIG. 2B  is a sectional view taken along a line II-II in  FIG. 2A . 
     The planetary gear device  1  includes: a sun gear  11  having external teeth  111  on its outer peripheral surface; an internal gear  12  having internal teeth  121  on its inner peripheral surface; a plurality of (three in the present embodiment) planetary gears  13  placed between the sun gear  11  and the internal gear  12 ; a carrier  14  including a plurality of (three) support shafts  141  configured to support the planetary gears  13 , respectively; and a combined bearing device  15  (see  FIG. 2A ) placed between each of the planetary gears  13  and its corresponding one of the support shafts  141 . The planetary gear  13  includes external teeth  131  meshing with the external teeth  111  of the sun gear  11  and the internal teeth  121  of the internal gear  12 . 
     The sun gear  11 , the internal gear  12 , and the carrier  14  are supported to be coaxially rotatable relative to each other on a rotation axis O. Further, the planetary gears  13  rotate on respective rotation axes O 1  to O 3  around the support shafts  141 . The planetary gears  13  revolve around the rotation axis O and rotate on the respective rotation axes O 1  to O 3 . In  FIGS. 2A, 2B , one planetary gear  13  rotating on the rotation axis O 1  is illustrated. Hereinafter, a direction parallel to the rotation axis O 1  is referred to as an axial direction, and a direction perpendicular to the rotation axis O 1  is referred to as a radial direction. 
     A shaft  110  is fixed to a central part of the sun gear  11  in a relatively non-rotatable manner. The planetary gear  13  is configured such that the support shaft  141  is passed through a shaft hole  130  penetrating through a central part of the planetary gear  13 . The carrier  14  supports the planetary gears  13  via the combined bearing devices  15  such that the planetary gears  13  can rotate and revolve. Further, the carrier  14  includes first and second disk portions  142 ,  143  between which the planetary gears  13  are sandwiched in the axial direction, an outer wall portion  144  configured to bridge respective end parts, on the outside-diameter side, of the first and second disk portions  142 ,  143 , and a fitting cylinder  145  fixed to an end part, on the inside-diameter side, of the second disk portion  143 . 
     A spline portion  145   a  to which a shaft (not shown) is fitted in a relatively non-rotatable manner is formed on the inner periphery of the fitting cylinder  145 . An opening  144   a  is formed on the outer wall portion  144  such that part of the planetary gear  13  projects from the opening  144   a . The external teeth  131  of the planetary gear  13  thus projecting from the opening  144   a  mesh with the internal teeth  121  of the internal gear  12 . 
     As illustrated in  FIG. 2A , both end parts of the support shaft  141  are fitted by pressing into fitting holes  142   a ,  143   a  formed in the first and second disk portions  142 ,  143 . The support shaft  141  has a cylindrical shape having a cavity  140  formed in its central part. An oil hole  141   b  communicating with the cavity  140  is opened on an outer peripheral surface  141   a . Lubricant flowing into the cavity  140  is supplied to the combined bearing device  15  from the oil hole  141   b.    
     The planetary gear  13  is configured such that a first axial end surface  13   a  facing a disk surface  142   b  of the first disk portion  142  of the carrier  14  and a second axial end surface  13   b  facing a disk surface  143   b  of the second disk portion  143  of the carrier  14  are formed as flat surfaces perpendicular to the axial direction. 
     The combined bearing device  15  includes a thrust roller bearing  2  and a radial-thrust integrated bearing  3 . The thrust roller bearing  2  is placed between the disk surface  143   b  of the second disk portion  143  of the carrier  14  and the second axial end surface  13   b  of the planetary gear  13 . The thrust roller bearing  2  includes a cage  21  made of synthetic resin and including a plurality of pockets  20  formed in a radial manner, and a plurality of rollers  22  provided such that the rollers  22  are accommodated in the pockets  20 , respectively. The rollers  22  roll on the disk surface  143   b  of the second disk portion  143  and the second axial end surface  13   b  of the planetary gear  13 . 
     With reference to  FIGS. 3 to 5 , the following describes a configuration of the radial-thrust integrated bearing  3  in detail.  FIG. 3  is a side view of the radial-thrust integrated bearing  3 .  FIG. 4A  is a sectional view taken along a line IVA-IVA in  FIG. 3 , and  FIG. 4B  is a sectional view taken along a line IVB-IVB in  FIG. 3 .  FIG. 5  is a perspective view illustrating a cage  4  of the radial-thrust integrated bearing  3 . 
     The radial-thrust integrated bearing  3  includes: a plurality of radial rollers  31  placed between the outer peripheral surface  141   a  of the support shaft  141  and the inner peripheral surface  130   a  of the shaft hole  130  of the planetary gear  13 ; a plurality of thrust rollers  32  placed between the disk surface  142   b  of the first disk portion  142  of the carrier  14  and the first axial end surface  13   a  of the planetary gear  13 ; and the cage  4  including a resin member  40  formed by injection molding. 
     The cage  4  includes a first holding portion  41  in which the radial rollers  31  are held, a second holding portion  42  in which the thrust rollers  32  are held, and a connecting portion  43  via which the first holding portion  41  is connected to the second holding portion  42 . The first holding portion  41 , the second holding portion  42 , and the connecting portion  43  are molded integrally by the resin member  40 . More specifically, as a resin material for the resin member  40 , nylon-66, polyphenylene sulfide (PPS) resin, polybutylene terephthalate (PBT) resin, or the like can be used preferably, for example. A reinforced fiber material such as glass fiber or carbon fiber may be added as needed. 
     The first holding portion  41  is defined by connecting a pair of annular bodies  411 ,  412  to each other in the axial direction by a plurality of columns  413 . A plurality of pockets  410  is formed between the columns  413 . The radial rollers  31  are accommodated in respective pockets  410  in a rotatable manner. In the present embodiment, nine pockets  410  are formed in the first holding portion  41 , and nine radial rollers  31  are accommodated in the pockets  410 , respectively. 
     The second holding portion  42  is defined by connecting an inner annular body  421  and an outer annular body  422  to each other in the radial direction by a plurality of columns  423 . A plurality of pockets  420  is formed in a radial manner between the columns  423 . The thrust rollers  32  are accommodated in respective pockets  420  in a rotatable manner. In the present embodiment, nine pockets  420  are formed in the second holding portion  42 , and nine thrust rollers  32  are accommodated in the pockets  420 , respectively. The columns  423  of the second holding portion  42  are provided in parts on the outer peripheral side from the pockets  410  of the first holding portion  41 . 
     The connecting portion  43  is defined to project radially from an outer peripheral surface  411   a  of the first annular body  411  out of the annular bodies  411 ,  412  of the first holding portion  41 . The first annular body  411  is placed on the first disk portion  142  side of the carrier  14 . The annular body  411  is integrally connected to the inner annular body  421  via the connecting portion  43 . The thrust roller bearing  2  is placed on the outer periphery of the second annular body  412 . 
     The connecting portion  43  has a plurality of through holes  430  extending in the axial direction. In other words, the connecting portion  43  is constituted by a plurality of projections  431  projecting radially from the outer peripheral surface  411   a  of the annular body  411 , and the through-holes  430  are formed between the projections  431 . 
     In the present embodiment, the connecting portion  43  is constituted by three projections  431 , and three through-holes  430  are formed in an arc shape in an axial view. Part of lubricant supplied from the oil hole  141   b  of the support shaft  141  flows to the outer periphery of the first holding portion  41  from the pockets  410  of the first holding portion  41  and further flows through the through-holes  430  in the axial direction, so that the part of the lubricant is supplied to the disk surface  142   b  side of the first disk portion  142 . 
     The cage  4  is formed by injection molding by injecting molten resin into a metal mold. In the present embodiment, the cage  4  is formed such that the resin member  40  is molded by injecting molten resins into the cavity of the metal mold from three places of the first holding portion  41  at the same time. More specifically, the molten resins are injected from radially inner sides of three columns  413  among the nine columns  413 . In  FIG. 4A , a part corresponding to a gate via which the molten resin is injected is surrounded by a broken line and indicated by a reference sign G. Further, in  FIG. 4B , the flows of the molten resins at the time of injection molding of the annular body  411  are indicated by arrows. 
     In meeting points of the molten resins, welds each indicated by a reference sign W in  FIG. 4B  are formed. Here, the weld is a joint-shaped part that is inevitably formed when the molten resins to join hit each other and is a part having a strength lower than other parts. In the present embodiment, three welds W extending linearly along the radial direction are formed in the resin member  40  at regular intervals (at every 120°) in the circumferential direction. 
     The welds W are formed over three parts, of the annular body  411 , that are axially aligned with three pockets  410  among the nine pockets  410  of the first holding portion  41 , the three projections  431 , and three columns  423  among the nine columns  423  of the second holding portion  42 . That is, the through-holes  430  of the connecting portion  43  are formed at positions deviating from the circumferential positions of the welds W, and the welds W are reinforced by the connecting portion  43  and the second holding portion  42 . Hereby, in comparison with a case where the welds W are formed at positions corresponding to the through-holes  430  of the connecting portion  43 , the strength of the cage  4  is increased. 
     The planetary gear device  1  is assembled in the following procedure, for example. That is, the radial-thrust integrated bearing  3  is placed on the outer periphery of the support shaft  141  fitted by pressing into the fitting hole  142   a  of the first disk portion  142 , and the planetary gear  13  is placed on the outer periphery of the first holding portion  41  of the radial-thrust integrated bearing  3 . Then, the thrust roller bearing  2  is placed on the outer periphery of the second annular body  412  of the first holding portion  41 , and the support shaft  141  is fitted by pressing into the fitting hole  143   a  of the second disk portion  143 . The outer wall portion  144  of the carrier  14  is integrated with the first disk portion  142 , and by fixing a first axial end of the outer wall portion  144  to an end part, on the outer peripheral side, of the second disk portion  143  by welding, for example, the carrier  14  in which the planetary gears  13  are supported rotatably is obtained. The planetary gear device  1  is completed by combining the carrier  14  and the planetary gears  13  with the sun gear  11  and the internal gear  12 . 
     Effects of Embodiment 
     In the embodiment described above, the first holding portion  41  in which the radial rollers  31  are held and the second holding portion  42  in which the thrust rollers  32  are held are molded integrally by the resin member  40 . Accordingly, while the rotation of the planetary gear  13  relative to the support shaft  141  is smoothly supported by the radial rollers  31  and the thrust rollers  32 , it is possible to restrain an increase in the number of components and the number of man-hours for assembly in the planetary gear device  1 . Further, the welds W are reinforced by the three projections  431  constituting the connecting portion  43 , and the through-holes  430  are each formed between the projections  431 . Hereby, it is possible to supply the lubricant to the thrust rollers  32  via the through-holes  430  and to restrain breakage of the cage  4  starting from the welds W. 
     Additional Matters 
     The present disclosure has been described based on the embodiment and its modification, but the embodiment and modification described above do not limit the disclosure according to Claims. Further, it should be noted that all combinations of features described in the embodiment may not necessarily be essential to the means for solving the problem of the disclosure. 
     Further, the present disclosure can be carried out by appropriately modifying the present disclosure by omitting some configurations or adding or replacing configurations within a range that does not deviate from the gist of the present disclosure. For example, the above embodiment describes a case where the thrust roller bearing  2  is placed between the disk surface  143   b  of the second disk portion  143  of the carrier  14  and the second axial end surface  13   b  of the planetary gear  13 . However, the thrust roller bearing  2  may not be used, provided that a thrust force generated in the planetary gear  13  is directed only toward the first disk portion  142 . 
     Further, the above embodiment describes a case where the resin member  40  is molded by injecting molten resin into the cavity of the metal mold from three places. However, the present disclosure is not limited to this, and the gate via which molten resin is injected may be provided at one place or two places or may be provided at four places or more. Further, the cage and the radial-thrust integrated bearing of the present disclosure may be usable in various devices other than the planetary gear device.