This application claims priority to Japanese Patent Application No. 2019-221413 filed on Dec. 6, 2019, incorporated herein by reference in its entirety.
The disclosure relates to a radial roller bearing cage made of resin.
In related art, some planetary gear devices used for transmissions of vehicles (e.g., automobiles) are configured such that a plurality of planetary gears is disposed between an external gear and an internal gear, and each of the planetary gears is rotatably supported by a radial roller bearing. The radial roller bearing includes a plurality of rollers and a cage configured to hold the rollers such that the rollers are rollable. Roller bearings used in planetary gear devices support rotation of planetary gears while the roller bearings receive centrifugal force caused by revolution of the planetary gears. Accordingly, in order to secure strength, cages made of metal have been widely used. However, due to request for weight reduction and cost reduction, there have been made attempts to employ cages made of resin (e.g., see Japanese Unexamined Patent Application Publication No. 2006-77801 (JP 2006-77801 A)).
A cage described in JP 2006-77801 A is configured such that two rib portions constituted by annular bodies facing each other at an interval in the axial direction of the cage and a plurality of bars arranged at predetermined intervals in the circumferential direction of the cage are integrally formed by use of a resin material. In each of the two rib portions, an annular core is embedded for improvement in strength. The annular core is made of a strength material higher in strength than the resin material. The core is made of a resin material combined with a metallic material such as rolled steel or reinforced fiber such as glass fiber.
In the cage described in JP 2006-77801 A, the core is embedded in each of the two rib portions, and therefore, man-hours at the time of manufacturing and weight increase. Although weight reduction and cost reduction are achieved in comparison with a metal cage, further weight reduction and further cost reduction have been requested. In consideration of the aforementioned circumstances, the inventor of the disclosure started to develop a resin cage having improved strength and found that the strength of the cage can be increased particularly by dispersing stress of annular bodies. Thus, the disclosure has been accomplished. That is, the disclosure provides a radial roller bearing cage made of resin and having improved strength.
One aspect of the disclosure relates to a radial roller bearing cage including a pair of annular bodies and a plurality of bars by which the annular bodies are axially connected to each other. The annular bodies and the bars are integrally formed by resin molding. A plurality of pockets separated from each other by the bars is provided between the annular bodies. A projection projecting radially inwardly is provided in at least one of parts of at least one of the annular bodies, the parts axially facing the pockets, respectively.
With the aspect of the disclosure, it is possible to improve the strength of the radial roller bearing cage made of resin.
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:
An embodiment of the disclosure will be described below with reference to
Overall Configuration of Planetary Gear Device
A 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 disposed 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; radial roller bearings 10 (see
The sun gear 11, the internal gear 12, and the carrier 14 are supported to be coaxially rotatable relative to each other around a rotation axis O. Further, the planetary gears 13 rotate about respective rotation axes O1 to O3 around the support shafts 141. The planetary gears 13 revolve around the rotation axis O and rotate around the respective rotation axes O1 to O3. In
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 inserted through a shaft hole 130 extending through a central part of the planetary gear 13, and the radial roller bearing 10 is disposed between an inner peripheral surface 130a of the shaft hole 130 and an outer peripheral surface 141a of the support shaft 141. The radial roller bearing 10 includes a cage 2 made of resin and a plurality of (nine in the present embodiment) rollers 3 made of metal. The rollers 3 are formed in a columnar shape and roll on the inner peripheral surface 130a of the shaft hole 130 of the planetary gear 13 and the outer peripheral surface 141a of the support shaft 141 along with rotation of the planetary gear 13.
The carrier 14 supports the planetary gears 13 via the radial roller bearings 10 such that the planetary gears 13 can rotate and revolve. Further, the carrier 14 includes first and second disk portions 142, 143 configured such that the planetary gears 13 are disposed between the first and second disk portions 142, 143 in the axial direction, an outer wall portion 144 configured to bridge respective end parts, on the outer peripheral side, of the first and second disk portions 142, 143, and a fitting tube 145 fixed to an end part, on the inner peripheral side, of the first disk portion 142.
A spline portion 145a to which a shaft (not shown) is fitted in a relatively non-rotatable manner is formed on the inner periphery of the fitting tube 145. An opening 144a is formed on the outer wall portion 144 such that part of the planetary gear 13 projects from the opening 144a. The external teeth 131 of the planetary gear 13 thus projecting from the opening 144a mesh with the internal teeth 121 of the internal gear 12. The washers 15 are each disposed between a corresponding one of the first and second disk portions 142, 143 and a corresponding one of the axial end faces 13a, 13b of the planetary gears 13.
As illustrated in
With reference to
The cage 2 includes a pair of annular bodies 21 having a ring shape, and a plurality of bars 22 provided between the annular bodies 21. The annular bodies 21 are connected to each other in the axial direction by the bars 22 (i.e., the annular bodies 21 are axially connected to each other by the bars 22). The annular bodies 21 and the bars 22 are integrally formed by resin molding. In other words, the annular bodies 21 and the bars 22 are made of resin, and are integral with each other. As a resin material for the annular bodies 21 and the bars 22, nylon-66 obtained by adding a predetermined amount of a reinforced fiber material such as glass fiber or carbon fiber, polyphenylene sulfide (PPS) resin, or polybutylene terephthalate (PBT) resin can be appropriately used, for example.
A plurality of pockets 20 separated from each other by the bars 22 is provided between the annular bodies 21. The number of the bars 22 and the number of the pockets 20 are the same as the number of the rollers 3 included in the radial roller bearing 10, and in the present embodiment, nine bars 22 are provided at regular intervals along the circumferential direction of the annular bodies 21. Each of the pockets 20 is defined into a rectangular shape by two bars 22 adjacent to each other and the annular bodies 21. The annular bodies 21 have the same shape and the same size.
The rollers 3 are restrained from moving away from the pockets 20 by inner-peripheral-side and outer-peripheral-side projections 223, 224 (see
On an outer peripheral surface 22a of each of the bars 22 in the cage 2, an oil groove 221 where lubricant flows is formed to extend in the axial direction. Further, on an inner peripheral surface 22b of each of the bars 22 in the cage 2, an oil groove 222 where lubricant flows is formed to extend in the axial direction. The oil groove 222 formed on the inner peripheral side of the bar 22 is formed in a linear shape within a range that reaches both axial end faces 2a, 2b of the cage 2, the range including respective inner peripheral surfaces 21a of the annular bodies 21.
The cage 2 is made of a single resin material. The cage 2 is formed by injection molding in which melted resin is injected into a metal mold. In
As illustrated in
When the carrier 14 rotates along with the rotation of the sun gear 11 or the internal gear 12, the cage 2 rotates around the support shaft 141 while the cage 2 receives centrifugal force caused by the revolution of the planetary gear 13. Therefore, the annular bodies 21 elastically deform into a substantially elliptical shape due to the centrifugal force, and thus, stress is caused therein. Particularly, when the stress concentrates on a part where the weld W is formed, breakage starting from the weld W easily occurs.
In view of this, in the disclosure, in order to improve strength by reducing stress concentration, a projection 211 projecting inwardly in the radial direction is provided in at least one of parts of at least one of the annular bodies 21, the parts respectively facing the pockets 20 in the axial direction. The projection 211 is provided at least at a position where the weld W is generated at the time of resin molding. In the present embodiment, the projections 211 are provided in parts of both of the annular bodies 21, the parts respectively facing both sides of all the pockets 20 in the axial direction.
As illustrated in
Each of the three welds W reaches an apex 211a having the highest projection height in the projection 211. That is, the weld W is formed over the whole projection 211 in its height direction (the radial direction). Here, the projection height indicates a distance from the extension line L1 in the radial direction of the cage 2. The apex 211a projects inwardly in the radial direction beyond the straight line L2, and a part of the roller 3 projects further inwardly in the radial direction beyond the apex 211a.
Note that, in the present embodiment, the circumferential width (the distance between both circumferential ends 211b) of the projection 211 is smaller than the opening width of the pocket 20 on the inner peripheral surface 22b, and the whole projection 211 is provided in the part facing the pocket 20 in the axial direction. However, the structure of the projection 211 is not limited to this structure, and a part of the projection 211 may be provided in a part facing the bar 22 in the axial direction. That is, both circumferential ends 211b of the projection 211 may be present at positions aligning with the bars 22 in the axial direction.
In
As illustrated in
In the meantime, in the radial roller bearing 10 according to the present embodiment, stress is dispersed in comparison with the radial roller bearing 10A according to the comparative example, and stress is greatly reduced in the part where the weld W is formed. Thus, breakage starting from the weld W can hardly occur, and thus, the strength of the cage 2 improves. Further, in the present embodiment, the projections 211 are provided in the parts respectively facing both sides of all the pockets 20 in the axial direction, the parts including the parts where the welds W are formed. Accordingly, stress concentration is reduced in the entire annular body 21 in the circumferential direction, and this also improves the strength of the cage 2.
The disclosure has been described based on the embodiment and its modification, but the embodiment and modification described above do not limit the disclosure.
Further, the disclosure can be carried out by appropriately modifying the embodiment by omitting some configurations or adding or replacing configurations within a range that does not depart from the scope of the disclosure.
Number | Date | Country | Kind |
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2019-221413 | Dec 2019 | JP | national |