JP2005076809A - Retainer for needle bearing and needle bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retainer for a needle bearing equipped with an enhanced reliability and provide such a needle bearing. <P>SOLUTION: The retainer for the needle bearing is structured so that a pair of adjoining column parts 12c have each a side face 12b to hold needles 11 and a holding part 12f overhung in the circumferential direction from the side face 12b, wherein the length S in radial direction of the side face 12c is 20% or more of the needle diameter D and the radius of curvature R of the inner side face of the holding part 12f is 20% or more of the needle diameter D, so that the distance δ between the inner side face of the holding part 12f and the outside surface of each needle 11 will never become zero even if the retainer 12 is deviated aside to the maximum by the centrifugal force, and it is possible to avoid premature wear or breakage of the inner side faces of the holding part 12f. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cage and needle rollers for needle roller bearings, and more particularly to a cage and needle roller bearings for needle roller bearings that can improve reliability.

In an automatic transmission mounted on a vehicle or the like, a planetary gear mechanism is generally used. Here, since the needle roller bearing uses a small diameter roller, it can be accommodated in a space where the difference between the inner ring outer diameter and the outer ring inner diameter is small, so that the planetary gear of the planetary gear mechanism can be rotated freely. It is preferable to use it for supporting because it contributes to the compactness of the automatic transmission on which it is mounted (see Patent Document 1).
JP 2002-349647 A

  By the way, in recent years, there is a tendency to increase the number of stages in an automatic transmission for the purpose of improving fuel consumption. However, if the automatic transmission, which is currently in the 4th speed, is to be multistaged, for example, to the 5th or 6th speed, the rotation speed and revolution speed of the planetary gear of the planetary gear mechanism that transmits power increases. is there. Along with such changes in specifications, needle roller bearings with cages have been developed that have lower friction and better lubricity than conventional needle roller bearings called so-called full rollers that do not use cages. .

  Here, in the planetary gear mechanism, the planetary gear revolves around the sun gear while rotating, but at this time the needle roller bearing supporting the planetary gear also rotates and revolves around the sun gear. Centrifugal force combining them is applied to the needle roller bearing. Therefore, when the needle roller bearing is provided with a cage, the cage is subjected to centrifugal force based on revolution, and at that time, the roller ball formed on the cage column is prevented. There is a problem that the roller repeatedly hits the overhanging portion, and there is a risk of causing breakage due to early wear or fatigue of the column portion.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a cage for a needle roller bearing and a needle roller bearing with improved reliability.

A cage for a needle roller bearing of the present invention is a cage for a needle roller bearing that rotatably supports a planetary gear in a planetary gear mechanism.
The retainer has an annular part and a plurality of pillars extending in the axial direction from the annular part, and holds the rollers between the neighboring pillars,
A pair of adjacent column parts has a side surface for holding the roller and a holding part protruding in the circumferential direction from at least a part of the side surface, and the radial length of the side surface is 20% or more of the roller diameter. And the radius of curvature of the inner side surface of the holding portion is 20% or more of the roller diameter.

  The cage for the needle roller bearing according to the present invention has a pair of adjacent column portions each having a side surface that holds the roller, and a holding portion that protrudes in the circumferential direction from at least a part of the side surface. The length in the radial direction of the roller is 20% or more of the roller diameter, and the radius of curvature of the inner surface of the holding portion is 20% or more of the roller diameter. Therefore, the needle roller bearing receives a centrifugal force due to revolution. Even in this case, contact between the roller and the holding portion can be avoided, and early wear and breakage can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of an automatic transmission 1 for a vehicle including a needle roller bearing according to the present embodiment. In FIG. 1, torque output from the crankshaft 2 of the engine is transmitted through a torque converter 3 and further decelerated to a plurality of stages through a plurality of planetary gear mechanisms 4, 5, 6, etc. The power is output to a wheel (not shown) via the differential gear 7 and the drive shaft 8.

  FIG. 2 is an exploded view of the planetary gear mechanism 4 (5 and 6 are basically the same). In FIG. 2, the planetary gear mechanism 4 includes a ring gear 4a having internal teeth, a sun gear 4b having external teeth, three planetary gears 4c meshing with the ring gear 4a and the sun gear 4b, and three pinion shafts 4e. The gear 4c is rotatably supported, and has a carrier 4d that can also rotate.

  The operating principle of the planetary gear mechanism 4 is shown in FIG. First, in the case of the first speed, as shown in FIG. 3A, a large reduction ratio can be obtained by setting the sun gear 4b to the drive side, the planetary gear 4c (carrier) to the driven side, and fixing the ring gear 4a. . Next, in the case of the second speed, as shown in FIG. 3 (b), the sun gear 4b is fixed, the planetary gear 4c (carrier) is set to the driven side, and the ring gear 4a is set to the drive side. A ratio is obtained. Further, in the case of the third speed, as shown in FIG. 3 (c), the sun gear 4b is fixed, the planetary gear 4c (carrier) is set to the drive side, and the ring gear 4a is set to the driven side, thereby obtaining a small reduction ratio. It is done. In the case of reverse, as shown in FIG. 3 (d), the sun gear 4b is driven, the planetary gear 4c (carrier) is fixed, and the ring gear 4a is driven, so that output is output with respect to the input. Can be reversed. In addition, the above shows an example of the operation of the planetary gear mechanism 4, and the operation is not necessarily limited to this operation.

  FIG. 4 is a diagram showing the needle roller bearing of the present embodiment incorporated in a planetary gear mechanism. As shown in FIG. 4, the needle roller bearing 10 is disposed between a pinion shaft (inner ring) 4e and a planetary gear (outer ring) 4c, and rotatably supports the planetary gear 4c. The needle roller bearing 10 includes a plurality of rollers 11 and a cage 12 that holds them. In the pinion shaft 4e, there is formed an oil passage 4f extending along the axis from the right side in FIG. 4 and extending to the outer peripheral surface at the center. The cage 12 is used for outer ring guidance.

  FIG. 5 is a perspective view of the needle roller bearing according to the present embodiment, and FIG. 6 is an enlarged view of the periphery of the roller by cutting the needle roller bearing at the center of the axis. As shown in FIG. 5, the cage 12 has a configuration in which a pair of annular portions 12 a are connected by a plurality of column portions 12 c. A space between the side surfaces 12b of the adjacent column portions 12c serves as a pocket for holding the rollers 11. Each column portion 12c has a reduced diameter at the center in the axial direction (that is, close to the axis of the cage 12), and the cage 12 having such a shape is called a welded cage. A recess 12d for preventing roller run-off is formed in the vicinity of the outer periphery of both ends of the column portion 12c. The recess 12d is an indentation formed when punching one plate material to form the column portion 12c and then pressing both ends of the column portion 12c using a tool (not shown). By forming the holding portion 12f projecting from the side surface 12b in the circumferential direction, the roller 11 functions to prevent the roller 11 from being separated outward in the radial direction (see FIG. 6).

In FIG. 6, the diameter of the roller 11 is D, the radial length of the straight portion of the side surface 12b that contacts and guides the roller 11 in the cross section of the column portion 12c is S, and the radius of curvature of the inner surface of the holding portion 12f is R. The following formula is established.
S ≧ 0.2 · D (1)
R ≧ 0.2 · D (2)

  The operation of this embodiment will be described. As shown in FIG. 3, the planetary gear 4c rotates around the pinion shaft 4e and revolves around the sun gear 4b. Accordingly, the needle roller bearing 10 receives a centrifugal force due to revolution, but at this time, the cage 12 is shifted toward the side far from the rotation center (that is, eccentric with respect to the axis of the pinion shaft 4e). (In the direction of the arrow in FIG. 6). In contrast, the roller 11 that rolls between the planetary gear 4c (outer ring) and the pinion shaft 4e (inner ring) has a substantially constant distance from the center of rotation. Accordingly, the concave portion 12d of the retainer 12 is close to the portion 11 depending on the location. However, in the present embodiment, since the cage 12 has a shape satisfying the above formulas (1) and (2), even if the cage 12 is maximally offset by the centrifugal force, the holding portion is located at the opposite side. Since the distance δ between the inner surface of 12f and the outer peripheral surface of 11 does not become too small, the contact frequency between the two decreases, thereby preventing early wear and breakage of the inner surface of the holding portion 12f. Further, the contact frequency between the roller 11 and the cage 12 is reduced even at the position where the cage 12 is displaced to the maximum by the centrifugal force.

  In particular, in the case of a cage in which the ratio of the roller diameter / PCD exceeds 0.1, the angle between the pockets (the angle between the center portions of the column portions) tends to increase. The present invention is effective because it is necessary to overhang and the holding portion becomes thin. Further, if the radial length S of the straight part on the side surface of the column part and the radius of curvature R of the inner side surface of the holding part become too large, the strength of the holding part may be lowered. .

  The present invention has been described with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate.

  The cage for the needle roller bearing according to the present invention has a pair of adjacent column portions that hold a roller and a holding portion that protrudes in the circumferential direction from at least a part of the side surface. The length in the radial direction is 20% or more of the roller diameter, and the radius of curvature of the inner surface of the holding portion is 20% or more of the roller diameter. Therefore, the needle roller bearing is subjected to centrifugal force due to revolution. Even in this case, contact between the roller and the holding portion can be avoided, and early wear and breakage can be suppressed.

It is sectional drawing of the automatic transmission of the vehicle containing the needle roller bearing concerning this Embodiment. 4 is an exploded view of the planetary gear mechanism 4. FIG. It is a figure which shows the operating principle of a planetary gear mechanism. It is a figure shown in the state where the needle roller bearing of this embodiment was built in the planetary gear mechanism. It is a perspective view of the needle roller bearing of this embodiment. It is the figure which cut the needle roller bearing of this Embodiment in the axial center, and expanded the circumference | surroundings of the roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Automatic transmission 4-6 Planetary gear mechanism 10 Needle roller bearing 11 Roller 12 Cage

Claims (2)

In a cage for a needle roller bearing that rotatably supports a planetary gear in a planetary gear mechanism,
The retainer has an annular part and a plurality of pillars extending in the axial direction from the annular part, and holds the rollers between the neighboring pillars,
A pair of adjacent column parts has a side surface for holding the roller and a holding part protruding in the circumferential direction from at least a part of the side surface, and the radial length of the side surface is 20% or more of the roller diameter. And the curvature radius of the inner peripheral surface of the said holding | maintenance part is 20% or more of roller diameters, The cage for needle roller bearings characterized by the above-mentioned. A needle roller bearing using the cage for a needle roller bearing according to claim 1.

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