JP2009204089A - Cage for needle roller bearing, and needle roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cage for a needle roller bearing, having reduced cost while securing reliability, and to provide the needle roller bearing. <P>SOLUTION: A difference is given to grinding work for the cage 12 to keep the surface roughness of an outer diameter guide face 12d better than the surface roughness of the end face of an annular portion 12a. This shortens a grinding work time for the end face 12e of the annular portion 12a to reduce cost. <P>COPYRIGHT: (C)2009,JPO&INPIT

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.

  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. In particular, centrifugal force due to revolution is applied to the needle roller bearing. Therefore, when the needle roller bearing is provided with a cage, the cage is pressed against the outer ring (inner peripheral surface of the planetary gear) by centrifugal force based on revolution, so that the sliding between the outer ring and the cage is performed. Movement will occur. Such sliding increases the drag resistance of the needle roller bearing, and may cause premature wear, abnormal heat generation, and deformation of the cage. In particular, if the surface roughness of the outer diameter guide surface of the cage is poor, the rotational speed of the cage that contacts the outer ring rapidly decreases due to the so-called braking phenomenon, and the roller collides with the column of the cage, causing repeated stress. There is a risk that fatigue failure will occur by applying. Further, washers are often arranged at both ends of the planetary gear in the axial direction, and problems such as wear due to sliding contact between the washers and the cage are also expected.
JP-A-2005-768107

  On the other hand, in Patent Document 1, in order to prevent friction and seizure of the outer diameter of the cage and the end surface, the outer diameter surface of the cage that slides with the inner diameter surface of the planetary gear, the cage and the slide of the washer and the adjacent bearing. Grinding and surface treatment are applied to the moving cage end face. However, if the surface of each part of the cage is ground, there is a problem that the cost increases.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a retainer and a needle roller bearing for a needle roller bearing that can reduce the cost while ensuring reliability.

The cage 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 portion and a plurality of column portions extending in the axial direction from the annular portion, and is configured to hold rollers between the adjacent column portions. It is used, and the roughness of the outer diameter guide surface of the cage is better (lower) than the roughness of the end surface of the cage.

  In the cage used for the planetary gear, the outer diameter surface of the cage is pressed against the inner diameter surface of the planetary gear by the centrifugal force received when the planetary gear revolves. Here, since the load in the axial direction is about 10% of the radial load, and the load on which the cage end face is pressed against a washer or the like is very small, the roughness of the end face is equal to that of the outer diameter face. I found that there is no need to do. As a result, for example, the outer diameter guide surface of the cage is carefully ground, but the end surface of the cage is roughly ground to limit the removal of welding marks, etc. By maintaining the roughness of the end face of the cage in a state worse than the roughness of the outer diameter guide surface of the cage, it is possible to prevent over-specification and to reduce costs by shortening the grinding time.

When the average roughness of the outer diameter guide surface of the cage is R1, and the average roughness of the end surface of the cage is R2, it is preferable that the following expression is satisfied.
1.1 ≦ R2 / R1 ≦ 7.0 (1)

  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 view 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 passing through the outer peripheral surface at the center. The cage 12 is used for outer ring guidance. A washer 4g is disposed between the carrier 4d and the planetary gear 4c.

  FIG. 5 is a perspective view of the cage of the needle roller bearing according to the present embodiment. As shown in the figure, the cage 12 has a configuration in which a pair of annular portions 12a are connected by a plurality of column portions 12b. A space for holding the rollers 11 is formed between the adjacent column portions 12b. Each column portion 12b has a reduced diameter portion 12c that is reduced in diameter in the center in the axial direction (that is, close to the axial line of the cage 12), and expands from both sides in the axial direction of the reduced diameter portion 12c to the annular portion 12a. The outer peripheral surface (indicated by double hatching in the figure) is an outer diameter guide surface (that is, a surface in sliding contact with the outer ring) 12d. The cage 12 having such a shape is called an M-type cage.

  In the present embodiment, the retainer 12 is formed by punching one plate material to form a column portion, and then rounding and welding both ends. Accordingly, since the surface roughness of the outer diameter guide surface 12d is poor as it is, the grinding is performed to keep the friction low even when the outer diameter guide surface 12d is in sliding contact with the inner peripheral surface of the planetary gear 4c. be able to. Thereby, the drag resistance of the needle roller bearing 10 can be reduced, early wear and abnormal heat generation can be suppressed, and further, the occurrence of a braking phenomenon that causes deformation or breakage of the cage 12 can be suppressed. Further, the end surface 12e of the annular portion 12a of the cage 12 also tends to have poor surface roughness due to the effect of welding. However, the welding surface is removed by grinding to improve the surface roughness. Friction at the time of sliding contact with the washer can be kept low.

  However, in this embodiment, the surface roughness of the outer diameter guide surface 12d is made better than the surface roughness of the end surface of the annular portion 12a by making a difference in the grinding process. Thereby, the grinding time of the end surface 12e of the annular portion 12a can be shortened, and the cost can be reduced. Such a technique can be similarly applied to a so-called corrugated cage in which the annular portion of the cage does not protrude in the radial direction with respect to the column portion. Although the same effect can be obtained by applying a coating such as manganese phosphate, it is desirable that the surface roughness of the outer diameter guide surface 12d be better than the surface roughness of the end surface of the annular portion 12a.

The present inventors conducted a test to confirm the effect of the present invention. Such a test was conducted using the cage revolution tester under the following conditions. The test results are shown in Table 1.
Number of career revolutions: 7500 min ^-1
Pinion rotation speed: 10000 min ^-1
Carrier revolution radius: 40mm
Gear inner diameter and cage PV value: 300 MPa · m / s
Lubricating oil: ATF
Lubricating oil supply amount: 0.1 L / min

According to the test results in Table 1, when the average roughness (Ra) of the outer diameter guide surface of the cage is R1, and the average roughness (Ra) of the end surface of the cage is R2, R2 / R1 In the range from 1.1 to 7.0, no galling or wear occurred, but when R2 / R1 was 1.0, galling occurred in the gear washer, and R2 / R1 was When 0.5, wear occurred in the gear inner diameter, and when R2 / R1 was 7.5, washer wear occurred. Accordingly, R2 / R1 is preferably in the following range.
1.1 ≦ R2 / R1 ≦ 7.0 (1)

  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. For example, the wear resistance can be improved by carbonitriding to a case-hardened steel (for example, SCM415) as prevention of seizure of the cage.

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 holder | retainer in the needle roller bearing of this Embodiment.

Explanation of symbols

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

Claims (3)

In a cage for a needle roller bearing that rotatably supports a planetary gear in a planetary gear mechanism,
The retainer has an annular portion and a plurality of column portions extending in the axial direction from the annular portion, and is configured to hold rollers between the adjacent column portions. A retainer for a needle roller bearing, wherein the outer diameter guide surface of the retainer has a roughness greater than that of an end surface of the retainer. The following formula is satisfied, where R1 is an average roughness of the outer diameter guide surface of the cage, and R2 is an average roughness of the end surface of the cage. Cage for needle roller bearings.
1.1 ≦ R2 / R1 ≦ 7.0 (1)   A needle roller bearing using the cage for a needle roller bearing according to claim 1 or 2.

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