JP2006009964A - Rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide long service life of a rolling bearing even under a condition in which thickness of oil film is extremely thin under low viscosity and diluted lubrication. <P>SOLUTION: Numerous recessed parts having a minute recessed shape are provided at random on a surface of at least a rolling body of the rolling bearing. Average area of the recessed part is in a scope of 30 to 100 μm<SP>2</SP>, and Rymax is in the range of 0.4 to 1.0. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rolling bearing, and can be applied to, for example, a roller bearing used in a shaft support portion of an automobile transmission.

  JP-A-2-16821 and JP-A-6-42536 describe rolling bearings in which minute irregularities are formed on the surface of a rolling element to improve oil film forming ability.

In the above prior art, as a countermeasure against damage due to poor lubrication such as peeling damage of roller bearings, a minute concave recess is provided on the rolling surface of the roller and / or the raceway surface of the inner and outer rings, and the surface roughness is set to the parameter Rqni. The value Rqni (L) / Rqni (C) of the ratio between the axial surface roughness Rqni (L) and the circumferential surface roughness Rqni (C) is ≦ 1.0, and the surface roughness The parameter Sk value is set to ≦ −1.6, so that the life is long regardless of whether the mating surface is rough or has a good finish.
Japanese Patent Laid-Open No. 2-168021 (page 2, upper left column, line 14 to upper right column, second line) JP-A-6-042536 (paragraph number 0009)

  In recent years, parts where rolling bearings such as automobile transmissions are used are becoming smaller and higher in output, and the usage environment such as lower viscosity of the lubricating oil tends to become higher load and higher temperature. For this reason, bearings are changing to a more severe lubrication environment than ever, and wear and surface-origin separation due to poor lubrication are more likely to occur.

  When the surface roughness is expressed by the parameter Rqni, the conventional concave portion having a concave shape has a ratio value Rqni (L) / Rqni of the axial surface roughness Rqi (L) and the circumferential surface roughness Rqni (C). (C) is 1.0 or less (Rqni ≧ 0.10), and the surface roughness parameter Sk value is set to −1.6 or less. Although it is designed to have a long service life, the effect may not be sufficiently exhibited when the oil film thickness is extremely thin under low viscosity / dilute lubrication.

In the rolling bearing of the present invention, an infinite number of minute concave recesses are provided at least on the surface of the rolling element, the average area of the recesses is in the range of 30 to 100 μm ² , and Rymax is 0.4 to 1. It is characterized by being within the range of .0. The parameter Rymax is the maximum value of the maximum height for each reference length (ISO 4287: 1997).

  As is well known, a rolling bearing is a mechanical element that supports a shaft that rotates or swings by a rolling motion of a rolling element (ball or roller). Usually, the rolling element is movably interposed between the race of the inner ring and the race of the outer ring, but there is a type that does not have an inner ring with the outer peripheral surface of the shaft as a direct race surface. The purpose of at least the surface of the rolling element is not to exclude the formation of a concave indentation on the raceway surface as well, and when the rolling element is a roller, not only on the rolling surface but also on the end surface. The purpose of this is not to exclude the formation of a concave / convex indentation.

  The invention according to claim 2 is the rolling bearing according to claim 1, wherein when the surface roughness of the surface provided with the recess is represented by a parameter Rqni, the axial surface roughness Rqni (L) and the circumferential surface roughness Rqni. The ratio value Rqni (L) / Rqni (C) to (C) is 1.0 or less. Here, the parameter Rqni is the square root of the value obtained by integrating the square of the height deviation from the roughness center line to the roughness curve in the section of the measured length and averaging the section, which is also known as the root mean square roughness. It is also called (ISO 4287: 1997). Rqni is obtained by numerical calculation from the cross-sectional curve and roughness curve recorded in an enlarged manner, and measured by moving the stylus of the roughness meter in the width direction and the circumferential direction.

According to the present invention, an oil film forming ability is improved by providing an innumerable number of minute concave concaves on the surface of the rolling element, and the oil film thickness is extremely thin under low viscosity and dilute lubrication. But it has a long life. In particular, by setting the average area of the indentation in the range of 30 to 100 μm ² and Rymax in the range of 0.4 to 1.0, it is possible to prevent oil film breakage even under lean lubrication. Compared to products, a long life can be obtained even under extremely thin oil film conditions.

The rolling bearing has an inner ring, an outer ring, and rolling elements as main components. Then, an infinite number of minute concave recesses are randomly formed on at least one of the rolling surfaces and end surfaces of the rolling elements and the raceway surfaces of the inner and outer rings (and the large rib surface for the inner ring of the tapered roller bearing) to form a minute rough surface. It is faced. This minute rough surface has an average area of depressions in the range of 30 to 100 μm ² , and Rymax of the surface provided with the depressions in the range of 0.4 to 1.0. Further, when the surface roughness is obtained in the axial direction and the circumferential direction of each surface and displayed by the parameter Rqni, the ratio of the axial surface roughness Rqni (L) to the circumferential surface roughness Rqni (C) The value Rqni (L) / Rqni (C) is 1.0 or less. As the surface processing for obtaining such a fine rough surface, a desired finished surface can be obtained by special barrel polishing, but a shot or the like may be used. Even when the oil film thickness is extremely thin, the average area of the concaves having a small concave shape is in the range of 30 to 100 μm ² and the depth is in the range of 0.4 to 1.0 μm in Ryni. An oil film forming effect can be exhibited, and a sufficiently long life effect can be obtained even under extremely severe lubrication conditions of an oil film parameter Λ = 0.13.

The measurement methods and conditions for the parameters Rymax and Rqni are exemplified as follows. When measuring the surface properties represented by these parameters for components such as rolling elements and rolling rings of rolling bearings, a single measured value can be relied on as a representative value. Should be measured.
Parameter calculation standard: JIS B 0601: 1994 (Surfcom JIS 1994)
Cut-off type: Gaussian Measurement length: 5λ
Cut-off wavelength: 0.25mm
Measurement magnification: × 10000
Measurement speed: 0.30 mm / s
Measurement location: Roller center measurement number: 2
Measuring device: Surface roughness measuring device Surfcom 1400A (Tokyo Seimitsu Co., Ltd.)
In the case of a micro concave recess provided on the rolling surface of the roller, the area ratio of the recess occupying the entire rolling surface is within a range of 5 to 20%, and the average area of the recess is arranged except for an equivalent circular diameter of 3 μmφ or less. Sometimes it is 30-100 μm ² . When Rymax is out of the range of 0.4 to 1.0, the area ratio of the dent exceeds 20%, and the average area exceeds 100 μm ² , the effective contact length decreases and the effect of long life tends to decrease. is there.

In order to make a quantitative measurement of the indentation, the roller surface can be enlarged and the image can be quantified from the image by a commercially available image analysis system. The white portion of the image is analyzed as a flat surface portion, and the minute depression is analyzed as a black portion. For example, when analyzed using Pierce's LA-525 image analysis system, the density of the original image is first clarified with an emphasis filter, and then an equivalent circle diameter of 3 μmφ or less, which is a very fine black portion, is removed with a noise eraser. . The size, distribution, and area ratio of the minute dents remaining after the removal by the noise eraser are obtained, and the roller surface is evaluated. The measurement conditions in that case are as follows, for example. Further, when measuring the area ratio and the average area of the indentation with respect to components such as rolling elements and raceway surfaces of the rolling bearing, similar to the above parameters Rymax and Rqni, even one measured value can be relied on as a representative value. It is good to measure two places that face each other in the diameter direction.
Observation field: 826 μm × 620 μm
Measurement location: Roller center measurement number: 2
FIG. 1 shows a first example of a rolling bearing. The rolling bearing 1 is a needle roller bearing in which a needle roller 2 is incorporated in an outer ring 3 as a rolling element, and a counter shaft 4 is supported by the needle roller 2. It is supposed to be. A description will be given of the results of manufacturing a plurality of types of needle roller bearings having surface treatments with different finishing surfaces on the surface of the needle rollers and performing a life test. As shown in FIG. 2, the needle roller bearing used for the life test has 15 outer diameters Dr = 33 mm, an inner diameter dr = 25 mm, a diameter D = 4 mm of the needle roller 2, and a length L = 25.8 mm. It is a bearing with the cage | basket 5 using the needle roller of this. Three types of test roller bearings with different surface roughness finishes were produced. That is, there are a bearing A (comparative example) subjected to superfinish after grinding, and a bearing B (comparative example) and a bearing C (example) in which an infinite number of minute concave recesses are formed. FIGS. 3 to 5 show the finished surface condition of the needle roller of each test bearing. 3 shows the surface roughness of the bearing A, FIG. 4 shows the surface roughness of the bearing B, and FIG. 5 shows the surface roughness of the bearing C. Table 1 shows a list of characteristic value parameters of the surface finish of each test bearing. In Table 1, the parameter Sk indicates the degree of distortion (skewness) of the distribution curve of the surface roughness (ISO 4287: 1997), and is a statistic that provides a measure of the asymmetry of the uneven distribution, such as a Gaussian distribution. In such a symmetric distribution, the Sk value is close to 0, and takes a negative value when the concave and convex portions are deleted, and takes a positive value in the opposite case. The Sk value can be controlled by selecting the rotation speed, processing time, workpiece input amount, tip type and size, etc., of the barrel polishing machine described above. By setting the parameter Sk value to -1.6 or less in both the width direction and the circumferential direction, the minute concave recess becomes an oil reservoir, and even when compressed, there is little oil leakage in the sliding direction and the right-angle direction, and an oil film is formed. Excellent in oil film formation and has the effect of minimizing surface damage. For Rqni (L / C), the bearings B and C are 1.0 or less, and the bearing A is a value around 1.0.

使用した試験装置は図６に概略図で示したようなラジアル荷重試験機１１で、回転軸１２の両側に試験軸受１を取り付け、回転と荷重を与えて試験を行なうものである。試験に用いたインナレース（相手軸）の仕上は研摩仕上のＲａ０．１０〜０．１６である。アウタレース（外輪）はいずれの場合も共通である。試験条件は以下のとおりである。
軸受ラジアル荷重：２０００ｋｇｆ
回転数：４０００ｒｐｍ
潤滑剤：クリセクオイルＨ８（試験条件で２ｃｓｔ）
図７に油膜パラメータΛ＝０．１３の下での寿命試験結果を示す。同図の縦軸がＬ1O寿命（ｈ）を表している。同図から明らかなとおり、軸受Ａが７８ｈ、軸受Ｂが８２ｈであったのに対して軸受Ｃは１２１ｈであった。このデータが示すように、実施例である軸受Ｃは、油膜パラメータΛ＝０．１３という非常に過酷な潤滑条件下でも長寿命効果を得ることができる。

The test apparatus used is a radial load tester 11 as schematically shown in FIG. 6, and the test bearings 1 are attached to both sides of the rotating shaft 12, and the test is performed by applying rotation and load. The finish of the inner race (mating shaft) used in the test is Ra 0.10 to 0.16 of the polished finish. The outer race (outer ring) is common in both cases. The test conditions are as follows.
Bearing radial load: 2000kgf
Rotation speed: 4000rpm
Lubricant: Crisecoil H8 (2 cst under test conditions)
FIG. 7 shows the life test results under the oil film parameter Λ = 0.13. The vertical axis of the figure represents the L1O life (h). As is clear from the figure, bearing A was 78h and bearing B was 82h, while bearing C was 121h. As this data shows, the bearing C as an example can obtain a long-life effect even under extremely severe lubrication conditions where the oil film parameter Λ = 0.13.

  Next, FIG. 8 shows a tapered roller bearing as a second example of the rolling bearing. The tapered roller bearing is a radial bearing that uses a tapered roller 16 as a rolling element, and a plurality of tapered rollers 16 are interposed between a raceway of the outer ring 13 and a raceway of the inner ring 14 so as to be able to roll. During operation, the rolling surface 17 of the tapered roller 16 is in rolling contact with the raceway of the outer ring 13 and the inner ring 14, and the large end surface 18 of the tapered roller 16 is in sliding contact with the inner surface of the large collar 15 of the inner ring 14. Therefore, in the case of the tapered roller 16, an infinite number of minute concave recesses may be formed on the large end surface 18 in addition to the rolling surface 17. Similarly, in the case of the inner ring 14, an infinite number of minute concave recesses may be formed on the inner surface of the large brim 5 in addition to the raceway surface.

  Conventional tapered roller bearings A and B (comparative example) in which the rolling surface of the tapered roller is finished to be smooth, and bearings C to E in which numerous indentations having a small concave shape are randomly formed on the rolling surface of the tapered roller. The life test conducted for (Comparative Example) and bearings F and G (Examples) will be described (see Table 2). The bearings A to G used are tapered roller bearings having an outer diameter of 81 mm and an inner diameter of 45 mm. In addition, the rolling surfaces of the rollers in the bearings A and B of the comparative example are processed by super finishing (superfinishing) after grinding, and are not subjected to indentation processing. The rolling surfaces of the rollers C to E of the comparative example and the bearings F and G of the example are formed with a myriad of indentations of minute concave shapes randomly by barrel polishing special processing. For Rqni (L / C), the roller bearings C to G are 1.0 or less, and the roller bearings A and B are about 1.0.

図１０に示す２円筒試験機を使用してピーリング試験を行い、金属接触率を評価した。図１０において、駆動側円筒２２（Ｄ円筒：Driver）と従動側円筒２４（Ｆ円筒：Follower）は各々の回転軸の片端に取り付けられ、２本の回転軸２６，２８はそれぞれプーリ３０，３２を介して別々のモータで駆動できるようになっている。Ｄ円筒２側の軸２６をモータで駆動し、Ｆ円筒２４はＤ円筒２２に従動させる自由転がりにした。Ｆ円筒２４は、表面処理に関して比較例と実施例の２種類を用意した。試験条件等詳細は表３のとおりである。

A peeling test was performed using a two-cylinder testing machine shown in FIG. 10, and the metal contact rate was evaluated. In FIG. 10, a driving side cylinder 22 (D cylinder: Driver) and a driven side cylinder 24 (F cylinder: Follower) are attached to one end of each rotating shaft, and two rotating shafts 26, 28 are pulleys 30, 32, respectively. Can be driven by a separate motor. The shaft 26 on the D cylinder 2 side was driven by a motor, and the F cylinder 24 was free-rolled to follow the D cylinder 22. For the F cylinder 24, two types of comparative examples and examples were prepared for the surface treatment. Details of the test conditions are shown in Table 3.

金属接触率の比較データを図９に示す。同図は横軸が経過時間、縦軸が金属接触率を表し、図９（Ｂ）は実施例の軸受におけるころの転動面の金属接触率を、図９（Ａ）は比較例の軸受におけるころの転動面の金属接触率を、それぞれ示す。これらの図を対比すれば、比較例に比べて実施例では金属接触率が改善されていることを明瞭に確認できる。言い換えれば、油膜形成率（＝１００％−金属接触率）が、実施例の軸受の方が比較例の軸受に比べて、運転開始時で１０％程度、試験終了時（２時間後）で２％程度、向上している。

The comparison data of metal contact ratio is shown in FIG. In this figure, the horizontal axis represents the elapsed time, the vertical axis represents the metal contact rate, FIG. 9B shows the metal contact rate of the rolling surface of the roller in the bearing of the example, and FIG. 9A shows the bearing of the comparative example. The metal contact ratios of the rolling surfaces of the rollers are shown respectively. Comparing these figures, it can be clearly confirmed that the metal contact ratio is improved in the embodiment as compared with the comparative example. In other words, the oil film formation rate (= 100% −metal contact rate) is about 10% at the start of operation and 2 at the end of the test (after 2 hours) in the bearing of the example compared to the bearing of the comparative example. % Improvement.

Cross section of needle roller bearing Cross section of needle roller bearing used for life test Roughness curve diagram showing the condition of the finished surface of the rolling element in the test bearing Roughness curve diagram showing the condition of the finished surface of the rolling element in the test bearing Roughness curve diagram showing the condition of the finished surface of the rolling element in the test bearing Schematic diagram of test equipment Graph showing life test results Cross section of tapered roller bearing A is a graph showing the metal contact rate of the comparative example, and B is a graph showing the metal contact rate of the example. Overall schematic diagram of a 2-cylinder testing machine

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rolling bearing 2 Rolling element 2a Indentation 3 Outer ring 4 Opposite shaft 5 Cage

Claims (2)

At least the surface of the rolling element is provided with an infinite number of minute concave recesses, the average area of the recesses is in the range of 30 to 100 μm ² , and Rymax is in the range of 0.4 to 1.0. A rolling bearing characterized by that.   When the surface roughness of the surface provided with the indentation is expressed by the parameter RMS, the ratio value Rqni (L) / Rqni (R) of the axial surface roughness Rqni (L) and the circumferential surface roughness Rqni (C) The rolling bearing according to claim 1, wherein C) is 1.0 or less.

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