JP2006022825A - Roller bearing for differential - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long service life to a roller bearing for a differential even under such a condition that an oil film thickness is extremely thin under low viscosity and lean lubrication conditions. <P>SOLUTION: An infinite number of micro recessed dents are formed, at random, at least in the surfaces of the rolling elements of the roller bearing for the differential. A surface roughness parameter Ryni for the surface in which the dents are formed is set within the range of 0.4 to 1.0 μm, and an Sk value is set to -1.6 or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an automotive differential roller bearing.

  FIG. 9 illustrates a typical automobile differential. The top of the figure is the front of the vehicle body and the bottom is the rear of the vehicle body. A drive pinion shaft 42 is accommodated in the front portion of the differential case 41 and is rotatably supported by a pair of tapered roller bearings 44 and 45. A propeller shaft (not shown) is connected to the front end portion of the drive pinion shaft 42, and a drive pinion gear (reduction small gear) 43 that meshes with a link gear (reduction large gear) 46 is fixed or integrally provided to the rear end portion. It is.

  The link gear 46 is connected to a differential gear case 47, and the differential gear case 47 is rotatably supported with respect to the differential case 41 by a pair of tapered roller bearings 48 and 49. Inside the differential gear case 47, a pair of pinion gears 50 and a pair of side gears 51 that mesh with the pinion gears 50 are disposed. The pinion gear 50 is fixed to the pinion shaft 52, and the side gear 51 is attached to the differential gear case 47 through a thrust washer. Left and right drive shafts (not shown) are connected to the inner diameter portions of the side gears 51 corresponding to the drive shafts (serration connection or the like).

The drive torque of the propeller shaft is transmitted through a path of drive pinion gear 43 → link gear 46 → differential gear case 47 → pinion gear 50 → side gear 51 → drive shaft. On the other hand, the driving resistance of the tire is transmitted from the drive shaft → the side gear 51 → the pinion gear 50.
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 used for roller bearings such as automobile differentials have been increasingly miniaturized and increased in output, and the usage environment such as lowering the viscosity of lubricating oil tends to increase in load and 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.

  JP-A-2-16821 and JP-A-6-42536 describe roller bearings in which minute irregularities are formed on the surface of a rolling element to improve oil film forming ability. These indentations of the minute concave shape have a value Rqni (L) / value of the ratio of the axial surface roughness Rqni (L) and the circumferential surface roughness Rqni (C) when the surface roughness is expressed by the parameter Rqni. The value of Rqni (C) is 1.0 or less (Rqni ≧ 0.10), and the surface roughness parameter Sk is set to −1.6 or less, so that even if the mating surface is rough, Even if the finished surface is good, it has a long life, but if the oil film thickness is extremely thin under low viscosity and dilute lubrication, the effect may not be fully exhibited.

  In the differential roller bearing according to the present invention, an infinite number of minute concave recesses are randomly provided on the surface of the rolling element, and the surface roughness parameter Ryni of the surface provided with the recesses is 0.4 μm ≦ Ryni ≦ 1.0 μm. In addition, the Sk value is −1.6 or less.

  Here, the parameter Ryni is the average value of the maximum height for each reference length, that is, the reference length is extracted in the direction of the average line from the roughness curve, and the interval between the peak line and the valley bottom line of this extracted portion is the roughness curve. It is a value measured in the direction of the vertical magnification (ISO 4287: 1997).

  The parameter Sk indicates the degree of skewness (skewness) of the roughness curve (ISO 4287: 1997), and is a statistic that is a measure of the asymmetry of the uneven distribution. The Sk value is close to 0 in a symmetric distribution such as a Gaussian distribution. That is, when the concave and convex portions are deleted, negative values are obtained, and in the opposite case, positive values are obtained. The Sk value can be controlled by selecting the rotational speed of the barrel sander, the processing time, the amount of workpiece input, the type and size of the chip, and the like. By setting the Sk value to -1.6 or less in both the width direction and the circumferential direction, the hollow with a minute concave shape becomes an oil reservoir, and even when compressed, there is little oil leakage in the sliding direction and the right-angle direction, so that an oil film is formed. Excellent, oil film formation is good, and has the effect of minimizing surface damage.

  As is well known, a roller bearing is a mechanical element that supports a shaft that rotates or swings by a rolling motion of a rolling element (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 reason why at least the surface of the rolling element is used is that it does not exclude the formation of a concave indentation on the raceway surface, and the concave shape is not only on the rolling surface of the rolling element but also on the end face. The purpose is not to exclude the formation of the depression.

  According to a second aspect of the present invention, in the differential roller bearing of the first aspect, a surface roughness parameter Rymax of the surface provided with the recess is 0.4 to 1.0. The parameter Rymax is the maximum value of the maximum height for each reference length (ISO 4287: 1997).

  According to a third aspect of the present invention, in the differential roller bearing of the first or second aspect, when the surface roughness of the surface provided with the recess is indicated by a parameter Rqni, the axial surface roughness Rqni (L) and the circumferential direction The ratio Rqni (L) / Rqni (C) to the surface roughness Rqni (C) is 1.0 or less. 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 measurement length and averaging it, and is also called the root mean square roughness. . 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, the surface roughness parameter Ryni of the surface provided with the indentation is set within a range of 0.4 μm ≦ Ryni ≦ 1.0 μm, and is suppressed to be smaller than before, thereby preventing oil film breakage even under lean lubrication. It is possible, and a long life can be obtained even under conditions where the oil film thickness is extremely thin compared to conventional products. As for the Sk value, -1.6 or less is the range advantageous for oil film formation in terms of the shape and distribution of the surface recess depending on the processing conditions. Therefore, the life of the automobile differential can be extended.

  The roller bearing for a differential of an automobile already described with reference to FIG. 9 includes an inner ring, an outer ring, and a rolling element 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 a surface roughness parameter Rqni of a surface provided with a depression within a range of 0.4 μm ≦ Rqni ≦ 1.0 μm, and an Sk value of −1.6 or less, preferably −4.9. It is the range of -1.6. Further, the surface roughness parameter Rymax of the surface provided with the depression is 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.

The measurement method and conditions of the parameters Ryni, Rymax, Sk, Rqni are exemplified as follows. When measuring the surface properties represented by these parameters for components such as rolling elements and races of roller 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.)
FIG. 1 shows a tapered roller bearing as an example of a roller 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 15 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 a smooth surface, 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 performed on the (comparative example) and the bearings F and G (examples) will be described (see Table 1). 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.

A peeling test was conducted using a two-cylinder testing machine shown in FIG. 2 to evaluate the metal contact rate. In FIG. 2, 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. It can be driven by a separate motor via The shaft 26 on the D cylinder 22 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 2.

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. 3 (A) shows the metal contact rate of the rolling surface of the roller in the bearing of the comparative example, and FIG. 3 (B) shows the bearing of the 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.

  Next, a comparative test test performed on bearing A (comparative example) with superfinish after grinding, and on bearing B (comparative example) and bearing C (example) in which an infinite number of minute concave recesses were formed. Is described. 3 to 5 show the finished surface conditions of the rollers of each test bearing in FIGS. Specifically, FIG. 3 shows the surface roughness of the bearing A (comparative example), FIG. 4 shows the surface roughness of the bearing B (comparative example), and FIG. 5 shows the surface roughness of the bearing C (example).

The test apparatus used is a radial load tester 11 as schematically shown in FIG. 7, and test bearings 1 are mounted on both sides of the rotary shaft 12 and the test is performed by applying rotation and load. The finish of the inner race (mating shaft) used for the test is Ra 0.10 to 1.16 μm of the polished finish. The outer race (outer ring) is also common. The test conditions are as follows.
Bearing radial load: 2000kgf
Rotation speed: 4000rpm
Lubricant: Crisecoil H8 (2 cst under test conditions)
FIG. 8 shows the life test results under the oil film parameter Λ = 0.13. The vertical axis of the figure represents the L10 life (h). As is clear from the figure, bearing A was 78h and bearing B was 82h, while bearing C was 121h. As shown by this data, the bearing C as an example can obtain a long life effect even under extremely severe lubricating conditions with a low viscosity and a thin oil film parameter Λ = 0.13.

Cross section of tapered roller bearing Overall schematic diagram of a 2-cylinder testing machine 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. 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 automobile differential

Explanation of symbols

13 Outer ring 14 Inner ring 16 Tapered roller

Claims (3)

  At least the surface of the rolling element is randomly provided with an infinite number of minute concave recesses, and the surface roughness parameter Ryni of the surface provided with the recesses is in the range of 0.4 μm ≦ Ryni ≦ 1.0 μm, and Sk A differential roller bearing having a value of -1.6 or less.   2. The differential roller bearing according to claim 1, wherein a surface roughness parameter Rymax of the surface provided with the recess is in a range of 0.4 to 1.0.   When the surface roughness of the surface provided with the depression is represented by the parameter Rqni, the value Rqni (L) / Rqni (R) of the ratio between the axial surface roughness Rqni (L) and the circumferential surface roughness Rqni (C) 3. The differential roller bearing according to claim 1, wherein C) is 1.0 or less.