阅读说明：本技术 滚动轴承 (Rolling bearing ) 是由 村田顺司 镰本繁夫 狮子原祐树 于 2020-04-23 设计创作，主要内容包括：滚动轴承包括：第一滚道表面(11)；第二滚道表面(12)；和可旋转地布置在第一滚道表面(11)与第二滚道表面(12)之间的多个滚动元件。在第一滚道表面(11)、第二滚道表面(12)和所述多个滚动元件的滚动表面中的至少一个表面上设置多个凹部(20)。凹部(20)的开口与所述至少一个表面的面积比率在5％至37％的范围内。每一个凹部(20)的开口的当量圆直径在1μm至27μm的范围内。每一个凹部(20)在与所述至少一个表面垂直的方向上的深度在3μm至10μm的范围内。将凹部(20)排除在外的所述至少一个表面的表面波度小于或等于0.2μm。(The rolling bearing includes: a first raceway surface (11); a second raceway surface (12); and a plurality of rolling elements rotatably arranged between the first raceway surface (11) and the second raceway surface (12). A plurality of recesses (20) are provided on at least one of the first raceway surface (11), the second raceway surface (12), and the rolling surfaces of the plurality of rolling elements. The area ratio of the opening of the recess (20) to the at least one surface is in the range of 5% to 37%. The equivalent circle diameter of the opening of each recess (20) is in the range of 1 μm to 27 μm. The depth of each recess (20) in a direction perpendicular to the at least one surface is in the range of 3 μm to 10 μm. The surface waviness of the at least one surface excluding the recesses (20) is less than or equal to 0.2 [ mu ] m.)

1. A rolling bearing characterized by comprising:

a first raceway surface (11);

a second raceway surface (12); and

a plurality of rolling elements rotatably arranged between the first and second raceway surfaces (11, 12), wherein

Providing a plurality of recesses (20) on at least one of the first raceway surface (11), the second raceway surface (12), and a rolling surface of the plurality of rolling elements,

an area ratio of an opening of the plurality of recesses (20) to the at least one surface is in a range of 5% to 37%,

the equivalent circular diameter of the opening of each recess (20) of the plurality of recesses (20) is in the range of 1 μm to 27 μm,

each recess (20) of the plurality of recesses (20) has a depth in a direction perpendicular to the at least one surface in a range of 3 μm to 10 μm, and

the surface waviness of the at least one surface excluding the plurality of recesses (20) is less than or equal to 0.2 μm.

2. Rolling bearing according to claim 1, characterized in that the rolling elements are rollers.

3. Rolling bearing according to claim 2, characterized in that each of the plurality of rolling elements is any one of a needle roller, a cylindrical roller and an oblong cylindrical roller.

Technical Field

The present invention relates to a rolling bearing.

Background

For example, a planetary gear used in a planetary gear mechanism in a transmission is rotatably supported on a support shaft of a carrier via a needle roller bearing. The needle roller bearing is lubricated by forcibly supplying lubricating oil from the support shaft side (refer to japanese unexamined patent application publication No. 2015-083861(JP 2015-083861A)).

In recent years, since the amount of lubricating oil forcibly supplied to bearings is reduced for the purpose of saving natural resources and energy, the amount of lubricating oil in bearings tends to be reduced, and further, the lubricating oil is dispersed by centrifugal force generated by the bearings rotating at higher speeds. When the amount of lubricating oil in the bearing is reduced, an oil film shortage occurs, which leads to a temperature rise and bearing seizure.

Disclosure of Invention

The invention provides a rolling bearing capable of inhibiting temperature rise and improving seizure resistance.

As a result of intensive studies, the inventors found that, by providing a plurality of recesses on at least one of the rolling surface of a rolling element and the raceway surface on which the rolling element rolls and setting the area ratio of the openings of the recesses, the equivalent circle diameter and the depth of each recess, and the surface waviness of the surface excluding the recesses within appropriate ranges, lubricating oil can be easily accumulated in the recesses, and the oil film thickness on the surface (i.e., the thickness of the oil film) can be increased. The inventors have completed the present invention based on such findings.

One aspect of the invention relates to a rolling bearing including: a first raceway surface; a second raceway surface; and a plurality of rolling elements rotatably disposed between the first and second raceway surfaces. A plurality of recesses are provided on at least one of the first raceway surface, the second raceway surface, and the rolling surfaces of the plurality of rolling elements. An area ratio of an opening of the plurality of recesses to the at least one surface is in a range of 5% to 37%. The equivalent circle diameter of the opening of each of the plurality of concave portions is in a range of 1 μm to 27 μm. A depth of each of the plurality of concave portions in a direction perpendicular to the at least one surface is in a range of 3 μm to 10 μm. The surface waviness of the at least one surface excluding the plurality of recesses is less than or equal to 0.2 μm.

In the rolling bearing according to the above aspect of the invention, the lubricating oil can be easily accumulated in the concave portion provided on at least one of the first raceway surface, the second raceway surface, and the rolling surfaces of the rolling elements, and the oil film thickness on the at least one surface can be increased. With this configuration, the oil film shortage on the at least one surface can be suppressed. Therefore, the temperature rise of the rolling bearing can be suppressed, and galling resistance can be improved.

The rolling elements may be rollers. In this case, a temperature rise of the rolling bearing including the rollers as the rolling elements can be suppressed, and galling resistance can be improved.

Each rolling element may be any one of a needle roller, a cylindrical roller, and a long cylindrical roller. In this case, the temperature rise of the rolling bearing including any one of the needle rollers, the cylindrical rollers, and the long cylindrical rollers (i.e., the rod-like rollers) as the rolling elements can be suppressed, and the galling resistance can be improved.

According to the rolling bearing of the above aspect of the present invention, the temperature rise can be suppressed, and the galling resistance can be improved.

Drawings

Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and wherein:

Fig. 1 is a partial sectional view of a planetary gear mechanism including a rolling bearing according to an embodiment of the invention;

FIG. 2 is a sectional view taken along line II-II in FIG. 1;

fig. 3 is an enlarged sectional view showing a rolling bearing;

fig. 4 is a graph showing the results of the evaluation test. In the graph, the vertical axis represents the oil film thickness variation amount, and the horizontal axis represents the area ratio of the concave portion;

fig. 5 is a graph showing the results of the evaluation test. In the graph, the vertical axis represents the oil film thickness variation, and the horizontal axis represents the equivalent circle diameter of the concave portion;

fig. 6 is a graph showing the results of the evaluation test. In the graph, the vertical axis represents the oil film thickness variation amount, and the horizontal axis represents the depth of the concave portion;

fig. 7 is a graph showing the results of the evaluation test. In the graph, the vertical axis represents the amount of change in oil film thickness, and the horizontal axis represents the surface waviness of the surface excluding the concave portion; and is

Fig. 8 is a table showing the results of the evaluation test.

Detailed Description

Fig. 1 is a partial sectional view of a planetary gear mechanism including a rolling bearing according to an embodiment of the present invention. Fig. 2 is a sectional view taken along line II-II in fig. 1. In fig. 1 and 2, a planetary gear mechanism 50 is used in a transmission of a vehicle (e.g., an automobile), for example. The planetary gear mechanism 50 includes a sun gear 51, an internal gear (ring gear) 52, a plurality of pinion gears 53, and a carrier 54.

The sun gear 51 is fitted to the outer periphery of the rotating shaft 61, and is rotatable integrally with the rotating shaft 61. The internal gear 52 is disposed radially outward of the sun gear 51 so as to be concentric with the sun gear 51. A plurality of planetary gears 53 (three planetary gears in the present embodiment) are arranged in the circumferential direction of the sun gear 51, and mesh with the outer periphery of the sun gear 51. Further, each of the planetary gears 53 meshes with the inner periphery of the internal gear 52.

The carrier 54 includes a plurality of shafts 55 and a pair of carrier bodies 56. Each of the shafts 55 supports a corresponding one of the planetary gears 53 such that the corresponding one of the planetary gears 53 can rotate via the rolling bearing 10. The carrier body 56 supports the respective ends of the shafts 55. With this configuration, each of the planet gears 53 rotates about the axis of the corresponding shaft 55 that supports the planet gear 53, and also rotates about the outer periphery of the sun gear 51.

Fig. 3 is an enlarged sectional view showing the rolling bearing. The rolling bearing 10 is a needle roller bearing, and includes a first raceway surface 11, a second raceway surface 12, a plurality of needle rollers (rolling elements) 13, and a cage 15. The first raceway surface 11 is provided at an axially central portion of the outer peripheral surface of the shaft 55. The second raceway surface 12 is provided on an inner peripheral surface of the planetary gear 53.

In fig. 2 and 3, the needle roller 13 is arranged to be able to roll between the first raceway surface 11 and the second raceway surface 12. The outer peripheral surfaces of the needle rollers 13 serve as rolling surfaces 14 that roll on the first and second raceway surfaces 11 and 12. The cage 15 has an annular shape, and holds the needle rollers 13 at predetermined intervals in the axial direction. The outer peripheral surface of the carrier 15 slidably contacts the inner peripheral surface of the planetary gear 53, so that the rotation of the carrier 15 is guided.

An oil passage 57 is provided in the shaft 55 for forcibly supplying lubricating oil to the inside of the rolling bearing 10. The oil passage 57 extends from one axial end (right end in fig. 3) of the shaft 55 toward the other axial end, extends radially outward from an axial center portion of the shaft 55, and is open at an outer peripheral surface of the shaft 55. A washer 58 is interposed between each carrier body 56 and the corresponding planetary gear 53.

A plurality of minute recesses 20 for accumulating lubricating oil are provided on the rolling surface 14 of each needle roller 13. These minute recessed portions 20 are formed, for example, as follows: minute uneven portions are formed by performing sand blast finishing on the rolling surface 14, and then barrel finishing is performed to remove the projections of the uneven portions. The shape of the recess 20 is set as described below so that the lubricating oil is easily accumulated.

The ratio of the area of the opening of the recess 20 to the area of the rolling surface 14, that is, the area ratio of the opening of the recess 20 to the rolling surface 14 (hereinafter, simply referred to as the area ratio a of the recess 20) is set to be greater than or equal to 5% and less than or equal to 37% (preferably, greater than or equal to 8% and less than or equal to 30%). In other words, the area ratio a of the concave portion 20 is setSet in the range of 5% to 37% (preferably, in the range of 8% to 30%). The area ratio a of the recesses 20 can be obtained by measuring the area of the opening of the recess 20 in one field of view when observing the rolling surface 14 and calculating the percentage (%) of the area of the opening to the area of the observation field of view. An area of an observation field of view is, for example, 0.4mm²。

The equivalent circle diameter of the opening of each recess 20 (hereinafter simply referred to as the equivalent circle diameter B of the recess 20) is set to be greater than or equal to 1 μm and less than or equal to 27 μm (preferably, greater than or equal to 8 μm and less than or equal to 27 μm). In other words, the equivalent circular diameter B of the concave portion 20 is set in the range of 1 μm to 27 μm (preferably, in the range of 8 μm to 27 μm). The equivalent circular diameter B of the concave portion 20 can be obtained by processing a captured image of the rolling surface 14 to measure the area S of the opening of each concave portion 20 in the rolling surface 14 and using the following formula.

B＝2×(S/π)^(1/2)

The depth from the opening to the bottom of the recess 20 in the direction perpendicular to the rolling surface 14 (hereinafter simply referred to as the depth C of the recess 20) is set to be greater than or equal to 3 μm and less than or equal to 10 μm (preferably, greater than or equal to 3 μm and less than or equal to 9.6 μm). In other words, the depth C of the concave portion 20 is in the range of 3 μm to 10 μm (preferably, in the range of 3 μm to 9.6 μm). Note that the value of the depth C of the concave portion 20 represents the maximum valley depth Pv specified in Japanese Industrial Standard (JIS) B0601-2001. The surface waviness of the rolling surface 14 excluding the recesses 20 (hereinafter simply referred to as surface waviness D) is set to 0.2 μm or less (preferably, 0.16 μm or less). In other words, the surface waviness D is set in a range of 0.2 μm or less (preferably, in a range of 0.16 μm or less). The value of the surface waviness D represents the arithmetic average waviness Wa specified in JIS B0601-2001.

Next, evaluation tests performed by the inventors to verify the effects obtained by the rolling bearing of the present invention will be described. In the evaluation test, nine sets of samples (bearing steel balls) were used. One set included three samples. Each set of samples was machined to have a plurality of recesses on a portion of the surface of the sample. Basically, as described above, the samples were processed by performing sand blasting dressing first and then performing roll dressing.

The three samples in each group were rotated at different rotation speeds (0.1m/s, 1.0m/s, and 2.0m/s) from each other with a small amount of lubricating oil applied (5. mu.l of low-viscosity oil was applied to the sample surface). Then, the change in the thickness of the oil film was measured at the central portion of each sample where the sample contacted the mating member (i.e., the mating member), and the area ratio of the recesses, the equivalent circle diameter and depth of the recesses, and the surface waviness of the processed surface were also measured.

The change in oil film thickness was measured by: a known three-wavelength optical interferometer (for example, refer to japanese unexamined patent application publication No. 2017-207316) is used to simultaneously measure the thickness of an oil film (i.e., the thickness of an oil film) on a processed surface on which recesses are provided and the thickness of an oil film on an unprocessed surface on which recesses are not provided, and calculate the difference between the measured oil film thicknesses. The difference between the oil film thicknesses is a value obtained by subtracting the oil film thickness on the unprocessed surface from the oil film thickness on the processed surface. This value will be referred to as an oil film thickness variation hereinafter. The oil film thickness variation indicates that the oil film thickness on the processed surface increases as the value of the oil film thickness variation increases.

Fig. 4 is a graph showing the results of the above-described evaluation test. In the graph, the vertical axis represents the oil film thickness variation amount, and the horizontal axis represents the area ratio of the concave portion. As shown in fig. 4, when the area ratio of the concave portion is in the range of 5% to 37% (in other words, when the area ratio of the concave portion is greater than or equal to 5% and less than or equal to 37%), the value of the oil film thickness variation is generally large, and the oil film thickness of the processed surface on which the concave portion is provided is large. Therefore, as can be seen from the graph, by setting the area ratio of the concave portion in the range of 5% to 37%, the lubricating oil can be more easily accumulated in the concave portion, and the oil film thickness can be made larger (i.e., the oil film thickness can be increased).

Fig. 5 is a graph showing the results of the above-described evaluation test. In the graph, the vertical axis represents the oil film thickness variation amount, and the horizontal axis represents the equivalent circle diameter of the concave portion. As shown in fig. 5, when the equivalent circle diameter of the concave portion is in the range of 1 μm to 27 μm, the value of the oil film thickness variation is generally large, and the oil film thickness of the processed surface on which the concave portion is provided is large. Therefore, as can be seen from the graph, by setting the equivalent circle diameter of the concave portion in the range of 1 μm to 27 μm, the lubricating oil can be more easily accumulated in the concave portion, and the oil film thickness can be made larger (i.e., the oil film thickness can be increased).

Fig. 6 is a graph showing the results of the above-described evaluation test. In the graph, the vertical axis represents the oil film thickness variation amount, and the horizontal axis represents the depth of the concave portion. As shown in fig. 6, when the depth of the concave portion is in the range of 3 μm to 10 μm, the value of the oil film thickness variation is generally large, and the oil film thickness of the processed surface on which the concave portion is provided is large. Therefore, as can be seen from the graph, by setting the depth of the concave portion in the range of 3 μm to 10 μm, the lubricating oil can be more easily accumulated in the concave portion, and the oil film thickness can be made larger (i.e., the oil film thickness can be increased).

Fig. 7 is a graph showing the results of the above-described evaluation test. In the graph, the vertical axis represents the amount of change in the oil film thickness, and the horizontal axis represents the surface waviness of the surface excluding the concave portion. As shown in fig. 7, when the surface waviness of the surface excluding the concave portion is in the range of 0.2 μm or less, the value of the oil film thickness variation is generally large, and the oil film thickness of the processed surface on which the concave portion is provided is large. Therefore, as can be seen from the graph, by setting the surface waviness of the surface excluding the concave portion in the range of 0.2 μm or less, the lubricating oil can be easily accumulated in the concave portion, and the oil film thickness can be made large (i.e., the oil film thickness can be increased).

Fig. 8 is a table showing the results of the above-described evaluation test. As shown in fig. 8, of the nine sets of samples a to J, only sample G (G-1, G-2, G-3) showed that all the oil film thickness variations had positive values, which means that the oil film thickness on the machined surface on which the recesses were provided was increased. Then, in each sample G, the area ratio of the concave portion had a value (15%) in the range of 5% to 37%, and the equivalent circle diameter of the concave portion was a value (15.31 μm) in the range of 1 μm to 27 μm. The depth of the concave portion has a value (4.788 μm) in a range of 3 μm to 10 μm, and the surface waviness of the surface excluding the concave portion has a value (0.148 μm) in a range of 0.2 μm or less. Therefore, as can be seen from the test results, by setting the area ratio of the recessed portions, the equivalent circular diameter and depth of the recessed portions, and the surface waviness of the surface excluding the recessed portions within the respective ranges as described above, lubricating oil can be easily accumulated in the recessed portions, and the oil film thickness on the machined surface on which the recessed portions are provided can be increased.

As described above, in the rolling bearing 10 of the present embodiment, the lubricating oil can be easily accumulated in the plurality of recesses 20 provided on the rolling surfaces 14 of the needle rollers 13, and the oil film thickness on the rolling surfaces 14 can be increased. With this configuration, the oil film shortage on the rolling surface 14 can be suppressed. Therefore, the temperature rise of the rolling bearing 10 can be suppressed, and galling resistance can be improved.

The above-described embodiments are to be considered in all respects as illustrative and not restrictive. That is, the rolling bearing according to the present invention is not limited to those described in the above-described embodiments shown in the drawings, and various modifications may be made within the scope of the present invention. For example, in the above-described embodiment, the concave portions 20 are provided on the rolling surfaces 14 of all the needle rollers 13. However, the recess 20 may be provided on the rolling surface 14 of the at least one needle roller 13. Further, the recess 20 may be provided on at least one of the first raceway surface 11, the second raceway surface 12, and the rolling surface 14 of the needle roller 13.

The rolling bearing of the present invention may be a roller bearing other than a needle roller bearing, such as a self-aligning roller bearing or a cylindrical roller bearing. The rolling elements of the rolling bearing may be cylindrical rollers other than needle rollers or long cylindrical rollers (i.e., rod-shaped rollers). Further, the rolling bearing may be a ball bearing including balls as rolling elements, in addition to the rolling bearing including rollers as rolling elements. Further, an example in which the rolling bearing of the present invention is applied to a planetary gear mechanism in a transmission is described. However, the application of the rolling bearing is not limited thereto.