JP2008019965A - Planetary gear device and rolling bearing - Google Patents

Abstract

Provided are a planetary gear device and a rolling bearing that have an excellent rolling fatigue life that hardly causes surface damage such as wear even when used under conditions where high-speed rotation and slip are likely to occur.
A planetary gear device includes a sun gear, a ring gear arranged concentrically with the sun gear, and a plurality of pinion gears that mesh with the sun gear and the ring gear and revolve around the sun gear. A pinion shaft 5 is inserted through the center hole of the pinion gear 3, and a plurality of needle rollers 6 are rotatably arranged between the inner surface 3 a of the center hole and the outer peripheral surface 5 a of the pinion shaft 5. The pinion gear 3 is rotatable about the pinion shaft 5 by a rolling bearing constituted by the inner surface 3a of the center hole 3 and the outer peripheral surface 5a of the pinion shaft 5 and 6. A portion of the rolling surface of the needle roller 6 that is 75% or more in area ratio is covered with a lubricating film made of a solid lubricant.
[Selection] Figure 2

Description

  The present invention relates to a planetary gear device. The present invention also relates to a rolling bearing used in a planetary gear device.

Normally, if a load is not applied to a rolling bearing so that P / C (P: dynamic equivalent load, C: basic dynamic load rating) exceeds 5% (generally 8.3%), the rolling element rolls. It is known that seizure occurs because the movement is inhibited and seizure occurs and the allowable rotational speed is not satisfied.
In particular, in a rolling bearing used for rotatably supporting a pinion gear in a planetary gear device (hereinafter sometimes referred to as a planetary gear device bearing), force is smoothly transmitted from the pinion gear to the pinion shaft. As can be seen, since a helical gear is used, slippage due to roller skew is likely to occur, and the traveling trace of the planetary shaft becomes twisted. The planetary gear unit bearing is used under high-speed rotation exceeding 10,000 min ⁻¹ .

Since the planetary gear unit bearing is a full needle roller bearing that does not have a cage, it must be used at a rotational speed lower than a dmN value of 150 to 300,000, which is a guideline for an allowable rotational speed. . Problems that are likely to occur in full needle roller bearings include seizure due to insufficient lubrication and peeling damage of rolling elements, but micro seizure (smearing) is particularly problematic.
As a technique for solving such a problem and improving the rolling fatigue life of an apparatus such as a rolling bearing, techniques for applying various treatments to the raceway surface and the rolling surface have been proposed. For example, in Patent Document 1, in a machine part having a sliding surface that is in sliding contact with being subjected to a thrust load, an infinite number of independent small depressions are provided on the sliding surface, and the average area of the minute depressions is 35 to 150 μm ² . It has been proposed that the area ratio occupied by the minute recesses is 10 to 40%.

In Patent Document 2, a solid lubricant film made of a molybdenum disulfide projecting material containing about 95% by mass or more of molybdenum disulfide having an average particle size of about 1 to 20 μm is selected from metal, resin, glass, and ceramics. It has been proposed to form on the surface of materials consisting of Further, in Patent Document 3, it is proposed to form a solid lubricant film having a thickness of 0.5 μm or less by fixing fine particles of molybdenum disulfide on at least one sliding contact surface of a screw shaft, a nut, and a ball. ing.
Japanese Patent No. 2554881 JP 2002-339083 A JP 2004-60742 A

However, in the technique described in Patent Document 1 described above, when a low-viscosity lubricating oil is used or the amount of lubricating oil is insufficient, the lubricating oil cannot be sufficiently retained in the minute recess, and wear or the like It was difficult to effectively prevent the surface damage of the. Further, in the above-mentioned Patent Document 2, there is room for further improvement in that it is difficult to cause surface damage such as wear because only the material of the solid lubricant film is specified. Furthermore, in the technique described in Patent Document 3 described above, the adhesion of the solid lubricating film may be insufficient, and the solid lubricating film may easily fall off.
Therefore, the present invention solves the problems of the prior art as described above, and even when used under conditions where high-speed rotation and slipping are likely to occur, excellent rolling fatigue is unlikely to cause surface damage such as wear. It is an object of the present invention to provide a planetary gear device and a rolling bearing having a long life.

  In order to solve the above problems, the present invention has the following configuration. That is, the planetary gear device of claim 1 according to the present invention includes a sun gear located at the center, a ring gear arranged concentrically with the sun gear, a pinion gear that meshes with the sun gear and the ring gear and revolves around the sun gear, A pinion shaft that is inserted through the center hole of the pinion gear and rotatably supports the pinion gear; and a plurality of rollers that are rotatably arranged between the inner surface of the center hole of the pinion gear and the outer peripheral surface of the pinion shaft; In the planetary gear device having the above structure, a portion of 75% or more in area ratio of the rolling surface of the roller is covered with a lubricant film made of a solid lubricant.

A planetary gear device according to a second aspect of the present invention is the planetary gear device according to the first aspect, wherein the thickness of the lubricating coating is 0.1 μm or more and 8 μm or less.
Furthermore, the planetary gear device according to a third aspect of the present invention is the planetary gear device according to the first or second aspect, wherein a depth of a portion of the rolling surface of the roller covered with the lubricant film is reduced. Is characterized in that a small indentation of 0.1 μm or more and 5 μm or less is formed.

  Furthermore, the rolling bearing according to claim 4 of the present invention includes a sun gear located at the center, a ring gear arranged concentrically with the sun gear, a pinion gear that meshes with the sun gear and the ring gear and revolves around the sun gear. A rolling bearing that is used in a planetary gear device and that rotatably supports the pinion gear, the outer peripheral surface of the pinion shaft inserted through the center hole of the pinion gear, the inner surface of the center hole of the pinion gear, and the pinion shaft And a plurality of rollers that are arranged to freely roll between the outer peripheral surface of the pinion gear and the inner surface of the center hole of the pinion gear, and the area ratio is 75% or more of the rolling surface of the rollers. Further, the present invention is characterized in that a lubricating coating composed of a solid lubricant is coated.

Furthermore, a rolling bearing according to a fifth aspect of the present invention is the rolling bearing according to the fourth aspect, wherein the thickness of the lubricating coating is not less than 0.1 μm and not more than 8 μm.
Furthermore, the rolling bearing according to claim 6 of the present invention is the rolling bearing according to claim 4 or claim 5, wherein the depth of the rolling surface of the roller covered with the lubricating coating is 0. ... A small indentation of 1 μm or more and 5 μm or less is formed.

  In such a planetary gear device and a rolling bearing, a lubricating film is coated on a portion of the rolling surface of the roller that is 75% or more in area ratio, and good lubricating properties are imparted to the rolling surface of the roller. Therefore, wear and heat generation are less likely to occur due to sliding contact with the inner surface of the center hole of the pinion gear and the outer peripheral surface of the pinion shaft. Therefore, even when used under conditions where high-speed rotation and slip are likely to occur, surface damage such as smearing, seizure, wear, and peeling is unlikely to occur on rollers, pinion gears, and pinion shafts, and rolling fatigue life is excellent. ing.

  If the ratio of the portion covered with the lubricating coating on the rolling surface of the roller is less than 75% in terms of area ratio, the lubricity becomes insufficient, the surface damage as described above occurs, and the rolling fatigue life is insufficient. There is a risk of becoming. In order to make such inconvenience less likely to occur, it is preferable to cover the roller rolling surface with a lubricating coating on the area ratio of 95% or more, most preferably 100%.

  Further, if the thickness of the lubricating coating is less than 0.1 μm, the lubricity may be insufficient, and if it exceeds 8 μm, the strength of the lubricating coating may be insufficient. Furthermore, the adhesion of the lubricating coating is increased by filling the fine recess with the lubricating coating, but if the depth of the micro-dent is less than 0.1 μm, there is a possibility that good adhesion of the lubricating coating cannot be obtained. . However, even if it exceeds 5 μm, no further effect can be expected. Therefore, the depth of the minute recess is preferably 5 μm or less.

  The planetary gear device and rolling bearing of the present invention have an excellent rolling fatigue life in which surface damage such as wear hardly occurs even when used under conditions where high-speed rotation and slip are likely to occur.

Embodiments of a planetary gear device and a rolling bearing according to the present invention will be described in detail with reference to the drawings. FIG. 1 is an exploded perspective view of a planetary gear device, and FIG. 2 is a cross-sectional view of a rolling bearing used in the planetary gear device of FIG.
1 includes a sun gear 1 through which a shaft (not shown) is inserted, a ring gear 2 disposed concentrically with the sun gear 1, a plurality of gears meshing with the sun gear 1 and the ring gear 2 and revolving around the sun gear 1 (FIG. 1). 3) and a carrier 4 that is arranged concentrically with the sun gear 1 and the ring gear 2 and rotatably supports the pinion gear 3.

A hole is formed at the center of the pinion gear 3, and a pinion shaft 5 fixed to the carrier 4 is inserted through the center hole. Further, a plurality of needle rollers 6 are rotatably arranged between the inner surface 3a of the center hole of the pinion gear 3 and the outer peripheral surface 5a of the pinion shaft 5, and the inner surface 3a of the center hole of the pinion gear 3 and the pinion The pinion gear 3 is rotatable about the pinion shaft 5 by a rolling bearing constituted by the outer peripheral surface 5 a of the shaft 5 and the plurality of rollers 6.
Of the rolling surfaces of the needle rollers 6 (contact portions with the inner surface 3a of the center hole of the pinion gear 3 and the outer peripheral surface 5a of the pinion shaft 5), the area ratio is 75% or more, and is configured with a solid lubricant. A lubricating coating (not shown) is coated.

  In such a planetary gear device, excellent lubricity is imparted by the lubricating coating, so that the rolling surface of the needle roller 6 and the pinion gear can be used even when used under conditions where high-speed rotation and slip are likely to occur. The inner surface 3a of the center hole 3 and the outer peripheral surface 5a of the pinion shaft 5 are less susceptible to surface damage such as smearing, seizure, wear, and peeling, and have an excellent rolling fatigue life. This lubricating coating only needs to be applied to at least the rolling surface of the needle roller 6. In addition, the lubricating coating may be applied to the inner surface 3 a of the center hole of the pinion gear 3 or the outer peripheral surface 5 a of the pinion shaft 5. Alternatively, all three surfaces may be covered.

  The thickness of the lubricating coating is preferably from 0.1 μm to 8 μm. Furthermore, it is preferable to form a minute recess having a depth of 0.1 μm or more and 5 μm or less in at least a portion of the rolling surface of the needle roller 6 covered with the lubricating coating. When the lubricating coating is applied to the inner surface 3a of the center hole of the pinion gear 3 and the outer peripheral surface 5a of the pinion shaft 5, it is preferable to form a minute recess also in that portion.

The lubricating coating is preferably formed by a shot peening method in which a solid lubricant powder is projected. In addition, the type of solid lubricant is not particularly limited. For example, graphite fluoride, molybdenum disulfide, polytetrafluoroethylene, polyethylene, fluororesin, nylon, polyacetal, polyolefin, polyester, metal soap, tungsten disulfide, Boron nitride, graphite, calcium fluoride, barium fluoride, tin, and tin alloys can be used.
In the present embodiment, a needle roller bearing has been described as an example of a rolling bearing used in a planetary gear device. However, the type of the rolling bearing is not limited to a needle roller bearing, and a cylindrical roller bearing. The present invention can also be applied to other types of roller bearings.

〔Example〕
The present invention will be described more specifically with reference to the following examples. A planetary gear device having substantially the same configuration as the planetary gear device shown in FIGS. 1 and 2 was prepared, a drive test was performed, and the occurrence of smearing of the pinion shaft after driving for 100 hours was evaluated.
Tables 1 and 2 show the pinion shaft diameter, needle roller diameter, and PCD of the planetary gear set used in the test. In any planetary gear unit, the number of needle rollers is 18, the length of the needle rollers is 10 mm, the radial clearance is 0.01 to 0.04 mm, and the circumferential clearance is 0.1 to 0.1 mm. 0.4 mm. Further, the material of the pinion shaft is SK85, the material of the pinion gear is SCM420, and the material of the needle roller is SUJ2.

  Further, the driving conditions of the planetary gear device, that is, the rotation speed and revolution speed of the pinion gear are as shown in Tables 1 and 2. The dmN value and the sliding speed when driving under such conditions are shown in Tables 1 and 2. It is also shown. The needle rollers were lubricated with 120 ° C. automatic transmission lubricating oil (ATF), and the amount thereof was 0.1 L / min per pinion gear.

Further, the lubricating coating coated on the rolling surface of the needle roller is as follows. In Examples 1 to 9, a lubricating film with an average thickness of 0.5 μm made of molybdenum disulfide (MoS ₂ ) was coated on the rolling surface of the needle roller at an area ratio of 85%. Yes. In addition, a minute recess having a depth of 0.5 μm is formed by a shot peening process on a portion of the rolling surface of the needle roller that is covered with the lubricating coating. About Comparative Examples 1-9, although the lubricating film is not coat | covered, the micro recess of depth 0.3micrometer is formed in the rolling surface of the needle roller by the barrel process.

  Here, a method for coating a lubricating coating composed of a solid lubricant will be described. The method for coating the lubricating coating is not particularly limited, but shot peening treatment is adopted. A shot peening apparatus was used for forming the lubricating coating, and a molybdenum disulfide powder having an average particle size of 5 μm or less (as defined in JIS R6001) was used as the solid lubricant as the shot material. The injection pressure is 196 to 882 kPa, and the injection time is 10 to 20 minutes. In addition, as for the mass of the needle roller used for one process, 1-6 kg is preferable.

  The thickness of the lubricating coating can be determined by measuring the diameter of the needle roller with a micrometer or the like before and after coating the lubricating coating. Or you may measure using an electron microscope (SEM). When using an electron microscope, first, a pyrrolidone solution of polyamide-imide, which is a thermosetting resin, is applied to the rolling surface of a needle roller provided with a lubricating coating, and cured by heating at 175 ° C. for 2 hours. A protective film was formed. The needle rollers were cut and embedded in an epoxy resin, and the cut surfaces of the needle rollers were mirror finished by buffing. Furthermore, in order to give unevenness, after corroding with a 3% picral solution for 5 seconds, a nano-order chromium layer was coated on the surface by sputtering to impart electrical conductivity. Then, for example, 30 fields of view of the cut surface were observed with an electron microscope at a magnification of 5000 times. Several points were measured for the thickness of the lubricating coating in each field of view, and the average value of these was determined, and this average value was taken as the thickness of the lubricating coating for that field of view. And the average value of the thickness of the lubricating film of 30 visual fields was calculated | required.

Next, the area ratio of the lubricating coating is measured by magnifying the rolling surface of the needle roller coated with the lubricating coating, for example, 1000 times with an electron microscope or the like. It can be determined from the measured area and the area of the portion observed with a microscope (for example, 0.1 mm ² ). Or you may measure using an electron beam microanalyzer (EPMA). An example is shown below. Using an electron beam microanalyzer, the rolling surface of a needle roller coated with a lubricating coating is observed at 30 magnifications at a magnification of 2000, and a square portion with a side of 200 μm is magnified by a factor of 1000 out of the portion where the lubricating coating is formed. Then, the characteristic X-ray intensity of molybdenum is measured. Then, assuming that the lubricating film is coated in a region where an intensity of 10 times or more of the characteristic X-ray intensity before coating the lubricating film is observed, a portion where the lubricating film is coated by image analysis of the result Are obtained, and the average value of 30 fields of view is calculated.

Next, although the method for forming the minute recess is not particularly limited, shot peening treatment and barrel treatment are adopted. The shot peening process was performed using a shot peening apparatus. For the shot material, steel balls, SiC, SiO ₂ , Al ₂ O ₃ , glass beads, etc. having an average particle diameter of 45 μm as defined in JIS R6001 can be used, and conditions of injection pressure 196 to 882 kPa and injection time 10 to 20 min. Then, the shot material was sprayed onto the rolling surface of the needle roller. In addition, as for the quantity of the needle roller processed at once, 1-6 kg is preferable.

The barrel treatment was performed using a blend of various media and additives to perform rough processing for forming large irregularities on the rolling surface of the needle rollers and finishing processing for adjusting the roughness of the plateau portion. In addition, you may give both a shot peening process and a barrel process to the rolling surface of a needle roller.
The method for measuring the depth of the minute recess is as follows. Using a three-dimensional non-contact surface shape measurement system, 30 views of the rolling surface of the needle roller were observed at a magnification of 100 times, and the obtained image was converted into a cross-sectional profile. Then, in each of the five cross sections in the X direction and the Y direction, the depth of the minute depression was measured, and the results were averaged.

  Next, the results of the drive test will be described. In Comparative Examples 1 to 6, smearing occurred. In Comparative Examples 1, 4, and 7, it was confirmed that the hardness of the pinion shaft decreased from Hv720 before the test to Hv550 after the test, and microseizure occurred. In Comparative Examples 2, 3, 5, and 8, it was confirmed that the hardness of the pinion shaft decreased to Hv450 after 100 hours of driving, and smearing accompanied by plastic flow occurred. In particular, Comparative Examples 6 and 9 were stopped because abnormal vibrations occurred in a very short time. And while generation | occurrence | production of smearing was confirmed by the pinion shaft and the needle roller, the hardness of the pinion shaft was reduced to Hv390.

  On the other hand, in Examples 1 to 5, 7 and 8, almost no decrease in the hardness of the pinion shaft after 100 hours of driving was observed, and the degree of smearing hardly occurred or a comparison of the same conditions. Mild compared to the example. For Examples 6 and 9 with a high sliding speed, the test was stopped due to the occurrence of smearing. However, compared with Comparative Examples 6 and 9 under the same conditions, the test was able to be driven for a long time (that is, the planetary gear unit was long). Lifespan).

In the planetary gear set used in this drive test, the needle roller of the rolling bearing had a single row specification, but the test result was the same for a double row specification. Moreover, even if the material of the pinion shaft was changed from SK85 to SUJ2, the same test result was obtained.
Next, the planetary gear device of Example 8 was prepared with various changes in the area ratio and thickness of the lubricating coating, the presence / absence and depth of the micro-indentation, and a driving test under the same driving conditions as in Example 8 Went. Then, when smearing occurred and at least one of vibration value, torque, and temperature exceeded a predetermined value, it was determined that the life was reached, and the test was terminated. The results are shown in Tables 3-5. In addition, the numerical value of the lifetime in Tables 3-5 is shown by the relative value when the lifetime of the comparative example 11 is set to 1.

  As can be seen from Tables 3 to 5, Examples 11 to 32 provided with a lubricating coating had a lifespan five times or more longer than Comparative Example 11 provided with no lubricating coating. In particular, Examples 19 to 26 and 29 to 32, in which a minute recess is formed on the rolling surface of the needle roller, have a longer life than Examples 11 to 18, 27, and 28 that do not have a minute recess. there were. Moreover, the thing which does not have a lubricating film like Comparative Examples 11-17, and the thing which has an area ratio of less than 75% even if it has had short life.

It is a disassembled perspective view of the planetary gear apparatus which is one Embodiment of this invention. It is sectional drawing which shows the structure of the rolling bearing used for the planetary gear apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sun gear 2 Ring gear 3 Pinion gear 3a Inner surface of center hole of pinion gear 4 Carrier 5 Pinion shaft 5a Outer surface of pinion shaft 6 Needle roller

Claims (6)

  A sun gear located at the center, a ring gear concentrically arranged with the sun gear, a pinion gear that meshes with the sun gear and the ring gear and revolves around the sun gear, and is inserted through a center hole of the pinion gear so as to rotatably support the pinion gear. A planetary gear device comprising: a pinion shaft that rotates; and a plurality of rollers that are rotatably arranged between an inner surface of a center hole of the pinion gear and an outer peripheral surface of the pinion shaft. A planetary gear device characterized in that a lubricating coating composed of a solid lubricant is coated on a portion having an area ratio of 75% or more.   2. The planetary gear device according to claim 1, wherein the lubricating coating has a thickness of 0.1 μm to 8 μm.   3. The indentation having a depth of 0.1 μm or more and 5 μm or less is formed in a portion of the rolling surface of the roller that is covered with the lubricating coating. 3. Planetary gear device.   Used in a planetary gear device comprising a sun gear located at the center, a ring gear concentrically arranged with the sun gear, and a pinion gear that meshes with the sun gear and the ring gear and revolves around the sun gear, the pinion gear being rotatable A rolling bearing to be supported, the outer surface of the pinion shaft inserted through the center hole of the pinion gear, the inner surface of the center hole of the pinion gear, and the outer surface of the pinion shaft and the inner surface of the center hole of the pinion gear And a roller having a lubricating film made of a solid lubricant is coated on a portion of the rolling surface of the roller that is 75% or more in area ratio. A rolling bearing characterized by   The rolling bearing according to claim 4, wherein the lubricating coating has a thickness of 0.1 μm or more and 8 μm or less.   6. The microrecess having a depth of 0.1 μm or more and 5 μm or less is formed in a portion of the rolling surface of the roller covered with the lubricating coating. Rolling bearing.

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