JP2006161887A - Needle roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a needle roller bearing having a longer service life while effectively suppressing the occurrence of smearing, seizure, wear or peeling due to insufficient oil films formed between members. <P>SOLUTION: The needle roller bearing comprises an outward member 51 having a raceway surface 52 on the inner peripheral face, an inward member 53 having a raceway surface 54 on the outer peripheral face, and a plurality of needle rollers 11 rollingly inserted between the raceway surface 52 of the outward member 51 and the raceway surface 54 of the inward member 53. Lubricating oil is filled in gap spaces formed between each of the raceway surfaces 52, 54 and each of the needle rollers 11. In at least either one of the inward member 53 or the needle roller 11, a recessed portion is formed at a depth of 0.05-8.0μm and further covered with a solid lubricant. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a needle roller bearing that is used in a high temperature or high speed environment, and more particularly to a needle roller bearing that is highly functional and suitable for engines, transmissions, and the like of automobiles, construction machines, and agricultural machines.

  Conventionally, needle roller bearings have a characteristic that the ratio of the outer diameter to the inner diameter is small, that is, the bearing has a relatively large load capacity for a thin wall bearing. Widely used for load parts.

  Among such needle roller bearings, in a planetary gear needle roller bearing that supports planetary gears widely used in transmissions and the like, force is smoothly transmitted from the planetary gears as outer members. In general, since a helical gear is used, the traveling trace of the planetary gear shaft corresponding to the inner member is twisted due to the force relationship. For this reason, non-uniform force acts on the needle rollers arranged between the planetary gear and the planetary gear shaft to cause edge load, skew, etc., resulting in reduced life, smearing and seizure. Is likely to occur.

  For this reason, conventionally, the needle rollers are crowned to reduce the edge load, and in order to prevent skew, the circumferential gap and radial gap are precisely managed to prevent the occurrence of skew. I have made some measures to suppress it.

Another problem is that from the viewpoint of improving fuel efficiency associated with CO ₂ emission regulations, seizure resistance at high speed rotation, or lean lubrication, combined with lower viscosity of the lubricating oil to increase rotational efficiency at high speed rotation. There is an increasing demand for improved durability below.

  Here, in order to ensure the lubricity of the conventional needle roller bearing in such an application, for example, the needle rollers are double-rowed, and up to the position between the needle rollers of the planetary gear shaft corresponding to the inner member. It is considered that an oil hole is provided from the shaft end and oil is supplied through the shaft hole. However, when the amount of oil is insufficient, peeling damage occurs on the transfer surface.

  As an example of the needle roller bearing which prevents this peeling damage, the ratio of the axial surface roughness RMS (L) to the circumferential surface roughness RMS (C), RMS (L) / RMS (C) is 1. There has been proposed a needle roller bearing in which the parameter SK value indicating the degree of distortion of the distribution curve of the surface roughness is negative, and the surface area ratio occupied by the depressions is 10 to 40%. (For example, refer to Patent Document 1).

Further, as another example of a conventional needle roller bearing, a shot peening apparatus is used to project a molybdenum disulfide projection material containing about 95% by weight or more of molybdenum disulfide having an average particle diameter of about 1 μm to about 20 μm, and a projection speed of 100 m. Needle roller bearings using surface modification technology that projects at / S or higher are known (see, for example, Patent Document 2).
Japanese Patent No. 2634495 (page 2-4, FIG. 1) JP 2002-339083 A (page 3)

  However, in the conventional needle roller bearing described in Patent Document 1, the ratio of the axial surface roughness RMS (L) to the circumferential surface roughness RMS (C), RMS (L) / RMS (C ) Is 1.0 or less, the parameter SK value indicating the degree of distortion of the distribution curve of the surface roughness is negative, and the surface area ratio occupied by the depressions is 10 to 40%. We are trying to achieve a long life for a certain peeling, but if only the oil sump with only minute recesses is used, and if the viscosity of the lubricant further decreases in the future, smearing, seizure, abrasion, peeling, etc. Can happen.

  Further, in the needle roller bearing described in Patent Document 2, a shot peening apparatus using a molybdenum disulfide projecting material containing about 95% by weight or more of molybdenum disulfide having an average particle diameter of about 1 μm to about 20 μm is used. Projection is performed at a projection speed of 100 m / s or more. However, when the solid phase is hard by simply projecting a soft solid lubricant, it is mechanically coupled with scientific bonds and anchor effects. Since the meshing is weak, the solid lubricant easily falls off and a sufficient effect cannot be obtained.

  Thus, in addition to the structure in which the lubricant is difficult to be supplied in the needle roller bearing, in recent years, there has been a demand for further increase in the maximum rotational speed of the planetary gear due to downsizing of the transmission or CVT. Along with this, the use temperature is considered to rise. In addition, with miniaturization, defects such as smearing, seizure, wear, and peeling have become more prominent than ever.

  Accordingly, the inventors of the present application have conducted intensive studies on a technique for extending the service life that can suppress smearing, seizure, wear, peeling, and the like under dilute lubrication while ensuring a rolling service life. As a result, smearing, seizure, and wear in the case where oil film formation is insufficient by forming a recess in at least one of the planetary gear shaft and the needle roller and covering with a solid lubricant rather than the planetary gear. And it has been found that there is an effect of suppressing peeling and the like.

  And when oil film formation is inadequate, when the mechanism of smearing, seizure, wear, peeling, etc. is applied to the needle rollers of radial needle roller bearings, only mechanical processing such as barrel processing and shot peening It has been found that initial familiarity occurs abruptly, thereby causing defects such as smearing, seizure, wear and peeling. As a countermeasure, the present inventors have found that the only means is to reduce the friction coefficient and coat the solid lubricant.

  The present invention has been made to remedy such problems, and its purpose is to effectively suppress smearing, seizure, abrasion, peeling, and the like caused by insufficient oil film formation between the members. Therefore, an object of the present invention is to provide a needle roller bearing that can extend the life.

The above object of the present invention can be achieved by the following constitution.
(1) An outer member having a raceway surface on the inner peripheral surface, an inner member having a raceway surface on the outer peripheral surface, and a rollable between the raceway surface of the outer member and the raceway surface of the inner member. A plurality of needle rollers inserted in the
A needle roller bearing in which a gap space formed between the raceway surface and the needle roller is filled with lubricating oil,
A needle roller bearing, wherein a recess having a depth of 0.05 to 8.0 μm is formed on at least one of the inner member or the needle roller, and further a solid lubricant is coated thereon.
(2) The needle roller bearing according to (1), wherein the concave portion coated with the solid lubricant has a raceway center line average roughness of R = 0.10 to 0.50 μmRa.
(3) The needle roller bearing according to (1) or (2), wherein the concave portion that covers the solid lubricant has a raceway surface hardness of HRC58 or higher.
(4) The needle-shaped member according to any one of (1) to (3), wherein the outer member is a planetary gear included in a planetary gear mechanism, and the inner member is a planetary gear shaft. Roller bearing.

  According to the needle roller bearing of the present invention, a recess having a depth of 0.05 to 8.0 μm is formed on at least one of the inner member and the needle roller, and further, the solid lubricant is coated. It is possible to effectively suppress smearing, seizure, wear, peeling, and the like that occur due to insufficient oil film formation between the members, thereby extending the life of the bearing.

  Hereinafter, an embodiment according to a needle roller bearing of the present invention will be described with reference to the drawings.

  1 is a sectional view of a needle roller bearing according to an embodiment of the present invention, FIG. 2 is a partially cutaway side view of an automatic transmission using the needle roller bearing shown in FIG. 1, and FIG. 3 is a needle roller bearing. 4 is an exploded perspective view of the planetary gear mechanism in which is incorporated, FIG. 4 is a cross-sectional view of the planetary gear in the planetary gear mechanism shown in FIG. 3, FIGS. 5 to 8 are operation explanatory views of the planetary gear mechanism shown in FIG. FIG. 10 is a distribution diagram showing the relationship between the average roughness and the life ratio at the center line of the raceway surface.

  As shown in FIG. 1, a needle roller bearing 10 according to an embodiment of the present invention includes a plurality of needle rollers 11 that roll on a raceway surface, and a cage 12 that holds the needle rollers 11 in a rollable manner. And a cage and roller type needle roller bearing.

  The needle roller bearing 10 includes a raceway surface 52 that the needle roller 11 has on an inner peripheral surface of a planetary gear (outer member) 51 of a planetary gear mechanism (shown in FIG. 3), and a planetary gear of the planetary gear mechanism 50. The shaft (inner member) 53 is interposed between the raceway surface 54 on the outer peripheral surface of the shaft 53 and the shaft (inner member) so as to be freely rollable. Moreover, the holder | retainer 12 hold | maintains the needle rollers 11 so that rolling is possible in the pocket 13 provided with two or more in the circumferential direction.

  The planetary gear shaft 53 is formed with a concave portion forming surface 55 having a concave portion having a depth of 0.05 to 8.0 μm on the surface, and the concave portion forming surface 55 has an average roughness of the raceway center line of R = 0.10. The hardness of the orbital surface is set to HRC58 or higher at ˜0.50 μmRa. Then, a solid lubricant is coated on the recess forming surface 55 in the gap space formed between the raceway surface 54 of the planetary gear shaft 53 and the needle roller 11.

  Here, the critical significance that the depth of the concave portion of the concave portion forming surface 55 is 0.05 to 8.0 μm is that when the solid lubricant is coated on the surface, if there is a concave portion, the solid lubricant is filled. be able to. Thereby, it shows a long life tendency as compared with the case where only the surface is coated. In order to obtain this effect, at least the depth of the recess is not more than 0.05 μm. On the other hand, if the depth of the recess exceeds 8.0 μm, this effect is saturated, so the thickness is made 10 μm or less. Moreover, in order to make the said effect | action more reliable, a more preferable range is 0.1-4.0 micrometers.

  In addition, the critical significance that the average roughness of the raceway surface center line of the concave surface 55 of the planetary gear shaft 53 is R = 0.10 to 0.50 μmRa is that a sufficient oil film is provided in a general rolling bearing. In order to ensure, it is well known that the track surface center line roughness is processed to be as low as possible. Therefore, for the purpose of forming a concave portion and filling the concave portion with a solid lubricant, the roughness is set to 0.10 μm or more, which is rougher than the raceway center line roughness of a normal rolling bearing. On the other hand, when the average roughness of the raceway center line is too rough, not only is this action saturated, but also the vibration increases, so the upper limit was made 0.50 μm. Moreover, in order to make the said effect | action more reliable, a more preferable range is 0.15-0.35 micrometer Ra.

  The planetary gear shaft 53 was made from JIS steel type SUJ2. And after carburizing or carbonitriding, quenching and tempering are performed, the total content of carbon concentration and nitrogen concentration on the finished product surface is 1.0% or more and 2.5 or less, and the hardness is HRC60 or more, The amount of retained austenite is 15% or more and 45% or less.

The recess forming surface 55 is produced by barreling the planetary gear shaft 53 and projecting a steel ball by shot peening. The shot peening injection conditions are an injection pressure of 5.0 kg / cm ² , an injection speed of 150 m / sec, and an injection time of 15 minutes. A steel ball having an average particle diameter of 45 μm according to JIS 6001 was used as the media under this condition, but it is not limited to a steel ball as long as the same concave portion can be formed. SiC, SiO ₂ , AI ₂ O ₃ , glass beads You may use shot agents, such as.

  Solid lubricants include industrial materials such as polyethylene, fluororesin, nylon, polyacetal, polyolefin, polyester, PTFE, metal soap, molybdenum disulfide, WS2, BN, graphite, calcium fluoride, barium fluoride, tin, tin alloy, etc. Is used. It is more preferable to select a material that is friendly to the global environment from these industrial materials.

The coating film of the solid lubricant is formed by shot peening. The injection conditions of this shot peening are an injection pressure of 5.0 kg / cm ² , an injection speed of 150 m / sec, and an injection time of 20 minutes. In this embodiment, shot peening is used as a method of forming a solid lubricant film, but the present invention is not limited to this. Other methods include thermoplastics such as solid lubricant and paraffin wax. There are a method of kneading a resin with high heat to obtain a semi-molten liquid, coating and baking, and a method of performing barrel processing as a pre-processing, and then filling a solid lubricant by plastic deformation.

  The needle roller bearing 10 of the present invention is incorporated in the planetary gear mechanism 50 and mounted on the automatic transmission 70 as shown in FIG. In the automatic transmission 70, torque output from an engine (not shown) is transmitted via a converter (not shown), and further decelerated to a plurality of stages via a planetary gear mechanism 50 combined in a plurality of rows. To a drive train (not shown) connected to the drive train (not shown).

  Next, the planetary gear mechanism 50 in which the needle roller bearing 10 of the present invention is incorporated will be described with reference to FIGS.

  As shown in FIG. 3, the planetary gear mechanism 50 includes a sun gear 56 through which a rotation shaft (not shown) is inserted, an internal gear 57 arranged concentrically with the sun gear 56, and the sun gear 56 and the internal gear. Three planetary gears 51 that mesh with the gears 57 and a carrier 58 that rotatably supports the planetary gears 51 and that is arranged concentrically with the sun gear 56 and the internal gear 57 are provided.

  As shown in FIG. 4, the planetary gear 51 is supported by the carrier 58 via a planetary gear shaft 53 fixed to the carrier 58, and the outer peripheral surface of the planetary gear shaft 53 and the inner peripheral surface of each planetary gear 51. The needle roller bearings 10 arranged between them are rotatable about the planetary gear shaft 53. Further, the planetary gear shaft 53 is provided with a lubricating oil supply hole 59 in the central portion in the radial direction, and the lubricating oil injected into the opening 60 on the end face rolls from the oil supply hole 59 opening in the cylindrical surface. Refueled on the surface.

  As shown in FIG. 5, the three planetary gears 51 arranged equally around the sun gear 56 mesh with internal gears 57 arranged around them. Here, when the automatic transmission 70 selects the first speed, the sun gear 56 is set to the drive side, the planetary gear 51 and the carrier 58 are set to the driven side, and the planetary gear 57 is fixed by fixing the internal gear 57. A large reduction ratio can be obtained from 51 and the carrier 58.

  As shown in FIG. 6, when the second transmission is selected for the automatic transmission 70, the sun gear 56 is fixed, the planetary gear 51 and the carrier 58 are driven and revolved, and the internal gear 57 is set to the drive side. Thus, a moderate reduction ratio can be obtained.

  As shown in FIG. 7, when the automatic transmission 70 selects the third speed, the sun gear 56 is fixed, the planetary gear 51 and the carrier 58 are on the drive side, and the internal gear 57 is on the driven side. Thus, a small reduction ratio can be obtained.

  As shown in FIG. 8, when the automatic transmission 70 is selected to move backward, the sun gear 56 is set to the driven side, the planetary gear 51 and the carrier 58 are fixed, and the internal gear 57 is set to the drive side. Thus, an output reversed with respect to the input can be obtained.

  Therefore, according to the needle roller bearing 10, the recess forming surface 55 having a recess with a depth of 0.05 to 8.0 μm formed on the planetary gear shaft 53 is covered with the solid lubricant, so that the lubrication path Is insufficient, or when low-viscosity lubricating oil is used, and when high-speed rotation and miniaturization are required, smearing, seizure, Wear and peeling can be effectively suppressed to extend the life of the bearing.

  Moreover, according to the needle roller bearing 10, since the raceway centerline average roughness of the recessed part formation surface 55 which coat | covers a solid lubricant is set to R = 0.10-0.50 micrometerRa, between each member. A sufficient oil film can be formed. Thereby, smearing, seizure, wear, peeling, and the like can be effectively suppressed, and the life of the bearing can be extended.

  Further, according to the needle roller bearing 10, since the hardness of the raceway surface 55 of the recess forming surface 55 to be coated with the solid lubricant is set to HRC58 or more, the lubrication path is not sufficiently secured or the low viscosity lubrication is performed. When oil is used, it is possible to effectively suppress smearing, seizure, abrasion, peeling, etc. that are likely to occur due to insufficient oil film formation between each member when high speed rotation and miniaturization are required. The life of the bearing can be extended.

  Furthermore, according to the needle roller bearing 10, the concave surface 55 having a depth of 0.05 to 8.0 [mu] m formed on the planetary gear shaft 53 is covered with the solid lubricant, so that the planetary gear In the automatic transmission 70 incorporating the mechanism 50, smearing, seizure, wear, peeling, and the like, which are caused by insufficient oil film formation, are effectively suppressed, and a long life is achieved to achieve the automatic transmission 70. Can improve the quality.

Below, the endurance test of the planetary gear mechanism 50 incorporating the needle roller bearing 10 performed for confirming the effect of the needle roller bearing 10 of the present invention will be described.
For this endurance test, planetary gear shafts with an outer diameter of 12.2 mm and a length of 28.2 mm were prepared. As a comparative example, two types of planetary gear shafts having different recess depths, raceway centerline average roughness, and hardness were used. In addition, these planetary gear shafts are formed by turning a steel material to a predetermined size, and then carburizing in an atmosphere of Rx gas + enriched gas for about 3 to 5 hours at 820 to 850 ° C. Was performed in an atmosphere of Rx gas + enrich gas + ammonia gas 5% for about 3 to 5 hours at 820 to 850 ° C., followed by quenching and tempering at a predetermined temperature. Further, it was manufactured by performing finish grinding.

  In the durability test method, needle rollers having an outer diameter of 2 mm and a length of 15 mm were interposed between the raceway surface of the planetary gear and the raceway surface of the planetary gear shaft so as to be freely rollable. Then, the planetary gear shaft was rotated under the conditions of a radial load of 4200 N, a rotational speed of 10,000 rpm, and a lubricating oil temperature of 150 ° C., and the time until peeling and seizure occurred was evaluated as the lifetime. An outer ring may be used instead of the planetary gear. The radial load was applied to the planetary gear through a support bearing (not shown). The numerical value of the life ratio is shown as a relative value when the test result of Comparative Example 1 is 1. The temperature of the supplied lubricating oil is 150 ° C., but the temperature of the planetary gear shaft under test is estimated to be about 10 ° C. higher due to heat generation. In the evaluation, the operation was continued under the above conditions, and when the vibration was twice the initial vibration, the life was determined when the bearing temperature rapidly increased and reached 185 ° C.

  As is apparent from Table 1, as a result of the durability test, Example 1 in which the depth of the concave portion is 0.05 μm, the raceway center line average roughness is 0.08 Ra, and the hardness is 61 HRC has a life ratio of 3.8. Example 2 in which the depth of the concave portion is 0.05 μm, the average roughness of the raceway surface center line is 0.1 Ra, and the hardness is 61 HRC, the life ratio becomes 5, the depth of the concave portion is 0.07 μm, In Example 3 in which the raceway centerline average roughness is 0.2 Ra and the hardness is 59 HRC, the life ratio is 7, the depth of the recess is 0.1 μm, the raceway centerline average roughness is 0.15 Ra, In Example 4 where the hardness is 61 HRC, the life ratio is 8.7, the depth of the recess is 0.5 μm, the average roughness of the raceway center line is 0.2 Ra, and the Example 5 where the hardness is 61 HRC is The life ratio became 10.

  Further, in Example 6 in which the depth of the concave portion is 2 μm, the average roughness of the raceway surface center line is 0.25 Ra, and the hardness is 62 HRC, the life ratio is 10, the depth of the concave portion is 4 μm, and the average average length of the raceway surface centerline. Example 7 with a roughness of 0.35 Ra and a hardness of 58 HRC has a life ratio of 7.5, a recess depth of 5 μm, a raceway centerline average roughness of 0.36 Ra, and a hardness of 61 HRC. In Example 8, the life ratio was 6, and in Example 9 in which the depth of the concave portion was 8 μm, the raceway center line average roughness was 0.5 Ra, and the hardness was 62 HRC, the life ratio was 4. In contrast, Comparative Example 2 in which the depth of the concave portion is 10 μm, the average roughness of the raceway center line is 0.6 Ra, and the hardness is 62 HRC has a life ratio of 1.2. Thus, since the depth of the recessed part in the planetary gear shaft according to the present invention of Examples 1 to 9 is in the range of 0.05 μm to 8.0 μm, it has a much longer life trend than Comparative Examples 1 and 2. showed that. Moreover, since the planetary gear shafts according to the present invention in Examples 1 to 9 have a raceway centerline average roughness in the range of 0.1 to 0.5 Ra, it is more likely to exhibit a longer life trend than in Example 1. This is evident by comparison with Examples 2-9.

  Next, as shown in FIG. 9, as a result of investigating the relationship between the depth of the recess and the life ratio, the portion where the depth of the recess of the recess forming surface 55 is in the range of 0.05 μm to 8.0 μm has a markedly long life trend. It is shown that the depth of the concave portion of the concave portion forming surface 55 is preferably in the range of 0.1 μm to 4.0 μm.

  Subsequently, as shown in FIG. 10, as a result of investigating the relationship between the raceway centerline average roughness and the life ratio, the portion where the raceway centerline average roughness is 0.1 to 0.5 Ra has a tendency to have a longer life. Show. More preferably, it is understood that the range of the raceway center line roughness is 0.15 to 0.35.

  Therefore, according to the needle roller bearing 10 of the present invention, the concave portion forming surface 55 having a concave portion with a depth of 0.05 to 8.0 μm formed on the planetary gear shaft 53 is coated with the solid lubricant, Since the raceway surface center line average roughness of the recess forming surface 55 is set to R = 0.10 to 0.50 μmRa, and the hardness of the raceway surface is set to HRC58 or higher, a sufficient lubrication path may not be secured. When low-viscosity lubricating oil is used, and when high-speed rotation and miniaturization are required, smearing, seizure, abrasion, peeling, etc. that are likely to occur due to insufficient oil film formation between each member are effective. It can be seen that a long life of the bearing can be achieved by suppressing the above.

In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably.
For example, the present invention can be applied to a needle roller bearing of a shell type, a solid type, or the like, instead of a cage & roller type composed of a needle roller and a cage as illustrated as a needle roller bearing. good.
The recess forming surface 55 is formed by barrel processing and shot peening, but may be formed by a processing method using a laser processing machine.

  In this embodiment, the concave member is formed and the solid lubricant is covered with the planetary gear shaft that is an inner member. However, the member may be applied to needle rollers instead of the planetary gear shaft. The present invention may be applied to both planetary gear shafts and needle rollers. Thereby, the lifetime can be further extended.

It is a needle roller bearing which is one embodiment concerning the present invention. FIG. 2 is a partially cutaway side view of an automatic transmission using the needle roller bearing shown in FIG. 1. It is a disassembled perspective view of the planetary gear mechanism in which the needle roller bearing is incorporated. It is sectional drawing of the planetary gear in the planetary gear mechanism shown in FIG. It is operation | movement explanatory drawing of the planetary gear mechanism shown in FIG. It is operation | movement explanatory drawing of the planetary gear mechanism shown in FIG. It is operation | movement explanatory drawing of the planetary gear mechanism shown in FIG. It is operation | movement explanatory drawing of the planetary gear mechanism shown in FIG. It is the distribution map which showed the relationship between the depth of a recessed part, and a lifetime ratio. It is the distribution map which showed the relationship between the average roughness in a track surface centerline, and a life ratio.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Needle roller bearing 11 Needle roller 12 Cage 13 Pocket 50 Planetary gear mechanism 51 Planetary gear (outer member)
52 orbital surface 53 planetary gear shaft (inner member)
54 Track Surface 56 Sun Gear 57 Internal Gear 58 Carrier 59 Refueling Hole 60 Opening 70 Automatic Transmission

Claims (4)

An outer member having a raceway surface on the inner peripheral surface, an inner member having a raceway surface on the outer peripheral surface, and a rollable insert between the raceway surface of the outer member and the raceway surface of the inner member A plurality of needle rollers,
A needle roller bearing in which a gap space formed between the raceway surface and the needle roller is filled with lubricating oil,
A needle roller bearing, wherein a recess having a depth of 0.05 to 8.0 μm is formed on at least one of the inner member and the needle roller, and further a solid lubricant is coated thereon.   2. The needle roller bearing according to claim 1, wherein the concave portion coated with the solid lubricant has a raceway centerline average roughness of R = 0.10 to 0.50 μmRa.   3. The needle roller bearing according to claim 1, wherein a hardness of a raceway surface of the concave portion to be coated with the solid lubricant is HRC58 or more.   The needle roller bearing according to any one of claims 1 to 3, wherein the outer member is a planetary gear included in a planetary gear mechanism, and the inner member is a planetary gear shaft.

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