JP2005351292A - Planetary gear device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive planetary gear device capable of extending the life of a pinion shaft by the action of needle rollers. <P>SOLUTION: In this planetary gear device 10 rotatably supporting a pinion gear having the needle rollers disposed on the inner periphery thereof on the pinion shaft 15 fixed to a carrier 14, a residual austenite amount on the raceway surface 15a of the pinion shaft 15 is 15 to 40 vol.%. A steel having an Si content of 0.5 wt.% or more is used as the raw material of the needle rollers 15. After the raw material is carbonitrided and quenched, high temperature tempering is applied thereto. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a planetary gear device used for a reduction gear or a transmission of an automobile or a machine tool, and more particularly to a planetary gear device suitable for use at high temperature and high speed rotation.

  Planetary gear devices are used in various applications such as reduction gears and transmissions. For example, a planetary gear device used in an automatic transmission of an automobile includes a rotating element of a sun gear, a ring gear, and a carrier, and these rotating elements are arranged concentrically around an output shaft. In addition, a pinion gear meshing with the sun gear and the ring gear is rotatably supported by a pinion shaft fixed to the carrier via a needle roller so that lubricating oil is supplied to each rotating element by the centrifugal force of each rotation. An oil passage is provided.

  However, since the planetary gear device has a complicated structure in which the pinion gear revolves while rotating, it is difficult to sufficiently supply the lubricating oil to the pinion shaft that supports the pinion gear and the needle roller. there were. Moreover, since the rotational speed of the pinion gear is the highest among the rotating elements, a large load tends to be applied to the pinion shaft that supports the pinion gear to support the centrifugal force acting on the pinion gear.

  Also, as a method of fixing the pinion shaft to the carrier, there are a method of fixing by providing a hole for inserting a fixing pin at the end of the pinion shaft and a method of fixing by crimping the end of the pinion shaft. is there. However, in order to reduce the size of the transmission in order to reduce the fuel consumption of an automobile, it is considered more advantageous to fix the pinion shaft by crimping.

  For the above reasons, in the conventional planetary gear device, the pinion shaft is made of JIS steel grade SK5 or the like, and the portion where the needle roller rolls is subjected to induction hardening, which is necessary as a rolling member. Hardness (Hv650 or more) was given. Further, when the peeling life due to poor lubrication or the like becomes a problem, the pinion shaft is made of JIS steel type SUJ2 or the like, and is subjected to carbonitriding or the like to ensure the life.

  In recent years, demands for reducing the fuel consumption of automobiles are increasing, and transmissions are becoming smaller and more efficient. Therefore, since the rotation speed of the pinion gear is increased, the load applied to the pinion shaft and the temperature rise, and the amount of lubricating oil tends to decrease, leading to a reduction in the life of the pinion shaft.

  Furthermore, since the temperature increases as the load increases, plastic deformation occurs in the pinion shaft, and this deformation causes slippage between the needle roller and the pinion shaft, which is caused by wear on the raceway surface or surface roughness. Therefore, there is a growing demand for longer life due to the problem of early peeling.

  By the way, the plastic deformation of the shaft tends to relieve the stress acting on the shaft by being exposed to a high temperature in a state where the load is applied even if the applied load is a load in the range of elastic deformation. This is considered to be a phenomenon in which the shape of the shaft approaches, and the amount of plastic deformation tends to increase as the amount of retained austenite increases. For this reason, in order to suppress plastic deformation, it is most effective to reduce the amount of retained austenite as much as possible. However, if the amount of retained austenite in the raceway surface layer decreases, the rolling fatigue life characteristics deteriorate, and the required durability cannot be obtained.

  Therefore, conventionally, as a method for preventing plastic deformation of the shaft, the tempering treatment is performed after the carbonitriding treatment, and the surface austenite amount and hardness are increased by induction hardening only the surface layer. A method is known in which rolling fatigue life characteristics are improved and plastic deformation is prevented by setting the amount of retained austenite in the core to 0% by volume (see, for example, Patent Document 1).

In addition, as a countermeasure against the surface fatigue peeling of the needle roller due to the high speed rotation and the low viscosity of the lubricating oil, using the steel having a high content of Si and Mn, carbonitriding, quenching, A technique is known in which the amount of retained austenite on the surface portion is set to 20 to 50% by volume by performing a tempering treatment (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 2002-4003 JP 2000-234147 A

  However, in the method described in Patent Document 1, as the pinion shaft becomes thinner as the transmission becomes smaller, the ratio of the surface layer having a high residual austenite amount to the entire pinion shaft increases, and the average of the entire pinion shaft As a result of the amount of retained austenite being increased, the effect of suppressing plastic deformation may be reduced. Further, no consideration is given to fixing the end of the pinion shaft to the carrier by caulking.

  On the other hand, the method described in Patent Document 2 has a problem that even if the effect of extending the life of the needle roller is obtained, the effect of extending the life of the pinion shaft cannot be obtained.

  The present invention has been made to ameliorate such problems, and an object thereof is to provide a planetary gear device that can extend the life of a pinion shaft by the action of a needle roller at a low cost. It is in.

The above object of the present invention is achieved by the following configurations.
1) A planetary gear device according to the present invention is a planetary gear device that rotatably supports a pinion gear having a needle roller disposed on an inner periphery thereof on a pinion shaft fixed to a carrier. The retained austenite on the raceway surface of the pinion shaft The amount is 15 to 40% by volume, and steel having a Si content of 0.5% by weight or more is used as a material for the needle roller, and after carbonitriding and quenching, high temperature tempering is performed. It is characterized by.

  2) The planetary gear device according to the present invention is the planetary gear device described in 1) above, wherein the N concentration of the surface portion of the needle roller is 0.2% by weight or more.

  3) A planetary gear device according to the present invention is the planetary gear device described in 1) or 2) above, wherein the amount of retained austenite on the surface of the needle roller is less than 20% by volume. To do.

  4) The planetary gear device according to the present invention is the planetary gear device according to any one of 1) to 3) above, wherein the surface roughness of the needle roller is equal to that of the raceway surface of the pinion shaft. It is characterized by being smaller than the surface roughness.

  5) The planetary gear device according to the present invention is the planetary gear device according to any one of 1) to 4), wherein the needle roller has a high temperature tempering range of 200 ° C to 300 ° C. It is characterized by that.

  6) The planetary gear device according to the present invention is the planetary gear device according to any one of 1) to 5) above, wherein the amount of retained austenite at the center of the pinion shaft is 0% by volume. It is characterized by that.

  7) The planetary gear device according to the present invention is the planetary gear device according to any one of 1) to 6), wherein the surface hardness of the end of the pinion shaft is 300 HV or less. Features.

  According to the planetary gear device of the present invention, it is possible to withstand this use even if the size and weight are further reduced and the use conditions are increased in speed and temperature, and the planetary gear device has a long life. Can be provided at low cost.

  Embodiments according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is an exploded perspective view showing an embodiment of a planetary gear device according to the present invention, FIG. 2 is a structural diagram of a principal part of the planetary gear device, FIG. 3 is a component table of a test needle roller used in an endurance test, 4 is a schematic diagram of the test apparatus, FIG. 5 is a table showing the results of the durability test, and FIG. 6 is a table showing the results of the durability test.

  As shown in FIG. 1, a planetary gear device 10 according to an embodiment of the present invention includes a sun gear 11 through which a shaft (not shown) is inserted, a ring gear 12 arranged concentrically with the sun gear 11, the sun gear 11 and the ring gear 12. A plurality of (three in FIG. 1) pinion gears 13 and a carrier 14 that are arranged concentrically with the sun gear 11 and the ring gear 12 and rotatably support the pinion gear 13.

  The pinion gear 13 is supported by the carrier 14 via a pinion shaft 15 fixed to the carrier 14, and includes a plurality of rolling elements disposed between the outer peripheral surface of the pinion shaft 15 and the inner peripheral surface of the pinion gear 13. A needle roller 16 is rotatable about the pinion shaft 15 as an axis.

  The needle roller 16 is made by carbonitriding and quenching using steel having a Si (silicon) content of 0.5% by weight or more as a raw material, followed by high temperature tempering. Therefore, the life of the planetary gear device 10 as a whole can be extended by subjecting only the needle roller 16 to a carbonitriding process and high-temperature tempering using a material having an increased Si content.

  Further, the needle roller 16 is subjected to carbonitriding and quenching using steel having a Si content of 0.5% by weight or more, and then subjected to high temperature tempering. In addition, the needle roller 16 remains on the surface of the needle roller 16. The amount of austenite is less than 20% by volume. Therefore, by increasing the tempering temperature so that the amount of retained austenite on the surface of the needle roller 16 is less than 20% by volume, the life of the pinion shaft 15 that is the counterpart member can be more effectively extended.

  Further, the surface roughness of the needle roller 16 is set to be smaller than the surface roughness of the raceway surface 15 a of the pinion shaft 15. Thereby, the life of the mating member can be extended.

  Further, the needle roller 16 is tempered at a high temperature in the range of 200 ° C. to 300 ° C. after being carbonitrided and quenched using steel having a Si content of 0.5% by weight or more. Created. Thereby, the rolling element which suppresses the surface fatigue of the pinion shaft 15 can be created.

  The surface-fatigue-type peeling at the needle roller 16 is caused by indentation on the raceway surface 15a of the pinion shaft due to the inclusion of foreign matter mixed in the lubricating oil, and occurs due to stress concentration at the edge of the indentation, or pinion due to insufficient lubrication. It is considered that metal contact occurs between the raceway surface 15a of the shaft 15 and the surface of the needle roller 15 and a large tangential force acts on the raceway surface 15a.

  It is known that increasing the amount of retained austenite, which has a high effect of reducing stress concentration, is effective in preventing surface fatigue-type delamination, and also reduces the indentation caused by foreign object biting. Therefore, increasing the hardness is known to be effective for extending the life. However, until now, only members that have a problem with their lifetime have been attracting attention, and thus no consideration has been given to the effects on the lifetime of the mating member.

  As a result of intensive research on the rolling element, that is, the needle roller 16, in order to solve the above-mentioned problems, the material of the needle roller 16 is made of steel with an increased Si content and further subjected to appropriate heat treatment and the like. It has been found that damage to the raceway surface 15a of the pinion shaft 15 as a member is reduced, and as a result, the life of the pinion shaft 15 can be extended.

  Si is an element necessary as a deoxidizer during steel making, but it is an effective element for improving the tempering softening resistance of steel. Also, when carbon is subjected to carbonitriding, the nitrogen concentration in the surface portion is reduced. The effect of increasing is an element. As a result of experiments by the present inventor, steel having a Si content of 0.5% by weight or more is used for the material of the needle roller 16 and subjected to quenching after carbonitriding, and further tempered at a high temperature of 200 ° C. Thus, it was found that the effect of suppressing the surface fatigue of the pinion shaft 15 can be obtained. For this reason, the minimum of Si content shall be 0.5 weight%. In order to obtain the effect, a more preferable lower limit of the Si content is 0.8% by weight. In addition, if the content is too large, the machinability of the material may be reduced and the cost may be increased, so the upper limit of the Si content is preferably 2.0% by weight. More preferably, the upper limit of the Si content is 1.5% by weight.

  If the tempering temperature of the needle roller 16 is too low, the effect of extending the life of the pinion shaft 15 cannot be obtained sufficiently. This is considered to be because if the tempering temperature is too low, the amount of soft retained austenite increases, so that the real contact area with the pinion shaft 15 increases and damage due to friction increases, and the lower limit of the tempering temperature. Is 200 ° C. Preferably, the tempering temperature is increased so that the amount of retained austenite on the surface portion of the needle roller 16 is less than 20% by volume, and more preferably, the amount of retained austenite on the surface portion of the needle roller 16 is 18% by volume or less. If the tempering temperature is selected, the life of the pinion shaft 15 can be extended more effectively.

  On the other hand, if the tempering temperature is excessively increased, the life of the needle roller 16 is decreased due to the decrease in hardness and the amount of retained austenite, and the life as a bearing is decreased. Therefore, the upper limit of the tempering temperature is 300 ° C. To do. At this time, in order to prevent the life of the bearing from being reduced due to a decrease in the life of the needle roller 16, a tempering temperature is selected so that the amount of retained austenite on the surface of the needle roller 16 is 5% by volume or more. It is preferable to do. More preferably, the amount of retained austenite on the surface portion of the needle roller 16 is 8% by volume or more.

  Furthermore, since the effect of reducing damage to the pinion shaft 15 increases as the N concentration in the surface portion of the needle roller 16 is increased, the lower limit of the surface N concentration of the needle roller 16 is preferably 0.2% by weight or more. More preferably, the content is 0.3% by weight or more. However, if the N concentration is too high, the effect is saturated, and if it is excessively high, a brittle nitride layer may be formed, which may deteriorate the life characteristics of the bearing. % Is preferable.

  Further, the concentration of C (carbon) in the surface portion of the needle roller 16 added simultaneously with N (nitrogen) by carbonitriding is adjusted so that the hardness of the HRC 58 required as the needle roller 16 is obtained. There is a need to. For this reason, it is preferable to adjust the C concentration so that the total of the C concentration and the N concentration on the surface portion of the needle roller 16 is 0.8% by weight or more. More preferably, the C concentration of the surface portion is 0.8% by weight or more, and more preferably 1.0% by weight or more. However, if the C concentration of the surface portion of the needle roller 16 is too high, coarse carbides may be deposited, and the life characteristics of the needle roller 16 itself may be deteriorated. %, And more preferably 2.0% by weight or less.

  Note that the amount of retained austenite, nitrogen concentration, or carbon concentration on the outermost surface where metal contact with the pinion shaft is important is important for the purpose of reducing damage to the pinion shaft that is the object of the present invention. The surface portion means a range of at least 1 μm from the outermost surface.

Subsequently, alloy elements of materials other than Si will be described.
About the C content of the material,
C is an element necessary for improving the hardness after quenching and tempering by converting the base into martensite. In the surface portion of the needle roller 16 of the present invention, C can be added simultaneously with N by carbonitriding, so that the C content of the material requires the center of the needle roller 16 in a completed state. Since the amount is sufficient if the strength can be ensured, the lower limit of the C content of the material is preferably 0.30% by weight or more. The needle roller core hardness is more preferably 650 HV or more, and the C content of the material is more preferably 0.80 wt% or more. However, if the C content of the raw material is too large, coarse carbides may be generated at the steel making stage and the rolling fatigue characteristics may be reduced, so the upper limit is made 1.20% by weight.

About the Mn content of the material,
Mn (manganese) is an element necessary as a deoxidizing agent and a desulfurizing agent at the time of steelmaking, and is preferably contained in an amount of 0.15% by weight or more in order to sufficiently obtain the effect. Moreover, since Mn is an element effective for improving hardenability, it is more preferable to contain 0.25% by weight or more. However, if the content is too high, the non-metallic inclusions may increase so much that the life characteristics may deteriorate, and the machinability such as the forgeability and machinability of the material will decrease. The upper limit of the Mn content is 2.0% by weight. In addition, it is possible to adjust the amount of retained austenite by tempering at a lower temperature as the content of Mn is lower, and considering that heat treatment of a needle roller having a small diameter does not require so high hardenability, From the viewpoint of cost, the upper limit of the Mn content is preferably 0.7% by weight.

About the Cr content of the material,
Cr (chromium) is an element effective for improving hardenability and temper softening resistance, and has an effect of strengthening the base and improving rolling fatigue life characteristics. It also has the function of improving wear resistance by forming fine and high hardness carbides and carbonitrides. Furthermore, it has the effect of increasing the C concentration of the carbonitriding layer, and is an effective element for improving the carbonitriding characteristics. In order to fully exhibit these actions and effects, the lower limit of the Cr content is 0.5% by weight. However, even if it is added in a large amount, not only the effect is saturated, but also by forming a passive film on the surface, there is a possibility that the carbonitriding property may be inhibited, so the upper limit of Cr content is 2.0. It is preferable to set it as weight%.

About O content of material,
Since O (oxygen) forms oxide-based non-metallic inclusions that are harmful to the rolling fatigue life characteristics, it is necessary to reduce the content thereof as much as possible, and the upper limit of the content is preferably 12 ppm. More preferably, it is 9 ppm or less.

  In addition to the above alloy elements, impurity elements inevitable in steelmaking (for example, P (phosphorus), S (sulfur), Ni (nickel), Cu (copper), Mo (molybdenum), V (vanadium), Al (Aluminum), Ti (titanium), Nb (niobium), etc.) are naturally included. Further, carbide forming elements such as Mo and V are effective for improving wear resistance by forming fine and high hardness carbonitride by carbonitriding, and may be added in a trace amount as long as the cost permits. However, the upper limit of the amount added is preferably 2% by weight or less in total.

  In addition, surface fatigue delamination is a phenomenon that occurs on the surface of the pole, which is largely caused by insufficient formation of the lubricating oil film and metal contact, so the effect of the surface shape and roughness on the progress of fatigue. From the results of research conducted by the present inventor, in order to obtain the effect of extending the life of the bearing by the needle roller 16, the roughness of the rolling element surface (rolling surface) is determined by the pinion shaft 15. It is necessary to make it less than the roughness of the track surface 15a.

  According to the planetary gear device 10, the needle roller 16 is prepared by carbonitriding and quenching using steel having a Si content of 0.5% by weight or more and further tempering at high temperature. Therefore, the life of the entire bearing can be extended by subjecting only the needle roller 16 to a carbonitriding process and high-temperature tempering using a material having an increased Si content. Therefore, even when a raceway shaft having a complicated shape that is difficult to apply long-life material heat treatment due to manufacturing problems and cost problems is used as an inner ring, the long-life planetary gear device 10 is inexpensive. It becomes possible to provide.

  Further, according to the planetary gear device 10, the needle roller 16 is subjected to carbonitriding and quenching using steel having a Si content of 0.5% by weight or more, followed by further high-temperature tempering and addition. Thus, the amount of retained austenite on the surface portion of the needle roller 16 is less than 20% by volume. If the tempering temperature of the needle roller 16 is too low, the effect of extending the life of the counterpart material cannot be obtained sufficiently. This is because when the tempering temperature is too low, the amount of soft retained austenite increases, and the real contact area with the pinion shaft 15 increases and damage due to friction increases. On the other hand, if the tempering temperature is too high, the life of the needle roller 16 is reduced due to the decrease in hardness and the amount of retained austenite, and the life as a bearing is reduced. Therefore, the life of the pinion shaft can be more effectively extended by increasing the tempering temperature so that the amount of retained austenite on the surface of the needle roller 16 is less than 20% by volume.

  According to the planetary gear device 10, the surface roughness of the needle roller 16 is set to be smaller than the surface roughness of the raceway surface 15 a of the pinion shaft 15. If the surface roughness of the needle roller 16 is larger than the surface roughness of the raceway surface of the pinion shaft 15, the effect of extending the life of the pinion shaft 15 is reduced and the life ratio is lowered. However, the life ratio is lower than the surface roughness of the pinion shaft 15. Therefore, the life of the pinion shaft 15 can be extended.

  Moreover, according to the planetary gear apparatus 10, after the needle roller 16 is carbonitrided and quenched using steel having a Si content of 0.5% by weight or more as a raw material, the needle roller 16 is further heated to 200 ° C to 300 ° C. The needle roller 16 as a rolling element that suppresses surface fatigue of the pinion shaft 15 can be created by tempering at a high temperature in the range of.

In order to confirm the operation and effect of the planetary gear device 10 of the present invention, the following durability test was performed.
(Durability test 1)
First, as shown in FIG. 3, 18 kinds of needle rollers A to R were prepared by combining a plurality of main chemical components, and an endurance test was performed using the test apparatus 100 shown in FIG. 4.

  As shown in FIG. 4, the test apparatus 100 includes a support bearing (not shown) on an outer ring (corresponding to the pinion gear 12) rotatably supported by the pinion shaft 101 by arranging a needle roller 110 on the inner periphery. Rotate while applying a load. At this time, after the pinion shaft 101 is formed using JIS steel type SUJ2 as a material, carbonitriding and annealing are performed to completely decompose the retained austenite of the entire pinion shaft 101 and at the same time, adjust the hardness to 300 HV or less. Further, the surface hardness of the track surface was adjusted to 700 HV to 850 HV and the amount of retained austenite was adjusted to 15 to 30% by volume by subjecting only the track surface portion to induction hardening and then tempering. In this way, the amount of retained austenite in the core is set to 0% by volume so that the plastic deformation during use is minimized, and the ends not subjected to induction hardening are hardened at 300 HV or less, which can be easily caulked. Furthermore, the finishing process was further performed so that the surface roughness of the raceway surface was 0.10 to 0.15 Ra, and it was used for the test as an invention example and a comparative example.

  In addition, the pinion shaft of the conventional example is adjusted to a hardness of 650 HV to 800 HV by subjecting the raceway surface portion to induction hardening and tempering after being formed using JIS steel type SK5 as a material, and the surface roughness of the raceway surface. Was subjected to finishing so as to be 0.10 to 0.15 Ra and used for the test. The outer ring is formed using JIS steel type SUJ2 as a raw material, and then the surface hardness of the raceway surface is adjusted to 700 HV to 800 HV by quenching and tempering, and the surface roughness of the raceway surface is 0.10 to 0 Finishing was performed so as to be 15 Ra and used for the test.

In the test, the time until peeling occurred was evaluated under the conditions of a radial load of 4 kN, a rotation speed of 8000 min ⁻¹ , and an oil temperature of 150 ° C. The used needle roller 110 has an outer diameter of 2 mm, and the pinion shaft has an outer diameter of 8 mm. Before the endurance test, grease containing 300 ppm of iron powder in advance was sealed in the bearing and operated for 10 minutes. After forming indentations on the raceway surface and rolling surface, cleaning was performed before use. The surface fatigue type peel life was evaluated.

The result of the durability test 1 is as shown in FIG. The needle rollers used as examples (invention examples) and comparative examples were subjected to the heat treatment shown in (a) or (b) below, and the surface roughness was 0.05 to 0.08 Ra. It was produced by performing a finishing process.
(Heat treatment conditions)
The heat treatment conditions in the durability evaluation are as follows.
(A): Carbon nitriding treatment at 800 ° C. to 860 ° C. × 2 to 6 hours, quenching, and tempering at 150 ° C. to 350 ° C. in an atmosphere of Rx gas + propane gas + ammonia gas.
(A): Heating to 800 ° C. to 860 ° C. in an Rx gas atmosphere, followed by quenching, and tempering at 150 ° C. to 300 ° C.

  In the test results shown in FIG. 5, the heat treatment type, tempering temperature, surface nitrogen concentration, surface carbon concentration, surface hardness and surface residual austenite amount (γR) of each test piece (needle roller) are combined. Show. The surface carbon concentration and nitrogen concentration are measured using an electron beam microanalyzer (EPMA), and quantitative analysis is performed from the outermost surface of the needle roller cross-section that has been mirror-polished to the center. The carbon concentration and nitrogen concentration were read. Further, the surface hardness was measured by using a Vickers hardness meter, and the amount of retained austenite was measured by directly measuring the surface of the needle roller using X-ray diffraction injection.

The test results in FIG. The lifetime of 18 is shown as a ratio in the case of 1. As is apparent from the test results of FIG. 5, it can be seen that all of the examples of the present invention have a lifetime that is three times longer than the conventional one.
No. which is a comparative example. No. 19 is a case where carbonitriding treatment is applied to the JIS steel type SUJ2 that has been used conventionally. 20 is Comparative Example No. This is a case where the tempering temperature of 19 is increased, but since the Si content is too low, the effect of extending the life of the mating member cannot be obtained, and the effect of extending the life is low.
Comparative Example No. 21 is an example of the present invention. This is a case where the tempering temperature of No. 1 is lowered to increase the amount of retained austenite on the surface, but the amount of retained austenite on the surface is too high, and it is considered that the life extension effect is lowered.
Comparative Example No. No. 22 has a low tempering temperature, and as a result, the life of the needle roller is reduced, so that the effect of extending the life is low.
Comparative Example No. No. 23 has not been subjected to carbonitriding, so the effect that the needle roller extends the life of the mating member is not obtained.

(Durability test 2)
Next, as shown in FIG. No. 1 was changed in the finishing process conditions to change the surface roughness. 24, no. 25, no. The effect of surface roughness on the surface fatigue-type peel life characteristics was evaluated by performing bearings using 26 types of needle rollers in the same manner as in the durability test 1.

The result of the durability test 2 is as shown in FIG.
If the surface roughness of the needle roller, which is a rolling element, increases, the effect of extending the life of the pinion shaft that is the counterpart member is reduced, so the life ratio decreases, but if the surface roughness of the pinion shaft is less than or equal to It can be seen that the effect can be sufficiently obtained. The smaller the surface roughness of the needle roller, the better. However, if the roughness of the needle roller (pinion shaft) is not larger than that of the mating roller, a sufficient effect can be obtained. As shown in FIG. 1, it has been found that the effect can be sufficiently obtained when 0.08 Ra or less.

  In addition, this invention is not limited to the said Example, In the range which does not deviate from the summary of this invention, it can change suitably. For example, in the embodiment, the test is performed with all rollers, but the same effect can be obtained with a cage roller with a cage. Moreover, although the example showed the example which tested the needle roller in 1 row, the same effect is acquired also in the planetary gear apparatus which has arranged the needle roller of the multiple rows. Further, it is possible to include improvements that can be easily made, such as changing the position and size of the oil hole of the pinion shaft.

It is a disassembled perspective view which shows one Embodiment of the planetary gear apparatus of this invention. It is principal part structure sectional drawing of a planetary gear apparatus. It is a component table | surface of the needle roller for a test used for the durability test. It is the schematic of a test apparatus. It is a table | surface which shows the result of an endurance test. It is a table | surface which shows the result of an endurance test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Planetary gear apparatus 11 Sun gear 12 Ring gear 13 Pinion gear 14 Carrier 15 Pinion shaft (counter member)
15a Track surface 16 Needle roller (rolling element)

Claims (7)

In a planetary gear device that rotatably supports a pinion gear having a needle roller on its inner periphery on a pinion shaft fixed to a carrier,
The amount of retained austenite on the raceway surface of the pinion shaft is 15 to 40% by volume, and steel containing 0.5% by weight or more of Si is used as a material for the needle roller, and carbonitriding and quenching are performed. A planetary gear device characterized by further high-temperature tempering.   2. The planetary gear device according to claim 1, wherein the N concentration of the surface portion of the needle roller is 0.2% by weight or more.   The planetary gear device according to claim 1 or 2, wherein the amount of retained austenite on the surface portion of the needle roller is less than 20% by volume.   The planetary gear device according to any one of claims 1 to 3, wherein a surface roughness of the needle roller is smaller than a surface roughness of a raceway surface of the pinion shaft.   The planetary gear device according to any one of claims 1 to 4, wherein high-temperature tempering of the needle roller is in a range of 200 ° C to 300 ° C.   The planetary gear device according to any one of claims 1 to 5, wherein the amount of retained austenite at the center of the pinion shaft is 0% by volume.   The planetary gear device according to any one of claims 1 to 6, wherein a surface hardness of the end portion of the pinion shaft is 300 HV or less.

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