JP2006118575A - Rolling bearing for windmill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing for a windmill for achieving a longer life by giving less damage to the surface of another member when used in the rotation supporting part of the windmill under the conditions of high load, vibration/impact load, non-load and acceleration/deceleration. <P>SOLUTION: The rolling bearing for the windmill to be used in the rotation supporting part of the windmill comprises a plurality of rolling elements 3 rollingly arranged between an inner ring 1 and an outer ring 2. Si content in the rolling element 3 is 0.5 wt% or more and the amount of austenite residing on the surface of the rolling element 3 is less than 20 vol%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rolling bearing for a wind turbine that is suitably used for a rotation support portion of a rotor of a wind turbine or a speed increaser disposed between a wind turbine blade and a generator.

FIG. 2 shows a propeller type windmill which is an example of a windmill. This windmill 30 is a tower in which a blade 51 for receiving wind energy, a rotor 52, a housing 53, and a housing 53 are installed at a height of about 50 m above the ground. As shown in FIG. 3, the speed increaser 40 and the generator 55 are accommodated in the housing 53 (see, for example, Patent Document 1).
As shown in FIG. 4, the speed increaser 40 includes an input shaft 41, a planetary gear 42, an internal gear 43, and a sun gear 44 in which a carrier (not shown) that supports the planetary gear shaft 42 a is integrated. An intermediate speed gear train including a stepped gear train, a cylindrical gear 47 coupled to the sun gear shaft 45 by a spline 46, and a cylindrical gear 48 disposed integrally with the intermediate shaft 49, is disposed at the end of the intermediate shaft 49. A high-speed gear train provided with the cylindrical gear 50 and the cylindrical gear 51 arranged on the output shaft 52, a case 53 for supporting these gear trains via a plurality of rolling bearings, and a tip of the intermediate shaft 49. Oil pump 54 and the like.

When wind energy is taken in and the blades 51 rotate, the rotation is transmitted from the rotor 52 to the input shaft 41 of the speed increaser 40, and the rotation of the input shaft 41 rotates at a low speed gear train, a medium speed gear train, and a high speed gear train. The speed is increased by the gear train and transmitted to the output shaft 52. The generator 55 is rotated by the rotation of the output shaft 52 to generate electric power.
The wind turbine 30 changes its direction in the direction in which the wind blows by controlling the wind direction, and the change in the wind speed can be stably controlled at the rated rotation speed by hydraulically controlling the blades 51, but is necessary for power generation. The wind speed is between 5 m / s and 20 m / s, and the change in the wind speed changes the rated output. When the wind speed is 20 m / s or more, the operation of the windmill 30 is stopped, and when the wind speed is 5 m / s or less, the wind turbine is irregularly rotated (swing) without generating power.

By the way, since the rolling bearing used for the rotor of a windmill and the rotation support part of a gearbox is used on severe conditions of receiving repeated shear stress under high surface pressure, it ensures a rolling fatigue life that can withstand the shear stress. There is a need.
Therefore, conventionally, high-carbon chromium steel (SUJ2) is used for the raceway (inner and outer rings) and rolling elements of the rolling bearing, and this is subjected to quenching and tempering, or SCR420, SCM420, SAE4320H, etc. By using case-hardened steel and subjecting it to carburizing or carbonitriding, quenching, and tempering, the required life is ensured by setting the surface hardness to Hv650-800.

  Also, in recent years, in order to extend the life of rolling bearings in a lubrication environment contaminated with foreign matter, steel with a high Si and Mn content is used as the material, and carbonitriding, quenching, and tempering are performed on this material. A technique is disclosed in which the amount of retained austenite in the surface portion is 20 to 50% by volume is used for a rolling member (inner ring, outer ring or rolling element) whose life is a problem, and the life as a rolling bearing is ensured. (For example, refer to Patent Document 2).

  In addition, surface damage is caused by slippage due to metal contact between the rolling elements, slip due to skew generated between the rolling elements and the inner and outer rings, and this surface damage is further promoted by so-called edge load and excessive contact pressure, It is known that it is effective to make the rolling surfaces and end surfaces of rolling elements (for example, rollers of full roller bearings) crowned against these edge loads and excessive contact pressures.

The technique for applying the crowning shape to the rolling elements is a known technique. MJohns and R.M. The so-called logarithmic crowning introduced in Gohar's paper is famous, but even if this logarithmic crowning is actually applied to the roller, it may not always be a long life, so it consists of a combination of straight lines and arcs. A crowning shape has been proposed, and the life of the bearing is extended by defining the crowning shape with a mathematical expression (for example, see Patent Document 3).
Japanese Patent Laid-Open No. 10-96463 Japanese Patent Laid-Open No. 7-190072 JP 2001-65574 A

  In recent years, wind turbines applied to wind power generators have been increasing in power generation and weight reduction. As a result, rolling bearings used in wind turbine rotors and gearboxes are used under increasingly high load conditions, and in addition, large vibrations and impact loads act on rolling bearings during gusts and typhoons. Further, surface damage due to slippage due to metal contact between the inner and outer rings of the bearing and the rolling elements and slippage due to metal contact between the rolling elements (for example, in the case of a full roller bearing) is more likely to occur. 3, it is difficult to obtain a sufficient surface damage reduction effect.

On the other hand, if the wind force is weak and there is almost no load acting on the rolling bearing, or if the wind speed is constantly changing and the rotation of the bearing is accelerated or decelerated, does the rolling element rotate while sliding against the raceway surface? Or, it becomes slippery and surface damage is likely to occur, causing a significant decrease in bearing life.
Rolling bearings used in wind turbine rotors and gearboxes that are applied to wind power generation are usually installed at a location about 50 m or more above the ground, so if the rolling bearings are damaged, a large replacement cost is required. Therefore, countermeasures to reduce the surface damage of the rolling bearing for wind turbines are required.

  The present invention has been made in response to such technical demands, and by reducing the friction between the inner ring and outer ring and the rolling elements and suppressing slippage due to metal contact, a high load is applied at the rotation support portion of the windmill. Even when used under conditions of vibration / impact load, no load, and acceleration / deceleration, it is possible to reduce the surface damage of the mating member, thereby extending the life of the mating member and hence the life of the rolling bearing. An object of the present invention is to provide a rolling bearing for a wind turbine.

In order to achieve the above object, the invention according to claim 1 is a rolling bearing for a windmill in which a plurality of rolling elements are rotatably arranged between an inner ring and an outer ring, and used for a rotation support portion of the windmill. And
The Si content of the rolling element is 0.5% by weight or more, and the amount of retained austenite on the surface of the rolling element is less than 20% by volume.
The invention according to claim 2 is characterized in that, in claim 1, the rolling element is subjected to a high-temperature tempering process in a range of 200 to 300 ° C. after being subjected to a carbonitriding process and a quenching process. To do.

According to a third aspect of the present invention, in the first or second aspect, the surface roughness of the rolling element is smaller than the surface roughness of at least one of the inner ring and the outer ring. The invention according to a fourth aspect is characterized in that, in any one of the first to third aspects, the N concentration of the surface portion of the rolling element is 0.2 to 2.0% by weight.
The invention according to claim 5 is characterized in that, in claim 1 or 2, a roller is used as the rolling element to form a full roller bearing.

  According to the present invention, the friction between the inner ring and the outer ring and the rolling element is achieved by setting the Si content of the rolling element to 0.5% by weight or more and the amount of retained austenite on the surface of the rolling element to less than 20% by volume. Slip due to metal contact can be suppressed, and even when used at high load, vibration / impact load, no load, acceleration / deceleration at the rotation support part of the wind turbine, Surface damage can be reduced, and as a result, the life of the mating member, and thus the life of the rolling bearing can be extended.

Moreover, after performing carbonitriding and quenching so that the surface N concentration is 0.2 to 2.0% by weight, the friction reducing effect is obtained by performing high temperature tempering at 200 to 300 ° C. The life can be further increased and the life can be further extended.
Further, by making the surface roughness of the rolling element smaller than the surface roughness of at least one of the inner ring and the outer ring, a further life extension effect can be obtained.

  Furthermore, in bearings that do not have a cage, such as full-roller bearings, surface damage due to metal contact between rolling elements becomes significant, but even in this case, the present invention improves friction characteristics and suppresses slippage. By doing so, it is possible to prevent a decrease in bearing life due to surface damage. In this case, by synthesizing at least one of the inner ring and the outer ring with a material different from that of the rolling elements, a synergistic effect of life extension can be obtained, and a long-life full complement roller bearing can be provided.

Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a full roller bearing for a wind turbine that is an example of an embodiment of the present invention includes a plurality of rollers (rolling elements) 3 between a raceway surface 1 </ b> A of an inner ring 1 and a raceway surface 2 </ b> A of an outer ring 2. Collar portions 10 and 20 for holding rollers 3 are formed at both ends in the axial direction of the outer diameter surface of the inner ring 1 and at one end portion in the axial direction of the inner diameter surface of the outer ring 2, respectively. A retaining ring 21 is attached to the other axial end of the inner diameter surface.

  Here, in this embodiment, the roller 3 has an Si content of 0.50 to 2.00% by weight, a C content of 0.30 to 1.20% by weight, and an Mn content of 0.20 to 2. 0.001% by weight, Cr content: 0.50 to 2.00% by weight, O content: 12 ppm or less, and after the material made of steel with the balance being Fe and inevitable impurities is processed into a predetermined shape, carbonitriding and By performing quenching treatment and further tempering treatment at 200 to 300 ° C., N concentration: 0.2 to 2.0 at the surface portion (range from the outermost surface of the rolling surface to 1 μm, for example) 3A % By weight, C concentration: 0.6 to 2.5% by weight, hardness: Hv 650 or more, residual austenite amount: less than 20% by volume (greater than 0% by volume).

As a result, it is used under the conditions of high load, vibration / impact load, no load, acceleration / deceleration in the rotor support of windmills and gearboxes applied to wind power generation. In the case where surface damage due to slippage due to metal contact or slippage due to metal contact between rollers 3 is likely to occur, friction characteristics between inner ring 1 and outer ring 2 between 3 and roller 3 are improved to suppress slippage. Can do.
As a result, it is possible to reduce the surface damage of the raceway surfaces 1A and 2A of the inner and outer rings 1 and 2 which are the counterpart members by delaying the generation and propagation of cracks from the stress concentration portion due to the tangential force, and also the rollers 3 themselves. The bearing life can be extended at a low cost.

Hereinafter, the critical significance of the numerical limitation of the present invention will be described.
[Si content of rolling element material: 0.50 to 2.00% by weight]
Si (silicon) is an element necessary for improving the resistance to temper softening while acting as a deoxidizer during steelmaking. In addition, when carbonitriding is performed on steel, there is also an effect of increasing the N concentration in the surface portion of the rolling element.
As a result of the experiments conducted by the present inventors, a carbonitriding treatment, a quenching treatment, and a high-temperature tempering treatment at 200 to 300 ° C. are performed using a steel having a Si content of 0.50% by weight or more as a rolling element material. As a result, it was confirmed that the effect of suppressing the surface damage of the raceway was obtained.
Therefore, the lower limit of the Si content of the rolling element material is 0.50% by weight, preferably 0.80% by weight.
On the other hand, if Si is contained excessively, the machinability of the material may be reduced and the cost may increase, so the upper limit of the Si content is preferably 2.00% by weight, more preferably 1.50% by weight. %.

[C content of rolling element material: 0.30 to 1.20% by weight]
C (carbon) is an element necessary for increasing the strength by converting the base into martensite. In the present invention, since it is possible to add C at the same time as N by carbonitriding in the surface portion of the rolling element, the C content of the material has the strength required for the core of the rolling element in the completed state. Therefore, the lower limit of the C content is preferably 0.30% by weight, and more preferably, the core hardness of the rolling element is preferably Hv650 or more. The lower limit is 0.80% by weight.
However, if the C content of the 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 of the C content is 1.20% by weight. It is preferable.

[Mn content of rolling element material: 0.20 to 2.00% by weight]
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 0.20% by weight or more in order to obtain sufficient effects. 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 Mn content is excessively large, non-metallic inclusions may increase so that the rolling life characteristics may be deteriorated, and the machinability such as the forgeability and machinability of the material is deteriorated. Therefore, the upper limit of the Mn content is preferably 2.00% by weight.

[Cr content of rolling element material: 0.50 to 2.00% by weight]
Cr (chromium) is an element effective for improving hardenability and temper softening resistance, and has the effect of strengthening the base and improving the 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 preferably 0.50% by weight.
However, even if a large amount of Cr is added, not only the effect is saturated, but also a passive film is formed on the surface portion, and there is a possibility that the carbonitriding property may be adversely affected, so the upper limit of Cr content Is preferably 2.00% by weight.

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

[About inevitable impurities]
In addition to the above alloy elements, impurity elements inevitable in steelmaking (for example, P, S, Ni, Cu, Mo, V, Al, Ti, Nb, etc.) are 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 2.00% by weight in total.

[About heat treatment]
First, after the raw material made of steel described above is processed into a roller shape by forging or cutting, it is heated and held for several hours in a furnace in which RX gas + enrich gas + ammonia gas is introduced at an ambient temperature of 800 to 860 ° C. Thus, the carbonitriding process is performed under such a condition that the N concentration of the surface portion of the roller is 0.2 to 2.0% by weight.
When the N concentration in the surface portion of the roller is less than 0.2% by weight, the effect of suppressing the surface damage of the bearing ring in contact with the roller may not be sufficiently obtained. On the other hand, the higher the N concentration in the roller surface portion, the higher the effect of suppressing the surface damage of the bearing ring. However, when the N concentration exceeds 2.0% by weight, the carbonitrided layer becomes brittle, and the full roller bearing As a result, sufficient rolling fatigue life may not be obtained. Therefore, the preferable range of the N concentration in the surface portion of the roller is 0.5 to 2.0% by weight.

In addition, with respect to the concentration of C added in the same manner as N by carbonitriding, the total of the N concentration and the C concentration is 0 so that the surface hardness Hv650 required as a bearing member can be obtained on the roller surface portion. It is preferable to adjust in the range of 8% by weight or more, and the lower limit of the C concentration in this case is 0.6% by weight.
On the other hand, if the C concentration in the surface portion of the roller is too high, coarse carbides precipitate and the rolling fatigue life of the roller itself cannot be obtained sufficiently. Therefore, the upper limit of the C concentration is 2.5% by weight, preferably 2%. 0.0% by weight.

Next, after quenching at 800 to 860 ° C., high temperature tempering at 200 to 300 ° C. is performed. At this time, if the tempering temperature is less than 200 ° C., there is a possibility that the amount of retained austenite at the surface portion of the roller cannot be less than 20% by volume. Therefore, the effect of reducing the surface damage of the inner and outer races in contact with the roller May not be sufficient.
On the other hand, when the tempering temperature exceeds 300 ° C., the hardness of the surface portion of the roller is lowered and the amount of retained austenite is insufficient, so that the rolling fatigue life of the roller itself may be lowered.

Here, when the tempering temperature is selected so that the amount of retained austenite on the surface portion of the roller is 7 to 18% by volume, the surface damage of the inner and outer rings as the counterpart member and the life reduction of the roller itself are effectively suppressed. Thus, the rolling fatigue life as a windmill full roller bearing can be effectively improved.
In addition, in order to further improve the rolling fatigue life as a full-roller bearing for wind turbines, the roller rolling surface is subjected to crowning, or the surface roughness of the roller rolling surface is adjusted to the surface roughness of the inner and outer ring raceway surfaces. It is preferable to make it smaller.

Furthermore, it is preferable that not only the roller but also the inner and outer rings which are mating members have a hardness of the raceway surface portion of Hv650 or more and a residual austenite amount of the surface portion of 45 vol% or less (over 0 vol%). .
Here, if the hardness of the raceway surface portion of the inner and outer rings is less than Hv 650, sufficient rolling fatigue life as the inner and outer rings may not be obtained.
Further, if the amount of retained austenite at the raceway surface portion of the inner ring exceeds 45% by volume, the material steel may be plastically deformed to shorten its life. In addition, the lower limit of the retained austenite amount on the raceway surface portion of the inner and outer rings is preferably 5% by volume in order to effectively suppress the surface damage of the raceway surface.

Residual austenite works effectively for stress relaxation at the indentation edge, and the improvement in hardness is effective for wear resistance and pressure indentation. Therefore, it is preferable to subject the inner and outer rings to carburizing or carbonitriding. However, unlike the carbonitriding process, the carburizing process does not form nitrides, and therefore the hardness is lower than that of the carbonitriding process. Therefore, it is more effective to perform the carbonitriding process.
In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.
For example, in the above-described embodiment, a full roller bearing is exemplified as the rolling bearing. However, the present invention may be applied to a rolling bearing having a cage, and a rolling bearing using balls other than rollers as rolling elements. The present invention may be applied.

In order to confirm the effect of the present invention, a windmill full roller bearing (inner diameter 160 mm, outer diameter 220 mm, width 36 mm) having substantially the same structure as in FIG. 1 was prepared and subjected to a life test.
Regarding the rollers, first, the materials shown in Table 1 were forged and processed into a predetermined shape, and then subjected to a predetermined heat treatment. Next, finishing such as grinding was performed to adjust the surface roughness (Ra) of the roller surface portion to 0.04 to 0.06 μm. The roller surface portion was crowned by a combination of a plurality of arcs.

The heat treatment shown in Table 1 as “carbonitriding → quenching → tempering” is as follows.
First, in the atmosphere of Rx gas + propane gas + ammonia gas, carbonitriding was performed by holding at 800-860 ° C. for 2-6 hours, followed by oil quenching, and then at 180-350 ° C. A tempering treatment was performed for 2 hours at a predetermined temperature in the range.

The heat treatment shown in Table 1 as “quenching → tempering” is as follows.
First, in an Rx gas atmosphere, after holding at 800 to 860 ° C. for 0.5 to 1 hour, oil quenching was performed, and then tempering treatment was performed at 180 ° C. for 2 hours.
At the surface portion of the roller thus obtained (the portion from the outermost surface of the rolling element to a depth of 1 μm), the N concentration and C concentration are measured by an electron beam microanalyzer (EPMA), and the amount of retained austenite γ _R is calculated. The hardness (Vickers hardness) was measured by an X-ray diffractometer, and the hardness (Vickers hardness) was measured by the Vickers hardness test method defined in JIS Z 2244.

  On the other hand, for the inner ring and outer ring, first, a material made of high-carbon chromium bearing steel type 2 (SUJ2) is processed into a predetermined shape, and then subjected to quenching and tempering to obtain a surface portion of the raceway surface (the outermost surface of the raceway surface). To a depth of 1 μm), hardness: Hv 680 or more, retained austenite amount: 7% by volume or less, and then finish processing such as grinding, the surface roughness (Ra) of the inner and outer ring raceway surface, It adjusted to 0.1-0.5 micrometer so that it might become larger than the surface roughness (Ra) of a roller surface part.

Assembled full roller bearings using the inner ring, outer ring, and rollers obtained in this way, and conducted a life test assuming a usage environment similar to that of a rotor of a wind turbine or a rotating support part of a gearbox that is likely to cause surface damage. went. This life test was performed by rotating the inner ring until peeling occurred on the roller surface, and the rotation time from the start of the life test until peeling occurred was defined as the life. The life is shown in Comparative Example No. 1 in Table 1. 16 of L ₁₀ life was expressed as a relative ratio when a 1. The test conditions are as follows.

[Life test conditions]
Load ratio (P / Cr): 0.45 P: Equivalent load (N), Cr: Basic dynamic load rating (N)
Rotational speed: 1000min ^-1
Lubricating oil: ♯68 turbine oil foreign matter :( composition) Fe ₃ C
(Hardness) HRC52
(Particle size) 74-147 μm
(Mixing amount) The mixing test results are shown in Table 1 so as to be 300 ppm in the lubricating oil.

As is apparent from Table 1, the invention is such that the steel composition of the roller, the heat treatment method, the tempering temperature, the N concentration of the surface portion, the C concentration of the surface portion, the amount of retained austenite on the surface portion, and the hardness of the surface portion are within the scope of the present invention. Example No. 1-No. 13 is Comparative Example No. Compared with Nos. 14 and 15, the service life is longer. A life of 2.2 to 3.7 times that of 16 was obtained.
Of the invention examples, those satisfying “Si content of roller: 0.75 to 2.00% by weight” and “N concentration of roller surface portion: 0.5 to 0.8% by weight” are particularly long. It is a life, and comparative example No. A life of 3.0 or more times 16 was obtained. This is considered to be because when the total amount of the Si content of the roller and the N concentration in the surface portion increases, the frictional resistance between the roller and the inner and outer rings is reduced, and the rolling fatigue life is improved.

On the other hand, Comparative Example No. In No. 14, since the tempering temperature was too high, the amount of retained austenite on the roller surface portion was insufficient, and the effect of reducing the stress concentration at the indentation edge formed on the roller could not be obtained sufficiently, and flaking occurred frequently on the roller. The service life was short.
Comparative Example No. In No. 15, since the tempering temperature was too low, the amount of retained austenite on the roller surface portion could not be within the range of the present invention (over 0 volume% and less than 20 volume%). Therefore, the life extension effect due to the friction reduction between the rollers and the inner and outer rings could not be sufficiently obtained, and the life was short.

From the above results, by setting the steel composition of the roller, the N concentration of the roller surface portion, the C concentration, the amount of retained austenite, and the hardness within the scope of the present invention, the rotor support of the wind turbine and the rotation support portion of the speed increaser Even when used in an environment where surface damage is likely to occur, it has been confirmed that the life of the full complement roller bearing can be extended.
Next, after processing the raw material shown in Table 2 into a predetermined shape, the inner ring and the outer ring were manufactured by performing predetermined heat treatment. And finishing processing, such as grinding, was given to these, and the surface roughness (Ra) of the raceway surface was adjusted to 0.1-0.5 micrometer. Table 2 also shows the N concentration, C concentration, and retained austenite amount (γR and hardness) of the raceway surface portion measured by the same method as described above.

The inner ring and outer ring thus obtained, and the invention example No. 1 in Table 1 described above. Assembling a full roller bearing using 1 roller (N concentration on roller surface: 0.6% by weight, residual austenite amount: 10% by volume, hardness: Hv802, surface roughness (Ra): 0.05 μm) The life test was performed under the same conditions as described above. The life is shown in Comparative Example No. 1 in Table 1. 16 of L ₁₀ life indicated as 1 and the relative ratio. The test results are also shown in Table 2.

As is apparent from Table 2, the amount of retained austenite on the raceway surface portions of the inner and outer rings is 45 volume% or less (over 0 volume%) and the hardness is Hv 650 or more. In Comparative Examples Nos. 21-30. Compared with Nos. 31 and 32, it has a longer life, and in Comparative Example No. A lifetime of 3.4 to 7.2 times that of 16 was obtained.
Inventive Example No. 1 in which different heat treatments were performed using steels having the same composition. 21 and Invention Example No. From the result of No. 22, invention example No. which performed the heat processing containing carbonitriding was carried out. No. 22 was Invention Example No. No. 22 which was subjected to heat treatment including carburization. It can be seen that the lifetime is longer than 21. This is because in the carburizing treatment, nitrides are not formed on the surface of the raceway surface, and a friction reducing effect cannot be obtained.

On the other hand, Comparative Example No. In No. 31, the amount of retained austenite at the surface of the raceway surface exceeded 45% by volume, so plastic deformation occurred in the material and the life was short. Comparative Example No. In No. 32, the amount of retained austenite could not be present on the surface of the raceway surface and the hardness was as low as less than Hv650, so durability could not be obtained and the life was short.
From the above results, not only for the rollers but also for the inner and outer rings as the counterpart members, the hardness of the raceway surface portion is Hv650 or more, and the retained austenite amount of the surface portion is 45 vol% or less (over 0 vol%). It was confirmed that the life of the full complement roller bearing can be further extended even when used in an environment where surface damage is likely to occur, such as a windmill roller or a rotation support portion of a speed increaser.

It was also confirmed that the life of the full roller bearing could be further increased by making the surface roughness of the roller surface portion smaller than the surface roughness of the raceway surface portion of the inner and outer rings.
Subsequently, invention example No. of Table 1 mentioned above. 1 having a surface roughness (Ra) adjusted to 0.02 μm was prepared. A full complement roller bearing was assembled in combination with 30 inner and outer rings, and a life test was conducted under the same conditions as described above.

  This full complement roller bearing is an invention example No. in Table 2. 30 (Surface roughness (Ra) of surface portion: combination of 0.05 μm roller and retained austenite amount of raceway surface portion: 45% by volume or less (over 0% by volume) and hardness: inner and outer rings of Hv650 or more)) The life is longer than that of Comparative Example No. 1 in Table 1. A lifetime of 8.3 times that of 16 was obtained. Thus, it has been found that the life of the full roller bearing can be further extended by making the surface roughness of the roller surface portion as small as possible.

It is principal part sectional drawing for demonstrating the full roller bearing for windmills which is an example of embodiment of this invention. It is the schematic which shows an example of a propeller type windmill. It is a figure which shows the inside of the housing of a propeller type | mold windmill. It is sectional drawing of the gearbox accommodated in the housing.

Explanation of symbols

1 Inner ring 2 Outer ring 3 Roller (rolling element)
30 Windmill 40 Gearbox 51 Blade 52 Rotor 55 Generator

Claims (5)

A plurality of rolling elements are disposed between an inner ring and an outer ring so as to be able to roll, and are rolling bearings for a windmill used for a rotation support portion of a windmill,
A rolling bearing for a windmill, wherein the rolling element has a Si content of 0.5% by weight or more and a residual austenite amount of a surface portion of the rolling element is less than 20% by volume.   2. The rolling bearing for a wind turbine according to claim 1, wherein the rolling element is subjected to a high temperature tempering process in a range of 200 to 300 ° C. after being subjected to a carbonitriding process and a quenching process.   The rolling bearing for a wind turbine according to claim 1 or 2, wherein a surface roughness of the rolling element is smaller than a surface roughness of at least one of the inner ring and the outer ring.   The rolling bearing for windmill according to any one of claims 1 to 3, wherein the N concentration in the surface portion of the rolling element is 0.2 to 2.0 wt%.   The rolling bearing for a wind turbine according to any one of claims 1 to 4, wherein a roller is used as the rolling element to form a full roller bearing.

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