JP2006046373A - Rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing having an excellent lubricity enabling its operation over a long period even under no-lubrication condition in which a lubricant such as a lubricating oil and a grease is not used and under such an environment in which the rolling element is brought into contact with a corrosive liquid such as a water, an acid, and an alkali and less producing contamination of an external environment due to the leakage of the lubricant. <P>SOLUTION: In this rolling element 1, rolling elements 13 and second rolling elements 14 formed of a resin structure are installed between the raceway surface 11a of an inner ring 11 and the raceway surface 12a of an outer ring 12. The resin component of the resin structure as the material of the second rolling elements 14 is formed mainly of at least one of a resin formable by melting and having corrosive resistance and a fluororesin. Also, the ratio D<SB>P</SB>/D<SB>N</SB>of the diameter D<SB>P</SB>of the second rolling elements 14 to the diameter D<SB>N</SB>of the rolling elements 13 is 0.987 to 1.013, and the ratio N<SB>P</SB>/N<SB>N</SB>of the quantity N<SB>P</SB>of the second rolling elements 14 to the quantity N<SB>N</SB>of the rolling elements 13 is 0.375 or below. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rolling bearing.

In general, rolling bearings are lubricated by circulating a lubricant such as lubricating oil or grease, or by enclosing them inside a rolling bearing. For example, Patent Documents 1 and 2 disclose rolling bearings that are lubricated by a lubricant filled in the bearing internal space and that are prevented from entering water or the like by contact-type seal members or labyrinth seals. Yes.
Further, Patent Document 3 discloses a rolling bearing in which a lubricating method different from the above is adopted, that is, a rolling bearing lubricated by a rolling element made of a resin composition incorporated together with a normal rolling element. The rolling elements made of this resin composition have hollow holes filled with lubricating oil, and are arranged between the inner and outer rings alternately with the steel rolling elements. Examples of the resin include polyamide resin, fluororesin, phenol resin, polyoxymethylene, polycarbonate, and the like.

Further, a plurality of loaded rolling elements that load the bearing load and one or more non-loaded rolling elements that do not load the bearing load are interposed between the inner and outer rings, and the non-loaded rolling elements have self-lubricating properties. A rolling bearing formed of a fluororesin (polytetrafluoroethylene or the like) is disclosed in Patent Document 4.
Japanese Utility Model Publication No. 55-34002 Japanese Utility Model Publication No. 57-56218 Japanese Patent Publication No. 37-9104 JP-A-7-145820

  However, in the lubrication methods of Patent Documents 1 and 2, since the seal lip portion wears with the rotation of the bearing, a gap is generated between the seal lip portion and a surface sliding on the seal lip portion, and water or the like is generated inside the bearing. Could intrude. In the case of the labyrinth seal, water or the like may enter the bearing from the gap space of the labyrinth seal. As a result, the lubricant inside the bearing is softened and deteriorated, and the lubricity is significantly reduced, and the inner ring, outer ring, and rolling elements made of metal materials adhere to each other, causing abnormal wear and seizure. Further, the life of the rolling bearing may be extremely shortened.

  Further, as described above, when the lubricant is softened, leakage and scattering to the outside of the bearing are remarkably increased, which may contaminate the external environment of the rolling bearing. In particular, in the manufacturing process of semiconductors, liquid crystal panels, hard disks, etc., if dust or impurities such as lubricant adhere to wafers, glass substrates, and aluminum substrates, they can cause defects such as defects and short circuits. There was a circumstance that a lubricant such as

  Further, in the lubrication method of Patent Document 3, since the heat resistance of the polyamide resin, polyoxymethylene, and polycarbonate is insufficient and is liable to be deformed, and the self-lubricating property is also insufficient, the lubrication filled in the hollow hole is performed. When the oil is depleted, there is a risk that significant wear and interfacial slip may occur, resulting in a short life of the rolling bearing. In addition, the phenolic resin, which is a thermosetting resin, has low mechanical strength and is brittle, so that the rolling element is likely to be chipped or locally broken, thereby causing wear and biting, which may shorten the life of the rolling bearing. there were. Furthermore, since the fluororesin has a low mechanical strength, the rolling elements are likely to be significantly worn, deformed and bitten, and the rolling bearing may have a short life.

  Furthermore, the lubrication method of Patent Document 4 does not disclose the diameter of the unloaded rolling element or the elastic modulus of the fluororesin so that the transfer of the fluororesin having self-lubricating property is suitably generated. Depending on the diameter and the elastic modulus of the fluororesin, it is difficult for transfer to occur, and the life of the rolling bearing may be shortened. Further, in the lubrication method of Patent Document 4, if the number of unloaded rolling elements is too large, the load applied to the loaded rolling elements becomes too large, and seizure occurs between the loaded rolling elements and the raceway surface. In some cases, the life of the rolling bearing is shortened.

  In such a conventional rolling bearing, no lubricant such as lubricating oil or grease is used, or in an environment in contact with a corrosive liquid such as water, acid or alkali (for example, the liquid vapor or It is difficult to operate over a long period of time in an environment where it is in contact with splashes or in the liquid. Further, there is a possibility that the lubricant leaks out from the rolling bearing and contaminates the external environment of the rolling bearing.

  Therefore, the present invention solves the problems of the conventional rolling bearing as described above, and under non-lubricated conditions where lubricants such as lubricating oil and grease are not used, and with corrosive liquids such as water, acid, and alkali. It is an object of the present invention to provide a rolling bearing that has excellent lubricity capable of operating over a long period of time even in a contact environment and is less likely to cause contamination of the external environment due to leakage of the lubricant.

In order to solve the above problems, the present invention has the following configuration. That is, the rolling bearing according to the first aspect of the present invention includes an inner ring, an outer ring, a plurality of rolling elements that are freely rollable between the inner ring and the outer ring, and between the inner ring and the outer ring. wherein the second rolling elements made of arranged resin composition together with the rolling elements, comprising a ratio D _P / D _N between the diameter D _N of the rolling element diameter D _P of the second rolling elements to zero. It is characterized by being 987 or more and 1.013 or less.

Since the second rolling element made of the resin composition slides on the raceway surfaces of the inner and outer rings, the resin composition having excellent self-lubricating property is transferred from the second rolling element to the raceway surface and lubrication is performed. Rolling bearings can operate over a long period of time. Further, since it is not necessary to use a lubricant such as lubricating oil or grease, the external environment is hardly contaminated by the leakage of the lubricant.
If the ratio D _P / D _N of the diameter D _P of the second rolling element and the diameter D _{N of the} rolling element (hereinafter also referred to as the diameter ratio D _P / D _N ) is less than 0.987, Since the contact force acting on the second rolling element becomes insufficient due to the sliding between the rolling element and the raceway surface, the resin composition is insufficiently transferred to the raceway surface and the life of the rolling bearing becomes insufficient. There is a fear. On the other hand, when the diameter ratio D _P / D _N is exceeded 1.013, the contact force acting on the second rolling elements by the sliding of the second rolling elements and the raceway surface is excessive, the second rolling elements Wear and damage may occur and the life of the rolling bearing may be insufficient.

The rolling bearing according to claim 2 of the present invention, in the rolling bearing according to claim 1, the ratio N _P / N _N between the number N _N of the rolling element and the number N _P of the second rolling elements are It is 0.375 or less.
With such a configuration, since the second rolling element supports an appropriate load, the contact force is appropriately generated, and the resin composition having excellent self-lubricity is transferred from the second rolling element to the raceway surface. It is transferred and lubricated. Therefore, the rolling bearing of the present invention can operate over a long period of time.

When (since sometimes, referred to as the number ratio N _P / N _N) ratio N _P / N _N between the number N _N number N _P and the rolling elements of the second rolling elements is 0.375 exceeded, the second Since the load supported by the rolling element becomes excessive, and the contact force acting on the second rolling element becomes excessive due to the sliding between the second rolling element and the raceway surface, the second rolling element is worn or damaged, causing rolling. The life of the bearing may be insufficient.
Furthermore, the rolling bearing according to claim 3 according to the present invention is the rolling bearing according to claim 1 or 2, wherein the resin component of the resin composition is a resin that can be melt-molded and has corrosion resistance, and It is characterized by having at least one of fluororesin as a main component.

  Furthermore, the rolling bearing of Claim 4 which concerns on this invention is a rolling bearing as described in any one of Claims 1-3. WHEREIN: The said inner ring | wheel, the said outer ring | wheel, and the said rolling element were comprised with the material which has corrosion resistance. It is characterized by that.

  The rolling bearing of the present invention can operate over a long period of time even in a non-lubricated environment where lubricants such as lubricating oil and grease are not used and in an environment where it contacts with corrosive liquids such as water, acid, and alkali. It has excellent lubricity that is possible, and contamination of the external environment due to leakage of the lubricant hardly occurs.

An embodiment of a rolling bearing according to the present invention will be described in detail with reference to a partial longitudinal sectional view of FIG.
1 is a deep groove ball bearing, and an inner ring 11 having a raceway surface 11a on the outer peripheral surface, an outer ring 12 having a raceway surface 12a facing the raceway surface 11a on the inner peripheral surface, and both raceway surfaces 11a and 12a. A plurality of rolling elements (balls) 13 that are arranged so as to be freely rollable between them, a second rolling element 14 made of a resin composition that is arranged together with the rolling elements 13 between both raceway surfaces 11a and 12a, and a rolling element. 13 and the second rolling element 14 are provided between the inner ring 11 and the outer ring 12 and a cage 15.

The resin composition that is the material of the second rolling element 14 has self-lubricating properties, and the resin component is mainly composed of at least one of a resin that can be melt-molded and has corrosion resistance, and a fluororesin. .
Further, the second rolling elements 14 are like the rolling elements 13 spherical, the ratio D _P / D _N between the diameter D _N of the diameter D _P and the rolling elements 13 of the second rolling elements 14, 0.987 or 1 .013 or less. The ratio N _P / N _N between the number N _N number N _P and the rolling elements 13 of the second rolling elements 14 are 0.375 or less. In FIG. 1, for convenience of explanation, the second rolling elements 14 than the rolling elements 13 is illustrated in small diameter ball, but the diameter D _N of the diameter D _P and the rolling elements 13 of the second rolling elements 14 The relationship is as described above.

The inner ring 11, the outer ring 12, and the rolling element 13 are preferably made of a corrosion-resistant material such as a metal material or ceramic. The cage 15 is preferably made of a metal material or a resin material. The type of the cage 15 is not particularly limited, and for example, a crown-shaped or corrugated cage can be used. However, the cage 15 may not be provided.
Below, the rolling bearing 1 of this embodiment is demonstrated in detail. First, the resin component of the resin composition that is the material of the second rolling element 14 will be described. The resin component of this resin composition is mainly composed of at least one of a resin that can be melt-molded and has corrosion resistance, and a fluororesin.

  Examples of resins that can be melt-molded and have corrosion resistance include polyethylene resin (PE), polypropylene resin (PP), polyacetal resin (POM), polyarylene sulfide resin (for example, polyphenylene sulfide resin (PPS)), polyether nitrile resin ( PEN), polyetheretherketone resin (PEEK), a blend of PEEK and polybenzimidazole (PEEK-PBI), and the like. These may be used alone or in combination of two or more. Of these, PPS and PEEK are excellent in self-lubrication and corrosion resistance, and are particularly suitable for rolling bearings used in corrosive environments where they come into contact with acids, alkalis, and the like.

  In addition, as the fluororesin, polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), Examples thereof include tetrafluoroethylene / hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), and chlorotrifluoroethylene / ethylene copolymer (ECTFE). These may be used alone or in combination of two or more. Among these, PTFE, PFA, ETFE, PVDF, and FEP are excellent in self-lubricating property and corrosion resistance, and are particularly suitable for rolling bearings used in corrosive environments that come into contact with acids, alkalis, and the like.

  A solid lubricant may be added to the resin composition that is the material of the second rolling element 14 in order to improve lubricity. Then, the solid lubricant is transferred from the second rolling element 14 to the raceway surfaces 11a and 12a together with the resin component of the resin composition, and a thin film having better lubricity is formed on the raceway surfaces 11a and 12a. Since the wear of the two rolling elements 14 is also reduced, the rolling bearing 1 can operate for a longer period.

Examples of solid lubricants include PTFE powder, graphite, hexagonal boron nitride (hBN), boronized graphite, fluorine mica, melamine cyanurate (MCA), and amino acid compound having a layered crystal structure (N-lauro-L-lysine) , Graphite fluoride, fluoride pitch, molybdenum disulfide (MoS ₂ ), tungsten disulfide (WS ₂ ), and the like.
The solid lubricant content in the resin composition is preferably 30% by mass or less. Even if the content exceeds 30% by mass, not only the improvement in lubricity cannot be expected, but also the mechanical strength of the resin composition itself is reduced, and the second rolling element 14 made of the resin composition is worn or deformed. May occur, and the life of the rolling bearing 1 may be shortened.

  The average particle size of the solid lubricant is preferably 0.1 μm or more and 20 μm or less. When the average particle size is less than 0.1 μm, aggregation is likely to occur when mixed with the resin composition as the base material, and the dispersion of the solid lubricant particles may become uneven. On the other hand, if it exceeds 20 μm, the smoothness of the surface of the second rolling element 14, which is a molded body, is lowered and the strength is lowered, so that the life of the rolling bearing 1 may be shortened.

In addition, as long as it does not impair the objective of this invention, you may mix | blend various additives with a resin composition. For example, antioxidants, heat stabilizers, UV absorbers, photoprotective agents, flame retardants, antistatic agents, fluidity improvers, non-tackifying agents, crystallization accelerators, nucleating agents, pigments, dyes, etc. It can be illustrated.
Next, the corrosion-resistant material (metal material, ceramics) which comprises the inner ring | wheel 11, the outer ring | wheel 12, and the rolling element 13 is demonstrated. Examples of the metal material include stainless steel (SUS440C, SUS304, SUS316, SUS316L, SUS630, etc.), beryllium copper, titanium alloy, glass, ceramics, cemented carbide, cermet, and the like. In addition, these materials may be used independently and may be used in combination of 2 or more types.

Ceramics include silicon nitride (Si ₃ N ₄ ), zirconia (ZrO ₂ ), alumina (Al ₂ O ₃ ), silicon carbide (SiC), aluminum nitride (AlN), boron carbide (B ₄ C) ) Series, titanium boride (TiB ₂ ) series, boron nitride (BN) series, titanium carbide (TiC) series, titanium nitride (TiN) series, or a ceramic composite material that combines two or more of these It can be illustrated. Such ceramics can be blended with a fibrous filler in order to improve strength, fracture toughness and the like. The type of fibrous filler is not particularly limited, and examples thereof include silicon carbide whiskers, silicon nitride whiskers, alumina whiskers, and aluminum nitride whiskers.

Examples of the glass include soda lime glass, borosilicate glass, BK-7, and black glass.
Further, among the α-type, α + β-type, and β-type, α + β-type and β-type titanium alloys that have high strength and have a hardness of Hv 400 or higher, which is necessary for a rolling bearing, are preferable. If the surface hardness is improved by subjecting the titanium alloy to a low temperature oxidation treatment after a solution treatment or a surface hardening heat treatment such as a nitriding treatment or an oxidation treatment, it is more preferable because the wear resistance is improved.

Further, as the cemented carbide, for example, WC—Co, WC—Cr ₃ C ₂ —Co, WC—TaC—Co, WC—TiC—Co, WC—NbC—Co, WC—TaC— NbC-Co, WC-TiC-TaC-NbC-Co, WC-TiC-TaC-Co, WC-ZrC-Co, WC-TiC-ZrC-Co, WC-TaC-VC-Co, Examples thereof include WC—Cr ₃ C ₂ —Co, WC—TiC—Cr ₃ C ₂ —Co, and WC—TiC—TaC. Examples of non-magnetic and excellent corrosion resistance include WC—Ni, WC—Cr ₃ C ₂ —Mo ₂ C—Ni, WC—Ti (C, N) —TaC, WC— Ti (C, N) system, Cr ₃ C ₂ —Ni system and the like can be mentioned.

Further, as the cermet, for example, TiC—Ni, TiC—Mo—Ni, TiC—Co, TiC—Mo ₂ C—Ni, TiC—Mo ₂ C—ZrC—Ni, TiC—Mo ₂ C -Co-based, Mo ₂ C-Ni-based, Ti (C, N) -Mo 2 C-Ni _{system, TiC-TiN-Mo 2 C} -Ni _{system, TiC-TiN-Mo 2 C} -Co -based, TiC-TiN -Mo _{2 C-TaC-Ni-based, TiC-TiN-Mo 2 C} -WC-TaC-Ni -based, TiC-WC-Ni type, Ti (C, N) -WC -Ni system, TiC-Mo-based, Ti (C, N) -Mo series, boride series (MoB-Ni series, B ₄ C / (W, Mo) B ₂ series, etc.) and the like.

Here, Ti (C, N) -Mo 2 C-Ni -based, Ti (C, N) -WC -Ni system, and Ti (C, N) respectively -Mo system, TiC-Mo ₂ C-Ni system , TiC-WC-Ni system, and TiC-Mo system are sintered in nitrogen gas.
Next, the resin material constituting the cage 15 will be described. The type of the resin material is not particularly limited. For example, PE, PP, POM, polyarylene sulfide resin (for example, PPS), PEEK, PEEK-PBI, PEN, aromatic polyimide resin (PI), thermoplastic polyimide Resin (TPI), polyamideimide resin (PAI), polyamide resin (PA), aromatic polyester resin, and fluororesin are preferred. Although the kind of this fluororesin is not specifically limited, For example, PTFE, PFA, ETFE, PVDF, FEP, PCTFE, ECTFE etc. are mention | raise | lifted. These resin materials may be used alone or in combination of two or more.

  Among these resin materials, it is preferable to use those having excellent heat resistance (excluding the above-mentioned resin materials excluding PE, PP, and POM). As a result, the friction and wear characteristics at the contact portion between the rolling element 13 and the cage 15 become excellent, wear of the rolling element 13 is suppressed, and the cage 15 in addition to the second rolling element 14 is also suppressed. Since the resin component is transferred to the raceway surfaces 11a and 12a and the lubricity is further improved, the rolling bearing 1 can operate for a longer period of time. Furthermore, if a thermoplastic resin that can be melt-molded is used, the cage can be manufactured by a melt molding method such as an injection molding method, so that the mass productivity of the cage is improved.

  A solid lubricant may be added to the resin material constituting the cage 15 in order to improve lubricity. Then, since the lubricity of the cage 15 is improved, the frictional force generated at the contact portion between the cage 15 and the rolling element 13 is reduced. Further, since the solid lubricant together with the resin constituting the cage 15 is transferred to the rolling elements 13 for lubrication, the friction generated in the inner ring 11, the outer ring 12, the contact portion between the cage 15 and the rolling elements 13 is reduced. Thus, the wear of the cage 15 and the rolling elements 13 and the wear of the thin film having excellent lubricity formed on the raceway surfaces 11a and 12a are suppressed. A suitable type of solid lubricant is the same as that of the second rolling element 14 described above.

The content of the solid lubricant in the resin material constituting the cage 15 is preferably 40% by mass or less. Even if the content exceeds 40% by mass, not only a further improvement in lubricity cannot be expected, but the mechanical strength of the resin material itself is lowered, and the cage 15 made of the resin material is likely to be worn or deformed. Thus, the life of the rolling bearing 1 may be shortened.
The average particle size of the solid lubricant is preferably 0.1 μm or more and 30 μm or less. When the average particle size is less than 0.1 μm, aggregation is likely to occur when mixed with the resin material as the base material, and the dispersion of the solid lubricant particles may become uneven. On the other hand, if it exceeds 30 μm, the smoothness of the surface of the cage 15 which is a molded body is lowered and the strength is lowered, so that the life of the rolling bearing 1 may be shortened.

  Furthermore, in order to improve mechanical strength, heat resistance, dimensional stability, wear resistance, and the like, a resin filler constituting the cage 15 can be blended with a fibrous filler. Since the deformation and wear during operation of the cage 15 can be suppressed, the rolling bearing 1 can operate stably over a longer period. The type of fibrous filler is not particularly limited, but aluminum borate whisker, potassium titanate whisker, carbon whisker, aramid fiber, aromatic polyimide fiber, liquid crystalline polyester fiber, graphite whisker, glass fiber, carbon fiber Boron fiber, silicon carbide whisker, silicon nitride whisker, alumina whisker, aluminum nitride whisker, wollastonite and the like.

The fibrous filler may be subjected to surface treatment with a silane or titanate coupling agent for the purpose of improving the adhesion with the resin material that is the base material or to uniformly disperse it in the base material. Good. Moreover, you may perform the surface treatment according to the other objective.
The aspect ratio of the fibrous filler is preferably 3 or more and 200 or less. When the fibrous filler has an aspect ratio of less than 3, the reinforcing effect of the resin material is not sufficiently exhibited, and when the aspect ratio exceeds 200, uniform dispersion during mixing becomes extremely difficult. The fiber diameter of the fibrous filler is not particularly limited, but the average fiber diameter is preferably 0.2 μm or more and 30 μm or less, and more preferably 0.3 μm or more and 5 μm or less.

Moreover, it is preferable that content of the fibrous filler in the resin material which comprises the holder | retainer 15 shall be 40 mass% or less. Even if the content exceeds 40% by mass, not only the improvement of the mechanical strength cannot be expected, but the melt fluidity of the resin material is remarkably lowered, and the moldability may be poor.
Further, the total content of the solid lubricant and the fibrous filler in the resin material constituting the cage 15 is preferably 50% by mass or less. Even if the content of each of the solid lubricant and the fibrous filler is 40% by mass or less, if the total content of both exceeds 50% by mass, the melt fluidity and mechanical strength of the resin material are significantly reduced. There is a risk.

  In addition, this embodiment shows an example of this invention, Comprising: This invention is not limited to this embodiment. For example, in the present embodiment, a deep groove ball bearing has been described as an example of a rolling bearing, but the present invention can be applied to various types of rolling bearings. For example, radial rolling bearings such as angular contact ball bearings, self-aligning ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, and self-aligning roller bearings, and thrust types such as thrust ball bearings and thrust roller bearings This is a rolling bearing.

〔Example〕
Hereinafter, the present invention will be described in detail with reference to examples.
1 except that the inner and outer ring materials, the rolling element material, the second rolling element material, the diameter ratio D _P / D _N , and the number ratio N _P / N _N are as shown in Table 1. 14 types of deep groove ball bearings having substantially the same structure as the rolling bearing 1 were prepared. This rolling bearing is a deep groove ball bearing corresponding to a nominal number 6001 (inner diameter: 10 mm, outer diameter: 26 mm, width: 8 mm, number of rolling elements N _N : 8, rolling element diameter D _N : 4.762 mm). It is.

  The cage is a crown-shaped cage manufactured by injection molding a resin composition in which 80% by mass of ETFE and 20% by mass of potassium titanate whiskers are mixed.

The materials of the inner and outer rings, rolling elements, and second rolling elements are as follows.
PP: Sun Allomer PB370A manufactured by Sun Allomer Co., Ltd.
-PE: Polypenco U-PE manufactured by Nippon Polypenco Co., Ltd.
PTFE: Teflon (registered trademark) PTFE manufactured by DuPont
-PVDF: Polypenco PVDF-SP manufactured by Nippon Polypenco Co., Ltd.
-Silicon nitride: NPN-3 manufactured by Nippon Tungsten Co., Ltd.
-Zirconia: NPZ-2 manufactured by Nippon Tungsten Co., Ltd.
Silicon carbide: TSC-1 manufactured by Toshiba Corporation
Cemented carbide: WC-Ni-Cr-based M61U manufactured by Sumitomo Electric Industries, Ltd.
Cermet: TiC-TaN-Ni-Mo based DUX40 manufactured by Nippon Tungsten Co., Ltd.
-Titanium alloy: Ti-15Mo-5Zr-3Al alloy In the case of a titanium alloy, after forming inner and outer rings by cutting, solution treatment and aging treatment were performed. The solution treatment is a treatment in which water cooling is performed after holding at 800 to 850 ° C. for 1 hour. The aging treatment is a treatment in which air cooling is performed after holding at 350 to 500 ° C. for 24 hours.

In the case of SUS316, the chromium oxide film (passive film) formed on the surface was removed by fluorination treatment (maintained at 300 ° C. in a nitrogen trifluoride (NF ₃ ) atmosphere). Then, after carburizing treatment (for example, maintained at 460 to 520 ° C. in an acetylene gas atmosphere at a pressure of 133 Pa or less), soft blasting was performed to form a carburized hardened layer having a Vickers hardness of 850 on the surface.

Such a deep groove ball bearing was mounted on a bearing rotation tester manufactured by Nippon Seiko Co., Ltd., and a rotation test was performed under the following conditions to evaluate durability (life). In addition, it was determined that the service life had been reached when the vibration value at the time of rotation increased to 5 times the initial value of the rotation. The results are summarized in Table 1. The numerical values of the lifetime shown in Table 1 are relative values when the lifetime of the deep groove ball bearing of Comparative Example 1 is 1.
The test conditions are as follows.

・ Test environment: Underwater ・ Environment temperature: Room temperature ・ Radial load: 98N
・ Rotation speed: 1000rpm
As can be seen from Table 1, since the deep groove ball bearings of Examples 1 to 10 are provided with the second rolling element made of the resin composition, compared with the deep groove ball bearing of Comparative Example 1 that is not provided with the second rolling element. Therefore, it has a long life even under corrosive environment in water. The deep groove ball bearings of Comparative Examples 2 and 3 had a short life because the diameter ratio D _P / _DN was outside the preferred range. Further, the deep groove ball bearing of Comparative Example 4 had a short life because the number ratio N _P / N _N was out of the preferred range.

Next, the correlation between the diameter ratio D _P / _DN and the lifetime was examined. In deep groove ball bearing of Example 1, to prepare a material obtained by variously changing the diameter ratio D _P / D _N, to evaluate durability in the same manner as described above. The results are shown in the graph of FIG. 2 (plotted with a circle). Further, the deep groove ball bearing of Example 1, rolling elements and silicon nitride made, are prepared and further made various changes to diameter ratio D _P / D _N, to evaluate durability in the same manner as described above. The results are also shown in the graph of FIG. 2 (plotted with □).

From the graph of FIG. 2, it can be seen that the deep groove ball bearing has a long life when the diameter ratio D _P / _DN is 0.987 or more and 1.013 or less regardless of the type of material of the rolling elements.
Next, the correlation between the number ratio N _P / N _N and the lifetime was examined. The deep groove ball bearing of Example 1 was prepared by variously changing the number ratio N _P / N _N , and durability was evaluated in the same manner as described above. The results are shown in the graph of FIG.

From the graph of FIG. 3, it is understood that the deep groove ball bearing has a long life when the number ratio N _P / N _N is 0.375 or less.

  The rolling bearing of the present invention can be used under non-lubricated conditions where no lubricant such as lubricating oil or grease is used, or in an environment where it comes into contact with corrosive liquids such as water, acid, alkali, etc. It can also be used in a contact environment or in the liquid. Therefore, for example, it can be suitably used for cleaning devices (wet cleaning devices or dry cleaning devices such as UV cleaning devices and ozone cleaning devices) used in the manufacturing process of semiconductors, liquid crystal panels, hard disks, etc., and food machinery. is there.

It is a fragmentary longitudinal cross-section which shows the structure of one Embodiment of the rolling bearing which concerns on this invention. It is a graph showing a correlation between the diameter ratio D _P / D _N and the rolling bearing life. The number ratio N _P / N _N is a graph showing the correlation between the life of the rolling bearing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rolling bearing 11 Inner ring 12 Outer ring 13 Rolling element 14 Second rolling element 15 Cage

Claims (4)

An inner ring, an outer ring, a plurality of rolling elements that are freely rollable between the inner ring and the outer ring, and a resin composition that is disposed with the rolling elements between the inner ring and the outer ring. and a two rolling elements, the rolling ratio D _P / D _N between the diameter D _N of the rolling element diameter D _P of the second rolling elements is characterized in that it is 0.987 or more 1.013 or less bearing. Rolling bearing according to claim 1, the ratio N _P / N _N between the number N _N of the rolling element and the number N _P of the second rolling elements is characterized in that it is 0.375 or less.   The rolling bearing according to claim 1 or 2, wherein the resin component of the resin composition is mainly composed of at least one of a resin that can be melt-molded and has corrosion resistance, and a fluororesin.   The rolling bearing according to any one of claims 1 to 3, wherein the inner ring, the outer ring, and the rolling elements are made of a material having corrosion resistance.

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