JP2007177842A - Rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing preventing shortening of a service life due to failure of a cage even in a severe bearing use condition requiring the strength of the cage and having lower torque than that of a grease-sealed bearing. <P>SOLUTION: A resin porous film is formed at least on a contact face of the surface of the cage 1 constituting the rolling bearing with rolling elements 9. The thickness of the film is 5 to 500 μm. The resin porous film has a communication hole obtained by forming a coating layer including resin and a pore forming material and then, extracting the pore forming material from the coating layer by using an extracting solvent which dissolves the pore forming material and does not resolve the resin. The resin porous film is impregnated with lubricating oil, and the peripheries of the plurality of rolling elements 9 are filled with lubricating grease 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rolling bearing using a cage in which a porous resin coating is formed on at least a contact surface with a rolling element.

The cage used for the conventional rolling bearing is made of metal, polyamide resin, polyacetal resin, polybutylene terephthalate resin, etc., and in particular, when synthetic resin is used, it is a simple substance of synthetic resin that can be injection molded, or synthetic resin Synthetic resin compositions reinforced by adding glass fibers, carbon fibers, organic fibers and the like to these molding materials have been used. Furthermore, in recent years, a cage for a rolling bearing in which a cage material is impregnated with a lubricant and has a lubrication function has been proposed.
For example, a cage for bearings (see Patent Document 1) in which a fluorinated oil is impregnated with a polyamide-imide resin molded into a porous shape by compression molding, a cage molded with an oil-containing plastic composed of a binder containing oil and a base material Further, a material impregnated with a lubricating oil (see Patent Document 2), a polyolefin resin and a lubricating oil mixed, a resin composition molded into a cage shape (see Patent Document 3), a synthetic resin in a fibrous form An oil conducting material and a lubricating oil are mixed, and the resin composition is molded into a cage shape (see Patent Document 4). A porous silica is impregnated with a lubricating oil and blended into a synthetic resin. Is formed into a cage shape (see Patent Document 5).

However, since the oil-impregnated resin and porous resin in each of the above patent documents are low in strength, when used as a bearing cage material, vibration and heat generation increase when the lubrication is poor during operation, causing damage and deformation. Since the movement of the rolling elements is hindered, the life may be shorter than the original life. Or, there is a risk that the same phenomenon may occur even under high speed conditions, conditions with a lot of vibrations, or conditions where the cage is loaded with variable loads.
In addition, the use of a high-strength metal cage can solve the problem of short life caused by the above-mentioned resin material. However, when a semi-solid lubricant such as lubricating grease is used, Due to the agitation resistance, there is a problem that the torque for rotating the rotating shaft supported by the bearing increases, and the torque fluctuation during rotation also increases.
Japanese Patent Laid-Open No. 61-6429 JP-A-1-93623 JP-A-8-21450 Japanese Patent Laid-Open No. 11-166541 JP 2002-98152 A

  The present invention has been made to address such problems, and even under severe bearing use conditions where the cage is required to be strong, the cage will not have a short life due to breakage. The purpose is also to provide a low-torque rolling bearing.

A rolling bearing according to the present invention is a rolling bearing comprising an inner ring and an outer ring arranged concentrically, a plurality of rolling elements interposed between the inner ring and the outer ring, and a cage for separately holding the rolling elements. A porous resin coating is formed on at least the contact surface of the cage with the rolling elements.
The porous resin film is impregnated with a lubricating oil.
Moreover, the thickness of the resin porous coating is 5 μm to 500 μm.

The resin porous coating is a coating layer containing a resin and a pore forming material, and then the pore forming material is dissolved from the coating layer using an extraction solvent that dissolves the pore forming material and does not dissolve the resin. It has the communicating hole obtained by extracting.
In addition, lubricating grease is sealed around the plurality of rolling elements.

  The rolling bearing of the present invention is formed by forming a porous resin coating having lubricity on at least a contact surface with a rolling element on the surface of a high-strength metal cage or fiber-reinforced resin cage. Even a required use can be suitably employed. In addition, since the coating is a resin porous coating, even when it falls off due to wear and intervenes on the rolling surface, it does not damage the rolling surface unlike a hard inorganic substance.

By impregnating the above-mentioned resin porous film with lubricating oil, it is possible to obtain excellent bearing characteristics for smoothly supplying the impregnated lubricating oil to the rolling surface.
Moreover, since the thickness of the resin porous coating is 5 μm to 500 μm, sufficient lubricating oil can be contained in the coating.
Further, when used together with the lubricating grease, the base oil consumed by the lubricating grease is supplied from the lubricating oil impregnated in the cage, so that the amount of the lubricating grease enclosed can be reduced.

The rolling bearing of the present invention has a cage in which a porous resin coating is formed on at least a contact surface with the rolling element. This coating was formed by baking a coating obtained by applying and drying a coating composition containing a resin and a pore-forming material on the surface of the cage to form a coating layer containing the resin and the pore-forming material. Thereafter, the porous resin film has communication holes obtained by extracting the pore forming material from the coating layer using an extraction solvent that dissolves the pore forming material and does not dissolve the resin. The resin porous coating has a thickness of 5 μm to 500 μm and can be impregnated with a lubricating oil.
Hereinafter, the porosity of the resin porous coating, the method of creating the resin coating composition for forming the resin porous coating, the method of forming the coating layer on the cage surface, the method of forming the resin porous coating, Description will be made in the order of a rolling bearing using a lubricating oil impregnation method and a cage having a resin porous coating.

When considering the porosity of a porous material having pores inside, there are a collection of spheres in which a plurality of spheres of porous material are gathered, and pores that are spaces in the gaps between the individual spheres. As a form that is packed most closely by point contact of spheres, there are face centered cubic lattice and hexagonal closest packing, and their filling rate is (volume of sphere ÷ volume of circumscribed cube) ÷ Calculated by (height ÷ base) ÷ (height of regular tetrahedron ÷ one side) and both are 74%. The porosity defined as (100-filling factor) is 26%.
The above calculation is a case where spheres of the same size are considered. However, when spheres of a plurality of sizes are filled, the filling rate becomes larger than the hexagonal close-packed filling, and the porosity becomes smaller.
Further, when the powdered spherical resin particles are sintered after compression molding, there is no point contact, and the spherical resin particles are deformed and brought into surface contact. For this reason, a filling rate becomes larger than a hexagonal close-packing, and a porosity becomes smaller. For this reason, the porosity of conventional sintered resin moldings is limited to about 20%.

上記、数１において、各符号の意味を以下に示す。
Ｖ；保持器表面に形成された樹脂多孔質被膜の洗浄前の体積
ρ；保持器表面に形成された樹脂多孔質被膜の洗浄前の密度
Ｗ；保持器表面に形成された樹脂多孔質被膜の洗浄前の重量
Ｖ₁；樹脂粉末の体積
ρ₁；樹脂粉末の密度
Ｗ₁；樹脂粉末の重量
Ｖ₂；気孔形成材の体積
ρ₂；気孔形成材の密度
Ｗ₂；気孔形成材の重量
Ｖ₃；洗浄後の樹脂多孔質被膜の体積
Ｗ₃；洗浄後の樹脂多孔質被膜の重量
Ｖ’₂；洗浄後に樹脂多孔質被膜に残存する気孔形成材の体積 In the present invention, the communication porosity is substantially the same definition as the above porosity, and means a porosity in a state where the pores are continuous. That is, it refers to the ratio of the total volume of pores that are continuous to the resin molded body.
Specifically, the communication porosity was calculated by the method shown in Equation (1) in Equation 1.

In the above Equation 1, the meaning of each symbol is shown below.
V: Volume ρ before cleaning of the resin porous coating formed on the cage surface; Density W before cleaning of the resin porous coating formed on the cage surface; W of the resin porous coating formed on the cage surface Weight V ₁ before washing; Volume ρ _{1 of} resin powder; Density W _{1 of} resin powder; Weight V _{2 of} resin powder; Volume ρ _{2 of} pore forming material; Density W _{2 of} pore forming material; Weight V of pore forming material ₃ ; Volume W ₃ of resin porous film after washing; Weight V ′ ₂ of resin porous film after washing; Volume of pore forming material remaining in resin porous film after washing

  In the present invention, a resin porous film having a communicating porosity of 10% or more, preferably 20% or more, more preferably 30% to 70% is obtained by the film forming method described below. If it is less than 10%, excellent sliding characteristics by oil lubrication cannot be shown. The resin porous film formed on the surface of the cage used in the rolling bearing of the present invention has a film thickness of 5 μm to several 100 μm, and has the same thickness as the pore size. Even the porosity can be communicated from the surface. In order to exhibit excellent sliding characteristics under conditions where the lubricant is dilute, it is preferable to have a communication porosity of 30% or more.

The resin porous film of the present invention is not particularly limited to its production method and material, and generally known coating methods can be adopted, for example, dipping method, spray method, tumbling method And electrostatic coating method.
The resin material used as the paint may be selected according to the coating method. For example, polyimide (hereinafter referred to as PI) resin, polytetrafluoroethylene (hereinafter referred to as PTFE) resin, epoxy resin, phenol resin, silicone resin, and thermoplastic elastomer such as urethane rubber, etc. It is done.
When used in an environment where the cage is exposed to high temperatures or under conditions where heat generation from sliding is large, the resin material is preferably a thermosetting resin, and PI resin is particularly preferred because of the advantages of wear resistance and long-term heat resistance. More preferred.
Moreover, even if ceramic powder such as silica powder or glass beads is blended in order to further improve the wear resistance, preferable results can be obtained, and in order to improve initial conformability, solid lubricant such as PTFE resin or molybdenum disulfide. Is preferable.

  The PI resin that can be used in the present invention is a resin having at least an imide bond in the molecule, and is bonded to the cage base material without being thermally deteriorated when the rolling bearing is used at a high temperature. Any resin having excellent properties can be used. For example, PI resin, PAI resin, polyester imide resin, polyester amide imide resin, etc. can be mentioned. Of these PI resins, PI resins and PAI resins are preferred. In addition, an aromatic PI resin or an aromatic PAI resin in which an imide bond or an amide bond is bonded via an aromatic group is particularly preferable. When the aromatic resin is used, the binding property to the cage substrate is excellent, and the heat resistance of the obtained coating layer is excellent. PI resin is a PI resin precursor obtained by ring-opening polyaddition reaction of acid dianhydride and diamine in an aprotic polar solvent such as N-methyl-2-pyrrolidone (NMP) or dimethylacetamide (DMAC). It can be obtained by heat-dehydrating and ring-closing polyamide carboxylic acid. The resin component in the wear-resistant and non-adhesive coating agent is used even in the state of polyamide carboxylic acid, in the state of PI resin, or even in the state where these are mixed. be able to.

A PAI resin is a resin having an imide bond and an amide bond in the molecule. The imide bond of the aromatic PAI resin may be a precursor such as polyamic acid, a closed imide ring, or a state in which they are mixed. Such aromatic PAI resins include PAI resins produced from aromatic primary diamines such as diphenylmethanediamine and aromatic tribasic acid anhydrides, such as mono- or diacyl halide derivatives of trimellitic acid anhydride, aromatic There are PAI resins produced from tribasic acid anhydrides and aromatic diisocyanate compounds such as diphenylmethane diisocyanate. Furthermore, as PAI resins having a larger ratio of imide bonds than amide bonds, aromatic, aliphatic or aliphatic There are PAI resins produced from cyclic diisocyanate compounds and aromatic tetrabasic acid dianhydrides and aromatic tribasic acid anhydrides, and any PAI resin can be used. Moreover, PI resin and PAI resin can also be used together.
The PI resin and PAI resin that can be used in the present invention are preferably resin solutions that can easily contain a pore-forming material described later. Moreover, PAI resin can also be used as a powder.

  Examples of the resin solvent that can be used in the present invention include ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate and ethyl acetate, aromatic hydrocarbons such as toluene and xylene, N-methyl-2-pyrrolidone (NMP), Aprotic polar resin solvents such as methyl isopyrrolidone (MIP), dimethylformamide (DMF), dimethylacetamide (DMAC), and the like can be used. These resin solvents preferably contain an aprotic polar component as an essential component. Moreover, an aprotic polar solvent and another resin solvent can be used together.

The pore-forming material that can be used in the present invention has a melting point higher than the firing temperature of the resin to prevent melting of the pore-forming material during firing, and is blended with the resin to form a coating layer, and then the resin Any substance that can be extracted from the coating layer by using an extraction solvent that dissolves the pore-forming material without dissolving the pore forming material can be used.
The pore-forming material is preferably an inorganic salt compound, an organic salt compound, or a mixture thereof, and particularly preferably a water-soluble substance that facilitates the washing and extraction process. Further, an alkaline substance, preferably a weak alkaline substance that can be used as a rust preventive is preferred. Examples of the weak alkali salt include organic alkali metal salts, organic alkaline earth metal salts, inorganic alkali metal salts, inorganic alkaline earth metal salts, and the like. It is preferable to use organic alkali metal salt or organic alkaline earth metal salt because the unextracted portion is removed and is relatively soft and difficult to damage the bearing rolling surface. In addition, you may use these metal salts 1 type or in mixture of 2 or more types. In addition, it is preferable to use a water-soluble weak alkali salt because inexpensive water can be used as the extraction solvent, and waste liquid treatment at the time of pore formation becomes easy.

Examples of water-soluble organic alkali metal salts that can be suitably used in the present invention include sodium benzoate (melting point 430 ° C.), sodium acetate (melting point 320 ° C.) or sodium sebacate (melting point 340 ° C.), sodium succinate, stearin. Examples include sodium acid. Sodium benzoate, sodium acetate, or sodium sebacate is particularly preferred because of its high melting point, compatibility with various resins, and high water solubility.
Examples of the inorganic alkali metal salt include potassium carbonate, sodium molybdate, potassium molybdate, sodium tungstate, sodium triphosphate, sodium pyrophosphate, and the like.

The average particle size of the pore-forming material that can be used in the present invention is preferably controlled to 1 μm to 500 μm. More preferably, it is in the range of 1 μm to 200 μm, and still more preferably 1 μm to 40 μm.
The mixing ratio of the pore-forming material in the present invention is 10% by volume or more, preferably 20% by volume or more, more preferably 30% by volume to 70% by volume with respect to the total amount including the resin powder and the pore-forming material.
Since the pore-forming material remaining in the coating layer after the extraction of the pore-forming material from the coating layer with the extraction solvent described later is very small, considering that the volume of the pore-forming material is approximately the volume of the communication hole, If the blending ratio is less than 10% by volume, the characteristic excellent sliding characteristics by oil lubrication cannot be shown. Further, in order to exhibit excellent sliding characteristics under the use conditions where the lubricant is dilute, it is preferable to blend 30% by volume to 70% by volume of a pore forming material.

The extraction solvent that can be used in the present invention is an extraction solvent that dissolves the pore-forming material and does not dissolve the resin. For example, water and alcohol-based, ester-based, and ketone-based solvents that are compatible with water are used. be able to. Among these, it is appropriately selected according to the above conditions depending on the type of resin and pore forming material. The extraction solvent can be used for the purpose of dispersing the pore-forming material in the resin coating composition and for the purpose of extracting the pore-forming material from the coating layer described later.
These extraction solvents may be used alone or in combination of two or more. It is preferable to use water because of its advantages such as easy waste liquid treatment and low cost.

The following method is mentioned as a method of obtaining the resin coating composition for forming a resin porous film in this invention.
(1) A method in which a pore-forming material is blended in a resin varnish obtained by dissolving a PI resin in a resin solvent and stirred uniformly.
(2) The PI-based resin powder and pore-forming material are blended in the extraction solvent, and the pore-forming material is dissolved by stirring to disperse the PI-based resin powder, and then the extraction solvent is removed to prepare the pore-forming material composition. obtain. Next, this pore forming material composition is blended in a resin solvent and uniformly stirred.
(3) A method in which the PI resin powder and the pore-forming material are mixed in a resin solvent and uniformly stirred.
(4) A method in which PI resin powder and pore-forming material are blended in a resin solvent and stirred uniformly, and then the resin solvent is removed and pulverized to obtain a powdery resin coating composition.
In the resin coating composition, PTFE resin powder may be blended with the resin coating composition for the purpose of improving the friction and wear resistance.

In the above method, the method for dissolving the pore-forming material in the extraction solvent and dissolving or dispersing the other components is not particularly limited as long as it is a method that can be mixed in the liquid. A ball mill, an ultrasonic disperser, a homogenizer Examples thereof include a juicer mixer and a Henschel mixer. It is also effective to add a small amount of a surfactant in order to suppress separation of the dispersion. At the time of mixing, the amount of extraction solvent is ensured so that the pore-forming material is completely dissolved by mixing.
As a method for removing the extraction solvent, methods such as heat evaporation, vacuum evaporation, bubbling with nitrogen gas, dialysis, and freeze-drying can be used. Since the method is easy and the equipment is inexpensive, it is preferable to remove the extraction solvent by heat evaporation.

  In the present invention, the solid content concentration in the resin coating composition is 5% to 50% by weight, preferably 5% to 40% by weight, and more preferably 5% to 30% by weight. If the solid content concentration is less than 5% by weight, the number of treatment steps for excess resin solvent increases, which is disadvantageous in the process. When the solid content concentration exceeds 50% by weight, the solid content amount is too large, and it becomes easy to cause nozzle clogging in an atomizing means such as a spray gun.

  In the present invention, as a method for removing the resin solvent from the cage in which the resin coating composition is applied by the above-described coating method or the like, a method such as heat evaporation, vacuum evaporation, bubbling with nitrogen gas, dialysis, or lyophilization is used. Can do. Since the technique is easy and the equipment is inexpensive, it is preferable to remove the resin solvent by drying with heat evaporation. The drying temperature is preferably maintained in the range of 5 ° C to 100 ° C for 10 minutes to 2 hours. Thereby, foaming of the coating film used as a coating layer after baking can be suppressed.

  The dried coating is then baked. The firing temperature is a temperature lower than the melting point of the pore forming material to be used, and a temperature range of 150 ° C. to 450 ° C. is appropriate. When sodium benzoate (melting point: 430 ° C) is used as the pore forming material, the firing temperature is 150 ° C to less than 430 ° C. When the temperature is lower than 150 ° C., the curing reaction of the binder resin or the like often does not proceed. The firing is preferably divided into several stages such as 80 ° C to 130 ° C to 180 ° C, and gradually raised to the firing temperature every 30 minutes to 120 minutes within a range of 30 minutes to 240 minutes. Thereby, the curing reaction of the binder resin or the like proceeds gradually and reliably, and a coating layer having uniform adhesion strength can be formed. In addition, it is possible to prevent the occurrence of itchiness, wrinkles, wrinkles, cracks and the like in the coating layer. The maximum temperature holding time during firing may be in the range of 15 minutes to 60 minutes, preferably 30 minutes to 45 minutes. When the maximum temperature holding time is less than 15 minutes, the curing reaction of the binder resin and the like is insufficient. Become. Furthermore, the manufacturing process takes longer time, which increases the cost.

  The cooling after the firing step may be performed through a step opposite to that during the firing step, or may be gradually cooled over a period of about 60 minutes to 180 minutes. By slowly cooling in this manner, the coating layer and the cage base material shrink uniformly and accurately, and a highly accurate cage can be obtained. The total firing time may be adjusted to about 2 hours to 10 hours.

Next, a method for forming a resin porous coating will be described. In this method, the pore forming material is extracted from the coating layer on the surface of the cage to obtain a resin porous coating.
In the present invention, the porous resin coating formed on the surface of the cage is prepared by dissolving the pore forming material contained in the coating layer and washing the coating layer with an extraction solvent that does not dissolve the resin. It is obtained by extracting. By performing this extraction treatment, the pore-forming material is dissolved, and after removal of the extraction solvent and drying, pores are formed in the portion filled with the pore-forming material, and a porous resin coating is obtained.
The type of the extraction solvent is as described above, and the extraction method may be a method of immersing in the extraction solvent for 1 to 100 hours or a method of washing with the extraction solvent.

  The thickness of the resin porous film thus obtained is preferably 5 μm to 500 μm. More preferably, it is 10 μm to 200 μm. If the thickness of the coating layer is less than 5 μm, abnormal noise and vibration during sliding due to widening of the gap with the counterpart material cannot be sufficiently suppressed, and if it exceeds 500 μm, the adhesion of the coating layer is poor. There is a fear. Further, if the thickness of the coating layer is too thin, there is a problem that a sufficient amount of lubricating oil cannot be retained.

Next, a method for impregnating the coating with lubricating oil will be described. The resin porous film formed on the surface of the cage can be used in a state of being impregnated with a lubricating oil in advance.
Examples of lubricating oils that can be impregnated include mineral oils such as spindle oil, refrigerator oil, turbine oil, machine oil, dynamo oil, paraffinic mineral oil, naphthenic mineral oil, polybutene, poly-α-olefin, alkylbenzene, and alkylnaphthalene. , Hydrocarbon synthetic oils such as alicyclic compounds, or natural oils and fats, polyol ester oils, phosphate esters, diester oils, polyglycol oils, silicone oils, polyphenyl ether oils, alkyl diphenyl ether oils, fluorinated oils, etc. Any commonly used lubricating oil such as non-hydrocarbon synthetic oil can be used without particular limitation.
In the above lubricating oil, as long as the purpose of the present invention is not impaired, an extreme pressure agent, an antioxidant, a rust inhibitor, a pour point depressant, an ashless dispersant, a metal detergent, an interface Activators, wear modifiers, etc. can be blended. As the antioxidant, phenol, amine, sulfur and the like can be used alone or in combination. In particular, since it is desired that the lubricating oil supplied from the porous resin coating impregnated with the lubricating oil does not undergo oxidative degradation over a long period of time, it is preferable to incorporate the antioxidant as described above.
The impregnation method may be any method that can impregnate the resin porous coating. The pressure reduction impregnation in which the resin porous film is immersed in an impregnation tank filled with lubricating oil and then impregnated under reduced pressure is preferable. Further, when a high viscosity silicone oil or the like is used, it can be impregnated under pressure. It is good also as a pressure-reduced-pressure impregnation combining these.

  In the present invention, the film formed on the surface of the cage is a resin porous film having 10% or more surface communication holes. Therefore, an oil film is easily formed by the dimple effect due to the pores on the surface. Since the lubricating oil penetrates into the material during use, it is possible to form a good oil film even in a non-lubricated state at startup. Further, when the initial sliding characteristics are important, a more preferable result can be obtained by impregnating the lubricant in advance.

  FIG. 1 shows a structural example of a rolling bearing cage in which the porous resin coating is formed at least on the contact surface with the rolling element. FIG. 1 is a partially enlarged perspective view of a crown-shaped cage in which a porous resin coating is formed. The rolling bearing retainer 1 is formed with a pair of opposing retainer claws 3 on the upper surface of an annular retainer body 2 at a constant pitch in the circumferential direction, and the opposing retainer claws 3 are arranged so as to approach each other. A rolling element holding pocket 4 for holding a ball as a rolling element is formed between the holding claws 3 while bending. Further, a flat portion 5 serving as a rising reference surface for the holding claws 3 is formed between the back surfaces of the holding claws 3 adjacent to each other in the adjacent pockets 4.

The rolling bearing cage 1 shown in FIG. 1 is obtained by applying the resin coating composition containing the pore forming material described above to the surface of the cage and baking the resulting coating to form a coating layer. It is obtained by extracting the pore-forming material using a solvent that dissolves the pore-forming material contained in the coating layer and does not dissolve the resin. The obtained film is a resin porous film having communication holes. The rolling bearing of the present invention is obtained by incorporating a cage having this coating. The coating formed on the cage can be preliminarily impregnated with a lubricant and incorporated in the rolling bearing. When incorporated in a rolling bearing without impregnation with a lubricant, a part of the base oil in the grease sealed in the rolling bearing can be stored in the communication hole of the coating. When the lubricant is consumed on the rolling surface, it is replenished from the communication hole of the coating.
In addition, as a material of a cage | basket, heat resistant resin materials, such as metal materials, such as copper alloy, stainless steel (SUS), an aluminum alloy, a titanium alloy, PI resin, and polyetheretherketone (PEEK) resin, etc. are employable.

An example of the rolling bearing of the present invention is shown in FIG. FIG. 2 is a cross-sectional view of a grease-filled deep groove ball bearing.
In the grease-filled deep groove ball bearing 6, an inner ring 7 having a rolling surface 7a on the outer peripheral surface and an outer ring 8 having a rolling surface 8a on the inner peripheral surface are arranged concentrically, and the rolling surface 7a of the inner ring and the outer ring roll. A plurality of rolling elements 9 are interposed between the surface 8a. The cage 1 includes a plurality of rolling elements 9 and a seal member 10 fixed to the outer ring 8 or the like. Lubricating grease 11 is enclosed around the rolling elements 9.

This bearing 6 can be used without enclosing the lubricating grease 11 when the surface coating is impregnated with lubricating oil in advance as the cage 1. In applications where low torque and torque stability are prioritized, it is possible to operate with only the lubricating oil contained in the cage without enclosing lubricating grease.
Further, even when lubricating grease is enclosed, the operation can be performed in a smaller amount than the amount of lubricating grease enclosed normally.
When encapsulating the lubricating grease, the base oil of the lubricating grease is the lubricating oil impregnated in the resin porous coating on the surface of the cage and the oil that mutually dissolves under the rolling bearing operating environment conditions. The mutually soluble oils are preferably oils having the same chemical structure, and more preferably, the lubricating oil and the base oil are the same type of oil and have substantially the same viscosity. preferable. By using together with this lubricating grease, since the base oil consumed by the lubricating grease is supplied from the lubricating oil impregnated in the cage, the amount of lubricating grease enclosed can be reduced. The amount of lubrication grease is 20% or less, preferably 5% to 20% of the total space volume of the bearing. If the amount of grease filled exceeds 20%, grease leakage and torque fluctuation may occur easily.

Examples of the base oil constituting the lubricating grease include mineral oils such as paraffinic mineral oil and naphthenic mineral oil, hydrocarbon synthetic oils such as polybutene, poly-α-olefin, alkylbenzene, alkylnaphthalene, and alicyclic compounds, or Natural oils and fats, polyol ester oils, phosphate esters, diester oils, polyglycol oils, silicone oils, polyphenyl ether oils, alkyl diphenyl ether oils, non-hydrocarbon synthetic oils such as fluorinated oils, etc. Any oil that is used can be used without particular limitation.
Examples of the thickener include metal soap-based thickeners such as aluminum soap, lithium soap, sodium soap, composite lithium soap, composite calcium soap, composite aluminum soap, and urea compounds such as diurea compounds and polyurea compounds. . These thickeners may be used alone or in combination of two or more.
Known additives for lubricating greases include, for example, extreme pressure agents, amine-based and phenol-based antioxidants, metal deactivators such as benzotriazole, viscosity index improvers such as polymethacrylate and polystyrene, and molybdenum disulfide. And solid lubricants such as graphite. These can be added alone or in combination of two or more.

The rolling bearing having the above-described configuration of the present invention has a small torque required for rotation and a small fluctuation in torque. For this reason, since excellent lubrication is performed over a long period of time, excellent durability is exhibited. Even when lubricating grease is sealed, the amount of lubricating grease charged can be made smaller than usual, so that a rolling bearing with less lubricating grease leakage can be obtained.
The rolling bearing of the present invention is not limited to a ball bearing, and can be used for a cylindrical roller bearing, a tapered roller bearing, and the like.

Example 1
A rolling bearing in which a porous resin coating impregnated with lubricating oil was formed on the surface of a metal container was used as a test bearing. The porous resin coating is a PAI resin paint (manufactured by Hitachi Chemical Co., Ltd., PAI-4250) and sodium triphosphate powder (Taihei Chemical Industrial Co., Ltd., sodium tripolyphosphate) at a solid content volume ratio of 1: 1. After mixing and painting on a metal cage by dipping method, drying, baking at 200 ° C for 3 hours, soaking in water at 80 ° C for 20 hours to extract sodium triphosphate powder, 120 ° C × It was made to dry in 3 hours. The thickness of the porous resin coating was adjusted so that the cage pocket surface was about 50 μm. Fluorine oil (Daikin Kogyo Co., Ltd., S200) was used as the lubricating oil, and the resin porous film was impregnated by a vacuum impregnation method. The vacuum bearing test shown below was performed using the obtained test bearing. The results are shown in Table 1.

<Vacuum bearing test>
Using a test bearing, a vacuum bearing test was performed under the following test conditions, and the bearing life and initial torque were measured. The life of the bearing was defined as the time until the torque was sufficiently higher than when it was stable. The initial torque was a value one hour after the start of the test.
Test conditions Test bearing: 608 equivalent (with shield)
Degree of vacuum: 1-10 x ^10-5 Pa
Load: Thrust load 390 N (Maximum contact surface pressure 2.0 GPa)
Rotation speed: 1000 rpm

Comparative Example 1
Ultra high molecular weight polyethylene powder (Mitsui Chemicals, Mipperon XM220) and sodium benzoate powder (Wako Pure Chemical Industries, Reagent) are charged into a mixer at a volume ratio of 1: 1 and mixed to obtain a mixed powder. It was. This mixed powder was molded by a heat compression molding method (200 ° C. × 30 minutes) and formed into a predetermined cage shape by cutting. This cut body was immersed in warm water at 80 ° C. for 100 hours to extract sodium benzoate powder, and dried at 120 ° C. for 3 hours to obtain a porous body. The porosity of the porous material was 49%. Fluorine oil (S-200, manufactured by Daikin Industries, Ltd.) was used as the lubricating oil, the cage was impregnated by the vacuum impregnation method, and the above-described vacuum bearing test was performed using the obtained test bearing. The results are shown in Table 1.

Comparative Example 2
The above-mentioned vacuum bearing test was performed using a test bearing obtained by enclosing fluorine grease (manufactured by Daikin Industries, Ltd., L200). The results are shown in Table 1.

表１に示すように実施例１の軸受は、比較例２のフッ素グリース封入軸受に比べ同等の寿命であり、また初期トルクは低かった。比較例１は、初期トルクは低いが、摺動発熱により保持器が融解し転動体の運動を阻害したため短寿命となった。

As shown in Table 1, the bearing of Example 1 had a life equivalent to that of the fluorine grease sealed bearing of Comparative Example 2, and the initial torque was low. In Comparative Example 1, although the initial torque was low, the cage was melted by sliding heat generation and the movement of the rolling element was hindered, so the life was shortened.

  The rolling bearing of the present invention does not have a short life due to breakage of the cage even under severe bearing use conditions where strength is required of the cage, and can provide a lower torque than a grease-filled bearing. For this reason, it has excellent durability with low torque and small fluctuation range, and there is little leakage of lubricating grease. For this reason, it can be used as a versatile basic part.

It is a partial expansion perspective view of the crown type cage in which the resin porous film is formed. It is sectional drawing of a grease enclosure deep groove ball bearing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Roller bearing cage 2 Cage body 3 Cage claw 4 Rolling element holding pocket 5 Flat part 6 Grease-filled deep groove ball bearing 7 Inner ring 8 Outer ring 9 Rolling element 10 Seal member 11 Lubricating grease

Claims (5)

A rolling bearing comprising an inner ring and an outer ring arranged concentrically, a plurality of rolling elements interposed between the inner ring and the outer ring, and a cage for separately holding the rolling elements,
A rolling bearing, wherein a porous resin coating is formed on at least a contact surface of the cage with a rolling element.   The rolling bearing according to claim 1, wherein the porous resin film is impregnated with a lubricating oil.   The rolling bearing according to claim 1 or 2, wherein the thickness of the resin porous coating is 5 µm to 500 µm.   The resin porous coating is a coating layer containing a resin and a pore-forming material, and then the pore-forming material is dissolved from the coating layer using an extraction solvent that dissolves the pore-forming material and does not dissolve the resin. 4. A rolling bearing according to claim 1, wherein the rolling bearing has a communication hole obtained by extraction.   The rolling bearing according to any one of claims 1 to 4, wherein lubricating grease is enclosed around the plurality of rolling elements.

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