JP2008138706A - Grease-filled roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease-filled roller bearing which effectively prevents the peeling resulting from hydrogen brittleness on a rolling element when used at high-temperature and high-speed rotation. <P>SOLUTION: The rolling bearing is provided with an inner ring 32 and an outer ring 33, and a plurality of rolling elements 34 disposed between the rolling surfaces of the inner and outer rings, and is filled with grease 37 around the rolling element 34. A phosphoric acid metal salt coating is formed in at least one surface selected from the rolling element surface 34a, the inner ring outside diameter surface 32a and an outer ring inside surface 33a. The grease is formed by compounding an additive to base grease consisting of a base oil and thickener. The additive contains at least one aluminum-based additive selected from aluminum powder and aluminum compound. The compound ratio of the aluminum additive is 0.05 to 10 parts by weight for base grease 100 parts by weight. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grease-filled rolling bearing, and in particular, a grease-filled rolling bearing used as an alternator, an electromagnetic clutch for a car air conditioner, an intermediate pulley, an electric motor such as an electric fan motor, a rolling bearing for an auxiliary machine, or a rolling bearing for a motor. Related to bearings.

  Electrical parts and accessories in automobiles, motors in industrial machines, and the like are required to be downsized, high performance, and high output year by year, and usage conditions are becoming stricter. For these, rolling bearings are used, and grease is mainly used for lubrication. However, due to severe conditions of use, such as high-speed rotation at high temperatures, specific peeling with a change in white structure due to sliding motion and hydrogen embrittlement, which will be described later, is early on the rolling surface of the rolling bearing. It is a problem.

  This specific exfoliation is different from the exfoliation from the inside of the rolling contact surface caused by normal metal fatigue, and is considered to be due to hydrogen embrittlement caused by hydrogen due to a fracture phenomenon that occurs from a relatively shallow surface of the rolling contact surface. Yes. As a method for preventing such a specific exfoliation phenomenon accompanied with a white structure change that occurs at an early stage, for example, a method of adding a passivating agent to the grease composition (see Patent Document 1) or a method of adding bismuth dithiocarbamate to the grease composition. A method of adding is known (see Patent Document 2). In addition, a method in which an oxide film or a metal thiophosphate film is provided on a bearing is also known (see Patent Document 3 and Patent Document 4).

However, in recent years, electrical components and accessories in automobiles, motors in industrial machines, etc., are increasingly used in rolling bearings at high temperatures, such as frequent high-speed operation-sudden deceleration operation-rapid acceleration operation-sudden stop. The method of adding a passivating agent or bismuth dithiocarbamate to grease or the method of forming an oxide film or a metal salt of thiophosphate is insufficient as a measure for preventing the peeling phenomenon.
JP-A-3-210394 JP-A-2005-42102 JP-A-2-190615 Japanese Patent Laid-Open No. 11-30236

  The present invention has been made to deal with such problems, and in a rolling bearing used under high temperature and high speed rotation, a grease-filled rolling bearing capable of effectively preventing separation due to hydrogen embrittlement on the rolling surface. The purpose is to provide.

  The grease-filled rolling bearing of the present invention is a rolling bearing comprising an inner ring and an outer ring, and a plurality of rolling elements interposed between the rolling surfaces of the inner and outer rings, and grease is sealed around the rolling elements. A metal phosphate coating is formed on at least one surface selected from the rolling element surface, the inner ring outer diameter surface and the outer ring inner diameter surface, and the grease is added to a base grease composed of a base oil and a thickener. The additive contains at least one aluminum-based additive selected from aluminum powder and aluminum compound, and the compounding ratio of the aluminum-based additive is 0.05 weight with respect to 100 parts by weight of the base grease. Part to 10 parts by weight.

The aluminum compound is at least one compound selected from aluminum carbonate and aluminum nitrate.
The thickener is a urea-based thickener.
Further, the base oil is at least one oil selected from alkyl diphenyl ether oil and poly-α-olefin oil.

The grease-filled rolling bearing of the present invention has a metal phosphate coating formed on at least one surface selected from the rolling element surface, the inner ring outer diameter surface, and the outer ring inner diameter surface. It is covered with a highly stable coating and is inertly treated to prevent metal contact and decomposition of the lubricant and grease that cause hydrogen generation. In addition, aluminum additive mixed with grease reacts on the frictional wear surface or the new metal surface exposed by wear, and an aluminum coating is formed on the bearing rolling surface along with iron oxide, and is found in bearings used in various industrial machines. Occurrence of unique peeling due to hydrogen embrittlement or the like can be suppressed. As a result, it is possible to dramatically improve the life of the bearing.
For this reason, it can be suitably used as a rolling bearing for automotive electrical components such as alternators, car air conditioner electromagnetic clutches, intermediate pulleys, and electric fan motors, and auxiliary machines.

As a result of intensive studies on rolling bearings that can effectively prevent peeling on the rolling surface due to hydrogen embrittlement, in rolling bearings filled with grease containing at least one aluminum-based additive selected from aluminum powder and aluminum compounds, A rapid acceleration / deceleration test was performed using a rolling bearing with a metal phosphate coating on at least one surface selected from the rolling element surface, inner ring outer diameter surface, and outer ring inner diameter surface. I found it to be extended.
The rolling bearing of the present invention has a hydrogen phosphate brittleness on the rolling surface by forming a metal phosphate film on the rolling surface of the bearing to prevent metal contact and the decomposition of lubricant and grease that cause hydrogen generation. Because it has both the effect of preventing delamination and the effect that the aluminum additive reacts even when the frictional wear surface of the bearing or the new metal surface exposed by wear is exposed, and an aluminum coating is formed on the bearing rolling surface along with iron oxide. It is considered that these effects of preventing specific exfoliation accompanied by white tissue change occurring on the rolling surface can be synergistically exhibited. The present invention is based on such knowledge.

The grease-enclosed rolling bearing of the present invention will be described with reference to FIG. FIG. 1 is a sectional view of a deep groove ball bearing showing an embodiment of the present invention. 2 to 4 are sectional views of deep groove ball bearings showing other embodiments of the present invention.
A grease-filled rolling bearing 1 shown in FIG. 1 includes an inner ring 2 and an outer ring 3 arranged concentrically, a rolling element 4 interposed between the inner ring 2 and the outer ring 3, a cage 5 that holds the rolling element 4, an inner ring 2 and an outer ring 3. The seal member 6 seals the axially opposite end openings of the outer ring and the grease 7 sealed in the bearing space. A chemically stable metal phosphate film is formed on the rolling element surface 4a. The grease 7 is a grease containing an aluminum-based additive described later.

  A grease-filled rolling bearing 11 shown in FIG. 2 includes an inner ring 12 and an outer ring 13 arranged concentrically, a rolling element 14 interposed between the inner ring 12 and the outer ring 13, a cage 15 that holds the rolling element 14, The seal member 16 seals the axially opposite end openings of the outer ring, and the grease 17 sealed in the bearing space. A chemically stable metal phosphate salt film is formed on the inner surface (including the rolling surface) 13a of the outer ring. The grease 17 is a grease containing an aluminum-based additive described later.

  A grease-filled rolling bearing 21 shown in FIG. 3 includes an inner ring 22 and an outer ring 23 arranged concentrically, a rolling element 24 interposed between the inner ring 22 and the outer ring 23, a cage 25 that holds the rolling element 24, The seal member 26 seals the axially opposite end openings of the outer ring, and the grease 27 sealed in the bearing space. A chemically stable metal phosphate salt film is formed on the inner ring outer diameter surface (including the rolling surface) 22a. The grease 27 is a grease containing an aluminum-based additive described later.

  4 includes an inner ring 32 and an outer ring 33 arranged concentrically, a rolling element 34 interposed between the inner ring 32 and the outer ring 33, a cage 35 for holding the rolling element 34, The seal member 36 seals the openings at both ends in the axial direction of the outer ring, and the grease 37 sealed in the bearing space. A chemically stable metal phosphate coating is formed on the rolling element surface 34a, the outer ring inner diameter surface (including the rolling surface) 33a, and the inner ring outer diameter surface (including the rolling surface) 32a. The grease 37 is a grease containing an aluminum-based additive described later.

  This rolling bearing is not particularly limited in its material and type of radial bearing, thrust bearing, etc., but the inner and outer rings and rolling elements are made of metal that can be treated with a phosphoric acid coating. Carbon chromium bearing steel, carburized steel, medium carbon alloy steel, machine structural steel, case-hardened steel, stainless steel, plating, white metal mixed with lead and tin, and other bearing alloys are possible.

  In the rolling bearing described above, a highly lipophilic metal phosphate coating is formed on at least one surface selected from the rolling element surface, the inner ring outer diameter surface, and the outer ring inner diameter surface. As a result, the oil film forming ability of the bearing raceway surface in a dilute lubrication environment can be increased and the incidence of metal contact can be lowered, so that the surface starting point with a very short life resulting from the occurrence of metal contact due to poor lubrication The occurrence of peeling can be prevented.

An example of a method for forming a metal phosphate salt film in the present invention will be described below. After the object to be coated is immersed in the phosphoric acid triester solution, grease or lubricating oil is applied or injected onto the friction surface and filled. The phosphoric acid triester is an organic phosphate compound represented by (RO) ₃ P═O (wherein R represents an aryl group, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group). Can use a commercially available industrial material as a plasticizer. These phosphate triesters include tricresyl phosphate (CH ₃ C ₆ H ₄ O) ₃ PO, triphenyl phosphate (C ₆ H ₅ O) ₃ PO, tributyl phosphate (C ₄ H ₉ O) ₃ PO Etc. The phosphoric acid triester as described above may be used by diluting with an organic solvent as required for handling. In order to react such triphosphate and bearing steel to form a metal phosphate film on the surface, it may be carried out while heating to increase the reaction rate. Sufficient film can be secured if immersed for a long time. The metal phosphate film formed on the surface is an iron phosphate film that is a reaction product of a phosphate triester and bearing steel. In addition to the iron phosphate, a part of iron phosphide is also generated on the friction sliding surface.
In addition, by mixing a phosphate metal salt such as phosphate triester or calcium phosphate in grease or lubricating oil in advance, the contact surface between the rolling element and the inner / outer ring is exposed to phosphoric acid due to the temperature rise during the operation of the bearing. It is also possible to form a metal salt film. This method has the advantage that it can be expected to always complement the wear of the coating.

The grease-enclosed rolling bearing according to the present invention is characterized in that grease containing an aluminum-based additive is used in addition to the formation of the metal phosphate salt coating on the bearing ring or the like.
The aluminum-based additive used in the present invention is at least one selected from an aluminum powder and an aluminum compound. Aluminum compounds include aluminum carbonate, aluminum sulfide, aluminum chloride, aluminum nitrate and its hydrate, aluminum sulfate, aluminum fluoride, aluminum bromide, aluminum iodide, aluminum oxide and its hydrate, aluminum hydroxide, selenium Aluminum fluoride, aluminum telluride, aluminum phosphate, aluminum phosphide, lithium aluminate, magnesium aluminate, aluminum selenate, aluminum titanate, aluminum zirconate and other inorganic aluminum, aluminum benzoate, aluminum citrate and other organic aluminum Is mentioned. These aluminum-based additives may be added to the grease alone or in combination of two or more.
Particularly preferable in the present invention is an aluminum powder having a high extreme pressure effect because it is excellent in heat resistance and hardly decomposes thermally.

The mixing ratio of the aluminum-based additive is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease. That is, (1) when the aluminum additive is only aluminum powder, 0.05 to 10 parts by weight of aluminum powder with respect to 100 parts by weight of the base grease, and (2) when the aluminum additive is only aluminum compound, 0.05 to 10 parts by weight of aluminum compound per 100 parts by weight of grease, and (3) when aluminum additive is aluminum powder and aluminum compound, aluminum powder and aluminum compound are added to 100 parts by weight of base grease. Combine 0.05 to 10 parts by weight.
If the blending ratio of the aluminum-based additive is less than 0.05 parts by weight, peeling on the rolling surface due to hydrogen embrittlement cannot be effectively prevented. Moreover, even if it exceeds 10 parts by weight, the anti-peeling effect will not be improved further.

Examples of base oils that can be used in the present invention include mineral oils such as spindle oil, refrigerator oil, turbine oil, machine oil, dynamo oil, highly refined mineral oil, liquid paraffin oil, polybutene oil, GTL oil synthesized by the Fischer-Tropsch method, Hydrocarbon synthetic oil such as poly-α-olefin oil, alkylnaphthalene oil, alicyclic compound, or natural oil, polyol ester oil, phosphate ester oil, polymer ester oil, aromatic ester oil, carbonate ester oil, Non-hydrocarbon synthetic oils such as diester oil, polyglycol oil, silicone oil, polyphenyl ether oil, alkyl diphenyl ether oil, alkylbenzene oil, and fluorinated oil can be used.
Among these, it is preferable to use alkyl diphenyl ether oil or poly-α-olefin oil excellent in heat resistance and lubricity.

Thickeners that can be used in the present invention include benton, silica gel, fluorine compounds, lithium soap, lithium complex soap, strong lucium soap, calcium complex soap, aluminum soap, aluminum complex soap, and other soaps, diurea compounds, polyurea compounds, etc. These urea compounds are mentioned.
Of these, urea compounds are desirable in view of heat resistance, cost, and the like.

  A urea compound is obtained by reacting an isocyanate compound and an amine compound. In order not to leave a reactive free radical, the isocyanate group of the isocyanate compound and the amino group of the amine compound are preferably blended so as to be approximately equivalent.

  A diurea compound is obtained by reaction of a diisocyanate and a monoamine, for example. Examples of the diisocyanate include phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, hexane diisocyanate, etc., and monoamines include octylamine, dodecylamine, hexadecylamine, stearylamine, Examples include oleylamine, aniline, p-toluidine, cyclohexylamine and the like. The polyurea compound can be obtained, for example, by reacting diisocyanate with a monoamine or diamine. Examples of the diisocyanate and monoamine include those similar to those used for the production of the diurea compound. Examples of the diamine include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, xylenediamine, And diaminodiphenylmethane.

By adding a thickener such as a urea compound to the base oil, a base grease for blending the aluminum additive and the like can be obtained. A base grease using a urea compound as a thickener is prepared by reacting an isocyanate compound and an amine compound in a base oil.
The blending ratio of the thickener in 100 parts by weight of the base grease is 1 to 40 parts by weight, preferably 3 to 25 parts by weight. If the content of the thickener is less than 1 part by weight, the thickening effect will be reduced, making it difficult to make grease, and if it exceeds 40 parts by weight, the resulting base grease will be too hard and the desired effect will not be obtained. Become.

  In addition to the aluminum-based additive, a known grease additive may be included as necessary. Examples of the additives include antioxidants such as organic zinc compounds, amines, and phenolic compounds, metal deactivators such as benzotriazole, viscosity index improvers such as polymethacrylate and polystyrene, molybdenum disulfide, and graphite. Examples include solid lubricants, metal sulfonates, rust inhibitors such as polyhydric alcohol esters, friction reducers such as organic molybdenum, oil agents such as esters and alcohols, and antiwear agents such as phosphorus compounds. These can be added alone or in combination of two or more.

  The grease-enclosed rolling bearing of the present invention suppresses the occurrence of peculiar delamination due to hydrogen embrittlement on the rolling surface of the bearing by forming a metal phosphate film on the bearing ring and enclosing grease containing an aluminum-based additive. can do. For this reason, ball bearings, cylindrical roller bearings, tapered roller bearings, spherical roller bearings, needle roller bearings, thrust cylindrical roller bearings, thrust tapered roller bearings, thrust needle roller bearings, thrust spherical roller bearings, etc. are also long. Can be used as a long-life bearing.

Examples 1 to 4 and Comparative Example 2
Dilute 7.36 g of tricresyl phosphate with 2-propanol to prepare 200 ml of tricresyl phosphate solution. To this solution, the inner and outer rings and rolling elements of bearing 6203 (NTN: deep groove ball bearing, SUJ2 steel) It was immersed for 2 hours at a temperature of 60 ° C. to form a metal phosphate film on the surface. After the coating was formed, other bearing parts were attached to form a test bearing for the rapid acceleration / deceleration test (see FIG. 1).

4,4-diphenylmethane diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., Millionate MT, hereinafter referred to as MDI) is dissolved in half of the base oil shown in Table 1 in the ratio shown in Table 1, and MDI is dissolved in the remaining half of the base oil. The monoamine which becomes 2 times the equivalent of was dissolved. The respective blending ratios and types are shown in Table 1.
A solution in which monoamine was dissolved was added while stirring the solution in which MDI was dissolved, and then the reaction was continued for 30 minutes at 100 ° C. to 120 ° C. to produce a diurea compound in the base oil.
To this, an aluminum-based additive (Comparative Example 2 was not blended) and an antioxidant were added at the blending ratio shown in Table 1, and the mixture was further stirred at 100 ° C to 120 ° C for 10 minutes. Thereafter, the mixture was cooled and homogenized with three rolls to obtain a grease.

In Table 1, the synthetic hydrocarbon oil used as the base oil is Shinflud 601 manufactured by Nippon Steel Chemical Co., Ltd. with a kinematic viscosity of 30 mm ² / sec at 40 ° C., and the alkyldiphenyl ether oil has a kinematic viscosity of 97 mm ² / sec at 40 ° C. Matsumura Oil Co., Ltd. and Moresco High Lube LB100 were used. Moreover, the hindered phenol by Sumitomo Chemical Co., Ltd. was used for antioxidant.

  The obtained grease was sealed in 1.9 g of the above test bearing and subjected to the following rapid acceleration / deceleration test to measure the bearing life time. The results are also shown in Table 1.

<Rapid acceleration / deceleration test>
A rapid acceleration / deceleration test was conducted on a rolling bearing in which a rotating shaft that supports a pulley around which a rotating belt of an alternator, which is an example of an electrical accessory, is wound, is supported by an inner ring. The rapid acceleration / deceleration test conditions were set at 1960 N for the load applied to the test bearing attached to the tip of the rotating shaft, the operating speed was set to 0 rpm to 18000 rpm, and a current of 0.1 A flows through the test bearing. The test was carried out in the state. The time during which abnormal peeling occurred in the test bearing, the vibration of the vibration detector exceeded 3 times the initial test value, and the generator stopped was defined as the bearing life time (h). The test was terminated after 750 hours.

Example 5
The test bearing (see FIG. 5) that was not subjected to the formation process of the metal phosphate coating was used, and in addition to the grease with the blending ratio shown in Table 1 obtained in the same manner as in Example 1. The same items as in Example 1 were measured in the same manner as in Example 1 except that 5 parts by weight of tricresyl phosphate was blended with 100 parts by weight of the base grease. The results are also shown in Table 1.

Comparative Example 1 and Comparative Examples 3 to 5
The same items as in Example 1 were measured except that a test bearing (see FIG. 5) that was not subjected to the metal phosphate coating formation treatment was used. The results are also shown in Table 1.

  As shown in Table 1, because of the synergistic action of grease and surface treatment, each example can effectively prevent specific exfoliation accompanied by white texture change occurring on the rolling surface, so it is excellent in rapid acceleration / deceleration tests. Yes. All of the rapid acceleration / deceleration tests of each example showed 750 hours or more.

  The grease-filled rolling bearing of the present invention can effectively prevent specific peeling accompanied with white structure change occurring on the rolling surface and has excellent bearing life, so an alternator, an electromagnetic clutch for a car air conditioner, an intermediate pulley, an electric fan motor, etc. The present invention can be suitably used for automotive electrical parts, rolling bearings for auxiliary machines, and motor bearings.

It is sectional drawing of the deep groove ball bearing which shows one Example of this invention. It is sectional drawing of the deep groove ball bearing which shows the other Example of this invention. It is sectional drawing of the deep groove ball bearing which shows the other Example of this invention. It is sectional drawing of the deep groove ball bearing which shows the other Example of this invention. It is sectional drawing of the deep groove ball bearing which shows the comparative example of this invention.

Explanation of symbols

1, 11, 21, 31, 41 Grease-filled rolling bearing 2, 12, 22, 32, 42 Inner ring 3, 13, 23, 33, 43 Outer ring 4, 14, 24, 34, 44 Rolling element 4a, 34a Rolling element surface 5, 15, 25, 35, 45 Cage 6, 16, 26, 36, 46 Seal member 7, 17, 27, 37, 47 Grease 13a, 33a Outer ring inner diameter surface 22a, 32a Inner ring outer diameter surface

Claims (4)

A rolling bearing comprising an inner ring and an outer ring, and a plurality of rolling elements interposed between the rolling surfaces of the inner and outer rings, wherein grease is sealed around the rolling elements, the rolling element surface, the inner ring outer diameter A metal phosphate salt film is formed on at least one surface selected from the surface and the inner surface of the outer ring,
The grease comprises a base grease composed of a base oil and a thickener, and the additive contains at least one aluminum-based additive selected from aluminum powder and an aluminum compound. A grease-enclosed rolling bearing characterized in that the mixing ratio of the system additive is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease.   2. The grease-filled rolling bearing according to claim 1, wherein the aluminum compound is at least one compound selected from aluminum carbonate and aluminum nitrate.   The grease-enclosed rolling bearing according to claim 1, wherein the thickener is a urea-based thickener.   4. The grease-filled rolling bearing according to claim 1, wherein the base oil is at least one oil selected from alkyl diphenyl ether oil and poly-α-olefin oil.

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