JP2007092013A - Lubricating grease and lubricating grease-filled roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricating grease excellent in a high temperature durability, also inhibiting the reaction of fluorine with steel and having a long life, and a roller bearing in which the lubricating grease is filled. <P>SOLUTION: This lubricating grease having fluorine-based components by using perfluoropolyether oil as base oil and fluorine resin powder as thickening agent is provided by adding an inorganic compound capable of forming a membrane on a metal surface. The inorganic compound is a molybdic acid salt such as potassium molybdate, sodium molybdate, etc., or a bismuth-based compound such as bismuth sulfate, etc. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high-temperature lubricating grease and a rolling bearing, and more particularly, to a fluorine-based high-temperature lubricating grease and a rolling bearing that are suitably used for an electrical accessory such as an automobile used at high temperatures and a fixing portion of an electrophotographic apparatus. Further, the present invention relates to a rolling bearing that has a relatively small amount of grease, such as in a vacuum, and is used under boundary lubrication conditions.

  The rolling bearing is filled with lubricating grease in order to impart lubricity. This lubricating grease is obtained by kneading base oil and thickener as main components, and synthetic oil such as mineral oil, ester oil, silicone oil, ether oil as base oil, and lithium soap as thickener. Metal soaps and urea compounds are generally used. In addition, various additives such as an antioxidant, a rust inhibitor, a metal deactivator, and a viscosity index improver are blended in the lubricating grease as necessary.

In recent years, along with demands for miniaturization, weight reduction, and quietness of automobiles, miniaturization, weight reduction, quietness improvement, and sealing in engine rooms have been attempted. High performance and high efficiency are required for the performance of the system. Since the life of the lubricating grease enclosed in the rolling bearing is usually shorter than the service life due to fatigue of the bearing itself, the life of the bearing itself depends on the life of the lubricating grease. For this reason, the lubricating grease used in these electrical accessories must withstand higher temperatures than urea-based lubricating grease.
Conventional grease used in rolling bearings used in fan clutches that reach high temperatures around 200 ° C is heat resistant using fluororesin powder as a thickener and perfluoropolyether (hereinafter referred to as PFPE) oil as the base oil. Fluorine-based lubricating grease with excellent properties is used.

In general, a roller bearing for a roll is frequently used in a fixing unit of a copying machine or a printer (printer) using an electrophotographic apparatus in order to rotatably support a fixing roller. The fixing unit is a part that fixes toner on the paper by pressurizing the toner that is charged and adhered to the paper at a high temperature of about 250 ° C. The roll support rolling bearing of the fixing unit is used at a high temperature. Many. In particular, since a heat roll has a heater inside a hollow shaft and heats from the inside, the bearing may be used at a temperature exceeding 200 ° C. In addition, heat roll-supported rolling bearings are sometimes used via resin heat insulating sleeves to lower the temperature of the bearings, but the temperature of the bearing end faces can still be close to 200 ° C due to radiant heat. Conventionally, as a sealing grease for a rolling bearing used under such a high temperature condition, a fluorine-based grease that is less likely to deteriorate at a high temperature and that provides a long life is generally used.
Generally, when the lubricant is exposed to vacuum, the base oil evaporates because the vapor pressure of the base oil is high. For this reason, the degree of vacuum does not increase, or measurement equipment provided in the vacuum chamber or the vacuum equipment is contaminated to cause a problem. As a countermeasure, fluorine-based grease has been often used to lubricate rolling bearings used in vacuum.

These fluorine-based greases exhibit good lubricity when a sufficient amount is present, but when supply to the rolling contact part or sliding part is insufficient and boundary lubrication occurs, the base oil PFPE oil and Steel (iron), which is a bearing material, reacts with the base oil, causing wear of the steel and shortening its life.
It is required to obtain a longer life by suppressing this reaction and utilizing the inherent heat resistance and lubricity of PFPE. As countermeasures, improvement of seizure resistance and wear resistance of fluorine grease by silica blending (film formation) (see Patent Document 1), improvement of rolling fatigue characteristics by blending organic antimony or organic molybdenum (see Patent Document 2), bismuth Improvement of rolling fatigue characteristics by compounding (see Patent Document 3), improvement of wear resistance and rust prevention of fluorine grease by compounding of fluorine organophosphorus compound (see Patent Document 4), molybdenum disulfide, synthetic mica, etc. Improvement in wettability of fluorine grease by blending layered mineral powder, metal salt such as metal soap, metal oxide, diamond powder, carbon compound such as graphite, melamine cyanurate and amino acid compound (see Patent Document 5), modification Fluorine by blending undecane mixture, modified butane, Cu phthalocyanine, Ca sulfonate, etc. Prevent deterioration of the grease (refer to Patent Document 6) are known.
However, none of these have been made by paying attention to the reaction between fluorine and steel, and the properties of fluorine grease have not been fundamentally improved.
JP 2005-97513 A JP 2000-303088 A JP-A-2005-42102 JP 2003-27079 A JP 2004-188607 A Japanese Patent Laid-Open No. 8-143883

  The present invention has been made in order to cope with such problems, and is excellent in high-temperature durability and long-life lubrication that suppresses the reaction between fluorine and steel and utilizes the heat resistance and lubricity inherent in PFPE. An object is to provide a grease and a rolling bearing in which the lubricating grease is enclosed.

  The lubricating grease of the present invention is a fluorinated lubricating grease containing PFPE oil as a base oil and a fluororesin powder as a thickener, and is characterized by adding an inorganic compound capable of forming a film on a metal surface.

The inorganic compound is a molybdate or a bismuth compound.
The molybdate is potassium molybdate or sodium molybdate.
The bismuth compound is bismuth sulfate.

  The grease-enclosed rolling bearing of the present invention comprises an inner ring and an outer ring arranged concentrically, and a plurality of rolling elements interposed between the inner ring and the outer ring, and the lubricating grease is enclosed around the rolling elements. It is characterized by being.

  The lubricating grease of the present invention is a lubricating grease containing PFPE oil as a base oil and a fluororesin powder as a thickening agent, and contains an inorganic compound capable of forming a film on the metal surface. With this coating, the reaction between fluorine and steel can be suppressed, and a long life can be obtained by utilizing the heat resistance and lubricity inherent to PFPE.

  The rolling grease-enclosed rolling bearing of the present invention is a lubricating grease that uses PFPE oil as a base oil and a fluororesin powder as a thickener, and contains lubricating grease containing an inorganic compound that can form a film on a metal surface. Therefore, it is excellent in high temperature durability, the reaction between fluorine and bearing steel can be suppressed by the coating, and a long life can be obtained by utilizing the heat resistance and lubricity inherent in PFPE. As a result, it can be suitably used as a rolling bearing used in automotive electrical equipment, office equipment and the like. Further, the amount of grease filled is relatively small, such as in a vacuum, and can be suitably used as a rolling bearing used under boundary lubrication conditions.

The fluorine-based lubricating grease that can be used in the present invention uses PFPE oil as a base oil and fluorine resin powder as a thickener.
As the PFPE oil, any compound in which a hydrogen atom of an aliphatic hydrocarbon polyether is substituted with a fluorine atom can be used. Examples of such PFPE oils include PFPE oils having side chains represented by the following chemical formulas 1 and 2 and linear PFPE oils represented by chemical formulas 3 to 5. These can be used alone or in combination. n and m are integers.
Fomblin Y (trade name of Montedison) is available as a commercial product of Chemical 1, and Krytox (trade name of DuPont) and Barrierta J Oil (trade name of Kluber) are available as commercial products of Chemical 2. Fomblin Z (trade name of Montedison) as the product, Fomblin M (trade name of Montedison) as the commercial product of Chemical 4, and Demnam (trade name of Daikin) as the commercial product of Chemical 5 it can.

The fluororesin powder that is a thickener has a high affinity with the PFPE oil, and a powder having high temperature stability and chemical resistance can be used.
Examples of fluororesins include perfluoro fluororesins such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). In particular, polytetrafluoroethylene (PTFE) is preferable because of high temperature stability and excellent chemical resistance.

  The fluorine-based lubricating grease of the present invention preferably contains 70 to 90% by weight of PFPE oil and 10 to 30% by weight of fluororesin powder based on the total amount of lubricating grease. By blending within this range, the grease can be adjusted to a preferable consistency that can reduce the torque for a long time with less leakage as the grease in the rolling bearing.

In the lubricating grease of the present invention, an inorganic compound is added as an additive capable of forming a film on the metal surface. Examples of the inorganic compound include metal powders such as molybdate and copper, metal oxides such as copper oxide and molybdenum oxide, inorganic bismuth compounds, and inorganic magnesium compounds.
By adding the above-mentioned inorganic compound, the inorganic compound decomposes and reacts on the frictional wear surface of the bearing portion or the like or the newly formed metal surface exposed by wear, and a film can be formed together with iron oxide.

  The molybdate that can be used in the present invention is preferably a metal salt. Examples of the metal constituting the metal salt include sodium, potassium, lithium, magnesium, calcium, copper, zinc, barium and the like. Of these, potassium molybdate or sodium molybdate is preferably used from the viewpoint of reactivity.

Examples of the inorganic bismuth (compound) that can be used in the lubricating grease of the present invention include bismuth powder, bismuth carbonate, bismuth chloride, bismuth nitrate and hydrates thereof, bismuth sulfate, bismuth fluoride, bismuth bromide, and bismuth iodide. , Bismuth oxyfluoride, bismuth oxychloride, bismuth oxybromide, bismuth oxyiodide, bismuth oxide and its hydrates, bismuth hydroxide, bismuth selenide, bismuth telluride, bismuth phosphate, bismuth oxyperchlorate, oxysulfuric acid Examples include bismuth, sodium bismuth, bismuth titanate, bismuth zirconate, and bismuth molybdate. In the present invention, sulfuric acid having a high extreme pressure effect is particularly preferable because of excellent heat resistance and resistance to thermal decomposition. Bismuth.
These inorganic bismuths may be added to grease by mixing one or two types.

Examples of inorganic magnesium (compound) that can be used in the lubricating grease of the present invention include magnesium powder, magnesium carbonate, magnesium chloride, magnesium nitrate and hydrates thereof, magnesium sulfate, magnesium fluoride, magnesium bromide, magnesium iodide, Magnesium oxyfluoride, magnesium oxychloride, magnesium oxybromide, magnesium oxyiodide, magnesium oxide and its hydrate, magnesium hydroxide, magnesium selenide, magnesium telluride, magnesium phosphate, magnesium oxyperchlorate, magnesium oxysulfate , Sodium magnesiumate, magnesium titanate, magnesium zirconate, magnesium molybdate and the like.
These inorganic magnesium may be added to grease by mixing one type or two types.

The lubricating grease of the present invention can contain known additives as necessary. As this additive, for example, antioxidants such as amine, phenol, sulfur, zinc dithiophosphate, extreme pressure agents such as chlorine, sulfur, phosphorus, zinc dithiophosphate, organic molybdenum, benzotriazole Examples thereof include metal deactivators such as polymethacrylate, polyisobutylene, and polystyrene, viscosity index improvers, wear inhibitors, detergent dispersants, and the like.
These additives can be added alone or in combination of two or more.

An example of a rolling bearing according to the present invention is shown in FIG. FIG. 1 is a cross-sectional view of a deep groove ball bearing.
In the rolling bearing 1, an inner ring 2 having an inner ring rolling surface 2a on the outer peripheral surface and an outer ring 3 having an outer ring rolling surface 3a on the inner peripheral surface are arranged concentrically, and the inner ring rolling surface 2a and the outer ring rolling surface 3a A plurality of rolling elements 4 are arranged between the two. The cage 5 is configured to hold the plurality of rolling elements 4, and the seal member 6 is fixed to the outer ring 3 or the like. Lubricating grease 7 is sealed at least around the rolling element 4.

Reference Example 1: for the entire manufacturing grease grease 1, PFPE oil (manufactured by DuPont, product name, Krytox 143AC, 40 ℃ kinematic viscosity 191 mm ²⁾ 67 wt%, the fluorine resin powder (manufactured by DuPont, product name After the addition of 33 wt%, the mixture was passed through a roll mill to obtain a semi-solid grease 1 which was a grease using fluororesin powder as a thickener and PFPE oil as a base oil.

Examples 1 to 2 and Comparative Example 1
Each grease was mixed and stirred at the ratio shown in Table 1 to obtain a lubricating grease. The blending ratio is weight% with respect to the whole grease.
The mixing grease and dropping point of the obtained mixed grease (Example 1 and Comparative Example 1) were measured. The penetration and dropping point were determined according to Japanese Industrial Standard JIS K2220. The results are shown in Table 1.

In addition, rolling bearings were manufactured by enclosing the lubricating grease of each example, which was 38% of the total space volume, in a bearing 6204ZZ cleaned with petroleum benzine. The obtained rolling bearing was evaluated in a high temperature durability test.
In the high temperature durability test, the bearing was rotated at a radial load of 67 N, a thrust load of 67 N, a rotation speed of 10000 rpm, and an ambient temperature of 200 ° C., and the time until the motor stopped due to overload was measured. The results are shown in Table 1.

表１に示すように、実施例１〜実施例２の潤滑グリースは比較例１よりも高温耐久試験に優れる。

As shown in Table 1, the lubricating greases of Examples 1 to 2 are superior to Comparative Example 1 in the high temperature durability test.

  The lubricating grease of the present invention is a fluorinated lubricating grease that uses PFPE oil as a base oil and fluororesin powder as a thickener, and contains an inorganic compound that forms a film on the metal surface. Therefore, it can be suitably used as a lubricating grease for rolling bearings used in automotive electrical equipment, office equipment, and the like. Further, the amount of grease filled is relatively small, such as in a vacuum, and can be suitably used for rolling bearings used under boundary lubrication conditions.

It is sectional drawing of a deep groove ball bearing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rolling bearing 2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Seal member 7 Lubrication grease

Claims (5)

  A lubricating grease comprising a perfluoropolyether oil as a base oil and a fluororesin powder as a thickener, wherein an inorganic compound capable of forming a film on a metal surface is added.   The lubricating grease according to claim 1, wherein the inorganic compound is a molybdate or a bismuth compound.   The lubricating grease according to claim 2, wherein the molybdate is potassium molybdate or sodium molybdate.   The lubricating grease according to claim 2, wherein the bismuth compound is bismuth sulfate. A rolling bearing comprising an inner ring and an outer ring arranged concentrically, and a plurality of rolling elements interposed between the inner ring and the outer ring, in which lubricating grease is sealed around the rolling elements,
5. A lubricating grease-enclosed rolling bearing, wherein the lubricating grease is the lubricating grease according to any one of claims 1 to 4.

Images