JP4653969B2 - Grease filled bearing for motor - Google Patents

Description

  The present invention relates to a grease-filled bearing for motors, and more particularly to a grease-filled bearing for motors for industrial machines and electrical equipment.

In recent years, miniaturization of motors has progressed, and bearings tend to be operated under higher surface pressure. Further, in the servo motor, acceleration and deceleration are increased during stop-operation, and accordingly, slip generated in the bearing is increased. As the use conditions become severe in this way, specific peeling accompanied with white structure change occurs early on the rolling surface of the rolling bearing, which 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 a fracture phenomenon that occurs from a relatively shallow portion of the surface of the rolling contact surface and is considered to be hydrogen embrittlement caused by hydrogen.
As a method for preventing such a specific peeling phenomenon accompanied by a white tissue change that occurs at an early stage, for example, a method of adding a passivating agent to a grease composition is known (Patent Document 1).
However, with the recent increase in the usage conditions of rolling bearings, it has become impossible to take sufficient measures by adding a passivating agent.
JP-A-3-210394

  The present invention has been made to cope with such a problem, and an object thereof is to provide a grease-filled bearing for a motor that can effectively prevent peeling on a rolling surface due to hydrogen embrittlement.

The grease-filled bearing for a motor of the present invention is a grease-filled bearing for a motor that supports a rotor of the motor, and the grease-filled bearing includes an inner ring and an outer ring, and a plurality of rolling elements interposed between the inner ring and the outer ring. A seal member for sealing the grease composition around the rolling elements is provided at both axial openings of the inner ring and the outer ring, and the grease composition is added to the base oil, a thickener and an additive. In which the additive contains at least a metal molybdate and an organic acid salt.
The metal molybdate is at least one metal molybdate selected from sodium molybdate, potassium molybdate and lithium molybdate.
The organic acid salt is a sodium salt of an organic acid having 1 to 20 carbon atoms. In addition, the organic acid is benzoic acid, sebacic acid, or succinic acid.
The blending ratio of each component is 0.01 to 5% by weight of the metal molybdate based on the entire grease composition, and 5 to 70% by weight of the organic acid salt based on the amount of the metal molybdate added. It is characterized by being made.
The thickener is a urea-based thickener.

A grease-filled bearing for a motor for supporting a rotor of a motor, wherein the grease composition enclosed in the bearing contains a molybdenum compound together with iron oxide on a frictional wear surface or a new ferrous metal surface exposed by wear in the bearing portion. It contains a metal molybdate capable of forming a containing film and an organic acid salt that promotes the formation of the film.

  The grease-enclosed bearing for motors of the present invention includes a grease composition encapsulated in the bearing, which contains a molybdate and an organic acid salt in grease composed of a base oil and a thickener. It can suppress the occurrence of peculiar delamination due to hydrogen embrittlement, which is seen in motor bearings used in automobiles and industrial machines where high-speed operation, rapid deceleration operation, and sudden stop are frequently performed. It becomes possible.

An example of a grease-filled bearing for a motor that supports the rotor of the motor is shown in FIG. FIG. 1 is a cross-sectional view of a deep groove ball bearing in which a grease composition is enclosed.
In the deep groove ball 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. Sealers 6 that are fixed to the cage 5, the outer ring 3, and the like that hold the plurality of rolling elements 4 are provided in the axially opposite end openings 8a, 8b of the inner ring 2 and the outer ring 3, respectively. A grease composition 7 is enclosed at least around the rolling element 4.

  An example of the motor is shown in FIG. FIG. 2 is a sectional view of the structure of the motor. The motor includes a stator 10 made of a magnet for a motor disposed on the inner peripheral wall of the jacket 9, a rotor 14 around which a winding 13 fixed to the rotating shaft 11 is wound, and a commutator fixed to the rotating shaft 11. 15, a brush holder 16 disposed on an end frame 18 supported by the jacket 9, and a brush 17 accommodated in the brush holder 16. The rotating shaft 11 is rotatably supported by the jacket 9 by a bearing 1 such as a ball bearing and a support structure for the bearing 1.

  In general-purpose motors such as AC motors and DC motors, miniaturization of motors has progressed, and bearings tend to be operated under higher surface pressure. Electric motors for industrial machinery such as servo motors, starter motors for automobiles, electric power steering motors, tilt motors for steering adjustment, blower motors, wiper motors, power window motors, and other motors for electrical equipment start-up and rapid acceleration operation -Since high-speed operation, rapid deceleration operation, and sudden stop are frequently repeated, the slip generated in the rolling bearing for the motor increases accordingly. As the usage conditions become severe, specific peeling with a change in the white structure occurs at an early stage on the rolling surface of the rolling bearing. Therefore, the rolling bearing for motors can be operated stably for a long period of time. And reliability are required.

  By blending molybdate and organic acid salt, the molybdate decomposes and reacts on the frictional wear surface or the new metal surface exposed by wear, and a molybdenum compound film is formed on the bearing rolling surface along with iron oxide. Furthermore, by using both molybdate and organic acid salt, as a result of surface analysis, it was found that the oxide film was thicker and the molybdenum content was higher than when only molybdate was blended. Therefore, it is considered that the organic acid salt has an effect of promoting the generation of the iron oxide and molybdenum compound coating on the bearing rolling surface. The iron oxide and molybdenum compound coating formed on the rolling surface of the bearing can suppress the generation of hydrogen due to the decomposition of the grease and prevent unique peeling due to hydrogen embrittlement.

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.
In the present invention, the metal that easily forms a film containing a molybdenum compound together with iron oxide reacts on the frictional wear surface or the newly formed iron-based metal surface exposed by wear in the bearing portion. Alkali metal salts of the salts are preferred. Suitable alkali metal molybdates include lithium molybdate, sodium molybdate or potassium molybdate, which can be used alone or as a mixture.

  The organic acid salt that can be used in the present invention can be any salt such as an aromatic organic acid, an aliphatic organic acid, or an alicyclic organic acid. As the organic acid, monobasic or polybasic organic acids can be used. Among these, an organic acid having a chemical structure having 1 to 20 carbon atoms is particularly preferable because it promotes formation of a film containing a molybdenum compound.

  Specific examples of organic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, pelargonic acid, capric acid, undecyl acid, lauric acid, tridecylic acid, myristic acid, pentadecyl Monovalent saturated fatty acids such as acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid and arachidic acid, monounsaturated fatty acids such as acrylic acid, crotonic acid, undecylenic acid, oleic acid and gadoleic acid, malonic acid and methylmalon Divalent saturation such as acid, succinic acid, methyl succinic acid, dimethyl malonic acid, ethyl malonic acid, glutaric acid, adipic acid, dimethyl succinic acid, pimelic acid, tetramethyl succinic acid, suberic acid, azelaic acid, sebacic acid, brassic acid Divalent unsaturated fatty acids such as fatty acids, fumaric acid, maleic acid, oleic acid, tartaric acid, Fatty acid derivatives such as phosphate, benzoic acid, phthalic acid, trimellitic acid, and aromatic organic acids such as pyromellitic acid.

  The organic acid is preferably a metal salt thereof, and a sodium salt is preferable among the metal salts. Preferred metal salts of organic acids include sodium benzoate, monosodium sebacate, disodium sebacate, monosodium succinate, and disodium succinate.

  Base oils that can be used in the present invention include mineral oils such as spindle oil, refrigerating machine oil, turbine oil, machine oil, dynamo oil, high-purity mineral oil, liquid paraffin, polybutene, poly-α-olefin, alkylnaphthalene, alicyclic compounds, etc. Hydrocarbon synthetic oil or natural oil, polyol ester oil, acid ester oil, polymer ester oil, aromatic ester oil, carbonate ester oil, diester oil, polyglycol oil, silicone oil, polyphenyl ether oil, alkyl diphenyl ether Non-hydrocarbon synthetic oils such as oil, alkylbenzene oil, and fluorinated oil can be used.

  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. In consideration of heat resistance, cost, and the like, a urea compound is desirable.

  Examples of the urea compound include a diurea compound and a polyurea compound. A diurea compound is obtained by reaction of 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.

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.
Base grease for blending various compounding agents by blending a urea compound with a base oil can be obtained. The base grease is produced by reacting an isocyanate compound and an amine compound in a base oil.

  The blending ratio of the thickener to the base grease is 1 to 40% by weight, preferably 3 to 25% by weight, based on the whole base grease. If the content of the thickener is less than 1% by weight, the thickening effect is reduced, making it difficult to make grease. If the content exceeds 40% by weight, the obtained base grease becomes too hard and the desired effect is difficult to obtain. Become.

  The blending ratio of molybdate and organic acid salt is 0.01-5% by weight of molybdate and the amount of molybdate added to the entire grease composition composed of the base grease and various compounding agents. On the other hand, the organic acid salt is mixed in an amount of 5 to 70% by weight. If the blending ratio of molybdate and organic acid salt is less than the above blending range, peeling on the rolling surface due to hydrogen embrittlement cannot be effectively prevented. Moreover, even if it exceeds the said range, the peeling prevention effect does not improve any more.

  In addition to a mixed compounding agent of molybdate and organic acid salt, a known additive for grease can be contained as required. Examples of the additives include organic zinc compounds, amine-based, phenol-based, sulfur-based antioxidants, metal deactivators such as benzotriazole, polymethacrylate, polystyrene and other viscosity index improvers, molybdenum disulfide, graphite. Examples thereof include solid lubricants such as metal sulfonates, rust preventives such as polyhydric alcohol esters, friction reducing agents such as organic molybdenum, oily agents such as esters and alcohols, and phosphorus-based antiwear agents. These can be added alone or in combination of two or more.

  Since the grease composition that can be used in the present invention can suppress the occurrence of peculiar peeling due to hydrogen embrittlement, the life of the grease-sealed bearing can be improved. 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. Can be used as grease.

Examples 1 to 13
4,4-Diphenylmethane diisocyanate (MDI) is dissolved in half of the base oil shown in Table 1 and Table 2 in the proportions shown in Table 1 and Table 2, and 4,4-diphenylmethane is dissolved in the remaining half of the base oil. A monoamine that was twice the equivalent of diisocyanate was dissolved. The respective blending ratios and types are as shown in Tables 1 and 2.
A solution in which monoamine is dissolved is added while stirring the solution in which 4,4-diphenylmethane diisocyanate is dissolved, and then the reaction is continued at 100 to 120 ° C. for 30 minutes to form a diurea compound in the base oil. It was.
To this, molybdate, organic acid salt and antioxidant were added at the blending ratios shown in Tables 1 and 2, and the mixture was further stirred at 100 to 120 ° C. for 10 minutes. Thereafter, the mixture was cooled and homogenized with three rolls to obtain a grease composition.

In Tables 1 and 2, the alkyl diphenyl ether oil used as the base oil is LB100 under the trade name of Matsumura Oil Co., Ltd., synthetic hydrocarbon oil is Shinflud 601 under the trade name of Nippon Steel Chemical Co., and polyol ester is the trade name of Kao Corporation. Kaolube 268 was used respectively. As the mineral oil, a paraffinic mineral oil having a kinematic viscosity of 30.7 mm ² / s (40 ° C.) was used.
As the antioxidant, alkylated diphenylamine was used.

  The obtained grease composition was subjected to a high-temperature high-speed test, a rapid acceleration / deceleration test, and a blending penetration measurement according to Japanese Industrial Standards. Test methods and test conditions are shown below. The results are shown in Tables 1 and 2.

High-temperature, high-speed test The grease composition obtained in each example was sealed in a rolling bearing for motor (6204), 1.8 g, respectively, and the bearing outer ring outer diameter temperature was 180 ° C, radial load was 67 N, and axial load was 67 N. It was rotated at a rotational speed of 10000 rpm, and the time until burn-in was measured.

Rapid Acceleration / Deceleration Test 1.8 g of the grease composition obtained in each example is enclosed in a rolling bearing for motor (6204), and the rotating shaft of an alternator, which is an example of an electrical accessory, is supported to apply a load. A rapid acceleration / deceleration test was carried out in a rolling bearing with internal rotation. The rapid acceleration / deceleration test conditions were set such that the load applied to the pulley attached to the tip of the rotating shaft was 3234 N and the rotation speed was 0 to 18000 rpm. Then, abnormal peeling occurred in the bearing, and the time when the generator stopped when the vibration of the vibration detector exceeded the set value was measured.

Example 14 and Example 15
Li-12-hydroxystearate was added to the base oil shown in Table 2, and dissolved by heating at 200 ° C. with stirring. In addition, each compounding ratio is as Table 2. Thereafter, the mixture was cooled, molybdate, organic acid salt and antioxidant were added at the blending ratio shown in Table 2, and homogenized with three rolls to obtain a grease composition. The grease composition was subjected to a high-temperature high-speed test and a rapid acceleration / deceleration test in the same manner as in Example 1. However, considering the heat resistance of Li soap grease, the high-temperature high-speed test was conducted at 150 ° C.

Comparative Examples 1 to 6
By the method according to Example 1, the thickener and base oil were selected at the blending ratios shown in Table 2 to adjust the base grease, and further additives were blended to obtain a grease composition. The obtained grease composition was evaluated by performing the same test as in Example 1. The results are shown in Table 2.

  As shown in Tables 1 and 2, each example can effectively prevent specific delamination accompanied by a white structure change occurring on the rolling surface of a rolling bearing for a motor, so a high-temperature high-speed test and a rapid acceleration / deceleration test Is excellent. All the rapid acceleration / deceleration tests in each example showed 300 hours or more.

  The grease-enclosed bearing for motors of the present invention can effectively prevent specific delamination accompanied with a change in white structure generated on the rolling surface of the bearing, and has excellent bearing life. It can be used for rolling bearings of automobile electrical parts such as electromagnetic clutches, intermediate pulleys, electric fan motors, and auxiliary machines.

It is sectional drawing of a deep groove ball bearing. It is sectional drawing of the structure of a motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Grease-filled bearing 2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Seal member 7 Grease composition

Claims (4)

A grease-filled bearing for a motor that supports a rotor of a motor, the grease-filled bearing comprising an inner ring and an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and a grease composition around the rolling elements A seal member for sealing the inner ring and the outer ring at both ends in the axial direction,
The grease composition is a grease composition comprising a base oil and a thickener and an additive,
The additive includes at least a metal molybdate and an organic acid salt,
The metal molybdate is at least one metal molybdate selected from sodium molybdate, potassium molybdate, and lithium molybdate, and the organic acid salt is a sodium salt of benzoic acid, sebacic acid, or succinic acid. A grease-filled bearing for motors.   0.01 to 5% by weight of the metal molybdate based on the entire grease composition, and 5 to 70% by weight of the organic acid salt based on the amount of the metal molybdate added. The grease-filled bearing for a motor according to claim 1. The grease-enclosed bearing for a motor according to claim 1 or 2, wherein the thickener is a urea-based thickener.   The grease-filled bearing for a motor according to any one of claims 1 to 3, wherein the base oil is a mixed oil of an alkyl diphenyl ether oil and a synthetic hydrocarbon oil.

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