JP2007285358A - Grease-filled bearing for motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease-filled bearing for a motor which can effectively prevent exfoliation on the rolling surface caused by hydrogen brittleness. <P>SOLUTION: A grease composition 7, which fills the grease-filed bearing 1 for the motor, is constituted by blending an additive with base grease comprised of base oil and thickener. The additive contains at least one aluminum-base additive selected from an aluminum powder and an aluminum compound, and the compounding ratio between the base grease and the aluminum-based additive is 0.05 to 10 pts.wt. to base grease of 100 pts.wt. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 usage conditions become severe in this way, there is a problem in that specific peeling accompanied with a white structure change occurs early on the rolling surface of the rolling bearing, and the bearing life is shortened.
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 an unusual peeling phenomenon accompanied by a white texture 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 ( Patent Document 2) is known.
However, due to the severe use conditions of rolling bearings used to support the rotor of motors in recent years, it has become impossible to take sufficient measures with the method of adding the passivating agent or bismuth dithiocarbamate. .
JP-A-3-210394 JP-A-2005-42102

  The present invention has been made in order to address such problems, and is capable of effectively preventing separation on the rolling surface due to hydrogen embrittlement under the use conditions of the rolling bearing used in the motor. The purpose is to provide.

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, In order to seal the grease composition around the rolling element, a seal member is provided at both axial openings of the inner ring and the outer ring. The grease composition includes a base oil, a thickener, A grease composition comprising an additive added to a base grease comprising the additive, wherein the additive contains at least one aluminum-based additive selected from aluminum powder and an aluminum compound, and the combination of the aluminum-based additive The ratio is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease.
The aluminum compound is at least one aluminum compound selected from aluminum powder, aluminum carbonate, and aluminum nitrate.
The thickener is a urea or lithium soap thickener.
The base oil is at least one oil selected from ester oils and poly-α-olefin oils.

  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 composition sealed in the bearing is an iron-based metal exposed by a frictional wear surface or wear in the bearing portion. It is characterized in that it contains at least one aluminum-based additive selected from aluminum powder and an aluminum compound, which can form a film containing aluminum and aluminum oxide together with iron oxide on the new surface.

  The grease composition to be sealed in the grease-sealed bearing for motors of the present invention is formed by blending at least one aluminum-based additive selected from aluminum powder and aluminum compound with a base grease composed of a base oil and a thickener. Therefore, to suppress the occurrence of peculiar delamination due to hydrogen embrittlement seen in motor bearings used in automobiles and industrial machinery where repeated starting, rapid acceleration, high speed, rapid deceleration, and sudden stop are frequently performed. This makes it possible to extend the life of grease-filled bearings for motors.

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 13 around which a winding 12 fixed to the rotating shaft 11 is wound, and a commutator fixed to the rotating shaft 11. 14, a brush holder 15 disposed on an end frame 17 supported by the jacket 9, and a brush 16 accommodated in the brush holder 15. 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 machines 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 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 adding at least one aluminum-based additive selected from aluminum powder and aluminum compound to the grease for the rolling bearing for motor, the aluminum powder adheres to the frictional wear surface or the new metal surface exposed by wear, or the aluminum compound Reacts, and a film containing aluminum and aluminum oxide together with iron oxide is formed on the bearing rolling surface.
The coating formed on the rolling surface of the bearing suppresses the generation of hydrogen due to the decomposition of the grease composition, and the hydrogen in the air in the bearing may be generated by electrolysis due to the current flowing through the motor. Intrusion can be prevented, and unique peeling due to hydrogen embrittlement can be prevented.

Examples of the aluminum-based additive to be added to the grease composition used in the grease-sealed bearing for motors of the present invention include aluminum powder, aluminum carbonate, aluminum sulfide, aluminum chloride, aluminum nitrate and hydrates thereof, aluminum sulfate, aluminum fluoride, Aluminum bromide, aluminum iodide, aluminum oxide and its hydrate, aluminum hydroxide, aluminum selenide, aluminum telluride, aluminum phosphate, aluminum phosphide, lithium aluminate, magnesium aluminate, aluminum selenate, titanic acid Examples thereof include aluminum, aluminum zirconate, aluminum benzoate, and aluminum citrate. These aluminum-based additives may be added to the base grease by mixing one type or two types.
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 compounding 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-based 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-based additive is only aluminum compound , 0.05 parts by weight to 10 parts by weight of the aluminum compound with respect to 100 parts by weight of the base grease. (3) When the aluminum additive is aluminum powder and an aluminum compound, Combine 0.05 parts by weight to 10 parts by weight with the aluminum compound.
If the blending ratio of the aluminum additive is less than this 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.

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, highly refined mineral oil, liquid paraffin, GTL oil synthesized by the Fischer-Tropsch process, polybutene, poly- Hydrocarbon synthetic oil such as α-olefin oil, alkylnaphthalene, alicyclic compound, or natural oil, polyol ester oil, phosphate ester oil, polymer ester oil, aromatic ester oil, carbonate ester oil, diester oil, Non-hydrocarbon synthetic oils such as polyglycol oil, silicone oil, polyphenyl ether oil, alkyldiphenyl ether oil, alkylbenzene oil, and fluorinated oil can be used.
Among these, it is preferable to use ester oils and poly-α-olefin oils excellent in heat resistance, lubricity and low noise.

  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 view of heat resistance, cost, etc., a urea compound or a lithium soap compound is desirable, and more desirably, a urea compound having excellent heat resistance.

  The urea compound is obtained by reacting an isocyanate compound with 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.

A base grease for blending the above-mentioned aluminum-based additive and the like by blending a thickener such as the above-mentioned urea-based compound with the base oil 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 thereof include solid lubricants, metal sulfonates, antirust agents such as polyhydric alcohol esters, friction reducing agents such as organic molybdenum, oily 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.

  Since the grease composition of 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, motors such as 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. It can be used as grease for bearings for automobiles.

Examples 1 to 5
In half of the base oil shown in Table 1, 4,4-diphenylmethane diisocyanate (trade name Millionate MT manufactured by Nippon Polyurethane Industry Co., Ltd., hereinafter referred to as MDI) is dissolved in the proportion shown in Table 1, and the remaining half In this base oil, a monoamine that was twice the equivalent of MDI 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 to 120 ° C. to produce a diurea compound in the base oil.
Additives were added to this at the blending ratio shown in Table 1, 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 Table 1, the synthetic hydrocarbon oil used as the base oil is Shinfluid 801 manufactured by Nippon Steel Chemical Co., Ltd. having a kinematic viscosity of 47 mm ² / sec at 40 ° C., and the ester oil is Kao Luve 268 manufactured by Kao Co., Ltd. 115, and the mineral oil used was a paraffinic mineral oil. Moreover, alkylated diphenylamine was used as the antioxidant.

  The obtained grease composition was subjected to a rapid acceleration / deceleration test and a high temperature high speed test. Test methods and test conditions are shown below. The results are shown in Table 1.

<Rapid acceleration / deceleration test>
Each of the rolling bearings for motors (6303) was filled with 1.8 g of the grease composition obtained in each example, and a pulley around which a rotating belt of an alternator as an example of an electrical accessory was wound was applied to apply a load. The rotating shaft to be supported was incorporated as a rolling bearing (test bearing) supported by an inner ring, and a rapid acceleration / deceleration test was conducted. The rapid acceleration / deceleration test conditions are such that the operating load is set to 1960 N for the test bearing attached to the end of the rotating shaft, the rotation speed is 0 rpm to 18000 rpm, and a current of 0.1 A flows in the test bearing. The test was conducted at Then, abnormal peeling occurred in the test bearing, the time when the vibration of the vibration detector exceeded the set value and the generator stopped (peeling life time, hr) was measured. The test was terminated after 300 hours.
This rolling bearing having a peeling occurrence life time of 300 hours or more was evaluated as having excellent performance for preventing the occurrence of peeling.

<High-temperature high-speed test>
The grease composition obtained in each of the examples was sealed in a rolling bearing for a motor (6204) in an amount of 1.8 g, and the outer diameter of the outer ring of the bearing was 180 ° C., a radial load of 67 N, and an axial load of 67 N. It was rotated at the number of rotations, and the time until burn-in was measured.

Examples 6 to 7 and Comparative Examples 4 to 5
Li-12-hydroxystearate was added to the base oil shown in Table 1, and dissolved by heating at 200 ° C. with stirring. In addition, each compounding ratio is as Table 1. Thereafter, the mixture was cooled, and the additive was added thereto at a blending ratio shown in Table 1, and homogenized with a three-roll 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. The results are shown in Table 1.

Comparative Examples 1 to 3
In accordance with the method according to Example 1, the base grease was prepared by selecting the thickener and the base oil at the blending ratio shown in Table 1, and the additive was further 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 1.

  As shown in Table 1, in each example, all the rapid acceleration / deceleration tests showed excellent results of 300 hours or more (peeling life time). This is considered to be because the specific exfoliation accompanied by the white texture change that occurs on the rolling surface can be effectively prevented by adding the aluminum-based additive at a predetermined ratio.

  The grease-enclosed bearing for motors of the present invention can effectively prevent specific delamination accompanied by a change in white structure generated on the rolling surface of the bearing, and is excellent in bearing life. It can be suitably used for bearings.

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

Explanation of symbols

1 Grease-filled bearing (rolling bearing)
DESCRIPTION OF SYMBOLS 2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Seal member 7 Grease composition 8a, 8b Opening 9 Jacket 10 Stator 11 Rotating shaft 12 Winding 13 Rotor 14 Commutator 15 Brush holder 16 Brush 17 End frame

Claims (5)

A grease-filled bearing for a motor that supports the rotor of the motor,
The grease-sealed bearing includes an inner ring and an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and openings in both axial ends of the inner ring and the outer ring for sealing a grease composition around the rolling elements. A seal member provided,
The grease composition is a grease composition formed by adding an additive 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 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. A grease-filled bearing for motors.   2. The grease-filled bearing for a motor according to claim 1, wherein the aluminum compound is at least one compound selected from aluminum carbonate and aluminum nitrate.   The grease-enclosed bearing for a motor according to claim 1 or 2, wherein the thickener is a urea-based or lithium soap-based thickener.   4. The grease-filled bearing for a motor according to claim 1, wherein the base oil is at least one oil selected from an ester oil and a poly-α-olefin oil.   A grease-enclosed bearing for a motor for supporting a rotor of a motor, wherein the grease composition enclosed in the bearing is made of aluminum and aluminum oxide together with iron oxide on a friction wear surface or a new ferrous metal surface exposed by wear in the bearing portion. A grease-enclosed bearing for motors, comprising at least one aluminum-based additive selected from aluminum powder and aluminum compounds, capable of forming a coating film containing.

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