JP5938500B2 - Grease filled bearing for motor - Google Patents

Description

  The present invention relates to grease-filled bearings for motors that are grease-lubricated, and more particularly to rolling bearings used in motors for industrial machines, electrical equipment, electric vehicle drives, and the like.

  In a motor that is used in an environment involving minute reciprocating motion or vibration, there is a possibility that a wear phenomenon (hereinafter referred to as fretting) generally referred to as fine movement wear may occur. For example, in an industrial machine motor such as a servo motor or a stepping motor, there is a risk that fretting occurs on the rolling surface of the bearing due to vibration during driving or a minute reciprocating motion. In addition, motors for electrical equipment used in automobiles, drive motors for electric cars and hybrid cars, etc. are fretting on bearing rolling surfaces due to slight vibrations caused by the power of engines and the like, as well as slight vibrations caused by the road surface environment during traveling. May occur. In particular, fretting tends to occur when a sufficient supply of lubricating oil to the bearing rolling surface cannot be obtained, such as in a low temperature environment.

  Further, along with the recent miniaturization of motors, miniaturization of motor bearings that support the rotor of the motor has been promoted. For this reason, the contact surface pressure applied to the members constituting the motor bearing tends to increase. In addition, the speed of rotation of the motor has been increased, and the acceleration / deceleration of the rotation of the motor bearing tends to increase when the motor is started and stopped. An increase in the surface pressure between the rolling elements and the raceway or an increase in slip due to sudden acceleration / deceleration easily causes oil film breakage (poor lubrication) at the portion. Thereby, a metal contact generate | occur | produces, it becomes easy to wear a rolling element and a bearing ring, and the possibility that the said fretting will arise also increases.

  Conventionally, various methods have been proposed to prevent such fretting, and one of them is a method for preventing fretting by selecting an appropriate lubricant. Among them, a grease in which at least one selected from oxidized paraffin, diphenyl hydrogen phosphite, and hexamethylphosphoric triamide is added to a urea-based thickener has been proposed (see Patent Document 1).

Japanese Patent No. 2576898

  However, it is considered that the grease disclosed in Patent Document 1 is difficult to sufficiently prevent fretting in a motor application in which minute reciprocation and vibration are likely to occur.

  In addition, the effect of improving the fretting resistance by the grease used for lubrication has not been fully elucidated. For example, even greases containing the same thickener may give conflicting results for fretting resistance depending on the test method. In addition, there are many reports that additives containing phosphorus compounds such as phosphates and phosphate esters are preferable, but their fretting resistance varies greatly depending on the structure of the phosphorus compound.

  The present invention has been made to cope with such problems, and has excellent fretting resistance while being used in an environment involving minute reciprocating motion and vibration, and wear on a bearing rolling surface. An object of the present invention is to provide a grease-filled bearing for a motor that can prevent this.

（式（１）（２）において、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５は、それぞれメチル基またはエチル基である。また、Ｒ_１とＲ_２とは、Ｒ_３とＲ_４とＲ_５とは、同一の基であっても異なる基であってもよい。） The grease-filled bearing for a motor according to the present invention supports the rotor of the motor, and includes an inner ring and an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and axial end openings of the inner ring and the outer ring. A grease composition containing a base oil, a thickener, and an additive around the rolling element, and the base oil contains ester oil as an essential component. The base oil has a kinematic viscosity at 40 ° C. of 20 to 50 mm ² / s, and the additive is at least one of phosphites represented by the formula (1) or (2) It contains seeds, and the content of the phosphite is 0.5 to 4 parts by weight based on 100 parts by weight of the total amount of the base oil and the thickener.

(In Formulas (1) and (2), R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each a methyl group or an ethyl group. R ₁ and R ₂ are R ₃ and R ₄ , respectively. And R ₅ may be the same group or different groups.)

  The base oil is a synthetic oil composed only of the ester oil or a mixed oil of the ester oil and a poly-α-olefin (hereinafter referred to as PAO) oil.

  The grease composition is characterized by not containing a phosphite other than those represented by the formula (1) or (2) and a phosphate ester having an organic group having 3 or more carbon atoms.

  The phosphite is dimethyl phosphite, diethyl phosphite, trimethyl phosphite, or triethyl phosphite.

  The thickener is a metal soap.

  The grease composition has a blending degree of 200 to 350.

  The grease-filled bearing for a motor is a deep groove ball bearing. Further, the grease-filled bearing for a motor is characterized in that it supports a rotor of a motor for industrial machinery, electrical equipment, or an electric vehicle drive.

The grease-enclosed bearing for motors of the present invention uses a base oil (synthetic oil) containing an ester oil as an essential component and a kinematic viscosity at 40 ° C. of 20 to 50 mm ² / s as an additive for the grease composition to be encapsulated. Among the phosphites, especially by using a composition containing a predetermined amount of the one represented by the above formula (1) or formula (2), while being used in an environment with minute reciprocating motion or vibration, It has excellent fretting resistance and can prevent fretting on the rolling surface of the bearing in a wide temperature range.

  For this reason, the grease-filled bearing for motors of the present invention can be suitably used as a bearing for supporting a rotor of an industrial machine motor, an electrical equipment motor, an electric vehicle drive motor, or the like.

It is sectional drawing of the deep groove ball bearing which shows one Example of the rolling bearing for motors of this invention. It is sectional drawing of the motor using the rolling bearing for motors of this invention.

  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. A cage for holding the plurality of rolling elements 4 is provided. In addition, seal members 6 fixed to the outer ring 3 and the like are provided in the axially opposite end openings 8a and 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. This grease composition 7 is a grease composition containing a predetermined phosphite as an additive to be described later.

  An example of a motor to which the grease-filled bearing for motors of the present invention is applied 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 the deep groove ball bearing 1 and a support structure for the bearing 1. The bearing 1 is a grease-filled bearing for a motor of the present invention.

  In addition to the deep groove ball bearing shown in FIG. 1, the sealed motor bearing of the present invention includes an angular ball bearing, a cylindrical roller bearing, a tapered roller bearing, a self-aligning roller bearing, a needle roller bearing, a thrust cylindrical roller bearing, and a thrust tapered roller. Bearings, thrust needle roller bearings, thrust spherical roller bearings, and the like can also be used. Among these, it is preferable to use a deep groove ball bearing having rotational accuracy at high speed, load resistance, and low cost.

  The grease composition enclosed in the grease-enclosed bearing for motors of the present invention includes a base oil, a thickener, and an additive, and the additive includes a predetermined phosphite.

（式（１）（２）において、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５は、それぞれメチル基またはエチル基である。また、Ｒ_１とＲ_２とは、Ｒ_３とＲ_４とＲ_５とは、同一の基であっても異なる基であってもよい。） The predetermined phosphite used in the grease composition is at least one phosphite represented by the following formula (1) or (2). The phosphorous acid ester represented by these formulas may be used individually by 1 type, or may mix 2 or more types.

(In Formulas (1) and (2), R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each a methyl group or an ethyl group. R ₁ and R ₂ are R ₃ and R ₄ , respectively. And R ₅ may be the same group or different groups.)

  Phosphites represented by formula (1) or formula (2) are, for example, phosphite diesters such as dimethyl phosphite, diethyl phosphite, methyl ethyl phosphite, trimethyl phosphite, phosphorus phosphite Phosphorous acid triesters such as triethyl acid, dimethyl ethyl phosphite, and methyl diethyl phosphite. Among these, dimethyl phosphite, diethyl phosphite, trimethyl phosphite, or triethyl phosphite is preferable.

  In the grease composition, the content of the phosphite is 0.5 to 4 parts by weight with respect to 100 parts by weight of the total amount of the base oil and the thickener. If the phosphite content is less than 0.5 parts by weight, the fretting resistance may not be improved. Moreover, even if the content of the phosphite exceeds 4 parts by weight, the fretting resistance is hardly improved further. In addition, when using 2 or more types of phosphites, let the total amount be in the said range.

  Moreover, it is preferable that the said grease composition does not contain phosphite other than the phosphite represented by the said Formula (1) or (2). Moreover, it is preferable that the phosphate ester which has a C3 or more organic group is not included. That is, it is preferable not to include anything other than the oxidized phosphorous acid ester represented by the above formula (1) or (2). When these phosphites and phosphates are included, the fretting resistance may be inferior.

  The grease composition uses the predetermined low molecular weight phosphite ester as an additive, and is conventionally blended to prevent fretting and surface-origin peeling, such as zinc dithiophosphate and tricresyl phosphate. Even when other phosphorus compounds and other extreme pressure agents are not blended, the occurrence of fretting can be prevented.

  Moreover, you may make the said grease composition contain well-known additives other than the said phosphite as needed. Such additives include antioxidants such as phenols and amines, rust inhibitors such as carboxylates and sulfonates, antiwear agents such as polyalkylene glycol and glycerin, chlorinated paraffin, sulfurized oil, organic Examples include extreme pressure agents such as molybdenum compounds, oiliness improvers such as higher fatty acids and synthetic esters, and solid lubricants such as graphite and molybdenum disulfide. In addition, these can be added individually or in combination of 2 or more types.

The base oil of the grease composition is a kinematic viscosity of 20 to 50 mm ² / s at 40 ° C., more preferably from 20 to 40 mm ² / s, most preferably 26~40mm ² / s. When the kinematic viscosity at 40 ° C. is less than 20 mm ² / s, the viscosity is too low and the oil film is likely to be cut off, and the oil is increased in evaporation. On the other hand, if the kinematic viscosity at 40 ° C. is higher than 50 mm ² / s, the supply of lubricating oil to the rolling surface is inferior, and fretting occurs in motor applications that are used in environments with minute reciprocating motion or vibration. It becomes easy. Further, since the torque of the bearing increases, the power loss during motor driving increases and the heat generation also increases. In addition, when using mixed oil as a base oil, it is preferable that dynamic viscosity of this mixed oil is in the said range.

  The type of base oil of the grease composition is not particularly limited as long as it satisfies the above kinematic viscosity range, and general oils usually used in the field of grease can be used. For example, mineral oil, synthetic oil, or these mixed oils are mentioned.

  Examples of the mineral oil include those obtained by a method usually used in a process for producing a lubricating oil in the oil refining industry, more specifically, a lubricating oil fraction obtained by atmospheric distillation and vacuum distillation of crude oil. Is obtained by performing one or more treatments such as solvent removal, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment.

  Examples of the synthetic oil include ester oils; PAO oils such as polybutenes, 1-octene oligomers, 1-decene oligomers or their hydrides; alkylnaphthalenes; alkylbenzenes; polyoxyalkylene glycols; polyphenyl ethers; dialkyl diphenyl ethers; Fluorine oil; GTL oil synthesized by Fischer-Tropsch method; and the like.

  Among these, since it is excellent in heat resistance and lubricity, it is preferable to use at least one oil selected from ester oil and PAO oil. In particular, it is preferable to make ester oil essential, and it is preferable to use mixed oil of ester oil and PAO oil as needed. When the mixed oil of ester oil and PAO oil is used, the mixing ratio is preferably PAO oil / ester oil (weight ratio) = 8/2 to 2/8.

  Ester oil is a compound that has an ester group in the molecule and is liquid at room temperature, and examples thereof include polyol ester oil, phosphate ester oil, polymer ester oil, aromatic ester oil, carbonate ester oil, and diester oil. It is done. Among these, aromatic ester oil or polyol ester oil is preferable.

  The aromatic ester oil is preferably a compound obtained by reacting an aromatic polybasic acid or a derivative thereof with a higher alcohol. Aromatic polybasic acids include aromatic tricarboxylic acids such as trimellitic acid, biphenyltricarboxylic acid and naphthalenetricarboxylic acid, aromatic tetracarboxylic acids such as pyromellitic acid, biphenyltetracarboxylic acid, benzophenonetetracarboxylic acid and naphthalenetetracarboxylic acid. Derivatives such as acids or acid anhydrides thereof may be mentioned. As the higher alcohol, aliphatic monohydric alcohols having 4 or more carbon atoms such as octyl alcohol and decyl alcohol are preferable. Examples of the aromatic ester oil include trioctyl trimellitate, tridecyl trimellitate, tetraoctyl pyromellitate and the like.

  The polyol ester oil is preferably a compound having a plurality of ester groups in a molecule obtained by a reaction between a polyol and a monobasic acid. The monobasic acid to be reacted with the polyol may be used alone or as a mixture. In the case of an oligoester, a dibasic acid may be used. Examples of the polyol include trimethylolpropane, pentaerythritol, dipentaerythritol, neopentyl glycol, 2-methyl-2-propyl-1,3-propanediol, and the like. Examples of the monobasic acid include monovalent fatty acids having 4 to 18 carbon atoms. For example, valeric acid, caproic acid, caprylic acid, enanthic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, tallow acid, stearic acid, caproleic acid, undecylenic acid, lindelic acid, tuzuic acid , Fizetheric acid, myristoleic acid, palmitoleic acid, petrothelic acid, oleic acid, elaidic acid, asclepic acid, vaccenic acid, sorbic acid, linoleic acid, linolenic acid, sabinic acid, ricinoleic acid and the like. Examples of polyol ester oils include trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, and the like.

  Other examples of diester oils include ditridecyl glutarate, di2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di3-ethylhexyl sebacate and the like.

  The thickener of the above-mentioned grease composition is not particularly limited, and general ones usually used in the field of grease can be used. For example, soap-type thickeners such as metal soaps and composite metal soaps, and non-soap-type thickeners such as benton, silica gel, urea compounds, urea / urethane compounds, and fluororesins can be used. Examples of the metal soap include sodium soap, calcium soap, aluminum soap and lithium soap. Examples of urea compounds and urea / urethane compounds include diurea compounds, triurea compounds, tetraurea compounds, other polyurea compounds, and diurethane compounds. Among these, it is preferable to use a urea compound or lithium soap in consideration of heat resistance, cost, and the like. In addition, urea compounds and lithium soaps are excellent in intervening properties and adhesion to rolling surfaces, and can easily prevent fretting.

  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, and hexane diisocyanate. Examples of the monoamine include octylamine, dodecylamine, hexadecylamine, stearylamine, 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 are the same as those used for producing the diurea compound. Examples of the diamine include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, xylenediamine, and diaminodiphenylmethane.

  In motors, quietness and low torque are required for their use, so among the above urea compounds, fats obtained by reacting diisocyanates such as diphenylmethane diisocyanate with aliphatic monoamines such as octylamine. It is preferable to use a group urea compound.

  A base grease for blending the above additives can be obtained by blending the base oil with a thickener such as lithium soap or urea compound. A base grease using a urea compound as a thickener is produced by reacting the diisocyanate with a monoamine in a base oil.

  The content of the thickener in 100 parts by weight of the base grease is preferably 3 to 40 parts by weight, and more preferably 5 to 30 parts by weight. It is suitable for obtaining the inherent lubricity of the grease composition to be within this range. If the content of the thickener is less than 3 parts by weight, the thickening effect is reduced and it becomes difficult to form a grease. When the content of the thickener exceeds 40 parts by weight, the obtained base grease becomes too hard, and it is difficult to obtain the desired effect.

  It is preferable that the penetration degree (JIS K 2220) of the grease composition is in the range of 200 to 350. When the consistency is less than 200, oil separation at a low temperature is small, resulting in poor lubrication and fretting is likely to occur. On the other hand, if the consistency exceeds 350, the grease is soft and easily flows out of the bearing, which is not preferable.

  Motors to which the rolling bearings for motors of the present invention can be applied include motors for industrial fans such as motors for ventilation fans, blower motors for fuel cells, cleaner motors, fan motors, servo motors and stepping motors, starter motors for automobiles, and electric power steering motors. And motors for electrical equipment such as steering adjustment tilt motors, blower motors, wiper motors, and power window motors, and drive motors for electric vehicles and hybrid vehicles. Further, the present invention can be applied to other motors used in an environment involving minute reciprocating motion and vibration.

  The present invention will be specifically described with reference to examples and comparative examples, but is not limited to these examples.

Examples 1 to 12 and Comparative Examples 1 to 4
As shown in Tables 1 to 3, a base grease was prepared by selecting a thickener and a base oil. The composition of the base grease is 100 parts by weight in total of the thickener and the base oil. Here, “lithium soap” which is a thickener in each table is lithium 12-hydroxystearate. In addition, with respect to the grease having “aliphatic urea” as a thickener, MDI (manufactured by Nippon Polyurethane Industry Co., Ltd .: MILLIONATE MT (main component: diphenylmethane diisocyanate)) is dissolved in half of the base oil shown in each table, Octylamine, which is twice the equivalent of MDI, was dissolved in the remaining half of the base oil, and these were mixed by stirring.

“Ester oil” in the tables in Examples 1 to 6 and Comparative Examples 1 and 2 is ester oil 1 (manufactured by Nippon Steel Chemical Co., Ltd .: Hatkor H3110, kinematic viscosity at 40 ° C. 12 mm ² / s (diester oil)) and Ester oil 2 (manufactured by ADEKA: ADEKA LUB 60Z01A, kinematic viscosity at 40 ° C. 32 mm ² / s (polyol ester oil)) was mixed in a ratio (weight ratio) of ester oil 1: ester oil 2 = 3: 7. Oil.

In addition, “PAO oil” in the tables in Examples 7 to 12 and Comparative Examples 3 to 4 is Shinflud 601 (kinematic viscosity at 40 ° C. 30 mm ² / s) manufactured by Nippon Steel Chemical Co., Ltd. ”Manufactured by Nippon Steel Chemical Co., Ltd .: Hatcoal H2362 (kinematic viscosity at 40 ° C. 72 mm ² / s (polyol ester oil). The base oils in Examples 7 to 12 and Comparative Examples 3 to 4 are the above ester oils: It is an oil mixed at a ratio (weight ratio) of PAO = 1: 3.

  Additives were added in the proportions shown in each table to 100 parts by weight of the base grease prepared above, and sufficiently stirred with a stirring deaerator to obtain a test grease. In Tables 2 and 3, 1) 2) is the same as 1) 2) shown in the lower part of Table 1. About the obtained test grease, it used for the fretting test shown below and measured the abrasion loss. The results are shown in each table.

<Fretting test>
In accordance with ASTM D4170, a performance evaluation test was performed using a Fafner fine movement wear tester. 51204J was used as a bearing, and the test time was 2 hours under the conditions of a maximum contact surface pressure of 1.7 GPa, a rocking cycle of 30 Hz, a rocking angle of 12 °, and an ambient room temperature (20 ° C). Evaluation was based on the amount of wear (mg) per bearing.

  As shown in Comparative Examples 1 and 3, when no additive was added, the anti-fretting performance was poor. Moreover, as shown in Comparative Examples 2 and 4, when an additive (TCP) other than the phosphite used in the present invention is added, the result is the same as when no additive is added, and the fretting performance can be improved. There wasn't. On the other hand, in each of the comparative examples, excellent fretting resistance could be obtained.

  The grease-enclosed bearing for motors of the present invention has excellent fretting resistance while being used in an environment with minute reciprocating motion and vibration, etc., and in a wide temperature range from low temperature to high temperature. Since fretting can be prevented, it can be suitably used as a bearing for supporting a rotor of an industrial machine motor, an electrical equipment motor, or an electric vehicle drive motor.

1 Deep groove ball bearing (grease bearing for motor)
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 (7)

A grease-filled bearing for a motor that supports a rotor of a motor, the bearing being provided in an inner ring and an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and openings at both axial ends of the inner ring and the outer ring A seal member provided, and a grease composition containing a base oil, a thickener, and an additive is enclosed around the rolling element,
The base oil is a synthetic oil containing ester oil as an essential component, and the kinematic viscosity of the base oil at 40 ° C. is 20 to 50 mm ² / s,
The additive contains at least one phosphite ester represented by formula (1) or (2), and the content of the phosphite ester is a total amount of the base oil and the thickener of 100. 0.5 to 4 parts by weight with respect to parts by weight,
The grease for motors, wherein the grease composition does not contain a phosphite other than the one represented by the formula (1) or (2) and a phosphate ester having an organic group having 3 or more carbon atoms Enclosed bearing.

(In Formulas (1) and (2), R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each a methyl group or an ethyl group. R ₁ and R ₂ are R ₃ and R ₄ , respectively. And R ₅ may be the same group or different groups.)   2. The grease-filled bearing for a motor according to claim 1, wherein the base oil is a synthetic oil composed only of the ester oil or a mixed oil of the ester oil and a poly-α-olefin oil.   The grease-filled bearing for a motor according to claim 1, wherein the phosphite is dimethyl phosphite, diethyl phosphite, trimethyl phosphite, or triethyl phosphite.   The grease-enclosed bearing for a motor according to any one of claims 1 to 3, wherein the thickener is a metal soap.   The grease-filled bearing for a motor according to any one of claims 1 to 4, wherein the grease composition has a penetration of 200 to 350.   The grease-filled bearing for motors according to any one of claims 1 to 5, wherein the grease-filled bearing for motors is a deep groove ball bearing.   The grease-filled bearing for a motor supports a rotor of a motor for industrial machinery, electrical equipment, or an electric vehicle drive, according to any one of claims 1 to 6. Grease bearings for motors.

Images