JP6534816B2 - Rolling bearing - Google Patents

Description

  The present invention relates to a grease-lubricated rolling bearing, and more particularly to a rolling bearing using a cage composed of two synthetic resin annular bodies facing in the axial direction.

  Generally, a rolling bearing comprises an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and a cage for holding the rolling elements, and grease is enclosed and lubricated around the rolling elements. ing. In recent years, in a rolling bearing used for a servomotor or the like, a synthetic resin cage which is excellent in noise reduction with respect to a metal cage and is lightweight may be used. As the synthetic resin cage, for example, a plurality of pockets for accommodating balls, which are rolling elements, are formed of an annular body of two sheets of synthetic resin facing each other in the axial direction, and each opposing surface of the two annular bodies It has been proposed that are formed at intervals in the circumferential direction (see Patent Document 1). In this cage, a grease reservoir having a rectangular cross section for storing grease is formed at both circumferential ends of each pocket, and a concave spherical surface along the outer periphery of the ball is formed at both axial ends of each pocket.

  As a synthetic resin cage improved from this cage, concave spherical surfaces along the outer periphery of the ball are formed at both circumferential direction ends of each pocket for accommodating the ball of the ball bearing, and at both axial direction ends of each pocket There has been proposed one in which a cylindrical surface extending in the radial direction of the cage along the outer periphery of the ball is formed (see Patent Document 2). In this cage, both axial ends of the pocket are cylindrical surfaces extending in the radial direction of the cage. Therefore, the phenomenon that the pocket moves to the outer diameter side by the diameter expansion deformation of the cage, and the cage When the phenomenon that the axial width of the pocket is narrowed by stretching the pocket in the circumferential direction simultaneously occurs, both axial ends of the pocket of the cage do not easily interfere with the ball.

  In addition, in rolling bearings in recent years, there is a possibility that specific peeling accompanied by a white texture change may occur in the rolling surface at an early stage due to the severe use conditions along with the demand for downsizing and high performance. This specific peeling is different from peeling from the inside of the rolling contact surface caused by ordinary metal fatigue, and is a fracture phenomenon that occurs from a relatively shallow location on the rolling contact surface, and hydrogen caused by hydrogen generated by decomposition of grease etc. It is considered brittle. For example, the grease is decomposed to generate hydrogen, which penetrates into the steel of the rolling bearing, which is considered to cause an early peeling caused by hydrogen embrittlement.

  As a method of suppressing a specific peeling phenomenon accompanied with such a white tissue change which occurs early, for example, a method of adding a passivating agent to grease (refer to Patent Document 3), a method of adding bismuth dithiocarbamate (See Patent Document 4) has been proposed.

  In addition, conventionally, in grease compositions used for rolling bearings, there is known one in which an alkanolamine derivative modified with a hydrophilic group is blended as a hydrophilic organic inhibitor (see Patent Document 5). The alkanolamine derivative is a salt of a dibasic acid such as dodecanoic acid or sebacic acid, or an acid such as boric acid, and an alkanolamine such as diethanolamine, aminotetrazole or diethylaminoethanol. In addition, as a lubricant composition excellent in heat resistance, mechanical stability, water resistance, rust resistance, load resistance, flame retardancy, etc., calcium phosphate tribasic and diethanolamine are contained in a base oil comprising mineral oil or synthetic oil. It has been proposed that a grease structure stabilizer such as a compound is blended (see Patent Document 6).

JP, 2008-64157, A JP, 2013-7468, A Unexamined-Japanese-Patent No. 3-210394 JP 2005-42102 A Unexamined-Japanese-Patent No. 11-279578 JP, 2008-156624, A

  As described above, generally, the synthetic resin cage is superior to the metal cage in quietness. However, in the case of a cage (a combined cage) consisting of two synthetic resin annular bodies facing in the axial direction, the possibility of producing noise or the like can not be excluded depending on the use conditions and the used grease. In particular, as in Patent Document 2, in the case where both axial end portions of the pocket in the mating cage are cylindrical surfaces, the cage may vibrate during the rotation of the bearing to generate noise. This is considered to be due to the fact that the ball's rotational movement is transmitted to the cage via the grease to vibrate. That is, when the axially opposite end portions of the pocket are cylindrical surfaces, the grease enclosed in the bearing space between the inner ring and the outer ring excessively intrudes between the cylindrical surface of the pocket of the cage and the outer peripheral surface of the ball Then, the cage is dragged to the surface of the rotating ball through the grease, which is considered to cause the vibration of the cage. The occurrence of such abnormal noise may vary depending on the type of grease.

  On the other hand, with respect to the above-mentioned peeling phenomenon, due to the further severeness of the use conditions along with the recent demand for downsizing and high performance of rolling bearings, such as in the conventional Patent Document 3 and Patent Document 4, The method of adding a mobilizing agent or bismuth dithiocarbamate has become insufficient as a countermeasure.

  Although there are some conventional grease compositions for rolling bearings that contain an alkanolamine salt as in Patent Document 5, the ability of the alkanolamine alone to prevent the peeling phenomenon is being studied. Absent. Further, with regard to the grease composition described in Patent Document 6, the ability to prevent the peeling phenomenon has not been studied, and depending on the specific combination of the essential components, the above-mentioned problem such as noise may be adversely affected. There is also a case to give.

  The present invention has been made to address such problems, and it is an object of the present invention to provide a rolling bearing capable of preventing generation of abnormal noise while effectively preventing separation on the bearing rolling surface due to hydrogen embrittlement. Do.

The rolling bearing of the present invention comprises an inner ring and an outer ring, a plurality of rolling elements interposed between the inner and outer rings, and a cage for holding the rolling elements, and sealing the grease composition around the rolling elements. The grease composition comprises a base oil, a thickener, and at least one additive selected from alkanolamines and molybdates, and the base oil has a behavior at 40 ° C. It is a poly-α-olefin oil (hereinafter also referred to as “PAO”) having a viscosity of 30 to 70 mm ² / s, and the thickening agent is a diurea compound obtained by reacting a diisocyanate component and a monoamine component. The monoamine component is an aliphatic monoamine and an alicyclic monoamine, and the additive is 0.1 to 0.1 parts by weight of the total amount of the base oil and the thickener. It is characterized in that 10 parts by weight is included.

  The alkanolamine is characterized in that it is a dialkanolamine or trialkanolamine. In particular, it is characterized by being diethanolamine.

  The additive contains only the alkanolamine as the additive, and the alkanolamine is contained in an amount of 2 to 8 parts by weight with respect to 100 parts by weight in total of the base oil and the thickener, or the molybdic acid as the additive It contains only a salt, and the molybdate is contained in an amount of 0.5 to 3 parts by weight with respect to 100 parts by weight in total of the base oil and the thickener.

  The cage is an annular body made of two sheets of synthetic resin axially opposed to each other, and on each opposing surface of the two annular bodies, a plurality of pockets for accommodating the rolling elements are circumferentially spaced. It is characterized in that it is formed.

The rolling bearing according to the present invention is a grease composition to be enclosed, which is made of a PAO having a kinematic viscosity of 30 to 70 mm ² / s at 40 ° C. as a base oil and an aliphatic / alicyclic diurea compound as a thickening agent. Allophone in case of using resin-made joint cage while preventing peeling on the bearing rolling surface due to hydrogen embrittlement effectively by blending alkanolamine as additive to base grease. Can be prevented.

1 is a cross-sectional view of a deep groove ball bearing showing one embodiment of a rolling bearing of the present invention. It is a circumferential direction fragmentary sectional view of the holder | retainer in FIG.

  The grease composition used for the rolling bearing of the present invention comprises a base oil, a thickener, and additives alkanolamine and / or molybdate. With regard to additives, when an alkanolamine is compounded, an alkanolamine in an iron-based metallic nascent surface exposed due to friction wear or wear even if the oil film becomes thin under severe conditions (boundary lubrication conditions) on the rolling surface. Can prevent direct contact between the iron-based metal surface and the grease. In addition, when the molybdate is compounded, the molybdate is decomposed and reacted on the above-mentioned iron-based metal surface to form a molybdenum compound film together with iron oxide. By these, generation | occurrence | production of hydrogen by decomposition | disassembly of grease can be suppressed and the special peeling by hydrogen embrittlement can be prevented. Furthermore, in the present invention, when the compounding retainer made of resin is used by limiting the compounding amount of these additives to a predetermined amount range and selecting the types of the base oil and the thickening agent (base grease) to be combined. And the like can prevent the generation of abnormal noise. This is considered to be due to the fact that the grease can be prevented from being excessively caught between the pocket surface of the cage and the ball outer peripheral surface.

  As the alkanolamine used in the above grease composition, primary isopropanol, monoethanolamine, and primary alkanolamines such as mono-n-propanolamine, N-alkyl monoethanolamine, and secondary such as N-alkyl monopropanolamine Mention may be made of tertiary alkanolamines such as alkanolamines, triethanolamine, cyclohexyldiethanolamine, tri (n-propanol) amine, triisopropanolamine, N, N-dialkylethanolamines, and N-alkyl (or alkenyl) diethanolamines. Further, they are classified into monoalkanolamines, dialkanolamines, trialkanolamines according to the number of alkanol groups, but in the present invention, iron ions are sandwiched by the chelating action of a plurality of hydroxyl groups (alkanol groups) and amino groups to It is preferable to use a dialkanolamine or a trialkanolamine because it is easy to prevent the exposure of the new metal surface.

  Among the above, it is preferable to use N-alkyl (or alkenyl) diethanolamine of the following formula (1) because it is excellent in compatibility with the base oil and the ability to prevent peeling phenomenon and also in availability.

R ₁ in the formula denotes a linear or branched alkyl group or alkenyl group having 1 to 20 carbon atoms. Moreover, 1-12 are preferable and, as for carbon atom number, 1-8 are more preferable. Specific compounds include, for example, N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine, N-butyldiethanolamine, N-pentyldiethanolamine, N-hexyldiethanolamine, N-heptyldiethanolamine, N-octyldiethanolamine, N Nonyldiethanolamine, N-decyldiethanolamine, N-undecyldiethanolamine, N-lauryldiethanolamine, N-tridecyldiethanolamine, N-myristyldiethanolamine, N-pentadecyldiethanolamine, N-palmityldiethanolamine, N-heptadecyldiethanolamine, N -Oleyl diethanolamine, N-stearyl diethanolamine, N-isostearyl Ethanolamine, N- nonadecyl diethanolamine, N- such eicosyl diethanolamine.

The alkanolamines may be used alone or in combination of two or more. Further, the alkanolamine is preferably liquid or paste at room temperature and use temperature. Moreover, it may be in a state of being dispersed in a solvent or the like. By using such an alkanolamine, the quietness of the bearing is unlikely to be adversely affected. In addition, even when the oil film on the rolling contact surface becomes thin, it easily enters the portion. The kinematic viscosity of the alkanolamine, preferably 10 to 100 mm ² / s at 40 ° C., and more preferably 40~70mm ² / s at 40 ° C..

  Examples of commercially available products of alkanolamines (tertiary diethanolamines) include Adekaqui Club FM-812, Adekaqui Club FM-832, and the like manufactured by Adeka.

  It is preferable that the molybdate used for the said grease composition is a metal salt. As a metal which comprises metal salt, sodium, potassium, lithium, magnesium, calcium, copper, zinc, barium etc. can be illustrated. It is preferable to use an alkali metal salt of molybdate because it easily forms the above-mentioned molybdenum compound film. Specifically, lithium molybdate, sodium molybdate, potassium molybdate and the like can be mentioned. The molybdate may be used singly or in combination of two or more.

  In the above grease composition, the blending ratio of at least one additive selected from alkanolamine and molybdate is 0.1 to 10 parts by weight with respect to 100 parts by weight in total of the base oil and the thickener. When alkanolamine and molybdate are used in combination, the total amount is in this range. Further, in order to further suppress the generation of abnormal noise, it is preferable to use a solid amount of molybdate as small amount compared with liquid alkanolamine. For example, (1) when only the alkanolamine is contained as the additive, 2 to 8 parts by weight with respect to 100 parts by weight in total of the base oil and the thickener, and (2) only molybdate as the additive When it is contained, it is preferable to be 0.5 to 3 parts by weight with respect to 100 parts by weight of the total amount of the base oil and the thickener. By setting the base oil and the thickening agent to be in the range of (1) or (2), generation of abnormal noise can be prevented while preventing occurrence of peeling as shown in the examples described later. . Note that “containing only an alkanolamine as the above additive” means selecting an alkanolamine in at least one additive selected from an alkanolamine and a molybdate, and does not include a molybdate, The formulation of other additives other than these is not excluded. The same applies to the case of selecting molybdate.

  The base oil of the above grease composition comprises PAO which is a synthetic hydrocarbon oil. PAO is a mixture of oligomers or polymers of alpha-olefins or isomerized alpha-olefins. Specific examples of α-olefins include 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1 -Nonadecene, 1-eicosene, 1-docosene, 1-tetradocosene etc. are mentioned, and usually these mixtures are used.

This base oil has a kinematic viscosity at 40 ° C. of 30 to 70 mm ² / s, more preferably 30 to 60 mm ² / s. If the kinematic viscosity at 40 ° C. is less than 30 mm ² / s, the viscosity is too low to cause breakage of the oil film, and the evaporation of the oil also increases. On the other hand, if the kinematic viscosity at 40 ° C. is higher than 70 mm ² / s, there is a possibility that abnormal noise may occur and the rotational torque may increase. When it is set as the mixed oil of multiple types of PAO from which kinematic viscosity differs, it is made for the dynamic viscosity of the mixed oil to become the said range.

  Among the urea compounds, the thickener of the above grease composition is an aliphatic / alicyclic diurea compound. The urea compound is obtained by reacting the polyisocyanate component with the monoamine component. The aliphatic and alicyclic diurea compounds are obtained using diisocyanate as a polyisocyanate component and using aliphatic monoamines and alicyclic monoamines as monoamine components. Among the above monoamine components, an aliphatic / alicyclic diurea compound obtained mainly from an aliphatic monoamine is unlikely to be excessively caught between the pocket surface and the ball outer peripheral surface of the resin-made combined cage. It is preferable that the amount of aliphatic monoamine is large. Specifically, it is preferable to set the aliphatic monoamine to 70 mol% or more with respect to the whole monoamine.

  As a diisocyanate which comprises a urea compound, phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, hexane diisocyanate etc. are mentioned. Examples of aliphatic monoamines include hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine, stearylamine and oleylamine. Cycloaliphatic monoamines include cyclohexylamine. In addition, in the case of the aromatic diurea compound which uses only an aromatic monoamine as a monoamine, there is a possibility that noise may be generated.

  A base oil is obtained by blending a base oil with a thickener. The base grease in the present invention is preferably produced by reacting the above-mentioned diisocyanate component and monoamine component in a base oil. The proportion of the thickener contained in the base grease is 1 to 40% by mass, preferably 3 to 25% by mass. If the content of the thickener is less than 1% by mass, the thickening effect is reduced and the formation of the grease becomes difficult, and if it exceeds 40% by mass, the obtained base grease becomes too hard to obtain the desired effect. Become.

  As a method of preparing the above-mentioned grease composition in the case of including an alkanolamine, first, a method of blending an alkanolamine with a base oil and preparing a thickener using this base oil, excluding the alkanolamine, a grease composition After adjustment, any of the methods of adding an alkanolamine thereto may be used. Since the alkanolamine contains an amino group, it is preferable to add the alkanolamine after the above-mentioned diisocyanate component and monoamine component are reacted in the base oil to prepare the base grease.

  The worked penetration (JIS K 2220) of the above-mentioned grease composition is preferably in the range of 200 to 350. If the consistency is less than 200, oil separation may be small, resulting in poor lubrication. On the other hand, when the consistency is more than 350, the grease is soft and tends to flow out of the bearing, which is not preferable.

  In the grease composition used for the rolling bearing of the present invention, the alkanolamine is present as it is, not in the form of a reaction product like a salt with an acid. Therefore, when an alkanolamine is contained, as an additive, an additive which forms a salt with an alkanolamine such as a fatty acid is not contained. The above-mentioned grease composition may contain known additives, if necessary, as long as the object of the present invention is not impaired. Additives include, for example, antioxidants such as organic zinc compounds, amines and phenolic compounds, metal deactivators such as benzotriazole, viscosity index improvers such as polymethacrylates and polystyrenes, molybdenum disulfide, graphite and the like Examples include solid lubricants, rust inhibitors such as metal sulfonates and polyhydric alcohol esters, esters, oiliness agents such as alcohols, and other antiwear agents. These can be added alone or in combination of two or more.

  Moreover, it is preferable that the said grease composition does not contain the alkali metal salt of an inorganic acid and the alkaline-earth metal salt of an inorganic acid for the purpose of preventing generation | occurrence | production of noise, etc. FIG. Here, as the inorganic acid, phosphoric acid (orthophosphoric acid), hydrochloric acid, nitric acid, sulfuric acid, boric acid etc. may be mentioned, and as the alkali metal and alkaline earth metal, lithium, sodium, potassium, calcium, strontium, barium etc. Can be mentioned. Specifically, tribasic calcium phosphate (calcium salt of orthophosphoric acid) and the like can be mentioned.

  An example of the rolling bearing of the present invention will be described based on FIG. 1 and FIG. FIG. 1 is a cross-sectional view of a deep groove ball bearing, and FIG. 2 is a partial cross-sectional view of the cage in FIG. 1 in the circumferential direction. As shown in FIG. 1, in the rolling bearing 1, an inner ring 2 having an inner ring rolling surface on the outer peripheral surface and an outer ring 3 having an outer ring rolling surface on the inner peripheral surface are concentrically arranged. A plurality of rolling elements (balls) 4 are arranged between the running surface. The rolling element 4 is held by a holder 5 made of synthetic resin. Further, the openings at both axial ends of the inner and outer rings are sealed by the seal member 6, and the above-mentioned grease composition 7 is enclosed at least around the rolling element 4. As shown in FIG. 2, the retainer 5 is formed by fixing two annular members 5a and 5b made of synthetic resin opposed in the axial direction by snap fitting with claws 5d. On each opposing surface of the two annular bodies 5a and 5b, a plurality of pockets 5c for accommodating the rolling elements (balls) 4 are formed at intervals in the circumferential direction.

  The two annular bodies 5a, 5b are obtained by injection molding of a synthetic resin. As the synthetic resin, for example, a composition can be used in which a polyamide resin, a polyphenylene sulfide resin, and a polyetheretherketone resin are used as a base resin, and glass fibers and carbon fibers are mixed therewith. The two annular bodies 5a and 5b have the same shape, and can be injection-molded using the same mold.

  Further, in the present invention, the material and shape of the cage are not particularly limited, and it is not a resin-made laminated cage shown in FIG. 2, but a machined or crowned resin-made cage or metal integrally formed. It is applicable also to a cage made of steel. Furthermore, in the resin-made joint cage shown in FIG. 2, concave spherical surfaces are formed along the outer periphery of the balls at the circumferential direction both end portions of the pockets accommodating balls which are rolling elements, and both axial ends of each pocket are formed. The portion may form a cylindrical surface extending radially of the cage along the periphery of the ball. In the present invention, the improvement of the grease to be sealed prevents the generation of abnormal noise when using a resin-made joint retainer (particularly, one having the above-mentioned cylindrical surface).

  The present invention will be specifically described by way of examples and comparative examples, but the present invention is not limited by these examples.

Examples 1 to 5 and Comparative Examples 1 to 4
First, base oils were prepared by mixing them alone or in the formulations shown in Table 1. Next, 4,4'-diphenylmethane diisocyanate (Millionate MT manufactured by Nippon Polyurethane Industry Co., Ltd., hereinafter referred to as "MDI") is dissolved in a half amount of this base oil at a ratio shown in Table 1, and the remaining half amount of base oil A monoamine equivalent to twice MDI was dissolved. A solution in which monoamine was dissolved was added while stirring a solution in which MDI was dissolved, and then stirring was continued at 100 to 120 ° C. for 30 minutes to be reacted to form a diurea compound in a base oil to obtain a base grease. Additives were added to this at a blending ratio shown in Table 1 and further sufficiently stirred. Thereafter, the mixture was homogenized with a three-roll mill to obtain a test grease. The added alkanolamines are all diethanolamine (ADEKA CRUBE FM-812 manufactured by ADEKA), and the molybdate is sodium molybdate.

  The rapid acceleration / deceleration test and the acoustic measurement test were conducted on the obtained grease. The test method and test conditions are shown below.

<Quick acceleration / deceleration test>
The above grease was sealed in an inner ring rotating rolling bearing (inner ring, outer ring, steel ball bearing steel SUJ2) supporting a rotating shaft, and a rapid acceleration / deceleration test was conducted. The conditions for the rapid acceleration / deceleration test are: in the atmosphere of 25 ° C., the load on the pulley attached to the end of the rotary shaft is 1960 N, the rotational speed is 0 rpm to 18000 rpm, and operating conditions are set. The test was carried out with 1% by mass of iron powder mixed therein, and with a current of 1.0 A flowing in the test bearing (6203). Then, the abnormal peeling occurred in the bearing, and the time (the peeling occurrence life (h)) in which the vibration of the vibration detector exceeded the set value and stopped was measured. The results are shown in Table 1.

<Sound test>
Install a rolling bearing (6312: resin matching cage (see Fig. 2), with a cylindrical surface) containing the above grease into the servomotor test machine, and apply a belt load of 3400N by pulling the pulley attached to the shaft with a belt. At the same time, the rotational speed was stepped up by 1000 rpm from 1000 rpm to 7000 rpm, and the sound at each rotation speed (generation of abnormal noise) was confirmed by hearing. Of the seven rotational speeds, the sum of the number of cases where a large abnormal noise occurred was 0 for "o", 1 for "「 ", and 2 or more for" x ". The results are shown in Table 1.

  As shown in Table 1, each Example which mix | blended the alkanolamine (diethanolamine) or the molybdate with the predetermined | prescribed base grease was able to prevent generation | occurrence | production of noise while extending peeling generation | occurrence | production lifetime time. The abnormal noise does not necessarily occur when the number of revolutions is high, but the test bearing of the same configuration may occur at a low number of revolutions and may not occur at a high number of revolutions.

  The rolling bearing of the present invention can prevent the generation of abnormal noise while effectively preventing the separation on the bearing rolling surface due to hydrogen embrittlement, and thus can be applied to various rolling bearings. In particular, it is a rolling bearing using a cage made of two synthetic resin annular bodies facing each other in the axial direction, and in the case of using existing grease, it can be suitably used for those which may generate noise.

DESCRIPTION OF SYMBOLS 1 rolling bearing 2 inner ring 3 outer ring 4 rolling element 5 cage 6 sealing member 7 grease composition

Claims (4)

A rolling bearing comprising an inner ring and an outer ring, a plurality of rolling elements interposed between the inner and outer rings, and a cage for holding the rolling elements, wherein a grease composition is enclosed around the rolling elements. ,
The grease composition comprises a base oil, a thickener, and at least one additive selected from alkanolamines and molybdates,
The base oil is a poly-α-olefin oil having a kinematic viscosity at 40 ° C. of 30 to 70 mm ² / s,
The thickener is a diurea compound obtained by reacting a diisocyanate component and a monoamine component, and the monoamine component is an aliphatic monoamine and an alicyclic monoamine.
A rolling bearing comprising only the alkanolamine as the additive, wherein the alkanolamine is contained in an amount of 2 to 8 parts by weight with respect to 100 parts by weight in total of the base oil and the thickener .   The rolling bearing according to claim 1, wherein the alkanolamine is a dialkanolamine or a trialkanolamine.   The rolling bearing according to claim 2, wherein the alkanolamine is diethanolamine. The cage is an annular body made of two sheets of synthetic resin opposed in the axial direction, and on each opposing surface of the two annular bodies, a plurality of pockets for accommodating the rolling element are circumferentially spaced. The rolling bearing according to any one of claims 1 to 3 , wherein the rolling bearing is formed.

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