JP2009121532A - Rolling bearing for high speed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing for high speed enabling satisfactorily coping with a high-speed rotation of ≥1,700,000 dmN value and miniaturization of a machine tool or the like and cutback of operating costs even with a small amount of enclosed grease. <P>SOLUTION: The rolling bearing for high speed includes an inner ring 2 and an outer ring 3, a plurality of rolling elements 4, and a seal member 6 for covering an opening of a space between the inner and outer rings. Grease 7 is enclosed around the rolling elements 4. A water-repellent and oil-repellent coating film 8a is formed at least on a part of an inner surface of a bearing in contact with the grease 7. In the grease 7, non-urea grease containing any urea compound is blended in the urea grease with the urea compound being the thickener. The urea thickener is obtained by reaction between a poly-isocyanate component and a monoamine component, the monoamine component containing ≥50 mol% of at least one selected from aliphatic monoamines and alicyclic monoamines based on all the monoamines. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a high-speed rolling bearing used for a rolling bearing that supports a high-speed rotating shaft such as a machine tool main spindle (spindle).

The main spindle of the machine tool is preferably one that rotates at a high speed in order to increase machining efficiency, and various lubrication techniques are applied to the bearings. As a lubrication method suitable for the spindle rotating at high speed, for example, methods such as oil mist lubrication, air-oil lubrication, and jet lubrication are known.
However, such a lubrication method requires ancillary equipment such as compressed air and an oil supply device, which is one of the causes of increasing the initial cost and running cost of machine tools. It can be said that this is a preferable lubrication method with less maintenance. For example, examples of the high-speed rolling bearing that supports a rotating shaft that rotates at a high speed of 2000 to 8000 rpm or higher include an angular ball bearing and a cylindrical roller bearing that support a machine tool spindle (spindle).

As shown in FIG. 9, the angular ball bearing 11 is capable of applying an axial load from one direction in addition to the radial load, and a straight line connecting the contact points of the steel ball 14 with the inner ring 12 and the outer ring 13 is formed. It has an angle (contact angle) α with respect to the radial direction. Grease is enclosed in a bearing space formed by the inner ring 12, the outer ring 13, and the steel ball 14.
Lubricants used in high-speed rolling bearings such as angular ball bearings and cylindrical roller bearings do not require maintenance such as lubrication and may be grease adjusted to a consistency that does not pollute the surrounding environment. preferable.

The lubrication characteristics and problems required for grease used in high-speed rolling bearings such as spindle rolling bearings are summarized below.
(A) In order to extend the lubrication life of a long-life rolling bearing as much as possible, lubricant (grease or its base oil) is supplied from the rolling bearing as described in (i) to (iii) below. It is necessary that it is difficult to leak, has excellent heat resistance of grease, and can form an oil film thickness necessary for lubrication.

(i) When rolling bearings are operated at high speed, the grease in the rolling bearings flows out of the bearings due to centrifugal force, or the base oil in the grease separates and flows out, and near the rolling surface where the contribution to lubrication is large. It is difficult to stay and is prone to poor lubrication. In order to prevent such a situation, a seal member such as a shield plate is attached to the rolling bearing. However, depending on the structure of the bearing, it may not be possible to attach the seal member. In some cases, the lubricant cannot be completely sealed.
In the case of a rolling bearing that is not operated at a high speed, excess grease that is pushed out from the frictional part due to the motion of the rolling elements and the cage may recirculate to some extent inside the bearing and contribute to lubrication again depending on the rotation conditions. However, in rolling bearings for supporting a rotating shaft such as a machine tool that rotates at high speed, the wind pressure generated inside the bearing hinders this recirculation, so that lubrication is liable to occur. For this reason, in rolling bearings rotating at high speed, only a small amount of grease contributes to lubrication, and the properties of the grease are particularly important. Further, the grease used for the high-speed rolling bearing needs to maintain the lubricating performance even with a small amount of grease.

(ii) When the operating conditions are increased, the rolling surface of the bearing locally generates heat and becomes high temperature. At this time, the grease with poor heat resistance is thermally deteriorated, and the life of the grease is remarkably shortened. For such problems, attempts have been made to use heat-resistant thickeners and base oils, or to add antioxidants. However, these attempts have not led to a sufficient improvement in durability.
(iii) Conventional grease with improved lubricity (oil film thickness) increases shear friction resistance and increases rotational torque and heat generation when base oil viscosity is increased. The base oil viscosity is kept low. For this reason, the oil film of the lubricating oil that has become low viscosity due to a temperature rise accompanying high speed may become thin and cause sliding wear.

  (B) Low torque (inhibition of temperature rise) Existing high-speed bearing grease keeps the base oil viscosity low as described above, but when the bearing rotates at high speed, the viscosity increases due to temperature rise. There is a problem that the oil film is remarkably lowered and an oil film having a thickness necessary for lubrication cannot be formed.

  (C) About low vibration property, the vibration of the bearing may be increased depending on the type of the thickener of grease. That is, the vibration of the rolling bearing lubricated with the grease containing the thickener that forms a large and hard aggregate increases.

As described above, when the conventional grease is used for a high-speed rolling bearing, there is a problem that the required physical properties such as long life, low torque and low vibration cannot be satisfied. As a countermeasure, grease containing a urea compound has been proposed (see Patent Documents 1 to 3), but the amount of oil supplied to the raceway surface is small, which is insufficient to obtain higher speed performance.
For example, Patent Document 3 discloses that a base oil having a kinematic viscosity at 40 ° C. of 15 mm ² / sec or more and 40 mm ² / sec or less and a content of 9 mass% or more and 14 mass% or less of the entire grease composition. A grease composition containing a diurea compound thickener and having a miscibility of 220 to 320 is disclosed.
However, even in the above grease composition, it is difficult to reduce the blending amount of thickener and reduce the amount of grease filled. Sufficient support for high-speed rotation of bearings, downsizing of machine tools, and reduction of operating costs It is difficult to make it possible.
In recent years, rolling bearings have been used more and more severely, and the rolling for spindles used at high-speed rotation with a dmN value, which is the product of pitch circle diameter dm (mm) and rotation speed N (rpm), is 1.7 million or more. The number of bearings is increasing. As the rotational speed of the bearing increases, it is difficult to satisfy all the performance required for the bearing with existing grease.
Japanese Patent Laid-Open No. 2000-169872 JP 2003-83341 A JP 2006-29473 A

  The present invention has been made in view of such a situation. Even if the amount of grease is small, for example, the dmN value that is the product of the pitch circle diameter dm (mm) and the rotational speed N (rpm) is 1.7 million. The purpose is to provide a high-speed rolling bearing that can sufficiently cope with the high-speed rotation described above, and that can make the machine tool compact and reduce the operating cost.

  The high-speed rolling bearing of the present invention is a high-speed rolling bearing that supports a shaft that rotates at high speed. The rolling bearing includes an inner ring and an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and the inner ring. And a seal member that covers the opening of the gap between the outer rings, and grease is sealed around the rolling elements, and a water / oil repellent coating is formed on at least a part of the bearing inner surface that contacts the grease. The above grease comprises a urea grease containing a urea compound as a thickener and a non-urea grease that does not contain the urea compound. The urea compound reacts with a polyisocyanate component and a monoamine component. The obtained monoamine component contains at least one monoamine selected from aliphatic monoamines and alicyclic monoamines in an amount of 50 It is characterized by being a monoamine component containing at least 1% by weight.

  The water / oil-repellent coating comprises (1) a part of the bearing inner surface of the seal member, (2) an inner diameter surface excluding the raceway surface of the outer ring and the bearing inner surface of the seal member, and (3) a raceway surface of the inner ring. It is characterized in that it is formed in at least one selected from the outer diameter surface excluding the surface and the bearing inner surface of the seal member and (4) the surface of the cage excluding the contact surface with the rolling element.

  The water / oil repellent coating is characterized by being formed using a silicon compound or a fluorine compound. The silicon compound is siloxane, and the fluorine compound is fluoroalkylsilane.

The thickener of the non-urea grease is a composite soap-type thickener or Na terephthalate, and the blending ratio of the non-urea thickener to the whole of the non-urea grease is 10 to 40% by weight. To do.
In addition, the base oil of the urea grease and the non-urea grease has a kinematic viscosity of 15 to 40 mm ² / sec.
The base oil is at least one selected from a synthetic hydrocarbon oil, an ester oil, and an alkyl diphenyl ether oil.

  The high-speed rolling bearing is a bearing that supports a main shaft of a machine tool. Further, the bearing is an angular ball bearing or a cylindrical roller bearing.

The grease to be sealed in the high-speed rolling bearing of the present invention is formed by blending a non-urea grease not containing the above urea compound with a urea grease having a predetermined urea compound as a thickening agent, so that a small amount of grease is charged. Even so, it is excellent in the ability to supply oil to the raceway surface under high speed rotation while maintaining the load resistance of the rolling bearing filled with this grease.
The monoamine component constituting the urea compound contains at least one monoamine selected from an aliphatic monoamine and an alicyclic monoamine in an amount of 50 mol% or more based on the total monoamine, so that even if it receives a high shearing force at high speed, The thickener is not easily broken, and the oil content in the grease can be stably supplied to the rolling surface by the capillary action of the thickener fiber.

  The high-speed rolling bearing according to the present invention encloses the grease and further forms a water / oil-repellent coating on at least a part of the inner surface of the bearing that comes into contact with the grease. The oil component can move toward the rolling surface, it does not flow out of the bearing, and the amount of oil necessary for bearing lubrication is stably supplied for a long period of time. An oil film having a required thickness is formed. For this reason, the bearing durability life under high-speed rotation is dramatically improved.

As a result of intensive studies on high-speed rolling bearings that can sufficiently cope with high-speed rotation even with a small amount of grease, and that can make machine tools compact and reduce operating costs, It has been found that by providing a water / oil repellent coating on at least a part of the inner surface of the bearing and enclosing a predetermined grease, it becomes a rolling bearing with a long life at high speed use.
If a water / oil-repellent coating is formed on at least a part of the inner surface of the bearing that comes into contact with the lubricant sealed in the bearing, such as lubricant or grease, the surface tension of the water / oil-repellent coating will be the lubricant. Is actively moved without staying on the surface of the coating. For this reason, since the predetermined lubricant that moves actively can always be present on the sliding surface such as the rolling surface and the rolling surface, the durability of the lubricating action is improved and a long-life rolling bearing is obtained. It is considered a thing. The present invention is based on such knowledge.

In the high-speed rolling bearing of the present invention, it is sufficient that a water / oil-repellent coating is formed on at least a part of the inner surface of the bearing that comes into contact with the sealed grease. The bearing structure is not particularly limited. For example, the angular ball bearing 1 shown in FIG. 1 can be illustrated. FIG. 1 is a cross-sectional view showing an example of a formation position of a water / oil repellent coating of an angular ball bearing according to an embodiment of the present invention. In the present invention, the water / oil repellent coating may be formed on at least a part of the inner surface of the bearing in contact with the grease 7, and is preferably formed on a portion other than the sliding surface. Here, the sliding surface includes the inner ring raceway surface 2a, the outer ring raceway surface 3a, the contact surface between the cage 5 and the rolling element 4, the surface of the rolling element 4, and the like.
In FIG. 1, the angular ball bearing 1 is a seal in which a bearing space in which a rolling element 4 is held by a cage 5 between an inner ring 2 and an outer ring 3 is fixed to a locking groove provided on an inner peripheral surface of the outer ring 3. Sealed by the member 6, a water / oil repellent coating 8 a is formed on a part of the bearing inner side surface of the seal member 6. Further, the following grease is sealed in a bearing space formed by the inner ring 2, the outer ring 3 and the rolling elements 4.
Note that a straight line connecting the contact points of the rolling elements 4 with the inner ring 2 and the outer ring 3 has a contact angle β with respect to the radial direction, so that a radial load and an axial load in one direction can be applied. Moreover, the rolling element 4 can also be made from ceramics, such as silicon nitride and silicon carbide.

2 to 4 are sectional views showing other examples of positions where the water / oil repellent coating is formed. In FIG. 2, a water- and oil-repellent coating 8b is provided on the inner diameter surface excluding the raceway surface 3a of the outer ring and the bearing inner side surface of the seal member 6, and in FIG. 3, the outer diameter surface excluding the raceway surface 2a of the inner ring, A water / oil repellent coating 8c is formed on the inner surface of the bearing of the seal member 6 and a water / oil repellent coating 8d is formed on the surface of the cage 5 excluding the contact surface with the rolling element 4 in FIG. ing. 2 to 4 are the same as those in FIG. 1 except for the water / oil repellent coating.
Although the formation positions of the water / oil repellent coating are individually shown in FIGS. 1 to 4, these formation positions may be used alone or in combination of two or more.

As another embodiment of the high-speed rolling bearing of the present invention, for example, a deep groove ball bearing 21 shown in FIG. 5 can be exemplified. FIG. 5 is a cross-sectional view showing an example of the formation position of the water / oil repellent coating of a deep groove ball bearing according to another embodiment of the present invention. In the present invention, the water / oil repellent coating may be formed on at least a part of the inner surface of the bearing in contact with the grease 27, and is preferably formed on a portion other than the sliding surface. Here, the sliding surface includes the inner ring raceway surface 22a, the outer ring raceway surface 23a, the contact surface between the cage 25 and the rolling element 24, the surface of the rolling element 24, and the like.
In FIG. 5, the deep groove ball bearing 21 is a seal in which a bearing space in which a rolling element 24 is held by a cage 25 between an inner ring 22 and an outer ring 23 is fixed to a locking groove provided on an inner peripheral surface of the outer ring 23. Sealed by the member 26, a water / oil repellent coating 28 a is formed on a part of the bearing inner side surface of the seal member 26. Further, the grease shown below is sealed in a bearing space formed by the inner ring 22, the outer ring 23, and the rolling elements 24.
In addition, the rolling element 24 can also be made from ceramics, such as silicon nitride and silicon carbide.

6 to 8 are cross-sectional views showing other examples of positions where the water / oil repellent coating is formed. In FIG. 6, a water and oil repellent coating 28b is provided on the inner diameter surface excluding the raceway surface 23a of the outer ring and the inner surface of the bearing of the seal member 26, and in FIG. 7, the outer diameter surface excluding the raceway surface 22a of the inner ring, A water / oil repellent coating 28c is formed on the bearing inner surface of the seal member 26, and a water / oil repellent coating 28d is formed on the surface of the cage 25 excluding the contact surface with the rolling element 24 in FIG. ing. 6 to 8 are the same as those in FIG. 5 except for the water / oil repellent coating.
Although the formation positions of the water- and oil-repellent coatings are individually shown in FIGS. 5 to 8, these formation positions may be used alone or in combination of two or more.

By forming the water / oil repellent coatings 8a to 8d and 28a to 28d on the bearing inner surface as shown in FIGS. 1 to 8, the encapsulated greases 7 and 27 become the water / oil repellent coatings 8a to 8d. , 28a to 28d are repelled by the surface tension and move actively without staying on the coating surface. Therefore, for example, the inner ring raceway surfaces 2a and 22a, the outer ring raceway surfaces 3a and 23a, the contact surfaces between the cages 5 and 25 and the rolling elements 4 and 24, and the rolling elements, which do not form these coatings 8a to 8d and 28a to 28d. The greases 7 and 27 are continuously supplied to the surfaces of 4 and 24, etc., so that the durability of the lubricating action is improved and a long-life rolling bearing is obtained.
In addition, by forming a water / oil repellent coating other than the sliding surface, the coating does not peel off due to sliding contact.

As a material used for forming the water / oil repellent coating, silicon-based or fluorine-based water / oil repellent can be used, and is not particularly limited. The water / oil repellent coating is preferably a coating made of a silicon-based water / oil repellent such as siloxane, or a water / oil repellent coating formed using fluoroalkylsilane.
As a commercial item, Nippon Mektron Co., Ltd. product: Knoxguard ST-420, Daikin Industries, Ltd .: Unidyne, Shin-Etsu Chemical Co., Ltd .: Perfluoroalkylsilane KBM7803 etc. are mentioned, for example.

In the high-speed rolling bearing of the present invention, it is sufficient that a water / oil repellent coating is formed on the inner surface of the bearing in contact with the grease, and the method for forming the coating is not particularly limited. In order to form a water / oil repellent film on the inner surface of the bearing in contact with the grease, for example, the rolling bearing is immersed in a liquid in which a silicon-based water / oil repellent such as siloxane is dispersed and then dried. As a result, a water / oil repellent film can be formed. Further, there are vacuum plating, physical vapor deposition (PVD), chemical vapor deposition (CVD), dry plating such as ion plating, or electroplating.
In addition, a commercially available water / oil repellent agent can be used to form a water / oil repellent coating by applying to the inner surface of the bearing in contact with the grease. Among these, it is not necessary to perform water and oil repellency treatment for each part, and processing costs are advantageous, so a method of immersing the rolling bearing in a liquid in which water and oil repellants are dispersed is adopted. It is preferable to do.

  The high-speed rolling bearing of the present invention preferably contains 1% by volume or more and less than 10% by volume of the volume of the bearing gap. If it is less than 1% by volume, the amount of grease necessary for lubrication will be insufficient and it will be easily depleted. If it is 10% by volume or more, the torque due to agitation is large and heat generation increases, the lubrication life is not improved, and the cost is increased, which is not preferable from the viewpoint of the environment.

  As the high-speed rolling bearing of the present invention, in addition to the angular ball bearing shown in FIGS. 1 to 4 and the deep groove ball bearing shown in FIGS. 5 to 8, a cylindrical roller bearing, a tapered roller bearing, a self-aligning roller bearing, and a needle-like roller bearing Roller bearings, thrust cylindrical roller bearings, thrust tapered roller bearings, thrust needle roller bearings, thrust self-aligning roller bearings, and the like can also be used. Among them, it is preferable to use an angular ball bearing or a cylindrical roller bearing because it has both rotational accuracy at high speed and load bearing performance.

  The high-speed rolling bearing of the present invention includes a urea-based compound in addition to the following urea grease containing a urea-based compound as a thickener, in addition to forming a water- and oil-repellent coating on the inner surface of the bearing in contact with the grease. It is characterized by using a grease formed by blending a non-urea grease that does not contain.

As the base oil that can be used for the urea grease and the non-urea grease, a lubricating oil having a kinematic viscosity at 40 ° C. (hereinafter simply referred to as kinematic viscosity) of 15 to 40 mm ² / sec can be used. In particular, a lubricating oil having a kinematic viscosity of 18 to 30 mm ² / sec is preferable. When the kinematic viscosity is less than 15 mm ² / sec, the viscosity is too low to obtain sufficient load resistance. Also, if the kinematic viscosity exceeds 40 mm ² / sec, oil supply to the raceway surface becomes insufficient with high-speed rotation, and the bearing life will be reached early.

As a kind of the base oil of the urea grease, a synthetic hydrocarbon oil, an ester oil, an alkyl diphenyl ether oil, or a mixed oil thereof is preferable.
Moreover, it is preferable that kinematic viscosities of synthetic hydrocarbon oil, ester oil, and alkyldiphenyl ether oil are 15 to 40 mm ² / sec. Even if it is a mixed oil as it is this range, the range of kinematic viscosity can be 15-40 mm < ² > / sec. In the case of a mixed oil, a synthetic hydrocarbon oil is preferably used as an essential component, and the synthetic hydrocarbon oil is preferably equal to or more in mass ratio than the ester oil or alkyl diphenyl ether oil.

Examples of the synthetic hydrocarbon oil include poly-α-olefins such as normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, 1-decene and ethylene co-oligomer.
Examples of ester oils include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl tartrate, methyl acetyl cinnolate, and the like, trioctyl trimellitate, trioctyl Aromatic ester oils such as decyl trimellitate and tetraoctyl pyromellitate, polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane verargonate, pentaerythritol-2-ethylhexanoate, and pentaerythritol verargonate And carbonate ester oil.
Examples of the alkyl diphenyl ether oil include monoalkyl diphenyl ether, dialkyl diphenyl ether, and polyalkyl diphenyl ether.

The urea compound (urea thickener) is obtained by reacting a polyisocyanate component and a monoamine component.
Examples of the polyisocyanate component include phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, and hexane diisocyanate. Of these, aromatic diisocyanates are preferred.
Moreover, the polyisocyanate obtained by reaction with excess diisocyanate by molar ratio with respect to diamine and this diamine can be used. Examples of the diamine include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, xylenediamine, and diaminodiphenylmethane.

The monoamine component is a monoamine component containing at least one selected from an aliphatic monoamine and an alicyclic monoamine in an amount of 50 mol% or more, preferably 80 mol% or more based on the total monoamine. By containing 50 mol% or more, it is not easily broken by the shearing force of the thickener under high speed, and the oil content in the grease can be stably supplied to the rolling surface by the capillary action of the thickener fiber. .
Examples of monoamines other than aliphatic monoamines and alicyclic monoamines include aromatic monoamines.
Examples of the aliphatic monoamine include hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine, stearylamine, and oleylamine. Among these, octylamine is preferable.
Examples of the alicyclic monoamine include cyclohexylamine.
Examples of the aromatic monoamine include aniline and p-toluidine, and among these, p-toluidine is preferable.

  The urea-based thickener is preferably blended in a proportion of 3 to 20% by weight with respect to the entire urea grease. In particular, the blending amount is preferably 5 to 15% by weight. As urea grease, if the blending amount is less than 3% by weight, the base oil retention capacity is not sufficient, and in particular, a large amount of oil is separated at one time at the initial stage of rotation, causing grease leakage and shortening the bearing life. On the other hand, if the blending amount exceeds 20% by weight, the amount of the base oil is relatively small, the oil supply ability is insufficient, the lubrication is insufficient early, and the bearing durability life is similarly shortened.

In addition to the synthetic hydrocarbon oil, ester oil, alkyl diphenyl ether oil, or mixed oils used as the base oil for urea grease, mineral oil, fluorine oil, silicone oil, etc. Can be used alone or in combination.
As the mineral oil, use can be made of a lubricant obtained from crude oil subjected to vacuum distillation, oil removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay purification, hydrorefining, and the like. .
As the fluorine oil, any compound in which a hydrogen atom of an aliphatic hydrocarbon polyether is substituted with a fluorine atom can be used, and examples thereof include perfluoropolyether oil. Examples of perfluoropolyether oils include perfluoropolyethers having side chains such as Fomblin Y (product name of Montedison) and Krytox (product name of DuPont), Fomblin Z (product name of Montedison), Examples include linear perfluoropolyethers such as Fomblin M (trade name of Montedison) and Demnam (trade name of Daikin).
As the silicone oil, any of so-called straight silicone oils such as dimethyl silicone oil and methylphenyl silicone oil and so-called modified silicone oils such as alkyl-modified silicone oil and aralkyl-modified silicone oil can be used.

  Examples of the non-urea thickener (non-urea thickener) include metal soap, Na terephthalamate, and polytetrafluoroethylene resin that are excellent in oil separation. Among these, metal soap is preferable. Examples of the metal soap thickener include lithium soaps such as lithium stearate and lithium 12-hydroxystearate, and composite lithium soaps. Moreover, barium soap, composite barium soap, aluminum soap, composite aluminum soap, calcium soap, composite calcium soap, sodium soap, composite sodium soap and the like can be mentioned. Of these, composite lithium soap, composite barium soap, and Na terephthalate that are excellent in oil supply and shear stability are preferable.

The non-urea grease is preferably blended at a rate of 10 to 80% by weight based on the total amount of grease. In particular, the blending amount is preferably 20 to 50% by weight. As non-urea grease, if the blending amount is less than 10% by weight, the oil supply to the rolling section is poor. If the blending amount exceeds 80% by weight, the fiber of the thickener tends to be broken at high speed, and the base oil cannot be supplied to the rolling section due to the capillary action of the thickener.
The thickener of non-urea grease is preferably contained in an amount of 10 to 40% by weight based on the total amount of non-urea grease. If the amount is less than 10% by weight, the grease is soft and easily leaks from the bearing due to shear. If the amount exceeds 40% by weight, the oil content in the grease is small and the oil supply performance may be deteriorated.

  In the present invention, a known grease additive may be contained in the mixed grease of urea grease and non-urea grease, if 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 include solid lubricants, metal sulfonates, rust inhibitors such as polyhydric alcohol esters, friction reducers such as organic molybdenum, oil 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. The content of these additives is preferably individually 0.05% by weight or more of the total amount of grease, and the total amount is preferably in the range of 0.15 to 10% by weight of the total amount of grease. In particular, when the total amount exceeds 10% by weight, not only an effect commensurate with the increase in content can be expected, but also the content of other components becomes relatively small, and these additives aggregate in the grease, Undesirable phenomena such as an increase in torque may be caused.

The present invention will be further described below with reference to examples, but the present invention is not limited thereto.
<Preparation of urea grease>
Urea grease U1-Urea grease U3
In half of the base oil shown in Table 1, 4,4′-diphenylmethane diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd .: Millionate MT, hereinafter referred to as MDI) is dissolved in the proportion shown in Table 1, and the remaining half of the base oil is dissolved. A monoamine having a double equivalent of MDI was dissolved in the solution. 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 with stirring at 100 to 120 ° C. for 30 minutes to produce a diurea compound in the base oil to obtain a urea grease sample.

<Preparation of non-urea grease>
Non-urea grease NU1 to non-urea grease NU3
A thickener was dissolved in the base oil shown in Table 1 to obtain a non-urea grease sample. The respective blending ratios and types are shown in Table 1.
As for Na terephthalate, methyl terephthalate mono-N-octadecylamide was reacted with sodium hydroxide using a base oil as a solvent to produce sodium-N-octadecyl terephthalate.

Examples 1 to 4
The above urea grease and non-urea grease were mixed at the ratio shown in Table 2 to obtain a grease sample. This grease sample was subjected to the centrifugal oil separation test shown below, and the centrifugal oil separation was measured. Further, the obtained grease sample was sealed in a rolling bearing treated with the following oil repellent agent and subjected to a normal temperature high speed grease test to measure a normal temperature high speed grease life time. These measurement results are also shown in Table 2.

<Centrifuge oil separation test>
Using a centrifuge, a 50 g grease sample was placed in a centrifuge tube, and the oil separation by centrifugation was calculated using the following formula when acceleration of 23000 G was applied for 7 hours at 40 ° C.
(Centrifugal oil separation,%) = (1−thickener concentration before test / thickener concentration after test) × 100

<Oil repellent treatment>
Rolling bearings (deep groove ball bearings: bearing dimensions: outer diameter 47) coated with fluorine water and oil repellent treatment agent (made by LION: Rainguard) on the inner surface of the seal member and dried at room temperature for 1 hour mm × inner diameter 20 mm × width 14 mm and angular ball bearings: bearing dimensions: outer diameter 150 mm × inner diameter 100 mm × width 24 mm).

<Normal Temperature High Speed Grease Test-Deep Groove Ball Bearing (6204)>
In a deep groove ball bearing (6204), 0.0235 g (about 0.5% by volume of the total space volume of the bearing) of a grease sample was sealed with the aim of the rolling surface, and a non-contact seal was made to prepare a test bearing. An axial load of 670 N and a radial load of 67 N were applied to the test bearing, and the test bearing was rotated at a rotational speed of 10000 rpm in a normal temperature environment. The time until seizure was measured as the grease life time. The dmN value, which is the product of the bearing pitch circle diameter (mm) and the rotational speed (rpm), in this durability test is 350,000.

<Normal Temperature High Speed Grease Test-Angular Contact Ball Bearing>
Roll the grease samples of Example 2, Comparative Example 1, Comparative Example 2 and Comparative Example 4 onto angular contact ball bearings (outer diameter 150 mm x inner diameter 100 mm, inner and outer rings SUJ2, rolling elements 13/32 inch silicon nitride balls) A test bearing was prepared by enclosing 3.0 g (about 10% by volume of the total bearing space) with the aim of surface and sealing it in a non-contact manner. The test bearing is cooled by outer cylinder cooling under a constant pressure of 1.8 GPa, and the bearing outer ring is rotated at a rotational speed of 14500 rpm while keeping the bearing outer ring at 50 ° C or less. The time until seizure is measured as the grease life time. did. The dmN value, which is the product of the pitch circle diameter (mm) and the rotational speed (rpm) of the bearing in this durability test, is 1.85 million. The measurement results are also shown in Table 2.

Comparative Example 1
The urea grease shown in Table 2 was used as a grease sample. This grease sample was subjected to the centrifugal oil separation test, and the centrifugal oil separation was measured. Further, the obtained grease sample was sealed in the rolling bearing subjected to the above-described oil repellent treatment, and subjected to a normal temperature high speed grease test, and a normal temperature high speed grease life time was measured. These measurement results are also shown in Table 2.

Comparative Example 2 to Comparative Example 5
Urea grease or non-urea grease shown in Table 2 was used as a grease sample. This grease sample was subjected to the centrifugal oil separation test, and the centrifugal oil separation was measured. Further, the obtained grease sample was sealed in a rolling bearing not subjected to the above oil repellent treatment, and subjected to a normal temperature high speed grease test to measure a normal temperature high speed grease life time. These measurement results are also shown in Table 2.

  As shown in Table 2, a water- and oil-repellent coating is formed on at least a part of the bearing inner surface that comes into contact with the grease. The grease is a urea grease containing a urea compound as a thickener, and the urea compound is added to the urea grease. The urea compound is obtained by reacting a polyisocyanate component and a monoamine component, and the monoamine component is at least one selected from an aliphatic monoamine and an alicyclic monoamine. It can be seen that high-speed rolling bearings filled with grease, which is a monoamine component containing 50 mol% or more of monoamine based on the total amount of monoamine, show excellent room temperature and high speed grease life in a normal temperature and high speed grease test.

  The high-speed rolling bearing of the present invention has a water- and oil-repellent coating formed on at least a part of the inner surface of the bearing that comes into contact with the grease, and contains grease containing a mixture of urea grease and non-urea grease. Bearing durability life under rotation is improved. For this reason, it can be suitably used as a rolling bearing incorporated in a spindle support part of a machine tool that slides and rotates at high speed such as a lathe, drilling machine, boring machine, milling machine, grinding machine, super finishing machine, and lapping machine. . In addition, unlike a method of continuously supplying lubricating oil such as the oil-air lubrication method, grease can be enclosed and used, so that the operating cost can be reduced and the space can be saved.

It is sectional drawing which shows an example of the formation position of the water-repellent and oil-repellent film of the angular ball bearing which is one Embodiment of this invention. It is sectional drawing which shows the other example of the formation position of the said water / oil repellent film. It is sectional drawing which shows the other example of the formation position of the said water / oil repellent film. It is sectional drawing which shows the other example of the formation position of the said water / oil repellent film. It is sectional drawing which shows an example of the formation position of the water-repellent and oil-repellent film of the deep groove ball bearing which is other embodiment of this invention. It is sectional drawing which shows the other example of the formation position of the said water / oil repellent film. It is sectional drawing which shows the other example of the formation position of the said water / oil repellent film. It is sectional drawing which shows the other example of the formation position of the said water / oil repellent film. It is sectional drawing which shows the conventional angular contact ball bearing.

Explanation of symbols

1,11 Angular contact ball bearings 2,12 Inner ring 3,13 Outer ring 4,14 Rolling elements (steel balls)
DESCRIPTION OF SYMBOLS 5 Cage 6 Seal member 7 Grease 8a, 8b, 8c, 8d Water repellent / oil repellent coating 21 Deep groove ball bearing 22 Inner ring 22a Inner ring rolling surface 23 Outer ring 23a Outer ring rolling surface 24 Rolling element 25 Cage 26 Seal member 27 Grease 28a, 28b, 28c, 28d Water / oil repellent coating

Claims (9)

A high-speed rolling bearing that supports a high-speed rotating shaft,
The rolling bearing includes an inner ring and an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and a seal member that covers an opening of a gap between the inner ring and the outer ring, and encloses grease around the rolling element. A water- and oil-repellent coating is formed on at least a part of the bearing inner surface in contact with the grease,
The grease comprises a urea grease containing a urea compound as a thickener and a non-urea grease containing no urea compound. The urea compound is obtained by reacting a polyisocyanate component and a monoamine component. A high-speed rolling bearing characterized in that the monoamine component is a monoamine component containing 50 mol% or more of at least one monoamine selected from an aliphatic monoamine and an alicyclic monoamine based on the total monoamine.   The water / oil-repellent coating comprises (1) a part of the bearing inner surface of the seal member, (2) an inner diameter surface excluding the raceway surface of the outer ring and a bearing inner surface of the seal member, and (3) a raceway surface of the inner ring. The outer diameter surface excluding the outer surface and the bearing inner surface of the seal member, and (4) at least one selected from the surface of the cage excluding the contact surface with the rolling element. Rolling bearing for high speed.   The high-speed rolling bearing according to claim 1 or 2, wherein the water / oil repellent coating is formed using a silicon compound or a fluorine compound.   The high-speed rolling bearing according to claim 1, wherein the silicon compound is siloxane, and the fluorine compound is fluoroalkylsilane.   The thickener of the non-urea grease is a composite soap thickener or Na terephthalate, and the blending ratio of the non-urea thickener to the whole of the non-urea grease is 10 to 40% by weight. The high-speed rolling bearing according to any one of claims 1 to 4. The rolling bearing for high speed according to any one of claims 1 to 5, wherein the base oil of the urea grease and the non-urea grease has a kinematic viscosity of 15 to 40 mm ² / sec.   The high-speed rolling bearing according to any one of claims 1 to 6, wherein the base oil is at least one selected from a synthetic hydrocarbon oil, an ester oil, and an alkyl diphenyl ether oil.   The high-speed rolling bearing according to any one of claims 1 to 7, wherein the high-speed rolling bearing is a bearing that supports a main shaft of a machine tool.   9. The high-speed rolling bearing according to claim 8, wherein the high-speed rolling bearing is an angular ball bearing or a cylindrical roller bearing.

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