JP2006071104A - Rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing capable of providing sufficient service life of a bearing easily and inexpensively even under use situation in which water is mixed into lubricant from the outside or by dew condensation or influence of vibration is exerted and being suitable for electical/auxiliary machinery of an automobile engine such as, in particular, an alternator. <P>SOLUTION: Hydrogen ion index pH of grease sealed inside the bearing is set to a scope of 7 to 13. When predetermined amount of organic metallic salt or ADTC is added to grease, predetermined amount of inorganic compound having average particle diameter of 2μm or less is added to grease or diurea compound containing aromatic amine or a mixture of diurea compound is added to grease as thickener, hydrogen ion index pH of grease is set to a scope of 5 to 13. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rolling bearing, and is particularly suitable for electrical equipment and auxiliary equipment for automobile engines such as an alternator used in a usage environment where moisture is mixed in a lubricant or is affected by high temperature, high speed rotation and vibration. It relates to rolling bearings.

  Conventionally, in a rolling bearing, a lubricant is sealed in an annular space defined by a rolling element and a bearing ring, thereby preventing seizure damage of the rolling bearing and a decrease in bearing life L.

  By the way, it is generally known that when moisture is mixed in the lubricant, its durability is greatly reduced. For example, when 6% of water is mixed in the lubricant, the bearing is compared with the case where water is not mixed. It has been reported that the rolling fatigue life of the steel sheet decreases from about a few to about one-twentieth (Non-patent Document 1; hereinafter referred to as “Document 1”).

  That is, it is clear from the above-mentioned document 1 that the mixing of moisture into the lubricant greatly affects the life characteristics (durability) of the rolling bearing, and a technique for preventing the mixing of moisture into the lubricant is conventionally known. Various studies have been made and developed depending on the application of the rolling bearing.

  As a rolling bearing used on the assumption that moisture enters the lubricant, for example, there is a work roll bearing for a rolling mill of steel material.

  Conventionally, the work roll bearing is sealed inside the bearing by attaching a contact rubber seal to a chock (bearing box) having the bearing inside, and preventing a large amount of rolling water from entering the chock. Although moisture has been prevented from being mixed into the lubricant, when the contact rubber seal is deteriorated or damaged, water can enter the chock, and as a result, moisture can also be mixed into the lubricant inside the bearing. For this reason, recently, a technique has been proposed in which a contact rubber seal is also attached to the inside of the bearing so as to prevent moisture from being mixed into the lubricant (Non-Patent Document 2; hereinafter referred to as “first prior art”). ).

  According to the first prior art, by using a contact rubber seal mounted on a chock outside the bearing and a contact rubber seal mounted on the inside of the bearing, moisture intrusion can be achieved only with the rubber contact seal mounted on the chock. Compared to the case of preventing it, the moisture concentration in the lubricant can be reduced from 40% to less than 10%, the consumption of the lubricant can be reduced to 1/200, and several times a year. It has been reported that no bearing damage has occurred.

  Moreover, in the work roll bearing described above, as another conventional technique for preventing moisture from being mixed into the lubricant, a technique for supplying the lubricant to the chock using compressed air as a carrier gas has also been proposed (Non-patent Document 3; Hereinafter referred to as “second prior art”).

  In the second prior art, it is possible to suppress moisture from being mixed into the lubricant by setting the air pressure in the chock to a high level using compressed air.

  Another important example of a rolling bearing in which moisture can enter into the lubricant is a bearing for an electrical / auxiliary machine of an automobile engine. Automotive engine electrical equipment / auxiliary bearings include bearings for auxiliary machines driven by belts outside the automobile engine, such as alternator bearings, car air conditioner electromagnetic clutch bearings, idler pulley bearings, water pump bearings, etc. However, these electrical equipment and auxiliary equipment bearings are prone to intrusion of muddy water and rainwater splashed from the road surface into the bearing, and for water pump bearings, circulating water for engine cooling enters the bearing. easy.

  From this point of view, a technology for improving the sealing performance of the built-in seal has been proposed as a means for preventing moisture from being mixed into the lubricant inside the bearing in a bearing for an electrical component / auxiliary machine of an automobile engine ( Non-Patent Documents 4 and 5; hereinafter referred to as “third prior art”).

  Further, in rolling bearings, it is generally reported that when a vibration is applied or the rigidity around the bearing is weak, the durability life of the bearing is significantly reduced (Non-patent Document 6; hereinafter referred to as “Document 2”). Called).

  In other words, when vibration is applied during operation, oil film formation between the raceway surface and the rolling surface is insufficient, tensile stress is applied to the contact surface, and the rotary shaft and the inner ring have a strong interference fit. When the rigidity of the bearing housing is reduced due to the engagement, tensile stress always acts on the raceway surface. As a result, even if there is no moisture mixed into the lubricant from the outside, the moisture originally contained in the lubricant There is a risk that the bearing will be peeled off early due to the influence of this, and the bearing life L will be reduced.

  However, the automobile engine electrical equipment / auxiliary machinery bearings are susceptible to vibration and the like because the vibration of the drive belt is directly transmitted and the rigidity of the bearing housing is low. Therefore, in order to avoid early flaking of the bearing due to the vibration, etc., it is proposed to use grease that acts as a buffer with an excellent vibration damping effect as a lubricant. (Non-Patent Document 7; hereinafter referred to as “fourth prior art”).

  Examples of other rolling bearings in which moisture can enter the lubricant include bearings for automobile wheels, guide roll bearings for continuous casting equipment for steel materials, backup roll bearings for rolling mills, and paper machine dryers. There are roll bearings.

  In automobile wheel bearings, moisture easily enters the lubricant due to the influence of muddy water and rainwater on the road surface. In addition, cooling water and rolling water easily enter the lubricant for the guide roll bearing of the continuous casting equipment for steel materials and the backup roll bearing of the rolling mill. Further, since the paper machine dryer roll bearing is used in a drying process of drying wet paper containing moisture, water vapor easily enters the bearing, and therefore the moisture concentration in the lubricant increases and the bearing is increased. (Non-Patent Document 8; hereinafter referred to as “Document 3”).

  Therefore, in the automotive wheel bearing, similar to the first prior art, a technique has been proposed in which a contact rubber seal outside the bearing and a contact rubber seal built in the bearing are used together or a high performance seal is used alone. (Non-patent document 9) In addition, with respect to a guide roll bearing and a backup roll bearing of a rolling mill, a contact rubber seal is used to prevent moisture from entering the lubricant. In addition, as is clear from the above-mentioned document 3, it is necessary to take measures for preventing moisture intrusion for the paper machine dryer roll bearing. Since it is generally used under high temperature conditions, it is difficult to apply contact rubber seals used for work roll bearings and automotive wheel bearings in consideration of heat resistance. It is considered to use rubber to prevent moisture from entering.

  That is, in the case of other rolling bearings such as automobile wheel bearings, in principle, contact rubber seals are used to mix water into the lubricant inside the bearings, as in the first and third prior arts. This is avoided as much as possible (hereinafter, these other conventional rolling bearing technologies are referred to as “fifth conventional technology”).

  On the other hand, when the temperature inside the housing of the bearing decreases and the dew point is reached when the machinery or automobile on which the rolling bearing is mounted is stopped, the water around the bearing condenses, resulting in water droplets. It has been reported that it adheres to the bearing or is mixed into the lubricant, thereby causing a reduction in the bearing life L (Non-patent Document 10; hereinafter referred to as “Document 4”). It has been reported that when the oxidative deterioration occurs, moisture is generated, and the generated moisture adheres to the bearing and causes a decrease in the bearing life L (Non-patent Document 11; hereinafter referred to as “Document 5”).

  According to these documents 4 and 5, even if moisture is not mixed directly into the lubricant from the outside, there may be a situation where moisture in the lubricant is contained due to environmental changes or the like, and therefore the bearing life L is reduced. In order to avoid this, it is necessary to consider means other than the contact rubber seal described above as a countermeasure against moisture intrusion into the lubricant.

Therefore, from this point of view, the use of martensitic stainless steel (SUS440C) as the bearing material used for the bearing prevents the occurrence of rust due to moisture adhesion to the bearing and prevents the durability from decreasing. (Non-patent document 12; hereinafter referred to as “sixth prior art”).
Shinzaburo Furumura, Shinichi Shirota, Kiyoshi Hirakawa: “Rolling fatigue from surface and internal origin”, NSK Bearing Journal, No. 636, pp. 1-10, 1977 K. YAMAMOTO, M. YAMAZAKI, M. AKIYAMA, K. FURUMURA: “Introducing of Sealed Bearings for Work Roll Necks in Rolling Mills”, Proceedings of the JSLE international Tribology Conference, pp. 609-614, July 8-10, 1985 , Tokyo, Japan NSK Technical Journal, No. 654, pp. 54-56, 1992 NSK Technical Journal, No. 660, pp. 15-22, 1995 NSK Technical Journal, No. 652, pp. 66-67, 1992 Yasuo Murakami, Hiromichi Takemura: “Study on Flaking Phenomena of Electrical Bearings”, Triumphology Conference Proceedings Organized by the Japan Society of Tribology (November 1993, pp. 295-298) NSK Technical Journal, No. 657, pp. 49-51, 1994 MJ Culter: “Paper machine bearing failure”, Tappi Journal, Vol. 79, No. 2, pp. 157-167, 1966 NSK Technical Journal, No. 647, pp. 55-57, 1987 Uchida Gonichi: NSK Technical Journal, No. 632, pp. 40-45, 1973 Masao Seki: Rolling fatigue Sinpodium Proceedings, pp. 125-130, 1993 Rolling Bearing Engineering Editorial Committee: Rolling Bearing Engineering, pp. 71-72, Yokendo (1976) P. Schatzberg, IM Felsen: “Effects of water and oxygen during rolling contact lubrication”, wear, 12, pp. 331-342, 1968 Edited by Japan Iron and Steel Institute: Steel Heat Treatment Revised 5th Edition pp. 563-568 (1989) E. Ioannides, B. Jacobson: “Dirty lubricants-reduced bearing life”, Ball Bearing Journal Special '89, pp. 22-27, 1989 NSK Technical Journal, No. 656, pp. 1, 1993

  By the way, the first prior art can reduce the moisture concentration in the lubricant from 40% to less than 10% as described above, and can reduce the consumption of the lubricant. As a result of investigating the actual use results of the work roll bearings, it was found that the seizure accidents were drastically reduced, but it was found that the service time until the occurrence of peeling, that is, the bearing life L was not improved so much. This is because the decrease in the seizure accident is due to a decrease in the outflow of the lubricant due to the contact rubber seal built in the bearing, and the reason why the bearing life L is not improved is due to the mixing of moisture into the lubricant. This is probably because the rolling fatigue strength of the bearing is significantly reduced.

  That is, it has been reported that the rolling fatigue strength of the bearing material is reduced by 32 to 48% even when a minute amount of water of about 100 ppm is mixed in the lubricant (Non-patent Document 13; 6 ”), when a contact rubber seal mounted on a chock outside the bearing and a contact rubber seal built in the bearing are used in combination, the lubricant can be suppressed until the moisture concentration in the lubricant is less than about 10%. It is not possible to completely prevent moisture from entering, and it is unavoidable that the rolling fatigue strength of the bearing material is reduced as pointed out in the document 6 mentioned above. That is, in the first prior art, since water cannot be completely prevented from being mixed into the lubricant, the rolling fatigue strength of the bearing material is reduced, and the bearing life L having the desired durability cannot be obtained. There is a point.

  Further, the second conventional technique prevents the ingress of moisture by increasing the air pressure in the chock, so that it does not depend on the waterproof capability of the contact rubber seal as in the first conventional technique. There is a problem that it is difficult to prevent the almost incomplete water intrusion such that the water concentration of the water is 100 ppm or less.

  Further, the third prior art is, in principle, like the first prior art, which prevents the ingress of moisture by the contact rubber seal, and suppresses the moisture concentration in the lubricant to 100 ppm or less as described above. This is difficult, and the desired durability cannot be obtained.

  Also in the fourth prior art, due to the recent high performance of automobiles, the operating temperature of bearings for electrical equipment and auxiliary equipment becomes higher, resulting in softening of the grease and lowering the vibration damping capacity of the grease. Further, there is a problem in that the early peeling of the bearing cannot be prevented, and it causes a decrease in the life of the bearing in combination with the above-described water penetration into the lubricant, and the desired durability cannot be obtained.

  That is, in recent years, there has been a need to narrow the space in the engine room of automobiles due to the popularization of so-called FF type automobiles for the purpose of reducing the size and weight and the demand for expansion of migration spaces. It is necessary to promote reduction in size and weight of engine accessories such as alternators to be mounted. On the other hand, there is a demand for higher performance and higher output of these engine accessories.

  However, when these engine accessories are downsized, a decrease in output cannot be avoided. For example, an alternator and an electromagnetic clutch for a car air conditioner compensate for the decrease in output by increasing the speed. Is also faster. Further, from the viewpoint of reducing the noise generated from the engine, the engine room is required to be sealed, and as the sealing of the engine room progresses, the temperature in the engine room becomes higher. The operating temperature of bearings for similar uses will also increase. Furthermore, the load applied to the bearing is increasing due to the increase in the tension of the drive belt, and therefore the use conditions of the rolling bearing used in the engine accessories are becoming increasingly severe.

  In addition, when electrical equipment / auxiliary bearings are used under such high temperature and high speed conditions, the softening of the grease is promoted, resulting in a decrease in the seizure resistance of the grease, and the vibration damping capability of the grease. Therefore, there is a problem that the bearing can be peeled early and desired durability cannot be obtained.

  Also, in the fifth prior art, in principle, as in the first prior art, a contact rubber seal is used, and there is a problem that it is difficult to prevent moisture from entering completely. .

  Furthermore, in the sixth prior art, the thermal conductivity of stainless steel is lower than that of the low alloy steel, so seizure damage is likely to occur, and the above-mentioned lubrication conditions in which moisture is mixed in the lubricant There is a problem that it is difficult to apply to a poor rolling bearing. Further, the corrosion resistance of the stainless steel is maintained by a passive film formed on the surface. However, in a rolling bearing, when the raceway surface of the raceway and the rolling surface of the rolling element come into contact, the passive film is As a result, the corrosion progresses selectively and holes (pits) are generated. As a result, there is also a problem that peeling damage starting from the holes is likely to occur. Furthermore, even in the case of manufacturing a bearing, in the case of stainless steel, since the quenching temperature is as high as 1010 to 1070 ° C., it is necessary to use a salt bath furnace as a heating furnace, and thus the production equipment may be increased. There is also a problem that there is (Non-Patent Document 14).

  In addition, since the stainless steel has a low thermal conductivity as described above, the grinding speed is reduced and the grinding cost is high. Further, the stainless steel is a high alloy steel, so the material cost is increased. There is also a problem of inviting.

  The present invention has been made in view of such problems, and has a sufficient bearing life even under conditions of use in which moisture is mixed into the lubricant from the outside or due to dew condensation or under the influence of vibration. An object of the present invention is to provide a rolling bearing that can be obtained easily and inexpensively.

  The applicant of the present application has conducted extensive research to obtain a rolling bearing capable of preventing the corrosion of the bearing portion even when used under lubricating conditions containing moisture in the lubricant. It is important to suppress the cathode reaction in the rubber to prevent hydrogen from being absorbed into the race, and for that purpose, it is effective to reduce the hydrogen ion concentration in the lubricant, in other words, the lubricant It was found that it is effective to raise the pH value of the hydrogen ion.

  According to the experiments conducted by the applicant of the present application, when an alkaline substance is added to the lubricant, when the hydrogen ion exponent pH of the lubricant is in the range of 7 to 13, the cathode reaction is suppressed and the rolling fatigue strength is increased. It turns out that it can be improved.

  The present invention has been made on the basis of such knowledge, and the rolling bearing according to the present invention is disposed so as to be able to roll between a race ring including an outer ring and an inner ring, and the outer ring and the inner ring. In a rolling bearing comprising a rolling element, wherein a lubricant is sealed in an annular space defined by the rolling element and the raceway, the hydrogen ion exponent pH of the lubricant is set to 7 to 13. This is the first feature.

  In addition, when an organic metal salt is contained in the lubricant, a chemical reaction film is formed on the steel surface of the bearing material to prevent metal-to-metal contact and reduce the coefficient of friction, resulting in load resistance, seizure resistance, It is known that wearability is improved.

  As a result of further diligent research focusing on the function of such an organic metal salt, the applicant of the present application has made it possible to improve the bearing speed by setting the hydrogen ion exponent pH to 5 or more when the lubricant contains an organic metal salt. The knowledge that peeling can be prevented was obtained. Furthermore, it was also found that the same effects as in the case of the organic metal salt can be obtained when ashless dialkyldithiocarbamic acid (ADTC) is contained in the lubricant instead of the organic metal salt.

  Therefore, the rolling bearing according to the present invention has a second feature that the organometallic salt or ADTC is contained in the lubricant, and the hydrogen ion exponent pH of the lubricant is set to 5 to 13.

  In addition to the above-described method of suppressing the cathodic reaction, the method of preventing the corrosion of the bearing part is also controlled by suppressing the formation of a minute gap itself that can be formed between the non-metallic inclusion on the bearing material and the metal substrate. It is considered effective to do this.

  On the other hand, it is thought that by forming an oil film at the interface between the rolling surface and the raceway surface, it is possible to reduce the tangential force between the rolling surface and the raceway surface and suppress the formation of a minute gap. It is done.

  As a result of further earnest research focusing on this point, the applicant of the present application contains fine particles composed of an inorganic compound having an average particle size of 2 μm or less in the lubricant, and the hydrogen ion exponent pH of the lubricant is 5 or more. As a result, a sufficiently strong oil film can be formed between the rolling surface and the raceway surface, thereby preventing metal-to-metal contact and improving the bearing life L under high temperature and high speed conditions. found.

  In view of this, the rolling bearing according to the present invention is characterized in that an inorganic compound having an average particle diameter of 2 μm or less is contained in the lubricant, and the hydrogen ion exponent pH of the lubricant is set to 5 to 13. It is said.

  Furthermore, from the research results of the applicant of the present application, in place of the inorganic compound, a diurea compound containing an aromatic amine or a mixture of two or more of the diurea compounds may be added to the lubricant as a thickener. Similarly, it has been found that a sufficiently strong oil film is formed between the rolling surface and the raceway surface.

  Therefore, in the rolling bearing according to the present invention, the lubricant thickener is composed of a diurea compound containing an aromatic amine or a mixture of two or more of the diurea compounds, and the lubricant has a hydrogen ion exponent pH of 5 to 13. The fourth feature is that it is set to.

  Furthermore, the rolling bearing of the present invention can achieve the intended purpose not only by the first to fourth features alone but also by appropriately combining the first to fourth features.

  As described above in detail, the rolling bearing according to the present invention includes a raceway ring composed of an outer ring and an inner ring, and a rolling element disposed so as to be able to roll between the outer ring and the inner ring. In the rolling bearing in which the lubricant is enclosed in the annular space defined by the raceway and the ring, the hydrogen ion exponent pH of the lubricant is set to 7 to 13, so that moisture is mixed in the lubricant. Even in the case of automobile engine electrical equipment and auxiliary machinery bearings, which are susceptible to the effects of moisture in the lubricant due to vibration or vibration, it is possible to prevent the occurrence of peeling at the bearing site and improve durability Can be achieved.

  In addition, when a predetermined amount of an organometallic salt or ADTC is added to the lubricant or an inorganic compound having an average particle size of 2 μm or less is added, the same effect as described above is obtained when the hydrogen ion exponent pH is in the range of 5 to 13. Further, when a diurea compound containing an aromatic amine is added to the lubricant as a thickener, the same effect as described above can be obtained when the hydrogen ion exponent pH is in the range of 5 to 13.

  Embodiments of the present invention will be described below.

[First Embodiment]
A rolling bearing is generally used by enclosing a lubricant in an annular space defined by a rolling element and a race. As described above, it is known that the rolling fatigue strength of the bearing material is reduced under lubrication conditions in which moisture is contained in the lubricant. It is unclear as to why the mixing of the material decreases rolling fatigue strength (Non-patent Document 15).

  Therefore, the present applicant first started to theoretically elucidate the above mechanism.

  When water is mixed in the lubricant, it is difficult to form an oil film even if the amount of water is very small, and the rolling elements and the raceway are in metal contact between the rolling surface and the raceway surface. The surface states of the rolling elements and the races are uneven and non-uniform, and inevitable non-metallic inclusions such as oxides and sulfides are formed on the rolling surfaces and raceways. If moisture is mixed in the lubricant, local water is formed when water enters the interface between these non-metallic inclusions and the metal substrate (matrix) mainly composed of Fe, and local corrosion occurs. To do. That is, since there is always a contact portion between the rolling element and the raceway in the vicinity of the interface, a tensile stress is always applied to the interface between the nonmetallic inclusions present on the raceway surface and the rolling surface and the metal substrate, Under such tensile stress, a minute gap is formed at the interface between the nonmetallic inclusion and the metal substrate. And when moisture is mixed in the lubricant, even if the amount of water is small, the viscosity of the water is lower than the viscosity of the lubricant, so that the moisture preferentially penetrates into the minute gap by capillary action, As a result, a corrosion reaction occurs in a minute gap. In addition, when the inner ring and the rotating shaft are fitted with an interference fit, since a tensile stress always acts on the raceway surface, a larger tensile stress is applied to the interface between the nonmetallic inclusion and the metal substrate. A gap is formed under the large tensile stress.

  In addition, in rolling bearings used for electrical equipment and auxiliaries of automobile engines such as alternators, the vibration of the drive belt is directly transmitted to the bearings and the rigidity of the bearing housing is low. The raceway surface of the race and the rolling surface of the rolling element make metal contact with high frequency. For this reason, the adhesion between the non-metallic inclusions present on the raceway surface and the rolling surface and the metal substrate is lowered to form a minute gap at the interface, and the moisture contained in the lubricant is reduced by the minute amount. There is a risk of entering a gap and causing a corrosion reaction, and this type of corrosion is likely to occur particularly on the outer ring raceway surface. Moreover, since the lubricant absorbs moisture from the atmosphere, it usually contains a certain amount of water, and even if there is no moisture mixed into the lubricant from the outside, it does not cause corrosion reaction due to the water originally contained in the lubricant. There is a risk of it happening.

  In this corrosion reaction, the corrosion product closes the entrance of the minute gap, so that it is difficult to supply oxygen from the surface to the minute gap, and the deepest metal base inside the gap becomes the anode, and the carbide and the metal other than the deepest part. The substrate serves as a cathode, and a hydrogen generation type corrosion reaction as shown in chemical reaction formulas 1 to 4 occurs.

  Here, H (ads) represents a hydrogen atom adsorbed on the surface of the bearing material, and H (abs) represents a hydrogen atom absorbed into the bearing material.

  That is, on the anode (anode) side, as shown in chemical reaction formula 1, Fe reacts with moisture to exhibit an oxidation reaction to release electrons, while on the cathode (cathode) side, oxygen supply to the inside of the minute gap is performed. As shown in Chemical Reaction Formula 2, hydrogen is adsorbed on the surface of the bearing material, and then, as shown in Chemical Reaction Formula 3, a part of the adsorbed hydrogen is diffused and absorbed inside the bearing material. Other than the adsorbed hydrogen, as shown in chemical reaction formula 4, hydrogen atoms adsorbed on the surface of the bearing material are combined to form hydrogen molecules (gas), and the hydrogen molecules are released to the outside. The On the cathode carbide, the progress of the chemical reaction formula 3 is almost negligible, so the chemical reaction of the chemical reaction formula 4 mainly occurs, but the reaction of the chemical reaction formulas 3 and 4 proceeds on the cathode metal substrate.

  For this reason, even when a very small amount of moisture intrudes into the gap during operation of the rolling bearing, the bearing material absorbs hydrogen, resulting in hydrogen embrittlement of the bearing material and a decrease in rolling fatigue strength. As a result, peeling occurs and the bearing life L is reduced.

  Therefore, from this point of view, it is necessary to prevent hydrogen embrittlement by suppressing hydrogen absorption inside the bearing material. To this end, in view of the mechanism of the corrosion reaction described above, the cathode reaction of the above chemical reaction formula 2 is suppressed. It is important to. And in order to suppress the cathode reaction of Chemical Reaction Formula 2, it is necessary to lower the hydrogen ion concentration in the lubricant. In other words, by increasing the hydrogen ion exponent pH in the lubricant, the reaction rate of the chemical reaction formula 2 can be lowered, and for that purpose, the hydrogen ion exponent pH needs to be limited to a range of 7 to 13. There is.

  Hereinafter, the hydrogen ion exponent pH of the lubricant and the composition of the lubricant (base oil, thickener, pH adjuster) in the present embodiment will be described.

[Hydrogen ion index pH of lubricant and composition of lubricant]
(1) Hydrogen ion index pH
Moisture dissolves a small amount of carbon dioxide contained in the atmosphere, and as a result, the hydrogen ion index often becomes acidic with a value of 7 or less, and hydrogen is added by adding an alkaline substance as a pH adjuster to the lubricant. The ion index pH can be increased, but in order to reduce the reaction rate of the chemical reaction formula 2 and achieve sufficient suppression of hydrogen absorption into the raceway material, thereby improving the bearing life L, It is necessary to set the hydrogen ion index pH to at least 7 or more. On the other hand, when the hydrogen ion index pH exceeds 13, the raceway surface and the rolling surface wear due to alkali corrosion, and the vibration during the driving of the rolling bearing becomes gradually remarkable. Therefore, in the present embodiment, the hydrogen ion exponent pH of the lubricant is limited to 7-13.

(2) Base oil The base oil responsible for the lubricating action is not particularly limited, and any oil that is normally used as a base oil for lubricating oil can be used, but it occurs when low-temperature fluidity is insufficient. cold startup abnormality and a kinematic viscosity at 40 ° C. in order to ensure the galling resistance by forming a stronger oil film 40~400mm ² / sec, preferably base oil 60~250mm ² / sec to obtain It is desirable to use

  Specifically, mineral oils, synthetic oils, and natural oils can be used as the base oil.

  As mineral oil-based lubricating oil, use the one that is refined by appropriately combining mineral oils under reduced pressure distillation, oil removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay purification, hydrorefining, etc. Can do.

  Examples of synthetic oils that can be used include hydrocarbon oils, aromatic oils, ester oils, ether oils, and the like.

  As the hydrocarbon oil, for example, normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, 1-decene, polyco-olefin (PAO) such as ethylene co-oligomer, or a hydride thereof may be used. it can.

  As the aromatic oil, alkylbenzene such as monoalkylbenzene and dialkylbenzene, alkylnaphthalene such as monoalkylnaphthalene, dialkylnaphthalene and polyalkylnaphthalene can be used.

  Examples of ester oils include diester oils such as dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate and methylacetyl cinnolate, trioctyl trimellitate, Aromatic ester oils such as decyl trimellitate and tetraoctyl pyromellitate, or polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, Furthermore, a complex ester oil which is an oligoester of a polyhydric alcohol and a mixed fatty acid of a dibasic acid / monobasic acid can be used.

  Examples of ether oils include polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, polypropylene glycol monoether, monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether (DAPE), pentaphenyl ether, tetraphenyl ether, Phenyl ether oils such as monoalkyl tetraphenyl ether and dialkyl tetraphenyl ether can be used.

  In addition, tricresyl phosphate, silicone oil, perfluoroalkyl ether, and the like can be used as other synthetic oils.

  In addition, the above listed lubricating oils can be used alone as a base oil, and a mixture prepared by mixing two or more kinds of the above lubricating oils to have a desired kinematic viscosity can also be used as a base oil.

(3) Thickener The thickener is contained in the lubricant in order to maintain the lubricant in a semisolid state and improve the properties (viscosity, elasticity, plasticity, etc.) of the oil. The thickener is a chain of molecules or crystals that form a fiber and is dispersed in a base oil to form a gel structure.

  Accordingly, the thickener is not particularly limited as long as it has a holding ability to hold the base oil in the gel structure. For example, a metal soap composed of Li, Na, etc., Li, Na, Ba, Ca It is possible to appropriately select and use a metal soap such as a composite metal soap selected from the above, or a urea compound such as a diurea compound or a polyurea compound.

  However, from the viewpoint of improving the heat resistance of the lubricant, it is preferable to use a diurea compound having a strong gel structure. The diurea compound is a compound obtained by reacting diisocyanates and monoamines under a predetermined condition, and is represented by the general formula (1).

Here, the amine residue represented by R ¹ or R ³ is, for example, a cyclohexyl group, an alkylcyclohexyl group having a carbon number C _n of n = 7 to 12 or a linear alkyl having a carbon number C _n of n = 8 to 20 The isocyanate residue represented by R ² is composed of a divalent aromatic ring-containing hydrocarbon group having a carbon number C _n of n = 6 to 15.

(4) pH adjuster A pH adjuster is added in order to make the hydrogen ion exponent pH of a lubricant into the range of 7-13. As described above, since water dissolves a small amount of carbon dioxide contained in the atmosphere, the hydrogen ion index of the lubricant is often acidic at 7 or less. In order to obtain 13, it is necessary to add an alkaline substance as a pH adjuster. As the alkaline substance, at least one selected from an amine compound, an organic metal salt, an organic acid metal salt, and an alkaline inorganic compound is selected. Can be used.

  As the amine compound, any of primary to tertiary amines represented by the general formulas (2) to (4) can be used.

Here, R ⁴ to R ⁶ is appropriately selected from carbon atoms C _n are the n = 1 to 24 aliphatic hydrocarbon group, alicyclic hydrocarbon group, aromatic hydrocarbon group, or a derivative thereof R ^{4 to} R ⁶ may be the same group or different groups.

  Examples of the aliphatic hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a dodecyl group, a tetradodecyl group, an octadecyl group, and an eicosyl group.

  A typical example of the alicyclic hydrocarbon group is a cyclohexyl group.

  Examples of the aromatic hydrocarbon group include a phenyl group, a methylphenyl group, and an ethylphenyl group.

  These derivatives include polyoxyalkylene groups, polyoxyethylene groups, polyoxyethylene groups, and the like.

The organic metal salt or an organic acid metal salt, carbon number C _n is n = 6 to 24 hydrocarbon chain constituting the alkyl group, the metal element constituting the metal salt is Na, K, Li-like alkaline At least one selected from metals, alkaline earth metals such as Mg, Ca, Ba, Al, Zn, and the like can be used.

Examples of the alkaline inorganic compound include metal hydroxides such as sodium hydroxide (NaOH), potassium hydroxide (KOH), aluminum hydroxide (Al (OH) ₃ ), sodium carbonate (Na ₂ CO ₃ ), potassium carbonate Metal borate such as (K ₂ CO ₃ ), lithium carbonate (Li ₂ CO ₃ ), sodium hydrogen carbonate (NaHCO ₃ ), etc., sodium borate (Na ₃ BO ₃ ), lithium borate (Li ₃ BO ₃ ) Metal silicates such as salts, sodium silicate (Na ₄ SiO ₄ ), and potassium silicate (K ₄ SiO ₄ ) can be used.

(5) Other additives In order to further improve the performance as a lubricant, if necessary, gelling agent, antioxidant, extreme pressure agent, oiliness agent, rust inhibitor, metal deactivator, viscosity index improvement It is also a preferred embodiment to include various additives such as an agent in the lubricant.

  Here, examples of the gelling agent include metal soap, benton, and silica gel, and examples of the antioxidant include amine-based, phenol-based, sulfur-based, and zinc thiophosphate. Examples of extreme pressure agents include chlorine, sulfur, phosphorus, zinc dithiophosphate, and organic molybdenum, and examples of oil agents include fatty acids and animal and vegetable oils. Furthermore, examples of the rust preventive include petroleum sulfonate, dinonyl naphthalene sulfonate, sorbitan ester and the like, and examples of the metal deactivator include benzotriazole, sodium nitrite and the like. Examples of the viscosity index improver include polymethacrylate, polyisobutylene, and polystyrene.

  These additives can be used alone or in combination of two or more. In addition, although the content rate of an additive is not specifically limited, Usually, it prepares so that the content rate in a lubricant may be 20 wt% or less.

  Next, the applicant of the present application also examined the peeling characteristics of each bearing portion when moisture was mixed in the lubricant.

  As described in the section of [Problems to be Solved by the Invention], when water is mixed in the lubricant, the time required for the rolling bearing to peel, that is, the bearing life L is reduced, but the bearing that is peeled off occurs. In general, the number of constituent parts is fixed wheels, and the frequency of separation decreases in the order of rotating wheels and rolling elements. The reason why the occurrence of delamination in the rolling elements is lower than the occurrence frequency of delamination in the races is because the hydrogen absorption of the rolling elements is less than the hydrogen absorption of the races. Conceivable.

  (1) Since the rolling speed of a rolling bearing is generally much faster than that of a raceway, even if a minute gap is formed on the rolling surface of the rolling element, moisture that has entered the minute gap is caused by centrifugal force. As a result, the progress of the corrosion reaction is suppressed, and the amount of hydrogen absorbed into the material is small.

  (2) Since the processing ratio of the rolling element from the casting material (ingot, bloom, billet, etc.) is larger than the processing ratio from the casting material of the raceway ring, the non-metallic inclusions present on the rolling surface of the rolling element are Smaller than non-metallic inclusions present on the raceway surface of the ring. Therefore, in the rolling element, the interface between the non-metallic inclusion and the metal substrate is small and shallow, so that the progress of the hydrogen generation type corrosion reaction is suppressed, and the amount of hydrogen absorbed into the material is small.

  The reason is considered.

  In addition, regarding the raceway, it is considered that the rotating wheel is less frequently peeled than the fixed wheel for the following reason. That is, in general, in a rotating wheel, even if water enters a minute gap formed on the raceway surface, it is likely to be blown away, so that it absorbs less hydrogen than a fixed wheel, and therefore it is considered that the frequency of separation is also reduced. However, when the inner ring and the rotating shaft are fitted with an interference fit, tensile stress always acts on the raceway surface of the rotating ring, so stress corrosion is promoted even when the inner ring is a rotating ring. The chemical reaction of the above chemical reaction formula 2 actively proceeds and the amount of hydrogen absorbed by the rotating wheel increases, and therefore the frequency of occurrence of peeling increases. In particular, when the tightening margin exceeds 7 / 10,000 of the shaft diameter of the rotating shaft or when using a tapered bore bearing with an interference fit, the frequency of occurrence of peeling of the rotating wheel is equal to or more than the frequency of occurrence of peeling of the fixed ring. It will be a lot. When the inner ring is a fixed ring and the inner ring and the rotating shaft are fitted by interference fit, the hydrogen absorption amount is larger than when the inner ring is fitted by clearance fit. Not too long.

  Also, in rolling bearings, focusing on the fact that the rolling contact surface of the rolling element and the raceway surface of the raceway are in metal contact, the metal substrate side inside the gap formed at the interface between the metal substrate and the nonmetallic compound is the anode. It is effective to change the corrosion form from local corrosion to contact corrosion using the metal substrate on the rolling surface of the rolling element as a cathode.

  The metal substrate existing on the rolling surface of the rolling element (hereinafter referred to as “rolling surface metal substrate”) is electrochemically more precious than the metal substrate existing on the raceway surface of the bearing ring (hereinafter referred to as “race ring metal substrate”). Thus, the metal substrate side in the gap can be used as an anode, and the metal substrate on the rolling surface can be used as a cathode. Thus, while the anode reaction occurs on the metal substrate side of the interface, the cathode reaction occurs on the rolling surface metal substrate, and oxygen can be easily supplied onto the rolling surface from the surroundings. As shown in FIGS. 5 and 6, the corrosion reaction becomes an oxygen consumption type corrosion reaction, and it is possible to suppress the hydrogen absorption into the bearing ring and prevent the bearing life from decreasing due to hydrogen embrittlement. In this case, the carbide inside the gap is still the cathode, but on the carbide, the chemical reaction formula 3 that causes hydrogen embrittlement hardly proceeds as described above, and mainly the chemical reaction formula 4 As the reaction proceeds, no hydrogen is absorbed into the race.

  Further, by increasing the concentration of retained austenite in the bearing material that has been completely quenched and tempered, a metal base that is inexpensive and electrochemically noble can be obtained.

  There are the following methods for increasing the concentration of retained austenite.

[Method of increasing the concentration of retained austenite]
(1) The starting temperature (Ms point) at which austenite transforms into martensite is adjusted.

  The Ms point is determined by the chemical composition of the material steel, the surface carbon concentration and surface nitrogen concentration added by carburizing or carbonitriding, the metal structure before quenching, the quenching temperature, the quenching time, and the like. For example, the higher the Mn content of the raw steel, the higher the concentration of retained austenite, and the higher the concentration of retained austenite already carburized before quenching, the higher the concentration of retained austenite, Get higher. Further, the smaller the particle size of the carbide, the higher the quenching temperature, and the longer the quenching temperature holding time, the higher the concentration of retained austenite.

  (2) Adjust the cooling rate during quenching.

  The slower the quenching cooling rate, the higher the concentration of retained austenite.

  (3) Adjust the tempering conditions.

  The lower the tempering temperature and the shorter the heating temperature during tempering, the higher the concentration of retained austenite.

  (4) Examine the implementation conditions for so-called sub-zero processing.

  The higher the treatment temperature of the sub-zero treatment that cools below room temperature, and the shorter the treatment time of the Cebu zero treatment, the higher the concentration of retained austenite. Further, the concentration of retained austenite increases when the sub-zero treatment is not performed.

  (5) No work hardening such as shot peening is performed.

  When the shot peening is not performed, the residual austenite concentration is higher than when the shot peening is performed.

  In addition, as described in the section of [Problems to be Solved by the Invention], it is technically difficult to suppress a corrosion reaction by using a high alloy steel such as stainless steel (SUS440C) as a bearing material. It is also disadvantageous economically, and it is preferable to use low alloy steel as the material steel for the bearing. For example, as the material steel of each bearing part, the chemical components are, for example, C: 0.10 to 1.10 wt%, Si: 0.75 wt% or less, Mn: 1.70 wt% or less, Cr: 1.80 wt% %: Mo: 1.50 wt% or less, Ni: 4.50 wt% or less, Cu: 0.30 wt% or less, Al: 0.050 wt% or less, balance: Fe and inevitable impurities (O, S, Ti, etc.), etc. It is effective to obtain a bearing part having a desired surface hardness by using a low alloy steel made of

  In addition, since the corrosion reaction in the bearing ring occurs due to a minute gap formed between the nonmetallic inclusions and the metal substrate, the generation of nonmetallic inclusions is suppressed in order to prevent the corrosion. For this purpose, the oxygen content, which is the cause of formation of oxides, sulfides and titanium compounds, which are constituents of non-metallic inclusions, is 9 ppm or less, the sulfur content is 50 ppm or less, and the titanium content is 40 ppm or less. It is desirable to make it. Furthermore, in order to obtain good adhesion between the non-metallic inclusions and the metal substrate and avoid the formation of minute gaps at the interface, the final refining method of the bearing material is performed by the ESR method or the VAR method. Is desirable.

[Second Embodiment]
In the first embodiment, by setting the hydrogen ion exponent pH in the range of 7 to 13, the absorption of hydrogen into the bearing material is suppressed to avoid hydrogen embrittlement, thereby reducing the bearing life L. However, in the second embodiment, an organic metal salt or an ashless dialkyldithiocarbamic acid (ADTC) is contained in the lubricant so that the nonmetallic inclusions and the metal substrate are mixed. In order to obtain a rolling bearing having a desired bearing life L as long as a strong reaction film is formed in a minute gap formed between them and the hydrogen ion exponent pH is 5 or less as long as it is 5 or more. did.

  The lubricant base oil, thickener, and pH adjuster are the same as those in the first embodiment. Hereinafter, the reaction film forming agent (organometallic salt or ADTC)) and hydrogen ion index pH will be described.

(1) Reaction film forming agent The action and effect when an organic metal salt is used as the reaction film forming agent will be described.

  Organometallic salts are conventionally used as additives for lubricants as extreme pressure agents and some antioxidants, but lubricants containing organometallic salts react chemically with the steel surface of bearing materials. A film is formed. In other words, by containing an organic metal salt in the lubricant, a strong reaction film made of an organic metal salt is formed in a minute gap formed between the non-metallic inclusions present on the surface of the bearing material and the metal substrate. . As a result, the metal-to-metal contact is prevented and the friction coefficient is lowered, and the load resistance, seizure resistance, and wear resistance can be improved.

  In addition, a specific organic metal salt is contained in the lubricant, and the above-described strong reaction film is formed in a minute gap before the hydrogen generation type corrosion reaction occurs, whereby the cathode reaction represented by the chemical reaction formula 2 is achieved. Or the diffusion of hydrogen atoms adsorbed on the surface of the bearing material to the inside of the bearing material is prevented, thereby preventing the early peeling of the bearing material and improving the bearing life L. Can do.

  As an organometallic salt having such an effect, a dialkyldithiocarbamic acid (DTC) compound represented by the general formula (5) or a dialkyldithiophosphoric acid (DTP) compound represented by the general formula (6) should be used. Can do.

n = 2, 3, 4,
x, y, z = 0, 1, 2, 3, 4
Here, M represents a metal species, and specifically, Sb, Bi, Sn, Ni, Te, Se, Fe, Cu, Mo, or Zn is used.

R ⁷ and R ⁸ may be the same group or different groups, and each represents an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an alkylaryl group, or an arylalkyl group. Particularly preferred groups include 1,1,3,3-tetramethylbutyl group, 1,1,3,3-tetramethylhexyl group, 1,1,3-trimethylhexyl group, 1,3-dimethylbutyl group. Group, 1-methylundecane group, 1-methylhexyl group, 1-methylpentyl group, 2-ethylbutyl group, 2-ethylhexyl group, 2-methylcyclohexyl group, 3-heptyl group, 4-methylcyclohexyl group, n-butyl Group, isobutyl group, isopropyl group, isoheptyl group, isopentyl group, undecyl group, eicosyl group, ethyl group, octadecyl group, octyl group, cyclooctyl group, cyclododecyl group, cyclopentyl group, dimethylcyclohexyl group, decyl group, tetradecyl group, Docosyl group, dodecyl group, tridecyl group, trimethylcyclohexyl group, Nyl group, propyl group, hexadecyl group, hexyl group, henicosyl group, heptadecyl group, heptyl group, pentadecyl group, pentyl group, methyl group, tert-butylcyclohexyl group, tert-butyl group, 2-hexenyl group, 2-methallyl group , Allyl group, undecenyl group, oleyl group, decenyl group, vinyl group, butenyl group, hexenyl group, heptadecenyl group, tolyl group, ethylphenyl group, isopropylphenyl group, tertiary butylphenyl group, secondary pentylphenyl group, n- Hexylphenyl group, tertiary octylphenyl group, isononylphenyl group, n-dodecylphenyl group, phenyl group, benzyl group, 1-phenylethyl group, 2-phenylethyl group, 3-phenylpropyl group, 1,1-dimethyl Benzyl group, 2-phenylisopropyl group, 3-phenylhexyl Group, benzhydryl group, there is a biphenyl group and the like, and these groups may be an ether bond.

  Moreover, as other organometallic salts, organozinc compounds represented by the general formulas (7) to (9) can also be used.

Here, R ⁹ and R ¹⁰ represent a hydrocarbon group or a hydrogen atom having a carbon number C _n of n = 1 to 18, and R ⁹ and R ¹⁰ may be the same group or different groups. .

In particular, mercaptobenzothiazole zinc (general formula (7)), benzamidothiophenol zinc (general formula (8)), and mercaptobenzimidazole zinc (general formula (3)) in which R ⁹ and R ¹⁰ are both hydrogen atoms. Can be preferably used.

  Further, as other organometallic salts, zinc alkylxanthates represented by the general formula (10) can also be used.

Here, R ¹¹ represents a hydrocarbon group having a carbon number C _n of n = 1 to 18.

  The organometallic salts represented by the general formulas (5) to (10) can be used alone or in combination of two or more, but the combination type is not particularly limited. .

  Moreover, the same effect as the organometallic salt mentioned above can be obtained even if ADTC such as methylenebisdialkyldithiocarbamic acid represented by the general formula (11) is used.

Here, R ¹² and R ¹³ represent a hydrocarbon group having a carbon number C _n of n = 1 to 18, and R ¹² and R ¹³ may be the same group or different groups.

(2) Addition amount of reaction film forming agent As mentioned above, organometallic salt or ADTC has the effect of suppressing the progress of the corrosion reaction by forming a reaction film in a minute gap, but if the content is less than 0.1 wt% Insufficient effect. On the other hand, although it is considered that the upper limit of the content rate is not particularly limited, the compound used as the reaction film forming agent is relatively expensive, and excessive addition of the reaction film forming agent causes a reaction with the bearing material. May be accelerated abnormally, leading to corrosion and abnormal wear. Therefore, considering such points, it is preferable to limit the content of the reaction film forming agent to 10 wt% or less, and in this embodiment, the addition amount of the reaction film forming agent is set to 0.1 to 10 wt%. In addition, the more preferable range of this addition amount is 0.1-5 wt%.

(3) Hydrogen ion index pH
By including a reaction film forming agent composed of an organic metal salt or ADTC in the lubricant, it is possible to prevent early peeling of the bearing material even in an acidic region having a hydrogen ion index pH of 7 or less. It is not sufficient to add a forming agent. In other words, when moisture is mixed in the lubricant and a new minute gap is generated due to tensile stress, the above-described hydrogen generation type corrosion reaction (chemical reaction) occurs immediately after the occurrence of the minute gap near the inlet of the minute gap. Reaction formulas 1 to 4) are considered to occur, but such a corrosion reaction proceeds while competing with the generation of corrosion products. For this reason, when the hydrogen ion concentration of the lubricant is high, in other words, when the hydrogen ion index pH is low, the rate of formation of corrosion products is high, and as a result, the reaction film is not sufficiently formed in the minute gaps, and the inside of the bearing material. The hydrogen absorption cannot be sufficiently suppressed. Therefore, it is necessary to add an alkaline pH adjuster to suppress the hydrogen ion concentration. In this embodiment, the lower limit of the hydrogen ion index pH is set to 5 in order to satisfy sufficient bearing reliability.

  On the other hand, even when a polyol ester oil having the most excellent lubricating properties among the synthetic base oils is used as the base oil, when the water is mixed in the lubricant and the hydrogen ion index pH becomes higher than 13, the base oil Oil may hydrolyze and deteriorate. Therefore, in the present embodiment, the upper limit of the hydrogen-Ioi index pH is set to 13 in order to avoid such a problem. For these reasons, the hydrogen ion exponent pH range is set to 5 to 13 in the second embodiment.

[Third Embodiment]
In the third embodiment, the oil film is formed between the raceway surface and the rolling surface by containing 0.001 to 3 wt% of fine particles made of an inorganic compound having an average particle size of 2 μm or less in the lubricant. The tangential force between the raceway and the rolling surface was reduced. And generation | occurrence | production of the micro clearance gap itself is suppressed by this, and durability improvement of a rolling bearing can be aimed at.

  As a method for preventing the progress of corrosion of the bearing part, there is a method for suppressing the progress of the chemical reaction formula 2 as in the first embodiment, but between the non-metallic inclusions on the raceway surface and the metal substrate. It is also possible to effectively prevent the progress of corrosion of the bearing portion by suppressing the formation of the formed minute gap itself.

  However, by forming an oil film between the rolling surface and the raceway surface, the tangential force between the rolling surface and the raceway surface can be reduced and the generation of a minute gap can be suppressed.

  That is, when a sufficiently retained oil film is formed between the rolling surface and the raceway surface, the oil film exhibits a so-called damping effect by acting like a buffering agent. It is known that the maximum load applied to the rolling element is reduced (Non-Patent Document 16), and by increasing the damping effect of such a lubricant, a tangent between the rolling surface and the raceway surface is obtained. The force is reduced, and the generation of the minute gap can be suppressed.

  The lubricant base oil, the thickener, and the pH adjuster are the same as those in the first and second embodiments described above, and fine particles and hydrogen made of an inorganic compound, which are the features of the third embodiment. The ion index pH will be described below.

(1) Composition of fine particles made of inorganic compound Fine particles made of inorganic compound are uniformly dispersed in the lubricant and receive large shear stress due to high-speed rotation or when the oil film becomes thin during high-temperature rotation Even so, the fine particles present in the oil film firmly hold the oil film on the contact surface between the rolling surface and the raceway surface, avoiding metal contact and improving the seizure life of the bearing.

  In addition, the fine particles made of such an inorganic compound penetrate into the fibrous thickener to make the gel structure even stronger.

Examples of inorganic compounds include SiO ₂ , Al ₂ O ₃ , MgO, TiO ₂ , PZT (Clebite, USA), ZnO and other metal oxides, Mg (OH) ₂ , Al (OH) ₃ , and Ca (OH) _2. Metal hydroxides such as MgCO ₃ , CaCO ₃ or the like, or hydrates thereof, metal nitrides such as Si ₃ N ₄ , ZrN, CrN, TiAlN, metal carbides such as SiC, TiC, WC, (Synthetic) viscosity minerals such as bentonite, smectite and mica, diamond and the like can be used, and solid lubricants such as MoS ₂ , graphite, BN and WS ₂ can be used.

  In order to improve the affinity with a base oil or a thickener, it is also preferable to use an inorganic compound whose surface has been modified to be lipophilic. Among the inorganic compounds, the inorganic compound itself increases. Metal oxides and viscous minerals having the action of a thickener are even more preferable.

(2) Particle size of fine particles made of an inorganic compound Fine particles made of an inorganic compound are finer than the gel structure formed by the thickener, and thus enter the fibrous thickener as described above. Thus, the gel structure of the thickener is further strengthened, the oil film forming ability is increased, or the damping effect of the lubricant is increased to contribute to the improvement of the bearing life L. Therefore, as long as the production cost does not become expensive, the smaller the particle diameter, the more preferable. When the average particle diameter is 1 μm or less, good seizure resistance can be exhibited. Furthermore, considering the seizure life, it is desirable that the particle diameter is smaller than the oil film of the base oil. That is, the oil film of the base oil used for the rolling bearing is practically 0.2 μm or less, and therefore the particle diameter is preferably 0.2 μm or less.

  On the other hand, when the average particle diameter exceeds 2 μm, the fine particles acting as foreign substances increase, which causes the wear of the raceway surface and rolling surface to be accelerated, leading to early damage of the bearing, and deteriorates the acoustic characteristics of the bearing. There is a risk of causing it. Therefore, in the present embodiment, the particle system of the inorganic compound is limited to an average particle diameter of 2 μm or less, preferably 0.2 μm or less.

  The shape of the fine particles is preferably as close to a sphere as possible. However, if the average particle diameter is 2 μm or less, the shape may be a polyhedron such as a cube or a rectangular parallelepiped or a needle shape.

(3) Addition amount of fine particles made of inorganic compound As described above, the addition of fine particles made of inorganic compound to the lubricant contributes to improving the durability of the bearing, but the addition amount is less than 0.001 wt%. However, when the added amount exceeds 3 wt%, the number of inorganic compound particles increases and wear is promoted, which adversely affects seizure resistance. Therefore, in the present embodiment, the amount of fine particles made of an inorganic compound is limited to 0.001 to 3 wt%, preferably 0.005 to 3 wt%.

(4) Hydrogen ion index pH
Oil film formation can be improved by incorporating fine particles made of an inorganic compound having an average particle size of 2 μm or less in the lubricant, whereby the hydrogen ion index pH is 7 or less. Although it is possible to prevent early peeling of the bearing material, it is not sufficient to add the fine particles as in the second embodiment. In other words, when moisture is mixed in the lubricant and a new minute gap is generated due to tensile stress, the above-described hydrogen generation type corrosion reaction (chemical reaction) occurs immediately after the occurrence of the minute gap near the inlet of the minute gap. Reaction formulas 1 to 4) are considered to occur, but such a corrosion reaction proceeds while competing with the generation of corrosion products. For this reason, when the hydrogen ion concentration of the lubricant is high, in other words, when the hydrogen ion index pH is low, the rate of formation of corrosion products is large, and as a result, a strong oil film is not sufficiently formed in the minute gaps. Hydrogen absorption into the water cannot be sufficiently suppressed. Therefore, as in the second embodiment, it is necessary to suppress the hydrogen ion concentration. In this embodiment, the lower limit of the hydrogen ion index pH is set to 5 in order to satisfy sufficient bearing reliability.

  On the other hand, as described in the second embodiment, when water is mixed in the lubricant and the hydrogen ion index pH is higher than 13, the base oil may be hydrolyzed and deteriorated. Therefore, in the present embodiment, the upper limit of the hydrogen Ioi index pH is set to 13 in order to avoid such a problem. For these reasons, in the third embodiment, the hydrogen ion exponent pH range is set to 5-13.

[Fourth Embodiment]
In the third embodiment, the thickener is not particularly limited. However, in the fourth embodiment, instead of adding an inorganic compound to the lubricant, a diurea compound containing an aromatic amine (hereinafter referred to as an “inorganic amine compound”) is used. , "Aromatic diurea compound" or a mixture of an aromatic diurea compound and a diurea compound not containing an aromatic amine (hereinafter referred to as "non-aromatic diurea compound") as a thickener. However, it is possible to obtain a rolling bearing having a desired bearing life L with good oil film formation.

  That is, as is clear from Document 7 described in the third embodiment, when an oil film that is sufficiently held between the rolling surface and the raceway surface is formed, the oil film exhibits a so-called damping effect. From this, it is known that the vibration level such as resonance and the maximum load applied to the rolling element are reduced, and the strength of the gel structure formed varies depending on the composition of the thickener. And if such a gel structure is made stronger, the ability to form an oil film between the rolling surface and the raceway surface increases, and as a result, the oil film reduces the tangential force between the raceway surface and the rolling surface. Further, it becomes difficult to form a minute gap at the interface between the non-metallic inclusion and the metal substrate, and the rolling fatigue of the rolling bearing can be improved.

  And the thickener which consists of a mixture of an aromatic diurea compound or this aromatic diurea compound and a non-aromatic diurea compound makes a gel structure still stronger, and can improve a rolling fatigue life.

  That is, the diurea compound is obtained by reacting diisocyanates and monoamines under predetermined conditions. The aromatic diurea compound is represented by the general formula (12) or (13), and the non-aromatic diurea compound is It is shown by general formula (14).

Here, R ¹⁴ is an aromatic amine residue, which is composed of an aromatic ring-containing hydrocarbon group having a carbon number C _n of n = 7 to 12, and specifically includes a toluoyl group, a xylyl group, β- Examples include a fensyl group, a t-butylphenyl group, a dodecylphenyl group, a benzyl group, and a methylbenzyl group.

R ¹⁶ is a non-aromatic amine residue, which represents a cyclohexyl group, an alkylcyclohexyl group having a carbon number C _n of n = 7 to 12 or a linear alkyl group having a carbon number C _n of n = 8 to 20, Specifically, cyclohexyl group, methyl cyclohexyl group, dimethyl cyclohexyl group, ethyl cyclohexyl group, diethyl cyclohexyl group, propyl cyclohexyl group, isopropyl cyclohexyl group, 1-methyl-3-propyl cyclohexyl group, butyl cyclohexyl group, pentyl cyclohexyl group, There are a pentylmethylcyclohexyl group, a hexylcyclohexyl group, an ethyl group, a butyl group, an octyl group, and the like, and it is particularly preferable to use a methylcyclohexyl group or an ethylcyclohexyl group.

R ¹⁵ is a diisocyanate residue, and is composed of a divalent aromatic ring-containing hydrocarbon group having a carbon number C _n of n = 6 to 15, and specifically represented by general formulas (15) to (17) A group is used.

Further, regarding the relationship between the aromatic amine residue R ¹⁴ and the non-aromatic amine residue R ¹⁶ , in the embodiment of the present invention, the aromatic cyclic molar ratio Z is defined as the formula (I), and the aromatic The group ring molar ratio Z is set to 0.5 to 0.95.

Z = number of moles of R ¹⁴ / (number of moles of R ¹⁴ + number of moles of R ¹⁶ ) (I)
That is, when the aromatic ring molar ratio Z is less than 0.5, the lubricant easily leaks to the outside, and the leakage resistance of the lubricant cannot be ensured, and the aromatic ring molar ratio Z is 0.95. If it exceeds 1, the fluidity is lowered and seizure resistance is lowered. Therefore, in the present embodiment, the aromatic ring molar ratio Z is set in the range of 0.5 to 0.95, and for that purpose, the compounds represented by the general formulas (12) to (14) are appropriately mixed. Can be produced.

When the non-aromatic amine residue R ¹⁶ is the alkyl cyclohexyl group, the aromatic ring molar ratio Z is preferably 0.65 to 0.85, and the non-aromatic amine residue R ¹⁶ is the linear alkyl group. In this case, the aromatic ring molar ratio Z is preferably 0.70 to 0.95.

  Further, when the content of the thickener in the lubricant is less than 8 wt%, the gelling ability is insufficient and sufficient hardness cannot be obtained, and the leakage of the lubricant increases. On the other hand, when the said content rate exceeds 35 wt%, durability at high temperature and high speed will deteriorate remarkably. For this reason, in this Embodiment, the content rate in the lubricant of a thickener was limited to 8-35 wt%. In addition, a preferable range is 17 to 33 wt%.

  In the above general formulas (12) to (14), examples of the diurea compound represented by the general formula (12) include compounds represented by the structural formulas (18) and (19). Examples of the diurea compound represented by () include compounds represented by structural formulas (21) to (23). Examples of the diurea compound represented by the general formula (14) include structural formulas (24) to (27). ).

  Examples of the present invention will be specifically described below.

[First embodiment]
The applicant of the present application uses a high-carbon chromium bearing steel type 2 (SUJ2) as a bearing material, and performs a quenching / tempering treatment (immersion quenching) to produce a bearing member. Then, a deep groove ball bearing with a contact rubber seal is assembled using the bearing material, grease having a different hydrogen ion index pH is sealed in an annular space defined by the rolling elements and the bearing ring, and the pulley of the alternator of the automobile engine As a side bearing, it was installed in a testing machine and a durability life test was conducted. The cage used was a plastic molded product, the inner ring being a rotating ring and the outer ring being a fixed ring.

The bearing specifications are as follows.
[Bearing specifications]
Identification number: 6303 Reinforced outer ring outer diameter D: φ47mm
Inner ring inner diameter d: φ17 mm
Assembly width t: 14 mm
Basic dynamic load rating C: 13500N
Rockwell C hardness HRC
Orbital ring: 62
Rolling elements: 63
Residual austenite concentration γ _R
Raceway surface of raceway: 10 vol%
Rolling surface of rolling element: 9 vol%
Residual austenite deviation Δγ _R : +1 vol%
The residual austenite deviation Δγ _R is obtained by subtracting the residual austenite concentration on the rolling surface of the rolling element from the residual austenite concentration on the raceway surface of the raceway. When there is a difference in residual austenite concentration between the inner ring and the outer ring, the deviation Δγ _R is calculated using the higher value.

  Table 1 shows the specifications of the grease subjected to this endurance life test and the test results of the endurance life test.

In Examples 1, 2, 5 and Comparative Example 51 in Table 1, the diurea compound A used as a thickener is a 4,4′-diphenylmethane diisocyanate (MDI) in which the diisocyanate residue R ² is a diphenylmethyl group. ) And cyclohexylamine (CHA) in which the amine residues R ¹ and R ³ are cyclohexyl groups are blended so that the molar ratio is 1: 2.

In Examples 3, 4, 6-8, and Comparative Examples 52-54, diurea compound B used as a thickener is composed of MDI, cyclohexylamine (CHA), and stearylamine (StA) in moles. It was prepared by blending so that the ratio was 1: 1: 1. In the diurea compound B, the diisocyanate residue R ² is a diphenylmethyl group, the amine residue R ¹ is a cyclohexyl group, and the amine residue R ³ is an octadodecyl group (stearyl group).

Moreover, as base oil, Examples 1-3, 6-8, and Comparative Example 51 use poly alpha olefin (PAO) whose kinematic viscosity in 40 degreeC is 48 mm < ² > / sec, Example 4, 5 and comparison. Examples 52 to 54 used dialkyl diphenyl ether (DAPE) having a kinematic viscosity at 40 ° C. of 100 mm ² / sec.

  The method for producing the grease is not particularly limited. In this example, the grease was produced as follows.

  First, a predetermined amount of MDI is added to the base oil and maintained at a predetermined temperature (70 to 80 ° C.) required for the reaction, and a predetermined amount of stearylamine (StA) and / or cyclohexylamine (CHA) is added thereto. The reaction is further heated to a temperature of 160 ° C. with stirring, and 0.5 wt% of 2,6-di-t-butyl-p-cresol derivative as an antioxidant is added, Allow to cool to near room temperature (about 20 ° C.) with stirring. And in such a cooling process, 3 wt% dinolyl naphthalene sulfonate barium as a rust preventive dispersed or dissolved in advance was added, and a predetermined pH adjuster was added. Finally, the product cooled to near room temperature was pulverized with a roll mill to obtain a grease.

As a pH adjuster, Example 1 and Comparative Examples 53 and 54 used octylamine (OcA), and Example 2 used stearylamine (StA). Further, Example 3 used Na ₂ CO ₃ and Example 4 used potassium carbonate (K ₂ CO ₃ ). Furthermore, Examples 5 and 6 used lithium stearate (StLi), and Examples 7 and 8 used NaOH. In Comparative Examples 51 and 52, no pH adjuster was added.

  The hydrogen ion index pH was measured by the following method. That is, a solvent in which toluene, 2-propanol and water were adjusted to a volume ratio of toluene: 2-propanol: water = 500: 495: 5 was prepared, and then 0.1 g of the prepared grease was added to the solvent at 25 ° C. After dissolving in 50 ml, the hydrogen ion exponent pH of the solvent was measured with a pH meter, and the measured value was taken as the hydrogen ion exponent pH of the grease.

  The blending consistency in Table 1 is a value that indicates the softness of the grease. In this example, the blending consistency is No. in the NLGI grade so as to be suitable for a sealed bearing. 2 (265-295), no. The mixing ratio of the base oil and the thickener was adjusted to 3 (220 to 250).

  The test conditions of the durability life test are as follows.

[Durable life test]
Test load F: 1890N
Average rotation speed n of the rotating shaft: 8000 rpm (2000-14000 rpm)
Lubricant: Special grease Grease amount: 2.3g
Although not shown in the drawing, the test load is the tension of the drive belt suspended on the pulley, and the tension of the drive belt is loaded on the pulley. Further, the load is applied to the pulley side bearing and the non-pulley side bearing, and the tension of the drive belt is adjusted so that the load received by the pulley side bearing is 1890N which is a test load. ing.

  The rotation speed of the rotating shaft was set to 30 seconds for both the acceleration time for acceleration from 2000 rpm to 14000 rpm and the deceleration time for deceleration from 14000 rpm to 2000 rpm, and the operation was repeated between 2000 rpm and 14000 rpm.

  In this example, moisture was not added to the lubricant. However, since the lubricant absorbs moisture from the atmosphere, it contains a certain amount of moisture even if moisture does not enter the lubricant from the outside. For this reason, when the moisture content contained in the lubricant was measured by the Karl Fischer method before the durability test, it was 0.08 to 0.15 wt% as shown in Table 1.

The life test is performed by preparing each of the bearings of Examples 1 to 8 and Comparative Examples 51 to 54 for each of the five bearings. The operation time of the first peeled bearing is defined as the bearing life L and compared with the rated life L _{10 of the} bearing. Thus, the durability life of the bearing was evaluated.

The rated life L ₁₀ of the bearing means that when bearings of the same size and the same lot are rotated under the same conditions, 90% of the total number of bearings can be rotated without causing separation due to rolling fatigue. The calculation time corresponding to the total number of revolutions, and in the case of deep groove ball bearings, the basic dynamic load rating C (N), the test load F (N), and the number of revolutions n (rpm) of the rotating shaft are expressed by Equation (II). .

L ₁₀ = (C / F) ³ × 10 ⁶ / (60n) (II)
Bearings manufactured using modern steel and processing technology are peeled off with an operating time less than the rated life L ₁₀ when a sufficient oil film is formed between the rolling surface of the rolling element and the raceway surface of the race. It is thought that there is nothing to do.

Therefore, even when containing water in the lubricant, the durability evaluation of the rolling bearing need to satisfy at least the rated life L _10. That is, not only when moisture is mixed into the lubricant from the outside, but when it is used in a situation where it is greatly affected by the moisture in the lubricant due to the influence of vibration etc. Peeling often occurs in the operating time of the rated life L ₁₀ or less. Therefore, for durability evaluation, it is necessary that the time at which peeling occurs is at least the rated life L ₁₀ or more. In the case of this example, the basic dynamic load rating C = 135000 N, the test load F = 1890 N, and the average rotational speed n of the rotating shaft n = 8000 rpm. Therefore, the rated life L _{10 of the} bearing is 759 hours from Equation (II). whether the life time until delamination exceeds the rated life L ₁₀ is the reference.

Table 1 As is apparent from Comparative Examples 51 to 54, the peeling in the bearing member to the case of an acidic reducing the hydrogen ion exponent pH of grease reaches the rated life L ₁₀ both occur. As the hydrogen ion exponent pH increases, the peeling characteristics are improved. However, in Comparative Examples 51 to 54, the hydrogen ion exponent pH of the grease is 6.9 or less. L ₁₀ can not be obtained more bearing life L, it can not be satisfied to ensure durability.

On the other hand, in Examples 1 to 8, the hydrogen ion exponent pH is in the range of 7 to 13, and the bearing life L of the rated life L ₁₀ or more can be obtained for all the test pieces. It turns out that it can satisfy sex.

In addition, the applicant of the present application, with respect to Example 7 and Comparative Examples 53 and 54, replaced with rolling elements having a residual austenite concentration of 11 vol% so that the residual austenite deviation Δγ _R was Δγ _R <0. The same endurance life test as described above was conducted, and all five test bearings of Example 7 ′ and Comparative Example 54 ′ corresponding to Example 7 and Comparative Example 54 passed the rated life L ₁₀ . However, no peeling occurred.

In contrast, in Comparative Example 53 ′ corresponding to Comparative Example 53, no peeling occurred even after the rated life L ₁₀ had elapsed for three of the test bearings, but one of the remaining two was 688 hours. And the other one was peeled off in 640 hours.

In this way, when the retained austenite deviation Δγ _R is set to Δγ _R <0, a bearing life L exceeding the rated life L ₁₀ can be obtained even if the hydrogen ion exponent pH is slightly smaller than when Δγ _R ≧ 0. I understand that I can do it.

[Second Embodiment]
As a second example, the applicant of the present application prepared a plurality of types of greases in which an organic metal salt or ADTC was added and a hydrogen ion index pH was adjusted with a pH adjuster, and was prepared in the same manner as in the first example. The finished grease was sealed in a deep groove ball bearing and tested for durability.

  In the second example, grease was produced as follows.

First, poly α-olefin (PAO) having a kinematic viscosity of 48 mm ² / sec at 40 ° C. was used as the base oil, and the addition amount of the diurea compound as a thickener was adjusted to 15 wt%. That is, a solution in which MDI is added to PAO as a base oil is maintained at a predetermined temperature (70 to 80 ° C.) required for the reaction, and then 1 mol of cyclohexylamine (CHA) and 1 mol of octadecylamine with respect to 11 mol of MD. Thus, cyclohexylamine (CHA) and octadecylamine were added to the solution and reacted.

  Then, the reaction product is heated to 160 ° C. with stirring, and 0.5 wt% of 2,6-di-t-butyl-p-cresol derivative is added as an antioxidant, and then around room temperature. Allow to cool to (about 20 ° C.) with stirring. Then, in such a cooling process, 3 wt% of barium dinolylnaphthalene sulfonate as a rust preventive dispersed or dissolved in advance was added, and a predetermined pH adjusting agent and a predetermined organometallic salt or ADTC were added. Finally, the product cooled to near room temperature was pulverized with a roll mill to obtain a grease.

  The grease has a blending consistency of NLGI grade No. 1 so as to be suitable for sealed bearings. 2 (265-295).

  The bearing specifications and the test conditions for the endurance life test are the same as those in the first embodiment, and the method for measuring the hydrogen ion exponent pH is the same as that in the first embodiment, so that the description thereof is omitted.

  Table 2 shows the specifications of the grease subjected to this endurance life test and the test results of the endurance life test.

The pH adjusting agent, Example 11 octylamine (Oca), Examples 12 to 14 are stearylamine (StA), Examples 15 and 16 are sodium octanoate (Ocna), Example 17 Potassium carbonate (K ₂ CO ₃ ) was used, and Comparative Examples 61 and 62 did not add a pH adjuster.

  As a reaction film forming agent, Examples 11 to 16 and Comparative Example 62 used organometallic salts. That is, Example 11 used molybdenum dialkyldithiocarbamate (MoDTC), and Example 12 used nickel dialkyldithiocarbamate (NiDTC). In addition, Example 13 used MoDTC and molybdenum dialkyldithiophosphate (MoDTP), and Example 14 used MoDTC and zinc dialkyldithiophosphate (ZnDTP). Further, Example 15 used antimony dialkyldithiocarbamate (SbDTC), Example 16 used bismuth dialkyldithiocarbamate (BiDTC), and Comparative Example 62 used tellurium dialkyldithiocarbamate (TeDTC). In Example 17, ADTC was used.

As is clear from Table 2, in Comparative Example 61, no reaction film forming agent was added, and since the hydrogen ion exponent pH was as low as 3.2, the progress of the cathode reaction in the hydrogen generation type corrosion reaction was suppressed. No test piece satisfying the rated life L ₁₀ (= 759 hours). In addition, there is a test piece that peels off in an extremely short time. In Comparative Example 62, an organic metal salt is added, so that a certain degree of durability improvement is observed. However, some test pieces have peeling at the rated life L ₁₀ or less. In Comparative Example 62, the Δ test piece was not significantly damaged in the life test, but slight peeling was observed when investigated after the test.

On the other hand, in Examples 11 to 17, the hydrogen ion exponent pH is 5.2 to 5.7, both of which are adjusted to 5 or more, and the reaction film forming agent (organic) of 1.0 to 3.0 wt%. This is a case where a metal salt or ADTC) is added, and it can be seen that the bearing life L of the rated life L ₁₀ or more can be obtained for all the test pieces, and the desired durability can be satisfied.

  Next, the applicant of the present application adds 0.01 wt% StA as a pH adjusting agent to the grease to adjust the hydrogen ion index pH to 5.1 to 5.3, while adding TeDTC as a reaction film forming agent. Greases with different amounts were prepared, and the relationship between the added amount of the reaction film forming agent and the bearing peeling (bearing life L) was examined.

  That is, the hydrogen ion index pH was adjusted to 5.1 to 5.3, and greases with different amounts of TeDTC were prepared. The grease was sealed in the deep groove ball bearing described above, and a durability life test was performed. The relationship between the addition amount of the forming agent and the bearing peeling (bearing life L) was examined.

  FIG. 1 is a characteristic diagram showing the relationship between TeDTC as a reaction film forming agent and bearing peeling, and four test pieces each subjected to an endurance test are addressed.

As is apparent from FIG. 1, the rated life L _{10 of the} test piece starts to improve from the point when the addition amount exceeds 0.07 wt%, and the effect on the bearing life L is sufficient when the addition amount is 0.1 wt% or more. It turns out to be a thing.

  In addition, while adding 1 wt% ZnDTC as an organic metal salt to the grease and changing the addition amount of OcA as a pH adjuster, a grease having a different hydrogen ion index pH was prepared, and the hydrogen ion index pH and bearing peeling (bearing) The relationship with the life L) was investigated.

  That is, greases containing the same type and the same added amount of reaction film forming agent and having different hydrogen ion index pH were prepared, and the endurance life test was conducted by enclosing the grease in the deep groove ball bearing described above. The relationship between pH and bearing peeling (bearing life L) was examined.

  FIG. 2 is a characteristic diagram showing the relationship between the hydrogen ion exponent pH of the grease and the peeling of the bearing, and four test pieces each subjected to an endurance test are addressed.

As is apparent from FIG. 2, when the hydrogen ion index pH is 4 or less, half of the test pieces peel off at the rated life L ₁₀ or less, and when the hydrogen ion index pH is about 4.4, the bearing life L shows a sign of improvement. can hydrogen ion exponent pH to obtain a rolling bearing having a bearing life L exceeding the rated life L ₁₀ at 5.1 or higher.

[Third embodiment]
As a third example, the applicant of the present application prepared a plurality of types of greases in which fine particles made of an inorganic compound having an average particle diameter of 2 μm or less were added and the hydrogen ion index pH was adjusted with a pH adjuster. As in the second embodiment, the grease thus produced was sealed in a deep groove ball bearing, and a durability life test was conducted.

  Table 3 shows the specifications of the grease subjected to this endurance life test and the test results of the endurance life test.

  In the third example, diurea compound A or diurea compound B was used as the thickener as in the first example, and PAO or DAPE was used as the base oil as in the first example.

  Then, the base oil and the thickener are added and reacted, and the reaction product is heated to 160 ° C. while stirring. Further, the antioxidant is added and sufficiently stirred. A predetermined amount of a pH adjuster and a metal oxide as an inorganic compound having an average particle diameter of 2 μm or less were added and cooled to near room temperature, and then the product was pulverized with a roll mill to obtain a grease.

As a pH adjuster, K ₂ CO ₃ was used in Example 21 and Comparative Example 72, OcA was used in Examples 22 and 26, and StA was used in Example 25. In Example 23 and Comparative Example 73, sodium stearate (StNa) was used, and in Example 24, sodium octoate (OcNa) was used.

In Example 26, Al ₂ O ₃ was used as the metal oxide as the inorganic compound, and MgO was used in the other cases.

  The grease is suitable for sealed bearings, and has a blending consistency of NLGI grade No. 2 (265-295) or No. 2 3 (220 to 250).

  The bearing specifications and the test conditions for the endurance life test are the same as those in the first embodiment, and the method for measuring the hydrogen ion exponent pH is the same as that in the first embodiment, so that the description thereof is omitted. Moreover, the test piece of each Example and a comparative example is four pieces.

As is apparent from Table 3, in Comparative Example 71, no inorganic compound was added and the hydrogen ion exponent pH was as low as 3.9, so that the cathode reaction in the hydrogen generation type corrosion reaction (chemical reaction formula 2) There is no specimen that satisfies the rated life L ₁₀ (= 759 hours), and there is also a specimen that exfoliates in an extremely short time. In Comparative Examples 72 and 73, since some improvement in durability is recognized because MgO fine particles are added, bearing life L exceeding the rated life L ₁₀ cannot be obtained with all the test pieces. .

On the other hand, in Examples 21 to 26, the hydrogen ion exponent pH was adjusted to 5.2 or more and 5 or more, and 0.001 to 1.0 wt% of metal oxide was added. It can be seen that the bearing life L of the rated life L ₁₀ or more can be obtained for all the test pieces, and the desired durability can be satisfied.

[Fourth embodiment]
As a fourth example, the applicant of the present application has prepared a plurality of types of greases in which a diurea compound containing an aromatic amine is added as a thickener and a hydrogen ion index pH is adjusted with a pH adjuster. The grease was sealed in a deep groove ball bearing and subjected to a durability life test and a grease leakage test.

  Table 4 shows the specifications of the grease produced in the fourth embodiment.

In the fourth example, tolylene diisocyanate (TDI) in which the diisocyanate residue R ¹⁵ is composed of a tolyl group or MDI composed of a diphenylmethyl group was used as a thickener. The aromatic amine residue R ¹⁴ uses p-toluidine consisting of a tolyl group or aniline consisting of a phenyl group (R ¹⁴ component), and the non-aromatic residue R ¹⁶ is cyclohexylamine (CHA) consisting of a cyclohexyl group or using stearylamine consisting of linear alkyl groups (StA) or octylamine (Oca) (R ¹⁶ component).

  As the base oil, DAPE, PAO, diester, polyol ester, and mineral oil were used.

Then, after adding TDI or MDI to the base oil and maintaining it at a predetermined temperature (70 to 80 ° C.), the aromatic amine residue R ¹⁴ and the non-aromatic amine so that the aromatic ring molar ratio Z becomes a predetermined ratio. A predetermined amount of a compound containing the residue R ¹⁶ is added and reacted, and the reaction product is heated to 160 ° C. while stirring and an antioxidant is added thereto, and then to around room temperature (about 20 ° C.). Allow to cool with stirring. Then, in such a cooling process, a rust inhibitor and a predetermined pH adjuster were added. Finally, the product cooled to near room temperature was pulverized with a roll mill to obtain a grease.

As the pH adjuster, K ₂ CO ₃ , OcNa, OcA, StNa, NaOH, StA were used.

  The grease was prepared by blending the ratio of base oil and thickener so that the blending consistency was about 200-300.

  Next, the hydrogen ion exponent pH of the grease was measured, and thereafter, the grease was enclosed in a deep groove ball bearing and subjected to a durability life test and a grease leakage test.

  Table 5 shows the hydrogen ion exponent pH of the grease and the test results of the endurance life test and the grease leakage test.

  The measurement method of the hydrogen ion index pH, the bearing specifications, and the test conditions of the endurance life test are the same as those in the first to third examples, and there are four test pieces in each example and comparative example.

As is clear from Table 5, since the diurea compound containing an aromatic amine in Comparative Example 81 and Comparative Example 82 are added to the lubricant as thickener, the rated life L ₁₀ in some specimens Some may be satisfied. However, the hydrogen ion exponent pH as low as 4.2 or 4.8, it is impossible to obtain a bearing life L exceeding the rated life L ₁₀ in all specimens.

In contrast, in Examples 31 to 41, a diurea compound containing an aromatic amine was added to the lubricant as a thickener, and the hydrogen ion exponent pH was adjusted to 5.1 to 8.0, both of which were adjusted to 5 or more. Therefore, it can be seen that the bearing life L of the rated life L ₁₀ or more can be obtained for all the test pieces, and the desired durability can be satisfied.

  Next, a grease leakage test will be described.

  The grease leakage test is performed under the following conditions by enclosing grease in a deep groove ball bearing with a contact rubber seal, and the amount of grease leaked by the end of the test is measured. It was determined to be an acceptable product. Each test piece is addressed to four pieces.

[Grease leakage test]
Bearing specifications: Identification number 6301 (Deep groove ball bearing)
Outer ring outer diameter D: φ37mm
Inner ring inner diameter d: φ12 mm
Assembly width t: 12 mm
Initial amount of grease: 1.6 g
Outer ring rotation speed: 14000 rpm
Inner ring temperature: 160 ° C
Radial load: 141kgf
Operating time: 20 hr
As is apparent from Table 5, Examples 40 and 41 obtained satisfactory results for the bearing life L because the hydrogen ion exponent pH of the grease was 5 or more, but the aromatic ring molar ratio Z was 0.00. Since it is as low as 30 or 0.40, the grease is softened at a high temperature and the amount of leakage exceeds 10 wt%.

  On the other hand, in Examples 31 to 39 and Comparative Examples 81 and 82, since the aromatic ring molar ratio Z was 0.5 or more, no leakage of grease was observed. Thereby, it turns out that Examples 31-39 can obtain the outstanding rolling bearing which satisfy | fills both the bearing life L and the leakage resistance of grease.

  FIG. 3 is a characteristic diagram showing the relationship between the addition amount (wt%) of the diurea compound and the aromatic ring molar ratio Z.

  If the addition amount is less than 8 wt%, the gelling ability is insufficient, so that sufficient hardness cannot be obtained and grease leakage may occur at a high temperature. Durability may be deteriorated. In addition, as described above, when the aromatic ring molar ratio Z is less than 0.5, grease may easily leak to the outside of the bearing, and sufficient leakage resistance may not be obtained. When Z exceeds 0.95, the fluidity of the grease decreases, and there is a risk that seizure damage will occur early.

Therefore, for the diurea compound, it is preferable that the addition amount shown in the region A is 8 to 35 wt% and the aromatic ring molar ratio Z is 0.5 to 0.95. Also, if from the measurement results in Table 4 were used cyclohexylamine (CHA) as R ¹⁶ component 0.65 to 0.85 indicating an aromatic ring molar ratio Z is the region B is preferred, stearylamine as R ¹⁶ component ( When a linear alkyl group such as StA) or octylamine (OcA) is used, the aromatic ring molar ratio Z is preferably 0.70 to 0.95 shown in the region B, and the addition amount of the diurea compound is more preferable. The range is 17 to 33 wt%.

It is a characteristic view which shows the relationship between the addition amount of TeDTC in a 2nd Example, and peeling lifetime. It is a characteristic view which shows the relationship between the hydrogen ion index | exponent pH and peeling lifetime in a 2nd Example. It is a characteristic view which shows the relationship between the addition amount of the diurea compound in 4th Example, and the aromatic ring molar ratio Z.

Claims (1)

A raceway ring composed of an outer ring and an inner ring, and a rolling element that is rotatably disposed between the outer ring and the inner ring, and lubricates an annular space defined by the rolling element and the raceway. In rolling bearings filled with agent,
A rolling bearing, wherein the lubricant has a hydrogen ion index pH of 7 to 13.