JP2008056839A - Grease composition and roller bearing for water pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition that suppresses occurrence of white texture flaking and corrosion thereby permitting the retention of good lubrication for long hours even when contaminated with moisture, and a roller bearing for a water pump that has the grease composition sealed therein and exhibits excellent water resistance. <P>SOLUTION: The grease composition comprises a base oil comprising at least one selected from among mineral oils and synthetic oils and a thickening agent, and further contains oleoyl sarcosine in a ratio of 0.1-5 mass% based on the total amount of the grease. The roller bearing for a water pump has encapsulated the grease composition therein. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a water-resistant grease composition that exhibits excellent lubricating performance even when water is mixed therein. The present invention also relates to a water pump rolling bearing rolling bearing incorporated in order to support the rotating shaft of an impeller in a water pump and exhibiting an excellent lubrication life.

  As shown in FIG. 1, a water pump 50 that pumps and circulates cooling water of an engine includes a plurality of water pump rolling elements that are arranged at intervals in an axial direction on a rotating shaft 52 to which an impeller 51 is fixed. It is configured to be supported on a casing 56 by a bearing 55. The cooling water is sealed by a mechanical seal 57 disposed between the impeller 51 and the rolling bearing 55. However, in the water pump rolling bearing 55, the sliding surface of the mechanical seal 57 with respect to the rotating shaft 52 is in a water-lubricated state, so that water vapor etc. leaks and enters the water pump rolling bearing 10 side. The water pump rolling bearing 55 is deteriorated. Therefore, in order to prevent water vapor or the like from entering the water pump rolling bearing 55 from the impeller 51 side, and to prevent leakage of lubricating grease enclosed in the bearing, a seal is provided on the impeller 51 side of the water pump rolling bearing 55. A device (not shown) is provided. The drive side 58 of the water pump rolling bearing 55 is also provided with a seal device (not shown) for preventing intrusion of dust from the outside and preventing leakage of lubricating grease sealed in the bearing. Yes.

  However, even if such sealing measures are taken, water may enter the bearing due to deterioration of the mechanical seal 57 or the sealing device over time, and the grease sealed in the water pump rolling bearing requires water resistance. Has been. It is known that when water is mixed in the encapsulated grease, the bearing life is greatly reduced. For example, Furumura et al., When 6% water is mixed in the lubricating oil (# 180 turbine oil), it rolls compared to the case where it does not mix. It has been reported that the fatigue life is reduced from a fraction to a twentieth (June Saburo Furumura, Shinichi Shirota, Kiyoshi Hirakawa: NSK Bearing Journal, No.636 , Pp.1-10, 1977). Schatzberg et al. Also reported that the rolling strength of steel decreased by 32 to 48% with only 100 ppm of water in the lubricating oil (P. Schtzberg, IMFelsen: Effects of water and oxygen during rolling contact lubrication, Wear 12, pp.331-342, 1968).

  Such a decrease in life is considered that hydrogen generated from mixed water acts on the bearing material and causes metal peeling called white tissue peeling. In order to prevent such peeling, grease added with a passive oxidizing agent such as sodium nitrite (for example, see Patent Document 1), grease added with an organic antimony compound or an organic molybdenum compound (for example, see Patent Document 2), Improvement of grease has been performed, such as grease added with an inorganic compound having a particle size of 2 μm or less (see, for example, Patent Document 3). These prevent the hydrogen from entering the bearing material by forming a film derived from the additive at the rolling contact portion, but rolling of the rolling element occurs due to vibration or speed change until the film is formed. Then, metal peeling may occur at the rolling contact portion.

  As measures other than the improvement of grease, use of stainless steel as a bearing material (for example, refer to Patent Document 4), making a rolling element made of ceramics (for example, refer to Patent Document 5), etc. have been proposed. Bearings made of these materials are generally expensive.

  In addition, iron such as bearing steel has a problem that corrosion (rust) is easily caused by water and abnormal noise is generated from the bearing. In bearings where water can be mixed, it is very important to have corrosion resistance, and corrosion resistance is simultaneously imparted by the same method as described above, but it has the effect of suppressing the occurrence of rust. Not enough.

Japanese Patent No. 2878749 Japanese Patent No. 3512183 Japanese Patent Laid-Open No. 9-169989 JP-A-3-173747 JP-A-4-244624

  The present invention has been made in view of such a situation, and even when moisture is mixed, a grease composition capable of suppressing the occurrence of white structure peeling and corrosion and maintaining good lubrication for a long time. The purpose is to provide. Another object of the present invention is to provide a rolling bearing for a water pump that is filled with such a grease composition and has excellent water resistance.

To achieve the above object, the present invention provides the following grease composition and water pump rolling bearing.
(1) containing at least one base oil selected from mineral oil and synthetic oil and a thickener, and containing oleoylsarcosine in a proportion of 0.1 to 5% by mass of the total amount of grease. A grease composition characterized.
(2) A rolling bearing for supporting the rotating shaft of the impeller in the water pump, wherein a plurality of rolling elements are rotatably arranged between the inner ring and the outer ring, and between the inner ring and the outer ring. A rolling bearing for a water pump, wherein the grease composition described in the above (1) is enclosed in a space formed with the rolling elements.

  The grease composition of the present invention exhibits excellent resistance to corrosion resistance and white tissue peeling by containing oleoylsarcosine having excellent rust prevention performance.

  In addition, the water pump rolling bearing of the present invention has an excellent lubrication life even when moisture is mixed in by enclosing such a grease composition.

  Hereinafter, the present invention will be described in detail.

  In the grease composition of the present invention, the base oil is selected from mineral oil and synthetic oil.

  Mineral oil can be used that is purified by appropriately combining vacuum distillation, oil removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, white clay purification, hydrorefining, and the like.

  Synthetic oils include hydrocarbon oils, aromatic base oils, ester oils, ether oils, and the like. Examples of the hydrocarbon oil include normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, poly-α-olefin such as 1-decene and ethylene co-oligomer, and hydrides thereof. Examples of the aromatic oil include alkylbenzenes such as monoalkylbenzene and dialkylbenzene, and alkylnaphthalenes such as monoalkylnaphthalene, dialkylnaphthalene and polyalkylnaphthalene. Examples of ester oils include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, and methyl acetyl cinolate, or trioctyl trimellitate. Aromatic ester oils such as tridecyl trimellitate and tetraoctyl pyromellitate, and further trimethylolpropane caprylate, trimethylolpropane verargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol verargonate, etc. Polyol ester oils, and complex ester oils that are oligoesters of polyhydric alcohols and mixed fatty acids of dibasic acids and monobasic acids are also exemplified. Examples of ether oils include polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, and polypropylene glycol monoether, or monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether, tetraphenyl ether, and monoalkyl tetra And phenyl ether oils such as phenyl ether and dialkyl tetraphenyl ether.

Said mineral oil and synthetic oil may each be used independently, and may be used as a mixture. Further, the base oil preferably has a kinematic viscosity at 40 ° C. is 10~400mm ² / s, more preferably 20~250mm ² / s, more preferably from 40~150mm ² / s. By setting the kinematic viscosity within the above range, it is possible to eliminate problems such as the generation of abnormal noise at low temperature startup and the loss of oil film at high temperatures.

  The thickener is not limited as long as it has the ability to form a gel structure and retain the base oil in the gel structure. For example, metal soap composed of Li, Na, etc., composite metal soap selected from Li, Na, Ba, Ca, etc., benton, silica gel, urea compound, urea / urethane compound, urethane compound, etc. However, since the rolling bearing for water pump tends to rotate at high speed and become high temperature, a urea compound, a urea-urethane compound, a urethane compound, or a mixture thereof is preferable in consideration of heat resistance of grease. Examples of urea compounds include diurea compounds, triurea compounds, tetraurea compounds, polyurea compounds, and mixtures thereof. Among these, a diurea compound, a urea / urethane compound, a diurethane compound or a mixture thereof is preferable, and a diurea compound is particularly preferable.

  The blending amount of the thickener is preferably 5 to 40% by mass of the total amount of the grease, and if it is less than 5% by mass, it becomes difficult to maintain the grease state, and if it exceeds 40% by mass, the grease becomes too hard and lubricated. This is not preferable because the state cannot be expressed sufficiently.

  In the present invention, oleoyl sarcosine is an essential additive. This oleoylzacolicin has excellent performance as a rust inhibitor. The content of oleoylsarcosine is 0.1 to 5% by mass of the total amount of grease, and if it is less than 0.1% by mass, sufficient rust prevention performance cannot be obtained, and even if it exceeds 5% by mass, it will be increased There is no improvement in commensurate effect. Considering these, the amount of oleoylsarcosine added is more preferably 0.5 to 3% by mass of the total amount of grease.

  In order to suppress the occurrence of white tissue peeling, it becomes more effective if it becomes easier to form an oxide film at the rolling contact portion in addition to the rust preventive action by oleoylsarcosine. Therefore, the grease composition includes dialkyldithiocarbamic acid compounds represented by the following general formula (1), dialkyldithiophosphate compounds represented by the general formula (2), and general formulas (3) to (5). It is preferable to add at least one organic metal salt selected from an organic zinc compound represented by the formula and a zinc alkylxanthate represented by the general formula (6).

In the general formulas (1) and (2), M represents a metal species, and specifically can be selected from Sb, Bi, Sn, Ni, Te, Se, Fe, Cu, Mo, and Zn. R ₁ and R ₂ may be the same group or different groups, and are selected from an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an alkylaryl group, and an arylalkyl group. Particularly preferred groups as R ₁ and R ₂ include 1,1,3,3-tetramethylbutyl group, 1,1,3,3-tetramethylhexyl group, 1,1,3-trimethylhexyl group, 1, 3-dimethylbutyl 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, trimethylcyclohexane Sil group, nonyl 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, tert-butylphenyl group, second pentylphenyl group N-hexylphenyl group, tertiary octylphenyl group, isononylphenyl group, n-dodecylphenyl group, phenyl group, benzyl group, 1-phenylmethyl group, 2-phenylethyl group, 3-phenylpropyl group, 1, 1-dimethylbenzyl group, 2-phenylisopropyl group, 3-phenyl Niruhekishiru group, benzhydryl group, there is a biphenyl group and the like, and these groups may have an ether group.

In the general formulas (3) to (5), R ₃ and R ₄ may be the same group or different groups, and are selected from a hydrocarbon group having 1 to 18 carbon atoms and a hydrogen atom. In particular, R ₃ and R ₄ are both hydrogen atoms, mercaptobenzothiazole zinc (general formula (3)), benzamidothiophenol zinc (general formula (4)), mercaptobenzimidazole zinc (general formula (5)). Can be preferably used.

In the general formula (6), _{R 5} is a hydrocarbon group having 1 to 18 carbon atoms.

  The amount of the above-mentioned organometallic salt added is 0.1 to 20% by mass based on the total amount of grease for both single use and mixed use. When the addition amount of the organic metal salt is less than 0.1% by mass, there is no effect in promoting the formation of an oxide film, and when it exceeds 20% by mass, an improvement in the effect corresponding to the increment cannot be obtained, and oxidation with the bearing material The reaction may be accelerated abnormally to cause corrosion and abnormal wear. The amount of the organic metal salt added is particularly preferably in the range of 0.5 to 10% by mass.

  In order to further improve various performances, other additives may be added to the grease composition as desired. For example, antioxidants, other rust inhibitors, extreme pressure agents, oiliness improvers, metal deactivators and the like can be added alone or in admixture of two or more.

  Examples of the antioxidant include amine-based antioxidants, phenol-based antioxidants, sulfur-based antioxidants, zinc dithiophosphate, and the like, but amine-based antioxidants and phenol-based antioxidants are preferable. Examples of amine-based antioxidants include phenyl-1-naphthylamine, phenyl-2-naphthylamine, diphenylamine, phenylenediamine, oleylamidoamine, and phenothiazine. Examples of phenolic antioxidants include pt-butyl-phenyl salicylate, 2,6-di-t-butyl-p-phenylphenol, and 2,2'-methylenebis (4-methyl-6-t-octylphenol). ), 4,4'-butylidenebis-6-t-butyl-m-cresol, tetrakis [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, , 3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, n-octadecyl-β- (4'-hydroxy-3 ', 5'- Di-t-butylphenyl) propionate, 2-n-octyl-thio-4,6-di (4′-hydroxy-3 ′, 5′-di-t-butyl) phenoxy-1,3,5-triazine, 4, 4 ' Thiobis (6-t-butyl -m- cresol), 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chloro-benzotriazole, and the like.

  Examples of other rust preventives include esters. Specifically, sorbitan monolaurate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate and other sorbitan esters, which are partial esters of polybasic carboxylic acid and polyhydric alcohol, polyoxyethylene laurate, polyoxy Examples thereof include alkyl esters such as ethylene oleate and polyoxyethylene stearate.

  Examples of the oil improver include fatty acids such as oleic acid and stearic acid, alcohols such as lauryl alcohol and oleyl alcohol, amines such as stearylamine and cetylamine, phosphate esters such as tricresyl phosphate, and animal and vegetable oils.

  Examples of extreme pressure agents include phosphorus-based, zinc dithiophosphate, and organic molybdenum.

  Examples of the metal deactivator include benzotriazole.

  The addition amount of these other additives is not limited as long as the effect of the present invention is not impaired, but is usually 0.1 to 20% by mass of the total amount of grease. If the addition amount is less than 0.1% by mass, the effect of addition is not sufficient, and even if added in excess of 20% by mass, the effect is saturated, and the amount of base oil is relatively small, so that the lubricity may be lowered. There is.

  Although there is no restriction | limiting in the manufacturing method of a grease composition, Generally, it is obtained by making a thickener react in base oil. At that time, a predetermined amount of oleoyl sarcosine is added to the obtained grease composition and sufficiently stirred with a kneader or a roll mill to be uniformly dispersed. Heating is also effective when performing this distance. Moreover, it is preferable on a process that another additive is added simultaneously with oleoyl sarcosine.

  The present invention also relates to a water pump rolling bearing (for example, the water pump rolling bearing 55 of FIG. 1) in which the above grease composition is enclosed. As mentioned above, water easily enters water bearings for water pumps. However, since the above grease composition contains oleoyl sylcosin, the water pump rolling bearings of the present invention are corroded even if moisture is mixed. Can be effectively suppressed, and white tissue peeling can also be effectively suppressed, resulting in a long life.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is further demonstrated, this invention is not restrict | limited at all by this.

(Examples 1-2, Comparative Examples 1-3)
Test greases were prepared with the formulations shown in Table 1. That is, a mineral oil in which 4,4-diphenylmethane diisocyanate is dissolved and a mineral oil in which octadecylamine is dissolved are mixed with stirring to form a urea base grease. After cooling, oleyl sarcosine (manufactured by Nippon Oil & Fats Co., Ltd.) and an antioxidant A predetermined amount of (p.p′-dioctyldiphenylamine; manufactured by Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was further stirred and defoamed to obtain the test grease of Example 1. Moreover, it replaced with mineral oil and obtained the test grease of Example 2 with the same process using the mixed oil of mineral oil and poly alpha olefin oil.

  For comparison, the urea base grease of Example 1 was used, only the antioxidant was added, and the test grease of Comparative Example 1, the antioxidant, and barium sulfonate were added to obtain the test grease of Comparative Example 2. . Further, the urea base grease of Example 2 was used, and an antioxidant and barium sulfonate were added to obtain a test grease of Comparative Example 3.

  The blending consistency of each test grease is LNGI No. Adjusted to 2. Each test grease was subjected to the following (1) rust prevention test and (2) bearing water resistance test. The results are also shown in Table 1.

(1) Rust prevention test A ball bearing “608” manufactured by NSK Ltd. is filled with test grease so as to occupy 20% by volume of the bearing space (space formed by the inner ring, outer ring and ball), and is kept at high humidity and temperature. After putting it in a tank (temperature of 80 ° C., humidity of 90%) for one week, the shaft was disassembled and the state of rust formation on the inner ring was visually observed. The case where rust was not observed was indicated as “A”, the case where rust was generated at 1 to 5 places was designated as “B”, and the case where rust was produced at 6 places or more was designated as “C”.
(2) Bearing water resistance test Test grease is sealed in a tapered roller bearing “HR32017 (inner diameter: 85 mm, outer diameter: 130 mm)” manufactured by NSK Ltd. to achieve a radial load of 35.8 N, an axial load of 15.7 N, and a rotational speed of 1500 rpm. The water was continuously rotated while water was injected from the outside into the bearing at a rate of 20 ml / h. Then, it was determined that peeling occurred when vibration occurred during rotation, and the number of occurrences of vibration within 100 hours (number of peeling occurrences) was counted. The test was performed 10 times for each test grease, and the occurrence probability of peeling was calculated from the following formula.
Peeling occurrence probability (%) = (number of peeling occurrence / number of tests) × 100

  As shown in Table 1, by encapsulating the grease composition of each example containing oleoyl sarcosine according to the present invention, the anti-rust performance and anti-peeling effect are extremely good and a long-life rolling bearing can be obtained. I understand.

It is a partial sectional view showing an example of a water pump.

Explanation of symbols

50 Water Pump 51 Impeller 52 Rotating Shaft 55 Roller Bearing for Water Pump 56 Casing 57 Mechanical Seal

Claims (2)

  It contains a base oil consisting of at least one selected from mineral oil and synthetic oil and a thickener, and contains oleoylsarcosine in a proportion of 0.1 to 5% by mass of the total amount of grease. Grease composition.   A rolling bearing for supporting a rotating shaft of an impeller in a water pump, wherein a plurality of rolling elements are rotatably disposed between an inner ring and an outer ring, and are formed between the inner ring and the outer ring. A rolling bearing for a water pump, wherein the grease composition according to claim 1 is enclosed in a space in which the rolling elements are disposed.

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