JP2010222560A - Grease composition, grease-packed bearing and universal joint for propeller shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition able to effectively prevent flaking of the rolling surfaces of a rolling bearing or the like caused by hydrogen embrittlement, excellent in high-temperature high-speed durability and able to be used for a long term, a grease-packed bearing in which the grease composition is packed, and a universal joint for propeller shafts in which the grease composition is packed. <P>SOLUTION: The grease-packed bearing 1 is equipped with an inner ring 2, an outer ring 3, and a plurality of rolling elements 4 and in which sealing members 6 for enclosing the grease composition 7 around the rolling elements have been disposed in both shaft-direction edge openings 8a, 8b of the inner ring 2 and the outer ring 3. The grease composition 7 comprises a base grease comprising a base oil and a thixotropic agent and an additive incorporated in the base grease. The aforesaid additive comprises at least one compound selected from plant-derived polyphenol compounds and decomposed compounds thereof and the blending ratio of the compound is 0.05-10 pts.wt. based on 100 pts.wt. of the base grease. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a grease composition, a grease-filled bearing, and a universal joint for a propeller shaft. Grease-enclosed bearings are related to automotive electrical components such as alternators, electromagnetic clutches for car air conditioners, intermediate pulleys, electric fan motors, rolling bearings for auxiliary machines, and rolling bearings for motors. The present invention relates to a constant velocity joint for a propeller shaft and a cardan joint for a propeller shaft.

  Electrical components and accessories in automobiles, motors in industrial machines, etc. are required to be downsized, high performance, and high output year by year, and usage conditions are becoming stricter. For these, rolling bearings are used, and grease is mainly used for lubrication. However, severe use conditions such as high-speed rotation at high temperatures cause a problem in that specific peeling accompanied by a change in white structure occurs at an early stage on the rolling surface of the rolling bearing.

  This specific exfoliation is a destructive phenomenon that occurs from a relatively shallow part of the surface of the rolling surface, unlike the internal peeling that occurs due to normal metal fatigue, and is caused by hydrogen generated by decomposition of the grease composition, etc. It is thought that the peeling due to hydrogen embrittlement. As a method for preventing such a specific peeling phenomenon accompanied by a white tissue change that occurs at an early stage, for example, a method of adding a passivating agent to a grease composition is known (see Patent Document 1). A method of adding bismuth dithiocarbamate to a grease composition is known (see Patent Document 2).

  In recent years, in general-purpose motors such as AC motors and DC motors, miniaturization of motors has progressed, and bearings that support rotors of the motors tend to be operated at higher speeds and higher surface pressures. Therefore, the lubricating composition is encapsulated to impart lubricity. This lubricating composition is obtained by kneading a base oil and a thickener and, if necessary, an additive. As the base oil, synthetic lubricating oil such as mineral oil, ester oil, silicone oil, ether oil, etc. As the thickener, a metal soap such as lithium soap or a urea compound is generally used. Moreover, as an additive, various additives, such as antioxidant, a rust inhibitor, a metal deactivator, a viscosity index improver, are mix | blended as needed. As the antioxidant, an organic zinc compound such as zinc alkyldithiophosphate, an amine compound such as alkylated diphenylamine, or the like is used alone or in combination.

  Motor bearings used in home appliances and industrial equipment are used at high temperature and high speed rotation, and are required to have excellent silence and high temperature and high speed durability. Conventionally, as a lubricating composition such as grease that has excellent durability at high temperature, suppresses abnormal noise during cold, and has excellent releasability under high temperature and high load, it has been added to a base oil consisting of synthetic hydrocarbon oil and ester oil. Lubricating compositions containing a funnel or the like are known (see Patent Document 3 and Patent Document 4). Further, as a lubricating composition having a long seizure life under high-temperature and high-speed rotation conditions, a grease composition containing 3 to 30% by weight of a thickener containing an ester oil as a base oil and an aliphatic diurea compound as an essential component is known. (See Patent Document 5).

  On the other hand, propeller shafts used for FW vehicles and 4WD vehicles are shafts connecting the transmission side and the differential gear side, and a universal joint is appropriately provided in the middle. Conventionally, as a lubricant for this universal joint, grease for wheel bearings and general-purpose grease (multipurpose grease) have been widely used.

JP-A-3-210394 JP-A-2005-42102 Japanese Patent Laid-Open No. 9-208982 JP-A-11-270566 JP 2001-107073 A

  However, in recent years, electrical components and accessories in automobiles, motors in industrial machines, etc., are increasingly used in rolling bearings at high temperatures, such as frequent high-speed operation-sudden deceleration operation-rapid acceleration operation-sudden stop. The method of adding the passivating agent of Patent Document 1 and the bismuth dithiocarbamate of Patent Document 2 has become insufficient as a measure for preventing the peeling phenomenon.

  Moreover, even when using a lubricating (grease) composition as in Patent Document 3 to Patent Document 5 or when adding a combination of conventional antioxidants to these, high-temperature, high-speed rotation of recent home appliances and industrial equipment, etc. When encapsulated in a bearing used in the above, there may be a case where the performance cannot be satisfied with respect to high temperature and high speed durability.

  In severe environments where propeller shaft universal joints such as sealed, high temperature, high speed, high torque, and high angle are used, the above-mentioned wheel bearing grease and general-purpose grease (multi-purpose grease) do not necessarily satisfy the performance. I can't say that. For this reason, it is desired to develop a grease for a universal joint of a propeller shaft that exhibits excellent performance even in the harsh environment.

  The present invention has been made to cope with such problems, and can effectively prevent peeling on a rolling surface such as a rolling bearing due to hydrogen embrittlement, and is excellent in high temperature and high speed durability and used for a long time. An object of the present invention is to provide a possible grease composition, a grease-filled bearing in which the grease composition is sealed, and a propeller shaft universal joint in which the grease composition is sealed.

  The grease composition of the present invention is a grease composition obtained by adding an additive to a base grease consisting of a base oil and a thickener, the additive comprising (1) a plant-derived polyphenol compound, and (2) It contains at least one compound selected from plant-derived polyphenol compound decomposition compounds, and the compounding ratio of the compound is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease. To do. The plant-derived polyphenol compound decomposition compound has a plurality of hydroxyl groups in one molecule.

  The plant-derived polyphenol compound is tannin. The plant-derived polyphenol compound is gallic acid or a derivative thereof. In particular, the gallic acid derivative is ethyl gallate. The plant-derived polyphenol compound is ellagic acid or a derivative thereof.

  The plant-derived polyphenol compound is chlorogenic acid or a derivative thereof. The plant-derived polyphenol compound is caffeic acid or a derivative thereof. The plant-derived polyphenol compound decomposition compound is quinic acid or a derivative thereof.

  The plant-derived polyphenol compound is curcumin or a derivative thereof.

  The plant-derived polyphenol compound is quercetin or a derivative thereof.

  The compounding ratio of the above compound is 0.1 to 5 parts by weight with respect to 100 parts by weight of the base grease.

The base oil is at least one oil selected from alkyl diphenyl ether oil, ester oil, and poly-α-olefin (hereinafter referred to as PAO) oil. The base oil is a mineral oil. The base oil has a kinematic viscosity at 40 ° C. of 10 to 100 mm ² / sec.

  The thickener is a urea compound. The thickener is a metal soap.

  The grease-sealed bearing of the present invention comprises an inner ring and an outer ring, and a plurality of rolling elements interposed between the inner ring and the outer ring, and a seal member for sealing a grease composition around the rolling elements is provided for the inner ring and the outer ring. A grease-enclosed bearing provided at both axial end openings of the outer ring, wherein the grease composition is encapsulated. The grease-filled bearing is a deep groove ball bearing.

  The grease-filled bearing is used for a motor of an industrial machine or an electrical equipment, and is a rolling bearing that supports a rotor of the motor. The grease-enclosed bearing is a rolling bearing used for automobile electrical equipment and auxiliary equipment.

  The propeller shaft universal joint of the present invention is a propeller shaft universal joint that transmits rotational torque from a transmission to the propeller shaft, and the universal joint is formed by sealing the grease composition.

  The grease composition of the present invention comprises at least one compound selected from (1) a plant-derived polyphenol compound and (2) a plant-derived polyphenol compound decomposition compound in a base grease comprising a base oil and a thickener. Therefore, by adding this grease composition to the bearing, it is possible to suppress the occurrence of peculiar delamination due to hydrogen embrittlement seen in bearings used in automobiles and industrial machinery. . In addition, the oxidation deterioration resistance can be improved as compared with a grease composition containing a conventional antioxidant and the like, and the life of the bearing can be extended under high temperature and high speed.

  Since the grease-enclosed bearing of the present invention encapsulates the above grease composition, it is possible to effectively prevent specific delamination accompanied by a change in white structure occurring on the rolling surface, excellent in oxidation resistance, and bearing life. Excellent. For this reason, it can be used as a bearing for automobile electrical equipment / auxiliary equipment, home appliances, industrial equipment and the like. In particular, alternators, electromagnetic clutches for car air conditioners, automotive electrical components such as intermediate pulleys and electric fan motors, rolling bearings for auxiliary machinery, motors for ventilation fans, blower motors for fuel cells, cleaner motors, fan motors, servo motors, stepping motors, etc. As a bearing for motors used in high-temperature and high-speed rotation, such as motors for industrial machinery, automotive starter motors, electric power steering motors, steering adjustment tilt motors, wiper motors, motors for electrical equipment such as power window motors, etc. It can be suitably used.

  Since the universal joint for propeller shafts of the present invention encloses the above grease composition, it is difficult to seize in a sealed environment subjected to high temperature and high speed centrifugal force, has excellent high temperature and high speed durability, and has a long life.

It is sectional drawing of the deep groove ball bearing which shows one Example of the grease enclosure bearing of this invention. It is sectional drawing which shows one Example of the grease enclosure bearing for motors of this invention. It is sectional drawing which shows one Example of the grease enclosure bearing for alternators of this invention. It is a partially cutaway sectional view of a constant velocity joint for propeller shafts showing an embodiment of a universal joint for propeller shafts of the present invention. It is a figure which shows the cardan joint for propeller shafts as another Example of the universal joint for propeller shafts of this invention.

  For rolling bearings, a grease composition containing at least one compound selected from (1) plant-derived polyphenol compounds and (2) decomposition compounds of plant-derived polyphenol compounds is enclosed, and a rapid acceleration / deceleration test and high temperature are conducted. The durability test showed that the bearing life can be extended. This is because the compound is easily attached to the metal surface of the bearing rolling surface by the action of the polar group (A), and the substance reacts on the frictional wear surface or the newly formed metal surface exposed by wear, causing the oxide film to roll on the bearing. By forming on the running surface, generation of hydrogen due to decomposition of the grease composition can be suppressed, and unique peeling due to hydrogen embrittlement on the bearing rolling surface can be prevented. (B) The above compound prevents oxidation of the grease composition. This is considered to be because it acts as an agent and can suppress oxidative deterioration. The present invention is based on these findings.

  The polyphenol compound that can be used in the present invention is an aromatic hydroxy compound having a plurality of hydroxyl groups in one molecule obtained by substituting a hydrogen atom of an aromatic hydrocarbon ring with a hydroxyl group (hydroxy group), and is derived from a plant.

  Moreover, the degradation compound of the plant-derived polyphenol compound is an aromatic or alicyclic hydroxy compound produced by hydrolysis of the polyphenol compound. In order to obtain the same effect as that of the polyphenol compound, the decomposition compound also preferably has a plurality of hydroxyl groups in one molecule.

  Examples of plant-derived polyphenol compounds or degradation compounds that can be used in the present invention include tannin, gallic acid, ellagic acid, chlorogenic acid, caffeic acid, quinic acid, curcumin, quercetin, pyrogallol, theaflavin, anthocyanin, rutin, lignan, Catechin etc. are mentioned. In addition, polyphenol compounds obtained from plant-derived sesamin, isoflavones, coumarins and the like can also be used. The above polyphenol compounds or their decomposition compounds may be used alone or in combination of two or more.

  Among these, tannin, gallic acid or derivatives thereof, ellagic acid or derivatives thereof, chlorogenic acid or derivatives thereof, caffeic acid or derivatives thereof, quinic acid or derivatives thereof, curcumin or It is preferable to use a derivative thereof, quercetin or a derivative thereof.

  Tannin used in the present invention is a polyphenol compound containing a large number of phenolic hydroxyl groups in the molecule and having a relatively large molecular weight as an acidic organic substance. The tannin is an astringent plant component present in oak skin, fushi (eroded), cocoon and the like, and is roughly classified into hydrolyzable tannin and condensed tannin depending on the chemical structure.

  Hydrolyzable tannin is hydrolyzed into polyhydric phenol acid and polyhydric alcohol by acid, alkali and enzyme. As the polyhydric phenol obtained, there are mainly two types of gallic acid and its dimer (in the free state, dehydration cyclization becomes tetracyclic ellagic acid). Examples of the polyhydric alcohol obtained include pyrogallol. Condensed tannin is obtained by condensing a plurality of molecules of catechin through carbon-carbon bonds. In the present invention, it is preferable to use a hydrolyzable tannin from which a decomposition product such as gallic acid, ellagic acid, pyrogallol and the like can be obtained.

Gallic acid and ellagic acid used in the present invention are polyhydric phenol acids (polyphenol compounds) obtained by hydrolyzing hydrolyzable tannin as described above. Gallic acid has a structure shown in the following formula (1), and ellagic acid has a structure shown in the following formula (2).

  Derivatives of gallic acid used in the present invention include gallic acid esters such as methyl gallate, ethyl gallate, propyl gallate, butyl gallate, pentyl gallate, hexyl gallate, heptyl gallate, and octyl gallate. Examples thereof include gallates such as bismuth. Of these, ethyl gallate is more preferred because of its excellent solubility in lubricating oil. Moreover, the same derivative can be used also about ellagic acid.

Chlorogenic acid used in the present invention is a polyphenol compound contained in coffee beans and the like, and has a structure represented by the following formula (3).

The caffeic acid used in the present invention is a hydrolyzate of chlorogenic acid, and is an aromatic hydroxy compound having three hydroxyl groups in the molecule in which a hydrogen atom of an aromatic hydrocarbon ring is substituted with a hydroxyl group. ).

The quinic acid used in the present invention is a hydrolyzate of chlorogenic acid, and is an alicyclic hydroxy compound having five hydroxyl groups in the molecule in which the hydrogen atom of the alicyclic hydrocarbon ring is substituted with a hydroxyl group, and the following formula It has the structure shown in (5).

Curcumin used in the present invention is a polyphenol compound contained in turmeric and the like, and has a structure represented by the following formula (6).

Quercetin used in the present invention is a polyphenol compound contained in citrus fruits and has a structure represented by the following formula (7).

  The blending ratio of at least one compound selected from a plant-derived polyphenol compound and its degradation compound is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease. Furthermore, it is preferably 0.1 to 5 parts by weight. If the compounding ratio of the above compound is less than 0.05 parts by weight, it is not possible to effectively prevent peeling on a rolling surface such as a rolling bearing due to hydrogen embrittlement. In addition, the grease cannot be effectively prevented from being deteriorated by oxidation. Even if the compounding ratio of the above compound exceeds 10 parts by weight, the anti-peeling effect and the effect of preventing the oxidative deterioration of the lubricant are hardly improved.

  Examples of base oils that can be used in the present invention include mineral oils such as spindle oil, refrigerator oil, turbine oil, machine oil, dynamo oil, highly refined mineral oil, liquid paraffin oil, polybutene oil, GTL oil synthesized by the Fischer-Tropsch method, Hydrocarbon synthetic oil such as PAO oil, alkylnaphthalene oil, alicyclic compound, or natural oil, polyol ester oil, phosphate ester oil, polymer ester oil, aromatic ester oil, carbonate ester oil, diester oil, poly Non-hydrocarbon synthetic oils such as ester oils such as glycol oils, silicone oils, polyphenyl ether oils, alkyl diphenyl ether oils, alkyl benzene oils, and fluorinated oils can be used. These may be used alone or in combination of two or more.

  PAO oils are usually a mixture of α-olefins or isomerized α-olefin oligomers or polymers. Specific examples of α-olefins include 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, -Nonadecene, 1-eicosene, 1-docosene, 1-tetradocosene and the like can be mentioned, and usually a mixture thereof is used.

  As the base oil of the grease composition of the present invention, it is preferable to use at least one oil selected from alkyl diphenyl ether oil, ester oil, and PAO oil because it is excellent in heat resistance and lubricity among the above base oils. . Alkyl diphenyl ether oil and ester oil are more preferably used in combination with PAO oil.

The kinematic viscosity at 40 ° C. of the base oil is preferably 10 to 100 mm ² / sec. More preferably, it is 10-70 mm < ² > / sec. If the kinematic viscosity is less than 10 mm ² / sec, the base oil will deteriorate in a short time, and the deteriorated product will accelerate the deterioration of the entire base oil. It becomes. Also, if the speed exceeds 100 mm ² / sec, the temperature rise of the bearings and the like due to the increase of the rotational torque will increase, especially under high speed rotation, and the grease will be sufficiently oxidized and deteriorated even if the above polyphenol compound is added. There is a risk that it cannot be prevented.

  As the thickener of the grease composition of the present invention, metal soap such as benton, silica gel, fluorine compound, lithium soap, lithium complex soap, strong lucium soap, calcium complex soap, aluminum soap, aluminum complex soap, diurea compound, polyurea Examples include urea compounds such as compounds. Of these, urea compounds are desirable in view of heat resistance, cost, and the like.

  A urea compound is obtained by reacting an isocyanate compound and an amine compound. In order not to leave a reactive free radical, the isocyanate group of the isocyanate compound and the amino group of the amine compound are preferably blended so as to be approximately equivalent.

  A diurea compound is obtained by reaction of a diisocyanate and a monoamine, for example. Examples of the diisocyanate include phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, hexane diisocyanate, etc., and monoamines include octylamine, dodecylamine, hexadecylamine, stearylamine, Examples include oleylamine, aniline, p-toluidine, cyclohexylamine and the like. The polyurea compound can be obtained, for example, by reacting diisocyanate with a monoamine or diamine. Examples of the diisocyanate and monoamine include those similar to those used for the production of the diurea compound. Examples of the diamine include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, xylenediamine, And diaminodiphenylmethane.

  A base grease for blending the above-mentioned polyphenol compound and the like by blending a thickener such as a urea compound with the base oil can be obtained. A base grease using a urea compound as a thickener is prepared by reacting an isocyanate compound and an amine compound in a base oil.

  The blending ratio of the thickener in 100 parts by weight of the base grease is 1 to 40 parts by weight, preferably 3 to 25 parts by weight. If the content of the thickener is less than 1 part by weight, the thickening effect will be reduced, making it difficult to make grease, and if it exceeds 40 parts by weight, the resulting base grease will be too hard and the desired effect will not be obtained. Become.

  In addition to the plant-derived polyphenol compound, a known grease additive may be contained as necessary. Examples of the additives include antioxidants such as organic zinc compounds and amine compounds, metal deactivators such as benzotriazole, viscosity index improvers such as polymethacrylate and polystyrene, and solid lubricants such as molybdenum disulfide and graphite. Rust preventives such as metal sulfonates and polyalcohol esters, friction reducing agents such as organic molybdenum, oily agents such as esters and alcohols, and antiwear agents such as phosphorus compounds. These can be added alone or in combination of two or more.

  The grease composition of the present invention can improve the life of a grease-sealed bearing by suppressing the occurrence of peculiar delamination due to hydrogen embrittlement and improving the oxidation resistance degradation of grease under high temperature and high speed. For this reason, ball bearings, cylindrical roller bearings, tapered roller bearings, spherical roller bearings, needle roller bearings, thrust cylindrical roller bearings, thrust tapered roller bearings, thrust needle roller bearings, thrust spherical roller bearings, etc. Can be used as grease.

  A bearing in which the grease composition of the present invention is enclosed will be described with reference to FIG. FIG. 1 is a sectional view of a deep groove ball bearing showing an embodiment of the grease-filled bearing of the present invention. In the grease-filled bearing 1, an inner ring 2 having an inner ring rolling surface 2a on the outer peripheral surface and an outer ring 3 having an outer ring rolling surface 3a on the inner peripheral surface are arranged concentrically, and the inner ring rolling surface 2a and the outer ring rolling surface 3a are arranged. A plurality of rolling elements 4 are arranged between the two. A cage 5 that holds the plurality of rolling elements 4 is provided. In addition, seal members 6 fixed to the outer ring 3 and the like are provided in the axially opposite end openings 8a and 8b of the inner ring 2 and the outer ring 3, respectively. A grease composition 7 is enclosed at least around the rolling element 4. In the grease composition 7, an additive containing at least one selected from the above-mentioned plant-derived polyphenol compounds and their decomposition compounds is blended in a base grease composed of a base oil and a thickener.

  A grease-filled bearing used in a motor as another embodiment of the grease-filled bearing of the present invention will be described with reference to FIG. FIG. 2 is a sectional view of the motor showing the grease-filled bearing for the motor of the present invention. The motor includes a stator 10 made of a magnet for a motor disposed on the inner peripheral wall of the jacket 9, a rotor 13 around which a winding 12 fixed to the rotating shaft 11 is wound, and a commutator fixed to the rotating shaft 11. 14, a brush holder 15 disposed on an end frame 17 supported by the jacket 9, and a brush 16 accommodated in the brush holder 15. The rotating shaft 11 is rotatably supported by the jacket 9 by a grease-filled bearing 1 and a support structure for the bearing 1. The grease-filled bearing 1 is the grease-filled bearing of the present invention.

  As another embodiment of the grease-enclosed bearing of the present invention, a grease-enclosed bearing used in an alternator which is an automobile electrical equipment / auxiliary machine will be described with reference to FIG. FIG. 3 is a sectional view of the structure of the alternator. In the alternator, a pair of frames 18 and 19 forming a housing which is a stationary member, a rotor rotating shaft 21 having a rotor 20 mounted thereon is rotatably supported by a pair of grease-filled bearings 1 and 1. A rotor coil 22 is attached to the rotor 20, and a three-winding stator coil 24 is attached to the stator 23 disposed on the outer periphery of the rotor 20 at a phase of 120 °. The rotor rotating shaft 21 is rotationally driven with a rotational torque transmitted by a belt (not shown) to a pulley 25 attached to the tip of the rotor rotating shaft 21. Since the pulley 25 is attached to the rotor rotating shaft 21 in a cantilever state, and vibration is also generated as the rotor rotating shaft 21 rotates at high speed, the grease-filled bearing 1 that supports the pulley 25 side in particular has a severe load. receive. The grease-filled bearing 1 is the grease-filled bearing of the present invention.

  An example of a universal joint for a propeller shaft according to the present invention will be described with reference to the drawings. FIG. 4 is a partially cutaway sectional view of a double offset constant velocity joint for a propeller shaft. As shown in FIG. 4, the constant velocity joint 26 for the propeller shaft includes an inner ring 27, an outer ring 28, a cage 29 and six steel balls 30. The inner ring 27 and the outer ring 28 have an axis line that houses the steel balls. With parallel tracks. The cage 29 plays a role of controlling the movement of the steel ball 30, but a cylindrical portion is provided on the inner surface as shown in FIG. 4 in order to make the steel ball 30 easy to roll. Further, the outer periphery of the outer ring 28 and the outer periphery of the shaft 31 are covered with a boot 32, and the space surrounded by the outer ring 28, the inner ring 27, the steel ball 30, the cage 29, the shaft 31, and the boot 32 is described above. The grease composition 33 of the present invention is enclosed.

  Another example of the universal joint for propeller shafts of the present invention will be described with reference to the drawings. FIG. 5 shows a cardan joint for a propeller shaft. FIG. 5A is a plan view and FIG. 5B is a front view. As shown in FIG. 5, the propeller shaft cardan joint 34 includes a first yoke 35 that is connected to the transmission and rotates, a second yoke 37 that transmits the rotational torque of the first yoke 35 to the propeller shaft 38, and these A cross-shaped cross is connected to the through hole provided in the bifurcated end portions 35a and 35a of the first yoke 35 and the through hole provided in the bifurcated end portions 37a and 37a of the second yoke 37. And a cruciform joint member 36 that transmits rotational torque from the first yoke 35 to the second yoke 37. The cross joint member 36 has short shafts 36a and 36b that cross in a cross shape, and the tip of the short shaft 36a is inserted into the through holes of the end portions 37a and 37a of the second yoke, and a needle bearing (not shown) is provided. Through the second yoke cap 37b and is connected and fixed to the end portions 37a and 37a of the second yoke by the engaging nut 37c. Similarly, the tip of the short shaft 36b is inserted into the through hole of the first yoke ends 35a, 35a, is rotatably supported via a needle bearing (not shown), and is engaged via the cap 35b of the first yoke. The nut 35c is connected and fixed to the end portions 35a and 35a of the first yoke. The above-described grease composition of the present invention is enclosed in a needle bearing that rotatably supports the distal ends of the short shafts 36a and 36b of the cross joint member.

  When the grease composition of the present invention is used in the above-described universal joint for propeller shafts, it is necessary to be inexpensive and excellent in oil film formation. Therefore, mineral oil such as turbine oil is used as the base oil and lithium as the thickener. It is preferable to use metal soap such as soap.

In each of the following examples and comparative examples, the PAO oil used as the base oil is trade name Sinfluid 601 manufactured by Nippon Steel Chemical Co., Ltd. having a kinematic viscosity of 30 mm ² / sec at 40 ° C., and the alkyl diphenyl ether oil is at 40 ° C. The product name Moresco High Lube LB100 with a kinematic viscosity of 97 mm ² / sec, manufactured by Matsumura Oil Co., Ltd., and the ester oil manufactured by Nippon Steel Chemical Co., Ltd. with a kinematic viscosity of 72 mm ² / sec at 40 ° C. Were used respectively. Moreover, the reagent made from Tokyo Chemical Industry was used for each polyphenol compound.

Examples 1 to 10
In half of the base oil shown in Table 1, 4,4-diphenylmethane diisocyanate (trade name Millionate MT manufactured by Nippon Polyurethane Industry Co., Ltd., hereinafter referred to as MDI) is dissolved in the proportion shown in Table 1, and the remaining half In this base oil, a monoamine that was twice the equivalent of MDI was dissolved. The respective blending ratios and types are shown in Table 1. A solution in which monoamine was dissolved was added while stirring the solution in which MDI was dissolved, and then the reaction was continued for 30 minutes at 100 ° C. to 120 ° C. to produce a diurea compound in the base oil. To this, a plant-derived polyphenol compound and the like and an antioxidant were added at a blending ratio shown in Table 1, and the mixture was further stirred at 100 to 120 ° C. for 10 minutes. Thereafter, the mixture was cooled and homogenized with three rolls to obtain a grease composition. The obtained grease composition was subjected to a rapid acceleration / deceleration test. Test methods and test conditions are shown below. The results are shown in Table 1.

<Rapid acceleration / deceleration test>
An alternator, which is an example of an electrical accessory, was simulated, and the grease composition was sealed in a rolling bearing for rotating an inner ring that supports a rotating shaft, and a rapid acceleration / deceleration test was performed. The rapid acceleration / deceleration test conditions are as follows: the load load on the pulley attached to the tip of the rotating shaft is set to 1960 N, the operating speed is set to 0 rpm to 18000 rpm, and a current of 0.1 A flows through the test bearing. The test was conducted. Then, abnormal peeling occurred in the bearing, and the time when the vibration of the vibration detector exceeded the set value and the generator stopped (peeling life time, h) was measured. The test was terminated after 500 hours.

Comparative Examples 1 to 3
A base grease was prepared by selecting a thickener and a base oil in the blending ratio shown in Table 1 by the method according to Example 1, and further blended with additives to obtain a grease composition. The obtained grease composition was evaluated by performing the same test as in Example 1. The results are shown in Table 1.

  As shown in Table 1, the rapid acceleration / deceleration tests of Examples 1 to 10 all showed 400 hours or more. This is considered to be due to the fact that the specific peeling accompanied with the white structure change generated on the bearing rolling surface could be prevented by the action of the plant-derived polyphenol compound blended as an additive of the grease composition. On the other hand, in Comparative Example 1 in which only the antioxidant (hindered phenol) was blended as an additive, the peeling occurrence life was significantly shorter than those in Examples 1 to 10.

Example 11 to Example 17
In half of the base oil shown in Table 2, MDI was dissolved in the proportion shown in Table 2, and in the remaining half of the base oil, monoamine that was twice the equivalent of MDI was dissolved. The blending ratio and type of each are shown in Table 2. A solution in which monoamine was dissolved was added while stirring the solution in which MDI was dissolved, and then the reaction was continued for 30 minutes at 100 ° C. to 120 ° C. to produce a diurea compound in the base oil. To this, a plant-derived polyphenol compound and the like were added at a blending ratio shown in Table 2, and the mixture was further stirred at 100 to 120 ° C. for 10 minutes. Thereafter, the mixture was cooled and homogenized with three rolls to obtain a grease composition. The obtained grease composition was subjected to high temperature durability test 1. Test methods and test conditions are shown below. The results are also shown in Table 2.

<High temperature durability test 1>
Rolling bearing (bearing dimensions: inner diameter 20 mm, outer diameter 47 mm, width 14 mm) is filled with 0.7 g of grease composition, bearing outer ring outer diameter temperature 150 ° C, radial load 67 N, axial load 67 N It was rotated at a rotational speed of 10000 rpm, and the time until seizure (high temperature high speed life (150 ° C.), h) was measured.

Comparative Example 4 and Comparative Example 5
In accordance with the method according to Example 11, the base grease was prepared by selecting the thickener and the base oil at the blending ratio shown in Table 2, and the additive was further blended to obtain a grease composition. The obtained grease composition was evaluated by conducting the same test as in Example 11. The results are also shown in Table 2.

Example 18
Lithium 12-hydroxystearate was added to the mineral oil at the blending ratio shown in Table 2, and dissolved by heating with stirring. Thereafter, the mixture was cooled, and plant-derived polyphenol compounds and the like were added thereto at a blending ratio shown in Table 2 and further stirred at 100 to 120 ° C. for 10 minutes. Thereafter, the mixture was cooled and homogenized with three rolls to obtain a grease composition. The obtained grease composition was subjected to high temperature durability test 2. Test methods and test conditions are shown below. The results are also shown in Table 2.

<High temperature durability test 2>
Rolling bearings (bearing dimensions: inner diameter 20 mm, outer diameter 47 mm, width 14 mm) are filled with 0.7 g of grease composition, bearing outer ring outer diameter temperature 120 ° C, radial load 67 N, axial load 67 N It was rotated at a rotational speed of 10000 rpm, and the time until seizure (high temperature high speed life (120 ° C.), h) was measured.

Comparative Example 6
The base grease used in Example 18 was blended with the additives shown in Table 2 to obtain a grease composition. The obtained grease composition was evaluated by conducting the same test as in Example 18. The results are also shown in Table 2.

  As shown in Table 2, Examples 11 to 17 exhibited excellent high temperature durability with a lifetime of 1400 hours or more in the high temperature durability test 1. This is considered to be because the plant-derived polyphenol compound blended as an additive of the grease composition was able to suppress oxidative deterioration of the grease composition. On the other hand, in Comparative Example 4, two types of antioxidants were used in combination using the same base oil as in Examples 11 to 17, but the life was significantly shorter than in Examples 11 to 17. It was. Further, even when a mineral oil / Li soap base grease was used, Example 18 to which a plant-derived polyphenol compound was added was 1.5 times or more higher in the high-temperature durability test 2 than Comparative Example 6 to which other antioxidants were added. High temperature durability was shown.

  The grease composition of the present invention can effectively prevent specific delamination accompanied with a white structure change occurring on the rolling surface, and is excellent in resistance to oxidation deterioration. Rolling bearings for automotive electrical components such as alternators, electromagnetic clutches for car air conditioners, intermediate pulleys, electric fan motors, and auxiliary machinery, etc. Motors for industrial fans such as motors for ventilation fans, blower motors for fuel cells, cleaner motors, fan motors, servo motors, stepping motors, automobile starter motors, electric power steering motors, tilt motors for steering adjustment, wiper motors, power window motors It can be suitably used as a bearing for a motor such as a motor for electrical equipment such asMoreover, the universal joint which encloses this grease composition can be suitably used as a universal joint for a propeller shaft used for a propeller shaft of an automobile.

1 Grease filled bearing (deep groove ball bearing)
DESCRIPTION OF SYMBOLS 2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Seal member 7 Grease composition 8a Both ends opening 8b Both ends opening 9 Jacket 10 Stator 11 Rotating shaft 12 Winding 13 Rotor 14 Commutator 15 Brush holder 16 Brush 17 End frame 18 frame 19 frame 20 rotor 21 rotor rotating shaft 22 rotor coil 23 stator 24 stator coil 25 pulley 26 constant velocity joint for propeller shaft 27 inner ring 28 outer ring 29 cage 30 steel ball 31 shaft 32 boot 33 grease composition 34 cardan joint for propeller shaft 35 First yoke 36 Cross-shaped joint member 37 Second yoke 38 Propeller shaft

Claims (22)

A grease composition in which an additive is blended with a base grease comprising a base oil and a thickener,
The additive contains at least one compound selected from a plant-derived polyphenol compound and its decomposition compound, and the compounding ratio of the compound is 0.05 to 10 parts by weight with respect to 100 parts by weight of the base grease. A grease composition.   The grease composition according to claim 1, wherein the degradation compound of the plant-derived polyphenol compound has a plurality of hydroxyl groups in one molecule.   The grease composition according to claim 1, wherein the plant-derived polyphenol compound is tannin.   The grease composition according to claim 1, wherein the plant-derived polyphenol compound is gallic acid or a derivative thereof.   The grease composition according to claim 4, wherein the gallic acid derivative is ethyl gallate.   The grease composition according to claim 1, wherein the plant-derived polyphenol compound is ellagic acid or a derivative thereof.   The grease composition according to claim 1, wherein the plant-derived polyphenol compound is chlorogenic acid or a derivative thereof.   The grease composition according to claim 1, wherein the plant-derived polyphenol compound is caffeic acid or a derivative thereof.   The grease composition according to claim 1 or 2, wherein the decomposition compound of the plant-derived polyphenol compound is quinic acid or a derivative thereof.   The grease composition according to claim 1, wherein the plant-derived polyphenol compound is curcumin or a derivative thereof.   The grease composition according to claim 1, wherein the plant-derived polyphenol compound is quercetin or a derivative thereof.   The grease composition according to any one of claims 1 to 11, wherein the compounding ratio of the compound is 0.1 to 5 parts by weight with respect to 100 parts by weight of the base grease.   The grease composition according to any one of claims 1 to 12, wherein the base oil is at least one oil selected from alkyl diphenyl ether oil, ester oil, and poly-α-olefin oil. .   The grease composition according to any one of claims 1 to 12, wherein the base oil is mineral oil. The grease composition according to claim 13 or 14, wherein the base oil has a kinematic viscosity at 40 ° C of 10 to 100 mm ² / sec.   The grease composition according to any one of claims 1 to 15, wherein the thickener is a urea compound.   The grease composition according to any one of claims 1 to 15, wherein the thickener is a metal soap. An inner ring and an outer ring, and a plurality of rolling elements interposed between the inner ring and the outer ring, and sealing members for sealing a grease composition around the rolling elements at openings in both axial ends of the inner ring and the outer ring A grease-filled bearing provided,
The grease-filled bearing according to claim 1, wherein the grease composition is the grease composition according to claim 1.   The grease-filled bearing according to claim 18, wherein the grease-filled bearing is a deep groove ball bearing.   20. The grease-filled bearing according to claim 18 or 19, wherein the grease-filled bearing is a rolling bearing used for a motor of an industrial machine or an electrical equipment.   20. The grease-enclosed bearing according to claim 18 or 19, wherein the grease-enclosed bearing is a rolling bearing used for automobile electrical equipment and auxiliary equipment. A universal joint for a propeller shaft that transmits rotational torque from the transmission to the propeller shaft,
A universal joint for a propeller shaft, wherein the universal joint is formed by enclosing the grease composition according to any one of claims 1 to 17.

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