JP2008196526A - Rolling device and alternator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling device hardly causing white structure flaking even when water intrudes into the inside, and excellent in durability and reliability. <P>SOLUTION: A deep groove ball bearing is provided with: an inner ring 1 having a raceway surface 1a on the periphery surface; an outer ring 2 having a raceway surface 2a opposed to the raceway surface 1a on the inner periphery surface; a plurality of rolling elements 3 rotatably arranged between both the raceway surfaces 1a, 2a; a retainer 4 for retaining the plurality of rolling elements 3 between the inner ring 1 and the outer ring 2; and sealing devices 5, 5 like a seal for covering the opening of a clearance between the inner ring 1 and the outer ring 2. A grease composition G for lubricating between the raceway surfaces 1a, 2a and the rolling elements 3 is enclosed in an internal space which is formed between the inner ring 1 and the outer ring 2 and in which the rolling elements 3 are disposed. The dielectric constant of the grease composition G is set to 3 or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rolling device such as a rolling bearing, a ball screw, a linear guide device, and a linear motion bearing. The present invention also relates to an alternator.

  In general, the life of a rolling bearing is greatly reduced when moisture is mixed in the lubricant. For example, Furumura et al. Reported that when 6% of water is mixed in lubricating oil (# 180 turbine oil), the fatigue life is reduced by a factor of 1 to 20 times compared to the case without mixing. (See Non-Patent Document 1). Schatzberg et al. Have reported that the rolling strength of steel is reduced by 32 to 48% when only 100 ppm of water is mixed in the lubricating oil (see Non-Patent Document 2).

  Bearings used in automotive electrical components and engine accessories (eg, alternators, intermediate pulleys, car air conditioner electromagnetic clutches, car air conditioner compressor pulleys, water pumps), gas heat pump electromagnetic clutches, compressors, motor bearings Are usually used under conditions of high temperature, high speed, and high load, the grease composition may decompose to generate hydrogen (see Patent Document 1). Therefore, there has been a problem that peeling accompanied by a change to a white structure due to hydrogen embrittlement (hereinafter, sometimes referred to as white structure peeling) is likely to occur.

  Rolling bearings used for electrical components such as alternators and intermediate pulleys and engine auxiliary machines are bearings for belt driven auxiliary machines outside the engine, so that muddy water and rainwater splashed from the road surface can easily enter. The water pump bearing is also more susceptible to intrusion of circulating water for engine cooling. Although the seal prevents water from entering the bearing to some extent, it is difficult to completely prevent intrusion.

  Furthermore, the engine of an automobile is a machine that repeatedly starts and stops, but when the engine is stopped, the temperature of the rolling bearing decreases to reach the dew point, and moisture in the air around the rolling bearing condenses and drops of water. And may be mixed into the grease sealed in the rolling bearing. And the water | moisture content which penetrate | invaded in the rolling bearing may decompose | disassemble and hydrogen may be generated (refer patent document 2). Rolling bearings used for electrical parts and engine accessories are driven by a pulley driven by a belt and are rotated, so that static electricity is likely to be generated between the belt and the pulley, and water is easily electrolyzed.

In addition, while the rolling bearing is normally rotating, the inner and outer rings are insulated by the oil film of the lubricant. However, if metal contact occurs due to strong vibrations, the inner and outer rings are connected at once. The potential difference that occurs is increased. Therefore, water is electrolyzed by the generated current voltage, and generation of hydrogen ions is facilitated. The hydrogen generated in this way penetrates into the bearing steel and white structure peeling occurs.
Japanese Patent No. 2878749 JP-A-11-72120 Shinzaburo Furumura, Shinichi Shirota, Kiyoshi Hirakawa, “Rolling Fatigue at Surface and Internal Origins”, NSK Bearing Journal, No.636, p.1-10, 1977 P. Schatzberg, IMFelsen, “Effects of water and oxygen during rolling contact Lubrication”, wear, 12, p.331-342, 1968

  As described above, automobile electrical components and engine accessories (for example, alternators, intermediate pulleys, electromagnetic clutches for car air conditioners, compressor pulleys for car air conditioners, water pumps), electromagnetic clutches for gas heat pumps, Compressors, motor bearings and the like have a problem in that water easily enters the inside, and static electricity is easily generated between the belt and the pulley, so that white tissue peeling is likely to occur.

  Accordingly, the present invention provides a rolling device that solves the above-described problems of the prior art and is less likely to cause white tissue peeling even when water enters inside, and has excellent durability and reliability. Is an issue. It is another object of the present invention to provide an alternator that is less likely to cause white tissue peeling even when water enters inside, and is excellent in durability and reliability.

  In order to solve the above problems, the present invention has the following configuration. That is, the rolling device according to claim 1 of the present invention includes an inner member having a raceway surface on the outer surface, and a raceway surface facing the raceway surface of the inner member, and is disposed outward of the inner member. A rolling member comprising: an outer member that is formed, a plurality of rolling elements that are arranged to freely roll between the raceway surfaces, and a grease composition that lubricates between the raceway surfaces and the rolling elements. In the apparatus, the grease composition has a relative dielectric constant of 3 or more.

Since the rolling device having such a configuration includes a grease composition having a high relative dielectric constant, even if static electricity is generated between the inner member and the outer member, the rolling device can be easily mitigated. Therefore, electrolysis of moisture that has entered the inside is unlikely to occur, so that white tissue peeling is unlikely to occur.
The rolling device according to a second aspect of the present invention is the rolling device according to the first aspect, wherein at least a part of the base oil of the grease composition is a synthetic oil.

Furthermore, an alternator according to a third aspect of the present invention includes the rolling device according to the first or second aspect.
Since the alternator having such a configuration includes a grease composition having a high relative dielectric constant, even if static electricity is generated between the inner member and the outer member of the rolling device, the alternator can be easily mitigated. . Therefore, electrolysis of moisture that has entered the inside is unlikely to occur, so that white tissue peeling is unlikely to occur.

The present invention can be applied to various rolling devices. For example, a rolling bearing, a ball screw, a linear guide device, a linear motion bearing, and the like.
Further, the inner member in the present invention means an inner ring when the rolling device is a rolling bearing, a screw shaft when the ball screw is also used, a guide rail when the linear guide device is used, and a linear motion bearing. Means each axis. The outer member is the outer ring when the rolling device is a rolling bearing, the nut when it is a ball screw, the slider when it is a linear guide device, and the outer cylinder when it is also a linear bearing. Each means.

  The rolling device and the alternator of the present invention are less likely to cause white tissue peeling even when water enters inside, and are excellent in durability and reliability.

DESCRIPTION OF EMBODIMENTS Embodiments of a rolling device and an alternator according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a structure of a deep groove ball bearing which is an embodiment of a rolling device according to the present invention. This deep groove ball bearing has an inner ring 1 having a raceway surface 1a on the outer peripheral surface, an outer ring 2 having a raceway surface 2a facing the raceway surface 1a on the inner peripheral surface, and a raceway between the raceway surfaces 1a and 2a. A plurality of rolling elements (balls) 3, a cage 4 that holds the plurality of rolling elements 3 between the inner ring 1 and the outer ring 2, and a seal that covers the opening of the gap between the inner ring 1 and the outer ring 2 Sealing devices 5 and 5. Note that the cage 4 and the sealing device 5 may not be provided.

  In an internal space formed between the inner ring 1 and the outer ring 2 in which the rolling elements 3 are provided, a grease composition G that lubricates between the raceway surfaces 1a and 2a and the rolling elements 3 is disposed. The relative dielectric constant of the grease composition G is 3 or more, and more preferably 4 or more. In addition, although the kind of base oil of this grease composition G is not specifically limited, A synthetic oil is preferable.

Below, each component which comprises the grease composition G is demonstrated in detail.
[About base oil]
The type of base oil of the grease composition G is not particularly limited. If the relative permittivity of the grease composition G is 3 or more, a lubricating oil generally used as the base oil of the grease composition is used. Can be used without problems.

However, the kinematic viscosity at 40 ° C. of the base oil is 18 mm ² / s or more in order to suppress the generation of noise at low temperature startup due to insufficient low temperature fluidity and seizure that occurs because an oil film is difficult to form at high temperatures. preferably less than 400 mm ² / s, more preferably less than 26 mm ² / s or more 250 mm ² / s, more preferably less than 30 mm ² / s or more 160 mm ² / s.

Specific examples of base oils include mineral oils, synthetic oils, and natural oils. As the mineral oil-based lubricating oil, preferred is a mineral oil purified by appropriately combining vacuum distillation, solvent removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, white clay purification, hydrorefining, and the like.
As the synthetic oil-based lubricating oil, aliphatic hydrocarbon oil, aromatic hydrocarbon oil, ester oil, ether oil and the like are preferable.

  Examples of the aliphatic hydrocarbon oil include normal α-olefins such as normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, 1-decene and ethylene co-oligomer, and hydrides thereof. Examples of the aromatic hydrocarbon oil include alkylbenzenes such as monoalkylbenzene, dialkylbenzene and polyalkylbenzene, and alkylnaphthalenes such as monoalkylnaphthalene, dialkylnaphthalene and polyalkylnaphthalene.

  Furthermore, as ester oil, diester oils such as dibutyl sebacate, di (2-ethylhexyl) sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, methylacetyl ricinolate, trioctyl trimellitate, Aromatic ester oils such as tridecyl trimellitate and tetraoctyl pyromellitate are listed. Furthermore, polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, mixed fatty acids of monobasic acids and dibasic acids and polyhydric alcohols And complex ester oils which are oligoesters.

  In addition, 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, tetraphenyl ether, pentaphenyl ether, monoalkyl. Examples thereof include phenyl ether oils such as tetraphenyl ether and dialkyl tetraphenyl ether.

Examples of synthetic oils other than the above include tricresyl phosphate, silicone oil, perfluoroalkyl ether oil, and the like.
Examples of natural lubricating oils include beef tallow, pork tallow, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, palm kernel oil, and other oils and hydrides thereof.
These base oils may be used alone or in combination of two or more. In order to increase the dielectric constant of the grease composition G, it is preferable to use ester oil or ether oil containing a polar group as at least a part of the base oil.

[About thickener]
The type of the thickener used for the grease composition G is not particularly limited, and is generally used as a thickener for the grease composition if the relative permittivity of the grease composition G is 3 or more. Things can be used without problems.
For example, metal soap (metal is aluminum, barium, calcium, lithium, sodium, etc.) and metal composite soap (metal is lithium, sodium, barium, calcium, aluminum, etc.) can be mentioned. In addition, non-soap-type compounds such as urea compounds (diurea, triurea, tetraurea, polyurea, etc.), inorganic compounds (silica gel, bentonite, etc.), urethane compounds (diurethane compounds, etc.), urea / urethane compounds, sodium terephthalate compounds, etc. A fungicide can also be used. These thickeners may be used alone or in appropriate combination of two or more.

  Considering the heat resistance of the grease composition G, a urea compound, a urea / urethane compound, a urethane compound, or a mixture thereof is preferable. Specifically, diurea, a urea / urethane compound, a diurethane compound or a mixture thereof is preferable, and diurea is particularly preferable. In order to increase the relative dielectric constant of the grease composition G, a thickener containing a metal element such as metal soap or metal composite soap is preferable.

[Additives]
In order to set the relative dielectric constant of the grease composition G to 3 or more, a conductivity imparting substance may be added. Examples thereof include surfactants such as antistatic agents, carbon black, carbon nanotubes, fullerenes and metal powders known as conductive substances. Carbon black is more preferable for reducing the volume resistivity and improving the durability of the rolling device. The addition amount of the conductivity imparting substance is set to such an amount that the relative dielectric constant of the grease composition G is 3 or more according to the type.

  In addition, various additives generally used in the grease composition may be added to the grease composition G as necessary in order to further improve various performances. Examples include antioxidants, rust inhibitors, extreme pressure agents, oiliness agents, metal deactivators, viscosity index improvers, and these additives may be used alone or in appropriate combination of two or more. May be used. The total content of the additives is not particularly limited as long as the object of the present invention is not impaired, but is preferably 10% by mass or less based on the entire grease composition G.

  As the antioxidant, anti-aging agents, ozone deterioration inhibitors, and antioxidants that are generally used for rubber, plastic, lubricating oil, and the like can be used without problems. For example, phenyl-1-naphthylamine, phenyl-2-naphthylamine, diphenyl-p-phenylenediamine, dipyridylamine, phenothiazine, N-methylphenothiazine, N-ethylphenothiazine, 3,7-dioctylphenothiazine, p, p'-dioctyldiphenylamine Amine antioxidants such as N, N′-diisopropyl-p-phenylenediamine, N, N′-di-sec-butyl-p-phenylenediamine, and phenols such as 2,6-di-tert-dibutylphenol It is a system antioxidant.

  Examples of the rust preventive include petroleum sulfonate, dinonyl naphthalene sulfonate, sorbitan ester and the like. Furthermore, examples of the extreme pressure agent include a chlorine-based extreme pressure agent, a sulfur-based extreme pressure agent, a phosphorus-based extreme pressure agent, zinc dithiophosphate, and organic molybdenum. Furthermore, examples of the oily agent include fatty acids such as oleic acid and stearic acid, animal and vegetable oils, and the like. Furthermore, examples of the metal deactivator include benzotriazole and sodium nitrite. Furthermore, examples of the viscosity index improver include polymethacrylate, polyisobutylene, polystyrene and the like.

[About manufacturing method of grease composition]
The manufacturing method of the grease composition G is not particularly limited, and can be manufactured by a general method. For example, a thickener is synthesized by a reaction in a base oil to obtain a grease composition. A predetermined amount of the additive may be added to the obtained grease composition and mixed. However, after the additive is added, it is necessary to sufficiently stir with a kneader or a roll mill to uniformly disperse the additive. This dispersion treatment may be performed while heating.

  In addition, this embodiment shows an example of this invention and this invention is not limited to this embodiment. For example, in the present embodiment, a deep groove ball bearing has been described as an example of the rolling device, but the present invention can be applied to various types of other rolling bearings. For example, radial rolling bearings such as angular contact ball bearings, self-aligning ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, and self-aligning roller bearings, and thrust types such as thrust ball bearings and thrust roller bearings This is a rolling bearing. Furthermore, the present invention can be applied not only to rolling bearings but also to various types of various rolling devices. For example, a ball screw, a linear guide device, a linear motion bearing, or the like.

〔Example〕
The present invention will be described more specifically with reference to the following examples. Eight types of grease compositions having the compositions shown in Tables 1 and 2 were produced and evaluated for various performances.

  These grease compositions comprise a base oil, a thickener and an additive. Base oils include polyol ester oil (POE), dialkyl diphenyl ether oil (ADE), poly α-olefin oil (PAO), mineral oil, or mixed oil (polyol ester oil and diester oil mixed at a ratio of 8: 2. ) Is used.

  As the thickener, diurea or lithium soap (lithium 12-hydroxystearate) is used. In the table, diurea A is a diurea compound having an alicyclic hydrocarbon group, and diurea B is a diurea compound having an alicyclic hydrocarbon group and a diurea compound having an aliphatic hydrocarbon group. It is a mixture, and the mixing ratio is 8: 2 by mass ratio. Diurea C is a diurea compound having an aliphatic hydrocarbon group, and diurea D is a mixture of a diurea compound having an alicyclic hydrocarbon group and a diurea compound having an aliphatic hydrocarbon group. The ratio is 3: 7 by weight. Diurea E is a mixture of a diurea compound having an aromatic hydrocarbon group and a diurea compound having an aliphatic hydrocarbon group, and the mixing ratio is 8: 2.

Furthermore, as the additive, a conductivity imparting substance, an antioxidant, and a rust inhibitor are used. The conductivity imparting substance is carbon black, the antioxidant is an amine-based antioxidant, and the rust inhibitor is petroleum sulfonate.
The contents of the thickener and the additive in the grease composition are as shown in the table (the unit is mass%), and the balance is the base oil. Furthermore, the penetration of the grease composition (NLGI consistency number) is also shown.

[Measurement method of relative permittivity]
The relative dielectric constants of these grease compositions were measured as follows. A grease composition is filled between two disc-shaped electrodes (diameter 38 mm, thickness 0.3 mm), and an LCR meter is connected to provide resistance and capacitance at various frequencies under an atmosphere of 25 ° C. It was measured. Then, the relative dielectric constant ε _r was determined by the following formula. The results are shown in Tables 1 and 2 and FIG.
ε _r = {(ε _r ′) ² + (ε _r ″) ² } ^1/2

Here, ε _r ′ is the real part of the complex dielectric constant and is C _p / C ₀ . Ε _r ″ is an imaginary part of the complex dielectric constant and is 1 / (2πfC ₀ R _p ). Here, f is the frequency (Hz), C _p is the grease composition capacitance (F), C ₀ is the air capacitance (F), and R _p is the grease composition resistance (Ω).

[About peel test]
Rolling bearings enclosing the grease compositions shown in Tables 1 and 2 were incorporated into an alternator. The rolling bearing is a deep groove ball bearing having an inner diameter of 17 mm, an outer diameter of 47 mm, and a width of 14 mm, and includes a contact rubber seal. The amount of the grease composition enclosed is 50% by volume of the internal space volume of the deep groove ball bearing.

An endurance test was conducted by rotating such an alternator with an engine as shown in FIG. Conditions of rotation is that repeated the maximum shifts to rotational speed and cycle operation of returning to the idle state of the aforementioned rotational speed 14000Min ^-1 in an idling state of the rotating speed (rotating inner ring) 2000 min ^-1. The time required for one cycle is about 6 seconds. The pulley load is 1570N.

Such a test is performed at room temperature without temperature control, and when 500 hours have passed or abnormal vibration has occurred in the alternator housing, the test is stopped and the raceway surface and internal structure of the deep groove ball bearing are removed. The presence or absence of peeling was confirmed by observation.
The results are shown in Tables 1 and 2. In addition, five deep groove ball bearings were evaluated for one type of grease composition, and the number of deep groove ball bearings in which no peeling occurred was displayed. For example, when 3 pieces out of 5 pieces are not peeled off and 2 pieces are formed, “3/5” is shown. As can be seen from Tables 1 and 2, the deep groove ball bearings of Examples 1 to 5 were less prone to peeling than the deep groove ball bearings of Comparative Examples 1 and 2 in which the relative permittivity of the grease composition was less than 3.

[About seizure test]
The grease compositions shown in Tables 1 and 2 were sealed in a deep groove ball bearing (inner diameter 25 mm, outer diameter 62 mm, width 17 mm) having shields at both ends. The amount of the grease composition enclosed is 35% by volume of the internal space volume of the deep groove ball bearing. Such a deep groove ball bearing was rotated for 1000 hours using a drive motor under the conditions of radial load 98N, axial load 98N, and rotation speed (inner ring rotation) 10000 min ⁻¹ . At this time, the temperature of the outer ring was controlled to 140 ° C.

However, if an overcurrent due to excessive torque occurs in the drive motor that rotates the deep groove ball bearing, or if the outer ring temperature exceeds 150 ° C. (temperature higher by 10 ° C. than the initial outer ring temperature), it is determined that seizure has occurred, The study was discontinued.
The results are shown in Tables 1 and 2. Note that three deep groove ball bearings were evaluated for one type of grease composition, and the number of deep groove ball bearings in which seizure did not occur is displayed. For example, when 2 out of 3 images are not seized and are generated in 1 image, “2/3” is indicated. As can be seen from Tables 1 and 2, the deep groove ball bearings of Examples 1 to 5 were less susceptible to seizure than the deep groove ball bearings of the reference examples.

  The present invention relates to a bearing, an electromagnetic clutch for a gas heat pump, a compressor used for an electrical component of an automobile or an engine auxiliary machine (for example, an alternator, an intermediate pulley, an electromagnetic clutch for a car air conditioner, a compressor pulley for a car air conditioner, a water pump). It can be applied to motor bearings.

It is a longitudinal cross-sectional view which shows the structure of the deep groove ball bearing which is one Embodiment of the rolling device which concerns on this invention. It is a graph which shows the dielectric constant of a grease composition. It is a figure explaining the method of a peeling test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner ring 1a Raceway surface 2 Outer ring 2a Raceway surface 3 Rolling element G Grease composition

Claims (3)

  An inner member having a raceway surface on the outer surface, an outer member having a raceway surface opposite to the raceway surface of the inner member, and arranged on the outer side of the inner member, and rolling between the both raceway surfaces In a rolling device comprising a plurality of freely arranged rolling elements, and a grease composition that lubricates between both raceway surfaces and the rolling elements, the relative permittivity of the grease composition is 3 or more A rolling device characterized by that.   The rolling device according to claim 1, wherein at least a part of the base oil of the grease composition is a synthetic oil.   An alternator comprising the rolling device according to claim 1.

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