JP2001159427A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing, capable of maintaining high quietness over a long period. SOLUTION: Before assembly, an inner ring, an outer ring, a rolling element and a cage are ultrasonically cleaned. By the cleaning, grains inside of a beating (a space formed of the inner ring outer peripheral surface, the outer ring inner peripheral surface, the rolling element, the cage, and a seal) and having the hardness of not less than Hv 800 (8 Gpa) have the mean grain diameter of not more than 2 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suitable rolling bearing, and more particularly to a hard disk drive (HDD), a video tape recorder (VTR), a digital audio tape recorder (DAT), and a laser beam printer (LB).
The present invention relates to a rolling bearing suitable for a rotation supporting portion such as P).

[0002]

2. Description of the Related Art The speed of technological innovation in the computer-related industry is higher than that in industries in other fields. In particular, HD
As for D, the existence period of one model is short, and new models have been developed one after another with high precision and compactness by introducing new technology. Along with this, rolling bearings used for information devices such as HDDs are required to have strict quietness year by year, and furthermore, to maintain a constant level of low noise for a long period of time.

[0003] Conventional HDD, VTR, DAT, L
Rolling bearings used for BP etc. are class 1000
It is manufactured under a clean environment of about 0, but only controls the filtration of the lubricant particles inside the bearing and then supplies it to the inside of the bearing.

[0004]

However, the conventional rolling bearing has a problem that high silence may not be maintained for a long period of time. The present invention has been made in view of such a problem of the related art, and an object of the present invention is to provide a rolling bearing that maintains high quietness for a long time.

[0005]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, the noise of the rolling bearing is reduced by the hard particles existing inside the bearing and the raceway surface of the outer and inner races. And the rolling surface of the rolling element was repeatedly hit, and the surface was roughened. Then, it was found that the noise of the rolling bearing can be reduced by setting the particle diameter and the abundance of the particles in a predetermined range.

Based on such knowledge, the present invention provides a bearing having a hardness Hv (in the space formed by the outer peripheral surface of the inner ring, the inner peripheral surface of the outer ring, the rolling elements, the cage, and the seal). A rolling bearing characterized in that particles having a Vickers hardness of 800 (8 GPa) or more have an average particle size of 2 μm or less. The present invention also provides a bearing interior (a space formed by an inner ring outer peripheral surface, an outer ring inner peripheral surface, a rolling element, a retainer, and a seal).
In addition, the hardness is Hv800 (8 GPa) or more and the average particle size is 2
The present invention provides a rolling bearing characterized in that particles having a size of more than μm are present and the number of the particles is 5 or less per unit surface area (cm ² ) inside the bearing.

[0007] In the bearing (space formed by the outer peripheral surface of the inner ring, the inner peripheral surface of the outer ring, the rolling elements, the cage and the seal), particles having a hardness of Hv800 (8 GPa) or more and an average particle diameter of more than 2 µm are provided. Is present, the number of the particles is preferably 2 or less per unit surface area (cm ² ) inside the bearing. The hardness of the target particles is Hv800 (8GP
a) The reason for the above is that the hardness of the raceway surface of the bearing ring and the rolling surface of the rolling element in a normal rolling bearing is Hv720 or more, and the particles that cause surface roughness are considered to be particles of Hv800 or more. That's why. As these particles,
For example, there are abrasive grains of a grindstone used at the time of processing, and glass fibers contained in a material in the case of a ceramic retainer. As abrasive grains, alumina (Hv2000), silicon carbide (Hv2800), hexagonal boron nitride (Hv2800)
And diamond (Hv2800 or more).

Further, even if the hardness is Hv800 or more,
Particles having a particle size of 2 μm or less hardly cause the above-described surface roughness even if they repeatedly hit the raceway surfaces of the outer and inner rings and the rolling surfaces of the rolling elements. Therefore, the average particle diameter of the particles having a hardness of Hv800 (8 GPa) or more existing inside the bearing is 2 μm.
The rolling bearing having a diameter of less than m is less likely to generate noise and has good acoustic characteristics over a long period of time.

In the rolling bearing of the present invention, it is preferable that an ester oil is contained as an initial lubricating oil to be sealed in the bearing in consideration of lubricity and heat resistance. The ester oil is not particularly limited, but is a diester oil obtained from a reaction between a dibasic acid and a branched alcohol, an aromatic ester oil obtained from a reaction between an aromatic tribasic acid and a branched alcohol, and a polyhydric alcohol and a monobasic acid. Binderd ester oil obtained from the reaction with is preferably used. In particular, aromatic ester oils, selected from hindered ester oils,
It is preferable to use them alone or as a mixture.

[0010] Diester oils include dioctyl adipate (DOA) and diisobutyl adipate (DIB).
A), dibutyl adipate (DBA), dioctyl azelate (DOZ), dibutyl sebacate (DBS), dioctyl sebacate (DOS), methyl acetyl-ricinoleate (MAR-N) and the like. As the aromatic ester oil, trioctyl trimellitate (TOT)
M), tridecyl trimellitate, tetraoctyl pyromellitate and the like.

Examples of the hindered ester oil include those obtained by appropriately reacting a polyhydric alcohol shown below with a monobasic acid. The monobasic acid reacted with the polyhydric alcohol may be used alone or in combination. Further, it may be used as a complex ester which is an oligoester of a polyhydric alcohol and a mixed fatty acid of a dibasic acid / monobasic acid.

The polyhydric alcohols include trimethylolpropane (TMP), pentaerythritol (PE),
Dipentaerythritol (DPE), neopentyl glycol (NPG), 2-methyl-2-propyl-1-3
-Propanediol (MPPD) and the like. As the basic acid, a C4 to C18 monovalent fatty acid is mainly used. Specifically, for example, acetic acid, valeric acid, caproic acid, caprylic acid, enanthic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, mystyric acid, palmitic acid, tallow fatty acid, sularic acid, caproleic acid, undecylenic acid, Lindelic acid, tuzunic acid, physeteric acid, myristolic acid, palmitoleic acid, petroselinic acid,
Oleic acid, elaidic acid, asclepic acid, vaccenic acid, sorbic acid, linoleic acid, linolenic acid, savininic acid, ricinoleic acid and the like.

The above-mentioned ester oil comprises at least 20% by weight or more of the total amount of the base oil, and when acoustic characteristics are taken into consideration, pentaerythritol enister or dipentaerythritol ester alone or in a mixture of 4 or more
It is desirable that the content be 0% by weight or more. 2 ester oils
If it is less than 0% by weight, sufficient high-temperature and high-speed durability cannot be obtained. The upper limit is not particularly limited.

Further, in addition to the above ester oils, refined mineral oils, synthetic hydrocarbon oils, and ether oils can be blended as base oil components. Refined mineral oils can be used in either naphthenic or paraffinic systems. As a synthetic hydrocarbon oil, poly-α-
Examples include olefin oils and synthetic oligomers of α-olefins and ethylene. Examples of the ether oil include a phenyl ether oil in which a C12 to C20 (di) alkyl chain of diphenyl, triphenyl, and tetraphenyl is derived. In particular, in consideration of high-temperature and high-speed durability, (di) alkyl polyphenylene oil is preferable. The mixing ratio of these is within 80% by weight from the definition of the amount of ester oil.

The viscosity of the base oil was 10
If it is less than mm ² / s, the thickness of the oil film is reduced, and there is a problem particularly in durability at high temperatures. If it exceeds 100 mm ² / s, heat is generated due to viscous resistance and slip is likely to occur, so that the seizure rejection rate increases. Therefore, the base oil viscosity is preferably selected within a range of 10 to 100 mm ² / s at a kinematic viscosity of 40 ° C. More preferably 10 to 80 m
m ² / s, more preferably within the range of ²⁰ to 70 mm ² / s.

Further, the durability of the lubricant film can be improved by adding a rust inhibitor, an oil agent, an antioxidant and the like to the lubricating oil. As the rust inhibitor, an organic metal sulfonic acid salt or ester is preferable. As the organic sulfonate, for example, dinonylnaphthalenesulfonic acid and heavy alkylbenzenesulfonic acid are used, and as the metal salts thereof, there are calcium sulfonate, parium sulfonate, sodium sulfonate and the like. As esters, polybasic carboxylic acids in sorbitan derivatives,
And partial esters of polyhydric alcohols include sorbitan monolaurate, sorbitan trilaurate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan monooleate and the like. Examples of the alkyl ester type include polyoxyethylene laurate, polyoxyethylene oleate, and polyoxyethylene stearate.

These rust inhibitors can be used alone or as a mixture of an organic metal sulfonic acid salt and an ester. Further, the content of the rust inhibitor is preferably at least 2% by weight based on the total amount of the lubricant composition. If the content of the rust inhibitor is less than 2% by weight, an effective rust preventive effect cannot be obtained. On the other hand, if it is added in excess of 20% by weight, not only is it not possible to expect a rust-preventive effect in accordance with the increase in the amount added, but it also causes a cost increase. Therefore, the content of the rust inhibitor is preferably 2 to 20% by weight.

The oily agent is preferably a higher fatty acid such as oleic acid or stearic acid, the higher alcohol is preferably lauryl alcohol or oleyl alcohol, the amine is preferably stearylamine or cetylamine, and the phosphate ester is preferably tricresyl phosphate. Can be used alone or as a mixture. The content of these oil agents is 0.5% by weight based on the total amount of the lubricant composition.
It is preferable that it is above. This content is 0.5% by weight
If it is less than 3, the effect of reducing wear cannot be obtained. Also, 1
Even if it is added in excess of 0% by weight, not only the effect corresponding to the increase in the added amount cannot be expected, but also a factor of cost increase. In consideration of acoustic characteristics, cost, and the like, the content of the oil agent is preferably 0.5 to 10% by weight. In addition,
5% by weight is preferred.

The antioxidant is preferably a mixture of a nitrogen-containing compound antioxidant and a phenolic antioxidant. Examples of the nitrogen-containing compound antioxidant include phenyl α-naphthylamine, diphenylamine, phenylenediamine, oleylamideamine, and phethiazine.
Examples of phenolic antioxidants include p-tert-butyl-phenyl salicylate, 2,6-di-tert-butyl-p-phenylphenol, 2,2′-methylenebis (4-methyl-6-tert-butylphenol),
2,2′-methylenebis (4-methyl-6-tert-
Octylphenol), 4,4'-butylidenebis-6
-Tert-butyl-m-cresol), tetrakis [methylene-3- (3 ′, 5′-di-tert-butyl-hydroxyphenyl) propionate] methane, 1,
3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, n-octadecyl-β- (4′-hydroxy-
3 ', 5'-di-tert-butylphenyl) propionate, 2-n-octyl-thio-4,6-di (4'-
(Hydroxy-3 ′, 5′-di-tet-butyl) phenoxy-1,3,5-triazine, 4,4′-thiobis-
[6-tert-butyl-m-cresol], 2-
(2′-hydroxy-3′-tert-butyl-5′-
Hindered phenols such as methylphenyl) -5-chlorobenzotriazole.

The content of these antioxidants is preferably 0.05% by weight or more based on the total amount of the lubricant composition. If the content is less than 0.05% by weight, the antioxidant effect of the lubricating oil is low, and sufficient lubricity cannot be maintained. Further, if it is added in excess of 10% by weight, not only the antioxidant effect of the lubricant cannot be expected in accordance with the increase in the amount added, but also a factor of cost increase. Therefore, the content of the antioxidant is preferably 0.05 to 10% by weight in consideration of acoustic characteristics and costs. Furthermore, 0.1 to 10
% By weight is preferred.

Further, the mixing ratio of the nitrogen-containing compound antioxidant and the phenolic antioxidant is preferably from 1: 9 to 9: 1. Within this range, the effect of preventing the lubricant from being oxidized is enhanced, and the acoustic characteristics at high temperatures and high speed rotation can be improved. It should be noted that the effect of improving the acoustic characteristics cannot be obtained only by adding only one of the nitrogen-containing compound antioxidant and the phenolic antioxidant.

In addition to these, the lubricating oils may contain conventionally known extreme pressure agents, viscosity index improvers, antiwear agents and the like. It is preferable that such an initial lubricating oil be sealed in the bearing and that a proper position in the bearing be lubricated with grease. Grease is a gel or semi-solid containing a lubricating oil (base oil). As the lubricating oil gradually seeps with the rotation of the bearing, poor lubrication in the initial rotation is improved as compared with the case of the initial lubricating oil alone. At the same time, the synergistic effect with the lubricating action of the lubricant film can improve the lubricating property itself and maintain the lubricating action for a long time.

The thickening agent for grease is prepared by adding a base material such as metal soaps such as barium, lithium and aluminum, and non-soaps such as diurea and lipophilic bentonite to a lubricating oil and heating and dissolving the same. Obtained by cooling. The product is a gel and can be placed directly in place on the cage. The content of the lubricating oil in the grease is not particularly limited, but is preferably at least 10% by weight, more preferably at least 30% by weight of the total weight of the grease. If the content is less than 10% by weight, the replenishment of the lubricating oil is not sufficient, and does not contribute to the improvement of the acoustic durability. Further, when the lubricating oil content increases, the grease tends to soften, and the desired consistency described later may not be obtained. Therefore,
The upper limit of the content is appropriately set in consideration of the consistency.

The grease needs to have a certain degree of shape retention because it needs to be present at the place where the bearing is applied, and must have a consistency greater than consistency No. 3 specified in "JIS K2220". It is preferred to have. Consistency No. specified in "JIS K2220"
If less than 3, the grease is too soft. Therefore, it flows during the rotation of the bearing, and a part thereof adheres to the raceway surface, restricts the rotation of the rolling element, causes slip, and causes surface damage. The upper limit of the consistency is not particularly defined.

The viscosity of the grease lubricating oil (base oil) is preferably 10 to 100 mm ² / s at 40 ° C. kinematic viscosity, similar to the initial lubricating oil base oil forming the lubricating oil film. 1
If it is less than 0 mm ² / s, there is a problem in durability at high temperatures, and if it exceeds 100 mm ² / s, slip tends to occur due to viscous resistance. It is preferable that the grease is filled in an appropriate place of the retainer so that the grease has a volume ratio of 15 to 50% of the bearing space and does not contact the raceway surfaces of the inner and outer rings and the rolling element surface. Here, the bearing space is a volume obtained by subtracting the volumes of the rolling elements and the retainer (and, in some cases, the seal member in some cases) from the volume of the ring-shaped space defined by the outer ring and the inner ring. If the amount of grease is less than 10% of the bearing space, the absolute amount is too small to obtain a lubricating oil replenishing effect. On the other hand, if it exceeds 50%, the grease hinders the rolling motion of the rolling element, and the possibility of the rolling element slipping and torque fluctuation increases.

[0026]

Embodiments of the present invention will be described below. An acoustic test of the rolling bearing was performed using a single-row deep groove ball bearing (with an inner diameter of 5 mm, an outer diameter of 2 mm, a width of 4 mm, and a rolling element diameter of 2.0 mm) with a contact number of 695 with a non-contact rubber seal. The inner ring, outer ring and rolling elements of this bearing are SUJ
After being formed from the material made of No. 2, it is subjected to ordinary quenching and tempering. In addition, as a cage,
A polyamide crown retainer was used.

First, before assembling, the inner ring, the outer ring, the rolling elements, and the cage were subjected to ultrasonic cleaning using an ultrasonic cleaner (frequency: 200 kHz, power: 600 W) manufactured by Kaijo Corporation. Here, by changing the cleaning time for each sample bearing, the number of particles and the average particle diameter present inside the bearing were changed. The longest washing time was 5 minutes. In addition, for each sample bearing, a plurality of specimen bearings that were cleaned under the same conditions were prepared, and the cleaning was performed for all the specimen bearings.

Next, for each of the sample bearings, a specimen bearing was assembled using the inner ring, the outer ring, the cage, and the rolling elements after cleaning. During this assembly, the grease was filled between the pockets of the retainer such that the area occupied by the grease in the bearing space was 35% by volume. As this grease,
The consistency is “JIS K2220 No. 3”
The base oil is ester-based and lithium 1
A grease containing 2-hydroxystearate was used.

The 20 sets of the inner ring, the outer ring, the retainer, and the rolling elements after the cleaning were not filled with grease, but were left as bearings for a specimen for measurement by a particle analyzer described later. Initial lubrication oil was filled in the assembled bearing. The initial lubricating oil used was dioctyl sebacate as a base oil, 4.45% by weight of calcium sulfonate as a thickener, 0.03% by weight of phenylenediamine and 0.02% of hindered phenol as antioxidants.
And lubricating oils each containing 0.5% by weight of tricresyl phosphate as an oiliness improver.

After the assembled bearing was immersed in the lubricating oil, the bearing was lifted up and blown with air to remove excess lubricating oil adhering to the bearing. Further, the bearing was centrifuged to remove excess lubricating oil in the bearing so that the thickness of the lubricating oil film in the bearing was 10 to 15 μm. The lubricating oil film thickness was adjusted by adjusting the magnitude of the centrifugal force and the rotation duration of the centrifuge.

As described above, the bearing was rotated for 5000 hours under the following conditions by using the bearing which had been lubricated with both the initial lubricating oil and the grease. <Rotation conditions> Bearing rotation speed: 7200 rpm (outer ring rotation) Axial load: 20 N Ambient temperature: 80 ° C. Using an Anderon meter, for each bearing, the sound level immediately after the start of the test (initial anderon value) and the sound after 5000 hours of rotation The level (anderon value after the rotation test) was measured. Then, the bearing whose anderon value after the rotation test was less than 1.1 times the initial anderon value was determined to have no change in acoustic characteristics due to rotation for 5000 hours (passed product), and the other bearings were rejected. did. For each sample bearing,
The percentage of specimen bearings that were rejected was calculated as the rejection rate (%).

On the other hand, the amount of particles present in the bearing and the average particle diameter are measured by using the above-mentioned 20 sets of the inner ring, the outer ring, the retainer, and the specimen bearing composed of the rolling elements for each sample bearing. Was performed as follows. First, the cage and the rolling element of the test sample bearing were placed in a sealed container washed with ultrapure water. Next, isopropanol for electronic industrial materials was added into the container, and after sealing, the container was shaken up and down for a predetermined time. Next, the liquid (isopropanol containing particles adhered to the retainer and the rolling elements) in the container was suction-filtered using a filter having a mesh of 0.4 μm. Next, the filter was passed through a particle analyzer “PT-1000” manufactured by Yokogawa Electric Corporation.
The chemical composition, average particle size, and number of particles remaining on the filter were measured.

The measured number is calculated as the number of the bearings of the specimen (20).
And the surface area inside the bearing (total area of the surfaces forming the space formed by the outer peripheral surface of the inner ring, the inner peripheral surface of the outer ring, the rolling elements, the cage and the seal, unit cm ² ) The number of particles per surface area (cm ² ) was calculated. The particles remaining on the filter were all alumina (H
v2000), silicon carbide (Hv2800), and hexagonal boron nitride (Hv2800 or more). These were the abrasive grains of the grindstone used in the processing.

From the above, for each sample bearing, the average particle size (μm) and number of particles (pieces / cm ² ) of the particles having a hardness of Hv 800 or more existing inside the bearing, and the rejection of the bearing by the acoustic test A rate (%) was obtained. These data were arranged in a three-dimensional graph shown in FIG. As can be seen from this graph, in the bearing of this embodiment, if the average particle size of the particles having a hardness of Hv 800 or more existing inside the bearing is 2 μm or less, the rejection rate of the bearing by the acoustic test is 0.1%. It is as follows. That is, even if particles having a hardness of Hv800 or more are present inside the bearing, by maintaining the average particle size of not more than 2 μm, high quietness can be maintained over a long period of time. It turns out that it becomes.

When particles having a hardness of Hv 800 or more and an average particle diameter exceeding 2 μm are present in the bearing,
If the number of the particles is 5 or less per unit surface area (cm ² ) inside the bearing, the rejection rate of the bearing by the acoustic test is 0.8% or less, and if the number is 2 or less, the bearing by the acoustic test is Are 0.2% or less. That is, inside the bearing, the hardness is Hv800 or more and the average particle size is 2
When particles exceeding μm are present, high quietness is maintained over a long period of time, and if the number of particles is 5 or less per unit surface area (cm ² ) inside the bearing, It is understood that the number is preferably two or less.

The grain size of the abrasive grains is usually 4 in average grain size.
μm or less, the hardness existing inside the bearing is Hv8
The average particle size of the particles having a size of 00 or more is usually 4 μm or less in average. Next, among the sample bearings described above, a bearing containing 5 particles / cm ^{2 of} silicon carbide (abrasive grains) having an average particle diameter of more than 2 μm inside the bearing was used, and the viscosity of the base oil of the initial lubricating oil used was determined. A test was conducted to examine changes in acoustic characteristics and seizure by changing the characteristics.

As the base oil, an ester oil was used, and base oils having different viscosities were prepared by blending ester oils having different viscosities. The rotation conditions were the same as above. Regarding the acoustic characteristics, the change in the anderon value before and after the rotation for 5000 hours was examined, and the rejection rate was calculated in the same manner as described above. Regarding the seizure, the ratio of the number of seizures after 5000 hours of rotation to the total number was calculated, and the value was taken as the rejection rate (%).

FIG. 2 is a graph showing these results. The base oil viscosity on the horizontal axis is the kinematic viscosity at 40 ° C. The rejection rate on the vertical axis is the sum of the rejection rate of the acoustic characteristics and the seizure property. (If the base oil viscosity is less than 10 mm ² / s, the rejection rate of the acoustic characteristics is dominant, and the base oil viscosity is 100 mm. ^If it exceeds ² / s, the seizure rejection rate is dominant). Base oil viscosity is 10
When it is less than mm ² / s, it was found that the oil film thickness was too thin and the rejection rate of the acoustic characteristics became high. Further, it was found that when the base oil viscosity exceeded 100 mm ² / s, the rejection rate of seizure increased due to an increase in viscous resistance.

[0039]

As described above, according to the present invention,
A rolling bearing is provided in which high quietness is maintained for a long time.

[Brief description of the drawings]

FIG. 1 shows each sample bearing manufactured in the embodiment.
4 is a graph showing the relationship between the average particle size (μm) and the number of particles (particles / cm ² ) of particles having a hardness of Hv 800 or more present inside the bearing and the rejection rate (%) of the bearing by an acoustic test.

FIG. 2 Base oil viscosity (40 ° C.) of initial lubricating oil used for bearing
3 is a graph showing the relationship between the kinematic viscosity at the time of test and the sum of the rejection rates obtained by the acoustic test and the seizure test.

Claims (1)

[Claims] 1. A hardness (Hv (Vickers hardness)) of 800 (8 GPa) existing inside a bearing (a space formed by an outer peripheral surface of an inner ring, an inner peripheral surface of an outer ring, a rolling element, a cage, and a seal).
A rolling bearing, wherein the average particle diameter of the above particles is 2 μm or less.