JP2002168258A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing having low torque at a low temperature but a high-speed revolution at a high temperature and capable of keeping a quietness property for a long time. SOLUTION: The rolling bearing is configured so that a plurality of rolling bodies 5 is held between an inner ring 2 and an outer ring 4 via a holder 7 at almost the same intervals so as to be capable of freely turning, and grease composed of a base oil containing 50 to 100 weight percent of specified trimethylol-propane ester is charged into the bearing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rolling bearing,
Particularly, it is suitable for a rotation support portion of a device which is rotated at a high speed such as a hard disk drive (HDD), a video tape recorder (VTR), a digital audio tape recorder (DAT), a laser beam printer (LBP), and has a high demand for quietness. It relates to a rolling bearing.

[0002]

2. Description of the Related Art The speed of technological innovation in the computer-related industry is higher than in other industrial fields. HDD in particular
In addition, new models have been introduced one after another, in which one model has a short existence period and new technologies for high accuracy and compactness are introduced. On the other hand, HDDs and other information recording devices such as those mentioned above are also required to have high speed and quietness, and the rolling bearings incorporated in these rotary supports are also improved in speed and quietness. Demands are becoming more stringent each year. In particular, for quiet operation, it is strongly desired that the noise be suppressed to a certain level or less and that the noise be maintained for a long time.

In response to such demands, rolling bearings incorporated in the spindle motor of the information recording apparatus include:
Conventionally, diester oils such as dioctyl sebacate and pentaerythritol ester, which are excellent in heat resistance, or tetraester oils as base oils, and greases containing lithium stearate and lithium hydroxystearate as thickeners are generally used. ing.

[0004] Further, with the advancement of information networks, these information recording devices are often carried outdoors and used outdoors, and are used in much lower temperature environments than indoors. For this reason, rolling bearings are also required to be excellent in startability at low temperatures. In order to improve the low-temperature startability, it is common to enclose grease using a base oil having a low kinematic viscosity.For example, a low-viscosity oil such as dioctyl sebacate is used in a high ratio such as tetraester oil or the like. The base oil mixed with is used.

[0005]

In accordance with the demand for increased recording density and portability, it is indispensable that the miniaturization of equipment and the high integration of the periphery of the equipment continue to be promoted in the future. A rise in temperature is expected. However, if a low-viscosity lubricating oil such as dioctyl sebacate is used at a high ratio as a grease base oil to improve low-temperature startability, it will be difficult to secure an oil film at high temperatures, and long-term quietness can be maintained. Disappears.

The present invention has been made to solve the above contradictory problems, and to provide a rolling bearing which has a low torque at a low temperature, can rotate at a high speed at a high temperature, and can maintain quietness for a long period of time. With the goal.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises a plurality of rolling elements rotatably held at substantially equal intervals between an inner ring and an outer ring via a retainer, A rolling bearing characterized by being filled with grease using a base oil containing 50 to 100% by weight of trimethylolpropane ester represented by the following general formula (1).

[0008]

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[0009] (wherein, R _1, R ₂ and R ₃ are both linear or branched alkyl group, saturated or unsaturated, be different from each other, may be the same, and R ₁ , R ₂
And the total number of carbon atoms of R ₃ is 4 to 29)

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a rolling bearing according to the present invention will be described in detail.

FIG. 1 is a sectional view of a main part showing a ball bearing which is an embodiment of a rolling bearing according to the present invention, wherein an inner ring 2 having an inner ring starting surface 1 on an outer peripheral surface and an outer ring starting surface 3 on an inner peripheral surface. A plurality of rolling elements such as balls 5 are held at substantially equal intervals by a retainer 7 between the outer ring 4 and the outer ring 4, and grease to be described later is provided in a bearing space formed by the inner ring 2, the outer ring 4 and the balls 5. (Not shown) is enclosed by a seal 6 to schematically form the structure.

The grease used in the present invention contains trimethylolpropane ester represented by the following general formula (1) in an amount of 50 to 100% by weight, preferably 60 to 100% by weight.
Particularly preferably used a base oil in a proportion of 70 to 100 wt%.

[0013]

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In the general formula (1), R ₁ , R ₂ and R ₃ are each a saturated or unsaturated straight-chain or branched alkyl group. And the total number of carbon atoms of R ₁ , R ₂ and R ₃ is 4 to 29
It is. When the average of the carbon number of R ₁ , R ₂ , and R ₃ exceeds 12, the starting torque at a low temperature increases and the acoustic characteristics at a high temperature deteriorate, as will be apparent from the examples described later. The above object of the present invention cannot be achieved. Also,
As the branched alkyl group, a group represented by (—CH ₂ CHR ₅ R ₆ ) is preferable. Particularly, R ₅ is a saturated linear alkyl group having 1 to 7 carbon atoms, and R ₆ is a saturated linear alkyl group having 4 to 8 carbon atoms. And the total number of carbon atoms of R ₅ and R ₆ is 5
-9 is preferable.

As preferred specific examples of the trimethylolpropane ester represented by the general formula (1), R ₁ , R ₂ , R
₃ is linear carbon number 4, branched carbon number 4, linear carbon number 6, branched carbon number 6, linear carbon number 7, branched carbon number 7, linear carbon number 8, branched carbon number 8, linear carbon number 9, trimethylolpropane esters having 9 or more branched carbon atoms, alone or in combination.

The trimethylolpropane ester represented by the general formula (1) has a viscosity lower than that of a tetraester generally used for improving low-temperature startability, and has a low viscosity at a high temperature. It has the advantage of excellent durability. Thus, the proportion of the base oil is as described above 50 wt% or more, more preferably higher. Further, the base oil may be used alone.

The lubricating oil used in combination as the base oil is not particularly limited, and examples thereof include mineral oil-based, synthetic oil-based, and natural oil-based lubricating oils. As the mineral oil-based lubricating oil, those obtained by appropriately combining mineral oil under reduced pressure distillation, oil removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay refining, hydrorefining and the like can be used. Examples of the synthetic oil-based lubricating base oil include a hydrocarbon-based oil, an aromatic-based oil, an ester-based oil, and an ether-based oil. Examples of the hydrocarbon-based oil include normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, and poly-α such as 1-decene and ethylene co-oligomer.
-Olefins or hydrides thereof.
Examples of the aromatic oil include alkylbenzenes such as monoalkylbenzene and dialkylbenzene, and alkylnaphthalenes such as monoalkylnaphthalene, dialkylnaphthalene, and polyalkylnaphthalene.
Examples of the ester oil include dibutyl sebacate, di-
Diester oils such as 2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl talate, methyl acetylsinolate, or trioctyl trimellitate, tridecyl trimellitate, tetraoctyl pyromellitate, etc. Aromatic ester oils, and further polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane velargonate, pentaerythritol-2-ethylhexanoate, and pentaerythritol belargonate, and also polyhydric alcohols Complex ester oils, which are oligoesters with mixed fatty acids of dibasic acids / monobasic acids, and the like can be mentioned. Examples of the ether-based oil include polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, and polypropylene glycol monoether, or monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether, tetraphenyl ether, monoalkyl Tetraphenyl ether,
And phenyl ether oils such as dialkyltetraphenyl ether. Other synthetic lubricating base oils include trithalyl phosphate, silicone oil, perfluoroalkyl ether and the like. Examples of the natural oil-based lubricating base oil include oils and fats such as beef tallow, lard, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, palm kernel oil, and hydrides thereof. These base oils can be used alone or as a mixture.

On the other hand, the thickener used in the grease is not particularly limited as long as it has a capability of forming a gel structure and retaining the base oil in the gel structure. For example, L
Metal soaps selected from i, Na, Ba, Ca, Al, and the like, or composite metal soaps thereof, benton, silica gel, urea compounds, urea / urethane compounds, and the like can be appropriately selected and used. Above all, in consideration of low noise, for example, lithium stearate and lithium 12-hydroxystearate are preferable. Further, in consideration of the heat resistance of the grease, a urea compound is preferable. For example, an aliphatic or alicyclic diurea compound or a polyurea compound is preferable. The content of these thickeners is suitably from 3 to 30% by weight, and more preferably from 5 to 25% by weight, based on the total amount of grease.

The grease may contain, in addition to the above components, various general-purpose additives such as an antioxidant, a rust inhibitor, an anticorrosive, and an antiwear agent in an appropriate amount, if necessary.

[0020] The consistency of the grease, JIS K220
No. 0 specified by No. 0 1 to No. 3, but is not limited to this. Further, grease amount to the rolling bearing, 5 a bearing space depending on the application
What is necessary is just to adjust so that it may occupy 30%. Further, the base oil described above may be applied to the inner ring 2, the outer ring 4, and the balls 5 in combination with grease, or may be injected into the bearing space.

The grease may be prepared by a known method. A predetermined amount of a thickener and, if necessary, an additive are added to the above base oil, and the mixture is kneaded using a kneader such as a kneader or a roll mill. Can be easily obtained.

[0022]

The present invention will be further described with reference to the following examples. [Example 1] was synthesized trimethylolpropane ester in the general formula (1) and R _1, R ₂ and 4 both the number of carbon atoms in R ₃ (Preparation of Test bearings) (TMP), the TMP is the total amount 0 to
Pentaerythritol (40% by weight)
A kinetic viscosity at 31 ° C. of 31 mm ² / sec) was prepared. The mixed oil is used as a base oil, and lithium 12
-Hydroxystearate, furthermore amine antioxidants,
An appropriate amount of a sulfonate-based rust inhibitor and a phosphorus-based abrasion inhibitor are added, and the consistency is determined using a roll mill according to JIS K2220.
In it is defined No. A test grease was prepared by kneading the mixture to obtain a test grease.

Then, a single row deep groove ball bearing (nominal number 69)
5; non-contact rubber seal (V type); inner diameter 5 mm x outer diameter 13
(mm × width 4 mm; ball diameter 2.0 mm), the test grease was sealed so as to occupy 15% of the bearing space, to produce a test bearing. The cage used was a crown-type cage made of polyamide.

(Low-Temperature Starting Torque Test) The above test bearing was mounted on a spindle of a spindle of a test apparatus, and an atmosphere temperature of 0 ° C.
It was rotated at 4800 rpm (outer ring rotation) under an axial load of 20 N, and the starting torque was measured with a strain gauge. The results are shown in FIG. In FIG. 2, the starting torque of a test bearing in which a test grease using TMP alone (100% by weight) of a base oil is sealed is set to 1, and the ratio is shown with respect to that. As is clear from the figure, the grease using the base oil containing TMP of 50% by weight or more is sealed at a lower temperature (0 ° C.) as compared with the case where the grease of less than 50% by weight is sealed. Starting torque of about 1/8 to 1
/ 2 can be reduced.

Example 2 (Preparation of Test Bearings) Various fatty acids having different numbers of carbon atoms were reacted with trimethylolpropane, and the total number of carbon atoms of R ₁ , R ₂ and R ₃ in the general formula (1) was calculated. Different T
MP was synthesized. Then, an appropriate amount of lithium 12-hydroxystearate, an amine-based antioxidant, a sulfonate-based rust inhibitor, and a phosphorus-based antiwear agent are added to each TMP,
Using a roll mill, the consistency is specified by JIS K2200. A test grease was prepared by kneading the mixture to obtain a test grease.

[0026] Then, a single-row deep groove ball bearing (bearing number 69
5; non-contact rubber seal (V type); inner diameter 5 mm x outer diameter 13
(mm × width 4 mm; ball diameter 2.0 mm), the test grease was sealed so as to occupy 15% of the bearing space, to produce a test bearing. The cage used was a crown-type cage made of polyamide.

(Low temperature starting torque test) The above test bearing was mounted on the spindle of a spindle of a test apparatus, and the atmosphere temperature was set at 0 ° C.
It was rotated at 4800 rpm (outer ring rotation) under an axial load of 20 N, and the starting torque was measured with a strain gauge. The results are shown in FIG. Incidentally, FIG. 3 is R _1, R _2, R ₃
The starting torque due to the difference in the average carbon number of
In this case, the ratio is shown assuming that 1 is 1. As is clear from the figure, the lower the average carbon number, the lower the starting torque at low temperatures. In particular, by enclosing a test grease using TMP having an average carbon number of 4 to 9 as a base oil, the starting torque can be increased. It can be seen that it can be kept low.

(Durability Life Test) Further, the same test bearing was rotated at 7200 rpm (outer ring rotation) under an ambient temperature of 80 ° C. and an axial load of 20 N, and an acoustic measurement was performed with an Anderon meter to evaluate the durability life. . That is,
When the bearing anderon value (initial anderon value) immediately after the test grease is sealed is measured and compared with the bearing anderon value after 5,000 hours of rotation, and the rise from the initial anderon value exceeds 1.0. Is rejected and 100
The pass rate (%) was calculated for zero test bearings. The results are shown in FIG. In FIG. 3, the pass rate of a test bearing in which a test grease containing TMP having an average carbon number of 4 as a base oil is enclosed is set to 1, and the ratio is shown. As is clear from the figure, the durable life deteriorates when the average carbon number is too large, but this is because the viscosity of the grease becomes too hard and slippage occurs between the raceway raceway surface and the rolling elements. It can be seen that the durability life can be improved by enclosing a test grease containing TMP having an average carbon number of 4 to 9 as a base oil.

From the above-mentioned low-tone starting torque test and durability life test, TMP having an average carbon number of R ₁ , R ₂ , and R ₃ of 4 to 9, that is, up to about 29 as the upper limit of the total number of carbon atoms is used as a base oil. It has been confirmed that by using grease, low torque at low temperature and quietness at high temperature can be satisfied at the same time.

[0030]

As described above, according to the present invention,
50-100 specific trimethylolpropane esters
By enclosing grease using a base oil containing by weight, low-temperature torque is low, and at the same time, high-speed rotation at high temperature is possible, and a rolling bearing that can maintain quietness for a long time is provided. . The rolling bearing of the present invention is particularly useful for a rotation support portion of an HDD, VTR, DAT, LBP, or the like.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a structure of a ball bearing which is one embodiment of a rolling bearing of the present invention.

FIG. 2 is a graph showing the relationship between the concentration of trimethylolpropane ester in a base oil and the bearing torque ratio at 0 ° C. startup obtained in an example.

FIG. 3 is a graph showing the relationship between the average carbon number of R ₁ , R ₂ , and R ₃ in the general formula (1) and the bearing torque ratio at 0 ° C. startup and the durability life ratio obtained in the example. .

[Explanation of symbols]

 2 inner ring 4 outer ring 5 ball 6 seal 7 cage

Claims (1)

[Claims] 1. A plurality of rolling elements are rotatably held at substantially equal intervals between an inner ring and an outer ring via a retainer, and trimethylolpropane ester represented by the following general formula (1) is provided. rolling bearing characterized by comprising encapsulating a grease using a base oil containing 50 to 100 wt%. Embedded image (Wherein, R ₁ , R ₂ and R ₃ are each a saturated or unsaturated linear or branched alkyl group, which may be different or the same, and R ₁ , R ₂ And the total number of carbon atoms of R ₃ is 4 to 29)