JP6744708B2 - Rolling bearing grease, rolling bearing, rolling bearing device and information recording/reproducing device - Google Patents

Description

The present invention relates to a rolling bearing grease, a rolling bearing, a rolling bearing device, and an information recording/reproducing device.

An information recording/reproducing apparatus such as a hard disk drive (HDD) is known as one that magnetically or optically records and reproduces various kinds of information on a disk. The information recording/reproducing apparatus generally includes a swing arm provided with a head gimbal assembly (magnetic head) for recording/reproducing a signal on/from a disk, a rolling bearing device serving as a fulcrum of rotation of the swing arm, and a swing arm. And an actuator for rotating the same. Signals can be recorded and reproduced by rotating the swing arm and moving the magnetic head to a predetermined position on the disk.

A rolling bearing device generally includes two rolling bearings each provided with a plurality of spherical rolling elements between an inner ring and an outer ring, and a shaft inserted inside the rolling bearings. The outer ring rotates around the axis of the shaft due to the rolling of the plurality of rolling elements, and the swing arm connected to the outer ring rotates accordingly. Since the rolling bearing is required to operate stably for a long period of time, grease is used for the purpose of smoothing the movement of the rolling conductor between the inner ring and the outer ring.

The grease for the rolling bearing of the information recording/reproducing device can reduce the torque of the rolling bearing and obtain excellent torque smoothness (the property that the torque is uniform in the rotating direction of the rolling bearing). It is required to improve the durability of the bearing. Further, if outgas from the grease accumulates in a gap between the magnetic head and the disk, a read/write operation of the information recording/reproducing apparatus will be inconvenient. Therefore, it is important that the grease for the rolling bearing has a small outgas amount.

With the recent increase in the density of HDDs and the increasing demand for server applications, the operating range and operating speed of the swing arm of the HDD, and the environmental temperature in which the HDD is used have become wider. Along with this, the grease provided in the rolling bearing device, which serves as the fulcrum of the rotation of the swing arm, has come to be exposed to various changing temperatures and lubricating conditions during use of the HDD.

As a grease for a rolling bearing of an information recording/reproducing apparatus used in such an environment, for example, Patent Document 1 discloses a base oil containing mineral oil and poly-α-olefin (hereinafter referred to as “PAO”), and a thickener. A grease containing an (urea compound or the like) and an extreme pressure agent (organic phosphorus compound or the like) and having excellent torque stability and durability is disclosed. Patent Document 2 discloses a grease that contains a base oil made of PAO, a thickener made of a diurea compound, and a metal carbamate and can reduce outgas.

JP, 2003-239954, A JP, 2013-174334, A

Outgas generated from grease is considered to be a major cause of malfunctions due to the adhesion of the magnetic head and the disk. Therefore, before the shipment, it is confirmed that the outgas amount of the rolling bearing device is within the predetermined range.
In addition to such outgas at the initial stage before the HDD is used, the present inventors oxidize and deteriorate the grease due to various temperature changes during use of the HDD, which causes outgas. It was concluded that the ease of operation has a great influence, and that a highly reliable HDD can be obtained by suppressing this oxidative deterioration. Further, as the oxidation deterioration of the grease progresses, poor lubrication occurs, which also affects the durability of the rolling bearing including this. Therefore, also from the viewpoint of obtaining an HDD having excellent durability, it is desired to suppress oxidative deterioration of grease.
However, the technologies of Patent Document 1 and Patent Document 2 have not been able to sufficiently satisfy the effect of reducing outgas. Further, in Patent Documents 1 and 2, oxidation deterioration of grease during use of the HDD was not considered.

An object of the present invention is to provide a rolling bearing grease which is excellent in the effect of reducing the amount of outgas. Furthermore, it is an object of the present invention to provide a rolling bearing grease which can suppress oxidative deterioration during use of the information recording/reproducing apparatus and which is excellent in durability.
Another object of the present invention is to provide a rolling bearing, a rolling bearing device and an information recording/reproducing device which use the above-mentioned rolling bearing grease.

（（１）式中、Ｒ^１及びＲ^２は、それぞれ独立して、炭素数１〜１２のアルキル基又は水素原子である。ただし、Ｒ^１及びＲ^２の少なくとも一方は、炭素数１〜１２のアルキル基である。）

（（２）式中、Ｒ^１１及びＲ^１２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^１３は、炭素数１〜８のアルキレン基であり、ｎは、１〜６の数である。Ｘ^１は、炭素数１〜２４の脂肪族ｍ価アルコールからｎ個の水酸基が除かれた残基であり、前記ｍは、１〜６であり、かつｎ以上の数である。ただし、ｎが５又は６のとき、前記Ｘ^１の脂肪族ｍ価アルコールの炭素数は２〜２４である。） The rolling bearing grease of the present invention comprises a base oil, a thickener, an amine-based antioxidant (A) represented by the following general formula (1), and a phenol-based oxidation represented by the following general formula (2). And at least one antioxidant selected from the antioxidant (B).

(In the formula (1), R ¹ and R ² are each independently an alkyl group having 1 to 12 carbon atoms or a hydrogen atom. However, at least one of R ¹ and R ² has 1 to 12 carbon atoms. Is an alkyl group.)

(In the formula (2), R ¹¹ and R ¹² are each independently an alkyl group having 1 to 8 carbon atoms, R ¹³ is an alkylene group having 1 to 8 carbon atoms, and n is 1 to 6). X ¹ is a residue obtained by removing n hydroxyl groups from an aliphatic m-hydric alcohol having 1 to 24 carbon atoms, and m is 1 to 6 and is a number of n or more. However, when n is 5 or 6, the number of carbon atoms of the aliphatic m-hydric alcohol of X ¹ is 2 to 24.)

The rolling bearing grease of the present invention preferably contains the amine-based antioxidant (A) and the phenol-based antioxidant (B).
The rolling bearing grease of the present invention preferably contains the amine-based antioxidant (A) in a larger amount by mass than the phenol-based antioxidant (B).
In the rolling bearing grease of the present invention, the base oil contains refined mineral oil classified into Group III in the base oil category defined by the American Petroleum Institute, and the refined mineral oil has a flash point of 240° C. or higher. It is preferably 250° C. or higher.
In the rolling bearing grease of the present invention, it is preferable that the base oil contains a mixture of a trimer and a pentamer of an α-olefin having 8 to 12 carbon atoms.
The rolling bearing grease of the present invention is preferably used for rolling bearings of information recording/reproducing devices.
The rolling bearing grease of the present invention is preferably used for rolling bearings of electronic device manufacturing apparatuses.

The rolling bearing of the present invention includes the rolling bearing grease of the present invention.
The rolling bearing device of the present invention includes a shaft and the rolling bearing of the present invention.
The information recording/reproducing apparatus of the present invention includes the rolling bearing device of the present invention.

The rolling bearing grease of the present invention is excellent in the effect of reducing the amount of outgas. Further, the grease can favorably suppress oxidative deterioration during use of the information recording apparatus. Furthermore, the grease has excellent durability in rolling bearings.
Further, in the rolling bearing, rolling bearing device and information recording/reproducing device of the present invention, the amount of outgas from the rolling bearing grease is reduced. Further, the grease is suppressed from being oxidized and deteriorated during use of the information recording/reproducing apparatus and is excellent in durability.

It is a perspective view showing an example of an information recording/reproducing apparatus of the present invention. FIG. 2 is a vertical cross-sectional view showing the vicinity of a rolling bearing device in the information recording/reproducing device of FIG. 1. It is sectional drawing which showed the rolling bearing apparatus of FIG. FIG. 4 is a plan view showing a rolling bearing in the rolling bearing device of FIG. 3. 5 is a sectional view of the rolling bearing of FIG. 4 taken along the line AA. FIG. It is a perspective view which showed the retainer of the rolling bearing of FIG. It is a graph which shows the result of having measured the time-dependent change of the evaporation loss in 85 degreeC. It is a graph which shows the result of having measured the time-dependent change of the evaporation loss in 100 degreeC. It is a graph which shows the result of having measured the time-dependent change of the evaporation loss in 130 degreeC.

[Grease for rolling bearings]
The rolling bearing grease (hereinafter, also simply referred to as “grease”) of the present invention comprises a base oil, a thickener, a specific amine-based antioxidant (A) and a specific phenol-based antioxidant (B). And at least one antioxidant selected from

<Antioxidant>
The antioxidant contained in the present invention includes a specific amine-based antioxidant (A) (hereinafter, also simply referred to as "(A) component") and a specific phenol-based antioxidant (B) (hereinafter, simply " It is also at least one selected from (B) component).
The grease of the present invention contains at least one antioxidant selected from the component (A) and the component (B) to reduce the amount of outgas. Further, it is possible to favorably suppress oxidative deterioration caused by various temperature changes during use of the information recording/reproducing apparatus using the grease of the present invention. As a result, not only in the initial stage immediately after the use of the information recording/reproducing apparatus is started or the use (driving) of the information recording/reproducing apparatus is interrupted (that is, the temperature is low), but also during its use (that is, the temperature is high) In (), the amount of outgas can be reduced. Furthermore, poor lubrication due to oxidative deterioration of grease can be suppressed, and durability can be improved.

（（１）式中、Ｒ^１及びＲ^２は、それぞれ独立して、炭素数１〜１２のアルキル基又は水素原子である。ただし、Ｒ^１及びＲ^２の少なくとも一方は、炭素数１〜１２のアルキル基である。） ≪(A) ingredient≫
The component (A) is an amine-based antioxidant represented by the following general formula (1).

(In the formula (1), R ¹ and R ² are each independently an alkyl group having 1 to 12 carbon atoms or a hydrogen atom. However, at least one of R ¹ and R ² has 1 to 12 carbon atoms. Is an alkyl group.)

R ¹ and R ² in the general formula (1) are each independently an alkyl group having 1 to 12 carbon atoms, and more preferably an alkyl group having 4 to 12 carbon atoms. The alkyl group may be linear or branched. As the alkyl group, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, an n-pentyl group, an i-pentyl group, a neopentyl group, t-pentyl group, 2-methylbutyl group, n-hexyl group, i-hexyl group, 3-methylpentyl group, ethylbutyl group, n-heptyl group, 2-methylhexyl group, n-octyl group, i-octyl group, 2-ethylhexyl group, 3-methylheptyl group, 1,1,3,3-tetramethylbutyl group, n-nonyl group, i-nonyl group, 1-methyloctyl group, ethylheptyl group, n-decyl group, 1 -Methylnonyl group, n-undecyl group, 1,1-dimethylnonyl group, n-dodecyl group and the like.
The alkyl group represented by R ¹ and R ² can be bonded to any position of the phenyl group, but is preferably p-position to the amino group.

Examples of the component (A) include monooctyldiphenylamine, monononyldiphenylamine, di(4-butylphenyl)amine, di(4-hexylphenyl)amine, di(4-octylphenyl)amine, di(4-nonylphenyl). ) Examples include amines. Among these, di(4-octylphenyl)amine is preferable. Further, as the component (A), a reaction product of N-phenylbenzenamine and 2,4,4-trimethylpentene may be used.

As the component (A), one type may be used alone, or two or more types may be used in combination.
The content of the component (A) is not particularly limited, but is preferably 0.05 to 2 mass% and more preferably 0.1 to 1 mass% with respect to the total mass of the grease. When the content of the component (A) is within the above-mentioned preferable range, the amount of outgas can be easily reduced. Furthermore, it becomes easy to suppress oxidative deterioration of the grease. This makes it easy to suppress the generation of outgas even when the information recording/reproducing apparatus is in use. Therefore, it becomes easy to reduce the total amount of outgas after the rolling bearing is manufactured and before it is used. Furthermore, it becomes easy to suppress poor lubrication due to oxidative deterioration of grease, and it becomes easy to improve durability.

（（２）式中、Ｒ^１１及びＲ^１２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^１３は、炭素数１〜８のアルキレン基であり、ｎは、１〜６の数である。Ｘ^１は、炭素数１〜２４の脂肪族ｍ価アルコールからｎ個の水酸基が除かれた残基であり、前記ｍは、１〜６であり、かつｎ以上の数である。ただし、ｎが５又は６のとき、前記Ｘ^１の脂肪族ｍ価アルコールの炭素数は２〜２４である。） ≪(B) ingredient≫
The component (B) is a phenolic antioxidant represented by the following general formula (2).

(In the formula (2), R ¹¹ and R ¹² are each independently an alkyl group having 1 to 8 carbon atoms, R ¹³ is an alkylene group having 1 to 8 carbon atoms, and n is 1 to 6). X ¹ is a residue obtained by removing n hydroxyl groups from an aliphatic m-hydric alcohol having 1 to 24 carbon atoms, and m is 1 to 6 and is a number of n or more. However, when n is 5 or 6, the number of carbon atoms of the aliphatic m-hydric alcohol of X ¹ is 2 to 24.)

In formula (2), R ¹¹ and R ¹² each independently represent an alkyl group having 1 to 8 carbon atoms, preferably an alkyl group having 2 to 6 carbon atoms, and more preferably an alkyl group having 3 to 5 carbon atoms. .. The alkyl group may be linear or branched. As the alkyl group, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, an n-pentyl group, an i-pentyl group, a neopentyl group, t-pentyl group, 2-methylbutyl group, n-hexyl group, i-hexyl group, 3-methylpentyl group, ethylbutyl group, n-heptyl group, 2-methylhexyl group, n-octyl group, i-octyl group, 2-ethylhexyl group, 3-methylheptyl group, 1,1,3,3-tetramethylbutyl group and the like can be mentioned. Among the above alkyl groups, t-butyl group is preferable, and both R ¹¹ and R ¹² are preferably t-butyl group.

R ¹³ is an alkylene group having 1 to 8 carbon atoms, and preferably an alkylene group having 1 to 3 carbon atoms. The alkylene group may be linear or may have a branched chain. Examples of the alkylene group include methylene group, ethylene group, n-propylene group, 1,2-propylene group, n-butylene group, 1,2-butylene group, n-hexylene group, n-heptylene group, n-octylene group. Etc. Among the alkylene groups, ethylene group is preferable.
n is a number of 1 to 6, and preferably 1 to 4.

X ¹ is a residue obtained by removing n hydroxyl groups from an aliphatic m-hydric alcohol having 1 to 24 carbon atoms, and m is 1 to 6. That is, X ¹ is a residue obtained by removing n hydroxyl groups from an aliphatic 1-to 6-valent alcohol having 1 to 24 carbon atoms.
Examples of the aliphatic 1- to hexavalent alcohol having 1 to 24 carbon atoms in X ¹ include, for example, methanol, ethanol, n-propanol, i-propanol, n-butanol, t-butanol, n-pentanol, 2-methylbutanol. , 3-methylbutanol, 2,2-dimethylpropanol, n-hexanol, 2-methylpentanol, 2-ethylbutanol, 2,3-dimethylbutanol, n-heptanol, 2-methylhexanol, 3-methylhexanol, 5 -Methylhexanol, n-octanol, 2-ethylhexanol, n-nonanol, 3,5,5-trimethylhexanol, decyl alcohol, monohydric alcohol such as 2,4,6-trimethylheptanol, neopentyl glycol, trimethylol Hindered alcohols such as ethane, trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, 1, Examples thereof include polyhydric alcohols such as 6-hexanediol, glycerin, diglycerin, triglycerin, sorbitol and mannitol. Among these, monohydric alcohols and hindered alcohols are preferable.

（（３）式中、Ｒ^２１及びＲ^２２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^２３は、炭素数１〜８のアルキレン基であり、Ｘ^２は、炭素数１〜２４の脂肪族１〜６価アルコールから１個の水酸基が除かれた残基である。） Examples of the component (B) include phenolic antioxidants represented by the following general formulas (3) to (8).

(In the formula (3), R ²¹ and R ²² are each independently an alkyl group having 1 to 8 carbon atoms, R ²³ is an alkylene group having 1 to 8 carbon atoms, and X ² is a carbon number. It is a residue in which one hydroxyl group is removed from 1 to 24 aliphatic 1- to 6-valent alcohols.)

R ²¹ and R ²² in the formula (3) are the same as R ¹¹ and R ¹² in the formula (2), respectively. Further, R ²³ in the formula (3) is the same as R ¹³ in the formula (2).
Examples of X ² in the formula (3) include monovalent aliphatic hydrocarbon groups having 1 to 24 carbon atoms.
The aliphatic hydrocarbon group may be linear or branched, and may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, the aliphatic hydrocarbon group may or may not have an ether bond between carbons. Furthermore, the aliphatic hydrocarbon group may be substituted with a hydroxy group or may not be substituted.
As X ² , a monovalent saturated aliphatic hydrocarbon group having 1 to 24 carbon atoms is preferable, and a monovalent saturated aliphatic hydrocarbon group having 1 to 18 carbon atoms is more preferable.

（（４）式中、Ｒ^３１及びＲ^３２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^３３は、炭素数１〜８のアルキレン基であり、Ｘ^３は、炭素数１〜２４の脂肪族２〜６価アルコールから２個の水酸基が除かれた残基である。）

(In the formula (4), R ³¹ and R ³² are each independently an alkyl group having 1 to 8 carbon atoms, R ³³ is an alkylene group having 1 to 8 carbon atoms, and X ³ is a carbon number. (This is a residue obtained by removing two hydroxyl groups from an aliphatic dihydric to hexahydric alcohol having 1 to 24.)

R ³¹ and R ³² in the formula (4) are the same as R ¹¹ and R ¹² in the formula (2), respectively. Further, R ³³ in the formula (4) is the same as R ¹³ in the formula (2).
Examples of X ³ in the formula (4) include a divalent aliphatic hydrocarbon group having 1 to 24 carbon atoms.
The aliphatic hydrocarbon group may be linear or branched, and may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, the aliphatic hydrocarbon group may or may not have an ether bond between carbons. Furthermore, the aliphatic hydrocarbon group may be substituted with a hydroxy group or may not be substituted.
X ³ is preferably a C 1-24 divalent saturated aliphatic hydrocarbon group which may have an ether bond between carbons, and 2-18 carbon atoms which may have an ether bond between carbons. The divalent saturated aliphatic hydrocarbon group of is more preferable.

（（５）式中、Ｒ^４１及びＲ^４２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^４３は、炭素数１〜８のアルキレン基であり、Ｘ^４は、炭素数１〜２４の脂肪族３〜６価アルコールから３個の水酸基が除かれた残基である。）

(In the formula (5), R ⁴¹ and R ⁴² are each independently an alkyl group having 1 to 8 carbon atoms, R ⁴³ is an alkylene group having 1 to 8 carbon atoms, and X ⁴ is a carbon number. It is a residue obtained by removing 3 hydroxyl groups from 1 to 24 aliphatic trihydric hexahydric alcohol.)

R ⁴¹ and R ⁴² in the formula (5) are the same as R ¹¹ and R ¹² in the formula (2), respectively. Further, R ⁴³ in the formula (5) is the same as R ¹³ in the formula (2).
Examples of X ⁴ in the formula (5) include trivalent aliphatic hydrocarbon groups having 1 to 24 carbon atoms.
The aliphatic hydrocarbon group may be linear or branched, and may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, the aliphatic hydrocarbon group may or may not have an ether bond between carbons. Furthermore, the aliphatic hydrocarbon group may be substituted with a hydroxy group or may not be substituted.
As X ⁴ , a trivalent saturated aliphatic hydrocarbon group having 1 to 24 carbon atoms which may have an ether bond between carbon atoms is preferable, and 3 to 18 carbon atoms which may have an ether bond between carbon atoms. The trivalent saturated aliphatic hydrocarbon group is more preferable.

（（６）式中、Ｒ^５１及びＲ^５２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^５３は、炭素数１〜８のアルキレン基であり、Ｘ^５は、炭素数１〜２４の脂肪族４〜６価アルコールから４個の水酸基が除かれた残基である。）

(In the formula (6), R ⁵¹ and R ⁵² are each independently an alkyl group having 1 to 8 carbon atoms, R ⁵³ is an alkylene group having 1 to 8 carbon atoms, and X ⁵ is a carbon number. It is a residue obtained by removing 4 hydroxyl groups from 1 to 24 aliphatic 4- to 6-hydric alcohols.)

R ⁵¹ and R ⁵² in the formula (6) are the same as R ¹¹ and R ¹² in the formula (2), respectively. Further, R ⁵³ in the formula (6) is the same as R ¹³ in the formula (2).
Examples of X ⁵ in the formula (6) include a tetravalent aliphatic hydrocarbon group having 1 to 24 carbon atoms.
The aliphatic hydrocarbon group may be linear or branched, and may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, the aliphatic hydrocarbon group may or may not have an ether bond between carbons. Furthermore, the aliphatic hydrocarbon group may be substituted with a hydroxy group or may not be substituted.
X ⁵ is preferably a tetravalent saturated aliphatic hydrocarbon group having 1 to 24 carbon atoms which may have an ether bond between carbons, and 4 to 18 carbon atoms which may have an ether bond between carbons. The tetravalent saturated aliphatic hydrocarbon group is more preferable.

（（７）式中、Ｒ^６１及びＲ^６２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^６３は、炭素数１〜８のアルキレン基であり、Ｘ^６は、炭素数２〜２４の脂肪族５〜６価アルコールから５個の水酸基が除かれた残基である。）

(In the formula (7), R ⁶¹ and R ⁶² are each independently an alkyl group having 1 to 8 carbon atoms, R ⁶³ is an alkylene group having 1 to 8 carbon atoms, and X ⁶ is a carbon number. It is a residue obtained by removing 5 hydroxyl groups from 2 to 24 aliphatic 5- or 6-valent alcohols.)

R ⁶¹ and R ⁶² in the formula (7) are the same as R ¹¹ and R ¹² in the formula (2), respectively. Further, R ⁶³ in the formula (7) is the same as R ¹³ in the formula (2).
Examples of X ⁶ in the formula (7) include a pentavalent aliphatic hydrocarbon group having 1 to 24 carbon atoms.
The aliphatic hydrocarbon group may be linear or branched, and may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, the aliphatic hydrocarbon group may or may not have an ether bond between carbons. Furthermore, the aliphatic hydrocarbon group may be substituted with a hydroxy group or may not be substituted.
As X ⁶ , a pentavalent saturated aliphatic hydrocarbon group having 2 to 24 carbon atoms which may have an ether bond between carbon atoms is preferable, and 5 to 18 carbon atoms which may have an ether bond between carbon atoms. The pentavalent saturated aliphatic hydrocarbon group is more preferable.

（（８）式中、Ｒ^７１及びＲ^７２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^７３は、炭素数１〜８のアルキレン基であり、Ｘ^７は、炭素数２〜２４の脂肪族６価アルコールから６個の水酸基が除かれた残基である。）

(In the formula (8), R ⁷¹ and R ⁷² are each independently an alkyl group having 1 to 8 carbon atoms, R ⁷³ is an alkylene group having 1 to 8 carbon atoms, and X ⁷ is a carbon number. It is a residue obtained by removing 6 hydroxyl groups from 2 to 24 aliphatic hexahydric alcohols.)

R ⁷¹ and R ⁷² in the formula (8) are the same as R ¹¹ and R ¹² in the formula (2), respectively. Further, R ⁷³ in the formula (8) is the same as R ¹³ in the formula (2).
Examples of X ⁷ in the formula (8) include hexavalent aliphatic hydrocarbon groups having 1 to 24 carbon atoms.
The aliphatic hydrocarbon group may be linear or branched, and may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, the aliphatic hydrocarbon group may or may not have an ether bond between carbons.
X ⁷ is preferably a C 6-24 saturated aliphatic hydrocarbon group having 2 to 24 carbon atoms which may have an ether bond between carbons, and 6 to 18 carbon atoms which may have an ether bond between carbons. The hexavalent saturated aliphatic hydrocarbon group of is more preferable.

Examples of the component (B) include octyl 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate and 3-(4-hydroxy-3,5-di-t-butylphenyl)propion. Decyl acid, dodecyl 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, stearyl 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, 3-( Oleyl 4-hydroxy-3,5-di-t-butylphenyl)propionate, benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy C7-C9 side chain alkyl ester, tetramethylene Bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], hexamethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], pentaerythritol Tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 3-(4-hydroxy-3,5-di-t-butylphenyl)propionic acid glycerin monoester and the like can be mentioned. .. Among these, benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy C7-C9 side chain alkyl ester, pentaerythritol tetrakis[3-(3,5-di-t-butyl- 4-hydroxyphenyl)propionate] is preferred.

As the component (B), one type may be used alone, or two or more types may be used in combination.
The content of the component (B) is not particularly limited, but is preferably 0.05 to 2% by mass, more preferably 0.1 to 1% by mass, based on the total mass of the grease. When the content of the component (B) is within the above-mentioned preferable range, outgassing is easily suppressed. Furthermore, it becomes easy to suppress the oxidative deterioration of the grease, and it becomes easy to suppress the generation of outgas even during use of the information recording/reproducing apparatus. Therefore, it becomes easy to reduce the total amount of outgas after the rolling bearing is manufactured and before it is used. Furthermore, it becomes easy to suppress poor lubrication due to oxidative deterioration of grease, and it becomes easy to improve durability.

From the viewpoint that the effect of the present invention is more easily obtained, it is preferable to use the component (B) among at least one antioxidant selected from the component (A) and the component (B). Further, it is preferable to have both the component (A) and the component (B). The component (A) is excellent in the antioxidant effect at a relatively high temperature exceeding 100° C., and the component (B) is particularly excellent in the antioxidant effect at room temperature to about 100° C. The rolling bearing of the information recording/reproducing apparatus has a wide operating range and operating speed of the swing arm, and a wide range of ambient temperature, and the grease contained in the bearing is also exposed to various changing temperatures. By having both the component (A) and the component (B), it is possible to reliably prevent the oxidative deterioration of the grease even when it is exposed to such various changing temperatures.
When both the component (A) and the component (B) are included, the total content of the component (A) and the component (B) is preferably 0.1 to 4% by mass, based on the total mass of the grease, and 0.1. 2 to 2 mass% is more preferable. Further, the mass ratio of the component (A) and the component (B) [content mass of the component (A)/content mass of the component (B)] is preferably 9/1 to 5/5, and 8/2 to 5/5. Is more preferable, and 8/2 to 6/4 is even more preferable.
Within the above preferable range, the amount of outgas can be further reduced.

<Base oil>
The base oil blended in the grease of the present invention is not particularly limited, but mineral oil, synthetic oil and the like can be mentioned.

As the mineral oil, a known mineral oil used as a base oil can be used, and examples thereof include naphthenic mineral oil, paraffinic mineral oil, hydrogenated mineral oil, solvent refined mineral oil and highly refined mineral oil.
Mineral oil may be used individually by 1 type, and may be used in combination of 2 or more type. For example, a plurality of mineral oils having different kinematic viscosities may be mixed and adjusted to a desired kinematic viscosity (average kinematic viscosity).

As the mineral oil, a refined mineral oil that is classified into Group III (GrIII) in the API (American Petroleum Institute, American Petroleum Institute) base oil category is preferable because a grease having a smaller outgas amount and excellent heat resistance can be obtained. Examples of the refined mineral oil include paraffinic mineral oil obtained by further hydrorefining a lubricating oil fraction obtained by distilling crude oil under atmospheric pressure. The refined mineral oil classified into Group III has a flash point of preferably 240° C. or higher, more preferably 250° C. or higher. Such a refined mineral oil has a high degree of refinement and can further reduce the amount of outgas. The reason for this is presumed that the low molecular weight components that cause outgas are reduced.

As the synthetic oil, a known synthetic oil used as a base oil can be used, and examples thereof include aliphatic hydrocarbon oils such as poly-α-olefin (PAO) and polybutene, aromatic hydrocarbon oils such as alkylbenzene and alkylnaphthalene, and polyol ester. , Ester oils such as phosphoric acid esters, ether oils such as polyphenyl ethers, polyalkylene glycol oils, silicone oils, and fluorine oils.
One of these synthetic oils may be used alone, or two or more thereof may be used in combination.

PAO is preferably used as the synthetic oil. As the PAO, a known PAO used as a base oil can be used without limitation, and for example, α-olefin (1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1- Pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 1-dococene, etc.) can be used as a starting material, and 3 to 5 mer or a mixture of 3 to 5 mer. Among them, as PAO, the amount of outgas is reduced, the evaporation loss at high temperature is reduced, the oxidative deterioration is suppressed, and an appropriate viscosity is obtained. A mixture of pentamers is preferred. A suitable viscosity range of this mixture is, for example, 27 to 54 mm ² /s (cSt) at 40°C. The 3 to 5 mer of the α-olefin having 8 to 12 carbon atoms may be used alone or in combination of two or more.
PAO may be used individually by 1 type, and may be used in combination of 2 or more type. For example, a plurality of PAOs having different kinematic viscosities may be mixed and adjusted to a desired kinematic viscosity (average kinematic viscosity).

As the base oil, mineral oil and PAO are preferably used in combination. In this case, it is preferable that the ratio of the mineral oil is 10 to 40 mass% with respect to 100 mass% of the base oil. Further, it is preferable that the content ratio of the PAO is higher than the content ratio of the mineral oil in the base oil.

Further, it is preferable that the kinematic viscosity ν ₁ of mineral oil at 40° C. is higher than the kinematic viscosity ν ₂ of PAO at 40° C. Since the kinematic viscosity ν ₁ of the mineral oil is higher than the kinematic viscosity ν _{2 of} PAO, the heat resistance of the mineral oil is likely to be increased. As a result, the amount of outgas from the mineral oil is reduced, and as a result, the amount of outgas from the base oil is likely to be reduced. Further, by combining PAO having a kinematic viscosity ν ₂ lower than the kinematic viscosity ν _{1 of} mineral oil, the kinematic viscosity ν of the base oil becomes low. Therefore, the grease is easily supplied to the portion of the rolling bearing where the rolling elements are rolling, and the lubricating effect of the grease is easily obtained.
The kinematic viscosity of the oil in the present invention means a value measured at 40° C. according to JIS K2283.
Further, when a plurality of base oils of the same kind having different kinematic viscosities are mixed, the kinematic viscosity of the mixture is considered as the kinematic viscosity of the base oil contained in the grease of the present invention.

The ratio ν ₁ /ν ₂ of the kinematic viscosity ν ₁ of mineral oil to the kinematic viscosity ν _{2 of} PAO is preferably 1.3 or more, and more preferably 1.5 or more, from the viewpoint of easily reducing the amount of outgas. Further, the ratio ν ₁ /ν ₂ is preferably 4 or less, more preferably 2 or less from the viewpoint of reducing the torque of the rolling bearing.

The kinematic viscosity ν _{1 of} mineral oil is preferably 40 mm ² /s or more, and more preferably 45 mm ² /s or more, from the viewpoint of easily reducing the amount of outgas. Further, the kinematic viscosity [nu ₁ of mineral oil, from the viewpoint of easily grease or base oil is supplied to the rolling surface of the rolling bearing, is preferably from 80 mm ² / s, more preferably at most 60 mm ² / s.

The kinematic viscosity ν _{2 of} PAO is preferably 20 mm ² /s or more, and more preferably 30 mm ² /s or more, from the viewpoint of easily reducing the amount of outgas. Further, the kinematic viscosity [nu ₂ of the PAO, from the viewpoint of the rolling elements of the rolling bearing is likely grease or base oil is supplied to the rolling surface is preferably not more than 60 mm ² / s, more preferably at most 40 mm ² / s.

Kinematic viscosity ν at 40 ° C. of the base oil is preferably ^{25~45mm 2 / s, 30~40mm 2 /} s is more preferable. When the kinematic viscosity ν of the base oil is at least the above lower limit value, the amount of outgas will be more easily reduced. If the kinematic viscosity ν of the base oil is less than or equal to the upper limit value, grease or base oil is easily supplied to the rolling surface of the rolling bearing, and applications requiring stable operation at low temperatures (for example, even at a low temperature of −30° C.) Even in in-vehicle applications where stable operation is required), it becomes easy to operate with low torque. In particular, when the ratio of mineral oil to 100 mass% of the base oil is 30 mass% or less, the outgas amount can be easily reduced if the kinematic viscosity ν of the base oil at 40° C. is 25 mm ² /s or more.

<Thickener>
The thickener serves to keep the grease semi-solid.
As the thickener, known thickeners usually used for rolling bearing greases can be used without limitation. As an example, as a known thickener used for the grease for rolling bearings of information recording/reproducing apparatus, for example, urea compounds, lithium soap, calcium soap, various complex soaps, silica gel, polytetrafluoroethylene, organized bentonite, etc. Can be mentioned. Among them, as the thickener, a urea compound is preferable, and a diurea compound having two urea bonds in one molecule is more preferable, from the viewpoint of excellent heat resistance.

Examples of the diurea compound include an aliphatic diurea compound whose terminal is an aliphatic group, an alicyclic diurea compound whose terminal is an alicyclic group, and an aromatic diurea compound whose terminal is an aromatic group.
Specific examples of diurea compounds include compounds obtained by the reaction of diisocyanates (phenylenediisocyanate, tolylenediisocyanate, etc.) with monoamines (octylamine, dodecylamine, stearylamine, aniline, p-toluidine, etc.).
Examples of lithium soaps include lithium stearate and lithium 12-hydroxystearate.
As the thickener, one kind may be used alone, or two or more kinds may be used in combination.

<Other ingredients>
The grease of the present invention may contain components other than those described above, if necessary.
As other components, known components usually used in grease can be used, and examples thereof include additives such as extreme pressure agents, rust preventives, oiliness improvers and metal deactivators.

Examples of extreme pressure agents include organic molybdenum compounds (molybdenum dithiocarbamate, molybdenum dithiophosphate, etc.), organic fatty acid compounds (oleic acid, naphthenic acid, succinic acid, etc.), organic phosphorus compounds (trioctyl phosphate, triphenyl phosphate, etc.) Triphenyl phosphate, triethyl phosphate and the like), phosphoric acid ester, zinc dithiocarbamate, antimony dithiocarbamate and the like.
As the extreme pressure agent, one type may be used alone, or two or more types may be used in combination.

Examples of the rust preventive agent include alkali metal salts or alkaline earth metal salts of organic sulfonic acids (calcium sulfonate, magnesium sulfonate, barium sulfonate, etc.), polyhydric alcohols (sorbitan monooleate, etc.) Partial esters and the like can be mentioned.
As the rust preventive agent, one type may be used alone, or two or more types may be used in combination.

The grease of the present invention may contain an antioxidant other than the component (A) and the component (B). However, from the viewpoint that the effects of the present invention are easily obtained, it is preferable that no antioxidant other than the components (A) and (B) is contained.

<Ratio of each component>
The ratio of the base oil to 100% by mass of the grease of the present invention is preferably 75 to 93% by mass, more preferably 80 to 90% by mass. When the ratio of the base oil is equal to or more than the lower limit value, grease or base oil is easily supplied to the rolling surface of the rolling bearing. When the ratio of the base oil is less than or equal to the above upper limit value, the grease is in a semi-solid state and hardly leaks or scatters.

10-40 mass% is preferable, and, as for the ratio of the mineral oil with respect to 100 mass% of base oils, 20-30 mass% is more preferable. When the proportion of mineral oil is at least the above lower limit value, it becomes easy to obtain a grease having a good balance of durability and torque smoothness. When the proportion of mineral oil is at most the above upper limit value, it becomes easy to obtain a grease in which the amount of outgas is sufficiently reduced.

The proportion of PAO relative to 100% by mass of base oil is preferably 50 to 90% by mass, more preferably 60 to 80% by mass. When the proportion of PAO is at least the lower limit value described above, it becomes easy to obtain a grease in which the amount of outgas is sufficiently reduced. When the proportion of PAO is equal to or less than the above upper limit value, it becomes easy to obtain a grease having a good balance of durability and torque smoothness.

70 mass% or more is preferable, as for the ratio of the total of mineral oil and PAO with respect to 100 mass% of base oil, 80 mass% or more is more preferable, and 90 mass% or more is further more preferable. When the total ratio of the mineral oil and PAO is equal to or more than the lower limit value, low torque grease can be easily obtained. The upper limit of the total ratio of the mineral oil and PAO is 100% by mass.

In the grease of the present invention, it is preferable that the proportion of PAO is larger than the proportion of mineral oil in the base oil, from the viewpoint of easily achieving both reduction of outgas amount and excellent durability.
The mass ratio of PAO to the mineral oil in the base oil (PAO/mineral oil) is preferably 1.25 to 9, more preferably 1.5 to 4. When the mass ratio is equal to or more than the lower limit value, the amount of outgas is likely to be reduced. When the mass ratio is not more than the upper limit value, durability and torque smoothness are likely to be enhanced.

The ratio of the thickener to 100% by mass of the grease of the present invention is preferably 7 to 20% by mass, more preferably 10 to 15% by mass. When the proportion of the thickener is not less than the above lower limit, it is easy to obtain a grease that is hard to leak and hard to scatter. When the proportion of the thickener is less than or equal to the above upper limit value, grease or base oil will be easily supplied to the rolling surface of the rolling bearing.

The ratio of the extreme pressure agent to 100% by mass of the grease of the present invention is preferably 0.2 to 4% by mass, more preferably 0.5 to 2% by mass.
The ratio of the rust preventive agent to 100% by mass of the grease of the present invention is preferably 0.2 to 4% by mass, more preferably 0.5 to 2% by mass.

[Information recording/reproducing device]
The rolling bearing, the rolling bearing device, and the information recording/reproducing device of the present invention can adopt known aspects except that the grease of the present invention is used. An example of the rolling bearing, rolling bearing device and information recording/reproducing device of the present invention will be described below.
The information recording/reproducing apparatus 1 of the present embodiment is an apparatus for writing on a disk (magnetic recording medium) D by a perpendicular recording method, and as shown in FIG. 1, a disk D, a swing arm 2, and an optical disk. It includes a waveguide 3, a laser light source 4, a head gimbal assembly (HGA) 5, a rolling bearing device 6, an actuator 7, a spindle motor (rotational drive unit) 8, a control unit 9, and a housing 10. There is.

The housing 10 accommodates each component of the information recording/reproducing apparatus 1.
The housing 10 has a quadrangular bottom 10a in a plan view, a peripheral wall (not shown) standing upright from the peripheral edge of the bottom 10a, and a lid (not shown) detachably fixed to the upper part of the peripheral wall to close the opening. And In the housing 10, the respective components are housed inside the peripheral wall portion on the bottom portion 10a. In FIG. 1, the peripheral wall and the lid are omitted for convenience.
The material of the housing 10 is not particularly limited, and examples thereof include metal materials such as aluminum.

The spindle motor 8 is attached to the bottom 10a of the housing 10 substantially at the center thereof. Further, the center hole formed in the center of the disc D is fitted into the spindle motor 8 so that the three discs D are detachably mounted. The spindle motor 8 can rotate the disk D in a fixed direction around the rotation axis L1.

The actuator 7 is attached to one corner portion of the bottom portion 10 a of the housing 10 so as to be located outside the disc D. The swing arm 2 extending toward the disc D is connected to the actuator 7. A rolling bearing device 6 is provided on the base end side of the swing arm 2. Driven by the actuator 7, the swing arm 2 rotates about a rotation axis L2 of the rolling bearing device 6 in a horizontal plane.

The swing arm 2 includes a base portion 2a connected to the actuator 7 and an arm portion 2b extending from the base portion 2a toward the disc D. The swing arm 2 is obtained, for example, by integrally forming the base portion 2a and the arm portion 2b by carving processing.
The base portion 2 a has a substantially rectangular parallelepiped shape, and is rotatably supported by the rolling bearing device 6 so as to surround the rolling bearing device 6.

The arm portion 2b has a flat plate shape and a taper shape that tapers from the base end portion toward the tip end portion. The arm portion 2b extends from the front surface (the surface opposite to the corner) 2d opposite to the rear surface 2c to which the actuator 7 is attached in the base 2a in the surface direction of the upper surface of the base 2a (in the horizontal plane). Is provided.
Further, in the swing arm 2 of this example, three arm portions 2b are provided in the height direction (vertical direction) of the base portion 2a so that the disc D is sandwiched between the arm portions 2b. That is, the arm portions 2b and the disc D are arranged so as to be alternately positioned in the height direction, and the arm portion 2b moves in the direction parallel to the disc surface (the surface of the disc D) D1 by driving the actuator 7. It is supposed to do.

A head gimbal assembly 5 is provided at the tip of the arm portion 2b of the swing arm 2. A laser light source 4 is provided on the side surface of the base 2 a of the swing arm 2. An optical waveguide 3 that connects the laser light source 4 and the head gimbal assembly 5 is provided on the base portion 2 a and the arm portion 2 b of the swing arm 2. As a result, light can be supplied from the laser light source 4 to the head gimbal assembly 5 via the optical waveguide 3.

The head gimbal assembly 5 includes a suspension 5a and a slider 5b attached to the tip of the suspension 5a.
The slider 5b has a near-field light generating element. When light is guided from the laser light source 4 to the slider 5b, the near-field light generating element generates near-field light. By using the near-field light, it is possible to record and reproduce various information on the disc D.
The near-field light generating element is composed of, for example, an optical minute aperture, a protrusion formed in a nanometer size, or the like.

The head gimbal assembly 5 moves in a direction parallel to the disk surface D1 together with the arm portion 2b of the swing arm 2 by driving the actuator 7. The swing arm 2 and the head gimbal assembly 5 are adapted to be retracted from the disk D by driving the actuator 7 when the rotation of the disk D is stopped.

The control unit 9 is connected to the laser light source 4. The control unit 9 can control the luminous flux of the light supplied to the slider 5b of the head gimbal assembly 5 by the current modulated according to the information.

<Rolling bearing device>
As shown in FIGS. 2 and 3, the rolling bearing device 6 includes a shaft 20, a sleeve 21 provided outside the shaft 20 coaxially with the shaft 20, and a sleeve 21 provided between the shaft 20 and the sleeve 21. And two rolling bearings 22.

The shaft 20 is a cylindrical rod-shaped member, and is erected from the bottom portion 10 a of the housing 10. The central axis of the shaft 20 serves as the rotation axis L2 when the swing arm 2 rotates.
A flange portion 20b having a diameter larger than that of the body portion 20a and a diameter-reduced portion 20c having a diameter smaller than that of the body portion 20a are sequentially provided on a portion of the shaft 20 on the bottom portion 10a side of the housing 10 toward the base end. ing. A male screw 20d is formed on the outer peripheral surface of the reduced diameter portion 20c.
By inserting the reduced diameter portion 20c of the shaft 20 into the hole 10b provided in the bottom portion 10a of the housing 10 and screwing the female screw 10c formed on the inner peripheral surface of the hole 10b and the male screw 20d of the reduced diameter portion 20c. The shaft 20 is erected on the bottom portion 10a of the housing 10. At this time, the lower surface of the flange portion 20b is in contact with the bottom portion 10a of the housing 10, whereby the shaft 20 is positioned in the height direction.

The sleeve 21 is a member formed in a cylindrical shape. The inner diameter of the sleeve 21 is substantially the same as the outer diameter of the flange portion 20b.
The sleeve 21 is installed so as to surround the shaft 20 from the outside in the radial direction, and its inner peripheral surface is separated from the outer peripheral surface of the shaft 20 at a predetermined interval. The central axis of the shaft 20 and the central axis of the sleeve 21 coincide with each other.
The sleeve 21 is directly press-fitted into the mounting hole 2e formed in the base portion 2a of the swing arm 2, is press-fitted through an elastic body such as a corrugated metal ring, or is adhesively fitted. By being combined, they are integrally combined with the swing arm 2.

A spacer portion 21 a is formed at the center of the inner peripheral surface of the sleeve 21 in the height direction so as to project inwardly over the entire circumference in the circumferential direction. Between the shaft 20 and the sleeve 21, two rolling bearings 22 are installed above and below the spacer portion 21a, respectively, and the distance between these two rolling bearings 22 is maintained at a predetermined distance.

<Rolling bearing>
The two rolling bearings 22 provided in the rolling bearing device 6 are the same.
As shown in FIGS. 3 to 6, the rolling bearing 22 includes an inner ring 30, an outer ring 31, a retainer 32, a plurality of rolling elements 33, and two shield plates 34.

The inner ring 30 is a cylindrical member.
The inner diameter of the inner ring 30 is dimensioned so that the shaft 20 can be inserted. In this embodiment, the inner diameter of the inner ring 30 is slightly larger than the outer diameter of the shaft 20. The shaft 20 is inserted inside the inner ring 30, and the inner ring 30 is fixed to the shaft 20 with an adhesive or the like.
The inner diameter of the inner ring 30 may be the same as or slightly smaller than the outer diameter of the shaft 20 as long as it can be installed on the shaft 20. In this case, the shaft 20 is press-fitted and fixed to the inner ring 30.

In the rolling bearing 22, a so-called inner ring preload can be adopted in which the inner ring 30 is fixed to the shaft 20 in a state where a preload is applied to the inner ring 30 relative to the shaft 20 in the axial direction. Accordingly, the rolling bearing 22 can be made highly rigid, and the resonance frequency (resonance point) of the rolling bearing device 6 can be increased. Therefore, the rolling bearing device 6 that can support higher speed rotation is obtained.
In the rolling bearing 22, a so-called outer ring preload may be adopted in which the outer ring 31 is fixed to the sleeve 21 in a state where a preload is applied to the outer ring 31 relative to the shaft 20 in the axial direction.

A concave inner ring rolling surface 30 a for guiding the rolling of the rolling elements 33 is formed on the outer circumferential surface of the inner ring 30 over the entire circumference of the inner ring 30. The inner ring rolling surface 30a has an arc-shaped cross section when cut along a plane passing through the center axis of the inner ring 30.
Examples of the material of the inner ring 30 include a metal material such as stainless steel. The inner ring 30 can be manufactured by, for example, forging or machining.

The outer ring 31 is a cylindrical member similar to the inner ring 30 having a larger diameter than the inner ring 30.
The outer ring 31 is fixed to the inner side of the sleeve 21, so that the outer ring 31 is installed outside the inner ring 30 while being separated from the inner ring 30. The inner ring 30 and the outer ring 31 are coaxially installed so that their central axes coincide with the central axis of the shaft 20.

At the axially intermediate portion of the inner peripheral surface of the outer ring 31, a concave outer ring rolling surface 31 a that guides the rolling of the rolling elements 33 is provided so as to face the inner ring rolling surface 30 a of the inner ring 30. It is formed all around. The outer ring rolling surface 31a has an arc-shaped cross section when cut along a plane passing through the central axis of the outer ring 31.
Examples of the material of the outer ring 31 include a metal material such as stainless steel. The inner ring 30 can be manufactured by, for example, forging or machining.

As shown in FIG. 6, the retainer 32 is formed of an annular body portion 32a and an upper portion of the body portion 32a, and has seven pairs of claw portions 32b that stand up in an arc shape so that the mutual distances approach each other toward the tips. , 32c. The seven pairs of claw portions 32b and 32c are provided at equal intervals in the circumferential direction of the retainer 32. Inside the pair of claw portions 32b and 32c, a ball pocket B having a substantially circular shape in a front view, which holds the rolling element 33 so as to be rollable, is formed.
The number of pairs of claws, that is, the number of ball pockets B is not limited to 7, and may be 6 or less, or 8 or more.

The inner diameter of the retainer 32 is larger than the outer diameter of the inner ring 30, and the outer diameter of the retainer 32 is smaller than the inner diameter of the outer ring 31. With the retainer 32 installed between the inner ring 30 and the outer ring 31, the rolling elements 33 are rotatably held in the respective ball pockets B. In this way, the rolling elements 33 are arranged between the inner ring rolling surface 30a of the inner ring 30 and the outer ring rolling surface 31a of the outer ring 31 in a state where the inner ring 30, the outer ring 31 and the retainer 32 do not interfere with each other.
The retainer 32 can rotate about the central axis L2 in a state where the rolling elements 33 are rollably held in the respective ball pockets B.
The material of the retainer 32 is not particularly limited, and examples thereof include resins such as polyamide resin.

A grease pocket G having a depth smaller than that of the ball pocket B is formed between the pair of claw portions 32b and 32c in the upper portion of the retainer 32 and the pair of adjacent claw portions 32b and 32c. That is, in the retainer 32, the ball pockets B and the grease pockets G are alternately formed in the circumferential direction by the plurality of pairs of claw portions 32b and 32c.

When the rolling element 33 rotates together with the retainer 32 in a state where the grease of the present invention is placed in the grease pocket G and the rolling element 33 is placed in the ball pocket B, the rolling from the grease pocket G to the inner ring 30 and the outer ring 31 is performed. Grease seeps out between the moving body 33 and the lubricating effect of the grease is obtained.
By using the grease for the rolling bearing 22 using the grease pocket G, the amount of grease used can be reduced. This makes it easy to suppress an increase in the amount of grease and an increase in the torque of the rolling bearing 22, and it becomes easy to obtain a sufficient degree of cleanliness required for reading and writing to the disk D.

The rolling element 33 in this example is spherical. The rolling element 33 is arranged in the ball pocket B of the retainer 32 between the inner ring rolling surface 30a of the inner ring 30 and the outer ring rolling surface 31a of the outer ring 31, and is formed on the inner ring rolling surface 30a and the outer ring rolling surface 31a. It is designed to roll along. The rolling elements 33 are evenly arranged in the circumferential direction by the retainer 32.
Although the number of rolling elements 33 is 7 in this example, it may be determined according to the number of ball pockets B in the retainer 32, and may be 6 or less, or 8 or more.
Examples of the material of the rolling elements 33 include metal materials such as bearing steel.

The shield plate 34 is an annular plate member that closes up and down the annular space formed between the inner ring 30 and the outer ring 31. The shield plates 34 are installed above and below the retainer 32 and the plurality of rolling elements 33 between the inner ring 30 and the outer ring 31. Each shield plate 34 is fixed to the outer ring 31 in a state where the outer peripheral edge portion of the shield plate 34 is inserted into the annular groove 40 for engagement formed in the outer ring 31.

(Mechanism of action)
In the information recording/reproducing apparatus 1, the grease of the present invention is arranged in the grease pocket G of the retainer 32 in the rolling bearing 22. When the swing arm 2 is rotated by driving the actuator 7, the grease arranged in the grease pocket G passes through the inner ring 30, the outer ring 31, and the side surface of the retainer 32, and is supplied between the inner ring 30, the outer ring 31, and the rolling element 33. Therefore, the lubricating effect of the grease is exhibited.
Since the grease of the present invention is used in the information recording/reproducing apparatus 1, the amount of outgas is sufficiently reduced. Therefore, outgas is less likely to be accumulated in the gap between the head gimbal assembly and the disk D, etc., and stable reading and writing can be performed. Also, excellent durability can be secured, and a low torque and excellent torque smoothness can be maintained for a long period of time.

(Other embodiments)
The rolling bearing, the rolling bearing device, and the information recording/reproducing device of the present invention are not limited to those described above as long as they use the grease of the present invention.
For example, the information recording/reproducing apparatus 1 including the rolling bearing 22 and the rolling bearing device 6 uses near-field light, but a rolling bearing using the grease of the present invention and a general HDD including the rolling bearing device, It may be an optical disk D device or the like.
Further, the application of the grease of the present invention is not limited to the information recording/reproducing apparatus, but can be applied to, for example, an electronic apparatus manufacturing apparatus that requires reduction of dust and outgas from the grease. Examples of the electronic device manufacturing apparatus include a semiconductor manufacturing apparatus, a liquid crystal manufacturing apparatus, a printed circuit board manufacturing apparatus, and the like.
Furthermore, the grease of the present invention can be used not only for rolling bearings but also as grease to be enclosed in, for example, a linear guide or a ball screw.

Further, the rolling bearing device may not include the sleeve. Specifically, for example, an annular spacer ring that keeps the distance between the rolling bearings at a predetermined distance is provided between two rolling bearings that are axially separated from each other on the outer side of the shaft, and a sleeve is provided. There may be no rolling bearing device. In this case, the outer ring of the rolling bearing can be directly press-fitted or adhesively fitted into the mounting hole formed at the base of the swing arm.
Further, the rolling elements in the rolling bearing may be cylindrical rollers.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following description.
The raw materials used in this example are as follows.
The kinematic viscosities of mineral oil, PAO and base oil in this example are measured at 40° C. according to JIS K2283 using a Canon-Fenske viscometer.

<(A) component>
A-1: Di(4-octylphenyl)amine.
<(B) component>
B-1: Benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy C7-C9 side chain alkyl ester.
B-2: Pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate].

<(A') component, comparative component of (A) component>
A′-1: Bis sebacate (1,2,2,6,6-pentamethyl-4-piperidyl).
<Comparative component of component (B') and component (B)>
B'-1: 2,6-di-tert-butyl-p-cresol.

[Measurement of outgas amount]
The amount of outgas of each of the following samples was measured as follows. The results are shown in Table 1.

<Measurement sample>
Reference sample: Refined mineral oil (those classified as Group III in the API base oil category.
Kinematic viscosity ν ₁ =47 mm ² /s).
Sample 1: A-1 with 0.2% by mass (based on the total mass) added to the reference sample.
Sample 2: 0.2% by mass (based on the total mass) of B-1 was added to the standard sample.
Sample 3: 0.2% by mass (based on the total mass) of B-2 was added to the standard sample.
Sample 4: 0.1% by mass of A′-1 and 0.1% by mass of zinc diamyldithiocarbamate (Zn-DTC) (based on the total mass) to the standard sample.
Sample 5: 0.2% by mass (based on the total mass) of B'-1 was added to the standard sample.

(Method of measuring outgas amount)
Each sample (4.5 to 5.5 mg) was evenly coated on a 15 mm square aluminum foil with a glass rod to obtain a measurement sample. The measurement sample was heated in an oven at 85° C. for 3 hours together with 5 μL (100 ng) of a standard reagent (hexadecane), and the generated gas was adsorbed to the collection tube. Then, the collection tube was installed in a thermal desorption device (TD-100) and heated to 320° C., and the gas generated from the collection tube was sent to a gas chromatograph mass spectrometer (GC-MS). In GC-MS, hold at 40° C. for 2 minutes, raise the temperature to 280° C. at 12° C./minute for 20 minutes, and hold at 280° C. for 20 minutes to obtain chromatogram data, and obtain the inside of GC-MS. The component was identified by the library of. The amount of outgas was calculated as the standard reagent based on the chromatogram peak (corresponding to 100 ng) of the standard reagent (hexadecane).

As shown in Table 1, Samples 1 to 3 containing the component (A) or the component (B) had a reduced outgas amount as compared with the reference sample. On the other hand, the outgas amount of the sample 4 containing the component (A′) was equivalent to that of the reference sample, and the outgas amount of the sample 5 containing the component (B′) was larger than that of the reference sample.
That is, it was confirmed from the results in Table 1 that the amount of outgas can be reduced by adding the component (A) or the component (B) to the base oil.

[Examples 1 and 2]
Each grease of Examples 1-2 was prepared as follows. Further, for each of the obtained greases of Examples 1 and 2, the measurement of the amount of outgas, the oxidation stability test, the durability test, and the grease bump test were performed as follows. The results are shown in Table 2.

<Example 1>
Refined mineral oil (classified as Group III in the API base oil category and having a flash point of 250° C. or higher. Kinematic viscosity ν ₁ =47 mm ² /s) and PAO (MIX; α-olefin having 8 or 10 carbon atoms) Was mixed with a mixture of 3 to 5 mers (having a kinematic viscosity ν ₂ =30 mm ² /s) at a mass ratio of 3:7 to obtain a base oil (kinematic viscosity ν=34 mm ² /s).
Then, the base oil and an alicyclic diurea compound (thickener) were used to form a grease, and A-1, B-1 and a rust inhibitor were added and mixed to prepare a grease of Example 1. The proportion of each component is such that the base oil is 85.8% by mass, the thickener is 12.5% by mass, A-1 is 0.5% by mass, and B-1 is 0.2% with respect to 100% by mass of grease. % By mass, and 1.0% by mass in rust preventive agent.

<Example 2>
The grease of Example 2 was prepared in the same manner as in Example 1 except that an extreme pressure agent was added and mixed in addition to A-1, B-1 and the rust preventive agent. The proportion of each component is 84.8% by mass of base oil, 12.5% by mass of thickener, 0.5% by mass of A-1 and 0.2% of B-1 with respect to 100% by mass of grease. %, the antirust agent was 1.0% by mass, and the extreme pressure agent was 1.0% by mass.

[Reference Example 1]
With respect to the rolling bearing grease α of a commercially available information recording/reproducing apparatus, the amount of outgas, the oxidation stability test, the durability test, and the grease bump test were performed as follows. The results are shown in Table 2. The grease α contains a urea compound as a thickener.

(Measurement of outgas amount)
Above (outgas amount) except that a 15 mm square aluminum foil was evenly coated with each grease (4.5 to 5.5 mg) of Examples 1 and 2 and Reference Example 1 by a glass rod was used as a measurement sample. The amount of outgas of each grease was measured in the same manner as the measurement method).

(Oxidation stability test)
According to JIS K2220, the sample pressurized to 755 kPa with an oxygen cylinder was heated to 99° C., and the pressure drop after 100 hours was measured.
This test is mainly for evaluating the oxidation stability when the grease is used for a long time, and the smaller the value, the better the oxidation stability.

(An endurance test)
The rolling bearing device 6 illustrated in FIGS. 3 to 6 is manufactured, the grease of each example is arranged in the grease pocket G of the retainer 32, and the continuous operation is performed under the following operating conditions, and the continuous operation with respect to the initial torque before the continuous operation is performed. The torque fluctuation width (hash) was measured as the ratio of the subsequent torque.
<<Operating conditions>>
Operating frequency: 30Hz
Operating angle: 10 deg
Operating time: 100 hours Operating environment temperature: 80°C

(Grease bump test)
The rolling bearing device 6 illustrated in FIGS. 3 to 6 is manufactured, the grease of each example is arranged in the grease pocket G of the retainer 32, the continuous operation is performed under the following operating conditions, and the torque immediately after the continuous operation is measured, It evaluated according to the following criteria.
<<Operating conditions>>
Operating frequency: 15Hz
Operating angle: 5 deg
Operating time: 50 hours Operating environment temperature: Room temperature << Evaluation criteria >>
◯: The torque immediately after the continuous operation hardly changes as compared with the initial torque before the continuous operation.
X: The torque immediately after the continuous operation changes greatly compared to the initial torque before the continuous operation.

As shown in Table 2, the greases of Examples 1 and 2 containing the component (A) and the component (B) had a small amount of outgas and were excellent in oxidation stability. Further, in Examples 1 and 2, torque fluctuation was small in both the durability test and the grease bump test, and excellent durability was exhibited.
On the other hand, in the commercially available rolling bearing grease α for information recording/reproducing apparatuses, the amount of outgas could not be sufficiently reduced, and the oxidation stability was also insufficient. Further, the grease α had a large torque fluctuation range in the durability test and was inferior in durability to Examples 1 and 2. Furthermore, in the grease bump test, the torque after continuous operation increased up to 6 times compared with the torque before continuous operation. It is considered that this is because the oxidized and deteriorated grease is accumulated at the edge portion of the operation range in the continuous operation to form bumps, or the wear is severe at the edge portion of the operation range in the continuous operation.

Furthermore, the tendency of oxidative deterioration when the grease of Example 2 and the commercially available grease α were held at 130° C. was observed by FT-IR. As a result, the tendency of oxidative deterioration of the grease α was confirmed after 1000 hours, whereas the tendency of the oxidative deterioration of the grease of Example 2 was not confirmed even after 2000 hours.

<Samples 6 to 41>
Evaluation oils containing the base oil and antioxidant shown in Table 3 were prepared. The content of the antioxidant was 0.2% by mass based on the total mass of the base oil and the antioxidant. When two kinds of antioxidants were used in combination, they were added so that the total amount would be 0.2% by mass.
The refined mineral oils GrIII and PAO(MIX) in Table 3 are the same as those used in Example 1.
“Refined mineral oil GrIII+PAO(MIX)” in Table 3 is a mixture of mineral oil and PAO in a mass ratio of 3:7, and is the same as the base oil of Example 1.
ADE in Table 3 is an alkyl diphenyl ether, and its kinematic viscosity ν ₂ is 100 mm ² /s (40° C.).
PE in Table 3 is pentaerythritol, and its kinematic viscosity ν ₂ is 120 mm ² /s (40° C.).
PAO (decene) in Table 3 is a mixture of trimers and pentamers (alpha)-olefin having 10 carbon atoms as a raw material (kinematic viscosity ν ₂ =30 mm ² /s (40° C.)).
A-1 and B-1 in Table 3 are the same as the antioxidant used in Example 1. “(A-1)+(B-1)” is a mixture of the two antioxidants, and the mixing ratio thereof is 1:1 on a mass basis.
A'-1 and B'-1 in Table 3 are the same as those used in Samples 4 and 5 above.

Looking at Table 3 in tandem, P1-A to P6-A, P1-E to P6-E and P1-F to P6-F are samples according to the comparative example containing the antioxidant of the comparative component (comparative product). ).
Looking at Table 3 in tandem, P1-B to P6-B, P1-C to P6-C and P1-D to P6-D are in accordance with the examples including the specific antioxidant included in the present invention. It is a sample (implemented product).

The amount of outgas was measured in the same manner as in Samples 1-5. The results are shown in Tables 4-9.

(Confirmation of oxidative deterioration)
5 g of each sample shown in Table 3 was placed in a beaker (dimension outside diameter×height: 30 mm×40 mm), and each beaker was allowed to stand in a constant temperature bath at 100° C. After 240 hours, the samples in each beaker were measured by FT-IR every 24 hours to evaluate the presence or absence of oxidative deterioration. In parentheses below the sample name in Table 10, the elapsed time (unit: time (h)) at which oxidative deterioration was first confirmed is shown. In addition, about the sample which was not measured, "-" was described in parentheses.

(Measurement of evaporation loss)
In a petri dish having an outer diameter of 41 mm (inner diameter of 37 mm) and a height of 8 mm (storage height of 5 mm), 5 g of the grease of Example 2 and Reference Example 1 was put, and the surface was smoothed at 85° C. and 100° C. Each petri dish was allowed to stand in a constant temperature bath set at each temperature of 130°C. Each petri dish was taken out at regular intervals, the weight was measured, and the evaporation loss (mass %) was calculated from the amount of change. The measurement was stopped when the oxidative deterioration became clear.
The results of the evaporation loss of each grease are shown in FIG. 7 (85° C.), FIG. 8 (100° C.), and FIG. 9 (130° C.) as graphs in which the horizontal axis represents elapsed time and the vertical axis represents evaporation loss. The smaller the evaporation loss, the more stable the grease. As is clear from the graph, in Example 2, the evaporation loss was smaller than that in Reference Example 1 under any temperature condition.

1 Information Recording/Reproducing Device 2 Swing Arm 3 Optical Waveguide 4 Laser Light Source 5 Head Gimbal Assembly 6 Rolling Bearing Device 7 Actuator 8 Spindle Motor 9 Controller 10 Housing 20 Shaft 21 Sleeve 22 Rolling Bearing 30 Inner Ring 31 Outer Ring 32 Retainer 33 Rolling Body 34 Shield Plate B Ball pocket G Grease pocket

Claims (11)

Base oil,
Thickener,
At least one antioxidant selected from the amine-based antioxidant (A) represented by the following general formula (1) and the phenol-based antioxidant (B) represented by the following general formula (2): Including,
The base oil contains a mixture of a trimer and a pentamer of three types of α-olefins having 8, 10, and 12 carbon atoms as a raw material, and a grease for rolling bearings.

(In the formula (1), R ¹ and R ² are each independently an alkyl group having 1 to 12 carbon atoms or a hydrogen atom. However, at least one of R ¹ and R ² has 1 to 12 carbon atoms. Is an alkyl group.)

(In the formula (2), R ¹¹ and R ¹² are each independently an alkyl group having 1 to 8 carbon atoms, R ¹³ is an alkylene group having 1 to 8 carbon atoms, and n is 1 to 6). X ¹ is a residue obtained by removing n hydroxyl groups from an aliphatic m-hydric alcohol having 1 to 24 carbon atoms, and m is 1 to 6 and is a number of n or more. However, when n is 5 or 6, the number of carbon atoms of the aliphatic m-hydric alcohol of X ¹ is 2 to 24.) Base oil,
Thickener,
An amine-based antioxidant (A) represented by the following general formula (1) ,
Phenolic antioxidant represented by the following general formula (2) (B), and comprises,
The base oil contains refined mineral oil classified into Group III in the base oil category defined by the American Petroleum Institute, and has a flash point of 240° C. or higher.

(In the formula (1), R ¹ and R ² are each independently an alkyl group having 1 to 12 carbon atoms or a hydrogen atom. However, at least one of R ¹ and R ² has 1 to 12 carbon atoms. Is an alkyl group.)

(In the formula (2), R ¹¹ and R ¹² are each independently an alkyl group having 1 to 8 carbon atoms, R ¹³ is an alkylene group having 1 to 8 carbon atoms, and n is 1 to 6). X ¹ is a residue obtained by removing n hydroxyl groups from an aliphatic m-hydric alcohol having 1 to 24 carbon atoms, and m is 1 to 6 and is a number of n or more. However, when n is 5 or 6, the number of carbon atoms of the aliphatic m-hydric alcohol of X ¹ is 2 to 24.) The rolling bearing grease according to claim 1, comprising the amine-based antioxidant (A) and the phenol-based antioxidant (B). The rolling bearing grease according to any one of claims 1 to 3, wherein the amine-based antioxidant (A) is contained in a larger amount than the phenol-based antioxidant (B) on a mass basis. The base oil contains refined mineral oil classified into Group III in the base oil category defined by the American Petroleum Institute, and the flash point of the refined mineral oil is 250° C. or higher. The rolling bearing grease according to any one of claims. The rolling bearing grease according to any one of claims 2 to 5, wherein the base oil contains a mixture of a trimer and a pentamer of an α-olefin having 8 to 12 carbon atoms. The rolling bearing grease according to any one of claims 1 to 6, which is used for a rolling bearing of an information recording/reproducing apparatus. The rolling bearing grease according to any one of claims 1 to 6, which is used for a rolling bearing of an electronic device manufacturing apparatus. A rolling bearing comprising the rolling bearing grease according to claim 1. A rolling bearing device comprising a shaft and the rolling bearing according to claim 9. An information recording/reproducing device comprising the rolling bearing device according to claim 10.

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