WO2024122448A1 - 流体動圧軸受、スピンドルモータおよびディスク駆動装置 - Google Patents

流体動圧軸受、スピンドルモータおよびディスク駆動装置 Download PDF

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Publication number
WO2024122448A1
WO2024122448A1 PCT/JP2023/043012 JP2023043012W WO2024122448A1 WO 2024122448 A1 WO2024122448 A1 WO 2024122448A1 JP 2023043012 W JP2023043012 W JP 2023043012W WO 2024122448 A1 WO2024122448 A1 WO 2024122448A1
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Prior art keywords
carbon atoms
group
branched alkyl
disk drive
fluid dynamic
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PCT/JP2023/043012
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English (en)
French (fr)
Japanese (ja)
Inventor
啄也 北島
順 八町
真太郎 ▲高▼田
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MinebeaMitsumi Inc
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MinebeaMitsumi Inc
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Priority to CN202380061000.XA priority Critical patent/CN119768490A/zh
Priority to US18/997,140 priority patent/US20260022306A1/en
Priority to JP2024562728A priority patent/JPWO2024122448A1/ja
Publication of WO2024122448A1 publication Critical patent/WO2024122448A1/ja
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M105/00—Lubricating compositions characterised by the base-material being a non-macromolecular organic compound
    • C10M105/78—Lubricating compositions characterised by the base-material being a non-macromolecular organic compound containing boron
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M169/00—Lubricating compositions characterised by containing as components a mixture of at least two types of ingredient selected from base-materials, thickeners or additives, covered by the preceding groups, each of these compounds being essential
    • C10M169/04—Mixtures of base-materials and additives
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M105/00—Lubricating compositions characterised by the base-material being a non-macromolecular organic compound
    • C10M105/08—Lubricating compositions characterised by the base-material being a non-macromolecular organic compound containing oxygen
    • C10M105/32—Esters
    • C10M105/34—Esters of monocarboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M105/00—Lubricating compositions characterised by the base-material being a non-macromolecular organic compound
    • C10M105/08—Lubricating compositions characterised by the base-material being a non-macromolecular organic compound containing oxygen
    • C10M105/32—Esters
    • C10M105/36—Esters of polycarboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M139/00—Lubricating compositions characterised by the additive being an organic non-macromolecular compound containing atoms of elements not provided for in groups C10M127/00 - C10M137/00
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C17/00—Sliding-contact bearings for exclusively rotary movement
    • F16C17/02—Sliding-contact bearings for exclusively rotary movement for radial load only
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C17/00—Sliding-contact bearings for exclusively rotary movement
    • F16C17/04—Sliding-contact bearings for exclusively rotary movement for axial load only
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B19/00—Driving, starting, stopping record carriers not specifically of filamentary or web form, or of supports therefor; Control thereof; Control of operating function ; Driving both disc and head
    • G11B19/20—Driving; Starting; Stopping; Control thereof
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B33/00—Constructional parts, details or accessories not provided for in the other groups of this subclass
    • G11B33/12—Disposition of constructional parts in the apparatus, e.g. of power supply, of modules
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
    • C10M2207/28—Esters
    • C10M2207/281—Esters of (cyclo)aliphatic monocarboxylic acids
    • C10M2207/2815—Esters of (cyclo)aliphatic monocarboxylic acids used as base material
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
    • C10M2207/28—Esters
    • C10M2207/282—Esters of (cyclo)aliphatic oolycarboxylic acids
    • C10M2207/2825—Esters of (cyclo)aliphatic oolycarboxylic acids used as base material
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2215/00—Organic non-macromolecular compounds containing nitrogen as ingredients in lubricant Compositions
    • C10M2215/02—Amines, e.g. polyalkylene polyamines; Quaternary amines
    • C10M2215/04—Amines, e.g. polyalkylene polyamines; Quaternary amines having amino groups bound to acyclic or cycloaliphatic carbon atoms
    • C10M2215/041—Amines, e.g. polyalkylene polyamines; Quaternary amines having amino groups bound to acyclic or cycloaliphatic carbon atoms used as base material
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2227/00—Organic non-macromolecular compounds containing atoms of elements not provided for in groups C10M2203/00, C10M2207/00, C10M2211/00, C10M2215/00, C10M2219/00 or C10M2223/00 as ingredients in lubricant compositions
    • C10M2227/06—Organic compounds derived from inorganic acids or metal salts
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2227/00—Organic non-macromolecular compounds containing atoms of elements not provided for in groups C10M2203/00, C10M2207/00, C10M2211/00, C10M2215/00, C10M2219/00 or C10M2223/00 as ingredients in lubricant compositions
    • C10M2227/06—Organic compounds derived from inorganic acids or metal salts
    • C10M2227/061—Esters derived from boron
    • C10M2227/0615—Esters derived from boron used as base material
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2020/00—Specified physical or chemical properties or characteristics, i.e. function, of component of lubricating compositions
    • C10N2020/01—Physico-chemical properties
    • C10N2020/077—Ionic Liquids
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2040/00—Specified use or application for which the lubricating composition is intended
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2040/00—Specified use or application for which the lubricating composition is intended
    • C10N2040/02—Bearings
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2040/00—Specified use or application for which the lubricating composition is intended
    • C10N2040/14—Electric or magnetic purposes
    • C10N2040/18—Electric or magnetic purposes in connection with recordings on magnetic tape or disc

Definitions

  • the present invention relates to a fluid dynamic bearing filled with a lubricating oil composition containing an ionic liquid that is less likely to cause read-write errors, and a spindle motor equipped with the fluid dynamic bearing.
  • the present invention also relates to a disk drive device equipped with the spindle motor.
  • Various lubricants such as grease and oil are used in the pivot assemblies used in the fulcrum portions of actuators in hard disk drives (HDDs) and in the bearings built into spindle motors to facilitate the operation of these parts and the drive of the devices.
  • HDDs hard disk drives
  • a rolling bearing filled with grease obtained by blending a diurea compound having at least one type of alicyclic hydrocarbon group and aliphatic hydrocarbon group in the skeleton as a thickening agent with a base oil containing an aromatic ester oil (Patent Document 1).
  • Ionic liquids are salts in a liquid state that are composed only of ions (anions and cations). Ionic liquids have characteristics such as low vapor pressure (non-volatility), high thermal stability, flame retardancy, low viscosity, and high ionic conductivity. In addition, various physical properties can be designed by combining cations and anions, so they are expected to be applied to various technical fields, including electrolytes and solvents. Due to the aforementioned characteristics of low vapor pressure, high thermal stability, and low viscosity, application of ionic liquids to the above-mentioned lubricants has also been considered. For example, a lubricant composition to which an ionic liquid has been added has been proposed for the purpose of maintaining low friction for a long period under high load conditions (Patent Document 2).
  • One of the causes of read/write errors in HDDs is the volatilization or evaporation of lubricant components sealed in the bearings built into the actuator or spindle motor.
  • the volatilized or evaporated lubricant components cool and condense on the surface of the magnetic disk or on the magnetic head, undergoing a phase transition to a liquid or solid, which is believed to be one of the causes of read/write errors. It is possible to suppress the amount of volatilization or evaporation of lubricant components that accompanies the temperature rise during HDD operation by selecting components such as low-volatility base oils, but it is difficult to completely eliminate the volatilization or evaporation of components. Furthermore, in conventional lubricants to which an ionic liquid has been added, including the lubricant composition described in Patent Document 2, no proposal has been made to date that takes into consideration the evaporation of components contained in the lubricant, such as the base oil.
  • the present invention aims to provide a fluid dynamic bearing filled with a lubricating oil composition containing a base oil and a specific ionic liquid, and to provide a spindle motor and a disk drive device equipped therewith that, by incorporating the fluid dynamic bearing into a spindle motor, can suppress evaporation of the lubricating oil composition provided in the fluid dynamic bearing, and even if the components of the lubricating oil composition evaporate or volatilize, can suppress adhesion of the evaporated/volatile components to magnetic disks, etc., thereby suppressing the occurrence of read/write errors in the HDD.
  • One aspect of the present invention is a fluid dynamic bearing containing a lubricating oil composition containing a base oil and an ionic liquid, the ionic liquid being: At least one cation selected from the group consisting of tetraalkylammonium cations represented by the following formula (B): An ionic liquid having at least one anion selected from the group consisting of a borate anion represented by the following formula (C-1), a borate anion represented by the following formula (C-2), and a borate anion represented by the following formula (C-3): This relates to fluid dynamic bearings.
  • R 5 , R 6 , R 7 , and R 8 each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms.
  • R 9 , R 10 , R 11 and R 12 each independently represent a linear or branched alkyl group having 1 to 22 carbon atoms.
  • the present invention also relates to a spindle motor equipped with a fluid dynamic bearing.
  • the present invention also relates to a disk drive device equipped with a spindle motor.
  • FIG. 1 is a conceptual diagram illustrating an example of a main structure of a spindle motor according to the present invention.
  • 1 is a schematic diagram illustrating an example of the structure of a drive device (disk drive device) according to the present invention;
  • the smaller fly height may create a negative pressure state between the magnetic head and the disk, in which case the surrounding gas may be compressed and condensed toward the space between the magnetic head and the disk, causing even a small amount of evaporated or volatile components to liquefy and adhere to the disk, etc.
  • the number of disks in the device has increased, and disk drive devices equipped with nine or more 3.5-inch disks have been released. In such devices, the spatial volume within the device has become even smaller. In an environment where the spatial volume is small and the fly height is on the order of several nm, even a small amount of contamination may lead to read/write errors.
  • disk drive devices whose internal space is filled with a gas (e.g., helium) that is less dense than air are also becoming popular.
  • the internal air pressure may be less than 1 atm. In that case, it becomes more difficult to suppress the evaporation and volatilization of the lubricant components.
  • HAMR heat-assisted magnetic recording
  • the temperature of the actuator head may locally reach a high temperature of 400°C. This causes the internal temperature of the HDD to rise, making the evaporation and volatilization of the lubricant components more likely to occur than ever before, and increasing the possibility of causing problems related to disk reading and writing.
  • the lubricating oil composition applied to the fluid dynamic bearing according to the present invention is characterized by being blended with a specific ionic liquid as described below.
  • the blending of this lubricating oil composition is expected to suppress the evaporation amount of the composition even when applied under a higher temperature environment such as a disk drive device adopting a heat-assisted magnetic recording method, and is expected to suppress the adhesion of the components to the magnetic disk, etc., even if the components evaporate or volatilize, and can contribute to suppressing the occurrence of read/write errors in HDDs caused by evaporated components.
  • the details are explained below.
  • FIG. 1 is a schematic diagram for explaining a fluid dynamic bearing according to an embodiment of the present invention and a spindle motor equipped with the fluid dynamic bearing. Note that the embodiments described below are illustrative of the present invention, and the present invention is not limited to these.
  • spindle motor 1 is used as a motor for driving a data storage device equipped with magnetic disks, optical disks, etc. used in computers. Overall, it is composed of a stator assembly 2 and a rotor assembly 3. Note that while spindle motor 1 in FIG. 1 is a rotating shaft type motor, the present invention can also be applied to fixed shaft type motors.
  • the stator assembly 2 is fixed to a cylindrical portion 5 that protrudes upward from a housing 4 (base plate) that constitutes the case of the data storage device.
  • a stator core 8 around which a stator coil 9 is wound is fitted and attached to the outer periphery of the cylindrical portion 5.
  • the rotor assembly 3 has a rotor hub 10, which is fixed to the upper end of the shaft portion 11 and rotates together with the shaft portion 11.
  • the shaft portion 11 is inserted into a sleeve 7, which is a bearing member, and is rotatably supported by the sleeve 7.
  • the sleeve 7 is fitted and fixed inside the cylindrical portion 5.
  • the lower cylindrical portion 10a of the rotor hub 10 rotates inside the housing 4, and a back yoke 13 is attached to the inner circumferential surface of the lower cylindrical portion 10a.
  • a rotor magnet 14 is fitted and fixed inside the back yoke 13 and is magnetized to multiple poles, namely north and south poles.
  • a recording disk such as a magnetic disk (not shown), which forms the storage section of a data storage device, is attached to the outer circumferential surface of the intermediate cylindrical section 15 of the rotor hub 10 of the rotor assembly 3, and rotates or stops when the spindle motor 1 is activated, and information is written and data is processed by a recording head (not shown).
  • a fluid dynamic bearing 6 is provided at the portion where the sleeve 7 rotatably supports the shaft portion 11 .
  • a large-diameter first recess 16 that opens downward is formed at the lower end of the sleeve 7, and a small-diameter second recess 17 is formed in the top surface of this first recess 16.
  • a counter plate (thrust receiving plate) 18 is fitted into the large-diameter first recess 16 and fixed thereto by means of welding, adhesive or the like, so that the inside of the sleeve 7 is kept airtight.
  • a thrust washer 19 is fitted and pressed into the lower end of the shaft 11, and this thrust washer 19 is positioned within the second recess 17 of the sleeve 7, facing the counter plate 18 and the top surface of the second recess 17, so as to rotate together with the shaft 11.
  • the gap between the sleeve 7 and the shaft 11, the gap between the thrust washer 19 and the second recess 17, and the gaps between the thrust washer 19 and the shaft 11 and the counter plate 18 are all interconnected, and the lubricating oil composition 12 described below is enclosed in these interconnected gaps.
  • the lubricating oil composition 12 is injected from between the sleeve 7 and the shaft 11.
  • the first radial dynamic pressure groove 20 and the second radial dynamic pressure groove 21 that generate dynamic pressure are formed axially apart on the inner peripheral surface of the sleeve 7 that faces the shaft portion 11.
  • the radial dynamic pressure grooves 20 and 21 generate dynamic pressure that causes the shaft portion 11 and the sleeve 7 to be in a non-contact state in the radial direction when the shaft portion 11 rotates.
  • the top surface of the second recess 17 that faces the upper end surface of the thrust washer 19 and the upper end surface of the counter plate 18 that faces the lower end surface of the thrust washer 19 are formed with the first thrust dynamic pressure groove 22 and the second thrust dynamic pressure groove 23, respectively.
  • the thrust dynamic pressure grooves 22 and 23 generate dynamic pressure for stably floating the shaft portion 11 in the thrust direction when the shaft portion 11 rotates. Due to the action of these dynamic pressure grooves, the shaft portion 11 can rotate stably at high speed in a non-contact state with respect to the sleeve 7.
  • Known patterns such as herringbone grooves and spiral grooves can be used as the dynamic pressure grooves.
  • FIG. 2 is a perspective view showing the overall configuration of a disk drive device 30 using the spindle motor according to this embodiment.
  • the disk drive device 30 of this embodiment comprises a substantially rectangular box-shaped base (base plate) 31, a spindle motor 1 mounted on this base 31, a magnetic disk 32 rotated by this spindle motor 1, a swing arm 33 having a magnetic head 34 that writes information to a predetermined position on the magnetic disk 32 and reads information from any position, a pivot assembly bearing device 35 that supports the swing arm 33 so that it can swing, an actuator 36 that drives the swing arm 33, and a control unit 37 that controls these devices.
  • the disk drive device of the present invention may be, for example, a disk drive device equipped with nine or more magnetic disks having a diameter of 3.5 inches. In such a device having a large number of disks, the spatial volume within the device is further reduced.
  • the disk drive device may have an internal space filled with a gas having a density lower than that of air. In a disk drive device whose internal space is filled with such a low-density gas, the air pressure within the device may be less than 1 atmosphere.
  • the disk drive device may also adopt a thermally assisted magnetic recording (HAMR) method as a recording method. In a disk drive device adopting a thermally assisted magnetic recording (HAMR) method, the temperature of the head portion of the actuator may locally reach a high temperature of 400°C.
  • HAMR thermally assisted magnetic recording
  • the lubricating oil composition used in the present embodiment described below exhibits low evaporation and volatility due to the adoption of a specific ionic liquid and furthermore a specific base oil, and the evaporated or evaporated components exhibit low adhesion to disks, etc. Therefore, in a fluid dynamic bearing and a spindle motor using this, evaporation of the components of the lubricating oil composition is suppressed even when driven at high temperatures, and disk read/write errors in disk drive devices due to adhesion of evaporated components to magnetic disks, etc. can be suppressed.
  • the present inventors have focused on the addition of an ionic liquid to a lubricating oil composition applied to a fluid dynamic bearing, and have found that an ionic liquid composed of a specific cation and an anion suppresses the evaporation amount of the lubricating oil composition.
  • the lubricating oil composition filled in the fluid dynamic bearing of the present invention will now be described.
  • the lubricating oil composition applied to the fluid dynamic bearing according to this embodiment essentially contains a specific ionic liquid.
  • lubricants have been made conductive as necessary to dissipate static electricity that is generated between parts due to rotational friction, and the addition of ionic liquids is being considered as one method for achieving this.
  • the ionic liquid used in the present invention in addition to imparting electrical conductivity, also serves to suppress the amount of evaporation of the lubricating oil composition and, when an ester oil is used as the base oil, to suppress hydrolysis of the ester oil.
  • the ionic liquid has at least one cation selected from the group consisting of tetraalkylammonium cations represented by the following formula (B) and at least one anion selected from the group consisting of borate anions represented by the following formula (C-1), borate anions represented by the following formula (C-2), and borate anions represented by the following formula (C-3).
  • R 5 , R 6 , R 7 , and R 8 each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms.
  • R 5 , R 6 , R 7 and R 8 each independently represent a linear or branched alkyl group having 5 to 18 carbon atoms.
  • examples of the alkyl group having 1 to 18 carbon atoms include methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups.
  • R 5 , R 6 , R 7 , and R 8 in the above formula (B) include a combination in which R 5 is a linear or branched alkyl group having 1 to 4 carbon atoms, and R 6 to R 8 are each independently a linear or branched alkyl group having 6 to 14 carbon atoms; a combination in which R 5 is a linear or branched alkyl group having 11 to 16 carbon atoms, and R 6 to R 8 are each independently a linear or branched alkyl group having 6 to 10 carbon atoms; or a combination in which R 5 to R 8 are each independently a linear or branched alkyl group having 6 to 12 carbon atoms.
  • the total number of carbon atoms of R 5 , R 6 , R 7 and R 8 in the above formula (B) can be, for example, 24 to 40.
  • Examples of the tetraalkylammonium cation represented by formula (B) include a tetrahexylammonium cation in which R 5 to R 8 are hexyl groups, a methyltri(octyl)ammonium cation in which R 5 is a methyl group and R 6 to R 8 are octyl groups, a (tetradecyl)tri(hexyl)ammonium cation in which R 5 is a tetradecyl group and R 6 to R 8 are hexyl groups, a tetraoctylammonium cation in which R 5 to R 8 are octyl groups, and a tetradecylammonium cation in which R 5 to R 8 are decyl groups.
  • the anion used in the ionic liquid according to the present invention is selected from the group consisting of a borate anion represented by formula (C-1), a borate anion represented by formula (C-2), and a borate anion represented by formula (C-3).
  • the borate anion is a preferred embodiment in view of the recent trend toward prohibiting or restricting the use of fluorine-based compounds.
  • R 9 , R 10 , R 11 and R 12 each independently represent a linear or branched alkyl group having 1 to 22 carbon atoms.
  • R 9 , R 10 , R 11 and R 12 in the above (C-1) each independently represent a linear or branched alkyl group having 1 to 22 carbon atoms, or each independently represent a linear or branched alkyl group having 1 to 10 carbon atoms, or each independently represent a linear or branched alkyl group having 6 to 10 carbon atoms, or each independently represent a linear or branched alkyl group having 1 to 8 carbon atoms, or each independently represent a linear or branched alkyl group having 1 to 6 carbon atoms, or each independently represent a linear or branched alkyl group having 1 to 2 carbon atoms.
  • Examples of the alkyl group having 1 to 22 carbon atoms in R 9 , R 10 , R 11 and R 12 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an eicosyl group, a heneicosyl group, and a
  • Examples of the combination of R 9 , R 10 , R 11 and R 12 in the above formula (C-1) include a combination in which R 9 to R 12 are each independently a linear or branched alkyl group having 1 to 8 carbon atoms, or a combination in which R 9 to R 12 are all methyl groups.
  • the ionic liquid used in the present invention may be, for example, any combination of cations and anions shown in (a) to (k) below.
  • the amount of the ionic liquid contained in the lubricating oil composition is not particularly limited and can be appropriately selected depending on the purpose.
  • the content of the base oil described below can be 0.01 mass % or more and 10 mass % or less, or 0.03 mass % or more and 1 mass % or less, or 0.03 mass % or more and 0.5 mass % or less.
  • the base oil is not particularly limited, and synthetic oils such as mineral oils, hydrocarbon synthetic oils, ester synthetic oils, and ether synthetic oils that are generally used as base oils in lubricating oils can be used alone or in combination.
  • synthetic oils such as mineral oils, hydrocarbon synthetic oils, ester synthetic oils, and ether synthetic oils that are generally used as base oils in lubricating oils can be used alone or in combination.
  • ester-based synthetic oils are preferably used because they easily dissolve the above-mentioned ionic liquid.
  • ester-based synthetic oils include monoester oils, diester oils, polyol ester oils, aromatic ester oils, etc.
  • the base oil used in the present embodiment contains at least one compound selected from the group consisting of aliphatic monoester compounds (monoester oils) and diester compounds (diester oils) having a specific alkyl chain length described below.
  • monoester oils aliphatic monoester compounds
  • diester oils diester oils having a specific alkyl chain length described below.
  • the inventors have come to adopt the above-mentioned aliphatic monoester compound or diester compound having an alkyl chain length of a certain length or more.
  • monoester oils and diester oils other than the aliphatic monoester compounds (monoester oils) and diester compounds (diester oils) having specific alkyl chain lengths listed below may be used or used in combination.
  • the monoester compound is represented by the formula (1).
  • R21 is a linear or branched alkyl group having a total of 10 or more carbon atoms, preferably a total of 23 or less carbon atoms.
  • the number of carbon atoms in the branched chain can be 10 or more, preferably 15 or less.
  • R22 is a linear or branched alkyl group having a total of 9 or more carbon atoms, preferably a total of 20 or less carbon atoms.
  • R22 is a branched alkyl group
  • the number of carbon atoms in the branched chain can be 7 or more, preferably 8 or less.
  • a branched chain is a portion branched from the main chain (the longest carbon chain counted from the carbon atom bonded to a carbonyl group or an oxygen atom), and the number of branched chains is not particularly limited.
  • one of R 21 and R 22 can be a linear alkyl group and the other can be a branched alkyl group.
  • monoester compound examples include, but are not limited to, the compounds shown below.
  • the diester compound is represented by formula (2).
  • R 23 -E 1 -R 24 -E 2 -R 25 (2)
  • R23 and R25 each independently represent a linear or branched alkyl group having a total of 8 or more carbon atoms, preferably a total of 10 or less carbon atoms.
  • the longest carbon chain may have 9 or more carbon atoms, preferably 9 carbon atoms, counting from the carbon atom bonded to E1 or E2 .
  • R 24 is a linear or branched alkylene group having a total of 4 or more carbon atoms, and preferably 6 or less carbon atoms.
  • R 23 and R 25 are both linear alkyl groups and R 24 is a branched alkylene group, or that R 23 and R 25 are both branched alkyl groups and R 24 is a linear alkylene group.
  • R 23 and R 25 can be the same group.
  • diester compound examples include, but are not limited to, the compounds shown below.
  • polyol ester oils include full esters of polyhydric alcohols [triols (e.g., trimethylolpropane), tetraols (e.g., pentaerythritol), hexaols (e.g., dipentaerythritol), etc.] and linear and/or branched fatty acids having 4 to 22 carbon atoms.
  • triols e.g., trimethylolpropane
  • tetraols e.g., pentaerythritol
  • hexaols e.g., dipentaerythritol
  • trimethylolpropane triheptanoate trimethylolpropane tricaprylate, trimethylolpropane tripelargonate, pentaerythritol tetraheptanoate, pentaerythritol tri(2-ethylhexanoate), pentaerythritol tetraoleate, and neopentyl polyol.
  • aromatic ester oils include esters of aromatic polycarboxylic acids such as phthalic acid, trimellitic acid, and pyromellitic acid with aliphatic monoalcohols having 4 to 16 carbon atoms. Specific examples include ditridecyl phthalate, trioctyl trimellitate, tri-2-ethylhexyl trimellitate, tridecyl trimellitate, tetraoctyl pyromellitate, and tetra-2-ethylhexyl pyromellitate.
  • the ratio of base oil to the total amount of the lubricating oil composition applied to the fluid dynamic bearing of the present invention can be the remainder excluding the amount of the ionic liquid described above and the amount of other additives that may be added as necessary.
  • the lubricating oil composition may contain, as necessary, additives that are usually used in lubricating oil compositions, within the range that does not impair the effects of the present invention.
  • the additives include extreme pressure additives, antioxidants, metal detergents, oiliness agents, anti-wear agents, metal deactivators, corrosion inhibitors, rust inhibitors, viscosity index improvers, pour point depressants, conductivity imparting agents, dispersants, antifoaming agents, and hydrolysis inhibitors.
  • the blending amount as the total amount of additives, can be, for example, 0.5 to 5 mass %, or 1 to 3 mass %, based on the lubricating oil composition.
  • Specific examples of the additives include, but are not limited to, the following:
  • Extreme pressure additives that can be used are conventional additives containing sulfur, chlorine, phosphorus, etc., and examples include phosphorus-based compounds such as phosphate esters, phosphites, and amine salts of phosphate esters, sulfur-based compounds such as sulfides and disulfides, chlorine-based compounds such as chlorinated paraffin and chlorinated diphenyl, and metal salts of sulfur-based compounds such as zinc dialkyldithiophosphate and molybdenum dialkyldithiocarbamate.
  • phosphorus-based compounds such as phosphate esters, phosphites, and amine salts of phosphate esters
  • sulfur-based compounds such as sulfides and disulfides
  • chlorine-based compounds such as chlorinated paraffin and chlorinated diphenyl
  • metal salts of sulfur-based compounds such as zinc dialkyldithiophosphate and molybdenum dialkyldithiocarbamate.
  • antioxidants examples include phenol-based antioxidants, diphenylamines, phosphorus-based antioxidants, sulfur-based compounds such as phenothiazine, etc. These antioxidants may be used alone or in combination.
  • phenol-based antioxidants particularly hindered phenol-based antioxidants selected from the group consisting of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 2,2-thio-diethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and octyl-3,5-di-tert
  • Antiwear agents include phosphates, phosphites, acid phosphates, and the like. However, from the viewpoint of disk adhesion, it is desirable to avoid the use of amine salts of acid phosphates which are commonly used as anti-wear agents.
  • rust inhibitor is dodecenyl succinic acid half ester.
  • metal deactivator include benzotriazole compounds and thiadiazole compounds.
  • viscosity index improvers include polyalkyl methacrylates, polyalkyl styrenes, and polybutenes.
  • pour point depressants include the above-mentioned viscosity index improvers such as polyalkyl methacrylate, polyalkylstyrene, and polybutene.
  • the conductivity imparting agent include nonionic surfactants and phenylsulfonic acid.
  • dispersant examples include polyalkenyl succinimide, polyalkenyl succinamide, polyalkenyl benzylamine, polyalkenyl succinate, and the like.
  • hydrolysis inhibitor examples include alkyl glycidyl ether type epoxy compounds, glycidyl ester type epoxy compounds, alicyclic epoxy compounds, carbodiimides, and the like.
  • a read/write error occurrence test was conducted using the ionic liquids of Examples 1 to 8 and Comparative Examples 1 to 3, which have the cations and anions shown in Table 1, and base oil A, according to the procedure described below.
  • the example numbers of the ionic liquids will also be treated as the example numbers for the evaluation of each test.
  • Base oil A 3-methyl-1,5-pentanediol di(n-undecanoate), CAS No. 1265799-70-9
  • this test especially the process of removing the cover of the disk drive device and reinstalling it, be carried out in a clean room to prevent contamination from the outside.
  • this test was carried out without applying sample oil, and it was confirmed that the disk drive device did not stop even after 96 hours, which was the test cut-off time.
  • the samples using the ionic liquids of Examples 1 to 8 had excellent evaporation characteristics and also excellent hydrolysis characteristics (E rating). Moreover, the sample using the ionic liquid of Comparative Example 1 showed inferior hydrolysis characteristics compared to Examples 1-8.
  • the sample of Comparative Example 1 showed evaporation amount characteristics similar to those of the Examples, but read/write errors occurred as shown in Table 2. This is thought to be one of the reasons why the sample according to the Examples not only suppresses the evaporation of components, but also suppresses the adhesion of those components to the magnetic disk, etc., even if evaporation or volatilization occurs, and this is one of the factors that lead to the suppression of read/write errors.

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PCT/JP2023/043012 2022-12-05 2023-11-30 流体動圧軸受、スピンドルモータおよびディスク駆動装置 Ceased WO2024122448A1 (ja)

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JP2004183868A (ja) * 2002-12-06 2004-07-02 Matsushita Electric Ind Co Ltd 流体軸受装置
JP2005290256A (ja) * 2004-04-01 2005-10-20 Matsushita Electric Ind Co Ltd 流体軸受装置、及びそれを用いたスピンドルモータ
JP2007039496A (ja) * 2005-08-01 2007-02-15 Nippon Steel Chem Co Ltd 流体軸受ユニット及び軸受用潤滑油組成物
JP2008133339A (ja) * 2006-11-28 2008-06-12 Nippon Densan Corp 潤滑剤並びにそれを用いたスピンドルモータ及び記録ディスク駆動装置
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