KR100342340B1 - Disc drive spindle motor having hydro bearing with lubricant optimized with disc drive compatible additives - Google Patents

Abstract

The disc drive 10 includes a housing 12, a central axis 80, a fixing member 34 fixed to the housing and coaxial with the central axis, and rotatable about the central axis with respect to the fixing member. And a typical member 36. Stator 38 is fixed relative to the housing. The rotor 70 is supported by the rotatable member and magnetically coupled to the stator. At least one data storage disc 16 is attached to and coaxial with the rotatable member. The hydraulic bearing 37 interconnects the stationary member and the rotatable member and has a basic fluid 84, an antioxidant additive, an anticorrosion additive, and a viscosity of at least 110, which is effective for suppressing catalyst degradation in the hydraulic bearing. A mixture of antiwear additives.

Description

DISC DRIVE SPINDLE MOTOR HAVING HYDRO BEARING WITH LUBRICANT OPTIMIZED WITH DISC DRIVE COMPATIBLE ADDITIVES}

Disk drive data storage devices known as "winchester" type disk drives are well known in the art. In a Winchester disk drive, digital data is written to and read from the thin layer of magnetizable material on the surface of the rotating disk. Write and read operations are performed through a transducer supported on the slider body. These sliders and transducers are sometimes referred to collectively as heads, and typically one head is associated with each disk surface. The head is selectively moved by an actuator device to one of a plurality of concentric data tracks that are circular on the disk surface under the control of an electronic circuit. Each slider body includes a self-acting air bearing surface. As the disc rotates, it pulls air below the air bearing surface, thereby lifting the slider, which creates a lifting force that allows the slider to fly over a few microinches of the disc surface.

The most commonly used type of actuator in disc drive devices currently being produced is a rotary moving coil actuator. The disc itself is typically mounted "stack" on the hub structure of a brushless DC spindle motor. The rotational speed of the spindle motor is precisely controlled by the motor drive circuit which controls the timing and power of the communication signal transmitted to the stator winding of the motor. A typical spindle motor has a speed of 3600 rpm. In current technology, the spindle motor rotational speed is increasing beyond 7200 rpm, 10,000 rpm.

One of the main sources of noise in disk-driven data storage devices is the spindle motor. Disc drive manufacturers have recently replaced conventional ball or roller bearings in spindle motors with "hydro" bearings, such as hydrodynamic bearings or hydrostatic bearings. We are looking for Hydraulic bearings are arranged on a fluid film that separates the bearing surface and are much monotonous and typically have lower vibrations than conventional ball bearings. Hydrodynamic bearings are self-pumping bearings that generate pressure internally to maintain fluid membrane separation. Hydrostatic bearings require an external pressurized fluid source to maintain fluid separation. The relative movement between the bearing surfaces in the hydraulic bearings ensures that no shearing elements which occur entirely within the fluid film cause any contact between the bearing surfaces.

This phenomenon is different from conventional boundary lubrication applications such as roller bearings, ball bearings and sliding bearings where the solid bearing surfaces often come into contact with each other to produce shear stresses at their interfaces, as opposed to the application of elastohydrodynamic lubrication. different. In such boundary applications, the primary use of lubricants is to modify the interface to reduce wear and friction. The interfacial chemical properties of lubricants are the most important factors.

In hydraulic bearing applications, overall different fluid properties are an important factor for the bearing's function. Boundary characteristics are an important factor only while starting and stopping disk rotation. During normal operation, bulk characteristics are the most important factor. Hydraulic bearings contemplated for use in disc drive devices are small units that do not deviate from the bearing and require a limited oil supply and low power consumption suitable for the long life of the bearing. Commercially available lubricants are inadequate for most small hydraulic bearings in disc drives.

The lubricant properties to be controlled and the degree of control to be achieved differ for each small hydraulic bearing for a disc drive. These characteristics include power consumption, viscosity and temperature dependence of the viscosity, migration, vapor pressure and evaporation rate, resistance to oxidation and corrosion, rheology, boundary properties and system compatibility. Viscosity determines power consumption and bearing stiffness, which must be relatively constant over various operating conditions. The lubricant must have a low movement so as not to leak out of the bearings. The lubricant must have high resistance to oxidation and reactivity to extend the life of the bearing. Rheology is the deformation and flow response to shear.

The lubricant must be compatible with other materials in the disc drive. For example, the movement or leakage of lubricant must not damage the interface between the head and the disk due to factors such as increased adhesive friction between the head and the disk or deteriorating head structure or head operation. The formation of fluids suitable for hydraulic bearing properties requires different considerations than the fluids to be used as lubricants for general use. Another disadvantage of commercially available lubricants is that they will have to contain one or more additives that are not provided by the manufacturer and are not compatible with the sensitive operation of the disk drive.

The present invention relates to a spindle motor for a disk drive data storage device, and more particularly to a lubricant mainly used in hydrodynamic bearings of the spindle motor.

1 is a plan view of a disk drive data storage device according to the present invention.

2 is a cross-sectional view of a hydrodynamic spindle motor in accordance with the present invention.

FIG. 3 is a cross sectional view of a hydrodynamic spindle motor with portions omitted for clarity and clarity along line 3-3 of FIG.

The disk drive data storage device of the present invention includes a housing, a central axis, a fixed member fixed to the housing and coaxial with the central axis, and a rotatable member rotatable about a central axis with respect to the fixed member. The stator is fixed with respect to the housing. The rotor is supported by the rotatable member and magnetically connected to the stator. At least one data storage disk is attached to and coaxial with the rotatable member. The hydraulic bearings comprise a mixture of base fluid, anti-oxidant additives, anti-corrosion additives and anti-wear additives which interconnect with the stationary member and the rotatable member and have a viscosity of at least 110, which additives degrade contact in the hydraulic bearings. It is effective in suppressing catalytic degradation.

In a preferred embodiment, the above mixture has a concentration of 0.25 to 3% by weight of the antioxidant additive, a concentration of 0.05 to 0.5% by weight of the anticorrosive additive and a concentration of 0.1 to 4% by weight of the antiwear additive. . Preferred base fluids are esters, synthetic hydrocarbons, mixtures of different esters or mixtures of different synthetic hydrocarbons. The antioxidant additive is preferably selected from the group consisting of amines and phenols. The anticorrosion additive is preferably selected from the group consisting of metallic sulfonates, long chain amines, carboxylic acid derivatives, thiadiazole derivatives, triazole derivatives, and amine phosphates. The antiwear additive is selected from the group consisting of dialkyl dithiophosphates, alkyl disulfides, alkyl polysulfides, aryl disulfides, aryl polysulfides, dithiocarbamates, salts of alkyl phosphates, molybdenum complexes, and neutral phosphate esters. desirable.

The disk drive data storage system further includes an actuator and a head supported by an actuator adjacent to the data storage disk for communicating with the disk. Preferred components of the lubricant are compatible with the interface between the head and the disk. For example, these components do not significantly increase the sticking friction between the disk and the head caused by the leakage of these components in the hydraulic bearings. In addition, these components do not cause degradation of the structure or operation of the head and disk.

The present invention relates to a disk drive data storage device comprising a hydrodynamic or hydrostatic bearing spindle motor having a lubricant composition optimized for the unique requirements of the disk drive. 1 is a plan view of a conventional disk drive 10 to which the present invention can be applied. The disc drive 10 includes a housing base 12 and a top cover 14. The housing base 12 can be combined with the top cover 14 to form a sealed environment to protect internal components from contamination by elements outside of the sealing environment.

The disk drive 10 further includes a disk pack 16 mounted for rotation of a spindle motor (not shown) by the disk clamp 18. The disc pack 16 includes a plurality of individual discs mounted for co-rotation about the central axis. Each disk surface has an associated head 20 mounted to the disk drive 10 for communicating with the disk surface. In the example shown in FIG. 1, the head 20 is supported by a flexure 22, which is attached to the head mounting arm 24 of the actuator body 26. The actuator shown in FIG. 1 is of a type known as a rotary moveable coiled actuator and comprises a voice coil motor (VCM), indicated at 28. The voice coil motor 28 rotates the actuator body 26 with the head 20 attached about the pivot shaft 30 to position the head 20 on the desired data track along the arcuate path 20. Although a rotary actuator is shown in FIG. 1, the present invention is also useful for disk drives having other types of actuators, such as linear actuators.

2 is a cross-sectional view of a hydrodynamic bearing spindle motor 32 according to the present invention. The spindle motor 32 includes a stationary member 34, a hub 36 and a stator 38. In the embodiment shown in FIG. 2, the fixing member is a shaft which is fixed and attached to the base 12 via the nut 40 and the washer 42. The hub 36 is interconnected with the shaft 34 via a hydrodynamic bearing 37 for rotation about the shaft 34. The bearing 37 comprises radial working surfaces 44 and 46 and axial working surfaces 48 and 50. Shaft 34 includes fluid ports 54, 56, 58 that supply lubricant 60 and help circulate fluid along the working surface of the bearing. Lubricant 60 is supplied to shaft 34 by a fluid source (not shown) that is connected to the interior of shaft 34 in a known manner.

The spindle motor 32 further comprises a thrust bearing 45 forming an axial working surface 48, 50 of the hydrodynamic bearing 37. The counterplate 62 supports the working surface 48 to provide axial stability to the hydrodynamic bearing and to position the hub 36 in the spindle motor 32. The zero ring 64 is installed between the counterplate 62 and the hub 36 to seal the hydrodynamic bearing. This seal prevents the hydrodynamic fluid 60 from escaping between the counterplate 62 and the hub 36.

The hub 36 includes a disk carrier member 66 and a central core 65 that support the disk pack 16 (see FIG. 1) for rotation about the shaft 34. The disc pack 16 is fixed on the disc carrier member 66 by the disc clamp 18 (see FIG. 1). A permanent magnet 70 operating as a rotor of the spindle motor 32 is attached to the outer diameter of the hub 36. The core 65 is made of a magnetic material and operates as a back-iron for the magnet 70. The rotor magnet 70 may be configured as a monolithic annular ring or may be composed of a plurality of individual magnets spaced apart about the circumference of the hub 36. Rotor magnet 70 is magnetized to form one or more magnetic poles.

Stator 38 is attached to base 912 and includes stator laminations 72 and stator windings 74. Stator winding 74 is attached to lamination 74. The stator winding 74 is radially spaced from the rotor magnet 70 so that the rotor magnet 70 and the hub 36 can rotate about the central axis 80. The stator 38 is attached to the base 12 via a known method, such as one or more C-clamps 76 secured to the base via bolts 78.

The commutation pulse applied to the stator winding 74 creates a rotating magnetic field that communicates with the rotor magnet 70 and allows the hub 36 to rotate about the central axis 80 on the bearing 37. The commutation pulse is a timed polatizaion-selected DC current pulse that is sent to sequentially selected stator windings to drive and control the speed of the rotor magnet.

In the embodiment shown in FIG. 2, the spindle motor 32 is a "below-hub type motor" in which the axial position of the stator 38 is below the hub 36. Stator 38 also has a radial position outside of hub 36 such that stator winding 74 is secured to inner diameter surface 82 of lamination 72. In other embodiments, the stator may be located inside the hub as opposed to being placed below the hub. The stator may have a radial position inside or outside the hub. In addition, the spindle motor may have a fixed shaft or a rotating shaft as shown in FIG. 2. In a rotary shaft spindle motor, the bearing is located between the rotary shaft and an outer stationary sleeve coaxial with the rotary shaft.

3 is a cross-sectional view of the hydrodynamic spindle motor 32 taken along line 3-3 of FIG. 2, with some portions omitted for clarity of illustration. Stator 38 includes lamination 72 and stator windings 74 coaxial with rotor magnet 70 and central core 65. Stator winding 74 includes phase windings W1, V1, U1, W2, V2 and U2 wound around teeth in lamination 72. The phase winding consists of a coil having a coil axis perpendicular to and intersecting the central axis 80. For example, the phase winding W1 has a coil axis 83 perpendicular to the central axis 80. The radial working surfaces 44, 46 of the hydrodynamic bearing 37 are formed by the outer diameter surface of the shaft 34 and the inner diameter surface of the central core 65. Radial working surfaces 44 and 46 are separated by lubricant 84 to maintain the spacing c during normal operation.

1. Optimization of lubricant viscosity

According to one aspect of the present invention, the lubricant comprises a mixture of base fluids selected to optimize power consumption and bearing load capacity (ie, bearing stiffness) for a particular hydrodynamic bearing design, and precisely define fluid viscosity. Used.

Power consumption P and bearing stiffness K are proportional to the fluid viscosity according to the following relationship.

Where μ _B is the absolute viscosity of the mixture of fluids, ω is the relative viscosity of the hub, and c is the gap, ie the spacing between the radial working surfaces 44,46 (or the axial working surfaces 48, 50). R is the axial working surface and / or the radial characteristic length.

In disc drive devices with compact hydrodynamic bearings, power and load capacity are important factors. Therefore, it is desirable to specify the exact viscosity at any particular temperature for the lubricant, and the desired viscosity varies with the size and structure of the spindle motor. Commercial lubricants cannot be used with any viscosity value. Lubricants of the present invention include mixtures of base fluids, each having a similar chemical composition but each having a different viscosity. The base fluid is precisely mixed to obtain an overall viscosity that is preferably within 10%, most preferably within 2-5% of the required viscosity. The base fluid is mixed according to the following relationship.

Where μ _B is the absolute viscosity of the mixture of base fluids at temperature T _C , T _C is the temperature at the desired viscosity, ν _n is the dynamic viscosity of base fluid n, n is an integer greater than 1, ρ _n is the density of the base fluid n, χ _n is the weight percentage ratio of the base fluid n, and χ ₁ + χ ₂ +. + χ _n = 1.

For example, n = 2, and if the kinematic viscosity ν of the desired mixture, ν _1> ν> ₂ so that when properly selecting the ν ₁ and ν ₂ can obtain a desired viscosity of the lubricant.

Preferred base fluids include perfluoropolyethers, esters, synthetic hydrocarbons and highly purified mineral hydrocarbons. Most preferred base fluids include diesters, polyol esters and polyalphaolefins (PAO). These base fluids can be mixed into compositions of each species, but preferred mixtures include compositions of ester only, compositions of polyalphaolefin only, and compositions of at least one ester and at least one polyalphaolefin only. In other embodiments of the present invention a single ester or polyalphaolefin may be used if the fluid meets other desired properties with the desired viscosity.

These most preferred base fluids have been found to offer several advantages over conventional petroleum-based hydrocarbons present in standard fluid lubricants in disk drive devices. These base fluids have less viscosity dependence on temperature, lower evaporation, lower vapor pressure, lower migration, better oxidation resistance, similar boundary performance that can be enhanced with additives, and good compatibility with other materials in the disc drive. , And good control of all properties due to known pure chemical compositions. Thus, these fluids minimize degradation of the head and disk interfaces and provide long life in bearings and disk drives.

In a preferred embodiment, the base fluid has a precise absolute viscosity of 4-10 centipoise (cP) at a temperature of about 70 ° C., at least 110 points, based on a volume to surface area (V / A) ratio of about 1.9 to 2.0 mm. It is mixed to obtain a modulus and an evaporation range of less than 1.0 × 10 ⁻³ mg / day-mm ² .

The base fluid is also used in disc drives under various conditions, such as high temperature or high humidity, where the base fluid's contribution to cohesive friction ("stick") between the head and the disc due to fluid leakage from the bearings to the disc. It is chosen to be similar to or less than the contribution of existing chemicals or lubricants. These chemicals and lubricants include, for example, greases and ferrofluidic seals.

2. Mixing lubricant and selected additives

In another aspect of the invention, the lubricant is a combination of a high viscosity base fluid (or mixture of base fluids) and an additive selected such that the mixture is compatible at the head-disk interface and is effective in preventing contact degradation. Mixtures.

The viscosity of the lubricant in hydrodynamic bearings decreases with increasing temperature. This lowering of viscosity results in lower power consumption and bearing load capacity for fluids of predetermined thickness. In disc drive devices with small hydrodynamic bearings, large variations in power consumption and bearing load capacity are unacceptable.

Viscosity (VI) is an arbitrary way of indicating the viscosity-temperature sensitivity of a lubricant and is often interpreted as the temperature dependency of viscosity. The higher viscosity of a fluid with a given viscosity indicates that the viscosity of the fluid changes less with temperature. Since power consumption is an important parameter for hydrodynamic bearings in small disk drives, high viscosity is required. Typical viscosities for various classes are shown in Table 1 below.

Chemical class of fluid Available VI Range Refined Paraffin Mineral 90-110 Synthetic Hydrocarbons (Polyalphaolefins) 120 to 170 Synthetic ester (diester) 120 to 200 Synthetic esters (polyols) 115-200 Perfluoropolyether 90 to 320

Ester fluids include hydrogen and carbon as well as oxygen, and some ester fluids offer inherent advantages to disk drive devices over natural and synthetic hydrocarbon fluids. These advantages include higher viscosity, higher oxidation resistance, improved boundary lubrication properties, lower migration and lower evaporation compared to synthetic hydrocarbons.

For example, commercially available diester fluids have high viscosity and good oxidation resistance but poor resistance to contact degradation upon metal to metal contact. For this reason, the oil's volume is so small that even minor breakdowns make it impossible to use commercially available diester fluids in small hydrodynamic bearings that adversely affect the bearing properties.

Commercially available fluids do not contain suitable metal inert additives to extend the life of the bearings. In addition, most commercially available fluids have components that are incompatible with the head-disk interface. Sometimes the exact composition of a commercially available fluid is not controlled by the manufacturer. Thus, the use of such fluids can lead to unexpected degradation of disk drive performance.

The lubricants of the present invention are superior to mixtures of high viscosity base fluids, such as diester fluids or polyalphaolefins, and commercially available ester and / or synthetic hydrocarbon mixtures, while the fluids are compatible at the head-disk interface. A combination of additives selected to provide anti-oxidation, corrosion protection and metal deactivation properties to the fluid to resist contact degradation.

Preferred types of antioxidants include inhibitors containing nitrogen and oxygen, such as amines (arylamines), phenols or mixtures thereof. Most preferred types of antioxidants include butylated hydroxytoluene (liquid hindered phenol), alkylated diphenyl amines, phenyl alpha naphthylamine or combinations of two or more of these antioxidants. Preferred treatment levels of these additives in the lubricating base fluid are from 0.25 to 3% by weight.

Preferred types of rust and corrosion inhibitors or metal passivators include metallic sulfonates, long chain amines, carboxylic acid derivatives, triadiazole derivatives, triazole derivatives, and amine phosphates. Most preferred types of rust and oxidation inhibitors or metal antifreeze agents are synthetic or mineral calcium sulfonates, synthetic or mineral barium sulfonates, alkenyl succinic acid derivatives and triazole derivatives. Preferred treatment levels of these additives in the lubricating base fluid are from 0.02 to 0.5% by weight.

Lubricants of the present invention further comprise additives for improving antiwear properties, high pressure metal contact properties and friction properties. Preferred additives of this type include neutral phosphate esters such as dialkyl dithiophosphates, alkyl disulfides, alkyl polysulfides, aryl disulfides, arylpolysulfides, dithiocarbamates, salts of alkyl phosphates, molybdenum complexes, triphenyl phosphates ( Triaryl and trialkyl), or combinations of one or more of these additives. Most preferred antiwear additives are zinc dialkyldithiophosphates, molybdenum disulfides, liquid amine phosphates, propylated triphenyl phosphates, and butanated triphenyl phosphates. Preferred treatment levels of these additives in the lubricating base fluid are from 0.1 to 4% by weight.

The above additives can be selected to mix high viscosity diester oils and / or synthetic hydrocarbons to obtain hydrodynamic fluids with significantly higher resistance to contact degradation than commercially available ester or synthetic hydrocarbon mixtures. . Testing of the various mixtures shows that they are compatible with the head-disk interface. These mixtures do not significantly increase the adhesive friction between the head and the disk and do not cause other interference in the head-disk interface. The mixture has also been found to be superior to purified paraffinic mineral fluids in terms of lifetime and power consumption under overload and high temperatures.

3. Application of high shear strength viscosity modulus fluid

In another aspect of the invention, the lubricant comprises a mixture of a base fluid and a shear-resistant viscosity modifier ("viscosity enhancer"). Viscosity enhancers reduce the temperature dependence of the viscosity of the base fluid. Temperature dependence of viscosity is a very important factor, and high temperature dependence is not always desirable for the function of miniature bearings for spindle motors. In order to minimize this effect, selected commercially available polymers are mixed with the base fluid according to the invention to improve the temperature-power consumption curve measured in the spindle motor. It has been observed that the dependence of power consumption on temperature is reduced.

In a preferred embodiment of the present invention, high molecular weight soluble polymer is added at 5-50% by weight to the base fluid, provided another suitable base fluid with improper temperature-viscosity behavior is provided. The molecular weight of this polymer is preferably 10,000 to 1,000,000 daltons. Preferred polymer viscosity modifiers include, but are not necessarily limited to, polyacrylates, polyisoprene and polystyrene.

Under the condition that the hydrodynamic bearing is faced with the compact according to the invention, the shear rate is at least 10 ⁶ per second. Shear rate is the width of the gap in the bearing (

It is defined as the rate of change of the viscosity of the bearing working surface over the interval c) shown. The shear state between the bearing surfaces limits the life of the viscosity modifier by breaking down the polymer. Since the viscosity effect depends on the length of the polymer chain, among other factors, the effectiveness of the viscosity enhancer is reduced by shear breakdown.

In a more preferred embodiment of the invention, the selected polymer viscosity modifiers belong to the class of polymers in which the stretch strength of at least 10,000 psi of solid polymer is resistant to thermal degradation of at least 250 ° F. and has high resistance to shear breakdown. . Therefore, the polymer has shear strength. Polymers of this class include soluble forms of materials such as polyphenylene sulfides, polyetheretherketones and polyetherimides, and the like, but are not necessarily limited to these materials.

In a more preferred embodiment of the invention, the solid polymer has an elongation strength of at least 14,000 psi and resistance to thermal degradation of at least 500 ° F. Polymers of this class include polyamide-imide, polyimide, polybenzimidazole and liquid crystalline polymers, but are not necessarily limited to these materials. In a more preferred embodiment, the solid polymer has a stretch strength of at least 20,000 psi and resistance to thermal degradation of at least 700 ° F. Polymers of this class include the buckytube and other buckminsterfullerene carbon forms, but are not necessarily limited to these materials.

In the most preferred embodiment, the polymer viscosity modifier has the properties of the previous group and is functionalized or chemically modified to provide antioxidant and metal deactivation protection to the fluid as described above.

Although the present invention has been described with reference to preferred embodiments, those skilled in the art will be able to make changes in form and detail without departing from the spirit of the invention.

Claims (20)

A housing; A central axis; A fixing member fixed to the housing and coaxial with the central axis; A stator fixed relative to the housing; A rotatable member rotatable about the central axis with respect to the fixed member; A rotor supported by the rotatable member and magnetically coupled to the stator; At least one data storage disk attached to the rotatable member and coaxial with the rotatable member; An actuator for supporting a head disposed proximate the data storage disk for communicating with the disk; A mixture of at least one basic fluid having a viscosity of at least 110 with an antioxidant additive at a concentration of 0.25-3% by weight and an antiwear additive at a concentration of 0.1-4% by weight, interconnecting the stationary member and the rotatable member A hydraulic bearing having a working surface separated by a lubricant composed of a lubricant, wherein the anti-oxidant additive is effective to reduce oxidation of the lubricant and the anti-wear additive is effective to reduce wear of the work surface. Drive data storage device. The method of claim 1, And the lubricant mixture is effective to counteract an increase in adhesive friction between the disk and the head caused by lubricant discharge from the hydraulic bearing. The method of claim 1, And the lubricant mixture further comprises an anticorrosive additive at a concentration of 0.02 to 0.5% by weight effective to reduce metal corrosion. The method of claim 1, And the base fluid is selected from the group consisting of diesters, polyol esters, polyalpha olefins, perfluoropolyethers, and mineral hydrocarbons. The disk drive data storage device of claim 1, wherein the base fluid is selected from the group consisting of diesters and polyol esters. The method of claim 1, And the antioxidant additive is selected from the group consisting of amines, phenols and mixtures thereof. The method of claim 1, And said antioxidant additive is comprised of a mixture of amines and phenols. The method of claim 1, Wherein said antioxidant additive is selected from the group consisting of butylated hydrotoluene, alkylated diphenyl amines and phenyl alpha naphthylamines. The method of claim 1, And said antioxidant additive is comprised of a mixture of at least two additives selected from the group consisting of butylated hydrotoluene, alkylated diphenyl amines and phenyl alpha naphthylamines. The method of claim 1, The lubricant mixture further comprises an anti-corrosion additive selected from the group consisting of metallic sulfonates, long chain amines, carboxylic acid derivatives, thiadiazole derivatives, triazole derivatives and amine phosphates. Storage device. The method of claim 1, The lubricant mixture further comprises an anticorrosive additive selected from the group consisting of synthetic calcium sulfonate, mineral calcium sulfonate, synthetic barium sulfonate, mineral barium sulfonate, alkenyl succinic acid derivatives and triazole derivatives. Disk drive data storage device. The method of claim 1, The antiwear additive is selected from the group consisting of dialkyl dithiophosphates, alkyl disulfides, alkyl polysulfides, aryl disulfides, aryl polysulfides, dithiocarbamates, salts of alkyl phosphates, molybdenum complexes and neutral phosphate esters. A disk drive data storage device. The method of claim 1, And wherein said antiwear additive is selected from the group consisting of triaryl phosphates and trialkyl phosphates. The method of claim 1, The antiwear additive is at least two selected from the group consisting of dialkyl dithiophosphates, alkyl disulfides, alkyl polysulfides, aryl disulfides, aryl polysulfides, dithiocarbamates, salts of alkyl phosphates, molybdenum complexes and neutral phosphate esters Disk drive data storage device, characterized in that consisting of additives. The method of claim 1, And the antiwear additive is selected from the group consisting of zinc dialkyl dithiophosphates, molybdenum disulfides, liquid amines, phosphates, propylated triphenyl phosphates and butylated triphenyl phosphates. The method of claim 1, The at least one basic fluid comprises at least two basic fluids selected from the group consisting of diesters, polyol esters and polyalphaolefins, wherein the at least two basic fluids in the mixture are different in viscosity Disk drive data storage device. A housing; A central axis; A fixing member fixed to the housing and coaxial with the central axis; A stator fixed relative to the housing; A rotatable member rotatable about the central axis with respect to the fixed member; A rotor supported by the rotatable member and magnetically coupled to the stator; At least one data storage disk attached to the rotatable member and coaxial with the rotatable member; An actuator for supporting a head disposed proximate the data storage disk for communicating with the disk; A hydraulic bearing interconnecting the stationary member and the rotatable member, the hydraulic bearing having a working surface separated by a lubricant composed of a mixture of an base additive having a viscosity of at least 110 and an antioxidant additive and an antiwear additive, The base fluid is selected from the group consisting of diesters, polyol esters, polyalphaolefins, perfluoropolyethers and mineral hydrocarbons; The antioxidant additive is selected from the group consisting of amines and phenols; The antiwear additive is selected from the group consisting of dialkyl dithiophosphates, alkyl disulfides, alkyl polysulfides, aryl disulfides, aryl polysulfides, dithiocarbamates, salts of alkyl phosphates, molybdenum complexes and neutral phosphate esters; And wherein the anti-oxidant additive is effective to reduce oxidation of the base fluid and the anti-wear additive is effective to reduce wear of the working surface. The method of claim 17, The lubricant mixture further comprises an anticorrosive additive at a concentration of 0.02 to 0.5% by weight, wherein the anticorrosive additive is a metallic sulfonate, long chain amine, carboxylic acid derivative, thiadiazole derivative, triazole derivative and amine phosphate. Disk drive data storage device, characterized in that selected from the group consisting of. The method of claim 17, And wherein the antioxidant additive has a concentration of 0.25 to 3 weight percent in the mixture. The method of claim 17, And wherein said antiwear additive has a concentration of 0.1 to 4 weight percent in said mixture.