Browse Prior Art Database

Fluid Bearing Spindle Motor with Special Lubricant

IP.com Disclosure Number: IPCOM000013718D
Original Publication Date: 2002-May-02
Included in the Prior Art Database: 2003-Jun-18
Document File: 3 page(s) / 51K

Publishing Venue

IBM

Abstract

Disclosed is a system of additives comprising oligomers of dioctyldiphenylamine and phenylnaphthylamine (Vanlube 9317), tricresyl phosphate, and optionally, a conductivity additive DuPont STADIS 450 formulated into synthetic oil, which then has superior thermal oxidative stability. The formulated oil will provide a longer lifetime than base oil without these additives when used in a fluid dynamic bearing (FDB) motor. The FDB oil must be electrically conductive and stable with respect to oxidation. Presently available FDB oils contain antistatic additives but are not formulated with antioxidant or metal passivator additives. The available FDB oils are adequate for light-duty applications such as VCR recorders. When the available FDB oils are employed in disk drive motors, and subjected to multiple start/stop operations, the bearing fails due to oil degradation. Additives were evaluated by formulating them into the base oils listed in Table 1. Table 1. The base oils used to evaluate the fluid dynamic bearing oil formulations. DOS di(2-ethyl hexyl) sebacate DOA di(2-ethyl hexyl) adipate TMP trimethylol propane ester of C7 acid, ICI Chemicals EMKARATE 1510 TRIH tricaproin, ethylene glycol trihexanoate

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Fluid Bearing Spindle Motor with Special Lubricant

Disclosed is a system of additives comprising oligomers of dioctyldiphenylamine and phenylnaphthylamine (Vanlube 9317), tricresyl phosphate, and optionally, a conductivity additive DuPont STADIS 450 formulated into synthetic oil, which then has superior thermal oxidative stability. The formulated oil will provide a longer lifetime than base oil without these additives when used in a fluid dynamic bearing (FDB) motor.

The FDB oil must be electrically conductive and stable with respect to oxidation. Presently available FDB oils contain antistatic additives but are not formulated with antioxidant or metal passivator additives. The available FDB oils are adequate for light-duty applications such as VCR recorders. When the available FDB oils are employed in disk drive motors, and subjected to multiple start/stop operations, the bearing fails due to oil degradation. Additives were evaluated by formulating them into the base oils listed in Table 1.

Table 1. The base oils used to evaluate the fluid dynamic bearing oil formulations.

DOS di(2-ethyl hexyl) sebacate DOA di(2-ethyl hexyl) adipate TMP trimethylol propane ester of C7 acid, ICI Chemicals EMKARATE 1510 TRIH tricaproin, ethylene glycol trihexanoate
DB31 Mobil Ester DB31 hexanedioic acid, isodecyl ester, isooctyl ester

The conductivity additive DuPont STADIS 450 is 22.5% Toluene, 19.3% dodecyl benzene sulfonic acid and 58.2% polymers. The toluene is a volatile carrier. The active ingredients are the dodecyl benzene sulfonic acid and the polymers. The polymers are polysulfone and polyamine in a 1 to 1 weight ratio. The antioxidant Vanlube 9317 was an oligomeric reaction mixture of octylated diphenylamine and alkylated phenyl napthylamine from R.T. Vanderbilt Corporation. The metal passivator TCP was tricresyl phosphate.

For each test, 10 grams of the formulation were placed in a three neck flask 40 steel ball bearings and 0.25 grams of leaded bronze powder (metals), and continuous stirring simulates intermittent contacts in the bearing at 150 C. Periodically, an aliquot of the hot oil was drawn dissolved in deuterated chloroform, and the proton nuclear magnetic resonance (NMR) spectrum was measured. Eventually, the NMR peaks broadened significantly between one sampling period and the next. The "lifetime" of the oil formulation was defined by the NMR peak broadening. The viscosity was measured before and after accelerated aging by capillary viscometry. The lifetime of the pure oils owas about 200 hours at 150C. The stability of the oil formulations was measured as a function of antioxidant and metal passivator. The lifetime of DOS oil increased up to a maximum of 790 hours with 1% TCP and 2% Vanlube 9317. The lifetime of DOA oil increased up to a maximum of 860 hours with 4% TCP and 2% Vanlube 9317. The lifetimes of TRIH and DB31 oil were 550 and 470 hours, respectively, with 2% each of

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TCP and Vanlube. The lifetime of TM...