HYDRODYNAMIC DISC DRIVE SPINDLE MOTOR HAVING HYDRO BEARING WITH LUBRICANT
A lubricating fluid contains a synthetic ester base fluid having a viscosity index of at least 110, from 0.01% to 5% by weight, based on the total weight of the lubricating fluid, of at least one tri-C 6 -C 14 -aryl phosphate, and from 0.01% by weight to 5% by weight, based on the total weight of the synthetic ester base fluid, of at least one carbodiimide.
1 . A spindle motor comprising:
a stationary member;
a rotatable member which is rotatable with respect to the stationary member; and
a hydro bearing interconnecting the stationary member and the rotatable member and having working surfaces separated by a lubricating fluid, wherein the lubricating fluid comprises:
a) a synthetic ester base fluid having a viscosity index of at least 110, and comprising: 3-methyl-1,5-pentanediol di(n-hexanoate), 3-methyl-1,5-pentane-diol di(n-heptanoate), 3-methyl-1,5-pentanediol di(n-octanoate), 3-methyl-1,5-pentanediol di(n-nonanoate), 3-methyl-1,5-pentanediol di(n-deaconate), 3-methyl-1,5-pentanediol di(n-undecanoate), 3-methyl-1,5-pentanediol di(n-dodecanoic), 3-methyl-1,5-pentanediol di(n-tridecanoate), or combinations thereof;
b) from 0.01% to 5% by weight, based on the total weight of the lubricating fluid, of at least one tri-C 6 -C 14 -aryl phosphate wherein each of the aryl groups has from 1 to 3 identical or different substituents selected from C 1 -C 12 -alkyl groups; and
c) from 0.01% to 5% by weight, based on the total weight of the lubricating fluid, of at least one carbodiimide, wherein the carbodiimide is selected from compounds of formula (II)
X—N═C═N—Y (II)
wherein
X and Y are identical or different and each represents a C 1 -C 20 -hydrocarbon residue which may be, or comprise, aliphatic, cycloaliphatic and aromatic groups.
2 . The spindle motor according to claim 1 , wherein the carbodiimide is present in a total amount of from 0.1% to 3% by weight of the lubricating fluid.
3 . The spindle motor according to claim 1 , wherein the carbodiimide is a di-aryl-carbodiimide.
4 . The spindle motor according to claim 1 , wherein each of the aryl groups on the tri-C 6 -C 14 -aryl phosphate has from 1 to 3 identical or different substituents selected from C 3 -C 6 -alkyl groups.
5 . The spindle motor according to claim 1 , wherein the tri-C 6 -C 14 -aryl phosphate is tricresyl phosphate.
6 . The spindle motor according to claim 1 , wherein the lubricating fluid further comprises an additive selected from the group consisting of antioxidants, corrosion inhibitors, viscosity index modifiers, pour point depressants, anti-foaming agents and electrically conductive, non-metallic additives.
7 . The spindle motor according to claim 6 , wherein the lubricating fluid comprises from 0.01% to 5% by weight, based on the total weight of the lubricating fluid, of at least one antioxidant.
8 . The spindle motor according to claim 6 , wherein the lubricating fluid comprises from 0.01% to 5% by weight, based on the total weight of the lubricating fluid, of at least one corrosion inhibitor.
9 . The spindle motor according to claim 6 , wherein the lubricating fluid comprises from 0.01% to 5% by weight, based on the total weight of the lubricating fluid, of at least one viscosity index modifier.
10 . The spindle motor according to claim 6 , wherein the lubricating fluid comprises from 0.01% to 5% by weight, based on the total weight of the lubricating fluid, of at least one pour point depressant.
11 . The spindle motor according to claim 6 , wherein the lubricating fluid comprises from 0.01% to 5% by weight, based on the total weight of the lubricating fluid, of at least one anti-foaming agent.
12 . The spindle motor according to claim 1 , wherein the lubricating fluid further comprises a polyalphaolefin base fluid.
13 . A spindle motor comprising:
a stationary member;
a rotatable member which is rotatable with respect to the stationary member; and
a hydro bearing interconnecting the stationary member and the rotatable member and having working surfaces separated by a lubricating fluid, wherein the lubricating fluid comprises:
a) a synthetic ester base fluid having a viscosity index of at least 110;
b) from 0.01% to 5% by weight, based on the total weight of the lubricating fluid, of at least one tri-C 6 -C 14 -aryl phosphate wherein each of the aryl groups has from 1 to 3 identical or different substituents selected from C 1 -C 12 -alkyl groups; and
c) from 0.01% to 5% by weight, based on the total weight of the lubricating fluid, of at least one carbodiimide.
14 . The spindle motor according to claim 13 , wherein the synthetic ester base fluid comprises
compounds of formula I,
wherein R 1 and R 2 are identical or different and each represents a straight-chain C 3 -C 17 -alkyl group which optionally carries a C 1 -C 3 -alkyl bonded to a secondary carbon of the chain; and Z is a straight-chain C 3 -C 10 -alkylene group which optionally carries a C 1 -C 3 -alkyl bonded to a carbon of the chain;
compounds of formula Ia,
wherein R 1 and R 2 are identical or different and each represents a straight-chain C 3 -C 17 -alkyl group which optionally carries a C 1 -C 3 -alkyl bonded to a secondary carbon of the chain; and Z is a straight-chain C 3 -C 10 -alkylene group which optionally carries a C 1 -C 3 -alkyl bonded to a carbon of the chain;
or combinations thereof.
15 . The spindle motor according to claim 13 , wherein the carbodiimide is a di-aryl-carbodiimide.
16 . The spindle motor according to claim 13 , wherein each of the aryl groups on the tri-C 6 -C 14 -aryl phosphate has from 1 to 3 identical or different substituents selected from C 3 -C 6 -alkyl groups.
17 . The spindle motor according to claim 13 , wherein the tri-C 6 -C 14 -aryl phosphate is tricresyl phosphate.
18 . The spindle motor according to claim 13 , wherein the lubricating fluid has a viscosity of from 15 cp to 80 cp at 0° C.
19 . The spindle motor according to claim 13 , wherein the synthetic ester base fluid comprises 3-methyl-1, 5-pentanediol di(n-hexanoate), 3-methyl-1,5-pentane-diol di(n-heptanoate), 3-methyl-1, 5-pentanediol di(n-octanoate), 3-methyl-1,5-pentanediol di(n-nonanoate), and 3-methyl-1,5-pentanediol di(n-deaconate), 3-methyl-1,5-pentanediol di(n-undecanoate), 3-methyl-1,5-pentanediol di(n-dodecanoic), and 3-methyl-1,5-pentanediol di(n-tridecanoate), or combinations thereof.
20 . A lubricating fluid comprising:
a) a synthetic ester base fluid having a viscosity index of at least 110;
b) from 0.01% to 5% by weight, based on the total weight of the lubricating fluid, of at least one tri-C 6 -C 14 -aryl phosphate wherein each of the aryl groups has from 1 to 3 identical or different substituents selected from C 1 -C 12 -alkyl groups; and
c) from 0.01% to 5% by weight, based on the total weight of the lubricating fluid, of at least one carbodiimide.