Fluid dynamic pressure bearing lubricant oil composition, fluid dynamic pressure bearing, and fluid dynamic pressure bearing apparatus

Patent metadata

Field	Value
Publication number	US-2025361908-A1
Application number	US-202318872477-A
Country	US
Kind code	A1
Filing date	Jun 6, 2023
Priority date	Jun 14, 2022
Publication date	Nov 27, 2025
Grant date	—

Abstract

A lubricating-oil composition for a fluid-dynamic bearing, which is to be used for a fluid-dynamic bearing ( 8 ) including radial dynamic pressure generating portions (A 1 , A 2 ) provided on an inner peripheral surface (Sa) of a porous body, has the following makeup. That is, a base oil having a kinematic viscosity of more than 30 mm 2 /s and 80 mm 2 /s or less at a temperature of 40° C. is used as a base oil of the lubricating-oil composition, and the makeup of the lubricating-oil composition is adjusted so that the lubricating-oil composition has a kinematic viscosity of 90 mm 2 /s or more and 140 mm 2 /s or less at a temperature of 40° C.

First claim

1 . A lubricating-oil composition for a fluid-dynamic bearing, the lubricating-oil composition being configured to be used for the fluid-dynamic bearing, which is formed of a porous body having inner pores, and comprises a radial dynamic pressure generating portion on an inner peripheral surface of the porous body,
wherein a base oil having a kinematic viscosity of more than 30 mm 2 /s and 80 mm 2 /s or less at a temperature of 40° C. is used as a base oil, and wherein the lubricating-oil composition has a kinematic viscosity of 90 mm 2 /s or more and 140 mm 2 /s or less at a temperature of 40° C.

2 . The lubricating-oil composition for a fluid-dynamic bearing according to claim 1 , wherein the base oil is a mixture of a non-polar oil and a polar oil, and a ratio of the non-polar oil to an entirety of the base oil is 20 wt % or more and 30 wt % or less.

3 . The lubricating-oil composition for a fluid-dynamic bearing according to claim 2 , wherein the non-polar oil is a synthetic hydrocarbon oil made from poly-α-olefin or a hydride of poly-α-olefin.

4 . The lubricating-oil composition for a fluid-dynamic bearing according to claim 2 , wherein the polar oil is an ester oil.

5 . A fluid-dynamic bearing obtained through impregnation of the inner pores with the lubricating-oil composition of claim 1 .

6 . The fluid-dynamic bearing according to claim 5 , wherein a dynamic pressure generating groove array region is formed as the radial dynamic pressure generating portion on the inner peripheral surface.

7 . The fluid-dynamic bearing according to claim 5 , wherein an inner diameter dimension is 2.0 mm or less, and an axial dimension is 3.5 mm or less.

8 . A fluid-dynamic bearing device, comprising:
the fluid-dynamic bearing of claim 5 ; a housing having an inner periphery to which the fluid-dynamic bearing is fixed; a rotator having a shaft portion inserted along an inner periphery of the fluid-dynamic bearing; and a radial bearing portion configured to radially support the shaft portion in a non-contact manner through an oil film of the lubricating-oil composition, which is formed in a radial bearing gap between the inner peripheral surface of the fluid-dynamic bearing and an outer peripheral surface of the shaft portion.

9 . The fluid-dynamic bearing device according to claim 8 , wherein the shaft portion being rotatable with respect to the fluid-dynamic bearing in a non-contact manner has an eccentricity ratio of up to 98%.

10 . A motor comprising the fluid-dynamic bearing device of claim 8 .

Assignees

• Ntn Toyo Bearing Co Ltd
• Nok Klueber Co Ltd

Inventors

• Komatsubara Shinji
• Osanai Dai

Classifications

• F16C2370/12

  Hard disk drives or the like · CPC title

• F16C17/107

  with at least one surface for radial load and at least one surface for axial load · CPC title

• F16C33/1065 Primary

  Grooves on a bearing surface for distributing or collecting the liquid · CPC title

• F16C33/109

  Lubricant compositions or properties, e.g. viscosity · CPC title

• F16C17/02

  for radial load only · CPC title