# US 2019/0245408 A1 · Fluid dynamic bearing device and motor with same

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- Number: US 2019/0245408 A1
- Document ID: US20190245408A1
- Status: Published application
- Kind: A1
- Application number: 16/314,771
- Filed: 2017-06-14
- Published: 2019-08-08
- Earliest claimed: 2016-07-14
- Assignees: Ntn Corporation
- Applicants: Ntn Corporation
- Inventors: Shinji KOMATSUBARA
- Web page: https://patentgrep.com/patent/US20190245408A1

## CPC

- H02K 5/167: using sliding-contact or spherical cap bearings
- F16C 17/02: for radial load only
- F16C 17/026: {with helical grooves in the bearing surface to generate hydrodynamic pressure, e.g. herringbone grooves}
- F16C 33/103: {retained in or near the bearing}
- F16C 33/104: {in a porous body, e.g. oil impregnated sintered sleeve}
- F16C 33/106: {Details of distribution or circulation inside the bearings, e.g. details of the bearing surfaces to affect flow or pressure of the liquid}
- F16C 33/107: {Grooves for generating pressure}
- F16C 33/128: {Porous bearings, e.g. bushes of sintered alloy}
- F16C 33/145: {of sintered porous bearings}
- F16C 35/02: in the case of sliding-contact bearings
- H02K 7/08: Structural association with bearings
- F16C 17/107: {with at least one surface for radial load and at least one surface for axial load}
- F16C 33/745: {by capillary action}
- F16C 2370/12: Hard disk drives or the like
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})
- F16C: SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS

## Abstract

A charging amount of lubricating oil (11) into an internal space of a housing (7) is adjusted so that, within a range of a use temperature, an oil level of the lubricating oil (11) is positioned on a lower side with respect to an upper end portion of a chamfered portion (8f) formed in an upper-end inner peripheral edge portion of a bearing member (8). The bearing member (8) integrally includes: a small-diameter cylindrical portion (81); and a large-diameter cylindrical portion (82). Under a state in which an upper end surface (8c) of the small-diameter cylindrical portion (81) is exposed to an atmosphere, the large-diameter cylindrical portion (82) is sandwiched from both sides in the axial direction with an annular member (9) and a bottom portion (7b) of the housing (7) so that the bearing member (8) is fixed along an inner periphery of the housing (7).

## Claims

### Claim 1

A fluid dynamic bearing device, comprising:
a housing having a bottomed cylindrical shape with an end portion on one end side in an axial direction being opened and an end portion on another end side in the axial direction being closed,
a bearing member, which is arranged along an inner periphery of the housing, and has a chamfered portion at an inner peripheral edge portion on one end side in the axial direction, the bearing member being porous; and
a radial bearing portion, which is configured to support the shaft member in a radial direction with an oil film of lubricating oil formed in a radial bearing gap defined between an inner peripheral surface of the bearing member and an outer peripheral surface of the shaft member to be inserted along an inner periphery of the bearing member,
wherein the shaft member is supported in a thrust direction by an inner bottom surface of the housing,
wherein a charging amount of the lubricating oil into an internal space of the housing is adjusted so that, within a range of a use temperature, an oil level of the lubricating oil is positioned on another end side in the axial direction with respect to the end portion of the chamfered portion on one end side in the axial direction,
wherein the bearing member integrally comprises:
a small-diameter cylindrical portion, which is arranged on one end side in the axial direction, and has a relatively smaller outer diameter dimension; and
a large-diameter cylindrical portion, which is arranged on another end side in the axial direction, and has a relatively larger outer diameter dimension, and
wherein, under a state in which an end surface of the small-diameter cylindrical portion on one end side in the axial direction is exposed to an atmosphere, the large-diameter cylindrical portion of the bearing member is sandwiched from both sides in the axial direction between an annular member, which is arranged between the small-diameter cylindrical portion and a tubular portion of the housing, and a bottom portion of the housing so that the bearing member is fixed along an inner periphery of the housing.

### Claim 2 (depends on 1)

The fluid dynamic bearing device according to claim 1, wherein fitting of the large-diameter cylindrical portion with respect to the tubular portion of the housing and fitting of the small-diameter cylindrical portion with respect to the annular member each comprise loose fitting.

### Claim 3 (depends on 1)

The fluid dynamic bearing device according to claim 1,
wherein the bearing member is formed of a porous body made of sintered metal, and
wherein the inner peripheral surface of the bearing member is molded in conformity with an outer peripheral surface of a sizing core.

### Claim 4 (depends on 3)

The fluid dynamic bearing device according to claim 3, wherein a ratio (t2/t1) of a radial thickness (t2) of the large-diameter cylindrical portion to a radial thickness (t1) of the small-diameter cylindrical portion is less than 2.5.

### Claim 5 (depends on 3)

The fluid dynamic bearing device according to claim 3, wherein a tapered surface which is gradually reduced in diameter from another end side in the axial direction toward one end side in the axial direction is formed in the outer peripheral surface of the small-diameter cylindrical portion.

### Claim 6 (depends on 5)

The fluid dynamic bearing device according to claim 5,
wherein a cylindrical surface having a constant diameter is formed on the outer peripheral surface of the small-diameter cylindrical portion, and
wherein the cylindrical surface is formed between the tapered surface and an end surface of the small-diameter cylindrical portion on one end side in the axial direction.

### Claim 7 (depends on 1)

The fluid dynamic bearing device according to claim 1, wherein a dynamic pressure generating portion configured to generate fluid dynamic pressure in the lubricating oil in the radial bearing gap is formed in the inner peripheral surface of the bearing member.

### Claim 8 (depends on 1)

The fluid dynamic bearing device according to claim 1, wherein the shaft member is insertable and removable with respect to the bearing member.

### Claim 9 (depends on 1)

The fluid dynamic bearing device according to claim 1, wherein an external force for urging the shaft member toward another end side in the axial direction is caused to act on the shaft member.

### Claim 10 (depends on 1)

The fluid dynamic bearing device according to claim 1, wherein a rotor comprising vanes for sending air is provided to the shaft member.

### Claim 11 (depends on 1)

A motor comprising the fluid dynamic bearing device according to claim 1.