Fluid dynamic pressure bearing and recording disk drive device comprising the same
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
F16C-033/02
F16C-033/06
F16C-033/04
출원번호
US-0908113
(2005-04-28)
등록번호
US-7380989
(2008-06-03)
우선권정보
JP-2004-134781(2004-04-28)
발명자
/ 주소
Murata,Itsuo
Osawa,Harushige
Feng,Ming
Tokunaga,Shinya
출원인 / 주소
Nidec Corporation
대리인 / 주소
Volentine & Whitt, PLLC
인용정보
피인용 횟수 :
1인용 특허 :
3
초록▼
In a radial minute gap between a substantially columnar shaft and an inner peripheral face of a substantially cylindrical sleeve, oil is retained and a radial dynamic pressure bearing is formed. A plurality of recessed portions are arranged in a circumferential direction on at least one of an outer
In a radial minute gap between a substantially columnar shaft and an inner peripheral face of a substantially cylindrical sleeve, oil is retained and a radial dynamic pressure bearing is formed. A plurality of recessed portions are arranged in a circumferential direction on at least one of an outer peripheral face of the shaft and the inner peripheral face of the sleeve and a first hill portion is provided to an axial end portion of each the recessed portion. Thus, it is possible to achieve a dynamic pressure bearing with which sufficient radial shaft support can be obtained in spite of a short axial length.
대표청구항▼
What is claimed is: 1. A dynamic pressure bearing device comprising: a substantially columnar shaft centered on and extending along a central axis; a sleeve in which the shaft is received, the sleeve being coaxial with the shaft such that an inner surface of the sleeve opposes, in a radial directio
What is claimed is: 1. A dynamic pressure bearing device comprising: a substantially columnar shaft centered on and extending along a central axis; a sleeve in which the shaft is received, the sleeve being coaxial with the shaft such that an inner surface of the sleeve opposes, in a radial direction perpendicular to the center axis, an outer surface of the shaft; and fluid retained between the sleeve and the shaft in the radial direction, wherein the shaft is rotatable relative to the sleeve in a circumferential direction of the sleeve with the fluid interposed therebetween, the sleeve has a plurality of first grooves in the inner surface thereof, the first grooves having opposite ends in the axial direction of the sleeve, and each of the first grooves having opposite sides in the circumferential direction of the inner surface of the sleeve, the sleeve also has a respective bank disposed adjacent each of at least one of the ends of the first grooves in the axial direction of the sleeve, each said bank being raised relative to the first grooves inwardly in the radial direction so as to prevent fluid from escaping axially from the first grooves, the first grooves being arrayed circumferentially along the inner surface of the sleeve, and the depth of each of the first grooves decreases in the circumferential direction in which the shaft rotates relative to the sleeve, whereby the pressure of fluid retained in the first grooves increases when the shaft rotates relative to the sleeve in said circumferential direction. 2. A dynamic pressure bearing device according to claim 1, wherein the radial distance between the sleeve and the central axis is smallest at the locations of a respective one of the opposite sides of the first grooves in the circumferential direction of the inner surface of the sleeve, and said distance is the same as the radial distance between the sleeve and the central axis at the locations of each said bank axially adjacent said respective one of the opposite sides of the first grooves. 3. A dynamic pressure bearing device according to claim 2, wherein the sleeve also has axially extending grooves in the inner surface thereof adjacent the opposite sides of the first grooves, and the radial distance between the central axis and the sleeve is largest at the locations of the axially extending grooves. 4. A dynamic pressure bearing device according to claim 1, further comprising: a thrust flange extending radially outward from a portion of the shaft such that a surface thereof is axially opposed to the sleeve, and wherein the sleeve has an end face axially opposed to the surface of the thrust flange, the fluid is also retained between the end face of the sleeve and the surface of the thrust flange, and at least one of the surface of the thrust flange and the end face has a spiral thrust dynamic pressure generating groove therein, whereby the end face of the sleeve, the surface of the thrust flange, and the fluid retained between the end face of the sleeve and the surface of the thrust flange form a pump-in type of thrust dynamic pressure bearing for radially inwardly increasing the pressure of the fluid when the shaft rotates relative to the sleeve in said circumferential direction. 5. A dynamic pressure bearing device according to claim 2, wherein the diameter of the end face of the sleeve is equal to or greater than the axial length of the inner surface of the sleeve. 6. A dynamic pressure bearing device according to claim 1, wherein the sleeve is substantially cylindrical, and further comprising a substantially cup-shaped bearing housing disposed radially outwardly of the sleeve. 7. A dynamic pressure bearing device according to claim 6, wherein the sleeve and the bearing housing are integral with each other. 8. A dynamic pressure bearing device according to claim 1, wherein: the shaft has a plurality of second grooves in the outer surface thereof, the second grooves having opposite ends in the axial direction of the shaft, and each of the second grooves having opposite sides in the circumferential direction of the outer surface of the shaft, the shaft also has a respective bank disposed adjacent each of at least one of the ends of the second grooves in the axial direction of the shaft, each said bank being raised relative to the second grooves outwardly in the radial direction so as to prevent fluid from escaping axially from the second grooves, the second grooves being arrayed circumferentially along the outer surface of the shaft, and the second grooves and each said bank of the shaft radially opposing, respectively, the first grooves and each said bank of the sleeve, and the depth of each of the second grooves increases in a circumferential direction in which the shaft rotates relative to the sleeve. 9. A dynamic pressure bearing device comprising: a substantially columnar shaft centered on and extending along a central axis; a sleeve in which the shaft is received, the sleeve being coaxial with the shaft such that an inner surface of the sleeve opposes, in a radial direction perpendicular to the center axis, an outer surface of the shaft; and fluid retained between the sleeve and the shaft in the radial direction, wherein the shaft is rotatable relative to the sleeve in a circumferential direction of the sleeve with the fluid interposed therebetween, the shaft has a plurality of grooves in the outer surface thereof, the grooves having opposite ends in the axial direction of the shaft, and each of the grooves having opposite sides in the circumferential direction of the outer surface of the shaft, the shaft also has a respective bank disposed adjacent each of at least one of the ends of the grooves in the axial direction of the shaft, each said bank being raised relative to the grooves outwardly in the radial direction so as to prevent fluid from escaping axially from the grooves, the grooves being arrayed circumferentially along the outer surface of the shaft, and depth of each of the grooves increases in a circumferential direction in which the shaft rotates relative to the sleeve, whereby the pressure of fluid retained in the grooves increases when the shaft rotates relative to the sleeve in said circumferential direction. 10. A dynamic pressure bearing device according to claim 9, wherein the radial distance between the shaft and the central axis is largest at the locations of a respective one of the opposite sides of the grooves in the circumferential direction of the outer surface of the shaft, and said distance is the same as the radial distance between the shaft and the central axis at the locations of each said bank axially adjacent said respective one of the opposite sides of the grooves. 11. A dynamic pressure bearing device according to claim 10, wherein the shaft also has axially extending grooves in the outer surface thereof adjacent the opposite sides of the grooves arrayed in the circumferential direction of the outer surface of the sleeve, and the radial distance between the shaft and the central axis is smallest at the locations of the axially extending grooves. 12. A dynamic pressure bearing device according to claim 9, further comprising: a thrust flange extending radially outward from a portion of the shaft such that a surface thereof is axially opposed to the sleeve, and wherein the sleeve has an end face axially opposed to the surface of the thrust flange, the fluid is also retained between the end face of the sleeve and the surface of the thrust flange, and at least one of the surface of the thrust flange and the end face has a spiral thrust dynamic pressure generating groove therein, whereby the end face of the sleeve, the surface of the thrust flange, and the fluid retained between the end face of the sleeve and the surface of the thrust flange form a pump-in type of thrust dynamic pressure bearing for radially inwardly increasing the pressure of the fluid when the shaft rotates relative to the sleeve in said circumferential direction. 13. A dynamic pressure bearing device according to claim 12, wherein the diameter of the end face of the sleeve is equal to or greater than the axial length of the inner surface of the sleeve. 14. A dynamic pressure bearing device according to claim 9, wherein the sleeve is substantially cylindrical, and further comprising a substantially cup-shaped bearing housing disposed radially outwardly of the sleeve. 15. A dynamic pressure bearing device according to claim 14, wherein the sleeve and the bearing housing are integral with each other. 16. A disk drive device comprising: a spindle motor to which a disk can be mounted, the spindle motor including a stator, a rotor magnet opposed to the stator, a rotor hub retaining the rotor magnet, and a dynamic pressure bearing supporting the rotor hub so as to be rotatable with the rotor magnet relative to the stator about a central axis, the dynamic pressure bearing comprising a substantially columnar shaft centered on and extending along the central axis, the shaft being integral with the rotor hub, a sleeve in which the shaft is received, the sleeve being coaxial with the shaft such that an inner surface of the sleeve opposes, in a radial direction perpendicular to the center axis, an outer surface of the shaft, and fluid retained between the sleeve and the shaft in the radial direction, wherein the shaft is rotatable relative to the sleeve in a circumferential direction of the sleeve with the fluid interposed therebetween, the sleeve has a plurality of first grooves in the inner surface thereof, the first grooves having opposite ends in the axial direction of the sleeve, and each of the first grooves having opposite sides in the circumferential direction of the inner surface of the sleeve, the sleeve also has a respective bank disposed adjacent each of at least one of the ends of the first grooves in the axial direction of the sleeve, each said bank being raised relative to the first grooves inwardly in the radial direction so as to prevent fluid from escaping axially from the first grooves, the first grooves being arrayed circumferentially along the inner surface of the sleeve, and the depth of each of the first grooves decreases in the circumferential direction in which the shaft rotates relative to the sleeve, whereby the pressure of fluid retained in the first grooves increases when the shaft rotates relative to the sleeve in said circumferential direction; a head operable to read and write data from and onto a disk of the type to be mounted to the spindle motor; and an actuator operable to move the head relative to a surface of the disk when the disk is mounted to the spindle motor. 17. A disk drive device comprising: a spindle motor to which a disk can be mounted, the spindle motor including a stator, a rotor magnet opposed to the stator, a rotor hub retaining the rotor magnet, and a dynamic pressure bearing supporting the rotor hub so as to be rotatable with the rotor magnet relative to the stator about a central axis, the dynamic pressure bearing comprising a substantially columnar shaft centered on and extending along the central axis, the shaft being integral with the rotor hub, a sleeve in which the shaft is received, the sleeve being coaxial with the shaft such that an inner surface of the sleeve opposes, in a radial direction perpendicular to the center axis, an outer surface of the shaft, and fluid retained between the sleeve and the shaft in the radial direction, wherein the shaft is rotatable relative to the sleeve in a circumferential direction of the sleeve with the fluid interposed therebetween, the shaft has a plurality of grooves in the outer surface thereof, the grooves having opposite ends in the axial direction of the shaft, and each of the grooves having opposite sides in the circumferential direction of the outer surface of the shaft, the shaft also has a respective bank disposed adjacent each of at least one of the ends of the grooves in the axial direction of the shaft, each said bank being raised relative to the grooves outwardly in the radial direction so as to prevent fluid from escaping axially from the grooves, the grooves being arrayed circumferentially along the outer surface of the shaft, and the depth of each of the grooves increases in a circumferential direction in which the shaft rotates relative to the sleeve, whereby the pressure of fluid retained in the grooves increases when the shaft rotates relative to the sleeve in said circumferential direction; a head operable to read and write data from and onto a disk of the type to be mounted to the spindle motor; and an actuator operable to move the head relative to a surface of the disk when the disk is mounted to the spindle motor.
Kloeppel, Klaus; Ilagan, Ronald G.; Nguyen, Diep L., Disk drive spindle with fluid journal bearing having increased radial clearance in axial end regions.
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